Drive support device and drive support method

Abstract

To suppress delay in response of a driver in an emergency when a support level is changed.SOLUTION: A drive support device can execute drive support of a vehicle 100 at a first support level and a second support level having a different degree of contribution to drive of a driver. The drive support device includes: an inter-vehicle distance detection unit 331 for detecting inter-vehicle distance between a vehicle and a preceding vehicle P; and a support level switching unit 332 for switching a support level in drive support to the support level satisfying switching conditions when the switching conditions to an arbitrary support level is satisfied. The first support level is the support level at which acceleration / deceleration of the vehicle is automatically performed but steering of the vehicle is not automatically performed. The second support level is the support level at which both acceleration / deceleration and steering of the vehicle are automatically performed. Conditions for switching to each support level include that the inter-vehicle distance is equal to or greater than reference distance. The reference distance in the conditions for switching to the second support level is longer than the reference distance in the conditions for switching to the first support level.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a driving assistance device and a driving assistance method. [Background technology]

[0002] Driving assistance devices that provide driving assistance to drivers have been known for some time (Patent Documents 1, 2, etc.). In particular, the device described in Patent Document 1 is capable of executing driving assistance control and autonomous driving control, and the inter-vehicle distance based on driving assistance control is made shorter than the inter-vehicle distance based on autonomous driving control. In addition, in the control described in Patent Document 1, when transitioning from driving assistance control to autonomous driving control, the inter-vehicle distance is changed, and then the driving control state is switched from driving assistance control to autonomous driving control. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-155463 [Patent Document 2] Japanese Patent Application Publication No. 11-342766 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the driving control state is switched from driving assistance control to autonomous driving control after the inter-vehicle distance is changed. On the other hand, in the device described in Patent Document 1, although driving assistance control can be performed at different assistance levels, the assistance level is changed regardless of the inter-vehicle distance.

[0005] However, since the higher the assistance level, the more likely the driver is to be slow to respond in an emergency, if the assistance level is changed regardless of the inter-vehicle distance, the driver may not be able to respond quickly in an emergency.

[0006] In view of the above-mentioned problems, an object of the present disclosure is to suppress delays in the driver's response in an emergency when changing the assistance level. [Means for solving the problem]

[0007] The gist of the present disclosure is as follows.

[0008] (1) A driving assistance device capable of performing driving assistance for a vehicle at a first assistance level and a second assistance level having different degrees of contribution to a driver's driving, a vehicle distance detection unit for detecting a vehicle distance between the vehicle and a preceding vehicle; an assistance level switching unit that switches the assistance level of the driving assistance to an assistance level for which a switching condition to an arbitrary assistance level is satisfied when the switching condition to the arbitrary assistance level is satisfied, The first assistance level is an assistance level in which acceleration and deceleration of the vehicle are performed automatically but steering of the vehicle is not performed automatically, The second assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically, The conditions for switching to each assistance level include the inter-vehicle distance being equal to or greater than a reference distance, A driving assistance device, wherein a reference distance in the condition for switching to the second assistance level is longer than a reference distance in the condition for switching to the first assistance level. (2) The vehicle is capable of performing driving assistance of the vehicle at a third assistance level in addition to the first assistance level and the second assistance level, The second assistance level requires the driver of the vehicle to view the road ahead, although both acceleration, deceleration, and steering of the vehicle are performed automatically. The third assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically and the driver of the vehicle does not need to view the front, The driving assistance device according to (1) above, wherein the reference distance in the condition for switching to the third assistance level is longer than the reference distance in the condition for switching to the second assistance level. (3) Further comprising a driving control unit that controls driving of the vehicle; The driving assistance device according to (1) or (2) above, wherein when an increase in the assistance level is requested while the vehicle is being driven at the first assistance level or the second assistance level, the driving control unit controls the driving of the vehicle so that the inter-vehicle distance increases. (4) A driving assistance device according to any one of (1) to (3) above, wherein the assistance level switching unit switches the assistance level to an assistance level that can be started based on the inter-vehicle distance when driving assistance at the highest assistance level is requested while the driving assistance is not being performed. (5) A driving assistance method for performing driving assistance for a vehicle at a first assistance level and a second assistance level having different degrees of contribution to the driver's driving, Detecting a distance between the vehicle and a preceding vehicle; When a switching condition to an arbitrary assistance level is satisfied, switching the assistance level of the driving assistance to the assistance level for which the switching condition is satisfied, The first assistance level is an assistance level in which acceleration and deceleration of the vehicle are performed automatically but steering of the vehicle is not performed automatically, The second assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically, The conditions for switching to each assistance level include the inter-vehicle distance being equal to or greater than a reference distance, A driving assistance method, wherein the reference distance in the condition for switching to the second assistance level is longer than the reference distance in the condition for switching to the first assistance level. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to reduce delays in the driver's response in an emergency when changing the assistance level. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic block diagram showing the configuration of a driving assistance system. [Figure 2] FIG. 2 is a functional block diagram of the processor of the ECU. [Figure 3] FIG. 3 is a diagram showing a state of vehicles traveling on one lane. [Figure 4] FIG. 4 is a flowchart showing the flow of the support level setting process for setting the support level. [Figure 5] FIG. 5 is a flowchart showing the flow of a driving assistance process for providing driving assistance based on a set assistance level. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings. In the following description, like components are designated by like reference numerals.

