Vehicle traction control system

• US 5,009,294 A
• Filed: 01/19/1990
• Issued: 04/23/1991
• Est. Priority Date: 01/19/1990
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Ghoneim, Youssef A.
• Primary Examiner(s): Bonck, Rodney H.
• Application Number:
  US07/467,436
• Time in Patent Office: 459 Days
• Field of Search: 192/1.22, 192/1.23, 192/1.24, 364/426.03, 180/197
• US Class Current: 477/185
• 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 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 vehicle traction control system includes both driven wheel brake control and engine torque output control for limiting acceleration wheel slip. A boundary condition is identified where engine torque output control alone can be used without braking to regulate the acceleration wheel slip to any desired value. When the traction control system determines that the boundary condition is not exceeded such that engine torque output control alone is capable of preventing an excessive slip condition, only engine torque is controlled to limit wheel slip. However, when the system determines the boundary condition is such that engine torque output control alone will not prevent an excessive slip condition, the brakes of the slipping wheel is then additionally controlled to limit acceleration wheel spin.

Claims

1. A traction control method for a vehicle having an engine for applying a driving torque to a driven wheel and having a brake for braking the driven wheel, the method comprising the steps of:

determining a wheel slip condition of the driven wheel;

controlling the driving torque applied to the driven wheel by the engine, when the determined wheel slip condition represents an excessive acceleration wheel slip condition, in direction to limit wheel slip to a desired slip value λ

^* ;

determining a condition where using only the step of controlling the driving torque would be incapable of preventing a trajectory of wheel slip from exceeding a predetermined maximum allowable slip value λ

_x ; and

controlling the brake for braking the driven wheel when it is determined that the step of controlling the driving torque would be incapable of preventing the trajectory of wheel slip from exceeding the predetermined maximum value λ

_x.

2. The traction control method of claim 1 wherein the step of controlling the brake controls the brake in direction to limit wheel slip to the desired value λ

^*.

3. The traction control method of claim 2 wherein the step of determining a condition where using only the step of controlling the driving torque would be incapable of preventing the trajectory of wheel slip from exceeding a predetermined maximum allowable slip value λ

_x includes;

determining wheel slip λ

_n ;

determining slip error Δ

λ

_n in accord with the expression Δ

λ

_n =λ

_n -λ

^* ; and

determining a rate of change Δ

λ

in the determined slip error Δ

λ

_n,

the condition where using only the step of controlling the driving torque would be incapable of preventing the trajectory of wheel slip from exceeding a predetermined maximum allowable slip value λ

_x being represented by the determined rate of change Δ

λ

in the determined slip error exceeding a predetermined threshold value Δ

λ

_Th.

4. The traction control method of claim 1 wherein the step of determining a condition where using only the step of controlling the driving torque would be incapable of preventing the trajectory of wheel slip from exceeding a predetermined maximum allowable slip value λ

_x includes;

determining wheel slip λ

_n ;

determining the rate of change λ

in the determined wheel slip λ

_n,

the condition where using only the step of controlling the driving torque would be incapable of preventing the trajectory of wheel slip from exceeding a predetermined maximum allowable slip value λ

_x being represented by the determined rate of change λ

exceeding a predetermined threshold value λ

_m.