JP2009214742A - Lane deviation preventive device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably obtain a target yaw moment required for preventing the deviation from a traveling lane of one's own vehicle by suppressing toe angle changes due to compliance steering. <P>SOLUTION: The lane deviation preventive device includes a lane deviation tendency determining means (a step S3, a step S4) determining a deviation tendency of a vehicle to the traveling lane, a braking force controlling means (a step S13, a step S14) adding yaw moment to the vehicle by controlling the braking force of wheels to generate braking force difference on right and left wheels when the lane deviation tendency determining means determines that the deviation tendency exists, and a compliance steering correcting means (a step S10) correcting braking force which the braking force controlling means generates on the wheels, on the basis of the toe angle change due to the compliance steering generated when the braking force is generated on the wheels. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

As conventional lane departure prevention control, there is one that generates a braking force difference between the left and right wheels when there is a possibility that the host vehicle departs from the traveling lane (for example, see Patent Document 1). Thereby, the target yaw moment is given to the own vehicle, and the own vehicle is prevented from deviating from the traveling lane.
JP 2000-33860 A

By the way, the toe angle changes due to the compliance steer generated when the braking force is generated on the wheel. For this reason, when a braking force difference is generated between the left and right wheels as in the conventional lane departure prevention control, the toe angle changes due to compliance steer. In this case, a yaw moment is generated in the vehicle due to the change in the toe angle, and the yaw moment necessary for preventing the vehicle from deviating from the traveling lane is too small or too large.
An object of the present invention is to appropriately obtain a target yaw moment necessary for suppressing a change in toe angle due to compliance steer and preventing deviation of the host vehicle from the traveling lane.

  In order to solve the above-mentioned problem, the present invention generates a braking force difference between the left wheel and the right wheel by controlling the braking force of the wheel when it is determined that the vehicle tends to deviate from the driving lane. Thus, the yaw moment is applied to the vehicle, and the braking force generated on the wheel is corrected based on the change in the toe angle caused by the compliance steer when the braking force is generated on the wheel.

  According to the present invention, it is possible to appropriately obtain the yaw moment necessary for preventing the deviation of the host vehicle from the traveling lane regardless of the change in the toe angle of the wheel due to the compliance steer.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
(Constitution)
The embodiment is a rear wheel drive vehicle equipped with the lane departure prevention apparatus according to the present invention. This vehicle is equipped with an automatic transmission and a conventional differential gear. This vehicle is equipped with a braking device capable of independently controlling the braking force of the left and right wheels for both the front and rear wheels.

FIG. 1 is a schematic configuration diagram showing the present embodiment.
In the figure, reference numeral 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. Normally, the brake fluid pressure boosted by the master cylinder 3 is supplied to the wheel cylinders 6FL to 6RR of the wheels 5FL to 5RR in accordance with the depression amount of the brake pedal 1 by the driver. Further, a brake fluid pressure control unit 7 is interposed between the master cylinder 3 and each wheel cylinder 6FL to 6RR.

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

  Further, this vehicle is equipped 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 can also independently control the drive torque of the rear wheels 5RL and 5RR. Further, when a driving torque command value is input from the braking / driving force control unit 8, the driving torque control unit 12 can also control the driving wheel torque according to the driving torque command value. 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.

In addition, this vehicle is equipped with an imaging unit 13 with an image processing function. The imaging unit 13 detects the position of the host vehicle in the traveling lane. For example, the imaging unit 13 is configured to capture an image with a monocular camera composed of a CCD (Charge Coupled Device) camera. An imaging unit 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. The imaging unit 13 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. Etc. 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.

In the present invention, the lane marker may be detected by detection means other than image processing. For example, the lane marker may be detected by a plurality of infrared sensors attached to the front of the vehicle, and the traveling lane may be detected based on the detection result.
Further, the present invention is not limited to the configuration in which the traveling lane is determined based on the white line. In other words, if there is no white line (lane marker) on the road to recognize the driving lane, the information on the road shape and surrounding environment obtained by image processing and various sensors, the driving range suitable for driving and driving A person may estimate the travel range where the vehicle should travel and determine the travel lane. For example, when there is no white line on the runway and both sides of the road are separated, the asphalt portion of the runway is determined as the travel lane. Moreover, what is necessary is just to determine a driving lane in consideration of the information, when there is a guardrail, a curb, etc. Further, the traveling lane curvature β may be calculated based on a steering angle δ of the steering wheel 21 described later.

  The vehicle is equipped with a navigation device 14. The navigation device 14 detects the longitudinal acceleration Yg or the lateral acceleration Xg generated in the host vehicle, or the yaw rate φ ′ (= dφ / dt) generated in the host vehicle. The navigation device 14 outputs the detected longitudinal acceleration Yg, lateral acceleration Xg, and yaw rate φ ′ to the braking / driving force control unit 8 together with the road information. The road information includes road type information indicating the road type such as the number of lanes, general roads, and highways. Each value may be detected by a dedicated sensor. That is, the longitudinal acceleration Yg and the lateral acceleration Xg are detected by the acceleration sensor. Further, the yaw rate φ ′ is detected by the yaw rate sensor.

  Further, this vehicle is equipped with a radar 16. The radar 16 sweeps the laser light forward and receives the reflected light from the preceding obstacle, thereby detecting the distance between the host vehicle and the front obstacle. The detection result by the radar 16 is used for processing in a follow-up running control (cruise control), a rear-end collision speed reducing brake device, or the like. The radar 16 outputs information on the position of the front obstacle to the braking / driving force control unit 8.

  Further, this vehicle is equipped with suspension stroke sensors 23FL to 23RR. The suspension stroke sensors 23FL to 23RR detect the suspension stroke St. The suspension stroke sensors 23FL to 23RR output the detected suspension stroke St to the braking / driving force control unit 8. In addition, this vehicle is equipped with a three-axis sensor 15. The triaxial sensor 15 detects the road gradient Sl. The triaxial sensor 15 outputs the detected road gradient Sl to the braking / driving force control unit 8.

  Further, the vehicle includes 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, an accelerator opening sensor 18 that detects an accelerator pedal depression amount, that is, an accelerator opening θt, A steering angle sensor 19 for detecting a steering angle (steering steering angle) δ of the steering wheel 21, a direction indicating switch 20 for detecting an operation of a direction indicator (turn signal switch) by a driver, and rotational speeds of the wheels 5FL to 5RR. The wheel speed sensors 22FL to 22RR for detecting the so-called wheel speed Vwi (i = fl, fr, rl, rr) are mounted. These sensors and the like output detected detection signals to the braking / driving force control unit 8.

