CN108195287B - A kind of measuring system suitable for trough type solar heat-collector bracket - Google Patents
A kind of measuring system suitable for trough type solar heat-collector bracket Download PDFInfo
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- CN108195287B CN108195287B CN201711454803.4A CN201711454803A CN108195287B CN 108195287 B CN108195287 B CN 108195287B CN 201711454803 A CN201711454803 A CN 201711454803A CN 108195287 B CN108195287 B CN 108195287B
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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
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Abstract
The present invention provides a kind of measuring system suitable for trough type solar heat-collector bracket, the system comprises measurement attachment, photographic equipment and computing devices, measurement attachment includes: supporting spring measurement attachment, absorbing pipe measurement attachment, rotary shaft measurement attachment, wherein supporting spring measures attachment, the position of the supporting spring of subsidiary trough type solar heat-collector bracket；Absorbing pipe measures attachment, the supporting point coordinate of the absorbing pipe of subsidiary trough type solar heat-collector bracket；Rotary shaft measures attachment, the position of subsidiary trough type solar heat-collector support rotating shaft；Photographic device is set up in trough type solar heat-collector bracket front end, and for acquiring picture, the picture transfer of computing device Built-in Image process instruction, photographic device acquisition carries out image procossing to the computing device, obtains the geometric sense of trough type solar heat-collector bracket.Measuring system provided by the invention has effectively proposed the precision of trough type solar heat-collector bracket measurement by installation measurement attachment.
Description
Technical Field
The invention relates to the technical field of photogrammetry, in particular to a measuring system suitable for a groove type solar thermal collector bracket.
Background
Energy is a material basis on which human beings rely to live, and along with the development and progress of society and economy, the requirements of people on energy are higher and higher. Solar energy is used as a clean and green new energy and is widely popularized and applied. The solar thermal power generation technology is mainly divided into four modes of a groove type, a tower type, a disc type and a Fresnel type, wherein the groove type solar thermal power generation technology is the most mature and has the most commercial operation condition. At present, the focus of the attention of the trough-type solar thermal power generation technology is how to improve the thermal power generation efficiency. The thermal efficiency expression is: etaThermal efficiency＝ρ·γ·(τ·α)
The solar collector is a parabolic mirror surface reflectivity, a truncation factor of the collector, an absorption rate of a coating on the surface of the heat absorption tube and a transmittance of a glass cover on the surface of the heat absorption tube. Therefore, the efficiency of the trough type solar thermal power generation depends on four influencing factors, and after the material attribute of the heat collector is determined, the parabolic mirror reflectivity, the absorption rate of the surface coating of the heat absorption tube and the transmittance of the surface glass cover of the heat absorption tube are also determined, so that in the later assembly operation, the factors influencing the efficiency of the trough type solar thermal power generation only have the truncation factor of the heat collector, and the truncation factor of the trough type solar thermal power collector with good light condensation is ensured to be more than 0.95.
For the trough type solar heat collector, the influence factors of the truncation factor are mainly the mirror surface shape precision and the bracket precision. In the past decades, a number of methods have been proposed for measuring specular surface shapes. The method comprises video scanning Hartmann optical measurement; applying a close-range photogrammetry method to the measurement of the trough type solar thermal collector; stripe reflection method of black and white stripes; color fringe reflection. Compared with the mature mirror surface shape measurement, the bracket measurement research is less. At present, the most widely used is the photogrammetry system QFoto developed by german aerospace center (DLR) in 2008, which is specially used for the surface shape and the bracket of the trough type solar thermal collector. However, the precision of the auxiliary measuring system in the prior art is low, and the accuracy of the measurement of the support is difficult to guarantee.
Therefore, in order to solve the above problems, a measuring system suitable for trough solar collector racks is needed.
