Patent ID: 7950274
Filing Date: 2011-05-31
Classification: B62D

Abstract:
1. A method for determining an absolute rotational position of a vehicle steering column, the vehicle steering column being operably coupled to a steering assist motor, the method comprising: determining a plurality of relative motor rotational position values from signals received from a relative position sensor operably coupled to the steering assist motor; determining a plurality of relative vehicle steering column rotational position values based on the plurality of relative motor rotational position values; determining whether a vehicle is being driven substantially straight relative to a longitudinal axis of the vehicle on a roadway; when the vehicle is being driven substantially straight, then performing the step of determining a rotational position offset value from the plurality of relative vehicle steering column rotational position values; and determining an absolute rotational position value from a current relative vehicle steering column rotational position value and the rotational position offset value, the absolute rotational position value being indicative of the absolute rotational position of the vehicle steering column; storing the absolute rotational position value in a memory device; determining an absolute rotational position range of the vehicle steering column based on a plurality of absolute rotational position values, and both an upper rotational position limit value and a lower rotational position limit value associated with the vehicle steering column; retrieving a stored last valid absolute rotational position value from said memory device; and if a first confidence value associated with a first of said plurality of absolute rotational position values is greater than a first threshold value, then selecting the first absolute rotational position value, else if a second confidence value associated with the absolute rotational position range is greater than a second threshold value, then selecting the absolute rotational position range, else if a third confidence value associated with the stored last valid absolute rotational position value is greater than a third threshold value, then selecting the stored last valid absolute rotational position value.