Determining steering angle of steering column of vehicle

• US 9,073,569 B2
• Filed: 03/19/2013
• Issued: 07/07/2015
• Est. Priority Date: 03/19/2013
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Di Cairano, Stefano
• Primary Examiner(s): Olszewski, John R
• Assistant Examiner(s): MELTON, TODD M
• Application Number:
  US13/847,129
• Publication Number:
  US 20140288779A1
• Time in Patent Office: 840 Days
• US Class Current: 1/1
• CPC Class Codes: B62D 15/0235 by measuring or deriving directly at the electric power steering motor
• CPC Class Codes: B62D 15/0245 Means or methods for determination of the central position of the steering system, e.g. straight ahead position
• CPC Class Codes: B62D 5/0481 monitoring the steering system, e.g. failures

Abstract

A system and a method determine a steering angle of a steering column of a vehicle as a sum of a shifted steering angle and an offset. The steering angle is updated by adjusting the offset in response to detecting incoherence between the steering angle and a lateral vehicle dynamic.

Claims

1. A method for determining a steering angle of a steering column of a vehicle, comprising:

determining the steering angle as a sum of a shifted steering angle and an offset; and

updating the steering angle by adjusting the offset in response to detecting an incoherence between the steering angle and a lateral vehicle dynamic, wherein the incoherence results in a negative value of a product of corresponding values of the steering angle and the lateral vehicle dynamic, wherein steps of the method are performed by a processor.

2. The method of claim 1, wherein the lateral vehicle dynamic includes at least one of a yaw rate, a lateral acceleration, a steering alignment torque, a steering torque, and a rotational speed of at least one wheel of the vehicle, and wherein the shifted steering angle includes at least one of an angle of a steering motor, a relative angle measured with respect to the steering angle, a value of the steering angle determined in a presence of an error, and an effective steering wheel angle shifted by the offset.

3. The method of claim 2, further comprising:

determining the lateral vehicle dynamic by low pass filtering a measurement of a vehicle sensor.

4. The method of claim 1, further comprising:

detecting the incoherence in response to determining the negative value of the product of corresponding values of the steering angle and the lateral vehicle dynamic.

5. The method of claim 4, further comprising:

adjusting the offset to make the product nonnegative.

6. The method of claim 5, further comprising:

repeating the detecting and the adjusting for a set of values of the steering angle and a set of values of the vehicle dynamics until a termination condition is met.

7. The method of claim 1, further comprising:

adjusting the offset with a product of the steering angle and a filtering gain.

8. The method of claim 7, further comprising:

initializing the filtering gain by α

(0), such that 0<

α

(0)<

1; and

decreasing the gain for each iteration until a termination condition is met, such that a final gain β

is 0<

β

<

α

(0).

9. The method of claim 1, further comprising:

initializing the steering angle;

determining a plurality of estimations of the steering angle, wherein each estimation is coherent with a corresponding lateral vehicle dynamic; and

adjusting the steering angle as a weighted average of the plurality of estimations of steering angle.

10. The method of claim 1, further comprising:

initializing the steering angle;

determining a left estimation of steering angle for a left turn of the steering wheel;

determining a right estimation of steering angle for a right turn of the steering wheel; and

determining the steering angle as an average of the left and right estimations.

11. The method of claim 1, further comprising:

adjusting the offset iteratively until a difference between the offset and an average value of the offset over a period of time is below a first threshold, and/or a variance of the offset over the period of time is below a second threshold.

12. The method of claim 11, further comprising:

determining the average value of the offset and the variance of the offset using an exponentially decaying filter.

13. The method of claim 11, further comprising:

determining the first and the second threshold using a confidence interval of a distribution of an error of the offset corresponding to a predetermined probability, such that the variance and the average of the offset satisfying the first and the second threshold guarantee that the error of the offset is smaller than a desired value with the predetermined probability.

14. The method of claim 1, further comprising

determining an uncertainty of the steering angle based on a difference between the offset and a variance of the offset over a period of time;

and

adjusting the offset iteratively until the uncertainty of the steering angle equals zero.

15. The method of claim 14, further comprising:

determining the uncertainty of the steering angle based on a difference between offsets separately determined from left and right turns of the vehicle.

16. The method of claim 14, further comprising:

determining the uncertainty of the steering angle based on a difference between offsets separately determined for different lateral vehicle dynamics.

17. A system for determining a steering angle of a steering column of a vehicle, comprising a processor for:

determining the steering angle as a sum of a shifted steering angle and an offset; and

for

updating the steering angle by adjusting the offset in response to detecting an incoherence between the steering angle and a lateral vehicle dynamic, wherein the incoherence results in a negative value of a product of corresponding values of the steering angle and the lateral vehicle dynamic.

18. A motor vehicle, comprising:

at least one sensor for measuring at least one lateral vehicle dynamic of the motor vehicle;

a sensor for measuring a signal representing a shifted steering angle; and

a processor for determining a steering angle of a steering column of the motor vehicle as a sum of a shifted steering angle and an offset, and for adjusting iteratively the steering angle in response to detecting an incoherence between the steering angle and the lateral vehicle dynamic, wherein the incoherence results in a negative value of a product of corresponding values of the steering angle and the lateral vehicle dynamic.

19. The motor vehicle of claim 18, wherein the signal represents an angle of a steering motor of an electric power steering system, and wherein the sensor is a steering motor sensor for measuring an angle of the steering motor.

20. The motor vehicle of claim 18, wherein the sensor is a relative encoder for measuring the signal representing an angle with respect to the steering angle.