Multi-mode Vibration Control Research Articles

A novel feedforward control technique for a flexible dual manipulator

This paper proposes a feedforward control technique for two flexible links attached to one motor to suppress residual vibrations in a point-to-point motion. In the proposed method, we attempt to express the trajectory of the joint angle using a combination of cycloidal and polynomial functions, which enables the easy generation of a smooth motion. The generated trajectory depends on the coefficients of the polynomial function. To minimize the residual vibrations of the two flexible links, the coefficients are tuned using a particle swarm optimization algorithm, which is a type of a metaheuristic algorithm. The optimal trajectory obtained by this approach can suppress residual vibrations; i.e., multimode vibration control can be realized. Simulations and experiments are performed to evaluate the applicability and effectiveness of the proposed method. We propose a novel trajectory generation method for suppressing residual vibrations.We address the point-to-point motion task of a flexible dual manipulator.The combination of cycloidal and polynomial functions can generate a smooth trajectory.Multimode vibration control can be realized by driving the manipulator along an optimal trajectory.

Composite multi-modal vibration control for a stiffened plate using non-collocated acceleration sensor and piezoelectric actuator

A novel active method for multi-mode vibration control of an all-clamped stiffened plate (ACSP) is proposed in this paper, using the extended-state-observer (ESO) approach based on non-collocated acceleration sensors and piezoelectric actuators. Considering the estimated capacity of ESO for system state variables, output superposition and control coupling of other modes, external excitation, and model uncertainties simultaneously, a composite control method, i.e., the ESO based vibration control scheme, is employed to ensure the lumped disturbances and uncertainty rejection of the closed-loop system. The phenomenon of phase hysteresis and time delay, caused by non-collocated sensor/actuator pairs, degrades the performance of the control system, even inducing instability. To solve this problem, a simple proportional differential (PD) controller and acceleration feed-forward with an output predictor design produce the control law for each vibration mode. The modal frequencies, phase hysteresis loops and phase lag values due to non-collocated placement of the acceleration sensor and piezoelectric patch actuator are experimentally obtained, and the phase lag is compensated by using the Smith Predictor technology. In order to improve the vibration control performance, the chaos optimization method based on logistic mapping is employed to auto-tune the parameters of the feedback channel. The experimental control system for the ACSP is tested using the dSPACE real-time simulation platform. Experimental results demonstrate that the proposed composite active control algorithm is an effective approach for suppressing multi-modal vibrations.

Independent modal resonant shunt for multimode vibration control of a truss-cored sandwich panel

To realize multimode vibration control of a truss-cored sandwich panel, an independent modal resonant shunt control method is proposed in this paper. In this method, each piezoelectric stack transducer is connected to a single resonant shunt which is tuned to control the vibration of a single mode, and the location of the transducer is optimized to get a maximal electromechanical coupling with this mode. It is found that the optimal values of the resistance and inductance can not be determined by using a single-mode model of the structure, and thus a practical optimization method is employed to optimize the resonant shunt, which is verified with numerical simulation. The result shows that this method can add significant damping ratio to the controlled modes, and the resonant shunt circuits of different modes have no effect on each other. Finally the control effect of resonant shunt is compared with viscoelastic damper. It is indicated that the parameters of the resonant shunt can be tuned to get better effect.

Experimental Study on Multi-Mode Vibration Control of a Stay Cable with a Passive Magnetorheological Damper

Effective vibration control technology for stay cables is extremely critical to safe operations of cable-stayed bridges. For super-long cables, passive linear damper cannot provide sufficient damping since it can be only optimum for a given mode of cable, while a long cable may vibrate with several modes. This paper focuses on multi-mode vibration control of stay cables with passive magnetorheological (MR) dampers. Firstly, a 21.6m-long model cable was designed and established in the laboratory.Then, control performance of the cable with a passive MR damper was tested. The test results show that modal damping ratios of the cable in the first four modes can be improved significantly with the MR damper. It is further demonstrated that optimal tuned passively operated MR damper can outperform the passive viscous damper.

Efficient Active Vibration Control of Smart Structures With Modified Positive Position Feedback Control Using Pattern Search Methods in the Presence of Instrumentation Phase Lead and Lag

For active vibration control applications, positive position feedback (PPF) type controller is quite suitable. These controllers are of low order so are easy to implement in practice. These controllers avoid the problem of control spillover also. However, a systematic design methodology is not available for the design of these controllers. For multimode vibration control applications, in the presence of instrumentation, controller design becomes even more difficult. In the present paper, a systematic design procedure has been suggested to design the PPF controller. The proposed controller is designed by minimizing the H2 or H∞ norm of the closed loop (CL) system. The direct search methods based on pattern search technique has been used. The controller designed in this way can provide uniform damping to all the modes. The problems caused by the instrumentation (i.e., phase lead and lag) and time delay actually present in the control loop can be completely eliminated. Since, the controller is designed by minimizing the H∞ norm of the closed loop system, it is robust in nature. With the proposed methodology, the use of other complicated frequency domain techniques to design the controller can be avoided.

