JP4678121B2 - 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.

As a conventional lane departure prevention device, when the host vehicle may deviate from the driving lane, the vehicle deviates from the driving lane by giving a yaw moment to the host vehicle by controlling the braking force to the wheels. In addition, there is a device for notifying the driver that the host vehicle may deviate from the traveling lane by applying the yaw moment (see, for example, Patent Document 1).
JP 2000-33860 A

For example, in Patent Document 1, a lateral deviation state of the traveling position of the vehicle from the reference position of the traveling lane is detected by the lateral deviation state detecting means, and braking force is applied to the wheels based on the detected lateral deviation state. Thus, a yaw moment is applied to the vehicle to prevent the vehicle from deviating from the traveling lane. As described above, in the technique disclosed in Patent Document 1, control for preventing lane departure is performed in consideration of only the positional relationship between the traveling lane and the host vehicle. However, depending on the running state of the vehicle, the vehicle behavior may become unstable due to the operation for preventing the lane departure. In this case, the driver feels uncomfortable.
Therefore, the present invention has been made in view of the above-described problems, and an object thereof is to provide a lane departure prevention device that can prevent lane departure without making vehicle behavior unstable.

The lane departure prevention apparatus according to the present invention detects that there is a tendency to deviate and generates a braking force of the same degree on the left and right wheels when the vehicle speed is greater than the vehicle speed determination threshold value that is a predetermined vehicle speed. The vehicle is decelerated to detect that there is a tendency to deviate, and when the vehicle speed is equal to or less than the vehicle speed determination threshold, a braking force difference is generated between the left and right wheels based on the target yaw moment. Give yaw moment to avoid lane departure .

According to the present invention, the departure avoidance yaw control is activated after the traveling state of the own vehicle is optimized such that the departure avoidance yaw control is activated after the own vehicle speed is made equal to or less than the own vehicle speed determination threshold value. Therefore, it is possible to stabilize vehicle behavior and prevent lane departure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. This embodiment is a rear-wheel drive vehicle equipped with the lane departure prevention apparatus of the present invention. This rear-wheel drive 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 a first embodiment of a lane departure prevention apparatus according to the present invention.
In the figure, reference numeral 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. Normally, the brake fluid pressure boosted by the master cylinder 3 according to the amount of depression of the brake pedal 1 by the driver is shown. 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 controls the braking fluid pressure of each wheel cylinder 6FL-6RR. Individual control is also possible.

  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.

  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. However, when a drive torque command value is input from the braking / driving force control unit 8, the drive torque is controlled. Drive wheel torque is also controlled according to the command value.
In addition, this vehicle is provided with an imaging unit 13 with an image processing function. The imaging unit 13 is 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 camera. This imaging part 13 is installed in the front part of the vehicle.

  The imaging unit 13 detects a lane marker such as a white line from a captured image in front of the host vehicle, and detects a traveling lane based on the detected lane marker. Further, the imaging unit 13 determines, based on the detected travel lane, an angle (yaw angle) φ 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 φ, lateral displacement X, travel lane curvature β, and the like to the braking / driving force control unit 8.

  The vehicle is provided with a navigation device 15. The navigation device 15 detects the longitudinal acceleration Xg or lateral acceleration Yg generated in the host vehicle, or the yaw rate φ ′ generated in the host vehicle. The navigation device 15 outputs the detected longitudinal acceleration Xg, lateral acceleration Yg, and yaw rate φ ′ to the braking / driving force control unit 8 together with 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.

  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 Acc. A steering angle sensor 19 for detecting the steering angle δ of the steering wheel 21, wheel speed sensors 22FL to 22RR for detecting the rotational speeds of the wheels 5FL to 5RR, so-called wheel speeds Vwi (i = fl, fr, rl, rr), A direction indicating switch 20 for detecting a direction indicating operation by the direction indicator is 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 left direction is the positive direction. That is, the yaw rate φ ′, the lateral acceleration Yg, and the yaw angle φ are positive values when turning left, and the lateral displacement X is a positive value when deviating leftward from the center of the traveling lane.
Next, a calculation processing procedure performed by the braking / driving force control unit 8 will be described with reference to FIG. This calculation process is executed by a timer interrupt 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 arithmetic process is updated and stored in the storage device as needed, and necessary information is read out from the storage device as needed.

  First, in step S1, various data are read from each sensor, controller, or control unit. Specifically, the longitudinal acceleration Xg, the lateral acceleration Yg, the yaw rate φ ′ and road information obtained by the navigation device 15, the wheel speeds Vwi, the steering angle δ, the accelerator opening Acc, the master cylinder hydraulic pressure detected by the sensors. Pmf, Pmr, direction switch signal, drive torque Tw from the drive torque control unit 12, and yaw angle φ, lateral displacement X, and travel lane curvature β are read from the imaging unit 15.

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. That is, for example, when ABS (Anti-lock Brake System) control or the like is operating, the estimated vehicle speed estimated in the ABS control is used as the vehicle speed V. Further, a value used for navigation information in the navigation device 15 may be used as the vehicle speed V.
Subsequently, in step S3, the traveling environment is determined. Specifically, the type of road on which the host vehicle is traveling and the traveling lane of the host vehicle are detected. And from the detection result, the direction based on the safety degree is determined. The determination is made based on road information, that is, the number of lanes, road type information indicating whether the road is a general road or a highway, and image information obtained by the imaging unit 13. FIG. 3 shows a specific processing procedure for determining the driving environment.

