| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a controller of an ultrasonic motor by which the over- resonance of the ultrasonic motor is efficiently and surely prevented by an inexpensive circuit construction. <P>SOLUTION: A vibration pattern of a vibrator is detected using a sensor signal output according to the amplitude of piezoelectric ceramics. An amplitude value AX of the amplitude sensor signal is compared with an allowable amplitude value A<SB>0</SB>(step S2), and when the amplitude value AX exceeds an allowable amplitude value A<SB>0</SB>, it makes a limiting frequency fmin higher and controls a driving frequency f so that a difference from a resonance frequency f<SB>0</SB>is larger (step S3). When the amplitude value AX of the amplitude sensor signal becomes the allowable amplitude value A<SB>0</SB>or smaller, the limiting frequency fmin and a reference limiting frequency fK<SB>0</SB>are compared (step S4), and when the fmin exceeds the fK<SB>0</SB>, it gradually makes the limiting frequency fmin lower and returns it to the reference limiting frequency fK<SB>0</SB>. <P>COPYRIGHT: (C)2003,JPO |
