A multi-degree-of-freedom ultrasonic motor using single-phase-driven vibrators

This paper presents a novel type of multi degree-of-freedom ultrasonic motors. Today, in various fields, actuators having multi degrees-of-freedom is needed. In the past, many multi-degree-of-freedom actuators have been developed. However, they are all still large and heavy. Thus, we propose a miniature multi-degree-of-freedom actuator using plural single-phase-driven ultrasonic vibrators. A single-phase-driven ultrasonic motor is known for its miniaturizing facility. On the other hand, it is also known for its lack of output force. Therefore, we proposed to use plural single-phase-driven vibrators and also tried to make one vibrator generate great force. This motor has many small vibrators; each one having four patterns in the thrust direction. By controlling the frequency of each vibrator, we can obtain multiple movements of a movable object. First, we proposed the principles of this motor. Next, we selected vibration modes and designed the size of a vibrator to be 10 x 7.5 x 0.9 mm(3) using finite element analysis. Finally, we measured frequency, vibration, and driving characteristics of the vibrators. The maximum thrust was about 3.14 N and the maximum torque was about 6 mN-m.