Method for controlling a string of vehicles

Abstract

The invention relates to a method for a string comprising a plurality of vehicles, including a lead vehicle and at least one follower vehicle, comprising the follower vehicle following, by means of vehicle-to-vehicle communication, the lead vehicle in a follower trajectory. The method comprises generating surroundings data, regarding the surroundings of at least a part of the string, generating, using the surroundings data, a backup trajectory, which is different from the follower trajectory, wherein the generated backup trajectory, or the surroundings data, is received by at least one of the at least one follower vehicle, wherein the receiving follower vehicle follows the generated backup trajectory, upon a determination of a predetermined condition for following the generated backup trajectory.

Claims

1. A method for controlling a string of vehicles comprising a lead vehicle and at least one follower vehicle following the lead vehicle in a follower trajectory by vehicle-to-vehicle communication, the method comprising: generating, by at least one of a control unit in the lead vehicle and a control unit outside the lead vehicle, surroundings data, regarding the surroundings of at least a part of the string of vehicles; and generating, by the control unit in the lead vehicle, using the surroundings data, a backup trajectory, which is different from the follower trajectory; receiving, by at least one of the at least one follower vehicle, the generated backup trajectory; and following, by the receiving follower vehicle, the generated backup trajectory, upon a determination of a predetermined condition that communications with the lead vehicle is lost; wherein the backup trajectory is generated before the determination of the predetermined condition that communications with the lead vehicle is lost.

2. The method of claim 1, wherein the backup trajectory is generated at least one of while or before the follower trajectory is followed.

3. The method of claim 1, wherein the generated backup trajectory is a planned trajectory.

4. The method of claim 1, the method further comprising storing, by a control unit in the receiving follower vehicle, the generated backup trajectory.

5. The method of claim 1, wherein the predetermined condition is an operational parameter below a predetermined safety threshold level.

6. The method of claim 1, wherein the predetermined condition is a signal received by the receiving follower vehicle representing a message that the follower trajectory should be abandoned.

7. The method of claim 6, wherein the signal is received from the lead vehicle.

8. The method of claim 1, the method further comprising generating, by the control unit in the lead vehicle, a plurality of backup trajectories in a time sequence.

9. The method of claim 8, wherein the followed backup trajectory is a latest received backup trajectory.

10. The method of claim 8, wherein the generated backup trajectories are correlated with respective execution windows, each execution window providing a time limit after which a respective backup trajectory may not be followed.

11. The method of claim 10, wherein the followed backup trajectory is a latest received backup trajectory, and the predetermined condition is the time limit of the latest received backup trajectory having been reached.

12. The method of claim 1, wherein the string comprises a plurality of follower vehicles, wherein a follower vehicle, behind the receiving follower vehicle, follows, during the following of the backup trajectory, the receiving follower vehicle in a further follower trajectory.

13. The method of claim 1, wherein the surroundings data is at least partly generated by the lead vehicle.

14. The method of claim 13, wherein the surroundings data generated by the lead vehicle represents signals from at least one sensor of the lead vehicle.

15. The method of claim 1, wherein the surroundings data is at least partly map data.

16. The method of claim 1, wherein the receiving follower vehicle generates the backup trajectory by use of the surroundings data.

17. The method of claim 1, wherein the control unit outside the lead vehicle generating the surroundings data is remote from the vehicles in the string.

18. The method of claim 1, the method further comprising determining, by the control unit in the lead vehicle, at least one vehicle feature of at least one of the at least one follower vehicle, wherein the generated backup trajectory is partly based on the determined vehicle feature.

19. The method of claim 1, wherein the generated backup trajectory is such that it guides the receiving follower vehicle out of a lane in which the receiving follower vehicle is travelling.

20. The method of claim 1, wherein the generated backup trajectory is provided in the form of a plurality of coordinates and/or a polynomial.

21. The method of claim 1, wherein the backup trajectory is generated at least partly based on a drivable area.

22. The method of claim 1, wherein the generated backup trajectory comprises speed data indicating a target speed of the receiving follower vehicle for at least one point along the generated backup trajectory.

23. The method of claim 1, wherein: the surroundings data is generated before the receiving follower vehicle follows the lead vehicle in the follower trajectory, and the receiving follower vehicle receives the generated backup trajectory or the surroundings data before the receiving follower vehicle follows the lead vehicle in the follower trajectory.

24. The method of claim 1, wherein the receiving follower vehicle is driverless.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

(2) In the drawings:

(3) FIG. 1 is a side view of vehicles in a string of platooning vehicles.

(4) FIG. 2 is a diagram depicting steps in an embodiment of a method performed by the vehicles in FIG. 1.

(5) FIG. 3 is a top view of two of the vehicles in FIG. 1, and a portion of a road on which they are travelling.

(6) FIG. 4 is a diagram depicting steps in a method according to an alternative embodiment of the invention.

(7) FIG. 5 is a top view of two vehicles participating in the method in FIG. 4, and a portion of a road on which they are travelling.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(8) FIG. 1 shows what is herein referred to as a lead vehicle 1, and follower vehicles 2, 3. In this example, the vehicles 1, 2, 3 are trucks with semitrailers. However, the invention is equally applicable to other types of vehicles, such as cars, buses and dump trucks.

