Masayuki Ueyama

Design of 2-DOF pyramid type ultrasonic motor

The design of an ultrasonic motor having 2-DOF is presented. The drive unit consists of four piezoelectric actuators arranged in a pyramid shape. Circular vibration at the apex generates a thrust when a rotor is pressed against the apex. The direction of the thrust within the tangent plane of the rotor is controlled by the displacement and phase differences among the four piezoelectric actuators. The theoretical analysis and design method of this actuator unit is presented. This actuator can rotate a spherical rotor. The orientation of the spherical rotor, which has three degree of freedom, is controlled by solving nonholonomic kinematics equations between the rotor and the drive unit. The solution is given in detail. The experimental results demonstrate that the direction and speed of the rotation of the spherical rotor are controllable.

Design of Ultrasonic Motor for Driving Spherical Surface

This paper presents a new ultrasonic motor, which uses two sets of actuator in order to control the direction of the thrust within the tangential plane at the contact point of the actuator and the rotor. The drive unit consists of four piezoelectric stack actuators arranged in a pyramid shape. Circular vibration at the apex generates a thrust when a rotor is pressed against the apex. The direction of the thrust within the tangent plane of the rotor is controlled by the amplitude and phase differences among the four actuators. This enables a spherical drive if a spherical surfaced rotor is used. Experiments have verified that the direction of the thrust was controllable by the ratio between the two drive signals, as predicted by the theoretical analysis.

Micro actuator with two piezoelectric elements placed at right angles

This paper describes the design and the several factors associated with micro actuator with two piezoelectric elements placed at right angles. Two driving methods at resonance frequency are proposed, phase-difference drive and single-phase drive. On and close degeneracy of the natural vibration modes are necessary for these methods. In this paper necessary conditions are described through kinetic models. These conditions can be controlled by mass of the tip. In kinetic models natural vibration modes correspond to spring-mass (-and-beam) systems. Degeneracy condition of natural vibration modes can be controlled by mass of the tip. On-degeneracy condition circular orbit can be obtained by two driving signals with a phase difference of 90 degrees. Close-degeneracy condition circular orbit can also be obtained by one driving signal. Theories are demonstrated through the finite element method and experimental studies.