[0012] <Vehicle control system configuration> The configuration of a driving assistance system 1 including a driving assistance device according to one embodiment will be described with reference to Figures 1 to 3. The driving assistance device can provide driving assistance for a vehicle 100 at a plurality of assistance levels that differ in the degree of contribution to the driver's driving. Figure 1 is a schematic block diagram showing the configuration of the driving assistance system 1.

[0013] A driving assistance system 1 is mounted on a vehicle 100 and performs driving assistance for the vehicle 100 at multiple assistance levels that differ in the degree of contribution to the driver's driving. As shown in FIG. 1 , in this embodiment, the driving assistance system 1 includes an exterior camera 11, a distance measurement sensor 12, a driver monitor camera 13, vehicle sensors 14, a human-machine interface (HMI) 15, a vehicle actuator 21, and an electronic control unit (hereinafter referred to as "ECU") 30. The exterior camera 11, the distance measurement sensor 12, the driver monitor camera 13, the vehicle sensors 14, the HMI 15, and the ECU 30 are communicatively connected, for example, via an in-vehicle network 25. The in-vehicle network 25 is, for example, a network that complies with a standard such as CAN (Controller Area Network). The ECU 30 is also connected to the vehicle actuator 21 via a signal line.

[0014] The exterior camera 11 is a device that captures images of the surroundings of the vehicle. In this embodiment, the exterior camera 11 captures images of the area ahead of the vehicle 100. The exterior camera 11 is, for example, a CMOS (Complementary Metal-Oxide Semiconductor) camera or a CCD (Charge-Coupled Device) camera that is sensitive to visible light. In this embodiment, the exterior camera 11 is mounted, for example, inside the vehicle 100 so that it faces the front of the vehicle 100. The exterior camera 11 captures images of the area ahead of the vehicle 100 at predetermined imaging intervals and generates images of the area ahead. Each time the exterior camera 11 generates an image, it outputs the generated image to the ECU 30 via the in-vehicle network 25.

[0015] The ranging sensor 12 is a sensor that measures the distance to an object present around the vehicle 100. In this embodiment, the ranging sensor 12 measures the distance to an object present ahead of the vehicle 100. In particular, in this embodiment, the ranging sensor 12 can measure the distance to a vehicle ahead of the vehicle 100. The ranging sensor 12 is, for example, a radar such as a millimeter-wave radar or a LIDAR. The ranging sensor 12 outputs the measurement results of the distance to the surrounding object to the ECU 30 via the in-vehicle network 25 at predetermined intervals.

[0016] The driver monitor camera 13 is a device that captures an image of the driver's face. In this embodiment, the driver monitor camera 13 is provided above the steering column and is positioned facing the driver so as to capture an image of the driver, specifically, the driver's face and part of the upper body. The driver monitor camera 13 includes a camera and a floodlight. For example, the camera is a CMOS camera or a CCD camera, and the floodlight is an LED (light-emitting diode). Furthermore, the floodlight is preferably a near-infrared LED so that the driver's face can be captured without causing discomfort to the driver even in low-light conditions such as at night, and the camera is preferably capable of detecting near-infrared light. The driver monitor camera 13 outputs the captured images to the ECU 30 at predetermined intervals via the in-vehicle network 25.

