Driving assist system

Driving assist control has plural control modes associated with plural scenes on a one-to-one basis. A scene corresponding to driving environment for a vehicle is a subject scene, and a selected control mode is one associated with the subject scene. Plural pieces of scene description information respectively define the plural scenes. Selected scene description information is one defining the subject scene and indicates parameters used in the driving assist control of the selected control mode. A processor executes the driving assist control of the selected control mode based on the parameters indicated by the selected scene description information, and switches the selected control mode by switching the selected scene description information. When the subject scene changes, the processor notifies an occupant of the vehicle of switching of the selected control mode before switching the selected scene description information and the selected control mode.

BACKGROUND

Technical Field

The present disclosure relates to a driving assist system that executes driving assist control having a plurality of control modes associated with a plurality of scenes on a one-to-one basis.

Background Art

Patent Literature 1 discloses a vehicle control system that executes automated driving control. Automated driving modes include a first automated driving mode and a second automated driving mode whose automation level is lower than that of the first automated driving mode. When a driving operation member is not operated by an occupant and a direction of a face or a line of sight of the occupant is within a first angular range, the first automated driving mode is executed. When the driving operation member is not operated by the occupant and the direction of the face or the line of sight of the occupant is within a second angular range larger than the first angular range, the second automated driving mode is executed.

Patent Literature 2 discloses a mode switching informing device mounted on a vehicle. The mode switching informing device informs switching between an automated driving mode and a manual driving mode.

LIST OF RELATED ART

SUMMARY

A driving assist system executes driving assist control that assists driving of a vehicle. Here, let us consider the driving assist control that has a plurality of control modes associated with a plurality of scenes on a one-to-one basis. The driving assist system recognizes a scene and executes the driving assist control of a control mode associated with the recognized scene. When the scene changes, the driving assist system switches the control mode accordingly.

However, the change in the scene recognized by the driving assist system is unperceivable by an occupant of the vehicle. Therefore, if the control mode is switched by the driving assist system without any prior notification, the occupant of the vehicle may feel a sense of strangeness with the switching of the control mode.

An object of the present disclosure is to provide a technique that is related to driving assist control having a plurality of control modes associated with a plurality of scenes on a one-to-one basis and that can reduce a sense of strangeness felt by an occupant of a vehicle when the scene changes.

In an aspect of the present disclosure, a driving assist system that assists driving of a vehicle is provided.

The driving assist system includes:

a processor configured to execute driving assist control that has a plurality of control modes associated with a plurality of scenes on a one-to-one basis; and

a memory device in which driving environment information indicating a driving environment for the vehicle and plural pieces of scene description information respectively defining the plurality of scenes are stored.

The processor recognizes a scene corresponding to the driving environment among the plurality of scenes as a subject scene, based on the driving environment information and the plural pieces of scene description information.

A selected control mode is one associated with the subject scene among the plurality of control modes.

Selected scene description information is one defining the subject scene among the plural pieces of scene description information and indicates parameters used in the driving assist control of the selected control mode.

The processor executes the driving assist control of the selected control mode based on the parameters indicated by the selected scene description information, and switches the selected control mode by switching the selected scene description information.

When the subject scene changes from a first scene to a second scene, the processor notifies an occupant of the vehicle of switching of the selected control mode before switching the selected scene description information and the selected control mode.

According to the present disclosure, when the subject scene changes from the first scene to the second scene, the driving assist system notifies the occupant of the vehicle of the switching of the selected control mode before switching the selected scene description information and the selected control mode. That is, the driving assist system does not execute the switching of the selected control mode with no prior notification but notifies the occupant of the vehicle in advance. Therefore, even when the switching of the selected control mode is subsequently executed, the sense of strangeness felt by the occupant of the vehicle is reduced.

EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the attached drawings.

1. Driving Assist Control According to Scene

1-1. Driving Assist Control

FIG. 1is a conceptual diagram for explaining a driving assist system100according to the present embodiment. The driving assist system100executes “driving assist control” that assists driving of a vehicle10. Typically, the driving assist system100is installed on the vehicle10. Alternatively, the driving assist system100may be placed in an external device outside the vehicle10and remotely execute the driving assist control. Alternatively, the driving assist system100may be distributed in the vehicle10and the external device.

The driving assist control includes at least one of steering control, acceleration control, and deceleration control of the vehicle10. That is, the driving assist system100assists the driving of the vehicle10by executing at least one of the steering control, the acceleration control, and the deceleration control. Such the driving assist control is exemplified by automated driving control, trajectory-following control, lane keep assist control (lane tracing assist control), adaptive cruise control (ACC), and so forth.

1-2. Scene and Control Mode

The driving assist control according to the present embodiment has a plurality of modes. A mode of the driving assist control is hereinafter referred to as a “control mode”. Different control modes require different contents of the driving assist control. Switching the control mode makes it possible to change the contents of the driving assist control. Particularly, in the present embodiment, the control mode of the driving assist control is dynamically switched according to a “scene.”

