Research on Design of MUH Attitude Stability Augmentation Control System
Fan, Shigang
2017-09-01
Attitude stability augmentation control system with a lower cost need to be designed so that MUH (Mini Unmanned Helicopter) can adapt to different types of geographic environment and fly steadily although the weather may be bad. Attitude feedback was calculated mainly by filtering estimation within attitude acquisition module in this system. Stability augmentation can be improved mainly by PI. This paper will depict running principle and designing process of MUH attitude stability augmentation control system and algorithm that is considered as an important part in this system.
Directory of Open Access Journals (Sweden)
Olha Sushchenko
2017-11-01
Full Text Available Purpose: The paper focuses on problems of design of robust precision attitude and heading reference systems, which can be applied in navigation of marine vehicles. The main goal is to create the optimization procedures for design of navigation and stabilization loops of the multimode gimballed system. The optimization procedure of the navigation loop design is based on the parametric robust H2/H∞-optimization. The optimization procedure of the stabilization loop design is based on the robust structural H∞-synthesis. Methods: To solve the given problem the methods of the robust control system theory and optimization methods are used. Results: The kinematical scheme of the precision gimballed attitude and heading reference system is represented. The parametrical optimization algorithm taking into consideration features of the researched system is given. Method of the mixed sensitivity relative to the researched system design is analyzed. Coefficients of the control laws of navigation loops are obtained based on optimization procedure providing compromise between accuracy and robustness. The robust controller of the stabilization loop was developed based on robust structural synthesis using method of the mixed sensitivity. Simulation of navigation and stabilization processes is carried out. Conclusions: The represented results prove efficiency of the proposed procedures, which can be useful for design of precision navigation systems of the moving vehicles.
Design and Stability of an On-Orbit Attitude Control System Using Reaction Control Thrusters
Hall, Robert A.; Hough, Steven; Orphee, Carolina; Clements, Keith
2016-01-01
Basic principles for the design and stability of a spacecraft on-orbit attitude control system employing on-off Reaction Control System (RCS) thrusters are presented. Both vehicle dynamics and the control system actuators are inherently nonlinear, hence traditional linear control system design approaches are not directly applicable. This paper has two main aspects: It summarizes key RCS design principles from earlier NASA vehicles, notably the Space Shuttle and Space Station programs, and introduces advances in the linear modelling and analyses of a phase plane control system derived in the initial development of the NASA's next upper stage vehicle, the Exploration Upper Stage (EUS). Topics include thruster hardware specifications, phase plane design and stability, jet selection approaches, filter design metrics, and RCS rotational maneuver logic.
Stoll, John C.
1995-01-01
The performance of an unaided attitude determination system based on GPS interferometry is examined using linear covariance analysis. The modelled system includes four GPS antennae onboard a gravity gradient stabilized spacecraft, specifically the Air Force's RADCAL satellite. The principal error sources are identified and modelled. The optimal system's sensitivities to these error sources are examined through an error budget and by varying system parameters. The effects of two satellite selection algorithms, Geometric and Attitude Dilution of Precision (GDOP and ADOP, respectively) are examined. The attitude performance of two optimal-suboptimal filters is also presented. Based on this analysis, the limiting factors in attitude accuracy are the knowledge of the relative antenna locations, the electrical path lengths from the antennae to the receiver, and the multipath environment. The performance of the system is found to be fairly insensitive to torque errors, orbital inclination, and the two satellite geometry figures-of-merit tested.
Mukhopadhyay, V.; Newsom, J. R.
1982-01-01
A stability margin evaluation method in terms of simultaneous gain and phase changes in all loops of a multiloop system is presented. A universal gain-phase margin evaluation diagram is constructed by generalizing an existing method using matrix singular value properties. Using this diagram and computing the minimum singular value of the system return difference matrix over the operating frequency range, regions of guaranteed stability margins can be obtained. Singular values are computed for a wing flutter suppression and a drone lateral attitude control problem. The numerical results indicate that this method predicts quite conservative stability margins. In the second example if the eigenvalue magnitude is used instead of the singular value, as a measure of nearness to singularity, more realistic stability margins are obtained. However, this relaxed measure generally cannot guarantee global stability.
Optimal Sliding Mode Controllers for Attitude Stabilization of Flexible Spacecraft
Directory of Open Access Journals (Sweden)
Chutiphon Pukdeboon
2011-01-01
Full Text Available The robust optimal attitude control problem for a flexible spacecraft is considered. Two optimal sliding mode control laws that ensure the exponential convergence of the attitude control system are developed. Integral sliding mode control (ISMC is applied to combine the first-order sliding mode with optimal control and is used to control quaternion-based spacecraft attitude manoeuvres with external disturbances and an uncertainty inertia matrix. For the optimal control part the state-dependent Riccati equation (SDRE and optimal Lyapunov techniques are employed to solve the infinite-time nonlinear optimal control problem. The second method of Lyapunov is used to guarantee the stability of the attitude control system under the action of the proposed control laws. An example of multiaxial attitude manoeuvres is presented and simulation results are included to verify the usefulness of the developed controllers.
The dynamics of CRM attitude change: Attitude stability
Gregorich, Steven E.
1993-01-01
Special training seminars in cockpit resource management (CRM) are designed to enhance crew effectiveness in multicrew air-transport cockpits. In terms of CRM, crew effectiveness is defined by teamwork rather than technical proficiency. These seminars are designed to promote factual learning, alter aviator attitudes, and motivate aviators to make use of what they have learned. However, measures of attitude change resulting from CRM seminars have been the most common seminar evaluation technique. The current investigation explores a broader range of attitude change parameters with specific emphasis on the stability of change between recurrent visits to the training center. This allows for a comparison of training program strengths in terms of seminar ability to effect lasting change.
Attitude stability analyses for small artificial satellites
International Nuclear Information System (INIS)
Silva, W R; Zanardi, M C; Formiga, J K S; Cabette, R E S; Stuchi, T J
2013-01-01
The objective of this paper is to analyze the stability of the rotational motion of a symmetrical spacecraft, in a circular orbit. The equilibrium points and regions of stability are established when components of the gravity gradient torque acting on the spacecraft are included in the equations of rotational motion, which are described by the Andoyer's variables. The nonlinear stability of the equilibrium points of the rotational motion is analysed here by the Kovalev-Savchenko theorem. With the application of the Kovalev-Savchenko theorem, it is possible to verify if they remain stable under the influence of the terms of higher order of the normal Hamiltonian. In this paper, numerical simulations are made for a small hypothetical artificial satellite. Several stable equilibrium points were determined and regions around these points have been established by variations in the orbital inclination and in the spacecraft principal moment of inertia. The present analysis can directly contribute in the maintenance of the spacecraft's attitude
2016-03-01
AND MISSION ANALYSIS FOR A SMALL SATELLITE EXPLOITING ENVIRONMENTAL DISTURBANCES FOR ATTITUDE STABILIZATION by Halis C. Polat March 2016...FOR A SMALL SATELLITE EXPLOITING ENVIRONMENTAL DISTURBANCES FOR ATTITUDE STABILIZATION 5. FUNDING NUMBERS 6. AUTHOR(S) Halis C. Polat 7...need a robust and accurate attitude control system. Due to the mass- and volume-constrained design environment of CubeSat, conventional methods are
Stabilization of rotational motion with application to spacecraft attitude control
DEFF Research Database (Denmark)
Wisniewski, Rafal
2000-01-01
for global stabilization of a rotary motion. Along with a model of the system formulated in the Hamilton's canonical from the algorithm uses information about a required potential energy and a dissipation term. The control action is the sum of the gradient of the potential energy and the dissipation force......The objective of this paper is to develop a control scheme for stabilization of a hamiltonian system. The method generalizes the results available in the literature on motion control in the Euclidean space to an arbitrary differrential manifol equipped with a metric. This modification is essencial...... on a Riemannian manifold. The Lyapnov stability theory is adapted and reformulated to fit to the new framework of Riemannian manifolds. Toillustrate the results a spacecraft attitude control problem is considered. Firstly, a global canonical representation for the spacecraft motion is found, then three spacecraft...
Stabilization of rotational motion with application to spacecraft attitude control
DEFF Research Database (Denmark)
Wisniewski, Rafal
2001-01-01
for global stabilization of a rotary motion. Along with a model of the system formulated in the Hamilton's canonical from the algorithm uses information about a required potential energy and a dissipation term. The control action is the sum of the gradient of the potential energy and the dissipation force......The objective of this paper is to develop a control scheme for stabilization of a hamiltonian system. The method generalizes the results available in the literature on motion control in the Euclidean space to an arbitrary differrential manifol equipped with a metric. This modification is essencial...... on a Riemannian manifold. The Lyapnov stability theory is adapted and reformulated to fit to the new framework of Riemannian manifolds. Toillustrate the results a spacecraft attitude control problem is considered. Firstly, a global canonical representation for the spacecraft motion is found, then three spacecraft...
Attitude Determination Error Analysis System (ADEAS) mathematical specifications document
Nicholson, Mark; Markley, F.; Seidewitz, E.
1988-01-01
The mathematical specifications of Release 4.0 of the Attitude Determination Error Analysis System (ADEAS), which provides a general-purpose linear error analysis capability for various spacecraft attitude geometries and determination processes, are presented. The analytical basis of the system is presented. The analytical basis of the system is presented, and detailed equations are provided for both three-axis-stabilized and spin-stabilized attitude sensor models.
Attitude Dynamics and Stability of a Simple Solar Photon Thruster
Directory of Open Access Journals (Sweden)
Anna D. Guerman
2013-01-01
Full Text Available This paper is dedicated to the development of a model of the attitude dynamics for a nonideal Simple Solar Photon Thruster (SSPT and to the analysis of sailcraft motions with respect to their centre of mass. Derivation of the expressions for force and torque due to solar radiation that is valid for the case, when there is a misalignment of the SSPT axis with the sun direction, is followed by study of sailcraft dynamics and stability properties. Analysis of stability shows that an ideally reflecting sail is unstable, while for a sailcraft with nonideal collector, the symmetry axis is stable with respect to the Sun direction for large variety of system parameters. The motion around symmetry axis is always unstable and requires an active stabilizer.
Spin-Stabilized Spacecrafts: Analytical Attitude Propagation Using Magnetic Torques
Directory of Open Access Journals (Sweden)
Roberta Veloso Garcia
2009-01-01
Full Text Available An analytical approach for spin-stabilized satellites attitude propagation is presented, considering the influence of the residual magnetic torque and eddy currents torque. It is assumed two approaches to examine the influence of external torques acting during the motion of the satellite, with the Earth's magnetic field described by the quadripole model. In the first approach is included only the residual magnetic torque in the motion equations, with the satellites in circular or elliptical orbit. In the second approach only the eddy currents torque is analyzed, with the satellite in circular orbit. The inclusion of these torques on the dynamic equations of spin stabilized satellites yields the conditions to derive an analytical solution. The solutions show that residual torque does not affect the spin velocity magnitude, contributing only for the precession and the drift of the spacecraft's spin axis and the eddy currents torque causes an exponential decay of the angular velocity magnitude. Numerical simulations performed with data of the Brazilian Satellites (SCD1 and SCD2 show the period that analytical solution can be used to the attitude propagation, within the dispersion range of the attitude determination system performance of Satellite Control Center of Brazil National Research Institute.
Hybrid spacecraft attitude control system
Renuganth Varatharajoo; Ramly Ajir; Tamizi Ahmad
2016-01-01
The hybrid subsystem design could be an attractive approach for futurespacecraft to cope with their demands. The idea of combining theconventional Attitude Control System and the Electrical Power System ispresented in this article. The Combined Energy and Attitude ControlSystem (CEACS) consisting of a double counter rotating flywheel assemblyis investigated for small satellites in this article. Another hybrid systemincorporating the conventional Attitude Control System into the ThermalControl...
Hybrid spacecraft attitude control system
Directory of Open Access Journals (Sweden)
Renuganth Varatharajoo
2016-02-01
Full Text Available The hybrid subsystem design could be an attractive approach for futurespacecraft to cope with their demands. The idea of combining theconventional Attitude Control System and the Electrical Power System ispresented in this article. The Combined Energy and Attitude ControlSystem (CEACS consisting of a double counter rotating flywheel assemblyis investigated for small satellites in this article. Another hybrid systemincorporating the conventional Attitude Control System into the ThermalControl System forming the Combined Attitude and Thermal ControlSystem (CATCS consisting of a "fluid wheel" and permanent magnets isalso investigated for small satellites herein. The governing equationsdescribing both these novel hybrid subsystems are presented and theironboard architectures are numerically tested. Both the investigated novelhybrid spacecraft subsystems comply with the reference missionrequirements.The hybrid subsystem design could be an attractive approach for futurespacecraft to cope with their demands. The idea of combining theconventional Attitude Control System and the Electrical Power System ispresented in this article. The Combined Energy and Attitude ControlSystem (CEACS consisting of a double counter rotating flywheel assemblyis investigated for small satellites in this article. Another hybrid systemincorporating the conventional Attitude Control System into the ThermalControl System forming the Combined Attitude and Thermal ControlSystem (CATCS consisting of a "fluid wheel" and permanent magnets isalso investigated for small satellites herein. The governing equationsdescribing both these novel hybrid subsystems are presented and theironboard architectures are numerically tested. Both the investigated novelhybrid spacecraft subsystems comply with the reference missionrequirements.
2002-11-27
than a liability. It stabilizes yaw and pitch by using a badminton -birdie type configuration, one like that pictured in Fig. 2. The basic principal...of metal or Kevlar that resemble the tape in a carpenter’s retractable tape measure. Fig. 2. Badminton -birdie-type spacecraft pitch-yaw stabilization...A second design uses a new passive aerodynamic pitch-yaw stabilization system. This latter system is based on the concept of a badminton birdie and
Attitude Stabilization Control of a Quadrotor UAV by Using Backstepping Approach
Directory of Open Access Journals (Sweden)
Xing Huo
2014-01-01
Full Text Available The modeling and attitude stabilization control problems of a four-rotor vertical takeoff and landing unmanned air vehicle (UAV known as the quadrotor are investigated. The quadrotor’s attitude is represented by the unit quaternion rather than Euler angles to avoid singularity problem. Taking dynamical behavior of motors into consideration and ignoring aerodynamic effect, a nonlinear controller is developed to stabilize the attitude. The control design is accomplished by using backstepping control technique. The proposed control law is based on the compensation for the Coriolis and gyroscope torques. Applying Lyapunov stability analysis proves that the closed-loop attitude system is asymptotic stable. Moreover, the controller can guarantee that all the states of the system are uniformly ultimately bounded in the presence of external disturbance torque. The effectiveness of the proposed control approach is analytically authenticated and also validated via simulation study.
Platform attitude data acquisition system
Digital Repository Service at National Institute of Oceanography (India)
Afzulpurkar, S.
A system for automatic acquisition of underwater platform attitude data has been designed, developed and tested in the laboratory. This is a micro controller based system interfacing dual axis inclinometer, high-resolution digital compass...
Stability of dynamical systems
Liao, Xiaoxin; Yu, P 0
2007-01-01
The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents
On the spacecraft attitude stabilization in the orbital frame
Directory of Open Access Journals (Sweden)
Antipov Kirill A.
2012-01-01
Full Text Available The paper deals with spacecraft in the circular near-Earth orbit. The spacecraft interacts with geomagnetic field by the moments of Lorentz and magnetic forces. The octupole approximation of the Earth’s magnetic field is accepted. The spacecraft electromagnetic parameters, namely the electrostatic charge moment of the first order and the eigen magnetic moment are the controlled quasiperiodic functions. The control algorithms for the spacecraft electromagnetic parameters, which allows to stabilize the spacecraft attitude position in the orbital frame are obtained. The stability of the spacecraft stabilized orientation is proved both analytically and by PC computations.
Spherical gyroscopic moment stabilizer for attitude control of microsatellites
Keshtkar, Sajjad; Moreno, Jaime A.; Kojima, Hirohisa; Uchiyama, Kenji; Nohmi, Masahiro; Takaya, Keisuke
2018-02-01
This paper presents a new and improved concept of recently proposed two-degrees of freedom spherical stabilizer for triaxial orientation of microsatellites. The analytical analysis of the advantages of the proposed mechanism over the existing inertial attitude control devices are introduced. The extended equations of motion of the stabilizing satellite including the spherical gyroscope, for control law design and numerical simulations, are studied in detail. A new control algorithm based on continuous high-order sliding mode algorithms, for managing the torque produced by the stabilizer and therefore the attitude control of the satellite in the presence of perturbations/uncertainties, is presented. Some numerical simulations are carried out to prove the performance of the proposed mechanism and control laws.
Models of complex attitude systems
DEFF Research Database (Denmark)
Sørensen, Bjarne Taulo
search algorithms and structural equation models. The results suggest that evaluative judgments of the importance of production system attributes are generated in a schematic manner, driven by personal value orientations. The effect of personal value orientations was strong and largely unmediated...... that evaluative affect propagates through the system in such a way that the system becomes evaluatively consistent and operates as a schema for the generation of evaluative judgments. In the empirical part of the paper, the causal structure of an attitude system from which people derive their evaluations of pork......Existing research on public attitudes towards agricultural production systems is largely descriptive, abstracting from the processes through which members of the general public generate their evaluations of such systems. The present paper adopts a systems perspective on such evaluations...
Satellite Attitude Control System Simulator
Directory of Open Access Journals (Sweden)
G.T. Conti
2008-01-01
Full Text Available Future space missions will involve satellites with great autonomy and stringent pointing precision, requiring of the Attitude Control Systems (ACS with better performance than before, which is function of the control algorithms implemented on board computers. The difficulties for developing experimental ACS test is to obtain zero gravity and torque free conditions similar to the SCA operate in space. However, prototypes for control algorithms experimental verification are fundamental for space mission success. This paper presents the parameters estimation such as inertia matrix and position of mass centre of a Satellite Attitude Control System Simulator (SACSS, using algorithms based on least square regression and least square recursive methods. Simulations have shown that both methods have estimated the system parameters with small error. However, the least square recursive methods have performance more adequate for the SACSS objectives. The SACSS platform model will be used to do experimental verification of fundamental aspects of the satellite attitude dynamics and design of different attitude control algorithm.
Convergent systems vs. incremental stability
Rüffer, B.S.; Wouw, van de N.; Mueller, M.
2013-01-01
Two similar stability notions are considered; one is the long established notion of convergent systems, the other is the younger notion of incremental stability. Both notions require that any two solutions of a system converge to each other. Yet these stability concepts are different, in the sense
Attitudes and beliefs among patients treated with mood stabilizers
DEFF Research Database (Denmark)
Kessing, Lars Vedel; Hansen, Hanne Vibe; Bech, Per
2006-01-01
that they previously had been or currently were in treatment with a mood stabilizer. A large proportion of the patients (40 to 80 %) had non-correct views on the effect of mood stabilizers. Older patients consistently had a more negative view on the doctor-patient relationship, more non-correct views on the effect...... psychiatrist, community psychiatry doctor, hospital doctor, other doctor). CONCLUSION: There is a need of improving knowledge and attitudes toward diagnosis and treatment especially among elder patients as this may add to improve the prognosis of depressive and bipolar disorders....... Compliance Questionnaire (MSQC) was mailed to a large population of patients with depressive or bipolar disorder representative of patients treated at their first contacts to hospital settings in Denmark. RESULTS: Of the 1005 recipients, 49.9 % responded to the letter and among these 256 indicated...
ATTITUDE DETERMINATION AND CONTROL SYSTEM OF KITSAT-1
Directory of Open Access Journals (Sweden)
Hyunwoo Lee
1996-06-01
Full Text Available The attitude dynamics of KITSAT-1 are modeled including the gravity gradient stabilization method. We define the operation scenario during the initial attitude stabilization period by means of a magnetorquering control algorithm. The required constraints for the gravity gradient boom deployment are also examined. Attitude dynamics model and control laws are verified by analyzing in-orbit attitude sensor telemetry data.
Attitude stabilization of a spacecraft equipped with large electrostatic protection screens
Nikitin, D. Yu.; Tikhonov, A. A.
2018-05-01
A satellite with a system of three electrostatic radiation protection (ERP) screens is under consideration. The screens are constructed as electrostatically charged toroidal shields with characteristic size of order equal to 100 m. The interaction of electric charge with the Earth's magnetic field (EMF) give rise to the Lorentz torque acting upon a satellite attitude motion. As the sizes of ERP system are large, we derive the Lorentz torque taking into account the complex form of ERP screens and gradient of the EMF in the screen volume. It is assumed that the satellite center of charge coincides with the satellite mass center. The EMF is modeled by the straight magnetic dipole. In the paper we investigate the usage of Lorentz torque for passive attitude stabilization for satellite in a circular equatorial orbit. Mathematical model for attitude dynamics of a satellite equipped with ERP interacting with the EMF is derived and first integral of corresponding differential equations is constructed. The straight equilibrium position of the satellite in the orbital frame is found. Sufficient conditions for stability of satellite equilibrium position are constructed with the use of the first integral. The gravity gradient torque is taken into account. The satellite equilibrium stability domain is constructed.
Chak, Yew-Chung; Varatharajoo, Renuganth
2016-07-01
Many spacecraft attitude control systems today use reaction wheels to deliver precise torques to achieve three-axis attitude stabilization. However, irrecoverable mechanical failure of reaction wheels could potentially lead to mission interruption or total loss. The electrically-powered Solar Array Drive Assemblies (SADA) are usually installed in the pitch axis which rotate the solar arrays to track the Sun, can produce torques to compensate for the pitch-axis wheel failure. In addition, the attitude control of a flexible spacecraft poses a difficult problem. These difficulties include the strong nonlinear coupled dynamics between the rigid hub and flexible solar arrays, and the imprecisely known system parameters, such as inertia matrix, damping ratios, and flexible mode frequencies. In order to overcome these drawbacks, the adaptive Jacobian tracking fuzzy control is proposed for the combined attitude and sun-tracking control problem of a flexible spacecraft during attitude maneuvers in this work. For the adaptation of kinematic and dynamic uncertainties, the proposed scheme uses an adaptive sliding vector based on estimated attitude velocity via approximate Jacobian matrix. The unknown nonlinearities are approximated by deriving the fuzzy models with a set of linguistic If-Then rules using the idea of sector nonlinearity and local approximation in fuzzy partition spaces. The uncertain parameters of the estimated nonlinearities and the Jacobian matrix are being adjusted online by an adaptive law to realize feedback control. The attitude of the spacecraft can be directly controlled with the Jacobian feedback control when the attitude pointing trajectory is designed with respect to the spacecraft coordinate frame itself. A significant feature of this work is that the proposed adaptive Jacobian tracking scheme will result in not only the convergence of angular position and angular velocity tracking errors, but also the convergence of estimated angular velocity to
Dynamic Stability of Maglev Systems,
1992-04-01
AD-A259 178 ANL-92/21 Materials and Components Dynamic Stability of Technology Division Materials and Components Maglev Systems Technology Division...of Maglev Systems Y. Cai, S. S. Chen, and T. M. Mulcahy Materials and Components Technology Division D. M. Rote Center for Transportation Research...of Maglev System with L-Shaped Guideway ......................................... 6 3 Stability of M aglev System s
Zhao, Yuejin
1996-06-01
In this paper, a new method for image stabilization with a three-axis image- stabilizing reflecting prism assembly is presented, and the principle of image stabilization in this prism assembly, formulae for image stabilization and working formulae with an approximation up to the third power are given in detail. In this image-stabilizing system, a single chip microcomputer is used to calculate value of compensating angles and thus to control the prism assembly. Two gyroscopes act as sensors from which information of angular perturbation is obtained, three stepping motors drive the prism assembly to compensate for the movement of image produced by angular perturbation. The image-stabilizing device so established is a multifold system which involves optics, mechanics, electronics and computer.
Interval stability for complex systems
Klinshov, Vladimir V.; Kirillov, Sergey; Kurths, Jürgen; Nekorkin, Vladimir I.
2018-04-01
Stability of dynamical systems against strong perturbations is an important problem of nonlinear dynamics relevant to many applications in various areas. Here, we develop a novel concept of interval stability, referring to the behavior of the perturbed system during a finite time interval. Based on this concept, we suggest new measures of stability, namely interval basin stability (IBS) and interval stability threshold (IST). IBS characterizes the likelihood that the perturbed system returns to the stable regime (attractor) in a given time. IST provides the minimal magnitude of the perturbation capable to disrupt the stable regime for a given interval of time. The suggested measures provide important information about the system susceptibility to external perturbations which may be useful for practical applications. Moreover, from a theoretical viewpoint the interval stability measures are shown to bridge the gap between linear and asymptotic stability. We also suggest numerical algorithms for quantification of the interval stability characteristics and demonstrate their potential for several dynamical systems of various nature, such as power grids and neural networks.
Plutonium stabilization and packaging system
International Nuclear Information System (INIS)
1996-01-01
This document describes the functional design of the Plutonium Stabilization and Packaging System (Pu SPS). The objective of this system is to stabilize and package plutonium metals and oxides of greater than 50% wt, as well as other selected isotopes, in accordance with the requirements of the DOE standard for safe storage of these materials for 50 years. This system will support completion of stabilization and packaging campaigns of the inventory at a number of affected sites before the year 2002. The package will be standard for all sites and will provide a minimum of two uncontaminated, organics free confinement barriers for the packaged material
Built on Rock or Sand? The Stability of Religiosity and Attitudes Towards Abortion
Sides, John M.
1998-01-01
This paper examines two questions. First, how stable is religiosity over time? Second, how does religiosity affect the stability of attitudes over time? I begin by discussing several reasons why religiosity might help to stabilize attitudes. Then, drawing on the 1992-94-96 National Election Study panel, I examine the stability of religious tradition, religious movement identification, church attendance, view of scripture, and the overall importance of religion. For the most part, these indica...
Attitude Estimation in Fractionated Spacecraft Cluster Systems
Hadaegh, Fred Y.; Blackmore, James C.
2011-01-01
An attitude estimation was examined in fractioned free-flying spacecraft. Instead of a single, monolithic spacecraft, a fractionated free-flying spacecraft uses multiple spacecraft modules. These modules are connected only through wireless communication links and, potentially, wireless power links. The key advantage of this concept is the ability to respond to uncertainty. For example, if a single spacecraft module in the cluster fails, a new one can be launched at a lower cost and risk than would be incurred with onorbit servicing or replacement of the monolithic spacecraft. In order to create such a system, however, it is essential to know what the navigation capabilities of the fractionated system are as a function of the capabilities of the individual modules, and to have an algorithm that can perform estimation of the attitudes and relative positions of the modules with fractionated sensing capabilities. Looking specifically at fractionated attitude estimation with startrackers and optical relative attitude sensors, a set of mathematical tools has been developed that specify the set of sensors necessary to ensure that the attitude of the entire cluster ( cluster attitude ) can be observed. Also developed was a navigation filter that can estimate the cluster attitude if these conditions are satisfied. Each module in the cluster may have either a startracker, a relative attitude sensor, or both. An extended Kalman filter can be used to estimate the attitude of all modules. A range of estimation performances can be achieved depending on the sensors used and the topology of the sensing network.
SmartScan: a robust pushbroom imaging concept for moderate spacecraft attitude stability
Janschek, K.; Tchernykh, V.; Dyblenko, S.; Harnisch, B.
2017-11-01
Pushbroom scan cameras with linear image sensors, commonly used for Earth observation from satellites, require high attitude stability during the image acquisition. Especially noticeable are the effects of high frequency attitude variations originating from micro shocks and vibrations, produced by momentum and reaction wheels, mechanically activated coolers, steering and deployment mechanics and other reasons. The SMARTSCAN imaging concept offers high quality imaging even with moderate satellite attitude stability on a sole opto-electronic basis without any moving parts. It uses real-time recording of the actual image motion in the focal plane of the remote sensing camera during the frame acquisition and a posteriori correction of the obtained image distortions on base of the image motion record. Exceptional real-time performances with subpixel accuracy image motion measurement are provided by an innovative high-speed onboard optoelectronic correlation processor. SMARTSCAN allows therefore using smart pushbroom cameras for hyper-spectral imagers on satellites and platforms which are not specially intended for imaging missions, e.g. micro satellites. The paper gives an overview on the system concept and main technologies used (advanced optical correlator for ultra high-speed image motion tracking), it discusses the conceptual design for a smart compact space camera and it reports on airborne test results of a functional breadboard model.
Plenoptic Attitude Monitoring System, Phase I
National Aeronautics and Space Administration — NASA is seeking an optical system capable of analyzing the attitude of wind tunnel models in real time, with a high angular resolution and robustness. To address...
Stability of risk attitudes and media coverage of economic news
Tausch, Franziska; Zumbuehl, Maria
2016-01-01
This paper investigates the impact of exogenous changes in individuals' perceived economic environment on their self-stated risk attitudes by exploiting changes in media coverage of economic news. We use information on risk attitudes from the German Socioeconomic Panel and combine it with data on the average daily frequency of economic news reports during the year and the month preceding the date of the risk attitude elicitation. Using fixed effects regressions we observe effects of both long...
Consumer attitudes to different pig production systems
DEFF Research Database (Denmark)
de Barcellos, Marcia Dutra; Grunert, Klaus G; Zhou, Yanfeng
2013-01-01
In many Western countries, consumers have shown an increasing interest to the way in which food products are being produced. This study investigates Chinese consumers' attitudes towards different pig production systems by means of a conjoint analysis. While there has been a range of studies...... on Western consumers' attitudes to various forms of food production, little is known about the level of Chinese consumers' attitudes. A cross-sectional survey was carried out with 472 participants in six Chinese cities. Results indicate that Chinese consumers prefer industrial pig production systems, where...... from Cluster 1 focus almost exclusively on the food safety aspect (food safety focused). Consumers from cluster 2 (indifferent) show generally weak attitudes to pig production systems in general. Cluster 3 (industrial production oriented) stands out by being very positive about industrial, large size...
Attitude Determination and Control Systems
Starin, Scott R.; Eterno, John
2011-01-01
designing and operating spacecraft pointing (i.e. attitude) systems.
Morocco; Financial System Stability Assessment
International Monetary Fund
2003-01-01
The Financial System Stability Assessment of Morocco reviews the reform program that is aimed at establishing a modern, market-oriented financial system that optimizes the mobilization of savings and the allocation of financial resources. It reviews the modernization of the banking sector and the development of competition within the sector, development of financial markets, and removal of constraints on financial system activity. It also provides reports on the Observance of Standards and Co...
STABILITY SYSTEMS VIA HURWITZ POLYNOMIALS
Directory of Open Access Journals (Sweden)
BALTAZAR AGUIRRE HERNÁNDEZ
2017-01-01
Full Text Available To analyze the stability of a linear system of differential equations ẋ = Ax we can study the location of the roots of the characteristic polynomial pA(t associated with the matrix A. We present various criteria - algebraic and geometric - that help us to determine where the roots are located without calculating them directly.
Long term stability of power systems
Energy Technology Data Exchange (ETDEWEB)
Kundur, P; Gao, B [Powertech Labs. Inc., Surrey, BC (Canada)
1994-12-31
Power system long term stability is still a developing subject. In this paper we provide our perspectives and experiences related to long term stability. The paper begins with the description of the nature of the long term stability problem, followed by the discussion of issues related to the modeling and solution techniques of tools for long term stability analysis. Cases studies are presented to illustrate the voltage stability aspect and plant dynamics aspect of long term stability. (author) 20 refs., 11 figs.
New stability and stabilization for switched neutral control systems
International Nuclear Information System (INIS)
Xiong Lianglin; Zhong Shouming; Ye Mao; Wu Shiliang
2009-01-01
This paper concerns stability and stabilization issues for switched neutral systems and presents new classes of piecewise Lyapunov functionals and multiple Lyapunov functionals, based on which, two new switching rules are introduced to stabilize the neutral systems. One switching rule is designed from the solution of the so-called Lyapunov-Metzler linear matrix inequalities. The other is based on the determination of average dwell time computed from a new class of linear matrix inequalities (LMIs). And then, state-feedback control is derived for the switched neutral control system mainly based on the state switching rules. Finally, three examples are given to demonstrate the effectiveness of the proposed method.
Stability in dynamical systems I
International Nuclear Information System (INIS)
Courant, E.D.; Ruth, R.D.; Weng, W.T.
1984-08-01
We have reviewed some of the basic techniques which can be used to analyze stability in nonlinear dynamical systems, particularly in circular particle accelerators. We have concentrated on one-dimensional systems in the examples in order to simply illustrate the general techniques. We began with a review of Hamiltonian dynamics and canonical transformations. We then reviewed linear equations with periodic coefficients using the basic techniques from accelerator theory. To handle nonlinear terms we developed a canonical perturbation theory. From this we calculated invariants and the amplitude dependence of the frequency. This led us to resonances. We studied the cubic resonance in detail by using a rotating coordinate system in phase space. We then considered a general isolated nonlinear resonance. In this case we calculated the width of the resonance and estimated the spacing of resonances in order to use the Chirikov criterion to restrict the validity of the analysis. Finally the resonance equation was reduced to the pendulum equation, and we examined the motion on a separatrix. This brought us to the beginnings of stochastic behavior in the neighborhood of the separatrix. It is this complex behavior in the neighborhood of the separatrix which causes the perturbation theory used here to diverge in many cases. In spite of this the methods developed here have been and are used quite successfully to study nonlinear effects in nearly integrable systems. When used with caution and in conjunction with numerical work they give tremendous insight into the nature of the phase space structure and the stability of nonlinear differential equations. 14 references
A Nonlinear Attitude Estimator for Attitude and Heading Reference Systems Based on MEMS Sensors
DEFF Research Database (Denmark)
Wang, Yunlong; Soltani, Mohsen; Hussain, Dil muhammed Akbar
2016-01-01
In this paper, a nonlinear attitude estimator is designed for an Attitude Heading and Reference System (AHRS) based on Micro Electro-Mechanical Systems (MEMS) sensors. The design process of the attitude estimator is stated with detail, and the equilibrium point of the estimator error model...... the problems in previous research works. Moreover, the estimation of MEMS gyroscope bias is also inclueded in this estimator. The designed nonlinear attitude estimator is firstly tested in simulation environment and then implemented in an AHRS hardware for further experiments. Finally, the attitude estimation...
Tritium systems test assembly stabilization
International Nuclear Information System (INIS)
Jasen, William G.; Michelotti, Roy A.; Anast, Kurt R.; Tesch, Charles
2004-01-01
The Tritium Systems Test Assembly (TSTA) was a facility dedicated to tritium technology Research and Development (R and D) primarily for future fusion power reactors. The facility was conceived in mid 1970's, operations commenced in early 1980's, stabilization and deactivation began in 2000 and were completed in 2003. The facility will remain in a Surveillance and Maintenance (S and M) mode until the Department of Energy (DOE) funds demolition of the facility, tentatively in 2009. A safe and stable end state was achieved by the TSTA Facility Stabilization Project (TFSP) in anticipation of long term S and M. At the start of the stabilization project, with an inventory of approximately 140 grams of tritium, the facility was designated a Hazard Category (HC) 2 Non-Reactor Nuclear facility as defined by US Department of Energy standard DOE-STD-1027-92 (1997). The TSTA facility comprises a laboratory area, supporting rooms, offices and associated laboratory space that included more than 20 major tritium handling systems. The project's focus was to reduce the tritium inventory by removing bulk tritium, tritiated water wastes, and tritium-contaminated high-inventory components. Any equipment that remained in the facility was stabilized in place. All of the gloveboxes and piping were rendered inoperative and vented to atmosphere. All equipment, and inventoried tritium contamination, remaining in the facility was left in a safe-and-stable state. The project used the End Points process as defined by the DOE Office of Environmental Management (web page http://www.em.doe.- gov/deact/epman.htmtlo) document and define the end state required for the stabilization of TSTA Facility. The End Points process added structure that was beneficial through virtually all phases of the project. At completion of the facility stabilization project the residual tritium inventory was approximately 3,000 curies, considerably less than the 1.6-gram threshold for a HC 3 facility. TSTA is now
Effect of Electrodynamic Forces on the Attitude Stabilization of a Satellite in Ecliptic orbits
Abdel-Aziz, Yehia
This work is based on the previous paper of the author [1]. The present paper is devoted to the investigation of the attitude dynamics of an ecliptic satellite moving in the magnetic field of the Earth. Eelectrodynamic forces result from the motion of a charged satelite relative to the magnetic field of the Earth. The torque due to electrodynamic effect of the Lorentz forces on the attitude stabilization of the satellite is studied with the detailed model of the Earth's magnetic field. A method for estimating the stable and unstable regions of the equilibrium positions based on Euler's equation is also discussed. The results show that Lorentz forces can affect the stablization of the satellite, in particular for highly eccentric orbits and also for large satellte. [1] Abdel-Aziz, Y. A. Attitude Stabilization of a Rigid Spacecraft in the Geomagnetic Field. AdSpR 40, 18-24, 2007.
Financial stability of banking system in China
Jiang, B
2014-01-01
This thesis aims at investigating the financial stability of China's banking system. Since the banking system is one of the most important financial intermediaries in the financial systems, the financial soundness of banks could secure the stability of the whole financial system. Two of the factors that may significantly increase imbalance of the banking system, and hence affect financial stability of an economy is the accumulated non-performing loans of banks and the macro-economic turbulenc...
Stabilization of classic and quantum systems
International Nuclear Information System (INIS)
Buts, V.A.
2012-01-01
It is shown that the mechanism of quantum whirligig can be successfully used for stabilization of classical systems. In particular, the conditions for stabilization of charged particles and radiation fluxes in plasma are found.
Stability problems for linear hyperbolic systems
International Nuclear Information System (INIS)
Eckhoff, K.S.
1975-05-01
The stability properties for the trivial solution of a general linear hyperbolic system of partial differential equations of the first order are studied. It is shown that results may be obtained by studying the stability properties of certain systems of ordinary differential equations which can be constructed from the hyperbolic system (the so-called transport equations). In some cases the associated stability problem for the transport equations can in fact be shown to be equivalent to the stability problem for the hyperbolic system, but in general the transport equations will only give the necessary conditions for stability. (Auth.)
Stabilized imploding liner fusion systems
International Nuclear Information System (INIS)
Book, D.L.; Cooper, A.L.; Ford, R.; Gerber, K.A.; Hammer, D.A.; Jenkins, D.J.; Robson, A.E.; Turchi, P.J.
1977-01-01
A new concept in imploding liner plasma compression is described in which a liquid metal liner is imploded by pistons driven by high-pressure gas, and stability of the inner surface against Rayleigh-Taylor modes is achieved by rotation. The principle has been demonstrated by using a water liner to compress air. This 'captive liner' offers the possibility of stable, reversible implosion-expansion cycles in which the plasma energy is recovered into the driving system, leading to reactor cycles with low Q and, hence, small size. A new method of setting up closed-field confinement geometries inside a liner using a rotating electron beam is described. Plasma currents induced by the beam provide initial plasma heating and generate the containment geometry. Persistence of plasma currents 100 times longer than the beam duration has been observed. Development of these methods could lead to a very compact thermonuclear reactor operating in the manner of a reciprocating engine. (author)
System and method for correcting attitude estimation
Josselson, Robert H. (Inventor)
2010-01-01
A system includes an angular rate sensor disposed in a vehicle for providing angular rates of the vehicle, and an instrument disposed in the vehicle for providing line-of-sight control with respect to a line-of-sight reference. The instrument includes an integrator which is configured to integrate the angular rates of the vehicle to form non-compensated attitudes. Also included is a compensator coupled across the integrator, in a feed-forward loop, for receiving the angular rates of the vehicle and outputting compensated angular rates of the vehicle. A summer combines the non-compensated attitudes and the compensated angular rates of the to vehicle to form estimated vehicle attitudes for controlling the instrument with respect to the line-of-sight reference. The compensator is configured to provide error compensation to the instrument free-of any feedback loop that uses an error signal. The compensator may include a transfer function providing a fixed gain to the received angular rates of the vehicle. The compensator may, alternatively, include a is transfer function providing a variable gain as a function of frequency to operate on the received angular rates of the vehicle.
Consumer attitudes towards domestic solar power systems
International Nuclear Information System (INIS)
Faiers, Adam; Neame, Charles
2006-01-01
The success of the UK policy to reduce carbon emissions is partly dependent on the ability to persuade householders to become more energy efficient, and to encourage installation of domestic solar systems. Solar power is an innovation in the UK but the current policy of stimulating the market with grants is not resulting in widespread adoption. This case study, using householders in central England, investigates householder attitudes towards characteristics of solar systems and identifies some of the barriers to adoption. The study utilises Diffusion of Innovations theory to identify attitudes towards system attributes, and isolates the characteristics that are preventing a pragmatic 'early majority' from adopting the technology. A group of 'early adopters', and a group of assumed 'early majority' adopters of solar power were surveyed and the results show that overall, although the 'early majority' demonstrate a positive perception of the environmental characteristics of solar power, its financial, economic and aesthetic characteristics are limiting adoption. Differences exist between the two groups showing support for the concept of a 'chasm' between adopter categories after Moore (Crossing the Chasm: Marketing and Selling High-tech Products to Mainstream Customers, second ed. Harper Perennial, New York). However, if consumers cannot identify the relative advantage of solar power over their current sources of power, which is supplied readily and cheaply through a mains system, it is unlikely that adoption will follow. Recommendations concerning the marketing and development of solar products are identified
High Accuracy Attitude Control System Design for Satellite with Flexible Appendages
Directory of Open Access Journals (Sweden)
Wenya Zhou
2014-01-01
Full Text Available In order to realize the high accuracy attitude control of satellite with flexible appendages, attitude control system consisting of the controller and structural filter was designed. When the low order vibration frequency of flexible appendages is approximating the bandwidth of attitude control system, the vibration signal will enter the control system through measurement device to bring impact on the accuracy or even the stability. In order to reduce the impact of vibration of appendages on the attitude control system, the structural filter is designed in terms of rejecting the vibration of flexible appendages. Considering the potential problem of in-orbit frequency variation of the flexible appendages, the design method for the adaptive notch filter is proposed based on the in-orbit identification technology. Finally, the simulation results are given to demonstrate the feasibility and effectiveness of the proposed design techniques.
The stability of protoplanet systems
Yoshinaga, K; Makino, J
1999-01-01
The authors investigated the stability of 10 protoplanet systems using three-dimensional N-body simulations. They found that the time scale of instability T depends strongly on the initial random velocities nu (eccentricities e and inclinations i) and orbital separations Delta a. For zero initial random velocities, they confirmed the result of Chambers et al. (1996, Icarus 119, 261-268) that T is proportional to exp( Delta a). For finite random velocities, they found that T depends strongly on the initial random velocities. The relation between T and Delta a is still expressed as log T=b+c Delta a. However, both b and c depend on initial random velocities and the slope, b, becomes smaller for larger nu . Even for relatively small initial eccentricities such as e~2r/sub H//a, where r/sub H/ is the Hill radius, the time scale can be reduced by a factor of 10 compared with the case of the zero random velocity. Therefore, the time scale of the formation of inner planets might be much shorter than what implied by ...
Systems of attitudes towards production in the pork industry
DEFF Research Database (Denmark)
Sørensen, Bjarne Taulo; Dutra de Barcellos, Marcia; Veflen Olsen, Nina
2012-01-01
Existing research on public attitudes towards agricultural production systems is largely descriptive, abstracting from the processes through which members of the general public generate their evaluations of such systems. The present paper adopts a systems perspective on such evaluations, understa...... by attitudes of an intermediate level of generality, suggesting that the dependent variables in the particular attitude system that was modelled here can be understood as value judgments in a literal sense....
Magnetospheric Multiscale (MMS) Mission Attitude Ground System Design
Sedlak, Joseph E.; Superfin, Emil; Raymond, Juan C.
2011-01-01
This paper describes the attitude ground system (AGS) design to be used for support of the Magnetospheric MultiScale (MMS) mission. The AGS exists as one component of the mission operations control center. It has responsibility for validating the onboard attitude and accelerometer bias estimates, calibrating the attitude sensors and the spacecraft inertia tensor, and generating a definitive attitude history for use by the science teams. NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland is responsible for developing the MMS spacecraft, for the overall management of the MMS mission, and for mission operations. MMS is scheduled for launch in 2014 for a planned two-year mission. The MMS mission consists of four identical spacecraft flying in a tetrahedral formation in an eccentric Earth orbit. The relatively tight formation, ranging from 10 to 400 km, will provide coordinated observations giving insight into small-scale magnetic field reconnection processes. By varying the size of the tetrahedron and the orbital semi-major axis and eccentricity, and making use of the changing solar phase, this geometry allows for the study of both bow shock and magnetotail plasma physics, including acceleration, reconnection, and turbulence. The mission divides into two phases for science; these phases will have orbit dimensions of l.2xl2 Earth radii in the first phase and l.2x25 Earth radii in the second in order to study the dayside magnetopause and the nightside magnetotail, respectively. The orbital periods are roughly one day and three days for the two mission phases. Each of the four MMS spacecraft will be spin stabilized at 3 revolutions per minute (rpm), with the spin axis oriented near the ecliptic north pole but tipped approximately 2.5 deg towards the Sun line. The main body of each spacecraft will be an eight-sided platform with diameter of 3.4 m and height of 1.2 m. Several booms are attached to this central core: two axial booms of 14.9 m length, two radial
Stability and stabilization of linear systems with saturating actuators
Tarbouriech, Sophie; Gomes da Silva Jr, João Manoel; Queinnec, Isabelle
2011-01-01
Gives the reader an in-depth understanding of the phenomena caused by the more-or-less ubiquitous problem of actuator saturation. Proposes methods and algorithms designed to avoid, manage or overcome the effects of actuator saturation. Uses a state-space approach to ensure local and global stability of the systems considered. Compilation of fifteen years' worth of research results.
Fuzzy stability and synchronization of hyperchaos systems
International Nuclear Information System (INIS)
Wang Junwei; Xiong Xiaohua; Zhao Meichun; Zhang Yanbin
2008-01-01
This paper studies stability and synchronization of hyperchaos systems via a fuzzy-model-based control design methodology. First, we utilize a Takagi-Sugeno fuzzy model to represent a hyperchaos system. Second, we design fuzzy-model-based controllers for stability and synchronization of the system, based on so-called 'parallel distributed compensation (PDC)'. Third, we reduce a question of stabilizing and synchronizing hyperchaos systems to linear matrix inequalities (LMI) so that convex programming techniques can solve these LMIs efficiently. Finally, the generalized Lorenz hyperchaos system is employed to illustrate the effectiveness of our designing controller
Consumer attitudes towards domestic solar power systems
Energy Technology Data Exchange (ETDEWEB)
Faiers, Adam [Institute of Water and Environment, Cranfield University at Silsoe, Silsoe, Bedfordshire, MK45 4DT (United Kingdom)]. E-mail: a.j.faiers.so2@cranfield.ac.uk; Neame, Charles [Institute of Water and Environment, Cranfield University at Silsoe, Silsoe, Bedfordshire, MK45 4DT (United Kingdom)]. E-mail: c.neame@cranfield.ac.uk
2006-09-15
The success of the UK policy to reduce carbon emissions is partly dependent on the ability to persuade householders to become more energy efficient, and to encourage installation of domestic solar systems. Solar power is an innovation in the UK but the current policy of stimulating the market with grants is not resulting in widespread adoption. This case study, using householders in central England, investigates householder attitudes towards characteristics of solar systems and identifies some of the barriers to adoption. The study utilises Diffusion of Innovations theory to identify attitudes towards system attributes, and isolates the characteristics that are preventing a pragmatic 'early majority' from adopting the technology. A group of 'early adopters', and a group of assumed 'early majority' adopters of solar power were surveyed and the results show that overall, although the 'early majority' demonstrate a positive perception of the environmental characteristics of solar power, its financial, economic and aesthetic characteristics are limiting adoption. Differences exist between the two groups showing support for the concept of a 'chasm' between adopter categories after Moore (Crossing the Chasm: Marketing and Selling High-tech Products to Mainstream Customers, second ed. Harper Perennial, New York). However, if consumers cannot identify the relative advantage of solar power over their current sources of power, which is supplied readily and cheaply through a mains system, it is unlikely that adoption will follow. Recommendations concerning the marketing and development of solar products are identified.
Spacecraft attitude and velocity control system
Paluszek, Michael A. (Inventor); Piper, Jr., George E. (Inventor)
1992-01-01
A spacecraft attitude and/or velocity control system includes a controller which responds to at least attitude errors to produce command signals representing a force vector F and a torque vector T, each having three orthogonal components, which represent the forces and torques which are to be generated by the thrusters. The thrusters may include magnetic torquer or reaction wheels. Six difference equations are generated, three having the form ##EQU1## where a.sub.j is the maximum torque which the j.sup.th thruster can produce, b.sub.j is the maximum force which the j.sup.th thruster can produce, and .alpha..sub.j is a variable representing the throttling factor of the j.sup.th thruster, which may range from zero to unity. The six equations are summed to produce a single scalar equation relating variables .alpha..sub.j to a performance index Z: ##EQU2## Those values of .alpha. which maximize the value of Z are determined by a method for solving linear equations, such as a linear programming method. The Simplex method may be used. The values of .alpha..sub.j are applied to control the corresponding thrusters.
