Active driven wheel lift identification for an automotive vehicle

• US 20040167701A1
• Filed: 02/26/2004
• Published: 08/26/2004
• Est. Priority Date: 02/26/2003
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Brewer, Michael Edward, Meyers, Joseph Carr, Brown, Todd Allen, Mattson, Keith Glenn
• Granted Patent: US 7,653,471 B2
• Time in Patent Office: Days
• US Class Current: 701/71
• CPC Class Codes: B60G 17/0162 mainly during a motion involving steering operation, e.g. cornering, overtaking B60G17/0164 takes precedence
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 2800/0194 transversal with regard to vehicle
• CPC Class Codes: B60G 2800/215 by applying a braking action on each wheel individually
• CPC Class Codes: B60G 2800/922 EBV - Electronic brake force distribution
• CPC Class Codes: B60R 2021/0018 Roll-over
• CPC Class Codes: B60R 2021/01327 Angular velocity or angular acceleration
• CPC Class Codes: B60R 21/0132 responsive to vehicle motion parameters , e.g. to vehicle longitudinal or transversal deceleration or speed value
• CPC Class Codes: B60T 2230/03 Overturn, rollover
• CPC Class Codes: B60T 2240/06 Wheel load; Wheel lift
• 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 8/17551 determining control parameters related to vehicle stability used in the regulation, e.g. by calculations involving measured or detected parameters
• CPC Class Codes: B60T 8/176 Brake regulation specially adapted to prevent excessive wheel slip during vehicle deceleration, e.g. ABS B60T8/1755 takes precedence
• CPC Class Codes: B60T 8/1769 specially adapted for vehicles having more than one driven axle, e.g. four-wheel drive vehicles
• CPC Class Codes: B60T 8/243 for roll-over protection

Abstract

A roll control system (16) for an automotive vehicle (10) is used to actively detect if one of the plurality of the driven wheels (12) is lifted. The system generates a pressure request to determine if the wheel has lifted. By comparing the change in wheel speed of a driven wheel to a change in wheel speed threshold the wheel lift status can be determined. The wheel speed change threshold may be dependent upon various vehicle operating conditions such as powertrain torque, braking torque and/or longitudinal force on the vehicle.

Claims

1. A method for determining wheel lift of a vehicle comprising:

determining a wheel departure angle;

determining a driveshaft torque;

when the wheel departure angle is greater than a wheel departure threshold and the driveshaft torque is less than a driveshaft torque threshold, performing an active wheel lift determination on a wheel; and

when the wheel departure angle is less than a wheel departure threshold and the driveshaft torque is greater than a driveshaft torque threshold, suppressing an active wheel lift on a wheel.

2. A method as recited in claim 1 wherein the drive shaft threshold is a function of engine torque.

3. A method as recited in claim 1 wherein the wheel departure angle comprises an absolute value of the wheel departure angle.

4. A method as recited in claim 1 wherein the wheel departure threshold is about 1 degree.

5. A method as recited in claim 1 wherein the drive shaft torque threshold is about 100 Nm.

6. A method of operating a vehicle comprising:

determining a predetermined condition;

in response to the predetermined condition entering a wheel lift determination;

continuing the wheel lift determination when a wheel lift suspected flag is true, a lifted status is true or a transient flag is false.

7. A method as recited in claim 6 wherein the predetermined condition comprises vehicle speed above a deactivation threshold.

8. A method as recited in claim 6 further setting said transient flag to true when a driveshaft torque is above a torque threshold and exiting a wheel lift determination.

9. A method as recited in claim 6 further comprising exiting the wheel lift determination when the transient flag is true.

10. A method as recited in claim 6 staying in, or continuing the wheel lift determination when the lifted status flag is true.

11. A method of determining a wheel lift status of a wheel comprising:

generating a predicted angular acceleration of a wheel;

measuring a wheel speed of the vehicle;

determining an actual acceleration in response to the wheel speed; and

determining a lifted condition by comparing the predicted angular acceleration and the wheel speed based acceleration.

12. A method as recited in claim 11 wherein generating a predicted angular acceleration of a wheel comprises generating a predicted angular acceleration of a wheel as a function of brake torque

13. A method as recited in claim 11 wherein generating a predicted angular acceleration of a wheel comprises generating a predicted angular acceleration of a wheel as a function of powertrain torque.

14. A method as recited in claim 11 wherein generating a predicted angular acceleration of a wheel comprises generating a predicted angular acceleration of a wheel as a function of longitudinal force on a tire.

15. A method as recited in claim 11 wherein brake torque is determined in response to a caliper pressure and a brake torque gain coefficient.

16. A method as recited in claim 11 wherein powertrain torque comprises a driveshaft torque.

17. A method as recited in claim 16 wherein said driveshaft torque comprises is a function of rear axle torque a rear axle ratio.

18. A method as recited in claim 16 wherein the rear axle torque is a function of estimated engine torque and torque converter gain.

