Patent Publication Number: US-2023148202-A1

Title: Vehicle control system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/019,804 filed Sep. 14, 2020, which is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2019-188898, filed on Oct. 15, 2019. The entire disclosures of the prior applications are considered part of the disclosure of the accompanying continuation application, and are hereby incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a vehicle control system that controls a vehicle performing automated driving. In particular, the present disclosure relates to a vehicle control system that controls a vehicle to follow a target trajectory. 
     BACKGROUND ART 
     Patent Literature 1 discloses a driving operation assist device for a vehicle. The driving operation assist device performs RP transmission control and following travel control. The RP transmission control controls an accelerator pedal reactive force and driving/braking forces based on a risk potential with respect to an obstacle. The following travel control controls the driving/braking forces so as to keep an inter-vehicle distance to the obstacle. When both the RP transmission control and the following travel control are activated, priority is given to the following travel control than to the RP transmission control. 
     List of Related Art 
     
         
         Patent Literature 1: Japanese Laid-Open Patent Application Publication No. 2007-313932 
       
    
     SUMMARY 
     Vehicle travel control that controls steering, acceleration, and deceleration of a vehicle is considered. In particular, let us consider a case where the vehicle travel control is executed such that the vehicle follows a target trajectory. During automated driving, the target trajectory is generated by an automated driving system. Then, the vehicle travel control is executed so that the vehicle follows the target trajectory for the automated driving. 
     Meanwhile, it is also envisioned that a “travel assist control function” which assists vehicle travel not constantly but as needed basis is applied to the vehicle. The travel assist control function controls at least one of the steering, the acceleration, and the deceleration of the vehicle as needed basis. If the travel assist control function intervenes in the automated driving, following performance with respect to the target trajectory for the automated driving is deteriorated. That is, continuity of the automated driving is decreased. This causes a sense of strangeness of an occupant of the vehicle. 
     An object of the present disclosure is to provide a technique that can suppress decrease in continuity of automated driving when vehicle travel control is executed so that the vehicle follows a target trajectory during the automated driving. 
     In an aspect of the present disclosure, a vehicle control system that controls a vehicle performing automated driving is provided. 
     The vehicle control system includes: 
     a vehicle travel control device configured to execute vehicle travel control that controls steering, acceleration, and deceleration of the vehicle such that the vehicle follows a target trajectory; and 
     an automated driving control device configured to generate a first target trajectory being the target trajectory for the automated driving of the vehicle. 
     The vehicle travel control device is further configured to: 
     determine whether or not an activation condition of travel assist control is satisfied, wherein the travel assist control controls at least one of the steering, the acceleration, and the deceleration for at least one of improving safety or comfort of travel of the vehicle, reducing a sense of strangeness or insecurity of an occupant of the vehicle, and stabilizing behavior of the vehicle; and 
     generate a second target trajectory being the target trajectory for the travel assist control when the activation condition is satisfied. 
     Even when the second target trajectory is generated during the automated driving, or when the second target trajectory is generated during the automated driving and a priority condition for giving priority to the first target trajectory is satisfied, the vehicle travel control device executes the vehicle travel control by giving more weight to the first target trajectory than to the second target trajectory. 
     The automated driving control device generates the first target trajectory for the automated driving of the vehicle. The vehicle travel control device generates the second target trajectory for the travel assist control when the activation condition of the travel assist control is satisfied. Even when the second target trajectory is generated during the automated driving, the vehicle travel control device executes the vehicle travel control by giving more weight to the first target trajectory than to the second target trajectory. It is thus possible to suppress influence of the travel assist control and to suppress deterioration of following performance with respect to the first target trajectory for the automated driving. That is, it is possible to suppress decrease in continuity of the automated driving. 
     Alternatively, when the second target trajectory is generated during the automated driving and the priority condition for giving priority to the first target trajectory is satisfied, the vehicle travel control device may execute the vehicle travel control by giving more weight to the first target trajectory than to the second target trajectory. As a result, it is possible to suppress decrease in continuity of the automated driving while appropriately utilizing the travel assist control. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a conceptual diagram for explaining an outline of a vehicle control system according to an embodiment of the present disclosure; 
         FIG.  2    is a block diagram schematically showing a configuration of the vehicle control system according to the embodiment of the present disclosure; 
         FIG.  3    is a conceptual diagram for explaining the outlie of the vehicle control system according to the embodiment of the present disclosure; 
         FIG.  4    is a conceptual diagram for explaining the outlie of the vehicle control system according to the embodiment of the present disclosure; 
         FIG.  5    is a block diagram showing a configuration example of an automated driving control device according to the embodiment of the present disclosure; 
         FIG.  6    is a block diagram showing an example of a first information acquisition device and first driving environment information in the automated driving control device according to the embodiment of the present disclosure; 
         FIG.  7    is a flow chart showing processing by the automated driving control device according to the embodiment of the present disclosure; 
         FIG.  8    is a block diagram showing a configuration example of a vehicle travel control device according to the embodiment of the present disclosure; 
         FIG.  9    is a block diagram showing an example of a second information acquisition device and second driving environment information in the vehicle travel control device according to the embodiment of the present disclosure; 
         FIG.  10    is a flow chart showing an example of processing related to travel assist control by the vehicle travel control device according to the embodiment of the present disclosure; 
         FIG.  11    is a conceptual diagram showing an example of processing in Step S 240  in  FIG.  10   ; 
         FIG.  12    is a conceptual diagram showing another example of processing in Step S 240  in  FIG.  10   ; 
         FIG.  13    is a conceptual diagram showing an example of processing in Step S 250  in  FIG.  10   ; 
         FIG.  14    is a flow chart showing another example of processing related to the travel assist control by the vehicle travel control device according to the embodiment of the present disclosure; 
         FIG.  15    is a block diagram showing a configuration of the vehicle travel control device according to a third modification example of the embodiment of the present disclosure; and 
         FIG.  16    is a block diagram showing a configuration of the vehicle control system according to a fourth modification example of the embodiment of the present disclosure. 
     
    
    
     EMBODIMENTS 
     Embodiments of the present disclosure will be described below with reference to the attached drawings. 
     1. Outline 
       FIG.  1    is a conceptual diagram for explaining an outline of a vehicle control system  10  according to the present embodiment. The vehicle control system  10  controls a vehicle  1 . Typically, the vehicle control system  10  is installed on the vehicle  1 . Alternatively, at least a part of the vehicle control system  10  may be placed in an external device outside the vehicle  1  and remotely control the vehicle  1 . That is, the vehicle control system  10  may be distributed in the vehicle  1  and the external device. 
     The vehicle  1  is an automated driving vehicle capable of automated driving. The automated driving here means one where a driver does not necessarily have to 100% concentrate on driving (e.g., so-called Level 3 or more automated driving). 
     The vehicle control system  10  manages the automated driving of the vehicle  1 . Moreover, the vehicle control system  10  executes “vehicle travel control” that controls steering, acceleration, and deceleration of the vehicle  1 . In particular, during the automated driving, the vehicle control system  10  executes the vehicle travel control such that the vehicle  1  follows a target trajectory TR. 
     The target trajectory TR includes at least a set of target positions [Xi, Yi] of the vehicle  1  in a road on which the vehicle  1  travels. In the example shown in  FIG.  1   , an X-direction is a forward direction of the vehicle  1 , and a Y-direction is a plane direction orthogonal to the X-direction. However, the coordinate system (X, Y) is not limited to the example shown in  FIG.  1   . The target trajectory TR may further include a target velocity [VXi, VYi] for each target position [Xi, Yi]. The target trajectory TR may include control range information such as upper and lower limits of the target position[Xi, Yi] and the target velocity [VXi, VYi], and desired traveling position range information. In order to make the vehicle  1  follow such the target trajectory TR, the vehicle control system  10  calculates a deviation (e.g., a lateral deviation, a yaw angle deviation, a velocity deviation, etc.) between the vehicle  1  and the target trajectory TR, and then performs the vehicle travel control such that the deviation decreases. 
