Driving Support Devices

Abstract

To provide a driving assist system characterized in that when there is a risk that a vehicle may deviate from a lane, the risk can be reduced, and that a possibility that a driver may feel annoying when intentionally coming off a lane is reduced.SOLUTION: When it is determined that another vehicle posing as an obstacle when a vehicle passes through a specific area devoid of a lane marker does not exist (S40), a standard virtual lane marker is delineated (S50). When it is determined that another vehicle posing as an obstacle when the vehicle passes through the specific area exists (S40), a corrective virtual lane marker is delineated so that the vehicle passes through a position away from the other vehicle with respect to the standard virtual lane marker (S60). When it is determined that a driver's arousal level has degraded (S20), if there is a risk that the vehicle may go across the delineated virtual lane marker and deviate from a lane (S70), lane deviation prevention control that is at least one of automated turning and alarm radiation is executed (S80).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a driving assistance device for a vehicle such as an automobile. [Background technology]

[0002] In lane departure prevention control performed by a vehicle driving assistance device, the position of the vehicle relative to the lane is detected, and when it is determined based on the detected vehicle position that there is a risk that the vehicle will deviate from the lane, at least one of automatic steering of the steered wheels and issuance of an alarm is performed.

[0003] One known lane departure prevention device is one that sets a virtual dividing line when a vehicle passes through a specific area such as an intersection where there are no lane dividing lines, and issues an alarm when it is determined that the vehicle is likely to cross the virtual dividing line and deviate from the lane. For example, this type of lane departure prevention device is described in Patent Document 1 below, and this type of lane departure prevention device can reduce the risk of the vehicle deviating from the lane when passing through a specific area. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2011-064825 Summary of the Invention

[0005] [Problem to be solved by the invention] However, in certain areas, such as intersections, other vehicles may be stopped and waiting to turn right or left, and drivers may intentionally cross the imaginary lane markings to avoid a collision with the other vehicles.

[0006] Conventional lane departure prevention devices, such as the lane departure prevention device described in Patent Document 1, automatically steer the steered wheels and issue an alarm even in the above-mentioned situations, which inevitably annoys the driver.

[0007] Conversely, in a situation where the driver's level of alertness is low, for example when the driver is fatigued from driving for a long period of time, it is preferable to automatically steer the steered wheels or issue an alarm when there is a risk that the vehicle will cross a virtual dividing line and deviate from the lane even when passing through a specific area.

[0008] A primary objective of the present invention is to provide a driving assistance device that can reduce the risk of a vehicle unintentionally deviating from its lane when passing through a specific area, and that reduces the risk of the driver feeling annoyed when the vehicle intentionally deviates from its lane.

[0009] [Means for solving the problems and effects of the invention] According to the present invention, there is provided a driving assistance device (100) including a control unit (driving assistance ECU 10) that executes lane departure prevention control of at least one of automatic steering of steered wheels (24) and issuance of an alarm when it is determined that there is a risk that a vehicle (50) will deviate from the lane by crossing a dividing line of a lane (54).

[0010] The control unit is configured to set standard virtual dividing lines (76L, 76R) (S50) when it determines that there are no other vehicles (84, 86) that would be an obstacle when the vehicle passes through a specific area (intersection 70) without lane markings (S40), and to set modified virtual dividing lines (78L, 78R) (S60) so as to pass through a position away from the other vehicles with respect to the standard virtual dividing lines when it determines that the driver's alertness has decreased (S20) and when it determines that there is a risk that the vehicle will deviate from the lane by crossing the set virtual dividing line (S70), to execute at least one lane departure prevention control (S80).

[0011] According to the above configuration, when it is determined that there is no other vehicle that would be an obstacle when the vehicle passes through a specific area without lane markings, a standard virtual marking is set. In contrast, when it is determined that there is another vehicle that would be an obstacle when the vehicle passes through the specific area, a modified virtual marking is set so as to pass through a position away from the other vehicle with respect to the standard virtual marking. Furthermore, when it is determined that the driver's wakefulness level is low, at least one of the lane departure prevention controls is executed when it is determined that there is a risk that the vehicle will deviate from the lane by crossing the set virtual marking.

