CN116204974B - Method for evaluating geometric consistency of CAD model of aeroengine blade part - Google Patents
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Abstract
The invention relates to a geometric consistency evaluation method of a CAD model of an aeroengine blade part, which comprises the steps of firstly, inputting an original CAD reference model A of the aeroengine blade part and a converted CAD model C to be evaluated, and completing automatic extraction, comparison, analysis and calculation of a surface geometric verification data set; secondly, aiming at the characteristics that the shape of the aeroengine blade part is complex, and the curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body are mostly in a free curved surface Nurbs form, a definition, sequencing and difference calculation method of a Nurbs form surface geometry verification data set is provided in a targeted manner, and the accuracy of the result is ensured; finally, the whole flow steps of the invention can be realized in an automatic mode, so that geometric consistency evaluation is quantitatively carried out after the CAD model of the engine blade part in the flying cooperation scene is converted.
Description
Technical Field
The invention belongs to the technical field of engine blade part design, and particularly relates to a geometric consistency evaluation method for a CAD model of an aeroengine blade part.
Background
In the current aircraft development and production mode, the aircraft and the engine are developed and produced as independent complex systems respectively. The aircraft design unit is decomposed to the engine development unit through indexes, the engine development unit independently completes development of the engine according to aircraft requirements, and then the engine is delivered to the aircraft development unit for flying and transmitting integration. The design method enables the development units of the aircraft and the engine to be respectively focused on the fields of the aircraft and the engine, but the development process cannot be fully iterated and communicated, so that difficulties and barriers exist in the integration process of the aircraft and the engine.
As aviation products develop, the interaction and fusion between aircraft and engines further deepens, and the concept of hair synergy is gradually proposed and applied. The flying hair cooperation means that an aircraft development unit and an engine development unit jointly define and maintain the size, the quality, the performance, the interface and the like of an engine in the development process, the global optimal integration level of the flying hair combination is improved, the product performance is improved, the risk is reduced, and the flying hair combined development work is carried out by adopting an integrated working mode.
With the wide application of the three-dimensional CAD technology, the CAD model replaces the traditional two-dimensional engineering drawing, and becomes a data base and core of each link of aviation product development. However, the development work of the current aircraft and engine is respectively carried out on the basis of the CATIA platform and the NX platform, and when the aircraft joint design is carried out, an engine model designed by the NX platform needs to be imported into the CATIA platform. The existing model conversion and importing work is realized based on STEP standards under the limitation of different commercial CAD platforms, but is limited by the differences of the underlying structures, tolerance standards and the like of different CAD platforms, the STEP-based 3D CAD model data conversion often has geometric defects and errors such as data loss, damage and the like, so that the converted model data has larger consistency difference compared with the original model data, and the quality of the converted data is not acceptable. The geometric consistency evaluation of the model data is to compare and verify the data quality of the original format and the three-dimensional CAD model converted into STEP format so as to ensure that the content of the original format and the three-dimensional CAD model are consistent, and the loss of information is required to be within an acceptable range.
The blade is one of key components of the aeroengine and has the structural characteristics of large size, complex structure, thin wall and large area. The blade body is the core and the processing difficulty of whole blade part, and every lamellar body is formed by a plurality of hyperboloid curved surfaces and auxiliary curved surface concatenation, and the curved surface complexity is higher, the concatenation is complicated, and processing requirement is accurate. Therefore, the precise geometric modeling of the blade becomes a necessary precondition for blade processing and is also an important precondition for the combined design of the flyer and the hair.
Unlike a typical part CAD model, the blade part CAD model is mainly a free-form surface, and a small number of blade part CAD models are Plane surfaces and quadric surfaces, including cylindrical surfaces Cylinder, conical surfaces Cone, spherical surfaces Sphere, circular ring surfaces Torus and the like. The mathematical expressions of the plane and the quadric surface are simple, the geometric characteristics such as a rotation axis, a radius and a rotation angle are relatively stable, and the practice shows that the geometric consistency of the plane and the quadric surface before and after conversion is better. However, the free-form surface is expressed in a non-uniform rational B-Spline (Nurbs, non Uniform Rational B-Spline) form in a CAD system, the structure of the surface is complex, the numerical value is unstable, and the geometric consistency before and after conversion is poor.
