CN117629064A - Automatic evaluation method and device for geometric parameters of parts - Google Patents
Automatic evaluation method and device for geometric parameters of parts Download PDFInfo
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- G—PHYSICS
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- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
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- G06T7/33—Determination of transform parameters for the alignment of images, i.e. image registration using feature-based methods
- G06T7/337—Determination of transform parameters for the alignment of images, i.e. image registration using feature-based methods involving reference images or patches
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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- G06T7/62—Analysis of geometric attributes of area, perimeter, diameter or volume
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Abstract
The invention discloses a method and a device for automatically evaluating geometric parameters of parts, wherein the method comprises the following steps: acquiring geometric information and labeling information of each curved surface in a part theoretical model, and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information; generating a motion track of the three-dimensional scanner as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner; according to the detection path planning of the part, a multi-axis mechanical arm is utilized to drive a three-dimensional scanner to automatically scan and measure the part, and real-point cloud data of the part are obtained; and (3) carrying out automatic registration, automatic segmentation and automatic evaluation on the cloud data of the real measurement points of the parts. The invention can automatically complete non-contact measurement and evaluation of the parts based on the part theoretical model, has high measurement efficiency and simple operation, and can effectively reduce the working strength of measuring staff.
Description
Technical Field
The invention belongs to the field of digital measurement and evaluation of geometric parameters, and particularly relates to an automatic evaluation method and device for geometric parameters of parts.
Background
The digital measurement technology of the parts at the present stage is still in a semi-automatic measurement stage, and for the similar parts, a fixed motion track can be set in an off-line programming mode, and various measurement devices are driven by a multi-axis mechanical arm to finish the measurement of the parts, so that corresponding measurement data are obtained; however, for different types of parts, a measurer needs to continuously and manually adjust the measurement position and measurement angle of the measurement device according to the real-time feedback result of the measurement data, and the repeated measurement has the problems of long time consumption, low efficiency and the like.
After the measured data of the part is obtained, the geometric parameter evaluation process is still in a semi-automatic state, the whole parameter evaluation process can only be completed step by step in a manual interaction mode, and particularly when the cloud data of huge real-time points are faced, the operation is complex, and the method is not suitable for a single-piece production mode. Particularly when special conditions occur in the measurement data, the evaluation mode based on macro-record batch processing reproduction often affects the accuracy of batch product data evaluation. The digital transformation of the geometric parameter measurement evaluation is realized, the digital transformation of the measurement equipment is required, and the automatic processing evaluation is required to be carried out on the measurement data according to the set count mode information, so that the development requirement of intelligent manufacturing can be met.
At present, automatic measurement and automatic evaluation of non-contact measurement equipment are still under study according to a theoretical model of a part, and numerous technologies are still needed to be overcome for realizing digital transformation of part detection.
Disclosure of Invention
The invention mainly aims to provide the automatic evaluation method and the device for the geometric parameters of the parts, which can automatically finish non-contact measurement and evaluation of the parts based on a part theoretical model, have high measurement efficiency and simple operation, and can effectively reduce the working strength of measuring staff.
One aspect of the invention provides a method for automatically evaluating geometric parameters of a part, comprising:
step S1: acquiring geometric information and labeling information of each curved surface in a part theoretical model, and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information;
step S2: generating a motion track of the three-dimensional scanner as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner;
step S3: according to the detection path planning of the part, a multi-axis mechanical arm is utilized to drive a three-dimensional scanner to automatically scan and measure the part, and real-point cloud data of the part are obtained;
step S4: and (3) carrying out automatic registration, automatic segmentation and automatic evaluation on the cloud data of the real measurement points of the parts.
Preferably, the step S1 includes:
analyzing the part theoretical model to obtain geometric information of each curved surface, wherein the geometric information comprises geometric features, geometric dimensions, tolerance and roughness;
and determining the corresponding relation between the labeling information and each curved surface according to the geometric characteristics of each curved surface, and establishing a curved surface labeling relation tree.
