CN106124034A - Thin-wall part operation mode based on machine vision test device and method of testing - Google Patents

Thin-wall part operation mode based on machine vision test device and method of testing Download PDF

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CN106124034A
CN106124034A CN201610807568.3A CN201610807568A CN106124034A CN 106124034 A CN106124034 A CN 106124034A CN 201610807568 A CN201610807568 A CN 201610807568A CN 106124034 A CN106124034 A CN 106124034A
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thin
wall part
industrial camera
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measured
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CN106124034B (en
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伍济钢
蒋勉
袁继广
张双健
王刚
石海波
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Hunan University of Science and Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01HMEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H9/00Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means

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Abstract

The present invention relates to a kind of thin-wall part operation mode based on machine vision test device and method of testing, thin-wall part operation mode based on the machine vision test device of the present invention includes industrial camera, light source, image collecting device and image processing apparatus;Described industrial camera and light source are placed in the front of thin-wall part to be measured, and the camera lens of industrial camera is towards the leading flank of thin-wall part to be measured, and the leading flank of thin-wall part to be measured is provided with multiple retroreflective feature point;Described industrial camera is connected with image capturing system by data wire;Image collecting device is connected with image processing apparatus.Thin-wall part operation mode based on the machine vision test apparatus structure of the present invention is flexible, need not the debugging process of complexity, low to surface of thin-walled parts prescription, and achieve non-cpntact measurement, do not change the vibration characteristics of thin-wall part to be measured, the operational modal parameter of thin-wall part, certainty of measurement and efficiency advantages of higher can be accurately measured.

Description

Thin-wall part operation mode based on machine vision test device and method of testing
Technical field
The present invention relates to a kind of thin-wall part operation mode based on machine vision test device and method of testing.
Background technology
Thin-wall part, due to lightweight, structure efficiency advantages of higher, is widely used the most in the industrial production.But Owing to the wall thickness of thin-wall part is the least relative to overall dimensions, and general rigidity is little, area big, so transporting in mechanical system It is easy to during row vibrate, thus causes the interference between mechanical part, send vibration noise, or long-term at machinery Motion in cause mechanical breakdown, excessive vibration even can cause destructive accident, therefore thin-wall part must be carried out mould State is tested.
Mode is the natural vibration characteristic of frame for movement, and each mode has specific natural frequency, a damping ratio With Mode Shape etc..These modal parameters can be by calculating or experimental analysis acquirement, such a calculating or analysis of experiments process It is referred to as model analysis.This analysis process if being obtained by finite element method, the most referred to as computational modal analysis;If Modal parameter is determined, referred to as experimental modal analysis by test acquisition system input and structure output;Cannot utilize for those The measurand of artificial excitation or Unknown worm excitation size cannot be carried out experimental modal test, and referred to as operation mode divides Analysis.Experimental modal test is use manual type excitation free state in the more satisfactory working environment of laboratory tested right As, carry out Modal Parameter Identification with the activation sequence of the structural response collected and input for analysis foundation and then obtain mode ginseng Number.Mainly sensed by acceleration touch sensor or use this contactless vibration-testing of laser doppler vialog Device measures.Experimental modal method of testing is primarily present the limitation of two aspects, and one requires that measurand is freely State, it two must be known input stimulus.Artificial excitation cannot be utilized for those or excitation size cannot be recorded Measurand cannot be carried out experimental modal test, is necessary for being operated model analysis, and the advantage of this method is to have only to obtain Taking output response data, it is not necessary to know input stimulus data, the vibration data collected derives from the work of structure actual vibration Make environment, test result more meet reality boundary condition, more can reflect structure dynamic characteristic under actual operating conditions, Have more engineering actual reference.
The method that acceleration transducer can also be used to be attached to object under test surface carries out the measurement of object mode, but by In the feature that thin-wall part self lightweight wall is thin so that the method is difficult to that thin-wall part carries out a high-precision mode and measures.Separately Outward, the mode for some labyrinth thin-wall parts is measured, and the spatial density of test may be had higher requirement, for terrible To a high-resolution measurement result of the whole audience, it usually needs measure the Vibration Condition of multiple spot, thus must be at body surface Arrange substantial amounts of sensor, and touch sensor is difficulty with the work of this respect.
