Force ripple compensation of the directly-driven linear motors via iterative tuning feed-forward controller

Abstract

Linear motors are promising in improving the manufacturing equipments’ performance because of eliminating the flexible coupling component. However, the force ripple produced by the linear motors directly causes the feed fluctuation and thus degrades the motion precision. This article utilizes a feed-forward controller added to the feedback one to compensate its effect for the sake of simplicity and robustness. Considering that the force ripple is periodic to the position, a position-dependent multi-order harmonic model is built and used as the feed-forward controller. In order to obtain the controller parameters for various applications, an iterative tuning method is proposed. This method has the advantage that both the high performance for different trajectories tracking and the robustness to disturbances are guaranteed. Experiments on a linear motor illustrate that the parameters converge rapidly. The results show that the tracking performance is improved greatly and the tracking errors are reduced by 60% at least.