[0017] The vehicle sensor 14 is a sensor that detects the state of the vehicle 100. The vehicle sensor 14 detects the running state and operation state of the vehicle 100. The vehicle sensor 14 includes, as sensors that detect the running state of the vehicle 100, for example, a speed sensor that detects the speed of the vehicle 100, an acceleration sensor that detects the acceleration of the vehicle 100, etc. In addition, the vehicle sensor 14 includes, as sensors that detect the running state of the vehicle 100, for example, a self-position sensor (e.g., a GPS sensor) that detects the self-position of the vehicle 100. The vehicle sensor 14 also includes, as sensors that detect the operation state of the vehicle 100, for example, a steering wheel grip sensor that detects whether the driver is gripping (or touching) the steering wheel, etc. The vehicle sensor 14 outputs the detection result to the ECU 30 via the in-vehicle network 25 at predetermined intervals.

[0018] The HMI 15 is an interface for inputting and outputting information between the driver or passenger and the driving assistance system 1. The HMI 15 includes an information providing device for providing various information to the driver or passenger, and an input device for the driver or passenger to perform input operations.

[0019] Specifically, the HMI 15 includes a display 16 as an information providing device for displaying text information or image information. The display 16 is an example of a display device for displaying images. The display 16 is a display device of any type, such as a liquid crystal display or an organic EL display. The display 16 is disposed so that at least the driver can check the screen. Therefore, the display 16 is disposed, for example, on an instrument panel, meter panel, or the like of the vehicle 100. The display 16 receives an image signal from the ECU 30 via the in-vehicle network 25 and displays an image in accordance with this image signal. Note that the vehicle 100 may also include another type of display device, such as a head-up display, as an information providing device.

[0020] The HMI 15 also has a speaker 17 as an information providing device. The speaker 17 is an example of a device that outputs audio. The speaker 17 receives an audio signal from the ECU 30 via the in-vehicle network 25 and outputs audio in accordance with the audio signal. Note that the HMI 15 may also include devices (e.g., a vibration device) other than the display 16 and the speaker 17 as an information providing device that provides various types of information to the driver or passengers.

[0021] Additionally, the HMI 15 has a touch panel 18 as an input device. The touch panel 18 is an example of a device that is touched by the driver or passenger to perform an input. When the driver or passenger performs an operation by touching the touch panel 18, the touch panel 18 outputs an operation signal to the ECU 30 via the in-vehicle network 25. Note that the HMI 15 may also have devices (e.g., buttons, switches, etc.) other than the touch panel 18 as an input device for the driver or passenger to perform an input operation.

[0022] The vehicle actuators 21 are actuators used to control the operation of the vehicle 100. Specifically, the vehicle actuators 21 include, for example, a drive actuator that controls an internal combustion engine or an electric motor for driving the vehicle 100, a braking actuator that controls brakes that brake the vehicle 100, and a steering actuator that controls steering of the vehicle 100. The vehicle actuators 21 control the acceleration, braking, and steering of the vehicle 100 in accordance with control signals transmitted from the ECU 30 via signal lines.

[0023] <Configuration of driving assistance device> The ECU 30 functions as a driving assistance device that performs driving assistance at a plurality of different assistance levels for the vehicle 100. Specifically, in this embodiment, driving assistance is performed at three assistance levels: a first assistance level, a second assistance level, and a third assistance level.

[0024] The first assistance level is an assistance level in which acceleration and deceleration of the vehicle 100 are performed automatically but steering of the vehicle 100 is not performed automatically, and corresponds to, for example, level 1 autonomous driving defined by the Society of Automotive Engineers (SAE). Therefore, at the first assistance level, the internal combustion engine or electric motor and brakes are controlled by the drive actuator and braking actuator among the vehicle actuators 21. However, at the first assistance level, the steering actuator among the vehicle actuators 21 is not controlled. The drive actuator and braking actuator are controlled so that the vehicle 100 travels at a preset speed when there is no preceding vehicle, and are controlled so that the inter-vehicle distance from the preceding vehicle becomes a predetermined first reference distance when there is a preceding vehicle.

[0025] The second assistance level is an assistance level in which both acceleration, deceleration, and steering of the vehicle 100 are performed automatically, but the driver is required to view the road ahead. This level corresponds to, for example, Level 2 automated driving defined by the SAE. Therefore, at the second assistance level, the internal combustion engine or electric motor and brakes are controlled by the vehicle actuator and braking actuator, and steering is controlled by the steering actuator. At the second assistance level, the drive actuator and braking actuator are controlled in the same manner as at the first assistance level. However, at the second assistance level, when a leading vehicle is present, the inter-vehicle distance from the leading vehicle is controlled to a predetermined second reference distance that is longer than the first reference distance. In addition, the steering actuator is controlled to keep the vehicle 100 within the lane. At the first and second assistance levels, if the driver is not viewing the road ahead, a warning is issued to encourage the driver to view the road ahead. If the driver still does not view the road ahead, the driving assistance at the second assistance level is discontinued.

