Patent ID: 12198444

FIG.1shows part of a road1comprising, in this example, three traffic lanes, respectively a lane located furthest to the right, called right-hand lane11, a central lane12and a lane located furthest to the left, called left-hand lane13, the right-hand lane11being located on the right-hand bank of the central lane12with respect to an observer facing downstream in the direction of travel and the left-hand lane13being located on the left-hand bank of the central lane12with respect to the same observer, and on which lanes the vehicle10moving from upstream to downstream is likely to travel. The road1having three traffic lanes according to the example ofFIG.1is laterally delimited by two opposing distal edges, respectively a distal edge formed by a hard shoulder14, which is located on the right-hand bank of the right-hand lane11, and by a distal edge formed by a central reservation15, which is located on the left-hand bank of the left-hand lane13. Moreover, each of the traffic lanes11,12and13of the road1is laterally delimited to the left and to the right by ground marking lines16.

The starting point is the observation that, depending on the type of ground marking lines that delimit each traffic lane, it is possible to determine the precise traffic lane in which the vehicle is situated. Based on this information, as will be explained in more detail hereinafter, the appropriate offset for shifting the vehicle to a greater or lesser extent in its lane will be provided so as to guarantee positioning of the vehicle that is able to promote acceptability of the autonomous mode to the user, specifically regardless of the objects present in the surroundings of the vehicle.

The invention therefore makes provision to detect the ground marking lines that are arranged laterally on either side of each of the traffic lanes in order to determine, from identifying these detected ground marking lines, the precise traffic lane on which the vehicle is situated. To this end, the vehicle10is equipped with a camera20, for example situated toward the front of the vehicle. In this case, it is preferably arranged at the top of the windshield, at the join with the roof of the vehicle, so as to make it possible to observe the scene located in front of the vehicle. It is advantageously possible to use the frontal camera installed on the windshield of the vehicle with the associated image processing capabilities, as used for example by obstacle detection systems fitted to certain vehicles and used for the lateral control of the vehicle, such as the Mobileye® system.

FIG.2illustrates a classification of the various types of ground marking lines likely to laterally delimit traffic lanes. The specific features for distinguishing between the various known types of ground marking lines relate in particular to the continuous or discontinuous nature of the line segments forming these lines, to the length of the line segments, and to the interval between them. Thus, for a leftmost traffic lane located on the side of a central reservation delimiting the two directions of travel of a road, the ground marking line laterally delimiting this lane from the adjacent central reservation may be for example either a line consisting of discontinuous line segments each having a length of 3 m and a regular interval between them of 10 m, such as the line T1inFIG.2, or a line of continuous line segments. For a central lane, the ground marking line delimiting this lane on each side may consist for example of a discontinuous line such as the line T1, T′1or T3illustrated inFIG.2. Lastly, for a rightmost traffic lane, located on the side of a hard shoulder, the ground marking line laterally delimiting this lane from the hard shoulder may for example consist of a discontinuous line such as the line T2, T′3or T4illustrated inFIG.2. In other words, the classification makes it possible to determine a traffic lane from among a left-hand lane, a central lane or a right-hand lane, on the basis of the specific features of the various types of ground marking lines.

Thus, based on the signal generated by the camera housed on board at the front of the vehicle, image processing algorithms associated with the camera and known per se are used to identify the type of ground marking lines located to the left and to the right of the vehicle and, based on the classification of the types of ground marking lines, the traffic lane on which the vehicle is situated is determined from among the left-hand lane, the central lane or the right-hand lane.

Additionally, on the basis of the position of the ground marking lines detected by the camera on each side of the vehicle, the width L of the lane on which the vehicle is situated is determined. Based on the lane width thus determined, a safety distance is calculated, which will be used to position the vehicle in its traffic lane, as will be explained in detail below. This safety distance is preferably defined as being the difference between the lane width L determined from the signal generated by the camera and the width of the vehicle l, which is information that is known by the system. This safety distance information, as well as the information about the traffic lane of the vehicle as determined in the previous step from the signal generated by the camera, will then be used to control the positioning of the vehicle in its traffic lane.

FIG.3shows a device comprising means designed to implement the method according to one embodiment of the invention. The device1comprises a first processing unit30, which receives the image signals from the camera20and is designed to execute an image processing operation in order to recognize and identify the types of ground marking lines. This image processing makes it possible, as explained above, to deduce therefrom the traffic lane on which the vehicle is situated, and also the width of this traffic lane and therefore the safety distance. The first processing unit30also receives signals provided by a sensor40designed to measure the speed of the vehicle. The first processing unit30may for example be the computer used in the on-board driving assistance system, commonly called ADAS (acronym for Advanced Driver Assistance System), fitted to the vehicle.