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

Next, calculation processing performed by the braking / driving force control unit 8 will be described.
FIG. 2 shows a calculation processing procedure performed by the braking / driving force control unit 8. For example, the arithmetic processing is executed by timer interruption every predetermined sampling time ΔT every 10 msec. Information obtained by the arithmetic processing is updated and stored in the storage device as needed, and necessary information is read from the storage device as needed.

  As shown in FIG. 2, when the process is started, first, in step S1, various data are read from each sensor, controller, and control unit. Specifically, the longitudinal acceleration Yg, lateral acceleration Xg, yaw rate φ ′ and road information obtained by the navigation device 14, road speed Vwi, steering angle δ, accelerator opening θt, master cylinder hydraulic pressure detected by each sensor Pmf, Pmr and direction switch signal, drive torque Tw from drive torque control unit 12, yaw angle φ, lateral displacement X and travel lane curvature β from imaging unit 13, suspension stroke St obtained from suspension stroke sensors 23FL-23RR, and The road gradient Sl obtained from the triaxial sensor 15 is read.

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

The vehicle speed V calculated in this way is preferably used during normal travel. 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. A value used for navigation information in the navigation device 14 can also be used as the vehicle speed V. The vehicle speed can also be calculated based on the AT axis output. In this case, the vehicle speed V is calculated by the following equation (2).
V = (2π · R) · W · (60/1000) (2)
Here, R is the ratio of the wheel radius to the differential gear (wheel radius / differential gear). W is the AT output shaft rotation speed (rpm).

Subsequently, in step S3, a lane departure tendency is determined. FIG. 3 shows the procedure of this determination process. FIG. 4 shows the definition of values used in this process.
As shown in FIG. 3, first, in step S41, an estimated lateral displacement Xs of the lateral position of the vehicle center of gravity after a predetermined time T is calculated. Specifically, using the yaw angle φ obtained in step S1, the traveling lane curvature β, the current vehicle lateral displacement X0, and the vehicle speed V obtained in step S2, the estimated lateral displacement is calculated by the following equation (3). Xs is calculated.
Xs = Tt · V · (φ + Tt · V · β) + X0 (3)
Here, Tt is the vehicle head time for calculating the forward gaze distance. When this vehicle head time Tt is multiplied by the own vehicle speed V, a forward gazing distance is obtained. Further, the estimated lateral displacement from the center of the traveling lane after the vehicle head time Tt becomes the estimated lateral displacement Xs in the future. According to the equation (3), for example, the estimated lateral displacement Xs increases as the yaw angle φ increases.

Subsequently, in step S42, departure determination is performed. Specifically, comparing the estimated lateral displacement Xs with a predetermined departure-tendency threshold value X _L. Here, departure-tendency threshold value X _L is generally a value that the vehicle can be grasped to be in the lane departure tendency. The departure tendency determination threshold value _XL is, for example, an experimental value or the like. Further, as a value indicating the position of the travel path of the boundary line, the following (4) can be calculated departure-tendency threshold value X _L by formula.
X _L = (L−H) / 2 (4)
Here, L is the lane width. H is the width of the vehicle. The lane width L is obtained by processing the captured image by the imaging unit 13. Further, the vehicle position may be obtained from the navigation device 14 or the lane width L may be obtained from the map data of the navigation device 14.

In FIG. 4, departure-tendency threshold value X _L has been set within the travel lane of the vehicle, the present invention is not limited thereto, it may be set outside of the travel lane. Moreover, it is not limited to determining that the host vehicle has a departure tendency before deviating from the traveling lane. For example, it may be determined that there is a departure tendency after at least one of the wheels deviates from the lane. In this case, the departure tendency determination threshold value _XL is set so as to obtain such a determination.

Determining _{(≧ X L | | Xs)} , there lane departure tendency and in step S42, when the estimated lateral displacement Xs is greater than or departure-tendency threshold value _{X L.} Further, when the estimated lateral displacement Xs is smaller than departure-tendency threshold value _{X L (| Xs | <X} L), it determines that there is no lane departure tendency.
Subsequently, in step S43, a departure determination flag Fout is set. That is, if it is determined in step S42 that there is a lane departure tendency (| Xs | ≧ X _L ), the departure determination flag Fout is turned ON (Fout = ON). Further, in step S42, when it is determined that no lane departure tendency _{(| Xs | <X L)} , turns OFF the departure flag Fout (Fout = OFF).

By the process of step S42 and step S43, for example, the vehicle is going away from the center of the lane, when the estimated lateral displacement Xs is equal to or greater than the departure-tendency threshold value _{X L (| Xs | ≧ X} L), departure The determination flag Fout is turned on (Fout = ON). Further, the vehicle (host vehicle Fout = ON state) is gradually restored to the lane center side, when the estimated lateral displacement Xs becomes less than departure-tendency threshold value _{X L (| Xs | <X} L ), The departure determination flag Fout is turned off (Fout = OFF). For example, when there is a tendency to deviate from the lane, the departure determination flag Fout is turned from ON to OFF if the braking control for preventing the deviation described later is performed or the driver himself performs an operation to avoid the lane departure. .

Subsequently, in step S44, the departure direction Dout is determined based on the lateral displacement X. Specifically, when the vehicle is laterally displaced leftward from the center of the lane, the direction is set as the departure direction Dout (Dout = left). Further, when the vehicle is laterally displaced from the center of the lane to the right, the direction is set to the departure direction Dout (Dout = right).
Subsequently, in step S4, the driver's intention to change lanes is determined. Specifically, the driver's intention to change the lane is determined as follows based on the direction switch signal and the steering angle δ obtained in step S1.

  When 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 S3, it is determined that the driver is intentionally changing the lane, and the departure determination flag Fout is set. Change to OFF (Fout = OFF). That is, it is changed to the determination result that there is no lane departure tendency. If 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 S3, the departure determination flag Fout is maintained and the departure determination flag Fout is kept ON. (Fout = ON). That is, the determination result that there is a tendency to depart from the lane is maintained.

When the direction indicating switch 20 is not operated, the driver's intention to change the lane is determined based on the steering angle δ. Specifically, when the driver is steering in the departure direction, when both the steering angle δ and the change amount of the steering angle (change amount per unit time) Δδ are equal to or larger than a set value, the driver Is intentionally changing the lane, and the departure determination flag Fout is changed to OFF (Fout = OFF). Note that the driver's intention may be determined based on the steering torque.
Thus, when the departure determination flag Fout is ON, the departure determination flag Fout is maintained ON when the driver has not intentionally changed the lane.

