CN115047208A - Vision-based uncertainty evaluation method for speed measurement system - Google Patents
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- 238000005259 measurement Methods 0.000 title claims abstract description 29
- 238000011156 evaluation Methods 0.000 title claims abstract description 15
- 238000003384 imaging method Methods 0.000 claims abstract description 16
- 238000000034 method Methods 0.000 claims abstract description 11
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 4
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 4
- 238000006073 displacement reaction Methods 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 7
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/36—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light
- G01P3/38—Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light using photographic means
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/20—Analysis of motion
- G06T7/269—Analysis of motion using gradient-based methods
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
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Abstract
The invention relates to a vision-based uncertainty evaluation method for a speed measurement system, which comprises the following steps: measuring input quantities of a measured object motion distance S', a camera main distance f, an object distance L and a camera frame rate k on an imaging plane, calculating an experimental standard deviation of the average values, and considering the experimental standard deviation as the standard uncertainty of the input quantities; determining the uncertainty of the synthetic standard introduced by the speed measuring part for calculating the object to be measured; obtaining a synthetic standard uncertainty component introduced by the positioning imaging part of the measured object; obtaining the uncertainty of a synthesis standard introduced in the image acquisition process; calculating the uncertainty of the velocity measurement synthesis standard of the measured object based on vision; and obtaining vision-based measurement spread uncertainty of the velocity of the measured object.
Description
Technical Field
The invention belongs to the field of optical measurement, and particularly relates to a speed measurement system uncertainty evaluation method based on vision.
Background
Since the first world war aircraft is used for military purposes, the role of military equipment taking the aviation technology as the core is increasingly prominent in modern war, the influence on the outcome of the war can be regarded as great importance, and the military equipment is an important factor for causing new military changes in the current world. If the foreign flying object is involved in the engine, the engine is irreversibly influenced. The damage degree of the engine caused by the foreign object entering the engine is greatly related to the speed of the foreign object, so that the speed of the foreign flying object needs to be measured.
The accuracy of measuring the speed of the foreign object is the key influencing the whole engine impact test, and the measurement accuracy of test parameters needs to be ensured to obtain real and credible data. In foreign countries, represented by the united states and europe, a great deal of research and analysis, numerical simulation and experimental verification are performed on airplane impact tests by means of departments and organizations such as the Federal Aviation Administration (FAA), the National Transportation Safety Board (NTSB), the International Bird Strike Committee (IBSC), the European Aviation Safety Agency (EASA), and the like. The engine impact test study in china began in the 80's of the 20 th century and was conducted only as a research in technical exploratory tests. With the rapid development of the engine industry, the independently developed engines continuously emerge, and the safety of the engines is more and more emphasized.
Because the pose of the aerial flying object is not fixed and the speed is high in the moving process, the traditional speed measuring means has deviation in the measured data under the influence of the actual using environment in the actual using process, and the accurate measurement of the speed of the flying object cannot be carried out. No specific literature report on the uncertainty evaluation of the flight speed of an impacting object is found at present.
Disclosure of Invention
The invention aims to provide an uncertainty evaluation method of a vision-based object speed measurement system, which can be used for realizing the uncertainty evaluation of the speed measurement of a flying object. The technical scheme is as follows:
a vision-based uncertainty evaluation method for a speed measurement system utilizes a measured object speed measurement system to perform vision-based speed measurement on a moving measured object, wherein the vision-based speed measurement comprises the steps of obtaining an image of the measured object and processing the image, and the uncertainty evaluation comprises the following steps:
firstly, setting the motion distance of the measured object as S, measuring the motion distance S 'of the measured object on the imaging plane, the main distance f of the camera, the object distance L and the frame rate k of the camera, and calculating the average value of the motion distance S', the main distance f of the camera, the object distance L and the frame rate k of the camera
