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 the presence of a preceding vehicle (12) or other object in the path of the controlled vehicle (10); controlling the speed of the controlled vehicle on the basis of a first speed control mode in the absence of a preceding vehicle or other object, the first speed control mode including the steps of sensing 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 minimize the difference between the driver set speed and the actual speed of the controlled vehicle; sensing 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 a desired spacing (RNG D ) between the controlled vehicle and the preceding vehicle or other object; obtaining a predetermined minimum allowable spacing (D MIN ) which is less than the desired spacing; controlling the speed of the controlled vehicle on the basis of a second speed control mode (MODE 1) when the actual spacing exceeds the desired spacing; controlling the speed of the controlled vehicle on the basis of a third speed control mode (MODE 2) when the actual spacing is less than the desired spacing, the third speed control mode including the steps of (a) calculating 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 speed (V O ) of the controlled vehicle approaches the speed (V T ) of the preceding vehicle or other object, 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 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 second or third speed control mode comprises the steps of reading a driver-set input indicative of a driver's preferred driving style; determining a maximum tolerable vehicle deceleration value (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 to the maximum tolerable vehicle deceleration when the calculated deceleration exceeds the maximum tolerable deceleration; and generating a warning when the calculated deceleration exceeds the maximum tolerable vehicle deceleration.

Claim 5

A method according to any preceding claim, wherein the step of controlling vehicle speed on the basis of the third 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 the calculated deceleration (A O ) on the basis of the desired braking reaction time.

Claim 6

A method of controlling the speed of a controlled vehicle comprising the steps of sensing the presence of a preceding object (12) in the path of the controlled vehicle (10); sensing the actual spacing (RNG A ) between the controlled vehicle and the object; sensing the relative speed between the controlled vehicle and the object; decelerating the controlled vehicle on the basis of a first speed control mode (MODE 1) when the actual spacing (RNG A ) exceeds a predetermined desired spacing (RNG D ), the first speed control mode being adapted to decelerate the controlled vehicle in such a manner that as the actual spacing approaches the desired spacing, the relative speed between the controlled vehicle and the object approaches zero and the deceleration of the controlled vehicle approaches zero; decelerating the controlled vehicle on the basis of a second speed control mode (MODE 2) when the actual spacing (RNG A ) is less than the predetermined desired spacing (RNG D ), the second control mode including the steps of (i) calculating 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 a predetermined minimum allowable spacing (D MIN ), the relative speed between the controlled vehicle and the object approaches zero, and the calculated deceleration value approaches zero; (ii) decelerating the controlled vehicle on the basis of the calculated deceleration value, (iii) decelerating the controlled vehicle at a predetermined deceleration value (A MIN ) when the calculated deceleration value (A O ) decreases to a value less than or equal to the predetermined deceleration value, and (iv) maintaining the controlled vehicle deceleration at the predetermined deceleration value until the actual spacing exceeds the desired spacing.