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Sample records for active rotor-blade vibration

  1. Active Control of Parametric Vibrations in Coupled Rotor-Blade Systems

    Christensen, Rene Hardam; Santos, Ilmar

    2003-01-01

    In rotor-blade systems basis as well as parametric vibration modes will appear due to the vibration coupling among flexible rotating blades and hub rigid body motion. Parametric vibration will typically occur when the hub operates at a constant angular velocity. Operating at constant velocity the...

  2. A Study of Active Rotor-Blade Vibration Control using Electro-Magnetic Actuation - Part I: Theory

    Christensen, Rene Hardam; Santos, Ilmar

    This is the first paper in a two-part study on active rotor-blade vibration control. Blade faults are a major problem in bladed machines, such as turbines and compressors. Moreover, increasing demands for higher efficiency, lower weight and higher speed imply that blades become even more...... onto the shaft if the system has identical tuned blades. Time-periodic modal state feedback controllers are designed based on the modal model and numerical simulations are provided to show the efficiency of the designed active controllers for a tuned as well as a mistuned rotor-blade system....... susceptible to vibrational problems. Passive damping methods, such as frictional damping, are typically used for this kind of machines, working very well at the specific design conditions. However, when the running conditions exceed the design specification, then passive damping devices become inefficient...

  3. Design optimization for active twist rotor blades

    Mok, Ji Won

    This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to

  4. A Study of Active Rotor-Blade Vibration Control using Electro-Magnetic Actuation - Part I: Theory

    Christensen, Rene Hardam; Santos, Ilmar

    2004-01-01

    actuators fixed directly in the blades. However, due to the impracticability and problems by fixing actuators in the rotating blades, it is for practical application of great interest to study whether the vibrations can be controlled using shaft-based actuators, i.e. electro-magnetic bearings. In this...... framework, the present paper gives a theoretical contribution into the controllability and observability analysis of rotor-blade systems with the aim of investigating this field. The analysis is based on time-variant modal analysis, due to the time-periodic dynamical characteristics of this kind of system...

  5. Optimization of helicopter rotor blade design for minimum vibration

    Davis, M. W.

    1984-01-01

    The optimization approach discussed is part of an ongoing effort to develop a general automated procedure for rotor blade design. This procedure can be used to determine the necessary geometric, structural, and material properties of a rotor system to achieve desired objectives relating to vibration, stress, and aerodynamic performance. The approach used for helicopter vibration is emphasized. Based on analytical studies performed at the United Technologies Research Center (UTRC), a simplified vibration analysis was developed to be used in conjunction with a forced response analysis in the optimization process. This simplified analysis improves the efficiency of the design process significantly. Results of applying this approach to the design of an existing rotor blade model are presented.

  6. Helicopter rotor blade design for minimum vibration

    Taylor, R. B.

    1984-01-01

    The importance of blade design parameters in rotor vibratory response and the design of a minimum vibration blade based upon this understanding are examined. Various design approaches are examined for a 4 bladed articulated rotor operating at a high speed flight condition. Blade modal shaping, frequency placement, structural and aerodynamic coupling, and intermodal cancellation are investigated to systematically identify and evaluate blade design parameters that influence blade airloads, blade modal response, hub loads, and fuselage vibration. The relative contributions of the various components of blade force excitation and response to the vibratory hub loads transmitted to the fuselage are determined in order to isolate primary candidates for vibration alleviation. A blade design is achieved which reduces the predicted fuselage vibration from the baseline blade by approximately one half. Blade designs are developed that offer significant reductions in vibration (and fatigue stresses) without resorting to special vibration alleviation devices, radical blade geometries, or weight penalties.

  7. Integral Twist Actuation of Helicopter Rotor Blades for Vibration Reduction

    Shin, SangJoon; Cesnik, Carlos E. S.

    2001-01-01

    Active integral twist control for vibration reduction of helicopter rotors during forward flight is investigated. The twist deformation is obtained using embedded anisotropic piezocomposite actuators. An analytical framework is developed to examine integrally-twisted blades and their aeroelastic response during different flight conditions: frequency domain analysis for hover, and time domain analysis for forward flight. Both stem from the same three-dimensional electroelastic beam formulation with geometrical-exactness, and axe coupled with a finite-state dynamic inflow aerodynamics model. A prototype Active Twist Rotor blade was designed with this framework using Active Fiber Composites as the actuator. The ATR prototype blade was successfully tested under non-rotating conditions. Hover testing was conducted to evaluate structural integrity and dynamic response. In both conditions, a very good correlation was obtained against the analysis. Finally, a four-bladed ATR system is built and tested to demonstrate its concept in forward flight. This experiment was conducted at NASA Langley Tansonic Dynamics Tunnel and represents the first-of-a-kind Mach-scaled fully-active-twist rotor system to undergo forward flight test. In parallel, the impact upon the fixed- and rotating-system loads is estimated by the analysis. While discrepancies are found in the amplitude of the loads under actuation, the predicted trend of load variation with respect to its control phase correlates well. It was also shown, both experimentally and numerically, that the ATR blade design has the potential for hub vibratory load reduction of up to 90% using individual blade control actuation. Using the numerical framework, system identification is performed to estimate the harmonic transfer functions. The linear time-periodic system can be represented by a linear time-invariant system under the three modes of blade actuation: collective, longitudinal cyclic, and lateral cyclic. A vibration

  8. A Study of Active Rotor-Blade Vibration Control using Electro-Magnetic Actuation - Part II: Experiment

    Christensen, Rene Hardam; Santos, Ilmar

    2004-01-01

    mistuning, can easily be generated by substitution or rearranging the blades. Six sets of electro-magnetic actuators are applied to the system in order to control the blades as well as the rotor vibrations. Four sets of actuators are mounted in the rotating disc acting directly onto each one of the blades....... The remaining two sets of actuators are applied to act directly onto the hub, working as an active radial bearing controlling the rotor lateral movement. The rig is equipped with sensors measuring blade and rotor vibrations. Actuators and sensors are connected to a digital signal processor running the...... control algorithm. Measurement signals and actuator control signals from the sensors and actuators fixed in the rotating disc are transmitted to the control unit through a slip-ring device. Various measured responses of both the controlled and the non-controlled system with identical blades and with...

  9. Turbine engine rotor blade fault diagnostics through casing pressure and vibration sensors

    In this study, an exact solution is provided for a previously indeterminate equation used for rotor blade fault diagnostics. The method estimates rotor blade natural frequency through turbine engine casing pressure and vibration sensors. The equation requires accurate measurements of low-amplitude sideband signals in the frequency domain. With this in mind, statistical evaluation was also completed with the goal of determining the effect of sampling time and frequency on sideband resolution in the frequency domain

  10. Dynamic response of active twist rotor blades

    Cesnik, Carlos E. S.; Shin, Sang Joon; Wilbur, Matthew L.

    2001-02-01

    Dynamic characteristics of active twist rotor (ATR) blades are investigated analytically and experimentally in this paper. The ATR system is intended for vibration and potentially for noise reductions in helicopters through individual blade control. An aeroelastic model is developed to identify frequency response characteristics of the ATR blade with integral, generally anisotropic, strain actuators embedded in its composite construction. An ATR prototype blade was designed and manufactured to experimentally study the vibration reduction capabilities of such systems. Several bench and hover tests were conducted and those results are presented and discussed here. Selected results on sensitivity of the ATR system to collective setting (i.e. blade loading), blade rpm (i.e. centrifugal force and blade station velocity), and media density (i.e. altitude) are presented. They indicated that the twist actuation authority of the ATR blade is independent of the collective setting up to approximately 10P, and dependent on rotational speed and altitude near the torsional resonance frequency due to its dependency on the aerodynamic damping. The proposed model captures very well the physics and sensitivities to selected test parameters of the ATR system. The numerical result of the blade torsional loads show an average error of 20% in magnitude and virtually no difference in phase for the blade frequency response. Overall, the active blade model is in very good agreement with the experiments and can be used to analyze and design future active helicopter blade systems.

  11. Novel controller design demonstration for vibration alleviation of helicopter rotor blades

    Ulker, Fatma Demet; Nitzsche, Fred

    2012-04-01

    This paper presents an advanced controller design methodology for vibration alleviation of helicopter rotor sys- tems. Particularly, vibration alleviation in a forward ight regime where the rotor blades experience periodically varying aerodynamic loading was investigated. Controller synthesis was carried out under the time-periodic H2 and H∞ framework and the synthesis problem was solved based on both periodic Riccati and Linear Matrix Inequality (LMI) formulations. The closed-loop stability was analyzed using Floquet-Lyapunov theory, and the controller's performance was validated by closed-loop high-delity aeroelastic simulations. To validate the con- troller's performance an actively controlled trailing edge ap strategy was implemented. Computational cost was compared for both formulations.

  12. Control of Rotor-Blade Coupled Vibrations Using Shaft-Based Actuation

    Christensen, Rene H.; Santos, Ilmar

    When implementing active control into bladed rotating machines aiming at reducing blade vibrations, it can be shown that blade as well as rotor vibrations can in fact be controlled by the use of only shaft-based actuation. Thus the blades have to be deliberately mistuned. This paper investigates....... The dependency of the controllability and observability on varying rotational speed and mode shape interaction phenomena between parametric and basis mode shape components are also analysed. Numerical results reveal a limitation of the achievable controllability and observability, once quantitative...... the dynamical characteristics of a mistuned bladed rotor and shows how, why and when a bladed rotor becomes controllable and observable if properly mistuned. As part of such investigation modal controllability and observability of a tuned as well as a mistuned coupled rotor-blade system are analysed...

  13. Development of an active twist rotor blade with distributed actuation and orthotropic material

    Wierach, Peter; Riemenschneider, Johannes; Keye, Stefan

    2005-05-01

    Individual blade control (IBC) as well as higher harmonic control (HHC) for helicopter rotors promises to be a method to increase flight performance and to reduce vibration and noise. For those controls, an additional twist actuation of the rotor blade is needed. The developed concept comprises the implementation of distributed piezoelectric actuation into the rotor blade skin. In order to maximize the twist within given constraints, as torsional rigidity and given actuator design, the concept takes advantage of an orthotropic rotor blade skin. That way, a combination of shear actuation with orthotropic coupling generates more twist than each one of these effects alone. Previous approaches with distributed actuation used actuators operating in +/-45° direction with quasi-isotropic composites. A FE-Model of the blade was developed and validated using a simplified demonstrator. The objective of this study was to identify the effects of various geometric and material parameters to optimize the active twist performance of the blades. The whole development was embedded in an iterative process followed by an objective assessment. For this purpose a detailed structural model on the basis of the BO105 model rotor blade was developed, to predict the performance with respect to rotor dynamics, stability, aerodynamics and acoustics. Rotor dynamic simulations provided an initial overview of the active twist rotor performance. In comparison to the BO105 baseline rotor a noise reduction of 3 dB was predicted for an active twist of 0.8° at the blade tip. Additionally, a power reduction of 2.3% at 87m/s based on a 2.5 to BO105 was computed. A demonstrator blade with a rotor radius of 2m has been designed and manufactured. This blade will be tested to prove, that the calculated maximum twist can also be achieved under centrifugal loads.

  14. Optimal Design and Acoustic Assessment of Low-Vibration Rotor Blades

    G. Bernardini

    2016-01-01

    Full Text Available An optimal procedure for the design of rotor blade that generates low vibratory hub loads in nonaxial flow conditions is presented and applied to a helicopter rotor in forward flight, a condition where vibrations and noise become severe. Blade shape and structural properties are the design parameters to be identified within a binary genetic optimization algorithm under aeroelastic stability constraint. The process exploits an aeroelastic solver that is based on a nonlinear, beam-like model, suited for the analysis of arbitrary curved-elastic-axis blades, with the introduction of a surrogate wake inflow model for the analysis of sectional aerodynamic loads. Numerical results are presented to demonstrate the capability of the proposed approach to identify low vibratory hub loads rotor blades as well as to assess the robustness of solution at off-design operating conditions. Further, the aeroacoustic assessment of the rotor configurations determined is carried out in order to examine the impact of low-vibration blade design on the emitted noise field.

  15. Contribution to Experimental Validation of Linear and Non-Linear Dynamic Models for Representing Rotor-Blade Parametric Coupled Vibrations

    Santos, Ilmar; Saracho, C.M.; Smith, J.T.;

    2004-01-01

    illustrate linear, non-linear and time-depending terms in a very transparent way. Although neither gyroscopic effect due to rotor angular vibrations nor higher blade mode shapes are considered in the analysis, the equations of motion of the rotor-blades system are still general enough for the purpose of the......This work gives a theoretical and experimental contribution to the problem of rotor-blades dynamic interaction. A validation procedure of mathematical models is carried out with help of a simple test rig, built by a mass-spring system attached to four flexible rotating blades. With this test rig...... the test rig by attaching the rigid rotor to a flexible foundation. The blades are modeled as Euler-Bernoulli beams. Using three different approaches to describe the beam deformation one achieves: (a) a linear model; (b) a linear beam model with second order terms; (c) a fully non-linear model. Tip...

  16. Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps

    Uğbreve;ur Dalli

    2011-01-01

    Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.

  17. Rotor blade vortex interaction noise

    Yu, Yung H.

    2000-02-01

    Blade-vortex interaction noise-generated by helicopter main rotor blades is one of the most severe noise problems and is very important both in military applications and community acceptance of rotorcraft. Research over the decades has substantially improved physical understanding of noise-generating mechanisms, and various design concepts have been investigated to control noise radiation using advanced blade planform shapes and active blade control techniques. The important parameters to control rotor blade-vortex interaction noise and vibration have been identified: blade tip vortex structures and its trajectory, blade aeroelastic deformation, and airloads. Several blade tip design concepts have been investigated for diffusing tip vortices and also for reducing noise. However, these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance. Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. The HHC technique has proved the substantial blade-vortex interaction noise reduction, up to 6 dB, while vibration and low-frequency noise have been increased. Tests with IBC techniques have shown the simultaneous reduction of rotor noise and vibratory loads with 2/rev pitch control inputs. Recently, active blade control concepts with smart structures have been investigated with the emphasis on active blade twist and trailing edge flap. Smart structures technologies are very promising, but further advancements are needed to meet all the requirements of rotorcraft applications in frequency, force, and displacement.

  18. Control of Rotor-Blade Coupled Vibrations Using Shaft-Based Actuation

    Christensen, Rene H.; Santos, Ilmar

    When implementing active control into bladed rotating machines aiming at reducing blade vibrations, it can be shown that blade as well as rotor vibrations can in fact be controlled by the use of only shaft-based actuation. Thus the blades have to be deliberately mistuned. This paper investigates......-based actuation in practice....

  19. Structural integrity design for an active helicopter rotor blade with piezoelectric flap actuators

    Lee, Jaehwan; Shin, SangJoon

    2011-04-01

    Helicopter uses a rotor system to generate lift, thrust and forces, and its aerodynamic environment is generally complex. Unsteady aerodynamic environment arises such as blade vortex interaction. This unsteady aerodynamic environment induces vibratory aerodynamic loads and high aeroacoustic noise. The aerodynamic load and aeroacoustic noise is at N times the rotor blade revolutions (N/rev). But conventional rotor control system composed of pitch links and swash plate is not capable of adjusting such vibratory loads because its control is restricted to 1/rev. Many active control methodologies have been examined to alleviate the problem. The blade using active control device manipulates the blade pitch angle with N/rev. In this paper, Active Trailing-edge Flap blade, which is one of the active control methods, is designed to reduce the unsteady aerodynamic loads. Active Trailing-edge Flap blade uses a trailing edge flap manipulated by an actuator to change camber line of the airfoil. Piezoelectric actuators are installed inside the blade to manipulate the trailing edge flap.

  20. The Torsional Vibration of Turbo Axis Induced by Unsteady Aerodynamic Force on Rotor blade

    ChenZuoyi; WuXiaofeng

    1998-01-01

    An algorithm for computing the 3-D oscillating flow field of the balde passage under the torsional vibration of the rotor is applied to analyze the stability in turbomachines.The induced flow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and parametric Polynomial Method.After getting the solution of the unsteady flow field,the work done by the unsteay aerodynamic force acting on the blade can be obtained.The negative or positive work is the criterion of the aeroelastic stability.Numerical results indicate that there are instabilities of the torsional vibration in some frequency bands.

  1. Optimization of an Active Twist Rotor Blade Planform for Improved Active Response and Forward Flight Performance

    Sekula, Martin K; Wilbur, Matthew L.

    2014-01-01

    A study was conducted to identify the optimum blade tip planform for a model-scale active twist rotor. The analysis identified blade tip design traits which simultaneously reduce rotor power of an unactuated rotor while leveraging aeromechanical couplings to tailor the active response of the blade. Optimizing the blade tip planform for minimum rotor power in forward flight provided a 5 percent improvement in performance compared to a rectangular blade tip, but reduced the vibration control authority of active twist actuation by 75 percent. Optimizing for maximum blade twist response increased the vibration control authority by 50 percent compared to the rectangular blade tip, with little effect on performance. Combined response and power optimization resulted in a blade tip design which provided similar vibration control authority to the rectangular blade tip, but with a 3.4 percent improvement in rotor performance in forward flight.

  2. Forward sweep, low noise rotor blade

    Brooks, Thomas F. (Inventor)

    1996-01-01

    A forward-swept, low-noise rotor blade includes an inboard section, an aft-swept section and a forward-swept outboard section. The rotor blade reduces the noise of rotorcraft, including both standard helicopters and advanced systems such as tiltrotors. The primary noise reduction feature is the forward sweep of the planform over a large portion of the outer blade radius. The rotor blade also includes an aft-swept section. The purpose of the aft-swept region is to provide a partial balance to pitching moments produced by the outboard forward-swept portion of the blade. The rotor blade has a constant chord width; or has a chord width which decreases linearly along the entire blade span; or combines constant and decreasing chord widths, wherein the blade is of constant chord width from the blade root to a certain location on the rotor blade, then decreases linearly to the blade tip thereafter. The noise source showing maximum noise reduction is blade-vortex interaction (BVI) noise. Also reduced are thickness, noise, high speed impulsive noise, cabin vibration and loading noise.

  3. Optimizing tuning masses for helicopter rotor blade vibration reduction including computed airloads and comparison with test data

    Pritchard, Jocelyn I.; Adelman, Howard M.; Walsh, Joanne L.; Wilbur, Matthew L.

    1992-01-01

    An optimization procedure is developed for locating tuning masses on a rotor blade so that vibratory loads are minimized and hub-shear harmonics are reduced without adding a large mass penalty. The airloads are computed by means of a helicopter analysis for the cases of three vs six tuning masses, with attention given to the prediction of changes in airloads. Frequencies, airloads, and hub loads are computed with the CAMRAD/JA helicopter analysis code and the Conmin general-purpose optimization program. The hub shear is found to be significantly reduced in both cases with the added mass, and the reduction of hub shear is demonstrated under three flight conditions. Comparisons with wind-tunnel data demonstrate that the correlation of mass location is good and the relationship between mass location and flight speed is predicted well by the model.

  4. Vibration crack corrosion behavior and failure mechanisms of highly alloyed duplex steels in steam turbine rotor blades

    The aim was to test the new duplex steel X3CrMnNiMoN 25 6 4 (A905) for its suitability as a steam turbine rotor blade material. Due to the increased proportion of manganese and nitrogen, compared to A903, in this duplex steel in the solution annealed state, an elastic limit of about 600 N/mm2 acceptable for steam turbine rotor blades was reached. A micro-duplex structure (recrystallized secondary structure) consisting of 50% each of ferrite and Austenite proved to be the optimum structure composition. To measure the SwRK behaviour, Woehler curves were produced in media containing corrosive NaCl. The mean stress was 250 N/mm2, partly 350 N/mm2. The maximum duration of the test was given as 3 x 107 load cycles at a frequency of 50 Hz. The experimental time was partly extended to 5 x 107 load cycles. In order to guarantee as realistic a test as possible, the Sw RK tests took place in aqueous NaCl solution saturated with air. To correspond to envorinmental conditions in actual operation, the electrolyte temperature was varied between 80deg and 150deg C, the Na Cl concentration of the solution was varied between very dilute (0.01 M) and nearly saturated (22%) and the pH value was varied between pH 8 and pH 3. Accompanying passive oxide layer investigations should give information on the thickness and morphology of the layers formed. (orig./MM)

  5. Numerical simulation of actuation behavior of active fiber composites in helicopter rotor blade application

    Paik, Seung Hoon; Kim, Ji Yeon; Shin, Sang Joon; Kim, Seung Jo

    2004-07-01

    Smart structures incorporating active materials have been designed and analyzed to improve aerospace vehicle performance and its vibration/noise characteristics. Helicopter integral blade actuation is one example of those efforts using embedded anisotropic piezoelectric actuators. To design and analyze such integrally-actuated blades, beam approach based on homogenization methodology has been traditionally used. Using this approach, the global behavior of the structures is predicted in an averaged sense. However, this approach has intrinsic limitations in describing the local behaviors in the level of the constituents. For example, the failure analysis of the individual active fibers requires the knowledge of the local behaviors. Microscopic approach for the analysis of integrally-actuated structures is established in this paper. Piezoelectric fibers and matrices are modeled individually and finite element method using three-dimensional solid elements is adopted. Due to huge size of the resulting finite element meshes, high performance computing technology is required in its solution process. The present methodology is quoted as Direct Numerical Simulation (DNS) of the smart structure. As an initial validation effort, present analytical results are correlated with the experiments from a small-scaled integrally-actuated blade, Active Twist Rotor (ATR). Through DNS, local stress distribution around the interface of fiber and matrix can be analyzed.

  6. Growian rotor blades: Production development, construction and test

    Thiele, H. M.

    1984-01-01

    Development and construction of three 50 m rotor blades for a 3 MW wind turbine are described. A hybrid concept was chosen, i.e., a load carrying inflexible steel spar and a glass fiber reinforced plastic skin. A test blade was constructed and static loading tests, dynamic vibration tests and fatigue tests on critical welds as well as at the connection between spar and blade skin were performed. All test results show good accordance with calculated values, and were taken into consideration during the construction of two rotor blades.

  7. Helicopter Rotor Blade Monitoring using Autonomous Wireless Sensor Network

    Sanchez Ramirez, Andrea; Loendersloot, Richard; Tinga, Tiedo; Basu, B

    2013-01-01

    The advancement on Wireless Sensor Networks for vibration monitoring presents important possibilities for helicopter rotor health and usage monitoring. While main rotor blades account for the main source of lift for helicopters, rotor induced vibration establishes an important source for understanding the rotor performance and blade condition. A discussion on the dual character of blades as rotating structures results in two different interrogation strategies for external and internal dynamic...

  8. Multiple piece turbine rotor blade

    Jones, Russell B; Fedock, John A

    2013-05-21

    A multiple piece turbine rotor blade with a shell having an airfoil shape and secured between a spar and a platform with the spar including a tip end piece. a snap ring fits around the spar and abuts against the spar tip end piece on a top side and abuts against a shell on the bottom side so that the centrifugal loads from the shell is passed through the snap ring and into the spar and not through a tip cap dovetail slot and projection structure.

  9. Multiple piece turbine rotor blade

    Kimmel, Keith D.; Plank, William L.

    2016-07-19

    A spar and shell turbine rotor blade with a spar and a tip cap formed as a single piece, the spar includes a bottom end with dovetail or fir tree slots that engage with slots on a top end of a root section, and a platform includes an opening on a top surface for insertion of the spar in which a shell made from an exotic high temperature resistant material is secured between the tip cap and the platform. The spar is tapered to form thinner walls at the tip end to further reduce the weight and therefore a pulling force due to blade rotation. The spar and tip cap piece is made from a NiAL material to further reduce the weight and the pulling force.

  10. Bistable devices for morphing rotor blades

    Johnson, Terrence

    This dissertation presents two bistable concepts for morphing rotor blades. These concepts are simple and are composed of bistable devices that act as coupling structures between an actuator and the rotor blade. Bistable or "snap-through" mechanisms have two stable equilibrium states and are a novel way to achieve large actuation output stroke at relatively modest effort for gross rotor morphing applications. This is because in addition to the large actuation stroke associated with the snap-through (relative to conventional actuator/ amplification systems) coming at relatively low actuation effort, no locking is required in either equilibrium state (since they are both stable). The first concept that is presented in this dissertation is a that is composed of a bistable twisting device that twists the tip of helicopter rotor blades. This work examines the performance of the presented bistable twisting device for rotor morphing, specifically, blade tip twist under an aerodynamic lift load. The device is analyzed using finite element analysis to predict its load carrying capability and bistable behavior. The second concept that is presented is a concept that is composed of a bistable arch for rotor blade chord extension. The bistable arch is coupled to a thin flat plate that is supported by rollers. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. In this work, a methodology is presented to design the bistable arches for chord morphing using the finite element analysis and pseudo-rigid body model method. This work also examines the effect of different arches, arch hinge size and shape, inertial loads and rigidity on arch performance. Finally, this work shows results from an experiment that was conducted to validate the developed numerical model and demonstrates how the arch can be actuated using a Nitinol Shape Memory Alloy (SMA) wire to extend the chord of a helicopter rotor blade.

  11. 14 CFR 27.661 - Rotor blade clearance.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 27.661 Section 27... AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure...

  12. 14 CFR 29.661 - Rotor blade clearance.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor blade clearance. 29.661 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.661 Rotor blade clearance. There must be enough clearance between the rotor blades and other parts of the structure...

  13. Tip cap for a rotor blade

    Kofel, W. K.; Tuley, E. N.; Gay, C. H., Jr.; Troeger, R. E.; Sterman, A. P. (Inventor)

    1983-01-01

    A replaceable tip cap for attachment to the end of a rotor blade is described. The tip cap includes a plurality of walls defining a compartment which, if desired, can be divided into a plurality of subcompartments. The tip cap can include inlet and outlet holes in walls thereof to permit fluid communication of a cooling fluid there through. Abrasive material can be attached with the radially outer wall of the tip cap.

  14. Free-form design of rotor blades

    This work investigates an integrated free-form approach for the design of rotor blades, where airfoil shapes are treated as unknowns. This leads to the simultaneous optimization of the chord, twist and structural design variables, together with the airfoil shapes along the blade. As airfoils are automatically tailored to the evolution of the blade, this process results in a better exploration of the solution space and relieves the user from the burden of up-front choices, leading to better final designs. The proposed approach is demonstrated by sizing a 2 MW wind turbine blade

  15. Structural characterization of rotor blades through photogrammetry

    Bernardini, Giovanni; Serafini, Jacopo; Enei, Claudio; Mattioni, Luca; Ficuciello, Corrado; Vezzari, Valerio

    2016-06-01

    This paper deals with the use of photogrammetry for the experimental identification of structural and inertial properties of helicopter rotor blades4. The identification procedure is based upon theoretical/numerical algorithms for the evaluation of mass and flexural stiffness distributions which are an extension of those proposed in the past by Larsen, whereas the torsional properties (stiffness and shear center position) are determined through the Euler–Bernoulli beam theory. The identification algorithms require the knowledge of the blade displacement field produced by known steady loads. These data are experimentally obtained through photogrammetric detection technique, which allows the identification of 3D coordinates of labeled points (markers) on the structure through the correlation of 2D digital photos. Indeed, the displacement field is simply evaluated by comparing the markers positions on the loaded configuration with those on the reference one. The proposed identification procedure, numerically and experimentally validated in the past by the authors, has been here applied to the structural characterization of two main rotor blades, designed for ultra-light helicopters. Strain gauges measurements have been used to assess the accuracy of the identified properties through natural frequencies comparison as well as to evaluate the blades damping characteristics.

  16. Single-crystal-material-based induced-shear actuation for vibration reduction of helicopters with composite rotor system

    In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. Special focus is given to the feasibility of implementing the benefits of the shear actuation mechanism along with elastic couplings of composite blades for achieving maximum vibration reduction. The governing equations of motion for composite rotor blades with surface bonded piezoceramic actuators are obtained using Hamilton's principle. The equations are then solved for dynamic response using finite element discretization in the spatial and time domains. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. A newly developed single-crystal piezoceramic material is introduced as an actuator material to exploit its superior shear actuation authority. Seven rotor blades with different elastic couplings representing stiffness properties similar to stiff-in-plane rotor blades are used to investigate the hub vibration characteristics. The rotor blades are modeled as a box beam with actuator layers bonded on the outer surface of the top and bottom of the box section. Numerical results show that a notable vibration reduction can be achieved for all the combinations of composite rotor blades. This investigation also brings out the effect of different elastic couplings on various vibration-reduction-related parameters which could be useful for the optimal design of composite helicopter blades

  17. Single-crystal-material-based induced-shear actuation for vibration reduction of helicopters with composite rotor system

    Pawar, Prashant M.; Jung, Sung Nam

    2008-12-01

    In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. Special focus is given to the feasibility of implementing the benefits of the shear actuation mechanism along with elastic couplings of composite blades for achieving maximum vibration reduction. The governing equations of motion for composite rotor blades with surface bonded piezoceramic actuators are obtained using Hamilton's principle. The equations are then solved for dynamic response using finite element discretization in the spatial and time domains. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. A newly developed single-crystal piezoceramic material is introduced as an actuator material to exploit its superior shear actuation authority. Seven rotor blades with different elastic couplings representing stiffness properties similar to stiff-in-plane rotor blades are used to investigate the hub vibration characteristics. The rotor blades are modeled as a box beam with actuator layers bonded on the outer surface of the top and bottom of the box section. Numerical results show that a notable vibration reduction can be achieved for all the combinations of composite rotor blades. This investigation also brings out the effect of different elastic couplings on various vibration-reduction-related parameters which could be useful for the optimal design of composite helicopter blades.

  18. Helicopter Rotor Blade With Free Tip

    Stroub, Robert H.; Young, Larry; Cawthorne, Matthew; Keys, Charles

    1992-01-01

    Free-tip rotor blades improve fuel efficiency and performance characteristics of helicopters. Outermost portion of blade pivots independently with respect to inboard portion about pitch axis parallel to blade axis, located forward of aerodynamic center. Centrifugal force acts on tension/torsion strap and biases tip nose-up. Airstream turns tip nose-down, other torques cause tip to "weathervane" to intermediate angular position resulting in net lift. Reduces fluctuations in lift, with two effects: flapwise vibratory loads on blade and vibratory loads on pitch-control mechanism reduced; negative lift produced by advancing fixed tip eliminated, reducing power required to achieve same overall lift. Applies to tilt rotors and tail rotors as well.

  19. Rotor blade online monitoring and fault diagnosis technology research

    Tesauro, Angelo; Pavese, Christian; Branner, Kim

    Rotor blade online monitoring and fault diagnosis technology is an important way to find blade failure mechanisms and thereby improve the blade design. Condition monitoring of rotor blades is necessary in order to ensure the safe operation of the wind turbine, make the maintenance more economical......, unbalancing of the rotor, icing and lightning. Research is done throughout the world in order to develop and improve such measurement systems. Commercial hardware and software available for the described purpose is presented in the report....

  20. Determination of the angle of attack on rotor blades

    Shen, Wen Zhong; Hansen, Martin Otto Laver; Sørensen, Jens Nørkær

    2009-01-01

    Two simple methods for determining the angle of attack (AOA) on a section of a rotor blade are proposed. Both techniques consist of employing the Biot-Savart integral to determine the influence of the bound vorticity on the velocity field. In the first technique, the force distribution along the...... techniques. The advantage of the proposed techniques, as compared with existing techniques, is that they can be used to determine the AOA on rotor blades under general flow conditions (e.g. operations in yaw or with dynamic inflow)....

  1. Blade lock for a rotor disk and rotor blade assembly

    Moore, Jerry H. (Inventor)

    1992-01-01

    A rotor disk 18 and rotor blade 26 assembly is disclosed having a blade lock 66 which retains the rotor blade against axial movement in an axially extending blade retention slot 58. Various construction details are developed which shield the dead rim region D.sub.d and shift at least a portion of the loads associated with the locking device from the dead rim. In one detailed embodiment, a projection 68 from the live rim D.sub.1 of the disk 18 is adapted by slots 86 to receive blade locks 66.

  2. Design of helicopter rotor blades for optimum dynamic characteristics

    Peters, D. A.; Ko, T.; Korn, A.; Rossow, M. P.

    1985-01-01

    The mass and stiffness distributions for helicopter rotor blades are tailored in such a way to give a predetermined placement of blade natural frequencies. The optimal design is pursued with respect of minimum weight, sufficient inertia, and reasonable dynamic characteristics. Finite element techniques are used as a tool. Rotor types include hingeless, articulated, and teetering.

  3. Efficient Beam-Type Structural Modeling of Rotor Blades

    Couturier, Philippe; Krenk, Steen

    2015-01-01

    The present paper presents two recently developed numerical formulations which enable accurate representation of the static and dynamic behaviour of wind turbine rotor blades using little modeling and computational effort. The first development consists of an intuitive method to extract fully cou...... application to a composite section with bend-twist coupling and a real wind turbine blade....

  4. Vibration Reduction Methods and Techniques for Rotorcraft Utilizing On-Blade Active Control Project

    National Aeronautics and Space Administration — Rotor blades adapted for vibration control have the added benefit of extended blade and rotor life, as well as improved passenger comfort. Approaches that have been...

  5. Aeroelasticity and structural optimization of composite helicopter rotor blades with swept tips

    Yuan, K. A.; Friedmann, P. P.

    1995-01-01

    This report describes the development of an aeroelastic analysis capability for composite helicopter rotor blades with straight and swept tips, and its application to the simulation of helicopter vibration reduction through structural optimization. A new aeroelastic model is developed in this study which is suitable for composite rotor blades with swept tips in hover and in forward flight. The hingeless blade is modeled by beam type finite elements. A single finite element is used to model the swept tip. Arbitrary cross-sectional shape, generally anisotropic material behavior, transverse shears and out-of-plane warping are included in the blade model. The nonlinear equations of motion, derived using Hamilton's principle, are based on a moderate deflection theory. Composite blade cross-sectbnal properties are calculated by a separate linear, two-dimensional cross section analysis. The aerodynamic loads are obtained from quasi-steady, incompressible aerodynamics, based on an implicit formulation. The trim and steady state blade aeroelastic response are solved in a fully coupled manner. In forward flight, where the blade equations of motion are periodic, the coupled trim-aeroelastic response solution is obtained from the harmonic balance method. Subsequently, the periodic system is linearized about the steady state response, and its stability is determined from Floquet theory.

  6. Sound generation by non-synchronously oscillating rotor blades in turbomachinery

    Zhou, Di; Wang, Xiaoyu; Chen, Jun; Jing, Xiaodong; Sun, Xiaofeng

    2015-10-01

    In this paper, the sound generation by non-synchronously oscillating rotor blades in axial compressor is investigated with emphasis on establishing an analytical model for the corresponding sound field inside an annular duct. In terms of the present model, it is found that the acoustic frequency and propagating modes generated by non-synchronously oscillating rotor blades are not only associated with the blade vibration frequency and rotational speed, but also depend on the cascade inter-blade phase angle (IBPA) and the interaction between blades, which is clearly distinguished from typical Doppler effect. Moreover, it is also shown that although the IBPA of cascade is non-constant practically, the characteristics of sound generation are only slightly affected. Besides, the present work has conducted experimental investigations in order to gain insight into the generation mechanism of such complex sound field. Excellent agreement between the model prediction and experimental measurement in the near and far fields is generally observed in the circumstances with different parameter settings. Since the present study links the sound generation with blade oscillation, it would be very helpful to the fault diagnosis of rotor non-synchronous oscillation to some extent.

  7. Lift capability prediction for helicopter rotor blade-numerical evaluation

    Rotaru, Constantin; Cîrciu, Ionicǎ; Luculescu, Doru

    2016-06-01

    The main objective of this paper is to describe the key physical features for modelling the unsteady aerodynamic effects found on helicopter rotor blade operating under nominally attached flow conditions away from stall. The unsteady effects were considered as phase differences between the forcing function and the aerodynamic response, being functions of the reduced frequency, the Mach number and the mode forcing. For a helicopter rotor, the reduced frequency at any blade element can't be exactly calculated but a first order approximation for the reduced frequency gives useful information about the degree of unsteadiness. The sources of unsteady effects were decomposed into perturbations to the local angle of attack and velocity field. The numerical calculus and graphics were made in FLUENT and MAPLE soft environments. This mathematical model is applicable for aerodynamic design of wind turbine rotor blades, hybrid energy systems optimization and aeroelastic analysis.

  8. Reliability analysis of rotor blades of tidal stream turbines

    Tidal stream turbines are used for converting kinetic energy of tidal currents into electricity. There are a number of uncertainties involved in the design of such devices and their components. To ensure safety of the turbines these uncertainties must be taken into account. The paper shows how this may be achieved for the design of rotor blades of horizontal-axis tidal stream turbines in the context of bending failure due to extreme loading. Initially, basic characteristics of such turbines in general and their blades in particular are briefly described. A probabilistic model of tidal current velocity fluctuations, which are the main source of load uncertainty, is then presented. This is followed by the description of reliability analysis of the blades, which takes into account uncertainties associated with tidal current speed, the blade resistance and the model used to calculate bending moments in the blades. Finally, the paper demonstrates how results of the reliability analysis can be applied to set values of the partial factors for the blade design. - Highlights: • A probabilistic model of the maximum of tidal current velocity fluctuations is proposed. • Reliability analysis of rotor blades of a tidal stream turbine is described. • Influence of pitch control system on the blade reliability is investigated. • Partial safety factors for the design of tidal turbine rotor blades are calibrated

  9. Thermographic inspection of a wind turbine rotor blade segment utilizing natural conditions as excitation source, Part I: Solar excitation for detecting deep structures in GFRP

    Worzewski, Tamara; Krankenhagen, Rainer; Doroshtnasir, Manoucher; Röllig, Mathias; Maierhofer, Christiane; Steinfurth, Henrik

    2016-05-01

    This study evaluates whether subsurface features in rotor blades, mainly made of Glass Fibre Reinforced Plastics (GFRP), can generally be detected with "solar thermography". First, the suitability of the sun is tested for acting as a heat source for applying active thermography on a 30 mm thick GFRP test specimen. Second, a defective rotor blade segment is inspected outdoors under ideal natural conditions using the sun as excitation source. Additionally, numerical FEM-simulations are performed and the comparability between experiment and simulation is evaluated for outdoor measurements.

  10. Development of a piezoelectric actuator for trailing-edge flap control of rotor blades

    Straub, Friedrich K.; Ngo, Hieu T.; Anand, V.; Domzalski, David B.

    1999-06-01

    Piezoelectric actuator technology has now reached a level where macro-positioning applications in the context of smart structures can be considered. One application with high payoffs is vibration reduction, noise reduction, and performance improvements in helicopters. Integration of piezoelectric actuators in the rotor blade is attractive, since it attacks the problem at the source. The present paper covers the development of a piezoelectric actuator for trailing edge flap control on a 34-foot diameter helicopter main rotor. The design of an actuator using bi-axial stack columns, and its bench, shake, and spin testing are described. A series of enhancements lead to an improved version that, together with use of latest stack technology, meets the requirements. Next steps in this DARPA sponsored program are development of the actuator and full scale rotor system for wind tunnel testing in the NASA Ames 40 X 80 foot wind tunnel and flight testing on the MD Explorer.

  11. Applying Pressure Sensitive Paint Technology to Rotor Blades

    Watkins, A. Neal; Leighty, Bradley D.; Lipford, William E.; Goodman, Kyle Z.; Crafton, Jim; Gregory, James W.

    2014-01-01

    This report will present details of a Pressure Sensitive Paint (PSP) system for measuring global surface pressures on rotorcrtaft blades in simulated forward flight at the 14- by 22-Foot Subsonic Tunnel at the NASA Langley Research Center. The basics of the PSP method will be discussed and the modifications that were needed to extend this technology for use on rotor blades. Results from a series of tests will also be presented as well as several areas of improvement that have been identified and are currently being developed for future testing.

  12. Acoustic design of rotor blades using a genetic algorithm

    Wells, V. L.; Han, A. Y.; Crossley, W. A.

    1995-01-01

    A genetic algorithm coupled with a simplified acoustic analysis was used to generate low-noise rotor blade designs. The model includes thickness, steady loading and blade-vortex interaction noise estimates. The paper presents solutions for several variations in the fitness function, including thickness noise only, loading noise only, and combinations of the noise types. Preliminary results indicate that the analysis provides reasonable assessments of the noise produced, and that genetic algorithm successfully searches for 'good' designs. The results show that, for a given required thrust coefficient, proper blade design can noticeably reduce the noise produced at some expense to the power requirements.

  13. A review of helicopter rotor blade tip shapes

    Brocklehurst, A.; Barakos, G. N.

    2013-01-01

    A review of helicopter rotor blade tip design technology has been carried out with a view to undertaking subsequent computations to evaluate the performance of new tip designs. The review starts by briefly looking at (fixed) wing tip design concepts and the underlying fluid mechanics on which they are based in order to see if there is any carry-over of ideas on which improved tip design concepts might be based. Then, rotor blade tip shapes that have been used, or suggested for use, on past and present rotorcraft are examined to obtain a better understanding of the helicopter tip design problem. In parallel, the review traces the development of analysis tools to evaluate the performance of the rotor and blade tip design. It is clear that in the past, the designer relied heavily on classical aerodynamic knowledge, supplemented by experience and intuition, supported by wind tunnel and model rotor testing, and relatively low-order aerodynamic calculations. New rotor designs were, and still are the subject of intensive flight test verification. However, recent development of Computational Fluid Dynamics (CFD) now offers an opportunity to accurately predict the viscous, compressible flow-field in the tip region, and thus predict the performance of new rotor and tip designs, provided that the solver has adequate resolution, is able to handle all aspects of the helicopter problem, and sufficient computational resources are available to complete the design in a practical time-scale.

  14. Photogrammetric detection technique for rotor blades structural characterization

    Enei, C.; Bernardini, G.; Serafini, J.; Mattioni, L.; Ficuciello, C.; Vezzari, V.

    2015-11-01

    This paper describes an innovative use of photogrammetric detection techniques to experimentally estimate structural/inertial properties of helicopter rotor blades. The identification algorithms for the evaluation of mass and flexural stiffness distributions are an extension of the ones proposed by Larsen, whereas the procedure for torsional properties determination (stiffness and shear center position) is based on the Euler-Prandtl beam theory. These algorithms rely on measurements performed through photogrammetric detection, which requires the collection of digital photos allowing the identification of 3D coordinates of labeled points (markers) on the structure through the correlation of 2D pictures. The displacements are evaluated by comparing the positions of markers in loaded and reference configuration. Being the applied loads known, the structural characteristics can be directly obtained from the measured displacements. The accuracy of the proposed identification algorithms has been firstly verified by comparison with numerical and experimental data, and then applied to the structural characterization of two main rotor blades, designed for ultra-light helicopter applications.

  15. Nondestructive evaluation of helicopter rotor blades using guided Lamb modes.

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2014-03-01

    This paper presents an application for turning and direct modes in a complex composite laminate structure. The propagation and interaction of turning modes and fundamental Lamb modes are investigated in the skin, spar and web sections of a helicopter rotor blade. Finite element models were used to understand the various mode conversions at geometric discontinuities such as web-spar joints. Experimental investigation was carried out with the help of air coupled ultrasonic transducers. The turning and direct modes were confirmed with the help of particle displacements and velocities. Experimental B-Scans were performed on damaged and undamaged samples for qualitative and quantitative assessment of the structure. A strong correlation between the numerical and experimental results was observed and reported. PMID:24210414

  16. Application of optimization methods to helicopter rotor blade design

    Chattopadhyay, A.; Walsh, J. L.

    1990-01-01

    A procedure for the minimum weight design of helicopter rotor blades with constraints on multiple coupled flap-lag natural frequencies, autorotational inertia, and centrifugal stress is presented. Optimum designs are obtained for blades with both rectangular and tapered planforms and are compared within a reference blade. The effects of higher-frequency constraints and stress constraints on the optimum blade designs are assessed. The results indicate that there is an increase in blade weight and a significant change in the design variable distributions with an increase in the number of frequency constraints. The inclusion of stress constraints has different effects on the wall thickness distributions of rectangular and tapered blades, but tends to increase the magnitude of the nonstructural segment weight distributions for both blade types.

  17. A new approach to helicopter rotor blade research instrumentation

    Knight, V. H., Jr.

    1978-01-01

    A rotor-blade-mounted telemetry instrumentation system developed and used in flight tests by the NASA/Langley Research Center is described. The system uses high-speed digital techniques to acquire research data from miniature pressure transducers on advanced rotor airfoils which are flight tested using an AH-1G helicopter. The system employs microelectronic PCM multiplexer-digitizer stations located remotely on the blade and in a hub-mounted metal canister. The electronics contained in the canister digitizes up to 16 sensors, formats this data with serial PCM data from the remote stations, and transmits the data from the canister which is above the plane of the rotor. Data is transmitted over an RF link to the ground for real-time monitoring and to the helicopter fuselage for tape recording.

  18. Optimization model for rotor blades of horizontal axis wind turbines

    LIU Xiong; CHEN Yan; YE Zhiquan

    2007-01-01

    This paper presents an optimization model for rotor blades of horizontal axis wind turbines. The model refers to the wind speed distribution function on the specific wind site, with an objective to satisfy the maximum annual energy output. To speed up the search process and guarantee a global optimal result, the extended compact genetic algorithm (ECGA) is used to carry out the search process.Compared with the simple genetic algorithm, ECGA runs much faster and can get more accurate results with a much smaller population size and fewer function evaluations. Using the developed optimization program, blades of a 1.3 MW stall-regulated wind turbine are designed. Compared with the existing blades, the designed blades have obviously better aerodynamic performance.

  19. Optimization methods applied to the aerodynamic design of helicopter rotor blades

    Walsh, Joanne L.; Bingham, Gene J.; Riley, Michael F.

    1987-01-01

    Described is a formal optimization procedure for helicopter rotor blade design which minimizes hover horsepower while assuring satisfactory forward flight performance. The approach is to couple hover and forward flight analysis programs with a general-purpose optimization procedure. The resulting optimization system provides a systematic evaluation of the rotor blade design variables and their interaction, thus reducing the time and cost of designing advanced rotor blades. The paper discusses the basis for and details of the overall procedure, describes the generation of advanced blade designs for representative Army helicopters, and compares design and design effort with those from the conventional approach which is based on parametric studies and extensive cross-plots.

  20. A study of autogiro rotor-blade oscillations in the plane of the rotor disk

    Wheatley, John B

    1936-01-01

    An analysis of the factors governing the oscillation of an autogiro rotor blade in the plane of the rotor disk showed that the contribution of the air forces to the resultant motion was small and that the oscillation is essentially a direct effect of the rotor-blade flapping motion. A comparison of calculated oscillations with those measured in flight on three different rotors disclosed that the calculations gave satisfactory agreement with experiment. The calculated air forces on the rotor blade appear to be larger than the experimental ones, but this discrepancy can be attributed to the deficiencies in the strip analysis.

  1. Optimization of rotor blades for combined structural, dynamic, and aerodynamic properties

    He, Cheng-Jian; Peters, David A.

    1990-01-01

    Optimal helicopter blade design with computer-based mathematical programming has received more and more attention in recent years. Most of the research has focused on optimum dynamic characteristics of rotor blades to reduce vehicle vibration. There is also work on optimization of aerodynamic performance and on composite structural design. This research has greatly increased our understanding of helicopter optimum design in each of these aspects. Helicopter design is an inherently multidisciplinary process involving strong interactions among various disciplines which can appropriately include aerodynamics; dynamics, both flight dynamics and structural dynamics; aeroelasticity: vibrations and stability; and even acoustics. Therefore, the helicopter design process must satisfy manifold requirements related to the aforementioned diverse disciplines. In our present work, we attempt to combine several of these important effects in a unified manner. First, we design a blade with optimum aerodynamic performance by proper layout of blade planform and spanwise twist. Second, the blade is designed to have natural frequencies that are placed away from integer multiples of the rotor speed for a good dynamic characteristics. Third, the structure is made as light as possible with sufficient rotational inertia to allow for autorotational landing, with safe stress margins and flight fatigue life at each cross-section, and with aeroelastical stability and low vibrations. Finally, a unified optimization refines the solution.

  2. OPTIMAT Blades. Reliable Optimal Use of Materials for Wind Turbine Rotor Blades. Final Report

    Janssen, L.G.J. [ECN Wind Energy, Petten (Netherlands); Van Wingerde, A.M.; Nijssen, R.P.L. [Knowledge Centre Wind Trubine Materials and Constructions, Delft (Netherlands); Philippidis, T.P. [University of Patras, Patras (Greece); Broendsted, P. [Risoe National Laboratory, Roskilde (Denmark); Dutton, A.G. [Council for the Central Laboratory of Research Councils CCLRC, Chilton, Didcot (United Kingdom); Kensche, C.W. [Deutsches Zentrum fuer Luft- und Raumfahrt, Berlin (Germany)

    2006-06-15

    As the required financial investments to achieve the expansion of the installed capacity of wind turbine grow, the economical pressure on reliable and structurally optimised blades, that are fit for their designed life, will increase. Very large blades may even become practically impossible without further knowledge of the material behaviour since the dominating loads on the material are caused by the blade mass. Therefore, a sound and accurate understanding of the structural behaviour of the material under all for wind turbine applications possible loading conditions is necessary. The project aims to provide accurate design recommendations for the optimised use of materials within wind turbine rotor blades and to achieve improved reliability. The major deliverable of the project will be improved design recommendations for the next generation of rotor blades. With the accurate and reliable design recommendations resulting from this project, reliable blades with optimised use of materials can be designed. The increased reliability and weight reduction of the blades will stimulate further the offshore exploitation with large capacity wind turbines. This supports the increase in wind energy and by that helps to reach the White Paper target of 40GW of installed power by 2010. The possible reduction of the material use will lower the impact on earth's resources and environment. The reduction can result from direct weight saving and from the increased reliability which prevents the need for replacements and waste of material. To execute the research activities a consortium was formed consisting of 10 research institutes from 7 EU countries; 5 wind turbine and/or blade manufactures from 3 EU countries; and the two leading certification bodies that carry out wind turbine certification throughout the world today. Over 3000 individual tests have been carried out on epoxy GFRP coupons, with numerous technical reports being issued to analyse and understand this data. The

  3. Smart helicopter rotors optimization and piezoelectric vibration control

    Ganguli, Ranjan; Viswamurthy, Sathyamangalam Ramanarayanan

    2016-01-01

    Exploiting the properties of piezoelectric materials to minimize vibration in rotor-blade actuators, this book demonstrates the potential of smart helicopter rotors to achieve the smoothness of ride associated with jet-engined, fixed-wing aircraft. Vibration control is effected using the concepts of trailing-edge flaps and active-twist. The authors’ optimization-based approach shows the advantage of multiple trailing-edge flaps and algorithms for full-authority control of dual trailing-edge-flap actuators are presented. Hysteresis nonlinearity in piezoelectric stack actuators is highlighted and compensated by use of another algorithm. The idea of response surfaces provides for optimal placement of trailing-edge flaps. The concept of active twist involves the employment of piezoelectrically induced shear actuation in rotating beams. Shear is then demonstrated for a thin-walled aerofoil-section rotor blade under feedback-control vibration minimization. Active twist is shown to be significant in reducing vibra...

  4. Helicopter rotor blade injury: a persistent safety hazard in the U.S. Army.

    Crowley, J S; Geyer, S L

    1993-09-01

    Rotor blade injuries are an inherent hazard of helicopter operations. To determine the recent incidence of rotor blade injuries in the U.S. Army, a review of accident records (1972-91) was conducted. Crash-related injuries were not included. During the study period, there were 24 blade strike injuries (12 involving the main rotor), 11 (46%) of which were fatal. Comparison with previous reports indicates a lower rotor blade injury rate in the last decade than in any previous period. The head was injured most frequently (65%), followed by the chest (17%) and abdomen (7%). Protective helmets helped to reduce injury in several instances. Flight crew comprised 49% of the victims, passengers 29%, ground crew 14%, and bystanders 8%. Helicopter crews must maintain situational awareness when around turning blades--professional training alone does not guarantee protection from rotor blade injury. PMID:8216149

  5. The Effect of Composite Flexures on Aeroelastic Stability of a Hingeless Rotor Blade

    Shi; Qinghua

    2007-01-01

    The effects of ply orientation angle of composite flexures on stability of hingeless rotor blade system are studied.The composite hingeless rotor blade system is simplified as a hub,a flap flexure and a lag flexure.pitch bearing and main blade.The kinematics formulations are inferred by employing the moderate deflection beam theory.The shear deformation and warping related to torsion are considered.The quasi-steady strip theory with dynamic inflow effects is applied to obtain the aerodynamic loads acting on the blade.Based on these.the set of finite element formulations of a hingeless rotor blade system is worked out.The numerical results show that the ply angle of the composite flexures has great effects on the aeroelastic stability of rotor blade.

  6. Rotor-blade wheel solves the sediment problems; Loepehjul loeser sedimentproblemer

    Bakken, Marte

    2009-07-01

    Test period in Peru is over for the recently developed rotor-blade wheel from the Norwegian firm DynaVec. The result shows that the wear and tear problems caused by sediments in great extent is solved. (AG)

  7. Method and apparatus for reducing rotor blade deflections, loads, and/or peak rotational speed

    Moroz, Emilian Mieczyslaw; Pierce, Kirk Gee

    2006-10-17

    A method for reducing at least one of loads, deflections of rotor blades, or peak rotational speed of a wind turbine includes storing recent historical pitch related data, wind related data, or both. The stored recent historical data is analyzed to determine at least one of whether rapid pitching is occurring or whether wind speed decreases are occurring. A minimum pitch, a pitch rate limit, or both are imposed on pitch angle controls of the rotor blades conditioned upon results of the analysis.

  8. Minimum weight design of helicopter rotor blades with frequency constraints

    Chattopadhyay, Aditi; Walsh, Joanne L.