The scene means a situation in which the vehicle10is. In particular, the scene is defined by a configuration (arrangement) of the vehicle10and a moving object around the vehicle10. The moving object is exemplified by another vehicle, a pedestrian, and the like around the vehicle10. A plurality of control modes are associated with a plurality of scenes on a one-to-one basis, and the control mode is dynamically switched according to the scene.

FIG. 2shows an example of a correspondence relationship between the plurality of scenes and the plurality of control modes. In the example shown inFIG. 2, a correspondence relationship between seven types of scenes S1to S7and seven types of control modes M1to M7is shown.

FIGS. 3 to 9are conceptual diagrams for explaining the scenes S1to S7, respectively. A configuration space CON shown in each ofFIGS. 3 to 9is a predetermined space around the vehicle10. The moving object contributing to the scene is the moving object existing in the configuration space CON. That is, each scene is defined by the configuration (arrangement) of the vehicle10and the moving object in the configuration space CON. Although the configuration space CON has a rectangular shape in the example shown inFIGS. 3 to 9, its shape is arbitrary. A center position of the configuration space CON may be a position of the vehicle10, or may be deviated from the position of the vehicle10. For example, the configuration space CON ahead of the vehicle10may be larger than the configuration space CON behind the vehicle10, because the moving object ahead of the vehicle10is particularly important in the driving assist control.

Hereinafter, the scenes S1to S7and the control modes M1to M7will be described with reference toFIGS. 2 to 9.

The scene S1and the control mode M1will be described with reference toFIGS. 2 and 3. The scene S1is a scene where there is no moving object in the configuration space CON. The control mode M1is associated with this scene S1. For example, the driving assist control of the control mode M1includes at least one of the trajectory-following control and the lane keep assist control. A target trajectory used in the trajectory-following control and the lane keep assist control is, for example, a center line of a travel lane L0in which the vehicle10travels.

The scene S2and the control mode M2will be described with reference toFIGS. 2 and 4. The vehicle10travels in the travel lane L0. The scene S2is a scene where a moving object11(e.g., a preceding vehicle) exists at a forward position in the same travel lane L0as the vehicle10. The control mode M2is associated with this scene S2. In the driving assist control of the control mode M2, the moving object11in front is included in a monitoring target. For example, the driving assist control of the control mode M2includes the adaptive cruise control (ACC) that follows the moving object11, in addition to the driving assist control of the control mode M1described above.

The scene S3and the control mode M3will be described with reference toFIGS. 2 and 5. An adjacent lane LA is adjacent to the travel lane L0in which the vehicle10travels. The scene S3is a scene where a moving object12(e.g., an adjacent vehicle) exists in the adjacent lane LA. The control mode M3is associated with this scene S3. In the driving assist control of the control mode M3, the moving object12in the adjacent lane LA is included in the monitoring target. For example, the driving assist control of the control mode M3includes such control that pays attention to and deals with a lane change (cutting-in) of the moving object12, in addition to the driving assist control of the control mode M1described above. The control for dealing with the lane change includes deceleration control, for example.

The scene S4and the control mode M4will be described with reference toFIGS. 2 and 6. The scene S4is a combination of the scene S2and the scene S3descried above. That is, the moving object11exists in the travel lane L0and the moving object12exists in the adjacent lane LA. The control mode M4is associated with this scene S4. In the driving assist control of the control mode M4, both of the moving object11in front and the moving object12in the adjacent lane LA are included in the monitoring target. The driving assist control of the control mode M4is a combination of the driving assist control of the control mode M2and the driving assist control of the control mode M3.

The scene S5and the control mode M5will be described with reference toFIGS. 2 and 7. There is an intersecting lane LB that intersects with the travel lane L0ahead of the vehicle10. The scene S5is a scene where a moving object13in the intersecting lane LB merges (proceeds) into the travel lane L0. The control mode M5is associated with this scene S5. In the driving assist control of the control mode M5, the moving object13is included in the monitoring target. For example, the driving assist control of the control mode M5includes such control that watches out for and avoids a collision with the moving object13, in addition to the driving assist control of the control mode M1described above. The control for avoiding the collision with the moving object13includes deceleration control, for example.

The scene S6and the control mode M6will be described with reference toFIGS. 2 and 8. There is an intersecting lane LB that intersects with the travel lane L0ahead of the vehicle10. The scene S6is a scene where a moving object14in front in the travel lane L0moves (goes out) into the intersecting lane LB. The control mode M6is associated with this scene S6. In the driving assist control of the control mode M6, the moving object14is included in the monitoring target. For example, the driving assist control of the control mode M6includes such control that does not follow the moving object14and pays attention to a behavior of the moving object14, in addition to the driving assist control of the control mode M1described above.

