JPH10175482A - Vehicle rear view field support device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a backward picture image, showing a backward advancing path of a vehicle, in a monitor, in a vehicle rear view field support device provided with a backward supervisory picture receiving part (camera) obtaining a backward supervisory picture image of the vehicle and a picture image display part (monitor) displaying the backward supervisory picture image. SOLUTION: Based on a detected steering angle of a front wheel and car speed value, a rear wheel moving locus at reversing time is calculated, the rear wheel moving locus is projected with a position of a backward supervisory picture receiving part (camera) serving as a point of view, a locus projection image data is formed, it is coordinate transformed, a linear image data is formed, the linear image data and backward supervisory picture image are synthesized and displayed in a picture image display part 2 (monitor). Preferably, so as to change a direction of the rearward supervisory picture receiving part 1 by a drive part through a control part based on at least a steering angle, with the driven backward supervisory picture receiving part 1 serving as a point of view, the locus projection image data is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear view support system for a vehicle, and more particularly to a rear view support system for displaying a rear view of a vehicle on an image display unit in a vehicle cabin through an imaging device.

[0001]

2. Description of the Related Art FIG. 23 schematically shows a configuration of a conventionally known vehicle rear view support device, in which a camera 1 serving as a rear monitoring imaging unit is attached to an upper rear portion of a vehicle (truck). In addition, a monitor 2 serving as an image display unit is provided in front of the driver's seat 11.

In this vehicle rear view support device, a monitor 2 displays the rear view of the vehicle, and assists the driver to drive backward without particularly turning around.

As a technique related to this, for example, Japanese Patent Application Laid-Open No. Hei 4-368241 discloses an apparatus that uses a camera and a monitor to photograph a blind spot behind and on a side of a commercial vehicle and displays the image to a driver. Has been proposed.

In this device, a monitor is installed around a console box so that a driver who is driving while looking ahead can look at a rear image without moving his / her gaze.

[0005] Further, for a driver who is accustomed to viewing the rearview mirror, if the image of the camera is displayed as it is,
Since the driver does not look like a mirror and feels uncomfortable, an image of the rear view is displayed on a monitor so that a left-right inverted image (mirror image) as seen by a mirror is obtained, thereby reducing the uncomfortable feeling of the driver.

[0006]

However, the device disclosed in Japanese Patent Application Laid-Open No. Hei 4-368241 is merely an auxiliary means. extremely difficult.

That is, since the monitor image when the driver retreats the vehicle is irrelevant to the retreat direction of the vehicle, an accident such as a collision with a rear object occurs if only the monitor image is used.

This is particularly remarkable for a vehicle such as a large truck having a large overhang from the rear wheels to the rear portion of the vehicle. This will be described with reference to a plan view of FIG.

In FIG. 24, a monitor 2 and a front wheel 1 are shown.
2a, 12b, rear wheels 13a, 13b, and rear wheel axle 14
Is located in a part that cannot be seen in a plane, but to make it easier to understand,
It is shown by a solid line instead of a broken line.

In this example, M indicates a portion (length) that overhangs from the rear wheel axle 14 horizontally in the rear direction, and the field of view of the camera 1 disposed at the position of the overhang length M is indicated by a range W. Have been.

Now, as shown, the front wheels 12a, 12b
Wheel 13a, 1 when the vehicle is moved backward while steering leftward
The trajectories 3b are rear wheel trajectories 15a and 15b, respectively.

That is, the rear wheel trajectories 15a and 15b are located at positions greatly deviated from the center of the camera view range W. This shift becomes more remarkable as the overhang length M becomes longer.

Therefore, when the vehicle 2 moves backward based on the rear view of the monitor 2, there is the following problem. (1) It is difficult to grasp what trajectory the rear wheel takes. (2) It is difficult to grasp which direction the vehicle is moving backward. (3) It is difficult to grasp how much the steering wheel should be turned.

Accordingly, the present invention provides a vehicle rear view support device including a rear monitoring imaging unit (camera) for obtaining a rear monitoring image of a vehicle and an image display unit (monitor) for displaying the rear monitoring image. An object of the present invention is to display a reverse image indicating a reverse course on a monitor.

[0015]

In order to achieve the above-mentioned object, a vehicle rear view support apparatus according to the present invention comprises a steering angle detecting section for detecting a steering angle of a front wheel, a vehicle speed detecting section, and a steering angle detecting section. A calculating unit that calculates a rear wheel movement trajectory at the time of reversing based on the respective detection values of the unit and the vehicle speed detection unit, and trajectory projection image data obtained by projecting the rear wheel movement trajectory with the rear monitoring imaging unit as a viewpoint. A perspective transformation unit for generating, a line image generation unit for performing coordinate transformation of the locus projection image data to generate line image data corresponding to the display screen of the image display unit, and synthesizing the line image data with the rear monitoring image And an image synthesizing unit for sending to the image display unit.

