JPH1191607A - Vehicle rear wheel steering controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vehicle from deviating from a driving lane positively when safety cannot be maintained if a driver controls the steering wheel in the direction of deviating from the driving lane. SOLUTION: A controller 12 reads in a switch signal from image recognition results such as the driving lane where the vehicle is running, a speed of each wheel through wheel speed sensors 7fl, 7fr, 7rl and 7rr, a steering wheel angle through a steering wheel angle sensor 8, a rear wheel steering angle through a rear wheel steering angle sensor 9, a yaw rate through a yaw rate sensor 13 and a turn signal lamp switch 14. A correcting condition judgment part 12b judges when the vehicle deviates from the driving lane if the deviation is not for turning, avoiding a risk or other reasonable reasons, but an unnecessary deviation. A target rear wheel steering angle computing part 12d computes a target rear wheel steering angle based on the preset four-wheel steering control roles. At this point, a rear wheel steering angle corrected value setting part 12c sets a corrected value to the four-wheel steering control rules in the direction that the vehicle head turnability lowers when a vehicle deviates from the current lane. A rear wheel steering amount setting output part 12e sets the amount of the rear wheel steering based on the target rear wheel steering angle and the rear wheel steering angle, outputs it to a motor drive 5 of the rear wheel steering part, and drives a rear wheel steering motor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear wheel steering control device for a vehicle which prevents unnecessary departure from a traveling lane of a vehicle.

[0002]

2. Description of the Related Art Conventionally, various types of steering angle control (4WS control) for steering front and rear wheels in order to improve running stability and mobility of a vehicle have been proposed and put into practical use. For example, Japanese Patent Application Laid-Open No. Sho 62-15168 discloses that a target yaw rate is determined from a front wheel steering angle and a vehicle speed, and a rear wheel steering angle proportional to a deviation between the target yaw rate and a yaw rate obtained from a host vehicle model calculation unit is given. A rear wheel steering control device for a vehicle is shown.

[0003] In recent years, a comprehensive driving assistance system (ADA: Active Drive Assist system) has been developed which actively assists the driving operation of a driver to improve safety. The function of the ADA system is to estimate various possibilities such as collision with a preceding vehicle, contact with an object, departure from a running lane, etc. from the running environment information of the vehicle and the running state of the own vehicle, and predict that safety cannot be maintained. In such a case, there is a function of notifying the driver and performing other controls.

A driving lane departure prevention function as driving assistance for a driver such as the ADA system is disclosed in, for example, JP-A-6-255514.
In this prior art, the stable driving potential energy that increases as the vehicle approaches the white line on the road is set, and the positional relationship between the vehicle and the white line changes due to steering, and the assist amount of power steering decreases when the stable driving potential energy increases. When the stable running potential energy decreases, the assist amount of the power steering is increased.

[0005]

However, such a conventional driving lane departure prevention function has a strong warning meaning to the driver, and if the driver steers without noticing the warning, the vehicle moves in the steering direction. It is not intended to actively prevent the vehicle from deviating from the traveling lane, for example, by traveling and deviating from the traveling lane. For this reason,
There is a demand for a vehicle that can positively prevent a deviation from the driving lane.

The present invention has been made in view of the above circumstances, and in a vehicle equipped with 4WS control, a driver can steer in a departure direction from a driving lane while obtaining the excellent stability inherent in 4WS control. It is an object of the present invention to provide a rear wheel steering control device for a vehicle that can positively prevent deviation from a traveling lane when safety cannot be maintained.

[0007]

According to a first aspect of the present invention, there is provided a vehicle rear wheel steering control apparatus for calculating a target rear wheel steering angle based on a predetermined control law. In a rear wheel steering control device for a vehicle which sets a rear wheel steering amount based on the rear wheel steering angle, a driving lane recognizing means for recognizing a driving lane of the own vehicle, and a condition based on a condition set in advance by the own vehicle. And rear wheel steering angle correction means for correcting the rear wheel steering angle in a direction in which the turning performance of the vehicle decreases when steering is performed in a direction deviating from the traveling lane of the host vehicle. .

In the rear wheel steering control device according to the first aspect of the present invention, first, the traveling lane of the own vehicle is recognized by the traveling lane recognition means. Further, a target rear wheel steering angle is calculated based on a predetermined control law. The rear wheel steering angle is determined by the rear wheel steering angle correction means when the vehicle is steered in a direction deviating from the travel lane of the vehicle under the conditions set in advance. Is corrected in the direction in which the characteristics are reduced. Then, the rear wheel steering amount is set based on the corrected rear wheel steering angle.

According to a second aspect of the present invention, there is provided a rear wheel steering control device for a vehicle, wherein the rear wheel steering angle correcting means promotes turning of the vehicle. At least one of reducing the relationship between the front wheels and the rear wheels in the opposite phase and increasing the relationship between the front wheels and the rear wheels in the same phase to weaken the turning of the vehicle increases the target rear wheel steering angle by turning the vehicle. Correction is made in the decreasing direction to prevent the vehicle from deviating from the traveling lane.

Further, the rear wheel steering control device according to the present invention according to the third aspect of the present invention is the vehicle rear wheel steering control device according to the first or second aspect, wherein the rear wheel steering angle correcting means includes: When the vehicle is deviating from the lane and the steering is performed in the direction of returning from the departure, the correction of the target rear wheel steering angle in the direction in which the turning performance of the vehicle is reduced is released, and the vehicle is deviated from the traveling lane. If the steering is performed in a direction to return from the deviation when the vehicle deviates, a normal return can be performed.

According to a fourth aspect of the present invention, there is provided a rear wheel steering control device for a vehicle according to any one of the first, second and third aspects. The correction means determines a correction amount according to at least one of a distance from a reference position defined substantially at the center between the traveling lanes of the own vehicle to the current position and a speed at which the own vehicle departs from the reference position. Accurate control can be performed according to the degree of departure from the lane.

Further, according to a fifth aspect of the present invention, there is provided a rear wheel steering control apparatus for a vehicle according to any one of the first, second, third and fourth aspects. The steering angle correction means reduces the rear wheel steering amount as the vehicle speed decreases, and prevents the rear wheels from being stationary.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention, FIG. 1 is a functional block diagram of a rear wheel steering control device of a vehicle, and FIG. 2 is an explanatory diagram showing a schematic configuration of a rear wheel steering control device of the vehicle. 3 is a characteristic diagram of each parameter set by the 4WS control law, and FIG. 4 is a flowchart of the rear wheel steering control.

In these figures, reference numeral 1 denotes a vehicle such as an automobile, and a front wheel steering unit 2 of the vehicle 1 includes a power steering device and the like, and is connected to a left front wheel 3fl and a right front wheel 3fr by a link mechanism. I have.

