CN201576308U

CN201576308U - Registration system for complex curved surface

Info

Publication number: CN201576308U
Application number: CN2009202101641U
Authority: CN
Inventors: 郭慧; 林大钧; 潘家祯
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2009-09-25
Filing date: 2009-09-25
Publication date: 2010-09-08
Anticipated expiration: 2019-09-25

Abstract

The utility model relates to a registration system for a complex curved surface, which comprises a curved surface CAD modeling device, a three-coordinate measuring machine and a registration solver. The curved surface CAD modeling device which includes geometric information of a curved surface is connected with a port at one edge of the registration solver, and the three-coordinate measuring machine is connected with the port at the other edge of the registration solver. Compared with the prior art, the registration system has the following characteristics: a theoretical model is accurate, the registration stability is high, the registration accuracy is good, the application range is wide, and the multi-dimensional variable registration can be realized.

Description

A kind of complex-curved registration arrangement

Technical field

The utility model relates to Machine Design and detection technique field, relates in particular to a kind of complex-curved registration arrangement.

Background technology

Complex-curved registration technology is widely used in the fields such as shape error detection, multi-viewpoint cloud reorientation, reverse-engineering, virtual reality, and it is the precondition of implementation model assessment, error analysis and data amalgamation.Because cad model designs in CAD design software coordinate system, measurement is to carry out in the coordinate system of measuring equipment, complex-curved measurement coordinate system objectively is being separate with design coordinate system (CAD coordinate system), measurement data and cad model do not have clear and definite size corresponding relation, add the complex-curved tangible reference characteristic that do not have, complex-curved mathematical model is very complicated, be difficult to find size corresponding relation accurately between complex-curved measuring basis and design basis, therefore complex-curved registration is key to the issue and difficult point always.If the two disunity will inevitably influence the result of calculation of follow-up error-detecting, model evaluation etc.

More common method for registering is least square method and iterative closest point method at present, and these two kinds of methods all come with some shortcomings.

The ultimate principle of least square method is to be target with the residual sum of squares (RSS) minimum between the two, have and calculate advantage simple, that be easy to realize, but it is not high enough by least square method result calculated precision, often than the big 1.8%-30% of precise results, thereby be not suitable for the high complex-curved registration of accuracy requirement.

The iterative closest point method at first must be found out two corresponding subclass between point set and point set, obtain the transformation matrix of two point sets then, its algorithm is simple, precision is higher, its less than one is the subclass that point set is the another one point set that two match points of requirement are concentrated, the 2nd, the relative initial position of two point sets is had relatively high expectations, the relative initial position of two point sets can not differ too big, when two groups of point set initial positions differ big, easily be absorbed in local minimum, and the convergence direction may be uncertain.

Summary of the invention

The purpose of this utility model is exactly to provide a kind of stability high, good, the widely used complex-curved registration arrangement of degree of accuracy for the defective that overcomes above-mentioned prior art existence.

The purpose of this utility model can be achieved through the following technical solutions:

A kind of complex-curved registration arrangement, it is characterized in that, this system comprises curved surface CAD model building device, three coordinate measuring machine and registration solver, described curved surface CAD model building device comprises the geological information of curved surface, be connected with the port on one side of registration solver, described three coordinate measuring machine is connected with the port of the another side of registration solver.

Described curved surface CAD model building device is the computing machine that the CAD design software is installed.

Compared with prior art, the utlity model has following advantage:

(1) theoretical model is accurate: cad model is the foundation of optimal comparison, and nurbs surface has extensive versatility, and setting up its theoretical model according to the CAD design information of curved surface has crucial effects to error evaluation;

(2) stability of registration: utilize robustness, the concurrency of genetic algorithm and characteristics with ability of searching optimum, complexity is carried out the thick registration of curved surface, can seek appropriate initial registration conversion fast, overcome traditional iterative closest point method to the demanding shortcoming of initial value, can be from the arbitrary initial relative position, the convergence that assurance is found the solution has improved counting yield, can accelerate to obtain desirable registration results;

(3) accuracy of registration: behind the thick registration again the using iterative closest point algorithms carry out the smart registration of secondary.Utilize the higher characteristics of iterative closest point law technology precision, overcome genetic algorithm method later stage long deficiency consuming time, improved accuracy of registration;

(4) realize the multidimensional variable registration: can obtain the result that simple iterative closest point method can't obtain, the multivariate registration in the three-dimensional data registration is had stronger robustness;

(5) popularity of Ying Yonging: can be applicable to NURBS represent complex-curved arbitrarily, the nurbs surface expression way not only has character such as partial controllable, standardization, differentiability, also the accurate expression for the parsing shape (as quadric surface, the surface of revolution etc.) of standard curved surface and free form surface provides a public mathematical form with design, in CAD/CAM and field of Computer Graphics, nurbs surface is widely used.