That is, the calculating section calculates the moving trajectory data of the rear wheel at the time of retreat from the steering angle detected by the steering angle detecting section and the vehicle speed detected by the vehicle speed detecting section.

Then, the perspective conversion unit converts the movement trajectory data of the rear wheel obtained by the calculation unit into projection image data on the projection screen when viewed from the viewpoint of the rear monitoring imaging unit (camera).

The projection image data is coordinate-converted by the line image generation unit into line image data that can be displayed corresponding to the display screen of the image display unit (monitor).

Further, the line image data and the rear monitor image information, which is an image of the camera, are synthesized on the screen by the image synthesizing unit and displayed on the image display unit.

As a result, the calculated moving trajectory of the rear wheel at the time of reversing is synthesized and displayed on the rear monitoring image on the image display unit, so that the driver can clearly recognize the reversing path of the vehicle.

Further, in the present invention, a drive unit for changing the direction of the rear monitoring imaging unit, and the drive unit based on at least the steering angle among the detected values of at least the steering angle detection unit and the vehicle speed detection unit. And a control unit for controlling the projection control unit, and the perspective transformation unit can generate the trajectory projection image data when the rear wheel movement trajectory is projected from the driven rear monitoring imaging unit as a viewpoint. .

That is, if the direction of the rear monitoring imaging unit is fixed, the rear view range is also fixed, and if the steering angle is increased, the predicted retreat trajectory falls out of the field of view of the rear monitoring imaging unit. Become.

In order to solve this problem, the direction of the rear monitoring imaging unit is changed at least according to the steering angle, and the locus projection image data is generated from the viewpoint of the rear monitoring imaging unit at this time. It is possible to monitor and display the predicted retreat trajectory.

When the steering angle is within a certain range, the control section shortens the focal length of the rear monitoring imaging section and adjusts the photographing observing angle. The horizontal angle of the section can be controlled according to the steering angle.

In the above-mentioned present invention, the calculation unit has a vehicle state map for classifying a vehicle state corresponding to the steering angle and the vehicle speed into a plurality of regions, and the steering angle and the vehicle speed are smaller than each threshold value. Sometimes, the rear wheel movement trajectory without considering the sideslip angle is calculated based only on the steering angle. It is also possible to calculate the rear wheel movement locus.

That is, when the steering angle and the vehicle speed are found to be small based on the map, it is not necessary to consider the side slip angle at the time of reversing. Good. Further, when it is found that the steering angle and the vehicle speed are large, it is necessary to consider the side slip angle. At this time, the rear wheel movement trajectory is calculated based on both the steering angle and the vehicle speed taking the side slip angle into consideration. Will do.

In the present invention described above, when the vehicle has an overhang from the rear wheel axle to the rear monitoring imaging unit, the rear wheel movement trajectory can be calculated in consideration of the overhang length. .

That is, when the rear monitoring imaging unit is attached to the rear of the vehicle having an overhang length from the rear wheel axle as shown in FIGS. May be shifted from the rear wheel axle and further converted to the projection image data.

Further, in the above-mentioned present invention, a shift position detecting section is further provided, and the image from the image synthesizing section is converted into the image only when the shift position detected by the shift position detecting section indicates the backward position. It can be displayed on the display unit.

That is, the shift position detecting section knows that the shift is at the reverse position, and the above-described composite image can be displayed only when the vehicle is in the reverse state.

Further, in the present invention, between the image synthesizing section and the image display section, image information for switching each image information from the image synthesizing section and an image information output section for outputting other image information. A switching unit may be provided.

That is, it is possible to display image information other than the backward monitoring image on the image display unit by switching the image by the image information switching unit.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment (1) FIG. 1 shows an embodiment (1) of a vehicle rear view support device according to the present invention, in which a steering angle sensor 3 which is a steering angle detecting section and a vehicle speed detecting section. The steering angle data and the speed data are respectively detected by the vehicle speed sensor 4 and sent to the trajectory calculation unit 5 which is the calculation unit.

The trajectory calculation unit 5 calculates the trajectory of the rear wheel when the vehicle is moving backward based on the steering angle data and the vehicle speed data, and sends the trajectory to the perspective transformation unit 6 as rear wheel trajectory data.

The perspective conversion unit 6 converts the rear wheel movement trajectory data into trajectory projection image data by a perspective transformation that projects the position of the camera 1 as a viewpoint.

The line image generating unit 7 performs coordinate transformation of the locus projection image data of the projection plane received from the perspective transformation unit 6 to generate line image data.

The line image data and the backward monitoring image input from the camera 1 are combined by the image combining unit 8 and displayed on the monitor 2.

A changeover switch section 9, which is an image information changeover section indicated by a broken line, is provided between the screen synthesizing section 8 and the monitor 2 to switch navigation information 10a, vehicle state information 10b such as meters and various indicators, and the like. It is connected to the switch unit 9 and displayed on the monitor 2 while switching.

