A PROPOSAL FOR ELECTRICALLY LEVITATING MICROMOTORS

Micromachined actuators and motors, occupying an area less than 1 mm2, have great potential in diverse applications. At present, however, the ability of these micromotors to reach their full potential is hampered by the presence of large friction forces that play a dominant role in the dynamic behavior. A novel design for substantially reducing or eliminating this friction by levitating the rotating disc of a variable-capacitance electric micromotor is proposed here. This design utilizes a resonant circuit driven by a radio-frequency a.c. voltage source to achieve stable levitation. The advantages of the proposed method include stable levitation without requiring a feedback signal and its ability to produce torque and motion using identical components of a micromotor. This paper analyzes the stability conditions necessary for the levitation circuit to achieve open-loop stable levitation and presents the dynamic analysis of a micromotor with a levitated rotor. The analysis is supported by digital simulation studies. The proposed levitation method can be used in many microdevices that require bearings and suspensions to enhance performance. © 1990.