| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress deterioration in drive performance in a self-sensing type ultrasonic motor which enables detection of the rotational position and the rotational speed of a movable body without using a sensor such as an encoder. <P>SOLUTION: An oscillating object (stator) drives the movable body (rotor) through the vibration of a piezoelectric element 12a, and detects the rotational position of the movable object by an output change from a detection electrode IS, occurring when a contact part of the oscillating object passes in the groove formed in the movable object. In this case, an amplitude detecting part 28 detects an output amplitude from the detection electrode IS, and a deviation calculating part 29 calculates a deviation with regard to an ideal amplitude value (the amplitude value of the optimum drive), and a control unit 24 changes the oscillation frequency of a drive voltage generating part 25 corresponding to the calculated result. Accordingly, the control unit vibrates the drive voltage generating part at a normal resonance frequency when the contact portion passes on a normal area without the groove, and the control unit lowers the oscillation frequency when the contact portion passes in the detection area with the groove to be matched with the resonance frequency, thereby suppressing the deterioration in the drive performance (torque). A position detecting part 30 detects the rotational position by a change in the drive frequency. <P>COPYRIGHT: (C)2010,JPO&INPIT |