[0026] The third assistance level is an assistance level in which both acceleration, deceleration, and steering of the vehicle 100 are performed automatically and the driver does not need to view the road ahead. This level corresponds to, for example, level 3 or higher automated driving specified by the SAE. Therefore, even at the third assistance level, the internal combustion engine or electric motor and brakes are controlled by the vehicle actuator and braking actuator, and steering is controlled by the steering actuator. In addition, even at the third assistance level, the drive actuator and braking actuator are controlled in the same manner as at the first assistance level. However, at the third assistance level, when a leading vehicle is present, the inter-vehicle distance from the leading vehicle is controlled to a predetermined third reference distance that is longer than the second reference distance. In addition, the steering actuator is controlled to keep the vehicle 100 within the lane. Furthermore, at the third assistance level, the driver does not need to view the road ahead, so no warnings or driving assistance is suspended even if the driver is not viewing the road ahead.

[0027] The ECU 30 controls the operation of the vehicle actuators 21 when performing driving assistance. The ECU 30 also controls the information to be provided from the information providing device of the HMI 15. Therefore, the ECU 30 controls the images displayed on the display 16 and the sounds output from the speaker 17. As shown in FIG. 1 , the ECU 30 has a communication interface 31, a storage unit 32, and a processor 33.

[0028] The communication interface 31 is a circuit for connecting the ECU 30 to the in-vehicle network 25 .

[0029] The memory unit 32 stores data. The memory unit 32 includes, for example, at least one of a volatile semiconductor memory, a non-volatile semiconductor memory, a hard disk drive (HDD), and a solid state drive (SSD). The memory unit 32 stores a computer program executed by the processor 33 of the ECU 30. The memory unit 32 also stores data used in the computer program executed by the processor 33, such as data transmitted from the outside camera 11. In addition, the memory unit 32 stores a high-precision map including road information for each lane and information on surrounding structures.

[0030] The processor 33 has one or more central processing units (CPUs) and their peripheral circuits. The processor 33 may further have other arithmetic circuits such as a logic operation unit or a numerical operation unit. The processor 33 executes a computer program stored in the storage unit 32.

[0031] 2 is a functional block diagram of the processor 33 of the ECU 30. As shown in FIG. 2, the processor 33 includes an inter-vehicle distance detection unit 331, an assistance level switching unit 332, a driving control unit 333, and a notification unit 334.

[0032] The inter-vehicle distance detection unit 331 detects the inter-vehicle distance between the vehicle 100 and a preceding vehicle that is traveling ahead of the vehicle 100 and in the same lane as the vehicle 100. FIG. 3 is a diagram showing vehicles traveling in one lane. In the example shown in FIG. 3, a preceding vehicle P is traveling just ahead of the vehicle 100 in the same lane as the vehicle 100. The inter-vehicle distance detection unit 331 detects the inter-vehicle distance Δd between the preceding vehicle P and the vehicle 100.

[0033] The inter-vehicle distance detection unit 331 receives as input an image captured by the exterior camera 11 and distance information measured by the distance measurement sensor 12. The inter-vehicle distance detection unit 331 calculates the inter-vehicle distance between the vehicle 100 and the preceding vehicle P based on the input image and distance information. Specifically, for example, the inter-vehicle distance detection unit 331 recognizes the preceding vehicle P based on the image captured by the exterior camera 11. In addition, the inter-vehicle distance detection unit 331 calculates the inter-vehicle distance Δd between the vehicle 100 and the preceding vehicle P based on distance information measured by the distance measurement sensor 12 for the position (direction) of the recognized preceding vehicle. The inter-vehicle distance detection unit 331 outputs the inter-vehicle distance Δd between the vehicle 100 and the preceding vehicle P calculated in this manner to the assistance level switching unit 332.

