A disc-type magneto-rheologic fluid damper
祝长生
2003-01-01
A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper,which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magneticfield of the disc-type MR fluid damper is analysed by the finite element method ; the controllability of the disctype MR fluid damper on the dynamic behaviour of a rotor system ; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil ; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.
A disc-type magneto-rheologic fluid damper
祝长生
2003-01-01
A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.
Experiment study of large-scale magnetorheological fluid damper
Guan, Xinchun; Li, Jinhai; Ou, Jinping
2005-05-01
Due to their character of low power requirement, rapid-response and large force, the dampers that made based on the special rheologic performance of magnetorheological fluid (MRF) have shown to be one kind of ideal semi-active vibration control devices for civil engineering structures and vehicles. In this paper, the character of magnetic circuit of MRF damper was firstly studied; based on above results, a large-scale MRF damper whose adjustable multiple is about 16 and maximum damping force is about 170kN was then designed and tested. Experimental results show that, under lower electrical current, same or opposite of electric current direction of multi-coils winding on the piston do not influence damping performance of MRF damper; however, under higher electrical current, inverse connecting of adjacent coils is apt to improve damping force of MRF damper.
A fully dynamic magneto-rheological fluid damper model
Jiang, Z.; Christenson, R. E.
2012-06-01
Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.
A New Generation of Magneto-Rheological Fluid Dampers
2007-11-02
active MRF damper. An Instron 8821S servo-hydraulic system is used to provide the input road profile. The actuator of the hydraulic unit is mounted...Presented at 8th International conference on Electrorheological (ER) Fluid and Magneto-rheological (MR) Suspensions, Nice, July 9- 13,2001 9...representing the excitation due to the road profile Instron Hydraulic Actuator Linear Slide System providing the movement of the masses 56 0 0.5 1
Dynamic analysis of electro- and magneto-rheological fluid dampers using duct flow models
Esteki, Kambiz; Bagchi, Ashutosh; Sedaghati, Ramin
2014-03-01
Magneto-rheological (MR) and electro-rheological (ER) fluid dampers provide a semi-active control mechanism for suppressing vibration responses of a structure. MR and ER fluids change their viscosity under the influence of magnetic and electrical fields, respectively, which facilitates automatic control when these fluids are used in damping devices. The existing models, namely the phenomenological models for simulating the behavior of MR and ER dampers, rely on various parameters determined experimentally by the manufacturers for each damper configuration. It is of interest to develop mechanistic models of these dampers which can be applied to various configurations so that their fundamental characteristics can be studied to develop flexible design solutions for smart structures. This paper presents a formulation for dynamic analysis of electro-rheological (ER) and magneto-rheological (MR) fluid dampers in flow and mix mode configurations under harmonic and random excitations. The procedure employs the vorticity transport equation and the regularization function to deal with the unsteady flow and nonlinear behavior of ER/MR fluid in general motion. The finite difference method has been used to solve the governing differential equations. Using the developed approach, the damping force of ER/MR dampers can be calculated under any type of excitation.
Jin Huang
2012-01-01
Full Text Available Magnetorheological (MR disk-type isolating dampers are the semi-active control devices that use MR fluids to produce controllable squeezing force. In this paper, the analytical endeavor into the fluid dynamic modeling of an MR isolating damper is reported. The velocity and pressure distribution of an MR fluid operating in an axisymmetric squeeze model are analytically solved using a biviscosity constitutive model. Analytical solutions for the flow behavior of MR fluid flowing through the parallel channel are obtained. The equation for the squeezing force is derived to provide the theoretical foundation for the design of the isolating damper. The result shows that with the increase of the applied magnetic field strength, the squeezing force is increased.
Multiphysics modeling of magnetorheological dampers
D Case
2016-09-01
Full Text Available The dynamics of a small scale magnetorheological damper were modeled and analyzed using multiphysics commercial finite element software to couple the electromagnetic field distribution with the non-Newtonian fluid flow. The magnetic flux lines and field intensity generated within the damper and cyclic fluid flow in the damper under harmonic motion were simulated with the AC/DC and CFD physics modules of COMSOL Multiphysics, respectively. Coupling of the physics is achieved through a modified Bingham plastic definition, relating the fluid's dynamic viscosity to the intensity of the induced magnetic field. Good agreement is confirmed between simulation results and experimentally observed resistance forces in the damper. This study was conducted to determine the feasibility of utilizing magnetorheological dampers in a medical orthosis for pathological tremor attenuation. The implemented models are thus dimensioned on a relatively small scale. The method used, however, is not specific to the damper's size or geometry and can be extended to larger-scale devices with little or no complication.
Structure Analysis for a New Type of Vane Hydraulic Damper Using Magneto-rheological Fluid
ZHANG Jin-qiu; FENG Zhan-zong; WANG Hong-tao
2008-01-01
Over recent years the progress in actuator and microelectronics technology has made intelligent suspension systems feasible. Based on conventional vane hydraulic damper, a new vane magneto-rheological fluid (MRF) damper with fail-safe capability is designed. Firstly, the mathematical model of damping moment is deduced based on the parallel-plate model and Bingham model of MR fluids. Secondly, some influence factors of damping adjustable multiple are analyzed to provide some ways for augmenting the damping adjustable multiple under the condition of keeping initial damping moment invariable. Finally, the magnetic circuit is designed, and magnetic field distribution is simulated with the magnetic finite element analysis software-AN,SOFT. The theory and simulation results confirm that the damping adjustable range of vane MRF damper can meet the requirement of heavy vehiele semi-active suspension system.
A semi-active control suspension system for railway vehicles with magnetorheological fluid dampers
Wei, Xiukun; Zhu, Ming; Jia, Limin
2016-07-01
The high-speed train has achieved great progress in the last decades. It is one of the most important modes of transportation between cities. With the rapid development of the high-speed train, its safety issue is paid much more attention than ever before. To improve the stability of the vehicle with high speed, extra dampers (i.e. anti-hunting damper) are used in the traditional bogies with passive suspension system. However, the curving performance of the vehicle is undermined due to the extra lateral force generated by the dampers. The active suspension systems proposed in the last decades attempt to solve the vehicle steering issue. However, the active suspension systems need extra actuators driven by electrical power or hydraulic power. There are some implementation and even safety issues which are not easy to be overcome. In this paper, an innovative semi-active controlled lateral suspension system for railway vehicles is proposed. Four magnetorheological fluid dampers are fixed to the primary suspension system of each bogie. They are controlled by online controllers for enhancing the running stability on the straight track line on the one hand and further improving the curving performance by controlling the damper force on the other hand. Two control strategies are proposed in the light of the pure rolling concept. The effectiveness of the proposed strategies is demonstrated by SIMPACK and Matlab co-simulation for a full railway vehicle with two conventional bogies.
Experimental and numerical studies of MR damper with prototype magnetorheological fluid
S. Kciuk
2010-03-01
Full Text Available Purpose: Results of experimental studies of a prototype magnetorheological damper at various magnitudes of control current as well as the manner of modelling electromagnetic phenomena occurring in the damper are presented in this paper.Design/methodology/approach: Model MR fluid was prepared using silicone oil OKS 1050 mixed with carbonyl iron powder CI. Furthermore, to reduce sedimentation, as stabilizers was added Aerosil 200. The observations of the surface morphology of carbonyl iron and fumed silica were carried out using Digital Scanning Electron Microscope SUPRATM25 ZEISS. The effect of magnetic field on magnetorheological fluid is modelled by the finite element method.Findings: The presented model meets the initial criteria, which gives ground to the assumption about its usability for determining the dynamics properties of mechanical systems, employing the finite element method using ANSYS software.Research limitations/implications: The elaborated model can be use for modelling the semi active car suspension dynamics.Originality/value: The actual-non-linear characteristics of magnetisation identified experimentally were used as the values of relative magnetic permeability of the piston housing material. The possibility of application, e.g. real characteristics of material magnetisation and faster and faster calculation machines make possibility the creation of more precise models and more adequate ones to reality.
Study on damping properties of magnetorheological damper
ZHOU Yu-feng; CHEN Hua-ling
2006-01-01
To research the properties of a new kind of smart controllable MR (magnetorheological) fluid,in this paper,the rheological models are discussed.On the basis of analyzing the structural forms of MR dampers,an improved structure of the MR damper is introduced;the properties of the novel MR damper are then tested.The experimental resuits reveal that the Herschel-Bulkley model predicts the force-velocity well;the damping properties of the ameliorated structure of the MR damper have improved;when the excitation is a trigonal signal,the MR damper reveals a thinning effect at high velocity;and when the excitation is a sinusoidal signal,the MR damper reveals a nonlinear hysteretic property between the damping force and relative velocity.Finally,the main unsolved problems have been put forward.
Dutta, Saikat; Chakraborty, G.
2015-09-01
A physical model of a type of commercially available magneto-rheological fluid based damper has been developed to study the input-output response characteristics. The impedance of the nonlinear device has been analyzed based on equivalent linearization method. The capability of isolating vibration with the help of such a damper has also been studied analytically. The damper is operated in passive mode while the excitation is kept harmonic. A novel method of obtaining the steady-state response of a damped oscillator is presented that uses a combination of harmonic balance method and the method of averaging. The isolating property of the damper has been measured by transmissibilities derived for equivalent linear system.
Optimal Control of Magnetorheological Fluid Dampers for Seismic Isolation of Structures
Ameen H. El-Sinawi
2013-01-01
Full Text Available This paper presents the modeling and control of a magnetorheological (MR damper, installed in Chevron configuration, at the base of a 20-story benchmark building. The building structural model is created using the commercial software package ETABS. The MR damper model is derived from Bouc-Wen hysteresis model which provides the critical nonlinear dynamics that best represents the MR damper under a wide range of operating conditions. System identification is used to derive a low-order nonlinear model that best mimics the nonlinear dynamics of the actual MR damper. Dynamic behavior of this low-order model is tested and validated over a range of inputs. The damper model has proven its validity to a high degree of accuracy against the nonlinear model. A Kalman filter is designed to best estimate the state of the structure-damper system for feedback implementation purposes. Using the estimated states, an LQG-based compensator is designed to control the MR damper under earthquake loads. To demonstrate the effectiveness of this control strategy, four historical earthquakes are applied to the structure. Controlled and uncontrolled floor accelerations and displacements at key locations are compared. Results of the optimally controlled model demonstrate superior performance in comparison to the uncontrolled model.
Magnetorheological Damper Working in Squeeze Mode
Xinglong Gong
2014-05-01
Full Text Available This research is focused on evaluation of the magnetorheological fluids (MRFs based damper which works in squeeze mode. The operation direction of this damper is parallel to the direction of the external magnetic field. Before testing, commercial software ANSYS was used to analyze the magnetic field distribution inside the damper generated by charging current in the coil. The performance of the damper was tested by using the MTS809 (produced by MTS Systems Corporation, USA. For simulation of this damper, a mathematical model was set up. Experimental results showed that the small squeezed MR damper could produce large damping force; for example, the maximum damping force is nearly 6 kN, while the amplitude is 1.2 mm, the frequency is 1.0 Hz, and the current is 2.0 A, and the damping force was controllable by changing the current in the coil. The damping force versus displacement curves are complex. We divide them into four regions for simulation. The maximum damper force increased quickly with the increasing of the current in coil. This kind of damper can be used in vibration isolation for precise equipment.
Theoretical Analysis of Magnetorheological Damper Characteristics in Squeeze Mode
Sapiński Bogdan
2015-06-01
Full Text Available The paper summarises the theoretical study of a magnetorheological (MR damper operated in squeeze mode, intended to be used as an actuator in a semi-active mount system in a car motor. The structural design and operating principle of the damper are described and a simplified model of the MR fluid flow in the gap is presented. The plots of the damper force generated by the MR damper are obtained for monoharmonic piston motion with respect to the centre point of the gap height and in the conditions of the control coil being supplied with direct current.
Marinică, Oana; Susan-Resiga, Daniela; Bălănean, Florica; Vizman, Daniel; Socoliuc, Vlad; Vékás, Ladislau
2016-05-01
In this paper, static magnetic properties and magnetorheological behavior of a set of 12 nano-micro composite magnetic fluids (CMFs) were studied. The samples with a ferromagnetic particle volume fraction ranging in a large interval φFe = (1 ÷ 44) % were prepared by adding carbonyl iron powder in a highly concentrated transformer oil-based ferrofluid (FF). The ferrofluid has the magnetite volume fraction of φFe3O4 = 22.90 % and saturation magnetization of Ms = 74 kA / m (930 Gs). No further additives were used in order to prevent sedimentation. It was noticed an increase of the static yield stress, of about 3 orders of magnitude, with the increase of the total solid volume fraction of samples and with the increase of the magnetic field, which varied between 0 kA/m and 950 kA/m. The dynamic yield stress (Herschel-Bulkley model) τHB of the samples strongly increases with the magnetic field and shows a slight tendency of saturation for higher intensities of the magnetic field. There is a less pronounced increase of τHB, about an order of magnitude with the increasing volume fraction of the iron particles. The relative viscosity increase induced by the magnetic field reaches a maximum for both considered shear rates: γ ṡ = 7.85s-1 and γ ṡ = 88.41s-1 and it was revealed an optimal volume fraction of Fe particles, φFe = 20 % , corresponding to a total volume fraction of φtot ≈ 38 % , at which the magnetoviscous effect has its maximum value. The magnetic properties and also the magnetorheological and the magnetoviscous behavior of highly concentrated ferrofluid-based CMFs can be controlled by the addition of iron microparticles in order to attain the optimal concentration for the envisaged engineering applications, rotating seals and magnetorheological vibration dampers.
A Novel Design of Magnetorheological Damper with Annular Radial Channel
Shisha Zhu
2016-01-01
Full Text Available With the development of automotive vibration technology, the semiactive suspension system with adjustable damping force and high reliability is taken seriously. The magnetorheological damper (MRD that applies intelligent material (magnetorheological fluid is the key element of this system. It can achieve a continuous and adjustable damping and then reaches the purpose of comfort. In order to improve the damping effect of MRD, this paper presents a MRD, which has magnetorheological (MR effect along annular radial channel. The paper completely designs the structure and magnetic circuit of MRD. Based on the theory of electromagnetism and MR fluid dynamics, the paper analyzes and tests the external characteristics of the MRD by the MATLAB/Simulink and the vibration experiment. The results compared with ordinary MRD reveal that the damping force obviously increases and has wide adjustable range, thus verifying the reasonableness of the damper design.
Flow Mode Magnetorheological Dampers with an Eccentric Gap
Choi, Young-Tai; Norman M. Wereley
2014-01-01
This paper analyzes flow mode magnetorheological (MR) dampers with an eccentric annular gap (i.e., a nonuniform annular gap). To this end, an MR damper analysis for an eccentric annular gap is constructed based on approximating the eccentric annular gap using a rectangular duct with a variable gap, as well as a Bingham-plastic constitutive model of the MR fluid. Performance of flow mode MR dampers with an eccentric gap was assessed analytically using both field-dependent damping force and dam...
A design strategy for magnetorheological dampers using porous valves
Hu, W; Robinson, R; Wereley, N M [Smart Structures Laboratory, Alfred Gessow Rotorcraft Center, Department of Aerospace Engineering, University of Maryland, College Park, MD 20742 (United States)], E-mail: wereley@umd.edu
2009-02-01
To design a porous-valve-based magnetorheological (MR) damper, essential design parameters are presented. The key elements affecting the damper performance are identified using flow analysis in porous media and an empirical magnetic field distribution in the porous valve. Based on a known MR fluid, the relationship between the controllable force of the damper and the porous valve characteristics, i.e. porosity and tortuosity, is developed. The effect of the porosity and tortuosity on the field-off damping force is exploited by using semi-empirical flow analysis. The critical flow rate for the onset of nonlinear viscous damping force is determined. Using the above design elements, an MR damper using by-pass porous valve is designed and tested. The experimental damper force and equivalent damping are compared with the predicted results to validate this design strategy.
A new magnetorheological damper for seismic control
Ding, Yang; Zhang, Lu; Zhu, Hai-Tao; Li, Zhong-Xian
2013-11-01
This paper proposes a new MR damper with bidirectional adjusting damping forces to enhance the fail-safe property of the MR damper. The structure of the composite magnetic circuits is improved for the new damper. Four prototype dampers are fabricated and tested by magnetic field tests and dynamic tests. The magnetic field distribution in the damping path and the dynamic properties of the dampers with different input currents are obtained. The Gompertz model is proposed to portray the dynamic behavior of the prototype dampers. The study shows that, due to the improved structure of composite magnetic circuits, the prototype dampers can maintain a medium damping force with zero current input. This behavior may ensure a better fail-safe property and avoid settlement of MR fluid compared with conventional MR dampers. Furthermore, the minimum and maximum output powers of the proposed dampers can be obtained at the states of the negative peak and positive peak of currents inputs, respectively. In addition, the dynamic range of controllable force is wider than that of conventional MR dampers. The analysis further shows that the proposed Gompertz model can precisely portray the nonlinear hysteretic behavior of the proposed dampers without complicated function forms.
Shah, Kruti; Xuan Phu, Do; Choi, Seung-Bok
2014-05-01
In this study, the rheological properties and an application of bi-dispersed magnetorheological fluid (MRF) based on plate-like iron particles are experimentally investigated. A bi-dispersed MR Fluid is prepared using two different micron-scale sizes of plate-like iron particles. In the absence of a magnetic field, the properties of the fluid are isotropic. Upon the application of a magnetic field, the magnetized particles form a chain aligned in the direction of the field, which promotes the appearance of a yield stress. The reversible transition from solid to liquid is the basic requirement of MR applications. Due to the anisotropy in the shape and formation of a less compact structure in the iron plate-like particles, weak sedimentation and good redispersibility of the proposed MR fluid are created. The physical properties of the proposed MR fluids are evaluated and applied to the design of a small-sized controllable MR vibration damper, which can be used for vibration control of a washing machine. The MR damper is a semi-active device that dissipates energy during vibration motion to increase the stability of the application system. Three different weight fractions of the bi-dispersed MR fluids are prepared, and their rheological properties are presented and discussed. Based on their rheological properties, the figures of merit of the proposed MR fluids are derived. A comparison of these figures of merit gives the nominal behavior of the MR fluids, which are important in the design of the application device. A stability test is also performed to check the settling rate of MR fluids per day. The change in damping force due to the problem of particles settling in the MRF and the field-dependent damping force are measured with the MR damper operated just after filling the MRF and with the MR damper operated after waiting for 48 h after filling. With basic rheological properties and outstanding mechanical properties, it is clearly demonstrated that the proposed MR
Novel design of a self powered and self sensing magneto-rheological damper
Meftahul Ferdaus, Mohammad; Rashid, M. M.; Bhuiyan, M. M. I.; Muthalif, Asan Gani Bin Abdul; Hasan, M. R.
2013-12-01
Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.
Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil
2016-06-01
A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.
Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil
2017-08-01
A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.
A seat suspension with a rotary magnetorheological damper for heavy duty vehicles
Sun, S. S.; Ning, D. H.; Yang, J.; Du, H.; Zhang, S. W.; Li, W. H.
2016-10-01
This paper presents the development of an innovative seat suspension working with a rotary magnetorheological (MR) fluid damper. Compared with a conventional linear MR damper, the well-designed rotary MR damper possesses several advantages such as usage reduction of magnetorheological fluid, low sealing requirements and lower costs. This research starts with the introduction of the seat suspension structure and the damper design, followed by the property test of the seat suspension using an MTS machine. The field-dependent property, amplitude-dependent performance, and the frequency-dependent performance of the new seat suspension are measured and evaluated. This research puts emphasis on the evaluation of the vibration reduction capability of the rotary MR damper by using both simulation and experimental methods. Fuzzy logic is chosen to control the rotary MR damper in real time and two different input signals are considered as vibration excitations. The experimental results show that the rotary MR damper under fuzzy logic control is effective in reducing the vibrations.
Wang Enrong; Ma Xiaoqing; Su Chunyi; Rakheja Subhash
2004-01-01
A generalized model is synthesized to characterize the asymmetric hysteresis force-velocity (F-v) properties of the magneto-rheological (MR) fluids damper.The model is represented as a function of the command current,excitation frequency,and displacement amplitude,based on the symmetric and asymmetric sigmoid functions.The symmetric hysteresis damping properties of the controllable MR-damper and properties of the conventional passive hydraulic damper can also be described by the proposed model.The validity of the model is verified by experiments,which show that the results calculated from the model are consistent with the measured data.In addition,it is shown that the model applies to a wide vibration frequency range.The proposed model has potential application in vehicle suspension design employing the symmetry MR-damper,and also in developing the asymmetry MR-damper especially for the vehicle suspension attenuation.
Vibration control of a structure using Magneto-Rheological grease damper
Sugiyama, Shinya; Sakurai, Tomoki; Morishita, Shin
2013-09-01
This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval due to the density difference between the particles and their career fluid. To overcome this defect, we have developed a new type of controllable working fluid using grease as the career of magnetic particles. Network of thickener in grease is expected to hold the magnetic particles and prevent them from settled down. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder of damper. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper worked effectively as a semi-active damper.
Application Of CFD To Modeling Of Squeeze Mode Magnetorheological Dampers
Gołdasz Janusz
2015-09-01
Full Text Available The so-called squeeze flow involves a magnetorheological (MR fluid sandwiched between two planar surfaces setting up a flow channel. The height of the channel varies according to a prescribed displacement or force profile. When exposed to a magnetic field of sufficient strength MR fluids develop a yield stress. In squeeze-mode devices the yield stress varies with both the magnetic field magnitude and the channel height. In this paper an unsteady flow model of an MR fluid in squeeze mode is proposed. The model is developed in Ansys Fluent R16. The MR material flow model is based on the apparent viscosity approach. In order to investigate the material's behaviour the authors prepared a model of an idealized squeeze-mode damper in which the fluid flow is enforced by varying the height of the channel. Using mesh animation, the model plate is excited, and as the mesh moves, the fluid is squeezed out of the gap. In the simulations the model is subjected to a range of displacement inputs of frequencies from 10 to 20 Hz, and local yield stress levels up to 30 kPa. The results are presented in the form of time histories of the normal force on the squeezing plate and loops of force vs. displacement (velocity.
Modeling of Magneto-Rheological Damper with Neural Network
无
2006-01-01
With the revival of magnetorheological technology research in the 1980's, its application in vehicles is increasingly focused on vibration suppression. Based on the importance of magnetorheological damper modeling, nonparametric modeling with neural network, which is a promising development in semi-active online control of vehicles with MR suspension, has been carried out in this study. A two layer neural network with 7 neurons in a hidden layer and 3 inputs and 1 output was established to simulate the behavior of MR damper at different excitation currents. In the neural network modeling, the damping force is a function of displacement, velocity and the applied current. A MR damper for vehicles is fabricated and tested by MTS; the data acquired are utilized for neural network training and validation. The application and validation show that the predicted forces of the neural network match well with the forces tested with a small variance, which demonstrates the effectiveness and precision of neural network modeling.
Modelling and Control of Magnetorheological Damper
Bhowmik, Subrata
damper is identified by both the standard parametric Bouc-Wen model and the non-parametric neural network model from an experimental data set generated by dynamic tests of the MR damper mounted in a hydraulic testing machine. The forward model represents the direct dynamics of the MR damper where...... contribution to the modelling of an MR damper is the use of experimental measurement data of a rotary MR damper that requires appropriate filtering. The semi-systematic optimisation procedure proposed in the thesis derives an effective neural network structure, where only velocity and damper force...... fuses the displacement and the acceleration data to get an accurate and robust estimate of the velocity. The simplicity of the network and the application of velocity in terms of KKF is a novel contribution of the thesis to the generation of a training set for neural network modelling of MR dampers...
Design and analysis of an innovative combined magneto-rheological damper-mount
Phu, Do Xuan; Chung, Jye Ung; Choi, Seung Bok
2015-04-01
In this paper, a new innovative modified high-loaded magneto-rheological fluid (MR in short) damper-mount is presented. The proposed damper-mount is designed based on two modes of MR fluid such as flow mode and shear mode, and it includes two separated electric coil for establishing magnetic field. The damping force of the damper-mount is analyzed based on the difference pressure between upper chamber and lower chamber. After analyzing the mathematical function of damping force, the proposed mount is optimized following the maximal damping force by using ANSYS software. Besides, there is a laboratorial MR fluid using in this optimization such as plate-like fluid MRF140. Results of optimization show that the requirement of damping force is obtain and the saturation of materials is in range of limitation.
Lee, Jae-Hoon; Han, Changwan; Ahn, Dongsu; Lee, Jin Kyoo; Park, Sang-Hu; Park, Seonghun
2013-01-01
We designed and validated a rotary magnetorheological (MR) damper with a specified damping torque capacity, an unsaturated magnetic flux density (MFD), and a high magnetic field intensity (MFI) for unmanned vehicle suspension systems. In this study, for the rotary type MR damper to have these satisfactory performances, the roles of the sealing location and the cover case curvature of the MR damper were investigated by using the detailed 3D finite element model to reflect asymmetrical shapes and sealing components. The current study also optimized the damper cover case curvature based on the MFD, the MFI, and the weight of the MR damper components. The damping torques, which were computed using the characteristic equation of the MR fluid and the MFI of the MR damper, were 239.2, 436.95, and 576.78 N·m at currents of 0.5, 1, and 1.5 A, respectively, at a disk rotating speed of 10 RPM. These predicted damping torques satisfied the specified damping torque of 475 N·m at 1.5 A and showed errors of less than 5% when compared to experimental measurements from the MR damper manufactured by the proposed design. The current study could play an important role in improving the performance of rotary type MR dampers.
Jae-Hoon Lee
2013-01-01
Full Text Available We designed and validated a rotary magnetorheological (MR damper with a specified damping torque capacity, an unsaturated magnetic flux density (MFD, and a high magnetic field intensity (MFI for unmanned vehicle suspension systems. In this study, for the rotary type MR damper to have these satisfactory performances, the roles of the sealing location and the cover case curvature of the MR damper were investigated by using the detailed 3D finite element model to reflect asymmetrical shapes and sealing components. The current study also optimized the damper cover case curvature based on the MFD, the MFI, and the weight of the MR damper components. The damping torques, which were computed using the characteristic equation of the MR fluid and the MFI of the MR damper, were 239.2, 436.95, and 576.78 N·m at currents of 0.5, 1, and 1.5 A, respectively, at a disk rotating speed of 10 RPM. These predicted damping torques satisfied the specified damping torque of 475 N·m at 1.5 A and showed errors of less than 5% when compared to experimental measurements from the MR damper manufactured by the proposed design. The current study could play an important role in improving the performance of rotary type MR dampers.
A mechanical energy harvested magnetorheological damper with linear-rotary motion converter
Chu, Ki Sum; Zou, Li; Liao, Wei-Hsin
2016-04-01
Magnetorheological (MR) dampers are promising to substitute traditional oil dampers because of adaptive properties of MR fluids. During vibration, significant energy is wasted due to the energy dissipation in the damper. Meanwhile, for conventional MR damping systems, extra power supply is needed. In this paper, a new energy harvester is designed in an MR damper that integrates controllable damping and energy harvesting functions into one device. The energy harvesting part of this MR damper has a unique mechanism converting linear motion to rotary motion that would be more stable and cost effective when compared to other mechanical transmissions. A Maxon motor is used as a power generator to convert the mechanical energy into electrical energy to supply power for the MR damping system. Compared to conventional approaches, there are several advantages in such an integrated device, including weight reduction, ease in installation with less maintenance. A mechanical energy harvested MR damper with linear-rotary motion converter and motion rectifier is designed, fabricated, and tested. Experimental studies on controllable damping force and harvested energy are performed with different transmissions. This energy harvesting MR damper would be suitable to vehicle suspensions, civil structures, and smart prostheses.
Mathematical model of a novel small magnetorheological damper by using outer magnetic field
Liutian Huang
2017-03-01
Full Text Available In order to realize small loading and small damping, a mini Magneto-rheological fluid (MRF damper is suggested by using new method of outer coils, and its physical model is established firstly. It was found that the landing force is only 1.74∼8N, the landing force is the third-order function with the current by polynomial fitting of the experimental data, which shows a force-current model. The results of force-displacement and force-velocity indicate that it has nonlinear hysteretic damping characteristics. Based on the new mini-mode principle and the damping characteristics, an improved nonlinear dynamics model is proposed, and its parameter expressions are obtained by parameter identification and regression fitting. Model curves fit well with experimental curves, and the improved model has fully demonstrated the dynamic characteristics of the mini-MRF damper. It will provide scientific method and physical model for the small MRF damper development.
Semi-active control of automotive suspension systems with magnetorheological dampers
Lam, Hiu Fung; Liao, Wei-Hsin
2001-08-01
Vibration in today's increasingly high-speed vehicles including automobiles severely affects their ride comfort and safety. The objective of this paper is to develop and study automotive suspension systems with magneto-rheological (MR) fluid dampers for vibration control in order to improve the passenger's comfort and safety. A two degree-of-freedom quarter car model is considered. A mathematical model of MR fluid damper is adopted. In this study, a sliding mode controller is developed by considering loading uncertainty to result in a robust control system. Two kinds of excitations are inputted in order to investigate the performance of the suspension system. The vibration responses are evaluated in both time and frequency domains. Compared to the passive system, the acceleration of the sprung mass is significantly reduced for the system with a controlled MR damper. Under random excitation, the ability of the MR fluid damper to reduce both peak response and root-mean-square response is also shown. The effectiveness of the MR suspension system is also demonstrated via hardware-in-the-loop simulation. The results of this study can be used to develop guidelines to effectively integrate automotive suspensions with MR dampers.
Optimization of Semi-active Seat Suspension with Magnetorheological Damper
Segla, Stefan; Kajaste, J.; Keski-Honkola, P.
The paper deals with modeling, control and optimization of semiactive seat suspension with pneumatic spring and magnetorheological damper. The main focus is on isolating vertical excitation from the cabin of a bucket-wheel excavator in order to protect the excavator driver against harmful vibration. Three different control algorithms are used to determine the desired semi-active damping force: skyhook control, balance control and combination of balance and skyhook controls. The dynamic behavior of the semi-active system is optimized using genetic algorithms. As the objective function the effective value of the seat (sprung mass) acceleration is used.
Bhowmik, Subrata; Weber, Felix; Høgsberg, Jan Becker
2013-01-01
This paper presents a systematic design and training procedure for the feed-forward backpropagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output an...
Dobre, A.; Andreescu, C. N.; Stan, C.
2016-08-01
Due to their simplicity and controllability, adaptive dampers became very popular in automotive engineering industry, especially in the passenger cars industry, in spite of technological obstacles inherent and the high cost of the magnetic fluid. “MagneRide” is the first technology which uses smart fluids in the shock absorbers of the vehicles adaptive suspensions. Since the discovery of the magneto-rheological effect there is a consistent progress regarding the control algorithms and hardware part itself. These magneto-rheological devices have a major potential which can be explored in various fields of applications. At present many companies make researches for the improvement of the response time and for obtaining a better response at low frequency and amplitude of the body car oscillations. The main objective of this paper is to determine the damping characteristic of a magnetorheological shock absorber of a passenger car. The authors aim to observe how to modify the damping characteristic by changing the intensity of the electric current. The experimental researches have being carried out on a complex and modern test bench especially built for testing shock absorbers, in order to compare the damping characteristic of the classical damper with the magneto-rheological damper.
Performance Analysis of a Magnetorheological Damper with Energy Harvesting Ability
Guoliang Hu
2016-01-01
Full Text Available A magnetorheological (MR damper with energy harvesting ability was proposed based on electromagnetic induction (EMI principle. The energy harvesting part was composed of a permanent magnet array and inducing coils which move vertically. This device could act as a linear power generator when the external excitation was applied, and the kinetic energy could be converted into electrical energy due to the relative linear motion between the magnets array and the inducing coils. Finite element models of both the MR damper part and the linear power generator part were built up separately to address the magnetic flux distributions, the magnetic flux densities, and the power generating efficiency using ANSYS software. The experimental tests were carried out to evaluate the damping performance and power generating efficiency. The results show that the proposed MR damper can produce approximately 750 N damping forces at the current of 0.6 A, and the energy harvesting device can generate about 1.0 V DC voltage at 0.06 m·s−1 excitation.
A novel magnetorheological damper based parallel planar manipulator design
Hoyle, A.; Arzanpour, S.; Shen, Y.
2010-05-01
This paper presents a novel parallel planar robot design which is low cost and simple in structure. The design addresses some of the problems, such as concentration of excessive load on the links and joints, due to wrong commanding signals being given by the controller. In this application two of the conventional actuators are replaced by magnetorheological (MR) dampers, and only one actuator is used to generate motion. The design paradigm is based on the concept that a moving object 'intuitively' follows the path with minimum resistance to its motion. This implies that virtual adoptable constraints can be used effectively to define motion trajectories. In fact, motion generation and adaptive constraints are two elements essential to implementing this strategy. In this paper, MR dampers are used to provide adjustable constraints and to guide the platform that is moved by the linear motor. The model of the MR dampers is derived using the Bouc-Wen model. This model is then used for manipulator simulation and controller design. Two controllers are developed for this manipulator: (1) a closed loop on/off one and (2) a proportional-derivative controller. Also, three different trajectories are defined and used for both the simulations and experiments. The results indicate a good agreement between the simulations and experiments. The experimental results also demonstrate the capability of the manipulator for following sophisticated trajectories.
Magnelok technology: a complement to magnetorheological fluids
Carlson, J. David
2004-07-01
Magnetorheological or MR fluids have been successfully used to enable highly effective semi-active control systems in automobile primary suspensions to control unwanted motions in civil engineering structures and to provide force-feedback in steer-by-wire systems. A key to the successful use of MR fluids is an appreciation and understanding of the balance and trade-off between the magnetically controlled on-state force and the ever-present off-state viscous force. In all MR fluid applications, one must deal with the fact that MR fluids never fully decouple or go to zero force in their off-state. Magnelok devices are a magnetically controlled compliment to traditional MR fluid devices that have been developed to enable a true force decoupling in the off-state. Magnelok devices may be embodied as linear or rotary dampers, brakes, lockable struts or position holding devices. They are particularly suitable for lock/un-lock applications. Unlike MR fluid devices they contain no fluid yet they do provide a variable level of friction damping that is controlled by the magnitude of the applied magnetic field. Magnelok devices are low cost as they easily accommodate relatively loose mechanical tolerances and require no seals or accumulator. A variety of controllable Magnelok devices and applications are described.
Bai, Xian-Xu, E-mail: bai@hfut.edu.cn [Department of Vehicle Engineering, Hefei University of Technology, Hefei 230009 (China); Wereley, Norman M.; Hu, Wei [Department of Aerospace Engineering, University of Maryland, College Park, Maryland 20742 (United States)
2015-05-07
A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between which the key structure, i.e., the inner bypass, is formed and MR fluids are energized, is designed to provide large dynamic range (i.e., ratio of field-on damping force to field-off damping force) and damping force range. The damping force performance of the MR damper is modeled using phenomenological model and verified by the experimental tests. In order to assess its feasibility and capability in vibration control systems, the mathematical model of a SDOF semi-active vibration control system based on the MR damper and skyhook control strategy is established. Using an MTS 244 hydraulic vibration exciter system and a dSPACE DS1103 real-time simulation system, experimental study for the SDOF semi-active vibration control system is also conducted. Simulation results are compared to experimental measurements.
A new vibration isolation bed stage with magnetorheological dampers for ambulance vehicles
Chae, Hee Dong; Choi, Seung-Bok
2015-01-01
The vibration experienced in an ambulance can lead to secondary injury to a patient and discourage a paramedic from providing emergency care. In this study, with the goal of resolving this problem, a new vibration isolation bed stage associated with magnetorheological (MR) dampers is proposed to ensure ride quality as well as better care for the patient while he/she is being transported. The bed stage proposed in this work can isolate vibrations in the vertical, rolling and pitching directions to reflect the reality that occurs in the ambulance. Firstly, an appropriate-sized MR damper is designed based on the field-dependent rheological properties of MR fluid, and the damping force characteristics of a MR damper are evaluated as a function of the current. A mechanical model of the proposed vibration isolation bed stage is then established to derive the governing equations of motion. Subsequently, a sliding mode controller is formulated to control the vibrations caused from the imposed excitation signals; those signals are directly measured using a real ambulance subjected to bump-and-curve road conditions. Using the controller based on the dynamic motion of the bed stage, the vibration control performance is evaluated in both the vertical and pitch directions. It is demonstrated that the magnitude of the vibration in the patient compartment of the ambulance can be significantly reduced by applying an input current to the MR dampers installed for the new bed stage.
Sassi, Sadok; Cherif, Khaled; Mezghani, Lotfi; Thomas, Marc; Kotrane, Asma
2005-08-01
The development of a powerful new magnetorheological fluid (MRF), together with recent progress in the understanding of the behavior of such fluids, has convinced researchers and engineers that MRF dampers are among the most promising devices for semi-active automotive suspension vibration control, because of their large force capacity and their inherent ability to provide a simple, fast and robust interface between electronic controls and mechanical components. In this paper, theoretical and experimental studies are performed for the design, development and testing of a completely new MRF damper model that can be used for the semi-active control of automotive suspensions. The MR damper technology presented in this paper is based on a completely new approach where, in contrast to in the conventional solutions where the coil axis is usually superposed on the damper axis and where the inner cylindrical housing is part of the magnetic circuit, the coils are wound in a direction perpendicular to the damper axis. The paper investigates approaches to optimizing the dynamic response and provides experimental verification. Both experimental and theoretical results have shown that, if this particular model is filled with an 'MRF 336AG' MR fluid, it can provide large controllable damping forces that require only a small amount of energy. For a magnetizing system with four coils, the damping coefficient could be increased by up to three times for an excitation current of only 2 A. Such current could be reduced to less than 1 A if the magnetizing system used eight small cores. In this case, the magnetic field will be more powerful and more regularly distributed. In the presence of harmonic excitation, such a design will allow the optimum compromise between comfort and stability to be reached over different intervals of the excitation frequencies.
Investigation on modeling and controability of a magnetorheological gun recoil damper
Hu, Hongsheng; Wang, Juan; Wang, Jiong; Qian, Suxiang; Li, Yancheng
2009-07-01
Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.
Vibration control of a semi-active railway vehicle suspension with magneto-rheological dampers
Jong-Seok Oh
2016-04-01
Full Text Available This article presents vibration control performances of a semi-active railway vehicle suspension system using a magneto-rheological damper tested on the roller rig. In order to evaluate control performances, a mathematical railway vehicle model with 15 degrees of freedom is first derived to represent the lateral, yaw and roll motions of the car body, bogie frame, and wheel set, respectively. Based on the formulated model, the design parameters of magneto-rheological damper are determined to undertake a compatible comparison with dynamic performances of conventional (existing passive railway vehicle suspension system. The designed magneto-rheological damper is manufactured and its field-dependent damping force characteristics are experimentally evaluated. Subsequently, in order to enhance the ride quality of a railway vehicle suspension equipped with magneto-rheological damper, a skyhook controller associated with an extended Kalman filter is designed in a state space representation. The railway suspension system incorporated with the car body and two bogies is then experimentally set up on the roller rig in order to evaluate the ride quality. It is demonstrated from experimental realization of the controller that the ride quality of the suspension system with magneto-rheological damper can be significantly enhanced compared with the existing passive suspension system.
A magnetorheological fluid based orthopedic active knee brace
Zite, Jamaal L.; Ahmadkhanlou, Farzad; Neelakantan, Vijay A.; Washington, Gregory N.
2006-03-01
The disadvantage of current knee braces ranges from high cost for customization to a loss in physical mobility and limited rehabilitative value. One approach to solving this problem is to use a Magnetorheological (MR) device to make the knee brace have a controllable resistance. Our design solution is to replace the manufacturer's joint with an rotary MR fluid based shear damper. The device is designed based on a maximum yield stress, a corresponding magnetic field, a torque and the MR fluid viscosity. The analytical and experimental results show the advantages and the feasibility of using the proposed MR based controllable knee braces.
The role of negative stiffness in semi-active control of magneto-rheological dampers
Høgsberg, Jan Becker
2011-01-01
The performance of external dampers depends on the particular combination of energy dissipation and stiffness, where in general damping increases with decreasing damper stiffness. It is therefore of great interest to minimize or even introduce negative damper stiffness. The present paper proposes...... adaptive control strategies for the applied voltage of a semi-active magneto-rheological damper. From linear equivalent models obtained by harmonic averaging it is found that these control strategies introduce equivalent negative stiffness, and by numerical simulations it is illustrated that they lead...
Experimental validation of a novel stictionless magnetorheological fluid isolator
Kelso, Shawn P.; Denoyer, Keith K.; Blankinship, Ross M.; Potter, Kenneth; Lindler, Jason E.
2003-07-01
Magnetorheological (MR) fluid damper design typically constitutes a piston/dashpot configuration. During reciprocation, the fluid is circulated through the device with the generated pressure providing viscous damping. In addition, the damper is also intended to accommodate off-axis loading; i.e., rotation moments and lateral loads orthogonal to the axis of operation. Typically two sets of seals, one where the piston shaft enters and exits the device and one between the piston and the cylinder wall, maintain alignment of the damper and seal the fluid from leaking. With MR fluid, these seals can act as sources of non-linear friction effects (stiction) and oftentimes possess a shorter lifespan due to the abrasive nature of the ferrous particles suspended in the fluid. Intelligently controlling damping forces must also accommodate the non-linear stiction behavior, which degrades performance. A new, unique MR fluid isolator was designed, fabricated and tested that directly addresses these concerns. The goal of this research was the development of a stiction-free MR isolator whose damping force can be predicted and precisely controlled. This paper presents experimental results for a prototype device and compares those results to model predictions.
Zhou, Q.; Nielsen, Søren R.K.; Qu, W.L.
2007-01-01
The paper deals with the control of sub- and superharmonic resonances by means of magnetorheological (MR) dampers of an inclined shallow cable caused by parametric excitation from harmonically varying support points. A mechanical model based on the Dahl hysteretic model is used to describe the dy...
Energy dissipation control of magneto-rheological damper
Høgsberg, Jan Becker; Krenk, Steen
2008-01-01
The efficiency of a damper depends on the amount of energy dissipation during a typical cycle experienced by the damper. For viscous dampers this leads to substantial frequency dependence. For dampers with hysteresis the tuning and efficiency also depends on the apparent amplitude of the damper...... response. For irregular damper response the amplitude is evaluated as the magnitude of closed hysteresis loops. These loops are identified in real time by the rainflow rules, stored in a Markov-type matrix and used to predict the magnitude of subsequent closed loops. From this prediction the properties...
Optimal design of a magnetorheological damper used in smart prosthetic knees
Gao, Fei; Liu, Yan-Nan; Liao, Wei-Hsin
2017-03-01
In this paper, a magnetorheological (MR) damper is optimally designed for use in smart prosthetic knees. The objective of optimization is to minimize the total energy consumption during one gait cycle and weight of the MR damper. Firstly, a smart prosthetic knee employing a DC motor, MR damper and springs is developed based on the kinetics characteristics of human knee during walking. Then the function of the MR damper is analyzed. In the initial stance phase and swing phase, the MR damper is powered off (off-state). While during the late stance phase, the MR damper is powered on to work as a clutch (on-state). Based on the MR damper model as well as the prosthetic knee model, the instantaneous energy consumption of the MR damper is derived in the two working states. Then by integrating in one gait cycle, the total energy consumption is obtained. Particle swarm optimization algorithm is used to optimize the geometric dimensions of MR damper. Finally, a prototype of the optimized MR damper is fabricated and tested with comparison to simulation.
Method of drilling with magnetorheological fluid
Zitha, P.L.J.
2003-01-01
A method of drilling a bore hole into a stratum, wherein via the drill hole drilling fluid is introduced and fed to the drill head. In order to avoid dilution or leak-off of the drilling fluid the same is in accordance with the invention a magnetorheological drilling fluid, and when an undesirable p
Analytical research of damping efficiency and heat generation of magnetorheological damper
Mitrouchev, P.; Klevinskis, A.; Bucinskas, V.; Dragasius, E.; Udris, D.; Morkvenaite-Vilkonciene, I.
2017-06-01
Magnetorheological (MR) dampers are currently used in various areas, such as: human prosthetics, seismic protection, active suspensions, safety systems, amongst other. This paper deals with the proper design of a MR damper in the innovative field for vibration control. A methodology for calculation some principal characteristics of the damper such as: electromagnet’s magnetic field value, emitted heat and damping force is presented. The methodology is based on analytic calculations of the characteristics and finite element method analysis. The obtained theoretical results were confirmed by performed experimental tests, thanks to a specially designed and realised MR damper. Two main geometrical characteristics of the damper, namely: piston thickness and electromagnet width were optimally chosen, thus allowing to reach maximum damping force.
Nonlinear modeling of adaptive magnetorheological landing gear dampers under impact conditions
Ahuré Powell, Louise A.; Choi, Young T.; Hu, Wei; Wereley, Norman M.
2016-11-01
Adaptive landing gear dampers that can continuously adjust their stroking load in response to various operating conditions have been investigated for improving the landing performance of a lightweight helicopter. In prior work, adaptive magnetorheological (MR) landing gear dampers that maintained a constant peak stroking force of 4000 lbf across sink rates ranging from 6 to 12 ft s-1 were designed, fabricated and successfully tested. In this follow-on effort, it is desired to expand the high end of the sink rate range to hold the peak stroking load constant for sink rates ranging from 6 to 26 ft s-1, thus extending the high end of the speed range from 12 (in the first study) to 26 ft s-1. To achieve this increase, a spring-based relief valve MR landing gear damper was developed. In order to better understand the MR landing gear damper behavior, a modified nonlinear Bingham Plastic model was formulated, and it incorporates Darcy friction, viscous forces across the MR and relief valves to better account for the damper force behavior at higher speeds. In addition, gas pressure inside the MR damper piston is considered so the total damper force includes a gas force. The MR landing gear damper performance is characterized using drop tests, and the experiments are used to validate model predictions data at low and high nominal impact speeds up to 26 ft s-1 (shaft velocity of 9.6 ft s-1).
2008-01-01
The control strategy is very important for semiactive control or active control systems. An integrated intelligent control strategy for building structures incorpo rated with magnetorheological (MR) dampers subjected to earthquake excitation is proposed. In this strategy, the time-delay problem is solved by a neural network and the control currents of the MR dampers are determined quickly by a fuzzy controller. Through a numerical example of a three-storey structure with one MR damper installed in the first floor, the seismic responses of the uncontrolled, the intelligently controlled, the passiveon controlled, and the passive-off controlled structures under different earthquake excitations are analyzed. Based on the numerical results, it can be found that the time domain and the frequency domain responses are reduced effectively when the MR damper is added in the structure, and the integrated intelligent control strategy has a better earthquake mitigation effect.
Extended neural network-based scheme for real-time force tracking with magnetorheological dampers
Weber, Felix; Bhowmik, Subrata; Høgsberg, Jan Becker
2014-01-01
This paper validates numerically and experimentally a new neural network-based real-time force tracking scheme for magnetorheological (MR) dampers on a five-storey shear frame with MR damper. The inverse model is trained with absolute values of measured velocity and force because the targeted...... current is a positive quantity. The validation shows accurate results except of small current spikes when the desired force is in the vicinity of the residual MR damper force. In the closed-loop, higher frequency components in the current are triggered by the transition of the actual MR damper force from...... the pre-yield to the post-yield region. A control-oriented approach is presented to compensate for these drawbacks. The resulting control force tracking scheme is validated for the emulation of viscous damping, clipped viscous damping with negative stiffness, and friction damping with negative stiffness...
Intesrated intelligent control analysis on semi-active structuresby using magnetorheological dampers
XU ZhaoDong; GUO YingQing
2008-01-01
The control strategy is very important for semi-active control or active control systems. An integrated intelligent control strategy for building structures incorpo-rated with magnetorheological (MR) dampers subjected to earthquake excitation is proposed. In this strategy, the time-delay problem is solved by a neural network and the control currents of the MR dampers are determined quickly by a fuzzy controller. Through a numerical example of a three-storey structure with one MR damper installed in the first floor, the seismic responses of the uncontrolled, the intelligently controlled, the passive-on controlled, and the passive-off controlled structures under different earthquake excitations are analyzed. Based on the nu-merical results, it can be found that the time domain and the frequency domain responses are reduced effectively when the MR damper is added in the structure, and the integrated intelligent control strategy has a better earthquake mitigation effect.
Zhou, Q.; Nielsen, Søren R.K.; Qu, W. L.
2006-01-01
Three-dimensional semi-active vibration control of an inclined sag cable with discrete magnetorheological (MR) dampers is investigated in this paper using the finite difference method (FDM). A modified Dahl model is used to describe the dynamic property of MR damper. The nonlinear equations of mo...
State of the art review of semi active control for magnetorheological dampers
Mughal, Umair Najeeb
2017-01-01
Earthquakes causes severe damage to badly designed structures or buildings to fail or collapse, and also have caused some damage to well-designed structures to malfunction due to the damage or failure of the equipment housed in the structure or building. The use magnetorheological dampers to mitigate the effect of external excitation is increased to resolve this. This article is a state of the art review of nonlinear analytical models to understand the efficacy of semi-active control theory for magnetorheological dampers. A nonlinear semi active control law is desired to be designed which atleast guarantees analytical closed loop stability in order to mitigate the effect of perturbations and drive the desired output to equilibrium.
Response of a quarter car model with optimal magnetorheological damper parameters
Prabakar, R. S.; Sujatha, C.; Narayanan, S.
2013-04-01
In this paper, the control of the stationary response of a quarter car model to random road excitation with a Magnetorheological (MR) damper as a semi-active suspension device is considered. The MR damper is a hypothetical analytical damper whose parameters are determined optimally using a multi-objective optimization technique Non-dominated Sorting Genetic Algorithm II (NSGA II). The hysteretic behaviour of the MR damper is characterized using Bingham and modified Bouc-Wen models. The multi-objective optimization problem is solved by minimizing the difference between the root mean square (rms) sprung mass acceleration, suspension stroke and the road holding responses of the quarter car model with the MR damper and those of the active suspension system based on linear quadratic regulator (LQR) control with the constraint that the MR damper control force lies between ±5 percent of the LQR control force. It is observed that the MR damper suspension systems with optimal parameters perform an order of magnitude better than the passive suspension and perform as well as active suspensions with limited state feedback and closer to the performance of fully active suspensions.
A Magnetorheological Fluid Damper for Rotor Applications
P. Forte
2004-01-01
field lines cross the MR film. Since the damping characteristics can be varied continuously by controlling the magnetic field, it is possible to have the optimum conditions for each regime of rotational speed. Preliminary tests are encouraging.
Phu, Do Xuan; Shah, Kruti; Choi, Seung-Bok
2014-06-01
This paper presents a new adaptive fuzzy controller and its implementation for the damping force control of a magnetorheological (MR) fluid damper in order to validate the effectiveness of the control performance. An interval type 2 fuzzy model is built, and then combined with modified adaptive control to achieve the desired damping force. In the formulation of the new adaptive controller, an enhanced iterative algorithm is integrated with the fuzzy model to decrease the time of calculation (D Wu 2013 IEEE Trans. Fuzzy Syst. 21 80-99) and the control algorithm is synthesized based on the {{H}^{\\infty }} tracking technique. In addition, for the verification of good control performance of the proposed controller, a cylindrical MR damper which can be applied to the vibration control of a washing machine is designed and manufactured. For the operating fluid, a recently developed plate-like particle-based MR fluid is used instead of a conventional MR fluid featuring spherical particles. To highlight the control performance of the proposed controller, two existing adaptive fuzzy control algorithms proposed by other researchers are adopted and altered for a comparative study. It is demonstrated from both simulation and experiment that the proposed new adaptive controller shows better performance of damping force control in terms of response time and tracking accuracy than the existing approaches.
Bhatti, Abdul Qadir
2013-08-01
A number of studies have been carried out to investigate the performance of viscoelastic dampers (VEDs) and magnetorheological dampers (MRDs) in controlling the seismic response of buildings, but very few of them regarding the effect of temperature on the behavior of those dampers. The energy absorption properties of the VEDs are dependent on the ambient temperature, excitation frequency and strain amplitude. Several mathematical models have been investigated for reproducing the experimental behavior of single degree of freedom VEDs and MEDs. Of these, only the fractional derivative model can reflect the influence of temperature which is, however, so complex that it is difficult to apply in structural analysis. In order to verify the effect of temperature, two case studies of structural element have been conducted: once using VED and once using MRD. Kelvin-Voigt mathematical model applied, they were investigated and after analyzing the results, the force vs. displacement showed that MRD achieved a high force capacity and a better performance than VED. Furthermore, the effect of the temperature in case of VED observed via plotting the dissipated energy hysteresis at different temperatures. These results validate the effect of the temperature as the lower the temperature the more viscous the dashpot element becomes, hence improving damping, but this is up to a specific low temperature.
Mixed Skyhook and FxLMS Control of a Half-Car Model with Magnetorheological Dampers
Piotr Krauze
2016-01-01
Full Text Available The problem of vibration attenuation in a semiactive vehicle suspension is considered. The proposed solution is based on usage of the information about the road roughness coming from the sensor installed on the front axle of the vehicle. It does not need any preview sensor to measure the road roughness as other preview control strategies do. Here, the well-known Skyhook algorithm is used for control of the front magnetorheological (MR damper. This algorithm is tuned to a quarter-car model of the front part of the vehicle. The rear MR damper is controlled by the FxLMS (Filtered-x LMS taking advantage of the information about the motion of the front vehicle axle. The goal of this algorithm is to minimize pitch of the vehicle body. The strategy is applied for a four-degree-of-freedom (4-DOF vehicle model equipped with magnetorheological dampers which were described using the Bouc-Wen model. The suspension model was subjected to the road-induced excitation in the form of a series of bumps within the frequency range 1.0–10 Hz. Different solutions are compared based on the transmissibility function and simulation results show the usefulness of the proposed solution.
Semi-active H∞ control of high-speed railway vehicle suspension with magnetorheological dampers
Zong, Lu-Hang; Gong, Xing-Long; Xuan, Shou-Hu; Guo, Chao-Yang
2013-05-01
In this paper, semi-active H∞ control with magnetorheological (MR) dampers for railway vehicle suspension systems to improve the lateral ride quality is investigated. The proposed semi-active controller is composed of a H∞ controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse MR damper model as the damper controller. First, a 17-degree-of-freedom model for a full-scale railway vehicle is developed and the random track irregularities are modelled. Then a modified Bouc-Wen model is built to characterise the forward dynamic characteristics of the MR damper and an inverse MR damper model is built with the ANFIS technique. Furthermore, a H∞ controller composed of a yaw motion controller and a rolling pendulum motion (lateral motion+roll motion) controller is established. By integrating the H∞ controller with the ANFIS inverse model, a semi-active H∞ controller for the railway vehicle is finally proposed. Simulation results indicate that the proposed semi-active suspension system possesses better attenuation ability for the vibrations of the car body than the passive suspension system.
Nonlinear Dynamics Analysis of the Semiactive Suspension System with Magneto-Rheological Damper
Hailong Zhang
2015-01-01
Full Text Available This paper examines dynamical behavior of a nonlinear oscillator which models a quarter-car forced by the road profile. The magneto-rheological (MR suspension system has been established, by employing the modified Bouc-Wen force-velocity (F-v model of magneto-rheological damper (MRD. The possibility of chaotic motions in MR suspension is discovered by employing the method of nonlinear stability analysis. With the bifurcation diagrams and corresponding Lyapunov exponent (LE spectrum diagrams detected through numerical calculation, we can observe the complex dynamical behaviors and oscillating mechanism of alternating periodic oscillations, quasiperiodic oscillations, and chaotic oscillations with different profiles of road excitation, as well as the dynamical evolutions to chaos through period-doubling bifurcations, saddle-node bifurcations, and reverse period-doubling bifurcations.
An inverse model for magnetorheological dampers based on a restructured phenomenological model
Qian, Li-Jun; Liu, Bo; Chen, Peng; Bai, Xian-Xu
2016-04-01
Magnetorheological dampers (MRDs), a semi-active actuator based on MR effect, have great potential in vibration/shock control systems. However, it is difficult to establish its inverse model due to its intrinsic strong nonlinear hysteresis behaviors, and sequentially the precise, fast and effective control could not be realized effectively. This paper presents an inverse model for MRDs based on a restructured phenomenological model with incorporation of the "normalization" concept. The proposed inverse model of MRDs is validated by the simulation of the force tracking. The research results indicate that the inverse model could be applied for the damping force control with consideration of the strong nonlinear hysteresis behaviors of the MRDs.
贾永枢; 周孔亢; 徐兴
2012-01-01
提出一种基于流动模式的汽车单出杆、双筒式磁流变减振器的结构与工作原理,该减振器采用已有汽车悬架双筒式普通液压减振器的设计标准制造,对现有双筒式减振器具有很强工艺继承性.根据Bingham流体模型建立双筒式磁流变减振器阻尼力数学模型,并提出该减振器的磁路设计方法；针对磁路的非轴对称特性,建立磁路三维有限元仿真模型,结合北京现代某款汽车前悬架减振器的技术要求和磁流变液流变特性,进行三维静态磁场分析,确定活塞磁路的主要参数.制作汽车双筒式磁流变减振器,并对此进行台架特性试验；通过试验与理论计算对比,结果表明理论计算数据与试验数据较吻合,所提出的双筒式磁流变减振器设计方法是可行的,对汽车双筒式磁流变减振器的设计使用具有指导意义.%The structure and working principle of a vehicle single-rod and twin-tube magnetorheological fluids(MRF) damper based on pressure driven flow mode is introduced. The MRF damper is designed with the existing manufacturing standards of ordinary hydraulic damper, which has a strong succession technology on the existing vehicle suspension damper. The mathematical model of damping force is established using non-Newtonian fluid model and Bingham plastic model, and magnetic circuit design method of the MRF damper is proposed. Based on the non-axisymmetric magnetic circuit of piston, a magnetic circuit three-dimensional finite element simulation model is established with the ANSYS software, and the magnetic circuit parameters are determined according to the technical requirements of a front Beijing Hyundai vehicle damper and the MRF rheological properties. The twin-tube MRF damper is designed and produced, and the experiment is done to test the damper characteristics. The simulation results are compared with testing results. The results show that they agree well, and the proposed design of
Unexpected shear strength change in magnetorheological fluids
Yu Tian
2014-09-01
Full Text Available Smart materials of magnetorheological (MR fluids could be turned from a liquid state into a solid state, which solidification extent or shear strength often increases monotonically with the applied magnetic field. In this study, the shear stress of a dilute MR fluid decreased with increasing applied magnetic field at a constant shear rate. The dynamic shear stress was significantly higher than the stable counterpart at medium magnetic fields. They are ascribed to the slow particle structure transformation. A higher shear rate and particle volume fraction could reduce the transient time and the shear strength difference.
