Methods and systems for estimating road surface friction

Patent metadata

Field	Value
Publication number	US-10131360-B2
Application number	US-201615236106-A
Country	US
Kind code	B2
Filing date	Aug 12, 2016
Priority date	Aug 12, 2016
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

Methods and systems are provided for determining a road surface friction coefficient and controlling a feature of the vehicle based thereon. In one embodiment, a method includes: receiving signals from an electronic power steering system and an inertial measurement unit; estimating parameters associated with an electronic power steering system model using an iterative optimization method; calculating an electronic power steering system variable using the electronic power steering system model, the estimated parameters and one or more of the received signals; determining whether the calculated electronic power steering system variable satisfies a fitness criterion; and when the calculated electronic power steering system variable does satisfy the fitness criterion, determining a road surface friction coefficient based on at least one of the estimated parameters.

First claim

What is claimed is:

1. A method, comprising:
receiving signals from an electric power steering system and an inertial measurement unit;
iteratively estimating parameters including a moment of inertia, a friction co-efficient, and a self-aligning torque coefficient associated with an electric power steering system model using a particle swarm optimization method and the signals;
determining whether the parameters satisfy a fitness criterion; and
when the estimated parameters satisfy the fitness criterion, determining a road surface friction coefficient based on at least one of the estimated parameters.

2. The method of claim 1 , further comprising detecting a slip angle and determining the road surface friction coefficient when the slip angle is less than a pre-determined value.

3. The method of claim 1 , wherein the estimated parameter chosen to base the determination of the road surface friction coefficient on is the self-aligning torque coefficient.

4. The method of claim 1 , further comprising calculating an electronic power steering system torque value using the electronic power steering system model, the estimated parameters, and one or more of the received signals; and comparing the calculated electric power steering system torque value with a measured torque value to determine the fitness criterion.

5. The method of claim 1 , determining an iteration count and wherein the fitness criterion is based on the iteration count.

6. The method of claim 1 , wherein the signals from the electric power steering system comprise a torsion bar angle and a total electric power steering delivered torque.

7. The method of claim 1 , wherein the signals from the inertial measurement unit comprise a yaw rate, a lateral speed, and a longitudinal speed.

8. The method of claim 1 , further comprising determining that the road surface friction coefficient indicates a wet surface and at least one of:
determining an autonomous actuating vehicle braking strategy;
communicating the road surface friction coefficient to a wireless communication system for alerting other vehicle drivers of the identified wet surface of low friction;
alerting a driver of a potential reduced traction between vehicle tires and the surface as a result of the wet surface;
alerting a driver to not use a driver assistance system; and
providing a notification of the wet surface to a vehicle controller, and the vehicle controller autonomously modifying a control setting of an automated control feature in response to the notification.

9. A system, comprising:
a non-transitory computer readable medium, comprising:
a first module configured to receive sensor signals from an electric power steering system and an inertial measurement unit, and to iteratively estimate parameters including a moment of inertia, a friction co-efficient, and a self-aligning torque coefficient associated with an electric power steering system model using a particle swarm optimization method;
a third module configured to determine whether the parameters satisfy a fitness criterion, and when the parameters do satisfy the fitness criterion, the third module is further configured to determine a road surface friction coefficient based on at least one of the estimated parameters; and
a fourth module configured to control one or more vehicle features based on the road surface friction coefficient.

10. The system of claim 9 , further comprising a slip angle sensor configured to detect a slip angle, wherein the third module is configured to determine the road surface friction coefficient when the slip angle is less than a pre-determined value.

11. The system of claim 9 , wherein the estimated value chosen to base the determination of the road surface friction coefficient on is the self-aligning torque coefficient.

12. The system of claim 9 , further comprising a second module configured to calculate an electronic power steering system torque value using the electronic power steering system model, the estimated values, and one or more of the received signals; and wherein the third module is configured to compare the calculated electric power steering system torque value with a measured torque value to determine the fitness criterion.

13. The system of claim 9 , wherein the third module is further configured to determine an iteration count and wherein the fitness criterion is based on the iteration count.

14. The system of claim 9 , wherein the third module determines the road surface coefficient by selecting the road surface coefficient from a trained database.

15. The system of claim 9 , wherein the signals from the electric power steering system comprise a torsion bar angle and a total electric power steering delivered torque.

16. The system of claim 9 , wherein the signals from the inertial measurement unit comprise a yaw rate, a lateral speed, and a longitudinal speed.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Sabri Yadollah
• Zimmerman Simon E
• Si Yingmei
• Schweitzer Steven T
• Zhao Qingrong
• Zhang Qi
• Moshchuk Nikolai K

Classifications

• B60W2552/40

  Coefficient of friction · CPC title

• B60T2210/12

  Friction · CPC title

• B60T2260/02

  Active Steering, Steer-by-Wire · CPC title

• B60W40/114

  Yaw movement · CPC title

• B60W50/14

  Means for informing the driver, warning the driver or prompting a driver intervention · CPC title