    1989-01-01

    The minimum weight design of helicopter rotor blades subject to constraints on fundamental coupled flap-lag natural frequencies has been studied in this paper. A constraint has also been imposed on the minimum value of the blade autorotational inertia to ensure that the blade has sufficient inertia to autorotate in case of an engine failure. The program CAMRAD has been used for the blade modal analysis and the program CONMIN has been used for the optimization. In addition, a linear approximation analysis involving Taylor series expansion has been used to reduce the analysis effort. The procedure contains a sensitivity analysis which consists of analytical derivatives of the objective function and the autorotational inertia constraint and central finite difference derivatives of the frequency constraints. Optimum designs have been obtained for blades in vacuum with both rectangular and tapered box beam structures. Design variables include taper ratio, nonstructural segment weights and box beam dimensions. The paper shows that even when starting with an acceptable baseline design, a significant amount of weight reduction is possible while satisfying all the constraints for blades with rectangular and tapered box beams.

  9. Fully integrated aerodynamic/dynamic optimization of helicopter rotor blades

    Walsh, Joanne L.; Lamarsh, William J., II; Adelman, Howard M.

    1992-01-01

    A fully integrated aerodynamic/dynamic optimization procedure is described for helicopter rotor blades. The procedure combines performance and dynamic analyses with a general purpose optimizer. The procedure minimizes a linear combination of power required (in hover, forward flight, and maneuver) and vibratory hub shear. The design variables include pretwist, taper initiation, taper ratio, root chord, blade stiffnesses, tuning masses, and tuning mass locations. Aerodynamic constraints consist of limits on power required in hover, forward flight and maneuvers; airfoil section stall; drag divergence Mach number; minimum tip chord; and trim. Dynamic constraints are on frequencies, minimum autorotational inertia, and maximum blade weight. The procedure is demonstrated for two cases. In the first case, the objective function involves power required (in hover, forward flight and maneuver) and dynamics. The second case involves only hover power and dynamics. The designs from the integrated procedure are compared with designs from a sequential optimization approach in which the blade is first optimized for performance and then for dynamics. In both cases, the integrated approach is superior.

  10. Ice accretion modeling for wind turbine rotor blades

    Chocron, D.; Brahimi, T.; Paraschivoiu, I.; Bombardier, J.A. [Ecole Polytechnique de Montreal (Canada)

    1997-12-31

    The increasing application of wind energy in northern climates implies operation of wind turbines under severe atmospheric icing conditions. Such conditions are well known in the Scandinavian countries, Canada and most of Eastern European countries. An extensive study to develop a procedure for the prediction of ice accretion on wind turbines rotor blades appears to be essential for the safe and economic operation of wind turbines in these cold regions. The objective of the present paper is to develop a computer code capable of simulating the shape and amount of ice which may accumulate on horizontal axis wind turbine blades when operating in icing conditions. The resulting code is capable to predict and simulate the formation of ice in rime and glaze conditions, calculate the flow field and particle trajectories and to perform thermodynamic analysis. It also gives the possibility of studying the effect of different parameters that influence ice formation such as temperature, liquid water content, droplet diameter and accretion time. The analysis has been conducted on different typical airfoils as well as on NASA/DOE Mod-0 wind turbine. Results showed that ice accretion on wind turbines may reduce the power output by more than 20%.

  11. Investigation of the impact of rain and particle erosion on rotor blade aerodynamics with an erosion test facility to enhancing the rotor blade performance and durability

    During their operational life span of around 20 years, the individual components of a wind turbine, especially the rotor blades, are exposed to extreme environmental influences. This is the result of the continuous exposure of wind turbines to the elements and of particularly high rotor blade tip speeds, which exceed a velocity of 90 m/s. These effects result in leading edge erosion. Rotor blades are therefore protected by special coating systems, e.g. varnishes and foils. The durability of those surface coatings varies depending on the location of the wind turbine and often proves to be insufficient. Additionally, there is no standardised test procedure for the evaluation of the durability and protective effect of the coating materials under the highly erosive conditions at the location of the wind turbines. In the course of this project, we will develop a testing procedure to evaluate the erosion of coating materials on actual leading edges of rotor blades, which will be applied in a test facility. The test rig will be capable of simulating a realistic application of rain and sand to gauge the effects of erosion. During the application, two test objects can be tested simultaneously. The geometry of the test objects will be adapted to represent that of real rotor blade tips. In order to generate comparable and transferable results, several challenges have to be met during the implementation, especially the realistic reproduction of environmental influences and the corrosion damage mechanism. In this regard, the duration of the test procedure is very important because a time lapse factor of 100-260 is intended. An operation of 20 years can thereby be simulated within 4 to 10 weeks

  12. Foreign Object Damage to Fan Rotor Blades of Aeroengine Part Ⅰ: Experimental Study of Bird Impact

    2007-01-01

    The conditions of experiment for bird impact to blades have been improved. The experiment of bird impact to the fan rotor blades of an aeroengine is carried out. Through analyzing the transient state response of blades impacted by bird and the change of blade profile before and after the impact, the anti-bird impact performance of blades in the first fan rotor is verified. The basis of anti-foreign object damage design for the fan rotor blades of an aeroengine is provided.

  13. Boundary Layer Transition Detection on a Rotor Blade Using Rotating Mirror Thermography

    Heineck, James T.; Schuelein, Erich; Raffel, Markus

    2014-01-01

    Laminar-to-turbulent transition on a rotor blade in hover has been imaged using an area-scan infrared camera. A new method for tracking a blade using a rotating mirror was employed. The mirror axis of rotation roughly corresponded to the rotor axis of rotation and the mirror rotational frequency is 1/2 that of the rotor. This permitted the use of cameras whose integration time was too long to prevent image blur due to the motion of the blade. This article will show the use of this method for a rotor blade at different collective pitch angles.

  14. Assessment Report on Innovative Rotor Blades (MAREWINT WP1,D1.3)

    McGugan, Malcolm; Leble, Vladimir; Pereira, Gilmar Ferreira

    The offshore wind energy industry faces many challenges in the short to medium term if it is to meet the ambitions of the global community for sustainable energy supply in the future. Not least among these challenges is the issue of rotor blades. Innovative design for “smart” rotor blades with...... innovative concept development for wind turbine blades. This covers models and experiments with damage measurement systems embedded within the composite material/structure and numerical methods investigating the effects of leading and trailing edge flaps on modifying the aerodynamic loads on the operating...

  15. A multi-fidelity framework for physics based rotor blade simulation and optimization

    Collins, Kyle Brian

    New helicopter rotor designs are desired that offer increased efficiency, reduced vibration, and reduced noise. Rotor Designers in industry need methods that allow them to use the most accurate simulation tools available to search for these optimal designs. Computer based rotor analysis and optimization have been advanced by the development of industry standard codes known as "comprehensive" rotorcraft analysis tools. These tools typically use table look-up aerodynamics, simplified inflow models and perform aeroelastic analysis using Computational Structural Dynamics (CSD). Due to the simplified aerodynamics, most design studies are performed varying structural related design variables like sectional mass and stiffness. The optimization of shape related variables in forward flight using these tools is complicated and results are viewed with skepticism because rotor blade loads are not accurately predicted. The most accurate methods of rotor simulation utilize Computational Fluid Dynamics (CFD) but have historically been considered too computationally intensive to be used in computer based optimization, where numerous simulations are required. An approach is needed where high fidelity CFD rotor analysis can be utilized in a shape variable optimization problem with multiple objectives. Any approach should be capable of working in forward flight in addition to hover. An alternative is proposed and founded on the idea that efficient hybrid CFD methods of rotor analysis are ready to be used in preliminary design. In addition, the proposed approach recognizes the usefulness of lower fidelity physics based analysis and surrogate modeling. Together, they are used with high fidelity analysis in an intelligent process of surrogate model building of parameters in the high fidelity domain. Closing the loop between high and low fidelity analysis is a key aspect of the proposed approach. This is done by using information from higher fidelity analysis to improve predictions made

  16. Composite structure of helicopter rotor blades studied by neutron- and X-ray radiography

    In order to inspect the possible defects in the composite structure of helicopter rotor blades combined neutron- and X-ray radiography investigations were performed at the Budapest Research Reactor. Imperfections in the honeycomb structure, resin rich or starved areas at the core-honeycomb surfaces, inhomogeneities at the adhesive filling and water percolation at the sealing interfaces of the honeycomb sections were discovered

  17. 14 CFR 29.653 - Pressure venting and drainage of rotor blades.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Pressure venting and drainage of rotor... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Rotors § 29.653 Pressure venting and drainage of rotor blades. (a) For each rotor blade— (1) There must...

  18. 14 CFR 27.653 - Pressure venting and drainage of rotor blades.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Pressure venting and drainage of rotor... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Rotors § 27.653 Pressure venting and drainage of rotor blades. (a) For each rotor blade— (1) There must be...

  19. Measurement of Rotor Blade Deformations of Wind Energy Converters with Laser Scanners

    Wind energy converters in operation are exposed to high stresses which result in large deformations of the rotor blades. In this paper a method for determination of deformations of rotating rotor blades is presented using multiple synchronous laser scanners and cameras. In a first step, multiple scanners in 1D mode are used which record cross sections at different positions along the rotor blades. By comparing the recorded cross sections with a CAD model of the rotor blade, the deformations in out-of-plane and torsional direction can be derived. In order to ensure that the positions of the cross sections are defined in the coordinate system of the wind energy converter, the nacelle is pre-scanned and a 3D transformation is performed using known coordinates from the manufacturer. To account for the relatively slow movement of the nacelle, it is observed by a photogrammetric camera. The results of the nacelle's motion are considered in the analysis of the 1D data. First test recordings were carried out with different measurement frequencies to enable comparisons of accuracy. Furthermore, first results of the cross-section measurements are presented. For the next step the 3D scans will be evaluated which have been acquired using a further instrument simultaneously with the 1D scans. In the same way as before the 3D points will be transferred to the reference system of the nacelle, and then combined with the 1D data

  20. Fatigue life prediction and strength degradation of wind turbine rotor blade composites

    Nijssen, R.P.L.

    2006-01-01

    Wind turbine rotor blades are subjected to a large number of highly variable loads, but life predictions are typically based on constant amplitude fatigue behaviour. Therefore, it is important to determine how service life under variable amplitude fatigue can be estimated from constant amplitude fat

  1. Aerodynamic design optimization of helicopter rotor blades including airfoil shape for hover performance

    Ngoc Anh Vu; Jae Woo Lee; Jung Il Shu

    2013-01-01

    This study proposes a process to obtain an optimal helicopter rotor blade shape for aerodynamic performance in hover flight.A new geometry representation algorithm which uses the class function/shape function transformation (CST) is employed to generate airfoil coordinates.With this approach,airfoil shape is considered in terms of design variables.The optimization process is constructed by integrating several programs developed by author.The design variables include twist,taper ratio,point of taper initiation,blade root chord,and coefficients of the airfoil distribution function.Aerodynamic constraints consist of limits on power available in hover and forward flight.The trim condition must be attainable.This paper considers rotor blade configuration for the hover flight condition only,so that the required power in hover is chosen as the objective function of the optimization problem.Sensitivity analysis of each design variable shows that airfoil shape has an important role in rotor performance.The optimum rotor blade reduces the required hover power by 7.4% and increases the figure of merit by 6.5%,which is a good improvement for rotor blade design.

  2. Design of a fibrous composite preform for wind turbine rotor blades

    Hansen, Jens Zangenberg; Brøndsted, Povl; Kofoed, M.

    2014-01-01

    The present work addresses the different factors and challenges one must cope with in the design process of a composite preform used for the load-carrying main laminate of a wind turbine rotor blade. The design process is split up into different key elements, each of which are presented and...

  3. Effects of rotating stall and surge on the first rotor blade row in a six stage industrial axial flow compressor

    Eisenberg, B.; Thomas, P.; Turanskyj, L.

    1995-12-31

    A six stage speed controlled research compressor representing the front section of an industrial axial flow compressor was fitted with a new wide chord controlled-diffusion-airfoil-bladed 1st stage rotor blade row. In order to check mechanical behaviour of this blade type when effected by rotating stall and surge the first stage blading was equipped with strain gauges. As the presence of rotating-stall changes also frequency spectrum of shaft vibration the output signals of three different types of transducers - i.e. strain gauge, dynamic wall pressure and shaft vibration - are compared. Rotating stall was detected by fast fourier transform (FFT) analysis of the pressure transducer`s output signal. In some cases a change of shaft vibration signals was observed. The compressor has a relatively small area of rotating stall which is located below 50% speed. Strain gauge measurements show a comapratively low stress level induced by rotating stall and surge in the first rotor blade row. Results of measurements taken during transient start-up and shut-down with different throttle valve positions behind the compressor are presented as well. (orig.) [Deutsch] Ein 6-stufiger drehzahlgeregelter Versuchskompressor, der dem vorderen Teil eines Industrie-Axialkompressors entspricht, wurde in der 1. Laufschaufelreihe mit einer neuen Breitschaufel mit `Controlled-diffusion`-Profilen versehen. Zur Ueberpruefung des mechanischen Verhaltens dieser neuen Beschaufelung im Kennfeld - insbesondere bei Auftreten von `Rotating-Stall` - wurden auf die Laufschaufeln Dehnungsmessstreifen appliziert. Da das Autreten von `Rotating-Stall` auch das Frequenzspektrum der Wellenschwingungen beeinflusst, wurden die Signale dreier verschiedener Aufnehmertypen - Dehnungsmessstreifen, dynamischer Wanddruck und Wellenschwingungen - verglichen. Das Auftreten von `Rotating-Stall` wurde ueber eine Frequenzanalyse des Ausgangssignals der dynamischen Wanddruckaufnehmer indiziert. In einigen Faellen wurde

  4. Active twist control methodology for vibration reduction of a helicopter with dissimilar rotor system

    In this work, an active vibration reduction of hingeless composite rotor blades with dissimilarity is investigated using the active twist concept and the optimal control theory. The induced shear strain on the actuation mechanism by the piezoelectric constant d15 from the PZN–8% PT-based single-crystal material is used to achieve more active twisting to suppress the extra vibrations. The optimal control algorithm is based on the minimization of an objective function comprised of quadratic functions of vibratory hub loads and voltage control harmonics. The blade-to-blade dissimilarity is modeled using the stiffness degradation of composite blades. The optimal controller is applied to various possible dissimilarities arising from different damage patterns of composite blades. The governing equations of motion are derived using Hamilton's principle. The effects of composite materials and smart actuators are incorporated into the comprehensive aeroelastic analysis system. Numerical results showing the impact of addressing the blade dissimilarities on hub vibrations and voltage inputs required to suppress the vibrations are demonstrated. It is observed that all vibratory shear forces are reduced considerably and the major harmonics of moments are reduced significantly. However, the controller needs further improvement to suppress 1/rev moment loads. A mechanism to achieve vibration reduction for the dissimilar rotor system has also been identified

  5. Simulation of unsteady flows through stator and rotor blades of a gas turbine using the Chimera method

    Nakamura, S.; Scott, J. N.

    1993-01-01

    A two-dimensional model to solve compressible Navier-Stokes equations for the flow through stator and rotor blades of a turbine is developed. The flow domains for the stator and rotor blades are coupled by the Chimera method that makes grid generation easy and enhances accuracy because the area of the grid that have high turning of grid lines or high skewness can be eliminated from the computational domain after the grids are generated. The results of flow computations show various important features of unsteady flows including the acoustic waves interacting with boundary layers, Karman vortex shedding from the trailing edge of the stator blades, pulsating incoming flow to a rotor blade from passing stator blades, and flow separation from both suction and pressure sides of the rotor blades.

  6. Wind turbine rotor blade monitoring using digital image correlation: a comparison to aeroelastic simulations of a multi-megawatt wind turbine

    Optical full-field measurement methods such as Digital Image Correlation (DIC) provide a new opportunity for measuring deformations and vibrations with high spatial and temporal resolution. However, application to full-scale wind turbines is not trivial. Elaborate preparation of the experiment is vital and sophisticated post processing of the DIC results essential. In the present study, a rotor blade of a 3.2 MW wind turbine is equipped with a random black-and-white dot pattern at four different radial positions. Two cameras are located in front of the wind turbine and the response of the rotor blade is monitored using DIC for different turbine operations. In addition, a Light Detection and Ranging (LiDAR) system is used in order to measure the wind conditions. Wind fields are created based on the LiDAR measurements and used to perform aeroelastic simulations of the wind turbine by means of advanced multibody codes. The results from the optical DIC system appear plausible when checked against common and expected results. In addition, the comparison of relative out-ofplane blade deflections shows good agreement between DIC results and aeroelastic simulations

  7. Rotating Shake Test and Modal Analysis of a Model Helicopter Rotor Blade

    Wilkie, W. Keats; Mirick, Paul H.; Langston, Chester W.

    1997-01-01

    Rotating blade frequencies for a model generic helicopter rotor blade mounted on an articulated hub were experimentally determined. Testing was conducted using the Aeroelastic Rotor Experimental System (ARES) testbed in the Helicopter Hover Facility (HBF) at Langley Research Center. The measured data were compared to pretest analytical predictions of the rotating blade frequencies made using the MSC/NASTRAN finite-element computer code. The MSC/NASTRAN solution sequences used to analyze the model were modified to account for differential stiffening effects caused by the centrifugal force acting on the blade and rotating system dynamic effects. The correlation of the MSC/NASTRAN-derived frequencies with the experimental data is, in general, very good although discrepancies in the blade torsional frequency trends and magnitudes were observed. The procedures necessary to perform a rotating system modal analysis of a helicopter rotor blade with MSC/NASTRAN are outlined, and complete sample data deck listings are provided.

  8. Aerodynamic analysis of potential use of flow control devices on helicopter rotor blades

    Tejero, F.; Doerffer, P.; Szulc, O.

    2014-08-01

    The interest in the application of flow control devices has been rising in the last years. Recently, several passive streamwise vortex generators have been analysed in a configuration of a curved wall nozzle within the framework of the UFAST project (Unsteady Effects of Shock Wave Induced Separation, 2005 - 2009). Experimental and numerical results proved that the technology is effective in delaying flow separation. The numerical investigation has been extended to helicopter rotor blades in hover and forward flight applying the FLOWer solver (RANS approach) implementing the chimera overlapping grids technique and high performance computing. CFD results for hover conditions confirm that the proposed passive control method reduces the flow separation increasing the thrust over power consumption. The paper presents the numerical validation for both states of flight and the possible implementation of RVGs on helicopter rotor blades.

  9. Aerodynamic analysis of potential use of flow control devices on helicopter rotor blades

    The interest in the application of flow control devices has been rising in the last years. Recently, several passive streamwise vortex generators have been analysed in a configuration of a curved wall nozzle within the framework of the UFAST project (Unsteady Effects of Shock Wave Induced Separation, 2005 – 2009). Experimental and numerical results proved that the technology is effective in delaying flow separation. The numerical investigation has been extended to helicopter rotor blades in hover and forward flight applying the FLOWer solver (RANS approach) implementing the chimera overlapping grids technique and high performance computing. CFD results for hover conditions confirm that the proposed passive control method reduces the flow separation increasing the thrust over power consumption. The paper presents the numerical validation for both states of flight and the possible implementation of RVGs on helicopter rotor blades.

  10. Shape Optimization of Rotor Blade for Pulp Pressure Screen Based on FLUENT

    Qu Qingwen

    2013-10-01

    Full Text Available The study got two modified blades by changing the structure and shape of the rotor blade of the pressure screen. Pulp flow field in the same condition is numerically simulated by the fluid dynamics software FLUENT. The pressure distribution is showed especially in the location of the sieve drum circle. The ideal blade structure is obtained by the pressure field compared with conventional blades. It has strong cleaning ability and not easy to blockage sieve drum. The shape of the rotor blade is optimized. The blade shape is analyzed to the influence law of energy consumption. It is proved that the new rotor has energy-saving advantages. It is significant to improve the performance of pulp screening equipment. The theoretical support for select of blade shape of bars is provided by analysis of flow field.

  11. Flow Modification over Rotor Blade with Suction Boundary Layer Control Technique

    Navneet Kumar

    2016-06-01

    Full Text Available The efficiency of transonic aircraft engines depend upon the performance of compressor rotor. To increase compressor rotors performance flow separation around rotor blades must be delayed and controlled. The aim was to control the flow separation of blades using suction boundary layer control method. Rotor blade has been modelled in designing software CATIA and then a suction surface has been created on blade and then import these geometries to ANSYS-CFX 14.5 for computational analysis of flow around blades. Suction slot has been applied at the trailing edge of suction surface and Shear stress transport model has been used for computational analysis. Two different suction mass flow rates 1 kg/s and 1.5 kg/s have been used here and boundary layer separation effects have been changed and this could be readily seen that the velocity vectors have reattached, preventing the boundary layer separation at the suction surface of the blade.

  12. Design of helicopter rotor blades for desired placement of natural frequencies

    Peters, D. A.; Ko, T.; Korn, A.; Rossow, M. P.

    1984-01-01

    The mass and stiffness distributions for helicopter rotor blades are to be tailored in such a way to give a predetermined placement of blade natural frequencies. This optimization problem is addressed in a methodical, step-by-step process in which each aspect of the optimization is studied in detail. Careful consideration is also given to the mathematical formulation of the problem and to the introduction of appropriate constraints.

  13. A new experimental method for determining local airloads on rotor blades in forward flight

    Berton, E.; Maresca, C.; Favier, D. [Aerodynamics and Biomechanics of Motion Laboratory, LABM, Parc Scientifique et technologique de Luminy, Case 918, 13288, Marseille Cedex 09 (France)

    2004-09-01

    This paper presents a new approach for determining local airloads on helicopter rotor blade sections in forward flight. The method is based on the momentum equation in which all the terms are expressed by means of the velocity field measured by a laser Doppler velocimeter. The relative magnitude of the different terms involved in the momentum and Bernoulli equations is estimated and the results are encouraging. (orig.)

  14. MEASUREMENTS OF PRESSURE DISTRIBUTIONS ON A ROTOR BLADE USING PSP TECHNIQUES

    Kidong Kim

    2011-12-01

    Full Text Available Surface pressure distributions on a rotating blade were measured by using pressure sensitive paint (PSP to understand aerodynamic characteristics of a rotor blade. The present study was conducted to investigate the PSP techniques for measuring the pressure distributions on a rotor blade. In order to perform the experiment, the PSP was required to response very fast due to rapid pressure fluctuations on a rotor blade. High energy excitation light source was also needed to acquire proper intensity images in a short excitation time. The techniques were based on a lifetime method. Qualitative pressure distributions on an upper surface of small scale rotor in hovering condition were measured as a preliminary experiment prior to forward flight conditions in the KARI low speed wind tunnel laboratory. From measured pressure distributions, striking pressure gradient was observed on an upper surface of rotor blade and the resulting pressure showed expected gradient depending on different collective pitch angles. ABSTRAK : Pengagihan tekanan permukaan ke atas berbilah putar disukat menggunakan cat sensitive tekanan (pressure sensitive paint (PSP untuk memahami sifat-sifat aerodinamik suatu berbilah putar. Kajian telah dijalankan untuk menyelidik teknik-teknik PSP dengan mengukur agihan tekanan ke atas suatu berbilah putar. Agar eksperimen dapat dijalankan dengan baik, PSP harus bertindak cepat kerana tekanan naik turun dengan pantas ke atas berbilah putar. Sumber cahaya ujaan tenaga tinggi diperlukan untuk mendapatkan imej keamatan wajar dalam jangka masa ujaan yang pendek. Teknik-teknik tersebut terhasil daripada kajian semasa hayat. Agihan tekanan kualitatif ke permukaan atas berskala kecil pemutar dalam keadaan mengapung diukur sebagai permulaan eksperimen, sebelum penerbangan kehadapan dalam makmal terowong angin laju rendah KARI. Daripada agihan tekanan yang disukat, kecerunan tekanan yang ketara diperolehi daripada permerhatian terhadap permukaan

  15. Foreign Object Damage to Fan Rotor Blades of Aeroengine Part Ⅱ: Numerical Simulation of Bird Impact

    Guan Yupu; Zhao Zhenhua; Chen Wei; Gao Deping

    2008-01-01

    Bird impact is one of the most dangerous threats to flight safety. The consequences of bird impact can be severe and, therefore, the aircraft components have to be certified for a proven level of bird impact resistance before being put into service. The fan rotor blades of aeroengine are the components being easily impacted by birds. It is necessary to ensure that the fan rotor blades should have adequate resistance against the bird impact, to reduce the flying accidents caused by bird impacts. Using the contacting-impacting algorithm, the numerical simulation is carried out to simulate bird impact. A three-blade computational model is set up for the fan rotor blade having shrouds. The transient response curves of the points corresponding to measured points in experiments, displacements and equivalent stresses on the blades are obtained during the simulation. From the comparison of the transient response curves obtained from numerical simulation with that obtained from experiments, it can be found that the variations in measured points and the corresponding points of simulation are basically the same. The deforming process, the maximum displacements and the maximum equivalent stresses on blades are analyzed. The numerical simulation verifies and complements the experiment results.

  16. An innovative medium speed wind turbine rotor blade design for low wind regime (electrical power generation)

    This paper describes the preliminary study of a small-scale wind turbine rotor blade (a low wind speed region turbine). A new wind turbine rotor blade (AE2 blade) for stand alone system has been conceptualized, designed, constructed and tested. The system is a reduced size prototype (half-scaled) to develop an efficient (adapted to Malaysian wind conditions)and cost effective wind energy conversion system (WECS) with local design and production technique. The blades were constructed from aluminium sheet with metal blending technique. The layout and design of rotor blade, its innovative features and test results are presented. Results from indoor test showed that the advantages of AE2 blade in low speed, with the potential of further improvements. The best rotor efficiency, CP attained with simple AE2 blades rotor (number of blade = 3) was 37.3% (Betz efficiency = 63%) at tip speed ratio (TSR) = 3.6. From the fabrication works and indoor testing, the AE2 blade rotor has demonstrated its structural integrity (ease of assembly and transportation), simplicity, acceptable performance and low noise level. (Author)

  17. Simultaneous BVI noise and vibration reduction in rotorcraft using actively-controlled flaps and including performance considerations

    Patt, Daniel A.

    This work presents the development and application of an active control approach for reduction of both vibration and noise induced by helicopter rotor blade vortex interaction (BVI). Control is implemented through single or dual actively controlled flaps (ACFs) on each blade. Low-speed helicopter flight is prone to severe BVI, resulting in elevated vibration and noise levels. Existing research has suggested that when some form of active control is used to reduce vibration, noise will increase and vice versa. The present research achieves simultaneous reduction of noise and vibration, and also investigates the physical sources of the observed reduction. The initial portion of this work focused on developing a tool for simulating helicopter noise and vibrations in the BVI flight regime. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades was developed and combined with an enhanced free-wake model and an acoustic prediction tool with provisions for blade flexibility. These elements were incorporated within an aeroelastic analysis featuring fully coupled flap-lag-torsional blade dynamics. Subsequently, control algorithms were developed that were effective for reducing noise and vibration even in the nonlinear BVI flight regime; saturation limits were incorporated constraining flap deflections to specified limits. The resulting simulation was also validated with a wide range of experimental data, achieving excellent correlation. Finally, a number of active control studies were performed. Multi-component vibration reductions of 40--80% could be achieved, while incurring a small noise penalty. Noise was reduced using an onboard feedback microphone; reductions of 4--10 dB on the advancing side were observed on a plane beneath the rotor when using dual flaps. Finally, simultaneous noise and vibration reduction was studied. A reduction of about 5 dB in noise on the advancing side combined with a 60% reduction in vibration was

  18. Fe Analysis of a Steam Turbine HP Rotor Blade Stage Concerning Material Effort, Dynamic Properties and Creep Damage Assessment

    Borkowski Paweł

    2016-03-01

    Full Text Available This paper is concerned with the 1st stage of HP rotor blade assembly steam turbine TK 120. The methodology was focused on the selection of mechanical properties and the way of the rotor disc modeling and estimating the degree of damage caused by creep. Then the dynamic interference between the frequencies of excitation and the natural frequencies was assessed. Static calculations were performed for the cyclic sectors consisting of the disc, disc blades, spacers and shrouding, including loads as temperature, mass forces from the angular velocity and the pressure on the blades. Then, the creep analysis using a Norton’s model and the modal analysis were performed. Static analysis gave information concerning the distributions of displacements, stress and strain components. In the creep analysis, the creep displacements and stress relaxation versus time were determined and the estimated degree of damage caused by creep was evaluated at each part of the rotor disc. In the modal analysis, the natural frequencies and modes of vibrations corresponding to the nodal diameters were found. The results of modal analysis were shown in the SAFE graph. Numerical calculations have shown that the rotor disc was a well-designed structure and did not reveal any dynamic interference.

  19. The Effect of Rotor Blade Speed to the Best Efficiency Point of Single Stage Axial Flow Compressor

    Sukri, Mohamad Firdaus; Wasbari, Faizil; Mat, Shafizal

    2010-06-01

    The best efficiency point is ideal operational point for any turbomachinery. Selections of turbomachines in industry such as pump, turbine, compressor, etc are basically based on their operating point. The best efficiency point is a point at the highest efficiency. Therefore, turbomachines with nearest operating point to best efficiency point will be chosen due to higher efficiency thus produce great reduction in cost saving. Different speed of rotor blade will cause effect to the best efficiency point, as well as different in rotor and stator blade angle. If angle of rotor and stator blade constant while speed of rotor blade increased, the net head produced by the compressor will also increased. Thus, it will increase the brake horse power and fluid horse power. Although the efficiency of the compressor increases if fluid horse power increased, the increasing in brake horse power will produce lower efficiency. In this paper, the effect of rotor blade speed on best efficiency point of an axial flow compressor will be investigated and discussed. Through this paper, the highest efficiency is only 73 %, achieved at rotor blade speed of 750 rpm with net head of 9.4 mmWG, and air volumetric flow rate of 0.56m3/s. For higher net head, the rotor blade speed must be increased, but the efficiency will decrease simultaneously. The type of compressor used in this research is single stage axial flow compressor; model Dixson FM36, manufactured by Dixson FA Engineering Sdn. Bhd.

  20. Advanced grid-stiffened composite shells for applications in heavy-lift helicopter rotor blade spars

    Narayanan Nampy, Sreenivas

    Modern rotor blades are constructed using composite materials to exploit their superior structural performance compared to metals. Helicopter rotor blade spars are conventionally designed as monocoque structures. Blades of the proposed Heavy Lift Helicopter are envisioned to be as heavy as 800 lbs when designed using the monocoque spar design. A new and innovative design is proposed to replace the conventional spar designs with light weight grid-stiffened composite shell. Composite stiffened shells have been known to provide excellent strength to weight ratio and damage tolerance with an excellent potential to reduce weight. Conventional stringer--rib stiffened construction is not suitable for rotor blade spars since they are limited in generating high torsion stiffness that is required for aeroelastic stability of the rotor. As a result, off-axis (helical) stiffeners must be provided. This is a new design space where innovative modeling techniques are needed. The structural behavior of grid-stiffened structures under axial, bending, and torsion loads, typically experienced by rotor blades need to be accurately predicted. The overall objective of the present research is to develop and integrate the necessary design analysis tools to conduct a feasibility study in employing grid-stiffened shells for heavy-lift rotor blade spars. Upon evaluating the limitations in state-of-the-art analytical models in predicting the axial, bending, and torsion stiffness coefficients of grid and grid-stiffened structures, a new analytical model was developed. The new analytical model based on the smeared stiffness approach was developed employing the stiffness matrices of the constituent members of the grid structure such as an arch, helical, or straight beam representing circumferential, helical, and longitudinal stiffeners. This analysis has the capability to model various stiffening configurations such as angle-grid, ortho-grid, and general-grid. Analyses were performed using an

  1. Thermographic inspection of wind turbine rotor blade segment utilizing natural conditions as excitation source, Part II: The effect of climatic conditions on thermographic inspections - A long term outdoor experiment

    Worzewski, Tamara; Krankenhagen, Rainer; Doroshtnasir, Manoucher

    2016-05-01

    The present study continues the work described in part I of this paper in evaluating a long-term-experiment, where a rotor blade segment of a wind turbine is exposed to the elements and thereby monitored with passive thermography. First, it is investigated whether subsurface features in rotor blades - mainly made of GFRP - can generally be detected with thermography from greater distances under favorable conditions. The suitability of the sun for acting as a heat source in applying active thermography has been tested in the previous study. In this study, the climatic influence on thermographic measurement is evaluated. It is demonstrated that there are favorable and unfavorable circumstances for imaging thermal contrasts which reflect inner structures and other subsurface features like potential defects. It turns out that solar radiation serves as a very effective heat source, but not at all times of day. Other environmental influences such as diurnal temperature variations also create temperature contrasts that permit conclusions on subsurface features. Particular scenarios are reconstructed with FEM-simulations in order to gain deeper insight into the driving mechanisms that produce the observed thermal contrasts. These investigations may help planning useful outdoor operations for inspecting rotor blades with thermography.

  2. Application of response surface techniques to helicopter rotor blade optimization procedure

    Henderson, Joseph Lynn; Walsh, Joanne L.; Young, Katherine C.

    1995-01-01

    In multidisciplinary optimization problems, response surface techniques can be used to replace the complex analyses that define the objective function and/or constraints with simple functions, typically polynomials. In this work a response surface is applied to the design optimization of a helicopter rotor blade. In previous work, this problem has been formulated with a multilevel approach. Here, the response surface takes advantage of this decomposition and is used to replace the lower level, a structural optimization of the blade. Problems that were encountered and important considerations in applying the response surface are discussed. Preliminary results are also presented that illustrate the benefits of using the response surface.

  3. Aerodynamic Data for Two Variants of Root Turbine Blade Sections for A 54" Turbine Rotor Blade

    Šimurda, David; Luxa, Martin; Šafařík, P.; Synáč, J.; Rudas, B.

    Düsseldorf: ASME, 2014, V02CT38A007-V02CT38A019. (2C). ISBN 978-0-7918-4562-2. [ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. Düsseldorf (DE), 16.06.2014-20.06.2014] R&D Projects: GA TA ČR(CZ) TA03020277; GA ČR(CZ) GAP101/10/1329 Institutional support: RVO:61388998 Keywords : steam turbine * rotor * blade cascade * root section Subject RIV: BK - Fluid Dynamics

  4. Vibrational optical activity

    Recent vibrational activity (VOA) research is discussed. The vibrational circular dichroism (VCD) experiments were carried out with a Fourier transform infrared spectrometer. One of the major anticipations from VOA spectroscopy is to be able to derive new pathways for determining the molecular structure. Shown is Fourier transform infrared absorption and VCD spectra of lyxopyranose in pyradine-d5 solvent. Raman optical activity measurements are discussed, and depolarized Raman and Raman optical activity spectra for (+)-alpha-pinene are presented. It was concluded that at present Raman optical activity can be measured in the entire vibrational spectral region, where as VCD has not been measured below 600 cm-1

  5. Wind-tunnel evaluation of an advanced main-rotor blade design for a utility-class helicopter

    Yeager, William T., Jr.; Mantay, Wayne R.; Wilbur, Matthew L.; Cramer, Robert G., Jr.; Singleton, Jeffrey D.

    1987-01-01

    An investigation was conducted in the Langley Transonic Dynamics Tunnel to evaluate differences between an existing utility-class main-rotor blade and an advanced-design main-rotor blade. The two rotor blade designs were compared with regard to rotor performance oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Tests were conducted in hover and over a range of simulated full-scale gross weights and density altitude conditions at advance ratios from 0.15 to 0.40. Results indicate that the advanced blade design offers performance improvements over the baseline blade in both hover and forward flight. Pitch-link oscillatory loads for the baseline rotor were more sensitive to the test conditions than those of the advanced rotor. The 4-per-rev vertical fixed-system load produced by the advanced blade was larger than that produced by the baseline blade at all test conditions.

  6. Classification of defects in honeycomb composite structure of helicopter rotor blades

    The use of non-destructive testing methods to qualify the state of rotor blades with respect to their expected flight hours, with the aim to extend their lifetime without any risk of breakdown, is an important financial demand. In order to detect the possible defects in the composite structure of Mi-8 and Mi-24 type helicopter rotor blades used by the Hungarian Army, we have performed combined neutron- and X-ray radiography measurements at the Budapest Research Reactor. Several types of defects were detected, analysed and typified. Among the most frequent and important defects observed were cavities, holes and or cracks in the sealing elements on the interface of the honeycomb structure and the section boarders. Inhomogeneities of the resin materials (resin-rich or starved areas) at the core-honeycomb surfaces proved to be an other important point. Defects were detected at the adhesive filling, and water percolation was visualized at the sealing interfaces of the honeycomb sections. Corrosion effects, and metal inclusions have also been detected

  7. Some issues on modeling atmospheric turbulence experienced by helicopter rotor blades

    Costello, Mark; Gaonkar, G. H.; Prasad, J. V. R.; Schrage, D. P.

    1992-01-01

    The atmospheric turbulence velocities seen by nonrotating aircraft components and rotating blades can be substantially different. The differences are due to the spatial motion of the rotor blades, which move fore and aft through the gust waves. Body-fixed atmospheric turbulence refers to the actual atmospheric turbulence experienced by a point fixed on a nonrotating aircraft component such as the aircraft's center of gravity or the rotor hub, while blade-fixed atmospheric turbulence refers to the atmospheric turbulence experienced by an element of the rotating rotor blade. An example is presented, which, though overly simplified, shows important differences between blade- and body-fixed rotorcraft atmospheric turbulence models. All of the information necessary to develop the dynamic equations describing the atmospheric turbulence velocity field experienced by an aircraft is contained in the atmospheric turbulence velocity correlation matrix. It is for this reason that a generalized formulation of the correlation matrix describing atmospheric turbulence that a rotating blade encounters is developed. From this correlation matrix, earlier treated cases restricted to a rotor flying straight and level directly into the mean wind can be recovered as special cases.

  8. Finite element simulation of core inspection in helicopter rotor blades using guided waves.

    Chakrapani, Sunil Kishore; Barnard, Daniel; Dayal, Vinay

    2015-09-01

    This paper extends the work presented earlier on inspection of helicopter rotor blades using guided Lamb modes by focusing on inspecting the spar-core bond. In particular, this research focuses on structures which employ high stiffness, high density core materials. Wave propagation in such structures deviate from the generic Lamb wave propagation in sandwich panels. To understand the various mode conversions, finite element models of a generalized helicopter rotor blade were created and subjected to transient analysis using a commercial finite element code; ANSYS. Numerical simulations showed that a Lamb wave excited in the spar section of the blade gets converted into Rayleigh wave which travels across the spar-core section and mode converts back into Lamb wave. Dispersion of Rayleigh waves in multi-layered half-space was also explored. Damage was modeled in the form of a notch in the core section to simulate a cracked core, and delamination was modeled between the spar and core material to simulate spar-core disbond. Mode conversions under these damaged conditions were examined numerically. The numerical models help in assessing the difficulty of using nondestructive evaluation for complex structures and also highlight the physics behind the mode conversions which occur at various discontinuities. PMID:26048172

  9. Panel/full-span free-wake coupled method for unsteady aerodynamics of helicopter rotor blade

    Tan Jianfeng; Wang Haowen

    2013-01-01

    A full-span free-wake method is coupled with an unsteady panel method to accurately predict the unsteady aerodynamics of helicopter rotor blades in hover and forward flight.The unsteady potential-based panel method is used to consider aerodynamics of finite thickness multi-bladed rotors,and the full-span free-wake method is applied to simulating dynamics of rotor wake.These methods are tightly coupled through trailing-edge Kutta condition and by converting doublet-wake panels to full-span vortex filaments.A velocity-field integration technique is also adopted to overcome singularity problem during the interaction between the rotor wake and blades.Helicopter rotors including Caradonna-Tung,UH-60A,and AH-1G rotors,are simulated in hover and forward flight to validate the accuracy of this approach.The predicted aerodynamic loads of rotor blades agree well with available measured data and computational fluid dynamics (CFD) results,and the unsteady dynamics of rotor wake is also well simulated.Compared to CFD,the present method obtains accurate results more efficiently and is suitable to rotorcraft aeroelastic analysis.

  10. Classification of defects in honeycomb composite structure of helicopter rotor blades

    Balasko, M. [KFKI Atomic Energy Research Institute, H-1525 Budapest, POB 49 (Hungary)]. E-mail: balasko@sunserv.kfki.hu; Svab, E. [Research Institute for Solid State Physics and Optics, H-1525 Budapest, POB 49 (Hungary); Molnar, Gy. [Aircraft Maintenance Branch of Hungarian Defence Forces, H-1885 Budapest, POB 25 (Hungary); Veres, I. [Aircraft Maintenance Branch of Hungarian Defence Forces, H-1885 Budapest, POB 25 (Hungary)

    2005-04-21

    The use of non-destructive testing methods to qualify the state of rotor blades with respect to their expected flight hours, with the aim to extend their lifetime without any risk of breakdown, is an important financial demand. In order to detect the possible defects in the composite structure of Mi-8 and Mi-24 type helicopter rotor blades used by the Hungarian Army, we have performed combined neutron- and X-ray radiography measurements at the Budapest Research Reactor. Several types of defects were detected, analysed and typified. Among the most frequent and important defects observed were cavities, holes and or cracks in the sealing elements on the interface of the honeycomb structure and the section boarders. Inhomogeneities of the resin materials (resin-rich or starved areas) at the core-honeycomb surfaces proved to be an other important point. Defects were detected at the adhesive filling, and water percolation was visualized at the sealing interfaces of the honeycomb sections. Corrosion effects, and metal inclusions have also been detected.

  11. An aeroelastic analysis of helicopter rotor blades incorporating piezoelectric fiber composite twist actuation

    Wilkie, W. Keats; Park, K. C.

    1996-01-01

    A simple aeroelastic analysis of a helicopter rotor blade incorporating embedded piezoelectric fiber composite, interdigitated electrode blade twist actuators is described. The analysis consist of a linear torsion and flapwise bending model coupled with a nonlinear ONERA based unsteady aerodynamics model. A modified Galerkin procedure is performed upon the rotor blade partial differential equations of motion to develop a system of ordinary differential equations suitable for numerical integration. The twist actuation responses for three conceptual full-scale blade designs with realistic constraints on blade mass are numerically evaluated using the analysis. Numerical results indicate that useful amplitudes of nonresonant elastic twist, on the order of one to two degrees, are achievable under one-g hovering flight conditions for interdigitated electrode poling configurations. Twist actuation for the interdigitated electrode blades is also compared with the twist actuation of a conventionally poled piezoelectric fiber composite blade. Elastic twist produced using the interdigitated electrode actuators was found to be four to five times larger than that obtained with the conventionally poled actuators.

  12. Aeroelastic Analysis of Helicopter Rotor Blades Incorporating Anisotropic Piezoelectric Twist Actuation

    Wilkie, W. Keats; Belvin, W. Keith; Park, K. C.

    1996-01-01

    A simple aeroelastic analysis of a helicopter rotor blade incorporating embedded piezoelectric fiber composite, interdigitated electrode blade twist actuators is described. The analysis consists of a linear torsion and flapwise bending model coupled with a nonlinear ONERA based unsteady aerodynamics model. A modified Galerkin procedure is performed upon the rotor blade partial differential equations of motion to develop a system of ordinary differential equations suitable for dynamics simulation using numerical integration. The twist actuation responses for three conceptual fullscale blade designs with realistic constraints on blade mass are numerically evaluated using the analysis. Numerical results indicate that useful amplitudes of nonresonant elastic twist, on the order of one to two degrees, are achievable under one-g hovering flight conditions for interdigitated electrode poling configurations. Twist actuation for the interdigitated electrode blades is also compared with the twist actuation of a conventionally poled piezoelectric fiber composite blade. Elastic twist produced using the interdigitated electrode actuators was found to be four to five times larger than that obtained with the conventionally poled actuators.

  13. Aeroelastic response and stability of tiltrotors with elastically-coupled composite rotor blades. Ph.D. Thesis

    Nixon, Mark W.

    1993-01-01

    There is a potential for improving the performance and aeroelastic stability of tiltrotors through the use of elastically-coupled composite rotor blades. To study the characteristics of tiltrotors with these types of rotor blades it is necessary to formulate a new analysis which has the capabilities of modeling both a tiltrotor configuration and an anisotropic rotor blade. Background for these formulations is established in two preliminary investigations. In the first, the influence of several system design parameters on tiltrotor aeroelastic stability is examined for the high-speed axial flight mode using a newly-developed rigid-blade analysis with an elastic wing finite element model. The second preliminary investigation addresses the accuracy of using a one-dimensional beam analysis to predict frequencies of elastically-coupled highly-twisted rotor blades. Important aspects of the new aeroelastic formulations are the inclusion of a large steady pylon angle which controls tilt of the rotor system with respect to the airflow, the inclusion of elastic pitch-lag coupling terms related to rotor precone, the inclusion of hub-related degrees of freedom which enable modeling of a gimballed rotor system and engine drive-train dynamics, and additional elastic coupling terms which enable modeling of the anisotropic features for both the rotor blades and the tiltrotor wing. Accuracy of the new tiltrotor analysis is demonstrated by a comparison of the results produced for a baseline case with analytical and experimental results reported in the open literature. Two investigations of elastically tailored blades on a baseline tiltrotor are then conducted. One investigation shows that elastic bending-twist coupling of the rotor blade is a very effective means for increasing the flutter velocity of a tiltrotor, and the magnitude of coupling required does not have an adverse effect on performance or blade loads. The second investigation shows that passive blade twist control via

  14. Design and optimization for strength and integrity of tidal turbine rotor blades

    Tidal turbine rotor blade fractures and failures have resulted in substantial damage and hence cost of repair and recovery. The present work presents a rotor blade design and optimization method to address the blade structural strength design problem. The generic procedure is applicable to both turbine rotors and propellers. The optimization method seeks an optimum blade thickness distribution across the span with a prescribed constant safety factor for all the blade sections. This optimization procedure serves two purposes: while maintaining the required structural strength and integrity for an ultimate inflow speed, it aims to reduce the material to a minimum and to maintain power generation efficiency or improve the hydrodynamic efficiency. The value of the chosen minimum safety factor depends on the actual working conditions of the turbine in which the sectional peak loading and frequency are used: the harsher the environment, the larger the required safety factor. An engineering software tool with both hydrodynamic and structural capabilities was required to predict the instantaneous loading acting on all the blade sections, as well as the strength of a local blade section with a given blade geometry and chosen material. A time-domain, 3D unsteady panel method was then implemented based on a marine propeller software tool and used to perform the optimization. A 3-blade 20-m tidal turbine that was prototyped in parallel with the current work for the Bay of Fundy was used as an example for optimization. The optimum thickness distribution for a required safety factor at the ultimate possible inflow speed resulted in 37.6% saving in blade material. The blade thickness and distribution as a function of a maximum inflow speed of 6 m/s is also presented. The blade material used in the example was taken as nickel–aluminium–bronze (NAB) but the procedure was developed to be applicable to propeller or turbine blades of basically any material. -- Highlights: ► A

  15. Extracting radar micro-Doppler signatures of helicopter rotating rotor blades using K-band radars

    Chen, Rachel; Liu, Baokun

    2014-06-01

    Helicopter identification has been an attractive topic. In this paper, we applied radar micro-Doppler signatures to identify helicopter. For identifying the type of a helicopter, besides its shape and size, the number of blades, the length of the blade, and the rotation rate of the rotor are important features, which can be estimated from radar micro-Doppler signatures of the helicopter's rotating rotor blades. In our study, K-band CW/FMCW radars are used for collecting returned signals from helicopters. By analyzing radar micro-Doppler signatures, we can estimate the number of blades, the length of the blade, the angular rotation rate of the rotating blade, and other necessary parameters for identifying the type of a helicopter.

  16. Integrated aerodynamic/dynamic/structural optimization of helicopter rotor blades using multilevel decomposition

    Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.

    1995-01-01

    This paper describes an integrated aerodynamic/dynamic/structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general-purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of global quantities (stiffness, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic designs are performed at a global level and the structural design is carried out at a detailed level with considerable dialog and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several examples.

  17. Inspection of spar-core bond in helicopter rotor blades using finite element analysis

    Chakrapani, Sunil Kishore; Barnard, Daniel J.; Dayal, Vinay

    2015-03-01

    This work focuses on inspection of spar-core bond of a helicopter rotor blade using finite element analysis. Structures which have high density, high stiffness cores can be very difficult to inspect due to various mode conversions. FEM was used to capture these mode conversions effectively. The structure consists of a thin spar section followed by a spar-core half space and another thin spar section. A Lamb wave excited in the spar section can mode convert into a Rayleigh wave in the spar-core section due to the coupling of the core material. This in turn mode converts back into a Lamb wave upon interacting with the next spar section. This work focuses solely on capturing the mode conversions between Rayleigh and Lamb modes at different discontinuities in the geometry.

  18. Wind energy conversion. Volume X. Aeroelastic stability of wind turbine rotor blades

    Wendell, J.

    1978-09-01

    The nonlinear equations of motion of a general wind turbine rotor blade are derived from first principles. The twisted, tapered blade may be preconed out of the plane of rotation, and its root may be offset from the axis of rotation by a small amount. The aerodynamic center, center of mass, shear center, and area centroid are distinct in this derivation. The equations are applicable to studies of forced response or of aeroelastic flutter, however, neither gravity forcing, nor wind shear and gust forcing are included. The equations derived are applied to study the aeroelastic stability of the NASA-ERDA 100 kW wind turbine, and solved using the Galerkin method. The numerical results are used in conjunction with a mathematical comparison to prove the validity of an equivalent hinge model developed by the Wind Energy Conversion Project at the Massachusetts Institute of Technology.

  19. Multilevel decomposition approach to integrated aerodynamic/dynamic/structural optimization of helicopter rotor blades

    Walsh, Joanne L.; Young, Katherine C.; Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.

    1994-01-01

    This paper describes an integrated aerodynamic, dynamic, and structural (IADS) optimization procedure for helicopter rotor blades. The procedure combines performance, dynamics, and structural analyses with a general purpose optimizer using multilevel decomposition techniques. At the upper level, the structure is defined in terms of local quantities (stiffnesses, mass, and average strains). At the lower level, the structure is defined in terms of local quantities (detailed dimensions of the blade structure and stresses). The IADS procedure provides an optimization technique that is compatible with industrial design practices in which the aerodynamic and dynamic design is performed at a global level and the structural design is carried out at a detailed level with considerable dialogue and compromise among the aerodynamic, dynamic, and structural groups. The IADS procedure is demonstrated for several cases.

  20. A practical approach to fracture analysis at the trailing edge of wind turbine rotor blades

    Eder, Martin Alexander; Bitsche, Robert; Nielsen, Magda;

    2014-01-01

    Wind turbine rotor blades are commonly manufactured from composite materials by a moulding process. Typically, the wind turbine blade is produced in two halves, which are eventually adhesively joined along their edges. Investigations of operating wind turbine blades show that debonding of the...... virtual crack closure technique (VCCT) is proposed, which can be used to identify critical areas in the adhesive joint of a trailing edge. The paper gives an overview of methods applicable for fracture cases comprising non-parallel crack faces in the realm of linear fracture mechanics. Furthermore, the...... VCCT is discussed in detail and validated against numerical analyses in 2D and 3D. Finally, the SERR of a typical blade section subjected to various loading conditions is investigated and assessed in order to identify potential design drivers for trailing edge details. Analysis of the blade section...

  1. Mach number scaling of helicopter rotor blade/vortex interaction noise

    Leighton, Kenneth P.; Harris, Wesley L.

    1985-01-01

    A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.

  2. Structural optimization of wind turbine rotor blades by multilevel sectional/multibody/3D-FEM analysis

    Bottasso, C. L.; Campagnolo, F.; Croce, A.;

    2014-01-01

    constraints. In addition, a buckling analysis is performed at the fine description level, which in turn affects the nonstructural blade mass. The updated constraint bounds and mass make their effects felt at the next coarse-level constrained design optimization, thereby closing the loop between the coarse and......The present work describes a method for the structural optimization of wind turbine rotor blades for given prescribed aerodynamic shape. The proposed approach operates at various description levels producing cost-minimizing solutions that satisfy desired design constraints at the finest modeling...... fine description levels. The multilevel optimization procedure is implemented in a computer program and it is demonstrated on the design of a multi-MW horizontal axis wind turbine rotor blade. © 2013 Springer Science+Business Media Dordrecht....

  3. Structural Optimization of Wind Turbine Rotor Blades by Multi-Level Sectional/Multibody/3DFEM Analysis

    Bottasso, C. L.; Campagnolo, F.; Croce, A.;

    constraints. In addition, a buckling analysis is performed at the fine description level, which in turn affects the non-structural blade mass. The updated constraint bounds and mass make their effects felt at the next coarse-level constrained design optimization, thereby closing the loop between the coarse......The present work describes a method for the structural optimization of wind turbine rotor blades for given prescribed aerodynamic shape. The proposed approach operates at various description levels producing cost-minimizing solutions that satisfy desired design constraints at the finest modeling...... and fine description levels. The multi-level optimization procedure is implemented in a computer program and it is demonstrated on the design of a multi-MW horizontal axis wind turbine rotor blade....

  4. Aerodynamics at off Design Performance of Root Section of Rotor Blade Last Stage of Large Output Steam Turbine

    Luxa, Martin; Synáč, J.; Šafařík, P.; Šimurda, D.