       FIG.  2    is a block diagram schematically showing a configuration of the vehicle control system  10  according to the present embodiment. The vehicle control system  10  includes an automated driving control device  100  and a vehicle travel control device  200 . The automated driving control device  100  and the vehicle travel control device  200  may be physically-separated devices, or may be an identical device. When the automated driving control device  100  and the vehicle travel control device  200  are physically-separated devices, they exchange necessary information via communication. 
     The automated driving control device  100  is responsible for management of the automated driving of the vehicle  1  among the functions of the vehicle control system  10 . In particular, the automated driving control device  100  generates the target trajectory TR for the automated driving of the vehicle  1 . For example, the automated driving control device  100  uses a sensor to detect (recognize) a situation around the vehicle  1 . Then, the automated driving control device  100  generates a travel plan of the vehicle  1  during the automated driving based on a destination and the situation around the vehicle  1 . The travel plan includes maintaining a current travel lane, making a lane change, avoiding an obstacle, and so forth. The automated driving control device  100  then generates the target trajectory TR required for the vehicle  1  to travel in accordance with the travel plan. 
     The target trajectory TR for the automated driving generated by the automated driving control device  100  is hereinafter referred to as a “first target trajectory TR1.” The automated driving control device  100  outputs the generated first target trajectory TR1 to the vehicle travel control device  200 . 
     On the other hand, the vehicle travel control device  200  is responsible for the vehicle travel control among the functions of the vehicle control system  10 . That is, the vehicle travel control device  200  controls the steering, the acceleration, and the deceleration of the vehicle  1 . In particular, the vehicle travel control device  200  controls the steering, the acceleration, and the deceleration of the vehicle  1  such that the vehicle  1  follows the target trajectory TR. In order to make the vehicle  1  follow the target trajectory TR, the vehicle travel control device  200  calculates a deviation (e.g., a lateral deviation, a yaw angle deviation, a velocity deviation, etc.) between the vehicle  1  and the target trajectory TR, and then performs the vehicle travel control such that the deviation decreases. 
     During the automated driving of the vehicle  1 , the vehicle travel control device  200  receives the first target trajectory TR1 from the automated driving control device  100 . Basically, the vehicle travel control device  200  executes the vehicle travel control such that the vehicle  1  follows the first target trajectory TR1. 
     The vehicle travel control device  200  according to the present embodiment further has a function of “travel assist control” (travel assist control function GD) that assists travel of the vehicle  1 . More specifically, the travel assist control controls at least one of the steering, the acceleration, and the deceleration of the vehicle  1  for at least one of improving safety or comfort of travel of the vehicle  1 , reducing a sense of strangeness or insecurity of an occupant of the vehicle  1 , and stabilizing behavior of the vehicle  1 . Such the travel assist control is exemplified by collision avoidance control, lane departure suppression control, damping control, vehicle stability control, and the like. The collision avoidance control assists avoidance of a collision between the vehicle  1  and a surrounding object (namely, an avoidance target). The lane departure suppression control suppresses the vehicle  1  from departing from a travel lane. The damping control suppresses pitching and rolling of the vehicle  1 . The vehicle stability control suppresses unstable behavior such as vehicle spin. 
     The vehicle travel control device  200  uses sensors to detect a situation around the vehicle  1  and a state of the vehicle  1 . Then, based on the detection result, the vehicle travel control device  200  (the travel assist control function GD) determines whether or not it is necessary to activate the travel assist control. In other words, the vehicle travel control device  200  determines whether or not an “activation condition” for activating the travel assist control is satisfied. When the activation condition is satisfied, the vehicle travel control device  200  (the travel assist control function GD) generates the target trajectory TR for the travel assist control. The target trajectory TR for the travel assist control generated by the vehicle travel control device  200  is hereinafter referred to as a “second target trajectory TR2.” 
     When the activation condition of the travel assist control is satisfied and the second target trajectory TR2 is generated during the automated driving, both the first target trajectory TR1 for the automated driving and the second target trajectory TR2 for the travel assist control are generated coincidentally. The first target trajectory TR1 and the second target trajectory TR2 are not necessarily consistent with each other. It is therefore necessary to arbitrate between the first target trajectory TR1 and the second target trajectory TR2 to determine a definitive target trajectory TR. 
     The vehicle travel control device  200  according to the present embodiment further has a function of arbitrating between the first target trajectory TR1 and the second target trajectory TR2 to determine the definitive target trajectory TR. In particular, according to the present embodiment, more priority is given to the first target trajectory TR1 for the automated driving than to the second target trajectory TR2 for the travel assist control, from the following point of view. 
     As an example,  FIG.  3    shows a situation where there is an avoidance target such as a pedestrian or an obstacle ahead of the vehicle  1 . The automated driving control device  100  recognizes the avoidance target and generates the first target trajectory TR1 required for the vehicle  1  to travel while avoiding a collision with the avoidance target. Moreover, the vehicle travel control device  200  provided with the travel assist control function GD also recognizes the same avoidance target and generates the second target trajectory TR2 that can avoid a collision with the avoidance target. In the example shown in  FIG.  3   , the first target trajectory TR1 demands at least the steering of the vehicle  1 , and the second target trajectory TR2 demands rapid deceleration of the vehicle  1 . 
     If priority is given to the second target trajectory TR2, following performance with respect to the first target trajectory TR1 for the automated driving is deteriorated, although it is possible to avoid the collision with the avoidance target. That is to say, continuity of the automated driving is decreased. This causes a sense of strangeness of an occupant of the vehicle  1 . On the other hand, the collision with the avoidance target can be avoided even by giving priority to the first target trajectory TR1. Furthermore, giving priority to the first target trajectory TR1 makes it possible to suppress influence of the travel assist control and to suppress deterioration of the following performance with respect to the first target trajectory TR1. 
     In an example shown in  FIG.  4   , both the first target trajectory TR1 and the second target trajectory TR2 demand the steering of the vehicle  1  in order to avoid the collision with the avoidance target. In this case also, giving priority to the first target trajectory TR1 makes it possible to suppress decrease in the continuity of the automated driving while avoiding the collision with the avoidance target. 
     As described above, the automated driving control device  100  is considered to recognize risks and the like ahead of the vehicle  1  and generate an appropriate first target trajectory TR1. In view of the above, even when the second target trajectory TR2 is generated during the automated driving, the vehicle travel control device  200  gives priority to the first target trajectory TR1. In other words, the vehicle travel control device  200  executes the vehicle travel control by giving more “weight” to the first target trajectory TR1 than to the second target trajectory TR2. It is thus possible to suppress the influence of the travel assist control and to suppress deterioration of the following performance with respect to the first target trajectory TR1 for the automated driving. That is, it is possible to suppress decrease in the continuity of the automated driving. 
     Giving more weight to the first target trajectory TR1 than to the second target trajectory TR2 includes selecting the first target trajectory TR1 as the definitive target trajectory TR. In this case, the vehicle travel control device  200  executes the vehicle travel control by using the first target trajectory TR1 as the target trajectory TR. In this case, the continuity of the automated driving is maintained. 
     In addition, giving more weight to the first target trajectory TR1 than to the second target trajectory TR2 includes combining the second target trajectory TR2 and the first target trajectory TR1 to determine the definitive target trajectory TR. Here, a weight (a first weight W1) of the first target trajectory TR1 with respect to the target trajectory TR is greater than a weight (a second weight W2) of the second target trajectory TR2 with respect to the target trajectory TR. Even in this case, decrease in the continuity of the automated driving is suppressed. 
