EP1887540B1 - Device and method for avoiding rear-end collisions - Google Patents

Abstract

The device has a sensor system determining relative speed between own motor vehicle and a following motor vehicle based on the relative speed. An evaluation unit determines a parameter which is compared with a stored reference value, and an action is initiated, if the parameter deviates from the value. The system determines an allocation of neighboring traces, where a probability for an overhauling process of the following motor vehicle is determined from the allocation of the traces. The evaluation unit selects parameter and value based on the probability for an overhauling procedure. An independent claim is also included for a procedure for the avoidance of rear end collisions of motor vehicles.

Description

The invention relates to a device and a method for avoiding rear-end collisions of motor vehicles.

From the DE 199 33 782 A1 a method for avoiding rear-end collisions by the observation of the rear traffic volume of a first motor vehicle is known, wherein the own speed of the first motor vehicle is determined, the relative speed and distance between the first motor vehicle and a subsequent motor vehicle is determined and a time is calculated, which remains, until the two motor vehicles would collide with one another, taking into account a predetermined value for the deceleration of the second motor vehicle and triggering a measure on the first motor vehicle when the calculated time is below a predetermined value.

From the DE 103 28 755 A1 a system is known for avoiding too short a distance from a following vehicle to a preceding vehicle, wherein the preceding vehicle has a device for determining the distance and the relative speed to the following vehicle, wherein based on the determined distance and the relative speed, a minimum distance is determined and Falling below the minimum distance measures are taken to avoid a further reduction of the distance, in order to avoid a possible rear-end collision.

From the EP 0443 185 A2 It is known to assist the driver in changing the lane of his own vehicle by monitoring the backward traffic.

Based on this prior art, the technical problem underlying the invention is to provide a device and a method for avoiding rear-end collisions of motor vehicles, which have an improved warning behavior.

The solution to the technical problem results from the objects with the features of claims 1 and 6. Further advantageous embodiments emerge from the dependent claims.

For this purpose, the device for avoiding rear-end collisions of motor vehicles comprises a sensor system with which at least the relative speed between a separate motor vehicle and a following motor vehicle is determined or calculated, depending on from the relative speed, a parameter can be determined by an evaluation unit, which is compared with a stored comparison value, wherein in a deviation from the comparison value, a measure is initiated to reduce the risk of collision, wherein by means of the sensor occupancy of neighboring tracks can be determined from the occupancy of the neighboring lanes a probability of an overtaking of the following motor vehicle is determined and the determined parameter and / or the stored comparison value is selected depending on the probability of an overtaking by the evaluation. The invention is based on the following findings, which relate to the advantages and disadvantages of different system activations.

A first possibility is that the system becomes active if the stopping distance of the following vehicle calculated by the system is smaller than the distance to the following vehicle measured by the environment sensors of the system. By stopping route is here meant the way the follower vehicle travels until the relative speed of the follower vehicle with respect to the own vehicle is zero.

The stopping distance s can be calculated approximately from the approaching speed V ₀ , the braking deceleration a _B and the reaction time t _R as follows: s = V ₀ * t _R + V ₀ ² / (2 * a _B ). The braking deceleration depends on the brake, tire and road conditions.

The approach speed can be detected by the environment sensors of the system: the braking deceleration of the following vehicle can be estimated by the system taking into account data of other systems installed in the own vehicle. These other systems include brake system, rain light sensor, road condition sensor and / or camera system. The response time from the driver of the follower vehicle can be estimated by the system.

A dead time of the braking system and a hesitant braking intervention by the driver of the follower vehicle and the reaction of a brake assist can also be taken into account in a more detailed calculation.

Advantage of this method for calculating the activation time is that the system activation, ie, inter alia, the warning to the driver of the follower vehicle, for example, by flashing lights, usually done so early that the correct reaction of the driver of the follower vehicle collision can be prevented. Disadvantage of this method is that with overtaking vehicles, which approach from behind with high speed and which change only shortly before the own vehicle the lane, it will come regularly to false warnings.

Another criterion for system activation may be the calculation of a Time To Collision (TTC). The TTC is calculated from the approach speed of the following vehicle V ₀ and the distance to the following vehicle x via TTC = x / V ₀ . If the TTC calculated by the system is less than a preset limit, the system becomes active.

The advantage of this method of calculating the warning time is that false warnings about shunting vehicles are less frequent. The collision speed of the rear-end collision and, with it, the severity of the accident are in any case reduced. Also, depending on the condition of the tire and the road, rear-end collisions at low and medium relative speeds can be avoided. At the latest at high relative speeds, however, the warning comes so late that the rear-end collision can no longer be prevented.

The point in time when the system becomes active is therefore a compromise. It must be chosen so that on the one hand as many system interventions take place in time, that the severity of the accident is minimized or the rear-end collision is prevented, and on the other hand as few unnecessary activations of the system take place.