ANFIS optimized semi-active fuzzy logic controller for magnetorheological dampers
César, Manuel Braz; Barros, Rui Carneiro
2016-11-01
In this paper, we report on the development of a neuro-fuzzy controller for magnetorheological dampers using an Adaptive Neuro-Fuzzy Inference System or ANFIS. Fuzzy logic based controllers are capable to deal with non-linear or uncertain systems, which make them particularly well suited for civil engineering applications. The main objective is to develop a semi-active control system with a MR damper to reduce the response of a three degrees-of-freedom (DOFs) building structure. The control system is designed using ANFIS to optimize the fuzzy inference rule of a simple fuzzy logic controller. The results show that the proposed semi-active neuro-fuzzy based controller is effective in reducing the response of structural system.
Dong, Xiaomin
2016-01-01
An axial flux permanent magnet energy harvester (AFPMEH) is proposed and analyzed for a vehicle magneto-rheological (MR) damper. The relationship between the output voltage and the input excitations are analytically developed. Under different constant rotation speeds and sinusoidal excitations, the harvesting energy is numerically computed for different loads of pure resistance and coil in the MR damper. To check the performance of the proposed AFPMEH for the MR damper, the AFPMEH and MR damper are fabricated individually. Experiments are performed to measure the harvesting energy of the AFPMEH and the damping characteristics of the MR damper under different excited conditions. The excited conditions include three constant rotation speeds and sinusoidal inputs. Load inputs of the pure resistance and the coil of the MR damper are considered. The results show that the time history of the generated voltage of the AFPMEH in experiment is agreed well with that of the AFPMEH in simulation. Under constant rotation speeds, the root mean square (rms) of loaded voltage will increase with the increment of load, whereas the rms of power will be affected by the amplitude of load. The MR damper powered by the AFPMEH can almost obtain the similar damping characteristics of that external power supply. Under sinusoidal inputs, the rms of loaded voltage will increase with the increment of external loads, whereas the rms of power will be almost kept as a constant. The damping range of the MR damper can also be enlarged over 30% comparing to off-state damping force. A quarter car model with an MR damper powered by the AFPMEH is developed to investigate the control performance. The on-off skyhook control is adopted to tune the input current of the MR damper. The vibration performance of the MR suspension is investigated under different roads and vehicle speeds. The numerical results show that the MR suspension with the AFPMEH under on-off skyhook control can achieve better ride comfort
Semi-active sliding mode control of vehicle suspension with magneto-rheological damper
Zhang, Hailong; Wang, Enrong; Zhang, Ning; Min, Fuhong; Subash, Rakheja; Su, Chunyi
2015-01-01
The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity ( F- v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.
Semi-active Sliding Mode Control of Vehicle Suspension with Magneto-rheological Damper
ZHANG Hailong; WANG Enrong; ZHANG Ning; MIN Fuhong; SUBASH Rakheja; SU Chunyi
2015-01-01
The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity (F-v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.
Vibration Analysis and Models of Adjacent Structures Controlled by Magnetorheological Dampers
Michela Basili
2017-01-01
Full Text Available This paper deals with the vibration analysis of adjacent structures controlled by a magnetorheological (MR damper and with the discussion of a numerical procedure for identification and definition of a reliable finite element model. The paper describes an extensive experimental campaign investigating the dynamic response, through shaking table tests, of a tridimensional four-story structure and a two-story structure connected by an MR device. Several base excitations and intensity levels are considered. The structures were tested in nonconnected and connected configuration, with the MR damper operating in passive or semiactive mode. Moreover, the paper illustrates a procedure for the structural identification and the definition of a reliable numerical model valid for adjacent structures connected by MR dampers. The procedure is applied in the original nonconnected configuration, which represents a linear system, and then in the connected configuration, which represents a nonlinear system due to the MR damper. In the end, the updated finite element model is reliable and suitable for all the considered configurations and the mass, damping, and stiffness matrices are derived. The experimental and numerical responses are compared and the results confirm the effectiveness of the identification procedure and the validation of the finite element model.
Zapoměl J.
2011-06-01
Full Text Available Lateral vibration of rotors can be significantly reduced by inserting the damping elements between the shaft and the casing. The theoretical analysis, confirmed by computational simulations, shows that to achieve the optimum compromise between attenuation of the oscillation amplitude and magnitude of the forces transmitted through the coupling elements between the rotor and the stationary part, the damping effect must be controllable. For this purpose, the squeeze film dampers lubricated by magnetorheological fluid can be applied. The damping effect is controlled by the change of intensity of the magnetic field in the lubricating film. This article presents a procedure developed for investigation of the steady state response of rigid rotors coupled with the casing by flexible elements and short magnetorheological dampers. Their lateral vibration is governed by nonlinear (due to the damping forces equations of motion. The steady state solution is obtained by application of a collocation method, which arrives at solving a set of nonlinear algebraic equations. The pressure distribution in the oil film is described by a Reynolds equation modified for the case of short dampers and Bingham fluid. Components of the damping force are calculated by integration of the pressure distribution around the circumference and along the length of the damper. The developed procedure makes possible to determine the steady state response of rotors excited by their unbalance, to determine magnitude of the forces transmitted through the coupling elements in the supports into the stationary part and is intended for proposing the control of the damping effect to achieve optimum performance of the dampers.
Insight into magnetorheological shock absorbers
Gołdasz, Janusz
2015-01-01
This book deals with magnetorheological fluid theory, modeling and applications of automotive magnetorheological dampers. On the theoretical side a review of MR fluid compositions and key factors affecting the characteristics of these fluids is followed by a description of existing applications in the area of vibration isolation and flow-mode shock absorbers in particular. As a majority of existing magnetorheological devices operates in a so-called flow mode a critical review is carried out in that regard. Specifically, the authors highlight common configurations of flow-mode magnetorheological shock absorbers, or so-called MR dampers that have been considered by the automotive industry for controlled chassis applications. The authors focus on single-tube dampers utilizing a piston assembly with one coil or multiple coils and at least one annular flow channel in the piston.
Magnetorheological fluids and applications to adaptive landing gear for a lightweight helicopter
Ahure-Powell, Louise A.
During hard landing or crash events of a helicopter there are impact loads that can be injurious to crew and other occupants as well as damaging to the helicopter structure. Landing gear systems are the first in line to protect crew and passengers from detrimental crash loads. The main focus of this research is to improve landing gear systems of a lightweight helicopter. Magnetorheological fluids (MRFs) provide potential solutions to several engineering challenges in a broad range of applications. One application that has been considered recently is the use of magnetorheological (MR) dampers in helicopter landing gear systems. In such application, the adaptive landing gear systems have to continuously adjust their stroking load in response to various operating conditions. In order to support this rotorcraft application, there is a necessity to validate that MRFs are qualified for landing gear applications. First, MRF composites, synthesized utilizing three hydraulic oils certified for use in landing gear systems, two average diameters of spherical magnetic particles, and a lecithin surfactant, are formulated to investigate their performance for potential use in a helicopter landing gear. The magnetorheology of these MR fluids is characterized through a range of tests, including (a) magnetorheology (yield stress and viscosity) as a function of magnetic field, (b) sedimentation analysis using an inductance-based sensor, (c) cycling of a small-scale MR damper undergoing sinusoidal excitations (at 2.5 and 5 Hz), and (d) impact testing of an MR damper for a range of magnetic field strengths and velocities using a free-flight drop tower facility. The performance of these MR fluids was analyzed, and their behavior was compared to standard commercial MR fluids. Based on this range of tests used to characterize the MR fluids synthesized, it was shown that it is feasible to utilize certified landing gear hydraulic oils as the carrier fluids to make suitable MR fluids
An investigation on a semi-active magnetorheological tuned liquid column damper (MR-TLCD)
Sun, H. X.; Wang, X. Y.
2016-04-01
this paper, a novel semi-active magnetorheological tuned liquid column damper (MR-TLCD) device combining tuned liquid column damper (TLCD) and magnetorheological damper (MRD) is devised for wind or earthquake vibration control of civil structures. In this device, a traditional moving head loss in the TLCD is replaced with a controlled MRD in the bottom or one side of the vertical column, which can easily and rapidly adjust the damping of the device. A semi-active experimental prototype MR-TLCD consisting of a shear rotary MRD and a TLCD is built. Based on the four basic presumptions, a dynamic model of the devised MR-TLCD is established using the Lagrange equation. In this equation, the formula of MRD employs the Bingham Boltzmann model. The natural frequency of the MR-TLCD is determined by the total central length and spring stiffness. It is worth noting that the natural frequency differs with the simple TLCD, because the device adds a joint spring. An equivalent linear damping expression is developed under harmonic excitation, and its mechanical model is developed using the equivalent period displacement and the coulomb friction force of MRD. At the same time, the equivalent damping can be adjusted by the real-time applied current, which can achieve the semi-active control performance. To validate the proposed frequency and damping model, Experimental test is conducted on a section area 150mm × 150mm and a total length 2.24m of the MR-TLCD dimensions. Comparisons are made between predicted and measured TLCD liquid surface displacement motion. The result shows the error of its nature frequency is only 2.29%.
Force effects on rotor of squeeze film damper using Newtonian and non-Newtonian fluid
Dominik, Šedivý; Petr, Ferfecki; Simona, Fialová
2017-09-01
This article presents the evaluation of force effects on rotor of squeeze film damper. Rotor is eccentric placed and its motion is translate-circular. The amplitude of rotor motion is smaller than its initial eccentricity. The force effects are calculated from pressure and viscous forces which were gained by using computational modeling. Two types of fluid were considered as filling of damper. First type of fluid is Newtonian (has constant viscosity) and second type is magnetorheological fluid (does not have constant viscosity). Viscosity of non-Newtonian fluid is given using Bingham rheology model. Yield stress is a function of magnetic induction which is described by many variables. The most important variables of magnetic induction are electric current and gap width which is between rotor and stator. Comparison of application two given types of fluids is shown in results.
Bifurcations and chaos of a vibration isolation system with magneto-rheological damper
Hailong Zhang
2016-03-01
Full Text Available Magneto-rheological (MR damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.
Bifurcations and chaos of a vibration isolation system with magneto-rheological damper
Zhang, Hailong [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China); Zhang, Ning [Magneto-electronics Lab, School of Physics and Technology, Nanjing Normal University, Nanjing 210046 (China); Min, Fuhong; Yan, Wei; Wang, Enrong, E-mail: erwang@njnu.edu.cn [Vibration Control Lab, School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing 210042 (China)
2016-03-15
Magneto-rheological (MR) damper possesses inherent hysteretic characteristics. We investigate the resulting nonlinear behaviors of a two degree-of-freedom (2-DoF) MR vibration isolation system under harmonic external excitation. A MR damper is identified by employing the modified Bouc-wen hysteresis model. By numerical simulation, we characterize the nonlinear dynamic evolution of period-doubling, saddle node bifurcating and inverse period-doubling using bifurcation diagrams of variations in frequency with a fixed amplitude of the harmonic excitation. The strength of chaos is determined by the Lyapunov exponent (LE) spectrum. Semi-physical experiment on the 2-DoF MR vibration isolation system is proposed. We trace the time history and phase trajectory under certain values of frequency of the harmonic excitation to verify the nonlinear dynamical evolution of period-doubling bifurcations to chaos. The largest LEs computed with the experimental data are also presented, confirming the chaotic motion in the experiment. We validate the chaotic motion caused by the hysteresis of the MR damper, and show the transitions between distinct regimes of stable motion and chaotic motion of the 2-DoF MR vibration isolation system for variations in frequency of external excitation.
Dutta, Saikat; Choi, Seung-Bok
2016-03-01
It is well known that Macpherson strut suspension systems are widely used in light and medium weight vehicles. The performance of these suspension systems can be enriched by incorporating magneto-rheological (MR) dampers and an appropriate dynamic model is required in order to find out the ride comfort and other performances properly in the sense of practical environment conditions. Therefore, in this work the kinematic and dynamic modeling of Macpherson strut suspension system with MR damper is presented and its responses are evaluated. The governing equations are formulated using the kinematic properties of the suspension system and adopting Lagrange’s equation. In the formulation of the model, both the rotation of the wheel assembly and the lateral stiffness of the tire are considered to represent the nonlinear characteristic of Macpherson type suspension system. The formulated mathematical model is then compared with equivalent conventional quarter car suspension model and the different dynamic responses such as the displacement of the sprung mass are compared to emphasize the effectiveness of the proposed model. Additionally, in this work the important kinematic properties of suspension system such as camber angle, king-pin angle and track width alteration, which cannot be obtained from conventional quarter car suspension model, are evaluated in time and frequency domains. Finally, vibration control responses of the proposed suspension system are presented in time and frequency domains which are achieved from the semi-active sky-hook controller.
Marcin BAJKOWSKI
2014-03-01
Full Text Available In this paper, the laboratory stand, dedicated for research and didactic purposes is presented. The stand allows investigating the parameters which characterizes the recoil effect in the 12,7 x 99 mm caliber arm. It is also possible to study the dependencies in the system with the parallel magnetorheological dampers, which are placed in the universal basis for weapon. The methodology of the research, as well as the experimental data and theoretical discussions concerning the components of the recoil force are provided. The part of the research devoted to the recoil effect was performed in a large-caliber arm configuration, which allows to fire shots in a laboratory conditions utilizing training bullets with reduced propellant charge. The experimental studies were also carried out for the rifle grenades. The results indicate the possibility of building a universal basis for 12,7 mm x 99 caliber weapons and can provide useful information for formulating the design assumptions for the controlled dampers with magnetorheological fluid, designed for special purposes.
Super-strong magneto-rheological fluids
Tao, R.
2001-03-01
A typical MR fluid is a suspension of magnetic particles of micrometer size in a liquid. Upon application of a strong magnetic field, the fluid turns into a solid. This process is reversible and the response time is of milliseconds. MR fluids presently have a yield shear stress around 80 kPa, which is adequate for applications in shock absorbers and vibration dampers, but is inadequate for automobile clutch etc. Efforts in searching for new materials in the past decades came with limited results. Thus we have developed a new approach to change the microstructure of MR fluids and make them super-strong. It is well known that under a strong magnetic field, the ideal structure of MR fluids is a body-centered tetragonal (bct) lattice. The mechanical strength of MR fluids strongly depends on the microstructure. A bct-lattice based thick column has a much higher yield stress than a single-chain structure. When a magnetic field is applied to a MR fluid, the particles first form chains. With time, the chains may aggregate into columns. However, the unassisted aggregation is not very useful, as it is slow and produces columns with a limited thickness. Our method is based on assisted aggregations. Immediately after a magnetic field is applied, we compress the MR fluid in the field direction before a shear force is applied. The compression pushes the induced chains together to form thick columns. This microstructure change greatly enhances the yield stress. The experiment on an iron-based MR fluid finds 800 kPa for the yield stress, ten times stronger than that without the compression. When the magnetic field is removed, the MR fluid still returns to the liquid state quickly. The upper limit of this structure-enhanced yield stress seems well above 800 kPa. The super-strong MR fluids are suitable for many industrial applications. *Supported by NSF Grant 0196022
Viscosity of magnetorheological fluids using Iron-silicon nanoparticles.
Kim, Jong Hee; Kim, CheolGi; Lee, Seung Goo; Hong, Tae Min; Choi, Joon Hong
2013-09-01
Fe-6.5Si fine particles were mechanically fabricated by a milling method for use in magnetorheological fluids. Oleic acid was used as a surfactant for the dispersed substance for preparing the hydrophobic fluid with silicon oil as a dispersing medium. Further, oleic acid and sodium dodecyl benzene sulfonate were used as surfactants, forming a bilayer structure, for preparing the hydrophilic fluid with polyethylene glycol as a dispersing medium. The adsorption of oleic acid onto the Fe-Si particles was achieved by oxidizing the particle surface with trimethylamine N-oxide dihydrate. In order to make a comparative examination of the fluid properties, ferromagnetic nanoparticles were synthesized by chemical precipitation and the subsequent process was accompanied under the same conditions as applied for the magnetorheological fluid. The fluid particles were characterized by magnetization measurements. The viscosity of the fluids was obtained at various concentrations under an external field. The viscosity values of the magnetorheological fluid were higher than those of the ferromagnetic fluid. Moreover, they increased considerably by using silicon oil as the dispersing medium as well as under an applied magnetic field and at higher fluid concentrations. The magnetorheological fluids may be effectively resistant to a strong impact from outside when the appropriate fluid concentration is used and a magnetic field is applied for increasing the shear strength of the fluids.
Jiang, Z.; Christenson, R.
2011-06-01
Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, such as earthquake, wave and wind excitation, thus reducing structural damage and preventing failure. The magneto-rheological (MR) fluid damper is a promising device for use in civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate dependent. Thus a challenging aspect of applying this technology is the development of accurate models to describe the behavior of such dampers for control design and evaluation purposes. In particular, a new type of experimental testing called real-time hybrid simulation (RTHS) combines numerical simulation with laboratory testing of physical components. As with any laboratory testing, safety is of critical importance. For RTHS in particular the feedback and dynamic interaction of physical and numerical components can result in potentially unstable behavior. For safety purposes, it is desired to conduct pretest simulations where the physical specimen is replaced with an appropriate numerical model yet the numerical RTHS component is left unchanged. These pretest simulations require a MR damper model that can exhibit stability and convergence at larger fixed integration time steps, and provide computational efficiency, speed of calculation, and accuracy during pretest verification of the experimental setup. Several models for MR dampers have been proposed, including the hyperbolic tangent, Bouc-Wen, viscous plus Dahl and algebraic models. This paper examines the relative performance of four MR damper models of large-scale 200 kN MR dampers as needed for pretest simulations of RTHS. Experimental tests are conducted on two large-scale MR dampers located at two RTHS test facilities at the Smart Structures Technology Laboratory at the University of Illinois at Urbana
Method and system for polishing materials using a nonaqueous magnetorheological fluid
Menapace, Joseph Arthur; Ehrmann, Paul Richard
2014-09-09
A nonaqueous magnetorheological fluid includes a primarily organic carrier liquid and magnetizable particles. The magnetorheological fluid also includes a buffer, a stabilizer, and water. A pH of the magnetorheological fluid is between 6.5 and 9.0.
Yazid, I. I. M.; Mazlan, S. A.; Imaduddin, F.; Zamzuri, H.; Choi, S. B.; Kikuchi, T.
2016-12-01
This paper presents mitigation behaviour of magnetorheological (MR) damper operated with a mixed working modes. A combination of the shear and squeeze modes is employed in the structure of MR damper to obtain the field-dependent normal yield stress as well as strengthen the squeeze effect. The experimental evaluation shows that when the piston is squeezing the bottom gap from the stroke of 25 to 26 mm, the sudden increase of squeeze force is observed confirming the existence of the mitigation effect. It is also observed that the magnitude of mitigation force is positively correlated with the magnitude of current given to the electromagnet. The measured peak mitigation forces are ranged from 722 N to 1032 N when the electromagnet currents are varied from 0.2 A to 0.8 A, respectively. The variable mitigation effect indicates that the concept can be further discussed as a potential impact protection feature in an MR damper.
Chunxiang Li
2012-01-01
Full Text Available Based on recent research by Li and Liu in 2011, this paper proposes the application of support vector machine- (SVM- based semiactive control methodology for seismic protection of structures with magnetorheological (MR dampers. An important and challenging task of designing the MR dampers is to develop an effective semiactive control strategy that can fully exploit the capabilities of MR dampers. However, amplification of the local acceleration response of structures exists in the widely used semiactive control strategies, namely “Switch” control strategies. Then the SVM-based semiactive control strategy has been employed to design MR dampers. Firstly, the LQR controller for the numerical model of a multistory structure formulated using the dynamic dense method is constructed by using the classic LQR control theory. Secondly, an SVM model which comprises the observers and controllers in the control system is designed and trained to emulate the performance of the LQR controller. Finally, an online autofeedback semiactive control strategy is developed by resorting to SVM and then used for designing MR dampers. Simulation results show that the MR dampers utilizing the SVM-based semiactive control algorithm, which eliminates the local acceleration amplification phenomenon, can remarkably reduce the displacement, velocity, and acceleration responses of the structure.
Zapoměl, J.; Ferfecki, P.
2016-09-01
A frequently used technological solution for minimization of undesirable effects caused by vibration of rotating machines consists in placing damping devices in the rotor supports. The application of magnetorheological squeeze film dampers enables their optimum performance to be achieved in a wide range of rotating speeds by adapting their damping effect to the current operating conditions. The damping force, which is produced by squeezing the layer of magnetorheological oil, can be controlled by changing magnetic flux passing through the lubricant. The force acting between the rotor and its frame is transmitted through the rolling element bearing, the lubricating layer and the squirrel spring. The loading of the bearing produces a time variable friction moment, energy losses, uneven rotor running, and has an influence on the rotor service life and the current fluctuation in electric circuits. The carried out research consisted in the development of a mathematical model of a magnetorheological squeeze film damper, its implementation into the computational models of rotor systems, and in performing the study on the dependence of the energy losses and variation of the friction moment on the damping force and its control. The new and computationally stable mathematical model of a magnetorheological squeeze film damper, its implementation in the computational models of rigid rotors and learning more on the energy losses generated in the rotor supports in dependence on the damping effect are the principal contributions of this paper. The results of the computational simulations prove that a suitable control of the damping force enables the energy losses to be reduced in a wide velocity range.
Particle Dynamics of Polydisperse Magnetorheological Fluids
Chiranjit Sarkar
2015-12-01
Full Text Available In the present research work, three dimensional simulations of magnetorheological fluids, containing soft magnetic polydisperse particles in silicone oil, has been presented. The computer simulation helps to visualize and analyze the formed transient microstructures. The initial positions of particle-centres were decided based on random distribution. The particle positions were updated considering magnetic, hydrodynamic and repulsions forces on each particle along with explicit time marching scheme. Finally the particle’s positions at 10 ms have been plotted. The yield behaviors of MRFXXS (small sized: 2 to 33 µm and MRFXXL (large sized: 45 to 212 µm have been estimated using particle dynamic simulations and the predicted results have been compared with the results obtained from experiments. Due to large number of particles and limitations of computer hardware, the yield behavior of MRFXXM1 i.e. mixed (2 to 212 µm sized magnetic particles could not be simulated. However, experiments were performed to investigate the yield behavior of MRFXXM1. The results show that MRFXXM1 is better than MRFXXS and MRFXXL.
Application of optimal homotopy asymptotic method to nonlinear Bingham fluid dampers
Marinca, Vasile; Bereteu, Liviu
2015-01-01
Magnetorheological fluids (MR) are stable suspensions of magnetizable microparticles, characterized by the property to change the rheological characteristics when subjected to the action of magnetic field. Together with another class of materials that change their rheological characteristics in the presence of an electric field, called electrorheological materials are known in the literature as the smart materials or controlled materials. In the absence of a magnetic field the particles in MR fluid are dispersed in the base fluid and its flow through the apertures is behaves as a Newtonian fluid having a constant shear stress. When the magnetic field is applying a MR fluid behavior change, and behaves like a Bingham fluid with a variable shear stress. Dynamic response time is an important characteristic for determining the performance of MR dampers in practical civil engineering applications. The purpose of this paper is to show how to use the Optimal Homotopy Asymptotic Method (OHAM) to solve the nonlinear d...
The Lubricity and Rheological Properties of Magnetorheological Fluids
Nowiński Emil
2016-10-01
Full Text Available The article presents results of tribological research carried on four ball tester and dynamic rheometer for different magnetorheological fluids. The wear test was conducted with and without magnetic field. The dynamic rheology measurement was done at wide range of velocity. The inteligent fluids differed from each other by an amount of solid phase and kind of base liquid.
Yoo, Jin-Hyeong; Murugan, Muthuvel; Wereley, Norman M.
2013-04-01
This study investigates a lumped-parameter human body model which includes lower leg in seated posture within a quarter-car model for blast injury assessment simulation. To simulate the shock acceleration of the vehicle, mine blast analysis was conducted on a generic land vehicle crew compartment (sand box) structure. For the purpose of simulating human body dynamics with non-linear parameters, a physical model of a lumped-parameter human body within a quarter car model was implemented using multi-body dynamic simulation software. For implementing the control scheme, a skyhook algorithm was made to work with the multi-body dynamic model by running a co-simulation with the control scheme software plug-in. The injury criteria and tolerance levels for the biomechanical effects are discussed for each of the identified vulnerable body regions, such as the relative head displacement and the neck bending moment. The desired objective of this analytical model development is to study the performance of adaptive semi-active magnetorheological damper that can be used for vehicle-occupant protection technology enhancements to the seat design in a mine-resistant military vehicle.
Park, Jhin Ha; Kim, Wan Ho; Shin, Cheol Soo; Choi, Seung-Bok
2017-01-01
This work compares the ride comfort of a passenger vehicle whose suspension system is equipped with two different magneto-rheological (MR) dampers: with and without bypass holes in the piston. In order to achieve this goal, two cylindrical type MR dampers, which otherwise have the same such geometrical dimensions as radius of piston, length of pole and distance between two poles, are designed based on a mathematical model and subsequently manufactured. One of MR dampers is then modified by making bypass holes in the piston bobbin structure to obtain a relatively low slope of damping force in the pre-yield region. The field-dependent damping force characteristics are investigated through both simulation and experiment. After characterizing the field-dependent damping force of the two MR dampers, a quarter car model is established to evaluate the ride comfort. In this work, a simple but very effective sky-hook controller is adopted, and vibration control performance is evaluated under two road profiles: bump and random road excitations. It is demonstrated through simulation and experiment that the MR damper with bypass holes provides better ride comfort to the car so equipped than that without.
A highly adaptive magnetorheological fluid robotic leg for efficient terrestrial locomotion
Jiang, Nan; Sun, Shuaishuai; Ouyang, Yiming; Xu, Min; Li, Weihua; Zhang, Shiwu
2016-09-01
To survive in nature, animals adjust the characteristics of their legs or fins to adapt the motion to their environment. Inspired by the locomotion of animals, a study on the tunable stiffness and damping of a leg will help in the development of intelligent locomotion robots. In this paper we report on the development and experiment of a novel and simple robotic leg that can be adapted to the environment via a smart magnetorheological fluid (MRF). The robotic leg consists of a rotation MRF damper, a torsional spring, a ‘foot’ and a ‘leg’. The curved part of the ‘foot’ makes contact with the grounds while the other end is linked to an outer cylinder of the MRF damper with an inelastic cable. The variable force arm rising from the MRF damper and the torsional spring can help the leg adapt to a changing environment. The characteristics of the MRF damper have been investigated and a model is built to describe its mechanical features when different currents are applied to the MRF damper. A test on a linear dynamic test instrument has been conducted to verify the accuracy of the model. The robotic leg is installed in a locomotion platform to investigate the speed of its locomotion and the cost of the transport; the result demonstrated the feasibility and adaptability of the leg when walking on hard terrain. Its simple structure, high adaptability, and easy control of the MRF leg helped in the design and development of a high performance field robot that can adapt to various environments.
Ayush Raizada
2016-01-01
Full Text Available This paper is based on the experimental study for design and control of vibrations in automotive vehicles. The objective of this paper is to develop a model for the highly nonlinear magnetorheological (MR damper to maximize passenger comfort in an automotive vehicle. The behavior of the MR damper is studied under different loading conditions and current values in the system. The input and output parameters of the system are used as a training data to develop a suitable model using Artificial Neural Networks. To generate the training data, a test rig similar to a quarter car model was fabricated to load the MR damper with a mechanical shaker to excite it externally. With the help of the test rig the input and output parameter data points are acquired by measuring the acceleration and force of the system at different points with the help of an impedance head and accelerometers. The model is validated by measuring the error for the testing and validation data points. The output of the model is the optimum current that is supplied to the MR damper, using a controller, to increase the passenger comfort by minimizing the amplitude of vibrations transmitted to the passenger. Besides using this model for cars, bikes, and other automotive vehicles it can also be modified by retraining the algorithm and used for civil structures to make them earthquake resistant.
Multifractality in dilute magnetorheological fluids under an oscillating magnetic field.
Moctezuma, R E; Arauz-Lara, J L; Donado, F
2014-12-01
A study of the multifractal characteristics of the structure formed by magnetic particles in a dilute magnetorheological fluid is presented. A quasi-two-dimensional magnetorheological fluid sample is simultaneously subjected to a static magnetic field and a sinusoidal magnetic field transverse to each other. We analyzed the singularity spectrum f(α) and the generalized dimension D(q) of the whole structure to characterize the distribution of the aggregates under several conditions of particle concentration, magnetic field intensities, and liquid viscosity. We also obtained the fractal dimension D(g), calculated from the radius of gyration of the chains, to describe the internal distribution of the particles. We present a thermodynamic interpretation of the multifractal analysis, and based on this, we discussed the characteristics of the structure formed by the particles and its relation with previous studies of the average chain length. We have found that this method is useful to quantitatively describe the structure of magnetorheological fluids, especially in systems with high particle concentration where the aggregates are more complex than simple chains or columns.
Zapoměl J.
2009-12-01
Full Text Available Rotors of all rotating machines are always slightly imbalanced. When they rotate, the imbalance induces their lateral vibration and forces that are transmitted via the bearings into the foundations. These phenomena are significant if the rotor accelerates or decelerates and especially if it passes over the critical speeds. The vibration can be reduced if the rotor supports are equipped with damping elements. To achieve optimum performance of the damper, the damping effect must be controllable. At present time, semiactive magnetorheological squeeze film dampers are a subject of intensive research. They work on a principle of squeezing a thin film of magnetorheological liquid. If magnetic field is applied, the magnetorheological liquid starts to flow only if the shear stress between two neighbourhood layers exceeds a limit value which depends on intensity of the magnetic field. Its change enables to control the damping force. In the mathematical models, the magnetorheological liquid is usually considered as Bingham one. Application of the computer modelling method for analysis of rotors supported by rolling element bearings and magnetorheological squeeze film dampers and turning at variable angular speed requires to set up the equations of motion of the rotor and to develop a procedure for calculation of the damping force. Derivation of the equations of motion starts from the first and second impulse theorems. The pressure distribution in the thin lubricating film can be described by a Reynolds equation modified for the case of Bingham liquid. In cavitated areas, it is assumed that pressure of the medium remains constant. The hydraulic force acting on the rotor journal is then obtained by integration of the pressure distribution around the circumference and along the length of the damper. Applicability of the developed procedures was tested by means of computer simulations and influence of the control of the damping force on vibration of the rotor
A flexible micro fluid transport system featuring magnetorheological elastomer
Behrooz, Majid; Gordaninejad, Faramarz
2016-02-01
This study presents a flexible magnetically-actuated micro fluid transport system utilizing an isotropic magnetorheological elastomer (MRE). Theoretical modeling and analysis of this system is presented for a two-dimensional model. This fluid transport system can propel the fluid by applying a fluctuating magnetic field on the MRE. The magneto-fluid-structure interaction analysis is employed to determine movement of the solid domain and the velocity of the fluid under a controllable magnetic field. The effects of key material, geometric, and magnetic parameters on the behavior of this system are examined. It is demonstrated that the proposed system can propel the fluid unidirectionally, and the volume of the transported fluid is significantly affected by some of the design parameters.
A New Damper for Tracked Vehicle Suspension
FAN Fu-sheng; LI Meng; XING Zhi; L(U) Jian-gang
2005-01-01
The passive suspension system of tracked vehicle is designed to get its suspension parameters based on a certain common velocity and a certain road surface roughness. Its performance optimization only exists in a certain operating mode without far-ranging adaptability. Holding the damper basic frame form and applying semi-active suspension system based on MR (magnetorheological) damper, the vehicle can keep its optimum efficiency between energy dissipation and vibration reduction in all kinds of operating modes. Theoretical analysis and experiments show that the damping performances provided by this MRF(magnetorheological fluids) vane damper are same as those provided by traditional damper, and the new damper has the better controllability and adaptability.
Semi-active Control of Magneto-Rheological Dampers with Negative Stiffness
Bhowmik, Subrata
2009-01-01
-rheological (MR) damper is among the most popular and promising devices due to its low power requirement, high dynamic range, high force capacity and robustness. The objective of this paper is to formulate semi -active feedback control methods based on simple linear damper models, which lead to increased damping...
Bhowmik, Subrata
2011-01-01
to determine the damper current based on the derived optimal damper force. For that reason an inverse MR damper model is also designed based on the neural network identification of the particular rotary MR damper. The performance of the proposed controller is compared to that of an optimal pure viscous damper......-displacement trajectories. The proposed neural network controller is therefore trained based on data derived from these desired forcedisplacement curves, where the optimal relation between friction force level and response amplitude is determined explicitly by simply maximizing the damping ratio of the targeted vibration....... The top floor displacement and acceleration of the base excited shear frame structure are selected as the performance parameters of this comparison. It is found by the simulations that the proposed control design yields a reduction in the structural response compared to the viscous case....
Bhowmik, Subrata
2011-01-01
to determine the damper current based on the derived optimal damper force. For that reason an inverse MR damper model is also designed based on the neural network identification of the particular rotary MR damper. The performance of the proposed controller is compared to that of an optimal pure viscous damper......-displacement trajectories. The proposed neural network controller is therefore trained based on data derived from these desired forcedisplacement curves, where the optimal relation between friction force level and response amplitude is determined explicitly by simply maximizing the damping ratio of the targeted vibration....... The top floor displacement and acceleration of the base excited shear frame structure are selected as the performance parameters of this comparison. It is found by the simulations that the proposed control design yields a reduction in the structural response compared to the viscous case....
Development of Magnetorheological Fluid Elastomeric Dampers for Helicopter Stability Augmentation
2005-01-01
condition, the system response will be easily solved. Using the same ODE solver, the RDES model can also be applied in the MATLAB Simulink program such that...Johnson D.E., and Turner D.M., “A Triboelastic Model for The Cyclic Mechanical Behavior of Filled Vulcanizates,” Rubber Chemistry and Technology, Vol. 68...61] Payne, A.R. and Whittaker, R.E., “Strain Dynamic Properties of Filled Rubbers,” Rubber Chemistry and Technology, Vol. 44, 1971, pp. 440-478. [62
Experimental Studies on High-Frequency Performance of the Inverse Control Magneto-Rheological Damper
DU Xiuli; LIAO Weizhang; NIU Dongxu
2006-01-01
Severe vibration of underground structures may be induced under blast loads.According to the characteristics of the explosion-induced ground shock wave,a new-type damper,inverse control magneto-rheological(MR) damper was designed to control the vibration.The high-frequency performance test of the MR damper was carried out on the small shaking table.It is shown that the performance can be modeled by use of the modified Bouc-Wen model,and the pa rameters of the model keep stable in the range of 15-50 Hz.
Static Performance of Surface Textured Magnetorheological Fluid Journal Bearings
D.A. Bompos
2015-09-01
Full Text Available Previous studies of journal bearings with artificial texturing on the bearing surface show potential benefits in certain cases. These benefits are usually focused on a specific operating area of the bearing, whereas under certain operating conditions the performance of the bearing is deteriorating due to the surface texturing. Gaining control over the viscosity of the lubricant may become a useful tool in order to take advantage of the surface texturing in a wider range of loads and journal velocities. One way to achieve this control is the use of magnetorheological fluid journal bearings. Magnetorheological fluids are solutions of iron based paramagnetic particles in conventional lubricant. Under the influence of an external magnetic field, these particles form chains, they hinder the flow of the lubricant and they ultimately alter its apparent viscosity. In this work the two techniques are combined in order to optimize the behaviour of the journal bearing in as much a variety of operating conditions as possible. Different shapes applied on the surface texturing will be examined.
Feng, Ju; Ying, Zu-Guang; Zhu, Wei-Qiu
2012-01-01
A minimax stochastic optimal semi-active control strategy for stochastically excited quasi-integrable Hamiltonian systems with parametric uncertainty by using magneto-rheological (MR) dampers is proposed. Firstly, the control problem is formulated as an n-degree-of-freedom (DOF) controlled......, uncertain quasi-integrable Hamiltonian system and the control forces produced by MR dampers are split into the passive part and the semi-active part. Then the passive part is incorporated into the uncontrolled system. After that, the stochastic optimal semi-active control problem is solved by applying...... the minimax stochastic optimal control strategy based on the stochastic averaging method and stochastic differential game. The worst-case disturbances and the optimal controls are obtained by the minimax dynamical programming equation with the constraints of disturbance bounds and MR damper dynamics. Finally...
Effect of pressure on the physical properties of magnetorheological fluids
A. Spaggiari
2013-01-01
Full Text Available To date, several applications of magnetorheological (MR fluids are present in the industrial world, nonetheless system requirements often needs better material properties. In technical literature a previous work shows that MR fluids exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices are rotary devices, this paper investigates the behaviour of MR fluids under pressure when a rotation is applied to shear the fluid. The system is designed in order to apply both the magnetic field and the pressure and follows a Design of Experiment approach. The experimental apparatus comprises a cylinder in which a piston is used both to apply the pressure and to shear the fluid. The magnetic circuit is designed to provide a nearly constant induction field in the MR fluid. The experimental apparatus measures the torque as a function of the variables considered and the yield shear stress is computed. The analysis of the results shows that there is a positive interaction between magnetic field and pressure, which enhances the MR fluid performances more than twice.
Fabrication and manipulation of polymeric magnetic particles with magnetorheological fluid
Rodriguez-Lopez, Jaime [Centro de Acustica Aplicada y Evaluacion No Destructivos (CAEND), CSIC-UPM, C/Serrano 144, 28006, Madrid (Spain); Shum, Ho Cheung, E-mail: ashum@hku.hk [Department of Mechanical Engineering, University of Hong Kong, 7/F Haking Wong Building, Pokfulam Road (Hong Kong); Elvira, Luis; Montero de Espinosa, Francisco [Centro de Acustica Aplicada y Evaluacion No Destructivos (CAEND), CSIC-UPM, C/Serrano 144, 28006, Madrid (Spain); Weitz, David A., E-mail: weitz@seas.harvard.edu [Department of Physics and School of Engineering and Applied Sciences, Harvard University, 9 and 15 Oxford Street, Cambridge, MA 02138 (United States)
2013-01-15
Polymeric magnetic microparticles have been created using a microfluidic device via ultraviolet (UV) polymerization of double emulsions, resulting in cores of magnetorheological (MR) fluids surrounded by polymeric shells. We demonstrate that the resultant particles can be manipulated magnetically to achieve triggered rupture of the capsules. This illustrates the great potential of our capsules for triggered release of active ingredients encapsulated in the polymeric magnetic microparticles. - Highlights: Black-Right-Pointing-Pointer Polymeric microparticles encapsulating MR fluids have been fabricated. Black-Right-Pointing-Pointer A double-emulsion-templated approach using microfluidic techniques has been used. Black-Right-Pointing-Pointer The monodisperse microparticles obtained are easily manipulated under magnetic field. Black-Right-Pointing-Pointer These microparticles have great potential for encapsulation-and-release applications.
A magnetorheological fluid-based controllable active knee brace
Ahmadkhanlou, Farzad; Zite, Jamaal L.; Washington, Gregory N.
2007-04-01
High customization costs and reduction of natural mobility put current rehabilitative knee braces at a disadvantage. A resolution to this problem is to integrate a Magnetorheological (MR) fluid-based joint into the system. A MR joint will allow patients to apply and control a resistive torque to knee flexion and extension. The resistance torque can also be continuously adjusted as a function of extension angle and patient strength (or as a function of time), which is currently impossible with state of the art rehabilitative knee braces. A novel MR fluid-based controllable knee brace is designed and prototyped in this research. The device exhibits large resistive torque in the on-state and low resistance in the offstate. The controllable variable stiffness, compactness, and portability of the system make it a proper alternative to current rehabilitative knee braces.
Design and development of magnetorheological fluid-based passive actuator.
Shokrollahi, Elnaz; Price, Karl; Drake, James M; Goldenberg, Andrew A
2015-08-01
We present the design and experimental validation of a magnetorheological (MR) fluid-based passive actuator for tele-robotic bone biopsy procedures. With Finite Element Method Magnet (FEMM) software, the required uniform magnetic field circuit design was simulated. An 1100 turn 24 AWG copper wire coil wrapped around a magnetic core was used to create a magnetic field. The field strength was measured with a Hall effect sensor, and compared to the simulation. The maximum magnetic field flux produced by a constant current of 1.4 A was 0.2 T, similar to the simulation results. A series of quasi-static experiments were conducted to characterize the forces generated by the MR fluid-based actuator under various currents up to 12 N. An analytical model was developed to validate the measurements from the passive actuator.
Intelligently Controllable Walker with Magnetorheological Fluid Brake
Kikuchi, Takehito; Tanida, Sosuke; Tanaka, Toshimasa; Kobayashi, Keigo; Mitobe, Kazuhisa
Caster walkers are supporting frames with casters and wheels. These tools are regularly utilized as life support tools or walking rehabilitation tools in hospitals, nursing homes and individual residences. Users of the walkers can easily move it thanks to its wheels and casters. However falling accidents often happen when it moves without users. The falling accident is very serious problem and one of leading causes of secondary injuries. In the other case, it is hard to move to desired directions if users have imbalance in their motor functions or sensory functions, e.g., hemiplegic patients. To improve safeness and operability of the walkers, we installed compact MR fluid brakes on the wheels and controlled walking speed and direction of the walker. We named this intelligently controllable walker, “i-Walker” and discussed on the control methods and experimental results in this paper. Preliminary trials for direction control of the first-generation of the i-Walker (i-Walker1) are presented. On the basis of the results, we improved the control method and hardware of the i-Walker1, and developed the second-generation (i-Walker2). System description and experimental results of the i-Walker2 are also described. The i-Walker2 has better operability and lower energy consumption than that of the i-Walker1. The line-tracing controller of the i-Walker2 well controls human motions during walking experiments on the target straight line.
Simulation of Magnetorheological Fluids Based on Lattice Boltzmann Method with Double Meshes
Xinhua Liu
2012-01-01
Full Text Available In order to study the rheological characteristics of magnetorheological fluids, a novel approach based on the two-component Lattice Boltzmann method with double meshes was proposed, and the micro-scale structures of magnetorheological fluids in different strength magnetic fields were simulated. The framework composed of three steps for the simulation of magnetorheological fluids was addressed, and the double meshes method was elaborated. Moreover, the various internal and external forces acting on the magnetic particles were analyzed and calculated. The two-component Lattice Boltzmann model was set up, and the flowchart for the simulation of magnetorheological fluids based on the two-component Lattice Boltzmann method with double meshes was designed. Finally, a physics experiment was carried out, and the simulation examples were provided. The comparison results indicated that the proposed approach was feasible, efficient, and outperforming others.
DESIGN METHOD OF MAGNETORHEOLOGICAL FLUID SHOCK ABSORBER FOR CAR SUSPENSION
LIAO Changrong; ZHANG Honghui; YU Miao; CHEN Weimin
2008-01-01
The Bingham constitutive model, which is previously used in depiction of magnetorheological (MR) fluids rheological behaviors for design devices, exhibits discontinuous characteristics in representation of pre-yield behaviors and post-yield behaviors. A Biviscous constitutive model is presented to depict rheological behaviors of MR fluids and design automotive shock absorber. Quasi-static flow equations of MR fluids in annular channels are set theoretically up based on Navier-Stokes equations and several rational simplifications are made. And both flow boundary conditions and flow compatibilities conditions are established. Meantime, analytical velocity profiles of MR fluids though annular channels are obtained via solution of the quasi-static flow equations using Biviscous constitutive model. The prediction methodology of damping force offered by MR fluid shock absorber is formulated and damping performances are predicated in order to determine design parameters. MR fluid shock absorber for Mazda 323 car suspension is designed and fabricated in Chongqing University, China. Measurements from sinusoidal displacement cycle by Shanchuan Shock Absorber Ltd. of China North Industry Corporation reveal that the analytical methodology and design theory are reasonable.
Synthesis and Characterization of Antifriction Magnetorheological Fluids for Brake
Chiranjit Sarkar
2013-07-01
Full Text Available Magnetorheological (MR fluids are smart materials with shear strength ranging between zero to 100 kPa under the influence of magnetic field. The present paper discusses the synthesis of MR fluid and its application in brake. In MR brake, gap between stator and rotor is filled with low (off-state viscosity MR fluid. On the application of magnetic field, MR fluid changes its state from liquid to semi-solid by aligning magnetic particles in chains. Due to such chaining action, yield strength of fluid increases, friction between stator and rotor increases and fulfils the braking function. The strength of magnetic particle is a function of relative speed between stator and rotor, applied magnetic field, and volume percentage of magnetic particle. In this study antifriction (off-state and strong chain (on-state CI based MR fluid has been prepared by mixing oleic acid as antifriction additives and tetramethylammonium hydroxide as surfactant to reduce the agglomeration of the MR fluid. Yield strengths of the synthesized MR fluid in on-state and off-state have been compared with commercially available MRF 241ES fluid. A flywheel based MR brake experimental setup has been developed to analyze the performance of designed and developed MR brake.Results show that synthesized MR fluid is stronger and faster in response compared to MRF 241ES fluid.Defence Science Journal, 2013, 63(4, pp.408-412, DOI:http://dx.doi.org/10.14429/dsj.63.2633
Field-controlled adhesion in confined magnetorheological fluids
Miranda, Jose; Lira, Sergio
2009-11-01
The study of reversible, functional, and controllable adhesives is a matter of considerable practical interest, and academic research. We report the adhesive response of a magnetorheological fluid confined between two parallel plates under a probe-tack test, when it is subjected to an applied magnetic field. Our analytical approach is based on a Darcy-like law formulation which considers a magnetic field-dependent yield stress behavior. The adhesion force is calculated in closed-form for two different configurations produced by a Helmholtz coils setup: uniform perpendicular, and nonuniform radial magnetic fields. In both cases, we verify that adhesion force is hugely increased as a result of the field-dependent nature of the yield stress. This provides a versatile way to obtain a shear resistant, tough structural adhesive through magnetic means.
Development of an isolator working with magnetorheological elastomers and fluids
Sun, S. S.; Yang, J.; Li, W. H.; Du, H.; Alici, G.; Yan, T. H.; Nakano, Masami
2017-01-01
This paper reports an isolator whose damping and stiffness can be simultaneously controlled by magnetorheological (MR) fluids and MR elastomers. A hydraulically actuated MTS machine was used to test this variable stiffness and damping isolator after its prototype. The field-dependent responses including stiffness variability and damping variability, together with the amplitude-dependent response and frequency-dependent responses were separately tested and analyzed successively. The experimental results prove the successful implementation of the as-designed MRE-F isolator with obvious variable damping and stiffness. A new phenomenological model incorporating Bingham model and four-parameter model was developed to describe the dynamic properties of the isolator. The successful development, experimental testing, and modelling of this innovative variable stiffness and damping isolator make the concept of variable stiffness and damping become feasible.
Fu, Qiang; Wang, Dai-Hua; Xu, Lei; Yuan, Gang
2017-04-01
Based on a two-bar linkage and a magnetorheological damper (MRD) with a double-ended structure and shearing operation mode of the magnetorheological fluid, an MRD-based prosthetic knee (MRPK) is realized. Utilizing the developed MRPK, an MRD-based lower limb prosthesis (MRLLP) is developed, modeled, and simulated in this paper, to analyse the effects of hysteresis of the integrated MRD on the swing angle of the shank of the MRLLP. Based on this, a sliding mode tracking control (SMTC) method for controlling the swing angle of the shank of the MRLLP is proposed to suppress hysteresis, along with a robustness analysis. Utilizing the SMTC method, co-simulations on controlling the swing angle of the shank of the MRLLP are carried out in ADAMS and Simulink. The simulation results show that the root mean square error (RMSE) of the swing angle of the shank of the MRLLP produced by the SMTC method is 80% less than that from the computed torque plus PD (CT+PD) control method. Therefore, the SMTC method is effective in suppressing hysteresis of the MRD. Furthermore, when the MRLLP is disturbed, the RMSE of the swing angle of the shank of the MRLLP produced by the SMTC method is 67% less than that from the CT+PD control method. Therefore, the SMTC method has strong robustness to random disturbance. A rapid control prototype of the MRLLP system and a corresponding experimental test system are established. On the established experimental test system, experiments are carried out on control of the swing angle of the shank of the MRLLP via the SMTC method. The results are compared with those from the ON/OFF and the CT+PD control methods. The experimental results show that the MRPK has controllable joint torque, and can be used to imitate the natural swing of a human knee joint. Additionally, the RMSE of the controlled swing angle of the shank of the MRLLP produced by the SMTC method is 34% less than that produced by the CT+PD control method and is 37% less than that from the ON
Effect of Particle Size on Shear Stress of Magnetorheological Fluids
Chiranjit Sarkar
2015-05-01
Full Text Available Magnetorheological fluids (MRF, known for their variable shear stress contain magnetisable micrometer-sized particles (few micrometer to 200 micrometers in a nonmagnetic carrier liquid. To avoid settling of particles, smaller sized (3-10 micrometers particles are preferred, while larger sized particles can be used in MR brakes, MR clutches, etc. as mechanical stirring action in those mechanisms does not allow particles to settle down. Ideally larger sized particles provide higher shear stress compared to smaller sized particles. However there is need to explore the effect of particle sizes on the shear stress. In the current paper, a comparison of different particle sizes on MR effect has been presented. Particle size distributions of iron particles were measured using HORIBA Laser Scattering Particle Size Distribution Analyser. The particle size distribution, mean sizes and standard deviations have been presented. The nature of particle shapes has been observed using scanning electron microscopy. To explore the effect of particle sizes, nine MR fluids containing small, large and mixed sized carbonyl iron particles have been synthesized. Three concentrations (9%, 18% and 36% by volume for each size of particles have been used. The shear stresses of those MRF samples have been measured using ANTON PAAR MCR-102 Rheometer. With increase in volume fraction of iron particles, the MR fluids synthesized using “mixed sized particles” show better shear stress compared to the MR fluids containing “smaller sized spherical shaped particles” and “larger sized flaked shaped particles” at higher shear rate.
Review of magnetorheological (MR) fluids and its applications in vibration control
MUHAMMAD Aslam; YAO Xiong-liang; DENG Zhong-chao
2006-01-01
Magnetorheological (MR) fluids are now well established as one of the leading materials for use in controllable structures and systems. Commercial application of MR fluids in various fields,particularly in the vibration control, has grown rapidly over the past few years. In this paper, properties of magnetorheological (MR) fluids ,its applications in suspensions of vehicles, suspension of trains, high buildings cable-stayed bridges have been discussed. The scope of MR fluids in future, problems and some suggestions are also presented. Finally, effectiveness of MR fluids in vibration control of marine diesel engine through experiment is briefly discussed by the author.
Enriched Imperialist Competitive Algorithm for system identification of magneto-rheological dampers
Talatahari, Siamak; Rahbari, Nima Mohajer
2015-10-01
In the current research, the imperialist competitive algorithm is dramatically enhanced and a new optimization method dubbed as Enriched Imperialist Competitive Algorithm (EICA) is effectively introduced to deal with high non-linear optimization problems. To conduct a close examination of its functionality and efficacy, the proposed metaheuristic optimization approach is actively employed to sort out the parameter identification of two different types of hysteretic Bouc-Wen models which are simulating the non-linear behavior of MR dampers. Two types of experimental data are used for the optimization problems to minutely examine the robustness of the proposed EICA. The obtained results self-evidently demonstrate the high adaptability of EICA to suitably get to the bottom of such non-linear and hysteretic problems.
Fang, Chen; Zhao, Bin Yuan; Chen, LeSheng; Wu, Qing; Liu, Nan; Hu, Ke Ao
2005-02-01
Magnetorheological (MR) fluid containing guar gum was prepared for the first time by ball-milling the guar gum powder together with silicone oil and carbonyl iron powder. By forming a coating layer over the ground carbonyl iron powder, the guar gum improves the sedimentation stability and thixotropy of the MR fluid effectively.
Geometric optimal design of MR damper considering damping force, control energy and time constant
Nguyen, Q H; Choi, S B [Smart Structures and Systems Laboratory, Department of Mechanical Engineering, INHA University, Incheon 402-751 (Korea, Republic of); Kim, K S [Department of Mechanical and Automotive Engineering, Kongju National University, Chonan 330-240 (Korea, Republic of)], E-mail: seungbok@inha.ac.kr
2009-02-01
This paper presents an optimal design of magnetorheological (MR) damper based on finite element analysis. The MR damper is constrained in a specific volume and the optimization problem identifies geometric dimensions of the damper that minimizes an objective function. The objective function is proposed by considering the damping force, dynamic range and the inductive time constant of the damper. After describing the configuration of the MR damper, a quasi-static modelling of the damper is performed based on Bingham model of MR fluid. The initial geometric dimensions of the damper are then determined based on the assumption of constant magnetic flux density throughout the magnetic circuit of the damper. Subsequently, the optimal design variables that minimize the objective function are determined using a golden-section algorithm and a local quadratic fitting technique via commercial finite element method parametric design language. A comparative work on damping force and time constant between the initial and optimal design is undertaken.
TECHNICAL NOTE: The strengthening effect of guar gum on the yield stress of magnetorheological fluid
Wu, Wei Ping; Zhao, Bin Yuan; Wu, Qing; Chen, LeSheng; Hu, Ke Ao
2006-08-01
In this paper we present a novel approach for producing obvious strengthening of the magnetorheological (MR) effect of MR fluids. Carbonyl iron powders coated with guar gum were used as magnetic particles in the MR fluid. Experimental results showed that inducing a guar gum coating not only greatly improved the sedimentation stability but also strengthened the yield stress of the MR fluid. An intermolecular force based model was proposed for explaining the strengthening effect.
Method to form a barrier in a reservoir with a magnetorheological fluid
Zitha, P. L.J.
2003-01-01
The invention relates to a method of winning oil from a source via a bored well, wherein a magnetorheological fluid is introduced into the source via the bored well to re duce the water content of the oil won. Oil drilling is resumed in the presence of a magnetic field, thereby increasing the oil yi
柏宗春; 李小宁
2012-01-01
For servo precise location of pneumatic rotary actuators, a novel servo pneumatic rotary actuator with a magnetorheological damper inside is designed. An integrated optimization design model for the structure and magnetism of the magnetorheological damper is proposed. A damping torque formula of the magnetorheological damper is derived. A comprehensive objective function is established by the linear weighting and summation method with the maximizing damping torque and minimizing damper size as single objective functions. An optimization scheme that can meet the saturation magnetic induction intension and core structure parameter requirements of the damper is obtained based on the genetic algorithm, and the damping properties of the damper is increased by 64.4%. The feasibility and credibility of the optimization scheme is validated by electromagnetic finite element analysis.%为了实现摆动气缸的伺服精确定位,研究开发了一种内置磁流变阻尼器的伺服摆动气缸.提出了磁流变阻尼器的结构与磁路的集成优化设计模型.推导了磁流变阻尼器的阻尼力矩公式.以最大阻尼力矩和最小磁流变阻尼器体积为单目标函数,利用线性加权和法建立综合目标函数.采用遗传算法获得满足饱和磁感应强度和阻尼器核心结构参数要求的最优方案,使阻尼器的阻尼性能提高了64.4％.经电磁有限元分析验证该优化方案是可行的.
E. Dragašius
2011-01-01
Full Text Available Using of magnetorheological fluids (MRF can reduce energy costs and weight and increase the devices speed and lifetime. In order to fully use all the qualities of MRF properties one must from time to time mix them and measure their properties. These systems are still being designed and tested in the laboratories. There are many structures with rheological fluid, but in many devices fluids are sealed and mechanical mixing and direct measurement of fluid properties are not possible. Effective stability control system for the rheological fluids, which supports homogeneity of the fluid, is described
THEORY AND EXPERIMENT ON THE VISCOUS HEATING OF FLUID DAMPER UNDER SHOCK ENVIRONMENT
CHU Deying; ZHANG Zhiyi; WANG Gongxian; HUA Hongxing; WANG Yu
2008-01-01
A specially designed fluid damper used as negative shock pulse generator in the shock resistance test system to dissipate the shock input energy in transient time duration is presented. The theoretical modeling based on the three-dimensional equation of heat transfer through a fluid element is created to predict the viscous heating in the fluid damper under shock conditions. A comprehensive experimental program that investigates the problem of viscous heating in the fluid damper under different shock conditions is conducted on the shock test machine to validate the analytical expression. Temperature histories for the fluid within the damper at two locations, the annular-orifice and the-end-of stroke of the damper, are recorded. The experimental results show that the theoretical model can offer a very dependable prediction for the temperature histories in the damper for increasing input velocity. The theoretical model and experimental data both clearly indicate that the viscous heating in the damper is directly related to the maximum shock velocity input and the pressure between the two sides of the piston head.
卫丽君; 李书
2012-01-01
Magneto-rheological damper model suitable for helicopter air resonance and momentum theory model of hover condition involving momentum theory were built in this paper. The equations of the two models with the dynamic equations of helicopter rotor/body coupling were solved by Simulink time domain simulation method to obtain the helicopter dynamic stability influenced by Magneto-rheological damper and compared the blade flapping and lagging impacted by Magneto-rheological dampers under different voltages. It could be conclude that under a certain voltage, Magneto-rheological damper was not influenced by duel-frequent excitation, and was good at restraining the helicopter air resonance.%建立了适用于直升机悬停状态动稳定性的磁流变减摆器模型,悬停状态下动力入流模型采用动量理论模型,与直升机旋翼/机体耦合动力学方程组联立,采用Simulink时域仿真的方法计算得到磁流变减摆器对悬停状态下直升机动稳定的影响,对比了不同电压下磁流变减摆器对桨叶挥舞摆振运动的影响.结果表明:对于磁流变减摆器,施加不同电压可得到不同的阻尼力,该性质可以抑制直升机悬停状态动不稳定性.
A prosthetic knee using magnetorhelogical fluid damper for above-knee amputees
Park, Jinhyuk; Choi, Seung-Bok
2015-04-01
A prosthetic knee for above-knee (AK) amputees is categorized into two types; namely a passive and an active type. The passive prosthetic knee is generally made by elastic materials such as carbon fiber reinforced composite material, titanium and etc. The passive prosthetic knee easy to walk. But, it has disadvantages such that a knee joint motion is not similar to ordinary people. On the other hand, the active prosthetic knee can control the knee joint angle effectively because of mechanical actuator and microprocessor. The actuator should generate large damping force to support the weight of human body. But, generating the large torque using small actuator is difficult. To solve this problem, a semi-active type prosthetic knee has been researched. This paper proposes a semi-active prosthetic knee using a flow mode magneto-rheological (MR) damper for AK amputees. The proposed semi-active type prosthetic knee consists of the flow mode MR damper, hinge and prosthetic knee body. In order to support weight of human body, the required energy of MR damper is smaller than actuator of active prosthetic leg. And it can control the knee joint angle by inducing the magnetic field during the stance phase.