Disclosure of Invention
The invention aims to provide a measuring system suitable for a bracket of a groove type solar thermal collector, which comprises a measuring accessory, a camera device and a calculating device, wherein the measuring accessory comprises a supporting sheet measuring accessory, a heat absorption pipe measuring accessory and a rotating shaft measuring accessory, wherein the supporting sheet measuring accessory, the heat absorption pipe measuring accessory and the rotating shaft measuring accessory are arranged on the supporting sheet measuring accessory, and the rotating shaft measuring accessory are arranged on the supporting sheet measuring accessory
The supporting sheet measuring accessory is used for being installed on a supporting sheet of the groove type solar thermal collector bracket and assisting in measuring the position of the supporting sheet of the groove type solar thermal collector bracket;
the supporting sheet measuring accessory comprises a connecting part, the connecting part radiates outwards to form three measuring arms, the end parts of the three measuring arms are respectively provided with first mark point positioning holes, and the position of the supporting sheet is positioned by utilizing the three first mark point positioning holes;
the heat absorption pipe measurement accessory is used for being mounted on a heat absorption pipe bracket of the groove type solar heat collector bracket and assisting in measuring the support point coordinates of the heat absorption pipe of the groove type solar heat collector bracket;
the heat absorption pipe measuring accessory is semicircular, a protruding part is arranged on one side face of the semicircle, and a second mark point positioning hole is formed in the position, corresponding to the protruding part, of the cross section of the heat absorption pipe measuring accessory;
the rotating shaft measuring accessory is used for being installed on a rotating shaft of the groove type solar thermal collector bracket and assisting in measuring the position of the rotating shaft of the groove type solar thermal collector bracket;
the camera device is erected at the front end of the groove type solar thermal collector support and used for collecting pictures, an image processing instruction is arranged in the computing device, and the pictures collected by the camera device are transmitted to the computing device for image processing to obtain the geometric quantity of the groove type solar thermal collector support.
Preferably, a side surface of the connecting part is provided with a mounting flat key.
Preferably, the blade measuring attachment determines that the position of the blade includes a blade support point coordinate and a blade angle.
Preferably, the first calibration point positioning hole is a counter bore.
Preferably, the parallelism error of the upper surface and the lower surface of the supporting sheet measuring accessory is 0.022mm, and the position error of the first marking point positioning hole is 0.09 mm.
Preferably, the flatness error of the contact surface of the heat absorption pipe measuring accessory and the heat absorption pipe bracket is 0.20mm, and the position error of the second mark point positioning hole is 0.15 mm.
Preferably, the accessory is measured to the rotation axis is the columnar structure spare, a column structure terminal surface has the apron that is used for the joint rotation axis, apron center department is equipped with the third mark point locating hole.
Preferably, the coaxiality error of the third index point positioning hole of the rotation axis measuring attachment is 0.10 mm.
Preferably, the rotating shaft measuring accessory is an annular sleeve with a bottom plate, and a fourth mark point positioning hole is formed in the center of the bottom plate of the annular sleeve.
Preferably, the coaxiality error of the fourth index point positioning hole of the rotation axis measuring attachment is 0.075 mm.
The invention provides a measuring system suitable for a trough type solar thermal collector bracket aiming at the defects in the aspect of measurement of the trough type solar thermal collector bracket in the prior art, measures each geometric quantity to be measured of the trough type solar thermal collector bracket by utilizing a photogrammetry method, and has the following advantages:
and designing a supporting sheet measuring accessory, and improving the measurement precision of the supporting sheet supporting point coordinate and the supporting sheet angle by controlling the processing error of the supporting sheet measuring accessory.
The measuring accuracy of the coordinates of the supporting point of the heat absorbing pipe is improved by designing the measuring accessory of the heat absorbing pipe and controlling the processing error of the measuring accessory of the heat absorbing pipe.
The rotary shaft measuring accessory is designed, and the measuring precision of the position and the direction of the central axis of the rotary shaft is improved by controlling the machining error of the rotary shaft measuring accessory.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:
figure 1 schematically shows a schematic view of a trough solar collector holder;
FIG. 2 is a schematic view of the blade measuring attachment of the present invention;
FIG. 3 is a schematic view of the blade and blade measuring attachment of the present invention installed;
FIG. 4 is a schematic view of the receiver tube measurement attachment of the present invention;
FIG. 5 is a schematic view of the absorber tubing holder and absorber tubing measurement attachment mounting of the present invention;
FIG. 6 shows a schematic view of the structure of a rotating shaft measurement accessory in one embodiment of the present invention;
FIG. 7 shows a schematic view of the mounting of a rotating shaft and a rotating shaft measurement accessory in one embodiment of the invention;
FIG. 8 shows a schematic view of the structure of a rotary shaft measuring attachment in another embodiment of the present invention;
figure 9 shows a schematic view of the mounting of the rotating shaft and the rotating shaft measuring attachment in another embodiment of the present invention.
