Driving assistance device and driving assistance method

Abstract

The present invention relates to a driving assistance device and a driving assistance method, which suppress a delay in response to a driver in an emergency when an assistance level is changed. The driving assistance device is capable of performing driving assistance of a vehicle (100) at a first assistance level and a second assistance level, the first assistance level and the second assistance level having different degrees of contribution to driving by a driver. The driving assistance device is provided with: an inter-vehicle distance detection unit (331) that detects the inter-vehicle distance between the vehicle and a preceding vehicle (P) of the vehicle; and an assistance level switching unit (332) that, when a switching condition to an arbitrary assistance level is satisfied, switches the assistance level of the driving assistance to the assistance level in which the switching condition is satisfied. The first assist level is an assist level in which acceleration and deceleration of the vehicle are automatically performed and steering of the vehicle is not automatically performed. The second assist level is an assist level at which both acceleration and deceleration and steering of the vehicle are automatically performed. The condition for switching to each assistance level includes a condition that the inter-vehicle distance is equal to or greater than a reference distance. The reference distance in the condition of switching to the second assist level is longer than the reference distance in the condition of switching to the first assist level.

Description

Technical Field

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

[0002] Driving assistance devices that assist the driver are known (Patent Documents 1 and 2, etc.). In particular, the device described in Patent Document 1 is capable of executing both driving assistance control and autonomous driving control, with the inter-vehicle distance under driving assistance control being narrower than the inter-vehicle distance under autonomous driving control. Furthermore, in the control described in Patent Document 1, when transitioning from driving assistance control to autonomous driving control, the driving control state switches from driving assistance control to autonomous driving control after the inter-vehicle distance has been changed.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-155463

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 11-342766 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] In the device described in Patent Document 1, the driving control state is switched from driving assistance control to autonomous driving control, but this is performed after the inter-vehicle distance has been changed. Meanwhile, in the device described in Patent Document 1, while driving assistance control can be executed at different assistance levels, the assistance level is changed independently of the inter-vehicle distance.

[0009] However, there is a tendency that the higher the assistance level, the longer the driver's response in an emergency. Therefore, if the assistance level is changed regardless of the inter-vehicle distance, the driver may not be able to respond quickly in an emergency.

[0010] In view of the above-mentioned problems, an object of the present disclosure is to suppress delays in driver's response in an emergency when changing the assistance level.

[0011] Technical solutions to problems

[0012] The gist of the present disclosure is as follows.

[0013] (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.

[0014] The driving assistance device comprises:

[0015] an inter-vehicle distance detecting unit for detecting an inter-vehicle distance between the vehicle and a preceding vehicle of the vehicle; and

[0016] an assistance level switching unit that switches the assistance level of the driving assistance to the assistance level that satisfies the switching condition when a switching condition to an arbitrary assistance level is satisfied;

[0017] The first assistance level is an assistance level in which acceleration and deceleration of the vehicle are automatically performed and steering of the vehicle is not automatically performed.

[0018] The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically.

[0019] The conditions for switching to each assistance level include the condition that the vehicle distance is greater than the reference distance.

[0020] The reference distance in the switching condition to the second assistance level is longer than the reference distance in the switching condition to the first assistance level.

[0021] (2) The driving assistance device according to (1) above,

[0022] In addition to the first assistance level and the second assistance level, the vehicle can also perform driving assistance for the vehicle at a third assistance level.

[0023] The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically and the driver of the vehicle is required to keep his eyes on the road ahead.

[0024] The third assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically, and the driver of the vehicle does not need to look ahead.

[0025] The reference distance in the switching condition to the third assistance level is longer than the reference distance in the switching condition to the second assistance level.

[0026] (3) The driving assistance device according to (1) or (2) above,

[0027] further comprising a driving control unit for controlling the driving of the vehicle,

[0028] The driving control unit controls driving of the vehicle so as to increase the inter-vehicle distance 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.

[0029] (4) The driving assistance device according to any one of (1) to (3) above,

[0030] The assistance level switching unit switches the assistance level to an assistance level that can be started based on the inter-vehicle distance when the driving assistance at the highest assistance level is requested without the driving assistance being executed.

