Optimal selection of input torque considering battery utilization for a hybrid electric vehicle

• US 20050080537A1
• Filed: 10/14/2004
• Published: 04/14/2005
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Heap, Anthony H., Cawthorne, William R., Hubbard, Gregory A.
• Granted Patent: US 7,200,476 B2
• Time in Patent Office: Days
• US Class Current: 701/51
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• 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 10/105 of electric type
• CPC Class Codes: B60W 20/11 using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance utilising navigation and traffic information in the control strategy B60W20/12
• CPC Class Codes: B60W 2510/1025 Input torque
• CPC Class Codes: B60W 30/1882 characterised by the working point of the engine, e.g. by using engine output chart
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/84 Data processing systems or methods, management, administration

Abstract

A preferred input torque for a hybrid powertrain is determined within a solution space of feasible input torques in accordance with a plurality of powertrain system constraints that results in a minimum overall powertrain system loss. System power losses and battery utilization costs are calculated at feasible input torques and a solution for the input torque corresponding to the minimum total powertrain system loss is converged upon to determine the preferred input torque.

Claims

1. Method for establishing a preferred operating point for a preselected powertrain operating parameter in a powertrain system having an energy storage system (ESS), comprising:

determining a feasible operating space for the preselected powertrain operating parameter and within said operating space determining corresponding ESS power and system power loss;

applying an ESS power utilization cost as function of ESS power to the system power loss to determine a total system loss;

searching the feasible operating space for a value of the operating parameter corresponding to a minimum total system loss; and

establishing the preferred operating point as the value in the operating parameter corresponding to the minimum total system loss.

2. The method of claim 1, wherein said preselected powertrain parameter comprises an input torque.

3. The method of claim 1, wherein said powertrain system includes an internal combustion engine, a transmission and an electric machine, and wherein the ESS comprises a battery.

4. The method of claim 1, wherein the ESS power utilization cost is a function of at least one ESS parameter.

5. The method of claim 4, wherein the at least one ESS parameter comprises a state of charge of the ESS, an amp-hour throughput of the ESS and ESS power.

6. The method of claim 1, wherein applying an ESS power utilization cost as a function of ESS power to the system power loss to determine a total system loss, further comprises:

determining a value of at least one ESS parameter;

determining the ESS power utilization cost as a function of the at least one ESS parameter; and

adding the ESS power utilization cost to the system power loss to determine the total system loss.

7. The method of claim 6, wherein the at least one ESS parameter comprises a state of charge of the ESS and an amp-hour throughput of the ESS.

8. The method of claim 7, wherein determining the ESS power utilization cost as a function of the at least one ESS parameter, further comprises:

determining an ESS power utilization cost factor as a function of the state of charge and the amp-hour throughput; and

multiplying ESS power by the ESS power utilization cost factor to determine the ESS power utilization cost.

9. The method of claim 8, further comprising:

shifting the ESS power by a shift value to a shifted ESS power, wherein the shift value is a function of the state of charge, and wherein multiplying the ESS power by the ESS cost factor utilizes the shifted ESS power.

10. The method of claim 9, wherein the shift value is a function of the state of charge such that at low states of charge the total system power loss is biased in a manner to effect reduced ESS power and at high states of charge the total system loss is biased in a manner to effect increased ESS power.

11. The method of claim 1, wherein said preferred operating point is periodically updated in accordance with the method of claim 1, and further wherein such periodic update proceeds during quiescent powertrain operation only when the value for the most recent search corresponds to a respective minimum total system loss that is at least a predetermined amount less than the respective minimum total system loss corresponding to the previously established preferred operating point.

12. The method of claim 1, wherein the system power loss is determined from a plurality of sub-system power losses.

13. The method of claim 1, wherein searching the feasible operating space for the operating point corresponding to the minimum total system loss comprises performing a section search utilizing a golden section ratio.