Experimental study and CFD simulation of rotational eccentric cylinder in a magnetorheological fluid
Omidbeygi, F. [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of); Hashemabadi, S.H., E-mail: hashemabadi@iust.ac.ir [Computational Fluid Dynamics Research Laboratory, School of Chemical Engineering, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of)
2012-07-15
In this study, a magnetorheological (MR) fluid is prepared using carbonyl iron filings and low viscosity lubricating oil. The effects of magnetic field and weight percentage of particles on the viscosity of the MR fluid have been measured using a rotational viscometer. The yield stress under an applied magnetic field was also obtained experimentally. In the absence of an applied magnetic field, the MR fluid behaves as a Newtonian fluid. When the magnetic field is applied, the MR fluid behaves like Bingham plastics with a magnetic field dependent yield stress. Afterward, the results compared with those of CFD simulation of two eccentric cylinders in the MR fluid. Results show that the influences of MR effects, caused by the applied magnetic field, on the model characteristics are significant and not negligible. The viscosity is enhanced by increasing of the magnetic field, eccentricity ratio and weight percentage of suspensions. The MR effects and increasing of weight percentage and eccentricity ratio also provide an enhancement in the yield stresses and required total torque for rotation of inner cylinder. Also the simulation results indicate a good representation of the experiment by the model. - Highlights: Black-Right-Pointing-Pointer Preparation of a magnetorheological fluid with carbonyl iron particles in lubricating oil. Black-Right-Pointing-Pointer Rheological measurement for influence of solid content and magnetic field intensity. Black-Right-Pointing-Pointer Simulation of eccentric rotating cylinder in prepared MR fluid with CFD techniques.
PAN Hua-jin; HUANG Hong-jun; ZHANG Ling-zhen; QI Jian-ying; CAO Shao-kun
2005-01-01
Gelatin-carbonyl iron composite particle was prepared by micro emulsion method. The analysis of scanning electron microscope(SEM) shows that the ultrafine particles are spheroids coated by gelatin, and the average sizes of particles are 3-10 μm. The specific saturation magnetization σs is 130.9 A·m2/kg, coercivity Hc is 0.823 A/m, and residual magnetism r is 4.98 Am2/kg for the composite particles. It is shown that the particles possess properties of soft magnetic. The yield stress of magnetorheological fluid(MRF) with composite particle reaches 70 kPa at 0.5 T magnetic induction. Magnetorheological effects are superior in lower magnetic field intensity and the subsidence stability of the MRF is excellent compared with pure carbonyl iron powder.
磁流变阻尼器的米氏模型及试验验证%MICHAELIS-MENTEN MODEL OF MAGNETORHEOLOGICAL DAMPER AND TEST VERIFICATION
张香成; 徐赵东; 王绍安; 沙凌峰
2013-01-01
为研究磁流变阻尼器(MRD)非线性滞回性能的影响因素,建立精确的MRD力学模型,对MRD进行力学性能试验,并基于米氏方程提出一个综合考虑电流、位移和频率影响的力学模型——米氏模型.对所提模型和传统经典力学模型进行数值模拟,并与试验结果进行对比分析,结果表明:该模型可以模拟MRD的非线性滞回性能、体现位移和频率对阻尼力及非线性滞回性能的影响.%To find the effect factors of the nonlinear hysteresis capability of a magnetorheological damper (MRD) and establish a precise mathematical model, a Michaelis-Menten (MM) Model was presented based on the MM equation which considers the effects of current, amplitude and frequency. Numerical simulations of the MM Model and traditional classical mathematic model were carried out to compare with the test results. Comparison results indicate that the MM Model could simulate the hysteresis capability of MRD and reflect the effects of current, amplitude and frequency on damping force and nonlinear hysteresis capability.
Vinod, Sithara; John, Reji; Philip, John
2017-02-01
Magnetorheological fluids have numerous engineering applications due to their interesting field assisted rheological behavior. Most commonly used dispersed phase in MR fluids is carbonyl iron (CI). The relatively high cost of CI warrants the need to develop cheaper alternatives to CI, without compromising rheological properties. With the above goal in mind, we have synthesized sodium sulphonate capped electrolytic iron based MR fluid and studied their magnetorheological properties. The results are compared with that of CI based MR fluid. EI and CI particles of average particle size of ∼10 μm with fumed silica particles additives are used in the present study. The dynamic yield stress for EI and CI based MR fluid were found to vary with field strength with an exponent of roughly 1.2 and 1.24, respectively. The slightly lower static and dynamic yield stress values of EI based MR fluid is attributed to the lower magnetization and polydispersity values. The dynamic yield stress showed a decrease of 18.73% and 61.8% for field strengths of 177 mT and 531 mT, respectively as the temperature was increased from 293 to 323 K. The optorheological studies showed a peak in the loss moduli, close to the crossover point of the storage and loss moduli, due to freely moving large sized aggregates along the shear direction that are dislodged from the rheometer plates at higher strains. Our results suggests that EI based MR fluids have magnetorheological behavior comparable to that of CI based MR fluids. As EI is much cheaper than CI, our findings will have important commercial implications in producing cost effective EI based MR fluids.
Autoregressive trispectrum and its slices analysis of magnetorheological damping device
陈丙三; 黄宜坚
2008-01-01
A combined magnetorheological damper combined with rubber spring and magnetorheological damper is addressed.This type of damping device has inherited the merits of rubber spring and the magnetorheological damper.The test damping device is made up of combined magnetorheological damper,amplitude controller,signal collecting device,computer software for dynamic analysis,etc.When a zeromean and non-Gaussian white noise interfere with the device,a time series autoregressive(AR) model is conducted by using the sampled experimental data.Trispectrum and its slices analysis are emerging as a new powerful technique in signal processing,which is put forward for investigating the dynamic characteristics of the magnetorheological vibrant device.The present of trispectrum and its slices analysis change with the variation of controllable working magnetic field of the damper correspondingly.It is indicated that AR trispectrum and its slices analysis methods are feasible and effective for investigation of magnetorheological vibrant device.
Wang, Guangshuo; Ma, Yingying; Li, Meixia; Cui, Guohua; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Tong, Yu; Dong, Xufeng
2017-01-01
In this study, magnesium ferrite (MgFe2O4) nanocrystal clusters were synthesized using an ascorbic acid-assistant solvothermal method and evaluated as a candidate for magnetorheological (MR) fluid. The morphology, microstructure and magnetic properties of the MgFe2O4 nanocrystal clusters were investigated in detail by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), X-ray diffraction (XRD) and superconducting quantum interference device (SQUID). The MgFe2O4 nanocrystal clusters were suspended in silicone oil to prepare MR fluid and the MR properties were tested using a Physica MCR301 rheometer fitted with a magneto-rheological module. The prepared MR fluid showed typical Bingham plastic behavior, changing from a liquid-like to a solid-like structure under an external magnetic field. Compared with the conventional carbonyl iron particles, MgFe2O4 nanocrystal clusters-based MR fluid demonstrated enhanced sedimentation stability due to the reduced mismatch in density between the particles and the carrier medium. In summary, the as-prepared MgFe2O4 nanocrystal clusters are regarded as a promising candidate for MR fluid with enhanced sedimentation stability.
Piao, YongJun; Choi, YounJung; Kim, JungJa; Kwan, TaeKyu; Kim, Nam-Gyun
2009-03-01
Adequate postural balance depends on the spatial and temporal integration of vestibular, visual, and somatosensory information. Especially, the musculoskeletal function (range of joint, flexibility of spine, muscular strength) is essential in maintaining the postural balance. Muscular strength training methods include the use of commercialized devices and repeatable resistance training tools (rubber band, ball, etc). These training systems cost high price and can't control of intensity. Thus we suggest a new training system which can adjust training intensity and indicate the center of pressure of a subject while the training was passively controlled by applying controlled electric current to the Magneto- Rheological damper. And we performed experimental studies on the muscular activities in the lower extremities during maintaining, moving and pushing exercises on an unstable platform with Magneto rheological dampers. A subject executed the maintaining, moving and pushing exercises which were displayed in a monitor. The electromyographic signals of the eight muscles in lower extremities were recorded and analyzed in the time and frequency domain: the muscles of interest were rectus femoris, biceps femoris, tensor fasciae latae, vastus lateralis, vastus medialis, gastrocnemius, tibialis anterior, and soleus. The experimental results showed the difference of muscular activities at the four moving exercises and the nine maintaining exercises. The rate of the increase in the muscular activities was affected by the condition of the unstable platform with MR dampers for the maintaining and moving exercises. The experimental results suggested the choice of different maintaining and moving exercises could selectively train different muscles with varying intensity. Furthermore, the findings also suggested the training using this system can improve the ability of postural balance.
Vibration control of an artificial muscle manipulator with a magnetorheological fluid brake
Tomori, H.; Midorikawa, Y.; Nakamura, T.
2013-02-01
Recently, proposed applications of robots require them to contact human safely. Therefore, we focus on pneumatic rubber artificial muscle. This actuator is flexible, light, and has high-power density. However, because the artificial muscle is flexible, it vibrates when there is a high load. Therefore, we paid attention to the magnetorheological (MR) fluid. We propose a control method of the MR brake considering energy of the manipulator system. By this control method, MR brake dissipates energy leading to vibration of the manipulator. In this paper, we calculated the energy and controlled the MR brake. And, we deliberated the proposal method by simulation using the dynamic model of the manipulator, and experiment.
Jingya Sun
2014-01-01
Full Text Available Dampers are widely applied to protect devices or human body from severe impact or harmful vibration circumstances. Considering that dampers with low velocity exponent have advantages in energy absorption, they have been widely used in antiseismic structures and shock buffering. Non-Newtonian fluid with strong shear-thinning effect is commonly adopted to achieve this goal. To obtain the damping mechanism and find convenient methods to design the nonlinear fluid damper, in this study, a hydraulic damper is filled with 500,000 cSt silicone oil to achieve a low velocity exponent. Drop hammer test is carried out to experimentally obtain its impact and buffering characteristics. Then a coupling model is built to analyze its damping mechanism, which consists of a model of impact system and a computational fluid dynamics (CFD model. Results from the coupling model can be consistent with the experiment results. Simulation method can help design non-Newtonian fluid dampers more effectively.
Torque Control of a Rehabilitation Teaching Robot Using Magneto-Rheological Fluid Clutches
Hakogi, Hokuto; Ohaba, Motoyoshi; Kuramochi, Naimu; Yano, Hidenori
A new robot that makes use of MR-fluid clutches for simulating torque is proposed to provide an appropriate device for training physical therapy students in knee-joint rehabilitation. The feeling of torque provided by the robot is expected to correspond to the torque performance obtained by physical therapy experts in a clinical setting. The torque required for knee-joint rehabilitation, which is a function of the rotational angle and the rotational angular velocity of a knee movement, is modeled using a mechanical system composed of typical spring-mass-damper elements. The robot consists of two MR-fluid clutches, two induction motors, and a feedback control system. In the torque experiments, output torque is controlled using the spring and damper coefficients separately. The values of these coefficients are determined experimentally. The experimental results show that the robot would be suitable for training physical therapy students to experience similar torque feelings as needed in a clinical situation.
Rizzo, R.
2017-01-01
In this paper an innovative multi-gap magnetorheological clutch is described. It is inspired by a device previously developed by the author’s research group and contains a novel solution based on electrodynamic effects, capable to considerably improve the transmissible torque during the engagement phase. Since this (transient) phase is characterized by a non-zero angular speed between the two clutch shafts, the rotation of a permanent magnets system, used to excite the fluid, induces eddy currents on some conductive material strategically positioned in the device. As a consequence, an electromagnetic torque is produced which is added to the torque transmitted by the magnetorheological fluid only. Once the clutch is completely engaged and the relative speed between the two shafts is zero, the electrodynamic effects vanish and the device operates like a conventional magnetorheological clutch. The system is investigated and designed by means a 3D FEM model and the performance of the device is experimentally validated on a prototype.
Osorio Ospina, Diana Marcela; Castro Navas, Irvin Jadway [Universidad del Valle, Escuela de Ingenieria de Materiales (Colombia); Perez Alcazar, German Antonio; Tabares, Jesus Anselmo, E-mail: jesus_tabares_8@hotmail.com [Universidad del Valle, Departamento de Fisica (Colombia)
2012-03-15
Magnetorheological (MR) fluids are new iron-based materials, whose applications include brakes, dampers, clutches, shock absorbers systems and polishing of optical surfaces (lens and mirrors). They are dependent on the size and shape of particles as the magnetic properties. Interested in the possibility of using iron-rich powders, commonly used in nondestructive testing, ranging in size from a few {mu}m to about 200 {mu}m and lower cost than those commercially used for MR fluids, a study of the structural and magnetic properties of iron-rich metallic particles by X-ray diffraction (XRD) and Moessbauer spectroscopy (MS) at room temperature has been done. Powders, as received, were separated into particle sizes smaller than 20 {mu}m (sample A) and in the range of 20-38 {mu}m (sample B) because these are the sizes generally required for applications in MR fluids. The particles whose sizes exceed the above values were ground in a high energy planetary mill for 3 h, using different values of rotational speed/time: 200 rpm for one hour, a pause of 10 s, 140 rpm for one hour, pause 10 s and then 175 rpm during the last hour. These powders were sieved to obtain particles smaller than 20 {mu}m (sample C). According XRD results, in all samples, only {alpha}-Fe (lattice parameter a = 2,867(2) Angstrom-Sign ) and Fe{sub 2}O{sub 3} (lattice parameter a 5,037(1) Angstrom-Sign and c = 13,755(8) Angstrom-Sign ) were present. The Moessbauer spectra were fitted with two sextets. The hyperfine parameters values allowed us to assign the highest relative area spectrum (sextet) corresponding to {alpha}-Fe and the second one to Fe{sub 2}O{sub 3} in accord to the XRD results. Thus, the preparation method using mechanical milling for diminishing the size of the metallic particles allowed us to get particles with size and magnetic properties that could lead to potentially MR fluids applications.
Synthesis and Characterisation of Nano Silver Particle-based Magnetorheological Fluids for Brakes
Chiranjit Sarkar
2015-05-01
Full Text Available Magnetorheological (MR fluids can be used as brake friction materials subject to heat transfer properties of the fluids to dissipate the heat generated during braking action. The aim of this manuscript is to synthesise MR fluids having higher heat transfer properties than that of the conventional MR fluid. The coating of nano-silver-particles, having thermal conductivity more than five-times than that of iron particles used in the MR fluids, has been tried to enhance the heat dissipation rate of MR fluids. To perform feasibility study on usage of silver particles, three composition of MR fluids (without any silver particles, with 0.25 per cent weight and 0.50 per cent weight silver particles were synthesised. The scanning electron microscopic photographs and EDX analysis of the iron particles have been presented. Shear strengths of all three different compositions of MR fluids were measured using magnetorheometer and the results have been plotted. The effect of silver particles on shear stress of MR fluids has been described. A flywheel-based MR brake experimental setup was developed to analyse the performance of synthesised MR fluids. ‘T’ type thermocouples were used to avail the temperature distribution of the fabricated MR brake. The results of temperature distribution of brakes containing three different compositions of MR fluids have been presented and compared.Defence Science Journal, Vol. 65, No. 3, May 2015, pp.252-258, DOI: http://dx.doi.org/10.14429/dsj.65.7879
Rodriguez-Lopez, J., E-mail: jaimerl@caend.upm-csic.es [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain); Elvira Segura, L.; Montero de Espinosa Freijo, F. [Centro de Acustica Aplicada y Ensayos No Destructivos, UPM-CSIC, 28006 Madrid (Spain)
2012-01-15
Variations in velocity of sound and amplitude of the signal of a commercial magnetorheological fluid under different magnetic fields are studied experimentally. Different factors such as orientation, uniformity, geometry and intensity of the magnetic field are investigated. An increase in the change of MR fluid acoustical properties is obtained when the magnetic field intensity is risen. In addition, these properties show an opposite behavior when a magnetic field is applied parallel or perpendicular to the ultrasound propagation. Experiments using an electromagnet and permanent magnets as the source of magnetic field are also compared. Properties such as anisotropy in sound velocity and amplitude make these materials interesting regarding applications. - Highlights: > First sound attenuation measurements as function of the magnetic field in MR fluids. > Sound velocity and attenuation anisotropy due to the microstructure is detected. > Geometry, intensity and uniformity of the magnetic field affect sound propagation.
STUDY ON ELECTRORHEOLOGICAL FLUID DAMPER FOR APPLICATION IN MACHINING CHATTER CONTROL
无
2003-01-01
The electrorheological fluid(ERF)is a kind of intelligent material with bright prospects for industry applications, which has viscoelastic characteristic under the applied electric field. The dynamic model of a milling system with an ERF damper is established, and the chatter suppression mechanism of the ER effect is discussed theoretically. Both the theoretical study and the experimental investigation show that the additional damping and additional stiffness produced by the ERF increase with the rise in the strength of electric field E, but their influence on the cutting stability is different. Only when both additional damping and additional stiffness cooperate, the milling chatter can be suppressed quickly and effectively. In additional, an ERF damper used on the arbor of horizontal spindle milling machine is developed, and a series of milling chatter control experiments are performed. The experimental results show that the milling chatter can be suppressed effectively by using the ER damper.
Qing-hua Zu
2015-01-01
Full Text Available The damping characteristics of the traditional dual mass flywheel (DMF cannot be changed and can only meet one of the damping requirements. Given that the traditional DMF cannot avoid the resonance interval in start/stop conditions, it tends to generate high-resonance amplitude, which reduces the lifetime of a vehicle’s parts and leads to vehicle vibration and noise. The problems associated with the traditional DMF can be solved through the magnetorheological fluid dual mass flywheel (MRF-DMF, which was designed in this study with adjustable damping performance under different conditions. The MRF-DMF is designed based on the rheological behavior of the magnetorheological fluid (MRF, which can be changed by magnetic field strength. The damping torque of the MRF-DMF, which is generated by the MRF effect, is derived in detail. Thus, the cosimulation between the drivetrain model built in AMESim and the control system model developed in Simulink is conducted. The controller of MRF-DMF is developed, after which the torsional vibration control test of drivetrain is carried out. The cosimulation and test results indicate that MRF-DMF with the controller effectively isolates torque fluctuation of the engine in the driving condition and exhibits high performance in suppressing the resonance amplitude in the start/stop conditions.
Agustín-Serrano, R. [Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Puebla, Puebla 72570, México (Mexico); Donado, F., E-mail: fernando@uaeh.edu.mx [Instituto de Ciencias Básicas e Ingeniería de la Universidad Autónoma del Estado de Hidalgo-AAMF, Pachuca 42184, México (Mexico); Rubio-Rosas, E. [Centro Universitario de Vinculación, Universidad Autónoma de Puebla, Puebla 72570, México (Mexico)
2013-06-15
An experimental study conducted on the rheological properties of a magnetorheological fluid based on submicrometric silica-coated magnetite particles dispersed in silicone oil is presented. We investigated the rheological behaviour when the system is simultaneously exposed to a static field and a sinusoidal field used as a perturbation. The results show that the perturbation modifies the rheological behaviour of the system and can be used to control its physical properties; however, the changes that are induced are smaller than expected from previous results for the aggregation of particles under magnetic perturbations. We discussed this difference in terms of the ratio between the magnetic energy and the thermal energy. We observed that a threshold magnetic field exists; below it, the yield stress is practically zero, whereas above it, the yield stress grows quickly. We discuss this result in terms of a model based on chain length distribution. - Highlights: ► We study a magnetorheological fluid under an oscillatory magnetic field. ► The exponential chain length distribution depends on the average chain length. ► A simple yield stress model based on the chain length distribution is proposed.
Chaos control and impact suppression in rotor-bearing system using magnetorheological fluid
Piccirillo, V.; Balthazar, J. M.; Tusset, A. M.
2015-11-01
In this paper a general dynamic model of a rotor-bearing system using magnetorheological fluid (MR) is presented. The mathematical model of the rotor-bearing system results from a Jeffcott rotor with two-degrees of freedom and discontinuous supports. The effect of magnetorheological fluid on vibration is investigated based on a model of a modified LuGre dynamical friction model. A comparison with equivalent rotor-bearing system is made to verify the contribution of MR in this system. In this study two different implementations of the control procedure are presented, one eliminating the chaotic behavior and the second suppressing the unbalancing vibration so as to avoid impact in rotor-bearing system. First, to control the undesirable chaos in rotor-bearing system a damped passive control methodology is used. On the other hand, to suppressing the impact vibration, the Fuzzy Logic Control is considered. Results demonstrate that undesirable behaviors of rotor can be avoided by varying the damping force.
Characteristic analysis of magnetorheological fluid based on different carriers
张建; 张进秋; 贾进峰
2008-01-01
In order to prepare special MRFs to satisfy the demands of tracked vehicle,two different carrier fluids were used to prepare MRFs.Preparation of MRF,which are based on carrier of special shock absorption fluid and 45# transformer oil,was finished.And characteristics of these samples were tested and analyzed.The results show that Tween-80 and Span-80 can improve the sedimentary stability,and the larger mass fraction can also increase the sedimentary stability.Using 45# transformer oil instead of special shock absorption fluid as a carrier of MRF,the shear yield stress remains nearly constant but the viscosity and the sedimentary stability are reduced.The MRF with diameter of 2.73 μm shows better sedimentary stability than that of the MRF with diameter of 2.30 μm,or 4.02 μm.Stearic acid obviously improves sedimentary stability and off-state viscosity,but has no function on the shear yield stress.In magnetic field of 237 kA/m,the shear yield stress of MRF based on special shock absorption fluid is 18.34 kPa and the shear yield stress of MRF based on 45# transformer oil is 14.26 kPa.
WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi
2008-01-01
A hardware-in-the-loop (HIL) test and simulation platform is developed in the laboratory, so as to validate the performance characteristics of the proposed skyhook-based asymmetric semi-active controller in Part I, and examine the validity of the proposed MR-damper model in a system surrounding. A real-time monitor is designed to assess and monitor the responses of the quarter-vehicle model in the HIL platform, and to select the excitation, controller synthesis, and the output displays. A drive current circuit hardware employing PID feedback technique is developed to compensate for the time delays from the servo-controller and drive current circuit, in which a small resistance is integrated in the current amplifier circuit to provide the feedback signal. The experiments were performed to measure the responses of the quarter-vehicle MR-suspension models with fixed current and the proposed semi-active MR-damping variations, under harmonic, rounded pulse and random road excitations. The measured data were compared with the corresponding model results to examine the model and controller validity, and revealed generally good agreements in the model and tested results and very little sensitivity of the tested responses to variations in the sprung mass. The HIL test results validate the effectiveness of the proposed skyhook-based semi-active asymmetric controller and its high robustness against the vehicle load variations in view of the intelligent vehicle suspension design.
Cylindrical Magnetorheological Fluid Variable Transmission Controlled by Shape-Memory Alloy
Song Chen
2012-01-01
Full Text Available Centrifugal fan is an important component of a ventilation system in a nuclear power plant. In this paper, we proposed a magnetorheological speed-adjustment system controlled by shape-memory alloy for centrifugal fan. A theoretical analysis of the effect of the applied magnetic field on the viscoplastic flow between two cylinders in the speed-adjustment system is presented. The expressions for the velocity in viscoplastic flow and the torque transmitted by MR fluids are derived. A sliding mode SMA switch is proposed to modify the magnetic field acting on working gap under thermal effect. The results indicate that with the increases of applied magnetic field, the torque transmitted by MR fluid goes up rapidly.
Influence of MR damper modeling on vehicle dynamics
de-J Lozoya-Santos, Jorge; Morales-Menendez, Ruben; Ramirez-Mendoza, Ricardo A.; Vivas-Lopez, Carlos A.
2013-12-01
The influence of magneto-rheological damper modeling in vehicle dynamics analysis is studied. Several tests using CarSim™ compare a four-corner controlled semi-active suspension for two different magneto-rheological damper models. The magneto-rheological damper characteristics were identified from experimental data. A model-free controller discards the influence of control and emphasizes the compliance of the magneto-rheological damper model; the characteristics of the vehicle index performance considered were comfort, road holding, handling, roll and suspension deflection. The comparison for magneto-rheological damper dynamics and semi-active suspension covers the automotive bandwidth. The results show that high precision of a magneto-rheological damper model as an isolated feature is not enough. The magneto-rheological damper model, as a component of a vehicle suspension, needs to simulate with passive precision and variable damping forces. The findings exhibit the requisite of accurate models for evaluation of semi-active control systems in classic tests. The lack of the friction component in a magneto-rheological damper model leads to an overestimation in handling and stability.
A comparative analysis of passive twin tube and skyhook MRF dampers for motorcycle front suspensions
Ahmadian, Mehdi; Gravatt, John
2004-07-01
A comparative analysis between conventional passive twin tube dampers and skyhook-controlled magneto-rheological fluid (MRF) dampers for motorcycle front suspensions is provided, based on single axis testing in a damper test rig and suspension performance testing in road trials. Performance motorcycles, while boasting extremely light suspension components and competition-ready performance, have an inherent weakness in comfort, as the suspension systems are designed primarily for racing purposes. Front suspension acceleration and shock loading transmit directly through the front suspension triple clamp into the rider's arms and shoulders, causing rapid fatigue in shoulder muscles. Magneto-rheological fluid dampers and skyhook control systems offer an alternative to conventional sport motorcycle suspensions - both performance and comfort can be combined in the same package. Prototype MRF dampers designed and manufactured specifically for this application require no more space than conventional twin tube designs while adding only 1.7 pounds total weight to the system. The MRF dampers were designed for high controllability and low power consumption, two vital considerations for a motorcycle application. The tests conducted include the dampers' force-velocity curve testing in a damper test rig and suspension performance based on damper position, velocity, and acceleration measurement. Damper test rig results show the MRF dampers have a far greater range of adjustability than the test vehicle's OEM dampers. Combined with a modified sky-hook control system, the MRF dampers can greatly decrease the acceleration and shock loading transmitted to the rider through the handlebars while contributing performance in manners such as anti-dive under braking. Triple clamp acceleration measurements from a variety of staged road conditions, such as sinusoidal wave inputs, will be compared to subjective test-rider field reports to establish a correlation between rider fatigue and the
Unal, Halil Ibrahim
2013-02-01
Conference photograph The 13th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (ERMR2012) was held in Ankara, Turkey at Gazi University in the Architect Kemaleddin historical hall on 2-6 July 2012. The first International Conference on Electrorheological Fluids and Magnetorheological Suspensions took place nearly 25 years ago and this conference continued the same tradition by providing an arena for researchers around the world to present their new research findings in these fields, and gave them the opportunity to learn about the latest research and technology and to renew their acquaintances. The meeting brought together scientists and engineers in multidisciplinary areas such as chemical engineering, mechanical engineering, materials science and engineering, physics, chemistry and polymer science and technology, to explore the state-of-art technology, identify key areas to be focused on and discuss their problems/issues. All oral presentations were held in a single session to enhance the interactions between the scientists and engineers. The ERMR2012 Conference included plenary lectures given by prominent leaders in their respective fields. About 130 participants from more than 50 organizations attended the conference and 15 plenary speeches, 64 oral presentations and 57 poster presentations took place in the following areas: (i) synthesis, characterization and processing of novel ER/MR materials, (ii) dynamics, chain and structure formation of ER/MR materials, (iii) ER/MR elastomers, ferrogels and their characterizations, (iv) rheological techniques and measurements of ER/MR materials, (v) modeling and simulations of ER/MR materials, (vi) device development and control techniques and (vii) applications of ER/MR materials. The ERMR2012 International Conference began with Turkish classical music performed by the musicians of the Ministry of Culture and Tourism. Rector Professor Dr R Ayhan welcomed the participants and the
Analysis of Influence of Temperature on Magnetorheological Fluid and Transmission Performance
Song Chen
2015-01-01
Full Text Available Magnetorheological (MR fluid shows different performances under different temperature, which causes so many problems like the reduction of rheological properties of MR fluid under a high temperature condition, the uncontrollability of shear stress, and even failure of transmission; on that basis, the influence of temperature on the performance of MR fluid and the cause of the rise in temperature of MR transmission device are analyzed in this paper; the shearing transmission performance of the MR transmission device under the effect of an external magnetic field and the influence of temperature on the shearing stress and transmission performance are analyzed. The study results indicate that temperature highly influences the viscosity of MR fluid, and the viscosity influences the shear stress of the MR fluid. The viscosity of MR fluid gradually declines when temperature rises from 100°C. Once the temperature exceeds 100°C, the viscosity would increase and the temperature stability would decline. Temperature obviously influences the characteristics of MR transmission, and particularly, highly influences the characteristics of MR transmission once being higher than 100°C. The chaining of the material in the magnetic field is influenced, which causes the reduction of the rheological properties, the uncontrollability of the shear stress, and even the failure of transmission.
Study on Theoretical Modeling of Semi-Active Electro-Rheological Fluid Damper
饶柱石; 傅志方; 张华良
2003-01-01
This paper emphases on analyzing and investigating the mechanical behavior of electro-rheological fluid (ERF) semi-active damper. Theoretical model was developed to describe the relationship between electric field and the resistance force of ERF flowing through two parallel plane electrodes. In the model, the pressure drop along electrodes was supposed to consist of two parts: one related with viscosity and the other related with dynamic yield shear stress. The concept of yield stress in fluence factor was developed inderiving the theoretical formula for calculating the pressure drop in the damper. The influences of some other factors, such as, nonideal Newtonian fluid and temperature have also been taken into account. Numerical and experimental work have been performed to prove the validity of the proposed model. The comparison of both results shows that the developed model is quite effective and practicable.
Smart mouse: 5-DOF haptic hand master using magneto-rheological fluid actuators
Kim, K. H.; Nam, Y. J.; Yamane, R.; Park, M. K.
2009-02-01
This paper is concerned with a haptic hand master intended to display force feedback at the fingertip of the human user. The haptic hand master, named 'Smart Mouse' has two significant differences from previous other hand masters: actuators and structure. Five passive actuators featured with magneto-rheological fluid are used to ensure the interface safety and the control stability. In order to eliminate the unnecessary reaction force and reduce muscular fatigue during operating, the mouse-like structure is adapted. Also, two assumptions are proposed for the simplicity of its kinematics and manufacturing; one is that the fingertips lies on a plane during grasping the objects, and the other is that the equilibrium point of the fingertip reaction forces is in the object. Due to these characteristics, the human hand operating the smart mouse has the kinematic configuration similar to a 5-DOF parallel manipulator.
Smart mouse: 5-DOF haptic hand master using magneto-rheological fluid actuators
Kim, K H; Nam, Y J; Park, M K [Graduated School of Mechanical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Yamane, R [Kokushikan University, 4-28-1 Setagaya, Setagaya-ku, Tokyo 154-8515 (Japan)], E-mail: mkpark1@pusan.ac.kr
2009-02-01
This paper is concerned with a haptic hand master intended to display force feedback at the fingertip of the human user. The haptic hand master, named 'Smart Mouse' has two significant differences from previous other hand masters: actuators and structure. Five passive actuators featured with magneto-rheological fluid are used to ensure the interface safety and the control stability. In order to eliminate the unnecessary reaction force and reduce muscular fatigue during operating, the mouse-like structure is adapted. Also, two assumptions are proposed for the simplicity of its kinematics and manufacturing; one is that the fingertips lies on a plane during grasping the objects, and the other is that the equilibrium point of the fingertip reaction forces is in the object. Due to these characteristics, the human hand operating the smart mouse has the kinematic configuration similar to a 5-DOF parallel manipulator.
Vibration control of flexible structures via electrorheological-fluid-based dampers
Wang, Kon-Well; Kim, Y. S.; Lee, H. S.; Shea, D. B.
1993-09-01
The semi-active control approach has been recognized to be effective for vibration suppression of flexible structures. The electrorheological (ER) fluid-based device is a good candidate for such applications. In this research, a new control law is developed to maximize the damping effect of ER dampers for structural vibration suppression under actuator constraints and viscous-frictional-combined damping. Both numerical simulations and experimental work have been carried out to evaluate and validate the theoretical predictions.
Gangadhara Shetty B
2011-10-01
Full Text Available Developing a sudden damping and its control which is demanded in many engineering applications with the existing conventional methods are difficult and critical too. A magnetorheological (MR fluid with good rheological properties can exhibit very fast damping characteristics and can be controlled just by varying the applied magnetic field to that fluid. Thus in this paper, a MR fluid is proposed with a non-edible vegetable oil such as Honge oil as a carrier liquid. Three samples of such MR fluid containing different percentages by volume of carbonyl iron powder as suspensions are prepared for comparing their rheological properties. An experimental setup consisting of a capillary viscometer with a pair of solenoid type of electromagnetic coils is developed. The rheological properties of the proposed MR fluid are investigated under the application of different magnetic fields and the results are presented. It was observed that the one of the samples containing 40 per cent by volume as suspensions exhibits a maximum viscosity of 334 Pa-s and yield stress of 13.23 kPa at a magnetic field of 0.3816 T. The results have been compared with those obtained by other researchers.Defence Science Journal, 2011, 61(6, pp.583-589, DOI:http://dx.doi.org/10.14429/dsj.61.331
Wind-induced vibration control of Hefei TV tower with fluid viscous damper
ZHANG Zhiqiang; Aiqun LI; Jianping HE; Jianlei WANG
2009-01-01
The Hefei TV tower is taken as an analytical case to examine the control method with a fluid viscous damper under wind load fluctuation. Firstly, according to the random vibration theory, the effect of fluctuating wind on the tower can be modeled as a 19-dimensional correlated random process, and the wind-induced vibration analysis of the tower subjected to dynamic wind load was further obtained. On the basis of the others' works, a bi-model dynamic model is proposed. Finally, a dynamic model is proposed to study the wind-induced vibration control analysis using viscous fluid dampers, and the optimal damping coefficient is obtained regarding the wind-induced response of the upper turret as optimization objectives. Analysis results show that the maximum peak response of the tower under dynamic wind load is far beyond the allowable range of the code. The wind-induced responses and the wind vibration input energy of the tower are decreased greatly by using a fluid viscous damper, and the peak acceleration responses of the upper turret is reduced by 43.4%.
Development of Magnetorheological Resistive Exercise Device for Rowing Machine
Vytautas Grigas
2016-01-01
Full Text Available Training equipment used by professional sportsmen has a great impact on their sport performance. Most universal exercisers may help only to improve the general physical condition due to the specific kinematics and peculiar resistance generated by their loading units. Training of effective techniques and learning of psychomotor skills are possible only when exercisers conform to the movements and resistance typical for particular sports kinematically and dynamically. Methodology of developing a magnetorheological resistive exercise device for generating the desired law of passive resistance force and its application in a lever-type rowing machine are described in the paper. The structural parameters of a controllable hydraulic cylinder type device were found by means of the computational fluid dynamics simulation performed by ANSYS CFX software. Parameters describing the magnetorheological fluid as non-Newtonian were determined by combining numerical and experimental research of the resistance force generated by the original magnetorheological damper. A structural scheme of the device control system was developed and the variation of the strength of magnetic field that affects the magnetorheological fluid circulating in the device was determined, ensuring a variation of the resistance force on the oar handle adequate for the resistance that occurs during a real boat rowing stroke.
Development of Magnetorheological Resistive Exercise Device for Rowing Machine.
Grigas, Vytautas; Šulginas, Anatolijus; Žiliukas, Pranas
2015-01-01
Training equipment used by professional sportsmen has a great impact on their sport performance. Most universal exercisers may help only to improve the general physical condition due to the specific kinematics and peculiar resistance generated by their loading units. Training of effective techniques and learning of psychomotor skills are possible only when exercisers conform to the movements and resistance typical for particular sports kinematically and dynamically. Methodology of developing a magnetorheological resistive exercise device for generating the desired law of passive resistance force and its application in a lever-type rowing machine are described in the paper. The structural parameters of a controllable hydraulic cylinder type device were found by means of the computational fluid dynamics simulation performed by ANSYS CFX software. Parameters describing the magnetorheological fluid as non-Newtonian were determined by combining numerical and experimental research of the resistance force generated by the original magnetorheological damper. A structural scheme of the device control system was developed and the variation of the strength of magnetic field that affects the magnetorheological fluid circulating in the device was determined, ensuring a variation of the resistance force on the oar handle adequate for the resistance that occurs during a real boat rowing stroke.
Chen, Yanhao; Lu, Qi; Jing, Bo; Zhang, Zhiyi
2016-09-01
This paper addresses dynamic modelling and experiments on a passive vibration isolator for application in the space environment. The isolator is composed of a pretensioned plane cable net structure and a fluid damper in parallel. Firstly, the frequency response function (FRF) of a single cable is analysed according to the string theory, and the FRF synthesis method is adopted to establish a dynamic model of the plane cable net structure. Secondly, the equivalent damping coefficient of the fluid damper is analysed. Thirdly, experiments are carried out to compare the plane cable net structure, the fluid damper and the vibration isolator formed by the net and the damper, respectively. It is shown that the plane cable net structure can achieve substantial vibration attenuation but has a great amplification at its resonance frequency due to the light damping of cables. The damping effect of fluid damper is acceptable without taking the poor carrying capacity into consideration. Compared to the plane cable net structure and the fluid damper, the isolator has an acceptable resonance amplification as well as vibration attenuation.
Seung-Bok eChoi
2014-10-01
Full Text Available This study is concerned with an investigation of the plate-like iron particles based MR suspensions under the application of magnetic fields to ascertain the influence of particle size in the rheological performance. A novel synthesis route to prepare magnetorheological fluid (MRF using two different sizes of plate-like iron particles is described in detail. Two different kinds of MRF are then prepared and their rheological properties are presented and discussed extensively. Steady shear flow and small amplitude dynamic oscillatory measurements are carried out in the presence of magnetic field. This experimental study reveals and highlights the importance of exploiting some parameters such as magnetic field strength, effect of particle size, magneto-viscous and visco-elastic properties of the suspending fluid. The magnetization of the fluids is also performed to explain the effect of particle size in the magnetic field which is directly correlated with the yield stress. In the absence of magnetic field, the properties of fluid are isotropic and upon the application of magnetic field the magnetized particles form a strong-chain like structures in the field direction which promotes the appearance of yield stress. This material is known as smart material whose properties amend from liquid to solid immediately after applying the magnetic field. It is found from this work that the large size particle based MRF exhibits high yield stress and strong chain structuration under the applying magnetic field.
Behrooz, Majid; Gordaninejad, Faramarz
2016-09-01
This paper presents a three-dimensional study of a controllable flexible magnetically-activated micropump. The tubular micropump employs magnetically induced deformation of magnetorheological elastomer and one-way flexible conical valves for fluid transport. Three-dimensional magneto-fluid-solid interaction analysis is employed to investigate the performance of the system. The effects of key material, geometric, and magnetic parameters on the effectiveness of the system are examined. It is demonstrated that the proposed system can propel the fluid unidirectionally, and the volume of the transported fluid is significantly affected by some of the design parameters.
FLUID-STRUCTURE INTERACTION OF HYDRODYNAMIC DAMPER DURING THE RUSH INTO THE WATER CHANNEL
XU Qing-xin; SHEN Rong-ying
2008-01-01
The hydrodynamic damper is a device to decrease the motion of armament carrier by use of the water resistance. When hydrodynamic damper rushes into the water channel with high velocity, it is a complicated flow phenomenon with fluid-structure interaction, free surface and moving interface. Numerical simulation using the Smoothed Particle Hydrodynamics (SPH) method coupled with the Finite Element (FE) method was successfully conducted to predict the dynamic characteristics of hydrodynamic damper. The water resistance, the pressure in the interface and the stress of structure were investigated, and the relationship among the peak of water resistance, initial velocity and actual draught was also discussed. The empirical formula was put forward to predict the water resistance. And it is found that the resistance coefficient is commonly in the range of 0.3≤C ≤0.5, when the initial velocity is larger than 50 m/s. It can be seen that the SPH method coupled with the FE method has many obvious advantages over other numerical methods for this complicated flow problem with fluid-structure interaction.
A magneto-rheological fluid mount featuring squeeze mode: analysis and testing
Chen, Peng; Bai, Xian-Xu; Qian, Li-Jun; Choi, Seung-Bok
2016-05-01
This paper presents a mathematical model for a new semi-active vehicle engine mount utilizing magneto-rheological (MR) fluids in squeeze mode (MR mount in short) and validates the model by comparing analysis results with experimental tests. The proposed MR mount is mainly comprised of a frame for installation, a main rubber, a squeeze plate and a bobbin for coil winding. When the magnetic fields on, MR effect occurs in the upper gap between the squeeze plate and the bobbin, and the dynamic stiffness can be controlled by tuning the applied currents. Employing Bingham model and flow properties between parallel plates of MR fluids, a mathematical model for the squeeze type of MR mount is formulated with consideration of the fluid inertia, MR effect and hysteresis property. The field-dependent dynamic stiffness of the MR mount is then analyzed using the established mathematical model. Subsequently, in order to validate the mathematical model, an appropriate size of MR mount is fabricated and tested. The field-dependent force and dynamic stiffness of the proposed MR mount are evaluated and compared between the model and experimental tests in both time and frequency domains to verify the model efficiency. In addition, it is shown that both the damping property and the stiffness property of the proposed MR mount can be simultaneously controlled.
State of the art of control schemes for smart systems featuring magneto-rheological materials
Choi, Seung-Bok; Li, Weihua; Yu, Miao; Du, Haiping; Fu, Jie; Do, Phu Xuan
2016-04-01
This review presents various control strategies for application systems utilizing smart magneto-rheological fluid (MRF) and magneto-rheological elastomers (MRE). It is well known that both MRF and MRE are actively studied and applied to many practical systems such as vehicle dampers. The mandatory requirements for successful applications of MRF and MRE include several factors: advanced material properties, optimal mechanisms, suitable modeling, and appropriate control schemes. Among these requirements, the use of an appropriate control scheme is a crucial factor since it is the final action stage of the application systems to achieve the desired output responses. There are numerous different control strategies which have been applied to many different application systems of MRF and MRE, summarized in this review. In the literature review, advantages and disadvantages of each control scheme are discussed so that potential researchers can develop more effective strategies to achieve higher control performance of many application systems utilizing magneto-rheological materials.
Neural Network modeling of forward and inverse behavior of rotary MR damper
Bhowmik, Subrata; Høgsberg, Jan Becker; Weber, Felix
2010-01-01
Magneto-rheological (MR) dampers have received considerable attention within the last decades, mainly because of their design simplicity, low power requirements, large force range and robustness. The most common models to describe the dynamic MR damper behavior are the Bouc-Wen model, the Lu...... of nonlinear problems. The present paper concerns the nonparametric neural network modeling of the dynamic behavior of a rotary MR damper. A rotary type MR damper consists of a rotating disk which is enclosed in a metallic housing filled with the MR fluid which is operated in shear mode. The dissipative torque......Gre friction model and the Dahl friction model. However, these mathematical approaches might be complicated due to the high degree of nonlinearity in the system under consideration. From a computational point of view the nonparametric neural network technique is very versatile in connection with most types...
Design of a New 4-DOF Haptic Master Featuring Magnetorheological Fluid
Byung-Keun Song
2014-08-01
Full Text Available This work presents a novel 4-degree-of-freedom (4-DOF haptic master using magnetorheological (MR fluid which is applicable to a robot-assisted minimally invasive surgery (RMIS system. By using MR fluid, the proposed haptic device can easily generate bidirectional repulsive torque along the directions of the required motions. The proposed master consists of two actuators: an MR bidirectional clutch associated with a planetary gear system and an MR clutch with a bevel gear system. After demonstrating the configuration, the torque models of MR actuators are mathematically derived based on the field-dependent Bingham model. An optimal design that accounts for spatial-limitation and the desired torque constraint is then undertaken. An optimization procedure based on finite element analysis is proposed to determine optimal geometric dimensions. Based on the design procedure, MR haptic master with the optimal parameters has been manufactured. In order to demonstrate the practical feasibility of the proposed haptic master, the field-dependent generating repulsive force is measured. In addition, a proportional-integral-derivative (PID controller is empirically implemented to accomplish the desired torque trajectories. It has been shown that the proposed haptic master can track the desired torque trajectory without a significant error.
Design and experimental evaluation of a tactile display featuring magnetorheological fluids
Han, Young-Min; Oh, Jong-Seok; Kim, Jin-Kuy; Choi, Seung-Bok
2014-07-01
This paper proposes a novel type of tactile display utilizing magnetorheological (Mr) fluid which can be applied to a robotic system in minimally invasive surgery to provide a surgeon with tactile information on remote biological tissues or organs. As a first step, an actuation mechanism for tactile function is devised utilizing the Mr fluid with a pin array mechanism. Based on the force responses of a human body, the tactile display is appropriately designed and a magnetic analysis is carried out to determine the design parameters using the finite element method. After evaluating the field-dependent force characteristics of the manufactured tactile display, a feed-forward control algorithm based on fuzzy logic is formulated to obtain the desired palpation force. Control performance is demonstrated via palpation force evaluation and psychophysical evaluation. In the results, the actual repulsive forces agreed well with the desired forces and the averaged relative error was less than 1.3%. In addition, the volunteers successfully recognized tactility with a favorable rating value of 3.36 on a five-point scale.
Forero-Sandoval, I. Y.; Vega-Flick, A.; Alvarado-Gil, J. J.; Medina-Esquivel, R. A.
2017-02-01
The thermal conductivity and viscosity of a magnetorheological suspension composed of carbonyl iron particles immerse in silicone oil were studied. Thermal wave resonant cavity was employed to measure the thermal diffusivity of the magnetorheological fluid as a function of an externally applied magnetic field. The dynamic viscosity was also measured and its relationship with the concentration of the particles and the magnetic field strength was investigated. The results show that higher concentrations of carbonyl iron particles as well as higher magnetic field intensities lead to a significant increase in thermal conductivity. The relationship between the thermal conductivity and the dynamic viscosity was explored. Our measurements were examined using an analytical relation between the thermal conductivity and the dynamic viscosity. The results show that by using highly viscous materials, the order induced in the micro particles can be kept for a relatively long time and therefore the increase in thermal conductivity can also be maintained.
李静; 陈健云; 柴健; 吕淑娟
2013-01-01
According to the vibration control problems of the offshore wind turbines under seismic load and wind load,the mechanical model of magneto-rheological (MR)damper and the relationship between the damping force and parameters of MR damper are presented here.The action principle of the fuzzy control algorithm in semi-active control is studied,and the Simulink simulation model is established,then the vibration control of the offshore wind turbines under the effects of seismic load and wind load is analyzed.For reducing the acceleration and displacement of the offshore wind turbines un-der the wind load and seismic load,the MR damper is used in the wind turbines.The result illustrates that this control method could effectively reduce the acceleration and displacement under the wind load and seismic load.%针对近海风机在地震动及风荷载联合作用下的振动控制问题，提出了基于磁流变阻尼器及模糊控制算法的半主动振动控制模型，研究了阻尼控制力与其构件参数之间的关系，并通过 Simulink 仿真模型对近海风机在地震荷载和风荷载作用下的振动控制进行了分析。计算结果表明，采用磁流变阻尼器能够有效的减小风荷载和地震荷载作用下近海风机结构的加速度和位移反应。
Rabbani, Yahya; Ashtiani, Mahshid; Hashemabadi, Seyed Hassan
2015-06-14
In this study, the stability and rheological properties of a suspension of carbonyl iron microparticles (CIMs) in silicone oil were investigated within a temperature range of 10 to 85 °C. The effect of adding two hydrophobic (stearic and palmitic) acids on the stability and magnetorheological effect of a suspension of CIMs in silicone oil was studied. According to the results, for preparing a stable and efficient magnetorheological (MR) fluid, additives should be utilized. Therefore, 3 wt% of stearic acid was added to the MR fluid which led to an enhancement of the fluid stability over 92% at 25 °C. By investigating shear stress variation due to the changes in the shear rate for acid-based MR fluids, the maximum yield stress was obtained by fitting the Bingham plastic rheological model at high shear rates. Based on the existing correlations of yield stress and either temperature or magnetic field strength, a new model was fitted to the experimental data to monitor the simultaneous effect of magnetic field strength and temperature on the maximum yield stress. The results demonstrated that as the magnetic field intensified or the temperature decreased, the maximum yield stress increased dramatically. In addition, when the MR fluid reached its magnetic saturation, the viscosity of fluid depended only on the shear rate.
Optimization of new magnetorheological fluid mount for vibration control of start/stop engine mode
Chung, Jye Ung; Phu, Do Xuan; Choi, Seung-Bok
2015-04-01
The technologies related to saving energy/or green vehicles are actively researched. In this tendency, the problem for reducing exhausted gas is in development with various ways. Those efforts are directly related to the operation of engine which emits exhausted gas. The auto start/stop of vehicle engine when a vehicle stop at road is currently as a main stream of vehicle industry resulting in reducing exhausted gas. However, this technology automatically turns on and off engine frequently. This motion induces vehicle engine to transmit vibration of engine which has large displacement, and torsional impact to chassis. These vibrations causing uncomfortable feeling to passengers are transmitted through the steering wheel and the gear knob. In this work, in order to resolve this vibration issue, a new proposed magnetorheological (MR) fluid based engine mount (MR mount in short) is presented. The proposed MR mount is designed to satisfy large damping force in various frequency ranges. It is shown that the proposed mount can have large damping force and large force ratio which is enough to control unwanted vibrations of engine start/stop mode.
Semi-active engine mount design using auxiliary magneto-rheological fluid compliance chamber
Mansour, H.; Arzanpour, S.; Golnaraghi, M. F.; Parameswaran, A. M.
2011-03-01
Engine mounts are used in the automotive industry to isolate engine and chassis by reducing the noise and vibration imposed from one to the other. This paper describes modelling, simulation and design of a semi-active engine mount that is designed specifically to address the complicated vibration pattern of variable displacement engines (VDE). The ideal isolation for VDE requires the stiffness to be switchable upon cylinder activation/deactivation operating modes. In order to have a modular design, the same hydraulic engine mount components are maintained and a novel auxiliary magneto-rheological (MR) fluid chamber is developed and retrofitted inside the pumping chamber. The new compliance chamber is a controllable pressure regulator, which can effectively alter the dynamic performance of the mount. Switching between different modes happens by turning the electrical current to the MR chamber magnetic coil on and off. A model has been developed for the passive hydraulic mount and then it is extended to include the MR auxiliary chamber as well. A proof-of-concept prototype of the design has been fabricated which validates the mathematical model. The results demonstrate unique capability of the developed semi-active mount to be used for VDE application.
Phu, D. X.; Choi, S. B.; Lee, Y. S.; Han, M. S.
2014-10-01
This paper presents a new design of a magnetorheological fluid (MR) mount for vibration control considering both vertical forces and horizontal moments such as are met in various engine systems, including a medium high-speed engine of ship. The newly designed mount, called a MR brake mount, offers several salient benefits such as small size and relatively high load capacity compared with a conventional MR engine mount that can control vertical vibration only. The principal design parameters of the proposed mount are optimally determined to achieve maximum torque with geometric and spatial constraints. Subsequently, the proposed MR mount is designed and manufactured based on the optimized design parameters. It is shown from experimental testing that the proposed mount, which combines MR mount with MR brake, can produce the desired force and torque to reduce unwanted vibration of a medium high-speed engine system of ship subjected to both vertical and horizontal exciting motions. In addition, it is verified that there is no large difference between experiment results and simulation results that are obtained from an analytical model derived in this work.
Effect of Confinement on the Aggregation Kinetics of Dilute Magnetorheological Fluids
Shahrivar, Keshvad; Carreón-González, Elizabeth; de Vicente, Juan
2017-10-01
The goal of this study is to investigate the field-driven structuration of model magnetorheological (MR) fluids in narrow gaps (below 1 mm) for high shear applications. With this in mind, we study the influence of confinement in the aggregation kinetics of dilute carbonyl iron suspensions under strong fields (λ ≈ {10}6) in rectangular microchannels using video-microscopy, image analysis and particle level dynamic simulations. Channel widths studied are ranged in the interval [75–1000 μm]. In these particular suspensions the experimental and simulation time scales according to: {t}{{s}}\\propto {λ }-1{φ }2{{D}}-2.614{W}* -0.227, where λ is the Lambda parameter, {φ }2{{D}} is the particle surface fraction and W* is the reduced microchannel width. We show that the effect of channel width is crucial in the dynamic exponent and in the saturation (long time) mean cluster size. In contrast, it has no effect in the onset of the tip-to-tip aggregation process.
Wang, Na; Li, Dong Heng; Li Song, Wan; Chao Xiu, Shi; Zhi Meng, Xiang
2016-10-01
In this paper, the effect of the surface textures of braking disc on the braking performance is experimentally investigated under the conditions of different working gaps and applied currents. For this purpose, a new configuration of magnetorheological fluid brake (MRB) with adjustable working gap is developed to improve the manufacturing accuracy and cost, and to reduce the problem of replacing the braking disc. In addition, the braking discs with three types of surface texture are designed and machined. Based on the test bed developed for the proposed MRB, a series of experiments are carried out on the manufactured prototype and the results are presented to obtain the relationship among the surface texture of the braking disc, applied current, working gap and the braking performance. The results show that the braking torque is significantly influenced by the working gap and surface texture of the braking disc, and the maximum braking torque is obtained on the conditions of 0.25 mm working gap and the braking disc with square surface texture.
Finite Difference Solution of Response Time Delay of Magneto-rhelological Damper
ZOU Mingsong; HOU Baolin
2009-01-01
Magneto-rhelological(MR) dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe manner of operation in cases of failure have made them attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Time response characteristic is one of the most important technical performances of MR dampers, and response time directly affects the control frequency, application range and the actual effect of MR dampers. In this study, one kind of finite difference solution for predicting the response time of magneto-rheological dampers from "off-state" to "on-state" is put forward. A laminar flow model is used to describe the flow in the MR valve, and a bi-viscous fluid flow model is utilized to describe the relationship of shear stress and shear rate of MR fluid. An explicit difference format is used to discretize the Novior-Stoks equation, and stability condition of this algorithm is built by Von-Neumann stability criterion. The pressure gradient along the flow duct is solved by a dichotomy algorithm with iteration, and the changing curve of the damping force versus time of MR damper is obtained as well. According to the abovementioned numerical algorithm, the damping forces versus time curves from "off-state" to "on-state" of a cylindrical piston type MR damper are computed. Moreover, the MR damper is installed in a material test system(MTS), the magnetic field in the wire circles of the MR damper is "triggered" when the MR damper is imposed to do a constant speed motion, and the damping force curves are recorded. The comparison between numerical results and experimental results indicates that this finite difference algorithm can be used to estimate the response time delay of MR dampers.
Yépez, L.D.; Carrillo, J.L. [Instituto de Física de la Universidad Autónoma de Puebla, Ciudad Universitaria, Edif. 110 A, Puebla 72570 (Mexico); Donado, F.; Sausedo-Solorio, J.M.; Miranda-Romagnoli, P. [Instituto de Ciencias Básicas e Ingeniería Universidad Autónoma del Estado de Hidalgo, Pachuca 42090, Pachuca (Mexico)
2016-06-15
The dynamical pattern formation of clusters of magnetic particles in a low-concentration magnetorheological fluid, under the influence of a superposition of two perpendicular sinusoidal fields, is studied experimentally. By varying the frequency and phase shift of the perpendicular fields, this configuration enables us to experimentally analyze a wide range of field configurations, including the case of a pure rotating field and the case of an oscillating unidirectional field. The fields are applied parallel to the horizontal plane where the fluid lies or in the vertical plane. For fields applied in the horizontal plane, we observed that, when the ratio of the frequencies increases, the average cluster size exhibits a kind of periodic resonances. When the phase shift between the fields is varied, the average chain length reaches maximal values for the cases of the rotating field and the unidirectional case. We analyze and discuss these results in terms of a weighted average of the time-dependent Mason number. In the case of a rotating field on the vertical plane, we also observe that the competition between the magnetic and the viscous forces determines the average cluster size. We show that this configuration generates a series of physically meaningful self-organization of clusters and transport phenomena. - Highlights: • A weighted average of the time-dependent Mason number is proposed. • The self-propelling clusters appear when a vertical rotating magnetic field is applied. • The largest average chain lengths are reached when frequencies are multiples one another. • Rotating and unidirectional alternating fields produce the largest average chain length values.
Jönkkäri, I.; Sorvali, M.; Huhtinen, H.; Sarlin, E.; Salminen, T.; Haapanen, J.; Mäkelä, J. M.; Vuorinen, J.
2017-09-01
In this study we have used liquid flame spray (LFS) process to synthetize γ-Fe2O3 nanoparticles of two different average sizes. Different sized nanoparticles were generated with two different liquid precursor feed rates in the spray process, higher feed rate resulting in larger nanoparticles with higher saturation magnetization. The nanoparticles were used in bidisperse magnetorheological fluids to substitute 5% of the micron sized carbonyl iron particles. To our knowledge this is the first time particles synthetized by the LFS method have been used in magnetorheological fluids. The bidisperse fluids showed significantly improved sedimentation stability compared to a monodisperse suspension with the same solid concentration. The tradeoff was an increased viscosity without magnetic field. The effect of the nanoparticles on the rheological properties under external magnetic field was modest. Finally, the dynamic oscillatory testing was used to evaluate the structural changes in the fluids under magnetic field. The addition of nanoparticles decreased the elastic portion of the deformation and increased the viscous portion.
Filip-Vacarescu Norin
2016-03-01
Full Text Available This paper discusses the concept of a hybrid damper made from a combination of two dissipative devices. A passive hysteretic device like steel Buckling Restrained Brace (BRB can be combined with a magneto-rheological (MR Fluid Damper in order to obtain a hybrid dissipative system. This system can work either as a semi-active system, if the control unit is available, or as a passive system, tuned for working according to performance based seismic engineering (PBSE scale of reference parameters (i.e. interstory drift.
Force-electrical characteristics of a novel mini-damper
Li, Junhui; Li, Fei; Tian, Qing; Zhou, Can; Xiao, Chengdi; Huang, Liutian; Wang, Wei; Zhu, Wenhui
2016-10-01
In order to develop small loading and small damping, a small magneto-rheological fluid (MRF) damper with built-in magnetic coils is researched, and the dynamics model of new mini-damper is established based on testing the mechanical properties of the damper. It is found that the damping landing force adjustable range will be best when the damping gap is 1.5 mm. The loading force of the mini-damper is only 1.95 N-8.25 N by adjusting the coil current from 0 A-0.8 A. The smooth damping force is the third-order function with the current by polynomial fitting of the experimental data. The result of dynamics tests shows hysteresis damping characteristics, and an improved nonlinear dynamic model is proposed by combining with the structure characteristics. The parameters of the improved dynamic model are identified by using parameter identification and regression fitting. It will provide the basis for the application of the mini-MRF damper.