[0012] Therefore, in a situation where there is another vehicle that may be an obstacle in a specific area, even if the driver intentionally drives the vehicle along a route away from the other vehicle so as not to collide with the other vehicle, the risk of the vehicle being determined to cross the modified virtual dividing line is reduced. Therefore, the risk of unnecessary lane departure prevention control being executed is reduced, and the risk of the driver feeling annoyed due to the lane departure prevention control can be reduced compared to a case where the modified virtual dividing line is not set.

[0013] In addition, according to the above configuration, when it is determined that the driver's level of alertness is low and it is determined that there is a risk that the vehicle will cross a set virtual dividing line and deviate from the lane, at least one of lane departure prevention controls is executed. Therefore, when there is a risk that the vehicle will cross a virtual dividing line and deviate from the lane when passing through a specific area, the risk of the vehicle crossing the virtual dividing line and deviating from the lane can be reduced by at least one of automatic steering of the steered wheels and issuance of an alarm.

[0014] In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are added in parentheses to the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols added in parentheses. Other objects, other features, and associated advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the drawings. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram showing a driving assistance device according to an embodiment of the present invention; [Diagram 2] A diagram showing a situation in which a vehicle is traveling at an angle relative to the longitudinal direction of the lane. [Diagram 3] 5 is a flowchart showing a lane departure prevention control routine at an intersection according to the embodiment. [Figure 4] FIG. 13 is a diagram showing a case where a vehicle passes through an intersection going straight through and where there are no waiting vehicles to turn right or left. [Diagram 5] FIG. 1 is a diagram showing a case where a vehicle passes through an intersection in which a vehicle is waiting to turn right while going straight. [Figure 6] FIG. 1 is a diagram showing a case where a vehicle passes straight through an intersection where a vehicle is waiting to turn left. [Figure 7] 1 is a diagram showing a case where a vehicle passes through an intersection by turning right at an intersection where there are no waiting vehicles to turn right or left; [Figure 8] 1 is a diagram showing a case where a vehicle is turning right and passing through an intersection where a vehicle is waiting to turn left. FIG. [Figure 9] 1 is a diagram showing a case where a vehicle is turning left when passing through an intersection where there are no waiting vehicles to turn right or left; [Figure 10] 1 is a diagram showing a case where a vehicle is turning left and passing through an intersection where a vehicle waiting to turn right is present; [Figure 11] 13 is a flowchart showing a modified example of a lane departure prevention control routine at an intersection. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A driving assistance device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] <Configuration> 1, a driving assistance device 100 according to an embodiment is applied to a vehicle 50 equipped with an electric power steering ECU 20, and includes a driving assistance ECU 10. In this specification, the electric power steering is referred to as EPS (short for Electric Power Steering) as necessary.

[0018] The driving assistance ECU 10 and the EPS ECU 20 are electronic control units each having a microcomputer as a main component, and are connected to each other via a controller area network (CAN) 52 so that they can transmit and receive information to each other. Each microcomputer includes a CPU, a ROM, a RAM, a non-volatile memory, an interface, and the like. The CPU is adapted to realize various functions by executing instructions (programs, routines) stored in the ROM. Some or all of these ECUs may be integrated into a single ECU.

[0019] As will be described in detail later, the ROM of the driving assistance ECU 10 stores a program for lane departure prevention control, and the CPU executes lane departure prevention control in accordance with the program. The driving assistance ECU 10 is connected to a front photographing camera sensor 12, a radar sensor 14, an interior photographing camera sensor 16, and an alarm device 18.

[0020] The forward photographing camera sensor 12 includes a camera unit and a recognition unit that recognizes targets such as white lines on a road by analyzing image data photographed by the camera unit. The camera unit photographs the scenery ahead of the vehicle 50. The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals.

[0021] 2, the camera sensor 12 recognizes white lines 56L and 56R that are dividing lines of a lane 54, and is also capable of detecting the relative positional relationship of the vehicle with respect to the lane 54 based on the relationship between the white lines and the position of the vehicle 50. Here, the position of the vehicle 50 refers to the position of the center of gravity 50A of the vehicle, but may also be the center position of the vehicle in a plan view. The lateral position of the vehicle, which will be described later, refers to the position of the center of gravity in the lane width direction, and the lateral speed of the vehicle refers to the speed of the center of gravity in the lane width direction. These are found based on the relative positional relationship between the white lines detected by the camera sensor 12 and the vehicle.