Along with the development of laser doppler vibration measuring technology, this contactless vibration-testing of laser doppler vialog senses Device has gradually been applied in the mode measurement of thin-wall part, solves sensor and thin-wall member produces the problem of additional mass, But vibration measurement with laser early stage debugging alignment complexity, adds debugging time and difficulty;And higher to testee surface quality requirements, In addition, also have some whole-field optically vibration measurement methods to can be applicable to the mould measurement of thin-wall part, as speckle-shearing deformation, Electronic speckle mode-interference and holographic interference etc., although these methods have a good whole audience vibration measurement characteristic, but generally individually Using laser as light source, light path is extremely complex, and measurement result is easily affected by extraneous vibration, is only used for possessing vibration isolation table Scientific research measurement is carried out, it is difficult to meet the demand of operation mode test in laboratory.
In sum, the existing operation mode method of testing about thin-wall part can not meet the demand in market, at this In the case of Zhong, for the operation mode test problem of thin-wall part, it is badly in need of one and will not increase additional mass, space to measured workpiece High, the easy to operate method for fast measuring of resolution meets the needs of industrial development.
Summary of the invention
In order to solve above-mentioned technical problem, the present invention provide a kind of flexible for installation, debugging easily, measure the base of efficiently and accurately Thin-wall part operation mode in machine vision tests device and method of testing, it is achieved that to the noncontact of thin-wall part operation mode, High-acruracy survey.
Technical scheme is as follows: a kind of thin-wall part operation mode based on machine vision test device, including work Industry camera, light source, image collecting device and image processing apparatus;Before described industrial camera and light source are placed in thin-wall part to be measured Side, the camera lens of industrial camera is provided with multiple retroreflective feature towards the leading flank of thin-wall part to be measured, the leading flank of thin-wall part to be measured Point;Described industrial camera is connected with image capturing system by data wire;Image collecting device is connected with image processing apparatus.
In above-mentioned thin-wall part operation mode based on machine vision test device, described industrial camera passes through spider It is fixed on the dead ahead of thin-wall part to be measured.
In above-mentioned thin-wall part operation mode based on machine vision test device, described industrial camera uses CCD industrial camera;Described light source uses LED light source.
In above-mentioned thin-wall part operation mode based on machine vision test device, spiral shell is passed through in one end of described thin-wall part Bolt is fixed on base.
A kind of thin-wall part operation mode method of testing based on machine vision, comprises the steps:
1st step: ask for the relative pose relation of industrial camera and thin-wall part to be measured, and the principal point coordinate to industrial camera (u0,v0), the equivalent focal length a of horizontal directionx, the equivalent focal length a of vertical directiony, distortion parameter γ demarcates;
2nd step: utilize power to hammer hammering thin-wall part to be measured into shape, utilize the full sequence figure of industrial camera this process of continuous acquisition Picture, is sent to image processing apparatus by image collecting device, carries out sequence specific primers-polymerase chain reaction, extracts each retroreflective feature point Vibration signal in units of pixel, according to the 1st step model and be translated into the vibration signal of effective unit;
3rd step: use stochastic subspace identification method to carry out mode the vibration information of the multiple retroreflective feature points extracted Parameter identification, obtains the operational modal parameter of thin-wall part to be measured.
The present invention compared with prior art, has the advantages that
(1) thin-wall part operation mode based on the machine vision test device of the present invention, utilizes machine vision metrology technology The displacement of the retroreflective feature point on tracking thin-wall part, the vibration information of multiple spot on available thin-wall part, and can be to the vibration of multiple spot Information carries out Synchronization Analysis, and then available operational modal parameter, and it is high that the present invention has spatial resolution, and efficiently and accurately etc. is excellent Point.
(2) the thin-wall part operation mode method of testing based on machine vision of the present invention does not affect the vibration spy of thin-wall part Property, flexible structure, easy to operate;When solving laser scanning vibration measuring, debugging alignment complexity, high to surface of thin-walled parts prescription Problem;And achieve non-cpntact measurement, do not change the vibration characteristics of thin-wall part to be measured, the work of thin-wall part can be accurately measured Modal parameter,
Accompanying drawing explanation
Fig. 1 is the structural representation of thin-wall part operation mode based on the machine vision test device of the present invention.
Fig. 2 is the retroreflective feature point of present invention layout drawing on thin-wall part to be measured.
Fig. 3 is the outline dimensional drawing of the thin-wall part to be measured of the present invention.
