JP4327817B2 - Lane departure prevention device - Google Patents

Description

  The present invention belongs to the technical field of a lane departure prevention device for preventing a departure when the host vehicle is about to depart from the traveling lane during traveling.

Conventionally, as a lane departure prevention device, it is determined that the host vehicle is likely to deviate from the traveling lane, and the driver can easily adjust the lateral deviation of the traveling position of the host vehicle from the reference position of the traveling lane. A technique for preventing a lane departure by outputting a steering control torque that can be overcome by a steering actuator has been proposed (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 11-96497

However, in the conventional lane departure prevention device, when it is determined that the host vehicle is about to depart from the traveling lane, the lane departure is prevented by the steering control using the steering actuator. There is a problem to do.
(1) To achieve lane departure prevention with high response during lane tracking control, it is necessary to change the steering angle in a short time, so it is necessary to use a high-performance steering actuator as the steering actuator. There is a problem that the steering burden on the driver is increased, and that the device is increased in size and cost.
(2) Even under conditions of understeering due to lane departure due to overspeed, steering control is performed with the vehicle speed unchanged, and there may be cases where the departure prevention control cannot be sufficiently performed.
(3) When steering control is performed with a large steering angle at the time of lane departure judgment, the steering angle change of the steered wheels is transmitted to the steering wheel as it is, especially when the driver is not aware of the departure. The driver who is holding the car may feel uncomfortable.

  Therefore, the present applicant can achieve prevention of lane departure with high response without using a new steering actuator with improved performance by using a technology for generating a braking force difference between the left and right wheels at the time of lane departure. Rather, the driver's cognition (the braking reaction with a difference between the left and right generates a change in the steering reaction force to the driver), and the lane departure due to overspeed can be improved (the braking force is generated. The vehicle speed decreases).

  That is, the object of the present invention is to improve driving safety as well as recognition to the driver and avoid departure in the situation of lane departure while achieving prevention of lane departure with high response. Therefore, it is an object of the present invention to provide a lane departure prevention apparatus that can generate a braking fluid pressure with good response and can more effectively perform lane departure avoidance control by a braking force.

In order to achieve the above object, in the present invention, in the lane departure prevention apparatus for giving a yaw moment to the host vehicle for preventing the departure when the host vehicle is about to depart from the traveling lane,
Deviation judgment means for judging that the host vehicle is likely to deviate from the driving lane,
Intention determination means for determining that the driver is trying to maintain the driving lane;
A case where it is determined that the driver is attempting to maintain the running lane by the intention determining means, when it the vehicle is deviating likely from the travel lane is determined by the deviation determining means, deviations Braking force control means for generating a yaw moment in a direction to avoid
When there is a possibility of departure, the departure determination means determines whether the departure possibility is low or high,
It said braking force control means, a low deviation likely level increases the brake fluid pressure to the extent that the braking force is not generated, control in accordance with departure possible levels have rows departure prevention control by the braking force difference at higher departing possible level The power is increased, and at least before the departure prevention control is performed, the driver is notified that the own vehicle is likely to depart from the driving lane .

Therefore, in the lane departure prevention apparatus of the present invention, when the departure determination unit determines that the host vehicle is about to depart from the traveling lane, the braking force control unit is configured to avoid the departure. A yaw moment is generated by the difference in braking force between the left and right wheels.
As a matter of course, deviation from the lane can be prevented with a high response by the difference in braking force between the left and right wheels. In the departure prevention control by the braking force control means, the vehicle is controlled in a more stable direction because it involves deceleration. There is a merit that you can.
In other words, if your vehicle is about to deviate from the driving lane, it means that the driver is not aware of or is aware of the situation that she is about to deviate, but has not yet fully moved to avoidance. The speed can be accompanied to give the driver a sense of security.
Further, when the vehicle departs from the lane when turning due to overspeed, there is an effect of further effectively preventing the departure of the lane by decelerating the vehicle speed.
In addition, since a steering actuator is not required to prevent deviation, it is very advantageous in terms of cost, and as an actuator for controlling the braking force of each wheel, an actuator for controlling the vehicle behavior can be used and the cost can be reduced. It can also be lowered.
Furthermore, in the case of a departure prevention system using a steering actuator, the steering reaction force is directly transmitted to the driver via the steering wheel. Therefore, when the driver's steering direction and the control steering direction are different, interference becomes a problem, and both steerings If the directions are the same, the driver will feel uncomfortable.
On the other hand, in the departure prevention control by the braking force control, a steering reaction force that interferes with the steering operation of the driver is not generated, and if the braking force difference is given to the left and right wheels by the departure prevention control, the driver deviates. When steering in the avoidance direction, there is also an advantage that the driver can recognize the steering direction for avoidance as the steering can be performed with a smaller force than usual (the size differs depending on the suspension type, steering type, etc.). I have it.
In addition, if there is a possibility of departure in the departure determination means, it is determined to a departure possibility level of whether the departure possibility is low or high, and the braking force control means does not generate braking force at the low departure possibility level. The braking hydraulic pressure is increased within the range, and the departure prevention control based on the difference in braking force is performed at a high departure possibility level.
Therefore, when shifting from a low deviability level to a high deviability level, the braking fluid pressure has been increased in a range where no braking force is generated in advance, so at the point of transition to a high deviability level, The brake fluid pressure for avoiding the vehicle is generated with good response, and the lane departure avoidance control by the braking force can be more effectively performed.
Therefore, while achieving prevention of lane departure with high response, in the situation of lane departure, it is possible to improve the driving safety and also improve the cognition to the driver, and avoid the departure. Therefore, the brake fluid pressure for generating the vehicle can be generated with good response, and the lane departure avoidance control by the braking force can be more effectively performed.