The scene S7and the control mode M7will be described with reference toFIGS. 2 and 9. The vehicle10travels in the travel lane L0. There is an oncoming lane (opposite lane) LC adjacent to the travel lane L0. The scene S7is a scene where a moving object15(e.g., an oncoming vehicle) exists in the oncoming lane LC. The control mode M7is associated with this scene S7. In the driving assist control of the control mode M7, the moving object15in the oncoming lane LC is included in the monitoring target. For example, the driving assist control of the control mode M7includes such control that pays attention to a behavior of the moving object15, in addition to the driving assist control of the control mode M1described above.

1-3. Scene Description Information

Scene description information is information defining the scene and prepared for each scene. As shown inFIG. 2, plural pieces of scene description information D1to D7define the plurality of scenes S1to S7, respectively. It can also be said that the plural pieces of scene description information D1to D7are associated with the plurality of control modes M1to M7on a one-to-one basis.

More specifically, the scene description information indicates parameters that define the scene (i.e., the configuration of the vehicle10and the moving object). The parameters defining the scene include vehicle parameters regarding the vehicle10and moving object parameters regarding the moving object.

The vehicle parameters regarding the vehicle10include, for example, a lane L0(=the travel lane L0) in which the vehicle10exists, a position X0of the vehicle10in a direction along the lane L0, a velocity V0of the vehicle10, and an orientation H0of the vehicle10. For simplicity, a direction of the velocity V0may be regarded as the orientation H0.

A moving object i (i=1 to k; k is an integer equal to or greater than 1) within the configuration space CON is considered. The moving object parameters regarding the moving object i include, for example, a type Ciof the moving object i, a lane Liin which the moving object i exists, a position Xiof the moving object i in a direction along the lane Li, a velocity Viof the moving object i, and an orientation Hiof the moving object i. For simplicity, a direction of the velocity Vimay be regarded as the orientation Hi.

It should be noted that in the present embodiment, the parameters such as the position and the velocity may be parameters in an absolute coordinate system or may be parameters in a relative coordinate system. For example, the relative coordinate system is fixed to the vehicle10and moves with a movement of the vehicle10. Typically, the origin of the relative coordinate system is a predetermined position on the vehicle10, but it is not limited to that.

A relative relationship of the moving object i with respect to the vehicle10is expressed by δLi=Li−L0, δXi=Xi−X0, and δVi=Vi−V0. These parameters δLi, δXi, and δVimay be used as the moving object parameters instead of Li, Xi, and Vi.

Some examples of the relative relationship of the moving object i with respect to the vehicle10are described with reference toFIG. 10. When the vehicle10passes over a moving object (i=1) in a left adjacent lane, the relative relationship of the moving object (i=1) is expressed by “δL1=−1, δX1<0, δV1<0.” When an inter-vehicle distance between the vehicle10and a moving object (i=2) in front is decreasing, the relative relationship of the moving object (i=2) is expressed by “δL2=0, δX2>0, δV2<0.” When a moving object (i=3) in a right adjacent lane passes over the vehicle10, the relative relationship of the moving object (i=3) is expressed by “δL3=1, δX3>0, δV3>0.”

The parameters indicated by the scene description information defining a scene are used in the driving assist control of the control mode associated with the scene. That is, the driving assist control of the control modes M1to M7is executed based on the scene description information D1to D7, respectively. It is possible to switch the control mode by switching the scene description information to be used.

1-4. Scene Recognition Processing

The driving assist system100executes “scene recognition processing” that recognizes the scene. In the scene recognition processing, driving environment information is used in addition to the above-described scene description information D1to D7.

The driving environment information is information indicating a driving environment for the vehicle10. For example, the driving environment information includes map information, vehicle position information, vehicle state information, surrounding situation information, and the like. The map information indicates a lane configuration around the vehicle10. The vehicle position information indicates a position and an orientation of the vehicle10. The vehicle state information indicates a state (e.g., velocity) of the vehicle10. The surrounding situation information includes information (position, velocity, etc.) of the moving object around the vehicle10. Typically, the driving environment information is obtained by sensors mounted on the vehicle10.

The driving assist system100recognizes a scene corresponding to the driving environment among the plurality of scenes S1to S7based on the driving environment information and the scene description information D1to D7. More specifically, the vehicle parameters can be recognized from the map information, the vehicle position information, and the vehicle state information. The moving object parameters can be recognized from the map information, the vehicle position information, the vehicle state information, and the surrounding situation information. It is therefore possible to determine to which one of the scenes S1to S7defined by the scene description information D1to D7the driving environment indicated by the driving environment information corresponds.

As an example, a driving environment where the moving object11exists in the travel lane L0and no moving object exists in the adjacent lane LA as shown inFIG. 4is considered. Since this driving environment is consistent with the scene description information D2, the scene S2is recognized as the scene corresponding to (consistent with) the driving environment. As another example, a driving environment where the moving object11exists in the travel lane L0and the moving object12exists in the adjacent lane LA as shown inFIG. 6is considered. Since this driving environment is consistent with the scene description information D4, the scene S4is recognized as the scene corresponding to (consistent with) the driving environment.

