JP4983089B2 - Lane departure prevention device - Google Patents

Description

  The present invention relates to a lane departure prevention apparatus for preventing a departure when a host vehicle is about to depart from a traveling lane.

In the lane departure prevention control disclosed in Patent Document 1, when there is a possibility that the host vehicle departs from the traveling lane, a braking force difference is applied to the left and right wheels, and a yaw moment is applied to the host vehicle. Is prevented from deviating from the driving lane.
JP 2000-33860 A

Here, in the lane departure prevention control disclosed in Patent Document 1, a camera is used as a lane recognition device for a lane division line forming a traveling lane. Note that the lane markings (including objects) include a solid white line, a dashed white line, botsdots (a bag hit on the road to indicate the lane marking), and the like.
However, it may be difficult for a camera as a lane line recognition device to recognize a lane line. For example, during the lane departure prevention control, a yaw moment is applied to the host vehicle, and thus the camera may temporarily make it difficult to recognize the lane line by rotating the host vehicle.
If the lane line cannot be accurately recognized, the yaw angle of the host vehicle with respect to the lane line that is the control target cannot be accurately detected in the lane departure prevention control due to erroneous recognition or detection delay of the lane line.
The subject of this invention is enabling it to detect correctly the yaw angle of the own vehicle with respect to a lane marking.

In order to solve the above-described problem, the present invention provides a lane departure prevention device that performs lane departure prevention control for preventing the own vehicle from deviating from the traveling lane based on a yaw angle of the own vehicle with respect to the traveling lane. Imaging means for imaging the travel lane, first yaw angle acquisition means for acquiring the yaw angle of the host vehicle with respect to the travel lane imaged by the imaging means, and lane departure prevention for preventing the host vehicle from departing from the travel lane Control means for performing control , yaw rate detecting means for detecting the yaw rate of the host vehicle, and the yaw rate detecting means at a reference yaw angle that is the yaw angle acquired by the first yaw angle acquiring means when the lane departure prevention control is started. a second yaw angle acquisition means that acquires the yaw angle by adding the integrated value of the detected yaw rate, the imaging state estimation hand to estimate the reduction in the imaging state of the travel lane by the imaging means When, wherein the imaging condition estimating means, when the lane departure prevention control is performed, the threshold for use in the imaging state to estimate whether or not the decrease, the imaging condition is decreased When the imaging state estimation unit estimates that the imaging state is reduced, the control unit uses the yaw angle acquired by the second yaw angle acquisition unit to correct the lane. It is characterized by performing departure prevention control.

  According to the present invention, in addition to the yaw angle of the host vehicle with respect to the travel lane obtained by imaging, by using the yaw angle of the host vehicle obtained by adding the integrated value of the yaw rate of the host vehicle to the reference yaw angle, Even when the traveling lane is difficult to recognize, the yaw angle of the host vehicle with respect to the traveling lane can be accurately detected.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
(Constitution)
The embodiment is a rear wheel drive vehicle equipped with the lane departure prevention apparatus according to the present invention. This vehicle is equipped with an automatic transmission and a conventional differential gear, and a braking device capable of independently controlling the braking force of the left and right wheels for both the front and rear wheels.
FIG. 1 is a schematic configuration diagram showing the present embodiment.
In the figure, reference numeral 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. It supplies to each wheel cylinder 6FL-6RR of each wheel 5FL-5RR. Further, a braking fluid pressure control unit 7 is interposed between the master cylinder 3 and each wheel cylinder 6FL-6RR, and the braking fluid pressure control unit 7 individually controls the braking fluid pressure of each wheel cylinder 6FL-6RR. It is also possible to control it.

The braking fluid pressure control unit 7 uses a braking fluid pressure control unit used for antiskid control and traction control, for example. The brake fluid pressure control unit 7 can control the brake fluid pressure of each of the wheel cylinders 6FL to 6RR independently, but when a brake fluid pressure command value is input from the braking / driving force control unit 8 described later, The brake fluid pressure is controlled according to the brake fluid pressure command value.
For example, the brake fluid pressure control unit 7 includes an actuator in the hydraulic pressure supply system. Examples of the actuator include a proportional solenoid valve capable of controlling each wheel cylinder hydraulic pressure to an arbitrary braking hydraulic pressure.

  The vehicle is provided with a drive torque control unit 12. The drive torque control unit 12 controls the drive torque to the rear wheels 5RL and 5RR which are drive wheels by controlling the operating state of the engine 9, the selected gear ratio of the automatic transmission 10, and the throttle opening of the throttle valve 11. To do. The drive torque control unit 12 controls the operating state of the engine 9 by controlling the fuel injection amount and ignition timing, and simultaneously controlling the throttle opening. The drive torque control unit 12 outputs the value of the drive torque Tw used for control to the braking / driving force control unit 8.

The drive torque control unit 12 can control the drive torque of the rear wheels 5RL and 5RR independently. When a drive torque command value is input from the braking / driving force control unit 8, the drive torque command unit 12 The drive wheel torque is controlled according to the value.
In addition, this vehicle is provided with an imaging unit 13 with an image processing function. The imaging unit 13 is provided for detecting the position of the host vehicle in the traveling lane for detecting the lane departure tendency of the host vehicle. For example, the imaging unit 13 is configured to capture an image with a monocular camera including a CCD (Charge Coupled Device) camera. The imaging unit 13 is installed in the front part of the vehicle.

