WO2000036435A1

WO2000036435A1 - Method for regulating a motor vehicle speed

Info

Publication number: WO2000036435A1
Application number: PCT/FR1999/003157
Authority: WO
Inventors: Gabriel Toffolo
Original assignee: Renault
Priority date: 1998-12-16
Filing date: 1999-12-15
Publication date: 2000-06-22
Also published as: EP1149307A1; FR2787586B1; FR2787586A1

Abstract

The invention concerns a method for regulating the speed of a motor vehicle equipped with means for detecting and monitoring mobile targets and onboard means for electronic control of the vehicle speed, and moving on a traffic lane among other vehicles running on adjacent parallel lanes in the same direction, such that it automatically regulates the speed according to a set speed value selected by the driver and to the relative speeds of the vehicles detected on its traffic lane and the adjacent lanes, by permanently analysing the traffic conditions within the detection field of onboard range finding means located at the front of the vehicle.

Description

SPEED CONTROL METHOD FOR MOTOR VEHICLE

The invention relates to a speed control method for a motor vehicle moving between several mobile vehicles traveling in the same direction, in particular in a situation of heavy traffic on several traffic lanes.

Currently, there are distance regulation systems - Adaptive Cruise Control ACC - allowing vehicles fitted with them to automatically respect a predetermined safety distance with the previous vehicle on the same traffic lane. The equipped vehicle automatically modulates its speed to keep this distance. As soon as the lane is clear in front of the equipped vehicle, its acceleration increases automatically to reach the set speed selected by the driver, and thus assist the driver in his driving task.

With the ACC system, the driver can select a cruising speed, above a minimum speed, fixed at around 40 km / h, using buttons on the steering wheel, and the vehicle speed then stabilizes at this speed reference. If a slower vehicle is detected in front of the equipped vehicle, on its lane, the speed is automatically modulated to adapt the distance to safety standards. This target detection is carried out by a radar or range finder 1 placed at the front of the vehicle, which calculates the position D _r and the relative speed V of the preceding vehicle. This information is sent to an electronic control computer 2, also on board the vehicle, which consequently controls the operation of the vehicle 3, by controlling the engine, by controlling the throttle valve, managing the reports of the automatic gearbox and possibly the brake pressure to act on the acceleration of the vehicle, as shown in the principle diagram of a current distance regulator, in Figure 1. Thanks to a dedicated interface, the driver is permanently informed of the state of the system.

Patent application No. 0 605 104 A1, in the name of JAGUAR, describes a system equipped with a fairly large horizontal field radar, of the order of 15 degrees, making it possible to detect and track several vehicles. Based on the trajectory prediction of the vehicle equipped with the ACC system and of the other vehicles preceding it, the system selects the closest target vehicle located on its trajectory. The distance and speed information relating to this chosen target vehicle are then sent to an on-board electronic computer, intended to modulate the acceleration of the vehicle by controlling the throttle valve or the brakes.

If these current systems meet the expectations of drivers in the event of smooth road traffic, on the other hand, their level of adaptation to heavy traffic is less satisfactory. Automatic accelerations or decelerations of the vehicle based on a single target vehicle, preceding it on the lane, is often no longer acceptable and no longer reflects the decision-making mechanism of a driver who assesses the road situation in a context more global with several variable targets. The current systems in particular do not resolve certain situations of heavy traffic. FIG. 2 schematically represents a situation of heavy traffic on several traffic lanes, in the same direction as the vehicle 20 equipped with the system. It concerns three lanes of traffic, the equipped vehicle being on lane C in the middle. With a conventional distance regulation system, as soon as the target vehicle 21 detected by the radar, since it is in the same lane as the equipped vehicle 20, has changed lanes, will fall back, for example, on the right lane, the system will allow maximum acceleration of the vehicle so that the speed reaches the set speed previously chosen by the driver. This solution is not satisfactory because it does not take into account either the other vehicles present on the adjacent right-hand and left-hand lanes G and detected in the beam 22, nor the significant speed differentials which may exist between these different vehicles.

FIG. 3 shows diagrammatically another situation of heavy traffic in which the vehicle 30 equipped with the ACC system follows a target vehicle 31 which is on its taxiway D and which begins to accelerate and to disengage on a lateral lane, in this case lane C in the middle to overtake a vehicle 32 slower than him, a truck for example. If the set speed of the equipped vehicle is high, 130 km / h for example, the vehicle will then accelerate to its maximum by overtaking the vehicles 33 which are to its left with sometimes a large difference in relative speed. This untimely speeding up on the right lane D can be dangerous, all the more more than the equipped vehicle will then brake behind the slow vehicle 32 which then enters the field of action 34 of the range finder of the vehicle and becomes its new target.

