A simple force ripple compensation method for linear motor servo system

Force ripple in Permanent Magnet Synchronous Linear Motor (PMLSM) is an important factor which prevents it from acquiring high positioning accuracy. In this paper, the main aspects of the force ripple in linear motor are analyzed, which include detent force, ripple force and friction. As force ripple is a function of the mover position with respect to the stator, and the position has direct relation with the electrical angle, a simple method to establish its look-up-table which using the electrical angel as the index is proposed and then it is compensated based on the table. Finally, experimental results in velocity loop which using PID and sliding mode controller are presented to verify the feasibility of the approach, and the conclusion that force ripple compensation is an effective way to improve the performance of the linear motor servo system is drawn.