Torque management algorithm for hybrid electric vehicles

• US 7,295,902 B2
• Filed: 04/30/2004
• Issued: 11/13/2007
• Est. Priority Date: 04/30/2004
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Salman, Mutasim A., Chen, Jyh-Shin, Chang, Man-Feng
• Primary Examiner(s): Tran; Dalena
• Application Number:
  US10/836,799
• Publication Number:
  US 20050246076A1
• Time in Patent Office: 1,292 Days
• Field of Search: 701/22, 180/65.1, 180/65.3, 180/69.4, 290/40.A, 290/40.B, 290/40.C, 290/40.R, 290/38.R, 290/45, 290/46, 318/8, 318/9, 318/34, 318/51, 318/52
• US Class Current: 701/22
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• 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 2050/0025 Transfer function weighting factor
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A system and method for determining a commanded engine and motor torque to minimize fuel consumption and manage battery state of charge in a hybrid electric vehicle. The method includes determining a penalty factor value that dictates the usage of the battery. A cost value is determined for every feasible engine torque for a selected or demanded vehicle torque and speed request. Each cost value is determined by a fuel consumption value, a change in the battery state of charge and the penalty factor value. The change in the battery state of charge is determined from the motor power and a nominal battery state of charge. For a specific penalty factor, a look-up table for optimal engine torque is generated for different requested vehicle torques at various vehicle speeds. A separate look-up table is provided for each penalty factor.

Claims

1. A method for providing torque management in a hybrid electric vehicle, said hybrid electric vehicle including an engine, an electric motor and a battery, said method comprising:

determining a penalty factor value that influences the usage of the battery and affects a torque allocation between the engine and the motor;

providing a requested vehicle torque value and a vehicle speed value;

selecting an engine torque value;

determining a fuel consumption value based on the engine torque value and the vehicle speed value;

determining a change in the battery state of charge value based on a motor torque value and the vehicle speed value; and

determining an optimal engine torque command from cost values based on the fuel consumption value, the change in the battery state of charge value and the penalty factor value.

2. The method according to claim 1 wherein determining an optimal engine torque command includes determining the cost values by multiplying the penalty factor value by the change in the battery state of charge value and adding the fuel consumption value to the multiplied change in the battery state of charge value and the penalty factor value.

3. The method according to claim 1 wherein determining the fuel consumption value includes determining a gear number based on the engine torque value and the vehicle speed value, determining a gear ratio value based on the determined gear number, dividing the engine torque value by the gear ratio value to generate an engine shaft torque value, multiplying the vehicle speed value by the gear ratio value to generate an engine shaft speed value, and determining the fuel consumption value based on the shaft torque value and the shaft speed value.

4. The method according to claim 3 wherein the gear number is determined by a gear number look-up table, the gear ratio is determined by a gear ratio look-up table and the fuel consumption value is determined by an engine look-up table.

5. The method according to claim 1 wherein determining a change in the battery state of charge value includes determining a motor input power value based on the motor torque value and the vehicle speed value, and determining the change in the battery state of charge based on the motor input power value and a nominal state of charge value.

6. The method according to claim 5 wherein determining the motor input power value includes using a motor look-up table and determining the change in the battery state of charge value includes using a battery look-up table.

7. The method according to claim 1 wherein determining an optimal engine torque command includes determining an optimal engine torque command from the cost values for every feasible engine torque value for a plurality of requested vehicle torque values and vehicle speed values for a penalty factor value.

8. The method according to claim 7 wherein each optimal engine torque command is added to an engine torque look-up table, wherein a plurality of the engine torque look-up tables are provided for a plurality of different penalty factor values.

9. The method according to claim 1 wherein determining an optimal engine torque command includes determining the optimal engine torque command offline.

10. The method according to claim 1 wherein determining the penalty factor value includes determining an upper bound battery charge limit, a lower bound battery charge limit and a nominal battery charge therebetween, and setting the penalty factor value to a first predetermined value if the battery state of charge value reaches the upper bound limit to increase electric motor use and setting the penalty factor value to a second predetermined penalty factor value if the battery state of charge value reaches the lower bound limit to decrease electric motor use.