[0031] (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 a driver's driving.

[0032] The driving assistance method comprises:

[0033] detecting a distance between the vehicle and a preceding vehicle of the vehicle; and

[0034] When a switching condition to an arbitrary assistance level is satisfied, the assistance level of the driving assistance is switched to the assistance level for which the switching condition is satisfied,

[0035] The first assistance level is an assistance level in which acceleration and deceleration of the vehicle are automatically performed and steering of the vehicle is not automatically performed.

[0036] The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically.

[0037] The conditions for switching to each assistance level include the condition that the vehicle distance is greater than the reference distance.

[0038] The reference distance in the switching condition to the second assistance level is longer than the reference distance in the switching condition to the first assistance level.

[0039] Effects of the Invention

[0040] According to the present disclosure, it is possible to suppress a situation in which the driver's response is delayed in an emergency when the assistance level is changed. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a block diagram schematically showing the configuration of a driving assistance system.

[0042] Figure 2 This is a functional block diagram of the ECU's processor.

[0043] Figure 3 This diagram shows vehicles traveling in one lane.

[0044] Figure 4 This is a flowchart showing the flow of the assist level setting process for setting the assist level.

[0045] Figure 5 This is a flowchart showing the flow of a driving assistance process for performing driving assistance based on a set assistance level.

[0046] Description of Reference Numerals

[0047] 1. Driving assistance system;

[0048] 30ECU;

[0049] 33 processors. DETAILED DESCRIPTION

[0050] Hereinafter, the embodiment will be described in detail with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals.

[0051] <Vehicle Control System Configuration>

[0052] Reference Figures 1 to 3 The configuration of a driving assistance system 1 including a driving assistance device according to an embodiment will be described. The driving assistance device can perform driving assistance for a vehicle 100 at a plurality of assistance levels having different degrees of contribution to the driver's driving. Figure 1 It is a block diagram schematically showing the configuration of the driving assistance system 1 .

[0053] The driving assistance system 1 is mounted on a vehicle 100 and performs driving assistance for the vehicle 100 at a plurality of assistance levels with different degrees of contribution to the driver's driving. Figure 1 As shown, in this embodiment, the driving assistance system 1 includes an exterior camera 11, a distance measuring sensor 12, a driver monitoring camera 13, a vehicle sensor 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 measuring sensor 12, the driver monitoring camera 13, the vehicle sensor 14, the HMI 15, and the ECU 30 are communicatively connected via, for example, an in-vehicle network 25. The in-vehicle network 25 is, for example, a network based on a standard such as CAN (Controller Area Network). Furthermore, the ECU 30 is connected to the vehicle actuator 21 via a signal line.

[0054] The exterior camera 11 is a device that captures the surroundings of the vehicle. In the present embodiment, the exterior camera 11 captures the front 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 the present embodiment, the exterior camera 11 is installed, for example, inside the vehicle 100, facing the front of the vehicle 100. The exterior camera 11 captures the area in front of the vehicle 100 at every predetermined capturing cycle and generates an image reflecting the area in front. Whenever the exterior camera 11 generates an image, it outputs the generated image to the ECU 30 via the in-vehicle network 25.

[0055] The ranging sensor 12 is a sensor that measures the distance to objects around the vehicle 100. In this embodiment, the ranging sensor 12 measures the distance to objects in front of the vehicle 100. In particular, in this embodiment, the ranging sensor 12 can measure the distance to the vehicle preceding the vehicle 100. The ranging sensor 12 is, for example, a radar such as a millimeter-wave radar or a laser radar (LIDAR). The ranging sensor 12 outputs the measurement results of the distance to surrounding objects to the ECU 30 via the in-vehicle network 25 at predetermined intervals.

[0056] The driver monitoring camera 13 is a device that takes a picture of the driver's face. In the present embodiment, the driver monitoring camera 13 is provided on the upper part of the steering column and is configured toward the driver in such a manner as to be able to take a picture of the driver, specifically, the driver's face and a part of the upper body. The driver monitoring camera 13 includes a camera and a projector. For example, the camera is a CMOS camera or a CCD camera, and the projector is an LED (light emitting diode). In addition, the projector is preferably a near-infrared LED, and the camera is also preferably capable of detecting near-infrared rays, so that the driver's face can be taken without causing discomfort to the driver even in low illumination such as at night. The driver monitoring camera 13 outputs the captured image to the ECU 30 via the in-vehicle network 25 at every predetermined period.

