Driving support system

A driving support system that supports driving of a vehicle executes steering support control that steers the vehicle in a first direction away from a risk factor in front of the vehicle. A target steering amount in the steering support control is represented by a function of a relative relationship parameter including a lateral distance between the vehicle and the risk factor. A straight road is a road having a curvature less than a first curvature. A curved road is a road having a curvature equal to or greater than the first curvature. When a road ahead from the vehicle to the risk factor includes the curved road, the driving support system reduces the target steering amount for the same relative relationship parameter or advances a start timing of the steering support control as compared to when the road ahead is the straight road.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-043105 filed on Mar. 12, 2020, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a driving support control that supports driving of a vehicle. In particular, the present disclosure relates to a risk avoidance control for avoiding risk factors in front of the vehicle.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2017-095100 discloses a collision avoidance system for vehicles. The collision avoidance system uses sensors to detect a pedestrian near the vehicle. The collision avoidance system then steers the vehicle to avoid a collision with the pedestrian while the vehicle overtakes the pedestrian.

SUMMARY

A risk avoidance control for avoiding the risk factors such as a pedestrian in front of the vehicle will be discussed. The risk avoidance control may include steering support control that steers the vehicle away from the risk factors. The situation in which such steering support control is operated is not limited to the situation in which the vehicle travels on a straight road. The steering support control can be operated even when the vehicle is traveling on a curved road.

However, if the steering support control is executed on a curved road with the same control strength as in the case of a straight road, an occupant of the vehicle (typically, the driver) may feel uneasy. For example, when the steering support control is further executed while the vehicle is turning on a curved road, the lateral acceleration of the vehicle is further increased, and the occupant may feel uneasy about the vehicle behavior. As another example, when the steering support control is executed in a direction opposite to a curved direction while the vehicle is turning on a curved road, the turning radius of the vehicle may increase, and the occupant may feel uneasy about the possibility that the vehicle may run off the curved road.

One object of the present disclosure is to provide a technique capable of reducing uneasiness of an occupant about a steering support control on a curved road regarding a risk avoidance control for avoiding risk factors in front of a vehicle.

A first aspect relates to a driving support system that supports driving of a vehicle. The driving support system includes: a storage device that stores driving environment information indicating a driving environment of the vehicle; and a processor that executes steering support control for steering the vehicle in a first direction away from a risk factor in front of the vehicle based on the driving environment information. A target steering amount in the steering support control is represented by a function of a relative relationship parameter including a lateral distance between the vehicle and the risk factor. A straight road is a road having a curvature less than a first curvature. A curved road is a road having a curvature equal to or greater than the first curvature. When a road ahead from the vehicle to the risk factor includes the curved road, the processor reduces the target steering amount for the same relative relationship parameter or advances a start timing of the steering support control as compared to when the road ahead is the straight road.

A second aspect has the following feature in addition to the first aspect. When the road ahead includes the curved road and the first direction is opposite to a curved direction of the curved road, the processor reduces the target steering amount for the same relative relationship parameter or advances the start timing of the steering support control as compared to the case where the first direction coincides with the curved direction.

A third aspect further has the following feature in addition to the first or second aspect. The processor reduces the target steering amount for the same relative relationship parameter or advances the start timing of the steering support control as the curvature of the curved road increases.

A fourth aspect further has the following features in addition to any of the first to third aspects. The processor sets a risk region around the risk factor and executes the steering support control such that the vehicle avoids the risk region. The processor reduces the target steering amount for the same relative relationship parameter by reducing the risk region.

A fifth aspect further has the following feature in addition to any of the first to fourth aspects. The risk factor includes at least one of a pedestrian, a bicycle, a two-wheeled vehicle, and a parked vehicle in front of the vehicle.

According to the present disclosure, the steering support control is executed in consideration of the road shape of the road ahead from the vehicle to the risk factor. Specifically, when the road ahead includes a curved road, the target steering amount of the steering support control is reduced or the start timing of the steering support control is advanced as compared with the case where the road ahead is a straight road. As a result, when the road ahead includes a curved road, the lateral movement amount of the vehicle due to the steering support control is reduced than when the road ahead is a straight road. Alternatively, the increase in the lateral acceleration of the vehicle due to the steering support control is suppressed. Therefore, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

DETAILED DESCRIPTION OF EMBODIMENTS

1-1. Driving Support Control

FIG.1is a conceptual diagram illustrating an overview of a driving support system10according to the present embodiment. The driving support system10executes a “driving support control” that supports driving of a vehicle1. The driving support control may be included in an autonomous driving control. Typically, the driving support system10is mounted on the vehicle1. Alternatively, at least a part of the driving support system10may be disposed in an external device outside the vehicle1to execute the driving support control remotely. That is, the driving support system10may be dispersedly disposed in the vehicle1and the external device.

The driving support control includes a “risk avoidance control” that avoids a risk factor3in front of the vehicle1. Specifically, the driving support system10automatically steers or/and decelerates the vehicle1to avoid the risk factor3in front of the vehicle1.

For example, inFIG.1, the vehicle1is traveling in a first lane L1in a roadway RW. A road shoulder RS is adjacent to the first lane L1. A pedestrian3A in the road shoulder RS in front of the vehicle1may enter the roadway RW (first lane L1). Thus, the pedestrian3A in the road shoulder RS in front of the vehicle1is the risk factor3. The risk avoidance control includes a “steering support control” that automatically steers the vehicle1so as to avoid the pedestrian3A in advance. Specifically, the driving support system10automatically steers the vehicle1in a direction away from the pedestrian3A (first direction) to avoid the pedestrian3A in advance.

The pedestrian3A may be replaced by a bicycle or a two-wheeled vehicle. Further, pedestrians, bicycles, two-wheeled vehicles, etc. in the roadway RW, besides the road shoulder RS, are included in the risk factor3.

