JP2012003421A - Traffic lane deviation alarm device and alarm method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for alarming against an traffic lane deviation when own vehicle drifts out of a running lane and reducing unnecessary emissions of alarms on traffic lane deviations.SOLUTION: A width of lane W of the lane where own vehicle is running is recognized and vehicle speed V of own vehicle is detected, and then a minimum width of lane Wis calculated based on the vehicle speed V. When the recognized width of lane W is smaller than the minimum width of lane W, an altered value d is calculated based on a difference between the recognized width of lane W and the minimum width of lane W, and the deviation determination threshold Th is set to a position altered outward of the lane by the altered value d from the determination reference value Thset with respect to a white line defining the running lane. Based on the set deviation determination threshold Th, deviation from the running lane of own vehicle is determined, and when a deviation is determined, an alarm on the deviation is emitted.

Description

  The present invention relates to a lane departure warning device and a warning method capable of suppressing an unnecessary lane departure warning when warning a departure from a travel lane of a vehicle.

Conventionally, various technologies have been developed to warn the driver of a departure when the vehicle deviates from the lane in which the vehicle is traveling. Further, in such a lane departure warning technology, a warning that is considered unnecessary for the driver is suppressed. Technology has been developed.
For example, in Patent Document 1, the frequency at which it is determined that there is a possibility of departure increases on roads with narrow lane widths, alarms occur frequently, and is troublesome for the driver. In the lane departure warning device, which shoots a road ahead of the host vehicle and issues a lane departure warning based on the position of the host vehicle with respect to the lane of the road, the lane width of the road Describes a technique for prohibiting a lane departure warning when the vehicle is less than an operation permission width (a width obtained by adding a predetermined width to the vehicle width).

JP 2005-346269 A

The technique described in Patent Document 1 simply prohibits the lane departure warning when the lane width is less than the operation permission width. However, even if the lane width is less than the operation permission width, it is desirable not to simply prohibit the lane departure warning, but to effectively function as necessary to suppress only unnecessary warnings.
The present invention has been devised in view of such a problem, and it is possible to suppress an unnecessary lane departure warning in consideration of the lane width of the traveling lane of the host vehicle and to appropriately alert the lane. An object is to provide a deviation warning device and a warning method.

  In order to achieve the above object, a lane departure warning device according to the present invention is a lane departure warning device that warns of a departure from the traveling lane of the host vehicle, wherein the position of the white line that defines the traveling lane is set to the position of the host vehicle. White line recognizing means for recognizing the vehicle, lane width recognizing means for recognizing the lane width of the traveling lane, vehicle speed detecting means for detecting the vehicle speed of the host vehicle, and the vehicle speed detected by the vehicle speed detecting means. A minimum lane width setting means for setting a minimum lane width, a departure determination threshold setting means for setting a departure determination threshold for the position of the white line, the departure determination threshold set by the departure determination threshold setting means, and the white line recognition means. Deviation determination means for comparing the position of the own vehicle to be recognized and determining deviation of the own vehicle, and alarm means for warning the deviation when the deviation determination means determines that there is a deviation of the own vehicle The departure determination threshold value setting means includes the minimum lane width and the lane when the lane width recognized by the lane width recognition means is smaller than the minimum lane width set by the minimum lane width setting means. A deviation value is calculated according to a difference from the lane width recognized by the width recognition means, and the deviation determination threshold value is set to a position where a determination reference value set at an arbitrary position with respect to the white line is changed to the outside of the lane by the change value. It is characterized by setting.

