JP5256934B2 - Lane departure prevention apparatus and method - Google Patents

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 a conventional lane departure prevention device, there is a device that prevents the own vehicle from deviating from the traveling lane by giving a yaw moment to the own vehicle when the own vehicle may deviate from the traveling lane ( For example, see Patent Document 1). Further, as a conventional lane departure prevention device, when a lane division line (boundary line) such as a white line or a center line cannot be detected, the lane departure line is estimated and lane departure prevention control is performed. . For example, the lane departure prevention control is performed based on the white line in the form of a broken line, the section where the white line cannot be detected, and the estimated white line.
JP 2000-33860 A

By the way, in the conventional lane departure prevention device, if the yaw moment is calculated based on the estimated lane marking, there is a problem that the yaw moment may become larger than necessary.
The subject of this invention is making it the magnitude | size of an appropriate yaw moment, even when estimating a lane marking.

In order to solve the above-mentioned problem, the present invention prevents the deviation of the host vehicle from the traveling lane based on the estimated lane marking when the detection accuracy of the lane marking is lowered by the lane marking detection means. Lane departure prevention control is performed. Then, when the time during which the detection accuracy of the lane marking is decreasing has passed a predetermined time that varies according to the own vehicle speed, correction is performed to reduce the control amount of the lane departure prevention control.

  According to the present invention, the correction for reducing the control amount of the lane departure prevention control is performed according to the time during which the detection accuracy of the lane marking is decreasing. As a result, even when the lane marking is estimated due to a decrease in the detection accuracy of the lane marking, the control amount of the lane departure prevention control can be set to an appropriate size.

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)
This embodiment is a vehicle equipped with a lane departure prevention apparatus according to the present invention. This vehicle is a rear wheel drive vehicle. The vehicle is equipped with an automatic transmission and a differential gear, and a braking device capable of independently controlling the braking force of the left and right wheels for both the front and rear wheels.
FIG. 1 is a schematic configuration diagram showing the present embodiment. In the figure, reference numeral 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. 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 marking (boundary line) such as a white line (lane marker) or a center line from a captured image in front of the host vehicle. The imaging unit 13 calculates various values based on the detected lane markings. Specifically, the imaging unit 13 calculates an angle (yaw angle) φr formed between the travel lane of the host vehicle and the longitudinal axis of the host vehicle, a lateral position X from the center of the travel lane, a travel lane curvature β, and the like. The imaging unit 13 outputs the calculated yaw angle (detected yaw angle) φr, lateral position (detected lateral position) X, travel lane curvature β, and the like to the braking / driving force control unit 8.

  The vehicle is equipped with a navigation device 14. The navigation device 14 detects the longitudinal acceleration Yg and lateral acceleration Xg generated in the host vehicle and the yaw rate φ ′ (= dφr / 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 can also 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.

  Moreover, this vehicle is equipped with various sensors. Specifically, this vehicle is equipped with a master cylinder pressure sensor 17 that detects an output pressure of the master cylinder 3, that is, a master cylinder hydraulic pressure Pm (Pmf). In addition, this vehicle is equipped with an accelerator opening sensor 18 that detects the amount of depression of the accelerator pedal, that is, the accelerator opening θt. In addition, this vehicle is equipped with a steering angle sensor 19 that detects a steering angle (steering steering angle) δ of the steering wheel 21. In addition, this vehicle includes a direction indicator switch 20 that detects an operation of a direction indicator (turn signal switch) by a driver, and a rotation speed of each wheel 5FL to 5RR, so-called wheel speed Vwi (i = fl, fr, rl, Wheel speed sensors 22FL to 22RR for detecting rr) are mounted. These sensors and the like output the detected detection signal to the braking / driving force control unit 8.

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 are read. Also, each wheel speed Vwi, steering angle δ, accelerator opening θt, master cylinder hydraulic pressure Pm, and direction switch signal detected by each sensor are read. Further, the driving torque Tw is read from the driving torque control unit 12, and the yaw angle φr, the lateral position X, and the travel lane curvature β are read from the imaging unit 13.

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. Vwrl and Vwrr are the wheel speeds of the left and right rear wheels, respectively. 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).

Next, in step S3 to calculate the lane between the estimated time t _b. Specifically, the imaging unit 13 turns on the inter-lane estimation flag Fline when the detection accuracy of the lane marking is lowered (Fline = ON). Then, the duration of the lane inter estimation flag has been turned ON, is calculated as the lane between the estimated times t _b. The lane between the estimated time t _b is a time detection accuracy of the lane marker is decreased. The lane between the estimated time t _b is the time when that estimates the lane marker, or it can be said that it is time estimates between the vehicle and the lane marker. Further, for example, when the lane marking is in the form of a broken line, the detection accuracy of the lane marking is reduced. Moreover, when the detection lateral position X varies, it can also be determined that the detection accuracy of the lane marking is lowered.

