CN111951401B - Precise three-dimensional geometric model construction method of pipeline elbow capable of being used for laser scanning - Google Patents
Precise three-dimensional geometric model construction method of pipeline elbow capable of being used for laser scanning Download PDFInfo
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Abstract
The invention provides a method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning, which comprises the following steps: constructing a three-dimensional geometric model of the pipeline elbow; extracting three-dimensional geometric model observations from a laser three-dimensional scan or other three-dimensional imaging sensor; carrying out model parameter initialization estimation; calculating model parameters by using a least square estimation method; the exact position, angle and size of the pipe bend in a three-dimensional space is estimated. The invention provides a method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning, which is characterized in that observation data such as point clouds are obtained through laser scanning, a three-dimensional geometric model of the pipeline elbow is built through three-dimensional reconstruction of the point clouds, and the precise position, angle and size of the elbow in a three-dimensional space are estimated, so that the method is applied to dynamic monitoring, completion drawing, point cloud registration, pipeline accessory detection and the like when fluid based on hydrodynamics passes through the elbow.
Description
Technical Field
The invention relates to the technical field of geographic information, in particular to a method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning.
Background
Piping (including water pipes, exhaust pipes, etc.) bends (displacement joints) are an integral part of the plumbing system of the water or chemical industry, which are typically used to connect and redirect piping. Pipeline system designers often need to know the exact location and volume of the connection to ensure perfect seamless splice when the pipeline is installed; on the other hand, in the field of fluid mechanics, more and more people are studying the flow characteristics of the fluid in the pipe bend (such as fluid velocity and pressure) in order to better manage the pipe system. And the geometric modeling of the pipeline elbow, the Reynolds Number (RN) at the elbow is calculated, the flow characteristic of the pipeline elbow is researched, and a model foundation is provided. In recent years, however, geometric modeling of pipe columns has become a hotspot of research, but modeling of pipe bends is still in an early stage of development. Zhao et al, proposes a geometric modeling method of an underground ferromagnetic pipeline, decomposing the pipeline/joint into a number of small three-dimensional circular/department units according to block elements, representing the four corners of each unit with a polar coordinate system defined at the centroid of the pipe/joint, thereby establishing a geometric model of the pipeline; moritani et al modeling pipes using conventional cylinder modeling methods, analyzing cylinder parameters using a three-dimensional hash table to match the central axis of conjugated pipes for point cloud registration. Rabanni et al, an integrated feature detection and point cloud registration method was developed that uses more than five geometric models to process point clouds of plants with complex piping systems, which can be used to process rich pipe scenes in industrial sites, etc., however this method does not focus on any pipe bends in the system. It follows that while geometric modeling of bends in a piping system can provide geometric information on the top of vertical/horizontal pipes, it is not an important concern.
In recent years, object geometric modeling based on defined structures has been applied in many fields. Chan et al establishes a polygonal lamp post geometric model, registers and fits the point cloud to estimate model parameters. Voinea et al, a method of modeling human spine geometry for medical purposes is presented. On the other hand, an accurate geometric model can estimate the volume of an object without completely measuring the surface of the object, and Chan et al propose a geometric model of an avian egg that uses a point cloud (incomplete cloud) of half of the surface of an egg obtained by a single scan to estimate the volume of the egg.
Existing studies on piping have not focused on modeling piping elbows, or on a single type of piping elbow. Therefore, a method for constructing a precise three-dimensional geometric model of a pipeline elbow which can be used for laser scanning is needed.
Disclosure of Invention
The invention provides a construction method of a precise three-dimensional geometric model of a pipeline elbow, which is used for overcoming the technical defects that the existing pipeline elbow lacks a precise three-dimensional geometric model, is difficult to precisely model the pipeline elbow and determine the coordinates, angles and dimensions of the pipeline elbow.
In order to solve the technical problems, the technical scheme of the invention is as follows:
A method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning comprises the following steps:
S1: constructing a three-dimensional geometric model of the pipeline elbow;
s2: extracting observations from a laser three-dimensional scan or other three-dimensional imaging sensor;
S3: carrying out model parameter initialization estimation;
s4: establishing an optimal model parameter estimation model by using a least square estimation method, and calculating the correction of the model parameter;
S5: the exact position, angle and size of the pipe bend in a three-dimensional space is estimated.
