METHOD FOR DETECTING A TRAFFIC TRAFFIC SITUATION IN A MOTOR VEHICLE

Description

[0001] The present invention relates to the field of autonomous driving of a motor vehicle on a traffic lane. More particularly, it relates to a method for detecting a traffic jam situation by a motor vehicle.

[0002] In OICA (International Organization of Motor Vehicle Manufacturers) Level 3 autonomous driving mode, the driver does not perform any operational driving tasks, such as accelerating, braking, or steering. These tasks are delegated to the vehicle's autonomous control system, which assumes complete control of the vehicle. The driver is therefore free to take their hands off the steering wheel to perform other tasks simultaneously, such as watching a movie on the vehicle's screen. However, Level 3 autonomous driving has a limited operating range and can only occur under certain environmental and traffic conditions. Specifically, Level 3 autonomy can only be activated at speeds below 60 km / h on divided highways, typically motorways, and in traffic jams.It is relatively easy to verify the activation conditions for this level of autonomy, which are linked to the vehicle being on a divided highway and not exceeding the 60 km / h speed limit, particularly using the navigation system and onboard sensors that measure the vehicle's speed. However, it is much more complex to assess whether the vehicle is in a traffic jam. A vehicle is considered to be in a traffic jam if it is "surrounded" in front, behind, and on its right and left sides by other vehicles or obstacles, such as walls or barriers; in other words, if the vehicle is constrained in all directions by other vehicles or obstacles in its immediate surroundings.

[0003] Obstacle detection sensors are used for this purpose. They emit a wave that is reflected off the surface of objects in the direction of propagation. Comparing the incident wave with its echo allows for the estimation of a propagation time, a phase shift, or a possible frequency shift, which in turn provides the distance between the sensor and the surface of the object producing the echo. The most common type of sensor used in automotive applications is radar. The principle of radar is based on the emission of an electromagnetic wave and the reception of the echo formed by this wave on a surface to estimate the distance to that surface. Furthermore, if the reflecting object is moving at a certain speed relative to the radar, the reflected wave will have a significantly different frequency from that of the incident wave, thus allowing for a measurement of the relative speed between the radar and the reflecting object.However, radar has several limitations. In particular, the analysis of radar data reveals numerous spurious echoes on the road or roadside. Therefore, to prevent this from causing a large number of false detections, stationary objects are generally filtered out by comparing their measured speed to the speed of the vehicle equipped with the radar. Thus, a stationary vehicle will not be detected. In other words, stationary objects are "invisible" to the radar. This is a significant obstacle to the deployment of Level 3 autonomous driving, as this autonomous driving mode can only be activated in traffic jams, whereas the most typical scenario of such a situation—all surrounding vehicles at a standstill—is not detected by the radar systems on the host vehicle. The availability of Level 3 autonomous driving is therefore severely limited.

[0004] Patent document WO201202099 describes a traffic congestion estimation device designed to warn drivers of hazardous road conditions. The device comprises a speed detection unit configured to detect the speed of a host vehicle, a distance detection unit configured to detect the inter-vehicle distance between the host vehicle and another vehicle, a calculation unit configured to calculate a correlation based on the results of the speed detection and inter-vehicle distance detection, and a traffic state estimation unit based on the results of the correlation calculation.

[0005] Although based on the principle of dividing radar beams into angular sectors, analyzing each sector independently, and combining detection data to estimate traffic conditions, this solution does not appear to implement filtering for stationary objects. Furthermore, it requires the use of high-end radar sensors capable of detecting surrounding zero-velocity objects. Document US2013 / 103296A1 presents similar drawbacks.

[0006] This solution is therefore not fully optimized and there is a need for an improved solution that increases the performance and robustness of traffic jam detection at a lower cost.

