JP3945489B2 - Lane departure prevention device - Google Patents

Description

  The present invention relates to a lane departure prevention device that prevents a departure when a host vehicle is about to depart from a traveling lane during traveling.

Conventionally, as this type of technology, for example, a steering control torque that can be easily overcome by a driver is generated by a steering actuator in accordance with a lateral deviation amount that is a distance from a reference position of a traveling lane to a traveling position of the host vehicle. If the vehicle tends to deviate from the driving lane based on the relative position relationship between the current position of the vehicle and the lane markings (for example, see Patent Document 1). When the determination is made, the braking force actuator is controlled, and a braking force is applied to the left and right wheels opposite to the departure direction, thereby generating a yaw moment in a direction avoiding the departure, and the traveling lane of the host vehicle. The thing etc. which prevented the deviation from are proposed (for example, refer patent document 2).
Japanese Patent Laid-Open No. 11-96497 JP 2001-310719 A

Incidentally, as described above, in the method for determining whether or not there is a tendency to deviate from the lane based on the lane division line of the traveling lane of the own vehicle and the current position of the own vehicle, the captured image in front of the vehicle is displayed. In many cases, by detecting the distance between the lane division line and the current position of the host vehicle based on this and determining that the vehicle is likely to depart from the driving lane when this is below a predetermined threshold, It is possible to control the vehicle behavior by generating an alarm at an optimal timing or generating a yaw moment in a direction to avoid a deviation at an optimal timing.
Here, when the width of the lane division line detected from the captured image changes, that is, when the lane width changes in the actual traveling lane, the vehicle and the lane more than the actual change in the vehicle posture. The relative relationship with the lane marking may change significantly.

In other words, if it is determined that the vehicle is about to deviate from the travel lane and the travel lane width is widened, the travel of the host vehicle is performed even when the distance of the vehicle from the center of the travel lane has not changed. Since the lane markings are separated from the vehicle itself, it is easy to deviate from the judgment conditions for judging that the vehicle has a tendency to deviate. As a result, the operation status of the deviation warning and the deviation prevention control becomes unstable. In addition, the control amount such as the yaw moment due to the deviation prevention control fluctuates, and the hunting of the deviation prevention control is activated and deactivated. There is a problem that fluctuations may become large and cause discomfort to the passenger.
Therefore, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and avoids frequent repetition of operation and non-operation of control for deviation prevention due to fluctuations in the travel lane width. 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, the lane departure prevention device according to the present invention assumes that a departure determination position for detecting a departure of the host vehicle is detected on the traveling lane based on the position of the lane division line of the traveling lane. Based on the departure determination position and the current traveling position of the host vehicle, it is detected whether or not the host vehicle has a tendency to depart.
Here, in a state where the host vehicle is detected as having a tendency to deviate from the lane, the lane width fluctuates, for example, when the host vehicle is enlarged, the lane width is separated from the host vehicle regardless of the travel position of the host vehicle. Accordingly, the departure determination position set based on this also moves away from the host vehicle, and it is likely to be determined that there is no lane departure tendency. For this reason, it is determined that there is no tendency to deviate from the lane temporarily, but after that, there may be a case where it is determined that there is a tendency to deviate from the lane again. Thus, the determination of the tendency to deviate from the lane frequently fluctuated. In this case, when a warning or vehicle behavior control for preventing lane departure is performed based on this determination, the warning may be frequently activated or deactivated, or the vehicle behavior fluctuation may increase. In some cases, the passenger may feel uncomfortable.

However, when the vehicle is detected to be in the lane departure tendency by the departing de detection means, the determination position variation suppressing means, because so as to suppress the variation with respect to the traffic lane center of deviation determining position, traveling It is avoided that the determination result by the deviation detecting means is switched due to the fluctuation of the lane width, and the alarm activation / deactivation is frequently switched or the vehicle behavior fluctuation is increased.

According to the lane departure prevention apparatus according to the present invention, when the departure detecting means detects that the host vehicle tends to depart from the lane, the deviation of the own vehicle set based on the position of the lane division line of the traveling lane is detected. Since the fluctuation of the deviation judgment position for detection with respect to the center of the driving lane is suppressed, the lane division line moves away or approaches from the own vehicle with the fluctuation of the driving lane width regardless of the driving state of the own vehicle. It can be avoided that the determination result by the deviation detecting means is switched due to the above.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic vehicle configuration diagram illustrating an example of a lane departure prevention apparatus according to the first embodiment. 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 of the left and right wheels independently of the front and rear wheels.
Reference numeral 1 in FIG. 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. Usually, the brake fluid pressure increased by the master cylinder 3 in accordance with the amount of depression of the brake pedal 1 by the driver. Is supplied to the wheel cylinders 6FL to 6RR of the wheels 5FL to 5RR. A braking fluid pressure control circuit 7 is interposed between the master cylinder 3 and the wheel cylinders 6FL to 6RR. In the braking fluid pressure control circuit 7, the braking fluid pressures of the wheel cylinders 6FL to 6RR can be individually controlled.

  The brake fluid pressure control circuit 7 uses a brake fluid pressure control circuit used for, for example, anti-skid control and 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 vehicle state control unit 8 described later.

  In addition, the vehicle controls the driving torque to the rear wheels 5RL and 5RR, which are driving wheels, by controlling the operating state of the engine 9, the selected transmission ratio of the automatic transmission 10, and the throttle opening of the throttle valve 11. A drive torque control unit 12 is provided. The operating state control of the engine 9 can be controlled, for example, by controlling the fuel injection amount and the ignition timing, and can also be controlled by controlling the throttle opening at the same time.

The drive torque control unit 12 can independently control the drive torque of the rear wheels 5RL and 5RR that are drive wheels, but the drive torque command value is input from the vehicle state control unit 8 described above. When this is done, the drive wheel torque is controlled with reference to the drive torque command value.
In addition, the vehicle includes a monocular camera 13 and a camera controller that are configured by a CCD camera or the like as a front external field recognition sensor for detecting the position of the host vehicle in the travel lane for determining departure from the travel lane of the host vehicle. 14 is provided. The camera controller 14 detects, for example, a lane marker such as a white line from a captured image in front of the host vehicle captured by the monocular camera 13 to detect a travel lane, and as shown in FIG. The yaw angle φ, that is, the direction of the host vehicle with respect to the travel lane, the lateral displacement X of the host vehicle from the center of the travel lane, the curvature ρ of the travel lane, the travel lane width W, and the like can be calculated.

The camera controller 14 performs travel lane detection using a travel lane detection area for detecting lane markers and the like, and calculates the data for the detected travel lane. For example, a technique described in Japanese Patent Application Laid-Open No. 11-296660 can be used for detecting the traveling lane.
Specifically, lane markers such as white lines on both sides of the traveling lane in which the host vehicle is traveling are detected, and the traveling lane in which the host vehicle is traveling is detected using the lane marker. Here, if a lane marker such as a white line is detected (scanned) over the entire captured image, the calculation load is large and time is required. Therefore, a smaller detection area (so-called window) is set in an area where a lane marker is likely to exist, and the lane marker is detected in the detection area. Generally, when the direction of the host vehicle with respect to the lane changes, the position of the lane marker displayed in the image also changes. For example, in Japanese Patent Laid-Open No. 11-296660, the direction of the host vehicle with respect to the lane is estimated from the steering angle θ, and the image The detection area is set in the area where the lane marker in the box will be projected.

  Then, for example, a filtering process that makes the boundary between the lane marker and the road surface stand out is performed, and a straight line that seems to be the boundary between the lane marker and the road surface is detected in each lane marker detection region, and one point (lane marker candidate point) on the straight line is detected as the lane marker. It is detected as a representative site. If the lane marker candidate points of each window obtained in this way are continued, it is possible to detect a traveling lane that is deployed ahead of the host vehicle.