  Subsequently, in step S4, an estimated lateral position is calculated. FIG. 3 shows an example of the calculation process. As shown in FIG. 3, first, in step S21, it is determined whether or not the inter-lane estimation flag Fline is ON. If the inter-lane estimation flag Fline is ON (Fline = ON), the process proceeds to step S22. If not (Fline = OFF), step S22 is skipped and the process proceeds to step S23.

In step S22, the lane between the estimated time t _b calculated in the step S3 determines whether a predetermined threshold (predetermined time) T _b below. The predetermined threshold value _Tb is an experimental value, an empirical value, or a theoretical value. The predetermined threshold value _Tb is changed according to the traveling state. Specifically, it is varied continuously (linearly) the predetermined threshold value T _b in accordance with the vehicle speed V. Figure 4 shows an example of the relationship between vehicle speed V and the predetermined threshold value T _b. As shown in FIG. 4, as the vehicle speed V is large, the predetermined threshold value T _b is reduced. In step S22, if the lane between the estimated time _{t b} is equal to or less than the predetermined threshold value _{T b (t b ≦ T b} ), the process proceeds to step S23. Further, when the lane between the estimated time _{t b} is greater than a predetermined threshold value _{T b (t b> T b} ), the process proceeds to step S24.

In step S23, an estimated lateral position (estimated lateral position value) Xe and a lateral position hold value tempXe are set based on the lateral position (detected lateral position, current value of lateral position) X read in step S1. Specifically, the estimated lateral position Xe and the lateral position hold value tempXe are set by the following formulas (3) and (4).
Xe = X (3)
tempXe = X (4)
Here, in step S23 which has proceeded when the inter-lane estimation flag Fline is ON (in the case of “Yes” in the determination of step S21), the estimated lateral position Xe and the lateral position are detected by the detected lateral displacement X whose detection accuracy is reduced. The position hold value tempXe can also be set. Further, the estimated lateral position Xe and the lateral position hold value tempXe can be set by the detected lateral displacement X estimated by a predetermined calculation. Further, the estimated lateral position Xe and the lateral position holding value tempXe can be set based on the detected lateral position X that can be detected immediately before the accuracy is not lowered.

After such setting, the processing of FIG. 3 is terminated (the processing is started again from step S21).
In step S24, it is determined whether or not the lateral position X is larger than the lateral position holding value tempXe. If the lateral position X is larger than the lateral position hold value tempXe (X> tempXe), the process proceeds to step S25. If the lateral position X is equal to or smaller than the lateral position holding value tempXe (X ≦ tempXe), the process proceeds to step S23.
In step S25, the estimated lateral position Xe is set to the lateral position holding value tempXe (Xe = tempXe). Then, the process of FIG. 3 is terminated (the process is started again from step S21).

In step S4, the estimated lateral position Xe is calculated as described above.
Subsequently, in step S4, an estimated yaw angle is calculated. FIG. 5 shows an example of the calculation process. As shown in FIG. 5, first, in step S41, it is determined whether or not the inter-lane estimation flag Fline is ON. If the inter-lane estimation flag Fline is ON (Fline = ON), the process proceeds to step S42. If not (Fline = OFF), step S42 is skipped and the process proceeds to step S43.

In step S42, the lane between the estimated time t _b calculated in the step S3 determines whether less than a predetermined threshold value T _b. Here, when the lane between the estimated time _{t b} is equal to or less than the predetermined threshold value _{T b (t b ≦ T b} ), the process proceeds to step S43. If the estimated lane time t _b is greater than the predetermined threshold value T _b (t _b > T _b ), the process proceeds to step S44.
In step S43, an estimated yaw angle (estimated yaw angle) φe and a yaw angle holding value tempφe are set based on the yaw angle (detected yaw angle, current value of yaw angle) φr read in step S1. Specifically, the estimated yaw angle φe and the yaw angle holding value tempφe are set by the following equations (5) and (6).
φe = φr (5)
tempφe = φr (6)

  Here, in step S43 which has proceeded when the inter-lane estimation flag Fline is ON (in the case of “Yes” in the determination of step S41), it can be set by the detected lateral displacement X whose detection accuracy is lowered. In other words, the estimated yaw angle φe and the yaw angle hold value tempφe can be set by the detected yaw angle φr obtained based on the detected lateral displacement X whose detection accuracy is lowered. Further, the estimated lateral position Xe and the lateral position hold value tempXe can be set by the detected yaw angle φr estimated by a predetermined calculation. Further, the estimated lateral position Xe and the lateral position holding value tempXe can be set by the detected yaw angle φr that can be detected immediately before the accuracy is not lowered.

