Vehicle speed control

1. A speed control system for a vehicle, comprising an electronic controller, wherein the electronic controller is configured to:

automatically cause the a vehicle to operate in accordance with a target speed value,

receive information relating to movement of at least a portion of a vehicle body, said information comprising: a measured value of vehicle body pitch angular acceleration, a measured value of vehicle body roll angular acceleration, and a measured value of vehicle body heave acceleration,

apply a gain to each of said measured value of vehicle body pitch angular acceleration, measured value of vehicle body roll angular acceleration, and measured value of vehicle body heave acceleration, and determining a signal indicative of comfort level therefrom; and

output a signal to automatically adjust the value of the target speed value in dependence on said signal indicative of comfort level.

2. A system according to claim 1 wherein the controller is further configured to determine an amount by which the target speed should be adjusted from the current value in dependence at least in part on the signal indicative of comfort level.

3. A system according to claim 2 wherein the controller is configured to determine the target speed value in further dependence on at least one parameter associated with movement of the vehicle over terrain selected from amongst: steering angle, vehicle speed, steering angle as a function of vehicle speed, a value of driving surface side slope, a driving surface gradient, and an amount of vehicle suspension articulation or suspension warp.

4. A system according to claim 2 wherein the controller is configured to determine a comfort derived maximum speed value dependent upon the signal indicative of comfort level and at least one further maximum speed value, the system being operable to cause the value of target speed to be set to the lower of the comfort derived maximum speed value and the at least one further maximum speed value.

5. A system according to claim 4 wherein the at least one further maximum speed value includes a user defined speed value corresponding to a maximum speed at which the user wishes to travel.

6. A system according to claim 4 wherein the at least one further maximum speed value includes a speed value being a maximum speed appropriate to an instant value of at least one further parameter associated with movement of the vehicle over terrain.

7. A system according to claim 2 wherein the controller is configured to iteratively adjust the target speed value to reduce a difference between the signal indicative of comfort level and a prescribed value or a prescribed range of values.

8. A system according to claim 7 wherein the controller is configured to calculate a value of desired vehicle acceleration or speed change in dependence on the value of the signal indicative of measured comfort level thereby to adjust the target speed value to reduce the difference between the signal indicative of measured comfort level and prescribed value or a prescribed range of values.

9. A system according to claim 1 wherein the controller is configured to receive a user input electrical signal and based on said user input electrical signal the controller is further configured to manipulate the amount by which the target speed value is adjusted.

10. A system according to claim 9 , wherein the controller is configured to receive a user input electrical signal and based on said user input electrical signal the controller is further configured to manipulate the amount by which the target speed value is adjusted and wherein based on the user input electrical signal the controller is configured to manipulate the value of the signal indicative of measured comfort level thereby to control the amount by which the target speed value is adjusted.

11. A system according to claim 10 wherein based on the user input electrical signal the controller is configured to manipulate a value of a reference signal, the controller being further configured to compare the reference signal to the signal indicative of measured comfort thereby to control the amount by which the target speed value is adjusted.

12. A system according to claim 11 wherein the controller is configured to control the amount by which the target speed value is adjusted in dependence upon the difference between the manipulated value of the reference signal and the signal indicative of measured comfort.

13. A system according to claim 1 , wherein the controller is configured to adjust the target speed value in dependence on data in respect of seat occupancy.

14. A system according to claim 1 further comprising an imaging device that, in use, monitors movement of the at least a portion of the body of an occupant.

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

16. A method of operating a speed control system of a vehicle, said method comprising:

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

receiving information relating to movement of at least a portion of a vehicle body, said information comprising: a measured value of vehicle body pitch angular acceleration, a measured value of vehicle body roll angular acceleration, and a measured value of vehicle body heave acceleration;

applying a gain to each of said measured value of vehicle body pitch angular acceleration, measured value of vehicle body roll angular acceleration, and measured value of vehicle body heave acceleration, to determine a signal indicative of measured comfort level; and

adjusting automatically the value of the target speed value in dependence on said signal indicative of measured comfort level.

17. A non-transitory carrier medium carrying a computer readable code for controlling a vehicle to carry out the method of claim 16 .