JPH07139909A - Method for measuring/controlling position of viewpoint - Google Patents

Abstract

PURPOSE:To provide a method for detecting a central position, a radius, positions of characteristic points of a cylinder such as an electric light pole or the like through operations of a stereo image thereby to detect a position of a manipulator, etc., and move/control the manipulator, etc. CONSTITUTION:In a first step, a stereo image is processed thereby to detect/ measure right and left positions of a cylinder, and calculate a central position of the cylinder as a center of the right and left, positions and also a radius from a distance of the right and left positions. In a second step, the stereo image is processed to detect a position of a characteristic point on a surface of the cylinder. In a next third step, a direction of a line connecting central point of the cylinder and the characteristic the point is obtained from the central position and radius of the cylinder and the position of the characteristic point, and a moving direction and a moving amount for a viewpoint necessary for covectly facing the view point to the cylinder are obtained. The viewpoint is consequently moved. The above process is repeated until a target position is obtained. In this manner, the viewpoint with a manipulator or the like can be correctly measured, and easily moved to an optional position by such a simple device as a personal computer without requiring skills.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is attached to the tip of a manipulator for an object having a cylindrical shape such as a utility pole, based on the left and right boundary position information of the cylindrical object and the position information of the feature points on the cylindrical surface. The present invention relates to a method of measuring a relative positional relationship between a tool and a cylindrical object, and controlling movement of the tool to a desired position with respect to the cylindrical object.

[0002]

2. Description of the Related Art Utility poles are important outdoor facilities for supporting communication and electric power, and cable relocation work on utility poles has been increasing in recent years as demand has increased. These works are so-called 3K works, and for reasons such as improvement of work environment and soaring labor costs, a work method by remote operation with a tool attached to the tip of the manipulator is currently being studied.
The problem here is to move the tip of the manipulator efficiently and with high accuracy to a suitable place to work. Conventionally, a camera is attached to the tip of a manipulator, and an operator carries out a moving operation while viewing the image on a monitor. However, since it is not possible to obtain distance information from one image, it is difficult for even an expert to properly move. In order to avoid this problem, a method of giving a perspective to the operator by taking a stereo image with two cameras and showing different left and right stereo images to the left and right eyes has also been studied (Michitaka Hirose, “How far can artificial reality be realized?”, Journal of Japan Society of Mechanical Engineers, Vol.93, No.863, pp.874-
880, 1990).

On the other hand, conventionally, there is known a stereo image measuring method for measuring a three-dimensional spatial position from a stereo image. Hereinafter, this stereo image measuring method will be briefly described.

The principle of stereo image measurement is shown in FIG. X, y, and z are used as the coordinates indicating the three-dimensional space, and u and v are used as the coordinates indicating the position on the image plane. x-axis and u-axis, z
The axis and the v-axis are parallel to each other, and the y-axis is parallel to the optical axis of the camera. Let O, which is the origin of the spatial coordinate system, be the midpoint of the projection centers F _l and F _r of the left and right cameras. When the distance between the camera and 2a, F _l, respectively coordinates in the three-dimensional space F _r (-a, 0,0), represented by (a, 0,0). The image plane of the actual camera is on the side opposite to the measurement target with respect to the projection center of the camera, but in order to make it easy to see the geometrical quantitative relationship described below, in FIG. It is drawn in a symmetrical position with respect to the center. At this time, assuming that the distance between the projection center and the image plane is f, 3 of the image origins O _l and O _{r on} the left and right camera image planes.
The dimensional space coordinates are (-a, f, 0), (a, f,
It is represented by 0). Hereinafter, l and r are used as subscripts indicating left and right images, and the origin O is referred to as a viewpoint.