  The vehicle also includes an acceleration sensor 15 that detects longitudinal acceleration Xg and lateral acceleration Yg generated in the host vehicle, a yaw rate sensor 16 that detects yaw rate γ generated in the host vehicle, an output pressure of the master cylinder 3, so-called master. A master cylinder pressure sensor 17 that detects the cylinder pressure Pm, an accelerator pedal depression amount, that is, an accelerator opening sensor 18 that detects the accelerator opening Acc, a steering angle sensor 19 that detects the steering angle θ of the steering wheel 21, and each wheel 5FL Are provided with wheel speed sensors 22FL to 22RR for detecting a rotational speed of 5RR, so-called wheel speed Vwi (i = FL to RR), and a direction indicating switch 20 for detecting a direction indicating operation by a direction indicator. It is output to the vehicle state control unit 8.

Further, the yaw angle φ of the host vehicle with respect to the travel lane detected by the camera controller 14, the lateral displacement X of the host vehicle from the center of the travel lane, the curvature ρ of the travel lane, the travel lane width W, and the drive torque control unit 12 are controlled. The driving torque Tw on the wheel shaft thus generated is also output to the vehicle state control unit 8.
If the detected vehicle traveling state data has left and right directionality, the left direction is the positive direction and the right direction is the negative direction. That is, the yaw rate γ, the lateral acceleration Yg, the steering angle θ, and the yaw angle φ are positive values when turning left and negative values when turning right. Further, the lateral displacement X becomes a positive value when shifted to the left from the center of the traveling lane, and becomes a negative value when shifted laterally. Further, the curvature ρ of the traveling lane becomes a positive value in the case of the left curve, and becomes a negative value in the case of the right curve.

  Further, the vehicle is provided with an alarm device 23 for warning the driver when a lane departure is detected by the vehicle state control unit 8. The alarm device 23 includes a speaker and a monitor for generating a sound and a buzzer sound, and issues a warning to the driver by display information and sound information.

  Next, the processing procedure of the arithmetic processing performed by the vehicle state control unit 8 will be described according to the flowchart of FIG. This calculation process is executed by a timer interrupt every predetermined sampling time ΔT (for example, 10 [ms]). In this flowchart, no communication step is provided, but information obtained by the arithmetic processing is updated and stored in the storage device as needed, and necessary information is read out from the storage device as needed.

In this calculation process, the outline will be described. First, in step S1, various data from each of the sensors, controllers, and control units are read, and then in step S2, the data is used to determine whether or not there is a tendency to deviate. deviation determination value Xw ^*, after calculating the Xc ^*, the process proceeds to step S3, deviation judgment value Xw, the update processing of Xc when necessary.
Next, the process proceeds to step S4, where an estimated lateral displacement Xs that is a predicted lateral deviation amount after a predetermined time is calculated, and a departure determination process is performed based on the estimated lateral displacement Xs and the departure determination values Xw and Xc (step S5). ). Then, a target yaw moment is calculated according to the result of the departure determination process (step S6), a process for generating an alarm for notifying the driver of the departure tendency (step S7), and a target yaw moment are generated. For this purpose, a braking / driving force control process (step S8) is performed, and an alarm and a yaw moment are generated as necessary.

  Specifically, in the process of step S1, the longitudinal acceleration Xg, lateral acceleration Yg, yaw rate γ, wheel speed Vwi, accelerator opening Acc, master cylinder pressure Pm, steering angle θ, direction detected by the sensors. The command switch signal, the yaw angle φ of the host vehicle relative to the travel lane from the camera controller 14, the lateral displacement X of the host vehicle from the center of the travel lane, the curvature ρ of the travel lane, the travel lane width W, and the drive torque control unit 12 Read drive torque Tw.

In addition, the traveling speed V of the host vehicle is calculated from the average value of the front left and right wheel speeds VwFL and VwFR, which are non-driven wheels, among the wheel speeds Vwi (i = FL to RR).
Here, the case where the traveling speed V is calculated based on the front left and right wheel speeds VwFL, VwFR has been described. For example, the vehicle is equipped with ABS control means for performing known anti-skid control, When the anti-skid control is performed by the ABS control means, the estimated vehicle speed estimated in the process of the anti-skid control may be used.

Next, the actual departure determination values Xw ^* and Xc ^* in step S2 are calculated according to the procedure shown in the flowchart of FIG. First, in step S11, an actual departure determination value Xw ^* for departure warning is calculated according to the travel lane width W read in step S1. Here, as shown in FIG. 5 (a), the actual departure judgment value Xw ^* for departure warning is inside by a predetermined value bw from the lane markings located at both ends of the traveling lane regardless of the traveling lane width W. Set to be. That is, the actual departure determination value Xw ^* is calculated from the following equation (1).
Xw ^* = 0.5 × W−bw (1)

Next, the process proceeds to step S12, and the lower limit value Xw ^* min of the actual departure judgment value Xw ^* for departure warning is calculated. The lower limit value Xw ^* min of the actual departure determination value Xw ^{* is} a lower limit value for preventing the lane departure determination condition from becoming too sensitive when the travel lane width becomes narrower than usual. Here, regardless of the travel lane width W, the actual departure determination value Xs ^* is set so as to be at least a predetermined value cw larger than the vehicle body width Wv. That is, the lower limit value Xw ^* min of the actual departure determination value Xw ^* is calculated from the following equation (2).
Xw ^* min = 0.5 × Wv + cw (2)

Next, the process proceeds to step S13, where the actual departure determination value Xw ^* calculated in step S11 is compared with the lower limit value Xw ^* min of the departure determination value calculated in step S12. If Xw ^* ≦ Xw ^* min, step S14 is performed. After the deviation determination value Xw ^* is limited to the lower limit value Xw ^* min, the process proceeds to step S15. When Xw ^* > Xw ^* min in step S13, the process proceeds to step S15.

That is, in the processing from step S11 to step S14, as shown in FIG. 5B, the actual departure determination value Xw ^* is Xw ^* while the travel lane width W is 2 · (Xw ^* min + bw) or less ^. When the travel lane width W is larger than 2 · (Xw ^* min + bw), the actual departure determination value Xw ^* is “Xw ^* = 0.5 × W− when the travel lane width W increases. It is set to increase in accordance with a straight line represented by bw ".

Next, in step S15, an actual departure determination value Xc ^* for departure prevention control is calculated according to the travel lane width W read in step S1. Here, the actual departure determination value Xc ^* for departure prevention control is set so as to be inward by a predetermined value bc from the lane line regardless of the travel lane width W, as shown in FIG. Therefore, the actual departure determination value Xc ^* for departure prevention control is calculated based on the following equation (3).
Xc ^* = 0.5 × W−bc (3)

Next, the process proceeds to step S16, and the lower limit value Xc ^* min of the actual departure judgment value Xc ^* for departure prevention control is calculated. The lower limit value Xc ^* min of the actual departure determination value Xc ^{* is} a lower limit value for preventing the lane departure determination condition from becoming excessively sensitive when the travel lane width W becomes narrower than usual. Here, regardless of the travel lane width W, the actual departure determination value Xc ^* is set to be a value that is at least a predetermined value cc greater than the vehicle body width Wv. That is, the lower limit value Xc ^* min of the actual departure determination value Xc ^* for departure prevention control is calculated according to the following equation (4).
Xc ^* min = 0.5 × Wv + cc (4)

Next, the process proceeds to step S17, where the actual departure determination value Xc ^* for departure prevention control calculated in step S15 is compared with the lower limit Xc ^* min of the actual departure determination value for departure prevention control calculated in step S16. When Xc ^* ≦ Xc ^* min, the routine proceeds to step S18, where the actual departure judgment value Xc ^* is limited to the lower limit value Xc ^* min. Then, the actual deviation determination value calculation process ends. If Xc ^* > Xc ^* min in step S17, the actual deviation determination value calculation process is terminated.

That is, in the processing from step S15 to step S18, as shown in FIG. 6B, when the traveling lane width W is 2 · (Xc ^* min + bc) or less, the actual departure judgment value Xc for departure prevention control is used. ^* Is limited to the lower limit value Xc ^* min, and when the travel lane width W is larger than 2 · (Xc ^* min + bc), as the travel lane width W increases, Xc ^* = 0.5 × W−bc It increases according to the straight line represented by

Next, the deviation determination value update process in step S3 is performed according to the procedure shown in the flowchart of FIG. That is, first, in step S21, the warning flag indicating whether or not the departure warning is generated by the warning device 23 is FW ≠ 0, or the departure determination flag indicating whether or not the yaw moment is generated by the departure prevention control is FLD ≠ 0. It is determined whether or not. When the warning flag is FW ≠ 0 or the departure judgment flag is FLD ≠ 0, it is determined that at least one of the departure warning and the departure prevention control is operating, the process proceeds to step S22, and the hold flag FHOLD is held. Is set to “1”.
On the other hand, if both the warning flag FW and the departure determination flag FLD are “0” in step S21, the process proceeds to step S23, and the holding flag FHOLD is set to “0” because the host vehicle does not tend to depart from the lane.