Detailed Description
The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, and related technical terms should be well known to those skilled in the art. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps, unless otherwise specified. The disclosure of the present invention will be explained by the following specific embodiments, and firstly, the trough type solar collector holder according to the present invention is explained, as shown in the schematic view of the trough type solar collector holder shown in fig. 1, the trough type solar collector holder includes a torsion box 105, a rotation shaft 103 is installed in the torsion box 105, and the rotation shaft 103 extends out of the torsion box 105. The trough solar collector bracket further comprises a cantilever beam 104, and the cantilever beam 104 contains the supporting sheet 101 therein. The heat absorbing pipe holder 102 is mounted on the rotary shaft 103. The absorber tube holder 102 mounts the absorber tubes.
The invention is suitable for a measuring system of a groove type solar heat collector bracket, and measures the geometric parameters of the groove type solar heat collector bracket, wherein the geometric parameters respectively comprise: the coordinates of the supporting point of the supporting sheet 101, the angle of the supporting sheet 101, the position of the heat absorbing pipe and the position and the direction of the rotating shaft 103. In actual measurement, since the geometric parameters cannot be directly measured by photogrammetry, indirect measurement by means of a measurement accessory is required.
Aiming at the defect of low measurement precision of the geometric parameters caused by low precision of a measurement accessory when the groove type solar heat collector bracket is indirectly measured, the measurement system suitable for the groove type solar heat collector bracket provided by the invention comprises the measurement accessory, photographic equipment and a computing device, wherein the measurement accessory comprises a supporting sheet measurement accessory, a heat absorption pipe measurement accessory and a rotating shaft measurement accessory.
The camera device is erected at the front end of the groove type solar thermal collector support and used for collecting pictures, an image processing instruction is arranged in the computing device, and the pictures collected by the camera device are transmitted to the computing device for image processing to obtain the geometric quantity of the groove type solar thermal collector support.
Fig. 2 is a schematic structural diagram of the blade-supporting measuring accessory of the present invention, and fig. 3 is a schematic mounting diagram of the blade-supporting and the blade-supporting measuring accessory of the present invention, wherein the blade-supporting measuring accessory is used for being mounted on a blade 101 of a trough-type solar collector bracket to assist in measuring the position of the blade of the trough-type solar collector bracket. The blade measurement accessory determines the position of the blade 101 including the blade support point coordinates and the blade angle. The processing error of the supporting sheet measuring accessory is solved by the geometric quantity to be measured of the bracket of the groove type solar heat collector, specifically: the parallelism error of the upper surface and the lower surface of the supporting sheet measuring accessory is 0.022mm, and the position error of the first mark point positioning hole is 0.09 mm.
The supporting sheet measuring accessory comprises a connecting part 201, the connecting part 201 radiates outwards to form three measuring arms 202, the end parts of the three measuring arms are respectively provided with a first marking point positioning hole 203, the position of the supporting sheet is positioned by utilizing the three first marking point positioning holes 203, and the first marking point positioning holes 203 are counter bores. In the embodiment, a flat key 204 is arranged on one side surface of the connecting part 201, and the supporting sheet measuring accessory is arranged with the supporting sheet 101 through the flat key 204.
In the specific measuring process, the circle center coordinates of the 3 first mark points obtained by photogrammetry are respectively set as (x)1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) Then the position (x) of the supporting sheet can be determined by the gravity center of three pointsp,yp,zp) Determining the blade normal vector (x) by fitting a plane at three pointsn,yn,zn)。
Fig. 4 is a schematic structural diagram of a heat absorbing pipe measuring accessory of the present invention, fig. 5 is a schematic diagram of an installation of a heat absorbing pipe support and a heat absorbing pipe measuring accessory of the present invention, and the heat absorbing pipe measuring accessory is used for being installed on a heat absorbing pipe support 102 of a trough-type solar collector support to assist in measuring the coordinates of a supporting point of a heat absorbing pipe of the trough-type solar collector support.
