KR20140024746A - System and method for measuring deformation structure - Google Patents

Abstract

The present invention relates to a method for measuring the deflection of a structure, which comprises as follows: a process of photographing an object of an adjacent camera preferred in a specific direction from individual cameras installed at previously set intervals at individual fixed points of a structure by a previously set cycle; a process of measuring a reference point for the orientation of the obtained images from the photography of each camera; a process of calculating the interior orientation element and the relative orientation element of the image whose reference point is measured; a process of performing absolute orientation through the measured reference point, and calculating a three-dimensional coordinate by the object based on the calculated interior orientation element and the relative orientation element in order to measure the deflection of the point where each camera is installed; and a process of correcting the cumulative error of the measured deflection.

Description

Structure displacement measuring system and method {SYSTEM AND METHOD FOR MEASURING DEFORMATION STRUCTURE}

The present invention relates to displacement measurement of a large structure by arranging stereo cameras in a row.

Civil or architectural structures are exposed to external loads such as traffic, earthquakes, gusts, Therefore, reasonable and precise design construction is also important for civil engineering or building construction, but proper maintenance work is very important to maintain the usability of the structure and to prolong the life of the structure. Recently, the importance of structural safety diagnosis system has increased as the number of large structures such as high-rise buildings and long bridges has increased. Such a structural safety diagnosis system can improve the stability of the structure by measuring, analyzing and diagnosing the dynamic behavior of the structures such as bridges and buildings. The structure safety diagnosis system requires many techniques such as structure damage identification method, data acquisition and transmission method, and the like.

These structural safety diagnosis systems use inclinometers, acceleration sensors, strain gauges, and PZT sensors to measure structural displacements. Although the measurement of displacement is very important, much research has not been done due to the difficulty of accessing the huge size of the structure. One of the most commonly used methods of structural displacement measurement is the use of contact-type sensors that require a linear variable differential transformer (LVDT) and a stable reference point at the bottom.

However, these sensors do not monitor the entire large structure due to the high price, and only the displacements of the structures are measured.

On the other hand, in order to improve the precision of measurement of displacement of a large structure, a method of enlarging an image through adjustment of a focal length of a camera is generally used. However, if the shooting distance is excessively large, the cost of the camera lens exponentially increases, so there is a limitation in securing accuracy through the camera focal distance.

Especially, in the case of a large structure, there are many problems in securing proper shooting distance. For example, in the case of a super-long bridge, the distance between the main mirror and the camera is several hundred meters to several kilometers.

In order to solve this problem, Pqrk et al. (2010) proposed a method of detecting the displacement of a skyscraper through linear array of cameras. They used the target geometry of Lee and Shinozoka (2006) And an algorithm for detecting the displacement through the number of moving pixels. In this proposal, it is assumed that the motion vector and the scale vector are kept constant when the displacement is detected through the change of the pixel value in the x direction and the pixel value in the y direction of the target. However, this assumption implies many errors. As the pixel usage range and the shooting range increase, the displacement calculation value shows the difference from the actual displacement. This indicates that the scale vector and the motion vector are not kept constant under any circumstances. It is dangerous to regard the displacement calculation value as an actual displacement as it is through this assumption, and it is difficult to obtain accuracy in displacement measurement.

Therefore, in the present invention, the stereo cameras are arranged in line at predetermined intervals for each predetermined point of the structure, and a target for displacement measurement is installed on the rear surface of each camera, so that targets of adjacent cameras that take precedence in a specific direction are preset. Taking a picture of each cycle, and measuring the displacement change of the installed point for each camera through the change of the photographed image, and using the adjacent camera and relative displacement for each camera to measure the final displacement of the structure with improved accuracy and accuracy To provide.

According to one aspect of the present invention, in the structure displacement measuring method, the process of photographing the object of the adjacent camera to take precedence in a specific direction from each camera installed at a predetermined interval for each predetermined point of the structure by a predetermined period, each of the cameras A process of surveying a reference point for orientation of an image acquired through star shooting, a process of calculating an internal expression element and a relative expression element of the image at which the reference point is surveyed, and an absolute expression through the measured reference point And calculating a three-dimensional coordinate for each object based on the calculated internal expression element and relative expression element to measure displacement of installed points for each camera, and correcting cumulative error of the measured displacement. It is characterized by.