  Hereinafter, the best mode for realizing the lane departure prevention apparatus of the present invention will be described based on Reference Example 1 and Example 2 shown in the drawings.

Reference example 1

First, the configuration will be described.
FIG. 1 is an overall system diagram showing a lane departure prevention apparatus of Reference Example 1. In this reference example 1, a rear-wheel drive vehicle (a vehicle equipped with an automatic transmission and a conventional differential) is assumed, and the braking device is assumed to be a braking device that can independently control the left and right braking force (braking fluid pressure) for both front and rear wheels. Yes.

  In the figure, 1 is a brake pedal, 2 is a booster, 3 is a master cylinder, and 4 is a reservoir. 10 and 20 indicate left and right front wheels, and 30 and 40 indicate left and right rear wheels, respectively. Each wheel has a brake disc 11, 21, 32, and 42, and a wheel cylinder 12, 22, 32, 42 that applies a brake force (braking force) to each wheel by frictionally holding the brake disc by supplying hydraulic pressure. When the hydraulic pressure is supplied from the pressure control unit 5 to the wheel cylinders 12, 22, 32, 42 of these brake units, each wheel is braked individually.

  The pressure control unit 5 includes an actuator for each hydraulic pressure supply system (each channel) on the front, rear, left and right sides. As the actuator, a proportional solenoid valve is used so that each wheel cylinder hydraulic pressure can be controlled to an arbitrary braking hydraulic pressure. Further, the hydraulic pressure from the master cylinder 3 is adjusted by an input signal from the braking / driving force controller 50 to control the brake hydraulic pressure supplied to the wheel cylinders 12, 22, 32, 42 of each wheel.

  The braking / driving controller 50 includes a vehicle front / rear, a signal from an acceleration sensor 53 for detecting lateral accelerations Xg and Yg, a yaw rate sensor 54 for detecting a yaw rate φ generated in the vehicle, and a wheel speed Vwi installed on each wheel. Signals from the wheel speed sensors 13, 23, 33, and 43 to be detected are respectively input. Further, a signal from the master cylinder hydraulic pressure sensor 55 for detecting the master cylinder hydraulic pressure Pm for detecting the operation amount of the brake pedal, and an accelerator opening sensor for detecting the accelerator opening Acc for detecting the operation amount of the accelerator pedal. 56 and a signal from the direction indicating switch 57 are also input. Further, a drive torque Tw on the wheel shaft is also input from the drive torque controller 60. Further, the driving torque is controlled via a driving torque controller 60 that controls the driving force torque of the driving wheels.

  The drive torque controller 60 performs engine control for controlling the fuel injection amount of the engine 6, throttle control for controlling the throttle opening by the throttle control device 7, and shift control for controlling the automatic transmission 8. The drive torque is controlled via a drive torque controller 60 that controls the drive force torque of the drive wheels.

  In addition, a monocular camera 51 and a camera controller 70 are mounted as an external recognition sensor for detecting the position of the host vehicle in the traveling lane for determining the departure of the vehicle. The yaw angle Φ of the host vehicle, the lateral displacement X from the center of the lane, and the curvature β of the travel lane are output to the braking / driving force controller 50 as signals relating to the position of the host vehicle.

  Further, in the first reference example, the steering angle sensor 52 is installed on the handle 9, and a signal of the steering angle θ detected by the steering angle sensor 52 is also output to the braking / driving force control controller 50. Further, a signal from the direction indicating switch 57 used for determining whether the driver is going to move in the traveling lane is also input to the braking / driving force control controller 50.