[0057] The vehicle sensor 14 is a sensor that detects the state of the vehicle 100. The vehicle sensor 14 detects the driving state and operating state of the vehicle 100. As a sensor for detecting the driving state of the vehicle 100, the vehicle sensor 14 includes, for example, a speed sensor that detects the speed of the vehicle 100, an acceleration sensor that detects the acceleration of the vehicle 100, and the like. In addition, as a sensor for detecting the driving state of the vehicle 100, the vehicle sensor 14 includes, for example, a self-position sensor that detects the self-position of the vehicle 100 (for example, a GPS sensor). In addition, for example, as a sensor for detecting the operating state of the vehicle 100, the vehicle sensor 14 includes a steering wheel grip sensor that detects whether the driver is holding the steering wheel (or whether he is touching the steering wheel). The vehicle sensor 14 outputs the detection results to the ECU 30 via the in-vehicle network 25 at every predetermined period.

[0058] The HMI 15 is an interface for inputting and outputting information between the driver or passenger and the driving support 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.

[0059] Specifically, as an information providing device, the HMI 15 includes a display 16 for displaying text information or image information. The display 16 is an example of a display device that displays 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 configured so that at least the driver can confirm its screen. Therefore, the display 16 is configured, for example, on the instrument panel or meter panel 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 according to the image signal. In addition, as an information providing device, the vehicle 100 may also include a display device of other types, such as a head-up display.

[0060] The HMI 15 also includes a speaker 17 as an information providing device. The speaker 17 is an example of a device that outputs sound. The speaker 17 receives sound signals from the ECU 30 via the in-vehicle network 25 and outputs sound in accordance with the sound signals. Furthermore, the HMI 15 may also include devices other than the display 16 and speaker 17 (e.g., a vibration device) to provide various information to the driver or passengers.

[0061] In addition, the HMI 15 includes a touch panel 18 as an input device. The touch panel 18 is an example of a device that performs input by touch by the driver or passenger. When the touch panel 18 is operated by the driver or passenger, the operation signal is output to the ECU 30 via the in-vehicle network 25. Furthermore, the HMI 15 may also include devices other than the touch panel 18 (e.g., buttons, switches, etc.) for input operations by the driver or passenger as input devices.

[0062] The vehicle actuator 21 is an actuator for controlling the driving of the vehicle 100. Specifically, the vehicle actuator 21 includes, for example, a drive actuator that controls the internal combustion engine or electric motor that drives the vehicle 100, a brake actuator that controls the brakes that brake the vehicle 100, and a steering actuator that controls the steering of the vehicle 100. The vehicle actuator 21 controls the acceleration, braking, and steering of the vehicle 100 in accordance with control signals transmitted from the ECU 30 via a signal line.

[0063] <Configuration of Driving Assistance Device>

[0064] 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 the present embodiment, driving assistance is performed at three assistance levels: a first assistance level, a second assistance level, and a third assistance level.

[0065] The first assistance level is an assistance level in which acceleration and deceleration of the vehicle 100 are automatically performed and steering of the vehicle 100 is not automatically performed, and is equivalent to, for example, level 1 automatic driving specified by the SAE (Society of Automotive Engineers). Therefore, at the first assistance level, the internal combustion engine or electric motor and the brake are controlled by the drive actuator and the brake actuator in the vehicle actuator 21. However, at the first assistance level, the steering actuator in the vehicle actuator 21 is not controlled. The drive actuator and the brake actuator are controlled in such a manner that the vehicle 100 travels at a preset set speed when there is no preceding vehicle, and are controlled in such a manner that the inter-vehicle distance to the preceding vehicle becomes a predetermined first reference distance when there is a preceding vehicle.