The rear wheel steering section 4 of the vehicle 1 is provided with a rear wheel steering motor 6 driven by a motor drive section 5. The power of the rear wheel steering motor 6 is transmitted to a worm or worm wheel. , Transmitted through the link mechanism,
The left rear wheel 3rl and the right rear wheel 3rr are steered.

Each of the wheels 3fl, 3fr, 3rl, 3rr has a wheel speed sensor (a left front wheel speed sensor 7fl, a right front wheel speed sensor 7fr, a wheel speed sensor ω1, ω2, ω3, ω4).
The left rear wheel speed sensor 7rl and the right rear wheel speed sensor 7rr) are used for detection.

The steering column of the steering wheel is provided with a steering wheel angle sensor 8 for detecting a steering wheel angle θH.
Is provided with a rear wheel steering angle sensor 9 for detecting the steering angle.

The vehicle 1 is provided with a stereo optical system. The stereo optical system includes a set of CCD cameras (a left camera 101 and a left camera 101, for example) using a solid-state imaging device such as a charge-coupled device (CCD). Right camera 10r)
These left and right CCD cameras 10l and 10r are respectively mounted at a certain interval in front of the ceiling in the vehicle interior,
Stereo images of objects outside the vehicle are taken from different viewpoints.

The CCD cameras 10l and 10r calculate the three-dimensional distance distribution over the entire image from the parallax of the same object based on the principle of triangulation, and process the distance distribution data to determine the road shape or a plurality of three-dimensional objects. It is connected to an image processor 11 for recognition.

That is, in the first embodiment of the present invention, a driving lane recognizing means for recognizing a driving lane of the own vehicle by the CCD cameras 101 and 10r and the image processor 11 is formed.

The image processor 11 is provided with the CC
Distance detection for searching for a portion in which the same object is captured in each of the micro regions in the two stereo images captured by the D cameras 10l and 10r, calculating the amount of displacement of the corresponding position, and calculating the distance to the object. Circuit 11a and the distance detection circuit 11
a distance image memory 11b for storing distance distribution data (distance image) in the form of an image which is the output of a, and an image processing computer for processing the distance distribution data to recognize road shapes and a plurality of three-dimensional objects And a unit 11c.

The image processor 11 is supplied with a vehicle speed signal and a steering angle signal from the control device 12, and these signals are inputted to the image processing computer unit 11c, and the road shape and the three-dimensional object are inputted. Is used for the recognition process.

In the road detection processing in the image processing computer unit 11c of the image processor 11, only white lines on an actual road are utilized by using three-dimensional position information based on distance images stored in the distance image memory 11b. Is separated and extracted, and the parameters of the built-in road model are corrected and changed so as to match the actual road shape, thereby recognizing the road shape and the traveling lane of the own vehicle.

In the object detection processing in the image processing computer unit 11c of the image processor 11, the distance images are divided at predetermined intervals in a grid pattern.
For each area, only data of a three-dimensional object that may be an obstacle to traveling is selected, and the detection distance is calculated. If the difference between the detection distances to the objects in the adjacent areas is equal to or smaller than the set value, the objects are regarded as the same object, while if the difference is equal to or larger than the set value, they are regarded as separate objects, and the contour image of the detected object is extracted.

The processing of generating a distance image and detecting a road shape and an object from the distance image are described in Japanese Patent Application Laid-Open Nos. Hei 5-265545 and Hei 6-177236 previously submitted by the present applicant. And the like.

The control device 12 includes the wheel speed sensors 7fl, 7fr, 7rl, 7rr, the steering wheel angle sensor 8, the rear wheel steering angle sensor 9, the yaw rate sensor 13 for detecting the actual yaw rate γ of the vehicle, and the vehicle. A turn signal switch 14 for determining the turning of the vehicle 1 is connected, signals from these sensors and switches are input, and the image processor 11 is connected to input a video signal. . Then, a necessary rear wheel steering angle is calculated based on these signals, and the motor drive unit 5 is operated.
, A drive signal is output.

As shown in FIG. 1, the control device 12
It mainly comprises a vehicle speed calculation unit 12a, a correction condition determination unit 12b, a rear wheel steering angle correction value setting unit 12c, a target rear wheel steering angle calculation unit 12d, and a rear wheel steering amount setting output unit 12e.

The vehicle speed calculator 12a calculates the wheel speeds ω1, ω from the wheel speed sensors 7fl, 7fr, 7rl, 7rr.
2, ω3, ω4 signals are input, and these signals are calculated by a preset mathematical formula (for example, the average value of the speed signals from the wheel speed sensors 7fl, 7fr, 7rl, 7rr is calculated). Then, a vehicle speed V is determined and output to the image processing computer unit 11c of the image processor 11, the correction condition determination unit 12b of the control device 12, and the target rear wheel steering angle calculation unit 12d. I have. If the value of the vehicle speed V can be detected with a vehicle speed sensor with a precision higher than a predetermined value, a vehicle speed signal from another vehicle speed detecting means may be used without being obtained from the four wheels.

The correction condition determination unit 12b receives the steering wheel angle θH from the steering wheel angle sensor 8, the operation signal from the turn signal switch 14, the vehicle speed V from the vehicle speed calculation unit 12a, and the video signal from the image processor 11. Then, it is determined whether or not a condition in which the traveling state of the vehicle 1 unnecessarily deviates from the traveling lane of the own vehicle in 4WS traveling is satisfied.

That is, even if the vehicle deviates from the lane, it is determined that the departure from the traveling lane of the own vehicle is a necessary deviation in a case of avoiding an obstacle in front of the vehicle or in a case of turning intentionally. The determination in the case of avoiding an obstacle in front is made by, for example, recognizing the presence of a preceding vehicle and other obstacles within a forward detection range set in accordance with the vehicle speed V and the like. When the distance relationship gradually changes in the safe direction or when the turn signal switch 14 is operated, it is determined that danger is avoided. In addition, the determination of intentionally turning is performed when the turn signal switch 14 is operated.

And, if it is not the necessary deviation described above,
A condition determination is made as to whether or not the own vehicle is traveling unevenly in the traveling lane and there is a risk of departure from the traveling lane. For example, when the traveling position of the own vehicle is within a set value from the reference position where the traveling position of the own vehicle is substantially at the center with respect to the left and right white lines, it is determined that there is no danger of departure from the traveling lane and output.

Further, when the running position of the own vehicle is deviated from the reference position in the running lane to the left or right white line by a set value or more, the steering direction of the steering is in a direction away from the reference position, or It is determined whether the direction returns to the reference position and output. This is because when the steering is performed in the direction of returning to the reference position, it can be determined that there is no risk of departure from the traveling lane.

Specifically, the white line on the side where the vehicle is deviated from the reference position of the traveling lane is set as a monitoring target, and how the steering is turned with respect to this monitoring target white line is described.
That is, by examining whether the vehicle approaches the monitored white line or separates from the monitored white line, it is determined whether the steering direction of the steering is away from the reference position or in the direction returning to the reference position. .

