WO2022152986A1

WO2022152986A1 - Method and device for monitoring the trajectory of a vehicle traveling on a traffic lane

Info

Publication number: WO2022152986A1
Application number: PCT/FR2021/052220
Authority: WO
Inventors: Luc VIVET
Original assignee: Psa Automobiles Sa
Priority date: 2021-01-18
Filing date: 2021-12-07
Publication date: 2022-07-21
Also published as: FR3118929A1; FR3118929B1

Abstract

The invention relates to a method and device for monitoring the trajectory of a vehicle traveling on a traffic lane. The method, implemented by a computer, comprises: a step of obtaining a short-term reference trajectory which could monitor the vehicle until a time instant t1; a step of obtaining a long-term reference trajectory that could monitor the vehicle after a time instant t2 which is greater than t1; and a step of determining a trajectory of the vehicle between instants t1 and t2 by merging the short-term reference trajectory and the long-term reference trajectory.

Description

DESCRIPTION

Title: Method and device for trajectory tracking of a vehicle traveling on a traffic lane

The present invention claims the priority of French application 2100430 filed on January 18, 2021, the content of which (text, drawings and claims) is incorporated herein by reference.

Technical area

The invention relates to methods and devices for following the trajectory of a vehicle, in particular an automobile, traveling on a traffic lane.

Technology background

To improve road safety, some contemporary vehicles are equipped with driving assistance functions or system(s), known as ADAS (from the English "Advanced Driver-Assistance System" or in French "Système d'aide à la conduct advanced "). ADAS systems implement trajectory tracking methods which use a short-term reference based on data captured by on-board sensors of a vehicle such as for example cameras or radars and a long-term reference to anticipate events such as bends or traffic signs from, for example, GPS data (from the English “Global Positioning System”, in French global location system).

A method for trajectory tracking of a vehicle must longitudinally stabilize a short-term reference trajectory to stabilize, for example, a speed regulation of a vehicle or else to compensate for errors in trajectory tracking due to the approximations of the sensors used . A vehicle trajectory tracking method must also longitudinally stabilize a long-term reference trajectory so that a vehicle's trajectory adapts to changes in the road environment. Trajectory tracking methods are known which laterally correct the trajectory of a vehicle so that the vehicle adapts to the road environment, in particular to the structure of the traffic lane on which the vehicle is traveling. This type of process makes it possible to obtain good lateral correction stability of the vehicle.

However, these methods do not make it possible to obtain longitudinal stabilization of a short- and long-term reference trajectory for which it is necessary to manage larger trajectory prediction time ranges compared to those to be managed for a lateral correction of path. Typically, a lateral correction requires time ranges of a few seconds to be managed, while a longitudinal stabilization requires ranges of the order of a minute, or even more.

The problem to be solved is to determine a longitudinal stabilization of short-term and long-term reference trajectory of a trajectory of a vehicle traveling on a traffic lane so as to be able to control actuators to a stable short-term reference trajectory and to prioritize long-term decisions such as for example interactions with the driver of the vehicle.

Summary of the invention

An object of the present invention is to improve the safety of vehicles traveling in a road environment.

Another object of the present invention is to improve the current methods of trajectory tracking of a vehicle traveling on a traffic lane.

According to a first aspect, the invention relates to a method for following the trajectory of a vehicle traveling on a traffic lane, said method being implemented by a computer, said method comprising: a step of obtaining a trajectory of short-term reference that the vehicle could follow until a time instant t1; a step of obtaining a long-term reference trajectory that the vehicle could follow after a time instant t2 greater than t1; and a step of determining a trajectory of the vehicle y3(t) between times t1 and t2 by merging the short-term reference trajectory and the long-term reference trajectory.

According to a particular embodiment, the trajectory y3(t) is obtained by:

with y1 (t) the short-term reference trajectory, y2(t) the long-term reference trajectory, k1 (t) a time evolution function of a first coefficient and k2(t) an evolution function time of a second coefficient.

According to a particular embodiment, the function k1 (t) is given by:

with t a current time instant.