In this manner, if the holding flag FHOLD is set in step S22 or step S23, the process proceeds to step S24. If the holding flag FHOLD is “0”, the process proceeds to step S25, and the deviation determination value updating process is performed. Do. That is, the actual departure determination value Xw ^* for departure warning set in the process of step S2 in FIG. 3 is set as the departure determination value Xw for departure warning, and the actual departure determination value Xc for departure prevention control is set in FIG. The actual departure judgment value Xc ^* for departure warning set in the process of S2 is set.
On the other hand, when the hold flag FHOLD is “1” in step S24, the departure determination values Xw and Xc for departure warning and departure prevention control are not updated. Thus, the deviation determination value update process is completed.

Next, the process of calculating the estimated lateral displacement Xs in step S4 is performed according to the procedure shown in the flowchart of FIG.
That is, first, in step S31, the forward gaze distance Ls is calculated by multiplying the traveling speed V of the host vehicle calculated in step S1 and the vehicle head time Tt.
Next, the process proceeds to step S32, the yaw angle φ with respect to the travel lane of the host vehicle read in step S1, the lateral displacement X of the host vehicle from the center of the travel lane, the curvature ρ of the travel lane, the travel speed V of the host vehicle, and A future estimated lateral displacement Xs is calculated according to the following formula (5) using the forward gaze distance Ls.

  Here, the case where the estimated lateral displacement Xs is calculated based on the above equation (5) has been described. However, the present invention is not limited to this. For example, as shown in the following equation (6), it acts on the vehicle. It may be calculated in consideration of the yaw rate to be performed. For example, when the accuracy of the yaw rate sensor 16 is high and noise is low, the deviation alarm and the deviation prevention control are activated at a more appropriate timing by calculating the estimated lateral displacement Xs in consideration of the yaw rate. It can also be released.

  Note that Tt is the vehicle head time for calculating the forward gaze distance, and when the vehicle head time Tt is multiplied by the traveling speed V of the host vehicle, the front gaze distance is obtained. That is, the estimated lateral displacement from the center of the traveling lane after the vehicle head time Tt becomes the estimated lateral displacement Xs in the future. As will be described later, in the present embodiment, when the estimated lateral displacement Xs in the future is equal to or greater than a predetermined deviation determination value, it is determined that the host vehicle may deviate from the traveling lane or tend to deviate.

In general, it takes a certain amount of time until the driver notices an alarm and performs a departure avoidance operation. Even if it is determined that there is a high possibility that the host vehicle will depart from the lane and the departure prevention control is activated, the own vehicle does not immediately move toward the center of the lane in which the vehicle is traveling along with the operation of the departure prevention control. However, although the speed of deviating from the lane becomes low, the vehicle moves toward the outside of the traveling lane until the vehicle turns to the inside of the lane. For this reason, it is desirable to set the vehicle head time Tt to a value larger than “0” [s] in order to prompt the driver to perform the lane departure prevention operation with a margin.

  Next, the departure determination process for determining whether or not the host vehicle tends to depart from the travel lane in step S5 is performed according to the procedure shown in the flowchart of FIG. First, in step S41, it is determined whether or not the direction indicating switch 20 is in an on state. If the direction indicating switch 20 is in an on state, the process proceeds to step S42 and the direction indicated by the direction indicating switch 20 and the estimated lateral direction calculated in step S4. It is determined whether or not the departure direction specified by the displacement Xs matches. Then, when they match, it is determined that the lane change is to be performed, the process proceeds to step S43, the lane change flag FLC is set to “1”, and then the process proceeds to later-described step S47.

On the other hand, if the indicated direction of the direction indicating switch 20 and the departure direction specified by the estimated lateral displacement Xs do not coincide with each other, it is determined that the lane change has not occurred and the routine proceeds to step S44, where the lane change flag FLC is set to “0”. Then, the process proceeds to step S47.
If the direction indicating switch 20 is not in the on state in step S41, the process proceeds to step S45 to determine whether or not a predetermined time has elapsed since the direction indicating switch 20 was switched from the on state to the off state. When a predetermined time has elapsed since the time when the direction indicating switch 20 was switched from the on state to the off state, the process proceeds to step S46, the lane change flag FLC is reset to “0”, and then the process proceeds to step S47. If not, the process proceeds to step S47 as it is. Note that the predetermined time may be considered that the traveling position of the host vehicle has reached a position from the center of the lane of the lane change destination from the time when the direction indicating switch 20 is switched to the OFF state at the later stage of the lane change. The possible time is set, for example, about 4 seconds.

In step S47, if the lane change flag FLC is “1” and the lane is being changed, the process proceeds to step S48, and if the lane is changing, a warning is generated if the lane is being changed. Therefore, the alarm flag FW is set to “0”.
On the other hand, if the lane change flag FLC is “0” and the lane is not being changed in step S47, the process proceeds to step S49 to determine the departure state of the vehicle. That is, the absolute value | Xs of the estimated lateral displacement Xs. It is determined whether or not | is equal to or greater than the departure determination value Xw for departure warning set in the process of step S3. If | Xs | ≧ Xw, it is determined that the vehicle has a departure tendency, and the process proceeds to step S50. When the sign of the estimated lateral displacement Xs is positive, it is assumed that the vehicle tends to deviate to the left, and the process proceeds from step S50 to step S51 to set the alarm flag FW to “1.” On the other hand, the estimated lateral displacement Xs is not Xs> 0. Sometimes, the process proceeds to step S52, and the warning flag FW is set to "-1".

  When the absolute value | Xs | of the estimated lateral displacement Xs is smaller than the deviation determination value Xw in step S49, the process proceeds to step S53, and the absolute value | Xs | of the estimated lateral displacement Xs is calculated from the deviation determination value Xw. When it is smaller than the value obtained by subtracting the hysteresis value Xh for avoiding departure warning hunting, the routine proceeds to step S54, where the warning flag FW is set to "0", otherwise, the departure determination process is terminated. If the warning flag FW is set in steps S48, S51, S52, and S54, the departure determination process is terminated.

  Next, the calculation of the target yaw moment in step S6 is performed according to the procedure shown in the flowchart of FIG. First, in step S61, it is determined based on the warning flag FW whether the departure warning is in operation. When the warning flag FW is “0”, the warning device 23 is not in operation and the host vehicle does not tend to deviate, the process proceeds to step S62, and the deviation determination flag FLD is set to “0”. On the other hand, if the warning flag is FW ≠ 0 in step S61, the warning device 23 is in operation and the host vehicle tends to deviate, the process proceeds to step S63, and the estimated lateral displacement Xs is calculated in step S3. It is determined whether or not the deviation determination value Xc for departure prevention control is satisfied. If Xs ≧ Xc, it is determined that the vehicle is deviating to the left and the process proceeds to step S64, and the deviation determination flag FLD is set to “1”. .

  On the other hand, if Xs ≧ Xc is not satisfied in step S63, the process proceeds to step S65 to determine whether the estimated lateral displacement Xs is equal to or less than the negative lateral displacement limit value “−Xc”. If it is determined that the vehicle departs from the lane, the process proceeds to step S66, and the departure determination flag FLD is set to "-1". On the other hand, if Xs ≦ −Xc is not satisfied in step S65, the process proceeds to step S67 to determine that the host vehicle is not in a departure state and set the departure determination flag FLD to “0”.

If it is determined in step S64 or step S66 that the departure determination flag FLD is set to "1" or "-1" and the vehicle departs from the left or right lane, the process proceeds to step S68, and the following equation (7) Accordingly, the target yaw moment Ms is calculated.
Ms = −K1 × K2 × (Xs−Xc) (7)
In the equation (7), K1 is a constant determined by vehicle specifications. K2 is a proportionality coefficient set according to the traveling speed V of the host vehicle, and is set as shown in FIG. 11, for example.

