An in-wheel type micro ultrasonic motor utilizing sector shaped piezoelectric vibrators

A micro ultrasonic motor using sector shaped piezoelectric ceramics vibrators has been designed and fabricated. This type micro motor has advantages, such as a high-torque driving, a low-profile, lightweight and compact structure. The outer diameter of vibrator was 9.8 mm, the inner diameter was 5.2 mm, and the thickness was 0.8 mm. The vibrator´s 1^st longitudinal mode and 2^nd bending mode resonance frequency were about 360 kHz. The ultrasonic motor rotated 164 rpm under the condition of an applied voltage of 20 V_p__p.