JP3246421B2 - Lane departure prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a vehicle by applying a steering control torque that the driver can easily overcome in addition to a steering torque applied by the driver in a direction to prevent the vehicle from deviating from the driving lane. The present invention relates to a lane departure prevention device for guiding lane departure prevention.

[0002]

2. Description of the Related Art In recent years, there has been developed a technology (driving guidance device) for grasping the position and attitude of a vehicle with respect to a traveling road, performing automatic driving control of a vehicle based on the position and guiding the driving of a driver. Is being developed. In the case of automatic cruise control, it is necessary to drive a car without relying on the driver at all, and various conditions such as the development of basic facilities (infrastructure) such as roads are premised on the practical application. Become.

[0003] On the other hand, in the case of a driving guide device, it is the driver who drives the car, and the driving guide device informs the driver of a driver's driving error and assists driving in a direction to eliminate the mistake. It is. Therefore, the driving guidance device has many technologies that can be realized even in the current road environment, and development of a driving guidance device with higher practicality is desired.

[0004] One of such driving guide devices is a lane departure prevention device. As this lane departure prevention device, there is a technology (Japanese Patent Laid-Open No. 63-214900) that issues a warning to a driving vehicle when a vehicle is inadvertently deviating from a driving lane. However, simply issuing a warning may not be effective for a driver who is dozing off, so that the steering control is more positively performed so that the vehicle travels at a certain position (for example, the center position) in the traveling lane. Technology (Japanese
Japanese Patent Application Laid-Open No.-104850) has also been proposed.

Further, in the case where the vehicle is controlled so as to maintain a fixed position in the traveling lane as described above, when the vehicle attempts to protrude from the traveling lane due to a temporary steering abnormality such as careless steering by a driver. If this control works, it may cause buffering with other vehicles. For this reason, in such a case, instead of returning the vehicle to a certain position in the driving lane, a technique of performing steering control so as to maintain a position biased to the side where the vehicle is going to protrude even in the driving lane ( JP-A-5-297939 has also been proposed.

[0006]

By the way, in the case of the lane departure prevention device which is one of the driving guide devices as described above,
In order to prevent the vehicle from deviating from the driving lane, it is necessary to apply a steering control torque through a steering actuator separately from the steering torque applied by the driver, but the steering control torque applied in this case is too small. The effect cannot be expected. On the other hand, if it is too large, the steering operation by the driver itself is hindered.

That is, the steering control torque for preventing the lane departure as the driving guide is for guiding the driver's steering operation or assisting the steering in the direction to eliminate the driver's steering error. And the driver is the driver. Accordingly, the main purpose of the application of the steering control torque in this case is to inform the driver that the vehicle is about to deviate from the driving lane, and the steering torque for actually holding the vehicle in the lane is I want to be added by the driver itself.

[0008] In particular, it is difficult to accurately determine whether the vehicle is about to deviate from the driving lane against the driver's will. For example, if the vehicle is about to deviate from the predetermined range in the driving lane, it can be determined that the vehicle is likely to deviate from the driving lane unexpectedly. Therefore, when the vehicle tries to deviate from the traffic lane, it is determined that the vehicle is deviating from the traffic lane.

When a control torque is generated by the steering actuator based on the above determination, the steering control is performed in a direction opposing the driver's steering operation when the driver intends to deviate from the traveling lane. Torque will be generated, and if the steering control torque is too large, it will interfere with the steering operation such as lane change by the driver's intention, and from this point too, make sure that the steering control torque does not become excessive. Want to.

[0010] When such a steering control torque is applied, it is generally considered that the driver responds according to the magnitude of the steering control torque. That is, when the steering control torque is increased, it is considered that the driver performs the steering operation for avoiding the lane departure relatively quickly. For this reason, the magnitude of the steering control torque does not simply become excessive, but also depends on the degree to which the vehicle is going to deviate from the traveling lane (for example, the amount of lateral displacement of the vehicle from the reference position of the traveling lane). Things to do
This is preferable for quickly and smoothly avoiding departure from the lane.

Further, the vehicle may be subjected to a lateral force depending on a road surface condition or a running condition, and such a lateral force affects the steering of the vehicle. For example, generally on a curved road,
Since lateral acceleration (so-called centrifugal force) acts on the vehicle according to the traveling speed and the turning radius, it is desired to set the magnitude and direction of the steering control torque in consideration of this point.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and does not hinder a driver's intentional steering operation, and is suitable in accordance with the degree of the vehicle trying to deviate from the lane, lateral acceleration, and the like. It is an object of the present invention to provide a lane departure prevention device that can appropriately guide a driver to avoid a lane departure by applying a proper steering control torque.

[0013]

Therefore, in the lane departure prevention apparatus according to the first aspect of the present invention, the lateral deviation amount calculating means calculates the lateral deviation amount of the traveling position of the vehicle from the reference position of the traveling lane, The control torque calculating means calculates a steering control torque based on the lateral displacement calculated by the lateral displacement calculating means. At this time, the control torque correction means of the control torque calculation means further corrects the control torque calculated based on the lateral displacement amount based on the lateral acceleration detected by the lateral acceleration detection means, and further corrects the control torque based on the lateral displacement amount and the lateral acceleration. Set a steering control torque large enough for the driver to easily overcome.