Kim, Hwan-Choong; Han, Chulhee; Kim, Pyunghwa; Choi, Seung-Bok
2015-08-01
This work proposes a new approach with which to measure the magnetic flux density using the characteristics of magnetorheological fluid (MRF) that is integrated with a variable resistor. For convenience, it is called a magnetorheological fluid variable resistor (MRF-VR) system in this study. The mechanism of the MRF-VR is based on the interaction between ferromagnetic iron particles of the MRF due to an external magnetic field, which causes its electrical resistance to be field dependent. Using this salient principle, the proposed MRF-VR system is constructed with electrodes and MRF, and its performance is demonstrated by evaluating its electrical resistive characteristics such as dimensional influence, response time, hysteresis and frequency response. After evaluating the performance characteristics, a feedback control system with a proportional-integral-derivative (PID) controller is established, and resistance-trajectory control experiments are carried out. Based on this MRF-VR system, a magnetic field-sensing system is constructed using a Wheatstone bridge circuit, and a polynomial model for calculating the magnetic flux density is formulated from the measured voltage. Finally, the accuracy and effectiveness of the proposed sensing system associated with the empirical polynomial model is successfully verified by comparing the calculated values of magnetic flux density with those measured by a commercial tesla meter.
Arief, Injamamul; Mukhopadhyay, P. K.
2016-01-01
In this paper we performed steady shear and oscillatory magnetorheological (MR) studies in magnetic fluids containing CoNi sub-micron sized clusters of 450 nm in diameter. Such Co-rich nanoclusters were synthesized by conventional homogeneous nucleation without any external surfactant or reducing agent in liquid polyol at elevated temperature. The x-ray diffraction, energy dispersive x-ray analysis, scanning and transmission electron microscopy studies were done for analyzing the sample composition and morphology. Two variants of fluid samples were prepared by dispersing 15 vol% and 20 vol% of CoNi powders in castor oil. Room temperature steady magnetoshear studies indicate viscoplastic behavior with stronger dependence of static yield stress on magnetization than a dipolar coupling that was operational in the dynamic yield stress. Magnetosweep measurements at constant shear rate showed interesting viscous relaxation at high magnetic fields. We also explored dynamical elastic behavior through oscillatory magnetorheological studies under both strain sweep and frequency sweep modes, and showed glass transition like phenomenon occurring in them above critical shear amplitudes.
H. P. Jagadish
2013-01-01
Full Text Available Squeeze film dampers are novel rotor dynamic devices used to alleviate small amplitude, large force vibrations and are used in conjunction with antifriction bearings in aircraft jet engine bearings to provide external damping as these possess very little inherent damping. Electrorheological (ER fluids are controllable fluids in which the rheological properties of the fluid, particularly viscosity, can be controlled in accordance with the requirements of the rotor dynamic system by controlling the intensity of the applied electric field and this property can be utilized in squeeze film dampers, to provide variable stiffness and damping at a particular excitation frequency. The paper investigates the effect of temperature and electric field on the apparent viscosity and dynamic (stiffness and damping characteristics of ER fluid (suspension of diatomite in transformer oil using the available literature. These characteristics increase with the field as the viscosity increases with the field. However, these characteristics decrease with increase in temperature and shear strain rate as the viscosity of the fluid decreases with temperature and shear strain rate. The temperature is an important parameter as the aircraft jet engine rotors are located in a zone of high temperature gradients and the damper fluid is susceptible to large variations in temperature.
Modeling of Semi-Active Vehicle Suspension with Magnetorhological Damper
Hasa Richard
2014-12-01
Full Text Available Modeling of suspension is a current topic. Vehicle users require both greater driving comfort and safety. There is a space to invent new technologies like magnetorheological dampers and their control systems to increase these conflicting requirements. Magnetorheological dampers are reliably mathematically described by parametric and nonparametric models. Therefore they are able to reliably simulate the driving mode of the vehicle. These simulations are important for automotive engineers to increase vehicle safety and passenger comfort.
Modeling of Semi-Active Vehicle Suspension with Magnetorhological Damper
Hasa, Richard; Danko, Ján; Milesich, Tomáš; Magdolen, Ľuboš
2014-12-01
Modeling of suspension is a current topic. Vehicle users require both greater driving comfort and safety. There is a space to invent new technologies like magnetorheological dampers and their control systems to increase these conflicting requirements. Magnetorheological dampers are reliably mathematically described by parametric and nonparametric models. Therefore they are able to reliably simulate the driving mode of the vehicle. These simulations are important for automotive engineers to increase vehicle safety and passenger comfort.
Improving the critical speeds of high-speed trains using magnetorheological technology
Sun, Shuaishuai; Deng, Huaxia; Li, Weihua; Du, Haiping; Qing Ni, Yi; Zhang, Jin; Yang, Jian
2013-11-01
With the rapid development of high-speed railways, vibration control for maintaining stability, passenger comfort, and safety has become an important area of research. In order to investigate the mechanism of train vibration, the critical speeds of various DOFs with respect to suspension stiffness and damping are first calculated and analyzed based on its dynamic equations. Then, the sensitivity of the critical speed is studied by analyzing the influence of different suspension parameters. On the basis of these analyses, a conclusion is drawn that secondary lateral damping is the most sensitive suspension damper. Subsequently, the secondary lateral dampers are replaced with magnetorheological fluid (MRF) dampers. Finally, a high-speed train model with MRF dampers is simulated by a combined ADAMS and MATLAB simulation and tested in a roller rig test platform to investigate the mechanism of how the MRF damper affects the train’s stability and critical speed. The results show that the semi-active suspension installed with MRF dampers substantially improves the stability and critical speed of the train.
Pang, J. N. I.; Harno, H. G.; Lee, V. C. C.
2017-07-01
An on-off skyhook semi-active control strategy via MR damper is proposed in this study to enhance the performance of a two degree-of-freedom (DOF) airfoil-based energy harvester. For simplicity, only the plunge mode of the airfoil model is examined. NACA0012 airfoil is selected as the vibrating body where energy is harvested and converted into electricity via piezoelectric transduction. Behavioural performance of an actual MR damper is represented numerically with MATLAB/SIMULINK blocks of a conventional Bouc-Wen model. Simulation of the airfoil model is also performed on MATLAB to acquire its dynamic responses. A comparison between passive and semi-actively controlled airfoil systems demonstrates that the proposed strategy is superior in three different aspects - versatility, energy harvesting and sustaining structural integrity.
WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi
2008-01-01
The design and analysis of an intelligent vehicle suspension with MR dampers should address hybrid semi-active control goals, such as rejection of current-switching discontinuity and MR-damper hysteresis, asymmetric damping from the symmetric MR-damper design, robustness on the vehicle operation parameter uncertainties and consideration of essential multiple suspension goals. Following the proposed skyhook-based asymmetric semi-active controller (Part Ⅰ) for achieving the above goals, herein, a set of suspension performance measures and three kinds of varying amplitude harmonic, rounded pulse and really measured random excitations are systematically defined, and the sensitivity of quarter-vehicle MR-suspension performance to variations in operating conditions is thoroughly analyzed. The results illustrate that the proposed skyhook-based semi-active MR-suspension in the asymmetric mode yields relatively superior dynamic responses to meet the multiple suspension performances of ride, rattle space, road-holding and dynamic tire force transmitted to the pavement, and has desirable robustness on variations in operating conditions of vehicle load and speed and the road roughness.
Viscous-Fluid-Spring Damper Retrofit of a Steel Moment Frame Structure
Hussain, Saif; Van Benschoten, Paul; Al Satari, Mohamed; Lin, Silian
2008-07-01
The subject building is a peculiar pre-Northridge steel moment resisting frame building. Upon investigating the existing lateral resisting system, numerous significant deficiencies were identified; inherent lack of redundancy, poor geometry and inadequate stiffness of the lateral resisting system. All of which resulted in an extremely soft 5-story structure with a primary torsional mode of vibration at T1 = 5.46 s. Significant structural modifications were deemed necessary to meet the "life-safety" performance objective as outlined in rehabilitation standards such as ASCE 41. Both increased stiffness and damping were required to adequately retrofit the building. Furthermore, adjacent building separation as well as deformation compatibility issues needed to be addressed and resolved. A three-dimensional computer model of the building was created using ETABS mathematically simulating the building's dynamic characteristics in its current condition. Multiple seismic retrofit systems were investigated such as Buckling Restrained Braced Frames (BRBF's). However, based on the performance effectiveness and constructability of the retrofit schemes studied, the Viscous-Fluid-Spring Damper (VFSD) system was proposed as the "optimum" solution for the building. The VFSD, was chosen because it combines the relatively compact size and minimally invasive constructability with the required properties (an elastomeric spring in parallel with a nonlinear velocity dependent viscous damper). A site-specific response spectrum was developed for the Design Basis Earthquake (DBE, 475 year return period) event, and three pairs of representative earthquake horizontal ground motion time-histories were scaled to match this DBE. The proposed scheme reduced the building maximum inter-story drift ratio from 5.4% to about 1%. Similarly, the maximum roof displacement was reduced by about 70% (23" to 7").
寇发荣
2015-01-01
For further improving vehicle ride comfort,a magneto-rheological damper for vehicle semi-active seat suspension is developed with its damping characteristic test conducted. After analyzing its force bearing condi-tion, a dynamics model for vehicle semi-active seat suspension is built, a corresponding skyhook control strategy is devised, and a simulation is performed on the skyhook control of seat under both random and sinusoidal excitation inputs. Meanwhile a physical prototype of semi-active seat suspension with magneto-rheological damper and its test bench system are developed with corresponding bench test carried out. The results indicate that the results of simu-lation basically well agree with test data and the magneto-rheological damper developed has a good damping control-lability. Compared to original passive seat suspension, the dynamic performances of vehicle semi-active seat with magneto-rheological damper are improved by some 30% with a significant effect of vibration attenuation.%为进一步提高汽车的乘坐舒适性，研发了一种汽车座椅半主动悬架用磁流变减振器，并对其进行阻尼特性试验，通过分析其受力情况，建立了汽车半主动座椅悬架动力学模型，设计了用于座椅磁流变半主动悬架的天棚控制策略，并在随机和正弦激励输入下进行了座椅天棚控制仿真计算，试制了磁流变半主动座椅物理样机及试验台架系统，开展了磁流变半主动座椅悬架的台架试验研究。结果表明，理论仿真和试验结果基本吻合，磁流变减振器阻尼可控性好；相对于被动座椅悬架，采用磁流变半主动座椅悬架后，座椅动态性能改善了30%左右，磁流变半主动座椅悬架减振效果显著。
Xinhua Liu
2017-07-01
Full Text Available In order to improve the response performance of a proportion integration differentiation (PID controller for magnetorheological fluids (MRF brake and to reduce the braking fluctuation rate, an improved fruit fly optimization algorithm for PID controller parameters tuning of MRF brake is proposed. A data acquisition system for MRF brake is designed and the transfer function of MRF brake is identified. Moreover, an improved fruit fly optimization algorithm (IFOA through integration of PID control strategy and cloud model algorithm is proposed to design a PID controller for MRF brake. Finally, the simulation and experiment are carried out. The results show that IFOA, with a faster response output and no overshoot, is superior to the conventional PID and fruit fly optimization algorithm (FOA PID controller.
Jaime Rodriguez-López
2015-12-01
Full Text Available This work proposes the use of quartz crystal microbalances (QCMs as a method to analyze and characterize magnetorheological (MR fluids. QCM devices are sensitive to changes in mass, surface interactions, and viscoelastic properties of the medium contacting its surface. These features make the QCM suitable to study MR fluids and their response to variable environmental conditions. MR fluids change their structure and viscoelastic properties under the action of an external magnetic field, this change being determined by the particle volume fraction, the magnetic field strength, and the presence of thixotropic agents among other factors. In this work, the measurement of the resonance parameters (resonance frequency and dissipation factor of a QCM are used to analyze the behavior of MR fluids in static conditions (that is, in the absence of external mechanical stresses. The influence of sedimentation under gravity and the application of magnetic fields on the shifts of resonance frequency and dissipation factor were measured and discussed in the frame of the coupled resonance produced by particles touching the QCM surface. Furthermore, the MR-fluid/QCM system has a great potential for the study of high-frequency contact mechanics because the translational and rotational stiffness of the link between the surface and the particles can be tuned by the magnetic field.
叶光湖; 吴光强
2015-01-01
Based on the stiffness test of air spring, a half vehicle vertical vibration model is established. Then, according to the characteristics of skyhook control and groundhook control, a combined control strategy for semi-active air suspension with magneto-rheological ( MR) damper is designed. The performances of suspension sys-tems with different control strategies are simulated with Matlab/Simulink. The comparison on the results of simula-tions in both time and frequency domains show that with combined control strategy, not only the ride comfort of vehi-cle can be enhanced, but also the handling stability of vehicle can be ensured, leading to the improvement of overall performance of vehicle.%根据空气弹簧刚度试验，建立了1/2汽车垂向振动模型。进而，依据天棚控制和地棚控制特点，设计了汽车磁流变减振器半主动空气悬架综合控制策略。在Matlab/Simulink环境下对带有不同控制策略的悬架系统进行性能仿真。对比时、频域仿真结果表明：采用综合控制策略不仅能提高汽车平顺性，且能保证汽车的操纵稳定性，使车辆综合性能得到改善。
Seismic energy dissipation study of linear fluid viscous dampers in steel structure design
A. Ras
2016-09-01
Full Text Available Energy dissipation systems in civil engineering structures are sought when it comes to removing unwanted energy such as earthquake and wind. Among these systems, there is combination of structural steel frames with passive energy dissipation provided by Fluid Viscous Dampers (FVD. This device is increasingly used to provide better seismic protection for existing as well as new buildings and bridges. A 3D numerical investigation is done considering the seismic response of a twelve-storey steel building moment frame with diagonal FVD that have linear force versus velocity behaviour. Nonlinear time history, which is being calculated by Fast nonlinear analysis (FNA, of Boumerdes earthquake (Algeria, May 2003 is considered for the analysis and carried out using the SAP2000 software and comparisons between unbraced, braced and damped structure are shown in a tabulated and graphical format. The results of the various systems are studied to compare the structural response with and without this device of the energy dissipation thus obtained. The conclusions showed the formidable potential of the FVD to improve the dissipative capacities of the structure without increasing its rigidity. It is contributing significantly to reduce the quantity of steel necessary for its general stability.
Seismic Retrofitting of an Existing Steel Railway Bridge by Fluid Viscous Dampers
Gangopadhyay, Avijit; Ghosh, Aparna Dey
2016-06-01
There are over a lakh of bridges in the Indian Railways, many of which have become seismically deficient, either through aging or due to inadequate seismic design considerations. The extensive damage of bridges all over the world in recent earthquakes has propelled significant advancement in earthquake protection and retrofitting of bridges. Amongst various passive control systems that are reliable as well as cost-effective, Fluid Viscous Dampers (FVDs) are proving to be successful in bridge vibration control. Orificed FVDs, commercially available as Taylor Devices, have already been successfully installed in several bridges worldwide. However, there has been no such application or study related to Indian railway bridges. In this paper, an existing thirty years' old railway bridge in Jharkhand, India, has been analyzed in SAP2000v14 considering reduced stiffness and found deficient when subjected to spectrum-compatible accelerograms. Subsequent retrofitting of the bridge superstructure with FVDs has been carried out and the results indicate substantial reductions in the responses of the bridge deck.
Seismic Retrofitting of an Existing Steel Railway Bridge by Fluid Viscous Dampers
Gangopadhyay, Avijit; Ghosh, Aparna Dey
2016-09-01
There are over a lakh of bridges in the Indian Railways, many of which have become seismically deficient, either through aging or due to inadequate seismic design considerations. The extensive damage of bridges all over the world in recent earthquakes has propelled significant advancement in earthquake protection and retrofitting of bridges. Amongst various passive control systems that are reliable as well as cost-effective, Fluid Viscous Dampers (FVDs) are proving to be successful in bridge vibration control. Orificed FVDs, commercially available as Taylor Devices, have already been successfully installed in several bridges worldwide. However, there has been no such application or study related to Indian railway bridges. In this paper, an existing thirty years' old railway bridge in Jharkhand, India, has been analyzed in SAP2000v14 considering reduced stiffness and found deficient when subjected to spectrum-compatible accelerograms. Subsequent retrofitting of the bridge superstructure with FVDs has been carried out and the results indicate substantial reductions in the responses of the bridge deck.
Reji John
2016-06-01
Full Text Available An intelligent semi-active anti-vibration mount using a magnetorheological (MR fluid is designed and developed for onboard applications. The mount consists of a load bearing elastomer, MR fluid chamber; MEMS based vibration sensor and a controller for closed loop feedback mechanism. The controller regulates the solenoid current in the MR fluid chamber, which in turn regulates the flow of MR fluid through the valve. Comparison of the performance of MR mount with a passive resilient rubber mount shows that the former provides 7 dB extra damping at resonance compared to the later and the isolation of MR mount starts at 10 Hz compared to 50 Hz by rubber mount. This mount can operate in real time, passive and active modes by using a closed loop feedback control mechanism. The efficacy of the mount for outdoor applications is evaluated by characterizing the mechanical, environmental, electrical and electromagnetic properties as per MIL-17185, JSS-55555 and IEC 61000 standards and found to be superior compared to passive mounts. The mount is being evaluated for onboard applications in INS Ranvijay.
Segla, S.
The paper deals with modelling and optimization of the half model of a passenger car with an ideal semi-active suspension, semi-active suspension equipped with magnetorheological dampers, passive suspension equipped with hydraulic dampers without control and compares their dynamic characteristics. The conventional skyhook control is used to control semi-active dampers taking into account the time delay. Selected parameters of the suspension systems are optimized for given road profiles using genetic algorithms. The results show that implementation of the magnetorheological dampers can lead to a significant improvement of the ride comfort and handling properties of passenger cars provided that the time delay is low enough.
Wang, Peng-yi; Wang, Zhong-jin, E-mail: wangzj@hit.edu.cn
2016-12-01
Magnetorheological fluid (MR fluid), a kind of smart material, has been used as a new pressure-carrying medium in magnetorheological pressure forming (MRPF). The mechanical property of MR fluid under the pressure significantly affects the sheet formability. However, there is little knowledge on the deformation behavior of MR fluid under three-dimensional stress states. In this paper, a new procedure via a combination of extrusion test and FEM simulation has been proposed to determine the flow stress of MR fluids. The experimental device for extrusion test of MR fluids was designed. The flow stresses of a MR fluid (MRF-J01T) under four different magnetic fields were determined through the proposed procedure. In addition, the obtained flow stresses were used in the following FEM simulations to verify the accuracy by comparing with the experimental results. The simulation results were in good agreement with the experimental data, which supports the correctness and practicability of the proposed method. - Highlights: • An effective procedure is proposed to determine the flow stress of MR fluids. • The rheological behaviour of a MR fluid during extrusion tests is studied. • Flow stress curves of a MR fluid under different magnetic fields are obtained.
Lee, Ho-Young; Kang, In Man; Shon, Chae-Hwa; Lee, Se-Hee
2015-05-01
A variable inductor with magnetorheological (MR) fluid has been successfully applied to power electronics applications; however, its thermal characteristics have not been investigated. To evaluate the performance of the variable inductor with respect to temperature, we measured the characteristics of temperature rise and developed a numerical analysis technique. The characteristics of temperature rise were determined experimentally and verified numerically by adopting a multiphysics analysis technique. In order to accurately estimate the temperature distribution in a variable inductor with an MR fluid-gap, the thermal solver should import the heat source from the electromagnetic solver to solve the eddy current problem. To improve accuracy, the B-H curves of the MR fluid under operating temperature were obtained using the magnetic property measurement system. In addition, the Steinmetz equation was applied to evaluate the core loss in a ferrite core. The predicted temperature rise for a variable inductor showed good agreement with the experimental data and the developed numerical technique can be employed to design a variable inductor with a high-frequency pulsed voltage source.
Lee, Ho-Young; Kang, In Man, E-mail: imkang@ee.knu.ac.kr [School of Electronics Engineering, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Shon, Chae-Hwa [Korea Electrotechnology Research Institute, Changwon 642-120 (Korea, Republic of); Lee, Se-Hee, E-mail: shlees@knu.ac.kr [Department of Electrical Engineering, Kyungpook National University, Daegu 702-701 (Korea, Republic of)
2015-05-07
A variable inductor with magnetorheological (MR) fluid has been successfully applied to power electronics applications; however, its thermal characteristics have not been investigated. To evaluate the performance of the variable inductor with respect to temperature, we measured the characteristics of temperature rise and developed a numerical analysis technique. The characteristics of temperature rise were determined experimentally and verified numerically by adopting a multiphysics analysis technique. In order to accurately estimate the temperature distribution in a variable inductor with an MR fluid-gap, the thermal solver should import the heat source from the electromagnetic solver to solve the eddy current problem. To improve accuracy, the B–H curves of the MR fluid under operating temperature were obtained using the magnetic property measurement system. In addition, the Steinmetz equation was applied to evaluate the core loss in a ferrite core. The predicted temperature rise for a variable inductor showed good agreement with the experimental data and the developed numerical technique can be employed to design a variable inductor with a high-frequency pulsed voltage source.
Heo, Gwanghee; Lee, Giu; Jeon, Joon-Ryong; Lee, WooSang
2006-03-01
Magneto-rheological fluid is the fluid which is controllable with applied magnetic fields. This fluid is effective as a semiactive control device such as MR damper. In this paper, a new MR technology is developed with squeeze mode smart damper. And various dynamic tests are performed to identify the dynamic characteristics of this device. This squeeze mode smart damper can be used permanently, and can be freely allocated at the sub-region of large structures such as buildings and civil engineering infrastructures. Various dynamic tests are carried out to evaluate the performance of the squeeze mode smart damper in many loading conditions. Force-displacement and force-velocity hysteresis loops are also investigated for evaluation of its dynamic performance. In order to predict the dynamic performance of this device, two types of analytical models are compared with experimental results. A power model based on the damping and velocity, and a Bingham model are adopted in the viewpoint of practical usage. These results verify that the developed smart damper is effective in semi-active control of civil structures.
马然; 朱思洪; 伊力达尔; 史俊龙; TalpurMA
2012-01-01
Aiming to the problem of poor performance of tractor vibration, a flow pattern was developed on the basis of a damping force mathematical model, which was presented with analyzing working pattern of the magnetorheological damper(MRD). According to working requirements of large wheel tractor front axle suspension, a single outstretch pole MRD was designed. Experiments were conducted to assess the impact of input current and the excitation rate on the shock absorber damping force. It is observed that the damping force controllable ratio reaches 5.9 in low speed situation. Whereas, it increases with the applied current to its peak value of 1.8 A and the maximum output damping force reaches at 1 370 N. Perceived results justify the validity of the design, and provide the evidence for controlling semi-active air suspension with adjustable damping.%针对拖拉机减振性能差的问题,在分析车辆磁流变减振器工作模式基础上,建立了基于流动模式的阻尼力理论计算模型.根据某大功率轮式拖拉机前桥悬架减振器的工作要求,研制了一种单出杆磁流变减振器.试验研究了输入电流和激励速度对减振器阻尼力的影响.试验结果表明:在低速情况下,阻尼力可控倍数达5.9；减振器饱和工作电流约1.8A,最大输出阻尼力约1370N.试验验证了所提设计思路和方法的有效性,并为阻尼可调式半主动空气悬架的控制研究提供了依据.
Hierarchical fuzzy identification of MR damper
Wang, Hao; Hu, Haiyan
2009-07-01
Magneto-rheological (MR) dampers, recently, have found many successful applications in civil engineering and numerous area of mechanical engineering. When an MR damper is to be used for vibration suppression, an inevitable problem is to determine the input voltage so as to gain the desired restoring force determined from the control law. This is the so-called inverse problem of MR dampers and is always an obstacle in the application of MR dampers to vibration control. It is extremely difficult to get the inverse model of MR damper because MR dampers are highly nonlinear and hysteretic. When identifying the inverse model of MR damper with simple fuzzy system, there maybe exists curse of dimensionality of fuzzy system. Therefore, it will take much more time, and even the inverse model may not be identifiable. The paper presents two-layer hierarchical fuzzy system, that is, two-layer hierarchical ANFIS to deal with the curse of dimensionality of the fuzzy identification of MR damper and to identify the inverse model of MR damper. Data used for training the model are generated from numerical simulation of nonlinear differential equations. The numerical simulation proves that the proposed hierarchical fuzzy system can model the inverse model of MR damper much more quickly than simple fuzzy system without any reduction of identification precision. Such hierarchical ANFIS shows the higher priority for the complicated system, and can also be used in system identification and system control for the complicated system.
Ma Junjin; Zhang Dinghua; Wu Baohai; Luo Ming; Chen Bing
2016-01-01
Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular can-tilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler–Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the pro-duct of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equa-tion of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests.
Positioning magnetorheological actuator
Mikhailov, Valery; Bazinenkov, Alexey; Akimov, Igor [Bauman Moscow State Technical University, 2-nd Baumanskaia st. 5, MT-11, 105005, Moscow (Russian Federation); Borin, Dmitry [Technische Universitaet Dresden, Chair of Magnetofluiddynamics, 01062, Dresden (Germany)], E-mail: mikhailov@bmstu.ru
2009-02-01
In this work we consider a construction of a positioning magnetorheological actuator based on bellow units, as well as dynamical model, which include such elements as a magnetically hysteresis, pressure loses in hydraulic system, nonlinearity of rheological behaviour of working fluid. Two operating modes of positioning actuator are taken into account and transients are presented. Dynamical modelling shows possibility for the improvement of a real control system and ensure of submicron precision of positioning with millisecond time of response.
Dominguez-Nuñez, L. A.; Silva-Navarro, G.
2014-04-01
The general study and applications of Magneto-Rhelogical (MR) dampers have been spread in the lasts years but only some studies have been focusing on the vibration control problems on rotor-bearings systems. Squeeze-Film Dampers (SFD) are now commonly used to passively control the vibration response on rotor-bearing systems because they can provide flexibility, damping and extend the so-called stability thresholds in rotating machinery. More recently, SFD are combined with MR or Electro-Rheological (ER) fluids to introduce a semiactive control mechanism to modify the rotordynamic coefficients and deal with the robust performance of the overall system response for higher operating speeds. There are, however, some theoretical and technological problems that complicate their extensive use, like the relationship between the centering spring flexibility and the rheological behavior of the smart fluid to produce the SFD forces. In this work it is considered a SFD with MR fluid and a set of circular section beams in a squirrel cage arrangement in combination with latex seals as centering springs. The mathematical model analysis includes the controllable viscoelastic properties associated to the MR fluid. The characterization of the SFD is made by the determination of some coefficients associated with a modified Choi-Lee-Park polynomial model. During the analysis is considered a rotor-bearing system modeled using finite element methods. The SFD with MR fluid is connected to an experimental platform to validate and experimentally evaluate the overall system. Finally, to improve the open-loop system performance, a methodology for the use of different control schemes is proposed.
Physical therapy applications of MR fluids and intelligent control
Dong, Shufang; Lu, Ke-Qian; Sun, J. Q.; Rudolph, Katherine
2005-05-01
Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents an optimal design of magneto-rheological fluid dampers for variable resistance exercise devices. Adaptive controls for regulating the resistive force or torque of the device as well as the joint motion are presented. The device provides both isometric and isokinetic strength training for various human joints.
Synthesis and characterization of magneto-rheological (MR fluids for MR brake application
Bhau K. Kumbhar
2015-09-01
Full Text Available Magneto rheological (MR fluid technology has been proven for many industrial applications like shock absorbers, actuators, etc. MR fluid is a smart material whose rheological characteristics change rapidly and can be controlled easily in presence of an applied magnetic field. MR brake is a device to transmit torque by the shear stress of MR fluid. However, MR fluids exhibit yield stress of 50–90 kPa. In this research, an effort has been made to synthesize MR fluid sample/s which will typically meet the requirements of MR brake applications. In this study, various electrolytic and carbonyl iron powder based MR fluids have been synthesized by mixing grease as a stabilizer, oleic acid as an antifriction additive and gaur gum powder as a surface coating to reduce agglomeration of the MR fluid. MR fluid samples based on sunflower oil, which is bio-degradable, environmentally friendly and abundantly available have also been synthesized. These MR fluid samples are characterized for determination of magnetic, morphological and rheological properties. This study helps identify most suitable localized MR fluid meant for MR brake application.
Zapoměl J.
2013-12-01
Full Text Available Unbalance is the principal source of increase of time varying forces transmitted between the rotor and its stationary part. Their magnitudes can be considerably reduced if the rotor is flexibly suspended and if the damping devices are added to the support elements. Their damping effect must be high for low rotor velocities and small for velocities approximately higher than the critical one to minimize the transmitted forces and the vibrations amplitude. This implies to achieve maximum efficiency of the damping elements, their damping effect has to be adaptable to the current operating conditions. Such technological solution is offered by application of a squeeze film magnetorheological damper. Its hybrid variant consisting of two damping units (one controllable in a serial arrangement is investigated in this paper. The damping takes place in two concentric lubricating films formed by normal and magnetorheological oils. The damper is equipped with an electric coil generating magnetic flux passing through the layer of the magnetorheological fluid. As resistance against its flow depends on magnetic induction, changing magnitude of the applied current enables to control the damping force. In the computational model, the rotor is considered to be absolutely rigid, unbalanced and the damping elements are represented by force couplings. The goal of the analysis is to study influence of the investigated magnetorheological damper on behaviour of a rigid rotor during different transient regimes. A special attention is focused on passing the rotor through the critical speed and on planning the dependence of the applied current on speed of the rotor rotation to achieve the optimum compromise between minimizing the transmitted forces and maximum attenuation of the rotor vibrations.
Development of Magnetorheological Fluids Based Haptic Display Systems%基于磁流变液的力/触觉再现系统研究进展
文辞; 宋爱国; 王爱民
2009-01-01
力/触觉再现技术是当前新兴的研究领域.介绍了最近10年来基于磁流变液的力/触觉再现系统的国内外研究进展情况.总结了基于磁流变液的力/触觉再现技术的研究内容,包括执行装置的结构设计、模型研究以及再现系统控制研究,讨论了基于磁流变液的力/触觉再现系统开发过程中的关键技术.如提高便携式触觉接口中执行装置的力矩/重量比.减小静态力、克服被动系统力/触觉表达局限性,指出了今后发展的趋势.阐述了基于磁流变液的力/触觉再现系统的优势,并展望了其应用前景.%The haptic display technology is a frontier research area currently. The developments of magneto-rheological fluids based haptic display systems in the last decade are introduced. Magnetorheological fluids based haptic display technique includes actuator design, modeling and display system control, some key issues are discussed, such as a high torque/weight ratio in portable haptie interfaces, a low static force and a limita-tion on presenting haptic of passive type systems. And the developing direction of a magnetorheological fluids based haptic display system in the future is pointed out. Finally the advantages of the system are presented and the application prospect is forecasted.
Arief, Injamamul; Mukhopadhyay, P.K., E-mail: pkm@bose.res.in
2016-01-01
In this paper we performed steady shear and oscillatory magnetorheological (MR) studies in magnetic fluids containing CoNi sub-micron sized clusters of 450 nm in diameter. Such Co-rich nanoclusters were synthesized by conventional homogeneous nucleation without any external surfactant or reducing agent in liquid polyol at elevated temperature. The x-ray diffraction, energy dispersive x-ray analysis, scanning and transmission electron microscopy studies were done for analyzing the sample composition and morphology. Two variants of fluid samples were prepared by dispersing 15 vol% and 20 vol% of CoNi powders in castor oil. Room temperature steady magnetoshear studies indicate viscoplastic behavior with stronger dependence of static yield stress on magnetization than a dipolar coupling that was operational in the dynamic yield stress. Magnetosweep measurements at constant shear rate showed interesting viscous relaxation at high magnetic fields. We also explored dynamical elastic behavior through oscillatory magnetorheological studies under both strain sweep and frequency sweep modes, and showed glass transition like phenomenon occurring in them above critical shear amplitudes. - Highlights: • A typical polymer/surfactant free polyol reduction method was used to synthesize large-scale Co{sub 0.9}Ni{sub 0.1} nanoclusters. • Room temperature rate-dependent magnetorheology of CoNi-nanoclusters based MR fluids revealed viscoplastic behavior. • Magnetic fields were replaced by powder particle magnetization (M) for better yield stress scaling. • In addition to previously reported M{sup 2}-dependence, higher order relations (~M{sup 3}) were also noted for static yield stress. • An interesting viscous relaxation phenomenon occurred at higher magnetic fields.
Salzman, S.; Romanofsky, H. J.; Clara, Y. I.; Giannechini, L. J.; West, Garrett J.; Lambropoulos, J. C.; Jacobs, S. D.
2013-09-01
Magnetorheological finishing (MRF) of polycrystalline, chemical-vapor-deposited (CVD) zinc sulfide (ZnS) and zinc selenide (ZnSe) can leave millimeter-size artifacts on the part surface. These pebble-like features come from the anisotropic mechanical and chemical properties of the ceramic material and from the CVD growth process itself. The resulting surface texture limits the use of MRF for polishing aspheric and other complex shapes using these important infrared (IR) ceramics. An investigation of the individual contributions of chemistry and mechanics to polishing of other polycrystalline ceramics has been employed in the past to overcome similar material anisotropy problems. The approach taken was to study the removal process for the different single-crystal orientations that comprise the ceramic, making adjustments to mechanics (polishing abrasive type and concentration) and polishing slurry chemistry (primarily pH) to equalize the removal rate for all crystal orientations. Polishing with the modified slurry was shown to prevent the development of surface texture. Here we present mechanical (microhardness testing) and chemical (acid etching) studies performed on the four single-crystal orientations of ZnS: 100, 110, 111, and 311. We found that the (111) plane is 35% to 55% harder and 30% to 40% more resistant to chemical etching than the other three planes. This relatively high degree of variation in these properties can help to explain the surface texture developed from MRF of the polycrystalline material. Theoretical calculations of microhardness, planar, and bond densities are presented and compared with the experimental data. Here surface characterization of these single-crystal orientations of ZnS for material removal and roughness with chemically modified MR fluids at various pH levels between pH 4 and pH 6 are presented for the first time.
Magneto-rheological defects and failures: A review
Wahid, SA; Ismail, I.; Aid, S.; Rahim, MSA
2016-02-01
Magneto-rheological fluid is the colloidal suspension of micron sized magnetic particles in a carrier fluid where defects and failures occur at many circumstances. This paper presents a review on defects and failures of magneto-rheological fluid in engineering applications. The most significant defect is hard cake which developed due to re-dispersion difficulties of remnant particles magnetization, leaving the magneto-rheological fluid ineffective. Clumping effect on the other hand is a separation of carrier fluid from the magnetic particles when magneto-rheological fluid is being exposed to higher magnetic field for an extended period of time. As clumping occurred, it leads to Fluid Particle Separation (FPS) which is believed altering the strength distribution of magneto-rheological fluid and therefore reducing the squeezing force. Another significant failure is magnetic particles oxidation of the magneto-rheological fluid. This paper also will discuss on stability problems which is the most challenged issue in magneto-rheological fluid technology. With the comprehensive review in this paper, researcher can design materials of magneto-rheological fluid for better properties.
Damping Force Tracking Control of MR Damper System Using a New Direct Adaptive Fuzzy Controller
Xuan Phu Do
2015-01-01
Full Text Available This paper presents a new direct adaptive fuzzy controller and its effectiveness is verified by investigating the damping force tracking control of magnetorheological (MR fluid based damper (MR damper in short system. In the formulation of the proposed controller, a model of interval type 2 fuzzy controller is combined with the direct adaptive control to achieve high performance in vibration control. In addition, H∞ (H infinity tracking technique is used in building a model of the direct adaptive fuzzy controller in which an enhanced iterative algorithm is combined with the fuzzy model. After establishing a closed-loop control structure to achieve high control performance, a cylindrical MR damper is adopted and damping force tracking results are obtained and discussed. In addition, in order to demonstrate the effectiveness of the proposed control strategy, two existing controllers are modified and tested for comparative work. It has been demonstrated from simulation and experiment that the proposed control scheme provides much better control performance in terms of damping force tracking error. This leads to excellent vibration control performance of the semiactive MR damper system associated with the proposed controller.
Theoretical and experimental study of magneto-rheological fluid disc brake
E.M. Attia
2017-06-01
The fluid is inserted between the rotating and fixed discs and a magnetic field is imposed on the fluid. In this paper, a complete test rig for an MR fluid disc brake is introduced. Experiments are conducted to measure the braking torque and speed of shaft during braking process and the results are presented at different voltage input to the brake. Also theoretical analysis for both MR brake and the mechanical system is developed and is solved numerically using finite difference method and Matlab software. Effect of current input to the MR brake, viscosity of fluid and design parameters is taken into consideration. A validation of the theoretical results with CFD model is introduced. The experimental results are performed and both angular velocity and the braking torque are obtained as responses during the braking process. A comparison between braking torques obtained from theoretical and experimental work shows agreement when voltage is 2 V at speed of 150 rpm and also agreement when voltage is 2 and 3 V at speed of 250 rpm.
Jin, Dejiang; Chen, Jiaqi; Huang, Jun
1998-01-01
According to the properties of Electro-Rheological/Magneto- Rheological Fluid (ER/MR fluid), a device whose stiffness can be adjusted by electric field and/or magnetic field was designed. The basic mechanical properties were analyzed theoretically. The relation of resistance of piston movement to sped of piston movement is discussed, especially asymptotically relation of slow moving and to fast moving was given. And the basic mechanical properties was tested actually. The stiffness of element combined a device with a spring was characterized with accumulation of energy of the unit in vibration. And then the character of stiffness change of the device element with change of yield stress of ER/MR fluid was discussed. The method of optimizing parameters to improve control capability for some condition was discussed. The results indicate that the device is an effective controllable stiffness element. For a controllable stiffness element, its best working state is that its critical resistance is nearly equal to vibration force. For the device used for high frequency, the duct with a larger width and gap is recommended. But for the device demanding large critical force, as used in civil engineering, the duct with larger length and smaller gap is recommended.
Adaptive Vibration Control System for MR Damper Faults
Juan C. Tudón-Martínez
2015-01-01
Full Text Available Several methods have been proposed to estimate the force of a semiactive damper, particularly of a magnetorheological damper because of its importance in automotive and civil engineering. Usually, all models have been proposed assuming experimental data in nominal operating conditions and some of them are estimated for control purposes. Because dampers are prone to fail, fault estimation is useful to design adaptive vibration controllers to accommodate the malfunction in the suspension system. This paper deals with the diagnosis and estimation of faults in an automotive magnetorheological damper. A robust LPV observer is proposed to estimate the lack of force caused by a damper leakage in a vehicle corner. Once the faulty damper is isolated in the vehicle and the fault is estimated, an Adaptive Vibration Control System is proposed to reduce the fault effect using compensation forces from the remaining healthy dampers. To fulfill the semiactive damper constraints in the fault adaptation, an LPV controller is designed for vehicle comfort and road holding. Simulation results show that the fault observer has good performance with robustness to noise and road disturbances and the proposed AVCS improves the comfort up to 24% with respect to a controlled suspension without fault tolerance features.
Xu, Lei; Wang, Dai-Hua; Fu, Qiang; Yuan, Gang; Hu, Lei-Zi
2016-11-01
In this paper, the principle and structure of the four-bar linkage prosthetic knee based on the magnetorheological effect (FLPKME) are proposed and realized by individually integrating the upper and lower link rods of the four-bar linkage with the piston rod and the outer cylinder of the magnetorheological (MR) damper. The integrated MR damper, in which the MR fluid is operated in the shear mode, has a double-ended structure. The prototype of the FLPKME is designed and fabricated. Utilizing the developed FLPKME, the lower limb prosthesis is developed, modeled, and simulated. On these bases, the control algorithm for the FLPKME is developed. A test platform for the FLPKME is developed and the performance of the FLPKME with seven constant currents and controlled currents by the control algorithm developed in this paper are experimentally tested. The results show that the FLPKME with a constant current of 1.6 A possesses the basic stable gait, and the FLPKME with the controlled currents by the control algorithm developed in this paper is able to track the motions well and to imitate the natural motions of a healthy human knee joint.
Analysis of hybrid viscous damper by real time hybrid simulations
Brodersen, Mark Laier; Ou, Ge; Høgsberg, Jan Becker
2016-01-01
Results from real time hybrid simulations are compared to full numerical simulations for a hybrid viscous damper, composed of a viscous dashpot in series with an active actuator and a load cell. By controlling the actuator displacement via filtered integral force feedback the damping performance...... of the hybrid viscous damper is improved, while for pure integral force feedback the damper stroke is instead increased. In the real time hybrid simulations viscous damping is emulated by a bang-bang controlled Magneto-Rheological (MR) damper. The controller activates high-frequency modes and generates drift...... in the actuator displacement, and only a fraction of the measured damper force can therefore be used as input to the investigated integral force feedback in the real time hybrid simulations....
Development of Magnetorheological Engine Mount Test Rig
Md Yunos Mohd Razali
2017-01-01
Full Text Available Ride comfort is an important factor in any road vehicle performance. Nonetheless, passenger ride comfort is sometimes affected by the vibrations resulting from the road irregularities. Vehicle ride comfort is also often compromised by engine vibration. Engine mount is one of the devices which act as vibration isolator from unwanted vibration from engine to the driver and passengers. This paper explains the development of the test rig used for laboratory testing of Magnetorheological (MR engine mount characterization. MR engine mount was developed to investigate the vibration isolation process. An engine mount test machine was designed to measure the displacement, relative velocity and damper force with respect to current supply to characterize the hysteresis behavior of the damper and as force tracking control of the MR engine mount.
Active vibration isolation platform on base of magnetorheological elastomers
Mikhailov, Valery P.; Bazinenkov, Alexey M.
2017-06-01
The article describes the active vibration isolation platform on base of magnetorheological (MR) elastomers. An active damper based on the MR elastomers can be used as an actuator of micro- or nanopositioning for a vibroinsulated object. The MR elastomers give such advantages for active control of vibration as large range of displacements (up to 1 mm), more efficient absorption of the vibration energy, possibility of active control of amplitude-frequency characteristics and positioning with millisecond response speed and nanometer running accuracy. The article presents the results of experimental studies of the most important active damper parameters. Those are starting current, transient time for stepping, transmission coefficient of the vibration displacement amplitude.
粘滞流体阻尼器冲击缓冲特性研究%Shock absorption characteristics of a viscous fluid damper
孙靖雅; 焦素娟; 张磊; 华宏星
2013-01-01
为获得粘滞流体阻尼器冲击缓冲特性,设计并制作一种非牛顿流体粘滞阻尼器样机,而后对其进行了不同高度下的冲击缓冲实验.为从流体力学角度分析阻尼力机理,建立改进幂律模型来描述硅油的粘度特性,并通过对实验数据的拟合获得其中待定参数.采用FLUENT软件并结合动网格技术,对阻尼器流场仿真后获得冲击载荷作用下阻尼力输出特性,将之与实验结果相对比,发现结果基本一致,可用于指导阻尼器初步设计.%To obtain shock absorption characteristics of a viscous fluid damper,a non-Newtonian fluid damper was designed and made,and then shock tests were performed for it under various height conditions.To analyze the damping force mechanism from the aspect of fluid dynamics,a modified power law function model was used to describe the viscosity of silicone oil,and the parameters of the model was determined with the measured viscosity data under various shear rates.CFD software FLUENT was adopted and combined with the dynamic meshing technology to obtain the characteristics of damping force under shock conditions.By comparing the results of tests and those of simulations,it was indicated that both the results approximately match each other and they can be used to guide damper designs.
Lin Wei; Li Zhongxian; Ding Yang
2008-01-01
In the field of civil engineering,magnetorheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds.In this paper,the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed.Meanwhile,a _trust-region method based instantaneous optimal semi-active control algorithm (TIOC) is proposed to improve the performance of the semi-active control system in a multiple damper situation.The proposed TIOC describes the control process as a bounded constraint optimization problem,in which an optimal semi active control force vector is solved by the trust-region method in every control step to minimize the structural responses.A numerical example of a railway station roof structure installed with MRF-04K dampers is presented.First,a modified Bouc-Wen model is utilized to describe the behavior of the selected MRF-04K damper.Then,two semi-active control systems,including the well-known clipped-optimal controller and the proposed TIOC controller,are considered.Based on the characteristics of the long-span spatially extended structure,the performance of the control system is evaluated under uniform earthquake excitation and traveUing-wave excitation with different apparent velocities.The simulation results indicate that the MR fluid damper-hased semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards.The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.
H. Shokrollahi
2016-03-01
Full Text Available The purpose of this work is to investigate the effects of the volume fraction and bimodal distribution of solid particles on the compression and tension behavior of the Co-ferrite-based magneto-rheological fluids (MRFs containing silicon oil as a carrier. Hence, Co-ferrite particles (CoFe2O4 with two various sizes were synthesized by the chemical co-precipitation method and mixed so as to prepare the bimodal MRF. The X-Ray Diffraction (XRD analysis, Fourier Transform Infrared Spectroscopy (FTIR, Laser Particle Size Analysis (LPSA and Vibrating Sample Magnetometer (VSM were conducted to examine the structural and magnetic properties, respectively. The results indicated that the increase of the volume fraction has a direct increasing influence on the values of the compression and tension strengths of fluids. In addition, the compression and tension strengths of the mixed MRF sample (1.274 and 0.647 MPa containing 60 and 550 nm samples were higher than those of the MRF sample with the same volume fraction and uniform particle size of 550 nm.
丁丁; 晏华; 杨健健; 胡志德; 张寒松
2015-01-01
A novel silicon oil⁃based magnetorheological fluids were prepared with carbonyl iron powder as magnetic par⁃ticles,SiO2 as thixotropic agents,and stearic acid,lauric acid,dimer acid,polyacrylic acid as the surfactants separatedly. The effect of surfactants on tribological properties of magnetorheological fluids was investigated by MMW⁃1P⁃utility tribom⁃eter,and the worn surface was observed by SEM to analyze the friction mechanism of silicon oil⁃based magnetorheological fluids.The results indicate that the carboxylic acid⁃based surfactants can enhance the viscosity of magnetorheological fluids and improve the tribological properties,however the wear mechanism of magnetorheological fluids is still the typical three body abrasive wear.Stearic acid and lauric acid are outstanding in tribological properties for the five kinds of surfactants.%以羰基铁粉为磁性颗粒， SiO2为触变剂，油酸、硬脂酸、月桂酸、二聚酸、聚丙烯酸分别作为表面活性剂，制备硅油基磁流变液；采用MMW⁃1P型多功能摩擦磨损试验机考察表面活性剂对磁流变液摩擦磨损性能的影响，采用扫描电子显微镜观察钢球磨痕表面形貌，分析硅油基磁流变液的摩擦机制。实验结果表明，羧酸基类表面活性剂的加入增加磁流变液的黏度，影响其摩擦学性能，但磁流变液的磨损机制仍为典型的三体磨粒磨损。研究的5种表面活性剂中，硬脂酸、月桂酸减摩抗磨效果较好。
麻建坐; 魏书华; 钟莉蓉
2013-01-01
基于形状记忆合金热效应下的形状记忆特性和磁流变液的流变特性,介绍了形状记忆合金控制的磁流变液无级传动的工作原理；建立了能控制励磁线圈电流大小的形状记忆合金温控开关输出行程与温度、结构参数、材料参数、工作载荷等参数之间的关系式；基于Herschel-Bulkley模型描述了磁流变液剪切应力随外加磁场变化的本构方程；建立了磁流变液无级传动的传递转矩与磁场参数、材料参数、尺寸参数和运动参数之间的关系式.研究结果表明:形状记忆合金温控开关的输出行程随温度的变化而变化,磁流变液无级传动的传递转矩随外加磁场的增大而增大,输出转速能根据来自散热器气流温度的高低实现连续调整.%Based on the shape memory effect of shape memory alloy under thermal effect and the rheological behavior of magnetorheological fluid,the relationships of the shape memory alloy temperature detect switch's output displacement with the temperature,the geometric parameters,the material parameters and the operating load was established. The shape memory alloy temperature detect switch was used to control the current that induced magnetic field. The Herschel-Bulkley model was used to describe the constitutive characteristics of magnetorheological fluid subjected to an applied magnetic field to derive the relationships of the magnetorheological fluid transmission torque with the magnetic field parameters, the magnetorheological fluid material parameters, the size parameters and the motion parameters. The results indicate that the output displacement of the shape memory alloy temperature detect switch can change rapidly with the temperature. The torque transmitted by magnetorheological fluid goes up rapidly with the increase of the applied magnetic field strength and the output angular velocity can be adjusted continuously by the air temperature from radiator.
磁流变液矩形夹层板的动力特性分析%Dynamics Analysis of Rectangular Sandwich Plates with Magnetorheological Fluid
张冲; 鲁刘磊
2013-01-01
作为一种新型智能材料，磁流变液的应用研究近年来倍受重视。从磁流变液的特性出发，对含磁流变液矩形夹层板结构的动力特性进行了研究。在经典的夹层板理论基础上，利用能量法建立了含磁流变液矩形夹层板结构的运动微分方程，导出了四边简支条件下的磁流变液矩形夹层板的固有频率和损耗因子的解析表达式。通过算例，分析了不同磁场强度对磁流变液矩形夹层板的固有频率和损耗因子的影响，并与有限元分析计算的结果进行了比较，两者结果吻合较好。分析和计算结果表明：随着外加磁场强度的增加，夹层板的固有频率和损耗因子均增大，说明磁流变液在外加磁场作用下对夹层板有明显的抑振作用。%As a kind of new intelligent materials, the application of magneto rheological fluid (MRF) has been paid much attention in recent years. According to the characteristics of MR fluid, this paper focuses on dynamics analysis of a rectangular sandwich plate with magneto-rheological fluid. Based on the classical laminated plate theory, the differential equation of motion of rectangular sandwich plate with magnet- rheological fluid is established by the Energy Method, and the analytical expression of the natural frequency and energy loss factor of the rectangular sandwich plate with simply supported on four sides is obtained. Moreover, through a specific example, this paper analyzes the influence of different magnetic field intensity on the natural frequency and loss factor of magnetic-rheological fluid rectangular sandwich plate, and the result is compared with that obtained by finite element analysis. Both results have good agreement. Both the natural frequency and loss factor of sandwich plate increase with increasing of the strength of the applied magnetic field. The results show that magneto-rheological fluid has a significant effect on vibration suppression
基于磁流变的动力吸振器特性分析%Characteristics of Dynamic Vibration Absorber Based on Magnetorheological Fluids
周乾; 黄其柏
2013-01-01
A intelligent dynamic vibration absorber (DVA) based on magnetorheological fluid (MRF) is presented. MRF has controllable shear modulus when it is exposed to an external magnetic field. It is used as a controllable elastic and damping element here. When the applied current is changed, the magnetic field through MRF will change,then the resonance frequency of the DVA will shift and increase the band of vibration absorption. The structure parameters of DVA are studied, and easy to control the system to select the parameters, intelligent adjust the DVA.%设计了一种基于磁流变液的智能动力吸振器,它利用磁流变液作为吸振器的弹性和阻尼元件,通过改变外加磁场,控制磁流变液的剪切模量来改变吸振器的固有频率,增大吸振器的吸振频带.并对吸振器的结构参数进行了研究,便于控制系统选择参数,智能调节吸振器.
Influence of wall texture on slip effect of magnetorheological fluids%壁面形貌对磁流变液滑移特性的影响
陈飞; 侯友夫; 田祖织
2013-01-01
To obtain the wall slip effect of magnetorheological fluids, the magnetorheological transmission properties test-bed was established, the influence rules of groove shapes, groove densities, groove depths, texture types of wall were researched respectively, the results indicate that wall slip intensity has relationship with surface textures of disk, of which the influence of groove shape of disk was indistinctive, and the triangular section shape was slightly better than rectangular; the increase of groove density can improve the capacity of torque transmitted, and the groove depth has a optimized value range from 0-0. 5mm, the wall texture slip intensity range from small to big is radialized wall, potholed wall, smooth wall and annular wall, the appearance of wall texture can improve the wall slip intensity about 10%.%为了分析传动壁面形貌对磁流变液滑移特性的影响规律,建立磁流变传动性能实验台,分析了传动壁面沟槽形状、沟槽密度、沟槽深度、纹理类型等对滑移强度的影响规律,研究发现,滑移强度与传动壁面表面形貌有关,壁面沟槽形状对滑移强度影响并不明显,三角形截面形状略优于矩形；增加沟槽密度可提升磁流变液的传动能力,沟槽深度在0～0.5mm范围内存在最优值；同心圆、光滑、凹坑及径向辐射条纹4种壁面形貌中,滑移强度由大到小依次是:径向辐射条纹、凹坑、光滑、同心圆,改变壁面形貌可使滑移强度提高10％.
杨建伟; 孙守光; 刘海波
2011-01-01
In order to improve automotive＇s riding performance and handling stability,an adaptive Neural Network（NN） relative control algorithm was applied to the semi-active suspension system and the controlled member is the Magnetorheological（MR） damper.Based on experimental test and academic analysis,a nonlinear Bingham model for MR damper damping force was obtained through data fitting,and an automotive semi-active suspension model with MR damper was built,which could be used to study the adaptative NN relative control method.The input of the model is a simulative road spectrum,and the controlled variables are the pitch angle acceleration and the vertical deformation＇s difference of the front and rear spring,and the evaluating indicators are the vertical centroidal acceleration of car body and the working space of the front and rear suspension.Then the simulation was carried on.Comparing with the passive suspension,the riding performance and the handling stability of designed semi-active suspension were improved,and the semi-active suspension system has self-adaptability to the working condition and better robust to the perturbation of the system parameters.%为了提高汽车的运行平顺性和操纵稳定性,以磁流变减振器为控制对象,提出了采用自适应神经网络相对控制方法的半主动悬架系统。在试验测试和理论分析的基础上,通过数据拟合得到磁流变减振器阻尼力的非线性Bingham模型,建立了基于该磁流变减振器的半主动悬架模型,并用该模型进行了自适应神经网络相对控制方法的研究。以模拟道路谱作为输入,以车身俯仰角加速度和车辆悬架前、后侧弹簧的垂向变形量之差作为控制量,把车身质心垂向加速度、前后悬架动行程作为评价指标来进行仿真研究。仿真结果表明,设计的半主动悬架与被动悬架相比,其平顺性
Jiajia Zheng
2014-02-01
Full Text Available A novel magnetorheological (MR damper with a multistage piston and independent input currents is designed and analyzed. The equivalent magnetic circuit model is investigated along with the relation between magnetic induction density in the working gap and input currents of the electromagnetic coils. Finite element method (FEM is used to analyze the distribution of magnetic field through the MR fluid region. Considering the real situation, coupling equations are presented to analyze the electromagnetic-thermal-flow coupling problems. Software COMSOL is used to analyze the multiphysics, that is, electromagnetic, thermal dynamic, and fluid mechanic. A measurement index involving total damping force, dynamic range, and induction time needed for magnetic coil is put forward to evaluate the performance of the novel multistage MR damper. The simulation results show that it is promising for applications under high velocity and works better when more electromagnetic coils are applied with input currents separately. Besides, in order to reduce energy consumption, it is recommended to apply more electromagnetic coils with relative low currents based on the analysis of pressure drop along the annular gap.
Enhanced damping for bridge cables using a self-sensing MR damper
Chen, Z. H.; Lam, K. H.; Ni, Y. Q.
2016-08-01
This paper investigates enhanced damping for protecting bridge stay cables from excessive vibration using a newly developed self-sensing magnetorheological (MR) damper. The semi-active control strategy for effectively operating the self-sensing MR damper is formulated based on the linear-quadratic-Gaussian (LQG) control by further considering a collocated control configuration, limited measurements and nonlinear damper dynamics. Due to its attractive feature of sensing-while-damping, the self-sensing MR damper facilitates the collocated control. On the other hand, only the sensor measurements from the self-sensing device are employed in the feedback control. The nonlinear dynamics of the self-sensing MR damper, represented by a validated Bayesian NARX network technique, are further accommodated in the control formulation to compensate for its nonlinearities. Numerical and experimental investigations are conducted on stay cables equipped with the self-sensing MR damper operated in passive and semi-active control modes. The results verify that the collocated self-sensing MR damper facilitates smart damping for inclined cables employing energy-dissipative LQG control with only force and displacement measurements at the damper. It is also demonstrated that the synthesis of nonlinear damper dynamics in the LQG control enhances damping force tracking efficiently, explores the features of the self-sensing MR damper, and achieves better control performance over the passive MR damping control and the Heaviside step function-based LQG control that ignores the damper dynamics.
Seismic response reduction of a three-story building by an MR grease damper
Sakurai, Tomoki; Morishita, Shin
2017-01-01
This paper describes an application of magneto- rheological (MR) grease dampers as seismic dampers for a three-story steel structure. MR fluid is widely known as a smart material with rheological properties that can be varied by magnetic field strength. This material has been applied to various types of devices, such as dampers, clutches, and engine mounts. However, the ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval because of the density difference between the particles and their carrier fluid. To overcome this defect, we developed a new type of controllable working fluid using grease as the carrier of magnetic particles. MR grease was introduced into a cylindrical damper, and the seismic performance of the damper was subsequently studied via numerical analysis. The analysis results of the MR grease damper were compared with those of other seismic dampers. We confirmed that the MR grease damper is an effective seismic damper.
