Showing papers on "Active vibration control published in 2007"

Engineering Analysis of Smart Material Systems

Abstract: Preface. 1. Introduction to Smart Material Systems. 2. Modeling Mechanical and Electrical Systems. 3. Mathematical Representations of Smart Material Systems. 4. Piezoelectric Materials. 5. Piezoelectric Material Systems. 6. Shape Memory Alloys. 7. Electroactive Polymer Materials. 8. Motion Control Applications. 9. Passive and Semiactive Damping. 10. Active Vibration Control. 11. Power Analysis for Smart Material Systems. References. Index.

Receptance Method in Active Vibration Control

Abstract: The pole/zero assignment problem is addressed using a method based on measured receptances. The approach, which is well known in passive structural modification, has not been used before in active vibration control. A number of significant advantages are claimed over the conventional state-space approach that uses the mass, damping, and stiffness matrices formed, for example, by finite elements. In fact, because the method is based solely upon measured vibration data, there is no need to evaluate or to know the M, C, and K matrices. It is demonstrated that all the poles may be assigned actively by the equivalent of a rank-1 modification to the dynamic stiffness matrix of the system. The assignment of zeros has a special significance in vibration suppression, because the vibration response at coordinatep vanishes completely when sinusoidal excitation is applied at coordinate q at the frequency of a zero of receptance H nn . A pole ofH pq may be eliminated by assigning a zero at the same frequency.

Modal Active Vibration Control of a Rotor Using Piezoelectric Stack Actuators

Abstract: This work deals with active vibration control of a rotating machine in both steady state and transient motion. Two stacks of piezoelectric ceramic orthogonally arranged in a plane localized at one of the bearings were used as the control actuators, using a modal control strategy. The optimal controller LQR was used to calculate the control gain, working together with an LQE observer that estimates the modal state. Simulation carried out on FEM model suggested the feasibility of the control strategy, and experimental tests using a physical test rig show good agreement with the numerical results, and confirm the efficiency of the strategy.

Comfort enhancement by an active vibration reduction system for a flexible railway car body

Abstract: In order to improve the ride comfort of lightweight railway vehicles, an active vibration reduction system using piezo-stack actuators is proposed and studied in simulations. The system consists of actuators and sensors mounted on the vehicle car body. Via a feedback control loop, the output signals of the sensors which are measuring the flexible deformation of the car body generate a bending moment, which is directly applied to the car body by the actuators. This bending moment reduces the structural vibration of the vehicle car body. Simulations have shown that a significant reduction in the vibration level is achieved.

Fuzzy Logic Control of a Non-linear Structural System against Earthquake Induced Vibration

Abstract: In this paper, the problem of active vibration control of multi-degree-of-freedom structures is considered. Fuzzy logic and PID controllers are designed to suppress structural vibrations against earthquakes under the non-linear soil-structure interaction. The advantage of the fuzzy logic approach is the ability to handle the non-linear behavior of the system. Non-linear behavior of the soil is modeled in the dynamics of the structural system with non-linear hysteric restoring forces. The simulated system has fifteen degrees of freedom, which is modeled using spring-mass-damper subsystems. A structural system was simulated against the ground motion of the destructive Kocaeli earthquake (Mw = 7.4) in Turkey on 17 August 1999. At the end of the study the time history of the storey displacements and accelerations, the control voltages and forces, and the frequency responses of both the uncontrolled and the controlled structures are presented. The performance of designed fuzzy logic control is checked using th...

Cable Vibration Control with a TMD-MR Damper System: Experimental Exploration

Abstract: Although traditional mechanical dampers can help reduce cable vibrations, they are not the most effective solution due to their position restrictions. Tuned mass dampers (TMDs) were proposed to overcome this limitation and have been proven effective for cable vibration mitigation according to previous research. However, the effectiveness of TMDs is very sensitive to the vibration frequency, which implies that TMDs designed for a specific vibration frequency may not be efficient for other frequencies. A new type of mechanical damper named the TMD magnetorheological (MR) damper system is proposed in the present study to address this problem. The feature of this proposed damper is the combination of the position flexibility of TMDs and the adjustability of MR dampers. The proposed damper system is attached to a 7.16-m-long cable to investigate its vibration reduction effectiveness and the dynamic properties of the combined cable-damper system. Experimental results show good vibration reduction effects of the TMD-MR system. The present study focuses on a conceptual exploration of the TMD-MR damper system for cable vibration mitigation through an experimental approach.