[0034] When a switching condition to an arbitrary support level is satisfied, the support level switching unit 332 switches the support level provided by the driving support device to the support level for which the switching condition is satisfied. The support level switching unit 332 receives the inter-vehicle distance Δd from the preceding vehicle P output from the inter-vehicle distance detection unit 331, the output of the driver monitor camera 13 (an image captured by the driver monitor camera 13), and the output of the vehicle sensor 14. The support level switching unit 332 also sets the support level for driving support, and outputs the set support level to the driving control unit 333 and the notification unit 334.

[0035] In this embodiment, the conditions for switching to the first support level include the inter-vehicle distance Δd from the preceding vehicle P being equal to or greater than a first reference distance. Therefore, when there is a request to switch the support level to the first support level, if the inter-vehicle distance Δd from the preceding vehicle P is less than the first reference distance, the support level is not switched to the first support level.

[0036] Additionally, the condition for switching to the first assistance level includes the driver gripping the steering wheel. The assistance level switching unit 332 determines whether the driver is gripping the steering wheel based on the output of the vehicle sensors 14, particularly the output of the steering wheel grip sensor. If it is determined that the driver is not gripping the steering wheel when a request to switch the assistance level to the first assistance level is made, the switching to the first assistance level is not performed.

[0037] Furthermore, the condition for switching to the first assistance level includes the driver's visual acuity. The assistance level switching unit 332 determines whether the driver is visually acuity based on the output of the driver monitor camera 13. For example, the assistance level switching unit 332 inputs an image acquired from the driver monitor camera 13 to a classifier that recognizes the upper and lower eyelids, and detects the distance between the recognized upper and lower eyelids as the degree of eye opening. The assistance level switching unit 332 also inputs the image acquired from the driver monitor camera 13 to a classifier that has been trained in advance to identify the positions of the pupil and the corneal reflex of the light source. The assistance level switching unit 332 then detects the gaze direction based on the identified positional relationship between the pupil and the corneal reflex. The assistance level switching unit 332 determines that the driver is not visually acuity when the detected degree of eye opening is less than a predetermined value and the driver has his eyes closed, or when the detected gaze direction is not a forward direction. On the other hand, when the eye opening degree is equal to or greater than a predetermined value and the line of sight is forward, the assistance level switching unit 332 determines that the driver is looking ahead. When a request to switch the assistance level to the first assistance level is made and it is determined that the driver is not looking ahead, the assistance level switching unit 332 does not switch to the first assistance level.

[0038] In this embodiment, the conditions for switching to the second support level include the inter-vehicle distance Δd from the preceding vehicle P being equal to or greater than a second reference distance. The second reference distance is longer than the first reference distance. Therefore, when a request to switch the support level to the second support level is made and the inter-vehicle distance Δd from the preceding vehicle P is less than the second reference distance, switching to the second support level is not performed.

[0039] In addition, the condition for switching to the second assistance level includes the driver viewing the road ahead. Whether the driver is viewing the road ahead is determined based on the output of the driver monitor camera 13, as described above. If it is determined that the driver is not viewing the road ahead when a request to switch the assistance level to the second assistance level is made, the assistance level is not switched to the second assistance level. Note that the condition for switching to the second assistance level does not include the driver holding the steering wheel.

[0040] Furthermore, in this embodiment, the conditions for switching to the third support level include the inter-vehicle distance Δd from the preceding vehicle P being equal to or greater than a third reference distance. The third reference distance is longer than the second reference distance. Therefore, when there is a request to switch the support level to the third support level, if the inter-vehicle distance Δd from the preceding vehicle P is less than the third reference distance, switching to the third support level is not performed.

[0041] In addition, the conditions for switching to the third assistance level include the location where the vehicle 100 is traveling being included in the high-precision map stored in the storage unit 32. Here, since the high-precision map does not necessarily cover all roads, the road where the vehicle 100 is currently traveling may not be included in the high-precision map. The assistance level switching unit 332, for example, determines the self-location of the vehicle 100 based on the output of the vehicle sensor 14, particularly the output of the self-location sensor, and determines whether the determined self-location is included in the high-precision map. When a request to switch the assistance level to the third assistance level is made and it is determined that the self-location of the vehicle 100 is not included in the high-precision map, the switching to the third assistance level is not performed.

[0042] Furthermore, the condition for switching to the third assistance level may include the speed of the vehicle 100 being equal to or less than a reference speed. The assistance level switching unit 332 determines whether the speed of the vehicle 100 is equal to or less than the reference speed based on the output of the vehicle sensor 14, particularly the output of the speed sensor. When a request to switch the assistance level to the third assistance level is made and it is determined that the speed of the vehicle 100 is not equal to or less than the reference speed, switching to the third assistance level is not performed.

