DETECTION OF DRIVER INTERVENTION DURING A TORQUE OVERLAY OPERATION IN AN ELECTRIC POWER STEERING SYSTEM

• US 20100152952A1
• Filed: 12/17/2008
• Published: 06/17/2010
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Ryu, Jihan, Lee, Yong H., Deng, Weiwen
• Granted Patent: US 8,170,751 B2
• Time in Patent Office: Days
• US Class Current: 701/29
• CPC Class Codes: B62D 1/286 Systems for interrupting non-mechanical steering due to driver intervention
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence

Abstract

A method for controlling an assisted steering maneuver in an electric power steering (EPS) system includes modeling steering dynamics during a torque overlay operation to generate a dynamic steering model (DSM), measuring vehicle operating values, and detecting a driver intervention in the torque overlay operation based on the DSM and the vehicle operating values. The torque overlay operation is overridden when driver intervention is detected, allowing the driver to regain control of the steering maneuver. A vehicle includes a steering wheel, a steering assist mechanism, and an EPS system having an electronic control unit (ECU) adapted to determine a present intent of a driver of the vehicle to interrupt application of the TOC based on a vehicle operating value transmitted by the driver to the steering wheel. The ECU is operable for interrupting the torque overlay operation when the present intent of the driver is determined.

Claims

1. A method for controlling a steering maneuver of a vehicle having an electric power steering (EPS) system and a steering wheel, the method comprising:

modeling a set of steering dynamics during a predetermined EPS state having an active torque overlay operation to thereby generate a dynamic steering model (DSM);

measuring a set of vehicle operating values;

processing the set of vehicle operating values and the DSM to thereby detect a driver intervention, wherein the driver intervention corresponds to a driver intent to override the torque overlay operation; and

automatically overriding the torque overlay operation when the driver intervention is detected.

2. The method of claim 1, wherein modeling a set of steering dynamics during a predetermined EPS state includes using a second-order transfer function to model the set of steering dynamics when the driver is not applying at least a threshold amount of steering torque to the steering wheel.

3. The method of claim 1, wherein measuring a set of vehicle operating values includes:

measuring a steering angle and measuring a steering torque.

4. The method of claim 1, wherein processing the set of vehicle operating values includes:

comparing at least one of a steering angle and a steering torque value to a corresponding calibrated threshold.

5. The method of claim 1, wherein the EPS includes a steering motor having an actual motor torque value, wherein processing the set of vehicle operating values includes at least one of:

processing a steering torque value through a low-pass filter to isolate a low-frequency torque signal, and passing an actual motor torque value through a high-pass filter to isolate a high-frequency noise component.

6. The method of claim 5, wherein processing the set of vehicle operating values further includes:

comparing at least one of the low-frequency torque signal and the high-frequency noise component to a corresponding threshold.

7. A method for controlling a steering maneuver in a vehicle having a steering device, an electric power steering (EPS) system operatively connected to the steering device, and a steering wheel mechanically coupled to the steering device, the EPS system including an electronic control unit (ECU) and a steering motor adapted to selectively assist in execution of the steering maneuver, the method comprising:

generating a dynamic steering model (DSM) for a hands-off EPS state, wherein the hands-off EPS state describes an EPS state during which a driver of the vehicle is applying less than a threshold minimum amount of steering torque to the steering wheel during an active torque overlay operation;

measuring a set of vehicle operating values, including a steering angle and a steering torque;

processing the set of vehicle operating values to thereby detect a driver intervention corresponding to a driver intent to override the torque overlay operation, including comparing a low-frequency noise component of the steering torque and a high-frequency noise component of the actual motor torque to a corresponding threshold; and

overriding the torque overlay operation when the driver intervention is detected.

8. The method of claim 7, wherein processing the set of vehicle operating values includes:

computing a calculated steering angle;

computing a gradient of each of the calculated steering angle and the measured steering angle;

calculating a difference between the gradients; and

comparing the difference to an allowable threshold.

9. The method of claim 7, wherein the steering device is configured as a dual rack-and-pinion device having a torsion bar, and wherein measuring a set of vehicle operating values includes measuring the steering torque generated within the torsion bar.

10. The method of claim 7, wherein generating a dynamic steering model (DSM) for a hands-off EPS state includes using a second-order transfer function to model the DSM.

11. A vehicle comprising:

a steering wheel;

an electric power steering (EPS) system having;

a rack-and-pinion device having a moveable rack portion;

a steering motor; and

an electronic control unit (ECU) in electrical communication with the steering wheel and the steering motor, the ECU being operable for selectively transmitting a torque overlay command (TOC) to the steering motor for movement of the rack portion during a predetermined EPS-assisted steering maneuver; and

an algorithm for determining a present intent of a driver of the vehicle to interrupt an application of the TOC based on a set of vehicle operating values, including a steering angle imparted by the driver to the steering wheel;

wherein execution of the algorithm interrupts the transmission of the TOC when the present intent of the driver is determined.

12. The vehicle of claim 11, wherein the rack-and-pinion device includes a torsion bar, and wherein the set of vehicle operating values includes a steering torque generated within the torsion bar.

13. The vehicle of claim 11, wherein the ECU is adapted to model a set of steering dynamics during a hands-off EPS-assisted steering maneuver to thereby generate a dynamic steering model (DSM), the hands-off EPS-assisted steering maneuver corresponding to a threshold minimum amount of steering torque being applied to the steering wheel by a driver of the vehicle during the torque overlay operation.

14. The vehicle of claim 11, wherein the ECU is configured to detect a threshold amount of high-frequency noise in an actual motor torque of the steering motor, and for determining the present intent of the driver based at least in part on the amount of high-frequency noise.

15. The vehicle of claim 14, including a high-pass filter, wherein the ECU is adapted to detect the threshold amount of high-frequency noise by processing the actual motor torque through the high-pass filter.

16. The vehicle of claim 11, wherein the ECU is configured to detect a threshold amount of low-frequency torque signal in an actual motor torque of the steering motor, and to detect the driver intervention based at least in part on the amount of low-frequency torque signal.

17. The vehicle of claim 16, including a low-pass filter, wherein the ECU is adapted to detect the threshold amount of low-frequency torque signal by processing the actual motor torque through the low-pass filter.

18. The vehicle of claim 11, wherein the ECU is adapted to compare each of the steering angle, the steering torque, and an actual motor torque of the steering motor to a corresponding threshold, and wherein the ECU is further adapted for determining the present intent of the driver to interrupt the application of the TOC when each of the steering angle, the steering torque, and the actual motor torque exceed their corresponding threshold values.