  In FIG. 11, the horizontal axis represents the vehicle traveling speed V, and the vertical axis represents the proportionality coefficient K2. The proportional coefficient K2 is set to a relatively large constant value KH when the traveling speed V is equal to or lower than the first threshold value Vs1, and the proportional coefficient K2 increases as the traveling speed V becomes larger than the first threshold value Vs1. The proportionality coefficient K2 decreases in inverse proportion, and when the traveling speed V becomes equal to or higher than the second threshold value Vs2, the proportionality coefficient K2 is set to a relatively small constant value KL. In other words, when the traveling speed V is relatively high, the proportional coefficient K2 is set to a relatively small value to suppress the target yaw moment, and avoiding unstable vehicle behavior due to the large yaw moment acting during high speed traveling. On the contrary, when the traveling speed V is relatively low, the proportional coefficient K2 is set to a relatively large value to ensure a sufficient target yaw moment and to generate a yaw moment so as to promptly recover from the deviation state. It is like that.

  On the other hand, when the departure determination flag FLD is set to “0” in the process of step S62 or step S67, that is, when it is determined that the host vehicle is not in a departure state, the process proceeds to step S69, and a yaw moment is generated. Therefore, “0” is set as the target yaw moment Ms. When the target yaw moment Ms is set in this way, the target yaw moment calculation process is terminated.

  Next, the alarm output process in step S7 is performed according to the procedure shown in the flowchart of FIG. First, in step S71, it is determined whether or not the alarm flag is FW ≠ 0. If FW ≠ 0, it is determined that there is a tendency to deviate. Then, the process proceeds to step S72 to activate the alarm device 23, and the voice or monitor screen is displayed. The driver is informed that the vehicle is in a lane departure tendency. On the other hand, if the warning flag is not FW ≠ 0, it is determined that there is no tendency to deviate, the process proceeds from step S71 to step S73, and if an alarm is issued by the alarm device 23, it is stopped.

  Here, the case has been described where the alarm device 23 is operated depending on whether or not the vehicle is in a deviated state regardless of the departure direction. For example, the alarm device 23 is connected to the driver from different directions on the left and right. It is configured so that a warning sound can be emitted. When the host vehicle tends to deviate from the lane on the left side, a warning sound is emitted from the left side to the driver, and conversely to the driver when the vehicle tends to deviate from the lane on the right side. An alarm sound may be emitted from the right side.

  In this case, the process may be performed according to the procedure shown in the flowchart of FIG. First, in step S81, it is determined whether or not the alarm flag is FW> 0. When FW> 0, the alarm device 23 is operated so as to generate an alarm sound from the left side in step S82 because it tends to deviate to the left side. If the warning flag is not FW> 0, the process proceeds from step S81 to step S83 to determine whether or not the warning flag is FW <0. If FW <0, there is a tendency to deviate to the right. Then, the alarm device 23 is operated so as to generate an alarm sound from the right side. If the warning flag is not FW> 0 and FW <0, the host vehicle does not tend to deviate, so the process proceeds from step S83 to step S85, and if the alarm device 23 is activated, this is stopped. .

Next, the braking / driving force control process of step S8 is performed according to the procedure shown in the flowchart of FIG. First, in step S91, it is determined whether or not the departure determination flag is FLD ≠ 0. If FLD is not 0, the host vehicle is not in a departure state, and the process proceeds to step S92, where the front left and right wheels 5FL, 5FR As the target brake fluid pressures PsFL and PsFR to the wheel cylinders 6FL and 6FR, the master cylinder pressure Pm is set, and as the target brake fluid pressures PsRL and PsRR to the wheel cylinders 6RL and 6RR of the rear left and right wheels 5RL and 5RR, both A rear wheel master cylinder pressure PmR is set.
The PmR is a rear wheel master cylinder pressure based on the front / rear braking force distribution with respect to the master cylinder pressure Pm read in step S1.

On the other hand, if the departure determination flag is FLD ≠ 0 in step S91, the process proceeds to step S93, where the case is divided according to the magnitude of the target yaw moment Ms, and the absolute value of the target yaw moment | Ms | Is less than the predetermined value Ms0, the process proceeds to step S94 to generate a difference only in the braking force of the rear left and right wheels. That is, the front left and right wheel target braking fluid pressure difference ΔPsF is set to “0”, and the rear left and right wheel target braking fluid pressure difference ΔPsR is set to the following equation (8). In Equation (8), T is a tread (which is the same for the front and rear wheels), KbR, and KbF, which will be described later, are conversion factors for converting braking force into braking fluid pressure, and are determined by brake specifications. .
ΔPsR = 2 × KbR × | Ms | / T (8)

On the other hand, when the absolute value | Ms | of the target yaw moment is equal to or greater than the predetermined value Ms0, the process proceeds from step S93 to step S95, and a difference is generated between the braking forces of the front, rear, left and right wheels. Specifically, the front left and right wheel target braking fluid pressure difference ΔPsF is calculated by the following equation (9), and the rear left and right wheel target braking fluid pressure difference ΔPsR is calculated by the following equation (10).
ΔPsF = 2 × KbF × (| Ms | −Ms0) / T (9)
ΔPsR = 2 × KbR × Ms0 / T (10)

Here, the case where the front and rear wheels are controlled has been described. However, for example, the control may be performed using only the front wheels. In this case, ΔPsF = 2 × KbF × | Ms | / T. You may do it.
If the left and right braking force difference is calculated for the front and rear wheels in this way, the process proceeds to step S96, and when the target yaw moment Ms is a negative value, that is, when the host vehicle is about to deviate in the left direction. The process proceeds to step S97, and the target braking fluid pressure Psi to each of the wheel cylinders 6FL to 6RR is calculated by the following equation (11).
PsFL = Pm
PsFR = Pm + ΔPsF
PsRL = PmR
PsRR = PmR + ΔPsR (11)

On the other hand, when the target yaw moment Ms is a value equal to or greater than zero, that is, when the host vehicle is about to depart from the lane in the right direction, the process proceeds to step S98, and the target braking fluid pressure Psi to each of the wheel cylinders 6FL-6RR is 12) Calculated by the equation.
PsFL = Pm + ΔPsF
PsFR = Pm
PsRL = PmR + ΔPsR
PsRR = PmR (12)

If the target braking force is calculated in any one of steps S92, S97, and S98 in this way, the process proceeds to step S99, and if the departure determination flag is FLD ≠ 0 and is in a departure state, the process proceeds to step S100. Then, the target drive torque Trq is calculated by the following equation (13).
Trq = f (Acc) −g (Ps) (13)

On the other hand, if the departure determination flag is not FLD ≠ 0 and there is no departure state, the process proceeds to step S101, and the target drive torque Trq is set to f (Acc).
The f (Acc) is a drive torque equivalent value calculated by an accelerator function f for calculating a drive torque corresponding to the accelerator opening Acc. Further, Ps in the equation (13) is a sum of the left and right wheel target braking fluid pressure differences ΔPsR and ΔPsF before and after being generated by the departure prevention control (Pg = ΔPsR + ΔPsF), and g (Ps) is the target braking. This is a braking torque equivalent value calculated by a function g for calculating a braking torque predicted to be generated by the sum Ps of fluid pressure differences.

If the target drive torque Trq is calculated in step S100 or step S101 in this way, the process proceeds to step S102, and the drive torque control unit 12 is controlled to generate the target drive torque Trq calculated in step S100 or step S101. A signal is output, and the target brake fluid pressure of each wheel calculated in any of steps S92, S97, and S98 is output to the brake fluid pressure control circuit 7.
The arithmetic processing shown in FIG. 3 is completed by the above processing. When a series of arithmetic processing is completed, the timer interrupt processing is terminated and the process returns to a predetermined main program.