  The lane departure warning method according to the present invention is a lane departure warning method for warning the departure of the host vehicle from the traveling lane, and recognizes the position of the white line defining the traveling lane with respect to the position of the host vehicle. A white line recognition step, a lane width recognition step for recognizing the lane width of the traveling lane, a vehicle speed detection step for detecting the vehicle speed of the host vehicle, and a minimum lane width according to the vehicle speed detected in the vehicle speed detection step A minimum lane width setting step, a departure determination threshold setting step for setting a departure determination threshold for the position of the white line, the departure determination threshold set in the departure determination threshold setting step, and the own vehicle recognized in the white line recognition step A departure determination step for determining a departure of the own vehicle by comparing with the position of the vehicle, and a warning step for warning the departure when the departure determination step determines that there is a departure of the own vehicle, The constant threshold value setting step recognizes the minimum lane width and the lane width recognition step when the lane width recognized in the lane width recognition step is smaller than the minimum lane width set in the minimum lane width setting step. A change value is calculated according to a difference from the lane width, and a deviation determination threshold value is set at a position where the determination reference value set at an arbitrary position with respect to the white line is changed to the outside of the lane by the change value. It is said.

  In each of the lane departure warning device and the warning method of the present invention, it is preferable that a change permission range for limiting the magnitude of the change value is set in advance.

  According to the lane departure warning device and warning method of the present invention, since the departure determination threshold is set in consideration of the lane width of the traveling lane of the host vehicle, an unnecessary lane departure warning is suppressed without stopping the warning function, Can be alarmed properly.

1 is a block diagram showing an overall configuration of a lane departure warning device according to an embodiment of the present invention. It is a flowchart which shows the warning method by the lane departure warning apparatus which concerns on one Embodiment of this invention. It is a table | surface which shows the fuzzy rule which the attention determination means of the lane departure warning apparatus which concerns on one Embodiment of this invention uses. It is a typical top view of the road which shows the departure determination threshold value which the departure determination threshold value setting means of the lane departure warning apparatus which concerns on one Embodiment of this invention sets. It is the minimum lane width setting map which prescribes | regulates the relationship between the vehicle speed and a lane width which the departure determination threshold value setting means of the lane departure warning apparatus which concerns on one Embodiment of this invention uses. (A), (b) is the typical top view of the road which shows the modification of the judgment reference value of the departure judgment threshold value which the departure judgment threshold value setting means of the lane departure warning device which concerns on one Embodiment of this invention sets. is there.

Hereinafter, embodiments of a lane departure warning device and a warning method thereof according to the present invention will be described with reference to the drawings. The present invention functions particularly effectively when a vehicle travels on a high-standard road such as an expressway.
[One Embodiment]
<Configuration>
As shown in FIG. 1, a lane departure warning device 1 according to an embodiment of the present invention includes a camera (imaging means) 2, a steering angle sensor 3, a winker sensor 4, an auxiliary brake sensor 5, a clutch sensor (shift). An operation sensor) 6, a vehicle speed sensor 7, an alarm unit 8, and an ECU (control unit) 10 are provided.

The camera 2 is an imaging unit that acquires an image of the road surface ahead of the traveling direction of the host vehicle, and the road image acquired by the camera 2 is input to the ECU 10.
The steering angle sensor 3 is a detecting means for detecting the steering angle of the steering wheel, the winker sensor 4 is a detecting means for detecting the operating state of the winker lever, and the auxiliary brake sensor 5 is an auxiliary brake such as an exhaust brake or a retarder. The clutch sensor 6 is a detection means for detecting the stepping operation state of the clutch as a shift operation, and the vehicle speed sensor 7 is a detection means for detecting the traveling speed of the host vehicle. .

Information acquired by the various sensors 3 to 7 is input to the ECU 10. A shift lever sensor may be provided instead of the clutch sensor 6 to detect the operation state of the transmission shift lever.
The warning means 8 issues a warning when the deviation determination means 16 described later determines that there is a vehicle departure, and operates based on a control signal from the ECU 10. Specifically, the alarm means 8 includes, for example, an alarm (vibration means), an alarm lamp (blink means), a display (display means), an actuator (vibration means) that vibrates a portion that contacts a driver such as a steering wheel or a seat. ) And the like.

