Design of Multi-Degree-of-Freedom Ultrasonic Micromotors

In this paper, we study a new configuration of an element actuator suitable for the two-dimensional array of multi-degree-of-freedom (MDOF) ultrasonic motors. To reduce acoustic coupling between element actuators, a thin disk structure is introduced. MDOF motions are achieved by the combination of vibrations of the column for three orthogonal directions due to the vibration of the thin disk. Only one piezoelectric element is used for one column instead of a stack of different types of piezoelectric elements to drive the vibrations. First, we describe the configuration of the actuator, an excitation method of each vibration, and the operating principles of the MDOF motion. Second, resonance frequencies of excited vibrations are tuned using finite element analysis. Finally, rotation of the ball rotor is discussed.