According to another aspect of the present invention, in the structure displacement measurement system, a plurality of cameras that are installed at predetermined intervals for each predetermined point of the structure and photographs objects of adjacent cameras that take precedence in a specific direction at predetermined intervals, and through a network Collecting captured image information from each of the connected cameras, identify the plurality of cameras to match and manage the image information collected from the cameras, and by measuring the reference point for the orientation of the collected image for each camera, the internal expression Calculates an element and a relative expression element, performs absolute expression through the measured reference point, calculates three-dimensional coordinates for each object, measures displacement of installed points for each camera, and calculates a cumulative error of the installed points for each camera. And a control server for calibrating.

The present invention is more economical than the measurement using an expensive sensor, and it is also possible to photograph a target attached to a preceding camera in a predetermined cycle by arranging a plurality of cameras in a line, So that the accuracy and precision of the displacement measurement can be improved.

1 is a schematic configuration diagram of an entire system for measuring structure displacement according to an embodiment of the present invention.
2 is an overall flowchart of a structure displacement measuring method according to an embodiment of the present invention.
3 is a plan view of a stereo camera according to an embodiment of the present invention.
Figure 4 is an exemplary view showing a point-by-point definition in the structure displacement measurement according to an embodiment of the present invention.
5 is a detailed block diagram of a control server in a structure displacement measuring system according to an exemplary embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be appreciated that those skilled in the art will readily observe that certain changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. To those of ordinary skill in the art.

The present invention is to measure the displacement of the structure, more specifically, the stereo cameras are arranged in a line at a predetermined interval for each predetermined point of the structure, by installing a target (target) for displacement measurement on the rear of each camera, Shooting targets of adjacent cameras that take precedence in a specific direction for each predetermined period, measuring displacement variation of installed points for each camera through the change of the photographed image, and using the adjacent cameras and relative displacements of the respective cameras. By measuring the final displacement of the camera, it is not only more economical than the measurement by the expensive sensor, but also a plurality of cameras are arranged in a line to photograph the targets attached to the preceding cameras at predetermined intervals. Adaptive adjustment according to characteristics improves the accuracy and accuracy of displacement measurement I want to provide alcohol.

The displacement measurement technique to which the present invention is applied is applicable to both maintenance and safety diagnosis of large structures including civil engineering and building structures. In the following description of the present invention, .

First, a structure displacement measuring system according to an embodiment of the present invention will be described with reference to FIG. 1.

1 is a schematic configuration diagram of an entire system for measuring structure displacement according to an embodiment of the present invention.

Referring to FIG. 1, the system 100 to which the present invention is applied includes a bridge structure 110, a plurality of cameras 0 to N-1, and a control server 114.

The bridge structure 110 includes a plurality of cameras for displacement measurement in a girder between at least two bridge piers, and the plurality of cameras 0 to N-1 may have at least two cameras in a fixed frame. It is fixed to form a pair, and a target, which is a target of photographing for displacement measurement, is attached to the rear of each camera, and is photographed by a neighboring camera trailing in a specific direction, that is, left or right.

In addition, the control server 114 interworks with a plurality of cameras (0 to N-1) through a network to match events generated in the camera, for example, image information photographed every predetermined period and camera identification information , Management and control.

The control server 114 may be a digital broadcasting terminal, a personal digital assistant (PDA), a smart phone, a tablet PC, an iPad, a 3G terminal, for example, an IMT- (UMTS) terminal, a Wideband Code Division Multiple Access (WCDMA) terminal, a GSM / GPRS (Universal Mobile Telecommunication Service) terminal and a UMTS (Universal Mobile Telecommunication Service) And the like. However, it will be apparent to those skilled in the art that the configuration according to the embodiments described herein may be applied to a fixed terminal such as a desktop computer.

Hereinafter, a structure displacement measuring method according to an embodiment of the present invention will be described with reference to FIG. 2.

2 is an overall flowchart of a structure displacement measurement method according to an embodiment of the present invention. Referring to FIG. 2, in step 210, an object of an adjacent camera having a specific direction, for example, a left or a right priority, is photographed by each camera installed at predetermined intervals for each predetermined point of a structure by a preset period.

That is, each camera is arranged in a line at a predetermined point of the structure to shoot the object of the back of the camera, for example, the target for displacement measurement in a predetermined period of the left or right in the reference direction, as shown in FIG. As described above, the camera to which the present invention is applied is fixed to at least two or more frames in a frame (not shown) to form a pair ((1, 2), (3, 4), (5, 6)), and the object is camera-specific. ((1, 2), (3, 4), (5, 6)) It is attached to the rear surface means the shooting targets (30, 31, 32) for displacement measurement.

