CN111351436A - Method for verifying precision of structural plane displacement vision measurement system - Google Patents
Method for verifying precision of structural plane displacement vision measurement system Download PDFInfo
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- CN111351436A CN111351436A CN202010151832.9A CN202010151832A CN111351436A CN 111351436 A CN111351436 A CN 111351436A CN 202010151832 A CN202010151832 A CN 202010151832A CN 111351436 A CN111351436 A CN 111351436A
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
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Abstract
The invention provides a method for verifying the precision of a structural plane displacement vision measurement system, and belongs to the technical field of optical measurement and civil engineering monitoring. Firstly, simulating and generating a series of images of positions of a plurality of measured targets at different moments in a plane according to the resolution of an electronic display screen by adopting drawing software in an arbitrary preset form, and simulating the adverse conditions of partial shielding of the measured targets according to requirements; then simulating illumination intensity change as required, and processing the images; and then making the image meeting the conditions into a non-compressed video file with a specified frame rate, finally outputting the non-compressed video file to an electronic display screen for full-screen playing, and simultaneously adopting a measuring system to perform tracking measurement calculation on a measuring target. The real displacement of all the measured targets at each moment can be very accurately calculated according to the preset motion parameters and the related parameters of the electronic display screen, so that quantitative error analysis can be carried out on the measurement result of each frame of the measurement system. The whole verification system is economical, simple, convenient, efficient and practical.
Description
Technical Field
The invention relates to a method for verifying the precision of a structural plane displacement vision measurement system, and belongs to the technical field of optical measurement and civil engineering monitoring.
Background
With the continuous development of computer vision technology and image acquisition equipment, the civil engineering structure dynamic displacement measurement method based on vision is more and more widely applied due to the advantages of long distance, non-contact, high precision and the like. The accuracy of the measurement system is affected by a variety of factors and needs to be verified before being applied to engineering practice. In the past, the measurement result of a linear variable differential transformer or a laser displacement sensor is generally used as an accurate value or a target value to verify the measurement accuracy of a measurement system. The prior method mainly has the following problems: (1) although the measurement result of the linear variable differential transformer or the laser displacement sensor has high precision, the measurement error is inevitable; (2) due to the fact that trigger signals are asynchronous or sampling of instruments is unstable, phase differences exist between the linear variable differential transformer or the laser displacement sensor and the measurement system, quantitative analysis is difficult to be carried out on each frame of result errors of the measurement system, and the root mean square error or the normalized root mean square error is mostly adopted to represent the whole errors of measurement; (3) the linear variable differential transformer or the laser displacement sensor is more convenient to measure one-dimensional motion, if the two-dimensional motion is measured, two sensors are needed, the operation is more complicated, and the economic cost is increased; (4) for the simulation of some unfavorable measurement conditions (such as illumination change and partial shielding of a target), other complicated steps (such as adjusting light and shade change of light or artificially shielding of the measured target) are also needed; (5) the linear variable differential transformer and the laser displacement sensor are expensive, complex to install, labor-consuming and time-consuming.
Disclosure of Invention
The invention aims to solve the technical problem of providing a novel economic, simple, convenient, efficient and practical verification method aiming at the defects of the existing video measurement system precision verification technology.
The technical scheme of the invention is as follows:
a method for verifying the precision of a structural plane displacement vision measurement system comprises the following steps:
(1) the method comprises the steps of drawing a rectangular frame with the size of m × n in proper drawing software (such as AutoCAD, Photoshop and the like) according to the resolution of an electronic display screen (such as a computer monitor, a television, an LED board and the like) of m × n, drawing a plurality of two-dimensional graphs with specified shapes and sizes in the rectangular frame as a measured object according to needs, outputting the measured object in the range of the rectangular frame as an image according to the proportion of 1:1 pixels, drawing new positions of the measured object in the rectangular frame according to preset motion parameters of each measured object, outputting a new image, forming a plurality of images which reflect different displacements of the measured object at different moments, namely different positions according to the method, cutting part of the measured object in order to simulate the shielded situation of the measured object, changing the shape of the measured object in such a way, conveniently processing related measured objects according to specified positions by related software according to the linear or non-linear change of simulated illumination intensity, and manufacturing a corresponding display frequency of the acquired and discrete pixels of the measured object in a full-screen display screen into a continuous dynamic display frame display frequency display screen.
(2) Determination of the true "dynamic displacement": the coordinate position difference, i.e. the relative displacement, between the measured objects in any two frames of images on the electronic display screen can be calculated by the coordinate difference of the measured objects in the drawing software (determined before drawing) and the pixel size on the electronic display screen. In other words, the real 'dynamic displacement' of all the measured targets at any moment can be accurately determined.
(3) And (3) verifying the precision of the measurement system: and (3) when the dynamic displacement is played, simultaneously adopting a measuring system to track and measure, further calculating the dynamic displacement of the measured target at any moment according to a specific method, comparing the measured and calculated result with the real result in the step (2), and verifying and evaluating the measuring precision of the measuring system at each moment and in the whole process according to the deviation of the measured and calculated result and the real result.
