Design, Simulation, and Fabrication of a Harmonic Drive Stepper Motor for Precise Rotation Application

In this article, for the first time, a novel stepper motor predicated on harmonic drive principles is introduced. The input rotation is generated by switching of electromagnetic attraction. This design has led to a low rotational speed without the deployment of gearbox, allowing for very accurate rotational positioning due to its small steps. In this motor, the rigid rotor is attracted to the stator in one point and rolls on the stator's inner surface by sequentially activating the stator poles. The rotor axis lag per revolution is equivalent to the difference between the stator's inner perimeter and the rotor's outer perimeter in a complete round of pole activation (transitional rotation). Due to this lagging, the rotor rotates at low rotational velocities. The rotational velocity and the rotation angle for each step decrease with a closer gap between the rotor and stator. The motor is designed for a positional rotation of 6.13° per transitional rotation. It becomes 6.35° in simulation and 6.25° in experiments. The maximum velocity of the motor is 500 rpm. The maximum accessible torque is 14.1 Nmm. Due to its adjustable resolution, accuracy, and simple driving system, the proposed motor could be used in precise positioning applications.