JP2010173367A - Lane deviation warning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lane deviation warning device enhancing an accuracy of warning timing. <P>SOLUTION: In the lane deviation warning processing, a lane border is recognized by applying image recognition processing to a road image inputted from an on-vehicle camera and a distance (DTLB) between the lane border and the vehicle is determined (S110-S130). A deviation speed is calculated based on a detection result of a vehicle speed sensor and an angle formed by an advancement direction of the vehicle specified from the road image and the lane border (S140), and a deviation acceleration is calculated based on a variation degree of the deviation speed (S150). A distance threshold value (DTLB-thre) is set using these calculation results and a predetermined prospective time (TTLC) (S160), and lane deviation warning is issued when DTLB is not more than DTLB-thre (S190). Namely, warning is issued at the timing taking into consideration the variation degree of the deviation speed, and thereby, an error of timing to the actual TTLC is reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lane departure warning device that issues a warning when a host vehicle is likely to depart from a traveling lane.

  Conventionally, by performing image recognition processing on image data captured by an in-vehicle camera, the relative positions of lane markings on the traveling lane and features indicating road edges with respect to the host vehicle are recognized, and these recognition results Based on the above, there is known a lane departure warning device that issues a warning when it is determined that there is a high possibility that the host vehicle will depart from the traveling lane.

  Specifically, in the lane departure warning device, a lane boundary representing a boundary line of a traveling lane is determined based on a relative position of a lane division line or a feature object, and a distance (Distance To Lane Boundary; Hereinafter, it is determined whether or not DTLB has reached a predetermined distance threshold (hereinafter referred to as DTLB_thre). When DTLB is equal to or less than DTLB_thre, it is considered that the host vehicle is highly likely to deviate from the travel lane (that is, deviate from the lane boundary) (see Non-Patent Document 1, for example).

  As an example of a lane departure warning device, in order to clarify the warning timing, the time (Time To Line Crossing; hereafter referred to as TTLC) that is expected until the vehicle departs from the lane boundary avoids lane departure. Devices that perform an alarm when a preset critical time is reached (hereinafter referred to as a TTLC priority device) are known.

  Specifically, in the TTLC priority type device, as shown in the following equation (i), the TTLC is fixed in advance to the critical time, and the departure speed Vd representing the speed at which the host vehicle approaches the lane boundary is multiplied by the TTLC. DTLB_thre is variably set, and the alarm timing is determined by comparing DTLB and DTLB_thre as described above.

DTLB_thre = Vd × TTLC (i)
More specifically, as shown in FIG. 4, the departure speed Vd is V as the traveling speed of the host vehicle, and θy as an angle between the traveling direction of the host vehicle and the lane boundary (hereinafter referred to as a lane yaw angle), Using the following equation (ii), it is calculated as an orthogonal component of the traveling speed V with respect to the lane boundary.

  Vd = Vsinθy (ii)

JIS D 0804, Japanese Industrial Standard, 2007/7/20

  However, in the conventional TTLC priority type device, the warning timing is determined by comparing the TTLC with the critical time when the departure speed Vd is assumed to be constant. There was a problem that it was vulnerable to changes in the angle θy. Specifically, for example, when entering a curve, or when the brake, accelerator, steering, etc. are operated, the difference between the actual TTLC and the critical time exceeds the allowable error, so the warning timing and lane departure avoidance are avoided. Therefore, there is a problem in that it may become inconsistent with the spare time for the vehicle, which may cause the driver to feel uncomfortable or uneasy.

  In order to solve the above problems, an object of the present invention is to provide a lane departure warning device that can improve the accuracy of warning timing.

  The lane departure warning device according to claim 1, which is an invention made to achieve the above object, is a device mounted on a vehicle, wherein the image acquisition means includes a traveling lane for the vehicle in an imaging range. The image is acquired, and the speed detecting means detects the traveling speed of the vehicle. Then, the alarm control means recognizes a lane boundary representing the boundary line of the traveling lane based on the road image acquired by the image acquisition means, and a distance between the lane boundary and the vehicle (hereinafter referred to as DTLB) is preset. An alarm is issued when the distance is below the threshold.

