TRACTION CONTROL SYSTEM OF VEHICLES COMBINING FEEDBACK CONTROL WITH FEEDFORWARD CONTROL

• US 20010003805A1
• Filed: 09/22/1998
• Published: 06/14/2001
• Est. Priority Date: 09/30/1997
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: KOIBUCHI, KEN
• Granted Patent: US 6,584,399 B2
• Time in Patent Office: Days
• US Class Current: 701/9
• 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 2240/06 Wheel load; Wheel lift
• 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 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2552/40 Coefficient of friction
• CPC Class Codes: B60W 2710/105 Output torque
• CPC Class Codes: F16H 63/50 Signals to an engine or motor

Abstract

A traction control system of a vehicle having a device for calculating a target traction torque of each of a pair of driving wheels based upon operating conditions of the vehicle, a device for calculating a target slip ratio of each of the pair of driving wheels based upon the target traction torque calculated therefor, and a device for controlling the engine and the brake system such that actual slip ratio of each of the pair of driving wheels coincides with the target slip ratio calculated therefor according to a feedback control, with a partial feedforward control of the engine and the brake system based upon the target traction torque.

Claims

1. A traction control system of a vehicle having a vehicle body, a plurality of wheels including at least one pair of driving wheels for suspending the vehicle body, an engine, a transmission for transmitting an output power of the engine to the driving wheels, a brake system for selectively braking rotation of at least the pair of driving wheels, and a steering system for steering the vehicle, the traction control system comprising:

means for calculating a target traction torque of each of the pair of driving wheels based upon operating conditions of the vehicle;

means for calculating a target slip ratio of each of the pair of driving wheels based upon the target traction torque calculated therefor, and

means for controlling the engine and the brake system such that actual slip ratio of each of the pair of driving wheels coincides with the target slip ratio calculated therefor according to a feedback control, with a partial feedforward control of the engine and the brake system based upon the target traction torque.

2. A traction control system according to

claim 1

, wherein the engine and brake system control means comprises:

means for calculating a feedback traction torque of each of the pair of driving wheels which will cancel a difference between the calculated slip ratio and the actual slip ratio of each of the pair of driving wheels;

means for calculating a sum of a value of the calculated target traction torque weighted with a feedforward control weighting factor and a value of the feedback traction torque weighted with a feedback control weighting factor with respect to each of the pair of driving wheels; and

means for controlling the engine to generate an output torque corresponding to the weighted sum of the target traction torque and the feedback traction torque with respect to each of the pair of driving wheels when the weighted sum is positive, while controlling the brake system to generate a braking torque at each of the pair of driving wheels corresponding to the weighted sum of the target traction torque and the feedback traction torque when said weighted sum is negative.

3. A traction control system according to

claim 2

, wherein the feedforward control weighting factor and the feedback control weighting factor are complementary to one another.

4. A traction control system according to

claim 2

, wherein the means for calculating the weighted sum of the feedforward traction torque and the feedback traction torque includes means for temporarily lowering the feedforward control weighting factor when the vehicle is running with an engine braking.

5. A traction control system according to

claim 2

, wherein the means for calculating the feedback traction torque comprises means for temporarily modifying the calculation of the feedback traction torque not to be dependent upon the target traction torque but to be dependent substantially upon vehicle speed when the vehicle is running with an engine braking.

6. A traction control system according to

claim 2

, wherein the means for calculating the feedback traction torque comprises means for temporarily modifying the calculation of the feedback traction torque not to be dependent upon the target traction torque but to be dependent substantially upon vehicle speed when a target slip ratio calculated based upon the target traction torque is larger than a predetermined threshold value.

7. A traction control system according to

claim 1

, wherein the target traction torque calculation means comprises:

means for calculating a yaw moment of the vehicle based upon steering angle of the steering system and vehicle speed;

means for equating the calculated yaw moment to a corresponding balance between a pair of traction forces of the pair of driving wheels;

means for equating a longitudinal acceleration of the vehicle to a corresponding sum of a pair of traction forces of the pair of driving wheels; and

means for deducing the values of the pair of traction forces from the above two relationships with regard to the yaw moment and the longitudinal acceleration.

8. A traction control system according to

claim 7

, wherein the target traction torque calculation means further comprises:

means for calculating a friction circle of each of the pair of driving wheels; and

means for trimming each of the deduced values of the pair of traction forces to be within each corresponding one of the friction circles calculated therefor.

9. A traction control system according to

claim 8

, wherein the friction circle calculation means comprises:

means for calculating each of longitudinal forces acting at the pair of driving wheels as a sum of a corresponding share of a force accelerating the vehicle at a longitudinal acceleration thereof, a force exerted thereto by the brake system, and a force for acceleration of rotation thereof against the inertia thereof;

means for calculating a longitudinal force acting at each of the pair of driving wheels as a sum of a corresponding share of a longitudinal force corresponding to an output torque of the torque converter calculated based upon rotation speed of the engine, a force exerted thereto by the brake system, and a force for acceleration of rotation thereof against the inertia thereof;

means for calculating each of ground contact forces acting at all of the wheels based upon longitudinal acceleration of the vehicle and lateral acceleration of the vehicle;

means for calculating each of ground contact forces acting at all of the wheels based upon longitudinal acceleration of the vehicle and lateral acceleration of the vehicle;

means for calculating slip angle of the vehicle body based upon lateral acceleration of the vehicle, vehicle speed and yaw rate;

means for calculating each of cornering forces of the pair of driving wheels based upon vehicle speed, a time based differential of the calculated slip angle of the vehicle, yaw rate and a time based differential thereof of the vehicle, and the ground contact forces calculated for all of the wheels; and

means for calculating a root of a sum of a square of the longitudinal force and a square of the cornering force with respect to each of the pair of driving wheels.

10. A traction control system according to

claim 9

, wherein the means for calculating the longitudinal forces acting at each of the pair of driving wheels cancels the longitudinal force based upon the output torque of the torque converter when the transmission is being shifted between speed stages.

11. A traction control system according to

claim 8

, wherein the friction circle calculation means further comprises means for judging if wheel speed of each of the pair of driving wheels is larger than vehicle speed beyond a first predetermined difference over a predetermined duration;

and

means for decreasing the radius of the friction circle of the corresponding wheel when the answer of the judgment is yes.

12. A traction control system according to

claim 11

, wherein the friction circle calculation means further comprises means for judging if wheel speed of each of the pair of driving wheels is larger than vehicle speed beyond a second predetermined difference larger than the first predetermined difference;

and

means for decreasing the radius of the friction circle of the corresponding wheel when the answer of the judgment id yes.

13. A traction control system according to

claim 11

, wherein the friction circle calculation means further comprises means for regaining the radius of the friction circle of the corresponding wheel when the answer of the judgment is no up to a standard friction circle radius.