JP2005178454A - Lane departure preventing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a driver to make an accurate route correction in a departure avoiding direction when his/her own vehicle is determined to have the possibility of departure from a travelling lane. <P>SOLUTION: This lane departure preventing device determines the possibility of departure from a travelling lane of its own vehicle based on the travelling condition of the vehicle and a road surface friction coefficient. When the possibility of departure is determined, a target yaw moment in the departure avoiding direction is calculated in consideration of the road surface friction coefficient. Furthermore, a required minimum deceleration amount for suppressing a feeling of discomfort to a passenger due to the yaw moment given to the vehicle is calculated base on the travelling condition of the vehicle. Departure preventing control is executed by the combination of yaw control and deceleration control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

As a conventional lane departure prevention device, the lane departure from the traveling lane of the host vehicle is judged, and the left and right wheels are controlled according to the estimated amount of departure from the future lane calculated based on the traveling state of the host vehicle. It is known to avoid lane departure by braking control that combines yaw control that generates a yaw moment in the vehicle by giving a power difference and deceleration control that applies braking force to each wheel so that the host vehicle decelerates. (For example, refer to Patent Document 1).
Japanese Unexamined Patent Publication No. 2003-112540 (page 7, FIG. 2)

However, in the above conventional lane departure prevention device, when a deviation from the driving lane is determined, the braking fluid pressure is calculated according to the estimated deviation from the future lane, and a yaw moment is given to the host vehicle. Therefore, there is an unsolved problem that the vehicle behavior when the yaw moment is generated when the friction coefficient between the running road surface and the tire is low may cause the passengers including the driver to feel uncomfortable.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and it is possible to perform departure avoidance control that hardly causes a sense of incongruity even when the road surface friction coefficient is low. An object of the present invention is to provide a lane departure prevention device that can be used.

  In order to achieve the above object, a lane departure prevention apparatus according to the present invention detects a traveling state of the host vehicle by a traveling state detection unit, estimates a road surface friction coefficient of the host vehicle traveling path by a friction coefficient estimation unit, and Based on the traveling state detected by the traveling state detecting means and the road surface friction coefficient estimated by the friction coefficient estimating means, the departure determining means determines that the host vehicle tends to depart from the traveling lane, and the departure determining means Yaw control based on the running condition detected by the running condition detecting means and the road surface friction coefficient estimated by the friction coefficient estimating means when it is determined that the host vehicle tends to deviate from the driving lane. The amount calculation means calculates the first braking force control amount of each wheel so that the yaw moment is generated in a direction that avoids the departure from the traveling lane of the host vehicle, and the traveling state detected by the traveling state detection means Base Then, the second braking force control amount of each wheel is calculated so that the host vehicle decelerates by the braking control amount calculating means, and calculated by the yaw control amount calculating means and the braking control amount calculating means by the braking force control means. The braking force of each wheel is controlled in accordance with the first and second braking force control amounts.

  According to the present invention, the departure determination is performed based on the traveling state of the host vehicle and the road surface friction coefficient of the host vehicle traveling path, and when the host vehicle tends to depart from the traveling lane, the road surface friction coefficient of the host vehicle traveling path is determined. In consideration, since the control amount of yaw control and deceleration control is calculated and braking control is performed, when the road surface friction coefficient is low, lane departure can be appropriately prevented by advancing the start timing of departure avoidance control, By setting the yaw moment generated in the vehicle to be small, it is possible to prevent the passenger from feeling uncomfortable due to vehicle behavior when the yaw moment is generated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. This vehicle is a rear wheel drive vehicle equipped with an automatic transmission and a conventional differential gear, and the braking device can control the braking force (braking fluid pressure) of the left and right wheels independently of the front and rear wheels.
In the figure, reference numeral 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, 4 is a reservoir, 9 is an engine, and 10 is an automatic transmission. Normally, the master pedal depends on the amount of depression of the brake pedal 1 by the driver. The brake fluid pressure boosted by the cylinder 3 is supplied to the wheel cylinders 6FL to 6RR of the front wheels 5FL, 5FR and the rear wheels 5RL, 5RR. Further, a braking fluid pressure control circuit 7 is interposed between the master cylinder 3 and each wheel cylinder 6FL-6RR. The braking fluid pressure control circuit 7 includes a braking fluid for each wheel cylinder 6FL-6RR. It is also possible to control the pressure individually.