The control means controls the steering actuator of the vehicle such that the control torque set by the control torque calculation means is generated in a direction to reduce the lateral shift amount. In this way, when the driver's own vehicle is likely to deviate from the lane, the driver can easily overcome the steering torque applied in a direction to prevent the vehicle from deviating from the driving lane, and the steering according to the amount of lateral displacement of the vehicle and the lateral acceleration acting on the vehicle. Control torque is applied by the steering actuator to prevent the vehicle from departing from the lane.

According to a second aspect of the present invention, in the lane departure prevention apparatus according to the present invention, the correction amount calculating means provided in the control torque correcting means determines the correction amount of the control torque based on the lateral acceleration detected by the lateral acceleration detecting means. Is calculated, and the correction amount adding means adds this correction amount to the control torque calculated based on the lateral displacement amount calculated by the lateral displacement amount calculating means. As a result, even when the amount of lateral displacement of the vehicle cannot be detected due to the road surface condition, the correction amount set according to the lateral acceleration applied to the vehicle is provided by the steering actuator separately from the steering force of the driver, and robustness is secured. You.

Further, in the lane departure prevention device according to the present invention, the lateral deviation calculating means first calculates the current lateral deviation of the vehicle, and adds the current lateral deviation to the current traveling direction of the vehicle. The lateral displacement change amount of the vehicle after a predetermined time obtained from the road curve situation is added to predict the lateral displacement amount of the vehicle after a predetermined time. Then, the predicted lateral shift amount is output to the control torque calculating means.

As a result, the degree to which the vehicle is going to deviate is grasped in advance, and an appropriate amount of steering control torque is applied, so that accurate guidance for lane departure prevention according to the situation is provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 to 11 show a lane departure prevention device as an embodiment of the present invention.
The lane departure prevention device (also referred to as a lane guidance system) is provided to prevent a vehicle from deviating from a driving lane in an automobile. When there is a possibility that the steering torque is different from the steering torque applied by the driver by the steering actuator 21 provided in the vehicle as shown in FIG. 1 (this steering torque is used to distinguish it from the steering torque applied by the driver). Control torque) to warn the driver during steering of a lane departure through a steering wheel (hereinafter, also referred to as a steering wheel) 20.

Of course, the steering control torque itself is also
The main purpose of this steering control torque is to alert the driver through the steering system, and to correct the position of the vehicle that is likely to deviate from the lane. It should be performed by a driver's steering operation that recognizes that the vehicle is likely to depart from the lane due to the application of the control torque.

Therefore, the present lane departure prevention device is shown in FIG.
As shown in FIG. 7, in order to recognize the position of the host vehicle with respect to the traveling lane, the camera 2 serving as an image pickup means for picking up an image of the road condition ahead of the vehicle 1 and image information from the image information from the camera 2 are appropriately processed. Image information processing means 3 for recognizing the left and right white line positions on the road ahead, and the amount of lateral deviation Δ after a predetermined time from the reference position of the traveling lane (traveling lane) of the vehicle from the white line position image information by the image information processing means
A lateral displacement amount calculating means 4A for predicting and calculating Y is provided.

It should be noted that the lateral deviation amount ΔY corresponds to a determination parameter relating to the degree that the vehicle 1 is likely to depart from the lane. The lateral displacement amount calculating means 4A is provided as a functional element in the traveling lane estimating means 4 for estimating the relative position of the traveling lane (traveling lane) with respect to the own vehicle. Further, the lane departure prevention device is provided with the lateral displacement amount calculating means 4A.
Is calculated based on the lateral deviation amount (lateral deviation) ΔY, that is, the degree of departure from the lane.
c, a steering actuator 21 that can apply a steering control torque to the steering system separately from the steering torque applied by the driver, and a steering control torque Tc calculated by the control torque calculation unit 5. Is the lateral displacement Δ
Steering actuator 2 so that it occurs in the direction to decrease Y
1 is provided with a control means (controller) 6 for controlling the controller 1.

Further, a switch (SW) 23 for selecting the operation of the lane departure prevention device is provided. Therefore, if you want to operate this device, turn on the switch 23,
If you do not want to operate this device, turn off switch 23,
It can be selected according to the driver's preference.
Further, for example, in the instrument panel (instrument panel), when the switch 23 is turned on or when a control torque for preventing lane departure is applied, an operation display section 24 for displaying the control torque is provided. I have.

The image information processing means 3, the traveling lane estimating means 4 (lateral displacement calculating means 4A), the control torque calculating means 5, and the controller 6 are electronic control units having a CPU, an input / output interface, a ROM, a RAM, and the like. It is configured as a unit. First, recognition of the position of the host vehicle with respect to the traveling lane, that is, calculation of the lateral deviation amount ΔY of the host vehicle will be described.

