Patent Publication Number: US-2023139389-A1

Title: Autonomous driving device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 17/520,261 filed Nov. 5, 2021, which is a continuation of U.S. application Ser. No. 17/325,901 filed May 20, 2021, which is a continuation of U.S. application Ser. No. 16/154,894 filed Oct. 9, 2018 (now U.S. Pat. No. 11,043,127 issued Jun. 22, 2021), which claims the benefit of priority from Japanese Patent Application No. 2017-213894, filed on Nov. 6, 2017. The entire disclosures of the prior applications are considered part of the disclosure of the accompanying continuation application, and are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an autonomous driving device. 
     BACKGROUND 
     For example, in Japanese Patent Application No. 2016-210380, an autonomous driving device that causes a host vehicle to autonomously travel based on a travel plan for the host vehicle traveling on a branch line to merge into a main line is disclosed. This autonomous driving device generates the travel plan in which a timing of merging into the main line changes according to the presence or absence of following vehicles traveling behind the host vehicle. 
     SUMMARY 
     When the host vehicle merges into the main line from the branch line, if merging into the main line is not easy such as when the main line is congested, this may cause a congestion to the following vehicles traveling on the branch line. Therefore, in this technical field, it is desirable to suppress the congestion of the following vehicles traveling on the branch line even if it is not easy to merge into the main line. 
     According to an aspect of the present disclosure, there is provided an autonomous driving device configured to set a target route for a host vehicle to merge into a main line from a branch line toward a destination set in advance based on map information in which a plurality of waypoints are set in advance in a lane along an extending direction of the lane, and to cause the host vehicle to travel along the set target route, the device comprising: a vehicle position recognition unit configured to recognize a position of the host vehicle on the map; a target route setting unit configured to select the waypoint from the plurality of waypoints, through which the host vehicle passes when merging into the main line from the branch line toward the destination based on the map information, the position of the host vehicle on the map recognized by the vehicle position recognition unit, and the destination, and to set the target route such that the host vehicle passes through the selected waypoint; an external situation recognition unit configured to recognize a travel situation of another vehicle traveling around the host vehicle on the main line if the host vehicle is traveling on the branch line; a merge determination unit configured to determine whether or not the merge into the main line from the branch line is easy according to a determination criteria set in advance based on the travel situation of the other vehicle traveling on the main line recognized by the external situation recognition unit; and a vehicle control unit configured to cause the host vehicle to autonomously travel along the target route set by the target route setting unit. If it is determined by the merge determination unit that the merge is not easy, the target route setting unit is configured to select the waypoint set at the position on an end edge side of the branch line as the waypoint closest to the end edge side on the branch line to be selected for setting the target route, compared to a case where it is determined that the merge is easy. 
     In the autonomous driving device, if it is not easy to merge into the main line, the target route is set, which causes the host vehicle to merge into the main line after traveling to the position closer to the end edge on the branch line compared to a case where the merge is easy. That is, if it is not easy to merge into the main line, the autonomous driving device causes the host vehicle to travel to a position closer to the end edge on the branch line compared to the case where the merge is easy. In this way, a space can be provided behind the host vehicle on the branch line. The following vehicle can travel in the space provided behind the host vehicle on the branch line. Therefore, even if it is not easy to merge into the main line, the autonomous driving device can suppress the congestion due to the following vehicles traveling on the branch line. 
     In the autonomous driving device, as the waypoint positioned closest to the end edge side of the branch line to be selected when it is determined by the merge determination unit that the merge is not easy, if the vehicle size of the host vehicle is small, the target route setting unit may select the waypoint set at the position at the end edge side of the branch line compared to a case where the vehicle size of the host vehicle is large. That is, if the vehicle size of the host vehicle is small, the autonomous driving device can cause the host vehicle to travel to a position closer to the end edge of the branch line compared to a case where the vehicle size of the host vehicle is large. As described above, the autonomous driving device can change the distance for traveling on the branch line according to the vehicle size of the host vehicle. 
     In the autonomous driving device, as the waypoint positioned closest to the end edge side on the branch line to be selected when it is determined by the merge determination unit that the merge is not easy, if the vehicle size of the other vehicle traveling on the main line is small, the target route setting unit may select the waypoint set at the position on the end edge side of the branch line compared to the case where the vehicle size of the other vehicle is large. That is, if the vehicle size of the other vehicle traveling on the main line is small, the autonomous driving device can cause the host vehicle to travel to a position closer to the end edge of the branch line compared to the case where the vehicle size of the other vehicle is large. As described above, the autonomous driving device can change the distance for traveling on the branch line according to the vehicle size of the other vehicle. 
