Method for controlling a vehicle distance control system

Abstract

A method for controlling a distance adjustment system, which is a system for adjusting the distance between a target vehicle (10) and a following vehicle (20), and is installed in the following vehicle, is disclosed, the method including: executing a control law (cmd) for adjusting distance that calculates potential set distances for a plurality of possible combinations of travel speeds of the following vehicle and the target vehicle; and determining a final set distance from the potential set distances pre-calculated by the control law for a given combination of travel speeds of the following vehicle and the target vehicle from the plurality of possible combinations.

Description

[Technical field]

[0001] The present invention relates to the field of vehicle driving assistance, more particularly to a method for controlling a system for adjusting vehicle distance. [Background technology]

[0002] Driving assistance functions available in current vehicles aim to improve ride comfort and reduce road hazards. To this end, functions are being developed that allow maintaining a predefined set or safe distance between two vehicles. For this purpose, ACC ("Adaptive Cruise Control") systems are available in certain vehicles. These systems are installed in a vehicle (called the following vehicle) and detect a preceding vehicle (called the target vehicle) by means of a laser or camera mounted on the following vehicle, and are able to estimate the speed and distance of the target vehicle and then control the speed of the following vehicle to maintain a safe distance. Road traffic regulations in many countries require that the following vehicle maintain a safe distance to avoid collisions, especially when the preceding vehicle is braking or stopping. The safe distance is mainly determined by the speed of the following vehicle. For example, according to French road traffic regulations, this safe distance corresponds to the distance that the following vehicle will travel within a prescribed time interval of at least two seconds. In other words, these regulations require that there must be a distance between the following vehicle and the target vehicle that corresponds to a drive of two seconds, since this time interval theoretically ensures the safety of the user even during sudden braking.

[0003] For example, from patent US 6,789,637, a distance control mechanism for a motor vehicle is known, which device is suitable for observing a set distance or a set time interval to a target vehicle depending on the driving speed. The distance control takes into account the shortest distance or the minimum time interval that can be specified by the driver when determining the set distance or the set time interval. In response to a situation of poor visibility detected by a sensor installed in the vehicle, the distance control device is set to increase the set time interval determined for normal visibility. The control device thus calculates the set distance by implementing a time interval that is adaptable depending on the visibility situation.

[0004] However, there are situations in which control of the safety distance behind the target vehicle according to the principles summarized above with reference to the prior art documents is not sufficient to allow avoidance of a collision, especially when the braking ability of the following vehicle is impaired, for example due to substantial wheel slip of the vehicle.

[0005] Therefore, in these specific situations and at high speeds, the time interval-based distance adjustments intended to implement these assistance functions do not provide sufficient guarantees regarding the ability to avoid potential collisions, even though the ultimate aim of the ACC function is to minimise road hazards as much as possible. Summary of the Invention

[0006] In view of the above, it is an object of the present invention to provide a method for controlling the adjustment of a safe distance from a target vehicle to overcome at least some of the shortcomings of the prior art, in particular to reduce scenarios in which a collision with a leading vehicle is unavoidable.

[0007] For the above purpose, the present invention provides a target vehicle (20) and the following car (10) It is a system that adjusts the distance between The above 1. A method for controlling an adjustment system installed in a following vehicle, comprising: A given time interval ( tTimegapDist ) and the following vehicle is determined to have a traveling speed of 0.01 m / s during the time interval. ( vEgo ) A first distance corresponds to the distance traveled according to ( dTimegap ) and, The above Following vehicle The running speed (vEgo) and The above the goal Car Ground speed ( vTarget ) and during emergency braking Before More details to come a predetermined deceleration value (aEgoSafetyDist) of the following vehicle corresponding to the deceleration of the target vehicle The deceleration rate corresponds to Before Recorded goal Car Predetermined deceleration value( aTargetSafetyDist ) A second distance calculated according to ( dSafetyDistStop ) and, Target vehicle when stationary The prescribed maximum speed for such impact is established based on the predetermined impact speed with ( vAccidentVelocity ) It is prescribed with respect to The above Following vehicle The above Ground speed ( vEgo ) And The above Maximum speed of following vehicles ( vAccidentVelocity ) and The above Predetermined deceleration value ( aEgoSafetyDist ) A third distance calculated according to ( dSafetyDistColl ) and, The above For target vehicle The above A fourth distance corresponds to the shortest stationary distance of the following vehicle; of Calculate , the above Control Law for Distance Regulation (cmd) and rear For a given combination of the travel speeds of the following vehicle and the target vehicle, the control rule Performer Calculated a set distance corresponding to the maximum value among the first distance, the second distance, the third distance, and the fourth distance To determine The present invention relates to a method comprising the steps of:

[0008] According to one particular embodiment, determining the final set distance includes evaluating a distance corresponding to the longest of the first, second, third, and fourth potential distances for a given combination of driving speeds of the following vehicle and the target vehicle.