The ECU 10 is an electronic control unit including a memory, a CPU, and the like, and includes a white line recognition unit 11, a lane width recognition unit 12, an attention determination unit 13, a lane change determination unit 14, a departure determination threshold setting unit 15, Deviation judging means 16 is provided as software (computer program).
The ECU 10 has a camera 2 and various sensors 3 to 7 connected to its input side, and an alarm means 8 connected to its output side. Based on information input from the camera 2 and various sensors 3 to 7, Various processes such as recognition, determination, and setting are performed, and the alarm unit 8 is controlled.

  The white line recognition means 11 performs image processing on the road surface image input from the camera 2 and individually recognizes the white line defining the travel lane (travel lane) in which the host vehicle is traveling on the left and right sides of the host vehicle. The positions of the white lines on the left and right sides with respect to the position of the host vehicle (in other words, the position of the host vehicle with respect to the traveling lane defined by the white line) are recognized. As a method for recognizing a white line, for example, a known method such as binarizing and scanning an image and viewing a luminance distribution can be used.

The lane width recognizing means 12 recognizes the lane width (hereinafter also referred to as a recognized lane width) W of the host vehicle traveling lane based on the white line recognized by the white line recognizing means 11. If the positions of the white lines on the left and right sides of the traveling lane are known, it is possible to know the distance between the white lines and inevitably obtain the lane width W.
The attention level determination means 13 is a means for determining the level of attention level of the driver who is driving. In addition, about attention determination, since the well-known thing explained in full detail in the patent 3039327 can be utilized, detailed description is abbreviate | omitted.

  Briefly, the attention determination means 13 is based on “monotonicity” reflecting the frequency of turn signal, auxiliary brake, and shift operation, “steering amount” that is an integrated value of corrected steering per unit time, and white line recognition. Attentiveness is determined by fuzzy reasoning using three items of “meander rate”, which is calculated by calculating the wobble of the vehicle. The turn signal operation information is obtained from the turn signal sensor 4, the auxiliary brake operation information is obtained from the auxiliary brake sensor 5, and the shift operation information is obtained from the clutch sensor 6.

  The monotonicity is an item set to quantify including both the passage of time and the monotonous feeling. In order to reflect the passage of time, the monotonicity is calculated in such a manner that the monotonicity gradually increases if no operation is performed. Moreover, in order to quantify the monotonous feeling, the frequency of turn signals, auxiliary brakes and shift operations is reflected. This is based on the knowledge of the present inventor that the frequency of the operation system corresponds to a monotonous road environment and traffic situation.

  The steering amount is a value obtained by integrating the absolute value of the amount of steering operation per unit time without distinguishing the left and right directions. According to the knowledge of the present inventor, the amount of steering is increased because the driver frequently performs fine correction steering normally, but when the attention is reduced, one correction steering is increased and the frequency is decreased, and the steering amount is decreased. As the attentiveness decreases further, the time when the correction steering is not performed at all appears, and the steering amount is further reduced. The steering amount is a measure that comprehensively shows such characteristics, and is calculated as an integrated value of corrected steering per unit time based on information on the steering angle acquired from the steering angle sensor 3.

  The meandering rate is a value for evaluating the traceability with respect to the white line, and is represented by the standard deviation per unit time of meandering data obtained by measuring the movement of the center point of the white line on both sides. When attention is maintained, the driver unconsciously tries to keep his vehicle in the driving lane, and judges the attention based on the inventor's knowledge that he rarely steps over the white line. It is adopted as one of the items to be performed.

The attention determining unit 13 defines a fuzzy rule as shown in FIG. 3, and determines the attention using the membership functions corresponding to the calculated monotonicity, steering amount, and meander rate. Here, the attention is obtained at levels from 1 to 5 in increments of 0.5. Level 1 is set to have the lowest attention and level 5 has the highest attention.
The lane change determination means 14 changes the lane based on the steering angle acquired from the steering angle sensor 3, the turn signal information acquired from the turn signal sensor 4, and the relative positional relationship between the white line recognized by the white line recognition means 11 and the host vehicle. It is determined whether or not it is in the middle. Specifically, any one of (1) the steering angle is equal to or greater than a predetermined angle set in advance, (2) the winker lever is operated, and (3) the white line and the host vehicle is established. When the relative positional relationship is closer than a predetermined value set in advance, it is determined that the lane change has been made in response to the driver's request.

