Lane Departure Prevention Device

Abstract

To provide a track deviation prevention device capable of appropriately executing track deviation prevention steering control in a case where an object is present in front of an own vehicle.SOLUTION: When determining that an own vehicle highly possibly departs from a track between a left side deviation regulation line and a right side deviation regulation line, an ECU executes track deviation prevention steering control of changing a steering angle so as to prevent the own vehicle from deviating from the track. When an object is present in front of the own vehicle, the ECU acquires, as a lateral margin distance, a larger distance out of a distance of a space formed between the object and a left lane marking in a track width direction and a distance of a space formed between the object and a right side lane marking in the track width direction. The ECU determines whether the probability is high that the own vehicle deviates from the track when the own vehicle passes by a side of the object, based on the lateral margin distance, and when determining that the probability is high, moves, by a predetermined offset distance to an outside of the track, a deviation regulation line on a side on which the own vehicle is expected to cross out of the left side deviation regulation line and the right side deviation regulation line.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lane departure prevention device capable of executing lane departure prevention steering control for changing the steering angle of a host vehicle so that the host vehicle does not deviate from a lane (for example, a driving lane) defined by left and right deviation regulation lines.

Background Art

[0002] One of the conventional lane departure prevention devices (hereinafter simply referred to as the "conventional device") obtains, for example, as shown in FIG. 9, the distance (for convenience, referred to as the "margin width") Wo between the side end point within the driving lane Ls of an obstacle OB and the white line LR on the right side when an obstacle OB exists in front of and on the left side of the host vehicle SV. Then, when the margin width Wo is smaller than the vehicle width Wc of the host vehicle SV (Wo < Wc), the conventional device determines that the host vehicle SV deviates from the driving lane Ls and prohibits the execution of lane departure prevention steering control (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] However, since the conventional device uniformly prohibits the execution of lane departure prevention steering control when the margin width Wo is smaller than the vehicle width Wc of the host vehicle SV, there is a problem that the function of lane departure prevention steering control cannot be used even when the host vehicle SV deviates from the driving lane Ls more than necessary when passing by the side of the obstacle OB.

[0005] The present invention has been made to address the above-described problems. That is, one of the objects of the present invention is to provide a lane departure prevention device capable of appropriately executing lane departure prevention steering control when a target exists in front of the host vehicle.

[0006] One aspect of the lane departure prevention device of the present invention (hereinafter also referred to as the "device of the present invention") is as follows: a surroundings sensor (11) for acquiring surrounding information including information on the positions of a left lane marking (LL) and a right lane marking (LR) of a road on which a host vehicle (SV) is traveling and information on the position of a target (OB) located in front of the host vehicle; a steering angle changing actuator (21, 22) capable of changing a steering angle of the host vehicle; When a steering control start condition is satisfied when the host vehicle is traveling on a road between a left departure restriction line (KL (left)) and a right departure restriction line (KL (right)), the control unit (10, 20) executes a road departure prevention steering control for changing the steering angle of the host vehicle by controlling the steering angle changing actuator so that the host vehicle does not deviate from the road (step 670, steps 760 to 780), Equipped with.

[0007] left side deviation rule The control line (KL (left)) is a line that is shifted to the left or right (usually the left) by a "first left distance (any of a1 to a5) that is equal to or greater than zero" from the left lane marking (LL). side deviation rule When the first left distance is "0", the control line coincides with the left dividing line (for example, the left white line) that divides the driving lane. right side deviation rule The control line (KL (right)) is a line that is shifted to the right or left (usually the right) by the "first right distance (any of a1 to a5) that is equal to or greater than zero." side deviation rule When the first right distance is "0", the control line coincides with a right-side dividing line (for example, a right white line) that divides the driving lane.

[0008] Furthermore, the control unit When the vehicle (SV) is traveling on the road and a target (OB) is present in front of the vehicle, the greater of: a distance in the road width direction of a space formed between the target and the left-side dividing line, and a distance in the road width direction of a space formed between the target and the right-side dividing line; Or, When a target is present ahead of the host vehicle while the host vehicle is traveling on the road, the greater of: a distance in the road width direction of a space formed between the target and the left departure restriction line, and a distance in the road width direction of a space formed between the target and the right departure restriction line; is obtained as the lateral margin distance (Wy) based on the peripheral information (step 570), Based on at least the lateral margin distance, when the host vehicle passes beside the target, side deviation rule Control line and right side deviation rule It is determined whether or not a deviation / passage determination condition is satisfied when there is a high possibility that the vehicle will deviate from the road by crossing one of the control lines (step 570); When it is determined that the deviation / passage determination condition is satisfied (step 570: Yes), side deviation rule Control line and right side deviation rule Among the control lines, at least the control line on the side where the host vehicle is expected to cross when passing beside the target is further moved by a predetermined offset distance (any of b1 to b5) toward the outside of the lane (step 630: No, step 680, step 650). It is structured as follows.

[0009] According to this, when the vehicle passes beside a target, the vehicle must “see the left and right lane lines (or the left lane line).” side deviation rule Control line and right side deviation ruleWhen there is a high possibility that the host vehicle will deviate from the lane by crossing one of the restriction lines (restriction line) on the side where the host vehicle is expected to cross, the restriction line on the side where the host vehicle is expected to cross is moved further outward of the lane by the offset distance. Therefore, even if the host vehicle deviates from the lane defined by the "restriction line before being moved by the offset distance" when passing beside the target, the lane departure prevention steering control is executed so that the host vehicle does not deviate from the lane defined by the "restriction line after being moved by the offset distance". Thus, the host vehicle can be driven so as not to deviate significantly outside the restriction line. Furthermore, since the restriction line on the side where the host vehicle is expected to cross is moved further outward of the lane by the offset distance, the deviation between the steering operation by the driver of the host vehicle and the steering by the lane departure prevention steering control is reduced. Thus, the possibility of the host vehicle feeling uncomfortable can be reduced.

[0010] In one aspect of the device of the present invention (step 570, step 580 and modification 1), The control unit a determination unit that determines whether the lateral margin distance (Wy) is equal to or less than a predetermined first distance threshold (WUth), and that determines that the deviation-passing determination condition is satisfied when it is determined that the lateral margin distance is equal to or less than the first distance threshold, and, The first distance threshold is changed based on the type of the target present ahead of the host vehicle.

[0011] The first distance threshold used to determine whether or not the vehicle deviates from the road or driving lane when passing beside a target varies depending on the type of target (e.g., a vehicle, a motorcycle, or a pedestrian). Therefore, according to this aspect, it is possible to accurately determine whether or not the deviation-passing determination condition is satisfied.

[0012] In one embodiment of the device of the present invention, The control unit The system is configured to determine whether the lateral margin distance (Wy) is less than a predetermined first distance threshold (WUth) and greater than or equal to a predetermined second distance threshold (WLth) that is smaller than the first distance threshold (step 570), and to determine that the deviation-passing determination condition is met when it is determined that at least the lateral margin distance is less than the first distance threshold and greater than or equal to the second distance threshold (step 570: Yes, step 580).

[0013] According to this aspect, when the lateral margin distance (Wy) is between the second distance threshold (WLth) and the first distance threshold (WUth), it is determined that the deviation-passing judgment condition is satisfied. In this way, the lateral margin distance (Wy) is compared not only with the first distance threshold (WUth) but also with the second distance threshold (WLth) because, when the lateral margin distance (Wy) is less than the second distance threshold (WLth), it is highly likely that the target is a preceding vehicle traveling ahead of the host vehicle, and therefore, it is unlikely that the host vehicle will pass beside the target. Therefore, according to this aspect, it is possible to more accurately determine whether the deviation-passing judgment condition is satisfied.

[0014] In this case, the control unit may be configured to change the first distance threshold based on the type of target present ahead of the host vehicle. According to this aspect, it is possible to accurately determine whether or not a deviation-passing determination condition is satisfied according to the type of target.

[0015] Furthermore, in this case, the control unit may be configured to change the second distance threshold based on the type of target present ahead of the host vehicle. According to this aspect, it is possible to more accurately determine whether or not the deviation-passing determination condition is satisfied depending on the type of target.