The result of the determination by the correction condition determination unit 12b is output to the rear wheel steering angle correction value setting unit 12c.

The rear wheel steering angle correction value setting unit 12c sets a map or the like set in advance according to the deviation distance Slane (the distance from the reference position to the vehicle) based on the determination result by the correction condition determination unit 12b. And sets the rear wheel steering angle correction values f1 and f2 in the target rear wheel steering angle calculation unit 12d.

As shown in the characteristic 1 of FIG. 3B, the rear wheel steering angle correction value f1 takes a smaller value than 1 until the departure distance Slane increases as the departure distance Slane increases. As shown in the characteristic of FIG. 3D, the angle correction value f2 is set such that the departure distance S increases as the departure distance Slane increases.
It has a characteristic that takes a value larger than 1 up to lane.

When the condition that the result of determination by the correction condition determination unit 12b deviates unnecessarily is satisfied, the rear wheel steering angle correction values f1, f2 are obtained from the maps of the rear wheel steering angle correction values f1, f2. The value of f2 is determined and set in the target rear wheel steering angle calculation unit 12d.

In the case other than the condition that the judgment result by the correction condition judging unit 12b unnecessarily deviates, the values of the rear wheel steering angle correction values f1 and f2 are determined to be 1 and the target steering angle correction values f1 and f2 are set to 1. This is set in the rear wheel steering angle calculation unit 12d so that no correction is made.

The target rear wheel steering angle calculating unit 12d receives the steering wheel angle θH from the steering wheel angle sensor 8, the vehicle speed V from the vehicle speed calculating unit 12a, and the yaw rate γ from the yaw rate sensor 13 and inputs the rear wheel steering angle correction. Value setting unit 12c
The rear wheel steering angle correction value is input from the controller and a target rear wheel steering angle δr ′ is calculated based on a predetermined control law in advance, and the target rear wheel steering angle δr ′ is calculated as the rear wheel steering amount setting output unit 12e. Is output as target rear wheel steering angle calculating means.

The 4WS control law set in the target rear wheel steering angle calculation section 12d is based on the well-known "control angle of steering wheel reverse phase + yaw rate in-phase control law" known in the first embodiment of the present invention. And is given by the following equation (1). δr ′ = − kδ0 · f1 · (θH / N) + kγ0 · f2 · γ (1) where kδ0 is a steering angle sensitive gain, kγ0 is a yaw rate sensitive gain, and N is a steering gear ratio.

The yaw rate sensitive gain kγ0 is calculated as shown in FIG.
The coefficient is given as shown by the characteristic of the reference value of (c), and is a coefficient that determines the steering amount of the rear wheel so as to eliminate the yaw rate γ. In addition, the steering wheel angle sensitive gain kδ0 is calculated as shown in FIG.
The coefficient is given as shown by the characteristic of the reference value of (a), and is a coefficient that determines the amount of steering of the rear wheels to give steering.

That is, the yaw rate sensitive gain kγ
0 is given so as to steer the rear wheels in phase with the yaw rate γ. As the yaw rate sensitive gain kγ0 is larger, the vehicle tends to proceed diagonally without turning and the yaw rate γ can be prevented from occurring. . In other words, the vehicle characteristics have reduced turning characteristics and improved stability. As described above, the yaw rate sensitive gain kγ0 is determined by the generated yaw rate γ
Can be regarded as a coefficient indicating how much the steering amount is given to the rear wheels to prevent the generation of the yaw rate γ.

However, the yaw rate sensitive gain kγ
If it is only 0, the vehicle cannot turn. To prevent this, a steering wheel angle sensitive gain kδ0 is set. That is, the turning characteristics of the vehicle are improved by steering the rear wheels in the opposite phase with respect to the steering wheel angle θH. Handle angle sensitive gain kδ for handle angle θH
The vehicle turns by setting the term of 0 to be larger. However, when the steering is returned to the neutral state, the control law includes only the term of the yaw rate sensitive gain kγ0, so that after the end of the turn, the rear wheels are steered in the direction of eliminating the yaw rate γ (the direction of eliminating the vehicle wobble). .

The steering wheel angle sensitive gain kδ0 is calculated based on the cornering power of the front wheels and the rear wheels.
When the vehicle speed is equal to or higher than a certain value, the value of the steering wheel angle sensitive gain kδ0 does not change. However, when the vehicle speed is close to 0, the steering wheel sensitivity gain kδ0
Is set to a small value.

With respect to the steering wheel angle sensitive gain kδ0 and the yaw rate sensitive gain kγ0 set as described above,
In the first embodiment of the present invention, the steering wheel angle sensitive gain kδ0 is multiplied by a rear wheel steering angle correction value f1 so that it can be corrected as shown by a characteristic 1 in FIG. The yaw rate sensitive gain kγ0 can be corrected as shown by the characteristic 4 in FIG. 3C by multiplying the rear wheel steering angle correction value f2.

That is, the steering angle sensitive gain kδ
For zero, by multiplying the rear wheel steering angle correction value f1, the absolute value is corrected to be smaller when the condition that unnecessarily deviates is satisfied. Steering in the opposite phase is reduced, and improvement in turning performance of the vehicle is reduced. Then, the correction is made larger as the deviation distance Slane is larger, up to a certain deviation distance Slane.

The yaw rate sensitive gain kγ0 is corrected by multiplying by a rear wheel steering angle correction value f2 so as to become larger than usual when the condition that unnecessarily deviates is satisfied. The rear wheels are made larger in phase to reduce the improvement in turning performance of the vehicle. And the correction is the deviation distance Slane
Is larger, the correction is increased to a certain departure distance Slane.

As described above, in the first embodiment of the present invention, the correction condition determining unit 12b and the rear wheel steering angle correction value setting unit 12c form a rear wheel steering angle correction unit. Note that the rear wheel steering angle correction value f set by the rear wheel steering angle correction value setting unit 12c.
The characteristic 1 is not limited to the characteristic 1 described above, and may be the characteristic 2 or the characteristic 3 as shown in FIG. 3B, for example.

The characteristic 2 rear wheel steering angle correction value f1 has a characteristic in which the departure distance Slane gradually decreases from 1 to 0 until a constant deviation distance Slane, and the characteristic 3 rear wheel steering angle correction value f1. Then, the departure distance Slane is a fixed departure distance Sla
It has a characteristic that gradually decreases from 1 to a negative value until ne.

For this reason, the correction (kδ0 · f1) of the steering angle sensitive gain kδ0 using the characteristics 1, 2, and 3 when the departure distance Slane is Sl1 is as shown in FIG.
When the condition that unnecessarily deviates from the rear wheel steering angle correction value f1 of the characteristic 2 is satisfied, it is always corrected to 0 and the rear wheels are not steered in the opposite phase with respect to the steering wheel angle θH. The improvement in turning performance is reduced. On the other hand, when the condition that unnecessarily deviates with the rear wheel steering angle correction value f1 of the characteristic 3 is satisfied, the rear wheels are always steered in the same phase with respect to the steering wheel angle θH to improve the turning performance of the vehicle. It is going to decrease.

