Thrust Force Control of Permanent Magnet Linear Synchronous Motor Based on Sliding Mode Variable Structure

Direct torque control of the rotating motor is extended to apply the thrust force control of permanent magnet linear synchronous motor in the paper. As we know the traditional direct torque control causes torque and magnetic flux linkage ripple and poor lower speed performances. It is also truth for linear motor. In addition exact mathematics model of linear motor is difficulty to build because of its special physical geometry with open ends. And the control of linear motor is more complex and difficulty comparing with other ones. Sliding mode variable structure strategy is an effective method for nonlinear control systems and has features of insensitivity to disturbances and parameters variation. Analysis results have shown that the system control performances based on sliding mode variable structure have been improved obviously. The thrust force ripple is reduced from 20% to 2.08%. The magnetic flux linkage ripple is reduced from 2.5% to 0.17%.