Verbeke, Wim; Van Kenhove, Patrick
2002-01-01
This article focuses on consumer reactions during and after the Coca-Cola crisis of June 1999 in Belgium. The research tests for associations between the personality trait "emotional stability," attitude toward the brand, and self-reported behavior. Cross-sectional data are collected from a sample of Coca-Cola drinkers between 19 and 22 years old. The data are analyzed through the specification and estimation of a structural equation model and ANOVA. A direct and positive effect of attitude toward the brand on the behavioral response is found. No direct effect of emotional stability on behavior is revealed. However, indirect effects of personality mediated by attitude are discovered. Further, emotional stability is found to correlate negatively with importance attached to information during the crisis. Fast and transparent communication with specific attention to lower emotional stability groups, as well as the inclusion of personality and attitude measurements in future health and food safety studies, are recommended.
DeKock, Brandon; Sanders, Devon; Vanzwieten, Tannen; Capo-Lugo, Pedro
2011-01-01
The FASTSAT-HSV01 spacecraft is a microsatellite with magnetic torque rods as it sole attitude control actuator. FASTSAT s multiple payloads and mission functions require the Attitude Control System (ACS) to maintain Local Vertical Local Horizontal (LVLH)-referenced attitudes without spin-stabilization, while the pointing errors for some attitudes be significantly smaller than the previous best-demonstrated for this type of control system. The mission requires the ACS to hold multiple stable, unstable, and non-equilibrium attitudes, as well as eject a 3U CubeSat from an onboard P-POD and recover from the ensuing tumble. This paper describes the Attitude Control System, the reasons for design choices, how the ACS integrates with the rest of the spacecraft, and gives recommendations for potential future applications of the work.
Exponential Stability of Switched Positive Homogeneous Systems
Directory of Open Access Journals (Sweden)
Dadong Tian
2017-01-01
Full Text Available This paper studies the exponential stability of switched positive nonlinear systems defined by cooperative and homogeneous vector fields. In order to capture the decay rate of such systems, we first consider the subsystems. A sufficient condition for exponential stability of subsystems with time-varying delays is derived. In particular, for the corresponding delay-free systems, we prove that this sufficient condition is also necessary. Then, we present a sufficient condition of exponential stability under minimum dwell time switching for the switched positive nonlinear systems. Some results in the previous literature are extended. Finally, a numerical example is given to demonstrate the effectiveness of the obtained results.
Dynamic Stability Experiment of Maglev Systems,
1995-04-01
This report summarizes the research performed on maglev vehicle dynamic stability at Argonne National Laboratory during the past few years. It also... maglev system, it is important to consider this phenomenon in the development of all maglev systems. This report presents dynamic stability experiments...on maglev systems and compares their numerical simulation with predictions calculated by a nonlinear dynamic computer code. Instabilities of an
MHD stability analysis of helical system plasmas
International Nuclear Information System (INIS)
Nakamura, Yuji
2000-01-01
Several topics of the MHD stability studies in helical system plasmas are reviewed with respect to the linear and ideal modes mainly. Difference of the method of the MHD stability analysis in helical system plasmas from that in tokamak plasmas is emphasized. Lack of the cyclic (symmetric) coordinate makes an analysis more difficult. Recent topic about TAE modes in a helical system is also described briefly. (author)
Stability of digital feedback control systems
Directory of Open Access Journals (Sweden)
Larkin Eugene
2018-01-01
Lag time characteristics are used for investigation of stability of linear systems. Digital PID controller is divided onto linear part, which is realized with a soft and pure lag unit, which is realized with both hardware and software. With use notions amplitude and phase margins, condition for stability of system functioning are obtained. Theoretical results are confirm with computer experiment carried out on the third-order system.
Some results on stability of difference systems
Directory of Open Access Journals (Sweden)
Xiao-Song Yang
2002-01-01
Full Text Available This paper presents some new results on existence and stability of equilibrium or periodic points for difference systems. First sufficient conditions of existence of asymptotically stable equilibrium point as well as the asymptotic stability of given equilibrium point are given for second order or delay difference systems. Then some similar results on existence of asymptotically stable periodic (equilibrium points to general difference systems are presented.
Boundary feedback stabilization of distributed parameter systems
DEFF Research Database (Denmark)
Pedersen, Michael
1988-01-01
The author introduces the method of pseudo-differential stabilization. He notes that the theory of pseudo-differential boundary operators is a fruitful approach to problems arising in control and stabilization theory of distributed-parameter systems. The basic pseudo-differential calculus can...
System design description PFP thermal stabilization
International Nuclear Information System (INIS)
RISENMAY, H.R.
1998-01-01
The purpose of this document is to provide a system design description and design basis for the Plutonium Finishing P1ant (PFP) Thermal Stabilization project. The sources of material for this project are residues scraped from glovebox floors and materials already stored in vault storage that need further stabilizing to meet the 3013 storage requirements. Stabilizing this material will promote long term storage and reduced worker exposure. This document addresses: function design, equipment, and safety requirements for thermal stabilization of plutonium residues and oxides
The Nature of Stability in Replicating Systems
Directory of Open Access Journals (Sweden)
Addy Pross
2011-02-01
Full Text Available We review the concept of dynamic kinetic stability, a type of stability associated specifically with replicating entities, and show how it differs from the well-known and established (static kinetic and thermodynamic stabilities associated with regular chemical systems. In the process we demonstrate how the concept can help bridge the conceptual chasm that continues to separate the physical and biological sciences by relating the nature of stability in the animate and inanimate worlds, and by providing additional insights into the physicochemical nature of abiogenesis.
STABILITY OF LINEAR SYSTEMS WITH MARKOVIAN JUMPS
Directory of Open Access Journals (Sweden)
Jorge Enrique Mayta Guillermo
2016-12-01
Full Text Available In this work we will analyze the stability of linear systems governed by a Markov chain, this family is known in the specialized literature as linear systems with Markov jumps or by its acronyms in English MJLS as it is denoted in [1]. Linear systems governed by a Markov chain are dynamic systems with abrupt changes. We give some denitions of stability for the MJLS system, where these types of stability are equivalent as long as the state space of the Markov chain is nite. Finally we present a theorem that characterizes the stochastic stability by means of an equation of the Lyapunov type. The result is a generalization of a theorem in classical theory.
Chinese consumers' attitude towards different pig production systems
DEFF Research Database (Denmark)
de Barcellos, Marcia Dutra; Grunert, Klaus G.; Yanfeng, Z.
2008-01-01
This study investigates Chinese consumers' attitude towards different pig production systems by means of a conjoint analysis. While there has been a range of studies on western consumers' attitudes to various forms of food production, little is known about such attitudes in other cultural contexts...... to food safety which furthermore can provide lean meat with consistent quality are also preferred compared to farms that have less focus on food safety. Chinese consumers also rejected imported pig breeds and tasty but variable meat....
Stability and boundary stabilization of 1-D hyperbolic systems
Bastin, Georges
2016-01-01
This monograph explores the modeling of conservation and balance laws of one-dimensional hyperbolic systems using partial differential equations. It presents typical examples of hyperbolic systems for a wide range of physical engineering applications, allowing readers to understand the concepts in whichever setting is most familiar to them. With these examples, it also illustrates how control boundary conditions may be defined for the most commonly used control devices. The authors begin with the simple case of systems of two linear conservation laws and then consider the stability of systems under more general boundary conditions that may be differential, nonlinear, or switching. They then extend their discussion to the case of nonlinear conservation laws and demonstrate the use of Lyapunov functions in this type of analysis. Systems of balance laws are considered next, starting with the linear variety before they move on to more general cases of nonlinear ones. They go on to show how the problem of boundary...
Stability of the Spanish version of the five-item Francis Scale of Attitude toward Christianity.
Miranda-Tapia, Giskar Alonso; Cogollo, Zuleima; Herazo, Edwin; Campo-Arias, Adalberto
2010-12-01
The aim of this study was to establish test-retest reliability of a Spanish version of the Francis Scale of Attitude toward Christianity (Campo-Arias, Oviedo, & Cogollo, 2009) among adolescent students in Cartagena, Colombia. A group of ninth grade students from two public schools in Colombia (N = 157) completed the five-item scale. Cronbach's alphas were .74 and .76 in the first and second administrations, respectively. Both Pearson's rho and intra-class correlation coefficient were .69. A Spanish translation of the 5-item scale had consistent stability over four weeks.
Stability analysis of fuzzy parametric uncertain systems.
Bhiwani, R J; Patre, B M
2011-10-01
In this paper, the determination of stability margin, gain and phase margin aspects of fuzzy parametric uncertain systems are dealt. The stability analysis of uncertain linear systems with coefficients described by fuzzy functions is studied. A complexity reduced technique for determining the stability margin for FPUS is proposed. The method suggested is dependent on the order of the characteristic polynomial. In order to find the stability margin of interval polynomials of order less than 5, it is not always necessary to determine and check all four Kharitonov's polynomials. It has been shown that, for determining stability margin of FPUS of order five, four, and three we require only 3, 2, and 1 Kharitonov's polynomials respectively. Only for sixth and higher order polynomials, a complete set of Kharitonov's polynomials are needed to determine the stability margin. Thus for lower order systems, the calculations are reduced to a large extent. This idea has been extended to determine the stability margin of fuzzy interval polynomials. It is also shown that the gain and phase margin of FPUS can be determined analytically without using graphical techniques. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.
Stability of large scale interconnected dynamical systems
International Nuclear Information System (INIS)
Akpan, E.P.
1993-07-01
Large scale systems modelled by a system of ordinary differential equations are considered and necessary and sufficient conditions are obtained for the uniform asymptotic connective stability of the systems using the method of cone-valued Lyapunov functions. It is shown that this model significantly improves the existing models. (author). 9 refs
Meniscus Stability in Rotating Systems
Reichel, Yvonne; Dreyer, Michael
2013-11-01
In this study, the stability of free surfaces of fluid between two rotating coaxial, circular disks is examined. Radially mounted baffles are used to form menisci of equal size. To the center of the upper disk, a tube is connected in which a separate meniscus is formed. Assuming solid-body rotation and ignoring dynamic effects, it is observed that the free surfaces between the disks fail to remain stable once the rotation speed exceeds a critical value. In other words, Rayleigh-Taylor instability ensues when the capillary forces fail to balance centrifugal forces. Dimensionless critical rotation speeds are studied by means of the Surface Evolver via SE-FIT for varied number of baffles, the normalized distance between the disks, and the normalized central tube radius. Drop tower tests are performed to confirm some of the numerical results. The computation also reveals that there are different modes of instability as a function of the relevant parameters. This study was funded by the space agency of the German Aerospace Center with resources of the Federal Ministry of Economics and Technology on the basis of a resolution of the German Bundestag under grant number 50 RL 1320.
On Stabilization of Nonautonomous Nonlinear Systems
International Nuclear Information System (INIS)
Bogdanov, A. Yu.
2008-01-01
The procedures to obtain the sufficient conditions of asymptotic stability for nonlinear nonstationary continuous-time systems are discussed. We consider different types of the following general controlled system: x = X(t,x,u) = F(t,x)+B(t,x)u, x(t 0 ) = x 0 . (*) The basis of investigation is limiting equations, limiting Lyapunov functions, etc. The improved concept of observability of the pair of functional matrices is presented. By these results the problem of synthesis of asymptotically stable control nonlinear nonautonomous systems (with linear parts) involving the quadratic time-dependent Lyapunov functions is solved as well as stabilizing a given unstable system with nonlinear control law.
System and method for determining stability of a neural system
Curtis, Steven A. (Inventor)
2011-01-01
Disclosed are methods, systems, and computer-readable media for determining stability of a neural system. The method includes tracking a function world line of an N element neural system within at least one behavioral space, determining whether the tracking function world line is approaching a psychological stability surface, and implementing a quantitative solution that corrects instability if the tracked function world line is approaching the psychological stability surface.
Simplified Stability Criteria for Delayed Neutral Systems
Directory of Open Access Journals (Sweden)
Xinghua Zhang
2014-01-01
Full Text Available For a class of linear time-invariant neutral systems with neutral and discrete constant delays, several existing asymptotic stability criteria in the form of linear matrix inequalities (LMIs are simplified by using matrix analysis techniques. Compared with the original stability criteria, the simplified ones include fewer LMI variables, which can obviously reduce computational complexity. Simultaneously, it is theoretically shown that the simplified stability criteria and original ones are equivalent; that is, they have the same conservativeness. Finally, a numerical example is employed to verify the theoretic results investigated in this paper.
Directory of Open Access Journals (Sweden)
Fei Song
2014-01-01
Full Text Available This paper proposed a robust fault-tolerant control algorithm for satellite stabilization based on active disturbance rejection approach with artificial bee colony algorithm. The actuating mechanism of attitude control system consists of three working reaction flywheels and one spare reaction flywheel. The speed measurement of reaction flywheel is adopted for fault detection. If any reaction flywheel fault is detected, the corresponding fault flywheel is isolated and the spare reaction flywheel is activated to counteract the fault effect and ensure that the satellite is working safely and reliably. The active disturbance rejection approach is employed to design the controller, which handles input information with tracking differentiator, estimates system uncertainties with extended state observer, and generates control variables by state feedback and compensation. The designed active disturbance rejection controller is robust to both internal dynamics and external disturbances. The bandwidth parameter of extended state observer is optimized by the artificial bee colony algorithm so as to improve the performance of attitude control system. A series of simulation experiment results demonstrate the performance superiorities of the proposed robust fault-tolerant control algorithm.
The Paradox of Middle-Class Attitudes in China: Democracy, Social Stability, and Reform
Directory of Open Access Journals (Sweden)
Ying Miao
2016-01-01
Full Text Available This article explores the seemingly paradoxical attitudes of the Chinese middle class towards democracy, social stability, and reform. Using fieldwork data from Ningbo, this article shows that a group of objective, middle-class individuals can concurrently display high levels of support for democratic principles and low levels of participation in real-life socio-political events. Being generally confident in China’s social stability, these individuals have little to no desire for significant democratic reform, or indeed any reform that occurs outside the purview of the state, as it is considered destabilising. By highlighting the distinction between how these members of the middle class respond to generic democratic concepts, real-life socio-political affairs, and the idea of democratic reform, this article argues that the Chinese middle class are aware of what “should be,” what “could be,” and what “is,” which lends their socio-political attitudes a paradoxical appearance.
Functional stability of cerebral circulatory system
Moskalenko, Y. Y.
1980-01-01
The functional stability of the cerebral circulation system seems to be based on the active mechanisms and on those stemming from specific of the biophysical structure of the system under study. This latter parameter has some relevant criteria for its quantitative estimation. The data obtained suggest that the essential part of the mechanism for active responses of cerebral vessels which maintains the functional stability of this portion of the vascular system, consists of a neurogenic component involving central nervous structures localized, for instance, in the medulla oblongata.
Uruguay; Financial System Stability Assessment
International Monetary Fund
2013-01-01
The buffers built in the aftermath of Uruguay’s 2002 banking crisis have shielded the financial sector from the effects of the global financial turmoil. Growth has been robust and the outlook continues to be favorable. However, inflation persists but capital inflows have improved, and policy measures have been taken in response. Uruguay exhibits no obvious signs of near-term domestic macrofinancial vulnerability. The external risks to the economy and the financial system come from a fragile g...
Sensitivity of system stability to model structure
Hosack, G.R.; Li, H.W.; Rossignol, P.A.
2009-01-01
A community is stable, and resilient, if the levels of all community variables can return to the original steady state following a perturbation. The stability properties of a community depend on its structure, which is the network of direct effects (interactions) among the variables within the community. These direct effects form feedback cycles (loops) that determine community stability. Although feedback cycles have an intuitive interpretation, identifying how they form the feedback properties of a particular community can be intractable. Furthermore, determining the role that any specific direct effect plays in the stability of a system is even more daunting. Such information, however, would identify important direct effects for targeted experimental and management manipulation even in complex communities for which quantitative information is lacking. We therefore provide a method that determines the sensitivity of community stability to model structure, and identifies the relative role of particular direct effects, indirect effects, and feedback cycles in determining stability. Structural sensitivities summarize the degree to which each direct effect contributes to stabilizing feedback or destabilizing feedback or both. Structural sensitivities prove useful in identifying ecologically important feedback cycles within the community structure and for detecting direct effects that have strong, or weak, influences on community stability. The approach may guide the development of management intervention and research design. We demonstrate its value with two theoretical models and two empirical examples of different levels of complexity. ?? 2009 Elsevier B.V. All rights reserved.
Impacts of Wind Power on Power System Stability
Vittal, E.; Keane, A.; Slootweg, J.G.; Kling, W.L.; Ackermann, T.
2012-01-01
This chapter examines how wind power will impact the stability of power systems. It focuses on the three aspects of power system stability: voltage stability, rotor angle stability and frequency stability. It completes a detailed analysis as to how wind power in power systems will impact the
A semi-physical simulation platform of attitude determination and control system for satellite
Directory of Open Access Journals (Sweden)
Yuanjin Yu
2016-05-01
Full Text Available A semi-physical simulation platform for attitude determination and control system is proposed to verify the attitude estimator and controller on ground. A simulation target, a host PC, many attitude sensors, and actuators compose the simulation platform. The simulation target is composed of a central processing unit board with VxWorks operating system and many input/output boards connected via Compact Peripheral Component Interconnect bus. The executable programs in target are automatically generated from the simulation models in Simulink based on Real-Time Workshop of MATLAB. A three-axes gyroscope, a three-axes magnetometer, a sun sensor, a star tracer, three flywheels, and a Global Positioning System receiver are connected to the simulation target, which formulates the attitude control cycle of a satellite. The simulation models of the attitude determination and control system are described in detail. Finally, the semi-physical simulation platform is used to demonstrate the availability and rationality of the control scheme of a micro-satellite. Comparing the results between the numerical simulation in Simulink and the semi-physical simulation, the semi-physical simulation platform is available and the control scheme successfully achieves three-axes stabilization.
Public attitudes towards nuclear power and alternative energy systems
International Nuclear Information System (INIS)
1984-10-01
Phase I of this study analyzed attitudes and beliefs of respondents drawn from Metro-Manila. The second phase utilized a sample drawn from residents near a geothermal power plant site in Southern Philippines. Four dimensions of beliefs (psychological/environmental risks, technological benefits/development, economic benefits/implications and socio-political implications/benefits) were identified through factor analysis of belief items on nuclear energy and refined empirically to determine perceptions of respondents about all energy systems. Identification of the relationships between dimensions provided insight into the shared perceptions about each energy system held by the various groups of respondents. The overall attitude of the respondents towards energy systems (nuclear, solar, hydro, geothermal and oil) was determined using three attitude measures: Fishbein model, Osgood's semantic differential technique, and direct response to unfavorability/favorability scale. The belief dimensions were correlated with the attitude measures to determine the degree of contribution of each dimension to attitude. A comparative analysis was made to differentiate attitudes and beliefs held by the PRO and CON nuclear groups, and by the subsamples: university students, science teachers and barangay leaders of the Metro-Manila sample. Attitudes and beliefs relating to the demographic variables were also examined for the two samples. (author)
Power system stabilizer control for wind power to enhance power system stability
Domínguez García, José Luís; Gomis Bellmunt, Oriol; Bianchi, Fernando Daniel; Sumper, Andreas
2011-01-01
The paper presents a small signal stability analysis for power systems with wind farm interaction. Power systems have damping oscillation modes that can be excited by disturbance or fault in the grid. The power converters of the wind farms can be used to reduce these oscillations and make the system more stable. These ideas are explored to design a power system stabilized (PSS) for a network with conventional generators and a wind farm in order to increase the damping of the oscillation...
Tuning PID attitude stabilization of a quadrotor using particle swarm optimization (experimental
Directory of Open Access Journals (Sweden)
Khodja Mohammed Abdallah
2017-01-01
Full Text Available Proportional, Integral and Derivative (PID controllers are the most popular type of controller used in industrial applications because of their notable simplicity and effective implementation. However, manual tuning of these controllers is tedious and often leads to poor performance. The conventional Ziegler-Nichols (Z-N method of PID tuning was done experimentally enables easy identification stable PID parameters in a short time, but is accompanied by overshoot, high steady-state error, and large rise time. Therefore, in this study, the modern heuristics approach of Particle Swarm Optimization (PSO was employed to enhance the capabilities of the conventional Z-N technique. PSO with the constriction coefficient method experimentally demonstrated the ability to efficiently and effectively identify optimal PID controller parameters for attitude stabilization of a quadrotor.
Vision and dual IMU integrated attitude measurement system
Guo, Xiaoting; Sun, Changku; Wang, Peng; Lu, Huang
2018-01-01
To determination relative attitude between two space objects on a rocking base, an integrated system based on vision and dual IMU (inertial determination unit) is built up. The determination system fuses the attitude information of vision with the angular determinations of dual IMU by extended Kalman filter (EKF) to obtain the relative attitude. One IMU (master) is attached to the measured motion object and the other (slave) to the rocking base. As the determination output of inertial sensor is relative to inertial frame, thus angular rate of the master IMU includes not only motion of the measured object relative to inertial frame but also the rocking base relative to inertial frame, where the latter can be seen as redundant harmful movement information for relative attitude determination between the measured object and the rocking base. The slave IMU here assists to remove the motion information of rocking base relative to inertial frame from the master IMU. The proposed integrated attitude determination system is tested on practical experimental platform. And experiment results with superior precision and reliability show the feasibility and effectiveness of the proposed attitude determination system.
Morocco; Financial System Stability Assessment: Update
International Monetary Fund
2008-01-01
This paper presents an update to the Financial System Stability Assessment on Morocco. Major reforms have been achieved since the 2002 Financial Sector Assessment Program (FSAP) within a policy of actively promoting economic and financial sector opening. The 2002 FSAP recommendations have been largely implemented. Although the financial system is stable and considerably more robust than in the past, the liberalization of capital flows and increased exchange rate flexibility present challenges...
A Novel Attitude Determination System Aided by Polarization Sensor
Directory of Open Access Journals (Sweden)
Wei Zhi
2018-01-01
Full Text Available This paper aims to develop a novel attitude determination system aided by polarization sensor. An improved heading angle function is derived using the perpendicular relationship between directions of E-vector of linearly polarized light and solar vector in the atmospheric polarization distribution model. The Extended Kalman filter (EKF with quaternion differential equation as a dynamic model is applied to fuse the data from sensors. The covariance functions of filter process and measurement noises are deduced in detail. The indoor and outdoor tests are conducted to verify the validity and feasibility of proposed attitude determination system. The test results showed that polarization sensor is not affected by magnetic field, thus the proposed system can work properly in environments containing the magnetic interference. The results also showed that proposed system has higher measurement accuracy than common attitude determination system and can provide precise parameters for Unmanned Aerial Vehicle (UAV flight control. The main contribution of this paper is implementation of the EKF for incorporating the self-developed polarization sensor into the conventional attitude determination system. The real-world experiment with the quad-rotor proved that proposed system can work in a magnetic interference environment and provide sufficient accuracy in attitude determination for autonomous navigation of vehicle.
A Novel Attitude Determination System Aided by Polarization Sensor.
Zhi, Wei; Chu, Jinkui; Li, Jinshan; Wang, Yinlong
2018-01-09
This paper aims to develop a novel attitude determination system aided by polarization sensor. An improved heading angle function is derived using the perpendicular relationship between directions of E-vector of linearly polarized light and solar vector in the atmospheric polarization distribution model. The Extended Kalman filter (EKF) with quaternion differential equation as a dynamic model is applied to fuse the data from sensors. The covariance functions of filter process and measurement noises are deduced in detail. The indoor and outdoor tests are conducted to verify the validity and feasibility of proposed attitude determination system. The test results showed that polarization sensor is not affected by magnetic field, thus the proposed system can work properly in environments containing the magnetic interference. The results also showed that proposed system has higher measurement accuracy than common attitude determination system and can provide precise parameters for Unmanned Aerial Vehicle (UAV) flight control. The main contribution of this paper is implementation of the EKF for incorporating the self-developed polarization sensor into the conventional attitude determination system. The real-world experiment with the quad-rotor proved that proposed system can work in a magnetic interference environment and provide sufficient accuracy in attitude determination for autonomous navigation of vehicle.
Preliminary Test of Adaptive Neuro-Fuzzy Inference System Controller for Spacecraft Attitude Control
Directory of Open Access Journals (Sweden)
Sung-Woo Kim
2012-12-01
Full Text Available The problem of spacecraft attitude control is solved using an adaptive neuro-fuzzy inference system (ANFIS. An ANFIS produces a control signal for one of the three axes of a spacecraft’s body frame, so in total three ANFISs are constructed for 3-axis attitude control. The fuzzy inference system of the ANFIS is initialized using a subtractive clustering method. The ANFIS is trained by a hybrid learning algorithm using the data obtained from attitude control simulations using state-dependent Riccati equation controller. The training data set for each axis is composed of state errors for 3 axes (roll, pitch, and yaw and a control signal for one of the 3 axes. The stability region of the ANFIS controller is estimated numerically based on Lyapunov stability theory using a numerical method to calculate Jacobian matrix. To measure the performance of the ANFIS controller, root mean square error and correlation factor are used as performance indicators. The performance is tested on two ANFIS controllers trained in different conditions. The test results show that the performance indicators are proper in the sense that the ANFIS controller with the larger stability region provides better performance according to the performance indicators.
Siswanto, Agus; Gunadin, Indar Chaerah; Said, Sri Mawar; Suyuti, Ansar
2018-03-01
The purpose of this research is to improve the stability of interconnection of South Sulawesi system caused by penetration new wind turbine in Sidrap area on bus 2 and in Jeniponto area on bus 34. The method used in this research was via software Power System analysis Toolbox (PSAT) under MATLAB. In this research, there are two problems that are evaluated, the stability of the system before and after penetration wind turbine into the system South Sulawesi system. From the simulation result shows that penetration of wind turbine on bus 2 Sidrap, bus 37 Jeniponto give effect oscillation on the system. The oscillation was damped by installation of Power System Stabilizer (PSS) on bus 29 area Sungguminasa, that South Sulawesi system stable according to normal condition.
Attitude Control System Design for the Solar Dynamics Observatory
Starin, Scott R.; Bourkland, Kristin L.; Kuo-Chia, Liu; Mason, Paul A. C.; Vess, Melissa F.; Andrews, Stephen F.; Morgenstern, Wendy M.
2005-01-01
The Solar Dynamics Observatory mission, part of the Living With a Star program, will place a geosynchronous satellite in orbit to observe the Sun and relay data to a dedicated ground station at all times. SDO remains Sun- pointing throughout most of its mission for the instruments to take measurements of the Sun. The SDO attitude control system is a single-fault tolerant design. Its fully redundant attitude sensor complement includes 16 coarse Sun sensors, a digital Sun sensor, 3 two-axis inertial reference units, 2 star trackers, and 4 guide telescopes. Attitude actuation is performed using 4 reaction wheels and 8 thrusters, and a single main engine nominally provides velocity-change thrust. The attitude control software has five nominal control modes-3 wheel-based modes and 2 thruster-based modes. A wheel-based Safehold running in the attitude control electronics box improves the robustness of the system as a whole. All six modes are designed on the same basic proportional-integral-derivative attitude error structure, with more robust modes setting their integral gains to zero. The paper details the mode designs and their uses.
A Dynamic Attitude Measurement System Based on LINS
Directory of Open Access Journals (Sweden)
Hanzhou Li
2014-08-01
Full Text Available A dynamic attitude measurement system (DAMS is developed based on a laser inertial navigation system (LINS. Three factors of the dynamic attitude measurement error using LINS are analyzed: dynamic error, time synchronization and phase lag. An optimal coning errors compensation algorithm is used to reduce coning errors, and two-axis wobbling verification experiments are presented in the paper. The tests indicate that the attitude accuracy is improved 2-fold by the algorithm. In order to decrease coning errors further, the attitude updating frequency is improved from 200 Hz to 2000 Hz. At the same time, a novel finite impulse response (FIR filter with three notches is designed to filter the dither frequency of the ring laser gyro (RLG. The comparison tests suggest that the new filter is five times more effective than the old one. The paper indicates that phase-frequency characteristics of FIR filter and first-order holder of navigation computer constitute the main sources of phase lag in LINS. A formula to calculate the LINS attitude phase lag is introduced in the paper. The expressions of dynamic attitude errors induced by phase lag are derived. The paper proposes a novel synchronization mechanism that is able to simultaneously solve the problems of dynamic test synchronization and phase compensation. A single-axis turntable and a laser interferometer are applied to verify the synchronization mechanism. The experiments results show that the theoretically calculated values of phase lag and attitude error induced by phase lag can both match perfectly with testing data. The block diagram of DAMS and physical photos are presented in the paper. The final experiments demonstrate that the real-time attitude measurement accuracy of DAMS can reach up to 20″ (1σ and the synchronization error is less than 0.2 ms on the condition of three axes wobbling for 10 min.
A Dynamic Attitude Measurement System Based on LINS
Li, Hanzhou; Pan, Quan; Wang, Xiaoxu; Zhang, Juanni; Li, Jiang; Jiang, Xiangjun
2014-01-01
A dynamic attitude measurement system (DAMS) is developed based on a laser inertial navigation system (LINS). Three factors of the dynamic attitude measurement error using LINS are analyzed: dynamic error, time synchronization and phase lag. An optimal coning errors compensation algorithm is used to reduce coning errors, and two-axis wobbling verification experiments are presented in the paper. The tests indicate that the attitude accuracy is improved 2-fold by the algorithm. In order to decrease coning errors further, the attitude updating frequency is improved from 200 Hz to 2000 Hz. At the same time, a novel finite impulse response (FIR) filter with three notches is designed to filter the dither frequency of the ring laser gyro (RLG). The comparison tests suggest that the new filter is five times more effective than the old one. The paper indicates that phase-frequency characteristics of FIR filter and first-order holder of navigation computer constitute the main sources of phase lag in LINS. A formula to calculate the LINS attitude phase lag is introduced in the paper. The expressions of dynamic attitude errors induced by phase lag are derived. The paper proposes a novel synchronization mechanism that is able to simultaneously solve the problems of dynamic test synchronization and phase compensation. A single-axis turntable and a laser interferometer are applied to verify the synchronization mechanism. The experiments results show that the theoretically calculated values of phase lag and attitude error induced by phase lag can both match perfectly with testing data. The block diagram of DAMS and physical photos are presented in the paper. The final experiments demonstrate that the real-time attitude measurement accuracy of DAMS can reach up to 20″ (1σ) and the synchronization error is less than 0.2 ms on the condition of three axes wobbling for 10 min. PMID:25177802
Power stability methods for parallel systems
International Nuclear Information System (INIS)
Wallach, Y.
1988-01-01
Parallel-Processing Systems are already commercially available. This paper shows that if one of them - the Alternating Sequential Parallel, or ASP system - is applied to network stability calculations it will lead to a higher speed of solution. The ASP system is first described and is then shown to be cheaper, more reliable and available than other parallel systems. Also, no deadlock need be feared and the speedup is normally very high. A number of ASP systems were already assembled (the SMS systems, Topps, DIRMU etc.). At present, an IBM Local Area Network is being modified so that it too can work in the ASP mode. Existing ASP systems were programmed in Fortran or assembly language. Since newer systems (e.g. DIRMU) are programmed in Modula-2, this language can be used. Stability analysis is based on solving nonlinear differential and algebraic equations. The algorithm for solving the nonlinear differential equations on ASP, is described and programmed in Modula-2. The speedup is computed and is shown to be almost optimal
System Design Description PFP Thermal Stabilization
International Nuclear Information System (INIS)
RISENMAY, H.R.
2000-01-01
The purpose of this document is to provide a system design description (SDD) and design basis for the Plutonium Finishing Plant (PFP) Thermal Stabilization project. The chief objective of the SDD is to document the Structures, Systems, and Components (SSCs) that establish and maintain the facility Safety Envelope necessary for normal safe operation of the facility; as identified in the FSAR, the OSRs, and Safety Assessment Documents (SADs). This safety equipment documentation should satisfy guidelines for the SDD given in WHC-SD-CP-TI-18 1, Criteria for Identification and Control of Equipment Necessary for Preservation of the Safety Envelope and Safe Operation of PFP. The basis for operational, alarm response, maintenance, and surveillance procedures are also identified and justified in this document. This document and its appendices address the following elements of the PFP Thermal Stabilization project: Functional and design requirements; Design description; Safety Envelope Analysis; Safety Equipment Class; and Operational, maintenance and surveillance procedures
Microprocessor system for temperature regulation and stabilization
International Nuclear Information System (INIS)
Nguyen Nhi Dien; Rodionov, K.G.
1989-01-01
Microprocessor based system for temperature regulation and stabilization of an operation external object is described. The system has the direct current amplifier working according to modulator-demodulator principle. The overal gain is 100, 1000, 2000. The maximum output signal is ±10 V. The power amplifier is a thyristor one and its line voltage is 220 V, 50 Hz. The output power is 0-2 kVA. The microcontroller has a remote display terminal. Data input is 8 and data output is one. Input and output voltage is ±(0-10) V. The preselection time for stabilization is within 1 s - 18 h. The program algorithm is given. 5 figs.; 1 tab
Swedish Homeowners' Attitude towards Water-Based Heating Systems
Energy Technology Data Exchange (ETDEWEB)
Gustavsson, L; Mahapatra, K [Mid Sweden Univ., Ecotechnology, SE-831 25 Oestersund (Sweden)
2008-10-15
In 2004 and 2007, we conducted questionnaire surveys of 1,500 randomly selected Swedish homeowners of detached houses to understand their attitude towards adopting an innovative heating system (IHS). The results showed that there was no substantial change in homeowners' attitude towards IHSs. More than 80% of the respondents did not intend to install a new heating system. Economic aspects and functional reliability were the most important factors in the respondents' choice of heating system while environmental factors were of less importance. Installers were the most frequently consulted source of information on heating systems. Respondents perceived the relative advantage of pellet boilers over oil or electricity-based heating systems, but bedrock heat pump system was ranked higher than pellet heating system in every aspect except for investment cost. Pellet heating system has advantages with respect to investment cost. District heating system was considered as most functionally reliable and automatic. Keywords: Heat sector, socio-economic aspects, market implementation
Treder, Alfred J.; Meldahl, Keith L.
The recorded histories of Shuttle/Orbiter attitude and Inertial Upper Stage (IUS) attitude have been analyzed for all joint flights of the IUS in the Orbiter. This database was studied to determine the behavior of relative alignment between the IUS and Shuttle navigation systems. It is found that the overall accuracy of physical alignment has a Shuttle Orbiter bias component less than 5 arcmin/axis and a short-term stability upper bound of 0.5 arcmin/axis, both at 1 sigma. Summaries of the experienced physical and inertial alginment offsets are shown in this paper, together with alignment variation data, illustrated with some flight histories. Also included is a table of candidate values for some error source groups in an Orbiter/IUS attitude errror model. Experience indicates that the Shuttle is much more accurate and stable as an orbiting launch platform than has so far been advertised. This information will be valuable for future Shuttle payloads, especially those (such as the Aeroassisted Flight Experiment) which carry their own inertial navigation systems, and which could update or initialize their attitude determination systems using the Shuttle as the reference.
Lewis, Christopher Alan; Cruise, Sharon Mary; McGuckin, Conor
2005-04-01
This study evaluated the test-retest reliability of the Francis Scale of Attitude toward Christianity short-form. 39 Northern Irish undergraduate students completed the measure on two occasions separated by one week. Stability across the two administrations was high, r = .92, and there was no significant change between Time 1(M = 25.2, SD = 5.4) and Time 2 (M = 25.7, SD = 6.2). These data support the short-term test-retest reliability of the Francis Scale of Attitude toward Christianity short-form.
Attitudes of Brazilian citizens towards pig production systems
DEFF Research Database (Denmark)
de Barcellos, Marcia Dutra; Kügler, Jens Oliver; Saab, Maria Stella Melo
to identify Brazilian citizen clusters. Respondents' socio-demographic profile, attitudes towards issues that are expected to influence the way how people evaluate pig meat production systems, and consumption frequency of various pork products were used as background information for profiling. Three clusters...... and consumption behaviour was found to be weak. As it was suggested for Europe (Krystallis et al., 2009), what people think in their role as citizens related to pig production does not appear to significantly influence their pork consumption choices.......The objective of this study is to map Brazilian citizen attitudes towards pig meat production systems and to investigate whether these attitudes associate with pork and pork product consumption. A conjoint experiment was carried out with empirical data collected from 475 respondents interviewed...
Attitudes of European citizens towards pig production systems
DEFF Research Database (Denmark)
Krystallis, Athanasios; de Barcellos, Marcia Dutra; Kügler, Jens Oliver
2009-01-01
The objective of the study is to map citizen attitudes towards pigmeat production systems, and to investigate whether these attitudes associate with pork and pork product consumption. A conjoint experimentwas carried out with empirical data collected from 1931 individuals in four European countries...... pork with specific fat content, and finally the preferred quality characteristics of the pork end-product. The results of the conjoint analysis were used for a subsequent cluster analysis in order to identify European citizen clusters. Respondents' socio-demographic profile, attitudes towards issues...... that are expected to influence the way people evaluate pig meat production systems, and consumption frequency of various pork products are used as background information to identify segment profiles. Pork appears to play a substantial role as a part of the diet for most respondents in the four countries...
Nonlinear physical systems spectral analysis, stability and bifurcations
Kirillov, Oleg N
2013-01-01
Bringing together 18 chapters written by leading experts in dynamical systems, operator theory, partial differential equations, and solid and fluid mechanics, this book presents state-of-the-art approaches to a wide spectrum of new and challenging stability problems.Nonlinear Physical Systems: Spectral Analysis, Stability and Bifurcations focuses on problems of spectral analysis, stability and bifurcations arising in the nonlinear partial differential equations of modern physics. Bifurcations and stability of solitary waves, geometrical optics stability analysis in hydro- and magnetohydrodynam
Earth Observing System (EOS) Aqua Launch and Early Mission Attitude Support Experiences
Tracewell, D.; Glickman, J.; Hashmall, J.; Natanson, G.; Sedlak, J.
2003-01-01
The Earth Observing System (EOS) Aqua satellite was successfully launched on May 4,2002. Aqua is the second in the series of EOS satellites. EOS is part of NASA s Earth Science Enterprise Program, whose goals are to advance the scientific understanding of the Earth system. Aqua is a three-axis stabilized, Earth-pointing spacecraft in a nearly circular, sun-synchronous orbit at an altitude of 705 km. The Goddard Space Flight Center (GSFC) Flight Dynamics attitude team supported all phases of the launch and early mission. This paper presents the main results and lessons learned during this period, including: real-time attitude mode transition support, sensor calibration, onboard computer attitude validation, response to spacecraft emergencies, postlaunch attitude analyses, and anomaly resolution. In particular, Flight Dynamics support proved to be invaluable for successful Earth acquisition, fine-point mode transition, and recognition and correction of several anomalies, including support for the resolution of problems observed with the MODIS instrument.
GOLD NETTING TO STRENGTHEN FINANCIAL SYSTEM STABILITY
Directory of Open Access Journals (Sweden)
Ahamed Kameel Mydin Meera
2017-08-01
Full Text Available Economic and financial crises seem to occur with increased frequency. Indeed now most countries, including several advanced economies like the US, Europe and Japan, are in serious economic recession. Employment and business opportunities have been much dampened. Inflation seems to be soaring globally and nations are witnessing widening gaps in income and wealth distribution. Many of these advanced economies are also facing shrinking population sizes that translate into aging problems and labor shortages. On top of those, there are environmental issues, including global warming. All these, in turn, have caused regional and global political conflicts and turmoil. The Arab Spring and the sovereign debt problems faced by some European countries like Greece are examples of this. Sustainability of economics and environment is thus of paramount concern of today. This paper considers those problems and suggests Interest-free Gold-based Electronic Netting System (IGENS as an effective way of injecting liquidity into the economy, practically free, that can spur business and employment while bringing about structural stability, inflation checked with both economic and environmental sustainability. Netting or muqassah is a transaction allowed in shari’ah and is practiced worldwide in different forms. Examples include the highly successful WIR Bank of Switzerland, various Local Exchange Trading Schemes (LETS and Bilateral and Multilateral Payment Arrangements between central banks. Keywords: Global crisis, Payment system, Gold, Netting, Muqassah, Liquidity, Sustainability, Financial system stability JEL Classification: E40, E42, E51
Student Attitudes toward Information Systems Graduate Program Design and Delivery
Thouin, Mark F.; Hefley, William E.; Raghunathan, Srinivasan
2018-01-01
This study examines student preferences regarding graduate management information systems (MIS) education. One hundred and eighty four graduate students responded to a survey exploring student attitudes towards degree program content, delivery format, and peer group interaction. Study results indicate that students prefer a program with an even…
Vibrations and stability of complex beam systems
Stojanović, Vladimir
2015-01-01
This book reports on solved problems concerning vibrations and stability of complex beam systems. The complexity of a system is considered from two points of view: the complexity originating from the nature of the structure, in the case of two or more elastically connected beams; and the complexity derived from the dynamic behavior of the system, in the case of a damaged single beam, resulting from the harm done to its simple structure. Furthermore, the book describes the analytical derivation of equations of two or more elastically connected beams, using four different theories (Euler, Rayleigh, Timoshenko and Reddy-Bickford). It also reports on a new, improved p-version of the finite element method for geometrically nonlinear vibrations. The new method provides more accurate approximations of solutions, while also allowing us to analyze geometrically nonlinear vibrations. The book describes the appearance of longitudinal vibrations of damaged clamped-clamped beams as a result of discontinuity (damage). It...
Stability and response bounds of non-conservative linear systems
DEFF Research Database (Denmark)
Pommer, Christian
2003-01-01
For a linear system of second order differential equations the stability is studied by Lyapunov's direct method. The Lyapunov matrix equation is solved and a sufficient condition for stability is expressed by the system matrices. For a system which satisfies the condition for stability the Lyapunov...
Low-cost attitude determination system using an extended Kalman filter (EKF) algorithm
Esteves, Fernando M.; Nehmetallah, Georges; Abot, Jandro L.
2016-05-01
Attitude determination is one of the most important subsystems in spacecraft, satellite, or scientific balloon mission s, since it can be combined with actuators to provide rate stabilization and pointing accuracy for payloads. In this paper, a low-cost attitude determination system with a precision in the order of arc-seconds that uses low-cost commercial sensors is presented including a set of uncorrelated MEMS gyroscopes, two clinometers, and a magnetometer in a hierarchical manner. The faster and less precise sensors are updated by the slower, but more precise ones through an Extended Kalman Filter (EKF)-based data fusion algorithm. A revision of the EKF algorithm fundamentals and its implementation to the current application, are presented along with an analysis of sensors noise. Finally, the results from the data fusion algorithm implementation are discussed in detail.
Attitude angular measurement system based on MEMS accelerometer
Luo, Lei
2014-09-01
For the purpose of monitoring the attitude of aircraft, an angular measurement system using a MEMS heat convection accelerometer is presented in this study. A double layers conditioning circuit that center around the single chip processor is designed and built. Professional display software with the RS232 standard is used to communicate between the sensor and the computer. Calibration experiments were carried out to characterize the measuring system with the range of - 90°to +90°. The curves keep good linearity with the practical angle. The maximum deviation occurs at the 90°where the value is 2.8°.The maximum error is 1.6% and the repeatability is measured to be 2.1%. Experiments proved that the developed measurement system is capable of measuring attitude angle.
System specification for the plutonium stabilization and packaging system
International Nuclear Information System (INIS)
1996-01-01
This document describes functional design requirements for the Plutonium Stabilization and Packaging System (Pu SPS), as required by DOE contract DE-AC03-96SF20948 through contract modification 9 for equipment in Building 707 at Rocky Flats Environmental Technology Site (RFETS)
Bank, Banking System, Macroprudential Supervision, Stability of Banking System
Directory of Open Access Journals (Sweden)
Tetiana Vasilyeva
2016-10-01
Full Text Available Intensification of financial development during last decade causes transformation of banking sector functioning. In particular, among the most significant changes over this period should be noted the next ones: convergence of financial market segments and appearance of cross-sector financial products, an increase of prevailing of financial sector in comparison with real economy and level of their interdependent, an intensification of crisis processes in financial and especially banking sector and a significant increase of the scale of the crisis consequences etc. thus, in such vulnerable conditions it is become very urgent to identify the relevant factors that can influence on the stability of banking sector, because its maintenance seems to be one of the most important preconditions of the stability of the national economy as a whole. Purpose of the article is to analyze key performance indicators of the Ukrainian banking system, clarify its main problems, identify relevant factors of the stability of the Ukrainian banking system and the character of their influence on the dependent variable. Realization of the mentioned above tasks was ensured by regression analysis (OLS regression. Analysis of key indicators that characterize current situation in the Ukrainian banking system found out the existence of numerous endogenous and exogenous problems, which, in turn, cause worsening most of analyzed indicators during 2013-2015. Unfavorable situation in Ukrainian banking system determined the necessity of identification of relevant factors of banking system stability to avoid transmission of financial shocks. According to the results of regression analysis on the stability of banking sector positively influence such factors as increase of interest margin to gross income ratio, reserves to assets ratio, number of branches, ratio of non-performing loans to total loans. Meanwhile, negative impact on stability of banking system has an increase of liquid
Car drivers' perceptions of electronic stability control (ESC) systems.
Vadeby, Anna; Wiklund, Mats; Forward, Sonja
2011-05-01
As a way to reduce the number of car crashes different in-car safety devices are being introduced. In this paper one such application is being investigated, namely the electronic stability control system (ESC). The study used a survey method, including 2000 private car drivers (1000 driving a car with ESC and 1000 driving a car without ESC). The main objective was to investigate the effect of ESC on driver behaviour. Results show that drivers report that they drive even more carelessly when they believe that they have ESC, than when they do not. Men are more risk prone than women and young drivers more than older drivers. Using the theory of planned behaviour the results show that attitude, subjective norm and perceived control explain between 62% and 67% of driver's variation of intentions to take risks. When descriptive norm was added to the model a small but statistically significant increase was found. The study also shows that more than 35% erroneously believe that their car is equipped with an ESC system. These findings may suggest that driver behaviour could reduce the positive effect ESC has on accidents. It also shows that drivers who purchase a new car are not well informed about what kind of safety devices the car is equipped with. These findings highlight the need for more targeted information to drivers. Copyright © 2010 Elsevier Ltd. All rights reserved.
Stability analysis of distributed order fractional chen system.
Aminikhah, H; Refahi Sheikhani, A; Rezazadeh, H
2013-01-01
We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results.
Stability Analysis of Distributed Order Fractional Chen System
Aminikhah, H.; Refahi Sheikhani, A.; Rezazadeh, H.
2013-01-01
We first investigate sufficient and necessary conditions of stability of nonlinear distributed order fractional system and then we generalize the integer-order Chen system into the distributed order fractional domain. Based on the asymptotic stability theory of nonlinear distributed order fractional systems, the stability of distributed order fractional Chen system is discussed. In addition, we have found that chaos exists in the double fractional order Chen system. Numerical solutions are used to verify the analytical results. PMID:24489508
Stabilization of Teleoperation Systems with Communication Delays: An IMC Approach
Directory of Open Access Journals (Sweden)
Yuling Li
2018-01-01
Full Text Available The presence of time delays in communication introduces a limitation to the stability of bilateral teleoperation systems. This paper considers internal model control (IMC design of linear teleoperation system with time delays, and the stability of the closed-loop system is analyzed. It is shown that the stability is guaranteed delay-independently. The passivity assumption for external forces is removed for the proposed design of teleoperation systems. The behavior of the resulting teleoperation system is illustrated by simulations.
Integrated Power and Attitude Control System (IPACS) technology developments
Eisenhaure, David B.; Bechtel, Robert; Hockney, Richard; Oglevie, Ron; Olszewski, Mitch
1990-01-01
Integrated Power and Attitude Control System (IPACS) studies performed over a decade ago established the feasibility of storing electrical energy in flywheels and utilizing the resulting angular momentum for spacecraft attitude control. Such a system has been shown to have numerous attractive features relative to more contemporary technology, and is appropriate to many applications (including high-performance slewing actuators). Technology advances over the last two decades in composite rotors, motor/generator/electronics, and magnetic bearings are found to support the use of IPACS for increasingly sophisticated applications. It is concluded that the concept offers potential performance advantages as well as savings in mass and life-cycle cost. Viewgraphs and discussion on IPACS are included.
Changing Student Attitudes using Andes, An Intelligent Homework System
van de Sande, Brett; Vanlehn, Kurt; Treacy, Don; Shelby, Bob; Wintersgill, Mary
2007-03-01
The size of introductory physics lectures often inhibits personal homework assistance and timely corrective feedback. Andes, an intelligent homework help system designed for two semesters of introductory physics, can fill this need by encouraging students to use sound problem solving techniques and providing immediate feedback on each step of a solution. On request, Andes provides principles-based hints based on previous student actions. A multi-year study at the U.S. Naval Academy demonstrates that students using Andes perform better than students working the same problems as graded pencil and paper homeworks. In addition, student attitude surveys show that Andes is preferred over other homework systems. These findings have implications for student attitudes toward, and mastery of, physics. See http://www.andes.pitt.edu for more information.
Attitude control system for a lightweight flapping wing MAV.