First, in step S <b> 11, the currently traveling road type (general road or highway) is acquired from the road information from the navigation device 15. Further, in step S12, the number of lanes of the currently traveling road is acquired from the road information from the navigation device 15.
Subsequently, in step S13, a white line portion (lane marking line portion) is extracted from the captured image obtained by the imaging unit 13. Here, as shown in FIG. 4, a case where the host vehicle is traveling on a three-lane road on one side will be described as an example. As shown in FIG. 4, the road is divided into first to fourth white lines LI1, LI2, LI3, and LI4 from the left side, and is configured as a three-lane road on one side. When the host vehicle travels on such a road, the captured image obtained for each lane is different. Further, the image formed by extracting the white line from the image also differs depending on the traveling lane.

  That is, when the host vehicle 100A is traveling in the left lane in the traveling direction, the captured image P obtained by the imaging unit 13 of the host vehicle 100A is mainly the first as shown in FIG. , A unique image constituted by the second and third white lines LI1, LI2, and LI3. Further, when the host vehicle 100B is traveling in the central lane, the captured image P obtained by the imaging unit 13 of the host vehicle 100B is mainly the first, second, and second as shown in FIG. 3 and the fourth white line LI1, LI2, LI3, LI4. Further, when the host vehicle 100C is traveling in the right lane in the traveling direction, the captured image P obtained by the imaging unit 13 of the host vehicle 100C is mainly the second as shown in FIG. , A unique image constituted by the third and fourth white lines LI2, LI3, and LI4. Thus, the configuration of the white line in the image differs depending on the travel lane.

  Subsequently, in step S14, the host vehicle travel lane (host vehicle travel lane) is determined. Specifically, the host vehicle travel lane is determined based on the information obtained in steps S12 and S13. In other words, the host vehicle travel lane is determined based on the number of lanes of the road on which the host vehicle is currently traveling and the captured image (image obtained by extracting the white line) obtained by the imaging unit 13. For example, an image obtained in accordance with the number of lanes and the traveling lane is previously stored as image data, and the image data prepared in advance and the number of lanes on the road on which the host vehicle is currently traveling and the current obtained by the imaging unit 13 The captured vehicle image (image obtained by extracting the white line) is compared to determine the vehicle lane.

  Subsequently, in step S15, the degree of safety in the left-right direction as viewed from the lane in which the host vehicle is traveling is determined. Specifically, the direction in which the degree of safety is low when the host vehicle deviates is held as information. Thus, when the safety level is low in the left direction when viewed from the lane in which the host vehicle is traveling, the direction is held as a low safety level direction (hereinafter referred to as a first obstacle existence direction) Sout ( Sout = left) When the safety level is low in the right direction when viewed from the lane in which the host vehicle is traveling, the direction is held as the first obstacle existence direction Sout (Sout = right). For example, the determination is made as follows.

  For example, in FIG. 4, when the host vehicle 100A is traveling in the left lane, the degree of safety is lower when the vehicle deviates to the left of the left lane than to deviate to the right of the left lane. This is because there is a road shoulder in the left direction of the left lane, and there is a high possibility that there is a wall, a guardrail, an obstacle, a cliff, or the like on the road shoulder. For this reason, when the vehicle deviates to the left in the left lane, that is, to the shoulder side, there is a high possibility that the host vehicle 100A will come into contact with these objects. Accordingly, when the host vehicle 100A is traveling in the left lane, it is determined that the first obstacle existence direction Sout is the left direction (Sout = left).

Further, when the host vehicle 100B is traveling in the central lane, the host vehicle 100B is still in the road regardless of the direction, and the safety degree is the same in the left and right directions with respect to the current traveling lane. become.
Further, when the host vehicle 100C is traveling in the right lane, the degree of safety is lower in the right direction, that is, when the vehicle deviates to the opposite lane than when the vehicle deviates to the left direction, that is, the adjacent lane. Therefore, in this case, when the host vehicle 100A is traveling in the right lane, it is determined that the first obstacle existence direction Sout is the right direction (Sout = right).

Moreover, when compared with ordinary roads and expressways, the width of shoulders on ordinary roads is narrower than that of expressways, there are many obstacles on the shoulders, and there are also pedestrians. For this reason, deviating to the shoulder side on a general road is less safe than deviating to the shoulder side on an expressway.
Further, when compared by the number of lanes, the safety degree is lower when the left side is the road shoulder and the right direction is one lane on the opposite lane. In this case, it is determined that the left and right directions are the first obstacle existence direction Sout (Sout = both).

  Note that, for example, since one-sided one-lane roads generally do not have a median strip or guardrail, a captured image when traveling on the one-sided one-lane road is as shown in FIG. . That is, the captured image when traveling on a one-lane road is the same as the captured image obtained by the imaging unit 13 of the vehicle 100A by traveling on the left lane of a three-lane road. Therefore, when it is assumed that the vehicle travels on a general road and an expressway, the presence direction of the first obstacle or the like cannot be determined only by the captured image. For this reason, the number of lanes of the road on which the host vehicle is currently traveling is obtained from the navigation device 15, and it is determined whether the currently traveling road is a one-lane or one-lane road. Thus, when driving on a one-lane road on one side, it can also be determined that the degree of safety is low in the right direction.