The heat absorption pipe measuring accessory is semicircular 301, a protruding part 302 is arranged on one side surface of the semicircle, and a second mark point positioning hole 303 is arranged at the position, corresponding to the protruding part 302, of the cross section of the heat absorption pipe measuring accessory. The receiver tube measurement accessory is mounted by the protrusion 302 being inserted into the central bore of the receiver tube holder 102. The processing error of the heat absorption pipe measuring accessory is calculated by the geometric quantity to be measured of the groove type solar heat collector support, the flatness error of the contact surface of the heat absorption pipe measuring accessory and the heat absorption pipe support is 0.20mm, and the position error of the second mark point positioning hole is 0.15 mm.
Determining the coordinates (x) of the supporting point of the heat absorbing pipe through the coordinates of the circle center of the second mark point in the specific measurement processa,ya,za) Specifically:
setting the circle center coordinate of the second mark point obtained by photogrammetry as (x)m,ym,zm) And then:
fig. 6 is a schematic view showing the structure of a rotating shaft measuring accessory in one embodiment of the present invention, and fig. 7 is a schematic view showing the installation of the rotating shaft and the rotating shaft measuring accessory in one embodiment of the present invention. The rotating shaft measuring accessory is a columnar structural memberA cover plate 402 for clamping the rotating shaft is arranged on one end face of the base plate 401, and a third mark point positioning hole 403 is formed in the center of the cover plate. The rotation axis measuring attachment is inserted into a center through hole of the rotation axis 103, and is engaged with the rotation axis 103 by the cover plate 402. The machining error of the rotating shaft measuring accessory is obtained by the geometric quantity to be measured of the groove type solar heat collector bracket, and the coaxiality error of the third mark point positioning hole of the rotating shaft measuring accessory is 0.10mm in one embodiment. Determining the coordinate of one point on the central axis of the rotating shaft by the circle center coordinate of the third mark point for the rotating shaft with the central through hole
Fig. 8 is a schematic structural diagram of a rotating shaft measuring accessory in another embodiment of the present invention, fig. 9 is a schematic diagram illustrating the installation of the rotating shaft and the rotating shaft measuring accessory in another embodiment of the present invention, in another embodiment, for a specific rotating shaft, the rotating shaft measuring accessory is a ring-shaped sleeve 501 with a bottom plate 502, and a fourth mark point positioning hole 503 is provided at the center of the bottom plate 502 of the ring-shaped sleeve. The rotating shaft measuring attachment is sleeved on the rotating shaft 103 through a ring-shaped sleeve 401. The machining error of the rotating shaft measuring accessory is obtained by the geometric quantity to be measured of the groove type solar heat collector bracket, and in another embodiment, the coaxiality error of the fourth mark point positioning hole of the rotating shaft measuring accessory is 0.075 mm. In another embodiment, for a rotating shaft without a central through hole, the coordinate of one point on the central axis of the rotating shaft is determined by the center coordinate of the fourth mark pointSpecifically, two points on the central axis of the rotating shaftThe central axis equation of the rotating shaft can be solved, so that the included angle theta between the central axis and the y-axis can be determineda：
In the above embodiments of the present invention, the maximum and minimum limit sizes of the measurement accessory respectively move a safety margin into the tolerance band, that is: the upper acceptance limit is the maximum limit size-safety margin (A), and the lower acceptance limit is the minimum limit size + safety margin (A), wherein the value of the safety margin A is determined according to the size tolerance of the measured workpiece, and the value of A can be 1/10 of the workpiece tolerance. The safety margin a corresponds to the uncertainty (μ) in the measurement, including the uncertainty μ 1 of the measuring device and other caused uncertainties, and μ 1 is 0.9A. From this, it was determined that the machining precision of the attachment was 9/100 times the error of the geometric parameter.