At present, a qualitative or quantitative method is used for evaluating geometric consistency after the CAD model of the engine blade part in the scene of the cooperation of the flying and the flying, and the problem becomes one of key technology and urgent requirements of the cooperation of the flying and the flying.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a geometric consistency evaluation method for CAD models of aero-engine blade parts, and provides a defining, sequencing and difference calculation method of Nurbs-form face geometric check data sets in a targeted manner for the condition that the shapes of the aero-engine blade parts are complex and most of the parts are free curved surfaces, and the geometric consistency evaluation is realized after the CAD models of the engine blade parts are converted by automatically extracting, comparing and analyzing and calculating the face geometric check data sets. The calculation accuracy of geometric data consistency evaluation is improved, and a quantitative analysis scheme is provided for consistency evaluation of the aero-engine blade parts.
In order to achieve the above purpose, the invention discloses the following technical scheme:
a geometric consistency evaluation method of CAD models of aero-engine blade parts comprises the following steps:
which comprises the following steps:
s1, inputting an original CAD reference model A of an aeroengine blade part, and converting the reference model A into an intermediate format of STEP standard to obtain a CAD model B; opening the model B by adopting a CATIA CAD platform, and converting the model B into a model C to be evaluated;
s2, analyzing the CAD reference model A of the blade part on an NX CAD platform, traversing the curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body to obtain a free-form curved surface Nurbs surface, and calculating to obtain a first geometric verification data Set 1 ：
Wherein,is the kth in the reference model A 1 Geometric verification data set of each surface, K 1 Is the number of Nurbs surfaces, k, in reference model A 1 N is a natural number;
s3, analyzing the CAD model C to be evaluated after the conversion of the blade parts on the CATIA CAD platform, traversing the blade body curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body to obtain a free curved surface Nurbs surface, and calculating to obtain a second geometric verification data Set 2 ：
Wherein,for the kth in the model C to be evaluated 2 Geometric verification data set of each surface, K 2 For the number of Nurbs surfaces, k, in model C to be evaluated 2 N is a natural number;
s4, using Set 1 Data in (a) is taken as a reference, and is Set 2 Re-ordering the data in the data Set to obtain a re-ordered data Set 3 ；
Wherein,for the kth in the model C to be evaluated 3 Geometric verification data set of each surface, K 3 For the number of Nurbs surfaces in model C to be evaluated, K 3 ＝K 2 ，k 3 N is a natural number; further, set 3 The data in the Set is a reference Set 1 Reordered data, when k 1 ＝k 3 <min(K 1 ,K 3 ) At the time of Set 1 [k 1 ]And Set 3 [k 3 ]Refers to a geometric check data set corresponding to the same plane;
s5, checking the first geometric check data Set 1 And reordered data Set 3 The geometric verification data in the data are subjected to item-by-item comparison calculation to obtain a geometric consistency distance set D of each item of data:
D＝{D k }＝{|Set 1 [k]-Set 3 [k]|，1≤k≤K,K＝max(K 1 ,K 3 ) And k is N ∈ -
Wherein, set 1 [k]Refers to a first geometric verification data Set 1 The kth element, set 3 [k]Refers to a reordered data Set 3 K is the maximum value of the number of Nurbs surfaces in the reference model A and the model C to be evaluated, and K and N are natural numbers; and D is k ＝|Set 1 [k]-Set 3 [k]The I is the geometric consistency distance between two groups of surface geometric verification data sets;
s6, obtaining a qualitative result of geometric consistency evaluation of the reference model A and the model C to be evaluated: according to Set 1 、Set 3 Drawing a model consistency evaluation thermodynamic diagram by two groups of surface geometry verification data, and qualitatively analyzing the geometrical consistency of the reference model A and the model C to be evaluated;
s7, obtaining a quantitative result R of geometric consistency evaluation of the reference model A and the model C to be evaluated:
wherein K is more than or equal to 1 and less than or equal to K, and K is N
Wherein k and N are natural numbers;
wherein, R is a floating point number, the value range is R epsilon [0, ], and the larger the value of R is, the larger the difference of geometric consistency between the reference model A and the model C to be evaluated is, and the worse the consistency is; the smaller the R value is, the smaller the geometrical consistency difference between the reference model A and the model C to be evaluated is, and the better the consistency is; when r=0, it means that the reference model a is geometrically identical to the model C to be evaluated.
