Contour Control For Direct Drive XY Table Based On Global Fast Terminal Sliding Mode Control

For the problem of nonlinearity and uncertainty of direct drive XY table by PMLSM ind complex contour error model, repetitive control and two-order sliding mode control were adopted to design the position servo system of PMLSM; The global fast Terminal sliding mode control was adopted to design the contour controller of direct drive XY table, n order to improve the contour precision.Firstly, mathematical models of PMLSM and XY table were established and their work principles were introduced. According to the characteristics of direct drive XY table driven by PMLSM, the causes that affect the contour precision were described. Meanwhile, ndirect control method and direct control method of XY table were introduced, on the basis of extensive reading and deep analysis home and abroad research information about XY table. Indirect control method improves the contour precision by improving tracking (?)recision of single axis. But it can not solve the dynamic incompatibility of double axes. However, for direct control method, its control objective is the contour error, which mproves the contour precision by provide additional control variables to X axis and Y axis. This method can solve the dynamic incompatibility problem and improved effectively the contour precision.Secondly, considering the periodic thrust fluctuation caused by end effect, to improve he tracking precision, repetitive control combined with two-order sliding model control was adopted to design position servo system. Two-order sliding mode control was adopted o design the speed controller, in order to restrain suddenly increasing load. The control aw of sliding mode used super-twisting algorithm, which was simple and easy to mplement. Meanwhile it can decrease chattering phenomenon effectively. Repetitive control and PD control were integrated to design the position controller, in order to restrain he periodic thrust fluctuation. The simulation results show that the integrated control strategy has high precision and strong robustness. And it can effectively eliminate the periodic thrust fluctuations caused by the end effect.Finally, nonlinear equivalent error model of XY table, which is easily calculated, was built using equivalent error method. And direct drive XY table contour controller was designed by global fast terminal sliding mode method. This control method can effectively solve problems of complex contour error mode, dynamic incompatibility of double axis and the uncertainty of the system. The global fast Terminal sliding mode control can make the states of the system converge to the equilibrium point in finite time, improving the response speed of contour controller and contour precision. Direct drive XY table of Yokogawa LM110 was selected as the controlled object. And MATLAB was adopted to simulate the designed system. The simulation results show that the proposed method based on global fast terminal sliding control can improve the contour precision and the robustness of the system by controlling the contour error directly.