The step S1 specifically includes:
Let the central coordinate of the pipe elbow be (X C,YC,ZC), the rotation angles of X, Y, Z axis in three directions be omega, ψ respectively, the parameters satisfy the following conversion relations:
Wherein (X, Y, Z) represents three-dimensional space coordinates after rotation about X and Z axes, and R 1 and R 3 represent rotation matrices of the X and Z axes, respectively;
And then the pipeline elbow rotates around the Y axis by an angle phi:
wherein (X p,Yp,Zp) represents three-dimensional space coordinates after being rotated around the Y axis, R 2 represents a Y axis rotation matrix, and the rotation angle is as follows:
Wherein θ is the angle between the pipe elbow and the X-axis, (0 ° < θ. Ltoreq.360°), and d is the elbow turning degree, 45 degrees, 90 degrees, etc.
In addition, p represents that the scanning point is located at the joint bending portion or the extended cylindrical straight tube portion, specifically defined as:
p＝1-sgn(H(X)·H(Z))
where sgn () represents a sign function (sign), and H () represents a sea-going step function (Heaviside);
finally, the elbow satisfies the following model equation:
wherein, Representing an observed quantity; /(I)Representing model parameters, when the pipe elbow is a non-junction-disc elbow,When the pipe elbow is a disc-shaped elbow, the method comprises the following steps ofQ represents the flange index, specifically defined as
So far, the three-dimensional geometric model of the elbow has been constructed, which model will be used for parametric initialization of S3, best estimation of S4 and calculation of the pipe elbow coordinates, angles and dimensions of S5.
The step S2 specifically includes: and scanning the elbow by utilizing a laser three-dimensional scanning or other three-dimensional imaging sensors to extract the observed quantity of the point cloud data.
The step S3 specifically includes: the initial estimation method of parameters based on cylinder fittings is utilized to perform initial estimation of model parameters, a thin layer (about 1cm thickness) point is extracted from point cloud data, an original center is calculated, an intersection point of two center shafts of a best fit cylinder is estimated to serve as an internal center point and an elbow diameter parameter D, rotation angles omega and ψ are estimated through a conversion relation and a golden section searching algorithm, finally distances between the original center point and the internal center point serve as initial estimation values of parameters A, and an axial origin translation A is carried out on the internal center point to calculate center coordinates (X C,YC,ZC).
The step S4 specifically includes: establishing an optimal estimation model by using a least square estimation method, and calculating the correction of model parameters by combining the observation data and a three-dimensional geometric model of the pipeline elbow, wherein an estimation model equation specifically comprises the following components:
wherein, For model parameters/>Or/>A1 represents the design matrix as the partial derivative of the model parameter, B1 represents the design matrix as the partial derivative of the observed value,/>Representing the residual vector, w represents the closed difference vector.
The step S5 specifically includes: and (3) calculating the coordinates, angles and sizes of the pipe elbow through the three-dimensional geometric model in the step (S1) by using the initial values of the parameters and the parameter correction calculated in the step (S4).
In the scheme, the laser three-dimensional scanning or other three-dimensional imaging sensors are used for scanning the pipeline elbow through the photogrammetry and geometric modeling method, the observed quantity is extracted, the model parameters are subjected to initial estimation, the best estimation of the model parameters is obtained through the combination of the least square estimation method, and finally the coordinates, the angles and the size parameters of the pipeline elbow are obtained.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
The invention provides a method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the present patent;
For the purpose of better illustrating the embodiments, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the actual product dimensions;
it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Example 1
The invention provides a new three-dimensional geometric equation of a pipeline elbow, a parameter initial value estimation method based on a cylinder fitting and a position, angle and size determination method of the pipeline elbow by using a least square estimation method. At present, to build a three-dimensional geometric model of a pipeline elbow with high accuracy and wide application range, different geometric models are required to be built by combining different types of pipeline elbows to measure a large number of elbows, and meanwhile, model parameters are required to be optimized and estimated. However, to date, the three-dimensional modeling method of the pipeline elbow based on the combination of the geometric model and the most estimation method has not been presented.
More specifically, in the prior art, a three-dimensional modeling method for a pipeline elbow by using laser scanning based on a mapping remote sensing principle does not exist temporarily, and the three-dimensional model method for the pipeline elbow based on the laser scanning provided by the invention is matched with a strict mathematical geometric model and an optimal estimation method, so that the pipeline elbow and the relative geometric performance thereof are objectively observed, calculated and analyzed.
In a specific implementation process, as shown in fig. 1, a method for constructing a precise three-dimensional geometric model of a pipe elbow capable of being used for laser scanning comprises the following steps:
S1: constructing a three-dimensional geometric model of the pipeline elbow;
s2: extracting observations from a laser three-dimensional scan or other three-dimensional imaging sensor;
S3: carrying out model parameter initialization estimation;
s4: establishing an optimal model parameter estimation model by using a least square estimation method, and calculating the correction of the model parameter;
S5: the exact position, angle and size of the pipe bend in a three-dimensional space is estimated.