Description of drawings

Fig. 1 is the synoptic diagram of this system;

Fig. 2 is model data and the measurement data before recessed registration of turbine blade;

Fig. 3 is the thick registration results of genetic algorithm iteration 50 times;

Fig. 4 is the result of the smart registration of iterative closest point;

Fig. 5 is simple ICP registration results.

Embodiment

Below in conjunction with the drawings and specific embodiments the utility model is elaborated.

Embodiment

A kind of complex-curved registration arrangement, its structure as shown in Figure 1, this system comprises curved surface CAD model building device, three coordinate measuring machine and registration solver, curved surface CAD model building device is the computing machine that the CAD design software is installed, the geological information that comprises curved surface adopts the NURBS function to make up curved surface NURBS model, is connected with the port on one side of registration solver, three-dimensional coordinates measurement machine testing curved surface prototype in kind is also handled and is obtained the measure dot number certificate, is connected with the port of registration solver another side.Data after the registration solver adopts the genetic algorithm comparison, calculates and revises curved surface NURBS model and handles.

Curved surface CAD modeling comprises the geological information of curved surface, utilize IGES file or DXF file to extract control vertex, node and weight factor information, make up curved surface NURBS model, the curved surface form that adopts the NURBS function representation to design a model, and nurbs surface dispersed along parametric direction, obtain an accurate goal directed point cloud, three-dimensional coordinates measurement machine testing curved surface prototype in kind, obtain the measure dot number certificate, the treated measurement point cloud that obtains, the registration solver adopts genetic algorithm that goal directed is put cloud and the measurement point cloud carries out thick registration, the registration transformation that obtains, measurement data is carried out initial transformation, obtain the measurement point data set behind the thick registration, the using iterative closest point algorithms is carried out smart registration and is calculated again, seek behind the thick registration measurement data and design a model nearest point set, adopt singular value decomposition method to calculate optimal transformation, till satisfying stopping criterion for iteration, obtain final registration results.

Adopt this system that the turbine blade concave surface is carried out registration, registration front end model data and measurement data figure are as shown in Figure 2, Fig. 2 has expressed curved design model before the registration and the relative position turbine blade concave surface cad model of measurement data is a smooth surface, to the forward face 3 d measurement data of gathering 900 curved surfaces in kind, the some cloud is depicted as measurement data in kind.

Utilization genetic algorithm method is carried out thick registration and is calculated, and the registration result calculated sees Table 1, and wherein iterations is that 50 o'clock registration effect is seen shown in Figure 3.

With the result of the genetic algorithm method iteration 50 times initial position as smart registration, the using iterative closest point algorithms is carried out the smart registration of secondary, and only the iteration optimum solution that just obtains registration 10 times sees Table 1, and the effect that realizes the secondary registration with this result as shown in Figure 4.

The registration results of table 1 spoon of blade cad model

And use merely that the ICP algorithm carries out a registration see Table 1, no longer continue to seek optimum solution after its result reaches 0.8867.Its registration results as shown in Figure 5, measurement point cloud and CAD curved surface direction are reverse, illustrate that ICP convergence of algorithm direction is unsettled, can not get optimum solution sometimes when measurement data and theoretical model initial position differ far away.

Comparison sheet 1 result as can be known, when measurement point and CAD theoretical model relative position differ big, only use iterative closest point algorithms, may be absorbed in local minimum, can't obtain best alignment, at this moment, adopt the genetic algorithm method to carry out thick registration, it is very effective adopting iterative closest point algorithms to carry out smart registration then, and the global optimizing performance of genetic algorithm method can guarantee that the secondary registration strategies obtains globally optimal solution.Relatively the result of the thick registration of genetic algorithm method 50 times, 100 times as can be known, as approximate solution, the two is more approaching.

In view of the genetic algorithm method in the slower shortcoming of computing late convergence, from the consideration of saving time, after the genetic algorithm method is moved thick registration of 50 generations, in conjunction with iterative closest point algorithms refinement computing, can guarantee to obtain optimum solution again, and higher efficient is arranged.

Fig. 3 shows, adopts the genetic algorithm method to carry out thick registration, and its convergence direction is correct, and as shown in Figure 4, after the calculating of secondary registration, measurement point and cad model have been realized best alignment.

Claims

1. complex-curved registration arrangement, it is characterized in that, this system comprises curved surface CAD model building device, three coordinate measuring machine and registration solver, described curved surface CAD model building device is connected with a port of registration solver, and described three coordinate measuring machine is connected with the another port of registration solver.

2. a kind of complex-curved registration arrangement according to claim 1 is characterized in that, described curved surface CAD model building device is the computing machine that the CAD modeling software is installed.