JPH0528401B2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention (Field of Industrial Application) The present invention relates to a course-following driving method for an unmanned vehicle, and more specifically, a method for photographing a driving line that indicates the driving route of an unmanned vehicle using an imaging device, and capturing the image. The present invention relates to a course-following driving method in an image-based unmanned vehicle, which runs an image-based unmanned vehicle along a driving route determined by image processing an image of a driving line taken by a device.

(Prior Art and Problems) The present applicant has developed an image processing system for this type of image-based unmanned vehicle that uses an imaging device to image the travel line that indicates the travel route, and provides a safe and secure way for the unmanned vehicle to travel along the travel line. Various applications have been previously filed regarding methods for determining rational travel routes.

One way to determine a driving route is to image-process a driving line captured by an imaging device, select multiple points on the driving line, and calculate a function of a curve that approximates the driving line from the selected points. Some use approximate curves as driving routes for unmanned vehicles.

(Problem to be Solved by the Invention) Incidentally, it is desirable for image-based unmanned vehicles to travel along the actual travel line accurately and reliably, but as described above, it is preferable to use an approximate curve of the travel line as the travel route. Because steering control is based on the approximate curve function, there are limits to how accurately and reliably an unmanned vehicle can travel along a travel line.

An object of the present invention is to provide a course following driving method for an image-based unmanned vehicle that allows the unmanned vehicle to travel accurately and reliably on an actual driving line.

Structure of the Invention (Means for Solving the Problems) In order to achieve the above object, an imaging device provided in an unmanned vehicle captures an image of a traveling line indicating the traveling route of the unmanned vehicle, and the traveling line in the image is Select multiple points along the same line, find the differential coefficient of the traveling line at the selected points, and use the obtained differential coefficient as the attitude angle of the unmanned vehicle at the selected point based on the differential coefficient of each selected point. The gist of this paper is a course-following method for an image-based unmanned vehicle that controls the steering angle.

(Function) The tangent (inclination) of the travel line at the selected point selected on the travel line in the image means the differential value, that is, the differential coefficient, at that selected point, and the differential coefficient is taken as the attitude angle of the unmanned vehicle. For example, at that selected point on the travel line, the unmanned vehicle will travel smoothly on the travel line. As a result, the differential coefficient of each selected point is used as the attitude angle of the unmanned vehicle at that selected point, and when driving from the selected point to the next selected point, the steering angle of the unmanned vehicle is determined based on the differential coefficient of both selected points. By controlling this, the unmanned vehicle will reliably travel on the driving line.

(Embodiment) Hereinafter, an embodiment of an unmanned vehicle travel control device embodying the image-based unmanned vehicle travel route determination method of the present invention will be described with reference to the drawings.

In FIG. 1, a support frame 2 is erected at the upper center position on the front side of the unmanned vehicle 1, and an image pickup device is installed at the upper center position of the frame 2.
A CCD (cnarge coupled device) camera 3 is provided. The CCD camera 3 is set on the support frame 2 so as to photograph an area 4a on the road surface 4 in front of the unmanned vehicle 1.

On the road surface 4, as shown in FIG. 2, a travel line 5 indicating the travel route of the unmanned vehicle 1 is drawn with a constant line width, and in this embodiment, it is drawn with a white paint different from the color of the road surface 4. It is. Then, the CCD camera 3 photographs the traveling line 5 having a constant line width.

Therefore, the CCD camera 3 captures the area 4a shown in FIG. 4 as the image 6 shown in FIG. 5, and the image 6 of the area 4a is used in this embodiment.
It consists of 256 x 256 pixels. and,
A signal (hereinafter referred to as a pixel signal) captured by the CCD camera 3 that captures the white running line 5 has a high output level, while a pixel signal that captures the road surface 4 has a low output level. In addition, in this example, CCD
Although illumination lamps 7 that illuminate the road surface 4 are installed below both sides of the camera 3 in order to facilitate image pickup by the camera 3, it is also possible to carry out the process without using the illumination lamps 7.

Next, the electrical configuration of the travel control device equipped with the unmanned vehicle 1 will be explained with reference to FIG.

The microcomputer 10 includes a central processing unit (hereinafter referred to as CPU) 11, a program memory 12 consisting of a read-only memory (ROM) that stores control programs, and a read/write memory that temporarily stores pixel data and other arithmetic processing results of the CPU 11. It is composed of a working memory 13 consisting of a replaceable memory (RAM), a timer 14, and the like. And the CPU 11 is the program memory 1
The control program stored in 2 determines the state of the driving line and also executes various arithmetic processing operations for driving such as steering control.

