CN113960069A - Method for establishing surface morphology of cable through laser line scanning - Google Patents
Method for establishing surface morphology of cable through laser line scanning Download PDFInfo
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- CN113960069A CN113960069A CN202111231309.8A CN202111231309A CN113960069A CN 113960069 A CN113960069 A CN 113960069A CN 202111231309 A CN202111231309 A CN 202111231309A CN 113960069 A CN113960069 A CN 113960069A
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- 230000003287 optical effect Effects 0.000 claims description 5
- 238000013528 artificial neural network Methods 0.000 description 6
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/952—Inspecting the exterior surface of cylindrical bodies or wires
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- G—PHYSICS
- 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
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2433—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring outlines by shadow casting
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
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Abstract
The invention discloses a method for establishing the surface morphology of a cable through laser line scanning, which comprises the following steps: s1, constructing a scanning robot; s2, emitting a laser line to the target cable through the laser line emitter, and acquiring the projection of the laser line on the surface of the target cable through the camera; s3, acquiring the entity coordinates of the target cable where the projection drawing is located through the positions of the cameras; s4, splicing the projection drawings based on the four sets of section coordinates to obtain an outer surface projection model of the target cable; and S5, obtaining coordinates and sizes of the poles and the catastrophes in the external surface projection model of the target cable, and completing the detection of the cable surface. The method can quickly and accurately detect the surface damage of the cable, and has low cost and high efficiency.
Description
Technical Field
The invention relates to the field of cable detection, in particular to a method for establishing the surface morphology of a cable through laser line scanning.
Background
At present, the detection method of apparent damage of the cable is roughly divided into a manual detection method, a laser scanning method, a machine learning neural network detection method and a machine vision defect detection method, wherein the manual detection method is to detect the surface of the cable through human eyes, is time-consuming and labor-consuming, has potential safety hazards, is subjective to cable damage, is easy to miss detection or false detection, and is not high in efficiency.
The laser scanning method is an automatic detection method for the surface defects of the cable, the collection principle is that the laser beam is emitted, the reflected laser is received, the time and the distance in the laser are measured, the defects are not detected visually, the time for processing and analyzing the three-dimensional space is long, the system has larger constitution volume, the equipment is expensive, and the popularization and the application are difficult.
The machine learning neural network detection method mainly comprises a BP neural network, an SCG neural network and an RBF neural network, wherein a finite element analysis model is established mainly through numerical simulation, and the position where damage occurs is estimated by inputting specific parameters and load working conditions of a cable and applying a neural network algorithm; under the condition of damage of different degrees, the identification precision is different, and the stability is weaker; when data is processed, the number of iterations is large, the workload is large, and the existing algorithm is not mature.
The above methods have the limitations of low efficiency, high cost, insufficient intelligence degree, etc.
Disclosure of Invention
In order to overcome the defects in the prior art, the method for establishing the surface morphology of the cable through laser line scanning provided by the invention solves the problem of low efficiency of the existing detection method.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that:
a method for establishing the surface morphology of a cable by laser line scanning is provided, comprising the steps of:
s1, constructing a scanning robot: the laser line emitters are respectively arranged on four sides of the inner side of the cable climbing vehicle, so that all the laser line emitters are on the same plane and are vertical to a target cable; installing a camera on each of four sides of the inner side of the cable climbing vehicle, so that all the cameras are on the same plane and are parallel to the plane where the laser emitter is located; the included angles between the sight lines of all the cameras and the target cable are equal;
s2, emitting laser lines to the target cable through the laser line emitter, and acquiring the projection of the laser lines on the surface of the target cable through the camera to obtain four groups of projection drawings;
s3, acquiring the entity coordinates of the target cable where the projection drawing is located through the positions of the cameras to obtain four sets of section coordinates;
s4, splicing the projection drawings based on the four sets of section coordinates to obtain an outer surface projection model of the target cable;
and S5, obtaining coordinates and sizes of the poles and the catastrophes in the external surface projection model of the target cable, and completing the detection of the cable surface.