The invention has the beneficial effects that: the invention adopts common drawing software to simulate and generate a plurality of measured targets in a plane according to the motion tracks in any preset form, and the motion tracks are manufactured into video files with specified frame rates and output to an electronic display screen for full-screen playing. The real displacement of all targets at each moment can be calculated very accurately (the only error is derived from the pixel precision on the electronic display screen and obviously can be ignored) according to the preset motion parameters and the related parameters on the electronic display screen, so that the quantitative error analysis can be carried out on the measurement result of each frame of the measurement system. The whole verification system only needs a computer and an electronic display screen, not only can conveniently simulate the change condition of the field illumination intensity and the adverse condition that the detected target is partially shielded, but also can provide an accurate reference result, so that the invention has very important engineering practical value.
Drawings
Fig. 1 is a schematic video of a plurality of two-dimensional measured objects moving in a plane generated by simulation according to the present invention. The video simulates the movement positions of 15 detected targets (solid circles) at different moments under the conditions of illumination intensity change and partial shielding of the targets, wherein F1 and … F9 are video frame numbers.
Detailed Description
The following detailed description of the embodiments of the invention is provided in connection with the accompanying drawings.
As shown in fig. 1, a method for verifying the accuracy of a structure plane displacement vision measurement system comprises the following steps:
(1) the resolution of the electronic display screen is m × n, the pixel size is e, a rectangular frame with the size of m × n is selected in drawing software, a plurality of (in this example, 15) solid circles with the specified diameter (in this example, 50 pixels) are drawn at equal intervals in the middle of the rectangular frame to serve as a measured object, and the measured object in the range of the rectangular frame outputs a first frame image according to the proportion of 1:1 pixels.
(2) And (3) drawing all the measured objects at different moments at corresponding positions in the rectangular frame according to the specified relative displacement of each measured object, and outputting a series of new images (9 frames are exemplified in the figure) according to the step (1). In order to simulate the situation that the measured target is blocked, the shape of the measured target can be cut. In order to simulate the illumination intensity variation condition, the image can be conveniently processed, such as programming by C + + and calling corresponding functions in OpenCV library.
(3) And (3) making an image sequence (such as C + + programming and calling a VideoWriter in an OpenCV library) into a non-compressed video file with a frame rate of f (not more than the refresh frequency of the electronic display screen), outputting the non-compressed video file to the electronic display screen for full-screen playing, and simultaneously tracking and measuring by using a measuring system.
(4) And calculating the dynamic displacement of the measured target at any moment based on the measurement result, comparing the measurement result with the real result, and evaluating the precision of the measurement system according to the deviation.
Claims (3)
1. A method for verifying the precision of a structural plane displacement vision measurement system is characterized by comprising the following steps:
(1) the method comprises the steps of simulating the dynamic displacement of a measured object in a two-dimensional plane, drawing a rectangular frame with the size of m × n according to the resolution of an electronic display screen of m × n, drawing a plurality of two-dimensional figures with specified shapes and sizes in the rectangular frame as the measured object, outputting the measured object in the range of the rectangular frame as an image according to the 1:1 pixel proportion, drawing new positions of the measured object in the rectangular frame according to preset motion parameters of the measured object, outputting a new image, forming a plurality of images reflecting different displacements of the measured object at a plurality of moments, namely different positions, manufacturing an image sequence into an uncompressed video file with a specified frame rate, playing the uncompressed video file on the electronic display screen in a full screen, and simulating the dynamic displacement in the two-dimensional plane of the measured object, wherein the dynamic displacement refers to the discrete jump and discontinuous displacement of the measured object between two adjacent frames of images;
(2) determination of the true "dynamic displacement": the coordinate position difference, namely the relative displacement, between the measured targets in any two frames of images on the electronic display screen can be accurately calculated by the coordinate difference of the measured targets and the pixel size on the electronic display screen;
(3) and (3) verifying the precision of the measurement system: and (3) when the dynamic displacement is played, simultaneously adopting a measuring system to track and measure, further calculating the dynamic displacement of the measured target at any moment, comparing the measured and calculated result with the real result in the step (2), and verifying and evaluating the measuring precision of each moment and the whole process of the measuring system according to the deviation of the measured and calculated result and the real result.
2. The method for verifying the accuracy of a structural plane displacement vision measuring system of claim 1, wherein the condition that the measured object is blocked is simulated, and the shape of the measured object is changed by cutting part of the measured object; and simulating the change condition of the light intensity of the detected target by processing the image brightness.
3. The method for verifying the accuracy of a structure plane displacement vision measuring system of claim 1 or 2, wherein the shape, size and number of the measured objects can be selected at will; the dynamic displacement form can also be set at will; the output dynamic displacement has no error, and other equipment is not required to acquire the displacement as a reference for verifying the precision of the measuring system.
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