Decoupled control of thrust and normal force in a double-layer single-sided linear induction motor
In this paper, a modified force decoupling method for improved servo control of a magnetically suspended double-layer single-sided linear induction motor (LIM) is presented. In this study, the primary is magnetically suspended under and moved along the double-layer secondary which consists of an aluminum plate with a back-iron. In order to decoupled the normal and thrust force, analytical expressions for the forces as function of the slip frequency and the primary current are obtained by curve fitting on steady-state FEM results. From these steady-state force models, the required current amplitude and slip frequency are solved for given force setpoints. The setpoints are generated by a position controller which is designed based on a dynamical model of the LIM. The dynamical model is estimated by injecting noise into a transient FE-model and measurements. Transient FEM simulations and measurements show the effectiveness of the proposed controller and decoupling method when they are used to magnetically suspend and position the LIM. (C) 2012 Elsevier Ltd. All rights reserved.
linear induction motor force decoupling position control magnetic levitation