Intelligent Learning Algorithms for Active Vibration Control

Abstract: This correspondence presents an investigation into the comparative performance of an active vibration control (AVC) system using a number of intelligent learning algorithms. Recursive least square (RLS), evolutionary genetic algorithms (GAs), general regression neural network (GRNN), and adaptive neuro-fuzzy inference system (ANFIS) algorithms are proposed to develop the mechanisms of an AVC system. The controller is designed on the basis of optimal vibration suppression using a plant model. A simulation platform of a flexible beam system in transverse vibration using a finite difference method is considered to demonstrate the capabilities of the AVC system using RLS, GAs, GRNN, and ANFIS. The simulation model of the AVC system is implemented, tested, and its performance is assessed for the system identification models using the proposed algorithms. Finally, a comparative performance of the algorithms in implementing the model of the AVC system is presented and discussed through a set of experiments.

Vibration suppression of laminated composite beams using actuators of giant magnetostrictive materials

Abstract: This paper presents a simulation of vibration suppression of a laminated composite beam embedded with actuators of a giant magnetostrictive material subjected to control magnetic fields. It has been found that the strains generated in the material are not only significantly larger than ones created by many other smart materials but also exhibit some inherent nonlinearities. To utilize the full potential of these materials in active vibration control, these nonlinearities should be characterized in the control system as accurately as possible. In this simulation of nonlinear dynamic controls, the control law with negative velocity feedback and the analytical nonlinear constitutive model of the magnetostrictive layer are employed. The numerical results show that this proposed approach is efficient not only in a linear zone but also in nonlinear zones (dead zone and saturation zone) of magnetostrictive curves in vibration suppression. Compared with those from the control system based on the linear constitutive relations of the material, it is found that the simulation results based on the linear model are efficient only when the magnetostrictive relations are located in the linear zone. Once the system has some departure from the linear zone, however, the results from the linear model become unacceptable. Finally, the effect of material properties, lamination schemes and location of the magnetostrictive layers on vibration suppression of the practical system is evaluated.

Active Vibration Suppression of a Smart Flexible Beam Using a Sliding Mode Based Controller

Abstract: This article investigates robust active vibration suppression of a flexible beam with a low dominant frequency using piezoceramic sensor and actuators. The piezoceramic sensor and actuators are in patch form and are surface-bonded to the cantilevered end of the flexible beam. The robust sliding mode control, which has the advantages of being robust to plant parameter variation, insensitive to the unmodeled dynamics, and easy to implement, is adopted in this article for active vibration control of the flexible beam. Unlike other commonly used vibration suppression methods, such as positive position feedback control, strain rate feedback control, and lead compensation, the sliding mode controller requires almost no knowledge of the flexible beam. To avoid the chattering problem commonly associated with sliding mode control, a smooth switching function employing a hyperbolic tangent function is used. A low pass filter is applied to the output of the sliding mode controller to avoid excitation of the higher m...

Design and optimization of voice coil motor for application in active vibration isolation

Abstract: To control the vibration transmitted from ground to the nano-precision measuring instruments has always been of great interest among the researchers. Vibration isolators typically reduce the vibration transmitted to the measuring instrument providing managed stiffness and damping through the transmitted path. Active isolators use control algorithms such as feedback or feed forward to provide the necessary control signal. In this paper, we propose optimized design of a voice coil motor (VCM) that can be used as an actuator to implement a suitable controller for active isolation using feedback control to attenuate the low frequency vibration of all six rigid body modes. Necessary force requirement has also been considered.

Modal control of a plate using a fuzzy logic controller

Abstract: This paper presents fuzzy logic based independent modal space control (IMSC) and fuzzy logic based modified independent modal space control (MIMSC) of vibration. The rule base of the controller consists of nine rules, which have been derived based upon simple human reasoning. Input to the controller consists of the first two modal displacements and velocities of the structure and the output of the controller is the modal force to be applied by the actuator. Fuzzy logic is used in such a way that the actuator is never called to apply effort which is beyond safe limits and also the operator is saved from calculating control gains. The proposed fuzzy controller is experimentally tested for active vibration control of a cantilevered plate. A piezoelectric patch is used as a sensor to sense vibrations of the plate and another piezoelectric patch is used as an actuator to control vibrations of the plate. For analytical formulation, a finite element method based upon Hamilton's principle is used to model the plate. For experimentation, the first two modes of the plate are observed using a Kalman observer. Real-time experiments are performed to control the first mode, the second mode and both modes simultaneously. Experiments are also performed to control the first mode by IMSC, the second mode by IMSC and both modes simultaneously by MIMSC. It is found that for the same decibel reduction in the first mode, the voltage applied by the fuzzy logic based controller is less than that applied by IMSC. While controlling the second mode by IMSC, a considerable amount of spillover is observed in the first mode and region just after the second mode, whereas while controlling the second mode by fuzzy logic, spillover effects are much smaller. While controlling two modes simultaneously, with a single sensor/actuator pair, appreciable resonance control is observed both with fuzzy logic based MIMSC as well as with direct MIMSC, but there is a considerable amount of spillover in the off-resonance region. This may be due to the sub-optimal location and/or an insufficient number of actuators. So, another smart plate with two piezoelectric actuators and one piezoelectric sensor is considered. Piezoelectric patches are fixed in an area where modal strains are high. With this configuration of the smart plate, experiments are conducted to control the first three modes of the plate and it is found that spillover effects are greatly reduced.