Tijmons, Sjoerd; Karásek, Matěj; de Croon, G C H E
2018-03-14
Robust attitude control is an essential aspect of research on autonomous flight of flapping wing Micro Air Vehicles. The mechanical solutions by which the necessary control moments are realised come at the price of extra weight and possible loss of aerodynamic efficiency. Stable flight of these vehicles has been shown by several designs using a conventional tail, but also by tailless designs that use active control of the wings. In this study a control mechanism is proposed that provides active control over the wings. The mechanism improves vehicle stability and agility by generation of control moments for roll, pitch and yaw. Its effectiveness is demonstrated by static measurements around all the three axes. Flight test results confirm that the attitude of the test vehicle, including a tail, can be successfully controlled in slow forward flight conditions. Furthermore, the flight envelope is extended with robust hovering and the ability to reverse the flight direction using a small turn space. This capability is very important for autonomous flight capabilities such as obstacle avoidance. Finally, it is demonstrated that the proposed control mechanism allows for tailless hovering flight. © 2018 IOP Publishing Ltd.
Stability of impulsive systems driven by renewal processes
Guerreiro Tome Antunes, D.J.; Hespanha, J.P.; Silvestre, C.J.
2009-01-01
Necessary and sufficient conditions are provided for stochastic stability and mean exponential stability of impulsive systems with jumps triggered by a renewal process, that is, the intervals between jumps are independent and identically distributed. The conditions for stochastic stability can be
Polynomial stabilization of some dissipative hyperbolic systems
Czech Academy of Sciences Publication Activity Database
Ammari, K.; Feireisl, Eduard; Nicaise, S.
2014-01-01
Roč. 34, č. 11 (2014), s. 4371-4388 ISSN 1078-0947 R&D Projects: GA ČR GA201/09/0917 Institutional support: RVO:67985840 Keywords : exponential stability * polynomial stability * observability inequality Subject RIV: BA - General Mathematics Impact factor: 0.826, year: 2014 http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=9924
Power system stability modelling, analysis and control
Sallam, Abdelhay A
2015-01-01
This book provides a comprehensive treatment of the subject from both a physical and mathematical perspective and covers a range of topics including modelling, computation of load flow in the transmission grid, stability analysis under both steady-state and disturbed conditions, and appropriate controls to enhance stability.
Stability of neutral type descriptor system with mixed delays
International Nuclear Information System (INIS)
Li Hong; Li Houbiao; Zhong Shouming
2007-01-01
In this paper, the stability problems of general neutral type descriptor system with mixed delays are considered. Some new delay-independent stability and robust stability criteria, which are simpler and less conservative than existing results, are derived in terms of the stability of a new operator I and linear matrix inequalities (LMIs). Therefore, criteria can be easily checked by utilizing the Matlab LMI toolbox
System design document for the plutonium stabilization and packaging system
International Nuclear Information System (INIS)
1996-01-01
The objective of this system is to stabilize and package plutonium metals and oxides of greater than 50% wt, as well as other selected isotopes, in accordance with the requirements for DOE standards for safe storage of these materials for 50 years. This document describes the highest level design information and user characteristics from an operational perspective. It provides guidance for developing procurement and installation specifications, interface requirements, and test plans
System design document for the plutonium stabilization and packaging system
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-05-08
The objective of this system is to stabilize and package plutonium metals and oxides of greater than 50% wt, as well as other selected isotopes, in accordance with the requirements for DOE standards for safe storage of these materials for 50 years. This document describes the highest level design information and user characteristics from an operational perspective. It provides guidance for developing procurement and installation specifications, interface requirements, and test plans.
Stability of miniature electromagnetic tracking systems
International Nuclear Information System (INIS)
Schicho, Kurt; Figl, Michael; Donat, Markus; Birkfellner, Wolfgang; Seemann, Rudolf; Wagner, Arne; Bergmann, Helmar; Ewers, Rolf
2005-01-01
This study aims at a comparative evaluation of two recently introduced electromagnetic tracking systems under reproducible simulated operating-room (OR) conditions: the recently launched Medtronic StealthStation TM Treon-EM TM and the NDI Aurora TM . We investigate if and to what extent these systems provide improved performance and stability in the presence of surgical instruments as possible sources of distortions compared with earlier reports on electromagnetic tracking technology. To investigate possible distortions under pseudo-realistic OR conditions, a large Langenbeck hook, a dental drill with its handle and an ultrasonic (US) scanhead are fixed on a special measurement rack at variable distances from the navigation sensor. The position measurements made by the Treon-EM TM were least affected by the presence of the instruments. The lengths of the mean deviation vectors were 0.21 mm for the Langenbeck hook, 0.23 mm for the drill with handle and 0.56 mm for the US scanhead. The Aurora TM was influenced by the three sources of distortion to a higher degree. A mean deviation vector of 1.44 mm length was observed in the vicinity of the Langenbeck hook, 0.53 mm length with the drill and 2.37 mm due to the US scanhead. The maximum of the root mean squared error (RMSE) for all coordinates in the presence of the Langenbeck hook was 0.3 mm for the Treon TM and 2.1 mm for the Aurora TM ; the drill caused a maximum RMSE of 0.2 mm with the Treon TM and 1.2 mm with the Aurora TM . In the presence of the US scanhead, the maximum RMSE was 1.4 mm for the Treon TM and 5.1 mm for the Aurora TM . The new generation of electromagnetic tracking systems has significantly improved compared to common systems that were available in the middle of the 1990s and has reached a high level of technical development. We conclude that, in general, both systems are suitable for routine clinical application
A Gimbal-Stabilized Compact Hyperspectral Imaging System, Phase II
National Aeronautics and Space Administration — The Gimbal-stabilized Compact Hyperspectral Imaging System (GCHIS) fully integrates multi-sensor spectral imaging, stereovision, GPS and inertial measurement,...
MATHEMATICAL MODEL OF TRIAXIAL MULTIMODE ATTITUDE AND HEADING REFERENCE SYSTEM
Directory of Open Access Journals (Sweden)
Olha Sushchenko
2017-07-01
Full Text Available Purpose: The paper deals with the mathematical description of the gimballed attitude and heading reference systems, which can be applied in design of strategic precision navigation systems. The main goal is to created mathematical description taking into consideration the necessity to use different navigations operating modes of this class of navigation systems. To provide the high accuracy the indirect control is used when the position of the gimballed platform is controlled by signals of gyroscopic devices, which are corrected using accelerometer’s signals. Methods: To solve the given problem the methods of the classical theoretical mechanics, gyro theory, and inertial navigation are used. Results: The full mathematical model of the gimballed attitude and heading reference system is derived including descriptions of different operating modes. The mathematical models of the system Expressions for control and correction moments in the different modes are represented. The simulation results are given. Conclusions: The represented results prove efficiency of the proposed models. Developed mathematical models can be useful for design of navigation systems of the wide class of moving vehicles.
Model predictive control of hybrid systems : stability and robustness
Lazar, M.
2006-01-01
This thesis considers the stabilization and the robust stabilization of certain classes of hybrid systems using model predictive control. Hybrid systems represent a broad class of dynamical systems in which discrete behavior (usually described by a finite state machine) and continuous behavior
Directory of Open Access Journals (Sweden)
Wang Bing
2013-02-01
Full Text Available GPS-based attitude system is an important research field, since it is a valuable technique for the attitude determination of platforms. There exist two classes approaches for attitude determination using the GPS. The one determines attitude via baseline estimates in two frames, the other one solves for attitude by incorporating the attitude parameters directly into the GPS measurements. However, comparisons between these two classes approaches have been unexplored. First of all, two algorithms are introduced in detail which on behalf of these two kinds of approaches. Then we present numerical simulations demonstrating the performance of our algorithms and provide a comparison evaluating.
Factor structure and gender stability in the multidimensional condom attitudes scale.
Starosta, Amy J; Berghoff, Christopher R; Earleywine, Mitch
2015-06-01
Sexually transmitted infections continue to trouble the United States and can be attenuated through increased condom use. Attitudes about condoms are an important multidimensional factor that can affect sexual health choices and have been successfully measured using the Multidimensional Condom Attitudes Scale (MCAS). Such attitudes have the potential to vary between men and women, yet little work has been undertaken to identify if the MCAS accurately captures attitudes without being influenced by underlying gender biases. We examined the factor structure and gender invariance on the MCAS using confirmatory factor analysis and item response theory, within-subscale differential item functioning analyses. More than 770 participants provided data via the Internet. Results of differential item functioning analyses identified three items as differentially functioning between the genders, and removal of these items is recommended. Findings confirmed the previously hypothesized multidimensional nature of condom attitudes and the five-factor structure of the MCAS even after the removal of the three problematic items. In general, comparisons across genders using the MCAS seem reasonable from a methodological standpoint. Results are discussed in terms of improving sexual health research and interventions. © The Author(s) 2014.
The influence of risk awareness on attitudes towards energy systems
International Nuclear Information System (INIS)
Schmidt, F.; Sachs, S.
1984-01-01
The implementation of energy systems needs acceptance by people. Acceptance is influenced by various factors, one of which is the attitude towards energy questions. Attitudes and behavioural intentions can be understood from inference and evaluation processes. Ajzen and Fishbein described this by a model which combines in an additive manner attitudes towards acts and norms to predict behavioural intentions and behaviour. The Fishbein model was used as a base for the simulation model REASON which simulates behavioural intentions. The model needs as input knowledge about the part of the world to be evaluated and values and criteria used to judge the conclusions of the inference process. The program provides as output the scores of the various criteria and accumulated evaluations of the options. In addition, if desired, a protocol of the inference process is available. REASON was applied to various energy-related questions. A detailed concept was developed for the selection of a heating system for a new home. The concept was used to simulate the behavioural intentions of home owners towards the installation of a heating system. Competing heating systems were evaluated by cost, safety, comfort, and environmental criteria as well as expectations of other persons or groups. The results of the simulations were partly compared with empirical data. Sensitivity studies were performed which show the influence of risk criteria (for instance safety of supply, influences on the environment, exploitation of resources, time perspective) combined with other criteria. Time dependent studies show the changing of intentions as a result of changing evaluation criteria and changes in knowledge about the environment. (author)
Finite-Time Stability and Stabilization of Nonlinear Quadratic Systems with Jumps
Directory of Open Access Journals (Sweden)
Minsong Zhang
2014-01-01
Full Text Available This paper investigates the problems of finite-time stability and finite-time stabilization for nonlinear quadratic systems with jumps. The jump time sequences here are assumed to satisfy some given constraints. Based on Lyapunov function and a particular presentation of the quadratic terms, sufficient conditions for finite-time stability and finite-time stabilization are developed to a set containing bilinear matrix inequalities (BLIMs and linear matrix inequalities (LMIs. Numerical examples are given to illustrate the effectiveness of the proposed methodology.
System evaluation of improved thermal stability jet fuels
Energy Technology Data Exchange (ETDEWEB)
Binns, K.E.; Dieterle, G.L.; Williams, T. [Univ. of Dayton Research Institute, OH (United States)
1995-05-01
A single-pass, single-tube heat exchanger device called the Phoenix rig and a single-pass, dual-heat exchanger system called the Extended Duration Thermal Stability Test system are specific devices/systems developed for evaluating jet fuel thermal stability. They have been used extensively in the evaluation of various jet fuels and thermal stability additives. The test results have indicated that additives can substantially improve the thermal stability of conventional jet fuels. Relationships of oxygen consumption, residence time, bulk, and wetted wall temperatures on coking deposits that form in the heated tubes have also been investigated.
Stability improvement of induction generator-based wind turbine systems
DEFF Research Database (Denmark)
Chen, Zhe; Hu, Y.; Blaabjerg, Frede
2007-01-01
The stability improvement of induction-generator-based wind turbine systems under power system fault conditions has been studied. Two types of generators are considered, namely rotor short-circuited induction generators and dynamic slip-controlled wound rotor induction generators. The factors...... affecting the stability are analysed. The characteristics of the induction-generator-based wind turbines are described, and possible methods of improving stability of the wind generators are discussed. The system modelling is presented, and then the discussed methods of improving stability are investigated...
Exploring the Teachers' Attitudes towards Inclusive Education System: A Study of Indian Teachers
Kumar, Anil
2016-01-01
This article explores the attitudes of university and school teachers towards inclusive education system. One hundred teachers having equal number of male and female population was included in the study. Participants were administered an attitude scale namely--Attitudes toward Inclusive Education Scale (ATIE), developed by Wilczenski (1992) to…
The algebraic criteria for the stability of control systems
Cremer, H.; Effertz, F. H.
1986-01-01
This paper critically examines the standard algebraic criteria for the stability of linear control systems and their proofs, reveals important previously unnoticed connections, and presents new representations. Algebraic stability criteria have also acquired significance for stability studies of non-linear differential equation systems by the Krylov-Bogoljubov-Magnus Method, and allow realization conditions to be determined for classes of broken rational functions as frequency characteristics of electrical network.
Effects of SMES units on power system stability
International Nuclear Information System (INIS)
Byerly, R.T.; Juves, J.A.
1980-01-01
A mathematical model suitable for representing SMES units in power system stability studies has been developed and incorporated into an existing large-scale stability program. Demonstration studies have been performed which emphasize the use of SMES units to improve the damping of oscillations associated with synchronizing power flow among generators. The capability exists to conduct stability studies of large systems which include SMES units
Energy dissipation/transfer and stable attitude of spatial on-orbit tethered system
Hu, Weipeng; Song, Mingzhe; Deng, Zichen
2018-01-01
For the Tethered Satellite System, the coupling between the platform system and the solar panel is a challenge in the dynamic analysis. In this paper, the coupling dynamic behaviors of the Tethered Satellite System that is idealized as a planar flexible damping beam-spring-mass composite system are investigated via a structure-preserving method. Considering the coupling between the plane motion of the system, the oscillation of the spring and the transverse vibration of the beam, the dynamic model of the composite system is established based on the Hamiltonian variational principle. A symplectic dimensionality reduction method is proposed to decouple the dynamic system into two subsystems approximately. Employing the complex structure-preserving approach presented in our previous work, numerical iterations are performed between the two subsystems with weak damping to study the energy dissipation/transfer in the composite system, the effect of the spring stiffness on the energy distribution and the effect of the particle mass on the stability of the composite system. The numerical results show that: the energy transfer approach is uniquely determined by the initial attitude angle, while the energy dissipation speed is mainly depending on the initial attitude angle and the spring stiffness besides the weak damping. In addition, the mass ratio between the platform system and the solar panel determines the stable state as well as the time needed to reach the stable state of the composite system. The numerical approach presented in this paper provides a new way to deal with the coupling dynamic system and the conclusions obtained give some useful advices on the overall design of the Tethered Satellite System.
Assessing Power System Stability Following Load Changes and Considering Uncertainty
Directory of Open Access Journals (Sweden)
D. V. Ngo
2018-04-01
Full Text Available An increase in load capacity during the operation of a power system usually causes voltage drop and leads to system instability, so it is necessary to monitor the effect of load changes. This article presents a method of assessing the power system stability according to the load node capacity considering uncertainty factors in the system. The proposed approach can be applied to large-scale power systems for voltage stability assessment in real-time.
Milanović, Jovica V
2017-08-13
Future power systems will be significantly different compared with their present states. They will be characterized by an unprecedented mix of a wide range of electricity generation and transmission technologies, as well as responsive and highly flexible demand and storage devices with significant temporal and spatial uncertainty. The importance of probabilistic approaches towards power system stability analysis, as a subsection of power system studies routinely carried out by power system operators, has been highlighted in previous research. However, it may not be feasible (or even possible) to accurately model all of the uncertainties that exist within a power system. This paper describes for the first time an integral approach to probabilistic stability analysis of power systems, including small and large angular stability and frequency stability. It provides guidance for handling uncertainties in power system stability studies and some illustrative examples of the most recent results of probabilistic stability analysis of uncertain power systems.This article is part of the themed issue 'Energy management: flexibility, risk and optimization'. © 2017 The Author(s).
NSRL 200 MeV linac beam energy stabilization system
International Nuclear Information System (INIS)
Huang Guirong; Pei Yuanji; Dong Sai
2001-01-01
By using the computer image processing technology and RF phase auto-shifting system, the ESS (Energy Stabilization System) was applied to 200 MeV Linac. the ESS adjusts beam energy automatically in a range of +-4 MeV. After adjustment beam energy stability is improved to +-6%
Learning and Understanding System Stability Using Illustrative Dynamic Texture Examples
Liu, Huaping; Xiao, Wei; Zhao, Hongyan; Sun, Fuchun
2014-01-01
System stability is a basic concept in courses on dynamic system analysis and control for undergraduate students with computer science backgrounds. Typically, this was taught using a simple simulation example of an inverted pendulum. Unfortunately, many difficult issues arise in the learning and understanding of the concepts of stability,…
Harmonics and voltage stability analysis in power systems including ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
two parameters affecting power quality – harmonics and voltage stability. ... is necessary to pay attention to energy system stability in the planning, management, and ... where k ∈ {m, m + 1,... ,n} and n is total number of the buses in the system.
System identification on two-phase flow stability
International Nuclear Information System (INIS)
Wu Shaorong; Zhang Youjie; Wang Dazhong; Bo Jinghai; Wang Fei
1996-01-01
The theoretical principle, experimental method and results of interrelation analysis identification for the instability of two-phase flow are described. A completely new concept of test technology and method on two-phase flow stability was developed by using he theory of information science on system stability and system identification for two-phase flow stability in thermo-physics field. Application of this method would make it possible to identify instability boundary of two-phase flow under stable operation conditions of two-phase flow system. The experiment was carried out on the thermohydraulic test system HRTL-5. Using reverse repeated pseudo-random sequences of heating power as input signal sources and flow rate as response function in the test, the two-phase flow stability and stability margin of the natural circulation system are investigated. The effectiveness and feasibility of identifying two-phase flow stability by using this system identification method were experimentally demonstrated. Basic data required for mathematics modeling of two-phase flow and analysis of two-phase flow stability were obtained, which are useful for analyzing, monitoring of the system operation condition, and forecasting of two-phase flow stability in engineering system
Development of a terminal voltage stabilization system for the FOTIA ...
Indian Academy of Sciences (India)
Abstract. A terminal voltage stabilization system for the folded tandem ion accelerator (FOTIA) was developed and is in continuous use. The system achieves good voltage stabilization, eliminates ground loops and noise interference. It incorporates a correcting circuit for compensating the mains frequency variations in the ...
On Robust Stability of Systems of Differential-Algebraic Equations
Directory of Open Access Journals (Sweden)
A. Shcheglova
2016-06-01
The sufficient conditions of robust stability for index-one and index-two systems are obtained. We use the values of real and complex stability radii obtained for system of ordinary differential equations solved with respect to the derivatives. We consider the example illustrating the obtained results.
Stability Analysis of Fractional-Order Nonlinear Systems with Delay
Directory of Open Access Journals (Sweden)
Yu Wang
2014-01-01
Full Text Available Stability analysis of fractional-order nonlinear systems with delay is studied. We propose the definition of Mittag-Leffler stability of time-delay system and introduce the fractional Lyapunov direct method by using properties of Mittag-Leffler function and Laplace transform. Then some new sufficient conditions ensuring asymptotical stability of fractional-order nonlinear system with delay are proposed firstly. And the application of Riemann-Liouville fractional-order systems is extended by the fractional comparison principle and the Caputo fractional-order systems. Numerical simulations of an example demonstrate the universality and the effectiveness of the proposed method.
Toluene stability Space Station Rankine power system
Havens, V. N.; Ragaller, D. R.; Sibert, L.; Miller, D.
1987-01-01
A dynamic test loop is designed to evaluate the thermal stability of an organic Rankine cycle working fluid, toluene, for potential application to the Space Station power conversion unit. Samples of the noncondensible gases and the liquid toluene were taken periodically during the 3410 hour test at 750 F peak temperature. The results obtained from the toluene stability loop verify that toluene degradation will not lead to a loss of performance over the 30-year Space Station mission life requirement. The identity of the degradation products and the low rates of formation were as expected from toluene capsule test data.
Decentralized linear quadratic power system stabilizers for multi ...
Indian Academy of Sciences (India)
Introduction. Modern excitation systems considerably enhance the overall transient stability of power systems ..... to the local bus rather than the angle δ measured with respect to the remote bus. ... With this in view, the linear and nonlinear per-.
Advances in power system modelling, control and stability analysis
Milano, Federico
2016-01-01
Advances in Power System Modelling, Control and Stability Analysis captures the variety of new methodologies and technologies that are changing the way modern electric power systems are modelled, simulated and operated.
Wind energy systems solutions for power quality and stabilization
Ali, Mohd Hasan
2012-01-01
Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases--and wind energy is a free, renewable resource. However, the induction machines commonly used as wind generators have stability problems similar to the transient stability of synchronous machines. To minimize power, frequency, and voltage fluctuations caused by network faults or random wind speed variations, control mechanisms are necessary. Wind Energy Systems: Solutions for Power Quality and Stabilization clearly explains how to solve stability and power quality issues of wind generator systems. Covering
Solving the stability-accuracy-diversity dilemma of recommender systems
Hou, Lei; Liu, Kecheng; Liu, Jianguo; Zhang, Runtong
2017-02-01
Recommender systems are of great significance in predicting the potential interesting items based on the target user's historical selections. However, the recommendation list for a specific user has been found changing vastly when the system changes, due to the unstable quantification of item similarities, which is defined as the recommendation stability problem. To improve the similarity stability and recommendation stability is crucial for the user experience enhancement and the better understanding of user interests. While the stability as well as accuracy of recommendation could be guaranteed by recommending only popular items, studies have been addressing the necessity of diversity which requires the system to recommend unpopular items. By ranking the similarities in terms of stability and considering only the most stable ones, we present a top- n-stability method based on the Heat Conduction algorithm (denoted as TNS-HC henceforth) for solving the stability-accuracy-diversity dilemma. Experiments on four benchmark data sets indicate that the TNS-HC algorithm could significantly improve the recommendation stability and accuracy simultaneously and still retain the high-diversity nature of the Heat Conduction algorithm. Furthermore, we compare the performance of the TNS-HC algorithm with a number of benchmark recommendation algorithms. The result suggests that the TNS-HC algorithm is more efficient in solving the stability-accuracy-diversity triple dilemma of recommender systems.
Stability of molecular dynamics simulations of classical systems
DEFF Research Database (Denmark)
Toxværd, Søren
2012-01-01
The existence of a shadow Hamiltonian for discrete classical dynamics, obtained by an asymptotic expansion for a discrete symplectic algorithm, is employed to determine the limit of stability for molecular dynamics (MD) simulations with respect to the time-increment h of the discrete dynamics....... The investigation is based on the stability of the shadow energy, obtained by including the first term in the asymptotic expansion, and on the exact solution of discrete dynamics for a single harmonic mode. The exact solution of discrete dynamics for a harmonic potential with frequency ω gives a criterion...... for the limit of stability h ⩽ 2/ω. Simulations of the Lennard-Jones system and the viscous Kob-Andersen system show that one can use the limit of stability of the shadow energy or the stability criterion for a harmonic mode on the spectrum of instantaneous frequencies to determine the limit of stability of MD...
Direct Self-Repairing Control for Quadrotor Helicopter Attitude Systems
Directory of Open Access Journals (Sweden)
Huiliao Yang
2014-01-01
Full Text Available A quadrotor helicopter with uncertain actuator faults, such as loss of effectiveness and lock-in-place, is studied in this paper. An adaptive fuzzy sliding mode controller based on direct self-repairing control is designed for such nonlinear system to track the desired output signal, when any actuator of this quadrotor helicopter is loss of effectiveness or stuck at some place. Moreover, using the Lyapunov stability theory, the stability of the whole system and the convergence of the tracking error can be guaranteed. Finally, the availability of the proposed method is verified by simulation on 3-DOF hover to ensure that the system performance under faulty conditions can be quickly recovered to its normal level. And this proposed method is also proved to be better than that of LQR through simulation.
Power system stabilizers based on modern control techniques
Energy Technology Data Exchange (ETDEWEB)
Malik, O P; Chen, G P; Zhang, Y; El-Metwally, K [Calgary Univ., AB (Canada). Dept. of Electrical and Computer Engineering
1994-12-31
Developments in digital technology have made it feasible to develop and implement improved controllers based on sophisticated control techniques. Power system stabilizers based on adaptive control, fuzzy logic and artificial networks are being developed. Each of these control techniques possesses unique features and strengths. In this paper, the relative performance of power systems stabilizers based on adaptive control, fuzzy logic and neural network, both in simulation studies and real time tests on a physical model of a power system, is presented and compared to that of a fixed parameter conventional power system stabilizer. (author) 16 refs., 45 figs., 3 tabs.
Solar Dynamic Power System Stability Analysis and Control
Momoh, James A.; Wang, Yanchun
1996-01-01
The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.
On the stability of preferences and attitudes before and after experiencing an electric vehicle
DEFF Research Database (Denmark)
Jensen, Anders Fjendbo; Cherchi, Elisabetta; Mabit, Stefan Lindhard
2013-01-01
-wave stated preference experiment where data was collected before and after the respondents experienced an electric vehicle for three months. We estimate a hybrid choice model using jointly the stated choices before and after the test period. The results show that individual preferences change significantly......In this study, we investigate the extent to which experience affects individual preferences for specific electric vehicle characteristics, individual attitudes toward the environment, and the impact of the attitudes on the choice between an electric and a conventional vehicle. We use a two...... after a real experience with an electric vehicle in the household. In particular, there are major changes in the preference for driving range, top speed, fuel cost, battery life and charging in city centres and train stations. In line with other studies, we find that environmental concern has a positive...
Global finite-time attitude stabilization for rigid spacecraft in the exponential coordinates
Shi, Xiao-Ning; Zhou, Zhi-Gang; Zhou, Di
2018-06-01
This paper addresses the global finite-time attitude stabilisation problem on the special orthogonal group (SO(3)) for a rigid spacecraft via homogeneous feedback approach. Considering the topological and geometric properties of SO(3), the logarithm map is utilised to transform the stabilisation problem on SO(3) into the one on its associated Lie algebra (?). A model-independent discontinuous state feedback plus dynamics compensation scheme is constructed to achieve the global finite-time attitude stabilisation in a coordinate-invariant way. In addition, to address the absence of angular velocity measurements, a sliding mode observer is proposed to reconstruct the unknown angular velocity information within finite time. Then, an observer-based finite-time output feedback control strategy is obtained. Numerical simulations are finally performed to demonstrate the effectiveness of the proposed finite-time controllers.
Stabilization of Neutral Systems with Saturating Actuators
Directory of Open Access Journals (Sweden)
F. El Haoussi
2012-01-01
to determine stabilizing state-feedback controllers with large domain of attraction, expressed as linear matrix inequalities, readily implementable using available numerical tools and with tuning parameters that make possible to select the most adequate solution. These conditions are derived by using a Lyapunov-Krasovskii functional on the vertices of the polytopic description of the actuator saturations. Numerical examples demonstrate the effectiveness of the proposed technique.
Stability and Hopf bifurcation analysis of a new system
International Nuclear Information System (INIS)
Huang Kuifei; Yang Qigui
2009-01-01
In this paper, a new chaotic system is introduced. The system contains special cases as the modified Lorenz system and conjugate Chen system. Some subtle characteristics of stability and Hopf bifurcation of the new chaotic system are thoroughly investigated by rigorous mathematical analysis and symbolic computations. Meanwhile, some numerical simulations for justifying the theoretical analysis are also presented.
Review of Power System Stability with High Wind Power Penetration
DEFF Research Database (Denmark)
Hu, Rui; Hu, Weihao; Chen, Zhe
2015-01-01
analyzing methods and stability improvement approaches. With increasing wind power penetration, system balancing and the reduced inertia may cause a big threaten for stable operation of power systems. To mitigate or eliminate the wind impacts for high wind penetration systems, although the practical......This paper presents an overview of researches on power system stability with high wind power penetration including analyzing methods and improvement approaches. Power system stability issues can be classified diversely according to different considerations. Each classified issue has special...... and reliable choices currently are the strong outside connections or sufficient reserve capacity constructions, many novel theories and approaches are invented to investigate the stability issues, looking forward to an extra-high penetration or totally renewable resource based power systems. These analyzing...
Probabilistic assessment of power system transient stability incorporating SMES
Energy Technology Data Exchange (ETDEWEB)
Fang, Jiakun, E-mail: Jiakun.Fang@gmail.com [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Yao, Wei [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Wen, Jinyu, E-mail: jinyu.wen@hust.edu.cn [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China); Cheng, Shijie; Tang, Yuejin; Cheng, Zhuo [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074 (China)
2013-01-15
Highlights: ► Probabilistic study of power system with wind farm and SMES is proposed. ► Quantitative relationship between system stability and SMES capacity is given. ► System stability increases with the capacity of the SMES. ► System stability decreases with the penetration of wind power. ► Together with the cost function, the coil size is optimized. -- Abstract: This paper presents a stochastic-based approach to evaluate the probabilistic transient stability index of the power system incorporating the wind farm and the SMES. Uncertain factors include both sequence of disturbance in power grid and stochastic generation of the wind farm. The spectrums of disturbance in the grid as the fault type, the fault location, the fault clearing time and the automatic reclosing process with their probabilities of occurrence are used to calculate the probability indices, while the wind speed statistics and parameters of the wind generator are used in a Monte Carlo simulation to generate samples for the studies. With the proposed method, system stability is ”measured”. Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve, together with the cost function, the coil size is optimized economically.
Probabilistic assessment of power system transient stability incorporating SMES
International Nuclear Information System (INIS)
Fang, Jiakun; Yao, Wei; Wen, Jinyu; Cheng, Shijie; Tang, Yuejin; Cheng, Zhuo
2013-01-01
Highlights: ► Probabilistic study of power system with wind farm and SMES is proposed. ► Quantitative relationship between system stability and SMES capacity is given. ► System stability increases with the capacity of the SMES. ► System stability decreases with the penetration of wind power. ► Together with the cost function, the coil size is optimized. -- Abstract: This paper presents a stochastic-based approach to evaluate the probabilistic transient stability index of the power system incorporating the wind farm and the SMES. Uncertain factors include both sequence of disturbance in power grid and stochastic generation of the wind farm. The spectrums of disturbance in the grid as the fault type, the fault location, the fault clearing time and the automatic reclosing process with their probabilities of occurrence are used to calculate the probability indices, while the wind speed statistics and parameters of the wind generator are used in a Monte Carlo simulation to generate samples for the studies. With the proposed method, system stability is ”measured”. Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve, together with the cost function, the coil size is optimized economically
Stability analysis of linear switching systems with time delays
International Nuclear Information System (INIS)
Li Ping; Zhong Shouming; Cui Jinzhong
2009-01-01
The issue of stability analysis of linear switching system with discrete and distributed time delays is studied in this paper. An appropriate switching rule is applied to guarantee the stability of the whole switching system. Our results use a Riccati-type Lyapunov functional under a condition on the time delay. So, switching systems with mixed delays are developed. A numerical example is given to illustrate the effectiveness of our results.
Decentralized linear quadratic power system stabilizers for multi ...
Indian Academy of Sciences (India)
Linear quadratic stabilizers are well-known for their superior control capabilities when compared to the conventional lead–lag power system stabilizers. However, they have not seen much of practical importance as the state variables are generally not measurable; especially the generator rotor angle measurement is not ...
An equilibrium point stabilization strategy for the Chen system
International Nuclear Information System (INIS)
Alvarez-Ramirez, Jose; Cevantes, Ilse; Femat, Ricardo
2004-01-01
The aim of this Letter is to address the equilibrium point stabilization problem of the Chen system by employing a simple linear feedback controller derived from time-scaling the dynamics of a single variable. The controller has the advantage of being easy to implement and a rigorous stability proof is provided based on singular perturbation arguments. Results are illustrated via numerical simulations
A Methodology to Efficiently Compare Operating System Stability
van der Kouwe, E.; Giuffrida, C.; Ghitulete, R.; Tanenbaum, A.S.
2015-01-01
Despite decades of advances in software engineering, operating systems (OSes) are still plagued by crashes due to software faults, calling for techniques to improve OS stability when faults occur. Evaluating such techniques requires a way to compare the stability of different OSes that is both
New Results of Global Exponential Stabilization for BLDCMs System
Fengxia Tian; Fangchao Zhen; Guopeng Zhou; Xiaoxin Liao
2015-01-01
The global exponential stabilization for brushless direct current motor (BLDCM) system is studied. Four linear and simple feedback controllers are proposed to realize the global stabilization of BLDCM with exponential convergence rate; the control law used in each theorem is less conservative and more concise. Finally, an example is given to demonstrate the correctness of the proposed results.
Electrostatic stabilizer for a passive magnetic bearing system
Post, Richard F.
2015-11-24
Electrostatic stabilizers are provided for passive bearing systems composed of annular magnets having a net positive stiffness against radial displacements and that have a negative stiffness for vertical displacements, resulting in a vertical instability. Further embodiments are shown of a radial electrostatic stabilizer geometry (using circuitry similar to that employed in the vertical stabilizer). This version is suitable for stabilizing radial (lateral) displacements of a rotor that is levitated by annular permanent magnets that are stable against vertical displacements but are unstable against radial displacements.
On the stability of some systems of exponential difference equations
Directory of Open Access Journals (Sweden)
N. Psarros
2018-01-01
Full Text Available In this paper we prove the stability of the zero equilibria of two systems of difference equations of exponential type, which are some extensions of an one-dimensional biological model. The stability of these systems is investigated in the special case when one of the eigenvalues is equal to -1 and the other eigenvalue has absolute value less than 1, using centre manifold theory. In addition, we study the existence and uniqueness of positive equilibria, the attractivity and the global asymptotic stability of these equilibria of some related systems of difference equations.
Stabilization at almost arbitrary points for chaotic systems
International Nuclear Information System (INIS)
Huang, C.-S.; Lian, K.-Y.; Su, C.-H.; Wu, J.-W.
2008-01-01
We consider how to design a feasible control input for chaotic systems via a suitable input channel to achieve the stabilization at arbitrary points. Regarding the nonlinear systems without naturally defined input vectors, we propose a local stabilization controller which works for almost arbitrary points. Subsequently, according to topologically transitive property for chaotic systems, the feedback control force is activated only when the trajectory passes through the neighboring region of the regulated point. Hence the global stabilization is achieved whereas the control effort of the hybrid controller is extremely low
Performance of the PBX-M passive plate stabilization system
International Nuclear Information System (INIS)
Kugel, H.W.; Bell, R.; Bernabei, S.
1994-02-01
The PBX-M passive plate stabilization system provides significant stabilization of long-wavelength external kink modes, the slowing of vertical instability growth rates, and the amelioration of disruption characteristics. The passive plate stabilization system has allowed the use of LHCD and IBW to induce current density and pressure profile modifications, and m = 1 divertor biasing for modifying edge plasma transport. Improvements in the passive plate system insulators and support structures have provided reliable operation. Impurity influxes with the close-fitting passive plates are low. Solid target boronization is applied routinely to reduce conditioning time and maintain clean conditions
On the stability of non-linear systems
International Nuclear Information System (INIS)
Guelman, M.
1968-09-01
A study is made of the absolute stability of nonlinear systems, using Liapounov's second method and taking into account the results obtained from V.M. Popov's work. The results already established are first presented, in particular concerning the frequency domain criterions for absolute stability of automatic control systems containing one single non linearity. The results have been extended to show the existence of a limiting parabola. New use is then made of the methods studied for deriving absolute stability criterions for a system containing a different type of non linearity. Finally, the results obtained are considered from the point of view of Aizerman's conjecture. (author) [fr
Recent Progress in Stability and Stabilization of Systems with Time-Delays
Directory of Open Access Journals (Sweden)
Magdi S. Mahmoud
2017-01-01
Full Text Available This paper overviews the research investigations pertaining to stability and stabilization of control systems with time-delays. The prime focus is the fundamental results and recent progress in theory and applications. The overview sheds light on the contemporary development on the linear matrix inequality (LMI techniques in deriving both delay-independent and delay-dependent stability results for time-delay systems. Particular emphases will be placed on issues concerned with the conservatism and the computational complexity of the results. Key technical bounding lemmas and slack variable introduction approaches will be presented. The results will be compared and connections of certain delay-dependent stability results are also discussed.
Computation of robustly stabilizing PID controllers for interval systems.
Matušů, Radek; Prokop, Roman
2016-01-01
The paper is focused on the computation of all possible robustly stabilizing Proportional-Integral-Derivative (PID) controllers for plants with interval uncertainty. The main idea of the proposed method is based on Tan's (et al.) technique for calculation of (nominally) stabilizing PI and PID controllers or robustly stabilizing PI controllers by means of plotting the stability boundary locus in either P-I plane or P-I-D space. Refinement of the existing method by consideration of 16 segment plants instead of 16 Kharitonov plants provides an elegant and efficient tool for finding all robustly stabilizing PID controllers for an interval system. The validity and relatively effortless application of presented theoretical concepts are demonstrated through a computation and simulation example in which the uncertain mathematical model of an experimental oblique wing aircraft is robustly stabilized.
Stability design considerations for mirror support systems in ICF lasers
International Nuclear Information System (INIS)
Tietbohl, G.L.; Sommer, S.C.
1996-10-01
Some of the major components of laser systems used for Inertial Confinement Fusion (ICF) are the large aperture mirrors which direct the path of the laser. These mirrors are typically supported by systems which consist of mirror mounts, mirror enclosures, superstructures, and foundations. Stability design considerations for the support systems of large aperture mirrors have been developed based on the experience of designing and evaluating similar systems at the Lawrence Livermore National Laboratory (LLNL). Examples of the systems developed at LLNL include Nova, the Petawatt laser, Beamlet, and the National Ignition Facility (NIF). The structural design of support systems of large aperture mirrors has typically been controlled by stability considerations in order for the large laser system to meet its performance requirements for alignment and positioning. This paper will discuss the influence of stability considerations and will provide guidance on the structural design and evaluation of mirror support systems in ICF lasers so that this information can be used on similar systems
Brazilian Citizens’ Opinions and Attitudes about Farm Animal Production Systems
Directory of Open Access Journals (Sweden)
Maria C. Yunes
2017-09-01
Full Text Available The inclusion of societal input is needed for food animal production industries to retain their “social license to operate”; failure to engage with the public on this topic risks the long-term sustainability of these industries. The primary aim of this study was to explore the beliefs and attitudes of Brazilians citizens not associated with livestock production towards farm animal production. A related secondary aim was to identify the specific beliefs and attitudes towards systems that are associated with restriction of movement. Each participant was shown pictures representing two of five possible major food animal industries (laying hens, beef cattle, pregnant sows, lactating sows, and poultry meat. Participants were presented a six pages survey that included demographic questions plus two sets of two pictures and a series of questions pertaining to the pictures. Each set of pictures represented a particular industry where one picture represented a housing type that is associated with behavioural restrictions and the other picture represented a system that allowed for a greater degree of movement. Participants were asked their perceptions on the prevalence of each system in Brazil, then their preference of one picture vs. the other, and the reasons justifying their preference. Immediately following, the participant repeated the same exercise with the second set of two pictures representing another industry followed by the same series of questions as described above. Quantitative data were analysed with mixed effects logistic regression, and qualitative responses were coded into themes. The proportion of participants that believed animals are reared in confinement varied by animal production type: 23% (beef cattle, 82% (poultry, 81% (laying hens, and 60% (swine. A large majority (79% stated that farm animals are not well-treated in Brazil. Overall, participants preferred systems that were not associated with behavioural restriction. The
Brazilian Citizens' Opinions and Attitudes about Farm Animal Production Systems.
Yunes, Maria C; von Keyserlingk, Marina A G; Hötzel, Maria J
2017-09-28
The inclusion of societal input is needed for food animal production industries to retain their "social license to operate"; failure to engage with the public on this topic risks the long-term sustainability of these industries. The primary aim of this study was to explore the beliefs and attitudes of Brazilians citizens not associated with livestock production towards farm animal production. A related secondary aim was to identify the specific beliefs and attitudes towards systems that are associated with restriction of movement. Each participant was shown pictures representing two of five possible major food animal industries (laying hens, beef cattle, pregnant sows, lactating sows, and poultry meat). Participants were presented a six pages survey that included demographic questions plus two sets of two pictures and a series of questions pertaining to the pictures. Each set of pictures represented a particular industry where one picture represented a housing type that is associated with behavioural restrictions and the other picture represented a system that allowed for a greater degree of movement. Participants were asked their perceptions on the prevalence of each system in Brazil, then their preference of one picture vs. the other, and the reasons justifying their preference. Immediately following, the participant repeated the same exercise with the second set of two pictures representing another industry followed by the same series of questions as described above. Quantitative data were analysed with mixed effects logistic regression, and qualitative responses were coded into themes. The proportion of participants that believed animals are reared in confinement varied by animal production type: 23% (beef cattle), 82% (poultry), 81% (laying hens), and 60% (swine). A large majority (79%) stated that farm animals are not well-treated in Brazil. Overall, participants preferred systems that were not associated with behavioural restriction. The preference for free
Power system small signal stability analysis and control
Mondal, Debasish; Sengupta, Aparajita
2014-01-01
Power System Small Signal Stability Analysis and Control presents a detailed analysis of the problem of severe outages due to the sustained growth of small signal oscillations in modern interconnected power systems. The ever-expanding nature of power systems and the rapid upgrade to smart grid technologies call for the implementation of robust and optimal controls. Power systems that are forced to operate close to their stability limit have resulted in the use of control devices by utility companies to improve the performance of the transmission system against commonly occurring power system
Earth System Stability Through Geologic Time
Rothman, D.; Bowring, S. A.
2015-12-01
Five times in the past 500 million years, mass extinctions haveresulted in the loss of greater than three-fourths of living species.Each of these events is associated with significant environmentalchange recorded in the carbon-isotopic composition of sedimentaryrocks. There are also many such environmental events in the geologicrecord that are not associated with mass extinctions. What makes themdifferent? Two factors appear important: the size of theenvironmental perturbation, and the time scale over which it occurs.We show that the natural perturbations of Earth's carbon cycle during thepast 500 million years exhibit a characteristic rate of change overtwo orders of magnitude in time scale. This characteristic rate isconsistent with the maximum rate that limits quasistatic (i.e., nearsteady-state) evolution of the carbon cycle. We identify this rate withmarginal stability, and show that mass extinctions occur on the fast,unstable side of the stability boundary. These results suggest thatthe great extinction events of the geologic past, and potentially a"sixth extinction" associated with modern environmental change, arecharacterized by common mechanisms of instability.
An Estimator for Attitude and Heading Reference Systems Based on Virtual Horizontal Reference
DEFF Research Database (Denmark)
Wang, Yunlong; Soltani, Mohsen; Hussain, Dil muhammed Akbar
2016-01-01
makes it possible to correct the output of roll and pitch of the attitude estimator in the situations without accelerometer measurements, which cannot be achieved by the conventional nonlinear attitude estimator. The performance of VHR is tested both in simulation and hardware environment to validate......The output of the attitude determination systems suffers from large errors in case of accelerometer malfunctions. In this paper, an attitude estimator, based on Virtual Horizontal Reference (VHR), is designed for an Attitude Heading and Reference System (AHRS) to cope with this problem. The VHR...... their estimation performance. Moreover, the hardware test results are compared with that of a high-precision commercial AHRS to verify the estimation results. The implemented algorithm has shown high accuracy of attitude estimation that makes the system suitable for many applications....
Stability and delay sensitivity of neutral fractional-delay systems.
Xu, Qi; Shi, Min; Wang, Zaihua
2016-08-01
This paper generalizes the stability test method via integral estimation for integer-order neutral time-delay systems to neutral fractional-delay systems. The key step in stability test is the calculation of the number of unstable characteristic roots that is described by a definite integral over an interval from zero to a sufficient large upper limit. Algorithms for correctly estimating the upper limits of the integral are given in two concise ways, parameter dependent or independent. A special feature of the proposed method is that it judges the stability of fractional-delay systems simply by using rough integral estimation. Meanwhile, the paper shows that for some neutral fractional-delay systems, the stability is extremely sensitive to the change of time delays. Examples are given for demonstrating the proposed method as well as the delay sensitivity.
Stability Analysis of a Reaction-Diffusion System Modeling Atherogenesis
Ibragimov, Akif; Ritter, Laura; Walton, Jay R.
2010-01-01
This paper presents a linear, asymptotic stability analysis for a reaction-diffusionconvection system modeling atherogenesis, the initiation of atherosclerosis, as an inflammatory instability. Motivated by the disease paradigm articulated by Ross
Stabilization of Networked Control Systems Under Feedback-based Communication
National Research Council Canada - National Science Library
Zhang, Lei; Hristu-Varsakelis, Dimitrios
2004-01-01
We study the stabilization of a networked control system (NSC) in which multiple sensors and actuators of a physical plant share a communication medium to exchange information with a remote controller...
Stability of position control system in JIPP T-II
International Nuclear Information System (INIS)
Sakurai, Keiichi; Tanahashi, Shygo
1980-01-01
Computations and experiments on the stability of a feedback control system for maintaining a plasma column in equilibrium are described. The time response of the displacement of the plasma to the desired position is examined by solving the equation of motion of the plasma column. We show that the stability of the feedback control system is improved by using an additional term which represents the shift velocity of the plasma column. (author)
Stability of magnetic tip/superconductor levitation systems
International Nuclear Information System (INIS)
Alqadi, M. K.
2015-01-01
The vertical stability of a magnetic tip over a superconducting material is investigated by using the critical state and the frozen image models. The analytical expressions of the stiffness and the vibration frequency about the equilibrium position are derived in term of the geometrical parameters of the magnet/superconductor system. It is found that the stability of the system depends on the shape of the superconductor as well as its thickness. (paper)
ON THE STABILIZATION OF THE LINEAR HYBRID SYSTEM STRUCTURE
Directory of Open Access Journals (Sweden)
Kirillov
2014-11-01
Full Text Available The linear control hybrid system, consisting of a fi- nite set of subsystems (modes having different dimensions, is considered. The moments of reset time are determined by some complementary function – evolutionary time. This function satisfies the special complementary ordinary differential equation. The mode stabilization problem is solved for some class of piecewise linear controls. The method of stabilization relies on the set of invariant planes, the existence of which is due to the special form of the hybrid system.
Preservation of stability and synchronization in nonlinear systems
Energy Technology Data Exchange (ETDEWEB)
Fernandez-Anaya, G. [Departamento de Fisica y Matematicas, Universidad Iberoamericana, Prol. Paseo de la Reforma 880, Lomas de Santa Fe, Mexico, D.F. 01210 (Mexico)], E-mail: guillermo.fernandez@uia.mx; Flores-Godoy, J.J. [Departamento de Fisica y Matematicas, Universidad Iberoamericana, Prol. Paseo de la Reforma 880, Lomas de Santa Fe, Mexico, D.F. 01210 (Mexico)], E-mail: job.flores@uia.mx; Femat, R. [Division de Matematicas Aplicadas y Sistemas Computacionales, IPICyT, Camino a la Presa San Jose 2055, Col. Lomas 4a. seccion, San Luis Potosi, San Luis Potosi 78216 (Mexico)], E-mail: rfemat@ipicyt.edu.mx; Alvarez-Ramirez, J.J. [Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, Mexico, D.F. 09340 (Mexico)], E-mail: jjar@xanum.uam.mx
2007-11-12
Preservation of stability in the presence of structural and/or parametric changes is an important issue in the study of dynamical systems. A specific case is the synchronization of chaos in complex networks where synchronization should be preserved in spite of changes in the network parameters and connectivity. In this work, a methodology to establish conditions for preservation of stability in a class of dynamical system is given in terms of Lyapunov methods. The idea is to construct a group of dynamical transformations under which stability is retained along certain manifolds. Some synchronization examples illustrate the results.
Preservation of stability and synchronization in nonlinear systems
International Nuclear Information System (INIS)
Fernandez-Anaya, G.; Flores-Godoy, J.J.; Femat, R.; Alvarez-Ramirez, J.J.
2007-01-01
Preservation of stability in the presence of structural and/or parametric changes is an important issue in the study of dynamical systems. A specific case is the synchronization of chaos in complex networks where synchronization should be preserved in spite of changes in the network parameters and connectivity. In this work, a methodology to establish conditions for preservation of stability in a class of dynamical system is given in terms of Lyapunov methods. The idea is to construct a group of dynamical transformations under which stability is retained along certain manifolds. Some synchronization examples illustrate the results
Theoretical bases on thermal stability of layered metallic systems
International Nuclear Information System (INIS)
Kadyrzhanov, K.K.; Rusakov, V.S.; Turkebaev, T.Eh.; Zhankadamova, A.M.; Ensebaeva, M.Z.
2003-01-01
The paper is dedicated to implementation of the theoretical bases for layered metallic systems thermal stabilization. The theory is based on the stabilization mechanism expense of the intermediate two-phase field formation. As parameters of calculated model are coefficients of mutual diffusion and inclusions sizes of generated phases in two-phase fields. The stabilization time dependence for beryllium-iron (Be (1.1 μm)-Fe(5.5 μm)) layered system from iron and beryllium diffusion coefficients, and inclusions sizes is shown as an example. Conclusion about possible mechanisms change at transition from microscopic consideration to the nano-crystal physics level is given
Stability of a slotted ALOHA system with capture effect
Onozato, Yoshikuni; Liu, Jin; Noguchi, Shoichi
1989-02-01
The stability of a slotted ALOHA system with capture effect is investigated under a general communication environment where terminals are divided into two groups (low-power and high-power) and the capture effect is modeled by capture probabilities. An approximate analysis is developed using catastrophe theory, in which the effects of system and user parameters on the stability are characterized by the cusp catastrophe. Particular attention is given to the low-power group, since it must bear the strain under the capture effect. The stability conditions of the two groups are given explicitly by bifurcation sets.
