Process for determining ideal vehicular performance

• US 6,233,505 B1
• Filed: 07/23/1999
• Issued: 05/15/2001
• Est. Priority Date: 05/02/1996
• Status: Expired due to Fees

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Original Assignee: Continental Teves AG & Co. OHG (Continental AG)
• Inventors: Endress, Ralf, Wanke, Peter, Kranz, Thomas, Duis, Holger
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/180,082
• Time in Patent Office: 662 Days
• Field of Search: 701/1, 701/69, 701/72, 701/73, 701/74, 701/83, 701/84, 701/89, 701/92, 303/143, 303/144, 303/148, 303/149, 303/154, 180/197
• US Class Current: 701/1
• CPC Class Codes: B60T 2230/02 Side slip angle, attitude angle, floating angle, drift angle
• CPC Class Codes: B60T 2270/86 Optimizing braking by using ESP vehicle or tire model
• CPC Class Codes: B60T 8/17551 determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters
• CPC Class Codes: B60T 8/17552 responsive to the tire sideslip angle or the vehicle body slip angle

Abstract

In order to adapt a simplified vehicle model to the driving behavior of a real automotive vehicle, it is possible to modify the slip rigidity values assumed to be constant in a linear model. After departure from the linear range of the lateral-force/slip-angle characteristic, a lower value can be assumed for the slip rigidities. However, this will involve the risk that the wheels of the rear axle are already in a slip angle range to which the lower slip rigidity is associated whereas the front wheels are still in the linear range of the lateral-force/slip-angle characteristic. This would impart to the vehicle model an oversteering behavior which should the more so be avoided if such a vehicle model is used for presetting the nominal value. This problem is solved, in the practice of the invention, by suggesting to modify only the slip rigidity values of the front axle while the ones of the rear axle are assumed to be constant.

Claims

1. A method of determining the nominal driving behavior of a two-axle vehicle during control of the two-axle vehicle in a curve, comprising the steps of:

monitoring slip angle,

if slip angle increases, continually reducing slip rigidity values C_L only of the wheels of the front axle so that the slope of the lateral-force/side-slip-angle characteristic assumes a smaller value C_NL wherein, once the lateral-force/side-slip-angle characteristic approaches a peak value, reducing the slip rigidity values with a growing slip angle continually such that the slope of the lateral-force/side-slip-angle characteristic is approximately zero, wherein the reduction toward a reduced slope and toward a zero slope of the lateral-force/side-slip-angle characteristic is effected once a first and a second predetermined threshold value, respectively, of a variable correlating with the slip angle is exceeded, wherein the predetermined threshold values are dependent on a calculated road friction coefficient, which is the greater the higher the road friction coefficient is, wherein the first threshold value for reduction of the slip rigidities C_L toward the smaller value C_NL of the slope is a predetermined slip angle α

_1/μ

and directly proportional to the road friction coefficient μ

.

2. A method according to claim 1, wherein the predetermined slip angle α

_1/μ

for reduction of the slip rigidities toward the smaller value C_NL of the slope is computed in accordance with equation α

_1/μ

=k₁*μ

, with k₁ being a constant value determined in a vehicle-specific way.

3. A method according to claim 1, wherein the second threshold value for reduction of the slip rigidities C_L toward a zero slope is a predetermined slip angle α

_2/μ

and has the following correlation to the friction coefficient μ

;

4. A method of determining the nominal driving behavior of a two-axle vehicle during control of the two-axle vehicle in a curve, comprising the steps of:

monitoring slip angle,

if slip angle increases, continually reducing slip rigidity values C_L only of the wheels of the front axle so that the slope of the lateral-force/side-slip-angle characteristic assumes a smaller value C_NL, wherein, once the lateral-force/side-slip-angle characteristic approaches a peak value, reducing the slip rigidity values with a growing slip angle continually such that the slope of the lateral-force/side-slip-angle characteristic is approximately zero, wherein the reduction toward a reduced slope and toward a zero slope of the lateral-force/side-slip-angle characteristic is effected once a first and a second predetermined threshold value, respectively, of a variable correlating with the slip angle is exceeded, wherein the predetermined threshold values are dependent on a calculated road friction coefficient, which is the greater the higher the road friction coefficient is, wherein the second threshold value for reduction of the slip rigidities C_L toward a zero slope is a predetermined slip angle α

_2/μ

and has the following correlation to the friction coefficient μ

;