  The brake fluid pressure control circuit 7 uses a brake fluid pressure control circuit used for, for example, anti-skid control or traction control. In this embodiment, the brake fluid pressures of the wheel cylinders 6FL to 6RR are independently set. It is configured so that the pressure can be increased or decreased. The brake fluid pressure control circuit 7 controls the brake fluid pressures of the wheel cylinders 6FL to 6RR in accordance with a brake fluid pressure command value from a control unit 8 described later.

  In addition, this vehicle includes a CCD camera 13 and a camera controller 14 as an external recognition sensor for detecting the position of the host vehicle in the traveling lane for determining the traveling lane departure prevention of the host vehicle. The camera controller 14 detects a lane marker by detecting a lane marker such as a road marking line from a captured image in front of the host vehicle captured by the CCD camera 13, and further detects the yaw angle Φ of the host vehicle relative to the lane, The lateral displacement X from the center of the lane, the curvature β of the traveling lane, the lane width L, and the like can be calculated, and these calculation signals are output to the control unit 8.

Further, the vehicle includes a master cylinder pressure sensor 16 as a braking operation deceleration amount detecting means for detecting an output pressure of the master cylinder 3, that is, a so-called master cylinder pressure Pm, and a steering angle sensor for detecting a steering angle δ of the steering wheel 19. 20, wheel speed sensors 21FL to 21RR for detecting the rotational speed of each wheel 5FL to 5RR, that is, so-called wheel speed Vw _j (j = FL to RR), a direction indicating switch 22 for detecting a direction indicating operation by a direction indicator, and a wiper operation Wiper switch 23 is provided, and these detection signals are output to the control unit 8.

If the detected vehicle traveling state data has left and right directions, the left direction is the positive direction. That is, the yaw angle Φ becomes a positive value when turning left, and the lateral displacement X becomes a positive value when it is shifted to the left from the center of the traveling lane.
Further, a warning device 24 is provided in front of the driver's seat to present a warning to the driver in response to an alarm signal AL from the control unit 8 when a deviation from the driving lane is detected. Built-in speaker for generating buzzer sound.
The control unit 8 functions as an anti-skid control (ABS) or vehicle behavior control (VDC) controller, estimates the friction coefficient μ between the running road surface and the tire, and stores the estimated road friction coefficient μ. It is configured to store in the device 25.

Next, the lane departure prevention control process performed by the control unit 8 will be described with reference to the flowcharts of FIGS. This lane departure prevention control process is executed by, for example, a timer interrupt process every 10 msec.
In this lane departure prevention control process, first, in step S1 of FIG. 2, various data from the sensors and controllers are read. Specifically, each wheel speed Vw _j detected by each sensor, master cylinder pressure Pm, steering angle δ, direction indicating switch signal WS, stroke amount Ls, vehicle yaw angle Φ with respect to the travel lane from the camera controller 14, The lateral displacement X from the center of the travel lane, the curvature β of the travel lane, and the travel lane width L are read.

Next, the process proceeds to step S <b> 2, and the road surface friction coefficient μ stored in the storage device 25 is read. This road surface friction coefficient μ is estimated by ABS at the time of brake operation by the driver, and the latest value is stored in the storage device 25. Note that the friction coefficient estimated for a predetermined time or a predetermined traveling distance from the present time may be stored, and the average value or the minimum value of the stored friction coefficients may be adopted as the road surface friction coefficient μ.
Next, in step S3, the vehicle speed V of the host vehicle is calculated from the average value of the front left and right wheel speeds Vw _FL and Vw _FR among the wheel speeds Vw _{FL to} Vw _RR read in step S1. The process proceeds to step S4.
V = (Vw _FL + Vw _FR ) / 2 (1)

In step S4, referring to the deviation determination time calculation map shown in FIG. 4, the time Tt [sec] until the host vehicle departs from the traveling lane is calculated according to the road surface friction coefficient μ estimated in step S2. .
In this deviation determination time calculation map, when the road surface friction coefficient μ is higher than the predetermined value μ _SET , the departure determination time Tt is set to the time Tt _SET , and when the road surface friction coefficient μ is equal to or less than the predetermined value μ _SET , the road surface friction coefficient μ as decreases, the departure determination time Tt is set to be calculated greater than the time Tt _sET. Here, the predetermined value μ _SET is a road surface friction coefficient that is determined to allow a target braking operation to be performed without causing the passenger to feel uncomfortable.