FIG. 2A is a flow chart showing an example of the operation algorithm of the embodiment (1) of the vehicle rear assistance device according to the present invention shown in FIG.

Hereinafter, referring to this flowchart, FIG.
The operation of the embodiment (1) shown in FIG. First, the trajectory calculation unit 5 determines whether or not the shift position is at the back (retreat position) (step S1), and if not, returns to the beginning (no at step S1).

In this case, a shift position detection signal by a shift position detection unit (not shown) such as a shift lever switch is necessary. However, step S1 is skipped and the following processing is continuously performed (monitor display). May be performed.

When the shift position is in the reverse position (Yes in step S1), the trajectory calculation unit 5 inputs the steering angle (δ) data from the steering angle sensor 3 (step S2), and the vehicle speed (V) from the vehicle speed sensor 4. Input data (Step S
3).

The trajectory calculation unit 5 has a vehicle state map shown in FIG. 2 (2). The vehicle state map classifies the vehicle state into an I region and a J region based on the values of the steering angle and the vehicle speed. doing.

The region I is a region in a vehicle state in which a moving trajectory can be calculated using equations (6) and (7) described later by applying a geometric model, and the threshold value V is so large that the vehicle speed V cannot be ignored. ₀ smaller area, the steering angle [delta] is [delta] ₀ smaller area is separated by space in line e, f, g are the respective boundaries of the area limited further by the combination of the vehicle speed V and the steering angle [delta] .

The J area is an area in a vehicle state other than the I area where a geometric model that cannot be applied to the following equations (6) and (7) does not apply. For example,
Region vehicle speed V is the threshold value greater than or equal _to V ₀ is also an example thereof.

The trajectory calculation unit 5 which has received the data of the steering angle δ and the vehicle speed V determines whether or not the vehicle state is in the region I based on the vehicle state map (steps S4 and S5).

In the case of the I region (yes in step S5)
s), Equations (6) and (7) of the geometric vehicle model described later
Based on the above, the trajectory calculation is executed to obtain the trajectory data (step S6).

In the case other than the area I (n in step S5)
o), the movement trajectory data is calculated with reference to a database that measures and stores the movement trajectory of the rear wheel with respect to the steering angle in advance (step S7).

That is, the movement trajectory data corresponding to each representative steering angle is measured in advance and is stored in a database.
The trajectory data of the representative steering angle is obtained by referring to this database, or the trajectory data corresponding to the intermediate steering angle is calculated by interpolation based on the database, thereby simplifying the calculation formula described later. .

The principle of calculating the trajectory of the rear wheel based on the steering angle δ and the vehicle speed V will be described below. FIG. 3 shows a front wheel 12 and a rear wheel 13 having a wheelbase L.
This figure geometrically shows a steady circular turning state in the case of a wheel model, in which the steering angle of the front wheels 12 is δ.

When the vehicle speed V is lower than the threshold value V ₀ , it can be assumed that no centrifugal force acts on the vehicle, no cornering force is applied to the front wheels 12 and the rear wheels 13, and no side slip angle occurs in the vehicle. However, this assumption does not hold when the vehicle speed V is greater than the threshold value V ₀ , as described later.

Accordingly, both the front wheel 12 and the rear wheel 13 travel in the direction in which the wheels face, and the vehicle makes a circular turn. The rotation center is a straight line b perpendicular to the traveling direction of the front wheel 12.
And the traveling direction of the rear wheel 13 at the intersection O _S of the perpendicular straight line c, the turning radius of the rear wheel 13 at this time becomes [rho.

Therefore, the wheel base L, the steering angle δ
And the turning radius ρ is as follows:

[0054]

L = ρtanδ ‥‥‥ Formula (1)

Further, when the steering angle δ is smaller than the threshold value δ ₀ shown in FIG. 2B, tan δ = δ holds, and the following equation is obtained.

[0056]

Ρ = L / δ ‥‥‥ Equation (2)

That is, the value obtained by dividing the wheel base L by the steering angle δ becomes equal to the turning radius ρ.

Generally, a centrifugal force acts on the center of gravity of a vehicle turning at the vehicle speed V. When the side slip angle of the wheel caused by the centrifugal force is taken into consideration, the turning radius ρ of the vehicle is as follows.

[0059]

Ρ = (1 + AV ² ) L / δ (3) where A is a specific constant that defines the steering characteristic of the vehicle by a stability factor.

In equation (3), a correction term AV ² proportional to the square of the vehicle speed V is added to equation (2).
When the vehicle speed V increases (J region), this correction term cannot be ignored.

FIG. 4 shows a case where the two-wheeled vehicle model of FIG. 3 corresponds to a four-wheeled vehicle. The position of the rear wheel of the two-wheeled vehicle model corresponds to the center P of the rear wheel axle 14. The distance to each of the rear wheel 13a and the rear wheel 13b is d.

