| 摘要 |
PURPOSE:To eliminate generation of noise, when a load fluctuates, by providing a drive for driving a motor with a frequency higher than a driver frequency when fluctuation is generated in the load relating to the ultrasonic motor. CONSTITUTION:A CPU93 fetched a detection signal from a limit switch to monitor whether one door mirror is opened or not, and when the door mirror is not opened, an open-drive signal in normal drive frequency region fm is continuously supplied to ultrasonic motors 5R, 5L, but when the door mirror id opened, the CPU 93 forms a control signal for generating AC voltages of the sine and cosine waves having frequencies in no-noise region fn in a normal rotational speed region Afa. In the control signal from the CPU93, an open action-drive signal having frequency on io-noise region fn is formed by a D/A converter 113, V/F converter 115, frequency divider 117 and a MOS power unit 119, and AC voltage of cosine and sine waves are supplied from transformers 89, 91 to the ultrasonic motors 5R, 5L rotated under a condition of no noise. |