(9) Each of the vehicles 1, 2, 3 comprises equipment 101, 201, 301 for platooning. For longitudinal control, the vehicles comprise in this example equipment for Cooperative Adaptive Cruise Control (CACC). The platooning equipment includes means for wireless communication with a radio transmitter and a radio receiver for so called Vehicle-to-Vehicle (V2V) communication, and a data communication processing device which is arranged to communicate with a control unit 102, 202, 302 of a respective vehicle control system. The control units 102, 202, 302 are herein also referred to as a group of control units. The wireless communication could be based on any suitable industry standard format, such as WiFi, radio modem, or Zigbee. This wireless communication could alternatively be based on a non-industry-standard format. The means for wireless communication is in this example also used for lateral control of the follower vehicles 2, 3.

(10) The lead vehicle 1 and the follower vehicles 2, 3 form parts of a string comprising a plurality of vehicles platooning, using autonomous vehicle following by means of the V2V communication. The lead vehicle is at the front of the string. In this example, a first 2 of the follower vehicles follows immediately behind the lead vehicle 1. In this example, only three vehicles are shown, but the string could comprise more than three vehicles, or only two vehicles.

(11) In the string each vehicle transmits wireless signals representative of the velocity and the acceleration of the transmitting vehicle, and vehicle features including the weight and dimensions of the transmitting vehicle. The vehicle immediately behind the respective transmitting vehicle receives said wireless signals from the transmitting vehicle. Thereby, in this vehicle platooning process, each vehicle, except the lead vehicle 1, is a receiving vehicle controlled to be at a relatively short distance from a transmitting vehicle immediately in front of the respective receiving vehicle.

(12) In addition, position coordinates of the lead vehicle 1 are repeatedly received by the follower vehicles 2, 3 from the lead vehicle, by the V2V communication. The position coordinates are used for lateral control of the follower vehicles. Thereby, the follower vehicles 2, 3 follow the lead vehicle 1 in what is herein referred to as a follower trajectory. The follower vehicles 2 may, or may not, be driverless.

(13) The vehicle control system of the respective receiving vehicle controls brakes, a drivetrain, and a steering function of the receiving vehicle based on the wireless signals received from the respective transmitting vehicle.

(14) It should be noted that in some embodiments, the vehicle control system of the respective receiving vehicle may control brakes, the drivetrain, and the steering function of the receiving vehicle based on the wireless signals received from a vehicle in front of the vehicle immediately in front of the respective receiving vehicle, e.g. from the lead vehicle at the front of the string, as an alternative to or in addition to wireless signals received from the vehicle immediately in front of the respective receiving vehicle. In some embodiments, all follower vehicles are at least partly controlled based on signals from the lead vehicle.

(15) The lead vehicle 1 comprises a sensor in the form of a radar sensor 111. The lead vehicle control unit 102 is arranged to receive signals from the sensor 111. In alternative embodiments, the sensor could be a LIDAR sensor or a camera. In some embodiments, the lead vehicle is equipped with a combination of sensors, e.g. a radar sensor and a LIDAR sensor, a radar sensor and a camera, a LIDAR sensor and a camera, or a radar sensor, a LIDAR sensor and a camera.

(16) The sensor 111 may also be used to detect obstacles in a region in front of the lead vehicle. This region includes part of a lane in which the lead vehicle is travelling. Said region also includes parts of areas outside of the lane in which the lead vehicle is travelling. The region in which obstacles can be detected by the sensor 111 includes a part of a shoulder of the road on which the vehicles are travelling. Said region includes a part of a lane which is adjacent to the lane in which the lead vehicle 1 is travelling. Such obstacles may be non-moving in relation to the road, or they may be moving. Also, by means of the sensor 111, the distance to, velocity of and acceleration of a vehicle in front of the lead vehicle may be determined. The sensor may be arranged to detect objects on the side of the vehicle string. This may be useful to detect vehicles moving faster than the vehicle string, and driving in the same direction, in another lane, or on a motorway on-ramp.

(17) With reference also to FIG. 2 an embodiment of a method according to the invention will be described. The lead vehicle 1 is moving along a lane of a road. The method comprises the follower vehicles 2, 3 following S1 the lead vehicle 1 in the follower trajectory. Thereby, all vehicles in the string are in the same lane.

(18) While moving, the lead vehicle 1 generates S2, by means of the sensor 111, surroundings data, regarding the surroundings, in this example the region in front of the lead vehicle 1. Thus, the surroundings data represents signals from the sensor 111.

(19) Additional surroundings data may be optionally provided to the lead vehicle in the form of map data. This may be done by a detailed map of the road being transmitted to the lead vehicle from a data handling device, which is located remote from the vehicles. The map could include, for example, information on the size of the road shoulder, on locations and appearances of motorway exit and entry raps, and permanent obstacles close to the road, etc. The position of the lead vehicle could be interposed to the map data, e.g. by means of the Global Positioning System (GPS). The map for a relatively long stretch of road ahead could be transmitted in a bulk data transmission to the lead vehicle 1. The map for a relatively long stretch of road ahead could be stored in a storage unit of the lead vehicle. Alternatively, the map data could be transmitted as required, as the lead vehicle moves along the road.

