| 摘要 |
PURPOSE:To prevent vibration of a driven body by so arranging that at least the lowest frequency component out of the frequency components of speed variation, obtained based on even times of the driving speed of an ultrasonic wave motor, does not equal nor approach the natural vibration frequency of the device. CONSTITUTION:A sheet carrying roller 9 is rotary driven through feedback control by means of an annular ultrasonic wave motor A. The ultrasonic wave motor A and the rotor 9, and the rotor 9 and an encoder 13 are coupled, respectively, through couplings having spring structures. Rotational condition of the roller 9 is detected through the encoder 13 and an ultrasonic wave motor driving circuit 5 drives the ultrasonic wave motor A with a predetermined speed. The natural vibration frequencies of a first resonance system relevant to the rotor 4 shaft and a second resonance system relevant to the rotor 9 shaft are set not to equal the frequency of speed variation corresponding to two bending phenomena of the ultrasonic wave motor A or the frequency of speed variation corresponding particularly to the number of standing wave in the fluctuation of traveling wave. |
