Note: A disk-shaft shaped high-speed rotary ultrasonic motor

We report a novel high-speed rotary ultrasonic motor, which works at the out-of-plane vibration mode (B₁₁ mode). This motor contains one tapered rotor and one metal disk-shaft shaped stator. The stator's vibration mode B₁₁ is excited by two pairs of piezoelectric ceramics attached to the bottom face of the disk. Through the traveling wave propagation at the contact faces, the shaft located at the center of the metal disk can effectively drive the rotor pressed onto it to rapidly rotate. One prototype motor with the appearance size of Φ 29 mm × 8 mm and a mass of 13 g is fabricated, and the experimental results show that it can rotate at a relatively high speed of up to 7000 rpm at the driving voltage of 350 V_p-p. The steady speed of the motor is 5000 rpm, and the maximum output torque is about 0.5 mN m. With merits of high speed revolution, a simple structure and a compact size, this motor is highly promising for many applications, such as precise instruments and miniaturized industrial robots.