[0066] The second assistance level is an assistance level in which acceleration, deceleration, and steering of the vehicle 100 are all performed automatically, and requires the driver to keep their eyes on the road. This corresponds to, for example, Level 2 automated driving as defined by the SAE. Therefore, in the second assistance level, the internal combustion engine or electric motor and brakes are controlled by the vehicle actuators and brake actuators, while steering is controlled by the steering actuator. The drive actuators and brake actuators are controlled in the second assistance level in the same manner as in the first assistance level. However, in the second assistance level, when a leading vehicle is present, control is performed to ensure that the inter-vehicle distance to the leading vehicle is a predetermined second reference distance that is longer than the first reference distance. Furthermore, the steering actuator is controlled to keep the vehicle 100 within its lane. Furthermore, in both the first and second assistance levels, a warning urging the driver to look ahead is issued if the driver is not looking ahead. If the driver continues to look ahead, driving assistance in the second assistance level is discontinued.

[0067] The third assistance level automatically accelerates, decelerates, and steers the vehicle 100, eliminating the need for the driver to look ahead. This level corresponds to, for example, automated driving levels 3 and above as defined by the SAE. Therefore, at this level, the internal combustion engine or electric motor and brakes are controlled by the vehicle actuators and brake actuators, while steering is controlled by the steering actuator. Otherwise, the drive actuators and brake actuators are controlled in the same manner as at the first assistance level. However, at this level, when a leading vehicle is present, control is performed to maintain the inter-vehicle distance to the leading vehicle at a predetermined third reference distance, which is longer than the second reference distance. Furthermore, the steering actuator is controlled to keep the vehicle 100 within its lane. Furthermore, at this level, the driver's eyesight is not required to be at this level. Therefore, even if the driver is not looking ahead, no warnings or suspension of driving assistance are issued.

[0068] The ECU 30 controls the operation of the vehicle actuator 21 when performing driving assistance. In addition, the ECU 30 controls the information to be provided from the information providing device of the HMI 15. Therefore, the ECU 30 controls the image displayed on the display 16 and the sound output from the speaker 17. Figure 1 As shown, the ECU 30 includes a communication interface 31 , a storage unit 32 , and a processor 33 .

[0069] The communication interface 31 is a circuit for connecting the ECU 30 to the in-vehicle network 25 .

[0070] The storage unit 32 stores data. The storage unit 32 includes, for example, at least one of a volatile semiconductor memory, a nonvolatile semiconductor memory, a hard disk drive (HDD), and a solid-state drive (SSD). The storage unit 32 stores computer programs executed by the processor 33 of the ECU 30. Furthermore, the storage unit 32 stores data used by the computer programs executed by the processor 33, such as data transmitted from the exterior camera 11. Furthermore, the storage unit 32 stores high-precision maps, including road information for each lane and information on surrounding structures.

[0071] The processor 33 includes one or more CPUs (Central Processing Units) and their peripheral circuits. The processor 33 may also include other arithmetic circuits such as a logic operation unit or a mathematical operation unit. The processor 33 executes computer programs stored in the storage unit 32.

[0072] Figure 2 33 is a functional block diagram of the processor 33 of the ECU 30. Figure 2 As shown, 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 .

[0073] 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 . Figure 3 FIG is a diagram showing a vehicle traveling in one lane. Figure 3 In the example shown, a preceding vehicle P is traveling immediately ahead of the vehicle 100 in the same lane as the vehicle 100 . The inter-vehicle distance detection unit 331 detects an inter-vehicle distance Δd between the preceding vehicle P and the vehicle 100 .

[0074] The inter-vehicle distance detection unit 331 receives inputs of an image captured by the exterior camera 11 and distance information measured by the ranging sensor 12. Based on the input image and distance information, the inter-vehicle distance detection unit 331 calculates the inter-vehicle distance between the vehicle 100 and the preceding vehicle P. Specifically, for example, the inter-vehicle distance detection unit 331 identifies the preceding vehicle P based on the image captured by the exterior camera 11. Furthermore, the inter-vehicle distance detection unit 331 calculates the inter-vehicle distance Δd between the vehicle 100 and the preceding vehicle P based on the distance information measured by the ranging sensor 12 with respect to the position (direction) of the identified preceding vehicle. The inter-vehicle distance detection unit 331 outputs the inter-vehicle distance Δd between the vehicle 100 and the preceding vehicle P thus calculated to the assist level switching unit 332.