Next, in step S5, as shown in FIG. 5, an estimated lateral displacement, that is, an estimated deviation value Xs after a predetermined time is calculated. Specifically, the lateral displacement X from the center of the traveling lane read in step S1, the lateral displacement speed dX calculated by differentiating the lateral displacement X, and the departure determination time Tt calculated in step S4. Based on the following equation (2), a deviation estimated value Xs is calculated, and the process proceeds to step S6.
Xs = dX × Tt + X (2)

Further, the estimated deviation value Xs is the vehicle yaw angle Φ with respect to the traveling lane of the host vehicle read in step S1, the lateral displacement X from the center of the traveling lane, the curvature β of the traveling lane, and the own vehicle calculated in step S3. Based on the vehicle speed V, it may be calculated according to the following equation (3).
Xs = Tt × V × (Φ + Tt × V × β) + X (3)
It should be noted that the deviation estimated value Xs becomes a positive value when deviating leftward.

The deviation estimated value Xs is compared with the position of the boundary line of the center of gravity of the vehicle in the travel lane, that is, the departure boundary line _XL, and the lane departure of the host vehicle is determined. First, in step S6, a departure boundary line _XL is calculated. The departure boundary line _XL is expressed by the following equation (4) by the travel lane width L and the width H of the host vehicle. The right side is a positive value.
X _L = ± (L−H) / 2 (4)
Next, in step S7, it is determined whether or not the absolute value | Xs | of the deviation estimated value Xs is greater than or equal to the absolute value | X _L | of the deviation boundary line X _L , and | Xs | <| X _L |. Sometimes, the process proceeds to step S8, the departure determination flag _Fout is reset to “0” which means that the host vehicle does not tend to deviate, and the process proceeds to step S13 described later.

Further, when | Xs | ≧ | X _L |, the process proceeds to step S9, the departure determination flag _Fout is set to “1” which means that the host vehicle tends to depart, and the process proceeds to step S10. Whether the estimated deviation value Xs is positive or negative is determined. When Xs ≧ 0, it is determined that the deviation is to the left, and the process proceeds to step S11. After the deviation direction flag _Dout is set to “1”, the process proceeds to step S13 described later. On the other hand, when Xs <0, it is determined that the deviation is to the right, and the process proceeds to step S12. After the deviation direction flag _Dout is set to “2”, the process proceeds to step S13.

Next, the driver's intention to change the lane is determined based on the direction indication switch and the steering angle. First, in step S13, it is determined whether or not the direction indicating switch 22 is in an on state. If it is in the on state, the process proceeds to step S14, where it is determined based on the operating direction of the direction indicating switch and the departure direction flag _Dout. It is determined whether or not the departure direction matches, and when both directions match, it is determined that the lane is changed, and the process proceeds to step S15, and the departure determination flag _Fout is reset to “0”. The process proceeds to step S17 described later. On the other hand, when both directions do not coincide with each other, it is determined that the lane is not changed, and the process proceeds to step S17 as will be described later.

If the result of the determination in step S13 is that the direction indicating switch 22 is in the OFF state, the process proceeds to step S16, where the steering angle δ is equal to or larger than the preset steering angle setting value δ _S and the steering angle change amount Δδ is predetermined. It is determined whether or not the set change amount setting value Δδ _S or more. If δ ≧ δ _S and Δδ ≧ Δδ _S, it is determined that the driver is willing to change the lane, and the process proceeds to step S15. Transition. On the other hand, when δ <δ _S or Δδ <Δδ _S, it is determined that the driver is not willing to change lanes, and the routine proceeds to step S17.