11. The method according to claim 1 wherein determining a penalty factor value includes determining if the battery state of charge value has reached a predetermined upper bound battery state of charge value, determining whether the penalty factor value is equal to a predetermined penalty factor value, setting the penalty factor value equal to the predetermined penalty factor value and storing an old penalty factor value if the battery state of charge value has reached the upper bound value and the penalty factor value does not equal the predetermined penalty factor value.

12. The method according to claim 11 wherein determining a penalty factor value includes determining whether the battery state of charge value is about equal to a nominal battery state of charge value, determining whether the penalty factor value is equal to the predetermined penalty factor value, and setting the penalty factor value equal to the stored penalty factor value plus a small correction value if the battery state of charge value is about equal to the nominal battery state of charge value and the penalty factor value is equal to the predetermined penalty factor value.

13. The method according to claim 1 wherein determining a penalty factor value includes determining whether the battery state of charge value has reached a predetermined lower bound battery state of charge value, determining whether the penalty factor value equals a predetermined penalty factor value, and storing an old penalty factor value and setting the penalty factor value equal to the predetermined penalty factor value if the battery state of charge value has reached the lower bound value and the penalty factor value does not equal the predetermined penalty factor value.

14. The method according to claim 13 wherein determining a penalty factor value includes determining whether the battery state of charge value is about equal to a nominal battery state of charge value, whether the penalty factor value is equal to the predetermined penalty factor value, and setting the penalty factor value equal to the stored penalty factor value less a small correction value if the battery state of charge value is about the nominal battery state of charge value and the penalty factor value is equal to the predetermined penalty factor value.

15. The method according to claim 1 wherein the penalty factor value is a negative number.

16. A method for providing torque management in a hybrid electric vehicle, said hybrid electric vehicle including an engine, an electric motor and a battery, said method comprising:

determining a penalty factor value that influences the usage of the battery, wherein determining the penalty factor value includes determining an upper bound battery charge limit, a lower bound battery charge limit and a nominal battery charge therebetween, and setting the penalty factor value to a first predetermined value if the battery state of charge value reaches the upper bound limit to increase electric motor use and setting the penalty factor value to a second predetermined penalty factor value if the battery state of charge value reaches the lower bound limit to decrease electric motor use;

providing a requested vehicle torque value and a vehicle speed value;

selecting an engine torque value;

determining a fuel consumption value based on the engine torque value and the vehicle speed value;

determining a change in the battery state of charge value based on a motor torque value and the vehicle speed value; and

determining an optimal engine torque command from cost values determined by multiplying the change in the battery state of charge value and the penalty factor value and adding the fuel consumption value to the multiplied change in the battery state of charge value and the penalty factor value, wherein determining an optimal engine torque command includes determining an optimal engine torque command from the cost values for every feasible engine torque value for a plurality of requested vehicle torque values and vehicle speed values for a penalty factor value.

17. The method according to claim 16 wherein determining the fuel consumption value includes determining a gear number based on the engine torque value and the vehicle speed value, determining a gear ratio value based on the determined gear number, dividing the engine torque value by the gear ratio value to generate an engine shaft torque value, multiplying the vehicle speed value by the gear ratio value to generate an engine shaft speed value, and determining the fuel consumption value based on the shaft torque value and the shaft speed value.

18. The method according to claim 17 wherein the gear number is determined by a gear number look-up table, the gear ratio is determined by a gear ratio look-up table and the fuel consumption value is determined by an engine look-up table.

19. The method according to claim 16 wherein determining a change in the battery state of charge value includes determining a motor input power value based on the motor torque value and the vehicle speed value, and determining the change in the battery state of charge based on the motor input power value and a nominal state of charge value.

20. The method according to claim 19 wherein determining the motor input power value includes using a motor look-up table and determining the change in the battery state of charge value includes using a battery look-up table.

21. The method according to claim 16 wherein each optimal engine torque command is added to an engine torque look-up table, wherein a plurality of the engine torque look-up tables are provided for a plurality of different penalty factor values.