The image information processing means 3 first takes in the original image 41 from the camera 2 and extracts a road white line from the original image 41, as shown in FIG. The image is converted into a two-dimensional image 42 as viewed from above. Next, the recognition of the white lines 12L and 12R is shown in FIG.
This will be described with reference to FIG. Here, the recognition of the white line 12L as the road side line at the left end of the traveling lane will be described. However, the same applies to the case where the white line 12R at the right end of the traveling lane is used as a reference. I will call it.

Next, in the image information recognizing means 3, FIG.
As shown in (a), the camera 2 provided in the vehicle 1 uses a camera 2 in a flat area to cover the area in front of the vehicle (for example, 5 m to 30 m).
m), the monochrome image information is fetched, and a part of the image in the vertical direction on the screen is omitted from the image information. Then, a plurality of horizontal lines 11 are set at regular intervals on this screen. The capture of the black-and-white image information is updated every minute control cycle. As shown in FIG. 3B, on each horizontal line 11, the left and right positions of the white line position on the previous screen are required. (Here, the left and right 50 pixels [do
t]) is set as the white line search area (processing target area) 10. For the first screen, the white line position on the straight road is used as the previous screen data.

Then, as shown in FIG. 3C, the brightness of each horizontal line is differentiated in the horizontal direction from the left. Reference numeral 14 in the drawing is a guardrail. By the way, a normal road surface has low luminance and a small change in luminance. On the contrary,
Since the brightness of the white line 12 is much higher than that of the normal road surface, when the brightness of the road is differentiated in this way, the luminance change is positive at the boundary point from the normal road surface to the white line 12, and the white line 12 changes to the normal road surface. Is obtained at the boundary point of which the luminance change becomes negative. An example of such differential data is shown in FIG.

Then, for each of the data of each horizontal line 11, peaks of the differential values appear in the order of plus and minus from the left, and the interval between the peaks is the white line 12.
Is extracted as a white line candidate as a combination that is considered to be appropriate (the interval from the positive peak to the negative peak is within 30 dots, for example).
As shown in FIG. 3E, the midpoint M is set to the white line candidate point 15.
Save as

Then, among these white line candidate points 15,
Only the point closest to the screen center is left as the final candidate point.
This means that, for example, when the vehicle 1 is traveling on the left side, the search area 1
The right side of 0 is a road surface with little change in normal luminance, and the white line candidate point 15 closest to this normal road surface can be determined as the white line 12. Therefore, further to the left of the white line 12,
Objects that cause noise (for example, guardrails 14)
Is present, the white line 12 can be reliably recognized from the image information captured by the camera 2.

Finally, as shown in FIG. 3F, the vertical continuity of the white line candidate points 15 in each horizontal line data is sequentially verified from the bottom of the screen. First, the inclination between the upper and lower ends of the white line 12 on the previous screen is calculated in advance.
Then, assuming that the lowest point 15A is the white line 12, it is verified whether or not the candidate point 15B on the horizontal line 11 which is only one line above is within the range of ± 50 dots of the inclination of the previous white line 12.

If the candidate point 15B falls within this range, it is regarded as a white line. If not, the candidate point 15B is rejected, and the coordinates interpolated from the above-mentioned inclination are regarded as the white line position. By performing the same operation for each horizontal line for this detection, a continuous white line 12 can be recognized. Such white line recognition work is continuously performed at a required cycle, and the recognition of the white line 12 is updated each time.

White line 12 as the roadside line at the right end of the traveling lane
The recognition of R is performed in the same manner. In the estimating means 4, the original image 41 recognized in each recognition cycle
The upper white lines 12R and 12L are converted into a two-dimensional image 42,
Based on the road centerline LC _R from traveling lane left to the road central line LC _L which can be estimated from the white line 12L traveling lane right edge of the white line 12R can estimate, and performs the estimation of the road centerline LC. And this road center line LC
, The lateral displacement amount ΔY ₀ and the deflection angle β at the present time are calculated by the lateral displacement amount calculating means 4A.

The declination β is, as shown in FIG. 4, the angle between the tangent to the curved road center line LC and the vehicle center line direction. Reference line position information at a first detection point (shown as perigee in the figure) which is a near detection level, and a second detection point (apogee in the figure, which is a predetermined distance L further from the vehicle 1 than this perigee) ) Is calculated from the reference line position information shown in FIG.

That is, the declination β is calculated as an angle between a straight line connecting the first detection point and the second detection point and the center line of the vehicle 1. The declination calculated in this way is a declination at an intermediate point (x mark in the figure) between the first detection point and the second detection point, and is a declination of a point at least a certain distance ahead of the vehicle 1. . In this example, the lateral distance between the vehicle center line (see point P1) and the road center line LC (see point LC1) at the first detection point closest to the vehicle (in the road width direction, that is, in the camera image direction). Is calculated as the lateral displacement amount (current lateral deviation) ΔY _{0 at the} present time. The second detection point is the first detection point.
A point (LC2, P2) that can be predicted to arrive after a predetermined time t from the detection point, that is, a point separated by a distance L obtained by multiplying the current vehicle speed V by the predetermined time t from the first detection point. First detection point (LC1) and second detection point (LC1)
The angle between the straight line connecting the detection point (LC2) and the center line (P1P2) of the vehicle 1 is calculated as the declination β.