Stabilization of model-based networked control systems
Energy Technology Data Exchange (ETDEWEB)
Miranda, Francisco [CIDMA, Universidade de Aveiro, Aveiro (Portugal); Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); Abreu, Carlos [Instituto Politécnico de Viana do Castelo, Viana do Castelo (Portugal); CMEMS-UMINHO, Universidade do Minho, Braga (Portugal); Mendes, Paulo M. [CMEMS-UMINHO, Universidade do Minho, Braga (Portugal)
2016-06-08
A class of networked control systems called Model-Based Networked Control Systems (MB-NCSs) is considered. Stabilization of MB-NCSs is studied using feedback controls and simulation of stabilization for different feedbacks is made with the purpose to reduce the network trafic. The feedback control input is applied in a compensated model of the plant that approximates the plant dynamics and stabilizes the plant even under slow network conditions. Conditions for global exponential stabilizability and for the choosing of a feedback control input for a given constant time between the information moments of the network are derived. An optimal control problem to obtain an optimal feedback control is also presented.
INFORMATION SYSTEMS EVALUATION CRITERIA BASED ON ATTITUDES OF GRADUATE STUDENTS
Directory of Open Access Journals (Sweden)
DAŘENA, František
2011-03-01
Full Text Available Importance of information systems in supporting business activities and managerial decision making is growing. Decisions related to selecting a suitable information system, including the technological background, human resources, procedures and information belong to one of the most difficult and most responsible ones. As in the case of other types of investments, assets and resources invested into information system should return in a reasonable time. There has been a lot of work done in the research and application of IS evaluation techniques to different kinds of information systems. Such evaluations involve a wide variety of technical and technological considerations made by technical experts, on the other hand impacts on management of the organization or financial impacts can be addressed. The objective of the paper is to reveal the preferences of graduate students related to their information systems evaluation and to propose a general framework for such evaluations. During the experimental period two surveys were carried out within the information systems course – at the beginning when the students were completely uninformed and at the end when the students had the knowledge of individual aspects of information systems, their role within organizations and process of information systems evaluation. The former survey used a simple scoring method whereas the latter relied on formal usage of the Analytical Hierarchy Process. The results show the differences in opinions of the students between these two surveys. Presented criteria hierarchy as well as the importance of individual evaluation criteria can be used for demonstration of attitudes of graduate students of management study programs and as a general framework for information systems evaluation.
Stability properties of nonlinear dynamical systems and evolutionary stable states
Energy Technology Data Exchange (ETDEWEB)
Gleria, Iram, E-mail: iram@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió-AL (Brazil); Brenig, Leon [Faculté des Sciences, Université Libre de Bruxelles, 1050 Brussels (Belgium); Rocha Filho, Tarcísio M.; Figueiredo, Annibal [Instituto de Física and International Center for Condensed Matter Physics, Universidade de Brasília, 70919-970 Brasília-DF (Brazil)
2017-03-18
Highlights: • We address the problem of equilibrium stability in a general class of non-linear systems. • We link Evolutionary Stable States (ESS) to stable fixed points of square quasi-polynomial (QP) systems. • We show that an interior ES point may be related to stable interior fixed points of QP systems. - Abstract: In this paper we address the problem of stability in a general class of non-linear systems. We establish a link between the concepts of asymptotic stable interior fixed points of square Quasi-Polynomial systems and evolutionary stable states, a property of some payoff matrices arising from evolutionary games.
Vision-Based Attitude and Formation Determination System, Phase I
National Aeronautics and Space Administration — To determine pointing and position vectors in both local and inertial coordinate frames, multi-spacecraft missions typically utilize separate attitude determination...
The Software Design for the Wide-Field Infrared Explorer Attitude Control System
Anderson, Mark O.; Barnes, Kenneth C.; Melhorn, Charles M.; Phillips, Tom
1998-01-01
The Wide-Field Infrared Explorer (WIRE), currently scheduled for launch in September 1998, is the fifth of five spacecraft in the NASA/Goddard Small Explorer (SMEX) series. This paper presents the design of WIRE's Attitude Control System flight software (ACS FSW). WIRE is a momentum-biased, three-axis stabilized stellar pointer which provides high-accuracy pointing and autonomous acquisition for eight to ten stellar targets per orbit. WIRE's short mission life and limited cryogen supply motivate requirements for Sun and Earth avoidance constraints which are designed to prevent catastrophic instrument damage and to minimize the heat load on the cryostat. The FSW implements autonomous fault detection and handling (FDH) to enforce these instrument constraints and to perform several other checks which insure the safety of the spacecraft. The ACS FSW implements modules for sensor data processing, attitude determination, attitude control, guide star acquisition, actuator command generation, command/telemetry processing, and FDH. These software components are integrated with a hierarchical control mode managing module that dictates which software components are currently active. The lowest mode in the hierarchy is the 'safest' one, in the sense that it utilizes a minimal complement of sensors and actuators to keep the spacecraft in a stable configuration (power and pointing constraints are maintained). As higher modes in the hierarchy are achieved, the various software functions are activated by the mode manager, and an increasing level of attitude control accuracy is provided. If FDH detects a constraint violation or other anomaly, it triggers a safing transition to a lower control mode. The WIRE ACS FSW satisfies all target acquisition and pointing accuracy requirements, enforces all pointing constraints, provides the ground with a simple means for reconfiguring the system via table load, and meets all the demands of its real-time embedded environment (16 MHz Intel
Preparation of Astaxanthin Nanodispersions Using Gelatin-Based Stabilizer Systems
Directory of Open Access Journals (Sweden)
Navideh Anarjan
2014-09-01
Full Text Available The incorporation of lipophilic nutrients, such as astaxanthin (a fat soluble carotenoid in nanodispersion systems can either increase the water solubility, stability and bioavailability or widen their applications in aqueous food and pharmaceutical formulations. In this research, gelatin and its combinations with sucrose oleate as a small molecular emulsifier, sodium caseinate (SC as a protein and gum Arabic as a polysaccharide were used as stabilizer systems in the formation of astaxanthin nanodispersions via an emulsification-evaporation process. The results indicated that the addition of SC to gelatin in the stabilizer system could increase the chemical stability of astaxanthin nanodispersions significantly, while using a mixture of gelatin and sucrose oleate as a stabilizer led to production of nanodispersions with the smallest particle size (121.4 ± 8.6 nm. It was also shown that a combination of gelatin and gum Arabic could produce optimal astaxanthin nanodispersions in terms of physical stability (minimum polydispersity index (PDI and maximum zeta-potential. This study demonstrated that the mixture of surface active compounds showed higher emulsifying and stabilizing functionality compared to using them individually in the preparation of astaxanthin nanodispersions.
Stabilization of switched nonlinear systems with unstable modes
Yang, Hao; Cocquempot, Vincent
2014-01-01
This book provides its reader with a good understanding of the stabilization of switched nonlinear systems (SNS), systems that are of practical use in diverse situations: design of fault-tolerant systems in space- and aircraft; traffic control; and heat propagation control of semiconductor power chips. The practical background is emphasized throughout the book; interesting practical examples frequently illustrate the theoretical results with aircraft and spacecraft given particular prominence. Stabilization of Switched Nonlinear Systems with Unstable Modes treats several different subclasses of SNS according to the characteristics of the individual system (time-varying and distributed parameters, for example), the state composition of individual modes and the degree and distribution of instability in its various modes. Achievement and maintenance of stability across the system as a whole is bolstered by trading off between individual modes which may be either stable or unstable, or by exploiting areas of part...
A study of offshore wind HVDC system stability and control
Energy Technology Data Exchange (ETDEWEB)
Liu, Hanchao; Sun, Jian [Rensselaer Polytechnic Institute, Troy, NY (United States). Dept. of Electrical, Computer and Systems Engineering
2011-07-01
This work is concerned with the stability and control of ac power collection buses in offshore wind farms with high-voltage dc (HVDC) transmission connection to onshore power grid. The focus of the work is high-frequency interactions among the wind turbines, the ac collection bus and the filters, as well as the HVDC rectifier. Both voltage-source converter and line-commutated converter based HVDC systems are considered. To study high-frequency stability, particularly harmonic resonance in the ac bus, small-signal impedance models are developed for the wind inverters and the HVDC rectifier by using harmonic linearization techniques. An impedance-based stability criterion is applied to assess system stability in both positive- and negative-sequence domain. Small-signal stability conditions and requirements are developed from analytical impedance models. Detailed system-level simulation is used to validated the small-signal analysis. The goal of the study is to develop system design and control techniques that minimize the cost of the offshore infrastructure while guaranteeing system stability and power quality. (orig.)
Experimental study of flame stability in biogas premix system
International Nuclear Information System (INIS)
Diaz G, Carlos A; Amell A Andres; Cardona Luis F
2008-01-01
Utilization of new renewable energy sources have had a special interest in last years looking for decrease the dependence of fossil fuels and the environmental impact generated for them. This work studies experimentally the flame stability of a simulated biogas with a volumetric composition of 60% methane and 40% carbon dioxide. The objective of this study is to obtain information about design and interchangeability of gases in premixed combustion systems that operate with different fuel gases. The critical velocity gradient was the stability criteria used. Utilization of this criteria and the experimental method followed, using a partial premixed burner, stability flame diagram of biogas studied had been obtained. Presence of carbon dioxide has a negative effect in flame stability, decreasing significantly the laminar flame speed and consequently, the stability range of biogas burners because of apparition of blow off.
Stability analysis of switched linear systems defined by graphs
Athanasopoulos, N.; Lazar, M.
2014-01-01
We present necessary and sufficient conditions for global exponential stability for switched discrete-time linear systems, under arbitrary switching, which is constrained within a set of admissible transitions. The class of systems studied includes the family of systems under arbitrary switching,
Analytical Prediction of the Spin Stabilized Satellite's Attitude Using The Solar Radiation Torque
International Nuclear Information System (INIS)
Motta, G B; Carvalho, M V; Zanardi, M C
2013-01-01
The aim of this paper is to present an analytical solution for the spin motion equations of spin-stabilized satellite considering only the influence of solar radiation torque. The theory uses a cylindrical satellite on a circular orbit and considers that the satellite is always illuminated. The average components of this torque were determined over an orbital period. These components are substituted in the spin motion equations in order to get an analytical solution for the right ascension and declination of the satellite spin axis. The time evolution for the pointing deviation of the spin axis was also analyzed. These solutions were numerically implemented and compared with real data of the Brazilian Satellite of Data Collection – SCD1 an SCD2. The results show that the theory has consistency and can be applied to predict the spin motion of spin-stabilized artificial satellites
The electric power engineering handbook power system stability and control
Grisby, Leonard L
2012-01-01
With contributions from worldwide leaders in the field, Power System Stability and Control, Third Edition (part of the five-volume set, The Electric Power Engineering Handbook) updates coverage of recent developments and rapid technological growth in essential aspects of power systems. Edited by L.L. Grigsby, a respected and accomplished authority in power engineering, and section editors Miroslav Begovic, Prabha Kundur, and Bruce Wollenberg, this reference presents substantially new and revised content. Topics covered include: * Power System Protection * Power System Dynamics and Stability *
Stability and stabilisation of a class of networked dynamic systems
Liu, H. B.; Wang, D. Q.
2018-04-01
We investigate the stability and stabilisation of a linear time invariant networked heterogeneous system with arbitrarily connected subsystems. A new linear matrix inequality based sufficient and necessary condition for the stability is derived, based on which the stabilisation is provided. The obtained conditions efficiently utilise the block-diagonal characteristic of system parameter matrices and the sparseness of subsystem connection matrix. Moreover, a sufficient condition only dependent on each individual subsystem is also presented for the stabilisation of the networked systems with a large scale. Numerical simulations show that these conditions are computationally valid in the analysis and synthesis of a large-scale networked system.
Optimal Parameter Selection of Power System Stabilizer using Genetic Algorithm
Energy Technology Data Exchange (ETDEWEB)
Chung, Hyeng Hwan; Chung, Dong Il; Chung, Mun Kyu [Dong-AUniversity (Korea); Wang, Yong Peel [Canterbury Univeristy (New Zealand)
1999-06-01
In this paper, it is suggested that the selection method of optimal parameter of power system stabilizer (PSS) with robustness in low frequency oscillation for power system using real variable elitism genetic algorithm (RVEGA). The optimal parameters were selected in the case of power system stabilizer with one lead compensator, and two lead compensator. Also, the frequency responses characteristics of PSS, the system eigenvalues criterion and the dynamic characteristics were considered in the normal load and the heavy load, which proved usefulness of RVEGA compare with Yu's compensator design theory. (author). 20 refs., 15 figs., 8 tabs.
Frequency Stability Improvement of Low Inertia Systems Using Synchronous Condensers
DEFF Research Database (Denmark)
Nguyen, Ha Thi; Yang, Guangya; Nielsen, Arne Hejde
2016-01-01
of converter interfaced components (wind turbine, HVDC, and Photovoltaic) may have negative effects on the stability of the power system. These components do not have enough inertia response to control frequency excursion, so the power grid can depend on few synchronous machines for frequency regulation...... and reduce the system inertia. Consequently, the frequency stability of the system will be easily jeopardized. To address these issues, the paper studies frequency characteristics of future Western Danish renewable-based system that uses a majority of wind turbine generators. Different scenarios of wind...
Stability Analysis for a Multi-Camera Photogrammetric System
Directory of Open Access Journals (Sweden)
Ayman Habib
2014-08-01
Full Text Available Consumer-grade digital cameras suffer from geometrical instability that may cause problems when used in photogrammetric applications. This paper provides a comprehensive review of this issue of interior orientation parameter variation over time, it explains the common ways used for coping with the issue, and describes the existing methods for performing stability analysis for a single camera. The paper then points out the lack of coverage of stability analysis for multi-camera systems, suggests a modification of the collinearity model to be used for the calibration of an entire photogrammetric system, and proposes three methods for system stability analysis. The proposed methods explore the impact of the changes in interior orientation and relative orientation/mounting parameters on the reconstruction process. Rather than relying on ground truth in real datasets to check the system calibration stability, the proposed methods are simulation-based. Experiment results are shown, where a multi-camera photogrammetric system was calibrated three times, and stability analysis was performed on the system calibration parameters from the three sessions. The proposed simulation-based methods provided results that were compatible with a real-data based approach for evaluating the impact of changes in the system calibration parameters on the three-dimensional reconstruction.
Nuclear Hybrid Energy System Model Stability Testing
Energy Technology Data Exchange (ETDEWEB)
Greenwood, Michael Scott [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cetiner, Sacit M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fugate, David W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2017-04-01
A Nuclear Hybrid Energy System (NHES) uses a nuclear reactor as the basic power generation unit, and the power generated is used by multiple customers as combinations of thermal power or electrical power. The definition and architecture of a particular NHES can be adapted based on the needs and opportunities of different localities and markets. For example, locations in need of potable water may be best served by coupling a desalination plant to the NHES. Similarly, a location near oil refineries may have a need for emission-free hydrogen production. Using the flexible, multi-domain capabilities of Modelica, Argonne National Laboratory, Idaho National Laboratory, and Oak Ridge National Laboratory are investigating the dynamics (e.g., thermal hydraulics and electrical generation/consumption) and cost of a hybrid system. This paper examines the NHES work underway, emphasizing the control system developed for individual subsystems and the overall supervisory control system.
Optimal boundary control and boundary stabilization of hyperbolic systems
Gugat, Martin
2015-01-01
This brief considers recent results on optimal control and stabilization of systems governed by hyperbolic partial differential equations, specifically those in which the control action takes place at the boundary. The wave equation is used as a typical example of a linear system, through which the author explores initial boundary value problems, concepts of exact controllability, optimal exact control, and boundary stabilization. Nonlinear systems are also covered, with the Korteweg-de Vries and Burgers Equations serving as standard examples. To keep the presentation as accessible as possible, the author uses the case of a system with a state that is defined on a finite space interval, so that there are only two boundary points where the system can be controlled. Graduate and post-graduate students as well as researchers in the field will find this to be an accessible introduction to problems of optimal control and stabilization.
Dynamic postural stability in blind athletes using the biodex stability system.
Aydoğ, E; Aydoğ, S T; Cakci, A; Doral, M N
2006-05-01
Three systems affect the upright standing posture in humans - visual, vestibular, and somatosensory. It is well known that the visually impaired individuals have bad postural balance. On the other hand, it is a well documented fact that some sports can improve postural balance. Therefore, it is aimed in this study to evaluate the dynamic postural stability in goal-ball athletes. Twenty blind goal-ball players, 20 sighted and 20 sedentary blind controls were evaluated using the Biodex Stability System. Three adaptation trials and three test evaluations (a 20-second balance test at a platform stability of 8) were applied to the blind people, and to the sighted with eyes open and closed. Dynamic postural stability was measured on the basis of three indices: overall, anteroposterior, and mediolateral. Means of each test score were calculated. The tests results were compared for the blind athletes, sighted (with eyes open and closed) subjects, and sedentary blind people. There were significant differences between the results of the blind people and the sighted subjects with regards to all of the three indices. Although the stability of goal-ball players was better than sedentary blinds', only ML index values were statistically different (4.47 +/- 1.24 in the goal-ball players; 6.46 +/- 3.42 in the sedentary blind, p = 0.04). Dynamic postural stability was demonstrated to be affected by vision; and it was found that blind people playing goal-ball 1 - 2 days per week have higher ML stability than the sedentary sighted people.
Stability analysis of switched linear systems defined by graphs
Athanasopoulos, Nikolaos; Lazar, Mircea
2015-01-01
We present necessary and sufficient conditions for global exponential stability for switched discrete-time linear systems, under arbitrary switching, which is constrained within a set of admissible transitions. The class of systems studied includes the family of systems under arbitrary switching, periodic systems, and systems with minimum and maximum dwell time specifications. To reach the result, we describe the set of rules that define the admissible transitions with a weighted directed gra...
Stability Analysis of Neural Networks-Based System Identification
Directory of Open Access Journals (Sweden)
Talel Korkobi
2008-01-01
Full Text Available This paper treats some problems related to nonlinear systems identification. A stability analysis neural network model for identifying nonlinear dynamic systems is presented. A constrained adaptive stable backpropagation updating law is presented and used in the proposed identification approach. The proposed backpropagation training algorithm is modified to obtain an adaptive learning rate guarantying convergence stability. The proposed learning rule is the backpropagation algorithm under the condition that the learning rate belongs to a specified range defining the stability domain. Satisfying such condition, unstable phenomena during the learning process are avoided. A Lyapunov analysis leads to the computation of the expression of a convenient adaptive learning rate verifying the convergence stability criteria. Finally, the elaborated training algorithm is applied in several simulations. The results confirm the effectiveness of the CSBP algorithm.
FINANCIAL SYSTEM STRUCTURE AND STABILITY DURING TRANSITION
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Firtescu Bogdan
2012-07-01
Full Text Available The process of transition from socialist economy to market economy was not considered an end in itself, but a necessity, and standing proof to achieve high levels of sustainable development. All former socialist countries are characterized by an early transition recession transformation result of the restructuring, loss of markets, tough competition from foreign products, best quality, or in other cases cheaper. To express the financial system structure in transition we take into discussion data that reflects representatives mutations and restructuring in Central and Eastern European countries, such Bulgaria, Czech Republic, Hungary, Poland and Romania. For all countries we show some important changes of financial system during transition and construct an image matrix that illustrates important indicators of financial system structure and their adjustment.
INERTIAL TECHNOLOGIES IN SYSTEMS FOR STABILIZATION OF GROUND VEHICLES EQUIPMENT
Directory of Open Access Journals (Sweden)
Olha Sushchenko
2016-12-01
Full Text Available Purpose: The vibratory inertial technology is a recent modern inertial technology. It represents the most perspective approach to design of inertial sensors, which can be used in stabilization and tracking systems operated on vehicles of the wide class. The purpose of the research is to consider advantages of this technology in comparison with laser and fiber-optic ones. Operation of the inertial sensors on the ground vehicles requires some improvement of the Coriolis vibratory gyroscope with the goal to simplify information processing, increase reliability, and compensate bias. Methods: Improvement of the Coriolis vibratory gyroscope includes introducing of the phase detector and additional excitation unit. The possibility to use the improved Coriolis vibratory gyroscope in the stabilization systems operated on the ground vehicles is shown by means of analysis of gyroscope output signal. To prove efficiency of the Coriolis vibratory gyroscope in stabilization system the simulation technique is used. Results: The scheme of the improved Coriolis vibratory gyroscope including the phase detector and additional excitation unit is developed and analyzed. The way to compensate bias is determined. Simulation of the stabilization system with the improved Coriolis vibratory gyroscope is carried out. Expressions for the output signals of the improved Coriolis vibratory gyroscope are derived. The error of the output signal is estimated and the possibility to use the modified Coriolis vibratory gyroscope in stabilization systems is proved. The results of stabilization system simulation are given. Their analysis is carried out. Conclusions: The represented results prove efficiency of the proposed technical decisions. They can be useful for design of stabilization platform with instrumental equipment operated on moving vehicles of the wide class.
Stakeholder Attitudes, Knowledge and Engagement in Local Road Systems Planning and Decision Making
2017-10-01
Political and policy dynamics associated with local road systems planning, management, and financing merit special attention. This study: 1) analyzes stakeholder attitudes, knowledge, and engagement about financing for local road system management, t...
Robust stability bounds for multi-delay networked control systems
Seitz, Timothy; Yedavalli, Rama K.; Behbahani, Alireza
2018-04-01
In this paper, the robust stability of a perturbed linear continuous-time system is examined when controlled using a sampled-data networked control system (NCS) framework. Three new robust stability bounds on the time-invariant perturbations to the original continuous-time plant matrix are presented guaranteeing stability for the corresponding discrete closed-loop augmented delay-free system (ADFS) with multiple time-varying sensor and actuator delays. The bounds are differentiated from previous work by accounting for the sampled-data nature of the NCS and for separate communication delays for each sensor and actuator, not a single delay. Therefore, this paper expands the knowledge base in multiple inputs multiple outputs (MIMO) sampled-data time delay systems. Bounds are presented for unstructured, semi-structured, and structured perturbations.
Transient stability risk assessment of power systems incorporating wind farms
DEFF Research Database (Denmark)
Miao, Lu; Fang, Jiakun; Wen, Jinyu
2013-01-01
fed induction generator has been established. Wind penetration variation and multiple stochastic factors of power systems have been considered. The process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been proposed......Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power systems. This paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment methods. The detailed model of double....... An investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed....
Competition and system stability -- The reward and the penalty
International Nuclear Information System (INIS)
Mansour, Y.
2000-01-01
The business protocols and rules of the competitive electricity market are resulting in fragmentation of the historical vertically integrated structures. Electric services are offered at either cost or market-based prices depending on their type and the level of competition in a particular product. System stabilizing measures are essential for maintaining system security, yet their value is either underestimated or not understood. This paper describes practical methods to quantify the value of some of the stabilizing measures and ways to ensure maintaining the dynamic security of the power systems through business procedures and monetary sanctions
FINANCIAL STABILITY OF THE UKRAINE NATIONAL SYSTEM OF PENSION INSURANCE
Directory of Open Access Journals (Sweden)
A. Khemii
2014-03-01
Full Text Available The system of pension insurance is a combination of created by the state legal, economic and organizational institutions and norms, providing financial support to citizens in the form of pensions. In the article analyzing the demographic situation and the condition of pension payments in the country today. In the terms of economic and social reforms, the level of financial stability the pension system is low. Therefore important is the analysis and exploring new methods to ensure financial stability of the Ukraine national system of pension insurance. The main institution of the national pension insurance is the National Pension Fund of Ukraine.
On stability of accelerator driven systems
International Nuclear Information System (INIS)
Makai, Mihaly
2003-01-01
An unsolved problem of energy production in nuclear reactors is the waste management. A large portion of the nuclear waste is the spent fuel. At present, two possibilities are seen. The first one is to 'wrap up' all the radioactive waste safely and to bury it at a remote quiet place where it can rest undisturbed until its activity decreases to a tolerable level. The second one is to exploit the excitation energy still present in the nuclear waste. In order to release that energy, the spent fuel is bombarded by high energy particles obtained from an accelerator. The resulting system is called accelerator driven system (ADS). In an ADS, the spent fuel forms a subcritical reactor, which is driven by an external source. (author)
Stability of time-delay systems via Lyapunov functions
Directory of Open Access Journals (Sweden)
Carlos F. Alastruey
2002-01-01
Full Text Available In this paper, a Lyapunov function candidate is introduced for multivariable systems with inner delays, without assuming a priori stability for the nondelayed subsystem. By using this Lyapunov function, a controller is deduced. Such a controller utilizes an input–output description of the original system, a circumstance that facilitates practical applications of the proposed approach.
On stability of fixed points and chaos in fractional systems
Edelman, Mark
2018-02-01
In this paper, we propose a method to calculate asymptotically period two sinks and define the range of stability of fixed points for a variety of discrete fractional systems of the order 0 logistic maps. Based on our analysis, we make a conjecture that chaos is impossible in the corresponding continuous fractional systems.
A real-time BWR stability measurement system
International Nuclear Information System (INIS)
March-Leuba, J.; King, W.T.
1988-01-01
This paper describes the characteristics of a portable, real-time system used for nonperturbational measurements of stability in boiling water reactors. The algorithm used in this system estimates the closed-loop asymptotic decay ratio using only the naturally occurring neutron noise and it is based on the univariate autoregressive methodology. (author)
Criteria for stability of linear dynamical systems with multiple delays ...
African Journals Online (AJOL)
In this study we considered a linear Dynamical system with multiple delays and find suitable conditions on the systems parameters such that for a given initial function, we can define a mapping in a carefully chosen complete metric space on which the mapping has a unique fixed point. An asymptotic stability theory for the ...
On stability of fixed points and chaos in fractional systems.
Edelman, Mark
2018-02-01
In this paper, we propose a method to calculate asymptotically period two sinks and define the range of stability of fixed points for a variety of discrete fractional systems of the order 0chaos is impossible in the corresponding continuous fractional systems.
Akinyemi, Felicia O.
2016-01-01
Technology use is evident in all spheres of human endeavour. Focusing on technology use in education, this paper examines teachers' attitudes towards geographic information system (GIS). An assessment was made of GIS teachers in Rwandan secondary schools. Key areas covered include how GIS is implemented in schools, teachers' attitudes and…
Stabilization of third-order bilinear systems using constant controls
Directory of Open Access Journals (Sweden)
A. E. Golubev
2014-01-01
Full Text Available This paper deals with the zero equilibrium stabilization for dynamical systems that have control input singularities. A dynamical system with scalar control input is called nonregular if the coefficient of input becomes null on a subset of the phase space that contains the origin. One of the classes of nonregular dynamical systems is represented by bilinear systems. In case of second-order bilinear systems the necessary and sufficient conditions for the zero equilibrium stabilizability are known in the literature. However, in general case the stabilization problem in the presence of control input singularities has not been solved yet.In this note we solve the problem of the zero equilibrium stabilization for the third-order bilinear dynamical systems given in a canonical form. The solution is found in the class of constant controls. The necessary and sufficient conditions are obtained for the zero equilibrium stabilizability of the bilinear systems in question.The dependence of the zero equilibrium stabilizability on system parameter values is analyzed. The general criteria of stabilizability by means of constant controls are given for the bilinear systems in question. In case when all the system parameters have nonzero values the necessary and sufficient stabilizability conditions are proved. The case when some of the parameters are equal to zero is also considered.Further research can be focused on extending the obtained results to a higher-order case of bilinear and affine dynamical systems. The solution of the considered stabilization problem should also be found not only within constant controls but also in a class of state feedbacks, particularly, in the case when stabilizing constant control does not exist.One of the potential application areas for the obtained theoretical results is automatic control of technical plants like unmanned aerial vehicles and mobile robots.
Directory of Open Access Journals (Sweden)
Jeevanandham Arumugam
2009-01-01
Full Text Available In this paper a classical lead-lag power system stabilizer is used for demonstration. The stabilizer parameters are selected in such a manner to damp the rotor oscillations. The problem of selecting the stabilizer parameters is converted to a simple optimization problem with an eigen value based objective function and it is proposed to employ simulated annealing and particle swarm optimization for solving the optimization problem. The objective function allows the selection of the stabilizer parameters to optimally place the closed-loop eigen values in the left hand side of the complex s-plane. The single machine connected to infinite bus system and 10-machine 39-bus system are considered for this study. The effectiveness of the stabilizer tuned using the best technique, in enhancing the stability of power system. Stability is confirmed through eigen value analysis and simulation results and suitable heuristic technique will be selected for the best performance of the system.
Gyroscopic stabilization and indefimite damped systems
DEFF Research Database (Denmark)
Pommer, Christian
a class of feasibel skew-Hermitian matrices A depending on the choise of M. The theory can be applied to dynamical systems of the form x''(t) + ( dD + g G) x'(t) + K x(t) = 0 where G is a skew symmetric gyrocopic matrix, D is a symmetric indefinite damping matrix and K > 0 is a positive definite stiffness......An important issue is how to modify a given unstable matrix in such a way that the resulting matrix is stable. We investigate in general under which condition a matrix M+A is stable,where M is an arbitrary matrix and A is skew-Hermitian. We show that if trace(M) > 0 it is always possible to find...
Robust stabilization of nonlinear systems: The LMI approach
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iljak D. D.
2000-01-01
Full Text Available This paper presents a new approach to robust quadratic stabilization of nonlinear systems within the framework of Linear Matrix Inequalities (LMI. The systems are composed of a linear constant part perturbed by an additive nonlinearity which depends discontinuously on both time and state. The only information about the nonlinearity is that it satisfies a quadratic constraint. Our major objective is to show how linear constant feedback laws can be formulated to stabilize this type of systems and, at the same time, maximize the bounds on the nonlinearity which the system can tolerate without going unstable. We shall broaden the new setting to include design of decentralized control laws for robust stabilization of interconnected systems. Again, the LMI methods will be used to maximize the class of uncertain interconnections which leave the overall system connectively stable. It is useful to learn that the proposed LMI formulation “recognizes” the matching conditions by returning a feedback gain matrix for any prescribed bound on the interconnection terms. More importantly, the new formulation provides a suitable setting for robust stabilization of nonlinear systems where the nonlinear perturbations satisfy the generalized matching conditions.
Power system stability enhancement using facts controllers: a review
International Nuclear Information System (INIS)
Abido, M. A
2009-01-01
In recent years, power demand has increased substantially while the expansion of power generation and transmission has been severely limited due to limited resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a power transfer-limiting factor. Flexible AC transmission systems (FACTS) controllers have been mainly used for solving various power system steady state control problems. However, recent studies reveal that FACTS controllers could be employed to enhance power system stability in addition to their main function of power flow control. The literature shows an increasing interest in this subject for the last two decades, where the enhancement of system stability using FACTS controllers has been extensively investigated. This paper presents a comprehensive review on the research and developments in the power system stability enhancement using FACTS damping controllers. Several technical issues related to FACTS installations have been highlighted and performance comparison of different FACTS controllers has been discussed. In addition, some of the utility experience, real-world installations, and semiconductor technology development have been reviewed and summarized. Applications of FACTS to other power system studies have also been discussed. About two hundred twenty seven research publications have been classified and appended for a quick reference. (author)
Differentiable dynamical systems an introduction to structural stability and hyperbolicity
Wen, Lan
2016-01-01
This is a graduate text in differentiable dynamical systems. It focuses on structural stability and hyperbolicity, a topic that is central to the field. Starting with the basic concepts of dynamical systems, analyzing the historic systems of the Smale horseshoe, Anosov toral automorphisms, and the solenoid attractor, the book develops the hyperbolic theory first for hyperbolic fixed points and then for general hyperbolic sets. The problems of stable manifolds, structural stability, and shadowing property are investigated, which lead to a highlight of the book, the \\Omega-stability theorem of Smale. While the content is rather standard, a key objective of the book is to present a thorough treatment for some tough material that has remained an obstacle to teaching and learning the subject matter. The treatment is straightforward and hence could be particularly suitable for self-study. Selected solutions are available electronically for instructors only. Please send email to textbooks@ams.org for more informatio...
A digital intensity stabilization system for HeNe laser
Wei, Zhimeng; Lu, Guangfeng; Yang, Kaiyong; Long, Xingwu; Huang, Yun
2012-02-01
A digital intensity stabilization system for HeNe laser is developed. Based on a switching power IC to design laser power supply and a general purpose microcontroller to realize digital PID control, the system constructs a closed loop to stabilize the laser intensity by regulating its discharge current. The laser tube is made of glass ceramics and its integrated structure is steady enough to eliminate intensity fluctuations at high frequency and attenuates all intensity fluctuations, and this makes it easy to tune the control loop. The control loop between discharge current and photodiode voltage eliminates the long-term drifts. The intensity stability of the HeNe laser with this system is 0.014% over 12 h.
Symmetry and stability of open quantum systems
International Nuclear Information System (INIS)
Scutaru, H.
1979-01-01
The presentation of the thesis involves an introduction and six chapters. Chapter 1 presents notions and results used in the other chpaters. Chapters 2-6 present our results which are focused on two notions: generalized observable and dynamic semigroup. These notions characterize a specific research domain (set up during the last 10 years) which is currently called quantum mechanics of open systems. The two notions (generalized observable and dynamic semigroup) are mathematically correlated. They belong to the set of completely positive linear applications among observable algebras. This fact, associated with that formulation of quantum mechanics according to which it is a special case of quantum mechanics namely, that for which the observable algebra is commutative, help to understand the similar essence of the results presented in chapter 2-6. Thus, the natural mathematical background has been achieved for our results; it is represented by that category whose objects are the observable algebras and whose morphisms are completely positive linear contractions generating unity within unity. These ideas are extensively presented in the introduction. The fact that the relations between classical mechanics and quantum mechanics can be rigorously treated as positive linear applications between classical observable algebras commutative and quantum observable algebras non-commutative, which are automatically fully positive, has been initially shown in our paper. (author)
Directory of Open Access Journals (Sweden)
Sang Cheol Lee
2016-12-01
Full Text Available This paper presents an algorithm for velocity-aided attitude estimation for helicopter aircraft using a microelectromechanical system inertial-measurement unit. In general, high- performance gyroscopes are used for estimating the attitude of a helicopter, but this type of sensor is very expensive. When designing a cost-effective attitude system, attitude can be estimated by fusing a low cost accelerometer and a gyro, but the disadvantage of this method is its relatively low accuracy. The accelerometer output includes a component that occurs primarily as the aircraft turns, as well as the gravitational acceleration. When estimating attitude, the accelerometer measurement terms other than gravitational ones can be considered as disturbances. Therefore, errors increase in accordance with the flight dynamics. The proposed algorithm is designed for using velocity as an aid for high accuracy at low cost. It effectively eliminates the disturbances of accelerometer measurements using the airspeed. The algorithm was verified using helicopter experimental data. The algorithm performance was confirmed through a comparison with an attitude estimate obtained from an attitude heading reference system based on a high accuracy optic gyro, which was employed as core attitude equipment in the helicopter.
Lee, Sang Cheol; Hong, Sung Kyung
2016-01-01
This paper presents an algorithm for velocity-aided attitude estimation for helicopter aircraft using a microelectromechanical system inertial-measurement unit. In general, high- performance gyroscopes are used for estimating the attitude of a helicopter, but this type of sensor is very expensive. When designing a cost-effective attitude system, attitude can be estimated by fusing a low cost accelerometer and a gyro, but the disadvantage of this method is its relatively low accuracy. The accelerometer output includes a component that occurs primarily as the aircraft turns, as well as the gravitational acceleration. When estimating attitude, the accelerometer measurement terms other than gravitational ones can be considered as disturbances. Therefore, errors increase in accordance with the flight dynamics. The proposed algorithm is designed for using velocity as an aid for high accuracy at low cost. It effectively eliminates the disturbances of accelerometer measurements using the airspeed. The algorithm was verified using helicopter experimental data. The algorithm performance was confirmed through a comparison with an attitude estimate obtained from an attitude heading reference system based on a high accuracy optic gyro, which was employed as core attitude equipment in the helicopter. PMID:27973429
Robust Stabilization of Nonlinear Systems with Uncertain Varying Control Coefficient
Directory of Open Access Journals (Sweden)
Zaiyue Yang
2014-01-01
Full Text Available This paper investigates the stabilization problem for a class of nonlinear systems, whose control coefficient is uncertain and varies continuously in value and sign. The study emphasizes the development of a robust control that consists of a modified Nussbaum function to tackle the uncertain varying control coefficient. By such a method, the finite-time escape phenomenon has been prevented when the control coefficient is crossing zero and varying its sign. The proposed control guarantees the asymptotic stabilization of the system and boundedness of all closed-loop signals. The control performance is illustrated by a numerical simulation.
Stability of DC Voltage Droop Controllers in VSC HVDC Systems
DEFF Research Database (Denmark)
Thams, Florian; Suul, Jon Are; D’Arco, Salvatore
2015-01-01
Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control implementations have been proposed in literature. This paper first classifies possible dc droop implementations in a simple framework. Then, the small-signal stability of a VSC-based conver......Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control implementations have been proposed in literature. This paper first classifies possible dc droop implementations in a simple framework. Then, the small-signal stability of a VSC...
Indefinite damping in mechanical systems and gyroscopic stabilization
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian
2009-01-01
This paper deals with gyroscopic stabilization of the unstable system Mx + D(x) over dot + K-x = 0, with positive definite mass and stiffness matrices M and K, respectively, and an indefinite damping matrix D. The main question if for which skew-symmetric matrices G the system Mx (D+ G)(x) over dot...... + K-x = 0 can become stable? After investigating special cases we find an appropriat solution of the Lyapunov matrix equation for the general case. Examples show the deviation of the stability limit found by the Lyapunov method from the exact value....
Prinzel, Lawrence J., III; Ellis, Kyle E.; Arthur, Jarvis J.; Nicholas, Stephanie N.; Kiggins, Daniel
2017-01-01
A Commercial Aviation Safety Team (CAST) study of 18 worldwide loss-of-control accidents and incidents determined that the lack of external visual references was associated with a flight crew's loss of attitude awareness or energy state awareness in 17 of these events. Therefore, CAST recommended development and implementation of virtual day-Visual Meteorological Condition (VMC) display systems, such as synthetic vision systems, which can promote flight crew attitude awareness similar to a day-VMC environment. This paper describes the results of a high-fidelity, large transport aircraft simulation experiment that evaluated virtual day-VMC displays and a "background attitude indicator" concept as an aid to pilots in recovery from unusual attitudes. Twelve commercial airline pilots performed multiple unusual attitude recoveries and both quantitative and qualitative dependent measures were collected. Experimental results and future research directions under this CAST initiative and the NASA "Technologies for Airplane State Awareness" research project are described.
On the stability of boundary layers in gas mantle systems
International Nuclear Information System (INIS)
Ohlsson, D.
1978-10-01
In this thesis a systematic investigation of the stability properties of the partially ionized boundary regions of gas mantle systems for a large class of dissipative magneto-hydrodynamic modes is presented. In the partially ionized boundary regions of gas mantle systems several strong stabilizing mechanisms arise due to coupling between various dissipative effects in certain parameter regions. The presence of neutral gas strongly enhances the stabilizing effects in a dual fashion. First in an indirect way by cooling the edge region and second in a direct way by enhancing viscous and heat conduction effects. It has, however, to be pointed out that exceptions from this general picture may be found. The stabilizing influence of neutral gas on a large class of electrostatic as well as electromagnetic modes in the boundary regions of gas blanket systems is contrary to what has been found in low density weakly ionized plasmas. In these latter cases presence of neutral gas has even been found to be responsible for the onset of entirely new classes of instabilities. Thus there is no universal stabilizing or destabilizing effect associated with plasma-neutral gas interaction effects. (author)
Congestion management enhancing transient stability of power systems
International Nuclear Information System (INIS)
Esmaili, Masoud; Shayanfar, Heidar Ali; Amjady, Nima
2010-01-01
In a competitive electricity market, where market parties try to maximize their profits, it is necessary to keep an acceptable level of power system security to retain the continuity of electricity services to customers at a reasonable cost. Congestion in a power system is turned up due to network limits. After relieving congestion, the network may be operated with a reduced transient stability margin because of increasing the contribution of risky participants. In this paper, a novel congestion management method based on a new transient stability criterion is introduced. Using the sensitivity of corrected transient stability margin with respect to generations and demands, the proposed method so alleviates the congestion that the network can more retain its transient security compared with earlier methods. The proposed transient stability index is constructed considering the likelihood of credible faults. Indeed, market parties participate by their security-effective bids rather than raw bids. Results of testing the proposed method along with the earlier ones on the New-England test system elaborate the efficiency of the proposed method from the viewpoint of providing a better transient stability margin with a lower security cost. (author)
Stability of Nonlinear Systems with Unknown Time-varying Feedback Delay
Chunodkar, Apurva A.; Akella, Maruthi R.
2013-12-01
This paper considers the problem of stabilizing a class of nonlinear systems with unknown bounded delayed feedback wherein the time-varying delay is 1) piecewise constant 2) continuous with a bounded rate. We also consider application of these results to the stabilization of rigid-body attitude dynamics. In the first case, the time-delay in feedback is modeled specifically as a switch among an arbitrarily large set of unknown constant values with a known strict upper bound. The feedback is a linear function of the delayed states. In the case of linear systems with switched delay feedback, a new sufficiency condition for average dwell time result is presented using a complete type Lyapunov-Krasovskii (L-K) functional approach. Further, the corresponding switched system with nonlinear perturbations is proven to be exponentially stable inside a well characterized region of attraction for an appropriately chosen average dwell time. In the second case, the concept of the complete type L-K functional is extended to a class of nonlinear time-delay systems with unknown time-varying time-delay. This extension ensures stability robustness to time-delay in the control design for all values of time-delay less than the known upper bound. Model-transformation is used in order to partition the nonlinear system into a nominal linear part that is exponentially stable with a bounded perturbation. We obtain sufficient conditions which ensure exponential stability inside a region of attraction estimate. A constructive method to evaluate the sufficient conditions is presented together with comparison with the corresponding constant and piecewise constant delay. Numerical simulations are performed to illustrate the theoretical results of this paper.
PWL approximation of nonlinear dynamical systems, part I: structural stability
International Nuclear Information System (INIS)
Storace, M; De Feo, O
2005-01-01
This paper and its companion address the problem of the approximation/identification of nonlinear dynamical systems depending on parameters, with a view to their circuit implementation. The proposed method is based on a piecewise-linear approximation technique. In particular, this paper describes the approximation method and applies it to some particularly significant dynamical systems (topological normal forms). The structural stability of the PWL approximations of such systems is investigated through a bifurcation analysis (via continuation methods)
AC system stabilization via phase shift transformer with thyristor commutation
Energy Technology Data Exchange (ETDEWEB)
Oliveira, Jose Carlos de; Guimaraes, Geraldo Caixeta; Moraes, Adelio Jose [Uberlandia Univ., MG (Brazil); Abreu, Jose Policarpo G. de [Escola Federal de Engenharia de Itajuba, MG (Brazil); Oliveira, Edimar Jose de [Juiz de Fora Univ., MG (Brazil)
1994-12-31
This article aims to present initially the constructive and operative forms of a phase-shift autotransformer which provides both magnitude and phase angle change through thyristor commutation, including a technic to reduce the number of thyristors. Following, it is proposed a control system to make such equipment an efficient AC system stabilizing tool. It is presented some simulation results to show the operation of this transformer in an electrical system. (author) 3 refs., 11 figs., 3 tabs.
Stabilization of discrete-time LTI positive systems
Directory of Open Access Journals (Sweden)
Krokavec Dušan
2017-12-01
Full Text Available The paper mitigates the existing conditions reported in the previous literature for control design of discrete-time linear positive systems. Incorporating an associated structure of linear matrix inequalities, combined with the Lyapunov inequality guaranteing asymptotic stability of discrete-time positive system structures, new conditions are presented with which the state-feedback controllers and the system state observers can be designed. Associated solutions of the proposed design conditions are illustrated by numerical illustrative examples.
Passivity Based Stabilization of Non-minimum Phase Nonlinear Systems
Czech Academy of Sciences Publication Activity Database
Travieso-Torres, J.C.; Duarte-Mermoud, M.A.; Zagalak, Petr
2009-01-01
Roč. 45, č. 3 (2009), s. 417-426 ISSN 0023-5954 R&D Projects: GA ČR(CZ) GA102/07/1596 Institutional research plan: CEZ:AV0Z10750506 Keywords : nonlinear systems * stabilisation * passivity * state feedback Subject RIV: BC - Control Systems Theory Impact factor: 0.445, year: 2009 http://library.utia.cas.cz/separaty/2009/AS/zagalak-passivity based stabilization of non-minimum phase nonlinear systems.pdf
Wavelength stabilized multi-kW diode laser systems
Köhler, Bernd; Unger, Andreas; Kindervater, Tobias; Drovs, Simon; Wolf, Paul; Hubrich, Ralf; Beczkowiak, Anna; Auch, Stefan; Müntz, Holger; Biesenbach, Jens
2015-03-01
We report on wavelength stabilized high-power diode laser systems with enhanced spectral brightness by means of Volume Holographic Gratings. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications with small absorption bandwidths. Wavelength stabilization of high-power diode laser systems is an important method to increase the efficiency of diode pumped solid-state lasers. It also enables power scaling by dense wavelength multiplexing. To ensure a wide locking range and efficient wavelength stabilization the parameters of the Volume Holographic Grating and the parameters of the diode laser bar have to be adapted carefully. Important parameters are the reflectivity of the Volume Holographic Grating, the reflectivity of the diode laser bar as well as its angular and spectral emission characteristics. In this paper we present detailed data on wavelength stabilized diode laser systems with and without fiber coupling in the spectral range from 634 nm up to 1533 nm. The maximum output power of 2.7 kW was measured for a fiber coupled system (1000 μm, NA 0.22), which was stabilized at a wavelength of 969 nm with a spectral width of only 0.6 nm (90% value). Another example is a narrow line-width diode laser stack, which was stabilized at a wavelength of 1533 nm with a spectral bandwidth below 1 nm and an output power of 835 W.
A Recursive Fuzzy System for Efficient Digital Image Stabilization
Directory of Open Access Journals (Sweden)
Nikolaos Kyriakoulis
2008-01-01
Full Text Available A novel digital image stabilization technique is proposed in this paper. It is based on a fuzzy Kalman compensation of the global motion vector (GMV, which is estimated in the log-polar plane. The GMV is extracted using four local motion vectors (LMVs computed on respective subimages in the logpolar plane. The fuzzy Kalman system consists of a fuzzy system with the Kalman filter's discrete time-invariant definition. Due to this inherited recursiveness, the output results into smoothed image sequences. The proposed stabilization system aims to compensate any oscillations of the frame absolute positions, based on the motion estimation in the log-polar domain, filtered by the fuzzy Kalman system, and thus the advantages of both the fuzzy Kalman system and the log-polar transformation are exploited. The described technique produces optimal results in terms of the output quality and the level of compensation.
An Application of UAV Attitude Estimation Using a Low-Cost Inertial Navigation System
Eure, Kenneth W.; Quach, Cuong Chi; Vazquez, Sixto L.; Hogge, Edward F.; Hill, Boyd L.
2013-01-01
Unmanned Aerial Vehicles (UAV) are playing an increasing role in aviation. Various methods exist for the computation of UAV attitude based on low cost microelectromechanical systems (MEMS) and Global Positioning System (GPS) receivers. There has been a recent increase in UAV autonomy as sensors are becoming more compact and onboard processing power has increased significantly. Correct UAV attitude estimation will play a critical role in navigation and separation assurance as UAVs share airspace with civil air traffic. This paper describes attitude estimation derived by post-processing data from a small low cost Inertial Navigation System (INS) recorded during the flight of a subscale commercial off the shelf (COTS) UAV. Two discrete time attitude estimation schemes are presented here in detail. The first is an adaptation of the Kalman Filter to accommodate nonlinear systems, the Extended Kalman Filter (EKF). The EKF returns quaternion estimates of the UAV attitude based on MEMS gyro, magnetometer, accelerometer, and pitot tube inputs. The second scheme is the complementary filter which is a simpler algorithm that splits the sensor frequency spectrum based on noise characteristics. The necessity to correct both filters for gravity measurement errors during turning maneuvers is demonstrated. It is shown that the proposed algorithms may be used to estimate UAV attitude. The effects of vibration on sensor measurements are discussed. Heuristic tuning comments pertaining to sensor filtering and gain selection to achieve acceptable performance during flight are given. Comparisons of attitude estimation performance are made between the EKF and the complementary filter.
Harmonics and voltage stability analysis in power systems including
Indian Academy of Sciences (India)
In this study, non-sinusoidal quantities and voltage stability, both known as power quality criteria, are examined together in detail. The widespread use of power electronics elements cause the existence of signiﬁcant non-sinusoidal quantities in the system. These non-sinusoidal quantities can create serious harmonic ...