After such setting, the processing of FIG. 5 is terminated (the processing is started again from step S41).
In step S44, it is determined whether the yaw angle φr is larger than the yaw angle hold value tempφe. If the yaw angle φr is larger than the yaw angle hold value tempφe (φr> tempφe), the process proceeds to step S45. If the yaw angle φr is equal to or less than the yaw angle hold value tempφe (φr ≦ tempφe), the process proceeds to step S43.

In step S45, the estimated yaw angle φe is set to the yaw angle hold value tempφe (φe = tempφe). Then, the process of FIG. 5 is terminated (the process is started again from step S41).
In step S5, the estimated yaw angle φe is calculated as described above.
Subsequently, in step S6, a lane departure tendency is determined. FIG. 6 shows an example of the processing procedure of this determination processing. FIG. 7 shows the definition of values used in this process.

As shown in FIG. 6, first, in step S61, the estimated lateral displacement Xs of the lateral position of the center of gravity of the vehicle after a predetermined time T is calculated. Specifically, using the yaw angle φr, the traveling lane curvature β and the lateral position (detected lateral position) X obtained in step S1, and the vehicle speed V obtained in step S2, the estimated lateral is calculated by the following equation (7). The displacement Xs is calculated.
Xs = Tt · V · (φr + Tt · V · β) + X (7)
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 value from the center of the traveling lane after the vehicle heading time Tt becomes the estimated lateral displacement in the future (forward gazing point estimated lateral displacement) Xs. According to the equation (7), for example, the estimated lateral displacement Xs increases as the yaw angle φr increases.

Subsequently, in step S62, 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, it can be calculated departure-tendency threshold value X _L by the following equation (8).
X _L = (L−H) / 2 (8)
Here, L is the lane width (see FIG. 7). H is the width of the vehicle (see FIG. 7). The imaging unit 13 obtains the lane width L by processing the captured image. Further, the position of the vehicle can be obtained from the navigation device 14, and the lane width L can be obtained from the map data of the navigation device 14.

Determining _{(≧ X L | | Xs)} , there lane departure tendency and in step S62, 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 S63, a departure determination flag Fout is set. That is, when it is determined in step S62 that there is a lane departure tendency (| Xs | ≧ X _L ), the departure determination flag Fout is turned ON (Fout = ON). Further, in step S62, 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 S62 and step S63, 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 S64, the departure direction Dout is determined based on the lateral position 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).
In step S6, the lane departure tendency is determined as described above.

Subsequently, in step S7, a control estimated lateral displacement is calculated as a deviation estimated value. Specifically, using the estimated lateral position Xe obtained in step S4, the estimated yaw angle φe obtained in step S5, the travel lane curvature β obtained in step S1, and the vehicle speed V obtained in step S2. The estimated control lateral displacement Xf is calculated by the following equation (9).
Xf = Tt · V · (φe + Tt · V · β) + Xe (9)
Here, Tt is the vehicle head time for calculating the forward gaze distance. In this equation (9), the estimated yaw angle φe is a control gain (proportional gain) of lane departure prevention control (deceleration control). According to the equation (9), the control estimated lateral displacement Xf increases as the estimated yaw angle φe increases. Further, as the estimated lateral position Xe increases, the control estimated lateral displacement Xf increases.

Subsequently, in step S8, the driver's intention to change lanes is determined. Specifically, the driver's intention to change the lane is determined as follows based on the direction switch signal and the steering angle δ obtained in step S1.
If the direction indicated by the direction switch signal (the blinker lighting side) is the same as the direction indicated by the departure direction Dout obtained in step S6, it is determined that the driver has intentionally changed the lane. Then, the departure determination flag Fout is changed to OFF (Fout = OFF). That is, it is changed to the determination result that there is no lane departure tendency. When the direction indicated by the direction switch signal (the blinker lighting side) is different from the direction indicated by the departure direction Dout obtained in step S6, the departure determination flag Fout is maintained. In this case, 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 consciously changing the lane. Then, the departure determination flag Fout is changed to OFF (Fout = OFF). It is also possible to determine the driver's intention 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 S9, when the departure determination flag Fout set (maintained) in step S8 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 yaw moment applied to the host vehicle. However, the alarm output timing is not limited to this, and can be set earlier than, for example, the start timing of giving the yaw moment to the host vehicle.

