Vehicle speed control system and method

Abstract

Embodiments of the present invention provide a vehicle control system comprising a plurality of speed control systems each operable to cause the vehicle to operate in accordance with a respective target speed, the system being operable wherein one at said plurality of speed control systems may be selected to control vehicle speed at a given moment in time, wherein when responsibility for speed control is transferred from a first one of the plurality of speed control systems to a second one of the speed control systems, the second one of the speed control systems is operable to set a value of target speed thereof to a value corresponding to that of the target speed of the first.

1 . A vehicle control system comprising a plurality of speed control systems each operable to cause the vehicle to operate in accordance with a respective target speed,
 wherein when responsibility for speed control is transferred from a first one of the plurality of speed control systems to a second one of the speed control systems, a value of target speed of the second speed control system is set to a value dependent on the target speed of the first speed control system.   
     
     
         2 . A vehicle control system according to  claim 1  operable to set the target speed of the second one of the speed control systems to the instant value of the target speed of the first one of the speed control systems when the second one of the speed control systems assumes responsibility for controlling vehicle speed from the first one of the speed control systems. 
     
     
         3 . A vehicle control system according to  claim 1  wherein one or more of the speed control systems may be operable to cause the vehicle to operate in accordance with a respective temporary maximum speed value that is less than the instant target speed in dependence on one or more parameters. 
     
     
         4 . A vehicle control system according to  claim 3  wherein one or more of the speed control systems are operable to resume operation at the target speed thereof if the temporary maximum speed value becomes greater than or equal to the target speed or the speed control system no longer causes the vehicle to operate in accordance with the temporary maximum speed value. 
     
     
         5 . A system according to  claim 3  operable to set the temporary maximum speed value of one or more of the speed control systems in dependence on a type of terrain in which the vehicle is operating. 
     
     
         6 . A system according to  claim 5  operable to receive one or more signals indicative of a type of terrain in which the vehicle is operating whereby the system may set the maximum allowable value of target speed. 
     
     
         7 . A vehicle control system according to  claim 1  operable to store data in respect of a previous value of target speed for one or more of the speed control systems, wherein if one said one or more speed control systems is reselected to be responsible for speed control following deselection thereof, the reselected system is operable to resume operation at the value of target speed employed by the reselected system when the system was last selected. 
     
     
         8 . A vehicle control system according to  claim 1  configured wherein if responsibility for speed control is transferred from the first one of the plurality of speed control systems to the second one of the speed control systems whilst the first is accelerating the vehicle to the target speed of the first, the second one of the speed control systems is operable to continue accelerating the vehicle at a rate corresponding to that of the first speed control system. 
     
     
         9 . A vehicle comprising a control system according to  claim 1 . 
     
     
         10 . A method of controlling a vehicle comprising:
 controlling a speed of a vehicle by means of one of a plurality of speed control systems; and   transferring responsibility from a first one of the plurality of speed control systems to a second one of the speed control systems,   the method comprising setting a value of target speed of the second one of the speed control systems to a value dependent on the target speed of the first one of the speed control systems when responsibility for speed control is transferred from the first one of the plurality of speed control systems to the second.   
     
     
         11 . A method according to  claim 10  comprising setting the value of target speed of the second one of the speed control systems to a value substantially equal to the target speed of the first one of the speed control systems. 
     
     
         12 . (canceled)