According to a particular embodiment, the function k2(t) is given by:

According to a particular embodiment, the time instant t2 is calculated from a surface delimited by the trajectories y1(t) and y2(t) from their origin to the time instant t2. According to a particular embodiment, the time instant t1 is the greatest value that meets the following constraints:

with t1 Min a configurable threshold value, deltaTmax a maximum value of the time interval between t1 and t2, aMax_C a maximum value of the derivative of the trajectory y3(t) and jMax_C a maximum value of the second derivative of the trajectory y3 (t).

According to a second aspect, the invention relates to a device for following the trajectory of a vehicle traveling on a traffic lane, the device comprising a memory associated with a processor configured for the implementation of the steps of the method according to the first aspect of the invention.

According to a third aspect, the invention relates to a vehicle, for example of the automotive type, comprising a device as described above according to the second aspect of the invention.

According to a fourth aspect, the invention relates to a computer program which comprises instructions adapted for the execution of the steps of the method according to the first aspect of the invention, this in particular when the computer program is executed by at least one processor.

Such a computer program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

According to a fifth aspect, the invention relates to a computer-readable recording medium on which is recorded a computer program comprising instructions for the execution of the steps of the method according to the first aspect of the invention.

On the one hand, the recording medium can be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM memory, a CD-ROM or a ROM memory of the microelectronic circuit type, or even a magnetic recording means or a hard disk. On the other hand, this recording medium can also be a transmissible medium such as an electrical or optical signal, such a signal being able to be conveyed via an electrical or optical cable, by conventional or hertzian radio or by self-directed laser beam or by other ways. The computer program according to the invention can in particular be downloaded from an Internet-type network.

Alternatively, the recording medium may be an integrated circuit in which the computer program is incorporated, the integrated circuit being adapted to execute or to be used in the execution of the method in question.

Brief description of figures

Other characteristics and advantages of the invention will emerge from the description of the non-limiting embodiments of the invention below, with reference to the appended figures 1 to 6, in which:

[Fig. 1] schematically illustrates a road environment in which a first vehicle travels, according to a particular embodiment of the present invention;

[Fig. 2] schematically illustrates a device on board the first vehicle of FIG. 1 and configured to implement the method for following the trajectory of a vehicle traveling on a traffic lane of FIG. 3, according to a particular embodiment of the present invention;

[Fig. 3] illustrates a flowchart of the different steps of a trajectory tracking method of a vehicle traveling on a traffic lane of Figure 1, according to a particular embodiment of the present invention;

[Fig. 4] schematically illustrates a temporal evolution of the coefficients used for trajectory merging, according to a particular embodiment of the present invention;

[Fig. 5] schematically illustrates a temporal evolution of a trajectory obtained by merging two reference trajectories, according to a particular embodiment of the present invention; and [Fig. 6] schematically illustrates a calculation of a time instant from a surface delimited by two reference trajectories, according to a particular embodiment of the present invention.

Description of embodiments

A method and a device for following the trajectory of a vehicle traveling on a traffic lane will now be described in the following with reference jointly to FIGS. 1 to 6. The same elements are identified with the same reference signs throughout. along the following description.

According to a particular embodiment, the invention relates to a method for following the trajectory of a vehicle traveling on a traffic lane which determines a trajectory of the vehicle as being a short-term reference trajectory that the vehicle could follow before an instant time t1 , as being a long-term reference trajectory that the vehicle could follow after a time instant t2 greater than t1 and as being a trajectory obtained by merging these two short- and long-term reference trajectories between the time instants t1 and t2.

The method makes it possible to obtain a short- and long-term longitudinal prediction of the trajectory of the vehicle. Typically, the prediction can go up to 2 minutes in cases of corner management with speed deviations of up to 180 km/h, well beyond what known methods of lateral trajectory correction allow ( of the order of 5 to 6 s).

The method makes it possible to merge a short-term reference trajectory and a long-term reference trajectory: one which acts as a short-term reference, which makes it possible to stabilize regulation, for example of the speed of the vehicle, and one which acts as long-term reference, to adapt the trajectory to the various changes in the environment.

