Traction control system using estimated road surface friction coefficient

• US 5,353,225 A
• Filed: 06/21/1991
• Issued: 10/04/1994
• Est. Priority Date: 06/21/1990
• Status: Expired due to Fees

• Current Assignee: Mazda Motor Corporation
• Original Assignee: Mazda Motor Corporation
• Inventors: Kawamura, Makoto, Tsuyama, Toshiaki, Nobumoto, Kazutoshi, Onaka, Toru
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): PARK, COLLIN
• Application Number:
  US07/718,959
• Time in Patent Office: 1,201 Days
• Field of Search: 364/426.01, 364/426.02, 364/426.03, 180/197
• US Class Current: 701/83
• CPC Class Codes: B60T 2270/208 adapted to friction condition
• CPC Class Codes: B60T 8/175 Brake regulation specially adapted to prevent excessive wheel spin during vehicle acceleration, e.g. for traction control safety devices for propulsion unit control responsive to, or preventing, skidding of wheels B60K28/16

Abstract

A traction control system for a motor vehicle having driving wheels and driven wheels includes a device for detecting the speed of each of the driving wheels of the vehicle, a device for detecting the speed of each of the driven wheels of the vehicle, a device for calculating a slip value of the driving wheels based on the detected speeds of the driving and driven wheels, a traction control device for controlling the driving wheel so that the slip value of each driving wheel is equal to a predetermined desired slip value when the slip value of each driving wheel is greater than the predetermined desired slip value, and a device for estimating a friction coefficient of a road surface which is employed when the predetermined desired slip value is determined. If slip of the driving wheel occurs when the vehicle is started, the estimating device calculates an acceleration of the driving wheel. The friction coefficient of the road surface is estimated based on an engine output when the acceleration of the driving wheel is greater than a predetermined value.

Claims

1. A traction control system for a motor vehicle, having driving wheels and driven wheels, comprising:

means for detecting a speed of each of the driving wheels of the vehicle and calculating an acceleration of the driving wheels;

means for detecting a speed of each of the driven wheels of the vehicle and calculating an acceleration of the driven wheels;

means for detecting an engine output;

means for calculating a slip value of the driving wheels based on the speeds of the driving and driven wheels detected;

means for determining whether the vehicle is starting;

traction control means for controlling the driving wheels so that the slip value of the driving wheels is equal to a predetermined desired slip value when the slip value of the driving wheels is greater than a predetermined slip value for starting a traction control operation; and

means for estimating a friction coefficient of a road surface which is employed when the predetermined desired slip value is determined, said friction coefficient estimating means estimating the friction coefficient of the road surface based on the engine output only when the vehicle is starting and the acceleration of the driving wheels is greater than a predetermined value, said friction coefficient estimating means estimating the friction coefficient of the road surface based on the acceleration of the driven wheels after the vehicle has started.

2. A traction control system according to claim 1, wherein said traction control means controls the driving wheels by controlling engine output and braking force.

3. A traction control system according to claim 2, wherein a predetermined desired slip value for controlling the braking force is greater than that for controlling the engine output.

4. A traction control system according to claim 1, wherein said traction control means controls the driving wheels by controlling engine output.

5. A traction control system according to claim 1, wherein said traction control means controls the driving wheels by controlling braking force.

6. A traction control system according to claim 1, wherein said slip value of the driving wheels is defined as a difference between speeds of the driving and driven wheels.

7. A traction control system for a motor vehicle, having driving wheels and driven wheels, comprising:

means for detecting a speed of each of the driving wheels of the vehicle and calculating an acceleration of the driving wheels;

means for detecting a speed of each of the driven wheels of the vehicle and calculating an acceleration of the driven wheels;

means for detecting an engine output;

means for calculating a slip value of the driving wheels based on the speeds of the driving and driven wheels detected;

traction control means for controlling the driving wheels so that the slip value of the driving wheels is equal to a predetermined desired slip value when the slip value of the driving wheels is greater than a predetermined slip value for starting a traction control operation; and

means for estimating a friction coefficient of a road surface which is employed when the predetermined desired slip value is determined, said friction coefficient estimating means estimating the friction coefficient of the road surface based on the engine output only when the speeds of the driven wheels are not greater than a predetermined value and the acceleration of the driving wheels is greater than a predetermined value, said friction coefficient estimating means estimating the friction coefficient of the road surface based on the acceleration of the driven wheels when the speeds of the driven wheels are greater than the predetermined value.

8. A traction control system according to claim 7, wherein said traction control means controls the driving wheels by controlling engine output and braking force.

9. A traction control system according to claim 8, wherein a predetermined desired slip value for controlling the braking force is greater than that for controlling the engine output.

10. A traction control system according to claim 7, wherein said traction control means controls the driving wheels by controlling engine output.

11. A traction control system according to claim 7, wherein said traction control means controls the driving wheels by controlling braking force.

12. A traction control system according to claim 7, wherein said slip value of the driving wheels is defined as a difference between speeds of the driving and driven wheels.

13. A traction control system for a motor vehicle, having driving wheels and driven wheels, said vehicle having an auotmatic transmission with a torque converter by which an engine output is transmitted to the driving wheels, said system comprising:

means for detecting a speed of each of the driving wheels of the vehicle and calculating an acceleration of the driving wheels;

means for detecting a speed of each of the driven wheels of the vehicle;

means for detecting an engine speed;

means for calculating a slip value of the driving wheels based on the speeds of the driving and driven wheels detected;

traction control means for controlling the driving wheels so that the slip value of the driving wheels is equal to a predetermined desired slip value when the slip value of the driving wheels is greater than a predetermined slip value for starting a traction control operation; and

means for estimating a friction coefficient of a road surface which is employed when the predetermined desired slip value is determined, said friction coefficient estimating means estimating the friction coefficient of the road surface based on the engine speed only when the vehicle is starting and the acceleration of the driving wheels is greater than a predetermined value.

14. A traction control system according to claim 13, wherein said vehicle has an automatic transmission with a torque converter by which an engine output is transmitted to the driving wheels.