Further, the correction of the steering wheel angle sensitive gain kδ0 may be performed not by the rear wheel steering angle correction value f1 according to the departure distance Slane but by the rear wheel steering angle correction value f3 according to the departure speed Vlane. .

The rear wheel steering angle correction value f3 is, for example, as shown in FIG.
As shown in (f), as the departure speed Vlane (the speed at which the host vehicle departs from the reference position) increases, the departure speed V
Characteristic 5, which takes a value smaller than 1 up to lane 5, departure speed Vla
Characteristic 6 in which ne gradually decreases from 1 to 0 until a constant departure speed Vlane, departure speed Vlane is constant departure speed V
Characteristic 7 that gradually decreases from 1 to a negative value until lane 7
Etc.

For this reason, the correction (kδ0 · f3) of the steering angle sensitive gain kδ0 using the characteristics 5, 6, and 7 when the departure speed Vlane is V11 is as shown in FIG.
When the condition that unnecessarily deviates from the rear wheel steering angle correction value f3 of the characteristic 5 is satisfied, the steering of the rear wheel in the opposite phase to the steering wheel angle θH is reduced to reduce the turning characteristic of the vehicle. Are to be improved. When the condition that unnecessarily deviates from the rear wheel steering angle correction value f3 of the characteristic 6 is satisfied, it is always corrected to 0 and the rear wheels are not steered in the opposite phase with respect to the steering wheel angle θH. The improvement in turning performance of the vehicle is reduced. Further, if the condition that unnecessarily deviates from the rear wheel steering angle correction value f3 of the characteristic 7 is satisfied, the steering wheel angle θ
With respect to H, the rear wheels are always steered in the same phase to reduce the turning performance of the vehicle.

Similarly, the correction of the yaw rate sensitive gain kγ0 is performed by correcting the rear wheel steering angle correction value f2 corresponding to the departure distance Slane.
Instead, the rear wheel steering angle correction value f4 according to the departure speed Vlane
It may be performed in. The rear wheel steering angle correction value f4 is
For example, as shown in the characteristic of FIG.
The characteristic has a characteristic that the value becomes larger than 1 up to a constant departure speed Vlane as the value of. Therefore, for the yaw rate sensitive gain kγ0, the rear wheel steering angle correction value f4
Is corrected to be larger than usual when the condition that unnecessarily deviates is satisfied, and the rear wheels are made in-phase with the yaw rate γ to reduce the improvement in turning performance of the vehicle It is supposed to. The correction is made such that the larger the departure speed Vlane is, the more constant the departure speed V
It is greatly corrected up to lane.

The rear wheel steering angle correction value f of the above characteristics 1, 2, 3
1, one of the characteristics 5, 6, and 7 of the rear wheel steering angle correction value f3, or the characteristics 1, 2, and 3 of the rear wheel steering angle correction value f
The steering angle sensitive gain kδ0 may be corrected based on both 1 and the characteristics 5, 6, 7 rear wheel steering angle correction value f3.

The yaw rate responsive gain k is determined by either the rear wheel steering angle correction value f2 or the rear wheel steering angle correction value f4, or both the rear wheel steering angle correction value f2 and the rear wheel steering angle correction value f4.
The correction of γ0 may be performed.

Further, it is needless to say that an effect can be obtained even if only one of the correction of the steering wheel angle sensitive gain kδ0 and the correction of the yaw rate sensitive gain kγ0 is performed depending on the vehicle.

Furthermore, when the vehicle speed is close to zero, the steering amount of the rear wheels is corrected so as to be eliminated, thereby preventing the rear wheels from being set off.

The rear wheel steering amount setting output unit 12 e is required from the target rear wheel steering angle δr ′ from the target rear wheel steering angle calculation unit 12 d and the rear wheel steering angle δr from the rear wheel steering angle sensor 9. Rear wheel steering amount setting output means for outputting a signal corresponding to the rear wheel steering amount to the motor drive unit 5 of the rear wheel steering unit 4 to drive the rear wheel steering motor 6 It is formed as.

Next, the operation of the first embodiment of the present invention having the above configuration will be described with reference to the flowchart of FIG. This figure 4
Is executed by the control device 12 at predetermined time intervals, and first, a step (hereinafter abbreviated as “S”) 101
The image recognition result is read from the image processor 11, the respective wheel speeds ω1, ω2, ω3, ω4 from the respective wheel speed sensors 7fl, 7fr, 7rl, 7rr, the steering wheel angle sensor 8 from the steering wheel angle sensor 8, and the rear wheel steering angle sensor. 9, the rear wheel steering angle δr, the yaw rate γ from the yaw rate sensor 13, and the switch signal from the turn signal switch 14.

Next, the routine proceeds to S102, where it is determined whether or not danger is avoided. The determination in S102 is a determination as to whether or not the departure of the vehicle from the traveling lane is a necessary deviation.
Specifically, whether or not to avoid obstacles ahead,
For example, it recognizes the presence of a preceding vehicle or other obstacles within a detection range in front set according to the vehicle speed V or the like, and the distance relationship between the obstacles and the host vehicle gradually changes in a safe direction, or the above-described turn. It is determined that the operation of the signal switch 14 is performed to avoid danger of avoiding an obstacle.

When it is determined in step S102 that danger is avoided, the process proceeds to step S103, where the rear wheel steering angle correction value setting unit 12c is set.
Then, the respective values of the rear wheel steering angle correction values f1 and f2 are determined to be 1, and are set in the target rear wheel steering angle calculation unit 12d to make no correction.

On the other hand, if it is determined in step S102 that it is other than danger avoidance, the process proceeds to step S104, in which the departure of the vehicle from the traveling lane is a necessary deviation when turning intentionally, that is, the turn signal switch 14 It is determined whether or not is activated.

The turn signal switch 14
Is operated, and when it is determined that the departure of the own vehicle from the traveling lane is a case where the vehicle deliberately turns, the process proceeds to S103, and the rear wheel steering angle correction value f1, Each value of f2 is determined to be 1 and set in the target rear wheel steering angle calculation unit 12d to make no correction.

If the turn signal switch 14 is not operated in step S104, the process proceeds to step S105, in which the vehicle is running unbalanced in the traveling lane and there is a risk of departure from the traveling lane. judge. For example, when the traveling position of the own vehicle is within a set value from the reference position where the traveling position of the vehicle is substantially at the center with respect to the left and right white lines, it is determined that there is no danger of departure from the traveling lane, and the process proceeds to S103. The value setting unit 12c determines the values of the rear wheel steering angle correction values f1 and f2 to be 1, and sets the values in the target rear wheel steering angle calculation unit 12d to make no correction.

