Optimal engine operating power management strategy for a hybrid electric vehicle powertrain

• US 7,398,147 B2
• Filed: 08/02/2005
• Issued: 07/08/2008
• Est. Priority Date: 08/02/2005
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Kuang, Ming, Andreae, Morgan, Kozarekar, Shailesh, Freyermuth, Vincent, Supina, Joseph, Syed, Fazal
• Primary Examiner(s): Black; Thomas G.
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/161,424
• Publication Number:
  US 20070032926A1
• Time in Patent Office: 1,071 Days
• Field of Search: 701/22
• US Class Current: 701/101
• 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 10/26 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 20/11 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 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2710/0644 Engine speed
• 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: Y10S 903/903 having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/905 Combustion engine

Abstract

A method is disclosed for managing power in a hybrid electric vehicle powertrain having multiple components, including an engine, a motor, a generator and a high voltage battery. Power losses in the individual components are computed. An engine speed corresponding to a minimum value for the power losses is selected to achieve optimal total powertrain efficiency.

Claims

1. An engine power management method for a hybrid electric vehicle powertrain having an engine, an electric generator, an electric motor, a battery electrically coupled to the generator and the motor, and gearing mechanically coupling the motor, the generator and the engine to define a power delivery system with a mechanical power flow path and an electrical power flow path as power is distributed to vehicle traction wheels, the method comprising the steps of:

determining engine power loss for a given vehicle speed and for a given total power command;

determining generator power loss for the given vehicle speed;

determining motor power loss for the given vehicle speed;

determining battery power loss for the given vehicle speed;

determining mechanical power loss for the given vehicle speed;

comparing the power losses for the engine, the generator, the motor, the battery and the mechanical power loss for a given vehicle speed;

and determining an engine speed corresponding to a minimum value for the compared power losses whereby the powertrain operates with an optimum total power delivery system efficiency.

2. The method set forth in claim 1 wherein the step of determining power loss for the engine comprises execution of a functional relationship of engine speed and engine torque.

3. The method set forth in claim 1 wherein the step of determining power loss for the generator comprises execution of a functional relationship of generator speed and generator torque.

4. The method set forth in claim 1 wherein the step of determining power loss for the motor comprises execution of a functional relationship of motor speed and motor torque.

5. The method set forth in claim 1 wherein the step of determining power loss for the battery comprises execution of a functional relationship of battery voltage and battery current.

6. The method set forth in claim 1 wherein the step of determining mechanical power loss comprises execution of a functional relationship of a total power command and vehicle speed.

7. The method set forth in claim 2 wherein engine torque is determined as a function of a total power command and actual engine speed.

8. The method set forth in claim 3 wherein generator speed is determined as a function of a desired engine speed and vehicle speed and generator torque is determined as a function of engine torque.

9. The method set forth in claim 4 wherein motor torque is determined as a function of vehicle speed and motor torque is determined as a function of engine torque, total power command and vehicle speed.

10. The method set forth in claim 5 wherein battery current is determined as a function of generator speed, generator torque, motor speed and motor torque and wherein battery voltage is determined as a function of battery current.

11. The method set forth in claim 1 wherein the step of determining a changed engine torque command during a transition period following a change in total power command;

computing an unfiltered engine torque command using the change in total power command and actual engine speed;

filtering the unfiltered engine torque command to effect a filter time lag to modify a rate of change of the engine torque command; and

increasing the engine torque command during the transition period whereby a quick response to a changed total power command is obtained.

12. The method set forth in claim 11 including the step of filtering an engine speed command following the change in total power command whereby a controlled rate of increase of the engine speed command is affected until a target engine speed is achieved corresponding to a changed total power command and a given vehicle speed.