The rear wheels 13a, 13 retreat with a turning radius ρ on a rectangular coordinate system (x, y) on the plane with the center P of the rear wheel axle 14 on the ground surface as the origin and the axle direction of the vehicle as the x axis.
The rear wheel trajectories 15a and 15b of FIG.

When the vehicle speed V is smaller than the threshold value V ₀ , the center of the circular turning of the vehicle is the point O _S (ρ, 0), and the rear wheel locus 15
a and 15b are given by the following equations (4),
It is represented by (5).

[0064]

(X−ρ) ² + y ² = (ρ + d) ² (4)

(X−ρ) ² + y ² = (ρ−d) ² (5)

Now, assuming that the vehicle has an overhang length M as shown in FIG. 9, the coordinate system (x, y) of the rear wheel axle 14 is translated by the overhang M in the y direction and corrected. In a coordinate system (x ', y') with the camera position Q on the upper surface as the origin, the rear wheel trajectories 15a, 15b
Can be rewritten as the following equations (6) and (7), respectively.

[0066]

(X′−ρ) ² + (y ′ + M) ² = (ρ + d) ² (6)

(X′−ρ) ² + (y ′ + M) ² = (ρ−d) ² Equation (7)

That is, the movement trajectory data of each rear wheel having the camera position Q on the ground surface as the origin can be obtained by using the equations (6) and (7).

Next, the perspective transformation unit 6 receives the movement trajectory data from the trajectory calculation unit 5 and performs perspective transformation when projecting the movement trajectory data from the camera position Q onto a plane at the focal length f (see FIG. 6). Execute (step S8).

Hereinafter, the principle of the perspective transformation will be described. FIG. 5 shows a coordinate system (x ′, y ′, z ′) obtained by adding the z ′ axis to the coordinate system (x ′, y ′) in FIG.
The camera 1 is located at a point R (0, 0, H) on the z ′ axis, and the rear wheel 1 on the ground surface (x ′, y ′ coordinate plane) at a look-down angle τ.
The rear wheel trajectories 15a and 15b at the time of retreating 3a and 13b are monitored. The following shows how the trajectory of the rear wheel appears on the monitor screen.

First, the origin Q of the coordinate system (x ', y', z ')
Is translated to the camera position R, and then rotated by an angle τ about the x ′ axis, is defined as a coordinate system (x ″, y ″, z ″) of the camera viewpoint.

Therefore, the point (x ', y', z ') of the coordinate system (x', y ', z') is changed to the point (x ", y") of the coordinate system (x ", y", z "). , Z ") is as follows.

[0072]

(Equation 8)

Here, since z ^' = 0 on the ground surface, equation (8) becomes as follows.

(Equation 9)

FIG. 6 shows a perspective transformation for projecting a target point K (x ′, y ′, 0) in a coordinate system (x ′, y ′, z ′) onto a plane T perpendicular to the y ″ axis. The projection plane T is located at a focal length f of the camera 1 from the viewpoint R of the camera 1.

In the figure, an orthogonal coordinate system (α, β) on the projection plane T has an origin at an intersection S between the y ″ axis and the projection plane T,
Straight lines that pass through the origin S and are parallel to the x "axis and the z" axis are the α axis and the β axis, respectively.

The target point K (x ', y', 0) on the ground viewed from the coordinate system (x ", y", z ") has already been transformed by the above equation (9). To project the point on the coordinate system (α, β),
It is sufficient to multiply z "to obtain α, β and plot on the αβ (T) plane.

That is, the projection from the coordinate system (x ", y", z ") to the coordinate system (α, β) is represented by the following equation.

[0078]

(Equation 10)

By substituting equation (9) into equation (10), the final perspective transformation is given by the following equation.

[Equation 11]

That is, the moving locus of the rear wheel can be converted into an image viewed from the camera position by using the equation (11).

Returning to FIG. 2, in step S8, the line image generating unit 7 further converts the perspective-transformed data into line image information to be displayed on the monitor screen, and sends it to the image synthesizing unit 8 (step S8).

Here, the principle of the coordinate conversion in the line image generation unit 7 will be described with reference to FIG. First, in the figure, a point of the coordinate system (α, β) on the projection plane is converted to a coordinate system (x
^* , Y ^* ), and the monitor screen 16
_{Has a} horizontal x ^* _{S IZE} vertical y ^* _SIZE .
Is the origin of the coordinate system (α, β).

Normally, the monitor screen 16 has the origin O at the upper left of the screen.
_A coordinate system (x ^* , y ^* ) composed of an x ^* axis having a positive value in the horizontal right direction and a y ^* axis having a positive value in the vertical direction is adopted. Then, points (pixels) constituting the image are arranged in this coordinate system (x ^* , y ^* ).

Therefore, the coefficients (Sx, Sx) for making the pixels on the monitor screen correspond to the points (α, β), respectively.
Multiplied by sy), further monitor the origin center of the screen S origin O _m after moving to y ^* = 0 (x ^* axis) by reversing the monitor screen with respect to the point (x ^*, y ^*) can be generated .

