METHODS AND SYSTEMS FOR A HYBRID VEHICLE

• US 20130297113A1
• Filed: 01/10/2013
• Published: 11/07/2013
• Est. Priority Date: 05/04/2012
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Banker, Adam Nathan, Doering, Jeffrey Allen, Gibson, Alex O'Connor, Reed, Dennis Craig, Yamazaki, Mark Steven
• Granted Patent: US 8,738,217 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• 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 20/40 Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers power-up or power-down of the driveline B60W30/192
• CPC Class Codes: B60W 20/50 Control strategies for responding to system failures, e.g. for fault diagnosis, failsafe operation or limp mode
• CPC Class Codes: B60W 2510/0208 Clutch engagement state, e.g. engaged or disengaged
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/0652 Speed change rate
• CPC Class Codes: B60W 2510/0657 Engine torque
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: Y10S 903/902 Prime movers comprising electrical and internal combustion motors

Abstract

Systems and methods for learning torque estimate errors and updating torque estimation models are presented. In one example, torque errors are learned during an engine shut-down, after a disconnect clutch coupled between an engine and an electric machine has been released. An updated torque estimation model is then used to control torque during subsequent engine operation to improve drive feel and vehicle performance.

Claims

1. A method for a hybrid vehicle, comprising:

during engine shut-down conditions,

releasing a disconnect clutch coupled between an engine and an electric machine in a vehicle driveline; and

estimating a torque error after disconnect clutch release based on deviations in one or more of engine torque, engine speed, and engine deceleration from their commanded values at the clutch release.

2. The method of claim 1, wherein the electric machine is a crankshaft integrated starter/generator (CISG), the CISG coupling the engine to a transmission and wheels of the vehicle driveline.

3. The method of claim 1, wherein the estimated torque error is stored as a function of engine speed and wherein the estimated torque error is learned after releasing the disconnect clutch and before fuel injection to the engine is deactivated.

4. The method of claim 1, further comprising, updating an engine torque estimation model with the estimated torque error.

5. The method of claim 4, further comprising, controlling the engine during a subsequent engine restart based on the updated engine torque estimation model.

6. The method of claim 1, wherein estimating the torque error includes, before releasing the disconnect clutch,

commanding an engine torque that will maintain a desired engine deceleration;

and

adjusting one or more engine operating parameters to maintain the commanded engine torque; and

after releasing the disconnect clutch,

determining the torque error based on a deviation of actual engine deceleration from the desired engine deceleration while the commanded engine torque is maintained.

7. A method for a hybrid vehicle driveline, comprising:

in response to idle-stop conditions,

selectively deactivating an engine and releasing a disconnect clutch coupled between the engine and a CISG, the CISG coupled to driveline transmission and wheels; and

while the engine is decelerating,

maintaining an engine torque command; and

learning an engine torque error based on a speed response of the engine upon release of the disconnect clutch.

8. The method of claim 7, wherein the engine torque command is selected to provide substantially zero torque across the disconnect clutch.

9. The method of claim 7, wherein the engine torque command is selected to decelerate the engine at an expected deceleration rate upon releasing the disconnect clutch.

10. The method of claim 9, wherein learning the engine torque error based on the speed response of the engine includes, estimating the engine torque error based on a deviation of an actual deceleration rate of the decelerating engine from the expected deceleration rate.

11. The method of claim 9, wherein learning the engine torque error based on the speed response of the engine includes, learning an engine torque over-estimation error if the engine decelerates slower than the expected deceleration rate, and learning an engine torque under-estimation error if the engine decelerates faster than the expected deceleration rate.

12. The method of claim 7, wherein the engine torque error is further learned based on a speed response of the CISG upon release of the disconnect clutch and while maintaining the engine torque command.

13. The method of claim 7, wherein releasing a disconnect clutch includes releasing a disconnect clutch while a vehicle speed is above a threshold speed.

14. The method of claim 7, further comprising, learning the engine torque error as a function of engine speed.

15. The method of claim 7, further comprising,

updating an engine torque estimation model with the learned torque error;

and

controlling an engine torque commanded during a subsequent engine restart based on the updated engine torque estimation model.

16. A hybrid vehicle method, comprising:

attempting to provide zero torque across a disconnect clutch upon clutch release, the clutch mechanically coupling an engine to an electric machine; and

learning errors in air and fueling required to provide the zero torque based on a speed profile of the engine and/or the electric machine for a duration following the clutch release.

17. The method of claim 16, wherein attempting to provide zero torque across the clutch includes determining an engine torque command that provides substantially zero torque and commanding the determined torque command immediately before the clutch release.

18. The method of claim 17, wherein learning errors based on the speed profile of the engine includes,

if an actual engine speed profile over the duration is higher than an expected engine speed profile, learning an error corresponding to an over-estimation of engine torque;

and

if the actual engine speed profile over the duration is lower than the expected engine speed profile, learning an error corresponding to an under-estimation of engine torque, wherein the expected engine speed profile is based on the engine torque command.

19. The method of claim 16, wherein the errors are learned as a function of engine speed and one or more engine actuator settings.

20. The method of claim 16, wherein learning errors includes learning errors during engine idle-stop conditions when a vehicle speed is higher than a threshold.