CN110360944B - Lifting hook deformation monitoring and displaying method based on three-dimensional point cloud - Google Patents
Lifting hook deformation monitoring and displaying method based on three-dimensional point cloud Download PDFInfo
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- 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
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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Abstract
The invention discloses a lifting hook deformation monitoring and displaying method based on three-dimensional point cloud, which is used for carrying out automatic deformation deviation calculation and coloring display on the basis of original three-dimensional point cloud data without deformation of a lifting hook and currently measured data, and mainly comprises the following steps: denoising the current hook data, and removing point cloud data outside the hook; calculating a rotation matrix and a translation vector to enable the data of the upper half part of the current lifting hook to be overlapped with the data of the upper half part of the original lifting hook; calculating a symmetrical plane of original hook data, and projecting the original data and the current data to the plane by taking the symmetrical plane as a reference; carrying out sectional statistics on the deviation between the two projection lines; mapping the deviation value to colors of different chromaticities; and redrawing each section of point cloud data by using the color representing the deviation. The invention can solve the problem that the deformation of each part of the lifting hook can not be accurately measured and visually displayed in manual measurement, and has the advantages of high precision, no need of manual participation, wide applicability and the like.
Description
Technical Field
The invention relates to the technical field of intelligent detection, in particular to a lifting hook deformation monitoring and displaying method based on three-dimensional point cloud.
Background
The lifting hook is a key stressed part on the crane, and is easy to deform, so that serious safety accidents are caused. Therefore, the State administration of quality supervision, inspection and quarantine issues a bridge crane as a safety technology supervision rule of hoisting machinery, and a special equipment inspection and detection mechanism needs to perform regular inspection work on the lifting hook according to the detection standard and the rule. But the deformation is multidimensional, and the manual detection is difficult to be carried out by means of visual measurement or traditional tools such as calipers and vernier calipers; in addition, the current detection data cannot be utilized to perform appropriate analysis and early warning on deformation development.
In recent years, techniques for monitoring three-dimensional deformation of a surface of an object can be classified into: the construction device directly measures and indirectly calculates two categories based on a large amount of measurement data.
The direct measuring device can only detect specific parameters generally, for example, the invention patent CN101634543A discloses a device and a method for detecting torsional deformation of a lifting hook, which constructs a device consisting of a clamp, a reference hook frame and a sliding measurement frame, and measures the deformation angle of the lifting hook by measuring key points on the contour line of the lifting hook. The utility model CN202209944 discloses an in-service crane hook torsional deformation measuring device, which is a device formed by welding a circular ring and a long rod, and is used for measuring the torsional deformation; utility model CN203187310U discloses a lifting hook deformation monitoring devices, through pasting the deformation range at the resistance strain gauge at the easy deformation position of lifting hook, output resistivity change signal sends for display instrument through wireless transmitter after handling. The visible measuring device needs to be manually installed, and the installation precision has great influence on the measurement.
The hook deformation is not one or more data which can be measured by a simple tool, and the data of the whole hook surface at the measuring time can be compared with the original and deformation-free data in an all-around mode. The analysis results are not only a quantitative measure of the current deformation, but also can be used to predict hook performance and service life using historical data. The complete data of the hook surface can be obtained by a three-dimensional measurement technology, and can be specifically divided into means based on binocular vision, three-dimensional laser, structured light and the like. The binocular vision is suitable for near distance measurement, and needs to be subjected to stereo matching according to the surface characteristics of an object, so that the density of data points is limited; laser measurement can be used for short distance or medium distance, but the cost is high; structured light is suitable for close-range measurement, and has high precision and dense data points. Patent CN202880687U discloses a crane hook three-dimensional deformation detection system, which uses structured light as a principle, and projects grating stripes to the hook through a projector, and two CCD cameras acquire images. The system does not further discuss how to resolve the three-dimensional data of the hooks from the image and how to perform deformation detection based on the data.
At present, the technology and equipment for three-dimensional measurement are mature, and dense and accurate three-dimensional data, namely point cloud, on the surface of an object can be obtained. However, if the lifting hook detection is concerned, how to analyze comprehensive and accurate deformation information from the lifting hook point cloud is still a problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a lifting hook deformation monitoring and displaying method based on three-dimensional point cloud.
The technical solution for realizing the purpose of the invention is as follows: a lifting hook deformation monitoring and displaying method based on three-dimensional point cloud comprises the following steps:
step 1, denoising current hook data and removing point cloud data outside a hook;
step 2, calculating a rotation matrix and a translation vector to enable the data of the upper half part of the current lifting hook to be overlapped with the data of the upper half part of the original lifting hook;
step 3, calculating a symmetrical plane of the original hook data, and projecting the original data and the current data to the plane by taking the symmetrical plane as a reference;
step 4, calculating the deviation between the two projection lines in a segmented manner;
and 5, mapping the deviation value to colors with different chromaticities, and redrawing each section of point cloud data by using the color representing the deviation.
Compared with the prior art, the invention has the following remarkable advantages: (1) the invention does not need to install auxiliary equipment on the monitored lifting hook, and is easy to implement; (2) the offset of the deformation part of the lifting hook can be automatically calculated, the deformation degree and the deformation part are displayed simultaneously, and the method has important statistical significance.