The lateral displacement amount calculating means 4A multiplies the declination angle β calculated as described above by the vehicle speed V of the vehicle detected by the vehicle speed sensor 32 and a predetermined time t, and calculates the lateral deviation change amount Δy ( [Delta] y = calculates β × V × t), the predicted lateral deviation by adding the lateral deviation (lateral deviation) [Delta] Y ₀ at the present time to (hereinafter, referred to simply as the lateral shift amount) [Delta] Y (= [Delta] Y
₀ + β × V × t). Further, the curvature (road curvature) ρ of the traveling lane is estimated based on the image information of the road center line. The predetermined time t is set to an appropriate time in consideration of the driver's general operation speed of the steering wheel 20 and the speed of recognition of road conditions by the image information processing means 3 and the like. Further, it may be variable according to the vehicle speed V, and the predetermined time t may be set so that the distance L from the first detection point to the second detection point is constant.

The control torque calculating means 5 calculates the steering control torque Tc based on the amount of lateral displacement of the vehicle with respect to the reference position of the traveling lane (the center position of the road width) thus calculated.
In this apparatus, the steering control torque Tc
There is a feature in the setting. That is, the steering control torque T
c is different from the steering torque used for automatic steering, and the main purpose is to warn the driver. Since the position of the vehicle is corrected by the driver's steering operation, the steering control torque Tc is determined by the driver's steering torque. The size is limited to a size that does not hinder the operation, that is, a size that the driver can easily overcome.

Therefore, even when the steering control torque Tc is applied in a direction to avoid the departure when the vehicle is likely to deviate from the lane, it is sufficient if the driver tries to perform the steering operation in the direction deviating from the lane. You can do this. Thus, emergency steering for retreating the vehicle out of the traveling lane can be easily performed, and even if the steering control torque Tc is applied at the time of lane change, the lane change is not hindered. .

In particular, in the present apparatus, not only the torque for preventing the vehicle from laterally shifting (laterally shifting preventing torque), but also the torque (for facilitating the steering of the steering wheel against the lateral acceleration applied to the vehicle). The steering control torque is set based on the steering assist torque.
That is, as shown in FIG.
A function 5B for calculating a lateral slip prevention torque Ty and multiplying the lateral slip prevention torque Ty by a predetermined gain Ky (steering control torque calculating means for side slip) 5B, and a value Ky · Ty calculated by the calculating means 5B include: Function to perform correction according to the lateral acceleration applied to the vehicle (steering control torque correction means)
5A.

The steering control torque correcting means 5A calculates a steering assist torque Tg and multiplies the steering assist torque Tg by a predetermined gain Kg (correction amount calculating means) 5a.
And the correction values Kg and Tg calculated by the correction amount calculation means 5a are added to the steering control torques Ky and Ty corresponding to the lateral deviation to perform the correction, and the steering control torque Tc (= KyTy).
+ Kg · Tg).

In the correction using the steering assist torque in accordance with the lateral acceleration, when the vehicle is subjected to lateral acceleration, a steering force opposing the lateral acceleration is required. This is because the steering control for preventing the lane departure can be performed without a sense of incongruity even on a curved road or the like.
Generally, when the vehicle is traveling on a curved road, the centrifugal force acting in the lateral direction of the vehicle acts in the direction that hinders turning according to the curvature of the curve and the traveling speed of the vehicle. Steering assist torque Tg according to the magnitude
Is added to correct the steering control torque.

Incidentally, since the lateral acceleration G includes not only the centrifugal force but also other steering influence factors applied to the vehicle such as a cant on the road surface, the control torque correction based on the lateral acceleration G by the present apparatus is not performed on the curved road. Is corrected not only for the centrifugal force but also for various steering influence factors acting on the vehicle. Here, a description will be given of the lateral displacement prevention torque Ty. As shown in FIG. 5, the control torque calculation means 5 sets the lateral displacement prevention torque Ty in proportion to the lateral displacement amount ΔY.
Set y. In FIG. 5, the abscissa regarding the lateral deviation amount ΔY indicates a lateral deviation to the right in the right direction, and a lateral deviation to the left in the left direction. The left steering indicates left steering and the downward steering indicates right steering guiding the vehicle to the right side of the lane.

That is, as shown in FIG. 5, when the vehicle deviates from the road center line to the right side, a left-side steering lateral deviation prevention torque Ty for guiding the vehicle to the left side of the lane is set according to the lateral deviation amount ΔY. If the vehicle deviates to the left from the road center line, a lateral deviation prevention torque Ty for right steering that guides the vehicle to the right side of the lane is set according to the lateral deviation amount ΔY. However, in each case, the magnitude of the lateral displacement prevention torque Ty is limited by a constant value Tym. Here, when the magnitude of the lateral deviation amount ΔY becomes Y1, the magnitude of the lateral deviation prevention torque Ty is limited to a constant value Tym. This limits the driver to a size that can be easily overcome, as described above.