On the other hand, if the running position of the own vehicle deviates from the reference position in the running lane to either side of the left and right white lines by a set value or more in S105, the process proceeds to S106, and the steering direction of the steering is changed to the above. Direction away from the reference position,
Alternatively, it is determined whether the direction is to return to the reference position. Specifically, the white line on the side where the vehicle is deviated from the reference position of the traveling lane is set as a monitoring target, and how the steering is turned with respect to this monitoring target white line, that is, how the steering vehicle approaches the monitoring target white line It is determined whether the steering direction of the steering is away from the reference position or the direction of returning to the reference position by examining whether the vehicle is moving away from the white line to be monitored.

If it is determined in step S106 that the steering direction of the steering wheel is to return to the reference position, it is determined that there is no danger of departure from the traveling lane, and the above-described step S103 is performed.
Then, the rear wheel steering angle correction value setting unit 12c determines the values of the rear wheel steering angle correction values f1 and f2 to be 1, and sets the values in the target rear wheel steering angle calculation unit 12d to make no correction.

If it is determined in step S106 that the steering direction of the steering is away from the reference position, it is determined that the vehicle departs unnecessarily from the traveling lane of the host vehicle.
In step 107, the rear wheel steering angle correction value setting section 12c searches a preset map or the like according to the deviation distance Slane to determine rear wheel steering angle correction values f1 and f2, and sets the target rear wheel angle. The rear wheel steering angle correction values f1 and f2 are set in the steering angle calculation unit 12d.

That is, S102, S104 to S1
Each of the processes 06 is a process performed by the correction condition determination unit 12b, and S103 and S107 are processes performed by the rear wheel steering angle correction value setting unit 12c.

In step S103 or S107, the target rear wheel steering angle calculation unit 12d sends the rear wheel steering angle correction values f1, f2
Then, the process proceeds to S108, where the target rear wheel steering angle calculating section 12d calculates the target rear wheel steering angle δr 'based on the above equation (1).

Then, the process proceeds to S109, in which the rear wheel steering amount setting output unit 12e outputs the target rear wheel steering angle δr 'from the target rear wheel steering angle calculation unit 12d and the rear wheel steering angle from the rear wheel steering angle sensor 9. After setting the required rear wheel steering amount from the angle δr,
Then, a signal corresponding to the rear wheel steering amount is output to the motor drive unit 5 of the rear wheel steering unit 4 to drive the rear wheel steering motor 6, and the program exits.

As described above, in the first embodiment of the present invention,
In a 4WS vehicle having a basic control law of "steering angle opposite phase + yaw rate in-phase control law", when a condition that the vehicle unnecessarily deviates is satisfied, the steering wheel is set so that the rear wheels tend to be in phase with the steering wheel angle. Since the angle-sensitive gain kδ0 is corrected, and the yaw rate-sensitive gain kγ0 is corrected so that the rear wheels tend to be in phase with the yaw rate, correction is made in the direction in which the turning performance of the vehicle decreases.
Even if the driver performs steering in the departure direction from the traveling lane, it is possible to positively prevent the deviation from the traveling lane.

In addition, since the 4WS control is used, the driver feels less uncomfortable with the front wheel-side auxiliary steering, and can perform fine tuning in accordance with the amount of deviation, thereby achieving a highly feasible system.

Further, by accurately detecting and controlling the case where the condition that the vehicle deviates unnecessarily is satisfied,
Under normal conditions, high stability of the 4WS control can be expected, and a 4WS vehicle can be realized in a cost-effective manner with little inherent hardware for preventing departure.

FIGS. 5 to 7 show a second embodiment of the present invention. FIG. 5 is a functional block diagram of a rear wheel steering control device of the vehicle, and FIG. 6 shows a schematic configuration of the rear wheel steering control device of the vehicle. FIG. 7 is a flowchart of the rear wheel steering control.
In the second embodiment of the present invention, the control law of 4WS is based on the yaw rate feedback system.

Therefore, in the second embodiment of the present invention, the control device 20 is different from the first embodiment of the present invention, and the control device 20 includes the wheel speed sensors 7fl, 7fr, 7rl, 7rl.
rr, a steering wheel angle sensor 8, a rear wheel steering angle sensor 9, a yaw rate sensor 13, and a turn signal switch 14 are connected, signals from these sensors and switches are input, an image processor 11 is connected, and a video signal is transmitted. Is to be entered. Then, a necessary rear wheel steering angle is calculated based on these signals, and the motor drive unit 5 is operated.
, A drive signal is output.

As shown in FIG. 5, the control device 20
It mainly comprises a vehicle speed calculation unit 12a, a correction condition determination unit 12b, a rear wheel steering angle correction value setting unit 20a, a target rear wheel steering angle calculation unit 20b, and a rear wheel steering amount setting output unit 12e.

The target rear wheel steering angle calculating unit 20b calculates the rear wheel steering angle correction value kg for the yaw rate steady-state gain Gr and the rear wheel steering angle correction for the yaw rate time constant Tr from the rear wheel steering angle correction value setting unit 20a. The value kt is input, the vehicle speed V is input from the vehicle speed calculator 12a, the steering wheel angle θH is input from the steering wheel angle sensor 8, the yaw rate γ is input from the yaw rate sensor 13, and the well-known “Yaw rate feedback system control law”. , The target rear wheel steering angle δr 'is calculated by the following equation based on the 4WS basic control law, and the target rear wheel steering angle δr' is output to the rear wheel steering amount setting output unit 12e. It is formed as a steering angle calculating means. δr ′ = kδr · (γ′−γ) (2) In the above equation (2), kδr is a constant set in advance through experiments and calculations, γ ′ is a target yaw rate, and the target yaw rate γ ′ Is calculated as follows: γ ′ = (kg · Gr) / (1+ (kt · Tr) · s) · δf (3) In the above formula (3), s is a Laplace operator,
δf is a front wheel steering angle (= θH / N; N is a steering gear ratio), which is calculated by approximating the response delay of the vehicle expressed by the secondary system to that of the primary system.

The steady-state yaw rate gain Gr is calculated as follows: Gr = (1 / (1 + A · V ² )) · (V / L) (4) where A is a stability factor and L is a wheel base. .

Further, the yaw rate time constant Tr is calculated by Tr = (m · Lf · V) / (2 · L · Kr) (5), where m is the vehicle mass, and Lf is the distance between the front wheel axis and the center of gravity. The distance, Kr, is the rear equivalent cornering power.

Here, as can be seen from the above equation (2), the target rear wheel steering angle δr ′ is changed according to the value of the target yaw rate γ ′. And the vehicle model is
As the value of the yaw rate steady gain Gr decreases, the stability with respect to steering improves and the turning performance decreases. Also, as the value of the yaw rate time constant Tr increases, the vehicle response to steering delays and the stability with respect to steering decreases. A model with improved turning characteristics.