One of the advantages is to adapt the trajectory of the vehicle to the road situation in the short and long term, in particular when the reference trajectories in the short and long term begin to diverge. The method avoids sudden changes in trajectory by merging two reference trajectories in the short and long term during a time interval causing a smooth transition between these two reference trajectories which induces increased driving comfort for the driver and the passengers of the vehicle.

The method makes it possible to configure trajectory tracking of a vehicle. This setting is easily configurable as will be seen later.

The method is advantageous because it can be implemented by a computer program which can be implemented from the hardware currently on board a vehicle.

[Fig. 1] schematically illustrates a road environment in which a vehicle is traveling, according to a particular embodiment of the present invention.

FIG. 1 illustrates a vehicle 10 traveling on a traffic lane 1001 in a given direction. A second vehicle 11 travels on a second traffic lane 1002 in an opposite direction.

Each vehicle 10 and 11 is advantageously equipped with a communication device for transmitting and receiving data intended for another vehicle and/or a server of a network infrastructure. Each communication device can be likened to a node of a network, for example an ad hoc wireless network.

The vehicles 10 and 11 advantageously communicate using a so-called V2X communication system, for example based on the 3GPP LTE-V or IEEE 802.11 p standards of ITS G5. In such a V2X communication system, each vehicle embeds a node to enable V2V vehicle-to-vehicle, V2I infrastructure vehicle and/or V2P vehicle-to-pedestrian (vehicle-to-pedestrian) communication, the pedestrians being equipped with mobile devices (for example a smart phone (“Smartphone”)) configured to communicate with the vehicles.

Network infrastructure includes, for example, communication devices

101, 102, each device 101, 102 corresponding for example to an antenna of a 4G or 5G LTE-type cellular network or to a UBR (“Roadside Unit”), each corresponding to a network node, in addition to the nodes equipping vehicles or pedestrians.

According to a particular embodiment, all the nodes (that is to say the communication devices associated with the vehicles 10 and 11 and the antennas or UBR 101, 102) of the network form, for example, an ad hoc wireless network (also called WANET (from the English “Wireless Ad Hoc Network”) or MANET (from the English “Mobile Ad Hoc Network”)), corresponding to a decentralized wireless network. The ad hoc wireless network advantageously corresponds to a vehicular ad hoc network (or VANET, standing for “Vehicular Ad hoc NETwork”) or to an intelligent vehicular ad hoc network (or InVANET, standing for “Intelligent Vehicular Ad hoc NETwork”), also known as the “GeoNetworking” network. In such a network, 2 or more vehicles each carrying a node can communicate with each other in the context of V2V vehicle-to-vehicle communication; each vehicle can communicate with the infrastructure set up as part of vehicle-to-infrastructure V2I communication; each vehicle can communicate with one or more pedestrians equipped with mobile devices (e.g. a smart phone as part of V2P vehicle-to-pedestrian communication.

The nodes corresponding to the antennas (or UBR) 101 and 102 are advantageously connected to one or more remote servers or to the “cloud” 100 (or in French “cloud”) via a wired and/or wireless connection. The antennas or UBR 101 and 102 can thus act as a relay between the “cloud” 100 and each vehicle 10 and 11.

The vehicles 10 and 11 correspond for example to so-called autonomous vehicles, that is to say vehicles whose driving is, at least in part, managed by one or more automatic systems. The level of autonomy of vehicles 10 and 11 is for example between 0 and 5 (0 for a vehicle having no autonomy and whose driving is under the total supervision of the driver and 5 for a completely autonomous vehicle).

The 5 levels of autonomy of the classification of the federal agency in charge of road safety are: - level 0: no automation, the driver of the vehicle fully controls the main functions of the vehicle (engine, accelerator, steering, brakes);

- level 1: driver assistance, automation is active for certain vehicle functions, the driver retaining overall control over the driving of the vehicle; cruise control is part of this level, like other aids such as TABS (anti-lock braking system) or ESP (programmed electro-stabilizer);

- level 2: automation of combined functions, the control of at least two main functions is combined in the automation to replace the driver in certain situations; for example, adaptive cruise control combined with lane centering allows a vehicle to be classified as level 2, as does automatic parking assistance;

- level 3: limited autonomous driving, the driver can hand over complete control of the vehicle to the automated system which will then be in charge of critical safety functions; however, autonomous driving can only take place under certain determined environmental and traffic conditions (only on the motorway, for example);

- level 4: complete autonomous driving under conditions, the vehicle is designed to carry out all the critical safety functions on its own over a complete journey; the driver provides a destination or navigation instructions but is not required to make himself available to regain control of the vehicle;

- level 5: completely autonomous driving without driver assistance in all circumstances.