The scene recognized by the scene recognition processing, that is, the scene corresponding to the driving environment is hereinafter referred to as a “subject scene ST.” The driving assist system100can detect a change in the subject scene ST by repeatedly recognizing the subject scene ST.

As another example, the driving assist system100may deduce the subject scene ST and its change from a viewpoint of a probability. An example of a method of deducing the subject scene ST and its change will be described with reference toFIGS. 11 and 12.

FIG. 11shows a scene at a time t. In the example shown inFIG. 11, a scene S(t) at the time t is the scene S3, and the moving object12exists in the adjacent lanes LA. An angle between the orientation H2of the moving object12and a lane longitudinal direction is denoted by θ.

FIG. 12shows examples of a scene S(t+δt) at a time t+δt. If the moving object12moves from the adjacent lane LA into the travel lane L0during the period δt, the scene S(t+δt) is the scene S2. The moving object12in this case is hereinafter referred to as a moving object12-2for the purpose of convenience. A probability P2that the scene S(t+δt) is the scene S2is expressed as follows.
P2=P(S(t+δt)=S2|S(t)=S3,θ)

On the other hand, if the moving object12keeps remaining in the adjacent lane LA during the period δt, the scene S(t+δt) is the scene S3. The moving object12in this case is hereinafter referred to as a moving object12-3for the purpose of convenience. A probability P3that the scene S(t+δt) is the scene S3is expressed as follows.
P3=P(S(t+δt)=S3|S(t)=S3,θ)

These probabilities P2and P3are formulated in advance based on a result of observation of a real traffic environment. To improve accuracy, other variables in addition to the angle θ may be taken into consideration. For example, the velocity Viof the moving object i and a lateral position of the moving object i in the lane may be used as the variables. A distance between a center position of the moving object i and a lane centerline or a distance between a side edge position of the moving object i and a lane boundary line is used as the lateral position of the moving object i.

Typically, the scene S(t+δt) at the time t+δt is deduced to be the scene with the highest probability. For example, when the probability P2is the highest, the scene S(t+δt) is deduced to be the scene S2. In this case, it is deduced that a change from the scene S3to the scene S2occurs. On the other hand, when the probability P3is the highest, the scene S(t+δt) is deduced to be the scene S3. In this case, it is deduced that no scene change occurs.

There may be a case where there is little difference between the highest probability and the second highest probability. In this case, not only the scene with the highest probability but also the scene with the second highest probability may be taken into consideration.

For instance, let us consider a situation where the probability P2and the probability P3are almost the same in the example shown inFIGS. 11 and 12. Such the situation may occur during a period when the moving object12makes a lane change from the adjacent lane LA to the travel lane L0. In that case, the moving object12-2is deemed to exist in the travel lane L0and the moving object12-3is deemed to exist in the adjacent lane LA as shown in a right column inFIG. 12. In other words, the scene S2with the probability P2and the scene S3with the probability P3are combined with each other. As a result, the scene S(t+δt) at the time t+δt is deduced to be the scene S4.

It should be noted that the case where the scene S(t) at the time t is the scene S3is described in the above example, and the same applies to other cases.

1-5. Driving Assist Control According to Subject Scene

As described above, the driving assist system100recognizes the subject scene ST by executing the scene recognition processing. One that defines the subject scene ST among the plural pieces of scene description information D1to D7is hereinafter referred to as “selected scene description information DS.” One associated with the subject scene ST among the plurality of control modes M1to M7is hereinafter referred to as a “selected control mode MS.” The subject scene ST, the selected scene description information DS, and the selected control mode MS are associated with each other.

The driving assist system100executes the driving assist control based on the selected scene description information DS. More specifically, the selected scene description information DS indicates the parameters used in the driving assist control of the selected control mode MS. The driving assist system100executes the driving assist control of the selected control mode MS based on the parameters indicated by the selected scene description information DS.

1-6. Mode Switching Processing

Furthermore, the driving assist system100detects a change in the subject scene ST by repeatedly executing the scene recognition processing. When the subject scene ST changes, it is necessary to switch the selected control mode MS accordingly. The driving assist system100can switch the selected control mode MS by switching the selected scene description information DS according to the change in the subject scene ST.

However, the change in the subject scene ST recognized by the driving assist system100is unperceivable by an occupant (e.g., a driver) of the vehicle10. Therefore, if the selected control mode MS is switched by the driving assist system100without any prior notification, the occupant of the vehicle10may feel a sense of strangeness with the switching. In order to reduce such the occupant's sense of strangeness, the driving assist system100according to the present embodiment executes “mode switching processing” as described below.