[0075] When a switching condition to any assistance level is satisfied, the assistance level switching unit 332 switches the assistance level of the driving assistance device to the assistance level that satisfies the switching condition. The assistance level switching unit 332 receives inputs such as the inter-vehicle distance Δd to the preceding vehicle P output from the inter-vehicle distance detection unit 331, the output of the driver monitoring camera 13 (the image captured by the driver monitoring camera 13), and the output of the vehicle sensor 14. Furthermore, the assistance level switching unit 332 sets the assistance level for driving assistance and outputs the set assistance level to the driving control unit 333 and the notification unit 334.

[0076] In this embodiment, the condition for switching to the first assistance level includes the condition that the inter-vehicle distance Δd from the preceding vehicle P is greater than or equal to a first reference distance. Therefore, when a request is made to switch the assistance level to the first assistance level, if the inter-vehicle distance Δd from the preceding vehicle P is less than the first reference distance, switching to the first assistance level is not performed.

[0077] In addition, the conditions for switching to the first assistance level include the driver's grip on 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 a request to switch the assistance level to the first assistance level is received and it is determined that the driver is not gripping the steering wheel, the driver is not switched to the first assistance level.

[0078] Furthermore, the conditions for switching to the first assistance level include the condition that the driver is looking forward. The assistance level switching unit 332 determines whether the driver is looking forward based on the output of the driver monitoring camera 13. For example, the assistance level switching unit 332 inputs the image acquired from the driver monitoring camera 13 into a recognizer that recognizes the upper and lower eyelids and detects the distance between the recognized upper and lower eyelids as the degree of eye opening. Alternatively, the assistance level switching unit 332 inputs the image acquired from the driver monitoring camera 13 into a recognizer that has been pre-trained to determine the positions of the pupil and the corneal reflection of a light source. Furthermore, the assistance level switching unit 332 detects the direction of gaze based on the determined positional relationship between the pupil and the corneal reflection. If the detected degree of eye opening is less than a predetermined value and the driver's eyes are closed, or if the detected direction of gaze is not forward, the assistance level switching unit 332 determines that the driver is not looking forward. On the other hand, if the degree of eye opening is greater than a predetermined value and the direction of gaze is forward, the assistance level switching unit 332 determines that the driver is looking forward. When a request is made to switch the assistance level to the first assistance level, if it is determined that the driver is not looking forward, switching to the first assistance level is not performed.

[0079] Furthermore, in this embodiment, the condition for switching to the second assistance level includes the condition that the inter-vehicle distance Δd from the preceding vehicle P is greater than or equal to a second reference distance. The second reference distance is longer than the first reference distance. Therefore, when a request is made to switch the assistance level to the second assistance level, if the inter-vehicle distance Δd from the preceding vehicle P is less than the second reference distance, switching to the second assistance level is not performed.

[0080] In addition, the conditions for switching to the second assistance level include the driver's eyesight. "Whether the driver is looking forward" is determined based on the output of the driver monitoring camera 13, as described above. When a request is made to switch the assistance level to the second assistance level, if it is determined that the driver is not looking forward, the switch to the second assistance level is not made. Furthermore, the conditions for switching to the second assistance level do not include the driver's grip on the steering wheel.

[0081] Furthermore, in this embodiment, the condition for switching to the third assistance level includes the condition that the inter-vehicle distance Δd from the preceding vehicle P is greater than or equal to a third reference distance. The third reference distance is longer than the second reference distance. Therefore, when a request is made to switch the assistance level to the third assistance level, if the inter-vehicle distance Δd from the preceding vehicle P is less than the third reference distance, the switch to the third assistance level is not performed.

[0082] In addition, the switching condition to the third assistance level includes the condition that the position where the vehicle 100 is traveling is included in the high-precision map stored in the storage unit 32. Here, the high-precision map does not necessarily cover all roads, so there is a case where the road where the vehicle 100 is currently traveling is not included in the high-precision map. The assistance level switching unit 332 determines the vehicle 100's own position based on the output of the vehicle sensor 14, in particular the output of the own position sensor, and determines whether the determined own position is included in the high-precision map. When a request is made to switch the assistance level to the third assistance level, if it is determined that the vehicle 100's own position is not included in the high-precision map, the switch to the third assistance level is not performed.