The imaging unit 13 detects a lane division line that forms a travel lane from a captured image in front of the host vehicle, and detects a travel lane based on the detected lane marker. Here, the lane markings (including objects) to be detected include a solid white line, a broken white line, and botsdots.
Furthermore, the imaging unit 13 determines, based on the detected travel lane, an angle (yaw angle) φr formed between the travel lane of the host vehicle and the longitudinal axis of the host vehicle, a lateral displacement X from the center of the travel lane, and a travel lane curvature. β and the like are calculated. The imaging unit 13 outputs the calculated yaw angle φr, lateral displacement X, travel lane curvature β, and the like to the braking / driving force control unit 8.

In the present invention, a lane marking may be detected by a detection means other than image processing. For example, the lane marking may be detected by a plurality of infrared sensors attached to the front of the vehicle, and the traveling lane may be detected based on the detection result.
Further, the present invention is not limited to the configuration in which the traveling lane is determined based on the lane division line. In other words, when there is no lane line for recognizing the driving lane on the road, information on the road shape and surrounding environment obtained by image processing and various sensors, the driving range suitable for the vehicle and the driver May estimate the runway range in which the host vehicle should travel and determine the travel lane as the travel lane. For example, when there is no lane division line on the runway and both sides of the road are separated, the asphalt portion of the runway is determined as the travel lane. Moreover, what is necessary is just to determine a driving lane in consideration of the information, when there is a guardrail, a curb, etc.

Further, the traveling lane curvature β may be calculated based on a steering angle δ of the steering wheel 21 described later.
The vehicle is provided with a navigation device 14. The navigation device 14 detects the longitudinal acceleration Yg or lateral acceleration Xg generated in the host vehicle or the yaw rate φ ′ generated in the host vehicle. The navigation device 14 outputs the detected longitudinal acceleration Yg, lateral acceleration Xg, and yaw rate φ ′ to the braking / driving force control unit 8 together with the road information. Here, the road information includes road type information indicating the number of lanes and whether the road is a general road or a highway.

Each value may be detected by a dedicated sensor. That is, the longitudinal acceleration Yg and the lateral acceleration Xg may be detected by the acceleration sensor, and the yaw rate φ ′ may be detected by the yaw rate sensor.
The vehicle is also provided with a radar 16 for measuring the distance between the host vehicle and the front obstacle by sweeping laser light forward and receiving the reflected light from the preceding obstacle. ing.
The radar 16 then outputs information on the position of the front obstacle to the braking / driving force control unit 8. The detection result by the radar 16 is used for processing in follow-up running control (cruise control), a rear-end collision speed reduction brake device, and the like.

  Further, in this vehicle, a master cylinder pressure sensor 17 that detects an output pressure of the master cylinder 3, that is, master cylinder hydraulic pressures Pmf and Pmr, and an accelerator opening sensor 18 that detects an accelerator pedal depression amount, that is, an accelerator opening θt. , A steering angle sensor 19 for detecting a steering angle (steering angle) δ of the steering wheel 21, a direction indicating switch 20 for detecting a direction indicating operation by a direction indicator, and a rotation speed of each of the wheels 5FL to 5RR, so-called wheel speed Vwi. Wheel speed sensors 22FL to 22RR for detecting (i = fl, fr, rl, rr) are provided. Detection signals detected by these sensors and the like are output to the braking / driving force control unit 8.

  When the detected vehicle traveling state data has left and right directions, the right direction is the positive direction in all cases. That is, the yaw rate φ ′, the lateral acceleration Xg, and the yaw angle φr are positive values when turning right, and the lateral displacement X is a positive value when deviating from the center of the traveling lane to the right. The longitudinal acceleration Yg takes a positive value during acceleration and takes a negative value during deceleration.

Next, calculation processing performed by the braking / driving force control unit 8 will be described.
FIG. 2 shows a calculation processing procedure performed by the braking / driving force control unit 8. The arithmetic processing is executed by timer interruption every predetermined sampling time ΔT every 10 msec., For example. Although no communication process is provided in the process shown in FIG. 2, information obtained by the calculation process is updated and stored in the storage device as needed, and necessary information is read out from the storage device as needed.

  As shown in FIG. 2, when the process is started, first, in step S1, various data are read from each sensor, controller, and control unit. Specifically, the longitudinal acceleration Yg, lateral acceleration Xg, yaw rate φ ′ and road information obtained by the navigation device 14, road speed Vwi, steering angle δ, accelerator opening θt, master cylinder hydraulic pressure detected by each sensor Pmf, Pmr, direction switch signal, driving torque Tw from the driving torque control unit 12, yaw angle φr, lateral displacement X and travel lane curvature β from the imaging unit 13 are read.

Subsequently, in step S2, the vehicle speed V is calculated. Specifically, the vehicle speed V is calculated by the following equation (1) based on the wheel speed Vwi read in step S1.
For front wheel drive V = (Vwr1 + Vwrr) / 2
For rear wheel drive V = (Vwfl + Vwfr) / 2
... (1)
Here, Vwfl and Vwfr are the wheel speeds of the left and right front wheels, and Vwrl and Vwrr are the wheel speeds of the left and right rear wheels. That is, in the equation (1), the vehicle speed V is calculated as an average value of the wheel speeds of the driven wheels. In this embodiment, since the vehicle is a rear-wheel drive vehicle, the vehicle speed V is calculated from the latter equation, that is, the wheel speed of the front wheels.