The measurement results obtained by photogrammetry performed by the measurement system suitable for the trough type solar collector bracket provided by the invention are analyzed.
The geometric quantities measured by the bracket of the groove type solar heat collector are respectively as follows: the coordinates of the supporting point of the supporting sheet, the angle of the supporting sheet, the position of the heat absorption tube and the position and the direction of the rotating shaft.
Generally, a world coordinate system Oxyz is constructed, a parabolic mirror surface f (x, y, z) is fitted by the coordinates of the supporting point of the supporting sheet and the normal vector of the corresponding supporting plane, then the central axis of the heat absorption tube is fitted by the coordinates of the supporting point of the heat absorption tube, and the direction vector of the central axis is calculated. Projecting a large amount of incident light rays to the mirror surface, calculating the distance between the reflected light rays and the central axis of the heat absorption tube, counting the number of the reflected light rays with the distance being smaller than the radius of the heat absorption tube, calculating a truncation factor, and finally analyzing the error of each geometric quantity under the condition that the truncation factor is larger than 0.95.
Mirror fitting model
The mirror surface is formed by the coordinates (x) of the supporting point of the supporting sheetp,yp,zp) And the corresponding support plane normal vector (x)n,yn,zn) Fitting to obtain the equation of the mirror surface:
f(x,y,z)＝a0x2+b0y2+j0z2+c0xy+d0yz+e0xz+f0x+g0y-z+i0＝0 (1)
the above formula can be used to calculate the partial derivatives of x, y and zObtaining normal vector of mirror surfaceComprises the following steps:
from the above formula, one can obtain:
suppose the ith point coordinate of the supporting point of the supporting sheet is (x)pi,ypi,zpi) The corresponding support plane normal vector is (x)ni,yni,zni) The following equation is obtained:
and (3) simultaneously connecting all supporting points of the supporting sheet to obtain an equation:
P＝(ATA)-1ATB (5)
wherein,the coefficients of the mirror equation can be determined from equation (5), resulting in the mirror equation.
Heat absorption pipe model
Let the coordinate of any point on the central axis of the heat absorption tube be (x)0,y0,z0) Then, the equation of the central axis of the heat absorption tube is:
let y00, and is modified from the above formula:
the spatial non-linear fitting problem can thus be converted into a linear fitting problem for two planes. Let the coordinates of the supporting point of the heat absorption tube be (x)a,ya,za) The ith support point coordinate is (x)ai,yai,zai) And then:
order toWhen m is 1, then:
the direction vector of the central axis of the heat absorption pipe can be determined by the formula (9)
Light ray description
The light reflection principle diagram of the trough solar mirror is shown in fig. 3. The incident light is vertically incident to the parabolic mirror and is reflected to the heat absorption tube through the mirror. Wherein,is the reflected ray direction vector.
The reflected ray direction vector is:
wherein,is the direction vector of the incident ray.
Establishment of truncation factor calculation model
The distance d between the reflected light and the central axis of the heat absorption tube is as follows:
wherein,is a vector formed by the reflected light and any point on the central axis of the heat absorption tube. And after the distances between all the reflected light rays and the central axis of the heat absorption tube are determined, counting the number of the reflected light rays with the truncation distance smaller than the radius of the heat absorption tube, thereby obtaining a truncation factor gamma.
It should be noted that although the distance between some reflected light beams and the central axis of the heat absorption tube is smaller than the radius of the heat absorption tube, these reflected light beams do not impinge on the heat absorption tube, and theoretically they impinge only on the extension line of the heat absorption tube, so it is necessary to project the reflected light beams and the central axis of the heat absorption tube onto the yOz plane, calculate the intersection point of the two projected light beams, and remove the part of the reflected light beams that do not meet the requirements by limiting the coordinates of the intersection point in the y direction.