[0016] In one embodiment of the device of the present invention, The control unit When the lane departure prevention steering control is being executed, it is determined whether the magnitude of the steering torque applied to the steering wheel of the vehicle is equal to or greater than the override judgment threshold (step 850), and when it is determined that the magnitude of the steering torque is equal to or greater than the override judgment threshold, the lane departure prevention control is stopped (step 850: Yes, steps 860 to 880).

[0017] Furthermore, the control unit When the lane departure prevention steering control is being executed and / or when the lane departure prevention steering control is in a state where it can be executed, the override judgment threshold is changed to a smaller value compared to when it is determined that the departure passing judgment condition is not satisfied (steps 820 to 840). In other words, the control unit sets the override determination threshold when it is determined that the deviation-passing determination condition is satisfied to a value smaller than the override determination threshold when it is not determined that the deviation-passing determination condition is satisfied.

[0018] According to this aspect, when the vehicle is likely to deviate from the road by crossing one of the "left restriction line and the right restriction line" when passing beside the target, the override determination threshold is changed to a small value. Therefore, in this case, when the driver performs a large steering operation, the steering operation is detected earlier, and the deviation prevention steering control is stopped. Therefore, the frequency with which the driver feels the deviation prevention steering control is bothersome can be reduced.

[0019] 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 enclosed in parentheses with respect to the configuration of the invention corresponding to the embodiments. However, each component of the present invention is not limited to the embodiments defined by the names and / or symbols. [Brief description of the drawings]

[0020] [Figure 1]FIG. 1 is a schematic diagram of a lane departure prevention device (implementation device) according to an embodiment of the present invention. [Diagram 2] Figure 2 includes (A) and (B). Figure 2 (A) is a plan view of a curved driving lane, and Figure 2 (B) is a plan view of a straight driving lane. [Diagram 3] FIG. 3 is a plan view of a driving lane showing various cases in which a target exists ahead of the host vehicle. [Figure 4] FIG. 4 is a plan view of a driving lane showing various cases in which a target exists ahead of the host vehicle. [Diagram 5] FIG. 5 is a flowchart showing a routine executed by the CPU of the driving assistance ECU shown in FIG. [Figure 6] FIG. 6 is a flowchart showing a routine executed by the CPU. [Figure 7] FIG. 7 is a flowchart showing a routine executed by the CPU. [Figure 8] FIG. 8 is a flowchart showing a routine executed by the CPU. [Figure 9] FIG. 9 is a plan view of a travel lane for explaining the operation of a conventional device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] <Configuration> A lane departure prevention device according to an embodiment of the present invention (hereinafter, may be referred to as a "lane departure avoidance device" or an "implementation device") is mounted on a vehicle (not shown). The vehicle on which the implementation device is mounted may be referred to as a "host vehicle" to distinguish it from other vehicles.

[0022] 1, the embodiment includes a driving assistance ECU 10, an electric power steering ECU (hereinafter referred to as "EPS·ECU") 20, and an alarm ECU 30. In the following, the driving assistance ECU 10 will be simply referred to as "DSECU."

[0023] Each of these ECUs is an electric control unit having a microcomputer as a main part. These ECUs are connected to each other via a controller area network (CAN) (not shown) so that they can transmit and receive information to each other. These ECUs may be integrated into one ECU.

[0024] A microcomputer includes a CPU, ROM, RAM, non-volatile memory, and an interface I / F, etc. The CPU is designed to realize various functions by executing instructions (programs, routines) stored in the ROM.

[0025] The implementation device includes an ambient sensor 11, a vehicle state sensor 12, an operation switch 13, a steering angle sensor 14, and a steering torque sensor 15. The DSECU is connected to these sensors and switches and receives their detection signals or output signals. Each of these sensors and switches may be connected to an ECU other than the DSECU. In this case, the DSECU receives the detection signal or output signal of the sensor from the ECU to which the "sensor or switch" is connected via the CAN.

[0026] The surroundings sensor 11 includes a camera sensor 11a, a radar sensor 11b, and a fusion unit (ECU) (not shown).

[0027] The camera sensor 11a includes a stereo camera and an image processing unit (ECU), not shown. The stereo camera captures images of the scenery in the left and right areas in front of the host vehicle SV, and obtains left front image data and right front image data.

[0028] As shown in (A) and (B) of FIG. 2, the image processing unit of the camera sensor 11a recognizes (detects) lane markings (i.e., left marking line LL and right marking line LR) based on the left front image data and right front image data. A typical example of a lane marking line is a white line (or a yellow line) on a road. Therefore, hereinafter, the lane marking line will also be referred to simply as a "white line." The left marking line LL and right marking line LR will be referred to as the left white line LL and the right white line LR, respectively.

[0029] The image processing unit acquires lane information including the following information every time a predetermined time elapses based on the recognized "left white line LL and right white line LR." The lane defined by the left white line LL and the right white line LR is also called the "driving lane."

[0030] Data indicating the shape of the driving lane in which the host vehicle SV is driving, and in this case, data indicating the "curve radius R or curvature Cv" of the lane center line Ld. The lane center line Ld is a line connecting the center points of the left white line LL and the right white line LR in the lane width direction of the driving lane.

[0031] Data indicating the positional relationship between the driving lane and the host vehicle SV, and more specifically, data including, for example, the parameters listed below (see (B) of FIG. 2).

[0032] ··The distance Dc in the lane width direction between the lane center line Ld and the reference point P on the vehicle SV. The reference point P on the host vehicle SV is the center point of the left and right front wheels on the axles of the left and right front wheels of the host vehicle SV.

[0033] Yaw angle θy, which is the angle between the direction of the lane center line Ld and the longitudinal axis direction of the host vehicle SV (i.e., the direction Cd in which the host vehicle SV is facing). The longitudinal axis of the host vehicle SV is an axis that passes through the center of the host vehicle SV in the vehicle width direction and extends in the longitudinal direction of the host vehicle SV. As shown in FIG. 2B, the yaw angle θy is an acute angle ranging from -90° to +90°, and is "0" when the direction Cd coincides with the direction of the lane center line Ld.

[0034] Furthermore, the image processing unit acquires target information including the information listed below every time a predetermined time elapses based on the left front image data and the right front image data. · Longitudinal distance Dfx of the target: The longitudinal distance Dfx of the target is a signed distance in the longitudinal direction of the host vehicle SV between the front end of the host vehicle SV and the target. · Lateral position Dfy of the target: The lateral position Dfy of the target is the signed distance between the center position of the target and the front-rear axis of the host vehicle SV in the vehicle width direction of the host vehicle SV. · Relative speed Vfx of the target: The relative speed Vfx of the target is the difference (=Vb-Vs) between the speed Vb of the target in the longitudinal direction of the host vehicle SV and the vehicle speed Vs of the host vehicle SV. Information indicating the type of target: The information indicating the type of target includes information indicating whether the target is a vehicle, a two-wheeled vehicle (motorcycle and bicycle), or a pedestrian. The information indicating the type of target is determined based on a well-known pattern matching method. Note that this function (function of identifying the type of target) may be executed by the DSECU. The distance in the direction of the road width (lane width) of the space formed between the target (e.g., the left end of the target) and the left white line LL, hereinafter also referred to as the left side distance. When the target is on the left white line LL, the left side distance is zero. The left side distance may also be the distance in the direction of the road width (lane width) of the space formed between the target (e.g., the left end of the target) and "the left side deviation control line before it is moved by the offset distance described below (the left side deviation control line obtained by moving the left dividing line to the left or right by a first left side distance that is equal to or greater than zero)." The distance in the direction of the road width (lane width) of the space formed between the target (e.g., the right end of the target) and the right white line LR, hereinafter also referred to as the right side distance. When the target is on the right white line LR, the right side distance is zero. The right side distance may be the distance in the direction of the road width (lane width) of the space formed between the target (e.g., the right end of the target) and "the right side departure control line before it is moved by the offset distance described below (the right side departure control line obtained by moving the right dividing line to the right or left by a first right distance that is equal to or greater than zero)." The larger of the left side distance and the right side distance is also called the "lateral margin distance or target side distance."

[0035] The above information acquired by the image processing unit is also called "camera sensor information."

[0036] The radar sensor 11b includes a "radar wave transmitting / receiving unit and a radar wave processing unit" that is realized by an ECU (not shown).

