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:
Mar. 17, 1987
Filed:
Feb. 21, 1985
Takayasu Ito, Katsuta, JP;
Hideo Nishijima, Katsuta, JP;
Isao Fukushima, Katsuta, JP;
Yoshio Fujimori, Katsuta, JP;
Yasunori Kobori, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Hitachi Video Engineering, Incorporated, Kanagawa, JP;
Abstract
An apparatus for driving a brushless motor, in which a ripple appearing in the rotation torque of the motor is cancelled by driving the motor with a signal current whose phase is opposite to that of and which has a waveform symmetrical with that of the torque ripple waveform, so that the motor can rotate accurately without any speed variation. In order to obtain such a signal current waveform, counter-electromotive forces induced in the stator coils of the motor are detected, and the level of the signal indicative of the detected counter-electromotive forces is controlled depending on the load and rotation speed of the motor to provide a control signal for controlling the motor drive current.