Subsequently, in step S10, it is determined whether or not to perform deceleration control of the host vehicle 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 S10, 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 S6 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. 8 shows an example of the relationship between the travel lane curvature β and the deceleration control determination threshold value _Xβ . As shown in FIG. 8, 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, as the vehicle speed V increases, the deceleration control determination threshold value _Xβ can be decreased.

In this step S10, when the subtraction value (| Xs | −X _L ) is equal to or larger than the deceleration control determination threshold value X _β (| Xs | −X _L ≧ X _β ), it is determined that the deceleration control is performed. Then, the deceleration control operation determination flag Fgs is set to ON (Fgs = ON). When the subtraction value (| Xs | −X _L ) is less than the deceleration control determination threshold value X _β (| Xs | −X _L <X _β ), it is determined not to perform the deceleration control. Then, the deceleration control operation determination flag Fgs is set to OFF (Fgs = OFF).

Incidentally, when the estimated lateral displacement Xs at the step S6 is more departure-tendency threshold value _{X L (| Xs | ≧ X} L), is set to ON and the departure flag Fout. Further, in step S10, the subtraction value (| Xs | -X _L) is equal to or larger than the threshold value X _beta deceleration control judgment is set to ON deceleration control flag Fgs. From these relationships, even if the departure determination flag Fout is set to ON, the setting is made 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 S11, 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, the target yaw moment Ms is calculated by the following equation (10) using the estimated lateral position Xe obtained in step S4.
Ms = K1 · K2 · (| Xe | −X _L ) (10)

  Here, K1 is a proportional gain determined from vehicle specifications. K2 is a gain that varies according to the vehicle speed V. Further, in this equation (10), the estimated lateral position Xe forms a control gain (proportional gain) of lane departure prevention control (yaw moment control). FIG. 9 shows an example of the gain K2. As shown in FIG. 9, 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 (10), the estimated lateral position Xe (absolute value) becomes larger, since the difference value between the estimated lateral position Xe (the absolute value) and the lateral displacement limit distance X _L increases, the target yaw moment Ms is growing. 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 S12, deceleration of deceleration control performed as lane departure prevention control is calculated. In this step S12, 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. The front brake target brake fluid pressure Pgf is calculated by the following equation (11) using the control estimated lateral displacement Xf calculated in step S7.
Pgf = Kgv · Kgx · (| Xf | −X _L −X _β ) (11)

  Here, Kgv and Kgx are conversion coefficients set based on the vehicle speed V and the lateral change amount dx, respectively. Further, Kgv and Kgx are also conversion coefficients for converting braking force into braking fluid pressure. FIG. 10 shows an example of the conversion coefficient Kgv. As shown in FIG. 10, in the low speed range, the conversion coefficient Kgv has a certain small value. When the vehicle speed V becomes greater than a certain value, the conversion coefficient Kgv increases as the vehicle speed V increases. Thereafter, when a certain vehicle speed V is reached, 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.

According to the equation (11), the target braking hydraulic pressure increases as the control estimated lateral displacement Xf (absolute value) increases. Further, from the relationship with the equation (9), the target braking hydraulic pressure increases as the estimated yaw angle φe increases. Further, the target braking hydraulic pressure increases as the estimated lateral position Xe increases.
Subsequently, in step S13, a target brake hydraulic pressure for each wheel is calculated. That is, the final braking fluid pressure is calculated based on the presence or absence of braking control for preventing lane departure. Specifically, it is calculated as follows.

When the departure determination flag Fout is OFF, that is, when the determination result that there is no lane departure tendency is obtained, as shown in the following equations (12) and (13), the target braking fluid pressure Psi (i = fl, fr, rl, rr) are set to the brake fluid pressures Pmf, Pmr.
Psfl = Psfr = Pmf (12)
Psrl = Psrr = Pmr (13)
Here, Pmf is the brake fluid pressure for the front wheels. Further, Pmr is the braking fluid pressure for the rear wheels, and is a value calculated based on the braking fluid pressure Pmf (Pm) for the front wheels in consideration of the front-rear distribution. For example, if the driver is performing a brake operation, the brake fluid pressures Pmf and Pmr are values corresponding to the operation amount of the brake operation.

On the other hand, when the departure determination flag Fout is ON, that is, when a determination result that there is a lane departure tendency is obtained, first, based on the target yaw moment Ms, the front wheel target braking hydraulic pressure difference ΔPsf and the rear wheel target braking hydraulic pressure difference ΔPsr are set. calculate. Specifically, the target braking hydraulic pressure differences ΔPsf and ΔPsr are calculated by the following equations (14) to (17).
When | Ms | <Ms1 ΔPsf = 0 (14)
ΔPsr = Kbr · Ms / T (15)
When | Ms | ≧ Ms1 ΔPsf = Kbf · (Ms / | Ms |) · (| Ms | −Ms1) / T (16)
ΔPsr = Kbr · (Ms / | Ms |) · Ms1 / T (17)
Here, Ms1 represents a setting threshold value. T indicates a tread. The tread T is set to the same value before and after for convenience. 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 generated on the wheels is distributed according to the magnitude of the target yaw moment Ms. 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 zero, 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. Let When the target yaw moment Ms is equal to or greater than the setting threshold value Ms1, a predetermined value is given to each target brake hydraulic pressure difference ΔPsr, ΔPsr, and a braking force difference is generated between the front, rear, left and right wheels.