[0022] The radar sensor 14 includes a radar transmitting / receiving unit and a signal processing unit (not shown), and the radar transmitting / receiving unit emits millimeter wave band radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves (i.e., reflected waves) reflected by a three-dimensional object (e.g., another vehicle) present within the emission range. The signal processing unit supplies information (hereinafter referred to as three-dimensional object information) indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, etc. to the driving assistance ECU 10 at predetermined time intervals based on the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, and the time from transmitting the millimeter wave to receiving the reflected wave.

[0023] The driving assistance ECU 10 acquires highly accurate three-dimensional object information by combining the target information supplied from the camera sensor 12 and the three-dimensional object information supplied from the radar sensor 14. Thus, the camera sensor 12 and the radar sensor 14 function as an obstacle detection device that detects an obstacle such as another vehicle stopped in front of the vehicle 12. Note that instead of the camera sensor 12, a LiDAR (Light Detection And Ranging) may be used.

[0024] The driving assistance ECU 10 also determines whether or not there is a risk that the vehicle 50 will deviate from the lane based on the target object information supplied from the camera sensor 12. In this case, the determination of whether or not there is a risk that the vehicle 50 will deviate from the lane by crossing a dividing line may be performed, for example, as follows. First, as shown in FIG. 2, an angle θy between the longitudinal direction 60 of the lane 54 and the traveling direction 62 of the vehicle is estimated based on image information of the front of the vehicle 50. The angle θy is a positive value when the traveling direction 62 of the vehicle 50 is to the left of the longitudinal direction 60 of the lane 54. The moving speed Vy of the vehicle 50 in a direction perpendicular to the longitudinal direction 60 of the lane 54 is estimated as Vsinθy based on the angle θy and the vehicle speed V.

[0025] Also, a distance Dy (not shown) in the lane width direction between the white line (white line 56L in the case of FIG. 2) on the side that the vehicle 50 is approaching and the center of gravity of the vehicle is estimated. Furthermore, when Dy-VyΔt is equal to or less than a preset reference value Dyc (a positive constant), where Δt is a preset time, it may be determined that the vehicle 50 is at risk of deviating from the lane. Note that, when the lane is curved, the above estimation and determination may be performed in the tangential direction of the lane at the center of gravity of the vehicle.

[0026] The in-vehicle camera sensor 16 is provided on the dashboard or steering column and includes a camera unit that captures the face of the driver and an image processing unit that processes image data of the driver's face captured by the camera unit. The image processing unit supplies the image data of the driver's face to the driving assistance ECU 10 at predetermined time intervals. Thus, the in-vehicle camera sensor 16 functions as a driver monitor camera.

[0027] The CPU of the driving assistance ECU 10 determines the degree of wakefulness of the driver based on the information of the image data of the driver's face, such as the driver's eye closing rate per minute, eye opening state, blinking frequency, or eye movement. The degree of wakefulness is a degree indicating that the driver is awake and not in a state of drowsiness due to lack of sleep or the like. The method of determining the degree of wakefulness is not particularly limited, and any method known in the art may be adopted. In addition, at least one of the driver's grip pressure on the steering wheel, pressing force on the armrest, heart rate, electromyographic information, and electroencephalogram pattern may be taken into consideration when determining the degree of wakefulness.

[0028] The warning device 18 is activated when the driving assistance ECU 10 determines that there is a risk that the vehicle 50 will deviate from the lane, and issues a warning as one of the lane departure prevention controls, that is, issues a warning that there is a risk of a collision of the vehicle 50. The warning device 18 may be any of a warning device that issues a visual warning such as a warning lamp, a warning device that issues an auditory warning such as a warning buzzer, and a warning that issues a physical warning such as seat vibration, or any combination thereof.

[0029] The EPS·ECU 20 can steer the steered wheels 24 as necessary by controlling the EPS device 22. Thus, the EPS·ECU 20 and the EPS device 22 constitute a steering device 26 that automatically steers the steered wheels 24 as necessary. When the driving assistance ECU 10 determines that it is necessary to correct the driving route of the vehicle 50, the EPS·ECU 20 performs automatic steering of the steered wheels 24 to correct the driving route of the vehicle 50, as another type of lane departure prevention control.

