The Research Of Segment Filtering Iterative Learning Control Method For Servo Systems

With the improvement of machining accuracy, people put forward high request for the control of servo system. The shape of the desired trajectory in actual servo system is often complicated, and the trajectory frequency distribution is dependent of time, exist the period of time concentrated with high frequency component. By introducing filters to ILC, the convergence range in frequency domain can be expanded, but at the expense of the tracking precision in high frequency region. Therefore, considering at the desired trajectory with high frequency component in the concentrated period, a segment filtering iterative learning control based on empirical mode decomposition(EMD) is proposed. Then, combined with contour error control method, cross coupling segment filtering iterative learning control is proposed. This thesis studies the content and results are as follows:Firstly, the iterative learning control methods and the contour error control methods are introduced, compared, analyzed and summarized.Secondly, the overall framework of the motor servo system based on EtherCAT is presented. And the mathematical model of three axis motor servo control system is studied.Thirdly, a kind of segment filtering ILC is proposed based on empirical mode decomposition method. The tracking error signal is decomposed into a finite number of intrinsic mode functions(IMFs). With the Hilbert transform, the IMFs yield the tracking error signal instantaneous frequencies as functions of time. On the basis of the ILC convergence condition and the time-frequency characteristics of the tracking error signal, the zero-phase filter is segmentally designed.Fourthly, combined cross coupling control and segment filtering iterative learning control, a cross coupling segment filtering iterative learning control is proposed for the three axis servo system. The effectiveness of the algorithm is verified by MATLAB simulation.Fifthly, according to the segment filtering ILC algorithm, the position controller, the iterative learning controller and the filter are programmed in CoDeSys. The experimental results show that the algorithm is very effective in practical application.Finally, the work of this thesis is summarized, and the research works also be prospected in the future.