     It should be noted that there is no need to always give priority to the first target trajectory TR1. In order to make more flexible operation possible, the priority may be conditionally given to the first target trajectory TR1. A condition for giving priority to the first target trajectory TR1 is hereinafter referred to as a “priority condition.” When the second target trajectory TR2 is generated during the automated driving and the priority condition is satisfied, the vehicle travel control device  200  may execute the vehicle travel control by giving more weight to the first target trajectory TR1 than to the second target trajectory TR2. As a result, it is possible to suppress decrease in the continuity of the automated driving while appropriately utilizing the travel assist control. Various examples of the priority condition will be described later. 
     The automated driving control device  100  and the vehicle travel control device  200  may be separately designed and developed. For example, the vehicle travel control device  200  responsible for the vehicle travel control is designed and developed by an automaker. On the premise of utilizing the vehicle travel control device  200 , an automated driving service provider can design and develop software for the automated driving control device  100 . In that sense, it can be said that the vehicle travel control device  200  is a platform for automated driving services. 
     Hereinafter, the vehicle control system  10  according to the present embodiment will be described in more detail. 
     2. Automated Driving Control Device  100   
     2-1. Configuration Example 
       FIG.  5    is a block diagram showing a configuration example of the automated driving control device  100  according to the present embodiment. The automated driving control device  100  is provided with a first information acquisition device  110 , a first control device  120 , and a first input/output interface  130 . 
     The first information acquisition device  110  acquires first driving environment information  150 . The first driving environment information  150  is information indicating a driving environment for the vehicle  1  and necessary for the automated driving of the vehicle  1 . 
       FIG.  6    is a block diagram showing an example of the first information acquisition device  110  and the first driving environment information  150 . The first information acquisition device  110  includes a first map information acquisition device  111 , a first position information acquisition device  112 , a first vehicle state sensor  113 , a first surrounding situation sensor  114 , and a first communication device  115 . The first driving environment information  150  includes first map information  151 , first position information  152 , first vehicle state information  153 , first surrounding situation information  154 , and first delivery information  155 . 
     The first map information acquisition device  111  acquires the first map information  151 . The first map information  151  indicates a lane configuration and a road shape. The first map information acquisition device  111  acquires the first map information  151  of a necessary area from a map database. The map database may be stored in a predetermined memory device mounted on the vehicle  1 , or may be stored in a management server outside the vehicle  1 . In the latter case, the first map information acquisition device  111  communicates with the management server to acquire the necessary first map information  151 . 
     The first position information acquiring device  112  acquires the first position information  152  indicating a position and an orientation of the vehicle  1 . For example, the first position information acquiring device  112  includes a GPS (Global Positioning System) device for measuring the position and the orientation of the vehicle  1 . The first position information acquisition device  112  may perform well-known localization to increase accuracy of the first position information  152 . 
     The first vehicle state sensor  113  acquires the first vehicle state information  153  indicating a state of the vehicle  1 . For example, the first vehicle state sensor  113  includes a vehicle speed sensor, a yaw rate sensor, an acceleration sensor, a steering angle sensor, and the like. The vehicle speed sensor detects a vehicle speed (i.e., a speed of the vehicle  1 ). The yaw rate sensor detects a yaw rate of the vehicle  1 . The acceleration sensor detects an acceleration (e.g., a lateral acceleration, a longitudinal acceleration, a vertical acceleration) of the vehicle  1 . The steering angle sensor detects a steering angle (a wheel turning angle) of the vehicle  1 . 
     The first surrounding situation sensor  114  recognizes (detects) a situation around the vehicle  1 . For example, the first surrounding situation sensor  114  includes at least one of a camera, a LIDAR (Laser Imaging Detection and Ranging), and a radar. The first surrounding situation information  154  indicates a result of recognition by the first surrounding situation sensor  114 . For example, the first surrounding situation information  154  includes target information about a target recognized by the first surrounding situation sensor  114 . The target is exemplified by a surrounding vehicle, a pedestrian, a roadside structure, an obstacle, a white line (lane marking), and the like. The target information includes information on a relative position and a relative velocity of the target with respect to the vehicle  1 . 
     The first communication device  115  communicates with the outside of the vehicle  1 . For example, the first communication device  115  communicates with an external device outside of the vehicle  1  via a communication network. The first communication device  115  may perform V2I communication (vehicle-to-infrastructure communication) with a surrounding infrastructure. The first communication device  115  may perform V2V communication (vehicle-to-vehicle communication) with a surrounding vehicle. The first delivery information  155  is information acquired through the first communication device  115 . For example, the first delivery information  155  includes information on the surrounding vehicle and road traffic information (e.g., road work zone information, accident information, traffic restriction information, traffic jam information, etc.). 
     It should be noted that a part of the first information acquisition device  110  may be included in the vehicle travel control device  200 . That is, the automated driving control device  100  and the vehicle travel control device  200  may share a part of the first information acquisition device  110 . In that case, the automated driving control device  100  and the vehicle travel control device  200  exchange necessary information with each other. 
     Referring again to  FIG.  5   , the first input/output interface  130  is communicably connected with the vehicle travel control device  200 . 
     The first control device  120  (i.e., a first controller) is an information processing device for executing a variety of processing. For example, the first control device  120  is a microcomputer. The first control device  120  is also called an ECU (Electronic Control Unit). More specifically, the first control device  120  includes a first processor  121  and a first memory device  122 . 
     A variety of information is stored in the first memory device  122 . For example, the first driving environment information  150  acquired by the first information acquisition device  110  is stored in the first memory device  122 . The first memory device  122  is exemplified by a volatile memory, a nonvolatile memory, an HDD (Hard Disk Drive), and the like. 
     The first processor  121  executes automated driving software which is a computer program. The automated driving software is stored in the first memory device  122  or recorded on a computer-readable recording medium. The functions of the first control device  120  (the first processor  121 ) are realized by the first processor  121  executing the automated driving software. 
     According to the present embodiment, the first control device  120  (the first processor  121 ) is responsible for the management of the automated driving of the vehicle  1 . In particular, the first control device  120  generates the first target trajectory TR1 for the automated driving of the vehicle  1 . Hereinafter, generating the first target trajectory TR1 will be described in more detail. 
     2-2. Generating First Target Trajectory 
       FIG.  7    is a flow chart showing processing by the first control device  120  (the first processor  121 ) of the automated driving control device  100  according to the present embodiment. During the automated driving of the vehicle  1 , the process flow shown in  FIG.  7    is repeatedly executed at a regular interval. 
     In Step S 110 , the first control device  120  acquires the first driving environment information  150  from the first information acquisition device  110 . The first driving environment information  150  is stored in the first memory device  122 . 
     In Step S 120 , the first control device  120  generates the first target trajectory TR1 for the automated driving of the vehicle  1 , based on the first driving environment information  150 . More specifically, the first control device  120  generates a travel plan of the vehicle  1  during the automated driving, based on the first driving environment information  150 . The travel plan includes maintaining a current travel lane, making a lane change, avoiding an obstacle, and so forth. Then, the first control device  120  generates the first target trajectory TR1 required for the vehicle  1  to travel in accordance with the travel plan, based on the first driving environment information  150 . 
     For example, the first control device  120  generates the first target trajectory TR1 for traveling while maintaining a current travel lane. More specifically, based on the first map information  151  (the lane configuration) and the first position information  152 , the first control device  120  recognizes a travel lane in which the vehicle  1  is traveling and acquires a configuration shape of the travel lane ahead of the vehicle  1 . Alternatively, based on the first surrounding situation information  154 , the first control device  120  may recognize a lane marking (i.e., a white line) of the travel lane and recognize a configuration shape of the travel lane ahead of the vehicle  1 . Then, the first control device  120  generates the first target trajectory TR1 for traveling while maintaining the travel lane, based on the configuration shape of the travel lane ahead of the vehicle  1 . 
