Design and evaluation of low-profile micro ultrasonic motors using sector shaped piezoelectric vibrators

A low-profile micro ultrasonic motor has been designed and fabricated. This motor has two sector shaped vibrators. The vibrators generate elliptical motion by the 1^st longitudinal mode and 2^nd bending mode. They are supported by planar elastic structure that combined with preload mechanism. Three types of preload systems were designed and evaluated. The thickness of one type was 0.6 mm. These vibrators have been oscillated around 340 kHz. The maximum rotation speed was 2.4 x 10³ rpm and the maximum starting torque was 98.8 muNm when the applied voltage was 20 V_p-p.