This coordinate conversion can be expressed by the following equation.

[0086]

(Equation 12)

In the conversion for displaying the movement locus of the rear wheel on the ground viewed from the camera on the monitor, x ^* and y ^* are obtained by substituting equation (11) into equation (12) as follows.

X ^* = x ^* _SIZE / 2 + Sx · f · x ′ / (y′cosτ + Hsinτ) (Equation 13)

Y ^* = y ^* _SIZE / 2−Sy · f (y′sinτ−Hcosτ) / (y′cosτ + Hsinτ) (Equation (14))

That is, the locus projection image data can be converted into line image data corresponding to the monitor using the equations (13) and (14).

Returning to FIG. 2, the image synthesizing unit 8 superimposes the line image information on the rear monitoring image information input from the camera 1 and outputs the line image information to the monitor 2, and the monitor 2 displays the moving trajectory of the rear wheel together with the rear view. (Step S9).

By looking at the rear field of view and the moving trajectory of the rear wheels displayed on the monitor screen, the driver can easily retreat the vehicle without feeling uncomfortable.

Embodiment (2): In the above embodiment (1), since the camera 1 is fixed, the rear view range captured by the camera 1 is a fixed range W as shown in FIG. is there.

Therefore, when the steering angle becomes large, the predicted backward course goes out of the field of view of the camera, and the effect of overlappingly displaying the predicted backward course is reduced.

Therefore, in the embodiment (2) described below,
As conceptually shown in FIG. 8, the rear view range is changed from W1 to W2 in accordance with the steering angle, and a reverse image showing the reverse trajectory of the vehicle is displayed on the monitor.

FIG. 9 shows such an embodiment (2). In this embodiment (2), in addition to the embodiment (1) of FIG. Is provided.

In general terms, the vehicle speed data and the steering angle data from the vehicle speed sensor 4 as the vehicle speed detecting unit and the steering angle sensor 3 as the steering angle detecting unit are transmitted to the arithmetic unit 5 for calculating the reverse trajectory and the control unit 20. Sent.

The control unit 20 calculates the focal length and the camera attitude angle of the camera 1 based on the vehicle speed data and the steering angle data, and the drive unit 21 drives the camera 1 based on those data. In addition, camera viewpoint position data, which is focal length data and attitude angle data, is sent to the perspective transformation unit 6. As described later, the control unit 20 needs at least the steering angle data, but may not need to use the vehicle speed data in some cases.

The arithmetic unit 5 calculates the trajectory of the rear wheels when the vehicle is moving backward based on the vehicle speed data and the steering angle data, and sends them to the perspective transformation unit 6 as rear wheel movement trajectory data.

The perspective transformation unit 6 performs perspective transformation based on the viewpoint position data of the camera 1 and converts the rear wheel movement locus data into locus projected image data.

A line image for synthesizing the perspective-transformed rear wheel movement trajectory data on a monitor screen is generated by a line image generation unit 7.
Generated by

The line image data and the backward monitoring image input from the camera 1 are synthesized by the image synthesizing unit 8 and displayed on the monitor 2.

The characteristic operation of the embodiment (2) will be described in detail below.

First, an embodiment of the camera driving section 21 shown in FIG. 9 will be described. The camera drive unit 21 includes a motor 21a for controlling a vertical angle (looking down angle) of the camera 1 and a motor 21b for controlling a horizontal angle of the camera 1, and changes a focal length. And a focal length control unit 21c as an optical lens mechanism capable of performing such operations.

The focal length control section 21c changes the focal length of the lens of the camera 1 so that the photographing range of the camera 1 can be widened or narrowed.

That is, if there is an imaging range as shown in FIG. 11, the horizontal angle of view and the vertical angle of view of the camera 1 are tan ^-1 (H / L) and tan ^-1 (V / L), respectively. Here, the focal length is defined as f, and the photographing surface size of the camera 1 (C
If the length and width of the CD light receiving unit are a and b, respectively,

H = (b / f) · L (15)

V = (a / f) · L (16) Therefore, if the above expression is substituted into the expression of the angle of view, the horizontal angle of view and the vertical angle of view of the camera are respectively tan ^{− 1} (b / f),
tan ^-1 (a / f).

Here, the control law of the focal length with respect to the steering angle will be described with reference to FIG. Driver fixes the focal length f as well off the handle until beyond the steering angle [delta] ₀ shown in line h to f _0, but the focal length f as shown by line segment i when it exceeds [delta] ₀ To increase the imaging range.

[0106] Further, the focal length f exceeds the steering angle [delta] ₁
Is fixed as shown by line j. This is the remaining focal length f
This is because if the image capturing range is excessively enlarged by reducing the value of, the small area cannot be seen.

At this time, when the focal length is changed from f ₀ to f ₁ , the photographing range is expanded from V ₀ to V _{1 as} shown in FIG.