    Plzeň: klub ASI-TURBOSTROJE Plzeň, 2007, s. 1-8. [Parní turbíny a jiné turbostroje 2007. Plzeň (CZ), 06.09.2007-07.09.2007] R&D Projects: GA ČR(CZ) GA101/05/2536 Institutional research plan: CEZ:AV0Z20760514 Keywords : steam turbine * aerodynamics * rotor blade Subject RIV: BK - Fluid Dynamics

  5. An experimental study of static and oscillating rotor blade sections in reverse flow

    Lind, Andrew Hume

    The rotorcraft community has a growing interest in the development of high-speed helicopters to replace outdated fleets. One barrier to the design of such helicopters is the lack of understanding of the aerodynamic behavior of retreating rotor blades in the reverse flow region. This work considers two fundamental models of this complex unsteady flow regime: static and oscillating (i.e., pitching) airfoils in reverse flow. Wind tunnel tests have been performed at the University of Maryland (UMD) and the United States Naval Academy (USNA). Four rotor blade sections are considered: two featuring a sharp geometric trailing edge (NACA 0012 and NACA 0024) and two featuring a blunt geometric trailing edge (ellipse and cambered ellipse). Static airfoil experiments were performed at angles of attack through 180 deg and Reynolds numbers up to one million, representative of the conditions found in the reverse flow region of a full-scale high-speed helicopter. Time-resolved velocity field measurements were used to identify three unsteady flow regimes: slender body vortex shedding, turbulent wake, and deep stall vortex shedding. Unsteady airloads were measured in these three regimes using unsteady pressure transducers. The magnitude of the unsteady airloads is high in the turbulent wake regime when the separated shear layer is close to the airfoil surface and in deep stall due to periodic vortex-induced flow. Oscillating airfoil experiments were performed on a NACA 0012 and cambered ellipse to investigate reverse flow dynamic stall characteristics by modeling cyclic pitching kinematics. The parameter space spanned three Reynolds numbers (165,000; 330,000; and 500,000), five reduced frequencies between 0.100 and 0.511, three mean pitch angles (5,10, and 15 deg), and two pitch amplitudes (5 deg and 10 deg). The sharp aerodynamic leading edge of the NACA 0012 airfoil forces flow separation resulting in deep dynamic stall. The number of associated vortex structures depends strongly

  6. Modal Vibration Control in Periodic Time-Varying Structures with Focus on Rotor Blade Systems

    Christensen, Rene Hardam; Santos, Ilmar

    2004-01-01

    overcome. Among others it is necessary, that the control scheme is capable to cope with non-linear time-varying dynamical system behaviour. However, rotating at constant speed the mathematical model becomes periodic time-variant. In this framework the present paper gives a contribution to design procedures...... results are provided to demonstrate the applicability and effectiveness of the technique. The results obtained shows that the control design technique is capable to cope with the time periodicity of this class of systems....

  7. Modal Vibration Control in Periodic Time-Varying Structures with Focus on Rotor-Blade Systems

    Christensen, Rene Hardam; Santos, Ilmar

    2003-01-01

    overcome. Among others it is necessary, that the control scheme is capable to cope with non-linear time-varying dynamical system behaviour. However, rotating at constant speed the mathematical model becomes periodic time-variant. In this framework the present paper gives a contribution to design procedures...... results are provided to demonstrate the applicability and effectiveness of the technique. The results obtained shows that the control design technique is capable to cope with the time periodicity of this class of systems....

  8. Design Framework for Vibration Monitoring Systems for Helicopter Rotor Blade Monitoring Using Wireless Sensor Networks

    Sanchez Ramirez, Andrea; Loendersloot, Richard; Jauregui Becker, Juan Manuel; Tinga, Tiedo; Chang, F.-K

    2013-01-01

    The pursue of methods for supporting Structural Health Monitoring (SHM) has been an important driver for the technological innovation in several engineering fields such as wireless communication, sensing and power harvesting. However, despite of the innovative and scientific value of these advances, the adoption of SHM and associated technologies by industry has not occurred at the expected pace. One of the possible reasons for this is the lack of a systematic design process for condition mon...

  9. Helicopter Rotor Blade Computation in Unsteady Flows Using Moving Overset Grids

    Ahmad, Jasim; Duque, Earl P. N.

    1996-01-01

    An overset grid thin-layer Navier-Stokes code has been extended to include dynamic motion of helicopter rotor blades through relative grid motion. The unsteady flowfield and airloads on an AH-IG rotor in forward flight were computed to verify the methodology and to demonstrate the method's potential usefulness towards comprehensive helicopter codes. In addition, the method uses the blade's first harmonics measured in the flight test to prescribe the blade motion. The solution was impulsively started and became periodic in less than three rotor revolutions. Detailed unsteady numerical flow visualization techniques were applied to the entire unsteady data set of five rotor revolutions and exhibited flowfield features such as blade vortex interaction and wake roll-up. The unsteady blade loads and surface pressures compare well against those from flight measurements. Details of the method, a discussion of the resulting predicted flowfield, and requirements for future work are presented. Overall, given the proper blade dynamics, this method can compute the unsteady flowfield of a general helicopter rotor in forward flight.

  10. Design, development, and hover testing of a helicopter rotor blade chord extension morphing system

    Gandhi, Farhan; Hayden, Eric

    2015-03-01

    A rotor blade chord extension system was designed, fabricated and hover tested, using electromechanical and pneumatic actuation. A 1.5 in actuator stroke output in the spanwise direction was converted into chordwise motion of a trailing-edge plate (TEP), via a rigid link. On the hover stand, with a 20 V dc input, the electromechanical actuator was shown to fully extend and retract the plate at rotational speeds up to 385 RPM (which put the system at a centrifugal loading of 209.5 g, or 47.2% of that on a Black Hawk helicopter at 73% span). The configuration was changed to reduce the actuator force requirement for the pneumatic actuator. The rotor test facility allowed a maximum of 105 psi pressure input through the rotary union (significantly lower than the rating of the actuator). At these moderate pressure inputs, full TEP deployment was observed at 315 RPM (140.2 g, or 31.6% of that on a Black Hawk helicopter at 73% span). The model prediction of TEP displacement versus pressure showed good correlation with test results.

  11. Minimum weight design of rectangular and tapered helicopter rotor blades with frequency constraints

    Chattopadhyay, Aditi; Walsh, Joanne L.

    1988-01-01

    The minimum weight design of a helicopter rotor blade subject to constraints on coupled flap-lag natural frequencies has been studied. A constraint has also been imposed on the minimum value of the autorotational inertia of the blade in order to ensure that it has sufficient inertia to autorotate in the case of engine failure. The program CAMRAD is used for the blade modal analysis and CONMIN is used for the optimization. In addition, a linear approximation analysis involving Taylor series expansion has been used to reduce the analysis effort. The procedure contains a sensitivity analysis which consists of analytical derivatives of the objective function and the autorotational inertia constraint and central finite difference derivatives of the frequency constraints. Optimum designs have been obtained for both rectangular and tapered blades. Design variables include taper ratio, segment weights, and box beam dimensions. It is shown that even when starting with an acceptable baseline design, a significant amount of weight reduction is possible while satisfying all the constraints for both rectangular and tapered blades.

  12. Control of LP Turbine Rotor Blade Underloading Using Stator Blade Compound Lean at Root

    PiotrLampart

    2000-01-01

    Due to a large gradient of reaction,LP rotor blades remain underloaded at the root over some range of volumetric flow rates.An interesting design to control the flow through the root passage of the overloaded stator and underloaded moving blade row is compound lean at the root of stator blades.The paper describes results of numerical investigations from a 3D NS solver FlowER conducted for several configurations of stator blade compund lean.The computations are carried out for a wide range of volumetric flow rates.accounting for the nominal operating regime as well as low and high load.It is found that compund lean induces additional blade force.streamwise curature and redistribution of flow parameters in the stage,including pressure and mass flow rate spanwise that can improve the flow conditions in both the stator and the rotor.The obtained efficiency improvements depend greatly on the flow regime,with the highest gains in the region of low load.

  13. OPTIMIZING THE SHAPE OF ROTOR BLADES FOR MAXIMUM POWER EXTRACTION IN MARINE CURRENT TURBINES

    J.A. Esfahani

    2012-12-01

    Full Text Available In this paper the shape of rotor blades in Marine Current Turbines (MCTs are investigated. The evaluation of hydrodynamic loads on blades is performed based on the Blade Element Momentum (BEM theory. The shape of blades is optimized according to the main parameters in the configuration and operation of these devices. The optimization is conducted based on the ability of the blades to harness the maximum energy during operating. The main parameters investigated are the tip speed ratio and angle of attack. Furthermore, the influence of these parameters on the maximum energy extraction from fluid flow over a hydrofoil is evaluated. It is shown that the effect of the angle of attack on power extraction is greater than that of the tip speed ratio, while both are found to be significant. Additionally, the proper angle of attack is the angle at which the lift to drag ratio is at its maximum value. However, if a proper angle of attack is chosen, the variations in power coefficient would not be effectively changed with small variations in the tip speed ratio.

  14. A preliminary investigation of finite-element modeling for composite rotor blades

    Lake, Renee C.; Nixon, Mark W.

    1988-01-01

    The results from an initial phase of an in-house study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of elastic couplings are presented. Large degree of freedom shell finite element models of an extension twist coupled composite tube were developed and analyzed using MSC/NASTRAN. An analysis employing a simplified beam finite element representation of the specimen with the equivalent engineering stiffness was additionally performed. Results from the shell finite element normal modes and frequency analysis were compared to those obtained experimentally, showing an agreement within 13 percent. There was appreciable degradation in the frequency prediction for the torsional mode, which is elastically coupled. This was due to the absence of off-diagonal coupling terms in the formulation of the equivalent engineering stiffness. Parametric studies of frequency variation due to small changes in ply orientation angle and ply thickness were also performed. Results showed linear frequency variations less than 2 percent per 1 degree variation in the ply orientation angle, and 1 percent per 0.0001 inch variation in the ply thickness.

  15. Effects of Unsteadiness Due to Wake Passing on Rotor Blade Heat Transfer

    Ameri, Ali A.; Rigby, David L.; Heidmann, James; Steinthorsson, Erlendur; Fabian, John C.

    2007-01-01

    14. ABSTRACT In a gas turbine engine, the turbine rotor blades are buffeted by the wakes of the vanes located upstream. There is a transient effect from the passing of wakes on the blade heat transfer. This transient effect has been computed for a representative rotor by introducing a wake upstream via an unsteady inlet flow boundary condition, or "gust" condition. Two cases of turbulent flow and laminar flow with Reynolds numbers of 385,000 and 385 respectively were considered. For the turbulent flow case a quasi-steady calculation was also performed. The variation in the unsteady heat transfer coefficient was found to be as high as 120 percent of the mean. For the turbulent flow case a quasisteady calculation was also performed. The time mean of the unsteady heat transfer, the mean of the quasi-steady variations and the steady results agree reasonably well on all blade locations except for the turbulent results which differ near the leading edge. The quasi-steady heat transfer results do not agree with the instantaneous unsteady results, although the time-mean values are similar.

  16. An analysis of rotor blade twist variables associated with different Euler sequences and pretwist treatments

    Alkire, K.

    1984-01-01

    A nonlinear analysis which is necessary to adequately model elastic helicopter rotor blades experiencing moderately large deformations was examined. The analysis must be based on an appropriate description of the blade's deformation geometry including elastic bending and twist. Built-in pretwist angles complicate the deformation process ant its definition. Relationships between the twist variables associated with different rotation sequences and corresponding forms of the transformation matrix are lasted. Relationships between the twist variables associated with first, the pretwist combined with the deformation twist are included. Many of the corresponding forms of the transformation matrix for the two cases are listed. It is shown that twist variables connected with the combined twist treatment are related to those where the pretwist is applied initially. A method to determine the relationships and some results are outlined. A procedure to evaluate the transformation matrix that eliminates the Eulerlike sequence altogether is demonstrated. The resulting form of the transformation matrix is unaffected by rotation sequence or pretwist treatment.

  17. Design of rotor blade for vertical axis wind turbine using double aerofoil

    Chougule, P.D.; Ratkovich, N.; Kirkegaard, P.H.; Nielsen, Soeren R.K. [Aalborg Univ.. Dept. of Civil Engineering, Aalborg (Denmark)

    2012-07-01

    Nowadays, small vertical axis wind turbines are receiving more attention compared to horizontal wind turbines due to their suitability in urban use,because they generate less noise, have bird free turbines and lower cost. There are few vertical axis wind turbines design with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has been made to utilize high lift technology in practice for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double aerofoil elements mainly used in aeroplane wing design. In this current work, two aerofoils are used to design a rotor blade for a vertical axis wind turbine to improve the power efficiency on the rotor. Double aerofoil blade design consists of a main aerofoil and a slat aerofoil. The parameters related to position and orientation of the slat aerofoil with respect to the main aerofoil defines the high lift. Orientation of slat aerofoil is a parameter of investigation in this paper. Computational fluid dynamics (CFD) have been used to obtain the aerodynamic characteristics of double aerofoil. The CFD simulations were carried out using Star CCM+ v7.04 (CD-adapco, UK) software. Aerofoils used in this work are selected from standard aerofoil shapes. (Author)

  18. Improved Active Vibration Isolation Systems

    2007-01-01

    The control force, feedback gain, and actuator stroke of several active vibration isolation systems were analyzed based on a single-layer active vibration isolation system. The analysis shows that the feedback gain and actuator stroke cannot be selected independently and the active isolation system design must make a compromise between the feedback gain and actuator stroke. The performance of active isolation systems can be improved by the joint vibration reduction using an active vibration isolation system with an adaptive dynamic vibration absorber. The results show that the joint vibration reduction method can successfully avoid the compromise between the feedback gain and actuator stroke. The control force and the object vibration amplitude are also greatly reduced.

  19. Unified continuum damage model for matrix cracking in composite rotor blades

    This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load

  20. Application of Out-of-Plane Warping to Control Rotor Blade Twist

    VanWeddingen, Yannick; Bauchau, Olivier; Kottapalli, Sesi; Ozbay, Serkan; Mehrotra, Yogesh

    2012-01-01

    The goal of this ongoing study is to develop and demonstrate the feasibility of a blade actuation system to dynamically change the twist, and/or the camber, of an airfoil section and, consequently, alter the in-flight aerodynamic loading on the blade for efficient flight control. The required analytical and finite element tools are under development to enable an accurate and comprehensive aeroelastic assessment of the current Full-Blade Warping and 3D Warping Actuated Trailing Edge Flap concepts. The feasibility of the current concepts for swashplateless rotors and higher harmonic blade control is also being investigated. In particular, the aim is to complete the following objectives, some of which have been completed (as noted below) and others that are currently ongoing: i) Develop a Vlasov finite element model and validate against the ABAQUS shell models (completed). ii) Implement the 3D warping actuation concept within the comprehensive analysis code DYMORE. iii) Perform preliminary aeroelastic simulations of blades using DYMORE with 3D warping actuation: a) Investigate the blade behavior under 1 per/rev actuation. Determine whether sufficient twist can be generated and sustained to achieve primary blade control. b) Investigate the behavior of a trailing edge flap configuration under higher harmonic excitations. Determine how much twist can be obtained at the harmonics 2-5 per/rev. iv) Determine actuator specifications such as the power required, load and displacements, and identify the stress and strain distributions in the actuated blades. In general, the completion of Item ii) above will give an additional research capability in rotorcraft dynamics analyses, i.e., the capability to calculate the rotor blade twist due to warping, something that is not currently available in any of the existing comprehensive rotorcraft analyses.

  1. Unified continuum damage model for matrix cracking in composite rotor blades

    Pollayi, Hemaraju; Harursampath, Dineshkumar [Nonlinear Multifunctional Composites - Analysis and Design Lab (NMCAD Lab) Department of Aerospace Engineering Indian Institute of Science Bangalore - 560012, Karnataka (India)

    2015-03-10

    This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load.

  2. The Seventh International Conference on Vibration Problems ICOVP 2005

    İnan, Esin; ICOVP-2005

    2007-01-01

    This volume presents the Proceedings of the Seventh International Conference on Vibration Problems, held in Istanbul, Turkey, 05-09 September 2005. As with the earlier conferences in the ICOVP series, the purpose of ICOVP-2005 was to bring together scientists with different backgrounds, actively working on vibration-related problems of engineering both in theoretical and applied fields. The main objective did not lie, however, in reporting specific results as such, but rather in joining/exchanging different languages, questions and methods developed in the respective disciplines, and to thus stimulate a broad interdisciplinary research. The topics, indeed, vary from the effect of ground motion on the stochastic response of suspension bridges to coupling effects between different vibrations in rotor-blade systems. All lectures delivered at the Conference are recorded in their full text. Audience: Scientists, researchers and graduate students in physics and engineering

  3. Inspection of helicopter rotor blades with the help of guided waves and "turning modes": Experimental and finite element analysis

    Barnard, Daniel; Chakrapani, Sunil Kishore; Dayal, Vinay

    2013-01-01

    Modern helicopter rotor blades constructed of composite materials offer significant inspection challenges, particularly at inner structures, where geometry and differing material properties and anisotropy make placement of the probing energy difficult. This paper presents an application of Lamb waves to these structures, where mode conversion occurs at internal geometric discontinuities. These additional modes were found to successfully propagate to the targeted regions inside the rotor and back out, allowing evaluation of the structure. A finite element model was developed to simulate wave propagation and mode conversion in the structure and aid in identifying the signals received in the laboratory experiment. A good correlation between numerical and experimental results was observed.

  4. Data Summary Report for the Open Rotor Propulsion Rig Equipped With F31/A31 Rotor Blades

    Stephens, David

    2014-01-01

    An extensive wind tunnel test campaign was undertaken to quantify the performance and acoustics of a counter-rotating open rotor system. The present document summarizes the portion of this test performed with the so-called Historical Baseline rotor blades, designated F31A31. It includes performance and acoustic data acquired at Mach numbers from take-off to cruise. It also includes the effect of propulsor angle of attack as well as an upstream pylon. This report is accompanied by an electronic data set including relevant acoustic and performance measurements for all of the F31A31 data.

  5. BVI induced vibration and noise alleviation by active and passive approaches

    Liu, Li

    This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

  6. Effects of Mie tip-vane on pressure distribution of rotor blade and power augmentation of horizontal axis wind turbine; Yokutan shoyoku Mie ben ni yoru suiheijiku fusha yokumenjo no atsuryoku bunpu no kaizen to seino kojo tono kankei

    Shimizu, Y.; Maeda, T.; Kamada, Y. [Mie Univ., Mie (Japan); Seto, H. [Mitsubishi Motors Corp., Tokyo (Japan)

    2000-04-01

    By recent developments of exclusive rotor blade, the efficiency of wind turbine is improved substantially. By measuring pressure on rotor blades of horizontal axis wind turbines rotating in wind tunnels, this report clarified relation between improvement of pressure distribution on main rotor blades by Mie vane and upgrade of wind turbine performance. The results under mentioned have been got by measuring pressure distribution on rotor blades, visualization by tuft, and measuring resistance of Mie vane. (1) The difference of pressure between suction surface and pressure surface on the end of rotor blade increase, and output power of wind turbine improves. (2) Vortex of blade end is inhibited by Mie vane. (3) The reason of reduction on wind turbine performance with Mie vane in aria of high rotating speed ratio is the increase of Mie vane flow resistance.(NEDO)

  7. Acoustic emission analysis in overall fatigue testing of a wind rotor blade; Schallemissionsanalyse beim Gesamtermuedungstest eines Windkraftrotorblattes

    Schulze, Eberhard; Frankenstein, Bernd; Schubert, Lars [Fraunhofer-Instiut fuer Zerstoerungsfreie Pruefverfahren (IZFP), Dresden (Germany)

    2009-07-01

    The Fraunhofer Institut fuer zerstoerungsfreie Pruefverfahren Dresden (IZFP-D, Fraunhofer Institute of Nondestructive Testing) is developing condition monitoring systems (CMS) for safety-relevant components. By permanent monitoring, e.g. of wind rotors, aircraft components or pipelines, these systems will ensure high avalability during the whole component life. Crack initiation, crack propagation or delamination can be detected and repaired at an early stage. Early repair will prolong the component life, and outage periods can be reduced. Currently, full-scale fatigue tests are made on a 40 m wind rotor blade of CFRP and GFRP materials. After a static pre-load period, 2,000,000 fatigue cycles will be applied. The contribution describes the measuring technology and the evaluation methods, in particular event identification and parametrization. Finally, the current experimental status is outlined, fatigue test results so far are presented, and development trends are indicated. (orig.)

  8. Comparison of composite rotor blade models: A coupled-beam analysis and an MSC/NASTRAN finite-element model

    Hodges, Robert V.; Nixon, Mark W.; Rehfield, Lawrence W.

    1987-01-01

    A methodology was developed for the structural analysis of composite rotor blades. This coupled-beam analysis is relatively simple to use compared with alternative analysis techniques. The beam analysis was developed for thin-wall single-cell rotor structures and includes the effects of elastic coupling. This paper demonstrates the effectiveness of the new composite-beam analysis method through comparison of its results with those of an established baseline analysis technique. The baseline analysis is an MSC/NASTRAN finite-element model built up from anisotropic shell elements. Deformations are compared for three linear static load cases of centrifugal force at design rotor speed, applied torque, and lift for an ideal rotor in hover. A D-spar designed to twist under axial loading is the subject of the analysis. Results indicate the coupled-beam analysis is well within engineering accuracy.

  9. Active control system for a rotor blade trailing-edge flap

    Duvernier, Marc; Reithler, Livier; Guerrero, Jean Y.; Rossi, Rinaldo A.

    2000-06-01

    Reducing the external noise is becoming a major issue for helicopter manufacturers. The idea beyond this goal is to reduce or even avoid the blade vortex interaction (BVI), especially during descent and flights over inhabited areas. This can be achieved by changing locally the lift of the blade. Several strategies to reach this goal are under investigation at EUROCOPTER such as the control of the local incidence of the blade by a direct lift flap. AEROSPATIALE MATRA Corporate Research Centre and AEROSPATIALE MATRA MISSILES proposed an actuator system able to answer EUROCOPTER's needs for moving a direct lift flap. The present paper describes the definition, manufacturing and testing of this new actuator system. This actuator is based on an electromagnetic patented actuation system developed by AEROSPATIALE MATRA MISSILES for missile and aeronautic applications. The particularity of this actuator is its ability to produce the desired force on its whole range of stroke. The flap is designed to be fitted on a DAUPHIN type blade produced by EUROCOPTER and the actuator system was designed to fit the room available within the blade and to produce the right amount of stroke and force within the required frequency range. Other constraints such as centrifugal loading were also taken into account. This paper describes briefly the specifications and the major characteristics of the actuating system and presents some results of its behavior on a representative composite test-bed manufactured by EUROCOPTER when subjected to realistic mechanical loads.

  10. Calibration of partial safety factors for wind turbine rotor blades against fatigue failure; Kalibrering af partielle sikkerhedsfaktorer for udmattelse af vindmoellerotorer

    Christensen, C.J.; Ronold, K.O.; Thoegersen, M.L.

    2000-08-01

    The report describes a calibration of partial safety factors for wind turbine rotor blades subjected to fatigue loading in flapwise and edgewise bending. While earlier models - developed by the authors - dealt with such calibrations for site-specific individual turbines only, the calibration model applied herein covers an integrated analysis with different turbines on different sites and with different blade materials. The result is an optimized set of partial safety factors, i.e. a set of safety factors that lead to minimum deviation from the target reliability of the achieved reliabilities over the selected scope of turbines, sites and materials. The turbines included in the study cover rated powers of 450-600 kW. The result from the calibration are discussed in relation to the partial safety factors that are given in the Danish codes for design of glass fibre reinforced rotor blades (DS472 and DS456). (au)

  11. A Critical Evaluation of Structural Analysis Tools used for the Design of Large Composite Wind Turbine Rotor Blades under Ultimate and Cycle Loading

    Lekou, D.J.; Bacharoudis, K. C.; Farinas, A. B.; Branner, Kim; Berring, Peter; CROCE, A.; Philippidis, T.P.; De Winkel, G.D.

    2015-01-01

    Rotor blades for 10-20MW wind turbines may exceed 120m. To meet the demanding requirements of the blade design, structural analysis tools have been developed individually and combined with commercial available ones by blade designers. Due to the various available codes, understanding and estimating the uncertainty introduced in the design calculations by using these tools is needed to allow assessment of the effectiveness of any future design modification. For quantifying the introduced uncer...

  12. Wind Tunnel Evaluation of a Model Helicopter Main-Rotor Blade With Slotted Airfoils at the Tip

    Noonan, Kevin W.; Yeager, William T., Jr.; Singleton, Jeffrey D.; Wilbur, Matthew L.; Mirick, Paul H.

    2001-01-01

    Data for rotors using unconventional airfoils are of interest to permit an evaluation of this technology's capability to meet the U.S. Army's need for increased helicopter mission effectiveness and improved safety and survivability. Thus, an experimental investigation was conducted in the Langley Transonic Dynamics Tunnel (TDT) to evaluate the effect of using slotted airfoils in the rotor blade tip region (85 to 100 percent radius) on rotor aerodynamic performance and loads. Four rotor configurations were tested in forward flight at advance ratios from 0.15 to 0.45 and in hover in-ground effect. The hover tip Mach number was 0.627, which is representative of a design point of 4000-ft geometric altitude and a temperature of 95 F. The baseline rotor configuration had a conventional single-element airfoil in the tip region. A second rotor configuration had a forward-slotted airfoil with a -6 deg slat, a third configuration had a forward-slotted airfoil with a -10 slat, and a fourth configuration had an aft-slotted airfoil with a 3 deg flap (trailing edge down). The results of this investigation indicate that the -6 deg slat configuration offers some performance and loads benefits over the other three configurations.

  13. ACTIVE VIBRATION ISOLATION OF MECHANICAL VIBRATION IN RAILWAY PASSENGER CAR

    Aleksander SŁADKOWSKI

    2015-06-01

    Full Text Available This paper presents an attempt of numerical description of the active vibration isolation system of railway passenger car. Computer simulations were performed for different speeds of the passenger car riding along the same track. Formal basis to solve the formulated research problem was achieved by using the law and the principles of mechanics and control theory. Model results clearly indicate that the use of active vibration reduction systems in rail transport can significantly increase comfort

  14. Novel active vibration absorber with magnetorheological fluid

    Gerlach, T.; Ehrlich, J.; Böse, H.

    2009-02-01

    Disturbing vibrations diminish the performance of technical high precision devices significantly. In search of a suitable solution for reducing these vibrations, a novel concept of active vibration reduction was developed which exploits the special properties of magnetorheological fluids. In order to evaluate the concept of such an active vibration absorber (AVA) a demonstrator was designed and manufactured. This demonstrator generates a force which counteracts the motion of the vibrating body. Since the counterforce is generated by a centrifugal exciter, the AVA provides the capability to compensate vibrations even in two dimensions. To control the strength of the force transmitted to the vibrating body, the exciter is based on a tunable MR coupling. The AVA was integrated in an appropriate testing device to investigate its performance. The recorded results show a significant reduction of the vibration amplitudes by an order of magnitude.

  15. Design and development of an active Gurney flap for rotorcraft

    Freire Gómez, Jon; Booker, Julian D.; Mellor, Phil H.

    2013-03-01

    The EU's Green Rotorcraft programme will develop an Active Gurney Flap (AGF) for a full-scale helicopter main rotor blade as part of its `smart adaptive rotor blade' technology demonstrators. AGFs can be utilized to provide a localized and variable lift enhancement on the rotor, enabling a redistribution of loading on the rotor blade around the rotor azimuth. Further advantages include the possibility of using AGFs to allow a rotor speed reduction, which subsequently provides acoustic benefits. Designed to be integrable into a commercial helicopter blade, and thereby capable of withstanding real in-flight centrifugal loading, blade vibrations and aerodynamic loads, the demonstrator is expected to achieve a high technology readiness level (TRL). The AGF will be validated initially by a constant blade section 2D wind tunnel test and latterly by full blade 3D whirl tower testing. This paper presents the methodology adopted for the AGF concept topology selection, based on a series of both qualitative and quantitative performance criteria. Two different AGF candidate mechanisms are compared, both powered by a small commercial electromagnetic actuator. In both topologies, the link between the actuator and the control surface consists of two rotating torque bars, pivoting on flexure bearings. This provides the required reliability and precision, while making the design virtually frictionless. The engineering analysis presented suggests that both candidates would perform satisfactorily in a 2D wind tunnel test, but that equally, both have design constraints which limit their potential to be further taken into a whirl tower test under full scale centrifugal and inertial loads.

  16. Adaptive Piezoelectric Absorber for Active Vibration Control

    Sven Herold

    2016-02-01

    Full Text Available Passive vibration control solutions are often limited to working reliably at one design point. Especially applied to lightweight structures, which tend to have unwanted vibration, active vibration control approaches can outperform passive solutions. To generate dynamic forces in a narrow frequency band, passive single-degree-of-freedom oscillators are frequently used as vibration absorbers and neutralizers. In order to respond to changes in system properties and/or the frequency of excitation forces, in this work, adaptive vibration compensation by a tunable piezoelectric vibration absorber is investigated. A special design containing piezoelectric stack actuators is used to cover a large tuning range for the natural frequency of the adaptive vibration absorber, while also the utilization as an active dynamic inertial mass actuator for active control concepts is possible, which can help to implement a broadband vibration control system. An analytical model is set up to derive general design rules for the system. An absorber prototype is set up and validated experimentally for both use cases of an adaptive vibration absorber and inertial mass actuator. Finally, the adaptive vibration control system is installed and tested with a basic truss structure in the laboratory, using both the possibility to adjust the properties of the absorber and active control.

  17. A methodology for exploiting the tolerance for imprecision in genetic fuzzy systems and its application to characterization of rotor blade leading edge materials

    Sánchez, Luciano; Couso, Inés; Palacios, Ana M.; Palacios, José L.

    2013-05-01

    A methodology for obtaining fuzzy rule-based models from uncertain data is proposed. The granularity of the linguistic discretization is decided with the help of a new estimation of the mutual information between ill-known random variables, and a combination of boosting and genetic algorithms is used for discovering new rules. This methodology has been applied to predict whether the coating of an helicopter rotor blade is adequate, considering the shear adhesion strength of ice to different materials. The discovered knowledge is intended to increase the level of post-processing interpretation accuracy of experimental data obtained during the evaluation of ice-phobic materials for rotorcraft applications.

  18. Design, fabrication, and testing of an ultrasonic de-icing system for helicopter rotor blades

    Palacios, Jose Luis

    A low-power, non-thermal ultrasonic de-icing system is introduced as a possible substitute for current electro-thermal systems. The system generates delaminating ultrasonic transverse shear stresses at the interface of accreted ice. A PZT-4 disk driven at 28.5 KHz (radial resonance of the disk) instantaneously de-bonds 2 mm thick freezer ice layers. The ice layers are accreted to a 0.7 mm thick, 30.4 cm x 30.4 cm steel plate at an environment temperature of -20°C. A power input of 50 Watts is applied to the actuator (50 V, 19.6 KV/m), which translates to a de-icing power of 0.07 W/cm2. A finite element model of the actuator bonded to the isotropic plate is used to guide the design of the system, and predicts the transverse shear stresses at the ice interface. Wind tunnel icing tests were conducted to demonstrate the potential use of the proposed system under impact icing conditions. Both glaze ice and rime ice were generated on steel and composite plates by changing the cloud conditions of the wind tunnel. Continuous ultrasonic vibration prevented impact ice formation around the actuator location at an input power not exceeding 0.18 W/cm 2 (1.2 W/in2). As ice thickness reached a critical thickness of approximately 1.2 mm, shedding occurred on those locations where ultrasonic transverse shear stresses exceeded the shear adhesion strength of the ice. Finite element transverse shear stress predictions correlate with observed experimental impact ice de-bonding behavior. To increase the traveling distance of propagating ultrasonic waves, ultrasonic shear horizontal wave modes are studied. Wave modes providing large modal interface transverse shear stress concentration coefficients (ISCC) between the host structure (0.7 mm thick steel plate) and accreted ice (2.5 mm thick ice layer) are identified and investigated for a potential increase in the wave propagation distance. Ultrasonic actuators able to trigger these optimum wave modes are designed and fabricated. Despite

  19. Software integration for automated stability analysis and design optimization of a bearingless rotor blade

    Gunduz, Mustafa Emre

    Many government agencies and corporations around the world have found the unique capabilities of rotorcraft indispensable. Incorporating such capabilities into rotorcraft design poses extra challenges because it is a complicated multidisciplinary process. The concept of applying several disciplines to the design and optimization processes may not be new, but it does not currently seem to be widely accepted in industry. The reason for this might be the lack of well-known tools for realizing a complete multidisciplinary design and analysis of a product. This study aims to propose a method that enables engineers in some design disciplines to perform a fairly detailed analysis and optimization of a design using commercially available software as well as codes developed at Georgia Tech. The ultimate goal is when the system is set up properly, the CAD model of the design, including all subsystems, will be automatically updated as soon as a new part or assembly is added to the design; or it will be updated when an analysis and/or an optimization is performed and the geometry needs to be modified. Designers and engineers will be involved in only checking the latest design for errors or adding/removing features. Such a design process will take dramatically less time to complete; therefore, it should reduce development time and costs. The optimization method is demonstrated on an existing helicopter rotor originally designed in the 1960's. The rotor is already an effective design with novel features. However, application of the optimization principles together with high-speed computing resulted in an even better design. The objective function to be minimized is related to the vibrations of the rotor system under gusty wind conditions. The design parameters are all continuous variables. Optimization is performed in a number of steps. First, the most crucial design variables of the objective function are identified. With these variables, Latin Hypercube Sampling method is used

  20. Actively controlled vibration welding system and method

    Cai, Wayne W.; Kang, Bongsu; Tan, Chin-An

    2013-04-02

    A vibration welding system includes a controller, welding horn, an active material element, and anvil assembly. The assembly may include an anvil body connected to a back plate and support member. The element, e.g., a piezoelectric stack or shape memory alloy, is positioned with respect to the assembly. The horn vibrates in a desirable first direction to form a weld on a work piece. The element controls any vibrations in a second direction by applying calibrated response to the anvil body in the second direction. A method for controlling undesirable vibrations in the system includes positioning the element with respect to the anvil assembly, connecting the anvil body to the support member through the back plate, vibrating the horn in a desirable first direction, and transmitting an input signal to the element to control vibration in an undesirable second direction.

  1. The spectral characteristics of rotor blade-vortex interaction noise - Experimental and mathematical results

    Martin, Ruth M.; Hardin, Jay C.

    1987-01-01

    The BVI impulsive content of a rotor acoustic signal is shown to appear in the mid-frequency range of the power spectrum, between the fifth and thirtieth harmonics of the blade passage frequency, concentrated at the harmonics of the blade passage frequency. These harmonics exhibit a humped or scalloped shape in this mid-frequency spectral region. Increased energy at the harmonics of the shaft frequency appears when the BVI impulsive content demonstrates unsteadiness and blade-to-blade differences in the time domain. A mathematical model of a generalized BVI acoustic signal and its power spectrum shows that the power spectrum is scalloped and filtered by a comb function. The spectrum amplitude is defined by the impulse amplitude and emission time. The scalloping of the spectrum is related to the emission time of the impulse itself, and the spacing of the comb function is related to the repetition time (period) of the impulse. The decay rate of the spectral humps is governed by the inverse of frequency squared. The mathematical model validates the characteristics observed in the data and verify that these characteristics are due to blade-vortex interaction activity.

  2. Dynamic survey of wind turbine vibrations

    Chiang, Chih-Hung; Hsu, Keng-Tsang; Cheng, Chia-Chi; Pan, Chieh-Chen; Huang, Chi-Luen; Cheng, Tao-Ming

    2016-04-01

    Six wind turbines were blown to the ground by the wind gust during the attack of Typhoon Soudelor in August 2015. Survey using unmanned aerial vehicle, UAV, found the collapsed wind turbines had been broken at the lower section of the supporting towers. The dynamic behavior of wind turbine systems is thus in need of attention. The vibration of rotor blades and supporting towers of two wind turbine systems have been measured remotely using IBIS, a microwave interferometer. However the frequency of the rotor blade can be analyzed only if the microwave measurements are taken as the wind turbine is parked and secured. Time-frequency analyses such as continuous wavelet transform and reassigned spectrograms are applied to the displacement signals obtained. A frequency of 0.44Hz exists in both turbines B and C at various operating conditions. Possible links between dynamic characteristics and structural integrity of wind turbine -tower systems is discussed.

  3. Rotor blade dynamic design

    Pritchard, Jocelyn I.; Adelman, Howard M.; Mantay, Wayne R.

    1989-01-01

    The rotor dynamic design considerations are essentially limitations on the vibratory response of the blades which in turn limit the dynamic excitation of the fuselage by forces and moments transmitted to the hub. Quantities which are associated with the blade response and which are subject to design constraints are discussed. These include blade frequencies, vertical and inplane hub shear, rolling and pitching moments, and aeroelastic stability margin.

  4. [Raman active vibrations of aluminosilicates].

    Pan, Feng; Yu, Xue-hui; Mo, Xuan-xue; You, Jing-lin; Wang, Chen; Chen, Hui; Jiang, Guo-chang

    2006-10-01

    Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations. PMID:17205741

  5. Active vibration control of lightweight floor systems

    Baader, J.; Fontana, M.

    2016-04-01

    Wide-span and lightweight floors are often prone to structural vibrations due to their low resonance frequency and poor material damping. Their dynamic behaviour can be improved using passive, semi-active or active vibration control devices. The following article proposes a novel method for the controller synthesis for active vibration control. An existing passive TMD (tuned mass damper) is modelled and equipped with an actuator in order to provide more efficient damping. Using an iterative optimization approach under constraints, an optimal controller is found which minimizes a quadratic cost function in frequency domain. A simulation of an existing test bench shows that the active vibration control device is able to provide increased damping compared to the passive TMD.

  6. Rotor Vibration Reduction Using Multi-Element Multi-Path Design

    Su, Keye

    Multi-Element Multi-Path (MEMP) structural design is a new concept for rotor vibration reduction. This thesis explores the possibility of applying MEMP design to helicopter rotor blades. A conceptual design is developed to investigate the MEMP blade's vibration reduction performance. In the design, the rotor blade is characterized by two centrifugally loaded beams which are connected to each other through linear and torsional springs. A computer program is built to simulate the behavior of such structures. Detailed parametric studies are conducted. The main challenges in this thesis involve the blade hub load vibration analysis, the blade thickness constraint and the blade parameter selection. The results show substantial vibration reduction for the MEMP design but the large relative deflection between the two beams, conceptualized as an internal spar and airfoil shell, remains a problem for further study.

  7. Active Vibration Damping of Solar Arrays

    Reinicke, Gunar; Baier, Horst; Grillebeck, Anton; Scharfeld, Frank; Hunger, Joseph; Abou-El-Ela, A.; Lohberg, Andreas

    2012-07-01

    Current generations of large solar array panels are lightweight and flexible constructions to reduce net masses. They undergo strong vibrations during launch. The active vibration damping is one convenient option to reduce vibration responses and limit stresses in facesheets. In this study, two actuator concepts are used for vibration damping. A stack interface actuator replaces a panel hold down and is decoupled from bending moments and shear forces. Piezoelectric patch actuators are used as an alternative, where the number, position and size of actuators are mainly driven by controllability analyses. Linear Quadratic Gaussian control is used to attenuate vibrations of selected mode shapes with both actuators. Simulations as well as modal and acoustic tests show the feasibility of selected actuator concepts.

  8. Development of a smart trailing-edge flap actuator with multistage stroke amplifier for a rotor blade

    Lee, Taeoh; Chopra, Inderjit

    2000-06-01

    The present research experimentally investigates the feasibility of a trailing-edge flap mechanism actuated in a helicopter rotor by piezoelectric stacks in conjunction with a dual-stage mechanical stroke amplifier to actively control vibration. A new mechanical leverage amplification concept was developed to extend the capability of a simple lever-fulcrum stroke amplifier. A refined prototype actuator and flap mechanism were designed and fabricated using five piezostacks. The bench-top test of the actuator showed 73.7 mils of free stroke and uniform displacement output up to a frequency of 150 Hz. Spin testing was performed in the vacuum chamber to evaluate the performance in rotating environment, and the refined prototype actuator showed approximately 13% loss in actuation stroke at 710 g of full-scale centrifugal loading. In the Open-Jet wind tunnel testing to simulate the aerodynamic loading environment, the peak-to-peak flap deflections above 8 degrees for freestream velocity of 120 ft/sec were obtained at different excitation frequencies. It demonstrated the capability of the refined prototype actuator in rotating environment to potentially reduce helicopter vibration.

  9. Active and passive vibration control of structures

    Spelsberg-Korspeter, Gottfried

    2014-01-01

    Active and Passive Vibration Control of Structures form an issue of very actual interest in many different fields of engineering, for example in the automotive and aerospace industry, in precision engineering (e.g. in large telescopes), and also in civil engineering. The papers in this volume bring together engineers of different background, and it fill gaps between structural mechanics, vibrations and modern control theory.  Also links between the different applications in structural control are shown.

  10. Active structures to reduce torsional vibrations

    Matthias, M.; Schlote, D.; Atzrodt, H.

    2013-03-01

    This paper describes the development of different active measures to reduce torsional vibrations in power trains. The measures are based on concepts developed for active mounts to reduce the transmission of structure-borne sound. To show the potential of these active measures and investigate their mode of operation to influence torsional vibrations, numerical simulations of powertrains with different active measures were done. First experimental results from tests on an experimental (reduced size) power train were used to align the numerical models. The work was done within the project 'LOEWE-Zentrum AdRIA: Adaptronik - Research, Innovation, Application' funded by the German federal state of Hessen, and the Project AKTos: 'Active control of torsional vibrations by coupling elements' placed in the research Framework program 'Navigation and Maritime Technology for the 21st Century' funded by the German Federal Ministry of Economics and Technology.

  11. A Dynamic Absorber With Active Vibration Control

    Huang, S.-J.; Lian, R.-J.

    1994-12-01

    The design and construction of a dynamic absorber incorporating active vibration control is described. The absorber is a two-degrees-of-freedom spring — lumped mass system sliding on a guide pillar, with two internal vibration disturbance sources. Both the main mass and the secondary absorber mass are acted on by DC servo motors, respectively, to suppress the vibration amplitude. The state variable technique is used to model this dynamic system and a decoupling PID control method is used. First, the discrete time state space model is identified by using the commercial software MATLAB. Then the decoupling controller of this multi-input/multi-output system is derived from the identified model. Finally the results of some experiments are presented. The experimental results show that the system is effective in suppressing vibration. Also, the performance of this control strategy for position tracking control is evaluated based on experimental data.

  12. Rotor Vibration Reduction via Active Hybrid Bearings

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... orifices machined in the bearing pads, one can alter the machine dynamic characteristics, thus enhancing its operational range. A mathematical model of the rotor-bearing system, as well as of the hydraulic system, is presented. Numerical results of the system frequency response show good agreement with...

  13. A New Framework For Helicopter Vibration Suppression; Time-Periodic System Identification and Controller Design

    Ulker, Fatma Demet

    In forward flight, helicopter rotor blades function within a highly complex aerodynamic environment that includes both near-blade and far-blade aerodynamic phenomena. These aerodynamic phenomena cause fluctuating aerodynamic loads on the rotor blades. These loads when coupled with the dynamic characteristics and elastic motion of the blade create excessive amount of vibration. These vibrations degrade helicopter performance, passenger comfort and contributes to high cost maintenance problems. In an effort to suppress helicopter vibration, recent studies have developed active control strategies using active pitch links, flaps, twist actuation and higher harmonic control of the swash plate. In active helicopter vibration control, designing a controller in a computationally efficient way requires accurate reduced-order models of complex helicopter aeroelasticity. In previous studies, controllers were designed using aeroelastic models that were obtained by coupling independently reduced aerodynamic and structural dynamic models. Unfortunately, these controllers could not satisfy stability and performance criteria when implemented in high-fidelity computer simulations or real-time experiments. In this thesis, we present a novel approach that provides accurate time-periodic reduced-order models and time-periodic H2 and H infinity controllers that satisfy the stability and performance criteria. Computational efficiency and the necessity of using the approach were validated by implementing an actively controlled flap strategy. In this proposed approach, the reduced-order models were directly identified from high-fidelity coupled aeroelastic analysis by using the time-periodic subspace identification method. Time-periodic H2 and Hinfinity controllers that update the control actuation at every time step were designed. The control synthesis problem was solved using Linear Matrix Inequality and periodic Riccati Equation based formulations, for which an in-house periodic

  14. Aeroelastic Stability of Damperless Rotor Blade%无减摆器旋翼桨叶气弹稳定性分析

    夏品奇; 周景良

    2012-01-01

    无减摆器旋翼具有桨毂结构简单、桨毂气动阻力小、桨毂维护简便等优点,但取消了桨毂减摆器后必须确保桨叶在摆振方向有足够的阻尼以保证桨叶的摆振稳定性.基于气弹耦合的方法是实现无减摆器旋翼桨叶摆振稳定性的一个有效方法.建立了无减摆器无铰式旋翼桨叶带有预锥角、下垂角、后掠角和预扭角等结构参数的非线性气弹动力学模型,利用伽辽金方法把桨叶偏微分运动方程简化为非线性常微分平衡方程和关于平衡位置的小扰动运动方程,分析了桨叶的气弹稳定性并进行了参数影响分析.数值结果表明,合理的桨叶结构参数和气弹耦合可确保无减摆器旋翼桨叶在摆振方向的气弹稳定性.%The damperless rotor has the advantage of the hub with simple structure, small aerodynamic drag and easy maintainance. However, without blade lag damper, the blade must have sufficient damping in the lag direction to ensure lag stability. And the aeroelastic coupling based method can approach that effectively. Therefore, the nonlinear aeroelastic dynamic model is established for the damperless and hingeless rotor blade with structural parameters of pre-cone angle, pre-droop angle, sweep angle and pre-twist angle. By using the Galerkin method, the partial differential equations of motion are simplified to the nonlinear ordinary differential balance equations and the small perturbation equations for the equilibrium positions. The blade aeroelastic stability and the parameters effects are analyzed. The numerical results show that reasonable structural parameters and aeroelastic coupling of blade can ensure the aeroelastic stability of damperless rotor blade in the lag direction.

  15. Wind Turbine Rotors with Active Vibration Control

    Svendsen, Martin Nymann

    This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general...... that these are geometrically well separated. For active vibration control in three-bladed wind turbine rotors the present work presents a resonance-based method for groups of one collective and two whirling modes. The controller is based on the existing resonant format and introduces a dual system...... system. As in the method for non-rotating systems, an explicit procedure for optimal calibration of the controller gains is established. The control system is applied to an 86m wind turbine rotor by means of active strut actuator mechanisms. The prescribed additional damping ratios are reproduced almost...

  16. Vibration damping with active carbon fiber structures

    Neugebauer, Reimund; Kunze, Holger; Riedel, Mathias; Roscher, Hans-Jürgen

    2007-04-01

    This paper presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was done with a finite element model (ANSYS). This paper describes how state space models are generated out of a structure based on the finite element model and how controller codes are integrated into finite element models for transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.

  17. Active control of vibrations in pedestrian bridges

    Álvaro Cunha; Carlos Moutinho

    1999-01-01

    This paper, apart from making a brief general reference to vibration problems in pedestrian bridges, as well as to the form of modelling of dynamic pedestrian loads, presents the use of a predictive control strategy for the numerical simulation of the dynamic response of actively controlled structures of this type. The consideration of this control strategy permitted the development of a computational model, which was applied to the study of a pedestrian cable-stayed bridge, in order to show ...

  18. Performance Data from a Wind-Tunnel Test of Two Main-rotor Blade Designs for a Utility-Class Helicopter

    Singleton, Jeffrey D.; Yeager, William T., Jr.; Wilbur, Matthew L.

    1990-01-01

    An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to evaluate an advanced main rotor designed for use on a utility class helicopter, specifically the U.S. Army UH-60A Blackhawk. This rotor design incorporated advanced twist, airfoil cross sections, and geometric planform. For evaluation purposes, the current UH-60A main rotor was also tested and is referred to as the baseline blade set. A total of four blade sets were tested. One set of both the baseline and the advanced rotors were dynamically scaled to represent a full scale helicopter rotor blade design. The remaining advanced and baseline blade sets were not dynamically scaled so as to isolate the effects of structural elasticity. The investigation was conducted in hover and at rotor advance ratios ranging from 0.15 to 0.4 at a range of nominal test medium densities from 0.00238 to 0.009 slugs/cu ft. This range of densities, coupled with varying rotor lift and propulsive force, allowed for the simulation of several vehicle gross weight and density altitude combinations. Performance data are presented for all blade sets without analysis; however, cross referencing of data with flight condition may be useful to the analyst for validating aeroelastic theories and design methodologies as well as for evaluating advanced design parameters.

  19. 开式转子叶片气动设计研究%Research on Aerodynamic Design of Open Rotor Blade

    刘政良; 严明; 洪青松

    2013-01-01

    参考现代民航飞机设计方案要求,完成了开式转子发动机叶片的气动设计工作。在设计过程中引入可压缩流动叶片数据改进了螺旋桨片条理论,使之适用于高亚声速来流的叶片设计。采用后掠叶片,NACA16系列叶型,前缘积叠方式。数值模拟结果与设计结果相近,基本满足气动设计要求。%Aerodynamic design of open rotor blade which refers to performance of engines which used on modern civil airplane is completed. Compressible blade data is introduced to optimize strip theory in order to satisfy blade design under high subsonic free stream. Sept blade, NACA-16 series data and leading edge accumulation is used. Numerical simulation is similar to the design which basicaly satisifed the design requirements.

  20. Nonlinear Equations of Motion for Cantilever Rotor Blades in Hover with Pitch Link Flexibility, Twist, Precone, Droop, Sweep, Torque Offset, and Blade Root Offset

    Hodges, D. H.

    1976-01-01

    Nonlinear equations of motion for a cantilever rotor blade are derived for the hovering flight condition. The blade is assumed to have twist, precone, droop, sweep, torque offset and blade root offset, and the elastic axis and the axes of center of mass, tension, and aerodynamic center coincident at the quarter chord. The blade is cantilevered in bending, but has a torsional root spring to simulate pitch link flexibility. Aerodynamic forces acting on the blade are derived from strip theory based on quasi-steady two-dimensional airfoil theory. The equations are hybrid, consisting of one integro-differential equation for root torsion and three integro-partial differential equations for flatwise and chordwise bending and elastic torsion. The equations are specialized for a uniform blade and reduced to nonlinear ordinary differential equations by Galerkin's method. They are linearized for small perturbation motions about the equilibrium operating condition. Modal analysis leads to formulation of a standard eigenvalue problem where the elements of the stability matrix depend on the solution of the equilibrium equations. Two different forms of the root torsion equation are derived that yield virtually identical numerical results. This provides a reasonable check for the accuracy of the equations.

  1. Development and whirl tower test of the SMART active flap rotor

    Straub, Friedrich K.; Kennedy, Dennis K.; Stemple, Alan D.; Anand, V. R.; Birchette, Terry S.

    2004-07-01

    A full scale Smart Material Actuated Rotor Technology (SMART) system with piezoelectric actuated blade flaps was developed and whirl tower tested. The development effort included design, fabrication, and component testing of rotor blades, trailing edge flaps, piezoelectric actuators, switching power amplifiers, and the data/power system. Simulations and model scale wind tunnel tests have shown that this system can provide 80% vibration reduction, 10dB noise reduction for a helicopter passing overhead, and substantial aerodynamic performance gains. Whirl tower testing of the 34-foot diameter rotor demonstrated the functionality, robustness, and required authority of the active flap system. The program involved extensive development work and risk reduction tests which resulted in a robust, high performance actuator and a tightly integrated actuator, flap, and blade system. The actuator demonstrated excellent performance during bench testing and has accumulated over 60 million cycles under a spectrum of loading conditions. The flight worthy active flap rotor blades were based on a modified design of the FAA certified MD900 Explorer production rotor blade. Whirl tower testing was conducted with full rotor instrumentation and a 5-component balance. The rotor was tested for 13 hours under a range of conditions, including 7 hours of flap operation. Flap inputs included open loop static and dynamic commands. The flaps showed excellent authority with oscillatory thrust greater than 10% of the steady baseline thrust. Various flap actuation frequency sweeps were run to investigate the dynamics of the rotor and the flap system. Limited closed loop tests used hub accelerations and hub loads for feedback. Proving the integration, robust operation, and authority of the flap system were the key objectives met by the whirl tower test. This success depended on tailoring the piezoelectric materials and actuator to the application and meeting actuator/blade integration requirements

  2. Self-Tuning Active Vibration Control of Flexible Beam Structures

    M.O. Tokhi; Hossain, M A

    1994-01-01

    This paper presents the design and performance evaluation of an adaptive active control mechanism for vibration suppression in flexible beam structures. A cantilever beam system in transverse vibration is considered. First order control finite difference methods are used to study the behaviour of the beam and develop a suitable test and verification platform. An active vibration control algorithm is developed within an adaptive control framework for broadband cancellation of vibration along t...

  3. Vibrational optical activity principles and applications

    Nafie, Laurence A

    2011-01-01

    This unique book stands as the only comprehensive introduction to vibrational optical activity (VOA) and is the first single book that serves as a complete reference for this relatively new, but increasingly important area of molecular spectroscopy. Key features:A single-source reference on this topic that introduces, describes the background and foundation of this area of spectroscopy.Serves as a guide on how to use it to carry out applications with relevant problem solving.Depth and breadth of the subject is presented in a logical, complete and progressive fashion. A

  4. Modeling of Axial Spring Stiffness in Active Vibration Controlled Drilling

    Pao William; Hashim Fakhruldin M; Parman Setyamartana

    2014-01-01

    During drilling process, substantial amount of vibration and shock are induced to the drill string. Active vibration controlled drilling is introduced to reduce the vibration and increase the efficiency of drilling process. In this system, two main components that determine the damping coefficient are magnetorheological (MR) damper and spring assembly. Performance of vibration damping system is depending on the viscosity of MR fluid in the damper and spring constant of spring assembly. One of...

  5. Passive and Active Vibration Control of Renewable Energy Structures

    Zhang, Zili

    2015-01-01

    The present thesis deals with fundamental researches on passive and active vibration control of renewable energy structures, and provides useful models for practical applications. Effective and robust vibration control methods have been explored for mitigating the lightly damped edgewise blade vibration and lateral tower vibration, with the main focus on structural control devices. Rigorous theoretical modeling of different dynamic system has been established, based on which detailed design a...