Incidentally, here, the driver's intention to change the lane is determined based on the steering angle δ and the steering angle change amount Δδ. However, the present invention is not limited to this. For example, the determination is made by detecting the steering torque. You may do it.
In step S17 of FIG. 3, based on the lane curvature β and the vehicle speed V, a parameter Xa that is a threshold for determining the necessity of deceleration control is calculated with reference to the parameter calculation map shown in FIG. The parameter calculation map is set so that the parameter Xa is calculated smaller as the curvature β is larger and the vehicle speed V is faster.

Next, in step S18, whether or not the value | Xs | − | X _L | obtained by subtracting the absolute value of the deviation boundary line X _L from the absolute value of the deviation estimated value Xs is greater than or equal to the parameter Xa calculated in step S17. When | Xs | − | X _L | ≧ Xa, that is, when the deviation estimated value Xs deviates from the deviation boundary line X _L by Xa or more, it is determined that deceleration control of the host vehicle is required. The process proceeds to step S19, the deceleration control operation flag Fgs is set to “1”, and then the process proceeds to step S21 described later. If the determination result in step S18 is | Xs | − | X _L | <Xa, the process proceeds to step S20, the deceleration control operation flag Fgs is set to “0”, and then the process proceeds to step S21.

In order to set the deceleration control operation flag Fgs in this way, for example, when the curve of the traveling lane ahead of the host vehicle is gentle and the estimated departure value Xs is small, Fgs = 0, so that the host vehicle is decelerated. There is no end to it, and the passengers do not have to feel uncomfortable.
Further, since the parameter Xa is set to decrease as the curvature β of the traveling lane of the host vehicle increases, for example, if a steep curve appears in front of the host vehicle, | Xs | − | X _L | ≧ Xa Since the deceleration control operation flag Fgs is set to “1”, the host vehicle is decelerated and an increase in the estimated departure value Xs is suppressed.

Further, since the parameter Xa is set so as to decrease as the host vehicle speed V increases, for example, when the host vehicle is traveling at high speed, | Xs | − | X _L | ≧ Xa and deceleration control operation is performed. Since the flag Fgs is set to “1”, the host vehicle is decelerated and an increase in the estimated departure value Xs is suppressed.
In step S21, it is determined whether or not the departure determination flag F _out is set to “1” which means that the own vehicle has a departure tendency. If F _out = 1, the process proceeds to step S22. Then, the alarm signal AL is output to the alarm device 24 to activate the alarm, and the process proceeds to step S23.

In step S23, the calculation of the following equation (5) is performed to calculate the target yaw moment Ms, and then the process proceeds to step S26 described later.
Ms = Ks × (Xs−X _L ) (5)
Here, Ks is a positive value that varies according to the vehicle speed V and the departure determination time Tt, and is calculated with reference to the gain calculation map shown in FIG. 7 based on the vehicle speed V and the departure determination time Tt. This gain calculation map is set so that the gain Ks is calculated to be smaller as the vehicle speed is faster and the time until departure is longer.

That is, the lower the friction coefficient μ between the road surface and the tire, the longer the time Tt until the departure is set. Therefore, the lower the friction coefficient μ, the smaller the gain Ks is calculated, and the smaller the yaw moment applied to the vehicle is calculated. become.
When the determination result in step S21 is F _out = 0, the process proceeds to step S24, the output of the alarm signal AL is stopped, then the process proceeds to step S25, and the target yaw moment Ms is expressed by the following equation (6). Is set to 0 (zero) based on the above, and then the process proceeds to step S26.
Ms = 0 (6)

In step S26, a target brake hydraulic pressure calculation process for calculating a target brake hydraulic pressure Ps _i (i = FL to RR) of each wheel according to the target yaw moment Ms and the master cylinder hydraulic pressure Pm is performed.
Then, the processing proceeds to step S27, to return from the output of the target brake hydraulic pressures Ps _FL ~Ps _RR calculated at step S26 to the brake hydraulic control circuit 7 to end the timer interrupt process to a predetermined main program .
In the step S26, it is determined whether perform target brake hydraulic pressure calculation processing shown in FIG. 8, first departure determination flag F _out in step S31 is reset to "0".