[0037] The radar wave transmitting / receiving unit, for example, emits millimeter waves (i.e., electromagnetic waves in the millimeter wave band) to the surrounding area of ​​the vehicle SV including the area ahead of the vehicle SV, and receives reflected waves generated when the emitted millimeter waves are reflected by a portion of a three-dimensional object (i.e., a reflection point). Note that the radar sensor 11b may be a radar sensor that uses electromagnetic waves (radar waves) in a frequency band other than the millimeter wave band.

[0038] The radar wave processor recognizes targets based on reflection point information including the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the time from transmitting the millimeter waves to receiving the reflected waves. The radar wave processor acquires the longitudinal distance Dfx of the recognized target, the azimuth θp of the target relative to the host vehicle SV, and the relative speed Vfx of the target. Furthermore, the radar wave processor acquires the positions of the sides and rear of the target based on the reflection point information. The information acquired by the radar wave processor is also referred to as "radar sensor information."

[0039] The fusion unit of the surrounding sensor 11 generates fusion information by integrating the camera sensor information and the radar sensor information. The fusion information includes target information such as the above-mentioned "longitudinal distance Dfx, lateral position Dfy, direction θp, relative speed Vfx, right-side distance, left-side distance and type" of the target, as well as lane information. The fusion unit transmits the fusion information to the DSECU every time a predetermined time has elapsed. Note that the function of the fusion unit may be realized by the DSECU. Furthermore, the surrounding sensor 11 may include only the camera sensor 11a, for example. In this case, the fusion unit may be omitted.

[0040] 1 is a sensor that acquires information (parameters) that indicate the motion state of the host vehicle. The vehicle state sensor 12 includes a vehicle speed sensor 12a, a yaw rate sensor 12b, and a lateral acceleration sensor 12c.

[0041] The vehicle speed sensor 12a detects the traveling speed (vehicle speed) Vs of the host vehicle SV, and outputs a signal indicative of the vehicle speed Vs. The yaw rate sensor 12b detects the yaw rate YRt of the host vehicle SV, and outputs a signal indicative of the yaw rate YRt (actual yaw rate YRt). The lateral acceleration sensor 12c detects acceleration (ie, lateral acceleration) Gy in the vehicle width direction of the host vehicle SV, and outputs a signal indicative of the lateral acceleration Gy.

[0042] The operation switch 13 is a switch operated by the driver of the vehicle SV to select whether or not the driver should enable the road departure prevention function (lane departure avoidance function). The operation switch 13 outputs an ON signal (high level signal) while it is pressed by the driver, and outputs an OFF signal (low level signal) while it is not pressed by the driver.

[0043] The lane departure prevention function is a "steering control of the host vehicle SV" that applies a steering assist torque to the steering mechanism to change the steering angle so that the position of the host vehicle SV (the side of the host vehicle SV) does not deviate from the lane toward the outside of the lane. This steering assist torque (steering assist force) is sometimes called a "departure prevention torque." The lane is the portion of the road between the "left side restriction line determined based on the left white line LL" and the "right side restriction line determined based on the right white line LR", and in most parts roughly corresponds to the "driving lane."

[0044] The steering angle sensor 14 detects a steering angle (rotation angle of the steering wheel SW) θ of the host vehicle SV, and outputs a signal representing the steering angle θ. The steering torque sensor 15 detects the steering torque Tq applied to a torsion bar incorporated between the steering shaft US of the vehicle SV and a steering gear mechanism (not shown), and outputs a signal representing the steering torque Tq.

[0045] The EPS·ECU 20 is a control device for a well-known electric power steering system. The EPS·ECU 20 is connected to a motor driver 21.

[0046] The motor driver 21 is connected to the steering motor 22. The steering motor 22 is incorporated in a steering gear mechanism (not shown). The steering motor 22 is an electric motor, and generates torque by power supplied from an on-board battery (not shown) via the motor driver 21. This torque is transmitted to the steering gear mechanism, and as a result, the left and right steered wheels are steered. That is, the steering motor 22, together with the motor driver 21, constitutes a "steering angle changing actuator" for changing the steering angle of the host vehicle SV.

[0047] When the EPS·ECU 20 receives a steering command from the DSECU while the lane departure prevention function is enabled, the EPS·ECU 20 drives the motor driver 21 based on the target torque specified by the steering command, thereby driving the steering motor 22. In other words, the EPS·ECU 20 changes the steering angle of the host vehicle SV based on the steering command.

[0048] The alarm ECU 30 is connected to a buzzer 31 and a display 32. The alarm ECU 30 can alert the driver by sounding the buzzer 31 in response to an instruction from the DSECU. Furthermore, the alarm ECU 30 can turn on an attention-calling mark (e.g., a warning lamp) on the display 32 or display an alarm image in response to an instruction from the DSECU.

[0049] (Overview of operation) When the lane departure prevention function is set to an enabled state, the DSECU monitors whether or not a "start condition for lane departure prevention steering control (hereinafter, sometimes simply referred to as a "steering control start condition")" is satisfied. The steering control start condition is a condition that is satisfied when there is a high possibility that the host vehicle SV (the body of the host vehicle SV) will deviate from the lane defined by the left and right "departure restriction lines" (move to the outside of the lane). An example of the steering control start condition will be described later.

[0050] When the DSECU determines that the steering control start condition is satisfied, it sends a steering command to the EPS·ECU 20 so that the host vehicle SV travels within the lane (i.e., on the lane center line Ld side of the left and right departure control lines), thereby changing the steering angle of the host vehicle SV. This control for automatically changing the steering angle is also called "departure prevention steering control." Departure prevention steering control itself is a well-known control. Departure prevention steering control is not started when there is a low possibility that the host vehicle SV will depart from the lane (when the steering control start condition is not satisfied) even if the lane departure prevention function is in an active state.

[0051] For example, when the driving lane of the host vehicle SV is a straight road, the left and right departure restriction lines are generally the left and right white lines LL and LR, respectively. In the following, for the sake of simplicity, it is assumed that the left and right departure restriction lines coincide with the left and right white lines LL and LR, respectively. Therefore, the driving lane defined by the left and right white lines LL and LR coincides with a part of the road defined by the left and right departure restriction lines (i.e., the road).

[0052] Incidentally, as shown in Cases 1 to 3 in Fig. 3, when the host vehicle SV is traveling in the travel lane Ls, there may be a case where an object (an obstacle, such as another vehicle, a two-wheeled vehicle, a pedestrian, etc.) OB is present ahead of the host vehicle SV. In this case, the DSECU acquires the above-mentioned lateral margin distance Wy.

[0053] The lateral margin distance Wy is the distance from the right end face of the target object OB to the right white line LR when the target object OB (the center of the target object in the lane width direction) is located to the left of the lane center line Ld. The lateral margin distance Wy is the distance from the left end face of the target object OB to the left white line LL when the target object OB is located to the right of the lane center line Ld.

[0054] As shown in case 1 of Fig. 3, when the lateral margin distance Wy of the target object OB is sufficiently large (i.e., when the lateral margin distance Wy>the first distance threshold value WUth), most drivers of the host vehicle SV pass beside the target object OB without causing the host vehicle SV to deviate from the driving lane Ls. That is, for example, when the target object OB is located on the left side of the driving lane Ls and the lateral margin distance Wy is sufficiently large, the driver of the host vehicle SV steers the host vehicle SV so that the right side of the host vehicle SV does not cross the right white line LR when the host vehicle SV passes beside the target object OB, as shown by the solid line L1 in case 1 of Fig. 4.

[0055] In this case, there is a high possibility that the departure prevention steering control will not be executed. Furthermore, even if the departure prevention steering control is executed in this case, the torque applied to the steering wheel SW by the departure prevention steering control is small, so that the driver is unlikely to feel bothered by the departure prevention steering control.

[0056] In contrast, as shown in case 2 of Fig. 3, when the lateral margin distance Wy of the target object OB is not sufficiently large (i.e., when the lateral margin distance Wy is equal to or less than the first distance threshold value WUth), most drivers of the host vehicle SV cause the host vehicle SV to deviate from the driving lane Ls and pass beside the target object OB. That is, for example, when the target object OB is located on the left side of the driving lane Ls and the lateral margin distance Wy is not sufficiently large, the driver of the host vehicle SV steers the host vehicle SV so that the right side of the host vehicle SV crosses the right white line LR when the host vehicle SV passes beside the target object OB, as shown by the dashed line L2 in case 2 of Fig. 4.