The vehicle speed V calculated in this way is preferably used during normal travel. For example, when an ABS (Anti-lock Brake System) control or the like is operating, an estimated vehicle speed estimated in the ABS control is used as the vehicle speed V. In addition, a value used for navigation information in the navigation device 14 may be used as the vehicle speed V.
Subsequently, in step S3, the yaw angle used in the lane departure tendency determination used in the lane departure tendency determination in the post-processing step S4 (hereinafter referred to as the lane departure tendency determination yaw angle) is set. Specifically, The lane departure tendency determination yaw angle is set by the processing procedure shown in FIG.

As shown in FIG. 3, when the process is started, first, in step S11, using the travel lane curvature β, the lateral acceleration Xg, and the yaw rate φ ′ read in step S1, the camera recognition state is determined by the following equation (2). A utility value _St is calculated.
S _t = N _j / (β · Xg · φ ′) (2)
Here, N _j is a value corresponding to the type of lane marking (including objects) such as a solid white line, a broken white line, and botsdots. The lane marking type correspondence value N _j gradually decreases in the order of a solid white line, a dashed white line, and botsdots. A botsdot is a saddle that has been struck on a road in order to recognize a driving lane.

According to equation (2), the larger the division mark type corresponding values N _j, camera recognizes state determination value S _t increases, lane curvature beta, as the lateral acceleration Xg and yaw rate φ'decreases, camera recognizes The state determination value _St increases.
Subsequently, in step S12, it is determined whether or not the departure determination flag Fout is ON. The departure determination flag Fout is a value set in step S4, which is post-processing. Therefore, the departure determination flag Fout used in the determination is the departure determination flag Fout at the time of the previous processing. The case where the departure determination flag Fout is set to ON is a case where there is a lane departure tendency, and the case where the departure determination flag Fout is set to OFF is a case where there is no lane departure tendency.

If the departure determination flag Fout is ON (Fout = ON), the process proceeds to step S13. If not (Fout = OFF), the process proceeds to step S14.
In step S13, in order to increase the correction camera recognition condition determining threshold value _{W th,} adds the addition value _{W f0} camera recognition condition determining threshold value _{W th (W th = W th} + W f0). Then, the process proceeds to step S14.

At step S14, and compares the calculated camera detection mode determination value S _t and the camera detection mode determination threshold W _th at step S11. If step S13 is performed, the camera recognition state determination threshold value W _th becomes a value corrected for increase (W _th = W _th + W _f0 ). Here, when the camera recognizes a state determination value _{S t} is less than the detection mode determination threshold _{W th (S t <W th} ), the process proceeds to step S15, otherwise _{(S t} ≧ _{W th),} step S16 Proceed to

In step S15, to set the camera recognized state determination flag _{N f} to 1 _(N f = 1), then the process proceeds to step S17, in step S16, the camera detection mode determination flag _{N f} is set to 0 _(N f = 0), and then the process proceeds to step S17.
In step S17, it is determined whether or not the camera recognition state determination flag _Nf is 1. If the camera recognition state determination flag N _f is 1 (N _f = 1), the process proceeds to step S18. Otherwise (N _f = 0), the process proceeds to step S19.

In step S18, it is determined whether or not the camera recognition state determination flag N _fz1 at the time of the previous process is zero. If the camera recognition state determination flag N _fz1 at the time of the previous process is 0 (N _fz1 = 0), the process proceeds to step S20. Otherwise (N _fz1 = 1), the process proceeds to step S21.
In step S20, the yaw angle obtained from the imaging unit 13 (hereinafter referred to as the yaw angle detection value) φr is set as the lane departure tendency determination yaw angle φc (φc = φr). Then, the process shown in FIG. 3 ends (step S3 ends and the process proceeds to step S4).

In step S21, the lane departure tendency determination yaw angle φc is calculated by the following equation (3).
φc = φc _z1 + φ ′ · (t _now −t _z1 ) (3)
Here, φc _z1 is the lane departure tendency determining yaw angle φc at the time of the previous processing. _{Also, t now} is the time of setting of the lane departure tendency determining yaw angle .phi.c (current processing _{time), t z1} is the time of the previous processing, _i.e., t now _{-t z1} at sampling time is there. As a result, the current lane departure tendency determination yaw angle as a value obtained by adding the yaw angle (φ ′ · (t _now −t _z1 )) considering the sampling time to the lane departure tendency determination yaw angle φc at the time of the previous processing. φc is obtained. The lane departure tendency determination yaw angle φc set in step S21 is hereinafter referred to as a corrected lane departure tendency determination yaw angle φc. Then, the process shown in FIG. 3 ends (step S3 ends and the process proceeds to step S4).

On the other hand, in step S19 the camera detection mode determination flag N _f proceeds in the case of 1, it sets a yaw angle detected value [phi] r to the lane departure tendency determining yaw angle φc (φc = φr). The lane departure tendency determination yaw angle φc set in step S20 is hereinafter referred to as an uncorrected lane departure tendency determination yaw angle φc. Then, the process shown in FIG. 3 ends (step S3 ends and the process proceeds to step S4).
Subsequently, in step S4, a lane departure tendency is determined.