Fig. 4 is the workflow diagram of the sequence specific primers-polymerase chain reaction of the present invention.
Fig. 5 is the program flow diagram of the image filtering denoising of the present invention.
Fig. 6 is the stochastic subspace identification method flow diagram of the present invention.
Fig. 7 is the first-order modal vibration shape of thin walled beam based on ANSYS finite element simulation.
Fig. 8 is the second-order modal vibration shape of thin walled beam based on ANSYS finite element simulation.
Fig. 9 is the one of the thin walled beam obtained according to the thin-wall part operation mode method of testing based on machine vision of the present invention Order mode state bending vibation mode picture.
Figure 10 is the thin walled beam obtained according to the thin-wall part operation mode method of testing based on machine vision of the present invention Second-order modal bending vibation mode picture.
Detailed description of the invention
The present invention is further illustrated below in conjunction with the accompanying drawings.
As it is shown in figure 1, the present invention thin-wall part operation mode based on machine vision test device, including tripod 1, At CCD industrial camera 2, LED light source 3, retroreflective feature point 4, thin-wall part to be measured 5, firm banking 6, image collecting device 7 and image Reason device 8.One end of thin-wall part 5 to be measured is fixed on base 6 by two bolts, and the other end is in free vacant state. As in figure 2 it is shown, be equidistantly provided with multiple retroreflective feature point 4, retroreflective feature point 4 on the centrage of the leading flank of thin-wall part 5 to be measured Using laser printing patch, laser printing, according to needing setting flexibly, is attached to be measured thin by retroreflective feature point 4 quantity before using On center line before wall pieces 5.CCD industrial camera 2 is horizontally fixed on the dead ahead of thin-wall part 5 to be measured, CCD work by spider 1 The camera lens of industry camera 2 is towards the leading flank of thin-wall part 5 to be measured;And it is connected to image collecting device 7, image acquisition by data wire Device 7 is connected with image processing apparatus 8, and LED light source 3 is arranged on the front of thin-wall part 5 to be measured, is positioned at CCD industrial camera 2 left Side.
Utilize the thin-wall part work based on machine vision of above-mentioned thin-wall part operation mode based on machine vision test device Make mode testing method, comprise the steps:
1st step: ask for the relative pose relation of CCD industrial camera 2 and thin-wall part 5 to be measured, and to CCD industrial camera 2 Principal point coordinate (u0,v0), the equivalent focal length a of horizontal directionx, the equivalent focal length a of vertical directiony, distortion parameter γ demarcates.
(1.1) CCD industrial camera 2 imaging process essence is the conversion process between several coordinate system, including world coordinates Being tied to the rigid body translation of camera coordinates system, CCD industrial camera 2 coordinate is tied to perspective transform and the image coordinate of image coordinate system Being tied to the conversion of image pixel coordinates system, its mathematical model is as follows:
z c u v 1 = 1 d x α u 0 0 1 d y v 0 0 0 1 · f 0 0 0 0 f 0 0 0 0 1 0 · R T 0 T 1 · X w p Y w p Z w p 1 = a x γ u 0 0 0 a y v 0 0 0 0 1 0 · R T 0 T 1 · X w p Y w p Z w p 1 = M 1 M 2 X w p Y w p Z w p 1 = M X w p Y w p Z w p 1 ... ( 1 )
In formula (1): f is the focal length of industrial camera;axFor the equivalent focal length on u axle;ayFor the equivalent focal length on v axle;(u0, v0) it is the principal point coordinate of image, distortion factor γ=f α, α are camera distortion characterising parameters, are obtained by camera calibration;When During γ=0, pixel planes is rectangle, and when γ ≠ 0, pixel planes is not rectangle;(Xc,Yc,Zc)、(Xwp,Ywp,Zwp) be respectively Coordinate under camera coordinates system and world coordinate system, R is the orthogonal spin matrix of unit of 3 × 3, and T is the translation matrix of 3 × 1, logical Cross camera calibration to obtain;M1It is 3 × 4 projection matrixes;M1For Intrinsic Matrix, by camera intrinsic parameter ax、ay、γ、u0、v0Determine; M2For outer parameter matrix, industrial camera determine relative to the outer parameter of world coordinate system.