[0009] According to one feature, the second Distance away (dSafetyDistStop) , The above Subsequent Car Ground speed ( vEgo ) and The travel speed ( vTarget ) Arrangement Before More details to come Car Predetermined deceleration value ( aEgoSafetyDist ) and The predetermined deceleration value of the target vehicle ( aTargetSafetyDist ) Using the following formula Calculated using TIFF0007634519000001.tif25170 and the parameters ( tSystemTolerance ) corresponds to the system delay time.

[0010] According to another feature, the third Distance away (dSafetyDistColl) , The above Following vehicle The above Ground speed ( vEgo ) , collision The above Specified maximum speed ( vAccidentVelocity ) , and The above Following vehicle The above Predetermined deceleration value ( aEgoSafetyDist ) Using the following formula Calculated using TIFF0007634519000002.tif15170 and the parameters ( tSystemTolerance ) corresponds to the system delay time.

[0011] The delay time of the system is preferably defined by the time it takes to reach the required braking force and / or the perceived reaction time of the system.

[0012] Other characteristics and advantages of the invention will emerge more clearly from a reading of the following description with reference to the single drawing, the latter being given by way of illustrative and non-limiting example. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic diagram of a distance adjustment system according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 1, the distance adjustment system according to the present invention aims to adjust a following vehicle 10 equipped with the system so that it can follow a vehicle ahead (referred to as a target vehicle 20) at a given distance (referred to as a safe distance). Typically, the following vehicle 10 is equipped with measuring means (e.g., radar type) that allows the distance and relative speed between the following vehicle and the target vehicle to be measured, and an on-board speed sensor that can provide information on the vehicle's speed.

[0015] The system's control law is then designed to provide acceleration and deceleration settings to be applied to the vehicle based on the measured relative distance, the speed of the following vehicle, and its relative speed to the target vehicle, in response to a set safe distance, in order to control the longitudinal position of the following vehicle relative to the target vehicle so as to maintain the distance between the following vehicle and the target vehicle substantially constant around a set value.

[0016] This adjustment is performed by acting on the engine torque and brakes depending on whether motive or braking force needs to be applied to the system to adhere to the set distance.

[0017] According to the invention, the control rule cmd of the adjustment system is based on the determination of a set distance selected from various definitions of the concept of safety distance, which will become apparent below, depending on a given combination of the driving speed vEgo of the following vehicle on the one hand and the driving speed vTarget of the target vehicle on the other hand.

[0018] The first definition of safe distance used in this control law is based on the concept of the distance traveled by a following vehicle within a given time interval (denoted as tTimegapDist).

[0019] This safety distance based on the observance of a given time interval from the preceding vehicle is more specifically the result of a regulatory requirement. Thus, road traffic regulations, particularly in France and Germany, require the following vehicle to keep a safe distance in order to avoid a collision when braking or stopping the preceding vehicle. The safety distance therefore corresponds to the distance that the following vehicle will travel within a given time interval tTimegapDist (set for example at 2 seconds in France and 1.8 seconds in Germany). These regulations therefore require a minimum distance to be kept based on said given time interval. In other words, this safety distance (denoted dTimegap) is calculated based on the given time interval tTimegapDist multiplied by the speed of the following vehicle relative to the preceding vehicle. dTimegap = vEgo × tTimegapDist

[0020] Therefore, the parameter tTimegapDist makes it possible to adjust this safety distance.

[0021] The table below provides the safety distance based on the time interval set to 2 seconds for various speeds (km / h) of the following and target vehicles. TIFF0007634519000003.tif141170

[0022] The second definition of the safe distance used in the control law cmd of the present invention is based on the concept of the vehicle stopping distance. It is the distance required for a vehicle to stop. This distance must be chosen relative to the leading vehicle so that the following vehicle can stop behind the leading vehicle even in the event of sudden braking of the leading vehicle. It is related to the estimated performance of the following and target vehicles in terms of braking ability, but also takes into account the delay times of the system.

[0023] Therefore, to determine this stopping distance, the estimated braking capability of the following vehicle (denoted as aEgoSafetyDist) and the estimated braking capability of the target vehicle (denoted as aTargetSafetyDist) must be taken into account. Additionally, the system delay time (denoted as tSystemTolerance) must also be taken into account, which depends for example on the time it takes to reach the required braking force and / or the system's perceived reaction time to an emergency braking situation.