When the determination result of step S31 is F _out = 0, the process proceeds to step S32, and the target braking hydraulic pressure Ps _FL of the front left wheel and the target braking hydraulic pressure Ps of the front right wheel as shown in the following equation (7) sets the _FR to 1/2 of the front wheel master cylinder pressure Pmf considering the rear distribution from the master cylinder pressure Pm, the following (8) of the target brake hydraulic pressures Ps _RL and rear right wheel of the rear left wheel as shown in the formula The target brake fluid pressure calculation process is terminated after setting the target brake fluid pressure Ps _RR to ½ of the rear wheel master cylinder pressure Pmr considering the front-rear distribution calculated from the master cylinder pressure Pm, and the predetermined main program is executed. Return.
Ps _FL = Ps _FR = Pmf / 2 (7)
Ps _RL = Ps _RR = Pmr / 2 (8)

On the other hand, when the determination result in step S31 is F _out = 1, the process proceeds to step S33, where it is determined whether or not the absolute value of the target yaw moment Ms is greater than or equal to a preset value Ms1. When Ms | <Ms1, the routine proceeds to step S34, where the target braking hydraulic pressure differences ΔPs _F and ΔPs _R are calculated based on the following equations (9) and (10), and only the difference between the braking forces of the rear left and right wheels is calculated. Then, the process proceeds to step S36 to be described later.
ΔPs _F = 0 (9)
ΔPs _R = K _br · Ms / T (10)
Here, T is the same tread for the front and rear wheels. _Kbr is a conversion coefficient for converting braking force into braking fluid pressure, and is determined by brake specifications.

On the other hand, when the determination result in step S33 is | Ms | ≧ Ms1, the process proceeds to step S35, and target brake hydraulic pressure differences ΔPs _F and ΔPs _R are calculated based on the following equations (11) and (12). Then, after setting so as to generate a difference in the braking force of each wheel, the process proceeds to step S36 described later.
ΔPs _F = K _bf · Ms / | Ms | · (| Ms | −Ms1) / T (11)
ΔPs _R = K _br · Ms / | Ms | · Ms1 / T (12)
Here, K _bf is a conversion coefficient for converting braking force into braking hydraulic pressure, and is determined by brake specifications. In this case, it is also possible to set ΔPs _F = K _bf · Ms / T by controlling only with the front wheels.

In step S36, it is determined whether or not the deceleration control operation flag Fgs is set to “1” meaning deceleration control operation. When Fgs = 1, the process proceeds to step S37 and is calculated in step S14. The target deceleration amount Ag is calculated based on the following equation (13) using the parameter Xa, and the process proceeds to step S39.
Ag = −Kv × (| Xs | − | X _L | −Xa) (13)
Here, Kv is a proportionality constant determined from vehicle specifications.

When the determination result of step S36 is Fgs = 0, the process proceeds to step S38, the target deceleration amount Ag is set to 0 (zero) based on the following equation (14), and then the process proceeds to step S39. .
Ag = 0 ……… (14)
In step S39, for the purpose of deceleration, the target braking hydraulic pressure Pg for generating braking force on both the left and right wheels is calculated based on the following equation (15), and then the process proceeds to step S40.
Pg = Kg × Ag (15)
Here, Kg is a proportionality constant determined from vehicle specifications. The target braking hydraulic pressure Pg calculated in this way is the minimum amount of deceleration required to suppress the passenger's uncomfortable feeling caused by the yaw moment applied to the vehicle during the departure avoidance control.