Drawings
FIG. 1 is a schematic diagram of a hook point cloud, coordinate system, and key points.
FIG. 2 is a schematic diagram of the hook deformation deflection calculation.
Detailed Description
A method for monitoring and displaying omnibearing deformation based on three-dimensional point cloud data of a lifting hook comprises the steps of solving a symmetrical plane of original lifting hook data, calculating a contour line projected to the plane by the original lifting hook data and current data, detecting a segmented deformation amount based on ray detection, and displaying the point cloud based on deformation deviation and tone mapping; the method specifically comprises the following steps:
s1, the point cloud collected by the three-dimensional measuring equipment by the hook and the coordinate system are shown in figure 1, the x axis and the z axis are respectively right and upward, and the y axis can be determined by a right hand rule. Recording an original and deformation-free hook point cloud as a point set P0, and recording a point cloud set collected by the three-dimensional measuring equipment as P1. Background noise removal for the set of points P1: any point therein is denoted as p (x, y, z); traversing the point cloud, if any point p satisfies:
{ P (x, y, z) ∈ P1| | | P | > d0}, deleting the point, and marking the set of the rest points as P, wherein d0 is a distance threshold.
S2, taking the upper half data of the point set P0 and P, calculating a 3 x 3 matrix R and a 3 x 1 vector t which satisfy the following formula,
n is the number of points in the point set P; the point set P is then transformed into the P0 coordinate system.
S3, calculating the symmetry plane of the original hook data set P0:
firstly, calculating a central point E of the point set, passing through a plane where the point E is parallel to XOZ, and recording as pi 0; secondly, calculating a symmetrical point set P0' of the point set P0 relative to the plane pi 0; then, a rotation matrix R and a translation vector t are obtained, so that the point set P0' is superposed with the point set P0 under the action of R and t; and finally, calculating the point of the optimal symmetry plane pi and a normal vector thereof according to the parameters.
And projecting the original point cloud set P0 of the lifting hook and the current point set P to the plane pi to obtain new point sets P0_ N and P _ N.
S4, searching a hook left side contour line L in a point set P0_ N, recording the lowest point A (xa, ya) and the top point B (xb, yb) of the contour line, and recording the point O1 as (xa, yb); likewise, the left-side contour line L1 is obtained by searching in the point set P _ N.
Making M rays from the O1 point, wherein the ray angle range is [180,270]]The angle is calculated clockwise, i.e. 0 deg. in the vertical direction on the plane of XOZ. Each ray intersects the contour lines L and L1 at two points, denoted as CiAnd Ci', i-1 … M, as shown in FIG. 2.
CiAnd Ci' distance between two points, i.e. deformation deviation at ray i, is recorded as Di。
S5, calculating all distance values DiAnd i is 1 … M, mapping to the HIS color space, and coloring and displaying the point cloud picture.
The invention is suitable for lifting hooks with different top shapes, and has practical significance for comparing deformation detection, namely deformation monitoring and trend analysis, of the same lifting hook at different periods.
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Examples
A method for monitoring and displaying omnibearing deformation based on three-dimensional point cloud data of a lifting hook comprises the following steps:
1) and denoising the current point cloud data. Since the acquisition environment of the point cloud data is generally considered to be a controllable environment, and the distance between the hook and the measuring equipment can be estimated during measurement, d0 can be set accordingly, and the noise data outside the hook can be deleted.
2) Hook monitoring is based on comparing current data with historical data, so that the current data set and the historical data set are transformed to be in the same coordinate system. Solving the optimization problem shown in the formula (1):
considering that the current hook may have deformation, if the calculation is performed by using all the data of the hook, an error is necessarily existed. Therefore, the upper half data of the hook without deformation is selected for calculation, P0 and P are the original point set and the currently measured point set of the hook respectively, and N is the number of points in P. And (3) solving the obtained R and t by using the formula (1), and calculating RP + t, namely transforming the current hook point cloud data P to a coordinate system of the original hook point cloud data P0.
Wherein, the upper half data is defined as follows:
searching a point with the minimum x component in the point set P, namely the leftmost edge point of the hook tip segment, marking the point as F, performing neighbor search from the point F, taking a point set meeting { P (x, y, z) | | | P-F | <50} as a hook tip segment, and marking the point set as pSharp; and traversing the point set pSharp, and searching a point with the largest z component, namely a hook tip vertex, which is marked as T (xt, yt, zt). And the set of points satisfying { p (x, y, z) | z > zt } is taken as the upper half data pAbove.
3) And calculating the symmetry plane of the hook raw data.