  Here, the departure speed calculation means is based on the travel speed detected by the speed detection means and the angle formed by the traveling direction of the vehicle specified from the road image and the lane boundary (hereinafter referred to as the lane yaw angle). A departure speed representing a speed at which the vehicle approaches the lane boundary is calculated. Then, the distance threshold setting means sets the distance threshold based on the departure speed calculated by the departure speed calculation means, the expected time fixed in advance so as to avoid the departure of the lane boundary, and the change in the departure speed. The gist.

  In the lane departure warning device configured in this way, even if the travel speed and the lane yaw angle change due to the driving operation, the distance threshold is variably set based on these changes, so that the expected time is It is possible to reduce an error between a preliminarily estimated margin time for avoiding a lane departure and an actual TTLC compared to before the change.

  Therefore, according to the lane departure warning device of the present invention, consistency between the warning timing and the margin time can be maintained, and the accuracy of the warning timing can be improved. Note that the DTLB and the lane yaw angle can be calculated by associating the position direction on the road image with the position direction of the vehicle based on parameters set in advance by known camera calibration.

Specifically, in the lane departure warning device according to the present invention, the distance threshold value setting means Vd represents the departure speed calculated by the departure speed calculation means, and the departure from the lane boundary can be avoided. Assuming that the expected time fixed in advance is TTLC and the correction value based on the change in the deviation speed Vd is A, the following formula (I)
DTLB_thre = Vd × TTLC + A (I)
The value DTLB_thre calculated by the above may be set as the distance threshold value.

In the lane departure warning device according to the present invention, as described in claim 3, the acceleration at which the vehicle approaches the lane boundary based on the change in the departure speed calculated by the departure speed calculation means by the departure acceleration calculation means. And the distance threshold setting means calculates α as the departure acceleration calculated by the departure acceleration calculation means, and the following equation (II)
A = (α × TTLC ² ) / 2 (II)
It is desirable that the value A calculated by the above is used as a correction value.

  In this case, it is not necessary to provide sensors for detecting the traveling acceleration of the vehicle. In addition to easily calculating the departure acceleration using the calculation result of the departure speed, the DTLB_thre is accurately determined using the departure acceleration. It can be corrected.

  Furthermore, in the lane departure warning device according to the present invention, the operation detecting means detects a driving operation performed by the driver of the vehicle, and the alarm prohibiting means is a detection result by the operation detecting means. When it is determined that the driving operation is a lane changing operation defined in advance, it is desirable to prohibit the alarm by the alarm control means.

  In other words, since there is a high possibility that the driver is intentionally approaching the lane boundary because there is a lane change operation by the driver, in such a case, it is unnecessary by prohibiting the lane departure warning. The possibility of bothering the driver by the warning can be reduced.

  Such a driving operation is desirably one that reflects the driver's intention. For example, as described in claim 5, the driving operation may be a steering wheel or turn signal operation. Specifically, the warning prohibiting means may prohibit the lane departure warning when the steering amount of the steering wheel is equal to or larger than a preset reference threshold value or when the turn signal is turned on.

  In the lane departure warning device according to the present invention, the warning performed by the warning control means may be any one of an audible alarm, a visual alarm, and a tactile alarm. In particular, a combination of these is desirable. In this case, the possibility that the driver does not notice the lane departure warning can be reduced.

The block diagram which shows the structure of the lane departure warning apparatus 1 to which this invention was applied. The flowchart which shows the detail of the lane departure warning process which CPU of the control part 10 performs. The graph for comparing DTLB_thre before correction and after correction. The auxiliary figure for demonstrating the definition of the departure speed Vd.

  Embodiments of the present invention will be described below with reference to the drawings.

<Configuration of lane departure warning device>
FIG. 1 is a block diagram showing a configuration of a lane departure warning device 1 to which the present invention is applied.