The correction amount calculating means 5a sets the steering assist torque Tg in proportion to the lateral acceleration G as shown in FIG. In FIG. 7, the abscissa regarding the lateral acceleration G indicates that the right direction indicates the effect of the lateral acceleration of the vehicle to the right.
The left direction indicates the effect of the lateral acceleration of the vehicle in the left direction, and the ordinate of the steering assist torque Tg indicates that the left direction in which the upward direction guides the vehicle to the left lane and the downward direction in which the vehicle guides the vehicle to the right lane. The right steering is shown.

As shown in FIG. 7, if lateral acceleration acts on the vehicle in the right direction, a left-hand steering assist torque Tg for guiding the vehicle to the left side of the lane is set in accordance with the lateral acceleration G. If lateral acceleration in the left direction acts, the steering assist torque T for right steering that guides the vehicle to the right side of the lane according to the lateral acceleration G.
Set g. However, in any case, the steering assist torque Tg
Is limited by a constant value Tgm. Here, if the magnitude of the lateral acceleration G becomes G1, the steering assist torque Tg
Is limited to a constant value Tgm. This limits the driver to a size that can be easily overcome, as described above.

The correction amount calculating means 5a multiplies the steering assist torque Tg thus calculated by an appropriate gain Kg. The correction amount adding means 5b performs correction in accordance with the lateral acceleration of the vehicle by adding the correction value to the steering control torque Ky · Ty corresponding to the lateral deviation calculated from the lateral deviation amount ΔY, and the steering control torque Tc (Tc = Ky × (Ty + Kg × Tg)
Is to be obtained.

The steering actuator 21 may be any actuator that can apply torque to the steering shaft. For example, as shown in FIG. 11, the steering actuator 21 is installed below the torsion bar (not shown) of the steering shaft 40 (on the power steering side). It may be constituted by the small electric torque motor 41 described above. In this case, the motor 4
1 is transmitted to the steering shaft 40 via a worm gear 42 including a worm 42a and a worm wheel 42b.
A torque limiter 43 is interposed between b and the steering shaft 40. The torque limiter 43 allows the driver to easily operate the handle 20 even if the motor 41 is stuck. In addition, the motor 41 has a maximum torque set to a necessary minimum, so that even if a failure occurs in the controller 6, an excessive steering load is not applied to the driver.

The output of the control torque calculation information is provided between the control torque calculation means 5 and the controller 6 such that the control torque actually exerted by the steering actuator 21 continues smoothly without sudden change. A low-pass filter 25 for performing a smoothing process is provided. The lane departure prevention device as one embodiment of the present invention is configured as described above.
Is performed as shown in FIG.

That is, it is determined whether or not the control switch 23 is on (step S10). If the control switch 23 is not on, the lane departure prevention process is not performed. If the control switch 23 is on, step S20 is performed. The following processing is performed. That is, first, the control torque calculating means 5 calculates a control torque according to the lateral displacement amount (step S20), and the control torque correcting means 5A corrects the control torque based on the lateral acceleration (step S30). Then, the steering actuator 21 is operated with a control amount corresponding to the control torque corrected based on the lateral acceleration, and a display signal is output to the operation display unit 24 (step S40).

The above processing will be described with reference to the block diagram of FIG. 10. In the driving lane, the driver side makes a proper judgment while visually recognizing this, and performs the steering operation. On the other hand, the lane departure prevention device (lane guidance system) first performs lane recognition for the traveling lane by image recognition through the camera 2 and performs a predetermined time from the reference position of the vehicle lane (here, the road center line LC). A lateral displacement amount ΔY is calculated later, and a lateral displacement prevention torque Ty is calculated from the lateral displacement amount ΔY. further,
The steering assist torque Tg is calculated from the lateral acceleration G detected through the lateral acceleration sensor 31. The steering control torque Tc is calculated by adding the steering assist torque Tg to the lateral displacement prevention torque Ty, and the steering actuator 21 is operated based on the steering control torque.

As a result, the steering torque of the driver and the control torque for steering by the steering actuator 21 are added and transmitted to the steered wheels 22 via the power steering device to steer the steered wheels 22. is there.
More specifically, when calculating the control torque, it is necessary to first calculate a lateral shift amount ΔY, which is an index of how much the vehicle deviates from the traveling lane after a predetermined time. In the present device, first, the relative position of the traveling lane (traveling lane) with respect to the own vehicle is estimated by the traveling lane estimating means 4, and the current lateral deviation amount ΔY ₀ is calculated based on the estimated position. Here, based on the image information from the camera 2, the lateral distance (the road width direction, the lateral distance of the camera image) between the vehicle center line and the road center line LC at the point (first detection point) closest to the vehicle based on the image information. Is calculated as a lateral shift amount (lateral deviation) ΔY ₀ .

That is, in the present apparatus, white line recognition is performed for the white line 12L at the left end of the running lane and the white line 12R at the right end of the running lane. Position (in other words, the position of the vehicle with respect to the traveling lane) is estimated.
The recognition of R will be described by taking the left white line 12L as an example.