Geometric errors of the trough solar collector bracket
The position and curvature of the mirror surface are directly influenced by the support point coordinates and the support sheet angle, so that the reflected light rays are changed; the coordinates of the supporting points of the heat absorbing pipes directly influence the positions of the heat absorbing pipes, so that part of light rays cannot be reflected to the heat absorbing pipes; when the position and direction of the rotating shaft are changed, the incident angle of the incident light changes, resulting in a change in the reflected light, thereby affecting the truncation factor.
Blade error simulation analysis
The supporting sheet error comprises a supporting sheet angle error and a supporting sheet supporting point coordinate error.
Angle of the supporting sheet
In the local coordinate system, when the supporting sheet rotates, the supporting sheet rotates around the x axis and rotates around the y axis, and the final truncation factor is not influenced when the supporting sheet rotates around the z axis. About the x-axisIs d θxThe angle of rotation about the y-axis being d θy。
Is a normal vector of the plane, and can be calculatedAnd obtaining the plane-supporting normal vector required by the fitted curved surface by the coordinates under the world coordinate system xyz.The coordinates in the local coordinate system are (0,0, 1).
The rotation angle of the supporting sheet is brought into the rotation matrix to obtain the normal vector of the supporting planeDescription under the world coordinate System (x)n,yn,zn) Comprises the following steps:
where θ is the rotation angle of the two coordinate systems around the y-axis in an ideal case. The angle of the supporting sheet can be reversely deduced by the normal vector.
Error in coordinates of supporting point of supporting sheet
The ideal coordinate of the supporting point of the supporting sheet is set asWhen random errors are superposed on the coordinates of the supporting points of the supporting sheet, the random errors are superposed on the x ' O ' y ' of the supporting plane and the random errors are superposed on the O ' z ' of the normal direction of the supporting plane respectively,
superposing random errors (dx, dy, dz) on ideal coordinates to obtain coordinates (x) of the supporting point coordinates of the supporting sheet under the world coordinate system xyzp,yp,zp) Namely:
simulation analysis of position error of heat absorption tube
The ideal coordinate of the supporting point of the heat absorption tube isSuperimposing random errors (dx)a,dya,dza) And the coordinate of the supporting point of the heat absorption tube is (x)a,ya,za) Comprises the following steps:
and (7) driving the coordinates of all the support points of the heat absorption pipes into a formula, and solving the direction vector of the central axis of the heat absorption pipes.
Simulation analysis of position and orientation errors of rotating shaft
The included angle between the central axis of the rotating shaft and the y axis is set as thetarThen the direction vector of the incident ray is changed from (0,0, -1) in the ideal case to (0, sin θ)r,cosθr) Namely:
and (3) superposing errors according to the method, calculating the coordinates of the supporting point of the supporting sheet, the normal vector, the position of the heat absorption tube and the direction vector of the incident light by using a formula (13-16), and substituting the calculated coordinates, the normal vector, the position of the heat absorption tube and the direction vector of the incident light into a formula (11-12) to perform simulation analysis of the truncation factor. And (3) independently analyzing the influence degree of each geometric quantity on the truncation factor, namely, only superposing errors on one of the geometric quantities at a time, and analyzing the errors of each geometric quantity of the bracket under the condition that the truncation factor is more than 0.95.
Independently analyzing the influence degree of each geometric quantity on the truncation factor
Each geometric quantity is independently analyzed, and the simulation result is as follows: standard deviation sigma of error of supporting point coordinate of supporting sheet in supporting planexyIs 3.0 mm; standard deviation sigma of error of supporting point coordinate of supporting sheet in normal direction of supporting planezIs 0.02 mm; standard deviation sigma of error of blade angleAngle of the supporting sheetIs 17 degrees; standard deviation sigma of error of heat absorption tube supporting point coordinateHeat absorption tubeIs 12 mm; standard deviation sigma of error of included angle between central axis of rotating shaft and y axisRotating shaftIs 1.5 degrees.
Comprehensively analyzing the influence degree of each geometric quantity on the truncation factor
In practical situations, the error terms of the geometric quantities exist simultaneously, so that in addition to the independent analysis of the influence of the geometric quantities on the truncation factor, the relationship between the geometric quantities needs to be analyzed, and then the comprehensive influence degree of all the geometric quantities on the truncation factor is analyzed on the basis of the relationship.
