Adaptive robust control of linear motors for precision manufacturing

Abstract

Linear motors are sensitive to disturbances and parameter variations. Certain types of linear motors such as the iron core are also subject to nonlinear effects due to periodic cogging force and force ripple. An adaptive robust controller based on the discontinuous projection method is constructed to address these issues. In particular, based on the particular 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 effect of various parametric uncertainties such as unknown weights, inertia, and motor parameters while certain robust control laws are used to handle the uncompensated uncertain nonlinearities effectively for high performance. Simulation results are shown to illustrate the effectiveness of the proposed algorithm.