Development of control algorithm to reduce force ripple for high speed Permanent Magnet Linear Motor( PMLM)

A permanent magnet linear motor (PMLM) is usually used in high precision motion. However, the force ripple affects the accuracy of the PMLM, and deteriorates the tracking performance. To achieve more precision motion, it is necessary to remove the force ripple in the PMLM. The force ripple can be divided to current dependent term and independent term by experiment. We first demonstrate to find a model of the force ripple expressed by Fourier series that is used to compensate the force ripple by feedforward controller. The proposed control scheme named hybrid controller is composed of the feedforward controller and the RLSE (recursive least square estimation) adaptive controller. The feedforward controller compensates the current independent components among the force ripple and the RLSE adaptive controller compensates the current dependent components of the force ripple. The performance of hybrid controller is verified by simulation and experiment.