Theory and application of multi-mode vibration control systems

The theoretical analysis of vibration control of multiple-degree-of-freedom structures with multi-mode vibration control systems is presented in this article. A new method of parameter optimization of the multiple-tuned mass damper system was proposed in order to obtain the best control effect, where the minimum of the dynamic magnification factor is used as the optimal objective. The numerical examples of parameter optimization indicate that optimal parameters can be obtained for the multiple-degree-of-freedom system to get satisfactory control effects. The application of the theory is used for the vibration control simulation of an offshore platform. The results indicate that reasonable control effects can be obtained by controlling the first mode and the control effects increase about 10% in average when the first two modes are controlled simultaneously.

A novel multimode negative inductance negative resistance shunted electromagnetic damping and its application on a cantilever plate

Based on the characteristic of the electromagnetic damping, a novel multimode vibration control treatment, negative inductance negative resistance electromagnetic shunt damping (NINR-EMSD), is proposed and employed to control multimode vibration of a cantilever plate. The negative inductance of the shunt impedance can cancel the inherent inductance of the electromagnet, and the impedance of circuit consisted of the coils and shunt will be a pure resistance and the shunt current will be frequency independent when the inductance of the shunt and the electromagnet are equal with each other. The negative resistance cancels the resistance of electromagnet, and as a result the resistance and the current of the closed circuit will change, which make it feasible to control the multimode vibration of the system. Electromechanical coupling coefficient is obtained based on the equivalent current method. The governing equation of the plate with the electromagnetic shunt damping (EMSD) is established according to Hamilton's principle. Multimode vibration control of the system is simulated and experiments are carried out to verify the performance of the NINR-EMSD. The numerical predictions and experimental results agree well with each other and show that: the negative inductance negative resistance (NINR) of the shunt impedance can increase the damping of the structure notably; the decrease of the resistance of shunt impedance have a significant contribution to the improvement of vibration control performance; the first four modes vibration of the plate can be suppressed simultaneously with the NINR-EMSD.

Analysis of energy conversion in two-mode vibration control using synchronized switch damping approach

The synchronized switch damping (SSD) approaches based on piezoelectric actuators have been successfully used in multimode vibration control of structures. By suppressing voltage inversion at some displacement extrema, the control performance of SSD approaches can be significantly improved. In this study, conversion of energy from mechanical to electrical in two-mode control is analyzed for different amplitude ratios and frequency ratios. The results show that the converted energy in two-mode control with voltage inversion at every extremum is smaller than the sum of the energies of the two modes in single-mode control, but the converted energy of the second mode in two-mode control may exceed that in single-mode control when the amplitude ratio of the second mode to the first mode is small enough. The influence of voltage threshold used to suppress voltage inversion on energy conversion of the system and each individual mode is also investigated. The converted energy of the first mode in two-mode control may be much larger than that in single-mode control when voltage inversion is suppressed suitably. The analytical results can successfully explain the phenomenon in the previous control experiments and can also be extended to multimode control.

MULTI-MODE VIBRATION CONTROL AND POSITION ERROR ANALYSIS OF PARALLEL MANIPULATOR WITH MULTIPLE FLEXIBLE LINKS

This paper presents multi-mode vibration control and analysis of moving platform position errors of a planar 3-PRR parallel manipulator with three flexible intermediate links using PZT transducers. The active vibration controller is designed in modal space with modal filters and modal synthesizers determined from the flexible link vibration characteristics. Estimation of the moving platform position error is conducted using measurements of the flexible link deflection from PZT sensors mounted on the flexible intermediate links. An effective strategy for determining the control gains to reduce the vibrations of higher order modes is proposed through modification of the independent modal space control (IMSC) method. The proposed independent modal control strategy is experimentally implemented with first two modes targeted for control on a parallel manipulator with multiple flexible links. The experimental results show that the vibrations of the first two modes are effectively suppressed, and the position error of the moving platform is substantially reduced.