Subsequently, in step S5, when the departure determination flag Fout set (maintained) in step S4 is ON, sound output or display output is performed as an alarm for avoiding lane departure.
As will be described later, when the departure determination flag Fout is ON, the application of the yaw moment to the host vehicle is started as the lane departure prevention control. Therefore, the alarm is output simultaneously with the application of the yaw moment to the host vehicle. However, the alarm output timing is not limited to this, and may be earlier than, for example, the start timing of applying the yaw moment to the vehicle.

Subsequently, in step S6, it is determined whether or not deceleration control of the host vehicle is performed as lane departure prevention control. In the lane departure prevention control of the present embodiment, the host vehicle is decelerated by deceleration control for the purpose of preventing the host vehicle from deviating from the lane. In step S6, it is determined whether or not to perform the deceleration control. Specifically, the subtraction value obtained by subtracting the lateral displacement limit distance X _L from the estimated lateral displacement Xs calculated in step S3 whether (| | Xs -X _L) is deceleration control determining threshold value X _beta or Determine whether.

Here, the deceleration control determination threshold value _Xβ is a value set according to the travel lane curvature β. FIG. 5 shows an example of the relationship between the travel lane curvature β and the deceleration control determination threshold value _Xβ . As shown in the figure, when the travel lane curvature β is small, the deceleration control determination threshold value X _β is a certain large value. When the travel lane curvature β becomes larger than a certain value, the travel lane curvature β increases while the deceleration control determination threshold value X _β decreases. When the traveling lane curvature β further increases, the deceleration control determination threshold value X _β becomes a certain small value. Further, the deceleration control determination threshold value _Xβ may be decreased as the vehicle speed V increases.

In this step S6, when the subtraction value (| Xs | −X _L ) is equal to or greater than the deceleration control determination threshold X _β (| Xs | −X _L ≧ X _β ), it is determined that the deceleration control is performed, The deceleration control operation determination flag Fgs is set to ON (Fgs = ON). Further, when the subtraction value (| Xs | −X _L ) is less than the deceleration control determination threshold value X _β (| Xs | −X _L <X _β ), the deceleration control is determined and the deceleration control is performed. The operation determination flag Fgs is set to OFF (Fgs = OFF).

Incidentally, when the estimated lateral displacement Xs in the step S3 is higher departure-tendency threshold value _{X L (| Xs | ≧ X} L), and setting to ON and the departure flag Fout, the subtraction value (| Xs If | −X _L ) is greater than or equal to the deceleration control determination threshold value X _β , even if the departure determination flag Fout is set to ON in relation to setting the deceleration control operation determination flag Fgs to ON, that setting Is after the deceleration control operation determination flag Fgs is set to ON. That is, in relation to the yaw moment application to the host vehicle that is performed when a deviation determination flag Fout, which will be described later, is turned on, the yaw moment is applied to the host vehicle after the deceleration control of the host vehicle is performed. .

Subsequently, in step S7, a target yaw moment Ms to be given to the host vehicle as lane departure prevention control is calculated. The target yaw moment Ms is a yaw moment that can sufficiently prevent the host vehicle from deviating from the lane. Specifically, by using the estimated lateral displacement Xs and lateral displacement limit distance X _L obtained in step S3, the target yaw moment Ms is calculated by the following equation (5).
Ms = K1 · K2 · (| Xs | −X _L ) (5)

Here, K1 is a proportional gain determined from vehicle specifications. K2 is a gain that varies according to the vehicle speed V. FIG. 6 shows an example of the gain K2. As shown in the figure, in the low speed range, the gain K2 has a certain large value. Further, when the vehicle speed V becomes larger than a certain value, the gain K2 decreases with an increase in the vehicle speed V. Then, when a certain vehicle speed V is reached, the gain K2 becomes a certain small value.
According to this equation (5), the larger the difference between estimated lateral displacement Xs and lateral displacement limit distance X _L is, target yaw moment Ms becomes larger. Further, the target yaw moment Ms is calculated when the departure determination flag Fout is ON. When the departure determination flag Fout is OFF, the target yaw moment Ms is set to zero.

Subsequently, in step S8, a target braking hydraulic pressure for generating the target yaw moment Ms is calculated. In the lane departure prevention control according to this embodiment, a braking force difference is generated between the left and right wheels to apply a yaw moment to the host vehicle. In step S8, a target braking hydraulic pressure difference that generates the braking force difference is calculated. Specifically, the target braking hydraulic pressure difference ΔP is calculated by the following equation (6) using the target yaw moment Ms calculated in step S7.
ΔP = Kgb · Ms (6)
Here, Kgb is a proportional gain determined from vehicle specifications.

Subsequently, in step S9, deceleration of deceleration control performed as lane departure prevention control is calculated. In step S9, the braking force generated in both the left and right wheels is calculated in order to realize the deceleration. Specifically, target braking hydraulic pressures Pgf and Pgr for generating such a braking force on both the left and right wheels are calculated. With respect to the target braking hydraulic pressure Pgf for the front wheels, the estimated lateral displacement Xs and lateral displacement limit distance X _L calculated in step S3 and the deceleration control determination threshold value X _β obtained in step S6 are described below. It calculates with (7) Formula.
Pgf = Kgv · Kgx · (| Xs | −X _L −X _β ) (7)

  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. FIG. 7 shows an example of the conversion coefficient Kgv. As shown in the figure, the conversion coefficient Kgv has a large value in the low speed range. Further, the conversion coefficient Kgv increases as the vehicle speed V increases when the vehicle speed V reaches a certain value. When the vehicle speed V is reached thereafter, the conversion coefficient Kgv becomes a certain large 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.

Subsequently, in Step S10, it calculates the distribution ratio H ₁ after the first liquid pre- according to the characteristics of compliance steer. In general, compliance steer is defined as follows.
When braking force is applied to the wheel, the braking force is transmitted to the link mechanism that connects the wheel and the vehicle body, and the bush of the link mechanism is bent. As a result, a toe change occurs on the wheel. Actively using and controlling this toe change becomes a compliance steer. This compliance steer includes a toe-out control in which the toe angle is directed outward (toe-out direction) (the front side of the wheel is opened) and a toe angle is directed inward (toe-in direction) (after the wheel). There is toe-in control that allows the side to open. Generally, compliance steer is determined from vehicle specifications. In general, in a two-wheel drive vehicle, the front wheels have a toe angle in the toe-out direction, and in a four-wheel drive vehicle, the front wheels have a toe-in angle in the toe-in direction. In both the two-wheel drive vehicle and the four-wheel drive vehicle, the rear wheel has a toe angle in the toe-in direction.