Next, the operation of the first embodiment will be described.
The vehicle state control unit 20 executes the arithmetic processing shown in FIG. 3 in a predetermined cycle, and based on the travel lane width W input from the camera controller 14, the actual departure judgment value Xw ^* for departure warning and departure prevention control The actual departure judgment value Xc ^* for the operation is sequentially calculated. At this time, if the vehicle is traveling straight ahead from the center of the lane where the lane width W is constant, neither the departure warning nor the departure prevention control is performed. Therefore, both the warning flag FW and the departure determination flag FLD are “ Set to 0 ”. For this reason, in the departure determination value update process of FIG. 7, the process proceeds from step S21 to step S23, and the hold flag is set to FHOLD = 0. Therefore, the process proceeds from step S24 to step S25, and the departure determination values Xw and Xc for departure warning and departure prevention control are the actual departure determination values according to the current travel lane width W calculated in step S2. Xw ^* and Xc ^* are updated and set, respectively.

Then, the estimated lateral displacement Xs is calculated based on the forward gaze distance Ls corresponding to the traveling speed V of the host vehicle (FIG. 8). At this time, no lane change is performed, so the process proceeds from step S47 to step S49 in FIG. Then, the estimated lateral displacement Xs is compared with the departure determination value Xc for departure prevention control set in step S3 of FIG.
At this time, since the host vehicle is traveling straight from the center of the travel lane, the lane is not being changed, and the estimated lateral displacement Xs is relatively small, the absolute value | Xs | of the estimated lateral displacement Xs is a departure determination for departure warning. In the deviation determination process of FIG. 9, the value shifts from step S49 to step S53 to step S54, and the warning flag is set to Fw = 0. For this reason, in the target yaw moment calculation process of FIG. 10, the process shifts from step S61 to step S62, and the departure determination flag FLD is set to “0”, so the target yaw moment is set to Ms = 0 (step S69). ).

  For this reason, in the braking / driving force control process of FIG. 14, the fluid pressure corresponding to the master cylinder pressure Pm is set as the target braking fluid pressure in the process of step S92, and the accelerator is used as the target drive torque Trq in the process of step S101. Since the driving torque according to the opening degree Acc is set, the target driving force according to the operation amount of the driver's accelerator pedal is generated and the braking force according to the master cylinder pressure Pm is generated. The vehicle behavior conforms to the driving operation of the driver without generating a yaw moment. At this time, since the alarm flag FW is set to “0”, in the alarm output process of FIG. 12, the process proceeds from step S71 to step S73, and the alarm device 23 is not operated. Therefore, no alarm is issued.

  From this state, when the host vehicle tends to deviate to the left and the estimated lateral displacement Xs increases and exceeds the departure judgment value Xw for departure warning, the driver turns on the direction indicating switch 20 for the purpose of changing the lane. In FIG. 9, since the direction indicated by the direction indicating switch 20 and the departure direction based on the estimated lateral displacement Xs are both on the left side and coincide with each other, it is determined that the lane is changed. Through S42, the process proceeds to step S43, and the lane change flag FLC is set to “1”.

  Therefore, the process proceeds from step S47 to step S48, and the warning flag FW is set to "0" because it is not necessary to issue a departure warning because the lane is being changed, and accordingly, the process proceeds from step S61 to step S62 in FIG. The departure determination flag FLD is set to “0”. Therefore, even if the estimated lateral displacement Xs increases with the lane change of the host vehicle, the alarm device 23 is not activated and the departure prevention control is not activated. There is no yaw moment acting on the vehicle.

  Then, when the lane change is completed and the direction indicating switch 20 is turned off, in the departure determination process of FIG. 9, the process proceeds from step S41 to step S45, and the lane change flag FLC is not updated until a predetermined time has elapsed. . Accordingly, in the latter half of the lane change, the direction indication switch 20 is turned off, but the departure warning or the departure prevention is performed even when the vehicle is still in a lane departure tendency and the estimated lateral displacement Xs is relatively large. The control is never activated.

  Then, when a predetermined time has elapsed from the time when the direction indicating switch 20 is turned off and it is possible to consider that the traveling position of the host vehicle in the lane to which the lane is changed has reached the center of the lane, the steps from step S45 are performed. Since the process proceeds to S46 and the lane change flag FLC is set to “0”, it is erroneously determined that there is a tendency to deviate in the latter half of the lane change and while the host vehicle is moving to the position from the center of the lane. Never happen.

When the vehicle tends to deviate to the left instead of changing the lane from this state, the direction determining switch 20 is in the off state in the departure determination process of FIG. 9, so that the process proceeds from step S41 to step S45 to step S47. At this time, since the lane change flag FLC is “0” and the lane is not being changed, the process proceeds to step S49.
At this time, in a state where the estimated lateral displacement Xs is lower than the departure judgment value Xw for departure warning, the warning flag FW is maintained at “0”, so the departure warning is not activated, but the estimated lateral displacement Xs is equal to or greater than the departure judgment value Xw. Then, the process proceeds from step S49 to step S51 through step S50, and the alarm flag FW is set to "1". For this reason, in the target yaw moment calculation process of FIG. 10, the process proceeds from step S61 to step S63, but still remains as long as the estimated lateral displacement Xs is smaller than the deviation determination value Xc for deviation prevention control calculated in step S3. Since it is not necessary to perform departure prevention control, the process proceeds from step S63 to step S65 through step S67, and the departure determination flag is set to FLD = 0.

Therefore, since the target yaw moment Ms is set to “0”, the yaw moment Ms is not generated at this time, and the vehicle behavior continues according to the driving operation of the driver, but the alarm flag FW is set to “1”. Therefore, in the alarm output process of FIG. 12, the process proceeds from step S71 to step S72, the alarm device 23 is activated, and the driver is notified of a tendency to deviate.
Accordingly, the driver can recognize that the own vehicle is in a tendency to deviate when the alarm device 23 is activated, and can perform an operation for avoiding the deviation, such as a deceleration operation or a steering operation.

  When the lane departure of the host vehicle further progresses and the estimated lateral displacement Xs becomes equal to or greater than the departure determination value Xc for departure prevention control, the routine proceeds from step S63 to step S64 in FIG. 10, and the departure determination flag is set to FLD = 1. In step S68, the target yaw moment Ms corresponding to the difference between the estimated lateral displacement Xs and the deviation determination value Xc, that is, the lateral deviation amount of the host vehicle is calculated. Therefore, the process proceeds from step S91 in FIG. 14 to step S93, and the target braking fluid pressure Psi is generated so as to generate a braking force difference between the left and right wheels only on the rear wheel side or on both the front and rear wheels according to the magnitude of the target yaw moment Ms. And the driving torque Trq is generated by suppressing the driving torque f (Acc) corresponding to the accelerator opening Acc by the braking torque g (Ps) corresponding to the braking force required for generating the target yaw moment Ms. The drive torque is controlled, and the yaw moment corresponding to the lateral deviation amount of the host vehicle is generated while avoiding the interference between the yaw moment and the drive torque, thereby preventing the departure.

  Then, when the warning or yaw moment is generated in this way, and the estimated lateral displacement Xs of the host vehicle is reduced by the driver performing the steering operation or the deceleration operation, the step shown in FIG. The process proceeds from step S63 to step S65 to step S67, where the departure determination flag FLD is set to “0”, the generation of the yaw moment is stopped, and the estimated lateral displacement Xs subtracts the hysteresis value Xh from the departure determination value Xw. When the value falls below the value “Xw−Xh”, the process proceeds from step S49 in FIG. 9 to step S54 through step S53, the alarm flag FW is reset to “0”, and the operation of the alarm device 23 is stopped. The

  From this state, the travel lane width W of the host vehicle changes. For example, as shown in FIG. 15, when the lane width is increased from the state B to the state A, the departure determination values Xw and Xc are The lane width W increases as the lane width W increases, and the departure determination condition becomes milder. Therefore, as the travel lane width W increases, the distance from the host vehicle to the lane marking increases, so that the departure determination values Xw and Xc can be set according to the distance, and the actual travel situation can be improved. A deviation determination can be made.