In a specific implementation process, the precise three-dimensional geometric model construction method for the pipeline elbow capable of being used for laser scanning is used for constructing a three-dimensional geometric model of the pipeline elbow based on geometric relations, and the optimal estimation of model parameters is obtained by utilizing observation data of three-dimensional scanning or imaging and combining a least square estimation method to obtain the position, angle and size parameters of the pipeline elbow. The three-dimensional geometric model with higher precision can be obtained by applying laser scanning based on the mapping remote sensing principle to perform three-dimensional modeling on the pipeline elbow.
Example 2
More specifically, on the basis of embodiment 1, the step S1 specifically includes:
Let the central coordinate of the pipe elbow be (X C,YC,ZC), the rotation angles of X, Y, Z axis in three directions be omega, ψ respectively, the parameters satisfy the following conversion relations:
Wherein (X, Y, Z) represents three-dimensional space coordinates after rotation about X and Z axes, and R 1 and R 3 represent rotation matrices of the X and Z axes, respectively;
And then the pipeline elbow rotates around the Y axis by an angle phi:
wherein (X p,Yp,Zp) represents three-dimensional space coordinates after being rotated around the Y axis, R 2 represents a Y axis rotation matrix, and the rotation angle is as follows:
Wherein θ is the angle between the pipe elbow and the X-axis, (0 ° < θ. Ltoreq.360°), and d is the elbow turning degree, 45 degrees, 90 degrees, etc.
In addition, p represents that the scanning point is located at the joint bending portion or the extended cylindrical straight tube portion, specifically defined as:
p＝1-sgn(H(X)·H(Z))
where sgn () represents a sign function (sign), and H () represents a sea-going step function (Heaviside);
finally, the elbow satisfies the following model equation:
wherein, Representing an observed quantity; /(I)Representing model parameters, when the pipe elbow is a non-junction-disc elbow,When the pipe elbow is a disc-shaped elbow, the method comprises the following steps ofQ represents the flange index, specifically defined as
So far, the three-dimensional geometric model of the elbow has been constructed, which model will be used for parametric initialization of S3, best estimation of S4 and calculation of the pipe elbow coordinates, angles and dimensions of S5.
More specifically, the step S2 specifically includes: and scanning the elbow by utilizing a laser three-dimensional scanning or other three-dimensional imaging sensors to extract the observed quantity of the point cloud data.
More specifically, the step S3 specifically includes: the method comprises the steps of carrying out model parameter initialization estimation by using a parameter initial value estimation method based on a cylinder fitting, extracting a thin layer (about 1cm thick) point from point cloud data, calculating an original center, estimating an intersection point of two central axes of a best fit cylinder as an internal center point and an elbow diameter parameter D, estimating a rotation angle through a conversion relation and a golden section search algorithm, finally taking the distance between the original center and the internal center point as an initial estimated value of a parameter A, and calculating a center coordinate by carrying out axial origin translation A on the internal center point.
More specifically, the step S4 specifically includes: establishing an optimal estimation model by using a least square estimation method, and calculating the correction of model parameters by combining the observation data and a three-dimensional geometric model of the pipeline elbow, wherein an estimation model equation specifically comprises the following components:
wherein, For model parameters/>Or/>A1 represents the design matrix as the partial derivative of the model parameter, B1 represents the design matrix as the partial derivative of the observed value,/>Representing the residual vector, w represents the closed difference vector.
More specifically, the step S5 specifically includes: and (3) calculating the coordinates, angles and sizes of the pipeline elbow by using the parameter initial value and the parameter correction calculated in the step S4 through the three-dimensional geometric model in the step S1.