Further, in step S1, the distance between two adjacent laser line emitters is equal, and the area of the laser line projected on the target cable by each laser line emitter is one-fourth of the length of the target cable cross-section circle.
Further, the specific method of step S3 is:
a space coordinate system is established by taking the axis direction in the scanning robot as the z axis and the direction of the laser ray emitter as the x axis, and the z-axis coordinate z of the target cable where the projection drawing is located is obtained according to the position of the camera*(ii) a According to the formula:
acquiring the physical coordinate (x) of a target cable where any target point of the projection drawing is positioned*,y*) Further obtain the physical coordinates (x) of the target cable where any target point of the projection drawing is located*,y*,z*) (ii) a Where cot represents the cotangent function; alpha is an included angle between a connecting line of the target point and the optical center of the camera and a central axis of the visual field of the camera; csc represents a cosecant function; theta represents the included angle between the central axis of the visual field of the camera and the laser plane; (u, v) are coordinates of the target point in the image coordinate system; l is from the optical center of the camera to the laser planeDistance of the faces; cos is a cosine function; f is the focal length of the camera when aimed at the target point.
The invention has the beneficial effects that: the method comprises the steps of emitting a laser line to a cable, collecting the projection of the laser line on the cable appearance, converting the coordinates of a camera system negative film to obtain the coordinates of the cable appearance entity, and further establishing a three-dimensional model or a point cloud model.
Drawings
FIG. 1 is a schematic flow diagram of the process;
FIG. 2 is a schematic view of the relative position of the scanning robot and the cable;
FIG. 3 is a schematic diagram of coordinate system transformation;
FIG. 4 is a perspective view of the cable without breakage;
FIG. 5 is a perspective view of a cable with a break;
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
As shown in fig. 1 and 2, the method for establishing the surface morphology of the cable by laser line scanning comprises the following steps:
s1, constructing a scanning robot: the laser line emitters are respectively arranged on four sides of the inner side of the cable climbing vehicle, so that all the laser line emitters are on the same plane and are vertical to a target cable (the cable also is a pull cable); installing a camera on each of four sides of the inner side of the cable climbing vehicle, so that all the cameras are on the same plane and are parallel to the plane where the laser emitter is located; the included angles between the sight lines of all the cameras and the target cable are equal;
s2, emitting laser lines to the target cable through the laser line emitter, and acquiring the projection of the laser lines on the surface of the target cable through the camera to obtain four groups of projection drawings;
s3, acquiring the entity coordinates of the target cable where the projection drawing is located through the positions of the cameras to obtain four sets of section coordinates;
s4, splicing the projection drawings based on the four sets of section coordinates to obtain an outer surface projection model of the target cable;
and S5, obtaining coordinates and sizes of the poles and the catastrophes in the external surface projection model of the target cable, and completing the detection of the cable surface.
In step S1, the distance between two adjacent laser line emitters is equal, and the area of the laser line projected on the target cable by each laser line emitter is a quarter of the length of the target cable cross-section circle.
The specific method of step S3 is: as shown in fig. 3, a space coordinate system is established by taking the axial direction in the scanning robot as the z-axis and the direction of the laser ray emitter as the x-axis, and the z-axis coordinate z of the target cable where the projection drawing is located is obtained according to the position of the camera*(ii) a According to the formula:
acquiring the physical coordinate (x) of a target cable where any target point of the projection drawing is positioned*,y*) Further obtain the physical coordinates (x) of the target cable where any target point of the projection drawing is located*,y*,z*) (ii) a Where cot represents the cotangent function; alpha is an included angle between a connecting line of the target point and the optical center of the camera and a central axis of the visual field of the camera; csc represents a cosecant function; theta represents the included angle between the central axis of the visual field of the camera and the laser plane; (u, v) are coordinates of the target point in the image coordinate system; l is camera lightThe distance from the center to the laser plane; cos is a cosine function; f is the focal length of the camera when aimed at the target point.