The situation in FIG. 4 corresponds to the case of a vehicle 40 equipped with an ACC system located behind a target vehicle 41 which is traveling behind a third slow vehicle 42, a truck at very low speed or in the process of slowing down sharply, in view of leaving its lane for example. The target vehicle 41 anticipates a lane change maneuver to avoid slowing down or even braking. The distance control system takes into account only the target vehicle 41 right in front of it and not the environment as a whole as the driver does who sees the road scene through the windows of the target vehicle, or as detected by the radars beyond the first vehicle.

These three situations previously described illustrate the limits of current distance control systems which only take into account the relative distance and speed information of the nearest vehicle, on the same traffic lane as the equipped vehicle, to automatically control the acceleration and deceleration of said vehicle. In heavy road traffic, these automatic control strategies can prove to be dangerous, or at least unsuited to the wishes of the driver of the equipped vehicle and of the other motorists around him.

To overcome these drawbacks, the invention proposes a method of regulating distance which no longer controls the accelerations of the vehicle as a function of a single target detected, but which takes into account the flow of vehicles traveling on several adjacent lanes, and in the same direction as the vehicle, and constituting its real environment. This new process makes it possible to considerably increase the safety and comfort of the driver and his passengers thanks to the traffic conditions in the adjacent lanes - such as the density of traffic, the speed of the different vehicles, ... - which become criteria. driver risk assessment.

For this, the object 4 ^e the invention is a method of regulating the speed of a vehicle equipped with means for detecting and monitoring moving targets, and on-board means for electronic control of the acceleration of the vehicle, and traveling on a traffic lane among other vehicles traveling on adjacent parallel lanes in the same traffic direction, characterized in that it automatically regulates the speed as a function of a portion of the set speed selected by the driver , and on the other hand the relative distance and speed of the vehicles detected on its traffic lane and adjacent lanes.

According to another characteristic, the method according to the invention comprises the following steps:

- permanent analysis of traffic conditions in the field of detection of on-board telemetry means at the front of the equipped vehicle,

- determination of a main target vehicle in the lane of the equipped vehicle,

- detection of vehicles in adjacent traffic lanes from their distance, - choice of decision rules for the application of vehicle acceleration control laws, to regulate the speed of the vehicle, based on the one hand on the presence of vehicles detected in the adjacent lanes and their relative speed and on the other hand the set speed selected by the driver.

Other characteristics and advantages of the invention will appear on reading the following description, illustrated by the following figures which, in addition to FIGS. 1 to 4 already described, are:

- Figure 5: a block diagram of a distance control method according to one invention; - Figure 6: an example of cutting the detection field of the rangefinder of a vehicle equipped with a distance controller 1 according to the invention;

- Figure 7: an example of a flow diagram of the distance control method according to the invention; FIG. 8: an example of a law for controlling the acceleration of the vehicle equipped according to the invention.

The block diagram of FIG. 5 illustrates the essential characteristic of the regulation method according to the invention, according to which the laws for controlling the acceleration of the vehicle are no longer single-target but multi-target, that is to say say that they take into account the relative distance and speed information of all the vehicles detected in the environment of the equipped vehicle, whether they are located on the same traffic lane as the said vehicle or on adjacent lanes, in the same flow direction. The vehicle equipped with a distance regulator is provided with a rangefinder 50, of radar or infrared type, delivering a flow of information on the N target vehicles detected, concerning their distances D _r ^ and their relative speeds V _r ^, i being an integer between 1 and N, to an on-board electronic computer 51. The latter ensures tracking and the choice of targets in the environment of the vehicle among the various objects of the road scene at the front of the vehicle. This computer establishes control laws from these different target vehicles to control the setpoint acceleration of the vehicle 52, by controlling the operation of the engine, the brakes, the automatic gearbox or sensors. This setpoint acceleration is established on the basis of the relative distance and speed of the equipped vehicle with respect to the selected targets, of the setpoint or safety distance and of the setpoint speed imposed by the driver.