The travel environment is determined in step S3 shown in FIG. 2 according to the processing procedure shown in FIG.
Subsequently, in step S4, a lane departure tendency is determined. Specifically, the processing procedure of this determination processing is as shown in FIG.
First, in step S21, the estimated departure time Tout is calculated. Specifically, the deviation predicted time Tout is calculated by the following equation (2) using dx as the change amount of the lateral displacement X (change amount per unit time), L as the lane width, and the lateral displacement X. (See FIG. 7 for values of X, dx, and L).
Tout = (L / 2−X) / dx (2)

According to the equation (2), the vehicle 100 that is laterally displaced by X from the center of the lane (X = 0) reaches the outside position region (for example, the road shoulder) separated from the position by the distance L / 2. The predicted time Tout can be obtained.
Note that the lane width L is obtained by the imaging unit 13 processing the captured image. Further, the position of the vehicle may be obtained from the navigation device 15 or the lane width L may be obtained from the map data of the navigation device 15.

  Subsequently, in step S22, a departure determination flag is set. Specifically, the predicted departure time Tout is compared with a predetermined first departure determination threshold value Ts. Here, if the predicted departure time Tout is less than the first departure determination threshold value Ts (Tout <Ts), it is determined that the departure (there is a departure tendency) and the departure determination flag Fout is turned on (Fout = ON). . If the predicted departure time Tout is equal to or greater than the first departure determination threshold value Ts (Tout ≧ Ts), it is determined that there is no departure (no departure tendency) and the departure determination flag Fout is turned off (Fout = OFF).

  By such processing in step S22, for example, when the host vehicle moves away from the center of the lane and the predicted departure time Tout becomes less than the first departure determination threshold value Ts (Tout <Ts), the departure determination flag Fout is turned on. (Fout = ON). Further, when the own vehicle (the own vehicle in the state where Fout = ON) returns to the lane center side and the estimated departure time Tout becomes equal to or longer than the first departure determination threshold value Ts (Tout ≧ Ts), the departure determination. The flag Fout is turned off (Fout = OFF). For example, when there is a tendency to deviate, if the braking control for avoiding deviation described later is performed, or if the driver himself performs an avoidance operation, the deviation determination flag Fout is changed from ON to OFF.

The first departure determination threshold value Ts can be changed. That is, for example, the first departure determination threshold value Ts can be set based on the safety degree obtained in step S3.
Subsequently, in step S23, 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, based on the direction switch signal and the steering angle δ obtained in step S1, the driver's intention to change lanes is determined as follows.
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 a determination result that there is no deviation.

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 deviates is maintained.
When the direction indicating switch 20 is not operated, the driver's intention to change lanes is determined based on the steering angle δ. That is, when the driver is steering in the departure direction, if the steering angle δ and the change amount of the steering angle (change amount per unit time) Δδ are equal to or larger than the set value, the driver consciously changes the lane. The departure determination flag Fout is changed to OFF (Fout = OFF).

Subsequently, in step S6, a control method for avoiding deviation is determined. Specifically, whether or not to perform a departure warning or braking control for avoiding departure, and further, when performing braking control for avoiding departure, the braking control method is determined.
Specifically, a departure warning is performed according to the ON / OFF state of the departure determination flag Fout obtained in step S5. Specifically, when the departure determination flag Fout is ON, that is, when the departure predicted time Tout is less than the first departure determination threshold value Ts, and in this case, it can be determined that the lane departure is not caused by the driver's operation. Implements a warning of deviation. For example, an alarm is generated by sound or the like.

Here, the departure determination flag Fout is ON (Tout <Ts), but the case where it can be determined that the lane does not deviate due to the steering operation by the driver, for example, the driver himself notices the departure tendency of the own vehicle. In this case, the departure determination flag Fout itself is still ON (Tout <Ts).
When the departure determination flag Fout is ON, the braking control method is also determined based on the first departure direction Sout obtained in step S3 and the second departure direction Dout obtained in step S4. Furthermore, a braking control method is also determined based on the vehicle speed V and the estimated departure time Tout. This will be described in detail later.

Subsequently, in step S7, a target yaw moment to be generated in the host vehicle is calculated. This target yaw moment is a yaw moment to be given to the host vehicle in order to avoid departure.
Specifically, the target yaw moment Ms is calculated by the following equation (3) based on the lateral displacement X and the change dx obtained in step S1.
Ms = K1 · X + K2 · dx (3)

Here, K1 and K2 are gains that vary according to the vehicle speed V. For example, FIG. 8 shows an example. As shown in FIG. 8, for example, the gains K1 and K2 are small values in the low speed range. When the vehicle speed V reaches a certain value, the gains K1 and K2 increase in response to the increase in the vehicle speed V, and then constant when the vehicle speed V reaches a certain value. Value.
Subsequently, in step S8, a deceleration for avoiding deviation is calculated. That is, the braking force applied to the left and right wheels for the purpose of decelerating the host vehicle is calculated. Here, the target braking fluid pressures Pgf and Pgr that give such braking force to both the left and right wheels are calculated. The target braking hydraulic pressure Pgf for the front wheels is calculated by the following equation (4).
Pgf = Kgv · V + Kgx · dx (4)