FIG.2is a conceptual diagram illustrating another example of the risk avoidance control. The risk factor3is not limited to an “explicit risk” such as the pedestrian3A described above. The risk factor3may also include a “potential risk”. For example, inFIG.2, there is a parked vehicle3B in the road shoulder RS in front of the vehicle1. The region beyond the parked vehicle3B is a blind spot, from which the pedestrian3C may pop out. Thus, the parked vehicle3B in front of the vehicle1is a risk factor3(potential risk). The risk avoidance control includes the steering support control that automatically steers the vehicle1so as to avoid the parked vehicle3B in advance. Specifically, the driving support system10steers the vehicle1in a direction away from the parked vehicle3B (first direction).

As described above, examples of the risk factor3include pedestrians, bicycles, two-wheeled vehicles, parked vehicles, that are in front of the vehicle1.

Here, a vehicle coordinate system (X, Y) is defined. The vehicle coordinate system (X, Y) is a relative coordinate system fixed to the vehicle1, and changes with the movement of the vehicle1. The X direction is a forward direction (traveling direction) of the vehicle1. The Y direction is a lateral direction of the vehicle1. The X direction and the Y direction are orthogonal to each other.

InFIGS.1and2, a trajectory TR0represents a trajectory of the vehicle1when the steering support control is not executed. When the steering support control is not executed, it is assumed that the vehicle1travels in parallel with the first lane L1. Thus, the trajectory TR0extends parallel to the first lane L1from the current position of the vehicle1. In the following description, a lateral distance Dy is the shortest distance between the trajectory TR0and the risk factor3. In other words, the lateral distance Dy is the distance in the Y direction between the vehicle1(trajectory TR0) and the risk factor3when the vehicle1passes by the risk factor3.

InFIGS.1and2, a first trajectory TR1represents a trajectory of the vehicle1when the steering support control is executed. When the steering support control is executed, the vehicle1moves in the first direction away from the risk factor3. A lateral movement amount δDy is the movement amount of the vehicle1in the first direction due to the steering support control. In other words, the lateral movement amount δDy is the movement amount of the vehicle1in the first direction as seen from the trajectory TR0.

1-2. Steering Support Control on Curved Road

Next, the steering support control on a curved road will be discussed. Here, a road having a curvature C equal to or greater than a first curvature Cth is defined as a “curved road”. On the other hand, a road having a curvature C less than the first curvature Cth is defined as a “straight road”. According to the present embodiment, the steering support control method differs between a curved road and a straight road. Hereinafter, various examples of the steering support control on a curved road will be described.

FIG.3is a conceptual diagram illustrating a first example (comparative example) of the steering support control on a curved road. InFIG.3, the curved road is curved to the right. The steering direction of the steering support control, that is, the first direction is also the right direction. That is, the first direction coincides with the curved direction of the curved road. It can be said that the steering support control steers the vehicle1toward the inside of the curved road.

In the comparative example, the steering support control is executed on a curved road with the same control strength as in the case of a straight road. The first trajectory TR1is the trajectory of the vehicle1in the case of the comparative example. The first lateral movement amount δDy1is the lateral movement amount δDy in the case of the comparative example.

However, if the steering support control is executed on a curved road with the same control strength as in the case of a straight road, the occupant of the vehicle1(typically, the driver) may feel uneasy. For example, when the steering support control is further executed while the vehicle1is turning on a curved road, the lateral acceleration of the vehicle1is further increased, and the occupant may feel uneasy about the vehicle behavior. In the comparative example shown inFIG.3, the lateral acceleration increases particularly near the point A. When the first lateral movement amount δDy1is large, the occupant may feel uneasy about the vehicle1approaching an oncoming vehicle4in an adjacent lane LA.

1-2-2. Second Example

FIG.4is a conceptual diagram illustrating a second example of the steering support control on a curved road. Similar to the situation in the above comparative example, the steering direction of the steering support control, that is, the first direction coincides with the curved direction of the curved road.

According to the second example, the control strength of the steering support control is weakened as compared with the case of the comparative example. Weakening the control strength of the steering support control means reducing (mitigating) the influence of the steering support control on the trajectory of the vehicle1. In other words, weakening the control strength of the steering support control means reducing the lateral movement amount δDy in the first direction away from the risk factor3.

A second trajectory TR2is the trajectory of the vehicle1in the case of the second example. A second lateral movement amount δDy2is the lateral movement amount δDy in the case of the second example. As shown inFIG.4, the second trajectory TR2is located between the trajectory TR0and the first trajectory TR1. That is, the second lateral movement amount δDy2is smaller than the first lateral movement amount δDy1in the case of the comparative example. As a result, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed as compared with the case of the comparative example. It can also be said that the driving support system10executes the steering support control so that the lateral movement amount δDy and the lateral acceleration of the vehicle1due to the steering support control become smaller than in the case of the comparative example.

As described above, according to the second example, when the road ahead from the vehicle1to the risk factor3includes a curved road, the driving support system10weakens the control strength of the steering support control as compared with the case where the road ahead is a straight road. Thus, the lateral movement amount δDy of the vehicle1due to the steering support control becomes relatively small. Further, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed. Therefore, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

1-2-3. Third Example

FIG.5is a conceptual diagram illustrating a third example of the steering support control on a curved road. Descriptions that overlap with the second example described above will be omitted as appropriate. In the third example, the curved road is curved to the left. On the other hand, the steering direction of the steering support control, that is, the first direction is the right direction. That is, the first direction is opposite to the curved direction of the curved road. It can be said that the steering support control steers the vehicle1toward the outside of the curved road.

In the case of the comparative example, the occupant (typically, the driver) of the vehicle1may feel uneasy. For example, a large lateral acceleration may be applied to the vehicle1near the point A inFIG.4, which may cause the occupant to feel uneasy about the vehicle behavior. Further, since the first direction is opposite to the curved direction, the turning radius of the vehicle1is increased, and the occupant may feel uneasy about the possibility that the vehicle1may run off of the curve road. Further, when the first lateral movement amount δDy1is large, the occupant may feel uneasy about the vehicle1approaching the oncoming vehicle4in the adjacent lane LA.