The classification of the International Organization of Motor Vehicle Manufacturers is similar to that listed above, with the difference that it has 6 levels, level 3 of the American classification being divided into 2 levels in that of the International Organization of Car manufacturers.

According to a particular embodiment, the first vehicle 10 may be a level 2 or higher vehicle, the first vehicle 10 possibly being equipped with driving assistance functions or system(s), known as ADAS. In a first operation, the first vehicle 10, for example an on-board computer of the first vehicle 10, obtains a short-term reference trajectory y1 (t). This trajectory y1(t) could be followed by a vehicle up to a time instant t1.

The trajectory y1(t) can be obtained from data coming from on-board peripheral sensors and possibly from cartographic data. The determination of the trajectory of a vehicle is widely known from the state of the art when it is based, for example, on the temporal position and the speed of the vehicle 10.

According to a variant, the first vehicle 10, for example an on-board computer of the first vehicle 10, receives from a remote data server a message comprising information which allows the first vehicle to determine the trajectory y1 (t), for example map data.

According to a variant, the first vehicle 10, for example an on-board computer of the first vehicle 10, receives from the second vehicle 11 a message comprising information on the second vehicle 11 which enables the first vehicle to determine the trajectory y1 (t).

The information received can, for example, be obtained by an on-board sensor of the second vehicle 11.

The information on the second vehicle 11 (and/or the information transmitted by the data server) can, for example, be transmitted in a data frame transmitted by the second vehicle 11 (and/or the information transmitted by the data server) to the first vehicle 10 via a wireless link according to a V2X type communication mode, either V2V or V2I.

According to a variant embodiment, a data frame, transmitted by the second vehicle 11 (and/or the information transmitted by the data server), comprises information which indicates a position, a speed, a change of direction or an acceleration of the second vehicle.

According to a particular embodiment, at least one of the transmitted data frames corresponds, for example, to a CAM (Cooperative Awareness Message" or in French "Cooperative warning message") as defined in the technical specification ETSI TS 102 637-2 v1.2.1 of March 2011 or to a DENM type frame (from the English "Decentralized Environmental Notification

Message” or in French “Decentralized environmental notification message”) as defined in the technical specification ETSI TS 102 637-3 v1.1.1 of September 2010.

A data frame is for example received from the network infrastructure, for example from the element 101, the second vehicle 11 (and/or the information transmitted by the data server) having transmitted this data frame to the infrastructure network which then retransmits it to the first vehicle 10.

According to another particular embodiment, the first vehicle 10 communicates with the second vehicle 11 according to a direct communication mode of the V2V type and a data frame is received directly from the second vehicle 11 .

A direct communication mode is for example compliant with:

- ITS G5 in Europe or DSRC (Dedicated Short Range Communications) in the United States of America, both of which are based on the IEEE 802.11 p standard; Where

- LTE-V Mode 4 (from English "Long-Term Evolution - Vehicle Mode 4" or in French "Evolution à long terme -véhicle Mode 4") which allows V2V communications, also called "sidelink" communications (or in French "side link")) based on a direct communication interface of LTE called PC5; such technology is described for example in the article entitled "Analytical Models of the Performance of C-V2X Mode 4 Vehicular Communications", written by Manuel Gonzalez-Martin, Miguel Sepulcre, Rafael Molina-Masegosa and Javier Gozalvez, and published in 2018 .

In a second operation, the first vehicle 10, for example an on-board computer of the first vehicle 10, obtains a long-term reference trajectory y2(t) of the first vehicle 10 on the traffic lane 1001 from GPS type data coming from sensors on board the first vehicle 10. This trajectory y2(t) could be followed by a vehicle after a time instant t2 greater than t1. In a third step, the first vehicle 10, for example an on-board computer of the first vehicle 10, determines a trajectory y3(t) of the first vehicle 10 between times t1 and t2 by merging the trajectory y1(t) and the trajectory y2(t).