[0007] To this end, the invention relates to a method for detecting a traffic jam situation according to claim 1, and, without being exhaustive, using a radar system fitted to a host motor vehicle, said radar system comprising multibeam radar sensors arranged at the rear and front corners of the host vehicle, the radar beams of each radar sensor being emitted in different given viewing directions so as to cover, for each radar sensor, a detection zone extending between a radial direction oriented obliquely forward and a radial direction oriented obliquely backward, each radar sensor being capable of providing, for each given viewing direction, the range distance of the radar beam emitted in said direction, the method being characterized in that it comprises the steps of: distribution of all radar beams emitted by the radar sensors according to a division of the vehicle's environment into four angular sectors, opposite each other, extending respectively towards the front and rear of the vehicle and towards the right and left sides of the vehicle, selection for each of the four angular sectors, from among the beams distributed in each of them for which no target is detected, of the beam with the shortest range distance, detection of the amplitude of the reflected beams corresponding respectively to said beams selected in the four angular sectors, and analysis of the duration of maintenance of the amplitude of said reflected beams relative to a predefined time threshold for each angular sector respectively, the process detecting a traffic jam situation when the analysis step simultaneously determines for the four angular sectors that said duration of amplitude maintenance is greater than or equal to said predefined time threshold.

[0008] Thanks to this combination of steps, it is possible to detect a traffic jam situation using radar sensors, even when surrounding vehicles are stopped.

[0009] Advantageously, the analysis step further includes a step of comparing the range distance of each selected beam in the four angular sectors with a predefined distance threshold for each angular sector respectively, the process detecting a traffic jam situation when the comparison step simultaneously determines for the four angular sectors that said range distance is less than or equal to said predefined distance threshold.

[0010] Preferably, said predefined distance threshold is set less than or equal to 5m, preferably equal to 3m, for angular sectors extending forward and backward from the host vehicle.

[0011] Preferably, said predefined distance threshold is set less than or equal to 2m, preferably equal to 1.5m, for angular sectors extending from the right and left sides of the host vehicle.

[0012] Advantageously, the process includes a step of activating an autonomous driving mode of the host vehicle when a traffic jam situation is detected.

[0013] Advantageously, said autonomous driving mode is adapted to ensure all operational driving tasks of the host vehicle.

[0014] The invention also relates to a device for detecting a traffic jam situation according to claim 7, and comprising, in a non-exhaustive manner, a radar system mounted on a host motor vehicle, said radar system comprising multibeam radar sensors arranged at the rear and front corners of said vehicle, the radar beams being emitted in different given viewing directions so as to cover, for each radar sensor, a detection zone extending between a radial direction oriented obliquely forward and a radial direction oriented obliquely backward, each radar sensor being capable of providing, for each given viewing direction, the range distance of the radar beam emitted in said direction, the device being characterized in that it comprises a unit for processing the emitted radar beams,adapted to operate a distribution of all radar beams emitted by the radar sensors according to a division of the vehicle's environment into four angular sectors, opposite in pairs, extending respectively towards the front and rear of the vehicle and towards the right side and left side of the vehicle, and to select for each of said four angular sectors, from among the beams distributed in each of them for which no target is detected, the beam having the shortest range distance, said processing unit comprising an analysis module adapted to verify the duration of the amplitude maintenance of the reflected beams corresponding respectively to said beams selected in the four angular sectors, relative to a predefined time threshold for each angular sector respectively,said device detects a traffic jam situation when said analysis module simultaneously determines, for the four angular sectors, that said duration of amplitude maintenance is greater than or equal to said predefined time threshold.

[0015] Advantageously, the device further includes a module for comparing the range distance of each selected beam in the four angular sectors with a predefined distance threshold for each angular sector respectively, the device detecting a traffic jam situation when the comparison module simultaneously determines for the four angular sectors that said range distance is less than or equal to said predefined distance threshold.

[0016] Advantageously, the device further includes a module for comparing the range distance of each selected beam in the four angular sectors with a predefined distance threshold for each angular sector respectively, the device detecting a traffic jam situation when the comparison module simultaneously determines for the four angular sectors that said range distance is less than or equal to said predefined distance threshold.

[0017] Advantageously, the device includes means of activating an autonomous vehicle control system when a traffic jam situation is detected.