Next, the operation will be described.
[Braking / driving force control processing]
FIG. 2 is a flowchart of an example of a control program executed by the braking / driving force control controller 50. This processing is performed by a regular interrupt at regular intervals in an operating system (not shown).

  First, in step S100, various data from the sensors 13, 23, 33, 43, 52, 53, 54, 55, 56, 57 and the controllers 60, 70 are read. From each sensor, longitudinal acceleration Xg, lateral acceleration Yg, yaw rate φ, each wheel speed Vwi (i = 1 to 4), accelerator opening Acc, master cylinder hydraulic pressure Pm, steering angle δ, and direction indicating switch 57 Further, the driving torque Tw is read from the driving torque control controller 60, and the yaw angle Φ of the vehicle relative to the traveling lane of the host vehicle, the lateral displacement X to the traveling lane, and the curvature β of the traveling lane are read from the camera controller 70, respectively. The camera controller 70 performs image processing on the forward video based on the signal from the camera 51, extracts and identifies the boundary line of the forward lane such as the white line or the center line, and obtains the yaw angle Φ, the lateral displacement X, and the curvature β. .

In the subsequent step S101, the vehicle speed V is calculated. In this reference example 1, during normal running, the vehicle speed V is calculated from the wheel speeds of the respective wheels according to the following formula and the average of the front wheel speeds.
V = (Vw1 + Vw2) / 2
Further, when the ABS control or the like is operating, the estimated vehicle speed estimated in the ABS control is used.

  In the subsequent step S102, the turning state is determined. In the first reference example, the turning state is determined using the yaw rate φ and the lateral acceleration Yg. (In either case, the left turn is positive.) When the lateral acceleration Yg is equal to or greater than the set value, it is determined that the vehicle is turning suddenly. Further, the yaw rate φ is also determined by comparing the steering angle δ shown in FIG. 3 with the target yaw rate φref determined by the vehicle speed V, such as understeer and oversteer of the vehicle.

In the subsequent step S103, a lane departure determination is performed. In this first reference example, a departure prediction time Tout until departure is calculated, and a lane departure is determined by comparison with a departure determination threshold value Ts. First, the amount of change dX of the lateral displacement X is calculated, and the estimated departure time Tout until the vehicle departs from the distance L / 2−X to the lane is calculated according to the following equation. (See Figure 4)
Tout = (L / 2−X) / dX (1)
However, Tout ≦ Tmax (maximum value limit: 0% countermeasure).

  Here, L is the lane width, and is calculated by processing the camera image. Further, the position of the vehicle may be taken from the map data as lane width information by navigation information. In the future, when the road infrastructure is improved, if the lane width is given by so-called road-to-vehicle communication from the infrastructure side, the information is also used. If the distance L / 2-X to the lane in the departure direction is known from information from the infrastructure (for example, a marker embedded in the road), the information is naturally used.

Next, the departure judgment threshold values Ts and Tout are compared, and when Tout <Ts, it is judged that the departure judgment is made, and the departure judgment flag Fout = ON. Conversely, when Tout ≧ Ts, Fout = OFF. Here, Ts does not have to be a constant value, and Ts may be changed to be small so that the control is activated earlier in the case of a sudden turn according to the determination of the turning state determined in step S102. . A change-over switch is set so that it can be switched in several stages, and the driver may select it. At the same time, the departure direction Dout is determined from the lateral displacement X. (Dout = right or left)
In this reference example 1, the deviation is determined from the lateral displacement X and the amount of change dX, but it deviates from the front lane based on the yaw angle Φ of the host vehicle, the curvature β of the traveling lane, the yaw rate of the vehicle, the steering angle, etc. It is good also as what estimates time Tout to perform.

  In the subsequent step S104, a driver intention determination is made as to whether or not the driver is changing lanes. In the first reference example, the driver's intention is determined by the direction indicating switch 57 and the steering angle. First, when the direction indicating switch 57 is operated and the direction indicated by the signal and the departure direction Dout determined in step S104 are the same, it is determined that the lane change is conscious and the departure determination is performed. The flag Fout is changed to OFF. On the other hand, if the direction is different from the departure direction Dout, there is a possibility of departure, so the departure determination flag is not changed. Even when the direction indicating switch 57 is not operated, if the driver is steering in the departure direction, the driver changes the lane if the steering angle δ and the change amount Δδ are equal to or greater than the set values. It is determined that there is an intention, and the departure determination flag Fout is changed to OFF. This is based on the idea that the direction of travel of the vehicle should basically be determined by the driver, and that the departure prevention system is only for assisting in preventing departure of the vehicle. Here, the intention of the driver is determined based on the steering angle and the amount of change in the steering angle, but may be detected based on the steering torque.

