Traction control algorithm for vehicle operation upon deformable road surfaces

• US 20040098188A1
• Filed: 01/06/2003
• Published: 05/20/2004
• Est. Priority Date: 07/06/2000
• Status: Active Grant

• Current Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Priemer, Douglas J., Dumm, Bernard W.
• Granted Patent: US 6,882,921 B2
• Time in Patent Office: Days
• US Class Current: 701/82
• CPC Class Codes: B60K 28/16 responsive to, or preventing, skidding of wheels brake control systems for vehicle drive stability B60T8/1755; arrangements responsive to a speed condition for adjusting wheel braking force B60T8/32; control of vehicle driving stability otherwise than by controlling the propulsion unit only B60W30/02; preventing wheel slippage by reducing power in rail vehicles B61C15/00
• CPC Class Codes: B60T 2270/211 Setting or adjusting start-control threshold
• 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
• CPC Class Codes: B60W 2552/00 Input parameters relating to infrastructure
• CPC Class Codes: B60W 40/06 Road conditions

Abstract

A vehicle traction control system is actuated when driven wheel slip (S_l) exceeds a predetermined slip threshold (T_s) to reduce the amount of driven wheel slip (S_l) by reducing the driven wheel speed. The traction control system also monitors vehicle deceleration. Upon detecting that the vehicle is decelerating and that the vehicle deceleration has exceed a deceleration threshold, the traction control system determines that the vehicle has encountered a deformable surface such as mud or deep snow. Upon detecting entry onto a deformable surface, the slip threshold (T_s) is linearly increased over a period of time to increase the driven wheel speed and thereby allow the wheels to churn through the deformable surface.

Claims

1. A traction control system for a vehicle comprising:

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a controller electrically connected to said wheel speed sensors, said controller operative to monitor said wheel speed signals and to calculate a wheel slip for each of said driven wheels and a vehicle deceleration, said controller also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said controller further operative while said driven wheel slip exceeds said slip threshold to monitor said vehicle deceleration and to generate a deformable surface signal upon said deceleration exceeding a predetermined deceleration threshold.

2. A traction control system according to claim 1 wherein said controller is further operable upon generating said deformable surface signal to increase said slip threshold.

3. A traction control system for a vehicle comprising:

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a microprocessor electrically connected to said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels and a vehicle deceleration, said microprocessor also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said microprocessor further operative to monitor said vehicle deceleration and to increase said slip threshold upon said vehicle deceleration exceeding a predetermined deceleration threshold.

4. A traction control system according to claim 3 wherein said slip threshold is increased as a function of time.

5. A traction control system according to claim 4 further including a maximum limit for said slip threshold whereby said slip threshold is increased to a maximum slip threshold limit and then held at said maximum slip threshold limit.

6. A traction control system according to claim 5 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=K_S*f(SANDCNT);

where Δ

T_s=said slip threshold increment;

K_S is a constant to scale the maximum value for the incremental increase Δ

T_s; and

SANDCNT=current value of an iteration counter.

7. A traction control system according to claim 6 wherein said microprocessor is operative upon said vehicle deceleration failing below said deceleration threshold to reduce said slip threshold back to an initial slip threshold.

8. A traction control system for a vehicle comprising:

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a microprocessor electrically connected to said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels and a vehicle deceleration, said microprocessor also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said microprocessor further operative while said driven wheel slip exceeds said slip threshold to monitor said vehicle deceleration and to increase said slip threshold upon said vehicle deceleration exceeding a predetermined deceleration threshold.

9. A traction control system according to claim 8 wherein said slip threshold is increased as a function of time.

10. A traction control system according to claim 9 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=K_S*f(SANDCNT);

where Δ

T_s=said slip threshold increment;

K_S is a constant to scale the maximum value for the incremental increase Δ

T_s; and

SANDCNT=current value of an iteration counter.

11. A traction control system according to claim 10 wherein said microprocessor is operative upon said driven wheel slip falling below said slip threshold and said vehicle deceleration falling below said predetermined deceleration threshold to reduce said slip threshold back to an initial slip threshold.

12. A traction control system for a vehicle comprising:

a torque requirement sensor adapted to sense a torque requirement of a vehicle engine;

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a microprocessor electrically connected to said torque requirement sensor and said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels and a vehicle deceleration, said microprocessor also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said microprocessor further operative to monitor said vehicle deceleration and torque requirement and to increase said slip threshold upon said vehicle deceleration exceeding a predetermined deceleration threshold and said torque requirement exceeding a predetermined torque threshold.

13. A traction control system according to claim 12 wherein said slip threshold is increased as a function of time.

14. A traction control system according to claim 13 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=K_S*f(SANDCNT);

where Δ

T_s=said slip threshold increment;

K_s is a constant to scale the maximum value for the incremental increase Δ

T_s; and

SANDCNT=current value of an iteration counter.