In the present embodiment, a braking force difference is generated between the left and right wheels in order to apply a yaw moment to the host vehicle as lane departure prevention control. That is, a yaw moment is applied to the host vehicle by generating a braking force on the deviation avoidance side wheel of the left and right wheels. For example, when there is a tendency to depart from the lane on the right side of the travel lane, a braking force is generated on the left wheel serving as a departure avoiding wheel (the braking force on the left wheel is greater than the braking force on the right wheel). For this reason, during lane departure prevention control, a toe angle change due to compliance steer occurs on the wheel on the departure avoidance side. For this reason, in step S10, in consideration of the toe angle change due to the compliance steer in the lane departure prevention control, and calculates the distribution ratio H ₁ after the first liquid pre-. Specifically, the first hydraulic pressure front-rear distribution ratio H ₁ is calculated according to the compliance steer by the following formulas (8) and (9).
(1) When front wheel compliance steer Cs is in the toe-in direction (toe-in control) H ₁ = MAPin (Cs) (8)
(2) When the front wheel compliance steer Cs is in the toe-out direction (toe-out control) H ₁ = MAPout (Cs) (9)
Here, by paying attention to the compliance steer Cs of the front wheel (front wheel departure avoidance side), and calculates the distribution ratio H ₁ after the first liquid pre-.

Figure 8 shows an example of a map showing the relationship between compliance steer Cs and distribution ratio H ₁ after the first liquid pre-. As shown in the figure, in the case of compliance steer Cs (toe-in control) in the toe-in direction, the first hydraulic pressure front-rear distribution ratio H ₁ (= MAPin (Cs)) is a positive value. Further, in the case of compliance steer Cs (toe-out control) in the toe-out direction, the first hydraulic pressure front-rear distribution ratio H ₁ (= MAPout (Cs)) is a negative value. According to FIG. 8, as the compliance steer (compliance steer characteristic) Cs has a stronger toe-in tendency, the first hydraulic pressure front-rear distribution ratio H ₁ becomes a positive value and a larger value. In other words, even with the same braking force, the more liable to change in the toe direction, distribution ratio H ₁ after the first liquid pre- becomes greater than a positive value. Further, as the compliance steer (compliance steer characteristic) Cs has a stronger toe-out tendency, the first hydraulic pressure front-rear distribution ratio H ₁ becomes a negative value and a smaller value (larger in absolute value). In other words, even with the same braking force, the more liable to change in the toe-out direction, (greater in absolute value) the first liquid pre- after distribution ratio H ₁ becomes a value less than the negative. This based on the map as shown in FIG. 8, to obtain a first liquid pre- after distribution ratio H ₁ corresponding to the compliance steer determined from vehicle specifications (characteristics of compliance steer) Cs. For example, if the compliance steer Cs of the vehicle is in the toe-out direction (toe-out control), the first hydraulic pressure front-rear distribution ratio H ₁ corresponding to the compliance steer Cs is obtained using the equation (9).

Further, the compliance steer amount (a change amount of the toe angle due to the compliance steer) changes according to the braking force. For this reason, the braking force and the compliance steer amount can be associated with a map or the like, and the compliance steer amount can be obtained based on the braking force. Then, to obtain a first liquid pre- after distribution ratio H ₁ corresponding to compliance steer amount so obtained. FIG. 9 shows an example of a map showing the relationship between the braking force and the compliance steer amount. It is assumed that a map as shown in the figure can be obtained from the vehicle specifications as the relationship between the braking force and the compliance steer amount. If the compliance steer characteristic has a tendency to easily generate a toe angle, the increase rate of the compliance steer amount increases with respect to the increase in braking force. If it says in the same figure, the characteristic of a compliance steer will become easy to produce a toe angle in order of a dotted line, a continuous line, and a dashed-dotted line. As a result, in the toe-in control in which the toe angle is easily generated, the change rate of the toe angle in the toe-in direction increases with an increase in the braking force. Further, in the toe-out control in which the toe angle is easily generated, the rate of change of the toe angle in the toe-out direction increases with an increase in the braking force.

By using FIG. 9, the compliance steer amount corresponding to the braking force can be obtained from the relationship between the braking force of the vehicle specifications of the host vehicle and the compliance steer amount. Here, the braking force value for obtaining the compliance steer amount is, for example, a value obtained from the target brake hydraulic pressure equivalent calculated to generate the target yaw moment Ms in step S8. Then, based on such compliance steer amount obtained by to obtain the distribution ratio H ₁ after the first liquid pre-. For example, the compliance steer amount in FIG. 9 is defined as a gain K, and the gain K is multiplied by a predetermined value (a reference value H _{0 of} the first hydraulic pressure front / rear distribution ratio H ₁ ) to obtain the first hydraulic pressure front / back distribution. The ratio H ₁ is obtained (H ₁ = K · H ₀ ). Thus, the distribution ratio H ₁ after the first liquid pre- corresponding to the braking force, can be obtained by matching the compliance steering characteristic.

Subsequently, in step S11, the hydraulic pressure front-rear distribution ratio is calculated from the suspension stroke.
In general, the toe angle changes according to the suspension stroke St by a measure such as so-called roll steer. For this reason, in this step S11, the distribution ratio before and after the hydraulic pressure is calculated in consideration of the suspension stroke St. Specifically, varying the gain Gt to be multiplied by the first liquid pre- after distribution ratio H ₁ calculated in step S10 in accordance with the suspension stroke St. That is, the first liquid pre- after distribution ratio H ₁ calculated in step S10, it is corrected by the suspension stroke St. The gain Gt is calculated by the following procedure.

First, based on the relationship between the suspension stroke St and the toe angle, the toe angle change amount ΔTd is calculated from the suspension stroke St read in step S1 by the following equation (10).
ΔTd = MAPsp (St) (10)
Here, MAPsp (St) is a map obtained in advance based on the relationship between the suspension stroke St and the toe angle change amount ΔTd. The suspension stroke St is an average value obtained for each of the front left and right wheels, or a value selected from either the left or right wheels according to the traveling scene.

  FIG. 10 shows an example of a map showing the relationship between the suspension stroke St and the toe angle change amount ΔTd. The characteristic of the solid line shown in the figure is that of the compliance steer for toe-out control, and the characteristic of the dotted line that is the opposite characteristic is that of the compliance steer for toe-in control. In the figure, when the suspension stroke St becomes zero, it indicates a state where there is no input to the suspension (a state where only the vehicle weight is present).

  As shown in the figure, in the case of compliance steer for toe-out control (solid line characteristic), when the suspension stroke St increases on the extension side, the toe angle change amount ΔTd in the toe-in direction increases. Further, when the suspension stroke St increases on the sinking side, the toe angle change amount ΔTd in the toe-out direction increases. Further, in the case of toe-in control compliance steer (dotted line characteristic), when the suspension stroke St increases on the extension side, the toe angle change amount ΔTd in the toe-out direction increases. Further, when the suspension stroke St increases on the sinking side, the toe angle change amount ΔTd in the toe-in direction increases.

