The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 04, 1991
Filed:
Sep. 21, 1989
Matsushita Electric Industrial Co., Ltd., Kadoma, JP;
Abstract
A driving apparatus for an ultrasonic motor which generates a driving force by using a piezoelectric member, wherein an oscillation frequency fd is varied so as to follow a driving frequency fm which is particular to a mechanical resonance frequency fro when the mechanical resonance frequency fro varies by influence of environment. For this purpose, current and voltage detectors are provided for respectively detecting the current corresponding to the mechanical vibration of the piezoelectric member and the voltage impressed on the piezoelectric member. The phase difference between the detected current and voltage is detected, and this phase difference is used to drive a variable frequency oscillator so as to maintain the phase difference constant. The output of the variable frequency oscillator is then used to drive the driving circuit for the piezoelectric member of the ultrasonic motor.