Stability analysis of nonlinear systems with slope restricted nonlinearities.
Liu, Xian; Du, Jiajia; Gao, Qing
2014-01-01
The problem of absolute stability of Lur'e systems with sector and slope restricted nonlinearities is revisited. Novel time-domain and frequency-domain criteria are established by using the Lyapunov method and the well-known Kalman-Yakubovich-Popov (KYP) lemma. The criteria strengthen some existing results. Simulations are given to illustrate the efficiency of the results.
Stability Analysis of Nonlinear Systems with Slope Restricted Nonlinearities
Directory of Open Access Journals (Sweden)
Xian Liu
2014-01-01
Full Text Available The problem of absolute stability of Lur’e systems with sector and slope restricted nonlinearities is revisited. Novel time-domain and frequency-domain criteria are established by using the Lyapunov method and the well-known Kalman-Yakubovich-Popov (KYP lemma. The criteria strengthen some existing results. Simulations are given to illustrate the efficiency of the results.
Asymptotic stability results for retarded differential systems | Igobi ...
African Journals Online (AJOL)
... matrices are used in formulating a Lyapunov functional. The introduction of convex set segment of a symmetric matrix is explored to establish boundedness of the first derivative of the formulated functional. The integral-differential equation is utilized in computing the maximum delay interval for the system to attain stability.
Stability of Rotor Systems: A Complex Modelling Approach
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob
1996-01-01
A large class of rotor systems can be modelled by a complex matrix differential equation of secondorder. The angular velocity of the rotor plays the role of a parameter. We apply the Lyapunov matrix equation in a complex setting and prove two new stability results which are compared...
Stability Analysis for Multi-Parameter Linear Periodic Systems
DEFF Research Database (Denmark)
Seyranian, A.P.; Solem, Frederik; Pedersen, Pauli
1999-01-01
This paper is devoted to stability analysis of general linear periodic systems depending on real parameters. The Floquet method and perturbation technique are the basis of the development. We start out with the first and higher-order derivatives of the Floquet matrix with respect to problem...
Robust stabilization of nonlinear systems by quantized and ternary control
Persis, Claudio De
2009-01-01
Results on the problem of stabilizing a nonlinear continuous-time minimum-phase system by a finite number of control or measurement values are presented. The basic tool is a discontinuous version of the so-called semi-global backstepping lemma. We derive robust practical stabilizability results by
Hyper-XACT, A Long-Life, High-Performance Attitude Determination & Control System
National Aeronautics and Space Administration — The Hyper-XACT is intended to extend the capabilities of CubeSat attitude control systems for longer duration missions with tighter performance requirements by...
Stochastic stability of four-wheel-steering system
International Nuclear Information System (INIS)
Huang Dongwei; Wang Hongli; Zhu Zhiwen; Feng Zhang
2007-01-01
A four-wheel-steering system subjected to white noise excitations was reduced to a two-degree-of-freedom quasi-non-integrable-Hamiltonian system. Subsequently we obtained an one-dimensional Ito stochastic differential equation for the averaged Hamiltonian of the system by using the stochastic averaging method for quasi-non-integrable-Hamiltonian systems. Thus, the stochastic stability of four-wheel-steering system was analyzed by analyzing the sample behaviors of the averaged Hamiltonian at the boundary H = 0 and calculating its Lyapunov exponent. An example given at the end demonstrated that the conclusion obtained is of considerable significance
Junaidi, Agus; Hamid, K. Abdul
2018-03-01
This paper will discuss the use of optimal control and Power System Stabilizer (PSS) in improving the oscillation of electric power system. Oscillations in the electric power system can occur due to the sudden release of the load (Switcing-Off). The oscillation of an unstable system for a long time causes the equipment to work in an interruption. To overcome this problem, a control device is required that can work effectively in repairing the oscillation. The power system is modeled from the Single Machine Infinite Bus Model (SMIB). The state space equation is used to mathematically model SMIB. SMIB system which is a plant will be formed togetherness state variables (State-Space), using riccati equation then determined the optimal gain as controller plant. Plant is also controlled by Power Stabilizer System using phase compensation method. Using Matlab Software based simulation will be observed response of rotor speed change and rotor angle change for each of the two controlling methods. Simulation results using the Simulink-MATLAB 6.1 software will compare the analysis of the plant state in Open loop state and use the controller. The simulation response shows that the optimal control and PSS can improve the stability of the power system in terms of acceleration to achieve settling-time and Over Shoot improvement. From the results of both methods are able to improve system performance.
A field experiment on power line stabilization by SMES system
International Nuclear Information System (INIS)
Irie, F.; Takeo, M.; Sato, S.; Katahira, O.; Fukui, F.; Takamatsu, M.
1992-01-01
In this paper field experiments on stabilization of a hydro power plant by a SMES system are reported, where a generator having a rating of 60 kW at 3.3kV is connected to a 6.6kV power distribution line. The SMES system is composed of two 30kVA GTO convertors and a superconducting magnet system with an energy of 30kJ at 100A. Experiments of stabilization for the generator fluctuation caused by a sudden insertion of inductors in the line are successfully performed for some control modes. The value of the SMES system to compensate for a short period voltage dip is also confirmed
Stabilization of computational procedures for constrained dynamical systems
Park, K. C.; Chiou, J. C.
1988-01-01
A new stabilization method of treating constraints in multibody dynamical systems is presented. By tailoring a penalty form of the constraint equations, the method achieves stabilization without artificial damping and yields a companion matrix differential equation for the constraint forces; hence, the constraint forces are obtained by integrating the companion differential equation for the constraint forces in time. A principal feature of the method is that the errors committed in each constraint condition decay with its corresponding characteristic time scale associated with its constraint force. Numerical experiments indicate that the method yields a marked improvement over existing techniques.
QFT Framework for Robust Tuning of Power System Stabilizers
DEFF Research Database (Denmark)
Alavi, Seyyed Mohammad Mahdi; Izadi-Zamanabadi, Roozbeh
2005-01-01
This paper discusses the use of conventional quantitative feedback design for Power System Stabilizer (PSS). An appropriate control structure of the PSS that is directly applicable to PSS, is described. Two desired performances are also proposed in order to achieve an overall improvement in damping...... and robustness. The efficiency of the proposed method is demonstrated on Single Machine Infinite Bus (SMIB) power system with level of uncertainty....
The Use of Nuclear Generation to Provide Power System Stability
Heather Wyman-Pain; Yuankai Bian; Furong Li
2016-01-01
The decreasing use of fossil fuel power stations has a negative effect on the stability of the electricity systems in many countries. Nuclear power stations have traditionally provided minimal ancillary services to support the system but this must change in the future as they replace fossil fuel generators. This paper explains the development of the four most popular reactor types still in regular operation across the world which have formed the basis for most reactor dev...
Stability properties of cold blanket systems for current driven modes
International Nuclear Information System (INIS)
Ohlsson, D.
1977-12-01
The stability problem of the boundary regions of cold blanket systems with induced currents parallel to the lines of force is formulated. Particular interest is focused on two types of modes: first electrostatic modes driven by the combined effects of a transverse resistivity gradient due to a spatially non-uniform electron temperature and a longitudinal current, second electromagnetic kink like modes driven by the torque arising from a transverse current density gradient and magnetic field perturbations. It is found that the combination of various dissipative and neutral gas effects introduces strong stabilizing effects within specific parameter ranges. For particular steady-state models investigated it is shown that these effects become of importance in laboratory plasmas at relatively high densities, low temperatures and moderate magnetic field strengths. Stability diagrams based on specific steady-state cold plasma blanket models will be presented
Stability Analysis of Periodic Systems by Truncated Point Mappings
Guttalu, R. S.; Flashner, H.
1996-01-01
An approach is presented deriving analytical stability and bifurcation conditions for systems with periodically varying coefficients. The method is based on a point mapping(period to period mapping) representation of the system's dynamics. An algorithm is employed to obtain an analytical expression for the point mapping and its dependence on the system's parameters. The algorithm is devised to derive the coefficients of a multinominal expansion of the point mapping up to an arbitrary order in terms of the state variables and of the parameters. Analytical stability and bifurcation condition are then formulated and expressed as functional relations between the parameters. To demonstrate the application of the method, the parametric stability of Mathieu's equation and of a two-degree of freedom system are investigated. The results obtained by the proposed approach are compared to those obtained by perturbation analysis and by direct integration which we considered to the "exact solution". It is shown that, unlike perturbation analysis, the proposed method provides very accurate solution even for large valuesof the parameters. If an expansion of the point mapping in terms of a small parameter is performed the method is equivalent to perturbation analysis. Moreover, it is demonstrated that the method can be easily applied to multiple-degree-of-freedom systems using the same framework. This feature is an important advantage since most of the existing analysis methods apply mainly to single-degree-of-freedom systems and their extension to higher dimensions is difficult and computationally cumbersome.
Asymptotic stabilization of nonlinear systems using state feedback
International Nuclear Information System (INIS)
D'Attellis, Carlos
1990-01-01
This paper studies the design of state-feedback controllers for the stabilization of single-input single-output nonlinear systems x = f(x) + g(x)u, y = h(x). Two approaches for the stabilization problem are given; the asymptotic stability is achieved by means of: a) nonlinear state feedback: two nonlinear feedbacks are used; the first separates the system in a controllable linear part and in the zeros-dynamic part. The second feedback generates an asymptotically stable equilibrium on the manifold where this dynamics evolves; b) nonlinear dynamic feedback: conditions are established under which the system can follow the output of a completely controllable bilinear system which uses bounded controls. This fact enables the system to reach, using bounded controls too, a desired output value in finite time. As this value corresponds to a state that lays in the attraction basin of a stable equilibrium with the same output, the system evolves to that point. The two methods are illustrated by examples. (Author) [es
An Effective Distributed Model for Power System Transient Stability Analysis
Directory of Open Access Journals (Sweden)
MUTHU, B. M.
2011-08-01
Full Text Available The modern power systems consist of many interconnected synchronous generators having different inertia constants, connected with large transmission network and ever increasing demand for power exchange. The size of the power system grows exponentially due to increase in power demand. The data required for various power system applications have been stored in different formats in a heterogeneous environment. The power system applications themselves have been developed and deployed in different platforms and language paradigms. Interoperability between power system applications becomes a major issue because of the heterogeneous nature. The main aim of the paper is to develop a generalized distributed model for carrying out power system stability analysis. The more flexible and loosely coupled JAX-RPC model has been developed for representing transient stability analysis in large interconnected power systems. The proposed model includes Pre-Fault, During-Fault, Post-Fault and Swing Curve services which are accessible to the remote power system clients when the system is subjected to large disturbances. A generalized XML based model for data representation has also been proposed for exchanging data in order to enhance the interoperability between legacy power system applications. The performance measure, Round Trip Time (RTT is estimated for different power systems using the proposed JAX-RPC model and compared with the results obtained using traditional client-server and Java RMI models.
Handbook of electrical power system dynamics modeling, stability, and control
Eremia, Mircea
2013-01-01
Complete guidance for understanding electrical power system dynamics and blackouts This handbook offers a comprehensive and up-to-date treatment of power system dynamics. Addressing the full range of topics, from the fundamentals to the latest technologies in modeling, stability, and control, Handbook of Electrical Power System Dynamics provides engineers with hands-on guidance for understanding the phenomena leading to blackouts so they can design the most appropriate solutions for a cost-effective and reliable operation. Focusing on system dynamics, the book details
Stability of detecting system using NaI(Tl)
International Nuclear Information System (INIS)
Zhuo Yunshang; Lei Zhangyun; Zen Yu; Gong Hua
1996-01-01
A detecting system using NaI(Tl) is widely used in research and industry of nuclear science and other fields. For providing the high accuracy and working well under inclement environment, the stability of detecting system using NaI(Tl) is very important. The variation of environment temperature, the change of counting rate and long time continuous working of detector will cause un-negligible effect on the measurement. Three approaches were used. They are: 1) temperature control (It makes the effect of the variation of environment temperature on the measurement negligible.); 2) spectrum stabilizing (It adjust the peak position of the spectrum when the counting rate changes.); and 3) auto-checking and adjusting (It adjusts the drift of the NaI(Tl) detecting system when it works continuously)
Distributed-Order Dynamic Systems Stability, Simulation, Applications and Perspectives
Jiao, Zhuang; Podlubny, Igor
2012-01-01
Distributed-order differential equations, a generalization of fractional calculus, are of increasing importance in many fields of science and engineering from the behaviour of complex dielectric media to the modelling of nonlinear systems. This Brief will broaden the toolbox available to researchers interested in modeling, analysis, control and filtering. It contains contextual material outlining the progression from integer-order, through fractional-order to distributed-order systems. Stability issues are addressed with graphical and numerical results highlighting the fundamental differences between constant-, integer-, and distributed-order treatments. The power of the distributed-order model is demonstrated with work on the stability of noncommensurate-order linear time-invariant systems. Generic applications of the distributed-order operator follow: signal processing and viscoelastic damping of a mass–spring set up. A new general approach to discretization of distributed-order derivatives and integrals ...
Fixed-Time Stability of the Hydraulic Turbine Governing System
Directory of Open Access Journals (Sweden)
Caoyuan Ma
2018-01-01
Full Text Available This paper studies the problem of fixed-time stability of hydraulic turbine governing system with the elastic water hammer nonlinear model. To control and improve the quality of hydraulic turbine governing system, a new fixed-time control strategy is proposed, which can stabilize the water turbine governing system within a fixed time. Compared with the finite-time control strategy where the convergence rate depends on the initial state, the settling time of the fixed-time control scheme can be adjusted to the required value regardless of the initial conditions. Finally, we numerically show that the fixed-time control is more effective than and superior to the finite-time control.
Stability and Change in Americans’ Foreign Language Policy Attitudes: 2000-2008
Directory of Open Access Journals (Sweden)
John P. Robinson
2011-08-01
Full Text Available The last decade has seen unprecedented policy emphasis on the Less Commonly Taught Languages (LCTLs – whether broadly, as indicated by the regular publication of lists of languages critical to the national interest, such as that of the US Department of Education (2010, or in the particular languages included in the multiple new Federal programs that comprise the National Security Language Initiative (NSLI, such as the National Language Service Corps, STARTALK, the Language Flagship, the English for Heritage Language Speakers program, or the NSLI for Youth, to cite several examples. The LCTLs predominate in these lists, reflecting a national level policy emphasis on the LCTLs. This emphasis derives from perceived and actual needs for specific LCTLs required for the common weal – for national security, economic well being, and social justice (Brecht et al., 2007; Brecht & Rivers, 2000. This emphasis, consisting in its entirety of programs promulgated, funded, and directed by the Federal government, stands in contrast to the ongoing perception in our professional fields that Foreign Languages (FLs, and the LCTLs among them, are under increasing and unprecedented stress in the educational system, and that furthermore, that the teaching of LCTLs lacks public support, or is even actively opposed in the broader US society (Wiley, 2007.
Adoption of innovative heating systems. Needs and attitudes of Swedish homeowners
Energy Technology Data Exchange (ETDEWEB)
Mahapatra, K; Gustavsson, L [Ecotechnology, Mid Sweden University, 831 25 Oestersund (Sweden)
2009-11-15
Questionnaire surveys of Swedish homeowners of detached houses were carried out in 2004 and 2007 to understand their needs and attitudes towards attributes of innovative heating systems (IHSs) comprised of a bedrock heat pump, district heating, or a wood pellet boiler. In each occasion 1,500 homeowners were randomly selected. The response rate was 42% in 2004 and 48% in 2007. Results showed that the majority of the respondents were satisfied with their existing heating system and did not intend to install new systems. Economic factors and functional reliability were the most important factors in the respondents' choices of heating system, while environmental factors were of lower importance. Among the IHSs, respondents had the most favorable attitude towards bedrock heat pumps followed by district heating and pellet boilers. But the attitude was more favorable towards electric boilers than for pellet boilers. The least favorable attitude was towards oil boilers. Between 2004 and 2007, there was a positive change in respondents' attitude towards IHSs and electric boilers, and a negative change in attitude towards resistance heaters and oil boilers.
Stability properties of a general class of nonlinear dynamical systems
Gléria, I. M.; Figueiredo, A.; Rocha Filho, T. M.
2001-05-01
We establish sufficient conditions for the boundedness of the trajectories and the stability of the fixed points in a class of general nonlinear systems, the so-called quasi-polynomial vector fields, with the help of a natural embedding of such systems in a family of generalized Lotka-Volterra (LV) equations. A purely algebraic procedure is developed to determine such conditions. We apply our method to obtain new results for LV systems, by a reparametrization in time variable, and to study general nonlinear vector fields, originally far from the LV format.
Stability properties of a general class of nonlinear dynamical systems
Energy Technology Data Exchange (ETDEWEB)
Gleria, I.M. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: iram@ucb.br; Figueiredo, A. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: annibal@helium.fis.unb.br; Rocha, T.M. [Filho Instituto de Fisica, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, Brasilia (Brazil). E-mail: marciano@helium.fis.unb.br
2001-05-04
We establish sufficient conditions for the boundedness of the trajectories and the stability of the fixed points in a class of general nonlinear systems, the so-called quasi-polynomial vector fields, with the help of a natural embedding of such systems in a family of generalized Lotka-Volterra (LV) equations. A purely algebraic procedure is developed to determine such conditions. We apply our method to obtain new results for LV systems, by a reparametrization in time variable, and to study general nonlinear vector fields, originally far from the LV format. (author)
Optimal Subinterval Selection Approach for Power System Transient Stability Simulation
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Soobae Kim
2015-10-01
Full Text Available Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval time step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system.
The pointer basis and the feedback stabilization of quantum systems
International Nuclear Information System (INIS)
Li, L; Chia, A; Wiseman, H M
2014-01-01
The dynamics for an open quantum system can be ‘unravelled’ in infinitely many ways, depending on how the environment is monitored, yielding different sorts of conditioned states, evolving stochastically. In the case of ideal monitoring these states are pure, and the set of states for a given monitoring forms a basis (which is overcomplete in general) for the system. It has been argued elsewhere (Atkins et al 2005 Europhys. Lett. 69 163) that the ‘pointer basis’ as introduced by Zurek et al (1993 Phys. Rev. Lett. 70 1187), should be identified with the unravelling-induced basis which decoheres most slowly. Here we show the applicability of this concept of pointer basis to the problem of state stabilization for quantum systems. In particular we prove that for linear Gaussian quantum systems, if the feedback control is assumed to be strong compared to the decoherence of the pointer basis, then the system can be stabilized in one of the pointer basis states with a fidelity close to one (the infidelity varies inversely with the control strength). Moreover, if the aim of the feedback is to maximize the fidelity of the unconditioned system state with a pure state that is one of its conditioned states, then the optimal unravelling for stabilizing the system in this way is that which induces the pointer basis for the conditioned states. We illustrate these results with a model system: quantum Brownian motion. We show that even if the feedback control strength is comparable to the decoherence, the optimal unravelling still induces a basis very close to the pointer basis. However if the feedback control is weak compared to the decoherence, this is not the case. (paper)
Research on Handling Stability of Steering-by-wire System
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Yuan Ying
2017-01-01
Full Text Available The main function of steer-by-wire (SBW system are improving steering characteristics, security and stability of the vehicle. In this paper, the variable steering ratio of SBW system is analyzed, and the method of steering ratio based on fuzzy control and neural network are researched. In order to solve the actual working condition, the wheel angle may not reach the expected value, this paper establishes a twodegree-of-freedom (2-DOF vehicle model, and a Matlab/Simulink simulation model, in which a control strategy based on PID controller is put forward to control the front wheel steering angle. Simulation results show that proposed control strategy based on fuzzy neural network can effectively reduce lateral deviation and improve the handling stability and comfortability of the vehicle.
Linear Quantum Systems: Non-Classical States and Robust Stability
2016-06-29
modulation and entanglement in a compound gradient echo memory, Physical Review A 93(2) 023809 2016. We present a theoretical model for a Kerr...Carvalho, M. Hedges and M R James, Analysis of the operation of gradient echo memories using a quantum input-output model, New Journal of Physics , 15...new structured uncertainty methods that ensure robust stability of quantum systems based on nominal linear models, and (v) physical realizability
Stability of Bifurcating Stationary Solutions of the Artificial Compressible System
Teramoto, Yuka
2018-02-01
The artificial compressible system gives a compressible approximation of the incompressible Navier-Stokes system. The latter system is obtained from the former one in the zero limit of the artificial Mach number ɛ which is a singular limit. The sets of stationary solutions of both systems coincide with each other. It is known that if a stationary solution of the incompressible system is asymptotically stable and the velocity field of the stationary solution satisfies an energy-type stability criterion, then it is also stable as a solution of the artificial compressible one for sufficiently small ɛ . In general, the range of ɛ shrinks when the spectrum of the linearized operator for the incompressible system approaches to the imaginary axis. This can happen when a stationary bifurcation occurs. It is proved that when a stationary bifurcation from a simple eigenvalue occurs, the range of ɛ can be taken uniformly near the bifurcation point to conclude the stability of the bifurcating solution as a solution of the artificial compressible system.
An alternative soil nailing system for slope stabilization: Akarpiles
Lim, Chun-Lan; Chan, Chee-Ming
2017-11-01
This research proposes an innovative solution for slope stabilization with less environmental footprint: AKARPILES. In Malaysia, landslide has become common civil and environmental problems that cause impacts to the economy, safety and environment. Therefore, effective slope stabilization method helps to improve the safety of public and protect the environment. This study focused on stabilizing surfacial slope failure. The idea of AKARPILES was generated from the tree roots system in slope stabilization. After the piles are installed in the slope and intercepting the slip plane, grout was pumped in and discharged through holes on the piles. The grout then filled the pores in the soil with random flow within the slip zone. SKW mixture was used to simulate the soil slope. There were two designs being proposed in this study and the prototypes were produced by a 3D printer. Trial mix of the grout was carried out to obtain the optimum mixing ratio of bentonite: cement: water. A series of tests were conducted on the single-pile-reinforced slope under vertical slope crest loading condition considering different slope gradients and nail designs. Parameters such as ultimate load, failure time and failure strain were recorded and compared. As comparison with the unreinforced slope, both designs of AKARPILES showed better but different performances in the model tests.
Dynamical stability of the holographic system with two competing orders
Energy Technology Data Exchange (ETDEWEB)
Du, Yiqiang [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); Lan, Shan-Quan [Department of Physics, Beijing Normal University,Beijing 100875 (China); Tian, Yu [School of Physics, University of Chinese Academy of Sciences,Beijing 100049 (China); State Key Laboratory of Theoretical Physics,Institute of Theoretical Physics, Chinese Academy of Science,Beijing 100190 (China); Zhang, Hongbao [Department of Physics, Beijing Normal University,Beijing 100875 (China); Theoretische Natuurkunde, Vrije Universiteit Brussel and The International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium)
2016-01-04
We investigate the dynamical stability of the holographic system with two order parameters, which exhibits competition and coexistence of condensations. In the linear regime, we have developed the gauge dependent formalism to calculate the quasi-normal modes by gauge fixing, which turns out be considerably convenient. Furthermore, by giving different Gaussian wave packets as perturbations at the initial time, we numerically evolve the full nonlinear system until it arrives at the final equilibrium state. Our results show that the dynamical stability is consistent with the thermodynamical stability. Interestingly, the dynamical evolution, as well as the quasi-normal modes, shows that the relaxation time of this model is generically much longer than the simplest holographic system. We also find that the late time behavior can be well captured by the lowest lying quasi-normal modes except for the non-vanishing order towards the single ordered phase. To our knowledge, this exception is the first counter example to the general belief that the late time behavior towards a final stable state can be captured by the lowest lying quasi-normal modes. In particular, a double relation is found for this exception in certain cases.
Modeling and Stability Analysis of Wedge Clutch System
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Jian Yao
2014-01-01
Full Text Available A wedge clutch with unique features of self-reinforcement and small actuation force was designed. Its self-reinforcement feature, associated with different factors such as the wedge angle and friction coefficient, brings different dynamics and unstable problem with improper parameters. To analyze this system, a complete mathematical model of the actuation system is built, which includes the DC motor, the wedge mechanism, and the actuated clutch pack. By considering several nonlinear factors, such as the slip-stick friction and the contact or not of the clutch plates, the system is piecewise linear. Through the stability analysis of the linearized system in clutch slipping phase, the stable condition of the designed parameters is obtained as α>arctan(μc. The mathematical model of the actuation system is validated by prototype testing. And with the validated model, the system dynamics in both stable and unstable conditions is investigated and discussed in engineering side.
Stabilization of Electromagnetic Suspension System Behavior by Genetic Algorithm
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Abbas Najar Khoda Bakhsh
2012-07-01
Full Text Available Electromagnetic suspension system with a nonlinear and unstable behavior, is used in maglev trains. In this paper a linear mathematical model of system is achieved and the state feedback method is used to improve the system stability. The control coefficients are tuned by two different methods, Riccati and a new method based on Genetic algorithm. In this new proposed method, we use Genetic algorithm to achieve the optimum values of control coefficients. The results of the system simulation by Matlab indicate the effectiveness of new proposed system. When a new reference of air gap is needed or a new external force is added, the proposed system could omit the vibration and shake of the train coupe and so, passengers feel more comfortable.
Directory of Open Access Journals (Sweden)
Muhammad H. Al-Malack
2016-07-01
Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.
Algorithm for Stabilizing a POD-Based Dynamical System
Kalb, Virginia L.
2010-01-01
This algorithm provides a new way to improve the accuracy and asymptotic behavior of a low-dimensional system based on the proper orthogonal decomposition (POD). Given a data set representing the evolution of a system of partial differential equations (PDEs), such as the Navier-Stokes equations for incompressible flow, one may obtain a low-dimensional model in the form of ordinary differential equations (ODEs) that should model the dynamics of the flow. Temporal sampling of the direct numerical simulation of the PDEs produces a spatial time series. The POD extracts the temporal and spatial eigenfunctions of this data set. Truncated to retain only the most energetic modes followed by Galerkin projection of these modes onto the PDEs obtains a dynamical system of ordinary differential equations for the time-dependent behavior of the flow. In practice, the steps leading to this system of ODEs entail numerically computing first-order derivatives of the mean data field and the eigenfunctions, and the computation of many inner products. This is far from a perfect process, and often results in the lack of long-term stability of the system and incorrect asymptotic behavior of the model. This algorithm describes a new stabilization method that utilizes the temporal eigenfunctions to derive correction terms for the coefficients of the dynamical system to significantly reduce these errors.
Attitude coordination of multi-HUG formation based on multibody system theory
Xue, Dong-yang; Wu, Zhi-liang; Qi, Er-mai; Wang, Yan-hui; Wang, Shu-xin
2017-04-01
Application of multiple hybrid underwater gliders (HUGs) is a promising method for large scale, long-term ocean survey. Attitude coordination has become a requisite for task execution of multi-HUG formation. In this paper, a multibody model is presented for attitude coordination among agents in the HUG formation. The HUG formation is regarded as a multi-rigid body system. The interaction between agents in the formation is described by artificial potential field (APF) approach. Attitude control torque is composed of a conservative torque generated by orientation potential field and a dissipative term related with angular velocity. Dynamic modeling of the multibody system is presented to analyze the dynamic process of the HUG formation. Numerical calculation is carried out to simulate attitude synchronization with two kinds of formation topologies. Results show that attitude synchronization can be fulfilled based on the multibody method described in this paper. It is also indicated that different topologies affect attitude control quality with respect to energy consumption and adjusting time. Low level topology should be adopted during formation control scheme design to achieve a better control effect.
Characterization and stability studies of emulsion systems containing pumice
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Marilene Estanqueiro
2014-04-01
Full Text Available Emulsions are the most common form of skin care products. However, these systems may exhibit some instability. Therefore, when developing emulsions for topical application it is interesting to verify whether they have suitable physical and mechanical characteristics and further assess their stability. The aim of this work was to study the stability of emulsion systems, which varied in the proportion of the emulsifying agent cetearyl alcohol (and sodium lauryl sulfate (and sodium cetearyl sulfate (LSX, the nature of the oily phase (decyl oleate, cyclomethicone or dimethicone and the presence or absence of pumice (5% w/w. While maintaining the samples at room temperature, rheology studies, texture analysis and microscopic observation of formulations with and without pumice were performed. Samples were also submitted to an accelerated stability study by centrifugation and to a thermal stress test. Through the testing, it was found that the amount of emulsifying agent affects the consistency and textural properties such as firmness and adhesiveness. So, formulations containing LSX (5% w/w and decyl oleate or dimethicone as oily phase had a better consistency and remained stable with time, so exhibited the best features to be used for skin care products.
Stability Analysis of a Reaction-Diffusion System Modeling Atherogenesis
Ibragimov, Akif
2010-01-01
This paper presents a linear, asymptotic stability analysis for a reaction-diffusionconvection system modeling atherogenesis, the initiation of atherosclerosis, as an inflammatory instability. Motivated by the disease paradigm articulated by Ross, atherogenesis is viewed as an inflammatory spiral with a positive feedback loop involving key cellular and chemical species interacting and reacting within the intimal layer of muscular arteries. The inflammatory spiral is initiated as an instability from a healthy state which is defined to be an equilibrium state devoid of certain key inflammatory markers. Disease initiation is studied through a linear, asymptotic stability analysis of a healthy equilibrium state. Various theorems are proved, giving conditions on system parameters guaranteeing stability of the health state, and a general framework is developed for constructing perturbations from a healthy state that exhibit blow-up, which are interpreted as corresponding to disease initiation. The analysis reveals key features that arterial geometry, antioxidant levels, and the source of inflammatory components (through coupled third-kind boundary conditions or through body sources) play in disease initiation. © 2010 Society for Industrial and Applied Mathematics.
Investigation on flow stability of supercritical water cooled systems
International Nuclear Information System (INIS)
Cheng, X.; Kuang, B.
2006-01-01
Research activities are ongoing worldwide to develop nuclear power plants with supercritical water cooled reactor (SCWR) with the purpose to achieve a high thermal efficiency and to improve their economical competitiveness. However, the strong variation of the thermal-physical properties of water in the vicinity of the pseudo-critical line results in challenging tasks in various fields, e.g. thermal-hydraulic design of a SCWR. One of the challenging tasks is to understand and to predict the dynamic behavior of supercritical water cooled systems. Although many thermal-hydraulic research activities were carried out worldwide in the past as well as in the near present, studies on dynamic behavior and flow stability of SC water cooled systems are scare. Due to the strong density variation, flow stability is expected to be one of the key items which need to be taken into account in the design of a SCWR. In the present work, the dynamic behavior and flow stability of SC water cooled systems are investigated using both numerical and theoretical approaches. For this purpose a new computer code SASC was developed, which can be applied to analysis the dynamic behavior of systems cooled by supercritical fluids. In addition, based on the assumptions of a simplified system, a theoretical model was derived for the prediction of the onset of flow instability. A comparison was made between the results obtained using the theoretical model and those from the SASC code. A good agreement was achieved. This gives the first evidence of the reliability of both the SASC code and the theoretical model
Evaluation of constraint stabilization procedures for multibody dynamical systems
Park, K. C.; Chiou, J. C.
1987-01-01
Comparative numerical studies of four constraint treatment techniques for the simulation of general multibody dynamic systems are presented, and results are presented for the example of a classical crank mechanism and for a simplified version of the seven-link manipulator deployment problem. The staggered stabilization technique (Park, 1986) is found to yield improved accuracy and robustness over Baumgarte's (1972) technique, the singular decomposition technique (Walton and Steeves, 1969), and the penalty technique (Lotstedt, 1979). Furthermore, the staggered stabilization technique offers software modularity, and the only data each solution module needs to exchange with the other is a set of vectors plus a common module to generate the gradient matrix of the constraints, B.
Stability and Bifurcation in Magnetic Flux Feedback Maglev Control System
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Wen-Qing Zhang
2013-01-01
Full Text Available Nonlinear properties of magnetic flux feedback control system have been investigated mainly in this paper. We analyzed the influence of magnetic flux feedback control system on control property by time delay and interfering signal of acceleration. First of all, we have established maglev nonlinear model based on magnetic flux feedback and then discussed hopf bifurcation’s condition caused by the acceleration’s time delay. The critical value of delayed time is obtained. It is proved that the period solution exists in maglev control system and the stable condition has been got. We obtained the characteristic values by employing center manifold reduction theory and normal form method, which represent separately the direction of hopf bifurcation, the stability of the period solution, and the period of the period motion. Subsequently, we discussed the influence maglev system on stability of by acceleration’s interfering signal and obtained the stable domain of interfering signal. Some experiments have been done on CMS04 maglev vehicle of National University of Defense Technology (NUDT in Tangshan city. The results of experiments demonstrate that viewpoints of this paper are correct and scientific. When time lag reaches the critical value, maglev system will produce a supercritical hopf bifurcation which may cause unstable period motion.
Methods to assess the stability of a bicycle rider system
Cooke, A.G.; Bulsink, Vera Elisabeth; Beusenberg, Mark; Dubbeldam, Rosemary; Bonnema, Gerrit Maarten; Poelman, Wim; Koopman, Hubertus F.J.M.
2012-01-01
The SOFIE (Intelligent Assisted Bicycles) project wishes to create performance and design guidelines for mechatronic appliances which improve the stability of electric bicycles, so-called intelligent stability assist devices (IAD). To achieve this goal, a stability hypothesis, an advanced
Lim, Yeerang; Lee, Wonsuk; Bang, Hyochoong; Lee, Hosung
2017-04-01
A thrust distribution approach is proposed in this paper for a variable thrust solid propulsion system with an attitude control system (ACS) that uses a reduced number of nozzles for a three-axis attitude maneuver. Although a conventional variable thrust solid propulsion system needs six ACS nozzles, this paper proposes a thrust system with four ACS nozzles to reduce the complexity and mass of the system. The performance of the new system was analyzed with numerical simulations, and the results show that the performance of the system with four ACS nozzles was similar to the original system while the mass of the whole system was simultaneously reduced. Moreover, a feasibility analysis was performed to determine whether a thrust system with three ACS nozzles is possible.
Automotive mechatronics automotive networking, driving stability systems, electronics
2015-01-01
As the complexity of automotive vehicles increases this book presents operational and practical issues of automotive mechatronics. It is a comprehensive introduction to controlled automotive systems and provides detailed information of sensors for travel, angle, engine speed, vehicle speed, acceleration, pressure, temperature, flow, gas concentration etc. The measurement principles of the different sensor groups are explained and examples to show the measurement principles applied in different types. Contents Basics of mechatronics.- Architecture.- Electronic control unit.- Software development.- Basic principles of networking.- Automotive networking.- Bus systems.- Automotive sensors.- Sensor measuring principles.- Sensor types.- Electric actuators.- Electrohydraulic actuators.- Electronic transmission control.- Electronic transmission control unit.- Modules for transmission control.- Antilock braking system.- Traction control system.- Electronic stability program.- Automatic brake functions.- Hydraulic modu...
A MARTe based simulator for the JET Vertical Stabilization system
Energy Technology Data Exchange (ETDEWEB)
Bellizio, Teresa, E-mail: teresa.bellizio@unina.it [Associazione EURATOM-ENEA-CREATE, University di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); De Tommasi, Gianmaria; Risoli, Nicola; Albanese, Raffaele [Associazione EURATOM-ENEA-CREATE, University di Napoli Federico II, Via Claudio 21, 80125 Napoli (Italy); Neto, Andre [Associacao EURATOM/IST, Inst. de Plasmas e Fusao Nuclear - Laboratorio Associado, Instituto Superior, Tecnico, P-1049-001 Lisboa (Portugal)
2011-10-15
Validation by means of simulation is a crucial step when developing real-time control systems. Modeling and simulation are an essential tool since the early design phase, when the control algorithms are designed and tested. This phase is commonly carried out in off-line environments such as Matlab and Simulink. A MARTe-based simulator has been recently developed to validate the new JET Vertical Stabilization (VS) system. MARTe is the multi-thread framework used at JET to deploy hard real-time control systems. This paper presents the software architecture of the MARTe-based simulator and it shows how this tool has been effectively used to evaluate the effects of Edge Localized Modes (ELMs) on the VS system. By using the simulator it is possible to analyze different plasma configurations, extrapolating the limit of the new vertical amplifier in terms of the energy of the largest rejectable ELM.
Absorbed energy for radiation crosslinking in stabilized PE systems
International Nuclear Information System (INIS)
Novakovic, Lj.; Gal, O.; Charlesby, A.
1990-01-01
A quantitative consideration on the absorbed energy consumption in various γ-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author)
Absorbed energy for radiation crosslinking in stabilized PE systems
Energy Technology Data Exchange (ETDEWEB)
Novakovic, Lj; Gal, O [Institut za Nuklearne Nauke Boris Kidric, Belgrade (Yugoslavia); Charlesby, A
1990-01-01
A quantitative consideration on the absorbed energy consumption in various {gamma}-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author).
Analyzing Drivers' Attitude towards HUD System Using a Stated Preference Survey
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Hongwei Guo
2014-02-01
Full Text Available It is very important for drivers to obtain driving information easily and efficiently. There are many advanced devices used for driving safety assistance. Of these assistance devices, the head-up display (HUD system can promote the reduction of driver's reaction time and improve spatial awareness. The drivers' attitude towards and preference for HUD system are crucial to design the functional framework and interface of HUD system. This study explored the relationships between drivers' attitude and HUD presentation image designs using stated preference data from questionnaire survey. The questionnaire included drivers' attitude towards the use of HUD and the preference for the information display zone and information display elements of the HUD. Contrastive analysis was adopted to examine the variations in drivers' attitude and preference for age and driving skills. According to the results, the participants have varying attitudes to HUD system, but most participants show relatively unified preference for the information display zone and information display elements. The results can also be used to customize a HUD presentation image which is in accordance with the drivers' feelings and preferences.
Measurement and protocol for evaluating video and still stabilization systems
Cormier, Etienne; Cao, Frédéric; Guichard, Frédéric; Viard, Clément
2013-01-01
This article presents a system and a protocol to characterize image stabilization systems both for still images and videos. It uses a six axes platform, three being used for camera rotation and three for camera positioning. The platform is programmable and can reproduce complex motions that have been typically recorded by a gyroscope mounted on different types of cameras in different use cases. The measurement uses a single chart for still image and videos, the texture dead leaves chart. Although the proposed implementation of the protocol uses a motion platform, the measurement itself does not rely on any specific hardware. For still images, a modulation transfer function is measured in different directions and is weighted by a contrast sensitivity function (simulating the human visual system accuracy) to obtain an acutance. The sharpness improvement due to the image stabilization system is a good measurement of performance as recommended by a CIPA standard draft. For video, four markers on the chart are detected with sub-pixel accuracy to determine a homographic deformation between the current frame and a reference position. This model describes well the apparent global motion as translations, but also rotations along the optical axis and distortion due to the electronic rolling shutter equipping most CMOS sensors. The protocol is applied to all types of cameras such as DSC, DSLR and smartphones.
MHD-Stabilization of Axisymmetric Mirror Systems Using Pulsed ECRH
International Nuclear Information System (INIS)
Post, R.F.
2010-01-01
This paper, part of a continuing study of means for the stabilization of MHD interchange modes in axisymmertric mirror-based plasma confinement systems, is aimed at a preliminary look at a technique that would employ a train of plasma pressure pulses produced by ECRH to accomplish the stabilization. The purpose of using sequentially pulsed ECRH rather than continuous-wave ECRH is to facilitate the localization of the heated-electron plasma pulses in regions of the magnetic field with a strong positive field-line curvature, e. g. in the 'expander' region of the mirror magnetic field, outside the outermost mirror, or in other regions of the field with positive field-line curvature. The technique proposed, of the class known as 'dynamic stabilization,' relies on the time-averaged effect of plasma pressure pulses generated in regions of positive field-line curvature to overcome the destabilizing effect of plasma pressure in regions of negative field-line curvature within the confinement region. As will also be discussed in the paper, the plasma pulses, when produced in regions of the confining having a negative gradient, create transient electric potentials of ambipolar origin, an effect that was studied in 1964 in The PLEIDE experiment in France. These electric fields preserve the localization of the hot-electron plasma pulses for a time determined by ion inertia. It is suggested that it may be possible to use this result of pulsed ECRH not only to help to stabilize the plasma but also to help plug mirror losses in a manner similar to that employed in the Tandem Mirror.
Feedback stabilization system for pulsed single longitudinal mode tunable lasers
Esherick, Peter; Raymond, Thomas D.
1991-10-01
A feedback stabilization system for pulse single longitudinal mode tunable lasers having an excited laser medium contained within an adjustable length cavity and producing a laser beam through the use of an internal dispersive element, including detection of angular deviation in the output laser beam resulting from detuning between the cavity mode frequency and the passband of the internal dispersive element, and generating an error signal based thereon. The error signal can be integrated and amplified and then applied as a correcting signal to a piezoelectric transducer mounted on a mirror of the laser cavity for controlling the cavity length.
Linear local stability of electrostatic drift modes in helical systems
International Nuclear Information System (INIS)
Yamagishi, O.; Nakajima, N.; Sugama, H.; Nakamura, Y.
2003-01-01
We investigate the stability of the drift wave in helical systems. For this purpose, we solve the linear local gyrokinetic-Poisson equation, in the electrostatic regime. As a model of helical plasmas, Large helical Device (LHD) is considered. The equation we apply is rather exact in the framework of linear gyrokinetic theory, where only the approximation is the ballooning representation. In this paper, we consider only collisionless cases. All the frequency regime can be naturally reated without any assumptions, and in such cases, ion temperature gradient modes (ITG), trapped electron modes (TEM), and electron temperature gradient modes (ETG) are expected to become unstable linearly independently. (orig.)
Preliminary hazards analysis of thermal scrap stabilization system. Revision 1
International Nuclear Information System (INIS)
Lewis, W.S.
1994-01-01
This preliminary analysis examined the HA-21I glovebox and its supporting systems for potential process hazards. Upon further analysis, the thermal stabilization system has been installed in gloveboxes HC-21A and HC-21C. The use of HC-21C and HC-21A simplified the initial safety analysis. In addition, these gloveboxes were cleaner and required less modification for operation than glovebox HA-21I. While this document refers to glovebox HA-21I for the hazards analysis performed, glovebox HC-21C is sufficiently similar that the following analysis is also valid for HC-21C. This hazards analysis document is being re-released as revision 1 to include the updated flowsheet document (Appendix C) and the updated design basis (Appendix D). The revised Process Flow Schematic has also been included (Appendix E). This Current revision incorporates the recommendations provided from the original hazards analysis as well. The System Design Description (SDD) has also been appended (Appendix H) to document the bases for Safety Classification of thermal stabilization equipment
Stability Tests of Positive Fractional Continuous-time Linear Systems with Delays
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Tadeusz Kaczorek
2013-06-01
Full Text Available Necessary and sufficient conditions for the asymptotic stability of positive fractional continuous-time linear systems with many delays are established. It is shown that: 1 the asymptotic stability of the positive fractional system is independent of their delays, 2 the checking of the asymptotic stability of the positive fractional systems with delays can be reduced to checking of the asymptotic stability of positive standard linear systems without delays.
On the asymptotic stability of nonlinear mechanical switched systems
Platonov, A. V.
2018-05-01
Some classes of switched mechanical systems with dissipative and potential forces are considered. The case, where either dissipative or potential forces are essentially nonlinear, is studied. It is assumed that the zero equilibrium position of the system is asymptotically stable at least for one operating mode. We will look for sufficient conditions which guarantee the preservation of asymptotic stability of the equilibrium position under the switching of modes. The Lyapunov direct method is used. A Lyapunov function for considered system is constructed, which satisfies the differential inequality of special form for every operating mode. This inequality is nonlinear for the chosen mode with asymptotically stable equilibrium position, and it is linear for the rest modes. The correlations between the intervals of activity of the pointed mode and the intervals of activity of the rest modes are obtained which guarantee the required properties.
2017-12-30
AFRL-RV-PS- AFRL-RV-PS- TR-2018-0008 TR-2018-0008 DEVELOPMENT OF A TORQUE SENSOR- BASED TEST BED FOR ATTITUDE CONTROL SYSTEM VERIFICATION AND...Sensor-Based Test Bed for Attitude Control System Verification & Validation 5a. CONTRACT NUMBER FA9453-15-1-0315 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...NUMBER 62601F 6. AUTHOR(S) Norman Fitz-Coy 5d. PROJECT NUMBER 4846 5e. TASK NUMBER PPM00015968 5f. WORK UNIT NUMBER EF125135 7. PERFORMING
Breaking Dense Structures: Proving Stability of Densely Structured Hybrid Systems
Directory of Open Access Journals (Sweden)
Eike Möhlmann
2015-06-01
Full Text Available Abstraction and refinement is widely used in software development. Such techniques are valuable since they allow to handle even more complex systems. One key point is the ability to decompose a large system into subsystems, analyze those subsystems and deduce properties of the larger system. As cyber-physical systems tend to become more and more complex, such techniques become more appealing. In 2009, Oehlerking and Theel presented a (de-composition technique for hybrid systems. This technique is graph-based and constructs a Lyapunov function for hybrid systems having a complex discrete state space. The technique consists of (1 decomposing the underlying graph of the hybrid system into subgraphs, (2 computing multiple local Lyapunov functions for the subgraphs, and finally (3 composing the local Lyapunov functions into a piecewise Lyapunov function. A Lyapunov function can serve multiple purposes, e.g., it certifies stability or termination of a system or allows to construct invariant sets, which in turn may be used to certify safety and security. In this paper, we propose an improvement to the decomposing technique, which relaxes the graph structure before applying the decomposition technique. Our relaxation significantly reduces the connectivity of the graph by exploiting super-dense switching. The relaxation makes the decomposition technique more efficient on one hand and on the other allows to decompose a wider range of graph structures.
Stability of power systems coupled with market dynamics
Meng, Jianping
This Ph.D. thesis presented here spans two relatively independent topics. The first part, Chapter 2 is self-contained, and is dedicated to studies of new algorithms for power system state estimation. The second part, encompassing the remaining chapters, is dedicated to stability analysis of power system coupled with market dynamics. The first part of this thesis presents improved Newton's methods employing efficient vectorized calculations of higher order derivatives in power system state estimation problems. The improved algorithms are proposed based on an exact Newton's method using the second order terms. By efficiently computing an exact gain matrix, combined with a special optimal multiplier method, the new algorithms show more reliable convergence compared with the existing methods of normal equations, orthogonal decomposition, and Hachtel's sparse tableau. Our methods are able to handle ill-conditioned problems, yet show minimal penalty in computational cost for well-conditioned cases. These claims are illustrated through the standard IEEE 118 and 300 bus test examples. The second part of the thesis focuses on stability analysis of market/power systems. The work presented is motivated by an emerging problem. As the frequency of market based dispatch updates increases, there will inevitably be interaction between the dynamics of markets determining the generator dispatch commands, and the physical response of generators and network interconnections, necessitating the development of stability analysis for such coupled systems. We begin with numeric tests using different market models, with detailed machine/exciter/turbine/governor dynamics, in the New England 39 bus test system. A progression of modeling refinements are introduced, including such non-ideal effects as time delays. Electricity market parameter identification algorithms are also studied based on real time data from the PJM electricity market. Finally our power market model is augmented by optimal
Steam Turbine Control Valve Stiction Effect on Power System Stability
International Nuclear Information System (INIS)
Halimi, B.
2010-01-01
One of the most important problems in power system dynamic stability is low frequency oscillations. This kind of oscillation has significant effects on the stability and security of the power system. In some previous papers, a fact was introduced that a steam pressure continuous fluctuation in turbine steam inlet pipeline may lead to a kind of low frequency oscillation of power systems. Generally, in a power generation plant, steam turbine system composes of some main components, i.e. a boiler or steam generator, stop valves, control valves and turbines that are connected by piping. In the conventional system, the turbine system is composed with a lot of stop and control valves. The steam is provided by a boiler or steam generator. In an abnormal case, the stop valve shuts of the steal flow to the turbine. The steam flow to the turbine is regulated by controlling the control valves. The control valves are provided to regulate the flow of steam to the turbine for starting, increasing or decreasing the power, and also maintaining speed control with the turbine governor system. Unfortunately, the control valve has inherent static friction (stiction) nonlinearity characteristics. Industrial surveys indicated that about 20-30% of all control loops oscillate due to valve problem caused by this nonlinear characteristic. In this paper, steam turbine control valve stiction effect on power system oscillation is presented. To analyze the stiction characteristic effect, firstly a model of control valve and its stiction characteristic are derived by using Newton's laws. A complete tandem steam prime mover, including a speed governing system, a four-stage steam turbine, and a shaft with up to for masses is adopted to analyze the performance of the steam turbine. The governor system consists of some important parts, i.e. a proportional controller, speed relay, control valve with its stiction characteristic, and stem lift position of control valve controller. The steam turbine has
Intraoperative computed tomography with integrated navigation system in spinal stabilizations.
