Adaptive robust precision motion control of linear motors with negligible electrical dynamics: Theory and experiments

Linear motors offer 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 difficulties in controlling such a system. This paper studies the high performance robust motion control of an epoxy core linear motor, which has negligible electrical dynamics due to the fast response of the electrical subsystem. A discontinuous projection based adaptive robust controller (ARC) is first constructed. The controller theoretically guarantees a prescribed transient performance and final tracking accuracy in general, while achieving asymptotic tracking in the presence of parametric uncertainties. A desired compensation ARC scheme is then presented, in which the regressor is calculated using reference trajectory information only. The resulting controller has several implementation advantages such as less on-line computation time, reduced effect of measurement noise, a separation of robust control design from parameter adaptation, and a faster adaptation rate. Both schemes are implemented and compared on an epoxy core linear motor. Extensive comparative experimental results are presented to illustrate the effectiveness and the achievable control performance of the two ARC designs.