DE10258617B4 - Method and device for triggering an automatic emergency braking operation of a vehicle - Google Patents

Abstract

A method for triggering an automatic emergency braking operation of a vehicle to avoid a collision of the vehicle with a preceding vehicle or to reduce the Auffahrfolgen, wherein a driver warning is triggered when at least one predetermined warning condition is met, characterized in that the fulfillment of the warning condition indicates that on the basis of the instantaneous driving situation of the vehicle given by the vehicle and / or the ascertained relative acceleration (a _rel ) between the vehicle and the vehicle ahead and a predetermined emergency brake delay (a _NB ) at expiration of a predetermined warning period (t _w ) automatic emergency braking is triggered, with the aim of the end of the automatic emergency braking a predetermined target _relative speed (v _{rel, z} ) and / or a predetermined target safety distance (d _z ) between the vehicle and the vehicle ahead pass.

Description

The The invention relates to a method and a device for triggering a automatic Emergency braking operation of a vehicle, in particular a truck, according to the preamble of claim 1 or the claim 22. The invention provides an assistance function for avoiding a Startup of the vehicle on a preceding vehicle or to Reduction of the consequences of an accident when it is unavoidable being the trigger a driver warning occurs when a given warning condition is met. The fulfillment the warning condition indicates that after a predetermined warning period has expired the automatic Emergency braking process trigger is.

In the publication DE 41 01 759 A1 is published an automatic braking system for a vehicle. The braking system generally includes a speed sensor for detecting the vehicle speed and a distance sensor for detecting the distance between the vehicle and the preceding vehicle. The braking system determines, based on the relative speed and the distance to the vehicle ahead, a time limit that is required for the vehicle to impact the preceding vehicle to alert the driver of the vehicle by operating an alarm device when the brake pedal is not depressed Boundary time becomes shorter than a predetermined limit time threshold. If the driver of the vehicle does not respond to the delivery of the alarm signal, the brake pedal, an automatic braking operation is performed after a fixed or variable predetermined time interval to reduce the vehicle speed to avoid impact on the vehicle ahead until the limit time again greater than the predetermined threshold time threshold.

by virtue of the way in which the setting of the predetermined threshold time threshold is done by the braking system, there is a possibility that the given Limit time limit is too short to complete by performing the automatic braking an impact on the preceding vehicle Avoid vehicle. to be able to. In this case, the exclusive consideration is the time limit until the impact is insufficient, and the braking system determined additionally based on the vehicle speed and the coefficient of friction between the road surface and the vehicle tire a stopping distance, which is to stop the vehicle is required. If the limit time is greater than the predetermined threshold time threshold, the Distance between vehicle and preceding vehicle but smaller as the particular stopping distance, so will also after delivery of the Alarm signal of the automatic braking of the vehicle carried out, and although until the distance again larger than the currently determined Stopping route is.

Either in the determination of the time limit as well as in the determination of the Stops it is disadvantageous that the consideration of the driving or Traffic situation is detected only in a simplified manner. In complex Traffic situations may therefore be subject to a risk of collision the preceding vehicle was not recognized or misjudged, so that the delivery of the alarm signal and thus possibly the implementation of the automatic braking too early, too late, not at all or done unnecessarily.

Out DE 199 21 238 A1 For example, there is known a safety drive control system for a vehicle having an alarm system and an automatic brake system. In this case, threshold values for alarm output and for automatic braking are determined according to a predicted delay. A selected threshold is compared to the distance from one's own vehicle to an obstacle to determine whether an alarm or an automatic braking is to be performed. The alarm can be done visually or acoustically.

It is therefore the object of the present invention, a method or to provide a device of the type mentioned in at in or in complex traffic situations the probability a false trip reduced the driver alarm and thus the automatic emergency braking operation becomes.

These The object is achieved by the features of claim 1 and of the patent claim 22 solved.

The driver warning is triggered when a predetermined warning condition is met, the fulfillment of the warning condition indicates that due to the current driving situation of the vehicle and a predetermined emergency brake delay at the end of a predetermined warning period to avoid a collision of the vehicle on the vehicle ahead or to reduce the Accident consequences, when a collision is unavoidable, the automatic emergency braking is triggered, with the aim of completion of the automatic emergency braking a predetermined target relative speed and / or vorgebe to achieve a target safety distance between the vehicle and the vehicle ahead. By appropriate specification of the target relative speed and / or the target safety distance can be achieved, inter alia, that the triggering of the driver alarm and thus the triggering of the automatic emergency braking process does not take place earlier than is necessary to avoid a collision with the preceding vehicle. The instantaneous driving situation results here at least from the determined acceleration of the vehicle and the determined relative acceleration between the vehicle and the vehicle ahead. By including these variables, it is possible that the danger of a collision of the vehicle with the preceding vehicle is reliably detected or correctly estimated in a large number of complex traffic situations. The use of the method according to the invention or the device according to the invention is particularly appropriate in connection with trucks, since it is precisely here due to the high vehicle masses that a collision with the vehicle in front generally has serious consequences. It not only a Auffahrgefahr on a preceding vehicle, but of course any other movable or fixed obstacle detected.

advantageous versions the method according to the invention go from the subclaims out.

advantageously, the driver warning is in for the driver of the vehicle visually and / or acoustically and / or haptically perceptible way. So it is possible the driver unmistakable to draw attention to the danger of collision the preceding vehicle exists and therefore at the expiry of the given Warning period of the automatic Emergency braking triggered becomes.

Around the automatic one To make emergency braking safer, the vehicle already can before its release kinetic energy can be withdrawn by adding a haptic to the driver the driver noticeable driver warning in the form of a partial braking operation of the vehicle takes place with a specified partial braking delay. The specified partial braking delay is smaller than the specified emergency brake delay.