The departure determination threshold setting means 15 is for setting the departure determination threshold Th used for the lane departure determination by the departure determination means 16 on the left and right sides of the host vehicle. As shown in FIG. 4, the deviation determination threshold setting means 15 sets the position of the center of the white line in the width direction as a reference value (determination reference value) Th ₀ for the deviation determination threshold Th. FIG. 4 is a plan view schematically showing the white line on the road and the own vehicle traveling in the driving lane so that the deviation determination threshold Th can be easily grasped, and each dimension such as the white line is expressed strictly. It is not a thing.

Further, the departure determination threshold value setting means 15 stores a minimum lane width setting map that defines the relationship between the vehicle speed V and the minimum lane width W _MIN as shown in FIG. The departure determination threshold setting means 15 includes a minimum lane width setting map, and thus also functions as a minimum lane width setting means.
Specifically, in the present embodiment, the minimum lane width setting map has a minimum lane width W _MIN of 3 m (a preset first minimum lane) when the vehicle speed V is equal to or less than 50 km / h (a preset first vehicle speed). Width), the minimum lane width W _MIN is set to 3.75 m (preset second minimum lane width) when the vehicle speed V is 80 km / h (second preset vehicle speed) or more, and the vehicle speed V is set to 50 km / h. When the vehicle speed V is greater than 80 km / h, the minimum lane width W _MIN is defined to increase linearly between the lower limit value 3 m and the upper limit value 3.75 m as the vehicle speed V increases. The specific method of defining the minimum lane width setting map is not limited to this. That is, for example, when the vehicle speed V is larger than 50 km / h and smaller than 80 km / h, the minimum lane width W _MIN is curved between the lower limit value 3 m and the upper limit value 3.75 m (a quadratic function or exponent) It may be specified to increase (functionally). Each numerical value may be set to other than the above values.

The departure determination threshold setting means 15 obtains the minimum lane width W _MIN corresponding to the vehicle speed V detected by the vehicle speed sensor 7 based on the minimum lane width setting map, and the recognized lane width W recognized by the lane width recognition means 12 is obtained. When it is smaller than this minimum lane width W _MIN (W <W _MIN ), a value obtained by dividing the difference between the minimum lane width W _MIN and the recognized lane width W by 2 is calculated as a change value d as shown in the following equation. To do.
d = (W _MIN −W) / 2
Next, as shown in FIG. 4, the position changed from the determination reference value Th ₀ to the outside of the lane by the amount of the change value d is set as the departure determination threshold Th. On the other hand, when the recognized lane width W recognized by the lane width recognizing means 12 is equal to or larger than the minimum lane width W _MIN (W ≧ W _MIN ), the determination reference value Th ₀ is set as it is as the departure determination threshold Th.

A change permission range is set in advance for the deviation determination threshold Th. The change permission range is a range in which the determination reference value Th ₀ is set as a boundary value inside the lane, and a position changed from the determination reference value Th ₀ by a predetermined value outside the lane is set as a boundary value outside the lane. That is, the magnitude of the change value d is limited by the change permission range. In the present embodiment, the predetermined value that is the upper limit of the change value d is, for example, 30 cm.

That is, for example, when driving on a road with a lane width of 3.25 m at 70 km / h, the minimum lane width W _MIN is determined as 3.5 m based on the minimum lane width setting map, and then the change value d is calculated as 12.5 cm. The deviation determination threshold Th on each of the left and right sides of the host vehicle is set at a position shifted from the determination reference value Th ₀ by 12.5 cm to the outside of the lane.
Further, for example, when traveling on a road with a lane width of 3.0 m at 80 km / h, the minimum lane width W _MIN is calculated as 3.75 m based on the minimum lane width setting map, and then the change value d is calculated as 37.5 cm. However, the change value d is changed to 30 cm due to the limitation of the change permission range, and the deviation determination threshold Th on each of the left and right sides of the host vehicle is set at a position shifted from the determination reference value Th ₀ by 30 cm outside the lane.

