Design of a plate type multi-DOF ultrasonic motor and its driving characteristics

Multi-DOF actuators have become more useful in the field of robotics, thanks to the increasing number of DOFs of systems. General features of ultrasonic motor are suitable for constructing a direct-drive multi-DOF actuator. However, those previously developed do not have advantages in volume and weight against the multi-DOF motion unit composed of several electromagnetic motors. In the present study authors develop a novel multi-DOF ultrasonic motor with a plate stator and a spherical rotor. First, a new driving principle of the motor is proposed. Next, the stator geometry is designed in detail using finite element method, and the prototype of the multi-DOF ultrasonic motor with plate stator is produced. The stator is relatively compact against the rotor. Then, vibration characteristics of the stator and driving characteristics of the motor have been measured, respectively. The result confirms that the motor successfully provides the multi-DOF motion of rotor around orthogonal axes by single plate stator. Finally, self-oscillation driving circuit for the motor is proposed.