[0043] The above-described conditions for switching to each support level are merely examples. Therefore, the conditions for switching to each support level may include one or more other conditions in addition to or instead of the above-described conditions. However, even in such cases, the conditions for switching to each support level must include a condition related to the inter-vehicle distance Δd from the preceding vehicle P. In addition, the first reference distance in the condition for switching to the first support level, the second reference distance in the condition for switching to the second support level, and the third reference distance in the condition for switching to the third support level must increase in this order.

[0044] The driving control unit 333 controls the driving of the vehicle 100. In particular, the driving control unit 333 controls the driving of the vehicle 100 at the assistance level set by the assistance level switching unit 332. The assistance level set by the assistance level switching unit 332 is input to the driving control unit 333. In addition, information necessary for driving the vehicle 100, such as an image captured by the outside camera 11 and distance information measured by the distance measuring sensor 12, is input to the driving control unit 333.

[0045] For example, when the assistance level is set to the first assistance level, the driving control unit 333 controls the drive actuator and the braking actuator. In particular, if a preceding vehicle P exists at this time, the driving control unit 333 controls the drive actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P becomes the first reference distance. Furthermore, when the assistance level is set to the second assistance level, the driving control unit 333 controls the drive actuator, the braking actuator, and the steering actuator. In particular, if a preceding vehicle P exists at this time, the driving control unit 333 controls the drive actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P becomes the second reference distance. Furthermore, when the assistance level is set to the third assistance level, the driving control unit 333 controls the drive actuator, the braking actuator, and the steering actuator. In particular, if a preceding vehicle P exists at this time, the driving control unit 333 controls the drive actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P becomes the third reference distance.

[0046] Furthermore, when the set assistance level (hereinafter also referred to as the "set assistance level") differs from the assistance level requested by the driver (hereinafter also referred to as the "requested assistance level"), the driving control unit 333 controls the drive actuator and the brake actuator so that the inter-vehicle distance Δd from the preceding vehicle P becomes a reference distance corresponding to the requested assistance level. Therefore, for example, when the set assistance level is the first assistance level and the requested assistance level is the second assistance level, the driving control unit 333 controls the drive actuator and the brake actuator so that the inter-vehicle distance Δd from the preceding vehicle P increases to the second reference distance. As a result, when the inter-vehicle distance Δd from the preceding vehicle P reaches the reference distance corresponding to the requested assistance level, the assistance level switching unit 332 determines that the switching condition (related to the inter-vehicle distance) of the requested assistance level is satisfied, and the set assistance level is switched.

[0047] As described above, the first reference distance, the second reference distance, and the third reference distance are longest in this order, so when an increase in the assistance level is requested while the vehicle 100 is being driven at the first assistance level or the second assistance level, the driving control unit 333 controls the driving of the vehicle 100 so as to increase the inter-vehicle distance. This allows the inter-vehicle distance to be increased in advance before the assistance level is changed.

[0048] When the assistance level of the vehicle 100 is switched, the notification unit 334 notifies the driver of the switch in assistance level. The notification unit 334 notifies the driver of the switch in assistance level via the information providing device of the HMI 15. The notification unit 334, for example, causes the display 16 to display the switch in assistance level and the support level after the switch. Alternatively, the notification unit 334, for example, causes the speaker 17 to output a sound indicating the switch in assistance level and the support level after the switch.

[0049] In this embodiment, the conditions for switching to each assistance level include the inter-vehicle distance being equal to or greater than a reference distance, and the second reference distance in the conditions for switching to the second assistance level is longer than the first reference distance in the conditions for switching to the first assistance level. Here, the second assistance level contributes less to the driver's driving than the first assistance level, and therefore the driver is more likely to respond slowly in an emergency. According to this embodiment, by making the second reference distance longer than the first reference distance, the driver's response slows down in an emergency when switching to the second assistance level.

[0050] In this embodiment, the third reference distance in the condition for switching to the third support level is longer than the second reference distance in the condition for switching to the second support level. The third support level contributes less to the driver's driving than the second support level, and therefore the driver is more likely to respond slowly in an emergency. According to this embodiment, the third reference distance is longer than the second reference distance, which prevents the driver from responding slowly in an emergency when switching to the third support level.

[0051] <Specific Control> Next, a specific control flow will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a flowchart showing the flow of a support level setting process for setting a support level. The illustrated support level setting process is executed by the processor 33.

