PURPOSE: To provide an ultrasonic motor having a stable operation and a high efficiency by a means for accurately detecting a current of a machine arm to be input to a piezoelectric element of a vibrator and a control/drive method using the detected result.
CONSTITUTION: A first series circuit having a piezoelectric element of an ultrasonic motor and a resistive element 9, and a second series circuit having a capacitive element 10 having a capacitance value substantially equal to that of the piezoelectric element and a resistive element 11 are connected in parallel with an output side of a booster transformer 7 for generating a drive voltage of the motor. A current of a machine arm to be input to the piezoelectric element is detected by a potential difference between intermediate connection points of the two series circuits, a detected current value is controlled thereby to drive the vibrator in a stable operation range.
NISHIKURA TAKAHIRO
SUMIHARA MASANORI
TAKEDA KATSU