[0083] Furthermore, the condition for switching to the third assistance level may also include the condition that the speed of the vehicle 100 is below a reference speed. The assistance level switching unit 332 determines whether the speed of the vehicle 100 is below the reference speed based on the output of the vehicle sensor 14, particularly the output of the speed sensor. When a request is made to switch the assistance level to the third assistance level, if it is determined that the speed of the vehicle 100 is not below the reference speed, switching to the third assistance level is not performed.

[0084] The above-described switching conditions for each assistance level are merely examples. Therefore, the switching conditions for each assistance level may include one or more other conditions in addition to or in place of the above-described conditions. However, even in this case, the switching conditions for each assistance level must include a condition related to the inter-vehicle distance Δd between the preceding vehicle P. Furthermore, the first reference distance in the switching condition for the first assistance level, the second reference distance in the switching condition for the second assistance level, and the third reference distance in the switching condition for the third assistance level must be increased in that order.

[0085] The driving control unit 333 controls the driving of the vehicle 100. Specifically, 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. Furthermore, the driving control unit 333 receives input of information necessary for driving the vehicle 100, such as images captured by the exterior camera 11 and distance information measured by the distance measuring sensor 12.

[0086] For example, when the assistance level is set to the first assistance level, the driving control unit 333 controls the driving actuator and the braking actuator. Specifically, when a preceding vehicle P is present, the driving control unit 333 controls the driving actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P is equal to the first reference distance. Furthermore, when the assistance level is set to the second assistance level, the driving control unit 333 controls the driving actuator, the braking actuator, and the steering actuator. Specifically, when a preceding vehicle P is present, the driving control unit 333 controls the driving actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P is equal to the second reference distance. Furthermore, when the assistance level is set to the third assistance level, the driving control unit 333 controls the driving actuator, the braking actuator, and the steering actuator. In particular, at this time, when there is a preceding vehicle P, the driving control unit 333 controls the driving actuator and the braking actuator so that the inter-vehicle distance Δd to the preceding vehicle P becomes the third reference distance.

[0087] 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 driving actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P becomes the 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 driving actuator and the braking actuator so that the inter-vehicle distance Δd from the preceding vehicle P increases to the second reference distance. Consequently, 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 for the requested assistance level (relating to the inter-vehicle distance) has been satisfied, and switches the set assistance level.

[0088] As described above, the first reference distance, the second reference distance, and the third reference distance increase in this order. Therefore, when a request is made to increase the assistance level while the vehicle 100 is being driven at the first or 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 before changing the assistance level.

[0089] When the assistance level of vehicle 100 is switched, notification unit 334 notifies the driver of the switch. Notification unit 334 notifies the driver of the switch via the information providing device of HMI 15. Notification unit 334, for example, causes display 16 to display the switch in assistance level and the switched assistance level. Alternatively, notification unit 334 causes speaker 17 to output a sound indicating the switch in assistance level and the switched assistance level.

[0090] In this embodiment, the conditions for switching to each assistance level include a condition that the inter-vehicle distance is greater than a reference distance. The second reference distance in the condition for switching to the second assistance level is longer than the first reference distance in the condition for switching to the first assistance level. In this case, the second assistance level contributes less to the driver's driving than the first assistance level, and therefore, the driver's response in an emergency is likely to be delayed. According to this embodiment, by making the second reference distance longer than the first reference distance, the driver's response in an emergency is prevented from being delayed when switching to the second assistance level.

[0091] Furthermore, in this embodiment, the third reference distance used in the conditions for switching to the third assistance level is longer than the second reference distance used in the conditions for switching to the second assistance level. In this case, the third assistance level contributes less to the driver's driving than the second assistance level, and therefore the driver's response in an emergency is likely to be delayed. According to this embodiment, by making the third reference distance longer than the second reference distance, the driver's response in an emergency is prevented from being delayed when switching to the third assistance level.

