Magnetic Gears for Aerospace Applications
Aaron Anderson with adviser K. Haran
Aaron worked as an intern at NASA Glenn Research Center in Cleveland, Ohio, during Summer 2018, on two related projects. The first was development of a rotating drives test rig intended to test magnetic gears and motors. This test rig was already partially planned and built. His contribution was installing test rig sensors and controls. He also developed a test plan for magnetic gear prototype characterization focusing on efficiency, vibration, and temperatures over the full range of speed and torque conditions. He updated a CAD model of a prototype magnetic gear to allow for improved instrumentation and testing on the test rig and assembled the updated prototype.
The second project was conducting a concentric magnetic gear literature review. He collected detailed information about each tested prototype magnetic gear available in the literature and reported important design trends and the current state of the art. The report will help NASA engineers continue developing magnetic gears for aerospace applications.
Magnetic gears provide functionality nearly identical to mechanical gears but using very different physics. Both traditional and magnetic gears transmit torque between components moving at different speeds. Traditional gears transmit the torque through mechanical contact between teeth, while magnetic gears use magnetic coupling, as in electric motors. Aaron found his U of I experience working in electric motors to be useful for the NASA team, since most of the group had worked primarily on mechanical gears and other mechanical systems, not magnetic systems. It was especially helpful to identify similarities between magnetic gears and motors during the literature review.
Concentric magnetic gears, as shown in Figure 14, use three concentric components for magnetic coupling to transmit torque. The inner component features a permanent magnet array distributed around the circumference. The outer one also features a permanent magnet array, but with a different number of poles. Between these two magnet arrays, there is a component with ferromagnetic pieces, whose number is chosen such that it modulates the fields from the inner and outer magnet arrays allowing them to couple. This magnetic coupling transmits torque at a ratio determined by the pole numbers on the two components. Similarly, permanent magnet electric motors use magnetic coupling between a set of permanent magnets and a set of electromagnets to generate torque.