In one embodiment of the invention, the laser line emitter and the camera form a camera system, and the camera system replaces the actual defect situation at the periphery of the cable section by the apparent projection of the laser line on the cable, so that each layer of the cable section is a layer of laser line in the camera system, and the scanning result is a cable outside graph consisting of a plurality of laser curve sections in succession; and (3) performing coordinate processing on the imaged image after scanning by using a mathematical method, and constructing each section acquired by the camera system into an actual appearance model of the cable through coordinate conversion. The moving scanning path of the camera system is the axis of the cable, namely a smooth curve. The cross sections scanned by the camera system are required to be connected in series according to the line shape (axis, which can be directly extracted by photographing) of the cable, the center line of the cable or the centroid position of each cross section is found, the coordinate system is changed all the time as the camera system moves all the time, and the whole three-dimensional model can be obtained through coordinate conversion and fusion.
In summary, the invention emits laser lines to the cable, collects the projection of the laser lines on the cable appearance, and converts the coordinates by calculating the negative coordinates of the camera system to obtain the coordinates of the cable appearance entity, and further establishes a three-dimensional model or a point cloud model, as shown in fig. 4, if the cable appearance is not damaged, the projection of the laser lines on the cable should be a smooth and continuous curve, as shown in fig. 5, if the cable is defective, a corner defect exists at a certain point of the cable, the projection of the laser lines has a pole or a mutation point, the damaged position of the cable surface can be known by the coordinates of the pole and the mutation point in the three-dimensional model or the point cloud model, and the size of the damaged area can be calculated by the coordinates of the damaged position, thereby realizing the rapid detection of the cable.
Claims (3)
1. A method of establishing the surface morphology of a cable by laser line scanning, comprising the steps of:
s1, constructing a scanning robot: the laser line emitters are respectively arranged on four sides of the inner side of the cable climbing vehicle, so that all the laser line emitters are on the same plane and are vertical to a target cable; installing a camera on each of four sides of the inner side of the cable climbing vehicle, so that all the cameras are on the same plane and are parallel to the plane where the laser emitter is located; the included angles between the sight lines of all the cameras and the target cable are equal;
s2, emitting laser lines to the target cable through the laser line emitter, and acquiring the projection of the laser lines on the surface of the target cable through the camera to obtain four groups of projection drawings;
s3, acquiring the entity coordinates of the target cable where the projection drawing is located through the positions of the cameras to obtain four sets of section coordinates;
s4, splicing the projection drawings based on the four sets of section coordinates to obtain an outer surface projection model of the target cable;
and S5, obtaining coordinates and sizes of the poles and the catastrophes in the external surface projection model of the target cable, and completing the detection of the cable surface.
2. The method of claim 1, wherein the spacing between two adjacent laser line emitters is equal in step S1, and the area of the laser line projected onto the target cable from each laser line emitter is one-quarter of the length of the target cable cross-sectional circle.
3. The method for establishing the surface morphology of the cable through laser line scanning as claimed in claim 1, wherein the specific method of step S3 is:
a space coordinate system is established by taking the axis direction in the scanning robot as the z axis and the direction of the laser ray emitter as the x axis, and the z-axis coordinate z of the target cable where the projection drawing is located is obtained according to the position of the camera*(ii) a According to the formula:
acquiring the physical coordinate (x) of a target cable where any target point of the projection drawing is positioned*,y*) Further obtain the physical coordinates (x) of the target cable where any target point of the projection drawing is located*,y*,z*) (ii) a Where cot represents the cotangent function; alpha is an included angle between a connecting line of the target point and the optical center of the camera and a central axis of the visual field of the camera; csc represents a cosecant function; theta represents the included angle between the central axis of the visual field of the camera and the laser plane; (u, v) are coordinates of the target point in the image coordinate system; l is the distance from the optical center of the camera to the laser plane; cos is a cosine function; f is the focal length of the camera when aimed at the target point.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114778560A (en) * | 2022-06-20 | 2022-07-22 | 国网江苏省电力有限公司常州供电分公司 | Overhead line detection method and system based on cable inspection robot |
| CN117758615A (en) * | 2023-12-26 | 2024-03-26 | 武汉市市政路桥有限公司 | Cable-stayed bridge construction monitoring equipment and method |
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