| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor capable of striking a balance between speed control by drive phase difference control and frequency tracking, and obtaining a stable driving state even in a low-speed range. <P>SOLUTION: The ultrasonic motor so configured as to control a driving speed by varying a drive phase difference includes a speed control circuit 111. The speed control circuit 111 switches an operation mode between a first operation mode and a second operation mode based on a target speed. In the first operation mode, a drive signal of a drive phase difference corresponding to the target speed is continuously generated. In the second operation mode, drive signals of multiple different drive phase differences are periodically generated in correspondence to the target speed. Of the multiple different drive phase differences, at least one drive phase difference (first drive phase difference) is configured such that the amplitude value of a vibration detection signal is taken as an amplitude value at which a phase difference can be detected by a phase difference detection unit. In operation in the second operation mode, a frequency control unit carries out frequency control during a period during which driving is carried out by a drive signal of the first drive phase difference. <P>COPYRIGHT: (C)2011,JPO&INPIT |