Zausinger, Stefan; Scheder, Ben; Uhl, Eberhard; Heigl, Thomas; Morhard, Dominik; Tonn, Joerg-Christian
2009-12-15
STUDY DESIGN.: A prospective interventional case-series study plus a retrospective analysis of historical patients for comparison of data. OBJECTIVE.: To evaluate workflow, feasibility, and clinical outcome of navigated stabilization procedures with data acquisition by intraoperative computed tomography. SUMMARY OF BACKGROUND DATA.: Routine fluoroscopy to assess pedicle screw placement is not consistently reliable. Our hypothesis was that image-guided spinal navigation using an intraoperative CT-scanner can improve the safety and precision of spinal stabilization surgery. METHODS.: CT data of 94 patients (thoracolumbar [n = 66], C1/2 [n = 12], cervicothoracic instability [n = 16]) were acquired after positioning the patient in the final surgical position. A sliding gantry 40-slice CT was used for image acquisition. Data were imported to a frameless infrared-based neuronavigation workstation. Intraoperative CT was obtained to assess the accuracy of instrumentation and, if necessary, the extent of decompression. All patients were clinically evaluated by Odom-criteria after surgery and after 3 months. RESULTS.: Computed accuracy of the navigation system reached /=2 mm without persistent neurologic or vascular damage in 20/414 screws (4.8%) leading to immediate correction of 10 screws (2.4%). Control-iCT changed the course of surgery in 8 cases (8.5% of all patients). The overall revision rate was 8.5% (4 wound revisions, 2 CSF fistulas, and 2 epidural hematomas). There was no reoperation due to implant malposition. According to Odom-criteria all patients experienced a clinical improvement. A retrospective analysis of 182 patients with navigated thoracolumbar transpedicular stabilizations in the preiCT era revealed an overall revision rate of 10.4% with 4.4% of patients requiring screw revision. CONCLUSION.: Intraoperative CT in combination with neuronavigation provides high accuracy of screw placement and thus safety for patients undergoing spinal stabilization
Kort-Butler, Lisa A; Sittner Hartshorn, Kelley J
2011-01-01
Research demonstrates a complex relationship between television viewing and fear of crime. Social critics assert that media depictions perpetuate the dominant cultural ideology about crime and criminal justice. This article examines whether program type differentially affects fear of crime and perceptions of the crime rate. Next, it tests whether such programming differentially affects viewers' attitudes about the criminal justice system, and if these relationships are mediated by fear. Results indicated that fear mediated the relationship between viewing nonfictional shows and lack of support for the justice system. Viewing crime dramas predicted support for the death penalty, but this relationship was not mediated by fear. News viewership was unrelated to either fear or attitudes. The results support the idea that program type matters when it comes to understanding people's fear of crime and their attitudes about criminal justice.
Attitude Control of Quad-rotor by Improving the Reliability of Multi-Sensor System
Energy Technology Data Exchange (ETDEWEB)
Yu, Dong Hyeon; Chong, Kil To [Chon-bok National University, Jeonju (Korea, Republic of); Park, Jong Ho [Seonam University, Namwon (Korea, Republic of); Ryu, Ji Hyoung [ETRI, Daejeon (Korea, Republic of)
2015-05-15
This paper presents the results of study for improving the reliability of quadrotor attitude control by applying a multi-sensor along with a data fusion algorithm. First, a mathematical model of the quadrotor dynamics was developed. Then, using the quadrotor mathematical model, simulations were performed using the improved reliability multi-sensor data as the inputs. From the simulation results, we designed a Gimbal-equipped quadrotor system. With the quadrotor in a hover state, we performed experiments according to the angle change of the user's specifications . We then calculated the attitude control data from the actual experimental data. Furthermore, with additional simulations, we verified the performance of the designed quadrotor attitude control system with multiple sensors.
Verifying Stability of Dynamic Soft-Computing Systems
Wen, Wu; Napolitano, Marcello; Callahan, John
1997-01-01
Soft computing is a general term for algorithms that learn from human knowledge and mimic human skills. Example of such algorithms are fuzzy inference systems and neural networks. Many applications, especially in control engineering, have demonstrated their appropriateness in building intelligent systems that are flexible and robust. Although recent research have shown that certain class of neuro-fuzzy controllers can be proven bounded and stable, they are implementation dependent and difficult to apply to the design and validation process. Many practitioners adopt the trial and error approach for system validation or resort to exhaustive testing using prototypes. In this paper, we describe our on-going research towards establishing necessary theoretic foundation as well as building practical tools for the verification and validation of soft-computing systems. A unified model for general neuro-fuzzy system is adopted. Classic non-linear system control theory and recent results of its applications to neuro-fuzzy systems are incorporated and applied to the unified model. It is hoped that general tools can be developed to help the designer to visualize and manipulate the regions of stability and boundedness, much the same way Bode plots and Root locus plots have helped conventional control design and validation.
Multistage position-stabilized vibration isolation system for neutron interferometry
Arif, Muhammad; Brown, Dennis E.; Greene, Geoffrey L.; Clothier, R.; Littrell, K.
1994-10-01
A two stage, position stabilized vibration isolation system has been constructed and is now in operation at the Cold Neutron Research Facility of the National Institute of Standards and Technology, Gaithersburg, MD. The system employs pneumatic isolators with a multiple input/multiple output pneumatic servo system based upon pulse width modulation control loops. The first stage consists of a 40,000 kg reinforced concrete table supported by pneumatic isolators. A large environmentally isolated laboratory enclosure rests on the concrete table. The second stage consists of a 3000 kg granite optical table located within the enclosure and supported by another set of pneumatic isolators. The position of the two stages is monitored by proximity sensors and inclinometers with 12 degrees of freedom. The system controls 12 independent pneumatic airsprings. The signals from these sensors are fed into a personal computer based control system. The control system has maintained the position of the two stages to better than 1 micrometers in translation and 5 (mu) rad in orientation for a period of a few months. A description of the system and its characteristics is given.
Currency System and Its Impact on Economic Stability
Directory of Open Access Journals (Sweden)
Desmadi Saharuddin
2017-05-01
Full Text Available A number of economic problems that occurred during the power of Mamluk (1250-1517 AD was considered as a result of the change to currency system, namely from the system of commodity-based money (gold and silver into paper-based money (fiat. Instability prices, decrease of trading activities, high of unemployment number were a number of economic indicators that occurred at that time. This issue of macro-economy was considered as a result of changes in the money system. This study analyzes the dynamic relationship between the price of gold as a representation of commodity money system and M2 as a representation of fiat money against the stability of economic indicators such as inflation, economic growth, stock prices, and unemployment and interest rates. This study found that both systems not vary significantly against each other in its influence on macroeconomic variables. It means that the two systems do not have contrast distinction. Indeed, it was found that the commodity-based money system is not free of inflation, as propagated by the supporters of the dinar and dirham (dinarist. DOI: 10.15408/aiq.v9i2.4749
A very high performance stabilization system for large mass bolometerexperiments
Energy Technology Data Exchange (ETDEWEB)
Arnaboldi, C. [Sezione INFN di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Universita di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Giachero, A., E-mail: Andrea.Giachero@mib.infn.it [Sezione INFN di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Universita di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Gotti, C. [Sezione INFN di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Universita di Firenze, Dipartimento di Elettronica e Telecomunicazioni, Via S. Marta 3, I-50139 Firenze (Italy); Pessina, G. [Sezione INFN di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy); Universita di Milano Bicocca, Piazza della Scienza 3, I-20126 Milano (Italy)
2011-10-01
CUORE is a large mass bolometric experiment, composed of 988 crystals, under construction in Hall A of the Gran Sasso Underground Laboratories (LNGS). Its main aim is the study of neutrinoless double beta decay of {sup 130}Te. Each bolometer is a 760 g crystal of Tellurium dioxide on which a Nuclear Transmutation Doped Ge thermistor, Ge NTD, is glued with proper thermal contact. The stability of the system is mandatory over many years of data taking. To accomplish this requirement a heating resistor is glued on each detector across which a voltage pulse can be injected at will, to develop a known calibrated heating power. We present the design solution for a pulse generator system to be used for the injection of such a small and short voltage pulse across the heaters. This system is composed by different custom PCB boards each of them having multi-channel independent outputs completely remotely programmable from the acquisition system, in pulse width and amplitude, through an on-board ARM7 microcontroller. Pulse amplitudes must be selectable, in order to handle each detector on its full dynamic range. The resolution of the output voltage is 12 bits over 10 V range. An additional 4 steps programmable voltage attenuator is added at every output. The width of any pulse can range from 100{mu}s to 25.5 ms. The main features of the final system are: stability and precision in pulses generation (at the level of less than a ppm/{sup o}C), low cost (thanks to the use of commercial components) and compact implementation.
Stability considerations of packed multi-planet systems
Gratia, Pierre; Lissauer, Jack
2018-04-01
I will present our first results of the outcomes of five packed, Earth-mass planetary simulations around a Sun-like star, whose initial separations in terms of their semi-major axes is determined by a multiple of their mutual Hill radius, the parameter beta. In our simulations, we will vary beta between 3.5 and and 9, with a special emphasis on the region around 8.5, where stability times are wildly different for small increments of beta. While the zero initial eccentricity case has been investigated before, we expand on it by allowing for initial nonzero eccentricities of one or more planets. Furthermore, we increase the simulated time by up to one order of magnitude reaching billions of orbits. This of course will determine more accurately the fate of systems that take a long time to go unstable. Both of these investigations have not been done before, thus our findings improve our understanding of the stabilities of closely-spaced planetary systems.
International Nuclear Information System (INIS)
1996-01-01
A meeting was held between DOE personnel and the BNFL team to review the proposed resolutions to DOE comments on the initial issue of the system specification and system design document for the Plutonium Stabilization and Packaging System. The objectives of this project are to design, fabricate, install, and start up a glovebox system for the safe repackaging of plutonium oxide and metal, with a requirement of a 50-year storage period. The areas discussed at the meeting were: nitrogen in can; moisture instrumentation; glovebox atmosphere; can marking bar coding; weld quality; NFPA-101 references; inner can swabbing; ultimate storage environment; throughput; convenience can screw-top design; furnacetrays; authorization basis; compactor safety; schedule for DOE review actions; fire protection; criticality safety; applicable standards; approach to MC and A; homogeneous oxide; resistance welder power; and tray overfill. Revised resolutions were drafted and are presented
Directory of Open Access Journals (Sweden)
Yuanhua Li
2015-01-01
Full Text Available Stability and stabilization of fractional-order interval system is investigated. By adding parameters to linear matrix inequalities, necessary and sufficient conditions for stability and stabilization of the system are obtained. The results on stability check for uncertain FO-LTI systems with interval coefficients of dimension n only need to solve one 4n-by-4n LMI. Numerical examples are presented to shown the effectiveness of our results.
Modified Schur-Cohn Criterion for Stability of Delayed Systems
Directory of Open Access Journals (Sweden)
Juan Ignacio Mulero-Martínez
2015-01-01
Full Text Available A modified Schur-Cohn criterion for time-delay linear time-invariant systems is derived. The classical Schur-Cohn criterion has two main drawbacks; namely, (i the dimension of the Schur-Cohn matrix generates some round-off errors eventually resulting in a polynomial of s with erroneous coefficients and (ii imaginary roots are very hard to detect when numerical errors creep in. In contrast to the classical Schur-Cohn criterion an alternative approach is proposed in this paper which is based on the application of triangular matrices over a polynomial ring in a similar way as in the Jury test of stability for discrete systems. The advantages of the proposed approach are that it halves the dimension of the polynomial and it only requires seeking real roots, making this modified criterion comparable to the Rekasius substitution criterion.
A fuzzy logic pitch angle controller for power system stabilization
Energy Technology Data Exchange (ETDEWEB)
Jauch, Clemens; Cronin, Tom; Sorensen, Poul [Wind Energy Department, Riso National Laboratory, PO Box 49, DK-4000 Roskilde, (Denmark); Jensen, Birgitte Bak [Institute of Energy Technology, Aalborg University, Pontoppidanstraede 101, DK-9220 Aalborg East, (Denmark)
2006-07-12
In this article the design of a fuzzy logic pitch angle controller for a fixed speed, active-stall wind turbine, which is used for power system stabilization, is presented. The system to be controlled, which is the wind turbine and the power system to which the turbine is connected, is described. The advantages of fuzzy logic control when applied to large-signal control of active-stall wind turbines are outlined. The general steps of the design process for a fuzzy logic controller, including definition of the controller inputs, set-up of the fuzzy rules and the method of defuzzification, are described. The performance of the controller is assessed by simulation, where the wind turbine's task is to dampen power system oscillations. In the scenario simulated for this work, the wind turbine has to ride through a transient short-circuit fault and subsequently contribute to the damping of the grid frequency oscillations that are caused by the transient fault. It is concluded that the fuzzy logic controller enables the wind turbine to dampen power system oscillations. It is also concluded that, owing to the inherent non-linearities in a wind turbine and the unpredictability of the whole system, the fuzzy logic controller is very suitable for this application. (Author).
International Nuclear Information System (INIS)
Yeghiazaryan, L.V.; Hakobyan, S.G.; Gharibyan, G.V.; Harutyunyan, G.S.; Galstyan, G.H.
2010-01-01
The description of the power systems operation stability failure caused by the system significant emergency states occurred during the last working period in Armenian and USA power systems is performed. With the use of PSSTME-31 software portfolio of Siemens Firm a design model is developed and transient electromechanical process calculations for Armenian power system are performed. The accuracy of the model is checked by comparing real-time transient state parameters and their reproduction calculation results.The Armenia - Iran current power transmission lines permissible limit under the condition of the static and dynamic stability requirements and in case of the new thermal power units maintenance are defined
On a program manifold's stability of one contour automatic control systems
Zumatov, S. S.
2017-12-01
Methodology of analysis of stability is expounded to the one contour systems automatic control feedback in the presence of non-linearities. The methodology is based on the use of the simplest mathematical models of the nonlinear controllable systems. Stability of program manifolds of one contour automatic control systems is investigated. The sufficient conditions of program manifold's absolute stability of one contour automatic control systems are obtained. The Hurwitz's angle of absolute stability was determined. The sufficient conditions of program manifold's absolute stability of control systems by the course of plane in the mode of autopilot are obtained by means Lyapunov's second method.
Decker, Thomas; Zapilko, Marina; Menrad, Klaus
2010-01-01
The decision for buying a heating system is a long-term one, as many different aspects have an influence on this choice which were analyzed in a Germany-wide, written survey. The respondents (only owners of a private house) had to answer questions about their attitude towards e.g. economic, convenience or ecological aspects related to heating systems and the respective combustibles. Using a multinomial logistic regression model the choice of the heating system is mainly explained by ecologica...
Attitudes and Perceptions of Students in a Systems Engineering E-Learnig Course
de Vega, Carolina Armijo; McAnally-Salas, Lewis; Lavigne, Gilles
2009-01-01
In this paper is reported the attitudes and perception of students in a systems Engineering e-learning course and a teacher with more than six years of experience teaching online courses. The paper reports the teacher and students' perceptions about the e-learning courses experience. Personalized interviews with some of the students were carried…
Lenard, Mary Jane; Wessels, Susan; Khanlarian, Cindi
2010-01-01
Using a model developed by Young (2000), this paper explores the relationship between performance in the Accounting Information Systems course, self-assessed computer skills, and attitudes toward computers. Results show that after taking the AIS course, students experience a change in perception about their use of computers. Females'…
Improving Power System Stability Using Transfer Function: A Comparative Analysis
Directory of Open Access Journals (Sweden)
G. Shahgholian
2017-10-01
Full Text Available In this paper, a small-signal dynamic model of a single-machine infinite-bus (SMIB power system that includes IEEE type-ST1 excitation system and PSS based on transfer fu¬n¬c¬¬tion structure is presented. The changes in the operating co¬n¬dition of a power system on dynamic performance have been exa¬m¬ined. The dynamic performance of the closed-loop system is ana¬lyzed base on its eigenvalues. The effectiveness of the par¬a¬m¬e¬t¬ers changes on dynamic stability is verified by simulation res¬u¬l¬ts. Three types of PSS have been considered for analysis: (a the derivative PSS, (b the lead-lag PSS or conventional PSS, and (c the proportional-integral-derivative PSS. The objective fu¬nc¬t¬i¬o¬n is formulated to increase the dam¬¬ping ratio of the electromechanical mode eigenvalues. Simu¬la¬tion results show that the PID-PSS performs better for less ov¬e¬r¬shoot and less settling time comp¬ared with the CPSS and DPSS un¬der different load ope¬ration and the significant system pa¬r¬am¬eter variation conditions.
Complex systems of biological interest stability under ionising radiations
International Nuclear Information System (INIS)
Maclot, Sylvain
2014-01-01
This PhD work presents the study of stability of molecular systems of biological interest in the gas phase after interaction with ionising radiations. The use of ionising radiation can probe the physical chemistry of complex systems at the molecular scale and thus consider their intrinsic properties. Beyond the fundamental aspect, this work is part of the overall understanding of radiation effects on living organisms and in particular the use of ionizing radiation in radiotherapy. Specifically, this study focused on the use of low-energy multiply charged ions (tens of keV) provided by the GANIL (Caen), which includes most of the experiments presented. In addition, experiments using VUV photons were also conducted at synchrotron ELETTRA (Trieste, Italy). The bio-molecular systems studied are amino acids and nucleic acid constituents. Using an experimental crossed beams device allows interaction between biomolecules and ionising radiation leads mainly to the ionization and fragmentation of the system. The study of its relaxation dynamics is by time-of-flight mass spectrometry coupled to a coincidences measurements method. It is shown that an approach combining experiment and theory allows a detailed study of the fragmentation dynamics of complex systems. The results indicate that fragmentation is generally governed by the Coulomb repulsion but the intramolecular rearrangements involve specific relaxation mechanisms. (author) [fr
Vehicle rollover risk and electronic stability control systems.
MacLennan, P A; Marshall, T; Griffin, R; Purcell, M; McGwin, G; Rue, L W
2008-06-01
Electronic stability control (ESC) systems were developed to reduce motor vehicle collisions (MVCs) caused by loss of control. Introduced in Europe in 1995 and in the USA in 1996, ESC is designed to improve vehicle lateral stability by electronically detecting and automatically assisting drivers in unfavorable situations. To examine the relationship between vehicle rollover risk and presence of ESC using a large national database of MVCs. A retrospective cohort study for the period 1995 through 2006 was carried out using data obtained from the National Automotive Sampling System General Estimates System. All passenger cars and sport utility vehicles (SUVs)/vans of model year 1996 and later were eligible. Vehicle ESC (unavailable, optional, standard) was determined on the basis of make, model, and model year. Risk ratios (RRs) and 95% CIs were calculated to compare rollover risk by vehicle ESC group. For all crashes, vehicles equipped with standard ESC had decreased risk of rollover (RR = 0.62, 95% CI 0.50 to 0.77) compared with vehicles with ESC unavailable. The association was consistent for single-vehicle MVCs (RR = 0.61, 95% CI 0.46 to 0.82); passenger cars had decreased rollover risk (RR = 0.77, 95% CI 0.52 to 1.12), but SUVs/vans had a more dramatically decreased risk (RR = 0.40, 95% CI 0.26 to 0.61). This study supports previous results showing ESC to be effective in reducing the risk of rollover. ESC is more effective in SUVs/vans for rollovers related to single-vehicle MVCs.
Byzantine-fault tolerant self-stabilizing protocol for distributed clock synchronization systems
Malekpour, Mahyar R. (Inventor)
2010-01-01
A rapid Byzantine self-stabilizing clock synchronization protocol that self-stabilizes from any state, tolerates bursts of transient failures, and deterministically converges within a linear convergence time with respect to the self-stabilization period. Upon self-stabilization, all good clocks proceed synchronously. The Byzantine self-stabilizing clock synchronization protocol does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period.
STABILITY OF SATELLITES IN CLOSELY PACKED PLANETARY SYSTEMS
International Nuclear Information System (INIS)
Payne, Matthew J.; Holman, Matthew J.; Deck, Katherine M.; Perets, Hagai B.
2013-01-01
We perform numerical integrations of four-body (star, planet, planet, satellite) systems to investigate the stability of satellites in planetary systems with tightly packed inner planets (STIPs). We find that the majority of closely spaced stable two-planet systems can stably support satellites across a range of parameter-space which is only slightly decreased compared to that seen for the single-planet case. In particular, circular prograde satellites remain stable out to ∼0.4 R H (where R H is the Hill radius) as opposed to 0.5 R H in the single-planet case. A similarly small restriction in the stable parameter-space for retrograde satellites is observed, where planetary close approaches in the range 2.5-4.5 mutual Hill radii destabilize most satellites orbits only if a ∼ 0.65 R H . In very close planetary pairs (e.g., the 12:11 resonance) the addition of a satellite frequently destabilizes the entire system, causing extreme close approaches and the loss of satellites over a range of circumplanetary semi-major axes. The majority of systems investigated stably harbored satellites over a wide parameter-space, suggesting that STIPs can generally offer a dynamically stable home for satellites, albeit with a slightly smaller stable parameter-space than the single-planet case. As we demonstrate that multi-planet systems are not a priori poor candidates for hosting satellites, future measurements of satellite occurrence rates in multi-planet systems versus single-planet systems could be used to constrain either satellite formation or past periods of strong dynamical interaction between planets
Absolute stability of nonlinear systems with time delays and applications to neural networks
Directory of Open Access Journals (Sweden)
Xinzhi Liu
2001-01-01
Full Text Available In this paper, absolute stability of nonlinear systems with time delays is investigated. Sufficient conditions on absolute stability are derived by using the comparison principle and differential inequalities. These conditions are simple and easy to check. In addition, exponential stability conditions for some special cases of nonlinear delay systems are discussed. Applications of those results to cellular neural networks are presented.
Canister positioning. Influence of fracture system on deposition hole stability
International Nuclear Information System (INIS)
Hoekmark, Harald
2003-11-01
The study concerns the mechanical behaviour of rock surrounding tunnels and deposition holes in a nuclear waste repository. The mechanical effects of tunnel excavation and deposition hole excavation are investigated by use of a tunnel scale numerical model representing a part of a KBS-3 type repository. The excavation geometry, the initial pre-mining state of stress, and the geometrical features of the fracture system are defined according to conditions that prevail in the TBM tunnel rock mass in Aespoe HRL. Comparisons are made between results obtained without consideration of fractures and results obtained with inclusion of the fracture system. The focus is on the region around the intersection of a tunnel and a deposition hole. A general conclusion is that a fracture system of the type found in the TBM rock mass does not have a decisive influence on the stability of the deposition holes. To estimate the expected extent of spalling, information about other conditions, e.g. the orientation of the initial stresses and the strength properties of the intact rock, is more important than detailed information about the fracture system
Finite-Time Stability and Controller Design of Continuous-Time Polynomial Fuzzy Systems
Directory of Open Access Journals (Sweden)
Xiaoxing Chen
2017-01-01
Full Text Available Finite-time stability and stabilization problem is first investigated for continuous-time polynomial fuzzy systems. The concept of finite-time stability and stabilization is given for polynomial fuzzy systems based on the idea of classical references. A sum-of-squares- (SOS- based approach is used to obtain the finite-time stability and stabilization conditions, which include some classical results as special cases. The proposed conditions can be solved with the help of powerful Matlab toolbox SOSTOOLS and a semidefinite-program (SDP solver. Finally, two numerical examples and one practical example are employed to illustrate the validity and effectiveness of the provided conditions.
An equivalent condition for stability properties of Lotka-Volterra systems
International Nuclear Information System (INIS)
Chu Tianguang
2007-01-01
We give a solvable Lie algebraic condition for the equivalence of four typical stability notions (asymptotic stability, D-stability, total stability, and Volterra-Lyapunov stability) concerning Lotka-Volterra systems. Our approach makes use of the decomposition of the interaction matrix into symmetric and skew-symmetric parts, which may be related to the cooperative and competitive interaction pattern of a Lotka-Volterra system. The present result covers a known condition and can yield a larger set of interaction matrices for equivalence of the stability properties
Energy Technology Data Exchange (ETDEWEB)
Gruzdev, I.A.; Ekimova, M.M.; Truspekova, G.A.
1982-01-01
Expressions are derived for an idealized model of a complex electric power system; these expressions define the greatest level of stability of an electric power system and the optimum combination of stabilization factors with automatic excitation control in a single power system. The possibility of increasing the level of stability of an electric power system with simultaneous strict automatic excitation control of the synychronous generators in several power systems is analyzed.
Co-simulation of heavy truck tire dynamics and electronic stability control systems (phase A).
2009-07-01
Electronic stability control (ESC) systems have been proven to be an effective means of preventing instability and loss of control on both passenger vehicles and heavy trucks. In addition, roll stability algorithms are an effective means of reducing ...
Stability and complexity of small random linear systems
Hastings, Harold
2010-03-01
We explore the stability of the small random linear systems, typically involving 10-20 variables, motivated by dynamics of the world trade network and the US and Canadian power grid. This report was prepared as an account of work sponsored by an agency of the US Government. Neither the US Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the US Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the US Government or any agency thereof.
Preliminary safety evaluation for the plutonium stabilization and packaging system
International Nuclear Information System (INIS)
Shapley, J.E.
1997-01-01
This Preliminary Safety Evaluation (PSE) describes and analyzes the installation and operation of the Plutonium Stabilization and Packaging System (SPS) at the Plutonium Finishing Plant (PFP). The SPS is a combination of components required to expedite the safe and timely storage of Plutonium (Pu) oxide. The SPS program will receive site Pu packages, process the Pu for storage, package the Pu into metallic containers, and safely store the containers in a specially modified storage vault. The location of the SPS will be in the 2736- ZB building and the storage vaults will be in the 2736-Z building of the PFP, as shown in Figure 1-1. The SPS will produce storage canisters that are larger than those currently used for Pu storage at the PFP. Therefore, the existing storage areas within the PFP secure vaults will require modification. Other modifications will be performed on the 2736-ZB building complex to facilitate the installation and operation of the SPS
A Pseudodifferential Approach to Distributed Parameter Systems and Stabilization
DEFF Research Database (Denmark)
Pedersen, Michael
1993-01-01
The recent developments in microlocal analysis and pdeudodifferential boundary calculus are well suited tools in the investigation of a large number of problems occurring in control theory for partial differential equations. We explain some of the basic ideas of a pseudodifferential model....... Differential Equations47 (1983); Appl. Math. Optim.10 (1983)). So far, this work seems to have simplified or unified many of the previous works cited above. We hope that in the future it will even provide stronger and newer results in the boundary control of distributed parameter systems....... (SIAM J. Control Optim.29 (1991)). The pseudo-differential techniques apply easily in the proof of existence of a feedback semigroup for the parabolic and hyperbolic evolution problems, and we reprove in this new setting some of the stabilization results of Lasiecka and Triggiani (see, e.g., J...
Stability and stabilization of nonlinear systems and Takagi-Sugeno's fuzzy models
Directory of Open Access Journals (Sweden)
Blanco Yann
2001-01-01
Full Text Available This paper outlines a methodology to study the stability of Takagi-Sugeno's (TS fuzzy models. The stability analysis of the TS model is performed using a quadratic Liapunov candidate function. This paper proposes a relaxation of Tanaka's stability condition: unlike related works, the equations to be solved are not Liapunov equations for each rule matrix, but a convex combination of them. The coefficients of this sums depend on the membership functions. This method is applied to the design of continuous controllers for the TS model. Three different control structures are investigated, among which the Parallel Distributed Compensation (PDC. An application to the inverted pendulum is proposed here.
Wu, Guo-Cheng; Baleanu, Dumitru; Zeng, Sheng-Da
2018-04-01
This study investigates finite-time stability of Caputo delta fractional difference equations. A generalized Gronwall inequality is given on a finite time domain. A finite-time stability criterion is proposed for fractional differential equations. Then the idea is extended to the discrete fractional case. A linear fractional difference equation with constant delays is considered and finite-time stable conditions are provided. One example is numerically illustrated to support the theoretical result.
Plasma control system upgrade and increased plasma stability in NSTX
Energy Technology Data Exchange (ETDEWEB)
Mastrovito, D., E-mail: dmastrovito@pppl.go [Princeton Plasma Physics Laboratory, P.O. Box 451 Princeton, NJ 08543 (United States); Gates, D.; Gerhard, S.; Lawson, J.; Ludescher-Furth, C.; Marsala, R. [Princeton Plasma Physics Laboratory, P.O. Box 451 Princeton, NJ 08543 (United States)
2010-07-15
Plasma control on the National Spherical Torus Experiment (NSTX) was previously accomplished using eight 333 MHz G4 processors built by Sky computers. Several planned improvements and additional control algorithms required significant upgrades to our real-time control computers and real-time data acquisition infrastructure. Several in-house modules have been designed and implemented including: the digital time stamp module (DITS) and for digital/analog front panel data port (FPDP) output, the FPDP output module digital/analog (FOMD/A). Standard Linux based Intel computers perform the real-time control tasks and InfiniBand as been employed for communication between a user-accessible 'host' server and the real-time computer. In addition to several independent real-time processes the General Atomics developed PCS (Bell (2006) ) system infrastructure continues to be used on NSTX. While maintaining previous functionality, improvements in the control system software include: an RWM feedback algorithm, beta feedback NBI control, more comprehensive error logging and trapping, more user-friendly interface, more complete archiving and restoring functionality, and better status reporting and diagnostic tools. Once completed, we succeeded in increasing overall plasma stability and decreasing control system latency by several times.
The mathematical model of dynamic stabilization system for autonomous car
Saikin, A. M.; Buznikov, S. E.; Shabanov, N. S.; Elkin, D. S.
2018-02-01
Leading foreign companies and domestic enterprises carry out extensive researches and developments in the field of control systems for autonomous cars and in the field of improving driver assistance systems. The search for technical solutions, as a rule, is based on heuristic methods and does not always lead to satisfactory results. The purpose of this research is to formalize the road safety problem in the terms of modern control theory, to construct the adequate mathematical model for solving it, including the choice of software and hardware environment. For automatic control of the object, it is necessary to solve the problem of dynamic stabilization in the most complete formulation. The solution quality of the problem on a finite time interval is estimated by the value of the quadratic functional. Car speed, turn angle and additional yaw rate (during car drift or skidding) measurements are performed programmatically by the original virtual sensors. The limit speeds at which drift, skidding or rollover begins are calculated programmatically taking into account the friction coefficient identified in motion. The analysis of the results confirms both the adequacy of the mathematical models and the algorithms and the possibility of implementing the system in the minimal technical configuration.
Directory of Open Access Journals (Sweden)
Qi Wu
Full Text Available From evolutionary reasoning, we derived a novel hypothesis that ingroup derogation is an evolved response of behavioral immune system which follows the smoke detector principle and the functional flexibility principle. This hypothesis was tested and supported across three experiments. In Experiment 1, participants' group membership was manipulated by using a minimal group paradigm. The results indicated that mere social categorization alone - a heuristic cue that implies the differentiation between "us" and "them" - was sufficient to elicit ingroup derogation among Chinese participants, and, such an intergroup bias was positively associated with the perceived vulnerability to diseases, which was also more consistently associated with ingroup attitudes. Experiment 2 extended and partially replicated Experiment 1 by showing that when there were cues of diseases in the immediate physical environment, Chinese participants exaggerated their attitudes of ingroup derogation. The results also showed that this effect was mainly driven by outgroup attraction. Experiment 3 changed the method of disease manipulation, and found that Chinese participants responded more strongly to disease cues originating from ingroup members and that they endorsed more ingroup derogation attitudes even when the ingroup and outgroup members were both displaying cues of diseases. Taken together, these results reveal the previously unexplored effects of infectious diseases on ingroup derogation attitudes, and suggest an interesting linkage between the evolved behavioral immune system and the ingroup derogation.
ATTITUDE TOWARDS THE USE OF LEARNING MANAGEMENT SYSTEM AMONG UNIVERSITY STUDENTS: A Case Study
Directory of Open Access Journals (Sweden)
Fuad A. A.TRAYEK
2013-07-01
Full Text Available Learning management system (LMS is a learning platform for both full time and distant learning students at the International Islamic University in Malaysia (IIUM. LMS becomes a tool for IIUM to disseminate information and learning resources to the students. The objectives of this study were to Ø investigate students' attitudes toward the use of LMS, Ø to verify the impact of perceived usefulness and perceived ease of use on attitude towards use of learning management system, Ø to examine the differences in attitudes toward the use of LMS between distance learning and full time students. There were 120 (70 full time and 50 distance learning students at the Institute of Education responded for the study. The collected data was analysed using descriptive statistics, t-test and Multiple Regression Analysis (MRA. The results of the study showed that perceived ease of use and perceived usefulness determine students' attitudes toward the use of LMS. However, this study did not find any significant differences between distance learning and full time students. According to the findings the study recommended that the University should continue using LMS because it is useful for both distance learning and full time students. Further suggestions are made to customize and upgrade the LMS suitable for innovative teaching and learning.
Performance of Power System Stabilizer (UNITROL D) in Benghazi North Power Plant
T. Hussein
2011-01-01
The use of power system stabilizers (PSSs) to damp power system swing mode of oscillations is practical important. Our purpose is to retune the power system stabilizer (PSS1A) parameters in Unitrol D produced by ABB– was installed in 1995in Benghazi North Power Plants (BNPPs) at General Electricity Company of Libya (GECOL). The optimal values of the power system stabilizer (PSS1A) parameters are determined off-line by a particle swarm optimization technique (PSO). The obj...
14 CFR 27.672 - Stability augmentation, automatic, and power-operated systems.
2010-01-01
... power-operated systems. 27.672 Section 27.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 27.672 Stability augmentation, automatic, and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show...
14 CFR 25.672 - Stability augmentation and automatic and power-operated systems.
2010-01-01
... power-operated systems. 25.672 Section 25.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 25.672 Stability augmentation and automatic and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated systems is necessary to show...
14 CFR 29.672 - Stability augmentation, automatic, and power-operated systems.
2010-01-01
... power-operated systems. 29.672 Section 29.672 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Construction Control Systems § 29.672 Stability augmentation, automatic, and power-operated systems. If the functioning of stability augmentation or other automatic or power-operated system is necessary to show...
STUDENTS’ ATTITUDES TOWARDS THE DEVELOPMENT OF AN ONLINE GUIDANCE COUNSELING SYSTEM
Directory of Open Access Journals (Sweden)
John Audi Perillo Bato
2016-12-01
Full Text Available Information and communication technology (ICT impacts the guidance counseling services (GCS in many higher education institutions (HEIs. However, many HEIs are experiencing the digital gap most especially in bridging ICT and GCS. This paper aims to measure the attitudes towards the development of an online guidance counseling system in a private university in the Philippines. All respondents are tertiary students during the 1st semester of the academic year 2014-2015 in a total of 348. An adapted survey questionnaire was used. The study shows that despite the students underutilizing the GCS, these students show positive attitudes towards the proposed system. The result implies that these students are capable of adapting to an online environment as an alternative to a face-to-face counseling setup. Based on the results, developing an online guidance counseling system is a promising initiative for this university.
Directory of Open Access Journals (Sweden)
Chen Qin
2013-01-01
Full Text Available This paper considers the problems of the robust stability and robust H∞ controller design for time-varying delay switched systems using delta operator approach. Based on the average dwell time approach and delta operator theory, a sufficient condition of the robust exponential stability is presented by choosing an appropriate Lyapunov-Krasovskii functional candidate. Then, a state feedback controller is designed such that the resulting closed-loop system is exponentially stable with a guaranteed H∞ performance. The obtained results are formulated in the form of linear matrix inequalities (LMIs. Finally, a numerical example is provided to explicitly illustrate the feasibility and effectiveness of the proposed method.
Stability and control of wind farms in power systems
Energy Technology Data Exchange (ETDEWEB)
Jauch, C.
2006-10-15
The Ph.D. project 'Stability and Control of Wind Farms in Power Systems' deals with some selected problems related to wind power in power systems. With increasing wind power penetration, wind turbines substitute the power production of conventional power plants. Therefore, wind turbines also have to take over the power system stabilisation and control tasks, that were traditionally carried out by conventional power plants. Out of the many aspects related to this problem, this project focuses on transient fault ride-through and power system stabilisation. The selection of turbine types considered in this project is limited to active-stall turbines and variable speed, variable pitch turbines with gearboxes and full-scale converter-connected synchronous generators. As a basis for the project, a study into the state of the art is conducted at the beginning of the project. Grid connection requirements that were in force, or published as drafts, at the time, and scientific literature related to the topic, are studied. The project is based on simulations of wind turbines in a power system simulations tool. Some of the models used in this project were readily available prior to the project; the development of others is part of the project. The most extensive modelling work deals with the design of the electrical part of the variable speed turbine and its controls. To simulate realistic grid operation the wind turbine models are connected to an aggregated model of the Nordic power system. For that purpose the Nordic power system model, which was available prior to the project, is extended with a realistic feeder configuration. It is commonly demanded from modern wind turbines, that they must not disconnect in case of transient faults. Therefore, controllers are designed that enable the two turbine types to ride through transient faults. With these transient fault controllers the wind turbines can stay connected to the grid, such that their generation capacity is
Stability and Control of Large-Scale Dynamical Systems A Vector Dissipative Systems Approach
Haddad, Wassim M
2011-01-01
Modern complex large-scale dynamical systems exist in virtually every aspect of science and engineering, and are associated with a wide variety of physical, technological, environmental, and social phenomena, including aerospace, power, communications, and network systems, to name just a few. This book develops a general stability analysis and control design framework for nonlinear large-scale interconnected dynamical systems, and presents the most complete treatment on vector Lyapunov function methods, vector dissipativity theory, and decentralized control architectures. Large-scale dynami
Improvement of Transient Stability of Power System by System Damping Series Resistor (SDSR)
上里, 勝実; 千住, 智信; 当銘, 秀之; 高原, 景滋; Uezato, Katsumi; Senjyu, Tomonobu; Toume, Hideyuki; Takahara, Keiji
1990-01-01
The system damping resistor is one of the method for improving the transient stability of power systems. The main circuit is the simple construction so that is low cost and is few abnormal surge, and is superior in ability of economy, reliability and maintenance. Conventionally, most of all system damping resistors have adopted the paralleled resistor, whereas the series resistor is used little.In this paper, we investigate the characteristics of the series resistor by comparing with the para...
A stability identification system for boiling water nuclear reactors
International Nuclear Information System (INIS)
Belblidia, L.A.; Chevrier, A.
1994-01-01
Boiling water reactors are subject to instabilities under low-flow, high-power operating conditions. These instabilities are a safety concern and it is therefore important to determine stability margins. This paper describes a method to estimate a measure of stability margin, called the decay ratio, from autoregressive modelling of time series data. A phenomenological model of a boiling water reactor with known stability characteristics is used to generate time series to validate the program. The program is then applied to signals from local power range monitors from the cycle 7 stability tests at the Leibstadt plant. (author) 7 figs., 2 tabs., 12 refs
Predictors of attitude and intention to use knowledge management system among Korean nurses.
Yun, Eun Kyoung
2013-12-01
Knowledge sharing using Knowledge Management (KM) systems helps nurses to understand and acquire appropriate knowledge that influences the quality of healthcare service. The purpose of this study was to identify organizational and individual factors influencing attitude and intention to use KM systems among Korean nurses. A cross-sectional survey design was used to study a sample of 245 nurses employed at five hospitals in Seoul. A multiple hierarchical regression was used to examine predictors of nurses' attitude and intention to use. From an individual perspective, nurse's informatics competency was identified as a significant factor influencing attitudes toward knowledge management usage within adhocracy and clan cultures. However, from an organizational perspective, level of hospital information system was identified as a significant factor influencing KM system usage within adhocracy cultures. The findings of this study will be helpful in better understanding and assessing the impact of the factors affecting the implementation of nursing knowledge management systems and in further developing successful managerial strategies using knowledge resources in healthcare settings. Copyright © 2013 Elsevier Ltd. All rights reserved.
LMI optimization approach to stabilization of time-delay chaotic systems
International Nuclear Information System (INIS)
Park, Ju H.; Kwon, O.M.
2005-01-01
Based on the Lyapunov stability theory and linear matrix inequality (LMI) technique, this paper proposes a novel control method for stabilization of a class of time-delay chaotic systems. A stabilization criterion is derived in terms of LMIs which can be easily solved by efficient convex optimization algorithms. A numerical example is included to show the advantage of the result derived
Energy Technology Data Exchange (ETDEWEB)
Vachirasricirikul, Sitthidet [Department of Electrical Engineering, Faculty of Engineering, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand); Ngamroo, Issarachai; Kaitwanidvilai, Somyot [Center of Excellence for Innovative Energy Systems, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)
2009-09-15
It is well known that the power output of microturbine can be controlled to compensate for load change and alleviate the system frequency fluctuations. Nevertheless, the microturbine may not adequately compensate rapid load change due to its slow dynamic response. Moreover, when the intermittent power generations from wind power and photovoltaic are integrated into the system, they may cause severe frequency fluctuation. In order to study the fast dynamic response, this paper applies electrolyzer system to absorb these power fluctuations and enhance the frequency control effect of microturbine in the microgrid system. The robust coordinated controller of electrolyzer and microturbine for frequency stabilization is designed based on a fixed-structure H{sub {infinity}} loop shaping control. Simulation results exhibit the robustness and stabilizing effects of the proposed coordinated electrolyzer and microturbine controllers against system parameters variation and various operating conditions. (author)
Ekrami, Yasamin; Cook, Joseph S.
2011-01-01
In order to mitigate catastrophic failures on future generation space vehicles, engineers at the National Aeronautics and Space Administration have begun to integrate a novel crew abort systems that could pull a crew module away in case of an emergency at the launch pad or during ascent. The Max Launch Abort System (MLAS) is a recent test vehicle that was designed as an alternative to the baseline Orion Launch Abort System (LAS) to demonstrate the performance of a "tower-less" LAS configuration under abort conditions. The MLAS II test vehicle will execute a propulsive coast stabilization maneuver during abort to control the vehicles trajectory and thrust. To accomplish this, the spacecraft will integrate an Attitude Control System (ACS) with eight hypergolic monomethyl hydrazine liquid propulsion engines that are capable of operating in a quick pulsing mode. Two main elements of the ACS include a propellant distribution subsystem and a pressurization subsystem to regulate the flow of pressurized gas to the propellant tanks and the engines. The CAD assembly of the Attitude Control System (ACS) was configured and integrated into the Launch Abort Vehicle (LAV) design. A dynamic random vibration analysis was conducted on the Main Propulsion System (MPS) helium pressurization panels to assess the response of the panel and its components under increased gravitational acceleration loads during flight. The results indicated that the panels fundamental and natural frequencies were farther from the maximum Acceleration Spectral Density (ASD) vibrations which were in the range of 150-300 Hz. These values will direct how the components will be packaged in the vehicle to reduce the effects high gravitational loads.
Transient stability probability evaluation of power system incorporating with wind farm and SMES
DEFF Research Database (Denmark)
Fang, Jiakun; Miao, Lu; Wen, Jinyu
2013-01-01
Large scale renewable power generation brings great challenges to the power system operation and stabilization. Energy storage is one of the most important technologies to face the challenges. This paper proposes a method for transient stability probability evaluation of power system with wind farm...... and SMES. Firstly, a modified 11-bus test system with both wind farm and SMES has been implemented. The wind farm is represented as a doubly fed induction generator (DFIG). Then a stochastic-based approach to evaluate the probabilistic transient stability index of the power system is presented. Uncertain...... the probability indices. With the proposed method based on Monte-Carlo simulation and bisection method, system stability is "measured". Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve...
The attitude to nuclear energy in comparison with other energy systems
International Nuclear Information System (INIS)
Fuchs, D.
1991-01-01
The subject of the study is the analysis of trends, the level and the determinants of the attitude to nuclear energy on the basis of survey data from representative samples. The emphasis is on analyzing the attitude to nuclear energy in the context of the so-called new political line of conflict. The most striking result of the trend analysis of the attitude to four energy systems - nuclear energy, coal, mineral oil, natural gas - was the drastic decline in the acceptance of nuclear energy in the time period covered by the available time series. The trends observed lead one to suppose that the evaluation of energy systems is no simple numbers game of the kind that means a more negative assessment of one energy system unavoidably leads to a more positive assessment of the other and vice versa, but that the individual energy systems are judged at least in part independently of one another. Effective public relations information and events may play an important part in changing attitudes to the individual energy systems. Structural factors are primarily a change in political values and an increased political competence on the part of the citizens. Both these factors taken together have created a greater perception of and sensitivity to the side-effects of the technical-industrial growth process. This aspect of the side-effects has been politicized by the New Social Movements particularly with reference to nuclear energy. Provided that political lines of conflict are important and lasting mechanisms for structuring, then nuclear energy will probably remain a constant theme, because of its importance in symbolizing fundamental problems at the technical-industrial growth process. (orig./HSCH) [de
Using a Remotely Piloted Aircraft System (RPAS) to analyze the stability of a natural rock slope
Salvini, Riccardo; Esposito, Giuseppe; Mastrorocco, Giovanni; Seddaiu, Marcello
2016-04-01
This paper describes the application of a rotary wing RPAS for monitoring the stability of a natural rock slope in the municipality of Vecchiano (Pisa, Italy). The slope under investigation is approximately oriented NNW-SSE and has a length of about 320 m; elevation ranges from about 7 to 80 m a.s.l.. The hill consists of stratified limestone, somewhere densely fractured, with dip direction predominantly oriented in a normal way respect to the slope. Fracture traces are present in variable lengths, from decimetre to metre, and penetrate inward the rock versant with thickness difficult to estimate, often exceeding one meter in depth. The intersection between different fracture systems and the slope surface generates rocky blocks and wedges of variable size that may be subject to phenomena of gravitational instability (with reference to the variation of hydraulic and dynamic conditions). Geometrical and structural info about the rock mass, necessary to perform the analysis of the slope stability, were obtained in this work from geo-referenced 3D point clouds acquired using photogrammetric and laser scanning techniques. In particular, a terrestrial laser scanning was carried out from two different point of view using a Leica Scanstation2. The laser survey created many shadows in the data due to the presence of vegetation in the lower parts of the slope and limiting the feasibility of geo-structural survey. To overcome such a limitation, we utilized a rotary wing Aibotix Aibot X6 RPAS geared with a Nikon D3200 camera. The drone flights were executed in manual modality and the images were acquired, according to the characteristics of the outcrops, under different acquisition angles. Furthermore, photos were captured very close to the versant (a few meters), allowing to produce a dense 3D point cloud (about 80 Ma points) by the image processing. A topographic survey was carried out in order to guarantee the necessary spatial accuracy to the process of images exterior
Event-triggered attitude control of spacecraft
Wu, Baolin; Shen, Qiang; Cao, Xibin
2018-02-01
The problem of spacecraft attitude stabilization control system with limited communication and external disturbances is investigated based on an event-triggered control scheme. In the proposed scheme, information of attitude and control torque only need to be transmitted at some discrete triggered times when a defined measurement error exceeds a state-dependent threshold. The proposed control scheme not only guarantees that spacecraft attitude control errors converge toward a small invariant set containing the origin, but also ensures that there is no accumulation of triggering instants. The performance of the proposed control scheme is demonstrated through numerical simulation.
Analysis of the gyroscopic stabilization of a system of rigid bodies
DEFF Research Database (Denmark)
Kliem, Wolfhard; Seyranian, Alexander P.
1997-01-01
We study the gyroscopic stability of a three-body system. A new method of finding stability regions, based on mechanism and criteria for gyroscopic stabilization, is presented. Of particular interest in this connection is the theory of interaction of eigenvalues. This leads to a complete 3......-dimensional analysis, which shows the regions of stability, divergence, and flutter of a simple model of a rotating spaceship....
Public Attitudes to Housing Systems for Pregnant Pigs.
Ryan, E B; Fraser, D; Weary, D M
2015-01-01
Understanding concerns about the welfare of farm animals is important for the development of socially sustainable production practices. This study used an online survey to test how views on group versus stall housing for pregnant sows varied when Canadian and US participants were provided information about these systems, including access to scientific papers, YouTube videos, Google images, and a frequently-asked-questions page (S1 Appendix). Initial responses and changes in responses after accessing the information were analyzed from Likert scores of 242 participants and from their written comments. Participants were less willing to accept the use of gestation stalls after viewing information on sow housing. For example, initially 30.4% of respondents indicated that they supported the use of gestation stalls; this declined to 17.8% after participants were provided additional information. Qualitative analysis of comments showed that supporters of gestation stalls expressed concern about the spread of disease and aggression between animals in less confined systems, whereas supporters of group housing placed more emphasis on the sow's ability to interact socially and perform natural behaviors. These results point to public opposition to the use of gestation stalls, and indicate that the more that the public learns about gestation stalls the less willing they will be to accept their use.
Stabilization and synchronization of Genesio-Tesi system via single variable feedback controller
International Nuclear Information System (INIS)
Wang Guangming
2010-01-01
This Letter investigates the stabilization and synchronization of Genesio-Tesi systems. Firstly, modifying the previous method, we stabilize the Genesio-Tesi system. Then, we synchronize two identical Genesio chaotic system by extending the obtained stabilization results. To the best of our knowledge, the above controllers obtained in this Letter are simpler than those obtained in the existing results. Finally, numerical simulations verify the effectiveness and the validity of the above theoretical results.
Simulation for transient stability study of the Taiwan power system - a nuclear majority system
International Nuclear Information System (INIS)
Huang, J.C.C.