[0030] As shown in Fig. 1, a steering shaft 30 to which a steering wheel 28 operated by a driver is integrally connected is provided with a torque sensor 32 for detecting a steering torque Ts. A signal indicating the steering torque Ts detected by the torque sensor 32 is input to the EPS·ECU 20. The EPS·ECU 22 controls the EPS device 22 in a manner known in the art based on the steering torque Ts and a vehicle speed detected by a vehicle speed sensor not shown in Fig. 1, thereby controlling the steering assist torque and reducing the steering burden on the driver. The signal indicating the steering torque Ts is input from the EPS·ECU 20 to the driving assistance ECU 10 via the CAN 52.

[0031] The ROM of the driving assistance ECU 10 stores a program for lane departure prevention control at an intersection corresponding to the flowchart shown in FIG. 2 as part of the lane departure prevention control, and the CPU executes the lane departure prevention control at the intersection in accordance with the program.

[0032] <Lane Departure Prevention Control Routine at Intersections> Next, a lane departure prevention control routine at an intersection according to the embodiment will be described with reference to the flowchart shown in Fig. 3. The lane departure prevention control according to the flowchart shown in Fig. 3 is repeatedly executed by the CPU of the driving assistance ECU 10 at a predetermined control period when a lane departure prevention control switch, not shown in Fig. 1, is on. In the following description, the lane departure prevention control at an intersection will be simply referred to as "control".

[0033] First, in step S10, the CPU determines whether or not the vehicle 50 is passing through an intersection, that is, whether or not the vehicle 50 is about to pass through the intersection or has already passed through the intersection. If the CPU makes a negative determination, it temporarily ends control, and if the CPU makes a positive determination, it proceeds to step S20.

[0034] In step S20, the CPU determines whether or not the driver's wakefulness determined as described above has fallen below a reference value based on the information of the image data of the driver's face supplied from the in-vehicle camera sensor 16. If the CPU determines that the driver's wakefulness is not a reference value, the CPU temporarily ends the control, whereas if the CPU determines that the driver's wakefulness is not a reference value, the CPU advances the control to step S30.

[0035] In step S30, the CPU determines whether the driver's intended traveling direction of the vehicle at the intersection is to go straight, turn right, or turn left, based on the position of the turn signal lever (not shown in FIG. 1).

[0036] In step S40, the CPU determines whether or not there is another vehicle in the intersection that may be an obstacle to the travel of vehicle 50 in the travel direction of the vehicle identified in step S30. If the CPU makes a positive determination, the control proceeds to step S60, and if the CPU makes a negative determination, the control proceeds to step S50.

[0037] In step S50, the CPU sets standard imaginary lane lines in the intersection area for the vehicle 50 to travel in the travel direction of the vehicle 50 identified in step S30, as will be described later with reference to a specific example. The standard imaginary lane lines may be set so as to smoothly connect the outer and inner lane lines of the lane in which the vehicle 50 is currently traveling, and the outer and inner lane lines of the lane in which the vehicle 50 will travel after passing through the intersection.

[0038] In step S60, the CPU sets a corrected virtual lane marking in the intersection area along which the vehicle 50 travels in the travel direction identified in step S30, as will be described later with reference to a specific example. The corrected virtual lane marking is set to pass through a position farther away from other vehicles than the standard virtual lane marking.

[0039] In step S70, the CPU determines, based on the relative positional relationship of the vehicle 50 with respect to the target detected by the camera sensor 12, whether there is a possibility that the vehicle will deviate from the lane by crossing the virtual demarcation line in a manner known in the art. When the CPU makes a negative determination, the control is temporarily terminated, and when the CPU makes an affirmative determination, the control proceeds to step S80.

[0040] In particular, when in addition to the front camera sensor 12, left and right side camera sensors and a rear camera sensor are provided, an overhead image of the entire circumference of the vehicle may be generated by processing the image data captured by each camera sensor in a manner known in the art. Further, a virtual demarcation line may be superimposed on the overhead image, and based on the position and moving direction of the vehicle with respect to the virtual demarcation line on the overhead image, it may be determined whether there is a possibility that the vehicle will deviate from the lane by crossing the virtual demarcation line.