  6. Automotive applications of rapid prototyping for active vibration control

    Bohn, C.; Svaricek, F. [Continental Gummi-Werke AG, Hannover (Germany); Karkosch, H.J.; Marienfeld, P.M. [ContiTech Vibration Control GmbH, Hannover (Germany)

    2001-07-01

    This paper presents some recent results of Continental's research and development activities in the area of active vibration control. First, a brief overview of different approaches to active noise and vibration control is given. This is followed by a discussion of the rapid controller prototyping process that is currently being introduced. Finally, some experimental results obtained in cooperation with an automobile manufacturer are presented. These results demonstrate that major noise and vibration attenuation can be achieved through active vibration control in automobiles. (orig.)

  7. Active Vibration Control of Piezolaminated Smart Beams

    V. Balamurugan

    2001-04-01

    Full Text Available This paper deals with the active vibration control of beam like structures with distributed piezoelectric sensor and actuator layers bonded on top and bottom surfaces of the beam. A finite element model based on Euler-Bernoulli beam theory has been developed. The contribution of the piezoelectric sensor and actuator layers on the mass and stiffness of the beam is considered. Three types of classical control strategies, namely direct proportional feedback, constant-gain negative velocity feedback and Lyapunov feedback and an optimal control strategy, linear quadratic regulator (LQR scheme are applied to study their control effectiveness. Also, the control performance with different types of loading, such as impulse loading, step loading, harmonic and random loading is studied

  8. Active balance system and vibration balanced machine

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2005-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass.

  9. Effect of Vibration Magnitude and Seated Posture on Reading Activity in Fore and AFT Vibration

    V. Kumar

    2013-08-01

    Full Text Available A large number of passengers prefer to utilize the time while commuting from one place to other in public transport like train, car and other vehicles. Traveling time can be utilized performing many sedentary activities e.g. Reading, writing, sketching etc. Reading activity is the most preferred activity for utilization of time. Experimental study has been performed to find the effect of vibration magnitude and different posture. Six healthy subjects were exposed sinusoidal vibrations, total 28 conditions while performing reading activity: one direction: fore and aft, two magnitudes: 0.6 and 1.2 ms-2 rms (un-weighted, seven frequencies: 2, 3, 4, 5, 6, 8, 10 Hz and two postures: vertical backrest and 30o inclined backrest. Significant effect of vibration magnitude and different posture are observed for both subjective and objective measure. Reading performance decreases with the increase vibration magnitude and with the inclined backrest conditions.

  10. Modelling of vibrational optical activity of fibrillar systems

    Kessler, Jiří; Kapitán, J.; Yamamoto, S.; Kiederling, T. A.; Bouř, Petr

    Vienna : Vienna University of Technology, 2015 - (Lendl, B.; Koch, C.; Kraft, M.; Ofner, J.; Ramer, G.). s. 504-505 ISBN 978-3-200-04205-6. [ICAVS8. International Conference on Advanced Vibrational Spectroscopy /8./. 12.07.2015-17.07.2015, Vienna] Institutional support: RVO:61388963 Keywords : vibrational optical activity * proteins * fibrills Subject RIV: CF - Physical ; Theoretical Chemistry

  11. Development of active vibration isolation system for precision machines

    Li, H. Z.; Lin, W. J.; Yang, G. L.

    2010-03-01

    It is a common understanding by manufacturers of precision machines that vibrations are a potentially disastrous threat to precision and throughput. To satisfy the quest for more stable processes and tighter critical dimension control in the microelectronics manufacturing industry, active vibration control becomes increasingly important for high-precision equipment developers. This paper introduced the development of an active vibration isolation system for precision machines. Innovative mechatronic approaches are investigated that can effectively suppress both environmental and payload-generated vibration. In this system, accelerometers are used as the feedback sensor, voice coil motors are used to generate the counter force, and a TI DSP controller is used to couple sensor measurements to actuator forces via specially designed control algorithms in real-time to counteract the vibration disturbances. Experimental results by using the developed AVI prototype showed promising performance on vibration attenuation. It demonstrated a reduction of the settling time from 2s to 0.1s under impulsive disturbances; and a vibration attenuation level of more than 20dB for harmonic disturbances. The technology can be used to suppress vibration for a wide range of precision machines to achieve fast settling time and higher accuracy.

  12. MEASUREMENT OF ANGULAR VIBRATION AMPLITUDE BY ACTIVELY BLURRED IMAGES

    GUAN Baiqing; WANG Shigang; LIU Chong; LI Qian

    2007-01-01

    A novel motion-blur-based method for measuring the angular amplitude of a high-frequency rotational vibration is schemed. The proposed approach combines the active vision concept and the mechanism of motion-from-blur, generates motion blur on the image plane actively by extending exposure time, and utilizes the motion blur information in polar images to estimate the angular amplitude of a high-frequency rotational vibration. This method obtains the analytical results of the angular vibration amplitude from the geometric moments of a motion blurred polar image and an unblurred image for reference. Experimental results are provided to validate the presented scheme.

  13. Innovation in Active Vibration Control Strategy of Intelligent Structures

    A. Moutsopoulou

    2014-01-01

    Full Text Available Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper presents sufficiently a recognizable advance in knowledge of active vibration control in intelligent structures.

  14. Active vibration control of doubly-curved panels

    Nourzad, Delphine

    2014-01-01

    This thesis considers active control of the vibration of doubly-curved panels. Such panels are widely used in vehicles such as cars and aircraft, whose vibration is becoming more problematic as the weight of these vehicles is reduced to control their CO2 emissions. The dynamic properties of doubly-curved panels are first considered and an analytic model which includes in-plane inertia is introduced. The results of this analytical model are compared with those from numerical modelling. Of part...

  15. Modeling of Axial Spring Stiffness in Active Vibration Controlled Drilling

    Pao William

    2014-07-01

    Full Text Available During drilling process, substantial amount of vibration and shock are induced to the drill string. Active vibration controlled drilling is introduced to reduce the vibration and increase the efficiency of drilling process. In this system, two main components that determine the damping coefficient are magnetorheological (MR damper and spring assembly. Performance of vibration damping system is depending on the viscosity of MR fluid in the damper and spring constant of spring assembly. One of the key issues that are unclear from the design is the correlation between the axial spring stiffness configuration and the damping force which needs to be tuned actively. There has been lack of studies on how the viscosity of MR fluid on the active vibration damper affects the damping stiffness of the whole system. The objective of the project is to extract the correlations for the viscous damping coefficient, equivalent spring stiffness and power input to the system. Simplified vibration model is thus created using Simulink, together with experimental data fed from APS Technology’s in-house team. Inputs of the simulation such as force exerted, mass of mandrel, spring constant and step time are based on the experimental data and can be adjusted to suit different experiments. By having the model, behavior of the system can be studied and analyzed. From the simulation, it is also observed that the relationship between damping coefficient and power input of the system is linear.

  16. Active Blade Vibration Control Being Developed and Tested

    Johnson, Dexter

    2003-01-01

    Gas turbine engines are currently being designed to have increased performance, lower weight and manufacturing costs, and higher reliability. Consequently, turbomachinery components, such as turbine and compressor blades, have designs that are susceptible to new vibration problems and eventual in-service failure due to high-cycle fatigue. To address this problem, researchers at the NASA Glenn Research Center are developing and testing innovative active blade vibration control concepts. Preliminary results of using an active blade vibration control system, involving a rotor supported by an active magnetic bearing in Glenn's Dynamic Spin Rig, indicate promising results (see the photograph). Active blade vibration control was achieved using feedback of blade strain gauge signals within the magnetic bearing control loop. The vibration amplitude was reduced substantially (see the graphs). Also, vibration amplitude amplification was demonstrated; this could be used to enhance structural mode identification, if desired. These results were for a nonrotating two-bladed disk. Tests for rotating blades are planned. Current and future active blade vibration control research is planned to use a fully magnetically suspended rotor and smart materials. For the fully magnetically suspended rotor work, three magnetic bearings (two radial and one axial) will be used as actuators instead of one magnetic bearing. This will allow additional degrees of freedom to be used for control. For the smart materials work, control effectors located on and off the blade will be considered. Piezoelectric materials will be considered for on-the-blade actuation, and actuator placement on a stator vane, or other nearby structure, will be investigated for off-the-blade actuation. Initial work will focus on determining the feasibility of these methods by performing basic analysis and simple experiments involving feedback control.

  17. Active vibration control of basic structures using macro fiber composites

    Yi, Guo; Wang, Jinming; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2011-03-01

    In the modern naval battle, as the anti-detection technique developing fleetly, enhancing submarine's hidden ability is becoming more and more important. However, in view of the worse control effect at low-frequency and weak adjustability to external influence, conventional passive vibration control can't satisfy the modern naval rigorous demands. Fortunately, active vibration control technology not only monitors the structure's real-time vibration, but also has more remarkable control effects and superior suitability. At the present time, it has a primary application in the vibration damping of ship engineering. In addition, due to functional materials rapidly developing, with the coming of piezoelectric composite materials, the advanced active control techniques have more applicability, lager damp amplitude and wider applied field, which basing on the piezoelectric-effect and inverse- piezoelectric-effect of piezoelectric materials. Especially, in the end of nineties, NASA had successfully manufactured the excellent macro fiber composite (MFC), which assembles actuating and sensing abilities. Comparing with the conventional piezoelectric ceramic materials, it provides the required durability, excellent flexibility, higher electromechanical coupling factors and stronger longitudinal actuating force by using interdigital electrodes. On the basis of the application of cantilever beam' active vibration control by using MFC actuators, this paper started with the mechanical characteristics of its actuating and sensing equations, and then investigated its piezoelectric feedback scale factor when equipped on the honeycomb aluminous panel. Finally, in order to validate the theoretical analysis method, the vibration control experiment of cantilever beam and honeycomb aluminous panel are built and tested with different activating force. The experimental results verify that MFC used in submarine structures' active vibration control are feasible and effective.

  18. Passive and Active Vibration Control of Renewable Energy Structures

    Zhang, Zili

    The present thesis deals with fundamental researches on passive and active vibration control of renewable energy structures, and provides useful models for practical applications. Effective and robust vibration control methods have been explored for mitigating the lightly damped edgewise blade...... vibration and lateral tower vibration, with the main focus on structural control devices. Rigorous theoretical modeling of different dynamic system has been established, based on which detailed design and analysis of the proposed control devices can be carried out. This thesis also explores technical...... solutions for wave energy point absorbers, in order to maximize the mean absorbed power and to deliver more smooth power to the grid. A novel suboptimal causal control law has been established for controlling the motion of the point absorber, and a new type of point absorber has also been proposed with...

  19. Active vibration control based on piezoelectric smart composite

    An aircraft’s vertical fin may experience dramatic buffet loads in high angle of attack flight conditions, and these buffet loads would cause huge vibration and dynamic stress on the vertical fin structure. To reduce the dynamic vibration of the vertical fin structure, macro fiber composite (MFC) actuators were used in this paper. The drive moment equations and sensing voltage equations of the MFC actuators were developed. Finite element analysis models based on three kinds of models of simplified vertical fin structures with surface-bonded MFC actuators were established in ABAQUS. The equivalent damping ratio of the structure was employed in finite element analysis, in order to measure the effectiveness of vibration control. Further, an open-loop test for the active vibration control system of the vertical fin with MFC actuators was designed and developed. The experimental results validated the effectiveness of the MFC actuators as well as the developed methodology. (paper)

  20. Active and passive vibration suppression for space structures

    Hyland, David C.

    1991-01-01

    The relative benefits of passive and active vibration suppression for large space structures (LSS) are discussed. The intent is to sketch the true ranges of applicability of these approaches using previously published technical results. It was found that the distinction between active and passive vibration suppression approaches is not as sharp as might be thought at first. The relative simplicity, reliability, and cost effectiveness touted for passive measures are vitiated by 'hidden costs' bound up with detailed engineering implementation issues and inherent performance limitations. At the same time, reliability and robustness issues are often cited against active control. It is argued that a continuum of vibration suppression measures offering mutually supporting capabilities is needed. The challenge is to properly orchestrate a spectrum of methods to reap the synergistic benefits of combined advanced materials, passive damping, and active control.

  1. Adaptive control of an active seat for occupant vibration reduction

    Gan, Zengkang; Hillis, Andrew J.; Darling, Jocelyn

    2015-08-01

    The harmful effects on human performance and health caused by unwanted vibration from vehicle seats are of increasing concern. This paper presents an active seat system to reduce the vibration level transmitted to the seat pan and the occupants' body under low frequency periodic excitation. Firstly, the detail of the mechanical structure is given and the active seat dynamics without external load are characterized by vibration transmissibility and frequency responses under different excitation forces. Owing the nonlinear and time-varying behaviour of the proposed system, a Filtered-x least-mean-square (FXLMS) adaptive control algorithm with on-line Fast-block LMS (FBLMS) identification process is employed to manage the system operation for high vibration cancellation performance. The effectiveness of the active seat system is assessed through real-time experimental tests using different excitation profiles. The system identification results show that an accurate estimation of the secondary path is achieved by using the FBLMS on-line technique. Substantial reduction is found for cancelling periodic vibration containing single and multiple frequencies. Additionally, the robustness and stability of the control system are validated through transient switching frequency tests.

  2. Integrated active sensor system for real time vibration monitoring

    Liang, Qijie; Yan, Xiaoqin; Liao, Xinqin; Cao, Shiyao; Lu, Shengnan; Zheng, Xin; Zhang, Yue

    2015-11-01

    We report a self-powered, lightweight and cost-effective active sensor system for vibration monitoring with multiplexed operation based on contact electrification between sensor and detected objects. The as-fabricated sensor matrix is capable of monitoring and mapping the vibration state of large amounts of units. The monitoring contents include: on-off state, vibration frequency and vibration amplitude of each unit. The active sensor system delivers a detection range of 0-60 Hz, high accuracy (relative error below 0.42%), long-term stability (10000 cycles). On the time dimension, the sensor can provide the vibration process memory by recording the outputs of the sensor system in an extend period of time. Besides, the developed sensor system can realize detection under contact mode and non-contact mode. Its high performance is not sensitive to the shape or the conductivity of the detected object. With these features, the active sensor system has great potential in automatic control, remote operation, surveillance and security systems.

  3. Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams

    Song, O.; Librescu, L.; Rogers, C. A.

    1992-01-01

    The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.

  4. Active control of noise radiation from vibrating structures

    Mørkholt, Jakob

    The thesis is concerned with the active control of randomly vibrating structures by means of feedback control, with particular emphasis on reducing the sound radiation from such structures. A time domain model of the structural and radiation dynamics of an actively controlled plate has been...... developed, based on the theory of radiation filters for estimating the sound radiation from multimodal vibrations. This model has then been used in simulations of optimal feedback control, with special emphasis of the stability margins of the optimal control scheme. Two different methods of designing...

  5. Integrated Passive and Active Vibration Control of Ultra-precision Lathe

    2000-01-01

    In ultra-precision cutting process, vibration is one of the key factors affecting the machining quality. In this paper, the damping methods of HCM-I Ultra-precision Lathe are discussed in both complete machine and slide. It is pointed out that integrated passive and active vibration control (IPAVC) by combining passive vibration control (PVC) and active vibration control (AVC) can not only eliminate high frequency vibration but also improve the damping effect to low frequency vibration. Experiment results show the effectiveness of the integrated passive and active vibration control.

  6. Active Vibration Reduction Of Rigid Rotor Supported By Journal Bearings

    Ondrouch, Jan; Ferfecki, Petr; Poruba, Z.

    Gliwice: Politechnika Slaska, 2009, s. 85-90. ISBN 978-83-60102-52-7. [International Seminar of Applied Mechanics /13./. Wisla (PL), 29.05.2009-31.05.2009] Institutional research plan: CEZ:AV0Z20760514 Keywords : rotor system * hydrodynamic bearing * active vibration reduction Subject RIV: JR - Other Machinery

  7. Prototype magnetorheological fluid damper for active vibration control system

    S. Duda

    2007-03-01

    Full Text Available Purpose: The paper presents a concept of a system for isolation from external vibration sources with use of a magnetorheological (MR dampers.Design/methodology/approach: Results of experimental studies of a prototype magnetorheological damper at various magnitudes of control current and the manner of modelling electromagnetic phenomena occurring in the damper are presented in this paper. The effect of magnetic field on magnetorheological fluid is modelled by the finite element method. The mathematical model of the system as well as the damper model are outlined along with the relevant control facilities. Numerical simulations were carried out for an exemplary excitation.Findings: The elaborated damper and applied control algorithms substantially influences the values for velocities and accelerations. Incorporation of a controllable damper into the stabilization system significantly decreases displacements of the mass to be stabilized being the results of shocks and bumps caused by excitations w(t as compared to similar displacement of the same mass when only a passive damper was used.Research limitations/implications: For the future research it is necessary to improve characteristics of elaborated damper in order to improve its efficiency.Practical implications: Many mechanical systems should separate from sources of vibrations. The active or semiactive vibration control systems offer a number of advantages as compared with passive systems so that better efficiency of vibration damping is assured.Originality/value: The paper presents new concept of vibration damper with magnetorheological fluids and way of its application in industrial practice.

  8. Vibration control of active structures an introduction

    Preumont, Andre

    2002-01-01

    This text is an introduction to the dynamics of active structures and to the feedback control of lightly damped flexible structures. The emphasis is placed on basic issues and simple control strategies that work.

  9. Modeling and vibration control of an active membrane mirror

    Ruggiero, Eric J.; Inman, Daniel J.

    2009-09-01

    The future of space satellite technology lies in ultra-large mirrors and radar apertures for significant improvements in imaging and communication bandwidths. The availability of optical-quality membranes drives a parallel effort for structural models that can capture the dominant dynamics of large, ultra-flexible satellite payloads. Unfortunately, the inherent flexibility of membrane mirrors wreaks havoc with the payload's on-orbit stability and maneuverability. One possible means of controlling these undesirable dynamics is by embedding active piezoelectric ceramics near the boundary of the membrane mirror. In doing so, active feedback control can be used to eliminate detrimental vibration, perform static shape control, and evaluate the health of the structure. The overall motivation of the present work is to design a control system using distributed bimorph actuators to eliminate any detrimental vibration of the membrane mirror. As a basis for this study, a piezoceramic wafer was attached in a bimorph configuration near the boundary of a tensioned rectangular membrane sample. A finite element model of the system was developed to capture the relevant system dynamics from 0 to 300 Hz. The finite element model was compared against experimental results, and fair agreement found. Using the validated finite element models, structural control using linear quadratic regulator control techniques was then used to numerically demonstrate effective vibration control. Typical results show that less than 12 V of actuation voltage is required to eliminate detrimental vibration of the membrane samples in less than 15 ms. The functional gains of the active system are also derived and presented. These spatially descriptive control terms dictate favorable regions within the membrane domain for placing sensors and can be used as a design guideline for structural control applications. The results of the present work demonstrate that thin plate theory is an appropriate modeling

  10. Active Vibration Control of Satellite Flexible Structures during Attitude Maneuvers

    Saeed Hemmati; Morteza Shahravi; Keramat Malekzadeh

    2013-01-01

    The purpose of this study is controlling active vibration of satellite flexible structures during attitude maneuvers. A smart structure is a structure which is able to sense and control active reaction to any external factors and stimulation. As it comes from the definition of smart structures, development of this knowledge depends on the materials science development, theories and strategies for control. In materials science, smart materials are developed in such a way that they are able to ...

  11. Neuroreceptor Activation by Vibration-Assisted Tunneling

    Hoehn, Ross D; Neven, Hartmut; Kais, Sabre

    2015-01-01

    G protein-coupled receptors (GPCRs) constitute a large family of receptor proteins that sense molecular signals on the exterior of a cell and activate signal transduction pathways within the cell. Modeling how an agonist activates such a receptor is fundamental for an understanding of a wide variety of physiological processes and it is of tremendous value for pharmacology and drug design. Inelastic electron tunneling spectroscopy (IETS) has been proposed as a model for the mechanism by which olfactory GPCRs are activated by a bound agonist. We apply this hypothesis to GPCRs within the mammalian nervous system using quantum chemical modeling. We found that non-endogenous agonists of the serotonin receptor share a particular IET spectral aspect both amongst each other and with the serotonin molecule: a peak whose intensity scales with the known agonist potencies. We propose an experiential validation of this model by utilizing lysergic acid dimethylamide (DAM-57), an ergot derivative, and its deuterated isotopo...

  12. Microgravity Active Vibration Isolation System on Parabolic Flights

    Dong, Wenbo; Pletser, Vladimir; Yang, Yang

    2016-07-01

    The Microgravity Active Vibration Isolation System (MAIS) aims at reducing on-orbit vibrations, providing a better controlled lower gravity environment for microgravity physical science experiments. The MAIS will be launched on Tianzhou-1, the first cargo ship of the China Manned Space Program. The principle of the MAIS is to suspend with electro-magnetic actuators a scientific payload, isolating it from the vibrating stator. The MAIS's vibration isolation capability is frequency-dependent and a decrease of vibration of about 40dB can be attained. The MAIS can accommodate 20kg of scientific payload or sample unit, and provide 30W of power and 1Mbps of data transmission. The MAIS is developed to support microgravity scientific experiments on manned platforms in low earth orbit, in order to meet the scientific requirements for fluid physics, materials science, and fundamental physics investigations, which usually need a very quiet environment, increasing their chances of success and their scientific outcomes. The results of scientific experiments and technology tests obtained with the MAIS will be used to improve future space based research. As the suspension force acting on the payload is very small, the MAIS can only be operative and tested in a weightless environment. The 'Deutsches Zentrum für Luft- und Raumfahrt e.V.' (DLR, German Aerospace Centre) granted a flight opportunity to the MAIS experiment to be tested during its 27th parabolic flight campaign of September 2015 performed on the A310 ZERO-G aircraft managed by the French company Novespace, a subsidiary of the 'Centre National d'Etudes Spatiales' (CNES, French Space Agency). The experiment results confirmed that the 6 degrees of freedom motion control technique was effective, and that the vibration isolation performance fulfilled perfectly the expectations based on theoretical analyses and simulations. This paper will present the design of the MAIS and the experiment results obtained during the

  13. Anharmonic Effects on Vibrational Spectra Intensities: Infrared, Raman, Vibrational Circular Dichroism, and Raman Optical Activity.

    Bloino, Julien; Biczysko, Malgorzata; Barone, Vincenzo

    2015-12-10

    The aim of this paper is 2-fold. First, we want to report the extension of our virtual multifrequency spectrometer (VMS) to anharmonic intensities for Raman optical activity (ROA) with the full inclusion of first- and second-order resonances for both frequencies and intensities in the framework of the generalized second-order vibrational perturbation theory (GVPT2) for all kinds of vibrational spectroscopies. Then, from a more general point of view, we want to present and validate the performance of VMS for the parallel analysis of different vibrational spectra for medium-sized molecules (IR, Raman, VCD, ROA) including both mechanical and electric/magnetic anharmonicity. For the well-known methyloxirane benchmark, careful selection of density functional, basis set, and resonance thresholds permitted us to reach qualitative and quantitative agreement between experimental and computed band positions and shapes. Next, the whole series of halogenated azetidinones is analyzed, showing that it is now possible to interpret different spectra in terms of mass, electronegativity, polarizability, and hindrance variation between closely related substituents, chiral spectroscopies being particular effective in this connection. PMID:26580121

  14. Active Vibration Control of a Monopile Offshore Structure

    Nielsen, Søren R. K.; Kirkegaard, Poul Henning; Thesbjerg, L.

    1996-01-01

    structure an active control technique has been proposed in corporation with the consulting company Rambøll, Esbjerg, Denmark. The proposed control technique is based on the relationship between the position of the separation points of the boundary layer flow and the drag term in the wave force on the......, it can be necessary to use an active or a passive vibration control system. However, for a monopile with severe space problems it can be difficult to locate a passive control system such as e.g. a tuned mass damper. Therefore, in order to active control wave introduced vibrations of a monopile...... cylinder. This concept has been experimentally investigated with a test model in stationary flow tests. The idea is to have a large drag coefficient when the cylinder moves opposite of the wave direction implying a relatively large damping excitation. When the structure moves in the wave direction a small...

  15. Wireless sensor networks for active vibration control in automobile structures

    Mieyeville, Fabien; Ichchou, Mohamed; Scorletti, Gérard; Navarro, David; Du, Wan

    2012-07-01

    Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control.

  16. Online identification of active absorbers in automotive vibration control

    Buttelmann, M.; Lohmann, B.; Vinogradski, M.; Nedeljkovic, N. [Bremen Univ. (Germany). Inst. fuer Automatisierungstechnik; Marienfeld, P. [ContiTech Vibration Control GmbH, Hannover (Germany); Svaricek, F. [Continental Gummi-Werke AG, Hannover (Germany)

    2001-07-01

    In the past, engine-related noise and vibration in the vehicle cabin was exclusively reduced by passive absorption. Today, modern actuators and control systems make an active noise reduction possible by introducing counteracting vibration at 180 degrees phase lag. Within a cooperation of the Institute of Automation Systems and Continental AG, an approach using active absorbers at the engine mounts is investigated. As the dynamic behaviour of the active absorbers and other elements in the secondary path are time-variant (depending on temperature, age and other factors), an online identification is carried out. By this, the implemented feedforward control strategy is supported on a precise and frequently updated model of the secondary path. The chosen approaches to online and offline identification are presented together with first results achieved in online identification and with the overall control system. (orig.)

  17. Wireless sensor networks for active vibration control in automobile structures

    Wireless sensor networks (WSNs) are nowadays widely used in monitoring and tracking applications. This paper presents the feasibility of using WSNs in active vibration control strategies. The method employed here involves active-structural acoustic control using piezoelectric sensors distributed on a car structure. This system aims at being merged with a WSN whose head node collects data and processes control laws so as to command piezoelectric actuators wisely placed on the structure. We will study the feasibility of implementing WSNs in active vibration control and introduce a complete design methodology to optimize hardware/software and control law synergy in mechatronic systems. A design space exploration will be conducted so as to identify the best WSN platform and the resulting impact on control. (paper)

  18. Vibration Suppression of a Helicopter Fuselage by Pendulum Absorbers : Rigid-Body Blades with Aerodynamic Excitation Force

    Nagasaka, Imao; Ishida, Yukio; Koyama, Takayuki; Fujimatsu, Naoki

    Currently, some kinds of helicopters use pendulum absorbers in order to reduce vibrations. Present pendulum absorbers are designed based on the antiresonance concept used in the linear theory. However, since the vibration amplitudes of the pendulum are not small, it is considered that the nonlinearity has influence on the vibration characteristics. Therefore, the best suppression cannot be attained by using the linear theory. In a helicopter, periodic forces act on the blades due to the influences of the air thrust. These periodic forces act on the blades with the frequency which is the integer multiple of the rotational speed of the rotor. Our previous study proposed a 2-degree-of-freedom (2DOF) model composed of a rotor blade and a pendulum absorber. The blade was considered as a rigid body and it was excited by giving a sinusoidal deflection at its end. The present paper proposes a 3DOF model that is more similar to the real helicopter, since the freedom of the fuselage is added and the periodic forces are applied to the blade by aerodynamic force. The vibration is analyzed considering the nonlinear characteristics. The resonance curves of rotor blades with pendulum absorbers are obtained analytically and experimentally. It is clarified that the most efficient condition is obtained when the natural frequency of the pendulum is a little bit different from the frequency of the external force. Various unique nonlinear characteristics, such as bifurcations, are also shown.

  19. Vibration control of cylindrical shells using active constrained layer damping

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  20. Actively Controlled Landing Gear for Aircraft Vibration Reduction

    Horta, Lucas G.; Daugherty, Robert H.; Martinson, Veloria J.

    1999-01-01

    Concepts for long-range air travel are characterized by airframe designs with long, slender, relatively flexible fuselages. One aspect often overlooked is ground induced vibration of these aircraft. This paper presents an analytical and experimental study of reducing ground-induced aircraft vibration loads using actively controlled landing gears. A facility has been developed to test various active landing gear control concepts and their performance. The facility uses a NAVY A6-intruder landing gear fitted with an auxiliary hydraulic supply electronically controlled by servo valves. An analytical model of the gear is presented including modifications to actuate the gear externally and test data is used to validate the model. The control design is described and closed-loop test and analysis comparisons are presented.

  1. Active Vibration Control of Rotor-Bearing Systems

    Blanco-Ortega, Andres; Silva-Navaro, Gerardo; Beltran-Carbajal, Francisco; Vela-Valdes, Luis Gerardo

    2010-01-01

    The active vibration control of a Jeffcott-like rotor through dynamic stiffness control and acceleration scheduling is addressed. The control approach consists of a servomechanism able to move one of the supporting bearings in such a way that the effective rotor length is controlled. As a consequence, the rotor stiffness and natural frequency are modified according to an off-line and smooth trajectory planning of the rotor speed/acceleration in order to reduce the unbalance response when pass...

  2. Active Vibration Suppression R and D for the NLC

    The nanometer scale beam sizes at the interaction point in linear colliders limit the allowable motion of the final focus magnets. We have constructed a prototype system to investigate the use of active vibration damping to control magnet motion. Inertial sensors are used to measure the position of a test mass, and a DSP based system provides feedback using electrostatic pushers. Simulation and experimental results for the control of a mechanically simple system are presented

  3. Adaptive active vibration isolation – A control perspective

    Landau Ioan Doré

    2015-01-01

    The paper will review a number of recent developments for adaptive feedback compensation of multiple unknown and time-varying narrow band disturbances and for adaptive feedforward compensation of broad band disturbances in the presence of the inherent internal positive feedback caused by the coupling between the compensator system and the measurement of the image of the disturbance. Some experimental results obtained on a relevant active vibration control system will illustrate the performance of the various algorithms presented.

  4. Active elastic metamaterials with applications in vibration and acoustics

    Pope, Simon A.; Laalej, Hatim; Daley, Stephen; Reynolds, Matthew

    2012-01-01

    Elastic metamaterials provide a new approach to solving existing problems in vibration and acoustics. They have also been associated with novel concepts such as acoustic invisibility and subwavelength imaging. To be applied to many of the proposed applications a metamaterial would need to have the desired mass density and elastic moduli over a prescribed frequency band. Importantly active metamaterials provide a degree of adaptability. This paper will focus on extending a previous theoretical...

  5. Active vibration control techniques for flexible space structures

    Parlos, Alexander G.; Jayasuriya, Suhada

    1990-01-01

    Two proposed control system design techniques for active vibration control in flexible space structures are detailed. Control issues relevant only to flexible-body dynamics are addressed, whereas no attempt was made to integrate the flexible and rigid-body spacecraft dynamics. Both of the proposed approaches revealed encouraging results; however, further investigation of the interaction of the flexible and rigid-body dynamics is warranted.

  6. Optically active vibrational modes of PPV derivatives on textile substrate

    In this work, MEH-PPV and BDMO-PPV films were deposited by spin-coating on “dirty” textile substrates of canvas, nylon, canvas with resin, jeans and on glass and the temperature dependence of the optical properties of them was studied by photoluminescence and Raman (300 K) techniques. The temperature dependence of the energy, of the half line width at half height of the purely electronic peak, of the integrated PL intensity and of the Huang-Rhys factor, S=I(01)/I(00), were obtained directly from the PL spectrum. For an analysis of the vibrational modes involved, Raman measurements were performed on substrates with and without polymers deposited and the results compared with those found in the literature. The films of MEH-PPV and BDMO-PPV showed optical properties similar to those films deposited on other substrates such as glass, metals, etc. It was observed an inversion of the first vibrational band in relation to the purely electronic peak with increasing temperature in the films deposited on nylon and canvas. The vibrational modes obtained by Raman were used to compose the simulation of the PL line shape of BDMO-PPV films on canvas and nylon, using a model proposed by Lin [29]. - Highlights: ► MEH-PPV and BDMO-PPV films were deposited by spin-coating on dirty textile. ► Their properties were studied by photoluminescence and Raman techniques. ► We observed inversion of first vibrational band in relation to purely electronic peak. ► Optically active vibrational modes of PPV derivatives were studied.

  7. Vibrations of wind power plants; Schwingungen von Windenergieanlagen

    NONE

    2010-07-01

    Within the meeting of the department vibration engineering of the Association of German Engineers (Duesseldorf, Federal Republic of Germany) between 3rd and 4th February, 2010 in Hanover (Federal Republic of Germany) the following lectures are presented: (1) Reduction of forced strengths generated by wagging and snaking of the rotor in the power strain of wind power plants (F. Mitsch); (2) Reduction of vibrations at wind power plants by means of active additional systems (S. Katz, S. Pankoke, N. Loix); (3) Reduction of vibrations by means of balancing and alignment (E. Becker, M. Kenzler); (4) Active absorber for reducing tonal emissions of vibration at wind power plants (R. Neugebauer, M. Linke, H. Kunze, M. Ulrich); (5) Control structures for damping torsion vibrations and peak loads in the power strain of wind power converters (C. Sourkounis); (6) Possibilities of a non-contact investigation of vibrations at wind power plants (R. Behrendt, E. Reimers, H. Wiegers); (7) Influences on the loadability of CMS statements (R. Wirth); (8) Recording modal structural properties with sensor grids and methods of operational modal analysis (A. Friedmann, D. Mayer, M. Koch, M. Kauba, T. Melz); (9) Early failure detection of damages of roller bearings in wind power gear units with variable speed (B. Hacke, G. Poll); (10) Condition monitoring in wind power plants - structure monitoring and life time monitoring of wind power plants (SCMS and LCMS) (H. Lange); (11) Development of a model-based structural health monitoring system for condition monitoring of rotor blades (C. Ebert, H. Friedmann, F.O. Henkel, B. Frankenstein, L. Schubert); (12) Efficient remote monitoring at wind power plants by means of an external diagnosis centre (G. Ceglarek); (13) Accurate turbine modelling at component and assembly level for durability and acoustic analysis (D. v. Werner, W. Hendricx); (14) Possibilities of the investigation of the dynamic behaviour of power strains in wind power plants by

  8. Coupled Torsional and Bending Vibrations of Actively Controlled Drillstrings

    YIGIT, A. S.; CHRISTOFOROU, A. P.

    2000-06-01

    The dynamics of actively controlled drillstrings is studied. The equations of motion are derived using a lumped parameter model in which the coupling between torsional and bending vibrations is considered. The model also includes the dynamics of the rotary drive system which contains the rotary table, the gearbox and an armature controlled DC motor. The interactions between the drillstring and the borehole which are considered, include the impacts of collars with the borehole wall as well as bit rotation-dependent weight and torque on bit (WOB and TOB). Simulation results obtained by numerically solving the equations of motion are in close qualitative agreement with field and laboratory observations regarding stick-slip oscillations. A linear quadratic regulator (LQR) controller is designed based on a linearized model and is shown to be effective in eliminating this type of oscillations. It is also shown that for some operational parameters the control action may excite large bending vibrations due to coupling with the torsional motion.

  9. Research of Air-Magnet Active Vibration Isolation System Based on H∞ Control

    Wen Xianglong

    2015-01-01

    Full Text Available Considering the uncertainty of air-magnet active vibration isolation system (AMAVIS, passive vibration isolation was combined with active vibration isolation, which adopted H∞ control strategies. System identification method was used to get the channel model. By adopting mixed sensitivity design strategy, weighting functions were chosen and H∞ controller was designed. Both simulation results and experimental results show AMAVIS based on H∞ control had satisfying effect of vibration reduction in assigned frequency band.

  10. 旋翼复合材料桨叶弹损穿孔的有限元建模方法%FINITE ELEMENT MODLEING METHOD OF COMPOSITE ROTOR BLADE WITH BALLISTIC PERFORATION

    孙中涛; 王华明

    2013-01-01

    军用直升机旋翼桨叶具有抗弹击设计要求.根据复合材料桨叶的结构特点和工作特性,提出了建立复合材料桨叶弹击穿孔有限元模型的等截面节点移除法,该建模方法先采用等截面拉伸建立桨叶典型结构段的三维模型,然后将弹孔处的节点移除以模拟桨叶的弹损状况.所建立的桨叶弹损模型具有较高的置信度和可接受的解算规模,可作为进一步研究复合材料桨叶抗弹击性能的基础.%The military helicopter rotor blade has design requirement of sustaining some kind of ballistic damage. According to the structural properties and operating characteristics of composite blades, this article provides an even cross-section and node removed method to build finite elements model of composite blade with ballistic perforation. This modeling method builds three-dimensional model of blade typical section by even cross-section tension, then nodes around bullet holes are removed to simulate ballistic damage of the blade. The model of ballistic blade built in this article has a high degree of confidence and an acceptable solver scale, it can be used for further research of composite blades performance of resisting ballistic damage.

  11. Smart materials and active noise and vibration control in vehicles

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, M. van [TNO Institute of Applied Physics, Delft (Netherlands)

    2001-07-01

    Results are presented for the reduction of sound radiated from a structure using different control methodologies. Two approaches for active structural acoustic control are mentioned to reduce sound radiated by the structure: the acoustic approach or the vibro-acoustic approach. In both cases integrated actuators in structure materials are necessary to realise feasible products. Furthermore the development of an efficient shaker for Active Isolation techniques is described. The prototype of TNO TPD can produce a force of 400 N up to 250 Hz at a good performance-volume ratio. To enhance the robustness of the active control applications, the use of the subspace identification based control methods are developed. The robustness property of subspace identification methods forms the basis of an accurate model updating mechanism, using small size data batches. The performed simulations reveal excellent robustness performance under very general noise conditions or during operation of the control system. Furthermore the development of the techniques can be exploited to realise sound comfort requirements to enhance audible communications of vehicle related applications. To anticipate to these developments in the automotive industry, TNO has set up a Sound and Vibrations Research Centre with Twente University and a research program on Smart Panels with the Delft University. To investigate the potential markets and applications for sound comfort in the means of transportation, TNO-TPD and the Institute of Sound and Vibration Research in England (ISVR) have agreed on a cooperative venture to develop and realise 'active control of electroacoustics' (ACE). (orig.)

  12. Real Time Vibration Control of Active Suspension System with Active Force Control using Iterative Learning Algorithm

    Kalaivani

    2013-09-01

    Full Text Available This paper presents concurrent vibration control of a laboratory scaled vibration isolator platform with Active Force Control (AFC using Iterative Learning Algorithm (ILA. The work investigates the performance of the traditional Proportional Integral Derivative Controller (PIDC with and without AFC using ILA for vibration suppression. The physical single degree of freedom quarter car has been interfaced with a personal computer using a National Instruments data acquisition card NI USB 6008. The controllers are designed and simulated using LabVIEW simulation software. The results infer that the PIDC with AFC using ILA works superior than the PIDC.

  13. Computational Fluid Dynamic Analysis of a Vibrating Turbine Blade

    Osama N. Alshroof

    2012-01-01

    Full Text Available This study presents the numerical fluid-structure interaction (FSI modelling of a vibrating turbine blade using the commercial software ANSYS-12.1. The study has two major aims: (i discussion of the current state of the art of modelling FSI in gas turbine engines and (ii development of a “tuned” one-way FSI model of a vibrating turbine blade to investigate the correlation between the pressure at the turbine casing surface and the vibrating blade motion. Firstly, the feasibility of the complete FSI coupled two-way, three-dimensional modelling of a turbine blade undergoing vibration using current commercial software is discussed. Various modelling simplifications, which reduce the full coupling between the fluid and structural domains, are then presented. The one-way FSI model of the vibrating turbine blade is introduced, which has the computational efficiency of a moving boundary CFD model. This one-way FSI model includes the corrected motion of the vibrating turbine blade under given engine flow conditions. This one-way FSI model is used to interrogate the pressure around a vibrating gas turbine blade. The results obtained show that the pressure distribution at the casing surface does not differ significantly, in its general form, from the pressure at the vibrating rotor blade tip.

  14. Active vibration control of multibody system with quick startup and brake based on active damping

    TANG Hua-ping; TANG Yun-jun; TAO Gong-an

    2006-01-01

    A kind of active vibration control method was presented based on active damping and optimization design for driving load of multibody system with quick startup and brake. Dynamical equation of multibody system with quick startup and brake and piezoelectric actuators intelligent structure was built. The optimum driving load was calculated by applying the presented method. The self-sensing and self-tuning closed-loop active vibration control in quick startup and brake process was realized. The control algorithm, using local velocity negative feedback, i.e. the output of a sensor only affects the output of the actuator collocated, can induce damping effectively to actively suppress the system vibration. Based on the optimization design for driving load of multibody system with quick startup and bake, the active damping of piezoelectric actuators intelligent structure was used to farther suppress the vibration of system. Theoretical analysis and calculation of numerical show that the proposed method makes the vibration of system decrease more than the optimal design method for driving load of multibody system.

  15. Vibrational spectra, structure and antioxidant activity of gossypol imine derivatives

    Ilkevych, N. S.; Schroeder, G.; Rybachenko, V. I.; Chotiy, K. Y.; Makarova, R. A.

    2012-02-01

    The structures and tautomeric equilibria of natural polyphenol gossypol and four its imine derivatives were studied by FT-IR-, NMR-spectroscopy and quantum chemistry methods. It was shown that gossypol Schiff bases exist in solution as enamine-enamine tautomer and hydrazones as imine-imine tautomer. Infrared absorption spectra of studied compounds were simulated using the PM3 method. The fundamental vibrational frequencies were evaluated using various scale factors which yield a good agreement between observed and calculated frequencies. Free radical scavenging activity of gossypol and its imine derivatives was evaluated using DPPH method. Antioxidant activity of studied compounds was characterized. Gossypol hydrazones were shown to be more efficient, while Schiff base to be less efficient as antioxidants in comparison with gossypol itself.

  16. Aerodynamic unsteady loads and vibrations of steam turbine L.P. blades

    In steam turbines, the aerodynamic sources of the blades vibrations for low pressure stages can induce a high stress level for some operating points. Therefore theoretical and experimental investigations are performed at E.D.F. They specially focus on the turbine rotor-stator interaction and the aerolastic rotor stability. A numerical method has been developed for predicting the aerodynamic damping of one cascade of profiles. The insteady flow calculation is based on the boundary element method, and is performed for the blade-to-blade surfaces. The results obtained on the first flexural mode for the L.P. blades of a 900 MW steam turbine, for several displacements and for several interblade phase angles, exhibits no instability of the rotor except low phase angles, but it is difficult to investigate these cases. The numerical results also support the relevance of the quasi-steady assumption. The same method has been used to calculate the rotor-stator interaction in the case of a potential flow. The main parameters are the gap between the two rows and the stator blade number/rotor blade number ratio (NR/NS). The results show that the dynamic loads strongly decrease with respect to the gap increase. Otherwise NR/NS = 2 (periodical pattern), which is a good approximation of the industrial value, provides slight unsteady loads on the rotor blades comparatively to other values

  17. Active vibration control of spatial flexible multibody systems

    Neto, Maria Augusta, E-mail: augusta.neto@dem.uc.pt [Universidade de Coimbra (Polo II), Departamento de Engenharia Mecanica, Faculdade de Ciencia e Tecnologia (Portugal); Ambrosio, Jorge A. C., E-mail: jorge@dem.ist.utl.pt [Instituto Superior Tecnico, Instituto de Engenharia Mecanica (Portugal); Roseiro, Luis M., E-mail: lroseiro@isec.pt [Instituto Superior de Engenharia de Coimbra, Departamento de Engenharia Mecanica (Portugal); Amaro, A., E-mail: ana.amaro@dem.uc.pt [Universidade de Coimbra (Polo II), Departamento de Engenharia Mecanica, Faculdade de Ciencia e Tecnologia (Portugal); Vasques, C. M. A., E-mail: cvasques@inegi.up.pt [Universidade do Porto, INEGI-Instituto de Engenharia Mecanica e Gestao Industrial (Portugal)

    2013-06-15

    In this work a flexible multibody dynamics formulation of complex models including elastic components made of composite materials is extended to include piezoelectric sensors and actuators. The only limitation for the deformation of a structural member is that they must remain elastic and linear when described in a coordinate frame fixed to a material point or region of its domain. The flexible finite-element model of each flexible body is obtained referring the flexible body nodal coordinates to the body fixed frame and using a diagonalized mass description of the inertia in the mass matrix and on the gyroscopic force vector. The modal superposition technique is used to reduce the number of generalized coordinates to a reasonable dimension for complex shaped structural models of flexible bodies. The active vibration control of the flexible multibody components is implemented using an asymmetric collocated piezoelectric sensor/actuator pair. An electromechanically coupled model is taken into account to properly consider the surface-bonded piezoelectric transducers and their effects on the time and spatial response of the flexible multibody components. The electromechanical effects are introduced in the flexible multibody equations of motion by the use of beam and plate/shell elements, developed to this purpose. A comparative study between the classical control strategies, constant gain and amplitude velocity feedback, and optimal control strategy, linear quadratic regulator (LQR), is performed in order to investigate their effectiveness to suppress vibrations in structures with piezoelectric sensing and actuating patches.

  18. Active vibration control of spatial flexible multibody systems

    In this work a flexible multibody dynamics formulation of complex models including elastic components made of composite materials is extended to include piezoelectric sensors and actuators. The only limitation for the deformation of a structural member is that they must remain elastic and linear when described in a coordinate frame fixed to a material point or region of its domain. The flexible finite-element model of each flexible body is obtained referring the flexible body nodal coordinates to the body fixed frame and using a diagonalized mass description of the inertia in the mass matrix and on the gyroscopic force vector. The modal superposition technique is used to reduce the number of generalized coordinates to a reasonable dimension for complex shaped structural models of flexible bodies. The active vibration control of the flexible multibody components is implemented using an asymmetric collocated piezoelectric sensor/actuator pair. An electromechanically coupled model is taken into account to properly consider the surface-bonded piezoelectric transducers and their effects on the time and spatial response of the flexible multibody components. The electromechanical effects are introduced in the flexible multibody equations of motion by the use of beam and plate/shell elements, developed to this purpose. A comparative study between the classical control strategies, constant gain and amplitude velocity feedback, and optimal control strategy, linear quadratic regulator (LQR), is performed in order to investigate their effectiveness to suppress vibrations in structures with piezoelectric sensing and actuating patches.

  19. Reduction of helicopter blade-vortex interaction noise by active rotor control technology

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Philippe, Jean J.; Prieur, Jean; Brooks, Thomas F.

    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade-vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

  20. Reduction of Helicopter Blade-Vortex Interaction Noise by Active Rotor Control Technology

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Brooks, Thomas F.; Philippe, Jean J.; Prieur, Jean

    1997-01-01

    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  1. Active Vibration Isolation System for Sub-microultra-precision Turning Machine

    2000-01-01

    Now vibration isolation of ultra-precision machine tool is usually achieved through air-springs systems. As far as HCM-I sub-micro turning machine developed by HIT, an active vibration isolation system that consists of air-springs and electro-magnetic actuators was presented. The primary function of air-springs is to support the turning machine and to isolate the high-frequency vibration. The electro-magnetic actuators controlled by fuzzy-neural networks isolate the low-frequency vibration. The experiment indicates that active vibration isolation system isolates base-vibration effectively in all the frequency range. So the vibration of the machine bed is controlled under 10-6g and the surface roughness is improved.

  2. Numerical Simulation of Supersonic Flow Field in Rotor Blade Cascade for Impulse Torpedo Turbine%纯冲动式鱼雷涡轮机动叶栅超音速流动数值仿真

    郭兆元; 曹浩; 赵卫兵

    2013-01-01

      为了研究鱼雷涡轮机通流道内的流动特征进而指导涡轮通流结构设计,在合理简化模型基础上,采用计算流体力学(CFD)方法对纯冲动式鱼雷涡轮发动机转子动叶流道内超音速流动状况进行了数值仿真,详细分析了叶栅内流动状况、总压损失、叶片气动载荷和温度载荷。仿真结果表明,动叶流道内流动比较复杂,攻角对其内的流动有较大影响,该数值越大,附面层分离越严重,激波越强,总压损失也越大;同一个叶片在经过喷嘴流域时,其气动载荷呈现先增大后减小的趋势,受交变的气动力作用,而叶片气动承受载荷越大其温度载荷就越小,叶片内的温度梯度就越小。%To study fluid characteristic in torpedo turbine flow passages and guide structure design of the flow passag-es, the flow field in rotor blade cascade of an impulse supersonic torpedo turbine was numerically investigated by computational fluid dynamics (CFD) method. The detail information of flow, total pressure loss, and aerodynamic load and temperature load on a blade were analyzed. Simulation results show that: flow in rotor flow passages is very com-plicated; blade incidence angle exerts significant effect on the flow; the larger the incidence angle, the more severe the boundary layer separation, the stronger the shock wave, and the more the total pressure loss; when a blade is pass through the nozzle area, the aerodynamic load on it first increases and then decreases; heavier aerodynamic load leads to smaller temperature load and temperature gradient in the blade.

  3. 鱼雷涡轮机叶片顶部气封流场数值研究%Numerical Investigation on the Tip Leakage Flow of Rotor Blade of Torpedo Turbine

    伊进宝; 赵卫兵; 师海潮

    2011-01-01

    A three-dimensional(3D) viscous and steady computational fluid dynamics(CFD) analysis is performed for calculating turbine rotor tip leakage flow field of a torpedo by solving RANS-Navier-Stocks equations. The effect of different seal structure on turbine passage efficiency and rotor tip leakage flow is studied. Different numbers of sealing fins at the rotor blade are simulated, and the influence of the number of sealing fins on turbine passage efficiency and rotor tip leakage flow characteristic is analyzed. The results show that the turbine efficiency is improved remarkably after applying the seal technology. Compared with comb-type seal structure, the labyrinth seal exhibits better airtight performance. The leakage flow in the labyrinth seal housing forms 3D vortex current which transform the kinetic energy of the leakage flow into heat energy, and leads to a decrease in the seal leakage flow rate of the labyrinth seal. Airtight performance gets better with increasing number of fins.%通过求解雷诺平均的NAVIER-STOKES方程组,数值计算了带气封围带结构的鱼雷涡轮机动叶顶部间隙内部3D流场及特性,研究了不同气封结构形式对涡轮机通流效率和动叶顶部泄漏流动的作用,比较了迷宫式气封不同齿数下动叶间隙泄漏气流的流动特性,分析了迷宫式气封齿数对鱼雷涡轮机通流效率和泄漏特性的影响.研究表明,在叶片顶部间隙中采用气封结构能够有效减小燃气泄露流量,提高涡轮机通流气动性能;在相同气封齿数下,迷宫式气封结构要比一般梳齿型气封结构密封效果好;迷宫气封通过气流在气封齿间空腔形成的3D涡流,将气流动能转化为热能,从而起到密封效果;气封齿数越多,密封效果越好,对涡轮机通流性能的改善也越大.

  4. Active low-frequency vertical vibration isolation system for precision measurements

    Wu, Kang; Li, Gang; Hu, Hua; Wang, Lijun

    2016-06-01

    Low-frequency vertical vibration isolation systems play important roles in precision measurements to reduce seismic and environmental vibration noise. Several types of active vibration isolation systems have been developed. However, few researches focus on how to optimize the test mass install position in order to improve the vibration transmissibility. An active low-frequency vertical vibration isolation system based on an earlier instrument, the Super Spring, is designed and implemented. The system, which is simple and compact, consists of two stages: a parallelogram-shaped linkage to ensure vertical motion, and a simple spring-mass system. The theoretical analysis of the vibration isolation system is presented, including terms erroneously ignored before. By carefully choosing the mechanical parameters according to the above analysis and using feedback control, the resonance frequency of the system is reduced from 2.3 to 0.03 Hz, a reduction by a factor of more than 75. The vibration isolation system is installed as an inertial reference in an absolute gravimeter, where it improved the scatter of the absolute gravity values by a factor of 5. The experimental results verifies the improved performance of the isolation system, making it particularly suitable for precision experiments. The improved vertical vibration isolation system can be used as a prototype for designing high-performance active vertical isolation systems. An improved theoretical model of this active vibration isolation system with beam-pivot configuration is proposed, providing fundamental guidelines for vibration isolator design and assembling.

  5. Tuning of active vibration controllers for ACTEX by genetic algorithm

    Kwak, Moon K.; Denoyer, Keith K.

    1999-06-01

    This paper is concerned with the optimal tuning of digitally programmable analog controllers on the ACTEX-1 smart structures flight experiment. The programmable controllers for each channel include a third order Strain Rate Feedback (SRF) controller, a fifth order SRF controller, a second order Positive Position Feedback (PPF) controller, and a fourth order PPF controller. Optimal manual tuning of several control parameters can be a difficult task even though the closed-loop control characteristics of each controller are well known. Hence, the automatic tuning of individual control parameters using Genetic Algorithms is proposed in this paper. The optimal control parameters of each control law are obtained by imposing a constraint on the closed-loop frequency response functions using the ACTEX mathematical model. The tuned control parameters are then uploaded to the ACTEX electronic control electronics and experiments on the active vibration control are carried out in space. The experimental results on ACTEX will be presented.

  6. Voice Coil Actuator for Active Vibration Isolation in Microgravity

    Brusa, E.; Carabelli, S.; Genta, G.; Maddaleno, F.; Silvagni, M.; Tonoli, A.