Generally speaking, if it becomes apparent from using the image signals and from identifying the types of ground marking lines that the vehicle is situated on the leftmost traffic lane or the rightmost traffic lane of the road, then the first processing unit30is designed to control the positioning of the vehicle in the lane, so as to shift the vehicle in the direction of the distal edge of the road with respect to the central axis of the lane. In this case, the positioning of the vehicle in its lane is controlled so as to decenter the vehicle in its lane by keeping an offset distance between the vehicle and the ground marking line that is located on the side of the distal edge of the road substantially constant, this offset distance preferably being equal to a fraction of the previously calculated safety distance.

On the other hand, if the traffic lane on which the vehicle is situated is determined as being the central traffic lane, then the first processing unit30is designed to control the positioning of the vehicle so as to center the vehicle in the traffic lane.

To control the positioning of the vehicle, the first processing unit30cooperates with a second processing unit50, which is for example the computer responsible for the electrically assisted steering of the vehicle. This computer receives control orders from the first processing unit30to act on the steering of the vehicle so as to shift or center the vehicle in its traffic lane, depending on the scenarios explained above.

Thus, according to the example ofFIG.1, if the vehicle10is traveling on the right-hand lane11, the positioning of the vehicle is controlled so as to decenter the vehicle in the lane11in the direction of the distal edge of the road, formed here by the hard shoulder14, and to keep the vehicle at an offset distance D with respect to the ground marking line16located on the side of the hard shoulder14, the offset distance D being for example chosen to be equal to ⅓ of the safety distance. In this case, the distance between the vehicle10and the opposing ground marking line16, delimiting the right-hand lane11with respect to the adjacent central lane12, is kept at ⅔ of the safety distance.

In the same way, if the vehicle10is traveling on the left-hand lane13, the positioning of the vehicle is controlled so as to decenter the vehicle in the lane11in the direction of the distal edge of the road, formed here by the central reservation15, and to keep the vehicle at an offset distance D, for example chosen to be equal to ⅓ of the safety distance, with respect to the ground marking line16located on the side of the central reservation15. Thus, the distance between the vehicle10and the opposing ground marking line16, delimiting the left-hand lane13with respect to the adjacent central lane12, is kept at ⅔ of the safety distance.

Finally, if the vehicle is traveling on the central lane12, the positioning is controlled so as to situate the vehicle in the center of the lane and to keep the vehicle at an offset distance D corresponding to half the safety distance with respect to each of the ground marking lines16delimiting the central traffic lane12on each side.

This strategy makes it possible to adjust the positioning of the vehicle in its traffic lane, independently of the other vehicles moving nearby, thereby allowing flexible driving without excessive trajectory variations. Furthermore, regardless of the traffic lane of the vehicle, the offset distance imposed by controlling the positioning of the vehicle makes it possible to leave a sufficient and acceptable safety margin with respect to another vehicle, overtaking or being overtaken, located in an adjacent lateral region close to the vehicle. This margin, imposed by the offset distance, makes it possible to promote acceptability of driving the vehicle in autonomous mode to the user, while at the same time guaranteeing safety.

According to one particular embodiment, there may be provision, when the vehicle is located in the left-hand lane, that is to say the lane adjacent to the central reservation, or the right-hand lane, that is to say the lane adjacent to the hard shoulder, for the offset distance of the vehicle in its lane to be settable on the basis of the speed of the vehicle. In particular, at low speeds, typically for vehicle speeds less than approximately 20 m/s, there is provision to shift the vehicle further in the direction of the ground marking line located on the side of the edge of the road, in other words to reduce the offset distance to be maintained with respect to this line. This strategy makes it possible to leave a larger clearance for bikers to pass, for example.

FIG.4illustrates one example of controlling the positioning of the vehicle in its traffic lane on the basis of the speed of the vehicle. In this example, the vehicle has a width equal to 2.128 m and is traveling in the left-hand lane, said lane having a width of 3.50 m. There is therefore a safety distance equal to 1.372 m. According to this example, for vehicle speeds less than 20 m/s, the offset distance of the vehicle with respect to the ground marking line laterally delimiting the left-hand lane is set at ¼ of the safety distance, that is to say 0.34 m, and then, for speeds of between substantially 20 m/s and 40 m/s, this offset distance is increased to ⅓ of the safety distance, that is to say 0.46 m, and lastly, for speeds greater than 40 m/s, this offset distance is set to half the safety distance, that is to say 0.69 m in this example.