1984-01-01
A transient stability program was developed for the Taiwan Power Company, which has a high proportion of nuclear generation in its power system. This program offers a new territory to investigate nuclear plant effects on the power system transient stability. This program also provides a high speed tool for the Taipower system operational planning. A generalized procedure of synchronous machine modeling for a large-scale stability study is presented. The merits and weaknesses of machine modeling can be comprehended through each item of this procedure. Three types of nonlinear synchronous machine modeling implemented into this stability program are derived by following this procedure. A robust subroutine was derived to perform the fourth order Runge-Kutta integration method, making the software programming neat and systematical. For simulating the nuclear plant influence on the system, this program implemented an additional four functions: load-limit operation simulated by a low-value gate in the governor model, bypass valve capacity monitored by sending out a warning message, rotor overspeed protection relay, and generator anti-motoring relay
Improvement of the transient stability using SFCL in Korean power systems
International Nuclear Information System (INIS)
Hwang, Intae; Lee, Seung Ryul; Seo, Sangsoo; Yoon, Jaeyoung; Kim, Chul-Hwan
2013-01-01
Highlights: •In Korea, the Special Protection System is applied for protecting the power system. •Hybrid SFCL is protecting the power system from viewpoint of the transient stability. •Basic hybrid SFCL system cannot recover during the auto-reclosing operation. •This paper performs analysis of transient stability using the novel hybrid SFCL. -- Abstract: This paper proposed a novel hybrid SFCL system for the enhancement of the transient stability in Korean power transmission system with auto-reclosing operation. The proposed SFCL system has an operation mechanism that the current limiting impedance is eliminated from the power system in a fault clearing time for the enhancement of the transient stability. Also, the system can cover the auto-reclosing operation of the transmission power system. This study analyzed an improvement of the special protection system by applying the proposed SFCL system to real power system in Korea
42: An Open-Source Simulation Tool for Study and Design of Spacecraft Attitude Control Systems
Stoneking, Eric
2018-01-01
Simulation is an important tool in the analysis and design of spacecraft attitude control systems. The speaker will discuss the simulation tool, called simply 42, that he has developed over the years to support his own work as an engineer in the Attitude Control Systems Engineering Branch at NASA Goddard Space Flight Center. 42 was intended from the outset to be high-fidelity and powerful, but also fast and easy to use. 42 is publicly available as open source since 2014. The speaker will describe some of 42's models and features, and discuss its applicability to studies ranging from early concept studies through the design cycle, integration, and operations. He will outline 42's architecture and share some thoughts on simulation development as a long-term project.
Attitudes towards using mobile applications for teaching mathematics in open learning systems
Directory of Open Access Journals (Sweden)
Bahjat Hamid Altakhyneh
2018-05-01
Full Text Available This study investigated attitudes towards teaching mathematics via mobile learning in open learning systems. The sample of the study consisted of 57 male and female students enrolled in the mathematics course in the department of educational studies at the Arab Open University/ Jordan for the academic year 2016/2017. Results of the study showed that positive student attitudes toward using mobile applications reached 80%. Each of the following scores is ranked as ascending: mathematical thinking (75%, achievement motivation (76%, developing social and emotional skills (77%, and application technology (96%. There was no statistical significance difference (α ≤0.01 between the variable type of general secondary certificate (scientific / arts stream as well as the nature of employment in terms of whether the learner was either an employee or non-employee. In light of results of the study, the researcher recommends using mobile applications in teaching courses of mathematics in open learning systems.
Amyloid fibril systems reduce, stabilize and deliver bioavailable nanosized iron
Shen, Yi; Posavec, Lidija; Bolisetty, Sreenath; Hilty, Florentine M.; Nyström, Gustav; Kohlbrecher, Joachim; Hilbe, Monika; Rossi, Antonella; Baumgartner, Jeannine; Zimmermann, Michael B.; Mezzenga, Raffaele
2017-07-01
Iron-deficiency anaemia (IDA) is a major global public health problem. A sustainable and cost-effective strategy to reduce IDA is iron fortification of foods, but the most bioavailable fortificants cause adverse organoleptic changes in foods. Iron nanoparticles are a promising solution in food matrices, although their tendency to oxidize and rapidly aggregate in solution severely limits their use in fortification. Amyloid fibrils are protein aggregates initially known for their association with neurodegenerative disorders, but recently described in the context of biological functions in living organisms and emerging as unique biomaterial building blocks. Here, we show an original application for these protein fibrils as efficient carriers for iron fortification. We use biodegradable amyloid fibrils from β-lactoglobulin, an inexpensive milk protein with natural reducing effects, as anti-oxidizing nanocarriers and colloidal stabilizers for iron nanoparticles. The resulting hybrid material forms a stable protein-iron colloidal dispersion that undergoes rapid dissolution and releases iron ions during acidic and enzymatic in vitro digestion. Importantly, this hybrid shows high in vivo iron bioavailability, equivalent to ferrous sulfate in haemoglobin-repletion and stable-isotope studies in rats, but with reduced organoleptic changes in foods. Feeding the rats with these hybrid materials did not result in abnormal iron accumulation in any organs, or changes in whole blood glutathione concentrations, inferring their primary safety. Therefore, these iron-amyloid fibril hybrids emerge as novel, highly effective delivery systems for iron in both solid and liquid matrices.
Green, K. N.; van Alstine, R. L.
This paper presents the current performance levels of the SDG-5 gyro, a high performance two-axis dynamically tuned gyro, and the DRIRU II redundant inertial reference unit relating to stabilization and pointing applications. Also presented is a discussion of a product improvement program aimed at further noise reductions to meet the demanding requirements of future space defense applications.
Design and Simulation of a Nano-Satellite Attitude Determination System
2009-12-01
4 D. SURVEY OF CUBESAT ATTITUDE DETERMINATION SYSTEMS... 6 1. Pumpkin IMI ADCS...imagery satellites are going through the same trend in resolution. They have improved in the past decade, from relatively low resolution at about 5m to...this is the nearly complete lack of a pre-packaged ADS. Until August of 2009, there was only one ADS available on the market. It was the Pumpkin
On-line tuning of a fuzzy-logic power system stabilizer
International Nuclear Information System (INIS)
Hossein-Zadeh, N.; Kalam, A.
2002-01-01
A scheme for on-line tuning of a fuzzy-logic power system stabilizer is presented. firstly, a fuzzy-logic power system stabilizer is developed using speed deviation and accelerating power as the controller input variables. The inference mechanism of fuzzy-logic controller is represented by a decision table, constructed of linguistic IF-THEN rules. The Linguistic rules are available from experts and the design procedure is based on these rules. It assumed that an exact model of the plant is not available and it is difficult to extract the exact parameters of the power plant. Thus, the design procedure can not be based on an exact model. This is an advantage of fuzzy logic that makes the design of a controller possible without knowing the exact model of the plant. Secondly, two scaling parameters are introduced to tune the fuzzy-logic power system stabilizer. These scaling parameters are the outputs of another fuzzy-logic system, which gets the operating conditions of power system as inputs. These mechanism of tuning the fuzzy-logic power system stabilizer makes the fuzzy-logic power system stabilizer adaptive to changes in the operating conditions. Therefore, the degradation of the system response, under a wide range of operating conditions, is less compared to the system response with a fixed-parameter fuzzy-logic power system stabilizer and a conventional (linear) power system stabilizer. The tuned stabilizer has been tested by performing nonlinear simulations using a synchronous machine-infinite bus model. The responses are compared with a fixed parameters fuzzy-logic power system stabilizer and a conventional (linear) power system stabilizer. It is shown that the tuned fuzzy-logic power system stabilizer is superior to both of them
On stabilization of linear systems with stochastic disturbances and input saturation
Stoorvogel, A.A.; Weiland, S.; Saberi, A.
2004-01-01
It is well-known that for linear systems internal asymptotic stability implies external stability in the sense that when the external input is in Lp then also the state will be in Lp. However, for the control of linear systems with saturation where the controlled system is nonlinear this implication
DEFF Research Database (Denmark)
Yoon, Changwoo; Bai, Haofeng; Wang, Xiongfei
2015-01-01
Stability analysis of distributed power generation system becomes complex when there are many numbers of grid inverters in the system. In order to analyze system stability, the overall network impedance will be lumped and needs to be analyzed one by one. However, using a unified bulky transfer-fu...... and then it is expanded for generalizing its concept to an overall radial structured network....
On the stability of non-linear systems; Sur la stabilite des systemes non-lineaires
Energy Technology Data Exchange (ETDEWEB)
Guelman, M [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires, services scientifiques
1968-09-01
A study is made of the absolute stability of nonlinear systems, using Liapounov's second method and taking into account the results obtained from V.M. Popov's work. The results already established are first presented, in particular concerning the frequency domain criterions for absolute stability of automatic control systems containing one single non linearity. The results have been extended to show the existence of a limiting parabola. New use is then made of the methods studied for deriving absolute stability criterions for a system containing a different type of non linearity. Finally, the results obtained are considered from the point of view of Aizerman's conjecture. (author) [French] Dans ce travail, on etudie la stabilite absolue des systemes non lineaires utilisant la deuxieme methode de Liapounov en tenant compte des resultats acquis a partir des travaux de V.M. Popov. On fait d'abord un expose des resultats deja etablis, en particulier en ce qui concerne les criteres frequentiels de stabilite absolue pour le cas d'un systeme de commande automatique comportant une seule non linearite. On a prolonge ces resultats jusqu'a l'etablissement de l'existence d'une parabole limite. On fait ensuite une nouvelle utilisation des methodes etudiees, etablissant des criteres de stabilite absolue pour un systeme comportant un type different de non linearite. On etudie enfin les resultats obtenus, dans l'optique de la conjecture de Aizerman. (auteur)
Thermal stability of α-amylase in aqueous cosolvent systems
Indian Academy of Sciences (India)
Prakash
The activity and thermal stability of α-amylase were studied in the presence of different concentrations of ... 2.1 Materials ..... unfavourable free energy of transfer of amino acid side ..... folded protein with a hydrophobic dye: evidence that molten.
Thermal stability of α-amylase in aqueous cosolvent systems
Indian Academy of Sciences (India)
Prakash
Department of Protein Chemistry and Technology, Central Food Technological Research ... Keywords. α-Amylase; cosolvents; preferential interaction parameters; thermal stability ...... simulations of trehalose as a 'dynamic reducer' for solvent.
Sensor fault detection and recovery in satellite attitude control
Nasrolahi, Seiied Saeed; Abdollahi, Farzaneh
2018-04-01
This paper proposes an integrated sensor fault detection and recovery for the satellite attitude control system. By introducing a nonlinear observer, the healthy sensor measurements are provided. Considering attitude dynamics and kinematic, a novel observer is developed to detect the fault in angular rate as well as attitude sensors individually or simultaneously. There is no limit on type and configuration of attitude sensors. By designing a state feedback based control signal and Lyapunov stability criterion, the uniformly ultimately boundedness of tracking errors in the presence of sensor faults is guaranteed. Finally, simulation results are presented to illustrate the performance of the integrated scheme.
Power system dynamics and stability with synchrophasor measurement and power system toolbox
Sauer, Peter W; Chow, Joe H
2017-01-01
This new edition addresses the needs of dynamic modeling and simulation relevant to power system planning, design, and operation, including a systematic derivation of synchronous machine dynamic models together with speed and voltage control subsystems. Reduced-order modeling based on integral manifolds is used as a firm basis for understanding the derivations and limitations of lower-order dynamic models. Following these developments, a multi-machine model interconnected through the transmission network is formulated and simulated using numerical simulation methods. Energy function methods are discussed for direct evaluation of stability. Small-signal analysis is used for determining the electromechanical modes and mode-shapes, and for power system stabilizer design. Time-synchronized high-sampling-rate phasor measurement units (PMUs) to monitor power system disturbances ave been implemented throughout North America and many other countries. In this second edition, new chapters on synchrophasor measurement ...
The Implementation of Satellite Attitude Control System Software Using Object Oriented Design
Reid, W. Mark; Hansell, William; Phillips, Tom; Anderson, Mark O.; Drury, Derek
1998-01-01
NASA established the Small Explorer (SNMX) program in 1988 to provide frequent opportunities for highly focused and relatively inexpensive space science missions. The SMEX program has produced five satellites, three of which have been successfully launched. The remaining two spacecraft are scheduled for launch within the coming year. NASA has recently developed a prototype for the next generation Small Explorer spacecraft (SMEX-Lite). This paper describes the object-oriented design (OOD) of the SMEX-Lite Attitude Control System (ACS) software. The SMEX-Lite ACS is three-axis controlled and is capable of performing sub-arc-minute pointing. This paper first describes high level requirements governing the SMEX-Lite ACS software architecture. Next, the context in which the software resides is explained. The paper describes the principles of encapsulation, inheritance, and polymorphism with respect to the implementation of an ACS software system. This paper will also discuss the design of several ACS software components. Specifically, object-oriented designs are presented for sensor data processing, attitude determination, attitude control, and failure detection. Finally, this paper will address the establishment of the ACS Foundation Class (AFC) Library. The AFC is a large software repository, requiring a minimal amount of code modifications to produce ACS software for future projects.
Salgotra, Aprajita; Pan, Somnath
2018-05-01
This paper explores a two-level control strategy by blending local controller with centralized controller for the low frequency oscillations in a power system. The proposed control scheme provides stabilization of local modes using a local controller and minimizes the effect of inter-connection of sub-systems performance through a centralized control. For designing the local controllers in the form of proportional-integral power system stabilizer (PI-PSS), a simple and straight forward frequency domain direct synthesis method is considered that works on use of a suitable reference model which is based on the desired requirements. Several examples both on one machine infinite bus and multi-machine systems taken from the literature are illustrated to show the efficacy of the proposed PI-PSS. The effective damping of the systems is found to be increased remarkably which is reflected in the time-responses; even unstable operation has been stabilized with improved damping after applying the proposed controller. The proposed controllers give remarkable improvement in damping the oscillations in all the illustrations considered here and as for example, the value of damping factor has been increased from 0.0217 to 0.666 in Example 1. The simulation results obtained by the proposed control strategy are favourably compared with some controllers prevalent in the literature. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.
Scout fourth stage attitude and velocity control (AVC) system feasibility study
Byars, L. B.
1975-01-01
The feasibility of incorporating a guidance system in the Scout fourth stage to achieve a significant improvement in expected payload delivery accuracy is studied. The technical investigations included the determination of the AVC equipment performance requirements, establishment of qualification and acceptance test levels, generation of layouts illustrating design approaches for the upper D and payload transition sections to incorporate the hardware, and the preparation of a vendor bid package. Correction concepts, utilizing inertial velocity and attitude, were identified and evaluated. Fourth stage attitude adjustments as determined from inertial velocity variation through the first three stages and a final velocity correction based upon the measured in-plane component errors at injection were employed. Results show radical reductions in apogee-perigee deviations.
Midterm Stability Evaluation of Wide-area Power System by using Synchronized Phasor Measurements
Ota, Yutaka; Ukai, Hiroyuki; Nakamura, Koichi; Fujita, Hideki
In recent years, the PMU (Phasor Measurement Unit) receives a great deal of attention as a synchronized measurement system of power systems. Synchronized phasor angles obtained by the PMU provide the effective information for evaluating the stability of a bulk power system. The aspect of instability phenomena during midterm tends to be more complicated, and the stability analysis using the synchronized phasor measurements is significant in order to keep a complicated power system stable. This paper proposes a midterm stability evaluation method of the wide-area power system by using the synchronized phasor measurements. By clustering and aggregating the power system to some coherent groups, the step-out is effectively predicted on the basis of the two-machine equivalent power system model. The midterm stability of a longitudinal power system model of Japanese 60Hz systems constructed by the PSA, which is a hybrid-type power system simulator, is practically evaluated using the proposed method.
Nakasuka, Shinichi; Miyata, Kikuko; Tsuruda, Yoshihiro; Aoyanagi, Yoshihide; Matsumoto, Takeshi
2018-04-01
The recent advancement of micro/nano/pico-satellites technologies encourages many universities to develop three axis stabilized satellites. As three axis stabilization is high level technology requiring the proper functioning of various sensors, actuators and control software, many early satellites failed in their initial operation phase because of shortage of solar power generation or inability to realize the initial step of missions because of unexpected attitude control system performance. These results come from failure to design the satellite attitude determination and control system (ADCS) appropriately and not considering "satellite survivability." ADCS should be designed such that even if some sensors or actuators cannot work as expected, the satellite can survive and carry out some of its missions, even if not full. This paper discusses how to realize ADCS while taking satellite survivability into account, based on our experiences of design and in-orbit operations of Hodoyoshi-3 and 4 satellites launched in 2014, which suffered from various component anomalies but could complete their missions.
An exploratory risk perception study of attitudes toward homeland security systems.
Sanquist, Thomas F; Mahy, Heidi; Morris, Frederic
2008-08-01
Understanding the issues surrounding public acceptance of homeland security systems is important for balancing security needs and potential civil liberties infringements. A psychometric survey was used in an exploratory study of attitudes regarding homeland security systems. Psychometric rating data were obtained from 182 respondents on psychological attributes associated with 12 distinct types of homeland security systems. An inverse relationship was observed for the overall rating attributes of acceptability and risk of civil liberties infringement. Principal components analysis (PCA) yielded a two-factor solution with the rating scale loading pattern suggesting factors of perceived effectiveness and perceived intrusiveness. These factors also showed an inverse relationship. The 12 different homeland security systems showed significantly different scores on the rating scales and PCA factors. Of the 12 systems studied, airport screening, canine detectors, and radiation monitoring at borders were found to be the most acceptable, while email monitoring, data mining, and global positioning satellite (GPS) tracking were found to be least acceptable. Students rated several systems as more effective than professionals, but the overall pattern of results for both types of subjects was similar. The data suggest that risk perception research and the psychometric paradigm are useful approaches for quantifying attitudes regarding homeland security systems and policies and can be used to anticipate potentially significant public acceptance issues.
Kulkov, V. M.; Medvedskii, A. L.; Terentyev, V. V.; Firsyuk, S. O.; Shemyakov, A. O.
2017-12-01
The problem of spacecraft attitude control using electromagnetic systems interacting with the Earth's magnetic field is considered. A set of dimensionless parameters has been formed to investigate the spacecraft orientation regimes based on dynamically similar models. The results of experimental studies of small spacecraft with a magnetic attitude control system can be extrapolated to the in-orbit spacecraft motion control regimes by using the methods of the dimensional and similarity theory.
Design development of the Apollo command and service module thrust vector attitude control systems
Peters, W. H.
1978-01-01
Development of the Apollo thrust vector control digital autopilot (TVC DAP) was summarized. This is the control system that provided pitch and yaw attitude control during velocity change maneuvers using the main rocket engine on the Apollo service module. A list of ten primary functional requirements for this control system are presented, each being subordinate to a more general requirement appearing earlier on the list. Development process functions were then identified and the essential information flow paths were explored. This provided some visibility into the particular NASA/contractor interface, as well as relationships between the many individual activities.
Self-organizing dynamic stability of far-from-equilibrium biological systems
Ivanitskii, G. R.
2017-10-01
One indication of the stability of a living system is the variation of the system’s characteristic time scales. Underlying the stability mechanism are the structural hierarchy and self-organization of systems, factors that give rise to a positive (accelerating) feedback and a negative (braking) feedback. Information processing in the brain cortex plays a special role in highly organized living organisms.
CISM Session on Bifurcation and Stability of Dissipative Systems
1993-01-01
The first theme concerns the plastic buckling of structures in the spirit of Hill’s classical approach. Non-bifurcation and stability criteria are introduced and post-bifurcation analysis performed by asymptotic development method in relation with Hutchinson’s work. Some recent results on the generalized standard model are given and their connection to Hill’s general formulation is presented. Instability phenomena of inelastic flow processes such as strain localization and necking are discussed. The second theme concerns stability and bifurcation problems in internally damaged or cracked colids. In brittle fracture or brittle damage, the evolution law of crack lengths or damage parameters is time-independent like in plasticity and leads to a similar mathematical description of the quasi-static evolution. Stability and non-bifurcation criteria in the sense of Hill can be again obtained from the discussion of the rate response.
Stability of superconducting cables for use in large magnet systems
International Nuclear Information System (INIS)
Tateishi, Hiroshi; Schmidt, C.
1992-01-01
The construction of large superconducting magnets requires the development of complicated conductor types, which can fulfill the specific requirements of different types of magnets. A rather hard boundary condition for large magnets is the presence of fast changing magnetic fields. In the Institute of Technical Physics of the Karlsruhe Nuclear Research Center, Germany, a superconducting cable was developed for use in poloidal field coils in Tokamak experiments. This 'POLO'-cable exhibits low losses in a magnetic ac-field and a high stability margin. In the present article the requirements on a superconducting cable are described, as well as the mechanisms of ac-losses and the calculation of the stability limit. Calculated values are compared with experimental data. Some unresolved problems concerning the stability of large magnets are discussed taking the example of the POLO-cable. (author)
Frequency scanning-based stability analysis method for grid-connected inverter system
DEFF Research Database (Denmark)
Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede
2017-01-01
This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion with conside......This paper proposes a frequency scanning-based impedance analysis for stability assessment of grid-connected inverter system, which is able to perform stability assessment without using system mathematical models and inherit the superior feature of impedance-based stability criterion...... with consideration of the inverter nonlinearities. Small current disturbance is injected into grid-connected inverter system in a particular frequency range, and the impedance is computed according to the harmonic-frequency response using Fourier analysis, and then the stability is predicted on the basis...... of the impedance stability criterion. The stability issues of grid-connected inverters with grid-current feedback and the converter-current feedback are addressed using the proposed method. The results obtained from simulation and experiments validate the effectiveness of the method. The frequency scanning...
Synchrophasor-Assisted Prediction of Stability/Instability of a Power System
Saha Roy, Biman Kumar; Sinha, Avinash Kumar; Pradhan, Ashok Kumar
2013-05-01
This paper presents a technique for real-time prediction of stability/instability of a power system based on synchrophasor measurements obtained from phasor measurement units (PMUs) at generator buses. For stability assessment the technique makes use of system severity indices developed using bus voltage magnitude obtained from PMUs and generator electrical power. Generator power is computed using system information and PMU information like voltage and current phasors obtained from PMU. System stability/instability is predicted when the indices exceeds a threshold value. A case study is carried out on New England 10-generator, 39-bus system to validate the performance of the technique.
Very high stability systems: LMJ target alignment system and MTG imager test setup
Compain, Eric; Maquet, Philippe; Kunc, Thierry; Marque, Julien; Lauer-Solelhac, Maxime; Delage, Laurent; Lanternier, Catherine
2015-09-01
Most of space instruments and research facilities require test equipment with demanding opto-mechanical stability. In some specific cases, when the stability performance directly drives the final performance of the scientific mission and when feasibility is questionable, specific methods must be implemented for the associated technical risk management. In present paper, we will present our heritage in terms of methodology, design, test and the associated results for two specific systems : the SOPAC-POS and the MOTA, generating new references for future developments. From a performance point of view, we will emphasis on following key parameters : design symmetry, thermal load management, and material and structural choices. From a method point of view the difficulties arise first during design, from the strong coupling between the thermal, mechanical and optical performance models, and then during testing, from the difficulty of conceiving test setup having appropriate performance level. We will present how these limitations have been overcome. SOPAC-POS is the target alignment system of the LMJ, Laser Mega Joule, the French inertial confinement fusion research center. Its stability has been demonstrated by tests in 2014 after 10 years of research and development activities, achieving 1μm stability @ 6m during one hour periods. MOTA is an Optical Ground Support Equipment aiming at qualifying by tests the Flexible Combined Imager (FCI). FCI is an instrument for the meteorological satellite MTG-I, a program of and funded by the European Space Agency and under prime contractorship of Thales Alenia Space. Optimized design will allow to get better than 0.2 μrad stability for one hour periods, as required for MTF measurement.
Design of rapid prototype of UAV line-of-sight stabilized control system
Huang, Gang; Zhao, Liting; Li, Yinlong; Yu, Fei; Lin, Zhe
2018-01-01
The line-of-sight (LOS) stable platform is the most important technology of UAV (unmanned aerial vehicle), which can reduce the effect to imaging quality from vibration and maneuvering of the aircraft. According to the requirement of LOS stability system (inertial and optical-mechanical combined method) and UAV's structure, a rapid prototype is designed using based on industrial computer using Peripheral Component Interconnect (PCI) and Windows RTX to exchange information. The paper shows the control structure, and circuit system including the inertial stability control circuit with gyro and voice coil motor driven circuit, the optical-mechanical stability control circuit with fast-steering-mirror (FSM) driven circuit and image-deviation-obtained system, outer frame rotary follower, and information-exchange system on PC. Test results show the stability accuracy reaches 5μrad, and prove the effectiveness of the combined line-of-sight stabilization control system, and the real-time rapid prototype runs stable.
On a program manifold’s stability of one contour automatic control systems
Directory of Open Access Journals (Sweden)
Zumatov S. S.
2017-12-01
Full Text Available Methodology of analysis of stability is expounded to the one contour systems automatic control feedback in the presence of non-linearities. The methodology is based on the use of the simplest mathematical models of the nonlinear controllable systems. Stability of program manifolds of one contour automatic control systems is investigated. The sufficient conditions of program manifold’s absolute stability of one contour automatic control systems are obtained. The Hurwitz’s angle of absolute stability was determined. The sufficient conditions of program manifold’s absolute stability of control systems by the course of plane in the mode of autopilot are obtained by means Lyapunov’s second method.
Directory of Open Access Journals (Sweden)
Gillani Syed Wasif
2017-03-01
Full Text Available A six-month longitudinal intervention arm study with a pre-post cross-sectional questionnaire-based survey was performed. A 3-phase objective structured clinical examination (OSCE design was utilized for evaluation of acceptance and attitude of pharmacy students towards clinical pharmacy services. The pre-OSCE survey showed increased disagreement with the role of clinical pharmacists, compared to a significant positive shift in attitude towards their services in the healthcare team after 6 months of the trial. Responses improved for awareness (the current healthcare system could be improved by involving pharmacists, p < 0.02 and positive attitude categories (doctors and nurses would be happy to welcome the services of competent clinical pharmacists as part of their team, p < 0.01 in addition to competency (pharmacists have sufficient clinical training to advise doctors and nurses, p < 0.01. The predictive model suggested a strong positive effect on patient interaction, medical information tasks, clinical decisions on drug-related problems (DRPs, and communication with healthcare professionals (R2 = 0.41, F = 1.51, p < 0.001.
Using Interactive Response Systems in Economics: utility and factors influencing students’ attitudes
Directory of Open Access Journals (Sweden)
Lydia Bares López
2017-04-01
Full Text Available The European Higher Education Area (EHEA involves changing traditional methods to promote innovative teaching experiences. This paper has two main aims: a to show evidence of the use of Interactive Response Systems (IRS to identify gaps in the understanding of the course contents and b to investigate factors influencing students’ attitudes towards the use of IRS. The experience was developed through a collective tutoring session in the subject of Economics using IRS. Economics is a first-year subject in the Degree of Business Administration and Management offered by the University of Cadiz, which includes contents of Microeconomics and Macroeconomics and uses economic models to explain the function of the economy and the behaviour of economic agents. Results show that IRS technique allows detecting gaps in learning and comprehension. From our econometric estimations, we also identify two strongly significant variables affecting students’ attitudes towards IRS: gender and received explanations regarding the use of IRS. Variables such as first enrolment in the subject and the number of hours devoted to studying have a positive and significant effect on the attitude to IRS, but at a lower level of significance (from 5% to 10%.
Stabilization and tracking controller for a class of nonlinear discrete-time systems
International Nuclear Information System (INIS)
Sharma, B.B.; Kar, I.N.
2011-01-01
Highlights: → We present recursive design of stabilizing controller for nonlinear discrete-time systems. → Problem of stabilizing and tracking control of single link manipulator system is addressed. → We extend the proposed results to output tracking problems. → The proposed methodology is applied satisfactorily to discrete-time chaotic maps. - Abstract: In this paper, stabilization and tracking control problem for parametric strict feedback class of discrete time systems is addressed. Recursive design of control function based on contraction theory framework is proposed instead of traditional Lyapunov based method. Explicit structure of controller is derived for the addressed class of nonlinear discrete-time systems. Conditions for exponential stability of system states are derived in terms of controller parameters. At each stage of recursive procedure a specific structure of Jacobian matrix is ensured so as to satisfy conditions of stability. The closed loop dynamics in this case remains nonlinear in nature. The proposed algorithm establishes global stability results in quite a simple manner as it does not require formulation of error dynamics. Problem of stabilization and output tracking control in case of single link manipulator system with actuator dynamics is analyzed using the proposed strategy. The proposed results are further extended to stabilization of discrete time chaotic systems. Numerical simulations presented in the end show the effectiveness of the proposed approach.
Energy Technology Data Exchange (ETDEWEB)
Berdnikov, V I; Birgel, E R; Kovalev, V D; Kuznestov, A N
1994-12-31
The development of the 500 kV UPS of Middle Volga, the complication of its configuration and operating conditions particularly in connection with concentration of the generating power at Balakovo NPS have aggravated the problem of stability of the Middle Volga UPS when high power is transmitted along the 500 kV transient system. In this case the necessity for improving control actions` dosage accuracy has also appeared. This work discusses solution to the above mentioned issue. (author) 3 figs.
DOA estimation for attitude determination on communication satellites
Directory of Open Access Journals (Sweden)
Yang Bin
2014-06-01
Full Text Available In order to determine an appropriate attitude of three-axis stabilized communication satellites, this paper describes a novel attitude determination method using direction of arrival (DOA estimation of a ground signal source. It differs from optical measurement, magnetic field measurement, inertial measurement, and global positioning system (GPS attitude determination. The proposed method is characterized by taking the ground signal source as the attitude reference and acquiring attitude information from DOA estimation. Firstly, an attitude measurement equation with DOA estimation is derived in detail. Then, the error of the measurement equation is analyzed. Finally, an attitude determination algorithm is presented using a dynamic model, the attitude measurement equation, and measurement errors. A developing low Earth orbit (LEO satellite which tests mobile communication technology with smart antennas can be stabilized in three axes by corporately using a magnetometer, reaction wheels, and three-axis magnetorquer rods. Based on the communication satellite, simulation results demonstrate the effectiveness of the method. The method could be a backup of attitude determination to prevent a system failure on the satellite. Its precision depends on the number of snapshots and the input signal-to-noise ratio (SNR with DOA estimation.
Experimental research of "microcable in a microconduct" system stability to effect of freezing water
Andreev, Vladimir A.; Burdin, Vladimir A.; Nikulina, Tatiana G.; Alekhin, Ivan N.; Gavryushin, Sergey A.; Nikulin, Aleksey G.; Praporshchikov, Denis E.
2011-12-01
Results of experimental researches of "optical microcable in a microduct" system stability to effect of freezing water are presented. It is shown this system is steadier to water freezing in comparison to lighten optical cable in protective polymer tube.
Preliminary Results on Asymptotic Stabilization of Hamiltonian Systems with Nonholonomic Constraints
Khennouf, H.; Canudas de Wit, C.; Schaft, A.J. van der
1995-01-01
This paper presents some preliminary results on asymptotic stabilization of nonholonomic mechanical systems using the Hamiltonian formulation proposed previously. Our work seeks to establish a general formulation for designing time-varying controllers for some mechanical system described in the
Exponential Stabilization of Underactuated Vehicles
Energy Technology Data Exchange (ETDEWEB)
Pettersen, K.Y.
1996-12-31
Underactuated vehicles are vehicles with fewer independent control actuators than degrees of freedom to be controlled. Such vehicles may be used in inspection of sub-sea cables, inspection and maintenance of offshore oil drilling platforms, and similar. This doctoral thesis discusses feedback stabilization of underactuated vehicles. The main objective has been to further develop methods from stabilization of nonholonomic systems to arrive at methods that are applicable to underactuated vehicles. A nonlinear model including both dynamics and kinematics is used to describe the vehicles, which may be surface vessels, spacecraft or autonomous underwater vehicles (AUVs). It is shown that for a certain class of underactuated vehicles the stabilization problem is not solvable by linear control theory. A new stability result for a class of homogeneous time-varying systems is derived and shown to be an important tool for developing continuous periodic time-varying feedback laws that stabilize underactuated vehicles without involving cancellation of dynamics. For position and orientation control of a surface vessel without side thruster a new continuous periodic feedback law is proposed that does not cancel any dynamics, and that exponentially stabilizes the origin of the underactuated surface vessel. A further issue considered is the stabilization of the attitude of an AUV. Finally, the thesis discusses stabilization of both position and attitude of an underactuated AUV. 55 refs., 28 figs.
Faria, Teresa; Oliveira, José J.
This paper addresses the local and global stability of n-dimensional Lotka-Volterra systems with distributed delays and instantaneous negative feedbacks. Necessary and sufficient conditions for local stability independent of the choice of the delay functions are given, by imposing a weak nondelayed diagonal dominance which cancels the delayed competition effect. The global asymptotic stability of positive equilibria is established under conditions slightly stronger than the ones required for the linear stability. For the case of monotone interactions, however, sharper conditions are presented. This paper generalizes known results for discrete delays to systems with distributed delays. Several applications illustrate the results.
The system of values, motivation and self-attitude: gender features in high school students
Directory of Open Access Journals (Sweden)
Irina I. Vartanova
2016-12-01
Full Text Available The paper presents the results of the value orientation research in high school students, Moscow, Russia. The sample (N=62 included 22 education and universal values and also self-attitude parameters using the four types of emotional attitude to learning. These types of motivation profile were obtained via pre-factorization estimates of the seven values of school life using the method of semantic differential, which allowed to estimate the severity of a positional or status motivation (1, achievement motivation (2, learning and cognitive motivation, (3 and motivation of affiliation (4. This enabled to further estimate the factor and correlation analysis of the parameters studied, which shows that the system of values is significantly different in males and females of the same age, even in relation to the same mean value of motivation. Motivation, values and self-attitude organize stable systems – on the current sample allocated the four most common systems, i.e. the four factors that are specific for both males and females. Simultaneously, there are systems of values dependent on expressiveness and the combination of a certain type of motivation, and independent of the type of motivation. Female educational and cognitive motivation and positional (status motivation related to the values were merged into one factor, but for males one factor includes achievement motivation and (with the opposite sign affiliation motivation. While the self-realization of females occurs in the process of learning (the value of «selfimprovement in their studies», and in the future they see an opportunity for self-realization through the value of «happy family life», the males with this motivation connect their opportunity for self-realization with other values, i.e. «health», «recognition by other team members», «my authority.»
Interferometric system for PM-level stability characterization
Verlaan, A.L.; Ellis, J.D.; Voigt, D.; Spronck, J.W.; Munnig Schmidt, R.H.
2010-01-01
We present a double sided, single pass Michelson heterodyne interferometer for dimensional stability measurements. In preliminary measurements, the double deadpath configuration (no sample) showed better than ±1.5 nm (2/) over 13 hours. A 30 mm stainless gauge block was then measured with a
Visual Neuroscience: Unique Neural System for Flight Stabilization in Hummingbirds.
Ibbotson, M R
2017-01-23
The pretectal visual motion processing area in the hummingbird brain is unlike that in other birds: instead of emphasizing detection of horizontal movements, it codes for motion in all directions through 360°, possibly offering precise visual stability control during hovering. Copyright © 2017 Elsevier Ltd. All rights reserved.
Fault Detection and Correction for the Solar Dynamics Observatory Attitude Control System
Starin, Scott R.; Vess, Melissa F.; Kenney, Thomas M.; Maldonado, Manuel D.; Morgenstern, Wendy M.
2007-01-01
The Solar Dynamics Observatory is an Explorer-class mission that will launch in early 2009. The spacecraft will operate in a geosynchronous orbit, sending data 24 hours a day to a devoted ground station in White Sands, New Mexico. It will carry a suite of instruments designed to observe the Sun in multiple wavelengths at unprecedented resolution. The Atmospheric Imaging Assembly includes four telescopes with focal plane CCDs that can image the full solar disk in four different visible wavelengths. The Extreme-ultraviolet Variability Experiment will collect time-correlated data on the activity of the Sun's corona. The Helioseismic and Magnetic Imager will enable study of pressure waves moving through the body of the Sun. The attitude control system on Solar Dynamics Observatory is responsible for four main phases of activity. The physical safety of the spacecraft after separation must be guaranteed. Fine attitude determination and control must be sufficient for instrument calibration maneuvers. The mission science mode requires 2-arcsecond control according to error signals provided by guide telescopes on the Atmospheric Imaging Assembly, one of the three instruments to be carried. Lastly, accurate execution of linear and angular momentum changes to the spacecraft must be provided for momentum management and orbit maintenance. In thsp aper, single-fault tolerant fault detection and correction of the Solar Dynamics Observatory attitude control system is described. The attitude control hardware suite for the mission is catalogued, with special attention to redundancy at the hardware level. Four reaction wheels are used where any three are satisfactory. Four pairs of redundant thrusters are employed for orbit change maneuvers and momentum management. Three two-axis gyroscopes provide full redundancy for rate sensing. A digital Sun sensor and two autonomous star trackers provide two-out-of-three redundancy for fine attitude determination. The use of software to maximize
Effect Mechanism of Penstock on Stability and Regulation Quality of Turbine Regulating System
Directory of Open Access Journals (Sweden)
Wencheng Guo
2014-01-01
Full Text Available This paper studies the effect mechanism of water inertia and head loss of penstock on stability and regulation quality of turbine regulating system with surge tank or not and proposes the construction method of equivalent model of regulating system. Firstly, the complete linear mathematical model of regulating system is established. Then, the free oscillation equation and time response of the frequency that describe stability and regulation quality, respectively, are obtained. Finally, the effects of penstock are analysed by using stability region and response curves. The results indicate that the stability and regulation quality of system without surge tank are determined by time response of frequency which only depends on water hammer wave in penstock, while, for system with surge tank, the time response of frequency depending on water hammer wave in penstock and water-level fluctuation in surge tank jointly determines the stability and regulation quality. Water inertia of penstock mainly affects the stability and time response of frequency of system without surge tank as well as the stability and head wave of time response of frequency with surge tank. Head loss of penstock mainly affects the stability and tail wave of time response of frequency with surge tank.
Krook, Melanie A.; Hagerman, Ann E.
2012-01-01
Polyphenols found in foods and beverages are under intense scrutiny for their potential beneficial effects on human health. We examined the stability of two bioactive polyphenols, epigallocatechin-O-gallate (EGCg) and 1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose (PGG), in a model digestive system at low oxygen tension with and without added digestive components and foods. Both compounds were stable at pH values of 5–6 and below, indicating gastric stability. Both compounds decomposed at pH 7.0. PGG was stabilized in a model system containing pepsin, pancreatin, bile and lipase, and/or baby food, but was not stabilized by dry cereal. EGCg was not stabilized by the addition of any biomolecule. The effects of polyphenols on human health should be evaluated in the context of their stability in the digestive tract with and without added digestive components and/or food. PMID:23028206
Stability Analysis of Interconnected Fuzzy Systems Using the Fuzzy Lyapunov Method
Directory of Open Access Journals (Sweden)
Ken Yeh
2010-01-01
Full Text Available The fuzzy Lyapunov method is investigated for use with a class of interconnected fuzzy systems. The interconnected fuzzy systems consist of J interconnected fuzzy subsystems, and the stability analysis is based on Lyapunov functions. Based on traditional Lyapunov stability theory, we further propose a fuzzy Lyapunov method for the stability analysis of interconnected fuzzy systems. The fuzzy Lyapunov function is defined in fuzzy blending quadratic Lyapunov functions. Some stability conditions are derived through the use of fuzzy Lyapunov functions to ensure that the interconnected fuzzy systems are asymptotically stable. Common solutions can be obtained by solving a set of linear matrix inequalities (LMIs that are numerically feasible. Finally, simulations are performed in order to verify the effectiveness of the proposed stability conditions in this paper.
Transient Stability Improvement of IEEE 9 Bus System Using Power World Simulator
Directory of Open Access Journals (Sweden)
Kaur Ramandeep
2016-01-01
Full Text Available The improvement of transient stability of power system was one of the most challenging research areas in power engineer.The main aim of this paper was transient stability analysis and improvement of IEEE 9 bus system. These studies were computed using POWER WORLD SIMULATOR. The IEEE 9 bus system was modelled in power world simulator and load flow studies were performed to determine pre-fault conditions in the system using Newton-Raphson method. The transient stability analysis was carried out using Runga method during three-phase balanced fault. For the improvement transient stability, the general methods adopted were fast acting exciters, FACT devices and addition of parallel transmission line. These techniques play an important role in improving the transient stability, increasing transmission capacity and damping low frequency oscillations.
Transient Stability Assessment of Power System with Large Amount of Wind Power Penetration
DEFF Research Database (Denmark)
Liu, Leo; Chen, Zhe; Bak, Claus Leth
2012-01-01
Recently, the security and stability of power system with large amount of wind power are the concerned issues, especially the transient stability. In Denmark, the onshore and offshore wind farms are connected to distribution system and transmission system respectively. The control and protection...... methodologies of onshore and offshore wind farms definitely affect the transient stability of power system. In this paper, the onshore and offshore wind farms are modeled in detail in order to assess the transient stability of western Danish power system. Further, the computation of critical clearing time (CCT...... plants, load consumption level and high voltage direct current (HVDC) transmission links are taken into account. The results presented in this paper are able to provide an early awareness of power system security condition of the western Danish power system....
A Practical Method for Implementing an Attitude and Heading Reference System
Directory of Open Access Journals (Sweden)
Rodrigo Munguía
2014-04-01
Full Text Available This paper describes a practical and reliable algorithm for implementing an Attitude and Heading Reference System (AHRS. This kind of system is essential for real time vehicle navigation, guidance and control applications. When low cost sensors are used, efficient and robust algorithms are required for performance to be acceptable. The proposed method is based on an Extended Kalman Filter (EKF in a direct configuration. In this case, the filter is explicitly derived from both the kinematic and error models. The selection of this kind of EKF configuration can help in ensuring a tight integration of the method for its use in filter-based localization and mapping systems in autonomous vehicles. Experiments with real data show that the proposed method is able to maintain an accurate and drift-free attitude and heading estimation. An additional result is to show that there is no ostensible reason for preferring that the filter have an indirect configuration over a direct configuration for implementing an AHRS system.
Directory of Open Access Journals (Sweden)
Stefanov Predrag Č.
2014-01-01
Full Text Available This paper deals with inter-area power oscillations damping enhancement by distributed energy resources contained in typical micro grid. Main idea behind this work is to use distributed generation and distributed storage, such as battery energy storage to mimic conventional power system stabilizer, but with regulating active power output, rather than reactive power, as in standard power system stabilizer realization. The analysis of the small signal stability is established for four-machine, two-area system, with inverter based micro grids in each area. Dynamic simulation results are included in this work and they show that proposed controller provides additional damping effect to this test system.
Goto, Tomoko; Zheng, Xiaodong; Klyce, Stephen D; Kataoka, Hisashi; Uno, Toshihiko; Yamaguchi, Masahiko; Karon, Mike; Hirano, Sumie; Okamoto, Shigeki; Ohashi, Yuichi
2004-01-01
To evaluate the tear film stability of patients before and after laser in situ keratomileusis (LASIK) using the tear film stability analysis system (TSAS). Prospective observational case series. New videokeratography software for a topographic modeling system (TMS-2N) was developed that can automatically capture consecutive corneal surface images every second for 10 seconds. Thirty-four subjects (64 eyes) who underwent myopia LASIK were enrolled in this study. All subjects were examined with the new system before LASIK and at 1 week, 1 month, 3 months, and 6 months after the surgery. Corneal topographs were analyzed for tear breakup time (TMS breakup time) and breakup area (TMS breakup area). Based on pre-LASIK TSAS analysis, subjects were separated into normal and abnormal TSAS value groups. The criteria for the normal group were either TMS breakup time more than 5 seconds or TMS breakup area less than 0.2. The percentage of the occurrence of superficial punctuate keratitis was compared between the two groups with regard to subject's dry eye signs and symptoms. Tear film stability decreased significantly during the early period after LASIK, as indexed by decreased TMS breakup time and increased TMS breakup area. Tear film instability resolved at 6 months after surgery. Before LASIK, 22 subjects (43 eyes) had normal TSAS evaluation and 12 subjects (21 eyes) were abnormal. After LASIK, among normal TSAS value eyes, 8 of 43 (18.6%) eyes developed superficial punctuate keratitis. In sharp contrast, 14 of 21 (66.7%) eyes in the abnormal group displayed superficial punctuate keratitis, correlating well with the patients' dry eye symptoms. The difference in the presence of superficial punctuate keratitis after LASIK between normal and abnormal TSAS value groups was statistically significant (P <.001). Subjects with abnormal TSAS evaluation also displayed resistance to dry eye treatment and had extended period of recovery. Tear film stability analysis can be a useful
Stability Analysis for Fractional-Order Linear Singular Delay Differential Systems
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Hai Zhang
2014-01-01
Full Text Available We investigate the delay-independently asymptotic stability of fractional-order linear singular delay differential systems. Based on the algebraic approach, the sufficient conditions are presented to ensure the asymptotic stability for any delay parameter. By applying the stability criteria, one can avoid solving the roots of transcendental equations. An example is also provided to illustrate the effectiveness and applicability of the theoretical results.
International Nuclear Information System (INIS)
Druzhinina, O V; Shestakov, A A
2002-01-01
A generalized direct Lyapunov method is put forward for the study of stability and attraction in general time systems of the following types: the classical dynamical system in the sense of Birkhoff, the general system in the sense of Zubov, the general system in the sense of Seibert, the general system with delay, and the general 'input-output' system. For such systems, with the help of generalized Lyapunov functions with respect to two filters, two quasifilters, or two filter bases, necessary and sufficient conditions for stability and attraction are obtained under minimal assumptions about the mathematical structure of the general system
Mission management, planning, and cost: PULSE Attitude And Control Systems (AACS)
1990-01-01
The Pluto unmanned long-range scientific explorer (PULSE) is a probe that will do a flyby of Pluto. It is a low weight, relatively low costing vehicle which utilizes mostly off-the-shelf hardware, but not materials or techniques that will be available after 1999. A design, fabrication, and cost analysis is presented. PULSE will be launched within the first decade of the twenty-first century. The topics include: (1) scientific instrumentation; (2) mission management, planning, and costing; (3) power and propulsion systems; (4) structural subsystem; (5) command, control, and communication; and (6) attitude and articulation control.
Stabilization of the RF system at the SPring-8 linac
Asaka, T; Hori, T; Kobayashi, T; Mizuno, A; Sakaki, H; Suzuki, S; Taniuchi, T; Yanagida, K; Yokomizo, H; Yoshikawa, H
2002-01-01
Beam energy variation of the SPring-8 linac was 1% or more at the start of beam commissioning. Depending on fluctuation, beam transmission efficiency from the linac to the booster synchrotron was significantly affected, and beam intensity in the booster synchrotron changed 20-30%. This caused delay of optimization of the various parameters in the booster synchrotron. More problematic, the beam intensities stored in each RF (radio frequency) bucket of the storage ring at SPring-8 were all different from each other. The users utilizing synchrotron radiation requested that the beam intensity in each RF bucket be as uniform as possible. It was thus a pressing necessity to stabilize the beam energy in the linac. Investigation of the cause has clarified that the various apparatuses installed in the linac periodically changed depending on circumstances and utilities such as the air conditioner, cooling water and electric power. After various improvements, beam energy stability in the linac of <0.06% rms was attai...
Attitudes and attitude change.
Bohner, Gerd; Dickel, Nina
2011-01-01
Attitudes and attitude change remain core topics of contemporary social psychology. This selective review emphasizes work published from 2005 to 2009. It addresses constructionist and stable-entity conceptualizations of attitude, the distinction between implicit and explicit measures of attitude, and implications of the foregoing for attitude change. Associative and propositional processes in attitude change are considered at a general level and in relation to evaluative conditioning. The role of bodily states and physical perceptions in attitude change is reviewed. This is followed by an integrative perspective on processing models of persuasion and the consideration of meta-cognitions in persuasion. Finally, effects of attitudes on information processing, social memory, and behavior are highlighted. Core themes cutting across the areas reviewed are attempts at integrative theorizing bringing together formerly disparate phenomena and viewpoints.
Directory of Open Access Journals (Sweden)
Ghouraf Djamel Eddine
2016-05-01
Full Text Available Power system stability considered a necessary condition for normal functioning of an electrical network. The role of regulation and control systems is to ensure that stability by determining the essential elements that influence it. This paper proposes a Particle Swarm Optimization (PSO based multiobjective function to tuning optimal parameters of Power System Stabilizer (PSS; this later is used as auxiliary to generator excitation system in order to damp electro mechanicals oscillations of the rotor and consequently improve Power system stability. The computer simulation results obtained by developed graphical user interface (GUI have proved the efficiency of PSS optimized by a Particle Swarm Optimization, in comparison with a conventional PSS, showing stable system responses almost insensitive to large parameter variations.Our present study was performed using a GUI realized under MATLAB in our work.
