Patent ID: 6760653
Filing Date: 2004-07-06
Classification: B62D

Abstract:
An electric power assisted steering system for a vehicle, the electric power assisted steering system comprising:a steering gear having a rack bar and a housing, the rack bar being movable linearly relative to the housing for turning steerable wheels of the vehicle; an electric motor, energization of the electric motor causing linear movement of the rack bar relative to the housing; at least one vehicle condition sensor for sensing a vehicle condition and generating a signal indicative of the vehicle condition; a motor current sensor for sensing an actual current of the electric motor and generating a signal indicative of the actual motor current; and a single integrated circuit including a main processor and a monitoring processor, the main processor receiving the at least one vehicle condition signal and, in response, controlling the electric motor by controlling the actual motor current delivered to the electric motor, the monitoring processor receiving the at least one vehicle condition signal and, in response, determining a desired motor current, the monitoring processor also receiving the actual motor current signal and using the actual motor current to determine if the actual motor current is in an acceptable range and thus, determining if the main processor is properly functioning, the main processor being a digital signal processor; and the monitoring processor being a microprocessor, the microprocessor having a longer processing time than the digital signal processor so that the monitoring processor lags the main processor.