The experimental standard deviation of the average values is calculated by using Bessel formula
The standard uncertainty, considered as an input quantity, is:
the second step, confirmDetermining the sensitivity coefficient of each input quantity in the first step, namely the partial derivative of the input quantity, and respectively obtaining the standard uncertainty component u introduced by the imaging size 1 (S'), standard uncertainty component u introduced by camera focal length 1 (f) Standard uncertainty component u introduced by object distance 1 (L), standard uncertainty component u introduced by the Camera frame Rate 1 (k) The method comprises the following steps:
thirdly, the uncertainty of the synthetic standard introduced by the speed measuring part of the measured object is as follows:
fourthly, the object plane and the image plane are not completely parallel, the angle deviation between the actual displacement direction of the measured object and the ideal displacement direction is theta, the error caused by the angle deviation theta in the actual displacement is delta S, and the standard uncertainty component introduced by the object plane positioning error is set as follows:
u 2 (d)＝ΔS＝S(1-cosθ)
fifthly, when the telecentric lens is used, calculating a standard uncertainty component introduced by the axial positioning error, actually having a very small included angle between the object side chief ray and the optical axis, namely the telecentricity beta of the telecentric lens, and setting the axial plane positioning error of the measuring device as delta y, wherein the standard uncertainty component introduced by the axial positioning error is as follows:
u 2 (β)＝Δy·sinβ
sixthly, the component of the uncertainty of the synthetic standard introduced by the positioning imaging part of the measured object is as follows:
seventhly, calculating the actual size d of the unit pixel according to the projection area of the photosensitive area of the target field of view (FOV) p Noise error is uniformly distributed in one pixel, and standard uncertainty component u introduced by camera noise is calculated 3 (d p )：
Eighthly, calculating a standard uncertainty component u introduced by the optical lens distortion according to the technical standard parameters of the standard uncertainty component u introduced by the lens distortion 3 (dis)；
And ninthly, synthesizing standard uncertainty components introduced in the image acquisition process are as follows:
tenth step, measuring the velocity of the object to be measured based on the vision to synthesize the standard uncertainty u c (qv) is:
the eleventh step, taking the inclusion factor k to 2, then the vision-based measurement of the velocity of the object expands uncertainty:
U(qv)＝ku c (qv)＝2u c (qv)。
further, the image processing method comprises the following steps: obtaining image edge gradient information by utilizing a Sobel operator through edge detection in sequence; extracting the edge of the measured object through edge sub-pixels; performing sub-pixel edge fitting, and extracting the centroid of the object from the fitted edge; and obtaining the movement distance S' of the measured object on the imaging plane according to the mass center transformation in different images.
The uncertainty evaluation method of the measured object speed measuring system based on vision provided by the invention has the advantages that the evaluation of the measurement result of the object speed measuring system on the flying measured object is relatively comprehensively realized from three aspects of the uncertainty of the synthetic standard introduced by the measured object positioning imaging part, the uncertainty of the synthetic standard introduced by the measured object positioning imaging part and the uncertainty of the synthetic standard introduced in the image acquisition process, and a reliable basis can be provided for evaluating the measurement accuracy of the object speed measuring system.
Drawings
FIG. 1 is a schematic diagram of a vision-based object velocity measurement system.
FIG. 2 is a graph of vision-based object velocity measurement uncertainty evaluation components
FIG. 3 is a flow chart of vision measurement
FIG. 4 is a schematic view of object plane offset
Detailed Description
The invention is described below with reference to the accompanying drawings and examples. Fig. 1 is a block diagram of the whole measurement system, wherein an object is projected by a projection device, a flying object is photographed by a high-speed camera, and an obtained picture of the flying object is transmitted to a computer for processing. The invention adopts a vision-based speed measurement method, which comprises the steps of obtaining an image of a measured object and processing the image. Sequentially carrying out edge detection and utilizing a Sobel operator to obtain image edge gradient information; extracting the edge of the measured object through edge sub-pixels; performing sub-pixel edge fitting, and performing centroid extraction on the fitted edge; and obtaining the imaging size of the movement distance of the measured object according to the mass center transformation in different images.