FIG. 4 shows the procedure of this determination process. FIG. 5 illustrates the definition of values used in this process.
As shown in FIG. 4, first, in step S31, an estimated lateral displacement Xs of the lateral position of the vehicle center of gravity after a predetermined time T is calculated. Specifically, the estimated lateral displacement Xs is calculated by the following equation (4) using the lane departure tendency determining yaw angle φc, the traveling lane curvature β, the current vehicle lateral displacement X0, and the vehicle speed V obtained in step S2. Is calculated.
Xs = Tt · V · (φc + Tt · V · β) + X0 (4)

Here, Tt is the vehicle head time for calculating the forward gaze distance, and when this vehicle head time Tt is multiplied by the own vehicle speed V, it becomes the front gaze distance. That is, the estimated lateral displacement from the center of the traveling lane after the vehicle head time Tt becomes the estimated lateral displacement Xs in the future.
Here, the lane departure tendency determination yaw angle φc in the equation (4) is the corrected lane departure tendency determination yaw angle φc or the lane departure tendency determination yaw angle φc set in step S3. According to the equation (4), the estimated lateral displacement Xs increases as the lane departure tendency determination yaw angle φc increases.

Subsequently, in step S32, departure determination is performed. Specifically, comparing the estimated lateral displacement Xs with a predetermined departure-tendency threshold value X _L.
Here, departure-tendency threshold value X _L is generally the vehicle is a value that can be grasped to be in the lane departure tendency is obtained in experiments or the like. For example, departure-tendency threshold value X _L is a value indicating the position of the travel path of the boundary line is calculated by the following equation (5).
X _L = (L−H) / 2 (5)
Here, L is the lane width, and H is the width of the vehicle. The lane width L is obtained by the imaging unit 13 processing the captured image. Further, the vehicle position may be obtained from the navigation device 14 or the lane width L may be obtained from the map data of the navigation device 14.

In FIG. 5, departure-tendency threshold value X _L has been set within the travel lane of the vehicle, the present invention is not limited thereto, it may be set outside of the travel lane. Also, the departure tendency determination threshold value X _L is not limited to that in which the departure tendency is determined before the own vehicle deviates from the traveling lane, but for example, the departure tendency is determined after at least one of the wheels has deviated from the lane. May be set.
In this step S32, when the estimated lateral displacement Xs is greater than or equal to the threshold X _L for determining the tendency to deviate (| Xs | ≧ X _L), determines that there is a lane departure tendency, the estimated lateral displacement Xs is for judging the departure tendency threshold If it is less than the value _{X L (| Xs | <X} L), it determines that there is no lane departure tendency.

Subsequently, in step S33, a departure determination flag Fout is set. That is, if it is determined in step S32 that there is a tendency to depart from the lane (| Xs | ≧ X _L ), the departure determination flag Fout is turned ON (Fout = ON). Further, in step S32, when it is determined that no lane departure tendency _{(| Xs | <X L)} , turns OFF the departure flag Fout (Fout = OFF).

By the process of step S32 and step S33, for example, the vehicle is going away from the center of the lane, when the estimated lateral displacement Xs is equal to or greater than the departure-tendency threshold value _{X L (| Xs | ≧ X} L), departure The determination flag Fout is turned on (Fout = ON). Further, the vehicle (host vehicle Fout = ON state) is gradually restored to the lane center side, when the estimated lateral displacement Xs becomes less than departure-tendency threshold value _{X L (| Xs | <X} L ), The departure determination flag Fout is turned off (Fout = OFF). For example, when there is a tendency to deviate from the lane, the departure determination flag Fout is changed from ON to OFF if braking control for avoiding departure described later is performed or the driver himself performs an avoidance operation.

Subsequently, in step S34, the departure direction Dout is determined based on the lateral displacement X. Specifically, when the vehicle is laterally displaced from the center of the lane to the left, the direction is set as the departure direction Dout (Dout = left), and when the vehicle is laterally displaced from the center of the lane to the right, the direction is changed to the departure direction Dout. (Dout = right).
As described above, the lane departure tendency is determined in step S4.

Subsequently, in step S5, the driver's intention to change lanes is determined. Specifically, the driver's intention to change the lane is determined as follows based on the direction switch signal and the steering angle δ obtained in step S1.
If the direction indicated by the direction switch signal (the blinker lighting side) is the same as the direction indicated by the departure direction Dout obtained in step S4, it is determined that the driver has intentionally changed the lane, and the departure determination flag Fout is changed to OFF (Fout = OFF). That is, it is changed to the determination result that there is no lane departure tendency.

When the direction indicated by the direction switch signal (the blinker lighting side) is different from the direction indicated by the departure direction Dout obtained in step S4, the departure determination flag Fout is maintained and the departure determination flag Fout is kept ON. (Fout = ON). That is, the determination result that there is a tendency to depart from the lane is maintained.
When the direction indicating switch 20 is not operated, the driver's intention to change the lane is determined based on the steering angle δ. That is, when the driver is steering in the departure direction, the driver is conscious when both the steering angle δ and the change amount of the steering angle (change amount per unit time) Δδ are equal to or greater than the set value. And the departure determination flag Fout is changed to OFF (Fout = OFF).

