JP4396223B2 - 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. In other words, the technique disclosed in Patent Document 1 merely prevents the deviation of the host vehicle in consideration of only the positional relationship between the traveling lane and the host vehicle. However, when considering that the host vehicle has deviated from the traveling lane, the host vehicle may approach an obstacle outside the traveling lane.
Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a lane departure prevention device that can prevent an approach to an obstacle while preventing a lane departure.

In order to solve the above-described problem, the lane departure prevention device according to the present invention provides at least a yaw moment to the own vehicle or decelerates the own vehicle by braking control when the own vehicle tends to deviate from the traveling lane. In the lane departure prevention device for avoiding the departure of the own vehicle from the traveling lane, when the own vehicle tends to deviate from the traveling lane and to the obstacle existing in the departure direction of the own vehicle from the own vehicle. When the relative time calculated based on the relative distance is smaller than a predetermined threshold value, at least the deceleration is performed.

In order to solve the above-described problem, the lane departure prevention device according to the present invention provides at least a yaw moment to the own vehicle or decelerates the own vehicle by braking control when the own vehicle tends to deviate from the traveling lane. Then, in the lane departure prevention apparatus for avoiding the departure of the host vehicle from the traveling lane, the yaw moment is applied to the host vehicle by generating a braking force difference between the left and right wheels and decelerating the host vehicle. In the case where the host vehicle tends to deviate from the driving lane, and the relative distance from the host vehicle to the obstacle present in the deviating direction of the host vehicle. If the relative time calculated based on the distance is smaller than a predetermined threshold value, at least the deceleration is performed.

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 (Charge Coupled Device) 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, this vehicle is provided with an ACC (adaptive cruise control) radar 16. The ACC radar 16 obtains information about a vehicle or an obstacle ahead of the lane adjacent to the own lane. Specifically, the ACC radar 16 obtains the presence / absence of the preceding vehicle, the relative distance Lc and the relative speed Vc with the preceding vehicle, and the like. Here, the forward vehicle or the like is, for example, a forward vehicle or the like stopped on a road shoulder, a forward vehicle or the like traveling in an adjacent lane. The ACC radar 16 outputs the presence / absence of the vehicle ahead, the relative distance Lc, and the relative speed Vc to the braking / driving force control unit 8.

  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. The steering angle sensor 19 for detecting the steering angle δ of the steering wheel 21, the direction indicating switch 20 for detecting the direction indicating operation by the direction indicator, and the rotational speeds of the wheels 5FL to 5RR, so-called wheel speed Vwi (i = fl, Wheel speed sensors 22FL to 22RR for detecting 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 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 from the center of the traveling lane to the left.
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 from the navigation device 15, obstacle information from the ACC radar 16, and image information obtained by the imaging unit 13. FIG. 3 shows a specific processing procedure for determining the driving environment.

In this process, a process based on the road information from the navigation device 15 is performed in step S10. Specifically, first, road information is acquired from the navigation device 15 in step S11. The road information to be acquired is information such as the number of lanes.
Subsequently, in step S12, the vehicle lane (travel lane) is determined with reference to the image information obtained by the imaging unit 13.
The determination of the travel lane (travel lane) will be described with reference to FIG. FIG. 4 shows an example in which the host vehicle 100 travels on a three-lane road on one side. 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 100 travels on such a road, the captured image obtained for each traveling lane is different.

  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 captured image by the imaging unit 13 differs depending on the traveling lane.

  Then, based on the road information from the navigation device 15, the host vehicle traveling lane is determined based on the number of lanes of the road on which the host vehicle is currently traveling and the captured image 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 travel lane of the host vehicle is determined by comparing the captured image of the vehicle.

