| 摘要 |
PURPOSE:To detect a rotating speed without magnetic noise by controlling the rotating speed of a movable element based on an electric signal responsive to an acceleration generated in the normal direction of the element. CONSTITUTION:When an electric signal of a predetermined frequency is applied from a first drive source 21 to a first piezoelectric element 4 and from a second drive source 22 to a second piezoelectric element 5, an approximate elliptical vibration is excited on the contact surface of an ultrasonic vibrator 2 with a movable element 3, and the element 3 is received by a driving force to be rotated. The rotating speed of the element 3 can be controlled by controlling the locus of the elliptical vibration excited on the vibrator 2, and the locus of the vibration can be controlled by the frequencies, amplitudes of an electric signals to be applied from the sources 21, 22 to the elements 4, 5, a phase difference of the signals of the two systems. Accordingly, the speed of the rotated element 3 is constant if the amplitude of the signal to be applied to the element 5 is constant. |