Then, using the toe angle change amount ΔTd calculated by the equation (10), the gain Gt is calculated by the following equation (11).
Gt = MAPtd (ΔTd) (11)
Here, MAPtd (ΔTd) is a map obtained in advance based on the relationship between the toe angle change amount ΔTd and the gain Gt.
FIG. 11 shows an example of a map showing the relationship between the toe angle change amount ΔTd and the gain Gt. FIG. 4A shows a compliance steer for toe-out control, and FIG. 4B shows a compliance steer for toe-in control.

  As shown in FIG. 6A, in the case of compliance steer in toe-out control, when the amount of change in toe angle in the toe-in direction increases, that is, when the suspension stroke St increases on the extension side, the gain Gt also increases. When the toe angle change amount in the toe-in direction exceeds a certain value, the gain Gt becomes a constant value (limit value) regardless of the toe angle change amount in the toe-in direction. Further, when the toe angle change amount in the toe-out direction increases, that is, when the suspension stroke St increases on the sinking side, the gain Gt also increases. When the toe angle change amount in the toe-out direction exceeds a certain value, the gain Gt becomes a constant value (limit value) regardless of the toe angle change amount in the toe-out direction. Here, the gain Gt limit value obtained corresponding to the toe angle change amount in the toe-out direction (sink amount of the suspension stroke St) corresponds to the toe angle change amount in the toe-in direction (elongation amount of the suspension stroke St). It becomes smaller than the limit value of the gain Gt obtained in this way.

  Further, as shown in FIG. 5B, in the case of compliance steer of toe-in control, when the amount of change in toe angle in the toe-out direction increases, that is, when the suspension stroke St increases on the extension side, the gain Gt also increases. When the toe angle change amount in the toe-out direction exceeds a certain value, the gain Gt becomes a constant value (limit value) regardless of the toe angle change amount in the toe-out direction. Further, when the amount of change in the toe angle in the toe-in direction increases, that is, when the suspension stroke St increases on the sinking side, the gain Gt also increases. When the toe angle change amount in the toe-in direction exceeds a certain value, the gain Gt becomes a constant value (limit value) regardless of the toe angle change amount in the toe-in direction. Here, the limit value of the gain Gt obtained corresponding to the toe angle change amount in the toe-in direction (sink amount of the suspension stroke St) corresponds to the toe angle change amount in the toe-out direction (elongation amount of the suspension stroke St). It becomes smaller than the limit value of the gain Gt obtained in this way. That is, the relationship between the gain Gt limit values is opposite to that in the compliance steer of toe-out control.

Subsequently, in Step S12, based on the road gradient Sl read in the step S1, to calculate the distribution ratio H ₂ after the second liquid pre-. Specifically, the road gradient Sl (upward slope, descending slope) in response to, and calculates the following expression (12) or (13) after the second liquid pre- by formula distribution ratio H _2.
(1) Sl> 0 (in the case of ascending slope)
H ₂ = MAPslu (Sl) (12)
(2) Sl <0 (in the case of descending slope)
H ₂ = MAPsld (Sl) (13)
Here, MAPslu (Sl), MAPsld ( Sl) is a map obtained in advance based on the relationship between road inclination Sl and the second liquid pre- after distribution ratio _{H 2.}

Figure 12 is an example of a map showing the relationship between the distribution ratio H ₂ after road gradient Sl and the second liquid before pressurization. As shown in the figure, when the uplink road gradient Sl increases, also increases the distribution ratio H ₂ after the second liquid pre-. Then, at a certain value or more uplink road gradient Sl, distribution ratio H ₂ after the second liquid pre- regardless upstream road gradient Sl becomes constant value (limit value). The relationship between the uplink road gradient Sl and the second liquid pre- after distribution ratio _{H 2} corresponds to the (12) equation MAPslu (Sl). Further, when the downlink road gradient Sl increases, distribution ratio H ₂ after the second liquid pre- decreases. Then, at a certain value or more road gradient Sl downlink, the second liquid pre- after distribution ratio H ₂ regardless down the road gradient Sl becomes constant value (limit value). Relationship road gradient Sl and the distribution ratio _{H 2} after the second liquid before pressurization of the downstream corresponds to the (13) equation MAPsld (Sl). Further, as shown in the drawing, as schematically, if the road inclination Sl upstream, second liquid pre- after distribution ratio H ₂ represents the positive, if the road inclination Sl downlink, after the second liquid pre- distribution ratio H ₂ indicates a negative value.

Subsequently, in step S13, a final hydraulic pressure front-rear distribution ratio is calculated. Specifically, the final hydraulic pressure distribution ratio H is calculated by the following equation (16) using the hydraulic pressure distribution ratios H ₁ and H ₂ and the gain Gt calculated in steps S10 to S12.
H = Gt · H ₁ + H ₂ (14)
Subsequently, in step S14, a target brake hydraulic pressure for each wheel is calculated. That is, the final braking fluid pressure is calculated according to the presence or absence of braking control for preventing lane departure (the state of the departure determination flag Fout and the deceleration control operation determination flag Fgs). Specifically, it is calculated as follows.

(1) When departure judgment flag Fout is ON (a result of determination that there is a lane departure tendency has been obtained), and the departure direction Dout is left (Dout = left), and deceleration control operation judgment flag Fgs is When the vehicle is OFF, that is, when the yaw moment is applied to the host vehicle so as to turn right, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (15). .
Psfl = 0
Psfr = ΔP + ΔP · H
Psrl = 0
Psrr = ΔP−ΔP · H
(15)

Here, the distribution ratio H after liquid pre- a sum of the post-distribution ratio H ₂ distribution ratio after the first liquid pre- H ₁ and the second liquid before pressurization. Focusing on the distribution ratio H ₁ after the first liquid pre-, distribution ratio H ₁ after the first liquid pre-, becomes positive in the case of a toe direction compliance steer Cs, negative in the case of toe-out direction of the compliance steer Cs Value (see FIG. 8). Therefore, according to the equation (15), in the case of the compliance steer Cs in the toe-in direction, the target braking hydraulic pressure Psfr on the right front wheel side is increased in the right front and rear wheels on the inside of the turn. On the other hand, in the case of the compliance steer Cs in the toe-out direction, the target braking hydraulic pressure Psrr on the right rear wheel side becomes larger.

  If the relationship between the braking force and the amount of compliance steer is taken into account (see FIG. 9), in the case of the compliance steer Cs in the toe-in direction, the greater the braking force (the greater the yaw moment), The target braking hydraulic pressure Psfr becomes larger. In the case of the compliance steer Cs in the toe-out direction, the target braking hydraulic pressure Psfr on the right rear wheel side increases as the braking force increases (the yaw moment increases).