As a result, since the rear side of the vehicle enters the photographing range, the look-down angle τ of the camera 1 is changed by driving the camera vertical angle control motor 21a shown in FIG. Try to reflect a little.

For example, the angle at which the camera looks down can be set as follows.

[0110]

[Equation 17]

Next, when the steering angle exceeds the value δ ₁ shown in FIG. 12, as shown in FIG. 14, the horizontal angle θ of the camera 1 is changed along the line segment l corresponding to the steering, and the steering angle is changed. Is δ
_{When 2} (δ ₁ <δ ₂ ) is exceeded, the horizontal angle of view θ of the camera 1 is fixed to θ ₀ as shown by the line segment m. This is the same in the reverse direction.

Next, this embodiment (2) will be described with reference to FIG.
When the movement trajectory of the rear wheel is calculated by the calculation unit 5, the equations (6) and (7) are obtained in the same manner as in the embodiment (1). FIG. 15 is merely a coordinate system viewed three-dimensionally by adding the z ′ coordinate axis where the camera 1 is arranged to the x′y ′ coordinate system of FIG.

Next, the camera drive control unit 20 and the rear wheel movement trajectory calculation unit 5 show the rear wheel movement trajectory data on the basis of the camera viewpoint position data (horizontal rotation angle θ, looking down angle τ, focal length f). A method of performing the perspective transformation in the transformation unit 6 will be described.

FIG. 16 shows a state in which the camera 1 installed at a height H with respect to the x'y 'coordinate on the ground surface is looked down at an angle τ from a horizontal plane by the motor 21a. '
In the coordinate system, a state in which the camera 1 is driven by the motor 21b and rotated in the horizontal direction (around the z 'axis) by θ in accordance with the control rule of FIG.

That is, the camera 1 is positioned at the point R on the z 'axis.
It is located at (0, 0, H), rotates around the z ′ axis by θ as shown in FIG. 16, and monitors the rear wheel movement trajectory at the ground surface (x′y ′ coordinate plane) at a look-down angle τ. And The following shows how the movement locus of the rear wheel appears on the monitor screen.

The principle of coordinate conversion from the coordinate system (x'y'z ') having the origin on the ground plane as shown in FIG. 17 to the coordinate system (x "y" z ") of the camera viewpoint position will be described.

First, by moving the origin on the ground surface in parallel in the z′-axis direction by H, rotating θ about the z′-axis, and further rotating τ about the y′-axis, coordinate conversion can be performed. Therefore, an expression indicating this coordinate conversion is as follows.

[0118]

(Equation 18)

That is, the above equation (18)
Is obtained by adding the rotation θ about the z ′ axis to the equation (8) corresponding to

Here, when the point (x′y ′) on the ground surface is viewed from the coordinate system of the camera viewpoint, z ′ = 0, so that the point (x′y ′) on the ground surface is three-dimensional. In a coordinate system from a typical camera viewpoint, the following expression is obtained.

[0121]

[Equation 19]

Since the focal length is f, the perspective transformation onto the camera screen plane is as shown in FIG. This is a coordinate system corresponding to FIG.

That is, the intersection point of y ″ on the camera screen projection plane is defined as the origin S, the α-axis parallel to the x ″ -axis and the z ″ -axis,
Assuming that there is an αβ coordinate system having a β axis, the projection from the x "y" z "coordinate system to the αβ plane coordinate system is expressed by the following equation.

[0124]

Α = (f / y ″) x ″ β = (f / y ″) z ″ Equation (20)

By substituting equation (19) into equation (20), the following relational expression is obtained in which the point (x'y ') on the ground plane is perspectively transformed on the αβ coordinate on the camera screen projection plane. Can be.

[0126]

(Equation 21)

Next, the coordinate conversion for generating a line image on the monitor screen from the camera screen projection plane in the line image generation unit 7 will be described.

Normally, as shown in FIG. 19, the monitor screen employs a coordinate system including an x ^* axis having a positive value in the horizontal right direction with the origin at the upper left of the screen and a y ^* axis having a positive value in the vertical direction. I have.

Therefore, in order to convert the point S (α, β) having the origin at the center of the screen projection screen into a coordinate system on the monitor screen, the conversion coefficients are Sx and Sy, and the size of the monitor screen is as shown in FIG. As described above, if X _SIZE and Y _SIZE are used, the expression (1)
As in 2), it can be expressed by the following equation.

[0130]

[Number 22] ^{x * = Sx · α + X} * SIZE / 2 y * = - (Sy · β-Y * SIZE / 2) ‥‥‥ formula (22)

Therefore, by substituting equation (21) into equation (22), it is possible to convert the locus projected image data into line image data corresponding to the monitor.

Then, the line image obtained as described above is synthesized with the input image from the camera 1 by the image synthesizing unit 8, and the image which is inverted left and right is displayed to the driver.

