Longitudinal-bending mode micromotor using multilayer piezoelectric actuator

Longitudinal-bending mode ultrasonic motors with a diameter of 3 mm were fabricated using stacked multilayer piezoelectric actuators, which were self-developed from hard lead zirconate titanate (PZT) ceramic. A bending vibration was converted from a longitudinal vibration with a longitudinal-bending coupler. The motors could be bidirectionally operated by changing driving frequency. Their starting and braking torque were analyzed based on the transient velocity response. With a load of moment of inertia 2.5/spl times/10/sup -7/ kgm/sup 2/, the motor showed a maximum starting torque of 127.5 /spl mu/Nm. The braking torque proved to be a constant independent on the motor´s driving conditions and was roughly equivalent to the maximum starting torque achievable with our micromotors.