Method, arrangement and system for estimating vehicle cornering stiffness

Patent metadata

Field	Value
Publication number	US-2016244068-A1
Application number	US-201615042683-A
Country	US
Kind code	A1
Filing date	Feb 12, 2016
Priority date	Feb 20, 2015
Publication date	Aug 25, 2016
Grant date	—

Abstract

A method, arrangement and system are described for estimating one or more vehicle cornering stiffness parameters (c f , c r ) in a linear vehicle operating region. The method includes reading sensor data representative of at least vehicle ( 1 ) longitudinal velocity (v x ), vehicle lateral acceleration (a y ), vehicle yaw rate (ω z ) and vehicle steering angle (δ), determining from the read sensor data if the cornering stiffness parameters (c f , c r ) are observable, and if so providing an estimate of the cornering stiffness parameters (c f , c r ) using a bicycle model that includes a model of tire relaxation dynamics.

First claim

What is claimed is:

1 . A method for estimating one or more vehicle cornering stiffness parameters in a linear operating region of a vehicle, the method comprising:
reading sensor data representative of at least a vehicle longitudinal velocity, a vehicle lateral acceleration, a vehicle yaw rate and a vehicle steering angle; determining from the sensor data read if vehicle cornering stiffness parameters are observable; and if so, generating a cornering stiffness parameter signal based on an estimate of the cornering stiffness parameters provided using a bicycle model that includes a model of tire relaxation dynamics.

2 . The method according to claim 1 wherein determining cornering stiffness parameter observability further comprises:
determining if the vehicle longitudinal velocity exceeds a minimum threshold;
determining if the vehicle lateral acceleration is below a maximum threshold;
determining if the vehicle yaw rate exceeds a minimum threshold; and
determining if the vehicle steering angle exceeds a minimum threshold.

3 . The method according to claim 1 wherein providing an estimate of the cornering stiffness parameters further comprises formulating and solving a weighted linear least squares problem using a standard recursive least squares approach.

4 . The method according to claim 3 wherein the weighted linear least squares problem, in order to involve the cornering stiffness parameters and tire relaxation dynamics, is formulated based on a description of a lateral motion of the vehicle that includes a relation between a slip angle and a lateral tire force at the center of a tire and a slip angle and a lateral tire force at the point of contact between a tire and a road surface.

5 . The method according to claim 4 wherein the description of the vehicle lateral motion includes a first order filter model for the relation between the slip angle and the lateral tire force at the center of a tire and the slip angle and the lateral tire force at the point of contact between the tire and the road surface according to
α f t =H ( s )α f

α r t =H ( s )α r

where

H


(
s
)

=

1

1
+

s



τ

and the notation with an exponent or superscript t, (term) t , indicates that the term is expressed in a tire coordinate system.

6 . The method according to claim 3 wherein the description of the lateral motion of the vehicle is defined as

c
f



H


(
s
)



(

δ
-

ω
z



l
f

+

l
r

v
x

)

+

c
f



(

ml
f



a
y

-

I
z



ω
.

z

)

c
r



(

l
f

+

l
r

)

=

ml
r



a
y

+

I
z



ω
.

z

l
f

+

l
r

where c f is the front cornering stiffness parameter; c r is the rear cornering stiffness parameter; ω z is the vehicle yaw rate; {dot over (ω)} z is the vehicle yaw acceleration; δ is the vehicle steering wheel angle; l f is the distance between a vehicle center of gravity and the front axle; l r is the distance between the vehicle center of gravity and the rear axle; I z is the vehicle yaw moment of inertia; m is the mass of the vehicle; v x is a longitudinal velocity of the vehicle; and a y is a lateral acceleration of the vehicle at the vehicle center of gravity.

7 . The method according to claim 1 wherein the weighted linear least squares problem is formulated to provide an estimation of both the front cornering stiffness and the rear cornering stiffness of the vehicle.

8

Assignees

• Volvo Car Corp

Inventors

• Thor Mikael
• Gustafsson Tony

Classifications

• B60W2520/125

  Lateral acceleration · CPC title

• B60W40/101 Primary

  Side slip angle of tyre · CPC title

• B60W2510/20

  Steering systems · CPC title

• B60W2520/10

  Longitudinal speed · CPC title

• B60W2520/14

  Yaw · CPC title