Squeeze Flow Analysis of Magnetorheological Fluids between Two Parallel Disks%磁流变液在平行圆盘间的挤压流动分析
路国平; 邓国红
2011-01-01
Magnetorheological Fluids （MRF） has the property that the viscosity can be quickly changed along with tions. Based on Navior changing Magnetic field intensity, it has a wide range of engineering applica- -Stokes＇ equation and principle of mass conservation, a new squeeze model of MRF＇ s flow between the two parallel disks is put forward, it improves the old Bi-viscosity model and this model is considered with the power law property and boundary slip condition. Then the distribu- tion of the radial velocity is determined, the distribution formula of radial velocity and pressure gradient and the expression formula of squeeze force are obtained. Another, the effect of slip coefficient and power law index on the flow field and squeeze force is also discussed. These provide theory basis for MRF＇ s application that based on squeeze flow.%基于N—S方程和质量守恒原理，充分考虑边界滑移条件以及磁流变液的幂率特性，改进了已有的双黏度模型，建立了磁流变液在圆盘间流动的新的挤压模型，确定了流场的速度分布特，最，得到了径向速度和压力梯度的分布式以及挤压力的表达式。对滑移系数和幂率指数对流场和挤压力的影响进行了分析，为磁流变液在基于挤压工作模式的工程应用提供理论依据。
磁流变液的可控电气特性研究%Research on controllable electric properties of magnetorheological fluid
黄悦华; 江玉欢; 李玲萍; 李闯; 徐兵森; 杨雄波
2015-01-01
Magnetorheological fluid(MRF)was prepared using carbonyl iron microparticles as dispersed phase and oleic acid as surfactant. Putting the MRF resistor in the controllable magnetic field, the change of electrical resistance with applied magnetic field and time was analyzed. It reveals that in the absence of magnetic field, the MRF resistor exhibits resistance up to 500MΩ, showing characteristics of insulators, but under increasingly applied field , the resistance decreases rapidly to almost a stable value of less than 200Ω. That is to say, the resistance of MRF could be controlled by changing the applied magnetic field. The giant change of MRF from high to low resistance is similar to the on-off of circuit switch, which provides a basis for studying the controllable electric properties of MRF.%为了研究磁流变液的可控电气特性，以微米级羰基铁粉为分散相、油酸为表面活性剂制备了一种磁流变液。将自制磁流变液电阻器置于可控磁场中，研究了磁流变液电阻随磁场及时间的变化。结果表明，当没有外加磁场时，电阻器电阻大于500MΩ，表现为绝缘体的特性。随外加磁场逐渐变大，电阻值开始迅速减小至200Ω以下后趋于稳定。随着外磁场的变化，电阻值可实现可控调节。磁流变液的这种高阻态到低阻态的转变类似电路开关的开启与断开状态，为研究磁流变液的可控电气特性提供了依据。
Bharathi Priya, C.; Gopalakrishnan, N.
2016-12-01
Magnetorheological (MR) dampers are devices that can be used for structural vibration reduction under seismic excitation. These devices are used in semi-active control which require less power compared to active devices and offer high reliability compared to passive devices. Despite the advantages of MR damper, use of these dampers in an effective way in a structure is highly challenging and a precise modelling is required as these dampers are highly non-linear. Among the parametric models available, Bouc-Wen model is widely used because of its effective modelling of the hysteretic force-velocity curve of MR damper. The parameters of Bouc-Wen model are damper dependent and hence need to be identified before utilising the damper for further simulation studies. In this work, the parametric identification of Bouc-Wen model for commercially available long stroke and short stroke MR damper (RD 8040-1 and RD 8041-1) is done. For this, experimental characterization of the dampers are carried out using hydraulic actuators mounted on a self-restraining frame. The damper is driven harmonically in the testing setup at various combinations of frequency, amplitude, current and displacement. Using the experimental characterization, parameters of Bouc-Wen model are identified by Levenberg-Marquardt optimization Algorithm (LMA). The identified parameters are validated by comparing with the experimental results. The identified parameters are believed to be worthwhile for the use of these MR dampers in further studies of real-time semi-active vibration control of structures.
Extended Kalman filter based structural damage detection for MR damper controlled structures
Jin, Chenhao; Jang, Shinae; Sun, Xiaorong; Jiang, Zhaoshuo; Christenson, Richard
2016-04-01
The Magneto-rheological (MR) dampers have been widely used in many building and bridge structures against earthquake and wind loadings due to its advantages including mechanical simplicity, high dynamic range, low power requirements, large force capacity, and robustness. However, research about structural damage detection methods for MR damper controlled structures is limited. This paper aims to develop a real-time structural damage detection method for MR damper controlled structures. A novel state space model of MR damper controlled structure is first built by combining the structure's equation of motion and MR damper's hyperbolic tangent model. In this way, the state parameters of both the structure and MR damper are added in the state vector of the state space model. Extended Kalman filter is then used to provide prediction for state variables from measurement data. The two techniques are synergistically combined to identify parameters and track the changes of both structure and MR damper in real time. The proposed method is tested using response data of a three-floor MR damper controlled linear building structure under earthquake excitation. The testing results show that the adaptive extended Kalman filter based approach is capable to estimate not only structural parameters such as stiffness and damping of each floor, but also the parameters of MR damper, so that more insights and understanding of the damage can be obtained. The developed method also demonstrates high damage detection accuracy and light computation, as well as the potential to implement in a structural health monitoring system.
电流变液阻尼器半主动控制的理论建模%Study on Theoretical Modeling of Semi-Active Electro-Rheological Fluid Damper
张华良; 饶柱石; 傅志方
2003-01-01
This paper emphases on analyzing and investigating the mechanical behavior of electro-theological fluid (ERF) semi-active damper. Theoretical model was developed to describe the relationship between electric field and the resistance force of ERF flowing through two parallel plane electrodes. In the model, the pressure drop along electrodes was supposed to consist of two parts: one related with viscosity and the other related with dynamic yield shear stress. The concept of yield stress influence factor was developed in deriving the theoretical formula for calculating the pressure drop in the damper. The influences of some other factors, such as, nonideal Newtonian fluid and temperature have also been taken into account. Numerical and experimental work have been performed to prove the validity of the proposed model. The comparison of both results shows that the developed model is quite effective and practicable.
Assessment of semi-active friction dampers
dos Santos, Marcelo Braga; Coelho, Humberto Tronconi; Lepore Neto, Francisco Paulo; Mafhoud, Jarir
2017-09-01
The use of friction dampers has been widely proposed for a variety of mechanical systems for which applying viscoelastic materials, fluid based dampers or other viscous dampers is impossible. An important example is the application of friction dampers in aircraft engines to reduce the blades' vibration amplitudes. In most cases, friction dampers have been studied in a passive manner, but significant improvements can be achieved by controlling the normal force in the contact region. The aim of this paper is to present and study five control strategies for friction dampers based on three different hysteresis cycles by using the Harmonic Balance Method (HBM), a numerical and experimental analysis. The first control strategy uses the friction force as a resistance when the system is deviating from its equilibrium position. The second control strategy maximizes the energy removal in each harmonic oscillation cycle by calculating the optimal normal force based on the last displacement peak. The third control strategy combines the first strategy with the homogenous modulation of the friction force. Finally, the last two strategies attempt to predict the system's movement based on its velocity and acceleration and our knowledge of its physical properties. Numerical and experimental studies are performed with these five strategies, which define the performance metrics. The experimental testing rig is fully identified and its parameters are used for numerical simulations. The obtained results show the satisfactory performance of the friction damper and selected strategy and the suitable agreement between the numerical and experimental results.
Design and Simulation of a Multi-cylindrical Magneto-rheological Fluid Clutch%多筒式磁流变液离合器的设计及仿真
2015-01-01
为满足 B 级轿车大转矩传递的要求，并克服高速旋转工况下离心力对磁流变液（Magneto-Rheological Fluid， MRF）的影响，提出了多筒式磁流变液离合器（Magneto-rheological Fluid Clutch，MFC）结构型式，设计了可以自动消除因工作温度变化导致磁流变液膨胀或收缩的压力平衡机构；同时，在 Ansoft Maxwell 中建立了离合器有限元分析模型，并对磁力线分布和磁场强度进行了仿真分析。结果表明：当励磁电流在2．5～3 A 之间时即可达到设计要求。%To meet the requirement of transmitting a large torque of B-class automobile and overcome the effects of centrifugal force under high speed rotating conditions on Magneto-Rheological Fluid (MRF),a multi-cylindrical Magneto-rheological Fluid Clutch (MFC)is proposed.A pressure balance mechanism is designed to avoid the expansion or contraction of MRF caused by the temperature changes.A finite ele-ment analysis model is built in Ansoft Maxwell,and the magnetic force line distribution and magnetic field intensity are simulated.The simulation result shows that the design goal can be realized when the excitation current is between 2.5 A and 3 A.
Fuzzy logic control of the building structure with CLEMR dampers
Zhang, Xiang-Cheng; Xu, Zhao-Dong; Huang, Xing-Huai; Zhu, Jun-Tao
2013-04-01
The semi-active control technology has been paid more attention in the field of structural vibration control due to its high controllability, excellent control effect and low power requirement. When semi-active control device are used for vibration control, some challenges must be taken into account, such as the reliability and the control strategy of the device. This study presents a new large tonnage compound lead extrusion magnetorheological (CLEMR) damper, whose mathematical model is introduced to describe the variation of damping force with current and velocity. Then a current controller based on the fuzzy logic control strategy is designed to determine control currents of the CLEMR dampers rapidly. A ten-floor frame structure with CLEMR dampers using the fuzzy logic control strategy is built and calculated by using MATLAB. Calculation results show that CLEMR dampers can reduce the seismic responses of structures effectively. Calculation results of the fuzzy logic control strategy are compared with those of the semi-active limit Hrovat control structure, the passive-off control structure, and the uncontrolled structure. Comparison results show that the fuzzy logic control strategy can determine control currents of CLEMR dampers quickly and can reduce seismic responses of the structures more effectively than the passive-off control strategy and the uncontrolled structure.
李杰; 彭勇波
2012-01-01
根据能量保守原理,将微观粒子运动的动能等效成宏观动态屈服的应变能,建立内秉悬浮粒子运动涨落的磁流变液剪切应力的随机多尺度模型.分析表明,悬浮粒子初始随机条件和Brownian运动,以及剪切应变加载过程中,链簇反复断裂、重组的先后次序和数目不均匀,导致系统宏观屈服性态的非线性涨落和随机涨落；同时,微观运动涨落在体积平均过程中被严重弱化,宏观随机涨落相对不明显.拟合Bingham剪变率本构模型则进一步表明,外加场强对宏观屈服性态的变异性有一定程度的影响,磁流变液装置设计中应该考虑物理参数的随机性.%Dynamic yield behavior of magnetorheological fluids is investigated by upscaling information of microscale interaction between particles, employing a large-scale molecular dynamical simulation technique, to macroscale bulk behavior. We conduct a stochastic multiscale model for dynamic yield of magnetorheological fluids based on equivalence of system energy at different scales. It is revealed that the dynamic yield exhibits nonlinear and stochastic fluctuations due to heterogeneity of sequence and number of cluster-sheet reconstructions under shear fields loading, as well as Brownian motion of suspensions with initial random conditions. Meanwhile, we investigate fluctuation of microscale particle motions, relationship between stress and strain, and constitutive relationship of shear rate. It is noted that the microscale thermal fluctuation is far more than macroscale variations since the upscaling from microscale to macroscale results in degradation of fluctuations. Besides, the macroscale variations relies on external magnetic field as in the constitutive relationship of shear rate, I. E. Bingham model, which is supposed to be considered in the design and optimization of magnetorheological devices.
Kielb, Robert E.; Griffin, Jerry H.
1987-01-01
Before 1975 turbine blade damper designs were based on experience and very simple mathematical models. Failure of the dampers to perform as expected showed the need to gain a better understanding of the physical mechanism of friction dampers. Over the last 10 years research on friction dampers for aeronautical propulsion systems has resulted in methods to optimize damper designs. The first-stage turbine blades on the Space Shuttle Main Engine (SSME) high-pressure oxygen pump have experienced cracking problems due to excessive vibration. A solution is to incorporate a well-designed friction dampers to attenuate blade vibration. The subject study, a cooperative effort between NASA Lewis and Carnegie-Mellon University, represents an application of recently developed friction damper technology to the SSME high-pressure oxygen turbopump. The major emphasis was the contractor's design known as the two-piece damper. Damping occurs at the frictional interface between the top half of the damper and the underside of the platforms of the adjacent blades. The lower half of the damper is an air seal to retard airflow in the volume between blade necks.
Menggang YANG; Zhengqing CHEN; Jianhua HU
2008-01-01
To mitigate the seismic response of selfanchored suspension bridges, equations of motion governing the coupled system of bridge- magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications.
Zong, Lu-Hang; Gong, Xing-Long; Guo, Chao-Yang; Xuan, Shou-Hu
2012-07-01
In this paper, a magneto-rheological (MR) damper-based semi-active controller for vehicle suspension is developed. This system consists of a linear quadratic Gauss (LQG) controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse model as the damper controller. First, a modified Bouc-Wen model is proposed to characterise the forward dynamic characteristics of the MR damper based on the experimental data. Then, an inverse MR damper model is built using ANFIS technique to determine the input current so as to gain the desired damping force. Finally, a quarter-car suspension model together with the MR damper is set up, and a semi-active controller composed of the LQG controller and the ANFIS inverse model is designed. Simulation results demonstrate that the desired force can be accurately tracked using the ANFIS technique and the semi-active controller can achieve competitive performance as that of active suspension.
Variable stiffness and damping magnetorheological isolator
Yang ZHOU; Xingyu WANG; Xianzhou ZHANG; Weihua LI
2009-01-01
This paper presents the development and characterization of a magnetorheological (MR) fluid-based variable stiffness and damping isolator. The prototype of the MR fluid isolator is fabricated, and its dynamic behavior is measured under various applied magnetic fields. The parameters of the model under various magnetic fields are identified, and the dynamic perfor-mance of the isolator is evaluated in simulation. Experi-mental results indicate that both the stiffness and damping capability of the developed MR isolator can be controlled by an external magnetic field.
A new controller for the seni-active suspension system with magnetor heological dampers
无
2003-01-01
A new sliding mode controller for semi-active suspension system with magnetorheological (MR) damper is presented in this paper. In the proposed sliding mode controller, a semi-active suspension based on the skyhook damper system is chosen as the reference model to be followed, and the control law is so determined that the asymptotically stable error dynamics occurs between the controlled state and the reference model state. Numerical simulations are carried out to study the performance of the new sliding mode controller. The results show that the proposed controller yields almost perfect tracking to the reference model and has a high robustness against model parameter uncertainties and disturbances.
Studies on structural vibration control with MR dampers using μGA
Li Hongnan; Chang Zhiguo; Song Gangbing
2005-01-01
A new approach to reducing the seismic response of spatial structures with magneto-rheological (MR) dampers is presented in this paper. The Genetic Algorithm with small populations (μGA) is used to optimize the control for the MR dampers to reduce structural vibration, which is difficult to achieve using classical optimal control. The advantages ofμGA are the use of global properties and that fewer conditions are required to obtain the optimal function. Numerical results demonstrate the effectiveness of the proposed method in reducing the seismic response of structures.
熊晨熙; 彭向和; 易成建
2011-01-01
The effects of oleic acid and lauric acid on the stabilization of magnetorheological fluids（MRF） were investigated experimentally.Several groups of samples were prepared,with both lauric acid and oleic acid as additives.The variations of the zero-field viscosity,mechanical property and sedimentation rate of these samples against time were tested,and the effects of volume fractions of lauric acid,oleic acid and carbonyl iron on the stabilization and mechanical property of the MRF samples were studied.The results indicated that the proper addition of lauric acid and oleic acid could significantly improve the mechanical property of magnetorheological fluids.%鉴于油酸和月桂酸2种表面活性剂对磁流变液稳定性所起到的不同的作用,制备了若干种不同配比的以油酸和月桂酸共同添加的磁流变液,测量它们的零场粘度、力学性能和沉降率-时间曲线,研究了月桂酸、油酸和羰基铁粉3种成分的含量对于磁流变液稳定性和力学性能的影响。结果表明合理的添加油酸和月桂酸对于制备零场粘度小且稳定性优良的磁流变液具有显著的效果。
Seismic response analysis of coupled building involving MR damper and elastomeric base isolation
M.K. Shrimali
2015-06-01
The present study investigates the comparative performance of three proposed schemes of coupled building control involving Magnetorheological (MR damper and elastomeric base isolation, named as, Semiactive, Hybrid 1 and Hybrid 2. The results of numerical study showed that Hybrid controls are more effective in controlling the response as compared to Semiactive control. Further, influence of device parameters on control performance has been investigated through a parametric study.
Torsional friction damper optimization
Ye, Shaochun; Williams, Keith A.
2006-06-01
A new approach for the analysis of friction dampers is presented in this work. The exact form of the steady-state solution for a friction damper implemented on a primary system is developed and numerical solutions are used to determine the optimum friction in a friction damper applied to a specific primary system. When compared to classical results presented by earlier authors, the new approach provides a more optimal solution. In addition, viscous damping in the primary system may be included with the new analysis approach. The ability to optimize a friction damper when viscous damping is included in the primary system is a significant improvement over earlier methods and shows potential for serving as a guide to realizing a more accurate estimate of the optimal damping for friction dampers.
Medium to long term behavior of MR dampers for structural control
Caterino, N.; Azmoodeh, B. M.; Occhiuzzi, A.
2014-10-01
The medium to long term behavior of a prototype magnetorheological (MR) damper for structural control of earthquake induced vibrations is investigated herein. Unlike some applications for which MR devices experience frequent dynamic loads, seismic dampers might not be used for most of their life, staying dormant for a long period until an earthquake hits the hosting structure. This work aims to evaluate the effectiveness of a MR damper after years of inactivity. A MR device has been tested twice, first in 2008 and then in 2013, after five years of absolute inactivity. The comparison between the results of the two tests is made in terms of force-displacement loops. It is shown that, after a 5-year rest, only part of the first stroke of the damper is characterized by an unexpected response of the damper. After half a stroke, the damper quickly returned to behave like in 2008, even if a slight non-reversible decrease of the reacting force has been recorded. The latter is found to be more evident (5-7%) for larger currents, less visible in the case of zero magnetic field. From the point of view of civil engineering, this decay of performance is definitely acceptable, being largely bounded within the limits of the uncertainties typically involved and taken into account in the structural design. Finally, starting from a literature review, the paper discusses the possible causes of the observed changes in the mechanical response of the damper over time.
Anisotropic characterization of magnetorheological materials
Dohmen, E.; Modler, N.; Gude, M.
2017-06-01
For the development of energy efficient lightweight parts novel function integrating materials are needed. Concerning this field of application magnetorheological (MR) fluids, MR elastomers and MR composites are promising materials allowing the adjustment of mechanical properties by an external magnetic field. A key issue for operating such structures in praxis is the magneto-mechanical description. Most rheological properties are gathered at laboratory conditions for high magnetic flux densities and a single field direction, which does not correspond to real praxis conditions. Although anisotropic formation of superstructures can be observed in MR suspensions (Fig. 1) or experimenters intentionally polymerize MR elastomers with anisotropic superstructures these MR materials are usually described in an external magnetic field as uniform, isotropic materials. This is due to missing possibilities for experimentally measuring field angle dependent properties and ways of distinguishing between material properties and frictional effects. Just a few scientific works experimentally investigated the influence of different field angles (Ambacher et al., 1992; Grants et al., 1990; Kuzhir et al., 2003) [1-3] or the influence of surface roughness on the shear behaviour of magnetic fluids (Tang and Conrad, 1996) [4]. The aim of this work is the introduction of a novel field angle cell allowing the determination of anisotropic mechanical properties for various MR materials depending on the applied magnetic field angle.
Towards a universal master curve in magnetorheology
Ruiz-López, José Antonio; Hidalgo-Alvarez, Roque; de Vicente, Juan
2017-05-01
We demonstrate that inverse ferrofluids behave as model magnetorheological fluids. A universal master curve is proposed, using a reduced Mason number, under the frame of a structural viscosity model where the magnetic field strength dependence is solely contained in the Mason number and the particle concentration is solely contained in the critical Mason number (i.e. the yield stress). A linear dependence of the critical Mason number with the particle concentration is observed that is in good agreement with a mean (average) magnetization approximation, particle level dynamic simulations and micromechanical models available in the literature.
Thermal chain model of electro- and magnetorheology
MARTIN,JAMES E.
2000-04-06
Steady shear 3-D simulations of electro- and magnetorheology in a uniaxial field are presented. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. To account for the uniaxial steady shear data the author proposes a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect.
Phu, Do Xuan; Shin, Do Kyun; Choi, Seung-Bok
2015-08-01
This paper presents a new adaptive fuzzy controller featuring a combination of two different control methodologies: H infinity control technique and sliding mode control. It is known that both controllers are powerful in terms of high performance and robust stability. However, both control methods require an accurate dynamic model to design a state variable based controller in order to maintain their advantages. Thus, in this work a fuzzy control method which does not require an accurate dynamic model is adopted and two control methodologies are integrated to maintain the advantages even in an uncertain environment of the dynamic system. After a brief explanation of the interval type 2 fuzzy logic, a new adaptive fuzzy controller associated with the H infinity control and sliding mode control is formulated on the basis of Lyapunov stability theory. Subsequently, the formulated controller is applied to vibration control of a vehicle seat equipped with magnetorheological fluid damper (MR damper in short). An experimental setup for realization of the proposed controller is established and vibration control performances such as acceleration at the driver’s seat are evaluated. In addition, in order to demonstrate the effectiveness of the proposed controller, a comparative work with two existing controllers is undertaken. It is shown through simulation and experiment that the proposed controller can provide much better vibration control performance than the two existing controllers.
基于多孔泡沫金属材料的简易磁流变阻尼器可行性研究%Feasibility on Low-cost MR Fluid Damper Based on Porous Metallic Foams
刘旭辉
2011-01-01
Aimed at the problems that MR damper is expensive,not easy to be sealed and easy to be disabled,a new method to applying the porous metallic foams as a carrier was proposed to solve these problems. The conception design of low-cost MR fluid damper based on porous metallic foams was introduced and feasibility was studied primarily. The initial results show that MR fluid can be stored in the porous metallic foams and drawn out to obtain the damping effect when the outer magnetic field is on.%针对磁流变液阻尼器价格昂贵及不易密封且易失效的问题,提出以多孔泡沫金属材料为载体,解决上述应用的瓶颈问题的新理念.介绍基于多孔泡沫金属材料的简易磁流变液阻尼器的概念设计,并对其可行性进行初步研究,初步研究结果表明多孔泡沫金属可以储存磁流变液,同时磁流变液在磁场作用下可以从泡沫金属溢出并实现阻尼功能.
Control strategies for friction dampers: numerical assessment and experimental investigations.
Coelho H.T.
2014-01-01
Full Text Available The use of friction dampers has been proposed in a wide variety of mechanical systems for which it is not possible to apply viscoelastic materials, fluid based dampers or others viscous dampers. An important example is the application of friction dampers in aircraft engines to reduce the blades vibration amplitudes. In most cases, friction dampers have been studied in a passive way, however, a significant improvement can be achieved by controlling the normal force in the dampers. The aim of this paper is to study three control strategies for friction dampers based on the hysteresis cycle. The first control strategy maximizes the energy removal in each harmonic oscillation cycle, by calculating the optimum normal force based on the last displacement peak. The second control strategy combines the first one with the maximum energy removal strategy used in the smart spring devices. Finally, is presented the strategy which homogenously modulates the friction force. Numerical studies were performed with these three strategies defining the performance metrics. The best control strategy was applied experimentally. The experimental test rig was fully identified and its parameters were used for the numerical simulations. The obtained results show the good performance for the friction damper and the selected strategy.
Elrod, David A.
1990-01-01
High side loads reduce the life of the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP) bearings. High stiffness damper seals were recommended to reduce the loads on the pump and turbine end bearings in the HPOTP. The seals designed for use on the pump end are expected to adequately reduce the bearing loads; the predicted performance of the planned turbine end seal is marginal. An alternative to the suggested turbine end seal design is a damper bearing with radial holes from the pressurized center of the turbopump rotor, feeding a smooth land region between two rough-stator/smooth-rotor annular seals. An analysis was prepared to predict the leakage and rotor dynamic coefficients (stiffness, damping, and added mass) of the damper bearing. Governing equations of the seal analysis modified to model the damper bearing; differences between the upstream conditions of the damper bearing and a typical annular seal; prediction of the damper bearing analysis; and assumptions of the analysis which require further investigation are described.
Yan, Gang; Zhou, Lily L.
2006-09-01
This study presents a design strategy based on genetic algorithms (GA) for semi-active fuzzy control of structures that have magnetorheological (MR) dampers installed to prevent damage from severe dynamic loads such as earthquakes. The control objective is to minimize both the maximum displacement and acceleration responses of the structure. Interactive relationships between structural responses and input voltages of MR dampers are established by using a fuzzy controller. GA is employed as an adaptive method for design of the fuzzy controller, which is here known as a genetic adaptive fuzzy (GAF) controller. The multi-objectives are first converted to a fitness function that is used in standard genetic operations, i.e. selection, crossover, and mutation. The proposed approach generates an effective and reliable fuzzy logic control system by powerful searching and self-learning adaptive capabilities of GA. Numerical simulations for single and multiple damper cases are given to show the effectiveness and efficiency of the proposed intelligent control strategy.
H∞ control of railway vehicle suspension with MR damper using scaled roller rig
Shin, Yu-Jeong; You, Won-Hee; Hur, Hyun-Moo; Park, Joon-Hyuk
2014-09-01
In this paper, a magneto-rheological (MR) damper was applied to the secondary suspension to reduce the vibration of a car body. The control performance of the MR damper was verified by numerical analysis with a 1/5 scale railway vehicle model in accordance with the similarity law. The analysis results were then validated in tests. In particular, the objective of the study was to understand how the control performance affected the dynamic characteristics of a railway vehicle and to systematically analyze the relationship between control performance and dynamic characteristics depending on various running speeds. To achieve this, experimental results for the dynamic characteristics of the scaled MR damper designed for the 1/5 scale railway vehicle model were applied to the railway vehicle model. The H∞ control method was applied to the controller. The means of designing the railway vehicle body vibration controller and the effectiveness of its results were studied.
Research on low-frequency mechanical characteristics of the MR dampers in ship isolators
YAO Xiong-liang; TIAN Zheng-dong; SHEN Zhi-hua; GUO Shao-jing
2008-01-01
A new isolator composed of a steel rope spring and a magneto-rheological (MR) damper was designed and a study on low-frequency mechanical characteristics of MR dampers in isolators was carried out. It used the characteristics of the MR damper,such as fast response,controllable damping,small energy consumption,wide dynamic scope,and great adaptation. The relationships between MR damping forces and influencing factors were analyzed based on experimental data. The results show that damping force is not only related to structural dimensions,but also closely related to controllable current and vibration frequency. Finally,the empirical formula for damping forces was corrected,and the relationship between correction coefficients and factors analyzed.
Optimizing parameters for magnetorheological finishing supersmooth surface
Cheng, Haobo; Feng, Zhijing; Wang, Yingwei
2005-02-01
This paper presents a reasonable approach to this issue, i.e., computer controlled magnetorheological finishing (MRF). In MRF, magnetically stiffened magnetorheological (MR) abrasive fluid flows through a preset converging gap that is formed by a workpiece surface and a moving rigid wall, to create precise material removal and polishing. Tsinghua University recently completed a project with MRF technology, in which a 66 mm diameter, f/5 parabolic mirror was polished to the shape accuracy of λ/17 RMS (λ=632.8nm) and the surface roughness of 1.22 nm Ra. This was done on a home made novel aspheric computer controlled manufacturing system. It is a three-axis, self-rotating wheel machine, the polishing tool is driven with one motor through a belt. This paper presents the manufacturing and testing processes, including establish the mathematics model of MRF optics on the basis of Preston equation, profiler test and relative coefficients, i.e., pressure between workpiece and tool, velocity of MR fluid in polishing spot, tolerance control of geometrical parameters such as radius of curvature and conic constant also been analyzed in the paper. Experiments were carried out on the features of MRF. The results indicated that the required convergent speed, surface roughness could be achieved with high efficiency.
Adaptive magnetorheological seat suspension for shock mitigation
Singh, Harinder Jit
This research focuses on theoretical and experimental analysis of an adaptive seat suspension employing magnetorheological energy absorber with the objective of minimizing injury potential to seated occupant of different weights subjected to broader crash intensities. The research was segmented into three tasks: (1) development of magnetorheological energy absorber, (2) biodynamic modeling of a seated occupant, and (3) control schemes for shock mitigation. A linear stroking semi-active magnetorheological energy absorber (MREA) was designed, fabricated and tested for intense impact conditions with piston velocities up to 8 m/s. MREA design was optimized on the basis of Bingham-plastic model (BPM model) in order to maximize the energy absorption capabilities at high impact velocities. Computational fluid dynamics and magnetic FE analysis were conducted to validate MREA performance. Subsequently, low-speed cyclic testing (0-2 Hz subjected to 0-5.5 A) and high-speed drop testing (0-4.5 m/s at 0 A) were conducted for quantitative comparison with the numerical simulations. Later, a nonlinear four degrees-of-freedom biodynamic model representing a seated 50th percentile male occupant was developed on the basis of experiments conducted on Hybrid II 50th percentile male anthropomorphic test device. The response of proposed biodynamic model was compared quantitatively against two different biodynamic models from the literature that are heavily implemented for obtaining biodynamic response under impact conditions. The proposed biodynamic model accurately predicts peak magnitude, overall shape and the duration of the biodynamic transient response, with minimal phase shift. The biodynamic model was further validated against 16 impact tests conducted on horizontal accelerator facility at NAVAIR for two different shock intensities. Compliance effects of human body were also investigated on the performance of adaptive seat suspension by comparing the proposed biodynamic model
Yang, C. S. Walter; DesRoches, Reginald
2014-03-01
This paper develops a smart hybrid rotary damper using a re-centering smart shape memory alloy (SMA) material as well as conventional energy-dissipating metallic plates that are easy to be replaced. The ends of the SMA and steel plates are inserted in the hinge. When the damper rotates, all the plates bend, providing energy dissipating and recentering characteristics. Such smart hybrid rotary dampers can be installed in structures to mitigate structural responses and to re-center automatically. The damaged energy-dissipating plates can be easily replaced promptly after an external excitation, reducing repair time and costs. An OpenSEES model of a smart hybrid rotary was established and calibrated to reproduce the realistic behavior measured from a full-scale experimental test. Furthermore, the seismic performance of a 3-story moment resisting model building with smart hybrid rotary dampers designed for downtown Los Angeles was also evaluated in the OpenSEES structural analysis software. Such a smart moment resisting frame exhibits perfect residual roof displacement, 0.006", extremely smaller than 18.04" for the conventional moment resisting frame subjected to a 2500 year return period ground motion for the downtown LA area (an amplified factor of 1.15 on Kobe earthquake). The smart hybrid rotary dampers are also applied into an eccentric braced steel frame, which combines a moment frame system and a bracing system. The results illustrate that adding smart hybrid rotaries in this braced system not only completely restores the building after an external excitation, but also significantly reduces peak interstory drifts.
Seismic response control of a complex structure using multiple MR dampers:experimental investigation
陈静; 徐幼麟; 瞿伟廉; 吴志伦
2004-01-01
This paper presents an experimental investigation on semi-active seismic response control of a multistory building with a podium structure using multiple magnetorheological (MR) dampers manipulated by a logic control algorithm. The experiments are performed in three phases on a seismic simulator with a slender 12-story building model representing a multi-story building and a relatively stiff 3-story building model typifying a podium structure. The first phase of the investigation is to assess control performance of using three MR dampers to link the 3-story building to the 12-story building, in which seismic responses of the controlled two buildings are compared with those of the two buildings without any connection and with rigid connection. The second phase is to investigate reliability of the semi-active control system and robustness of the logic control algorithm when 2 out of 3 MR dampers fail and when the electricity supply to MR dampers is completely stopped. The last phase is to examine sensitivity of semi-active control performance of two buildings to change in ground excitation. The experimental results show that multiple MR dampers with the logic control algorithm can achieve a significant reduction in seismic responses of both buildings. The proposed semi-active control system is of high reliability and good robustness.
Damping force control of a vehicle MR damper using a Preisach hysteretic compensator
Seong, Min-Sang; Choi, Seung-Bok; Han, Young-Min
2009-07-01
This paper presents damping force control performances of a magnetorheological (MR) damper via a new control strategy considering hysteretic behavior of the field-dependent damping force. In order to achieve this goal, a commercial MR damper, Delphi Magneride™ which is applicable to a high-class passenger vehicle is adopted and its field-dependent damping force is experimentally evaluated. The MR damper has two types of damping force hysteretic behavior. The first is velocity-dependent hysteresis and the other is field-dependent hysteresis. Since the magnetic field is directly connected with control input, the field-dependent hysteresis largely affects the control performances of the MR damper system. To consider the field-dependent hysteretic behavior of the MR damper, a Preisach hysteresis model is established and its first-order descending (FOD) curves are experimentally identified. Subsequently, a feedforward hysteretic compensator associated with the biviscous model and inverse Bingham model is formulated to achieve the desired damping force. The control algorithm is experimentally implemented and damping force controllability for sinusoidal and arbitrary trajectories is evaluated in terms of accuracy and input magnitude. In addition, vibration control performances of the MR suspension system are experimentally evaluated with a quarter-vehicle test facility.
Tan Shilan, Salihah; Amri Mazlan, Saiful; Ido, Yasushi; Hajalilou, Abdollah; Jeyadevan, Balachandran; Choi, Seung-Bok; Azhani Yunus, Nurul
2016-09-01
This work proposes different sizes of the plate-like particles from conventional spherical carbonyl iron (CI) particles by adjusting milling time in the ball mill process. The ball mill process to make the plate-like particles is called a solid-state powder processing technique which involves repeated welding, fracturing and re-welding of powder particles in a high-energy ball mill. The effect of ball milling process on the magnetic behavior of CI particles is firstly investigated by vibrating sample magnetometer. It is found form this investigation that the plate-like particles have higher saturation magnetization (about 8%) than that of the spherical particles. Subsequently, for the investigation on the sedimentation behavior the cylindrical measurement technique is used. It is observed from this measurement that the plate-like particles show slower sedimentation rate compared to the spherical particles indicating higher stability of the MR fluid. The field-dependent rheological properties of MR fluids based on the plate-like particles are then investigated with respect to the milling time which is directly connected to the size of the plate-like particles. In addition, the field-dependent rheological properties such as the yield stress are evaluated and compared between the plate-like particles based MR fluids and the spherical particles based MR fluid. It is found that the yield shear stress of the plate-like particles based MR fluid is increased up to 270% compared to the spherical particles based MR fluid.
A magnetorheological actuation system: test and model
John, Shaju; Chaudhuri, Anirban; Wereley, Norman M.
2008-04-01
Self-contained actuation systems, based on frequency rectification of the high frequency motion of an active material, can produce high force and stroke output. Magnetorheological (MR) fluids are active fluids whose rheological properties can be altered by the application of a magnetic field. By using MR fluids as the energy transmission medium in such hybrid devices, a valving system with no moving parts can be implemented and used to control the motion of an output cylinder shaft. The MR fluid based valves are configured in the form of an H-bridge to produce bi-directional motion in an output cylinder by alternately applying magnetic fields in the two opposite arms of the bridge. The rheological properties of the MR fluid are modeled using both Bingham plastic and bi-viscous models. In this study, the primary actuation is performed using a compact terfenol-D rod driven pump and frequency rectification of the rod motion is done using passive reed valves. The pump and reed valve configuration along with MR fluidic valves form a compact hydraulic actuation system. Actuator design, analysis and experimental results are presented in this paper. A time domain model of the actuator is developed and validated using experimental data.
Experimental Investigation into Magnetortheological Damper Subjected to Impact Loads
XIANG Hengbo; FANG Qin; GONG Ziming; WU Hao
2008-01-01
A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation.But at present,the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads.In this paper,a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied experimentally in order to investigate its isolation performance under the impact loads.A new mechanical model of MRD was proposed according to the data obtained by impact test.A good agreement between the numerical results and test data was observed,which showed that the model was good to simulate the dynamic properties of MRD under impact loads.It is also demonstrated that MRD can improve the acceleration and displacement response of the structure obviously under impact loads.
Semi-Active Control of Wave-Induced Vibration for Offshore Platforms by Use of MR Damper
李华军; 王树青; 嵇春艳
2002-01-01
The objective of the present research is to examine the effectiveness of the lateral vibration control of wave-excited re-sponse of offshore platforms with magneto-rheological (MR) damper. In this study, the offshore platform is simplified to bewave force is determined with a white noise via a designed filter. A semi-active control method based on optimal control the-ory is proposed considering that the yield stress of the MR damper can be varied continuously within a certain range. The dy-namics of SDOF structure coupled with the MR damper is investigated. Numerical simulation demonstrates that the MRdamper with this control strategy can significantly reduce the maximum responses and the root-mean-square (RMS) values.
Menapace, J A; Ehrmann, P R; Bickel, R C
2009-11-05
Over the past year we have been working on specialized MR fluids for polishing KDP crystals. KDP is an extremely difficult material to conventionally polish due to its water solubility, low hardness, and temperature sensitivity. Today, KDP crystals are finished using single-point diamond turning (SPDT) tools and nonaqueous lubricants/coolants. KDP optics fabricated using SPDT, however, are limited to surface corrections due to tool/method characteristics with surface quality driven by microroughness from machine pitch, speed, force, and diamond tool character. MRF polishing offers a means to circumvent many of these issues since it is deterministic which makes the technique practical for surface and transmitted wavefront correction, is low force, and is temperature independent. What is lacking is a usable nonaqueous MR fluid that is chemically and physically compatible with KDP which can be used for polishing and subsequently cleaned from the optical surface. In this study, we will present the fluid parameters important in the design and development of nonaqueous MR fluid formulations capable of polishing KDP and how these parameters affect MRF polishing. We will also discuss requirements peculiar to successful KDP polishing and how they affect optical figure/finish and laser damage performance at 1064 nm and 532 nm.
Nutation damper for the AMPTE-IRM satellite: Final Report
Truckenbrodt, A.; Schultysik, B.; Mehltretter, J. P.
1983-01-01
The design, computations, and testing of the nutation damper for the AMPTE-IRM satellite are described. The nutation motions of the satellite excite fluid oscillations in the closed tube system; kinetic energy is destroyed (converted to heat) through tube/fluid friction, constriction of the stream by cross sectional change, and formation of turbulence by stream enlargement. This energy is extracted from the satellite such that nutation is reduced. Tests were carried out in a pendulum testing device and the time constants were calculated. Findings showed that the damper remained within the originally specified values and provided for good dynamic behavior of the satellite.
Dynamic damper pressure fluctuation in the pumping systems
O.V. Korolyov
2016-05-01
Full Text Available Inertial part of any devices and equipment (e.g., pumps, hung or mounted on the resilient frame and being under the influence of the disturbing force that works at a constant frequency, may be subject to fluctuations, especially near of the resonance area. For elimination these fluctuations, you can resort to the use of a dynamic damper. Aim: The aim of the work is an analytical study of various dynamic dampers to reduce pressure fluctuation problems in pumping systems. Materials and Methods: A comparative analysis of efficiency of functioning was carried out for two types of dynamic dampers - hydraulic and mechanical. Results: The technique for calculating of dynamic damper of fluid pressure fluctuations in the hydraulic and mechanical pumps is presented. Algorithms of calculations are reported to engineering applications and implemented in the production process. The calculations show that the use of dynamic mechanical dampers is expedient at high frequency pumps, and, with increasing frequency of the pump by 6 times, winning in the dimensions of the damper in 3.5 times.
廖昌荣; 陈伟民; 余淼; 黄尚廉
2001-01-01
A magnetorheological fluid (MR fluid)shock absorber model is analyzed theoretically using Newtonain fluid and idealized nonlinear Bingham plastic model respectively for the mixed mode of flow mode and shear mode. In the light of the technician requirements for Changan mini-automobile, a MR fluid shock absorber is designed and fabricated using commercial MR fluid. The nonlinear MR fluid shock absorber model is validated experimentally. The results reveal that the shock absorber model is reasonable and the MR fluid shock absorber for a specific application can be designed according to the MR fluid shock absorber model presented.%根据牛顿流体模型和滨汉塑性流体模型，分别对混合工作模式的汽车磁流变减振器进行了理论分析研究。按照长安微型汽车的技术要求，设计和制作了汽车磁流变减振器，并对此进行了试验测试。试验结果表明，应用所提出的理论分析模型是可行的，对设计特殊阻尼特性的磁流变减振器有一定的指导意义。
Semi-active vibration absorber based on real-time controlled MR damper
Weber, F.
2014-06-01
A semi-active vibration absorber with real-time controlled magnetorheological damper (MR-SVA) for the mitigation of harmonic structural vibrations is presented. The MR damper force targets to realize the frequency and damping adaptations to the actual structural frequency according to the principle of the undamped vibration absorber. The relative motion constraint of the MR-SVA is taken into account by an adaptive nonlinear control of the internal damping of the MR-SVA. The MR-SVA is numerically and experimentally validated for harmonic excitation of the primary structure when the natural frequency of the passive mass spring system of the MR-SVA is correctly tuned to the targeted structural resonance frequency and when de-tuning is present. The results demonstrate that the MR-SVA outperforms the passive TMD at structural resonance frequency by at least 12.4% and up to 60.0%.
ER dampers in vibroprotection systems of precision equipment
Korobko, Evguenia V.; Shulman, Zinovy P.; Danilevski, Leonid N.
1998-06-01
The increased requirements on the accuracy of measurements with the aid of large-weight electronic-optical devices have entailed heavy demands for their efficient protection against low-vibration vibrations produced by an occasional external load or operator's pushes. In these cases, the means of active protection against vibrations used, e.g., in adjustment stands are considered to be the most efficient ones. Among actuating mechanisms of such systems, i.e. hydro- and pneumohydraulic, electromechanical and friction devices, the viscous-friction dampers show much promise since use of electrorheological fluids in the latter allows their functional capabilities to be extended owing to control of the elastoviscous parameters of a working fluid. An analysis is made of vibrations of a single-mass system (an electronic microscope column) whose vibroprotection scheme includes four ER-dampers. Their control is accomplished by a voltage unit in discrete as well as in follow-up linear and logarithmic regimes. The results obtained are compared with experimental data for the systems without dampers, with passive dampers and controllable ER-dampers. The latter are shown to be advantageous, in particular, a three- fold decrease of the Q-factor of the system under forced vibration is reached in the optimum control.
Arief, Injamamul; Mukhopadhyay, P.K., E-mail: pkm@bose.res.in
2014-09-01
Flower-like nanostructures of NiCo (1:1) in the presence of Jeffamine was synthesized by homogeneous nucleation in 1, 2-propanediol for 3 h. Morphological characterizations performed by scanning and transmission electron microscopy (FESEM and TEM) revealed the average size distribution of 700 nm containing 2D nanosheets of ∼30 nm thickness. The nanoflowers crystallize exclusively in face-centered cubic structures and were confirmed by x-ray diffraction studies. Various factors, including nature of polyol, concentrations of base and metal salts in precursor proved to affect the geometry of nanoflowers. Magnetic studies revealed the ferromagnetic nature of NiCo nanoflowers with high saturation magnetization and low coercivity (108.6 emu/g and 78.4 Oe). The enhanced shear properties and yield stress of dimorphic MR fluid containing nanoflowers of NiCo in ferrofluids can be attributed to stronger microstructure formation in the presence of magnetic field.
GENERATION OF ASYMMETRIC F-v CHARACTERISTICS FOR SYMMETRIC MR DAMPERS
WANG Enrong; YE Biaoming; MA Xiaoqing; SU Chunyi; RAKHEJA Subhash
2006-01-01
An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological (MR) dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the "on-off" control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.
Semiactive Self-Tuning Fuzzy Logic Control of Full Vehicle Model with MR Damper
Mahmut Paksoy
2014-09-01
Full Text Available Intelligent controllers are studied for vibration reduction of a vehicle consisting in a semiactive suspension system with a magnetorheological(MR damper. The vehicle is modeled with seven degrees of freedom as a full vehicle model. The semiactive suspension system consists of a linear spring and an MR damper. MR damper is modeled using Bouc-Wen hysteresis phenomenon and applied to a full vehicle model. Fuzzy Logic based controllers are designed to determine the MR damper voltage. Fuzzy Logic and Self-Tuning Fuzzy Logic controllers are applied to the semiactive suspension system. Results of the system are investigated by simulation studies in MATLAB-Simulink environment. The performance of the semiactive suspension system is analyzed with and without control. Simulation results showed that both Fuzzy Logic and Self-Tuning Fuzzy Logic controllers perform better compared to uncontrolled case. Furthermore, Self-Tuning Fuzzy Logic controller displayed a greater improvement in vibration reduction performance compared to Fuzzy Logic controller.
Vibration Control of Vehicle Suspension System by Electrorheological Damper
ZHAO Xia; ZHANG Yong-fa
2006-01-01
An overview of electrorheological (ER) fluid characteristics is given. Based on the Bingham plasticity model and a simple parallel-plate model, the operation principle of ER damper is presented and a four-DOF dynamic model of a vehicle suspension is constructed. Then a semi-active control of vehicle suspension system by ER damper is obtained. According to the semi-active control theory, the acceleration frequency characteristic is achieved with Matlab toolbox. Simulation results show that the vibration of the suspension system is well controlled.
Optimal control of gun recoil in direct fire using magnetorheological absorbers
Singh, Harinder J.; Wereley, Norman M.
2014-05-01
Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using a nonlinear Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with low or high recoil loads imply low or high rate of fire, respectively. The gun recoil absorber performance is also analyzed for perturbations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery position (ready to reload and fire) without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.
Magnetostriction of engineered magnetorheological elastomers
Rieger, William; Kassner, Chris; von Lockette, Paris; Lofland, Samuel
2012-02-01
We have completed a study of the magnetostriction and poison ratio of several types of magnetorheological elastomers (MREs), including both hard and soft magnetic materials in silicone rubber matrices. While both random and aligned soft magnetic particles gave large (˜1%) magnetostriction, hard magnetic powders provided minimal actuation, regardless of whether they were aligned or not. In addition, we have created engineered lattices of magnetic wires and find the actuation highly dependent on the sample shape, and the angle of the magnetic field with respect to the alginment axis. We also propose some new structures based on hard magnetic wires which should provide piezomagnetic response.
MR Damper Controlled Vibration Absorber for Enhanced Mitigation of Harmonic Vibrations
Felix Weber
2016-12-01
Full Text Available This paper describes a semi-active vibration absorber (SVA concept based on a real-time controlled magnetorheological damper (MR-SVA for the enhanced mitigation of structural vibrations due to harmonic disturbing forces. The force of the MR damper is controlled in real-time to generate the frequency and damping controls according to the behaviour of the undamped vibration absorber for the actual frequency of vibration. As stiffness and damping emulations in semi-active actuators are coupled quantities the control is formulated to prioritize the frequency control by the controlled stiffness. The control algorithm is augmented by a stiffness correction method ensuring precise frequency control when the desired control force is constrained by the semi-active restriction and residual force of the MR damper. The force tracking task is solved by a model-based feed forward with feedback correction. The MR-SVA is numerically and experimentally validated for the primary structure with nominal eigenfrequency and when de-tuning of −10%, −5%, +5% and +10% is present. Both validations demonstrate that the MR-SVA improves the vibration reduction in the primary structure by up to 55% compared to the passive tuned mass damper (TMD. Furthermore, it is shown that the MR-SVA with only 80% of tuned mass leads to approximately the same enhanced performance while the associated increased relative motion amplitude of the tuned mass is more than compensated be the reduced dimensions of the mass. Therefore, the MR-SVA is an appropriate solution for the mitigation of tall buildings where the pendulum mass can be up to several thousands of metric tonnes and space for the pendulum damper is limited.
WANG Enrong; YING Liang; WANG Wanjun; RAKHEJA Subhash; SU Chunyi
2008-01-01
A modified skyhook-based semi-active controller is proposed for implementing an asymmetric control suspension design with symmetric magneto-rheological (MR) dampers. The controller is formulated in current form, which is modulated by integrating a continuous modulation and an asymmetric damping force generation algorithms, so as to effectively minimize switching and hysteretic effects from the MR-damper. The proposed controller is implemented with a quarter-vehicle MR-suspension model, and its relative response characteristics are thus evaluated in terms of defined performance measures under varying amplitude harmonic, rounded pulse and random excitations. The sensitivity of the semi-active suspension performance to variations in controller parameters is thoroughly evaluated. The results illustrate that the proposed skyhook-based asymmetric semi-active MR-suspension controller has superior robustness on the system parameter variations, and can achieve desirable multi-objective suspension performance.
Active Vibration Dampers For Rotating Machinery
Kascack, Albert F.; Ropchock, John J.; Lakatos, Tomas F.; Montague, Gerald T.; Palazzolo, Alan; Lin, Reng Rong
1994-01-01
Active dampers developed to suppress vibrations in rotating machinery. Essentially feedback control systems and reciprocating piezoelectric actuators. Similar active damper containing different actuators described in LEW-14488. Concept also applicable to suppression of vibrations in stationary structures subject to winds and earthquakes. Active damper offers adjustable suppression of vibrations. Small and lightweight and responds faster to transients.
Gągorowski, Andrzej
2012-06-01
This paper presents an original approach to the problem of controlling a magnetorheological suspension of a driver's seat for optimal reduction of whole-body vibration. The concept consists in taking into consideration the individual personal features (biomechanical parameters) of the driver in the control process of a MR damper by using human generated signals. The proposed algorithm enables the adaptation of the suspension for an individual driver and specific road conditions. The actual research has focused on numerical simulations with a complex model of the human-seat-vehicle system. The human model representing a specific driver has been described by several biomechanical parameters such as masses of body structures, moments of inertia, and stiffness and damping of the spine, intervertebral discs, spinal muscles and ligaments.
Characteristic analysis of the lower limb muscular strength training system applied with MR dampers.
Yu, Chang Ho; Piao, Young Jun; Kim, Kyung; Kwon, Tae Kyu
2014-01-01
A new training system that can adjust training intensity and indicate the center pressure of a subject was proposed by applying controlled electric current to the Magneto-Rheological damper. The experimental studying on the muscular activities were performed in lower extremities during maintaining and moving exercises, which were processed on an unstable platform with Magneto rheological dampers and recorded in a monitor. The electromyography (EMG) signals of the eight muscles in lower extremities were recorded and analyzed in certain time and frequency domain. Muscles researched in this paper were rectus femoris (RF), biceps femoris (BF), tensor fasciae latae (TFL), vastuslateralis (VL), vastusmedialis (VM), gastrocnemius (Ga), tibialis anterior (TA), and soleus (So). Differences of muscular activities during four moving exercises were studied in our experimental results. The rate of the increment of the muscular activities was affected by the condition of the unstable platform with MR dampers, which suggested the difference of moving exercises could selectively train each muscle with varying intensities. Furthermore, these findings also proposed that this training system can improve the ability of postural balance.
Self-locking MRF latches and dampers
Magnac, G; Claeyssen, F; Vial, K; Le Letty, R; Sosnicki, O; Benoit, C [Cedrat Technologies S.A., Meylan (France)], E-mail: actuator@cedrat.com
2009-02-01
MRF actuators are new electromechanical components using Magneto Rheological Fluids (MRF). When submitted to a high enough magnetic field, MRF switch from a liquid to a near solid body. New MRF actuators were developed in order to reach three aims: to offer a blocking force without power consumption which can be strongly reduced by applying a current, to provide an electrically-controllable resistive force over a stroke of 30 mm, to perform the control of the force in a very short time, typically in a few milliseconds. Thus, these MRF actuators can be used for two main applications: damper and latch - lock. Experiments on two versions of the actuator (a single piston rod and a feed through output axis) allow getting a blocking force around 100N, which is more than 10 times the actuator weight (its mass is 700gr). The current and electric power required to cancel the blocking force are only 1.6A and 4W. the paper further presents the design and the electromechanical properties of the Self-braking MRF Actuators for dampers and latches and new results on the control of these actuators.
Modelling and Experimental Investigation of an Active Damper
Rafael Luís Teixeira
2006-01-01
Full Text Available This paper presents a validation methodology of the dynamic behavior of an active viscous damper. The damper has two flexible metallic bellows connected to a rigid reservoir filled with fluid. When one of the bellows is connected to a vibrating structure a periodic flow passes through a variable internal orifice and the damping effect is produced. The size of the orifice is adjusted by a controlled linear piezoelectric actuator that positions the conical core into a conical cavity. The device finite element structural model consists of the valve body and its conical core that are assumed rigid and the flexible bellows are represented by two pistons with elastic suspensions. The flow developed inside the damper is modeled considering the fluid-structure interation, using the Lagrangean-Eulerian formulation. To validate the proposed model a prototype was constructed and experimental tests and numerical simulations are accomplished in the time domain, applying harmonic excitations. The results are compared using curves that relate the damping coefficient with the orifice size and with the input velocity applied at the bellows face. However, for the proper control design and system operation, the direct use of the finite element model becomes unviable due to its high computational time. Then, a reduced second order discrete dynamic model for the damper was developed. The model parameters are identified by analysis in the frequency domain, using impulsive excitation force, for constant and variable orifice sizes. At low excitation frequencies, the damper prototype behaves like a single degree of freedom system which damping factor changes with the orifice size A fuzzy controller was designed and it generates the orifice reference size associated to the desired damping factor. The active system presented better performance when compared to the passive one.
Przybylski, Michal; Sun, Shuaishuai; Li, Weihua
2016-10-01
Most existing vibration isolators and dampers based on magnetorheological (MR) materials need electrical power to feed magnetic coils to stimulate the MR material, so if there is a loss of power, such as during a strong earthquake or system failure, they are unable to protect the structure. This paper outlines the design and test of a controllable multilayered magnetorheological elastomer (MRE) isolator based on a circular dipolar Halbach array; which is a set of magnets that generates a strong and uniform magnetic field. Combining an MRE layered isolator system with the Halbach array allows for constant vibration isolation with very low power consumption, where the power generated is only used to adjust the Halbach position. When this system was tested it successfully altered the lateral stiffness and damping force by 81.13% and 148.72%, respectively. This paper also includes an extended analysis of the magnetic field generated by the circular dipolar Halbach array and a discussion of the improvements that may potentially improve the range of magnetic fields generated.
Optimal design of a new multipole bilayer magnetorheological brake
Shiao, Yaojung; Ngoc, Nguyen Anh; Lai, Chien-Hung
2016-11-01
This article presents a new high-torque multipole bilayer magneto-rheological brake (MRB). This MRB has a unique structural design with multiple electromagnetic poles and multiple media layers of magnetorheological fluid (MRF). The MRB has two rotors located on the outer and inner sides of a six-pole stator, and therefore, it can provide higher torque and a larger torque-to-volume ratio (TVR) than conventional single- or multipole single-layer MRBs can. Moreover, the problem of potential MRF leakage is solved by using cylindrical separator rings around the stator. In this study, first, the structure of the proposed MRB is introduced. An analog magnetic circuit was built for the MRB to investigate the effects of the MRB parameters on the magnetic field intensity of the MRF layers. In addition, a 3D electromagnetic model of the MRB was developed to simulate and examine the magnetic flux intensity and corresponding braking torque. An approximate optimization method was then applied to obtain the optimal geometric dimensions for the major dimensional parameters of the MRB. The MRB was manufactured and tested to validate its torque and dynamic characteristics. The results showed that the proposed MRB exhibited great enhancement of the braking torque and TVR.
Electrorheological Damper and Its Application for Semi-Active Suspension System
ZHAO Xia; ZHANG Yong-fa
2007-01-01
A semi-active control of vehicle suspension system with electrorheological (ER) damper is presented.ER fluid characteristics are introduced based on the Bingham plasticity model first.Then ER damper working force is given.Finally a quarter car model with ER damper is constructed.The skyhook control strategy is adopted to simulate the amplitude-frequency characteristics and the vibration of suspension system under random road excitation on the basis of ER damper characteristics.The response curves of the vertical acceleration,the suspension dynamic working space and the tyre dynamic loading are obtained.Simulation results show that the acceleration is reduced effectively and then the ride comfort is improved by the skyhook control law.
Application of tuned liquid damper in vibration suppression of wind towers
Poshnejad, A. [Ryerson Polytechnic Univ., Toronto, ON (Canada)
2010-07-01
The structural responses of a wind turbine were simulated with an attached damping tuned liquid damper (TLD) designed to control vibrations. The proposed TLD was an annular liquid container designed to be installed below the nacelle around the tower body. The TLD-structure system was formulated as a nonlinear coupled response between the TLD hydrodynamic force and the structure response. The effectiveness of the damper was compared with the dampers typically used in antenna designs. A circuit shallow TLD was used as a vibration damper. The sloshing behaviour of water was then modelled using a computational fluid dynamics (CFD) tool and an equivalent mechanical model. Vibration dynamics were considered for the rotor blades; the mechanical-electrical drive train; the yaw system; and the entire wind turbine. Results of the investigation demonstrated that the TLD effectively increased the damping of the wind tower. tabs., figs.
X. M. Dong
2013-01-01
Full Text Available Due to the short duration of impulsive impact of an aircraft during touchdown, a traditional landing gear can only achieve limited performance. In this study, a magnetorheological (MR absorber is incorporated into a landing gear system; an intelligent control algorithm, a human simulated intelligent control (HSIC, is proposed to adaptively tune the MR absorber. First, a two degree-of-freedom (DOF dynamic model of a landing gear system featuring an MR absorber is constructed. The control model of an MR damper is also developed. After analyzing the impact characteristic during touchdown, an HSIC is then formulated. A genetic algorithm is adopted to optimize the control parameters of HSIC. Finally, a numerical simulation is performed to validate the proposed damper and the controller considering the varieties of sink velocities and sprung masses. The simulations under different scenarios show that the landing gear system based on the MR absorber can greatly reduce the peak impact load of sprung mass within the stroke. The biggest improvement of the proposed controller is over 40% compared to that of skyhook controller. Furthermore, HSIC exhibits better adaptive ability and strong robustness than skyhook controller under various payloads and sink velocities.
Design optimization of a magnetorheological brake in powered knee orthosis
Ma, Hao; Liao, Wei-Hsin
2015-04-01
Magneto-rheological (MR) fluids have been utilized in devices like orthoses and prostheses to generate controllable braking torque. In this paper, a flat shape rotary MR brake is designed for powered knee orthosis to provide adjustable resistance. Multiple disk structure with interior inner coil is adopted in the MR brake configuration. In order to increase the maximal magnetic flux, a novel internal structure design with smooth transition surface is proposed. Based on this design, a parameterized model of the MR brake is built for geometrical optimization. Multiple factors are considered in the optimization objective: braking torque, weight, and, particularly, average power consumption. The optimization is then performed with Finite Element Analysis (FEA), and the optimal design is obtained among the Pareto-optimal set considering the trade-offs in design objectives.
Adaptive tuning of elasto-plastic damper
Høgsberg, Jan Riess; Krenk, Steen
2007-01-01
Hysteretic dampers are frequency independent, and thereby otentially effective for several structural vibration modes, provided that the inherent amplitude dependence can be controlled. An adaptive tuning procedure is proposed, aiming at elimination of the amplitude dependence by adjusting...... the damper parameter(s) with respect to the magnitude of the damper motion. The procedure is demonstrated in terms of the bilinear elasto-plastic damper model, and optimality corresponds to maximum modal damping. A parametric solution for the damping ratio is obtained by a two-component system reduction...... in controlling the amplitude dependence, resulting in equal damping for the first vibration modes....