The driver's intention may be determined based on the steering torque.
Thus, when the departure determination flag Fout is ON, the departure determination flag Fout is maintained ON when the driver has not intentionally changed the lane.
Subsequently, in step S6, when the departure determination flag Fout is ON, a sound output or display output is performed as an alarm for preventing lane departure.

As will be described later, when the departure determination flag Fout is ON, the application of the yaw moment to the host vehicle is started as the lane departure prevention control. Therefore, the alarm is output simultaneously with the application of the yaw moment to the host vehicle. However, the alarm output timing is not limited to this, and may be earlier than, for example, the start timing of the yaw moment application.
Subsequently, in step S7, a target yaw moment Ms to be given to the vehicle as lane departure prevention control is calculated.

Specifically, the target yaw moment Ms is calculated by the following equation (6) based on the estimated lateral displacement Xs obtained and lateral displacement limit distance X _L in the step S4.
Ms = K1 · K2 · (| Xs | −X _L ) (6)
Here, K1 is a proportional gain determined from vehicle specifications, and K2 is a gain that varies according to the vehicle speed V. FIG. 6 shows an example of the gain K2. As shown in FIG. 6, for example, the gain K2 has a large value in the low speed range, and decreases when the vehicle speed V reaches a certain value. Then, when the vehicle speed V reaches a certain vehicle speed V, the gain K2 decreases at a constant value. It becomes.

According to the equation (6), the larger the difference between estimated lateral displacement Xs and lateral displacement limit distance X _L is, target yaw moment Ms becomes larger.
The target yaw moment Ms is calculated when the departure determination flag Fout is ON, and the target yaw moment Ms is set to 0 when the departure determination flag Fout is OFF.
Subsequently, in step S8, a target brake hydraulic pressure for each wheel is calculated. That is, the final braking fluid pressure is calculated based on whether or not the lane departure prevention control is performed. Specifically, it is calculated as follows.

When the departure determination flag _Fout is OFF, that is, when a determination result that there is no lane departure tendency is obtained, as shown in the following equations (7) and (8), the target braking hydraulic pressure Psi (i) of each wheel = Fl, fr, rl, rr) are set to the brake fluid pressures Pmf, Pmr.
Psfl = Psfr = Pmf (7)
Psrl = Psrr = Pmr (8)
Here, Pmf is the brake fluid pressure for the front wheels. Further, Pmr is the braking fluid pressure for the rear wheels, and is a value calculated based on the braking fluid pressure Pmf for the front wheels in consideration of the front-rear distribution. For example, if the driver is performing a brake operation, the brake fluid pressures Pmf and Pmr are values corresponding to the operation amount of the brake operation.

On the other hand, when the departure determination flag _Fout is ON, that is, when a determination result that there is a lane departure tendency is obtained, based on the target yaw moment Ms calculated in step S7, the front wheel target braking hydraulic pressure difference ΔPsf and the rear wheel A target braking hydraulic pressure difference ΔPsr is calculated. Specifically, the target braking hydraulic pressure differences ΔPsf and ΔPsr are calculated by the following equations (9) to (12).
When | Ms | <Ms1, ΔPsf = 0 (9)
ΔPsr = Kbr · | Ms | / T (10)
When | Ms | ≧ Ms1 ΔPsf = Kbf · (| Ms | −Ms1) / T (11)
ΔPsr = Kbr · Ms1 / T (12)
Here, Ms1 represents a setting threshold value. T represents a tread. This tread T is set to the same value before and after for simplicity. Kbf and Kbr are conversion coefficients for the front wheels and the rear wheels when the braking force is converted into the braking hydraulic pressure, and are determined by the brake specifications.

  Thus, the distribution of the braking force generated by the wheels is determined according to the magnitude of the target yaw moment Ms. That is, when the target yaw moment Ms is less than the setting threshold value Ms1, the front wheel target braking hydraulic pressure difference ΔPsf is set to 0, a predetermined value is given to the rear wheel target braking hydraulic pressure difference ΔPsr, and a braking force difference is generated between the left and right rear wheels. In addition, when the target yaw moment Ms is equal to or greater than the setting threshold value Ms1, a predetermined value is given to each target braking hydraulic pressure difference ΔPsr, ΔPsr, and a braking force difference is generated between the front, rear, left and right wheels.

If the departure determination flag Fout is ON, the final target braking fluid pressure Psi (i = fl, fr) of each wheel is calculated based on the departure direction Dout using the calculated target braking fluid pressure differences ΔPsf, ΔPsr. , Rl, rr). That is, when the departure direction Dout is left (Dout = left), that is, when there is a lane departure tendency with respect to the left lane, the target braking fluid pressure Psi (i = fl, fr, rl) of each wheel is calculated according to the following equation (13). , Rr).
Psfl = Pmf
Psfr = Pmf + ΔPsf
Psrl = Pmr
Psrr = Pmr + ΔPsr
... (13)

Further, when the departure direction Dout is right (Dout = right), that is, when there is a lane departure tendency with respect to the right lane, the target braking fluid pressure Psi (i = fl, fr, rl) of each wheel according to the following equation (14) , Rr).
Psfl = Pmf + ΔPsf
Psfr = Pmf
Psrl = Pmr + ΔPsr
Psrr = Pmr
(14)
According to the equations (13) and (14), the braking force difference between the left and right wheels is generated so that the braking force of the wheel on the lane departure avoidance side is increased.
Further, as shown in the equations (13) and (14), the brake operation by the driver, that is, the target brake fluid pressure Psi (i = fl, fr, rl) of each wheel in consideration of the brake fluid pressures Pmf, Pmr. , Rr). Then, the braking / driving force control unit 8 uses the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) calculated for each wheel thus calculated as a braking fluid pressure command value to the braking fluid pressure control unit 7. Output.

