CN101865660A - New method for automatically measuring thickness of propeller blades - Google Patents
New method for automatically measuring thickness of propeller blades Download PDFInfo
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- CN101865660A CN101865660A CN201010106001A CN201010106001A CN101865660A CN 101865660 A CN101865660 A CN 101865660A CN 201010106001 A CN201010106001 A CN 201010106001A CN 201010106001 A CN201010106001 A CN 201010106001A CN 101865660 A CN101865660 A CN 101865660A
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Abstract
The invention provides a new method for automatically measuring the thickness of propeller blades, which takes an image as a basis to carry out non-contact automatic detection of the thickness of the propeller blades. The method comprises the following steps: firstly collecting the images of the propeller blades by utilizing equipment such as a computer, a projector, a camera and the like; acquiring a coordinate of a two-dimensional image coordinate system of all the projective points of the blades by taking a digital image processing technology as a basis; calculating a coordinate of a three-dimensional real-world coordinate system of all the projective points of the blades by utilizing a camera calibration model; and finally calculating the thickness of the propeller blade by utilizing the computer.
Description
Technical field:
The invention belongs to screw propeller and measure association area, particularly a kind of contactless new method for automatically measuring of the thickness of propeller blades based on image.
Technical background:
Screw propeller provides thrust for ship's navigation, is the vital part of marine propuision system.The quality of screw propeller directly affects Ship Propeling efficient.In order to ensure the workmanship of screw propeller, State Bureau of Technical Supervision has issued the national standard of relevant metal airscrew technical requirement, has carried out standard to comprising many technical indicators such as thickness of propeller blades.Propeller blade is the important assurance that realizes the propulsive performance of screw propeller, attributes such as the thickness of blade are the key factors of guaranteeing the screw propeller quality of production, in the production run of screw propeller, to carry out measurement repeatedly to the thickness of blade, so that provide foundation for the further processing of blade.Therefore, the accurate measurement that leaf is thick for the manufacturing accuracy that ensures screw propeller, realizes that the design performance of screw propeller has very important significance.
At present, thickness of propeller blades measures by coordinate measuring machine generally that each point coordinate of blade calculates.Propeller blade is one group of multidirectional inclination, the helically twisted body that changes curvature, the face and the line majority that characterize the blade surface geometry shape are both crooked, tilt again, and twisted characteristics, the length of each relative contour is the basic parameter of decision blade cross sectional shape, and the shape in each cross section is the basis that constitutes the blade global shape.Therefore, when measuring blade thickness, often be difficult to find accurately simultaneously the positioning reference of a certain parameter on each concerned direction, or the difficult value that directly records some parameter, often need to adopt special testing tool and specific detection method, even also will adopt the approximation parameters of some hypothesis to go to substitute those complicated parameter.The contact mode that existing coordinate measuring machine adopts is carried out propeller blade and is measured the accurate location of the blade face of needs and the corresponding measurement point of blade back when also being difficult to carry out the blade thickness measurement.These measuring machine bulky need the pointwise measurement of coordinates is all carried out in the different measurement cross section of each blade in screw propeller manufacturing process, and measuring process wastes time and energy, and have had a strong impact on the efficient of measuring, and can not realize automatic measurement.In addition, existing coordinate measuring machine utilizes rotary axis, beam type transverse arm and travelling carriage to support and mobile measuring staff gauge head carries out the measurement of screw propeller different cross section, it is this because structural nonlinears such as the transverse arm distortion that factors such as deadweight cause also influences the further raising of measuring accuracy.Existing coordinate measuring machine contact type measurement mode, also being difficult to carry out on-line measurement for the screw propeller process provides means.
The present invention is relevant thickness of propeller blades new measurement method.It is to utilize image to carry out the contactless and digitized measurement of propeller blade that the blade thickness new method of measuring that the present invention proposes belongs to.The measuring method of utilizing the present invention to propose can be carried out the measurement of thickness of propeller blades quickly and easily.Because what the present invention proposed is non-contact digital measuring method, different with the principle of existing screw propeller coordinate measuring machine, therefore can solve the deficiency of existing screw propeller coordinate measuring machine.Based on the thickness of propeller blades new method of measuring that the present invention proposes, can carry out the automatic measurement of thickness of propeller blades, make quality new effective detection means is provided for guaranteeing screw propeller.