In the subsequent step S105, it is determined whether or not to issue a departure warning. In the first reference example, the determination is made by comparing the estimated departure time Ts calculated in step S102 with the warning determination threshold value Tw. The alarm determination threshold value Tw is calculated by the following equation in conjunction with the departure determination threshold value Ts.
Tw = Ts + Tm (2)
Here, Tm is a set time (constant) from when the alarm is activated until when the departure prevention control is activated. An alarm is activated at Tout <Tw. Further, once activated, the alarm continues to operate until Tout ≧ Tw + Th. Here, Th is a hysteresis for avoiding alarm hunting.

In subsequent step S106, a target yaw moment Ms to be generated in the vehicle is calculated. In the first reference example, the target yaw moment Ms is calculated from the lateral displacement X and the amount of change dX according to the following equation.
Ms = K1 · X + K2 · dX (3)
Here, K1 and K2 are gains that vary according to the vehicle speed V (see FIG. 5). Further, the target yaw moment Ms may be calculated according to the following equation from the yaw angle Φ with respect to the travel lane of the host vehicle, the lateral displacement X, and the forward travel lane curvature β.
Ms = Ka · Φ + Kb · X + Kc · β (3) ′
Here, Ka, Kb, and Kc are gains that vary according to the vehicle speed V (see FIGS. 5 and 6).

In the subsequent step S107, the target brake hydraulic pressure Psi (subscript is the subscript) according to the departure determination flag, the target yaw moment Ms calculated in step S106, the master cylinder hydraulic pressure Pm, and the turning state determined in step S102. Each wheel is indicated). When the departure determination flag Fout = OFF, the target brake hydraulic pressure for each wheel is the master cylinder hydraulic pressure.
Psfl = Psfr = Pm (4)
Psrl = Psrr = Pmr (5)
Here, Pmr is a rear wheel master cylinder hydraulic pressure in consideration of the front-rear distribution calculated from Pm.

On the other hand, when the departure determination flag Fout = ON, depending on the magnitude of the target yaw moment, if the target yaw moment is smaller than the set value, a difference is generated in the braking force of the left and right rear wheels, and the larger value is set. Causes a braking force difference between the front, rear, left and right wheels. First, target braking hydraulic pressure differences ΔPsf and ΔPsr are calculated from the target yaw moment Ms by the following equation. (It distributes to the front and rear wheels as follows according to the size of Ms.)
1) In case of Ms <Ms1 (set value) ΔPsf = 0 (6)
ΔPsr = 2 · Kbr · Ms / T (7)
2) When Ms ≧ Ms1 (set value) ΔPsf = 2 · Kbf · (Ms−Ms1) / T (8)
ΔPsr = 2 · Kbr−Ms1 / T (9)
Here, T represents a tread. (For simplicity, the front and rear treads are the same.) Kbf and Kbr are conversion coefficients for converting the braking force into the braking hydraulic pressure, and are determined by the brake specifications. I decided to control only the front wheels,
ΔPsf = 2 · Kbf · Ms / T (10)
It is good.

Next, based on the turning state determination and the departure direction, it is determined whether braking force is generated on both the left and right wheels for the purpose of decelerating the vehicle, and the master brake hydraulic pressure Pm, which is a braking operation by the driver, is also taken into account, and the target braking of each wheel The hydraulic pressure Psi is calculated. As an example, the case of turning left is described.
1) When trying to deviate inside the turn (| φ | ≧ | φref |)
Psfl = Pm
Psfr = Pm + ΔPsf (11)
Psrl = Pmr
Psrr = Pmr + ΔPsr
2) When not turning suddenly (Yg <Yg1) and trying to deviate to the outside of the turn (| φ | <| φref |)
Psfl = Pm + ΔPsf
Psfr = Pm (12)
Psrl = Pmr + ΔPsr
Psrr = Pmr
3) When sudden turning (Yg ≧ Yg1) and trying to deviate to the outside of the turn (| φ | <| φref |)
Psfl = Pm + ΔPyaw + ΔPsf
Psfr = Pm + ΔPyaw (13)
Psrl = Pmr + ΔPsf
Psrr = Pmr
here,
ΔPyaw = Ky · | φref−φ | (14)
The deceleration is generated according to the amount of understeer of the vehicle. Here, Ky is a control gain, which is constant regardless of the vehicle speed V.

