Optimal Engine Operating Power Management Strategy for a Hybrid Electric Vehicle Powertrain

• US 20110010032A1
• Filed: 09/20/2010
• Published: 01/13/2011
• 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
• Granted Patent: US 8,041,495 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• 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 at least two of a group comprising an engine, a motor, a generator and a high voltage battery. Power losses in the individual components are computed. An engine operating speed and torque for a given vehicle speed and total power command is determined so that total power losses for powertrain components are minimized.

Claims

1. An engine power management method for a hybrid electric vehicle powertrain having power delivery components comprising 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 multiple power flow paths as engine mechanical power and motor and generator power are distributed to vehicle traction wheels, the method comprising the steps of:

determining a pre-calibrated power delivery loss for the individual components for various vehicle speeds;

determining a pre-calibrated minimum value for the component power delivery loss value for the various vehicle speeds;

determining a pre-calibrated engine speed corresponding to the minimum power loss values for the various vehicle speeds;

entering the pre-calibrated engine speeds in a table; and

selecting from the table an engine speed corresponding to minimum total powertrain power losses whereby the powertrain operates with optimum total power delivery system efficiency for a given total power command.

2. The method sets forth in claim 1 including 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.

3. The method set forth in claim 2 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 effected until a target engine speed is achieved corresponding to a changed total power command and a given vehicle speed.

4. The method set forth in claim 2 including the step of determining a changed engine torque command during the 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.

5. An engine power management method for a hybrid electric vehicle powertrain having separate power delivery components including at least an engine and an electric motor, the components defining power flow paths to vehicle traction wheels, the method comprising the steps of:

determining a pre-calibrated power delivery loss for the power delivery components for a given engine speed, the engine speed being stored in a data storing medium;

determining a minimum power delivery loss for a given engine speed and a total engine power command by adjusting an engine speed command;

adjusting an engine torque command to a value corresponding to the engine speed command, whereby, for a given vehicle speed and total power command, there is an engine speed such that a total powertrain power loss is a minimum.

6. The method set forth in claim 5 wherein the data storage medium is a read-only memory portion of an electronic vehicle system controller.

7. The method set forth in claim 5 wherein the data storage medium is configured to store in a look-up table a value of pre-calibrated engine speeds for each vehicle speed and for each total power command such that total powertrain power loss is of minimum value, whereby maximum powertrain efficiency is achieved.

8. The method set forth in claim 7 wherein the look-up table is pre-calibrated and developed off-line.

9. An engine power management method for a hybrid electric vehicle powertrain having separate components including at least two of a group comprising an engine, an electric motor, a generator, a battery and power transfer gearing, the components defining power flow paths to vehicle traction wheels, the method comprising the steps of:

determining an engine speed for a given vehicle speed and a given total power command to minimize total powertrain power losses;

those losses being a function of total power command and vehicle speed;

total power command and vehicle speed, together with multiple values for engine speed, being inputs for calculating power losses for the components;

adding the component losses together to obtain total powertrain loss;

determining an engine speed corresponding to minimum total power loss and storing it as data in an electronic computer memory; and

accessing the data to obtain an engine speed corresponding to various total power commands and vehicle speeds that will achieve a minimum total power loss, whereby maximum total powertrain efficiency is achieved.

10. The method set forth in claim 9 wherein the step of accessing the data is followed by adjusting engine torque to a value corresponding to the stored engine speed.