Collision warning system and method for a motor vehicle
View Patent ↗A collision warning system and method for a motor vehicle. A measuring device in the vehicle is provided for measuring the distance dx to a second vehicle traveling ahead, the distance signal being delivered to an evaluation device in the first vehicle. The evaluation device continuously calculates a deceleration a subject vehicle demand , which is applied by the vehicle after expiration of a driver reaction time T reaction in order that a remaining distance dx remaining to the second vehicle traveling ahead can be maintained. If a subject vehicle demand exceeds an instantaneous deceleration that can be achieved by an adaptive cruise control (“ACC”) system, a system limit warning is transmitted, prompting the vehicle driver to brake with additional appropriate force. If a subject vehicle demand exceeds an assumed vehicle deceleration that can be generated by braking on the part of the driver, a collision warning signal is transmitted independently of the ACC system.
1. A collision warning method for a vehicle, the vehicle having a device for measuring the distance from the vehicle to a second vehicle traveling ahead and a control unit programmed to generate a warning when a danger of collision of the vehicle and the second vehicle is determined, the method comprising the steps of:
repetitively calculating in the control unit a deceleration rate for the vehicle sufficient to maintain a preselected distance between the vehicle and the second vehicle when the vehicle is decelerated subsequent to expiration of a braking reaction time of the driver of the vehicle, the calculation being based at least in part on a relative speed of the vehicle and the second vehicle, the distance between the vehicle and the second vehicle, a deceleration rate for the second vehicle and the preselected distance;
repetitively comparing the calculated deceleration rate for the vehicle against a deceleration rate associated with vehicle braking initiated by the driver of the vehicle; and
generating a collision warning signal when the calculated deceleration rate for the vehicle exceeds the deceleration rate associated with vehicle braking initiated by the driver of the vehicle;
wherein the deceleration rate for the vehicle “a subject vehicle demand ” is calculated according to:
a
subject
vehicle
demand
=
-
dv
1
2
2
·
(
dx
1
-
dx
remaining
)
+
a
front_
0
where:
dv 1 =the relative speed of the vehicle and the second vehicle at the expiration of the braking reaction time of the driver of the vehicle,
dx 1 =the distance between the vehicle and the second vehicle at the expiration of the braking reaction time of the driver of the vehicle,
dx remaining =the preselected distance between the vehicle and the second vehicle at the end of deceleration of the vehicle, and
a front — o =the deceleration rate for the second vehicle.
2. The method according to claim 1 , wherein the vehicle includes an adaptive cruise control system, and further comprising the steps of repetitively comparing the calculated deceleration rate for the vehicle against a vehicle deceleration rate that can be achieved by the adaptive cruise control system, and generating a system limit warning when the calculated vehicle deceleration rate exceeds the vehicle deceleration rate that can be achieved by the adaptive cruise control system.
3. The method according to claim 2 , further comprising the step of automatically initiating braking of the vehicle when the system limit warning is generated.
4. The method according to claim 3 , wherein vehicle deceleration resulting from the automatically initiated braking is limited to a rate less than the maximum possible deceleration of the vehicle.
5. The method according to claim 2 , wherein the system limit warning is at least one of an audible and visual and tactile signal.
6. The method according to claim 1 , wherein the preselected distance is 0-30 meters.
7. The method according to claim 1 , wherein the braking reaction time of the driver of the vehicle when the driver is not initiating braking of the vehicle is 0.5-3.0 seconds.
8. The method according to claim 1 , wherein the braking reaction time of the driver of the vehicle when the driver is initiating braking of the vehicle is 0.1-2.0 seconds.
9. The method according to claim 1 , further comprising the step of automatically initiating braking of the vehicle when the collision warning is generated.
10. The method according to claim 9 , wherein vehicle deceleration resulting from the automatically initiated braking is limited to a rate less than the maximum possible deceleration of the vehicle.
11. The method according to claim 1 , wherein the collision warning is at least one of an audible and visual and tactile signal.
12. A system for warning the driver of a vehicle of an impending collision with a second vehicle traveling ahead, the system comprising:
means for measuring a distance from the vehicle to the second vehicle traveling ahead;
a control unit;
means associated with the control unit for repetitively calculating a deceleration rate for the vehicle sufficient to maintain a preselected distance between the vehicle and the second vehicle when the vehicle is decelerated subsequent to expiration of a braking reaction time of the driver of the vehicle, the calculation being based at least in part on a relative speed of the vehicle and the second vehicle, the distance between the vehicle and the second vehicle, a deceleration rate for the second vehicle and the preselected distance;
means for repetitively comparing the calculated deceleration rate for the vehicle against a deceleration rate associated with vehicle braking initiated by the driver of the vehicle; and
means for generating a collision warning signal when the calculated deceleration rate for the vehicle exceeds the deceleration rate associated with vehicle braking initiated by the driver of the vehicle;
wherein the means for calculating the deceleration rate for the vehicle “a subject vehicle demand ” effects the formula:
a
subject
vehicle
demand
=
-
dv
1
2
2
·
(
dx
1
-
dx
remaining
)
+
a
front_
0
where:
dv 1 =the relative speed of the vehicle and the second vehicle at the expiration of the braking reaction time of the driver of the vehicle,
dx 1 =the distance between the vehicle and the second vehicle at the expiration of the braking reaction time of the driver of the vehicle,
dx remaining =the preselected distance between the vehicle and the second vehicle at the end of deceleration of the vehicle, and
a front — o =the deceleration rate for the second vehicle.
13. The system according to claim 12 , further comprising an adaptive cruise control system, means for repetitively comparing the calculated deceleration rate for the vehicle against a vehicle deceleration rate that can be achieved by the adaptive cruise control system, and means for generating a system limit warning when the calculated vehicle deceleration rate exceeds the vehicle deceleration rate that can be achieved by the adaptive cruise control system.
14. The system according to claim 13 , further comprising means for automatically initiating braking of the vehicle when the system limit warning is generated.
15. The system according to claim 14 , wherein vehicle deceleration resulting from the automatically initiated braking is limited to a rate less than the maximum possible deceleration of the vehicle.
16. The system according to claim 13 , wherein the system limit warning is at least one of an audible and visual and tactile signal.
17. The system according to claim 12 , wherein the preselected distance is 0-30 meters.
18. The system according to claim 12 , wherein the braking reaction time of the driver of the vehicle when the driver is not initiating braking of the vehicle is 0.5-3.0 seconds.
19. The system according to claim 12 , wherein the braking reaction time of the driver of the vehicle when the driver is initiating braking of the vehicle is 0.1-2.0 seconds.
20. The system according to claim 12 , further comprising means for automatically initiating braking of the vehicle when the collision warning is generated.
21. The system according to claim 20 , wherein vehicle deceleration resulting from the automatically initiated braking is limited to a rate less than the maximum possible deceleration of the vehicle.
22. The system according to claim 12 , wherein the collision warning is at least one of an audible and visual and tactile signal.