Ultra-compact, zero-power magnetic latching piezoelectric inchworm motor with integrated position sensor

Abstract

This paper reports the design, fabrication and characterization of a large-stroke, piezoelectrically actuated linear motor with zero-power latching for portable electronics. The motor consists of a stator having a micromachined piezoelectric actuator and a high-permeability metal guide, a permanent magnet rotor, and an integrated position sensor. The rotor is tethered to the metal guide by magnetostatic attraction due to its permanent magnets. The resulting frictional forces are sufficient to immobilize the rotor to the stator. This does not require any power, and the combined bearing-braking feature is thus termed zero-power latching. The integrated position sensor demonstrates the feasibility of precisely monitoring the rotor position. The completed actuator has a volume of 1 mm(w) × 3 mm(t) × 5 mm(l). With a 50 kHz driving frequency, precision of 5 μm at a scalable full-stroke of 5 mm and a speed of 10 mm/s at 50 kHz was achieved. A capacitive position sensor was also designed into the motor, and was able to determine the rotor position with a sensitivity of 1 fF/μm.