Figure 6 is a top view of the detection field 61 of a rangefinder 60 fitted to the front of a vehicle V _R having a speed control device. This vehicle is traveling on the central lane C, in the middle of the right L and left G lanes of the roadway. An axis OX, of origin 0 at the rangefinder and ordinates X towards the front of the vehicle, makes it possible to measure the distance of the target vehicles C ^ from the equipped vehicle. Several zones are defined in each of the three lanes G, C and D according to their distance from the equipped vehicle. For example, at a maximum distance D-, from 20 meters from said vehicle, three horizontal zones Z _ql , Z _cl and Z are defined ₍ ^ ₁ corresponding to the three traffic lanes respectively left G, central C and right D. Similarly, between D ₂ = 40 meters and D ₃ = 80 meters from the vehicle, we can define three other zones Z ₂ , Z _o and Z _d21 etc .... These areas allow the calculation of the decision rules used by the process control laws according to the invention which govern the dynamics of the vehicle.

FIG. 7 is an example of a flow diagram of the different stages of the distance regulation process, leading to four types of decision rules.

During step (a), the method is concerned with the presence of a target vehicle in front of the vehicle equipped V _R in its lane.

If no target vehicle is detected, step (a) leads to step (f) of memorizing information of absence of main target, followed by a step (g) of detection of vehicles traveling on the adjacent lanes, intended to fulfill one of the characteristics of the invention which consists in modulating the speed of the equipped vehicle even if no main target vehicle is present on its lane.

On the other hand, if a target vehicle C ₁ is detected in the traffic lane, the method proceeds to step (b) of detection of another target vehicle C ₂ , traveling in front of the first vehicle on the same traffic lane to a greater distance, however, less than a pre-established threshold, for example 130 meters. If the method does not detect any target C ₂ , then the main target vehicle C- ^ is unique and this information is stored in step (e).

On the other hand, if a target vehicle C ₂ is correctly detected, the method proceeds to the next step (c) of assessing the dynamics of this second target vehicle. It is a question of considering the more or less dangerous character of this second target C ₂ compared to the first target C ^, which can be evaluated in particular as a function of the collision time. It is for example necessary to compare the ratio between the distance and the speed of this second vehicle C ₂ with the same ratio for the first target C ₁ .

If the method considers that the second target vehicle C ₂ is less dangerous than the first target C ^, it does not take it into account and considers only a single target C- ,. This main target information C-, unique, is stored in step (e).

Otherwise, in step (d), the method decides on the existence of a virtual target C, associating the first target vehicle C- ^ and the second target vehicle C ₂ located in front to take into account the information. relating to these two vehicles. Step (d) also consists in memorizing the information of the presence of such a virtual target C _v to be taken into account thereafter.

In step (g), the method considers the vehicles traveling on one of the lanes adjacent to that of the vehicle equipped V _R , more particularly on the left lane used by fast vehicles which overtake. For vehicles with driving on the right, like those driving in the UK, we are interested in the right lane.

If no vehicle is detected on this left lane, the method seeks to detect the presence of vehicles on the right lane, adjacent to that of the equipped vehicle, in step (h).

In the case where no vehicle is detected on the right, the next step (i) consists in applying a type of decision rules No. 4, characteristic of conventional single-target distance regulation systems.

In the case where one or more vehicles are detected on the right lane, while there is no vehicle in the left lane, step (j) consists in comparing their average speed with a speed minimum ^, fixed around 60 to 70 km / h.

If the calculated average speed is greater than this threshold ^v τnin '^ - ^th process proceeds to step (i) of application of decision rules No. 4.

If the average speed is lower than - ^^ the process applies, in step (k), another type of decision rules N ° 3 multi-targets, with as main target that defined in one of the three steps (crazy) .

In the case where vehicles are present in the left lane of the vehicle equipped V _R - step (g) -, the method detects in step (1) the presence of vehicles located in the right lane.

If vehicles are then detected, this corresponds to a traffic situation on both lanes adjacent to the equipped vehicle, then step (m) consists in applying a type of decision rules No. 1 multi-targets.

However, if vehicles are not detected to the right of the equipped vehicle, step (n) also consists in applying multi-target decision rules, but of another type No. 2.

According to a general principle, these different decision rules correspond to learning the criteria which influence the behavior of the driver when driving. As shown in FIG. 6, the zones are distinguished for example according to three values of distance D ,, D ₂ and D ₃ relative to the equipped vehicle and according to the three traffic lanes G, C and D defined from the position of the vehicle equipped with range finder.