In the subsequent step S108, the driving force of the driving wheel is calculated. In the first reference example, when the sudden turn shown in step S107 and the vehicle is going to deviate to the outside of the turn, even if the accelerator operation is performed, the throttle is closed to prevent acceleration ( The target throttle opening TVOS is 0). In other cases, the throttle is controlled in accordance with the driver's accelerator operation. That is, during non-operation, the target throttle opening TVOS is set according to the accelerator opening Acc.
1) When sudden turning (Yg ≧ Ygl) and trying to deviate to the outside of the turn (| φ | <| φref |)
TVOS = 0 (15)
2) In other cases, TVOS = Acc (16)
In the subsequent step S109, a drive signal is output to the pressure control unit 5 and the drive torque controller 60 in accordance with the target brake hydraulic pressure Psi and the target drive torque Tes.

[Lane departure prevention action]
Therefore, when it is determined that the vehicle is likely to deviate from the driving lane based on the lane departure determination in step S103 and the intention determination in step S104 that the driver is not at the time of lane change, and the possibility of departure is determined. The process proceeds from step S106 to step S107 to step S108 to step S109, and the braking / driving force of each wheel is controlled so as to generate a yaw moment in a direction to avoid the deviation, as shown in FIGS. Regardless of whether the vehicle is traveling straight or turning, it is possible to prevent the vehicle from departing from the traveling lane and to efficiently deviate from the lane by decelerating the vehicle even during a sudden turn.

  That is, when the vehicle travels straight ahead and the departure determination flag Fout = ON, as shown in FIG. 7, when the target yaw moment Ms is smaller than the set value Ms1, depending on the magnitude of the target yaw moment Ms, the above ( As shown in Equations (6) and (7), if there is a difference in the braking force between the left and right rear wheels, and if it is greater than the set value Ms1, then as shown in Equations (8) and (9) above, The brake force difference is generated with.

  Further, when the vehicle is about to deviate to the inside of the turn, as shown in FIG. 8, at least a braking / driving force is generated on the outer wheel before the turn (see Equation (11)), thereby yawing in a direction to avoid the departure during the turn. Moments can be generated.

  Further, when the vehicle is making a sudden turn and is about to deviate to the outside of the turn, as shown in FIG. (See 13) and (14)). This makes it possible to generate a yaw moment in a direction that avoids deviation when turning.

Reference example 2

  Reference Example 2 will be described with reference to the drawings.

  First, the configuration will be described. FIG. 10 is an overall system diagram showing the lane departure prevention apparatus of Reference Example 2. In the first reference example, in addition to the configuration of the first reference example shown in FIG. 1, a steering actuator 58 incorporating a steering angle sensor 52 is installed in the handle 9, and a steering torque command signal Tref from the steering controller 80 is added. Accordingly, automatic steering control can also be performed. Further, a signal of the steering angle θ from the steering actuator 58 is output to the braking / driving force control controller 50 through the steering controller 80. Other configurations are the same as those of the reference example 1 shown in FIG.

  In this reference example 2, the function of preventing lane departure is the same as in reference example 1. However, by providing the steering actuator 58, the vehicle is maintained at a target position (for example, the center of the lane) in the lane by steering. This can be performed by the actuator 58 (corresponding to lane keep control or lane guide control).

  Further, when it is difficult to maintain the lane due to a sudden turn or the like and the departure determination is made (step S103), if the lane keeping control by the steering actuator 58 is continued, the control steering amount is increased or controlled. Since the interference with the driving force control becomes a problem, the steering control avoids the departure from the lane by the departure control by the braking / driving force control, and restricts the control to the increase side until the departure determination is canceled. In this reference example 2, after the departure determination, the control steering angle δg is set as the maximum limit even if a control amount larger than the control steering angle δg at the departure determination is calculated. Conversely, it is possible to switch back.

  The overall system diagram showing the lane departure prevention apparatus of the first embodiment is the same as the system shown in FIG. 1, and illustration and description thereof are omitted.

  Further, the braking / driving force control process in the first embodiment is also the same as FIG. 2 showing a flowchart of an example of a control program executed by the braking / driving force control controller 50 except for step S103 and step S107. Hereinafter, step S103 and step S107 including different processes will be described.

