Optimal force control of a permanent magnet linear synchronous motor based on a magnetic equivalent circuit model

Abstract

This paper is concerned with the high dynamic and energy efficient operation of permanent magnet linear synchronous motors (PMLSM). In particular, a novel optimal force control strategy is developed and experimentally validated on a test bench. The proposed control concept is based on a detailed nonlinear magnetic equivalent circuit (MEC) model which, in contrast to classical dq-models, is able to systematically capture nonlinear magnetic saturation effects and non-harmonic motor quantities. The core of the control strategy is an optimization problem which calculates optimal currents and flux linkages such that the desired forces are accurately tracked and, at the same time, the ohmic losses in the coils are minimized. The control strategy comprises a flatness-based feedforward controller and a nonlinear PI-type feedback controller. Experimental results on a test bench confirm that the proposed control concept improves both the control accuracy and the energy efficiency and outperforms state-of-the-art field-oriented control concepts based on the dq-model.