The CPU 11 scans and controls the CCD camera 3 via the input/output interface 15 and the A/D converter 16 at regular intervals based on the time measured by the timer 14, and also scans and controls the pixel signals from the CCD camera 3. The pixel data is converted into pixel data via the A/D converter 16 and the bus controller 17 and stored in the working memory 13.

When the A/D converter 16 converts the pixel signal from the CCD camera 3 from an analog value to a digital value,
It is determined whether each pixel signal is equal to or greater than a predetermined set value. Then, the A/D converter 16 sets the pixel to "1" for the white traveling line 5 part when the pixel signal is greater than the set value, and on the other hand, when the pixel signal is less than the set value, the dark colored part of the road surface 4. The bus controller 17 binarizes each pixel signal that is sequentially input so that the pixel is set to "0" and converts it into pixel data.
The data is stored in the working memory 13 via the .

Therefore, the working memory 13 includes the CCD camera 3.
The image 6 taken by the user will be stored as 256×256 pixel data.

The binarization level controller 18 is connected to the CPU 1
1 based on the control signal from the A/D converter 1.
The setting value data for 6 to be binarized is sent to the same A/D.
The signal is output to a converter 16. The drive controller 19 controls the driving motor 20 and steering mechanism 21 for driving the unmanned vehicle 1 based on control signals from the CPU 11 as well. The drive motor 20 determines the traveling speed V of the unmanned vehicle 1, and the steering mechanism 21 determines the steering angle Θ of the unmanned vehicle 1.

In this embodiment, the motor 20 is controlled so that the unmanned vehicle 1 always travels at a preset constant travel speed V.

In addition, in this embodiment, for convenience of explanation, the scanning control of the CCD camera 3 is performed in the horizontal direction (y-axis direction) with respect to the screen.
Although a scanning method is adopted in which the scanning moves from the top of the screen to the bottom (in the x-axis direction), it goes without saying that other scanning methods may be used.

Next, the processing operation of the CPU 11 configured as described above will be explained.

Now, based on the control signal from CPU11, the CCD
When the camera 3 is scan-controlled, since the camera 3 is not perpendicular to the road surface 4 but is taking images at a certain angle of inclination, an image of the front area 4a shown in FIG. 6 as shown in FIG. 7 is created. 6. The image 6 captured by the CCD camera 3 is converted into an A/D signal as a pixel signal.
The A/D converter 16 determines whether each pixel signal is a pixel signal for the traveling line 5 or a pixel signal for the road surface 4 and processed as pixel data via the bus controller 17. data is transferred to the memory 13 for use.

When the pixel data is transferred to the working memory 13, the CPU 11 calculates the inclination at a point near the unmanned vehicle 1 on the travel line 5 based on the pixel data.
That is, when the traveling line 5 is represented by a certain curve, a processing operation is executed to obtain the differential coefficient (differential value) at that point, that is, the attitude angle Φ of the unmanned vehicle 1.

First, as shown in FIG. 7, pixel data of one horizontal pixel column corresponding to the lowest check lines L0a and L0b of the image 6 is read out, and each line L0
After determining the pixel data of the traveling line 5 on the check line L0b and the pixel data of the road surface 4 and finding the center position C0a of the traveling line 5 that intersects the line L0a, the pixel data of the traveling line 5 on the check line L0b is determined.
Similarly, the check line L0b is obtained from the pixel data group of
Find the center position C0b of the travel line 5 that intersects the .

These center positions C0a and C0b are determined by the x-axis being the 128th vertical pixel column counting from the left in each pixel that makes up the image 6, and the y-axis being the 128th horizontal pixel column counting from the top. It is calculated using the x and y coordinates.

The CPU 11 projectively transforms both the center positions C0a and C0b, that is, the center positions C0a and C0 obtained from the image 6.
Which position Q0a,Q on the actual area 4a is 0b?
Determine whether it is in 0b. This is as mentioned above
Since the CCD camera 3 does not image the road surface 4 vertically, this process is performed to match the difference between the travel line 5 in the image 6 and the actual travel line 6 in the area 4a. The conversion method can be easily understood by referring to, for example, Japanese Patent Application No. 60-283852 (Japanese Unexamined Patent Publication No. 62-140110) previously filed by the present applicant.

In addition, the center position Q0a obtained by this projective transformation,
Q0b is the traveling direction passing through the center of the unmanned vehicle 1 on the Y axis,
The line that divides the area 4a into left and right halves is the X axis, and the intersection of both axes (origin) is the current position of the unmanned vehicle 1 (more precisely, the position of the CCD camera 3) HP.
I'm looking for the Y coordinate.