     As another example, the first control device  120  may generate the first target trajectory TR1 for making a lane change. More specifically, based on the first map information  151  (the lane configuration), the first position information  152 , and a destination, the first control device  120  plans to make a lane change in order to reach the destination. Then, the first control device  120  generates the first target trajectory TR1 for realizing the lane change, based on the first map information  151  (the lane configuration), the first position information  152 , the first vehicle state information  153 , and the first surrounding situation information  154  (the positions of other vehicles). 
     As yet another example, the first control device  120  may generate the first target trajectory TR1 for avoiding a collision between the vehicle  1  and a surrounding object. More specifically, based on the first surrounding situation information  154  (the target information), the first control device  120  recognizes an avoidance target (e.g., a surrounding vehicle, a pedestrian) ahead of the vehicle  1 . Furthermore, based on the first vehicle state information  153  and the first surrounding situation information  154  (the target information), the first control device  120  predicts respective future positions of the vehicle  1  and the avoidance target and calculates a possibility that the vehicle  1  collides with the avoidance target. If the possibility that the vehicle  1  collides with the avoidance target is equal to or higher than a threshold, the first control device  120  generates the first target trajectory TR1 for avoiding the collision based on the first vehicle state information  153  (the target information) and the first surrounding situation information  154 . Typically, the first target trajectory TR1 for avoiding the collision demands at least one of the steering and the deceleration. 
     In Step S 130 , the first control device  120  outputs the generated first target trajectory TR1 to the vehicle travel control device  200  via the first input/output interface  130 . Every time the first target trajectory TR1 is updated, the latest first target trajectory TR1 is output to the vehicle travel control device  200 . 
     3. Vehicle Travel Control Device  200   
     3-1. Configuration Example 
       FIG.  8    is a block diagram showing a configuration example of the vehicle travel control device  200  according to the present embodiment. The vehicle travel control device  200  is provided with a second information acquisition device  210 , a second control device  220 , a second input/output interface  230 , and a travel device  240 . 
     The second information acquisition device  210  acquires second driving environment information  250 . The second driving environment information  250  is information indicating a driving environment for the vehicle  1  and necessary for the vehicle travel control and the travel assist control by the vehicle travel control device  200 . 
       FIG.  9    is a block diagram showing an example of the second information acquisition device  210  and the second driving environment information  250 . The second information acquisition device  210  includes a second map information acquisition device  211 , a second position information acquisition device  212 , a second vehicle state sensor  213 , a second surrounding situation sensor  214 , and a second communication device  215 . The second driving environment information  250  includes second map information  251 , second position information  252 , second vehicle state information  253 , second surrounding situation information  254 , and second delivery information  255 . 
     The second map information acquisition device  211  acquires the second map information  251 . The second map information  251  indicates a lane configuration and a road shape. The second map information acquisition device  211  acquires the second map information  251  of a necessary area from a map database. The map database may be stored in a predetermined memory device mounted on the vehicle  1 , or may be stored in a management server outside the vehicle  1 . In the latter case, the second map information acquisition device  211  communicates with the management server to acquire the necessary second map information  251 . 
     The second position information acquiring device  212  acquires the second position information  252  indicating a position and an orientation of the vehicle  1 . For example, the second position information acquiring device  212  includes a GPS device for measuring the position and the orientation of the vehicle  1 . The second position information acquisition device  212  may perform well-known localization to increase accuracy of the second position information  252 . 
     The second vehicle state sensor  213  acquires the second vehicle state information  253  indicating a state of the vehicle  1 . For example, the second vehicle state sensor  213  includes a vehicle speed sensor, a yaw rate sensor, an acceleration sensor, a steering angle sensor, and the like. The vehicle speed sensor detects a vehicle speed (i.e., a speed of the vehicle  1 ). The yaw rate sensor detects a yaw rate of the vehicle  1 . The acceleration sensor detects an acceleration (e.g., a lateral acceleration, a longitudinal acceleration, a vertical acceleration) of the vehicle  1 . The steering angle sensor detects a steering angle (a wheel turning angle) of the vehicle  1 . 
     The second surrounding situation sensor  214  recognizes (detects) a situation around the vehicle  1 . For example, the second surrounding situation sensor  214  includes at least one of a camera, a LIDAR, and a radar. The second surrounding situation information  254  indicates a result of recognition by the second surrounding situation sensor  214 . For example, the second surrounding situation information  254  includes target information about a target recognized by the second surrounding situation sensor  214 . The target is exemplified by a surrounding vehicle, a pedestrian, a roadside structure, an obstacle, a white line (lane marking), and the like. The target information includes information on a relative position and a relative velocity of the target with respect to the vehicle  1 . 
     The second communication device  215  communicates with the outside of the vehicle  1 . For example, the second communication device  215  communicates with an external device outside of the vehicle  1  via a communication network. The second communication device  215  may perform V2I communication (vehicle-to-infrastructure communication) with a surrounding infrastructure. The second communication device  215  may perform V2V communication (vehicle-to-vehicle communication) with a surrounding vehicle. The second delivery information  255  is information acquired through the second communication device  215 . For example, the second delivery information  255  includes information on the surrounding vehicle and road traffic information (e.g., road work zone information, accident information, traffic restriction information, traffic jam information, etc.). 
     It should be noted that the first information acquisition device  110  and the second information acquisition device  210  may be partially identical. For example, the first map information acquisition device  111  and the second map information acquisition device  211  may be identical. The first position information acquisition device  112  and the second position information acquisition device  212  may be identical. The first vehicle state sensor  113  and the second vehicle state sensor  213  may be identical. That is to say, the automated driving control device  100  and the vehicle travel control device  200  may share a part of the second information acquisition device  210 . In that case, the automated driving control device  100  and the vehicle travel control device  200  exchange necessary information with each other. 
     Referring again to  FIG.  8   , the second input/output interface  230  is communicably connected with the automated driving control device  100 . 
     The travel device  240  includes a steering device  241 , a driving device  242 , and a braking device  243 . The steering device  241  turns (i.e., changes a direction of) a wheel of the vehicle  1 . For example, the steering device  241  includes a power steering (EPS: Electric Power Steering) device. The driving device  242  is a power source that generates a driving force. The driving device  242  is exemplified by an engine, an electric motor, an in-wheel motor, and the like. The braking device  243  generates a braking force. 
     The second control device  220  (i.e., a second controller) is an information processing device for executing a variety of processing. For example, the second control device  220  is a microcomputer. The second control device  220  is also called an ECU. More specifically, the second control device  220  includes a second processor  221  and a second memory device  222 . 
     A variety of information is stored in the second memory device  222 . For example, the second driving environment information  250  acquired by the second information acquisition device  210  is stored in the second memory device  222 . The second memory device  222  is exemplified by a volatile memory, a nonvolatile memory, an HDD, and the like. 
     The second processor  221  executes vehicle travel control software which is a computer program. The vehicle travel control software is stored in the second memory device  222  or recorded on a computer-readable recording medium. The functions of the second control device  220  (the second processor  221 ) are realized by the second processor  221  executing the vehicle travel control software. 
     3-2. Vehicle Travel Control 
     The second control device  220  (the second processor  221 ) executes the “vehicle travel control” that controls the steering, the acceleration, and the deceleration of the vehicle  1 . The second control device  220  executes the vehicle travel control by controlling an operation of the travel device  240 . More specifically, the second control device  220  controls the steering (turning of the wheel) of the vehicle  1  by controlling an operation of the steering device  241 . The second control device  220  controls the acceleration of the vehicle  1  by controlling an operation of the driving device  242 . The second control device  220  controls the deceleration of the vehicle  1  by controlling an operation of the braking device  243 . 
