Micro thermal actuator aided micro ultrasonic motor actuation

This paper presents a non-contact approach of controlling the rotor motion of a surface micromachined ultrasonic motor, driven by bulk PZT plates. The bulk-PZT actuates the hub-stator at its resonances, some of which are whispering gallery modes and a rotating wave generated on the stator couples shear forces to the air between the stator and the rotor causing a drag force pushing the rotor. Aided by a set of thermal actuators, to apply forces in addition to those applied by the ultrasonic stator, the thermal actuators are able to enhance the ultrasonic motor reliability. We have used infrared imaging to measure the temperature profile near the thermal actuators. The thermal actuators change the temperature of the air, substrate, and the rotor. We have observed that the thermal actuators result in smooth rotation at 100 - 300 rpm with the PZT actuation voltages of 5.4 - 7.1 Vpp.