On the other hand, when the state transitions from state B to state C and the travel lane width W becomes narrower, the departure determination values Xw and Xc become narrower as the travel lane width W decreases, and the departure determination conditions are more severe. Become. Accordingly, as the travel lane width W decreases, the distance from the host vehicle to the lane marking decreases, so that departure determination values Xw and Xc can be set in accordance with the distance, and the actual travel situation can be improved. A deviation determination can be made.
At this time, since the lower limit value corresponding to the vehicle body width Wv is set for the departure determination values Xw and Xc, the departure determination values Xw and Xc become too small as the travel lane width W decreases. Accordingly, the departure determination condition becomes too severe, and it can be avoided that it is determined that there is a tendency to depart from the lane even if there is a slight lateral deviation.

Then, in a state where the departure determination values Xw and Xc are updated in accordance with the fluctuation of the travel lane width W in this way, the own vehicle tends to depart from the lane, and the estimated lateral displacement Xs of the own vehicle becomes the departure determination value Xw or Xc. When this is the case, the warning flag FW or the departure determination flag FLD is set to “1”. Therefore, in the departure determination value update process of FIG. 7, the process proceeds from step S21 to step S22, and the hold flag FHOLD is set to “1”. For this reason, the processing is ended as it is from step S24, and the deviation determination values Xw and Xc are not updated. The hold flag FHOLD is set to “1” while it is determined that either the alarm flag FW or the deviation determination flag FLD is not “0” but tends to deviate in the right or left direction. The departure determination values Xw and Xc are not updated, and when it is determined that both the alarm flag FW and the departure determination flag FLD are “0” and there is no departure tendency, the process proceeds from step S21 to step S23 and the hold flag FHOLD is “0”. ”, The process proceeds from step S24 to step S25, and the deviation determination values Xw and Xc are updated.
That is, when the departure warning or departure prevention control is activated, the travel lane width W at the time when the departure warning or departure prevention control is activated from this point until the release of both of these operations. The departure determination values Xw and Xc corresponding to the above are held, and based on this, it is determined whether or not there is a lane departure tendency.

  Here, when the departure determination is performed based on the departure determination values Xw and Xc corresponding to the travel lane width W even while the departure warning or the departure prevention control is operating, for example, the travel lane width W increases, When transitioning from state B to state A in FIG. 15, if it is determined that the host vehicle is in a departure state in state B before the travel lane width W fluctuates at this time, The deviation determination values Xc and Xw increase with the increase. Therefore, in some cases, as shown in the state A, the departure estimated value Xs is lower than these departure determination values Xc and Xw, and the vehicle becomes a departure tendency before sufficiently recovering from the departure tendency. It may be judged that there is not. For this reason, the departure prevention control and the departure warning are canceled before the vehicle state of the host vehicle sufficiently recovers from the departure tendency. In some cases, the departure warning and the departure prevention control are naturally continued by the passenger. The departure warning or departure prevention control may be suddenly released in a state where it is recognized that the user feels uncomfortable. In addition, if the departure prevention control is canceled before sufficiently recovering from the departure tendency, the control amount by the departure prevention control will vary, and the passenger will feel uncomfortable with the variation in the control amount. There is a case.

In addition, since the host vehicle has not sufficiently recovered from the departure tendency, the estimated lateral displacement Xs again exceeds the departure determination value Xc or Xw relatively quickly, and departure prevention control and departure warning are started again. Will be. In other words, the occupant may feel uncomfortable when the departure prevention control and the departure warning are frequently activated and deactivated.
However, as described above, when it is detected that there is a departure tendency, the departure determination values Xc and Xw at the time of departure tendency detection are held, and based on this, departure warning and departure prevention control operation determination are performed. Thus, regardless of the change in the travel lane width W, the departure prevention control and the departure warning can be canceled when the traveling state of the host vehicle is reliably recovered from the lane departure tendency. Therefore, the control amount greatly fluctuates due to the departure prevention control and departure warning being canceled before the vehicle completely recovers from the lane departure tendency, or the departure prevention control and departure warning are frequently switched. It can be avoided that the passenger feels uncomfortable due to the above.

On the other hand, when the travel lane width W becomes narrower from the state determined to have a tendency to depart from the lane as shown in state B in FIG. When the departure warning values Xw and Xc are updated, the position of the own vehicle with respect to the lane marking changes, and the departure determination values Xw and Xc tend to decrease. For this reason, the degree of decrease in the travel lane width W is large. For example, the departure determination value Xc decreases relatively greatly. Therefore, the control amount of the departure prevention control calculated according to the difference between the departure determination value Xc and the estimated lateral displacement Xs greatly fluctuates. Since vehicle behavior such as deceleration fluctuates, the passenger may be uncomfortable in some cases.
However, as described above, the departure determination value Xc is held when it is determined that the vehicle has a tendency to deviate, so that the control amount of the departure prevention control greatly varies according to the variation of the travel lane width W. Therefore, it is possible to avoid giving the passenger a sense of incongruity.

Next, a second embodiment of the present invention will be described.
The second embodiment is the same as the first embodiment except that the procedure of the deviation determination value update process executed in step S3 in FIG. Reference numerals are assigned and detailed description thereof is omitted.
In the second embodiment, the deviation determination value update process is performed according to the procedure shown in the flowchart of FIG.
That is, the processing from step S21 to step S23 is the same as that of the first embodiment, and when the warning flag is FW ≠ 0 or the deviation determination flag is FLD ≠ 0, the process proceeds to step S22 and the hold flag FHOLD Is set to "1", and when both the alarm flag FW and the departure determination flag FLD are "0", the process proceeds to step S23, and the hold flag FHOLD is set to "0".

  If the hold flag FHOLD is “0” and the previous departure warning and departure prevention control has not been activated, the process proceeds to step S111, where the coefficients aw and ac of the low-pass filter for updating the departure determination value are A small constant value, that is, values aw1 and ac1 with fast response speed are set. On the other hand, if the hold flag FHOLD is “1” and at least one of the previous departure warning and departure prevention control is activated, the process proceeds to step S112, where a large time constant, that is, the response speed is set. Slow values aw2 and ac2 are set, respectively. The time constants aw1 and aw2 satisfy 0 <aw1 <aw2 <1, and the time constants ac1 and ac2 are values satisfying 0 <ac1 <ac2 <1.

If the time constant of the low-pass filter is set in this way, the process proceeds to step S113, and is specified by the following equations (14) and (15) using the time constant set in step S111 or step S112. Low-pass filter processing is performed, and the deviation determination value is updated.
Xw (k) = aw (k) * Xw (k-1) + (1-aw (k)) Xw ^* (k)
(14)
Xc (k) = ac (k) * Xc (k-1) + (1-ac (k)) Xc ^* (k)
...... (15)

That is, when the departure warning and departure prevention control are not activated, the departure determination values Xw and Xc are updated so as to coincide with the actual departure determination values Xw ^* and Xc ^* calculated in step S2 at a relatively fast response speed. When either of the departure warning and departure prevention control is operating, the departure determination values Xw and Xc coincide with the actual departure determination values Xw ^* and Xc ^* calculated in step S2 at a relatively slow response speed. Update to
Therefore, when neither the departure warning nor the departure prevention control is operating, the departure determination values Xw, Xc are set so as to coincide with the departure determination values Xw ^* , Xc ^* according to the travel lane width W at this time relatively quickly. Since the update is performed, the departure determination can be accurately performed according to the relative relationship between the current lane marking and the position of the host vehicle.

On the other hand, when either the departure warning or the departure prevention control is activated, if the travel lane width W changes, Xw ^* and Xc ^* calculated accordingly also change. The values Xw and Xc also vary. At this time, the response speed is made slower in the low-pass filter processing when the deviation determination values Xw and Xc are updated to Xw ^* and Xc ^* .

  Therefore, as shown in FIG. 17, when the travel lane width W is increased from the state A determined to be a lane departure tendency and the state C is shifted to, the low pass filter process is performed as described above. The deviation determination value Xc gradually increases, and the difference between the estimated lateral displacement Xs of the host vehicle and the deviation determination value Xc gradually varies. The control amount set according to the difference also gradually changes.

  Here, when the deviation determination value Xc is changed in accordance with the change in the travel lane width W accompanying the transition from the state A to the state C, depending on the case, the change in the difference between the estimated lateral displacement Xs and the estimated deviation value Xc. And the control amount of the departure prevention control set in accordance with the difference between the estimated lateral displacement Xs and the departure determination value Xc may vary. For this reason, the vehicle behavior may change and give a sense of incongruity.