[0041] In step S80, the CPU executes lane departure prevention control. That is, the CPU activates the warning device 18 to issue a warning indicating that there is a possibility that the vehicle 50 will deviate from the lane by crossing the virtual demarcation line. Further, the CPU outputs a command signal for automatic steering to the EPS·ECU 22, and the EPS device 22 automatically steers the steering wheels 24 so that the vehicle 50 does not deviate from the lane by crossing the virtual demarcation line.

[0042] <Specific Example of Lane Departure Prevention Control at an Intersection> Next, with reference to FIGS. 4 to 10, specific examples C1 to C9 of lane departure prevention control at an intersection performed in a situation where the driver's wakefulness is reduced will be described. In FIGS. 4 to 10, reference numeral 70 indicates an intersection, reference numeral 72 indicates the outer demarcation line of the road, and reference numeral 74 indicates the median (inner demarcation line). Further, reference numerals 76L and 76R respectively indicate the left and right standard virtual demarcation lines, and reference numerals 78L and 78R respectively indicate the left and right corrected virtual demarcation lines.

[0043] <C1: When the vehicle 50 is going straight and there is no waiting vehicle in the intersection (FIG. 4)> Figure 4 shows a case where the vehicle 50 passes straight through an intersection 70 where there are no waiting vehicles for turning right or left. In this case, based on the outer dividing line 72 and the inner dividing line 74 of the lane 80 on which the vehicle 50 is currently traveling, and the outer dividing line 72 and the inner dividing line 74 of the lane 82 on which the vehicle 50 will travel after passing through the intersection 70, the standard virtual dividing lines 76L and 76R on the left and right are set. As shown in Figure 4, the left virtual dividing line 76L is set as a straight line that smoothly connects the outer dividing lines 72 of the lanes 80 and 82, and the right virtual dividing line 76R is set as a straight line that smoothly connects the inner dividing lines 74 of the lanes 80 and 82.

[0044] <C2: When the vehicle 50 goes straight and there are waiting vehicles for turning right in the intersection (Figure 5)> Figure 5 shows a case where the vehicle 50 passes straight through an intersection 70 where there is a waiting vehicle 84 for turning right. In this case, the modified virtual dividing lines 78L and 78R are set to pass through positions farther from the waiting vehicle 84 than the standard virtual dividing lines 76L and 76R on the left and right, respectively, except at both ends. As shown in Figure 5, the modified virtual dividing lines 78L and 78R draw curves that bulge in the direction away from the waiting vehicle 84 with respect to the standard virtual dividing lines 76L and 76R on the left and right, respectively.

[0045] <C3: When the vehicle 50 goes straight and there are waiting vehicles for turning left in the intersection (Figure 6)> Figure 6 shows a case where the vehicle 50 passes straight through an intersection 70 where there is a waiting vehicle 86 for turning left. In this case, the modified virtual dividing lines 78L and 78R are set to pass through positions farther from the waiting vehicle 86 than the standard virtual dividing lines 76L and 76R on the left and right, respectively, except at both ends. As shown in Figure 6, the modified virtual dividing lines 78L and 78R draw curves that bulge in the direction away from the waiting vehicle 86 with respect to the standard virtual dividing lines 76L and 76R on the left and right, respectively.

[0046] <C4: When the vehicle 50 turns right and there are no waiting vehicles in the intersection (Figure 7)> Figure 7 shows a case where the vehicle 50 passes through an intersection 70 without left or right turning waiting vehicles by making a right turn. In this case, based on the outer dividing line 72 and the inner dividing line 74 of the lane 80 on which the vehicle 50 is currently traveling, and the outer dividing line 72 and the inner dividing line 74 of the lane 88 on which the vehicle 50 travels after passing through the intersection 70 by making a right turn, the left and right standard virtual dividing lines 76L and 76R are set. As shown in Figure 7, the left virtual dividing line 76L is set as an arc line connecting the outer dividing lines 72 of the lanes 80 and 88, and the right virtual dividing line 76R is set as an arc line connecting the inner dividing lines 74 of the lanes 80 and 88.