(Operation)
The operation is as follows.
While the vehicle is running, various data are read (step S1), the vehicle speed V is calculated (step S2), and the lane departure tendency determination yaw angle φc is set (selected) (step S3). Subsequently, a future estimated lateral displacement (estimated deviation value) Xs is calculated based on the set lane departure tendency determination yaw angle (yaw angle without correction lane departure tendency determination or corrected lane departure tendency determination yaw angle) φc. At the same time, the lane departure tendency is determined (departure determination flag Fout is set) based on the calculated estimated lateral displacement Xs (step S4), and the determination result of the lane departure tendency (departure determination flag Fout) is sent to the driver. Is corrected based on the intention to change the lane (step S5). Based on the determination result of the lane departure tendency, a warning is output (step S6).

Then, estimated lateral displacement Xs and lateral displacement limit distance X _L and (step S7) calculates the target yaw moment Ms on the basis of, based on the state of departure flag Fout, each wheel based on the target yaw moment Ms The target brake hydraulic pressure Psi (i = fl, fr, rl, rr) is calculated, and the calculated target brake hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated as a brake fluid pressure control unit 7. (Step S8). Thereby, a yaw moment is given to the own vehicle in accordance with the lane departure tendency of the own vehicle.

(Function and effect)
Next, functions and effects will be described.
As described above, (when the judgment at "Yes" in the step S14) when the camera recognizes a state determination value S _t is less than the detection mode determination threshold W _th, a camera recognition condition determination flag N _f 1 In addition to setting (N _f = 1, step S15), if the camera recognition state determination flag N _fz1 at the time of the previous processing is 0 (if the determination in step S17 is “Yes”, the determination in step S18 is “ In the case of “Yes”, the yaw angle detection value φr obtained from the imaging unit 13 is set to the lane departure tendency determination yaw angle φc used this time (step S20). Then, (in the case of "Yes" in the determination of the step S14) when the camera recognizes a state determination value _{S t} is less than the detection mode determination threshold _{W th,} camera recognizes state determination flag _{N fz1} previous time If it is 1 (if “No” in the determination in step S18), the yaw angle (φ ′ · (t _now −t _z1 )) in consideration of the sampling time in the yaw angle φc for lane departure tendency determination at the time of the previous processing. As a value obtained by adding the lane departure tendency determination yaw angle φc to be used this time (step S21).

Yaw Thereby, from the time when the camera recognizes a state determination value S _t is less than the recognition condition determining threshold value W _th, the yaw angle detected value φr obtained from the imaging unit 13 as an initial value, considering sampling time The lane departure tendency determination yaw angle φc is corrected by adding the angle (φ ′ · (t _now −t _z1 )). That is, the yaw angle detected value φr is the initial value, by adding the integral value of the period of the yaw rate φ'camera detection mode determination value S _t is less than the detection mode determination threshold W _th, lane departure A tendency determination yaw angle φc is calculated. The yaw rate φ ′ used at this time may be a value obtained at the time of each process, or may be a fixed value, for example, a value at the time of starting correction (when the yaw angle detection value φr is set as an initial value).

On the other hand, the camera detection mode determination value S _t partial line type corresponding values N _j, lane curvature beta, (see the equation (2)) is calculated based on the lateral acceleration Xg and yaw rate the? ', Camera recognizes state judgment value S _t, the more division lines type correspondence value N _j becomes smaller, or the driving lane curvature beta, the lateral acceleration Xg and yaw rate φ'increases, decreases. That is, when the traveling lane curvature β, the lateral acceleration Xg and the yaw rate φ ′ increase, or the lane line type corresponding value N _j decreases (the lane line is in the order of a solid white line, a dashed white line, and a botsdot If the degree of recognition of the lane markings by the imaging unit 13 is predicted to be low, the camera recognition state determination value _St is decreased.

Therefore, a condition to correct the lane departure tendency determining yaw angle .phi.c, and when the camera recognizes a state determination value S _t is less than the detection mode determination threshold W _th the recognition of lane markings by the imaging unit 13 In such a case, the yaw angle detection value φr obtained from the imaging unit 13 is used as an initial value, and the yaw angle (φ ′ · (t _now −t _z1 )) is added to correct the lane departure tendency determination yaw angle φc. The lane departure determination is performed based on the lane departure tendency determination yaw angle (corrected lane departure tendency determination yaw angle) φc.

