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. 11, 1991
Filed:
Apr. 21, 1989
John A Miller, Rochester Hills, MI (US);
Richard S Leemhuis, Rochester Hills, MI (US);
Rajamouli Gunda, Rochester Hills, MI (US);
Vickers, Incorporated, Troy, MI (US);
Abstract
An electrohydraulic servo system in which a microprocessor-based controller directs a pulse width modulated control signal to a servo valve for controlling flow of hydraulic fluid therethrough. Duration of each half-cycle in the pulse width modulated control signal is separately controlled by selectively incrementing or decrementing duration of the half-cycle in increments of the microprocessor clock period. Signal transition is controlled by a timer interrupt in which time required to enter the interrupt routine is measured following generation of the interrupt, and further operation is delayed by a complementary time, so that control signal transition takes place a fixed preselected number of clock periods after generation of a timer interrupt. In this way, timer interrupt latency is eliminated, and resolution of the pulse width modulated signal is enhanced through individual duration control of the signal half-cycles while maintaining a fixed modulated signal period.