Method of controlling a motor vehicle

1. A method of controlling a motor vehicle having an engine driveably connected to an input of a driveline via an electronically controlled clutch, the method comprising:

while the motor vehicle is in a drive mode of operation, in response to an indication that coasting is desirable, automatically transitioning to a coasting mode of operation by controlling the engine to move the driveline into a lash state in which no torque is being transmitted by the driveline and, while the driveline is in the lash state, automatically disengaging the electronically controlled clutch; and

operating the motor vehicle in the coasting mode of operation.

2. The method of claim 1 wherein the indication that coasting is desirable is a tip-out of torque demand by a driver of the motor vehicle.

3. The method of claim 1 wherein controlling the engine to move the driveline into the lash state comprises:

reducing a torque output from the engine to reduce wind-up in the driveline; and

after the wind-up in the driveline has been eliminated, controlling a rotational speed of the engine to move the driveline into the lash state.

4. The method of claim 3 further comprising controlling the rotational speed of the engine to maintain the driveline in the lash state for a minimum period of time before disengaging the electronically controlled clutch.

5. The method of claim 1 further comprising controlling a rotational speed of the engine at an idle speed while the motor vehicle is in the coasting mode of operation.

6. The method of claim 5 further comprising, in response to tip-in of torque demand by a driver of the motor vehicle, automatically transitioning from the coasting mode of operation to the drive mode of operation by:

controlling the rotational speed of the engine to synchronize it with a rotational speed of the input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, increasing a torque output from the engine in a controlled manner to produce wind-up in the driveline;

continuing to increase the torque output from the engine until a predefined level of torque has been attained; and

operating the motor vehicle in the drive mode of operation.

7. The method of claim 5 further comprising, in response to a request for engine braking, automatically transitioning the motor vehicle from the coasting mode of operation to a resistive drive mode of operation by:

controlling the rotational speed of the engine to synchronize it with a rotational speed of the input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, reducing a torque request to the engine to zero; and

operating the motor vehicle in the resistive drive mode of operation.

8. The method of claim 1 further comprising shutting-down the engine while in the coasting mode of operation.

9. The method of claim 8 further comprising, in response to tip-in of torque demand by a driver of the motor vehicle, automatically transitioning the motor vehicle from the coasting mode of operation to the drive mode of operation by:

starting the engine;

controlling a rotational speed of the engine to synchronize it with a rotational speed of the input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, increasing a torque output from the engine in a controlled manner to produce wind-up in the driveline;

continuing to increase the torque output from the engine until a predefined level of torque has been attained; and

operating the motor vehicle in the drive mode of operation.

10. A motor vehicle comprising:

an engine selectively connected to an input to a driveline by an electronically controlled clutch;

an accelerator pedal sensor to provide a signal indicative of a driver torque demand; and

an electronic controller to control operation of the engine and engagement of the electronically controlled clutch programmed to automatically transition the motor vehicle from a drive mode of operation to a coasting mode of operation in response to the signal from the accelerator pedal sensor indicating that a torque demand tip-out has occurred by:

controlling the engine to move the driveline into a lash state in which no torque is being transmitted by the driveline, and

while the driveline is in the lash state, automatically disengaging the electronically controlled clutch to enter the coasting mode of operation.

11. The vehicle of claim 10 wherein the electronic controller is programmed to control the engine to move the driveline into the lash state by:

decreasing, in a controlled manner, a torque output from the engine to remove wind-up from the driveline; and

after the wind-up has been removed from the driveline, controlling a rotational speed of the engine to move the driveline into the lash state.

12. The vehicle of claim 10 wherein the electronic controller is further programmed to transition the motor vehicle from the coasting mode of operation to the drive mode of operation in response to the signal from the accelerator pedal sensor indicating that a torque demand tip-in has occurred by:

controlling a rotational speed of the engine to synchronize it with a rotational speed of the input to the driveline; and

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, increasing a torque output from the engine in a controlled manner to produce wind-up in the driveline;

continuing to increase the torque output from the engine until a predefined level of torque has been attained; and

operating the motor vehicle in the drive mode of operation.

13. The vehicle of claim 10 wherein the electronic controller is programmed to detect an impact signature indicating that the driveline has traversed from the lash state to a non-lash state.

14. A method of controlling a motor vehicle comprising:

while in a drive mode of operation, responding to a tip-out of torque demand by controlling an engine to move a driveline into a lash state and then, while the driveline is in the lash state, automatically disengaging an electronically controlled clutch to transition into a coasting mode of operation; and

operating in the coasting mode of operation.

15. The method of claim 14 wherein controlling the engine to move the driveline into the lash state comprises:

reducing a torque output from the engine to reduce wind-up in the driveline;

after the wind-up in the driveline has been eliminated, controlling a rotational speed of the engine to move the driveline into the lash state; and

controlling the rotational speed of the engine to maintain the driveline in the lash state for a minimum period of time before disengaging the electronically controlled clutch.

16. The method of claim 14 further comprising controlling a rotational speed of the engine at an idle speed while the motor vehicle is in the coasting mode of operation.

17. The method of claim 16 further comprising, in response to tip-in of torque demand:

controlling the rotational speed of the engine to synchronize it with a rotational speed of an input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, automatically engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, increasing a torque output from the engine in a controlled manner to produce wind-up in the driveline;

continuing to increase the torque output from the engine until a predefined level of torque has been attained; and

operating the motor vehicle in the drive mode of operation.

18. The method of claim 16 further comprising, in response to a request for engine braking:

controlling the rotational speed of the engine to synchronize it with a rotational speed of an input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, automatically engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, reducing a torque request to the engine to zero; and

operating the motor vehicle in a resistive drive mode of operation.

19. The method of claim 14 further comprising shutting-down the engine while in the coasting mode of operation.

20. The method of claim 19 further comprising, in response to tip-in of torque demand:

starting the engine;

controlling a rotational speed of the engine to synchronize it with a rotational speed of an input to the driveline;

upon achieving synchronization of the rotational speed of the engine and the rotation speed of the input to the driveline, automatically engaging the electronically controlled clutch;

after the electronically controlled clutch is engaged, increasing a torque output from the engine in a controlled manner to produce wind-up in the driveline;

continuing to increase the torque output from the engine until a predefined level of torque has been attained; and

operating the motor vehicle in the drive mode of operation.