22. The method according to claim 16 wherein determining an optimal engine torque command includes determining the optimal engine torque command offline.

23. An apparatus for providing torque management in a hybrid electric vehicle, said hybrid electric vehicle including an engine, an electric motor and a battery, said apparatus comprising:

a penalty factor system for providing a penalty factor value that influences the usage of the battery and affects a torque allocation between the engine and the motor;

a fuel consumption system for determining a fuel consumption value based on a predetermined engine torque value and a requested vehicle speed value;

a battery state of charge system for determining a change in the state of charge of the battery value based on a motor torque value and the vehicle speed value; and

a cost function system for determining an optimal engine torque command from cost values calculated from the fuel consumption value, the change in the battery state of charge value and the penalty factor value.

24. The apparatus according to claim 23 wherein the cost function system multiplies the penalty factor value by the change in the battery state of charge value and adds the fuel consumption value to the multiplied change in the battery state of charge value and the penalty factor value.

25. The apparatus according to claim 23 wherein the fuel consumption system includes a gear number look-up table for determining a gear number based on the engine torque value and the vehicle speed value, a gear ratio table for determining a gear ratio value of the gear number, a divider for dividing the engine torque value by the gear ratio value to generate an engine shaft torque value, a multiplier for multiplying the vehicle speed value by the gear ratio value to generate an engine shaft speed value, said fuel consumption system determining the fuel consumption value based on the shaft torque value and the shaft speed value.

26. The apparatus according to claim 23 wherein the battery state of charge system includes a motor look-up table for determining a motor input power value based the motor torque value and the vehicle speed value, and a battery look-up table for determining the change in the battery state of charge value based on the motor input power value and a nominal state of charge value.

27. The apparatus according to claim 23 wherein the cost function system determines an optimal engine torque command from the cost values for every feasible engine torque value for a plurality of requested vehicle torque values and vehicle speed values for a penalty factor value.

28. The apparatus according to claim 23 wherein the cost function system includes a plurality of engine torque look-up tables for an optimal engine torque command for a particular penalty factor value.

29. The apparatus according to claim 23 wherein the penalty factor system determines the penalty factor value by determining an upper bound battery charge limit, a lower bound battery charge limit and a nominal battery charge therebetween, said penalty factor system setting the penalty factor value to a first predetermined value if the battery state of charge value reaches the upper bound limit to increase electric motor use and sets the penalty factor value to a second predetermined penalty factor value if the battery state of charge value reaches a lower bound limit to decrease electric motor use.

30. The apparatus according to claim 23 wherein the penalty factor system determines if the battery state of charge value has reached a predetermined upper bound battery state of charge value, determines whether the penalty factor value is equal to a predetermined penalty factor value, sets the penalty factor value equal to the predetermined penalty factor value and stores an old penalty factor value if the battery state of charge value has reached the upper bound value and the penalty factor value does not equal the predetermined penalty factor value.

31. The apparatus according to claim 30 wherein the penalty factor system determines whether the battery state of charge value is about equal to a nominal battery state of charge, determines whether the penalty factor value is equal to the predetermined penalty factor value, and sets the penalty factor value equal to the stored penalty factor value plus a small correction value if the battery state of charge value is about equal to the nominal battery state of charge value and the penalty factor value is equal to the predetermined penalty factor value.

32. The apparatus according to claim 23 wherein the penalty factor system determines whether the battery state of charge value has reached a predetermined lower bound battery state of charge value, determines whether the penalty factor value equals a predetermined penalty factor value, and stores an old penalty factor value and sets the penalty factor value equal to the predetermined penalty factor value if the battery state of charge has reached the lower bound value and the penalty factor value does not equal the predetermined penalty factor value.

33. The apparatus according to claim 32 wherein the penalty factor system determines whether the battery state of charge value is about equal to a nominal battery state of charge value, whether the penalty factor value is equal to the predetermined penalty factor value, and sets the penalty factor value equal to the stored penalty factor value less a small correction value if the battery state of charge value is about the nominal battery state of charge value and the penalty factor value is equal to the predetermined penalty factor value.