  As shown in FIG. 1, a lane departure warning device 1 is a device mounted on a vehicle such as an automobile, and is mounted on a vehicle speed sensor 2 that detects the traveling speed of the vehicle, for example, on the center front side of the vehicle, An in-vehicle camera 3 that captures a landscape including a traveling road ahead of the vehicle and outputs image data (corresponding to a road image), and a steering wheel (hereinafter abbreviated as steering) Sg when operated by the driver of the vehicle A steering torque sensor 4 for detecting a torque amount and a winker switch (hereinafter abbreviated as a winker SW) 5 for detecting an operation state of the winker are provided.

  Further, the lane departure warning device 1 includes a steering torque application unit 6 that adds a weak steering torque for warning to the steering Sg in the direction of avoiding lane departure, a buzzer generation unit 7 that generates a warning buzzer, and a warning lamp. A meter display unit 8 for lighting and displaying on the meter, and a control unit 10 that executes various processes based on the inputs from the sensors / switches 2 to 5 and controls the alarm generation units 6 to 8. It has.

  The control unit 10 is configured around a well-known microcomputer including a CPU, ROM, RAM, I / O, a bus line, and the like. Among these, the CPU uses a RAM as a work area to store a program stored in the ROM. Based on this, the lane departure warning process described in detail below is executed. The ROM stores camera parameters (internal parameters and external parameters) of the in-vehicle camera 3. Camera parameters are specified in advance by well-known camera calibration. Among them, internal parameters are based on the camera's focal length, etc., and external parameters are based on the camera's mounting position, orientation, etc. Point to.

<Lane departure warning processing>
Next, FIG. 2 is a flowchart showing details of the lane departure warning process executed by the CPU of the control unit 10. This process is started when the power of the lane departure warning device 1 is turned on, and is repeatedly executed at a predetermined control period Δt until the power (or the IG switch of the vehicle) is turned off.

  First, when this process is started, in S110, the road image is acquired by storing the image data input from the in-vehicle camera 3 in the RAM.

  In subsequent S120, based on the road image acquired in S110 and the camera parameters stored in the ROM, a process for recognizing a relative position of a lane marking on the traveling lane or a feature indicating the end of the road with respect to the vehicle ( Image recognition processing). For the image recognition process, a known image processing method such as edge detection or pattern detection is used.

  In the subsequent S130, a lane boundary representing the boundary line of the traveling lane is determined based on the relative position of the lane marking line or the feature object recognized in S120, and the distance (Distance To Lane Boundary) between the lane boundary and the host vehicle is determined. ; Hereinafter abbreviated as DTLB) in the RAM. Note that the lane boundary here refers to a boundary line determined by, for example, a center line of the lane marking line or a feature other than the lane marking line. As the DTLB here, for example, the distance between the front wheel outer side on the lane boundary side of the vehicle and the lane boundary is used.

In subsequent S140, based on the lane boundary determined in S130 and the camera parameters stored in the ROM, an angle (hereinafter referred to as lane yaw angle) θy formed by the traveling direction of the vehicle and the lane boundary is calculated. Based on the yaw angle and the detection result (traveling speed V) of the vehicle speed sensor 2, a departure speed Vd representing the speed at which the vehicle approaches the lane boundary is expressed by the following equation (1).
Vd = Vsin θy (1)
The deviation speed Vd calculated here is stored in the RAM.

In subsequent S150, based on the previous value Vd ′ and the current value Vd of the departure speed stored in the RAM, the departure period α representing the acceleration at which the vehicle approaches the lane boundary is expressed as (2)
α = (Vd−Vd ′) / Δt (2)
Calculated by

In subsequent S160, the DTLB_thre that is the distance from the lane boundary (corresponding to the distance threshold) at which the lane departure warning should be started is calculated in advance so that the driver can avoid the lane departure by the calculation results of S140 and S150. Based on the fixed expected time (Time To Line Crossing; hereinafter abbreviated as TTLC), the following formula (3)
DTLB_thre = Vd × TTLC + (α × TTLC ² ) / 2 (3)
Use to set. That is, the equation (3) adds a correction value A (= (α × TTLC ² ) / 2) based on the departure acceleration α to the conventional setting for calculating DTLB_thre by multiplying only the departure speed Vd by TTLC. Means.

