Study Of Compensation Method For Dual Linear Motors Numerical Control Tables Precision Contour Tracking Control

This paper aims to slove the problem of nonlinear friction, system parameter perturbation, uncertainties and the parameter mismatch between two axes which affects the contour accuracy of XY table servo system directly driven by two Permanent Magnet Linear Synchronous Motors. A compound control scheme combining integral sliding model and sliding model state observer with the cross coupling controller was adapted to control XY table; the control strategy combining the global fast Terminal sliding mode position control and H $velocity feedback control with Tangential-Contouring control was adopted to improve the contour control precision of XY table and realize precision contour tracking control.Firstly, this paper was on the basis of extensive reading and deep analysis home and abroad research literature about dual linear motors direct driven XY table, the work principles of PMLSM was described, the mathematical models of PMLSM and direct driven XY table were established and analyzed. According to the work characteristics of XY table system, analyzing the course of its operation would inevitably produce contour error, so the contour error was defined, the factors that affect the contour precision were described, and the common contour error model of XY table was established. For the high speed and high precision CNC table, how to eliminate the system contour error and improve the contour tracking control precision of the system, achieving the direct drive XY table coordinate control. Therefore, it is necessary to design servo controllers to achieve the precision contour tracking control of XY table.Secondly, the control strategy combining integral sliding mode controller with sliding mode state observer was adapted in the single axis, and mainly compensating the effect of friction that act on the XY table, obtaining a smaller postion error. The cross-coupling controller acting between the two axes, in order to eliminate the effect of the gain parameters and dynamic parameters mismatch and further reduce the contour error. Simulation results show that the proposed control method can reduce the effect to XY table performance and achieve high accuracy contour control in the presence of friction.Finally, the control strategy combining the global fast Terminal sliding mode position control and H $velocity feedback control with Tangential-Contouring control was adapted to design direct drive XY table system. This control method can effectively solve the load disturbances, system parameter perturbation, the system uncertainty and the parameter mismatch between two axes, and in finite time can rapidly make the states of the system converge to the equilibrium point in finite time, and achieve decoupling control between two axes, algorithm was simple and easy to implement, thus enhance the response speed of the table and contour control accuracy.In this paper, dual linear motors directly driven XY table was selected as the controlled object for deep study. It is easy to simulate and analyze the above control strategies under the application of MATLAB software. The simulation results show that compared with dual linear motors driven XY table contour tracking control based on the friction compensation, robust tracking control can be better to solve the problem of nonlinear friction, system parameter perturbed, uncertainties and the parameter mismatch between two axes, and achieve XY table fast tracking control, enhance the robustness and contour control precision of XY table servo system.