According to a variant, in a fourth operation, the speed of the first vehicle 10 is modified according to the trajectory y3(t).

For example, the speed of the first vehicle 10 is reduced when a regulator or speed limiter of the first vehicle 10 is activated and this as soon as the speed of the first vehicle 10 is excessive with respect to the trajectory y3(t) of the first vehicle 10 , such as approaching a turn or a stop.

An on-board computer of the first vehicle 10 implementing the above operations determines for example one or more speed setpoints. This or these speed instructions are for example transmitted to an on-board ADAS system of the first vehicle 10, for example the cruise control system (or in English "Cruise Control") or the adaptive cruise control system, called ACC (of the English “Adaptive Cruise Control”), such an ACC system equipping, for example, vehicles with a level of autonomy at least equal to 2.

The data used to determine the trajectory y1 (t) are obtained from sensors of an on-board object detection system(s) of the first vehicle 10, this or these systems forming for example part of the ADAS systems of the first vehicle 10 By way of example, the sensor(s) associated with these object detection systems correspond to one or more of the following sensors:

- one or more millimeter wave radars arranged on the first vehicle 10, for example at the front, at the rear, on each front/rear corner of the first vehicle; each radar is adapted to emit electromagnetic waves and to receive the echoes of these waves returned by one or more objects, with the aim of detecting obstacles and their distances vis-à-vis the first vehicle 10; and or

- one or more LIDAR(s) (from the English “Light Detection And Ranging”, or

"Detection and estimation of the distance by light" in French), a LIDAR sensor corresponding to an optoelectronic system composed of a laser transmitter device, a receiver device comprising a light collector (to collect the part of the light radiation emitted by the transmitter and reflected by any object located on the path of the light rays emitted by the transmitter) and a photodetector which transforms the collected light into an electrical signal; a LIDAR sensor thus makes it possible to detect the presence of objects situated in the emitted light beam and to measure the distance between the sensor and each detected object; and or

- one or more cameras (associated or not with a depth sensor) for the acquisition of one or more images of the environment around the first vehicle 10 located in the field of vision of the camera or cameras.

The data from this or these sensors vary according to the type of sensor. When it is a radar or a LIDAR, the data correspond for example to distance data between points of the detected object and the sensor. Each detected object is thus represented by a cloud of points (each point corresponding to a point of the object receiving the radiation emitted by the sensor and reflecting at least part of this radiation), the cloud of points representing the envelope (or a part of the envelope) of the detected object as seen by the sensor and ultimately by the first vehicle 10 carrying the sensor. In the case of a video camera, the data correspond to data associated with each pixel of the acquired image or images, for example gray level values coded on for example 8, 10, 12 or more bits for each color channel, for example RGB (from English “Red, Green, Blue” or in French “Rouge, vert, bleu”).

The processing of these data from these on-board sensors allows the first vehicle 10 to obtain information on the second vehicle 11, for example information on the current speed of the second vehicle 11 and/or information relating to the current distance between the first vehicle 10 and second vehicle 11 .

This information is used by the first vehicle 10, for example by a computer implementing the operations described with regard to this process, to determine the trajectory y1(t) of the first vehicle 10.

This or these speed instructions can supply the cruise control system or the ACC system of the first vehicle 10 to control the speed of the first vehicle 10. This thus allows the first vehicle 10 to anticipate any change in the road environment such as the appearance of objects on the traffic lane or to anticipate the appearance of traffic signs. This makes it possible to anticipate the possible interaction of a vehicle with the driver, possibly the taking over of the vehicle by the driver. This thus makes it possible to improve the safety of the first vehicle 10 as well as that of their respective passengers.

[Fig. 2] schematically illustrates a device on board the first vehicle of FIG. 1 and configured to implement the method for following the trajectory of a vehicle traveling on a traffic lane of FIG. 3, according to a particular embodiment of the present invention.

