Method of speed control for a vehicle
A vehicle is adapted to sense a condition of use in which a maximum speed control speed is reduced. The condition of use may be indicated by a sensor of the vehicle, or selected according to the kind of terrain across which the vehicle is travelling. Selection of terrain type may be manual or automatic, and may enable a selection of sensors appropriate to the terrain type. A vehicle driver may select a speed control speed lower than the permitted maximum.
1. A method of automatically controlling a speed of a vehicle to maintain a control speed, said method comprising:
detecting a plurality of off-road conditions of the vehicle;
determining a maximum-speed control speed appropriate to each of the detected off-road conditions; and
automatically setting a maximum-speed control speed appropriate to the detected off-road condition corresponding to a minimum of the determined maximum speed control speeds appropriate to each of the detected off-road conditions.
2. The method set forth in claim 1 comprising enabling selection of off-road speed control.
3. The method set forth in claim 1 comprising enabling selection of off-road speed control when an off-road condition has been detected.
4. The method set forth in claim 1 , including controlling vehicle speed to match a set-speed, the method comprising permitting variation of vehicle set-speed whilst speed control is enabled in said off-road condition.
5. The method set forth in claim 1 , comprising providing an override for said set maximum-speed control speed.
6. The method set forth in claim 1 , comprising selecting an off-road condition of the vehicle and automatically setting said maximum-speed control speed.
7. The method set forth in claim 6 , comprising determining said maximum-speed control speed by selecting a plurality of parameters to be detected, an identity of the selected parameters being dependent upon the selected off-road condition, and determining the maximum-speed control speed according to a value of the plurality of parameters.
8. The method set forth in claim 6 , wherein said off-road condition is selected automatically by a system of the vehicle.
9. The method set forth in claim 1 , comprising repeatedly setting a maximum-speed control speed in accordance with one or more detected conditions of the vehicle.
10. The method set forth in claim 9 , and repeated at a frequency of greater than 10 Hz.
11. The method set forth in claim 1 , comprising setting the maximum-speed control speed in dependence on whether a vehicle is cresting a slope.
12. The method set forth in claim 1 , wherein a reduction in the maximum-speed control speed is temporary.
13. An electronic control unit for automatically controlling the speed of a vehicle to maintain a control speed, the electronic control unit adapted to detect a plurality of off-road conditions of the vehicle, calculate a maximum-speed control speed appropriate to each of the detected off-road conditions, and set a maximum-speed control speed appropriate to said condition corresponding to a minimum of the calculated maximum-speed control speeds appropriate to each of the detected off-road conditions.
14. The control unit defined in claim 13 operable to enable selection of off-road speed control.
15. The control unit defined in claim 13 operable to enable selection of off-road speed control when an off-road condition has been detected.
16. The control unit defined in claim 13 , wherein said set maximum-speed control speed is automatically enabled upon detecting of an off-highway condition.
17. The control unit defined in claim 13 , wherein said set maximum-speed control speed is dependent upon a selected terrain.
18. A vehicle incorporating the electronic control unit of claim 13 .
19. The vehicle defined in claim 18 , and having a terrain sensor for automatically detecting one of a plurality of off-road conditions.