     In the autonomous driving device, as the waypoint positioned closest to the end edge side on the branch line to be selected when it is determined by the merge determination unit that the merge is not easy, if the speed of other vehicle traveling on the main line is high, the target route setting unit may be configured to select the waypoint set at the position on the end edge side of the branch line compared to the case where the speed of other vehicle is low. That is, if the speed of other vehicle traveling on the main line is high, the autonomous driving device can cause the host vehicle to travel to a position closer to the end edge of the branch line compared to the case where the speed of other vehicle is low. As described above, the autonomous driving device can change the distance for traveling on the branch line according to the speed of the other vehicle. For example, if the speed of the other vehicle is high, the distance for the host vehicle to travel on the branch line becomes long. In this case, the autonomous driving device can appropriately accelerate the host vehicle up to, for example, the speed of the other vehicle. 
     According to the present disclosure, even if it is not easy to merge into the main line, it is possible to suppress the congestion of the following vehicles traveling on the branch line. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating a schematic configuration of an autonomous driving device according to an embodiment. 
         FIG.  2    is a diagram illustrating waypoints set on lanes on a map. 
         FIG.  3    is a diagram illustrating a target route on the map when merging into the main line is easy. 
         FIG.  4    is a diagram illustrating a target route on the map when merging into the main line is not easy. 
         FIG.  5    illustrates a class classification table for classifying the vehicle according to a vehicle size. 
         FIG.  6    is a graph for selecting the waypoint at an end edge portion of the branch line based on the vehicle size and a speed of other vehicles. 
         FIG.  7    is a flowchart illustrating a flow of processing for generating the target route and a travel plan for causing the host vehicle to merge into the main line from the branch line. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the embodiment of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same reference numerals will be given to the same elements, and the descriptions thereof will not be repeated. 
     An autonomous driving device  100  illustrated in  FIG.  1    is mounted on a host vehicle V such as a passenger car, and performs an autonomous driving control of the host vehicle V. The autonomous driving device  100  starts the autonomous driving control of the host vehicle V when a start operation (such as pressing a start button for starting the autonomous driving) for the autonomous driving control is performed by the occupant. 
     The autonomous driving control is a vehicle control that causes the host vehicle V to autonomously travel toward a destination set in advance. In the autonomous driving control, the driver does not need to perform a driving operation, and the host vehicle V travels autonomously. 
     As illustrated in  FIG.  1   , the autonomous driving device  100  includes an electronic control unit (ECU)  10  that performs overall management of the system. The ECU  10  is an electronic control unit including a central processing unit (CPU), read only memory (ROM), random access memory (RAM). In the ECU  10 , for example, various functions are realized by loading a program stored in the ROM into the RAM and executing the program loaded in the RAM by the CPU. The ECU  10  may be configured with a plurality of electronic control units. 
     The ECU  10  is connected to a GPS receiver  1 , an external sensor  2 , an internal sensor  3 , a map database  4 , an human machine interface (HMI)  5 , and an actuator  6 . 
     The GPS receiver  1  measures a position of the host vehicle V (for example, the latitude and longitude of the host vehicle V) by receiving signals from three or more GPS satellites. The GPS receiver  1  transmits information on the measured position of the host vehicle V to the ECU  10 . 
     The external sensor  2  is a detection device that detects a surrounding environment of the host vehicle V. The external sensor  2  includes at least one of a camera and a radar sensor. 
     The camera is an imaging device that images the external situation of the host vehicle V. The camera is provided on the inside of a windshield of the host vehicle V. The camera transmits the imaging information relating to the external situation of the host vehicle V to the ECU  10 . The camera may be a monocular camera or may be a stereo camera. The stereo camera has two imaging units that are arranged so as to reproduce a binocular parallax. The image information of the stereo camera also includes information on the depth direction. 
     The radar sensor is a detection device that detects obstacles around the host vehicle V using radio waves (for example, millimeter waves) or light. The radar sensor includes, for example, at least one of the millimeter wave radar or a light detection and ranging (LIDAR). The radar sensor transmits the radio wave or light to the surroundings of the host vehicle V, and detects the obstacles by receiving radio waves or light reflected from obstacles. The radar sensor transmits the detected obstacle information to the ECU  10 . The obstacles include fixed obstacles such as guard rails and buildings, as well as moving obstacles such as pedestrians, bicycles, and other vehicles. 
     The internal sensor  3  is a detection device that detects a traveling state of the host vehicle V. The internal sensor  3  includes a vehicle speed sensor, an accelerator sensor, and a yaw rate sensor. The vehicle speed sensor is a measuring device that measures a speed of the host vehicle V. As the vehicle speed sensor, for example, a vehicle wheel speed sensor is used, which is provided on vehicle wheels of the host vehicle V or on a drive shaft rotating integrally with vehicle wheels, and measures a rotational speed of the vehicle wheels. The vehicle speed sensor transmits the measured vehicle speed information (wheel speed information) to the ECU  10 . 
     The accelerator sensor is a measuring device that measures an acceleration of the host vehicle V. The accelerator sensor includes, for example, a longitudinal accelerator sensor that measures acceleration in the longitudinal direction of the host vehicle V and a lateral accelerator sensor that measures a lateral acceleration of the host vehicle V. The accelerator sensor, for example, transmits the acceleration information of the host vehicle V to the ECU  10 . The yaw rate sensor is a measuring device that measures a yaw rate (rotation angular velocity) around the vertical axis at the center of gravity of the host vehicle V. As the yaw rate sensor, for example, a Gyro sensor can be used. The yaw rate sensor transmits the measured yaw rate information of the host vehicle V to the ECU  10 . 