    2002-01-01

    Many microgravity experiments require very low levels of acceleration which cannot be achieved on the International Space Station due to the residual vibration. A vibration isolation system is then usually devised between the experiment and the space station to obtain the desired accelerations at the experiment level. The very low frequency threshold required by the isolation specifications makes passive solutions for the isolation difficult to implement. This is mainly due to the practical impossibility of achieving high values of compliance of the elastic suspension. Furthermore, the unavoidable connections of uncertain characteristics between the experiment and the space station makes the problem even more difficult to be addressed. Disturbance reduction can be performed by means of active vibration isolation, based on magnetic suspension technology acting both at rack and at scientific experiment levels. The stiffness and damping of the active suspension can be tuned by the control loop to minimise the acceleration of the payload. The mechatronic design of an active magnetic suspension for vibration isolation in microgravity has been performed by resorting to the so-called voice-coil configuration, after a preliminary trade-off analysis of the available magnetic actuators and materials. The optimisation of the actuator layout was developed with respect to the design airgap and force density (N/kg of actuator) and force resolution requirements, by demonstrating that the configuration based on Lorentz magnetic force is more suitable for the above application in terms of stability, bi- directionality of the actuation, cross coupling effects and linearity of the force. The aim of the design was the maximisation of the actuation force/mass ratio. The FEM analysis of the voice coil allowed to investigate the flux leakage and the cross coupling effects between the actuation forces along the three principal directions of the active device. A procedure for the numerical

  7. Active vibration and balance system for closed cycle thermodynamic machines

    Qiu, Songgang (Inventor); Augenblick, John E. (Inventor); Peterson, Allen A. (Inventor); White, Maurice A. (Inventor)

    2004-01-01

    An active balance system is provided for counterbalancing vibrations of an axially reciprocating machine. The balance system includes a support member, a flexure assembly, a counterbalance mass, and a linear motor or an actuator. The support member is configured for attachment to the machine. The flexure assembly includes at least one flat spring having connections along a central portion and an outer peripheral portion. One of the central portion and the outer peripheral portion is fixedly mounted to the support member. The counterbalance mass is fixedly carried by the flexure assembly along another of the central portion and the outer peripheral portion. The linear motor has one of a stator and a mover fixedly mounted to the support member and another of the stator and the mover fixedly mounted to the counterbalance mass. The linear motor is operative to axially reciprocate the counterbalance mass. A method is also provided.

  8. Cryogenic Ion Vibrational Spectroscopy of - CH Activation Intermediates

    Marsh, Brett; Garand, Etienne

    2013-06-01

    Despite the rather simple composition of alkanes the strength of their C-C and C-H bonds has made controlled, selective reaction of these compounds an unrealized goal of synthetic chemistry. The field was pioneered by Shilov and coworkers in 1969 when they observed the exchange of H and D in methane that was bubbled into an acidic solution of K_2PtCl_4. The Shilov reaction has since been extended to induce oxidation of methane selectively to methanol and has become the standard bearer of CH activation despite its limitations. The mechanism for the reaction, while inferred from kinetics studies, is still largely uncharacterized. Here, we present our work towards applying cryogenic ion vibrational spectroscopy (CIVS) to capture the intermediate species of this reaction with a focus on the σ-CH adduct formed between methane and Pt(II) complexes that is believed to be crucial to the selectivity and rate of this reaction.

  9. Extended aeroelastic analysis for helicopter rotors with prescribed hub motion and blade appended penduluum vibration absorbers

    Bielawa, R. L.

    1984-01-01

    The mathematical development for the expanded capabilities of the G400 rotor aeroelastic analysis was examined. The G400PA expanded analysis simulates the dynamics of all conventional rotors, blade pendulum vibration absorbers, and the higher harmonic excitations resulting from prescribed vibratory hub motions and higher harmonic blade pitch control. The methodology for modeling the unsteady stalled airloads of two dimensional airfoils is discussed. Formulations for calculating the rotor impedance matrix appropriate to the higher harmonic blade excitations are outlined. This impedance matrix, and the associated vibratory hub loads, are the rotor dynamic characteristic elements for use in the simplified coupled rotor/fuselage vibration analysis (SIMVIB). Updates to the development of the original G400 theory, program documentation, user instructions and information are presented.

  10. Performance of active vibration control technology: the ACTEX flight experiments

    Nye, T. W.; Manning, R. A.; Qassim, K.

    1999-12-01

    This paper discusses the development and results of two intelligent structures space-flight experiments, each of which could affect architecture designs of future spacecraft. The first, the advanced controls technology experiment I (ACTEX I), is a variable stiffness tripod structure riding as a secondary payload on a classified spacecraft. It has been operating well past its expected life since becoming operational in 1996. Over 60 on-orbit experiments have been run on the ACTEX I flight experiment. These experiments form the basis for in-space controller design problems and for concluding lifetime/reliability data on the active control components. Transfer functions taken during the life of ACTEX I have shown consistent predictability and stability in structural behavior, including consistency with those measurements taken on the ground prior to a three year storage period and the launch event. ACTEX I can change its modal characteristics by employing its dynamic change mechanism that varies preloads in portions of its structure. Active control experiments have demonstrated maximum vibration reductions of 29 dB and 16 dB in the first two variable modes of the system, while operating over a remarkable on-orbit temperature range of -80 °C to 129 °C. The second experiment, ACTEX II, was successfully designed, ground-tested, and integrated on an experimental Department of Defense satellite prior to its loss during a launch vehicle failure in 1995. ACTEX II also had variable modal behavior by virtue of a two-axis gimbal and added challenges of structural flexibility by being a large deployable appendage. Although the loss of ACTEX II did not provide space environment experience, ground testing resulted in space qualifying the hardware and demonstrated 21 dB, 14 dB, and 8 dB reductions in amplitude of the first three primary structural modes. ACTEX II could use either active and/or passive techniques to affect vibration suppression. Both experiments trailblazed

  11. Active Vibration Isolation Control: Comparison of Feedback and Feedforward Control Strategies Applied to Coriolis Mass-Flow Meters (I)

    Ridder, de, J.; Hakvoort, W.B.J.; van Dijk

    2015-01-01

    In this paper we describe the design, implementation and results of multi degree of freedom (DOF) active vibration control for a Coriolis mass-flow meter (CMFM). Without vibration control, environmental vibrational disturbances results in nanometre movement of the fluid-conveying tube which causes erroneous mass-flow measurements. In order to reduce the transmissibility from external vibrations to the internal tube displacement active vibration control is applied. A comparison of a feedback c...

  12. Aerodynamics of Rotor Blades for Quadrotors

    Bangura, Moses; Naldi, Roberto; Mahony, Robert

    2016-01-01

    In this report, we present the theory on aerodynamics of quadrotors using the well established momentum and blade element theories. From a robotics perspective, the theoretical development of the models for thrust and horizontal forces and torque (therefore power) are carried out in the body fixed frame of the quadrotor. Using momentum theory, we propose and model the existence of a horizontal force along with its associated power. Given the limitations associated with momentum theory and the inadequacy of the theory to account for the different powers represented in a proposed bond graph lead to the use of blade element theory. Using this theory, models are then developed for the different quadrotor rotor geometries and aerodynamic properties including the optimum hovering rotor used on the majority of quadrotors. Though this rotor is proven to be the most optimum rotor, we show that geometric variations are necessary for manufacturing of the blades. The geometric variations are also dictated by a desired th...

  13. Methods of making wind turbine rotor blades

    Livingston, Jamie T. (Pensacola, FL); Burke, Arthur H. E. (Gulf Breeze, FL); Bakhuis, Jan Willem (Nijverdal, NL); Van Breugel, Sjef (Enschede, NL); Billen, Andrew (Daarlerveen, NL)

    2008-04-01

    A method of manufacturing a root portion of a wind turbine blade includes, in an exemplary embodiment, providing an outer layer of reinforcing fibers including at least two woven mats of reinforcing fibers, providing an inner layer of reinforcing fibers including at least two woven mats of reinforcing fibers, and positioning at least two bands of reinforcing fibers between the inner and outer layers, with each band of reinforcing fibers including at least two woven mats of reinforcing fibers. The method further includes positioning a mat of randomly arranged reinforcing fibers between each pair of adjacent bands of reinforcing fibers, introducing a polymeric resin into the root potion of the wind turbine blade, infusing the resin through the outer layer, the inner layer, each band of reinforcing fibers, and each mat of random reinforcing fibers, and curing the resin to form the root portion of the wind turbine blade.

  14. Active vibration control of a rotor-bearing system based on dynamic stiffness

    Andrés Blanco Ortega; Francisco Beltrán Carbajal; Gerardo Silva Navarro; Marco Antonio Oliver Salazar

    2010-01-01

    This paper presents an active vibration control scheme to reduce unbalance induced synchronous vibration in rotorbearing systems supported on two ball bearings, one of which can be automatically moved to control the effective rotor length and, as an immediate consequence, the rotor stiffness. This dynamic stiffness control scheme, based on frequency analysis, speed control and acceleration scheduling, is used to avoid resonant vibration of a rotor system when it passes (runup or coast down) t...

  15. Stress optimization of leaf-spring crossed flexure pivots for an active Gurney flap mechanism

    Freire Gomez, Jon; Booker, Julian D; Mellor, Phil

    2015-01-01

    The EU’s Green Rotorcraft programme is pursuing the development of a functional and airworthy Active Gurney Flap (AGF) for a full-scale helicopter rotor blade. Interest in the development of this ‘smart adaptive rotor blade’ technology lies in its potential to provide a number of aerodynamic benefits, which would in turn translate into a reduction in fuel consumption and noise levels. The AGF mechanism selected employs leaf-spring crossed flexure pivots. These provide important advantages ove...

  16. Active control of structural vibration with on-line secondary path modeling

    YANG Tiejun; GU Zhongquan

    2004-01-01

    An active control strategy with on-line secondary path modeling is proposed and applied in active control of helicopter structural vibration. Computer simulations of the secondary path modeling performance demonstrate the superiorities of the active control strategy. A 2-input 4-output active control simulation for a helicopter model is performed and great reduction of structural vibration is achieved. 2-input 2-output and 2-input 4-output experimental studies of structural vibration control for a free-free beam are also carried out in laboratory to simulate a flying helicopter. The experimental results also show better reduction of the structural vibration, which verifies that the proposed method is effective and practical in structural vibration reduction.

  17. Stall Inception Process and Prospects for Active Hub-Flap Control in Three-Stage Axial Flow Compressor

    Tomoya OKADA; Atsushi KAWAJIRI; Yutaka OHTA; Eisuke OUTA

    2008-01-01

    The possibility to apply the active hub-flap control method, which is a proven rotating stall control method for a single-stage compressor, to a 3-stage axial compressor is experimentally discussed, where complex rotating stall inception processes ate observed. The research compressor is a 3-stage one and could change the stagger angle settings for rotor blades and stator vanes. Sixteen rotor blade/stator vane configuration patterns were tested by changing stagger angle for the stator vanes. By measurement of surface-pressure fluctuation, stall inception proc-esses are investigated and the measured pressure fluctuation data is used as a predictive signal for rotating stall. The experimental results show that the stall detection system applied to active hub-flap control in a single-stage compressor could be usefully applied to that in a 3-stage compressor with a more complex stall inception process.

  18. Active control of structural vibration by piezoelectric stack actuators

    NIU Jun-chuan; ZHAO Guo-qun; HU Xia-xia

    2005-01-01

    This paper presents a general analytical model of flexible isolation system for application to the installation of high-speed machines and lightweight structures. Piezoelectric stack actuators are employed in the model to achieve vibration control of flexible structures, and dynamic characteristics are also investigated. Mobility technique is used to derive the governing equations of the system. The power flow transmitted into the foundation is solved and considered as a cost function to achieve optimal control of vibration isolation. Some numerical simulations revealed that the analytical model is effective as piezoelectric stack actuators can achieve substantial vibration attenuation by selecting proper value of the input voltage.

  19. Semimanufacture intended to be mounted on a vibrating wall or a vibrating panel for actively damping vibrations of the wall, wall or panel provided with such semimanufacture, system provided with a semimanufacture and a control unit, wall or panel provided with a control unit and method for damping audible vibrations of a wall or panel

    Goeje, de, Marius; Overbeek, van, Wendy M.; Waal, de, P.R.; Berkhoff, Arthur P.; Nederveen, Peter J.

    2006-01-01

    A semimanufacture intended to be mounted on a vibrating wall or a vibrating panel for actively damping the vibrations in the wall or the panel with frequencies which are at least partly audible, wherein the semimanufacture is provided with a plate wherein the plate is integrated with: at least one vibration source for generating vibrations which, in use, damp the vibrations of the wall or the panel, at least one vibration sensor for detecting the vibrations in the wall or in the panel and wir...

  20. Active vibration control for high speed train bogies

    Peiffer, Alexander; Storm, Stefan; Röder, Arno; Maier, Rudolf; Frank, Paul-Gerhard

    2005-02-01

    This report deals with the design of an active vibration control (AVC) system integrated into the primary suspension of the bogie of a German high-speed train (ICE). As a design case a prototype bogie (WU92) for the ICE2 was taken. This paper comprises all parts and stages of the development of an AVC system. First, a transfer path analysis was performed in order to identify the main paths of propagation and to determine the boundary conditions at the actuator contact points. A detailed FE-analysis performed on the basis of an already existing FE-model serves as a support to investigate the actuator performance and evaluate several actuator concepts. However, the evaluation of a multifold of varying configurations of actuator, error sensor and monitor sensor positions is obviously not possible in the experiment, but is in the simulation. Based on the simulations and the experiments the control system is implemented on a digital signal processor (DSP) system. The structure borne noise level was determined during running tests at the ICE3 and measurements at the WU92 installed in the test rig. The design of the actuator system includes the layout of the specific system as well as the selection of the piezoelectric elements. A specifically developed amplifier drives the actuators. Finally the system is integrated into one axle of the WU92 and tested during roller-rig measurements.

  1. 汽轮发电机组转子-轮盘-叶片系统耦合扭转振动研究%The Coupled Torsional Vibrations Research of Rotor-blade Disk-vane System in Steam Turbine

    郭力; 朱均

    2001-01-01

    在传统的汽轮发电机转子系统强度及振动计算中,转子、叶片是分开考虑的,忽略了相互间的耦合作用.随着大扭曲长叶片的普遍采用,进行精确的转子-轮盘-叶片耦合振动分析对防止叶片、轮盘、转子事故已很有必要,本文提出了一种转子、轮系耦合扭转振动的分析方法,将耦合系统分为主部件转子和分支部件轮盘-叶片系统,分支部件的各阶模态可简化为等效的质量-弹簧系统,这样可以将原来大规模耦合振动系统降阶为低阶等效的小规模耦合系统,进而求出其频率和振型.

  2. Active Lubrication for Reducing Wear and Vibration: A combination of Fluid Power Control and Tribology

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...

  3. Active damping of vibrations in high-precision motion systems

    Babakhani, Bayan

    2012-01-01

    Technology advancements feed the need for ever faster and more accurate industrial machines. Vibration is a significant source of inaccuracy of such machines. A light-weight design in favor of the speed, and avoiding the use of energy-dissipating materials from the structure to omit any source of inaccuracy, contribute to a low structural damping. The goal of this research is to investigate the addition of damping to the rotational vibration mode of a linearly actuated motion system to • achi...

  4. Innovation in Active Vibration Control Strategy of Intelligent Structures

    A. Moutsopoulou; G. E. Stavroulakis; Pouliezos, A.

    2013-01-01

    Large amplitudes and attenuating vibration periods result in fatigue, instability, and poor structural performance. In light of past approaches in this field, this paper intends to discuss some innovative approaches in vibration control of intelligent structures, particularly in the case of structures with embedded piezoelectric materials. Control strategies are presented, such as the linear quadratic control theory, as well as more advanced theories, such as robust control theory. The paper ...

  5. Active Control of Machine-Tool Vibration in a Lathe

    Claesson, Ingvar; Håkansson, Lars

    1997-01-01

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration is a frequent problem, which affects the result of the machining, in particular the surface finish. The tool life is also influenced by the vibrations. When the working environment is considered, noise is frequently introduced by dynamic motion between the cutting tool and the workpiece. By proper machine design, e.g. improved stiffness of the machine structure, the problem of relative dynami...

  6. Acceleration/vibration combined environment activities. Interim report

    The combining of two environments, i.e., linear acceleration and vibration, for use in laboratory testing to determine the damage to some mechanical devices when simultaneously subjected to these two environments, is discussed. The use of a Genisco centrifuge with an Unholtz-Dickie vibration machine mounted on it is described. Initial efforts at operating a shaker on the centrifuge have not been completely successful, so modifications to the system are being made

  7. Fast Fourier transformation in vibration analysis of physically active systems

    Vibration of all physical systems may be expressed as the summation of an infinite number of sine and cosine terms known as Fourier series. The basic vibration analysis tool used is the frequency 'spectrum' (a graph of vibration where the amplitude of vibration is plotted against frequency). When a particular rotating component begins to fail, its vibration tends to increase. Spectra graphs are powerful diagnostic tool for detecting components' degradation. Spectra obtained with accelerometers located at the various locations on the components and their analysis in practice from rotating machines enable early detecting of incipient failure. Consequence of unexpected failure can be catastrophic and costly. This study provides basis to relate defective component by its constituent frequencies and then to the known discrete frequency of its 'signature' or 'thumbprint' to predict and verify the sustained dynamic behavior of machine designs harmful effects of forced vibration. The spectra for gearbox of a vane with teeth damaged fault are presented here which signified the importance of FFT analysis as diagnostic tool. This may be helpful to predictive maintenance of the machinery. (author)

  8. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    Seung-Bok Choi

    2013-02-01

    Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

  9. DESIGN AND ANALYSIS OF NOVEL ACTIVE ACTUATOR TO CONTROL LOW FREQUENCY VIBRATIONS OF SHAFT SYSTEM

    2008-01-01

    Aiming at providing with high-load capability in active vibration control of large-scale rotor system, a new type of active actuator to simultaneously reduce the dangers of low frequency flexural and torsional vibrations is designed. The actuator employs electro-hydraulic system and can provide a high and circumferential load. To initialize new research, the characteristics of various kinds of active actuators to control rotor shaft vibration are briefly introduced. The purpose of this paper is to introduce the preliminary results via presenting the structure, functions and operating principles, in particular, the working process of the electro-hydraulic system of the new actuator which includes a set of high speed electromagnetic valves and a series of sloping cone-shaped openings, and presenting the transmission relationships among the control parameters from control signals into the valves to active load onto shaft. The course of the work is dynamic, and a series of spatial forces and moments are put on the shaft to get an external resultant force to reduce excitations that induce vibration of shafts. By checking states of vibration, the actuator can control the impulse width and the interval of injection time for applying different control force to a vibration shaft in two circumference directions through the regulating action of a set of combination directional control valves. The results from simulating analysis and experiment show evidence of that this design can satisfy the case of active process of decreasing of flexural and torsional vibrations.

  10. Active Vibration Suppression of a 3-DOF Flexible Parallel Manipulator Using Efficient Modal Control

    Quan Zhang

    2014-01-01

    Full Text Available This paper addresses the dynamic modeling and efficient modal control of a planar parallel manipulator (PPM with three flexible linkages actuated by linear ultrasonic motors (LUSM. To achieve active vibration control, multiple lead zirconate titanate (PZT transducers are mounted on the flexible links as vibration sensors and actuators. Based on Lagrange’s equations, the dynamic model of the flexible links is derived with the dynamics of PZT actuators incorporated. Using the assumed mode method (AMM, the elastic motion of the flexible links are discretized under the assumptions of pinned-free boundary conditions, and the assumed mode shapes are validated through experimental modal test. Efficient modal control (EMC, in which the feedback forces in different modes are determined according to the vibration amplitude or energy of their own, is employed to control the PZT actuators to realize active vibration suppression. Modal filters are developed to extract the modal displacements and velocities from the vibration sensors. Numerical simulation and vibration control experiments are conducted to verify the proposed dynamic model and controller. The results show that the EMC method has the capability of suppressing multimode vibration simultaneously, and both the structural and residual vibrations of the flexible links are effectively suppressed using EMC approach.

  11. Influence of local vibration on plasma creatine phosphokinase (CPK) activity.

    Okada, A; Okuda, H.; Inaba, R; Ariizumi, M

    1985-01-01

    This study was designed to obtain basic information about the mechanism of the occurrence of muscular disorders after exposure to vibration. The hind legs of rats were exposed to acute and chronic local vibration at frequencies of 30, 60, 120, 240, 480, and 960 Hz with a constant acceleration of 50 m/sec2. The exposure time was four hours for acute, and four hours a day for two weeks continuously for chronic exposure. Blood was collected after exposure to measure plasma creatine phosphokinase...

  12. Application of Piezofilms for Excitation and Active Damping of Blade Flexural Vibration

    Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan

    2015-01-01

    Roč. 40, č. 1 (2015), s. 59-69. ISSN 0137-5075 Institutional support: RVO:61388998 Keywords : vibration suppression * parametric antiresonance * active damping * PVDF films Subject RIV: BI - Acoustics Impact factor: 0.565, year: 2014

  13. Nonlinear parametrically excited vibration and active control of gear pair system with time-varying characteristic

    刘爽; 王进进; 刘金杰; 李雅倩

    2015-01-01

    In the present work, we investigate the nonlinear parametrically excited vibration and active control of a gear pair system involving backlash, time-varying meshing stiffness and static transmission error. Firstly, a gear pair model is established in a strongly nonlinear form, and its nonlinear vibration characteristics are systematically investigated through different approaches. Several complicated phenomena such as period doubling bifurcation, anti period doubling bifurcation and chaos can be observed under the internal parametric excitation. Then, an active compensation controller is designed to suppress the vibration, including the chaos. Finally, the effectiveness of the proposed controller is verified numerically.

  14. Optimal semi-active vibration absorber for harmonic excitation based on controlled semi-active damper

    The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper. (paper)

  15. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    Seung-Bok Choi; Juncheol Jeon; Jung Woo Sohn; Heung Soo Kim

    2013-01-01

    In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an excite...

  16. Experimental Active Vibration Control in Truss Structures Considering Uncertainties in System Parameters

    2008-01-01

    This paper deals with the study of algorithms for robust active vibration control in flexible structures considering uncertainties in system parameters. It became an area of enormous interest, mainly due to the countless demands of optimal performance in mechanical systems as aircraft, aerospace, and automotive structures. An important and difficult problem for designing active vibration control is to get a representative dynamic model. Generally, this model can be obtained using finite eleme...

  17. Active Vibration Control for a CNC Milling Machine

    Ford, Derek G.; Myers, Alan; Haase, Frerk; Lockwood, Stephen; Longstaff, Andrew P.

    2013-01-01

    There is a requirement for improved three-dimensional surface characterisation and reduced tool wear when modern computer numerical control (CNC) machine tools are operating at high cutting velocities, spindle speeds and feed rates. For large depths of cut and large material removal rates, there is a tendency for machines to chatter caused by selfexcited vibration in the machine tools leading to precision errors, poor surface finish quality, tool wear and possible machine damage. This s...

  18. A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra

    Ganesan, Aravindhan; Wang, Feng

    2013-01-01

    Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations domina...

  19. Effect of vibration frequency on agonist and antagonist arm muscle activity

    Rodríguez Jiménez, Sergio; Benítez Herrera, Adolfo; García González, Miguel Ángel; Moras-Feliu, Gerard; Maffiuletti, Nicola A

    2015-01-01

    Purpose This study aimed to assess the effect of vibration frequency (fout) on the electromyographic (EMG) activity of the biceps brachii (BB) and triceps brachii (TB) muscles when acting as agonist and antagonist during static exercises with different loads. Methods Fourteen healthy men were asked to hold a vibratory bar as steadily as possible for 10 s during lying row (pulling) and bench press (pushing) exercise at fout of 0 (non-vibration condition), 18, 31 and 42 Hz with loads of 20, ...

  20. Adaptive Control of Machine-Tool Vibration Based on an Active Tool Holder Shank with an Embedded Piezo Ceramic Actuator

    Pettersson, Linus; Håkansson, Lars; Claesson, Ingvar; Olsson, Sven

    2001-01-01

    In the turning operation chatter or vibration is a common problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lathe...

  1. A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra*

    Ganesan, Aravindhan; Brunger, Michael J.; Wang, Feng

    2013-11-01

    Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations dominate the VOA spectra (i.e., VCD and ROA) > 3000 cm-1 reflecting the side chain structures of the amino acids. Finally the carboxyl and the C(2)H modes of aliphatic amino acids, together with the side chain vibrations, are very active in the VCD/IR and ROA/Raman spectra, which makes such the vibrational spectroscopic methods a very attractive means to study biomolecules.

  2. Terfenol-D driven flaps for helicopter vibration reduction

    Fenn, Ralph C.; Downer, James R.; Bushko, Dariusz A.; Gondhalekar, Vijay; Ham, Norman D.

    1996-02-01

    The utility of helicopter aviation is limited by the high vibration levels caused by the interaction of each rotor blade with the wake of preceding blades. Existing full-blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration. A blade mounted Terfenol-D actuator was developed for the high-weight-penalty helicopter application. The optimum coil to Terfenol-D volume ratio was derived that gives the highest mechanical power output for a small actuator envelope and mass. A fixed ability to dissipate coil resistive losses is assumed. The magnetostrictive actuation system will weigh less than 1% of gross vehicle weight, and use only 0.7% of cruise power. Other required subsystems of the vibration reduction system are available from commercial sources or are described in the literature. Helicopter vibration reduction greater than 90% is predicted because of superior actuator performance and individual blade control. This magnetostrictive actuator technology will also produce future helicopter systems having lower noise and higher performance. Such advances will significantly improve the utility and competitiveness of helicopters for civilian and military transportation.

  3. Design of active whole-spacecraft vibration isolation based on voice-coil motor

    Chi, Weichao; Cao, Dengqing; Huang, Wenhu

    2014-03-01

    In the launching process of a spacecraft, the dynamic environment is very complex, so a vibration isolator is widely used for preventing the spacecraft from being damaged. This paper focused on a whole-spacecraft vibration isolation platform with the purpose of isolating the shock and noise transmitting directly to the spacecraft in the process of launching. The isolator is designed based on a model of circular payload adapter fitting. A voice-coil motor is designed and optimized as the active control actuator to provide proper feedback force to reduce the amplitude of the vibration, and is fixed in the whole-spacecraft vibration isolation platform, with sensors collocated on one side of the voice-coil motor in the vertical direction. The LQR control strategy is designed for the preliminary model of the isolation system in the vertical direction. Numerical simulation results are given to verify the effectiveness of the proposed isolation unit consisted of the voicecoil actuators.

  4. A new online secondary path modeling method for adaptive active structure vibration control

    This paper proposes a new variable step size FXLMS algorithm with an auxiliary noise power scheduling strategy for online secondary path modeling. The step size for the secondary path modeling filter and the gain of auxiliary noise are varied in accordance with the parameters available directly. The proposed method has a low computational complexity. Computer simulations show that an active vibration control system with the proposed method gives much better vibration attenuation and modeling accuracy at a faster convergence rate than existing methods. National Instruments’ CompactRIO is used as an embedded processor to control simply supported beam vibration. Experimental results indicate that the vibration of the beam has been effectively attenuated. (papers)

  5. RESEARCH ON ACTIVE VIBRATION CONTROL BASED ON COMBINED MODEL FOR COUPLED SYSTEMS

    Niu Junchuan; Zhao Guoqun; Song Kongjie

    2004-01-01

    A novel combined model of the vibration control for the coupled flexible system and its general mathematic description are developed. In presented model, active and passive controls as well as force and moment controls are combined into a single unit to achieve the efficient vibration control of the flexible structures by multi-approaches. Considering the complexity of the energy transmission in the vibrating system, the transmission channels of the power flow transmitted into the foundation are discussed, and the general forces and the corresponding velocities are combined into a single function, respectively. Under the control strategy of the minimum power flow, the transmission characteristics of the power flow are investigated. From the presented numerical examples, it is obvious that the analytical model is effective, and both force and moment controls are able to depress vibration energy substantially.

  6. Detection of Rotor Forced Response Vibrations Using Stationary Pressure Transducers in a Multistage Axial Compressor

    William L. Murray

    2015-01-01

    Full Text Available Blade row interactions in turbomachinery can lead to blade vibrations and even high cycle fatigue. Forced response conditions occur when a forcing function (such as impingement of stator wakes occurs at a frequency that matches the natural frequency of a blade. The objective of this research is to develop the data processing techniques needed to detect rotor blade vibration in a forced response condition from stationary fast-response pressure transducers to allow for detection of rotor vibration from transient data and lead to techniques for vibration monitoring in gas turbines. This paper marks the first time in the open literature that engine-order resonant response of an embedded bladed disk in a 3-stage intermediate-speed axial compressor was detected using stationary pressure transducers. Experiments were performed in a stage axial research compressor focusing on the embedded rotor of blisk construction. Fourier waterfall graphs from a laser tip timing system were used to detect the vibrations after applying signal processing methods to uncover these pressure waves associated with blade vibration. Individual blade response was investigated using cross covariance to compare blade passage pressure signatures through resonance. Both methods agree with NSMS data that provide a measure of the exact compressor speeds at which individual blades enter resonance.

  7. Active Suppression of Drilling System Vibrations For Deep Drilling

    Raymond, David W.; Blankenship, Douglas A.; Buerger, Stephen; Mesh, Mikhail; Radigan, William Thomas; Su, Jiann-Cherng

    2015-10-01

    The dynamic stability of deep drillstrings is challenged by an inability to impart controllability with ever-changing conditions introduced by geology, depth, structural dynamic properties and operating conditions. A multi-organizational LDRD project team at Sandia National Laboratories successfully demonstrated advanced technologies for mitigating drillstring vibrations to improve the reliability of drilling systems used for construction of deep, high-value wells. Using computational modeling and dynamic substructuring techniques, the benefit of controllable actuators at discrete locations in the drillstring is determined. Prototype downhole tools were developed and evaluated in laboratory test fixtures simulating the structural dynamic response of a deep drillstring. A laboratory-based drilling applicability demonstration was conducted to demonstrate the benefit available from deployment of an autonomous, downhole tool with self-actuation capabilities in response to the dynamic response of the host drillstring. A concept is presented for a prototype drilling tool based upon the technical advances. The technology described herein is the subject of U.S. Patent Application No. 62219481, entitled "DRILLING SYSTEM VIBRATION SUPPRESSION SYSTEMS AND METHODS", filed September 16, 2015.

  8. Semimanufacture intended to be mounted on a vibrating wall or a vibrating panel for actively damping vibrations of the wall, wall or panel provided with such semimanufacture, system provided with a semimanufacture and a control unit, wall or panel provided with a control unit and method for damping audible vibrations of a wall or panel

    Goeje, de Marius; Overbeek, van Michiel Wilbert R.M.; Waal, van der Adri; Berkhoff, Arthur P.; Nederveen, Peter J.

    2006-01-01

    A semimanufacture intended to be mounted on a vibrating wall or a vibrating panel for actively damping the vibrations in the wall or the panel with frequencies which are at least partly audible, wherein the semimanufacture is provided with a plate wherein the plate is integrated with: at least one v

  9. Active Vibration Control of a Monopile Offshore Structure

    Nielsen, Søren R. K.; Kirkegaard, Poul Henning; Thesbjerg, L.

    1999-01-01

    cylinder of the platform, so the drag force in the generalized Morison equation is increased whenever it is acting in the opposite direction of the cylinder motion, whereas an unchanged drag force is applied, whenever it is acting co-directionally to the cylinder motion. The inertial force of the wave load...... is not subjected to control. The increased drag force is obtained by forcing the boundary layers to separate by blowing air into the boundary layer from the inside through small holes in the cylinder surface placed at a relatively large distance from the water surface. The control is specified by the...... wave conditions, where reductions in the vibration level of up to 50% have been registered....

  10. Active vibration suppression through positive acceleration feedback on a building-like structure: An experimental study

    Enríquez-Zárate, J.; Silva-Navarro, G.; Abundis-Fong, H. F.

    2016-05-01

    This work deals with the structural and dynamic analysis of a building-like structure consisting of a three-story building with one active vibration absorber. The base of the structure is perturbed using an electromagnetic shaker, which provides forces with a wide range of excitation frequencies, including some resonance frequencies of the structure. One beam-column of the structure is coupled with a PZT stack actuator to reduce the vibrations. The overall mechanical structure is modeled using Euler-Lagrange methodology and validated using experimental modal analysis and Fine Element Method (FEM) techniques. The active control laws are synthesized to actively attenuate the vibration system response via the PZT stack actuator, caused by excitation forces acting on the base of the structure. The control scheme is obtained using Positive Acceleration Feedback (PAF) and Multiple Positive Acceleration Feedback (MPAF) to improve the closed-loop system response. Some experimental results are included to illustrate the overall system performance.

  11. Experimental Comparison of two Active Vibration Control Approaches: Velocity Feedback and Negative Capacitance Shunt Damping

    Beck, Benjamin; Schiller, Noah

    2013-01-01

    This paper outlines a direct, experimental comparison between two established active vibration control techniques. Active vibration control methods, many of which rely upon piezoelectric patches as actuators and/or sensors, have been widely studied, showing many advantages over passive techniques. However, few direct comparisons between different active vibration control methods have been made to determine the performance benefit of one method over another. For the comparison here, the first control method, velocity feedback, is implemented using four accelerometers that act as sensors along with an analog control circuit which drives a piezoelectric actuator. The second method, negative capacitance shunt damping, consists of a basic analog circuit which utilizes a single piezoelectric patch as both a sensor and actuator. Both of these control methods are implemented individually using the same piezoelectric actuator attached to a clamped Plexiglas window. To assess the performance of each control method, the spatially averaged velocity of the window is compared to an uncontrolled response.

  12. Maximizing semi-active vibration isolation utilizing a magnetorheological damper with an inner bypass configuration

    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

  13. Maximizing semi-active vibration isolation utilizing a magnetorheological damper with an inner bypass configuration

    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.

  14. Research on the Identification Modeling of Air-Magnet Active Vibration Isolation System

    Wen Xianglong

    2015-01-01

    Full Text Available The methods of the identification modeling of air-magnet active vibration isolation system (AMAVIS are studied. Difference equation model and transfer function model are established respectively in the time domain and frequency domain. The models are analyzed and proved by the experiment. Identification results show that the order of frequency identification is higher than the time identification model. But when it comes to accuracy and convergence, frequency identification model has obvious advantage. This paper provides evidence for subsequent active vibration control. The conclusion is the basic of subsequent experiment and research.

  15. A robust vibration control for a multi-active mount system subjected to broadband excitation

    In this study, a frequency-shaped sliding mode control design is presented for the robust vibration control of a multi-active mount system in the presence of parametric uncertainties whose upper bounds are assumed to be known. The proposed mount system consists of four active mounts supporting vibration-sensitive equipment. Each active mount—constituted of a rubber element, an inertial mass and two piezostack actuators connected in serial configuration—can be modeled as a two-stage vibration isolator. After formulating the governing equations of motions of the mount system, a desired dynamic is specified in the frequency domain, and control laws are then derived to drive the system dynamics to the desired one based on Lyapunov's theorem. Simulations are performed in the frequency range from 100 to 1000 Hz in order to evaluate the effectiveness of the active mount system associated with the frequency-shaped sliding mode controller. It is demonstrated that the dynamic of the active mount system can approach the desired dynamic as the controller is activated. It also shown that robust vibration control performance is achieved in the presence of the parametric uncertainties

  16. Nonlinear parametrically excited vibration and active control of gear pair system with time-varying characteristic

    Liu, Shuang; Wang, Jin-Jin; Liu, Jin-Jie; Li, Ya-Qian

    2015-10-01

    In the present work, we investigate the nonlinear parametrically excited vibration and active control of a gear pair system involving backlash, time-varying meshing stiffness and static transmission error. Firstly, a gear pair model is established in a strongly nonlinear form, and its nonlinear vibration characteristics are systematically investigated through different approaches. Several complicated phenomena such as period doubling bifurcation, anti period doubling bifurcation and chaos can be observed under the internal parametric excitation. Then, an active compensation controller is designed to suppress the vibration, including the chaos. Finally, the effectiveness of the proposed controller is verified numerically. Project supported by the National Natural Science Foundation of China (Grant No. 61104040), the Natural Science Foundation of Hebei Province, China (Grant No. E2012203090), and the University Innovation Team of Hebei Province Leading Talent Cultivation Project, China (Grant No. LJRC013).

  17. A tubular dielectric elastomer actuator: Fabrication, characterization and active vibration isolation

    Sarban, R.; Jones, R. W.; Mace, B. R.; Rustighi, E.

    2011-01-01

    This contribution reviews the fabrication, characterization and active vibration isolation performance of a core-free rolled tubular dielectric elastomer (DE) actuator, which has been designed and developed by Danfoss PolyPower A/S. PolyPower DE material, PolyPower (TM), is produced in thin sheets......) highlight the dominant dynamic characteristics of the core-free tubular actuator. It has been observed that all actuators have similar dynamic characteristics in a frequency range up to 1 kHz. A tubular actuator is then used to provide active vibration isolation (AVI) of a 250 g mass subject to shaker...... generated 'ground vibration'. An adaptive feedforward control approach is used to achieve this. The tubular actuator is shown to provide excellent isolation against harmonic vibratory disturbances with attenuation of the resulting 5 and 10 Hz harmonics being 66 and 23 dB, respectively. AVI against a narrow...

  18. Active Control of Machine-Tool Vibration in a CNC Lathe Based on an Active Tool Holder Shank with Embedded Piezo Ceramic Actuators

    Pettersson, Linus; Håkansson, Lars; Claesson, Ingvar; Olsson, Sven

    2001-01-01

    In the turning operation chatter or vibration is a frequent problem affecting the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. However, machine-tool vibration control systems are usually not applicable to a general lat...

  19. A laser-optical sensor system for blade vibration detection of high-speed compressors

    Neumann, Mathias; Dreier, Florian; Günther, Philipp; Wilke, Ulrich; Fischer, Andreas; Büttner, Lars; Holzinger, Felix; Schiffer, Heinz-Peter; Czarske, Jürgen

    2015-12-01

    Improved efficiency as well as increased lifetime of turbines and compressors are important goals in turbomachinery development. A significant enhancement to accomplish these aims can be seen in online monitoring of the operating parameters of the machines. During the operation of compressors it is of high interest to predict critical events like flutter or stall which can be achieved by observing blade deformations and vibrations. We have developed a laser Doppler distance sensor (LDDS), which is capable of simultaneously measuring the radial blade expansions, the circumferential blade deflections as well as the circumferential velocities of the rotor blade tips. As a result, an increase of blade vibrations is measured before stall at characteristic frequencies. While the detected vibration frequencies and the vibration increase are in agreement with the measurement results of a commercial capacitive blade tip timing system, the measured values of the vibration amplitudes differ by a factor of three. This difference can be mainly attributed to the different measurement locations and to the different measurement approaches. Since the LDDS is applicable to metal as well as ceramic, carbon-fiber and glass-fiber reinforced composite blades, a universally applicable sensor system for stall prediction and status monitoring is presented.

  20. IIR filtering based adaptive active vibration control methodology with online secondary path modeling using PZT actuators

    Boz, Utku; Basdogan, Ipek

    2015-12-01

    Structural vibrations is a major cause for noise problems, discomfort and mechanical failures in aerospace, automotive and marine systems, which are mainly composed of plate-like structures. In order to reduce structural vibrations on these structures, active vibration control (AVC) is an effective approach. Adaptive filtering methodologies are preferred in AVC due to their ability to adjust themselves for varying dynamics of the structure during the operation. The filtered-X LMS (FXLMS) algorithm is a simple adaptive filtering algorithm widely implemented in active control applications. Proper implementation of FXLMS requires availability of a reference signal to mimic the disturbance and model of the dynamics between the control actuator and the error sensor, namely the secondary path. However, the controller output could interfere with the reference signal and the secondary path dynamics may change during the operation. This interference problem can be resolved by using an infinite impulse response (IIR) filter which considers feedback of the one or more previous control signals to the controller output and the changing secondary path dynamics can be updated using an online modeling technique. In this paper, IIR filtering based filtered-U LMS (FULMS) controller is combined with online secondary path modeling algorithm to suppress the vibrations of a plate-like structure. The results are validated through numerical and experimental studies. The results show that the FULMS with online secondary path modeling approach has more vibration rejection capabilities with higher convergence rate than the FXLMS counterpart.

  1. Active Vibration Isolation Using a Voice Coil Actuator with Absolute Velocity Feedback Control

    Yun-Hui Liu

    2013-11-01

    Full Text Available This paper describes the active vibration isolation using a voice coil actuator with absolute velocity feedback control for highly sensitive instruments (e.g., atomic force microscopes which suffer from building vibration. Compared with traditional isolators, the main advantage of the proposed isolation system is that it produces no isolator resonance. The absolute vibration velocity signal is acquired from an accelerator and processed through an integrator, and is then input to the controller as a feedback signal. The controller output signal then drives the voice coil actuator to produce a sky-hook damper force. In practice, the phase response of the integrator at low frequencies (2~6 Hz deviates from 90 degree which is the exact phase difference between the vibration velocity and acceleration. Therefore, an adaptive filter is used to compensate for the phase error. Analysis of this active vibration isolation system and comparison of model predictions to experimental results indicate that the proposed method significantly reduces transmissibility at resonance without incurring increased transmissibility at higher frequencies.

  2. Regular physical activity reduces the effects of Achilles tendon vibration on postural control for older women.

    Maitre, J; Serres, I; Lhuisset, L; Bois, J; Gasnier, Y; Paillard, T

    2015-02-01

    The aim was to determine in what extent physical activity influences postural control when visual, vestibular, and/or proprioceptive systems are disrupted. Two groups of healthy older women: an active group (74.0 ± 3.8 years) who practiced physical activities and a sedentary group (74.7 ± 6.3 years) who did not, underwent 12 postural conditions consisted in altering information emanating from sensory systems by means of sensory manipulations (i.e., eyes closed, cervical collar, tendon vibration, electromyostimulation, galvanic vestibular stimulation, foam surface). The center of foot pressure velocity was recorded on a force platform. Results indicate that the sensory manipulations altered postural control. The sedentary group was more disturbed than the active group by the use of tendon vibration. There was no clear difference between the two groups in the other conditions. This study suggests that the practice of physical activities is beneficial as a means of limiting the effects of tendon vibration on postural control through a better use of the not manipulated sensory systems and/or a more efficient reweighting to proprioceptive information from regions unaffected by the tendon vibration. PMID:24853711

  3. Active Lubrication: Feasibility and Limitations on Reducing Vibration in Rotating Machinery

    Nicoletti, Rodrigo; Santos, Ilmar

    2003-01-01

    In the present work, experimental results show the feasibility of reducing the amplitude of resonance peaks in rotor-bearing test rig, in the frequency domain, by using active lubricated bearings. The most important consequence of this vibration reduction in rotating machines is the feasibility o...

  4. Active Lubrication: Feasibility and Limitations on Reducing Vibration in Rotating Machinery

    Nicoletti, Rodrigo; Santos, Ilmar

    2004-01-01

    In the present work, experimental results show the feasibility of reducing the amplitude of resonance peaks in rotor-bearing test rig, in the frequency domain, by using active lubricated bearings. The most important consequence of this vibration reduction in rotating machines is the feasibility o...

  5. Finite element based design of software for integrated passive and active vibration control

    2001-01-01

    Presents the design scheme developed for design of software forIntegrated Passive and Active Vibration Control(IPAVC) and the coding of a prototyne system, and the selection of the famous finite element program MSC/NASTRAN as an important module of software to deal with large and complicated structures and systems with an example to demonstrate the prototype system.

  6. Nonplanar Tertiary Amides in Rigid Chiral Tricyclic Dilactams. Peptide Group Distortions and Vibrational Optical Activity

    Pazderková, Markéta; Profant, V.; Hodačová, J.; Šebestík, Jaroslav; Pazderka, T.; Novotná, P.; Urbanová, M.; Šafařík, Martin; Buděšínský, Miloš; Tichý, Miloš; Bednárová, Lucie; Baumruk, V.; Maloň, Petr

    2013-01-01

    Roč. 117, č. 33 (2013), s. 9626-9642. ISSN 1520-6106 R&D Projects: GA ČR GAP205/10/1276 Institutional support: RVO:61388963 Keywords : spirodilactams * amide bond * vibrational circular dichroism * non-planarity * Raman optical activity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.377, year: 2013

  7. The Influence of Whole-Body Vibration on Creatine Kinase Activity and Jumping Performance in Young Basketball Players

    Fachina, Rafael; da Silva, Antônio; Falcão, William; Montagner, Paulo; Borin, João; Minozzo, Fábio; Falcão, Diego; Vancini, Rodrigo; Poston, Brach; de Lira, Claudio

    2013-01-01

    Purpose: To quantify creatine kinase (CK) activity changes across time following an acute bout of whole-body vibration (WBV) and determine the association between changes in CK activity and jumping performance. Method: Twenty-six elite young basketball players were assigned to 3 groups: 36-Hz and 46-Hz vibration groups (G36 and G46, respectively)…

  8. Inverse eigenvalue problems in vibration absorption: Passive modification and active control

    Mottershead, John E.; Ram, Yitshak M.

    2006-01-01

    The abiding problem of vibration absorption has occupied engineering scientists for over a century and there remain abundant examples of the need for vibration suppression in many industries. For example, in the automotive industry the resolution of noise, vibration and harshness (NVH) problems is of extreme importance to customer satisfaction. In rotorcraft it is vital to avoid resonance close to the blade passing speed and its harmonics. An objective of the greatest importance, and extremely difficult to achieve, is the isolation of the pilot's seat in a helicopter. It is presently impossible to achieve the objectives of vibration absorption in these industries at the design stage because of limitations inherent in finite element models. Therefore, it is necessary to develop techniques whereby the dynamic of the system (possibly a car or a helicopter) can be adjusted after it has been built. There are two main approaches: structural modification by passive elements and active control. The state of art of the mathematical theory of vibration absorption is presented and illustrated for the benefit of the reader with numerous simple examples.

  9. Active Tuned Mass Dampers for Control of In-Plane Vibrations of Wind Turbine Blades

    Fitzgerald, B.; Basu, Biswajit; Nielsen, Søren R.K.

    2013-01-01

    This paper investigates the use of active tuned mass dampers (ATMDs) for the mitigation of in-plane vibrations in rotating wind turbine blades. The rotating wind turbine blades with tower interaction represent time-varying dynamical systems with periodically varying mass, stiffness, and damping...... matrices. The aim of this paper is to determine whether ATMDs could be used to reduce in-plane blade vibrations in wind turbines with better performance than compared with their passive counterparts. A Euler–Lagrangian wind turbine mathematical model based on energy formulation was developed for this...... purpose, which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations. Also, the interaction between the blades and the tower including the tuned mass dampers is considered. The wind turbine with tuned mass dampers was subjected to gravity...

  10. Reducing friction-induced vibration using intelligent active force control (AFC) with piezoelectric actuators

    S M Hashemi-Dehkordi; A R Abu-Bakar; M Mailah

    2012-12-01

    In this paper, a novel approach to reduce the effect of mode coupling that causes friction induced vibration (FIV) is proposed by applying an intelligent active force control (AFC)-based strategy employing piezoelectric actuators with hysteresis effect to a simplified two degree-of-freedom mathematical model of a friction-induced vibration system. At first, the model is simulated and analysed using a closed loop pure Proportional-Integral-Derivative (PID) controller. Later, it is integrated with the intelligent AFC with fuzzy logic (FL) estimator and simulated under similar operating condition. After running several tests with different sets of operating and loading conditions, the results both in time and frequency domains show that the PID controller with the intelligent AFC is much more effective in reducing the vibration, compared to the pure PID controller alone.

  11. A reduced energy supply strategy in active vibration control

    In this paper, a control strategy is presented and numerically tested. This strategy aims to achieve the potential performance of fully active systems with a reduced energy supply. These energy needs are expected to be comparable to the power demands of semi-active systems, while system performance is intended to be comparable to that of a fully active configuration. The underlying strategy is called 'global semi-active control'. This control approach results from an energy investigation based on management of the optimal control process. Energy management encompasses storage and convenient restitution. The proposed strategy monitors a given active law without any external energy supply by considering purely dissipative and energy-demanding phases. Such a control law is offered here along with an analysis of its properties. A suboptimal form, well adapted for practical implementation steps, is also given. Moreover, a number of numerical experiments are proposed in order to validate test findings

  12. Evaluation of the Effectiveness of an Active Magnetic Damper (AMD) in Damping Subsynchronous Vibrations in a Flexible Rotor

    Mendoza, Hector

    2000-01-01

    Subsynchronous vibrations such as those caused by rotor instability represent one of the most harrowing scenarios of rotor vibration. They are related to a great diversity of destabilizing forces and some of them are not well understood yet. Therefore, special attention must be paid to this type of vibration. Active Magnetic Bearings (AMBs) monitor the position of the shaft and change the dynamics of the system accordingly to keep the rotor in a desired position, offering the possibility of...

  13. Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control

    Ullah Khan, Irfan; Wagg, David; Sims, Neil D.

    2016-08-01

    This paper presents a new hybrid active and semi-active control method for vibration suppression in flexible structures. The method uses a combination of a semi-active device and an active control actuator situated elsewhere in the structure to suppress vibrations. The key novelty is to use the hybrid controller to enable the magneto-rheological damper to achieve a performance as close to a fully active device as possible. This is achieved by ensuring that the active actuator can assist the magneto-rheological damper in the regions where energy is required. In addition, the hybrid active and semi-active controller is designed to minimize the switching of the semi-active controller. The control framework used is the immersion and invariance control technique in combination with sliding mode control. A two degree-of-freedom system with lightly damped resonances is used as an example system. Both numerical and experimental results are generated for this system, and then compared as part of a validation study. The experimental system uses hardware-in-the-loop to simulate the effect of both the degrees-of-freedom. The results show that the concept is viable both numerically and experimentally, and improved vibration suppression results can be obtained for the magneto-rheological damper that approach the performance of an active device.

  14. Cooperative Control Method of Active and Semiactive Control: New Framework for Vibration Control

    Kazuhiko Hiramoto

    2014-01-01

    A new control design framework for vibration control, the cooperative control of active and semiactive control, is proposed in the paper. In the cooperative control, a structural system having both of an actuator and a semiactive control device, for example, MR damper and so forth, is defined as the control object. In the proposed control approach, the higher control performance is aimed by the cooperative control between the active control with the actuator and the semiactive control with th...

  15. Vibrational and Electronic optical Activity of the Chiral Disulphide Group: Implications for Disulphide Bridge Conformation

    Bednárová, Lucie; Bouř, Petr; Maloň, Petr

    2010-01-01

    Roč. 22, č. 5 (2010), s. 514-526. ISSN 0899-0042 R&D Projects: GA ČR(CZ) GA203/07/1335; GA ČR GA202/07/0732; GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : disulphide bridge * circular dichroism * vibrational optical activity * Raman optical activity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.892, year: 2010

  16. Wind-Tunnel Tests of a Bridge Model with Active Vibration Control

    Hansen, H. I.; Thoft-Christensen, Palle; Mendes, P. A.;

    The application of active control systems to reduce wind vibrations in bridges is a new area of research. This paper presents the results that were obtained on a set of wind tunnel tests of a bridge model equipped with active movable flaps. Based on the monitored position and motion of the deck......, the flaps are regulated by a control algorithm so that the wind forces exerted on them counteract the deck oscillations....

  17. Underwater sound and vibrations due to oil & gas activities

    Beek, P.J.G. van; Binnerts, B.; Nennie, E.D.; Benda-Beckmann, S. von

    2014-01-01

    In the oil & gas industry there is a trend towards more subsea activities. To improve gas recovery from existing and new fields at greater depths, the produced gas will be compressed, processed and transported via subsea templates and underwater networks (pipelines, flexible risers, etc.). Besides t

  18. Smart Materials and Active Noise and Vibration Control in Vehicles

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, van M.

    2001-01-01

    The paper presents the results for the reduction of sound radiated from a structure using different control methodologies, and discusses two approaches for active structural acoustic control: the acoustic approach or the vibro-acoustic approach. Integrated actuators in structure material are necessa

  19. Effectiveness of a passive-active vibration isolation system with actuator constraints

    Sun, Lingling; Sun, Wei; Song, Kongjie; Hansen, Colin H.

    2014-05-01

    In the prediction of active vibration isolation performance, control force requirements were ignored in previous work. This may limit the realization of theoretically predicted isolation performance if control force of large magnitude cannot be supplied by actuators. The behavior of a feed-forward active isolation system subjected to actuator output constraints is investigated. Distributed parameter models are developed to analyze the system response, and to produce a transfer matrix for the design of an integrated passive-active isolation system. Cost functions comprising a combination of the vibration transmission energy and the sum of the squared control forces are proposed. The example system considered is a rigid body connected to a simply supported plate via two passive-active isolation mounts. Vertical and transverse forces as well as a rotational moment are applied at the rigid body, and resonances excited in elastic mounts and the supporting plate are analyzed. The overall isolation performance is evaluated by numerical simulation. The simulation results are then compared with those obtained using unconstrained control strategies. In addition, the effects of waves in elastic mounts are analyzed. It is shown that the control strategies which rely on unconstrained actuator outputs may give substantial power transmission reductions over a wide frequency range, but also require large control force amplitudes to control excited vibration modes of the system. Expected power transmission reductions for modified control strategies that incorporate constrained actuator outputs are considerably less than typical reductions with unconstrained actuator outputs. In the frequency range in which rigid body modes are present, the control strategies can only achieve 5-10 dB power transmission reduction, when control forces are constrained to be the same order of the magnitude as the primary vertical force. The resonances of the elastic mounts result in a notable increase

  20. Initial Aerodynamic and Acoustic Study of an Active Twist Rotor Using a Loosely Coupled CFD/CSD Method

    Boyd, David D. Jr.

    2009-01-01

    Preliminary aerodynamic and performance predictions for an active twist rotor for a HART-II type of configuration are performed using a computational fluid dynamics (CFD) code, OVERFLOW2, and a computational structural dynamics (CSD) code, CAMRAD -II. These codes are loosely coupled to compute a consistent set of aerodynamics and elastic blade motions. Resultant aerodynamic and blade motion data are then used in the Ffowcs-Williams Hawkins solver, PSU-WOPWOP, to compute noise on an observer plane under the rotor. Active twist of the rotor blade is achieved in CAMRAD-II by application of a periodic torsional moment couple (of equal and opposite sign) at the blade root and tip at a specified frequency and amplitude. To provide confidence in these particular active twist predictions for which no measured data is available, the rotor system geometry and computational set up examined here are identical to that used in a previous successful Higher Harmonic Control (HHC) computational study. For a single frequency equal to three times the blade passage frequency (3P), active twist is applied across a range of control phase angles at two different amplitudes. Predicted results indicate that there are control phase angles where the maximum mid-frequency noise level and the 4P non -rotating hub vibrations can be reduced, potentially, both at the same time. However, these calculated reductions are predicted to come with a performance penalty in the form of a reduction in rotor lift-to-drag ratio due to an increase in rotor profile power.