In step 212, the reference point for the orientation of the image acquired through the camera-specific photographing is surveyed, and in step 214, an internal orientation element and a relative orientation element of the image in which the reference point is measured. To calculate.

The internal facial expression element calculation is performed by correcting the distortion generated through the image capturing and converting the coordinate of the photographed object into a coordinate system having the camera projection center as an origin. You can adjust the exact reference point and focal length of the camera lens through the internal representation of the object's coordinates as input.

The relative facial expression element calculation is performed by setting a relative inclination relation between a pair of cameras and discarding the difference through matching with a point determined as the same point in an overlapping area with respect to the photographed object. You can adjust the position of the right and left camera and the coordinate relation when shooting stereo.

In order to calculate the relative expression element, at least five reference points are required for the object to be photographed.

In operation 216, an absolute orientation is performed through the reference point measured in operation 212.

Here, the absolute expression is to convert the displacement calculated through the three-dimensional relative coordinates obtained on the basis of the internal and relative expression elements calculated in step 214 to the actual displacement, the displacement obtained through the relative coordinates is the actual displacement is Because it is not displacement in relative coordinates, it is performed by correcting the tilt and accumulation in the captured image because of the need for the actual conversion process.

Thereafter, in step 218, the three-dimensional coordinates for each object are calculated based on the calculated internal expression elements and relative expression elements, and in step 220, the displacements of the installed points of the cameras are measured. It is performed by recognizing the displacement change amount of the point where the corresponding camera is installed through the acquired image, and the final displacement of the structure through the relative displacement with the neighboring camera that takes precedence in the specific direction.

In step 222, the cumulative error of the measured displacement is corrected.

In this case, the cumulative error correction may be performed by minimizing the measured relative displacement of the object n with respect to the object n-1 and the final determination value of the object n displacement with respect to the object n-1 by using the least square method. In order to perform the following equation (4).

Prior to the description of Equation 4, in the case of the displacement measurement through the camera alignment in the system to which the present invention is applied, a cumulative error may occur because of the final displacement amount through the relative displacement measurement, and the displacement may be zero due to the accumulated error. Since the final displacement of the point assumed may not be zero, the least square method can be used to cancel the cumulative error, and the least square method is used to minimize the error caused by minimizing the deviation between the observed value and the theoretically assumed expected value. To calibrate.

The principle of such cumulative error correction is as follows.

Suppose that n = 1, 2, 3, ..., N.

If the displacement of the first point Target 0 is assumed to be 0, the displacement of each point may be defined as shown in FIG. 4.

In addition, the displacement may be expressed as in Equation 2 below.

가 된다.Where

.

Since there is an error in the relative displacement measurement, the final decision value is the measurement value plus the residual.

Therefore, it can be expressed as Equation 3 below.

의 차가 최소가 되어야하기 때문에 하기의 수학식 4와 같이 수행할 수 있다.And, to correct the error by the first-square method mentioned above

Since the difference must be minimum, it can be performed as in Equation 4 below.

이기 때문에 S를 하기의 수학식 5와 같이 표현할 수 있다.Also,

Therefore, S can be expressed as shown in Equation 5 below.

In order to minimize the cumulative error, S should be the minimum value.

Therefore, Equation 6 below.

Therefore, the actual relative displacement is as shown in Equation 7 below.

Generalizing Equation 7 is as follows.

In the above, the structure displacement measuring method according to an exemplary embodiment of the present invention has been described.

Hereinafter, a configuration of a control server in a structure displacement measuring system according to an exemplary embodiment of the present invention will be described with reference to FIG. 5.

5 is a detailed block diagram of a control server in a structure displacement measuring system according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the control server 500 to which the present invention is applied includes an image collector 510, a storage 512, and a controller 514.

Under the control of the control unit 514, the image collecting unit 510 is installed at predetermined intervals for each predetermined point of the structure, and photographs a plurality of cameras 51 and 52 for photographing objects of adjacent cameras that take precedence in a specific direction at predetermined intervals. , 53).

The storage unit 512 identifies and manages a plurality of images output from the image collection unit 510 for each camera under the control of the controller 514 to match and store the collected image information.

The control unit 514 includes a reference point measurement unit 516, a calculation unit 518, a displacement measurement unit 524, and a cumulative error correction unit 526, which are collected for each camera through the reference point measurement unit 516. The reference point for the expression of the image (orientation) is measured and output, after calculating the internal expression element and the relative expression element through the internal expression 520 and the relative expression 522 of the calculation unit 518, the measured reference point After performing the absolute expression through the absolute expression 523 using the output to the displacement measuring unit 524.