     In particular, the second control device  220  executes the vehicle travel control such that the vehicle  1  follows the target trajectory TR. In this case, the second control device  220  calculates a deviation between the vehicle  1  and the target trajectory TR based on the target trajectory TR, the second position information  252 , and the second vehicle state information  253 . The deviation includes a lateral deviation (i.e., an Y-direction deviation), a yaw angle deviation (i.e., an azimuth angle deviation), and a velocity deviation. Then, the second control device  220  performs the vehicle travel control such that the deviation between the vehicle  1  and the target trajectory TR decreases. 
     In the vehicle travel control, the second control device  220  calculates a control amount for controlling the travel device  240 , that is, a control amount of at least one of the steering, the acceleration, and the deceleration. The control amount required for the vehicle  1  to follow the target trajectory TR, that is, the control amount required for reducing the deviation between the vehicle  1  and the target trajectory TR is hereinafter referred to as a “required control amount CON.” The required control amount CON is exemplified by a target steering angle, a target yaw rate, a target velocity, a target acceleration, a target deceleration, a target torque, a target current, and the like. The second control device  220  controls the operation of the travel device  240 , that is, controls at least one of the steering, the acceleration, and the deceleration in accordance with the required control amount CON. 
     For example, the steering control using the steering device  241  is as follows. The second control device  220  calculates a target yaw rate required for reducing the deviation between the vehicle  1  and the target trajectory TR. Furthermore, the second control device  220  calculates a target steering angle according to a yaw rate deviation which is a difference between the target yaw rate and an actual yaw rate. The actual yaw rate is detected by the second vehicle state sensor  213  and included in the second vehicle state information  253 . The target steering angle becomes larger as the yaw rate deviation becomes larger. Then, the second control device  220  performs feedback control of the steering device  241  such that an actual steering angle follows the target steering angle. The actual steering angle is detected by the second vehicle state sensor  213  and included in the second vehicle state information  253 . 
     3-3. Processing Related to Travel Assist Control 
     The second control device  220  (the second processor  221 ) further executes the “travel assist control” that assists the travel of the vehicle  1 . The travel assist control controls at least one of the steering, the acceleration, and the deceleration of the vehicle  1  for at least one of improving safety or comfort of the travel of the vehicle  1 , reducing a sense of strangeness or insecurity of an occupant of the vehicle  1 , and stabilizing behavior of the vehicle  1 . The travel assist control is exemplified by collision avoidance control, lane departure suppression control, damping control, vehicle stability control, and the like. The collision avoidance control assists avoidance of a collision between the vehicle  1  and a surrounding object (namely, an avoidance target). The lane departure suppression control suppresses the vehicle  1  from departing from a travel lane. The damping control suppresses pitching and rolling of the vehicle  1 . The vehicle stability control suppresses unstable behavior such as vehicle spin. 
       FIG.  10    is a flow chart showing an example of processing related to the travel assist control by the second control device  220  (the second processor  221 ). The process flow shown in  FIG.  10    is repeatedly executed at a regular interval. Here, the automated driving of the vehicle  1  is in execution. 
     3-3-1. Step S 210   
     In Step S 210 , the second control device  220  acquires the second driving environment information  250  from the second information acquisition device  210 . The second driving environment information  250  is stored in the second memory device  222 . Moreover, the second control device  220  receives information indicating the first target trajectory TR1 from the automated driving control device  100  via the second input/output interface  230 . The information indicating the first target trajectory TR1 is stored in the second memory device  222 . 
     3-3-2. Step S 220   
     In Step S 220 , the second control device  220  determines whether or not the travel assist control needs to be activated based on the second driving environment information  250 . In other words, the second control device  220  determines whether or not the “activation condition” for activating the travel assist control is satisfied, based on the second driving environment information  250 . 
     As an example of the travel assist control, let us consider the collision avoidance control. Based on the second surrounding situation information  254  (the target information), the second control device  220  recognizes an avoidance target (e.g., a surrounding vehicle, a pedestrian) ahead of the vehicle  1 . Furthermore, based on the second vehicle state information  253  and the second surrounding situation information  254  (the target information), the second control device  220  predicts respective future positions of the vehicle  1  and the avoidance target and calculates a possibility that the vehicle  1  collides with the avoidance target. The activation condition of the collision avoidance control is that the possibility that the vehicle  1  collides with the avoidance target is equal to or higher than a threshold. 
     As another example of the travel assist control, let us consider the lane departure suppression control. For example, when the vehicle  1  wobbles within the travel lane and comes close to a lane marking (a white line) of the travel lane, the lane departure suppression control steers the vehicle  1  so as to return back to a center of the travel lane. For that purpose, the second control device  220  recognizes, based on the second surrounding situation information  254 , the lane marking of the travel lane in which the vehicle  1  is traveling and monitors a distance between the vehicle  1  and the lane marking. A first activation condition of the lane departure suppression control is that the distance between the vehicle  1  and the lane marking of the travel lane becomes less than a predetermined distance threshold. 
     In addition, the lane departure suppression control decelerates the vehicle  1  when predicting that the vehicle  1  is not able to turn a curve located ahead of the vehicle  1 . For that purpose, the second control device  220  acquires a road shape in front of the vehicle  1  based on the second map information  251  and the second position information  252 . Then, the second control device  220  determines, based on the road shape and the second vehicle state information  253  (the vehicle speed, etc.), whether or not the vehicle  1  is able to turn the curve located ahead of the vehicle  1  without departing from the travel lane. At this time, the second control device  220  may perform the determination in consideration of a road surface condition (a road surface friction coefficient). The road surface condition can be estimated by a well-known technique utilizing the second vehicle state information  253  or the second surrounding situation information  254 . A second activation condition of the lane departure suppression control is that it is determined that the vehicle  1  is not able to turn the curve located ahead of the vehicle  1  without departing from the travel lane. 
     When the activation condition of the travel assist control is satisfied (Step S 220 ; Yes), the processing proceeds to Step S 230 . On the other hand, when the activation condition of the travel assist control is not satisfied (Step S 220 ; No), the processing proceeds to Step S 250 . 
     3-3-3. Step S 230   
     The second control device  220  generates the second target trajectory TR2 for the travel assist control. For example, the second target trajectory TR2 for the collision avoidance control demands at least one of the steering and the deceleration of the vehicle  1  in order to avoid the collision with the avoidance target. 
     As another example, when the first activation condition of the lane departure suppression control is satisfied, the second target trajectory TR2 demands such the steering that returns the vehicle  1  back to the center of the travel lane. When the second activation condition of the lane departure suppression control is satisfied, the second target trajectory TR2 demands the deceleration of the vehicle  1  in order to suppress lane departure at the curve ahead. 
     The second control device  220  stores information of the second target trajectory TR2 in the second memory device  222 . After that, the processing proceeds to Step S 240 . 
     3-3-4. Step S 240   
     Both the first target trajectory TR1 for the automated driving and the second target trajectory TR2 for the travel assist control exist coincidentally. Therefore, the second control device  220  arbitrates between the first target trajectory TR1 and the second target trajectory TR2. In particular, according to the present embodiment, the second control device  220  executes the vehicle travel control by giving more priority to the first target trajectory TR1 than to the second target trajectory TR2. In other words, the second control device  220  executes the vehicle travel control by giving more “weight” to the first target trajectory TR1 than to the second target trajectory TR2. 
       FIG.  11    is a conceptual diagram showing an example of the processing in Step S 240 . The second control device  220  performs arbitration processing that determines a definitive target trajectory TR based on the first target trajectory TR1 and the second target trajectory TR2. The target trajectory TR is expressed by the following Equation (1). 