[0057] In this case, if the left and right departure control lines are still set to the "left white line LL and right white line LR" as in the conventional device, a large torque is applied to the steering wheel SW by the departure prevention steering control. Therefore, the driver is likely to find the departure prevention steering control annoying.

[0058] Conventional devices may be configured to disable the lane departure prevention function in such cases (see, for example, case 2 in FIG. 3 and case 2 in FIG. 4). However, in this case, the departure prevention steering control is not executed even when the driver causes the host vehicle SV to deviate more than necessary from the departure restriction line (i.e., when the host vehicle SV deviates significantly from the driving lane Ls). As a result, conventional devices configured in this way cannot fully utilize the lane departure prevention function.

[0059] Therefore, as a result of extensive research, the inventors have found that when the vehicle SV passes beside the object OB, whether or not the driver will cause the vehicle SV to deviate from the driving lane Ls can be determined based on whether or not the lateral margin distance Wy is equal to or less than a threshold value WUth. The threshold value WUth is a value that changes depending on the type of object (e.g., a vehicle, a motorcycle, or a pedestrian), and is referred to as the "departure-passing determination upper limit value WUth" or the "first distance threshold value WUth."

[0060] More specifically, if the lateral margin distance Wy is greater than the upper limit value WUth for deviation-passing judgment, many drivers pass beside the target OB without causing their vehicle SV to deviate from the driving lane Ls (see case 1 in FIG. 3 and case 1 in FIG. 4). In contrast, if the lateral margin distance Wy is less than the upper limit value WUth for deviation-passing judgment, many drivers pass beside the target OB while causing their vehicle SV to deviate from the driving lane Ls (see case 2 in FIG. 3 and case 2 in FIG. 4).

[0061] The inventors have also found that, as shown in case 3 of FIG. 3, when the lateral margin distance Wy of the target OB is less than the "deviation-passing judgment lower limit value WLth, which is smaller than the deviation-passing judgment upper limit value WUth," the target OB is highly likely to be a preceding vehicle, and the driver of the host vehicle SV will not attempt to pass beside the target OB (will not attempt to overtake it). In other words, in this case, the host vehicle SV is unlikely to deviate from the driving lane Ls. The deviation-passing judgment lower limit value WLth is also a value that is predetermined to change depending on the type of target OB, and may be referred to as the "second distance threshold value WLth."

[0062] Based on this knowledge, the implementation device is configured to compare the lateral margin distance Wy with each of the upper limit value (first distance threshold) WUth for deviation-passing judgment and the lower limit value (second distance threshold) WLth for deviation-passing judgment, and determine whether there is a high possibility that the host vehicle SV will cross either the left white line LL or the right white line LR and deviate outside the driving lane Ls.

[0063] Then, when the implementation device judges that there is a high possibility that the vehicle SV will deviate from the driving lane Ls when passing the side of the target OB (i.e., when WLth≦Wy≦WUth), it keeps the lane departure avoidance device in an active state and moves the "line on the departure side" of the "left departure regulation line (left white line LL in this example) and the right departure regulation line (right white line LR in this example)" to the outside of the lane by a "predetermined offset distance." The "outside of the lane" refers to the departure side of the lane, and means the direction in which the vehicle SV is expected to deviate from the lane.

[0064] As a result, the host vehicle SV is caused to travel, for example, as shown by the dashed line L2 in case 2 of Fig. 4. In this case, even if departure prevention steering control is executed, the torque applied to the steering wheel SW by the departure prevention steering control is small, so that the driver is unlikely to feel bothered by the departure prevention steering control.

[0065] Furthermore, when the magnitude (|Tq|) of the steering torque Tq detected by the steering torque sensor 15 becomes equal to or greater than the override judgment threshold TqORth, the implementing device sets the lane departure prevention function to an inactive state so that the driver's steering operation is given priority (overridden) over the lane departure prevention steering control.

[0066] However, when the implementing device determines that there is a high possibility that the vehicle SV will deviate from the driving lane Ls when passing the side of the target OB (i.e., when WLth≦Wy≦WUth), it changes the override determination threshold value TqORth from the normal value TqH to "a value TqL smaller than the value TqH."

[0067] As a result, when the driver intentionally performs a large steering operation in a case where there is a high possibility that the host vehicle SV will deviate from the driving lane Ls when passing by the side of the target object OB, the possibility that the departure prevention steering control will not be executed (the departure prevention steering control will be stopped) increases. Therefore, when the driver intentionally performs a large steering operation when the host vehicle SV passes by the side of the target object OB, the driver's steering operation is more likely to be given priority, so that the frequency with which the driver feels the departure prevention steering control is bothersome can be reduced.

[0068] (Actual operation) The CPU of the DSECU (hereinafter simply referred to as "CPU") executes each of the routines shown in the flowcharts of Figures 5 to 8 every time a predetermined time has elapsed. Note that the various flags used below are set to "0" in an initialization routine executed by the CPU when an ignition key switch (not shown) of the host vehicle SV is moved from the OFF position to the ON position. Furthermore, in this initialization routine, the left departure restriction line is set to the left white line LL, and the right departure restriction line is set to the right white line LR.

[0069] 1. Lane departure detection 5, the CPU starts the process at step 500 and proceeds to step 510 to determine whether the value of the deviation prevention function enable flag XLDA is "1." The deviation prevention function enable flag XLDA is also referred to simply as the "enable flag XLDA."

[0070] The CPU executes a routine not shown in the figure to determine whether the deviation prevention function enabling condition is satisfied, and if the deviation prevention function enabling condition is satisfied, sets the value of the enable flag XLDA to 1. The deviation prevention function enabling condition is satisfied, for example, when both the following condition A1 and condition A2 are satisfied.

[0071] << Deviation prevention function effective conditions >> (Condition A1) The operation switch 13 is pressed while the deviation prevention function is set to disabled. (Condition A2) A predetermined time (disabled duration) has elapsed since the deviation prevention function was disabled.

[0072] The CPU executes a routine (not shown) to determine whether or not the deviation prevention function disable condition is satisfied, and if the deviation prevention function disable condition is satisfied, sets the value of the enable flag XLDA to 0. The deviation prevention function disable condition is satisfied, for example, when either of the following conditions B1 and B2 is satisfied.

[0073] <<Conditions for disabling deviation prevention function>> (Condition B1) The operation switch 13 is pressed while the deviation prevention function is set to be enabled. (Condition B2) With the departure prevention function set to enabled, the magnitude (|Tq|) of the steering torque Tq becomes equal to or greater than the override determination threshold TqORth due to the driver's steering operation (override) (see steps 850 and 860 described below).

[0074] When the value of the valid flag XLDA is not "1", the CPU judges "No" in step 510, proceeds directly to step 595, and ends this routine for the time being. On the other hand, when the value of the valid flag XLDA is "1", the CPU judges "Yes" in step 510, and proceeds to step 520.

[0075] In step 520, the CPU determines whether the value of the deviation-passing determination flag XDP is "0." The value of the deviation-passing determination flag XDP is set to "1" when it is determined that there is a high possibility that the host vehicle SV will deviate from "the driving lane defined by the left-side marking line and the right-side marking line (more specifically, the road defined by the left-side deviation restriction line before being moved by the offset distance described later and the right-side deviation restriction line before being moved by the offset distance described later)" when passing the side of the target OB (see steps 570 and 580 described later).

[0076] When the value of the deviation / passage determination flag XDP is not "0", the CPU makes a "No" determination in step 520, proceeds directly to step 595, and temporarily ends this routine. In contrast, when the value of the deviation / passage determination flag XDP is "0", the CPU makes a "Yes" determination in step 520, and proceeds to step 530.

[0077] In step 530, the CPU determines whether or not a target to be controlled (target object) is present ahead of the vehicle SV based on the fusion information from the surrounding sensor 11. In this example, the types of objects recognized as target objects are any of vehicles (other vehicles), two-wheeled vehicles (motorcycles and bicycles), and pedestrians. Note that the objects recognized as target objects may include other types of objects (for example, construction signs and pylons placed on the road, etc.).