Modeling a magneto-rheological soft starter for use with belt conveyors
Tian Zuzhi; Hou Youfu
2012-01-01
The theory of magnetic circuit design,the constitutive equations of a magneto-rheological fluid,and the load properties of belt conveyors were used to design a magneto-rheological soft starter test-bed.The magnetic field distribution in the working gap was analyzed and the current-speed relationship was investigated.A mathematical model for the time response was deduced.The results show that a linear relationship between current and magnetic field is seen when the magnetic materials are not saturated and the magnetic field is uniform in the working section.The rotation speed of the driven shaft changes linearly with increasing time.The response is rapid and can be as short as milliseconds.This meets the starting requirements of belt conveyors.
High-damping-performance magnetorheological material for passive or active vibration control
Liu, Taixiang; Yang, Ke; Yan, Hongwei; Yuan, Xiaodong; Xu, Yangguang
2016-10-01
Optical assembly and alignment system plays a crucial role for the construction of high-power or high-energy laser facility, which attempts to ignite fusion reaction and go further to make fusion energy usable. In the optical assembly and alignment system, the vibration control is a key problem needs to be well handled and a material with higher damping performance is much desirable. Recently, a new kind of smart magneto-sensitive polymeric composite material, named magnetorheological plastomer (MRP), was synthesized and reported as a high-performance magnetorheological material and this material has a magneto-enhanced high-damping performance. The MRP behaves usually in an intermediate state between fluid-like magnetorheological fluid and solid-like magnetorheological elastomer. The state of MRP, as well as the damping performance of MRP, can be tuned by adjusting the ratio of hard segments and soft segments, which are ingredients to synthesize the polymeric matrix. In this work, a series of MRP are prepared by dispersing micron-sized, magneto-sensitive carbonyl iron powders with related additives into polyurethane-based, magnetically insensitive matrix. It is found that the damping performance of MRP depends much on magnetic strength, shear rate, carbonyl iron content and shear strain amplitude. Especially, the damping capacity of MRP can be tuned in a large range by adjusting external magnetic field. It is promising that the MRP will have much application in passive and active vibration control, such as vibration reduction in optical assembly and alignment system, vibration isolation or absorption in vehicle suspension system, etc.
Magnetorheological effect in the magnetic field oriented along the vorticity
Kuzhir, P., E-mail: pavel.kuzhir@unice.fr; Magnet, C.; Fezai, H.; Meunier, A.; Bossis, G. [Laboratory of Condensed Matter Physics, CNRS UMR7336, University of Nice-Sophia Antipolis, 28 Avenue Joseph Vallot, 06100 Nice (France); Rodríguez-Arco, L.; López-López, M. T. [Department of Applied Physics, University of Granada, Campus de Fuentenueva, 18071 Granada (Spain); Zubarev, A. [Department of Mathematical Physics, Ural Federal University, 51 Prospekt Lenina, 620083 Ekaterinburg (Russian Federation)
2014-11-01
In this work, we have studied the magnetorheological (MR) fluid rheology in the magnetic field parallel to the fluid vorticity. Experimentally, the MR fluid flow was realized in the Couette coaxial cylinder geometry with the magnetic field parallel to the symmetry axis. The rheological measurements were compared to those obtained in the cone-plate geometry with the magnetic field perpendicular to the lower rheometer plate. Experiments revealed a quasi-Bingham behavior in both geometries with the stress level being just a few dozens of percent smaller in the Couette cylindrical geometry at the same internal magnetic field. The unexpectedly high MR response in the magnetic field parallel to the fluid vorticity is explained by stochastic fluctuations of positions and orientations of the particle aggregates. These fluctuations are induced by magnetic interactions between them. Once misaligned from the vorticity direction, the aggregates generate a high stress independent of the shear rate, and thus assimilated to the suspension apparent (dynamic) yield stress. Quantitatively, the fluctuations of the aggregate orientation are modeled as a rotary diffusion process with a diffusion constant proportional to the mean square interaction torque. The model gives a satisfactory agreement with the experimental field dependency of the apparent yield stress and confirms the nearly quadratic concentration dependency σ{sub Y}∝Φ{sup 2.2}, revealed in experiments. The practical interest of this study lies in the development of MR smart devices with the magnetic field nonperpendicular to the channel walls.
Real-Time Driving Simulation of Magneto-Rheological Active Damper Stryker Suspension
2011-10-24
driver’s seat location. The Belgian Block terrain was developed using Non Uniform Rational B-Spline ( NURBS ), discussed next in more detail. Though...suspensions. For the Munson Gravel course a bump mapping technique utilizing Non-Uniform Rational B-Spline ( NURBS ) was used to produce road roughness...representative of a gravel road. The NURBS were generated using the root mean square for the gravel road. 5. RIDE DEMONSTRATION RESULTS A team of
Frequency analysis of a semi-active suspension with magneto-rheological dampers
Andronic, Florin; Mihai, Ioan; Suciu, Cornel; Beniuga, Marius
2015-02-01
Suspension systems for motor vehicles are constantly evolving in order to ensure vehicle stability and traffic safety under all driving conditions. The present work aims to highlight the influence factors in the case of a quarter car model for semi-active suspensions. The functions that must be met by such suspension systems are first presented. Mathematical models for passive systems are first illustrated and then customized for the semi-active case. A simulation diagram was conceived for Matlab Simulink. The obtained simulation results allow conducting a frequency analysis of the passive and semi-active cases of the quarter car model. Various charts for Passive Suspension Transmissibility and for the Effect of Damping on Vertical Acceleration Response were obtained for both passive and semi-active situations. Analysis of obtained results allowed evaluating of the suspension systems behavior and their frequency dependence. Significant differences were found between the behaviors of passive and semi-active suspensions. It was found that semi-active suspensions ensure damping in accordance to the chosen control method, and are much more efficient than passive ones.
Luis Augusto Lara-Valencia
2014-01-01
Full Text Available En este artículo se implementa um novedoso proyecto de control estructural numérico en una edificación de dos pisos con el obj etivo de reducir vibraciones debidas a cargas de tipo transiente. La est ructura analizada corresponde a un prototipo experimental debid amente caracterizado y modelado de acuerdo con la hipótesis del diafra gma. El controlador utilizado se basa en la acción de un par de amortiguadores magnetoreológicos (MR reales cuyo funcionamient o es emulado a través del denominado modelo fenomenológico. Los disipadores son gobernados por un sistema numérico basado en re des neuronales artificiales del tipo NARX con la capacidad de determinar fuerzas óptimas de control y voltajes a través de un modelo de predicción y un modelo inverso, los cuales son de us o inédito en este tipo de sistemas. Los resultados obtenidos muestran que el proyecto de control basado en redes neuronales desarrollado en este trabajo es un controlador confiable y eficiente, consiguiendo r educciones de hasta 69% en los valores pico de respuesta.
焦驰宇; 张恺; 张连普; 龙佩恒
2013-01-01
对桥梁阻尼器参数确定方法的相关文献进行了回顾,指出现有常用参数分析法费时费力；而简化分析法存在仅适用于结构保持在弹性阶段、无法考虑罕遇地震下支座摩擦及墩柱轻度损伤等复杂情况的弊端.以非线性静力分析获得的能力曲线为基础,利用性能点、目标点求解时获得的关键参数,结合等效弹性单自由度体系附加非线性粘滞阻尼器的参数确定公式,提出了考虑支座摩擦和墩柱损伤的桥用阻尼器参数确定方法.将该方法应用于某三跨连续梁桥抗震加固分析,验证了该方法的实用性及准确性.指出了该方法具有的优势及使用时需注意的问题.本文方法可用于中小跨径桥梁抗震加固时液体粘滞阻尼器的参数确定.%By reviewing parameter determination methods for fluid viscous damper ( FVD) applied in structural engineering, the defect of time consuming when using parameter analysis method, and the defect of not considering the bearing friction and other nonlinearity when using normal simplified method were pointed out. A new parameter determinations method which can easily and quickly consider the above effects was proposed. It can be expressed as follows; based on the pushover curve given by nonlinear static analysis, getting the key parameters when calculating performance point and target point, then substituting them into the structural dynamic formula of elastic SDF system with non - linear fluid viscous dampers, the approprite parameter of the viscous damper can be achieved. Taking a seismic retrofitting example of a three-span continuous girder bridge using FVD, the accuracy and practicality of the parameter determination method given in the paper was validated. The advantages and some problems which should be noticed when using this method were given. The parameter determination method can be used in similar seismic retrofit design of medium and small-span bridges when FVD were
Analysis of Train Suspension System Using MR dampers
RamaSastry, DVA; Ramana, K. V.; Mohan Rao, N.; Siva Kumar, SVR; Priyanka, T. G. L.
2016-09-01
This paper deals with introducing MR dampers to the Train Suspension System for improving the ride comfort of the passengers. This type of suspension system comes under Semi-active suspension system which utilizes the properties of MR fluid to damp the vibrations. In case of high speed trains, the coach body is subjected to vibrations due to vertical displacement, yaw and pitch movements. When the body receives these disturbances from the ground,the transmission of vibrations to the passenger increases which affect the ride comfort. In this work, the equations of motion of suspension system are developed for both conventional passive system and semi-active system and are modelled in Matlab/Simulink and analysis has been carried out. The passive suspension system analysis shows that it is taking more time to damp the vibrations and at the same time the transmissibility of vibrations is more.Introducing MR dampers,vertical and angular displacements of the body are computed and compared. The results show that the introduction of MR dampers into the train suspension system improves ride comfort.
Dzung Nguyen, Sy; Kim, Wanho; Park, Jhinha; Choi, Seung-Bok
2017-04-01
Vibration control systems using smart dampers (SmDs) such as magnetorheological and electrorheological dampers (MRD and ERD), which are classified as the integrated structure-SmD control systems (ISSmDCSs), have been actively researched and widely used. This work proposes a new controller for a class of ISSmDCSs in which high accuracy of SmD models as well as increment of control ability to deal with uncertainty and time delay are to be expected. In order to achieve this goal, two formualtion steps are required; a non-parametric SmD model based on an adaptive neuro-fuzzy inference system (ANFIS) and a novel fuzzy sliding mode controller (FSMC) which can weaken the model error of the ISSmDCSs and hence provide enhanced vibration control performances. As for the formulation of the proposed controller, first, an ANFIS controller is desgned to identify SmDs using the improved control algorithm named improved establishing neuro-fuzzy system (establishing neuro-fuzzy system). Second, a new control law for the FSMC is designed via Lyapunov stability analysis. An application to a semi-active MRD vehicle suspension system is then undertaken to illustrate and evaluate the effectiveness of the proposed control method. It is demonstrated through an experimental realization that the FSMC proposed in this work shows superior vibration control performance of the vehicle suspension compared to other surveyed controller which have similar structures to the FSMC, such as fuzzy logic and sliding mode control.
Numerical Study on Nonlinear Semiactive Control of Steel-Concrete Hybrid Structures Using MR Dampers
Long-He Xu
2013-01-01
Full Text Available Controlling the damage process, avoiding the global collapse, and increasing the seismic safety of the super high-rise building structures are of great significance to the casualties’ reduction and seismic losses mitigation. In this paper, a semiactive control platform based on magnetorheological (MR dampers comprising the Bouc-Wen model, the semi-active control law, and the shear wall damage criteria and steel damage material model is developed in LS-DYNA program, based on the data transferring between the main program and the control platform; it can realize the purpose of integrated modeling, analysis, and design of the nonlinear semi-active control system. The nonlinear seismic control effectiveness is verified by the numerical example of a 15-story steel-concrete hybrid structure; the results indicate that the control platform and the numerical method are stable and fast, the relative displacement, shear force, and damage of the steel-concrete structure are largely reduced using the optimal designed MR dampers, and the deformations and shear forces of the concrete tube and frame are better consorted by the control devices.
Theoretical research on aggregative dynamic pressure damper
HU Jun-hua; CAO Shu-ping; LUO Xiao-hui; NIU Zi-hua; XIN Ji-song
2009-01-01
To broaden the frequency width and increase the damping coefficient of a dynamic pressure damper, we designed an aggregative dynamic pressure damper (ADPD). Combined with the advantages of traditional dynamic pressure dampers (TDPD), ADPD can not only increase the damping coefficient in wide frequency range for valve control system, but also absorb partial pressure pulsations and impacts in the low and high frequency fields. Based on the theoretical research and the analysis compared with TDPD, we concluded that the ADPD was superior to the TDPD in the middle high frequency field, and the main parameters influencing the performance of the damper were the damping stiffness, orifice flow coefficient, pre-charge pressure, and the volume of the damper accumulator.
Ezio Santagata
2014-01-01
Full Text Available Magneto-rheological fluids are materials that exhibit a significant change in their rheological properties in the presence of a magnetic field. Because of such a field-dependent behavior, they can act as smart materials in applications in which changeable performances are desired. In road pavement engineering, the use of bitumen-based magneto-rheological fluids may open innovative scenarios related to the construction of smart pavement sections and to the investigation of damage mechanisms in binders and mixtures. The research work presented in this study explored magneto-rheological properties of several field-responsive bituminous binders obtained from two different base bitumens combined with multi-wall carbon nanotubes and powder iron. The experimental program included oscillatory shear loading tests at different temperatures, performed in the strain controlled mode by means of a dynamic shear rheometer equipped with a magneto-rheological device. The investigation was carried out with the specific goal of identifying critical issues which should be taken into account in materials preparation, testing procedures and data analysis. Undesired overheating of specimens during testing was identified and taken into account for a correct interpretation of experimental data. Thus, while the field-sensitivity of carbon nanotubes was found to be negligible as a result of the magnetic shielding action of bitumen, it was shown that powder iron can significantly affect the magneto-rheological properties of bituminous binders when employed in sufficiently high amounts. Moreover, obtained results indicated that selection of base bitumen is a key factor in designing bituminous-based smart materials. Practical implications which derive from the study are mainly relative to the fine-tuning of laboratory characterization procedures which should necessarily overcome current limitations in temperature regulation and magnetic field generation. Experimental data
Yang, Pingan; Yu, Miao; Fu, Jie
2016-03-01
As a kind of new Magnetorheological (MR) material, MR Gel (MRG) can be regarded as the analog of MR fluid (MRF), which can overcome the iron particles sedimentation and unstable application of MRF. Normally, the storage modulus of conventional MRG is relatively small, although it has a very high relative MR effect. Therefore, practical engineering application of conventional MRG has been restricted more or less. In this work, an MRG with high magneto-induced shear storage modulus and excellent relative MR effect has been fabricated by incorporating Ni-coated multi-walled carbon nanotubes (Ni-coated MWCNTs). And several polyurethane-based MRG composites with the addition of Ni-coated MWCNTs were prepared. The dynamic mechanical property of those MRG composites with applying magnetic field is researched through an advanced commercial rheometer. The experimental results indicated that the initial storage modulus and magneto-induced modulus in sample 4 (containing 6 wt% of the Ni-coated MWCNTs) were approximately 4.45 and 2.27 times than that in the sample 1 (without Ni-coated MWCNTs). Moreover, the relative MR effect of sample 4 can reach 3427 %. The high modulus of sample 4 can be mainly attributed to the following points. One is the Ni-coated MWCNTs can be aligned along the direction of the magnetic field within the matrix which provided a better reinforcing efficiency. The other is Ni-coated MWCNTs can be made to form a better bonding between the iron particles and the matrix. It is concluded that this study provides a meaningful way to improve the mechanical properties of MRG and expected to promote the application of MRG in practice.
Hybrid viscous damper with filtered integral force feedback control
Høgsberg, Jan; Brodersen, Mark L.
2016-01-01
In hybrid damper systems active control devices are usually introduced to enhance the performance of otherwise passive dampers. In the present paper a hybrid damper concept is comprised of a passive viscous damper placed in series with an active actuator and a force sensor. The actuator motion...
Isolation and damping properties of magnetorheologic elastomers
Collette, C; Kroll, G; Avraam, M; Preumont, A [University of Brussels, 50 av. F.D. Roosevelt, 1050 Brussels (Belgium); Saive, G [Techspace Aero (SAFRAN Group), 121, route de Liers, 4041 Herstal (Belgium); Guillemier, V [MATIS Benelux, 121, route de Liers, 4041 Herstal (Belgium)], E-mail: christophe.collette@ulb.ac.be
2009-02-01
This paper considers two systems based on a magnetorheological elastomer (MRE): a MRE isolator under a frequency varying harmonic excitation and a MRE Dynamic Vibration Absorber (DVA) mounted on a frequency-varying structure under a random excitation. It is shown that the commandability of the elastomer improves the isolation performances in the first case, and decreases the stress level in the structure in the second case.
Development of Magnetorheological Engine Mount Test Rig
Md Yunos Mohd Razali; Harun Mohamad Hafiz; Sariman M.Z.; Mat Yamin A.K.
2017-01-01
Ride comfort is an important factor in any road vehicle performance. Nonetheless, passenger ride comfort is sometimes affected by the vibrations resulting from the road irregularities. Vehicle ride comfort is also often compromised by engine vibration. Engine mount is one of the devices which act as vibration isolator from unwanted vibration from engine to the driver and passengers. This paper explains the development of the test rig used for laboratory testing of Magnetorheological (MR) engi...
Silva Navarro, Gerardo; Cabrera Amado, Alvaro [Cinvestav, IPN, Mexico, D.F. (Mexico)
2007-11-15
This paper deals with the problem of semiactive balancing control of a rotor-bearing system, where one journal bearings is supported on two radial Magneto-Rheological (MR) dampers. The mathematical model of the rotor-bearing system results from an orthotropic Jeffcott-like model and the dynamics associated to the MR dampers, whose rheological properties depend on the current inputs. For control purposes we use the Choi-Lee-Park polynomial for the MR dampers, which is quite consistent with the tpical nonlinear and complex hysteresis behavior and also simplifies the physical implementation on an experimental setup. The semiactive control scheme for the unbalance reponse of the rotor-bearing system is synthesized using sliding-mode control techniques. Some numerical and experimental results are included to illustrate the dynamic performance and robustness of the overall system. [Spanish] En este trabajo se abora el problema de control semiactivo del desbalance en un sistema rotor-chumacera, donde una de las chumaceras convencionales se monta sobre una suspension con dos amortiguadores Magneto-Reologicos (MR) radiales. El modelo matematico del sistema rotorchumacera se obtiene de un modelo tipo Jefcott ortotropico y la dinamica de los amortiguadores MR, cuyas propiedades reologicas dependen de las corrientes electricas de alimentacion. Para propositos de control se emplea el modelo polinomial de Choi-Lee-Park para los dos amortiguadores MR, el cual es consistente con el tipico comportamiento no-lineal y de histeresis, permitiendo simplificar su implementacion fisica en una plataforma experimental. El esquema de control semiactivo de la respuesta al desbalance, en el sistema rotor-chumacera, se basa en las tecnicas de control por modos deslizantes. Se presentan algunos resultados de simulacion numerica y experimentos que utilizan el funcionamiento y robustez del sistema completo.
Method of hardening a fluid mass
Zitha, P.L.J.; Jansen, J.D.
2003-01-01
The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally
Method of hardening a fluid mass
Zitha, P.L.J.; Jansen, J.D.
2003-01-01
The invention relates to a method of hardening a fluid mass in contact with a wall, in a desirable shape. According to the invention, the fluid mass is a magneto-rheological fluid mixture that in addition to at least one hardening component comprises a particulate magnetic component, with minimally
Viscoplastic flow in an extrusion damper
Syrakos, Alexandros; Georgiou, Georgios C; Tsamopoulos, John
2016-01-01
Numerical simulations of the flow in an extrusion damper are performed using a finite volume method. The damper is assumed to consist of a shaft, with or without a spherical bulge, oscillating axially in a containing cylinder filled with a viscoplastic material of Bingham type. The response of the damper to a forced sinusoidal displacement is studied. In the bulgeless case the configuration is the annular analogue of the well-known lid-driven cavity problem, but with a sinusoidal rather than constant lid velocity. Navier slip is applied to the shaft surface in order to bound the reaction force to finite values. Starting from a base case, several problem parameters are varied in turn in order to study the effects of viscoplasticity, slip, damper geometry and oscillation frequency to the damper response. The results show that, compared to Newtonian flow, viscoplasticity causes the damper force to be less sensitive to the shaft velocity; this is often a desirable damper property. The bulge increases the required...
Auxiliary mass damper for Cardan suspended gyro
Rosenberg, J.; Kahana, A.
The paper describes a damping system for a spin-stabilized platform which involves the use of an auxiliary mass connected to the gimbal system by means of a spring and a viscous dash-pot. The damper inertia is insignificant in comparison with the platform inertia, resulting in a simplified model in which the nutational frequency is taken to be the forced frequency. An analysis is made of the interaction between the stabilized platform and the damper, which causes the appearance of three natural frequencies instead of the nutational frequency. The experimental realization of the auxiliary mass damper is discussed.
Zhang, Zili; Nielsen, Søren R. K.; Basu, Biswajit
2015-01-01
Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g. This facilit......Tuned liquid dampers (TLDs) utilize the sloshing motion of the fluid to suppress structural vibrations and become a natural candidate for damping vibrations in rotating wind turbine blades. The centrifugal acceleration at the tip of a wind turbine blade can reach a magnitude of 7–8g...... studied in the numerical simulation. It is shown that the one-mode model is able to predict the sloshing force and the damped structural response accurately, since the primary damping effect on the structure is achieved by the first sloshing mode of the fluid. Although it is unable to predict the fluid...
Development of a multi-pole magnetorheological brake
Shiao, Yaojung; Nguyen, Quang-Anh
2013-06-01
This paper presents a new approach in the design and optimization of a novel multi-pole magnetorheological (MR) brake that employs magnetic flux more effectively on the surface of the rotor. MR brakes with conventional single ring-type electromagnetic poles have reached the limits of torque enhancement. One major reason is the limitation of the magnetic field strength within the active area of the MR fluid due to the geometric constraints of the coil. The multi-pole MR brake design features multiple electromagnetic poles surrounded by several coils. As a result, the active chaining areas for the MR fluid are greatly increased, and significant brake torque improvement is achieved. The coil structure, as a part of the stator, becomes flexible and customizable in terms of space usage for the winding and bobbin design. In addition, this brake offers extra options in its dimensions for torque enhancement because either the radial or the axial dimensions of the rotor can be increased. Magnetic circuit analysis was conducted to analyze the effects of the design parameters on the field torque. After that, simulations were done to find the optimal design under all major geometric constraints with a given power supply. The results show that the multi-pole MR brake provides a considerable braking torque increase while maintaining a compact and solid design. This is confirmation of its feasibility in actual braking applications.
Modelling of Dampers and Damping in Structures
Høgsberg, Jan Riess
2006-01-01
The present thesis consists of an extended summary and four papers concerning damping of structures and algorithmic damping in numerical analysis. The first part of the thesis deals with the efficiency and the tuning of external collocated dampers acting on flexible structures. The dynamics...... and the maximum attainable damping are found by maximizing the expression for the damping ratio. The theory is formulated for linear damper models, but may also be applied for non-linear dampers in terms of equivalent linear parameters for stiffness and damping, respectively. The format of the expressions...... only realizable by means of active control. The present thesis demonstrates how stiffness affects both the performance and the tuning of the damper. The final part of the thesis considers algorithmic damping in connection with Newmark time integration. The damping characteristics of the Newmark method...
Development of ER fluid-based actuators for rotorcraft flexbeam applications
Kamath, Gopalakrishna M.; Wereley, Norman M.
1995-05-01
A numerical study of electrorheological (ER) dampers is presented. Two models, the Newtonian and the Bingham plastic models are used to characterize the ER fluid behavior. Damping performance of two damper configurations, the Moving Electrode and the Fixed Electrode configurations, is studied. The effects of electrode gap sizes, the field strength and the ER fluid model used are quantified. The study provides a basis for design of ER-fluid based dampers.
The Dissipative Column: A New Hysteretic Damper
Bruno Palazzo; Paolo Castaldo; Ivana Marino
2015-01-01
A new replaceable hysteretic damper to better control seismic building damage, consisting of two or more adjacent steel vertical elements connected to each other with continuous mild/low strength steel shear links, is proposed and investigated in this paper. New Dampers, called Dissipative Columns (DC), continuously linked with X-shaped steel plates, provide additional stiffness and damping to a lateral system by using a basic and minimally invasive construction element: the column. Working i...
Results from the AGS Booster transverse damper
Russo, D.; Brennan, M.; Meth, M.; Roser, T.
1993-01-01
To reach the design intensity of 1.5 [times] 10[sup 13] protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s[sup [minus]1] have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.
Results from the AGS Booster transverse damper
Russo, D.; Brennan, M.; Meth, M.; Roser, T.
1993-06-01
To reach the design intensity of 1.5 {times} 10{sup 13} protons per pulse in the AGS Booster, transverse coupled bunch instabilities with an estimated growth rate of 1500s{sup {minus}1} have to be dampened. A prototype transverse damper has been tested successfully using a one turn digital delay and closed orbit suppression implemented in a programmable gate array. An updated damper, which includes an algorithm to optimize damping for a changing betatron rune, will also be presented.
Design and control of multifunctional magnetorheological actuators for assistive knee braces
Guo, H. T.; Liao, W. H.
2010-04-01
This paper is aimed at developing a novel multifunctional actuator utilizing magnetorheological (MR) fluids. As a key component for assistive knee braces, the actuator can work with multiple functions as motor, clutch and brake in order to meet the requirement of normal human walking. In this paper, design considerations including configurations, materials selection, mechanical and electromagnetic designs are illustrated. Prototype of the multifunctional actuator is fabricated, and each of its functions is investigated. Control strategies for mimicking normal human walking using the multifunctional actuator are illustrated. Adaptive control algorithm is adopted. Experiments on torque and speed tracking are conducted. The results show that the developed multifunctional actuator is promising for assistive knee braces.
Optimum connecting dampers to reduce the seismic responses of parallel structures
Zhu, H. P.; Ge, D. D.; Huang, X.
2011-04-01
Parameters of connecting dampers between two adjacent structures and twin-tower structure with large podium are optimized through theoretical analysis. The connecting visco-elastic damper (VED) is represented by the Kelvin model and the connecting viscous fluid damper (VFD) is represented by the Maxwell model. Two optimization criteria are selected to minimize the vibration energy of the primary structure and to minimize the vibration energy of both structures. Two representative numerical examples of adjacent structures and one three-dimensional finite element model of a twin-tower with podium structure are used to verify the correctness of the theoretical approach. On the one hand, by means of theoretical analysis, the first natural circular frequencies and total mass of the two structures can be taken as parameters in the general formula to get the optimal parameters of the coupling dampers. On the other hand, using the Kanai-Tajimi filtered white-noise ground motion model and several actual earthquake records, the appropriate parameters of two types of linking dampers are obtained through extensive parametric studies. By comparison, it can be found that the results of parametric studies are consistent with the results of theoretical studies for the two types of dampers under the two optimization criteria. The effectiveness of VED and VFD is investigated in terms of the seismic response reduction of the neighboring structures. The numerical results demonstrate that the seismic response and vibration energy of parallel structures are mitigated significantly. The performances of VED and VFD are comparable to one another. The explicit formula of VED and VFD can help engineers in application of coupled structure control strategies.
Study on optimum arrangement of hysteretic dampers in frame structure
无
2007-01-01
The earthquake mitigation effect of hysteretic dampers is not only related to the number, stiffness,strength, deformation ability of dampers but also to the strength and stiffness of the structure. This paper studied the condition that structures should be in when the hysteretic dampers mitigated seismic action most effectively and made appropriate numerical analysis to verify the effectiveness of theory derivation. The inelastic seismic responses were analyzed for the SDOF system that the shear strength ratio of the damper system was taken differently and the result showed that when the ratio was in the vicinity of the optimum strength ratio of the damper system, the displacement of the structure was minimum and the energy dissipation of dampers was maximum, which indicated that the dampers mitigated seismic action most effectively. The result also indicated that the hysteretic dampers had significant earthquake mitigation effect when the strength ratio β changed in a relatively wide range.
Kwon, Seung Hyuk; Choi, Hyoung Jin; Lee, Jung Won; Hong, Kwang Pyo; Cho, Myeong Woo
2013-06-01
Magnetorheological (MR) fluids are colloidal suspensions of soft magnetic particles dispersed in a non-magnetic liquid. Among their applications, MR polishing has attracted considerable attention owing to its smart control of the polishing characteristics for dedicated microelectromechanical system applications. To improve the polishing characteristics of MR fluids, we fabricated carbonyl iron (CI) microspheres coated with xanthan gum (XG) by using a solvent casting method. The morphologies and densities of both pure CI and CI/XG particles were characterized using a scanning electron microscope and a pycnometer, respectively. In addition, the rheological characteristics of the MR fluids under various applied magnetic field strengths were examined using a rotational rheometer. The MR polishing characteristics were conducted using an MR polishing machine to examine the surface roughness and the material removal by MR polishing with added nano-ceria slurry abrasives.
An Experimental Study on Steel and Teflon Squeeze Film Dampers
Asad A. Khalid
2006-01-01
Full Text Available In this paper, the vibration analysis on Teflon and steel squeeze film dampers has been carried out. At different frequency ranges, vibration amplitude and the resonance frequency are measured. The eccentricity ratio at resonance speed has been determined. Results show that the vibration amplitude of the steel damper is 10% less at resonance compared with the Teflon damper. On the other hand, saving weight of 36% has been achieved by using the Teflon damper.
Magnetorheology of hybrid colloids obtained by spin-coating and classical rheometry
Aslam, Raheema; Shahrivar, Keshvad; de Vicente, Juan; González-Viñas, Wenceslao
2016-07-01
Hybrid colloids composed of micron-sized ferromagnetic (carbonyl iron) and diamagnetic (silica) particles suspended in cyclohexanone, behave as, non-Newtonian, magnetorheological fluids. We measure and compare the magnetic field-dependent viscosity of hybrid diluted colloids using spin-coating and conventional magnetorheometry. We extend a previously developed model for simple colloids to this kind of hybrid colloids. As in the previous model, the viscosity of the colloidal suspension under applied fields can be derived from the surface coverage of the dry spin-coated deposits for each type of particles, and from the viscosity of the colloid at zero field. Also, our results allow us to obtain the evaporation rate of the solvent as a function of the rotation speed. Finally, we also measure the viscosity of the same suspension with a torsional parallel plate magnetorheometer under uniaxial DC magnetic fields aligned in the velocity gradient direction of a steady shearing flow. The experimental results under different conditions and the effect of each component on the magnetorheological properties of the resulting colloid are discussed. Standard spin-coating technique can be used both to characterize smart materials—complex fluids as well as to fabricate films with arbitrary solvents by tuning their viscosity by means of external fields.
Marcin BAJKOWSKI
2014-06-01
Full Text Available This paper presents the laboratory stand, designed for research and didactic purposes. The stand allows investigating the performance of the programmable system for controlling the recoil effect in the small caliber arm–shooter configuration. The system incorporates synchronized magnetorheological (MR damper. The aim of the study is to describe the influence of the damping of a high-energy pulse from small caliber arm, on the value of the thrust force. For the considered set of MR dampers the range of the operating currents for the MR coil is experimentally selected and adjusted. In the study of the results the emphasis is put on the influence of MR damper on the force characteristics, which directly affects the accuracy of the weapon. The obtained results show that the proposed system special object–MR damper–shooter, has a major, positive effect on the accuracy by reducing the components of the recoil. A scheme of the laboratory stand is presented. Basic parameters of the investigated system and research results are discussed
Improved Nutation Damper for a Spin-Stabilized Spacecraft
Woodard, Mark A.
2004-01-01
A document proposes an improved liquid- ring nutation damper for a spin-stabilized spacecraft. The improvement addresses the problem of accommodating thermal expansion of the damping liquid. Heretofore, the problem has been solved by either (1) filling the ring completely with liquid and accommodating expansion by attaching a bellows or (2) partially filling the ring and accepting the formation of bubbles. The disadvantage of (1) is that a bellows is expensive and may not be reliable; the disadvantage of (2) is that bubbles can cause fluid lockup and consequent loss of damping. In the improved damper, the ring would be nearly completely filled with liquid, and expansion would be accommodated, but not by a bellows. Instead, an escape tube would be attached to the ring. The escape tube would be positioned and oriented so that the artificial gravitation and the associated buoyant force generated by the spin of the spacecraft would cause the bubbles to migrate toward the tip of the tube. In addition, when the spacecraft was on the launch pad, the escape tube would be at the top of the ring, so that bubbles would rise into the tube.
Qin Xiangjun; Zhang Xun'an; Sheldon Cherry
2008-01-01
The recently proposed mega-sub controlled structure (MSCS), a new type of structure associated with the design and construction of super-tall buildings, has attracted the attention of designers for use in enhancing the control effectiveness in mega-fi'ame buildings. In this paper, a dynamic equation and method to assemble parameter matrixes for a mega-sub controlled structure under random wind loads is presented. Semi-active control using magnetorheological dampers for the MSCS under random wind loads is investigated, and is compared with a corresponding system without dampers. A parametric study of the relative stiffness ratio and relative mass ratio between the mega-frame and the substructures, as well as the additional column stiffness ratio that influences the response control effectiveness of the MSCS, is discussed. The studies reveal, for the first time, that different control mechanisms exist. The results indicate that the proposed structure employing semi-active control can offer an effective control mechanism. Guidelines for selecting parameters are provided based on the analytical study.
Weiqing Fu
2017-03-01
Full Text Available The conventional isolation structure with rubber bearings exhibits large deformation characteristics when subjected to infrequent earthquakes, which may lead to failure of the isolation layer. Although passive dampers can be used to reduce the layer displacement, the layer deformation and superstructure acceleration responses will increase in cases of fortification earthquakes or frequently occurring earthquakes. In addition to secondary damages and loss of life, such excessive displacement results in damages to the facilities in the structure. In order to overcome these shortcomings, this paper presents a structural vibration control system where the base isolation system is composed of rubber bearings with magnetorheological (MR damper and are regulated using the innovative control strategy. The high-order single-step algorithm with continuity and switch control strategies are applied to the control system. Shaking table test results under various earthquake conditions indicate that the proposed isolation method, compared with passive isolation technique, can effectively suppress earthquake responses for acceleration of superstructure and deformation within the isolation layer. As a result, this structural control method exhibits excellent performance, such as fast computation, generic real-time control, acceleration reduction and high seismic energy dissipation etc. The relative merits of the continuity and switch control strategies are also compared and discussed.
The Dissipative Column: A New Hysteretic Damper
Bruno Palazzo
2015-02-01
Full Text Available A new replaceable hysteretic damper to better control seismic building damage, consisting of two or more adjacent steel vertical elements connected to each other with continuous mild/low strength steel shear links, is proposed and investigated in this paper. New Dampers, called Dissipative Columns (DC, continuously linked with X-shaped steel plates, provide additional stiffness and damping to a lateral system by using a basic and minimally invasive construction element: the column. Working in a way similar to coupled shear walls, the proposed element behavior is theoretically analyzed at linear and non-linear ranges. In fact, considering different restrained cases, a parametric analysis is developed in order both to evaluate the effect of the main geometrical and structural parameters and to provide the design capacity curves of this new damper. The DC can be considered a new damping device, easy to install in new as well as existing buildings in order to protect them from seismic damage.
A magnetic damper for first mode vibration reduction in multimass flexible rotors
Kasarda, M. E. F.; Allaire, P. E.; Humphris, R. R.; Barrett, L. E.
1989-01-01
Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems, and would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. An experimental test rig is described which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.
Numerical analysis on aeolian vibration of transmission lines with Stockbridge dampers
LI Li; KONG De-yi; LONG Xiao-hong; FANG Qin-han
2008-01-01
We used computational fluid dynamics (CFD) and mode superposition method instead of the energy balance method to compute transmission line aeolian vibrations induced by the Karman vortex. Firstly, we obtained the wind power inputs using CFD theory. The result is effective for aeolian vibration analyses compared with the power which were measured in wind tunnel tests. Then a new aeolian excitation was derived using the wind power equivalent principle, and the aeolian vibration distribution along transmission lines and the wind power input obtained by CFD can be account. Secondly, we formulated the motion equation of a conductor-damper system and derived a semi-analytial solution using the mode superposition method. The Stockbridge-type dampers attached were simplified to the forces transmitted by the clamps. Finally, the semi-analytical solution can be solved by iterative methods. Taking a 1 000 kV Ultra High Voltage transmission line as an example, we analyzed the line with and without dampers by the semi-analytical solution. Compared with the results which were computed by the energy balance method, the semi-analytical solution is precise enogh for aeolian vibration analyses. Besides, we also analyzed the influence of damper position and quantity.
Dynamic damping property of magnetorheological elastomer
李剑锋; 龚兴龙
2008-01-01
Magnetorheological elastomer(MRE) is a new kind of smart materials,its dynamic mechanic performances can be controlled by an applied magnetic field.MRE is usually used as a stiffness-changeable spring in the semi-active vibration absorber.In order to get perfect vibration control effect,low dynamic damping of MRE is need.But the dynamic damping of MRE was not studied deeply in the past.The dynamic damping of MRE was studied and analyzed.The influences of different test conditions including test strain amplitude,test frequency and test magnetic field were deeply studied.MRE sample and pure silicone rubber sample were prepared and tested under different conditions.The test results show that the main source of dynamic damping is the friction between iron particles and rubber matrix.And the friction is mainly influenced by the strain amplitude and test magnetic field.
Chen, Kaikai; Zhang, Wen Ling; Shan, Lei; Zhang, Xiangjun; Meng, Yonggang; Choi, Hyoung Jin; Tian, Yu
2014-10-01
Magnetorheological (MR) fluids based on carbonyl iron (CI) particles coated with graphene oxide (GO) and sunflower oils were studied and compared with MR fluids (MRFs) prepared with CI particles added with GO sheets. Adding GO sheets into CI had a negligible effect on the rheological properties of the MRF. Coating the spheres with GO markedly decreased the shear strength at high shear rates due to the remarkable lubricating function of the GO surface. Different behaviors were observed in the shear thickening phenomenon when the GO surface changed the mechanical interaction between particles. The results demonstrated the importance of the role of interparticle friction for MRF in shear mode and discussed the weak shear thickening phenomenon with fine lubricating coating layers and oils.
Structural Vibration Control Using Solid Particle Damper
Haseena. A
2015-11-01
Full Text Available In this paper the effectiveness of a solid particle damper to control structural vibration is experimentally investigated. The vibration control performance and its influencing parameters are examined by a Multi Degree of Freedom (MDOF structure attached with a particle damper (PD under horizontal excitation. In a particle damping system damping is achieved using solid particles or granules and is a passive damping method. Here the enclosure filled with particles is attached to the primary structure undergoing vibration. As the primary structure vibrates, particles undergo inelastic collision within the enclosure resulting high amount of energy dissipation. Based on the analytical study of undamped frame in ANSYS WORKBENCH, dimensions of the frame were fixed and shake table study of a two storied steel frame with and without damper system are carried out. Results shows that effectiveness of damping depends on various parameters like mass, particle size, shape etc. The effectiveness is compared with a friction damper (FD and is observed that PD is more efficient than FD since 31.80% energy is dissipated more in PD compared to FD
Nonlinear Study of Industrial Arc Spring Dampers
Lahriri, Said; Santos, Ilmar; Hartmann, Henning
2011-01-01
The objective of this paper is to present a numerical approach for analyzing parameter excited vibrations on a gas compressor, induced by the nonlinear characteristic of the arc spring feature of certain designs of squeeze film dampers, SFDs. The behavior of the journal is studied in preparation ...
游仕平; 游世辉; 曾德长
2012-01-01
Magnetorheological rubber can be controlled its stiffness and strength by the external magnetic field. Meanwhile, it resolved the problem of the particles settling and poor stability of the magnetorheological fluids, so magnetorheological rubber has become a new type of intelligent materials and received the widespread attention at home and abroad. The nylon cord reinforced magnetorheological rubber based on NR/SBR ( natural rubber/styrene butadiene rubber) blend was prepared for the first time, and studied its static mechanical properties and dynamic magnetorheological effect through the Zwick/Roell electronic pull machine and magneto-combined dynamic mechanical analysis. The results show that the tensile strength of magnetorheological rubber can be greatly improved and the shear modulus and the zero-field shear storage modulus of magnetorheological rubber are enhanced by adding the nylon cord, when joined three layers of nylon cord, its tensile strength can be achieved 17.8 MPa and the zero-field shear storage modulus is 2.87 MPa. But, with the increment of nylon cord, its magnetorheological effect is lower.%由于可通过外加磁场来控制磁敏橡胶的刚度和强度,同时可解决磁流变液颗粒沉降、稳定性差的问题,因此磁敏橡胶成为国内外广泛关注的一种新型智能材料.制备了尼龙帘线增强型天然橡胶/丁苯橡胶( natural rubber/styrenebutadiene rubber,NR./SBR)并用胶基磁敏橡胶,采用Zwick/Roell电子拉力机和力磁耦合动态力学分析仪研究其静态力学性能和动态磁流变效应.结果表明,尼龙帘线的加入可以极大地提高磁敏橡胶的抗拉强度,同时也可提高磁敏橡胶的剪切模量和零场剪切储能模量；当加入三层帘线时,其抗拉强度可达到17.8 MPa,零场剪切储能模量为2.87 MPa;但随着尼龙帘线的增多,其磁流变效应则降低.
Semi-active model predictive control for 3rd generation benchmark problem using smart dampers
Yan Guiyun; Sun Bingnan; Lü Yanping
2007-01-01
A semi-active strategy for model predictive control (MPC), in which magneto-rheological dampers are used as an actuator, is presented for use in reducing the nonlinear seismic response of high-rise buildings. A multi-step predictive model is developed to estimate the seismic performance of high-rise buildings, taking into account of the effects of nonlinearity, time-variability, model mismatching, and disturbances and uncertainty of controlled system parameters by the predicted error feedback in the multi-step predictive model. Based on the predictive model, a Kalman-Bucy observer suitable for semi-active strategy is proposed to estimate the state vector from the acceleration and semi-active control force feedback.The main advantage of the proposed strategy is its inherent stability, simplicity, on-line real-time operation, and the ability to handle nonlinearity, uncertainty, and time-variability properties of structures. Numerical simulation of the nonlinear seismic responses of a controlled 20-story benchmark building is carried out, and the simulation results are compared to those of other control systems. The results show that the developed semi-active strategy can efficiently reduce the nonlinear seismic response of high-rise buildings.
Chen, Shaoshan; Li, Shengyi; Peng, Xiaoqiang; Hu, Hao; Tie, Guipeng
2015-02-20
A new nonaqueous and abrasive-free magnetorheological finishing (MRF) method is adopted for processing a KDP crystal. MRF polishing is easy to result in the embedding of carbonyl iron (CI) powders; meanwhile, Fe contamination on the KDP crystal surface will affect the laser induced damage threshold seriously. This paper puts forward an appropriate MRF polishing process to avoid the embedding. Polishing results show that the embedding of CI powders can be avoided by controlling the polishing parameters. Furthermore, on the KDP crystal surface, magnetorheological fluids residua inevitably exist after polishing and in which the Fe contamination cannot be removed completely by initial ultrasonic cleaning. To solve this problem, a kind of ion beam figuring (IBF) polishing is introduced to remove the impurity layer. Then the content of Fe element contamination and the depth of impurity elements are measured by time of flight secondary ion mass spectrometry. The measurement results show that there are no CI powders embedding in the MRF polished surface and no Fe contamination after the IBF polishing process, respectively. That verifies the feasibility of MRF polishing-IBF polishing (cleaning) for processing a KDP crystal.
Optimal design and selection of magneto-rheological brake types based on braking torque and mass
Nguyen, Q. H.; Lang, V. T.; Choi, S. B.
2015-06-01
In developing magnetorheological brakes (MRBs), it is well known that the braking torque and the mass of the MRBs are important factors that should be considered in the product’s design. This research focuses on the optimal design of different types of MRBs, from which we identify an optimal selection of MRB types, considering braking torque and mass. In the optimization, common types of MRBs such as disc-type, drum-type, hybrid-type, and T-shape types are considered. The optimization problem is to find an optimal MRB structure that can produce the required braking torque while minimizing its mass. After a brief description of the configuration of the MRBs, the MRBs’ braking torque is derived based on the Herschel-Bulkley rheological model of the magnetorheological fluid. Then, the optimal designs of the MRBs are analyzed. The optimization objective is to minimize the mass of the brake while the braking torque is constrained to be greater than a required value. In addition, the power consumption of the MRBs is also considered as a reference parameter in the optimization. A finite element analysis integrated with an optimization tool is used to obtain optimal solutions for the MRBs. Optimal solutions of MRBs with different required braking torque values are obtained based on the proposed optimization procedure. From the results, we discuss the optimal selection of MRB types, considering braking torque and mass.
Contributions to modeling functionality of a high frequency damper system
Sirbu, E. A.; Horga, S.; Vrabioiu, G.
2016-08-01
Due to the necessity of improving the handling performances of a motor vehicle, it is imperative to understand the suspensions properties that affects ride and directional respons.The construction of a fero-magnetic shock absorber is based on two bellows interconnected by a pipe-line. Through this pipe-line the fero-magnetic fluid is carried between the two bellows. The damping characteristic of the shock absorber is affected by the viscosity of the fero-magnetic fluid. The viscosity of the fluid, is controlled through a electric coil mounted on the bellows connecting pipe-line. Modifying the electrical field of the coil, the viscosity of the fluid will change, finally affecting the damping characteristic of the shock absorber. A recent system called „CCD Pothole Suspension” is implemented on Ford vehicles. By modifying the dampning characteristic of the shock absorbers, vehicle daynamics can be improved; also the risk of damaging the suspension will be decreased. The approach of this paper is to analyze the behaviour of the fero magnetic damper, thus determining how it will affect the performances of the vehicle suspensions. The experimental research will provide a better understanding of the behavior of the fero-magnetic shock absorber, and the possible advantages of using this system.
A geometrical optimization of a magneto-rheological rotary brake in a prosthetic knee
Gudmundsson, K. H.; Jonsdottir, F.; Thorsteinsson, F.
2010-03-01
Magneto-rheological (MR) fluids have been successfully introduced to prosthetic devices. One such device is a biomechanical prosthetic knee that uses MR fluids to actively control its rotary stiffness. The brake is rotational, utilizing the MR fluid in shear mode. In this study, the geometrical design of the MR brake is addressed. This includes the design of the magnetic circuit and the geometry of the fluid chamber. Mathematical models are presented that describe the rotary torque of the brake. A novel perfluorinated polyether (PFPE)-based MR fluid is introduced, whose properties are tailored for the prosthetic knee. On-state and off-state rheological measurements of the MR fluid are presented. The finite element method is used to evaluate the magnetic flux density in the MR fluid. The design is formulated as an optimization problem, aiming to maximize the braking torque. A parametric study is carried out for several design parameters. Subsequently, a multi-objective optimization problem is defined that considers three design objectives: the field-induced braking torque, the off-state rotary stiffness and the weight of the brake. Trade-offs between the three design objectives are investigated which provides a basis for informed design decisions on furthering the success of the MR prosthetic knee.
Energy based optimization of viscous-friction dampers on cables
Weber, F.; Boston, C.
2010-04-01
This investigation optimizes numerically a viscous-friction damper connected to a cable close to one cable anchor for fastest reduction of the total mechanical cable energy during a free vibration decay test. The optimization parameters are the viscous coefficient of the viscous part and the ratio between the friction force and displacement amplitude of the friction part of the transverse damper. Results demonstrate that an almost pure friction damper with negligibly small viscous damping generates fastest cable energy reduction over the entire decay. The ratio between the friction force and displacement amplitude of the optimal friction damper differs from that derived from the energy equivalent optimal viscous damper. The reason for this is that the nonlinearity of the friction damper causes energy spillover from the excited to higher modes of the order of 10%, i.e. cables with attached friction dampers vibrate at several frequencies. This explains why the energy equivalent approach does not yield the optimal friction damper. Analysis of the simulation data demonstrates that the optimally tuned friction damper dissipates the same energy per cycle as if each modal component of the cable were damped by its corresponding optimal linear viscous damper.
Wan-quan Jiang; Jing-jing Yao; Xing-long Gong; Lin Chen
2008-01-01
In order to obtain magnetorheological(MR) elastomers with high magnetorheological effect,a family of anisotropic rubber-based MR elastomers was developed using a new form of chemical modification.Three different kinds of surfactants,i.e.anionic,nonionic and compound surfactants,were employed separately to modify iron particles.The MR effect was evaluated by measuring the dynamic shear modulus of MR elastomer with a magneto-combined dynamic mechanical analyzer.Results show that the relative MR effect can be up to 188% when the iron particles are modified with 15% Span 80.Besides the surface activity of Span 80,however,such high modifying effect is partly due to the plasticizing effect of Span 80.Compared with the single surfactant,the superior surface activity of compound surfactant makes the relative MR effect reach 77% at a low content of 0.4%.Scanning electron microscope observation shows that the modification of compound surfactant results in perfect compatibility between particles and rubber matrix and special self-assembled structure of particles.Such special structure has been proved beneficial to the improvement of the relative MR effect.
Weilian QU; Jianwei TU
2009-01-01
A vertical ship lift under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the ship lift towers. This paper proposes a roof magnetorheological (MR) intelligent isolation system to prevent the seismic whipping effect on machinery structures. Theoretically, the dynamic models of MR damper and the mechanical model of ship lift was established, the inverse neural network controlling algorithm was proposed and the fundamental semi-active control equation for the Three-Gorges ship lift where the MR intelligent isolation system was installed was deduced. Experimentally, the experimental model of the ship lift was given, the vibrating table experiment of the MR intelligent isolation system controlling the whipping effect was carried out and the results of the inverse neural network control strategy and passive isolation strategy were compared. In practical aspect, the large-scale MR damper (500kN) and a sliding support with limited stiffness were designed and fabricated. It was proven that the MR intelligent isolation system with proper control strategy can greatly reduce the seismic whipping effect on the top workshop of the ship lift and be simple and effective enough to be applied to real engineering structures.
Configuration optimization of dampers for adjacent buildings under seismic excitations
Bigdeli, Kasra; Hare, Warren; Tesfamariam, Solomon
2012-12-01
Passive coupling of adjacent structures is known to be an effective method to reduce undesirable vibrations and structural pounding effects. Past results have shown that reducing the number of dampers can considerably decrease the cost of implementation and does not significantly decrease the efficiency of the system. The main objective of this study was to find the optimal arrangement of a limited number of dampers to minimize interstorey drift. Five approaches to solving the resulting bi-level optimization problem are introduced and examined (exhaustive search, inserting dampers, inserting floors, locations of maximum relative velocity and a genetic algorithm) and the numerical efficiency of each method is examined. The results reveal that the inserting damper method is the most efficient and reliable method, particularly for tall structures. It was also found that increasing the number of dampers does not necessarily increase the efficiency of the system. In fact, increasing the number of dampers can exacerbate the dynamic response of the system.
Application of particle damper on electronic packages for spacecraft
Veeramuthuvel, P.; Shankar, K.; Sairajan, K. K.
2016-10-01
Particle damping is an effective method of passive vibration control, which is of recent research interest. This paper presents a novel application of particle damper on an electronic package of a spacecraft, tested at ISRO Satellite Centre. The effectiveness of particle damper on the random vibration response of electronic package for spacecraft application exposed to random vibration environments experienced during the launch is studied. The use of particle damper under shock environments are also demonstrated. Optimal particle damper parameters were used based on the design guidelines derived from previous publications of the authors. The comparison of particle damper effectiveness under random vibration loads with respect to the shape of the particle damper capsule and packing ratio are also examined.
Study on coupled shock absorber system using four electromagnetic dampers
Fukumori, Y.; Hayashi, R.; Okano, H.; Suda, Y.; Nakano, K.
2016-09-01
Recently, the electromagnetic damper, which is composed of an electric motor, a ball screw, and a nut, was proposed. The electromagnetic damper has high responsiveness, controllability, and energy saving performance. It has been reported that it improved ride comfort and drivability. In addition, the authors have proposed a coupling method of two electromagnetic dampers. The method enables the characteristics of bouncing and rolling or pitching motion of a vehicle to be tuned independently. In this study, the authors increase the number of coupling of electromagnetic dampers from two to four, and propose a method to couple four electromagnetic dampers. The proposed method enables the characteristics of bouncing, rolling and pitching motion of a vehicle to be tuned independently. Basic experiments using proposed circuit and motors and numerical simulations of an automobile equipped with the proposed coupling electromagnetic damper are carried out. The results indicate the proposed method is effective.
Mesoscopic magnetomechanical hysteresis in a magnetorheological elastomer.
Biller, A M; Stolbov, O V; Raikher, Yu L
2015-08-01
Field-induced magnetostatic interaction in a pair of identical particles made of a magnetically soft ferromagnet is studied. It is shown that due to saturation of the ferromagnet magnetization, this case differs significantly from the (super)paramagnetic one. A numerical solution is given, discussed, and compared with that provided by a simpler model (nonlinear mutual dipoles). We show that for multidomain ferromagnetic particles embedded in an elastomer matrix, as for paramagnetic ones in the same environment, pair clusters may form or break by a hysteresis scenario. However, the magnetization saturation brings in important features to this effect. First, the bistability state and the hysteresis take place only in a limited region of the material parameters of the system. Second, along with the hysteresis jumps occurring under the sole influence of the field, the "latent" hysteresis is possible which realizes only if the action of the field is combined with some additional (nonmagnetic) external factor. The obtained conditions, when used to assess the possibility of clustering in real magnetorheological polymers, infer an important role of mesoscopic magnetomechanical hysteresis for the macroscopic properties of these composites.
Fabrication and properties of magnetorheological elastomers based on CR/ENR self-crosslinking blends
Wang, Yonghong; Zhang, Xinru; Oh, Jaeeung; Chung, Kyungho
2015-09-01
Magnetorheological elastomers (MREs) are intelligent materials, which are widely used as dampers to eliminate vibration. In this study, a new kind of MREs was designed using carbonyl iron particles (CIPs), carbon black (CB) and self-crosslinking blends, which were fabricated by reacting polychloroprene rubber with epoxidized natural rubber (CR/ENR blends). The interaction mechanism among CIPs, CB and a matrix in the fabrication process was discussed in detail. The morphology of isotropic MREs (i-MREs) and anisotropic MREs (a-MREs) was observed by scanning electron microscopy (SEM). The effect of CIP volume content on the mechanical properties of MREs was investigated. The effect of CIP volume content on the shear storage modulus, MR effect and loss factor was studied using a modified dynamic mechanical analyzer (DMA). The results revealed that the chain-like distribution of CIPs became more pronounced with increasing CIP content in a-MREs, whereas CIPs distributed uniformly in i-MREs. CIPs and CB bonded well with the rubber matrix as a result of their surface attraction effect to CR and ENR molecular chains. Therefore, MREs had excellent mechanical properties. The promoting effect of CB and CIPs on the self-crosslinking reaction was verified by crosslink density assessment. The shear storage modulus of MREs increased with the increase of CIP content, and the MR effect of i-MREs remarkably increased, while a-MREs decreased due to the obvious increase in initial storage modulus with increasing CIP content. The loss factor of MREs decreased obviously with the increase of CIP content.
Hailong, Zhang; Enrong, Wang; Fuhong, Min; Ning, Zhang
2016-03-01
The magneto-rheological damper (MRD) is a promising device used in vehicle semi-active suspension systems, for its continuous adjustable damping output. However, the innate nonlinear hysteresis characteristic of MRD may cause the nonlinear behaviors. In this work, a two-degree-of-freedom (2-DOF) MR suspension system was established first, by employing the modified Bouc-Wen force-velocity (F-v) hysteretic model. The nonlinear dynamic response of the system was investigated under the external excitation of single-frequency harmonic and bandwidth-limited stochastic road surface. The largest Lyapunov exponent (LLE) was used to detect the chaotic area of the frequency and amplitude of harmonic excitation, and the bifurcation diagrams, time histories, phase portraits, and power spectrum density (PSD) diagrams were used to reveal the dynamic evolution process in detail. Moreover, the LLE and Kolmogorov entropy (K entropy) were used to identify whether the system response was random or chaotic under stochastic road surface. The results demonstrated that the complex dynamical behaviors occur under different external excitation conditions. The oscillating mechanism of alternating periodic oscillations, quasi-periodic oscillations, and chaotic oscillations was observed in detail. The chaotic regions revealed that chaotic motions may appear in conditions of mid-low frequency and large amplitude, as well as small amplitude and all frequency. The obtained parameter regions where the chaotic motions may appear are useful for design of structural parameters of the vibration isolation, and the optimization of control strategy for MR suspension system. Projects supported by the National Natural Science Foundation of China (Grant Nos. 51475246, 51277098, and 51075215), the Research Innovation Program for College Graduates of Jiangsu Province China (Grant No. KYLX15 0725), and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK20131402).
BNL 56 MHz HOM Damper Prototype Fabrication at JLab
Huque, Naeem A. [Jefferson Lab., Newport News, VA (United States); Daly, Edward F. [Jefferson Lab., Newport News, VA (United States); Clemens, William A. [Jefferson Lab., Newport News, VA (United States); McIntyre, Gary T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wu, Qiong [Brookhaven National Lab. (BNL), Upton, NY (United States); Seberg, Scott [Brookhaven National Lab. (BNL), Upton, NY (United States); Bellavia, Steve [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-09-01
A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider's (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.
Stochastic seismic response of building with super-elastic damper
Gur, Sourav; Mishra, Sudib Kumar; Roy, Koushik
2016-05-01
Hysteretic yield dampers are widely employed for seismic vibration control of buildings. An improved version of such damper has been proposed recently by exploiting the superelastic force-deformation characteristics of the Shape-Memory-Alloy (SMA). Although a number of studies have illustrated the performance of such damper, precise estimate of the optimal parameters and performances, along with the comparison with the conventional yield damper is lacking. Presently, the optimal parameters for the superelastic damper are proposed by conducting systematic design optimization, in which, the stochastic response serves as the objective function, evaluated through nonlinear random vibration analysis. These optimal parameters can be employed to establish an initial design for the SMA-damper. Further, a comparison among the optimal responses is also presented in order to assess the improvement that can be achieved by the superelastic damper over the yield damper. The consistency of the improvements is also checked by considering the anticipated variation in the system parameters as well as seismic loading condition. In spite of the improved performance of super-elastic damper, the available variant of SMA(s) is quite expensive to limit their applicability. However, recently developed ferrous SMA are expected to offer even superior performance along with improved cost effectiveness, that can be studied through a life cycle cost analysis in future work.
BNL 56 MHz HOM damper prototype fabrication at JLAB
Huque, N.; McIntyre, G.; Daly, E. F.; Clemens, W.; Wu, Q.; Seberg, S.; Bellavia, S.
2015-05-03
A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.