In step S103, a lane departure determination is performed. In the second reference example, a predicted departure time Tout until departure is calculated, and the possibility of lane departure is determined by comparison with departure determination threshold values Ts1 and Ts2. First, the amount of change dX of the lateral displacement X is calculated, and the estimated departure time Tout until the vehicle departs from the distance L / 2-X to the lane is calculated according to the following equation (see FIG. 4).
Tout = (L / 2−X) / dX (2)
However, Tout ≦ Tmax (maximum value limit: 0% countermeasure). Here, L is the lane width, and is calculated by processing the camera image. Next, the departure judgment threshold values Ts1, Ts2 and Tout are compared, and the departure possibility level Fout is
When Tout <Ts2, it is determined that there is a high possibility of departure, and Fout = 2
When Ts2 <Tout <Ts1, it is determined that there is a possibility of deviation, and Fout = 1
In the case of Tout ≧ Ts1, it is determined that there is no possibility of deviation, and Fout = 0
And Here, Ts1 and Ts2 do not have to be constant values, and Ts1 and Ts2 are changed to be small so that the control is activated earlier in the case of a sudden turn according to the determination of the turning state determined in step S102. Etc. A change-over switch is set so that it can be switched in several stages, and the driver may select it. At the same time, the departure direction Dout is also determined from the lateral displacement X (Dout = right or left). Also, Ts1 is set to a value larger than Ts2. In the first embodiment, the deviation is determined from the lateral displacement X and the amount of change dX. However, the vehicle deviates from the front lane based on the yaw angle Φ of the host vehicle, the curvature β of the traveling lane, the yaw rate of the vehicle, the steering angle, and the like. It is good also as what estimates time Tout to perform.

In step S107, the target braking hydraulic pressure Psi of each wheel (subscript is a subscript) according to the departure possibility level, the target yaw moment Ms calculated in step S106, the master cylinder hydraulic pressure Pm, and the turning state determined in step S102. Each wheel is indicated). When the possibility of departure Fout = 0, the target brake hydraulic pressure for each wheel is the master cylinder hydraulic pressure.
Psfl = Psfr = Pm (5)
Psrl = Psrr = Pmr (6)
Here, Pmr is a rear wheel master cylinder hydraulic pressure in consideration of the front-rear distribution calculated from Pm. Further, when the possibility of departure Fout = 1, the target braking hydraulic pressure of each wheel calculated in (5) and (6) is a value smaller than the maximum hydraulic pressure P0 in a range where no braking force is generated. If so, set it to P0. On the other hand, in the case of the possibility of departure Fout = 2, depending on the magnitude of the target yaw moment, if the target yaw moment is smaller than the set value, a difference is generated in the braking force between the left and right rear wheels, which is larger than the set value. In this case, a braking force difference is generated between the front, rear, left and right wheels (similar to step S107 in FIG. 2).

  As described above, in the first embodiment, the departure possibility level is determined according to the expected departure time, and it is determined that there is a possibility that the departure is not high, such as driving with a slight wobble. In the case (Fout = 1), the brake fluid pressure is increased within a range where no braking force is generated, and it is determined that there is a high possibility of departure and it is necessary to avoid the departure (Fout = 2). Then, departure avoidance control is started.

  As a result, it is possible to avoid unnecessarily inconvenience to the driver by operating the control more than necessary, and when it is necessary to generate a braking force for avoiding a deviation, braking is performed in a range where the braking force is not generated in advance. Since the hydraulic pressure is increased, control responsiveness can be improved, and control that avoids deviation can be performed more effectively.

  The overall system diagram showing the lane departure prevention apparatus of the second embodiment is the same as the system shown in FIG. 1, and illustration and description thereof are omitted.

  The braking / driving force control process in the second embodiment is also the same as FIG. 2 showing a flowchart of an example of a control program executed by the braking / driving force control controller 50, except for steps S103 and S107. Step S107 is the same as that in Reference Example 2. Hereinafter, step S103 including different processing will be described.

  In the second embodiment, as shown in FIG. 11, a virtual lane having a virtual lane width L ′ is set inside the actual lane width L, and deviation from the virtual lane width L ′ is expected. The case is a possibility of departure possibility level 1, and the case where a departure from the actual lane width L is expected is assumed to be a departure possibility level 2.

In step S103, the estimated departure time until the departure is calculated for each of the actual lane and the virtual lane.
Tout1 = (L ′ / 2−X) / dX (18)
Tout2 = (L / 2−X) / dX (19)
However, Toutl, Tout2 ≦ Tmax (maximum value limit: 0% countermeasure).
Next, the departure judgment threshold value Ts is compared with Tout1 and Tout2, and the departure possibility level Fout is
When Tout2 <Ts: Fout = 2
When Tout2 ≧ Ts and Tout1 <Ts: Fout = 1
When Tout1 ≧ Ts: Fout = 0
And Here, Ts does not have to be a constant value, and Ts may be changed to be small so that the control is activated earlier in the case of a sudden turn according to the determination of the turning state determined in step S102. . A change-over switch is set so that it can be switched in several stages, and the driver may select it. At the same time, the departure direction Dout is also determined from the lateral displacement X (Dout = right or left).