The rear wheel steering angle correction value setting unit 20a searches a preset map or the like according to the deviation distance Slane based on the determination result by the correction condition determination unit 12b, and retrieves the target rear wheel steering angle. The calculation unit 20b provides the rear wheel steering angle correction value kg for the yaw rate steady gain Gr and the yaw rate time constant T
A rear wheel steering angle correction value kt for r is set.

That is, when the condition that the judgment result by the correction condition judging section 12b deviates unnecessarily is satisfied, the map of the rear wheel steering angle correction values kg and kt is obtained from each map of the rear wheel steering angle correction values kg and kt. The value is determined and set in the target rear wheel steering angle calculation unit 20b.

When the condition that the judgment result by the correction condition judging section 12b deviates unnecessarily does not hold, the values of the rear wheel steering angle correction values kg and kt are determined to be 1 and the target value is determined. The setting is made in the rear wheel steering angle calculating section 20b so that no correction is made.

The rear wheel steering angle correction value kg for the yaw rate steady-state gain Gr is, for example, a value smaller than 1, and the larger the deviation distance Slane, the more constant the deviation distance S
The characteristic is set so as to decrease to lane, and as the deviation distance Slane increases, the yaw rate steady gain G
r is corrected to be smaller than usual so that the turning property is reduced.

The rear wheel steering angle correction value kt with respect to the yaw rate time constant Tr is, for example, a value larger than 1, and the larger the deviation distance Slane, the more the constant deviation distance S
The characteristic is set so as to increase up to lane, and as the departure distance Slane increases, the yaw rate time constant Tr is corrected to a value larger than usual, and the turning performance is reduced.

As described above, in the second embodiment of the present invention,
The correction condition determination unit 12b and the rear wheel steering angle correction value setting unit 20a form a rear wheel steering angle correction unit.

It should be noted that unnecessary deviation from the traveling lane may be prevented by using only the rear wheel steering angle correction value kg for the yaw rate steady gain Gr or the rear wheel steering angle correction value kt for the yaw rate time constant Tr. good.

The rear wheel steering angle correction value kg for the yaw rate steady-state gain Gr and the rear wheel steering angle correction value kt for the yaw rate time constant Tr are not limited to those determined according to the departure distance, but are determined according to the departure speed. Alternatively, it may be determined based on both the departure distance and the departure speed.

Next, the operation of the second embodiment of the present invention having the above configuration will be described with reference to the flowchart of FIG. This FIG.
Is executed by the control device 20 at predetermined time intervals. First, in step S101, an image recognition result is read from the image processor 11, and the wheel speed sensors 7f
From l, 7fr, 7rl, 7rr, each wheel speed ω1, ω2, ω3,
ω4, the steering wheel angle θH from the steering wheel angle sensor 8, the rear steering angle δr from the rear steering angle sensor 9, the yaw rate γ from the yaw rate sensor 13, and the switch signal from the turn signal switch 14.

Then, the process proceeds to S102, where it is determined whether or not danger is avoided. If danger is avoided, the process proceeds to S201, where the rear wheel steering angle correction values kg and kt are set by the rear wheel steering angle correction value setting unit 20a. Is set to 1 and set in the target rear wheel steering angle calculation unit 20b to make no correction.

On the other hand, if it is determined in step S102 that it is other than danger avoidance, the process proceeds to step S104, in which the departure of the vehicle from the traveling lane is a necessary deviation when turning intentionally, that is, the turn signal switch 14 It is determined whether or not is activated.

The turn signal switch 14
Is operated, and when it is determined that the departure of the host vehicle from the traveling lane is intentional turning, the process proceeds to S201, and the rear wheel steering angle correction value kg, Each value of kt is determined to be 1, and is set in the target rear wheel steering angle calculation unit 20b, so that no correction is made.

If the turn signal switch 14 is not operated in step S104, the flow advances to step S105 to determine whether or not the own vehicle is running unbalanced in the driving lane and there is a risk of departure from the driving lane. judge. For example, with respect to the left and right white lines, when the traveling position of the own vehicle is within a set value from the reference position at the substantially center, it is determined that there is no risk of departure from the traveling lane, and the process proceeds to S201, where the rear wheel steering angle correction is performed. The value setting unit 20a determines the values of the rear wheel steering angle correction values kg and kt to be 1, and sets the values in the target rear wheel steering angle calculation unit 20b to make no correction.

On the other hand, if it is determined in S105 that the running position of the own vehicle is deviated from the reference position in the running lane to one of the left and right white lines by a set value or more, the process proceeds to S106, and the steering direction of the steering is changed. Direction away from the reference position,
Alternatively, it is determined whether the direction is to return to the reference position.

If it is determined in step S106 that the steering direction of the steering wheel is returning to the reference position, it is determined that there is no danger of departure from the traveling lane, and the above-described step S201 is performed.
Then, the rear wheel steering angle correction value setting unit 20a determines each value of the rear wheel steering angle correction values kg and kt to be 1 and sets the same in the target rear wheel steering angle calculation unit 20b to make no correction.

If it is determined in S106 that the steering direction of the steering is away from the reference position, it is determined that the vehicle departs unnecessarily from the traveling lane of the host vehicle.
In 202, the rear wheel steering angle correction value setting unit 20a searches a preset map or the like in accordance with the deviation distance Slane to determine a rear wheel steering angle correction value kg, kt, and determines the target rear wheel. The rear wheel steering angle correction values kg and kt are set in the steering angle calculation unit 20b.

That is, S102, S104 to S1
Steps 06 are performed by the correction condition determination unit 12b, and S201 and S202 are performed by the rear wheel steering angle correction value setting unit 20a.

In step S201 or S202, the rear wheel steering angle correction values kg, kt are transmitted to the target rear wheel steering angle calculating section 20b.
Then, the process proceeds to S203, where the target rear wheel steering angle calculating section 20b calculates the target rear wheel steering angle δr 'based on the above equation (2).

Next, proceeding to S109, the rear wheel steering amount setting output section 12e outputs the target rear wheel steering angle δr 'from the target rear wheel steering angle calculation section 20b and the rear wheel steering angle from the rear wheel steering angle sensor 9. After setting the required rear wheel steering amount from the angle δr,
Then, a signal corresponding to the rear wheel steering amount is output to the motor drive unit 5 of the rear wheel steering unit 4 to drive the rear wheel steering motor 6, and the program exits.

As described above, in the second embodiment of the present invention,
In the case of a 4WS vehicle having a basic control law based on the “control law of the yaw rate feedback method”, when a condition that the vehicle unnecessarily deviates is satisfied, the yaw rate steady gain Gr
Is corrected to be smaller than usual, and the yaw rate time constant Tr
Is corrected to a value larger than usual, so that turning performance is reduced, so that even if the driver steers in the departure direction from the driving lane, it is possible to positively prevent the departure from the driving lane Become. Further, the same effects as those described in the first embodiment of the present invention can be obtained.