Preferably, the step S2 includes:
based on geometric information of each curved surface in the part theoretical model, establishing a directed bounding box of each curved surface according to a directed bounding box algorithm, and determining the spatial position of each curved surface;
under the constraint of the space position information of each curved surface, determining a scanning viewpoint plan according to the geometric characteristics of the three-dimensional scanner viewing cone;
and carrying out path planning on all the obtained part scanning viewpoints based on a greedy algorithm of virtual simulation collision constraint conditions, and calculating to obtain an optimal three-dimensional scanner motion track serving as a detection path planning.
Preferably, the step S3 includes:
according to the spatial position relation of the multi-axis mechanical arm, carrying out gesture calculation on the motion trail of the three-dimensional scanner to obtain a motion control program of the multi-axis mechanical arm;
the multi-axis mechanical arm drives the three-dimensional scanner to move to the designated viewpoint position and the designated measurement direction according to the motion control program, and automatic scanning measurement of the part is carried out to obtain real-point cloud data of the part.
Preferably, the step S3 further includes:
carrying out space alignment on the first real-point cloud data of the part and a theoretical model, and then carrying out three-dimensional curved surface reconstruction on the real-point cloud data through a rolling ball algorithm;
analyzing the quality of the triangular mesh reconstructed by the curved surface through a hole boundary algorithm, and determining the incomplete position of the actual measurement data of the curved surface;
determining the incomplete positions of the curved surface point cloud data which can be covered by a plurality of scanning viewpoints through a minimum inclusion sphere algorithm;
and determining the scanning viewpoint and the measuring angle of the secondary scanning measurement according to the constraint conditions, and generating the motion trail of the three-dimensional scanner again.
Preferably, the step S4 includes:
carrying out space position registration alignment on the part theoretical model and the real-point cloud data through a point cloud registration algorithm;
based on the part theoretical model and the curved surface labeling relation tree, carrying out automatic segmentation on cloud data of real measurement points of each curved surface of the part;
based on a least square discrimination method, establishing a curved surface dimensional tolerance evaluation model library;
fitting and evaluating the real-point cloud data of each curved surface according to the established curved surface dimensional tolerance evaluation model library, and outputting an evaluation report of each curved surface.
Another aspect of the present invention provides an automatic part geometry evaluation apparatus comprising:
the model automatic analysis module is used for acquiring geometric information and labeling information of each curved surface in the part theoretical model and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information;
the automatic detection path planning generation module is used for generating a three-dimensional scanner motion trail as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner;
the automatic measurement module is used for driving the three-dimensional scanner to automatically scan and measure the part by utilizing the multi-axis mechanical arm according to the detection path planning of the part, so as to obtain real-time point cloud data of the part;
and the automatic evaluation module is used for automatically registering the cloud data of the real measurement points of the part, automatically dividing and automatically evaluating each curved surface.
Preferably, the device further comprises a computer and a communication module, wherein the model automatic analysis module, the detection path planning automatic generation module and the automatic evaluation module are integrated in the computer, and information transmission is carried out between the computer and the automatic measurement module through the communication module.
According to the automatic evaluation method and the automatic evaluation device for the geometric parameters of the parts, the non-contact measurement and evaluation of the parts can be automatically completed based on the theoretical model of the parts, the measurement efficiency is high, the operation is simple, and the working strength of measuring staff can be effectively reduced.
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For a clearer description of the technical solutions of the present invention, the following description will be given with reference to the attached drawings used in the description of the embodiments of the present invention, it being obvious that the attached drawings in the following description are only some embodiments of the present invention, and that other attached drawings can be obtained by those skilled in the art without the need of inventive effort:
FIG. 1 is a flow chart of a method for automatically evaluating geometric parameters of a part in accordance with one embodiment of the present invention;
FIG. 2 is a schematic structural view of an automatic evaluation device for geometric parameters of parts according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides an automatic evaluation method for geometric parameters of a part, and fig. 1 is a flow chart of the automatic evaluation method for geometric parameters of the part according to one embodiment of the invention. As shown in fig. 1, the automatic evaluation method for geometric parameters of a part according to an embodiment of the present invention includes steps S1 to S4.