Farther it is possible, the automatic one Emergency brake operation only then trigger when a given emergency braking condition is met and the given one Warning period has expired. So again may the need of the automatic Emergency braking operation to be checked before its release.

The emergency braking deceleration or an associated variable, such as the emergency brake pressure, the emergency braking force or the emergency braking torque, can be specified either fixed or adjustable. In the latter case, it is possible to determine, depending on variables such as the Fahrzeugmas se, the Belagreibwert the wheel brake of the vehicle, the road condition or visibility, for example, an actually achievable maximum braking delay and the value of the predetermined emergency brake delay according to the determined tasächlich achievable Set maximum brake delay. The value of the emergency brake delay can also be predefined in a fixed manner, in which case it is preferable to assume an average achievable maximum braking delay whose value is typically in the range between 5 m / s ² and 7 m / s ² .

The same applies to the default of the warning period, which is also fixed or adjustable can be done. A fixed warning period has the advantage that the driver of the time of triggering the automatic emergency braking is known and this does not arrive unexpectedly or unpredictably. An appropriate value of the predetermined warning period may be due be determined by driving tests. This is typically in the range between 1.7 and 2.3 seconds. On the other hand, it is conceivable the value of the given warning period depending on variables that For example, the vehicle mass, the Belagreibwert the Radbremseinrichtungen of the vehicle, the road conditions or the visibility, adjust. In this case, preferably, a minimum value of the warning period predetermined, which should not be fallen below, so the driver in principle sufficient time remains, to the release of the automatic emergency braking prepare or intervene before.

Also the target relative speed can either be fixed or adjustable be specified. It is advantageous if the value of a fixed predetermined target relative speed is approximately zero. In this Case, the vehicle's own speed through the automatic emergency braking only as far as absolutely necessary decreases to propel the vehicle to the preceding vehicle Vehicle reliable to prevent. Anything about it going beyond reducing the airspeed is unnecessary and represents in particular for subsequent vehicles an additional Danger.

Further The target safety distance can also be fixed or adjustable become. A setting of the value of the target safety distance can either in dependence of sizes that For example, the vehicle mass, the brake lining friction of the wheel brake of the vehicle, the road condition, the vehicle speed or the visibility describe, or be done manually by the driver of the vehicle. In this case, a minimum value for the target safety distance is preferably given, so that too close to the driving ahead Vehicle with completion of the automatic emergency braking prevented becomes. For the sake of simplicity, the specification of the value of the target safety distance are also fixed, typically this is then between Zero and a few meters.

advantageously, is omitted in the presence of driver activity and / or reduction the risk of collision triggering a driver warning and / or the intensity of the driver warning is adjusted. In this way it is avoided that the driver of the vehicle unnecessarily triggered driver warnings as disturbing and the device according to the invention permanently shuts off, so that the inventive method is not performed.

Farther may be in the presence of driver activity and / or reduction the Auffahrgefahr an already triggered driver warning ended and / or changed be and / or the trigger the automatic emergency braking process remain under. First, the driver of the vehicle as long as possible given the opportunity to take appropriate countermeasures to avoid the Jump on the leading vehicle to meet, and on the other is a meantime unnecessary become no longer maintained and / or a driver warning in the meantime unnecessary become self-employed Emergency braking not even triggered.

It is possible, the automatic one Emergency braking automatically at the end of the specified warning period trigger, provided the driver warning is not during the predetermined warning period is aborted. In this case the driver of the vehicle is the time of release of the vehicle automatic Emergency braking known, and he has opportunity to take appropriate countermeasures to avoid the collision with the vehicle ahead to meet.

Around the success of an already triggered automatic Emergency braking not by premature termination of pages to endanger the driver, this is only canceled when a determined emergency brake time has expired and / or if the given target relative speed and the predetermined target safety distance are reached. The emergency braking time depends from the current driving situation when triggering the automatic emergency braking operation, the predetermined emergency brake delay, the target relative velocity and the target safety distance.

advantageously, the driver warning consists of at least two warning levels within the predetermined warning period of the driver warning in chronological succession triggered with each warning level a predetermined warning level duration assigned. Thus, it is possible the driver warning by using different urgency warning levels with the urgency of the warning levels with decrease of until release of the automatic Emergency braking process can increase remaining time, allowing the driver on the shorter Expected time to trigger of the automatic Notbremsvorgangs is pointed out.

The Warning level duration of a warning level can be fixed or adjustable be predetermined. A fixed warning level period has the Advantage that the driver of the time of triggering any subsequent Warning level and / or the automatic Notbremsvorgangs is known and this is not unexpected or unpredictable arrives.

Besides it is possible, the value of the warning level duration of a warning level as a function of Set sizes, For example, the vehicle mass, the brake lining friction of the Wheel brake devices of the vehicle, the visibility or describe the road surface. So, for example the last and thus usually most urgent warning level will be triggered earlier, the less favorable the ratios to avoid the collapse by triggering the automatic emergency braking operation.

Furthermore, there is the possibility, after triggering a first warning level, to trigger at least one further warning level only if one of the further warning level respectively assigned, predetermined warning condition is fulfilled. Thus, the necessity of triggering each further warning level can be checked and the Triggering unnecessary, avoid the actual Auffahrgefahr inappropriate warning levels.

at Presence of driver activity and / or reducing the Auffahrgefahr at least one of already triggered Warning levels are terminated and / or the triggering of other warning levels are omitted. This avoids that the driver of the vehicle unnecessarily triggered warning levels as disturbing feels and the device of the invention disabled. It is also possible to use an already triggered alert level, which is for example in the form of an optical driver warning, up to the expiration of the predetermined warning period and just do not trigger further warning levels to alert the driver to the potential to indicate existing danger of collision.