Summary of the invention:
The objective of the invention is with the image is contactless full-automatic measurement that thickness of propeller blades is carried out on the basis.When utilizing this method to carry out the measurement of thickness of propeller blades, do not need the accurate location of the corresponding measurement point of blade face and blade back, belong to contactless all automatic measurement.
In order to reach above-mentioned target, the technical solution used in the present invention is: utilize digital projector that the projection dot matrix that computing machine generates automatically is incident upon screw propeller to be measured surface, utilize ccd video camera to obtain the image of propeller blade, blade image is carried out digitized processing, obtain the two dimensional image coordinate system pixel coordinate of all subpoints, utilize through the camera model of demarcating and carry out the mapping that all subpoint two-dimensional pixel coordinates of blade to three-dimensional real-world coordinates are, obtain the three-dimensional coordinate that all subpoints in three-dimensional real-world coordinates are according to the binocular vision Theoretical Calculation, make up the three-dimensional coordinate model of blade, and utilize the thickness of COMPUTER CALCULATION propeller blade.
The computing machine that the present invention includes the projection dot matrix generates and collection, all subpoint two dimensional image coordinate system pixel coordinates of blade image obtain, the three-dimensional real-world coordinates of all subpoints are coordinate Calculation, the structure of propeller blade three-dimensional coordinate model and the several steps such as calculating of blade thickness.The concrete steps that the present invention includes are as follows:
1) collection of generation of the computing machine of projection dot matrix and blade image
Generate dot matrix according to blade shape by computer programming, utilize projector that dot matrix is incident upon propeller blade to be measured surface, utilize 2 ccd video cameras to set up the binocular vision image capturing system, adopt suitably illumination in case of necessity, gather blade blade face and each 2 width of cloth of blade back image of comprising subpoint respectively.
2) subpoint two dimensional image coordinate system pixel coordinate obtains
At the blade blade face that collects and the image of blade back, carry out the digitized processing of image, obtain the two dimensional image coordinate system pixel coordinate of all subpoints with this.
3) the three-dimensional real-world coordinates of subpoint is a coordinate Calculation
According to the transformation relation between video camera imaging model, camera coordinate system and the three-dimensional real-world coordinates system, set up the projection matrix of reflection propeller blade all subpoint pixel coordinates of surface and three-dimensional real-world coordinates relation, setting up based on the three-dimensional real-world coordinates of all subpoints of pixel coordinate by the demarcation of projection matrix is the Coordinate Calculation model.The three-dimensional real-world coordinates of utilizing the binocular vision principle to calculate all subpoints is a coordinate.
4) structure of propeller blade three-dimensional coordinate model
Three-dimensional real-world coordinates based on blade blade face and blade back surface projection's point is a coordinate, three-dimensional coordinate to blade back surface projection's point carries out conversion, make the three-dimensional coordinate of itself and propeller blade blade face surface projection's point form relative position relation one to one, make up the three-dimensional coordinate model of propeller blade.
5) calculating of thickness of propeller blades
Propeller blade three-dimensional coordinate model to make up at first calculates the blade face of same vertical direction and the distance of blade back subpoint, and transformed coordinate system calculates blade thickness then, finally utilizes the computer realization thickness of propeller blades to calculate.
Advantage of the present invention: the present invention is to be the contactless automatic measurement that thickness of propeller blades is carried out on the basis with the image, so the present invention has contactless and advantage digitized measurement.The present invention does not need directly to contact the metal surface of blade, does not have defectives such as gauge head wearing and tearing.This method can realize the automatic measurement of thickness of propeller blades easily, and therefore, the present invention can be for the shortening screw propeller process-cycle, reducing production costs provides effective measurement means.