(2) When departure judgment flag Fout is ON (a result of determination that there is a lane departure tendency has been obtained), and the departure direction Dout is right (Dout = right), and deceleration control operation determination flag Fgs is When the vehicle is OFF, that is, when the yaw moment is applied to the host vehicle so as to turn left, the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (16).
Psfl = ΔP + ΔP · H
Psfr = 0
Psrl = ΔP−ΔP · H
Psrr = 0
... (16)

  According to the equation (16), in the case of the compliance steer Cs in the toe-in direction, the target braking hydraulic pressure Psfr on the left front wheel side increases in the left front and rear wheels on the inside of the turn. On the other hand, in the case of the compliance steer Cs in the toe-out direction, the target braking hydraulic pressure Psrr on the left rear wheel side increases. If the relationship between the braking force and the amount of compliance steer is taken into account (see FIG. 9), in the case of the compliance steer Cs in the toe-in direction, the greater the braking force (the greater the yaw moment), The target braking hydraulic pressure Psfr becomes larger. In the case of the compliance steer Cs in the toe-out direction, the target braking hydraulic pressure Psfr on the left rear wheel side increases as the braking force increases (the yaw moment increases).

(3) When the departure determination flag Fout is ON, the departure direction Dout is left (Dout = left), and the deceleration control operation determination flag Fgs is ON, that is, the vehicle is turned rightward. When the host vehicle is decelerated while the yaw moment is applied, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (17).
Psfl = Pgf / 2
Psfr = Pgf / 2 + ΔP + ΔP · H
Psrl = Pgr / 2
Psrr = Pgr / 2 + ΔP−ΔP · H
... (17)

(4) When the departure determination flag Fout is ON, the departure direction Dout is “right” (Dout = right), and the deceleration control operation determination flag Fgs is ON, that is, the vehicle is yawed to turn left. When the host vehicle is decelerated while applying a moment, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (18).
Psfl = Pgf / 2 + ΔP + ΔP · H
Psfr = Pgf / 2
Psrl = Pgr / 2 + ΔP−ΔP · H
Psrr = Pgr / 2
... (18)

(5) When the departure determination flag Fout is OFF, that is, when the determination result that there is no lane departure tendency is obtained, the target brake hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is zero. become. However, if the driver is operating the brake, the braking fluid pressures Pmf and Pmr corresponding to the amount of braking operation are used to calculate the target braking fluid pressure Psi (for each wheel) according to the following equations (19) and (20). i = fl, fr, rl, rr) is calculated.
Psfl = Psfr = Pmf (19)
Psrl = Psrr = Pmr (20)
Here, Pmf is the brake fluid pressure for the front wheels. Further, Pmr is a brake fluid pressure for the rear wheel, for example, a value calculated based on the brake fluid pressure Pmf for the front wheel in consideration of the front / rear distribution.

(6) When the driver performs a brake operation and the departure determination flag Fout and the deceleration control operation determination flag Fgs are turned on, the brake fluid pressures Pmf and Pmr corresponding to the operation amount of the brake operation by the driver are set. In addition, the target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated. For example, when the driver performs a brake operation, the departure determination flag Fout is ON, the departure direction Dout is left (Dout = left), and the deceleration control operation determination flag Fgs is OFF. The target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated by the following equation (21).
Psfl = Pmf
Psfr = Pmf + ΔP + ΔP · H
Psrl = Pmr
Psrr = Pmr + ΔP−ΔP · H
(21)

  As described above, the target brake fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is set according to the brake operation state by the driver and the states of the departure determination flag Fout and the deceleration control operation determination flag Fgs. calculate. Then, the braking / driving force control unit 8 uses the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) calculated for each wheel thus calculated as a braking fluid pressure command value to the braking fluid pressure control unit 7. Output.

(Operation and action)
Operation and action are as follows.
While the vehicle is traveling, various data are read (step S1) and the vehicle speed V is calculated (step S2). Subsequently, a future estimated lateral displacement (deviation estimated value) Xs is calculated, and a lane departure tendency determination (setting of the departure determination flag Fout) is performed based on the calculated estimated lateral displacement Xs (step S3). Then, the determination result of the lane departure tendency (deviation determination flag Fout) is corrected based on the driver's intention to change the lane (step S4). And warning output is performed based on the determination result of the lane departure tendency (step S5).

Further, a target yaw moment Ms to be applied to the host vehicle as lane departure prevention control is calculated, and a target braking hydraulic pressure difference ΔP is calculated based on the calculated target yaw moment Ms (steps S7 and S8). On the other hand, the estimated lateral displacement Xs from the departure-tendency threshold value X subtraction _{value L} and the obtained by subtracting the basis of the comparison result between (| | Xs -X _L) and the deceleration control threshold value X _beta, deceleration A control operation determination flag Fgs is set (step S6). Further, deceleration (target braking hydraulic pressure Pgf) of deceleration control executed as lane departure prevention control is calculated (step S9).

On the other hand, based on compliance steer, calculates the distribution ratio H ₁ after the first liquid pre-, based on the suspension stroke St, calculates a gain Gt as a correction value of the distribution ratio H ₁ after the first liquid pre- (the Step S10, Step S11). Further, based on the road gradient Sl, it calculates a distribution ratio _{H 1} after the second liquid pre- (step S12). Then, the final hydraulic pressure front-rear distribution ratio H is calculated using the calculated hydraulic front-back distribution ratios H ₁ and H ₂ and the gain Gt (step S13).

  Subsequently, the target brake fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is determined according to the presence or absence of braking control for preventing lane departure (the state of the departure determination flag Fout and the deceleration control operation determination flag Fgs). ) Is calculated (step S14). At this time, the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated using the hydraulic pressure front-rear distribution ratio H. Then, the calculated target brake fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is output to the brake fluid pressure controller 7 as a brake fluid pressure command value. Thereby, the yaw moment according to the lane departure tendency can be given to the own vehicle. And depending on the case, the own vehicle can be decelerated.

  Here, as described above, in the lane departure prevention control, the yaw moment is applied to the host vehicle by generating braking force on the front and rear wheels located on the lane departure avoidance side (turning inside). Then, the braking force distribution of the front and rear wheels, that is, the braking hydraulic pressure distribution is determined by the hydraulic pressure front / rear distribution ratio H (formulas (15) to (18)). Here, if the hydraulic pressure front-rear distribution ratio H is a positive value, the braking fluid pressure on the front wheel side increases and the braking fluid pressure on the rear wheel side decreases. And the tendency becomes strong, so that the hydraulic pressure front-rear distribution ratio H increases. Further, if the hydraulic pressure front / rear distribution ratio H is a negative value, the braking fluid pressure on the rear wheel side increases and the braking fluid pressure on the front wheel side decreases. And the tendency becomes strong, so that the hydraulic pressure front-rear distribution ratio H increases.

