Method for performing a braking maneuver using a vehicle braking assistant

Abstract

In a braking maneuver using a braking assistant (9) in a motor vehicle (3), the braking assistant (9) initiates an automatic braking maneuver when an actual distance (a) between the motor vehicle (3) and an object (5) located ahead of the motor vehicle (3) becomes less than a specified minimum distance (a.sub.min). Then an acceleration of the decelerating vehicle (3) is ascertained during the braking maneuver, and if the acceleration is positive then the braking maneuver initiated by the braking assistant (9) is automatically interrupted.

Claims

1. A method of performing a braking maneuver using a braking assistant in a motor vehicle, wherein: the braking assistant initiates an automatic braking maneuver when a distance between the motor vehicle and an object located ahead of the motor vehicle is less than a predetermined minimum distance, an acceleration of the motor vehicle during the automatic braking maneuver is ascertained, wherein the acceleration is defined as positive for an increasing speed in a forward travel direction of the motor vehicle and for a decreasing speed in a backward travel direction of the motor vehicle, a current change in speed of the motor vehicle is ascertained by integration of the acceleration using an acceleration integrator, excluding determining a direction of travel of the motor vehicle other than as indicated indirectly by the ascertained acceleration being positive or negative, and when the ascertained acceleration is positive, in response thereto the automatic braking maneuver is automatically interrupted.

2. The method according to claim 1, wherein the acceleration is ascertained as an acceleration signal by an onboard acceleration sensor.

3. The method according to claim 1, a low-pass filter is used as the acceleration integrator.

4. The method according to claim 1, wherein the current change in speed of the motor vehicle is compared with a specified speed threshold.

5. The method according to claim 4, wherein, when the current change in speed exceeds the specified speed threshold, the automatic braking maneuver is automatically interrupted.

6. A method of braking a motor vehicle with an automatic braking assistant system of the motor vehicle, comprising steps: a) initiating an automatic braking of the motor vehicle with the automatic braking assistant system; b) while the automatic braking is proceeding, with a sensor of the motor vehicle producing a sensor signal that is indicative of an acceleration of the motor vehicle, and evaluating the sensor signal to determine a sign of the acceleration, wherein the sign of the acceleration is defined as positive for an increasing speed in a forward travel direction of the motor vehicle and for a decreasing speed in a backward travel direction of the motor vehicle; c) ascertaining a current change in speed of the motor vehicle by integrating the acceleration using an acceleration integrator; d) excluding determining a direction of travel of the motor vehicle other than as indicated indirectly by the sign of the acceleration; and e) when the sign of the acceleration is positive while the automatic braking is proceeding, then in response thereto automatically interrupting the automatic braking of the motor vehicle with the automatic braking assistant system.

7. The method according to claim 6, further comprising the step: when the sign of the acceleration is negative while the automatic braking is proceeding, then in response thereto automatically continuing the automatic braking of the motor vehicle with the automatic braking assistant system.

8. The method according to claim 6, wherein the step a) comprises detecting a spacing distance between the motor vehicle and an object located in front of the motor vehicle, comparing the detected spacing distance to a distance threshold, and when the detected spacing distance falls below the distance threshold then in response thereto performing the initiating of the automatic braking of the motor vehicle.

9. The method according to claim 8, further comprising the step: when the sign of the acceleration is negative while the automatic braking is proceeding, then in response thereto automatically continuing the automatic braking of the motor vehicle with the automatic braking assistant system.

10. The method according to claim 1, wherein when the ascertained acceleration is negative, in response thereto the automatic braking maneuver is automatically continued.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following exemplary embodiments of the invention are explained in more detail using a drawing. This shows as follows:

(2) FIG. 1 a first traffic situation with two vehicles following one behind the other in a forward travel direction, and maintaining more than a specified minimum distance (a.sub.min) between the vehicles, and

(3) FIG. 2 a second traffic situation with the two vehicles travelling backwards, and where the actual distance (a) falls below the specified minimum distance (a.sub.min).

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(4) FIG. 1 shows a traffic situation 1, in which an ego-vehicle or subject vehicle 3 and an object located ahead of the ego-vehicle 3, e.g. another vehicle 5, are travelling one behind the other in a lane 7 in the same direction of movement x, in forwards direction, at a distance a. The distance between the two vehicles is above a specified minimum distance a.sub.min (a>a.sub.min).

(5) The ego-vehicle 3 is equipped with a braking assistant 9 with an acceleration sensor 11. By means of the braking assistant 9, in the event of an impending collision, when therefore the other vehicle 5 brakes, a braking maneuver of the ego-vehicle 3 is initiated. Here the acceleration sensor 11 ascertains the acceleration of the ego-vehicle 3. The braking assistant 9 uses the sign of the ascertained acceleration signal to ascertain the direction of movement of the ego-vehicle 3.

(6) In this case, when the other vehicle 5 brakes, the distance a between the two vehicles 3,5 reduces and the braking assistant 9 initiates a braking maneuver when the distance a falls below the specified minimum distance a.sub.min, in order to restore the required minimum distance a.sub.min. The speed of the ego-vehicle 3 reduces in the forwards direction due to the braking. The acceleration signal accordingly takes a negative value. The braking maneuver is accordingly continued until the minimum distance a.sub.min has been achieved again.

(7) In the traffic situation 21 shown in FIG. 2, in addition to the two vehicles 3, 5 there is an obstruction in the form of a further vehicle 23 that is backing or reversing in the lane 7. The other vehicle 5 located ahead of the ego-vehicle 3 is accordingly travelling backwards to avoid the obstruction 23. At the same time the ego-vehicle 3 is also travelling backwards, to avoid a collision with the other vehicle 5.

(8) In this case, however, the other vehicle 5 is travelling backwards faster than the ego-vehicle 3, so that the distance a between the two vehicles 3, 5 falls to a level below the critical specified minimum distance a.sub.min (a<a.sub.min). Because the actual distance a is below the minimum distance a.sub.min the braking assistant 9, which has no knowledge of the direction of travel, thus in this case the backwards direction, initiates a braking maneuver, in an attempt to increase the distance between the two vehicles 3, 5.

(9) The response by the braking assistant 9 would thus lead to the actual collision between the two vehicles 3, 5 that is to be avoided. Through further intervention of the braking assistant 9, however, such a collision is prevented. By ascertaining the acceleration, the starting direction of movement of the vehicle 3 is ascertained. The acceleration signal ascertained by means of the acceleration sensor 11 in this case takes a positive value during the braking maneuver. In this case the initiated braking maneuver is interrupted by the braking assistant 9 and thus a collision between the two vehicles 3,5 is avoided or at least the seriousness of the consequences of such a collision is reduced.

LIST OF REFERENCE NUMERALS

(10) 1 Traffic situation 3 Ego-vehicle 5 Object 7 Lane 9 Braking assistant 11 Acceleration sensor 21 Traffic situation 23 Obstacle