First, as shown in FIG.
On a level ground in front of the vehicle (for example, 5 m to 30 m).
The monochrome image information m) is fetched at every minute control cycle, and a plurality of horizontal lines 11 are set at regular intervals on this screen at each cycle. Then, as shown in FIG.
On each horizontal line 11, a required range (for example, left and right 50 pixels [do]) of the white line position on the previous screen
t]) is set as the white line search area (processing target area) 10. In the initial screen, a white line position on a straight road is used as previous screen data.

From such image information, as shown in FIG. 3 (c), the brightness of each horizontal line is differentiated in the horizontal direction from the left, respectively, and the differential data of each such horizontal line [FIG.
From the left], the peaks of the differential value appear in the order of plus and minus from the left, and the interval between the peaks is considered to be appropriate as the white line 12 (the interval from the plus peak to the minus peak is, for example, within 30 dots). ) Are extracted as white line candidates, and the midpoint thereof is stored as a white line candidate point 15 (see FIG. 3E).

Then, among these white line candidate points 15,
Only the point closest to the screen center is left as the final candidate point.
By limiting the white line candidate point 15 to the one closest to the center of the screen in this way, an object that causes noise (for example, the guardrail 14 or a vehicle in another traveling lane) exists outside the white line 12. Even in this case, the white line 12 can be reliably recognized from the image information obtained by the camera 2.

Finally, as shown in FIG. 3F, the continuity of the white line candidate points 15 in each horizontal line data in the vertical direction is sequentially verified from the bottom of the screen. First, the inclination between the upper and lower ends of the white line 12 on the previous screen is calculated in advance. If the lowermost point 15A is the white line 12, the candidate point 15B on the upper horizontal line 11 is the inclination ± 5 of the previous white line 12.
0 dot is compared, and candidate point 1
If 5B falls within this range, it is regarded as a white line. If not, the candidate point 15B is rejected, and the coordinates calculated by interpolation from the above-mentioned inclination are regarded as the position of the white line.

By performing such an operation for each horizontal line, continuous white lines 12 can be recognized. Such white line recognition work is continuously performed at a required cycle, and the recognition of the white line 12 is updated each time.
In this manner, the white lines 12L, 1 on the left and right of the traveling lane are periodically repeated.
Recognition of 2R is performed in the same manner.

The estimating means 4 calculates each road center line L
C _L, roads and averages the LC _R centerline LC (= LC _L + _L
C _R ) is calculated. Road center line LC estimated in this way
Based on the lateral shift amount at the present time (horizontal deviation) Calculation of [Delta] Y ₀ is performed, the distance further, and the reference line position information at the first detection point away from the vehicle by a predetermined distance, further from the vehicle 1 than the perigee The declination β between the tangent to the curved road center line LC and the vehicle center line direction is calculated from the reference line position information at the second detection point separated by L.

Here, a point at which the second detection point can be predicted to arrive at a predetermined time t after the first detection point, that is, a distance L obtained by multiplying the current vehicle speed V by the predetermined time t from the first detection point. , The angle formed by the straight line connecting the first detection point and the second detection point and the center line of the vehicle 1 is calculated as the argument β. When the current lateral deviation amount ΔY ₀ and the declination β are calculated in this way, the traveling lane estimating means 4 further sets the declination β to the vehicle speed V detected by the vehicle speed sensor 32 and the predetermined time t. To calculate a lateral shift change amount Δy (Δy = β × V × t), add the current lateral shift amount (lateral deviation) ΔY ₀ to the predicted lateral shift amount ΔY (= ΔY ₀ + β) after a predetermined time t. × V × t) is calculated. Further, the curvature (road curvature) ρ of the traveling lane is calculated based on the calculated declination β.

The calculation of the lateral displacement prevention torque Ty by the control torque calculation means 5 is performed using a map, a table or an arithmetic expression as shown in FIG. The lateral displacement prevention torque Ty is
It is proportional to the amount of lateral displacement ΔY, and its magnitude is limited by a constant value. That is, as shown in FIG. 5, when the vehicle shifts to the right from the road center line, a left-side steering prevention torque Ty for guiding the vehicle to the left side of the lane is set in accordance with the side shift amount ΔY. If the vehicle shifts from the left to the right, a lateral deviation prevention torque Ty for right steering that guides the vehicle to the right side of the lane is set according to the lateral deviation amount ΔY, but in any case, the magnitude of the lateral deviation prevention torque Ty is limited by a constant value Tym. .

By limiting the side slip prevention torque Ty in this way, the side slip prevention torque Ty does not become excessive, and the magnitude of the side slip prevention torque Ty is maintained to such an extent that the driver can easily overcome. Therefore, by applying the lateral displacement prevention torque Ty, the driver senses the lane departure (departure from the road center line) and the direction of correction from the steering feeling of the steering wheel 20 and the like. The operation is performed promptly. The side slip prevention torque Ty itself is effective not only for warning the driver, but also for correcting the vehicle position. Further, the warning by the side slip prevention torque Ty is also effective for, for example, a driver of inattentive driving. In this case, the driver is encouraged to prevent inattentive driving while preventing a deviation from the lane.