     The map database  4  is a database that stores map information. The map database  4  is formed, for example, in a hard disk drive (HDD) mounted on the host vehicle V. The map information includes position information on the road (lane), information on the shape of the road (shape of the lane) (for example, a curve, types of straight lines, a curvature of the curve or the like), position information on the intersection, information on position of the merge point and the branch, and information on the position of buildings. The map database  4  may be stored in a server that can communicate with the host vehicle V. 
     The map information includes information on the lanes that constitutes the road. In addition, a plurality of waypoints are set in advance on the lane included in the map information along the extending direction of the lane. These waypoints are used when a below-described target route setting unit  15  sets the target route. For example, as illustrated in  FIG.  2   , the waypoints P are set on each lane even at the merge point. The merging point is an area where the branch line and the main line are connected. 
     Specifically, when a branch line L 20  merges into a main line L 10  at the merge point, a plurality of waypoints P are set along the extension direction of the branch line L 20  on the branch line L 20 . The plurality of waypoints P are set at a predetermined interval. In addition, the waypoints P are set at predetermined positions in the width direction of the branch line L 20  (for example, the center positions). Here, the main line L 10  is configured with a first main line L 11  and a second main line L 12 . On the first main line L 11  also, similarly to the branch line L 20 , a plurality of waypoints P are set along the extension direction of the first main line L 11 . In addition, on the second main line L 12  also, similarly to the branch line L 20 , a plurality of waypoints P are set along the extension direction of the second main line L 12 . 
     The HMI  5  is an interface that performs inputting and outputting of the information between the autonomous driving device  100  and the driver. The HMI  5  includes, for example, a display, a speaker, and the like. The HMI  5  outputs an image on the display and outputs a voice from the speaker according to a control signal from the ECU  10 . The HMI  5  also includes an input unit for the occupant to perform input operations such as an input button, a touch panel, and a voice input device. 
     The actuator  6  is a device used for controlling the host vehicle V. The actuator  6  includes at least a drive actuator, a brake actuator, and a steering actuator. The drive actuator controls a driving force of the host vehicle V by controlling an amount of air (throttle opening degree) supplied to the engine according to the control signal from the ECU  10 . If the host vehicle V is a hybrid vehicle, in addition to the amount of air supplied to the engine, the control signal from the ECU  10  is input to a motor as a power source, and the driving force of the vehicle is controlled. If the host vehicle V is an electric vehicle, the control signal from the ECU  10  is input to a motor as a power source, and the driving force of the vehicle is controlled. The motor as the power source in these cases configures the actuator  6 . 
     The brake actuator controls the brake system according to the control signal from the ECU  10  and controls a braking force applied to the wheels of the host vehicle V. For example, a hydraulic brake system can be used as the brake system. The steering actuator controls the driving of an assist motor controlling a steering torque of an electric power steering system according to the control signal from the ECU  10 . In this way, the steering actuator controls the steering torque of the host vehicle V. 
     Next, a functional configuration of the ECU  10  will be described. The ECU  10  includes a vehicle position recognition unit  11 , an external situation recognition unit  12 , a travel state recognition unit  13 , a merge determination unit  14 , a target route setting unit  15 , a travel plan generation unit  16 , and a vehicle control unit  17 . A part of the functions of the ECU  10  may be performed by a server capable of communicating with the host vehicle V. 
     The vehicle position recognition unit  11  recognizes a position of the host vehicle V on the map based on the position information from the GPS receiver  1  and the map information in the map database  4 . In addition, the vehicle position recognition unit  11  recognizes position information on the fixed obstacles such as electric poles included in the map information in the map database  4  and the position of the host vehicle V using the result of detection performed by the external sensor  2  using the simultaneous localization and mapping (SLAM) technology. The vehicle position recognition unit  11  may recognize the position of the vehicle on the map using a known method. 
     The external situation recognition unit  12  recognizes the external situation around the host vehicle V based on the result of detection performed by the external sensor  2 . The external situation includes the positions of the obstacles with respect to the host vehicle V, relative speeds of obstacles with respect to the host vehicle V, and the moving direction of the obstacles with respect to the host vehicle V. The obstacles also include other vehicles that travel on the main line to which the branch line merges when the host vehicle V travels on the branch line at the merge point. That is, the external situation recognized by the external situation recognition unit  12  includes the travel situation of other vehicles that travel on the main line around the host vehicle V, if the host vehicle V is traveling on the branch line. The external situation recognition unit  12  recognizes the external situation of the host vehicle V using known methods based on at least one of the image captured by the camera and the obstacle information from the radar sensor. 
