Method of controlling the speed of a vehicle

Claim 1

A method of controlling the speed of a controlled vehicle comprising the steps of sensing (54) the presence of a preceding vehicle (12) or other object in the path of the controlled vehicle (10); sensing (52) the actual spacing (RNG A ) between the controlled vehicle and the preceding vehicle or other object when a preceding vehicle or other object is determined to be present; ascertaining (58) a desired spacing (RNG D ) between the controlled vehicle and the preceding vehicle or other object; controlling the speed of the controlled vehicle on the basis of a first speed control mode (MODE 1) when the actual spacing exceeds the desired spacing; and controlling (88) the speed of the controlled vehicle on the basis of a second speed control mode (MODE 2) when the actual spacing is less than the desired spacing; characterised by sensing (52) the relative speed between the controlled vehicle and the preceding vehicle or other object; obtaining (112) a predetermined minimum allowable spacing (D MIN ) which is less than the desired spacing; and in that the second speed control mode includes the steps of (a) calculating (136) a vehicle deceleration value (A O ) by which to decelerate the controlled vehicle, the deceleration value being calculated such that as the actual spacing approaches the minimum allowable spacing, the relative speed between the controlled vehicle and the preceding vehicle or other object approaches zero, and the calculated deceleration value approaches zero; (b) decelerating the controlled vehicle on the basis of the calculated deceleration value; (c) decelerating the controlled vehicle at a predetermined deceleration value (A MIN ) when the calculated deceleration value decreases to a value less than or equal to the predetermined deceleration value; and (d) maintaining the controlled vehicle deceleration at the predetermined deceleration value until the actual spacing exceeds the desired spacing.

Claim 4

A method according to any one of Claims 1 to 3, wherein the step of controlling vehicle speed on the basis of the first or second speed control mode (MODE 1, MODE 2) comprises the steps of reading a driver-set input indicative of a driver's preferred driving style; determining (59) a maximum tolerable vehicle deceleration (A D ) on the basis of the driver-set input; comparing the calculated deceleration (A O ) to the maximum tolerable vehicle deceleration; limiting the deceleration of the controlled vehicle (10) to the maximum tolerable vehicle deceleration when the calculated deceleration exceeds the maximum tolerable deceleration; and generating (128) a warning when the calculated deceleration exceeds the maximum tolerable vehicle deceleration.

Claim 5

A method according to any one of Claims 1 to 4, wherein the step of controlling vehicle speed on the basis of the second speed control mode (MODE 2) comprises the steps of reading a driver-set input indicative of a driver's preferred driving style; determining a desired braking reaction time (T RB ) on the basis of the driver-set input; and adjusting (142) the calculated deceleration (A O ) on the basis of the desired braking reaction time.

Claim 6

A method according to any one of Claims 1 to 5, comprising the additional step of controlling the speed of the controlled vehicle (10) on the basis of a third speed control mode in the absence of a preceding vehicle (12) or other object, the third speed control mode including the steps of sensing (50) a driver-set speed (V SET ) set by the driver as the desired speed of the controlled vehicle, and controlling the speed of the controlled vehicle so as to minimise the difference between the driver-set speed and the actual speed (V O ) of the controlled vehicle.