In view of this, according to the third example, the control strength of the steering support control is weakened as compared with the case of the comparative example. A third trajectory TR3is the trajectory of the vehicle1in the case of the third example. A third lateral movement amount δDy3is the lateral movement amount δDy in the case of the third example. The third trajectory TR3is located between the trajectory TR0and the first trajectory TR1. That is, the third lateral movement amount δDy3is smaller than the first lateral movement amount δDy1in the case of the comparative example. As a result, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed as compared with the case of the comparative example. As a result, as in the case of the second example described above, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

In the case of the third example, the steering direction of the steering support control, that is, the first direction is opposite to the curved direction of the curved road. Thus, the feeling that the vehicle1may run off of the curved road is stronger than in the case of the second example described above (seeFIG.4). Therefore, in the case of the third example, the driving support system10may further weaken the control strength of the steering support control as compared with the case of the second example described above. In this case, the third trajectory TR3is located between the trajectory TR0and the second trajectory TR2. The third lateral movement amount δDy3is further smaller than the second lateral movement amount δDy2in the case of the second example. As a result, the uneasiness that the vehicle1may run off of the curved road is sufficiently reduced.

1-2-4. Fourth Example

FIG.6is a conceptual diagram illustrating a fourth example of the steering support control on a curved road. In the fourth example, as in the situation in the second example described above, the first direction coincides with the curved direction of the curved road. Descriptions that overlap with the second example will be omitted as appropriate.

First, as a comparative example, a case where the steering support control is started on a curved road at the same timing as in the case of a straight road will be discussed. In the case of the comparative example, the steering support control starts at a first start timing TS1. The first trajectory TR1is the trajectory of the vehicle1in the case of the comparative example.

According to the fourth example, the start timing of the steering support control is earlier as compared with the case of the comparative example. As shown inFIG.6, the driving support system10starts the steering support control at a second start timing TS2that is earlier than the first start timing TS1. A fourth trajectory TR4is the trajectory of the vehicle1in the case of the fourth example.

Since the start timing of the steering support control is earlier, the curvature of the fourth trajectory TR4is smaller than the curvature of the first trajectory TR1even when the lateral movement amount δDy (control strength) is the same. Thus, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed as compared with the case of the comparative example. It can also be said that the driving support system10executes the steering support control so that the lateral acceleration of the vehicle1due to the steering support control becomes smaller than in the case of the comparative example. Since the increase in the lateral acceleration is suppressed, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

The second example and the fourth example can also be combined. That is, the driving support system10may weaken the control strength of the steering support control and advance the start timing of the steering support control as compared with the case of the comparative example. In this way, the uneasiness of the occupant regarding the steering support control on the curved road is further reduced.

1-2-5. Fifth Example

FIG.7is a conceptual diagram illustrating a fifth example of the steering support control on a curved road. In the fifth example, as in the situation in the third example described above, the first direction is opposite to the curved direction of the curved road. Descriptions that overlap with the third and fourth examples will be omitted as appropriate.

According to the fifth example, the start timing of the steering support control is earlier as compared with the case of the comparative example. As shown inFIG.7, the driving support system10starts the steering support control at a third start timing TS3that is earlier than the first start timing TS1. A fifth trajectory TR5is the trajectory of the vehicle1in the case of the fifth example.

Since the start timing of the steering support control is earlier, the curvature of the fifth trajectory TR5is smaller than the curvature of the first trajectory TR1even when the lateral movement amount δDy (control strength) is the same. Thus, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed as compared with the case of the comparative example. As a result, as in the case of the fourth example described above, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

In the case of the fifth example, the steering direction of the steering support control, that is, the first direction is opposite to the curved direction of the curved road. Thus, the feeling that the vehicle1may run off of the curved road is stronger than in the case of the fourth example described above (seeFIG.6). Therefore, in the case of the fifth example, the driving support system10may further advance the start timing of the steering support control as compared with the case of the fourth example described above. In this case, the third start timing TS3is further earlier than the second start timing TS2in the case of the fourth example. As a result, the uneasiness such that the vehicle1may run off of the curved road is sufficiently reduced.

The third example and the fifth example can also be combined. That is, the driving support system10may weaken the control strength of the steering support control and advance the start timing of the steering support control as compared with the case of the comparative example. In this way, the uneasiness of the occupant regarding the steering support control on the curved road is further reduced.

As described above, the driving support system10according to the present embodiment executes the steering support control for steering the vehicle1in the first direction away from the risk factor3in front of the vehicle1. In particular, the driving support system10executes the steering support control in consideration of the road shape of the road ahead from the vehicle1to the risk factor3. Specifically, when the road ahead includes a curved road, the driving support system10weakens the control strength of the steering support control or advances the start timing of the steering support control as compared with the case where the road ahead is a straight road. As a result, the lateral movement amount δDy of the vehicle1due to the steering support control becomes relatively small. Alternatively, the increase in the lateral acceleration of the vehicle1due to the steering support control is suppressed. Therefore, the uneasiness of the occupant regarding the steering support control on the curved road is reduced.

When the first direction is opposite to the curved direction of the curved road, the driving support system10may weaken the control strength of the steering support control or may advance the start timing of the steering support control as compared with the case where the first direction coincides with the curved direction. As a result, the uneasiness such that the vehicle1may run off of the curved road is sufficiently reduced.

Hereinafter, the driving support system10according to the present embodiment will be described in more detail.

2. Driving Support System

2-1. Configuration Example

FIG.8is a block diagram schematically showing a configuration example of the vehicle1and the driving support system10according to the present embodiment. In particular,FIG.8shows a configuration example related to the risk avoidance control. The vehicle1includes a sensor group20and a traveling device30.

The sensor group20includes a position sensor21, a vehicle state sensor22, and a recognition sensor23. The position sensor21detects the position and orientation of the vehicle1. Examples of the position sensor21include a Global Positioning System (GPS) sensor. The vehicle state sensor22detects the state of the vehicle1. Examples of the vehicle state sensor22include a vehicle speed sensor, a yaw rate sensor, a lateral acceleration sensor, a steering angle sensor, and the like. The recognition sensor23recognizes (detects) the situation around the vehicle1. Examples of the recognition sensor23include a camera, a radar, a laser imaging detection and ranging (LIDAR), and the like.