  According to the second embodiment, the possibility that the own vehicle deviates from the actual lane width L is not high. However, when the possibility that the own vehicle deviates from the virtual lane width L ′ is high, the possibility of deviating 1 When there is a high possibility of deviating from the lane width L, it is determined as a deviating possibility level 2. Therefore, when driving somewhat meandering, it is determined as a deviating possibility level 1 and the brake fluid pressure is increased. I will leave it alone. As a result, it is possible to prevent the driver from performing the departure avoidance control more than necessary, to reduce the troublesomeness for the driver, and to generate the braking force for avoiding the departure in advance. Since the brake fluid pressure is increased within a range where no braking force is generated, the control response can be improved, and the control for avoiding the deviation can be performed more effectively.

Reference example 3

  The overall system diagram showing the lane departure prevention apparatus of Reference Example 3 is the same as the system shown in FIG. 1, and illustration and description thereof are omitted.

  FIG. 12 is a view showing a flowchart of an example of a control program executed by the braking / driving force control controller 50 in Reference Example 3. Regarding this braking / driving force control processing, steps S100 to S108 are shown in FIG. The same as Reference Example 1 shown in FIG. Hereinafter, step S109 and step S110 will be described.

  In step S109, the target brake hydraulic pressure Psi calculated in step S107 is converted into an intermittent command value Psi ′. This conversion method is shown in FIG. That is, the target hydraulic pressure is increased or decreased by ΔPd at a predetermined period td with respect to the target braking hydraulic pressure Psi calculated based on the target yaw moment. Since the purpose of this period td is to generate vibrations due to pressure fluctuations, the period td is set to a time that allows the braking device to respond to the command value. Further, the magnitude ΔPd to be increased / decreased is set to a value smaller than the target braking fluid pressure Psi, the pressure change width on the pressure increase side is equal to the pressure change width on the pressure decrease side, and the time of the command value Psi ′ converted intermittently is obtained. The average value is set to be equal to Psi.

  In step S110, a drive signal is output to the pressure control unit 5 and the drive torque controller 60 according to the target brake fluid pressure Psi and the target drive torque Tes.

  Therefore, according to the reference example 3, when the departure determination means determines that the host vehicle is about to depart from the driving lane, the yaw moment is generated in a direction to avoid the departure by controlling the braking / driving force of each wheel. By doing so, it is possible to avoid deviation from the traveling lane and to generate the braking force intermittently, thereby making it possible for the driver to reliably recognize the deviation from the traveling lane.

Reference example 4

  The overall system diagram showing the lane departure prevention apparatus of Reference Example 4 is the same as the system shown in FIG. 1, and illustration and description thereof are omitted.

  Further, the braking / driving force control process in Reference Example 4 is the same as the flowchart of an example of the control program executed by the braking / driving force control controller 50 shown in FIG. 12 except for step S109. Hereinafter, step S109 will be described.

  In step S109, the target braking fluid pressure Psi calculated in step S107 is converted into an intermittent command value Psi ′, and the period td and the change width ΔPd for changing the braking force intermittently are set as the expected deviation time. It can be changed accordingly.

  An example of how to change the period td is shown in FIG. The value of the period td is determined according to the difference between the estimated departure time Tout and the threshold value Ts, and is determined so that the period td becomes a smaller value as the estimated departure time becomes shorter than the threshold value. FIG. 14B shows a setting example of the change width ΔPd. The change width ΔPd is determined according to the difference between the expected departure time Tout and the threshold value Ts, and the change width ΔPd does not exceed Psi as the expected departure time becomes shorter than the threshold value. , Determined to be a larger value.

  Further, as a general frequency characteristic in the pressure control unit of the braking device, as the period td is shortened, the actual change in the braking force tends to become smaller with respect to the change in the command value. As shown in FIG. 15, it is assumed that the value is set larger than a value necessary to compensate for this frequency.

  Therefore, according to Reference Example 4, when it is determined by the departure determining means that the host vehicle is about to depart from the driving lane, the yaw moment is generated in a direction to avoid the departure by controlling the braking / driving force of each wheel. To avoid the departure from the driving lane, and as the braking fluid pressure increases, the warning effect that makes the driver recognize the departure is further increased because the braking fluid pressure is generated with shorter and larger vibrations. Is possible.