  Then, the final target brake fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated using the target brake fluid pressure differences ΔPsf, ΔPsr calculated as described above and the target brake fluid pressures Pgf, Pgr for deceleration. ) Is calculated. Specifically, the final target brake hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated with reference to the deceleration control operation determination flag Fgs obtained in step S10.

That is, when the departure determination flag Fout is ON and the deceleration control operation determination flag Fgs is OFF, that is, the determination result that there is a lane departure tendency is obtained, but only the yaw moment is applied to the vehicle, The target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated from the equation (18).
Psfl = Pmf
Psfr = Pmf + ΔPsf
Psrl = Pmr
Psrr = Pmr + ΔPsr
... (18)

Further, when the departure determination flag Fout is ON and the deceleration control operation determination flag Fgs is ON, that is, when the vehicle is decelerated while giving a yaw moment to the vehicle, the target of each wheel is expressed by the following equation (19). The brake fluid pressure Psi (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
... (19)

  Further, as shown in the equations (18) and (19), the brake operation by the driver, that is, the target brake fluid pressure Psi (i = fl, fr, rl) of each wheel in consideration of the brake fluid pressures Pmf, Pmr. , Rr). Then, the braking / driving force control unit 8 uses the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) calculated for each wheel thus calculated as a braking fluid pressure command value to the braking fluid pressure control unit 7. Output.

It should be noted that the target braking hydraulic pressures of the respective wheels shown in the equations (18) and (19) are obtained when the departure direction Dout is left (Dout = left), that is, when there is a lane departure tendency with respect to the left lane. Is. For example, when the departure direction Dout is right, the target brake hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel corresponding to the equation (18) can be calculated by the following equation (20).
Psfl = Pmf + ΔPsf
Psfr = Pmf
Psrl = Pmr + ΔPsr
Psrr = Pmr
... (20)

(Operation and action)
While the vehicle is traveling, various data are read (step S1) and the vehicle speed V is calculated (step S2). Then, to calculate the lane between the estimated time _{t b} (step S3). Then, based on the lane between the estimated time t _b calculated, to calculate the estimated lateral position Xe and the estimated yaw angle .phi.e (Step S4, Step S5, FIG. 3, FIG. 5). Further, a control estimated lateral displacement Xf is calculated based on the calculated estimated lateral position Xe and estimated yaw angle φe (step S7).

  On the other hand, based on the estimated lateral displacement Xs, a departure determination flag Fout is set (lane departure tendency is determined) (step S6). Then, the determination result is changed according to the driver's intention to change the lane (step S8). Further, a deceleration control operation determination flag Fg is set (determination of deceleration control determination) based on the estimated lateral displacement Xs (step S10). Then, the target yaw moment Ms is calculated based on the estimated lateral position Xe previously calculated (step S11). Further, deceleration of deceleration control is calculated based on the control estimated lateral displacement Xf previously calculated (step S12).

  Then, an alarm is output based on the departure determination flag Fout (step S9). Further, based on the departure determination flag Fout and the deceleration control operation determination flag Fgs, the target braking hydraulic pressure Psi (i = fl, fr, rl, rr) of each wheel is calculated (step S13). Then, the calculated target braking fluid pressure Psi (i = fl, fr, rl, rr) of each wheel is output to the braking fluid pressure control unit 7 (step S13). Thus, a warning is output according to the lane departure tendency of the host vehicle, and a yaw moment is applied to the host vehicle. Further, depending on the case, the host vehicle is decelerated.

Further, the details of the lane departure prevention control are as follows.
When the lane line (boundary line) can be detected, the target yaw moment Ms is determined based on the detected lateral position X (Xe) based on the detected lane line (step S21 → step S23). It is calculated (step S11). Further, based on the detected lateral position X (Xe) and detected yaw angle φr (φe) based on the detected lane marking (step S21 → step S23, step S41 → step S43), the deceleration (target braking fluid) Pressure) is calculated (step S7, step S12).