The device 2 corresponds for example to a device on board the first vehicle 10, for example a computer. The device 2 is for example configured to transmit and/or receive data according to a V2X type link, to determine one or more instructions.

The device 2 is for example configured for the implementation of the operations described with regard to FIG. 1 and/or the steps of the method described with regard to FIG. 3. Examples of such a device 2 comprise, without being limited thereto , on-board electronic equipment such as a vehicle's on-board computer, an electronic computer such as an ECU ("Electronic Control Unit"), a smart phone, a tablet, a laptop computer. The elements of device 2, individually or in combination, can be integrated in a single integrated circuit, in several integrated circuits, and/or in discrete components. The device 2 can be made in the form of electronic circuits or software (or computer) modules or else a combination of electronic circuits and software modules. According to different particular embodiments, the device 2 is coupled in communication with other similar devices or systems and/or with communication devices, for example a TCU (from the English “Telematic Control Unit” or in French “Unité Telematics Control"), for example via a communication bus or through dedicated input/output ports. The device 2 comprises one (or more) processor(s) 20 configured to execute instructions for carrying out the steps of the method and/or for executing the instructions of the software or software embedded in the device 2. The processor 20 can include integrated memory, an input/output interface, and various circuits known to those skilled in the art. Device 2 further comprises at least one memory

21 corresponding for example to a volatile and/or non-volatile memory and/or comprises a memory storage device which may comprise volatile and/or non-volatile memory, such as EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, magnetic or optical disk.

The computer code of the on-board software or software comprising the instructions to be loaded and executed by the processor is for example stored on the memory 21 .

According to a particular and non-limiting embodiment, the device 2 comprises a block

22 interface elements to communicate with external devices, for example a remote server or the “cloud”, other nodes of the ad hoc network. Block 22 interface elements include one or more of the following interfaces:

- RF radiofrequency interface, for example of the Bluetooth® or Wi-Fi® type, LTE (from English "Long-Term Evolution" or in French "Evolution à long terme"), LTE-Advanced (or in French LTE-advanced );

- USB interface (from the English "Universal Serial Bus" or "Universal Serial Bus" in French);

- HDMI interface (from the English “High Definition Multimedia Interface”, or “Interface Multimedia Haute Definition” in French);

- LIN interface (from English “Local Interconnect Network”, or in French “Réseau interconnecté local”).

Data are for example loaded to the device 2 via the interface of block 22 using a Wi-Fi® network such as according to IEEE 802.11, an ITS G5 network based on IEEE 802.11 p or a mobile network such as a 4G network (or LTE Advanced according to 3GPP release 10 - version 10) or 5G, in particular an LTE-V2X network.

According to another particular embodiment, the device 2 comprises a communication interface 23 which makes it possible to establish communication with other devices (such as than other computers of the on-board system) via a communication channel 24. The communication interface 23 corresponds for example to a transmitter configured to transmit and receive information and/or data via the communication channel 24. The interface communication 23 corresponds for example to a wired network of the CAN type (from the English “Controller Area Network” or in French “Réseau de Contrôleurs”), CAN FD (from the English “Controller Area Network Flexible Data-Rate” or in French “Flexible Data Rate Controller Network”), FlexRay (standardized by ISO 17458) or Ethernet (standardized by ISO/IEC 802-3).

According to an additional particular embodiment, the device 2 can supply output signals to one or more external devices, such as a display screen, one or more loudspeakers and/or other peripherals respectively via interfaces output not shown.

[Fig. 3] illustrates a flowchart of the different steps of a method for following the trajectory of a vehicle according to a particular embodiment of the present invention.

In a first step 31 , the trajectory y1 (t) is obtained.

In a second step 32, the trajectory y2(t) is obtained.

In a third step 33, a trajectory y3(t) of the vehicle is determined between times t1 and t2 by merging trajectory y1(t) and trajectory y2(t).

According to a particular embodiment, the trajectory y3(t) is given by:

with k1(t) a function representing the temporal evolution of a first coefficient and k2(t) a function representing the temporal evolution of a second coefficient.