[0078] If the object does not exist in front of the host vehicle SV, the CPU judges "No" in step 530, proceeds directly to step 595, and ends this routine for the time being. On the other hand, if the object exists in front of the host vehicle SV, the CPU judges "Yes" in step 530, and proceeds to step 540.

[0079] In step 540, the CPU calculates the absolute speed Vz of the target object, and determines whether the absolute speed Vz is within a speed range according to the type of the target object. The absolute speed Vz of a certain target object is calculated by adding the vehicle speed Vs of the host vehicle SV to the relative speed Vfx of the target object. For example, the speed range used in step 540 is as follows. A, B, and C below are all positive values. When the type of the target object is a vehicle: -A km / h to the vehicle speed Vs of the host vehicle SV. When the type of the target object is a two-wheeled vehicle: -B km / h to the vehicle speed Vs of the host vehicle SV. When the type of the target object is a pedestrian: in the range from -C km / h to the vehicle speed Vs of the host vehicle SV. As a result, among the targets present ahead of the host vehicle SV, targets moving away from the host vehicle SV (ie, targets with a positive relative speed Vfx) are excluded from the target objects.

[0080] If there is no target whose absolute speed Vz is within the above-mentioned speed range, the CPU judges "No" in step 540, proceeds directly to step 595, and ends this routine for the time being. On the other hand, if there is a target whose absolute speed Vz is within the above-mentioned speed range, the CPU judges "Yes" in step 540, and proceeds to step 550.

[0081] In step 550, the CPU calculates a collision prediction time TTC for each of the objects. The collision prediction time TTC is the time from the current time until the host vehicle SV and the object collide with each other, assuming that the host vehicle SV and the object maintain their current motion state. The collision prediction time TTC is calculated, for example, by dividing the longitudinal distance Dfx of the object by the magnitude |Vfx| of the relative speed Vfx of the object (TTC=Dfx / |Vfx|). If multiple objects are selected as the object, the object having the shortest collision prediction time TTC among the objects is selected as the final object. In step 550, the CPU further determines whether the collision prediction time TTC of the final object is equal to or less than the collision time threshold TTCth.

[0082] If the collision prediction time TTC of the final object is greater than the collision time threshold TTCth, the CPU judges "No" in step 550, proceeds directly to step 595, and ends this routine for the time being. On the other hand, if the collision prediction time TTC of the final object is equal to or less than the collision time threshold TTCth, the CPU judges "Yes" in step 550 and proceeds to step 560.

[0083] In step 560, the CPU determines "a deviation-passing judgment upper limit value (first distance threshold) WUth and a deviation-passing judgment lower limit value (second distance threshold) WLth" by applying the final type of the target to a lookup table (map) MapWth (see FIG. 3). The deviation-passing judgment upper limit value WUth and the deviation-passing judgment lower limit value WLth may hereinafter be simply referred to as the "upper limit value WUth" and the "lower limit value WLth", respectively.

[0084] The lookup table MapWth specifies the relationship between the type of target and each of the "upper limit value WUth" and "lower limit value WLth". The upper limit value WUth is set to a value greater than the lower limit value WLth. The upper limit value WUth and the lower limit value WLth are created for each type of target based on data on how many drivers drive their vehicle SV (what steering operation they perform) when the vehicle SV passes beside the target. According to this lookup table MapWth, for example, when the type of target is a vehicle, the upper limit value WUth and the lower limit value WLth are set to values ​​WU1 and WL1, respectively.

[0085] Next, the CPU proceeds to step 570 and obtains the above-mentioned lateral margin distance Wy. Furthermore, in step 570, the CPU determines whether "the lateral margin distance Wy is equal to or greater than the lower limit value WLth and equal to or less than the upper limit value WUth." That is, the CPU determines whether the deviation / passage determination condition expressed by the following inequality is satisfied.

[0086] <<Deviation / Pass Judgment Conditions>> WLth≦Wy≦WUth

[0087] For example, when the object OB is in the position shown in Case 1 of FIG. 3 (a position straddling the left white line of the driving lane), the lateral margin distance Wy is greater than the upper limit value WUth. In this case, most of the drivers of the host vehicle SV pass beside the final object OB without causing the host vehicle SV to deviate from "the road defined by the left deviation restriction line before being moved by the offset distance described later and the right deviation restriction line before being moved by the offset distance described later". For example, in this case, most of the drivers of the host vehicle SV do not perform a steering operation that causes the host vehicle SV to deviate from either "the left deviation restriction line set at the left white line LL and the right deviation restriction line set at the right white line LR" to the outside of the road.

[0088] For example, when the object OB is in the position shown in Case 2 of FIG. 3 (the left region of the driving lane), the lateral margin distance Wy is equal to or less than the upper limit WUth and equal to or more than the lower limit WLth. In this case, most of the drivers of the host vehicle SV pass beside the final object OB while causing the host vehicle SV to deviate from "the road defined by the left departure restriction line before being moved by the offset distance described later and the right departure restriction line before being moved by the offset distance described later". For example, in this case, most of the drivers of the host vehicle SV perform a steering operation to cause the host vehicle SV to deviate from either "the left departure restriction line set at the left white line LL and the right departure restriction line set at the right white line LR" to the outside of the road.

[0089] When the object OB is in the position shown in Case 3 of FIG. 3 (approximately in the center region of the driving lane), the lateral margin distance Wy is smaller than the lower limit WLth. In this case, the object is, for example, another vehicle (i.e., a preceding vehicle) traveling in the same direction as the host vehicle SV, and most of the drivers of the host vehicle SV do not attempt to pass by the side of the object. In other words, most of the drivers of the host vehicle SV do not perform steering operations that cause the host vehicle SV to deviate from "the road defined by the left deviation restriction line before being moved by the offset distance described later and the right deviation restriction line before being moved by the offset distance described later". For example, in this case, most of the drivers of the host vehicle SV do not perform steering operations that cause the host vehicle SV to deviate from either "the left deviation restriction line set, for example, at the left white line LL, and the right deviation restriction line set, for example, at the right white line LR" to the outside of the road.

[0090] From the above, only when the deviation-passing judgment condition is met is it likely that the driver of the host vehicle SV will pass by the final target object OB while causing the host vehicle SV to deviate from "the path defined by the left deviation control line (before it is moved by the offset distance described below) and the right deviation control line (before it is moved by the offset distance described below)."

[0091] If the deviation-passing judgment condition is not satisfied, the CPU judges "No" at step 570, proceeds directly to step 595, and ends this routine for the time being. In contrast, if the deviation-passing judgment condition is satisfied, the CPU judges "Yes" at step 570, and proceeds to step 580. The CPU sets the value of the deviation-passing judgment flag XDP to "1" at step 580. That is, the CPU judges that there is a high possibility that the driver of the host vehicle SV will pass by the final object OB while causing the host vehicle SV to deviate from the road. Thereafter, the CPU proceeds to step 595, and ends this routine for the time being.

[0092] 2. Determination of start of lane departure prevention steering control (departure prevention steering control) At a predetermined timing, the CPU starts the process from step 600 in FIG. 6, and proceeds to step 610 to determine whether the deviation prevention function enable flag XLDA is "1".

[0093] When the value of the valid flag XLDA is not "1", the CPU judges "No" in step 610, proceeds directly to step 695, and ends this routine for the time being. On the other hand, when the value of the valid flag XLDA is "1", the CPU judges "Yes" in step 610, and proceeds to step 620.

[0094] In step 620, the CPU determines whether the value of the departure prevention steering control execution flag XJ is "0." The value of the departure prevention steering control execution flag XJ is set to "1" while the departure prevention steering control is being executed (see "step 670, and steps 720 and 750 in FIG. 7" described later).

[0095] When the value of the execution flag XJ is not "0" (i.e., when departure prevention steering control is being executed), the CPU judges "No" in step 620 and proceeds directly to step 695 to temporarily end this routine. In contrast, when the value of the execution flag XJ is "0", the CPU judges "Yes" in step 620 and proceeds to step 630.

[0096] In step 630, the CPU determines whether the value of the deviation-passing determination flag XDP is "0." If the value of the deviation-passing determination flag XDP is "0," the CPU determines "Yes" in step 630 and proceeds to step 640, where it determines the "correction distance Df of the deviation restriction line KL" shown in FIG. 2B and case 2 in FIG. 4 using the lookup table MapDfα.