When the position of the host vehicle exceeds the departure determination threshold Th based on the position of the host vehicle recognized by the white line recognition unit 11 and the departure determination threshold Th set by the departure determination threshold setting unit 15. In addition, it is determined that the host vehicle has deviated from the lane.
Note that a switch for turning on and off the departure warning function by the lane departure warning device 1 may be provided at a position near the driver, such as an instrument panel, and may be operated by the driver.

The ECU 10 configured as described above performs control according to the flowchart shown in FIG.
First, in step S10 (position recognition step, lane width recognition step and attention determination step), the white line recognition means 11 recognizes the position of the white line and the position of the host vehicle, and the lane width recognition means 12 recognizes the lane width W. In addition, the attention level is determined by the attention level determination means 13. Thereafter, the process proceeds to step S20.

In step S20 (vehicle speed detection step, minimum lane width setting step, and departure determination threshold setting step), the vehicle speed V of the host vehicle is detected by the vehicle speed sensor 7, and then the departure determination threshold setting means 15 is based on the minimum lane width setting map. The minimum lane width W _MIN is obtained according to the vehicle speed V detected by the vehicle speed sensor 7. Then, by comparing the recognized lane width W, which is recognized by its minimum lane width W _MIN and step S10, if the recognition lane width W is smaller than the minimum lane width W _MIN, the minimum lane width W _MIN recognition lane width W The deviation determination threshold value Th is set by shifting from the determination reference value Th ₀ to the outside of the lane on the left and right sides by the change value d obtained from the above. At this time, when the change value d is limited by the change permission range, the change value d is set within a range that the change permission range allows to the maximum. If the recognized lane width W is equal to or greater than the minimum lane width W _MIN , the determination reference value Th ₀ is set as it is as the departure determination threshold value Th. Thereafter, the process proceeds to step S30.

In step S30 (deviation determination step), the departure determination means 16 determines the departure of the host vehicle based on the departure determination threshold Th set in step S20. If it is determined that there is a deviation, the process proceeds to step S40, and if not, the process returns to the beginning of the flow.
In step S40 (lane change determination step), the lane change determination means 14 determines whether the lane is being changed. If it is determined that the lane is being changed, the process returns to the beginning of the flow; otherwise, the process proceeds to step S50.

In step S50 (alarm prohibition step), the attention level determination means 13 determines whether or not the attention level is equal to or higher than a predetermined value (for example, level 4 or higher). If the attention is higher than the predetermined value, the process returns to the beginning of the flow, and if not, the process proceeds to step S60. That is, if the attention is higher than the predetermined value in step S50, the alarm is prohibited.
In step S60 (alarm process), the alarm means 8 issues an alarm.

  The flow consisting of steps S10 to S60 is repeated at a predetermined cycle while the vehicle is traveling.

<Action and effect>
Since the lane departure warning device according to an embodiment of the present invention is configured as described above, the following operations and effects are achieved.

The minimum lane width W _MIN is obtained from the vehicle speed V as the lane width that should be the driving lane, and the deviation determination threshold Th is set by shifting the change value d from the determination reference value Th ₀ to the outside of the lane, that is, the minimum lane width W _MIN Is set so that departure judgment is performed based on the virtual white line, so that unnecessary lane departure warnings that occur frequently when the lane width is narrow are suppressed in consideration of the lane width of the driving lane. be able to.

That is, in consideration of the fact that there is a certain degree of correlation between the speed limit and the lane width on an actual road, the lane width W _MIN that should be secured at the minimum in accordance with the vehicle speed V when determining the lane departure warning. By setting this, it is possible to suppress frequent occurrence of lane departure warnings because the lane width is too small.
As a result, the acceptability of the driver's main lane departure warning is improved, and the number of cases where the driver turns off the departure warning function with a switch is reduced, so that the driver's contribution to driving support is also improved. .

