Characteristics of an ultrasonic motor capable of generating a multi-degrees of freedom motion

The importance of generating a multi-degrees of freedom (DOF) motion is increasingly growing in order to develop dexterous robots. Authors developed a bar-shaped ultrasonic motor capable of generating a multi-DOF motion. The multi-DOF ultrasonic motor consists of a bar-shaped stator and a spherical rotor. The spherical rotor is rotated around three perpendicular axes by the three natural vibrations excited on the stator. In the present study, the driving and control characteristics around one driving axis, which is perpendicular to the stator's geometric axis, are measured in detail. Namely, the relationship between the frequency of the input signal and the rotational speed, the relationship between the torque and the rotational speed and the step response of the ultrasonic motor are measured. The maximum rotational speed and the maximum torque are 183 rpm and 5 mNm, respectively. The rotational speed is controlled successfully.