The calculation of the number of vehicles and their speed inside these different zones is modeled to take this information into account when modulating the speed of the vehicle equipped with a distance controller.

In a distance regulation system, the acceleration law of the equipped vehicle r _{v is} expressed as a function of the relative speed V _r and of the difference between the relative distance D _r and the safety distance D _s , in the form of a sum weighted by coefficients K _γ and K ^ according to equation (E- ^):

(E _T. ) Γ _V = K _v * V _r + K _d * (D _r - D _s ) This acceleration r _γ is always less than a maximum authorized r _rnaχ threshold, fixed around lm / s ² to ensure good comfort for the passengers of the vehicle.

As has been said during the description of the flow diagram of the method according to the invention, it is first of all necessary to define the type of main target that the equipped vehicle will follow, memorized during the three stages (d), (e ) or (f). Whatever the type of main target stored, the method performs a first processing phase common to the three types of rules, before performing a second phase specific to each type.

During the first step (o) of determining the vehicle acceleration control law, in this first phase, following step (f), the method considers that there is no vehicle main target, therefore the acceleration r _v of the vehicle will be equal to the maximum authorized acceleration r _maχ :

After step (e), it is considered that there is only one target vehicle C ₁ traveling in front of the equipped vehicle, in its travel lane, so the acceleration r _c -, setpoint to be applied to the equipped vehicle to regulate on the target C ^, is expressed according to the equation (E-,) previously written from a weighted sum of the relative speed V _r of the vehicle and the difference between its relative distance D and the safety distance D _s :

^r cl = ^κ v * ^v r + ^κ d * (° r ^"D s) K _γ and K _d being predefined weighting coefficients, for example K _d ≈ 0.02 and K _v ≈ 0.2.

After step (d), the method considers the existence of a virtual target C _γ from the two vehicles C- ^ and C ₂ present on the traffic lane of the equipped vehicle. Equation (E ^) is applicable to two vehicles:

r _cl = κ _v * v _rl + κ _d * (D _rl - D _S1 ) ^r C2 = ^K v * ^V r2 ^{+ K} d * ( ^D r2 ^"D s ₂ ⁾

The method then compares the reference accelerations r _cl and r _C2 with respect to the vehicles C-, and c ₂ , one with respect to the other, as well as their deviation. If the setpoint acceleration r _c2 with respect to the second vehicle is less than the setpoint acceleration r _cι with respect to the first and if their deviation is greater than a threshold T _s fixed for example at 40%, the acceleration r _γ of the equipped vehicle is expressed as a function of the two accelerations r _cι and r _c2 according to equation (E ₂ ):

^{Ξi r} C2 < ^r Cl ^and I ^r C2 - ^r Cll ^r s then r _γ = K * r _cl + (i-κ) * r _C2 (E ₂ )

with K: coefficient less than 1, depending on the measurement accuracy on the acceleration.

Once the expression of the acceleration r of the vehicle has been calculated in step (o), the method completes a step (p) for comparing the speed of the vehicles with the set speed V _c selected by the driver. If their speed is below this threshold, these vehicles are taken into account. Step (q) consists of classifying each vehicle in an area of the detection range of the vehicle telemetry means, which is determined according to the left or right geographical character of the adjacent lane of traffic where the vehicle is present and according to its distance to the equipped vehicle.

In step (r), each zone Z • or ZJJ is assigned a coefficient • or k _dj _ of weighting characteristic of the distance to the equipped vehicle, which will be used subsequently to calculate the average of the speeds.

Then, step (s) consists in creating, in each zone where no vehicle has been detected, a fictitious vehicle having a traveling speed equal to the speed setpoint selected by the driver of the equipped vehicle.

For vehicles traveling on the left lane, respectively on the right, in relation to the lane of the equipped vehicle, the average speed is calculated using the weighting coefficients _ respectively k ^, assigned to each zone, i being an integer between 1 and n.

After this first processing phase, common to the three types of decision rules, each of these types completes its own second phase.

Decision rules No. 1 correspond to the case where vehicles are present in front of the equipped vehicle, on the two traffic lanes adjacent to his, on the left and on the right. In stages (d), (e) and (f), the characteristic of the vehicle in question has been stored. as a target to be taken into account on the lane of the equipped vehicle.

The method compares the difference <S in average speed between the vehicles detected on the left and on the right to a threshold V _s to estimate whether there is a significant speed difference between the two lanes.