8 to 11 show a third embodiment of the present invention. FIG. 8 is a functional block diagram of a vehicle rear wheel steering control device, and FIG. 9 is a schematic configuration of a vehicle rear wheel steering control device. FIG. 10 is a diagram for explaining a characteristic of a steering wheel angle sensitive gain based on a front wheel steering angle proportional type 4WS control law, and FIG. 11 is a flowchart of rear wheel steering control. Incidentally, Embodiment 3 of the present invention
Is based on the front-wheel steering angle proportional control method of 4WS.

Therefore, in the third embodiment of the present invention, the control device 30 is different from the first embodiment, and the control device 20 includes the wheel speed sensors 7fl, 7fr, 7rl, 7rl.
rr, a steering wheel angle sensor 8, a rear wheel steering angle sensor 9, and a turn signal switch 14 are connected.
A signal is input from the switch, and the image processor 11 is connected to input a video signal. Then, a necessary rear wheel steering angle is calculated based on these signals, and a drive signal is output to the motor drive unit 5.

[0104] As shown in FIG.
It mainly comprises a vehicle speed calculation unit 12a, a correction condition determination unit 12b, a rear wheel steering angle correction value setting unit 30a, a target rear wheel steering angle calculation unit 30b, and a rear wheel steering amount setting output unit 12e.

The target rear wheel steering angle calculating section 30b receives the rear wheel steering angle correction value f10 for the steering wheel angle sensitive gain kf0 described later from the rear wheel steering angle correction value setting section 30a, and outputs the vehicle speed calculating section. The vehicle speed V is input from the steering wheel angle sensor 12a, and the steering wheel angle θH is input from the steering wheel angle sensor 8. Based on the 4WS basic control rule based on the well-known “control rule of the front wheel steering angle proportional method”, the target rear wheel steering angle δr is calculated by the following equation. 'And calculates the target rear wheel steering angle δr' to the rear wheel steering amount setting output unit 12e. δr ′ = f10 · kf0 · (θH / N) (6) kf0 = (− 2 · L·Lr · Kf · Kr + Lf · Kf · m · V ² ) / (2 · L·Lf · Kf · Kr + Lr · Kr) · M · V ² ) (7) where Lr is the distance between the rear wheel axle and the center of gravity, and Kf is the front equivalent cornering power.

As shown in FIG. 10, when the vehicle speed V exceeds a predetermined value (V30 in the figure), the steering wheel angle sensitive gain kf0 becomes a positive value, and the rear wheels are in phase with the steering wheel angle θH. Is controlled. Conversely, when the vehicle speed V becomes smaller than a fixed value (V30 in the figure), the steering wheel angle sensitive gain kf0 becomes a negative value, and the rear wheels are controlled to have the opposite phase with respect to the steering wheel angle θH. The vehicle speed V30 is calculated as follows: V30 = ((2 · L·Lr · kr) / (m · Lf))
^1/2 .

The rear wheel steering angle correction value setting unit 30a searches a preset map or the like according to the departure distance Slane based on the result of the determination by the correction condition determination unit 12b, and retrieves the target rear wheel steering angle. A rear wheel steering angle correction value f10 for the steering wheel angle sensitive gain kf0 is set in the calculation unit 30b.

That is, when the condition that the judgment result by the correction condition judgment section 12b deviates unnecessarily is satisfied, the value of the rear wheel steering angle correction value f10 is determined from the map of the rear wheel steering angle correction value f10. The target rear wheel steering angle calculation unit 30b is set.

If the condition that the judgment result by the correction condition judgment unit 12b deviates unnecessarily does not hold, the value of the rear wheel steering angle correction value f10 is determined to be 1 and the target rear wheel steering is determined. It is set in the angle calculation unit 30b so that no correction is performed.

As shown in FIG. 10, the rear wheel steering angle correction value f10 for the steering wheel angle sensitive gain kf0 is set to a reference value (kf0) as shown in FIG. In the region where the value (kf0) is positive, correction is made so as to strengthen the in-phase tendency, and in the region where the rear wheels are in opposite phase with respect to the steering wheel angle θH, that is, in the region where the reference value (kf0) is negative, the opposite phase tendency is weakened. The correction is made as described above (characteristic 9 in the figure), and the turning characteristic of the vehicle is reduced by this correction.

The correction range is set such that the larger the departure distance Slane or the departure speed Vlane becomes, the larger the departure distance Slane or the departure speed Vlane becomes.

As described above, in the third embodiment of the present invention,
The correction condition determination unit 12b and the rear wheel steering angle correction value setting unit 30a form a rear wheel steering angle correction unit.

The steering angle sensitivity gain kf0 may be corrected by either increasing the in-phase tendency or weakening the anti-phase tendency to reduce the turning performance of the vehicle.

Further, the rear wheel steering angle correction value f10 for the steering wheel angle sensitive gain kf0 is not limited to the value determined according to the departure distance, but may be determined according to the departure speed, or both the deviation distance and the departure speed. May be determined by the following.

Next, the operation of the third embodiment of the present invention having the above configuration will be described with reference to the flowchart of FIG. The program shown in FIG. 11 is executed by the control device 30 at predetermined time intervals. First, in S101, the image processor 1
1, the image recognition result is read from the respective wheel speed sensors 7fl, 7fr, 7rl, 7rr, and the respective wheel speeds ω1, ω2,
ω3, ω4, the handle angle θH from the handle angle sensor 8
The rear wheel steering angle δr from the rear wheel steering angle sensor 9 and the switch signal from the turn signal switch 14 are read.

Then, the process proceeds to S102, where it is determined whether or not to avoid danger. In the case of danger avoidance, the process proceeds to S301, where the rear wheel steering angle correction value f10 is set to 1 by the rear wheel steering angle correction value setting unit 30a. It is determined and set in the target rear wheel steering angle calculation unit 30b to make no correction.

On the other hand, if it is determined in step S102 that it is other than danger avoidance, the process proceeds to step S104, where the departure of the own vehicle from the traveling lane is a necessary deviation when turning intentionally, that is, the turn signal switch 14 It is determined whether or not is activated.

The turn signal switch 14
Is operated, and when it is determined that the departure of the host vehicle from the traveling lane is intentionally turning, the process proceeds to S301, and the rear wheel steering angle correction value setting unit 30a sets the rear wheel steering angle correction value f10. The value is set to 1 and the target rear wheel steering angle calculation unit 30 is set.
It is set to b and no correction is made.

If the turn signal switch 14 is not activated in S104, the process proceeds to S105, in which the vehicle is running unbalanced in the traveling lane, and there is a risk of departure from the traveling lane. judge. For example, when the traveling position of the own vehicle is within a set value from the reference position where the traveling position of the vehicle is substantially at the center with respect to the left and right white lines, it is determined that there is no danger of departure from the traveling lane, and the process proceeds to S301. The value of the rear wheel steering angle correction value f10 is determined to be 1 by the value setting unit 30a, and is set in the target rear wheel steering angle calculation unit 30b to make no correction.