By looking at the rear view and the moving trajectory of the rear wheel projected on the monitor screen, the driver can see the predicted trajectory without protruding from the monitor screen even if the driver turns the steering wheel greatly. It becomes possible to back. In addition, safe driving can be expected because an appropriate view can be obtained.

In the above description, the camera 1 has the steering angle δ
However, the control method of the camera 1 may be switched by dividing the area A and the area B by adding the vehicle speed V as shown in FIG.

That is, in the area A, as shown in FIG. 21, the control unit 20 decreases the focal length f of the camera lens according to the steering angle when the steering angle becomes larger than the value δ _0. Further, the camera looking-down angle is adjusted based on the equation (17) (line segment i). If the steering angle is further increased, the horizontal angle θ of the camera 1 may be controlled according to the steering angle, as shown by the line segment la in FIG. 22, to obtain an appropriate rear view range.

However, there is a vehicle state in the area B.
Indicates the case where the reverse vehicle speed is high, and the driver
You have to look further ahead. Therefore, B
If there is a vehicle state in the area, the focal length control law in FIG.
As shown in the figure, the value δ₀From before (line h)
To f₀And gradually decrease the value (line segment i ′) to obtain the value δ _Three
And the value f₁(Line segment j ').

As shown in FIG. 22, the horizontal angle θ is increased from the steering angle δ ₃ (line segment lb) to speed up the horizontal operation of the camera 1.

During the steering operation, the vehicle condition becomes A
When the state changes from B to B or from B to A, it is assumed that a transition is made to the illustrated control law.

At this time, when the focal length f is reduced, FIG.
As shown in FIG. 3, the photographing range is enlarged. As a result, the rear side of the vehicle enters the shooting range, and as described above,
The looking angle τ of the camera 1 is changed by driving the camera vertical angle control motor 21a so that the vehicle body is slightly reflected on the monitor screen.

Similarly, when the steering angle is further increased, the attitude angle of the camera 1 is controlled as shown in FIG. This control law increases the camera horizontal angle θ from the steering angle when the focal length f is fixed and stops at a constant steering angle, as in FIG.

Therefore, the horizontal rotation operation of the camera 1 is started and stopped earlier in the case where the vehicle state is in the region B than in the case where the vehicle state is in the region A.

Then, similarly to the control of the focal length, when the vehicle state changes on the way, the control rule is switched on the way.

In this embodiment (2) as well, the rear wheel movement trajectory may be calculated in consideration of the side slip angle of the wheel when the centrifugal force is applied according to the vehicle speed by the above equation (3).

When the vehicle has an overhang from the rear wheel axle to the rear monitoring imaging section, the arithmetic section may calculate the rear wheel movement trajectory in consideration of the overhang length.

Further, the image from the image synthesizing section may be displayed on the image display section only when the shift position indicates the retreat position, and the image is displayed between the image synthesizing section and the image display section. An image information switching unit for switching each image information from the combining unit and the image information output unit that outputs other image information is provided, and by switching the images, the image display unit displays image information other than the rear monitoring image. Is also good.

[0146]

As described above, according to the vehicle rear view support device according to the present invention, the rear wheel movement trajectory at the time of retreat is calculated based on the detected front wheel steering angle and vehicle speed value. Is generated using the position of the rear monitoring imaging unit (camera) as a viewpoint, and the trajectory projection image data is subjected to coordinate transformation to generate line image data. Since the image is synthesized and displayed on the image display unit (monitor), the driver can easily recognize the retreat position of the own vehicle from the relationship between the displayed line image and the rear monitoring image, and expect safe driving. it can.

Further, the direction of the rear monitoring imaging section is changed by the driving section based on at least the steering angle, and the perspective transformation section converts the locus projection image data using the driven rear monitoring imaging section as a viewpoint. If it is generated, even if the steering wheel operation is performed, the predicted retreat trajectory can be constantly seen in the monitor image, and the safety can be further secured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment (1) of a vehicle rear view support device according to the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment (1) of the vehicle rear view support device according to the present invention and a vehicle state map.

FIG. 3 is a graph showing a principle for geometrically calculating a turning radius using a motorcycle model.

FIG. 4 is a graph showing a coordinate system of a trajectory of a rear wheel when the four-wheel vehicle model retreats according to the embodiment (1) of the vehicle rear view support device according to the present invention.

FIG. 5 is a perspective view (1) illustrating perspective conversion in a perspective conversion unit used in the embodiment (1) of the vehicle rear view support device according to the present invention.

FIG. 6 is a perspective view (2) illustrating perspective conversion performed by a perspective conversion unit used in the embodiment (1) of the vehicle rear view support device according to the present invention.

FIG. 7 is a graph showing coordinate conversion in a line image generation unit used in the embodiment (1) of the vehicle rear view support device according to the present invention.

FIG. 8 is a diagram showing a camera view range and a predicted rear wheel trajectory for explaining the concept of the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 9 is a block diagram showing an embodiment (2) of a vehicle rear view support device according to the present invention.