If the difference ό ^~ _γ is less than the threshold V _s , we consider that the vehicles travel almost at the same speed on both the left and right lanes and we then compare the average speed on the left V with the average speed y at right V _d .

In the case where V is greater than V _d , then the maximum speed V--., Of the regulated vehicle is less than the product of the average speed on the left V by a multiplier coefficient K ₁ , greater than 1, for example equal to 1 , 2, and the maximum acceleration r _max is less than a function f ^ _ decreasing with the average speed on the two channels:

if δ _v <V _s and if V _g > V _d , ^{then v} max < ^κ l * ^v g ^{and r} max < ^f l £ < ^V g ^{+ V} d> / ² ]

In the case where V _d is less, the maximum speed V is less than the product of the right average speed V _d by a multiplier coefficient K ₂ greater than 1. K ₂ can also be equal to 1.2 for example. Maximum acceleration meets the same criteria as above:

then V.max <κ ₂ * v _d ^{and r} max < ^f l [< ^v g ^{+ v} d> ² ]

FIG. 8 is an example of a law for controlling the maximum acceleration r _maχ of the vehicle equipped with a distance regulator according to the invention, as a function of the average speed on the two lanes.

If the difference ό ^* is greater than the threshold V _s , two cases arise corresponding to the fact that the vehicles on the left travel faster than those in the right lane, or the reverse.

If the average speed on the left V is greater than the average speed on the right V _d , then the maximum speed V__ _v of the equipped vehicle is less than the product of the average speed on the left V by a multiplying coefficient Ko determined by calibration.

If it is the average speed on the right V _d which is greater than that on the left, the maximum speed V of the equipped vehicle is less than the product of the average speed on the right V _d by a multiplying coefficient K ₄ , also determined by calibration.

In the two previous cases, the maximum acceleration ^rr mmaaxx ^eeΞstt iinnfféérriieeuurree à à unun ffoonnccttiioonn ff ₂₂ cd decreasing with the average speed on the two channels:

aalloorrss ^v Vm.ax < ^κ 3 V,

if 5δ-v> V _Ξ and if V _d > V _g , then V, max < ^κ 4 * ^v g eett rr, _maχ <f ₂ [(V + V _d ) / 2] In all the cases mentioned in these decision rules No. 1, the maximum speed of the equipped vehicle may be lower than the set speed selected by the driver.

Decision rules No. 2 correspond to the case where vehicles are present on the adjacent lane to the left of the equipped vehicle, whose driving is on the left, while no vehicle is detected on the adjacent lane on the right. In steps (d), (e) and (f), the characteristic of the determined target vehicle has been stored.

After the first processing phase, the method takes into account only vehicles having a speed V lower than the set speed V _c selected by the driver. Those who go faster cannot change the behavior of the vehicle. Thus, the maximum speed V _maχ of the equipped vehicle is less than the product of the average speed on the left lane by a multiplier coefficient K ₅ greater than 1. It can be equal to 1.4. In addition, the maximum acceleration r _maχ of the vehicle is less than the product of the decreasing function f ₂ of the average speed V by a y multiplier coefficient K _g :

if V <V _c , ^{then V} max < ^K 5 * ^V g

The type of multi-target decision rules N ° 3 corresponds to the case where no vehicle is detected on the left lane compared to the equipped vehicle and where the vehicles are traveling on the adjacent right lane with a speed below a minimum speed threshold _mj _, of the order of 60 or 70 km / h. Still after the first processing phase, the method only takes into account vehicles having a speed lower than the set speed selected by the driver of the equipped vehicle. Then the maximum speed of the equipped vehicle is lower than the product of the average speed on the right lane by a multiplier coefficient K ₇ , greater than 1. It can be chosen equal to 2. In addition, the maximum acceleration r _maχ of the vehicle is less than the product of the decreasing function f ₂ by a multiplying coefficient Kg:

IF v <v _c , then ^V max < ^K 7 * v _d

Thanks to the method according to the invention, taking into account the vehicles traveling on the adjacent lanes makes it possible to automatically modulate the speed of a vehicle relative to the other vehicles of the traffic flow, in complete safety and while respecting the comfort desired by the vehicle passengers.

