| 摘要 |
PURPOSE:To suppress impact and to improve positioning accuracy by taking logical product of a control pulse, having duty ratio variable from 100% to 0% according to the moving position of a ultrasonic motor, and a driving signal having resonance frequency of the ultrasonic motor and then performing drive control of the ultrasonic motor based on the logical product. CONSTITUTION:A judgment is made whether the moving position of a ultrasonic motor has reached to a predetermined slow down point from the count of a down counter 18. AND gates 12, 14 produce logical products of a control pulse CP having duty ratio variable from 100% to 0% according to the moving position of the ultrasonic motor, and signal A outputted from an oscillator 11 and having resonance frequency of the ultrasonic motor and signal B produced by subjecting the signal A to phase shift by 90 deg. through a phase shifts, respectively. The ultrasonic motor is then subjected to drive control based on the output signals from the AND gates 12, 14. Consequently, the ultrasonic motor is started at maximum speed and then subjected to gradual speed down toward a target position in which it is finally stopped accurately. |