The uncertainty evaluation method is implemented as follows:
first, the moving distance of the moving object in fig. 1 is S, the moving distance of the measured object on the imaging plane of the camera is S', the main distance f of the camera, the object distance L, and the frame rate k of the camera are measured, and the average value is obtained
The experimental standard deviation of the mean values is calculated by using Bessel formula
The standard uncertainty, considered as an input quantity, is:
secondly, determining the sensitivity coefficient of each input quantity in the first step, namely the partial derivative of the input quantity, and respectively obtaining the standard uncertainty component u introduced by the imaging size 1 (S'), standard uncertainty component u introduced by camera focal length 1 (f) Standard uncertainty component u introduced by object distance 1 (L), standard uncertainty component u introduced by the Camera frame Rate 1 (k) The method comprises the following steps:
thirdly, the uncertainty of the synthetic standard introduced by the speed measuring part of the measured object is as follows:
fourthly, as shown in fig. 4, the object plane AC and the image plane EF are not completely parallel, the angle deviation between the actual displacement direction of the measured object and the ideal displacement direction is θ, the error caused by the angle deviation θ in the actual displacement is Δ S, and the standard uncertainty component introduced by the object plane positioning error is:
u 2 (d)＝ΔS＝S(1-cosθ)
fifthly, when the telecentric lens is used, calculating a standard uncertainty component introduced by the axial positioning error, actually having a very small included angle between the object side chief ray and the optical axis, namely the telecentricity beta of the telecentric lens, and setting the axial plane positioning error of the measuring device as delta y, wherein the standard uncertainty component introduced by the axial positioning error is as follows:
u 2 (β)＝Δy·sinβ
sixthly, the component of the synthetic standard uncertainty introduced by the positioning imaging part of the measured object is as follows:
seventhly, calculating the actual size d of the unit pixel according to the projection area of the photosensitive area of the target field of view (FOV) p Noise due to the sub-pixel image extraction techniqueUniformly distributing the acoustic errors in one pixel, and calculating a standard uncertainty component u introduced by the camera noise 3 (d p )：
And eighthly, calculating a standard uncertainty component u introduced by the optical lens distortion according to the technical standard parameters of the standard uncertainty component u introduced by the lens distortion 3 (dis)。
And ninthly, the component of uncertainty of the synthesis standard introduced in the image acquisition process is as follows:
tenth step, measuring the velocity of the object to be measured based on the vision to synthesize the standard uncertainty u c (qv) is:
the eleventh step, taking the inclusion factor k to 2, then the vision-based object velocity measurement expands the uncertainty:
U(qv)＝ku c (qv)＝2u c (qv)。
Claims (2)
1. a vision-based uncertainty evaluation method for a speed measurement system utilizes the speed measurement system of a measured object to carry out vision-based speed measurement on the measured object in motion, the vision-based speed measurement comprises the steps of obtaining an image of the measured object and processing the image, and the uncertainty evaluation comprises the following steps:
the first step, setting the movement distance of the measured object as S, measuring the input quantity of the movement distance S', the main distance f, the object distance L and the frame rate k of the camera on the imaging plane, and calculating the average value of the input quantity
The experimental standard deviation of the mean values is calculated by using Bessel formula
The standard uncertainty, considered as an input quantity, is:
secondly, determining the sensitivity coefficient of each input quantity in the first step, namely the partial derivative of the input quantity, and respectively obtaining the standard uncertainty component u introduced by the imaging size 1 (S'), standard uncertainty component u introduced by camera focal length 1 (f) Standard uncertainty component u introduced by object distance 1 (L), standard uncertainty component u introduced by the Camera frame Rate 1 (k) The method comprises the following steps:
thirdly, the uncertainty of the synthetic standard introduced by the speed measuring part of the measured object is as follows:
fourthly, the object plane and the image plane are not completely parallel, the angle deviation between the actual displacement direction of the measured object and the ideal displacement direction is theta, the error caused by the angle deviation theta in the actual displacement is delta S, and the standard uncertainty component introduced by the object plane positioning error is set as follows:
u 2 (d)＝ΔS＝S(1-cosθ)
fifthly, when the telecentric lens is used, calculating a standard uncertainty component introduced by the axial positioning error, actually forming a very small included angle between the object side chief ray and the optical axis, namely the telecentricity beta of the telecentric lens, and setting the axial plane positioning error of the measuring device as delta y, wherein the standard uncertainty component introduced by the axial positioning error is as follows:
u 2 (β)＝Δy·sinβ
sixthly, the component of the synthetic standard uncertainty introduced by the positioning imaging part of the measured object is as follows:
seventhly, calculating the actual size d of the unit pixel according to the projection area of the photosensitive area of the target field of view (FOV) p Noise error is uniformly distributed in one pixel, and standard uncertainty component u introduced by camera noise is calculated 3 (d p )：
Eighthly, calculating a standard uncertainty component u introduced by the optical lens distortion according to the technical standard parameters of the standard uncertainty component u introduced by the lens distortion 3 (dis)；
And ninthly, the component of uncertainty of the synthesis standard introduced in the image acquisition process is as follows:
tenth step, measuring the velocity of the object to be measured based on the vision to synthesize the standard uncertainty u c (qv) is:
the eleventh step, taking the inclusion factor k to 2, then the vision-based measurement of the velocity of the object expands uncertainty:
U(qv)＝ku c (qv)＝2u c (qv)。
2. the method for assessing uncertainty in a velocity measurement system according to claim 1, wherein the image processing method comprises: obtaining image edge gradient information by utilizing a Sobel operator through edge detection in sequence; extracting the edge of the measured object through edge sub-pixels; fitting the edges of the sub-pixels, and extracting the centroid of the object from the fitted edges; and obtaining the movement distance S' of the measured object on the imaging plane according to the mass center transformation in different images.
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| CN115790401A (en) * | 2023-02-09 | 2023-03-14 | 西北工业大学 | Displacement measurement method based on visual measurement and related equipment |
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