  In subsequent S170, the DTLB stored in S130 is compared with the DTLB_thre set in S160 to determine whether DTLB is equal to or less than DTLB_thre. If the determination is affirmative, the process proceeds to S180. If a negative determination is made, the process proceeds to S110.

  In S180, based on the detection results of the sensors / switches 4 and 5, it is determined whether or not the driving operation performed by the driver is a lane changing operation defined in advance. The process proceeds to S110, and if a negative determination is made, the process proceeds to S190. Specifically, the lane change operation is an operation that can be considered that the driver intentionally approaches the lane boundary. Based on the detection result of the steering torque sensor 4, the steering torque amount is equal to or greater than a predetermined reference threshold value. In some cases, or when the winker is in an ON state based on the input signal of the winker SW5.

  In S190, a lane departure warning is generated via each of the alarm generation units 6-8, and the process proceeds to S110. Specifically, a command for adding a weak steering torque for warning to the steering Sg in a direction opposite to the lane boundary, a command for generating a warning buzzer, and a command for lighting a warning lamp on the meter Is output to a corresponding alarm generation unit among the steering torque application unit 6, the buzzer generation unit 7, and the meter display unit 8.

<Operation example>
Next, for example, when the vehicle traveling speed V is constant and the lane yaw angle θy changes with time as shown in FIG. 3A, before the correction of DTLB_thre set in S160 of the lane departure warning process. By comparing the corrected values, the warning timing by the lane departure warning device 1 is verified. In the following, the calculation formula (i) of DTLB_thre before correction (conventional) and the calculation formula (3) of DTLB_thre after correction (present invention) are shown again.

DTLB_thre = Vd × TTLC (i)
DTLB_thre = Vd × TTLC + (α × TTLC ² ) / 2 (3)
As shown in FIG. 3 (b), DTLB_thre changes according to the departure speed Vd regardless of before and after the correction, and thus is set to increase with the increase in the lane yaw angle θy, and decreases in the lane yaw angle θy. Accordingly, it is set to be smaller (it is constant while the lane yaw angle θy does not change).

  However, the DTLB_thre before correction changes while maintaining continuity at the start of change P and Q of the lane yaw angle θy, whereas the corrected DTLB_thre is larger at the start P of increase of the lane yaw angle θy. Thus, they differ in that they react discontinuously so as to become smaller at the start of lowering Q of the lane yaw angle θy.

  What is important here is that the departure acceleration α increases when the lane yaw angle θy rises, so the time (actual TTLC) that the vehicle is expected to depart from the lane boundary after the alarm timing is expected. The time is shorter than the margin time for avoiding the lane departure estimated in advance, and when the lane yaw angle θy is lowered, the actual TTLC is longer than the margin time.

  For this reason, when the conventional calculation method is used, when the lane yaw angle θy changes, the alarm timing and the allowance time cannot be matched, whereas the lane departure warning device 1 increases the lane yaw angle θy. At the time and at the time of descent, since the reaction is always performed in advance to increase and decrease the DTLB_thre, it is possible to reduce the error between the actual TTLC and the margin time compared to before correction. The lane departure warning device 1 configured as described above operates in the same manner even when the traveling speed V changes.

  In the above embodiment, S110 is the image acquisition means, the vehicle speed sensor 2 is the speed detection means, S120, S130, S170 and S190 are the alarm control means, S140 is the departure speed calculation means, S160 is the distance threshold setting means, and S150 is The departure acceleration calculation means, the steering torque sensor 4 and the turn signal SW5 correspond to operation detection means, and S180 corresponds to an alarm prohibition means.

<Effect>
As described above, in the lane departure warning device 1 according to the present embodiment, the distance threshold (DTLB_thre) is variably set based on the change in the departure speed Vd, so that an appropriate warning is given at a timing according to the behavior of the vehicle. Can be performed.