[0018] The invention further relates to a motor vehicle characterized in that it comprises a device as described in any one of claims 7 to 9

[0019] Other features and advantages of the invention will become clear from the description given below, which is by way of example and not limitation, with reference to the accompanying drawings in which: [ Fig. 1 [ ] is a schematic top view illustrating the implementation of the method according to the invention. Fig. 2 ] schematically illustrates an embodiment of a unit for processing emitted radar beams, for the implementation of the method of the invention.

[0020] In this description, the terms front, rear, right, left are designated with respect to the front and rear directions of the vehicle and with respect to the normal direction of travel of this vehicle.

[0021] In reference to the figure 1 An object detection system installed on a host motor vehicle 10 is illustrated. The object detection system includes four object detection sensors arranged at the four corners of the vehicle, respectively a front left corner sensor 21, a front right corner sensor 22, a rear left corner sensor 23 and a rear right corner sensor 24. These corner sensors are, for example, positioned at the lateral ends of one face of the front and rear bumpers of the vehicle.These object detection sensors 21-24 can be, for example, radar sensors and, in particular, multibeam radar sensors capable of emitting radar beams in various given viewing directions so that each radar sensor 21-24 can scan a detection area extending over a given angular range, for example, approximately 180°, between a radial direction oriented obliquely forward and a radial direction oriented obliquely backward. The detection area of ​​each radar sensor 21-24 is substantially semicircular in shape.

[0022] The detection area of ​​the radar sensor 21 located on the front left corner extends over an angular range of substantially 180° delimited between a radial direction oriented obliquely towards the front right and a substantially opposite radial direction oriented obliquely towards the rear left, so that the detection area covered by the radar sensor 21 located on the front left corner extends over the front of the vehicle and the left side of the vehicle.

[0023] Similarly, the detection area of ​​the radar sensor 22 located on the front right corner extends over an angular range of approximately 180° delimited between a radial direction oriented obliquely towards the front left and a radial direction oriented obliquely towards the rear right, so that the detection area covered by the radar sensor 22 located on the front right corner extends over the front of the vehicle and the right side of the vehicle.

[0024] Similarly, the detection area of ​​the radar sensor 23 located on the rear left corner extends over an angular range of approximately 180° delimited between a radial direction oriented obliquely towards the front left and a radial direction oriented obliquely towards the rear right, so that the detection area covered by the radar sensor 23 located on the rear left corner extends over the rear of the vehicle and the left side of the vehicle.

[0025] Finally, the detection area of ​​the radar sensor 24 located on the right rear corner extends over an angular range of approximately 180° delimited between a radial direction oriented obliquely towards the front left and a radial direction oriented obliquely towards the right rear, so that the detection area covered by the radar sensor 24 located on the right rear corner extends over the rear of the vehicle and the right side of the vehicle.

[0026] Thus, the 21-24 corner radar sensors are capable of detecting objects in the vehicle's environment both on the right and left sides of the vehicle and on the front and rear of the vehicle.

[0027] The detection zones of the radar sensors located on the front left and right corners partially overlap on the front of the vehicle, the detection zones of the radar sensors located on the front left and rear left corners partially overlap on the left side of the vehicle, the detection zones of the radar sensors located on the rear left and right corners partially overlap on the rear of the vehicle and the detection zones of the radar sensors located on the rear right and front right corners partially overlap on the right side of the vehicle.

[0028] Each radar sensor 21-24 emits beams of electromagnetic waves, respectively Df_l, Df_r, Dr_1, Dr_r, in a given line of sight to space, so as to cover the corresponding detection area of ​​the radar sensor. When a radar beam encounters an object located within the detection area, the beam is reflected. By measuring the time of flight (the time it takes for the beam to travel from the radar sensor to the object and back), the distance between the sensor and the object is determined. Furthermore, if the reflecting object is moving at a certain speed, the resulting frequency shift between the emitted and reflected beams allows for a measurement of the reflecting object's velocity.

[0029] Thus, the detection system installed on the host vehicle receives detection information relating to a set of moving objects positioned within the detection zones of the system's radar sensors. Specifically, the distance between an object and the radar sensor and the object's speed are associated with each detected moving object.

