WO2024116365A1 - Driving assistance device, driving assistance method, and recording medium - Google Patents

Abstract

The present invention provides a driving assistance device that assists driving of a vehicle capable of performing following control, the driving assistance device executing: an acquisition process for acquiring vehicle characteristic information pertaining to a characteristic of other vehicles traveling around the vehicle; and a preceding vehicle proposing process for assuming any one or more first other vehicles from among the other vehicles as preceding vehicles, identifying a second other vehicle that is a following vehicle of the vehicle when the first other vehicles are assumed to be the preceding vehicles, and proposing the preceding vehicle on the basis of preference information regarding surrounding vehicles of a driver of the vehicle and the vehicle characteristic information pertaining to the first other vehicles and the second other vehicle.

Description

Driving assistance device, driving assistance method, and recording medium

This disclosure relates to a driving assistance device, a driving assistance method, and a recording medium.

In recent years, vehicles equipped with adaptive cruise control (ACC) functions that allow a vehicle to follow a preceding vehicle have been put into practical use. Adaptive cruise control is a control that allows a vehicle to automatically follow a preceding vehicle while maintaining a target inter-vehicle distance that is set according to the vehicle's speed, etc.

Regarding such following control functions, for example, Patent Document 1 discloses a leading vehicle selection assistance device that acquires host vehicle information including information that can identify the vehicle's current position and planned driving route, acquires other vehicle information including information that can identify the current position, speed, and planned driving route of other vehicles that are candidates for preceding vehicles, calculates a merging cost that represents the burden on the driver until the host vehicle merges with the other vehicles based on the host vehicle information and other vehicle information, and narrows down the candidates for preceding vehicles.

Patent Document 2 also discloses a following control device that sets an inter-vehicle distance according to the driver's characteristics, calculates an inter-vehicle distance according to the driving conditions of the surrounding vehicles, and calculates a target inter-vehicle distance between the vehicle and the preceding vehicle based on the inter-vehicle distance according to the driver's characteristics and the inter-vehicle distance according to the driving conditions of the surrounding vehicles, thereby controlling the vehicle's speed.

International Publication No. 2016/170635 JP 2008-189055 A

However, the technologies disclosed in Patent Documents 1 and 2 above are technologies for selecting a leading vehicle and setting the distance from the leading vehicle based on predetermined conditions, and neither of them takes into consideration the following vehicle when the vehicle is made to follow the leading vehicle. Therefore, there is a risk that a situation may arise where the following control function has to be stopped even though the leading vehicle has been determined and following has begun due to the following vehicle, for example, when the safety of the following vehicle is low, such as when the vehicle is closing the gap, or when the vehicle does not want to be followed by the same following vehicle for a long period of time.

This disclosure has been made in consideration of the above problems, and the purpose of this disclosure is to provide a driving assistance device, driving assistance method, and recording medium that can suggest a leading vehicle by taking into account not only the leading vehicle but also vehicles that could potentially follow when performing following control.

In order to solve the above problem, according to one aspect of the present disclosure, there is provided a driving assistance device that assists driving of a vehicle capable of performing following control to cause the vehicle to travel by following a preceding vehicle, the driving assistance device including one or more processors and one or more memories communicably connected to the one or more processors, the one or more processors executing an acquisition process for acquiring vehicle characteristic information related to the characteristics of other vehicles traveling around the vehicle, and a preceding vehicle suggestion process for assuming any one or more first other vehicles among the other vehicles as the preceding vehicle, identifying a second other vehicle that will be a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and proposing the preceding vehicle based on preference information related to the surrounding vehicles of the driver of the vehicle and the vehicle characteristic information of the first other vehicle and the second other vehicle.

In addition, according to another aspect of the present disclosure to solve the above problem, there is provided a driving assistance method for assisting driving of a vehicle capable of performing following control to cause the vehicle to travel by following a preceding vehicle, in which the one or more processors execute processes including acquiring vehicle characteristic information regarding the characteristics of other vehicles traveling around the vehicle, assuming any one or more first other vehicles among the other vehicles as the preceding vehicle, identifying a second other vehicle that is a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and proposing the preceding vehicle based on preference information of the driver of the vehicle regarding the surrounding vehicles and the vehicle characteristic information of the first other vehicle and the second other vehicle.

Furthermore, in order to solve the above problem, according to another aspect of the present disclosure, a non-transitory tangible recording medium is provided that has recorded thereon a computer program that causes one or more processors to execute an acquisition process for acquiring vehicle characteristic information related to the characteristics of other vehicles traveling around the vehicle, and a preceding vehicle suggestion process for assuming any one or more of the other vehicles as a first other vehicle as a preceding vehicle, identifying a second other vehicle that is a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and suggesting the preceding vehicle when performing following control based on preference information of the driver of the vehicle regarding the surrounding vehicles and the vehicle characteristic information of the first other vehicle and the second other vehicle.

As described above, according to the present disclosure, when performing following control, it is possible to suggest a leading vehicle by taking into consideration not only the leading vehicle but also vehicles that could potentially follow.

1 is a schematic diagram illustrating a configuration example of a vehicle equipped with a driving assistance device according to an embodiment of the present disclosure. 2 is a block diagram showing a configuration example of a driving assistance device according to the embodiment; FIG. 4 is a flowchart showing a main routine of a control process performed by the driving assistance device according to the embodiment; 5 is a flowchart of a host vehicle-based preceding vehicle proposing process performed by the driving assistance device according to the first embodiment. 4 is an explanatory diagram showing an example of setting a preceding vehicle by the driving assistance device according to the embodiment; FIG. 11 is an explanatory diagram showing another example of setting a preceding vehicle by the driving assistance device according to the embodiment; FIG. FIG. 13 is an explanatory diagram showing an example in which a preceding vehicle is set taking into consideration only the preceding vehicle match degree. 10 is an explanatory diagram showing an example in which a preceding vehicle is set by the driving assistance device according to the embodiment, taking into account a preceding vehicle match degree and a following vehicle match degree. FIG. 5 is an explanatory diagram showing an example of setting a target inter-vehicle distance according to a preceding vehicle matching degree by the driving assistance device according to the embodiment; FIG. 11 is an explanatory diagram showing an example in which the driving assistance device according to the embodiment sets the target inter-vehicle distance to a value smaller than the reference inter-vehicle distance when the preceding vehicle match degree of the preceding vehicle is "high." FIG. 11 is an explanatory diagram showing an example in which the driving assistance device according to the embodiment sets the target inter-vehicle distance to a value greater than the reference inter-vehicle distance when the preceding vehicle match degree of the preceding vehicle is "low." FIG. FIG. 10 is an explanatory diagram showing a setting example in which the driving support device according to the embodiment adjusts the target inter-vehicle distance according to the visibility (vehicle size) of the driver of the vehicle; 4 is an explanatory diagram showing an example in which a target inter-vehicle distance is set based on a preceding vehicle match degree and a following vehicle match degree by the driving assistance device according to the embodiment; FIG. 11 is a diagram for explaining an example of a situation in which a preceding vehicle is re-suggested by the driving assistance device according to the embodiment; FIG. 10 is an explanatory diagram showing an area in which a preceding vehicle is re-proposed based on a following duration or a followed-behind duration by the driving assistance device according to the embodiment; FIG. 10 is a flowchart illustrating an example of a process for determining whether to re-suggest a preceding vehicle by the driving assistance device according to the embodiment. 13 is a flowchart of a preceding vehicle suggestion process that takes into consideration the comfort of the following vehicle by a driving assistance device according to a second embodiment. 4 is an explanatory diagram showing an example of setting a preceding vehicle based on a preceding vehicle match degree and a following vehicle reference match degree by the driving assistance device according to the embodiment; FIG.

Below, a preferred embodiment of the present disclosure will be described in detail with reference to the attached drawings. Note that in this specification and drawings, components having substantially the same functional configuration will be denoted by the same reference numerals to avoid redundant description.

In this specification, a vehicle that executes following control and follows a preceding vehicle is referred to as the "own vehicle." Also, a vehicle that the own vehicle follows when executing following control is referred to as the "preceding vehicle." Also, a vehicle that travels behind the own vehicle when executing following control is referred to as the "following vehicle."

