Vehicle speed control system and method

1. A vehicle speed control system operable to cause a vehicle to operate in accordance with a target speed value, the system being operable automatically to:

perform a direction change operation wherein the system causes a speed of the vehicle to reduce to a value not exceeding a direction change speed limit value, being a maximum speed at which a transmission of the vehicle is permitted to adopt a configuration corresponding to travel in an opposite direction to an instant configuration, if the vehicle speed exceeds the direction change speed limit value when the direction change operation is commenced;

to cause a transmission of the vehicle to adopt a configuration corresponding to travel in the opposite direction to the instant configuration when the speed has reduced to a value not exceeding the direction change speed limit value, and

accelerate the vehicle from rest following a change in configuration of the transmission from travel in a first direction to travel in a second direction opposite the first at a moment selected in dependence on suspension system articulation.

2. A system according to claim 1 operable automatically to cause the vehicle to operate in accordance with a target speed value following a direction change operation.

3. A system according to claim 1 operable to cause the vehicle to operate in accordance with a forward direction target speed value when travelling in a forward direction and a reverse direction target speed value when travelling in a reverse direction opposite the forward direction.

4. A system according to claim 3 wherein the forward direction target speed value is substantially equal to the reverse direction target speed value.

5. A system according to claim 3 operable to limit the value of the reverse direction target speed value to a maximum reverse direction target speed value.

6. A system according to claim 1 operable to perform the direction change operation in response to user selection of a transmission mode corresponding to travel in an opposite direction.

7. A system according to claim 1 operable to accelerate the vehicle from rest following a change in configuration of the transmission from travel in a first direction to travel in a second direction opposite the first when the suspension system of a newly trailing axle is in a configuration corresponding substantially to a maximum excursion of a body of the vehicle in a downward direction prior to acceleration from rest.

8. A system according to claim 1 operable to perform a rock-away operation in which the system causes the vehicle repeatedly to perform the direction change operation.

9. A system according to claim 8 wherein when the system is performing said rock-away operation, the system is operable automatically to perform a direction change operation in response to detection of a step in a driving surface.

10. A system according to claim 1 operable to allow a user to command execution of a direction change operation by selecting a transmission operating mode corresponding to travel in an opposite direction to that of the instant transmission operating mode.

11. A system according to claim 1 configured to apply a braking system to control vehicle speed while the direction change operation is in progress.

12. A system according to claim 11 configured to apply a braking system to control vehicle speed to prevent vehicle speed from exceeding the direction change speed limit value whilst the direction change operation is in progress.

13. A system according to claim 1 configured to employ a braking system to prevent rollback once a gear corresponding to travel in the opposite direction has been selected.

14. A system according to claim 13 configured to cause the vehicle to come to rest by means of the braking system and subsequently to prevent rolling in a direction opposite the intended new direction of travel, by means of the braking system, when a direction change operation is performed.

15. A system according to claim 14 configured to release the braking system once sufficient torque is being applied to one or more wheels by a powertrain and/or as a consequence of gravitation force to permit the vehicle to move in the newly selected direction without experiencing rolling in the opposite direction.

16. A vehicle comprising a system according to claim 1 .

17. A method of controlling a vehicle by means of a speed control system, comprising:

causing a vehicle to operate in accordance with a target speed value; and

automatically performing a direction change operation, whereby performing the direction change operation comprises causing a speed of the vehicle to reduce to a value not exceeding a direction change speed limit value, being a maximum speed at which a transmission of the vehicle is permitted to adopt a configuration corresponding to travel in an opposite direction to an instant configuration, if the vehicle speed exceeds the direction change speed limit value when the direction change operation is commenced;

performing the direction change operation further comprises causing a transmission of the vehicle to adopt a configuration corresponding to travel in an opposite direction to the instant configuration when the vehicle speed does not exceed the direction change speed limit value; and

accelerating the vehicle from rest following a change in configuration of the transmission from travel in a first direction to travel in a second direction opposite the first at a moment selected in dependence on suspension system articulation.

18. A method according to claim 17 comprising applying a braking system to control vehicle speed whilst the direction change operation is in progress.

19. A method according to claim 18 comprising applying a braking system to control vehicle speed to prevent vehicle speed from exceeding the direction change speed limit value whilst the direction change operation is in progress.

20. A method according to claim 17 comprising employing a braking system to prevent rollback once a gear corresponding to travel in the opposite direction has been selected.

21. A method according to claim 20 comprising causing the vehicle to come to rest by means of the braking system and subsequently preventing rolling in a direction opposite the intended new direction of travel, by means of the braking system, when a direction change operation is performed.

22. A method according to claim 21 comprising releasing the braking system once sufficient torque is being applied to one or more wheels by a powertrain and/or as a consequence of gravitation force to permit the vehicle to move in the newly selected direction without experiencing rolling in the opposite direction.

23. An electronic controller for a vehicle having a storage medium associated therewith storing instructions that when executed by the controller causes the control of the operation of a brake system of a vehicle in accordance with the method of claim 17 .

24. A non-transitory, computer-readable storage medium storing instructions thereon that when executed by one or more electronic processors causes the one or more electronic processors to carry out the method of claim 17 .