[0092] <Specific Control>

[0093] Next, refer to Figure 4 and Figure 5 , explain the specific control process. Figure 4 1 is a flowchart showing the flow of an assist level setting process for setting the assist level. The illustrated assist level setting process is executed by the processor 33 .

[0094] like Figure 4 As shown, in the assistance level setting process, first, the assistance level switching unit 332 determines whether there is a difference between the current set assistance level and the required assistance level (step S11). The required assistance level is input by the driver, for example, via the input device of the HMI 15, in particular, the touch panel 18. For example, when driving assistance is not being performed, when the driver inputs any one of the first to third assistance levels as the required assistance level, it is determined that there is a difference between the set assistance level and the required assistance level. Alternatively, for example, when the third assistance level is input as the required assistance level, the switching condition to the third assistance level has not been met so far, and the assistance level is set to the first assistance level or the second assistance level, it is also determined that there is a difference between the set assistance level and the required assistance level. When it is determined in step S11 that there is no difference between the set assistance level and the required assistance level, the assistance level switching unit 332 maintains the current set assistance level (step S12).

[0095] On the other hand, if it is determined in step S11 that the set assistance level differs from the requested assistance level, 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 assistance level switching unit 332 determines whether the inter-vehicle distance Δd detected by the inter-vehicle distance detection unit 331 is greater than or equal to the reference distance corresponding to the requested assistance level (step S14). For example, if the requested assistance level is the second assistance level, the assistance level switching unit 332 determines whether the inter-vehicle distance Δd is greater than or equal to the second reference distance.

[0096] If it is determined in step S14 that the inter-vehicle distance Δd is greater than the reference distance corresponding to the requested assistance level, the assistance level switching unit 332 determines whether other switching conditions corresponding to the requested assistance level are met (step S15). For example, if the requested assistance level is the second assistance level, the assistance level switching unit 332 determines whether the driver is looking straight ahead. If it is determined in step S15 that other switching conditions corresponding to the requested assistance level are met, the assistance level switching unit 332 sets the requested assistance level to the new assistance level (step S16). On the other hand, if it is determined in step S15 that other switching conditions corresponding to the requested assistance level are not met, the assistance level switching unit 332 does not change the assistance level and maintains the currently set assistance level (step S17).

[0097] If it is determined in step S14 that the inter-vehicle distance Δd is less than the reference distance corresponding to the requested assistance level, the assistance level switching unit 332 determines whether the inter-vehicle distance Δd is greater than or equal to the reference distance corresponding to an assistance level lower than the requested assistance level (step S18). Therefore, for example, if the requested assistance level is the second assistance level, the assistance level switching unit 332 determines whether the inter-vehicle distance Δd is greater than or equal to the first reference distance. Alternatively, for example, if the requested assistance level is the third assistance level, the assistance level switching unit 332 determines whether the inter-vehicle distance Δd is greater than or equal to 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 an assistance level lower than the requested assistance level, the assistance level switching unit 332 does not change the assistance level and maintains the currently set assistance level (step S12).

[0098] If it is determined in step S14 that the inter-vehicle distance Δd is greater than the reference distance corresponding to an assistance level lower than the requested assistance level, the assistance level switching unit 332 determines whether other switching conditions corresponding to the lower assistance level for which the inter-vehicle distance Δd is greater than the reference distance are satisfied (step S19). For example, if the lower assistance level for which the inter-vehicle distance Δd is greater than the reference distance is the first assistance level, the assistance level switching unit 332 determines whether the driver is holding the steering wheel and whether the driver is looking forward. If it is determined in step S19 that other switching conditions corresponding to the lower assistance level are satisfied, the assistance level switching unit 332 sets the lower assistance level as the new assistance level (step S20). On the other hand, if it is determined in step S19 that other switching conditions corresponding to the lower assistance level are not satisfied, the assistance level switching unit 332 does not change the assistance level and maintains the currently set assistance level (step S12).