Shallow Water Tuned Liquid Dampers
Krabbenhøft, Jørgen
researchers on TLDs termed wave breaking. A large part of the energy dissipation in the fluid is anticipated to stem from the turbulence in the vicinity of the moving hydraulic jump, and in order to verify this supposition the effect of bottom friction is included in the mathematical model. Studies reveal...... in connection with sloshing has used cumbersome, computationally expensive and somewhat outdated numerical solution schemes. We compare a state of the art, high order, shock capturing method with a simpler low order scheme and find that the simple scheme is adequate for simulating shallow water sloshing...
A new method for speed control of a DC motor using magnetorheological clutch
Nguyen, Quoc Hung; Choi, Seung-Bok
2014-03-01
In this research, a new method to control speed of DC motor using magnetorheological (MR) clutch is proposed and realized. Firstly, the strategy of a DC motor speed control using MR clutch is proposed. The MR clutch configuration is then proposed and analyzed based on Bingham-plastic rheological model of MR fluid. An optimal designed of the MR clutch is then studied to find out the optimal geometric dimensions of the clutch that can transform a required torque with minimum mass. A prototype of the optimized MR clutch is then manufactured and its performance characteristics are experimentally investigated. A DC motor speed control system featuring the optimized MR clutch is designed and manufactured. A PID controller is then designed to control the output speed of the system. In order to evaluate the effectiveness of the proposed DC motor speed control system, experimental results of the system such as speed tracking performance are obtained and presented with discussions.
徐海鹏; 张红辉; 余昭
2011-01-01
The single-ended Magneto-rheological( MR) damper with controllable damping and simple structure, has become one of hotspots in the fileds of semi-actively structure vibration. The auxiliary stiffness of MR damper is not fully covered due to the physical modeling complexity of compensation. Based on the MR damper with gas-floating piston compensation, the theoretical model was built to analyze the composition and influence factors of output force. , and which has important application value in MR damper design. In view of damping-displacement characteristics, the auxiliary stiffness of MR damper provides the reference for structure design.%单出杆结构磁流变阻尼器因其阻尼力可控、结构简单等特点,成为结构半主动振动抑制应用研究的热点.由于补偿物理建模的复杂性,现有研究中一般未考虑附加刚度问题,仅有个别开展了相关试验研究.以浮动活塞-气室补偿单出杆磁流变阻尼器为研究对象,建立了阻尼器理论模型,分析了输出力的构成及影响因素,具有重要的实用价值.从示功特性角度,重点探讨了阻尼器附加刚度特性,为单出杆磁流变阻尼器设计提供重要参考.
Non-linear magnetorheological behaviour of an inverse ferrofluid
de Gans, B.J.; Hoekstra, Hans; Mellema, J.
1999-01-01
The non-linear magnetorheological behaviour is studied of a model system consisting of monodisperse silica particles suspended in a ferrofluid. The stress/strain curve as well as the flow curve was measured as a function of volume fraction silica particles and field strength, using a home-made
Broadband Liquid Dampers to Stabilize Flexible Spacecraft Structures
Kuiper, J.M.
2012-01-01
Mass-spring and liquid dampers enable structural vibration control to attenuate single, coupled lateral and torsional vibrations in diverse structures. Out of these, the passively tuned liquid damper (TLD) class is wanted due to its broad applicability, extreme reliability, robustness, long life tim
Vibration Isolation and Transmissibility Characteristics of Passive Sequential Damper
M.S. Patil
2004-01-01
Full Text Available This paper presents a half-car model (4-degrees-of-freedom employing nonlinear passlve sequential damper. The vibration isolation and transmrssibility effect on the vehicle's centre ofgravity (C.G. has been studied. The results have been compared for transmissibility, displacement, and velocity transient response for half-car model having nonlinear passive sequentialhydropneumatic damper under different terrain excitation.
Z-Damper: A New Paradigm for Attenuation of Vibrations
José Luis Pérez-Díaz
2016-06-01
Full Text Available Magnetic linear gear provides a new and unique opportunity for coupling mechanical impedances and optimizing vibration damping. In the present paper a new magneto-mechanical vibration damper (the so-called Z-damper is described. Its expected theoretical dynamic behavior shows a particularly high damping capability, a low frequency, as well as an optimal behavior for high frequencies.
Recentering Shape Memory Alloy Passive Damper for Structural Vibration Control
Hui Qian
2013-01-01
Full Text Available This paper presents a preliminary study on the evaluation of an innovative energy dissipation system with shape memory alloys (SMAs for structural seismic protection. A recentering shape memory alloy damper (RSMAD, in which superelastic nitinol wires are utilized as energy dissipation components, is proposed. Improved constitutive equations based on Graesser and Cozzarelli model are proposed for superelastic nitinol wires used in the damper. Cyclic tensile-compressive tests on the damper with various prestrain under different loading frequencies and displacement amplitudes were conducted. The results show that the hysteretic behaviors of the damper can be modified to best fit the needs for passive structural control applications by adjusting the pretension of the nitinol wires, and the damper performance is not sensitive to frequencies greater than 0.5 Hz. To assess the effectiveness of the dampers for structural seismic protection, nonlinear time history analysis on a ten-story steel frame with and without the dampers subjected to representative earthquake ground motions was performed. The simulation results indicate that superelastic SMA dampers are effective in mitigating the structural response of building structures subjected to strong earthquakes.
Efficiency and tuning of viscous dampers on discrete systems
Main, Joseph A.; Krenk, Steen
2005-01-01
An approximate solution is developed to the complex eigenproblem associated with free vibrations of a discrete system with several viscous dampers, in order to facilitate optimal placement and sizing of added dampers in structures. The approximate solution is obtained as an interpolation between ...
Research on Effect of SMA Damper in Passive Control
Peng Gang; Fan Jian; Li Li; Tan Jiaxiang
2003-01-01
In this article, mechanics model of SMA center tension from damper is developed. According to the theory of Brinson constitutive model and thermodynamics first law, damper thermodynamics non-linear equation has been developed. Dynamics non-linear equation of frame structure under operation of SMA damper and its solution have been worked out; the software of seismic response analysis for frame structure and of damper characteristic analysis have been compiled with MATLAB software, and the examples have been computed with it. The result indicates that SMA damper has obvious damp characteristics and it can provide with obvious restraint effect for seismic response of frame structure. Decreasing rate of displacement and velocity on top of frame structure reaches 50 %-60 %. The result is in accordance with other pundits experimentation results, which indicates that the above methods are correct and useful.
Inelastic Seismic Response of Building with Friction Damper
Banerjee, Susanta; Patro, Sanjaya K.
2016-12-01
Dampers are used to control response of structure in recent years. Seismic response is reduced by adding energy dissipation capacity to the building. Dampers are provided to dissipate energy to reduce the damages on buildings. Relative displacement of two floors are opposed by damper elements. Dampers dissipate energy with no or little degradation in strength and stiffness. This work presents the response of structure with energy dissipation device i.e. friction damper built on soft soil when the structure is subjected to a ground motion. Parameters that influence strength and stiffness of structure and energy dissipating device are studied. Response of structure with energy dissipating device is analyzed and it is shown that building with damper shows better performance during earthquake. Building structures are designed using results from elastic analysis, though inelastic behavior well observed during the earthquake. Actual response of the structure can be estimated in the inelastic range by using nonlinear structural analysis programs. Inelastic Damage indices of structural component, overall building are computed by formulating Modified Park and Ang model. Nonlinear analysis program IDARC 2D is used for modeling and analysis. Modeling of friction damper is done using a Wen-Bouc model without stiffness and strength or strength degradation. These devices are modeled with an axial diagonal element. Pseudo force approach is introduced to consider the forces in damper elements, that is, forces in damper elements are subtracted from external load vector. Smooth hysteretic model is used to model response of friction dampers. Nonlinear dynamic analysis is carried out using Newmark-Beta integration method and the pseudo-force method. Damaged state of structure is obtained to observe whether elements are cracked, yielded or failed during analysis. Response parameters such as lateral floor displacement, storey drift, base shear are also computed.
Takayama, M.; Tada, H.; Morita, K. (Fukuoka University, Fukuoka (Japan). Faculty of Engineering)
1992-09-01
The dynamic properties of the newly developed lead damper for base isolation systems were studied experimentally which is featured by its energy absorption capacity two times that of conventional ones. Three U-type 99.99 purity lead dampers of 180 mm in shank diameter were prepared as specimens, and excited by moving a H-shape steel beam by actuator according to sinusoidal or seismic wave form in the direction parallel or perpendicular to the bend section of specimens. As a result, in general, their restoring force patterns were similar to that of perfect rigid-plastic ones, and the exciting frequency had small effect on bearing force in a frequency range over 0.05 Hz. The damper could follow seismic displacement enough in seismic wave exciting, and although cracks were developed in the upper portion of the damper by repeated exciting, the damper could absorb energy throughout excitation without any ruptures. 2 refs., 26 figs., 5 tabs.
Bikić Siniša M.; Uzelac Dušan N.; Bukurov Maša Ž.; Radojčin Milivoj T.; Pavkov Ivan S.
2016-01-01
This paper is focused on the mathematical model of the Air Torque Position dampers. The mathematical model establishes a link between the velocity of air in front of the damper, position of the damper blade and the moment acting on the blade caused by the air flow. This research aims to experimentally verify the mathematical model for the damper type with non-cascading blades. Four different types of dampers with non-cascading blades were considered: single...
Arief, Injamamul; Mukhopadhyay, P.K., E-mail: pkm@bose.res.in
2014-06-01
Cubic and spherical Fe{sub 55}Co{sub 45} alloyed microstructures were synthesized by borohydride reduction from aqueous solutions of metallic precursors, using stabilizers and polymer. Monosodium citrate, sodium acetate and PEG 6000 were utilized as electrostatic stabilizers and polymeric surface modifier. Suitable reaction conditions were maintained for synthesis of predominantly larger particles (0.7 µm to 1.2 µm), that facilitates use in magnetorheological fluids. Surface morphological studies by scanning electron microscopy revealed well shaped cubic and spherical geometry for the citrate and polymer-stabilized Fe{sub 55}Co{sub 45} alloys, while the alloy compositions remained nearly the same for both. X-ray diffractions of the as-prepared and annealed samples under various temperatures showed high degree of crystallinity with increasing temperatures. Studies of D.C. magnetization of the systems reveal that the particles have a core–shell structure, with inner magnetic core having a diameter around 30 nm with a log-normal distribution. Magnetorheological studies were performed with 8 vol% suspensions of as-synthesized particles dispersed in silicone oil (viscosity 30 mPa s at 25 °C) under different magnetic fields. Detailed studies of the magnetorheological properties were studied on these systems for practical use.
Dynamic mechanical behavior magnetorheological nanocomposites containing CNTs: A review
Ismail, Rozaina; Ibrahim, Azmi; Hamid, Hanizah Ab.; Mahmood, Mohamad Rusop; Adnan, Azlan
2016-07-01
Carbon nanotubes (CNTs) based polymer composites have variety of engineering applications due to their excellent mechanical, electrical, chemical, magnetic, etc. properties. This paper is an attempt to present a coherent yet concise review of as many of these publications as possible on the mechanical aspect of the Magnetorheological Elastomer (MRE) composites with the addition of multi-walled carbon nanotubes (CNTs). The dynamic mechanical response of the MR nanocomposites to applied magnetic fields has been investigated through dynamic mechanical analysis. It is found that a small amount of carbon nanotubes can effectively improve the mechanical performance of conventional MR elastomers. In summary, multi-walled carbon nanotubes reinforced magnetorheological composite has been developed to take advantage of both the smart MR technology and outstanding properties of carbon nanotubes. Furthermore review is also carried out on the capability of carbon nanotubes to impart the stiffness and damping performance encountered with the properties of CNT based Natural Rubber.
Regression analysis application for designing the vibration dampers
A. V. Ivanov
2014-01-01
Full Text Available Multi-frequency vibration dampers protect air power lines and fiber optic communication channels against Aeolian vibrations. To have a maximum efficiency the natural frequencies of dampers should be evenly distributed over the entire operating frequency range from 3 to 150 Hz. A traditional approach to damper design is to investigate damper features using the fullscale models. As a result, a conclusion on the damper capabilities is drawn, and design changes are made to achieve the required natural frequencies. The article describes a direct optimization method to design dampers.This method leads to a clear-cut definition of geometrical and mass parameters of dampers by their natural frequencies. The direct designing method is based on the active plan and design experiment.Based on regression analysis, a regression model is obtained as a second order polynomial to establish unique relation between the input (element dimensions, the weights of cargos and the output (natural frequencies design parameters. Different problems of designing dampers are considered using developed regression models.As a result, it has been found that a satisfactory accuracy of mathematical models, relating the input designing parameters to the output ones, is achieved. Depending on the number of input parameters and the nature of the restrictions a statement of designing purpose, including an optimization one, can be different when restrictions for design parameters are to meet the conflicting requirements.A proposed optimization method to solve a direct designing problem allows us to determine directly the damper element dimensions for any natural frequencies, and at the initial stage of the analysis, based on the methods of nonlinear programming, to disclose problems with no solution.The developed approach can be successfully applied to design various mechanical systems with complicated nonlinear interactions between the input and output parameters.
Theoretical Research of Magnetorheological Shock Absorber Damping Force
Andrius Klevinskis
2014-02-01
Full Text Available In the article an overview of magnetorheological shock absorbertypes is presented, theoretical calculations of heat dispersion,magnetic field strength produced by shock absorber as well asmaximum power of electromagnet are provided. The article alsoprovides device damping force in line with a change of devicetemperature. In the end of the research the results of experimentare presented in the graph format as well as the conclusions.
Yeganeh Fallah, Arash; Taghikhany, Touraj
2015-12-01
Recent decades have witnessed much interest in the application of active and semi-active control strategies for seismic protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its fault detection observer and fault-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ faults which are used for calculating a fault distribution matrix. Then the fault-tolerant sliding mode controller reconfigures itself by the fault distribution matrix and accommodates the fault effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed fault-tolerant control system. It was shown that the fault-tolerant control system maintains the performance of the structure at an acceptable level in the post-fault case.
Space Shuttle Damper System for Ground Wind Load Tests
Robinson, G. D.; Holt, J. R.; Chang, C. S.
1973-01-01
An active damper system which was originally developed for a 5.5% Saturn IB/Skylab Ground Winds Model was modified and used for similar purposes in a Space Shuttle model. A second damper system which was originally used in a 3% Saturn V/Dry Workshop model was also modified and made compatible with the Space Shuttle model to serve as a back-up system. Included in this final report are descriptions of the modified damper systems and the associated control and instrumentation.
Modelling and control of vehicle magnetorheological seats based on bond graph%基于键图的车辆磁流变座椅建模与控制
高芳; 赵强; 李瑰贤
2012-01-01
A five degree-of-freedom (DOF) physical model for human body-seat and a modified Bouc-Wen model of magnetorheological damper are established and discussed. Based on these two models, a power bond-graph model is further presented for the vehicle magnetorheological seats. The bond-graph model is completed with the 20-Sim software. A proportion-integration-differentiation (PID) control algorithm is designed based on this bond graph model. Simulation shows that this model can accurately describethedynamiccharacteristicsofthewholesystemandprovidesavaluedreferenceforthesemi-activecontrolofhumanbody-seat.% 分析和建立了人体-座椅的五自由度运动的物理模型以及磁流变阻尼器的修正Bouc-Wen模型，进而提出了车辆磁流变座椅的功率键合图模型，在20-Sim中给出了键合图模型的具体实现。基于此键图模型设计了比例-积分-微分(PID)控制算法。仿真结果表明：该键图模型能够较准确描述整个系统的动态特性，对人体座椅的半主动控制研究具有参考作用。
The Development of Electrorheological Fluids for AN Automotive Semi-Active Suspension System
Weyenberg, Thomas R.; Pialet, Joseph W.; Petek, Nicholas K.
The feasibility of electrorheological (ER) dampers for an automotive semi-active suspension was evaluated in a three phase program. In the first phase, ER fluid performance targets were derived. The desired ride and handling attributes of the suspension system were translated into damper specifications, which were then translated into the ER fluid performance targets. The damper specifications included dynamic range, bandwidth, power draw, and packaging. The ER fluid performance parameters then included zero-field viscosity, ER stress, response time, and power density. In the second phase, the dampers and the ER fluid were developed to meet the performance targets. Trade-offs were made between damper design and fluid formulation to achieve the desired damper dynamic range and power draw. A state-diagram approach using screen test data was used to select candidate ER fluids. In the third phase of the program, a prototype semi-active suspension system using fast, continuously variable ER dampers was installed on a demonstration vehicle. Heave, pitch, and roll motions of the vehicle were controlled by applying voltages independently to the four dampers as determined by a modified sky-hook algorithm. The system was designed to respond in less than 10 ms with an average power requirement less than 40 W for normal road surfaces and handling. Laboratory data from a pressure driven flow screen test and a damper test are presented that document the ER fluid performance specification and selection process. Vehicle performance data are presented that demonstrate the features of ER technology for the semi-active suspension application. Remaining issues for commercialization of ER fluids are discussed.
On the principle of impulse damper: A concept derived from impact damper
Chatterjee, S.
2008-05-01
The present article discusses a new principle of active vibration control of lightly damped flexible structural members. The basic scheme mimics the working principle of impact dampers. Control efforts are in the form of impulses generated by expanding and contracting a mass loaded lead zirconium titanate (PZT) stack actuator at suitable values of the states of the system. Efficacy of the damper is demonstrated in mitigating free vibration, forced vibration and self-excited vibration of a single-degree-of-freedom primary system. Effects of various parameters are studied to reveal the existence of optimum control parameters in controlling free vibration. Finally, a dynamic control law is proposed to generate the hysteretic control commands for expanding and contracting the actuator. The hysteretic part of the control command is generated by a first-order nonlinear ordinary differential equation (ODE). The proposed scheme is thought to be useful for controlling vibrations of a wide class of systems ranging from macro- to microscale applications like microelectromechanical systems (MEMS), microrobots, and other micromachines, etc. If adaptively used, the damper can perform optimally without requiring an explicit mathematical model of the system and the global dynamic information thereof.
Lin, Wei; Li, Zhongxian; Ding, Yang
2008-12-01
In the field of civil engineering, magneto rheological fluid (MRF) damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a trust-region method based instantaneous optimal semi-active control algorithm (TIOC) is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semiactive control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc-Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.
LHC Damper Beam commissioning in 2010
Höfle, W; Schokker, M; Valuch, D
2011-01-01
The LHC transverse dampers were commissioned in 2010 with beam and their use at injection energy of 450 GeV, during the ramp and in collisions at 3.5 TeV for Physics has become part of the standard operations pro- cedure. The system proved important to limit emittance blow-up at injection and to maintain smaller than nominal emittances throughout the accelerating cycle. We describe the commissioning of the system step-by-step as done in 2010 and summarize its performance as achieved for pro- ton as well as ion beams in 2010. Although its principle function is to keep transverse oscillations under control, the system has also been used as an exciter for abort gap clean- ing and tune measurement. The dedicated beam position measurement system with its low noise properties provides additional possibilities for diagnostics.
An optimization study for viscous dampers between adjacent buildings
Kandemir-Mazanoglu, Elif Cagda; Mazanoglu, Kemal
2017-05-01
This paper investigates optimum viscous damper capacity and number for prevention of one-sided structural pounding between two adjacent buildings under earthquake motion. The buildings assumed as shear-type structures are modeled by using lumped mass-stiffness technique. Impact forces due to pounding is simulated by nonlinear elastic spring approximation called Hertz model. A parametric study is conducted by varying storey number and stiffness of buildings in addition to the capacity of the viscous dampers. Pounding force and supplemental damping ratio for each case are presented based upon newly defined nondimensional natural frequency parameter ratio. An optimization procedure for determination of viscous damper capacity is developed based on modified supplemental damping ratio equation. Results are compared with each other to clarify the effect of variation in building parameters on pounding forces and viscous damper capacity.
Vibrations of a Shallow Cable with a Viscous Damper
Krenk, Steen; Nielsen, Søren R. K.
2002-01-01
The optimal tuning and effect in terms of modal damping of a viscous damper mounted near the end of a shallow cable are investigated. The damping properties of free vibrations are extracted from the complex wavenumber. The full solution for the lower modes is evaluated numerically, and an explicit...... and rather accurate analytical approximation is obtained, generalizing recent results for a taut cable. It is found that the effect of the damper on the nearly antisymmetric modes is independent of the sag and the stiffness parameter. In contrast, the nearly symmetric modes develop regions of reduced motion...... near the ends, with increasing cable stiffness, and this reduces the effect of the viscous damper. Explicit results are obtained for the modal damping radio and for optimal tuning of the damper....
A design point correlation for losses due to part-span dampers on transonic rotors
Roberts, W. B.
1978-01-01
The design-point losses caused by part-span dampers were correlated for 21 transonic axial-flow fan rotors that had tip speeds varying from 350 to 488 meters per second and design pressure ratios of 1.5 to 2.0. The additional loss attributable to the damper and the total region along the blade height influenced were correlated with selected aerodynamic and geometric parameters. The maximum damper loss correlated well with the mean inlet Mach number at the damper location, the geometric parameters of leading- and trailing-edge damper radius normalized by mean passage height and damper aerodynamic chord, respectively, and the aerodynamic loading parameter of the blade camber divided by the solidity at the damper location. The region of damper influence extended over a mean passage height of the order of 10 to 15 times the maximum damper thickness.
Improving Seismic Performance of Concrete Buildings with Special Moment Frames Using Viscous Damper
Mohammad Javad Dehghan
2015-07-01
Full Text Available Abstract: The present study attempted to investigate the effect of viscous damper on the performance of 10 and 16-story structures. Data modeling was done based on PERFORM 3D software and energy absorption amount was examined in different modes through viscous dampers. To investigate the effects of the so called dampers on the seismic behavior of the structures, the performance of special moment frames with and without viscous damper with the 20% to 30% Resistance against earthquake damages was considered. Also, hysteresis diagram was studied. The research findings revealed an appropriate effect of viscous dampers on decreasing seismic effects of earthquake such that the structure with damper showed significant energy Dissipation comparing to the structure without damper and the damper with higher damping force plays a more effective role in increasing energy dissipation. Therefore, viscous dampers with higher damping percentage (30% have a good capability to retrofit structures.
无
2002-01-01
The smart properties of homogeneous electrorheological fluid (HERF) containing side-chain type liquid crystalline polymer were studied and an actual HERF damper with an adjustable viscosity was produced.A mechanical model of the HERF smart damper was established on the basis of experiment and theoretical analysis.Then a controlled equation of SDOF structure by HERF damper was derived and a semi-active control strategy based on optimal sliding displacement of damper was presented.The simulation results for a single story frame structure indicate that HERF,which may avoid some defects of common particles-suspended ER fluids,is an excellent smart material with better stability.Using the semi-active control strategy presented,HERF smart damper controlled could effectively reduce seismic responses of structures and keeps the control stable at all times.
Self-tuning tuned mass damper (TMD)
Griffin, Steven
2017-04-01
Tuned mass dampers (TMD) are heavily damped resonant devices which add damping to lightly damped, vibrational modes of a structure by dynamically coupling into the lightly damped modes. In practice, a TMD is a damped spring/mass resonator that is tuned so that its frequency is close to a lightly damped mode on the host structure. The TMD is attached to the host structure at a location of large amplitude motion for the mode to be dampened, and its motion is coupled into the host structure's motion. If the TMD is tuned correctly, two damped vibrational modes result, which take the place of the original lightly damped mode of the host structure and heavily damped mode of the TMD. Since aerospace structures tend to respond unfavorably at lightly damped modes in the presence of a dynamic disturbance environment, introduction of one or several TMDs can greatly reduce the dynamic response of a structure by damping problematic modes. A self-tuning TMD is described that can perform all the steps necessary to automatically tune itself and minimize the response of a structure with lightly damped modes and a dynamic excitation. The self-tuning TMD concept introduced here uses a voice coil / magnet combination as -an actuator which enables an innovative stiffness adjustment mechanism -a loss mechanism for the tuned mass damper -a means of excitation for identifying lightly damped modes of the host structure Along with an accelerometer and a tethered power supply/computer, the self-tuning TMD can automatically identify and damp lightly damped modes.
Bikić Siniša M.
2016-01-01
Full Text Available This paper is focused on the mathematical model of the Air Torque Position dampers. The mathematical model establishes a link between the velocity of air in front of the damper, position of the damper blade and the moment acting on the blade caused by the air flow. This research aims to experimentally verify the mathematical model for the damper type with non-cascading blades. Four different types of dampers with non-cascading blades were considered: single blade dampers, dampers with two cross-blades, dampers with two parallel blades and dampers with two blades of which one is a fixed blade in the horizontal position. The case of a damper with a straight pipeline positioned in front of and behind the damper was taken in consideration. Calibration and verification of the mathematical model was conducted experimentally. The experiment was conducted on the laboratory facility for testing dampers used for regulation of the air flow rate in heating, ventilation and air conditioning systems. The design and setup of the laboratory facility, as well as construction, adjustment and calibration of the laboratory damper are presented in this paper. The mathematical model was calibrated by using one set of data, while the verification of the mathematical model was conducted by using the second set of data. The mathematical model was successfully validated and it can be used for accurate measurement of the air velocity on dampers with non-cascading blades under different operating conditions. [Projekat Ministarstva nauke Republike Srbije, br. TR31058
A novel eddy current damper: theory and experiment
Ebrahimi, Babak; Khamesee, Mir Behrad [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada); Golnaraghi, Farid, E-mail: khamesee@mecheng1.uwaterloo.c [Mechatronic Systems Engineering, Simon Fraser University, Surrey, British Columbia, V3T 0A3 (Canada)
2009-04-07
A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s{sup -2} (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m{sup -1} is achievable with the fabricated prototype. This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.
The Effective Design of Bean Bag as a Vibroimpact Damper
A.Q. Liu
2000-01-01
Full Text Available The technique of a bean bag damper has been effectively applied in many engineering fields to control the vibroimpact of a structural system. In this study, the basic parameters responsible for the design of an effective bean bag: the size of beans, the mass ratio of the bean bag to the structure to which it is attached, the clearance distance and the position of the bag, are studied by both theoretical and experimental analyses. These will provide a better understanding of the performance of the bean bag for optimisation of damper design. It was found that reducing the size of beans would increase the exchange of momentum in the system due to the increase in the effective contact areas. Within the range of mass ratios studied, the damping performance of the damper was found to improve with higher mass ratios. There was an optimum clearance for any specific damper whereby the maximum attenuation could be achieved. The position of the bag with respect to nodes and antipodes of the primary structure determined the magnitude of attenuation attainable. Furthermore, the limitations of bean bags have been identified and a general criteria for the design of a bean bag damper has been formulated based on the study undertaken. It was shown that an appropriately configured bean bag damper was capable of reducing the amplitude of vibration by 80% to 90%.
Galván Duque-Gastélum, Carlos; Quiñones-Uriostegui, Ivett; Mendoza, Felipe; Rodríguez, Gerardo
2014-07-01
Ortheses are devices that assist in the function of the limbs, contributing with stability and support to the involved joints. KAFOs (knee-ankle-foot orthosis) are mainly indicated for people with muscular or neural diseases that affect the lower limbs. The actual designs of knee hinges for KAFOs compromise the stability and mobility of the limb. In this work, it was tested the feasibility of a design for a knee hinge for KAFO that should be able to modify its mechanical resistance depending on the gait phase. Orthotics biomechanical criteria and gait biomechanical requirements were considered. It was proposed an electromagnetic system in order to modify the hinge damping. In the future, the system will be interacting with a magnetorheological fluid (MR) which can change its rheological properties when a magnetic field is applied, thus, reaching different damping constants with the designed hinge. The diameter of the internal pipes required for the MR fluid to freely circulate within the orthosis was established. It was observed that the original design of the proposed orthotic hinge is feasible; however, some proposals are presented in order to achieve a better performance of the orthosis.
Wang, Guangshuo; Ma, Yingying; Tong, Yu; Dong, Xufeng
2016-03-01
In this study, monodisperse Fe3O4 nanoparticles were synthesized successfully using a sonochemical method in the presence of 3-aminopropyltriethoxysilane (APTES). The morphology, microstructure and magnetic properties of the bare Fe3O4 and APTES-coated Fe3O4 were investigated in detail by TEM, XRD, FTIR and SQUID. It was found that APTES-coated Fe3O4 showed relatively good dispersion with a narrow size distribution of 8.4 ± 2.1 nm diameter. The functionalization of Fe3O4 was proved to be covalent linking between Fe3O4 and APTES. The field-dependent magnetization curve indicated superparamagnetic behavior of Fe3O4-APTES with a saturation magnetization (M s) of 70.5 emu g-1 at room temperature. A magnetorheological (MR) fluid was prepared using the obtained Fe3O4-APTES nanoparticles with 25 wt% particles, and its MR properties were tested using a Physica MCR301 rheometer fitted with an MRmodule. The results showed that the as-prepared APTES-coated Fe3O4 nanoparticle-based MR fluid exhibited typical MR effects, with increasing viscosity, shear stress and yield stress depending on the applied magnetic field strength.
Modeling friction phenomena and elastomeric dampers in multibody dynamics analysis
Ju, Changkuan
The first part of this dissertation focuses on the development, implementation and validation of models that capture the behavior of joints in a realistic manner. These models are presented within the framework of finite element based, nonlinear multibody dynamics formulations that ensure unconditional nonlinear stability of the computation for complex systems of arbitrary topology. The proposed approach can be divided into three parts. First, the joint configuration: this purely kinematic part deals with the description of the configuration of the joint and the evaluation of the relative distance and relative tangential velocity between the contacting bodies. Second, the contact conditions: in most cases, contact at the joint is of an intermittent nature. The enforcement of the unilateral contact condition is a critical aspect of the computational procedure. And finally, the contact forces: this last part deals with the evaluation of the forces that arise at the interface between contacting bodies. The advantage of the proposed approach is that the three parts of the problem can be formulated and implemented independently. Many articulated rotor helicopters use hydraulic dampers, which provide high levels of damping but are also associated with high maintenance costs and difficulties in evaluating their conditions due to the presence of seals, lubricants and numerous moving parts, all operating in a rotating frame. To avoid problems associated with hydraulic dampers, the industry is now switching to elastomeric lead-lag dampers that feature simpler mechanical design, lower part count, and result in "dry" rotors. However, the design of robust elastomeric dampers is hampered by the lack of reliable analytical tools that can be used to predict their damping behavior in the presence of large multi-frequency motions experienced by the rotor and thus the damper. The second part of this dissertation focuses on the development of an elastomeric damper model which predicts
Teramura, A.; Yoshihara, J.; Nakamura, M.; Nakamura, T.; Yasui, Y. (Obayashi Corp., tokyo (Japan))
1991-02-10
In case of adopting thick laminated rubber bearing to the base isolation system to reduce earthquake forces, it is necessary to equip it with a vertical damper system in order to supplement the low damping characteristics. A damper system was then developed to be structured of plural cylindrical steel pipes, different in diameter, and high viscosity silicon material injected thereinto. Together with introducing that damper system in summary and simultaneously showing it in method to calculate the damping force, the present report further explained result of verification test, performed by an installed base-isolated building. As a result of analyzing test result, upon calculating/deriving the damper in damping force with the frequency and deformation dependency, taken into consideration as proper to viscous fluid material, correspondence was confirmed to almost cover a vibration range of micronm to mm. Also by horizontal input force test, it was confirmed for the moving joint of damper to follow the large horizontal deformation. As a result of enforced vibration test on a 140t weight base-isolated building, equiped with thick laminated rubber bearings and installed with a vibrator, damping performance was shown to almost correspond to its designed initial value. 11 figs., 2 tabs.
鲁光涛; 李友荣; 王志刚; 宋钢兵
2015-01-01
This paper studies the transmission torque characteristics of a rotary drum magneto-rheological coupler. Based on the Bingham model of magneto-rheological damper, a new Bingham model for predicting the transmission torque of magneto-rheological coupler is proposed, and in this new model, the rotational speed ratio of the inner and outer drum of the coupler is used as the input parameter. In this paper, the exponential model is used to compute the Coulomb damping torque and the experimental results indicate that, when the coil current remains constant, the curves between the transmission torque and rotational speed ration are nearly the same as the load increases and decreases, and there is no hysteresis in the curves. For speed ratio of less than 1.3, the torque increases greatly, and for speed ratio of higher than 1.3, it increases much slowly. The proposed Bingham model can correctly predict the transmission torque of magneto-rheological coupler.%针对一种旋转圆筒式磁流变液联轴器,提出了用于预测磁流变液联轴器工作转矩的修正宾汉模型.在该宾汉模型中采用磁流变液联轴器主动转筒和从动转筒之间的转速比 n 作为宾汉模型的输入参数,并采用指数模型描述磁致库仑阻尼力矩.实验结果表明,当线圈电流恒定时,在负载由小-大-小变化过程中,不同初始转速下的转矩-转速比曲线基本重合,且在负载正向增大和反向减小过程中,磁流变液联轴器工作转矩变化曲线基本重合,未形成滞环.当转速比较小(n1.3),工作转矩随负载增大增速减缓,其变化曲线斜率均为0.05,整个转矩-转速比变化曲线与磁流变液联轴器宾汉模型完全吻合,利用磁流变液联轴器力矩宾汉模型可以预测和确定其工作转矩.
Analysis and Design of Circular Plate MR Fluids Brake
Yang Yan; Lin Chang-Hua; Li Hui; Zhou Jing
2004-01-01
A magnetorheological (MR) fluids brake is a device to achieve brake by shear force of MR fluids. A MR rotary brake has the property that its braking torque changes quickly in response to an external magnetic field. In this study, the design method of the circular plate MR fluids brake is investigated theoretically. The equation of the torque transmitted by the MR fluids in the brake is derived to provide the theoretical foundation in the design of the brake. Based on this equation, after mathematically manipulated, the calculations of the volume, thickness and width of the MR fluids within the circular plate MR fluids brake are yield.
Size dependence of magnetorheological properties of cobalt ferrite ferrofluid
Radhika, B.; Sahoo, Rasmita; Srinath, S., E-mail: srinath@uohyd.ac.in [School of Physics, University of Hyderabad, Hyderabad-500040 (India)
2015-06-24
Cobalt Ferrite nanoparticles were synthesized using co-precipitation method at reaction temperatures of 40°C and 80°C. X-Ray diffraction studies confirm cubic phase formation. The average crystallite sizes were found to be ∼30nm and ∼48nm for 40°C sample and 80°C sample respectively. Magnetic properties measured using vibrating sample magnetometer show higher coercivety and magnetization for sample prepared at 80°C. Magnetorheological properties of CoFe2O4 ferrofluids were measured and studied.
Nakano, M.; Yonekawa, T. [Yamagata University, Yamagata (Japan). Faculty of Engineering
1995-01-25
This paper reports the examination result of the pressure response of an electrorheological suspension fluid (obtained when the particles of a strong acid ion-exchange resin are dispersed on silicon oil and whose rheological characteristics vary with the action in the external electric field) in an electrorheological (ER) damper model (experimental equipment consisting of an ER valve with plane parallel electrode and a piston cylinder). A rectangular wave voltage is applied to the ER valve to obtain the pressure fall components based on the steady ER effect of an ER fluid flowing between the plane parallel electrodes. The intensity of the electric field and the dependence on the flow velocity were formulated by an approximate function. The flow velocity dependency of this ER effect does not coincide with the theoretical analysis result based on a Bingham fluid model. The pressure in a cylinder presents the transient response of a first-order lag to the rectangular wave voltage input to the ER valve. The time constant value in this case can be explained by considering the compressibility of the residual air in the ER fluid. 11 refs., 11 figs.
Granular dampers: does particle shape matter?
Pourtavakoli, Hamzeh; Parteli, Eric J. R.; Pöschel, Thorsten
2016-07-01
By means of particle-based numerical simulations using the discrete element method, we address the question of how the performance of granular dampers is affected by the shape of the granular particles. In consistence with previous experiments performed with nearly spherical particles we find that independently of the particles’ shape, the granular system is characterized by a gas-like regime for small amplitudes of the container’s oscillation and by a collect-and-collide regime for large amplitude forcing. Both regimes are separated by an optimal operation mode—the critical amplitude of the damping oscillation for which the energy dissipation is maximal—which is independent of the particle shape for given conditions of particle mass, material properties and number of particles. However, in the gas-like regime, we find that spherical particles lead to more efficient energy dissipation compared to complex shaped particles of the same mass. In this regime, a dependence on the damper’s efficiency on the particle shape is found.
Optimizing of the higher order mode dampers in the 56MHz SRF cavity
Wu, Q.; Ben-Zvi, I.
2010-01-27
Earlier, we reported that a 56 MHz cavity was designed for a luminosity upgrade of the RHIC, and presented the requirements for Higher Order Mode (HOM) damping, the design of the HOM dampers, along with measurements and simulations of the HOM dampers. In this report, we describe our optimization of the dampers performance, and the modifications we made to their original design. We also optimized the number of the HOM dampers, and tested different configurations of locations for them.
A Series-LC-Filtered Active Damper for AC Power Electronics Based Power Systems
Wang, Xiongfei; Blaabjerg, Frede; Loh, Poh Chiang
2015-01-01
This paper proposes an active damper with a series LC-filter for suppressing resonances in an ac power electronics based power system. The added filter capacitor helps to lower the voltage stress of the converter to be used for implementing the damper. Unlike active filters for the compensation...... is built, where the damper is integrated into a grid-connected converter. The results obtained from the experiments demonstrate the stability enhancement of ac power electronics based power systems by the active damper....
Experimental Study of Hysteretic Steel Damper for Energy Dissipation Capacity
Daniel R. Teruna
2015-01-01
Full Text Available This study aims to evaluate energy absorption capacity of hysteretic steel damper for earthquake protection of structures. These types of steel dampers are fabricated from mild steel plate with different geometrical shapes on the side part, namely, straight, concave, and convex shapes. The performance of the proposed device was verified experimentally by a series of tests under increasing in-plane cyclic load. The overall test results indicated that the proposed steel dampers have similar hysteretic curves, but the specimen with convex-shaped side not only showed stable hysteretic behavior but also showed excellent energy dissipation capabilities and ductility factor. Furthermore, the load-deformation relation of these steel dampers can be decomposed into three parts, namely, skeleton curve, Bauschinger part, and elastic unloading part. The skeleton curve is commonly used to obtain the main parameters, which describe the behavior of steel damper, namely, yield strength, elastic stiffness, and postyield stiffness ratio. Moreover, the effective stiffness, effective damping ratio, cumulative plastic strain energy, and cumulative ductility factor were also derived from the results. Finally, an approximation trilinear hysteretic model was developed based on skeleton curve obtained from experimental results.
Darlow, M.; Zorzi, E.
1981-01-01
A comprehensive guide for the design of elastomer dampers for application in rotating machinery is presented. Theoretical discussions, a step by step procedure for the design of elastomer dampers, and detailed examples of actual elastomer damper applications are included. Dynamic and general physical properties of elastomers are discussed along with measurement techniques.
A novel energy absorber based on magnetorheological gel
Pang, Haoming; Xuan, Shouhu; Sun, Chuanlin; Gong, Xinglong
2017-10-01
In this work, a novel magnetorheological energy absorber (MREA) was designed by using magnetorheological gel (MRG) as the damping medium. The proposed MREA had tunable piston gap distances and variable inner magnetic flux density distribution. The piston gap distance could be varied from 7–2 mm and the magnetic flux density at the gap increased from 120–860 mT, respectively. Under both low velocity compression and high speed impact, the damping could be divided into three parts. In the impact test, the velocity of a drop hammer could be reduced from to 3.4–0 m s‑1 within a very short time (13 ms) and distance (17 mm). The maximum damping force of the MREA reached to as high as 8 kN. The damping force could also be adjusted by changing the current input. Under a 2 A current, the energy absorption ratio increased about 23% (from 4.13–5.07 J mm‑1).
Control of a haptic gear shifting assistance device utilizing a magnetorheological clutch
Han, Young-Min; Choi, Seung-Bok
2014-10-01
This paper proposes a haptic clutch driven gear shifting assistance device that can help when the driver shifts the gear of a transmission system. In order to achieve this goal, a magnetorheological (MR) fluid-based clutch is devised to be capable of the rotary motion of an accelerator pedal to which the MR clutch is integrated. The proposed MR clutch is then manufactured, and its transmission torque is experimentally evaluated according to the magnetic field intensity. The manufactured MR clutch is integrated with the accelerator pedal to transmit a haptic cue signal to the driver. The impending control issue is to cue the driver to shift the gear via the haptic force. Therefore, a gear-shifting decision algorithm is constructed by considering the vehicle engine speed concerned with engine combustion dynamics, vehicle dynamics and driving resistance. Then, the algorithm is integrated with a compensation strategy for attaining the desired haptic force. In this work, the compensator is also developed and implemented through the discrete version of the inverse hysteretic model. The control performances, such as the haptic force tracking responses and fuel consumption, are experimentally evaluated.
Choi, Seung-Hyun; Kim, Soomin; Kim, Pyunghwa; Park, Jinhyuk; Choi, Seung-Bok
2015-06-01
In this study, we developed a novel four-degrees-of-freedom haptic master using controllable magnetorheological (MR) fluid. We also integrated the haptic master with a vision device with image processing for robot-assisted minimally invasive surgery (RMIS). The proposed master can be used in RMIS as a haptic interface to provide the surgeon with a sense of touch by using both kinetic and kinesthetic information. The slave robot, which is manipulated with a proportional-integrative-derivative controller, uses a force sensor to obtain the desired forces from tissue contact, and these desired repulsive forces are then embodied through the MR haptic master. To verify the effectiveness of the haptic master, the desired force and actual force are compared in the time domain. In addition, a visual feedback system is implemented in the RMIS experiment to distinguish between the tumor and organ more clearly and provide better visibility to the operator. The hue-saturation-value color space is adopted for the image processing since it is often more intuitive than other color spaces. The image processing and haptic feedback are realized on surgery performance. In this work, tumor-cutting experiments are conducted under four different operating conditions: haptic feedback on, haptic feedback off, image processing on, and image processing off. The experimental realization shows that the performance index, which is a function of pixels, is different in the four operating conditions.
Synthesis and Magnetorheology Study of Iron Oxide and Iron Cobalt Oxide Suspensions
Syang-Peng Rwei
2013-01-01
Full Text Available This study investigates the magnetorheology (MR of polydimethylsiloxane (PDMS that contains magnetic powders of various compositions, shapes, and concentrations. Two magnetic powders, Fe3O4 and CoFe2O4, were synthesized. TEM images reveal that a powder of spherical particles was obtained at high temperature. A powder with nonspherical star shape was synthesized at low temperature. A rheological test confirmed a typical Bingham behavior for all the MR fluids prepared in this study. Experimental results demonstrated that the cobalt ferrite exhibited a more superior yield stress than the ferrite compound. A magnetic powder of larger particles was found to have higher yield stress. Moreover, the spherical particles yielded a higher yield stress than the star-shaped particles. The “saturated magnetic strength” increased with the loading of the magnetic powder. Finally, the results demonstrate that 12 wt% CoFe2O4 nanopowder (10 nm dispersed in the PDMS liquid exhibited a large range of yield stresses (0 to 644 Pa.
Nguyen, Q. H.; Choi, S. B.
2012-01-01
This research focuses on optimal design of different types of magnetorheological brakes (MRBs), from which an optimal selection of MRB types is identified. In the optimization, common types of MRB such as disc-type, drum-type, hybrid-types, and T-shaped type are considered. The optimization problem is to find the optimal value of significant geometric dimensions of the MRB that can produce a maximum braking torque. The MRB is constrained in a cylindrical volume of a specific radius and length. After a brief description of the configuration of MRB types, the braking torques of the MRBs are derived based on the Herschel-Bulkley model of the MR fluid. The optimal design of MRBs constrained in a specific cylindrical volume is then analysed. The objective of the optimization is to maximize the braking torque while the torque ratio (the ratio of maximum braking torque and the zero-field friction torque) is constrained to be greater than a certain value. A finite element analysis integrated with an optimization tool is employed to obtain optimal solutions of the MRBs. Optimal solutions of MRBs constrained in different volumes are obtained based on the proposed optimization procedure. From the results, discussions on the optimal selection of MRB types depending on constrained volumes are given.
Ouyang, Qing; Zheng, Jiajia; Li, Zhaochun; Hu, Ming; Wang, Jiong
2016-11-01
This paper aims to analyze the effects of combined working coils of magnetorheological (MR) absorber on the shock mitigation performance and verify the controllability of MR absorber as applied in the recoil system of a field gun. A physical scale model of the field gun is established and a long-stroke MR recoil absorber with four-stage parallel electromagnetic coils is designed to apply separate current to each stage and generate variable magnetic field distribution in the annular flow channel. Based on dynamic analysis and firing stability conditions of the field gun, ideal recoil force-stroke profiles of MR absorber at different limiting firing angles are obtained. The experimental studies are carried out on an impact test rig under different combinations of current loading: conventional unified control mode, separate control mode and timing control mode. The fullness degree index (FDI) is defined as the quantitative evaluation criterion of the controllability of MR absorber during the whole recoil motion. The results show that the force-stroke profile of the novel MR absorber can approach the ideal curve within 25 degrees of the limiting firing angle through judicious exploitation of the adjustable rheological properties of MR fluid.
A novel squeeze mode based magnetorheological valve: design, test and evaluation
Li, Zhihua; Zhang, Xinjie; Guo, Konghui; Ahmadian, Mehdi; Liu, Yang
2016-12-01
Magnetorheological (MR) devices have been investigated intensively nowadays, of which MR valve is an important and hot application with the challenges of acquiring high pressure drop within compact configurations. Hence, a novel squeeze mode based MR valve (SMRV) is proposed in this paper, with highlights of high pressure drop and low power consumption within a compact and transplantable structure. SMRV’s characteristics are studied and its core parts are designed including the initial gaps, magnetic circuit and returning spring. The uniform-saturation magnetic intensity principle is proposed and a co-simulation optimal platform is developed to optimize magnetic intensity of the SMRV dimensions. Then, a prototype is developed and its steady-state performance is evaluated. The test results demonstrate that a pressure drop of 10.8 MPa and a controllable ratio of 5 at 1.0 A applied current are achieved within a transplantable configuration. Meanwhile, SMRV only consumes 1/400 W control power to dissipate 1 W fluid power and its power-volume consumption rate, P C · V/P D, is 3.3 × 102 mm3, which has a brilliant application prospect in hydraulic or mechatronic systems.
Durability investigation on torque control of a magneto-rheological brake: experimental work
Kim, Wan Ho; Park, Jhin Ha; Kim, Gi-Woo; Shin, Cheol Soo; Choi, Seung-Bok
2017-03-01
This study experimentally investigates the torque control durability of a disc brake featuring a magneto-rheological (MR) fluid. An appropriate size of MR disc brake is designed based on a mathematical model, and a prototype is manufactured. A small-scale laboratory-scale test bed is then developed using a DC motor, in-line torque sensor, and the MR brake. S45C and S20C steels are inserted into a tapered hole on the surface of the brake disc. After 105 cycles of operation in shear mode, the wear properties of the MR brake are characterized by average surface roughness measurements, scanning electron microscope images, and energy dispersive x-ray spectra. The torque control performances before and after the operation cycles are examined using open-loop control and closed-loop proportional-integral-derivative control. As expected, the control performance degraded after 105 cycles of operation in the open-loop case, but not in the closed-loop case. This aspect is demonstrated by the sinusoidal torque-tacking control performance before and after the operation cycles.
Design of a 7-DOF haptic master using a magneto-rheological devices for robot surgery
Kang, Seok-Rae; Choi, Seung-Bok; Hwang, Yong-Hoon; Cha, Seung-Woo
2017-04-01
This paper presents a 7 degrees-of-freedom (7-DOF) haptic master which is applicable to the robot-assisted minimally invasive surgery (RMIS). By utilizing a controllable magneto-rheological (MR) fluid, the haptic master can provide force information to the surgeon during surgery. The proposed haptic master consists of three degrees motions of X, Y, Z and four degrees motions of the pitch, yaw, roll and grasping. All of them have force feedback capability. The proposed haptic master can generate the repulsive forces or torques by activating MR clutch and MR brake. Both MR clutch and MR brake are designed and manufactured with consideration of the size and output torque which is usable to the robotic surgery. A proportional-integral-derivative (PID) controller is then designed and implemented to achieve torque/force tracking trajectories. It is verified that the proposed haptic master can track well the desired torque and force occurred in the surgical place by controlling the input current applied to MR clutch and brake.
Design of the magnetorheological mount with high damping force for medium speed diesel generators
Kang, O.-H.; Kim, W.-H.; Joo, W. H.; Park, J.-H.
2013-04-01
This paper investigates the controllable magnetorheological (MR) mount for the marine diesel-generator (D/G) sets. Sometimes, significant vibrations over the allowable limit are observed on the D/G sets due to their huge excitation forces. Because the severe vibration can lead to structural damages to the D/G sets, it should be reduced to below the limit. Although passive mounts with rubber isolators are usually used, the vibration reduction performance is not always sufficient. In addition, expecting that the vibration levels required by customers will get more severe, semi-active vibration isolation system needs to be developed. To the aim, the valve (flow) mode type of MR mount has been designed. Especially, the annular-radial configuration was adopted to enhance the damping force within the restricted space. The geometry of the mount has been optimized to obtain the required damping force and the magnetic field analysis has been carried out using ANSYS APDL. To verify the performance of the developed MR mount, excitation test was conducted and the dynamic characteristics were identified. Since damping property of the MR fluid is changed by the applied magnetic field strength and excitation frequency, responses to changing applied currents and frequencies were obtained. From the results, damping performance of the MR mount was evaluated.
A NEW STOCHASTIC OPTIMAL CONTROL STRATEGY FOR HYSTERETIC MR DAMPERS
YingZuguang; NiYiqing; KoJanming
2004-01-01
A new stochastic optimal control strategy for randomly excited quasi-integrable Hamiltonian systems using magneto-theological (MR) dampers is proposed. The dynamic behavior of an MR damper is characterized by the Bouc-Wen hysteretic model. The control force produced by the MR damper is separated into a passive part incorporated in the uncontrolled system and a semi-active part to be determined. The system combining the Bouc-Wen hysteretic force is converted into an equivalent non-hysteretic nonlinear stochastic control system. Then Ito stochastic differential equations are derived from the equivalent system by using the stochastic averaging method. A dynamical programming equation for the controlled diffusion processes is established based on the stochastic dynamical programming principle. The non-clipping nonlinear optimal control law is obtained for a certain performance index by minimizing the dynamical programming equation. Finally, an example is given to illustrate the application and effectiveness of the proposed control strategy.
DARHT-II Injector Transients and the Ferrite Damper
Waldron, Will; Reginato, Lou; Chow, Ken; Houck, Tim; Henestroza, Enrique; Yu, Simon; Kang, Michael; Briggs, Richard
2006-08-04
This report summarizes the transient response of the DARHT-II Injector and the design of the ferrite damper. Initial commissioning of the injector revealed a rise time excited 7.8 MHz oscillation on the diode voltage and stalk current leading to a 7.8 MHz modulation of the beam current, position, and energy. Commissioning also revealed that the use of the crowbar to decrease the voltage fall time excited a spectrum of radio frequency modes which caused concern that there might be significant transient RF electric field stresses imposed on the high voltage column insulators. Based on the experience of damping the induction cell RF modes with ferrite, the concept of a ferrite damper was developed to address the crowbar-excited oscillations as well as the rise-time-excited 7.8 MHz oscillations. After the Project decided to discontinue the use of the crowbar, further development of the concept focused exclusively on damping the oscillations excited by the rise time. The design was completed and the ferrite damper was installed in the DARHT-II Injector in February 2006. The organization of this report is as follows. The suite of injector diagnostics are described in Section 2. The data and modeling of the injector transients excited on the rise-time and also by the crowbar are discussed in Section 3; the objective is a concise summary of the present state of understanding. The design of the ferrite damper, and the small scale circuit simulations used to evaluate the ferrite material options and select the key design parameters like the cross sectional area and the optimum gap width, are presented in Section 4. The details of the mechanical design and the installation of the ferrite damper are covered in Section 5. A brief summary of the performance of the ferrite damper following its installation in the injector is presented in Section 6.
Optimal placement of dampers and actuators based on stochastic approach
无
2002-01-01
A general method is developed for optimal application of dampers and actuators by installing them at optimal location on seismic-resistant structures. The study includes development of a statistical criterion, formulation of a general optimization problem and establishment of a solution procedure. Numerical analysis of the seismic response in time-history of controlled structures is used to verify the proposed method for optimal device application and to demonstrate the effectiveness of seismic response control with optimal device location. This study shows that the proposed method for the optimal device application is simple and general, and that the optimally applied dampers and actuators are very efficient for seismic response reduction.
Smart fluids and their applications - perspectives for new actuators
Boese, H.; Trendler, A. [Fraunhofer-Institut fuer Silicatforschung (ISC), Wuerzburg (Germany)
2000-07-01
The rheological behaviour of electrorheological and magnetorheological fluids is drastically and reversibly changed by strong electric or magnetic fields, respectively. The fact that the rheological properties are controllable can be used for many technical applications. Both kinds of smart fluids can be synthesized from various combinations of materials, which opens wide possibilities to adapt the fluid properties and the design of the actuatoric devices in which the fluid is used. An overview of the most relevant properties and a description of some of the possible applications of smart fluids are given. (orig.)
Damping of edgewise vibration in wind turbine blades by means of circular liquid dampers
Basu, Biswajit; Zhang, Zili; Nielsen, Søren R.K.
2016-01-01
This paper proposes a new type of passive vibration control damper for controlling edgewise vibrations of wind turbine blades. The damper is a variant of the liquid column damper and is termed as a circular liquid column damper (CLCD). Rotating wind turbine blades generally experience a large...... the coupling between the blade and the tower. The performance of the damper is evaluated under various rotational speeds of the rotor. A special case in which the rotational speed is so small that the gravity dominates the motion of the liquid is also investigated. Further, the legitimacy of the decoupled...
Squeeze Film Dampers Executing Small Amplitude Circular-Centered Orbits in High-Speed Turbomachinery
Sina Hamzehlouia
2016-01-01
Full Text Available This work represents a pressure distribution model for finite length squeeze film dampers (SFDs executing small amplitude circular-centered orbits (CCOs with application in high-speed turbomachinery design. The proposed pressure distribution model only accounts for unsteady (temporal inertia terms, since based on order of magnitude analysis, for small amplitude motions of the journal center, the effect of convective inertia is negligible relative to unsteady (temporal inertia. In this work, the continuity equation and the momentum transport equations for incompressible lubricants are reduced by assuming that the shapes of the fluid velocity profiles are not strongly influenced by the inertia forces, obtaining an extended form of Reynolds equation for the hydrodynamic pressure distribution that accounts for fluid inertia effects. Furthermore, a numerical procedure is represented to discretize the model equations by applying finite difference approximation (FDA and to numerically determine the pressure distribution and fluid film reaction forces in SFDs with significant accuracy. Finally, the proposed model is incorporated into a simulation model and the results are compared against existing SFD models. Based on the simulation results, the pressure distribution and fluid film reaction forces are significantly influenced by fluid inertia effects even at small and moderate Reynolds numbers.
Effect of nonlinearity of connecting dampers on vibration control of connected building structures
Masatoshi eKasagi
2016-01-01
Full Text Available The connection of two building structures with dampers is one of effective vibration control systems. In this vibration control system, both buildings have to possess different vibration properties in order to provide a higher vibration reduction performance. In addition to such condition of different vibration properties of both buildings, the connecting dampers also play an important role in the vibration control mechanism. In this paper, the effect of nonlinearity of connecting dampers on the vibration control of connected building structures is investigated in detail. A high-damping rubber damper and an oil damper with and without relief mechanism are treated. It is shown that, while the high-damping rubber damper is effective in a rather small deformation level, the linear oil damper is effective in a relatively large deformation level. It is further shown that, while the oil dampers reduce the response in the same phase as the case without dampers, the high-damping rubber dampers change the phase. The merit is that the high-damping rubber can reduce the damper deformation and keep the sufficient space between both buildings. This can mitigate the risk of building pounding.
Seismic design of steel structures with lead-extrusion dampers as knee braces
monir, Habib Saeed; Naser, Ali
2008-07-01
One of the effective methods in decreasing the seismic response of structure against dynamic loads due to earthquake is using energy dissipating systems. Lead-extrusion dampers (LED)are one of these systems that dissipate energy in to one lead sleeve because of steel rod movement. Hysteresis loops of these dampers are approximately rectangular and acts independent from velocity in frequencies that are in the seismic frequency rang. In this paper lead dampers are considered as knee brace in steel frames and are studied in an economical view. Considering that lead dampers don't clog structural panels, so this characteristic can solve brace problems from architectural view. The behavior of these dampers is compared with the other kind of dampers such as XADAS and TADAS. The results indicate that lead dampers act properly in absorbing the induced energy due to earthquake and good function in controlling seismic movements of multi-story structures
Vibrations of a Shallow Cable with a Viscous Damper
Krenk, Steen; Nielsen, Søren R. K.
2002-01-01
The optimal tuning and effect in terms of modal damping of a viscous damper mounted near the end of a shallow cable are investigated. The damping properties of free vibrations are extracted from the complex wavenumber. The full solution for the lower modes is evaluated numerically, and an explici...
Exploring the performance of a nonlinear tuned mass damper
Alexander, Nicholas A.; Schilder, Frank
2009-01-01
We explore the performance of a nonlinear tuned mass damper (NTMD), which is modeled as a two degree of freedom system with a cubic nonlinearity. This nonlinearity is physically derived from a geometric configuration of two pairs of springs. The springs in one pair rotate as they extend, which re...
Conductive magnetorheological elastomer: fatigue dependent impedance-mechanic coupling properties
Wang, Yu; Xuan, Shouhu; Ge, Lin; Wen, Qianqian; Gong, Xinglong
2017-01-01
This work investigated the relationship between the impedance properties and dynamic mechanical properties of magnetorheological elastomers (MREs) under fatigue loading. The storage modulus and the impedance properties of MREs were highly influenced by the pressure and magnetic field. Under the same experimental condition, the two characteristics exhibited similar fatigue dependent change trends. When pressure was smaller than 10 N, the capacitance of MRE could be divided into four sections with the increase of the cyclic numbers. The relative equivalent circuit model was established to fit the experimental results of the impedance spectra. Each parameter of circuit element reflected the change of fatigue loading, relative microstructure of MRE, MRE-electrode interface layer, respectively. Based on the above analysis, the real-time and nondestructive impedance method was demonstrated to be high potential on detecting the fatigue of the MRE device.