  1. Modeling and experimental vibration analysis of nanomechanical cantilever active probes

    Nanomechanical cantilever (NMC) active probes have recently received increased attention in a variety of nanoscale sensing and measurement applications. Current modeling practices call for a uniform cantilever beam without considering the intentional jump discontinuities associated with the piezoelectric layer attachment and the NMC cross-sectional step. This paper presents a comprehensive modeling framework for modal characterization and dynamic response analysis of NMC active probes with geometrical discontinuities. The entire length of the NMC is divided into three segments of uniform beams followed by applying appropriate continuity conditions. The characteristics matrix equation is then used to solve for system natural frequencies and mode shapes. Using an equivalent electromechanical moment of a piezoelectric layer, forced motion analysis of the system is carried out. An experimental setup consisting of a commercial NMC active probe from Veeco and a state-of-the-art microsystem analyzer, the MSA-400 from Polytec, is developed to verify the theoretical developments proposed here. Using a parameter estimation technique based on minimizing the modeling error, optimal values of system parameters are identified. Mode shapes and the modal frequency response of the system for the first three modes determined from the proposed model are compared with those obtained from the experiment and commonly used theory for uniform beams. Results indicate that the uniform beam model fails to accurately predict the actual system response, especially in multiple-mode operation, while the proposed discontinuous beam model demonstrates good agreement with the experimental data. Such detailed and accurate modeling framework can lead to significant enhancement in the sensitivity of piezoelectric-based NMC sensors for use in variety of sensing and imaging applications

  2. Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

    Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.

    2014-01-01

    This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

  3. Bilinear Robust Control for Vertical Vibration in Railway Vehicle with Semi-Active Suspensions

    Umehara, Ryuichi; Otsuki, Masatsugu; Yoshida, Kazuo

    It is well known that the vibration control problem for automobiles and railway vehicles with semi-active suspensions is classified as a control problem in a bilinear system. Bullet trains and railway vehicles have lighter body in order to improve acceleration; these vibrations in the body are easily induced by various disturbances due to rigid and elastic dynamics. Currently, passive dampers such as air suspensions and axle springs are installed on railway vehicle trucks as countermeasures for such vibrations. This study presents an effective controller, based on the H∞ theory, for vibration suppression in railway vehicles and describes a method of synthesizing this robust controller by considering unstructured and structured uncertainties that are applicable to a bilinear system. The performance of the proposed controller and its robustness toward uncertainties are examined by numerical calculations that simulate a railway vehicle subjected to disturbances due to vertical uneven railway tracks, the variations in its mass due to boarding passengers, and the modeling errors caused by non-controlled modes. This enables a comparison of the proposed control method with the conventional one in terms of the robustness toward parameter variation. Thus, this result shows the high robustness and usefulness of the proposed controller.

  4. Study on Component Synthesis Active Vibration Suppression Method Using Zero-placement Technique

    Zhang Jianying; Liu Tun; Zhao Zhiping

    2008-01-01

    The component synthesis active vibration suppression method (CSVS) can be applied to suppress the vibration of flexible systems.By this method, several same or similar time-varying components are arranged according to certain rules along the time axis. The synthesized command can suppress the arbitrary unwanted vibration harmonic while achieving the desired rigid body motion. The number of the components increases rapidly when the number of harmonic vibration is growing. In this article, the CSVS based on zero-placement technique is used to construct the synthesized command to suppress the multi-harmonics simultaneously in the discrete domain.The nature of zero-placement method is to put enough zeros to cancel system poles at necessary points. The designed synthesized command has equal time intervals between each component and which is much easier to be implemented. Using this method, the number of components increases linearly with the increasing of the number of being suppressed harmonics. For the spacecraft with flexible appendages, CSVS based on zero-placement is used to design the time optimal large angle maneuver control stategy. Simulations have verified the validity and superiority of the proposed approach.

  5. Origin invariance in vibrational resonance Raman optical activity

    Vidal, Luciano N., E-mail: lnvidal@utfpr.edu.br; Cappelli, Chiara, E-mail: chiara.cappelli@unipi.it [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Moruzzi 3, 56124 Pisa (Italy); Egidi, Franco [Department of Chemistry, University of Washington, Seattle, Washington 98195 (United States); Barone, Vincenzo [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy)

    2015-05-07

    A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

  6. Active Vibration Control of the Smart Plate Using Artificial Neural Network Controller

    Mohit

    2015-01-01

    Full Text Available The active vibration control (AVC of a rectangular plate with single input and single output approach is investigated using artificial neural network. The cantilever plate of finite length, breadth, and thickness having piezoelectric patches as sensors/actuators fixed at the upper and lower surface of the metal plate is considered for examination. The finite element model of the cantilever plate is utilized to formulate the whole strategy. The compact RIO and MATLAB simulation software are exercised to get the appropriate results. The cantilever plate is subjected to impulse input and uniform white noise disturbance. The neural network is trained offline and tuned with LQR controller. The various training algorithms to tune the neural network are exercised. The best efficient algorithm is finally considered to tune the neural network controller designed for active vibration control of the smart plate.

  7. Semi-active variable stiffness vibration control of vehicle seat suspension using an MR elastomer isolator

    This paper presents a study on continuously variable stiffness control of vehicle seat suspension using a magnetorheological elastomer (MRE) isolator. A concept design for an MRE isolator is proposed in the paper and its behavior is experimentally evaluated. An integrated seat suspension model, which includes a quarter-car suspension and a seat suspension with a driver body model, is used to design a sub-optimal H∞ controller for an active isolator. The desired control force generated by this active isolator is then emulated by the MRE isolator through its continuously variable stiffness property when the actuating condition is met. The vibration control effect of the MRE isolator is evaluated in terms of driver body acceleration responses under both bump and random road conditions. The results show that the proposed control strategy achieves better vibration reduction performance than conventional on–off control

  8. Active vibration control of smart grid structure by multiinput and multioutput positive position feedback controller

    Kwak, Moon K.; Heo, Seok

    2007-07-01

    This paper is concerned with the active vibration control of a grid structure equipped with piezoceramic sensors and actuators. The grid structure is a replica of the solar panel commonly mounted on satellites, which contains complex natural mode shapes. The multiinput and multioutput positive position feedback (PPF) controller is considered as an active vibration controller for the grid structure. A new concept, the block-inverse technique, is proposed to cope with more modes than the number of actuators and sensors. This study also deals with the stability and the spillover effect associated with the application of the multiinput multioutput PPF controller based on the block-inverse technique. It was found that the theories developed in this study are capable of predicting the control system characteristics and its performance. The new multiinput multioutput PPF controller was applied to the test structure using a digital signal processor and its efficacy was verified by experiments.

  9. Vibrational spectroscopic and non-linear optical activity studies on nicotinanilide : A DFT approach

    The molecular structure of nicotinanilide was optimized by the DFT/B3LYP method with cc-pVTZ basis set using Gaussian 09 program. The first order hyperpolarizability of the molecule was calculated, which exhibits the higher nonlinear optical activity. The natural bond orbital analysis confirms the presence of intramolecular charge transfer and the hydrogen bonding interaction, which leads to the higher nonlinear optical activity of the molecule. The Frontier molecular orbitals analysis of the molecule shows that the delocalization of electron density occurs within the molecule. The lower energy gap indicates that the hydrogen bond formation between the charged species. The vibrational frequencies were calculated and assigned on the basis of potential energy distribution calculation using the VEDA 4.0 program and the corresponding vibrational spectra were simulated. Hence, the nicotinanilide molecule can be a good candidate for second-order NLO material

  10. Active vibration control using state space LQG and internal model control methods

    Mørkholt, Jakob; Elliott, S.J.

    Two ways of designing discrete time robust H2-controllers for feedback broadband active vibration control are compared through computer simulations. The methods are based on different models of disturbance and plant transfer functions, but yield controllers with identical properties. Two simple...... ways of introducing robustness into the H2-design are compared, and finally an efficient way of designing a practical IIR-controller is proposed....

  11. Optimization of Active Vibration Control of a Laser Pattern Generator in Micro Lithography

    Carlqvist, Per; Brattström, Patrik; During, Carl

    2010-01-01

    The extreme precision requirements in semiconductor manufacturing drive the need for an active vibration isolation system in a laser pattern generator. Optimization has been performed and evaluated in a model using a high level programming tool [1]. The areas of optimization were 1) Decoupling strategies for decentralized control and 2) Improved feed forward control. Only a limited description of the model itself is given here. More about the model is presented in [2] and [3].

  12. Phase and gain control policies for robust active vibration control of flexible structures

    Zhang, Kai; Scorletti, Gérard; Ichchou, Mohamed; Mieyeville, F.

    2013-01-01

    The interest of this paper is to develop a general and systematic robust control methodology for active vibration control of flexible structures. For this purpose, first phase and gain control policies are proposed to impose qualitative frequency-dependent requirements on the controller to consider a complete set of control objectives. Then the proposed control methodology is developed by employing phase and gain control policies in the dynamic output feedback H∞ control: according to the set...

  13. Absolute Configuration of a Cyclic Dipeptide Reflected in Vibrational Optical Activity: Ab Initio and Experimental Investigation

    Li, X.; Hopmann, K. H.; Hudecová, Jana; Stensen, W.; Novotná, J.; Urbanová, M.; Svendsen, J. S.; Bouř, Petr; Ruud, K.

    2012-01-01

    Roč. 116, č. 10 (2012), s. 2554-2563. ISSN 1089-5639 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant ostatní: AV ČR(CZ) M200550902 Institutional research plan: CEZ:AV0Z40550506 Keywords : cyclic dipeptide * vibrational otpical activity * density functional theory * dispersion * electronic circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.771, year: 2012

  14. Electronic and Vibrational Optical Activity of Several Peptides Related to Neurohypophyseal Hormones: Disulfide Group Conformation

    Pazderková, Markéta; Bednárová, Lucie; Dlouhá, Helena; Flegel, Martin; Lebl, M.; Hlaváček, Jan; Setnička, V.; Urbanová, M.; Hynie, S.; Klenerová, V.; Baumruk, V.; Maloň, Petr

    2012-01-01

    Roč. 97, č. 11 (2012), s. 923-932. ISSN 0006-3525 R&D Projects: GA ČR GAP205/10/1276 Grant ostatní: GA UK(CZ) 578212 Institutional research plan: CEZ:AV0Z40550506 Keywords : neurohypophyseal hormones * disulfide bridge * Raman optical activity * vibrational circular dichroism Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.879, year: 2012

  15. Vibration reduction in helicopter rotors using an active control surface located on the blade

    Millott, T. A.; Friedmann, P. P.

    1992-01-01

    A feasibility study of vibration reduction in a four-bladed helicopter rotor using individual blade control (IBC), which is implemented by an individually controlled aerodynamic surface located on each blade, is presented. For this exploratory study, a simple offset-hinged spring restrained model of the blade is used with fully coupled flap-lag-torsional dynamics for each blade. Deterministic controllers based on local and global system models are implemented to reduce 4/rev hub loads using both an actively controlled aerodynamic surface on each blade as well as conventional IBC, where the complete blade undergoes cyclic pitch change. The effectiveness of the two approaches for simultaneous reduction of the 4/rev hub shears and hub moments is compared. Conventional IBC requires considerably more power to achieve approximately the same level of vibration reduction as that obtained by implementing IBC using an active control surface located on the outboard segment of the blade. The effect of blade torsional flexibility on the vibration reduction effectiveness of the actively controlled surface was also considered and it was found that this parameter has a very substantial influence.

  16. Active vibration control of a smart pultruded fiber-reinforced polymer I-beam

    Song, G.; Qiao, P.; Sethi, V.; Prasad, A.

    2004-08-01

    Advanced and innovative materials and structures are increasingly used in civil infrastructure applications. By combining the advantages of composites and smart sensors and actuators, active or smart composite structures can be created and be efficiently adopted in practical structural applications. This paper presents results on active vibration control of pultruded fiber-reinforced polymer (FRP) composite thin-walled I-beams using smart sensors and actuators. The FRP I-beams are made of E-glass fibers and polyester resins. The FRP I-beam is in a cantilevered configuration. The PZT (lead zirconate titanate) type of piezoelectric ceramic patches are used as smart sensors and actuators. These patches are surface bonded near the cantilevered end of the I-beam. Utilizing results from modal analyses and experimental modal testing, several active vibration control methods, such as position feedback control, strain rate feedback control and lead compensation, are investigated. Experimental results demonstrate that the proposed methods achieve effective vibration control of FRP I-beams. For instance, the modal damping ratio of the strong direction first bending mode increases by more than 1000% with positive position feedback control.

  17. Active vibration control on a quarter-car for cancellation of road noise disturbance

    Belgacem, Walid; Berry, Alain; Masson, Patrice

    2012-07-01

    In this paper, a methodology is presented for the cancellation of road noise, from the analysis of vibration transmission paths for an automotive suspension to the design of an active control system using inertial actuators on a suspension to reduce the vibrations transmitted to the chassis. First, experiments were conducted on a Chevrolet Epica LS automobile on a concrete test track to measure accelerations induced on the suspension by the road. These measurements were combined with experimental Frequency Response Functions (FRFs) measured on a quarter-car test bench to reconstruct an equivalent three dimensional force applied on the wheel hub. Second, FRFs measured on the test bench between the three-dimensional driving force and forces at each suspension/chassis linkage were used to characterize the different transmission paths of vibration energy to the chassis. Third, an experimental model of the suspension was constructed to simulate the configuration of the active control system, using the primary (disturbance) FRFs and secondary (control) FRFs also measured on the test bench. This model was used to optimize the configuration of the control actuators and to evaluate the required forces. Finally, a prototype of an active suspension was implemented and measurements were performed in order to assess the performance of the control approach. A 4.6 dB attenuation on transmitted forces was obtained in the 50-250 Hz range.

  18. Enzyme activation and catalysis: characterisation of the vibrational modes of substrate and product in protochlorophyllide oxidoreductase.

    Sytina, Olga A; Alexandre, Maxime T; Heyes, Derren J; Hunter, C Neil; Robert, Bruno; van Grondelle, Rienk; Groot, Marie Louise

    2011-02-14

    The light-dependent reduction of protochlorophyllide, a key step in the synthesis of chlorophyll, is catalyzed by the enzyme protochlorophyllide oxidoreductase (POR) and requires two photons (O. A. Sytina et al., Nature, 2008, 456, 1001-1008). The first photon activates the enzyme-substrate complex, a subsequent second photon initiates the photochemistry by triggering the formation of a catalytic intermediate. These two events are characterized by different spectral changes in the infra-red spectral region. Here, we investigate the vibrational frequencies of the POR-bound and unbound substrate, and product, and thus provide a detailed assignment of the spectral changes in the 1800-1250 cm(-1) region associated with the catalytic conversion of PChlide:NADPH:TyrOH into Chlide:NADP(+):TyrO(-). Fluorescence line narrowed spectra of the POR-bound Pchlide reveal a C=O keto group downshifted by more than 20 cm(-1) to a relatively low vibrational frequency of 1653 cm(-1), as compared to the unbound Pchlide, indicating that binding of the chromophore to the protein occurs via strong hydrogen bond(s). The frequencies of the C=C vibrational modes are consistent with a six-coordinated state of the POR-bound Pchlide, suggesting that there are two coordination interactions between the central Mg atom of the chromophore and protein residues, and/or a water molecule. The frequencies of the C=C vibrational modes of Chlide are consistent with a five-coordinated state, indicating a single interaction between the central Mg atom of the chromophore and a water molecule. Rapid-scan FTIR measurements on the Pchlide:POR:NADPH complex at 4 cm(-1) spectral resolution reveal a new band in the 1670 cm(-1) region. The FTIR spectra of the enzyme activation phase indicate involvement of a nucleotide-binding structural motif, and an increased exposure of the protein to solvent after activation. PMID:21103538

  19. Active vibration reduction by optimally placed sensors and actuators with application to stiffened plates by beams

    This study concerns new investigation of active vibration reduction of a stiffened plate bonded with discrete sensor/actuator pairs located optimally using genetic algorithms based on a developed finite element modeling. An isotropic plate element stiffened by a number of beam elements on its edges and having a piezoelectric sensor and actuator pair bonded to its surfaces is modeled using the finite element method and Hamilton’s principle, taking into account the effects of piezoelectric mass, stiffness and electromechanical coupling. The modeling is based on the first order shear deformation theory taking into account the effects of bending, membrane and shear deformation for the plate, the stiffening beam and the piezoelectric patches. A Matlab finite element program has been built for the stiffened plate model and verified with ANSYS and also experimentally. Optimal placement of ten piezoelectric sensor/actuator pairs and optimal feedback gain for active vibration reduction are investigated for a plate stiffened by two beams arranged in the form of a cross. The genetic algorithm was set up for optimization of sensor/actuator placement and feedback gain based on the minimization of the optimal linear quadratic index as an objective function to suppress the first six modes of vibration. Comparison study is presented for active vibration reduction of a square cantilever plate stiffened by crossed beams with two sensor/actuator configurations: firstly, ten piezoelectric sensor/actuator pairs are located in optimal positions; secondly, a piezoelectric layer of single sensor/actuator pair covering the whole of the stiffened plate as a SISO system. (paper)

  20. Theory of vibration protection

    Karnovsky, Igor A

    2016-01-01

    This text is an advancement of the theory of vibration protection of mechanical systems with lumped and distributed parameters. The book offers various concepts and methods of solving vibration protection problems, discusses the advantages and disadvantages of different methods, and the fields of their effective applications. Fundamental approaches of vibration protection, which are considered in this book, are the passive, parametric and optimal active vibration protection. The passive vibration protection is based on vibration isolation, vibration damping and dynamic absorbers. Parametric vibration protection theory is based on the Shchipanov-Luzin invariance principle. Optimal active vibration protection theory is based on the Pontryagin principle and the Krein moment method. The book also contains special topics such as suppression of vibrations at the source of their occurrence and the harmful influence of vibrations on humans. Numerous examples, which illustrate the theoretical ideas of each chapter, ar...

  1. Vibration Analysis of Large Composite Blade Wind Turbine

    Yuqiao Zheng

    2013-09-01

    Full Text Available This paper presents a recently developed the finite model method for analysis of horizontal axis wind turbine blades.Free vibration equation is proposed based on theory of  the classical lamination and  Lagrange method.. A 40 m rotor blade was chosen as a example study to validate the static and dynamic behaviour predicted by shell model built in ANSYS,Given uncertainty of material properties involved,An accurate agreement was found for static deformation curves, as well as a good prediction of the lowest frequency modes in terms of resonance frequencies, the highest (eighth frequency modes show only a fair agreement as expected for an FE model,Flap-wise, edge-wise and  torsional  natural  frequencies of  a  variable  length  blade  have been investigated,The results show that the approach used in this study is very efficient and produces improved designs as compared with a reference or baseline design.

  2. Influence of delayed excitation on vibrations of turbine blades couple

    Půst L.

    2013-06-01

    Full Text Available In the presented paper, the computational model of the turbine blade couple is investigated with the main attention to the influence two harmonic excitation forces, having the same frequency and amplitude but with moderate delay in time. Time delay between the exciting harmonic forces depends on the revolutions of bladed disk, on the number of blades on a rotating disk and on the number of stator blades. The reduction of resonance vibrations realized by means of dry friction between the shroud blade-heads increases roughly proportional to the difference of stator and rotor blade-numbers and also to the magnitude of dry friction force. From the analysis of blade couple with direct contact it was proved that the increase of friction forces causes decrease of resonance peaks, but the influence of elastic micro-deformations in the contact surfaces (modeled e.g. by the modified Coulomb dry friction law is rather small. Analysis of a blade couple with a friction element shows that the lower number of stator blades has negligible influence on the amplitudes of both blades, but decreases amplitudes of the friction element oscillations. Similarly the increase of friction forces causes a decrease of resonance peaks, but an increase of friction element amplitudes.

  3. Active vibration control using a novel three-DOF precision micro-stage

    In this paper, we present an active vibration control system which is constructed based on a novel three-degrees-of-freedom (DOF) precision micro-stage. Unlike the traditional tripod systems, the proposed micro-stage is established to guarantee the compactness (60 mm(h) × 160 mm(d)) and the simplicity of its structure as well as the appropriate vertical/horizontal stiffness and the repeatability, which are essential in achieving the accuracy of sub-micrometers. First, combined with a finite element method (FEM), a physical model for the proposed micro-stage is constructed and its physical parameters, such as stiffness and damping coefficients, are estimated to predict the experimental results with high fidelity. In order to overcome the dynamic variations naturally stemming from the payload as well as the parameter uncertainties, a robust control system is then proposed to efficiently mitigate the vibration with a scale of sub-micrometers. Compared to the conventional control strategy, the proposed robust control scheme successfully establishes the active vibration control system and its performance is examined and validated through extensive experiments

  4. Independent modal variable structure fuzzy active vibration control of thin plates laminated with photostrictive actuators

    He Rongbo; Zheng Shijie

    2013-01-01

    Photostrictive actuators can produce photodeformation strains under illumination of ultraviolet lights.They can realize non-contact micro-actuation and vibration control for elastic plate structures.Considering the switching actuation and nonlinear dynamic characteristics of photostrictive actuators,a variable structure fuzzy active control scheme is presented to control the light intensity applied to the actuators.Firstly,independent modal vibration control equations of photoelectric laminated plates are established based on modal analysis techniques.Then,the optimal light switching function is derived to increase the range of sliding modal area,and the light intensity self-adjusting fuzzy active controller is designed.Meanwhile,a continuous function is applied to replace a sign function to reduce the variable structure control (VSC) chattering.Finally,numerical simulation is carried out,and simulation results indicate that the proposed control strategy provides better performance and control effect to plate actuation and control than velocity feedback control,and suppresses vibration effectively.

  5. Experimental Active Vibration Control in Truss Structures Considering Uncertainties in System Parameters

    Douglas Domingues Bueno

    2008-01-01

    Full Text Available This paper deals with the study of algorithms for robust active vibration control in flexible structures considering uncertainties in system parameters. It became an area of enormous interest, mainly due to the countless demands of optimal performance in mechanical systems as aircraft, aerospace, and automotive structures. An important and difficult problem for designing active vibration control is to get a representative dynamic model. Generally, this model can be obtained using finite element method (FEM or an identification method using experimental data. Actuators and sensors may affect the dynamics properties of the structure, for instance, electromechanical coupling of piezoelectric material must be considered in FEM formulation for flexible and lightly damping structure. The nonlinearities and uncertainties involved in these structures make it a difficult task, mainly for complex structures as spatial truss structures. On the other hand, by using an identification method, it is possible to obtain the dynamic model represented through a state space realization considering this coupling. This paper proposes an experimental methodology for vibration control in a 3D truss structure using PZT wafer stacks and a robust control algorithm solved by linear matrix inequalities.

  6. Active vibration control of flexible cantilever plates using piezoelectric materials and artificial neural networks

    Abdeljaber, Osama; Avci, Onur; Inman, Daniel J.

    2016-02-01

    The study presented in this paper introduces a new intelligent methodology to mitigate the vibration response of flexible cantilever plates. The use of the piezoelectric sensor/actuator pairs for active control of plates is discussed. An intelligent neural network based controller is designed to control the optimal voltage applied on the piezoelectric patches. The control technique utilizes a neurocontroller along with a Kalman Filter to compute the appropriate actuator command. The neurocontroller is trained based on an algorithm that incorporates a set of emulator neural networks which are also trained to predict the future response of the cantilever plate. Then, the neurocontroller is evaluated by comparing the uncontrolled and controlled responses under several types of dynamic excitations. It is observed that the neurocontroller reduced the vibration response of the flexible cantilever plate significantly; the results demonstrated the success and robustness of the neurocontroller independent of the type and distribution of the excitation force.

  7. Design and Experimental Study of a VCM-Based Stewart Parallel Mechanism Used for Active Vibration Isolation

    Weichao Chi

    2015-07-01

    Full Text Available This paper presents the design and experimental study of a voice coil motor (VCM-based Stewart platform used for active vibration isolation. The high precision payloads carried on the satellites always require an extremely stable environment to work properly. Installing a vibration isolation device between the vibration sources and precision payloads is an efficient method for dissipating vibration energy. A Stewart platform with active damping is designed to isolate the vibration transferring from the satellite to the payloads in six degrees-of-freedom. First, the kinematics and dynamical equations of a Stewart platform with spherical joints at both the base and top of each leg are established with Newton-Euler Method in task space and joint space. Second, the H∞ Control Theory is employed to design a robust controller for the linearized system with parameter uncertainty, noise and sensor errors. Finally, an experimentation study on the vibration of the payload supported by a Stewart platform with VCM actuator is conducted. The feasibility and effectiveness of the vibration isolation system are verified by comparing the amplitude-frequency characteristics of the active control system with that of the passive control system and the system without damping.

  8. Buck-boost converter for simultaneous semi-active vibration control and energy harvesting for electromagnetic regenerative shock absorber

    Li, Peng; Zhang, Chongxiao; Kim, Junyoung; Yu, Liangyao; Zuo, Lei

    2014-04-01

    Regenerative semi-active suspensions can capture the previously dissipated vibration energy and convert it to usable electrical energy for powering on-board electronic devices, while achieve both the better ride comfort and improved road handling performance at the same time when certain control is applied. To achieve this objective, the power electronics interface circuit connecting the energy harvester and the electrical loads, which can perform simultaneous vibration control and energy harvesting function is in need. This paper utilized a buck-boost converter for simultaneous semi-active vibration control and energy harvesting with electromagnetic regenerative shock absorber, which utilizes a rotational generator to converter the vibration energy to electricity. It has been found that when the circuit works in discontinuous current mode (DCM), the ratio between the input voltage and current is only related to the duty cycle of the switch pulse width modulation signal. Using this property, the buck-boost converter can be used to perform semi-active vibration control by controlling the load connected between the terminals of the generator in the electromagnetic shock absorber. While performing the vibration control, the circuit always draw current from the shock absorber and the suspension remain dissipative, and the shock absorber takes no additional energy to perform the vibration control. The working principle and dynamics of the circuit has been analyzed and simulations were performed to validate the concept.

  9. Semi-active vibration control in cable-stayed bridges under the condition of random wind load

    This paper aims at an experimental study on the real-time vibration control of bridge structures using a semi-active vibration control method that has been in the spotlight recently. As structures are becoming larger and larger, structural harmful vibration caused by unspecified external forces such as earthquakes, gusts of wind, and collisions has been brought to attention as an important issue. These harmful vibrations can cause not only user anxiety but also severe structural damage or even complete failure of structures. Therefore, in view of structural safety and economical long-term maintenance, real-time control technology of the harmful structural vibration is urgently required. In this paper, a laboratory-scale model of a cable-stayed bridge was built, and a shear-type MR damper and a semi-active vibration control algorithm (Lyapunov and clipped optimal) were applied for the control of harmful vibration of the model bridge, in real time. On the basis of the test results, each semi-active control algorithm was verified quantitatively. (papers)

  10. Active vibration control of clamped beams using positive position feedback controllers with moment pair

    This paper investigates the active vibration control of clamp beams using positive position feedback (PPF) controllers with a sensor/ moment pair actuator. The sensor/moment pair actuator which is the non-collocated configuration leads to instability of the control system when using the direct velocity feedback (DVFB) control. To alleviate the instability problem, a PPF controller is considered in this paper. A parametric study of the control system with PPF controller is first conducted to characterize the effects of the design parameters (gain and damping ratio in this paper) on the stability and performance. The gain of the controller is found to affect only the relative stability. Increasing the damping ratio of the controller slightly improves the stability condition while the performance gets worse. In addition, the higher mode tuned PPF controller affects the system response at the lower modes significantly. Based on the characteristics of PPF controllers, a multi-mode controllable SISO PPF controller is then considered and tuned to different modes (in this case, three lowest modes) numerically and experimentally. The multi-mode PPF controller can be achieved to have a high gain margin. Moreover, it reduces the vibration of the beam significantly. The vibration levels at the tuned modes are reduced by about 11 dB

  11. Active Vibration Control of a Nonlinear Beam with Self- and External Excitations

    J. Warminski

    2013-01-01

    Full Text Available An application of the nonlinear saturation control (NSC algorithm for a self-excited strongly nonlinear beam structure driven by an external force is presented in the paper. The mathematical model accounts for an Euler-Bernoulli beam with nonlinear curvature, reduced to first mode oscillations. It is assumed that the beam vibrates in the presence of a harmonic excitation close to the first natural frequency of the beam, and additionally the beam is self-excited by fluid flow, which is modelled by a nonlinear Rayleigh term for self-excitation. The self- and externally excited vibrations have been reduced by the application of an active, saturation-based controller. The approximate analytical solutions for a full structure have been found by the multiple time scales method, up to the first-order approximation. The analytical solutions have been compared with numerical results obtained from direct integration of the ordinary differential equations of motion. Finally, the influence of a negative damping term and the controller's parameters for effective vibrations suppression are presented.

  12. Magnetic force driven six degree-of-freedom active vibration isolation system using a phase compensated velocity sensor

    A six-axis active vibration isolation system (AVIS) is developed using voice coil actuators. Point contact configuration is employed to have an easy assembly of eight voice coil actuators to an upper and a base plates. The velocity sensor, using an electromagnetic principle that is commonly used in the vibration control, is investigated since its phase lead characteristic causes an instability problem for a low frequency vibration. The performances of the AVIS are investigated in the frequency domain and finally validated by comparing with the passive isolation system using the atomic force microscope images.

  13. Resonant passive-active vibration absorber with integrated force feedback control

    Høgsberg, Jan; Brodersen, Mark L.; Krenk, Steen

    2016-04-01

    A general format of a two-terminal vibration absorber is constructed by placing a passive unit in series with a hybrid unit, composed of an active actuator in parallel with a second passive element. The displacement of the active actuator is controlled by an integrated feedback control with the difference in force between the two passive elements as input. This format allows passive and active contributions to be combined arbitrarily within the hybrid unit, which results in a versatile absorber format with guaranteed closed-loop stability. This is demonstrated for resonant absorbers with inertia realized passively by a mechanical inerter or actively by the integrated force feedback. Accurate calibration formulae are presented for two particular absorber configurations and the performance is subsequently demonstrated with respect to both equal modal damping and effective response reduction.

  14. Resonant passive–active vibration absorber with integrated force feedback control

    Høgsberg, Jan Becker; Brodersen, Mark Laier; Krenk, Steen

    2016-01-01

    A general format of a two-terminal vibration absorber is constructed by placing a passive unit in series with a hybrid unit, composed of an active actuator in parallel with a second passive element. The displacement of the active actuator is controlled by an integrated feedback control with the...... difference in force between the two passive elements as input. This format allows passive and active contributions to be combined arbitrarily within the hybrid unit, which results in a versatile absorber format with guaranteed closed-loop stability. This is demonstrated for resonant absorbers with inertia...... realized passively by a mechanical inerter or actively by the integrated force feedback. Accurate calibration formulae are presented for two particular absorber configurations and the performance is subsequently demonstrated with respect to both equal modal damping and effective response reduction....

  15. Application of a Broadband Active Vibration Control System to a Helicopter Trim Panel

    Cabell, R.H.; Schiller, N.H.; Simon, F.

    2013-01-01

    This paper discusses testing of a broadband active vibration control concept on an interior trim panel in a helicopter cabin mockup located at ONERA's Centre de Toulouse. The control system consisted of twelve diamond-shaped piezoelectric actuators distributed around a 1.2m x 1.2m trim panel. Accelerometers were mounted at the four vertices of each diamond. The aspect ratio of the diamond was based on the dielectric constants of the piezoelectric material in order to create an actuator-sensor...

  16. Vibration characterization of an active magnetic bearing supported rotor / J. Bean

    Bean, Jaco

    2011-01-01

    The McTronX Research group at the Potchefstroom campus of the North-West University, aims to establish a knowledge base on active magnetic bearing (AMB) systems. Up to date, the group has established a firm knowledge base on various topics related to AMB systems. A recent focus was the design and development of a high speed AMB supported rotor system called the rotor delevitation system (RDS) to analyse rotor drops. During the testing phase of the RDS, the machine exhibited vibrations, of whi...

  17. Stimulated light scattering in an active medium with overheating-ionizational and vibrational-thermal instabilities

    Fedorov, S. V.

    1990-05-01

    Nonstationary stimulated scattering (SS) increments are obtained in different instability zones of a saturated emission beam and under various heat-release conditions in the active-medium, and the characteristics of these SS increments are analyzed. The effects of the vibrational-thermal instability of the medium and the superheating-ionizational instability of the discharge on the SS charactistics are explained. The coefficients of SS gains due to temperature waves and inversion waves are examined. Estimates are obtained of SS increments and of typical scales of radiation instability in inverted CO2-laser mixtures.

  18. Test and theory for piezoelectric actuator-active vibration control of rotating machinery

    Palazzolo, A. B.; Lin, R. R.; Alexander, R. M.; Kascak, A. F.; Montague, J.

    1989-01-01

    The application of piezoelectric actuators for active vibration control (AVC) of rotating machinery is examined. Theory is derived and the resulting predictions are shown to agree closely with results of tests performed on an air turbine driven-overhung rotor. The test results show significant reduction in unbalance, transient and sub-synchronous responses. Results from a 30-hour endurance test support the AVD system reliability. Various aspects of the electro-mechanical stability of the control system are also discussed and illustrated. Finally, application of the AVC system to an actual jet engine is discussed.

  19. A study on the effects of Kalman Filter on performance of IPMC-Based Active Vibration Control Scheme

    Bandopadhya, Dibakar; Njuguna, James A. K.

    2010-01-01

    This paper evaluates the effectiveness and performance of Ionic Polymer Metal Composite (IPMC) based active vibration control scheme equipped with the Kalman estimation algorithm. To assess the vibration attenuation efficiency, a rotating flexible manipulator has been modelled integrating two IPMC actuators following the modal approach. The elastic displacements as generalized coordinates for estimating optimal performance is carried out next by discretizing the elastic motion through the ass...

  20. Theoretical and Numerical Experiences on a Test Rig for Active Vibration Control of Mechanical Systems with Moving Constraints

    M. Rinchi; Gambini, E.

    2004-01-01

    Active control of vibrations in mechanical systems has recently benefited of the remarkable development of robust control techniques. These control techniques are able to guarantee performances in spite of unavoidable modeling errors. They have been successfully codified and implemented for vibrating structures whose uncertain parameters could be assumed to be time-invariant. Unfortunately a wide class of mechanical systems, such as machine tools with carriage motion realized by a ball-screw,...

  1. Active Vibration Control of Axial Piston Machine using Higher Harmonic Least Mean Square Control of Swash Plate

    Kim, Taeho; Ivantysynova, Monika

    2016-01-01

    Noise emission is a major drawback of the positive displacement machine. The noise source can be divided into structure borne noise source (SBNS) and fluid borne noise source (FBNS). Passive techniques such as valve plate optimization have been used for noise reduction of axial piston machines. However, passive techniques are only effective for limited operating conditions or at least need compromises in design. In this paper, active vibration control of swash plate is investigated for vibrat...

  2. Lower Arm Muscle Activation during Indirect-Localized Vibration: The Influence of Skill Levels When Applying Different Acceleration Loads

    Padulo, Johnny; Di Giminiani, Riccardo; Dello Iacono, Antonio; Zagatto, Alessandro M.; Migliaccio, Gian M.; Grgantov, Zoran; Ardigò, Luca P.

    2016-01-01

    We investigated the electromyographic response to synchronous indirect-localized vibration interventions in international and national table tennis players. Twenty-six male table tennis players, in a standing position, underwent firstly an upper arms maximal voluntary contraction and thereafter two different 30-s vibration interventions in random order: high acceleration load (peak acceleration = 12.8 g, frequency = 40 Hz; peak-to-peak displacement = 4.0 mm), and low acceleration load (peak acceleration = 7.2 g, frequency = 30 Hz, peak-to-peak displacement = 4.0 mm). Surface electromyography root mean square from brachioradialis, extensor digitorum, flexor carpi radialis, and flexor digitorum superficialis recorded during the two vibration interventions was normalized to the maximal voluntary contraction recording. Normalized surface electromyography root mean square was higher in international table tennis players with respect to national ones in all the interactions between muscles and vibration conditions (P 0.05). The difference in normalized surface electromyography root mean square between international table tennis players and national ones increased in all the muscles with high acceleration load (P 0.05). The muscle activation during indirect-localized vibration seems to be both skill level and muscle dependent. These results can optimize the training intervention in table tennis players when applying indirect-localized vibration to lower arm muscles. Future investigations should discriminate between middle- and long-term adaptations in response to specific vibration loads. PMID:27378948

  3. ANALYSIS OF AN ELECTROSTRICTIVE STACK ACTUATORFOR ACTIVE TRAILING EDGE FLAPS

    2000-01-01

    Helicopter is a complex dynamic system with many rotating components. The rotor blades operate in a highly complex aerodynamic environment. The vibratory hub load, which is caused by cyclic variation of centrifugal and aerodynamic load of the rotating blades in flight, is transmitted to the fuselage, resulting in serious vibration and noise of the structure. It is one of the most important exciting sources in helicopters.  There has long been a desire to reduce helicopter vibration and to improve its performance. Control schemes adopted so far can be classified as either passive or active control technologies. The passive technologies include optimization of rotor hub, blade and the fuselage, hub or blade mounted passive vibration absorbers and anti-resonant vibration isolators. One of the major disadvantages with passive technologies is that they are designed to provide maximum vibration reduction at a specific frequency; therefore, their performance is degraded significantly with changes in the operating conditions of the rotor system.  With the development of computer science and active control technology, increasing efforts have been devoted to active control technologies to benefit helicopter vibration suppression in recent years. Earlier studies include Higher Harmonic Control (HHC)[1] and Individual Blade Control (IBC)[2], which is aimed to reduce the vibratory blade load by oscillating the blade in pitch motion using hydraulic actuators. It is successful in suppressing the vibration of the fuselage; however, its application is limited by serious energy consumption.  To overcome these difficulties, a new concept in helicopter vibration control is the smart rotor system. In this scheme, actuators are embedded in composite blades. They are used to activate the trailing edge flaps in higher harmonic pitch motion to adjust the lift force actively. Under the regulation of a control system, the vibratory hub load can be counteracted actively at

  4. The Influence of Semi-active Dampers on the Vibration Behaviour of Passenger Cars

    Schneider, Sebastian; Brechter, Daniel; Janßen, Andreas; Mauch, Heiko

    The number of mechatronic components in modern car suspensions is increasing continuously to solve conflicts concerning design goals. Thus, changes in the vibration behaviour of the vehicle are caused. It needs to be ascertained whether this influence has to be taken into account when determining the fatigue life of a car and its components. Therefore, changes of the loads are studied in measurements and multi-body simulations of a passenger car with semi-active dampers. The evaluation of the forces at the wheel centre and at the shock absorber tower shows that different settings of semi-active dampers have an influence on fatigue life of the chassis and the car body. It is concluded that these effects need to be taken into account when determining fatigue life. Furthermore, multi-body simulations have been successfully applied to study the influence of semi-active dampers on the loads.

  5. Active absorber for damping audio-frequency noise emissions at wind power plants. Active vibration damping; Aktiver Tilger zur Unterdrueckung tonaler Schallemissionen an Windenergieanlagen. Aktive Schwingungstilgung

    Neugebauer, R.; Linke, M.; Kunze, H.; Ullrich, M. [Fraunhofer Institut fuer Werkzeugmaschinen und Umformtechnik (IWU), Chemnitz / Dresden (Germany)

    2010-07-01

    Structural vibrations of a wind turbine's drive train are one of the main reasons for noise emissions. Mechanical vibrations are transferred through the structure and emitted as noise by large surfaces, e.g. tower and nacelle. Dominant vibration excitation is caused for example by the gear mesh. If the gear mesh frequency is coinciding with the frequency of a structural resonance, the emitted noise contains noticeable single tones. German immission control law requires a ''tonal penalty'' up to 6 dB, if the emitted noise contains annoying tones. To ensure compliance with immission limits those tones must be reduced or eliminated. For wind turbines running with variable speed an active vibration absorber has been developed, whose absorber frequency and damping is adapted corresponding to the alternating vibration excitation. (orig.)

  6. Optimal and robust modal control of a flexible structure using an active dynamic vibration absorber

    This paper is concerned with feedback vibration control of a lightly damped flexible structure that has a large number of well-separated modes. A single active electrical dynamic absorber is used to reduce a particular single vibration mode selectively or multiple modes simultaneously. The absorber is realized electrically by feeding back the structural acceleration at one position to a collocated piezoceramic patch actuator via a controller consisting of one or several second order lowpass filters. A simple analytical method is presented to design a modal control filter that is optimal in that it maximally flattens the mobility frequency response of the target mode, as well as robust in that it works within a prescribed maximum control spillover of 2 dB at all frequencies. Experiments are conducted with a free–free beam to demonstrate its ability to control any single mode optimally and robustly. It is also shown that an active absorber with multiple such filters can effectively control multiple modes simultaneously

  7. Optimal placement of piezoelectric active bars in vibration control by topological optimization

    Guozhong Zhao; Jian Wang; Yuanxian Gu

    2008-01-01

    A continuous variable optimization method and a topological optimization method are proposed for the vibra-tion control of piezoelectric truss structures by means of the optimal placements of active bars. In this optimization model, a zero-one discrete variable is defined in order to solve the optimal placement of piezoelectric active bars. At the same time, the feedback gains are also optimized as conti-nuous design variables. A two-phase procedure is proposed to solve the optimization problem. The sequential linear pro-gramming algorithm is used to solve optimization problem and the sensitivity analysis is carried out for objective and constraint functions to make linear approximations. On the basis of the Newmark time integration of structural tran-sient dynamic responses, a new sensitivity analysis method is developed in this paper for the vibration control problem of piezoelectric truss structures with respect to various kinds of design variables. Numerical examples are given in the paper to demonstrate the effectiveness of the methods.

  8. Active alignment and vibration control system for a large airborne optical system

    Kienholz, David A.

    2000-04-01

    Airborne optical or electro-optical systems may be too large for all elements to be mounted on a single integrating structure, other than the aircraft fuselage itself. An active system must then be used to maintain the required alignment between elements. However the various smaller integrating structures (benches) must still be isolated from high- frequency airframe disturbances that could excite resonances outside the bandwidth of the alignment control system. The combined active alignment and vibration isolation functions must be performed by flight-weight components, which may have to operate in vacuum. A testbed system developed for the Air Force Airborne Laser program is described. The payload, a full-scale 1650-lb simulated bench, is mounted in six degrees- of-freedom to a vibrating platform by a set of isolator- actuators. The mounts utilize a combination of pneumatics and magnetics to perform the dual functions of low-frequency alignment and high-frequency isolation. Test results are given and future directions for development are described.

  9. Dynamics and Control of Lateral Tower Vibrations in Offshore Wind Turbines by Means of Active Generator Torque

    Zili Zhang

    2014-11-01

    Full Text Available Lateral tower vibrations of offshore wind turbines are normally lightly damped, and large amplitude vibrations induced by wind and wave loads in this direction may significantly shorten the fatigue life of the tower. This paper proposes the modeling and control of lateral tower vibrations in offshore wind turbines using active generator torque. To implement the active control algorithm, both the mechanical and power electronic aspects have been taken into consideration. A 13-degrees-of-freedom aeroelastic wind turbine model with generator and pitch controllers is derived using the Euler–Lagrangian approach. The model displays important features of wind turbines, such as mixed moving frame and fixed frame-defined degrees-of-freedom, couplings of the tower-blade-drivetrain vibrations, as well as aerodynamic damping present in different modes of motions. The load transfer mechanisms from the drivetrain and the generator to the nacelle are derived, and the interaction between the generator torque and the lateral tower vibration are presented in a generalized manner. A three-dimensional rotational sampled turbulence field is generated and applied to the rotor, and the tower is excited by a first order wave load in the lateral direction. Next, a simple active control algorithm is proposed based on active generator torques with feedback from the measured lateral tower vibrations. A full-scale power converter configuration with a cascaded loop control structure is also introduced to produce the feedback control torque in real time. Numerical simulations have been carried out using data calibrated to the referential 5-MW NREL (National Renewable Energy Laboratory offshore wind turbine. Cases of drivetrains with a gearbox and direct drive to the generator are considered using the same time series for the wave and turbulence loadings. Results show that by using active generator torque control, lateral tower vibrations can be significantly mitigated for

  10. Study on the application of active balancing device to solve the vibration problem for the rotor with bending fault

    He Lidong; Shen Wei; Gao Jinji; Zhou Weihua

    2006-01-01

    The rotor with bending faults that occurrs on the rotating machinery usually vibrates seriously. This paper investigates to apply the active balancing device on a flexible rotor with bending faults to solve the vibration problem. Two problems are studied by finite element method firstly: Where the balance actuator is fixed on the shaft and how much the balancing capacity of the active balancing device is needed. The experiment is then carried out on the test rig, which consists of a flexible rotor with bending faults. The test results indicate that the bending rotor peak vibration response can be decreased from 550μm to 40μm below by using the active balancing device. The peak vibration response decreases approximately by 93%. The synchronous vibration due to the rotor bending faults can be controlled effectively by using active balancing device. The active balancing device is especially adapted to solve the problem caused by thermal distortion with time-variation and randomness, which is varied with working conditions, thus it has good practical value in practice.

  11. Active vibration control of piezoelectric bonded smart structures using PID algorithm

    Zhang Shunqi; Rüdiger Schmidt; Qin Xiansheng

    2015-01-01

    Thin-walled structures are sensitive to vibrate under even very small disturbances. In order to design a suitable controller for vibration suppression of thin-walled smart structures, an electro-mechanically coupled finite element (FE) model of smart structures is developed based on first-order shear deformation (FOSD) hypothesis. Considering the vibrations generated by various disturbances, which include free and forced vibrations, a PID control is implemented to damp both the free and force...

  12. Nonlinear Dynamical Analysis on Four Semi-Active Dynamic Vibration Absorbers with Time Delay

    Yongjun Shen

    2013-01-01

    Full Text Available In this paper four semi-active dynamic vibration absorbers (DVAs are analytically studied, where the time delay induced by measurement and execution in control procedure is included in the system. The first-order approximate analytical solutions of the four semi-active DVAs are established by the averaging method, based on the illustrated phase difference of the motion parameters. The comparisons between the analytical and the numerical solutions are carried out, which verify the correctness and satisfactory precision of the approximate analytical solutions. Then the effects of the time delay on the dynamical responses are analyzed, and it is found that the stability conditions for the steady-state responses of the primary systems are all periodic functions of time delay, with the same period as the excitation one. At last the effects of time delay on control performance are discussed.

  13. Vibration-induced auditory-cortex activation in a congenitally deaf adult.

    Levänen, S; Jousmäki, V; Hari, R

    1998-07-16

    Considerable changes take place in the number of cerebral neurons, synapses and axons during development, mainly as a result of competition between different neural activities [1-4]. Studies using animals suggest that when input from one sensory modality is deprived early in development, the affected neural structures have the potential to mediate functions for the remaining modalities [5-8]. We now show that similar potential exists in the human auditory system: vibrotactile stimuli, applied on the palm and fingers of a congenitally deaf adult, activated his auditory cortices. The recorded magnetoencephalographic (MEG) signals also indicated that the auditory cortices were able to discriminate between the applied 180 Hz and 250 Hz vibration frequencies. Our findings suggest that human cortical areas, normally subserving hearing, may process vibrotactile information in the congenitally deaf. PMID:9705933

  14. [EFFECTS OF WHOLE-BODY VIBRATION TRAINING ON BODY COMPOSITION AND PHYSICAL FITNESS IN RECREATIONALLY ACTIVE YOUNG ADULTS].

    Martínez-Pardo, Esmeraldo; Martínez-Ruiz, Enrique; Alcaraz, Pedro E; Rubio-Arias, Jacobo A

    2015-01-01

    In the last decade, it has been suggested that whole- body vibration training (WBV) may increase neuromuscular performance and consequently affect the muscular improvement as either acute response to vibration or chronic adaptation training. Vibrating platforms generate frequencies from 5-45 Hz and vertical oscillations of 1-11 mm peak to peak, affecting more or less intensity acceleration changing by combining frequency and amplitude. Vibration training, in a session as various offers different results in regard to changes in body composition and in increasing the vertical jump, sprint, and the different manifestations of force development. These promising results await further research to establish parameters (duration, frequency and amplitude) with vibration stimulation in young active subjects. This literature review provides an update on the scientific evidence on the body vibrations in order to answer the question whether WBV, meaning the exercise by increasing the gravitational load collection, is a treatment option if the aim is to improve neuromuscular function, flexibility, balance, agility, coordination and body composition. PMID:26545648

  15. Automotive applications of active vibration control: a control engineering point of view; Aktive Schwingungskompensation im Kfz aus regelungstechnischer Sicht

    Svaricek, F.; Bohn, C.; Haertel, V. [Continental AG, Hannover (Germany). Strategische Technologie; Karkosch, H.J. [ContiTech Vibration Control GmbH, Hannover (Germany)

    2001-07-01

    Modern control applications will become increasingly important in the area of vehicle riding comfort. An attractive future application in this area is the use of active vibration control in engine mounting concepts, particularly since conventional engine mounts are approaching their inherent limitations. This paper gives an overview of the active control of engine-induced vibrations. After a brief introduction to the requirements that a modern engine mounting concept needs to fulfill, an overview of the history of active noise and vibration control is given. This is followed by a discussion of feedforward and feedback control concepts that have been successfully applied to active noise and vibration control. The paper concludes with a detailed description of an active vibration control system with active absorbers that is used to compensate periodic, engine-induced chassis vibrations. (orig.) [German] Moderne Steuer- und Regelungsverfahren werden im Kraftfahrzeug auch im Komfortbereich eine zunehmende Bedeutung erlangen. Der Bereich der Aggregatelagerung von Kraftfahrzeugen koennte in den naechsten Jahren als weitere Anwendungen hinzukommen, da hier die konventionelle Lagerungstechnik immer mehr an ihre Grenzen stoesst. Der vorliegende Beitrag gibt hierzu einen Ueberblick ueber die aktive Kompensation von Aggregateschwingungen. Nach einer kurzen Darstellung der Anforderungen und Aufgaben einer modernen Aggregatelagerung wird zunaechst ein Blick auf die Geschichte der aktiven Schall- und Schwingungskompensation geworfen. Anschliessend werden Steuer- und Regelungskonzepte vorgestellt und diskutiert, die in der Literatur erfolgreich bei Aufgaben der aktiven Schall- und Schwingungskompensation eingesetzt wurden. Der Beitrag schliesst mit der detaillierten Darstellung des Aufbaus und der Wirkungsweise eines aktiven Tilgersystems zur Kompensation von periodischen Aggregateschwingungen. (orig.)

  16. Time-domain filtered-x-Newton narrowband algorithms for active isolation of frequency-fluctuating vibration

    Li, Yan; He, Lin; Shuai, Chang-geng; Wang, Fei

    2016-04-01

    A time-domain filtered-x Newton narrowband algorithm (the Fx-Newton algorithm) is proposed to address three major problems in active isolation of machinery vibration: multiple narrowband components, MIMO coupling, and amplitude and frequency fluctuations. In this algorithm, narrowband components are extracted by narrowband-pass filters (NBPF) and independently controlled by multi-controllers, and fast convergence of the control algorithm is achieved by inverse secondary-path filtering of the extracted sinusoidal reference signal and its orthogonal component using L×L numbers of 2nd-order filters in the time domain. Controller adapting and control signal generation are also implemented in the time domain, to ensure good real-time performance. The phase shift caused by narrowband filter is compensated online to improve the robustness of control system to frequency fluctuations. A double-reference Fx-Newton algorithm is also proposed to control double sinusoids in the same frequency band, under the precondition of acquiring two independent reference signals. Experiments are conducted with an MIMO single-deck vibration isolation system on which a 200 kW ship diesel generator is mounted, and the algorithms are tested under the vibration alternately excited by the diesel generator and inertial shakers. The results of control over sinusoidal vibration excited by inertial shakers suggest that the Fx-Newton algorithm with NBPF have much faster convergence rate and better attenuation effect than the Fx-LMS algorithm. For swept, frequency-jumping, double, double frequency-swept and double frequency-jumping sinusoidal vibration, and multiple high-level harmonics in broadband vibration excited by the diesel generator, the proposed algorithms also demonstrate large vibration suppression at fast convergence rate, and good robustness to vibration with frequency fluctuations.

  17. Improved training of neural networks for the nonlinear active control of sound and vibration.

    Bouchard, M; Paillard, B; Le Dinh, C T

    1999-01-01

    Active control of sound and vibration has been the subject of a lot of research in recent years, and examples of applications are now numerous. However, few practical implementations of nonlinear active controllers have been realized. Nonlinear active controllers may be required in cases where the actuators used in active control systems exhibit nonlinear characteristics, or in cases when the structure to be controlled exhibits a nonlinear behavior. A multilayer perceptron neural-network based control structure was previously introduced as a nonlinear active controller, with a training algorithm based on an extended backpropagation scheme. This paper introduces new heuristical training algorithms for the same neural-network control structure. The objective is to develop new algorithms with faster convergence speed (by using nonlinear recursive-least-squares algorithms) and/or lower computational loads (by using an alternative approach to compute the instantaneous gradient of the cost function). Experimental results of active sound control using a nonlinear actuator with linear and nonlinear controllers are presented. The results show that some of the new algorithms can greatly improve the learning rate of the neural-network control structure, and that for the considered experimental setup a neural-network controller can outperform linear controllers. PMID:18252535

  18. Escape conditioning and low-frequency whole-body vibration - The effects of frequency, amplitude, and controls for noise and activation.

    Wike, E. L.; Wike, S. S.

    1972-01-01

    Seven experiments are reported on low-frequency whole-body vibration and rats' escape conditioning in a modified Skinner box. In the first three studies, conditioning was observed but was independent of frequency. In experiment four, the number of escape responses was directly related to vibration amplitude. Experiment five was a control for vibration noise and noise termination; experiments six and seven studied vibration-induced activation. Noise termination did not produce conditioning. In experiment six, subjects made more responses when responding led to termination than when it did not. In experiment seven, subjects preferred a bar which terminated vibration to one which did not.

