A 1.6-mm, metal tube ultrasonic motor

A miniaturized metal tube ultrasonic motor, the dimensions of which are 1.6 mm in diameter and 6 rum in length, was developed. Two flattened surfaces with 90-degrees were ground on the outer surface of the stator. Two PZT-based piezoelectric ceramics were bonded onto these flat surfaces. The asymmetrical surface of the stator developed the split of the two degenerated orthogonal bending modes, resulting in a wobble motion. The working frequency of the 1.6-mm motor with 6 mm in length was 130 kHz. A torque of 0.5 mNm was reached at a maximum power of 45 mW with a speed of 45 rad/sec. The maximum efficiency was 16%.