1. First embodiment
(1-1. Overall configuration of the vehicle)
First, an example of the overall configuration of a vehicle equipped with a driving assistance device according to an embodiment of the present disclosure will be described.

FIG. 1 is a schematic diagram showing an example of the configuration of a vehicle 1.
The vehicle 1 is configured as a two-wheel drive four-wheel vehicle in which a driving torque output from a driving force source 9 that generates a driving torque is transmitted to a left front wheel and a right front wheel. The driving force source 9 may be an internal combustion engine such as a gasoline engine or a diesel engine, a driving motor, or may include both an internal combustion engine and a driving motor.

Vehicle 1 may be a four-wheel drive vehicle that transmits drive torque to the front and rear wheels. Vehicle 1 may also be an electric vehicle equipped with two drive motors, for example a motor for driving the front wheels and a motor for driving the rear wheels, or an electric vehicle equipped with drive motors corresponding to each wheel. If vehicle 1 is an electric vehicle or hybrid electric vehicle, vehicle 1 is equipped with a secondary battery that stores power supplied to the drive motor, and a generator such as a motor or fuel cell that generates power to charge the battery.

Vehicle 1 is equipped with a driving force source 9, an electric steering device 15, and brake devices 17LF, 17RF, 17LR, 17RR (hereinafter collectively referred to as "brake devices 17" unless a distinction is required) as devices used to control the operation of vehicle 1. Driving force source 9 outputs driving torque that is transmitted to front wheel drive shaft 5F via a transmission and differential mechanism 7 (not shown). The operation of driving force source 9 and the transmission is controlled by a vehicle control unit 41 that includes one or more electronic control devices (ECU: Electronic Control Unit).

The front-wheel drive shaft 5F is provided with an electric steering device 15. The electric steering device 15 includes an electric motor and a gear mechanism (not shown), and is controlled by the vehicle control unit 41 to adjust the steering angle of the front wheels. During manual driving, the vehicle control unit 41 controls the electric steering device 15 based on the steering angle of the steering wheel 13 by the driver. During automatic driving, the vehicle control unit 41 controls the electric steering device 15 based on the set steering angle or steering angular speed.

Brake devices 17LF, 17RF, 17LR, and 17RR apply braking force to each wheel. Brake devices 17 are configured as hydraulic brake devices, for example, and vehicle control unit 41 adjusts the hydraulic pressure supplied to each brake device 17 by controlling the drive of hydraulic unit 16. If vehicle 1 is an electric vehicle or hybrid electric vehicle, brake devices 17 are used in conjunction with regenerative braking using a drive motor.

The vehicle control unit 41 includes one or more electronic control devices that control the driving of the driving force source 9, the electric steering device 15, and the hydraulic unit 16. If the vehicle 1 is equipped with a transmission that changes the speed of the output from the driving force source 9 and transmits it to the wheels 3, the vehicle control unit 41 has a function of controlling the driving of the transmission. The vehicle control unit 41 is configured to be able to acquire information transmitted from the driving assistance device 50, and is configured to be able to execute automatic driving control of the vehicle 1.

The vehicle 1 also includes forward-facing cameras 31LF, 31RF, a rearward-facing camera 31R, a vehicle status sensor 33, a Global Navigation Satellite System (GNSS) sensor 35, a vehicle-to-vehicle communication unit 37, and a notification device 43.

The front photographing cameras 31LF, 31RF and the rear photographing camera 31R constitute an ambient environment sensor for acquiring information on the ambient environment of the vehicle 1. The front photographing cameras 31LF, 31RF photograph the area in front of the vehicle 1 and generate image data. The rear photographing camera 31R photographs the area behind the vehicle 1 and generates image data. The front photographing cameras 31LF, 31RF and the rear photographing camera 31R are equipped with imaging elements such as CCD (Charged Coupled Devices) or CMOS (Complementary Metal Oxide Semiconductor), and transmit the generated image data to the driving assistance device 50. In the vehicle 1 shown in FIG. 1, the front photographing cameras 31LF, 31RF are configured as stereo cameras including a pair of left and right cameras, but the front photographing cameras may be monocular cameras.

In addition to the forward-facing cameras 31LF and 31RF, the surrounding environment sensor may also include a camera mounted on the side mirror to capture the left or right rear view. In addition, the surrounding environment sensor may also include one or more of the following sensors: LiDAR (Light Detection And Ranging), a radar sensor such as a millimeter-wave radar, and an ultrasonic sensor.

The vehicle condition sensor 33 consists of at least one sensor that detects the operating state and behavior of the vehicle 1. The vehicle condition sensor 33 includes at least one of, for example, a steering angle sensor, an accelerator position sensor, a brake stroke sensor, a brake pressure sensor, or an engine speed sensor. The vehicle condition sensor 33 also includes at least one of, for example, a vehicle speed sensor, an acceleration sensor, or an angular velocity sensor. The vehicle condition sensor 33 transmits a sensor signal indicating the detected information to the driving assistance device 50.

The GNSS sensor 35 receives satellite signals from positioning satellites such as GPS (Global Positioning System) satellites. The GNSS sensor 35 transmits the position information of the vehicle 1 contained in the received satellite signals to the driving assistance device 50. In addition to the GPS sensor, the GNSS sensor 35 may also be equipped with an antenna that receives satellite signals from other satellite systems that identify the position of the vehicle 1.

The vehicle-to-vehicle communication unit 37 is an interface for communicating with other vehicles that are within a predetermined distance from the vehicle 1. The driving assistance device 50 transmits and receives information to and from other vehicles via the vehicle-to-vehicle communication unit 37.

The notification device 43 is driven by the driving assistance device 50 and notifies the driver of various information by means of image display, audio output, etc. The notification device 43 includes, for example, a display device provided in the instrument panel and a speaker provided in the vehicle 1. The display device may be a display device of a navigation system. The notification device 43 may also include a HUD (head-up display) that displays information on the front window superimposed on the scenery around the vehicle 1.

(1-2. Driving Assistance Device)
Next, the driving assistance device 50 according to this embodiment will be described in detail.

(1-2-1. Configuration example)
The driving assistance device 50 functions as a device that assists in driving a vehicle by executing a computer program by a processor such as one or more CPUs (Central Processing Units). The computer program is a computer program for causing the processor to execute the operations to be performed by the driving assistance device 50, which will be described later. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 53 provided in the driving assistance device 50, or may be recorded on a recording medium built into the driving assistance device 50 or any recording medium that can be externally attached to the driving assistance device 50.

Recording media for recording computer programs may include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs, DVDs, and Blu-ray (registered trademark); magneto-optical media such as floptical disks; memory elements such as RAM and ROM; flash memories such as USB memory and SSDs; and other media capable of storing programs.

FIG. 2 is a block diagram showing an example of the configuration of the driving support device 50 according to this embodiment.
The driving assistance device 50 is connected to an ambient environment sensor 31, a vehicle state sensor 33, a GNSS sensor 35, and an inter-vehicle communication unit 37 via a dedicated line or communication means such as a controller area network (CAN) or a local inter net (LIN). A vehicle control unit 41 and a notification device 43 are also connected to the driving assistance device 50. Note that the driving assistance device 50 is not limited to an electronic control device mounted on the vehicle 1, and may be a terminal device such as a smartphone or a wearable device.

The driving assistance device 50 includes a processing unit 51, a memory unit 53, a map data memory unit 55, and a vehicle characteristic information memory unit 57. The processing unit 51 is configured with one or more processors such as a CPU and various peripheral components. A part or all of the processing unit 51 may be configured with updatable firmware or the like, or may be a program module executed by commands from the CPU or the like.

(Memory unit)
The storage unit 53 is composed of one or more storage elements such as RAM or ROM communicably connected to the processing unit 51. However, there is no particular limitation on the type or number of the storage units 53. The storage unit 53 stores information such as computer programs executed by the processing unit 51, various parameters used in the calculation process, detection data, and calculation results.

(Map data storage unit)
The map data storage unit 55 is configured with a storage element such as a RAM or a ROM communicably connected to the processing unit 51, or a storage medium such as a HDD, a CD, a DVD, an SSD, a USB flash, a storage device, etc. The map data stored in the map data storage unit 55 is configured to be able to identify the position of the vehicle 1 based on the position information detected by the GNSS sensor 35. For example, the map data is associated with latitude and longitude information, and the processing unit 51 can identify the position of the vehicle 1 on the map data based on the latitude and longitude information of the vehicle 1 detected by the GNSS sensor 35.