[0099] Through this control, in this embodiment, if driving assistance is requested at the third assistance level, the highest level, while driving assistance is not being performed, the assistance level switching unit 332 switches the assistance level to the third assistance level when the inter-vehicle distance Δd is greater than the third reference distance. However, in this case, the assistance level switching unit 332 also switches the assistance level to the second assistance level when the inter-vehicle distance Δd is less than the third reference distance and greater than the second reference distance. Furthermore, in this case, the assistance level switching unit 332 switches the assistance level to the first assistance level when the inter-vehicle distance Δd is less than the second reference distance and greater than the first reference distance. Therefore, when driving assistance is requested at the highest assistance level while driving assistance is not being performed, the assistance level switching unit 332 switches the assistance level to the assistance level that can be initiated based on the inter-vehicle distance. This allows driving assistance to be provided at the highest possible assistance level.

[0100] Figure 5 3 is a flowchart showing the flow of a driving assistance process for performing driving assistance based on a set assistance level. The driving assistance process shown in the figure is executed by the processor 33.

[0101] like Figure 5As shown, in the driving assistance process, first, the driving control unit 333 determines whether there is a difference between the current set assistance level and the required assistance level in the same manner as step S11 (step S31). If it is determined in step S31 that there is no difference between the set assistance level and the required assistance level, the driving control unit 333 performs driving assistance at the current set assistance level in such a manner that the inter-vehicle distance becomes the same as the current set assistance level (step S32). On the other hand, if it is determined in step S31 that there is a difference between the set assistance level and the required assistance level, the driving control unit 333 performs driving assistance at the current set assistance level in such a manner that the inter-vehicle distance becomes the same as the required assistance level (step S33). Therefore, for example, when the required assistance level is the second assistance level and the current set assistance level is the first assistance level, the driving control unit 333 controls the drive actuator and the brake actuator in such a manner that the inter-vehicle distance Δd becomes the first reference distance, and does not control the steering actuator.

[0102] Furthermore, in the above embodiment, the driving assistance device is capable of performing driving assistance at three assistance levels: the first assistance level, the second assistance level, and the third assistance level. However, the driving assistance device only needs to be capable of performing driving assistance at the first assistance level and the second assistance level, and may not be capable of performing driving assistance at the third assistance level.

[0103] As mentioned above, although the preferred embodiment related to this disclosure was described, this disclosure is not limited to these embodiments, and various corrections and changes can be made within the scope of the description of the claims.

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, wherein: The driving assistance device comprises: an inter-vehicle distance detecting unit for detecting an inter-vehicle distance between the vehicle and a preceding vehicle of the vehicle; and an assistance level switching unit that switches the assistance level of the driving assistance to the assistance level that satisfies the switching condition when a switching condition to an arbitrary assistance level is satisfied; The first assistance level is an assistance level in which acceleration and deceleration of the vehicle are automatically performed and steering of the vehicle is not automatically performed. The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically. The conditions for switching to each assistance level include the vehicle distance being greater than the reference distance, The reference distance in the switching condition to the second assistance level is longer than the reference distance in the switching condition to the first assistance level.

2. The driving assistance device according to claim 1, In addition to the first assistance level and the second assistance level, the vehicle can also perform driving assistance for the vehicle at a third assistance level. The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically and requires the driver of the vehicle to keep his eyes on the road ahead. The third assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically and the driver of the vehicle does not need to look ahead. The reference distance in the switching condition to the third assistance level is longer than the reference distance in the switching condition to the second assistance level.

3. The driving assistance device according to claim 1 or 2, further comprising a driving control unit for controlling the driving of the vehicle, The driving control unit controls driving of the vehicle so as to increase the inter-vehicle distance 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.

4. The driving assistance device according to any one of claims 1 to 3, The assistance level switching unit switches the assistance level to an assistance level that can be started based on the inter-vehicle distance when the driving assistance at the highest assistance level is requested without the driving assistance being executed.

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 a driver's driving, wherein: The driving assistance method comprises: detecting a distance between the vehicle and a preceding vehicle of the vehicle; and When a switching condition to an arbitrary assistance level is satisfied, the assistance level of the driving assistance is switched 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 automatically performed and steering of the vehicle is not automatically performed. The second assistance level is an assistance level in which acceleration, deceleration and steering of the vehicle are all performed automatically. The conditions for switching to each assistance level include the vehicle distance being greater than the reference distance, The reference distance in the switching condition to the second assistance level is longer than the reference distance in the switching condition to the first assistance level.

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