Here, Kgv and Kgx are conversion coefficients that are set based on the vehicle speed V and the lateral change amount dx, respectively, for converting the braking force into the braking hydraulic pressure. For example, FIG. 9 shows an example. As shown in FIG. 9, for example, the conversion coefficients Kgv and Kgx have large values in the low speed range, and when the vehicle speed V reaches a certain value, the conversion coefficients Kgv and Kgx decrease in response to the increase in the vehicle speed V, It becomes a constant value.
Then, based on the target braking hydraulic pressure Pgf for the front wheels, the target braking hydraulic pressure Pgr for the rear wheels considering the front-rear distribution is calculated.
Thus, in step S8, deceleration for avoiding deviation (specifically, target braking hydraulic pressures Pgf, Pgr) is obtained.
Subsequently, in step S9, a target brake hydraulic pressure for each wheel is calculated. In other words, the final braking fluid pressure is calculated based on the presence or absence of the departure avoidance braking control. Specifically, it is calculated as follows.

(1) When the departure determination flag Fout is OFF (Fout = OFF), that is, when the determination result that there is no departure is obtained, as shown in the following equations (5) and (6), the target braking fluid for each wheel The pressure Psi (i = fl, fr, rl, rr) is set to the master cylinder hydraulic pressure Pmf, Pmr.
Psfl = Psfr = Pmf (5)
Psrl = Psrr = Pmr (6)
Here, Pmf is the master cylinder hydraulic pressure for the front wheels. Pmr is a master cylinder hydraulic pressure for the rear wheels, and is a value calculated based on the master cylinder hydraulic pressure Pmf for the front wheels in consideration of the front-rear distribution.

(2) When the departure determination flag Fout is ON (Fout = ON), that is, when a determination result indicating departure is obtained, first, based on the target yaw moment Ms, the front wheel target braking fluid pressure difference ΔPsf and the rear wheel target braking fluid The pressure difference ΔPsr is calculated. Specifically, the target braking hydraulic pressure differences ΔPsf and ΔPsr are calculated by the following equations (7) to (10).
In the case of Ms <Ms1, ΔPsf = 0 (7)
ΔPsr = 2 · Kbr · Ms / T (8)
When Ms ≧ Ms1 ΔPsf = 2 · Kbf · (Ms−Ms1) / T (9)
ΔPsr = 2 · Kbr · Ms1 / T (10)

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.
In this way, the braking force applied to the wheels is distributed 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. Further, when the target yaw moment Ms is equal to or larger 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.

  When the departure determination flag Fout is ON (Fout = ON), the final wheels are calculated using the target braking hydraulic pressure differences ΔPsf, ΔPsr and the deceleration target braking hydraulic pressures Pgf, Pgr calculated as described above. Target brake hydraulic pressure Psi (i = fl, fr, rl, rr) is calculated. Specifically, the final target brake hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated based on the braking control method determined in step S6.

Here, the braking control method determined in step S6 will be described.
In step S6, when the departure determination flag Fout is ON, the braking control method is determined based on the first obstacle existence direction Sout and the departure direction Dout. Further, when the departure determination flag Fout is ON, the braking control method is determined based on the vehicle speed V and the estimated departure time Tout.
First, regarding the braking control method that is determined based on the first obstacle existence direction Sout and the departure direction Dout when the departure determination flag Fout is ON, in the state of the first obstacle existence direction Sout and the departure direction Dout. A description will be given by dividing into cases (first case to third case).

(First Case) When the first obstacle existence direction Sout and the departure direction Dout do not coincide with each other, a yaw moment for avoiding departure is applied to the vehicle until the departure determination flag Fout is turned off. Thus, braking control (hereinafter referred to as deviation avoidance yaw control) is performed.
Here, the magnitude of the yaw moment applied to the vehicle in order to avoid the departure is the target yaw moment Ms. The yaw moment is applied to the vehicle by making a difference in the braking force applied to the left and right wheels. Specifically, as described above, when the target yaw moment Ms is less than the setting threshold value Ms1, a braking force difference is generated between the left and right rear wheels to apply the target yaw moment Ms to the vehicle. When the target yaw moment Ms is equal to or greater than the setting threshold value Ms1, a braking force difference is generated between the front, rear, left and right wheels, and the target yaw moment Ms is applied to the vehicle.
Further, the case where the departure determination flag Fout is changed from ON to OFF is when braking control for avoiding departure is performed or the driver himself performs an avoidance operation when there is a departure tendency.

(Second Case) When the first obstacle existence direction Sout matches the departure direction Dout and the road type R obtained in Step S3 is a general road, the departure is continued until the departure determination flag Fout is turned OFF. Perform avoidance yaw control.
Further, a second departure judgment threshold value Tr (Ts>Tr> 0) less than the first departure judgment threshold value Ts is defined, and the predicted departure time Tout is smaller than the second departure judgment threshold value Tr. When this happens, in addition to the departure avoidance yaw control, braking control for decelerating the vehicle (hereinafter referred to as departure avoidance deceleration control) is performed. This departure avoidance deceleration control is performed by applying the same level of braking force to the left and right wheels.
Here, since the predicted departure time Tout is an indicator of the magnitude of the departure tendency, the fact that the departure prediction time is smaller than the second departure determination threshold value Tr means that the departure tendency is larger than the second threshold value. It shall be equivalent.