According to the actual structure, the position and the direction of the rotating shaft and the coordinates of the supporting point of the heat absorbing pipe are mutually independent, and the coordinates are respectively independent from the coordinates of the supporting point of the supporting sheet and the supporting angle of the supporting sheet, but the relationship between the coordinates of the supporting point of the supporting sheet and the supporting angle of the supporting sheet is not independent and is related, so that the geometric relationship between the coordinates of the supporting point of the supporting sheet and the supporting point of the supporting sheet needs to be analyzed. In practice, the rotation of the blade is divided into two cases, i.e., the rotation of the blade as a whole about the y-axis and the rotation of the contact portion of the blade with the mirror surface about the x-axis.
When the supporting point of the supporting sheet rotates around the y axis by thetayAfter the corner, the support point coordinate difference is: Δ x ═ xn-xt,Δz＝zn-zt. The rotating angle of the whole supporting sheet around the y axis is as follows:
when the supporting point of the supporting sheet rotates around the x axis by thetaxAfter the corner, the support point coordinate difference is: y isn-yt,Δz＝zn-zt. The angle of rotation about the x-axis with the mirror contact portion is:
during comprehensive analysis, firstly, errors of all geometric quantities obtained through independent analysis are simultaneously superposed on all geometric quantities, then on the basis, the errors are reduced, simulation analysis is carried out, and finally, the errors of all geometric quantities of the groove type solar heat collector bracket are obtained under the condition that the truncation factor is larger than 0.95.
Since the blade support point coordinates are related to the blade angle, σxyOr σzWhen changed, σAngle of the supporting sheetChanges will follow. So that when changing the error level, only σ needs to be changedxy、σz、σHeat absorption tubeAnd σRotating shaftFour variables are required. The errors of the geometric quantities measured by the present invention are shown in table 1.
Table 1 error of each geometric quantity measured by the present invention
| Geometric error term of support to be measured | Error of the measurement |
| The coordinate of the supporting point of the supporting sheet has errors in the supporting plane | ±1.5mm |
| The coordinates of the supporting point of the supporting sheet have errors in the normal direction of the supporting plane | ±0.36mm |
| Coordinate error of supporting point of heat absorption tube | ±2.4mm |
| Included angle error between rotating shaft and y-axis | ±2.4° |
According to the analysis, when the system provided by the invention meets the heat collection efficiency, the error of the coordinates of the supporting point of the supporting sheet in the supporting plane is +/-1.5 mm, the error of the coordinates of the supporting point of the supporting sheet in the normal direction of the supporting plane is +/-0.36 mm, the error of the angle of the supporting sheet is 2.4 degrees, and the error of the included angle between the central axis of the rotating shaft and the y axis is 2.4 degrees. Under the condition of ensuring the heat collection efficiency of the trough type solar heat collector, the measured geometric errors of the trough type solar heat collector are low, and the measurement precision is improved.
The invention provides a measuring system suitable for a trough type solar thermal collector bracket aiming at the defects in the aspect of measurement of the trough type solar thermal collector bracket in the prior art, measures each geometric quantity to be measured of the trough type solar thermal collector bracket by utilizing a photogrammetry method, and has the following advantages:
and designing a supporting sheet measuring accessory, and improving the measurement precision of the supporting sheet supporting point coordinate and the supporting sheet angle by controlling the processing error of the supporting sheet measuring accessory.
The measuring accuracy of the coordinates of the supporting point of the heat absorbing pipe is improved by designing the measuring accessory of the heat absorbing pipe and controlling the processing error of the measuring accessory of the heat absorbing pipe.
