Methods and systems for estimating road surface friction coefficient using self aligning torque

Patent metadata

Field	Value
Publication number	US-2016101782-A1
Application number	US-201414510862-A
Country	US
Kind code	A1
Filing date	Oct 9, 2014
Priority date	Oct 9, 2014
Publication date	Apr 14, 2016
Grant date	—

Abstract

Methods and systems for determining road surface information in a vehicle. In one embodiment, the method includes: determining at least one condition assessment value based on steering data; determining a feature set to include at least one of self-aligning torque (SAT), slip angle, SAT variance, steering rate, and lateral acceleration based on the condition assessment value; processing steering data obtained during a steering maneuver and associated with the feature set using a pattern classification technique; and determining a surface type based on the processing.

First claim

What is claimed is:

1 . A method for determining road surface information in a vehicle, comprising:
determining at least one condition assessment value based on steering data; determining a feature set to include at least one of self-aligning torque (SAT), slip angle, SAT variance, steering rate, and lateral acceleration based on the condition assessment value; processing steering data obtained during a steering maneuver and associated with the feature set using a pattern classification technique; and determining a surface type based on the processing.

2 . The method of claim 1 , wherein the at least one condition assessment value is a steering mode that is associated with a steering rate.

3 . The method of claim 1 , wherein the at least one condition assessment value is a SAT mode that is associated with a linearity of the SAT.

4 . The method of claim 1 , further comprising determining a steering maneuver type, and wherein the determining the feature set and the processing the steering data is based on the steering maneuver type.

5 . The method of claim 4 , wherein the steering maneuver type is at least one of a steering out maneuver and a non-steering out maneuver.

6 . The method of claim 5 , further comprising determining a steering maneuver type, and wherein the determining the surface type is based on a default value when the steering maneuver type is determined to be the non-steering out maneuver.

7 . The method of claim 1 , wherein the determining the feature set comprises determining the feature set to include SAT and slip angle.

8 . The method of claim 7 , further comprising:
determining a slip angle to be greater than a threshold, and wherein the determining the condition assessment value comprises determining a SAT mode to be linear and determining the steering mode to be normal steering, and wherein the determining the feature set to include SAT and slip angle is based on the slip angle being greater than a threshold, the SAT mode being linear, and the steering mode being normal steering.

9 . The method of claim 1 , wherein the determining the feature set comprises determining the feature set to include SAT, SAT variance, and slip angle.

10 . The method of claim 9 , further comprising:
determining a slip angle to be within a range, and wherein the determining the condition assessment value comprises determining a SAT mode to be linear and determining the steering mode to be normal steering, and wherein the determining the feature set to include SAT, SAT variance, and slip angle is based on the slip angle being within the range, the SAT mode being linear, and the steering mode being normal steering.

11 . The method of claim 1 , wherein the determining the feature set comprises determining the feature set to include lateral acceleration, steering rate, and slip angle.

12 . The method of claim 11 , further comprising:
determining a slip angle to be greater than a threshold, and wherein the determining the condition assessment value comprises determining a SAT mode to be linear and determining the steering mode to be fast steering, and wherein the determining the feature set to include lateral acceleration, steering rate, and slip angle is based on the slip angle being greater than the threshold, the SAT mode being linear, and the steering mode being fast steering.

13 . The method of claim 1 , wherein the determining the feature set comprises determining the feature set to include lateral acceleration.

14 . The method of claim 13 , further comprising:
wherein the determining the condition assessment value comprises determining a SAT mode to be nonlinear, and wherein the determining the feature set to include lateral acceleration is based on the SAT mode being nonlinear.

15 . The method of claim 1 , further comprising determining a surface value based on the surface type.

16 . The method of claim 1 , wherein the pattern classification technique includes at least one of a linear discriminant analysis and a support vector machine analysis.

17 . The method of claim 1 , further comprising confirming the surface type based on an evaluation of lateral acceleration.

18 . The method of claim 1 , further comprising determining a final surface type based on a plurality of determined surface types within a temporal moving window.

19 . A system for determining road surface information in a vehicle, comprising:
a condition assessment module that determines at least one condition assessment value based on steering data; a feature set determination module that determines a feature set to include at least one of self-aligning torque (SAT), slip angle, SAT variance, steering rate, and lateral acceleration based on the condition assessment value; and a surface classification module that processes the steering data obtained during a steering maneuver and associated with the feature set using a pattern classification technique to determine a surface type.

20 . The system of claim 19 further comprising a decision making module that determines a final surface type based on a plurality of determined surface types within a temporal moving window.

Assignees

• Gm Global Tech Operations Inc

Inventors

• Ghoneim Youssef A
• Zhao Qingrong
• Zhang Qi
• Litkouhi Bakhtiar B
• Si Yingmei
• Sidlosky David M
• Boatman Valarie V
• Ahmed Sami

Classifications

• B60W2520/14

  Yaw · CPC title

• B60W2540/18

  Steering angle · CPC title

• B60W2520/10

  Longitudinal speed · CPC title

• B60W40/068 Primary

  Road friction coefficient · CPC title

• B60W2520/20

  Sideslip angle · CPC title