     The travel state recognition unit  13  recognizes the travel state of the vehicle based on the result of measurement performed by the internal sensor  3 . The travel state includes the speed of the vehicle, the acceleration of the vehicle, and the yaw rate of the vehicle. Specifically, the travel state recognition unit  13  recognizes the speed of the vehicle based on the vehicle speed information from the vehicle speed sensor. The travel state recognition unit  13  recognizes the acceleration of the vehicle based on the vehicle speed information from the accelerator sensor. The travel state recognition unit  13  recognizes the direction of the vehicle based on the yaw rate information from the yaw rate sensor. 
     The merge determination unit  14  determines whether or not the merge into the main line from the branch line is easy if the host vehicle 
     V merges into the main line from the branch line at the merge point. The merge determination unit  14  performs the determination whether or not the merge is easy when the host vehicle V reaches the merge point. The merge determination unit  14  may determine whether or not the merge is easy when the host vehicle V reaches a position where a distance to the merge point is within a predetermined distance. Here, the merge determination unit  14  recognizes whether or not the host vehicle V reaches the merge point based on, for example, the position information of the host vehicle V recognized by the vehicle position recognition unit  11  and the map information in the map database  4 . 
     The merge determination unit  14  determines whether or not the merge into the main line from the branch line is easy based on the travel situation of another vehicle V 1  traveling on the main line recognized by the external situation recognition unit  12  according to determination criteria set in advance. This determination criteria is set in advance in the merge determination unit  14 . 
     Hereinafter, various specific examples of determining whether or not the merge is easy will be described explained. Here, as illustrated in  FIG.  2   , a case where the host vehicle V merges into the first main line L 11  from the branch line L 20  will be described as an example. 
     For example, as a first determination method, the merge determination unit  14  can perform the determination whether or not the merge is easy according to the determination criteria set in advance based on a degree of congestion of the other vehicle traveling on the first main line L 11 . The determination criteria set in advance here means that it is determine that the merge is not easy if the degree of congestion is equal to or greater than a determination criteria value used for the degree of congestion, and it is determined that the merge is easy if the degree of congestion is smaller than the determination criteria value used for the degree of congestion. 
     Specifically, the merge determination unit  14  recognizes the degree of congestion (density) of the other vehicle traveling on the first main line L 11  based on the position of the other vehicle recognized by the external situation recognition unit  12 . The merge determination unit  14  determines that the merge is not easy if the recognized degree of congestion is equal to or greater than the determination criteria value used for the degree of congestion. The merge determination unit  14  determines that the merge is easy if the recognized degree of congestion is smaller than the determination criteria value used for the degree of congestion. 
     For example, as a second determination method, the merge determination unit  14  can determine whether or not the merge is easy according to a determination criteria set in advance based on a free space on the first main line L 11 . The free space on the first main line L  11  is a free space at the merge point on the first main line L 11  existing around the host vehicle V traveling on the branch line L 20 . The determination criteria set in advance here means that it is determine that the merge is not easy if a width (length of the first main line L 11  in the extending direction) of the free space is less than a determination criteria value used for the free space, and it is determined that the merge is easy if the width of the free space is equal to or greater than the determination criteria value used for the free space. 
     Specifically, the merge determination unit  14  recognizes the free space on the first main line L 11  based on the position of the other vehicle recognized by the external situation recognition unit  12 . The merge determination unit  14  determines that the merge is not easy if the width of the recognized free space (the length of the first main line L 11  in the extending direction) is less than the determination criteria value used for the free space. The merge determination unit  14  determines that the merge is easy if the width of the recognized free space (the length of the first main line L 11  in the extending direction) is equal to or greater than the determination criteria value used for the free space. 
     Even if it is determined in the second determination method that the free space having the width greater than the determination criteria value exists on the first main line L 11 , as a third determination method, the merge determination unit  14  may further determine whether or not the merge is easy based on the travel situation of other vehicles. Here, the merge determination unit  14  determines whether or not the merge is easy according to a determination condition set in advance based on a relative speed between the other vehicle traveling on the first main line L 11  at the merge point and the host vehicle V traveling on the branch line L 20 . 
     The determination condition set in advance here means that it is determined that the merge is not easy if the relative speed between the other vehicle traveling on the first main line L 11  and the host vehicle V is equal to or higher than the determination criteria value used for the relative speed, and it is determined that the merge is easy if the relative speed between the other vehicle traveling on the first main line L 11  and the host vehicle V is lower than the determination criteria value used for relative speed. 
     Specifically, the merge determination unit  14  recognizes the relative speed between the other vehicle traveling on the first main line L 11  at the merge point and the host vehicle V based on the result recognition performed by the external situation recognition unit  12 . The merge determination unit  14  determines that the merge is not easy if the recognized relative speed is equal to or higher than the determination criteria value used for relative speed. The merge determination unit  14  determines that the merge is easy if the recognized relative speed is lower than the determination criteria value used for relative speed. If there are a plurality of other vehicles traveling on the first main line L 11 , the merge determination unit  14  may use an average value of the relative speeds for the determination, or may use the relative speed between the host vehicle V and another vehicle selected based on a predetermined condition for the determination. 