Conveniently, the presence of driver activity due to an operation is at least one of the controls of the vehicle detected, the control in particular for amendment the longitudinal or lateral dynamics of the vehicle is used. To the controls that for recognizing driver activity are eligible to count For example, the accelerator pedal, the brake pedal, the clutch pedal, the steering wheel or the direction sensors of the vehicle.

A Reducing the risk of collision can be easily determined by means of a with time increasing distance between vehicle and preceding Vehicle and / or a relative speed decreasing over time be detected between the vehicle and the vehicle ahead.

Around the risk of a collision of the vehicle with the vehicle ahead Detect vehicle reliably even in complex traffic situations or assess correctly to be able to is the current driving situation of the vehicle depending the determined distance between the vehicle and the vehicle ahead and / or the determined speed of the vehicle and / or the determined relative acceleration between the vehicle and the vehicle ahead Vehicle and / or the determined acceleration of the vehicle and / or the road inclination and / or friction between the roadway and the vehicle wheels certainly.

In order to the danger of possible secondary accidents can be reduced when triggered of the automatic Emergency braking operation a warning of driving ahead and / or behind Vehicles are made. For this example, the brake lights, the vehicle horn, the hazard warning lights or the driving or high beam of the vehicle operated.

The inventive method or the device according to the invention for triggering an automatic Emergency braking operation of a vehicle is described below with reference to the drawings explained in more detail. there demonstrate:

1 a schematic representation of an embodiment of an apparatus for performing the method according to the invention,

2a An embodiment of the method according to the invention in the form of a flow chart,

2 B an alternative embodiment of the method according to the invention,

2c a further alternative embodiment of the method according to the invention and

3 an exemplary representation of the timing of the method according to the invention.

1 shows a device 5 for triggering an automatic emergency braking operation of a vehicle. This provides an assistance function for avoiding the drive-up of the vehicle to a preceding vehicle, wherein at least the Auffahrfolgen be reduced if the approach to the preceding vehicle is unavoidable. For this purpose, the device 5 a sensor unit 11 on, with a distance sensor 6 for measuring the distance d between the vehicle and the vehicle ahead and a relative speed sensor 12 for measuring the relative velocity v _rel between the vehicle and the vehicle ahead. The corresponding measurement signals become an evaluation unit 7 fed. In order to achieve a higher measurement accuracy, different, in each case the most suitable physical measuring method can be used ver to measure the distance d and the relative velocity v _rel . As a distance sensor 6 and / or relative speed sensor 12 For example, radar sensors are used.

In a vehicle with manual transmission, the device 5 an accelerator pedal 8th , a brake pedal 9 and a clutch pedal 10 on. The accelerator pedal 8th acts with an accelerator pedal sensor 15 together, the accelerator pedal deflection 1 registered and converted into a corresponding signal. A brake pedal sensor 16 detects the brake pedal deflection s and generates a corresponding signal. The signals become the evaluation unit 7 fed. A clutch pedal deflection w of the clutch pedal 10 is through one with the evaluation unit 7 connected clutch pedal encoder 17 detected. Of course, in a vehicle with an automatic transmission or an automated manual transmission, clutch pedal is missing 10 and clutch pedal encoder 17 , Furthermore, a steering wheel 18 available, that with a steering angle sensor 19 interacts with the steering wheel 18 set steering wheel angle α registered and converted into a corresponding signal. The speeds of the vehicle wheels, not shown, are by means of wheel speed sensors 20 detected. The signals of the steering angle sensor 19 and the wheel speed sensors 20 also become the evaluation unit 7 fed.

In addition, the evaluation unit 7 next to an operation of the direction generator 25 the vehicle mass, the Bremsbelagreibwert the wheel brake of the vehicle, the visibility and the road condition considered. The vehicle mass results from the sum of the vehicle blank mass and the loaded and / or attached mass. The vehicle mass is determined either automatically by means of an evaluation unit 7 connected mass determination unit 26 , for example, by type of in DE 38 43 818 C1 Published device, or alternatively by means of manual input by the driver via a ground input unit 27 , The consideration of the Bremsbelagreibwerts the wheel brake is carried out, for example, according to the in DE 199 11 902 C1 represented method, preferably by the evaluation unit 7 mitausführt is. To determine the surrounding visibility and the road condition are appropriate sensors 28 . 29 available.

The evaluation unit 7 in turn controls a drive means control after evaluation of the signals carried on them 35 the drive means 36 , a brake control 37 the brake fluid 38 and thus the wheel brake devices 39 of the vehicle, an optical warning device 45 , an acoustic warning device 46 , the vehicle horn 47 and lighting fixtures 48 of the vehicle. The drive means 36 of the vehicle are only by the drive means control 35 The clarity is in addition to the drive means control 35 also to the drive means 36 associated powertrain, the engine, transmission, etc., not shown. To the lighting devices 48 For example, the hazard warning lights, the brake lights or the driving and high beam of the vehicle.

The assistance function is to carry out the method according to the invention via a with the evaluation 7 connected switch 49 activated and deactivated. The desk 49 is, for example, part of a user interface of a combination control unit already present in the vehicle.