Claims

1. Method for regulating the speed of a vehicle equipped with means for detecting and monitoring mobile targets by telemetry and on-board means for electronic control of the acceleration of the vehicle, and moving on a lane of traffic other vehicles traveling on adjacent parallel lanes in the same traffic direction, characterized in that it comprises the following stages: in the detection field (61) telemetry means (50) on board the front of the vehicle, d 'axis

(OX) oriented towards the front of the vehicle and whose origin (0) is located at the level of the telemetry means, definition of several zones on the taxiway (C) centered on the vehicle and on the adjacent taxiways (L, R) as a function of their distance from the equipped vehicle,

- permanent analysis of traffic conditions in the different zones of the detection field (61) of the telemetry means on board the front of the equipped vehicle,

- determination of a main target vehicle in the lane of the equipped vehicle,

- detection of vehicles in adjacent traffic lanes from their distance,

- choice of decision rules for the application of vehicle acceleration control laws, to regulate the vehicle speed, based on the one hand on the presence of detected vehicles in the traffic lane and in the adjacent lanes and their relative speed, and on the other hand the set speed selected by the driver.

2. Method for regulating the speed of a vehicle according to claim 1, characterized in that, in the event of detection of two vehicles (C ^ and C2) preceding the vehicle equipped on its lane, it comprises:

a step (c) of assessing the dynamics of the second detected vehicle with respect to the first and of its dangerous nature, in particular by the collision time, followed by:

. in the case where the second vehicle (C2) is more dangerous than the first vehicle (C_), a step (d) of decision and memorization of the existence of a single virtual target (C _v ) associating the two vehicles ( C] _ and C2);

. in the case where the second vehicle (C2) is less dangerous than the first vehicle (C_), a step (e) of decision and memorization of the existence of a single target constituted by the first vehicle (C] _) .

3. Method for regulating the speed of a vehicle according to claim 1, characterized in that, in the absence of a vehicle on the adjacent traffic lane, to the left of the equipped vehicle, it comprises: - a step (h ) vehicle detection on the adjacent taxiway, right;

- a step (1) of taking single target decision rules (N ° 4) in the event of absence on the right;

- a step (k) of taking multi-target decision rules (No. 3) in the presence of vehicles on the right whose average speed is above a predetermined threshold.

4. Method for regulating the speed of a vehicle according to claim 1, characterized in that, in the event presence of vehicles on the traffic lane adjacent to the left of the equipped vehicle, it includes:

- a step (1) of detecting vehicles on the traffic lane adjacent to the right; - a step (m) or (n) of making multi-target decision rules, distinct according to the presence or absence of vehicles on the right.

5. Method for regulating the speed of a vehicle according to claim 1, characterized in that, in order to make the choice of multi-target decision rules with a view to applying the laws for controlling the acceleration of the vehicle, it performs a first processing phase comprising: - a step (o) of determining the law for controlling the acceleration of the equipped vehicle;

a step (p) of comparing the speed of the vehicles with the set speed selected by the driver and this set point; a step (q) for classifying each vehicle in an area of the detection field of the telemetry means of the equipped vehicle, determined according to the left or right geographical character of the adjacent vehicle traffic lane and according to its distance from the equipped vehicle, and to which a distance weighting coefficient is assigned in step (r);

- a step (s) of creation, in each zone where no vehicle has been detected, of a fictitious vehicle having a displacement speed equal to the set speed.

6. Method for regulating the speed of a vehicle according to claim 5, characterized in that the step (o) determining the vehicle acceleration control law is such that:

- in the absence of the main target vehicle noted in step (f), the acceleration (T _v ) of the vehicle is equal to the maximum authorized acceleration (r _max );

- in the presence of a single target vehicle (C _] _) traveling in front of the equipped vehicle, the target acceleration (T _] _) of the vehicle is equal to the weighted sum of the relative speed (V _r ) of the vehicle and the difference between its relative distance (D _r ) and the safety distance (D _s ): T _cl = K _v * V _r + K _d * (D _r - D _s )

- in the event of the existence of a virtual target (C _v ) defined from two vehicles (C] _ and C2) present on the traffic lane of the equipped vehicle, if the set acceleration (Fc2) relative to the second vehicle (C2) is less than the setpoint acceleration (TΓJI) compared to the first vehicle (C_) and if their deviation | T _Q 2 ~ ^r Cl I is greater than a fixed threshold (T _s ), the acceleration (IN) of the vehicle is expressed by: r _v = K * r _cl + (i-κ) * r _c2 with K: coefficient less than 1, depending on the measurement accuracy on acceleration.