         TR=W 1× TR 1+ W 2× TR 2  Equation (1)
 
     A first weight W1 is a weight of the first target trajectory TR1 with respect to the target trajectory TR. A second weight W2 is a weight of the second target trajectory TR2 with respect to the target trajectory TR. The first weight W1 is greater than the second weight W2 (i.e., W1&gt;W2). In other words, the first weight W1 is greater than 0.5 and equal to or less than 1, and the second weight W2 is equal to or greater than 0 and less than 0.5. The first weight W1 being 1 and the second weight W2 being 0 are equivalent to that the first target trajectory TR1 is selected as the target trajectory TR. 
     The second control device  220  calculates the required control amount CON required for the vehicle  1  to follow the target trajectory TR. Then, the second control device  220  controls the operation of the travel device  240 , that is, controls at least one of the steering, the acceleration, and the deceleration in accordance with the required control amount CON. 
       FIG.  12    is a conceptual diagram showing another example of the processing in Step S 240 . The processing shown in  FIG.  12    also is included in “the executing the vehicle travel control by giving more weight to the first target trajectory TR1 than to the second target trajectory TR2.” 
     More specifically, the second control device  220  calculates the required control amount CON required for the vehicle  1  to follow the first target trajectory TR1 as a “first required control amount CON1.” In addition, the second control device  220  calculates the required control amount CON required for the vehicle  1  to follow the second target trajectory TR2 as a “second required control amount CON2.” Then, the second control device  220  performs arbitration processing that determines a definitive required control amount CON by combining the first required control amount CON1 and the second required control amount CON2. The required control amount CON is expressed by the following Equation (2). 
         CON=W 1× CON 1+ W 2× CON 2  Equation (2)
 
     A first weight W1 is a weight of the first required control amount CON1 with respect to the required control amount CON. A second weight W2 is a weight of the second required control amount CON2 with respect to the required control amount CON. The first weight W1 is greater than the second weight W2 (i.e., W1&gt;W2). In other words, the first weight W1 is greater than 0.5 and equal to or less than 1, and the second weight W2 is equal to or greater than 0 and less than 0.5. The first weight W1 being 1 and the second weight W2 being 0 are equivalent to that the first required control amount CON1 is selected as the required control amount CON. 
     When the required control amount CON is determined, the second control device  220  controls the operation of the travel device  240 , that is, controls at least one of the steering, the acceleration, and the deceleration in accordance with the required control amount CON. The processing shown in  FIG.  12    also brings about the same effects as in the case of  FIG.  11   . 
     3-3-5. Step S 250   
     The activation condition of the travel assist control is not satisfied, and thus the second target trajectory TR2 is not generated. The second control device  220  executes the vehicle travel control by using the first target trajectory TR1 received from the automated driving control device  100  as the target trajectory TR. That is, the second control device  220  executes the vehicle travel control such that the vehicle  1  follows the first target trajectory TR1. 
       FIG.  13    is a conceptual diagram showing the processing in Step S 250 . The second control device  220  calculates the required control amount CON(=CON1) required for the vehicle  1  to follow the target trajectory TR (=TR1). Then, the second control device  220  controls the operation of the travel device  240 , that is, controls at least one of the steering, the acceleration, and the deceleration in accordance with the required control amount CON(=CON1). 
     4. Priority Condition 
     There is no need to always give priority to the first target trajectory TR1. In order to make more flexible operation possible, the priority may be conditionally given to the first target trajectory TR1. Hereinafter, a case where a “priority condition” for giving priority to the first target trajectory TR1 is taken into consideration will be described. 
       FIG.  14    is a flow chart showing the processing related to the travel assist control in the case where the priority condition is taken into consideration. An overlapping description with the foregoing  FIG.  10    will be omitted as appropriate. Compared to the foregoing  FIG.  10   , Step S 235  and Step S 260  are added after Step S 230 . 
     In Step S 235 , the second control device  220  determines whether or not the priority condition for giving priority to the first target trajectory TR1 is satisfied. When the priority condition is satisfied (Step S 235 ; Yes), the processing proceeds to Step S 240 . 
     On the other hand, when the priority condition is not satisfied (Step S 235 ; No), the processing proceeds to Step S 260 . In Step S 260 , the second control device  220  executes the vehicle travel control by giving more priority to the second target trajectory TR2 than to the first target trajectory TR1. In other words, the second control device  220  executes the vehicle travel control by giving more weight to the second target trajectory TR2 than to the first target trajectory TR1. For example, the second control device  220  executes the vehicle travel control by using the second target trajectory TR2 as the target trajectory TR. As a result, the effects of the travel assist control are sufficiently obtained. 
     In this manner, the priority is not always but conditionally given to the first target trajectory TR1. It is therefore possible to suppress decrease in the continuity of the automated driving while appropriately utilizing the travel assist control. 
     Hereinafter, various examples of the priority condition will be described. It should be noted that the priority condition may include two or more of the various examples described below as long as no contradiction occurs. When at least any priority condition is satisfied (Step S 235 ; Yes), the processing proceeds to Step S 240 . 
     4-1. First Example 
     In the following description, a “first steering direction” is a steering direction required for the vehicle  1  to follow the first target trajectory TR1, that is, a steering direction required by the automated driving control device  100 . On the other hand, a “second steering direction” is a steering direction required for the vehicle  1  to follow the second target trajectory TR2, that is, the steering direction required by the travel assist control. 
     A first example of the priority condition is that “the first steering direction is the same as the second steering direction.” When this priority condition is satisfied, the automated driving control device  100  is considered to recognize risks from the same point of view as the travel assist control. Giving priority to the first target trajectory TR1 required by the automated driving control device  100  makes it possible to secure the continuity of the automated driving while achieving equivalent effects as in the case of the travel assist control. 
     The second control device  220  can determine whether or not the first steering direction is the same as the second steering direction by comparing the second position information  252  (i.e., the position and orientation of the vehicle  1 ), the first target trajectory TR1, and the second target trajectory TR2. Alternatively, the second control device  220  may calculate the first required control amount CON1 and the second required control amount CON2 described above and compare the first required control amount CON1 and the second required control amount CON2 to determine whether or not the first steering direction is the same as the second steering direction. In the present example, the first required control amount CON1 includes a first steering control amount for steering in the first steering direction, and the second required control amount CON2 includes a second steering control amount for steering in the second steering direction. 
     4-2. Second Example 
     A second example of the priority condition is that “the first steering direction is opposite to the second steering direction.” When this priority condition is satisfied, there is a possibility that the travel assist control function GD of the vehicle travel control device  200  has low performance. Giving priority to the first target trajectory TR1 required by the automated driving control device  100  makes it possible to suppress influence of the low-performance travel assist and to suppress decrease in the continuity of the automated driving. 
     The second control device  220  can determine whether or not the first steering direction is opposite to the second steering direction by comparing the second position information  252 , the first target trajectory TR1, and the second target trajectory TR2. Alternatively, the second control device  220  may determine whether or not the first steering direction is opposite to the second steering direction by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-3. Third Example 
     Here, a case where the target trajectory TR includes not only the target position [Xi, Yi] of the vehicle  1  but also the target velocity [VXi, VYi] (see  FIG.  1   ) is considered. A third example of the priority condition is that “deceleration is required to follow the first target trajectory TR1, and deceleration is also required to follow the second target trajectory TR2 as well.” When this priority condition is satisfied, the automated driving control device  100  is considered to recognize risks from the same point of view as the travel assist control. Giving priority to the first target trajectory TR1 required by the automated driving control device  100  makes it possible to secure the continuity of the automated driving while achieving equivalent effects as in the case of the travel assist control. 
     The second control device  220  can determine whether or not the third example of the priority condition is satisfied by comparing the second vehicle state information  253  (i.e., the vehicle speed), the first target trajectory TR1, and the second target trajectory TR2. Alternatively, the second control device  220  may calculate the first required control amount CON1 and the second required control amount CON2 described above and compare the first required control amount CON1 and the second required control amount CON2 to determine whether or not the third example of the priority condition is satisfied. In the present example, the first required control amount CON1 includes a first deceleration control amount for decelerating, and the second required control amount CON2 includes a second deceleration control amount for decelerating. 