The CPU 11 runs a running line 5 that runs from the center positions Q0a, Q0b to the check lines L0a, L0b.
Calculate the slope (differential coefficient of running line 5) Φ0,
The slope Φ0 is stored in the working memory 13.

That is, if the coordinate positions of the center positions Q0a and Q0b are (X0a, Y0a) and (X0b, Y0b), respectively, the slope Φ0 can be determined as follows.

ΔX=X0a−X0b ΔY=Y0a−Y0b Φ0=tan ^-1 (ΔX/ΔY) Next, the CPU 11 passes the current position HP of the unmanned vehicle 1 and the center position Q0b on the traveling line 5, and at the center position Q0b. The differential coefficient F' (X0b) is ΔX/ΔY
(=tanΦ0) Function of cubic curve L F(x)=aX ³
Find +bX ² +cX+d.

In this calculation, in this example, the current position is
The differential coefficient F'(0) is set to be 0 at HP. Based on the above conditions, the function F of the cubic curve L
Once (x) is determined, the CPU 11 determines this function F(x) as the travel route from the current position HP of the unmanned vehicle 1 to the center position Q0b on the travel line 5 in the area 4a.

When the travel route is determined, the CPU 11 drives the drive motor 20 to cause the unmanned vehicle 1 to travel at a predetermined constant speed V, and performs control processing to control the steering mechanism 21 based on this function F(x).

This processing is a processing operation for driving the unmanned vehicle 1 from the current position HP to the center position Q0b of the travel line 5 along the cubic curve L of the function F(x),
A processing operation of determining the attitude angle Φ at the current traveling position from the function F(x), determining the steering angle Θ so that the unmanned vehicle 1 has the attitude angle Φ at the time, and controlling the operation of the steering mechanism 21. be.

In the case of this embodiment, steady turning driving is adopted to perform this steering control, and this driving is a driving that turns with a constant radius R when the steering angle Θs is held constant, as shown in FIGS. 8 and 9. If ΔΦ is the change in the attitude angle Φ after ΔT seconds, V is the traveling speed, and D is the wheel base of the unmanned vehicle 1, then the following formula holds true.

ΔΦ=V・Θs・ΔT/D R=D/Θs Then, from both equations, in order to change the attitude angle Φ by ΔΦ while advancing by V・ΔT, the radius R (=V・ΔT/ΔΦ ), and from its radius R, the steering angle Θs (=D/R=D・ΔΦ/V・
ΔT). Therefore, the CPU 11 calculates the steering angle Θs for each ΔT based on the above equation, and controls the operation of the steering mechanism 21 to cause the unmanned vehicle 1 to travel along the cubic curve L.

The details can be easily understood by referring to the contents described in Japanese Patent Application No. 60-283851 and Japanese Patent Application No. 60-281399, which were previously filed by the present applicant.

When unmanned vehicle 1 starts running, CPU 1
1 determines the slope of a plurality of selected points on the travel line 5 captured based on the pixel data of the image 6, that is, the differential coefficient (differential value) of each point when the travel line 5 is represented by a certain curve. Perform processing operations.

The CPU 11 sets first check lines L1a and L1b at predetermined spacing positions adjacent to the check lines L0a and L0b, and performs corresponding operations in the same way as the process obtained using the check lines L0a and L0b at the bottom of the image 6. After reading out the pixel data of one horizontal pixel column and determining the pixel data of the running line 5 and the pixel data of the road surface 4 in each of the lines L1a and L1b, and finding the center position C1a of the running line 5 that intersects the line L1a, Check line L1
From the pixel data group of the running line 5 on b, the running line 5 that intersects the check line L1b is similarly selected.
Find the center position C1b.

The CPU 11 has the center position C1a obtained from image 6,
At which position Q0a on the actual area 4a is C1b?
If it is in Q0b, projective transformation is performed in the same way as above. Then, the CPU 11 calculates the slope Φ1 of the running line 5 passing between the check lines L1a and L1b from the center positions Q1a and Q1b (the differential coefficient of the running line 5), and stores the slope Φ1 in the working memory 13.

That is, as shown in FIG. 10, the coordinate positions of the center positions Q1a and Q1b are respectively (X1
a, Y1a), (X1b, Y1b), the slope Φ1 can be obtained as follows in the same way as above.