(1.2) utilize CCD industrial camera 2 imaging model, use plane gridiron pattern scaling board to determine CCD industrial camera 2 Inside and outside parameter, in the field range of CCD industrial camera 2, gather 25 width gridiron pattern scaling board images of different positions and pose, to 25 Width uncalibrated image utilizes the program write to carry out focus extraction, and calibrated and calculated obtains intrinsic parameter and the distortion of CCD industrial camera 2 Parameter, by a wherein width scaling board with CCD industrial camera 2 relative pose relation as CCD industrial camera 2 and thin-wall part 5 to be measured Relative pose relation.
2nd step: firmly hammer hammering thin-wall part to be measured 5, wherein the input stimulus of power hammer is unknown, and thin-wall part 5 to be measured is in constraint Under the conditions of produce vibration, the full sequence image of CCD industrial camera 2 this process of continuous acquisition, transmitted by image collecting device 7 To image processing apparatus 8, carry out sequence specific primers-polymerase chain reaction, extract the vibration signal of each retroreflective feature point 4, according to the 1st step Model is also translated into the vibration signal of effective unit.
(2.1) according to the position of 12 retroreflective feature points 4 in the first two field picture and the peak swing of thin-wall part to be measured 5, Determine a maximum test zone ROI;In the present invention, only consider the Mode Shape of the level fluctuation of thin-wall part 5 to be measured, to be measured Thin-wall part 5 vertical direction vibrate, in the image of 640 × 480 pixels, thin-wall part 5 to be measured image width all the time In field range, when the pixel in picture altitude direction reaches some, when there is peak swing in thin-wall part 5 the most to be measured, It is further added by the pixel that processes to result substantially without affecting, but the whole calculating time can be increased.Therefore, on picture altitude direction Only process one part of pixel number, process the time with shortening.Therefore, can be manually interactive to the first two field picture of each sequence image Frame selects rectangular testing zone ROI, the width of test zone ROI to be picture traverse, and height is upper and lower peak swing, test zone ROI can be automatically used for ensuing all two field pictures after determining.
(2.2) use adaptive wavelet threshold denoising method that the image in test zone ROI is processed;
(2.3) grey linear transformation is used to strengthen the brightness of image the test zone ROI after filtering and noise reduction;In vibration During, owing to the sample rate of CCD industrial camera 2 is higher, time of exposure is short, uses common LED light source 3 to increase whole visual field Brightness, but due to thin-wall part 5 up-down vibration to be measured, may result in the uneven illumination of partial sequence image, cause follow-up point Cut incomplete, use grey linear transformation can improve the contrast of foreground and background, it is to avoid subsequent singulation is made mistakes.
(2.4) maximum between-cluster variance threshold segmentation method is used to extract the spot area of 12 retroreflective feature points;Maximum kind Between variance method be that image histogram is separated at a certain threshold value, calculate the variance between separate two groups, when variance reaches When being worth greatly, segmentation threshold is optimal threshold.Then utilize this threshold value that image is carried out segmentation and be converted into bianry image.
(2.5) use the spot area of the morphological method 12 retroreflective feature points to splitting to carry out morphology and close fortune Calculate.
(2.6) according to the size of retroreflective feature point facula area after above-mentioned process, choose suitably height area threshold, pick Remove other interference regions in image so that remaining bianry image only comprises the hot spot of retroreflective feature point, calculate each instead The center-of-mass coordinate of light characteristic point hot spot, and it is recorded as the preservation of measuring point pixel coordinate, the abscissa u in units of pixel and vertical coordinate v;The mathematical formulae extracting facula mass center is as follows:
u = Σ i = 1 M Σ j = 1 N i f ( i , j ) / Σ i = 1 M Σ j = 1 N f ( i , j ) v = Σ i = 1 M Σ j = 1 N j f ( i , j ) / Σ i = 1 M Σ j = 1 N f ( i , j ) ... ( 2 )
In formula (2): M, N represent that spot area has the pixel composition of M row N row;I represents the row at pixel place;J table Show the row at pixel place;F (i, j) be i-th row jth row pixel gray value.
(2.7) according to the sequence image order gathered, the vibration displacement signal of each retroreflective feature point 4 is extracted successively, And pixel unit is converted into the physical unit of reality by the model set up according to the 1st step, it is thus achieved that the reality of 12 retroreflective feature points 4 Vibration displacement signal.