  Further, since the change permission range is set in advance with respect to the departure determination threshold Th, it is possible to prevent the departure determination threshold Th from being set outside the lane more than the actual white line, without impairing safety. Unnecessary alarms can be suppressed.

[Others]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention.

For example, in the above embodiment, the white line recognition unit 11 recognizes the white line by performing image processing on the image captured by the camera 2, but the method of recognizing the white line is not limited to this. For example, a lane marker laid on the road is used. It may be used to recognize the position of the white line or the own vehicle.
Even if the white line cannot be sufficiently extracted by image processing, the white line is estimated using a known method based on the position of the host vehicle and the surrounding road environment, and the estimated white line is recognized as an actual white line. Also good. At this time, it is preferable that the camera 2 captures images including other vehicles, sidewalks, guard rails, roadside trees, road shoulders, and the like in addition to the white lines so that the white line recognition means 11 recognizes them.

Further, the white line recognition unit 11 may not be configured as a component in the ECU 10. That is, the white line recognition means 11 may be provided as a camera 2 ECU separately from the ECU 10 and information recognized by the white line recognition means 11 may be input to the ECU 10.
In the above embodiment, the attention determining unit 13 determines the attention using fuzzy inference from the monotonicity, the steering amount, and the meandering rate, but the specific method for determining the attention is not limited to this. The attention may be determined by other known methods. For example, the camera may further include a camera for photographing the driver's face, and use the number of blinks and the time (opening value of the eye) during a predetermined time. It may be determined, or may be determined using the line-of-sight direction. Further, instead of determining the attention level by the level, the attention level may be determined by another scale such as a percentage. Furthermore, the attention determination unit 13 itself may not be provided. That is, the step of determining the attention level from step S10 in the flowchart shown in FIG. 2 may be omitted, and the step S50 for determining whether the attention level is equal to or greater than a predetermined value may be omitted.

  In the above embodiment, the lane change determination means 14 determines whether or not the lane is being changed based on the steering angle, the blinker information, the white line, and the relative positional relationship of the host vehicle. The specific method is not limited to this, and the driver's intentional lane change may be determined by another known method. For example, it is simply detected by the winker sensor 4 that the winker lever is operated. For example, it may be determined that the lane change is valid.

In the above-described embodiment, the departure determination threshold value setting unit 15 shifts the departure determination threshold value Th from the determination reference value Th _{0 by the} same change value d on each of the left and right sides. In such a case, the left and right values may be set separately, for example, by increasing the change value d on the marginal space side. The marginal space is preferably recognized by the white line recognition means 11.

That is, the departure determination threshold setting means 15 obtains the minimum lane width W _MIN corresponding to the vehicle speed V based on the minimum lane width setting map, and the recognized lane width W recognized by the lane width recognition means 12 is based on the minimum lane width W _MIN . Is smaller (W <W _MIN ), first, a difference (W _MIN −W) between the minimum lane width W _MIN and the recognized lane width W is obtained, and the change value d ₁ on the marginal space side is changed to the change value on the opposite side. set to be larger than d _2, and a value obtained by adding the change value d ₁ and the change value d ₂ may be such that the magnitude of the difference (W _MIN -W). It is preferable that a change permission range is set in advance for each of the change values d ₁ and d ₂ .

Further, in the above embodiment, the departure determination threshold setting means 15 previously provided the minimum lane width setting map as shown in FIG. 5 to obtain the minimum lane width W _MIN , but without such a map, for example, The minimum lane width W _MIN may be obtained by a predefined formula.
In the above-described embodiment, the change permission range of the change value d (d ₁ , d ₂ ) applied to the departure determination threshold Th is described as being a position shifted by 30 cm from the determination reference value Th ₀ to the outside of the lane. The size of is not limited to this, and the change permission range may not necessarily be provided.