It is assumed that a point P in the three-dimensional space is projected onto points I _l (u _l , v _l ) and I _r (u _r , v _r ) on the left and right image planes. In stereo image measurement, I _l and I _r are _displayed on the image.
Is determined, and the three-dimensional space coordinates (x, y, z) of the point P are obtained based on the principle of triangulation. Here, since the optical axes of the two cameras are on the same plane and the x axis and the u axis are parallel to each other, v ₁ and v _r have the same value. Therefore, in the following, both are represented by v without distinction. As shown in FIG. 5, due to the geometrical condition that the straight lines F _l I _l and F _r I _r intersect at the point P, the coordinates u _l , u _r , v on the image plane and the coordinates x in the three-dimensional space are set. , y, the relationship between z _{is, x = a (u l +} u r) / (u l -u r) (1) y = 2af / (u l -u r) (2) z = 2av / (u l −u _r ) (3)

Next, taking digital image processing as an example,
A block diagram of a device configuration for performing such stereo image measurement is shown in FIG. TV cameras 1-1 and 1-2
The image captured in (1) is converted into a temporally continuous video signal while being scanned for each scanning line. This video signal is sampled by a sampler of the digitizer 2 into hundreds of vertical and horizontal pixels per screen like a grid pattern. At the same time, the A / D converter quantizes the density corresponding to the amount of light incident on each pixel into several hundreds of gradations. In this way, the image is stored in the image memory 3 as information including the coordinates indicating the position of the pixel and the density there. Since the brightness of the object boundary projected on the image plane usually changes greatly, the computer (CPU) 4 performs a differentiation process on the image stored in the image memory 3 to determine a place where the brightness changes. The projected position of the object boundary is detected. By performing such processing on the left and right images, corresponding points I _l (u _l , v _l ) and I _r (u _r , v _r ) on the respective image planes can be obtained. By performing interpolation calculation or the like, the influence of digitization in determining the projection position can be made small enough to be ignored. As described above, in the stereo image processing, the image plane coordinates u _l , u _r , and v of the object projection point are measured, and the three-dimensional space coordinates x, y, and z are indirectly measured.

[0007]

As described above, in the conventional cable replacement work on telephone poles, when the operator moves the manipulator by remote control while looking at the stereo image, a special image control can be performed. In addition to the need for various devices, there are problems that the operator is burdened with eye fatigue and the like.

The present invention has been made in order to solve such a problem, and an object thereof is to perform arithmetic processing on a stereo image to measure a cylinder center position, a radius, and a feature point position with high accuracy, and to operate the manipulator. The object of the present invention is to provide a method for measuring the position and controlling the movement of the vehicle. Specifically, by processing the stereo image with a computer, the center position and radius of the utility pole and the position of the feature point on the utility pole are directly measured, and the relative positional relationship between the manipulator and the utility pole is calculated based on this information. Then, we propose a method of moving and controlling the manipulator.

[0009]

In order to achieve the above object, the viewpoint position measurement control method of the present invention uses a stereo image processing to measure and control the position of the viewpoint of a cylindrical object. In the method of directly facing the viewpoint with respect to the feature point on the surface, the first step of calculating the stereo image, measuring the left and right boundary positions of the cylinder, and calculating the cylinder center position and the radius from the interval, Similarly, a second step of computing the stereo image to calculate the position of the characteristic point on the cylindrical surface, and the cylindrical center position, radius, and characteristic point position calculated from the first and second steps from the cylindrical center position. The third step is to obtain the direction of the straight line connecting the line and the feature point, and to obtain the direction of movement of the viewpoint and the amount of the line of sight necessary to make the line straight.

[0010]

In the viewpoint position measuring and controlling method of the present invention, the stereo image is arithmetically processed to measure the left and right positions of the cylinder, the center position of the cylinder is calculated as the center position of them, and the radius is calculated from the interval between the two. The position of the feature point on the surface is calculated, the direction of the straight line connecting the cylinder center position and the feature point is calculated from these cylinder center position, radius, and feature point position, and the moving direction of the viewpoint required to make it straight And ask for the amount. In this way, with a device as simple as a personal computer, it is possible to accurately measure the point of view and to confront it, without requiring skill.
It facilitates the movement control of the viewpoint to the desired position.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