3rd step: use stochastic subspace identification method can carry out mould the vibration information of the multiple retroreflective feature points extracted State parameter identification, obtains the operational modal parameter of thin-wall part 5 to be measured.
Experimental verification:
Utilize the thin-wall part operation mode method of testing based on machine vision of the present invention, be aluminum to material, a length of 777mm, wide 50mm, the operational vibration mode of the thin walled beam of thick 2mm tests, and CCD industrial camera 2 produces for IMI company Industrial camera, adjusts the distance of CCD industrial camera 2 and thin walled beam, makes the image of thin walled beam be positioned at whole visual field, record CCD Industrial camera, from thin walled beam about 2.4m, is connected with image collecting device 7 by data wire, and LED light source 3 is placed in left front, thin Wall beam one end is unsettled, and the other end is bolted on base 6, and the side surface midline of thin walled beam posts retroreflective feature point 4.
Being first turned on image collecting device 7 and set the parameter of CCD industrial camera 2, camera frame frequency is 200fps, during exposure Between be 900us, resolution is 640 × 480, and firmly hammer hammering thin walled beam, meanwhile, carries out sequential image acquisition, by gathered Data process at image processing apparatus 8, it is possible to obtain the operational modal parameter of thin walled beam.
According to the size of thin walled beam, utilize ANSYS software, the DM module in workbench directly establishes thin-walled The threedimensional model of beam, thin walled beam material is aluminum, density 2750kg/m3, Young's modulus is 6.9 × 1010Pa, Poisson's ratio is 0.35. In view of simple in construction herein, selecting the mode of automatic grid division, sizing grid is 1.5mm, gives FEM (finite element) model here Environment plus some suitable constraint simulation experiments.Table 1 is the modal parameter that Finite Element Simulation Analysis obtains with this method, removes Go swing and the vibration shape of translation occurred in finite element simulation.Can show that the front second-order modal of the finite element analysis of thin walled beam is intrinsic Frequency is respectively 3.71HZ and 22.81HZ, and with the error of experiment test value the most all within 10%, the mode of two kinds of methods is divided Analysis effect is basically identical, only exists some fine distinctions.But owing in experiment, some complicated factors are cannot in simulations Simulation, the most just determine the necessity that these difference exist.Therefore, the mode test result obtained by this method is correct 's.
Table 1 Finite Element Simulation Analysis obtains Comparative result with this method
Order Finite element simulation frequency (Hz) admittedly The solid frequency (Hz) that this method obtains The damping ratios identified
1 3.73 3.54 0.01
2 22.94 22.78 0.02

Claims (7)

1. thin-wall part operation mode based on a machine vision test device, is characterized in that: include industrial camera, light source, figure As harvester and image processing apparatus;Described industrial camera and light source are placed in the front of thin-wall part to be measured, industrial camera Camera lens is towards the leading flank of thin-wall part to be measured, and the leading flank of thin-wall part to be measured is provided with multiple retroreflective feature point;Described industry Camera is connected with image capturing system by data wire;Image collecting device is connected with image processing apparatus.
Thin-wall part operation mode based on machine vision the most according to claim 1 test device, is characterized in that: described Industrial camera is fixed on the dead ahead of thin-wall part to be measured by spider.
Thin-wall part operation mode based on machine vision the most according to claim 1 test device, is characterized in that: described Industrial camera uses CCD industrial camera;Described light source uses LED light source.
Thin-wall part operation mode based on machine vision the most according to claim 1 test device, is characterized in that: described One end of thin-wall part is bolted on base.
5. thin-wall part operation mode based on the machine vision test that a kind utilizes in claim 1-4 described in any claim The thin-wall part operation mode method of testing based on machine vision of device, comprises the steps:
1st step: ask for the relative pose relation of industrial camera and thin-wall part to be measured, and the principal point coordinate (u to industrial camera0, v0), the equivalent focal length a of horizontal directionx, the equivalent focal length a of vertical directiony, distortion parameter γ demarcates;
2nd step: utilize power to hammer hammering thin-wall part to be measured into shape, utilize the full sequence image of industrial camera this process of continuous acquisition, logical Cross image collecting device and be sent to image processing apparatus, carry out sequence specific primers-polymerase chain reaction, extract each retroreflective feature point with picture Element is the vibration signal of unit, according to the 1st step model and be translated into the vibration signal of effective unit;
3rd step: use stochastic subspace identification method to carry out modal parameter the vibration information of the multiple retroreflective feature points extracted Identify, obtain operational modal parameter.
