Electric power assisted steering system

Abstract

A combined angular position and torque sensor assembly for use in an electric power assisted steering system having an input part for connection to an upper column shaft, an output part for connection to a lower column shaft, a torsion bar that interconnects the input shaft and the output shaft, first and second upper column angular position sensors that each produce at least one output signal that is dependent on the angular position of the upper column shaft; and a processing means unit which produces a first torque signal indicative of the torque carried by the torsion bar. The processing unit further includes a component for producing a first absolute angular position signal by processing the output signals of the first and secondary sensors in a first way and a second absolute angular position signal processing the output of the same two sensors in a different way, and further includes a cross checker that performs a cross check between the two absolute position signals.