In the above embodiment, the determination reference value Th ₀ of the departure determination threshold Th is the center position of the white line, but may be an arbitrary position with respect to another white line, for example, as shown in FIG. it the inner position of the white line may be used as the determination reference value Th _0, a position outside of the white line may be used as the determination reference value Th _0, as shown in Figure 6 (b).
Further, in the above-described embodiment, the departure determination unit 16 actually steps the virtual white line defined by the departure determination threshold Th when the position of the host vehicle actually exceeds the departure determination threshold Th. However, when a deviation is predicted, it may be determined that there is a deviation. That is, for example, when the vehicle speed V acquired from the vehicle speed sensor 7 or the steering angle acquired from the steering angle sensor 3 is used and the departure from the lane is predicted to exceed the departure determination threshold Th after a predetermined time, It may be determined that there is a vehicle departure.

1 Lane departure warning device 2 Camera (imaging means)
3 Steering angle sensor 4 Blinker sensor 5 Auxiliary brake sensor 6 Clutch sensor (shift operation sensor)
7 Vehicle speed sensor (vehicle speed detection means)
8 Alarm means 10 ECU
DESCRIPTION OF SYMBOLS 11 White line recognition means 12 Lane width recognition means 13 Attention power determination means 14 Lane change determination means 15 Deviation determination threshold setting means (minimum lane width setting means)
16 Deviation judging means d Change value Th Deviation judgment threshold Th ₀ judgment reference value W recognized lane width W _MIN minimum lane width

Claims (3)

A lane departure warning device that warns of a departure from the traveling lane of the own vehicle,
White line recognition means for recognizing the position of the white line defining the travel lane with respect to the position of the host vehicle;
Lane width recognition means for recognizing the lane width of the travel lane;
Vehicle speed detection means for detecting the vehicle speed of the host vehicle;
Minimum lane width setting means for setting a minimum lane width according to the vehicle speed detected by the vehicle speed detection means;
Deviation determination threshold setting means for setting a deviation determination threshold for the position of the white line;
Deviation determination means for comparing the departure determination threshold set by the departure determination threshold setting means with the position of the own vehicle recognized by the white line recognition means, and for determining the departure of the own vehicle;
Alarm means for warning the departure when the departure determining means determines that there is a departure from the own vehicle;
When the lane width recognized by the lane width recognizing unit is smaller than the minimum lane width set by the minimum lane width setting unit, the departure determination threshold setting unit is configured to recognize the minimum lane width and the lane width recognizing unit. A change value is calculated in accordance with the recognized difference with the lane width, and the deviation determination threshold is set at a position where the determination reference value set at an arbitrary position with respect to the white line is changed to the outside of the lane by the change value. A lane departure warning device. The lane departure warning device according to claim 1, wherein the departure determination threshold setting means is preset with a change permission range that limits the magnitude of the change value. A lane departure warning method for warning a departure of a host vehicle from a driving lane,
A white line recognition step for recognizing the position of the white line defining the travel lane with respect to the position of the host vehicle;
A lane width recognition step for recognizing the lane width of the travel lane;
A vehicle speed detection step of detecting the vehicle speed of the host vehicle;
A minimum lane width setting step for setting a minimum lane width according to the vehicle speed detected in the vehicle speed detection step;
A deviation determination threshold setting step for setting a deviation determination threshold for the position of the white line;
A departure determination step for comparing the departure determination threshold set in the departure determination threshold setting step with the position of the own vehicle recognized in the white line recognition step to determine a departure from the own vehicle;
A warning step for warning the departure when the departure determination step determines that there is a departure of the host vehicle,
In the departure determination threshold setting step, when the lane width recognized in the lane width recognition step is smaller than the minimum lane width set in the minimum lane width setting step, the minimum lane width and the lane width recognition step The change value is calculated according to the difference from the lane width recognized in step S2, and the deviation determination threshold value is set at a position where the determination reference value set at an arbitrary position with respect to the white line is changed to the outside of the lane by the change value. A lane departure warning method.

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