[0047] <C5: When the vehicle 50 makes a right turn and there are left-turn waiting vehicles inside the intersection (Figure 8)> Figure 8 shows a case where the vehicle 50 passes through an intersection 70 with a left-turn waiting vehicle 86 by making a right turn. In this case, except for both ends, the modified virtual dividing lines 78L and 78R are set at positions farther from the waiting vehicle 86 than the left and right standard virtual dividing lines 76L and 76R, respectively. As shown in Figure 8, the modified virtual dividing lines 78L and 78R draw curves deformed in the direction away from the waiting vehicle 86 with respect to the left and right standard virtual dividing lines 76L and 76R, respectively.

[0048] <C6: When the vehicle 50 makes a left turn and there are no waiting vehicles inside the intersection (Figure 9)> Figure 9 shows a case where the vehicle 50 passes through an intersection 70 without left or right turning waiting vehicles by making a left turn. In this case, based on the outer dividing line 72 and the inner dividing line 74 of the lane 80 on which the vehicle 50 is currently traveling, and the outer dividing line 72 and the inner dividing line 74 of the lane 90 on which the vehicle 50 travels after passing through the intersection 70 by making a left turn, the left and right standard virtual dividing lines 76L and 76R are set. As shown in Figure 9, the left virtual dividing line 76L is set as an arc line connecting the outer dividing lines 72 of the lanes 80 and 90, and the right virtual dividing line 76R is set as an arc line connecting the inner dividing lines 74 of the lanes 80 and 90.

[0049] <C7: When the vehicle 50 makes a left turn and there are waiting vehicles for a right turn inside the intersection (Fig. 10)> Fig. 10 shows the case where the vehicle 50 passes through the intersection 70 with a left turn while there are waiting vehicles 84 for a right turn. In this case, except for both ends, the modified virtual dividing lines 78L and 78R are set at positions farther from the waiting vehicles 84 than the standard virtual dividing lines 76L and 76R on the left and right sides respectively. As shown in Fig. 10, the modified virtual dividing lines 78L and 78R draw curves deformed in the direction away from the waiting vehicles 84 with respect to the standard virtual dividing lines 76L and 76R on the left and right sides respectively.

[0050] In the cases of C1, C4, and C6 above, based on the determination of whether the vehicle 50 may cross the standard virtual dividing lines 76L and 76R, it is determined whether the vehicle deviates from the lane when the vehicle passes through the intersection 70. When it is determined that the vehicle 50 may cross the standard virtual dividing line 76L or 76R, the warning device 18 is activated to issue a warning, and at the same time, the automatic steering of the steering wheel 24 is performed to correct the driving path of the vehicle so that the vehicle 50 does not cross the standard virtual dividing line 76L or 76R.

[0051] On the other hand, in the cases of C2, C3, C5, and C7, based on the determination of whether the vehicle 50 may cross the modified virtual dividing lines 78L and 78R, it is determined whether the vehicle deviates from the lane when the vehicle passes through the intersection 70. When it is determined that the vehicle 50 may cross the modified virtual dividing lines 78L and 78R, the warning device 18 is activated to issue a warning, and at the same time, the automatic steering of the steering wheel 24 is performed to correct the driving path of the vehicle so that the vehicle 50 does not cross the modified virtual dividing lines 78L and 78R.

[0052] As can be seen from the above description, according to the embodiment, when it is determined that there are no other vehicles 84, 86 that would be an obstacle when the vehicle 50 passes through the intersection 70 as a specific area without lane markings (S40), the standard virtual markings 76L or 76R are set (S50). In contrast, when it is determined that there is another vehicle that would be an obstacle when the vehicle passes through the specific area (S40), the corrected virtual markings 78L and 78R are set so as to pass through a position away from the other vehicles with respect to the standard virtual markings (S60). Furthermore, when it is determined that the driver's level of alertness is reduced (S20), and when it is determined that there is a risk that the vehicle will cross the set virtual markings and deviate from the lane (S70), automatic steering of the steered wheels and issuance of an alarm, i.e., lane departure prevention control, is executed (S80).

[0053] Therefore, in a situation where there is another vehicle that is an obstacle at an intersection, even if the driver intentionally drives the vehicle along a route away from the other vehicle so as not to collide with the other vehicle, the risk of the vehicle being determined to cross the modified virtual dividing line is reduced. Therefore, the risk of unnecessary lane departure prevention control being executed is reduced, and the risk of the driver feeling annoyed due to the lane departure prevention control can be reduced compared to a case where the modified virtual dividing line is not set.

