Direct Thrust Force Control Based On Integral Sliding Mode For Permanent Magnet Linear Synchronous Motor

Permanent magnet linear synchronous motor(PMLSM)has been widely used in industrial production owing to the advantages of large thrust,fast response and high precision.PMLSM is susceptible to uncertainties such as parameter variation,unmodeled dynamics and friction,at the same time,direct thrust force control system can produces large thrust ripple.Therefore,the integral sliding mode controller and the dual boundary layer sliding mode observer were designed to improve the robustness and tracking of the direct thrust control system and reduce the thrust ripple.Firstly,the basic structure and working principle of PMLSM were introduced.The causes of uncertainties in PMLSM and the impact on system control precision were analyzed.The dynamic mathematical models of PMLSM with uncertainties was established,and the basic principle and coordinate transformations of PMLSM direct thrust control system were expounded,which laid the foundation for the design of integral sliding mode controller and dual boundary layer sliding mode observerThen,a direct thrust force control scheme based on integral sliding mode for PMLSM servo system was proposed for the problems of ripple in the thrust force,steady state error and other issues.Considering speed and thrust force as the state variables,a second order nonlinear state space model was established in a synchronously rotating stator flux vector reference system.According to the space state,an integral sliding mode control law was established to replace the independent speed controller and thrust force controller.This simplified the control structure of the system and improved dynamic response of the system.The saturated function was selected as the switching function to reduce the chattering of sliding mode control and eliminated the steady state error in speed tracking,improving the robustness of the system.Lyapunov stability analysis to prove the stability of the controller was provided.The effectiveness and feasibility of the proposed scheme is verified by system simulations.Finally,in order to solve the problem that the integral sliding mode controller was susceptible to high frequency noise when acquiring the second derivative of speed,a dual boundary layer sliding mode observer was designed to estimate the speed.The observer can adaptively adjust the range of motion of the observer,so that the estimation error and the boundary layer thickness change synchronously.The observer robustness was enhanced.The system simulation results demonstrate the feasibility of the dual boundary layer sliding mode observer.