Further, at this time, it is determined which side of the host vehicle travel lane has a shoulder. When there is a road shoulder on the left side when viewed from the vehicle lane, the road shoulder direction Rg is set to the left side (Rg = left). Further, when there is a road shoulder on the right side when viewed from the vehicle lane, the road shoulder direction Rg is set to the right side (Rg = right). Further, when there are road shoulders on both sides when viewed from the vehicle lane, the road shoulder direction Rg is set to both sides (Rg = both).
For example, when the host vehicle is traveling on the left lane on a one-side three-lane road or one-side two-lane road, the shoulder direction Rg is on the left side (Rg = left), and the host vehicle is on one-side three-lane road or one-side two-lane road. When traveling in the right lane, the shoulder direction Rg is on the right side (Rg = right). Further, when the vehicle is traveling on a one-lane road on one side, the road shoulder direction Rg becomes both directions (Rg = both).

  On the other hand, in step S20, processing based on obstacle information from the ACC radar 16 is performed. Specifically, first, in step S21, the position of an obstacle existing ahead is detected based on the obstacle information from the ACC radar 16. That is, when there is an obstacle ahead, the position where the obstacle exists is detected. Specifically, when an obstacle such as a vehicle is present in the left lane as viewed from the host vehicle lane, the obstacle direction LJ is set to the left (LJ = left). Further, when an obstacle such as a vehicle is present in the right lane as viewed from the host vehicle lane, the obstacle direction LJ is set to the right (LJ = right). Further, when an obstacle such as a vehicle is present on both lanes when viewed from the vehicle lane, the obstacle direction LJ is set to both sides (LJ = both).

In subsequent step S22, based on the obstacle information from the ACC radar 16, the relative distance Lc and the relative speed Vc with the detected obstacle are detected.
Here, when the speed of an obstacle such as another vehicle is faster than the own vehicle, the relative speed Vc becomes a positive value. Therefore, when the relative speed Vc is negative, the host vehicle is in an approaching state to an obstacle such as another vehicle.
Then, based on the processing results obtained in Steps S10 and S20, in Step S31, the degree of safety in the left-right direction viewed from the lane in which the host vehicle is traveling is determined.

  Specifically, when the host vehicle deviates, the direction in which the degree of safety is low 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 an obstacle direction) Sout (Sout = left), when the safety degree is low in the right direction when viewed from the lane in which the host vehicle is traveling, the direction is held as an obstacle existence direction Sout (Sout = right). For example, the determination is made as follows.

Here, as shown in FIG. 6, the case where the host vehicle 100 is traveling on the left lane of a three-lane highway will be described as an example.
(First Case) There is a case where another vehicle 101C is traveling in the right lane of the traveling lane of the host vehicle 100, the relative distance to the other vehicle 101C is short, and the relative speed is a negative value. . Here, the case where the relative speed is a negative value refers to a case where the host vehicle 100 is in an approaching state to the other vehicle 101C as described above.

  (2nd case) The other vehicle 101A is drive | working the left lane of the driving lane of the own vehicle 100, relative distance with the said other vehicle 101A is short, and also relative speed may become a negative value. . As shown in FIG. 6, when the host vehicle 100 is traveling in the left lane, the left side of the traveling lane of the host vehicle 100 is a shoulder (outside) A. In this case, since the other vehicle 101A exists on the road shoulder, the other vehicle 101A is a vehicle that slowly drives the road shoulder A or stops at the road shoulder A.

(Third Case) Another vehicle 100B is traveling in front of the host vehicle 100 in the same traveling lane, the relative distance to the other vehicle 101A is short, and the relative speed may be a negative value. .
For example, in the first to third cases, in the first case, since the degree of safety in the right direction is low, the right direction is set to the obstacle existence direction Sout (Sout = right). The same applies when the host vehicle 100 is traveling in the right lane. That is, since a median strip S generally exists on a highway, when the host vehicle 100 is traveling in the right lane, a rightward departure is less safe. As a result, the obstacle existence direction Sout becomes the right direction (Sout = right). Further, in the second case, since the degree of safety of the deviation to the left becomes low, the left direction is set to the obstacle existence direction Sout (Sout = left).

  In the third case, there is a possibility that after avoiding the departure, the vehicle may come into contact with another vehicle 100B traveling forward in the same lane. However, when another vehicle 100B is traveling ahead in the same lane, the host vehicle 100 can avoid the front vehicle 100B by the function of ACC (adaptive cruise control). Accordingly, in this case, the obstacle direction of existence Sout is determined based on the presence of a road shoulder or an adjacent lane of the vehicle as in the first case and the second case.

