Research On Active Vibration Isolation Control Method Of Two-degree-of-freedom Piezoelectric Driving Platform

With the rapid development of science and technology and industrial technology,many industries have higher and higher requirements on the bearing capacity,working accuracy,operation stability and other aspects of mechanical devices,and the vibration isolation control of mechanical equipment has become increasingly urgent and important.Especially in many application fields such as aerospace applications,astronomical observation and military operations,the demand for stable platforms with extremely high vibration isolation capability is increasing.In order to improve the quality of high-resolution images and the accuracy of attitude control,how to eliminate the influence of micro vibration on satellites in orbit has become one of the important directions in the future development of aerospace.Passive vibration isolation has a simple structure and does not need to provide additional energy,but it cannot isolate low frequency vibration and eliminate the influence of resonance peak.However,in aerospace vehicles,micro vibration below 100 Hz is common and usually fatal.In order to eliminate the micro vibration below 100 Hz in aerospace vehicles,active vibration isolation control(AVC)has started to develop rapidly.In this paper,the nonlinear dynamics and control algorithm of the active vibration isolation system of a two degree of freedom piezoelectric driven platform are studied to meet the needs of spacecraft micro vibration isolation.The two degree of freedom piezoelectric drive platform is selected as the actuator of the active vibration isolation system.The control strategy of the active vibration isolation,the hysteresis nonlinear modeling of the piezoelectric actuator and the compensation control are studied,and the two degree of freedom active vibration isolation experimental platform is built for experimental verification.The main research work is as follows:(1)Piezoelectric actuator is selected as the actuator of the active vibration isolation system with two degrees of freedom,and the input and output of the piezoelectric actuator are hysteretic rate dependent,which will bring large errors.Therefore,the rate dependent hysteresis model should be adopted to describe the hysteresis loop at different frequencies.Because the traditional Bouc-Wen model cannot describe the asymmetry and rate dependent hysteresis characteristics of the actual actuator hysteresis loop,and the parameters are redundant.The traditional Hammerstein model,which is composed of Bouc-Wen model and second-order transfer function model or ARX model in series,is also inaccurate.Therefore,this paper proposes a new Hammerstein model consisting of the improved Bouc-Wen model and fractional transfer function model.In order to accelerate the convergence speed,avoid falling into local solution,and solve the problem of difficult identification of fractional transfer function model,an artificial bee colony algorithm(Dec-ABC)combining differential evolution strategy and chaos search strategy is proposed to identify model parameters.Compared with the traditional differential evolution algorithm or the traditional artificial bee colony algorithm,this algorithm has faster convergence speed and higher identification accuracy.(2)The feedforward control based on Bouc-Wen hysteresis inverse model is discussed.Because of the rate dependent hysteresis characteristics of piezoelectric actuator,the control accuracy does not meet the expected requirements.In order to make up for the deficiency of feedforward control,a new fractional order neural network sliding mode control method is proposed based on the Hammerstein model,which is composed of Bouc-Wen inverse model and fractional order transfer function model,by combining fractional order theory,neural network and sliding mode control.The simulation results show that the control method greatly improves the tracking accuracy and eliminates the hysteresis nonlinearity.Compared with the fractional order sliding mode control method based on extended state observer,the fractional order sliding mode control method based on single parameter adaptive law and the proportional integral sliding mode control method based on feedforward compensation,this method has faster response time and smaller tracking error.(3)Because the active vibration isolation control of piezoelectric actuator with two degrees of freedom is carried out,the piezoelectric actuator on X axis and Y axis has coupling effect.So,it is necessary to design decoupling controller.The decoupling controller is designed to reduce the negative impact of the coupling effect between piezoelectric actuators on the output accuracy of the system.The decoupling control experiment verifies the effectiveness of the two directional controllers.The vibration isolation controllers of X axis and Y axis are designed respectively under the action of feedforward,decoupling and feedback to precisely control the vibration isolation system of two degree of freedom piezoelectric actuator.The experimental research is carried out on the two degree of freedom active vibration isolation platform.The experimental results show that the micro vibration isolation effect of the two degree of freedom active vibration isolation system designed in this paper is good.