Derivation of stiffness matrix in constitutive modeling of magnetorheological elastomer
Leng, D.; Sun, L.; Sun, J.; Lin, Y.
2013-02-01
Magnetorheological elastomers (MREs) are a class of smart materials whose mechanical properties change instantly by the application of a magnetic field. Based on the specially orthotropic, transversely isotropic stress-strain relationships and effective permeability model, the stiffness matrix of constitutive equations for deformable chain-like MRE is considered. To valid the components of shear modulus in this stiffness matrix, the magnetic-structural simulations with finite element method (FEM) are presented. An acceptable agreement is illustrated between analytical equations and numerical simulations. For the specified magnetic field, sphere particle radius, distance between adjacent particles in chains and volume fractions of ferrous particles, this constitutive equation is effective to engineering application to estimate the elastic behaviour of chain-like MRE in an external magnetic field.
Rheological properties of carbon nanotubes-reinforced magnetorheological elastomer
Aziz, S. A. A.; Mazlan, SA; Nik Ismail, N. I.; Ubaidillah; Khairi, MHA; Yunus, NA
2017-01-01
Magnetorheological elastomer (MRE) based on the natural rubber with different types of multiwall carbon nanotubes (MWCNT) as additives were synthesized. MRE with pristine MWCNTs was prepared as a control and the carboxylated (MWCNT-COOH), as well as hydroxylated (MWCNT-OH) were introduced as new additives in MRE. Their rheological properties under different magnetic field were evaluated by using the rheometer (MCR 302, AntonPaar, Austria) equipped with the electromagnetic device. The dependency of MREs towards excitation frequencies under different magnetic field was investigated. It is shown that the storage modulus and loss factor of MRE with functionalized MWCNTs exhibited noticeable increment in MR performance compared to control parallel with the frequencies increment.
Magneto-dependent stress relaxation of magnetorheological gels
Xu, Yangguang
2017-09-01
The stress relaxation behaviors of magnetorheological (MR) gels under stepwise shear loading are systematically investigated. The particle-enhanced effect, the magneto-induced effect, and the temperature-enhanced effect on the stress relaxation of MR gels are discussed. For further analysis of the magneto-induced stress relaxation mechanism in MR gels, a phenomenological model is established to describe the stress relaxation behavior of the matrix and the magnetic particle chains. All characteristic parameters introduced in the model, i.e. relaxation time, instantaneous modulus, and stable modulus, have well-defined physical meanings and are fitted based on the experimental results. The influence of each parameter on the macroscopic response is discussed and it is found that the relaxation stress induced by the magneto-mechanical coupling effect plays an important role in the stress relaxation process of MR gels.
Research on reducing the edge effect in magnetorheological finishing.
Hu, Hao; Dai, Yifan; Peng, Xiaoqiang; Wang, Jianmin
2011-03-20
The edge effect could not be avoided in most optical manufacturing methods based on the theory of computer controlled optical surfacing. The difference between the removal function at the workpiece edge and that inside it is also the primary cause for edge effect in magnetorheological finishing (MRF). The change of physical dimension and removal ratio of the removal function is investigated through experiments. The results demonstrate that the situation is different when MRF "spot" is at the leading edge or at the trailing edge. Two methods for reducing the edge effect are put into practice after analysis of the processing results. One is adopting a small removal function for dealing with the workpiece edge, and the other is utilizing the removal function compensation. The actual processing results show that these two ways are both effective on reducing the edge effect in MRF.
Stiffness control of magnetorheological gels for adaptive tunable vibration absorber
Kim, Hyun Kee; Kim, Hye Shin; Kim, Young-Keun
2017-01-01
In this study, a stiffness feedback control system for magnetorheological (MR) gel—a smart material of variable stiffness—is proposed, toward the design of a tunable vibration absorber that can adaptively tune to a time varying disturbance in real time. A PID controller was designed to track the required stiffness of the MR gel by controlling the magnitude of the target external magnetic field pervading the MR gel. This paper proposes a novel magnetic field generator that could produce a variable magnetic field with low energy consumption. The performance of the MR gel stiffness control was validated through experiments that showed the MR gel absorber system could be automatically tuned from 56 Hz to 67 Hz under a field of 100 mT to minimize the vibration of the primary system.
Self-powered discrete time piezoelectric vibration damper
Konak, Michael J.; Powlesland, Ian G.; van der Velden, Stephen P.; Galea, Stephen C.
1997-11-01
Structural vibration suppression is of great interest to the aircraft industry as it can reduce the amplitude of excessive vibration in lightly damped panels caused by conditions in their operational environment. One technique of suppressing vibration is to use passive damping techniques such as constrained layered damping incorporating viscoelastic materials. However these techniques may not be acceptable because of weight concerns or extreme temperature variations. Over the past decade much work has been done by researchers on the use of piezoelectric ceramic devices, using passive and active techniques, for structural vibration suppression. The passive piezoelectric damping devices consist of a piezoelectric element and either a resistive or resonant shunt. The resonant circuit shunt, which is analogous to a mechanical vibration absorber, gives better vibration reduction compared to the resistor shunt. This device requires a large value of inductance in order to be tuned to a particular structural vibration mode. A large value inductor can be made by a using a gyrator type circuit however the circuit needs external power. A method of vibration control using a discrete time controller and piezoelectric devices is presented. That is, this paper describes the concept of a self-powered discrete time piezoelectric vibration damper which does not need tuning to the structural resonant frequency and is powered by piezoelectric elements, i.e. does not need an external power supply. This device is referred to as a strain amplitude minimization patch (STAMP) damper. A brief description of the theory used and of the scheme is presented. Also the operation of this device is compared with other 'passive' techniques, involving piezoelectric elements, such as the resistive passive damper and the parallel resonant passive damper cases. Experimental results presented, on a cantilevered beam, demonstrate the concept and show that the device, even in its current underdeveloped
Sohn, Jung Woo; Jeon, Juncheol; Nguyen, Quoc Hung; Choi, Seung-Bok
2015-08-01
In this paper, a disc-type magneto-rheological (MR) brake is designed for a mid-sized motorcycle and its performance is experimentally evaluated. The proposed MR brake consists of an outer housing, a rotating disc immersed in MR fluid, and a copper wire coiled around a bobbin to generate a magnetic field. The structural configuration of the MR brake is first presented with consideration of the installation space for the conventional hydraulic brake of a mid-sized motorcycle. The design parameters of the proposed MR brake are optimized to satisfy design requirements such as the braking torque, total mass of the MR brake, and cruising temperature caused by the magnetic-field friction of the MR fluid. In the optimization procedure, the braking torque is calculated based on the Herschel-Bulkley rheological model, which predicts MR fluid behavior well at high shear rate. An optimization tool based on finite element analysis is used to obtain the optimized dimensions of the MR brake. After manufacturing the MR brake, mechanical performances regarding the response time, braking torque and cruising temperature are experimentally evaluated.
Chen, Lin; Sun, Limin; Nagarajaiah, Satish
2016-09-01
Lateral dampers have been extensively studied and implemented for supplementing modal damping in cable vibration mitigation. When considering the cable flexural stiffness that is actually present, albeit small, there is another degree of freedom of the cable at the lateral damper, namely the rotation, that can be constrained by a rotational damper to achieve larger additional damping. This is of particular significance for long cables where the near-anchorage lateral damper alone is usually insufficient. The problem of a cable with bending stiffness, attached with both lateral and rotational dampers at an intermediate point, is therefore considered in this study. The characteristic equation of the resulting system is formulated by assembling the dynamic stiffness from the two segments divided by the damper, which is subsequently solved using argument principle method. Dynamics of the controlled system is thus discussed in general through parametric analysis. For the case where the damper location is close to the anchorage, asymptotic solutions for complex frequency and damping ratio are provided; explicit formulas for determining the optimal damper coefficients are also derived. It is found that when the lateral and rotational damper coefficients are properly balanced, the proposed strategy can achieve up to 30 percent damping enhancement compared to the case with only the lateral damper, in practical cable bending stiffness range.
Performance of RC Structures Equipped with Steel and Aluminium X-Plate Dampers
Manchalwar, A.; Bakre, S. V.
2016-12-01
The supplementary energy dissipation using dampers represents an efficient technique for the seismic protection of structural system. Also, the optimal damper location in the building helps in reducing damper cost along with maximum response reduction. In this work, an effort has been made to use the X-plate metallic damper made of steel and aluminium for seismic response control. In the first phase of work, the building has been analysed without and with full dampers under real earthquake ground motion. The response quantities such as maximum displacement, max interstory drift, axial force, shear force and bending moment are compared. The results obtained after the analysis shows that the response quantities are reduced significantly thus establishing the effectiveness of damper to dissipate the input seismic energy. It is important to find out the optimal damper location format in the building to improve its efficiency and reduce total cost of dampers to accomplish the max reduction in the response of the building. Therefore, the second phase of work focuses on the optimal location of the damper in the building. To obtain the optimal damper location, the concept of genetic algorithm is used.
Wang, Yonghong; Zhang, Xinru; Chung, Kyungho; Liu, Chengcen; Choi, Seung-Bok; Choi, Hyoung Jin
2016-11-01
To improve mechanical and magnetorheological properties of magnetorheological elastomers (MREs), a facile method was used to fabricate high-performance MREs which consisted of the core-shell complex microparticles with an organic-inorganic network structure dispersed in an ethylene propylene diene rubber. In this work, the proposed magnetic complex microparticles were in situ formed during MREs fabrication as a result of strong interaction between matrix and CIPs using carbon black as a connecting point. The morphology of both isotropic (i-MREs) and anisotropic MREs (a-MREs) was observed by scanning electron microscope (SEM). The effects of carbonyl iron particle (CIP) volume content on mechanical properties and hysteresis loss of MREs were investigated. The effects of CIP volume content on the shear storage modulus, MR effect and loss tangent were studied using a modified dynamic mechanical analyzer under applied magnetic field strengths. The results showed that the orientation effect became more pronounced with increasing CIPs in the a-MREs, whereas CIPs distributed uniformly in the i-MREs. The tensile strength, tear strength and elongation at break decreased with increasing CIP content up to 40 vol.%, while the hardness increased. It is worth noting that the tensile strength of i-MREs and a-MREs containing 40 vol.% CIPs still had high mechanical properties as a result of good compatibility between complex microparticles and rubber matrix. The MR performance of shear storage modulus and damping properties of MREs increased remarkably with CIP content due to strong dipole-dipole interaction of complex microparticles. Besides, the hysteresis loss increased with increasing CIP content as a result of magnetic field induced interfacial sliding between complex microparticles.
Particle size dependent rheological property in magnetic fluid
Wu, Jie; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn
2016-06-15
The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe{sub 3}O{sub 4} nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field. - Highlights: • 40 nm, 100 nm and 200 nm Fe{sub 3}O{sub 4} nanospheres were dispersed in water. • The magnetorheological effect increased with increasing the particle sizes. • Molecular dynamic simulation was used in this article.
Seismic Behavior of Posttensioned Concrete Bridge Piers with External Viscoelastic Dampers
Anxin Guo
2016-01-01
Full Text Available This paper investigates the seismic performance of posttensioned concrete piers with external viscoelastic dampers to improve the energy dissipation capacity of this type of structure. An installation scheme for viscoelastic dampers on bridge piers is proposed, and the mechanical models of the damper are analyzed according to the installation scheme. By attaching the viscoelastic dampers to the posttensioned bridge piers, the analytical model of the hybrid system is established using the OpenSees finite element analysis package. Cyclic behavior and time history analyses are conducted on a posttensioned bridge with and without viscoelastic dampers using the established finite element model. The analysis results indicate that the viscoelastic dampers can effectively improve the seismic performance of the bridge structures with posttensioned piers.
Air Damper Sizing for the Decay Heat Removal System of the PGSFR
Kim, Dehee; Lee, Tae-Ho [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2014-10-15
Decay heat removal system (DHRS) of the PGSFR begins to work when the air dampers installed at the air intakes and outlets of the sodium-to-air heat exchangers are open. Reliability of the DHRS strongly depends on the damper opening because the air flow passing through the shell side of a sodium-to-air heat exchanger removes the heat transferred from the reactor core and primary coolant to the final heat sink, the atmosphere. Therefore, damper sizing as well as its arrangement is significant for the DHRS operation. In this work, a systematic sizing approach is introduced and air damper sizing of the DHRS has been carried out following the addressed sizing procedure. A systematic damper sizing procedure has been addressed and the DHRS damper sizing has been carried out following the sizing procedure and an arrangement strategy has been decided to promote the DHRS operational reliability.
Performance analysis of a semi-active railway vehicle suspension featuring MR dampers
Kim, Hwan-Choong; Choi, Seung-Bok; Lee, Gyu-Seop; An, Chae-Hun; You, Won-Hee
2014-03-01
This paper presents performance analysis of semi-active railway vehicle suspension system using MR damper. In order to achieve this goal, a mathematical dynamic model of railway vehicle is derived by integrating car body, bogie frame and wheel-set which can be able to represent lateral, yaw and roll motion. Based on this model, the dynamic range of MR damper at the railway secondary suspension system and design parameters of MR damper are calculated. Subsequently, control performances of railway vehicle including car body lateral motion and acceleration of MR damper are evaluated through computer simulations. Then, the MR damper is manufactured to be retrofitted with the real railway vehicle and its characteristics are experimentally measured. Experimental performance of MR damper is assessed using test rig which is composed of a car body and two bogies.
Kröger, M; Hess, S
2003-01-01
We review, apply and compare diverse approaches to the theoretical understanding of the dynamical and rheological behaviour of ferrofluids and magnetorheological (MR) fluids subject to external magnetic and flow fields. Simple models are introduced which are directly solvable by nonequilibrium Brownian or molecular dynamics computer simulation. In particular, the numerical results for ferrofluids quantify the domain of validity of uniaxial alignment of magnetic moments (in and) out of equilibrium. A Fokker-Planck equation for the dynamics of the magnetic moments - corresponding to the Brownian dynamics approach - and its implications are analysed under this approximation. The basic approach considers the effect of external fields on the dynamics of ellipsoid shaped permanent ferromagnetic domains (aggregates), whose size should depend on the strength of flow and magnetic field, the magnetic interaction parameter and concentration (or packing fraction). Results from analytic calculations and from simulation ar...
Schümann, M.; Borin, D. Y.; Huang, S.; Auernhammer, G. K.; Müller, R.; Odenbach, S.
2017-09-01
Magnetorheological elastomers are a type of smart hybrid material where elastic properties of a soft elastomer matrix are combined with magnetic properties of magnetic micro particles. This combination leads to a complex interplay of magnetic and elastic phenomena, of which the magnetorheological effect is the best described. In this paper, magnetically hard NdFeB-particles were used to obtain remanent magnetic properties. X-ray microtomography has been utilised to analyse the particle movement induced by magnetic fields. A particle tracking was performed; thus, it was possible to characterise the movement of individual particles. Beyond that, a comprehensive analysis of the orientation of all particles was performed at different states of magnetisation and global particle arrangements. For the first time, this method was successfully applied to a magnetorheological material with a technically relevant amount of magnetic NdFeB-particles. A significant impact of the magnetic field on the rotation and translation of the particles was shown.
Design and testing of a regenerative magnetorheological actuator for assistive knee braces
Ma, Hao; Chen, Bing; Qin, Ling; Liao, Wei-Hsin
2017-03-01
In this paper, a multifunctional magneto-rheological actuator with power regeneration capability, named regenerative magnetorheological actuator (RMRA), is designed for gait assistance in the knee joint. RMRA has motor and magnetorheological (MR) brake parts working in parallel that can harvest energy through regenerative braking. This novel design provides multiple functions with good energy efficiency. The configuration and basic design of the RMRA are first introduced. Then geometrical optimization of the MR brake is conducted based on a parameterized model, and multiple factors are considered in the design objectives: braking torque, weight, and power consumption. After the optimal design is obtained, an RMRA prototype is fabricated and associated driver circuits are designed. Finally, multiple functions of the RMRA, especially three different braking modes, are modeled and tested. Experimental results of RMRA output performances in all working modes match the modeling and simulation. Assistive knee braces with the developed RMRA are promising for future applications in gait assistance and rehabilitation.
Wojciech HOMIK
2011-01-01
The short explanation of usefulness of rubber torsional dampers in crankshaft in multi-cylinder engines is presented. The description of the construction and operation of rubber torsional damper is also included. In the rubber torsional damper, the damping is achieved as the effect of internal friction resulting from the deformation of the rubber material. This deformation appears while the internal rubber elasticity is overloaded. Both the physical and mechanical rubber properties depend on ...
Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy
2013-09-01
Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy by Andrew James Murray and Dr. JinHyeong Yoo...Aberdeen Proving Ground, MD 21005 ARL-TN-0566 September 2013 Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe... Magnetostrictive Shunt Damper Performance Using Iron (Fe)- Gallium (Ga) Alloy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6
MEMS mass-spring-damper systems using an out-of-plane suspension scheme
Abdel Aziz, Ahmed Kamal Said
2014-02-04
MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) using an out-of-plane (or vertical) suspension scheme, wherein the suspensions are normal to the proof mass, are disclosed. Such out-of-plane suspension scheme helps such MEMS mass-spring-damper systems achieve inertial grade performance. Methods of fabricating out-of-plane suspensions in MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) are also disclosed.
HOM Dampers or not in Superconducting RF Proton Linacs
Tückmantel, Joachim
2009-01-01
Circular machines are plagued by Coupled Bunch Instabilities, driven by impedance peaks, irrespectively of their frequency relation to machine lines; hence all cavity Higher Order Modes are possible drivers. This is the fundamental reason that all superconducting RF cavities in circular machines are equipped with HOM dampers. This raises the question if HOM damping would not be imperative also in high current proton linacs where a mechanism akin to CBI might exist. To clarify this question we have simulated the longitudinal bunched beam dynamics in linacs, allowing bunch-to-bunch variations in time-of-arrival. Simulations were executed for a generic proton linac with properties close to SNS or the planned SPL at CERN. It was found that for monopole HOMs with high Qext large beam scatter or even beam loss cannot be excluded. Therefore omitting HOM dampers on superconducting RF cavities in high current proton linacs, even pulsed ones, is a very risky decision.
On the nonlinear design of industrial arc spring dampers
Lahriri, Said; Santos, Ilmar; Hartmann, Henning
2011-01-01
The objective of this paper is to present a numerical approach for analyzing parameter excited vibrations on a gas compressor, induced by the nonlinear characteristic of the arc spring feature of certain designs of squeeze film dampers, SFDs. The behavior of the journal is studied in preparation...... acting on the SFD are presented. It is worth mentioning, that the maps and diagrams can be used as design guidance....
On the nonlinear design of industrial arc spring dampers
Lahriri, Said; Santos, Ilmar; Hartmann, Henning
2011-01-01
The objective of this paper is to present a numerical approach for analyzing parameter excited vibrations on a gas compressor, induced by the nonlinear characteristic of the arc spring feature of certain designs of squeeze film dampers, SFDs. The behavior of the journal is studied in preparation...... acting on the SFD are presented. It is worth mentioning, that the maps and diagrams can be used as design guidance....
THE THEORETICAL FOUNDATIONS OF VIBRATION DAMPERS BY ROLLING FRICTION
L. M. Bondarenko
2015-06-01
Full Text Available Purpose. There are some unresolved issues in vibration damping – the lack of engineering calculations for the vibration dampers by rolling friction; the absence of evidence of their application appropriateness. Considering this fact, the authors suggest to prove that the dampers based on rolling friction, are similar in rate of oscillation damping by hydraulic shock absorbers. At the same time, they are easier for the hydraulic design, and easily amenable to manual adjustment, both in automatic and manual mode. Methodology. Fixed techniques of practice in order to determine amplitudes of the oscillations of a shock absorber led to a predetermined result and will apply this theory in the calculation of other vibration dampers. Findings. Analysis of the formulas and graphs leads to the following conclusions and recommendations: 1 the nature of the oscillation damping at vibration dampers by rolling friction is close to their decay in the viscous resistance; 2 when conducting the necessary experiments the shock absorber rolling can be recommended as alternatives to hydraulic ones. The research results of this task will help implement the new trend in reduction of dynamic loads in vehicles. Originality. With the help of theoretical curves to determine the coefficients of rolling friction the dependences for determining the amplitudes of the oscillations in the vertical movement of cargo were obtained. At the same time, the previously proposed analytical dependence for determining the coefficient of rolling friction contains only conventional mechanical constants of the contacting bodies and there geometrical dimensions. Practical value. Due to the existing well-known disadvantages of hydraulic shock absorbers it would be logical to apply shock absorbers that are technologically convenient in manufacturing and easy to adjust the damping rate. The proposed theory can be used in the design of shock absorbers rolling as an alternative to the hydraulic
Wojciech HOMIK
2011-01-01
Full Text Available The short explanation of usefulness of rubber torsional dampers in crankshaft in multi-cylinder engines is presented. The description of the construction and operation of rubber torsional damper is also included. In the rubber torsional damper, the damping is achieved as the effect of internal friction resulting from the deformation of the rubber material. This deformation appears while the internal rubber elasticity is overloaded. Both the physical and mechanical rubber properties depend on temperature change. In cooperation with rubber dampers manufacturer the experimental investigations are made in order to establish the influence of temperature change on torsional stiffness and damping.
Optimal arrangement of viscoelastic dampers for seismic control of adjacent shear-type structures
Xiao HUANG; Hong-ping ZHU
2013-01-01
The optimal arrangement of viscoelastic dampers (VEDs) used to link two adjacent shear-type structures under seismic excitation was investigated.A two-step optimal design method is proposed.First,optimal parameter expressions of the Kelvin model are used to calculate the optimal stiffness and damping coefficient of the VEDs.Then,using the two-step optimal design method,taking the quadratic performance index as the optimization objective,the optimal arrangement of the dampers is determined.General rules about the optimal arrangement of the VEDs were obtained.The results show that the placement of only one damper between two adjacent shear-type structures should be avoided; if more than one damper is used,they should be distributed on the top and lower floors of the structures.Optimization of the number of dampers had little effect on response reduction.The most important factor was the optimization of the placement of the dampers.Through comparative study,for buildings of equal and unequal heights,the optimal parameters of dampers from parametric studies were shown to match the theoretical results for different numbers and placements of dampers.The level of response reduction was shown to be sensitive to the damping coefficient of the dampers.
Edgewise vibration control of wind turbine blades using roller and liquid dampers
Zhang, Z. L.; Nielsen, S. R. K.
2014-06-01
This paper deals with the passive vibration control of edgewise vibrations by means of roller dampers and tuned liquid column dampers (TLCDs). For a rotating blade, the large centrifugal acceleration makes it possible to use roller dampers or TLCDs with rather small masses for effectively suppressing edgewise vibrations. The roller dampers are more volumetrically efficient due to the higher mass density of the steel comparing with the liquid. On the other hand, TLCDs have their advantage that it is easier to specify the optimum damping of the damper by changing the opening ratio of the orifice. In this paper, 2-DOF nonlinear models are suggested for tuning a roller damper or a TLCD attached to a rotating wind turbine blade, ignoring the coupling between the blade and the tower. The decoupled optimization is verified by incorporating the optimized damper into a more sophisticated 13- DOF wind turbine model with due consideration of the coupled blade-tower-drivetrain vibrations, quasi-static aeroelasticity as well as a collective pitch controller. Performances of the dampers are compared in terms of the control efficiency and the practical applications. The results indicate that roller dampers and TLCDs at optimal tuning can effectively suppress the dynamic response of wind turbine blades.
Seismic Response Control of Offshore Platform Structures with Shape Memory Alloy Dampers
LI Hong-nan; HE Xiao-yu; HUO Lin-sheng
2005-01-01
In this study, the seismic response control of offshore platform structures with Shape Memory Alloy (SMA) dampers is investigated. A new SMA damper and its restoring force model are introduced for the calculation of seismic response reduction. Based on an actual platform structure and its mechanical model, the parameters which may affect the rate of shock absorption are analyzed, such as the number, position and characteristics of the SMA dampers andthe condition of the site where the platform is located. The results show that the SMA damper is an effective control device for offshore platforms and satisfactory control can be achieved by proper selection of the parameters.
Active tuned mass damper for damping of offshore wind turbine vibrations
Brodersen, Mark Laier; Bjørke, Ann-Sofie; Høgsberg, Jan Becker
2017-01-01
An active tuned mass damper (ATMD) is employed for damping of tower vibrations of fixed offshore wind turbines, where the additional actuator force is controlled using feedback from the tower displacement and the relative velocity of the damper mass. An optimum tuning procedure equivalent...... to the tuning procedure of the passive tuned mass damper combined with a simple procedure for minimizing the control force is employed for determination of optimum damper parameters and feedback gain values. By time domain simulations conducted in an aeroelastic code, it is demonstrated that the ATMD can...
Sound reduction at a target point inside an enclosed cavity using particle dampers
Hu, Li; Shi, Yaogui; Yang, Qiliang; Song, Gangbing
2016-12-01
The purpose of this paper is to develop a novel structural damping approach to reduce the sound pressure at a target point inside an enclosed cavity. In this approach, particle dampers filled with either metal or nonmetal particles are used. The dissipation mechanisms of such dampers are primarily related to the friction and collision of particle-wall and particle-particle contacts. In this research, each panel contribution was first analyzed to identify the panel that contributes the most to the target point. The proposed particle dampers were then attached to this panel for sound reduction. In the numerical process, a Particle Dampers Cyclic Iterative Method (PDCIM) was proposed for extracting the damping loss factor of the particle dampers to compute the sound pressure of a target point in the cavity with the particle dampers. For further comparative studies, simulation experiments are conducted for three cases: a case with the particle dampers, a case with the empty particle containers and a case with the equivalent mass. The numerical study found that the case with the particle dampers had the best sound reduction effect. Later, model tests were carried out to validate the numerical results. Experimental test results revealed that the particle dampers are remarkably effective for reducing the sound inside the enclosed cavity.
Fermilab 500 GeV main accelerator rf cavity 128 MHz mode damper
Kerns, Q.A.; Miller, H.W.
1977-01-01
The Fermilab 500-GeV main accelerating system has been operating for a year now with the aid of 128-MHz mode dampers. Such dampers proved to be necessary to achieve stable operation and a reasonably smooth slow spill at intensities of approximately 2 x 10/sup 13/ protons per pulse, and furthermore are low-cost and reliable. The approach used to identify troublesome modes, the observed beam blow-up without dampers, and the steps taken to design and install suitable dampers on eighteen main ring cavities are discussed. Spectrum analyzer pictures help illustrate the performance.
A Method to Simulate the MR Fluid in ANSYS%一种在ANSYS中模拟磁流变液的方法
张挣鑫; 刘黔会; 黄方林
2011-01-01
The magnetorheological fluid (MRF) is consistent with the mechanical properties of Newtonian fluid when no external magnetic field is present, at this time it can be modeled using FLUID142 in ANSYS. However, when exposed to a magnetic field, the MRF is also showing some solid-like characteristics, at present, there is no exactly appropriate element type in ANSYS to model MRF. This paper presents a method to simulate the mechanical behavior of magnetorheological fluid subjected to magnetic field in the pre-yield region in ANSYS. The main idea is devide an MRF element into two coincident elements, one of them has density and viscosity without shear modulus while another has shear modulus without density and viscosity. Take a simply supported MRF sandwich beam as an example, comparing the results with the theoretical analysis and experimental study of Ref. [ 1 ], this method can obtain good results and reasonable conclusion, verified the validity of finite element analysis in this paper. This kind of method which can be called Coincident Elements Method provides a new way to model the structures with MRF or MR dampers in ANSYS, and it also has some inspiration for the future development of related elements in ANSYS.%磁流变液在零场时,符合牛顿流体的力学特征,在ANSYS中可用流体单元FLUID142模拟.而处于磁场作用下的磁流变液还呈现出一定的类固体特征,在ANSYS中尚无完全合适的单元进行模拟.本文提出一种在ANSYS中模拟磁流变液在屈服前阶段力学行为的方法,即重合单元法,主要思想是采用重合的两种单元分别模拟磁流变液的流体特性和粘弹性固体特性.以一磁流变液夹层简支梁为研究对象,采用本文提出的分析方法对其进行有限元计算,通过与文献[1]的理论分析及实验研究结果比较,本文方法所得结果与之相近,验证了本文有限元分析方法的有效性.在目前尚无完全合适单元模拟磁流变液的情况下,
Vibration control using a variable coil-based friction damper
Amjadian, Mohsen; Agrawal, Anil K.
2017-04-01
This paper is focused on the analytical model, design, and simulation of a variable coil-based friction damper (VCBFD) for vibration control of structures. The proposed VCBFD is composed of a soft ferromagnetic plate, made of a linear magnetic material, and two identical thick rectangular air-core coils connected in parallel, each one attached to the plate through a friction pad. The friction force is provided by a normal force produced through an attractive electromagnetic interaction between the air-core coils (ACs) and the soft ferromagnetic plate when sliding relative to each other. The magnitude of the normal force in the damper is varied by a semi-active controller that controls the command current passing through the ACs. To demonstrate the efficiency of the proposed VCBFD and its semi-active controller, it has been implemented on a two-degree-of-freedom (2DOF) base-isolated model subjected to the acceleration components of three records of strong earthquakes. The results show that the performance of the proposed VCBFD in its passive-on mode is overshadowed by the undesirable effects of stick-slip motion. However, the damper in its semi-active mode is more successful in not only reducing the displacement of the base-floor but also avoiding stick-slip motion, due to acting completely in its sliding phase.
Performance of a New Fine Particle Impact Damper
Guangqiang Han
2008-09-01
Full Text Available The energy dissipation mechanisms of conventional impact damper (CID are mainly momentum exchange and friction. During the impact process, a lot of vibration energy cannot be exhausted but reverberated among the vibration partners. Besides, the CID may produce the additional vibration to the system or even amplify the response in the low-frequency vibration. To overcome these shortcomings, this paper proposes a new fine particle impact damper (FPID which for the first time introduces the fine particle plastic deformation as an irreversible energy sink. Then, the experiments of the cantilevered beam with the CID and that with the FPID are, respectively, carried out to investigate the behavior of FPID. The experimental results indicate that the FPID has a better performance in vibration damping than in the CID and the FPID works well in control of the vibration with frequency lower than 50Ã¢Â€Â‰Hz, which is absent to the non-obstructive particle damper. Thus, the FPID has a bright and significant application future because most of the mechanical vibration falls in the range of low freqency.
Waleed F. Faris
2008-01-01
Full Text Available This work is devoted to the fabrication and investigation of the Squeeze Film Dampers (SFDs which are widely used in many applications. This include the fabrication of a test rig and several dampers with different sizes and two different materials which composite and non-composite. Composite dampers (Glass/epoxy, each consists of 30 layers, were fabricated by hand lay-up method. Outer and inner diameters of all the fabricated dampers were maintained as 60 and 40 mm respectively. Non-composite dampers (Steel were fabricated and tested using turning machine. Three dampers of different lengths were examined for both materials. A rotor-bearing system for the analysis has been designed and fabricated. The test rig consists of mild steel shaft, two supports, oil pressure system, and two self-alignment ball bearings were fixed on each end support. Two squeeze film dampers were used for the two support ends. Vibration amplitude has been examined for all the fabricated dampers at different shaft rotational speeds. The first resonance speed was examined for all the dampers tested. Results show that the vibration amplitude of the steel damper was lower than Glass/epoxy dampers with the same L/D ratio. On the other hand, a considerable weight saving has been achieved by using Glass/epoxy composite dampers. It has been found that the performance of squeeze film damper improved with increasing length/diameter ratio (L/D within the range tested.
Phu, Do Xuan; Choi, Seung-Bok
2015-02-01
In this work, a new high-load magnetorheological (MR) fluid mount system is devised and applied to control vibration in a ship engine. In the investigation of vibration-control performance, a new modified indirect fuzzy sliding mode controller is formulated and realized. The design of the proposed MR mount is based on the flow mode of MR fluid, and it includes two separated coils for generating a magnetic field. An optimization process is carried out to achieve maximal damping force under certain design constraints, such as the allowable height of the mount. As an actuating smart fluid, a new plate-like iron-particle-based MR fluid is used, instead of the conventional spherical iron-particle-based MR fluid. After evaluating the field-dependent yield stress of the MR fluid, the field-dependent damping force required to control unwanted vibration in the ship engine is determined. Subsequently, an appropriate-sized MR mount is manufactured and its damping characteristics are evaluated. After confirming the sufficient damping force level of the manufactured MR mount, a medium-sized ship engine mount system consisting of eight MR mounts is established, and its dynamic governing equations are derived. A new modified indirect fuzzy sliding mode controller is then formulated and applied to the engine mount system. The displacement and velocity responses show that the unwanted vibrations of the ship engine system can be effectively controlled in both the axial and radial directions by applying the proposed control methodology.
Viscoelastic Parameter Model of Magnetorheological Elastomers Based on Abel Dashpot
Fei Guo
2014-04-01
Full Text Available In this paper, a parametric constitutive model based on Abel dashpot is established in a simple form and with clear physical meaning to deduce the expression of dynamic mechanical modulus of MREs. Meanwhile, in consideration for the pressure stress on MREs in the experiment of shear mechanical properties or the application to vibration damper, some improvements are made on the particle chain model based on the coupled field. In addition, in order to verify the accuracy of the overall model, five groups of MREs samples based on silicone rubber with different volume fractions are prepared and the MCR51 rheometer is used to conduct the experiment of dynamic mechanical properties based on frequency and magnetic field scanning. Finally, experimental results indicate that the established model fits well with laboratory data; namely, the relationship between the dynamic modulus of MREs and changes in frequency and magnetic field is well described by the model.
A magnetorheological clutch for efficient automotive auxiliary device actuation
F. Bucchi
2013-01-01
Full Text Available In this paper the results of a project funded by Regione Toscana aimed at reducing the power absorption of auxiliary devices in vehicles are presented. In particular the design, testing and application of a magnetorheological clutch (MR is proposed, aimed at disengaging the vacuum pump, which draws in air from the power-brake booster chamber, in order to reduce the device power absorption. Several clutch preliminary studies done to choose the clutch geometry and the magnetic field supply are illustrated. The final choice consisted in an MR clutch with permanent magnet, which satisfied size, torque and fail-safe specifications. The clutch characteristics, in terms of torque versus slip, were obtained experimentally for three different clutch prototypes on an ad-hoc developed test bench.As result of a preliminary simulation, a comparison between the power absorption of a current production vacuum pump, an innovative vacuum pump and both vacuum pumps coupled with the MR clutch is presented. The New European Driving Cycle is considered for simulating the vacuum pump operation both in urban and highway driving. Results show that the use of the innovative vacuum pump reduces the device consumption of about 35%, whereas the use of MR clutch coupled with the innovative vacuum pump reduces it up to about 44% in urban driving and 50% in highway driving.
Structural transformations in magnetorheological slurries induced by perturbations
de la Calleja Mora, E. M.; Carrillo, J. L.; Mendoza, M. E.; Donado, F.
2013-04-01
The pattern formation produced by the aggregation of the particles in magnetorheological dispersions when they are in the presence of a static magnetic field, and the process of reconstruction of these structures induced by the application of magnetic perturbations, are investigated experimentally and theoretically. Under the influence of a static magnetic field the aggregation of the dispersed particles generates a multifractal structure, whose corresponding hierarchical structure has been characterized by means of its mass fractal dimensions and other correlations. When this system is perturbed by an oscillatory magnetic field, in addition to the static one, the dispersion rearranges becoming, for certain values of the amplitude and frequency of the perturbation, a more compact and relatively more ordered structure. Here, the analysis of these phenomena is approached as if the pattern formation were a kind of glassy transformation in a supercooled liquid, and the effect of the perturbation were an annealing process. The role of the temperature is taken here by the ratio of the intensities of the applied fields. From high resolution photographs taken at different stages of the structure evolution, it is possible to calculate some complexity measures such as the singularity spectrum, the lacunarity index, enthalpy and the configurational entropy. On this basis it is possible to describe quantitatively these glassy-like transformations. The relaxation time that distinguishes between a cooling process that leads the structure to a glassy or a crystalline one, is experimentally obtained.
Statistical analysis of magnetically soft particles in magnetorheological elastomers
Gundermann, T.; Cremer, P.; Löwen, H.; Menzel, A. M.; Odenbach, S.
2017-04-01
The physical properties of magnetorheological elastomers (MRE) are a complex issue and can be influenced and controlled in many ways, e.g. by applying a magnetic field, by external mechanical stimuli, or by an electric potential. In general, the response of MRE materials to these stimuli is crucially dependent on the distribution of the magnetic particles inside the elastomer. Specific knowledge of the interactions between particles or particle clusters is of high relevance for understanding the macroscopic rheological properties and provides an important input for theoretical calculations. In order to gain a better insight into the correlation between the macroscopic effects and microstructure and to generate a database for theoretical analysis, x-ray micro-computed tomography (X-μCT) investigations as a base for a statistical analysis of the particle configurations were carried out. Different MREs with quantities of 2–15 wt% (0.27–2.3 vol%) of iron powder and different allocations of the particles inside the matrix were prepared. The X-μCT results were edited by an image processing software regarding the geometrical properties of the particles with and without the influence of an external magnetic field. Pair correlation functions for the positions of the particles inside the elastomer were calculated to statistically characterize the distributions of the particles in the samples.
Performance prediction of serpentine type compact magnetorheological brake prototype
Ubaidillah, Wibowo, A.; Adiputra, D.; Tjahjana, D. D. D. P.; Rahman, M. A. A.; Mazlan, S. A.
2017-01-01
A magnetorheological brake (MRB) with serpentine flux type for ankle-foot orthosis (rehabilitation device) was assessed its performance regarding braking torque and dynamic range. This assessment was conducted based on a problem that the MRB did not generate sufficient braking torque for the orthosis device. The braking capability was appraised through analytical approached based on the prototype design. The magnetic circuit of the MRB design was firstly investigated its capability for generating magnetic flux at braking surface area using finite element method magnetic (FEMM) software. Governing equation was derived to determine the braking performance i.e. braking torque and dynamic range as a function of applied current. The main factors influencing the braking performance were magneto-induced shear stress, the clearance between rotor and stator, and braking surface area. Especially for shear stress, this factor was totally influenced by the magnetic flux generated within the braking area. These all factors were contained within the governing equation. Furthermore, the braking performances were determined by solving the governing equation according to the design parameters. As a result, the governing equation can be used for improving the MRB design to get a better braking performances.
An Evaluation of Magneto Rheological Dampers for Controlling Gun Recoil Dynamics
Mehdi Ahmadian
2001-01-01
Full Text Available The application of magneto rheological dampers for controlling recoil dynamics is examined, using a recoil demonstrator that includes a single-shot 50 caliber BMG rifle action and a MR damper. The demonstrator is selected such that it can adequately represent the velocities that commonly occur in weapons with a recoil system, and can be used for collecting data for analyzing the effects of MR dampers on recoil dynamics. The MR damper is designed so that it can work effectively at the large velocities commonly occurring in gun recoil, and also be easily adjusted to reasonably optimize the damper performance for the recoil demonstrator. The test results show that it is indeed possible to design and use MR dampers for recoil applications, which subject the damper to relative velocities far larger than the applications that such dampers have commonly been used for (i.e., vehicle applications. Further, the results indicate that the recoil force increases and the recoil stroke decreases nonlinearly with an increase in the damping force. Also of significance is the fact that the adjustability of MR dampers can be used in a closed-loop system such that the large recoil forces that commonly occur upon firing the gun are avoided and, simultaneously, the recoil stroke is reduced. This study points to the need for several areas of research including establishing the performance capabilities for MR dampers for gun recoil applications in an exact manner, and the potential use of such dampers for a fire out of battery recoil system.
ER fluid applications to vibration control devices and an adaptive neural-net controller
Morishita, Shin; Ura, Tamaki
1993-07-01
Four applications of electrorheological (ER) fluid to vibration control actuators and an adaptive neural-net control system suitable for the controller of ER actuators are described: a shock absorber system for automobiles, a squeeze film damper bearing for rotational machines, a dynamic damper for multidegree-of-freedom structures, and a vibration isolator. An adaptive neural-net control system composed of a forward model network for structural identification and a controller network is introduced for the control system of these ER actuators. As an example study of intelligent vibration control systems, an experiment was performed in which the ER dynamic damper was attached to a beam structure and controlled by the present neural-net controller so that the vibration in several modes of the beam was reduced with a single dynamic damper.
Salzman, S.; Giannechini, L. J.; Romanofsky, H. J.; Golini, N.; Taylor, B.; Jacobs, S. D.; Lambropoulos, J. C.
2015-10-01
We present a modified version of zirconia-coated carbonyl-iron (CI) particles that were invented at the University of Rochester in 2008. The amount of zirconia on the coating is increased to further protect the iron particles from corrosion when introduced to an acidic environment. Five low-pH, magnetorheological (MR) fluids were made with five acids: acetic, hydrochloric, nitric, phosphoric, and hydrofluoric. All fluids were based on the modified zirconia-coated CI particles. Off-line viscosity and pH stability were measured for all acidic MR fluids to determine the ideal fluid composition for acidic MR finishing of chemical-vapor-deposited (CVD) zinc sulfide (ZnS) and other infrared (IR) optical materials, such as hot-isostatic-pressed (HIP) ZnS, CVD zinc selenide (ZnSe), and magnesium fluoride (MgF2). Results show significant reduction in surface artifacts (millimeter-size, pebble-like structures on the finished surface) for several standard-grade CVD ZnS substrates and good surface roughness for the non-CVD MgF2 substrate when MR finished with our advanced acidic MR fluid.
Additive role of attapulgite nanoclay on carbonyl iron-based magnetorheological suspension
Chae, HS
2014-09-01
Full Text Available -1 Colloid Polym Sci DOI 10.1007/s00396-014-3389-3 Additive role of attapulgite nanoclay on carbonyl iron- based magnetorheological suspension Hyun Sik Chae1, Shang Hao Piao1, Arjun Maity2 and Hyoung Jin Choi1 1Department of Polymer Science...
Edgewise vibration control of wind turbine blades using roller and liquid dampers
Zhang, Zili; Nielsen, Søren R.K.
2014-01-01
model with due consideration of the coupled blade-tower-drivetrain vibrations, quasi-static aeroelasticity as well as a collective pitch controller. Performances of the dampers are compared in terms of the control efficiency and the practical applications. The results indicate that roller dampers...
Semiactive Vibration Control of a Wind Turbine Tower using an MR Damper
Kirkegaard, Poul Henning; Nielsen, Søren R. K.; Poulsen, B. L.;
2002-01-01
For fatigue vibration reduction modern wind turbines are installed with different kind of passive systems such as a tuned mass damper or a tuned liquid damper. However, passive control systems are limited because they cannot adapt to broadbanded loading conditions, i.e. they perform well for the ...
Verbaan, Cornelis A. M.; Peters, Gerrit W. M.; Steinbuch, Maarten
2017-01-01
In this paper we demonstrate the advantage of applying viscoelastic materials instead of purely viscous materials as damping medium in mechanical dampers. Although the loss modulus decreases as function of frequency in case of viscoelastic behavior, which can be interpreted as a decrease of damping, the viscoelastic behavior still leads to an increased modal damping for mechanical structures. This advantage holds for inertial-mass-type dampers that are tuned for broad-banded resonance damping. It turns out that an increase of the storage modulus as function of frequency contributes to the effectiveness of mechanical dampers with respect to energy dissipation at different mechanical resonance frequencies. It is shown that this phenomenon is medium specific and is independent of the amount of damper mass.
SEISMIC Analysis of high-rise buildings with composite metal damper
Chen Ruixue
2015-01-01
Full Text Available This paper mainly studies on the mechanical characteristics and application effect of composite metal damper in the high-rise buildings via the numerical simulation analysis. The research adopts the elastic and elastic-plastic dynamic approach and the displacement time history response and damper energy dissipation capacity and so on of the high-rise building are compared and analyzed before and after installation. The analysis found that the energy dissipation characteristic of metallic dampers is good. High-rise building story drift significantly is reduced and the extent of damage of the walls and coupling beams is decreased, achieved a good energy dissipation effect. Composite metal damper can effectively and economically improve the seismic performance of high-rise buildings, meet the requirement of the 3-level design for seismic resistance. The result has certain reference significance for the application of metallic damper in the high-rise buildings.
The Investigation of a Shape Memory Alloy Micro-Damper for MEMS Applications
Chongdu Cho
2007-09-01
Full Text Available Some shape memory alloys like NiTi show noticeable high damping property inpseudoelastic range. Due to its unique characteristics, a NiTi alloy is commonly used forpassive damping applications, in which the energy may be dissipated by the conversion frommechanical to thermal energy. This study presents a shape memory alloy based micro-damper, which exploits the pseudoelasticity of NiTi wires for energy dissipation. Themechanical model and functional principle of the micro-damper are explained in detail.Moreover, the mechanical behavior of NiTi wires subjected to various temperatures, strainrates and strain amplitudes is observed. Resulting from those experimental results, thedamping properties of the micro-damper involving secant stiffness, energy dissipation andloss factor are analyzed. The result indicates the proposed NiTi based micro-damper exhibitsgood energy dissipation ability, compared with conventional materials damper.
Optimal Tuning of Amplitude Proportional Coulomb Friction Damper for Maximum Cable Damping
Weber, Felix; Høgsberg, Jan Becker; Krenk, Steen
2010-01-01
This paper investigates numerically the optimal tuning of Coulomb friction dampers on cables, where the optimality criterion is maximum additional damping in the first vibration mode. The expression for the optimal friction force level of Coulomb friction dampers follows from the linear viscous...... damper via harmonic averaging. It turns out that the friction force level has to be adjusted in proportion to cable amplitude at damper position which is realized by amplitude feedback in real time. The performance of this adaptive damper is assessed by simulated free decay curves from which the damping...... is estimated. It is found that the damping efficiency agrees well with the expected value at the theoretical optimum. However, maximum damping is larger and achieved at a force to amplitude ratio of 1.4 times the analytical value. Investigations show that the increased damping results from energy spillover...
Proposed Configurations for the Use of Smart Dampers with Bracings in Tall Buildings
A. M. Aly Sayed Ahmed
2012-01-01
Full Text Available This paper presents wind-induced response reduction in a very slender building using smart dampers with proposed bracings-lever mechanism system. The building presents a case study of an engineered design that is instructive. The paper shows that shear response and flexural response of tall buildings present two very different cases for vibration suppression. Smart dampers are implemented optimally in the building to reduce its response in the lateral directions for both structural safety and occupant comfort concerns. New bracings-lever mechanism configurations are proposed for the dampers to improve their performance. The study shows how the proposed configurations can enable application to flexural response and scenarios where the interstory drift is not enough for dampers to work effectively. In addition, a decentralized bang-bang controller improved the performance of the smart dampers.
SANTEN-fuse AS ANEARTHQUAKE DAMPER FOR PENDOPO JOGLO
MAER Bisatya W.
2015-07-01
Full Text Available The 2006 Yogyakarta earthquake resulted in collapse of several traditional buildings in Yogyakarta, including joglos. This fact indicates that joglos are quite vulnerable to low-frequency ground shaking. The stability and rigidity of a joglo building are provided by the core of the building, i.e. the rong-rongan structure, in which connection of sakaguru (the column-sunduk (the long span beam-kili (the short span beam has a rigid characteristic. This rigid rong-rongan structure behaves elastically during an earthquake event, and attracts large inertia force. This research aims to increase the structure performance of the rong-rongan by adding “SANTEN-fuse,” an earthquake vibration damper, and by changing the joint connection of sakaguru-sunduk-kili to be that of a pin connection, but not changing the physical appearance of rong-rongan. Santen, whose function is to transfer the load of the roof from blandar to sunduk and from pangeret to kili, is modified so that it has frictional damper characteristic. This “SANTEN-fuse” can resist shear force up to certain level before it slides and acting as a damper. With the reduced stiffness, which leads to reduced inertia force, the overall structural responses are expected to be lower. An experimental quantitative method was used by doing a simulation using SAP2000 software to verify the idea. The pendopo dalem Yudonegaran a joglo house in Yogyakarta was chosen as a case study. Non-linear time history analysis was conducted. Simulation results showed that the proposed modification of rong-rongan structure by using “SANTEN-fuse”, performed better than the original rong-rongan structure.
Simultaneous optimization of force and placement of friction dampers under seismic loading
Fleck Fadel Miguel, Letícia; Fleck Fadel Miguel, Leandro; Holdorf Lopez, Rafael
2016-04-01
It is known that the use of passive energy-dissipation devices, such as friction dampers, reduces considerably the dynamic response of a structure subjected to earthquake ground motions. Nevertheless, the parameters of each damper and the best placement of these devices remain difficult to determine. Some articles on optimum design of tuned mass dampers and viscous dampers have been published; however, there is a lack of studies on optimization of friction dampers. The main contribution of this article is to propose a methodology to simultaneously optimize the location of friction dampers and their friction forces in structures subjected to seismic loading, to achieve a desired level of reduction in the response. For this purpose, the recently developed backtracking search optimization algorithm (BSA) is employed, which can deal with optimization problems involving mixed discrete and continuous variables. For illustration purposes, two different structures are presented. The first is a six-storey shear building and the second is a transmission line tower. In both cases, the forces and positions of friction dampers are the design variables, while the objective functions are to minimize the interstorey drift for the first case and to minimize the maximum displacement at the top of the tower for the second example. The results show that the proposed method was able to reduce the interstorey drift of the shear building by more than 65% and the maximum displacement at the top of the tower by approximately 55%, with only three friction dampers. The proposed methodology is quite general and it could be recommended as an effective tool for optimum design of friction dampers for structural response control. Thus, this article shows that friction dampers can be designed in a safe and economic way.
Zucca, S.; Berruti, T.; Cosi, L.
2016-09-01
Friction dampers are used to reduce vibration amplitude of turbine blades. The dynamics of these assemblies (blades + dampers) is nonlinear and the analysis is challenging from both the experimental and the numerical point of view. The study of the dynamics of blades with a tip damper is the aim of the present paper. The blades with axial-entry fir tree attachment carry a damper in a pocket between the blade covers. Pin dampers significantly affect the resonance frequency of the first blade bending mode and introduces non linearity due to friction contacts. A test rig, made of two blades held in a fixture by an hydraulic press with one damper between the blades was used for the experimental activity. Three different types of dampers (cylindrical, asymmetrical, wedge) have been experimentally investigated and experiments have shown that asymmetrical damper performs better than the others. The response of the blades with the asymmetrical damper was then simulated with a non linear code based on the Harmonic Balance Method (HBM). In the analysis, both the blade and the damper are modelled with the Finite Elements and then the matrices reduced with the Craig- Bampton Component Mode Synthesis (CB-CMS), while the periodical contact forces are modelled with state-of-the-art node-to-node contact elements. Numerical analysis has shown a strong influence of the actual extent of the contact area on the dynamics of the assembly. A model updating process was necessary. In the end, the numerical predictions match very well with the experimental curves.
Zhong, Xianyun; Hou, Xi; Yang, Jinshan
2016-09-01
Nickel is the unique material in the X-ray telescopes. And it has the typical soft material characteristics with low hardness high surface damage and low stability of thermal. The traditional fabrication techniques are exposed to lots of problems, including great surface scratches, high sub-surface damage and poor surface roughness and so on. The current fabrication technology for the nickel aspheric mainly adopt the single point diamond turning(SPDT), which has lots of advantages such as high efficiency, ultra-precision surface figure, low sub-surface damage and so on. But the residual surface texture of SPDT will cause great scattering losses and fall far short from the requirement in the X-ray applications. This paper mainly investigates the magnetorheological finishing (MRF) techniques for the super-smooth processing on the nickel optics. Through the study of the MRF polishing techniques, we obtained the ideal super-smooth polishing technique based on the self-controlled MRF-fluid NS-1, and finished the high-precision surface figure lower than RMS λ/80 (λ=632.8nm) and super-smooth roughness lower than Ra 0.3nm on the plane reflector and roughness lower than Ra 0.4nm on the convex cone. The studying of the MRF techniques makes a great effort to the state-of-the-art nickel material processing level for the X-ray optical systems applications.
Takeda, T.; Yamanobe, S.; Niihara, Y. [Kajima Corp., Tokyo (Japan)
1994-10-31
It is important in designing a PC cable-stayed bridge to properly estimate the seismic response of the bridge for reduction of the response. In this paper, an improvement of the seismic resistance of PC cable-stayed bridges when dampers are installed between the deck and piers and lateral vibration of the deck is restricted is investigated using a time history response model. PC cable-stayed bridges with a span length of 400 m, particularly two types of bridges of harp and semi-harp are investigated and the following is found by analyzing the case where there are installed hysteresis type dampers (with 1 cm yield displacement and secondary rigidity assumed to be 1/10 times that of initial rigidity, the initial rigidity being parametrically changed.) or viscous type dampers (a damping factor is changed.) The result shows that the dampers can reduce the seismic response of a PC cable-stayed bridge and that a semi-harp configuration of stay cables where stay cable members are substantially vertically arranged is more effective than a harp configuration for the seismic performance of PC cable-stayed bridges. The damper partly bear inertial force of the bridge upon earthquake whereby tension of the stay cable members is reduced and bending moment of the deck is reduced. There is existing an optimum characteristic value of the damper concerning the bending moment of the piers. 5 refs., 7 figs., 2 tabs.
LHC Abort Gap Cleaning with the Transverse Damper
Gianfelice-Wendt, E; Höfle, Wolfgang; Kain, V; Meddahi, M; Shaposhnikova, E; Koschik, A
2010-01-01
In the Large Hadron Collider, LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD X for various LHC optics configurations, including the estimated multipolar errors.
A Piecewise Hysteresis Model for a Damper of HIS System
Kaidong Tian
2016-01-01
Full Text Available A damper of the hydraulically interconnected suspension (HIS system, as a quarter HIS, is prototyped and its damping characteristic is tested to characterize the damping property. The force-velocity characteristic of the prototype is analyzed based on a set of testing results and accordingly a piecewise hysteresis model for the damper is proposed. The proposed equivalent parametric model consists of two parts: hysteresis model in low speed region and saturation model in high speed region which are used to describe the hysteresis phenomenon in low speed and nonhysteresis phenomenon in high speed, respectively. The parameters of the model are identified based on genetic algorithm by setting the constraints of parameters according to their physical significances and the corresponding testing results. The advantages of the model are highlighted by comparing to the nonhysteresis model and the permanent hysteresis model. The numerical simulation results are compared with the testing results to validate the accuracy and effectiveness of the proposed model. Finally, to further verify the proposed model’s wide applicability under different excitation conditions, its results are compared to the testing results in three-dimensional space. The research in this paper is significant for the dynamic analysis of the HIS vehicle.
Free vibrations of a taut cable with a general viscoelastic damper modeled by fractional derivatives
Sun, Limin; Chen, Lin
2015-01-01
This study extends dynamic understanding of a taut cable with a viscous damper at arbitrary location to that with a general linear viscoelastic (VE) damper portrayed by a five-parameter fractional derivative model (FDM). The FDM is able to describe a generalized relationship between force and deformation of viscoelastic dampers (material) in a wide frequency range, which can simulate a practical damper including its support condition or a secondary tie between neighboring cables. Free vibrations of the passively controlled cable system have then been formulated analytically through complex modal analysis. For the restricted case that the FDM is installed close to one cable anchorage, asymptotic solutions for the system complex frequency and modal damping are presented; explicit formulas have also been derived to determine the maximal attainable damping and corresponding optimum FDM parameters, based on which effects of frequency-dependent damper properties are appreciated. Considering the FDM located at arbitrary location, the three distinct regimes of frequency evolutions observed for a cable with a viscous damper have been generalized to that with a VE damper; also, new characteristics of the regime diagram and the frequency evolution in each regime are observed.
An Analytical Study of Fire Out of Battery Using Magneto Rheological Dampers
Mehdi Ahmadian
2002-01-01
Full Text Available The application of magneto rheological dampers for controlling the dynamics of a fire out-of-battery recoil system is examined, using a dynamic simulation of a 105mm cannon. Upon providing a brief background on MR dampers and fire out-of-battery dynamics, we will describe the simulation model, along with some of the results obtained from the model. The simulation results show that although conventional hydraulic recoil dampers can be designed and tuned to control fire out-of-battery dynamics as effectively as MR dampers, they are not able to perform well when firing faults are encountered. The results show that MR dampers are able to adapt to the firing faults such as pre-fire, hang-fire, and misfire and provide "soft recoil" under all firing conditions. The inability of conventional hydraulic dampers to adapt to the firing faults can yield recoil dynamics that seriously jeopardize the performance of the gun. Therefore, the results presented here show that MR dampers may provide an enabling technology in achieving fire out-of-battery under all firing conditions.
Driveline Torsional Analysis and Clutch Damper Optimization for Reducing Gear Rattle
Huwei Wu
2016-01-01
Full Text Available This paper describes a research work on driveline modeling, torsional vibration analysis, and clutch damper parameters optimization for reducing transmission gear rattle on the vehicle creeping condition. Firstly, major driveline components, including quasi-transient engine, multistage stiffness clutch damper, detailed manual transmission and differential mechanism, and LuGre tire, are modeled, respectively. Secondly, powertrain system modeling adopting a two-stage stiffness clutch damper is constructed and analyzed. Transient responses predicted by the model show that the driveline undergoes severe torsional vibration and transmission gear rattle phenomenon. By analysis, it is concluded that the clutch damper works jumping between the first- and second-stage stiffness, which results in this problem for the creeping condition. Then, a three-stage stiffness clutch damper is proposed innovatively to solve this problem. It is shown that severe driveline vibration and gear rattle phenomenon are inhibited effectively. Finally, it draws a conclusion that clutch damper parameters could have a great effect on driveline vibration and gear rattle phenomenon and a three-stage stiffness clutch damper could be utilized to solve gear rattle phenomenon efficiently on the vehicle creeping condition.
Guerineau E.L.C.
2016-01-01
Full Text Available Auxiliary Mass Damper‘s (AMD performance is susceptible to changes in the frequency or in the excitation force’s nature. Therefore, to improve the robustness of the AMD it’s necessary to design new systems which are tunable and that could be used over large frequency range. In this work a friction damper, which is an association in series of a spring and a scratcher, is used to tune the AMD at the same time it dissipates the mechanical energy of the principal mass by changing the normal force on the scratcher. Three normal force control strategies, and two combinations of them, are studied: i The normal force is assumed constant; ii The normal force is obtained from the solution of the equation of motion assuming null displacement for the principal mass; iii The normal force is obtained based on the vibratory system’s state variables condition, guarantying that the direction of the friction force promotes the movement of the principal mass toward its static equilibrium position. The effectiveness of the proposed tunable AMD, where the adaptability is obtained by controlling the normal force on the smart friction damper, is evaluated based on mass and frequency ratios variations for each strategy.