  Furthermore, the direction where the safety level is low in relation to an obstacle such as another vehicle is held as information. Here, first, a relative time Tj (= Lc / Vc) from the host vehicle to the obstacle is calculated using the relative distance Lc and the relative speed Vc between the host vehicle and the obstacle. Subsequently, the relative time Tj is compared with a predetermined threshold value. Here, when the relative time Tj is smaller than the predetermined threshold value, the direction Aout in which the obstacle exists (hereinafter referred to as the direction in which the accessible obstacle etc. exists) Aout is held. Specifically, when the obstacle is present in the left direction, the left direction is set as the accessible direction Aout (Aout = left). Further, when the obstacle exists in the right direction, the right direction is set as the accessible direction Aout (Aout = right). When the obstacle exists in both directions, the both directions are set as the accessible direction Aout (Aout = both).

As described above, the travel environment is determined in step S3.
Subsequently, in step S4, a lane departure tendency is determined. The processing procedure of this determination processing is specifically as shown in FIG.
First, in step S41, 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. 8 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 S42, 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 the process of step S42, 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 S43, 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.
For example, a departure warning is activated according to the ON / OFF state of the departure determination flag Fout obtained in step S5. For example, when the departure determination flag Fout is ON (Tout <Ts), but it can be determined that the lane does not deviate due to a steering operation by the driver, a departure warning is performed. For example, an alarm is given by sound or display.

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 (Tout <Ts), based on the obstacle existence direction Sout obtained in step S3, the accessibility obstacle existence direction Aout obtained in step S3, and the departure direction Dout obtained in step S4. Thus, a braking control method for avoiding deviation is also determined. 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. 9 shows an example. As shown in FIG. 9, for example, the gains K1 and K2 are small values in the low speed range, and when the vehicle speed V reaches a certain value, the gains K1 and K2 increase corresponding 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. 10 shows an example. As shown in FIG. 10, 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 factors 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.

  Thus, 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 fluid pressure differences ΔPsf and ΔPsr and the deceleration target braking fluid pressures Pgf and 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 obstacle existence direction Sout, the accessibility obstacle existence direction Aout, and the departure direction Dout. With respect to this, the braking control method will be described by dividing into cases (fourth to sixth cases) in the state of the obstacle existence direction Sout, the accessibility possibility obstacle existence direction Aout, and the departure direction Dout.

(Fourth Case) If the obstacle direction, such as the direction Sout and the departure direction Dout do not match, a yaw moment for avoiding departure is applied to the vehicle until the departure determination flag Fout is turned off. Brake 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.

(Fifth Case) When the obstacle etc. existence direction Sout and the departure direction Dout coincide with each other, the departure avoidance yaw control is performed until the departure determination flag Fout is turned OFF.
Furthermore, a second departure determination threshold value Tb (Ts>Tb> 0) less than the first departure determination threshold value Ts is defined, and the predicted departure time Tout is smaller than the second departure determination threshold value Tb. When this occurs (Tout <Tb), 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.

(Sixth Case) When the presence direction Aout such as the accessibility possibility obstacle coincides with the departure direction Dout, the departure avoidance yaw control is performed until the departure determination flag Fout is turned off.
Further, a third departure determination threshold value Tr (Ts ≧ Tr> 0) less than the first departure determination threshold value Ts is defined, and the predicted departure time Tout is shorter than the third departure determination threshold value Tr. When this happens (Tout <Tr), departure avoidance deceleration control is performed in addition to departure avoidance yaw control.

  Here, the third departure determination threshold value Tr is set based on the relative time Tj. Specifically, the third deviation determination threshold value Tr is set to a larger value as the relative time Tj is shorter. FIG. 11 shows an example of the setting. As shown in FIG. 11, the third deviation determination threshold value Tr is set to a larger value as the relative time Tj is shorter. The third departure determination threshold value Tr is set to the first departure determination threshold value Ts at the maximum.

