An ultrasonic motor driving device comprises: a detecting unit for detecting a phase difference between a high-frequency drive voltage waveform applied to a drive electrode of an ultrasonic motor and a voltage waveform outputted by a monitor electrode generating frequency voltage in accordance with the...http://www.google.es/patents/US5508579?utm_source=gb-gplus-sharePatente US5508579 - Ultrasonic motor driving device
