Model-based flux control of an electropermanent magnet for adaptive zero power gravity compensation

Abstract

This paper presents a model-based flux control for a variable reluctance actuator with an electropermanent magnet, used for adaptive zero power gravity compensation in magnetic levitation systems. With the hysteresis of the electropermanent magnet being identified and approximated, tailored current pulses are applied by the model-based flux control to tune the magnetization of the electropermanent magnet. In this way, the resulting stationary reluctance force compensates the gravitational force of the levitated mover mass. Based on the identified hysteresis, a non-linear control law is derived, which is extended by an integrator term to compensate modelling uncertainties. In comparison to the state of the art model-free control, the model-based control increases the force tuning rate by a factor of 14 to 19 N/s and improves the robustness of the experimental system in variable mover positions.