In step S40, the departure direction of the host vehicle is determined. When the vehicle deviates to the right, the target braking hydraulic pressure Ps _j of each wheel is calculated based on the following equation (16), and deviates to the left. If the target brake fluid pressure Ps _j for each wheel is calculated based on the following equation (17), the target brake fluid pressure calculation process is terminated, and the program returns to a predetermined main program.
Ps _FL = Pmf / 2 + ΔPs _F / 2 + Pg / 4
Ps _FR = Pmf / 2−ΔPs _F / 2 + Pg / 4
Ps _RL = Pmr / 2 + ΔPs _R / 2 + Pg / 4
Ps _RR = Pmr / 2−ΔPs _R / 2 + Pg / 4 (16)
Ps _FL = Pmf / 2−ΔPs _F / 2 + Pg / 4
Ps _FR = Pmf / 2 + ΔPs _F / 2 + Pg / 4
Ps _RL = Pmr / 2−ΔPs _R / 2 + Pg / 4
Ps _RR = Pmr / 2 + ΔPs _R / 2 + Pg / 4 (17)

In the lane departure prevention control process of FIG. 2, the process of step S4 corresponds to the departure determination time calculating means, the processes of steps S5 to S9 correspond to the departure determination means, and steps S23, S25 and S33 to S35 of FIG. The processing corresponds to the yaw control amount calculation means, and the processing in steps S36 to S39 corresponds to the braking control amount calculation means.
Accordingly, it is assumed that the host vehicle is traveling straight along a traveling lane on a high μ road. In this case, in the departure prevention control process of FIG. 2, the departure estimated value Xs satisfying | Xs | <| X _L | is calculated in step S5. Therefore, the process proceeds from step S7 to step S8, and the departure determination flag F _out = 0, indicating that there is no tendency to deviate, and in step S21 in FIG. 3, the process proceeds to step S24 to stop the alarm. In step S25, the target yaw moment Ms is set to “0”. The Thus, the target braking pressure Ps _FL ~Ps _RR of each wheel 5FL~5RR in step S32 in FIG. 8, the master cylinder pressures Pmf and Pmr according to the brake operation of the driver are respectively set, the driver's steering operation The running state corresponding to is continued.

From this state, it is assumed that the vehicle gradually begins to deviate leftward from the center position of the travel lane due to the driver's sideways look. In this case, since the friction coefficient μ is estimated to be higher than the predetermined value μ _SET , the departure determination time Tt is set to the time Tt _SET which is the lower limit value in step S4. Departing the estimated value Xs is calculated over departing boundary X _L in step S5, the process proceeds from step S7 to step S9, a state indicating that the departure tendency is a departure determination flag F _out = 1, As a result of the determination in step S21, the process proceeds to step S22 to activate an alarm, and in step S23, the target yaw moment Ms is calculated based on the equation (5).

Here, since the road surface friction coefficient μ is a high value, the gain Ks is set to a large value, and the target yaw moment Ms is calculated to be larger than when traveling on a low μ road. Then, the calculated target brake hydraulic pressure Pg according to the running state in step S39 in FIG. 8, the (19) based on the target braking pressure Ps _FL ~Ps _RR of each wheel 5FL~5RR is set to formula Thus, in the departure avoidance direction, the deceleration control that generates a braking force corresponding to the target braking fluid pressure Pg calculated according to the traveling state and the yaw control that gives the vehicle a yaw moment in consideration of the road surface friction coefficient μ Correct the course in the right direction.

  Thus, when the host vehicle tends to deviate from the driving lane, the deviating prevention control is performed by combining the yaw control and the deceleration control. Therefore, a difference in braking force is applied to each wheel so that the yaw moment is given to the vehicle by the yaw control. This makes it possible to accurately correct the course in the departure avoidance direction and to generate a braking force according to the traveling state of the host vehicle by the deceleration control, so that the occupant's A sense of incongruity can be reduced.

It is assumed that the host vehicle tends to deviate in the left direction from the center position of the traveling lane while traveling on a low μ road. In this case, since the friction coefficient μ is estimated to be equal to or less than the predetermined value μ _SET , the departure determination time Tt is calculated to be larger than the time Tt _{SET in} step S4.
Thus, when the vehicle is traveling on the low friction coefficient road, the departure judgment time Tt is calculated to be large. Therefore, even when the lateral displacement X is the same, the departure estimation is performed as compared with the case where the vehicle is traveling on the high friction coefficient road. The value Xs is greatly calculated. Thus, in the determination of the deviation estimate Xs in step S7, by advancing the timing is determined to be the departure boundary line X _L or more, it is possible to advance the timing of starting the braking control for avoiding departure, Safer departure avoidance control can be performed.