2 shows an embodiment of the method according to the invention in the form of a flow chart. Before this is discussed in more detail, some basics are explained in detail for a better understanding.

wobei sich die Geschwindigkeit v(t) zum Zeitpunkt t aus

ergibt. s(0) ist die vom Fahrzeug zum Zeitpunkt t = 0 zurückgelegte Strecke, dementsprechend ist v(0) die Geschwindigkeit und a(0) die Beschleunigung des Fahrzeugs zum Zeitpunkt t = 0. Daraus folgt

woraus sich wegen v(0) = konst. die Beziehung

ergibt. Weiterhin wird angenommen, dass die Beschleunigung a(t) des Fahrzeugs zu jedem Zeitpunkt t den konstanten Wert a(0) besitzt. In diesem Fall ergibt sich s(t) = s(0) + v(0)dt + 12 a(0)t2, (5)bzw. aus Gleichung (2) v(t) = v(0) + a(0)t. (6) For the distance s (t) traveled by a vehicle at time t

where the velocity v (t) at time t

results. s (0) is the distance traveled by the vehicle at time t = 0, accordingly v (0) is the speed and a (0) is the acceleration of the vehicle at time t = 0

from which, because of v (0) = const., the relation

results. Further, it is assumed that the acceleration a (t) of the vehicle has the constant value a (0) every time t. In this case results s (t) = s (0) + v (0) dt + 1 2 a (0) t 2 , (5) or from equation (2) v (t) = v (0) + a (0) t. (6)

The vehicle is now to be preceded by another vehicle, with the preceding vehicle being subsequently identified with the index "v." The relative speed v _rel (t) between the vehicle and the vehicle ahead at time t is passed through V rel (t) = V (t) - v v (t) (7) Are defined. The relative velocity v _rel (t) is thus positive when the vehicle approaches the preceding vehicle. Equation (6) yields V rel (t) = V rel (0) + a rel (0) t (8)

In a corresponding manner, a relative acceleration a _rel (t) between the vehicle and the vehicle ahead is defined at the time t, a rel (t) = a (t) - a v (T). (9)

The distance d (t) between the vehicle and the vehicle ahead at the time t results from d (t) = d (0) - s (t) + s v (T), from which, on the basis of equations (5) and (8), the relationship d (t) = d (0) - v rel (0) t - 1 2 a rel (0) t 2 (10) follows.

In the following, t _{tc is} the time that must elapse before the time when the vehicle approaches the vehicle in front ("time-to-crash").

• – Im ersten Fall fährt das Fahrzeug auf das noch fahrende vorausfahrende Fahrzeug auf.
• – Im zweiten Fall kommt das vorausfahrende Fahrzeug noch vor dem Auffahren des Fahrzeugs auf das vorausfahrende Fahrzeug zum Stillstand.

Furthermore, for the sake of simplification, it is assumed that the accelerations of the vehicle and the vehicle ahead are constant over time. Due to this simplification, two cases have to be distinguished when determining the time t _tc :

• - In the first case, the vehicle starts on the still driving vehicle ahead.
• In the second case, the vehicle in front comes to a standstill before the vehicle drives onto the preceding vehicle.

In the second case, due to the accelerations assumed to be constant over time, the preceding vehicle would reverse its direction of movement after it had come to a standstill. Of course, that's not the case in reality. In this case, an unnecessarily early triggering of an automatic emergency braking operation would result. In order to avoid this, the first and the second case must be treated separately, in the second case, the acceleration a _{v of} the preceding vehicle is zero from its standstill time point.

As a general rule An approach to the preceding vehicle occurs when the Distance d (t) between vehicle and preceding vehicle to zero becomes.

In the first case, therefore, the time t _tc until the approach to the preceding vehicle due to equation (10) a rel (0) t 2 tc + 2v rel (0) t tc - 2d (0) = 0. (11)

If a _rel (0) = 0, but v _rel (0) ≠ 0, then it also applies

This is

The solution of the quadratic equation (11) is

gegeben. Für den Abstand d(t) zwischen Fahrzeug und vorausfahrendem Fahrzeug zum Zeitpunkt t_still,v gilt damit nach Gleichung (10)

In the second case, the time t is _{still, v} to standstill of the preceding vehicle according to equation (6) for v _v (0) ≥ 0 by

given. For the distance d (t) between the vehicle and the vehicle ahead at time t _{still, v} is valid according to equation (10)

For the distance d (t) between the vehicle and the vehicle ahead at any time t ≥ t _{stil, v} applies d (t) = d (t still, v ) - v (t still, v ) (t - t still, v ) - 1 2 at still, v ) (t - t still, v ) 2 , (17)

According to equation (6)

Furthermore, due to the assumption made constant acceleration at still, v ) = a, (19) and thus

An approach to the preceding vehicle takes place when the distance d (t) between the vehicle and the vehicle ahead becomes zero. Thus, the time t _tc - t is determined to be _{quiet, v} between standstill of the vehicle ahead and the approach of the vehicle to the vehicle in front

An automatic emergency braking operation to avoid a collision of the vehicle on the advance vehicle is to be triggered when the distance d (0), the relative speed v _rel (0), the acceleration a (0) of the vehicle and the acceleration a _v (0) of the preceding vehicle in a certain relationship to each other. In order to determine this relationship, in a first step, the emergency braking deceleration a _NB required for avoiding start-up is determined. The automatic emergency braking operation is carried out with the aim of achieving a predetermined target _relative speed v _{rel, z} = 0 and a predetermined target safety distance d _z between the vehicle and the vehicle ahead when it is completed. The target safety distance d _z can be zero here, but as a rule it is assumed to be greater than zero for safety, for example of the order of a few meters.

mit der relativen Notbremsverzögerung arel,NB = aNB – av(0). (23) In the first case, due to the simplifying assumption of constant accelerations, the preceding vehicle maintains its acceleration a even after the automatic emergency braking operation has ended. The emergency braking time t _NB is given by equation (8)

with the relative emergency brake delay a rel, NB = a NB - a v (0). (23)

For the distance d (t), which results at the end of the automatic emergency braking, the equation (10) applies

Equating with d _z gives for the required emergency brake delay a _NB

According to the emergency braking deceleration a _{NB is} specified. In this case, equation (25) can be displayed more clearly by transformation, 2 (a NB - a v (0)) (d (0) - d z ) = -V 2 rel (0). (26)

It Thus, in the first case, an automatic emergency braking process is triggered when the relationship described in equation (25) or (26) is satisfied.