ΔX=X1a−X1b ΔY=Y1a−Y1b Φ1=tan ⁻¹ (ΔY/ΔX) When the slope Φ1 of the running line 5 at the first check lines L1a and L1b is determined, the CPU 11
Thereafter, in the same manner, the positions C2a, C2b to C8a, C8 on each check line are moved up to the eighth check line L8a, L8b at regular intervals.
b, Q2a, Q2b to Q8a, Q8b, and slopes (differential coefficients) Φ2 to Φ8 are determined and sequentially stored in the working memory 13.

This group of differential coefficients Φ1, Φ2 to Φ8 is area 4
Each position Q1 when moving on the travel line 5 in a
b, the attitude angle Φ at Q2b to Q8b is shown. Therefore, at each position Q1b, Q2b to Q8b of the travel line 5 in the area 4a, the unmanned vehicle 1
By controlling the steering angle Θ via the steering mechanism 21 so that the attitude angle Φ becomes Φ1, Φ2 to Φ8, it becomes possible to move the unmanned vehicle 1 along the same traveling line 5.

Note that this eighth check line L8a, L8b
Regarding the calculation of the slope Φ8 up to, the CPU 11 at least ensures that the unmanned vehicle 1 travels on the quadratic curve L and finishes by the center position Q0b on the travel line 5.

When the unmanned vehicle 1 reaches the center position Q0b on the traveling line 5, the attitude angle Φ of the unmanned vehicle 1 is controlled to the above-mentioned Φ0, so the CPU 11 smoothly rides on the traveling line 5 and returns to the aforementioned traveling line 5.
It will move towards the upper position Q1b. At this time, the CPU 11 reads the differential coefficient Φ1 of the position Q1b stored in the working memory 13, and this Φ1,
The above Φ0, the traveling speed V of the unmanned vehicle 1, and the time ΔT to reach the position Q1b (ΔT differs depending on the section. In this case, if the distance between Q _1b and Q _0b is regarded as a straight line and this distance is l ₀₁ , then ΔT ₀₁ = l ₀₁ /V)
and the steering angle Θ (D=ΔΦ/V・ΔT;
Note that the steering mechanism 21 is driven and controlled by controlling ΔΦ=Φ1−Φ0). As a result, the unmanned vehicle 1 is located at the position Q1b
You will get on the running line 5 and reach the destination smoothly.

When unmanned vehicle 1 reaches position Q1b, CPU1
1 reads the differential coefficient Φ2 of the position Q2b to be moved next from the working memory 13, and calculates this Φ2 and the above Φ
1. Speed V of unmanned vehicle 1, time to reach position Q2b ΔT = l ₁₂ /V; l ₁₂ is the straight line distance between Q _2b and Q _1b ) and length D of the wheel base of unmanned vehicle 1
Based on this, the current steering angle Θ is controlled in the same manner as described above, and the steering mechanism 21 is driven and controlled. After that, by repeating the same operation, the CPU
11 allows the unmanned vehicle 1 to travel smoothly through each of the positions Q3b to Q8b.

In this way, in this embodiment, the travel line 5 taken by the CCD camera 3 from the current position is placed on the 3
When finding the function F(X) of the following curve L, travel line 5
Since the differential coefficient Φ0 of the traveling line 5 at the position Q0b where the car rides on is determined as an element of the function F(X), the unmanned vehicle 1 traveling along the cubic curve L will surely ride on the position Q0b and reach the same position Q0b. When this happens, the attitude angle Φ of the unmanned vehicle 1 will match the differential coefficient Φ0, and the unmanned vehicle 1 will ride on the traveling line 5 smoothly.
Therefore, the CCD after riding on travel line 5
It is possible to move to a travel route determined based on pixel data of the travel line 5 captured by the camera 3.

Furthermore, in this embodiment, since the cubic curve L is used such that the attitude angle Φ is zero at the current position HP, the steering angle Θ is zero when starting the unmanned vehicle 1, so it is not necessary to change the steering angle suddenly. This allows for smooth steering operation.

Further, in this embodiment, the traveling route after the unmanned vehicle 1 reaches the position Q0b is determined by differential coefficients Φ1 to Q8b for the positions Q1b to Q8b on the traveling line 5 based on the pixel data of the traveling line 5 captured by the CCD camera 3.
Find Φ8 and find the differential coefficient Φ of this position Q1b to Q8b.
Since the steering angle Θ is controlled based on 1 to Φ8, that is, the attitude angle Φ of the unmanned vehicle 1, the unmanned vehicle 1 can run along the traveling line 5 itself as a traveling trajectory.