The traveling device30includes a steering device31, a driving device32, and a braking device33. The steering device31steers the wheels of the vehicle1. For example, the steering device31includes a power steering (electric power steering (EPS)) device. The driving device32is a driving power source that generates a driving force. Examples of the driving device32include an engine, an electric motor, an in-wheel motor, and the like. The braking device33generates a braking force.

The driving support system10includes at least a control device100. The driving support system10may include the sensor group20. The driving support system10may include the traveling device30.

The control device100controls the vehicle1. Typically, the control device100is a microcomputer mounted on the vehicle1. The control device100is also referred to as an electronic control unit (ECU). Alternatively, the control device100may be an information processing device outside the vehicle1. In that case, the control device100communicates with the vehicle1and controls the vehicle1remotely.

The control device100includes a processor110and a storage device120. The processor110executes various processes. Various types of information are stored in the storage device120. Examples of the storage device120include a volatile memory, a non-volatile memory, and the like. When the processor110executes a control program that is a computer program, various processes executed by the processor110(control device100) are realized. The control program is stored in the storage device120or recorded on a computer-readable storage medium.

2-2. Information Acquisition Process

The processor110(control device100) executes an “information acquisition process” for acquiring driving environment information200indicating the driving environment of the vehicle1. The driving environment information200is acquired based on the detection results of the sensor group20mounted on the vehicle1. The acquired driving environment information200is stored in the storage device120.

FIG.9is a block diagram showing an example of the driving environment information200. The driving environment information200includes vehicle position information210, vehicle state information220, surrounding situation information230, map information260, and the like.

The vehicle position information210is information indicating the position and orientation of the vehicle1. The processor110acquires the vehicle position information210from the detection result of the position sensor21.

The vehicle state information220is information indicating the state of the vehicle1. Examples of the state of the vehicle1include a vehicle speed, a yaw rate, a lateral acceleration, a steering angle, and the like. The processor110acquires the vehicle state information220from the detection result of the vehicle state sensor22.

The surrounding situation information230is information indicating the surrounding situation of the vehicle1. The surrounding situation information230includes the information obtained by the recognition sensor23. For example, the surrounding situation information230includes image information indicating the surrounding situation of the vehicle1captured by the camera. As another example, the surrounding situation information230includes measurement information measured by the radar or the LIDAR. Further, the surrounding situation information230includes road configuration information240and object information250.

The road configuration information240is information regarding the road configuration around the vehicle1. The road configuration around the vehicle1includes lane markings (white lines) and road edge objects. The road edge objects are three-dimensional obstacles that indicate the edge of the road. Examples of the road edge objects include curbs, guardrails, walls, median strips, and the like. The road configuration information240indicates at least the positions of the lane markings and the road edge objects (positions relative to the vehicle1).

For example, by analyzing the image information obtained by the camera, the lane marking can be identified and the relative position of the lane marking can be calculated. Examples of the image analysis method include a semantic segmentation and an edge detection. Similarly, by analyzing the image information, the road edge object can be identified and the relative position of the road edge object can be calculated. Alternatively, the relative position of the road edge object can be acquired from radar measurement information.

The object information250is information regarding the object around the vehicle1. Examples of the object include pedestrians, bicycles, two-wheeled vehicles, other vehicles (preceding vehicles, parked vehicles, oncoming vehicles, etc.), and the like. The object information250indicates the relative position and the relative speed of the object with respect to the vehicle1. For example, by analyzing the image information obtained by the camera, the object can be identified and the relative position of the object can be calculated. It is also possible to identify the object and acquire the relative position and the relative speed of the object based on the radar measurement information. The object information250may include the moving direction and the moving speed of the object. The moving direction and the moving speed of the object can be calculated by tracking the position of the object.

The map information260indicates a lane arrangement, a road shape, and the like. The control device100acquires the map information260of the required area from a map database. The map database may be stored in a predetermined storage device mounted on the vehicle1, or may be stored in a management server outside the vehicle1. In the latter case, the processor110communicates with the management server to acquire the necessary map information260.

2-3. Vehicle Travel Control

The processor110(control device100) executes a “vehicle travel control” that controls the traveling of the vehicle1. The vehicle travel control includes a steering control for controlling the steering of the vehicle1, an acceleration control for controlling the acceleration of the vehicle1, and a deceleration control for controlling the deceleration of the vehicle1. The processor110executes the vehicle travel control by controlling the traveling device30. Specifically, the processor110executes the steering control by controlling the steering device31. Further, the processor110executes the acceleration control by controlling the driving device32. Further, the control device100executes the deceleration control by controlling the braking device33.

2-4. Risk Avoidance Control

The processor110(control device100) executes a driving support control that supports the driving of the vehicle1. The driving support control includes a risk avoidance control that avoids a risk factor3in front of the vehicle1. The risk avoidance control is a vehicle travel control for avoiding the risk factor3in front of the vehicle1, and includes at least one of the steering control and the deceleration control. The processor110executes the risk avoidance control based on the above-mentioned driving environment information200.

FIG.10is a flowchart showing a process related to the risk avoidance control according to the embodiment of the present disclosure. The process flow shown inFIG.10is repeatedly executed at regular cycles.

In step S100, the processor110executes the above-mentioned information acquisition process. That is, the processor110acquires the driving environment information200based on the detection result of the sensor group20. The driving environment information200is stored in the storage device120.

In step S200, the processor110determines whether there is the risk factor3in front of the vehicle1. In other words, the processor110determines whether the risk factor3is recognized in the region in front of the vehicle1. The risk factor3includes at least one of pedestrians, bicycles, two-wheeled vehicles, and parked vehicles in front of the vehicle1.