     4-4. Fourth Example 
     A fourth example of the priority condition is that “deceleration is required to follow the first target trajectory TR1 and acceleration is required to follow the second target trajectory TR2.” When this priority condition is satisfied, there is a possibility that the travel assist control function GD of the vehicle travel control device  200  has low performance. Giving priority to the first target trajectory TR1 makes it possible to suppress influence of the low-performance travel assist and to suppress decrease in the continuity of the automated driving. 
     The second control device  220  can determine whether or not the fourth example of the priority condition is satisfied by comparing the second vehicle state information  253  (i.e., the vehicle speed), the first target trajectory TR1, and the second target trajectory TR2. Alternatively, the second control device  220  may determine whether or not the fourth example of the priority condition is satisfied by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-5. Fifth Example 
     A fifth example is a modification of the third example. In the following description, a “first deceleration” is a deceleration required for the vehicle  1  to follow the first target trajectory TR1, that is, a deceleration required by the automated driving control device  100 . On the other hand, a “second deceleration” is a deceleration required for the vehicle  1  to follow the second target trajectory TR2, that is, a deceleration required by the travel assist control. 
     In the fifth example, a case where the second deceleration is equal to or higher than a deceleration threshold is considered in particular. The deceleration threshold is an upper limit of a deceleration range desired in terms of stable behavior of the vehicle  1 . When the second deceleration is equal to or higher than the deceleration threshold, the travel assist control function GD of the vehicle travel control device  200  is considered to have low performance. 
     In view of the above, a fifth example of the priority condition is that “the second deceleration is equal to or higher than the deceleration threshold and the first deceleration is lower than the second deceleration.” Giving priority to the first deceleration (i.e., the first target trajectory TR1) makes it possible to relax the high deceleration state and suppress unstable behavior of the vehicle  1 . 
     The second control device  220  calculates the first required control amount CON1 and the second required control amount CON2. The first required control amount CON1 includes a first deceleration control amount for generating the first deceleration. The second required control amount CON2 includes a second deceleration control amount for generating the second deceleration. The second control device  220  can determine whether or not the fifth example of the priority condition is satisfied by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-6. Sixth Example 
     In the fifth example described above, it is also possible to replace the deceleration with a lateral acceleration (lateral G). In the following description, a “first lateral acceleration” is a lateral acceleration required for the vehicle  1  to follow the first target trajectory TR1, that is, a lateral acceleration required by the automated driving control device  100 . On the other hand, a “second lateral acceleration” is a lateral acceleration required for the vehicle  1  to follow the second target trajectory TR2, that is, a lateral acceleration required by the travel assist control. A lateral acceleration threshold is an upper limit of a lateral acceleration range desired in terms of stable behavior of the vehicle  1 . When the second lateral acceleration is equal to or higher than the lateral acceleration threshold, the travel assist control function GD of the vehicle travel control device  200  is considered to have low performance. 
     A sixth example of the priority condition is that “the second lateral acceleration is equal to or higher than the lateral acceleration threshold and the first lateral acceleration is lower than the second lateral acceleration.” Giving priority to the first lateral acceleration (i.e., the first target trajectory TR1) makes it possible to relax the high lateral acceleration state and suppress unstable behavior of the vehicle  1 . 
     The second control device  220  calculates the first required control amount CON1 and the second required control amount CON2. The first required control amount CON1 includes a first travel control amount for generating the first lateral acceleration. The second required control amount CON2 includes a second travel control amount for generating the second lateral acceleration. The second control device  220  can determine whether or not the sixth example of the priority condition is satisfied by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-7. Seventh Example 
     A seventh example of the priority condition includes that “the second required control amount CON2 is less than a predetermined value or the first required control amount CON1.” For example, the seventh example of the priority condition includes that “the second deceleration is lower than a predetermined deceleration or the first deceleration.” As another example, the seventh example of the priority condition includes that “the second lateral acceleration is lower than a predetermined lateral acceleration or the first lateral acceleration.” Similarly, the seventh example of the priority condition includes that “a second steering angle required to follow the second target trajectory TR2 is less than a predetermined steering angle or a first steering angle required to follow the first target trajectory TR1.” 
     When the second required control amount CON2 is less than the predetermined value or the first required control amount CON1, it is considered that urgency of the travel assist control is low and the travel assist control has limited effectiveness. Giving priority to the first required control amount CON1 (i.e., the first target trajectory TR1) makes it possible to suppress influence of the travel assist and to suppress decrease in the continuity of the automated driving. 
     The second control device  220  calculates the first required control amount CON1 and the second required control amount CON2. Then, the second control device  220  determines whether or not the seventh example of the priority condition is satisfied by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-8. Eighth Example 
     An eighth example of the priority condition includes that “the first required control amount CON1 is less than the second required control amount CON2.” For example, the eighth example of the priority condition includes that “the first deceleration is lower than the second deceleration.” As another example, the eighth example of the priority condition includes that “the first lateral acceleration is lower than the second lateral acceleration.” Similarly, the eighth example of the priority condition may include that “the first steering angle required to follow the first target trajectory TR1 is smaller than the second steering angle required to follow the second target trajectory TR2.” 
     A fact that the first required control amount CON1 is less than the second required control amount CON2 means that the second required control amount CON2 is unnecessarily excessive. Giving priority to the first required control amount CON1 (i.e., the first target trajectory TR1) makes it possible to suppress influence of the travel assist and to suppress decrease in the continuity of the automated driving. 
     The second control device  220  calculates the first required control amount CON1 and the second required control amount CON2. Then, the second control device  220  determines whether or not the eighth example of the priority condition is satisfied by comparing the first required control amount CON1 and the second required control amount CON2. 
     4-9. Ninth Example 
     In the following description, first reliability is reliability of the automated driving control device  100 . Second reliability is reliability of the travel assist control by the vehicle travel control device  200 . A ninth example of the priority condition is that “the first reliability is higher than the second reliability.” Giving priority to the first target trajectory TR1 makes it possible to suppress influence of the low-reliability travel assist and to suppress decrease in the continuity of the automated driving. 
     Various examples can be considered as a method of calculating the reliability. For example, the reliability is calculated from a sensor configuration and a sensor performance of each of the automated driving control device  100  and the vehicle travel control device  200 . 
     The first information acquisition device  110  of the automated driving control device  100  includes the first surrounding situation sensor  114  (see  FIGS.  5  and  6   ). The sensor that can be used as the first surrounding situation sensor  114  is exemplified a cameras, a LIDAR, a radar, a sonar, and so forth. The first reliability increases as the number of types of the sensors included in the first surrounding situation sensor  114  increases. The first reliability increases as the number of sensors of the same type included in the first surrounding situation sensor  114  increases. For example, when the first surrounding situation sensor  114  includes a plurality of cameras for imaging the front, rear, left, and right directions of the vehicle  1 , respectively, the first reliability becomes high. The first reliability increases as the performance (e.g., a field of view, resolution, effective range, spatial resolution, etc.) of each sensor included in the first surrounding situation sensor  114  becomes higher. The first reliability is calculated in advance by the use of a predetermined map or the like. Alternatively, the first reliability may be calculated in real time based on a state (normal/failure) of each sensor included in the first surrounding situation sensor  114 . The first reliability may be a numerical value or may be a rank (level). 
     On the other hand, the second information acquisition device  210  of the vehicle travel control device  200  includes the second surrounding situation sensor  214  (see  FIGS.  8  and  9   ). The second reliability of the second surrounding situation sensor  214  can be calculated as in the case of the first reliability of the first surrounding situation sensor  114 . 