When the estimated departure value Xs that is greater than or equal to the departure boundary line X _L is calculated in step S5, the process proceeds from step S7 to step S9, and the departure determination flag F _out = 1, indicating that there is a departure tendency. Then, the process proceeds to step S22 as a result of the determination in step S21, and an alarm is activated. In step S23, the target yaw moment Ms is calculated based on the equation (5).

Here, since the road surface friction coefficient μ is a low value, the gain Ks is set to a small value, and the target yaw moment Ms is calculated to be smaller than when traveling on a high μ road. Then, the calculated target brake hydraulic pressure Pg according to the running state in step S39 in FIG. 8, the (19) based on the target braking pressure Ps _FL ~Ps _RR of each wheel 5FL~5RR is set to formula Thus, in the departure avoidance direction, the deceleration control that generates a braking force corresponding to the target braking fluid pressure Pg calculated according to the traveling state and the yaw control that gives the vehicle a yaw moment in consideration of the road surface friction coefficient μ Correct the course in the right direction.

  Therefore, when the vehicle is traveling on the low friction coefficient road, the gain Ks for calculating the target yaw moment Ms is calculated to a small value, and the target yaw moment Ms is made smaller than that when traveling on the high friction coefficient road. Since the yaw moment generated in the host vehicle is reduced in order to avoid departure, that is, the braking hydraulic pressure generated in each wheel can be reduced, the occupant feels uncomfortable by the yaw control because the road surface friction coefficient is low. It can prevent giving.

In this way, when the host vehicle tends to depart from the driving lane, the yaw control and the deceleration control are combined to perform the departure prevention control, and the braking in the yaw control and the deceleration control is performed in consideration of the friction coefficient of the host vehicle traveling path. Since the hydraulic pressure is calculated, appropriate deviation avoidance control according to the road surface friction coefficient can be performed.
Also, an estimated lateral displacement after a predetermined time, that is, an estimated deviation value is calculated based on the lateral displacement of the host vehicle, and a deviation is determined based on the estimated deviation value. The lower the road surface friction coefficient, the larger this predetermined time. Since the setting is made, the timing of starting the braking control for avoiding the departure can be advanced, and the departure from the traveling lane can be avoided without causing the passenger to feel uncomfortable.

In addition, the lower the road friction coefficient, the smaller the gain for calculating the yaw moment generated in the vehicle in order to avoid deviation, so the braking force generated in each wheel can be set smaller, and the lower friction coefficient Proper departure avoidance control can be performed by preventing the passenger from feeling uncomfortable by traveling on the road.
In addition, the friction coefficient between the road surface and the tire is estimated by ABS, and the estimated friction coefficient is stored in the storage device, so that the estimation time of the road surface friction coefficient can be saved, and the braking control for avoiding the deviation is performed. Can be done quickly.

In the above embodiment, the case where the friction coefficient between the road surface and the tire is estimated by ABS at the time of the driver's braking operation is described. However, the present invention is not limited to this, and the friction coefficient between the road surface and the tire is calculated by VDC. You may make it estimate.
Moreover, in the said embodiment, you may make it estimate a road surface friction coefficient with a navigation system. In this case, the road information (general road / highway) is judged by the navigation system, and if the vehicle is driving on a general road, such as a signal or a turning corner, it will enter the toll booth when driving on the highway. Since deceleration is performed at times, the friction coefficient is estimated at this time, and the estimated friction coefficient may be stored in the storage device.

Furthermore, in the above embodiment, a road friction coefficient may be estimated according to the wiper speed by receiving a signal from the wiper switch. In this case, detects the wiper speed during wiper operation, when the wiper speed is fast sets a mu of friction coefficient in a predetermined low friction coefficient value mu _L, a predetermined high friction a mu of friction coefficient when the wiper speed is slow it may be set to a number μ _H. Here, μ _H > μ _L.

