CN113158121A - Alignment algorithm for two or more high-precision laser line scanners - Google Patents
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Abstract
The invention discloses an alignment algorithm of two or more high-precision laser line scanners, which belongs to the field of alignment algorithms of laser line scanners and comprises the following steps: and S1, rigidly connecting a plurality of scanners, synchronizing the plurality of scanners, and enabling initial measurement results to be in original coordinate systems of the respective scanners. According to the invention, no moving part is needed, and all equipment is in a static state during calibration, so that the calibration precision is greatly improved; in addition, the measuring time of the invention is extremely short, so any environmental noise and stability have little influence on the measuring result, as long as the calibration block and the measuring equipment are relatively stable and the rigidity between the measuring equipment is good; the calibration equipment of the method has low processing difficulty; it can be extended to the alignment of multiple laser scanners, such as the alignment of multiple laser line scanner clusters.
Description
Technical Field
The present invention relates to the field of alignment algorithms for laser line scanners, and more particularly to an alignment algorithm for two or more high precision laser line scanners.
Background
In order to realize networking work of double scanners or multiple scanners, the alignment work of the double scanners or the multiple scanners is crucial, and an alignment algorithm is responsible for putting all the scanners into a unified coordinate system, so that data of each single laser line scanner has a coordinate system converted into the unified coordinate system, and data fusion is realized. The precision of the alignment algorithm directly determines the measurement precision of the networked scanner cluster, and is a key core algorithm.
In the double-scanner double-hole calibration rod method in the prior art, each scanner needs to be subjected to laser coplanarity operation, and the coplanarity precision directly influences the alignment precision of equipment. The secondary alignment method cannot accommodate situations when the scanner cannot guarantee coplanarity. This alignment method provides a low calibration accuracy for rotational misalignment of the scanner along the Y-axis. When multiple scanners are aligned, the multiple scanners are required to be coplanar, the alignment condition of the scanners cannot be met when the scanners are not coplanar, human intervention is needed, which scanner corresponds to which fixed point is manually selected, and full-automatic alignment operation cannot be realized;
the alignment method for realizing the double scanners or the multiple scanners by combining the linear guide rails in the prior art has the defects that the alignment method is large in investment and high-precision linear guide rails need to be added. During the whole alignment process, the alignment accuracy of the scanner can be directly influenced by environmental interference when the measuring equipment is in motion. The alignment accuracy is directly related to the accuracy of the linear guide.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide an alignment algorithm for two or more high-precision laser line scanners so as to solve the problems that the scanners need to carry out some preprocessing work, the scanners are not coplanar, the alignment cannot be finished, and personnel intervention is needed.
In order to solve the above problems, the present invention adopts the following technical solutions.
An alignment algorithm for two or more high precision laser line scanners comprising the steps of:
s1, rigidly connecting a plurality of scanners, synchronizing the plurality of scanners, and enabling initial measurement results to be in original coordinate systems of the scanners;
s2, all scanners measure the calibration block at the same time, the original scanning point cloud is divided into P points according to the calculation of the first derivative0P1Segment, P2P3Segment, P4P5A segment;
s3, P0P1Segment, P2P3Segment, P4P5Best fitting of the line to the segment to obtain a straight lineLine P0P1，P2P3And P4P5Calculate P0P1And P2P3The intersection calculation yields P1(P2). Calculating P4P5And P2P3The intersection calculation yields P3(P4)；
S4, calculating plane P013And P145；
S5, calculating P013And P145Intersecting to obtain an expression of a straight line Q;
s6, creating a sphere R with the center of P2P3 and the radius of | P2P3 |/2;
s7, calculating the intersection point P of the straight line Q and the sphere Ru1And Pu2；
S8 as PuCentered on the vector PuP2For one direction of a defined coordinate system, in PuCentered on the vector PuP3Another direction of the defined coordinate system;
s9, generating a plurality of 4x4 rotation matrixes by a plurality of scanners, and placing all the scanners in a unified coordinate system;
s10, repeating the steps S3-14 to generate a plurality of measuring results, so that data redundancy is generated, and errors and distribution can be calculated;
and S11, finishing calibration.
As a further description of the above technical solution:
the number of the scanners is two or more.
As a further description of the above technical solution:
the calibration block in S2 is a corner reflector composed of three surfaces that are perpendicular to each other, or a square or a rectangular block.