(Third Case) When the first obstacle existence direction Sout and the departure direction Dout coincide with each other and the road type R obtained in step S3 is a highway, the departure is continued until the departure determination flag Fout is turned off. Perform avoidance yaw control.
Further, in this case, when the predicted departure time Tout becomes 0, the departure avoidance deceleration control is performed in addition to the departure avoidance yaw control.
In the case of the third case, similarly to the second case, the departure avoidance deceleration control is performed even when the departure prediction time Tout becomes smaller than the second departure determination threshold value Tr. Also good. In this case, for example, when the estimated departure time Tout becomes 0, the deceleration of the host vehicle by the departure avoidance deceleration control is further increased. As a result, when the predicted departure time Tout becomes smaller than the second departure determination threshold value Tr, and further when the predicted departure time Tout becomes 0, the departure avoidance deceleration control is activated. In this case, when the estimated departure time Tout becomes 0, the deceleration of the host vehicle becomes larger.

Next, a braking control method that is determined based on the vehicle speed V and the predicted departure time Tout when the departure determination flag Fout is ON will be described.
Specifically, the departure avoidance deceleration control is performed before the departure avoidance yaw control based on the vehicle speed V and the estimated departure time Tout. Here, the processing procedure will be described with reference to FIG.
First, in step S31, the predicted departure time Tout and the first departure determination threshold value Ts are compared. If the predicted departure time Tout is less than the first departure determination threshold value Ts (Tout <Ts), the process proceeds to step S32, and if the predicted departure time Tout is greater than or equal to the first departure determination threshold value Ts (Tout ≧ Ts). ), The process shown in FIG. 10 is exited.

  In step S32, the vehicle speed V is compared with a predetermined threshold value Vc which is a first threshold value. Here, the threshold value Vc is a limit value of the vehicle speed at which the host vehicle can stably travel even if a yaw moment is applied to the host vehicle on a predetermined road corresponding to the lower limit value of the road on which the road surface μ is paved, That is, it is the speed of the vehicle stability limit obtained from the equation of motion of the vehicle on the premise of giving the yaw moment. That is, when the yaw moment is applied at a vehicle speed higher than the threshold value Vc, the vehicle behavior tends to be unstable. The threshold value Vc is set according to the magnitude of the yaw moment applied to the host vehicle for avoiding the departure.

If the vehicle speed V is greater than the threshold value Vc (V> Vc), the process proceeds to step S33. If the vehicle speed V is equal to or less than the threshold value Vc (V ≦ Vc), the process proceeds to step S34.
In step S33, departure avoidance deceleration control is selected. And the process from step S31 is started again.
On the other hand, in step S34, deviation avoidance yaw control is selected. And the process from step S31 is started again.

By the above processing, as long as the vehicle speed V is greater than the threshold value Vc and the predicted departure time Tout is less than the first departure determination threshold value Ts, the departure avoidance deceleration control is performed, and the predicted departure time Tout is the first predicted time Tout. When it is less than one departure determination threshold value Ts and the vehicle speed V is less than or equal to the threshold value Vc, departure avoidance yaw control is performed.
In some cases, the braking control method performed in the first to third cases may be different from the braking control method performed based on the vehicle speed V and the estimated departure time Tout. In this case, the braking control method based on the vehicle speed V and the estimated departure time Tout is preferentially performed.

  In step S5, if the direction indicated by the direction switch signal (the blinker lighting side) is the same as the direction indicated by the second departure direction Dout obtained in step S4, the departure determination flag Fout is changed to OFF. (Fout = OFF). When the estimated departure time Tout is less than the first departure determination threshold value Ts (Tout <Ts), the departure determination flag Fout is set to ON. Therefore, the processing of FIG. 10 is conditional on the departure determination flag Fout being ON.

In step S6, as described above, various braking control methods are determined based on the first obstacle existence direction Sout, the departure direction Dout, the vehicle speed V, and the estimated departure time Tout.
In step S9, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated corresponding to such various braking control methods.
For example, in the deviation avoidance yaw control in the first to third cases, the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (11). .
Psfl = Pmf
Psfr = Pmf + ΔPsf
Psrl = Pmr
Psrr = Pmr + ΔPsr
(11)

In the case of the second and third cases, deviation avoidance yaw control and departure avoidance deceleration control are performed. In this case, the target braking hydraulic pressure Psi of each wheel is expressed by the following equation (12). (I = fl, fr, rl, rr) is calculated.
Psfl = Pmf + Pgf / 2
Psfr = Pmf + ΔPsf + Pgf / 2
Psrl = Pmr + Pgr / 2
Psrr = Pmr + ΔPsr + Pgr / 2
(12)

Further, as shown by the equations (11) and (12), the deceleration operation by the driver, that is, the target brake fluid pressure Psi (i = fl, fr, rl, rr) is calculated.
The above is the process of step S9. Thus, in step S9, the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated based on the state of the departure determination flag Fout. When the departure determination flag Fout is ON, the target of each wheel corresponding to the various braking control methods determined in accordance with the state of the first obstacle existence direction Sout and the departure direction Dout in step S6. The brake fluid pressure Psi (i = fl, fr, rl, rr) is calculated.