The side slip prevention torque Ty is calculated not only by the current side slip amount ΔY ₀ but also by the side slip change amount Δy after a predetermined time t predicted from the vehicle speed V and the declination β in the current side slip amount ΔY _0. Since it is determined on the basis of the predicted lateral shift amount ΔY obtained by the addition, the degree of deviation of the vehicle is estimated in advance, and control can be performed to prevent the vehicle from deviating so that control delay does not occur. Guidance for departure prevention can be given accurately according to the situation.

Further, in the control torque calculating means 5, the control torque correcting means 5A calculates the control torque based on the lateral acceleration G as shown in FIG.
The steering assist torque Tg is calculated using a map, a table, or an arithmetic expression as shown in FIG.
Since the steering control torque Tc is set by adding the value obtained by adding the gain Kg to the steering control torque Ky · Ty corresponding to the lateral deviation, for example, when traveling on a curved road, the curvature of the curve, the vehicle While the lateral acceleration G acting on the vehicle according to the traveling speed and the cant of the road surface acts in the direction that hinders turning, correction is performed by the steering assist torque Tg according to the magnitude of the lateral acceleration G. As a result, the steering control torque T
There is also an effect that a situation in which c becomes large or small and gives a feeling of strangeness to the driver is eliminated.

Further, even when the lane recognition is not normal due to the road surface condition, the lateral acceleration G can be detected through the lateral acceleration sensor 31, so that the steering assist torque Tg can be applied. Lane guidance control can be continued. That is, robustness can be ensured. Further, the steering control torque Tc is smoothed by the low-pass filter 25 and output, so that the steering control torque generated by the steering actuator 21 smoothly continues without abrupt change, thereby preventing lane departure. There is also an advantage that the control of can be stabilized.

The calculation of the lateral deviation prevention torque Ty by the control torque computing means 5 is not limited to the characteristic shown in FIG. 5 with respect to the lateral deviation amount ΔY. In other words, the lateral displacement prevention torque Ty may be any value that acts to reduce the lateral displacement amount ΔY as it increases. In particular, in a region where the lateral displacement amount ΔY is small, the lateral displacement prevention torque Ty is set to 0, and in this region (dead zone) If the magnitude of the lateral deviation amount ΔY is larger than ()), the lateral deviation prevention torque Ty may be set according to the lateral deviation amount ΔY. In this case, the lateral deviation prevention torque Ty may be linearly increased with respect to the lateral deviation amount ΔY, or may be increased stepwise.

Further, as shown in FIG. 6, when the magnitude of the lateral deviation ΔY is larger than that of the dead zone, the lateral deviation Δ
A lateral displacement prevention torque T of a certain magnitude in the direction in which Y decreases
y1 may be set. In addition, the calculation of the steering assist torque Tg by the control torque correction means 5A is not limited to the characteristic shown in FIG.

That is, the steering assist torque Tg may be such that the larger the lateral acceleration G, the greater the tendency to eliminate this effect. For example, as shown in FIG. Assuming that the steering assist torque Tg is 0 and the lateral acceleration G is larger than this area (dead zone), the steering assist torque Tg may be set according to the lateral acceleration G.

Further, in the present embodiment, the vehicle center line direction is regarded as the traveling direction of the vehicle, and the amount of lateral deviation ΔY is calculated as the road center line L
Although the calculation is based on the declination β formed between the tangent of C and the direction of the vehicle center line, in a real vehicle, the traveling direction of the vehicle is determined by the steering wheel angle θ. Do not match. For this reason, a slight error occurs in the lateral displacement amount ΔY depending on the steering wheel angle θ.

Therefore, a predicted position of the vehicle reaching the predetermined time t after maintaining the current steering wheel angle θ is calculated, and a straight line connecting the predicted position and the current vehicle position is obtained as the vehicle traveling direction. Then, the angle between the traveling direction of the vehicle and the tangent to the road center line LC is defined as the corrected declination β ′, and a predetermined time t based on the corrected declination β ′.
Lateral deviation amount ΔY (ΔY = ΔY ₀ + β ′ × V ×
Calculate t).

By calculating the corrected deflection angle β 'taking into account the steering wheel angle θ in this manner, the accuracy of predicting the lateral deviation amount ΔY is improved, and a more appropriate steering control torque Tc according to the driving situation can be obtained. Can be granted. Further, in the present embodiment, the lateral acceleration G is detected through the lateral acceleration sensor 32. However, the curvature ρ of the curve calculated by the lateral displacement amount calculating means 4A and the vehicle speed V detected by the vehicle speed sensor 32 are used.
From this, the lateral acceleration G (G = ρ × V ² ) may be calculated.
However, in this case, it is desirable to use the lateral acceleration sensor 32 together in order to ensure robustness when the lane recognition is lost.