  Thereby, when the third departure determination threshold value Tr is set to the same value as the first departure determination threshold value Ts (Tr = Ts), the departure avoidance yaw control and the departure avoidance deceleration control operate simultaneously, When the third departure determination threshold value Tr is set smaller than the first departure determination threshold value Ts (Tr <Ts), the departure avoidance deceleration control is activated after the departure avoidance yaw control. Furthermore, since the third departure determination threshold value Tr becomes larger as the relative time Tj becomes shorter, the start timing of departure avoidance deceleration control becomes earlier as the relative time Tj becomes shorter. Here, the start timing of departure avoidance deceleration control is the earliest when it operates simultaneously with departure avoidance yaw control.

  In step S6, various braking control methods are determined according to the states of the obstacle existence direction Sout, the accessibility obstacle existence direction Aout, and the departure direction Dout. That is, according to the states of the obstacle existence direction Sout, the accessibility possibility obstacle existence direction Aout, and the departure direction Dout, only the departure avoidance yaw control or the combination of departure avoidance yaw control and departure avoidance deceleration control The braking control method for avoiding deviation is determined.

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 case of the fourth to sixth 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 cases of the fifth and sixth cases, the deviation avoidance yaw control and the departure avoidance deceleration control are performed. In this case, the target brake 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, various braking control methods determined in accordance with the state of the obstacle existence direction Sout, the accessible obstacle existence direction Aout, and the departure direction Dout in step S6. Correspondingly, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel 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 (step S3, FIG. 3). Specifically, the direction in which obstacles such as road shoulders and other vehicles are present is set as the obstacle existence direction Sout. Furthermore, when the relative time Tj regarding the obstacle is smaller than a predetermined threshold, the direction in which the obstacle exists is set as the accessibility direction Aout.

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.

  In addition, 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 presence direction Sout of the obstacle, the presence direction Aout of the accessibility possibility obstacle and the departure direction Dout, the presence / absence of alarm start for departure avoidance, the presence / absence of braking control for departure avoidance Then, the method for executing the braking control for avoiding the 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).

  Then, the target braking hydraulic pressure Psi () of each wheel for realizing the braking control method determined based on the departure determination flag Fout, the obstacle existence direction Sout, the accessibility obstacle existence direction Aout, and the departure direction Dout. i = fl, fr, rl, rr) is calculated, and this target brake fluid pressure Psi (i = fl, fr, rl, rr) is output to the brake fluid pressure control unit 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, the vehicle behavior when the braking control is performed in the fourth to sixth cases will be described with reference to FIGS.
As described above, the fourth case is a case where the existence direction Sout of the first obstacle and the departure direction Dout do not match. That is, as shown in FIG. 12, the vehicle 100A traveling in the left lane on the one-side three-lane road (the vehicle 100A at the intermediate position in FIG. 12) tends to deviate in the right direction. Alternatively, as shown in FIG. 12, the host vehicle 100 </ b> C (the host vehicle 100 </ b> C in the uppermost position in FIG. 12) traveling in the right lane tends to deviate leftward on a three-lane road on one side. Alternatively, the host vehicle B traveling in the central lane tends to deviate leftward or rightward. That is, the host vehicle 100 deviates from the host vehicle travel lane on the road.

In this case, deviation avoidance yaw control is performed. Thereby, the own vehicle can avoid deviation. On the other hand, the driver can feel the acceleration in the lateral direction or the deceleration in the traveling direction by the departure avoiding operation of the vehicle, and can know that the own vehicle is in a tendency to depart.
Further, as described above, the fifth case is a case where the obstacle existence direction Sout matches the departure direction Dout. That is, as shown in FIG. 12, in the three-lane road on one side, 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. Or, as shown in FIG. 12, the vehicle 100C traveling in the right lane on the one-side three-lane road (the 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. Further, when the predicted departure time Tout becomes smaller than the second departure determination threshold value Tb, departure avoidance deceleration control is performed in addition to departure avoidance yaw control. Thereby, the own vehicle avoids deviation.