19. A method as recited in claim 16 wherein the rear axle torque is a function of estimated engine torque, torque converter gain, transmission gear ration and rear axle ratio.

20. A method as recited in claim 11 wherein the longitudinal force is a function of a normal force and a coefficient of friction.

21. A method as recited in claim 11 wherein measuring wheel speed comprises measuring wheel speed from a wheel speed sensor.

22. A method as recited in claim 11 wherein generating a predicted angular acceleration comprises generating a predicted angular acceleration for a grounded wheel and a predicted angular acceleration for a lifted wheel and wherein the step of comparing comprises comparing the actual acceleration to the predicted angular acceleration for a grounded wheel and a predicted angular acceleration for a lifted wheel.

23. A method as recited in claim 11 wherein when the actual acceleration is greater than the predicted angular acceleration for the grounded wheel, generating a ground wheel signal.

24. A method as recited in claim 11 wherein when the actual acceleration is less than the predicted angular acceleration for the lifted wheel, generating a lifted wheel signal.

25. A method of controlling a vehicle comprising:

determining a predicted change in wheel speed;

measuring an actual change in wheel speed of the vehicle; and

determining a lifted condition by comparing the predicted change in wheel speed and the actual change in wheel speed.

26. A method as recited in claim 25 wherein the predicted change in wheel speed is a function of a predicted acceleration, time and a slip ratio.

27. A method as recited in claim 25 wherein the predicted acceleration is determined in response to a plurality of predicted accelerations.

28. A method as recited in claim 25 further comprising determining a build cycle or a release cycle, changing the predicted change in wheel speed by an offset factor in response to the build cycle or release cycle.

29. A method as recited in claim 25 wherein the offset factor is a function of low gear.

30. A method as recited in claim 25 wherein the offset factor is a function of throttle position.

31. A method as recited in claim 25 wherein the offset factor is a function of positive toque.

32. A method as recited in claim 25 wherein the offset factor is a function of a small negative slip.

33. A method as recited in claim 25 further comprising determining a build cycle or a release cycle, changing the predicted change in wheel speed by a gain factor in response to the build cycle or release cycle.

34. A method as recited in claim 25 wherein the predicted change is for a pair of wheels on one side of the vehicle.

35. A method of controlling a vehicle having wheels comprising:

determining a 4×

4 drive mode;

performing active driven wheel lift detection in response to the 4×

4 drive mode by collectively determining a lifted or non-lifted status for a pair of wheels on either side of the vehicle.

36. A method as recited in claim 35 wherein when the drive mode comprises a two wheel high mode, performing wheel lift detection is performed from a front wheel using a non-driven active wheel lift method.

37. A method of controlling a vehicle having a plurality of wheels comprising:

assigning each wheel of the plurality of wheels a driven status or non-driven status;

performing active driven wheel lift on driven wheels;

performing non-driven active lift on non-driven wheels;

determining a wheel lift status for each wheel in response to the steps of performing active driven wheel lift and performing non-driven wheel lift.

38. A method as recited in claim 37 wherein determining a wheel lift status comprises determining absolutely grounded status, absolutely lifted status, possibly grounded status and possibly lifted status.

39. A method as recited in claim 37 wherein performing active driven wheel lift comprises initiating a build cycle;

and after the build cycle, initiating a release cycle.

40. A method as recited in claim 39 further comprising exiting a build cycle when a wheel speed is less than a speed threshold.

41. A method as recited in claim 39 further comprising exiting a build cycle when wheel slip is less than −

20%.

42. A method as recited in claim 39 further comprising exiting a build cycle when driver is braking.

43. A method as recited in claim 39 wherein during the release cycle, generating a predicted angular acceleration of a wheel;

measuring a wheel speed of the vehicle;

determining an actual acceleration in response to the wheel speed; and

determining a lifted condition by comparing the predicted angular acceleration and the wheel speed based acceleration.

44. A method as recited in claim 43 wherein the predicted change in wheel speed is a function of a predicted acceleration, time and a slip ratio.

45. A method as recited in claim 44 wherein the predicted acceleration is determined in response to a plurality of predicted accelerations.

46. A method as recited in claim 37 wherein performing active non-driven wheel lift comprises initiating a build cycle;

and after the build cycle, initiating a release cycle.

47. A method as recited in claim 37 wherein assigning a drive mode comprises assigning a drive mode in response to vehicle configuration.

48. A method as recited in claim 37 further comprising reassigning a wheel having a non-driven status to a driven status in response to driver braking.

49. A method as recited in claim 37 further comprising reassigning the wheel having the driven status to the non-driven status upon release of driver braking.

50. A method as recited in claim 37 wherein prior to assigning, disengaging a differential.

51. A method as recited in claim 37 wherein prior to assigning, requesting an engine torque reduction when the driveshaft toque is above a threshold.

52. A method as recited in claim 37 wherein during the step of performing active driven wheel lift, exiting active driven wheel lift when the driveshaft torque is above a driveshaft torque threshold.