(20) It should be noted that the type of surroundings data may change depending on the circumstances. For example, some surroundings data may be transmitted from a remote, stationary source, but such surroundings data may not be received due to circumstances, e.g. if the vehicles are driving in a tunnel. Thereby the surroundings data may be based only on sensor signals.

(21) Reference is made also to FIG. 3. Using the surroundings data, the lead vehicle repetitively generates S3 backup trajectories BT1 for the follower vehicles 2, 3, which are different from the follower trajectory. The backup trajectories are generated separated by predetermined time intervals. Upon generating each backup trajectory, BT1, the respective backup trajectory is sent to the follower vehicles 2, 3. Thus, the follower vehicles 2, 3 repetitively receives S4 a new backup trajectory from the lead vehicle 1.

(22) As they are received, the backup trajectories are stored in a respective memory of the respective control unit 202, 302 of the respective follower vehicle control system.

(23) The follower vehicles 2, 3 will not follow a backup trajectory, unless a predetermined condition S5 is determined, i.e. established to exist. The predetermined condition could be any of a plurality of conditions, including lost V2V communication with the lead vehicle 1, an operational parameter, e.g. of a follower vehicle 2, 3, being below a predetermined safety threshold level, and a signal sent by the lead vehicle, representing a message that the follower trajectory should be abandoned.

(24) If such a predetermined condition is determined S5 by the follower vehicles 2, 3, the follower vehicles execute S6, i.e. follow, the latest received backup trajectory BT1. As can be seen in FIG. 3, the backup trajectory BT1 in this example is such that it guides the follower vehicles 2, 3 out of the lane L in which they are travelling, and onto a shoulder S of the road. Thus, the follower vehicles are steered out of the lane L. Also, while following the backup trajectory, the follower vehicles are braked to a stop.

(25) The backup trajectory BT1 is provided in the form of a series of coordinates from which a polynomial is formed. For the braking of the follower vehicles 2, 3, the backup trajectory BT1 comprises speed data indicating a target speed of the follower vehicles 2, 3 at a plurality of points P1, P2, P3 along the backup trajectory BT1.

(26) In this example, a second 3 of the follower vehicles, following the first follower vehicle 2, follows, during the execution of the backup trajectory BT1, the first follower vehicle 2 in a further follower trajectory. Thus, as the first follower vehicle 2 follows the backup trajectory, the second follower vehicle 3 receives, in a traditional CACC fashion, V2V signals representative of the velocity and the acceleration of the first follower vehicle 2, and control in dependence thereof its velocity and acceleration, so as to follow the first follower vehicle in a further follower trajectory. Alternatively, the second follower vehicle 3 may execute, i.e. follow, the backup trajectory BT1 independently of the first follower vehicle 2.

(27) It should be noted that in this example, the lead vehicle receives, via the V2V communication, from a transmitting vehicle, before the later vehicle joins the string, vehicle features including the weight and dimensions of the transmitting vehicle. Thereby, the sequentially generated backup trajectories BT1 are partly based on the vehicle features of the transmitting vehicle. However, in alternative embodiments, generated backup trajectories BT1 are not based on vehicle features of follower vehicles.

(28) It should also be noted that in this example, a vehicle seeking to join the string, will not join the string, until it has received a backup trajectory.

(29) It should also be noted that in some embodiments, the sequentially generated and received backup trajectories are correlated with respective execution windows. Each execution window provides a time limit after which the respective backup trajectory BT1 may not be executed. In such embodiments, a predetermined condition, leading to the execution of a backup trajectory, may be that the time limit of the latest received backup trajectory BT1 has been reached.

(30) Reference is made to FIG. 4, depicting steps in a method according to an alternative embodiment of the invention. The method in FIG. 4 is similar to the one described with reference to FIG. 2, except for the following differences:

(31) Instead of the follower vehicles 2, 3 receiving the backup trajectories, the follower vehicles receive S201 from the lead vehicle 1 surroundings data, generated by the lead vehicle 1. This surroundings data is updated continuously or repetitively. Therefore, surroundings data is received repetitively by the follower vehicles 2, 3. Based on the received surrounding data, the follower vehicles repetitively generate a backup trajectory.

(32) Reference is also made to FIG. 5. In the embodiment in FIG. 4, the surrounding data comprises data describing a drivable area DA. This is an area in front of the follower vehicles 2, 3, which is, as determined by means of the lead vehicle sensor 111 (FIG. 1) and map data, determined to be free from of obstacles and suitable to drive in. The drivable area DA is updated continuously or repetitively. The drivable area DA may be generated by the lead vehicle 1, or by the follower vehicles 2, 3 based on surroundings data received by the lead vehicle 1.

(33) During the repetitive generation of backup trajectories, the follower vehicles 2, 3 generate each new backup trajectory BT1 based on the latest drivable area DA. Thereby, the follower vehicles 2, 3 generate a suitable backup trajectory which is completely within the boundaries of the drivable area.

(34) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.