  Further, the sixth case is a case where the presence direction Aout and the departure direction Dout coincide with each other as described above. That is, as shown in FIG. 6, when the own vehicle 100 traveling in the left lane tends to deviate in the left direction, there is another vehicle 100A in the deviating direction, and the other vehicle 100A This is a case where the relative time Tj is smaller than a predetermined value. Alternatively, when the host vehicle 100 traveling in the left lane tends to deviate in the right direction, another vehicle 100C exists in the deviating direction, and the relative time Tj with the other vehicle 100C is greater than a predetermined value. This is the case. That is, when the own vehicle 100 deviates, there is a high possibility that the own vehicle will come into contact with another vehicle within a predetermined time.

In this case, deviation avoidance yaw control is performed. Furthermore, when the predicted departure time Tout becomes smaller than the third departure determination threshold value Tr, departure avoidance deceleration control is performed in addition to departure avoidance yaw control. Thereby, the own vehicle avoids deviation.
Here, when the third departure determination threshold value Tr is set to the same value as the first departure determination threshold value Ts (Tr = Ts), the departure avoidance yaw control and the departure avoidance deceleration control operate simultaneously, When the third departure determination threshold value Tr is set smaller than the first departure determination threshold value Ts (Tr <Ts), the departure avoidance deceleration control is activated after the departure avoidance yaw control. Further, the deviation avoidance deceleration control is activated earlier as the relative time Tj is shorter.

In addition to such braking control for avoiding deviation, 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.
In FIG. 12, the black wheels indicate the wheels to which the hydraulic pressure is generated and the braking force is applied. 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.

Next, the effect will be described.
As described above, when the relative time Tj is smaller than the predetermined threshold value, the direction in which the obstacle exists is held as the approaching obstacle etc. existence direction Aout. Then, when the presence direction Aout such as the accessibility possibility obstacle coincides with the departure direction Dout, the departure avoidance deceleration control is performed in addition to the departure avoidance yaw control. As a result, the relative time calculated based on the relative distance from the host vehicle to the obstacle existing in the departure direction of the host vehicle when the host vehicle tends to deviate from the traveling lane is a predetermined threshold value. If it is smaller, at least deceleration control for avoiding deviation is performed.

  Thereby, even if the host vehicle deviates from the traveling lane, the host vehicle can be prevented from coming into contact with an obstacle. Further, even when there is an obstacle in the departure direction of the host vehicle, frequent deceleration can be prevented by decelerating only when the relative time to reach is smaller than a predetermined threshold. . As a result, it is possible to prevent the driver from feeling annoyed by the control for preventing the departure from the vehicle.

  Further, the departure avoidance yaw control is performed, and then the departure avoidance deceleration control is performed. Thereby, it is possible to prevent the driver from feeling annoyed by the control for avoiding deviation. For example, when the departure avoidance yaw control is performed, the driver can feel the acceleration in the lateral direction or the deceleration in the traveling direction by the departure avoidance operation of the vehicle, and can know that the own vehicle is in a departure tendency. As a result, the driver avoids departure as a steering operation or the like. Thus, departure avoidance may be completed before intervention of departure avoidance deceleration control. As a result, the departure avoidance deceleration control does not always operate to avoid departure. For this reason, it is possible to prevent the driver from being bothered by the departure avoidance deceleration control by performing departure avoidance deceleration control after performing departure avoidance yaw control. In particular, the departure avoidance deceleration control is more troublesome to the driver than the departure avoidance yaw control, and therefore it is effective to reduce the operation of such departure avoidance deceleration control.

Further, as described above, the third deviation determination threshold value Tr is set to a larger value as the relative time Tj is shorter. Thereby, the shorter the relative time Tj, the earlier the intervention timing of the departure avoidance deceleration control. By doing in this way, even if the own vehicle deviates from the traveling lane, the own vehicle can be effectively prevented from suddenly approaching the obstacle.
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 braking control (deviation avoidance yaw control) is performed so that the yaw moment for avoiding the departure is applied to the vehicle, and the braking control (departure avoidance) for decelerating to avoid the 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.

  For example, in the above-described embodiment, when the vehicle has a tendency to deviate from the driving lane, and the relative time between the own vehicle and the obstacle present in the departure direction of the own vehicle is smaller than a predetermined threshold value. The departure avoidance deceleration control is performed after the departure avoidance yaw control, but the present invention is not limited to this. For example, at least departure avoidance deceleration control is performed, such as departure avoidance yaw control after departure avoidance deceleration control.