[0024] As mentioned above, the definition of the safety distance based on this stopping distance is aimed at making it possible to avoid a collision in case of sudden braking of the preceding vehicle, in other words, if the distance kept by the following vehicle from the target vehicle corresponds to this stopping distance, the following vehicle can stop behind the suddenly braking target vehicle with a guaranteed deceleration.

[0025] This safety distance (expressed as dSafetyDistStop) is calculated as follows according to the driving speeds vEgo and vTarget of the following vehicle and the target vehicle, respectively, and predetermined deceleration values ​​aEgoSafetyDist and aTargetSafetyDist of the following vehicles (following vehicle and target vehicle) corresponding to the deceleration of the following vehicles (following vehicle and target vehicle) during emergency braking: TIFF0007634519000004.tif24170

[0026] In order to provide a certain safety margin when determining the stopping distance, the following vehicle is set to have a lower braking capability (for example, approximately 2 m / s 2 ). In other words, aEgoSafetyDist-aTargetSafetyDist≡2m / s 2 The table below shows aEgoSafetyDist=-3.7m / s 2 and aTargetSafetyDist=-5.7m / s 2It takes as input parameters dSafetyDistStop and provides a value of the safety distance based on the stopping distance dSafetyDistStop calculated for various combinations of the following vehicle and target vehicle speeds (km / h).

[0027] Additionally, the system delay time tSystemTolerance is set to 0.4 seconds. TIFF0007634519000005.tif141170

[0028] As a result, for example, when the speed of the following vehicle and the speed of the target vehicle are both equal to 50 km / h, the target vehicle can move at a speed of -5.7 m / s while maintaining a safe distance of approximately 14.7 m from the target vehicle. 2 Assuming that the following vehicle is braking at a deceleration of -3.7 m / s to stop behind the target vehicle, 2 A deceleration of 0.1 is sufficient.

[0029] If the target speed is considered to be equal to zero, then -3.7m / s for various speeds of the following vehicle. 2 The first column of the above table allows one to take into account the situation where there is a stationary object (be it a vehicle or a pedestrian) in front of the vehicle by providing the distance required to stop behind this stationary object with a deceleration equal to

[0030] The third definition of the safe distance used in the control law cmd of the present invention is based on the fact that it determines a certain crash speed below a prescribed speed while the preceding vehicle is stationary.

[0031] The crash speed is the impact speed at the moment when the vehicle hits an obstacle. A safety distance based on compliance with this specific crash speed can potentially accommodate mainly two different use cases. The first use case concerns a situation where a leading target vehicle detects an obstacle in front of it and avoids it without slowing down. In such a situation, the following vehicle can therefore only detect the obstacle after and at the earliest during the preceding vehicle's avoidance maneuver. The second use case concerns a situation where a target vehicle ahead of the following vehicle is involved in a chain reaction and comes to a standstill much earlier than in the case of emergency braking. Nevertheless, the safety distance required for the following vehicle needs to be able to accommodate these situations.

[0032] This definition of the safety distance based on a predetermined crash speed takes into account two parameters already defined in relation to the second definition of the safety distance based on the stopping distance summarized above, namely the delay time tSystemTolerance of the system of the following vehicle and its estimated maximum braking capability EgoSafetyDist. The safety distance is defined so that the collision speed of the following vehicle and the preceding vehicle (or object) is less than a specified maximum collision speed (represented as vAccidentVelocity).

[0033] This safety distance (denoted as dSafetyDistColl) is calculated according to the speed of the following vehicle vEgo, the prescribed collision speed vAccidentVelocity, and a predetermined deceleration value aEgoSafetyDist of the following vehicle, taking into account the delay time of the system, as follows: TIFF0007634519000006.tif24170

[0034] The table below shows aEgoSafetyDist=-3.7m / s 2 , vAccidentVelocity=50km / h, and tSystemTolerance=0.4s as input parameters to provide values ​​of safety distance based on a given collision speed dSafetyDistColl calculated for various combinations of following and target vehicle speeds (km / h). TIFF0007634519000007.tif142170

[0035] The fourth definition of the safe distance used in the control rule cmd of the present invention is based on the concept of the required minimum stationary distance of the following vehicle to the target vehicle. This required minimum stationary distance (denoted as dTargetDistMin) is more specifically selected to provide the driver of the vehicle with a sense of security, especially in situations where the autonomous driving mode of the vehicle is no longer available, while still providing the vehicle with enough space to avoid stationary objects in front of the vehicle when it approaches them.

[0036] From a safety point of view, the minimum rest distance of the following vehicle should be chosen to be greater than zero. As an example, if there is a vehicle ahead of the following vehicle, dTargetDistMin is set equal to 3m, if the following vehicle is preceded by an unidentified object or if the following vehicle arrives at an accident scene, dTargetDistMin is set equal to 5m.