[0052] As shown in FIG. 4, in the assistance level setting process, the assistance level switching unit 332 first determines whether the currently set assistance level and the requested assistance level differ (step S11). The requested assistance level is input by the driver, for example, via an input device of the HMI 15, particularly the touch panel 18. For example, when driving assistance is not being performed and the driver inputs one of the first to third assistance levels as the requested assistance level, it is determined that the set assistance level and the requested assistance level differ. Alternatively, for example, even if the third assistance level is input as the requested assistance level, the condition for switching to the third assistance level has not been satisfied and the assistance level has been set to the first assistance level or the second assistance level, it is also determined that the set assistance level and the requested assistance level differ. If it is determined in step S11 that the set assistance level and the requested assistance level do not differ, the assistance level switching unit 332 maintains the currently set assistance level (step S12).

[0053] On the other hand, if it is determined in step S11 that the set support level and the requested support level differ, the inter-vehicle distance detection unit 331 detects the inter-vehicle distance Δd between the vehicle 100 and the preceding vehicle P (step S13). Next, the support level switching unit 332 determines whether the inter-vehicle distance Δd detected by the inter-vehicle distance detection unit 331 is equal to or greater than a reference distance corresponding to the requested support level (step S14). For example, if the requested support level is the second support level, the support level switching unit 332 determines whether the inter-vehicle distance Δd is equal to or greater than the second reference distance.

[0054] If it is determined in step S14 that the inter-vehicle distance Δd is equal to or greater than the reference distance corresponding to the requested support level, the support level switching unit 332 determines whether or not other switching conditions corresponding to the requested support level are satisfied (step S15). For example, if the requested support level is the second support level, the support level switching unit 332 determines whether or not the driver is visually checking the road ahead. If it is determined in step S15 that other switching conditions corresponding to the requested support level are satisfied, the support level switching unit 332 sets the requested support level to a new support level (step S16). On the other hand, if it is determined in step S15 that other switching conditions corresponding to the requested support level are not satisfied, the support level switching unit 332 does not change the support level and maintains the currently set support level (step S17).

[0055] If it is determined in step S14 that the inter-vehicle distance Δd is less than the reference distance corresponding to the requested support level, the support level switching unit 332 determines whether the inter-vehicle distance Δd is equal to or greater than the reference distance corresponding to a support level lower than the requested support level (step S18). Therefore, for example, if the requested support level is the second support level, the support level switching unit 332 determines whether the inter-vehicle distance Δd is equal to or greater than the first reference distance. Also, for example, if the requested support level is the third support level, the support level switching unit 332 determines whether the inter-vehicle distance Δd is equal to or greater than the first reference distance or the second reference distance. If it is determined in step S14 that the inter-vehicle distance Δd is less than the reference distance corresponding to a support level lower than the requested support level, the support level switching unit 332 does not change the support level and maintains the currently set support level (step S12).

[0056] If it is determined in step S14 that the inter-vehicle distance Δd is equal to or greater than the reference distance corresponding to a support level lower than the requested support level, the support level switching unit 332 determines whether or not other switching conditions corresponding to the lower support level at which the inter-vehicle distance Δd was equal to or greater than the reference distance are satisfied (step S19). For example, if the lower support level at which the inter-vehicle distance Δd was equal to or greater than the reference distance is the first support level, the support level switching unit 332 determines whether or not the driver is gripping the steering wheel and whether or not the driver is looking ahead. If it is determined in step S19 that other switching conditions corresponding to the lower support level are satisfied, the support level switching unit 332 sets this lower support level as the new support level (step S20). On the other hand, if it is determined in step S19 that other switching conditions corresponding to the lower support level are not satisfied, the support level switching unit 332 does not change the support level and maintains the currently set support level (step S12).

[0057] By controlling in this manner, in this embodiment, when driving assistance at the third assistance level, which is the highest assistance level, is requested when driving assistance is not being performed and the inter-vehicle distance Δd is equal to or greater than the third reference distance, the assistance level switching unit 332 switches the assistance level to the third assistance level. However, even in such a case, when the inter-vehicle distance Δd is less than the third reference distance and equal to or greater than the second reference distance, the assistance level switching unit 332 switches the assistance level to the second assistance level. In addition, when the inter-vehicle distance Δd is less than the second reference distance and equal to or greater than the first reference distance, the assistance level switching unit 332 switches the assistance level to the first assistance level. Therefore, when driving assistance at the highest assistance level is requested when driving assistance is not being performed, the assistance level switching unit 332 switches the assistance level to an assistance level that can be started based on the inter-vehicle distance. As a result, driving assistance is performed at the highest possible assistance level.