     The second control device  220  acquires first reliability information indicating the first reliability of the automated driving control device  100 . For example, the first reliability information is provided in advance from a developer of the automated driving control device  100 . As another example, the first control device  120  of the automated driving control device  100  may calculate the first reliability and transmit the first reliability information to the vehicle travel control device  200  through the first input/output interface  130 . As yet another example, the first control device  120  of the automated driving control device  100  may transmit information necessary for calculating the first reliability to the vehicle travel control device  200  through the first input/output interface  130 . In that case, the second control device  220  calculates the first reliability based on the information received from the automated driving control device  100  to generate the first reliability information. The first reliability information is stored in the second memory device  222 . 
     Moreover, the second control device  220  acquires second reliability information indicating the second reliability of the travel assist control. For example, the second reliability information is provided in advance from a developer of the vehicle travel control device  200 . As another example, the second control device  220  may calculate the second reliability and generate the second reliability information. The second reliability information is stored in the second memory device  222 . Then, the second control device  220  determines whether or not the first reliability is higher than the second reliability by comparing the first reliability information and the second reliability information. 
     4-10. Tenth Example 
     Here, as an example of the travel assist control, let us consider the collision avoidance control that assists avoidance of a collision between the vehicle  1  and a surrounding object. When the activation condition of the collision avoidance control is satisfied, the second control device  220  predicts severity of damage due to the collision based on the second driving environment information  250 . 
     For example, the severity increases as the relative velocity between the vehicle  1  and the object (avoidance target) becomes higher. The severity when the object is a human is higher than the severity when the object is a non-human. If hardness and/or a size of the object is identified based on a result of detection of the object, information thereof may be taken into consideration. A collision form (front collision, offset collision, side collision, etc.) may be taken into consideration. The severity may be calculated by the use of a predetermined map. The severity may be a numerical value or may be a rank (level). 
     A tenth example of the priority condition is that “the severity of damage due to the collision between the vehicle  1  and the surrounding object is less than a threshold.” In other words, the tenth example of the priority condition is that “influence of the collision between the vehicle  1  and the surrounding object is negligibly small.” Giving priority to the first target trajectory TR1 makes it possible to suppress decrease in the continuity of the automated driving. 
     5. MODIFICATION EXAMPLES 
     5-1. First Modification Example 
     The activation condition of the travel assist control in Step S 220  may be variably set according to an operating state of the vehicle  1 . 
     As an example, let us consider a case where a driver operates the vehicle  1  manually. In this case, the travel assist control is expected to make up for the driver&#39;s mistake in the manual driving operation. However, if the travel assist control is activated too early, the manual driving operation by the driver is hindered and thus comfort is deteriorated. In view of the above, in the case of the manual driving, the activation condition is set so that the travel assist control is less likely to be activated as compared with the case of the automated driving. Moreover, the activation condition is set so that the travel assist control is more likely to be activated as the automated driving level becomes higher. 
     As another example, let us consider a case where an operator of a control center remotely controls the vehicle  1 . In the case of the remote control, the operator recognizes an object by checking camera image transmitted from the vehicle  1  and the like, and issues an instruction to the vehicle  1 . However, a delay and/or a mistake in the object recognition and the instruction timing may occur due to communication delay and/or limited camera performance (angle of view, resolution). In view of the above, in the case of the remote control, the activation condition is set so that the travel assist control is more likely to be activated as compared with the other cases. 
     5-2. Second Modification Example 
     In Step S 230 , the second control device  220  may directly calculate the control amount of the travel device  240  for the travel assist control without generating the second target trajectory TR2. The control amount of at least one of the steering, the acceleration, and the deceleration required for the travel assist control is hereinafter referred to as a “travel assist control amount.” For example, the second control device  220  calculates the travel assist control amount of at least one of the steering and the deceleration required for avoiding a collision with the avoidance target. The travel assist control amount corresponds to the second required control amount CON2 described above. 
     The “second target trajectory TR2” in the above-described embodiment is replaced with the “travel assist control amount.” That is, even when the travel assist control amount is calculated during the automated driving, the second control device  220  executes the vehicle travel control by giving more weight to the first target trajectory TR1 than to the travel assist control amount (Step S 240 ). In other words, the second control device  220  executes the vehicle travel control by giving more weight to the first required control amount CON1 than to the travel assist control amount (see  FIG.  12   ). 
     Alternatively, when the travel assist control amount is calculated during the automated driving, the second control device  220  determines whether or not the priority condition for giving priority to the first target trajectory TR1 is satisfied (Step S 235 ). For example, the second control device  220  compares the first required control amount CON1 and the travel assist control amount to determine whether or not the priority condition is satisfied. When the priority condition is satisfied (Step S 235 ; Yes), the second control device  220  executes the vehicle travel control by giving more weight to the first target trajectory TR1 than to the travel assist control amount (Step S 240 ). On the other hand, when the priority condition is not satisfied (Step S 235 ; No), the second control device  220  executes the vehicle travel control by giving more weight to the travel assist control amount than to the first target trajectory TR1 (Step S 260 ). 
     The same effects as in the case of the above-described embodiment can be obtained even by the present modification example. 
     5-3. Third Modification Example 
       FIG.  15    is a block diagram showing a configuration of the vehicle travel control device  200  according to a third modification example of the present embodiment. The second control device  220  (the second processor  221 ) generates log information  260  regarding the above-described Step S 240  (see  FIGS.  10  and  14   ), and stores the log information  260  in the second memory device  222 . 
     The log information  260  includes at least a position where Step S 240  has been executed. The log information  260  may include the first target trajectory TR1 and the second target trajectory TR2. The log information  260  may include the second driving environment information  250  acquired in a certain period of time including a timing when Step S 240  has been executed. 
     Such the log information  260  is useful. For example, it is possible to exclude the position where Step S 240  has been executed from an automated driving permitted zone (or ODD (Operational Design Domain)). As another example, it is possible to analyze a difference between the first target trajectory TR1 and the second target trajectory TR2. As yet another example, it is possible to analyze a reason of inconsistency between the first target trajectory TR1 and the second target trajectory TR2. 
     The second control device  220  may transmit the log information  260  to an automated driving management server through the second communication device  215 . The automated driving management server performs setting of the automated driving permitted zone and various analyses based on the log information  260 . 
     5-4. Fourth Modification Example 
       FIG.  16    is a block diagram showing a configuration of the vehicle control system  10  according to a fourth modification example of the present embodiment. The vehicle control system  10  includes an information acquisition device  310 , a control device  320 , and a travel device  340 . 
     The information acquisition device  310  acquires driving environment information  350 . The information acquisition device  310  is the same as the first information acquisition device  110  or the second information acquisition device  210 . The driving environment information  350  is the same as the first driving environment information  150  or the second driving environment information  250 . The travel device  340  is the same as to the travel device  240 . 
     The control device  320  includes a processor  321  and a memory device  322 . A variety of information is stored in the memory device  322 . For example, the driving environment information  350  acquired by the information acquisition device  310  is stored in the memory device  322 . The processor  321  executes a control program. The control program is stored in the memory device  322  or recorded on a computer-readable recording medium. A variety of processing by the control device  320  is realized by the processor  321  executing the control program. 
     The control device  320  has both of the function of the first control device  120  of the automated driving control device  100  and the function of the second control device  220  of the vehicle travel control device  200 . That is, the information acquisition device  310  and the control device  320  correspond to the automated driving control device  100 , and the information acquisition device  310 , the control device  320 , and the ravel device  340  correspond to the vehicle travel control device  200 . 
     A generalization is as follows. The vehicle control system  10  according to the present embodiment includes one processor (i.e., the processor  321 ) or a plurality of processors (i.e., the first processor  121  and the second processor  221 ). The one or more processors executes the processing as the automated driving control device  100  and the vehicle travel control device  200  based on the driving environment information stored in one or more memory devices.