Then, such a liquid pre- after distribution ratio H, is obtained distribution ratio after the first liquid pre- H ₁ and a sum of the distribution ratio H ₂ after the second liquid pre-. Distribution ratio H ₁ after the first liquid pre-, if the front wheel is a toe direction compliance steer Cs, a positive value. And as the toe-in tendency becomes stronger, the first hydraulic pressure front-rear distribution ratio H ₁ becomes a positive value and a larger value (see FIG. 8). Further, after the first liquid pre- distribution ratio H ₁ is front wheel if the toe-out direction of the compliance steer Cs, it becomes a negative value. Then, as the toe-out tendency becomes stronger, the first liquid pre- after distribution ratio H ₁ becomes a smaller value with a negative value (see FIG. 8). Therefore, if the front wheel is a compliance steer Cs in the toe-in direction, the hydraulic pressure front / rear distribution ratio H increases. That is, the braking fluid pressure on the front wheel side increases and the braking fluid pressure on the rear wheel side decreases. And the degree of the increase and decrease becomes large, so that the toe-in tendency becomes strong. Further, if the front wheel is a compliance steer Cs in the toe-out direction, the hydraulic pressure front / rear distribution ratio H is small. That is, the braking fluid pressure on the front wheel side decreases and the braking fluid pressure on the rear wheel side increases. And the degree of the reduction | decrease and increase becomes large, so that the toe-out tendency becomes strong. Thereby, the yaw moment of the host vehicle generated by the change in the toe angle of the front wheels due to the compliance steer Cs can be suppressed. For example, if the front wheel is a compliance steer Cs in the toe-out direction, a change in the toe angle of the front wheel in the toe-out direction is suppressed by suppressing the generation of the braking force of the front wheel, resulting in the change in the toe angle. Yaw moment can be suppressed.

Further, the first hydraulic pressure front-rear distribution ratio H ₁ corresponding to the braking force is obtained by matching the compliance steer characteristic (see FIG. 9). The braking force here is a braking force (corresponding to the target braking fluid pressure) for generating the target yaw moment Ms, that is, a braking force according to a lane departure tendency. Accordingly, when the lane departure tendency is high and the braking force is increased, it is possible to increase the degree of increase and decrease in the brake fluid pressure of the front wheels and the rear wheels as described above. For example, when the front wheel is in compliance steer Cs in the toe-out direction, as the braking force increases, the degree of decrease in the brake fluid pressure on the front wheel side and the degree of increase in the brake fluid pressure on the rear wheel side both increase. Thereby, regardless of the braking force, a change in the toe angle of the front wheels in the toe-out direction can be appropriately suppressed.

In the relationship with the suspension stroke, multiplied by the gain Gt to distribution ratio H ₁ after the first liquid pre- and (see the step S11) to be changed according to the gain Gt to the suspension stroke St. As a result, the braking force for applying the yaw moment to the vehicle is corrected based on the change in the toe angle of the wheel due to the suspension stroke, and a desired yaw moment is obtained. For example, when the front wheel is a compliance steer in the toe-out direction and the suspension is extended (when the extension amount of the stroke St increases), the toe angle changes in the toe-in direction. This means that when the front wheel is in compliance steer in the toe-out direction, the toe angle changes in the toe-in direction, which means that the lateral force cannot be obtained with the front wheel (the yaw moment shared by the front wheel) cannot be obtained. I can say that. For this reason, when the front wheel is in compliance steer in the toe-out direction and the toe angle changes in the toe-in direction, the gain Gt is increased (see FIG. 11 (a)), so that the rear wheel By gaining lateral force, a desired yaw moment (target yaw moment) can be obtained in the entire vehicle. Also, when the front wheel is in compliance steer in the toe-out direction and the sinking sinks (when the amount of sinking of the stroke St increases), the toe angle changes in the toe-out direction. In such a case, while increasing the gain Gt (see FIG. 11A), which is smaller than the change in the toe angle in the toe-in direction, the change in the toe angle of the front wheels in the toe-out direction is suppressed. The desired yaw moment (target yaw moment) can be obtained.

In the relationship with the road gradient, and increases the second liquid pre- after distribution ratio H ₂ when up the road gradient Sl increases. Further, when the downlink road gradient Sl increases have reduced the second liquid pre- after distribution ratio H ₂ (see FIG. 12). Therefore, if it is an upward road gradient S1, the hydraulic pressure front-rear distribution ratio H is increased. That is, the braking fluid pressure on the front wheel side increases and the braking fluid pressure on the rear wheel side decreases. As the upward road gradient Sl increases, the degree of increase and decrease increases. Further, if the road gradient is Sl, the hydraulic pressure front / rear distribution ratio H is small. That is, the braking fluid pressure on the front wheel side decreases and the braking fluid pressure on the rear wheel side increases. And the degree of the reduction | decrease and increase becomes large, so that the downhill road gradient Sl becomes large. Thereby, the yaw moment which generate | occur | produces in the own vehicle by the toe angle change of the front wheel by a road gradient can be suppressed. For example, in the case of a downward slope, by suppressing the generation of the braking force of the front wheels, the change in the toe angle of the front wheels can be suppressed, and as a result, the yaw moment resulting from the change in the toe angle can be suppressed.

This embodiment can also be realized by the following configuration.
That is, in this embodiment, the hydraulic pressure front-rear distribution ratio is changed according to the compliance steer. On the other hand, the brake fluid pressure of the entire front and rear wheels can be changed. That is, without considering the hydraulic pressure front / rear distribution ratio, the brake hydraulic pressure of the front wheels, rear wheels, or both front and rear wheels is increased or decreased. The wheels referred to here are wheels positioned on the inner side of the turn by applying a yaw moment to the host vehicle.

  As a result, the yaw moment generated in the host vehicle due to the change in the toe angle due to the compliance steer is the same as that for correcting the yaw moment applied to the host vehicle by the lane departure prevention control. Can be offset. For example, the yaw moment generated in the lane departure direction due to the change in the toe angle due to the compliance steer can be canceled by increasing the brake fluid pressure of the front wheels, rear wheels, or both front and rear wheels.

In this embodiment, the braking force is controlled by controlling the braking fluid pressure. On the other hand, the braking force can be controlled by another mechanical structure or electrically (for example, an electric motor).
In this embodiment, various maps and tables are specifically described with reference to FIGS. However, since the map and table are determined by other conditions such as vehicle specifications, the map and table have other characteristics (the opposite characteristics in extreme examples) as long as the effects of the present invention can be obtained. ).

