Experiments in the Commutation and Motion Planning of a Spherical Stepper Motor

This paper addresses the commutation and motion planning of a spherical stepper motor in which the poles of the stator are electromagnets and the poles of the rotor (rotating ball) are permanent magnets. The stator only overlaps a very small area of the rotor, leading to a design that has a much wider range of unhindered motion than other spherical stepper motors in the literature. The problem with having a small stator is that it makes commutation and motion planning a difficult problem. We first explore the techniques and model used to construct the proper sequence of stator activations that result in the desired rotor trajectory. Experimental results are then presented for the model and prototype we have constructed.