(Vehicle characteristic information storage unit)
The vehicle characteristic information storage unit 57 is configured by a storage element such as a RAM or ROM connected to the processing unit 51 so as to be able to communicate with it, or a storage medium such as a HDD, CD, DVD, SSD, USB flash, or storage device. The vehicle characteristic information storage unit 57 stores vehicle characteristic information relating to the characteristics of the vehicle together with identification information of the driver of the vehicle 1. The vehicle characteristic information includes at least any one of information on safety, comfort, environmental friendliness, or driving characteristics when the vehicle 1 is a preceding vehicle of the vehicle that executes the following control. The vehicle characteristic information also includes at least any one of information on safety, comfort, and driving characteristics when the vehicle 1 is a following vehicle of the vehicle that executes the following control.

The safety information when a vehicle is a leading vehicle is information that evaluates whether the vehicle can safely use the tracking control function with the vehicle as the leading vehicle. The safety information when a vehicle is a leading vehicle includes, for example, the compliance status of traffic rules, the installation status of the vehicle's safety equipment or safety functions, and vehicle size information. Examples of the compliance status of traffic rules include whether the vehicle returns to the normal lane from the overtaking lane after overtaking another vehicle, whether the headlights are turned on at night, whether the speed limit is observed, and whether traffic signal indications are observed. Examples of the installation status of the vehicle's safety equipment or safety functions include whether the vehicle is equipped with an emergency brake function, whether the vehicle is equipped with a sensor that senses the rear, and whether the vehicle is equipped with a system that acquires driving information from an external server. Examples of the vehicle size information include whether the vehicle is a large vehicle that significantly obstructs visibility. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of the evaluation are not limited to the above examples.

The information on comfort when a vehicle is a leading vehicle is information that evaluates whether the vehicle can comfortably use the tracking control function with the vehicle as the leading vehicle. The information on comfort when a vehicle is a leading vehicle includes, for example, information on whether the cleanliness of the exhaust gas is high, whether the running noise is low, whether the model or function of the vehicle is similar to that of the vehicle, and whether the destination is close to the destination of the vehicle. The cleanliness of the exhaust gas is a factor that affects the dirtiness of the vehicle and the smell inside the vehicle, and the order of cleanliness increases from engine vehicles to hybrid electric vehicles, pure electric vehicles, and fuel cell vehicles. The running noise is a factor that affects the noise heard inside the vehicle. The model or function of the vehicle is a factor that affects whether the vehicle can continue to follow comfortably. The destination is a factor that affects the time that tracking control can be continued without changing the leading vehicle. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of evaluation are not limited to the above examples.

Information on environmental friendliness when a vehicle is a leading vehicle is information that evaluates whether the vehicle can use the tracking control function in an environmentally friendly manner with the vehicle as the leading vehicle. Information on environmental friendliness when a vehicle is a leading vehicle includes, for example, information on vehicle size. Information on vehicle size is a factor that affects whether the leading vehicle can act as a windbreak for the vehicle and reduce fuel consumption or power consumption. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of evaluation are not limited to the above examples.

Information on driving characteristics when a vehicle is a leading vehicle is information that evaluates whether the driving characteristics of the leading vehicle are similar to the driving characteristics of the vehicle itself. Information on driving characteristics when a vehicle is a leading vehicle includes, for example, information on the following distance when driving manually, average vehicle speed relative to the speed limit or legal speed, deceleration rate when entering a curve or intersection, speed when going through a curve, acceleration/deceleration rate when accelerating/decelerating, or steering angular velocity when operating the steering wheel. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of evaluation are not limited to the above examples.

In addition, the safety information when a vehicle is a following vehicle of the own vehicle is information that evaluates whether the own vehicle can safely use the following control function in a state where the vehicle is being followed. The safety information when a vehicle is a following vehicle of the own vehicle includes, for example, information on the compliance with traffic rules, the installation status of the vehicle's safety equipment or safety functions, the vehicle size, and the vehicle design. Examples of the compliance with traffic rules include whether the vehicle returns from the overtaking lane to the normal lane after overtaking another vehicle, whether the headlights are turned on at night, and whether an appropriate distance between vehicles is maintained. Examples of the installation status of the vehicle's safety equipment or safety functions include whether the vehicle is equipped with an emergency brake function, whether the vehicle is equipped with a system that acquires driving information from an external server, and the like. Examples of the vehicle size information include whether the vehicle is a large vehicle that significantly blocks rear visibility, or whether the vehicle is a large vehicle that can cause significant damage when rear-ended. Examples of the vehicle design information include whether the headlights are placed in a high position that is dazzling when turned on. Each piece of information may be shown as a value evaluated on multiple levels (e.g., five levels) or as information on classified items, but the content and method of evaluation are not limited to the above examples.

The comfort information when a vehicle is following the own vehicle is information that evaluates whether the own vehicle can comfortably use the following control function while being followed by the vehicle. The comfort information when a vehicle is following the own vehicle includes, for example, information on whether the driving noise is quiet. Driving noise is a factor that affects the noise heard inside the vehicle cabin. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of evaluation are not limited to the above examples.

Information on driving characteristics when a vehicle is following the own vehicle is information that evaluates whether the own vehicle will be tailgated when using the following control function while being followed by the vehicle. Information on driving characteristics when a vehicle is following the own vehicle includes, for example, information on the following distance when driving manually, steering operation, and whether the driving is done with consideration for other vehicles. Each piece of information may be shown as a value evaluated on multiple levels (for example, five levels) or may be shown as information on classified items, but the content and method of evaluation are not limited to the above examples.

(Preference information storage unit)
The preference information storage unit 59 is configured by a storage element such as a RAM or ROM connected to the processing unit 51 in a communicable manner, or a storage medium such as a HDD, CD, DVD, SSD, USB flash, or storage device. The preference information storage unit 59 stores preference information on surrounding vehicles traveling around the vehicle 1 together with identification information of the driver of the vehicle 1. The preference information on the surrounding vehicles includes at least any one of safety, comfort, environmental friendliness, and driving characteristics required of the surrounding vehicles. The preference information on the surrounding vehicles may be information on the vehicle characteristics stored in the vehicle characteristic information storage unit 57 when the vehicle 1 is a preceding vehicle and a following vehicle of the vehicle to be followed, which is used as preference information for the surrounding vehicles.

In this embodiment, the preference information regarding surrounding vehicles further includes information on the allowable following duration, which is the maximum continuous time that vehicle 1 is permitted to follow the same preceding vehicle, and information on the allowable followed duration, which is the maximum continuous time that vehicle 1 is permitted to be followed by the same following vehicle. The allowable following duration and the allowable followed duration may each be set by the driver of vehicle 1, or may be learned based on the driver's past driving conditions.

(1-2-2. Functional configuration of the processing unit)
Next, the functional configuration of the processing unit 51 of the driving support device 50 will be described. The processing unit 51 includes an acquisition unit 61, a leading vehicle suggestion unit 63, a vehicle distance setting unit 67, a following control unit 69, and a notification processing unit 65. These units are functions realized by execution of a computer program by one or more processors such as a CPU. However, some or all of the acquisition unit 61, the leading vehicle suggestion unit 63, the vehicle distance setting unit 67, the following control unit 69, and the notification processing unit 65 may be configured using analog circuits.

(Acquisition Department)
The acquisition unit 61 acquires vehicle characteristic information of other vehicles traveling around the vehicle 1. In this embodiment, the acquisition unit 61 communicates with other vehicles present within a predetermined distance from the vehicle 1 via the vehicle-to-vehicle communication unit 37, and acquires information about the other vehicles from the other vehicles. The information about the other vehicles includes the position of the other vehicles on the map data, the moving direction and vehicle speed of the other vehicles, and the vehicle characteristic information stored in the control device. The information about the position of the other vehicles on the map data can be detected by a GNSS sensor in the other vehicles. The information about the moving direction of the other vehicles can be detected based on a time change in the position information in the other vehicles. The information about the vehicle speed of the other vehicles can be detected by a speed sensor in the other vehicles. The vehicle characteristic information of the other vehicles may be information stored in a vehicle characteristic information storage unit of the other vehicles.