In step S1, geometric information and labeling information of each curved surface in the part theoretical model are obtained, and a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information is established. Step S1 further comprises:
step S11: analyzing a part theoretical model by means of secondary development functions of various modeling software or various geometric inner cores to obtain geometric information therein, wherein the geometric information comprises information such as geometric characteristics (such as edges, surfaces and corresponding special attributes), geometric dimensions, tolerances, roughness and the like, and theoretical model files comprise STEP, STP, IGES, CATPART, SLDPRT, PRT and other format files;
step S12: according to the inherent geometric characteristics of each curved surface, the problem that the corresponding relation with the associated curved surface is difficult to correspond due to the fact that the dimensional tolerance marking is not standard is solved, the corresponding relation of each node in the analysis information is automatically arranged, and therefore a curved surface marking relation tree which represents the corresponding relation between each curved surface and marking information is built.
In one embodiment, an automatic model analysis module is developed by means of the secondary development function of CATIA, information such as geometric characteristics, size and tolerance labels of each curved surface in the CATIA model of a certain part is read, meanwhile, the problem that the associated curved surface is difficult to correspond due to the fact that the dimensional tolerance labels are not standard is solved according to the inherent geometric attributes of each curved surface, the corresponding relation of each node in analysis information is automatically arranged, and therefore a relation tree of each curved surface and the corresponding label information is built.
For example, when cylindricity is marked at the position of the edge, the program searches the surface where the edge is located according to the design rule, and automatically correlates the cylindrical surface with the properties of diameter, axis and the like with cylindricity instead of other curved surfaces such as a plane, a spherical surface and the like adjacent to the cylindrical surface.
In step S2, a motion trajectory of the three-dimensional scanner is generated as a detection path plan of the part based on the geometric information of each curved surface in the part theoretical model and the geometric features of the three-dimensional scanner.
Specifically, based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner, a scanning viewpoint plan and a measuring direction are generated, a detection path plan is generated, and the detection path plan is stored and generated as a detection model. Step S2 further comprises:
step S21: based on geometric information of each curved surface in the part theoretical model, establishing a directed bounding box of each curved surface according to a directed bounding box algorithm, so as to determine the spatial position of each curved surface;
step S22: under the constraint of the space position information of each curved surface, determining a single measurement visual range according to the geometric characteristics (including a field of view, a visual angle and a visual depth) of a visual cone of a preset three-dimensional scanner, determining a measurement direction according to the normal vector of the curved surface, and obtaining the plan of a part scanning viewpoint under the constraint of the space position of the curved surface;
step S23: and (3) carrying out path planning on all the obtained part scanning viewpoints based on a greedy algorithm of virtual simulation collision constraint (namely, the space position of each curved surface directional bounding box), and calculating to obtain an optimal three-dimensional scanner motion track as a detection path planning.
In step S3, according to the detection path planning of the part, the three-dimensional scanner is driven by the multi-axis mechanical arm to automatically scan and measure the part, so as to obtain the cloud data of the real-time point of the part.
Specifically, the gesture of the motion track of the three-dimensional scanner is calculated according to the spatial position relation of the multi-axis mechanical arm, a related motion control program is generated, and the multi-axis mechanical arm drives the three-dimensional scanner to perform non-contact measurement on the parts, so that the real-time point cloud data of the parts are obtained. Step S3 further comprises:
step S31: according to the spatial position relation of the multi-axis mechanical arm, carrying out gesture calculation on the motion trail of the three-dimensional scanner to obtain a motion control program of the multi-axis mechanical arm;
step S32: the multi-axis mechanical arm drives the three-dimensional scanner to move to the designated viewpoint position and the designated measurement direction according to the motion control program, and automatic scanning measurement of the part is carried out to obtain real-point cloud data of the part.