On the other hand, if it is determined in S105 that the running position of the own vehicle is deviated from the reference position in the running lane to one of the left and right white lines by a set value or more, the process proceeds to S106, and the steering direction of the steering is changed. Direction away from the reference position,
Alternatively, it is determined whether the direction is to return to the reference position.

If it is determined in step S106 that the steering direction of the steering wheel is to return to the reference position, it is determined that there is no danger of departure from the traveling lane, and the above-described step S301 is performed.
Then, the rear wheel steering angle correction value setting unit 30a determines the value of the rear wheel steering angle correction value f10 to be 1 and sets the value in the target rear wheel steering angle calculation unit 30b to make no correction.

If it is determined in step S106 that the steering direction of the steering is away from the reference position, it is determined that the vehicle departs unnecessarily from the traveling lane of the host vehicle.
Proceeding to 302, the rear wheel steering angle correction value setting unit 30a searches a preset map or the like according to the deviation distance Slane to determine a rear wheel steering angle correction value f10, and sets the target rear wheel steering angle. The rear wheel steering angle correction value f10 is set in the calculation unit 30b.

That is, S102, S104 to S1
Each of the processes 06 is a process performed by the correction condition determination unit 12b, and S301 and S302 are processes performed by the rear wheel steering angle correction value setting unit 30a.

After setting the rear wheel steering angle correction value f10 in the target rear wheel steering angle calculation unit 30b in S301 or S302, the process proceeds to S303, where the target rear wheel steering angle calculation unit 3
At 0b, the target rear wheel steering angle δr 'is calculated based on the above equations (6) and (7).

Then, the program proceeds to S109, in which the rear wheel steering amount setting output unit 12e outputs the target rear wheel steering angle δr 'from the target rear wheel steering angle calculating unit 30b and the rear wheel steering angle from the rear wheel steering angle sensor 9. After setting the required rear wheel steering amount from the angle δr,
Then, a signal corresponding to the rear wheel steering amount is output to the motor drive unit 5 of the rear wheel steering unit 4 to drive the rear wheel steering motor 6, and the program exits.

As described above, in the third embodiment of the present invention,
4W with "Front wheel steering angle proportional control law" as the basic control law
In the S vehicle, when the condition that the vehicle deviates unnecessarily is satisfied, the steering wheel angle sensitive gain kf0 is corrected so as to increase the in-phase tendency in a region where the rear wheels are in phase with the steering wheel angle θH. In a region where the rear wheels are in opposite phase with respect to θH, the turning characteristic is corrected so as to weaken the tendency to reverse phase, so that the turning performance is reduced, so even if the driver steers in the departure direction from the driving lane. It is possible to positively prevent the deviation from the traveling lane. Further, the same effects as those described in the first embodiment of the present invention can be obtained.

It is needless to say that the present invention is not limited to the 4WS control rules shown in the above embodiments of the present invention, but can be applied to other 4WS control rules.

In the above embodiments of the present invention, the rear wheel steering is performed by the rear wheel steering motor.
For example, the rear wheels may be steered by a hydraulic system or the like.

[0129]

As described above, according to the present invention,
In a vehicle equipped with the 4WS control, if the driver cannot steer the vehicle in the departure direction from the driving lane while maintaining the excellent stability inherent in the 4WS control and cannot maintain safety, the vehicle must actively deviate from the driving lane. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a vehicle rear wheel steering control device according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram illustrating a schematic configuration of a vehicle rear wheel steering control device according to the first embodiment of the present invention;

FIG. 3 is a characteristic diagram of each parameter set by a 4WS control law according to the first embodiment of the present invention;

FIG. 4 is a flowchart of rear wheel steering control according to the first embodiment of the present invention.

FIG. 5 is a functional block diagram of a rear wheel steering control device for a vehicle according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating a schematic configuration of a vehicle rear wheel steering control device according to a second embodiment of the present invention;

FIG. 7 is a flowchart of rear wheel steering control according to a second embodiment of the present invention.

FIG. 8 is a functional block diagram of a rear wheel steering control device for a vehicle according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a schematic configuration of a rear wheel steering control device of a vehicle according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram of a characteristic of a steering wheel angle sensitive gain according to a front wheel steering angle proportional type 4WS control law according to a third embodiment of the present invention;

FIG. 11 is a flowchart of a rear wheel steering control according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 vehicle 2 front wheel steering unit 3fl, 3fr, 3rl, 3rr wheel 4 rear wheel steering unit 5 motor drive unit 6 rear wheel steering motor 7fl, 7fr, 7rl, 7rr wheel speed sensor 8 handle angle sensor 9 rear wheel steering angle sensor 10l 10r CCD camera (traveling lane recognizing means) 11 Image processor (traveling lane recognizing means) 12 controller 12a vehicle speed calculating section 12b correction condition determining section (rear wheel steering angle correcting means) 12c rear wheel steering angle correction value setting section (rear wheel) Steering angle correction means) 12d Target rear wheel steering angle calculation unit 12e Rear wheel steering amount setting output unit 13 Yaw rate sensor 14 Turn signal switch

Claims (5)

[Claims] 1. A rear-wheel steering control device for calculating a target rear-wheel steering angle based on a predetermined control law and setting a rear-wheel steering amount based on the rear-wheel steering angle. Driving lane recognition means for recognizing a lane;
When the vehicle is steered in a direction deviating from the traveling lane of the vehicle under the conditions set in advance, the rear wheel steering angle is corrected in a direction in which the turning performance of the vehicle decreases. A rear wheel steering control device comprising a rear wheel steering angle correction unit. 2. The method according to claim 1, wherein the rear wheel steering angle correcting means reduces a relationship between the front wheels and the rear wheels in the opposite phase direction for prompting the vehicle to turn.
At least one of increasing the relationship between the front wheel and the rear wheel in the in-phase direction for weakening the turning of the vehicle is to correct the target rear wheel steering angle in a direction in which the turning performance of the vehicle decreases. 2. The rear wheel steering control device according to claim 1. 3. The rear-wheel steering angle correcting means reduces the turning performance of the vehicle at the target rear-wheel steering angle when the vehicle is deviating from the driving lane and the steering is performed in a direction to return from the departure. The rear wheel steering control device according to claim 1 or 2, wherein the correction in the direction to be performed is released. 4. The rear wheel steering angle correcting means determines at least one of a distance from a reference position defined substantially at the center between the traveling lanes of the own vehicle to a current position and a speed at which the own vehicle departs from the reference position. 4. The rear wheel steering control device according to claim 1, wherein the correction amount is determined according to the correction amount. 5. The vehicle according to claim 1, wherein the rear wheel steering angle correction means decreases the rear wheel steering amount as the vehicle speed decreases. Rear wheel steering control device.