[0058] 5 is a flowchart showing the flow of the driving assistance process for providing driving assistance based on the set assistance level. The illustrated driving assistance process is executed by the processor 33.

[0059] 5, in the driving assistance processing, first, the driving control unit 333 determines whether the currently set assistance level and the requested assistance level differ, as in step S11 (step S31). If it is determined in step S31 that the set assistance level and the requested assistance level do not differ, the driving control unit 333 executes driving assistance at the currently set assistance level so that the inter-vehicle distance corresponds to the currently set assistance level (step S32). On the other hand, if it is determined in step S31 that the set assistance level and the requested assistance level differ, the driving control unit 333 executes driving assistance at the currently set assistance level so that the inter-vehicle distance corresponds to the requested assistance level (step S33). Therefore, for example, if the requested assistance level is the second assistance level and the currently set assistance level is the first assistance level, the driving control unit 333 controls the drive actuator and the braking actuator so that the inter-vehicle distance Δd becomes the first reference distance, but does not control the steering actuator.

[0060] In the above embodiment, the driving assistance device can perform driving assistance at three assistance levels: first assistance level, second assistance level, and third assistance level. However, the driving assistance device does not necessarily have to perform driving assistance at the third assistance level as long as it can perform driving assistance at the first assistance level and the second assistance level.

[0061] Although the preferred embodiments according to the present disclosure have been described above, the present disclosure is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. [Explanation of symbols]

[0062] 1. Driving assistance systems 30 ECU 33 processors

Claims

1. A driving assistance device capable of performing driving assistance for a vehicle at a first assistance level and a second assistance level having different degrees of contribution to a driver's driving, a vehicle distance detection unit for detecting a vehicle distance between the vehicle and a preceding vehicle; an assistance level switching unit that switches the assistance level of the driving assistance to an assistance level for which a switching condition to an arbitrary assistance level is satisfied when the switching condition to the arbitrary assistance level is satisfied, the first assistance level is an assistance level in which acceleration and deceleration of the vehicle are performed automatically but steering of the vehicle is not performed automatically; The second assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically, The conditions for switching to each assistance level include the inter-vehicle distance being equal to or greater than a reference distance, A driving assistance device, wherein a reference distance in the condition for switching to the second assistance level is longer than a reference distance in the condition for switching to the first assistance level.

2. The vehicle is capable of performing driving assistance of the vehicle at a third assistance level in addition to the first assistance level and the second assistance level, The second assistance level requires the driver of the vehicle to view the road ahead, although both acceleration, deceleration, and steering of the vehicle are performed automatically. The third assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically and the driver of the vehicle does not need to view the front, The driving assistance device according to claim 1 , wherein the reference distance in the condition for switching to the third assistance level is longer than the reference distance in the condition for switching to the second assistance level.

3. Further, a driving control unit that controls driving of the vehicle is provided.

3. The driving assistance device according to claim 1, wherein when an increase in the assistance level is requested while the vehicle is being driven at the first assistance level or the second assistance level, the driving control unit controls the driving of the vehicle so that the inter-vehicle distance increases.

4. 3. The driving assistance device according to claim 1, wherein when the driving assistance at the highest assistance level is requested while the driving assistance is not being performed, the assistance level switching unit switches the assistance level to an assistance level that can be started based on the inter-vehicle distance.

5. A driving assistance method for performing driving assistance for a vehicle at a first assistance level and a second assistance level having different degrees of contribution to driving of a driver, Detecting a distance between the vehicle and a preceding vehicle; When a switching condition to an arbitrary assistance level is satisfied, switching the assistance level of the driving assistance to the assistance level for which the switching condition is satisfied, the first assistance level is an assistance level in which acceleration and deceleration of the vehicle are performed automatically but steering of the vehicle is not performed automatically; The second assistance level is an assistance level in which both acceleration / deceleration and steering of the vehicle are performed automatically, The conditions for switching to each assistance level include the inter-vehicle distance being equal to or greater than a reference distance, A driving assistance method, wherein the reference distance in the condition for switching to the second assistance level is longer than the reference distance in the condition for switching to the first assistance level.

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