(Advancing Vehicle Proposal Department)
The preceding vehicle suggestion unit 63 sets a preceding vehicle when the host vehicle 1 executes following control. The preceding vehicle suggestion unit 63 assumes one or more first other vehicles among the other vehicles whose information is acquired by the acquisition unit 61 as a preceding vehicle, and specifies a second other vehicle that will be a following vehicle of the host vehicle 1 when the first other vehicle is assumed to be the preceding vehicle. In addition, the preceding vehicle suggestion unit 63 sets the preceding vehicle based on preference information regarding surrounding vehicles of the driver of the host vehicle 1 and vehicle characteristic information of the first other vehicle and the second other vehicle.

In this embodiment, the preceding vehicle suggestion unit 63 sets the preceding vehicle according to the preferences of the driver of the vehicle 1. Specifically, for each assumed combination of a first other vehicle and a second other vehicle, the preceding vehicle suggestion unit 63 calculates the degree of match between the vehicle characteristic information of the first other vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles (hereinafter also referred to as the "preceding vehicle match degree") and the degree of match between the vehicle characteristic information of the second other vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles (hereinafter also referred to as the "following vehicle match degree"). In addition, the preceding vehicle suggestion unit 63 sets the preceding vehicle based on the preceding vehicle match degree and the following vehicle match degree.

(Notification processing unit)
The notification processing unit 65 issues a predetermined notification to the user by controlling the driving of the notification device 43. In this embodiment, the notification processing unit 65 issues a notification of at least the proposal of the leading vehicle determined by the leading vehicle proposal unit 63, the proposal of a change to the leading vehicle, and the start of control to follow the leading vehicle. The notification processing unit 65 issues a predetermined notification to the user by outputting sound or voice, or displaying an image or text.

(Vehicle distance setting unit)
The inter-vehicle distance setting unit 67 sets a target inter-vehicle distance between the preceding vehicle and the host vehicle 1 during tracking control, in accordance with a degree of match (preceding vehicle match degree) of vehicle characteristic information of the preceding vehicle to preference information of the driver of the host vehicle 1 regarding the surrounding vehicles. The inter-vehicle distance setting unit 67 may set the target inter-vehicle distance in accordance with a degree of match (following vehicle match degree) of vehicle characteristic information of the following vehicle to preference information of the driver of the vehicle 1 regarding the surrounding vehicles, in addition to the preceding vehicle match degree.

(Follow-up control unit)
The following control unit 69 sets driving conditions for making the vehicle 1 follow the preceding vehicle at the following distance set by the following distance setting unit 67, and transmits the driving conditions to the vehicle control unit 41. For example, the following control unit 69 detects the surrounding environment of the vehicle 1 based on detection data transmitted from the surrounding environment sensor 31 at a predetermined sampling period, and sets a target acceleration/deceleration for making the vehicle 1 follow the preceding vehicle while maintaining the target following distance while avoiding collision with an obstacle or another vehicle. The following control unit 69 may set a target steering angle for making the vehicle 1 follow the preceding vehicle along the driving lane. The following control unit 69 transmits the set target steering angle and target acceleration/deceleration to the vehicle control unit 41. The vehicle control unit 41 controls the running of the host vehicle 1 based on the acquired information on the target steering angle and target acceleration/deceleration.

(1-2-3. Operation of the driving support device)
Next, an example of a processing operation by the processing unit 51 of the driving support device 50 according to this embodiment will be described with reference to a flowchart.

FIG. 3 is a flow chart showing a main routine of the processing operation of the processing unit 51.
First, the processing unit 51 starts the execution of a process for suggesting a preceding vehicle (step S11). The processing unit 51 may start the execution of the process for suggesting a preceding vehicle based on an instruction input by a user, or may start the execution of the process for suggesting a preceding vehicle when the vehicle starts traveling on a predetermined road such as an expressway or a traveling area.

Then, the acquisition unit 61 of the processing unit 51 acquires information about other vehicles traveling around the host vehicle 1 (step S13). Specifically, the acquisition unit 61 communicates with one or more other vehicles that are present within a predetermined distance from the host vehicle 1 via the vehicle-to-vehicle communication unit 37, and acquires from each other vehicle the position of the other vehicle on the map data, the direction of movement and speed of the other vehicle, and vehicle characteristic information of the other vehicle. The vehicle characteristic information of each other vehicle includes at least any one of information regarding safety, comfort, environmental friendliness, or driving characteristics when the other vehicle is a preceding vehicle and a following vehicle of the vehicle executing the following control.

Next, the preceding vehicle suggestion unit 63 sets a preceding vehicle to be suggested to the driver. In this embodiment, the preceding vehicle suggestion unit 63 executes a process to set a suggested preceding vehicle according to the preferences of the driver of the host vehicle 1 (hereinafter also referred to as "host vehicle-based preceding vehicle suggestion process").

FIG. 4 shows a flowchart of the host vehicle-based preceding vehicle proposing process.
The preceding vehicle suggestion unit 63 selects an arbitrary first other vehicle from among the other vehicles acquired by the acquisition unit 61, and assumes it as the preceding vehicle (step S31). The preceding vehicle suggestion unit 63 selects, for example, from among other vehicles traveling in the same direction as the host vehicle 1 on the road on which the host vehicle 1 is traveling, a vehicle that is close to the host vehicle 1 as the first other vehicle. However, the method of selecting the first other vehicle is not particularly limited.

Then, the preceding vehicle suggestion unit 63 identifies a second other vehicle that will be the following vehicle of the host vehicle 1 when the selected first other vehicle is assumed to be the preceding vehicle (step S33). For example, the preceding vehicle suggestion unit 63 identifies as the second other vehicle a vehicle traveling within a predetermined distance behind the first other vehicle in the driving lane in which the first other vehicle is traveling. The predetermined distance in this case may be set, for example, within a range of 5 to 30 m depending on the vehicle speed of the first other vehicle or the second other vehicle. If there is no corresponding second other vehicle, the preceding vehicle suggestion unit 63 records that there is no vehicle that corresponds to the second other vehicle.

Next, the preceding vehicle suggestion unit 63 calculates the degree of match of the vehicle characteristic information of the first other vehicle to the preference information of the driver of the vehicle 1 regarding the surrounding vehicles (preceding vehicle match degree), and the degree of match of the vehicle characteristic information of the second other vehicle to the preference information of the driver of the vehicle 1 regarding the surrounding vehicles (following vehicle match degree) (step S35). The preceding vehicle match degree is shown as the degree of match between each item of the preference information of the driver of the vehicle 1 regarding the preceding vehicle stored in the preference information storage unit 59 and each item of the vehicle characteristics obtained from the first other vehicle when the first other vehicle is the preceding vehicle. Similarly, the following vehicle match degree is shown as the degree of match between each item of the preference information of the driver of the vehicle 1 regarding the following vehicle stored in the preference information storage unit 59 and each item of the vehicle characteristics obtained from the second other vehicle when the second other vehicle is the following vehicle.

The degree of match may be, for example, the ratio of the number of items with matching evaluations to the total number of each item. When each item is shown as a value evaluated on a multiple-level scale, the degree of match may be determined not only based on whether the evaluated values match, but also by weighting according to how many levels the evaluated values differ. Note that when a first other vehicle is selected and there is no other vehicle equivalent to the second other vehicle, the degree of match with the following vehicle of the second other vehicle is set to a preset specified value. The specified value may be, for example, 100 (%), but may be set to any other value.

Next, the preceding vehicle suggestion unit 63 judges whether or not to end the calculation of the preceding vehicle match degree and the following vehicle match degree (step S37). Specifically, the preceding vehicle suggestion unit 63 judges whether or not there remains a combination of a first other vehicle and a second other vehicle for which the preceding vehicle match degree and the following vehicle match degree have not been calculated, among the other vehicles traveling in the same moving direction on the road on which the host vehicle 1 is traveling, acquired by the acquisition unit 61. The preceding vehicle suggestion unit 63 may continue to calculate the preceding vehicle match degree and the following vehicle match degree until it has calculated the preceding vehicle match degree and the following vehicle match degree by assuming that all other vehicles traveling in the same moving direction on the road on which the host vehicle 1 is traveling are the first other vehicles. In addition, the preceding vehicle suggestion unit 63 may continue to calculate the preceding vehicle match degree and the following vehicle match degree until it has calculated the preceding vehicle match degree and the following vehicle match degree by assuming that a predetermined number of other vehicles traveling in the same moving direction on the road on which the host vehicle 1 is traveling are the first other vehicles, in order of distance from the host vehicle 1.

