Relative steering angle sensor diagnostic for momentary signal dropout
First Claim
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1. A method of detecting faults of a relative position offset steering angle sensor in a vehicle, said method comprising the steps of:
- iteratively adjusting said relative position offset in response to predetermined vehicle parameters;
comparing a voltage from said angle sensor to a fault threshold;
measuring a duration of time that said comparing step indicates a fault;
if a fault is indicated for A duration of time greater that a first predetermined duration then suspending said adjusting step;
if said fault ceases to be indicated prior to reaching a second predetermined duration then resuming said adjusting step; and
if said fault continues to be indicated until reaching said second predetermined duration then generating a faulted sensor signal.
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Abstract
Diagnostic monitoring of electrical signals from a quadrature sensor used for vehicle steering angle detection includes comparing the signals with a fault threshold (i.e., out-of-range voltages). A controller distinguishes between events of short enough duration that they do not cause loss of position accuracy and those where signal transitions were potentially missed.
44 Citations
16 Claims
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1. A method of detecting faults of a relative position offset steering angle sensor in a vehicle, said method comprising the steps of:
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iteratively adjusting said relative position offset in response to predetermined vehicle parameters;
comparing a voltage from said angle sensor to a fault threshold;
measuring a duration of time that said comparing step indicates a fault;
if a fault is indicated for A duration of time greater that a first predetermined duration then suspending said adjusting step;
if said fault ceases to be indicated prior to reaching a second predetermined duration then resuming said adjusting step; and
if said fault continues to be indicated until reaching said second predetermined duration then generating a faulted sensor signal. - View Dependent Claims (2, 3, 4, 5, 6)
counting a number of occurrences when said fault is indicated; and
generating said faulted sensor signal if said number equals a predetermined number.
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3. The method of claim 1 further comprising the steps of:
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integrating a total time that said fault is indicated during all occurrences; and
generating said faulted sensor signal if said total time exceeds a predetermined time.
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4. The method of claim 1 wherein said iteratively adjusting step is comprised of:
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a fast zeroing sequence wherein said relative position offset can change value at a first rate; and
a fine-tuning sequence wherein said relative position offset can change value at a second rate slower than said first rate.
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5. The method of claim 4 further comprising the steps of:
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determining a difference between a value of said relative offset when said adjusting step is suspended and a value of said relative offset after said fast zeroing sequence when said adjusting step is resumed; and
generating said faulted sensor signal if said difference exceeds a predetermined difference.
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6. The method of claim 1 wherein said adjusting step is suspended after said faulted sensor signal is generated.
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7. Apparatus for a vehicle comprising:
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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. - View Dependent Claims (8, 9, 10)
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11. 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:
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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. - View Dependent Claims (12, 13, 14, 15, 16)
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Specification