In a preferred embodiment, the surface geometry of the model verifies the properties S k The expression is:
S k ＝{P，V}
wherein P is a sampling point set and represents the space position data of the curved surface of the blade part; v is a sampling point unit external normal vector set and represents the space distortion degree of the curved surface of the blade part;
the P and V acquisition process is as follows: taking the kth surface on the model, defining the kth surface as F, setting the sampling point numbers m and n along the parameters U and V, and uniformly sampling the kth surface to obtain m multiplied by n sampling point sets P and sampling point unit external normal vector sets V on the outer surface F:
P＝{P ij ，1≤i≤m，1≤j≤n}
V＝{V ij ，1≤i≤m，1≤j≤n}
wherein P is ij Is each sampling point, V, on the outer surface F ij Is the outer surface F at the sampling point P ij The unit external normal vector at the position, i and j are positive integers.
Further, in a preferred embodiment, in the step S4, a reordered data Set is obtained 3 The method specifically comprises the following steps:
s41, taking out the first geometric check data Set 1 The data of the ith surface in (1), the initial value of i is 1;
s42, traversing the second geometric check data Set 2 Taking out the data of the j-th surface, wherein the initial value of j is 1, and calculating the distance d between the midpoints of the i and j surfaces ij And d is to ij Add to set C i In (3), namely:
C i ＝{d ij ，1≤i≤K 2 and i.epsilon.N })
Wherein K is 2 The number of Nurbs surfaces in the model C to be evaluated;
s43, pair set C i Ordering the data to obtain the minimum value d min Will d min The data of the j-th surface in the corresponding S42 is added to the Set 3 In the step, the data of the j-th surface is simultaneously Set 2 Delete in the middle;
s44, judging whether i is equal to Set 1 The number of face data, if yes, ends, otherwise i=i+1, S41 is executed until i is equal to Set 1 Number of face data.
Further, in a preferred embodiment, the step S5 of geometrically verifying the geometrical consistency distance between the two sets of face geometry data sets specifically includes the steps of:
two groups of surface geometry verification data sets are respectively set as follows: s is S 1 ＝{P 1 ，V 1 }，S 2 ＝{P 2 ，V 2 }，S 1 、S 2 The geometrical consistency distance between the two is D
Wherein,is S 1 Middle sampling point->Is S 1 Middle sampling point unit external normal vector, +.>Is S 2 Middle sampling point->Is S 2 Middle sampling point unit external normal vector; />For the absolute distance between the sampling points, +.>The distances m and n between the external vector vectors are the number of sampling points along the parameters U and V, and i and j are positive integers.
Further, the number of Nurbs surfaces in the reference model A is not equal to the number of Nurbs surfaces in the model C to be evaluated, i.e. K in step S2 1 And K in step S3 2 Are not equal.
It may be preferable that, in step S5, when k>min(K 1 ,K 3 ) At time D k ＝|Set 1 [k]I or I Set 3 [k]|。
Compared with the prior art, the invention has the following beneficial effects:
compared with the prior art, the invention has positive and obvious effect. Firstly, the method can complete automatic extraction, comparison and analysis calculation of the surface geometry verification data set only by inputting an original CAD reference model A of the aeroengine blade part and a converted CAD model C to be evaluated; secondly, the method aims at the characteristics that the shape of the aeroengine blade part is complex, the curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body are mostly in the form of a free curved surface Nurbs, and the definition, the sequencing and the difference calculation methods of a Nurbs form surface geometry verification data set are provided in a targeted manner, so that the accuracy of the result is ensured; finally, the whole flow of the invention can be automatically realized, and geometric consistency evaluation can be quantitatively carried out after the CAD model of the engine blade part in the flying cooperation scene is converted.
Drawings
FIG. 1 is a flow diagram of a CAD model geometric consistency evaluation method of an aero-engine blade part of the invention;
FIG. 2 is a schematic illustration of an example of an aircraft engine blade assembly model according to the present invention;
FIG. 3 is a schematic view of a three-dimensional structure of a CAD reference model A of a blade part according to the present invention;
fig. 4 is a schematic diagram of a three-dimensional structure of a model C to be evaluated of a blade part CAD of the present invention;
FIG. 5 is a schematic diagram of the extraction result of the geometric verification data set of the CAD reference model A of the blade part according to the present invention;
FIG. 6 is a schematic diagram of the extraction result of the geometric verification data set of the CAD model C to be evaluated of the blade part;
fig. 7 shows D when k=23 in a preferred embodiment of the invention 23 Is a schematic diagram of the calculation process;
fig. 8 is a model consistency evaluation thermodynamic diagram of a model C to be evaluated according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the attached drawings.
