The Study Of Permanent Magnet Linear Synchronous Motor Sliding Mode Control

Linear servo motor drive system show its superiority performance in precision, exceed precision feed, high speed and ultra high speed move, because it doesn’t need any intermediate conversion and eliminates the impact of the mechanical transmission chain. However, the factors, such as load varieties and external disturbances, would directly influence the performance of the servo system without attenuation because of the direct transmission. End-effects, load disturbance and the parameter changes of the linear motor system would also reduce the system performance and machining precision of the machine tools, which increases the difficulty in the control. Therefore, sliding mode control strategies are adopted to overcome load disturbance and the parameter changes problem.Based on the analysis of the basic principle of operating and coordinate transformation of PMLSM, its model was established in d-q coordinates. In addition, the vector control technique of PMLSM was given.Based on the d-q coordinate model of PMLSM in rotor coordinates and the sliding mode control (SMC) theory, a speed sliding mode controller which uses integral and linear sliding surface was designed. The control system which has velocity and current double closed-loop decomposed structure was based on vector control method. The sliding mode controller was designed based on the exponent reaching law to weaken the intrinsic chattering problem of SMC on sliding surface. Indeed, the variable exponent reaching law control algorithm was proposed based on the exponent reaching law, which made the sliding gain and the speed error signal into a nonlinear relationship. The simulation results in Simulink show that this controller can improve the robustness of the control, and can effectively restrain the chattering of SMC, which cause by the higher sliding gain.Based on the analysis of terminal sliding mode (TSM) control theory, non-singular TSM was applied in PMLSM position servo controller. The advantage of this control method is that both the time to reach the sliding surface from any initial system state and the time to reach equilibrium point when in the sliding mode are finite. The proposed scheme can also guarantee global non-singularity and stability of system, eliminate high frequency chattering of control signals, and improve response speed and precision. The simulation results in Simulink show that the non-singular TSM control have the character of quick dynamic response, robustness, low chattering. VisSim/Embedded Control Developer can directly generate the source code and download to the target chip. This will greatly save development time and funding. Non-singular TSM controller is modeled based on VisSim. The reasonability and effectiveness have been testified by the simulation results in VisSim.