1-6-1. Situation where Notification is Made

Hereinafter, the subject scene ST before the change is referred to as a “first scene” and the subject scene ST after the change is referred to as a “second scene.” When the subject scene ST changes from the first scene to the second scene, the driving assist system100notifies the occupant of the vehicle10of the switching of the selected control mode MS before switching the selected scene description information DS and the selected control mode MS. That is, the driving assist system100does not execute the switching of the selected control mode MS with no prior notification but notifies the occupant of the vehicle10in advance. Therefore, even when the switching of the selected control mode MS is subsequently executed, the sense of strangeness felt by the occupant of the vehicle10is reduced.

FIG. 13is a conceptual diagram for explaining an example of the mode switching processing according to the present embodiment. The subject scene ST before the change (i.e., the first scene) is the scene S2. That is, the moving object11exists in the travel lane L0and no moving object exists in the adjacent lane LA. The driving assist system100executes the driving assist control of the control mode M2based on the scene description information D2.

After that, the number of moving objects included in the configuration space CON increases. More specifically, the moving object12in the adjacent lane LA is added. That is, the subject scene ST changes from the scene S2to the scene S4. In this case, it is necessary to switch the selected scene description information DS from the scene description information D2to the scene description information D4, and to switch the selected control mode MS from the control mode M2to the control mode M4. The driving assist system100according to the present embodiment notifies the occupant of the vehicle10of the switching before executing the switching. Therefore, even when the switching of the selected control mode MS is subsequently executed, the sense of strangeness felt by the occupant of the vehicle10is reduced.

In particular, in the example shown inFIG. 13, the number of moving objects to be considered in the driving assist control increases. In other words, the number of parameters and the types of parameters used in the driving assist control are increased due to the switching of the selected scene description information DS. Therefore, the switching of the selected scene description information DS (i.e., the selected control mode MS) is likely to cause control discontinuity and thus a discontinuous change in behavior of the vehicle10. According to the present embodiment, the switching is notified in advance to the occupant of the vehicle10, and thus the sense of strangeness felt by the occupant is reduced even if the behavior of the vehicle10changes discontinuously.

FIG. 14is a conceptual diagram for explaining another example of the mode switching processing according to the present embodiment. The subject scene ST before the change (i.e., the first scene) is the scene S3. That is, the moving object12exists in the adjacent lane LA. The driving assist system100executes the driving assist control of the control mode M3based on the scene description information D3.

After that, the type of the moving object included in the configuration space CON changes. More specifically, the moving object12in the adjacent lane LA moves out of the configuration space CON and concurrently the moving object13in the intersecting lane LB intersecting with the travel lane L0moves into the configuration space CON. That is, the subject scene ST changes from the scene S3to the scene S5. In this case, it is necessary to switch the selected scene description information DS from the scene description information D3to the scene description information D5, and to switch the selected control mode MS from the control mode M3to the control mode M5. The driving assist system100according to the present embodiment notifies the occupant of the vehicle10of the switching before executing the switching. Therefore, even when the switching of the selected control mode MS is subsequently executed, the sense of strangeness felt by the occupant of the vehicle10is reduced.

In particular, in the example shown inFIG. 14, the type of the moving object to be considered in the driving assist control changes. In other words, the type of the parameters used in the driving assist control is changed due to the switching of the selected scene description information DS. Therefore, the switching of the selected scene description information DS (i.e., the selected control mode MS) is likely to cause control discontinuity and thus a discontinuous change in behavior of the vehicle10. According to the present embodiment, the switching is notified in advance to the occupant of the vehicle10, and thus the sense of strangeness felt by the occupant is reduced even if the behavior of the vehicle10changes discontinuously.

A generalization of the examples shown inFIGS. 13 and 14is as follows. At least a part of the parameters indicated by the selected scene description information DS regarding the second scene after the change is not indicated by the selected scene description information DS regarding the first scene before the change. In other words, at least a part of the parameters indicated by the selected scene description information DS regarding the second scene after the change is different from the parameters indicated by the selected scene description information DS regarding the first scene before the change. In this case, the switching of the selected scene description information DS (i.e., the selected control mode MS) is likely to cause the control discontinuity and thus the discontinuous change in the behavior of the vehicle10. It is therefore preferable to beforehand notify the occupant of the vehicle10of the switching.

When notifying the occupant of the vehicle10of the switching, the driving assist system100may request the occupant for “approval” of the switching. When the occupant approves the switching, the driving assist system100executes the switching. On the other hand, when the occupant refuses the switching, the driving assist system100requests a driver of the vehicle10to perform manual driving. It is thus possible to reflect an intention of the occupant of the vehicle10in the mode switching processing. This is preferable from a viewpoint of convenience.

1-6-2. Situation where Notification is not Made

The notification to the occupant of the vehicle10is not always performed. In some cases, the driving assist system100may execute the switching of the selected scene description information DS and the selected control mode MS without beforehand notifying the occupant of the vehicle10of the switching of the selected control mode MS. As a result, excessive notifications are suppressed.

As an instance, the situation shown inFIG. 15is considered. The subject scene ST before the change is the scene S4. That is, the moving object11exists in the travel lane L0and the moving object12exists in the adjacent lane LA. The driving assist system100executes the driving assist control of the control mode M4based on the scene description information D4.