[0030] However, as explained in the introduction, when an object is stationary, it is not detected by the radar sensor. Nevertheless, each radar sensor provides, for each radar beam emitted in a given direction of view, a range for its beam if it does not detect a target. This range is defined as either the beam encountering no obstacle, or the distance at which the emitted beam encounters an obstacle, but that obstacle is stationary and therefore does not generate a detection signal. Thus, this range for the beam if it does not detect a target can be either the maximum range of the emitted radar beam, corresponding to the case where it encounters no obstacle, or the distance at which the emitted radar beam encounters an obstacle, corresponding to the case of a stationary obstacle. In the absence of detection, it is not possible to distinguish between these different possible scenarios.

[0031] Also, rather than exploiting detection information resulting from the encounter of a radar beam with a moving object located in the detection zone, the method of the invention provides for exploiting information relating to the range distance of the beams by direction of aiming when the emitted beam does not detect a target, to enable the detection of a stationary object in the environment of the vehicle, typically a stationary vehicle, or a barrier along the traffic lane.

[0032] To this end, it is planned, initially, to distribute all the radar beams Df, Df, Dr, Dr, emitted by the radar sensors 21-24 according to a division of the vehicle's environment 10 into four angular sectors Zfront, Zrear, Zleft, Zright. These angular sectors are paired opposite each other and extend respectively towards the front and rear of the vehicle, and towards the left and right sides of the vehicle. More precisely, the front angular sectors Zfront and Zrear each extend to the front and rear of the vehicle, preferably symmetrically on either side of the vehicle's longitudinal median axis X. The angular sector Zleft extends along the left side of the vehicle between the front and rear angular sectors, and the angular sector Zright extends along the right side of the vehicle between the front and rear angular sectors. As illustrated in the figure 1 The radar beams Df and Df, grouped in the angular sector Zfront extending towards the front of vehicle 10, are represented according to a first graphic code; the radar beams Dr and Df, grouped in the angular sector Zrear extending towards the rear of vehicle 10, are represented according to a second graphic code; the radar beams Df and Dr, grouped in the angular sector Zleft extending towards the left side of vehicle 10, are represented according to a third graphic code; and the radar beams Df and Df, grouped in the angular sector Zright extending towards the right side of vehicle 10, are represented according to a fourth graphic code. The radar beams thus distributed in these four angular sectors Zfront, Zrear, Zleft, and Zright allow for the definition of new detection zones specifically covering the front, rear, left side, and right side of the vehicle, respectively.

[0033] The configuration of the four angular sectors can be adjusted using two settings, allowing for the adjustment of the extent of the front angular sector (Z front) and the rear angular sector (Z rear), respectively. Thus, the front angular sector (Z front) has an angular extent defined by the angle α between the vehicle's longitudinal median axis X and a radial edge of the front angular sector (Z front). Similarly, the rear angular sector (Z rear) has an angular extent defined by the angle β between the vehicle's longitudinal median axis X and a radial edge of the rear angular sector (Z rear).

[0034] Then, for each of the four angular sectors thus defined, a selection is made of the radar beam which has the shortest range distance, among the radar beams distributed in each of them for which no target is detected.

[0035] We thus note D front, the beam with the shortest range distance among the beams gathered in the angular sector Z front extending to the front of the vehicle, D rear, the beam with the shortest range distance among the beams gathered in the angular sector Z rear extending to the rear of the vehicle, D left, the beam with the shortest range distance among the beams gathered in the angular sector Z left extending from the left side of the vehicle and D right, the beam with the shortest range distance among the beams gathered in the angular sector Z right extending from the right side of the vehicle.

