Motion Control Of CNC Machine Tool Feed Servo System Based On Iterative Learning And Cross-coupling

With the rapid development of manufacturing industry the requirements for the machining accuracy of CNC machine tools has become higher.However,in the machining process,the dynamic response of each axis of the feed servo system is inconsistent,which will lead to the reduction of machining accuracy.So,aiming to address this problem,the motion control of CNC machine tool feed servo system is studied in this paper.As well as a control method combining iterative learning control with cross-coupling structure is proposed to improve the tracking accuracy of the single axis of the feed servo system,by using the iterative learning control method for the single axis of the feed servo system,and then the cross-coupling control structure is used for the multi-axis linkage of the feed servo system to suppress the contour error caused by the multi-axis linkage.Firstly,the structure of the feed servo system of NC machine tool is analyzed,and its mechanical transmission part and control part are modeled respectively.on this basis,according to the parameters of the experimental platform,the specific expression of transfer function of single axis feed servo system is obtained.Furthermore,the stability of the transfer function is analyzed based on MATLAB,and the transfer function zeropole distribution map show that the feed servo system is stable.Finally,the closed-loop transfer function of the single-axis feed servo system is obtained,which can be used to carry out the following research of single-axis tracking error control and multi-axis linkage contour error control.The iterative learning control algorithm is applied,and the iterative learning control strategy is adopted in the position loop of the single-axis feed servo,so as to overcome the shortcomings of the traditional PID control that the repetition of the trajectory is not considered and the repetitive error data is not fully utilized.Firstly,the theories of PID control and iterative learning control are introduced respectively.Then,aiming at the single-axis feed servo system,the simulation models of PID control and iterative learning control are built respectively in the MATLAB/Simulink,and with comparing of the two output trajectories by tracking the same triangle wave trajectory at the same time,the control effect of iterative learning control is verified.The cross-coupling structure is used in the two-axis motion control,and the advantages of iterative learning control and cross-coupling structure are combined.So a cross-coupling iterative learning control strategy is proposed to improve the control performance of two-axis motion control of NC machine tool feed servo system.With the aid of this method,the problem that only by reducing the single-axis tracking error is difficult to reduce the contour error in the motion control of multi-axis system,is addressed effectively.Aiming to verify the effectiveness of the control strategy,the XY numerical control experimental platform is built based on the previous theoretical analysis,and the tracking experiments are carried out to verify the circular trajectory and the engine cylinder block profile trajectory respectively furtherly.Moreover,the analysis and evaluation of the experimental data show that the control effect of the control strategy used in this paper is better than other traditional control methods.