The processor110determines whether there is the risk factor3in front of the vehicle1based on the surrounding situation information230(particularly, the road configuration information240and the object information250). Whether there is the risk factor3in the roadway RW or whether there is the risk factor3in the road shoulder RS can be determined by comparing the position of the risk factor3with the position of the lane marking. Alternatively, whether there is the risk factor3in the roadway RW or whether there is the risk factor3in the road shoulder RS can be determined by comparing the position of the risk factor3with the lane arrangement shown in the map information260.

When the risk factor3in front of the vehicle1is recognized (step S200; Yes), the process proceeds to step S300. In other cases (step S200; No), the process returns to step S100.

In step S300, the processor110determines whether the operating condition of the risk avoidance control is satisfied.

For example, the operating condition of the risk avoidance control includes that “a margin time T up to the risk factor3is less than an operating threshold Tth”. The margin time T is the time required for the vehicle1to travel from the current position to the position closest to the risk factor3. The trajectory TR0shown inFIGS.1to7represents a trajectory of the vehicle1when the steering support control is not executed. It can be said that the margin time T is the time until the vehicle1comes closest to the risk factor when the vehicle1travels along the trajectory TR0at the current vehicle speed. Typically, the timing at which the vehicle1comes closest to the risk factor3is the timing at which the vehicle1passes by the risk factor3.

The processor110can estimate the trajectory TR0based on the driving environment information200. For example, the road configuration information240indicates the relative positions of the lane markings (white lines) and the road edge objects. Based on the road configuration information240, the processor110can recognize the roadway RW or the first lane L1, and can estimate the trajectory TR0parallel to the roadway RW or the first lane L1. As another example, the processor110can obtain the road shape in front of the vehicle1from the map information260, and can estimate the trajectory TR0based on the road shape and the vehicle position information210.

The current vehicle speed of the vehicle1is obtained from the vehicle state information220. The relative position of the risk factor3with respect to the vehicle1is obtained from the object information250. The processor110can calculate the margin time T up to the risk factor3based on the trajectory TR0, the current vehicle speed of the vehicle1, and the relative position of the risk factor3. Then, the processor110determines whether the operating condition of the risk avoidance control is satisfied by comparing the margin time T with the operating threshold Tth.

The operating condition of the risk avoidance control may further include that “the lateral distance Dy is smaller than a lateral distance threshold”. As shown inFIGS.1to7, the lateral distance Dy is the shortest distance between the trajectory TR0and the risk factor3. The lateral distance threshold (safety margin) may increase as the vehicle speed increases and may decrease as the vehicle speed decreases.

The operating condition of the risk avoidance control may further include that the vehicle speed of the vehicle1is equal to or higher than a certain speed.

When the operating condition of the risk avoidance control is satisfied (step S300; Yes), the process proceeds to step S400. On the other hand, when the operating condition of the risk avoidance control is not satisfied (step S300; No), the process proceeds to step S500.

In step S400, the processor110executes the risk avoidance control, that is, activates the risk avoidance control. The risk avoidance control is a vehicle travel control for avoiding the risk factor3, and includes at least one of the steering control and the deceleration control. In particular, the steering control for avoiding the risk factor3is the “steering support control” according to the present embodiment. In the steering support control, the processor110steers the vehicle1in the first direction away from the risk factor3based on the driving environment information200.

FIG.11is a conceptual diagram illustrating an example of the steering support control. The processor110sets a risk region RSK around the recognized risk factor3. The risk region RSK is a region where it is desired that the vehicle1does not pass. A margin distance dm is a parameter representing the size of the risk region RSK. The margin distance dm may be a constant value or may be variable. For example, the margin distance dm may be variably set depending on the vehicle speed of the vehicle1. In that case, as the vehicle speed increases, the margin distance dm increases. The position of the risk factor3is obtained from the object information250. The vehicle speed is obtained from the vehicle state information220. Thus, the processor110can set the risk region RSK based on the object information250and the vehicle state information220.

Further, the processor110generates a target trajectory TRt so that the vehicle1avoids the risk region RSK. The target trajectory TRt includes the target position and the target speed of the vehicle1in the roadway RW. The current position of the vehicle1is obtained from the vehicle position information210. The vehicle speed is obtained from the vehicle state information220. The position of the roadway RW is obtained from the road configuration information240or the map information260. Therefore, the processor110can generate the target trajectory TRt based on the risk region RSK and the driving environment information200.

Then, the processor110executes the vehicle travel control so that the vehicle1follows the target trajectory TRt. In particular, the processor110executes the steering support control so that the vehicle1follows the target trajectory TRt. Specifically, the processor110calculates a target steering amount (target steering angle) θt required for the vehicle1to follow the target trajectory TRt. The current steering angle of the vehicle1is obtained from the vehicle state information220. The processor110controls the steering device31to steer the wheels such that the target steering amount θt is realized.

The magnitude of the target steering amount θt depends on the magnitude of the lateral distance Dy between the vehicle1and the risk factor3and the risk region RSK (margin distance dm). For example, when the lateral distance Dy is small, the target trajectory TRt bends greatly in the Y direction in order to secure the margin distance dm. As a result, the target steering amount θt required to follow the target trajectory TRt also increases. In contrast, when the lateral distance Dy is sufficiently large and the margin distance dm is secured, the target steering amount θt becomes small.

The above is generally described as follows. The target steering amount θt in the steering support control is represented by a function of a relative relationship parameter Pr. The relative relationship parameter Pr represents the relative relationship between the vehicle1and the risk factor3. This relative relationship parameter Pr includes at least the lateral distance Dy between the vehicle1and the risk factor3. As the lateral distance Dy decreases, the target steering amount θt required to avoid the risk factor3increases. The relative relationship parameter Pr may further include the relative speed between the vehicle1and the risk factor3. The relative relationship parameter Pr is obtained from the driving environment information200(particularly the object information250). The processor110calculates (determines) the target steering amount θt depending on the relative relationship parameter Pr. Then, the processor110executes the steering support control based on the target steering amount θt.

In step S500, processor110does not execute the risk avoidance control. That is, the processor110does not activate the risk avoidance control. When the risk avoidance control is already being executed, the processor110stops the risk avoidance control.