Description of drawings:
Accompanying drawing 1 is the step of thickness of propeller blades new method for automatically measuring;
Accompanying drawing 2 is thickness of propeller blades measuring system structural representations;
Accompanying drawing 3 is video camera imaging model synoptic diagram;
Accompanying drawing 4 is that thickness of propeller blades calculates synoptic diagram.
Embodiment:
Below in conjunction with accompanying drawing, the automatic new measurement method of the thickness of propeller blades based on image method that the present invention proposes is described, its know-why and specific implementation method are as follows:
Fig. 1 is the key step of thickness of propeller blades new method for automatically measuring, this method is measured with the method for image, at first generate the projection dot matrix and be incident upon screw propeller surface and images acquired by computer programming, obtain the two dimensional image coordinate system pixel coordinate of all subpoints of blade blade face and blade back surface then, and be coordinate according to the three-dimensional real-world coordinates of all subpoints of binocular vision Theoretical Calculation, make up the three-dimensional coordinate model of propeller blade based on this and calculate blade thickness.The present invention just can realize the automatic measurement of thickness of propeller blades according to this step.
Fig. 2 is the system architecture synoptic diagram that thickness of propeller blades is measured automatically.By digital projector the dot matrix that computing machine generates automatically is incident upon the propeller blade surface, utilizes two video camera L and R images acquired.In the camera coordinates system, the X-axis of video camera L and R overlaps, and Y-axis and Z axle are parallel to each other respectively, Z-direction is the camera light direction of principal axis, L is consistent with change in coordinate axis direction in the R coordinate system, and the XOY face is parallel to the plane of delineation, simultaneously initial point (photocentre) side-play amount of video camera L and R is fixed.This has just guaranteed the consistance of propeller blade subpoint Z-direction coordinate in two camera coordinates systems and the determinacy of measuring system.
Fig. 3 is a video camera imaging model synoptic diagram, and comprising three-dimensional real-world coordinates in this model is O
wX
wY
wZ
w, camera coordinate system O
cX
cY
cZ
c, image coordinate system O
0UV (unit is a pixel), image physical coordinates are O
1XY (unit is a millimeter).The imaging process of blade is exactly the transfer process between above four coordinate systems.Among the present invention,, realize that two dimensional image coordinate system coordinate is a Coordinate Calculation to three-dimensional real-world coordinates according to the depth information of all subpoints of binocular imaging Theoretical Calculation.
(U V) is two dimensional image coordinate system pixel coordinate to note; (X is a coordinate for the image physical coordinates Y); (X
c, Y
c, Z
c) be two dimensional image coordinate system pixel coordinate; (X
w, Y
w, Z
w) for real-world coordinates is a three-dimensional coordinate, the calculated relationship between each coordinate system is as follows:
1) two dimensional image coordinate system pixel coordinate and image physical coordinates are the coordinate Calculation relation
Wherein, (U
0, V
0) for the image physical coordinates be XO
1The coordinate round dot of Y, dx, dy are respectively on the image planes each pixel along the physical size of X-axis and Y direction.
2) physical coordinates of note subpoint in the image of the left and right sides is that coordinate is respectively (X
L, Y
L) and (X
R, Y
R), according to the binocular camera imaging theory, camera coordinate system coordinate and image physical coordinates are that the relation of coordinate is as follows:
f/Z
c＝X
L/X
c
f/Z
c＝X
R/(X
c-b)
f/Z
c＝Y
L/Y
c＝Y
R/Y
c
Thus, can calculate the depth information of this subpoint:
Z
c＝fb/|X
L-X
R| (2)
Wherein, f is used focus of camera in the measuring system of the present invention, and b is the distance of left and right cameras photocentre.