First, a stereo image measuring method for a cylindrical surface will be described with reference to FIG. FIG. 1 is a cross-sectional view taken along v = 0 when a cylinder A having a central axis in the z-axis direction is added to FIG. Normally, the xy plane is parallel to the ground surface and horizontal, and the z axis is parallel to the central axis of the cylinder A and vertical,
Since the explanation can be simplified, two-dimensional measurement on the xy plane will be considered below. Further, hereinafter, as shown in FIG. 1, the quantities relating to the left and right of the cylinder are represented by subscripts L and R, respectively. Using the stereo image measurement method described in the prior art,
Coordinates (x _L , y _L ) of the left and right boundary points L and R of the cylinder, (x _R ,
y _R ). The coordinates (x _C , y _C ) of the center position C of the cylinder are set as the center positions of these two points, that is, x _C = (x _L + x _R ) / 2, y _C = (y _L + y _R ) / Calculate as 2. Also, the radius p, half i.e. p = the distance between the two points ^{_{((x L -x R) 2}} + (y L -y R) 2)
^Calculated as 0.5 / 2. Although (x _C , y _C ), p obtained by these calculations is not an exact solution, y _C ≈ 0 (or y _C ≈ p), that is, it is approximate except at an extreme place where the cylinder center position is near the viewpoint. Holds true.

Next, the viewpoint position measurement control method in this embodiment will be described with reference to FIG. As shown in FIG. 2, the characteristic point M on the surface of the cylinder A is at a position on the circumference rotated by θ around the cylinder center point C, and the coordinates of this point are (x _M , y _M ). The coordinates of the feature point M can be obtained by the stereo image measuring method described in the related art. In the case of FIG. 2, the following equation is obtained from the geometrical relationship.

X _M = x _C + psin θ (4) y _M = y _C −p cos θ (5) Moving the viewpoint to a position where the feature point M can be seen from the left and right cameras, that is, the viewpoint on the arc ⌒LR in FIG. Moving the position does not require precise movement control and can be easily performed by an operator's operation. From equations (4) and (5), the angle θ from the measurement coordinates (x _C , y _C ) of the cylinder center point C and the measurement coordinates (x _M , y _M ) of the feature point M is θ = −tan ⁻¹ ( _{(x M -x C) / (} y M -y C)) obtained as (6). However, the range of θ is −90 ° <θ <90 ° because the measurement condition of the characteristic point M, that is, the characteristic point M is visible from the left and right cameras.

Now, as shown in FIG. 2, the viewpoint O ₁ before the face-to-face conversion is performed.
Is x ₁ y ₁ , and the coordinate of the viewpoint O ₂ after face-to-face correspondence is x ₂
and be represented by y _2, first, the viewpoint O ₁ rotated by an angle theta,
Next, consider t _x translation along the x ₂ axis, which is the x axis after rotation, to make it face-to-face. In this case, t _x is t _x = x _C cos θ + y _C sin θ (7) from the geometrical relation, and therefore the rotation angle θ required for the confrontation obtained from the formula (6) is expressed _by the formula (6) ), The translation amount t _x is obtained. Since the distance between the viewpoint and the center of the cylinder after facing is y _C cos θ−x _C sin θ, the manipulator is moved from the viewpoint O ₂ to the desired position along the y ₂ axis in the facing state based on this information. You can move up to. However, since the measurement error included in the image plane projection point propagates to these θ and t _x , the manipulator may be brought close to the cylindrical surface while repeating the above-described measurement and facing.

This embodiment will be described below with reference to specific examples.

Now, it is assumed that the distance 2a between the left and right cameras is 20 cm, the focal length of the camera lens is 5 mm, and the sampling interval on the image plane having a size of 1 pixel is 10 μm. The diameter of the cylinder is 30 cm, and the center position is (0.3 m, 1 m).
It is assumed that This embodiment will be specifically described with reference to the flowchart of FIG. 3 through the simulation under such conditions. In the following, all units of length are m, and this m is omitted below.

(A) First step In the first step, the left and right boundary positions of the cylinder are measured by stereo image processing, the center position of the cylinder is set as the center of the measured values, and the radius from the distance between the left and right boundary positions is measured. Is a step of calculating. Under the above-mentioned simulation conditions, the position of the image plane projection point on the boundary of the cylindrical surface is actually obtained. Here, in order to reduce the influence of digitization, it is assumed that the interpolation method is used for the boundary position determination calculation projected on the image, and the calculation is performed using a non-digitized value. As an example of this interpolation calculation method, Yujihiko Nomura et al., “Sub-pixelization and error analysis of edge position measurement”,
IEICE Transactions (D-II), J73-D-II, p
p. 1458-1467 (1990).