Step S32 further includes:
step S321: resetting the multi-axis mechanical arm, and performing zero marking treatment on the initial position;
step S322: according to the motion control program, transmitting a motion in-place pulse signal to a computer through a communication module after each multi-axis mechanical arm moves in place;
step S323: after receiving the in-place pulse signals of the multi-axis mechanical arm, the computer controls the three-dimensional scanner to perform scanning measurement, receives and processes real-time measurement point cloud data, and sends a current position measurement ending signal to the computer every time the viewpoint position measurement is ended;
step S324: after receiving the current position measurement end signal, the computer continuously sends a movement starting pulse instruction to the multi-axis mechanical arm, and the multi-axis mechanical arm drives the three-dimensional scanner to move to the appointed viewpoint position and the appointed measurement direction according to the preset control program, so that automatic scanning measurement of the part is completed, and real-time point cloud data of the part are obtained.
In the case where the second repair scan measurement is required, step S3 further includes:
step S33: carrying out space alignment on the real-point cloud data of the part obtained for the first time and a theoretical model, and then carrying out triangular meshing on the real-point cloud data by calculating polygonal point cloud through a rolling ball algorithm;
step S34: analyzing the quality of the triangular mesh reconstructed by the curved surface through a hole boundary algorithm, particularly performing key analysis on point cloud data of a corresponding relevant curved surface in a curved surface labeling relation tree, and determining the incomplete position of the actual measurement data of the curved surface through hole distribution of the triangular mesh, density distribution of the point cloud data, outlier noise distribution and the like;
step S35: determining incomplete positions of curved surface point cloud data which can be covered by a plurality of scanning viewpoints through a minimum inclusion sphere algorithm;
step S36: and determining the scanning viewpoint and the measuring angle of the secondary scanning measurement according to the constraint conditions, so as to regenerate the motion trail measured by the three-dimensional scanner.
In step S4, automatic registration, automatic segmentation of each curved surface, and automatic evaluation are performed on the real-time point cloud data of the part. Step S4 further comprises:
s41: performing automatic filtering and space alignment on single-measurement multi-frame measurement point cloud data and double-repetition measurement point cloud data, wherein the automatic filtering mainly removes outlier noise in the point cloud data, and performs space position registration alignment on a part theoretical model and real-point cloud data through a point cloud registration algorithm, such as an iterative closest point algorithm (ICP), normal distribution transformation registration (NDT) and feature invariance-based registration (ORB/FPFH/NARF);
s42: judging the attribution relation of the curved surface based on a part theoretical model and a curved surface labeling relation tree through the corresponding relation between a theoretical curved surface and actual measurement Qu Miandian cloud data and the mapping relation between a theoretical curved surface boundary and an actual measurement curved surface boundary, such as the change of the distance from a point to the curved surface and the normal vector included angle, so as to complete automatic segmentation of cloud data of real points of each curved surface of the part, maintain the spatial position of each curved surface, and particularly keep the corresponding relation between a reference and a corresponding evaluation surface;
s43: based on the least square discrimination method, a related curved surface dimensional tolerance evaluation model library is established, wherein the model library comprises a fitting method of straight lines, circles, planes, spherical surfaces, conical surfaces, cylindrical surfaces, paraboloids and NURBS curved surfaces and an evaluation method of corresponding dimensional tolerance, and a test of a geometric element evaluation data set is passed. The fitting method is a least square double fitting method, global optimization is performed through a least square fitting algorithm based on a genetic algorithm to obtain an initial value of a fitting parameter, LM (Levenberg-Marquardt) fitting calculation is performed to obtain an optimal value of the fitting parameter in order to improve the fitting precision, and a corresponding tolerance value is calculated on the basis of surface fitting;
s44: and fitting and evaluating the real-point cloud data of each curved surface based on the curved surface dimensional tolerance evaluation model library, and sorting, summarizing and outputting an evaluation report of each curved surface.