If the preceding vehicle suggestion unit 63 does not determine that the calculation of the preceding vehicle match degree and the following vehicle match degree is to be ended (S37/No), it returns to step S31 and repeats the selection of the next first other vehicle, the identification of the second other vehicle, and the calculation of the preceding vehicle match degree and the following vehicle match degree. On the other hand, if the preceding vehicle suggestion unit 63 determines that the calculation of the preceding vehicle match degree and the following vehicle match degree is to be ended (S37/Yes), it sets the optimal preceding vehicle based on the calculated preceding vehicle match degree and following vehicle match degree (step S39). For example, the preceding vehicle suggestion unit 63 sets the first other vehicle of the combination of the first other vehicle and the second other vehicle that maximizes the sum of the preceding vehicle match degree and the following vehicle match degree as the preceding vehicle.

In this case, the first other vehicle may be set by excluding combinations of the first other vehicle and the second other vehicle for which the preceding vehicle match degree of the first other vehicle is less than a preset reference minimum value. Alternatively, the first other vehicle may be set by excluding combinations of the first other vehicle and the second other vehicle for which at least one of the preceding vehicle match degree of the first other vehicle and the following vehicle match degree of the second other vehicle is less than a preset reference minimum value. This makes it possible to prevent either the preceding vehicle or the following vehicle from being a vehicle that does not meet the preferences of the driver of the vehicle 1, even if the sum of the preceding vehicle match degree and the following vehicle match degree is large.

FIG. 5 is an explanatory diagram showing an example of setting a leading vehicle based on the leading vehicle match degree and the following vehicle match degree. FIG. 5 shows the leading vehicle match degree and following vehicle match degree (leading vehicle match degree/following vehicle match degree) of each of other vehicles 81, 83, 85, 87 traveling in the same direction on the same driving lane. Furthermore, the leading vehicle suggestion unit 63 is configured to set a leading vehicle from among combinations of first other vehicles and second other vehicles in which the leading vehicle match degree and following vehicle match degree are both 50% or higher.

When only the degree of match between the vehicle characteristic information of the other vehicle that may be the preceding vehicle and the preference information of the driver of the own vehicle 1 is taken into consideration, the other vehicle 85 with the highest preceding vehicle match degree is selected as the preceding vehicle. However, in this case, the following vehicle match degree of the other vehicle 87 that will be the following vehicle is 20%, and if the other vehicle 85 is selected as the preceding vehicle, the safety or comfort of the driver of the own vehicle 1 will be reduced by the other vehicle 87 that will be the following vehicle.

In response to this, the preceding vehicle suggestion unit 63 of the driving assistance device 50 according to this embodiment sets as the preceding vehicle the first other vehicle with the largest sum of the preceding vehicle match degree and the following vehicle match degree from among combinations of the first other vehicle and the second other vehicle in which the preceding vehicle match degree and the following vehicle match degree are both 50% or more. In the example shown in FIG. 5, the preceding vehicle suggestion unit 63 sets the other vehicle 81 as the preceding vehicle. This allows the driver of the host vehicle 1 to drive between a preceding vehicle that meets the driver's preferences and a following vehicle that meets the driver's preferences, thereby reducing anxiety and stress during tracking control.

FIG. 6 is an explanatory diagram showing another example of setting a preceding vehicle based on the preceding vehicle match degree and the following vehicle match degree. FIG. 6 shows the preceding vehicle match degree and following vehicle match degree (preceding vehicle match degree/following vehicle match degree) of each of other vehicles 91, 92, 93, 94, 95 traveling in the same direction on the same driving lane into which the host vehicle 1 merges. Another vehicle 96 is traveling in a driving lane adjacent to the driving lane into which the host vehicle 1 merges. The preceding vehicle suggestion unit 63 is configured to set a preceding vehicle from among combinations of a first other vehicle and a second other vehicle in which the preceding vehicle match degree and following vehicle match degree are both 50% or higher.

When only the degree of match between the vehicle characteristic information of the other vehicle that may be the leading vehicle and the preference information of the driver of the vehicle 1 is taken into consideration, the other vehicle 94 with the highest leading vehicle match degree is selected as the leading vehicle. However, in this case, the following vehicle match degree of the other vehicle 87 that will be the following vehicle is 20%, and if the other vehicle 85 is selected as the leading vehicle, the following vehicle 87 will reduce the safety or comfort of the driver of the vehicle 1. For this reason, as shown in FIG. 7, if the other vehicle 96 traveling in the adjacent driving lane cuts in front of the other vehicle 94 that is the leading vehicle for the vehicle 1, when the other vehicle 94 suddenly brakes and the vehicle 1 suddenly brakes as a result of the other vehicle 94 applying the brakes, the braking of the following vehicle 95 is delayed, and it is considered that it will collide with the vehicle 1 from behind.

In response to this, the leading vehicle suggestion unit 63 of the driving support device 50 according to this embodiment sets the first other vehicle with the maximum sum of the leading vehicle match degree and the following vehicle match degree as the leading vehicle from among the combinations of the first other vehicle and the second other vehicle in which the leading vehicle match degree and the following vehicle match degree are both 50% or more. In the example shown in FIG. 6, the leading vehicle suggestion unit 63 sets the other vehicle 93 as the leading vehicle. This allows the driver of the vehicle 1 to drive between the leading vehicle that matches his/her preference and the following vehicle that matches his/her preference, thereby reducing anxiety and stress during the following control. For this reason, as shown in FIG. 8, when the other vehicle 96 that was driving in the adjacent driving lane cuts in front of the vehicle 1, the following vehicle 94 can also apply the brakes appropriately in response to the sudden braking of the vehicle 1, thereby avoiding a rear-end collision with the vehicle 1. It is considered that the other vehicle 94 will be rear-ended by the following vehicle 95.

The method of setting the leading vehicle based on the leading vehicle match degree and the following vehicle match degree is not limited to the method of setting the leading vehicle from among combinations of first and second other vehicles in which the leading vehicle match degree and following vehicle match degree are both 50% or more. For example, the leading vehicle suggestion unit 63 may select a first other vehicle with the highest following vehicle match degree of the second other vehicle from among the identified first and second other vehicles in which the leading vehicle match degree is equal to or greater than a preset minimum value (e.g., 70%). This allows the host vehicle to travel between the first and second other vehicles with the highest following vehicle match degree while ensuring a match degree equal to or greater than a predetermined standard for the leading vehicle.

Returning to FIG. 3, after the preceding vehicle suggestion unit 63 sets the preceding vehicle in step S15, the notification processing unit 65 notifies the driver of the set preceding vehicle (step S17). Specifically, the notification processing unit 65 controls the operation of the notification device 43, and notifies the driver of information that can identify the preceding vehicle that is recommended to be followed. For example, the notification processing unit 65 may display the position of the other vehicle recommended as the preceding vehicle on map data, or may notify by text display or audio output. Alternatively, the notification may notify information such as the model, color, license plate number, etc. of the other vehicle recommended as the preceding vehicle.

Then, the following control unit 69 determines whether or not to start executing following control to make the host vehicle 1 follow the preceding vehicle that is in front of the host vehicle 1 (step S19). The following control unit 69 may start executing following control, for example, in accordance with an operational input by the driver instructing the host vehicle 1 to start executing following control, or may automatically start executing following control when it detects that the host vehicle 1 has moved behind the preceding vehicle proposed in step S17. Note that when starting execution of following control in accordance with an operational input by the driver, the preceding vehicle that the host vehicle 1 is made to follow may be the preceding vehicle proposed in step S17, or may be a preceding vehicle different from the proposed preceding vehicle.