The rotary shaft measuring accessory is designed, and the measuring precision of the position and the direction of the central axis of the rotary shaft is improved by controlling the machining error of the rotary shaft measuring accessory.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims (8)
1. The measuring system suitable for the groove type solar heat collector bracket is characterized by comprising a measuring accessory, a camera device and a calculating device, wherein the measuring accessory comprises a supporting sheet measuring accessory, a heat absorption pipe measuring accessory and a rotating shaft measuring accessory, and the supporting sheet measuring accessory, the heat absorption pipe measuring accessory and the rotating shaft measuring accessory are arranged on the supporting sheet measuring accessory
The supporting sheet measuring accessory is used for being installed on a supporting sheet of the groove type solar thermal collector bracket and assisting in measuring the position of the supporting sheet of the groove type solar thermal collector bracket;
the supporting sheet measuring accessory comprises a connecting part, the connecting part radiates outwards to form three measuring arms, the end parts of the three measuring arms are respectively provided with a first mark point positioning hole, the position of the supporting sheet is positioned by utilizing the three first mark point positioning holes,
during the measurement process, the circle center coordinates of the 3 first mark points obtained by photogrammetry are respectively set as (x)1,y1,z1)、(x2,y2,z2)、(x3,y3,z3) Then the position (x) of the supporting sheet can be determined by the gravity center of three pointsp,yp,zp) Determining the blade normal vector (x) by fitting a plane at three pointsn,yn,zn)；
The heat absorption pipe measurement accessory is used for being mounted on a heat absorption pipe bracket of the groove type solar heat collector bracket and assisting in measuring the support point coordinates of the heat absorption pipe of the groove type solar heat collector bracket;
the heat absorption pipe measuring accessory is semicircular, a protruding part is arranged on one side surface of the semicircle, a second mark point positioning hole is arranged at the position, corresponding to the protruding part, of the cross section of the heat absorption pipe measuring accessory, the heat absorption pipe measuring accessory is embedded into a central hole of the heat absorption pipe bracket through the protruding part for installation,
determining the coordinates (x) of the supporting point of the heat absorbing pipe through the coordinates of the circle center of the second mark point in the measuring processa,ya,za)，
Setting the circle center coordinate of the second mark point obtained by photogrammetry as (x)m,ym,zm) And then:
the rotating shaft measuring accessory is used for being installed on a rotating shaft of the groove type solar thermal collector bracket to assist in measuring the position of the rotating shaft of the groove type solar thermal collector bracket, and the rotating shaft measuring accessory is a columnar structural member or an annular kit;
when the rotating shaft measuring accessory is a columnar structural part, one end face of the columnar structure is provided with a cover plate for clamping the rotating shaft, the center of the cover plate is provided with a third mark point positioning hole, the rotating shaft measuring accessory is embedded into the central through hole of the rotating shaft and is clamped with the rotating shaft by the cover plate,
when the rotating shaft measuring accessory is an annular external member, the annular external member is provided with a bottom plate, a fourth mark point positioning hole is formed in the center of the bottom plate of the annular external member, and the rotating shaft measuring accessory is sleeved on the rotating shaft through the annular external member;
determining the coordinate of one point on the central axis of the rotating shaft through the third mark point or the fourth mark point in the measuring processFrom two points on the central axis of the rotating shaft The central axis equation of the rotating shaft can be solved, so that the included angle theta between the central axis and the y-axis can be determineda：
The camera device is erected at the front end of the groove type solar thermal collector support and used for collecting pictures, an image processing instruction is arranged in the computing device, and the pictures collected by the camera device are transmitted to the computing device for image processing to obtain the geometric quantity of the groove type solar thermal collector support.
2. The system of claim 1, wherein the connecting portion is provided with a flat key on one side.
3. The system of claim 1, wherein the blade measurement accessory determines the position of the blade including a blade support point coordinate and a blade angle.
4. The system of claim 1, wherein the first marker point locating hole is a counterbore.
5. The system of claim 1, wherein the blade measuring attachment has an error of parallelism of upper and lower surfaces of 0.022mm and an error of position of the first index point positioning hole of 0.09 mm.
6. The system of claim 1, wherein the flatness error of the tubing measurement accessory and tubing holder contact surface is 0.20mm and the positional error of the second index point locating hole is 0.15 mm.
7. The system of claim 1, wherein the rotation axis measurement accessory third index point locating hole has a concentricity error of 0.10 mm.
8. The system of claim 1, wherein the rotation axis measurement accessory's fourth index point locating hole has a concentricity error of 0.075 mm.
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