3. Adjustment of Operating Condition

As described above, the operating condition of the risk avoidance control includes that “the margin time T up to the risk factor3is less than the operating threshold Tth”. By adjusting this operating condition, the start timing of the risk avoidance control (steering support control) can be adjusted. Hereinafter, various examples of methods for adjusting the operating condition of the risk avoidance control will be described. “Condition adjustment information300” shown inFIG.12is used to adjust the operating condition of the risk avoidance control. The condition adjustment information300is created in advance and stored in the storage device120.

3-1. First Example

FIG.13is a flowchart illustrating a first example of adjusting the operating condition of the risk avoidance control.FIG.13shows the details of step S300described above.

In step S310, the processor110determines whether the road ahead from the vehicle1to the risk factor3is a straight road. A straight road is a road having a curvature C less than the first curvature Cth. A curved road is a road having a curvature C equal to or greater than the first curvature Cth. For example, the road configuration information240indicates the relative positions of the lane markings (white lines) and the road edge objects. Based on the road configuration information240, the road ahead of the vehicle1can be recognized and the curvature C of the road ahead can be calculated. As another example, the processor110can obtain the road shape in front of the vehicle1from the map information260, and can calculate the curvature C from the road shape.

When the road ahead is a straight road (step S310; Yes), the process proceeds to step S320. On the other hand, when the road ahead includes a curved road (step S310; No), the process proceeds to step S330.

In step S320, the processor110sets the operating threshold Tth to a first operating threshold Tth1. Then, the process proceeds to step S340.

In step S330, the processor110sets the operating threshold Tth to a second operating threshold Tth2. The second operating threshold Tth2is larger than the first operating threshold Tth1(Tth2>Tth1). Then, the process proceeds to step S340.

In step S340, the processor110determines whether the operating condition of the risk avoidance control is satisfied. When the operating threshold Tth is the first operating threshold Tth1, the operating condition is satisfied at the first start timing TS1. On the other hand, when the operating threshold Tth is the second operating threshold Tth2, the operating condition is satisfied at the second start timing TS2that is earlier than the first start timing TS1. That is, when the road ahead is a curved road, the start timing of the steering support control is earlier than when the road ahead is a straight road (seeFIGS.6and7). When the operating condition is satisfied (step S340; Yes) the process proceeds to step S400. On the other hand, when the operating condition is not satisfied (step S340; No) the process proceeds to step S500.

The information of the operating threshold Tth (Tth1, Tth2) is included in the condition adjustment information300. The processor110refers to the condition adjustment information300and selects the operating threshold Tth depending on the road shape of the road ahead. This makes it possible to variably set the start timing of the steering support control depending on the road shape of the road ahead.

3-2. Second Example

FIG.14is a flowchart illustrating a second example of adjusting the operating condition of the risk avoidance control. Descriptions that overlap with the first example shown inFIG.13will be omitted as appropriate. Steps S310and S320are the same as in the first example. When the road ahead includes a curved road (step S310; No), the process proceeds to step S331.

In step S331, the processor110recognizes the steering direction (first direction) by the steering support control, assuming that the steering support control is activated. For example, when there is the risk factor3in the road shoulder RS on the left side of the first lane L1, the steering direction away from the risk factor3is the right direction. Generally speaking, the steering direction of the steering support control is determined based on the positional relationship between the vehicle1, the risk factor3, and the roadway RW (first lane L1). The position of the vehicle1is obtained from the vehicle position information210. The relative position of the risk factor3is obtained from the object information250. The position of the roadway RW (first lane L1) is obtained from the road configuration information240or the map information260. Thus, the processor110can recognize the steering direction of the steering support control based on the driving environment information200.

Then, the processor110determines whether the steering direction of the steering support control coincides with the curved direction of the curved road. The curved direction is obtained from the road configuration information240or the map information260. When the steering direction coincides with the curved direction (step S331; Yes), the process proceeds to step S332. On the other hand, when the steering direction is opposite to the curved direction (step S331; No), the process proceeds to step S333.

In step S332, the processor110sets the operating threshold Tth to the second operating threshold Tth2. The second operating threshold Tth2is larger than the first operating threshold Tth1(Tth2>Tth1). Then, the process proceeds to step S340.

In step S333, the processor110sets the operating threshold Tth to a third operating threshold Tth3. The third operating threshold Tth3is further larger than the second operating threshold Tth2(Tth3>Tth2). Then, the process proceeds to step S340.

In step S340, the processor110determines whether the operating condition of the risk avoidance control is satisfied. When the operating threshold Tth is the second operating threshold Tth2, the operating condition is satisfied at the second start timing TS2that is earlier than the first start timing TS1. When the operating threshold Tth is the third operating threshold Tth3, the operating condition is satisfied at the third start timing TS3that is further earlier than the second start timing TS2. That is, when the steering direction is opposite to the curved direction (seeFIG.7), the start timing of the steering support control is earlier than when the steering direction coincides with the curved direction (seeFIG.6). When the operating condition is satisfied (step S340; Yes) the process proceeds to step S400. On the other hand, when the operating condition is not satisfied (step S340; No) the process proceeds to step S500.

The information of the operating threshold Tth (Tth1, Tth2, Tth3) is included in the condition adjustment information300. The processor110refers to the condition adjustment information300and selects the operating threshold Tth depending on the road shape of the road ahead and the steering direction. This makes it possible to variably set the start timing of the steering support control depending on the road shape of the road ahead and the steering direction.

3-3. Third Example

FIG.15is a conceptual diagram illustrating a third example of adjusting the operating condition of the risk avoidance control. In the third example, the operating threshold Tth increases as the curvature C of the road ahead increases. For example, as shown inFIG.15, the operating threshold Tth increases monotonically as the curvature C increases. As another example, the operating threshold Tth may increase stepwise as the curvature C increases. Thus, as the curvature C increases, the start timing of the risk avoidance control (steering support control) becomes earlier.

