Method of sensing excessive slip in a wheel slip control system

• US 5,315,519 A
• Filed: 10/03/1991
• Issued: 05/24/1994
• Est. Priority Date: 10/03/1991
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Chin, Yuen-Kwok, Ghoneim, Youssef A.
• Primary Examiner(s): Chin, Gary
• Assistant Examiner(s): DAY, JULIE
• Application Number:
  US07/770,269
• Time in Patent Office: 964 Days
• Field of Search: 364/426.02, 364/426.01, 364/426.03, 180/147, 303/100, 303/110, 303/105, 303/112, 303/103, 303/95, 303/97, 303/93
• US Class Current: 701/72
• 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 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• 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: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/48 connecting the brake actuator to an alternative or additional source of fluid pressure , e.g. traction control systems

Abstract

The onset of an excessive slip condition in a slip controller is determined so that it is adaptable to the actual drive torque conditions between the driven wheel and the road surface so as to achieve the desired acceleration or braking characteristics for all vehicle driving conditions including while the vehicle is traveling on a curved road surface. At low vehicle speeds, slip control is enabled when the value of a predetermined function of the difference in speeds of the driven and undriven wheels exceeds a threshold that is a function of the vehicle turn radius and at high vehicle speeds when the value of a predetermined function of a wheel slip ratio exceeds the threshold that is a function of the vehicle turn radius. The vehicle speed below which slip control is enabled based on a wheel speed function and above which traction control is enabled based on the wheel slip function increases with an increasing vehicle steering angle.

Claims

1. A method of controlling slip between a wheel of a vehicle and a road surface, the method comprising the steps of:

sensing wheel speed;

sensing vehicle speed;

sensing vehicle turn radius;

determining a wheel speed index value that is a predetermined function of the difference between the sensed wheel speed and the sensed vehicle speed;

determining a wheel slip index value that is a predetermined function of the ratio of the sensed vehicle speed and the sensed wheel speed;

determining a speed enable threshold that is a predetermined function of the sensed vehicle turn radius;

determining a slip enable threshold that is a predetermined function of the sensed vehicle turn radius; and

controlling wheel slip (A) when the sensed vehicle speed is less than a vehicle speed threshold and the wheel speed index value is greater than the speed enable threshold and (B) when the sensed vehicle speed is greater than the vehicle speed threshold and the wheel slip index is greater than the slip enable threshold.

2. The method of claim 1 wherein the vehicle speed threshold is a predetermined function of the vehicle turn radius.

3. A method of controlling slip between a wheel of a vehicle and a road surface, the method comprising the steps of:

sensing wheel speed ω

_d ;

sensing vehicle speed ω

_u ;

sensing vehicle turn radius α

;

determining a wheel speed index value S.sub.ω

du in accord with the expression (C.sub.ω

du *ω

_du)+ω

_du, where C.sub.ω

du is a calibration constant, ω

_du is the difference between ω

_d and ω

_u, and ω

_du is the rate of change in ω

_du ;

determining a wheel slip index value S.sub.λ

du in accord with the expression (C.sub.λ

du *λ

_du)+λ

_du, where C.sub.λ

du is a calibration constant, λ

_du is equal to 1-(ω

_u /ω

_d), and λ

_du is the rate of change in λ

_du ;

determining a speed enable threshold that is a predetermined function of α

;

determining a slip enable threshold that is a predetermined function of α

;

determining a vehicle speed threshold that is a predetermined function of α

; and

controlling wheel slip (A) when the sensed vehicle speed is less than a vehicle speed threshold and S.sub.ω

du is greater than the speed enable threshold and (B) when the sensed vehicle speed is greater than the vehicle speed threshold and λ

_du is greater than the slip enable threshold.

4. A traction control method for a vehicle having left and right side driven wheels, left and right side undriven wheels, and an engine for applying driving torque to the left and right side driven wheels, the method comprising, for each right and left side of the vehicle, the steps of:

determining the driven wheel speed ω

_u ;

determining the undriven wheel speed ω

_d ;

determining vehicle speed V;

determining vehicle turn radius α

;

determining a difference speed ω

_du between the determined wheel speeds ω

_u and ω

_d ;

determining a wheel speed index value S.sub.ω

du that is a predetermined function of the difference speed ω

_du ;

determining a wheel slip index value S.sub.λ

du that is a predetermined function of the ratio of the wheel speeds ω

_u and ω

_d ;

determining a speed enable threshold that is a predetermined function of the determined vehicle turn radius α

;

determining a slip enable threshold that is a predetermined function of the determined vehicle turn radius α

; and

limiting the applied driving torque to the driven wheel to limit acceleration slip (A) when the determined vehicle speed V is less than a vehicle speed threshold and the wheel speed index value S.sub.ω

du is greater than the speed enable threshold and (B) when the sensed vehicle speed is greater than the vehicle speed threshold and the wheel slip index value S.sub.λ

d is greater than the slip enable threshold.

5. The method of claim 4 wherein the vehicle speed threshold is a predetermined function of the determined vehicle turn radius α

.

6. The method of claim 5 wherein the predetermined function of the difference speed is defined by the expression (C.sub.ω

du *ω

_du)+ω

_du, where C.sub.ω

du is a calibration constant and ω

_du is the rate of change in ω

_du, and the predetermined function of the ratio of the wheel speeds ω

_u and ω

_d is defined by the expression (C.sub.λ

du *λ

_du)+λ

_du, where C.sub.λ

du is a calibration constant, λ

_du is equal to 1-(ω

_u /ω

_d), and λ

_du is the rate of change in λ

_du.