[0036] In a subsequent step, the amplitude of the reflected beams corresponding to the selected beams in the four angular sectors is detected, and the duration for which the amplitude of these beams is maintained relative to a predefined time threshold for each angular sector. In other words, the aim is to verify whether, for each of the four angular sectors, the reflected amplitude of the selected beam that does not detect a target and has the shortest range is maintained for a minimum time corresponding to the predefined time threshold. If so, a stationary obstacle, typically equivalent to a stationary vehicle, is considered to be present in the angular sector under consideration.In this way, a traffic jam situation is detected when the analysis step simultaneously determines for the four angular sectors Z front, Z rear, Z left, Z right, that the duration of amplitude maintenance is greater than or equal to the predefined time threshold for the corresponding angular sector.

[0037] To that end, as illustrated in the figure 2 An analysis module 30 for the duration of amplitude maintenance of selected beams relative to predefined time threshold values ​​can consist of a low-pass filter whose time constant τi is of the same order of magnitude as the predefined time threshold for each angular sector Zi (i = front, rear, left, right). Thus, the low-pass filter 30 filters the selected beams with the shortest range distance whose reflected amplitude is maintained for a duration greater than or equal to the predefined time threshold for each angular sector considered.

[0038] According to a preferred embodiment of the invention illustrated in the figure 2 Once it has been verified that the amplitude of the selected beams with the shortest range remains constant for a predefined time threshold, the range of each selected beam in the four angular sectors is then compared with a predefined distance threshold for each angular sector. The information relating to this comparison for each angular sector Zi, denoted Info_Zi (i = front, rear, left, right), which is preferably a Boolean value, is determined by a comparison module 40, by comparing, for each angular sector, the range of the previously filtered selected beams with at least one threshold. According to the example implementation of the figure 2 We use two thresholds corresponding to a hysteresis function, we have:

[0039] Info_Z i = 0 if the range distance of the selected beam for the corresponding angular sector is greater than a first low threshold D down i defined for the angular sector in question, or

[0040] Info_Z i =1 if said range distance is less than or equal to a second upper threshold D up i defined for the angular sector in question and greater than the lower threshold D down i.

[0041] Alternatively, since both thresholds are equal to a single distance threshold, we have: Info_Z i = 0 if the range distance of the selected beam for the corresponding angular sector is greater than the predefined single distance threshold for the angular sector in question, Info_Z i = 1 if said range distance is less than or equal to said threshold.

[0042] For example, this predefined distance threshold is set less than or equal to 5m, preferably equal to 3m, for the angular sectors Z front and Z rear extending forward and backward from the host vehicle 10. Regarding the angular sectors Z right and Z left extending from the right and left sides of the host vehicle 10, this distance threshold is, for example, set less than or equal to 2m, preferably equal to 1.5m.

[0043] It is therefore considered that if the range distance of the selected beam for a given angular sector is below this threshold, there is a stationary obstacle, comparable to a stationary vehicle, in the immediate vicinity of the vehicle for that angular sector.

[0044] The state of the boolean values ​​info_Zi, determined by the comparison module 40, is used as input to an AND gate 50. The output of this AND gate, TJD_Flag, is used to validate the detection of a traffic jam. Thus, if the condition for comparing the range distances of the selected beams with the predefined distance threshold is met simultaneously in all four angular sectors, the output signal TJD_Flag goes high, thereby validating the detection of a traffic jam. This traffic jam detection validation signal, TJD_Flag, is provided to an activation input of the vehicle's autonomous control system, specifically a vehicle autonomous control system adapted to operate at Level 3 autonomy, thereby activating that system.Since the process just described makes it possible to detect a traffic jam situation even when the surrounding vehicles are stopped, the availability of such a system is very significantly improved.