The operating threshold Tth is represented by a function of the curvature C of the road ahead. The function may be a mathematical formula or a map generated in advance. The information of the function is included in the condition adjustment information300. The processor110uses the function shown in the condition adjustment information300to set the operating threshold Tth depending on the curvature C of the road ahead. Thus, the processor110can advance the start timing of the steering support control as the curvature C increases.

The third example can be combined with either one of the first example and the second example described above.

4. Adjustment of Control Strength of Steering Support Control

The control strength of the steering support control may be adjusted in place of or in conjunction with the adjustment of the operating condition described above. Hereinafter, various examples of methods for adjusting the control strength of the steering support control will be described. “Control adjustment information400” shown inFIG.16is used to adjust the control strength of the steering support control. The control adjustment information400is created in advance and stored in the storage device120.

4-1. First Example

FIG.17is a flowchart illustrating a first example of adjusting the control strength of the steering support control.FIG.17shows the details of step S400described above.

In step S410, the processor110determines whether the road ahead from the vehicle1to the risk factor3is a straight road. This determination method is the same as step S310(seeFIG.13) described above. When the road ahead is a straight road (step S410; Yes), the process proceeds to step S420. On the other hand, when the road ahead includes a curved road (step S410; No), the process proceeds to step S430.

In step S420, the processor110sets the control strength of the steering support control to a relatively strong level.

In step S430, the processor110sets the control strength of the steering support control weaker than that in step S420.

Weakening the control strength of the steering support control means reducing (mitigating) the influence of the steering support control on the trajectory of the vehicle1. In other words, weakening the control strength of the steering support control means reducing the lateral movement amount δDy in the first direction away from the risk factor3. Further, in other words, weakening the control strength of the steering support control means reducing the target steering amount θt in the steering support control. As the target steering amount θt increases, the lateral movement amount δDy in the first direction away from the risk factor3increases. In contrast, as the target steering amount θt decreases, the lateral movement amount δDy in the first direction away from the risk factor3decreases. That is, the control strength of the steering support control can be weakened by reducing the target steering amount θt.

Generally, as in the following equation (1), the target steering amount θt is represented by a function f of the relative relationship parameter Pr. The relative relationship parameter Pr includes at least the lateral distance Dy between the vehicle1and the risk factor3. The relative relationship parameter Pr may further include the relative speed between the vehicle1and the risk factor3.
θt=f(Pr)  Equation (1):

When compared under the condition that the relative relationship parameters Pr are the same, the target steering amount θt in step S430(curved road) is smaller than the target steering amount θt in step S420(straight road). That is, the processor110sets the target steering amount θt for the same relative relationship parameter Pr smaller in the case of step S430than in the case of step S420.

For example, in step S420, the processor110calculates a first target steering amount θt1using a first function f1(see the following equation (2)). On the other hand, in step S430, the processor110calculates a second target steering amount θt2using a second function f2. The first function f1and the second function f2are set so that the second target steering amount θt2is smaller than the first target steering amount θt1when compared under the condition that the relative relationship parameters Pr are the same.
θt1=f1(Pr)
θt2=f2(Pr)<f1(Pr)  Equation (2):

As an example, the steering support control based on the risk region RSK shown inFIG.11above will be discussed. In this case, the function f includes the following processes: [a] setting the risk region RSK (margin distance dm); [b] generating the target trajectory TRt based on the risk region RSK and the relative relationship parameter Pr (lateral distance Dy); and [c] calculating the target steering amount θt based on the target trajectory TRt. Of these, by reducing the risk region RSK (margin distance dm) in the process [a], the target steering amount θt for the same relative relationship parameter Pr can be reduced. Specifically, the first function f1is set to calculate the first target steering amount θt1using a first margin distance dm1. On the other hand, the second function f2is set to calculate the second target steering amount θt2using a second margin distance dm2that is smaller than the first margin distance dm1. As a result, the second target steering amount θt2becomes smaller than the first target steering amount θt1when compared under the condition that the relative relationship parameters Pr are the same.

The information of each function f (f1, f2) is included in the control adjustment information400. The processor110selects the function f depending on the road shape of the road ahead and calculates the target steering amount θt using the selected function f. Thereby, the magnitude of the target steering amount θt, that is, the control strength of the steering support control can be variably set depending on the road shape of the road ahead.

4-2. Second Example

FIG.18is a flowchart illustrating a second example of adjusting the control strength of the steering support control. Descriptions that overlap with the first example shown inFIG.17will be omitted as appropriate. Steps S410and S420are the same as in the first example. When the road ahead includes a curved road (step S410; No), the process proceeds to step S431.

In step S431, the processor110determines whether the steering direction (first direction) of the steering support control coincides with the curved direction of the curved road. This determination method is the same as step S331(seeFIG.14) described above. When the steering direction coincides with the curved direction (step S431; Yes), the process proceeds to step S432. On the other hand, when the steering direction is opposite to the curved direction (step S431; No), the process proceeds to step S433.

In step S432, the processor110sets the control strength of the steering support control weaker than that in step S420.

In step S433, the processor110sets the control strength of the steering support control further weaker than that in step S432. That is, when the steering direction is opposite to the curved direction (seeFIG.5), the control strength of the steering support control is weaker than when the steering direction coincides with the curved direction (seeFIG.4).

Further specifically, when compared under the condition that the relative relationship parameters Pr are the same, the target steering amount θt in step S433is smaller than the target steering amount θt in step S432. That is, the processor110sets the target steering amount θt for the same relative relationship parameter Pr smaller in the case of step S433than in the case of step S432.