  Therefore, according to the lane departure warning device 1 of the present embodiment, the consistency between the warning timing and the margin time can be maintained, the accuracy of the warning timing can be improved, and the driver feels uncomfortable or uneasy. The possibility of giving a feeling can be reduced.

  Further, since the lane departure warning device 1 applies a steering torque to the steering Sg in the direction opposite to the lane boundary at the time of warning, the driver can smoothly start the lane departure avoidance operation.

  Furthermore, since the lane departure warning device 1 repeatedly executes the lane departure warning processing at a predetermined control period Δt, the departure acceleration α (and hence DTLB_thre) can be easily calculated, and thus the control burden can be reduced. .

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, In the range which does not deviate from the summary of this invention, it is possible to implement in various aspects.

  For example, in the lane departure warning device 1 of the above embodiment, an alarm buzzer is generated as an audible alarm, an alarm lamp is generated as a visual alarm, and an alarm steering torque is generated as a tactile alarm. However, the present invention is not limited thereto, and a warning sound or image may be output in conjunction with a navigation device or the like, or the steering Sg may be vibrated.

  Moreover, although the lane departure warning apparatus 1 of the said embodiment is comprised so that the vehicle-mounted camera 3 may be provided, you may utilize the vehicle-mounted camera with which another vehicle-mounted apparatus is not an essential component.

  DESCRIPTION OF SYMBOLS 1 ... Lane departure warning device, 2 ... Vehicle speed sensor, 3 ... Car-mounted camera, 4 ... Steering torque sensor, 5 ... Blinker SW, 6 ... Steering torque application part, 7 ... Buzzer generation part, 8 ... Meter display part, 10 ... Control Department.

Claims (6)

Image acquisition means for acquiring a road image including a travel lane for the vehicle in an imaging range;
Speed detecting means for detecting the traveling speed of the vehicle;
Based on the road image acquired by the image acquisition means, recognizes a lane boundary representing the boundary line of the travel lane, and issues an alarm when the distance between the lane boundary and the vehicle is equal to or less than a preset distance threshold. Alarm control means to perform,
A deviation representing the speed at which the vehicle approaches the lane boundary based on the traveling speed detected by the speed detection means and the angle formed by the traveling direction of the vehicle specified from the road image and the lane boundary. A deviation speed calculating means for calculating a speed;
A distance threshold setting means for setting the distance threshold based on a departure speed calculated by the departure speed calculation means, an expected time fixed in advance so as to avoid a departure from the lane boundary, and a change in the departure speed;
A lane departure warning device comprising: The distance threshold value setting means sets the departure speed calculated by the departure speed calculation means to Vd, the expected time fixed in advance to avoid the departure of the lane boundary, TTLC, and a correction value based on the change in the departure speed A The following formula (I)
DTLB_thre = Vd × TTLC + A (I)
The lane departure warning device according to claim 1, wherein the value DTLB_thre calculated by the step is set as the distance threshold. A departure acceleration calculating means for calculating a departure acceleration representing an acceleration at which the vehicle approaches the lane boundary based on a change in the departure speed calculated by the departure speed calculating means;
The distance threshold setting means uses the departure acceleration calculated by the departure acceleration calculation means as α, and the following formula (II)
A = (α × TTLC ² ) / 2 (II)
The lane departure warning device according to claim 2, wherein the correction value is set to the value A calculated by the above equation. Operation detecting means for detecting a driving operation performed by a driver of the vehicle;
Based on the detection result by the operation detection means, when the driving operation is a lane change operation defined in advance, an alarm prohibiting means for prohibiting an alarm by the alarm control means;
The lane departure warning device according to any one of claims 1 to 3, further comprising:   The lane departure warning device according to claim 4, wherein the driving operation is an operation of a steering wheel or a winker.   The lane according to any one of claims 1 to 5, wherein the alarm by the alarm control means is an audible alarm, a visual alarm, a tactile alarm, or a combination thereof. Deviation warning device.