In the second case, the preceding vehicle comes to a standstill before the automatic emergency braking process is completed. For the distance d (t) between the vehicle and the vehicle ahead, due to the equations (12) and (17) for any times t> t _{still, v}

gegeben. Damit und mit Gleichung (27) ergibt sich

The period of time after the vehicle in front has come to a standstill until the automatic emergency braking operation has ended is determined by equation (18)

given. This and equation (27) result

und mit Gleichung (7) schließlich

By Ausmultiplizieren follows from it

and with equation (7) finally

The required emergency brake delay a _NB is here so

If the emergency brake deceleration a _{NB is} specified, equation (32) can be displayed more clearly by transformation, a NB (v 2 v (0) - 2a v (0) (d (0) - d z )) = a v (0) v 2 (0). (33)

It Thus, in the second case, an automatic emergency braking operation is triggered when the relationship described in equation (32) or (33) is satisfied.

A warning period t _w predetermined in the exemplary embodiment before triggering the automatic emergency braking operation should trigger a driver warning. For the relative speed V _rel (0) and the distance d (0) at the time of triggering the driver warning applies v rel (0) = v rel, NB - a rel (0) t w , (34) d (0) = d NB + t w v rel (0) + 1 2 t 2 w a rel (0). (35)

In this case, d _NB or v _{rel, NB} denote the distance or the relative speed between the vehicle and the vehicle ahead at the time the automatic emergency braking operation is triggered. If equations (34) and (35) are used in equation (26), the result in the first case is -2 (a NB - a v (0)) (d (0) - d z - t w v rel (0) - 1 2 t 2 w a rel (0)) = (v rel (0) + a rel (0) t w ) 2 , (36) where in equation (26) d (0) has been replaced by d _NB and v _rel (0) by v _{rel, NB} . It follows a rel (0) (a NB - a (0)) t 2 w + 2v rel (0) (a NB - a (0)) t w - 2a rel, NB (d (0) - d z ) - v 2 rel (0) = 0. (37)

The release the driver warning occurs in the first case when the in equation (37).

Furthermore, applies to the speeds of the vehicle and the vehicle ahead v (0) = v NB - a (0) t w , (38) v v (0) = v v, NB - a v (0) t w , (39) where v _NB and v _{v, NB} respectively _, the speed of the vehicle and that of the preceding vehicle at the time of triggering the automatic emergency braking operation.

If equations (38) and (39) are used in equation (33), the result is in the second case a NB (0) (v v (0) + a v (0) t w ) 2 - 2a NB a v (0) (d (0) - t w v rel (0) - 1 2 a rel (0) t 2 w - d z ) = a v (0) (v (0) + a (0) t w ) 2 , (40) wherein in equation (33) d (0) has been replaced by d _NB , v (0) by v _NB and v _v (0) by v _{v, NB} . From equation (40) follows (a NB (a 2 v (0) + a v (0) a rel (0)) - a v (0) a 2 (0)) t 2 w + 2a v (0) (a NB v v (0) - a (0) v (0) + a NB v rel (0)) t w + a NB v 2 v (0) - a v (0) v 2 (0) - 2a NB a v (0) (d (0) - d z ) = 0 (41) and from this using Equations (9) and (7) a v (0) a (0) (a NB - a (0)) t 2 w + 2a v (0) (a NB - a (0)) v (0) t w + a NB v 2 v (0) - a v (0) v 2 (0) - 2a NB a v (0) (d (0) - d z ) = 0. (42)

The release the driver warning is thus in the second case, if the in equation (42) specified warning condition is met.

The driver warning should consist of at least two warning levels, which are triggered in succession, each warning level is assigned a predetermined Warnstufenzeitdauer. A predetermined warning stage time t _h before triggering the automatic emergency braking operation, a warning level is triggered, in which the driver warning in haptic perceptible manner, again a predetermined warning stage time t _oa before triggering the haptic driver warning to trigger another warning level, in which the driver warning in optically and / or acoustically perceptible manner. The warning time duration t _{w of} the driver warning is given in this case by the sum of the predetermined warning time period t _{oa of} the visual and / or acoustic driver warning and the predetermined warning time period t _{h of} the haptic driver warning. The haptic driver warning takes place in the form of a partial braking of the vehicle with a predetermined partial braking delay a _TB , which is smaller than the predetermined emergency brake delay a _NB . Accordingly, both the speed change during the visual and / or acoustic as well as during the haptic driver warning must be considered separately.

The distance and the relative speed at the time the driver warning is triggered by v rel (0) = v rel, NB (0) - a rel (0) t oa - a rel, TB (0) t H , (44) d (0) = d NB + (t H + t oa ) v rel (0) + t H t oa a rel (0) + 1 2 t 2 oa a rel (0) + 1 2 t 2 H a rel, h (0), (45) With a rel, h (0) = a TB - a v (0) (46) described. Here, v _{rel, NB is} the relative speed and d _{NB is} the distance between the vehicle and the vehicle in front at the time of triggering the automatic emergency braking operation. If equations (44) and (45) are used in equation (26), the result is in the first case -2 (a NB - a v (0)) (d (0) - (t oa + t H ) v rel (0) - t H t oa a rel (0) - 1 2 t 2 oa a rel (0) - 1 2 t 2 H a rel, h (0) - d z ) = (v rel (0) + a rel (0) t oa + a rel, h (0) t H ) 2 , (47) where in equation (26) d (0) has been replaced by d _NB and v _rel (0) by v _{rel, NB} . It follows a rel (0) (a NB - a (0)) t 2 oa + 2 ((a NB - a (0)) v rel (0) + (a NB - a TB ) a rel (0) t H ) t oa - 2 (a NB - a v (0)) (d (0) - d z ) + 2 (a NB - a v (0)) v rel (0) t H + (a NB - a v (0)) a rel, h (0) t 2 H - (v rel (0) + a rel, h (0) t H ) 2 = 0. (48)

The release the driver warning with the two warning levels takes place in the first case, when the warning condition given in equation (48) is satisfied.

