| 摘要 |
PURPOSE:To drive a supersonic motor stably, by varying driving frequency such that the current of a mechanical arm and applied voltage have their reference phases when a piezoelectric body is driven. CONSTITUTION:A supersonic motor 7 drive is provided with a microcomputer 1 which reads in mechanical arm current and determines a reference phase for performing optical driving so as to very the drive frequency such that the mechanical arm current Im to be detected during driving and applying voltage have the reference phases. Furthermore, a D/A converter 2, a voltage controlled oscillation circuit 3, power amplifier circuits 5, 6, a mechanical arm current detecting circuit 8, a peak holder 9, an A/D converter 10 and a phase detecting circuit 11 are provided. Amplitude of total current or the mechanical arm current is detected so as to detect phase of the mechanical arm current Im with respect to applying voltage at a point where the supersonic motor 7 can be driven stably with low voltage under a predetermined load. Then frequency of AC voltage to be applied onto a piezoelectric body is varied with reference to the phase. |