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 for converting braking force into braking hydraulic pressure, which are set based on the yaw angle φ and the travel lane curvature β, respectively.

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 processing in step S4 of the ACC radar 16 and the braking / driving force control unit 8 realizes a contact time detection unit that detects the contact time, and the imaging unit 13, The processing in the navigation device 15 and the braking / driving force control unit 8 (step S1, step S3) realizes a departure tendency detecting means for detecting the departure tendency of the host vehicle from the traveling lane. The processing in step S4 realizes a departure tendency detecting means for detecting the departure tendency of the host vehicle from the traveling lane, and the processing in step S6 of the braking / driving force control unit 8 is performed by the traveling environment detecting means. Based on the driving environment and the departure tendency detected by the departure tendency detection means, the amount of yaw moment and the deceleration are reduced. The setting means for setting the amount of burden is realized, and the processing of step S7 of the braking / driving force control unit 8 is based on the amount of yaw moment set by the setting means and deviates from the driving lane of the own vehicle. A target yaw moment calculating means for calculating a target yaw moment to avoid is realized, and the process of step S8 of the braking / driving force control unit 8 is based on the deceleration sharing amount set by the setting means. The step S9 of the braking / driving force control unit 8 is executed when the deviation tendency detecting means detects the deviation tendency. Based on the calculated target yaw moment and the deceleration control amount calculated by the deceleration control amount calculation means, the braking force of each wheel is determined. It realizes the braking force control means Gosuru.

  Further, in the process of step S6 of the braking / driving force control unit 8, since the braking control method is determined based on the contact time, the process of step S6 is based on the contact time detected by the contact time detecting means. The change means for changing the control content of the braking force control means is also realized.

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 the figure which gave and demonstrated the case where the own vehicle was drive | working the left lane of the highway of 2 lanes on one side about acquisition of obstacle presence direction Sout. 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. FIG. 10 is a characteristic diagram in which the third deviation determination threshold value Tr can be set to a larger value as the relative time Tj is shorter. It is the figure used for description of the braking control method at the time of the 4th-6th case.

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 16 ACC radar 17 Master cylinder pressure sensor 18 Accelerator opening sensor 19 Steering angle sensor 22FL 22RR Wheel speed sensor

Claims (4)

In the lane departure prevention device for avoiding the departure of the own vehicle from the traveling lane by applying at least a yaw moment to the own vehicle by braking control or decelerating the own vehicle when the own vehicle tends to deviate from the traveling lane,
Giving the yaw moment to the host vehicle by generating a braking force difference between the left and right wheels, and decelerating the host vehicle by generating equal braking force on the left and right wheels,
When the own vehicle has a tendency to deviate from the driving lane and the relative time calculated based on the relative distance from the own vehicle to the obstacle existing in the departure direction of the own vehicle is smaller than a predetermined threshold value, A lane departure prevention apparatus characterized by performing at least the deceleration. A relative time calculating means for calculating the relative time;
A departure tendency detecting means for detecting a departure tendency of the host vehicle from the traveling lane;
Setting means for setting a yaw moment share amount and a deceleration share amount based on the departure tendency detected by the departure tendency detection means;
Target yaw moment calculating means for calculating a target yaw moment for avoiding deviation from the traveling lane of the host vehicle based on the yaw moment sharing amount set by the setting means;
A deceleration control amount calculating means for calculating a deceleration control amount based on the deceleration sharing amount set by the setting means;
When the departure tendency detection means detects the departure tendency, the control of each wheel is controlled 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. Braking force control means for controlling power;
Changing means for changing the control content of the braking force control means based on the relative time detected by the relative time calculation means;
The lane departure prevention apparatus according to claim 1, further comprising:   The lane departure prevention apparatus according to claim 1 or 2, wherein the deceleration start timing is advanced as the relative time is shorter. Lane departure prevention apparatus according to any one of claims 1 to 3, characterized in that the deceleration after applying the yaw moment.

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