  However, as shown in FIG. 17, when the lane width changes from state A to state C, the deviation determination value Xc is not increased with the change in lane width, but as shown in state B of FIG. Since the deviation determination value Xc is gradually changed to suppress the fluctuation, it is possible to suppress the fluctuation of the control amount of the deviation prevention control due to the fluctuation of the deviation determination value Xc. Therefore, as the travel lane width W increases, the deviation determination value Xc is made to coincide with the value according to the travel lane width W while suppressing the fluctuation of the departure prevention control amount, and the relative relationship between the actual vehicle and the lane markings Deviation warning and deviation prevention control can be performed without delay with respect to the relationship, and it can be prevented that the lane departure judgment ability is impaired.

  On the contrary, the same applies to the case where the travel lane width W decreases, and the variation of the departure determination value Xc is suppressed. Therefore, by reducing the departure determination value Xc as the travel lane width W decreases. Even when the departure determination value Xc is further smaller than the estimated lateral displacement Xs and the departure degree is further increased, the variation of the departure determination value Xc is suppressed. Sufficient control force for preventing departure without causing a delay with respect to the relative positional relationship between the actual lane marking line and the host vehicle, by making the departure determination value Xc coincide with a value corresponding to the travel lane width while suppressing fluctuations Can be generated.

  Therefore, also in the second embodiment, as in the first embodiment, the departure warning and the departure prevention control are performed according to the variation of the departure determination values Xw and Xc accompanying the variation of the travel lane width W. It is possible to avoid being controlled to be activated or deactivated, and to suppress changes in vehicle behavior due to fluctuations in the control amount of deviation prevention control accompanying fluctuations in the travel lane width W, thereby preventing stable deviations. Control can be performed.

Next, a third embodiment of the present invention will be described.
The third embodiment is the same as the second embodiment except that the processing procedure of the deviation determination value update process is partially different. Detailed description is omitted.
In the third embodiment, the deviation determination value update process is performed according to the procedure shown in the flowchart of FIG. That is, when both the warning flag FW and the departure determination flag FLD are “0” and both the departure warning and departure prevention control are not operating, the process proceeds from step S24 to step S111, and the second embodiment and the second embodiment described above. Similarly, the deviation determination values Xw and Xc are updated by performing a low-pass filter process with a fast response speed.

On the other hand, when at least one of the warning flag FW and the departure determination flag FLD is not “0”, the process proceeds from step S24 to step S121, and it is determined whether or not the travel lane width W is being reduced. This determination is made, for example, by comparing the previous travel lane width W with the current travel lane width W, or based on the fluctuation state of the travel lane width W in a predetermined period in the past.
Then, when the travel lane width W is being reduced, the process proceeds from step S121 to step S111, and the departure determination values Xw and Xc are updated at a relatively fast response speed. When the travel lane width W is not being reduced, step is performed. The process proceeds to S112, and the departure determination values Xw and Xc are updated at a relatively slow response speed.

Therefore, when the travel lane width W changes while the departure warning or departure prevention control is activated, for example, the travel lane width W increases, that is, the lane division line moves away from the host vehicle regardless of the vehicle behavior of the host vehicle. In such a case, the departure determination values Xw and Xc increase at a sufficiently slow speed with respect to the vehicle behavior, so that the variation in the control amount by the departure prevention control is suppressed and the lane width W is adjusted. By setting the departure determination value Xc, an accurate departure determination can be performed. On the other hand, when the travel lane width W decreases, the lane marking may approach the host vehicle regardless of the vehicle behavior of the host vehicle. Since the deviation determination value is updated by the low-pass filter process having a faster response speed compared to the case where the travel lane width W that changes to become larger is increased, the difference between the deviation determination value Xc and the estimated lateral position Xs is determined. The departure warning and departure prevention control are activated without delaying the relative relationship between the actual vehicle and the lane line while suppressing the fluctuation of the corresponding control amount and the fluctuation of the estimated lateral displacement Xs. It is possible to prevent the lane departure determination ability from being impaired as much as possible.
Needless to say, this third embodiment can provide the same operational effects as those of the second embodiment.

Next, a fourth embodiment of the present invention will be described.
The fourth embodiment is the same as the third embodiment except that the processing procedure of the deviation determination value update process is partially different. Therefore, the same reference numerals are given to the same parts, and Detailed description is omitted.
In the fourth embodiment, the deviation determination value update process is performed according to the procedure shown in the flowchart of FIG. That is, when both the alarm flag FW and the departure determination flag FLD are “0”, the holding flag FHOLD is set to “0” as in the third embodiment, and the process proceeds to step S111 for comparison. The deviation determination values Xw and Xc are updated by performing a low-pass filter process with a high dynamic response speed. On the other hand, when the warning flag is FW ≠ 0 or the departure determination flag is FLD ≠ 0, the process proceeds from step S24 to step S131, and the current vehicle behavior with respect to the travel lane is determined. That is, the absolute value | φ | of the yaw angle with respect to the traveling lane read in step S1 is compared with the threshold value ε that allows the yaw angle φ to be determined to be a sufficiently small value. The absolute value | X | of the lateral displacement is compared with a threshold value Xth that can be determined that the lateral displacement X is a sufficiently small value. When | φ | ≦ ε or | X | ≦ Xth, the yaw angle φ and the lateral displacement X with respect to the traveling lane are sufficiently small, and even if the operation of the departure warning or departure prevention control is stopped in this state, the operation immediately thereafter Since it can be predicted that there will be no lane departure tendency again, the process proceeds to step S111, and the departure determination values Xw and Xc are updated at a relatively fast response speed.

  On the other hand, when the yaw angle φ and the lateral displacement X are not | φ | ≦ ε or | X | ≦ Xth, that is, the yaw angle φ and the lateral displacement X are large to a certain extent. When the operation of the departure prevention control is stopped, when it is predicted that the vehicle is likely to deviate from the lane immediately after that, the process proceeds to step S121, and then whether or not the travel lane width W is being reduced. Determine. When the travel lane width W is decreasing, the process proceeds from step S121 to step S111, and the departure determination values Xw and Xc are updated at a relatively fast response speed. By making a departure judgment in accordance with the relative relationship between the lane marking line and the host vehicle, the lane departure judgment can be made more reliably.

On the other hand, if the travel lane width W is not being reduced, the process proceeds from step S121 to step S112, the departure determination values Xw and Xc are updated at a relatively slow response speed, and the departure determination value Xc and the estimated lateral displacement Xs are updated. The deviation of the deviation prevention control amount according to the difference is suppressed.
Here, if the yaw angle φ is reduced by the departure warning and departure prevention control, and the vehicle's departure tendency becomes sufficiently small, the traveling state of the vehicle with respect to the lane becomes stable, so the traveling lane width W increases. Even if it does, the operation | movement and non-operation | movement hunting by deviation prevention control do not occur easily. Therefore, the departure determination value is updated to a value corresponding to the current travel lane width W relatively quickly, so that the departure determination can be accurately performed in accordance with the relative relationship between the actual lane marking line and the host vehicle. it can.

  Conversely, when the vehicle behavior of the host vehicle is not stable, such as when the yaw angle with respect to the travel lane is not sufficiently small, such as after the start of departure warning or departure prevention control, the travel lane width W increases in the vehicle departure direction. Then, when the departure determination value is set according to the travel lane width W, as described above, it is determined that there is a departure tendency, or it is determined that there is no departure tendency, and it is difficult for stable departure determination to be performed. It becomes. However, as described above, since the update speed of the departure judgment value is slowed, fluctuations in the control amount of the departure prevention control can be suppressed, and the passenger feels uncomfortable with changes in vehicle behavior due to this departure prevention control. Can be avoided, and frequent switching of the judgment that there is a tendency to deviate can be avoided.