3) three-dimensional real-world coordinates is coordinate and camera coordinate system coordinate Calculation relation
Wherein, R is the rotation matrix of 3*3, and T is the translation matrix of 3*1,0=(0,0,0)
T
Therefore, image coordinate system two-dimensional pixel coordinate and real-world coordinates are that calculated relationship between the three-dimensional coordinate is as follows:
Among the present invention, at first set the camera calibration template, based on the imaging model of video camera, be the corresponding relation of coordinate according to the pixel coordinate and the three-dimensional real-world coordinates of calibration point, find the solution the inside and outside parameter (being rotation matrix R and translation matrix T) of video camera and calculate the distortion factor of camera lens.Application image coordinate system two-dimensional pixel coordinate and real-world coordinates are the calculated relationship between the three-dimensional coordinate then, and the three-dimensional real-world coordinates of calculating all subpoints is a coordinate.
Fig. 4 is the thickness of propeller blades schematic diagram calculation, describes with example, and in Fig. 4 measuring method of the present invention, the thickness of propeller blades Calculation Method is described below: for blade face subpoint P
1(x
1, y
1, z
1), at first find with its blade back subpoint T in same vertical direction (x, y z), and calculate | P
1The value of T|; Then coordinate system XOY rotation is obtained new coordinate system X
1OY
1, in this coordinate system according to subpoint P
1The grazing angle at place is calculated the one-tenth-value thickness 1/10 ‖ P of propeller blade
1P
2|, as shown in Figure 4.
Claims (4)
1. the new method for automatically measuring of thickness of propeller blades is characterized in that with the image being the non-contact measurement that thickness of propeller blades is carried out on the basis, may further comprise the steps:
The computing machine generation of projection dot matrix and the collection of blade image;
All subpoint two dimensional image coordinate system pixel coordinates obtain;
The three-dimensional real-world coordinates of all subpoints is a coordinate Calculation;
The structure of propeller blade digital model;
The calculating of thickness of propeller blades.
2. the new method for automatically measuring of thickness of propeller blades according to claim 1, it is characterized in that: the calculating of all subpoint two dimensional image coordinate system pixel coordinates of described propeller blade, generate the projection dot matrix by computing machine and be incident upon the propeller blade surface, utilize ccd video camera to gather the image of propeller blade to be measured, appliance computer Digital Image Processing algorithm extracts the two dimensional image coordinate system pixel coordinate of all subpoints of propeller blade.
3. the new method for automatically measuring of thickness of propeller blades according to claim 1, it is characterized in that: the three-dimensional real-world coordinates of described all subpoints of propeller blade is in the process of coordinate Calculation, comprises that the demarcation of the ccd video camera of gathering the propeller blade image, the rectification of distortion of camera model, three-dimensional real-world coordinates are Coordinate Calculation.
4. the new method for automatically measuring of thickness of propeller blades according to claim 1, it is characterized in that: the calculating of described thickness of propeller blades is the three-dimensional coordinate based on all subpoints of propeller blade that calculate, by the calculating of computer realization thickness of propeller blades.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010106001A CN101865660A (en) | 2010-02-05 | 2010-02-05 | New method for automatically measuring thickness of propeller blades |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010106001A CN101865660A (en) | 2010-02-05 | 2010-02-05 | New method for automatically measuring thickness of propeller blades |
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| Publication Number | Publication Date |
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| CN101865660A true CN101865660A (en) | 2010-10-20 |
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ID=42957478
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| CN201010106001A Pending CN101865660A (en) | 2010-02-05 | 2010-02-05 | New method for automatically measuring thickness of propeller blades |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011120202A1 (en) * | 2010-04-01 | 2011-10-06 | 南京太阳升科技有限公司 | New method for propeller digital detection |
| CN106844966A (en) * | 2017-01-23 | 2017-06-13 | 江苏科技大学 | A kind of propeller blade face blade back Precise modeling |
-
2010
- 2010-02-05 CN CN201010106001A patent/CN101865660A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011120202A1 (en) * | 2010-04-01 | 2011-10-06 | 南京太阳升科技有限公司 | New method for propeller digital detection |
| CN106844966A (en) * | 2017-01-23 | 2017-06-13 | 江苏科技大学 | A kind of propeller blade face blade back Precise modeling |
| CN106844966B (en) * | 2017-01-23 | 2019-07-16 | 江苏科技大学 | A kind of propeller blade face blade back Precise modeling |
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Open date: 20101020 |