| 摘要 |
PURPOSE:To enhance stability against external impact by subjecting a voltage signal, taken out from ultrasonic motor current, to rectification, amplification and conversion into a DC signal, comparing the DC signal with a reference potential, and making a judgment whether output frequency of a VCO is in the proximity of resonance frequency. CONSTITUTION:A voltage signal Vin is induced from a piezoelectric element current I and inputted to a rectifier/amplifier 5, output Vm therefrom is then converted through a smoothing unit 11 into a DC signal Vm'. A second reference voltage generator 13 produces a second reference voltage Vcomp from final achieving 2 voltage Vo of the reference voltage Vref. The signal Vm' from the piezoelectric element is then compared with the second reference voltage Vcomp, and if Vm' > Vcomp a reset 2 signal is produced to turn a transistor 405 ON thus discharging a capacitor 404 and stopping a motor. If Vm' < Vcomp, the piezoelectric element current I is fed back and the motor driving current is stabilized in the proximity of resonance frequency and drives the ultrasonic motor. |
