MS Student Nina Ayar with Advisor K. Haran

The demand for small high-torque machines is steadily increasing due to the growing need for precise, low-cost motors capable of operating in tight spaces, especially in applications such as robotics, automation, and medical devices.  Permanent magnet vernier machines (PMVM) are a promising topology, delivering high torque at low speeds and having fairly small torque ripple.  This research focuses on the design and development of a small-scale PMVM that can deliver high torque and enable the precise spatial encoding in a portable MRI system.  Previous iterations of the MRI device utilized stepper motors to drive the magnetic arrays necessary for imaging. However, the large form factor of the stepper motors rendered the system bulky and difficult to maneuver, motivating this research direction. PMVMs achieve high torque at low speeds without additional mechanical components due to the vernier effect—a magnetic gearing phenomenon that enhances torque production by leveraging the interaction between the magnetic field harmonics in the air gap.  Finite element analysis of the proposed design shows a machine capable of meeting the system requirements, achieving an average torque of 2.0 Nm and dimensioned 50 x 50 x 80 mm3, sufficient to overcome the pull forces between the magnetic arrays.  This work is supported by the UIUC ECE Department and the Grainger Center for Electric Machinery and Electromechanics (CEME).

Figure 17. CAD Model of Optimized Design.

Figure 18. Torque Output of Optimized Design.