Showing papers on "Active vibration control published in 2016"

Active vibration control for a flexible string system with input backlash

Abstract: In this study, the authors are concerned with the active vibration control of a flexible string system with input backlash. For vibration suppression, active control is applied at the right boundary of the flexible string. To deal with the input backlash, a novel ‘disturbance-like’ term is proposed in the control design. A physically motivated Lyapunov function is employed to design boundary control law to ensure the vibration suppression and guarantee the stability of the closed-loop system. Numerical simulations illustrate the effectiveness of the proposed control method.

Hysteresis modeling and displacement control of piezoelectric actuators with the frequency-dependent behavior using a generalized Bouc–Wen model

Abstract: Piezoelectric actuators (PAs) are widely used in precision positioning control and active vibration control. However, positioning accuracy can be compromised by the hysteresis of PAs. We can put forward a model to accurately describe the hysteresis and then compensate the hysteretic effect to solve the above problem based on the proposed model. In order to model the hysteresis of a PA which possesses the asymmetrical characteristics and the frequency-dependent behavior, a generalized Bouc–Wen model is developed for the PA. A model-based control using the proposed generalized Bouc–Wen model is applied to force the output displacement of the PA to track the desired displacement accurately thereafter. Experiments are conducted to validate this new approach. The results highlight significantly improved accuracy in the displacement control of the PA.

Optimal placement of piezoelectric actuators on plate structures for active vibration control via modified control matrix and singular value decomposition approach using modified heuristic genetic algorithm

Abstract: The present work deals with the optimal placement of piezoelectric actuators on a thin plate using modified control matrix and singular value decomposition (MCSVD) approach. The MCSVD is considered as the fitness function and optimal positions of the actuators are obtained by maximizing it with MHGA (modified heuristic genetic algorithm). Vibration suppression has been studied for simply supported plate with piezoelectric patches in optimal positions to suppress first specified modes using LQR (linear quadratic regulator) controller. It is observed that the positions of patches obtained with this approach give greater vibration suppression, reduced computational requirements, and provide global optimum solution only.

Vibration responses and suppression of variable stiffness laminates with optimally steered fibers and magnetostrictive layers

Abstract: This paper examines the vibration of fiber-steered laminated plates, such as those used in the skins of a sandwich panel, manufactured by automated fiber placement. We use third-order shear deformation theory, hybrid Fourier-Galerkin method, and numerical integration technique to predict their vibration responses, and to study the role of manufacturing defects, in particular gaps and overlpas, as well as the parameters representing the stiffness of the sandwich core. With the aim of improving both structural and vibration performance, we first adopt a passive approach to search for optimal fiber paths that can concurrently maximize the undamped dynamic out-of-plane and in-plane stiffness of laminates with gaps and overlaps. To further reduce vibration, we then follow an active approach that uses magnetostrictive layers to suppress the structural vibration of laminates with optimal vibration characteristics. The results of the vibration analysis show that for plates with gaps, as opposed to those with overlaps, the dynamic out-of-plane deflection has a higher amplitude and a lower frequency than that of a defect-free plate. In addition, the results show that magnetostrictive layers with a higher gain control can lead to a lower vibration frequency, and better attenuate the vibration response of the panel.

Harmonic Current Suppression of an AMB Rotor System at Variable Rotation Speed Based on Multiple Phase-Shift Notch Filters

Abstract: An active magnetic bearing (AMB) rotor system has such advantages as no friction and active vibration control. However, harmonic current caused by mass imbalance and sensor runout of magnetically suspended rotor system will lead to harmonic vibration. The harmonic current frequency is changed with the variation of rotation speed. The harmonic current suppression at variable rotation speed is a challenging research topic. In order to suppress harmonic current in AMB whose frequencies are integer multiples of the rotation frequency of rotor and to maintain system stability, multiple phase-shift notch filters are proposed in this paper. The closed-loop stability is ensured by adjusting the phase at variable rotation speed. Experiments are carried out on vibration measurement table and magnetically suspended flywheel prototype to show the effectiveness of the proposed method.