A Hybrid Damper Composed of Elastomer and Piezo Ceramic for Multi-Mode Vibration Control

This study develops a hybrid damper for multi-modal vibration by combining an elastomer and a piezo ceramic element. The basic idea is to obtain satisfactory damping in the low frequency range, where elastomer does not work well, by introducing a piezoelectric element. In this hybrid damper, the elastomer comprises a dynamic absorber with a metal plate of small mass that deals with higher-frequency vibration, while piezo ceramic comprises a shunt damper with an electric shunt circuit that works for lower-frequency vibration. The effectiveness of this approach is examined through vibration control of a cantilever beam. The aim is to suppress the 1st mode vibration with the shunt damper and the 2nd mode with the dynamic absorber. With appropriate tuning procedures for the control parameters, vibration suppression of more than 10dB is attained in each mode.

A current-flowing electromagnetic shunt damper for multi-mode vibration control ofcantilever beams

In this paper, a multi-mode electromagnetic shunt damper employing the current-flowingmethod is newly developed for the semi-active vibration control of flexible structures. Theelectromagnetic shunt damper, which is used for the electromagneto-mechanical couplingtransduction between vibrating structures and the electrical shunt circuit, consists of a coiland a permanent magnet. The conducting coil is attached to the cantilever beams and thetwo ends of the coil are connected to the current-flowing shunt circuit for the reductionof vibration. For the analytical and experimental validation of the multi-modeelectromagnetic shunt damper, the first two modes of the cantilever beam are semi-activelycontrolled. In light of the frequency responses, the vibration and damping characteristics ofthe flexible beams with the electromagnetic shunt damper are investigated withreference to changes in the circuit parameters. Also, the time responses of theintegrated systems with an initial condition are experimentally examined forvalidation of the proposed damper. The effect of the magnetic intensity on the shuntdamping is studied by varying the gap between the aluminum beam and thepermanent magnet. The theoretical prediction of the frequency response of theelectromagneto-mechanically coupled beams shows good agreement with the experimentalresults. The present results show that the current-flowing electromagnetic shunt dampercan be successfully applied to reduce the multi-mode vibration of flexible structures.

Multi-modal vibration control using a synchronized switch based on a displacementswitching threshold

A new semi-active method for multi-mode vibration control using the nonlinearsynchronized switch damping (SSD) approach based on a displacement switching thresholdis proposed in this paper. Several extensions of the SSD approach, including SSDI (SSD oninductance), SSDV (SSD on a voltage source), enhanced SSDV, and adaptive SSDV, havebeen developed to improve the control of the single-mode vibration, but the weaknessof the SSD approach for multi-modal vibration control has not been solved. Inall these extensions of the SSD approach, the switch is controlled by the samealgorithm, that is, it reverses the voltage of the piezoelectric element at all extrema ofdisplacement. This switching algorithm is effective in single-mode control, but it leads toover-frequent switching in multi-mode control. In the method proposed in thisstudy, an improved switching algorithm based on a displacement threshold, whichprevents the switch in the shunt circuit from over-frequent on-and-off actions andaccordingly increases the converted energy to improve the control performance, isproposed. The switching algorithm is applied to an SSDI system and used in thevibration damping of a beam with two excited modes. Compared to the classicalSSDI approach, the control performance of the first mode is improved from 3.7 to18.2 dB, but that of the second mode is slightly worse, having changed from 3.46 to2.6.

Multimode vibration control using several piezoelectric transducers shunted with a multiterminal network

In this paper a new approach is presented to reduce vibrations for one- and two-dimensional mechanical structures, as beam or thin plates, by means of several piezoelectric transducers shunted with a proper electric network system. The governing equations of the whole system are coupled to each other through the direct and converse piezoelectric effect. More in detail, the mechanical equations are expressed in accordance with the modal theory considering n vibration modes and the electrical equations reduce to the one-dimensional charge equation of electrostatics for each of n considered piezoelectric transducers. In this electromechanical system, a shunting electric device forms an electric subsystem working as multi degrees of freedom (dof’s) damped vibration absorber for the mechanical subsystem. Herein, it is introduced a proper transformation of the electric coordinates in order to approximate the governing equations for the whole shunted system with n uncoupled, single mode piezoelectric shunting systems that can be readily damped by the methods reported in literature. A further numerical optimisation problem on the spatial distribution of the piezoelectric elements allows to achieve a better performance. Numerical case studies of two relevant systems, a double clamped beam and a fully clamped plate, allow to take into account issues relative to the proposed approach. Laboratory experiments carried out in real time on a beam clamped at both ends consent to validate the proposed technique.