In addition, in this case, there is no need to calculate a certain function for the travel area 5 in the area 4a and use a curve based on that function as the travel route, and the differential coefficients Φ1 to Φ8 at each position Q1b to Q8b are stored in the working memory 13. Since it is only stored, the storage capacity of the working memory 13 can be very small.

Note that the present invention is not limited to the embodiments described above; for example, in the embodiments described above,
The function F(X) up to Q _0b is made to be a cubic curve L, but the point is that the running line 5 at position Q0b
Any function (for example, an n-th order function) may be used as long as it has a differential coefficient that matches the differential coefficient Φ0 of .

Furthermore, in the embodiment, the interval between each check line, for example, the first check line L1a, L1b
Although the interval is not particularly limited, the interval may be changed as appropriate as long as the differential coefficient at that position can be calculated.

In addition, in the above embodiment, after projective transformation, each position Q
The differential coefficients Φ1 to Φ8 of 1b to Q8b were obtained, and the differential coefficients of each of Q1b to Q8b in image 6 were obtained and the obtained differential coefficients were projectively transformed to area 4.
Differential coefficient Φ1 of each position Q1b to Q8b in a
~Φ8 may be determined.

Further, in the embodiment described above, the first to eighth check lines are set, but it goes without saying that the number may be changed as appropriate. In this case, increasing the number allows for more accurate driving.

In addition, in the above embodiment, the traveling route (cubic curve) for riding on the traveling line 5 is determined by the function F(x)=aX ³ +bX ²
+c It's okay. For example, in this example, image 6 is
Since it is 256×256, there are 256 positions Q0b. Then, if the differential coefficient Φ0 is set in steps of 5 degrees, it becomes (180°/5°-1)・256=8960, which means that 8960 types of cubic curves L need only be prepared in advance, that is, made into a table. . Therefore, calculation processing time is reduced.

Furthermore, in the embodiment, each position Q1b to Qnb
Read out the differential coefficients Φ1 to Φ8, and calculate these Φ1 to Φ
8. Current steering angle Θ based on traveling speed V, time ΔT and wheelbase length D
(=D・ΔΦ/V・ΔT) to drive and control the steering mechanism 21, but since the traveling speed V, time ΔT, and wheelbase length D are known in advance, each differential coefficient Φ1 The steering angle Θ corresponding to each ΔΦ=Φm−Φm−1 obtained from ~Φ8 may be made into a table and stored in the program memory 12 for implementation. In this case, the calculation processing time will be shortened. Furthermore, although the above embodiment was carried out on the assumption that the traveling speed V is constant, it is also possible to obtain the traveling speed V at any given time using a vehicle speed sensor and perform the above calculation process using the determined traveling speed V. Of course.

Effects of the Invention As described in detail above, the present invention has an excellent effect of allowing an unmanned vehicle to travel accurately and reliably on an actual travel line.

[Brief explanation of the drawing]

Figure 1 is a side view of an unmanned vehicle that embodies this invention, Figure 2 is a plan view of the same, Figure 3 is an electric block circuit diagram of the control device installed in the unmanned vehicle, and Figure 4 is an image captured by a CCD camera. Diagram showing areas to be
The figure is an explanatory diagram to explain the image taken by the CCD camera, Figure 6 is a diagram to explain the differential coefficient of the running line at each check line in the area, and Figure 7 is an explanatory diagram at each check line in the image. A diagram for explaining the running line, Figure 8 is an explanatory diagram for explaining steady turning travel, Figure 9 is a diagram showing the relationship between attitude angle and radius, and Figure 10 is an explanation for determining the differential coefficient. It is a diagram. In the figure, 1 is an unmanned vehicle and 3 is an imaging device.
CCD camera, 5 is the running line, 6 is the image, 10
is a microcomputer, 11 is a central processing unit (CPU), 12 is a program memory, 13 is a working memory, 16 is an A/D converter, 19 is a drive controller, 20 is a drive motor, 21 is a steering mechanism, L0a, L0b ~L8a, L8b are check lines, Φ0 to Φ8 are differential coefficients, Φ is attitude angle, Q0
a, Q0b to Q8a, Q8b are positions.

Claims (1)

[Claims] 1 An imaging device installed in an unmanned vehicle captures an image of a travel line indicating the travel route of the unmanned vehicle, selects multiple points along the same line in the image, and calculates the travel line at the selected point. A course following driving method for an image-based unmanned vehicle that calculates a differential coefficient, uses the determined differential coefficient as the attitude angle of the unmanned vehicle at the selected point, and controls the steering angle based on the differential coefficient of each selected point.