After that, the number of moving objects and the types of moving objects included in the configuration space CON decrease. More specifically, the moving object12in the adjacent lane LA moves out of the configuration space CON. That is, the subject scene ST changes from the scene S4to the scene S2. In this case, it is necessary to switch the selected scene description information DS from the scene description information D4to the scene description information D2, and to switch the selected control mode MS from the control mode M4to the control mode M2.

In the example shown inFIG. 15, the number of parameters and the types of parameters used in the driving assist control are decreased due to the switching of the selected scene description information DS. In this case, the switching of the selected scene description information DS (i.e., the selected control mode MS) does not cause the control discontinuity and the discontinuous change in behavior of the vehicle10. In this case, the sense of strangeness is not caused. Therefore, it is not always necessary to beforehand notify the occupant of the vehicle10of the switching.

A generalization is as follows. In order to distinguish from the above-described case where the notification is made (see Section 1-6-1), the subject scene ST before the change is referred to as a “third scene”, and the subject scene ST after the change is referred to as a “fourth scene.” When the subject scene ST changes from the third scene to the fourth scene, the driving assist system100executes the switching of the selected scene description information DS and the selected control mode MS without beforehand notifying the occupant of the vehicle10of the switching of the selected control mode MS. Since excessive notifications are suppressed, processing load applied on the driving assist system100is reduced. Moreover, since some notifications are omitted, the switching of the selected control mode MS is quickly achieved. Furthermore, discomfort with the excessive notifications is suppressed.

In particular, when all of the parameters indicated by the selected scene description information DS regarding the fourth scene are included in the parameters indicated by the selected scene description information DS regarding the third scene, the control discontinuity is not caused and thus the behavior of the vehicle10does not change discontinuously. In this case, the occupant of the vehicle10does not feel the sense of strangeness with the switching of the selected scene description information DS and the selected control mode MS. It is therefore preferable to execute the switching without beforehand notifying the occupant of the vehicle10of the switching. Since an unnecessary notification is suppressed, processing load applied on the driving assist system100is reduced. Moreover, since the unnecessary notification is omitted, the switching of the selected control mode MS is quickly achieved. Furthermore, discomfort with the unnecessary notification is suppressed.

Hereinafter, the driving assist system100according to the present embodiment will be described in more details.

2. Configuration Example of Driving Assist System

FIG. 16is a block diagram schematically showing a configuration example of the driving assist system100according to the present embodiment. The driving assist system100includes a control device (controller)110, an information acquisition device120, a travel device130, and an HMI (Human-Machine Interface) unit140.

The information acquisition device120acquires the driving environment information200. The driving environment information200is information indicating a driving environment for the vehicle10and necessary for the driving assist control.

FIG. 17is a block diagram showing an example of the information acquisition device120and the driving environment information200. The information acquisition device120includes a map information acquisition device121, a position information acquisition device122, a vehicle state sensor123, a surrounding situation sensor124, and a communication device125. The driving environment information200includes map information210, position information220, vehicle state information230, surrounding situation information240, and delivery information250.

The map information acquisition device121acquires the map information210. The map information210indicates at least a lane configuration. It is possible to recognize the number of lanes, lane merging, lane branching, lane intersection, and the like by reference to the map information210. The map information acquisition device121acquires the map information210of a required area from a map database. The map database may be stored in a predetermined memory device mounted on the vehicle10, or may be stored in a management server outside the vehicle10. In the latter case, the map information acquisition device121communicates with the management server to acquire the necessary map information210.

The position information acquisition device122acquires the position information220that indicates a position and an attitude (e.g. orientation) of the vehicle10. For example, the position information acquisition device122includes a GPS (Global Positioning System) device that measures the position and the orientation (azimuth) of the vehicle10. The position information acquisition device122may further include an attitude sensor that detects the attitude of the vehicle10.

The vehicle state sensor123acquires the vehicle state information230that indicates a state of the vehicle10. For example, the vehicle state sensor123includes a vehicle speed sensor, a yaw rate sensor, an acceleration sensor, a steering angle sensor, and so forth. The vehicle speed sensor detects a vehicle speed (i.e., a speed of the vehicle10). The yaw rate sensor detects a yaw rate of the vehicle10. The acceleration sensor detects an acceleration (e.g., a lateral acceleration, a longitudinal acceleration, and a vertical acceleration) of the vehicle10. The steering angle sensor detects a steering angle of the vehicle10.

The surrounding situation sensor124recognizes (detects) a situation around the vehicle10. For example, the surrounding situation sensor124includes at least one of a camera, a LIDAR (Laser Imaging Detection and Ranging), and a radar. The surrounding situation information240indicates a result of recognition by the surrounding situation sensor124. For example, the surrounding situation information240includes target information regarding a target recognized by the surrounding situation sensor124. The target is exemplified by a surrounding vehicle, a white line, an obstacle, a roadside structure, and so forth. The target information includes information on a relative position and a relative velocity of the target with respect to the vehicle10.