The invention provides a geometric consistency evaluation method of a CAD model of an aeroengine blade part, which is shown in figure 1 and comprises the following steps:
s1, inputting an original CAD reference model A of an aeroengine blade part, wherein the reference model A is built on an NX CAD platform, the file format suffix is prt, the reference model A is converted into an intermediate format of STEP standard, a CAD model B is obtained, and the model B file format suffix is STEP. And opening the model B by adopting a CATIA CAD platform, converting the model B into a model C to be evaluated, and carrying out file format suffix of the model C to be evaluated to be CATPart. The model C to be evaluated is a model to be subjected to geometric consistency evaluation, and the original reference model A is a reference CAD model during geometric consistency evaluation;
s2, analyzing an original CAD reference model A of the blade part by adopting an OpenC++ technology and a secondary development interface on an NX CAD platform, traversing a blade body curved surface, a splicing surface, a chamfer surface, a transition surface and the like of the blade part, obtaining a Nurbs surface and calculating to obtain a first geometric verification data Set 1 ：
Wherein,is the kth in the reference model A 1 Geometric verification data set of each surface, K 1 Is the number of Nurbs surfaces, k, in reference model A 1 N is a natural number.
S3, analyzing a CAD model C to be evaluated after the conversion of the blade parts by adopting a CATIA CAA technology and a secondary development interface on a CATIA CAD platform, traversing the curved surface, the splicing surface, the chamfer surface, the transition surface and the like of the blade body of the CAD model C to obtain a Nurbs surface and calculating the Nurbs surface to obtain a second geometric verification data Set 2 ：
Wherein,for the kth in the model C to be evaluated 2 Geometric verification data set of each surface, K 2 For the number of Nurbs surfaces, k, in model C to be evaluated 2 N is a natural number.
Wherein, in general, within the scope of the present application, the number of Nurbs surfaces in the reference model A is not equal to the number of Nurbs surfaces in the model C to be evaluated, i.e. K in step S2 1 And K in step S3 2 Are not equal.
S4, using Set 1 Data in (a) is taken as a reference, and is Set 2 Re-ordering the data in the data Set to obtain re-ordered data Set 3 ；
Wherein,for the kth in the model C to be evaluated 3 Geometric verification data set of each surface, K 3 For the number of Nurbs surfaces in model C to be evaluated, K 3 ＝K 2 ，k 3 N is a natural number.
Wherein, set 3 The data in the Set is a reference Set 1 The reordered data can ensure that when k 1 ＝k 3 <min(K 1 ,K 3 ) At the time of Set 1 [k 1 ]And Set 3 [k 3 ]Refers to the same face of the geometrically verified dataset.
S5, to Set 1 、Set 3 The geometrical check data of the surface in the model are subjected to item-by-item comparison calculation to obtain a geometrical consistency distance set D of each item of data:
D＝{D k }＝{|Set 1 [k]-Set 3 [k]|，1≤k≤K,K＝max(K 1 ,K 3 ) And k is N ∈ -
Wherein, set 1 [k]Refers to a Set 1 The kth element, set 3 [k]Refers to a Set 3 K is the maximum value of the number of Nurbs surfaces in the reference model A, C, and K and N are natural numbers.
Wherein D is k ＝|Set 1 [k]-Set 3 [k]And I is the geometric consistency distance between the two groups of surface geometric verification data sets. In particular, when k>mi n(K 1 ,K 3 ) At time D k ＝|Set 1 [k]I or I Set 3 [k]|。
S6, obtaining a reference model A and to-be-evaluated on the basis of the step S5Qualitative results of the evaluation of geometric consistency of the valence model C: according to Set 1 、Set 3 The geometric check data of the two groups of surfaces draws a model consistency evaluation thermodynamic diagram, and the geometric consistency of the reference model A and the model C to be evaluated is qualitatively analyzed.
S7, obtaining quantitative results R of geometric consistency evaluation of the reference model A and the model C to be evaluated on the basis of the step S5:
wherein K is more than or equal to 1 and less than or equal to K, and K is N
Wherein k and N are natural numbers.
