Method and system for determining an optimal steering angle in understeer situations in a vehicle

• US 8,244,435 B2
• Filed: 04/26/2007
• Issued: 08/14/2012
• Est. Priority Date: 04/27/2006
• Status: Expired due to Fees

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Inventors: Lauer, Peter, Raste, Thomas
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US12/296,136
• Publication Number:
  US 20090319128A1
• Time in Patent Office: 1,937 Days
• Field of Search: 701 41- 42, 180/6.2, 342/71, 475 18- 19
• US Class Current: 701/42
• CPC Class Codes: B60W 30/045 Improving turning performance
• CPC Class Codes: B60W 50/16 Tactile feedback to the driver, e.g. vibration or force feedback to the driver on the steering wheel or the accelerator pedal
• CPC Class Codes: B62D 6/003 in order to control vehicle yaw movement, i.e. around a vertical axis B62D6/007 takes precedence
• CPC Class Codes: B62D 6/006 using a measured or estimated road friction coefficient
• CPC Class Codes: B62D 6/008 Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A method for determining an optimal steering angle in understeer situations of a vehicle is described. To assist a driver in reliably stabilizing the vehicle during an understeer situation while driving, a model-based driving traction coefficient factor, a model-based kinematic factor, and a float angle are taken into account in the determination of a steering angle. A limited steering angle δ_v,lim at which a maximum lateral force is set, is determined by addition of the driving traction coefficient factor, the kinematic factor, and the float angle. A system suitable for implementation of the method is also described.

Claims

1. A method for determining an optimum steering angle (δ

_v,lim) in understeering situations of a vehicle comprising the steps of;

(a) accounting for a first portion which represents an adhesion coefficient in a lateral direction;

(b) accounting for a second portion which represents a kinematic portion;

(c) accounting for a third portion which represents an attitude angle by estimating the attitude angle during the understeering according to a relationship β

≈

0, wherein β

is defined as the attitude angle; and

(d) adding the portion of the adhesion coefficient, the kinematic portion and the attitude angle to calculate the steering angle (δ

_v,lim).

2. A method for determining an optimum steering angle (δ

_v,lim) in understeering situations of a vehicle comprising the steps of;

(a) accounting for a first portion which represents an adhesion coefficient in a lateral direction by accounting for a coefficient of friction of an underlying surface (μ

^₀) that is defined by the equation μ

^₀=max(μ

_va, μ

_CoG, μ

_HA), wherein μ

_va represents the adhesion for a front axle of the vehicle and is defined by the equation

3. The method as claimed in claim 2, wherein the steering angle is determined by the equation:

4. A method for determining an optimum steering angle (δ

_v,lim) in understeering situations of a vehicle comprising the steps of;

(a) accounting for a first portion which represents an adhesion coefficient in a lateral direction;

(b) accounting for a second portion which represents a kinematic portion;

(c) accounting for a third portion which represents an attitude angle;

(d) adding the portion of the adhesion coefficient, the kinematic portion and the attitude angle to calculate the steering angle (δ

_v,lim); and

(e) using the steering angle δ

_v,lim or a steering angle δ

_v,lim which is multiplied by a factor k as a setpoint value for a steering angle control means or a steering torque control means.

5. The method as claimed in claim 4, wherein the steering torque control means is activated according to a relationship that is defined by the equation δ

_v,lim<

|δ

_v|, wherein δ

_v is defined as a wheel steering angle of a front axle of the vehicle.

6. The method as claimed in claim 4, wherein the steering torque control means is deactivated according to a relationship that is defined by the equation δ

_v,lim<

|δ

_v|, wherein δ

_v is defined as a wheel steering angle of a front axle of the vehicle.

7. A device for determining an optimum steering angle in understeer situations of a vehicle, comprising:

a determining unit configured to determine a stabilizing steering angle by accounting for a model-based portion of an adhesion coefficient, a model-based kinematic portion and an attitude angle; and

one of a steering angle control means or a steering torque control means configured to use the stabilizing steering angle or a stabilizing steering angle which is multiplied by a factor k as a setpoint value for controlling one of a steering angle or a steering torque, respectively.