사장교 케이블의 감쇠성능 향상을 위한 댐퍼의 비선형성 연구

This study offers a design procedure of optimum cable damper for multi-mode vibration control with nonlinear damper and also investigates the relation between mode and amplitude dependency. The proposed multi-mode damping index, which is defined as a potential energy loss ratio of cable vibration, is a main component of optimization problem of optimum nonlinear damper. In order to include the amplitude dependency of nonlinear damper, three types of multi-mode patterns such as ambient vibration, support excitation and rain-wind induced vibration are assumed. The optimum damper exponent depends on amplitude patterns. In case of ambient vibration, optimum factor is less than 0.5 and in case of support excitation or rain-wind induced vibration it is between 0.5 and 1.0.

Experimental Demonstration of H∞ Control based Active Vibration Suppression in Composite Fin-tip of Aircraft using Optimally Placed Piezoelectric Patch Actuators

The goal of this study is the multi-mode structural vibration control in the composite fin-tip of an aircraft. Structural model of the composite fin-tip with surface bonded piezoelectric actuators is developed using the finite element method. The finite element model is updated experimentally to reflect the natural frequencies and mode shapes accurately. A model order reduction technique is employed for reducing the finite element structural matrices before developing the controller. Particle swarm based evolutionary optimization technique is used for optimal placement of piezoelectric patch actuators and accelerometer sensors to suppress vibration. H∞ based active vibration controllers are designed directly in the discrete domain and implemented using dSpace® (DS-1005) electronic signal processing boards. Significant vibration suppression in the multiple bending modes of interest is experimentally demonstrated for sinusoidal and band limited white noise forcing functions.

Multimode vibration control of a smart model frame structure

This paper investigates multimodal vibration control of a three-story model structuralframe by using surface bonded PZT (lead zirconate titanate) type piezoceramic patches.Piezoceramic is one of the smart materials. Complete control systems design is synthesizedon the model frame using system identification and a pole placement controller. A timedomain based subspace system identification is performed to identify the firstthree modes of the structural frame. A fit of 90% is achieved in identificationresults. A full-state pole placement feedback controller is designed based on theidentified model. To implement the full-state feedback controller, the design of a stateestimator is also performed. Experimental results demonstrate the effectiveness ofmultimodal active control of the smart frame structure using pole placement control.

Optimal design of viscous dampers for multi-mode vibration control of bridge cables

Viscous dampers have been widely used for mitigating rain–wind-induced vibration of bridge stay cables. Designing a damper with optimal damping in a specific mode may leave the cable susceptible to vibration in other modes, and it is almost impossible to specify a priori the dominant mode in which optimal performance should be achieved. In the present paper, a new method for optimal design of viscous dampers to achieve multi-mode cable vibration control is developed. With reference to a cable–damper model taking into account cable sag, inclination and bending stiffness, a method to determine the optimal damper size for cable vibration control in assigned multiple modes is proposed based on optimal LQG control theory. The system damping ratios obtained from the proposed strategy are thus found to satisfy the Irwin’s criterion for all the assigned modes. Case studies of prototype cables on a real cable-stayed bridge which experienced rain–wind-induced oscillation show the efficiency of the proposed method.

164 柔軟搬送システムの運動と振動の制御

164 柔軟搬送システムの運動と振動の制御

321 多モード連結制振を対象とした連結バネとダンパーの最適配置に関する研究(建築構造物の制御II)(OS 建築構造物の制御)

This paper proposes a new method to obtain the optimal values of connecting springs and dampers and those optimal locations for controlling multi-vibration modes in connected buildings. This method is based on the stationary point theory which is well known for designing tuned mass dampers optimally, and its rectification approach for modifying the optimal values of connecting springs and dampers, because vibration mode shapes are changed by connected springs. The effectiveness of the proposed method is demonstrated through a simulation example of the multi-mode vibration control of a pair of three-lumped-mass models.

Neural Network Discrimination in Intelligent Vibration Control

The overall goal of this study lies in the multi-mode structural vibration control for systems, based on spatial information. In order to accomplish this task, a neural network was designed to identify the shape of the dominant vibration mode by using properly located piezoelectric sensors. The network then chose a set of scaling gains for a fuzzy logic controller that had been optimally tuned for that particular mode’s shape. Next, a fuzzy logic controller was employed to control the vibratory system. The novel technique was experimentally verified on an aluminum cantilever beam system that was augmented with two lead zirconate titanate (PZT) actuators and two PZT sensors. The optimized control strategy was then compared to traditional fuzzy logic control. Finally the mass of the plant was increased by over a factor of 1.5 and the same controller was used to adequately stop vibration.