Furthermore applies to the speeds of the vehicle and the vehicle ahead at the time of triggering the driver warning v v (0) = v v, NB - a v (0) (t oa + t H ), (49) v (0) = v NB - a (0) t oa - a TB t H , (50)

Substituting equations (49), (50) and (45) into equation (33) yields in the second case a NB (v v (0) + a v (0) (t oa + t H )) 2 - 2a v (0) a NB (d (0) - (t H + t oa ) v rel (0) - t H t oa a rel (0) - 1 2 a rel (0) t 2 oa - 1 2 a rel, h (0) t 2 H - d z )) = a v (0) (v (0) + a (0) t oa + a TB t H ) 2 , (51) wherein in equation (33) d (0) has been replaced by d _NB , v (0) by v _NB and v _v (0) by v _{v, NB} . It follows a NB (v v (0) + a v (0) t H ) + a v (0) t oa ) 2 - 2a v (0) a NB (d - t H v rel (0) - t oa v rel (0) - t H t oa a rel (0) - 1 2 a rel (0) t 2 oa - 1 2 a rel, h (0) t 2 H - d z 2 = a v (0) ((v (0) + a TB t H ) + a (0) t oa ) 2 (52) and finally a v (0) a (0) (a NB - a (0)) t 2 oa + (2a NB a v (0) (v v (0) + a v (0) t H ) + 2a NB a v (0) v rel (0) + 2a NB a v (0) a rel (0) t H - 2a v (0) a (0) (v (0) + a TB t H )) T oa + a NB (v v (0) + a v (0) th) 2 - 2a NB a v (0) (d (0) - d z ) + 2a NB a v (0) t H v rel (0) + a v (0) a NB a rel, h (0) t 2 H - a v (0) (v (0) + a TB t H ) 2 = 0. (53)

Equation (53) can be further simplified a v (0) a (0) (a NB - a (0)) t 2 oa + (2a NB a v (0) (v (0) + a (0) t H ) - 2a v (0) a (0) (v (0) + a TB t H )) T oa + a NB (v v (0) + a v (0) t H ) 2 - 2a NB a v (0) (d (0) - d z ) + 2a NB a v (0) t H v rel (0) + a v (0) a NB a rel, h (0) t 2 H - a v (0) (v (0) + a TB t H ) 2 = 0. (54)

The release the driver warning with the two warning levels thus takes place in the second Case when the warning condition given in equation (54) is satisfied.

In 2 an embodiment of the method according to the invention is shown in the form of a flow chart. The process is in a first main step 60 started or stopped when activating or deactivating the assistance function by the driver of the vehicle.

In a second main step 61 is from the evaluation unit 7 based on the means of the sensor device 11 determined distance d and the relative velocity v _rel between the vehicle and the vehicle ahead and by means of the wheel speed sensors 20 determined speed v of the vehicle, the speed v _{v of} the preceding vehicle, the acceleration a of the vehicle, the acceleration a _{v of} the preceding vehicle and the relative acceleration a _rel between the vehicle and the vehicle ahead. The quantities listed above are in this case generally functions of the time t. Furthermore, in the second main step 61 the specification of the warning duration t _w , a first predetermined warning stage time t _oa , a second predetermined warning stage time t _h , the target _{safety distance} d _z , the target _{relative speed} v _rel.z , the partial braking _delay a _TB , the relative partial braking delay a _{rel, h} and the emergency brake delay a _NB , These variables are in each case specified either in a fixed manner or adjustable. An adjustment takes place, for example, as a function of the vehicle mass, the brake pad friction coefficient of the wheel brake devices, the road surface or the visibility. The emergency braking time t _NB can be calculated from the aforementioned variables.

In a third main step 62 It is checked whether a given by the equation (48) or (54) first warning stage condition for triggering a first warning stage in which the driver warning visually and / or acoustically occurs, is met.

If the first warning level condition is fulfilled, then in a fourth main step 63 triggered the first alert level of the driver warning. At the same time, a first time counter T _{1 is} started. In the first warning level, the driver warning takes place in an optically and / or acoustically perceptible manner. An optical driver warning is, for example, in the form of flashing signals or danger symbols or by showing the remaining time until the triggering of the automatic emergency braking operation by means of the optical warning device 45 implemented. In contrast, when an acoustic driver warning, for example, an alarm signal or a voice alarm by means of the acoustic warning device 46 given, in addition, it is provided, for example, additionally mute radio and telephone to avoid distraction of the driver.

If, on the other hand, the first warning level condition is not met, the method sequence returns to the second main step 61 back.

Will be in a fifth main step 64 the existence of a termination criterion - for example, the Presence of driver activity and / or a reduction of Auffahrgefahr - found so is in a first side step 80 checks whether the first time counter T _{1 is} smaller than the predetermined warning time t _w . If this is the case, the procedure returns to the first secondary step 60 back until the first time counter T _{1 is} at least equal to the predetermined warning time t _w . If this is the case, in a subsequent second substep 81 the first warning level of the driver warning ends, and the process returns to the second main step 61 back. Thus, the optical and / or acoustic driver warning occurring in the first warning stage is maintained until the end of the warning period t _w , in order to alert the driver to a potentially existing risk of collision. Further warning levels or the automatic emergency braking process are not triggered due to the fulfilled termination criterion.