Further, when the detection accuracy of the lane marking is lowered due to the white line or the like in the form of a broken line, the target yaw moment Ms is set based on the estimated lateral position Xe (step S21 → step S22 → step S23). It is calculated (step S11). Further, based on the estimated lateral position Xe and the estimated yaw angle φe (step S21 → step S22 → step S23, step S41 → step S42 → step S43), the deceleration (target braking fluid pressure) is calculated (the above-described step). Step S7, Step S12).
In the present embodiment, as described above, the estimated lateral position Xe and the estimated yaw angle φe are obtained, that is, the lateral position and yaw angle of the host vehicle with respect to the lane marking are estimated. Such an estimation is equivalent to estimating the lane markings themselves.

  In addition, when the detection accuracy of the lane marking is lowered, the estimated lateral (estimated lateral position Xe, estimated yaw angle φe), that is, if the estimated time of the lane marking is elapsed for a predetermined time, The position Xe is set to the horizontal position holding value tempXe (step S25). Further, the estimated yaw angle φe is set to the yaw angle holding value tempφe (step S45). Based on the estimated lateral position Xe (lateral position holding value tempXe), the target yaw moment Ms is calculated (step S11). That is, the target yaw moment Ms is calculated based on the lateral position holding value tempXe that is a constant value (step S11). Further, the deceleration (target braking fluid pressure) is calculated based on the estimated lateral position Xe (lateral position holding value tempXe) and the estimated yaw angle φe (yaw angle holding value tempφe) (steps S7 and S12). ). That is, the deceleration (target braking hydraulic pressure) is calculated based on the lateral position holding value tempXe and the yaw angle holding value tempφe that are constant values (steps S7 and S12). Accordingly, the estimated lateral position Xe and the estimated yaw angle φe are not changed (limited) even in the estimation period of the lane marking. Therefore, the target yaw moment Ms and the deceleration (target braking fluid pressure) are prevented from becoming unnecessarily large due to the estimated value (estimated lateral position Xe, estimated yaw angle φe) or the estimated lane marking. it can.

  In addition, the detected lateral position X and the detected yaw angle φr (values when the detection accuracy of the lane marking is lowered) are larger than the lateral position held value tempXe and the yaw angle held value tempφe. Based on these conditions, the target yaw moment Ms and the like are calculated based on the lateral position hold value tempXe and the like (steps S24 and S44). Thus, the values for calculating the target yaw moment Ms and the deceleration are selected low. As a result, the target yaw moment Ms and deceleration (target braking fluid pressure) are prevented from becoming larger than necessary.

  The above lane departure prevention control is implemented. In the determination to intervene the lane departure prevention control (determination of lane departure tendency, deceleration control determination), unlike the case of calculating the control amount (target yaw moment, deceleration) of the lane departure prevention control, the detected value ( The detected lateral position X and the detected yaw angle φr) are used (steps S6 and (7)). That is, the intervention determination of the lane departure prevention control and the calculation of the control amount of the lane departure prevention control are performed using different values. Specifically, the intervention determination of the lane departure prevention control is performed using the camera detection line by the imaging unit 13. Thereby, it is prevented that the lane departure prevention control is not ended by using the estimated value.

(Modification of this embodiment)
(1) In this embodiment, when the inter-lane estimation time t _b is larger than the predetermined threshold value T _b (t _b > T _b ), the target yaw is based on the lateral position hold value tempXe and the yaw angle hold value tempφe. The moment Ms and deceleration (target braking fluid pressure) are calculated. In contrast, without using a predetermined threshold value T _b, depending on the lane between the estimated time t _b, the target yaw moment Ms and the deceleration (target brake fluid pressure) can also be calculated. For example, more lanes between the estimated time t _b is lengthened, the estimated value (the estimated lateral position Xe, the estimated yaw angle .phi.e) controlled variable (yaw moment, deceleration) based on (continue to successively smaller) will reduce the .

(2) By multiplying the target yaw moment Ms or deceleration (target braking fluid pressure), which is the control amount of the lane departure prevention control, by directly multiplying the control gain and correcting the control gain, the target yaw moment Ms or deceleration ( (Target braking hydraulic pressure) can also be corrected.
In this embodiment, the imaging unit 13 realizes a lane marking detection unit that detects a lane marking. Further, the processing of step S6 and step S10 of the braking / driving force control unit 8 includes lane departure tendency determining means for determining a departure tendency of the host vehicle from the traveling lane based on the lane marking detected by the lane marking detection means. Is realized. Further, the process of step S13 of the braking / driving force control unit 8 is based on the lane marking detected by the lane marking detection means when the lane departure tendency determination means determines that a departure tendency has occurred. A departure prevention control means for performing lane departure prevention control for preventing the departure of the host vehicle from the traveling lane is realized. Further, the processing of steps S3 to S5 and step S7 of the braking / driving force control unit 8 is based on the estimated lane marking when the detection accuracy of the lane marking is lowered by the lane marking detection means. The lane departure prevention control means for performing the lane departure prevention control for preventing the departure of the host vehicle from the traveling lane, and the control amount of the lane departure prevention control is reduced according to the time when the detection accuracy of the lane marking is lowered. A control amount correcting means for correcting is realized.