     For example, as a fourth determination method, even if it is determined in the second determination method that the free space having the width greater than the determination criteria value exists on the first main line L 11 , the merge determination unit  14  may further determine whether or not the merge is easy based on the travel situation of the other vehicle. Here, the merge determination unit  14  determines whether or not merge is easy according to a preset determination condition based on the speed of other vehicles traveling on the first main line L  11  at the merge point. 
     The determination condition set in advance here means that, for example, it is determined that the merge is not easy if the speed of the other vehicle traveling on the first main line L 11  is lower than the speed of the host vehicle V, and it is determined that the merge is easy if the speed of the other vehicle traveling on the first main line L 11  is higher than the speed of the host vehicle V. The case where the speed of the other vehicle traveling on the first main line L 11  is lower than the speed of the host vehicle V means the case where the host vehicle V needs to decelerate when the host vehicle V merges into the first main line L 11 . 
     Specifically, the merge determination unit  14  recognizes the speed of the other vehicle traveling on the first main line L 11  at the merging point based on the result of recognition performed by the external situation recognition unit  12 . The merge determination unit  14  determines that the merge is not easy if the recognized speed of the other vehicles is lower than the speed of the host vehicle V recognized by the travel state recognition unit  13 . The merge determination unit  14  determines that the merge is easy if the recognized speed of the other vehicle is equal to or higher than the speed of the host vehicle V recognized by the travel state recognition unit  13 . If there are a plurality of other vehicles, the merge determination unit  14  may use the speeds of other vehicles selected based on the predetermined condition for the determination. 
     For example, as a fifth determination method, the merge determination unit  14  can perform the determination whether or not the merge is easy according to the determination criteria set in advance based on the travel situation of other vehicles traveling on the first main line L 11  and the normal target route. The normal target route here means a target route set by the target route setting unit  15  which will be described in detail later, and is a target route at the time of merging into the first main line L  11  from the branch line L 20 . The determination criteria set in advance here means that it is determined that the merge is not easy if it is predicted that the merge into the first main line L 11  from the branch line L 20  is difficult or that the merge cannot be performed when the host vehicle V travels along the normal target route due to the relationship with the travel situation of other vehicles. In addition, the determination criteria set in advance here means that it is determined that the merge is easy if it is predicted that the merge into the first main line L 11  from the branch line L 20  can be performed when the host vehicle V travels along the normal target route due to the relationship with the travel situation of other vehicles. 
     For example, even if the free space exists on the first main line L 11  under the situation that the host vehicle V travels on the branch line L 20 , depending on the position of the other vehicle (due to a fact that the other vehicle obstruct the traveling of the host vehicle V), in some cases, the host vehicle V cannot enter the free space if the host vehicle V travels along the normal target route. As described above, the merge determination unit  14  predicts whether or not the host vehicle V can merge into the first main line L 11  when the host vehicle V autonomously travels along the normal target route, based on the travel situation of the other vehicle traveling on the main line L 11  recognized by the external situation recognition unit  12  and the normal target route. The merge determination unit  14  determines that merge is not easy if it is predicted that the host vehicle V cannot merge into the first main line L 11  or the merge is difficult. The merge determination unit  14  determines that merge is easy if it is predicted that the host vehicle V can merge into the first main line L 11 . 
     The merge determination unit  14  may determine whether or not the merge is easy by combining at least two of the first to fifth determination methods described above. 
     The target route setting unit  15  sets the target route based on the map information in the map database  4 , the position of the host vehicle V recognized by the vehicle position recognition unit  11 , and the destination set in advance. The target route is a route from the current position of the host vehicle V on the map to the destination. The destination may be a destination set by the occupant or may be a destination autonomously set by the autonomous driving device  100  using a well-known method (destination estimation processing or the like). 
     In this case, the target route setting unit  15  selects a waypoint to pass through when traveling toward the destination among the waypoints set on the lane in the map information. The target route setting unit  15  sets the target route such that the host vehicle V passes through the selected waypoint. That is, the target route setting unit  15  sets the target route by connecting the selected waypoints. 
     A target route that causes the host vehicle V to merge into the main line from the branch line towards the destination set in advance is included in this target route. When setting the target route for the host vehicle V to merge into the main line from the branch line, the target route setting unit  15  sets target routes different from each other in a case where it is determined by the merge determination unit  14  that the merge is easy and in a case where it is determined that the merge is not easy. Hereinafter, a specific example of the target route for merging into the main line from the branch line will be described. Here, as illustrated in  FIG.  3   , the case where the host vehicle V merges into the first main line L 11  from the branch line L 20  will be described as an example. 
     The target route setting unit  15  sets the normal target route or the target route for the time when the merge is not easy as the target route. First, the normal target route set by the target route setting unit  15  will be described. If it is determined by the merge determination unit  14  that the merge is easy, the target route setting unit  15  sets a normal target route T. Specifically, the target route setting unit  15  select the waypoints P to pass through when the host vehicle V merges into the first main line L 11  from the branch line L 20  toward the destination among the waypoints P set on the branch line L 20  and the first main line L 11  in the map information. The target route setting unit  15  sets the normal target route T by connecting the selected waypoints P. The target route setting unit  15  can set the target route T by a well-known method using the waypoints P. In  FIG.  3   , the waypoints P selected for setting the normal target route T are indicated by bold rectangles. 