[0097] More specifically, the CPU determines whether the road shape is "sharp curve, gentle curve, or straight" based on the road shape (the radius of curvature R or the curvature Cv=1 / (radius of curvature R) of the lane center line Ld of the driving lane). For example, when the magnitude of the radius of curvature R is smaller than a value R1, the CPU determines that the road shape is a sharp curve. When the magnitude of the radius of curvature R is equal to or larger than a value R1 and smaller than a value R2, the CPU determines that the road shape is a gentle curve. When the magnitude of the radius of curvature R is equal to or larger than a value R2, the CPU determines that the road shape is a straight line.

[0098] Then, when the road shape is either a sharp curve or a gentle curve, a correction distance Df is calculated depending on whether the deviation restriction line KL to be corrected is on the outside (outer circumference side) or inside (inner circumference side) of the curve (see lookup table MapDfα in step 640). For example, when the host vehicle SV is traveling on a road that curves to the left, the right side of the road is the outside of the curve, and the left side of the road is the inside of the curve.

[0099] According to the table MapDfα, the correction distance Df is calculated as follows. Correction distance Df=a1 on the outside of the curve when the road shape is a sharp curve Correction distance Df=a2 on the outside of the curve when the road shape is a gentle curve Correction distance Df=a3 when the road shape is straight Correction distance Df=a4 on the inside of the curve when the road shape is a gentle curve Correction distance Df=a5 on the inside of the curve when the road shape is a sharp curve

[0100] According to the table MapDfα shown in this example, the values ​​a1 to a3 are each set to "0", and the values ​​a4 and a5 are each set to a positive value. The value a5 is greater than the value a4. These values ​​an (n is an integer from 1 to 5, i.e., the values ​​a1, a2, a3, a4, and a5) are also called "first left distance" when the side to which the value is applied is the left side, and are called "first right distance" when the side to which the value is applied is the right side. The value an (n is an integer from 1 to 5) may include 0, and may include positive or negative values, and its magnitude is, for example, about 1 / 10 to 1 / 20 of the travel lane width. However, the value an (n is an integer from 1 to 5) is generally preferably a positive value greater than or equal to 0.

[0101] Next, the CPU proceeds to step 650, where it determines the left departure regulation line based on the left white line LL and the corresponding correction distance Df, and determines the right departure regulation line based on the right white line LR and the corresponding correction distance Df. In other words, the CPU determines the line obtained by moving the left white line LL by the corresponding correction distance Df to the outside (left side) of the driving lane as the corrected left departure regulation line. If the correction distance Df for the left white line LL is "0", the corrected left departure regulation line coincides with the left white line LL. If the correction distance Df is a negative value, the corrected left departure regulation line becomes a line obtained by moving the left white line LL to the right by the value |Df|. Furthermore, the CPU determines the line obtained by moving the right white line LR by the corresponding correction distance Df to the outside (right side) of the driving lane as the corrected right departure regulation line. If the correction distance Df for the right white line LR is "0", the corrected right departure regulation line coincides with the right white line LR. Furthermore, when the correction distance Df is a negative value, the right departure restriction line after correction is a line obtained by shifting the right white line LR to the left by the value |Df|.

[0102] Furthermore, the CPU calculates the sum of the distance Ds from the reference point P of the vehicle SV to the white line on the side where the vehicle SV is about to deviate from the "roadway defined by the left-side departure control line and the right-side departure control line" (hereinafter referred to as the "departure side") and the correction distance Df as the "departure margin distance Dsy (=Ds+Df)." The white line on the departure side is the white line between the left white line LL and the right white line LR, whichever is closer to the reference point P.

[0103] For example, in the example shown in Fig. 2A, the sum of the distance Ds between the reference point P and the left white line LL and the correction distance Df for the left white line LL is calculated as the departure margin distance Dsy. For example, in the example shown in Fig. 2B, the sum of the distance Ds between the reference point P and the right white line LR and the correction distance Df for the right white line LR is calculated as the departure margin distance Dsy.

[0104] Next, the CPU proceeds to step 660 in Fig. 6 and determines whether or not a steering control start condition (a start condition for steering control to prevent deviation from the road) is satisfied. The steering control start condition is satisfied, for example, when both of the following conditions C1 and C2 are satisfied.

[0105] <<Start conditions for lane departure prevention steering control>> (Condition C1) The departure margin distance Dsy is equal to or smaller than the departure prevention steering start threshold value Dref, which is a positive predetermined value. (Condition C2) The traveling direction of the host vehicle SV indicated by the yaw angle θy is a direction toward the departure restriction line on the departure side.

[0106] The deviation prevention steering start threshold Dref is set to, for example, a value obtained by adding a predetermined small positive value γ to 1 / 2 the vehicle width WSV of the host vehicle SV (=(WSV / 2)+γ), but is not limited to this.

[0107] When the start condition of the departure prevention steering control is not satisfied, the CPU judges "No" in step 660, proceeds directly to step 695, and temporarily ends this routine. In contrast, when the start condition of the departure prevention steering control is not satisfied, the CPU judges "Yes" in step 660, proceeds to step 670, and sets the value of the steering control execution flag XJ to "1." This starts the departure prevention steering control as described below (see steps 760 to 780 in FIG. 7).

[0108] On the other hand, when the CPU proceeds to step 630, if the value of the deviation-passing determination flag XDP is "1" (not "0"), the CPU determines "No" in step 630 and proceeds to step 680. Then, in step 680, the CPU determines the correction distance Df of the deviation restriction line KL using the lookup table MapDfβ.

[0109] More specifically, as described above, the CPU determines whether the road shape is "sharp curve, gentle curve, or straight." If the road shape is either a sharp curve or a gentle curve, the CPU calculates the correction distance Df depending on whether the deviation regulation line KL to be corrected is on the outside (outer circumference side) of the curve or the inside (inner circumference side) of the curve (see the lookup table MapDfβ in step 640).

[0110] According to the table MapDfβ, the correction distance Df is calculated as follows. When the road shape is a sharp curve, the correction distance on the outside of the curve is Df=a1+b1. When the road shape is a gentle curve, the correction distance on the outside of the curve is Df = a2 + b2 Correction distance Df=a3+b3 when the road shape is straight When the road shape is a gentle curve, the correction distance on the inside of the curve is Df=a4+b4. When the road shape is a sharp curve, the correction distance on the inside of the curve is Df=a5+b5

[0111] The value an (n is an integer from 1 to 5) is as described above. In this example, the values ​​b1, b2, and b3 are equal positive values. The value b4 is a positive value smaller than the value b1, and the value b5 is a positive value smaller than the value b4. These values ​​bn (n is an integer from 1 to 5, i.e., the values ​​b1, b2, b3, b4, and b5) are basically positive values, and in particular, the value b3 is a positive value.

[0112] Therefore, when the value of the deviation-passing judgment flag XDP is "1" (i.e., when there is a high possibility that the driver of the vehicle SV will cause the vehicle SV to deviate from the driving lane or road and pass by the object OB), the deviation restriction line is moved further to the deviation side (outside the driving lane) as viewed from the driving lane, compared to when the value of the deviation-passing judgment flag XDP is "0". Note that the value b5 may be "0", and in this case, only when the road shape is a sharp curve and the deviation direction is on the inside of the curve, the deviation restriction line is not moved from the deviation restriction line when the value of the deviation-passing judgment flag XDP is "0". In other words, all of these values ​​bn (n is an integer from 1 to 5, i.e., the values ​​b1, b2, b3, b4, and b5) need not be "0". Among these values ​​bn (n is an integer from 1 to 5, i.e., the values ​​b1, b2, b3, b4, and b5), values ​​that are not "0" are referred to as "offset distances".

[0113] Thereafter, the CPU proceeds to the above-mentioned steps 650 and 660, and if the determination in step 660 is "Yes", the CPU proceeds to step 670. As a result, when the value of the departure-passing determination flag XDP is "1", the departure margin distance Dsy becomes larger when the host vehicle SV is about to deviate from the driving lane as it attempts to pass beside the target, compared to when the value of the departure-passing determination flag XDP is "0", so the timing to start executing departure prevention steering control is effectively delayed.

[0114] 3. Determination of execution and termination of deviation prevention steering control At a predetermined timing, the CPU starts the process from step 700 in FIG. 7, and proceeds to step 710 to determine whether the deviation prevention function enable flag XLDA is "1".

