Relative steering angle sensor diagnostic for momentary signal dropout

Apparatus for a vehicle comprising:

• a steering shaft rotation sensor for producing pulses in response to rotation of a steering shaft of said vehicle;
• a controller;
• and
• a wire connection between said steering shaft rotation sensor and said controller;
• wherein said controller counts said pulses to track a position of said steering shaft and maintains a relative position offset from a center position of said steering shaft, said controller determining said center position and iteratively adjusting said relative position offset in response to predetermined vehicle parameters;
• wherein said controller comprises a voltage comparator for comparing a voltage from said wire connection to a fault threshold, and further comprises a timer for measuring a duration of time that said voltage comparator indicates a fault;
• wherein said controller suspends said iterative adjustment of said relative position offset when said duration of time reaches a first predetermined duration;
• wherein said controller resumes said iterative adjustment of said relative position offset if said voltage comparator ceases to indicate a fault prior to reaching a second predetermined duration;
• and
• wherein said controller generates a faulted sensor signal if said voltage comparator continues to indicate a fault when said duration of time reaches said second predetermined duration.

A controller for a vehicle control system, said control system including a steering angle sensor and a wire connection between said controller and said steering angle sensor, said controller comparing a voltage at said wire connection with a fault threshold, said controller having operational states comprising:

• a recovery state wherein a relative position offset is iteratively adjusted at a fast rate in response to predetermined vehicle parameters until a criteria for a valid relative position offset is satisfied;
• a valid state entered from said recovery state when said criteria for a valid relative position offset is satisfied and wherein said relative position offset is iteratively adjusted at a slow rate in response to said predetermined vehicle parameters;
• a tentative state entered when said comparison indicates a fault, wherein a duration of said fault is measured, wherein said iterative adjustment of said relative position offset is suspended, wherein a transition to said valid state is made if said duration is less than a first predetermined duration, and wherein a transition to said recovery state is made if said duration is between said first predetermined duration and a second predetermined duration;
• and
• a faulted state entered if said duration is greater than said second predetermined duration and wherein a faulted sensor signal is generated.