     A waypoint P closest to the end edge E side on the branch line L 20 , which is selected from the waypoints P on the branch line L 20  to set the normal target route T, is set as an end edge waypoint Pa. In an example illustrated in  FIG.  3   , the waypoint P at immediately in front of the position of the host vehicle V on the map is the end edge waypoint Pa. That is, in the example illustrated in  FIG.  3   , the end edge waypoint Pa becomes the target route for the host vehicle V to quickly merge into the first main line L 11  after the host vehicle V reaches the merging point. In addition, a waypoint P connected to the end edge waypoint Pa, which is selected from the waypoints P to be selected for setting the normal target route T on the first main line L 11 , is set as a start edge waypoint Pb. In order to suppress a sudden behavior change of host vehicle V at the time of merging into first main line L 11  from the branch line L 20 , the target route setting unit  15  can select the start edge waypoint Pb based on a well-known method. 
     In addition, if the merge determination unit  14  determines that the merge is not easy, the target route setting unit  15  sets the target route for the time when the merge is not easy. Specifically, the target route setting unit  15  selects a waypoint P from the waypoints P set on the branch line L 20  and the first main line L 11  in the map information as illustrated in  FIG.  4    for the host vehicle V to pass through when merging into the first main line L 11  from the branch line L 20  toward the destination. However, as the end edge waypoint Pa on the branch line L 20  to be selected to set the route T 1  for the time when the merge is not easy, the target route setting unit  15  selects a waypoint P set at the position at the end edge E side of the branch line L 20  compared to the case where it is determined that the merge is easy. That is, the target route setting unit  15  changes the waypoint P to be selected as the end edge waypoint Pa based on the result of determination performed by the merge determination unit  14 . The target route setting unit  15  sets the target route T 1  for the time when the merge is not easy by connecting the selected waypoints P. 
     Here, the target route setting unit  15  selects the waypoint P existing at a position separated by a distance L from the end edge E on the branch line L 20  as the end edge waypoint Pa for setting the target route T 1  for the time when the merge is not easy. The target route setting unit  15  may use a constant value as the distance L or may change the distance L based on a predetermined condition. 
     Hereinafter, various examples for the target route setting unit  15  to change the distance L for selecting the end edge waypoint Pa will be described. 
     For example, the target route setting unit  15  can determine the distance L based on a vehicle size of the host vehicle V. The vehicle size is classified by types such as a motorcycle, a passenger car, and a truck. The vehicle size becomes larger in an order of the motorcycle, the passenger car, and the truck. Specifically, the target route setting unit  15  sets the distance L to be short if the vehicle size of the host vehicle V is small compared to a case where the vehicle size of the host vehicle V is large. That is, if the vehicle size of the host vehicle V is small, the target route setting unit  15  sets the waypoint P closer to the end edge E side of the branch line L 20  as the end edge waypoint Pa compared to the case where the vehicle size of the host vehicle V is large. 
     For example, the target route setting unit  15  can determine the distance L based on the vehicle size of another vehicle V 1  traveling on the first main line L 11 . Another vehicle V 1  traveling on the first main line L 11  means another vehicle V 1  that obstructs the traveling of the host vehicle V or another vehicle V 1  around the host vehicle V when the host vehicle V merges into the first main line L 11  along the target route. For example, another vehicle V 1  traveling on the first main line L 11  means another vehicle V 1  that obstructs the traveling of the host vehicle V or another vehicle V 1  around the host vehicle V when the host vehicle V merges into the first main line L 11  along the initial target route set in advance. For example, the initial target route may be set a waypoint P at a position separated by a reference distance set in advance from the end edge E on the branch line L 20  as an end edge waypoint Pa. The end edge waypoint Pa in the initial target route is positioned at the position closer to the end edge E side of the branch line L 20  than the end edge waypoint Pa in the normal target route T. Another vehicle V 1  specified by a method other than a method using the initial target route may be used as another vehicle V 1  traveling on the first main line L 11 . 
     Specifically, if the vehicle size of the other vehicle V 1  traveling on the first main line L 11  is small, the target route setting unit  15  sets the distance L to be short compared to a case where the vehicle size of another vehicle V 1  traveling on the first main line L 11  is large. That is, if the vehicle size of another vehicle V 1  traveling on the first main line L 11  is small, the target route setting unit  15  selects the waypoint P positioned closer to the end edge E side of the branch line L 20  as the end edge waypoint Pa compared to the case where the vehicle size of the other vehicle V 1  traveling on the first main line L 11  is large. 
