Research On Active Vibration Isolation With Piezoelectric Actuators

With the application and development of high-precision spacecrafts,in order to improve the quality of high-resolution images and the accuracy of attitude control,how to eliminate the effects of micro vibration when the stellite working on orbit has become one of the important directions for the future development of aerospace industry.The passive vibration isolation is of simple structure,no more extra energy,but it cannot isolate low frequency vibration and eliminate the influence of the resonant peak.Therefore,the paper adopts active vibration isolation technology pointed at the micro vibration,selecting piezoelectric ceramic material as the actuator,studying the control strategy of the active vibration isolation,the modeling and compensation control of nonlinear hysteresis for piezoelectric actuator,and building the single axis active vibration platform for experimental verification.The main research work is as follows.In view of the high precision adjustment of the sensitive load such as the telescope,the attitude control torque at the low frequency must be transmitted and micro vibration disturbance at the high frequency need be isolated.The two kinds of standards for vibration isolation caused by different locations of the isolator in the space system are analyzed in detail firstly.The evaluation standard of force transfer which contributes to the high precision adjustment is used as the evaluation index of the effect for vibration isolation by means of the establishment of mathematical models and theoretical studies.Selecting interaction force between the objects as feedback for active vibration isolation by means of the research on the effect of vibration isolation for the system by different feedbacks.The PID control and model reference adaptive control are used as the simulation study.The results show that PID has less ability to suppress white noise,while adaptive control has better isolation performance and robustness for white noise.Combination of adaptive control and PID can improve the isolation performance of adaptive control at high frequency,which can not only achieve better performance for vibration isolation at low frequency,but can also maintain attenuation at high frequency.Then the linear two order model and nonlinear hysteresis are adopted to describe the hysteresis loop at different frequencies in view of the rate dependent characteristics of the piezoelectric actuator.Since the traditional Bouc-Wen cannot describe the asymmetrical property of the hysteresis loop for the actual piezoelectric actuator,and the parameters in the model are redundant,the normalized Bouc-Wen mathematical model is derived from the traditional Bouc-Wen,and the polynomial is introduced to describe the asymmetric hysteresis behavior.In order to speed up the convergence and avoid falling into the local solutions,the self-adaptive differential evolution algorithm is developed for the parameter identification of the nonlinear hysteresis part.An experiment for the parameter identification of piezoelectric ceramic actuator is set up.The experimental results show that the proposed model can well represent the hysteresis characteristics under different frequencies,and eliminate the redundancy of the parameters.Compared with particle swarm algorithm and traditional differential evolution algorithm,adaptive differential evolution algorithm can be faster and more accurate to find the optimal solution.Next the compensation control of nonlinear hysteresis is carried on respectively based on inverse hysteresis model and unknown hysteresis nonlinearity.The feedforward control based on the inverse Bouc-Wen model is discussed,which results in the low control precision because of the observer error.Thus,introducing PID control to improve the tracking accuracy and eliminate the hysteresis nonlinearity.The simulation results show the hysteresis nonlinearity of the composite control that consists of feedforward control and PID control reduces 90% compared to feedforward control.Then the linear auto disturbance rejection controller with unknown hysteresis nonlinearity is designed,which can estimate the disturbance of hysteresis by the linear extended state observer.The simulation results show that LADRC has high performance of tracking the target trajectory and impact interference and improves the robustness of the system.Therefore,it can be seen the controllers designed are effective.The last one is the research on the experiment for the single axis active vibration isolation platform.The structural design and control algorithm of the single axis is the basis of the multi axis active vibration isolation.The suspension mode is used to counteract gravity and simulate the outer space environment.A corresponding experimental control system is set up.The experimental research on PID control and MRAC is carried out.The effect of PID control is poor.MRAC eliminates the resonance peak at the broadband range of 40~300Hz for vibration isolation,and the effect of micro vibration at high frequency isolation is better.