  Further, in this embodiment, the lane departure tendency determination step for determining the departure tendency of the host vehicle with respect to the traveling lane based on the lane division line detected by the lane division line detection means, and the departure tendency in the lane departure tendency determination step. If it is determined that the vehicle has occurred, lane departure prevention control is performed based on the lane line detected by the lane line detection unit to prevent the vehicle from deviating from the traveling lane, and the lane line detection unit detects the lane line detection unit. When the detection accuracy of the lane marking is lowered, a lane departure prevention control step for performing lane departure prevention control for preventing the departure of the host vehicle from the traveling lane based on the estimated lane marking, and detection of the lane marking A lane departure prevention method comprising: a control amount correction step for performing correction to reduce the control amount of the lane departure prevention control according to the time when the accuracy is reduced. That.

(Effect in this embodiment)
(1) Lane departure prevention for preventing deviation of the host vehicle from the traveling lane based on the estimated lane marking when the lane marking detection means has lowered the detection accuracy of the lane marking. Control is in progress. Then, the control amount correction means corrects the control amount of the lane departure prevention control to be small according to the time when the detection accuracy of the lane marking is decreasing. Specifically, correction is performed to reduce the control amount of the lane departure prevention control as the time during which the detection accuracy of the lane markings is lowered becomes longer.

As a result, even when the lane marking is estimated due to a decrease in the detection accuracy of the lane marking, the control amount (yaw moment, deceleration) of the lane departure prevention control can be appropriately set. For example, if the time during which the detection accuracy of the lane line is decreased (estimated time of the lane line) becomes longer, an error increases with the actual lane line. For example, the case where the own vehicle is traveling on a curved road can be mentioned. For example, there is a scene in which a lane marking is estimated when there is a departure tendency inside a curved road.
Thus, when the error between the actual lane markings increases, the control amount may increase more than necessary. On the other hand, the control amount of the lane departure prevention control is set to an appropriate size by performing correction to reduce the control amount of the lane departure prevention control according to the time when the detection accuracy of the lane marking is decreasing. it can.

(2) When a predetermined time has elapsed during which the detection accuracy of the lane marking is decreasing, correction is performed to reduce the control amount of the lane departure prevention control.
When a certain amount of time has elapsed in which the detection accuracy of the lane markings has decreased, it is possible to prevent inadvertent correction by correcting the control amount of the lane departure prevention control to be small.
(3) The predetermined time is changed according to the vehicle speed. Thereby, the control amount of the lane departure prevention control can be reduced corresponding to the vehicle behavior. As a result, the control amount of the lane departure prevention control can be set to an appropriate size according to the vehicle behavior.

(4) The predetermined time is reduced as the host vehicle speed increases. Thereby, the control amount of the lane departure prevention control can be reduced earlier as the own vehicle becomes larger. As a result, the control amount of the lane departure prevention control can be set to an appropriate size according to the vehicle behavior.
(5) The departure prevention control means performs lane departure prevention control for preventing the departure of the own vehicle from the traveling lane based on the detected value of the traveling state of the own vehicle with respect to the lane marking detected by the lane marking detection means. Yes. In such a case, the control amount correction means corrects the detected value of the traveling state of the host vehicle with respect to the lane marking to correct the control amount for the lane departure prevention control.
Thereby, the control amount of the lane departure prevention control can be set to an appropriate size in correspondence with the traveling state of the host vehicle.

(6) The control amount correction means corrects the control amount for the lane departure prevention control by limiting the change in the detected value of the traveling state of the host vehicle with respect to the lane marking.
Thereby, the correction | amendment which makes the control amount of lane departure prevention control small can be performed on the basis of the detected value of the driving state of the own vehicle with respect to a lane marking. As a result, the control amount of the lane departure prevention control that is optimal for the traveling state of the host vehicle can be achieved.
The departure prevention control means performs lane departure prevention control for preventing the departure of the host vehicle from the traveling lane based on the detected value of the traveling state of the host vehicle with respect to the lane marking detected by the lane marking detection means. . On the premise of such a configuration, the change in the detected value of the traveling state of the host vehicle with respect to the lane marking is limited, and correction is performed to reduce the control amount of the lane departure prevention control. That is, the detection value used for the lane departure prevention control is corrected, and the control amount of the lane departure prevention control is corrected.