  19. An Innovative Transponder-Based Interferometric Radar for Vibration Measurements

    Ground-based radar interferometry has recently emerged as an innovative technology of remote sensing, able to accurately measure the static or dynamic displacement of several points of a structure. This technique in the last couple of years has been applied to different types of structures, such as bridges, towers and chimneys. This paper presents a prototype system developed by IDS, originally aimed at measuring the structural vibrations of helicopter rotor blades, based on an interferometric technique and constituted by combination of a radar sensor and a series of transponders installed on the target structure. The main advantages of this solution with respect to conventional interferometric radars, are related to the increased spatial resolution of the system, provided by the possibility to discriminate different transponders installed within the same resolution cell of the radar sensor, and to the reduction of the ambient noise (e.g. multi-path) on the radar measurement. The first feature allows the use of the microwave technology even on target areas with limited dimensions, such as industrial facilities, while the second aspect may extend the use of radar interferometric systems to complex scenarios, where multi-reflections are expected due to the presence of natural targets with high reflectivity to the radar signal. In the paper, the system and its major characteristics are first described; subsequently, application to the measurement of ambient vibration response of a lab set-up is summarized. Then the data acquired on a rotating mock-up are reported and analyzed to identify natural frequencies and mode shapes of the investigated structure.

  20. An Innovative Transponder-Based Interferometric Radar for Vibration Measurements

    Coppi, F.; Cerutti, A.; Farina, P.; De Pasquale, G.; Novembrini, G.

    2010-05-01

    Ground-based radar interferometry has recently emerged as an innovative technology of remote sensing, able to accurately measure the static or dynamic displacement of several points of a structure. This technique in the last couple of years has been applied to different types of structures, such as bridges, towers and chimneys. This paper presents a prototype system developed by IDS, originally aimed at measuring the structural vibrations of helicopter rotor blades, based on an interferometric technique and constituted by combination of a radar sensor and a series of transponders installed on the target structure. The main advantages of this solution with respect to conventional interferometric radars, are related to the increased spatial resolution of the system, provided by the possibility to discriminate different transponders installed within the same resolution cell of the radar sensor, and to the reduction of the ambient noise (e.g. multi-path) on the radar measurement. The first feature allows the use of the microwave technology even on target areas with limited dimensions, such as industrial facilities, while the second aspect may extend the use of radar interferometric systems to complex scenarios, where multi-reflections are expected due to the presence of natural targets with high reflectivity to the radar signal. In the paper, the system and its major characteristics are first described; subsequently, application to the measurement of ambient vibration response of a lab set-up is summarized. Then the data acquired on a rotating mock-up are reported and analyzed to identify natural frequencies and mode shapes of the investigated structure.

  1. Semi-Active Control of Three-Dimensional Vibrations of an Inclined Sag Cable with Magnetorheological Dampers

    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...... fulfilled at which the optimal tuned viscous damper is designed, the MR damper and the viscous damper are performing equally well; however, if the response of the cable is dominated by several modes, the MR damper can achieve better vibration reduction effect compared with viscous damper. Especially, if the...... control effect and the robustness of the proposed semi-active control rule are also examined....

  2. Effect of hydrostatic and uniaxial pressure on structural properties and Raman active lattice vibrations in Bi2Te3

    The lattice parameters of the hexagonal unit cell, the atomic parameters, and the shift of the Raman active vibrations are measured of p-Bi2Te3 under uniaxial and hydrostatic pressure. The structural investigations are performed by neutron diffraction, and the lattice vibrations are studied by Raman scattering. The results of the diffraction experiments constitute a direct experimental confirmation of the weak bonding between the sandwiches in this narrow gap semiconductor with sandwich structure. As a consequence, some Raman active phonon modes show a rather strong dependence upon uniaxial pressure up to Δν/Δp = 1.9 x 10-8 cm-1/Pa. (author)

  3. VARIATIONS IN NEUROMUSCULAR ACTIVITY OF THIGH MUSCLES DURING WHOLE-BODY VIBRATION IN CONSIDERATION OF DIFFERENT BIOMECHANICAL VARIABLES

    Dennis Perchthaler

    2013-09-01

    Full Text Available The intention of this study was to systematically analyze the impact of biomechanical variables in terms of different vibration frequencies, amplitudes and knee angles on quadriceps femoris and hamstring activity during exposure to whole-body vibration (WBV. 51 healthy men and women (age 55 ± 8 years voluntary participated in the study and were randomly allocated to five different vibration-frequency groups. Each subject performed 9 static squat positions (3 amplitudes x 3 knee angles on a side alternating vibration platform. Surface electromyography (EMG was used to record the neuromuscular activity of the quadriceps femoris and hamstring muscles. Maximal voluntary contractions (MVCs were performed prior to the measurements to normalize the EMG signals. A three-way mixed ANOVA was performed to analyze the different effects of the biomechanical variables on muscle activity. Depending on the biomechanical variables, EMG muscle activity ranged between 18.2 and 74.1 % MVC in the quadriceps femoris and between 5.2 and 27. 3 % MVC in the hamstrings during WBV. The highest levels of muscle activation were found at high frequencies and large amplitudes. Especially in the quadriceps femoris muscle, a WBV frequency of 30 Hz led to a significant increase in muscle activity compared to the other tested frequencies. However, it seems that knee angle is only relevant for the quadriceps femoris muscle. The results of this study should give more information for developing individual training protocols for WBV treatment in different practical applications

  4. Neural networkbased semi-active control strategy for structural vibration mitigation with magnetorheological damper

    Bhowmik, Subrata

    2011-01-01

    This paper presents a neural network based semi-active control method for a rotary type magnetorheological (MR) damper. The characteristics of the MR damper are described by the classic Bouc-Wen model, and the performance of the proposed control method is evaluated in terms of a base exited shear......-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...... mode of the structure. The neural network control is then developed to reproduce the desired force based on damper displacement and velocity as network input, and it is therefore referred to as an amplitude dependent model reference control method. An inverse model of the MR damper is needed to...

  5. Neural network based semi-active control strategy for structural vibration mitigation with magnetorheological damper

    Bhowmik, Subrata

    2011-01-01

    This paper presents a neural network based semi-active control method for a rotary type magnetorheological (MR) damper. The characteristics of the MR damper are described by the classic Bouc-Wen model, and the performance of the proposed control method is evaluated in terms of a base exited shear......-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...... mode of the structure. The neural network control is then developed to reproduce the desired force based on damper displacement and velocity as network input, and it is therefore referred to as an amplitude dependent model reference control method. An inverse model of the MR damper is needed to...

  6. Design and experiments of an active isolator for satellite micro-vibration

    Li Weipeng

    2014-12-01

    Full Text Available In this paper, a soft active isolator (SAI derived from a voice coil motor is studied to determine its abilities as a micro-vibration isolation device for sensitive satellite payloads. Firstly, the two most important parts of the SAI, the mechanical unit and the low-noise driver, are designed and manufactured. Then, a rigid-flexible coupling dynamic model of the SAI is built, and a dynamic analysis is conducted. Furthermore, a controller with a sky-hook damper is designed. Finally, results from the performance tests of the mechanical/electronic parts and the isolation experiments are presented. The SAI attenuations are found to be more than −20 dB above 5 Hz, and the control effect is stable.

  7. Effect of Vibration Frequency on Serratus Anterior Muscle Activity during Performance of the Push-up Plus with a Redcord Sling

    Kim, Eui-ryong; Oh, Jae-Seop; Yoo, Won-Gyu

    2014-01-01

    [Purpose] We investigated the effect of vibration at various frequencies on serratus anterior (SA) muscle activity. [Subjects] Ten male subjects were recruited. [Methods] The subjects performed the push-up plus exercise supported by straps above the surface and vertical ropes in the Redcord sling. During the push-up plus, vibrations of 0, 30, 50, or 90 Hz were applied to the Redcord sling using a mechanical vibration apparatus attached to the rope. SA muscle activity was recorded using electr...

  8. Vibration reduction in helicopter rotors using an actively controlled partial span trailing edge flap located on the blade

    Millott, T. A.; Friedmann, P. P.

    1994-01-01

    This report describes an analytical study of vibration reduction in a four-bladed helicopter rotor using an actively controlled, partial span, trailing edge flap located on the blade. The vibration reduction produced by the actively controlled flap (ACF) is compared with that obtained using individual blade control (IBC), in which the entire blade is oscillated in pitch. For both cases a deterministic feedback controller is implemented to reduce the 4/rev hub loads. For all cases considered, the ACF produced vibration reduction comparable with that obtained using IBC, but consumed only 10-30% of the power required to implement IBC. A careful parametric study is conducted to determine the influence of blade torsional stiffness, spanwise location of the control flap, and hinge moment correction on the vibration reduction characteristics of the ACF. The results clearly demonstrate the feasibility of this new approach to vibration reduction. It should be emphasized than the ACF, used together with a conventional swashplate, is completely decoupled from the primary flight control system and thus it has no influence on the airworthiness of the helicopter. This attribute is potentially a significant advantage when compared to IBC.

  9. Effects of a whole body vibration training program on strength, power, and functional tests in the physically active elderly

    Renata Gonçalves da Silva

    2009-04-01

    Full Text Available The aim of this study was to investigate the effect of a whole body vibration training program on knee extensor isokinetic peak torque, average power, and functional tests in the physically active elderly. Forty-seven subjects, who participated in a training program for the elderly, were recruited. The subjects were divided into two groups: whole body vibration group (WBV (n=24, 70.7±5.8 years, 62.7±12.3 kg and 155.9±8.0 cm and control group (n=23. 70.0±5.7 years, 65.3±10.7 kg and 157.9±6.6 cm. The WBS group underwent whole body vibration exercise and their regular training program for 13 weeks, 2 times per week, whereas the control group performed the regular training program only. Whole body vibration training was not effective in increasing isokinetic peak torque, average power, or performance in the functional tests. On the other hand, the regular training program was effective in increasing elbow flexor strength endurance, distance covered in the 6-min walk test, and speed in the timed up and go test. The results suggest that vibration training is not effective in modifying functionality or muscle strength and power in the physically active elderly.

  10. Design of a one-chip board microcontrol unit for active vibration control of a naval ship mounting system

    This work presents an experimental implementation of a user-tunable one-chip board microcontrol unit which is specifically designed for vibration control of the active mounting system for naval ships. The proposed mounting system consists of four active mounts supporting vibration-sensitive equipment. Each active mount constitutes a rubber element, an inertial mass and the piezostack actuator. It is designed for particular applications that require effective isolation performance against wide frequency ranges, such as naval ship equipment. After describing the configuration of the active mount, dynamic characteristics of the rubber element and the piezostack actuator are experimentally identified. Accordingly, the proposed mounting system is constructed and the governing equations of motion are formulated. In order to attenuate the unwanted vibrations transferred from the upper mass, a feedforward controller with fast Fourier algorithm is designed and experimentally realized using the one-chip microcontrol board which is specially made for this practical application. In order to evaluate the performance of the one-chip microcontrol unit, vibration control results of the proposed active mounting system are presented in the frequency domain. (technical note)

  11. Semi-active friction tendons for vibration control of space structures

    Garrido, Hernán; Curadelli, Oscar; Ambrosini, Daniel

    2014-10-01

    Semi-active vibration control systems are becoming popular because they offer both the reliability of passive systems and the versatility of active control without high power demands. In this work, a new semi-active control system is proposed and studied numerically. The system consists of variable-friction dampers linked to the structure through cables. Auxiliary soft springs in parallel with these friction dampers allow them to return to their initial pre-tensioned state. Using cables makes the system suitable for deployable, flexible and lightweight structures, such as space structures (spacecraft). A control system with three control laws applied to a single-degree-of-freedom structure is studied. Two of these laws are derived by using Lyapunov theory, whereas the third one is developed heuristically. In order to assess the performance of the control system, a parametric study is carried out through numerical simulations. An application of the proposed method to multi-degree-of-freedom structures is also presented and demonstrated through a numerical example. The system in semi-active mode is more effective than in passive mode and its effectiveness is less sensitive to loss of pre-tension.

  12. An exploration of active hard mount vibration isolation for precision equipment

    Poel, van der, E.

    2010-01-01

    Vibrations due to environmental disturbances can cause a loss of accuracy in high-precision equipment. To reduce the vibration levels, the equipment is commonly mounted on soft mounts. However, the soft mount's low support stiffness may introduce difficulties in the response to direct disturbances and with the equipment levelling. In this thesis, an alternative vibration isolation concept is investigated, which uses stiff supports (hard mounts). The increased support stiffness circumvents the...

  13. Prediction of rotor blade-vortex interaction using Volterra integrals

    The theory of Volterra integral equations for nonlinear system is applied to the prediction of the nonlinear aerodynamic response of an NACA 0012 airfoil experiencing blade-vortex interaction. The phenomenon is first modeled in two-dimensions using an Euler/Navier-Stoke code, and the resulting unsteady aerodynamic flow field sequences are appropriately combined to form a training dataset. The Volterra kernels are identified in the time-domain characteristics of the selected data, which is in turn used to predict the nonlinear aerodynamic response of the airfoil. The Volterra kernel based data is then compared against a standard airfoil response. The predicted lift time histories of the airfoil are shown to be in good agreement with the aerodynamic data. (author)

  14. Dynamic characteristics of rotor blades with pendulum absorbers

    Murthy, V. R.; Goglia, G. L.

    1977-01-01

    The point transmission matrix for a vertical plane pendulum on a rotating blade undergoing combined flapwise bending, and chordwise bending and torsion is derived. The equilibrium equation of the pendulum is linearized for small oscillations about the steady state. A FORTRAN program was written for the case of a vertical plane pendulum attached to a uniform blade with flapwise bending degree of freedom for cantilever boundary conditions. The frequency has a singular value right at the uncoupled pendulum natural frequency and thus introduces two frequencies corresponding to the nearest natural frequency of the blade without pendulum. In both of these modes it was observed that the pendulum deflection is large. One frequency can be thought of as a coupled pendulum frequency and the other as a coupled bending and pendulum frequency.

  15. IEC-TC88WG8 testing of rotor blades

    Delft, D.R.V. van [Delft Univ. of Technology, STEVIN Lab., Delft (Netherlands)

    1996-09-01

    In 1994 the TC88 of IEC installed a working group (WG8) to draft a guideline on blade testing. This paper gives a description of the task of the working group. Furthermore it gives a report of the progress of the work and summarizes the possible contents of the working group document on blade testing. (au)

  16. Metal Rubber Sensor Appliquis for Rotor Blade Air Project

    National Aeronautics and Space Administration — Thin film Metal RubberTM sensor appliqus have the potential to reduce the time, complexity and cost of measuring air flow-induced skin friction during the...

  17. Sweep-twist adaptive rotor blade : final project report.

    Ashwill, Thomas D.

    2010-02-01

    Knight & Carver was contracted by Sandia National Laboratories to develop a Sweep Twist Adaptive Rotor (STAR) blade that reduced operating loads, thereby allowing a larger, more productive rotor. The blade design used outer blade sweep to create twist coupling without angled fiber. Knight & Carver successfully designed, fabricated, tested and evaluated STAR prototype blades. Through laboratory and field tests, Knight & Carver showed the STAR blade met the engineering design criteria and economic goals for the program. A STAR prototype was successfully tested in Tehachapi during 2008 and a large data set was collected to support engineering and commercial development of the technology. This report documents the methodology used to develop the STAR blade design and reviews the approach used for laboratory and field testing. The effort demonstrated that STAR technology can provide significantly greater energy capture without higher operating loads on the turbine.

  18. Power harvesting using piezomaterial in a helicopter rotor blade

    Jong, de P.H.; Boer, de A.; Loendersloot, R.; Hoogt, van der P.J.M.

    2010-01-01

    Current power harvesting research has focused on bending beams and determining power output under a given excitation. For the European CleanSky – Green Rotor Craft project a tool is being developed which optimizes the piezoelectric material and placement thereof for power harvesting. It focuses on b

  19. Rotor blade full-scale fatigue testing technology and research

    Nielsen, Per Hørlyk; Berring, Peter; Pavese, Christian; Branner, Kim

    Full scale fatigue test is an important part of the development and design of wind turbine blades. Testing is also needed for the approval of the blades in order for them to be used on large wind turbines. However, usually only one prototype blade is tested. Fatigue test of wind turbine blades was...... presented in this report giving the blade test facility operator a guide to choose the method that best fit the needs and economic constraints. The state of the art method is currently dual axis mass resonance, where the purpose of the test is to emulate the loads the blades encounter in operation....

  20. Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

    Jörg Bergner; Dietmar K. Hennecke; Martin Hoeger; Karl Engel

    2003-01-01

    For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.

  1. Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

    Jörg Bergner

    2003-01-01

    Full Text Available For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.

  2. Darmstadt Rotor No. 2, II: Design of Leaning Rotor Blades

    Bergner J.; Hennecke K. D.; Hoeger M.; Engel K.

    2003-01-01

    For Darmstadt University of Technology's axial singlestage transonic compressor rig, a new three-dimensional aft-swept rotor was designed and manufactured at MTU Aero Engines in Munich, Germany. The application of carbon fiber–reinforced plastic made it possible to overcome structural constraints and therefore to further increase the amount of lean and sweep of the blade. The aim of the design was to improve the mechanical stability at operation that is close to stall.To avoid the hazard of r...

  3. Tip Cascade Aerodynamics of Turbine Rotor Blade 1220mm

    Synáč, J.; Rudas, B.; Šťastný, M.; Luxa, Martin; Šimurda, David; Šafařík, Pavel

    Praha: TechSoft Engineering s.r.o., 2009 - (Moštěk, M.), s. 37-45 ISBN 978-80-254-4651-5. [Současné trendy při návrhu a výpočtu turbostrojů. Praha (CZ), 02.06.2009-04.06.2009] Institutional research plan: CEZ:AV0Z20760514 Keywords : aerodynamics * blade cascade * transonic flow * loss * turbine Subject RIV: BK - Fluid Dynamics

  4. Tip Cascade Aerodynamics of Turbine Rotor Blade 1220 mm

    Rudas, B.; Synáč, J.; Šťastný, M.; Luxa, Martin; Šimurda, David; Šafařík, Pavel

    Plzeň: Západočeská univerzita v Plzni, 2010, s. 1-6. ISBN N. [Turbostroje 2010. Plzeň (CZ), 22.09.2010-23.09.2010] Institutional research plan: CEZ:AV0Z20760514 Keywords : tip blade cascade * CFD simulation * high-speed aerodynamic Subject RIV: BK - Fluid Dynamics

  5. Computation of transonic potential flow on helicopter rotor blades

    Costes, M.; Jones, H. E.

    1987-01-01

    Two computer codes, the full-potential three-dimensional (FP3D) code and the full-potential rotor (FPR) code have recently been developed. Both of these codes solve the three-dimensional conservative formulation of the full potential equation. The FPR code was developed at the U.S. Army Aeroflightdynamics Directorate (AFDD) while the FP3D code was a joint development by ONERA and AFDD. Both of these codes were used to predict the nonlifting, unsteady flow over a rotor operating at high advance ratio and tip speed. Three different rotor tip planform shapes were studied: a rectangular tip, a 30 deg aft swept tip and a 30 deg forward swept tip. Results of these computations are compared to results obtained using an earlier small-disturbances code. Also, the lifting flow over a rectangular tip operating at a slightly different condition was computed. These results are also compared with the small disturbances computations and with experimental results.

  6. Methods for testing of geometrical down-scaled rotor blades

    Branner, Kim; Berring, Peter

    requirements for experimental facilities are very demanding and furthermore the time for performing the experimental test campaign and the cost are not well suitable for most research projects. This report deals with the advantages, disadvantages and open questions of using down-scaled testing on wind turbine......Full scale fatigue test is an important part of the development and design of wind turbine blades. Testing is also needed for the approval of the blades in order for them to be used on large wind turbines. Fatigue test of wind turbine blades was started in the beginning of the 1980s and has been...... scale MW wind turbine blade are very time consuming and expensive. For the industry that means that the tests, both static and fatigue, are not a tool in or a part of the design process. In the academic community, full scale testing of modern and future wind turbine blades are even more challenging as...

  7. Rotating Camera System for Propeller and Rotor Blade Deformation Measurements

    Boden, Fritz; Stasicki, Boleslaw; Szypula, Marek

    2015-01-01

    Within the EU project AIM² project a rotating stereoscopic camera system was designed, build and successfully flight tested in order to apply the non-intrusive Image Pattern Correlation Technique (IPCT) to 360° propeller deformation measurements. The complete system was affixed to the axis of the aircraft engine rotating together with the propeller at its full rotational speed. It enabled the direct measurement of the propeller blades shape as well as its local pitch angle under real operatin...

  8. Distinct Skeletal Muscle Gene Regulation from Active Contraction, Passive Vibration, and Whole Body Heat Stress in Humans

    Petrie, Michael A.; Kimball, Amy L.; McHenry, Colleen L.; Suneja, Manish; Yen, Chu-Ling; Sharma, Arpit; Shields, Richard K.

    2016-01-01

    Skeletal muscle exercise regulates several important metabolic genes in humans. We know little about the effects of environmental stress (heat) and mechanical stress (vibration) on skeletal muscle. Passive mechanical stress or systemic heat stress are often used in combination with many active exercise programs. We designed a method to deliver a vibration stress and systemic heat stress to compare the effects with active skeletal muscle contraction. Purpose: The purpose of this study is to examine whether active mechanical stress (muscle contraction), passive mechanical stress (vibration), or systemic whole body heat stress regulates key gene signatures associated with muscle metabolism, hypertrophy/atrophy, and inflammation/repair. Methods: Eleven subjects, six able-bodied and five with chronic spinal cord injury (SCI) participated in the study. The six able-bodied subjects sat in a heat stress chamber for 30 minutes. Five subjects with SCI received a single dose of limb-segment vibration or a dose of repetitive electrically induced muscle contractions. Three hours after the completion of each stress, we performed a muscle biopsy (vastus lateralis or soleus) to analyze mRNA gene expression. Results: We discovered repetitive active muscle contractions up regulated metabolic transcription factors NR4A3 (12.45 fold), PGC-1α (5.46 fold), and ABRA (5.98 fold); and repressed MSTN (0.56 fold). Heat stress repressed PGC-1α (0.74 fold change; p < 0.05); while vibration induced FOXK2 (2.36 fold change; p < 0.05). Vibration similarly caused a down regulation of MSTN (0.74 fold change; p < 0.05), but to a lesser extent than active muscle contraction. Vibration induced FOXK2 (p < 0.05) while heat stress repressed PGC-1α (0.74 fold) and ANKRD1 genes (0.51 fold; p < 0.05). Conclusion: These findings support a distinct gene regulation in response to heat stress, vibration, and muscle contractions. Understanding these responses may assist in developing regenerative

  9. Active vibration control of a smart plate using a piezoelectric sensor–actuator pair at elevated temperatures

    A new scheme for active structural vibration control using piezoelectric patches at elevated temperatures is analytically derived and experimentally verified. A control law is derived using augmented piezoelectric constitutive equations which include the temperature dependence of piezoelectric stress coefficient (e31) and permittivity ( element of 33). Since the temperature dependence of 'e31' and ' element of 33' is not analytically known, their experimental values measured at elevated temperatures are used. Using augmented constitutive equations, a finite element model of a smart two-dimensional isotropic plate instrumented with a collocated piezoelectric sensor–actuator pair is derived. A control law for active vibration control of the first mode of the smart cantilevered plate is derived using negative velocity feedback. Active vibration control of the first mode of a smart cantilevered plate is experimentally achieved at elevated temperatures ranging from 25 to 75 °C under two cases: (i) using a control law which ignores the temperature dependence of 'e31' and ' element of 33' and (ii) using a control law which includes the temperature dependence of 'e31' and ' element of 33'. A comparison between these two control laws shows that: (i) active vibration control (AVC) performance is not maintained at elevated temperatures using a control law which ignores the temperature dependence of 'e31' and ' element of 33' and (ii) AVC performance is maintained at elevated temperatures when we use a control law which includes the temperature dependence of 'e31' and ' element of 33'

  10. Implementation of local feedback controllers for vibration supression of a truss using active struts

    McClelland, Robert; Lim, Tae W.; Bosse, Albert; Fisher, Shalom

    1996-05-01

    This paper describes the design and implementation of local feedback controllers for active vibration suppression of a laboratory truss referred to as the Naval Research Laboratory (NRL) space truss. The NRL space truss is a 3.7 meter, 12-bay aluminum laboratory truss used as a testbed to explore smart structures technologies for future Navy spacecraft missions. To conduct real-time control and data acquisition for the implementation of controllers, a digital signal processor based system is used. Two piezoceramic active struts are employed in this experimental study. Each strut is instrumented with a force transducer and a displacement sensor. Modal strain energy computed using a refined finite element model was used to select the optimum locations of the two actuators to ensure controllability of the first two structural modes. Two local feedback controllers were designed and implemented, an integral force feedback and an integral plus double-integral force feedback. The controllers were designed independently for each active strut using classical control design techniques applied to an identified model of the system dynamics. System identification results and controller design procedure are described along with closed loop test results. The test results show up to a factor of 1/110 attenuation of the truss tip motion due to sinusoidal resonant input disturbances and up to 100 times increase in damping of the lower frequency modes of the truss.

  11. Active vibration control of Flexible Joint Manipulator using Input Shaping and Adaptive Parameter Auto Disturbance Rejection Controller

    Li, W. P.; Luo, B.; Huang, H.

    2016-02-01

    This paper presents a vibration control strategy for a two-link Flexible Joint Manipulator (FJM) with a Hexapod Active Manipulator (HAM). A dynamic model of the multi-body, rigid-flexible system composed of an FJM, a HAM and a spacecraft was built. A hybrid controller was proposed by combining the Input Shaping (IS) technique with an Adaptive-Parameter Auto Disturbance Rejection Controller (APADRC). The controller was used to suppress the vibration caused by external disturbances and input motions. Parameters of the APADRC were adaptively adjusted to ensure the characteristic of the closed loop system to be a given reference system, even if the configuration of the manipulator significantly changes during motion. Because precise parameters of the flexible manipulator are not required in the IS system, the operation of the controller was sufficiently robust to accommodate uncertainties in system parameters. Simulations results verified the effectiveness of the HAM scheme and controller in the vibration suppression of FJM during operation.

  12. Active Pneumatic Vibration Control by Using Pressure and Velocity Measurements and Adaptive Fuzzy Sliding-Mode Controller

    Jia-Wei Wu

    2013-07-01

    Full Text Available This paper presents an intelligent control strategy to overcome nonlinear and time-varying characteristics of a diaphragm-type pneumatic vibration isolator (PVI system. By combining an adaptive rule with fuzzy and sliding-mode control, the method has online learning ability when it faces the system’s nonlinear and time-varying behaviors during an active vibration control process. Since the proposed scheme has a simple structure, it is easy to implement. To validate the proposed scheme, a composite control which adopts both chamber pressure and payload velocity as feedback signal is implemented. During experimental investigations, sinusoidal excitation at resonance and random-like signal are input on a floor base to simulate ground vibration. Performances obtained from the proposed scheme are compared with those obtained from passive system and PID scheme to illustrate the effectiveness of the proposed intelligent control.

  13. Lead-Lag Control for Helicopter Vibration and Noise Reduction

    Gandhi, Farhan

    1995-01-01

    As a helicopter transitions from hover to forward flight, the main rotor blades experience an asymmetry in flow field around the azimuth, with the blade section tangential velocities increasing on the advancing side and decreasing on the retreating side. To compensate for the reduced dynamic pressure on the retreating side, the blade pitch angles over this part of the rotor disk are increased. Eventually, a high enough forward speed is attained to produce compressibility effects on the advancing side of the rotor disk and stall on the retreating side. The onset of these two phenomena drastically increases the rotor vibratory loads and power requirements, thereby effectively establishing a limit on the maximum achievable forward speed. The alleviation of compressibility and stall (and the associated decrease in vibratory loads and power) would potentially result in an increased maximum forward speed. In the past, several methods have been examined and implemented to reduce the vibratory hub loads. Some of these methods are aimed specifically at alleviating vibration at very high flight speeds and increasing the maximum flight speed, while others focus on vibration reduction within the conventional flight envelope. Among the later are several types passive as well as active schemes. Passive schemes include a variety of vibration absorbers such as mechanical springs, pendulums, and bifilar absorbers. These mechanism are easy to design and maintain, but incur significant weight and drag penalties. Among the popular active control schemes in consideration are Higher Harmonic Control (HHC) and Individual Blade Control (IBC). HHC uses a conventional swash plate to generate a multi-cyclic pitch input to the blade. This requires actuators capable of sufficiently high power and bandwidth, increasing the cost and weight of the aircraft. IBC places actuators in the rotating reference frame, requiring the use of slip rings capable of transferring enough power to the actuators

  14. Natural vibration of pre-twisted shear deformable beam systems subject to multiple kinds of initial stresses

    Leung, A. Y. T.; Fan, J.

    2010-05-01

    Free vibration and buckling of pre-twisted beams exhibit interesting coupling phenomena between compression, moments and torque and have been the subject of extensive research due to their importance as models of wind turbines and helicopter rotor blades. The paper investigates the influence of multiple kinds of initial stresses due to compression, shears, moments and torque on the natural vibration of pre-twisted straight beam based on the Timoshenko theory. The derivation begins with the three-dimensional Green strain tensor. The nonlinear part of the strain tensor is expressed as a product of displacement gradient to derive the strain energy due to initial stresses. The Frenet formulae in differential geometry are employed to treat the pre-twist. The strain energy due to elasticity and the linear kinetic energy are obtained in classical sense. From the variational principle, the governing equations and the associated natural boundary conditions are derived. It is noted that the first mode increases together with the pre-twisted angle but the second decreases seeming to close the first two modes together for natural frequencies and compressions. The gaps close monotonically as the angle of twist increases for natural frequencies and buckling compressions. However, unlike natural frequencies and compressions, the closeness is not monotonic for buckling shears, moments and torques.

  15. An exploration of active hard mount vibration isolation for precision equipment

    Poel, van der Gerrit Wijnand

    2010-01-01

    Vibrations due to environmental disturbances can cause a loss of accuracy in high-precision equipment. To reduce the vibration levels, the equipment is commonly mounted on soft mounts. However, the soft mount's low support stiffness may introduce difficulties in the response to direct disturbances a

  16. Semi-active control of three-dimensional vibrations of an inclined sag cable with magnetorheological dampers

    Zhou, Q.; Nielsen, S. R. K.; Qu, W. L.

    2006-09-01

    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 motion of cable-dampers system are first established, which accounts for coupling between in-plane and out-of-plane motions, and also for the displacement of the support points. A MR damper can be considered as a variable friction damper approximately, so a semi-active control strategy based on the modulated homogeneous friction algorithm is proposed. Taking a typical short cable as an example, the vibration reduction ability with optimally controlled MR dampers is verified numerically by comparison with the viscous damper tuned to a single mode response. The analysis show that, if the conditions are fulfilled at which the optimal tuned viscous damper is designed, the MR damper and the viscous damper are performing equally well; however, if the response of the cable is dominated by several modes, the MR damper can achieve better vibration reduction effect compared with viscous damper. Especially, if the amplitude of the support point motion less than a threshold value, MR damper can prevent subharmonic excitation caused by support point motion from taking place, consequently, MR damper achieves significant vibration reduction compared to viscous damper. In addition, the influence of measurement noise on control effect and the robustness of the proposed semi-active control rule are also examined.

  17. Active vibration-suppression systems applied to twin-tail buffeting

    Hopkins, Mark A.; Henderson, Douglas A.; Moses, Robert W.; Ryall, Thomas G.; Zimcik, David G.; Spangler, Ronald L., Jr.

    1998-06-01

    Buffeting is an aeroelastic phenomenon that plagues high performance aircraft, especially those with twin vertical tails. Unsteady cortices emanate form wing/fuselage leading edge extensions when these aircraft maneuver at high angles of attack. These aircraft are designed such that the vortices shed while maneuvering at high angels of attack and improve the lift-to-drag ratio of the aircraft. With proper placement and sizing of the vertical tails, this improvement may be maintained without adverse effects to the tails. However, there are tail locations and angels of attack where these vortices burst and immerse the vertical tails in their wake inducing severe structural vibrations. The resulting buffet loads and severe vertical tail response because an airframe life and maintenance concern as life cycle costs increased. Several passive methods have been investigated to reduce the buffeting of these vertical tails with limited success. As demonstrated through analyses, wind-tunnel investigations, and full-scale ground tests, active control system offer a promising solution to alleviate buffet induced strain and increase the fatigue life of vertical tails. A collaborative research project including the US, Canada, and Australia is in place to demonstrate active buffet load alleviation systems on military aircraft. The present paper provides details on this collaborative project and other research efforts to reduce the buffeting response of vertical tails in fighter aircraft.

  18. Finite element modeling of stiffened piezolaminated plates and shells with piezoelectric layers for active vibration control

    In this paper, a piezolaminated stiffened shell element is formulated. This piezoelectric shell element is a 9-noded, isoparametric, shear flexible and field-consistent element with five elastic degrees of freedom at each node and one electric degree of freedom per element per piezoelectric layer. The stiffener element is a three-noded isoparametric beam element with three degrees of freedom at each node. The effect of the stiffener is incorporated by internally constraining the stiffener displacement fields to the relevant shell displacement fields and hence this formulation allows the positioning of the stiffener element anywhere within the shell element along lines of natural coordinates, which gives a great flexibility in the choice of the mesh size. This stiffened shell element is validated for static deflection and dynamic response with the results available in literature. The active control performance of the stiffened composite plate and shell structures with distributed piezoelectric sensors and actuators are studied using a number of examples. The active vibration control is carried out using the LQR optimal control

  19. Numerical Simulation of a Semi-Active Vibration Control Device Based on Superelastic Shape Memory Alloy Wires

    Cismasiu, Corneliu; Santos, Filipe P. Amarante Dos

    2010-01-01

    The proposed semi-active vibration control device originates from a passive control system, based on SE austenitic wires. In its semi-active version, the system monitors the feedback measurements and based on this information, continuously adjust the strain in the SE wires in order to improve its dynamical characteristics. The strain accumulation in the wires is a result of the motion of the structure itself, with no need of external energy input in the system. To avoid relaxation phenomena, ...

  20. Active aeroelastic flutter analysis and vibration control of supersonic beams using the piezoelectric actuator/sensor pairs

    The active vibration control of all kinds of structures by using the piezoelectric material has been extensively investigated. In this paper, the active aeroelastic flutter characteristics and vibration control of supersonic beams applying the piezoelectric material are studied further. The piezoelectric materials are bonded on the top and bottom surfaces of the beams to act as the actuator and sensor so that the active aeroelastic flutter suppression for the supersonic beams can be conducted. The supersonic piston theory is adopted to evaluate the aerodynamic pressure. Hamilton's principle with the assumed mode method is used to develop the dynamical model of the structural systems. By using the standard eigenvalue methodology, the solutions for the complex eigenvalue problem are obtained. A negative velocity feedback control strategy is used to obtain active damping. The aeroelastic flutter bounds are calculated and the active aeroelastic flutter characteristics are analyzed. The impulse responses of the structural system are obtained by using the Houbolt numerical algorithm to study the active aeroelastic vibration control. The influences of the non-dimensional aerodynamic pressure on the active flutter control are analyzed. From the numerical results it is observed that the aeroelastic flutter characteristics of the supersonic beams can be significantly improved and that the aeroelastic vibration amplitudes can be remarkably reduced, especially at the flutter points, by using the piezoelectric actuator/sensor pairs which can provide an active damping. Within a certain value of the feedback control gain, with the increase of it, the flutter aerodynamic pressure (or flutter velocity) can be increased and the control results are also improved

  1. The Effect of a Single Session of Whole-Body Vibration Training in Recreationally Active Men on the Excitability of the Central and Peripheral Nervous System

    Chmielewska Daria

    2014-07-01

    Full Text Available Vibration training has become a popular method used in professional sports and recreation. In this study, we examined the effect of whole-body vibration training on the central nervous system and muscle excitability in a group of 28 active men. Subjects were assigned randomly to one of two experimental groups with different variables of vibrations. The chronaximetry method was used to evaluate the effect of a single session of whole-body vibration training on the excitability of the rectus femoris and brachioradialis muscles. The examination of the fusing and flickering frequencies of the light stimulus was performed. An increase in the excitability of the quadriceps femoris muscle due to low intensity vibrations (20 Hz frequency, 2 mm amplitude was noted, and a return to the initial values was observed 30 min after the application of vibration. High intensity vibrations (60 Hz frequency, 4 mm amplitude caused elongations of the chronaxy time; however, these differences were not statistically significant. Neither a low intensity vibration amplitude of 2 mm (frequency of 20 Hz nor a high intensity vibration amplitude of 4 mm (frequency of 60 Hz caused a change in the excitability of the central nervous system, as revealed by the average frequency of the fusing and flickering of the light stimulus. A single session of high intensity whole-body vibration did not significantly decrease the excitability of the peripheral nervous system while the central nervous system did not seem to be affected.

  2. Active Vibration Isolation of Micro-Manufacturing Platform Based on Neural Network

    2002-01-01

    The micromation and precision of the Micro-Electromechanical System demand that its manufacturing, measuring and assembling must work in a micro-manufacturing platform with good ability to isolate vibrations. This paper develops a vibration isolation system of micro-manufacturing platform. The brains of many kinds of birds can isolate vibrations well, such as woodpecker's brain. When a woodpecker pecks the wood at the speed as 1.6 times as the velocity of sound, its brain will tolerate the wallop 1 500 time...

  3. Phase and gain control policies for robust active vibration control of flexible structures

    The interest of this paper is to develop a general and systematic robust control methodology for active vibration control of flexible structures. For this purpose, first phase and gain control policies are proposed to impose qualitative frequency-dependent requirements on the controller to consider a complete set of control objectives. Then the proposed control methodology is developed by employing phase and gain control policies in the dynamic output feedback H∞ control: according to the set of control objectives, phase and gain control policies incorporate necessary weighting functions and determine them in a rational and systematic way; on the other hand, with the appropriate weighting functions efficient H∞ control algorithms can automatically realize phase and gain control policies and generate a satisfactory H∞ controller. The proposed control methodology can be used for both SISO and MIMO systems with collocated or non-collocated sensors and actuators. In this paper, it is validated on a non-collocated piezoelectric cantilever beam. Both numerical simulations and experimental results demonstrate the effectiveness of the proposed control methodology. (paper)

  4. Active vibration control of a full scale aircraft wing using a reconfigurable controller

    Prakash, Shashikala; Renjith Kumar, T. G.; Raja, S.; Dwarakanathan, D.; Subramani, H.; Karthikeyan, C.

    2016-01-01

    This work highlights the design of a Reconfigurable Active Vibration Control (AVC) System for aircraft structures using adaptive techniques. The AVC system with a multichannel capability is realized using Filtered-X Least Mean Square algorithm (FxLMS) on Xilinx Virtex-4 Field Programmable Gate Array (FPGA) platform in Very High Speed Integrated Circuits Hardware Description Language, (VHDL). The HDL design is made based on Finite State Machine (FSM) model with Floating point Intellectual Property (IP) cores for arithmetic operations. The use of FPGA facilitates to modify the system parameters even during runtime depending on the changes in user's requirements. The locations of the control actuators are optimized based on dynamic modal strain approach using genetic algorithm (GA). The developed system has been successfully deployed for the AVC testing of the full-scale wing of an all composite two seater transport aircraft. Several closed loop configurations like single channel and multi-channel control have been tested. The experimental results from the studies presented here are very encouraging. They demonstrate the usefulness of the system's reconfigurability for real time applications.

  5. Adaptive Active Control of Machine-Tool Vibration In a Lathe

    Claesson, Ingvar; Håkansson, Lars

    1998-01-01

    In the turning operation the relative dynamic motion between cutting tool and workpiece, or vibration, is a frequent problem, which affects the result of the machining, and in particular, the surface finish. Tool life is also influenced by vibration. Noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. With proper machine design, i.e. improved stiffness of the machine structure, the problem of relative dynamic motion betw...

  6. Reduction of structural weight, costs and complexity of a control system in the active vibration reduction of flexible structures

    This paper concerns the active vibration reduction of a flexible structure with discrete piezoelectric sensors and actuators in collocated pairs bonded to its surface. In this study, a new fitness and objective function is proposed to determine the optimal number of actuators, based on variations in the average closed loop dB gain margin reduction for all of the optimal piezoelectric pairs and on the modes that are required to be attenuated using the optimal linear quadratic control scheme. The aim of this study is to find the minimum number of optimally located sensor/actuator pairs, which can achieve the same vibration reduction as a greater number, in order to reduce the cost, complexity and power requirement of the control system. This optimization was done using a genetic algorithm. The technique may be applied to any lightly damped structure, and is demonstrated here by attenuating the first six vibration modes of a flat cantilever plate. It is shown that two sensor/actuator pairs, located and controlled optimally, give almost the same vibration reduction as ten pairs. These results are validated by comparing the open and closed loop time responses and actuator feedback voltages for various numbers of piezoelectric pairs using the ANSYS finite element package and a proportional differential control scheme. (paper)

  7. Structural, vibrational spectroscopic and nonlinear optical activity studies on 2-hydroxy- 3, 5-dinitropyridine: A DFT approach

    Asath, R. Mohamed; Premkumar, S.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com [Department of Physics, N.M.S.S.V.N College, Madurai-625019 (India); Jawahar, A. [Department of Chemistry, N.M.S.S.V.N College, Madurai-625019 (India)

    2015-06-24

    The conformational analysis was carried out for 2-Hydroxy- 3, 5-dinitropyridine molecule using potential energy surface scan and the most stable optimized conformer was predicted. The vibrational frequencies and Mulliken atomic charge distribution were calculated for the optimized geometry of the molecule using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intramolecular charge transfer studies and the calculation of ionization energy, electron affinity, global hardness, chemical potential, electrophilicity index and softness values of the title molecule were carried out. The nonlinear optical activity of the molecule was studied by means of first order hyperpolarizability, which was computed as 7.64 times greater than urea. The natural bond orbital analysis was performed to confirm the nonlinear optical activity of the molecule.

  8. Structural, vibrational spectroscopic and nonlinear optical activity studies on 2-hydroxy- 3, 5-dinitropyridine: A DFT approach

    Asath, R. Mohamed; Premkumar, S.; Jawahar, A.; Mathavan, T.; Dhas, M. Kumara; Benial, A. Milton Franklin

    2015-06-01

    The conformational analysis was carried out for 2-Hydroxy- 3, 5-dinitropyridine molecule using potential energy surface scan and the most stable optimized conformer was predicted. The vibrational frequencies and Mulliken atomic charge distribution were calculated for the optimized geometry of the molecule using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intramolecular charge transfer studies and the calculation of ionization energy, electron affinity, global hardness, chemical potential, electrophilicity index and softness values of the title molecule were carried out. The nonlinear optical activity of the molecule was studied by means of first order hyperpolarizability, which was computed as 7.64 times greater than urea. The natural bond orbital analysis was performed to confirm the nonlinear optical activity of the molecule.

  9. Structural, vibrational spectroscopic and nonlinear optical activity studies on 2-hydroxy- 3, 5-dinitropyridine: A DFT approach

    The conformational analysis was carried out for 2-Hydroxy- 3, 5-dinitropyridine molecule using potential energy surface scan and the most stable optimized conformer was predicted. The vibrational frequencies and Mulliken atomic charge distribution were calculated for the optimized geometry of the molecule using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intramolecular charge transfer studies and the calculation of ionization energy, electron affinity, global hardness, chemical potential, electrophilicity index and softness values of the title molecule were carried out. The nonlinear optical activity of the molecule was studied by means of first order hyperpolarizability, which was computed as 7.64 times greater than urea. The natural bond orbital analysis was performed to confirm the nonlinear optical activity of the molecule

  10. Free Vibration of Partially Supported Cylindrical Shells

    Mirza, S.; Y. Alizadeh

    1995-01-01

    The effects of detached base length on the natural frequencies and modal shapes of cylindrical shell structures were investigated in this work. Some of the important applications for this type of problem can be found in the cracked fan and rotor blades that can be idealized as partially supported shells with varying unsupported lengths. A finite element model based on small deflection linear theory was developed to obtain numerical solutions for this class of problems. The numerical results w...

  11. Application of Time Delay Consideration on Bridge Vibration Control Method with Active Tendons

    Lezin Seba MINSILI

    2010-12-01

    Full Text Available For many years bridge structures have been designed or constructed as passive structures that rely on their mass and solidity to resist external forces, while being incapable of adapting to the dynamics of an ever-changing environment. When the rigidity assumption is not met in particular for high-rise structures like bridge towers, a proper dynamic model should be established and conclusions made on the differential vibration of the tower when it is investigated out of the bridge system. The present work outlines a vibration control method by tendons on the tower of cable supported structures considering time delay effects, based on the discrete-time Linearization of the Feedback Gain Matrix. The efficiency of this vibration control method first proposed on the design process of a local bridge in Cameroon, is more compatible to the control of civil structures and is of great interest in accordance with simulation results.

  12. The actuated performance of multi-layer piezoelectric actuator in active vibration control of honeycomb sandwich panel

    Luo, Yajun; Xie, Shilin; Zhang, Xinong

    2008-11-01

    This paper discusses the use of the multi-layer piezoelectric actuator (MPA) in the active vibration control of the honeycomb sandwich panel (HSP). A literature overview of the available works is first presented. And the main motivation using the MPA in the AVC of HSP is discussed. Then, the honeycomb core is in advance treated as an orthotropic plate. The governing equations of the system are derived by the Hamilton principle on the basis of both displacement and transverse tress assumptions. The formulations of the actuation force/moment are obtained and indicate that the actuation force/moment are two four-order polynomial function of the piezoelectric layers number. Finally, active control experiments of a cantilever honeycomb sandwich panel (CHSP) are performed using the MPA. The control law of proportional velocity feedback is adopted in the experiments. These experiments include the resonant vibration control and the sinusoidal swept of the control system at the case of different piezoelectric layers number. The results show that the MPA can effectively control the vibration of the high damping HSP, and the control performance per voltage by the proposed actuator can be improved significantly through increasing the piezoelectric patch number. Consequently, the MPA exhibits better actuation capability than that with only single layer.

  13. Active vibration reduction of a flexible structure bonded with optimised piezoelectric pairs using half and quarter chromosomes in genetic algorithms

    The optimal placement of sensors and actuators in active vibration control is limited by the number of candidates in the search space. The search space of a small structure discretized to one hundred elements for optimising the location of ten actuators gives 1.73 × 1013 possible solutions, one of which is the global optimum. In this work, a new quarter and half chromosome technique based on symmetry is developed, by which the search space for optimisation of sensor/actuator locations in active vibration control of flexible structures may be greatly reduced. The technique is applied to the optimisation for eight and ten actuators located on a 500×500mm square plate, in which the search space is reduced by up to 99.99%. This technique helps for updating genetic algorithm program by updating natural frequencies and mode shapes in each generation to find the global optimal solution in a greatly reduced number of generations. An isotropic plate with piezoelectric sensor/actuator pairs bonded to its surface was investigated using the finite element method and Hamilton's principle based on first order shear deformation theory. The placement and feedback gain of ten and eight sensor/actuator pairs was optimised for a cantilever and clamped-clamped plate to attenuate the first six modes of vibration, using minimization of linear quadratic index as an objective function.

  14. The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

    Perera, Angelo S.; Thomas, Javix; Poopari, Mohammad R.; Xu, Yunjie

    2016-01-01

    Vibrational optical activity spectroscopies, namely vibrational circular dichroism (VCD) and Raman optical activity (ROA), have been emerged in the past decade as powerful spectroscopic tools for stereochemical information of a wide range of chiral compounds in solution directly. More recently, their applications in unveiling solvent effects, especially those associated with water solvent, have been explored. In this review article, we first select a few examples to demonstrate the unique sen...

  15. Vibration sense and sympathetic vasoconstrictor activity in patients with occlusive arterial disease

    Bjerre-Jepsen, K; Henriksen, O; Parm, Martin Lehnsbo; Agerskov, K; Tønnesen, K H

    1983-01-01

    The function of sympathetic vasoconstrictor fibres was studied in 18 patients with occlusive arterial disease of the legs and somatic neuropathy, as evidenced as an increased vibration perception threshold. Nine patients suffered from long-term diabetes mellitus. Sympathetic vasoconstrictor funct...

  16. ACTIVE VIBRATION REDUCTION OF RIGID ROTOR BY KINEMATIC EXCITATION OF BUSHES OF JOURNAL BEARINGS

    Ondrouch, Jan; Ferfecki, Petr; Poruba, Z.

    2009-01-01

    Roč. 49, č. 2 (2009), s. 107-110. ISSN 0543-5846 Institutional research plan: CEZ:AV0Z20760514 Keywords : bearing * controller * rotor system * vibration reduction Subject RIV: JR - Other Machinery Impact factor: 0.439, year: 2009

  17. Optimal placement and active vibration control for piezoelectric smart flexible cantilever plate

    Qiu, Zhi-cheng; Zhang, Xian-min; Wu, Hong-xin; Zhang, Hong-hua

    2007-04-01

    Some flexible appendages of spacecraft are cantilever plate structures, such as sun plate and satellite antenna. Thus, vibration problem will be caused by parameter uncertainties and environmental disturbances. In this paper, piezoelectric ceramics patches are used as sensors and actuators to suppress the vibration of the smart flexible clamped plate. Firstly, modal equations and piezoelectric control equations of cantilever plate are derived. Secondly, an optimal placement method for the locations of piezoelectric actuators and sensors is developed based on the degree of observability and controllability indices for cantilever plate. The bending and torsional modes are decoupled by the proposed method using bandwidth Butterworth filter. Thirdly, an efficient control method by combining positive position feedback and proportional-derivative control is proposed for vibration reduction. The analytical results for modal frequencies, transient responses and control responses are carried out. Finally, an experimental setup of piezoelectric smart plate is designed and built up. The modal frequencies and damping ratios of the plate setup are obtained by identification method. Also, the experimental studies on vibration control of the cantilever plate including bending modes and torsional modes are conducted. The analytical and experimental results demonstrate that the presented control method is feasible, and the optimal placement method is effective.

  18. Basis Set Dependence of Vibrational Raman and Raman Optical Activity Intensities.

    Cheeseman, James R; Frisch, Michael J

    2011-10-11

    We present a systematic study of the basis set dependence of the backscattering vibrational Raman intensities and Raman Optical Activity (ROA) intensity differences. The accuracies of computed Raman intensities and ROA intensity differences for a series of commonly used basis sets are reported, relative to large reference basis sets, using the B3LYP density functional. This study attempts to separately quantify the relative accuracies obtained from particular basis set combinations: one for the geometry optimization and force field computation and the other for the computation of Raman and ROA tensors. We demonstrate here that the basis set requirements for the geometry and force fields are not similar to those of the Raman and ROA tensors. The Raman and ROA tensors require basis sets with diffuse functions, while geometry optimizations and force field computations typically do not. Eleven molecules were examined: (S)-methyloxirane, (S)-methylthirane, (R)-epichlorhydrin, (S)-CHFClBr, (1S,5S)-α-pinene, (1S,5S)-β-pinene, (1S,4S)-norborneneone, (M)-σ-[4]-helicene, an enone precursor to a cytotoxic sesquiterpene, the gauche-gauche conformer of the monosaccharide methyl-β-d-glucopyranose, and the dipeptide Ac-(alanine)2-NH2. For the molecules examined here, intensities and intensity differences obtained from Raman and ROA tensors computed using the aug-cc-pVDZ basis set are nearly equivalent to those computed with the larger aug-cc-pVTZ basis set. We find that modifying the aug-cc-pVDZ basis set by removing the set of diffuse d functions on all atoms (while keeping the diffuse s and p sets), denoted as aug(sp)-cc-pVDZ, results in a basis set which is significantly faster without much reduction in the overall accuracy. In addition, the popular rDPS basis set introduced by Zuber and Hug offers a good compromise between accuracy and efficiency. The combination of either the aug(sp)-pVDZ or rDPS basis for the computation of the Raman and ROA tensors with the 6-31G

  19. Continuation and Bifuration Analysis in Helicopter Aeroelastic Stability Problems

    Rezgui, Djamel; Lowenberg, Mark H.; Jones, Mark; Monteggia, Claudio

    2014-01-01

    The dynamics of rotary wing systems are complex and typically feature highly nonlinear and often unsteady aerodynamics, as well as aeroelastic influences. In ongoing efforts to reduce noise and vibration, active devices such as trailing edge flaps on the rotor blades are being studied and these devices can introduce further nonlinearities. Therefore, it is important to be able to evaluate the stability of the overall system with a proper understanding of the global nonlinear behavior. Numeric...

  20. Identification of Rotorcraft Structural Dynamics from Flight and Wind Tunnel Data

    McKillip, Robert M., Jr.

    1997-01-01

    Excessive vibration remains one one of the most difficult problems that faces the helicopter industry today, affecting all production helicopters at some phase of their development. Vibrations in rotating structures may arise from external periodic dynamic airloads whose frequencies are are close to the natural frequencies of the rotating system itself. The goal for the structures engineer would thus be to design a structure as free from resonance effects as possible. In the case of a helicopter rotor blade these dynamic loads are a consequence of asymmetric airload distribution on the rotor blade in forward flight, leading to a rich collection of higher harmonic airloads that force rotor and airframe response. Accurate prediction of the dynamic characteristics of a helicopter rotor blade will provide the opportunity to affect in a positive manner noise intensity, vibration level, durability, reliability and operating costs by reducing objectionable frequencies or moving them to a different frequency range and thus providing us with a lower vibration rotor. In fact, the dynamic characteristics tend to define the operating limits of a rotorcraft. As computing power has increased greatly over the last decade, researchers and engineers have turned to analyzing the vibrational characteristics of aerospace structures at the design and development stage of the production of an aircraft. Modern rotor blade construction methods lead to products with low mass and low inherent damping so careful design and analysis is required to avoid resonance and an undesirable dynamic performance. In addition, accurate modal analysis is necessary for several current approaches in elastic system identification and active control.

