Engine Power Demand Load-Leveling for a Hybrid Electric Vehicle

• US 20100017054A1
• Filed: 06/12/2009
• Published: 01/21/2010
• Est. Priority Date: 07/21/2008
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Lear, Christopher Alan, Okubo, Carol Louise, Frederick, Kenneth
• Granted Patent: US 8,676,415 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 2240/441 Speed
• CPC Class Codes: B60L 2240/486 Operating parameters
• CPC Class Codes: B60L 58/12 responding to state of charge [SoC]
• 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 20/13 in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/105 Output torque
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 30/18 Propelling the vehicle
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power
• CPC Class Codes: F02D 2041/1432 the system including a filter, e.g. a low pass or high pass filter
• CPC Class Codes: F02D 2200/501 Vehicle speed
• CPC Class Codes: F02D 2200/503 Battery correction, i.e. corrections as a function of the state of the battery, its output or its type
• CPC Class Codes: F02D 2200/702 : Road conditions
• CPC Class Codes: F02D 41/107 : and deceleration
• CPC Class Codes: F02D 41/1497 : With detection of the mechanical response of the engine
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries

Abstract

A method for controlling a demand for engine power in a control for an engine in a hybrid electric vehicle with power-split characteristics. Following transitions from acceleration or deceleration operating modes to a steady-state operating mode, power demand excursions from road-load power are attenuated or avoided by filtering the power demand using a filter constant that changes within battery power constraints as a function of a normalized driver demand for power at traction wheels for the vehicle.

Claims

1. A method for controlling a driver demand for motive power in a vehicle powered by an engine and a battery, the method comprising the steps of:

computing available battery power constraints as a function of battery charge and discharge power;

computing a filter constant that changes within the battery power constraints as a function of a difference between driver demand for power and road-load power;

filtering power demand using the filter constant during steady-state vehicle operation when the driver attempts to maintain a constant vehicle speed, whereby power demand excursions from road-load power are attenuated.

2. The method set forth in claim 1 wherein the difference between driver demand for power and road-load power is normalized whereby the filter constant is independent of the battery constraints, which change as a function of battery charge and discharge power limits.

3. A method for controlling an engine power demand in a hybrid electric vehicle having an engine with an electronic control unit, a generator, a motor, a battery and gearing establishing a mechanical power flow path from the engine to vehicle traction wheels and an electro-mechanical power flow path to the vehicle traction wheels, the method comprising the steps of:

determining a road-load power;

measuring battery state-of-charge (SOC);

measuring a driver demand for power at the traction wheels;

calculating a control filter constant that is a function of road-load power;

filtering the driver demand for power using the calculated control filter constant to obtain a filtered driver demand for power;

calculating a battery power request within limits for the battery state-of-charge; and

computing an engine power demand as a function of the filtered driver demand for power and the battery power request whereby excursions of a driver demand for power are attenuated to improve an engine response to vehicle acceleration and deceleration requests and to reduce engine speed variations during a steady-state vehicle operating mode.

8. The method set forth in claim 3 wherein the step of computing an engine power demand includes subtracting a battery power discharge from a filtered driver demand for power request and adding estimated power losses to obtain a total engine power demand.

10. The method set forth in claim 3 wherein the control filter constant is computed during repetitive time steps of the electronic control unit by normalizing the driver demand for power during a time interval corresponding to a steady-state operating mode of the vehicle, the filter constant providing a fast filtering characteristic during a vehicle acceleration mode and during a vehicle deceleration mode and providing a slow filtering characteristic during the vehicle steady-state operating mode.

4. A method for controlling an engine power demand in a hybrid electric vehicle having an engine with an electronic control unit, a generator, a motor, a battery and gearing establishing a mechanical power flow path from the engine to vehicle traction wheels and an electro-mechanical power flow path to the vehicle traction wheels, the method comprising the steps of:

determining a road-load power;

measuring battery state-of-charge SOC);

measuring a driver demand for power at the traction wheels;

calculating a control filter constant that is a function of road-load power;

filtering the driver demand for power using the calculated control filter constant to obtain a filtered driver demand for power;

computing a maximum power for filtering the driver demand for power at the traction wheels during a steady-state vehicle operating mode;

calculating a battery power request within limits for the battery state-of-charge; and

computing an engine power demand as a function of the filtered driver demand for power and the battery power request whereby excursions of a driver demand for power are attenuated to improve an engine response to vehicle acceleration and deceleration requests and to reduce engine speed variations during a steady-state vehicle operating mode.

6. The method set forth in claim 4 wherein the maximum power for filtering is a function of at least one of a battery state-of-charge and a battery state-of-charge limit.

9. The method set forth in claim 4 wherein the step of computing an engine power demand includes adding a battery power charge request to a filtered driver demand for power and adding estimated power losses to obtain a total engine power demand.

11. The method set forth in claim 4 wherein the control filter constant is computed during repetitive time steps of the electronic control unit by normalizing the driver demand for power during a time interval corresponding to a steady-state operating mode of the vehicle, the filter constant providing a fast filtering characteristic during a vehicle acceleration mode and during a vehicle deceleration mode and providing a slow filtering characteristic during the vehicle steady-state operating mode.

5. A method for controlling an engine power demand in a hybrid electric vehicle having an engine with an electronic control unit, a generator, a motor, a battery and gearing establishing a mechanical power flow path from the engine to vehicle traction wheels and an electromechanical power flow path to the vehicle traction wheels, the method comprising the steps of:

determining a road-load power;

measuring battery state-of-charge SOC);

measuring a driver demand for power at the traction wheels;

calculating a control filter constant that is a function of road-load power;

filtering the driver demand for power using the calculated control filter constant to obtain a filtered driver demand for power;

computing, within a limit for battery state-of-charge, a maximum power for filtering the driver demand for power at the traction wheels during a steady-state vehicle operating mode;

computing, within a limit for battery state-of-charge, a minimum power for filtering the driver demand for power at the wheels during the steady-state vehicle operating mode;

the maximum power for filtering and the minimum power for filtering being respectively greater and less than the road-load power at a given instant in the steady-state operating mode;

calculating a battery power request; and

computing an engine power demand as a function of the filtered driver demand for power and the battery power request whereby excursions of a driver demand for power are attenuated to improve an engine response to vehicle acceleration and deceleration requests and to reduce engine speed variations during a steady-state vehicle operating mode.

7. The method set forth in claim 5 wherein the minimum power for filtering is a function of at least one of a battery state-of-charge and a battery discharge limit.

12. The method set forth in claim 5 wherein the control filter constant is computed during repetitive time steps of the electronic control unit by normalizing the driver demand for power during a time interval corresponding to a steady-state operating mode of the vehicle, the filter constant providing a fast filtering characteristic during a vehicle acceleration mode and during a vehicle deceleration mode and providing a slow filtering characteristic during the vehicle steady-state operating mode.