Control of engine start for a hybrid system

• US 8,731,753 B2
• Filed: 08/24/2011
• Issued: 05/20/2014
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Smith, Anthony L., Yang, Hong, Bucknor, Norman K., He, Yongsheng
• Primary Examiner(s): Jabr, Fadey
• Assistant Examiner(s): Ramesh, Krishnan
• Application Number:
  US13/216,311
• Publication Number:
  US 20120083952A1
• Time in Patent Office: 1,000 Days
• Field of Search: None
• US Class Current: 701/22
• CPC Class Codes: B60K 6/442 Series-parallel switching type
• 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 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 2510/081 Speed
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: B60W 2710/081 Speed
• CPC Class Codes: F02N 2300/102 Control of the starter motor speed; Control of the engine speed during cranking
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A powertrain includes an electric motor providing propulsion torque to a transmission input shaft, an internal combustion engine, and an engine disconnect clutch selectively providing torque transfer between the engine and the motor. A method to control a flying engine start in the powertrain includes monitoring an output torque request, determining the propulsion torque to the transmission input shaft based upon the output torque request, determining a compensation torque to be provided to the engine disconnect clutch for the flying engine start, and controlling the motor to provide a motor torque based upon a sum of the propulsion torque and the compensation torque.

Claims

1. A control-module implemented method to control a flying engine start in a powertrain comprising an electric motor providing a propulsion torque to a transmission input shaft, an internal combustion engine, and an engine disconnect clutch selectively providing torque transfer between the engine and the motor, the method comprising:

monitoring an output torque request;

determining the propulsion torque to the transmission input shaft based upon the output torque request;

monitoring a desired input speed;

determining a synchronization speed based upon the desired input speed;

determining, by a controller, a desired engine activation speed profile based upon the synchronization speed, comprising;

determining a first stage wherein a compensation torque is provided from the motor to the engine through the engine disconnect clutch to accelerate the engine from a stopped state to an engine firing speed;

once the engine firing speed is achieved, determining a second stage wherein the engine provides torque to accelerate the engine while simultaneously reducing the compensation torque provided from the motor to the engine;

determining a third stage subsequent to the second stage wherein the compensation torque is provided to the engine by the motor to control the engine to the synchronization speed; and

determining a fourth stage wherein the engine disconnect clutch is locked; and

controlling the motor to provide a motor torque based upon a sum of the propulsion torque and the compensation torque.

2. The method of claim 1, wherein monitoring the desired input speed comprises monitoring a desired input speed profile;

and

wherein determining the synchronization speed comprises determining the synchronization speed based upon the desired input speed profile and a capability of the engine to accelerate.

3. The method of claim 1, wherein the engine firing speed comprises a minimum engine firing speed.

4. The method of claim 3, wherein the compensation torque is determined using an open-loop clutch control term and a closed-loop clutch control term;

and

wherein determining the engine activation speed profile further comprises determining the second stage wherein an engine torque command is limited to be less than the open-loop clutch control term.

5. The method of claim 1, wherein the compensation torque is determined using an open-loop clutch control term and a closed-loop clutch control term;

and

wherein determining the engine activation speed profile further comprises determining the second stage wherein an engine torque command is limited to be less than the open-loop clutch control term.

6. The method of claim 1, wherein determining the engine activation speed profile further comprises determining the second stage wherein a torque capacity of the engine disconnect clutch is reduced to a nonzero minimum value.

7. The method of claim 1, wherein the engine firing speed comprises a minimum engine firing speed.

8. The method of claim 1, wherein controlling the motor is based upon a sum of the propulsion torque, the compensation torque, and a driveline active damping control torque.

9. The method of claim 1, wherein determining the compensation torque comprises:

determining a torque required to turn the engine; and

determining the compensation torque based upon the torque required to turn the engine.

10. The method of claim 1, wherein determining the compensation torque comprises determining an open-loop clutch control term and a closed-loop clutch control term.

11. The method of claim 10, wherein determining the open-loop clutch control term comprises utilizing an engine disconnect clutch pressure-to-torque feed-forward compensation value.

12. The method of claim 1, wherein determining the compensation torque comprises:

determining the compensation torque based upon an engine starting position.

13. The method of claim 1, further comprising reducing a torque capacity of a transmission clutch to dampen an effect of the flying engine start upon an output torque of the transmission, wherein the transmission clutch includes a first element coupled to the motor and a second element coupled to the transmission input shaft for selectively providing torque transfer between the motor and the transmission when the transmission clutch is engaged.

14. The method of claim 1, further comprising reducing a torque capacity of the engine disconnect clutch to dampen an effect of the flying engine start upon an output torque of the transmission.

15. The method of claim 1, further comprising controlling a second motor to provide a second motor torque based upon the sum of the propulsion torque and the compensation torque.

16. System to control a flying engine start in a powertrain comprising an electric motor providing a propulsion torque to a transmission input shaft of a transmission, an internal combustion engine, and an engine disconnect clutch selectively providing torque transfer between the engine and the motor, the system comprising:

the motor; and

a control module configured for;

monitoring an output torque request;

determining the propulsion torque to the transmission input shaft based upon the output torque request;

monitoring a desired input speed;

determining a synchronization speed based upon the desired input speed;

determining a desired engine activation speed profile based upon the synchronization speed, comprising;

determining a first stage wherein a compensation torque is provided to the engine through the engine disconnect clutch to accelerate the engine from a stopped state to an engine firing speed, once the engine firing speed is achieved,

determining a second stage wherein the engine provides torque to accelerate the engine while simultaneously reducing the compensation torque provided to the engine,

determining a third stage subsequent to the second stage wherein the compensation torque is provided to the engine by the motor to control the engine to the synchronization speed, and

determining a fourth stage wherein the engine disconnect clutch is locked; and

controlling the motor to provide a motor torque based upon a sum of the propulsion torque and the compensation torque.