Wherein, R is floating point number, the value range is R epsilon [0, ], the larger the value of R is, the larger the geometrical consistency difference between the reference model A and the model C to be evaluated is, the worse the consistency is; the smaller the R value is, the smaller the geometrical consistency difference between the reference model A and the model C to be evaluated is, and the better the consistency is. When r=0, it means that the reference model a and the model C to be evaluated are geometrically identical.
The following describes the specific steps of the geometric consistency assessment method of the present invention by way of an example of a specific application with reference to fig. 1-8:
s1, inputting an original CAD reference model A of an aeroengine blade part, wherein the reference model A is constructed on an NX CAD platform, the file format suffix is prt, the reference model A is converted into an intermediate format of STEP standard, a CAD model B is obtained, and the model B file format suffix is STEP. And opening the model B by adopting a CATIA CAD platform, and converting the model B into a model C to be evaluated, wherein the file format suffix of the model C to be evaluated is CATPart. The model C to be evaluated is the model to be evaluated for geometric consistency, and the original reference model A is the reference CAD model during geometric consistency evaluation.
Fig. 2 shows an aircraft engine blade assembly model, in which the blade parts are assembled from 90 individual blades, of which a single blade part is chosen for analysis in the present embodiment for the sake of clarity. The reference model A of the blade part CAD is shown in fig. 3, and the model C to be evaluated of the blade part CAD is shown in fig. 4.
S2, analyzing an original CAD reference model A of the blade part by adopting an OpenC++ technology and a secondary development interface on an NX CAD platform, traversing a blade body curved surface, a splicing surface, a chamfer surface, a transition surface and the like of the blade part, obtaining a Nurbs surface and calculating to obtain a first geometric verification data Set 1 ：
Wherein,is the kth in the reference model A 1 Geometric verification data set of each surface, K 1 Is the number of Nurbs surfaces, k, in reference model A 1 N is a natural number.
The step can be realized by automatic programming of a software program, and fig. 5 is a program output screenshot of partial results extracted from a geometric verification data set of a CAD reference model A of a blade part, wherein K is a value obtained by extracting a geometric verification data set of the CAD reference model A of the blade part 1 ＝46。
S3, analyzing a CAD model C to be evaluated after the conversion of the blade parts by adopting a CATIA CAA technology and a secondary development interface on a CATIA CAD platform, traversing the curved surface, the splicing surface, the chamfer surface, the transition surface and the like of the blade body of the CAD model C to obtain a Nurbs surface and calculating the Nurbs surface to obtain a second geometric verification data Set 2 ：
Wherein,for the kth in the model C to be evaluated 2 Geometric verification data set of each surface, K 2 For the number of Nurbs surfaces, k, in model C to be evaluated 2 N is a natural number.
The step can also be realized by automatic programming of a software program, and fig. 6 shows several models C to be evaluated of the blade part CADProgram output screenshot of what to check the partial result of the dataset extraction, where K 2 ＝76。
S4, using Set 1 Data in (a) is taken as a reference, and is Set 2 Re-ordering the data in the data Set to obtain re-ordered data Set 3 ；
Wherein,for the kth in the model C to be evaluated 3 Geometric verification data set of each surface, K 3 For the number of Nurbs surfaces in model C to be evaluated, K 3 ＝K 2 ，k 3 N is a natural number.
After ordering, K 3 ＝K 2 ＝76。
S5, to Set 1 、Set 3 The geometrical check data of the surface in the model are subjected to item-by-item comparison calculation to obtain a geometrical consistency distance set D of each item of data:
D＝{D k }＝{|Set 1 [k]-Set 3 [k]|，1≤k≤K,K＝max(K 1 ,K 3 ) And k is N ∈ -
Wherein k=max (K 1 ,K 3 )＝max(46,76)＝76。
When k=23 in fig. 7, D 23 From the calculation process of (D) 23 ＝0+0+79+0.0536+48.040+0.0978+23.979+0.0536+0+0+24.066+0.0702+48.040+24.066+0.0702+0+0＝192.615。
S6, obtaining qualitative results of geometric consistency evaluation of the reference model A and the model C to be evaluated on the basis of the step S5: according to Set 1 、Set 3 The geometric check data of the two groups of surfaces draws a model consistency evaluation thermodynamic diagram, and the geometric consistency of the reference model A and the model C to be evaluated is qualitatively analyzed.
