Engine speed control for an engine in a hybrid electric vehicle powertrain for improved noise, vibration and harshness

• US 8,583,301 B2
• Filed: 02/15/2008
• Issued: 11/12/2013
• Est. Priority Date: 02/15/2008
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Okubo, Shunsuke, Bryan, Paul Stephen
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): TISSOT, ADAM D
• Application Number:
  US12/032,184
• Publication Number:
  US 20090210108A1
• Time in Patent Office: 2,097 Days
• Field of Search: 701/22, 180/65.1, 180/65.21, 180/65.265, 180/65.28
• US Class Current: 701/22
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 2240/486 Operating parameters
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• 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 2510/244 Charge state
• CPC Class Codes: B60W 2510/248 Age of storage means
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/16 Ratio selector position
• CPC Class Codes: B60W 2710/105 Output 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: G01M 15/12 by monitoring vibrations
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/84 Data processing systems or methods, management, administration

Abstract

A control strategy is disclosed for regulating speed of an engine in a hybrid electric vehicle powertrain that includes an electric motor and gearing. An electrical power flow path and a mechanical power flow path are established. Electrical power is coordinated with mechanical power to effect an arbitrated engine speed for a given power demand that will result in an acceptable noise, vibration and harshness (NVH) characteristic for the powertrain and an acceptable powertrain efficiency.

Claims

1. A method comprising:

adjusting engine speed using a microprocessor-based controller for an engine in a hybrid electric vehicle powertrain to achieve an arbitrated engine speed that will effect a desired noise, vibration and harshness (NVH) powertrain characteristic and an acceptable powertrain efficiency, the powertrain comprising an electric motor that complements power of the engine, and gearing defining power flow paths from the motor and the engine to vehicle traction wheels, the arbitrated engine speed based on

available engine power at a target engine speed that is less than an engine speed that results in best powertrain efficiency for a given driver requested power,

a battery power bias for desired noise, vibration and harshness that is equal to a difference between the driver requested power and the available engine power at the target engine speed,

and battery power at a steady state battery state-of-charge.

2. A method comprising:

controlling engine speed in a hybrid vehicle using a controller configured to adjust engine speed in response to a target engine speed for desired powertrain noise, vibration and harshness (NVH) that is less than an optimum speed for engine efficiency, an engine power at the target speed, and

a calculated NVH bias battery power equal to the difference between the engine power at the target speed and a driver requested power.

5. The method set forth in claim 2, wherein the driver demanded wheel power is a function of vehicle traction wheel speed and a demanded traction wheel torque.

8. The method set forth in claim 2, wherein the optimum speed for engine efficiency corresponds to an engine power that is lower than a maximum available engine power.

10. The method set forth in claim 2, wherein the target engine speed for a given traction wheel speed is a function of a driver-controlled accelerator pedal position.

3. A method for adjusting engine speed for an engine in a hybrid electric vehicle powertrain to achieve an arbitrated engine speed that will effect a desired noise, vibration and harshness (NVH) powertrain characteristic and an acceptable powertrain efficiency, the powertrain comprising an electric motor that complements power of the engine, and gearing defining parallel power flow paths from the motor and the engine to vehicle traction wheels, the method comprising:

determining an engine speed (N₁) that results in desired noise, vibration and harshness (NVH);

determining an engine speed (N₂) that results in engine best attainable powertrain efficiency for current operating conditions;

calculating a battery power bias (P_bias) that will protect the engine during operation under abnormal operating conditions;

determining available engine power at a target engine speed N, where N=N₁, when N₁ is less than N₂;

monitoring battery state of charge SOC;

determining engine power needed to maintain battery power P_SOC at steady state SOC;

calculating a difference between a driver requested engine power and engine power available at the target engine speed N to determine battery power needed (P_bias-NVH) to effect desired NVH;

determining the maximum of values for P_bias-NVH, P_bias and P_SOC;

calculating a difference between driver requested power and the battery power (P_SOC) to determine engine power P_engine, and calculating an engine speed based on P_engine; and

operating the engine using a controller at an arbitrated engine speed that results in desired NVH and acceptable powertrain efficiency.

4. The method set forth in claim 3, wherein determining P_bias-NVH includes limiting battery power to battery hardware limits.

6. The method set forth in claim 3, wherein the driver demanded wheel power is a function of vehicle traction wheel speed and a demanded traction wheel torque.

7. The method set forth in claim 3 wherein calculating the batter power bias (P_bias-NVH) is done within power limits of the battery.

9. The method set forth in claim 3, wherein the best engine efficiency corresponds to an engine power at a given engine speed that is lower than the maximum engine power at that engine speed.

11. The method set forth in claim 3, wherein the engine speed (N₁) for a given traction wheel speed is a function of a driver-controlled accelerator pedal position.

12. A method, comprising:

controlling an engine of a hybrid electric vehicle powertrain having a battery powered electric motor and gearing defining parallel power flow paths from the electric motor and the engine to vehicle traction wheels using a controller to operate the engine at a lower engine speed relative to an engine speed associated with best available powertrain efficiency for a current vehicle speed to achieve a desired NVH characteristic.

13. The method of claim 12 further comprising:

increasing motor torque to deliver a desired power to the vehicle traction wheels based on a driver-controlled accelerator pedal position.

14. The method of claim 12 wherein operating the engine comprises adjusting a target engine speed based on demanded vehicle power associated with a driver-controlled accelerator pedal position and the current vehicle speed, the method further comprising:

adjusting battery power such that motor power associated with the adjusted battery power complements engine power associated with the lower engine speed and the current vehicle speed to provide the demanded vehicle power.

15. The method of claim 12 wherein the lower engine speed is retrieved from a look-up table based on the current vehicle speed, accelerator pedal position, and the desired NVH characteristic.

16. The method of claim 12 wherein operating the engine includes operating the engine to deliver less than maximum available engine power for the current vehicle speed.

17. A method for controlling a hybrid electric vehicle comprising:

controlling engine speed using a controller to a target engine speed corresponding to the lower of a first engine speed based on driver demanded power and current vehicle speed, and a second engine speed based on desired NVH, the target engine speed being less than an optimum speed for engine efficiency; and

controlling a battery powered electric motor using a controller to complement engine power to deliver the driver demanded power.

18. The method of claim 17 wherein operating the motor comprises adjusting battery power delivered to the motor based on the driver demanded power and the target engine speed.

19. A method comprising:

controlling an engine in a hybrid vehicle using a vehicle controller configured to;

calculate a target engine speed for desired powertrain noise, vibration and harshness (NVH), where the target engine speed is less than an optimum speed for engine efficiency;

calculate an engine power at the target engine speed;

calculate an NVH bias battery power equal to the difference between the engine power at the target engine speed and a driver requested power;

calculate a steady state battery power;

calculate a final engine power equal to the difference between the driver requested power and the greater of the NVH bias battery power and the steady state battery power; and

command a final engine speed based on the final engine power to operate at an arbitrated engine speed that results in the desired NVH and the acceptable powertrain efficiency that is less than otherwise achievable powertrain efficiency for current operating conditions.