System and method for controlling lash crossing in a vehicle powertrain

1. A vehicle, comprising:

a motor;

an engine selectively coupled to the motor via a clutch; and

a controller configured to, in response to a vehicle wheel torque reversal, open the clutch to disconnect the engine from the motor, command the engine to operate in a speed control mode, and control a motor output torque through a region surrounding the vehicle wheel torque reversal to reduce torque disturbances in a vehicle driveline.

2. The vehicle of claim 1 , wherein the vehicle wheel torque reversal is triggered by an accelerator pedal tip out.

3. The vehicle of claim 1 , wherein the region surrounding the vehicle wheel torque reversal is determined from motor operating parameters.

4. The vehicle of claim 1 , wherein the controller is further configured to close the clutch to connect the engine to the motor responsive to a powertrain torque being outside the region surrounding the vehicle wheel torque reversal.

5. The vehicle of claim 1 , wherein operation in the speed control mode includes controlling an engine speed to match that of a motor speed.

6. The vehicle of claim 1 , wherein the controller is further configured to command the engine to exit the speed control mode responsive to a powertrain torque being outside the region surrounding the vehicle wheel torque reversal.

7. A control system for a vehicle having an engine selectively coupled to a motor via a clutch, comprising:

a controller configured to, in response to a vehicle wheel torque reversal, disengage the clutch to disconnect the engine from the motor, operate the engine in a sailing mode, and modulate motor torque according to a predefined rate of change through a lash region surrounding the vehicle wheel torque reversal to reduce torque disturbances in a driveline.

8. The control system of claim 7 , wherein the torque disturbances include lash in gear meshes of the driveline.

9. The control system of claim 7 , wherein the vehicle wheel torque reversal is from positive to negative and triggered by an accelerator pedal tip out.

10. The control system of claim 7 , wherein the controller is further configured to reengage the clutch to couple the engine with the motor responsive to a powertrain torque being outside the lash region.

11. The control system of claim 7 , wherein operating the engine in the sailing mode includes controlling the engine to rotate at a speed equal to a motor speed.

12. The control system of claim 7 , wherein the controller is further configured to exit the sailing mode through reengagement of the clutch responsive to a powertrain torque being outside the lash region.

13. A method for controlling a vehicle having an engine selectively coupled to a motor via a clutch, comprising:

in response to a vehicle wheel torque reversal, disengaging the clutch to disconnect the engine from the motor, controlling the engine to operate in a speed control mode, and controlling motor torque to reduce a powertrain torque at a predefined rate through a lash region surrounding the vehicle wheel torque reversal to reduce torque disturbances in a vehicle driveline.

14. The method of claim 13 , wherein operation in the speed control mode includes controlling an engine speed to match that of a motor speed.

15. The method of claim 13 , further comprising:

commanding the engine to exit the speed control mode responsive to the powertrain torque being outside the lash region.

16. The method of claim 13 , wherein the vehicle wheel torque reversal is from positive to negative and triggered by an accelerator pedal tip out.

17. The method of claim 13 , further comprising:

reengaging the clutch to couple the engine to the motor responsive to the powertrain torque being outside the lash region.

18. The method of claim 13 , wherein the lash region is determined from motor operating parameters.