If the following control unit 69 does not determine that execution of following control should be started (S19/No), the process returns to step S13, and each unit of the processing unit 51 repeats the process of each step described above. On the other hand, if the following control unit 69 determines that execution of following control should be started (S19/Yes), the vehicle distance setting unit 67 sets a target vehicle distance between the preceding vehicle and the host vehicle 1 during following control according to the preceding vehicle matching degree (step S21). In this embodiment, the vehicle distance setting unit 67 corrects a previously set reference vehicle distance based on a specified condition, and sets the target vehicle distance. The reference vehicle distance is set to a value that varies according to, for example, the vehicle speed of the host vehicle 1.

FIG. 9 is an explanatory diagram showing the target inter-vehicle distance that is set according to the preceding vehicle coincidence degree.
In the example shown in Fig. 9, the vehicle distance setting unit 67 divides the preceding vehicle matching degree into three levels, "low", "medium" and "high", and when the preceding vehicle matching degree of the preceding vehicle is "medium", sets the reference vehicle distance to the target vehicle distance. Also, when the preceding vehicle matching degree of the preceding vehicle is "high", the vehicle distance setting unit 67 sets the target vehicle distance to a value smaller than the reference vehicle distance. This creates a situation in which it is difficult for another vehicle 103, whose preceding vehicle matching degree is lower than the current preceding vehicle 101, to enter between the preceding vehicle 101 and the subject vehicle 1, as shown in Fig. 10, and it is possible to continue the following control without changing the preceding vehicle 101.

On the other hand, when the preceding vehicle's preceding vehicle matching degree is "low", the vehicle distance setting unit 67 sets the target vehicle distance to a value greater than the reference vehicle distance. This makes it possible to reduce the influence of the preceding vehicle on the vehicle 1. Also, as shown in FIG. 11, a situation is created in which another vehicle 103 with a preceding vehicle matching degree higher than the current preceding vehicle 101 can easily enter between the preceding vehicle 101 and the vehicle 1, and the vehicle 1 can change to the preceding vehicle 103 with the higher preceding vehicle matching degree without the vehicle 1 having to change lanes.

Furthermore, the vehicle distance setting unit 67 may correct the target vehicle distance according to the vehicle size related to the forward visibility of the driver of the vehicle 1, among the items of the preceding vehicle match degree of the preceding vehicle. FIG. 12 is an explanatory diagram showing a setting example in which the target vehicle distance is adjusted according to the visibility (vehicle size) of the driver of the vehicle 1. The vehicle distance setting unit 67 increases the target vehicle distance the more likely it is that the visibility of the driver of the vehicle 1 will decrease, that is, the larger the vehicle size of the preceding vehicle. However, an upper limit value of the target vehicle distance is set so that the vehicle distance between the preceding vehicle and the vehicle 1 does not become too large. This reduces the range in which the driver of the vehicle 1 cannot see beyond the preceding vehicle, thereby ensuring the safety of the vehicle 1.

The vehicle distance setting unit 67 may also set the target vehicle distance by taking into consideration the following vehicle match degree of the following vehicle in addition to the preceding vehicle match degree. FIG. 13 is an explanatory diagram showing an example of setting the target vehicle distance based on the preceding vehicle match degree and the following vehicle match degree. It is assumed that the preceding vehicle match degree of the preceding vehicle 105 is 40%, and the following vehicle match degree of the following vehicle 107 is 80%.

In FIG. 13, the distance from the preceding vehicle 105 that the host vehicle 1 is following to the following vehicle 107 of the host vehicle 1 is 200 m. The reference inter-vehicle distance according to the current vehicle speed of the host vehicle 1 is 60 m, and the setting range of the target inter-vehicle distance that is adjusted according to the preceding vehicle match degree and the following vehicle match degree is set to plus or minus 15 m. If the preceding vehicle match degree of the preceding vehicle 105 is 40% and the following vehicle match degree of the following vehicle 107 is 80%, the inter-vehicle distance setting unit 67 corrects the target inter-vehicle distance according to the ratio of the match degrees.

Specifically, because the ratio of the preceding vehicle match degree to the following vehicle match degree is 1:2, the vehicle distance setting unit 67 increases the vehicle distance with the preceding vehicle 105, which has a low match degree, and sets the target vehicle distance so that the position of the front of the host vehicle 1 is in a position that divides the setting range of the target vehicle distance (45 to 75 m) into a ratio of 2:1. In this way, the vehicle distance is set taking into consideration the safety, comfort, etc. of the driver of the host vehicle 1 with respect to each of the preceding vehicle 105 and the following vehicle 107, depending on the preceding vehicle match degree of the preceding vehicle 105 and the following vehicle match degree of the following vehicle 107.

Next, the following control unit 69 sets the driving conditions of the host vehicle 1 so that the distance between the host vehicle and the preceding vehicle becomes the target distance, and outputs the set driving conditions to the vehicle control unit 41 (step S23). Specifically, the following control unit 69 obtains the distance between the host vehicle and the preceding vehicle detected by the surrounding environment sensor 31, and sets the target acceleration/deceleration of the host vehicle 1 so that the distance between the host vehicle and the preceding vehicle becomes the target distance set in step S21. The following control unit 69 may further detect the left and right boundaries of the driving lane, and set a target steering angle or target steering angular speed for driving the host vehicle 1 within the driving lane to follow the preceding vehicle. In this way, the vehicle control unit 41, which has received the information on the driving conditions, can control the driving of the driving force source 9, the electric steering device 15, and the hydraulic unit 16, thereby causing the host vehicle 1 to follow the preceding vehicle.

Then, the following control unit 69 determines whether or not to stop the execution of the following control (step S25). For example, the following control unit 69 determines to stop the execution of the following control according to an operation input by the driver of the vehicle 1 to stop the execution of the following control. If the following control unit 69 does not determine to stop the execution of the following control (S25/No), the leading vehicle suggestion unit 63 determines whether or not to re-suggest a leading vehicle (step S27). For example, the leading vehicle suggestion unit 63 may determine whether or not the driver of the vehicle 1 has performed an operation input to change the leading vehicle. In addition, the leading vehicle suggestion unit 63 may determine whether or not to re-suggest a leading vehicle depending on whether a predetermined condition is met.

14 and 15 are diagrams for explaining examples of situations in which a preceding vehicle is re-proposed. As shown in FIG. 14, in a situation in which the host vehicle 1 is following another vehicle 113 and another vehicle 115 is following the host vehicle 1, if the host vehicle 1 continues to follow the other vehicle 113 for a long period of time, the driver of the other vehicle 113 may feel uneasy. Similarly, if the other vehicle 115 continues to follow the host vehicle 1 for a long period of time, the driver of the host vehicle 1 may feel uneasy. For this reason, the preceding vehicle suggestion unit 63 may re-propose a preceding vehicle when the duration during which the host vehicle 1 is following the same preceding vehicle (following duration) exceeds a predetermined time, or when the duration during which the host vehicle 1 is being followed by the same following vehicle (followed duration) exceeds a predetermined time.

Specifically, as shown in FIG. 15, if the following duration or the followed duration is both within a predetermined time, the leading vehicle suggestion unit 63 continues the following control without re-proposing a leading vehicle. In addition, if at least one of the following duration or the followed duration exceeds a predetermined time, the leading vehicle suggestion unit 63 re-proposes a leading vehicle.

FIG. 16 is a flowchart showing an example of a process for determining whether or not to re-propose a preceding vehicle. The preceding vehicle proposal unit 63 determines whether the duration since the host vehicle 1 started following the current preceding vehicle (following duration) has exceeded a predetermined allowable following duration (step S41). If the preceding vehicle proposal unit 63 determines that the following duration has exceeded the predetermined allowable following duration (S41/Yes), it determines that it is necessary to re-propose a preceding vehicle (step S45).

On the other hand, if the preceding vehicle proposal unit 63 does not determine that the following duration has exceeded the predetermined allowable following duration (S41/No), it determines whether the duration since the vehicle 1 began to be followed by the current following vehicle (followed duration) has exceeded the predetermined allowable followed duration (step S43). If the preceding vehicle proposal unit 63 determines that the followed duration has exceeded the predetermined allowable followed duration (S43/Yes), it determines that it is necessary to re-propose the preceding vehicle (step S45). On the other hand, if the preceding vehicle proposal unit 63 does not determine that the followed duration has exceeded the predetermined allowable followed duration (S43/No), it determines that it is unnecessary to re-propose the preceding vehicle (step S47).