If, on the other hand, the abort criterion is not fulfilled, then in a seventh main step 66 a second warning level of the driver warning is triggered, as soon as in a previous sixth main step 65 it is determined that the first time counter T _{1 is} at least equal to the first predetermined warning period time t _oa . On the other hand, if the first time counter T ₁ is smaller than the first predetermined warning level time period t _oa , the method sequence returns to the fifth main step 64 back.

In the second warning level the driver warning takes place in haptic perceptible manner, in the form of a partial braking operation of the vehicle with the predetermined partial braking delay a _TB . When the second warning level is triggered, a second time counter T ₂ is simultaneously started.

In this embodiment is assumed by a total of two warning levels, from which the driver warning consists. Also conceivable is any other number of warning levels, where in the driver warning in each case visually and / or acoustically and / or haptic perceptible way.

Will be in an eighth main step 67 If the abort criterion is met, for example according to the presence of driver activity and / or reduction of the risk of collision, then in a third subsidiary step 82 the first warning level and the second warning level of the driver warning ends, and the process returns to the second main step 61 back. It is also conceivable to maintain the first warning level until the end of the warning period t _{w in} order to alert the driver to a potential risk of collision.

However, the abort criterion is in the eighth main step 67 not fulfilled, becomes in a tenth main step 69 the first and the second warning level of the driver warning ended and the automatic emergency braking by appropriate control of the braking means 36 and the drive means 38 triggered once in a previous ninth major step 69 it is determined that the second time counter T _{2 is at} least equal to the second predetermined warning time period t _h . At the same time, there is a warning of vehicles in front and / or behind, by the lighting devices 48 of the vehicle, which include, for example, the hazard warning lights, the brake lights or the driving or high beam, or the vehicle horn 47 be operated. When the automatic emergency braking operation is triggered, an emergency brake time counter T _NB is also started.

In an eleventh main step 70 It is checked whether the emergency brake time counter T _{NB is} smaller than the determined emergency brake time t _NB . As long as this is not the case, the procedure returns to the eleventh main step 70 back. An already triggered automatic emergency braking can therefore not be prematurely terminated. As soon as the emergency brake time counter T _{NB is} at least equal to the determined emergency braking time t _NB , in a fourth subsidiary step 83 both the first warning level of the driver warning and the automatic emergency braking process terminated, the process sequence then back to the second main step 61 returns.

The fifth main step 64 and in the sixth main step 67 The checked abort criterion is fulfilled if the driver's attention can be drawn to the driver's attention or if there is no longer an emergency situation due to a reduction in the risk of a collision. The presence of driver activity is detected on the basis of an actuation of at least one of the operating elements of the vehicle, wherein the operating element is used in particular for changing the longitudinal or transverse dynamics of the vehicle. In connection with a change in the longitudinal or lateral dynamics are, for example, accelerator pedal 8th , Brake pedal 9 , Clutch pedal 10 or steering wheel 18 , But also as a result of an operation of the direction generator 25 can be closed to the driver's attention. In the case of the accelerator pedal 8th , the brake pedal 9 , the clutch pedal 10 or the steering wheel 18 it is expedient to conclude on a driver's activity, if the change in the accelerator pedal deflection l, the brake pedal deflection s, the Kupplungspedalauslenkung w or the steering wheel angle α each exceeds a certain predetermined threshold.

A reduction in the danger of a collision is detected, for example, on the basis of an increasing distance d between the vehicle and the vehicle traveling ahead over time and / or an amount of the relative speed v _rel between the vehicle and the vehicle in front which decreases over time. Again, the abort criterion is only met, for example, if the increase in the distance d between the vehicle and the vehicle ahead and / or the decrease in the relative velocity v _rel between the vehicle and the vehicle ahead are above predetermined threshold values.

2 B shows an alternative embodiment of the method according to the invention in the form of a supplement to the in 2a illustrated flow chart. The second warning level of the driver warning is triggered here only if in a first additional step 65 ' it is determined that an associated, given second warning stage condition according to equation (37) or (42) is satisfied. If this is not the case, in a fifth secondary step 84 checks whether the first time counter T _{1 is} smaller than the predetermined warning time t _w . If this is the case, the procedure returns to the fifth secondary step 84 back until the first time counter T _{1 is} at least equal to the predetermined warning time t _w . If that is the case, in a subsequent sixth substep 88 the first warning level of the driver warning ends, and the process returns to the second main step 61 back. Thus, here too, the visual and / or acoustic driver warning occurring in the first warning stage is maintained until the end of the warning period t _{w in} order to alert the driver to a potential risk of collision.

2c shows a further alternative embodiment of the method according to the invention in the form of a further supplement of in 2a illustrated flow chart. The automatic emergency braking process is only triggered if in a second additional step 68 ' it is determined whether an associated, given emergency braking condition according to equation (37) or (42) is met. If this is not the case, it will be in a seventh substep 86 the second warning level of the driver warning ends, and the process returns to the second main step 61 back.

It is conceivable that in 2 B and 2c shown embodiments to combine with each other.

3 finally shows an exemplary representation of the timing of the method according to the invention, assuming that no termination criterion is met and the automatic emergency braking is triggered. When the first warning level is triggered, the driver warning takes place in an optically and / or acoustically perceptible manner, at the same time the first time counter T _{1 is} started. If the first time counter T _{1 reaches} the first predetermined warning stage duration t _oa , the second warning stage is triggered, which takes place in a haptic perceptible manner in the form of a partial braking operation. At the same time, the second time counter T _{2 is} started. The first warning level of the driver warning is still maintained, and it is also conceivable to end this triggering the second warning level. If the second time counter reaches the second predetermined warning step duration t _h , the second warning step and possibly also the first warning step of the driver warning are ended and the automatic emergency braking process is triggered. At the same time the emergency brake time counter T _{NB is} triggered. If the emergency brake time counter T _{NB reaches} the determined emergency braking time t _NB , the first warning level of the driver warning and the automatic emergency braking operation are ended.