This is where the invention begins by determining a probability for an overtaking operation, for which purpose an occupancy of neighboring tracks is detected. In addition to the pure existence of objects in the neighboring track, their speed is preferably also recorded. If the determination now shows that the likelihood of an overtaking process is low, an early warning is given, for example by using the stopping distance as the parameter. Accordingly, the "Time To Collision" is then used, for example, as parameter with a high passing probability. The likelihood of the overtaking process is thus used to select a parameter or, if the parameter itself is not changed, to adjust the stored comparison value. At high Überhölwahrscheinlichkeit so the limit or comparison value for the distance or the time is reduced or vice versa low set high. In these cases deviation is to be understood as falling short of the given comparison value. The adaptation to the probability can be binary, stepped or continuous. The measures for avoiding the rear-end collision can be complex. In addition to the flashing lights or other sources of illumination already mentioned, interventions in the driving dynamics of the preceding and / or following vehicle are also conceivable, as are activations of passive and / or active occupant protection devices.

In a preferred embodiment, the sensor system for detecting the occupancy of the neighboring tracks comprises a radar sensor and / or a camera and / or an ultrasound sensor, wherein preferably on the sensors existing vehicle assistance systems such as camera of the lane departure warning, or a video-based parking or reversing aid, radar or lidar of Adaptive Cruise Control or ultrasonic sensors Park Distance Control, lane change assistance systems or a park steering assistance system is used.

In a further preferred embodiment, vehicle surroundings conditions are determined by means of the sensor system, such as crash barriers, curbs or green strips.

In a further preferred embodiment, the device is part of or associated with a lane change assistance system, since the information about the likelihood of an overtaking process is also of interest for the lane change assistance system.

If, for example, another vehicle approaches on its own lane, the approach warning device may intervene as described above. At the same time, the probability is calculated whether and, if so, on which neighboring lane the approaching vehicle will overtake. From an adjustable probability limit, the driver is warned against a lane change on the page in question. The warning can be known to be e.g. by a warning lamp in the exterior mirror or a haptic steering torque done.

In a further preferred embodiment, the distance to the following motor vehicle is detected, wherein at a relative speed of zero, a warning occurs when the distance is smaller than a minimum distance. In this case, the time gap between the own vehicle and the following vehicle preferably serves as a triggering criterion. The time gap t _{z is} calculated here from the own speed of the own vehicle V _E and the distance to the following vehicle x to t _z = x / V _E. The airspeed is communicated to the system by other control devices of the own vehicle. The distance to the following vehicle is determined by the environment sensors of the system.

The time gap has to be set in such a way that on the one hand a warning is given ahead of critical situations and on the other hand unnecessary triggers are prevented.

Furthermore, in the calculation of the warning time a braking of the own vehicle can be taken into account. The warning to the rear traffic then takes place earlier. The braking deceleration of the own vehicle is communicated to the system by the brake system.

Different embodiments of the warning strategy are possible. A possible embodiment is that to avoid false alarms a hazard warning or the triggering of an actuator only takes place when the own vehicle delays itself. This can also be done dynamically, i. H. Below a speed which can be parameterized, the system reacts even if the own vehicle does not decelerate. Above this speed, your own vehicle reacts with warning or actuators only if the vehicle itself also delays.

Furthermore, the known emergency brake warning flashing can be extended. In this system, rear lights are actuated for the purpose of warning the following traffic as soon as a predetermined upper braking deceleration of the own vehicle is exceeded. The system is extended by activating only if the environment sensors of the system recognize a follower vehicle in the lane behind the driver's own vehicle. This avoids unnecessary warnings.

Fig. 1a - g

verschiedene Szenarien, bei denen auf eine belegte Nachbarspur und somit geringe Überholwahrscheinlichkeit geschlossen wird und

Fig. 2

ein schematisches Blockschaltbild einer Vorrichtung zur Vermeidung von Auffahrunfällen.

The invention will be explained in more detail below with reference to a preferred embodiment. The figures show:

Fig. 1a - g

various scenarios in which an occupied adjacent lane and thus low probability of overtaking is concluded and

Fig. 2

a schematic block diagram of a device for avoiding rear-end collisions.

The Fig. 1a - g show the different scenarios for the detection of an occupied adjacent lane on the example of a vehicle with sensors that have a detection area, which is behind and to the left and right of your own vehicle. The vehicle is here a left-hand drive, and the planned overtaking should be left. Plotted in white is the relevant monitored area. Listed are only the cases in which a follower vehicle, which drives on the same lane as the own vehicle, approaches the own vehicle from behind.

The adjacent lane is then occupied when a vehicle is on the side lane between the following vehicle and the own vehicle and hereby Fig. 1a falling behind or Fig. 1b as fast as your own vehicle drives or Fig. 1c faster than your own vehicle, but slower than the following vehicle drives or Fig. 1d as fast as the following vehicle next to or shortly before the following vehicle drives. Furthermore, the adjacent lane is occupied when Fig. 1e a vehicle is located behind the follower vehicle and on the secondary lane approaches from behind so fast that the following vehicle can not safely change the lane. Furthermore, the neighbor track is then occupied, if Fig. 1f a vehicle on the secondary lane drives as oncoming traffic or if Fig. 1g the neighboring lane is occupied by structural measures such as crash barriers or posts.