Here, under the above-mentioned simulation conditions, a tangent line is drawn from the projection center of the camera to the cylindrical surface, and the position of the intersection of this tangent line and the image plane, that is, the pixel position of the projection point is geometrically calculated. The results in this example, the left of the left camera shown in FIG. 1, the right cylinder boundary, left right camera, the projected point u _l of right cylindrical _{boundary, L, u l, R,} u r, L, u r, The values of _R are 122.772, 286.435, and 24.90, respectively.
It was determined to be 7, 179.697 pixels. When the coordinates (x _L , y _L ) and (x _R , y _R ) of the left and right positions of the cylinder are calculated based on these coordinates by the formulas (1) and (2), they are (0.151, 1.022), respectively. ), (0.437, 0.93
8), from which the center coordinates (x _C , y _C ) of the cylinder and the radius p are (0.294, 0.979) and 0.14, respectively.
It was asked to be 9. As described above, since these values are not exact solutions, errors due to approximation are included.

(B) Second step The second step is a step of measuring the positions of the feature points on the cylindrical surface by stereo image processing as in the first step.
Similar to the first step, the coordinates (x _M ,
Calculation of y _M gave (0.375, 0.870).

(C) Third step In the third step, the center position C (x _C , y _C ) of the cylinder calculated in the first and second steps, the radius p, and the feature point M (x _M ,
y _M ) position is a step of obtaining the direction of a straight line CM connecting the cylinder center position C and the feature point M, calculating the moving direction and the amount of the viewpoint required to make the face straight, and moving the viewpoint. . The center coordinates of the cylinder calculated in the first step (0.29
4, 0.979) (= (x _C , y _C )) and the coordinates (0.375, 0.870) (= 0.375, 0.870) of the feature point on the cylindrical surface in the second step.
Substituting (x _M , y _M )) into equation (6), θ is 36.6.
It was calculated as °. Further, when the value of (x _C , y _C ) and the value of θ were substituted into the equation (7) to obtain the parallel movement amount t _x , this value was 0.82.

FIG. 4 illustrates the above results.
In FIG. 4, O ₁ is the initial position of the viewpoint before face-up,
O ₂ is the facing viewpoint position, and C, t _x , and θ are true values. On the other hand, O ₂ ′, C ′, t _x ′, θ ′
Indicates the calculated position or value. It can be seen that the error included in the measured value of the cylinder center position is considerably faced by one measurement of the face-to-face position. If the viewpoint position that has been directly faced by the above is ended if it is the target position, and if it is not the target position, the viewpoint is brought closer to the utility pole, and the measurement is repeated again at the approached position, so that any desired distance is obtained. Can be directly faced.

In the above embodiment, the case of two-dimensional measurement has been described as an example for simplification of description, but it goes without saying that the present invention can be similarly applied to the case of three-dimensional measurement.

[0024]

As described above, according to the present invention, the stereo images are arithmetically processed to measure the left and right positions of the cylinders, the center positions of the cylinders are calculated as the center positions thereof, and the diameter is calculated as the distance between the two. , Calculate the position of the feature point on the cylindrical surface, find the direction of the straight line connecting the cylinder center position and the feature point from these cylinder center position, radius, and feature point position, and Since the movement direction and its amount are obtained, the advantage is obtained that a device as simple as a personal computer does not require skill and the viewpoint can be accurately measured and directly faced to easily move to any desired position.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a cylinder center position / radius calculation model by a stereo image measuring method according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a viewpoint position measurement control method in the above embodiment.

FIG. 3 is a flowchart for explaining the above embodiment.

FIG. 4 is a diagram for explaining a specific example of the above embodiment.

FIG. 5 is a diagram for explaining the principle of stereo image measurement.

FIG. 6 is a block diagram showing a device configuration for performing stereo image measurement.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Minoru Shiragata 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A method for calculating a stereoscopic image in a method of directing a viewpoint to a feature point on a cylindrical surface when measuring and controlling the position of the viewpoint with respect to a cylindrical object using stereo image processing. Then, the left and right boundary positions of the cylinder are measured, and the center position and radius of the cylinder are calculated from the intervals.
And a second step of calculating the position of the feature point on the cylindrical surface by similarly processing the stereo image, and the cylindrical center position and radius calculated in the first and second steps,
A viewpoint including a third step of determining a direction of a straight line connecting the cylindrical center position and the feature point from the feature point position, and determining a moving direction of the viewpoint and an amount of the viewpoint required for making the face straight. Position measurement control method.