[0115] When the value of the validity flag XLDA is not "1", the CPU determines "No" in step 710 and proceeds to step 720. The CPU sets the value of the steering control execution flag XJ to "0" in step 720, and then proceeds to step 760. In contrast, when the value of the validity flag XLDA is "1", the CPU determines "Yes" in step 710 and proceeds to step 730.

[0116] In step 730, the CPU determines whether the value of the steering control execution flag XJ is "1." When the value of the steering control execution flag XJ is not "1," the CPU determines "No" in step 730 and proceeds directly to step 760. In contrast, when the value of the steering control execution flag XJ is "1," the CPU determines "Yes" in step 730 and proceeds to step 740.

[0117] The CPU determines whether or not a termination condition for the deviation prevention steering control is satisfied in step 740. The termination condition for the deviation prevention steering control is satisfied when, for example, both of the following conditions D1 and D2 are satisfied.

[0118] <<Start condition of deviation prevention steering control>> (Condition D1) The departure margin distance Dsy is greater than the departure prevention steering start threshold Dref plus a small positive value Δ (=Dref+Δ). Note that the value Δ may be "0". (Condition D2) The direction of travel of the vehicle SV indicated by the yaw angle θy is not toward the departure control line on the departure side (it is toward the departure control line on the opposite side to the departure control line determined to be on the departure side when the departure prevention steering control starts).

[0119] When the termination condition of the departure prevention steering control is not satisfied, the CPU judges "No" in step 740 and proceeds directly to step 760. In contrast, when the termination condition of the departure prevention steering control is satisfied, the CPU judges "Yes" in step 740 and proceeds to step 750 to set the value of the steering control execution flag XJ to "0". After that, the CPU proceeds to step 760.

[0120] When the CPU proceeds to step 760, it determines whether or not the value of the steering control execution flag XJ is "1." When the value of the steering control execution flag XJ is not "1," the CPU determines "No" in step 760, proceeds directly to step 795, and ends this routine for the time being. In contrast, when the value of the steering control execution flag XJ is "1," the CPU determines "Yes" in step 760, sequentially performs the processes of steps 770 and 780 described below, and then proceeds to step 795 and ends this routine for the time being.

[0121] Step 770: The CPU calculates the target control amount (in this example, the target torque Tqtgt) according to the following formula. Tqtgt = K1 (Vs 2 / R)+K2·Ds'+K3·θy+K4·(Yr*-Yr)

[0122] In this formula, K1, K2, K3, and K4 are control gains, and their signs (plus or minus) are determined depending on whether the driving lane is a right curve, a left curve, or a straight line, and whether the departure restriction line on the departure side is on the left or right side. That is, the signs of the control gains are determined so that the target torque Tqtgt is "a value that causes the host vehicle SV to follow the lane center line Ld and move toward the lane center line Ld." Note that R is the curve radius, θy is the yaw angle described above, Yr* is the target yaw rate, and Yr is the actual yaw rate of the host vehicle detected by the yaw rate sensor 12b. Ds' is called the side distance, and is calculated based on the following formula. Side distance Ds' = Threshold Dref for starting steering to prevent deviation - deviation margin distance Dsy

[0123] Therefore, the target torque Tqtgt is calculated so that its absolute value |Tqtgt| increases as the side distance Ds' increases. Furthermore, the target torque Tqtgt is calculated so that its absolute value |Tqtgt| increases as the traveling direction of the host vehicle SV indicated by the yaw angle θy is on the departure side and the magnitude |θy| of the yaw angle θy increases.

[0124] The fourth term on the right side of the above formula (K4·(Yr*-Yr)) may be omitted. Such a method of calculating the target torque Tqtgt is well known and is disclosed in, for example, JP 2018-79835 A and JP 2020-11562 A.

[0125] Step 780: The CPU transmits a steering command including the target torque Tqtgt as information to the EPS·ECU 20. That is, the CPU drives the steering motor 22 via the EPS·ECU 20, and causes the steering motor 22 to generate a steering assist torque that coincides with the target torque Tqtgt. As a result, a "lane departure prevention steering control" is executed that prevents the host vehicle SV from departing from the departure restriction line on the departure side.

[0126] 4. Override decision At a predetermined timing, the CPU starts the process from step 800 in FIG. 8, and proceeds to step 810 to determine whether the value of the deviation prevention function enable flag XLDA is "1".

[0127] When the value of the valid flag XLDA is not "1", the CPU judges "No" in step 810, proceeds directly to step 895, and ends this routine for the time being. On the other hand, when the value of the valid flag XLDA is "1", the CPU judges "Yes" in step 810, and proceeds to step 820.

[0128] In step 820, the CPU determines whether the value of the deviation-passing determination flag XDP is "0". When the value of the deviation-passing determination flag XDP is "0", the CPU determines "Yes" in step 820 and proceeds to step 830, where it sets the override determination threshold TqORth to the normal first predetermined value TqH. After that, the CPU proceeds to step 850. Note that the override determination threshold TqORth is set to the normal first predetermined value TqH in the initialization routine described above.

[0129] In contrast, when the value of the deviation / passage determination flag XDP is not "0" (when it is "1"), the CPU determines "No" in step 820 and proceeds to step 840, where it sets the override determination threshold TqORth to "a second predetermined value TqL that is smaller than the first predetermined value TqH". After that, the CPU proceeds to step 850.

[0130] The CPU determines whether or not the magnitude (|Tq|) of the steering torque Tq is equal to or greater than the override determination threshold TqORth in step 850. If the magnitude (|Tq|) of the steering torque Tq is less than the override determination threshold TqORth, the CPU determines "No" in step 850 and proceeds directly to step 895 to temporarily end this routine.

[0131] On the other hand, if the magnitude (|Tq|) of the steering torque Tq is equal to or greater than the override determination threshold TqORth, the CPU determines "Yes" in step 850 and sequentially performs the processes of steps 860 to 880 described below, and then proceeds to step 895 to temporarily end this routine.

[0132] Step 860: The CPU sets the value of the deviation prevention function enable flag XLDA to “0”. Step 870: The CPU sets the value of the departure prevention steering control execution flag XJ to “0”. Step 880: The CPU sets the value of the deviation-passage determination flag XDP to “0”.

[0133] In this way, when the value of the departure-passing determination flag XDP is "1" (i.e., when there is a high possibility that the driver of the host vehicle SV will cause the host vehicle SV to deviate from the driving lane and pass by the target OB), the override determination threshold value TqORth is set to "a second predetermined value TqL smaller than the first predetermined value TqH." Therefore, a large steering operation by the driver is detected earlier, whereby the lane departure prevention function is disabled, and if departure prevention steering control is being executed, the departure prevention steering control is stopped (prohibited).

[0134] As a result, when the vehicle SV is likely to deviate from either the left white line or the right white line when passing the side of the target OB, if the driver intentionally performs a steering operation, the departure prevention steering control is likely not to be executed. Therefore, the driver's steering operation is more likely to be given priority, and the frequency with which the driver feels the departure prevention steering control is bothersome can be reduced. Note that the CPU may determine whether or not the value of the steering control execution flag XJ is "1" between steps 810 and 820. In this case, when the value of the steering control execution flag XJ is "1", the CPU proceeds to step 820, and when the value of the steering control execution flag XJ is not "1", the CPU proceeds to step 895. Furthermore, the CPU may be configured to determine whether or not the value of the steering control execution flag XJ is "1" in step 810, instead of determining whether or not the value of the departure prevention function valid flag XLDA is "1". That is, the CPU may switch the override judgment threshold TqORth between the "first predetermined value TqH" and the "second predetermined value TqL" at least when lane departure prevention steering control is being executed (i.e., when the lane departure prevention function is set to enabled) and when the lane departure prevention steering control is in a state where it can be executed.

[0135] The present invention is not limited to the above-described embodiment, and various modifications as described below can be adopted within the scope of the present invention.

[0136] <Variation 1> For example, the deviation-passing judgment condition may be a condition that is satisfied when the lateral margin distance Wy is equal to or less than an upper limit value (first distance threshold) WUth (i.e., when Wy≦WUth). Furthermore, in this case, when the CPU executes step 540, if the relative speed Vfx of a target ahead of the host vehicle SV is within the forward vehicle relative speed range (−S1 (km / h) to +S1 (km / h)), the target may be excluded from the target object.

