Research On Precision Contour Control Method Of Three Axis Motion Table

With the development of the modern industrial technology,the complexity and precision of CNC machining components are continuously improved.Therefore,ensuring the control precision of multi-axis CNC machine tool is necessary development trend of industrial processing in the current.In this thesis, the servo control system of three axis motion platform driven by permanent magnet linear synchronous motor is used as the research object,which is influenced by the nonlinear, strong coupling, dynamic uncertainty, and the interference of environmental factors.To solve the problem,a simplified three axis contour error estimation model is established.The controller is designed from two aspects of single axis position and the overall contour, so the contour accuracy and anti-disturbance capability of the servo drive system of three axis motion tables are ensured.This theoretical foundation which the research of multi-axis servo drive control system are established.Firstly,The two axis and multi axis direct drive motion platform of the domestic and foreign contour control technology development status are described in this thesis.The structure and working principle of permanent magnet linear synchronous motor and mathematical model of three axis motion platform are introduced.A contour error model of three axis motion table is established by using the method of contour error estimation.Compared with the traditional contour error estimation model, the proposed method can effectively reduce the computational complexity of the system,which can be applied to any nonlinear curve.The contour error is compensated by using the vector synthesis method,in order to ensure the accuracy of the contour.Secondly,in order to solve the influence of three axis motion platform load disturbance and parameter mismatch problem etc.The tracking control method of position and speed double closed loop is used in the single axis.Proportional control is used as position loop controller and PDFF control is used as speed loop controller.This method can make up for the deficiencies of PI and IP control, improving the system’s rapidity and reducing the tracking error.The contour controller is designed by using the improved cross coupling control scheme,and the compensation of the contour error is placed in front of the position controller.The improved method is used to ensure that the size and direction of the contour error’scompensation can be the most appropriate matching,improving the processing accuracy of the system.By using Matlab/Simulink show the scheme of the designed controller can guarantee the tracking and contour accuracy of the system.Finally,on the basis of the designed single-axis controller,the model reference adaptive intelligent control method is added to the model,in order to further improve the system’s tracking and contour accuracy.The method can effectively eliminate the error caused by the changes of external factors and system characteristics,which adjusts the parameters of the controller in real time,having good tracking performance.The improved cross coupling controller is still used to coordinate control among three axes,which solves the periodic contour errors.By using Matlab/Simulink to analysis,the simulation result are compared the added with the not added MRAC system.The added system’s tracking error and the overall contour error of the system are improved by an order of magnitude,proving the added MRAC system has better control effect.