Position Control for Hysteresis Motors: A Field-oriented Control Approach

This paper studies modeling and field-oriented control for hysteresis motors, targeting at improving the torque control bandwidth for the hysteresis motors and thus enabling them for position servo applications. The hysteresis motor class includes a wide range of motors with solid steel rotors, which generate torque via the magnetic hysteresis effect of the rotor material. Previously, hysteresis motors have been mainly used under open-loop synchronous/asynchronous operation. However, they are also attractive in servo application in some special environments such as in vacuum and high temperature scenarios. In this paper, we study modeling and control of hysteresis motors, and explore the position control of these motors. An equivalent circuit model for hysteresis motors that describes the motor's transient dynamics is introduced, and a state space model is being derived. This model is being used to construct a rotor flux observer for field-oriented control. Two hysteresis motors, with Cobalt alloy rotor and D2 tool steel rotor, respectively, were tested. Experimental results show that the position control loop for both hysteresis motors can reach 60 Hz cross-over frequency bandwidth. To the authors' best knowledge, this is the first experimental study for field-oriented control for hysteresis motors.