[0137] <Variation 2> When the deviation-passing judgment condition is not met, the CPU of the DSECU may set the left-side lane marking to a line shifted to the left by a first left-side distance shown in Table 1, which is determined according to the road shape, as the left-side deviation control line, and may set the right-side lane marking to a line shifted to the right by a first right-side distance shown in Table 1, which is determined according to the road shape, as the right-side deviation control line.

[0138] Furthermore, when the departure-passing judgment condition is met, the CPU of the DSECU may set the left-side lane marking to a line shifted to the left by the "sum of the first left-side distance and the left-side offset distance" shown in Table 1, which is determined according to the road shape, as the left-side departure control line, and may set the right-side lane marking to a line shifted to the right by the "sum of the first right-side distance and the right-side offset distance" shown in Table 1, which is determined according to the road shape, as the right-side departure control line.

[0139] In addition, each value of the "first left side distance and first right side distance" shown in Table 1 is "a positive or negative value including 0 (preferably a value greater than or equal to 0)", and each value of the "left side offset distance and right side offset distance" shown in Table 1 is "a value greater than 0".

[0140] [Table 1]

[0141] <Variation 3> The DSECU may transmit an alarm command to the alarm ECU 30 while the departure prevention steering control is being executed, and may use the buzzer 31 and / or the display 32 to notify the driver that the departure prevention steering control is being executed.

[0142] <Modification 4> The DSECU may calculate a target steering angle θtgt instead of the target torque Tqtgt as the target control amount in the departure prevention steering control, and transmit a steering command including this information to the EPS·ECU 20. In this case, the EPS·ECU 20 may drive the steering motor 22 based on the target steering angle θtgt specified by the steering command, the vehicle speed Vs, etc., thereby causing the actual steering angle to match the target steering angle θtgt.

[0143] As described above, the lateral clearance distance Wy is the distance in the road width direction of a space formed between a target object present in front of the vehicle and the left-side lane marking and the distance in the road width direction of a space formed between the target object and the right-side lane marking, whichever is larger; the distance in the travel path width direction of the space formed between the target and the left deviation control line (the left deviation control line before being moved by the offset distance) and the distance in the travel path width direction of the space formed between the target and the right deviation control line (the right deviation control line before being moved by the offset distance), whichever is larger; may be also possible. [Explanation of symbols]

[0144] 10... driving assistance ECU (DSECU), 11... surrounding sensor, 11a... camera sensor, 11b... radar sensor, 12... vehicle state sensor, 12a... vehicle speed sensor, 12b... yaw rate sensor, 12c... lateral acceleration sensor, 13... operation switch, 14... steering angle sensor, 15... steering torque sensor, 20... EPS ECU, 21... motor driver, 22... steering motor.

Claims

1. a surroundings sensor that acquires surrounding information including information on the positions of a left and right lane markings of a road on which the host vehicle is traveling and information on the position of a target located in front of the host vehicle; a steering angle changing actuator capable of changing a steering angle of the host vehicle; a control unit that executes a lane departure prevention steering control for changing a steering angle of the host vehicle by controlling the steering angle changing actuator so that the host vehicle does not deviate from the lane when a steering control start condition is satisfied in a state in which the host vehicle is traveling on a lane between a left departure restriction line obtained by moving the left lane marking to the left or right by a first left distance that is equal to or greater than zero and a right departure restriction line obtained by moving the right lane marking to the right or left by a first right distance that is equal to or greater than zero, the control unit executing a lane departure prevention steering control for changing a steering angle of the host vehicle by controlling the steering angle changing actuator so that the host vehicle does not deviate from the lane ... Equipped with The control unit When the vehicle is traveling on the road and a target is present ahead of the vehicle, a distance in a width direction of the lane of a space formed between the target and the left-side lane marking and a distance in a width direction of the lane of a space formed between the target and the right-side lane marking, whichever is larger; Or, the greater of the distance in the travel lane width direction of a space formed between the target and the left deviation control line and the distance in the travel lane width direction of a space formed between the target and the right deviation control line; is obtained as a lateral margin distance based on the peripheral information, determining whether or not a deviation-passing determination condition is satisfied based on at least the lateral margin distance, the deviation-passing determination condition being satisfied when there is a high possibility that the host vehicle will deviate from the road by crossing one of the left deviation control line and the right deviation control line when passing beside the target; When it is determined that the deviation-passing determination condition is satisfied, at least one of the left deviation restriction line and the right deviation restriction line, which is a restriction line that is expected to be crossed when the host vehicle passes beside the target, is further moved by a predetermined offset distance toward the outside of the road. It was configured as follows: In a lane departure prevention device, The control unit a determination unit that determines whether the lateral margin distance is equal to or less than a predetermined first distance threshold, and that determines that the deviation-passing determination condition is satisfied when it is determined that the lateral margin distance is equal to or less than the first distance threshold, and, The first distance threshold is changed based on a type of the target present in front of the host vehicle. Lane departure prevention device.

2. A surroundings sensor that acquires surrounding information including information about the positions of left and right dividing lines of a road on which the vehicle is traveling and information about the positions of targets located in front of the vehicle; a steering angle changing actuator capable of changing a steering angle of the host vehicle; a control unit that executes a lane departure prevention steering control for changing a steering angle of the host vehicle by controlling the steering angle changing actuator so that the host vehicle does not deviate from the lane when a steering control start condition is satisfied in a state in which the host vehicle is traveling on a lane between a left departure restriction line obtained by moving the left lane marking to the left or right by a first left distance that is equal to or greater than zero and a right departure restriction line obtained by moving the right lane marking to the right or left by a first right distance that is equal to or greater than zero, the control unit executing a lane departure prevention steering control for changing a steering angle of the host vehicle by controlling the steering angle changing actuator so that the host vehicle does not deviate from the lane ... Equipped with The control unit When the vehicle is traveling on the road and a target is present ahead of the vehicle, a distance in a width direction of the lane of a space formed between the target and the left-side lane marking and a distance in a width direction of the lane of a space formed between the target and the right-side lane marking, whichever is larger; Or, the greater of the distance in the travel lane width direction of a space formed between the target and the left deviation control line and the distance in the travel lane width direction of a space formed between the target and the right deviation control line; is obtained as a lateral margin distance based on the peripheral information, determining whether or not a deviation-passing determination condition is satisfied based on at least the lateral margin distance, the deviation-passing determination condition being satisfied when there is a high possibility that the host vehicle will deviate from the road by crossing one of the left deviation control line and the right deviation control line when passing beside the target; When it is determined that the deviation-passing determination condition is satisfied, at least one of the left deviation restriction line and the right deviation restriction line, which is a restriction line that is expected to be crossed when the host vehicle passes beside the target, is further moved by a predetermined offset distance toward the outside of the road. It was configured as follows: In a lane departure prevention device, The control unit the controller is configured to determine whether the lateral margin distance is equal to or less than a predetermined first distance threshold and equal to or more than a predetermined second distance threshold smaller than the first distance threshold, and determine that the deviation-passing determination condition is satisfied when it is determined that the lateral margin distance is equal to or less than the first distance threshold and equal to or more than the second distance threshold. Lane departure prevention device.

3. In the lane departure prevention device according to claim 2, The control unit The first distance threshold is changed based on a type of the target present in front of the host vehicle. Lane departure prevention device.

4. In the lane departure prevention device according to claim 3, The control unit The second distance threshold is changed based on a type of the target present in front of the host vehicle. Lane departure prevention device.

5. The lane departure prevention device according to any one of claims 1 to 4, The control unit When the lane departure prevention steering control is being executed and / or when the lane departure prevention steering control is in an executable state, the control unit is configured to determine whether or not a magnitude of a steering torque applied to a steering wheel of the host vehicle is equal to or greater than an override determination threshold, and when it is determined that the magnitude of the steering torque is equal to or greater than the override determination threshold, to stop the lane departure prevention steering control; Furthermore, The control unit When it is determined that the deviation-passing determination condition is satisfied, the override determination threshold is changed to a smaller value than when it is determined that the deviation-passing determination condition is not satisfied. Lane departure prevention device.

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