Multi-axis Coordinated Motion Control Based On Sliding Mode Variable Structure Control Strategy Study

Coordinated multi-axis control is one of the most important technologies in the motion control system, and it has found a very wide application in semiconductors, high-speed/high-precision machining, optoelectronics industry, medical equipment and etc. With rapid advances in microprocessor technology and power electronics, coordinated multi-axis motion control has become increasingly more practical. More and more researchers pay attention to this field. This paper, based on analysis of traditional coordination strategy, designs a biaxial synchronization system, which coordinating sliding mode control to improve system performance.To large extent, multi-axis motion control system's performance lies in coordination control strategy. In multi-axis motion control system, the problems of various response delay and parameter mismatch exist between each axis, when multi-dimensional movement is controlled, the error is occurred by each actuator, for the dynamic influence of each axis, the contour error is occurred. And as a result, it depreciates the system performance. Traditionally, controllers were designed individually for each axis, which were used to minimize the multi dynamic effects among the multiple axes and to improve both tracking and contouring accuracy. And most of the cross-coupled controller use feedback control strategy, which based on the means of compensation to each axis. Cross-coupled control (CCC) has been developed to improve contouring performance for biaxial contour motion systems. However, it is complicated to apply the CCC to arbitrary contour motion, because additional calculations are required to obtain the variable cross-coupling gains. Thus in this paper, according to the analysis of multi-axis control strategy, each axis of the biaxial motion control system is controlled with the method of sliding-mode control(SMC), which aims at improving the robust and adaptation to the load disturbance. And with the application of variable gain cross-coupling control, the tracking and contouring errors are reduced simultaneously.To address the above issues, firstly, the general mathematical model of induction motor was presented, and then simplified by the means of field-oriented vector control. The strategy of cross-coupling control was discussed, based on which the error model of Cartesian coordinate system was established, accordingly the biaxial coordinate motion control system was designed. As AC servo system's characteristics of nonlinear, parameter changes, unmodelled states, strong disturbance, to ensure system's dynamic and static performance and to improve the robust and adaptation to the load disturbance, the cross-coupling control and the sliding mode control strategy are used in the multi-axis control system. In order to improve the system's adaptive capacity and stability and solve the phenomenon of chaptering, multi-axis controller was designed with dynamic sliding mode control and limitary sliding mode control strategy, simulation results certified their effectiveness.