The communication device125communicates with the outside of the vehicle10. For example, the communication device125communicates with an external device outside the vehicle10through a communication network. The communication device125may perform a V2I communication (vehicle-to-infrastructure communication) with a surrounding infrastructure. The communication device125may perform a V2V communication (vehicle-to-vehicle communication) with a surrounding vehicle. The delivery information250is information acquired through the communication device125. For example, the delivery information250includes information (e.g., a position, an orientation, a velocity, and the like) of the surrounding vehicle acquired through the V2V communication.

The travel device130includes a steering device, a driving device, and a braking device. The steering device turns (i.e., changes a direction of) a wheel of the vehicle10. For example, the steering device includes a power steering (EPS: Electric Power Steering) device. The driving device is a power source that generates a driving force. The driving device is exemplified by an engine, an electric motor, an in-wheel motor, and the like. The braking device generates a braking force.

The HMI unit140is an interface for proving the occupant (e.g., the driver) of the vehicle10with information and receiving information from the occupant. More specifically, the HMI unit140includes an input device and an output device. The input device is exemplified by a touch panel, a switch, a microphone, and the like. The output device is exemplified by a display device, a speaker, and the like.

The control device (controller)110includes a processor111and a memory device112. For example, the control device110is a microcomputer. A variety of information is stored in the memory device112. For example, plural pieces of scene description information D1to Dn respectively defining the plurality of scenes S1to Sn are stored in the memory device112(here, n is an integer equal to or greater than 2). In addition, the driving environment information200acquired by the information acquisition device120is stored in the memory device112.

The processor111executes a variety of processing by executing a computer program. The computer program is stored in the memory device112or recorded on a computer-readable recording medium.

For example, the processor111acquires the driving environment information200from the information acquisition device120and stores the driving environment information200in the memory device112.

Moreover, the processor111executes vehicle travel control that controls travel of the vehicle10. More specifically, the processor111executes the vehicle travel control by controlling an operation of the travel device130. The vehicle travel control includes the steering control, the acceleration control, and the deceleration control. The steering control is performed through the steering device. The acceleration control is performed through the driving device. The deceleration control is performed through the braking device.

The processor111executes the driving assist control by appropriately executing the vehicle travel control. More specifically, the processor111creates a travel plan required for the driving assist control based on the driving environment information200. For example, the travel plan includes a target trajectory including a target position and a target velocity. The processor111generates the target trajectory based on the driving environment information200. Then, the processor111executes the vehicle travel control such that the vehicle10travels in accordance with the travel plan.

Hereinafter, a process flow of the driving assist control according to the scene will be described.

3. Process Flow

FIG. 18is a flow chart showing processing by the driving assist system100according to the present embodiment.

In Step S100, the information acquisition device120acquires the driving environment information200(seeFIG. 17). The control device110(i.e., the processor111) receives the driving environment information200from the information acquisition device120and stores the driving environment information200in the memory device112.

In Step S200, the processor111executes the scene recognition processing (see Section 1-1). The scene description information D1to Dn and the driving environment information200are stored in the memory device112. Based on the scene description information D1to Dn and the driving environment information200, the processor111recognizes a scene corresponding to the driving environment indicated by the driving environment information200as the “subject scene ST.”

More specifically, the lane configuration is obtained from the map information210. The position and the orientation of the vehicle10are obtained from the position information220. The speed of the vehicle10is obtained from the vehicle state information230. The information (e.g., the position, the orientation, the velocity) of the moving object i around the vehicle10is obtained from the surrounding situation information240or the distribution information250. That is, it is possible to recognize the vehicle parameters and the moving object parameters based on the driving environment information200. Therefore, it is possible to determine to which scene defined by the scene description information the driving environment indicated by the driving environment information200corresponds.

In Step S300, the processor111determines whether or not a change in the subject scene ST occurs. When a change in the subject scene ST occurs (Step S300; Yes), the processing proceeds to Step S400. On the other hand, when the subject scene ST is not changed (step S300; No), the processing skips Step S400and proceeds to Step S500.

In Step S400, the processor111executes the mode switching processing. Various examples of the mode switching processing will be described later.

In the subsequent Step S500, the processor111executes the driving assist control based on the selected scene description information DS. More specifically, the selected scene description information DS indicates the parameters used in the driving assist control of the selected control mode MS. The processor111executes the driving assist control of the selected control mode MS based on the parameters indicated by the selected scene description information DS.

Hereinafter, various examples of the mode switching processing (Step S400) will be described.

3-1. First Example

FIG. 19is a flow chart showing a first example of the mode switching processing. In Step S420, the processor111notifies the occupant of the vehicle10of the switching of the selected control mode MS through the HMI unit140(i.e., the output device). For example, the notification includes at least one of a display notification and a voice notification.