  Here, it is also possible to correct the detection value used for determining the departure tendency and, as a result, correct the control amount of the lane departure prevention control. However, if the detection value for determining the departure tendency is corrected, the lane departure prevention control may not be completed. Therefore, by correcting the detection value used for the lane departure prevention control without correcting the detection value used for determining the departure tendency, the lane departure prevention control does not end as such. Can be prevented.

(7) The detected value of the traveling state of the host vehicle with respect to the lane marking is at least one of the lateral position of the host vehicle with respect to the lane marking and the yaw angle of the host vehicle with respect to the lane marking.
Thereby, the correction | amendment which makes the control amount of lane departure prevention control small can be performed on the basis of the horizontal position of the own vehicle with respect to a lane marking, and the yaw angle of the own vehicle with respect to a lane marking. As a result, it is possible to obtain an optimal control amount for lane departure prevention control corresponding to the lateral position and yaw angle of the host vehicle.
(8) The control amount correction means corrects the control amount of the lane departure prevention control by correcting the control gain of the lane departure prevention control.
Thereby, the control amount of the lane departure prevention control can be easily set to an appropriate size.

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 calculation processing content of the estimated horizontal position by the said control unit. It is a characteristic diagram showing the relationship between vehicle speed V and the lane between the estimated time t _b. It is a flowchart which shows the calculation processing content of the estimated yaw angle by the said control unit. It is a flowchart which shows the processing content of determination of the lane departure tendency by the said control unit. It is a diagram used for explanation of the estimated lateral displacement Xs and 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.

Explanation of symbols

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

Claims (7)

Lane marking detection means for detecting a lane marking;
Based on the lane markings detected by the lane marking detection means, lane departure tendency determination means for determining the departure tendency of the vehicle relative to the traveling lane;
When the lane departure tendency determination means determines that a departure tendency has occurred, lane departure prevention control is performed to prevent the vehicle from departing from the traveling lane based on the lane division line detected by the lane division line detection means. Deviation prevention control means to perform,
With
The departure prevention control means prevents the departure of the host vehicle from the traveling lane based on the estimated lane division line when the detection accuracy of the lane division line is lowered by the lane division line detection means. Control
Further comprising control amount correction means for performing correction to reduce the control amount of the lane departure prevention control when a predetermined time has elapsed when the detection accuracy of the lane marking is decreasing ,
The predetermined time is, the lane departure prevention apparatus characterized that you change according to vehicle speed. Wherein the more the host vehicle speed is large, the lane departure prevention apparatus according to claim 1, wherein the predetermined time is reduced. The departure prevention control means performs lane departure prevention control for preventing a deviation of the host vehicle from the traveling lane based on a detected value of the traveling state of the host vehicle with respect to the lane marking detected by the lane marking detection unit. And
Wherein the control amount correction means, said by correcting the detection value of the traveling condition of the vehicle with respect to a lane marker, according to claim 1 or 2, characterized in that a correction to reduce a control amount of the lane departure prevention control The lane departure prevention device according to claim 1. Wherein the control amount correction means, by limiting the change in the detection value of the traveling condition of the vehicle with respect to the lane marker, claim 3, characterized in that a correction to reduce a control amount of the lane departure prevention control The lane departure prevention device according to claim 1. Detection values of the running state of the vehicle with respect to the lane marker, claim 3, characterized in that the lateral position and the lane marker of the vehicle relative to the lane marker is at least one of the yaw angle of the vehicle Or the lane departure prevention apparatus of 4 or 4 . The said control amount correction | amendment means correct | amends which makes the control amount of the said lane departure prevention control small by correct | amending the control gain of the said lane departure prevention control, The any one of Claims 1-5 characterized by the above-mentioned. The lane departure prevention device according to claim 1. Based on the lane marking detected by the lane marking detection means, a lane departure tendency determination step for determining a departure tendency of the host vehicle with respect to the traveling lane;
When it is determined in the lane departure tendency determination step that a departure tendency has occurred, lane departure prevention control is performed to prevent the departure of the host vehicle from the traveling lane based on the lane division line detected by the lane division line detection means. When the detection accuracy of the lane marking is lowered by the lane marking detection means, the lane departure prevention control is performed to prevent the vehicle from deviating from the traveling lane based on the estimated lane marking. Control steps;
A control amount correction step for performing correction to reduce the control amount of the lane departure prevention control when a predetermined time has elapsed when the detection accuracy of the lane marking is decreasing; and
Have,
It said predetermined time, the lane departure prevention method comprising Rukoto varied according to vehicle speed.

Images