[0069]

As described above in detail, according to the lane departure prevention device of the present invention, when the host vehicle is about to deviate from the traveling lane, the driver's steering force is set in such a direction as to prevent this. Separately, a steering control torque that the driver can easily overcome is given by the steering actuator, so that the steering operation by the driver's intention is not hindered,
It is possible to provide guidance for preventing lane departure by applying steering control torque, and the steering control torque is set to a magnitude corresponding to the amount of lateral deviation of the vehicle and the lateral acceleration acting on the vehicle, so that the vehicle may deviate. It is possible to apply a steering control torque of an appropriate magnitude in accordance with the degree of an attempt to be made and in consideration of the curve condition of the road surface,
Guidance for lane departure prevention can be accurately given according to the situation.

According to the lane departure prevention device of the present invention, the steering control torque set according to the amount of lateral deviation of the vehicle is corrected by the correction set according to the lateral acceleration applied to the vehicle. The amount of correction is set according to the lateral acceleration applied to the vehicle, even if the lateral displacement of the vehicle cannot be detected due to the road surface condition. Since it is provided, robustness can be ensured.

Further, according to the lane departure prevention device of the present invention, not only the current lateral displacement amount of the vehicle, but also
Predict a lateral shift change amount of the vehicle after a predetermined time from the current traveling direction of the vehicle and a curve state of a road, and predict the lateral shift amount after a predetermined time by adding the lateral shift change amount to the current lateral shift amount. As a result, the degree to which the vehicle is going to deviate can be grasped in advance, an appropriate amount of steering control torque can be applied, and guidance for lane departure prevention can be given appropriately according to the situation. Can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a lane departure prevention device as one embodiment of the present invention.

FIG. 2 is a diagram illustrating image processing for driving lane recognition according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating traveling lane recognition according to an embodiment of the present invention in the order of (a) to (f).

FIG. 4 is a schematic plan view illustrating travel lane recognition.

FIG. 5 is a diagram showing an example of a map for setting a side slip prevention torque applied to the lane departure prevention device as one embodiment of the present invention.

FIG. 6 is a diagram showing another example of a map for setting a side slip prevention torque applied to the lane departure prevention device as one embodiment of the present invention.

FIG. 7 is a diagram showing an example of a setting map of a steering assist torque according to the lane departure prevention device as one embodiment of the present invention.

FIG. 8 is a diagram showing another example of a setting map of the steering assist torque according to the lane departure prevention device as one embodiment of the present invention.

FIG. 9 is a flowchart illustrating an operation of the lane departure prevention device as one embodiment of the present invention.

FIG. 10 is a block diagram illustrating the operation of the lane departure prevention device as one embodiment of the present invention.

FIG. 11 is a schematic diagram showing an example of a configuration of a steering actuator provided in the lane departure prevention device as one embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 vehicle 2 camera 3 image information processing means 4 traveling lane estimating means 4A lateral shift amount calculating means 5 control torque calculating means 5A control torque correcting means 5B steering control torque calculating means for side shift 5a correction amount calculating means 5b correction amount adding means 6 control Means (controller) 20 Steering wheel (handle) 21 Steering actuator 22 Steering wheel 23 Switch 24 Operation display unit 25 Low-pass filter 31 Lateral acceleration sensor (lateral acceleration detecting means) 32 Vehicle speed sensor 40 Steering shaft 41 Small electric torque motor 42 Worm gear 43 Torque Limiter LC Road Center Line

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-7-81602 (JP, A) JP-A-4-108081 (JP, A) JP-A-8-85469 (JP, A) JP-A-7-85 104850 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 6/00

Claims (3)

(57) [Claims] The present invention provides a steering control torque of a degree that can be easily overcome by a driver in addition to a steering torque applied by a driver in a direction to prevent the vehicle from deviating from a traveling lane. A lane departure prevention device that guides prevention of lane departure of the vehicle, comprising: a lateral deviation amount calculating unit that calculates a lateral deviation amount of a traveling position of the vehicle from a reference position of the traveling lane; Control torque calculating means for calculating a control torque based on the calculated lateral displacement amount; and control for controlling the steering actuator such that the control torque calculated by the control torque calculating means is generated in a direction to reduce the lateral displacement amount. And a lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle, wherein the control torque calculating means controls the control based on the lateral displacement amount. Characterized in that the control torque correction means for correcting, based torque to lateral acceleration detected by the lateral acceleration detecting means is provided, the lane departure prevention apparatus. 2. The control torque correction means, comprising: a correction amount calculation means for calculating a correction amount of the control torque based on the lateral acceleration detected by the lateral acceleration detection means; 2. The lane departure prevention device according to claim 1, further comprising a correction amount adding means for adding. 3. The lateral displacement amount calculating means adds a lateral displacement change amount of the vehicle after a predetermined time obtained from the current traveling direction of the vehicle and a curve state of a road to the current lateral displacement amount of the vehicle. Predicting the amount of lateral displacement of the vehicle after a predetermined time,
3. The lane departure prevention device according to claim 1, wherein the predicted lateral shift amount is output to the control torque calculating means.