In Step S450after Step S420, the processor111executes the switching of the selected control mode MS. More specifically, the processor111switches the selected control mode MS by switching the selected scene description information DS according to the change in the subject scene ST.

According to the first example, the switching of the selected control mode MS is not executed with no prior notification but beforehand notified to the occupant of the vehicle10. Therefore, the occupant's sense of strangeness with the switching is reduced.

3-2. Second Example

FIG. 20is a flow chart showing a second example of the mode switching processing. An overlapping description with the first example will be omitted as appropriate.

In Step S410prior to Step S420, the processor111determines whether or not a “notification condition” is satisfied. The notification condition is a condition for executing Step S420. More specifically, the notification condition is that “at least a part of the parameters indicated by the selected scene description information DS regarding the second scene after the change is not indicated by the selected scene description information DS regarding the first scene before the change” (see Section 1-6-1,FIGS. 13 and 14).

When the notification condition is satisfied (Step S410; Yes), the processing proceeds to Step S420and the prior notification to the occupant of the vehicle10is made. When the notification condition is satisfied, the control discontinuity and thus the discontinuous change in the behavior of the vehicle10are likely to occur in the mode switching (Step S450). However, the switching is notified in advance to the occupant of the vehicle10, and thus the sense of strangeness felt by the occupant is reduced even if the behavior of the vehicle10changes discontinuously.

On the other hand, when the notification condition is not satisfied (Step S410; No), the processing skips Step S420and proceeds to Step S450. That is, the mode switching (Step S450) is executed without prior notification to the occupant of the vehicle10. When the notification condition is not satisfied, the control discontinuity is not caused and thus the behavior of the vehicle10does not change discontinuously (see Section 1-6-2,FIG. 15). Since an unnecessary notification is suppressed, processing load applied on the driving assist system100is reduced. Moreover, since the unnecessary notification is omitted, the switching of the selected control mode MS is quickly achieved. Furthermore, discomfort with the unnecessary notification is suppressed.

3-3. Third Example

FIG. 21is a flow chart showing a third example of the mode switching processing. An overlapping description with the first example will be omitted as appropriate.

In Step S420, the processor111notifies the occupant of the vehicle10of the switching of the selected control mode MS through the HMI unit140(i.e., the output device). This Step S420includes Step S425that requests the occupant for “approval” of the switching.

The occupant (e.g., the driver) approves or refuses the switching by using the HMI unit140(i.e., the input device). When the occupant approves the switching (Step S430; Yes), the processing proceeds to Step S450. As a result, the same effects as in the case of the first example are obtained.

On the other hand, when the occupant refuses the switching (Step S430; No), the processing proceeds to Step S460. In Step S460, the processor111requests, through the HMI unit140(i.e., the output device), the driver of the vehicle10to perform manual driving. At the same time, the processor111may issue an alarm.

In response to the request for manual driving, the driver of the vehicle10performs the manual driving (Step S600). During execution of the manual driving, the processor111may beforehand switch the selected scene description information DS. Furthermore, the processor111may notify, through the HMI unit140(i.e., the output device), the driver that “resumption of the driving assist control of the selected control mode MS is possible.” The driver uses the HMI unit140(i.e., the input device) to instruct the driving assist system100to resume the driving assist control. In this manner, it is possible to efficiently resume the driving assist control.

According to the third example, as described above, the occupant of the vehicle10is requested to approve the switching of the selected control mode MS. When the occupant approves the switching, the switching is executed. On the other hand, when the occupant refuses the switching, the switching is not executed automatically, and instead the manual driving is required. It is thus possible to reflect an intention of the occupant of the vehicle10in the mode switching processing. This is preferable from a viewpoint of convenience.

3-4. Fourth Example

FIG. 22is a flow chart showing a fourth example of the mode switching processing. The fourth example is a combination of the second example and the third example. An overlapping description with the second and third examples will be omitted as appropriate.

In Step S410, the processor111determines whether or not the notification condition is satisfied. When the notification condition is satisfied (Step S410; Yes), the processing proceeds to Step S420. On the other hand, when the notification condition is not satisfied (Step S410; No), the processing proceeds to Step S450.

In Step S420, the processor111notifies the occupant of the vehicle10of the switching of the selected control mode MS. At this time, the processor111requests the occupant for approval of the switching (Step S425).

When the occupant approves the switching (Step S430; Yes), the processing proceeds to Step S450. In Step S450, the processor111executes the switching of the selected control mode MS.

On the other hand, when the occupant refuses the switching (Step S430; No), the processing proceeds to Step S460. In Step S460, the processor111requests the driver of the vehicle10to perform manual driving.

According to the fourth example, both of the effects by the second example and the effects by the third example are obtained.

3-5. Fifth Example

If the subject scene ST after the change is highly dangerous, the processor111may not only make the notification to the occupant of the vehicle10but also forcibly activate an emergency avoidance mode.