For example, in step S420, the processor110calculates the first target steering amount θt1using the first function f1(see the following equation (3)). In step S432, the processor110calculates the second target steering amount θt2using the second function f2. In step S433, the processor110calculates a third target steering amount θt3using a third function f3. The first function f1and the second function f2are set so that the second target steering amount θt2is smaller than the first target steering amount θt1when compared under the condition that the relative relationship parameters Pr are the same. Similarly, the second function f2and the third function f3are set so that the third target steering amount θt3is smaller than the second target steering amount θt2.
θt1=f1(Pr)
θt2=f2(Pr)<f1(Pr)
θt3=f3(Pr)<f2(Pr)  Equation (3):

The information of each function f (f1, f2, f3) is included in the control adjustment information400. The processor110refers to the control adjustment information400and selects the function f depending on the road shape of the road ahead and the steering direction to calculate the target steering amount θt using the selected function f. Thereby, the magnitude of the target steering amount θt, that is, the control strength of the steering support control can be variably set depending on the road shape of the road ahead and the steering direction.

4-3. Third Example

In the third example, the processor110further weakens the control strength of the steering support control as the curvature C of the road ahead increases.

More specifically, when compared under the condition that the relative relationship parameters Pr are the same, the target steering amount θt decreases as the curvature C increases. That is, the processor110sets the target steering amount θt for the same relative relationship parameter Pr smaller as the curvature C increases.

For example, as in the following equation (4), the target steering amount θt is represented by a function g of the relative relationship parameter Pr and the curvature C. The function g is set such that, when compared under the condition that the relative relationship parameters Pr are the same, the target steering amount θt decreases as the curvature C increases.
θt=g(Pr,C)  Equation (4):

FIG.19is a graph showing an example of the function g. As the curvature C increases, the target steering amount θt decreases. As the curvature C increases, the target steering amount θt may decrease monotonically or stepwise.

FIG.20is a graph showing another example of the function g. In the example shown inFIG.20, the margin distance dm of the risk region RSK depends on the curvature C of the road ahead. More specifically, as the curvature C increases, the margin distance dm decreases. Thus, as the curvature C increases, the target steering amount θt decreases. As the curvature C increases, the margin distance dm may decrease monotonically or stepwise.

The information of the function g is included in the control adjustment information400. The processor110calculates the target steering amount θt depending on the curvature C using the function g shown in the control adjustment information400. Thereby, the magnitude of the target steering amount θt, that is, the control strength of the steering support control can be variably set depending on the curvature C of the road ahead.

The third example can be combined with either one of the first example and the second example described above.

5. Adjustment of Start Timing of Steering Support Control

Instead of adjusting the operating condition of the risk avoidance control in step S300, the start timing of the steering support control may be adjusted “directly” in step S400. Hereinafter, various examples of methods for adjusting the start timing of the steering support control will be described.

5-1. First Example

FIG.21is a flowchart illustrating a first example of adjusting the start timing of the steering support control.FIG.21shows the details of step S400described above.

In step S410, the processor110determines whether the road ahead from the vehicle1to the risk factor3is a straight road. This determination method is the same as step S310(seeFIG.13) described above. When the road ahead is a straight road (step S410; Yes), the process proceeds to step S450. On the other hand, when the road ahead includes a curved road (step S410; No), the process proceeds to step S460.

In step S450, the processor110sets the start timing of the steering support control to a relatively later timing.

In step S460, the processor110sets the start timing of the steering support control to a timing earlier than that in step S450. That is, when the road ahead includes a curved road, the start timing of the steering support control is earlier than when the road ahead is a straight road (seeFIGS.6and7).

For example, the processor110sets the start timing of the steering support control to a timing delayed from the reference timing by a delay time td. In step S450, the processor110sets the delay time td to a first delay time td1. On the other hand, in step S460, the processor110sets the delay time td to a second delay time td2. The second delay time td2is shorter than the first delay time td1(td2<td1).

The information of the delay time td (td1, td2) is included in the control adjustment information400. The processor110refers to the control adjustment information400and selects the delay time td depending on the road shape of the road ahead. This makes it possible to variably set the start timing of the steering support control depending on the road shape of the road ahead.

5-2. Second Example

FIG.22is a flowchart illustrating a second example of adjusting the start timing of the steering support control. Descriptions that overlap with the first example shown inFIG.21will be omitted as appropriate. Steps S410and S450are the same as in the first example. When the road ahead includes a curved road (step S410; No), the process proceeds to step S461.

In step S461, the processor110determines whether the steering direction (first direction) of the steering support control coincides with the curved direction of the curved road. This determination method is the same as step S331(seeFIG.14) described above. When the steering direction coincides with the curved direction (step S461; Yes), the process proceeds to step S462. On the other hand, when the steering direction is opposite to the curved direction (step S461; No), the process proceeds to step S463.

In step S462, the processor110sets the start timing of the steering support control to a timing earlier than that in step S450. For example, the processor110sets the delay time td to the second delay time td2, which is shorter than the first delay time td1(td2<td1).

In step S463, the processor110sets the start timing of the steering support control to a timing earlier than that in step S462. For example, the processor110sets the delay time td to a third delay time td3, which is further shorter than the second delay time td2(td3<td2). Thus, when the steering direction is opposite to the curved direction (seeFIG.7), the start timing of the steering support control is earlier than when the steering direction coincides with the curved direction (seeFIG.6).

The information of the delay time td (td1, td2, td3) is included in the control adjustment information400. The processor110refers to the control adjustment information400and selects the delay time td depending on the road shape of the road ahead and the steering direction. This makes it possible to variably set the start timing of the steering support control depending on the road shape of the road ahead and the steering direction.

5-3. Third Example

FIG.23is a flowchart illustrating a third example of adjusting the start timing of the steering support control. In the third example, the delay time td decreases as the curvature C of the road ahead increases. For example, as shown inFIG.23, as the curvature C increases, the delay time td decreases monotonically. As another example, as the curvature C increases, the delay time td may decrease stepwise. Thus, as the curvature C increases, the start timing of the risk avoidance control (steering support control) becomes earlier.

The delay time td is represented by a function of the curvature C of the road ahead. The function may be a mathematical formula or a map generated in advance. The information of the function is included in the control adjustment information400. The processor110uses the function shown in the control adjustment information400to set the delay time td depending on the curvature C of the road ahead. Thus, the processor110can advance the start timing of the steering support control as the curvature C increases.

The third example can be combined with either one of the first example and the second example described above.