7. Method for regulating the speed of a vehicle according to claim 4, characterized in that, in the case where vehicles are present on the two lanes of traffic adjacent to that of the team vehicle, the multi-target decision rules (Ν ° l) include a step of comparing the difference (δ _v ) in average speed between the vehicles detected on the left and on the right with a threshold (V _s ), followed by:

. in the case where this difference (δ _v ) is less than the threshold (V _s ):

- a step of comparing the average speed (Vg) of the vehicles on the left with the average speed (V _d ) of the vehicles on the right, with

* in the case where (Vg) is greater than (V _d ), then the maximum speed (V _max ) of the regulated vehicle is less than the product of the average speed (Vg) on the left by a greater multiplier (K _] _) at 1, and the maximum acceleration (r _max ) is less than a function (f_) decreasing with the average speed on the two channels:

then V _max <K _X * V _g and r _max <f _x [(V _g + V _d ) / 2]

* in the case where (V _d ) is greater than (V _g ), then the maximum speed (v ^" _max ) of the regulated vehicle is lower than the product of the average speed (V _d ) on the right by a multiplying coefficient (K2) greater than 1, and the maximum acceleration (r _max ) is less than a function (f_) decreasing with the average speed on the two channels:

then V _max <K ₂ * V _d and r _max <fx [(V _g + V _d ) / 2], and. in the case where this deviation (supérieur _v ) is greater than the threshold

⁽ V _s ⁾ :

* in the case where (V _g ) is greater than (V), then the maximum speed (V _max ) of the regulated vehicle is less than the product of the average speed (V _g ) at left by a multiplying coefficient (K3) determined by calibration: if δ _v <V _s and if Vg> V, then V _max <K _λ * V _g * in the case where (Vg) is less than (V), then the maximum speed (V _max ) of the regulated vehicle is lower than the product of the average speed (V) on the right by a multiplying coefficient (K4) determined by calibration: if δv> V _s and if V _d > V _g , then V _max < K ₄ * V _g with in both cases the maximum acceleration (r _max ) lower than a decreasing function f2 with the average speed on the two channels: r _max <f ₂ [(V _g + V _d ) / 2] .

8. Method for regulating the speed of a vehicle according to claim 5, characterized in that, in the case where vehicles are present on the adjacent lane to the left of the equipped vehicle, while no vehicle is detected on the adjacent right lane, the multi-target decision rules (No. 2) take into account only vehicles with a speed (V) lower than the set speed (V _c ) selected by the driver and decide that the maximum speed (V _max ) of the equipped vehicle is less than the product of the average speed (Vg) on the left lane by a multiplier (K5) greater than 1 and the maximum acceleration (r _max ) of the equipped vehicle is less than the product of the function f2 (Vg) decreasing with respect to the average speed on the left (Vg) by a multiplying coefficient (Kg):

then V _max <K ₅ * V _g and r _max <K ₆ * f ₂ (V _g ).

9. A method of regulating the speed of a vehicle according to claim 5, characterized in that, in the case where no vehicle is detected on the adjacent lane of the vehicle equipped to its left and where vehicles are traveling on the adjacent right lane with a speed below a minimum threshold, the multi-target decision rules (No. 3) take into account only vehicles having a speed lower than the set speed selected by the driver, and the maximum speed (V _max ) of the equipped vehicle is less than the product of the average speed

(V) on the right lane by a multiplying coefficient (K7), greater than 1, and the maximum acceleration (r _max ) of the vehicle is less than the product of the function f2 (V) decreasing with respect to the average speed at straight line (V _d ) by a multiplying coefficient. (Kg): if V <V _c then V _max <K ₇ * V _d tr _max <K ₈ * f ₂ (V _d ).

10. A method of regulating the speed of a vehicle according to claim 2, characterized in that, in the case of the existence of a virtual target (C _v ) unique associating two vehicles (C] _ and C2) preceding the vehicle equipped on its traffic lane, it compares the target accelerations (Tçi and P ^) compared to these two vehicles relative to each other, as well as their deviation, and if the acceleration compared to the second vehicle (Tç ^) ^is less than that compared to the first vehicle (Tς] _) and if their difference is greater than a threshold (T _s ) fixed for example at 40%, the acceleration of the equipped vehicle is expressed in function of the two accelerations (TΓJI and r _C 2) according to equation ⁽ E ₂ ⁾ : if r _c2 <r _cl and | r _c2 _ r _cl | > r _s then r _γ = K * r _cl + (i-κ) * r _c2 (E ₂ ) with K: coefficient less than 1, depending on the measurement accuracy on acceleration.