Research On Control System Of 2-DOF High Precision Macro-Micro Positioning Station

With the continuous development of scanning probe microscope,microelectronic processing,micro-nano operation and other fields,scientific research and industrial production are increasingly demanding large-stroke and ultra-high-precision motion platforms.The 2-DOF macro-micro composite positioning system takes into account the advantages of the large stroke of the macro-motion system and the ultra-high precision of the micro-motion system,and can effectively solve the technical contradiction between ultra-high precision and large-stroke.The emphasis and difficulty of building a large-stroke high-precision positioning system is that the control requirements of the macro and micro motion subsystems are quite different,so a suitable composite control method is needed to coordinate the movement of the two parts.At the same time,the reaction force generated by the driver's output will cause the macro and micro parts to interact with each other and cause coupling problems.This will also affect the overall performance and accuracy.In this paper,a 2-DOF macro-micro composite positioning system is designed and built using the characteristics of piezoelectric ceramics with high accuracy and fast response,and a large linear motor travel speed.And control simulation research is conducted for the control strategies and the coupling problem in the macro-micro composite system.Firstly,a 2-DOF macro-moving platform was designed and built with vertical series structure which is simple and easy to maintain.The driver used an ironless permanent magnet synchronous linear motor.With the nonlinear controller,the positioning accuracy could reach the micron level with high movement speed.The control system of the macro platform was improved by using a two-dimensional encoder,which reduces the vertical error of the macro platform and improves the tracking accuracy.The micro-motion platform is the parallel micromotion platform designed by our laboratory.The driver of this micro-motion platform is piezoelectric ceramic,which can achieve nano-level accuracy,but also has the disadvantage of hysteresis and nonlinearity.Therefore,this paper uses single neuron PID control to improve the control performance of the micro-motion platform.Based on the establishment of the dynamic model of the macro-motion platform and the micro-motion platform separately,this paper establishes the control simulation model of the macro-micro composite platform in MATLAB.For more reliability of the simulation results,try to restore the true control structure,such as the introduction of pressure Hysteresis model of electric ceramics.By comparing several mainstream composite control structures,four improved control methods for this macro-micro composite platform are proposed,and different control methods are simulated in the Simulink application to obtain step response simulation results.By analyzing the error and dynamic performance,the most suitable control method of the macro-micro composite platform double-feedback micro-following-macro method.Introduce several multi-input multi-output(MIMO)control decoupling methods to solve the mechanical coupling problem between the two parts of the macro and micro,and use the auto disturbance rejection controller that does not depend on the coupling model to solve the macromicro coupling problem.Then the simulation results prove this methods can effectively improve the positioning accuracy.