Steven P Nimer

US Patent:

55241689, Jun 4, 1996

Filed:

Mar 3, 1995

Appl. No.:

8/398271

Inventors:

Harold R. Macks - Detroit MI
Steven P. Nimer - Walled Lake MI
Gregory J. Dygert - Warren MI

Assignee:

Ford Motor Company - Dearborn MI

International Classification:

H02P 5165

US Classification:

388814

Abstract:

In two embodiments of the present invention, the speed of a DC motor is determined by examining the signal at the negative terminal of the motor. The signal is high-pass-filtered to extract the AC component of the signal. The frequency of this signal is, in almost all cases, proportional to the speed of the motor. This signal is then fed into a comparator, which converts the signal into a square wave, which is then input into a microprocessor. The microprocessor determines the frequency of the square wave. If the frequency of the square wave is below a threshold of acceptable motor speed, the microprocessor can turn off the motor and provide a malfunction indication. If the frequency of the square wave is above a second threshold of acceptable motor speed, the microprocessor can likewise turn off the motor and provide a malfunction indication.