HYBRID ROAD GRADE DETERMINATION SYSTEM

• US 20070293994A1
• Filed: 10/26/2006
• Published: 12/20/2007
• Est. Priority Date: 06/20/2006
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Zerbini, Mark A., Tamai, Goro
• Granted Patent: US 8,620,498 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 2006/268 Electric drive motor starts the engine, i.e. used as starter motor
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60L 2240/486 Operating parameters
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 10/18 including control of braking systems
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2510/105 Output torque
• CPC Class Codes: B60W 2530/10 Weight
• CPC Class Codes: B60W 2530/20 Tyre data
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 40/072 Curvature of the road
• CPC Class Codes: B60W 40/076 Slope angle of the road
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A method of regulating operation of a hybrid vehicle traveling on a surface having a grade includes determining a drive force of the hybrid vehicle, calculating a brake pressure value and determining whether a grade freeze condition exists based on the brake pressure value. The method further includes calculating a grade value of the surface based on the drive force when the freeze condition does not exist and regulating operation of the hybrid vehicle based on the grade value.

Claims

1. A grade determination system for a hybrid electric vehicle that travels on a surface comprising:

a first module that determines a drive force of said hybrid vehicle;

a second module that determines whether a grade freeze condition exists based on a brake pressure value and that calculates a grade value of said surface based on said drive force when said freeze condition does not exist; and

a third module that regulates operation of said hybrid vehicle based on said grade value.

2. The grade determination system of claim 1 wherein said second module holds said grade value equal to a previous grade value when said freeze condition exits.

3. The grade determination system of claim 2 wherein operation of said hybrid vehicle is regulated based on said grade value upon expiration of a predetermined time period after said freeze condition transitions from existing to not existing.

4. The grade determination system of claim 1 wherein a brake on status is indicated when said brake pressure value exceeds a threshold value, wherein said grade freeze condition exists when said brake on status is indicated.

5. The grade determination system of claim 1 further comprising a fourth module that calculates a chassis braking force based on said brake pressure value and a vehicle speed, wherein said grade value is further determined based on said chassis braking force.

6. The grade determination system of claim 1 wherein said grade value is calculated as a tangent of a cosine of a quotient of a grade force and a product of a hybrid vehicle mass and a gravitational constant.

7. The grade determination system of claim 1 further comprising filtering said grade value.

8. The grade determination system of claim 1 wherein said second module monitors a plurality of grade freeze conditions and indicates that said freeze condition does not exist when one of said plurality of freeze conditions is not true.

9. The grade determination system of claim 8 wherein said plurality of freeze conditions include at least one of a brake on condition, a shift in progress condition, a time since a gear shift being less than a respective threshold time condition, a time since a range shift being less than a respective threshold time condition, a reduced vehicle speed condition, a time since a wheel slip was detected being less than a respective threshold time condition, a rate of throttle change condition, a time since a throttle change being less than a respective threshold time condition, a rate of braking change condition, a time since a braking change being less than a respective threshold time condition and a time since a fuel off event being less than a respective threshold time condition.

10. A method of regulating operation of a hybrid vehicle traveling on a surface having a grade, comprising:

determining a drive force of said hybrid vehicle;

calculating a brake pressure value;

determining whether a grade freeze condition exists based on said brake pressure value;

calculating a grade value of said surface based on said drive force when said freeze condition does not exist, and

regulating operation of said hybrid vehicle based on said grade value.

11. The method of claim 10 further comprising holding said grade value equal to a previous grade value when said freeze condition exits.

12. The method of claim 11 further comprising regulating operation of said hybrid vehicle based on said grade value upon expiration of a predetermined time period after said freeze condition transitions from existing to not existing.

13. The method of claim 10 further comprising indicating a brake on status when said brake pressure value exceeds a threshold value, wherein said grade freeze condition exists when said brake on status is indicated.

14. The method of claim 10 further comprising calculating a chassis braking force based on said brake pressure value and a vehicle speed, wherein said grade value is further determined based on said chassis braking force.

15. The method of claim 10 further comprising said grade value as a tangent of a cosine of a quotient of a grade force and a product of a hybrid vehicle mass and a gravitational constant.

16. The method of claim 10 further comprising filtering said grade value.

17. The method of claim 10 further comprising:

monitoring a plurality of grade freeze conditions; and

indicating that said freeze condition does not exist when one of said plurality of freeze conditions is not true.

18. The method of claim 17 wherein said plurality of freeze conditions include at least one of a brake on condition, a shift in progress condition, a time since a gear shift being less than a respective threshold time condition, a time since a range shift being less than a respective threshold time condition, a reduced vehicle speed condition, a time since a wheel slip was detected being less than a respective threshold time condition, a rate of throttle change condition, a time since a throttle change being less than a respective threshold time condition, a rate of braking change condition, a time since a braking change being less than a respective threshold time condition and a time since a fuel off event being less than a respective threshold time condition.

19. A method of regulating operation of a hybrid vehicle based on a grade of a surface, on which the hybrid vehicle is traveling, comprising:

determining a drive force of said hybrid vehicle;

calculating a brake pressure value;

determining whether a grade freeze condition exists based on said brake pressure value;

calculating a grade value of said surface based on said drive force when said freeze condition does not exist;

indicating a brake on status when said brake pressure value exceeds a threshold value, wherein said grade freeze condition exists when said brake on status is indicated;

holding said grade value equal to a previous grade value when said freeze condition exits; and

inhibiting a transition to an engine off mode of said hybrid vehicle based on said grade value.

20. The method of claim 19 further comprising regulating operation of said hybrid vehicle based on said grade value upon expiration of a predetermined time period after said freeze condition transitions from existing to not existing.

21. The method of claim 19 further comprising calculating a chassis braking force based on said brake pressure value and a vehicle speed, wherein said grade value is further determined based on said chassis braking force.

22. The method of claim 19 further comprising said grade value as a tangent of a cosine of a quotient of a grade force and a product of a hybrid vehicle mass and a gravitational constant.

23. The method of claim 19 further comprising filtering said grade value.

24. The method of claim 19 further comprising:

monitoring a plurality of grade freeze conditions; and

indicating that said freeze condition does not exist when one of said plurality of freeze conditions is not true.

25. The method of claim 24 wherein said plurality of freeze conditions include at least one of a shift in progress condition, a time since a gear shift being less than a respective threshold time condition, a time since a range shift being less than a respective threshold time condition, a reduced vehicle speed condition, a time since a wheel slip was detected being less than a respective threshold time condition, a rate of throttle change condition, a time since a throttle change being less than a respective threshold time condition, a rate of braking change condition, a time since a braking change being less than a respective threshold time condition and a time since a fuel off event being less than a respective threshold time condition.