Fig. 8 is a model consistency evaluation thermodynamic diagram of the model C to be evaluated, as can be seen from the figure: the geometrical consistency distance of the support part of the engine blade part is smaller, the accuracy before and after conversion is kept better, and the geometrical consistency is better. The curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body are free curved surfaces, so that the blade body has complex shape, larger geometric consistency distance and poorer geometric consistency.
S7, obtaining quantitative results R of geometric consistency evaluation of the reference model A and the model C to be evaluated on the basis of the step S5:
wherein K is more than or equal to 1 and less than or equal to K, and K is N
Wherein k and N are natural numbers.
In practical engineering application, average geometrical consistency distance is generally used for measuring consistency quality of the model before and after conversion, and the average geometrical consistency distance is R ave
In this example of the present invention,
wherein R is ave Is a floating point number, and has a value range of R ave ∈[0，∞]，R ave The larger the value is, the larger the geometrical consistency difference between the reference model A and the model C to be evaluated is, and the worse the consistency is; r is R ave The smaller the value is, the smaller the geometrical consistency difference between the reference model A and the model C to be evaluated is, and the better the consistency is; when R is ave When=0, it means that the reference model a is geometrically identical to the model C to be evaluated. And when R is ave <At 50, the geometric consistency of the representative reference model A and the model C to be evaluated is not greatly different, and the error is in an acceptable range.
By describing the embodiment, the beneficial technical effects of the invention are as follows: the method for quantitatively describing the geometric consistency of the original CAD reference model of the aeroengine blade part and the converted CAD model to be evaluated is provided, only the original CAD reference model A of the aeroengine blade part and the converted CAD model to be evaluated C are required to be input, and the automatic extraction, comparison and analysis calculation of the surface geometric verification data set can be completed without other input, so that the data support is provided for realizing the geometric consistency evaluation after the conversion of the CAD model of the aeroengine blade part.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (4)
1. A geometric consistency evaluation method of a CAD model of an aeroengine blade part is characterized by comprising the following steps: which comprises the following steps:
s1, inputting an original CAD reference model A of an aeroengine blade part, and converting the reference model A into an intermediate format of STEP standard to obtain a CAD model B; opening the model B by adopting a CATIA CAD platform, and converting the model B into a model C to be evaluated;
s2, analyzing the CAD reference model A of the blade part on an NX CAD platform, traversing the curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body to obtain a free-form curved surface Nurbs surface, and calculating to obtain a first geometric verification data Set 1 ：
Wherein,is the kth in the reference model A 1 Every surfaceIs a geometric check data set, K 1 Is the number of Nurbs surfaces, k, in reference model A 1 N is a natural number;
s3, analyzing the CAD model C to be evaluated after the conversion of the blade parts on the CATIA CAD platform, traversing the blade body curved surface, the splicing surface, the chamfer surface and the transition surface of the blade body to obtain a free curved surface Nurbs surface, and calculating to obtain a second geometric verification data Set 2 ：
Wherein,for the kth in the model C to be evaluated 2 Geometric verification data set of each surface, K 2 For the number of Nurbs surfaces, k, in model C to be evaluated 2 N is a natural number;
s4, using Set 1 Data in (a) is taken as a reference, and is Set 2 Re-ordering the data in the data Set to obtain a re-ordered data Set 3 ；
Wherein,for the kth in the model C to be evaluated 3 Geometric verification data set of each surface, K 3 For the number of Nurbs surfaces in model C to be evaluated, K 3 ＝K 2 ，k 3 N is a natural number; further, set 3 The data in the Set is a reference Set 1 Reordered data, when k 1 ＝k 3 <min (K 1 ,K 3 ) At the time of Set 1 [k 1 ]And Set 3 [k 3 ]Refers to a geometric check data set corresponding to the same plane;
s5, correcting the first geometryTest dataset Set 1 And reordered data Set 3 The geometric verification data in the data are subjected to item-by-item comparison calculation to obtain a geometric consistency distance set D of each item of data:
D＝{D k }＝ {|Set 1 [k]-Set 3 [k]|，1≤k≤K,K＝max(K 1 ,K 3 ) And k is N ∈ -