First, the central point of the point set P is calculated
The E passing point is parallel to the XOZ plane and is recorded as pi 0;
next, a set of points P0' is calculated for the set of points P0 relative to plane Π 0. According to Householder transformation, if any point in the point set P0 is regarded as a vector P0, and if a point q is passed through a symmetry plane and a normal vector is n, a symmetry point P0' of P0 relative to the plane is (I-nn)T) p0+2dn, where d is the distance of the q point to the plane and I is the identity matrix; all the symmetric points form a point set P0';
then, a rotation matrix R and a translation vector t are obtained according to the principle of the formula (1), so that the point set P0' is superposed with the point set P0 under the action of R and t;
finally, the optimal symmetry plane n of the point set P can be determined by the normal vector v and the point m in the following formula:
v is a matrix (I-nn)T) R, in each feature vector, a feature vector corresponding to a feature value-1;
the vector corresponding to m is 1/2 (R (2dv) + t);
the two point cloud sets respectively project towards the plane pi. As can be seen from the knowledge of vector calculation, if the vector of any point is x0, the projection point vector x 0' of the point on plane Π is x 0-x 0 v;
4) searching a hook left side contour line L in a point set P0', recording a lowest point A (xa, ya) and a hook tip top point B (xb, yb) of the contour line, and recording a point O1 as (xa, yb), as shown in FIG. 1; similarly, searching in point set P1' obtains its left side contour L1.
M rays are taken from the O1 point, and the angle range of the rays is [180,270] °. Each ray intersects the contour lines L and L1 at two points denoted as Ci and Ci', i being 1 … M. The distance between two points Ci and Ci', i.e. the deformation deviation at the ray i, is denoted as Di, as shown in FIG. 2.
5) And mapping all the distance values Di to the HSI color space for displaying. As known from image color space knowledge, H represents chroma and has a value range of [0,2pi ]. If the value range of H is set, such as [1/6pi, 4/3pi ], S is 1, and V is 255, the color range is from yellow to blue. And discretizing the value ranges of the Di and the H into M magnitude levels, corresponding to each other one by one, and coloring corresponding points in the original image.
Claims (3)
1. A lifting hook deformation monitoring and displaying method based on three-dimensional point cloud is characterized by comprising the following steps:
step 1, denoising current hook data and removing point cloud data outside a hook; the method specifically comprises the following steps:
recording an original and deformation-free hook point cloud as a point set P0, and recording a point cloud set currently acquired by three-dimensional measurement equipment as P1; background noise removal for the set of points P1: and recording any point as p (x, y, z), traversing the point cloud, and if the any point p satisfies the following conditions: { P (x, y, z) ∈ P1| | | P | > d0}, deleting the point, and marking a set formed by the rest points as P;
step 2, calculating a rotation matrix and a translation vector to enable the data of the upper half part of the current lifting hook to be overlapped with the data of the upper half part of the original lifting hook; the method specifically comprises the following steps:
taking the data of the upper half of the point sets P0 and P, calculating a rotation matrix R and a translation vector t which satisfy the following formulas:
n is the number of points in the point set P; transforming the point set P into a P0 coordinate system;
step 3, calculating a symmetrical plane of the original hook data, and projecting the original data and the current data to the plane by taking the symmetrical plane as a reference; the method specifically comprises the following steps:
calculating a central point E of the point set P, passing through a plane where the point E is parallel to the XOZ, and recording as pi 0;
calculating a mirror point set P0' of the point set P0 relative to the plane pi 0;
solving a rotation matrix R and a translation vector t, so that the point set P0' is superposed with the point set P0 under the action of R and t;
calculating the point of the optimal symmetry plane pi and a normal vector thereof;
projecting the original point cloud set P0 of the lifting hook and the current point set P to the plane pi to obtain new point sets P0_ N and P _ N;
step 4, calculating the deviation between the two projection lines in a segmented manner;
and 5, mapping the deviation numerical value to colors with different chromaticities, and redrawing each section of point cloud data by using the color representing the deviation.
2. The lifting hook deformation monitoring and displaying method based on the three-dimensional point cloud as claimed in claim 1, wherein the step 4 specifically comprises:
searching a hook left side contour line L in a point set P0_ N, recording a lowest point A (xa, ya) and a hook tip top point B (xb, yb) of the contour line, and recording a point O1 as (xa, yb); similarly, searching in the point set P _ N to obtain a left side contour line L1;
making M rays from the O1 point, wherein the ray angle range is [180,270]](iv) DEG; each ray intersects the contour lines L and L1 at two points, denoted as CiAnd Ci’，i＝1…M；
CiAnd Ci' distance between two points, i.e. deformation deviation at ray i, is recorded as Di。
3. The lifting hook deformation monitoring and displaying method based on the three-dimensional point cloud as claimed in claim 2, wherein the step 5 specifically comprises: all the distance values D are calculatediMapping to HIS color space, and coloring and displaying the point cloud picture.
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| US8028436B2 (en) * | 2009-03-24 | 2011-10-04 | Machining And Welding By Olsen, Inc. | Hook for detection of chain sling failure |
| CN202880687U (en) * | 2012-08-27 | 2013-04-17 | 浙江省特种设备检验研究院 | Three-dimensional deformation detecting system of lifting hook of crane |
| CN203187310U (en) * | 2013-04-17 | 2013-09-11 | 新乡市恒创机械设备有限公司 | Lifting hook deformation monitoring device |
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| CN106780386B (en) * | 2016-12-16 | 2019-11-26 | 武汉理工大学 | A kind of 3 D laser scanning deformation extraction method for evaluating reliability |
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