Claims (22)

A method for triggering an automatic emergency braking operation of a vehicle to avoid a collision of the vehicle with a preceding vehicle or to reduce the Auffahrfolgen, wherein a driver warning is triggered when at least one predetermined warning condition is met, characterized in that the fulfillment of the warning condition indicates that on the basis of the instantaneous driving situation of the vehicle given by the vehicle and / or the ascertained relative acceleration (a _rel ) between the vehicle and the vehicle ahead and a predetermined emergency brake delay (a _NB ) at expiration of a predetermined warning period (t _w ) automatic emergency braking is triggered, with the aim of ending the automatic emergency braking operation a predetermined target _relative speed (v _{rel, z} ) and / or a predetermined target safety distance (d _z ) between the vehicle and the vehicle in front to e rreichen. Method according to claim 1, characterized in that that the driver warning in for the driver of the vehicle visually and / or acoustically and / or haptically perceptible manner. A method according to claim 2, characterized in that a haptic perceptible to the driver of the vehicle driver warning in the form of a partial braking operation of the vehicle with a predetermined part braking deceleration (a _TB), wherein the predetermined partial braking deceleration (a _TB) is smaller than the predetermined Notbremsverzögerung (a _NB) is. Method according to one of claims 1 to 3, characterized in that the automatic emergency braking operation is triggered only when a given emergency braking condition is met and the predetermined warning period (t _w ) has expired. Method according to one of claims 1 to 4, characterized in that the emergency brake delay (a _NB ) is predetermined fixed or adjustable. Method according to one of claims 1 to 5, characterized in that the warning period (t _w ) is predetermined fixed or adjustable. Method according to one of claims 1 to 6, characterized in that the target _relative speed (v _{rel, z} ) is predetermined fixed or adjustable. A method according to claim 7, characterized in that the value of a fixed predetermined target _relative speed (v _{rel, z} ) between the vehicle and the vehicle ahead is approximately zero. Method according to one of claims 1 to 8, characterized in that the target safety distance (d _z ) is predetermined fixed or adjustable. Method according to one of claims 1 to 9, characterized that in the presence of driver activity and / or reduction the risk of collision triggering the driver warning is omitted. Method according to one of claims 1 to 10, characterized that in the presence of driver activity and / or reduction the Auffahrgefahr an already triggered driver warning ended and / or changed will and / or the triggering of the automatic Emergency braking is omitted. Method according to one of claims 1 to 11, characterized in that the automatic emergency braking operation is automatically triggered at the end of the predetermined warning period (t _w ), unless the driver warning is canceled during the predetermined warning period (t _w ). Method according to one of claims 1 to 12, characterized in that an already initiated automatic emergency braking operation is aborted when a determined emergency brake time (t _NB ) and / or if the predetermined target _relative speed (v _{rel, z} ) and the predetermined target safety distance (d _z ) are reached. Method according to one of claims 1 to 13, characterized in that the driver warning consists of at least two warning levels, which are triggered within the predetermined warning period (t _w ) of the driver warning in chronological succession, each warning level is assigned a predetermined Warnstufenzeitdauer. Method according to claim 14, characterized in that that the warning level duration of a warning level is fixed or adjustable is predetermined. Method according to claim 14 or 15, characterized that after triggering a first warning level only then at least one further warning level triggered is, if one of the further warning level respectively assigned, given Warning level condition fulfilled is. Method according to one of claims 14 to 16, characterized that in the presence of driver activity and / or reduction Auffahrgefahr terminated at least one of the already triggered warning levels will and / or the triggering further warning levels is omitted. Method according to one of claims 1 to 17, characterized that the presence of driver activity due to an operation at least a control element, in particular for changing the longitudinal or Transverse dynamics of the vehicle is detected. Method according to one of claims 1 to 18, characterized in that a reduction of Auffahrgefahr based on a time increasing distance (d) between the vehicle and driving ahead the vehicle and / or a relative speed (v _rel ) decreasing over time between the vehicle and the vehicle ahead. Method according to one of claims 1 to 19, characterized in that the current driving situation of the vehicle as a function of the determined distance (d) between the vehicle and the vehicle ahead and / or the determined relative speed (v _rel ) between the vehicle and the vehicle ahead and / or the determined speed (v) of the vehicle and / or the determined relative acceleration (a _rel ) between the vehicle and the vehicle ahead and / or the determined acceleration (a) of the vehicle and / or the road inclination and / or determined by coefficients of friction between the road and the vehicle wheels becomes. Method according to one of claims 1 to 20, characterized that when triggered of the automatic Emergency braking operation a warning of driving ahead and / or behind Vehicles are done. Device for carrying out an automatic emergency braking operation of a vehicle in order to avoid a collision of the vehicle with a vehicle in front or to reduce the number of ascents, with an evaluation unit ( 7 ), whereby upon fulfillment of one in the evaluation unit ( 7 ) stored warning condition from the evaluation unit ( 7 ) a driver warning is triggered, characterized in that the fulfillment of the in the evaluation unit ( 7 ), given predetermined warning condition indicates that on the basis of taking into account the determined acceleration (a) of the vehicle and / or the determined relative acceleration (a _rel ) given between the vehicle and the vehicle ahead current driving situation of the vehicle and a predetermined emergency brake delay (a _NB ) at expiration a predetermined warning period (t _w ) from the evaluation unit ( 7 ) an automatic emergency braking operation by suitable control of braking means ( 38 ) of the vehicle, with the aim of achieving a predetermined target _relative speed (v _{rel, z} ) and / or a predetermined target safety distance (d _z ) between the vehicle and the vehicle ahead on completion of the automatic emergency braking operation.