  In Reference Example 4, the effect can also be obtained by fixing the intermittent time td and changing only ΔPd according to Ts−Tout.

It is a whole system figure which shows the lane departure prevention apparatus in the reference example 1. It is a flowchart of an example of the control program performed by the braking / driving force control controller in Reference Example 1. It is a figure which shows the target yaw rate characteristic with respect to the steering angle which represented the vehicle speed as a parameter. It is a figure showing the condition which is likely to deviate from a driving path of the lane width L. It is a gain characteristic figure with respect to the vehicle speed V of gain K1, K2, Ka, Kb used for the calculation formula of the target yaw moment. It is a gain characteristic view with respect to the vehicle speed V of the gain Kc used for the calculation formula of the target yaw moment. It is a figure which shows the lane departure prevention effect by the braking force difference of right and left at the time of straight ahead. It is a figure which shows the lane departure prevention effect by the right-and-left braking force difference at the time of departure to the inside of the turning direction during turning. It is a figure which shows the lane departure prevention effect by the right-and-left braking force difference at the time of the departure in the turning direction outside during turning. It is a whole system figure which shows the lane departure prevention apparatus in the reference example 2. It is a figure showing the condition which is likely to deviate from a travel path of the lane width L and the virtual lane width L 'in Example 2. 10 is a flowchart of an example of a control program executed by a braking / driving force control controller in Reference Example 3. 12 is a braking fluid pressure change characteristic diagram in Reference Example 3. FIG. It is a setting characteristic diagram for setting the change cycle and change width of the brake fluid pressure in Reference Example 4 according to the expected departure time. FIG. 10 is a braking fluid pressure change width (amplitude) characteristic diagram for compensating for frequency characteristics in Reference Example 4;

Explanation of symbols

10, 20 Left and right front wheels 30, 40 Left and right rear wheels 11, 21, 31, 41 Brake discs 12, 22, 32, 42 Wheel cylinders 13, 23, 33, 43 Wheel speed sensor 1 Brake pedal 2 Booster 3 Reservoir 4 Master cylinder 5 Pressure servo unit 53 Front / rear acceleration sensor 56 Accelerator opening sensor 50 Controller 6 Engine 7 Throttle opening controller 8 Transmission 60 Drive torque control controller 55 Master cylinder hydraulic pressure sensor 51 Camera 70 Camera controller 58 Steering actuator 54 Yaw rate sensor 52 Rudder angle sensor 57 Direction indicator switch 80 Steering controller

Claims (4)

In the lane departure prevention device that gives the vehicle a yaw moment for preventing departure when the host vehicle is about to depart from the driving lane,
Deviation judgment means for judging that the host vehicle is likely to deviate from the driving lane,
Intention determination means for determining that the driver is trying to maintain the driving lane;
A case where it is determined that the driver is attempting to maintain the running lane by the intention determining means, when it the vehicle is deviating likely from the travel lane is determined by the deviation determining means, deviations Braking force control means for generating a yaw moment in a direction to avoid
When there is a possibility of departure, the departure determination means determines whether the departure possibility is low or high,
It said braking force control means, a low deviation likely level increases the brake fluid pressure to the extent that the braking force is not generated, control in accordance with departure possible levels have rows departure prevention control by the braking force difference at higher departing possible level A lane departure prevention apparatus characterized by increasing power and notifying the driver that the host vehicle is about to depart from the traveling lane before at least performing the departure prevention control . The lane departure prevention apparatus according to claim 1,
The departure determination means estimates the time until departure from the departure direction from one or more detected values of the vehicle speed, the vehicle yaw angle with respect to the traveling lane, the lateral displacement, and the forward traveling lane curvature, A lane departure prevention apparatus characterized in that a possibility of departure is determined when the time falls within a set value, and the possibility level is determined according to the estimated time until departure. The lane departure prevention apparatus according to claim 1,
The departure determination means assumes a virtual lane width that is narrower than the traveling lane width, and sets a low departure possibility level 1 when a departure from the virtual lane width is expected. A lane departure prevention apparatus characterized in that it is a means for setting a high departure possibility level 2 when a departure is expected. The lane departure prevention apparatus according to any one of claims 1 to 3,
The braking force control means generates a target yaw moment to be generated in a vehicle necessary for preventing the vehicle from deviating from the traveling lane based on one or more detection values of the vehicle yaw angle, lateral displacement, and forward traveling lane curvature with respect to the traveling lane. A lane departure prevention apparatus characterized in that it is a means for calculating and calculating a braking force to be generated on each wheel in accordance with the target yaw moment.

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