  Further, when the lateral displacement X with respect to the traveling lane of the host vehicle becomes sufficiently small, the update speed of the departure judgment value is increased, so that the lateral displacement X with respect to the traveling lane becomes sufficiently small and surely deviates from the lane. While it is not determined that the recovery has occurred, the deviation determination value is updated at a relatively slow response speed. Therefore, it is possible to suppress the variation in the control amount due to the departure prevention control, and to avoid giving the passenger a sense of incongruity due to the variation in the vehicle behavior due to the departure prevention control. Needless to say, the same effects as those of the third embodiment can be obtained.

In each of the above embodiments, the alarm generating means for generating an alarm when the estimated lateral displacement Xs becomes greater than or equal to the departure determination value Xw and the yaw moment when the estimated lateral displacement Xs becomes greater than or equal to the departure determination value Xc. However, the present invention can also be applied to the case where only one of them is provided.
In each of the above embodiments, the case where the yaw moment generating means that avoids the departure by generating the yaw moment in the host vehicle has been described as the departure prevention control means, but the present invention is not limited to this. Rather, for example, when a departure is detected, the vehicle is decelerated and the speed of the vehicle until it departs is reduced, and a steering actuator is provided to prevent lane departure by steering control in a direction that avoids the departure. It is also possible to apply a steering control means or the like configured as described above, and in this case as well, it is possible to obtain the same effect as described above.

Moreover, although each said embodiment demonstrated the case where it each performed independently, it is not restricted to this, It is also possible to perform combining several of these.
In each of the above embodiments, the case where the host vehicle tends to deviate in the left direction has been described, but it is needless to say that the same effect can be obtained when the vehicle tends to deviate in the right direction.

  Here, in each of the above-described embodiments, the processing in steps S2 and S3 in FIG. 3 corresponds to the determination position setting means, and the processing in step S5 corresponds to the deviation detection means. Further, in the first embodiment, the process of step S24 in FIG. 7 does not update the deviation determination values Xw and Xc, and in the second embodiment, the process proceeds from step S24 in FIG. 16 to step S112. Then, the process of setting a slower response speed value as the low-pass filter coefficient, in the third embodiment, the process proceeds from step S24 in FIG. 18 to step S112 through step S112. In the fifth embodiment, the process of setting a slow value, the process of moving from step S24 in FIG. 19 to step S112 through steps S131 and S121, and the process of setting a slower response speed as a low-pass filter coefficient, respectively, This corresponds to the determination position fluctuation suppressing means.

  Further, in the flowchart of FIG. 18 of the third embodiment and the flowchart of FIG. 19 of the fourth embodiment, the processing for determining whether the lane width W is being reduced is step S121. 3, the process of calculating the target yaw moment in step S6 of FIG. 3 and generating the braking / driving force corresponding to the target yaw moment corresponds to the departure prevention control means, and the process of step S7 corresponds to the alarm generation means.

It is a schematic block diagram which shows an example of the vehicle carrying the lane departure prevention apparatus in this invention. It is explanatory drawing for demonstrating the vehicle state quantity computed with the camera controller of FIG. It is a flowchart which shows an example of the process sequence of the arithmetic processing performed within the vehicle state control unit of FIG. It is a flowchart which shows an example of the process sequence of the deviation determination value calculation process performed by step S2 of FIG. It is explanatory drawing for demonstrating the calculation method of the deviation determination value for deviation warnings. It is explanatory drawing for demonstrating the calculation method of the deviation determination value for deviation prevention control. It is a flowchart which shows an example of the process sequence of the deviation determination value update process performed by step S3 of FIG. It is a flowchart which shows an example of the process sequence of the estimated lateral displacement calculation process performed by step S4 of FIG. It is a flowchart which shows an example of the process sequence of the deviation determination process performed by step S5 of FIG. It is a flowchart which shows an example of the process sequence of the target yaw moment calculation process performed by step S6 of FIG. FIG. 11 is a control map used in the target yaw moment calculation process of FIG. 10. FIG. It is a flowchart which shows an example of the process sequence of the alarm output process performed by FIG.3 S7. It is a flowchart which shows the other example of the alarm output process performed by step S7 of FIG. It is a flowchart which shows an example of the process sequence of the braking / driving force control process performed by FIG.3 S8. It is explanatory drawing with which it uses for operation | movement description of this invention. It is a flowchart which shows an example of the process sequence of the deviation determination value update process in the 2nd implementation of this invention. It is explanatory drawing with which it uses for operation | movement description of 2nd Embodiment. It is a flowchart which shows an example of the process sequence of the deviation determination value update process in the 3rd implementation of this invention. It is a flowchart which shows an example of the process sequence of the deviation determination value update process in the 4th implementation of this invention.

Explanation of symbols

5FL to 5RR Wheel 6FL to 6RR Wheel cylinder 7 Braking fluid pressure control circuit 8 Vehicle state control unit 9 Engine 12 Drive torque control unit 13 Monocular camera 14 Camera controller 15 Acceleration sensor 16 Yaw rate sensor 17 Master cylinder pressure sensor 18 Accelerator opening sensor 19 Steering angle sensor 20 Direction indication switches 22FL to 22RR Wheel speed sensor 23 Alarm device

Claims (10)

Determination position setting means for assuming a deviation determination position on the traveling lane for detecting a deviation of the host vehicle based on the position of the lane division line of the traveling lane;
Lane departure prevention comprising: a departure detection unit configured to detect whether or not the host vehicle has a departure tendency based on the departure determination position set by the determination position setting unit and the current travel position in the travel lane of the host vehicle. In the device
A lane departure prevention apparatus, comprising: determination position fluctuation suppression means that suppresses fluctuation of the departure determination position with respect to the center of the traveling lane when the departure detection means detects that the host vehicle is in a lane departure tendency. The determination position fluctuation suppressing means does not suppress fluctuation of the deviation determination position with respect to the center of the driving lane when the deviation detection means does not detect that the host vehicle tends to deviate from the lane. The lane departure prevention apparatus according to claim 1. Lane width variation detecting means for detecting whether or not the lane width of the traveling lane of the host vehicle has changed,
The determination position fluctuation suppression means suppresses fluctuation of the deviation determination position with respect to the center of the traveling lane when it is detected that there is a lane departure tendency and the lane width fluctuation detection means detects a change in the lane width expansion direction. The lane departure prevention apparatus according to claim 1 or 2, wherein the lane departure prevention apparatus according to claim 1 or 2 is configured. Lane width variation detecting means for detecting whether or not the lane width of the traveling lane of the host vehicle has changed,
The determination position fluctuation suppressing means does not suppress the fluctuation of the deviation determination position with respect to the center of the traveling lane when it is detected that there is a lane departure tendency and the lane width fluctuation detection means detects a change in the lane width reduction direction. The lane departure prevention apparatus according to any one of claims 1 to 3, wherein the lane departure prevention apparatus is configured as described above. The determination position fluctuation suppressing means, even if that is the lane departure tendency is detected, when the yaw angle with respect to the traffic lane of the vehicle remote small by the threshold value, the traffic lane center of the deviation determining position The lane departure prevention apparatus according to any one of claims 1 to 4, wherein fluctuations with respect to the vehicle are not suppressed. Even if it is detected that there is a tendency to deviate from the lane , the determination position fluctuation suppressing means is configured such that when the lateral displacement with respect to the reference line of the travel lane of the host vehicle becomes sufficiently small, the center of the travel lane at the departure determination position The lane departure prevention apparatus according to any one of claims 1 to 5, wherein fluctuations with respect to the vehicle are not suppressed. 7. The determination position fluctuation suppression means maintains the departure determination position at a departure determination position with respect to the center of the traveling lane when the lane departure tendency is detected. The lane departure prevention apparatus according to claim 1.   The said determination position fluctuation | variation suppression means changes the said deviation determination position with the slower change degree than the time of non-suppression, The any one of Claims 1-6 characterized by the above-mentioned. Lane departure prevention device.   Deviation prevention means for controlling the vehicle behavior of the host vehicle in a direction to avoid the departure when the departure determination means detects that the departure tendency is detected and to generate an alarm when the departure determination is detected. The lane departure prevention apparatus according to any one of claims 1 to 8, further comprising at least one of control means.   10. The lane departure according to claim 9, wherein the determination position detection means individually sets a departure determination position for the alarm generation means and a departure determination position for the departure prevention control means. Prevention device.

Images