Active vibration control of an arbitrary thick smart cylindrical panel with optimally placed piezoelectric sensor/actuator pairs

Abstract: Active vibration suppression of a simply supported, arbitrarily thick, transversely isotropic circular cylindrical host panel, integrated with spatially distributed piezoelectric actuator and sensor layers, is investigated based on the linear three dimensional exact piezo-elasticity theory. To assist control system design, system identification is conducted by applying a frequency domain subspace approximation method based on N4SID algorithm using the first few structural modes of the system. The state space model is constructed from system identification and used for state estimation and development of control algorithm. The optimal electrode configuration for the collocated piezoelectric actuator–sensor pair is found by applying a genetic optimization procedure based on maximization of a quantifiable objective function considering the controllability, observability and spillover prevention of the identified system. A linear quadratic Gaussian (LQG) optimal controller is subsequently designed and simulated based on the identified model of optimally configured smart structure in order to actively control the system response in both frequency and time domains. The dynamic performance and effectiveness of the optimized vibration control system is demonstrated for two different types of external mechanical excitations (i.e., impulsive load and white noise disturbance). The accuracy of dynamic analysis is established with the aid of a commercial finite element package and the data available in the literature.

Vibration control of collocated smart structures using H ∞ modified positive position and velocity feedback

Abstract: In this paper, H∞ modified positive position feedback (HMPPF) and H∞ modified positive velocity feedback (HMPVF) controllers are developed as two innovative controllers for active vibration reduction in flexible collocated structures. The controllers use the concept of modified positive feedback and are enhanced by the H∞ feedback design to provide effective vibration suppression of multiple modes. An aluminum cantilever beam is used to experimentally evaluate the performance of the two controllers. The objective of the HMPPF controller is to suppress vibration displacement when all of the fundamental modes are excited. In this case which considers the first three modes of the flexible structure, overall vibration displacement is reduced to 38% of the uncontrolled value. The HMPVF, on the other hand, uses the control energy to reduce the vibration velocity to the lowest possible value. Vibration velocity amplitude using the HMPVF approach was reduced more than displacement, which makes this controller mor...

Analysis on nonlinear stiffness and vibration isolation performance of scissor-like structure with full types

Abstract: Due to its simple structure and good deployable characteristics, scissor-like structure (SLS) is widely used in many fields, such as mechanical engineering, structure engineering, and aerospace engineering. Because of its inherent structural characteristics, a SLS can possess superior nonlinearities both in equivalent stiffness and damping only with linear component. It also has high loading capacity and excellent equilibrium stability. Thus, it is promising as a vibration isolator. Based on recent findings, a theoretical study is herein executed to build up a universal stiffness model of full types of SLS (including 6 assembly types), considering mass of scissor arm, Coulomb and viscous friction forces in joint parts. Plus more, perturbation method (PM) and average method (AM) are applied to investigate vibration isolation performances of SLS with different assembly types and installation parameters and to compare them with known quasi-zero-stiffness vibration isolators in the literature. Finally, a simulation is done to testify the presented findings and to compare them with former studies. It is shown that: without changing its overall structure and outside dimensions, a SLS vibration isolator can have significantly different nonlinear stiffness for specific nonlinear characteristics only through adjusting assembly type, installation parameters, and initial deformation of its linear component. Since allowable workspace of a vibration isolator is always limited by isolation object and its surrounding structure, this finding indicates a new way to design and modify vibration isolation performance of a system. It will greatly expand application of SLS in vibration isolation.

Tuning of a vibration absorber with shunted piezoelectric transducers

Abstract: In order to reduce structural vibrations in narrow frequency bands, tuned mass absorbers can be an appropriate measure. A quite similar approach which makes use of applied piezoelectric elements, instead of additional oscillating masses, are the well-known resonant shunts, consisting of resistances, inductances, and possibly negative capacitances connected to the piezoelectric element. This paper presents a combined approach, which is based on a conventional tuned mass absorber, but whose characteristics can be strongly influenced by applying shunted piezoceramics. Simulations and experimental analyses are shown to be very effective in predicting the behavior of such electromechanical systems. The vibration level of the absorber can be strongly attenuated by applying different combinations of resistant, resonant, and negative capacitance shunt circuits. The damping characteristics of the absorber can be changed by applying a purely resistive or resonant resistant shunt. Additionally, the tuning frequency of the absorber can be adapted to the excitation frequency, using a negative capacitance shunt circuit, which requires only the energy to supply the electric components.