  In this embodiment, the processing of step S3 and step S4 of the braking / driving force control unit 8 realizes a lane departure tendency determination means for determining the departure tendency of the vehicle with respect to the traveling lane. In addition, the processing of step S13 and step S14 of the braking / driving force control unit 8 is performed by controlling the braking force of the wheels between the left wheel and the right wheel when the lane departure tendency determination means determines that there is a departure tendency. A braking force control means for applying a yaw moment to the vehicle by generating a braking force difference is realized. Further, the processing in step S10 of the braking / driving force control unit 8 corrects the braking force generated by the braking force control means on the wheel based on the change in the toe angle caused by the compliance steer generated when the braking force is generated on the wheel. The compensation means for compliance steer is realized.

  In this embodiment, when the vehicle tends to deviate from the driving lane, a braking force difference is generated between the left wheel and the right wheel to give the vehicle a yaw moment for preventing lane departure. The braking force of the wheel that generates a braking force difference between the left wheel and the right wheel can suppress the yaw moment generated in the vehicle due to the change in the toe angle due to the compliance steer when the braking force is generated on the wheel. The lane departure prevention method set in is realized.

(effect)
The effect of this embodiment is as follows.
(1) When it is determined that the host vehicle tends to deviate from the traveling lane, the braking force of the wheels is controlled to generate a braking force difference between the left and right wheels, thereby giving a yaw moment to the host vehicle. Yes, the braking force generated on the wheel is corrected based on the toe angle change caused by the compliance steer when the braking force is generated on the wheel. As a result, the yaw moment necessary for preventing the deviation of the host vehicle from the traveling lane can be obtained regardless of the change in the toe angle due to the compliance steer.

(2) The braking force is corrected in a direction to suppress the yaw moment generated in the host vehicle due to the change in the toe angle due to the compliance steer. Thereby, it is possible to appropriately obtain the yaw moment necessary for preventing deviation of the host vehicle from the traveling lane.
(3) A yaw moment is applied to the host vehicle by generating a braking force difference between the left and right front and rear wheels, and the braking force is corrected by changing the hydraulic pressure front-rear distribution ratio. Accordingly, it is possible to suppress the yaw moment generated in the host vehicle due to the change in the toe angle due to the compliance steer while achieving the desired yaw moment (target yaw moment) by maintaining the absolute amount of the braking force to be generated.

(4) The braking force for applying the yaw moment to the host vehicle is corrected based on the change in the toe angle of the wheel due to the suspension stroke. Thereby, it is possible to appropriately obtain the yaw moment necessary for preventing deviation of the host vehicle from the traveling lane.
(5) The braking force is corrected based on the change in the toe angle of the wheel due to the road surface gradient of the traveling road. Specifically, the braking force is corrected in a direction to suppress the yaw moment generated in the vehicle due to the change in the toe angle of the wheel due to the road surface gradient of the traveling road. Thereby, it is possible to appropriately obtain the yaw moment necessary for preventing deviation of the host vehicle from the traveling lane.

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 control unit which comprises the said lane departure prevention apparatus. It is a flowchart which shows the processing content of determination of the lane departure tendency by the said control unit. It is a diagram used to describe such estimated lateral displacement Xs and deviation judgment threshold value X _L. FIG. 6 is a characteristic diagram showing a relationship between a travel lane curvature β and a deceleration control determination threshold value _Xβ . It is a characteristic view which shows the relationship between the vehicle speed V and the gain K2. It is a characteristic view which shows the relationship between the vehicle speed V and the gain Kgv. It is a characteristic diagram showing the relationship between the compliance steer Cs and distribution ratio H ₁ after the first liquid pre-. FIG. 6 is a characteristic diagram showing a relationship between braking force and compliance steer amount (toe angle change amount). FIG. 6 is a characteristic diagram showing a relationship between a suspension stroke St and a toe angle change amount ΔTd. FIG. 6 is a characteristic diagram showing a relationship between a toe angle change amount ΔTd and a gain Gt. Is a characteristic diagram showing the relationship between the distribution ratio H ₂ after road gradient Sl and the second liquid before pressurization.

Explanation of symbols

  6FL to 6RR wheel cylinder, 7 brake fluid pressure control unit, 8 braking / driving force control unit, 9 engine, 12 drive torque control unit, 13 imaging unit, 14 navigation device, 15 3-axis sensor, 16 radar, 17 master cylinder pressure sensor , 18 accelerator opening sensor, 19 steering angle sensor, 22FL-22RR wheel speed sensor, 23FL-23RR suspension stroke sensor

Claims (6)

A lane departure tendency determination means for determining a vehicle departure tendency with respect to a traveling lane;
When the lane departure tendency determining means determines that there is a departure tendency, the braking force for controlling the braking force of the wheels and generating a braking force difference between the left wheel and the right wheel to give a yaw moment to the vehicle Control means;
Compliance steer correcting means for correcting the braking force generated by the braking force control means on the wheel based on a toe angle change caused by the compliance steer generated when the braking force is generated on the wheel;
A lane departure prevention apparatus comprising:   2. The lane departure prevention apparatus according to claim 1, wherein the compliance steer correcting unit corrects a braking force in a direction to suppress a yaw moment generated in the vehicle due to a change in a toe angle due to the compliance steer. The braking force control means gives a yaw moment to the vehicle by generating a braking force difference between the left and right left and right wheels, respectively.
The lane departure prevention apparatus according to claim 1 or 2, wherein the compliance steering correction means corrects the braking force by changing a braking force distribution of front and rear wheels.   Suspension stroke detecting means for detecting the suspension stroke of the wheel, and suspension stroke correcting means for correcting the braking force of the wheel based on a change in the toe angle of the wheel due to the suspension stroke detected by the suspension stroke detecting means. The lane departure prevention apparatus according to any one of claims 1 to 3.   Road surface gradient detecting means for detecting a road surface gradient of a traveling road of the vehicle, and road surface gradient correcting means for correcting a braking force of the wheel based on a change in toe angle of the wheel due to the road surface gradient detected by the road surface gradient detecting means. The lane departure prevention apparatus according to any one of claims 1 to 4, further comprising: When the vehicle tends to deviate from the driving lane, a yaw moment for preventing lane departure is given to the vehicle by generating a braking force difference between the left wheel and the right wheel,
The braking force of the wheel that generates a braking force difference between the left wheel and the right wheel can suppress the yaw moment generated in the vehicle due to the change in the toe angle due to the compliance steer when generating the braking force on the wheel. A lane departure prevention method characterized by setting.

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