[0054] According to the embodiment, when it is determined that the driver's alertness is low (S20) and it is determined that there is a risk that the vehicle will cross a set virtual dividing line and deviate from the lane (S70), lane departure prevention control is executed (S80). Therefore, in a situation in which the driver's alertness is low, when there is a risk that the vehicle will cross the virtual dividing line and deviate from the lane when passing through a specific area, the lane departure prevention control is executed to reduce the risk that the vehicle will cross the virtual dividing line and deviate from the lane.

[0055] In particular, according to the embodiment, the vehicle travel direction at the intersection intended by the driver is identified (S30), and standard virtual lane lines 76L and 76R or modified virtual lane lines 78L and 78R are set for the identified travel direction (S50, S60). Thus, it is possible to avoid the standard virtual lane lines or modified virtual lane lines being set in vain for a vehicle travel direction that is not intended by the driver.

[0056] In the embodiment, the determination as to whether the driver's alertness has fallen below the reference value is performed between steps S10 and S30. However, as shown in Fig. 11 as a modification example, the determination as to whether the driver's alertness has fallen below the reference value (step S65) may be performed between steps S50 and S60 and step S70. However, according to the embodiment, the determination is performed prior to steps S40 to S60, so that it is possible to avoid unnecessary setting of the standard virtual lane line or the modified virtual lane line in a situation where the driver's alertness has not fallen below the reference value.

[0057] Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present invention.

[0058] For example, in the above-described embodiment, lane departure prevention control involves issuance of a warning by activation of the warning device 18 and automatic steering of the steered wheels 24 by the EPS device 22. However, one of the issuance of a warning and the automatic steering of the steered wheels 24 may be omitted.

[0059] Furthermore, in the above-described embodiment, the specific intersection where there are no lane markings is an intersection, but the specific area may be an area other than a crossroads, such as a T-junction or a Y-junction.

[0060] In addition, in the above-described embodiment, virtual dividing lines are set when the vehicle turns right and left at an intersection, but the setting of virtual dividing lines at an intersection may be limited to when the vehicle travels straight.

[0061] In addition, in the above-described embodiment, it is determined in step S20 whether the driver's alertness has decreased, but the determination of whether the driver's alertness has decreased may be omitted.

[0062] Furthermore, in the above embodiment, the driving direction of the vehicle at the intersection intended by the driver is identified in step S30, and the standard imaginary lane lines 76L, 6R and the modified imaginary lane lines 78L, 78R are set for the driving direction identified in steps S50 and S60. However, step S30 may be omitted, and the standard imaginary lane lines and the modified imaginary lane lines may be set for all directions in which the vehicle may travel.

[0063] Furthermore, if the revised virtual dividing line excessively extends beyond the outer or inner dividing line, the lane departure prevention control may be modified so that an alarm is output to temporarily stop the vehicle until the revised virtual dividing line stops excessively extending beyond the outer or inner dividing line. [Explanation of symbols]

[0064] 10...driving assistance ECU, 12...forward-viewing camera sensor, 14...radar sensor, 16...indoor-viewing camera sensor, 18...alarm device, 20...electric power steering ECU, 22...EPS device, 24...steered wheels, 50...vehicle, 54...lane, 56, 58...white line, 70...intersection, 76L, 76R...standard virtual dividing line, 78L, 78R...modified virtual dividing line, 100...lane departure prevention device

Claims

[Claim 1] A driving assistance device including a control unit that performs lane departure prevention control of at least one of automatic steering of steered wheels and issuance of an alarm when it is determined that a vehicle is at risk of crossing a lane marking and departing from the lane, The control unit is configured to set a standard virtual dividing line when it determines that there are no other vehicles that would be an obstacle to the vehicle passing through a specific area without lane markings, and to set a corrected virtual dividing line that passes through a position away from the other vehicles with respect to the standard virtual dividing line when it determines that there are other vehicles that would be an obstacle to the vehicle passing through the specific area, and further to execute at least one of the lane departure prevention controls when it determines that the driver's alertness has decreased and that there is a risk that the vehicle will deviate from the lane by crossing the set virtual dividing line.

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