Abstract
To lighten driving motor is an important problem for the robot, and a light ultrasonic motor is expected. However, it is not possible to use it as a servo drive motor because the velocity range is narrow, and especially there is no continuousness in the low speed region of the positive or reversal. Then, the improvement of the lowest rotational speed was attempted by superimposing the voltage of a frequency different from the motor drive frequency. The rotational speed fluctuation was measured as the evaluation characteristic. As a result, it became clear that the rotational speed fluctuation is low as for superimposing a frequency away than driving frequency.