The above is the calculation processing by the braking / driving force control unit 8. Then, the braking / driving force control unit 8 uses the target braking fluid pressure Psi (i = fl, fr, rl, rr) calculated for each wheel calculated in step S9 as a braking fluid pressure command value to the braking fluid pressure controller 7. Output.
The lane departure prevention apparatus as described above generally operates as follows.
First, various data are read from each sensor, controller, and control unit (step S1). Subsequently, the vehicle speed V is calculated (step S2).
Subsequently, the traveling environment is determined, and the direction in which the degree of safety is low (the first obstacle etc. existence direction Sout) is determined (step S3, FIG. 3). For example, when the host vehicle 100A is traveling in the left lane in FIG. 4, the direction of the first obstacle etc. is set to the left.

Further, the departure determination flag Fout is set based on the estimated departure time Tout, and the departure direction Dout is determined based on the lateral displacement X (step S4, FIG. 7).
Further, the driver's intention to change the lane is determined based on the departure direction Dout thus obtained and the direction indicated by the direction switch signal (the blinker lighting side) (step S5).
For example, when the direction indicated by the direction switch signal (the blinker lighting side) and the direction indicated by the departure direction Dout are the same, it is determined that the driver has intentionally changed the lane. In this case, the departure determination flag Fout is changed to OFF.

  Further, when the direction indicated by the direction switch signal (the blinker lighting side) is different from the direction indicated by the departure direction Dout, the departure determination flag Fout is maintained when it is ON. For example, if the direction indicated by the direction switch signal (the blinker lighting side) is different from the direction indicated by the departure direction Dout, the departure behavior of the vehicle is not the vehicle behavior due to the driver's intention such as a lane change by the driver. Since it can be considered, if the departure determination flag Fout is ON, it is maintained.

Based on the departure determination flag Fout, the first obstacle existence direction Sout, and the departure direction Dout, the presence or absence of an alarm for avoiding departure, the presence or absence of braking control for avoiding departure, and the braking control for avoiding departure Is determined (step S6).
Further, the target yaw moment Ms is calculated based on the lateral displacement X and the change amount dx (step S7), and the deceleration for avoiding deviation is calculated (step S8).

  And the target braking hydraulic pressure Psi (i = fl, fr, rl, each wheel) for realizing the braking control method determined based on the departure determination flag Fout, the first obstacle etc. existence direction Sout and the departure direction Dout rr) is calculated, and this target brake fluid pressure Psi (i = fl, fr, rl, rr) is output to the brake fluid pressure controller 7 as a brake fluid pressure command value (step S9). The braking fluid pressure control unit 7 individually controls the braking fluid pressures of the wheel cylinders 6FL to 6RR based on the braking fluid pressure command value. As a result, when the vehicle tends to deviate, a predetermined vehicle behavior is exhibited according to the traveling environment.

Here, in the case of the first case to the third case, the vehicle behavior when the braking control is performed will be described with reference to FIGS. 11 and 12.
As described above, the second case is a case where the first obstacle existence direction Sout matches the departure direction Dout and the road type R is a general road. That is, as shown in FIG. 11, when the host vehicle 100 is traveling in one lane on one side such that the left side is the road shoulder X and the right side is the opposite lane (center lane L5 side), the host vehicle 100 ( This is the case where the host vehicle 100 at the uppermost position in FIG. 11 tends to deviate leftward or the vehicle (the host vehicle 100 at the intermediate position in FIG. 11) tends to deviate to the right.

  In this case, deviation avoidance yaw control is performed. Further, when the predicted departure time Tout becomes shorter than the second departure determination threshold Tr, departure avoidance deceleration control is performed in addition to departure avoidance yaw control. Thereby, the own vehicle avoids deviation. On the other hand, the driver can feel the departure avoidance operation of the vehicle as the acceleration in the lateral direction or the deceleration in the traveling direction, and can know that the own vehicle tends to depart.

  Further, as described above, the third case is a case where the first obstacle existence direction Sout matches the departure direction Dout and the road type R is a highway. That is, as shown in FIG. 12, in the three-lane road, the own vehicle 100A traveling in the left lane (the own vehicle 100A in the uppermost position in FIG. 12) tends to deviate in the left direction. Alternatively, as shown in FIG. 12, in a three-lane road, the host vehicle 100C traveling in the right lane (the host vehicle 100C at the intermediate position in FIG. 12) tends to deviate in the right direction.

In this case, deviation avoidance yaw control is performed. Thereby, the own vehicle can avoid deviation. Further, when the predicted departure time Tout becomes 0, that is, when it is determined that the host vehicle has deviated from the traveling lane, the departure avoidance deceleration control is performed in addition to the departure avoidance yaw control.
In FIG. 11 and FIG. 12, wheels that are black are wheels that generate a hydraulic pressure and are given a braking force. That is, when either one of the left and right wheels is a black wheel, there is a difference in hydraulic pressure or braking force between the left and right wheels. In this case, a yaw moment is given to the vehicle. Even if the left and right wheels are black wheels, there may be a difference in the hydraulic pressure values. In this case, it is confirmed that the vehicle is being subjected to deceleration control while a yaw moment is applied to the vehicle. Show. This relationship is the same in subsequent drawings.

