Research On Micro-Vibration Simulator With Piezoelectric Actuators

The micro-vibration generated by the spacecraft during its orbital flight is extremely complex,seriously affecting the performance and the life of the high-precision instruments carried on the spacecraft.Before the launch of the spacecraft,the ground vibration test of the instruments is critical.In order to simulate the complex micro-vibration environment accurately,a piezoelectric-driven micro-vibration simulator is studied in this paper.This dissertation focuses on the optimal design of the configuration,the hysteresis modeling of the piezoelectric actuator and the acceleration hysteresis compensation.The simulation and the experiments of the six-DOF micro-vibration simulation platform is carried out as well.The specific research content is as follows:The dynamic isotropic optimization design of a six-degree-of-freedom micro-vibration simulator,which is based on the Stewart platform is studied.According to the Kane method,it is deduced that the Stewart platform has the analytic condition of dynamic complete isotropy,when the lower platform is fixed.It is pointed out that the Stewart platform with circular symmetric plane cannot have dynamic complete isotropy.The projection gradient descent method is used to optimize the configuration,which not only obtains more isotropic configuration parameters,but also greatly reduced the optimization time.The rate-dependent hysteresis modeling of piezoelectric actuators is studied.Compared with the Bouc-Wen hysteresis model,the accuracy of SVM hysteresis model based on NARMAX is improved significantly.A feed-forward plus feedback composite controller based on inverse hysteresis model is designed.The maximum relative error of displacement tracking experiment is 2.5%.Compared with feedback control,the tracking accuracy is improved by at least 45%.The acceleration hysteresis compensation control of the single-axis micro-vibration simulator is studied.Considering the time complexity of SVM,this paper proposes an acceleration hysteresis model based on MFNN,which greatly reduced the time required for training.The maximum relative error of the model on the test set is 0.48%.In addition,the complex signal prediction experiment shows the great generality of the model.Based on the inverse MFNN model of acceleration hysteresis,a feed-forward controller is designed,which significantly reduces the non-linear characteristics of the system.The acceleration compensation experiments show that the designed feed-forward controller can significantly improve the tracking accuracy,and the maximum relative error is less than 2.5%.The Z-direction linear acceleration tracking performance of the six-DOF micro-vibration simulator is studied.A virtual prototype model is established in ADAMS.By comparing the output force of each leg and the acceleration of the upper platform with the same displacement input,it is verified that the theoretical model of the micro-vibration simulator has great accuracy.A sliding mode controller based on computational moment method is proposed to control the six-DOF micro-vibration simulator.The simulation and experiments is carried out respectively with the sinusoidal signal and the tracking signal with variable frequency and amplitude,which verify the effectiveness of the controller.Finally,the concluding remarks and further research directions are provided.