The allowable following duration and the allowable followed duration may be set to the same time, or may be set to different times. The allowable following duration and the allowable followed duration may each be set to any time by the driver, or may be automatically set by the processor based on the following duration and the followed duration during the driver's past driving. Note that the conditions for determining whether to re-suggest a leading vehicle are not limited to the above examples.

Returning to FIG. 3, if the leading vehicle suggestion unit 63 determines that the leading vehicle should be re-proposed (S27/Yes), the process returns to step S13, and each unit of the processing unit 51 repeatedly executes the process of each step described above. On the other hand, if the leading vehicle suggestion unit 63 does not determine that the leading vehicle should be re-proposed (S27/No), the following control unit 69 returns to step S23, and sets the driving conditions of the host vehicle 1 so that the inter-vehicle distance from the leading vehicle becomes the target inter-vehicle distance, and repeats the process of outputting the set driving conditions to the vehicle control unit 41. Then, if the following control unit 69 determines in step S25 that the execution of the following control should be stopped (S25/Yes), it ends the following control (step S29).

As described above, the driving assistance device 50 according to this embodiment acquires vehicle characteristic information on the characteristics of other vehicles traveling around the vehicle 1, assumes at least one of the other vehicles, a first other vehicle, as a leading vehicle, and identifies a second other vehicle that will follow the vehicle 1 when the first other vehicle is assumed to be the leading vehicle. The driving assistance device 50 also proposes a leading vehicle in accordance with the preferences of the driver of the vehicle 1 based on preference information on the surrounding vehicles of the driver of the vehicle 1 and vehicle characteristic information of the first other vehicle and the second other vehicle. For this reason, the driving assistance device 50 can propose to the driver not only a leading vehicle to be followed by the vehicle 1, but also a leading vehicle that can be a following vehicle and that is in line with the preferences of the driver of the vehicle 1. This makes it possible to execute following control of the vehicle 1 at a driving position that is in line with the driver's safety, comfort, environmental friendliness, and driving characteristics.

The driving assistance device 50 according to this embodiment also sets the suggested preceding vehicle based on the degree of match between the vehicle characteristic information of the first other vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles, and the degree of match between the vehicle characteristic information of the second other vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles. Therefore, it is possible to suggest to the driver a preceding vehicle with which the vehicle 1 can travel between the preceding vehicle and the following vehicle that have many items matching the driver's preferences.

The driving assistance device 50 according to this embodiment is further configured to be capable of executing a vehicle distance setting process that sets a target vehicle distance between the preceding vehicle and the vehicle 1 during following control, depending on the degree of match between the vehicle characteristic information of the preceding vehicle and the preference information of the driver of the vehicle 1 regarding surrounding vehicles. Therefore, when the vehicle is made to follow a preceding vehicle with a relatively low degree of match, the vehicle distance is increased, and a decrease in the driver's safety, comfort, etc. can be suppressed.

The driving assistance device 50 according to this embodiment is configured to set a target inter-vehicle distance between the vehicle 1 and the preceding vehicle in accordance with the degree of match between the vehicle characteristic information of the preceding vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles, and the degree of match between the vehicle characteristic information of the following vehicle and the preference information of the driver of the vehicle 1 regarding the surrounding vehicles. Therefore, the inter-vehicle distance between the vehicle 1 and the preceding vehicle can be set in consideration of the inter-vehicle distance between the vehicle 1 and the following vehicle in accordance with the degree of match not only with the preceding vehicle but also with the following vehicle.

In addition, in the driving assistance device 50 according to this embodiment, the preference information of the driver of the vehicle 1 regarding the surrounding vehicles includes information on the allowable following duration, which is the maximum continuous time allowed for the vehicle 1 to follow the same preceding vehicle, and information on the allowable followed duration, which is the maximum continuous time allowed for the vehicle 1 to be followed by the same following vehicle. The driving assistance device 50 is configured to execute the vehicle-based preceding vehicle proposal process again to propose a preceding vehicle to be followed when the following duration exceeds the allowable following duration or the followed duration exceeds the allowable followed duration. Therefore, the privacy of the preceding vehicle and the vehicle 1 is maintained, and following control can be executed while changing the preceding vehicle.

2. Second embodiment
Next, a driving assistance device according to a second embodiment of the present disclosure will be described.
The driving support device according to the first embodiment is configured to set a preceding vehicle between which the vehicle 1 travels and which follows a preceding vehicle according to the preferences of the driver of the vehicle 1, and to propose the preceding vehicle to the driver. In the second embodiment, the vehicle 1 is further configured to propose a preceding vehicle for the vehicle 1 to follow, taking into consideration the preferences of the driver of the vehicle that may become the following vehicle with respect to the preceding vehicle.

Below, the differences between the driving assistance device according to this embodiment and the driving assistance device according to the first embodiment will be explained.

FIG. 17 is a flowchart showing the preceding vehicle suggestion process in this embodiment, specifically showing the process executed in step S15 of the flowchart in FIG. 3. In this embodiment, the preceding vehicle suggestion unit 63 executes a process (hereinafter also referred to as "preceding vehicle suggestion process taking into consideration following vehicle comfort") of setting a suggested preceding vehicle so that the preceding vehicle match degree of the host vehicle 1 is equal to or exceeds a predetermined standard not only based on the preferences of the driver of the host vehicle 1 but also on other vehicles that may be following the host vehicle 1.

Similar to steps S31 to S33 of the flowchart in FIG. 4, the preceding vehicle suggestion unit 63 selects an arbitrary first other vehicle from among the other vehicles acquired by the acquisition unit 61 and assumes it to be the preceding vehicle (step S51), and further identifies a second other vehicle that will be the following vehicle of the host vehicle 1 when the selected first other vehicle is assumed to be the preceding vehicle (step S53).

Next, the preceding vehicle suggestion unit 63 calculates the degree of match of the vehicle characteristic information of the first other vehicle to the preference information of the driver of the vehicle 1 regarding the preceding vehicle (preceding vehicle match degree), and the degree of match of the vehicle characteristic information of the vehicle 1 to the preference information of the driver of the second other vehicle regarding the preceding vehicle (following vehicle reference match degree) (step S55). The preceding vehicle match degree is shown as the degree of match between each item of the preference information of the driver of the vehicle 1 regarding the preceding vehicle stored in the preference information storage unit 59 and each item of the vehicle characteristics when the first other vehicle is the preceding vehicle, obtained from the first other vehicle. The following vehicle reference match degree is shown as the degree of match between each item of the preference information of the driver of the second other vehicle regarding the preceding vehicle, obtained from the second other vehicle, and each item of the vehicle characteristics when the vehicle 1 is the preceding vehicle. The preceding vehicle match degree and the following vehicle reference match degree may be values calculated in the same way as the preceding vehicle match degree described in the first embodiment.

Next, the preceding vehicle suggestion unit 63 determines whether or not to end the calculation of the preceding vehicle match degree and the following vehicle reference match degree (step S57). Specifically, similar to step S37 in the flowchart of FIG. 4, the preceding vehicle suggestion unit 63 determines whether or not there remains a combination of a first other vehicle and a second other vehicle for which the preceding vehicle match degree and the following vehicle reference match degree have not been calculated, among the other vehicles traveling in the same direction on the road on which the host vehicle 1 is traveling and acquired by the acquisition unit 61.

If the preceding vehicle suggestion unit 63 does not determine that the calculation of the preceding vehicle match degree and the following vehicle criteria match degree is to be terminated (S57/No), it returns to step S51 and repeats the selection of the next first other vehicle, the identification of the second other vehicle, and the calculation of the preceding vehicle match degree and the following vehicle criteria match degree. On the other hand, if the preceding vehicle suggestion unit 63 determines that the calculation of the preceding vehicle match degree and the following vehicle criteria match degree is to be terminated (S57/Yes), it sets the optimal preceding vehicle based on the calculated preceding vehicle match degree and following vehicle criteria match degree (step S59).

In this embodiment, the leading vehicle suggestion unit 63 excludes combinations of a first other vehicle and a second other vehicle for which the following vehicle criteria match degree is less than a preset minimum reference value. The leading vehicle suggestion unit 63 sets any combination of a first other vehicle as a leading vehicle from among combinations of a first other vehicle and a second other vehicle for which the following vehicle criteria match degree is equal to or greater than the minimum reference value. This makes it possible to increase the comfort of the second other vehicle, which may be a following vehicle of the host vehicle 1, when driving following the host vehicle 1.