The embodiment of the invention also provides an automatic evaluation device for the geometric parameters of the parts, which comprises the following steps:
the model automatic analysis module is used for acquiring geometric information and labeling information of each curved surface in the part theoretical model and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information;
the automatic detection path planning generation module is used for generating a three-dimensional scanner motion trail as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner;
the automatic measurement module is used for driving the three-dimensional scanner to automatically scan and measure the part by utilizing the multi-axis mechanical arm according to the detection path planning of the part, so as to obtain real-time point cloud data of the part;
and the automatic evaluation module is used for automatically registering the cloud data of the real measurement points of the part, automatically dividing and automatically evaluating each curved surface.
In one example, as shown in fig. 2, the device for automatically evaluating geometric parameters of a part according to the embodiment of the present invention further includes a computer 1 and a communication module 2, wherein the model automatic analysis module, the detection path planning automatic generation module, and the automatic evaluation module are integrated in the computer 1, the automatic measurement module includes a multi-axis mechanical arm 3 and a three-dimensional scanner 4 mounted on the multi-axis mechanical arm 3, and information transmission is performed between the computer 1 and the automatic measurement module through the communication module 2.
Specific examples of the automatic evaluation device for part geometric parameters in this embodiment may be referred to above for limitation of the automatic evaluation method for part geometric parameters, and will not be described herein. The modules in the automatic part geometric parameter assessment device can be realized in whole or in part by software, hardware and a combination thereof.
The automatic evaluation method and the device for the geometric parameters of the parts have the following beneficial effects:
1. the invention automatically generates the part detection model containing the detection path based on the theoretical model of the part, carries a three-dimensional scanner to measure and complete the automatic measurement process of the part through a multi-axis mechanical arm, acquires the real-point cloud data of the part, realizes the automatic evaluation of the geometric parameters related to the curved surface corresponding to the dimensional tolerance marking based on the marking information in the established curved surface dimensional tolerance evaluation model library and the theoretical model and the characteristics of each curved surface, outputs a corresponding evaluation report, realizes the automatic evaluation of the geometric parameters of the part, changes the flow of manually adjusting the measuring equipment of the three-dimensional scanner by original detection personnel and manually and interactively and fussy processing the evaluation of the measurement point cloud data, realizes the non-contact digital measurement and evaluation of the part, has the advantages of high measurement efficiency, simple operation and the like, and effectively reduces the labor intensity of inspection personnel.
2. According to the invention, the related analysis information of the part theoretical model is applied to the whole flow of part detection evaluation, so that a single different part can complete the planning of a detection path on line, and the automatic measurement of the part is realized. Particularly, based on the established curved surface dimensional tolerance evaluation model library, the automatic evaluation of geometric parameters of each curved surface is realized on the basis of automatic segmentation of various labeling curved surface actual point clouds, and the method is suitable for single or batch part production modes. The automatic evaluation method and the device for the geometric parameters of the parts greatly promote the digital transformation work of the measurement and evaluation of the geometric parameters of the parts.
While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that modifications may be made to the described embodiments in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive of the scope of the invention, which is defined by the appended claims.
Claims (8)
1. An automatic assessment method for geometric parameters of a part is characterized by comprising the following steps:
step S1: acquiring geometric information and labeling information of each curved surface in a part theoretical model, and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information;
step S2: generating a motion track of the three-dimensional scanner as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner;
step S3: according to the detection path planning of the part, a multi-axis mechanical arm is utilized to drive a three-dimensional scanner to automatically scan and measure the part, and real-point cloud data of the part are obtained;
step S4: and (3) carrying out automatic registration, automatic segmentation and automatic evaluation on the cloud data of the real measurement points of the parts.