In the specific implementation process, the position, angle and size parameters of the pipeline elbow are optimally estimated by combining a least square estimation method through a photogrammetry and geometric modeling method and using a three-dimensional laser scanning or other three-dimensional imaging sensor to obtain the point cloud data observed quantity.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (5)
1. A method for constructing a precise three-dimensional geometric model of a pipeline elbow capable of being used for laser scanning is characterized by comprising the following steps: the method comprises the following steps:
S1: constructing a three-dimensional geometric model of the pipeline elbow;
the method comprises the following steps:
Let the central coordinate of the pipe elbow be (X C,YC,ZC), the rotation angles of X, Y, Z axis in three directions be omega, ψ respectively, the parameters satisfy the following conversion relations:
Wherein, (X, Y, Z) represents three-dimensional space coordinates after rotation about the X-axis and the Z-axis, and R 1 and R 3 represent rotation matrices of the X-axis and the Z-axis, respectively; and then the pipeline elbow rotates around the Y axis by an angle phi:
wherein (X p,Yp,Zp) represents three-dimensional space coordinates after being rotated around the Y axis, R 2 represents a Y axis rotation matrix, and the rotation angle is as follows:
Wherein θ is the angle between the pipe elbow and the X-axis, 0 ° < θ is less than or equal to 360 °, and d is the elbow turning degree, 45 degrees and 90 degrees;
in addition, p represents that the scanning point is located at the joint bending portion or the extended cylindrical straight tube portion, specifically defined as:
p＝1-sgn(H(X)·H(Z))
wherein sgn () represents a sign function, and H () represents a step function of the sea-going seide;
finally, the elbow satisfies the following model equation:
wherein, Representing an observed quantity; /(I)Representing model parameters, when the pipe elbow is a non-junction-disc elbow,When the pipe elbow is a disc-shaped elbow, the method comprises the following steps ofQ represents the flange index, specifically defined as
S2: extracting observations of a three-dimensional geometric model from a laser three-dimensional scan or other three-dimensional imaging sensor;
S3: carrying out model parameter initialization estimation;
s4: establishing an optimal model parameter estimation model by using a least square estimation method, and calculating the correction of the model parameter;
s5: the exact position, angle and size of the pipe bend in a three-dimensional space is estimated.
2. The method for constructing a precise three-dimensional geometric model of a pipe elbow for laser scanning according to claim 1, wherein the step S2 is specifically: and scanning the elbow by utilizing a laser three-dimensional scanning or other three-dimensional imaging sensors to extract the observed quantity of the point cloud data.
3. The method for constructing a precise three-dimensional geometric model of a pipe elbow for laser scanning according to claim 2, wherein the step S3 is specifically: the method comprises the steps of carrying out model parameter initialization estimation by using a parameter initial value estimation method based on a cylinder fitting, extracting a thin layer of points from point cloud data, calculating an original center, estimating the intersection point of two central axes of a best fit cylinder as an internal center point and an elbow diameter parameter D, estimating rotation angles omega and ψ through a conversion relation and a golden section search algorithm, finally taking the distances between the original center and the internal center point as initial estimation values of parameters A, and calculating a center coordinate (X C,YC,ZC) by carrying out axial origin translation A on the internal center point.
4. A method for constructing a precise three-dimensional geometric model of a pipe elbow for laser scanning according to claim 3, wherein said step S4 is specifically: establishing an optimal estimation model by using a least square estimation method, and calculating the correction of model parameters by combining the observation data and a three-dimensional geometric model of the pipeline elbow, wherein an estimation model equation specifically comprises the following components:
wherein, For model parameters/>
Or (b)A1 represents the design matrix as the partial derivative of the model parameter, B1 represents the design matrix as the partial derivative of the observed value,/>Representing the residual vector, w represents the closed difference vector.
5. The method for constructing a precise three-dimensional geometric model of a pipe elbow for laser scanning according to claim 4, wherein the step S5 is specifically: and (3) calculating the coordinates, angles and sizes of the pipe elbow through the three-dimensional geometric model in the step (S1) by using the initial values of the parameters and the parameter correction calculated in the step (S4).
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| CN105136054A (en) * | 2015-04-27 | 2015-12-09 | 北京工业大学 | Fine structure deformation monitoring method and system based on ground three-dimensional laser scanning |
| CN109147038A (en) * | 2018-08-21 | 2019-01-04 | 北京工业大学 | Pipeline three-dimensional modeling method based on three-dimensional point cloud processing |
| CN111429563A (en) * | 2020-03-10 | 2020-07-17 | 山东大学 | Pipeline three-dimensional reconstruction method, system, medium and equipment based on deep learning |
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| CN105136054A (en) * | 2015-04-27 | 2015-12-09 | 北京工业大学 | Fine structure deformation monitoring method and system based on ground three-dimensional laser scanning |
| CN109147038A (en) * | 2018-08-21 | 2019-01-04 | 北京工业大学 | Pipeline three-dimensional modeling method based on three-dimensional point cloud processing |
| CN111429563A (en) * | 2020-03-10 | 2020-07-17 | 山东大学 | Pipeline three-dimensional reconstruction method, system, medium and equipment based on deep learning |
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