Trw Limited

Trw Automotive U.S. LLC

Ivan J Williams

Joseph D Miller

William C Fennessy

A vehicle electric assist steering system ( ) includes a switching circuit ( ) for providing electrical power to an electric motor ( ) of the vehicle steering system. The switching circuit ( ) has a temperature condition. A temperature sensor ( ) is coupled with the switching circuit ( ) for providing an output signal ( ) having a value indicative of the temperature condition of the switching circuit ( ). A stall detector ( ) is responsive to the output signal ( ). The stall detector ( ) is operable to reduce power to the electric motor to different level during a stall condition based on the sensed temperature condition of the switching circuit ( ).

Method and apparatus for detecting a motor stall condition in an electric assist steering system

A vehicle electric assist steering system (10) includes a stall detector (70) for detecting a stall condition of a variable reluctance electric motor (26). The stall detector (70) monitors a torque command signal (48) which is responsive to steering torque applied by the vehicle operator to the vehicle steering wheel (12). The stall detector (70) also monitors a commutation sensor (74) which indicates motor commutation. The stall detector (70) determines the existence of a stall condition in response to the torque command signal (48) greater than a predetermined value and no motor commutation. The stall detector (70) controls the gain of an adjustable gain amplifier (52). The adjustable gain amplifier (52) controls current applied to the motor (26). The current applied to the motor (26) is limited when the stall detector (70) detects a stall condition. An Over-use detector (70) determines the existence of an over-use condition by integrating the torque command signal (48).

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Rolling Hills, CA, United States of America

Ivan J Williams