Thin-wall part operation mode method of testing based on machine vision the most according to claim 5, the 1st step concrete operations are such as Under:
(1.1) industrial camera imaging process essence is the conversion process between several coordinate system, is tied to camera including world coordinates The rigid body translation of coordinate system, industrial camera coordinate is tied to the perspective transform of image coordinate system and image coordinate is tied to image pixel The conversion of coordinate system, its mathematical model is as follows:
z c u v 1 = 1 d x 0 u 0 0 1 d y v 0 0 0 1 · f 0 0 0 0 f 0 0 0 0 1 0 · R T 0 T 1 · X w p Y w p Z w p 1 = a x γ u 0 0 0 a y v 0 0 0 0 1 0 · R T 0 T 1 · X w p Y w p Z w p 1 = M 1 M 2 X w p Y w p Z w p 1 = M X w p Y w p Z w p 1 ... ( 1 )
In formula: f is the focal length of industrial camera;axFor the equivalent focal length on u axle;ayFor the equivalent focal length on v axle;(u0,v0) for scheming The principal point coordinate of picture, distortion factor γ=f α, α are camera distortion characterising parameters, are obtained by camera calibration;When γ=0, Pixel planes is rectangle, and when γ ≠ 0, pixel planes is not rectangle;(Xc,Yc,Zc)、(Xwp,Ywp,Zwp) it is respectively camera coordinates Coordinate under system and world coordinate system, R is the orthogonal spin matrix of unit of 3 × 3, and T is the translation matrix of 3 × 1, by camera mark Fixed acquisition;M1It is 3 × 4 projection matrixes;M1For Intrinsic Matrix, by camera intrinsic parameter ax、ay、γ、u0、v0Determine;M2For outer ginseng Matrix number, is determined relative to the outer parameter of world coordinate system by industrial camera;
(1.2) utilize industrial camera imaging model, use plane gridiron pattern scaling board to determine the inside and outside parameter of industrial camera, Gather 25 width gridiron pattern scaling board images of different positions and pose in the field range of industrial camera, 25 width uncalibrated images are utilized and writes Program carry out focus extraction, calibrated and calculated obtains intrinsic parameter and the distortion parameter of industrial camera, will wherein a width scaling board with The relative pose relation of industrial camera is as the relative pose relation of industrial camera Yu thin-wall part to be measured.
Thin-wall part operation mode method of testing based on machine vision the most according to claim 5, the 2nd step concrete operations are such as Under:
(2.1) according to position and the peak swing of thin-wall part to be measured of retroreflective feature points multiple in the first two field picture, one is determined Individual test zone ROI;
(2.2) use adaptive wavelet threshold denoising method that the image in test zone ROI is processed;
(2.3) grey linear transformation is used to strengthen the brightness of image the test zone ROI after filtering and noise reduction;
(2.4) maximum between-cluster variance threshold segmentation method is used to extract the spot area of multiple retroreflective feature points;
(2.5) spot area of the morphological method multiple retroreflective feature points to splitting is used to carry out closing operation of mathematical morphology;
(2.6) according to the size of retroreflective feature point facula area after above-mentioned process, choose area threshold, weed out in image other Interference region so that only comprise the hot spot of retroreflective feature point in remaining image, calculates the barycenter of each retroreflective feature point hot spot Coordinate, and it is recorded as the preservation of measuring point pixel coordinate, the abscissa u in units of pixel and vertical coordinate v;Extract the number of facula mass center Formula is as follows:
u = Σ i = 1 M Σ j = 1 N i f ( i , j ) / Σ i = 1 M Σ j = 1 N f ( i , j ) v = Σ i = 1 M Σ j = 1 N j f ( i , j ) / Σ i = 1 M Σ j = 1 N f ( i , j ) ... ( 2 )
In formula: M, N represent that spot area has the pixel composition of M row N row;I represents the row at pixel place;J represents pixel The row at some place;F (i, j) be i-th row jth row pixel gray value;
(2.7) according to the sequence image order gathered, the vibration displacement signal of each retroreflective feature point is extracted successively, and according to Pixel unit is converted into the physical unit of reality by the model that the 1st step is set up, it is thus achieved that the actual vibration position of multiple retroreflective feature points Shifting signal.
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