In the same way, a planned overtaking process on the right side can also be taken into account in the warning strategy.

Similarly, scenarios for a vehicle with additional sensors, which also detect the area in front of the own vehicle, can be set up.

In the Fig. 2 is a schematic block diagram of a device 1 for preventing rear-end collisions shown, which is part of a lane change assistance system. The device 1 comprises an evaluation unit 2. The evaluation unit 2 is designed with different sensors 3-8 and 9-12. The sensors 3-8 serve to detect objects in neighboring tracks including their speed. The sensor systems 3-8 are, for example, in detail a camera 3 of a lane departure warning system, a radar sensor 4 of an adaptive cruise control, ultrasonic sensors 5 of a parking distance control, ultrasonic sensors 6 of a park assist system, a radar sensor 7 and / or a camera Lane change assistance system and a camera 8 for monitoring the rear traffic. It is understood that it is not necessary for the invention that all mentioned systems or sensors are present.

By means of the sensors 9-12 a road condition is determined. Specifically, the sensor systems are a braking system 9, a rain-light sensor 10, a road condition sensor 11 and a camera system 12, wherein also here not necessarily all sensors 9-12 must be present. The data of the sensors 9-12 are taken into account in particular in the calculation of the stopping distance.

The sensors 3-8 provide their data and / or preprocessed data to the evaluation unit 2, which determines among other things a probability of an overtaking operation. Further, the evaluation unit 2 determines a parameter which is compared with a stored comparison value. The parameter is for example a "time to collision" or a stopping distance. If the determined parameter falls short of the predetermined comparison value, the evaluation unit 2 triggers a measure by activating an actuator system 13 which, for example, is a flashing light and / or an active and / or passive occupant protection device and / or a control device for influencing the longitudinal dynamics of the vehicle Motor vehicle is. Depending on the determined probability of a passing process, the evaluation unit selects either a different parameter or a different comparison value. The important thing is to be warned earlier if the probability of overtaking is low, and later if the probability of overtaking is high.

Claims (10)

1. Apparatus for preventing rear-end collisions of motor vehicles, comprising a sensor system which can be used to determine or calculate at least the relative speed between a motor vehicle in question and a motor vehicle travelling behind, it being possible for a parameter to be determined by an evaluation unit as a function of the relative speed, the said parameter being compared with a stored comparison value, with a measure being initiated in order to reduce the risk of a rear-end collision when there is a deviation from the comparison value, characterized in that the sensor system (3-8) can be used to determine the occupation of neighbouring lanes, a probability of the motor vehicle travelling behind performing an overtaking operation being determined from the occupation of the neighbouring lanes, and the determined parameter and/or the stored comparison value being selected by the evaluation unit (2) as a function of the probability of an.overtaking operation.
2. Apparatus according to Claim 1, characterized in that the sensor system (3-8) for detecting the occupation of the neighbouring lane comprises a radar sensor (4, 7) and/or a camera (3, 8) and/or an ultrasound sensor (5, 6).
3. Apparatus according to Claim 1 or 2, characterized in that conditions in the area surrounding the driving lane are determined by means of the sensor system (3-8).
4. Apparatus according to one of the preceding claims, characterized in that the apparatus (1) is a constituent part of a lane-changing assistance system or is connected to the said lane-changing assistance system.
5. Apparatus according to one of the preceding claims, characterized in that the distance from the motor vehicle travelling behind is detected, with a warning being given when the distance is less than a minimum value at a relative speed of zero.
6. Method for preventing rear-end collisions of motor vehicles by means of a sensor system, with which at least the relative speed between the motor vehicle in question and a motor vehicle travelling behind is determined or calculated, with a parameter being determined by an evaluation unit as a function of the relative speed, the said parameter being compared with a stored comparison value, with a measure being initiated in order to reduce the risk of a rear-end collision when there is a deviation from the comparison value, characterized in that the sensor system (3-8) is used to determine the occupation of neighbouring lanes, a probability of the motor vehicle travelling behind performing an overtaking operation being determined from the occupation of the neighbouring lanes, and the determined parameter and/or the stored comparison value being selected by the evaluation unit (2) as a function of the probability of an overtaking operation.
7. Method according to Claim 6, characterized in that the sensor system (3-8) for detecting the occupation of neighbouring lanes comprises a radar sensor (4, 7) and/or a camera (3, 8) and/or an ultrasound sensor (5, 6).
8. Method according to Claim 6 or 7, characterized in that conditions in the area surrounding the vehicle are determined by means of the sensor system (3-8).
9. Method according to Claims 6 to 8, characterized in that the determined probability of an overtaking operation is transmitted to a lane-changing assistance system.
10. Method according to one of Claims 6 to 9, characterized in that the distance from the motor vehicle travelling behind is detected, with a warning being given when the distance is less than a minimum value at a relative speed of zero.

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