  1. NONLINEAR OPTICS: Stimulated scattering of light in an active medium with overheating-ionization and vibrational-thermal instabilities

    Fedorov, S. V.

    1990-05-01

    Transient stimulated scattering increments are derived and investigated for various ranges of instability of a saturable radiation beam and under various conditions of heat evolution in an active medium. An allowance is made for the influence of a vibrational-thermal instability of the medium and for an overheating-ionization instability of a discharge on the stimulated scattering characteristics. The stimulated scattering gain is considered for temperature waves and for inversion waves. Estimates are obtained of the increments and characteristic scales of the radiation instability in inverted CO2 laser mixtures.

  2. A Novel Hybrid Error Criterion-Based Active Control Method for on-Line Milling Vibration Suppression with Piezoelectric Actuators and Sensors

    Xingwu Zhang; Chenxi Wang; Gao, Robert X.; Ruqiang Yan; Xuefeng Chen; Shibin Wang

    2016-01-01

    Milling vibration is one of the most serious factors affecting machining quality and precision. In this paper a novel hybrid error criterion-based frequency-domain LMS active control method is constructed and used for vibration suppression of milling processes by piezoelectric actuators and sensors, in which only one Fast Fourier Transform (FFT) is used and no Inverse Fast Fourier Transform (IFFT) is involved. The correction formulas are derived by a steepest descent procedure and the control...

  3. Comparison of the Electronic and Vibrational Optical Activity of a Europium(III) Complex

    Wu, Tao; Hudecová, Jana; You, X. Z.; Urbanová, M.; Bouř, Petr

    2015-01-01

    Roč. 21, č. 15 (2015), s. 5807-5813. ISSN 0947-6539 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA13-03978S; GA ČR GA15-09072S Grant ostatní: GA AV ČR(CZ) M200551205 Institutional support: RVO:61388963 Keywords : chirality * electronic states * lanthanides * luminescence * Raman spectroscopy * vibrational spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.731, year: 2014

  4. Active Vibration Reduction of Titanium Alloy Fan Blades (FAN1) Using Piezoelectric Materials

    Choi, Benjamin; Kauffman, Jeffrey; Duffy, Kirsten; Provenza, Andrew; Morrison, Carlos

    2010-01-01

    The NASA Glenn Research Center is developing smart adaptive structures to improve fan blade damping at resonances using piezoelectric (PE) transducers. In this paper, a digital resonant control technique emulating passive shunt circuits is used to demonstrate vibration reduction of FAN1 Ti real fan blade at the several target modes. Single-mode control and multi-mode control using one piezoelectric material are demonstrated. Also a conceptual study of how to implement this digital control system into the rotating fan blade is discussed.

  5. Active vibration suppression in a flexible cantilever beam using fuzzy logic controllers

    This paper presents a novel control system to find suitable solution for addressing the vibration problems in fixed-free cantilever beam system structures. The solution n is generated using fuzzy logic controller (FLC) utilizing single and multiple control actuators. The fuzzy controller employs the error (between a reference model output and the cantilever response) and error change to generate the control input increment in order to preserve the desired reference model performance. The controller is tested within a simulation environment. Results show that an excellent control performance is possible. (author). 14 refs. 3 tab., 15 figs

  6. Active Vibration Control of Elastic Beam by Means of Shape Memory Alloy Layers

    Chen, Q.; Levy, C.

    1996-01-01

    The mathematical model of a flexible beam covered with shape memory alloy (SMA) layers is presented. The SMA layers are used as actuators, which are capable of changing their elastic modulus and recovery stress, thus changing the natural frequency of, and adjusting the excitation to, the vibrating beam. The frequency factor variation as a function of SMA Young's modulus, SMA layer thickness and beam thickness is discussed. Also control of the beam employing an optimal linear control law is evaluated. The control results indicate how the system reacts to various levels of excitation input through the non-homogeneous recovery shear term of the governing differential equation.

  7. Experimental investigation of active vibration control using neural networks and piezoelectric actuators

    Jha, Ratneshwar; Rower, Jacob

    2002-02-01

    The use of neural networks for identification and control of smart structures is investigated experimentally. Piezoelectric actuators are employed to suppress the vibrations of a cantilevered plate subject to impulse, sine wave and band-limited white noise disturbances. The neural networks used are multilayer perceptrons trained with error backpropagation. Validation studies show that the identifier predicts the system dynamics accurately. The controller is trained adaptively with the help of the neural identifier. Experimental results demonstrate excellent closed-loop performance and robustness of the neurocontroller.

  8. Vibrational spectroscopic, structural and nonlinear optical activity studies on 2-amino-3-chloro-5-trifluoromethyl pyridine: A DFT approach

    Asath, R. Mohamed; Premkumar, S.; Rekha, T. N.; Jawahar, A.; Mathavan, T.; Benial, A. Milton Franklin

    2016-05-01

    The conformational analysis was carried out for 2-amino-3-chloro-5-trifluoromethylpyridine using potential energy surface (PES) scan and the most stable optimized conformer was predicted. The theoretical vibrational frequencies were calculated for the optimized geometry using DFT/B3LYP cc-pVQZ basis set by Gaussian 09 Program. The vibrational frequencies were assigned on the basis of potential energy distribution calculation using VEDA 4.0 program package. The Mulliken atomic charge values were calculated. In the Frontier molecular orbitals analysis, the molecular reactivity, kinetic stability, intermolecular charge transfer studies and the calculation of ionization energy, electron affinity, global hardness, chemical potential, electrophilicity index and softness of the molecule were carried out. The nonlinear optical (NLO) activity was studied and the first order hyperpolarizability value was computed, which was 3.48 times greater than the urea. The natural bond orbital analysis was also performed to confirm the NLO activity of the molecule. Hence, the ACTP molecule is a promising candidate for NLO materials.

  9. A wave-based design of semi-active piezoelectric composites for broadband vibration control

    Fan, Y.; Collet, M.; Ichchou, M.; Li, L.; Bareille, O.; Dimitrijevic, Z.

    2016-05-01

    This paper deals with the design of periodic piezoelectric structures for broadband vibration control. By shunting identical negative capacitances to the periodically distributed piezoelectric patches, a wide and continuous band gap is created so as to cover the frequency range of interest. This way the modal density of the structure is reduced and the modal shapes are localized at the boundaries. A large proportion of the energy can then be removed or dissipated by a small number of dampers or energy harvesters integrated within the negative capacitance circuits. A design process is proposed to achieve the wide band gap. The overall amount of piezoelectric materials is constrained in order to keep mass of structures low. The wave electromechanical coupling factor is proposed and used as a criterion. This allows to reach the largest width of the band gap by using a stable value of negative capacitance. The control of multiple high-order modes of a cantilever beam is considered as an example. The vibration reduction performance of the designed piezoelectric structures is presented and the influences of band gap resonance, resistor and the boundary condition are discussed. The proposed approach is fully based on wave characteristics and it does not rely on any modal information. It is therefore promising for applications at mid- and high frequencies where the access to the exact modal information is difficult.

  10. Development of an active vertical vibration control system for high speed railway vehicles; Jogekei active seishin seigyo sochi no kaihatsu (300X Shinkansen shiken sharyo deno soko shiken kekka)

    Shirai, S.; Otsuka, T. [Central Japan Railway Company, Nagoya (Japan); Nishi, Y.; Matsushima, H.; Danbata, K. [Kawasaki Heavy Industries, Ltd., Kobe (Japan)

    1999-09-15

    With an objective to improve riding comfort in the 300X system Shinkansen vehicle, development has been made on an active vibration control system which gives force to the vehicle body forcibly by a hydraulic actuator to suppress vertical vibration. The H {infinity} control was used in designing the controller. The controller to control vertical translation and pitch vibration in the vehicle body controls frequency in the vicinity of about 1 Hz being resonant frequency of a suspension system. However, it does not control frequency band of 8 to 9 Hz being resonant frequency of the vehicle bending vibration. In turn, the controller to control the vehicle bending vibration controls frequency band of 8 to 9 Hz only. This allows the interference to be ignored nearly completely. As a result of the stationary test, it was verified that the vibration can be reduced by the active vibration control system also on the vehicle bending vibration, which had conventionally been handled by improving rigidity of the vehicle or by turning the bogie spring and damper systems. Good result has also been obtained from a driving test using test vehicles. (NEDO)

  11. Vibration control in accelerators

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  12. Application of Energy Finite Element Method in Active Vibration Control of Piezoelectric Intelligent Beam

    Jinhua Xie

    2012-01-01

    Full Text Available Based on the transmission and equilibrium relationship of vibration energy in beam-like structures, the Galerkin weighted residual method was applied to equation discretization. An equivalent transformation of feedback element was suggested to develop the Energy Finite Element model of a composite piezoelectric cantilever beam driven by harmonic excitation on lateral direction, with both systems with and without time delay being studied and the power input estimation of harmonic excitation was discussed for the resolution of Energy Finite Element function. Then the energy density solutions of the piezoelectric coupling beam through Energy Finite Element Method (EFEM and classical wave theory were compared to verify the EFEM model, which presented a good accordance. Further investigation was undertaken about the influence of control parameters including the feedback gain and arrangement of piezoelectric patches on characteristics of system energy density distribution.

  13. Analysis and testing of an integrated semi-active seat suspension for both longitudinal and vertical vibration control

    Bai, Xian-Xu; Jiang, Peng; Pan, Hui; Qian, Li-Jun

    2016-04-01

    An integrated semi-active seat suspension for both longitudinal and vertical vibration control is analyzed and tested in this paper. The seat suspension consists of a switching mechanism transforming both longitudinal and vertical motions into a rotary motion and a real-time damping-controllable system-a rotary magnetorheological (MR) damper working in pure shear mode and its corresponding control system. The switching mechanism employs the parallelogram frames as a motion guide which keeps the seat moving longitudinally and vertically. At the same time, both longitudinal and vertical motions are transformed into a reciprocating rotary motion that is transmitted to the rotary MR damper after an amplification by a gear mechanism. Both the longitudinal and vertical vibrations can be attenuated in real time through controlling the damping force (or torque) of the rotary MR damper. The mathematical model of the seat suspension system is established, simulated, and analyzed. The experimental test based on the test rig in Hefei University of Technology is implemented, and the results of simulation and experimental test are compared and analyzed.

  14. Multi Objective Robust Active Vibration Control for Flexure Jointed Struts of Stewart Platforms via H∞ and μ Synthesis

    Liu Lei; Wang Benli

    2008-01-01

    Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for ac- tive/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H∞ controller is less than that of μ controller, but the order of μ controller is higher than that of H∞ controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.

  15. A point-wise fiber Bragg grating displacement sensing system and its application for active vibration suppression of a smart cantilever beam subjected to multiple impact loadings

    In this work, active vibration suppression of a smart cantilever beam subjected to disturbances from multiple impact loadings is investigated with a point-wise fiber Bragg grating (FBG) displacement sensing system. An FBG demodulator is employed in the proposed fiber sensing system to dynamically demodulate the responses obtained by the FBG displacement sensor with high sensitivity. To investigate the ability of the proposed FBG displacement sensor as a feedback sensor, velocity feedback control and delay control are employed to suppress the vibrations of the first three bending modes of the smart cantilever beam. To improve the control performance for the first bending mode when the cantilever beam is subjected to an impact loading, we improve the conventional velocity feedback controller by tuning the control gain online with the aid of information from a higher vibration mode. Finally, active control of vibrations induced by multiple impact loadings due to a plastic ball is performed with the improved velocity feedback control. The experimental results show that active vibration control of smart structures subjected to disturbances such as impact loadings can be achieved by employing the proposed FBG sensing system to feed back out-of-plane point-wise displacement responses with high sensitivity. (paper)

  16. Active control of vibration using a fuzzy control method based on scaling universes of discourse

    Si, Hongwei; Li, Dongxu

    2007-06-01

    Large flexible space structures are complex in structural dynamic characteristics. The control method based on custom control theory and modern control theory is difficult to solve for the complex problem. The fuzzy controller is not dependent on the accurate model. But the precision of a conventional fuzzy controller is not good, and the adaptive ability of a conventional fuzzy controller is limited. The fuzzy controller can make the system surge. Scaling universes of discourse is an effective method to improve the performance of the fuzzy controller. This paper is aimed at the difficult problem of designing a stable adaptive controller based on scaling universes of discourse, and letting input membership function and output membership function be denoted as input universes of discourse and the center value of output membership function, respectively. A kind of Lyapunov function, designed as an adaptive law of input universes of discourse and the center value of output membership function, was then adopted. A kind of stable self-adaptive fuzzy controller based on scaling universes of discourse is designed in this paper for the vibration control of a large flexible space truss driven by piezoelectric sensors and actuators (PZTs).

  17. Control of transient vibrations due to stage movements in 6-dof active pneumatic table by inertial force compensation

    Sun, Jong-Oh; Kim, Kwang-joon

    2013-10-01

    Passive pneumatic tables are popularly used in precision measurements or processes for isolation of ground vibrations over frequency ranges higher than resonance frequencies of a few Hz typically. Recently, active pneumatic tables are also used often because the passive systems are liable to table excitations in the low resonance frequency ranges, causing long settling times. In studies on the active tables, disturbances onto the tables were often regarded to be unknown and, hence, feedback control algorithms were implemented. However, the disturbances are mostly due to inertial forces due to movement of equipment on the table, e.g., x-y stages. Such a movement is given relative to the table as command inputs. Since absolute motion of the table is normally measured in an active isolation table, absolute motion of the equipment can be easily estimated for calculation of the inertial force exerted onto the table by the moving equipment. Consequently, by compensating dynamic pressure inside the pneumatic chamber to counteract with the inertia force due to the equipment motion, resultant forces acting onto the table can be made zero. In this paper, how to apply the proposed feed-forward control algorithm to a 6-degree of freedom active pneumatic table with time-delay pneumatic control is presented. Performance of the inertial force compensation control evaluated through experiments is also discussed.

  18. Electrorheological vibration system

    Korobko, Evguenia V.; Shulman, Zinovy P.; Korobko, Yulia O.

    2001-07-01

    The present paper is devoted to de3velopment and testing of an active vibration system. The system is intended for providing efficient motion of a piston in a hydraulic channel for creation of shocks and periodic vibrations in a low frequency range by means of the ER-valves based on an electrosensitive working me dium, i.e. electrorheological fluids. The latter manifests the electrorheological (ER) effect, i.e. a reversible change in the rheological characteristics of weak-conducting disperse compositions in the presence of constant and alternating electric fields. As a result of the experimental study of the dependence of viscoelastic properties of the ER-fluid on the magnitude and type of an electric field, the optimum dimensions of the vibrator and the its valves characteristics of the optimal electrical signal are determined. For control of an ER- vibrator having several valves we have designed a special type of a high-voltage two-channel impulse generator. Experiments were conducted at the frequencies ranged from 1- 10 Hz. It has been shown, that a peak force made 70% of the static force exercised by the vibrator rod. A phase shift between the input voltage and the load acceleration was less than 45 degree(s)C which allowed servocontrol and use of the vibrator for attendant operations. It was noted that a response of the vibrator to a stepwise signal has a delay only of several milliseconds.

  19. Ship Vibrations

    Sørensen, Herman

    1997-01-01

    Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board......Methods for calculating natural frequencies for ship hulls and for plates and panels.Evaluation of the risk for inconvenient vibrations on board...

  20. Vibrational imaging of glucose uptake activity in live cells and tissues by stimulated Raman scattering microscopy (Conference Presentation)

    Hu, Fanghao; Chen, Zhixing; Zhang, Luyuan; Shen, Yihui; Wei, Lu; Min, Wei

    2016-03-01

    Glucose is consumed as an energy source by virtually all living organisms, from bacteria to humans. Its uptake activity closely reflects the cellular metabolic status in various pathophysiological transformations, such as diabetes and cancer. Extensive efforts such as positron emission tomography, magnetic resonance imaging and fluorescence microscopy have been made to specifically image glucose uptake activity but all with technical limitations. Here, we report a new platform to visualize glucose uptake activity in live cells and tissues with subcellular resolution and minimal perturbation. A novel glucose analogue with a small alkyne tag (carbon-carbon triple bond) is developed to mimic natural glucose for cellular uptake, which can be imaged with high sensitivity and specificity by targeting the strong and characteristic alkyne vibration on stimulated Raman scattering (SRS) microscope to generate a quantitative three dimensional concentration map. Cancer cells with differing metabolic characteristics can be distinguished. Heterogeneous uptake patterns are observed in tumor xenograft tissues, neuronal culture and mouse brain tissues with clear cell-cell variations. Therefore, by offering the distinct advantage of optical resolution but without the undesirable influence of bulky fluorophores, our method of coupling SRS with alkyne labeled glucose will be an attractive tool to study energy demands of living systems at the single cell level.

  1. Active Vibration Isolation System for Mobile Launch Platform Ground Support Equipment Project

    National Aeronautics and Space Administration — Balcones Technologies, proposes to adapt actively controlled suspension technology developed for high performance off-road vehicles to address NASA's requirement...

  2. Application of the Correlation Method to Vibrational Spectra of C60 and Other Fullerenes: Predicting the Number of IR- and Raman-Active Bands

    Nakamoto, Kazuo; McKinney, Michael A.

    2000-06-01

    The C60 molecule (Buckyball/soccer ball) exhibits only 4 IR and 10 Raman bands although it possesses 174 (3 x 60 - 6) normal vibrations. This striking reduction in the number of observed bands is evidently due to the molecule's extremely high symmetry (Ih point group). First, the 120 symmetry elements of its truncated icosahedral structure are identified and the local (site) symmetry of the carbon atoms (Cc) is determined. Use of molecular models greatly facilitates the process in determining the local and molecular symmetries. Then the correlation method is used to derive a table that classifies the 174 normal vibrations into the respective symmetry species of the Ih point group. In this method, symmetry properties of atomic displacements in terms of the local point group (Cc) are correlated with those in terms of the molecular point group (Ih). After the normal vibrations are classified into respective symmetry species, the numbers of IR- and Raman-active vibrations can be determined by the symmetry selection rules for IR and Raman spectra. The vibrational spectra of C60 and C70 (rugby ball) are analyzed by the above procedure, and the results obtained for C28, C32, C50, and dodecahedrane are provided.

  3. Optimal placement of sensors and actuators for active vibration reduction of a flexible structure using a genetic algorithm based on modified Hinfinity

    This paper is concerned with active vibration reduction of a square isotropic plate, mounted rigidly along one edge to form a cantilever. Optimal placement of ten piezoelectric sensor/actuator pairs is investigated using a genetic algorithm to suppress the first six modes of vibration. A new objective function is developed based on modified Hinfinity to locate the sensor/actuator pairs. The plate, with piezoelectric sensor/actuator pairs bonded to its surfaces, is modelled using the finite element method and Hamilton's principle based on first order shear deformation theory including bending, membrane, and shear deformation effects. The effects of piezoelectric mass, stiffness and electromechanical coupling are taken into account. The first six natural frequencies are validated by comparison with the finite element ANSYS package using two dimensional SHELL63 and three dimensional SOLID45 elements and also experimentally. Vibration reduction for the cantilever plate with piezoelectric patches bonded in the optimal location was investigated to attenuate the first six modes of vibration using a linear optimal control scheme. The new fitness function has reduced the computational cost and given greater vibration reduction than other previously published results.

  4. Effect of vibration on osteoblastic and osteoclastic activities: Analysis of bone metabolism using goldfish scale as a model for bone

    Suzuki, N.; Kitamura, K.; Nemoto, T.; Shimizu, N.; Wada, S.; Kondo, T.; Tabata, M. J.; Sodeyama, F.; Ijiri, K.; Hattori, A.

    In osteoclastic activity during space flight as well as hind limb unloading by tail suspension, inconsistent results have been reported in an in vivo study. The bone matrix plays an important role in the response to physical stress. However, there is no suitable in vitro co-culture system of osteoblasts and osteoclasts including bone matrix. On the other hand, fish scale is a calcified tissue that contains osteoblasts, osteoclasts, and bone matrix, all of which are similar to those found in human bones. Recently, we developed a new in vitro model system using goldfish scale. This system can detect the activities of osteoclasts and osteoblasts with tartrate-resistant acid phosphatase and alkaline phosphatase as the respective markers and precisely analyze the co-relationship between osteoblasts and osteoclasts. Using this system, we analyzed the bone metabolism under various degrees of acceleration (0.5-, 1-, 2-, 4-, and 6-G) by vibration with a G-load apparatus. After loading for 5 and 10 min, the scales were incubated for 6 and 24 h. The osteoblastic and osteoclastic activities were then measured. The osteoblastic activities gradually increased corresponding to 1-G to 6-G acceleration. In addition, ER mRNA expression was the highest under 6-G acceleration. On the other hand, the osteoclastic activity decreased at 24 h of incubation under low acceleration (0.5- and 1-G). This change coincided with TRAP mRNA expression. Under 2-G acceleration, the strength of suppression in osteoclastic activity was the highest. The strength of the inhibitory action under 4- and 6-G acceleration was lower than that under 2-G acceleration. In our co-culture system, osteoblasts and osteoclasts in the scale sensitively responded to several degrees of acceleration. Therefore, we strongly believe that our in vitro co-culture system is useful for the analysis of bone metabolism under loading or unloading.

  5. Research on semi-active seismic isolation and vibration damping technology using new system for nuclear facilities

    Seismic isolation structure has been widely used in civil engineering and construction industry and its validity was observed at the Kobe Earthquake in 1995. A layered rubber isolator, which has been mostly deployed, is not good at uncertain loading conditions of external forces because of its seismic isolation structure of a resonance period and also becomes unstable at limiting deformation. Recently a ball isolator with guide or roller-guide has been introduced instead of it. As for a new seismic isolation system for nuclear facilities, semi-active seismic isolation and vibration damping system has been proposed with a ball isolator and a controllable friction damper using smart materials (magneto-rheological fluid). Effects of adhesion of a ball isolator due to aging and semi-active control on smart materials damper have been tested using small test modules. Analysis model of a ball isolator dependent on contact stress has been also developed. Larger mockup tests and their detailed analysis will be needed for their deployment for nuclear facilities. (T. Tanaka)

  6. The effect of time delay on control stability of an electromagnetic active tuned mass damper for vibration control

    Hassan, A.; Torres-Perez, A.; Kaczmarczyk, S.; Picton, P.

    2016-05-01

    The aim of this paper is to investigate the effect of time delays on the stability of a zero-placement position and velocity feedback law for a vibratory system comprising harmonic excitation equipped with an electromagnetic active tuned mass damper (ATMD). The purpose of the active control is broadening the vibration attenuation envelope of a primary mass to a higher frequency region identified as from 50±0.5Hz with a passive tuned mass damper (TMD) to a wider range of 50±5Hz with an ATMD. Stability conditions of the closed-loop system are determined by studying the position of the system closed-loop poles after the introduction of time delays for different excitation frequencies. A computer simulation of the model predicted that the proposed control system is subject to instability after a critical time delay margin dependent upon the frequency of excitation and the finding were experimentally validated. Three solutions are derived and experimentally tested for minimising the effect of time delays on the stability of the control system. The first solution is associated with the introduction of more damping in the absorber system. The second incorporates using a time-delayed ATMD by tuning its original natural resonant frequency to beyond the nominal operational frequency range of the composite system. The third involves an online gain tuning of filter coefficients in a dual arrangement of low-pass and high-pass filters to eliminate the effect time delays by manipulating the signal phase shifts.

  7. Vibration sensor

    This invention relates to a sensor for detecting the vibrations of a liquid, specifically designed for detecting low frequency vibrations transmitted by a high temperature liquid, particularly the liquid metal coolant of a fast reactor. It comprises a piezoelectric transducer inside a cavity closed by a membrane in contact with the liquid and in which a vacuum is made. The membrane is connected to one of the sides of the transducer, called the first side, through a mechanical vibration transmitting part made of a thermal insulation material. The other side of the transducer, termed second side, is blocked and the cavity has at least one leak-tight passage for an electric conductor

  8. Feasibility of Applying Active Lubrication to Reduce Vibration in Industrial Compressors

    Santos, Ilmar; Nicoletti, Rodrigo; Scalabrin, A.

    2004-01-01

    the orifices distributed over the sliding surface. The dynamic coefficients of tilting-pad bearings with and without active lubrication and their influence on an industrial compressor of 391 Kg, which operates with a maximum speed of 10,200 rpm, are analyzed. In the original compressor design, the...... bearing housings are mounted on squeeze-film dampers in order to ensure reasonable stability margins during full load condition (high maximum continuous speed). Instead of having a combination of tilting-pad bearings and squeeze-film dampers, another design solution is proposed and theoretically......In this paper the complete set of modified Reynolds´ equations for the active lubrication is presented. The solution of such a set of equations allows the determination of stiffness and damping coefficients of actively lubricated bearings. These coefficients are not just dependent on Sommerfeld...

  9. Testing of piezofilms for actuation and active control of blade flexural vibration

    Pešek, Luděk; Půst, Ladislav; Bula, Vítězslav; Cibulka, Jan

    Krakow: EAA, 2014. ISBN 978-83-61402-28-2. ISSN 2221-3767. [Forum Acusticum /7./. Krakow (PL), 07.09.2014-12.09.2014] Institutional support: RVO:61388998 Keywords : piezo * vibro-actuation * active damping Subject RIV: BI - Acoustics

  10. Vibrational Raman Optical Activity of 1-Phenylethanol and 1-Phenylethylamine: Revisiting Old Friends

    Kapitán, J.; Johannessen, Ch.; Bouř, Petr; Hecht, L.; Barron, L. D.

    2009-01-01

    Roč. 21, S1 (2009), E4-E12. ISSN 0899-0042 R&D Projects: GA AV ČR IAA400550702 Institutional research plan: CEZ:AV0Z40550506 Keywords : ROA * Raman * anharmonic correction * optical activity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.677, year: 2009

  11. A study of online plant modelling methods for active control of sound and vibration

    Laugesen, Søren

    Active control systems using the filtered-x algorithm require plant models to describe the relations between the secondary sources and the error sensors. For practical applications online plant modelling may be required if the environment changes significantly. In this study, two dominant methods...

  12. Stress optimization of leaf-spring crossed flexure pivots for an active Gurney flap mechanism

    Freire Gómez, Jon; Booker, Julian D.; Mellor, Phil H.

    2015-04-01

    The EU's Green Rotorcraft programme is pursuing the development of a functional and airworthy Active Gurney Flap (AGF) for a full-scale helicopter rotor blade. Interest in the development of this `smart adaptive rotor blade' technology lies in its potential to provide a number of aerodynamic benefits, which would in turn translate into a reduction in fuel consumption and noise levels. The AGF mechanism selected employs leaf-spring crossed flexure pivots. These provide important advantages over bearings as they are not susceptible to seizing and do not require maintenance (i.e. lubrication or cleaning). A baseline design of this mechanism was successfully tested both in a fatigue rig and in a 2D wind tunnel environment at flight-representative deployment schedules. For full validation, a flight test would also be required. However, the severity of the in-flight loading conditions would likely compromise the mechanical integrity of the pivots' leaf-springs in their current form. This paper investigates the scope for stress reduction through three-dimensional shape optimization of the leaf-springs of a generic crossed flexure pivot. To this end, a procedure combining a linear strain energy formulation, a parametric leaf-spring profile definition and a series of optimization algorithms is employed. The resulting optimized leaf-springs are proven to be not only independent of the angular rotation at which the pivot operates, but also linearly scalable to leaf-springs of any length, minimum thickness and width. Validated using non-linear finite element analysis, the results show very significant stress reductions relative to pivots with constant cross section leaf-springs, of up to as much as 30% for the specific pivot configuration employed in the AGF mechanism. It is concluded that shape optimization offers great potential for reducing stress in crossed flexure pivots and, consequently, for extending their fatigue life and/or rotational range.

  13. Analysis of Beat Vibration for Active Magnetic Bearing System%主动磁悬浮轴承系统拍振现象分析

    高辉; 徐龙祥

    2011-01-01

    Vibration analysis plays an important role in the research of active magnetic bearing(AMB) system. However, the established system mathematical models which combine the controller with the dynamic response are relatively few. The vibration equations of radial AMB subsystems are built on the basis of the stress analysis of high speed rotor system, referring the influences of the frequency characteristics of adopted incomplete differential PID controller on the generalized magnetic bearing dynamic stiffness and rotor dynamic unbalance response. The vibration modes existing in AMB system can be obtained by solving the vibration equations. One is free vibration because of the inherent frequency, and the other is harmonic vibration due to unbalanced excitation response. And the produced beat vibration phenomenon is explained when the two kinds of vibration frequency are similar. Through adjusting the control current, the generalized dynamic stiffness of magnetic bearings and as well as the inherent frequency of the system can be changed, thus resulting in the weakening of beat vibration. Simulation and experimental results can verify the "beat vibration" phenomenon and the damping effect after changing the active control. The mechanical model can provide the simulation platform for the research of vibration compensation algorithm of AMB system.%振动分析是研究主动磁悬浮轴承(Active magnetic bearings,AMB)系统的一个重要部分,但是目前结合控制器以及动态不平衡响应建立的系统数学模型相对较少.通过对高速主动磁悬浮轴承转子系统受力分析,参考所使用的不完全微分PID控制器的频率特性对AMB广义动刚度的影响以及对转子动态不平衡激励响应的影响,建立径向子系统的力学振动方程.通过此振动方程的解,得出AMB系统存在的振动形式.一种是由于系统固有频率存在而产生的自由振动,另一种是由于不平衡响应存在而产生的简谐振动,并

  14. Semi-active vibration control based on unsymmetrical synchronized switch damping: Analysis and experimental validation of control performance

    Ji, Hongli; Qiu, Jinhao; Cheng, Li; Nie, Hong

    2016-05-01

    In semi-active synchronized switch damping (SSD) approaches for structural vibration control, the damping effect is achieved by properly switching the voltage on the piezoelectric actuators. Unsymmetrical SSD switch circuit has been designed in the previous paper to increase the effective voltage range on the PZT actuator for improvement of the control performance. In this study, analysis and experimental validation of control performance of a synchronized switch damping system based on the unsymmetrical switch circuit are carried out. First the model of an unsymmetrical SSD system is presented and the working principle is introduced. The general expression of the switched voltage on the piezoelectric actuator is derived. Based on its periodicity in steady-state control, the harmonic components of the actuator voltage are derived using Fourier series expansion. Next, the displacement response of the system is derived under combined actions of the excitation and switched voltage. Finally, a setup of a flexible beam with unsymmetrical switch circuit is used to demonstrate the control performance under different voltage sources and to verify the theoretical results. The results show that the control performance mainly depends on the voltage range on the PZT. A higher effective voltage range can be generated in unsymmetrical SSDV than in symmetrical SSDV and better control performance can be achieved at the same negative actuator voltage. The unsymmetrical SSDV makes better utilization of the actuator capability.

  15. Online Structural Health Monitoring and Parameter Estimation for Vibrating Active Cantilever Beams Using Low-Priced Microcontrollers

    Gergely Takács

    2015-01-01

    Full Text Available This paper presents a structural health monitoring and parameter estimation system for vibrating active cantilever beams using low-cost embedded computing hardware. The actuator input and the measured position are used in an augmented nonlinear model to observe the dynamic states and parameters of the beam by the continuous-discrete extended Kalman filter (EKF. The presence of undesirable structural change is detected by variations of the first resonance estimate computed from the observed equivalent mass, stiffness, damping, and voltage-force conversion coefficients. A fault signal is generated upon its departure from a predetermined nominal tolerance band. The algorithm is implemented using automatically generated and deployed machine code on an electronics prototyping platform, featuring an economically feasible 8-bit microcontroller unit (MCU. The validation experiments demonstrate the viability of the proposed system to detect sudden or gradual mechanical changes in real-time, while the functionality on low-cost miniaturized hardware suggests a strong potential for mass-production and structural integration. The modest computing power of the microcontroller and automated code generation designates the proposed system only for very flexible structures, with a first dominant resonant frequency under 4 Hz; however, a code-optimized version certainly allows much stiffer structures or more complicated models on the same hardware.

  16. First-Principles Predictions of Vibrational Raman Optical Activity of Globular Proteins

    Kessler, Jiří; Kapitán, J.; Bouř, Petr

    2015-01-01

    Roč. 6, č. 16 (2015), s. 3314-3319. ISSN 1948-7185 R&D Projects: GA ČR GAP208/11/0105; GA ČR GA15-09072S Grant ostatní: GA MŠk(CZ) LM2010005; GA MŠk(CZ) ED3.2.00/08.0144 Institutional support: RVO:61388963 Keywords : molecular property tensors * activity spectra * spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.458, year: 2014 http://pubs.acs.org/doi/pdf/10.1021/acs.jpclett.5b01500

  17. A study of online plant modelling methods for active control of sound and vibration

    Laugesen, Søren

    1996-01-01

    Active control systems using the filtered-x algorithm require plant models to describe the relations between the secondary sources and the error sensors. For practical applications online plant modelling may be required if the environment changes significantly. In this study, two dominant methods...... for online plant modelling are compared by simulation. One approach yields convincing results in terms of converge, but sometimes the steady state performance can be suboptimal, because the plant models are erroneous. Another approach gives results close to the theoretically optimal for a broadband...

  18. Prediction of BVI Noise for an Active Twist Rotor Using a Loosely Coupled CFD/CSD Method and Comparison to Experimental Data

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.; Boyd, David Douglas, Jr.

    2012-01-01

    Numerical predictions of the acoustic characteristics of an Active Twist Rotor (ATR), using two methods to compute the rotor blade aerodynamics and elastic blade motion are compared to experimental data from a wind tunnel test in the NASA Langley Transonic Dynamics Tunnel (TDT) in 2000. The first method, a loosely coupled iterative method, utilizes the Computational Fluid Dynamics (CFD) code OVERFLOW 2 and the Computational Structural Dynamics (CSD) code CAMRAD II. The second method utilizes the CAMRAD II free-wake model only. The harmonic active-twist control to the main rotor blade system is identified with three parameters - harmonic actuation frequency, actuation amplitude, and control phase angle. The resulting aerodynamics and blade motion data from the two methods are then used in the acoustics code PSU-WOPWOP to predict acoustic pressure on a spherical array of equally spaced observers surrounding the rotor. This spherical distribution of pressure is used to compute the sound power level representing baseline and actuated conditions. Sound power levels for three categories of noise are defined as - blade-vortex interaction sound power level (BVIPWL), low frequency sound power level (LFPWL), and overall sound power level, OAPWL. Comparisons with measured data indicate the CFD/CSD analysis successfully captures the trends in sound power levels and the effects of active-twist control at advance ratios of 0.14 and 0.17. The free-wake model predictions show inconsistent sound power levels relative to the trends in the experimental and CFD data. This paper presents the first ever comparison between CFD/CSD acoustic predictions for an active-twist rotor and experimental measurements.

  19. The use of active vibration control for the reduction of ICE interior noise

    Schirmacher, R. [Mueller-BBM GmbH - Beratende Ingenieure fuer Akustik, Planegg (Germany)

    2001-07-01

    First generation ICE high speed trains show a disturbing low frequency noise of about 100 Hz audible inside the coaches. It is excited by unround wheels, propagates via the bogie to the body of the coach and is finally radiated as airborne sound. A mixed concept of active suspension at the bogie in connection with adaptive residual noise minimisation inside the passenger compartment is successfully applied to the problem. A prototype system utilizing piezo ceramic actuators was installed and tested on the rolling rig of Deutsche Bahn in Munich. The noise level reductions at single harmonics were more than 12 dB averaged over the whole compartment and more than 20 dB at single seats. Measurement results and practical experiences with the system are reported. (orig.)

  20. VIBRATION ISOLATION SYSTEM PROBABILITY ANALYSIS

    Smirnov Vladimir Alexandrovich

    2012-10-01

    Full Text Available The article deals with the probability analysis for a vibration isolation system of high-precision equipment, which is extremely sensitive to low-frequency oscillations even of submicron amplitude. The external sources of low-frequency vibrations may include the natural city background or internal low-frequency sources inside buildings (pedestrian activity, HVAC. Taking Gauss distribution into account, the author estimates the probability of the relative displacement of the isolated mass being still lower than the vibration criteria. This problem is being solved in the three dimensional space, evolved by the system parameters, including damping and natural frequency. According to this probability distribution, the chance of exceeding the vibration criteria for a vibration isolation system is evaluated. Optimal system parameters - damping and natural frequency - are being developed, thus the possibility of exceeding vibration criteria VC-E and VC-D is assumed to be less than 0.04.

  1. Random Vibrations

    Messaro. Semma; Harrison, Phillip

    2010-01-01

    Ares I Zonal Random vibration environments due to acoustic impingement and combustion processes are develop for liftoff, ascent and reentry. Random Vibration test criteria for Ares I Upper Stage pyrotechnic components are developed by enveloping the applicable zonal environments where each component is located. Random vibration tests will be conducted to assure that these components will survive and function appropriately after exposure to the expected vibration environments. Methodology: Random Vibration test criteria for Ares I Upper Stage pyrotechnic components were desired that would envelope all the applicable environments where each component was located. Applicable Ares I Vehicle drawings and design information needed to be assessed to determine the location(s) for each component on the Ares I Upper Stage. Design and test criteria needed to be developed by plotting and enveloping the applicable environments using Microsoft Excel Spreadsheet Software and documenting them in a report Using Microsoft Word Processing Software. Conclusion: Random vibration liftoff, ascent, and green run design & test criteria for the Upper Stage Pyrotechnic Components were developed by using Microsoft Excel to envelope zonal environments applicable to each component. Results were transferred from Excel into a report using Microsoft Word. After the report is reviewed and edited by my mentor it will be submitted for publication as an attachment to a memorandum. Pyrotechnic component designers will extract criteria from my report for incorporation into the design and test specifications for components. Eventually the hardware will be tested to the environments I developed to assure that the components will survive and function appropriately after exposure to the expected vibration environments.

  2. DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

    YANG Qingjun; LI Jun; WANG Zuwen

    2006-01-01

    A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance,nonlinearities compensation and motion flow rate compensation (MFRC) are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions:one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to rune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

  3. An optically transparent thin-layer electrochemical cell for the study of vibrational circular dichroism of chiral redox-active molecules.

    Domingos, Sérgio R; Luyten, Henk; van Anrooij, Fred; Sanders, Hans J; Bakker, Bert H; Buma, Wybren J; Hartl, František; Woutersen, Sander

    2013-03-01

    An optically transparent thin-layer electrochemical (OTTLE) cell with a locally extended optical path has been developed in order to perform vibrational circular dichroism (VCD) spectroscopy on chiral molecules prepared in specific oxidation states by means of electrochemical reduction or oxidation. The new design of the electrochemical cell successfully addresses the technical challenges involved in achieving sufficient infrared absorption. The VCD-OTTLE cell proves to be a valuable tool for the investigation of chiral redox-active molecules. PMID:23556803

  4. An optically transparent thin-layer electrochemical cell for the study of vibrational circular dichroism of chiral redox-active molecules

    Domingos, Sérgio R.; Luyten, Henk; van Anrooij, Fred; Sanders, Hans J.; Bakker, Bert H.; Buma, Wybren J.; Hartl, František; Woutersen, Sander

    2013-03-01

    An optically transparent thin-layer electrochemical (OTTLE) cell with a locally extended optical path has been developed in order to perform vibrational circular dichroism (VCD) spectroscopy on chiral molecules prepared in specific oxidation states by means of electrochemical reduction or oxidation. The new design of the electrochemical cell successfully addresses the technical challenges involved in achieving sufficient infrared absorption. The VCD-OTTLE cell proves to be a valuable tool for the investigation of chiral redox-active molecules.

  5. Urban vibrations

    Morrison, Ann; Knudsen, L.; Andersen, Hans Jørgen

    2012-01-01

    In   this   paper   we   describe   a   field   study   conducted   with   a   wearable   vibration   belt   where   we   test   to   determine   the   vibration   intensity   sensitivity   ranges   on   a   large   diverse   group   of   participants   with   evenly   distributed  ages  and......   lab   studies   in   that   we   found   a   decreased   detection   rate   in   busy   environments.   Here   we   test   with   a   much   larger   sample   and   age   range,   and   contribute   with   the   first   vibration  sensitivity  testing  outside  the  lab  in  an  urban   public...

  6. Helicopter rotor dynamics and aeroelasticity - Some key ideas and insights

    Friedmann, Peretz P.

    1990-01-01

    Four important current topics in helicopter rotor dynamics and aeroelasticity are discussed: (1) the role of geometric nonlinearities in rotary-wing aeroelasticity; (2) structural modeling, free vibration, and aeroelastic analysis of composite rotor blades; (3) modeling of coupled rotor/fuselage areomechanical problems and their active control; and (4) use of higher-harmonic control for vibration reduction in helicopter rotors in forward flight. The discussion attempts to provide an improved fundamental understanding of the current state of the art. In this way, future research can be focused on problems which remain to be solved instead of producing marginal improvements on problems which are already understood.

  7. Vibrating minds

    2009-01-01

    Ed Witten is one of the leading scientists in the field of string theory, the theory that describes elementary particles as vibrating strings. This week he leaves CERN after having spent a few months here on sabbatical. His wish is that the LHC will unveil supersymmetry.

  8. Vibrating Manipulation

    SHEN Guo-quan; CUI Yi-jun

    2003-01-01

    @@ As a manipulation with unique therapeutic effect in TCM Tuina manipulations, Vibrating manipulation has significantly stronger effection on viscera, blood vessel, smooth muscle and gland secretion than other Tuina manipulations and it is mainly used in internal medicine, gynecology and miscellaneous diseases.

  9. Vibration sensor

    Matěj, J.

    2015-01-01

    This paper lays out a design of a system for reading the radar antenna gearbox vibrations. Firstly it names different types of sensors and defines their suitability for this usage. It describes their important electric and frequency properties. Secondly it shows a design of the data transmission system from the transducer to a computer and describes measured data changes according to the gearbox faults.

  10. Study on active control methods. Part 3. ; Absolute vibration control system'' by modern control theory. Active seishin gijutsu ni kansuru kenkyu. 3. ; Gendai seigyo wo mochiita zettai seishin ni tsuite

    Kageyama, M.; Nohata, A.; Teramura, A.; Yasui, Y.; Okada, H. (Obayashi Corp., Tokyo (Japan))

    1991-08-10

    The absolute vibration control method by advanced optimal regulator theory was studied in order to reduce the acceleration response of a base-isolated building by active control at the base to hold the building in absolute space. The optimal regulator theory is originally a control method based on the feedback control theory. In the present study, however, application of the feedforward control theory, which is indispensable to the absolute vibration control, was also investigated. The performance by using this control method, in which large conventional actuators were applied to an actual base-isolated building, was analytically compared with that by the classic control method used from the past. As a result, it was found that this control method had a better effect compared with the classic control method. It is considered that absolute vibration control by a generally-used type of large-sized actuator is possible even at the time of a major earthquake. 5 refs., 19 figs.

  11. Genetic algorithm based active vibration control for a moving flexible smart beam driven by a pneumatic rod cylinder

    Qiu, Zhi-cheng; Shi, Ming-li; Wang, Bin; Xie, Zhuo-wei

    2012-05-01

    A rod cylinder based pneumatic driving scheme is proposed to suppress the vibration of a flexible smart beam. Pulse code modulation (PCM) method is employed to control the motion of the cylinder's piston rod for simultaneous positioning and vibration suppression. Firstly, the system dynamics model is derived using Hamilton principle. Its standard state-space representation is obtained for characteristic analysis, controller design, and simulation. Secondly, a genetic algorithm (GA) is applied to optimize and tune the control gain parameters adaptively based on the specific performance index. Numerical simulations are performed on the pneumatic driving elastic beam system, using the established model and controller with tuned gains by GA optimization process. Finally, an experimental setup for the flexible beam driven by a pneumatic rod cylinder is constructed. Experiments for suppressing vibrations of the flexible beam are conducted. Theoretical analysis, numerical simulation and experimental results demonstrate that the proposed pneumatic drive scheme and the adopted control algorithms are feasible. The large amplitude vibration of the first bending mode can be suppressed effectively.

  12. High fidelity simulation of non-synchronous vibration for aircraft engine fan/compressor

    Im, Hong-Sik

    calculated results agree excellently with the experiment. (4) NASA Stage 35 speed line and radial profiles to validate the steady state mixing plane BC for multistage computation. Excellent agreement is obtained between the computation and experiment. (5) NASA Rotor 67 full annulus and single passage FSI simulation at near peak condition to validate phase lag BC. The time shifted phase lag BC accurately predicts blade vibration responses that agrees better with the full annulus FSI simulation. The DDES methodology is used to investigate the stall inception of NASA Rotor 67. The stall process begins with spike inception and develops to full stall. The whole process is simulated with full annulus of the rotor. The fully coupled FSI is then used to simulate the stall flutter of NASA Rotor 67. The multistage simulations of a GE aircraft engine high pressure compressor (HPC) reveal for the first time that the travelling tornado vortex formed on the rotor blade tip region is the root cause for the NSV of the compressor. The rotor blades under NSV have large torsional vibration due to the tornado vortex propagation in the opposite to the rotor rotation. The tornado vortex frequency passing the suction surface of each blade in the tip region agrees with the NSV frequency. The predicted NSV frequency based on URANS model with rigid blades agrees very well with the experimental measurement with only 3.3% under-predicted. The NSV prediction using FSI with vibrating blades also obtain the same frequency as the rigid blades. This is because that the NSV is primarily caused by the flow vortex instability and the no resonance occurs. The blade structures respond passively and the small amplitudes of the blade vibration do not have significant effect on the flow. The predicted frequency using DDES with rigid blades is more deviated from the experiment and is 14.7% lower. The reason is that the DDES tends to predict the rotor stall earlier than the URANS and the NSV can be achieved only at

  13. A Novel Hybrid Error Criterion-Based Active Control Method for on-Line Milling Vibration Suppression with Piezoelectric Actuators and Sensors.

    Zhang, Xingwu; Wang, Chenxi; Gao, Robert X; Yan, Ruqiang; Chen, Xuefeng; Wang, Shibin

    2016-01-01

    Milling vibration is one of the most serious factors affecting machining quality and precision. In this paper a novel hybrid error criterion-based frequency-domain LMS active control method is constructed and used for vibration suppression of milling processes by piezoelectric actuators and sensors, in which only one Fast Fourier Transform (FFT) is used and no Inverse Fast Fourier Transform (IFFT) is involved. The correction formulas are derived by a steepest descent procedure and the control parameters are analyzed and optimized. Then, a novel hybrid error criterion is constructed to improve the adaptability, reliability and anti-interference ability of the constructed control algorithm. Finally, based on piezoelectric actuators and acceleration sensors, a simulation of a spindle and a milling process experiment are presented to verify the proposed method. Besides, a protection program is added in the control flow to enhance the reliability of the control method in applications. The simulation and experiment results indicate that the proposed method is an effective and reliable way for on-line vibration suppression, and the machining quality can be obviously improved. PMID:26751448

  14. A Novel Hybrid Error Criterion-Based Active Control Method for on-Line Milling Vibration Suppression with Piezoelectric Actuators and Sensors

    Xingwu Zhang

    2016-01-01

    Full Text Available Milling vibration is one of the most serious factors affecting machining quality and precision. In this paper a novel hybrid error criterion-based frequency-domain LMS active control method is constructed and used for vibration suppression of milling processes by piezoelectric actuators and sensors, in which only one Fast Fourier Transform (FFT is used and no Inverse Fast Fourier Transform (IFFT is involved. The correction formulas are derived by a steepest descent procedure and the control parameters are analyzed and optimized. Then, a novel hybrid error criterion is constructed to improve the adaptability, reliability and anti-interference ability of the constructed control algorithm. Finally, based on piezoelectric actuators and acceleration sensors, a simulation of a spindle and a milling process experiment are presented to verify the proposed method. Besides, a protection program is added in the control flow to enhance the reliability of the control method in applications. The simulation and experiment results indicate that the proposed method is an effective and reliable way for on-line vibration suppression, and the machining quality can be obviously improved.

  15. Vibration sensors

    These sensors, which aim is the surveillance of the fast breeder reactor internal structure, were designed considering the following requirements: - long term utilization under low frequencies conditions (1 to 50 Hz) and detection of accelerations lower than 0,01 g, - operation with a temperature up to 6000C and receiving important neutron and gamma flux. Monoaxial sensors with a liquid vibrating mass (sodium) were thus developed, based on the electromagnetic flow meter principles (Faraday effect)

  16. Quantum mechanical calculation of electric fields and vibrational Stark shifts at active site of human aldose reductase.

    Wang, Xianwei; Zhang, John Z H; He, Xiao

    2015-11-14

    Recent advance in biophysics has made it possible to directly measure site-specific electric field at internal sites of proteins using molecular probes with C = O or C≡N groups in the context of vibrational Stark effect. These measurements directly probe changes of electric field at specific protein sites due to, e.g., mutation and are very useful in protein design. Computational simulation of the Stark effect based on force fields such as AMBER and OPLS, while providing good insight, shows large errors in comparison to experimental measurement due to inherent difficulties associated with point charge based representation of force fields. In this study, quantum mechanical calculation of protein's internal electrostatic properties and vibrational Stark shifts was carried out by using electrostatically embedded generalized molecular fractionation with conjugate caps method. Quantum calculated change of mutation-induced electric field and vibrational Stark shift is reported at the internal probing site of enzyme human aldose reductase. The quantum result is in much better agreement with experimental data than those predicted by force fields, underscoring the deficiency of traditional point charge models describing intra-protein electrostatic properties. PMID:26567650

  17. A novel triple-actuating mechanism of an active air mount for vibration control of precision manufacturing machines: experimental work

    With the goal of vibration control and isolation in a clean room, we propose a new type of air mount which consists of pneumatic, electromagnetic (EM), and magnetorheological (MR) actuators. The air mount is installed below a semiconductor manufacturing machine to reduce the adverse effects caused by unwanted vibration. The proposed mechanism integrates the forces in a parallel connection of the three actuators. The MR part is designed to operate in an air spring in which the EM part is installed. The control logic is developed with a classical method and a switching mode to avoid operational mismatch among the forces developed. Based on extended microprocessors, a portable, embedded controller is installed to execute both nonlinear logic and digital communication with the peripherals. The pneumatic forces constantly support the heavy weight of an upper structure and maintain the level of the air mount. The MR damper handles the transient response, while the EM controller reduces the resonance response, which is switched mutually with a threshold. Vibration is detected by laser displacement sensors which have submicron resolution. The impact test results of three tons load weight demonstrate practical feasibility by showing that the proposed triple-actuating mechanism can reduce the transient response as well as the resonance in the air mount, resulting in accurate motion of the semiconductor manufacturing machine. (technical note)

  18. Active vibration control of a cylindrical structure using flexible piezoactuators: experimental work in air and water environments

    In the present work, the modal characteristics and vibration control performance of a cylindrical structure in air and water are experimentally investigated, and the results are presented in time and frequency domains. In order to achieve this goal, an end-capped cylindrical shell structure is considered as a host structure, and MFC (macro fiber composite) actuators, which are flexible, are bonded on the surface of the structure. After manufacturing a cylindrical shell structure with aluminum, a modal test is carried out, and the natural frequencies of the proposed structure are obtained and analyzed. To verify the modal test results, a finite element analysis is also performed, and the results are compared with the modal test results. By using the experimentally obtained modal characteristics, a state space control model is established. An optimal controller is then designed in order to control the unwanted vibration and is experimentally realized. It has been shown that the structural vibration can be effectively decreased with the optimal control methodology in both air and water environmental conditions. (technical note)

  19. Quantum mechanical calculation of electric fields and vibrational Stark shifts at active site of human aldose reductase

    Wang, Xianwei [Center for Optics and Optoelectronics Research, College of Science, Zhejiang University of Technology, Hangzhou, Zhejiang 310023 (China); State Key Laboratory of Precision Spectroscopy, Institute of Theoretical and Computational Science, East China Normal University, Shanghai 200062 (China); Zhang, John Z. H.; He, Xiao, E-mail: xiaohe@phy.ecnu.edu.cn [State Key Laboratory of Precision Spectroscopy, Institute of Theoretical and Computational Science, East China Normal University, Shanghai 200062 (China); NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Shanghai 200062 (China)

    2015-11-14

    Recent advance in biophysics has made it possible to directly measure site-specific electric field at internal sites of proteins using molecular probes with C = O or C≡N groups in the context of vibrational Stark effect. These measurements directly probe changes of electric field at specific protein sites due to, e.g., mutation and are very useful in protein design. Computational simulation of the Stark effect based on force fields such as AMBER and OPLS, while providing good insight, shows large errors in comparison to experimental measurement due to inherent difficulties associated with point charge based representation of force fields. In this study, quantum mechanical calculation of protein’s internal electrostatic properties and vibrational Stark shifts was carried out by using electrostatically embedded generalized molecular fractionation with conjugate caps method. Quantum calculated change of mutation-induced electric field and vibrational Stark shift is reported at the internal probing site of enzyme human aldose reductase. The quantum result is in much better agreement with experimental data than those predicted by force fields, underscoring the deficiency of traditional point charge models describing intra-protein electrostatic properties.

  20. Quantum mechanical calculation of electric fields and vibrational Stark shifts at active site of human aldose reductase

    Recent advance in biophysics has made it possible to directly measure site-specific electric field at internal sites of proteins using molecular probes with C = O or C≡N groups in the context of vibrational Stark effect. These measurements directly probe changes of electric field at specific protein sites due to, e.g., mutation and are very useful in protein design. Computational simulation of the Stark effect based on force fields such as AMBER and OPLS, while providing good insight, shows large errors in comparison to experimental measurement due to inherent difficulties associated with point charge based representation of force fields. In this study, quantum mechanical calculation of protein’s internal electrostatic properties and vibrational Stark shifts was carried out by using electrostatically embedded generalized molecular fractionation with conjugate caps method. Quantum calculated change of mutation-induced electric field and vibrational Stark shift is reported at the internal probing site of enzyme human aldose reductase. The quantum result is in much better agreement with experimental data than those predicted by force fields, underscoring the deficiency of traditional point charge models describing intra-protein electrostatic properties