Wherein, set 1 [k]Refers to a first geometric verification data Set 1 The kth element, set 3 [k]Refers to a reordered data Set 3 K is the maximum value of the number of Nurbs surfaces in the reference model A and the model C to be evaluated, and K and N are natural numbers; and D is k ＝|Set 1 [k]-Set 3 [k]The I is the geometric consistency distance between two groups of surface geometric verification data sets;
s6, obtaining a qualitative result of geometric consistency evaluation of the reference model A and the model C to be evaluated: according to Set 1 、Set 3 Drawing a model consistency evaluation thermodynamic diagram by two groups of surface geometry verification data, and qualitatively analyzing the geometrical consistency of the reference model A and the model C to be evaluated;
s7, obtaining a quantitative result R of geometric consistency evaluation of the reference model A and the model C to be evaluated:
wherein k and N are natural numbers;
wherein, R is a floating point number, the value range is R epsilon [0, ], and the larger the value of R is, the larger the difference of geometric consistency between the reference model A and the model C to be evaluated is, and the worse the consistency is; the smaller the R value is, the smaller the geometrical consistency difference between the reference model A and the model C to be evaluated is, and the better the consistency is; when r=0, it means that the reference model a is geometrically identical to the model C to be evaluated;
surface geometry verification attribute S of model k The expression is:
S k ＝{P，V}
wherein P is a sampling point set and represents the space position data of the curved surface of the blade part; v is a sampling point unit external normal vector set and represents the space distortion degree of the curved surface of the blade part;
the P and V acquisition process is as follows: taking the kth surface on the model, defining the kth surface as F, setting the sampling point numbers m and n along the parameters U and V, and uniformly sampling the kth surface to obtain m multiplied by n sampling point sets P and sampling point unit external normal vector sets V on the outer surface F:
P＝{P ij ，1≤i≤m，1≤j≤n}
V＝{V ij ，1≤i≤m，1≤j≤n}
wherein P is ij Is each sampling point, V, on the outer surface F ij Is the outer surface F at the sampling point P ij The unit external normal vector at the position, i and j are positive integers;
in the step S4, a reordered data Set is obtained 3 The method specifically comprises the following steps:
s41, taking out the first geometric check data Set 1 The data of the ith surface in (1), the initial value of i is 1;
s42, traversing the second geometric check data Set 2 Taking out the data of the j-th surface, wherein the initial value of j is 1, and calculating the distance d between the midpoints of the i and j surfaces ij And d is to ij Add to set C i In (3), namely:
C i ＝{d ij ，1≤i≤K 2 and i.epsilon.N })
Wherein K is 2 The number of Nurbs surfaces in the model C to be evaluated;
s43, pair set C i Ordering the data to obtain the minimum value d min Will d min The data of the j-th surface in the corresponding S42 is added to the Set 3 In the step, the data of the j-th surface is simultaneously Set 2 Delete in the middle;
s44, judging whether i is equal to Set 1 The number of face data, if yes, ends, otherwise i=i+1, S41 is executed until i is equal to Set 1 Number of face data.
2. The method for evaluating geometric consistency of CAD models of aircraft engine blade parts according to claim 1, wherein the method comprises the following steps: the geometric consistency distance between the two groups of surface geometric verification data sets in the step S5 specifically comprises the following steps:
two groups of surface geometry verification data sets are respectively set as follows: s is S 1 ＝{P 1 ，V 1 }，S 2 ＝{P 2 ，V 2 }，S 1 、S 2 The geometrical consistency distance between the two is D
Wherein,is S 1 Middle sampling point->Is S 1 Middle sampling point unit external normal vector, +.>Is S 2 Middle sampling point->Is S 2 Middle sampling point unit external normal vector; />For the absolute distance between the sampling points, +.>The distances m and n between the external vector vectors are the number of sampling points along the parameters U and V, and i and j are positive integers.
3. The geometric consistency evaluation method for CAD model of aeroengine blade part according to claim 1The method is characterized in that: the number of Nurbs surfaces in the reference model A is not equal to the number of Nurbs surfaces in the model C to be evaluated, namely K in the step S2 1 And K in step S3 2 Are not equal.
4. The method for evaluating geometric consistency of CAD models of aircraft engine blade parts according to claim 1, wherein the method comprises the following steps: in step S5, when k>min(K 1 ,K 3 ) Geometric consistency distance D k ＝|Set 1 [k]I or I Set 3 [k]|。
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