Claims

1. Method for detecting a traffic congestion situation by means of a radar system equipping a host motor vehicle (10), said radar system comprising multi-beam radar sensors (21-24) arranged at the rear and front corners of the host vehicle, said sensors being capable of detecting moving objects only, the radar beams being emitted in various given targeted directions in such a manner as to cover, for each radar sensor, a detection zone extending between a radial direction oriented obliquely towards the front and a radial direction oriented obliquely towards the rear, each radar sensor being capable of supplying, for each given targeted direction, the range of the radar beam emitted in said direction if no moving object is detected therein, the method being characterized in that it comprises steps for: - distribution of all of the radar beams (Df_l, Df_r, Dr_l, Dr_r) emitted by the radar sensors according to a division of the environment of the vehicle into four angular sectors (Zfront, Zrear, Zleft, Zright), in opposing pairs, respectively extending towards the front and towards the rear of the vehicle and towards the right side and towards the left side of the vehicle, - selection for each of the four angular sectors, from amongst the beams distributed into each of them for which no target is detected, of the beam (Dfront, Drear, Dleft, Dright) having the shortest range, - detection of the amplitude of the reflected beams corresponding respectively to said beams selected within the four angular sectors, and - analysis of the period of time for which the amplitude of said reflected beams is maintained with respect to a predefined time threshold for each angular sector, respectively, the method detecting a traffic congestion situation when the analysis step determines, simultaneously for the four angular sectors, that said period of time for which the amplitude is maintained is greater than or equal to said predefined time threshold.

2. Method according to Claim 1, characterized in that the analysis step furthermore comprises a step for comparing the range of each beam selected within the four angular sectors with a predefined distance threshold for each angular sector respectively, the method detecting a traffic congestion situation when the comparison step determines, simultaneously for the four angular sectors, that said range is less than or equal to said predefined distance threshold.

3. Method according to Claim 2, characterized in that said predefined distance threshold is fixed at less than or equal to 5 m, preferably equal to 3 m, for the angular sectors extending towards the front and towards the rear of the host vehicle.

4. Method according to Claim 2 or 3, characterized in that said predefined distance threshold is fixed at less than or equal to 2 m, preferably equal to 1.5 m, for the angular sectors extending from the right side and from the left side of the host vehicle.

5. Method according to Claim 1 or 2, characterized in that it comprises a step for activating an autonomous driving mode of the host vehicle when a traffic congestion situation is detected.

6. Method according to Claim 3, characterized in that said autonomous driving mode is designed to provide all of the operational driving tasks of the host vehicle.

7. Device for detecting a traffic congestion situation comprising a radar system on board a host motor vehicle (10), said radar system comprising multi-beam radar sensors (21-24) arranged at the rear and front corners of said vehicle, said sensors being capable of detecting moving objects only, the radar beams being emitted in various given targeted directions in such a manner as to cover, for each radar sensor, a detection zone extending between a radial direction oriented obliquely towards the front and a radial direction oriented obliquely towards the rear, each radar sensor being capable of supplying, for each given targeted direction, the range of the radar beam emitted in said direction if no moving object is detected therein, the device being characterized in that it comprises a unit for processing the emitted radar beams, designed to apply a distribution of all of the radar beams (Df_l, Df_r, Dr_l, Dr_r) emitted by the radar sensors according to a division of the environment of the vehicle into four angular sectors (Zfront, Zrear, Zleft, Zright), in opposing pairs, respectively extending towards the front and towards the rear of the vehicle and towards the right side and towards the left side of the vehicle, and to select for each of said four angular sectors, from amongst the beams distributed into each of them for which no target is detected, the beam (Dfront, Drear, Dleft, Dright) having the shortest range, said processing unit comprising an analysis module (30) designed to verify the period of time for which the amplitude of the reflected beams, corresponding respectively to said beams selected within the four angular sectors, is maintained with respect to a predefined time threshold for each angular sector respectively, said device detecting a traffic congestion situation when said analysis module determines, simultaneously for the four angular sectors, that said period of time for which the amplitude is maintained is greater than or equal to said predefined time threshold.

8. Device according to Claim 7, characterized in that it furthermore comprises a module (40) for comparing the range of each beam selected within the four angular sectors with a predefined distance threshold for each angular sector respectively, the device detecting a traffic congestion situation when the comparison module determines, simultaneously for the four angular sectors, that said range is less than or equal to said predefined distance threshold.

9. Device according to Claim 7 or 8, characterized in that it comprises means for activating a system for controlling the autonomous mode of the vehicle when a traffic congestion situation is detected.

10. Motor vehicle, characterized in that it comprises a device according to any one of Claims 7 to 9.