Modelling and testing of a frictionless levitated micromotor

This paper describes a frictionless micromotor, in which an aluminium rotor is levitated, constrained laterally and rotated by electromagnetic induction. The initial application for this motor is in a novel rotating yaw-rate sensor. The stable levitation and torque are produced by the use of high-frequency magnetic fields generated by a multi-pole stator coil. The results of analytic and finite-element modelling of the static and dynamic characteristics of the motor are presented, and the factors which affect the stability of the levitation system and the maximum speed of rotation are examined in depth, along with suggestions for further improvements. During initial testing the motor achieved angular velocities in excess of 1000 rpm, with controlled levitation heights of 5-35 mu m. The motor has run for over 100 h without degradation, and because of the absence of friction excellent reliability is expected.