2. The method for automatically evaluating geometric parameters of a part according to claim 1, wherein said step S1 comprises:
analyzing the part theoretical model to obtain geometric information of each curved surface, wherein the geometric information comprises geometric features, geometric dimensions, tolerance and roughness;
and determining the corresponding relation between the labeling information and each curved surface according to the geometric characteristics of each curved surface, and establishing a curved surface labeling relation tree.
3. The method for automatically evaluating geometric parameters of a part according to claim 1 or 2, wherein said step S2 comprises:
based on geometric information of each curved surface in the part theoretical model, establishing a directed bounding box of each curved surface according to a directed bounding box algorithm, and determining the spatial position of each curved surface;
under the constraint of the space position information of each curved surface, determining a scanning viewpoint plan according to the geometric characteristics of the three-dimensional scanner viewing cone;
and carrying out path planning on all the obtained part scanning viewpoints based on a greedy algorithm of virtual simulation collision constraint conditions, and calculating to obtain an optimal three-dimensional scanner motion track serving as a detection path planning.
4. A method for automatic assessment of geometrical parameters of parts according to any one of claims 1 to 3, characterized in that said step S3 comprises:
according to the spatial position relation of the multi-axis mechanical arm, carrying out gesture calculation on the motion trail of the three-dimensional scanner to obtain a motion control program of the multi-axis mechanical arm;
the multi-axis mechanical arm drives the three-dimensional scanner to move to the designated viewpoint position and the designated measurement direction according to the motion control program, and automatic scanning measurement of the part is carried out to obtain real-point cloud data of the part.
5. The method for automatically evaluating geometric parameters of a part according to claim 4, wherein said step S3 further comprises:
carrying out space alignment on the first real-point cloud data of the part and a theoretical model, and then carrying out three-dimensional curved surface reconstruction on the real-point cloud data through a rolling ball algorithm;
analyzing the quality of the triangular mesh reconstructed by the curved surface through a hole boundary algorithm, and determining the incomplete position of the actual measurement data of the curved surface;
determining the incomplete positions of the curved surface point cloud data which can be covered by a plurality of scanning viewpoints through a minimum inclusion sphere algorithm;
and determining the scanning viewpoint and the measuring angle of the secondary scanning measurement according to the constraint conditions, and generating the motion trail of the three-dimensional scanner again.
6. The method for automatically evaluating geometric parameters of a part according to any one of claims 1 to 5, wherein said step S4 comprises:
carrying out space position registration alignment on the part theoretical model and the real-point cloud data through a point cloud registration algorithm;
based on the part theoretical model and the curved surface labeling relation tree, carrying out automatic segmentation on cloud data of real measurement points of each curved surface of the part;
based on a least square discrimination method, establishing a curved surface dimensional tolerance evaluation model library;
fitting and evaluating the real-point cloud data of each curved surface according to the established curved surface dimensional tolerance evaluation model library, and outputting an evaluation report of each curved surface.
7. An automatic assessment device for geometric parameters of a part, comprising:
the model automatic analysis module is used for acquiring geometric information and labeling information of each curved surface in the part theoretical model and establishing a curved surface labeling relation tree representing the corresponding relation between each curved surface and the labeling information;
the automatic detection path planning generation module is used for generating a three-dimensional scanner motion trail as a detection path plan of the part based on geometric information of each curved surface in the part theoretical model and geometric characteristics of the three-dimensional scanner;
the automatic measurement module is used for driving the three-dimensional scanner to automatically scan and measure the part by utilizing the multi-axis mechanical arm according to the detection path planning of the part, so as to obtain real-time point cloud data of the part;
and the automatic evaluation module is used for automatically registering the cloud data of the real measurement points of the part, automatically dividing and automatically evaluating each curved surface.
8. The automatic part geometric parameter assessment device according to claim 7, further comprising a computer and a communication module, wherein the automatic model analysis module, the automatic detection path planning generation module and the automatic evaluation module are integrated in the computer, and information transmission is carried out between the computer and the automatic measurement module through the communication module.
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