In this case, the internal facial expression element calculation is obtained by correcting the distortion generated through the image capturing and converting the coordinate of the photographed object into a coordinate system having the camera projection center as the origin, A relative inclination relation between a pair of cameras is set so as to obtain differences by eliminating the difference through matching with respect to a point judged to be the same point in an overlapping area with respect to the photographed object.

Further, the absolute facial expression is obtained by transforming the displacement calculated through the three-dimensional relative coordinate obtained based on the calculated inner facial element and the relative facial expression element into the actual displacement.

The displacement measuring unit 524 calculates the three-dimensional coordinates for each object to measure the displacement of the installed point for each camera, and corrects this in the cumulative error correction unit 526.

As described above, the operation of the structure displacement measuring system and method according to the present invention can be made. Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications can be made without departing from the scope of the present invention. have. Accordingly, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by equivalents of the claims and the claims.

510: image collecting unit 512: storage unit
514: control unit 516: reference point surveying unit
518: calculation unit 512: displacement measuring unit

Claims (12)

In the structure displacement measuring method,
Photographing objects of adjacent cameras that take precedence in a specific direction in each camera installed at predetermined intervals for each predetermined point of the structure at predetermined intervals;
Surveying a reference point for orientation of an image obtained by photographing each camera;
Calculating an internal expression element and a relative expression element of the image at which the reference point is measured;
Performing absolute expression through the measured reference point, calculating three-dimensional coordinates for each object based on the calculated internal expression element and relative expression element, and measuring displacement of installed points for each camera;
The structure displacement measuring method comprising the step of correcting the cumulative error of the measured displacement. The method according to claim 1,
And correcting the distortion generated by the image capturing, and converting the coordinates of the photographed object into a coordinate system having the camera projection center as the origin. 2. The method according to claim 1,
And setting a relative inclination relationship between a pair of cameras and canceling the difference by matching a point determined to be the same point in a region overlapping the photographed object. 2. The method according to claim 1,
And a displacement calculated through the three-dimensional relative coordinates obtained based on the calculated internal and relative expression elements. The method of claim 1, wherein the correcting of the cumulative error comprises:
In order to minimize the measured relative displacement of object n with respect to object n-1 and the final determinant of object n displacement with respect to object n-1, using the least square method, the following equation is performed. Characterized in the structure displacement measurement method.

The method of claim 1,
The camera is a structure displacement measuring method, characterized in that at least two or more cameras are fixed to the frame to form a pair, the object is attached to the rear of each camera is a shooting target for displacement measurement. The method of claim 1, wherein the step of measuring the displacement comprises:
Recognizing a displacement change amount at a point where the camera is installed through the image obtained by the predetermined period;
And recognizing a final displacement of the structure through a relative displacement with a neighboring camera preferentially in the specific direction. A system for measuring displacement displacement,
A plurality of cameras installed at predetermined intervals for each predetermined point of the structure and photographing objects of adjacent cameras that take precedence in a specific direction at predetermined intervals;
Collecting photographing image information from each camera connected through a network, identifying the plurality of cameras, matching and managing image information collected from the corresponding cameras, and surveying reference points for orientation of the collected images for each camera. Calculate an internal expression element and a relative expression element, perform absolute expression through the measured reference point, calculate three-dimensional coordinates for each object, measure displacement of installed points for each camera, and measure Structure displacement measuring system comprising a control server for correcting the cumulative error. 9. The control server according to claim 8,
In order to minimize the final relative value of the measured relative displacement of the object n with respect to the object n-1 and the object n displacement with respect to the object n-1 to cancel the cumulative error using the least square method in correcting the cumulative error, Structure displacement measuring system, characterized in that to perform the equation.

9. The method according to claim 8,
And correcting the distortion generated by the image capturing and converting the coordinates of the photographed object into a coordinate system having the camera projection center as the origin. The method of claim 8, wherein the relative expression factor calculation,
And setting a relative inclination relationship between a pair of cameras to cancel the difference by matching a point determined to be the same point in a region overlapping the photographed object. The method of claim 8, wherein the absolute expression,
Structure displacement measurement system, characterized in that obtained by converting the displacement calculated through the three-dimensional relative coordinates obtained on the basis of the calculated internal expression element and relative expression element to the actual displacement.

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