     For example, the target route setting unit  15  can determine the distance L based on the speed of the other vehicle V 1  traveling on the first main line L 11 . Specifically, if the speed of the other vehicle V 1  traveling on the first main line L 11  is high, the target route setting unit  15  sets the distance L to be less compared to the case where the speed of the other vehicle V 1  traveling on the first main line L 11  is low. That is, if the speed of the other vehicle V 1  traveling on the first main line L 11  is high, the target route setting unit  15  selects the waypoint P positioned closer to the end edge E side of branch line L 20  as end edge waypoints Pa compared to the case where the speed of the other vehicle V 1  traveling on the first main line L 11  is low. 
     The target route setting unit  15  may use any one method or a combination of two or more of the three methods (the method using the vehicle size of another vehicle V 1 , a method using the speed of another vehicle V 1 , a method using the vehicle size of the host vehicle V) for determining the distance L described above. 
     Specifically, if the combination of all the three methods for determining the distance L is used, the target route setting unit  15  can determine the distance L using the classification table illustrated in  FIG.  5    and the graph illustrated in  FIG.  6   . In this case, first, The target route setting unit  15  selects a class that corresponds to the vehicle size of the host vehicle V and the vehicle size of the other vehicle V 1  traveling on the first main line L 11  from “A” to “C” using the classification table illustrated in  FIG.  5   . Next, the target route setting unit  15  selects a graph corresponding to the class selected using the classification table in  FIG.  5    from the graphs “A” to “C” illustrated in  FIG.  6   . The target route setting unit  15  can determine the distance L based on the selected graph and the speed of the other vehicle V 1  traveling on the first main line L  11 . 
     If it is determined by the merge determination unit  14  that the merge is not easy, the target route setting unit  15  sets the target route T 1  for the time when the merge is not easy. On the other hand, if it is determined by the merge determination unit  14  that merge is easy, the target route setting unit  15  sets the normal target route T. The target route T 1  for the time when the merge is not easy is a path for the host vehicle V to merge into the first main line L 11  after traveling closer to the end edge E side of the branch line L 20  compared to the normal target route T. 
     If the merge determination unit  14  determines whether the merge is easy or not using the fifth determination method, the target route setting unit  15  tentatively generates a normal target route T when the host vehicle V reaches the merging point (or approaches the merging point). The merge determination unit  14  determines whether or not the merge is easy based on the normal target route T tentatively generated by the target route setting unit  15 . The target route setting unit  15  may generate the normal target route T or the target route T 1  for the time when the merge is not easy based on the result of determination performed by the merge determination unit  14 . 
     The travel plan generation unit  16  generates the travel plan of the host vehicle V based on the target route set by the target route setting unit  15 , the map information in the map database  4 , the position of the host vehicle V on the map recognized by the vehicle position recognition unit  11 , the external situation of the host vehicle V recognized by the external situation recognition unit  12 , and the travel state of the vehicle recognized by the travel state recognition unit  13 . This travel plan is a travel plan for causing the host vehicle V to autonomously travel along the target route set by the target route setting unit  15 . 
     The travel plan includes a speed plan and a steering plan. The speed plan includes a control target value (for example, a target vehicle speed and a target acceleration or deceleration) of the host vehicle V according to a position on the target route of host vehicle V. The position on the target route is the position on the map in the extending direction of the target route. The position on the target route means a vertical set position set at a predetermined interval (for example,  1 m) each in the extending direction of the target route. The control target value is set in association with each vertical set position on the target route. The travel plan generation unit  16  sets the vertical set position on the target route at a predetermined interval, and generates the speed plan in the travel plan by setting the control target value for each vertical set position. The travel plan generation unit  16  generates the steering plan in the travel plan by setting a target trajectory of the travel of the host vehicle V using a well-known method. 
     The vehicle control unit  17  performs the autonomous driving control for the vehicle based on the travel plan generated by the travel plan generation unit  16 . The vehicle control unit  17  performs the autonomous driving control for the vehicle by transmitting a control signal to the actuator  6 . That is, the vehicle control unit  17  causes the host vehicle V to autonomously travel based on the travel plan along the target route set by the target route setting unit  15 . 
     Next, a flow of processing for generating the target route and the travel plan for causing the host vehicle V to merge into the main line from the branch line will be described. The processing in the flowchart illustrated in  FIG.  7    starts when the host vehicle V traveling on the branch line reaches the merging point (or approaches the merging point within a predetermined distance). In addition, the execution of the processing illustrated in  FIG.  7    is repeated to start at a predetermined time interval. 
     The vehicle control unit  17  controls the travel of the host vehicle V based on a new travel plan generated at each time by the travel plan generation unit  16 . 
     As illustrated in  FIG.  7   , when the host vehicle V reaches the merging point, the merge determination unit  14  determines whether or not merge into the main line is easy (S 101 ). If the merge is easy (YES in S 101 ), the target route setting unit  15  sets a normal target route as the target route (S 102 ). The travel plan generation unit  16  generates a travel plan based on the normal target route set by the target route setting unit  15  (S 103 ). When the travel plan is generated, the vehicle control unit  17  controls the travel of the host vehicle V based on the newly generated travel plan. 