FIG. 18 is an explanatory diagram showing an example of setting a leading vehicle based on the leading vehicle match degree and the following vehicle reference match degree. FIG. 18 shows the leading vehicle match degree (A) and the following vehicle reference match degree (B) of each of the other vehicles 121, 123, 125, and 127 traveling in the same direction on the same driving lane. In other words, the leading vehicle match degree (A) indicates the match degree of the other vehicle as a leading vehicle as seen from the host vehicle 1, and the following vehicle reference match degree (B) indicates the match degree of the host vehicle 1 as a leading vehicle as seen from the other vehicles. In addition, the leading vehicle suggestion unit 63 is configured to set a leading vehicle from among combinations of the first other vehicle and the second other vehicle in which the leading vehicle match degree and the following vehicle reference match degree are both 50% or more.

In the example shown in FIG. 18, the preceding vehicle suggestion unit 63 excludes the other vehicle 127, whose preceding vehicle match rate is less than 50%, from the preceding vehicle candidates. Also, although the other vehicle 125 has the highest preceding vehicle match rate (100%), the other vehicle 127, which will be the following vehicle of the host vehicle 1 when the other vehicle 125 is the preceding vehicle of the host vehicle 1, has a following vehicle criteria match rate of less than 50%, so the preceding vehicle suggestion unit 63 excludes the other vehicle 125 from the preceding vehicle candidates.

On the other hand, when other vehicles 121 and 123 are assumed to be the preceding vehicles of vehicle 1, the following vehicle criteria matching degrees (50%, 70%) of other vehicles 123 and 125, which are the following vehicles of vehicle 1 when other vehicles 121 and 123 are assumed to be the preceding vehicles of vehicle 1, are 50% or more, so that preceding vehicle suggestion unit 63 sets one of other vehicles 121 and 123 as the proposed preceding vehicle. In the example shown in FIG. 18, when other vehicle 121 is assumed to be the preceding vehicle, the sum of the preceding vehicle matching degree (90%) of the first other vehicle 121 and the following vehicle criteria matching degree (50%) of the second other vehicle 123 is 140%. Also, when other vehicle 123 is assumed to be the preceding vehicle, the sum of the preceding vehicle matching degree (80%) of the first other vehicle 123 and the following vehicle criteria matching degree (70%) of the second other vehicle 125 is 140%. The preceding vehicle suggestion unit 63 sets the other vehicle 123 for which the sum of the preceding vehicle match degree of the first other vehicle and the following vehicle reference match degree of the second other vehicle is the largest as the preceding vehicle to be suggested.

However, the preceding vehicle suggestion unit 63 may set the preceding vehicle so that the following vehicle criteria matching degree is the highest, or may set the preceding vehicle so that the preceding vehicle matching degree is the highest.

The driving assistance device according to this embodiment executes the following control function in accordance with the flowchart shown in FIG. 3, except for the process of setting the preceding vehicle to be suggested to the driver as described above (step S15). Therefore, the driving assistance device according to this embodiment can not only set a preceding vehicle that meets the preferences of the driver of the vehicle 1, but also set a preceding vehicle that ensures the comfort of the driver of the vehicle following the vehicle 1.

　A preferred embodiment of the present disclosure has been described in detail above with reference to the attached drawings, but the present disclosure is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present disclosure pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

1: Vehicle (own vehicle), 31: Surrounding environment sensor, 31LF/31RF: Front camera, 31R: Rear camera, 33: Vehicle state sensor, 35: GNSS sensor, 37: Vehicle-to-vehicle communication unit, 41: Vehicle control unit, 43: Notification device, 50: Driving support device, 51: Processing unit, 53: Storage unit, 55: Map data storage unit, 57: Vehicle characteristic information storage unit, 59: Preference information storage unit, 61: Acquisition unit, 63: Leading vehicle suggestion unit, 65: Notification processing unit, 67: Vehicle distance setting unit, 69: Following control unit

Claims (8)

1. A driving assistance device that assists driving of a vehicle capable of performing following control to cause the vehicle to follow a preceding vehicle,
   one or more processors; and one or more memories communicatively coupled to the one or more processors;
   the one or more processors:
   An acquisition process of acquiring vehicle characteristic information related to characteristics of other vehicles traveling around the vehicle;
   a preceding vehicle suggestion process for assuming one or more first other vehicles among the other vehicles as the preceding vehicle, identifying a second other vehicle that is a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and suggesting the preceding vehicle based on preference information regarding surrounding vehicles of a driver of the vehicle and the vehicle characteristic information of the first other vehicle and the second other vehicle;
   A driving assistance device that performs the following:
2. the one or more processors:
   setting the proposed preceding vehicle based on a degree of match between the vehicle characteristic information of the first other vehicle and preference information of the driver of the vehicle regarding the surrounding vehicles, and a degree of match between the vehicle characteristic information of the second other vehicle and preference information of the driver of the vehicle regarding the surrounding vehicles;
   The driving assistance device according to claim 1 .
3. the one or more processors:
   and further executing a vehicle distance setting process for setting a target vehicle distance between the preceding vehicle and the vehicle during the following control in accordance with a degree of match between the vehicle characteristic information of the preceding vehicle and preference information of a driver of the vehicle regarding the surrounding vehicles.
   The driving assistance device according to claim 1 .
4. the one or more processors:
   setting the target inter-vehicle distance between the preceding vehicle and the vehicle in accordance with a degree of match between the vehicle characteristic information of the preceding vehicle and preference information of the driver of the vehicle regarding the surrounding vehicles, and a degree of match between the vehicle characteristic information of the following vehicle and preference information of the driver of the vehicle regarding the surrounding vehicles;
   The driving assistance device according to claim 3.
5. The preference information of the driver of the vehicle regarding the surrounding vehicles includes information on an allowable following duration, which is a maximum continuous time for which the vehicle is allowed to follow the same leading vehicle, and information on an allowable followed duration, which is a maximum continuous time for which the vehicle is allowed to be followed by the same following vehicle,
   the one or more processors:
   When the following duration exceeds the allowable following duration or the followed duration exceeds the allowable followed duration, the preceding vehicle suggestion process is executed again to suggest the preceding vehicle to be followed.
   The driving assistance device according to claim 1 .
6. The vehicle characteristic information of the other vehicle further includes preference information of a driver of the other vehicle regarding the surrounding vehicle,
   the one or more processors:
   2. The driving assistance device according to claim 1, wherein from among the other vehicles, the first other vehicle is proposed as the preceding vehicle such that a degree of match between the vehicle characteristic information of the first other vehicle and the preference information of the driver of the vehicle regarding the surrounding vehicles is equal to or greater than a predetermined standard, and a degree of match between the vehicle characteristic information of the second other vehicle and the preference information of the driver of the vehicle regarding the surrounding vehicles is equal to or greater than a predetermined standard.
7. A driving assistance method for assisting driving of a vehicle capable of performing following control for causing the vehicle to follow a preceding vehicle, comprising:
   the one or more processors:
   Obtaining vehicle characteristic information relating to characteristics of other vehicles traveling around the vehicle;
   Assume that any one or more of the first other vehicles among the other vehicles is the preceding vehicle, and identify a second other vehicle that is a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and propose the preceding vehicle based on preference information regarding surrounding vehicles of a driver of the vehicle and the vehicle characteristic information of the first other vehicle and the second other vehicle;
   A driving assistance method comprising the steps of:
8. One or more processors,
   An acquisition process of acquiring vehicle characteristic information related to characteristics of other vehicles traveling around the vehicle;
   a preceding vehicle suggestion process for assuming one or more of the first other vehicles among the other vehicles as a preceding vehicle, identifying a second other vehicle that is a following vehicle of the vehicle when the first other vehicle is assumed to be the preceding vehicle, and suggesting the preceding vehicle when performing following control based on preference information regarding surrounding vehicles of the driver of the vehicle and the vehicle characteristic information of the first other vehicle and the second other vehicle;
   A non-transitory tangible recording medium on which a computer program for executing the above is recorded.
   

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