14. Method for determining a preferred input torque for operating an electrically variable transmission (EVT) including an input, an output and an electric machine having known coupling relationships, and an energy storage system (ESS), comprising:

determining current EVT operating conditions including input, output and electric machine speeds;

determining system constraints in electric machine torque, ESS power and input torque at current EVT operating conditions;

providing a target output torque producible within said system constraints;

calculating aggregate system power losses corresponding to feasible input torques that can produce the target output torque within said system constraints;

calculating ESS power utilization costs as a function of ESS power corresponding to feasible input torques, wherein the ESS power utilization costs are adapted for application to the aggregate system power losses;

applying the ESS power utilization costs to the aggregate system power losses to determine total system losses corresponding to feasible input torques that can produce the target output torque within said system constraints;

converging upon a feasible input torque corresponding to a substantially minimum total system loss; and

selecting as the preferred input torque the feasible input torque corresponding to the substantially minimum total system loss.

15. The method of claim 14, wherein calculating aggregate system power losses comprises:

calculating individual sub-system power losses; and

summing the individual sub-system power losses.

16. The method of claim 15, wherein individual sub-system power losses are selected from the group consisting of an input source power loss, an electric machine power loss and an accessory power loss.

17. The method of claim 14, wherein the ESS power utilization cost is also a function of at least one ESS parameter.

18. The method of claim 17, wherein the at least one ESS parameter comprises a state of charge of the ESS, an amp-hour throughput of the ESS and ESS power.

19. The method of claim 14, wherein calculating ESS power utilization costs as a function of the ESS power further comprises:

determining a value of at least one ESS parameter; and

determining the ESS power utilization costs as a function of ESS power and the at least one ESS parameter.

20. The method of claim 19, wherein the at least one ESS parameter comprises a state of charge of the ESS and an amp-hour throughput of the ESS.

21. The method of claim 20, wherein determining the ESS power utilization costs as a function of the ESS power and the at least one ESS parameter, further comprises:

determining an ESS cost factor as a function of the state of charge and the amp-hour throughput; and

multiplying the ESS cost factor by the ESS power corresponding to feasible input torques to obtain the ESS power utilization costs.

22. The method of claim 21, further comprising:

shifting the ESS power by a shift value to a shifted ESS power, wherein the shift value is a function of the state of charge, and wherein multiplying the ESS power by the ESS cost factor utilizes the shifted ESS power.

23. The method of claim 22, wherein the shift value is a function of the state of charge such that at low states of charge the total system power loss is biased in a manner to effect reduced ESS power and at high states of charge the total system loss is biased in a manner to effect increased ESS power.

24. The method of claim 14, wherein said applying the ESS costs to the aggregate power losses to determine total system losses corresponding to feasible input torques that can produce the target output torque within said system constraints, further comprises:

adding the ESS power utilization costs to the aggregate system power losses to determine the total system losses.

25. The method of claim 14, wherein said preferred input torque is periodically updated in accordance with the method of claim 14, and further wherein such periodic update proceeds during quiescent powertrain operation only when the most recently selected feasible input torque corresponds to a respective substantially minimum total system loss that is at least a predetermined amount less than the respective substantially minimum total system loss corresponding to the previously selected feasible input torque.

26. The method of claim 14, wherein converging upon a feasible input torque comprises performing a section search in feasible input torques and corresponding total system losses.

27. The method of claim 26, wherein said section search comprises a golden section ratio.

28. The method of claim 14, wherein converging upon a feasible input torque comprises performing an iterative derivative convergence.

29. The method of claim 14, wherein converging upon a feasible input torque comprises performing polynomial estimations.

30. Method for attributing a virtual power loss to battery utilization in a hybrid electric vehicle system for use in controlling the system comprising:

providing a first battery power utilization cost factor as a function of battery state of charge and battery power;

providing a second battery power utilization cost factor as a function of battery throughput; and

determining a virtual power loss term as a function of the first and second battery power utilization cost factors and battery power.

31. The method as claimed in claim 30 wherein determining the virtual power loss term comprises:

individually multiplying each of the first and second battery power utilization cost factors by battery power and summing the products thereof.

32. The method as claimed in claim 30 wherein determining the virtual power loss term comprises:

multiplying the first battery power utilization cost factor by the second battery power utilization cost factor by battery power.