Moreover, in the said embodiment, although the case where a driver | operator is not changing lanes and alerting | reporting when it is in a lane departure tendency was demonstrated, it is not limited to this, but alerting | reporting is performed There may be a difference between the timing and the timing at which braking control (yaw control and deceleration control) is performed. Since G is applied to the driver by using the braking control, the braking control itself can have a warning effect.
Furthermore, although the case where the present invention is applied to a rear wheel drive vehicle has been described in the above embodiment, the present invention can also be applied to a front wheel drive vehicle. In this case, in step S3, among the wheel speeds Vw _FL ~Vw _RR, left and right wheel speeds Vw _RL after a non-driven wheels, may be calculated vehicle speed V of the host vehicle from an average value of Vw _RR.

It is a schematic structure figure showing an embodiment of the present invention. 6 is a first half of a flowchart showing a lane departure prevention control process executed by the control unit 8 of FIG. 1 in the embodiment of the present invention. It is the second half part of the flowchart which shows the lane departure prevention control process performed with the control unit 8 of FIG. 1 in embodiment of this invention. It is a deviation judgment time calculation map. It is a figure explaining a deviation estimated value. It is a parameter calculation map. It is a gain calculation map. It is a flowchart which shows the target brake hydraulic pressure calculation process in the lane departure prevention control process of FIG.

Explanation of symbols

6FL to 6RR Wheel cylinder 7 Braking fluid pressure control circuit 8 Control unit 9 Engine 13 CCD camera 14 Camera controller 16 Master cylinder pressure sensor 20 Steering angle sensor 21FL to 21RR Wheel speed sensor 22 Direction indication switch 23 Wiper switch 24 Alarm device 25 Storage device

Claims (8)

In a lane departure prevention apparatus for controlling the host vehicle so as to avoid a departure from the traveling lane of the host vehicle,
Estimated by the running condition detecting means for detecting the running condition of the own vehicle, the friction coefficient estimating means for estimating the road surface friction coefficient of the own vehicle running path, the running condition detected by the running condition detecting means and the friction coefficient estimating means Based on the determined road surface friction coefficient, the departure determination means for determining that the host vehicle tends to deviate from the traveling lane, and when the departure determination means determines that the own vehicle tends to depart from the traveling lane Based on the running condition detected by the running condition detecting means and the road surface friction coefficient estimated by the friction coefficient estimating means, a yaw moment is generated in a direction that avoids the departure of the own vehicle from the running lane. Based on the yaw control amount calculating means for calculating the first braking force control amount for each wheel and the running state detected by the running state detecting means, the second braking force for each wheel so that the host vehicle decelerates. System A braking control amount calculating means for calculating an amount; a control for controlling the braking force of each wheel according to the first and second braking force control amounts calculated by the yaw control amount calculating means and the braking control amount calculating means; A lane departure prevention device comprising power control means.  The travel state detection means detects a lateral displacement of the host vehicle with respect to the travel lane, and the departure determination means determines a lateral displacement of the host vehicle with respect to the travel lane after a predetermined time based on the lateral displacement detected by the travel state detection means. Deviation judgment is performed based on the estimated value of the lateral displacement and the deviation judgment time calculation means for setting the predetermined time according to the road surface friction coefficient estimated by the friction coefficient estimation means. The lane departure prevention apparatus according to claim 1.   The lane departure prevention apparatus according to claim 2, wherein the departure determination time calculation means sets the predetermined time to be larger as the road surface friction coefficient estimated by the friction coefficient estimation means is lower.   2. The lane according to claim 1, wherein the yaw control amount calculation unit calculates the first braking force control amount of each wheel to be smaller as the road surface friction coefficient estimated by the friction coefficient estimation unit is lower. Deviation prevention device.   The lane departure prevention apparatus according to claim 1, wherein the friction coefficient estimating means estimates a road surface friction coefficient by anti-skid control.   The lane departure prevention apparatus according to claim 1, wherein the friction coefficient estimating means estimates a road surface friction coefficient by vehicle behavior control.   The lane departure prevention device according to claim 1, wherein the friction coefficient estimating means estimates a road surface friction coefficient by a navigation system.   The lane departure prevention apparatus according to claim 1, wherein the friction coefficient estimating unit estimates a road surface friction coefficient based on a wiper wiping speed.

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