Shen, H; Xu, Y; Dickinson, B T
2014-11-18
Inspired by sensing strategies observed in birds and bats, a new attitude control concept of directly using real-time pressure and shear stresses has recently been studied. It was shown that with an array of onboard airflow sensors, small unmanned aircraft systems can promptly respond to airflow changes and improve flight performances. In this paper, a mapping function is proposed to compute aerodynamic moments from the real-time pressure and shear data in a practical and computationally tractable formulation. Since many microscale airflow sensors are embedded on the small unmanned aircraft system surface, it is highly possible that certain sensors may fail. Here, an adaptive control system is developed that is robust to sensor failure as well as other numerical mismatches in calculating real-time aerodynamic moments. The advantages of the proposed method are shown in the following simulation cases: (i) feedback pressure and wall shear data from a distributed array of 45 airflow sensors; (ii) 50% failure of the symmetrically distributed airflow sensor array; and (iii) failure of all the airflow sensors on one wing. It is shown that even if 50% of the airflow sensors have failures, the aircraft is still stable and able to track the attitude commands.
Stabilization and regulation of nonlinear systems a robust and adaptive approach
Chen, Zhiyong
2015-01-01
The core of this textbook is a systematic and self-contained treatment of the nonlinear stabilization and output regulation problems. Its coverage embraces both fundamental concepts and advanced research outcomes and includes many numerical and practical examples. Several classes of important uncertain nonlinear systems are discussed. The state-of-the art solution presented uses robust and adaptive control design ideas in an integrated approach which demonstrates connections between global stabilization and global output regulation allowing both to be treated as stabilization problems. Stabilization and Regulation of Nonlinear Systems takes advantage of rich new results to give students up-to-date instruction in the central design problems of nonlinear control, problems which are a driving force behind the furtherance of modern control theory and its application. The diversity of systems in which stabilization and output regulation become significant concerns in the mathematical formulation of practical contr...
Fast simulation of wind generation for frequency stability analysis in island power systems
Energy Technology Data Exchange (ETDEWEB)
Conroy, James [EirGrid, Dublin (Ireland)
2010-07-01
Frequency stability is a major issue for power system planning and operation in an island power system such as Ireland. As increasing amounts of variable speed wind generation are added to the system, this issue becomes more prominent, as variable speed wind generation does not provide an inherent inertial response. This lack of an inertial response means that simplified models for variable speed wind farms can be used for investigating frequency stability. EirGrid uses DIgSILENT Power Factory (as well as other software tools) to investigate frequency stability. In PowerFactory, an automation program has been created to convert detailed wind farm representation (as necessary for other types of analysis) to negative load models for frequency stability analysis. The advantage of this approach is much-improved simulation speed without loss of accuracy. This approach can also be to study future wind energy targets, and long-term simulation of voltage stability. (orig.)
Some stability and boundedness criteria for a class of Volterra integro-differential systems
Directory of Open Access Journals (Sweden)
Jito Vanualailai
2002-01-01
Full Text Available Using Lyapunov and Lyapunov-like functionals, we study the stability and boundedness of the solutions of a system of Volterra integrodifferential equations. Our results, also extending some of the more well-known criteria, give new sufficient conditions for stability of the zero solution of the nonperturbed system, and prove that the same conditions for the perturbed system yield boundedness when the perturbation is $L^2$.
A summary of impacts of wind power integration on power system small-signal stability
Yan, Lei; Wang, Kewen
2017-05-01
Wind power has been increasingly integrated into power systems over the last few decades because of the global energy crisis and the pressure on environmental protection, and the stability of the system connected with wind power is becoming more prominent. This paper summaries the research status, achievements as well as deficiencies of the research on the impact of wind power integration on power system small-signal stability. In the end, the further research needed are discussed.
ANALYSIS OF PERTURBED MOTION STABILITY OF WHEELER VEHICLES BRAKES CONTROL SYSTEM
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V. Verbytskiyi
2011-01-01
Full Text Available The analysis of the perturbed motion stability of the brake automatic control system on the basis of Lyapunov’s second method is carried out. Using transformations of Lurie there has been ob-tained the canonical form of the system of equations of automatic control. It allowed determining the necessary and sufficient conditions of the asymptotic stability of the system irrespective of its initial condition and a definite choice of the admissible characteristic of the regulator.
A comparative study of voltage stability indices in a power system
Energy Technology Data Exchange (ETDEWEB)
Sinha, A.K. [I.I.T., Kharagpur (India). Dept. of Electrical Engineering; Hazarika, D. [Assam Engineering College (India)
2000-11-01
The paper compares the effectiveness of voltage stability indices in providing information about the proximity of voltage instability of a power system. Three simple voltage stability indices are proposed and their effectiveness is compared with some of the recently proposed indices. The comparison is carried out over a wide range of system operating conditions by changing the load power factor and feeder X/R ratios. Test results for the IEEE 57 bus and IEEE 118 bus system are presented. (author)
Mittag-Leffler Stability Theorem for Fractional Nonlinear Systems with Delay
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S. J. Sadati
2010-01-01
Full Text Available Fractional calculus started to play an important role for analysis of the evolution of the nonlinear dynamical systems which are important in various branches of science and engineering. In this line of taught in this paper we studied the stability of fractional order nonlinear time-delay systems for Caputo's derivative, and we proved two theorems for Mittag-Leffler stability of the fractional nonlinear time delay systems.
Reduced Attitude Control of a Robotic Underwater Vehicle
Directory of Open Access Journals (Sweden)
Bláha Lukáš
2017-01-01
Full Text Available This paper deals with stabilization and reduced attitude control of a robotic underwater vehicle. The vehicle is assumed to be able to perform a full stable rotations around all axes in underwater space, that is why the standard bottom-heavy structure is not used. The system preferably uses a vectored-thrust arrangement and is built as an overactuated system, which enables to gain a better robustness and guarantees a stable controlled motion even if some thruster suddenly stop working. Because the heading angle cannot be measured, the reduced attitude control strategy is designed and the stability of reduced state of the system is proved using perturbation method.
Results on stabilization of nonlinear systems under finite data-rate constraints
Persis, Claudio De
2004-01-01
We discuss in this paper a result concerning the stabilization problem of nonlinear systems under data-rate constraints using output feedback. To put the result in a broader context, we shall first review a number of recent contributions on the stabilization problem under data-rate constraints when
Investigation of external and internal shock in the stability of Indonesia’s financial system
Directory of Open Access Journals (Sweden)
Maulina Vinus
2017-07-01
Full Text Available The objective of this research is to develop a financial system stability index and analyze the internal and external factors that we expect to affect the stability of the Indonesian financial system. We measured the single model of financial system stability index (FSSI from year 2004M03 to2014M09 in Indonesia, and compiled a single quantitative measure based on aggregate internal factors and external factors to capture and predict the shocks of the financial system stability. Stability parameters were composed of composite indicators on different bases. In addition, we developed a comprehensive index component associated with the relevant market conditions, including banking soundness index, financial vulnerability index, and regional economic climate index. Results stated that US economic growth and economic growth of ASEAN countries positively affected financial stability. In addition, current account, exchange rate, inflation, interest rate were shown to negatively affect financial stability. The results of this study imply that internal factors have a strong influence on the financial stability. Therefore, the central bank should give a fast and correct response to the changes of external and internal financial environment, especially for internal factors through monetary policy.
International Nuclear Information System (INIS)
Chen, S.-F.
2009-01-01
The asymptotic stability problem for discrete-time systems with time-varying delay subject to saturation nonlinearities is addressed in this paper. In terms of linear matrix inequalities (LMIs), a delay-dependent sufficient condition is derived to ensure the asymptotic stability. A numerical example is given to demonstrate the theoretical results.
Analysis of the Gyroscopic Stabilization of a System of Rigid Bodies
DEFF Research Database (Denmark)
Kliem, Wolfhard; Kliem, Wolfhard
1996-01-01
We study the gyroscopic of a three-body system. A new method offinding stability regions, based on mechanism and criteria for gyroscopicstabilization, is presented. Of particular interest in this connection isthe theory of interaction of eigenvalues. This leads to a complete 3-dimensionalanalysis......, which shows the regions of stability, divergence, and flutter ofa simple model of a rotating spaceship....
Students' Understanding of Equilibrium and Stability: The Case of Dynamic Systems
Canu, Michaël; de Hosson, Cécile; Duque, Mauricio
2016-01-01
Engineering students in control courses have been observed to lack an understanding of equilibrium and stability, both of which are crucial concepts in this discipline. The introduction of these concepts is generally based on the study of classical examples from Newtonian mechanics supplemented with a control system. Equilibrium and stability are…
Equilibrium and stability of high-beta plasma in a finite l=+-1 toroidal system
International Nuclear Information System (INIS)
Shiina, S.; Saito, K.; Todoroki, J.; Hamada, S.; Gesso, H.; Nogi, Y.; Osanai, Y.; Yoshimura, H.
1983-01-01
The equilibrium and stability are theoretically and experimentally investigated of high-beta plasma in the Modified Bumpy Torus, which is an asymmetric closed-line system with fairly large l=0 and l=+-1 field components. The finiteness of the l=+-1 component induces significant stabilizing effects due both to self formation of a magnetic well and to the conducting wall. (author)
Exponential stability of switched linear systems with time-varying delay
Directory of Open Access Journals (Sweden)
Satiracoo Pairote
2007-11-01
Full Text Available We use a Lyapunov-Krasovskii functional approach to establish the exponential stability of linear systems with time-varying delay. Our delay-dependent condition allows to compute simultaneously the two bounds that characterize the exponential stability rate of the solution. A simple procedure for constructing switching rule is also presented.
Stability and Hopf bifurcations in a competitive Lotka-Volterra system with two delays
International Nuclear Information System (INIS)
Song Yongli; Han Maoan; Peng Yahong
2004-01-01
We consider a Lotka-Volterra competition system with two delays. We first investigate the stability of the positive equilibrium and the existence of Hopf bifurcations, and then using the normal form theory and center manifold argument, derive the explicit formulas which determine the stability, direction and other properties of bifurcating periodic solutions
The beauty of simple adaptive control and new developments in nonlinear systems stability analysis
Energy Technology Data Exchange (ETDEWEB)
Barkana, Itzhak, E-mail: ibarkana@gmail.com [BARKANA Consulting, Ramat Hasharon (Israel)
2014-12-10
Although various adaptive control techniques have been around for a long time and in spite of successful proofs of stability and even successful demonstrations of performance, the eventual use of adaptive control methodologies in practical real world systems has met a rather strong resistance from practitioners and has remained limited. Apparently, it is difficult to guarantee or even understand the conditions that can guarantee stable operations of adaptive control systems under realistic operational environments. Besides, it is difficult to measure the robustness of adaptive control system stability and allow it to be compared with the common and widely used measure of phase margin and gain margin that is utilized by present, mainly LTI, controllers. Furthermore, customary stability analysis methods seem to imply that the mere stability of adaptive systems may be adversely affected by any tiny deviation from the pretty idealistic and assumably required stability conditions. This paper first revisits the fundamental qualities of customary direct adaptive control methodologies, in particular the classical Model Reference Adaptive Control, and shows that some of their basic drawbacks have been addressed and eliminated within the so-called Simple Adaptive Control methodology. Moreover, recent developments in the stability analysis methods of nonlinear systems show that prior conditions that were customarily assumed to be needed for stability are only apparent and can be eliminated. As a result, sufficient conditions that guarantee stability are clearly stated and lead to similarly clear proofs of stability. As many real-world applications show, once robust stability of the adaptive systems can be guaranteed, the added value of using Add-On Adaptive Control along with classical Control design techniques is pushing the desired performance beyond any previous limits.
ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process
Directory of Open Access Journals (Sweden)
E. K. Boukas
2004-01-01
Full Text Available This paper considers the stabilization problem of the class of continuous-time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI-based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.
Stability and Bifurcation Analysis in a Maglev System with Multiple Delays
Zhang, Lingling; Huang, Jianhua; Huang, Lihong; Zhang, Zhizhou
This paper considers the time-delayed feedback control for Maglev system with two discrete time delays. We determine constraints on the feedback time delays which ensure the stability of the Maglev system. An algorithm is developed for drawing a two-parametric bifurcation diagram with respect to two delays τ1 and τ2. Direction and stability of periodic solutions are also determined using the normal form method and center manifold theory by Hassard. The complex dynamical behavior of the Maglev system near the domain of stability is confirmed by exhaustive numerical simulation.
Mean Square Exponential Stability of Stochastic Switched System with Interval Time-Varying Delays
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Manlika Rajchakit
2012-01-01
Full Text Available This paper is concerned with mean square exponential stability of switched stochastic system with interval time-varying delays. The time delay is any continuous function belonging to a given interval, but not necessary to be differentiable. By constructing a suitable augmented Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, a switching rule for the mean square exponential stability of switched stochastic system with interval time-varying delays and new delay-dependent sufficient conditions for the mean square exponential stability of the switched stochastic system are first established in terms of LMIs. Numerical example is given to show the effectiveness of the obtained result.
Energy Technology Data Exchange (ETDEWEB)
Shaorong, Wu; Dazhong, Wang; Meisheng, Yao; Jinhai, Bo; Yunxian, Tong; Shengyao, Jiang; Bing, Han [Institute of Nuclear Energy and Technology, Tsingua Univ., Beijing (China)
1997-09-01
Appropriately scaled ``Loop Stability`` tests and ``Channel Stability`` tests were performed with single heated channel system and two parallel channel system separately at the Institute of Nuclear Energy Technology (INET) of the Tsinghua University in China. A broad range of several operational parameters such as heating power, system pressure, test inlet subcooling and resistance coefficient were investigated. It was found that under certain geometric conditions and operating parameters a self-sustaining, low frequency, even amplitude mass flow oscillation may be excited at very low steam qualities and subcooling conditions. Stability maps under different conditions have been provided to assist the design of the NHR. (author). 6 refs, 15 figs.
A Design of Power System Stabilization for SVC System Using a RVEGA
Energy Technology Data Exchange (ETDEWEB)
Chung, Hyeng Hwan; Hur, Dong Ryol; Lee, Jeong Phil; Wang, Yong Peel [Dong-A University, Pusan (Korea)
2001-07-01
In this paper, it is suggested that the selection method of parameter of Power System Stabilizer (PSS) with robustness in low frequency oscillation for Static VAR Compensator (SVC) using a Real Variable Elitism Genetic Algorithm (RVEGA). A SVE, one of the Flexible AC Transmission System (FACTS), constructed by a fixed capacitor (FC) and a thyristor controlled reactor (TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. The proposed PSS parameters are optimized using RVEGA in order to maintain optimal operation of generator under the various operating conditions. To decrease the computational time, real variable string is adopted. To verify the robustness of the proposed method, we considered the dynamic response of generator speed deviation and generator terminal voltage by applying a power fluctuation and three-phase fault at heavy load, normal load and light load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system. (author). 20 refs., 14 figs., 3 tabs.
Security region-based small signal stability analysis of power systems with FSIG based wind farm
Qin, Chao; Zeng, Yuan; Yang, Yang; Cui, Xiaodan; Xu, Xialing; Li, Yong
2018-02-01
Based on the Security Region approach, the impact of fixed-speed induction generator based wind farm on the small signal stability of power systems is analyzed. Firstly, the key factors of wind farm on the small signal stability of power systems are analyzed and the parameter space for small signal stability region is formed. Secondly, the small signal stability region of power systems with wind power is established. Thirdly, the corresponding relation between the boundary of SSSR and the dominant oscillation mode is further studied. Results show that the integration of fixed-speed induction generator based wind farm will cause the low frequency oscillation stability of the power system deteriorate. When the output of wind power is high, the oscillation stability of the power system is mainly concerned with the inter-area oscillation mode caused by the integration of the wind farm. Both the active power output and the capacity of reactive power compensation of the wind farm have a significant influence on the SSSR. To improve the oscillation stability of power systems with wind power, it is suggested to reasonably set the reactive power compensation capacity for the wind farm through SSSR.
Power system stabilization by SMES using current-fed pwm power conditioner
International Nuclear Information System (INIS)
Ishikawa, T.; Akita, S.; Taniguchi, H.; Kosho, S.; Tanaka, T.
1988-01-01
A superconducting magnetic energy storage (SMES) unit, consisted of superconducting coil and AC/DC power conditioner, can be used to suppress various kinds of instability that may cause service interruption in electric power system as it has high controllability of input/output electric power. Power system stabilizing ability of SMES has been examined experimentally by using model power system and small SMES unit. Current-fed PWM power conditioner was used to obtain maximum stabilizing effect by controlling active and reactive power simultaneously and independently. Power conditioner configuration, operating characteristics and control scheme for power system stabilization are also described. Results from experiments show the effectiveness of SMES on power system stabilization
Directory of Open Access Journals (Sweden)
Huang Tingwen
2009-01-01
Full Text Available This paper studies the exponential stability of a class of periodically time-switched nonlinear systems. Three cases of such systems which are composed, respectively, of a pair of unstable subsystems, of both stable and unstable subsystems, and of a pair of stable systems, are considered. For the first case, the proposed result shows that there exists periodically switching rule guaranteeing the exponential stability of the whole system with (sufficient small switching period if there is a Hurwitz linear convex combination of two uncertain linear systems derived from two subsystems by certain linearization. For the second case, we present two general switching criteria by means of multiple and single Lyapunov function, respectively. We also investigate the stability issue of the third case, and the switching criteria of exponential stability are proposed. The present results for the second case are further applied to the periodically intermittent control. Several numerical examples are also given to show the effectiveness of theoretical results.
Users' attitude towards science and technology database system : INIS user needs survey
International Nuclear Information System (INIS)
Fukazawa, Takeyasu; Takahashi, Satoko; Yonezawa, Minoru; Kajiro, Tadashi; Mineo, Yukinobu; Habara, Takako; Komatsubara, Yasutoshi; Hiramatsu, Nobuaki; Habara, Tadashi.
1995-01-01
The International Nuclear Information System (INIS) is the world's leading information system on the peaceful use of nuclear energy which is being operated by the International Atomic Energy Agency (IAEA) in collaboration with its member-states and other international organizations. After more than 20 years of the operation of INIS, a user needs survey was conducted with the aim of assisting the INIS Secretariat to decide which way INIS should go. This report describes users' attitude towards that system on the basis of the conclusions drawn from the questionnaires sent out to the users by the Japan Atomic Energy Research Institute, the INIS national center in Japan, in close collaboration with the Japan Information Center of Science and Technology. (author)
Feldman, D; Altman, R
1985-01-01
The effects of a teacher personality construct (abstract vs. concrete conceptual system) and two pupil variables (race, school behavior) on 454 regular classroom teachers' attitudes toward mainstreaming were determined. Following administration of the Conceptual Systems Test, teachers were randomly assigned a profile of a mildly mentally retarded student that held pupil IQ and school achievement constant while varying pupil's race and school behavior. Subjects responded on an integration inventory comprised of three subscales: social-psychological classroom environment, self-actualization, and classroom cohesiveness. Results revealed a significant main effect on the behavior variable and a significant Personality X Race interaction on all inventory dimensions, suggesting that these teachers perceived maladaptive behavior of mainstreamed retarded students as a significant threat to a conducive instructional atmosphere and the capability of nonretarded students to achieve to their potential. These results have implications for inservice training for teachers based on the pupil race and teacher conceptual system findings.
On-board landmark navigation and attitude reference parallel processor system
Gilbert, L. E.; Mahajan, D. T.
1978-01-01
An approach to autonomous navigation and attitude reference for earth observing spacecraft is described along with the landmark identification technique based on a sequential similarity detection algorithm (SSDA). Laboratory experiments undertaken to determine if better than one pixel accuracy in registration can be achieved consistent with onboard processor timing and capacity constraints are included. The SSDA is implemented using a multi-microprocessor system including synchronization logic and chip library. The data is processed in parallel stages, effectively reducing the time to match the small known image within a larger image as seen by the onboard image system. Shared memory is incorporated in the system to help communicate intermediate results among microprocessors. The functions include finding mean values and summation of absolute differences over the image search area. The hardware is a low power, compact unit suitable to onboard application with the flexibility to provide for different parameters depending upon the environment.
Stability of limit cycles in autonomous nonlinear systems
Czech Academy of Sciences Publication Activity Database
Náprstek, Jiří; Fischer, Cyril
2014-01-01
Roč. 49, č. 8 (2014), s. 1929-1943 ISSN 0025-6455 R&D Projects: GA AV ČR(CZ) IAA200710902; GA ČR(CZ) GA103/09/0094; GA ČR(CZ) GC13-34405J Institutional support: RVO:68378297 Keywords : limit cycle * nonlinear oscillator * stability Subject RIV: JM - Building Engineering Impact factor: 1.949, year: 2014 http://link.springer.com/article/10.1007/s11012-014-9899-8
Solar Sail Attitude Control System for the NASA Near Earth Asteroid Scout Mission
Orphee, Juan; Diedrich, Ben; Stiltner, Brandon; Becker, Chris; Heaton, Andrew
2017-01-01
An Attitude Control System (ACS) has been developed for the NASA Near Earth Asteroid (NEA) Scout mission. The NEA Scout spacecraft is a 6U cubesat with an eighty-six square meter solar sail for primary propulsion that will launch as a secondary payload on the Space Launch System (SLS) Exploration Mission 1 (EM-1) and rendezvous with a target asteroid after a two year journey, and will conduct science imagery. The spacecraft ACS consists of three major actuating subsystems: a Reaction Wheel (RW) control system, a Reaction Control System (RCS), and an Active Mass Translator (AMT) system. The reaction wheels allow fine pointing and higher rates with low mass actuators to meet the science, communication, and trajectory guidance requirements. The Momentum Management System (MMS) keeps the speed of the wheels within their operating margins using a combination of solar torque and the RCS. The AMT is used to adjust the sign and magnitude of the solar torque to manage pitch and yaw momentum. The RCS is used for initial de-tumble, performing a Trajectory Correction Maneuver (TCM), and performing momentum management about the roll axis. The NEA Scout ACS is able to meet all mission requirements including attitude hold, slews, pointing for optical navigation and pointing for science with margin and including flexible body effects. Here we discuss the challenges and solutions of meeting NEA Scout mission requirements for the ACS design, and present a novel implementation of managing the spacecraft Center of Mass (CM) to trim the solar sail disturbance torque. The ACS we have developed has an applicability to a range of potential missions and does so in a much smaller volume than is traditional for deep space missions beyond Earth.
Delavault, Stéphanie; Prieur, Pascal; Liénart, Thomas; Robert, Alain; Guidotti, Pierre-Yves
2018-04-01
Microscope is a CNES-ESA-ONERA-CNRS-OCA-DLR-ZARM mission dedicated to the test of the Equivalence Principle with an improved accuracy of 10-15. The 300 kg drag-free microsatellite was launched on April 25th 2016 into a 710 km dawndusk sun-synchronous orbit for a 2-year mission. To comply with stringent requirements, the drag-free and attitude control system (DFACS) involves the scientific accelerometer as main sensor and a set of 8 cold gas proportional thrusters. Once in mission mode, within the CNES drag-free expertise center (CECT) the DFACS team provides several services to the system and to the scientific mission center: cold gas monitoring and management, `Attitude' ancillary data, DFACS expertise ancillary data. For this purpose, expertise tools have been implemented in the CECT, using the flexibility and efficiency of Matlab™ utilities. This paper presents the role of the CECT within the mission and details the expertise activities of the DFACS team illustrated with some typical in flight results.
A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA
Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao
2015-10-01
Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.
Using the global positioning satellite system to determine attitude rates using doppler effects
Campbell, Charles E. (Inventor)
2003-01-01
In the absence of a gyroscope, the attitude and attitude rate of a receiver can be determined using signals received by antennae on the receiver. Based on the signals received by the antennae, the Doppler difference between the signals is calculated. The Doppler difference may then be used to determine the attitude rate. With signals received from two signal sources by three antennae pairs, the three-dimensional attitude rate is determined.
L2-stability of the Vlasov-Maxwell-Boltzmann system near global Maxwellians
International Nuclear Information System (INIS)
Ha, Seung-Yeal; Xiao, Qinghua; Xiong, Linjie; Zhao, Huijiang
2013-01-01
We present a L 2 -stability theory of the Vlasov-Maxwell-Boltzmann system for the two-species collisional plasma. We show that in a perturbative regime of a global Maxwellian, the L 2 -distance between two strong solutions can be controlled by that between initial data in a Lipschitz manner. Our stability result extends earlier results [Ha, S.-Y. and Xiao, Q.-H., “A revisiting to the L 2 -stability theory of the Boltzmann equation near global Maxwellians,” (submitted) and Ha, S.-Y., Yang, X.-F., and Yun, S.-B., “L 2 stability theory of the Boltzmann equation near a global Maxwellian,” Arch. Ration. Mech. Anal. 197, 657–688 (2010)] on the L 2 -stability of the Boltzmann equation to the Boltzmann equation coupled with self-consistent external forces. As a direct application of our stability result, we show that classical solutions in Duan et al. [“Optimal large-time behavior of the Vlasov-Maxwell-Boltzmann system in the whole space,” Commun. Pure Appl. Math. 24, 1497–1546 (2011)] and Guo [“The Vlasov-Maxwell-Boltzmann system near Maxwellians,” Invent. Math. 153(3), 593–630 (2003)] satisfy a uniform L 2 -stability estimate. This is the first result on the L 2 -stability of the Boltzmann equation coupled with self-consistent field equations in three dimensions
DEFF Research Database (Denmark)
Scholderer, Joachim
2010-01-01
An attitude can be defined as the evaluation of an object as positive or negative. The term "object" in this definition should be understood in a broad sense; an attitude object may be any concrete or abstract entity that is in some way represented in our thoughts and memory. In other words......, attitude objects are simply the things we like or dislike. Consumer researchers are mainly interested in attitude objects of two classes, products and services, including the attributes, issues, persons, communications, situations, and behaviours related to them. Research on consumer attitudes takes two...... perspectives: Understanding attitude structure: how is an attitude cognitively represented in a consumer's mind, including its components (intra-attitudinal structure) and its associations with other psychological variables (inter-attitudinal structure)? Understanding information processing: what...
Attitudes and Attitude Change.
Albarracin, Dolores; Shavitt, Sharon
2018-01-04
This review covers research on attitudes and attitude change published between 2010 and 2017. We characterize this period as one of significant progress toward an understanding of how attitudes form and change in three critical contexts. The first context is the person, as attitudes change in connection to values, general goals, language, emotions, and human development. The second context is social relationships, which link attitude change to the communicator of persuasive messages, social media, and culture. The third context is sociohistorical and highlights the influence of unique events, including sociopolitical, economic, and climatic occurrences. In conclusion, many important recent findings reflect the fact that holism, with a focus on situating attitudes within their personal, social, and historical contexts, has become the zeitgeist of attitude research during this period.
Stability of dynamical systems on the role of monotonic and non-monotonic Lyapunov functions
Michel, Anthony N; Liu, Derong
2015-01-01
The second edition of this textbook provides a single source for the analysis of system models represented by continuous-time and discrete-time, finite-dimensional and infinite-dimensional, and continuous and discontinuous dynamical systems. For these system models, it presents results which comprise the classical Lyapunov stability theory involving monotonic Lyapunov functions, as well as corresponding contemporary stability results involving non-monotonicLyapunov functions.Specific examples from several diverse areas are given to demonstrate the applicability of the developed theory to many important classes of systems, including digital control systems, nonlinear regulator systems, pulse-width-modulated feedback control systems, and artificial neural networks. The authors cover the following four general topics: - Representation and modeling of dynamical systems of the types described above - Presentation of Lyapunov and Lagrange stability theory for dynamical sy...
Aircraft Landing and Attitude Control Using Dynamic Matrix Control
Directory of Open Access Journals (Sweden)
George Cristian Calugaru
2017-06-01
Full Text Available This paper proposes a method for an efficient control of the aircraft landing and attitude through Dynamic Matrix Control. The idea of MPC structures used in aircraft control has been well established during the last few years, but some aspects require further investigation. With this in mind, the paper proposes structures for aircraft landing and aircraft attitude control by using single DMC controllers for landing and respectively one DMC controller for each of the attitude axis (pitch attitude hold, bank angle hold and heading hold. The model used for analysis of the aircraft landing structure is based on the last phase of landing. Also, the model used to illustrate the attitude control is that of a pitch attitude hold system of a N250-100 aircraft. Simulations are performed for a variety of control and prediction horizons, taking into account the possibility of adding a weighting factor for the control actions. Apart from separate studies on step reference variations, for some use cases, a generic reference trajectory is provided as a control purpose of the system. Results show a better performance of the proposed method in terms of control surface transition and protection of the actuators involved and a better time response in stabilizing the aircraft attitude. Overall, the aspects shown ensure an improved aircraft attitude control and landing stabilization.
Short term outcome of posterior dynamic stabilization system in degenerative lumbar diseases
Directory of Open Access Journals (Sweden)
Mingyuan Yang
2014-01-01
Conclusion: Dynamic stabilization system treating lumbar degenerative disease showed clinical benefits with motion preservation of the operated segments, but does not have the significant advantage on motion preservation at adjacent segments, to avoid the degeneration of adjacent intervertebral disk.
Directory of Open Access Journals (Sweden)
G. Kondrat'ev
1999-10-01
Full Text Available In this article some ideas of Hamilton mechanics and differential-algebraic Geometry are used to exact definition of the potential function (Bellman-Lyapunov function in the optimal stabilization problem of smooth finite-dimensional systems.
General Output Feedback Stabilization for Fractional Order Systems: An LMI Approach
Directory of Open Access Journals (Sweden)
Yiheng Wei
2014-01-01
Full Text Available This paper is concerned with the problem of general output feedback stabilization for fractional order linear time-invariant (FO-LTI systems with the fractional commensurate order 0<α<2. The objective is to design suitable output feedback controllers that guarantee the stability of the resulting closed-loop systems. Based on the slack variable method and our previous stability criteria, some new results in the form of linear matrix inequality (LMI are developed to the static and dynamic output feedback controllers synthesis for the FO-LTI system with 0<α<1. Furthermore, the results are extended to stabilize the FO-LTI systems with 1≤α<2. Finally, robust output feedback control is discussed. Numerical examples are given to illustrate the effectiveness of the proposed design methods.
Parker, David Huw
1989-01-01
Although small scale magnetic suspension and balance systems (MSBSs) for wind tunnel use have been in existence for many years, they have not found general application in the production testing of flight vehicles. One reason for this is thought to lie in the relatively limited range of attitudes over which a wind tunnel model may be suspended. Modifications to a small MSBS to permit the suspension and control of axisymmetric models over angles of attack from less than zero to over ninety degrees are reported. Previous work has shown that existing arrangement of ten electromagnets was unable to generate one of the force components needed for control at extreme attitudes. Examination of possible solutions resulted in a simple alteration to rectify this deficiency. To generate the feedback signals to control the suspended model, an optical position sensing system using collimated laser beams and photodiode arrays was installed and tested. An analytical basis was developed for distributing the demands for force and moment needed for model stabilization amonge the electromagnets over the full attitude range. This was implemented by an MSBS control program able to continually adjust the distribution for the instantaneous incidence in accordance with prescheduled data. Results presented demonstrate rotations of models from zero to ninety degrees at rates up to ninety degrees per second, with pitching rates rising to several hundred degrees per second in response to step-change demands. A study of a design for a large MSBS suggests that such a system could be given the capability to control a model in six degrees of freedom over an unlimited angle of attack range.
Analysis and improvement of digital control stability for master-slave manipulator system
International Nuclear Information System (INIS)
Yoshida, Koichi; Yabuta, Tetsuro
1992-01-01
Some bilateral controls of master-slave system have been designed, which can realize high-fidelity telemanipulation as if the operator were manipulating the object directly. While usual robot systems are controlled by software-servo system using digital computer, little work has been published on design and analysis for digital control of these systems, which must consider time-delay of sensor signals and zero order hold effect of command signals on actuators. This paper presents a digital control analysis for single degree of freedom master-slave system including impedance models of both the human operator and the task object, which clarifies some index for the stability. The stability result shows a virtual master-slave system concepts, which improve the digital control stability. We first analyze a dynamic control method of master-slave system in discrete-time system for the stability problem, which can realize high-fidelity telemanipulation in the continuous-time. Secondly, using the results of the stability analysis, the robust control scheme for master-slave system is proposed, and the validity of this scheme is finally confirmed by the simulation. Consequently, it would be considered that any combination of master and slave modules with dynamic model of these manipulators is possible to construct the stable master-slave system. (author)
Robust D-Stability Controller Design for a Ducted Fan Unmanned Aerial Vehicle
Directory of Open Access Journals (Sweden)
Xiao-lu Ren
2014-01-01
Full Text Available This paper deals with the aerodynamic modeling of a small ducted fan UAV and the problem of attitude stabilization when the parameter of the vehicle is varied. The main aerodynamic model of the hovering flight UAV is first presented. Then, an attitude control is designed from a linearization of the dynamic model around the hovering flight, which is based on the H∞ output feedback control theory with D-stability. Simulation results show that such method has good robustness to the attitude system. They can meet the requirements of attitude control and verify further the feasibility of such a control strategy.
Application of a Modal Approach in Solving the Static Stability Problem for Electric Power Systems
Sharov, J. V.
2017-12-01
Application of a modal approach in solving the static stability problem for power systems is examined. It is proposed to use the matrix exponent norm as a generalized transition function of the power system disturbed motion. Based on the concept of a stability radius and the pseudospectrum of Jacobian matrix, the necessary and sufficient conditions for existence of the static margins were determined. The capabilities and advantages of the modal approach in designing centralized or distributed control and the prospects for the analysis of nonlinear oscillations and rendering the dynamic stability are demonstrated.
Stabilization of periodic solutions in a tethered satellite system by damping injection
DEFF Research Database (Denmark)
Larsen, Martin Birkelund; Blanke, Mogens
2009-01-01
presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilizing the open-loop equilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...
Wind Power Impact to Transient and Voltage Stability of the Power System in Eastern Denmark
DEFF Research Database (Denmark)
Rasmussen, Joana; Jørgensen, Preben; Palsson, Magni Thor
2005-01-01
Voltage stability, transient stability and reactive power compensation are extremely important issues for largescale integration of wind power in areas distant from the main transmission system in Eastern Denmark. This paper describes the application of a dynamic wind farm model in simulation...... studies for assessments of a large wind power penetration. The simulation results reveal problems with voltage stability due to the characteristic of wind turbine generation as well as the inability of the power system to meet the reactive power demand. Furthermore, the established model is applied...
Stability of underground excavations in a repository system
International Nuclear Information System (INIS)
Calash, A.Y.; Greer, J.C.; Andrea, S.J.; Chowdhury, A.H.; Nguyen, V.V.
1988-01-01
The DOE is investigating the feasibility of constructing a deep geologic repository at the Hanford Site, Washington, for the permanent disposal of nuclear waste. The underground openings associated with the repository design include shafts, tunnels, emplacement rooms and boreholes. The stability of these underground openings, the extent and characteristics of the disturbed zones due to excavation, and their effects on groundwater flow path and travel time have a primary influence on the performance assessment of the Hanford Site as a nuclear waste repository. This study is being done in accordance with the requirements of the NRC. Results of structural analyses of shafts and tunnels under in situ stresses and/or medium weight are presented in this paper. Four different analyses were carried out to analyze the shaft: a plane strain model, axisymmetric model, 3-D model of a single material medium, and 3-D model of a three material medium
Classical stability of direct products of spheres in gravitational systems
International Nuclear Information System (INIS)
Yasuda, O.
1984-01-01
Classical stability of Einstein spaces Ssup(d1) x x x x x Ssup(dn) (dsub(j) >= 2) against all fluctuations is investigated in euclidean gravity with a cosmological constant. It is shown that Ssup(d) is classically stable, while Ssup(d1) x x x x x Ssup(dn) (n >= 2) is classically unstable. As a generalization of this analysis it is proved that a compact Einstein space B 1 x x x x x Bsub(n) (n >= 2) which is a direct product of each Einstein space is classically unstable. Non-Einstein spaces M 2 x S 4 (M 2 x S 2 x S 2 ) are also considered in six-dimensional Einstein-Maxwell theory and are shown to be classically stable (unstable). (orig.)
Dynamic Voltage Stability Studies using a Modified IEEE 30-Bus System
Directory of Open Access Journals (Sweden)
Oluwafemi Emmanuel Oni
2016-09-01
Full Text Available Power System stability is an essential study in the planning and operation of an efficient, economic, reliable and secure electric power system because it encompasses all the facet of power systems operations, from planning, to conceptual design stages of the project as well as during the systems operating life span. This paper presents different scenario of power system stability studies on a modified IEEE 30-bus system which is subjected to different faults conditions. A scenario whereby the longest high voltage alternating current (HVAC line is replaced with a high voltage direct current (HVDC line was implemented. The results obtained show that the HVDC line enhances system stability more compared to the contemporary HVAC line. Dynamic analysis using RMS simulation tool was used on DigSILENT PowerFactory.
Directory of Open Access Journals (Sweden)
Yuriy Briskin
2015-08-01
Full Text Available Purpose: to determine the peculiarities of the functional state of cardiorespiratory system in women with postmastectomy syndrome with different types of attitude to the disease. Material and Methods: analysis of the literature and empirical data; rheography, spirography, the definition of the type of attitude to the disease of personality questionnaires of Institute of Behtereva; methods of mathematical statistics. 115 women with postmastectomy syndrome on clinical stage of rehabilitation were involved in this study. Results: in women with intra- and interpsychic types of attitude to the disease decreased reserve capacity of the cardiovascular and respiratory systems respectively. Conclusions: It was proved that women with a rational relationship to the type of disease show significantly better results of the cardiovascular system compared to interpsychic and intrapsychic.
Tseng, Kuo-Hung; Chang, Chi-Cheng; Lou, Shi-Jer
2012-01-01
This study aims to explore how high school students collaboratively solve problems in a web problem-based learning (WPBL) system in an 8-week digital logic course using discourse analysis. Employing in-depth interviews, this study also investigated the students' attitudes toward the WPBL system. The number of teaching assistants' responses had a…
Artvinli, Eyup
2010-01-01
The purpose of this study is to determine the place of Geographic Information Systems (GIS) in teaching geography, the general level of secondary school students' attitudes towards Geography Information Systems and whether this changes according to different variables. The population of the research consists of the students studying in Istanbul,…
Directory of Open Access Journals (Sweden)
Maria Cristina Rodrigues Azevedo Joly
Full Text Available This study aimed to analyze the efficiency of the Cloze Oriented System (COS considering its relation with reading attitude and its validity. The Electronic Program Comprehension (EPC for students from K1 to K4 based on the COS parts of stories from the Brazilian Children's literature was applied in eighteen class-hours. The 40 subjects, ten in each grade, of both genders aged 7 to 11 years, were evaluated before and after the EPC with a Cloze test. They answered the Elementary Reading Attitude Survey too, in a printed protocol adapted to Portuguese, to evaluate the reading attitude of the students and the influence of the EPC in the academic and recreational reading. The results showed that the performance in reading comprehension of all the subjects was higher after taking part in the EPC, and also had significant differences in reading attitude, according to the results of the T of Wilcoxon statistic test. A correlation between comprehension performance before and after the EPC and the reading attitude was verified. There was significant difference for academic reading attitude in the post-test between proficient readers and the one's that has low skill.
Thermal Stabilization of Cryogenic System in Superconducting Cyclotron
International Nuclear Information System (INIS)
Shin, Seung Jae; Kim, Kyung Min; Cho, Hyung Hee; Hong, Bong Hwan; Kang, Joon Sun; Ahn, Dong Hyun
2011-01-01
Radiology has some useful applications for medical purpose. For cancer therapy, the superconducting cyclotron should generate heavy ion beams. It radiates heavy ion beams to cancer patients. In order to make cyclotron system stable, the cryogenic system which makes superconducting state should work constantly. However, radiation heat transfer of cryogenic system should be considered because liquid helium's boiling point is extremely low and there is huge temperature difference between the cryogenic system and ambient temperature. Accordingly, thermal analysis should be carried out. In this paper, the numerical analysis of the cryogenic system in practical superconducting cyclotron show temperature distribution and suggest the number of coolers using ANSYS Workbench program
International Nuclear Information System (INIS)
Amjady, Nima; Ansari, Mohammad Reza
2008-01-01
The introduction of liberalized electricity markets in many countries has resulted in more highly stressed power systems. On the other hand, operating points of a power system are acceptable in the feasible region, which is surrounded by the borders of different stabilities. Power system instability is critical for all participants of the electricity market. Determination of different stability margins can result in the optimum utilization of power system with minimum risk. This paper focuses on the small disturbance voltage stability, which is an important subset of the power system global stability. This kind of voltage stability is usually evaluated by static analysis tools such as continuation power flow, while it essentially has dynamic nature. Besides, a combination of linear and nonlinear analysis tools is required to correctly analyze it. In this paper, a hybrid evaluation method composed of static, dynamic, linear, and nonlinear analysis tools is proposed for this purpose. Effect of load scenario, generation pattern, branch and generator contingency on the small disturbance voltage stability are evaluated by the hybrid method. The test results are given for New England and IEEE68 bus test systems. (author)
Wu, Bing-Fei; Ma, Li-Shan; Perng, Jau-Woei
This study analyzes the absolute stability in P and PD type fuzzy logic control systems with both certain and uncertain linear plants. Stability analysis includes the reference input, actuator gain and interval plant parameters. For certain linear plants, the stability (i.e. the stable equilibriums of error) in P and PD types is analyzed with the Popov or linearization methods under various reference inputs and actuator gains. The steady state errors of fuzzy control systems are also addressed in the parameter plane. The parametric robust Popov criterion for parametric absolute stability based on Lur'e systems is also applied to the stability analysis of P type fuzzy control systems with uncertain plants. The PD type fuzzy logic controller in our approach is a single-input fuzzy logic controller and is transformed into the P type for analysis. In our work, the absolute stability analysis of fuzzy control systems is given with respect to a non-zero reference input and an uncertain linear plant with the parametric robust Popov criterion unlike previous works. Moreover, a fuzzy current controlled RC circuit is designed with PSPICE models. Both numerical and PSPICE simulations are provided to verify the analytical results. Furthermore, the oscillation mechanism in fuzzy control systems is specified with various equilibrium points of view in the simulation example. Finally, the comparisons are also given to show the effectiveness of the analysis method.
Educational effects using a robot patient simulation system for development of clinical attitude.
Abe, S; Noguchi, N; Matsuka, Y; Shinohara, C; Kimura, T; Oka, K; Okura, K; Rodis, O M M; Kawano, F
2017-11-01
The aim of this study was to assess the effectiveness of improving the attitude of dental students towards the use of a full-body patient simulation system (SIMROID) compared to the traditional mannequin (CLINSIM) for dental clinical education. The participants were 10 male undergraduate dental students who had finished clinical training in the university hospital 1 year before this study started. They performed a crown preparation on an upper pre-molar tooth using SIMROID and CLINSIM as the practical clinical trials. The elapsed time for preparation was recorded. The taper of the abutment teeth was measured using a 3-dimensional shape-measuring device after this trial. In addition, a self-reported questionnaire was collected that included physical pain, treatment safety and maintaining a clean area for each simulator. Qualitative data analysis of a free format report about SIMROID was performed using text mining analysis. This trial was performed twice at 1-month intervals. The students considered physical pain, treatment safety and a clean area for SIMROID significantly better than that for CLINSIM (P mining analysis, most of the students wrote that SIMROID was similar to real patients. The use of SIMROID was proven to be effective in improving the attitude of students towards patients, thereby giving importance to considerations for actual patients during dental treatment. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Hauser, Mirjam; Jonas, Klaus; Riemann, Rainer
2011-10-01
Consumer food choice behaviour in post-industrial countries is complex and influenced by a multitude of interacting variables. This study looked at the antecedents of behaviour and examined salient food-related values and attitudes. To discover personal meanings and patterns of everyday food choices across different situations we used a qualitative approach in the form of repertory grid interviews. An analysis of the personal constructs elicited from a representative sample of 100 Swiss consumers revealed elaborated value systems. The food-related values can be summarised as: authenticity/naturalness, conviviality, health, quality/indulgence, convenience, and price. The salience of these values and their negatively evaluated counterparts differed for various social eating situations and product categories. Consumers' personal values also differed significantly from their perception of current trends in eating culture. In every-day food choices interdependent food-related values compete and are thus a possible cause of ambivalence and conflicts. The findings offer explanations of discrepancies between values/attitudes and behaviour that may be due to situational constraints and habits. Implications for companies include the need for strategic realignment to regain consumers' trust by providing comprehensive value-congruent food solutions that also consider health and ethical criteria. Copyright © 2011 Elsevier Ltd. All rights reserved.
Ullan, A M; Fernández, E; Badia, M; Lorente, F; Malmierca, F; Zapatero, I
2013-08-01
Many factors affect the assessment and treatment of pain, among them being the knowledge and attitudes of clinical staff. The goal of this work was to determine the opinions and attitudes of clinical staff from two hospitals on the different aspects of the assessment and treatment of children's pain. A cross-sectional, descriptive study was conducted using a self-administered questionnaire issued to clinical staff. The questionnaire was given to the professionals, doctors, and nursing staff of the paediatric services of two hospitals, and to an incidental sample of paediatric doctors. Of the 146 questionnaires sent out, 105 were completed. Participants indicated that standardised scales and physiological recordings were the least frequently used methods to assess children's pain. Participants considered that pharmacological techniques for the treatment of pain were used more frequently than non-pharmacological techniques, at all ages. Participants acknowledged being significantly more knowledgeable about pharmacological methods to relieve paediatric pain than about non-pharmacological methods. There is margin for improvement in systems for the assessment and treatment of children's pain as regards the more frequent and standardised use of techniques and standardised tools for the assessment of pain, and the greater administration of non-pharmacological strategies for its treatment. Copyright © 2012 Asociación Española de Pediatría. Published by Elsevier Espana. All rights reserved.
Directory of Open Access Journals (Sweden)
Mohammadtaghi Hamidi Beheshti
2010-01-01
Full Text Available We propose a fractional-order controller to stabilize unstable fractional-order open-loop systems with interval uncertainty whereas one does not need to change the poles of the closed-loop system in the proposed method. For this, we will use the robust stability theory of Fractional-Order Linear Time Invariant (FO-LTI systems. To determine the control parameters, one needs only a little knowledge about the plant and therefore, the proposed controller is a suitable choice in the control of interval nonlinear systems and especially in fractional-order chaotic systems. Finally numerical simulations are presented to show the effectiveness of the proposed controller.
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L. F. Araghi
2014-01-01
Full Text Available Stability of switching systems with an infinite number of subsystems is important in some structure of systems, like fuzzy systems, neural networks, and so forth. Because of the relationship between stability of a set of matrices and switching systems, this paper first studies the stability of a set of matrices, then and the results are applied for stability of switching systems. Some new conditions for globally uniformly asymptotically stability (GUAS of discrete-time switched linear systems with an infinite number of subsystems are proposed. The paper considers some examples and simulation results.
Evaluation of Laser Stabilization and Imaging Systems for LCLS-II - Final Paper
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Barry, Matthew [Auburn Univ., AL (United States)
2015-08-20
By combining the top performing commercial laser beam stabilization system with the most ideal optical imaging configuration, the beamline for the Linear Accelerator Coherent Light Source II (LCLS-II) will deliver the highest quality and most stable beam to the cathode. To determine the optimal combination, LCLS-II beamline conditions were replicated and the systems tested with a He-Ne laser. The Guidestar-II and MRC active laser beam stabilization systems were evaluated for their ideal positioning and stability. Both a two and four lens optical imaging configuration was then evaluated for beam imaging quality, magnification properties, and natural stability. In their best performances when tested over fifteen hours, Guidestar-II kept the beam stable over approximately 70-110um while the MRC system kept it stable over approximately 90-100um. During short periods of time, Guidestar-II kept the beam stable between 10-20um, but was more susceptible to drift over time, while the MRC system maintained the beam between 30-50um with less overall drift. The best optical imaging configuration proved to be a four lens system that images to the iris located in the cathode room and from there, imaged to the cathode. The magnification from the iris to the cathode was 2:1, within an acceptable tolerance to the expected 2.1:1 magnification. The two lens configuration was slightly more stable in small periods of time (less than 10 minutes) without the assistance of a stability system, approximately 55um compared to approximately 70um, but the four lens configurations beam image had a significantly flatter intensity distribution compared to the two lens configuration which had a Gaussian distribution. A final test still needs to be run with both stability systems running at the same time through the four lens system. With this data, the optimal laser beam stabilization system can be determined for the beamline of LCLS-II.
Interpreting Popov criteria in Lure´ systems with complex scaling stability analysis
Zhou, J.
2018-06-01
The paper presents a novel frequency-domain interpretation of Popov criteria for absolute stability in Lure´ systems by means of what we call complex scaling stability analysis. The complex scaling technique is developed for exponential/asymptotic stability in LTI feedback systems, which dispenses open-loop poles distribution, contour/locus orientation and prior frequency sweeping. Exploiting the technique for alternatively revealing positive realness of transfer functions, re-interpreting Popov criteria is explicated. More specifically, the suggested frequency-domain stability conditions are conformable both in scalar and multivariable cases, and can be implemented either graphically with locus plotting or numerically without; in particular, the latter is suitable as a design tool with auxiliary parameter freedom. The interpretation also reveals further frequency-domain facts about Lure´ systems. Numerical examples are included to illustrate the main results.