Modeling and robust output feedback tracking control of a single-phase rotary motor with cylindrical Halbach array

The single-phase electromagnetic motor with a circular Halbach array design offers the advantage of generating a large torque. However, to the authors´ best knowledge, no existing literature has presented the tracking control of this motor. This is probably due to its DC gain and time constants that are rotary-position-varying. This paper first models a typical two-pole single phase rotary motor based on a Halbach circular array with considerations of its back-EMF, frictional torques and position dependent characteristics. Next, a dual-relay configuration is applied in a closed-loop to identify the model parameters through limit cycle experiments. Next, a composite controller that composes of a model-based controller, a time-delay compensator and a sliding mode controller, was proposed with the capability to achieve the high-speed tracking of a reference trajectory in the presence of model uncertainty and external disturbances. A non-linear high gain observer was designed to estimate unknown states to allow output feedback realization. An experiment was conducted to ascertain the performance of the proposed composite controller and to benchmark it to a PID controller with a model-based feedforward element. The proposed controller presents a noticeable improvement and offers a clearly viable alternative to the PID controller for this particular application.