According to a particular example of embodiment illustrated in FIG. 4, the functions k1(t) and k1 (t) evolve over time according to the following rules:

The trajectory y3(t) follows a temporal evolution illustrated in figure 5

The temporal instants t1 and t2 are calculated at each instant in order to keep a temporal progression of the trajectory y3(t).

According to a particular embodiment example illustrated in FIG. 6, the time instant t2 is calculated from a surface delimited by the trajectories y1(t) and y2(t) from their origin to the time instant t2.

Thus, the time instant t2 can be parameterized by defining a threshold value Smax that the surface must not exceed. As soon as the surface reaches a maximum value without exceeding this threshold value, the corresponding time instant t2 is retained for merging the trajectories y1(t) and y2(t).

with t2max a predetermined maximum value of t2.

According to a particular embodiment, the maximum value t2max is a constant value, for example of the order of 5s.

According to a variant, the maximum value Smax can be reduced or even equal to 0 if the trajectories y1(t) and y2(t) are too different from each other. The difference between the trajectories y1 (t) and y2(t) can be estimated by an increment ratio

between the differences in the values of the trajectories y2(t) and y1(t) at two successive time instants t and t'.

According to a particular embodiment, the time instant t1 is calculated so that the derivative and the second derivative of the trajectory y3(t) do not exceed threshold values.

And for t1 (possibly negative), the largest value that meets the following constraints:

• t1 >=t1 Min

• t1 <=t2-deltaTmax

• t1 such that

with t1 Min a configurable threshold value, for example equal to -1 Os, deltaT max a configurable maximum value of the time interval between t1 and t2, for example equal to 1s, aMax_C a maximum value of the derivative of the trajectory y3 (t), for example equal to 1 m/s ² and jMax_C a maximum value of the second derivative of the trajectory y3(t), for example equal to 1 m/s ³ .

According to a particular embodiment, the time instants t1 and t2 are chosen equal when the trajectory y1 (t) is no longer attainable in the short term by the vehicle.

In this case, the change of trajectory takes place without a transition period between the trajectory y1 (t) and y2(t).

Optionally, in a fourth step 34, the speed of the first vehicle 10 is modified according to the trajectory y3(t).

The variants and examples of the operations described in relation to Figure 1 apply to the steps of the method of Figure 3.

Of course, the invention is not limited to the embodiments described above but extends to a method for following the trajectory of a vehicle traveling on a lane of traffic and to the device configured for the implementation of the method in any road situation which may involve 2 or even several vehicles.

The invention also relates to a vehicle, for example an automobile or more generally a land motor vehicle, comprising the device 2 of FIG. 2.

Claims

1 . Method for following the trajectory of a vehicle traveling on a traffic lane, said method being implemented by a computer, said method comprising: a step (31) of obtaining a short-term reference trajectory that could be followed the vehicle until a time instant t1; a step (32) for obtaining a long-term reference trajectory that the vehicle could follow after a time instant t2 greater than t1; and a step (33) of determining a trajectory of the vehicle y3(t) between the instants t1 and t2 by merging the short-term reference trajectory and the long-term reference trajectory.

2. Method according to claim 1, for which the trajectory y3(t) is obtained by:

3. Method according to claim 2, for which the function k1 (t) is given by:

with t a current time instant.

4. Method according to claim 3, for which the function k2(t) is given by:

5. Method according to claim 4, for which time instant t2 is calculated from a surface delimited by trajectories y1(t) and y2(t) from their origin to time instant t2.

6. Method according to claim 4 or 5, for which the time instant t1 is the greatest value which meets the following constraints: t1 >=t1 Min t1 <=t2-deltaTmax t1 such that

t1 such that

7. Device for trajectory tracking of a vehicle traveling on a traffic lane comprising a memory associated with at least one processor configured for the implementation of the steps of the method according to any one of claims 1 to 6.

8. Vehicle comprising a device according to claim 7.

9. Computer program product comprising instructions adapted for the execution of the steps of the method according to one of claims 1 to 6, when the computer program is executed by at least one processor.

10. A computer-readable recording medium on which is recorded a computer program comprising instructions for carrying out the steps of the method according to any one of claims 1 to 6.