Dynamic Vibration Absorber with Negative Stiffness for Rotor System

Abstract: To suppress the vibration of a rotor system, a vibration absorber combining negative stiffness with positive stiffness together is proposed in this paper. Firstly, the negative stiffness producing mechanism using ring type permanent magnets is presented and the characteristics of the negative stiffness are analyzed. Then, the structure of the absorber is proposed; the principles and nonlinear dynamic characteristics of the absorber-rotor system are studied numerically. Finally, experiments are carried out to verify the numerical conclusions. The results show that the proposed vibration absorber is effective to suppress the vibration of the rotor system, the nonlinearity of the negatives stiffness affects the vibration suppression effect little, and the negative stiffness can broaden the effective vibration control frequency range of the absorber.

Adaptive Piezoelectric Absorber for Active Vibration Control

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

Optimizing time delay feedback for active vibration control of a cantilever beam using a genetic algorithm

Abstract: Active vibration control using time delay for a cantilever beam is developed in this paper. The equation of motion of the system is developed using the discrete standard formulation, and the discrete quadratic function is used to design the controller. The original contribution in this paper is using a genetic algorithm to determine the optimal time delay feedback for active vibration control of a cantilever beam. Simulations of the beam demonstrated that the genetic algorithm correctly identified the time delay which produced the quickest attenuation of unwanted vibrations for both mode one and mode two. In terms of frequency response, the optimal time delay for both modes reduced the resonant amplitude. In a mixed mode situation, the simulation demonstrated that an optimal time delay could be identified.

Real-Time Performance of Mechatronic PZT Module Using Active Vibration Feedback Control.

Abstract: This paper proposes an innovative mechatronic piezo-actuated module to control vibrations in modern machine tools. Vibrations represent one of the main issues that seriously compromise the quality of the workpiece. The active vibration control (AVC) device is composed of a host part integrated with sensors and actuators synchronized by a regulator; it is able to make a self-assessment and adjust to alterations in the environment. In particular, an innovative smart actuator has been designed and developed to satisfy machining requirements during active vibration control. This study presents the mechatronic model based on the kinematic and dynamic analysis of the AVC device. To ensure a real time performance, a H2-LQG controller has been developed and validated by simulations involving a machine tool, PZT actuator and controller models. The Hardware in the Loop (HIL) architecture is adopted to control and attenuate the vibrations. A set of experimental tests has been performed to validate the AVC module on a commercial machine tool. The feasibility of the real time vibration damping is demonstrated and the simulation accuracy is evaluated.

A vision-based vibration sensing and active control for a piezoelectric flexible cantilever plate:

Abstract: A visual sensor is used to measure the vibration of a piezoelectric flexible cantilever plate. To decrease the image processing time and satisfy the requirement of real-time application, the searching range is limited by selecting region of interest images and using a tracking technique. After image processing, including median filter, image segmentation for object recognition, least squares technique, the vibrations of bending and torsional modes for flexible plate can be obtained. The visual measured signals are used as feedback to suppress the excited vibrations. The conventional proportional plus derivative (PD) control and finite-time control algorithms are designed and implemented. The experiments are conducted. The decoupling of measurement of the bending and torsional vibrations is realized by the visual sensor accompany with applying the image processing methods. Experimental results demonstrate that the designed control algorithm can suppress the low-frequency vibration effectively. Furthermore, the finite-time controller can damp out the small amplitude vibration much better than that of the PD control.

Experimental studies on active vibration control of smart plate using a modified PID controller with optimal orientation of piezoelectric actuator

Abstract: This paper presents a design, development and experimental verification of an active vibration control system of aluminum plate. The active structure consists of an aluminum rectangular plate as th...

Vibration Theory and Applications with Finite Elements and Active Vibration Control: Palazzolo/Vibration Theory and Applications with Finite Elements and Active Vibration Control

Abstract: Vibration theory and applications with finite elements and active vibration control , Vibration theory and applications with finite elements and active vibration control , کتابخانه دیجیتال دانشگاه علوم پزشکی اصفهان