15. A traction control system according to claim 14 wherein said torque requirement is proportional to an engine throttle opening and further wherein said minimum torque threshold is proportional to a minimum engine throttle opening.

16. A traction control system according to claim 15 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=[KSANDMULT*(TPS−

MINTQR)*SANDCNT]/(256−

MNTPS);

where Δ

T_s=said slip threshold increment;

KSANDMULT=a constant to scale the maximum value for the incremental increase Δ

T_s;

TPS=actual throttle opening;

MINTQR=said predetermined minimum torque threshold; and

SANDCNT=current value of an iteration counter.

17. A traction control system according to claim 16 further including a maximum limit for said slip threshold whereby said slip threshold is increased by said slip threshold increment to a maximum slip threshold limit and then held at said maximum slip threshold limit.

18. A traction control system according to claim 17 wherein said microprocessor is operative upon said vehicle deceleration falling below said deceleration threshold to reduce said slip threshold back to an initial slip threshold.

19. A traction control system for a vehicle comprising:

a torque requirement sensor adapted to sense a torque requirement of a vehicle engine;

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a microprocessor electrically connected to said torque requirement sensor and said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels and a vehicle deceleration, said microprocessor also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said microprocessor further operative, while said driven wheel slip exceeds said slip threshold, to monitor said vehicle deceleration and torque requirement and to increase said slip threshold upon said vehicle deceleration exceeding a predetermined deceleration threshold and said torque requirement exceeding a predetermined torque threshold.

20. A traction control system according to claim 19 wherein said slip threshold is increased as a function of time.

21. A traction control system according to claim 20 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=K_S*f(SANDCNT);

where Δ

T_s=said incremental slip threshold increase;

Ks is a constant to scale the maximum value for the incremental increase Δ

T_s; and

SANDCNT=current value of an iteration counter.

22. A traction control system according to claim 21 wherein said slip threshold is increased by a slip threshold increment, said slip threshold increment being calculated in accordance with the formula:

Δ

T_s=[KSANDMULT*(TPS−

MINTQR)*SANDCNT]/(256−

MINTS);

where Δ

T_s=said incremental slip threshold increase;

KSANDMULT=a constant to scale the maximum value for the incremental increase Δ

T_s;

TPS=actual throttle opening;

MINTQR=said predetermined minimum torque threshold; and

SANDCNT=an iteration counter.

23. A traction control system in accordance with claim 22 wherein said deceleration threshold is a first deceleration threshold and further wherein said microprocessor is operative to calculate a lateral acceleration of the vehicle and, upon detecting a vehicle lateral acceleration in excess of a predetermined lateral acceleration threshold, to replace said first deceleration threshold with a second deceleration threshold, said second deceleration threshold being greater than said first deceleration threshold.

24. A traction control system in accordance with claim 23 further including a predetermined time delay which is actuated upon said vehicle deceleration exceeding said deceleration threshold and runs prior to any increase of said slip threshold.

25. A traction control system according to claim 24 wherein said microprocessor is operative upon said driven wheel slip falling below said slip threshold and said vehicle deceleration falling below said deceleration threshold to reduce said slip threshold.

26. A traction control system for a vehicle comprising:

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative to generate wheel speed signals; and

a microprocessor electrically connected to said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels, said microprocessor also operative, upon a driven wheel slip exceeding a slip threshold, to reduce said driven wheel slip below said slip threshold, said microprocessor further operative, while said driven wheel exceeds said slip threshold, to increase said slip threshold.

27. A traction control system according to claim 26 wherein said slip threshold is increased as a function of time.

28. A traction control system for a vehicle comprising:

a torque requirement sensor adapted to sense a torque requirement of a vehicle engine;

a plurality of wheel speed sensors adapted to sense the speed of associated vehicle wheels, said wheel speed sensors operative while said driven wheel exceeds said slip threshold to generate wheel speed signals; and

a microprocessor electrically connected to said torque requirement sensor and said wheel speed sensors, said microprocessor operative to monitor said wheel speed signals and calculate a wheel slip for each of said driven wheels, said microprocessor also operative upon a driven wheel slip exceeding a slip threshold to reduce said driven wheel slip below said slip threshold, said microprocessor further operative, while said driven wheel exceeds said slip threshold, to monitor said vehicle torque requirement and to increase said slip threshold upon said torque requirement exceeding a predetermined torque threshold.

29. A traction control system according to claim 28 wherein said slip threshold is increased as a function of time.

30. A traction control system according to claim 29 wherein said torque requirement is a function of a vehicle engine throttle opening.