  Further, as described above, the first case is a case where the first obstacle existence direction Sout and the departure direction Dout do not match. That is, as shown in FIG. 12, in the three-lane road, the own vehicle 100A traveling in the left lane (the own vehicle 100A in the intermediate position in FIG. 12) tends to deviate in the right direction. Alternatively, as shown in FIG. 12, in a three-lane road, the host vehicle 100C traveling in the right lane (the host vehicle 100C in the uppermost position in FIG. 12) tends to deviate to the left. Alternatively, the host vehicle B traveling in the central lane tends to deviate leftward or rightward. In this case, deviation avoidance yaw control is performed. Thereby, the own vehicle can avoid deviation.

Further, departure avoidance deceleration control is performed as long as the vehicle speed V is greater than the threshold value Vc and the estimated departure time Tout is less than the first departure determination threshold value Ts. Further, departure avoidance yaw control is performed when the predicted departure time Tout is less than the first departure determination threshold value Ts and the vehicle speed V is less than or equal to the threshold value Vc.
Here, it demonstrates using FIG. FIG. 13 shows the relationship between the speed and the target yaw moment Ms. FIG. 13 shows a case where the target yaw moment Ms changes in proportion to the vehicle speed V for the sake of simplicity.

As shown in FIG. 13, assuming that the estimated departure time Tout is less than the first departure determination threshold value Ts, departure avoidance deceleration control is performed as long as the vehicle speed V is greater than the threshold value Vc, and the vehicle speed V When the value becomes equal to or less than the threshold value Vc, deviation avoidance yaw control is performed. The deviation avoidance yaw control is control using the target yaw moment Ms corresponding to the vehicle speed V as a target value.
In addition to the braking control for avoiding the deviation as described above, a warning is given by sound and display. For example, the alarm is started at a predetermined timing simultaneously with the start of the brake control or prior to the brake control.

Next, the effect will be described.
As described above, when the vehicle speed V is greater than the threshold value Vc and the predicted departure time Tout is less than the first departure determination threshold value Ts, departure avoidance deceleration control is performed, and the predicted departure time Tout is determined as the first departure determination. When the vehicle speed V is less than the threshold value Tc and less than the threshold value Ts, the deviation avoidance yaw control is performed.
As a result, the departure avoidance yaw control can be activated after the traveling state of the host vehicle is set to the optimum state, so that the vehicle behavior can be stabilized and the lane departure can be prevented.

  Further, the threshold value Vc is a limit value of the vehicle speed at which the host vehicle can travel stably (that is, exhibit steady vehicle behavior) even if a yaw moment is applied to the host vehicle. As a result, the deviation avoidance yaw control can be operated at the optimum speed. In other words, there are a request to intervene in a deviation avoidance yaw control as soon as possible to avoid a departure and a request to perform a deviation avoidance yaw control to stabilize the vehicle behavior and avoid a departure. The threshold value Vc is realized. As a result, since it is possible to prevent the departure avoidance deceleration control from being operated unnecessarily, that is, since the departure avoidance deceleration control is operated at the minimum necessary, the departure avoidance deceleration control, Furthermore, it is possible to prevent the driver itself from being bothered by the control for avoiding deviation.

The embodiment of the present invention has been described above. However, the present invention is not limited to being realized as the above-described embodiment.
That is, in the above-described embodiment, the case where the departure avoidance deceleration control is performed only when the vehicle speed V is greater than the threshold value Vc and the estimated departure time Tout is less than the first departure determination threshold value Ts is described. is doing. However, it goes without saying that the present invention is not limited to this. That is, if the vehicle speed V is greater than the threshold value Vc, the departure avoidance deceleration control is performed, or if the estimated departure time Tout is less than the first departure determination threshold value Ts, the departure avoidance deceleration control is performed. It may be.

  In the above-described embodiment, braking control (deviation avoidance yaw control) is performed so that a yaw moment for avoiding departure is applied to the vehicle, and braking control (departure avoidance) for decelerating to avoid departure. The method of combination with the speed reduction control), the operation sequence thereof, and the control amount (the magnitude of the yaw moment and the magnitude of the deceleration) have been specifically described. However, it goes without saying that the present invention is not limited to this.

Further, in the above-described embodiment, the estimated departure time Tout is calculated based on the lateral displacement X and the amount of change dx (see equation (2) above). However, the deviation prediction time Tout may be obtained by other methods. For example, the predicted departure time Tout may be obtained based on the yaw angle φ, the travel lane curvature β, the yaw rate φ ′, or the steering angle δ.
In the above-described embodiment, the driver's intention to change the lane is obtained based on the steering angle δ and the change amount Δδ of the steering angle (see step S5). However, the driver's intention to change lanes may be obtained by other methods. For example, the driver's intention to change the lane may be obtained based on the steering torque.

In the above-described embodiment, the target yaw moment Ms is calculated based on the lateral displacement X and the change amount dx (see the above formula (3)). However, the target yaw moment Ms may be obtained by other methods. For example, as shown in the following equation (13), the target yaw moment Ms may be calculated based on the yaw angle φ, the lateral displacement X, and the travel lane curvature β.
Ms = K3 · φ + K4 · X + K5 · β (13)
Here, K3, K4, and K5 are gains that vary according to the vehicle speed V.

In the above-described embodiment, the target braking hydraulic pressure Pgf for the front wheels is described using a specific equation (see the equation (4)). However, it is not limited to this. For example, the target braking hydraulic pressure Pgf for the front wheels may be calculated by the following equation (14).
Pgf = Kgv · V + Kgφ · φ + Kgβ · β (14)
Here, Kgφ and Kgβ are conversion coefficients that are set based on the yaw angle and the travel lane curve, respectively, for converting the braking force into the braking hydraulic pressure.