As a further description of the above technical solution:
the expression of Q in S5 is (x, y, z) epsilon R3:a1x+b1y+c1z＝d1The expression of the space ball in S6 is (x-x)0)2+(y-y0)2+(z-z0)2＝r2。
Compared with the prior art, the invention has the advantages that:
(1) the scheme has the greatest advantages that no moving part is needed, and all equipment is in a static state during calibration, so that the calibration precision is greatly improved;
in addition, the measuring time of the invention is extremely short, so any environmental noise and stability have little influence on the measuring result, as long as the calibration block and the measuring equipment are relatively stable and the rigidity between the measuring equipment is good;
the method has small processing difficulty of the calibration equipment and only has the following two requirements:
1. the smaller the flatness of the planes A, B and C, the higher the precision;
2. the higher the mutual perpendicularity of the planes A, B and C, the more accurate;
it can be extended to the alignment of multiple laser scanners, such as the alignment of multiple laser line scanner clusters.
Drawings
FIG. 1 is a schematic view of the scanning of the present invention;
FIG. 2 is a schematic view of a scan fit of the present invention;
FIG. 3 is a schematic diagram of a calibration block according to the present invention;
FIG. 4 is a schematic view of the calibration of line Q of the present invention;
FIG. 5 is a schematic view of the calibration of the ball R of the present invention;
FIG. 6 is a schematic diagram of a scanning method according to the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention;
referring to fig. 1, 2, 4 and 5, in the present invention, an alignment algorithm for two or more high precision laser line scanners comprises the following steps:
s1, rigidly connecting a plurality of scanners, synchronizing the plurality of scanners, and enabling initial measurement results to be in original coordinate systems of the scanners;
s2 all scansThe instrument simultaneously measures the calibration block, the original scanning point cloud is divided into P points according to the calculation of the first derivative0P1Segment, P2P3Segment, P4P5A segment;
s3, P0P1Segment, P2P3Segment, P4P5Best fitting of the line is performed to obtain a straight line P0P1，P2P3And P4P5Calculate P0P1And P2P3The intersection calculation yields P1(P2). Calculating P4P5And P2P3The intersection calculation yields P3(P4)；
S4, calculating plane P013And P145；
S5, calculating P013And P145Intersecting to obtain an expression of a straight line Q;
s6, creating a sphere R with the center of P2P3 and the radius of | P2P3 |/2;
s7, calculating the intersection point P of the straight line Q and the sphere Ru1And Pu2；
S8 as PuCentered on the vector PuP2Is one direction of a defined coordinate system (can be arbitrarily selected in XYZ axes), and is represented by PuCentered on the vector PuP3Is another direction of a defined coordinate system (P can be arbitrarily selected in XYZ axes)uP2Axial directions other than defined);
s9, generating a plurality of 4x4 rotation matrixes by a plurality of scanners, and placing all the scanners in a unified coordinate system;
s10, repeating the steps S3-14 to generate a plurality of measuring results, so that data redundancy is generated, and errors and distribution can be calculated;
and S11, finishing calibration.
In the present invention, the mathematical description of the algorithm is such that when 3 planes are perpendicular two by two, one plane intersects the 3 planes, while passing through the three planes but not the intersection of the 3 planes. Let 3 planes be planes A, BAnd C, setting the intersection point of the three planes as PuPlane L intersects ABC at Lla,Llb,LlcPoint P0,P1On a straight line LlaUpper, point P2,P3On a straight line LlbUpper, point P4,P5On a straight line LlcIn order to be according to P0-P5XYZ coordinates of Pu are calculated, and then coordinates of all scanners are unified according to the coordinates;
the calibration method has the advantages that no moving part is needed, and all equipment is in a static state during calibration, so that the calibration precision is greatly improved;
in addition, the measuring time of the invention is extremely short, so any environmental noise and stability have little influence on the measuring result, as long as the calibration block and the measuring equipment are relatively stable and the rigidity between the measuring equipment is good;
the method has small processing difficulty of the calibration equipment and only has the following two requirements:
1. the smaller the flatness of the planes A, B and C, the higher the precision;
2. the higher the mutual perpendicularity of the planes a, B, C, the more precise.
Please refer to fig. 6, in which: the number of the scanners is two or more.
In the present invention, the present invention can be extended to the alignment of multiple laser scanners, such as the alignment of multiple laser line scanner clusters.
Please refer to fig. 3, in which: the calibration block in S2 is a corner reflector composed of three surfaces that are perpendicular to each other, or a square or a rectangular block.
In the invention, the three surfaces of the calibration block are ensured to be vertical pairwise, the measurement precision is improved and the calculation is convenient.
