Adaptive Robust Precision Motion Control of Linear Motors with Ripple Force Compensations

Linear motors o er several advantages over their rotary counterparts in many applications requiring linear motion by eliminating mechanical transmission mechanisms. However, these advantages are obtained at the expense of added diÆculties in controlling such a system. This paper studies the high performance robust motion control of an iron core linear motor which is subject to signi cant nonlinear force ripples. A discontinuous projection based desired compensation adaptive robust controller (ARC) is constructed. In particular, based on the special structures of various periodic nonlinear forces, design models consisting of known basis functions with unknown weights are used to approximate those unknown nonlinear forces. On-line parameter adaptation is then utilized to reduce the e ect of various parametric uncertainties while certain robust control laws are used to handle the uncompensated uncertain nonlinearities. The resulting controller achieves a guaranteed transient performance and a guaranteed nal tracking accuracy in the presence of both parametric uncertainties and uncertain nonlinearities. In addition, in the presence of parametric uncertainties, the controller achieves asymptotic output tracking. Extensive comparative experimental results are obtained for the motion control of an iron core linear motor and verify the high performance of the proposed scheme. The work is supported in part by the National Science Foundation under the CAREER grant CMS-9734345 and in part by a grant from Purdue Research Foundation