[0037] From a safety point of view, these values ​​are sufficient. Moreover, human behavior in traffic jam situations is generally quite different. Therefore, in traffic jams, the stopping distance of a vehicle relative to a preceding vehicle is much shorter than the above set values.

[0038] The set distance required by the control law for the adjustment system is then the result of a selection among the various definitions of the safe distance as summarized above, this selection being made depending on the speed of the following vehicle and the speed of the target vehicle.

[0039] More specifically, the control law is designed to determine, for each possible combination of the speeds of the following vehicle and the target vehicle, a set distance (denoted as d_cons) that corresponds to the maximum value of the safety distance required according to the first, second, third and fourth definitions summarized above.

[0040] The set distance d_cons required for this following vehicle adjustment system is therefore calculated for each combination of following vehicle and target vehicle speeds as follows: d_cons=max(dTimegap,dSafetyDistStop,dSafetyDistColl,dTargetDistMin)

[0041] The following table shows the values ​​of the set distance calculated as above for different combinations of speeds (km / h) of the following and target vehicles, based on examples provided for the different definitions adopted for the safety distance. This table therefore contains the set distances that the following vehicles must observe with respect to the target vehicle. TIFF0007634519000008.tif142170

[0042] Assuming that the measuring means installed in the following vehicle perform accurate detection of the distance from the preceding target object or vehicle, it can be established that there is no risk of collision if the adjustment distance is longer than the specified set distance.

[0043] It can be seen that the maximum required set distance is associated with the approach of the following vehicle to a stationary target object. This situation is reflected in the first column of the above table, which specifies the set distance for a target with a zero speed. In this first column, a relatively low estimated braking capacity of the following vehicle aEgoSafetyDist=-3.7m / s is required to avoid a safety risk to the traffic behind the following vehicle. 2 A safety distance based on the stopping distance is calculated for the following vehicle. The required set distance based on the stopping distance calculation becomes shorter as the braking ability of the following vehicle increases.

Claims

1. A method for controlling a system for adjusting the distance between a target vehicle (20) and a following vehicle (10), the adjustment system being mounted on said following vehicle, comprising: a first distance (dTimegap) calculated based on a predetermined time interval (tTimegapDist) for avoiding a collision with the target vehicle, the first distance corresponding to a distance traveled by the following vehicle within the time interval according to its traveling speed (vEgo); a second distance (dSafetyDistStop) calculated according to the traveling speed (vEgo) of the following vehicle, the traveling speed (vTarget) of the target vehicle, a predetermined deceleration value (aEgoSafetyDist) of the following vehicle corresponding to the deceleration of the following vehicle at the time of emergency braking, and a predetermined deceleration value (aTargetSafetyDist) of the target vehicle corresponding to the deceleration of the target vehicle at the time of emergency braking; a third distance (dSafetyDistCol) established based on a predetermined collision speed with the target vehicle when stationary and calculated according to the traveling speed (vEgo) of the following vehicle, a prescribed maximum speed for collision (vAccidentVelocity) and the predetermined deceleration value (aEgoSafetyDist) of the following vehicle; a fourth distance corresponding to a minimum stationary distance of the following vehicle relative to the target vehicle for avoiding the target vehicle when the following vehicle approaches the target vehicle; executing a control law (cmd) for adjusting said distance, the control law computing determining, for a given combination of the traveling speeds of the following vehicle and the target vehicle, a maximum value among the first distance, the second distance, the third distance, and the fourth distance calculated according to the control rule as a set distance; A method comprising:

2. The second distance (dSafetyDistStop) is calculated by the following formula using the traveling speed (vEgo) of the following vehicle, the traveling speed (vTarget) of the target vehicle, and the predetermined deceleration value (aEgoSafetyDist) of the following vehicle and the predetermined deceleration value (aTargetSafetyDist) of the target vehicle:

2. The method of claim 1, wherein the system is operated according to the following formula: and a parameter (tSystemTolerance) corresponds to the delay time of the system.

3. The third distance (dSafetyDistCol) is calculated by the following formula using the traveling speed (vEgo) of the following vehicle, the specified maximum speed for a collision (vAccidentVelocity), and the predetermined deceleration value (aEgoSafetyDist) of the following vehicle:

3. The method according to claim 1, wherein the system is calculated by: and a parameter (tSystemTolerance) corresponds to the delay time of the system.

4. 4. A method according to claim 2 or 3, characterized in that the delay time of the system is defined by the time it takes to reach a required braking force and / or by the perceived reaction time of the system.

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