     If it is determined that the merge is not easy (NO in S 101 ) in S 101 , the target route setting unit  15  determines the distance L used for selecting the end edge waypoint Pa (S 104 ). After the distance L is determined, the target route setting unit  15  determines the waypoint P set at the position separated from the end edge by the distance L on the branch line as the end edge waypoint Pa. The target route setting unit  15  sets the target route for the time when the merge is not easy such that the host vehicle V passes through the end edge waypoint Pa (S 105 ). The travel plan generation unit  16  generates a travel plan based on the target route for the time when the merge is not easy to set by the target route setting unit  15  (S 106 ). The vehicle control unit  17  controls the travel of the host vehicle V based on the newly generated travel plan. 
     As described above, in the autonomous driving device  100 , for example, if it is not easy for the host vehicle V traveling on the branch line L 20  to merge into the first main line L 11  at the merging point illustrated in  FIG.  2   , a target route T 1  for the time when the merge is not easy (refer to  FIG.  4   ) is set, which causes the host vehicle V to merge into the first main line L 11  after traveling to the position closer to the end edge E on the branch line L 20  compared to a case where the merge is easy. That is, if the merge to the first main line L 11  is not easy, the autonomous driving device  100  causes the host vehicle V to travel to a position closer to the end edge E on the branch line L 20  compared to the case where the merge is easy. In this way, a space can be provided behind the host vehicle V on the branch line L 20 . A following vehicle traveling behind the host vehicle V on the branch line L 20  can travel to the end of the branch line L 20  (end edge E side) while traveling in the space provided behind the host vehicle V on the branch line L 20 . Therefore, even if the merge into the first main line L 11  is not easy, the autonomous driving device  100  can suppress the congestion due to the following vehicles traveling on the branch line L 20 . 
     In addition, since the host vehicle V merges into the first main line L 11  after traveling to the end edge E side on the branch line L 20 , it is possible to prevent the following vehicle traveling on the branch line L 20  from passing through the left side of the host vehicle V to overtake when the host vehicle V merges into first main line L 11 . Therefore, the autonomous driving device  100  can reduce the necessity of considering the following vehicle which passes through the left side of the host vehicle V when the host vehicle V autonomously travels. In addition, since the host vehicle V merges at the back of the first main line L 11  (the side closer to the end edge E on the branch line L 20 ), the autonomous driving device  100  can reduce the necessity of considering other vehicles merged from the branch line L 20  after the host vehicle V merges into the first main line L 11 . 
     The autonomous driving device  100  changes the position of the end edge waypoint Pa when setting the target route T 1  for the time when the merge is not easy based on various conditions. For example, if the vehicle size of the host vehicle V is small, the target route setting unit  15  of the autonomous driving device  100  selects the waypoint P set at the position of the end edge E side on the branch line L 20  as the end edge waypoint Pa compared to the case where the vehicle size of the host vehicle V is large. That is, if the vehicle size of the host vehicle V is small, the autonomous driving device  100  can cause the host vehicle V to travel to a position closer to the end edge E on the branch line L 20  compared to the case where the vehicle size of the host vehicle V is large. As described above, the autonomous driving device  100  can change the distance for traveling on the branch line L 20  according to the vehicle size of the host vehicle V. 
     For example, if the vehicle size of another vehicle V 1  traveling on the first main line L 11  is small, the target route setting unit  15  of the autonomous driving device  100  selects the waypoint P set at the position closer to the end edge E side of the branch line L 20  as the end edge waypoint Pa compared to the case where the vehicle size of the other vehicle V 1  is large. That is, if the vehicle size of the other vehicle V 1  traveling on the first main line L 11  is small, the autonomous driving device  100  can cause the host vehicle V to travel to a position closer to the end edge E on the branch line L  20  compared to the case where the vehicle size of the other vehicle V 1  is large. As described above, the autonomous driving device  100  can change the traveling distance on the branch line L 20  according to the vehicle size of the other vehicle V 1 . 
     for example, if the speed of another vehicle V 1  traveling on the first main line L 11  is high, the target route setting unit  15  of the autonomous driving device  100  selects the waypoint P set at the position closer to the end edge E side of the branch line L 20  as the end edge waypoint Pa compared to the case where the speed of the other vehicle V 1  is low. That is, if the speed of the other vehicle V 1  traveling on the first main line L  11  is high, the autonomous driving device  100  can cause the host vehicle V to travel to a position closer to the end edge E on the branch line L 20  compared to the case where the speed of the other vehicle V 1  is low. As described above, the autonomous driving device  100  can change the traveling distance on the branch line L 20  according to the speed of the other vehicle V 1 . For example, if the speed of the other vehicle V 1  is high, the distance for the host vehicle V to travel on the branch line L 20  becomes long. In this case, the autonomous driving device  100  can appropriately accelerate the host vehicle V up to, for example, the speed of the other vehicle V 1 . 
     As described above, an embodiment of the present disclosure has been described, however, the present disclosure is not limited to the embodiment described above. For example, the road shape of the merging point described with reference to  FIGS.  2  to  4    is merely an example, and is not limited to the road shape having such a merging point.