On the other hand, when the camera recognition state determination value _{St is} greater than or _equal to the recognition state determination threshold value W _th (when “No” is determined in Step S14), that is, the lane marking is recognized by the imaging unit 13. When the degree is predicted to be high, the lane departure tendency determination yaw angle φc (the step S19, the uncorrected lane departure tendency determination yaw angle φc) that is the yaw angle detection value φr obtained from the imaging unit 13 is used. Lane departure judgment.
Note that after the camera detection mode determination value S _t is less than the threshold value for W _th determination recognized state, if the camera detection mode determination value S _t is more than the recognition condition determining threshold value W _th, corrected The lane departure determination based on the lane departure tendency determination yaw angle φc is switched to the lane departure determination based on the uncorrected lane departure tendency determination yaw angle φc.

  For example, as shown in FIG. 7A, when the lane marking is a solid white line 101, the imaging unit 13 detects the yaw angle detection value φr obtained by detecting the solid white line 101 as a departure tendency determination yaw. As the angle (yaw angle for determining lane departure tendency without correction) φc, the lane departure determination is performed. As shown in FIG. 7B, when the lane division line is botsdots 102, the yaw rate φ ′ is A lane departure determination is made based on the lane departure tendency determination yaw angle (corrected lane departure tendency determination yaw angle) φc estimated based on this.

As described above, it is possible to prevent erroneous recognition and detection delay of the lane marking when the recognition degree of the lane marking by the imaging unit 13 is low, and perform lane departure prevention control with an appropriate control amount and timing. It can be carried out.
When there is a lane departure tendency (Fout = ON), that is, when lane departure prevention control is performed, the camera recognition state determination threshold value _Wth is increased and corrected (in the determination of step S12). If "Yes", step S13). Thus, if you are lane departure prevention control, camera recognizes state determination value S _t is then tends to the determination result of the less than camera recognition condition determining threshold value W _th (the step S14), and correction Lane departure determination based on the lane departure tendency determination yaw angle φc is performed. By doing so, it was obtained from the imaging unit 13 that it is highly possible that the degree of recognition of the lane marking by the imaging unit 13 is low because the yaw moment was given to the host vehicle by the lane departure prevention control. A lane departure determination based on a corrected lane departure tendency determination yaw angle φc, instead of the yaw angle detection value φr, and the recognition of the lane division line by the imaging unit 13 is low. Thus, lane departure prevention control can be performed at an appropriate control amount and timing.

The embodiments of the present invention have been described above. However, the present invention may be realized as an embodiment with the following configuration.
That is, the lane departure prevention control may be performed by the processing procedure as shown in FIG. That is, in step S12, it is determined whether or not the departure determination flag Fout is ON. If the departure determination flag Fout is ON (Fout = ON), the process proceeds to step S15. If not (Fout = OFF), the process proceeds to step S16. move on. In step S15, similarly to the above embodiments, to set the camera recognized state determination flag _{N f} to 1 _(N f = 1), at step S16, similarly to the above embodiment, the camera recognized state determination flag _{N f} 0 Set to. That is, after determining the departure flag Fout, regardless of the relationship between the camera detection mode determination value S _t and the camera detection mode determination threshold W _th, sets the camera recognized state determination flag N _f. Then, when the departure flag Fout is ON (Fout = ON), the camera detection mode determination flag N _f by setting to 1, is carried out lane departure determination based on the corrected lane departure tendency determining yaw angle .phi.c. In this case, the corrected lane departure tendency determination yaw angle φc is calculated using the yaw angle detection value φr obtained from the imaging unit 13 at the start of the lane departure prevention control as an initial value (steps S20 and S21).

Thus, it was the yaw moment is applied to the vehicle by the lane departure prevention control, regardless of the size of the camera detection mode determination value S _t, possible recognition of the lane dividing line by the imaging unit 13 is lower Lane departure determination based on the corrected lane departure tendency determination yaw angle φc, and erroneous recognition or detection delay of the lane division line when the recognition degree of the lane division line by the imaging unit 13 is low Lane departure prevention control can be performed with an appropriate control amount and timing.

Further, in the above embodiment, when the camera recognition state determination flag _Nf is 1, that is, when it is predicted that the recognition degree of the lane marking by the imaging unit 13 is low, the lane departure tendency determination yaw for no correction. The angle is switched from the angle φc to the corrected lane departure tendency determination yaw angle φc. On the other hand, when it is predicted that the recognition degree of the lane line by the imaging unit 13 is low, the yaw angle φc for determining the lane departure tendency without correcting the current value and the yaw angle lane departure tendency determining yaw for the current value are corrected. The lane departure determination can also be performed using the lane departure tendency determination yaw angle φc having a smaller difference from the previous value of the lane departure tendency determination yaw angle φc. Thereby, it is possible to prevent the departure tendency determination yaw angle φ from becoming extremely large or discontinuous. For example, it is possible to prevent the lane departure prevention control from changing suddenly.

  Note that a method for selecting the smaller difference between the previous lane departure tendency determination yaw angle φc and the corrected lane departure tendency determination yaw angle φc of the previous lane departure tendency determination yaw angle φc. Is a corrected lane departure tendency determination of the present value with respect to the difference between the previous value lane departure tendency determination yaw angle φc and the previous value of the lane departure tendency determination yaw angle φc. This can be realized by providing a comparison means for comparing the difference in the yaw angle φc for use.

