Iterative Learning Control Of Three-axis Motion Platform Based On Real-time Contour Error Estimation

With the development of science and technology,the requirements for products are higher and higher.Therefore,ensuring high-precision contour machining is the trend of NC machine tools in the future.This thesis takes the three-axis motion platform driven by permanent magnet synchronous linear motor as the research object.In order to solve the influence of uncertain factors such as parameter variation,external interference and friction,the real-time contour error estimation model is designed and established,and the single axis position controller and contour controller are designed to ensure the tracking accuracy and contour machining accuracy of the three-axis motion platform.Firstly,this thesis introduces the structure and working principle of the three-axis motion platform driven by permanent magnet synchronous linear motor,analyzes various factors affecting the contour error of the system,and establishes the accurate mathematical model of the three-axis motion platform.Based on the analysis of the contour error of the three-axis motion platform,the three-axis linear contour error model is deduced and established.Then,in order to meet the requirements of strong robustness of the system and achieve high-precision tracking control of permanent magnet synchronous linear motor,a single axis adaptive inverse sliding mode position controller is designed by combining the characteristics of adaptive control and inverse sliding mode control.It can identify the disturbance in the system on-line,effectively improve the single axis position tracking accuracy and improve the robustness of the system.The stability of the control strategy is verified by function.The simulation results show that the adaptive backstepping sliding mode controller has strong robustness when the system is subject to nonlinear disturbance,and the chattering phenomenon is suppressed,which meets the requirements of single axis tracking accuracy of the system.Finally,in order to further improve the machining accuracy of the system,a realtime contour error estimation method based on the instantaneous curvature of the reference trajectory and a cross coupled iterative learning controller are designed.The contour error calculated by the real-time contour estimation model is distributed to each axis in proportion after the cross coupling iterative learning controller,so as to match the dynamic characteristics of each axis.The simulation model of real-time contour error estimation method and cross coupling iterative learning control is built in Matlab / Simulink.The simulation results show that the designed controller effectively improves the contour machining accuracy.