Characteristic Analysis And Control Method Of Three-degree-of-freedom Piezoelectric Drive Platform

The Piezoelectric-driven micro-positioning platform has the advantages of compact size,large output force and rapid response.It has great application prospects and is widely used in integrated circuits,medical devices,aerospace,precision machining and robotics.However,the piezoelectric ceramic material that constitutes the piezoelectric ceramic actuator itself has hysteresis nonlinearity.The performance of the piezoelectric-driven micro-positioning platform is seriously affected,the positioning accuracy of the platform is reduced,and even the whole system is unstable,which makes it limited in the field of ultra-precision positioning.Therefore,by correcting and compensating the hysteresis nonlinearity of the piezoelectricdriven micro-positioning platform to improve its motion positioning accuracy and make the platform have better dynamic characteristics,it has become one of the hot issues in modern precision positioning technology in recent years.In view of the above hysteresis nonlinear problems,the following contents are studied in this thesis :Firstly,the structural composition and working principle of the three-degree-of-freedom piezoelectric-driven micro-positioning platform were analyzed.The key driving element of the piezoelectric-driven micro-positioning platform is the piezoelectric ceramic actuator.Due to its own hysteresis nonlinear characteristics,the positioning accuracy of the micropositioning platform will be affected.Therefore,its structural characteristics were analyzed theoretically.Combined with the experimental test results,the nonlinear characteristics such as hysteresis and creep of the platform were deeply explored,which provided important theoretical support for further research on hysteresis modeling and control methods.Then,the motion characteristics of the three-degree-of-freedom piezoelectric-driven micro-positioning platform were analyzed.According to the Lagrange equation of motion,the dynamical model was established,and the PID control method was used to reduce the influence of hysteresis nonlinearity on the tracking control of piezoelectric-driven micropositioning platform.The simulation and experimental results show that the piezoelectricdriven micro-positioning platform can control its trajectory to a certain extent under the action of PID controller,but the tracking error is large.In order to further reduce the influence of hysteresis nonlinearity,the hysteresis model is regarded as the research target,and the established PI model has poor accuracy.Therefore,the dead-zone operator was introduced into the PI model,and the MPI model with non-singular symmetry was improved on the basis of the PI model.The parameters of the MPI model were obtained by the identification algorithm,and then the threshold vector and weight coefficient of the inverse model were calculated,and the MPI hysteresis inverse model was obtained.Compared with the PI model,the MPI model has higher accuracy,and the hysteresis loops in three directions can be effectively fitted.Finally,in order to further improve the positioning accuracy of the micro-positioning platform,the MPI hysteresis inverse model was used as the feedforward controller of the control system.Combined with PID control and fuzzy PID control,two composite control schemes were designed.Through simulation analysis,when sinusoidal signal and triangular signal are used as the trajectory tracking signal of the platform,the two composite control methods have smaller control error than PID,which proves the effectiveness of the two composite controllers.