Method and apparatus for controlling an electric powered assisted steering system using an adaptive blending torque filter

Abstract

An apparatus and method for controlling an electric steering assist system, which system provides assist in response to a steering control signal, the apparatus comprising: torque sensing means ( ) operatively connected to a vehicle hand wheel ( ) for providing a torque signal (Ts) indicative of applied steering torque, blending filter means connected to the torque sensing means ( ) for providing a blended filtered torque signal having a first functional characteristic at torque frequencies less than a blending frequency and a second functional characteristic at torque frequencies greater than the blending frequency, the blending filter means including a low pass filter ( ) which passes all frequencies below the blending frequency and a high pass filter ( ) which passes all frequencies above the blending frequency, steering assist means for providing steering assist in response to a control signal, control means operatively connected to the blending filter means for providing said control signal to the steering assist means in response to the blended filtered torque signal, and means ( ) whereby high frequency gain of the steering assist system is arranged to be low for on-center operation of the hand wheel and relatively higher for off-center operation.