Please refer to fig. 4 and 5, wherein: the expression of Q in S5 is (x, y, z) epsilon R3:a1x+b1y+c1z＝d1The expression of the space ball in S6 is (x-x)0)2+(y-y0)2+(z-z0)2＝r2。
In the invention, because the surfaces ABC are mutually vertical, the following steps are carried out:
a)PuP1and P4P5Is vertical, PuP4And P0P1Is vertical, then PuMust be in sum with P4P5Perpendicular and passing through P1Plane (P) of145) The above step (1);
b)Pumust also be in the sum P0P1Perpendicular and passing through P4Plane (P) of013) The above step (1);
c) plane P145A plane P of kneading013Intersect to give a straight line Q, then PuMust be on that straight line;
also because the faces ABC are perpendicular to each other, the angle P2PuP3Must be at right angles, therefore PuIs positioned at P2P3Is a sphere R of diameter;
the line-sphere intersection has 2 solutions, which may be real solutions and imaginary solutions, but because of the precondition that the surface ABC is vertical, the formula is determined to have two real solutions, the rule of selecting one of the two solutions is very simple, because one of the two solutions is positioned above the plane L and the other is positioned below the plane L, the alignment results of the two scanners select the upper solution if the upper solution is selected, otherwise, the lower solution is selected;
Puafter calculation, a coordinate system is created, using PuAs origin, vector PuP2Is the X axis, PuP3A coordinate system is created for the Y-axis, since this coordinate system is created as a calibration block coordinate system, since the position and attitude of each scanner in the coordinate system of the calibration block is determined therefrom, and a conversion relationship between the scanners can be calculated, this conversion relationship being the result of the calibration.
The foregoing is only a preferred embodiment of the present invention; the scope of the invention is not limited thereto. Any person skilled in the art should be able to cover the technical scope of the present invention by equivalent or modified solutions and modifications within the technical scope of the present invention.
Claims (4)
1. An alignment algorithm for two or more high precision laser line scanners, characterized by: the method comprises the following steps:
s1, rigidly connecting a plurality of scanners, synchronizing the plurality of scanners, and enabling initial measurement results to be in original coordinate systems of the scanners;
s2, all scanners measure the calibration block at the same time, the original scanning point cloud is divided into P points according to the calculation of the first derivative0P1Segment, P2P3Segment, P4P5A segment;
s3, P0P1Segment, P2P3Segment, P4P5Best fitting of the line is performed to obtain a straight line P0P1，P2P3And P4P5Calculate P0P1And P2P3The intersection calculation yields P1(P2). Calculating P4P5And P2P3The intersection calculation yields P3(P4)；
S4, calculating plane P013And P145；
S5, calculating P013And P145Intersecting to obtain an expression of a straight line Q;
s6, creating a sphere R with the center of P2P3 and the radius of | P2P3 |/2;
s7, calculating the intersection point P of the straight line Q and the sphere Ru1And Pu2；
S8 as PuCentered on the vector PuP2For one direction of a defined coordinate system, in PuCentered on the vector PuP3Another direction of the defined coordinate system;
s9, generating a plurality of 4x4 rotation matrixes by a plurality of scanners, and placing all the scanners in a unified coordinate system;
s10, repeating the steps S3-14 to generate a plurality of measuring results, so that data redundancy is generated, and errors and distribution can be calculated;
and S11, finishing calibration.
2. The alignment algorithm for two or more high precision laser line scanners of claim 1 wherein: the number of the scanners is two or more.
3. The alignment algorithm for two or more high precision laser line scanners of claim 1 wherein: the calibration block in S2 is a corner reflector composed of three surfaces that are perpendicular to each other, or a square or a rectangular block.
4. The alignment algorithm for two or more high precision laser line scanners of claim 1 wherein: the expression of Q in S5 is (x, y, z) epsilon R3:a1x+b1y+c1z＝d1The expression of the space ball in S6 is (x-x)0)2+(y-y0)2+(z-z0)2＝r2。
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Citations (4)
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| JP2009168472A (en) * | 2008-01-10 | 2009-07-30 | Zenrin Co Ltd | Calibration device and calibration method of laser scanner |
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| US20190026899A1 (en) * | 2017-07-19 | 2019-01-24 | Carl Zeiss Industrielle Messtechnik Gmbh | Determining a mark in a data record with three-dimensional surface coordinates of a scene, captured by at least one laser scanner |
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- 2021-04-23 CN CN202110442748.7A patent/CN113158121A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009168472A (en) * | 2008-01-10 | 2009-07-30 | Zenrin Co Ltd | Calibration device and calibration method of laser scanner |
| CN101726257A (en) * | 2009-12-22 | 2010-06-09 | 西安交通大学 | Multiple large range laser scanning measurement method |
| US20190026899A1 (en) * | 2017-07-19 | 2019-01-24 | Carl Zeiss Industrielle Messtechnik Gmbh | Determining a mark in a data record with three-dimensional surface coordinates of a scene, captured by at least one laser scanner |
| CN108994827A (en) * | 2018-05-04 | 2018-12-14 | 武汉理工大学 | A kind of robot measurement-system of processing scanner coordinate system automatic calibration method |
Non-Patent Citations (2)
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| 吴军;王玲容;黄明益;彭智勇;: "多几何约束下的鱼眼相机单像高精度标定", 光学学报, no. 11, 12 June 2018 (2018-06-12) * |
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