  In the above-described embodiment, the yaw angle detection value (φr, yaw angle for determining lane departure tendency without correction φc) and the yaw angle obtained by correcting the so-called yaw angle detection value with the yaw rate (lane correction tendency determination yaw without correction). Based on the angle φc), lane departure is determined as lane departure prevention control. On the other hand, the control amount of the lane departure prevention control can also be calculated. That is, for example, when the recognition degree of the lane line by the imaging unit 13 is predicted to be high, the yaw moment in the lane departure prevention control is calculated based on the detected value of the yaw angle, and the lane line by the imaging unit 13 is calculated. Is predicted to be low, the yaw moment in the lane departure prevention control is calculated based on the detected value of the yaw angle, and the lane is calculated based on the yaw angle obtained by correcting the detected value of the yaw angle with the yaw rate. The yaw moment in the departure prevention control is calculated.

  In the description of the embodiment, the imaging unit 13 realizes an imaging unit that images a traveling lane and a first yaw angle acquisition unit that acquires the yaw angle of the host vehicle with respect to the traveling lane captured by the imaging unit. The navigation device 14 or the yaw rate sensor realizes a yaw rate detecting means for detecting the yaw rate of the host vehicle, and the processing in step S21 of the braking / driving force control unit 8 is performed by detecting the yaw rate detected by the yaw rate detecting means at a reference yaw angle. The second yaw angle acquisition means for acquiring the yaw angle by adding the integral values of the control values is realized, and the processes of steps S4 to S8 of the braking / driving force control unit 8 are the first and second yaw angle acquisition means. Based on the yaw angle acquired by the vehicle, a control means for performing lane departure prevention control for preventing the host vehicle from departing from the traveling lane is realized. That.

In the description of the above embodiment, the processing of step S11 and step S14 of the braking / driving force control unit 8 realizes an imaging state estimation unit that estimates a decrease in the imaging state of the traveling lane by the imaging unit. The process of step S13 of the driving force control unit 8 realizes a correction unit that corrects a predetermined threshold value close to the yaw angle determination value when the lane departure prevention control is performed.
In the above embodiment, the yaw angle of the host vehicle with respect to the travel lane obtained by imaging is corrected by the yaw angle of the host vehicle obtained by adding the integral value of the yaw rate detection value of the host vehicle to the reference yaw angle, Based on the corrected yaw angle, lane departure prevention control for preventing the host vehicle from departing from the traveling lane is realized.

It is a schematic structure figure showing vehicles of an embodiment of the present invention. It is a flowchart which shows the processing content of the control unit of the lane departure prevention apparatus with which a vehicle is mounted. It is a flowchart which shows the processing content of the setting (selection) of the yaw angle for lane departure tendency determination by the said control unit. It is a flowchart which shows the processing content of determination of the lane departure tendency by the said control unit. It is a diagram used for explanation of the estimated lateral displacement Xs and the departure tendency determination threshold value X _L. It is a characteristic view which shows the relationship between the vehicle speed V and the gain K2. It is the figure used for description of the effect | action and effect of this invention. It is a flowchart which shows the other processing content of the setting (selection) of the yaw angle for lane departure tendency determination by the said control unit.

Explanation of symbols

  6FL to 6RR wheel cylinder, 7 brake fluid pressure control unit, 8 braking / driving force control unit, 9 engine, 12 drive torque control unit, 13 imaging unit, 14 navigation device, 16 radar, 17 master cylinder pressure sensor, 18 accelerator opening Sensor, 19 Steering angle sensor, 22FL-22RR Wheel speed sensor

Claims (3)

Imaging means for imaging the traveling lane;
First yaw angle acquisition means for acquiring the yaw angle of the host vehicle with respect to the travel lane imaged by the imaging means;
Control means for performing lane departure prevention control for preventing the vehicle from deviating from the traveling lane;
A yaw rate detecting means for detecting the yaw rate of the host vehicle;
A second yaw angle obtained by adding the integral value of the yaw rate detected by the yaw rate detection means to the reference yaw angle obtained by the first yaw angle acquisition means at the start of the lane departure prevention control. Acquisition means ;
Imaging state estimation means for estimating a decrease in the imaging state of the traveling lane by the imaging means,
When the lane departure prevention control is performed, the imaging state estimation unit estimates that the imaging state is lower than a threshold value used when estimating whether or not the imaging state is lower. Correct in the direction that makes it easier ,
The control means performs the lane departure prevention control using the yaw angle acquired by the second yaw angle acquisition means when the imaging state estimation means estimates that the imaging state is lowered. Prevention device.   The difference between the yaw angle acquired by the first yaw angle acquisition unit with respect to the previous yaw angle used in the lane departure prevention control and the yaw angle acquired by the second yaw angle acquisition unit with respect to the previous yaw angle. Comparing means for comparing with the difference, and the control means, based on the comparison result of the comparing means, the yaw angle acquired by the first yaw angle acquiring means and the yaw angle acquired by the second yaw angle acquiring means 2. The lane departure prevention device according to claim 1, wherein the lane departure prevention control is performed based on a yaw angle having a smaller difference.   The first yaw angle acquisition means acquires the yaw angle of the host vehicle with respect to the traveling lane based on the lane marking taken by the imaging means, and the control means recognizes the lane marking by the imaging means. When the lane departure prevention control is performed, the yaw angle acquired by the second yaw angle acquisition unit is preferentially used over the yaw angle acquired by the first yaw angle acquisition unit. The lane departure prevention apparatus according to claim 1 or 2, characterized in that:

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