Further, in the above-described embodiment, the target braking hydraulic pressure differences ΔPsf and ΔPsr between the front wheels and the rear wheels are calculated in order to realize the deviation avoidance yaw control (see the equations (7) and (8)). . However, it is not limited to this. For example, the deviation avoidance yaw control may be realized only by the target brake hydraulic pressure difference ΔPsf of the front wheels. In this case, the target braking hydraulic pressure difference ΔPsf of the front wheels is calculated by the following equation (15).
ΔPsf = 2 · Kbf · Ms / T (15)

  In the description of the above-described embodiment, the process of step S4 of the braking force control unit 8 realizes a departure tendency detecting means for detecting the departure tendency of the host vehicle from the traveling lane, and the braking force control unit The process of step S6 of FIG. 8 includes setting means for setting a yaw moment sharing amount and a deceleration sharing amount based on the traveling environment detected by the traveling environment detection means and the departure tendency detected by the departure tendency detection means. In step S7 of the braking force control unit 8, the target yaw moment for avoiding deviation from the traveling lane of the host vehicle is determined based on the yaw moment sharing amount set by the setting means. A target yaw moment calculating means for calculating is realized, and the processing of step S8 of the braking force control unit 8 is performed. Realizes a deceleration control amount calculation means for calculating a deceleration control amount based on the deceleration sharing amount set by the setting means. The processing of step S9 of the braking force control unit 8 and the processing shown in FIG. , When the departure tendency detecting means detects the departure tendency, based on the target yaw moment calculated by the target yaw moment calculation means and the deceleration control amount calculated by the deceleration control amount calculation means. The braking force control means for controlling the braking force is realized, and the processing of FIG. 10 of the braking force control unit 8 compares the own vehicle speed with the first threshold value, the second tendency and the second tendency. Timing setting means for setting the predetermined timing is realized based on the comparison result with the threshold value.

It is a schematic block diagram which shows embodiment of the vehicle carrying the lane departure prevention apparatus of this invention. It is a flowchart which shows the processing content of the braking / driving force control unit which comprises the said lane departure prevention apparatus. It is a flowchart which shows the processing content of the driving environment determination of the said braking / driving force control unit. It is a figure which shows the vehicle which is drive | working the one side 3 lane road. It is a figure which shows the picked-up image which a vehicle obtains in each lane position, when a vehicle drive | works the said one side 3 lane road. It is a flowchart which shows the processing content of the deviation tendency determination of the said braking / driving force control unit. It is the figure used for description of deviation prediction time Tout. It is a characteristic view which shows the characteristic of the gains K1 and K2 used for calculation of the target yaw moment Ms. It is a characteristic view which shows the characteristic of the conversion factors Kgv and Kgx used for calculation of the target brake hydraulic pressure Pgf. It is a flowchart which shows the content of the determination process of the braking control method based on the vehicle speed V and the estimated deviation time Tout, which is a process of the braking / driving force control unit. It is the figure used for description of the braking control method in the case of the 2nd case. It is the figure used for description of the braking control method in the case of the 3rd case. FIG. 6 is a characteristic diagram used to explain departure avoidance deceleration control and departure avoidance yaw control performed based on the vehicle speed V;

Explanation of symbols

6FL to 6RR Wheel cylinder 7 Braking fluid pressure control unit 8 Braking / driving force control unit 9 Engine 12 Drive torque control unit 13 Imaging unit 15 Navigation device 17 Master cylinder pressure sensor 18 Accelerator opening sensor 19 Steering angle sensor 22FL to 22RR Wheel speed sensor

Claims (3)

In a lane departure prevention apparatus for adjusting the braking force to the wheels and sharing the yaw moment for avoiding the lane departure to be given to the own vehicle and the deceleration of the own vehicle to avoid the departure of the own vehicle from the traveling lane,
When the degree of departure tendency of the host vehicle is greater than a predetermined departure determination threshold, departure tendency detection means for detecting that there is a departure tendency;
The target yaw moment for calculating the target yaw moment for giving the yaw moment for avoiding the lane departure to the own vehicle is larger when the degree of the departure tendency of the own vehicle is smaller than when the degree of deviation tendency is smaller. A calculation means;
Braking force control means for controlling the braking force of each wheel,
The braking force control means detects that the departure tendency detecting means detects that there is a departure tendency, and when the own vehicle speed is greater than the own vehicle speed judgment threshold value that is a predetermined vehicle speed, the same braking force is applied to the left and right wheels. Is generated, the vehicle is decelerated, the departure tendency detecting means detects that there is a departure tendency, and the vehicle speed is equal to or less than the vehicle speed determination threshold value, the left and right wheels are moved based on the target yaw moment. A lane departure prevention apparatus characterized in that a braking force difference is generated and a yaw moment for avoiding the lane departure is applied to the host vehicle. The self-vehicle speed determination threshold value is a limit speed at which the own vehicle exhibits stable vehicle behavior under a predetermined condition when a yaw moment for avoiding lane departure is applied. Lane departure prevention device.   3. The lane departure prevention apparatus according to claim 1, wherein the target yaw moment calculating unit increases the target yaw moment when the target yaw moment is larger than when the host vehicle speed is small.

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