Robust integral variable structure controller and pulse-width pulse-frequency modulated input shaper design for flexible spacecraft with mismatched uncertainty/disturbance

Abstract: This paper presents a dual-stage control system design method for the flexible spacecraft attitude maneuvering control by use of on-off thrusters and active vibration control by input shaper. In this design approach, attitude control system and vibration suppression were designed separately using lower order model. As a stepping stone, an integral variable structure controller with the assumption of knowing the upper bounds of the mismatched lumped perturbation has been designed which ensures exponential convergence of attitude angle and angular velocity in the presence of bounded uncertainty/disturbances. To reconstruct estimates of the system states for use in a full information variable structure control law, an asymptotic variable structure observer is also employed. In addition, the thruster output is modulated in pulse-width pulse-frequency so that the output profile is similar to the continuous control histories. For actively suppressing the induced vibration, the input shaping technique is used to modify the existing command so that less vibration will be caused by the command itself, which only requires information about the vibration frequency and damping of the closed-loop system. The rationale behind this hybrid control scheme is that the integral variable structure controller can achieve good precision pointing, even in the presence of uncertainties/disturbances, whereas the shaped input attenuator is applied to actively suppress the undesirable vibrations excited by the rapid maneuvers. Simulation results for the spacecraft model show precise attitude control and vibration suppression.

Active vibration control of smart plates with partially debonded multilayered PZT actuators

Abstract: The influence of actuator damage on the performance of closed loop vibration control is numerically evaluated. Debonding is considered a damage mode and finite element procedures are subsequently developed to introduce its effect on system matrices, namely elastic and electro-elastic stiffness. A simple modelling scheme for multiple debonding is proposed, which can also idealize multiple delamination in the host laminate. Debonding in actuators in general has reduced their load carrying appreciably as well as vibration control characteristics. Therefore, incorporating such a damage mode in the control design as an uncertainty parameter would help to realize a damage-tolerant active vibration control system. It is interesting to note that debonding in actuators has influenced both active damping and active stiffening effects.

Robust Active Vibration Control for Rail Vehicle Pantograph

Abstract: This paper deals with vibration control for a light rail vehicle's pantographs. The concepts of force cancellation, skyhook damper, and contact wire-following spring are jointly applied to constitute an effective controller for vibration suppression. Performance of the control system is evaluated on the basis of variations of displacement and acceleration between the pantograph and contact wire. An active control law is developed by means of a linear quadratic regulator design to derive a stabilizing control law for the pantograph system with the time-varying contact force between the pantograph shoe and catenary. A systematic optimization process with Pareto set and variable weights for the design of active suspension parameters of the pantograph using a constrained multiobjective evolutionary algorithm is developed. Extensive simulations are well performed to verify our proposed design.

Active vibration suppression of a flexible beam with piezoceramic patches using robust model reference control

Abstract: This paper presents a novel approach to active vibration suppression of a flexible beam with piezoceramic sensor and actuator. This approach employs a robust model reference controller which has the ability to handle model uncertainties. The proposed controller ensures effective active vibration suppression of the flexible beam by dramatically increasing its damping. Asymptotic stability of the closed-loop system is guaranteed as proved by Lyapunov's direct method. To demonstrate the controller's effectiveness in active vibration control and its robustness to model uncertainties, experiments, including varying the mass of the flexible beams, are conducted. Experiments show that the robust model reference control achieves rapid vibration suppression even in the presence of uncertain model parameters.

Vibration control of a functionally graded material plate patched with piezoelectric actuators and sensors under a constant electric charge

Abstract: In this paper active vibration control of functionally graded material (FGM) plates using piezoelectric sensor/actuator patches is studied. A simply supported FGM rectangular plate which is bonded with a piezoelectric rectangular patch (patches) on the top and/or bottom surface(s) as actuators/sensors is considered. When a constant electric charge is imposed, the governing differential equations of the motion are derived using classical laminated plate theory (CLPT). The solution for the motion equation is obtained using a Fourier series method and the effect of feedback gain and FGM volume fraction on the plate frequency and displacement (w) are studied. It is noticed that increasing the feedback gain leads to the reduction of frequency and displacement and therefore a better control of the plate's vibration. Moreover, by increasing the value of the FGM volume fraction the resonant frequency decreases.