FIG. 10 is a perspective view showing an embodiment of a camera driving unit used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 11 is a view for explaining an imaging range of a camera in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 12 is a graph showing a control law of a focal length with respect to a steering angle used in an embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 13 is a diagram showing a photographing range by changing a focal length in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 14 is a graph showing a control law of a camera horizontal angle with respect to a steering angle used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 15 is a graph showing a coordinate system of a trajectory of a rear wheel when the four-wheel vehicle model retreats according to the embodiment (2) of the vehicle rear visibility support device according to the present invention.

FIG. 16 is a perspective view (1) illustrating perspective conversion in a perspective conversion unit used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 17 is a perspective view (2) illustrating perspective conversion in a perspective conversion unit used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 18 is a perspective view (3) illustrating perspective conversion in a perspective conversion unit used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 19 is a graph showing coordinate transformation in a line image generation unit used in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 20 is a graph showing a vehicle state for switching a control rule in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 21 is a graph showing a control law of a focal length corresponding to a vehicle state in the embodiment (2) of the vehicle rear visibility support device according to the present invention.

FIG. 22 is a graph showing a control law of a camera horizontal angle corresponding to a vehicle state in the embodiment (2) of the vehicle rear view support device according to the present invention.

FIG. 23 is a side view of a general vehicle equipped with a rear view support device.

FIG. 24 is a plan view showing an example of the field of view and the trajectory of the rear wheels when the vehicle equipped with the rear view support device is moved backward.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Backward monitoring imaging part (camera) 2 Image display part (monitor) 3 Steering angle detection part (steering angle sensor) 4 Vehicle speed detection part (vehicle speed sensor) 5 Calculation part (trajectory calculation part) 6 Perspective conversion part 7 Line image generation part Reference Signs List 8 image synthesizing unit 9 image information switching unit (switching switch unit) 10a navigation information 10b other vehicle state information 11 driver's seat 12,12a, 12b front wheel 13,13a, 13b rear wheel 14 rear wheel axle 15,15a, 15b rear wheel Trajectory 16 Monitor screen 20 Control unit 21 Camera driving unit 21a Camera vertical angle control motor 21b Camera horizontal angle control motor 21c Focal length control unit L Wheelbase M Overhang W Camera view range In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (7)

[Claims] 1. A vehicle rear view support device comprising: a rear monitoring imaging section for obtaining a rear monitoring image of a vehicle; and an image display section for displaying the rear monitoring image, wherein a steering angle detecting section for detecting a steering angle of a front wheel; A vehicle speed detecting unit, a calculating unit that calculates a rear wheel moving trajectory at the time of retreat based on at least the steering angle among the detected values of the steering angle detecting unit and the vehicle speed detecting unit, and calculating the rear wheel moving trajectory. A perspective transformation unit that generates trajectory projection image data when the rear monitoring imaging unit is projected as a viewpoint; and a line that transforms the trajectory projection image data to generate line image data corresponding to a display screen of the image display unit. A rear view assistance system for a vehicle, comprising: an image generation unit; and an image synthesis unit that synthesizes the line image data with the rear monitoring image and sends the rear monitoring image to the image display unit. 2. The drive unit according to claim 1, wherein the drive unit changes the direction of the rear monitoring imaging unit, and the drive unit is based on at least the steering angle among the detected values of the steering angle detection unit and the vehicle speed detection unit. A control unit for controlling the
And a perspective transformation unit that generates the trajectory projection image data when projecting the rear wheel movement trajectory from the driven rear monitoring imaging unit as a viewpoint. 3. The control unit according to claim 2, wherein, when the steering angle is within a certain range, the control unit shortens the focal length of the rear monitoring imaging unit and adjusts the photographing observing angle. And a horizontal angle of the rear monitoring imaging section is controlled according to a steering angle. 4. The vehicle according to claim 1, wherein the calculation unit has a vehicle state map for classifying a vehicle state corresponding to the steering angle and the vehicle speed into a plurality of regions, and When the vehicle speed is smaller than each threshold value, the rear wheel movement trajectory that does not consider the sideslip angle is calculated based only on the steering angle. A rear view support system for a vehicle, wherein the rear wheel movement locus is calculated in consideration of a side slip angle. 5. The rear wheel moving unit according to claim 1, wherein the arithmetic unit considers the overhang length when the vehicle has an overhang from the rear wheel axle to the rear monitoring imaging unit. A vehicle rear view support device characterized by calculating a trajectory. 6. The image synthesizing section according to claim 1, further comprising a shift position detecting section, wherein the shift position detecting section detects the shift position only when the shift position detected by the shift position detecting section indicates the retreat position. A rear view support device for a vehicle, wherein an image is displayed on the image display unit. 7. An image information output from an image information output section for outputting the image synthesis section and other image information between the image synthesis section and the image display section, according to claim 1. A rear view support device for a vehicle, further comprising an image information switching unit for switching between the two.