CN117272522A

CN117272522A - Portable aircraft curved surface skin rivet hole profile measurement system and method thereof

Info

Publication number: CN117272522A
Application number: CN202311551871.8A
Authority: CN
Inventors: 侯典明; 刘启伟
Original assignee: Shanghai Miyu Network Technology Co ltd
Current assignee: Shanghai Miyu Network Technology Co ltd
Priority date: 2023-11-21
Filing date: 2023-11-21
Publication date: 2023-12-22
Anticipated expiration: 2043-11-21
Also published as: CN117272522B

Abstract

The invention relates to the field of aircraft skin manufacturing, and discloses a portable aircraft curved surface skin rivet hole profile measuring system and method, wherein the measuring system comprises the following steps: placing the portable measuring device on a curved surface to be measured; the position of the measuring device is adjusted through the video window, so that the hole site to be measured is positioned at the center of the video window; starting a line laser sensor and a servo motor, and controlling a scanning position through the servo motor to perform scanning; data of the line laser sensor and the motor encoder are collected and processed in real time, wherein the data fusion, the key point analysis and the point cloud segmentation, the filtering dimension reduction, the coordinate transformation, the point cloud slicing, the construction of a two-dimensional point cloud array, the normal estimation and the feature extraction are included; and outputting a measurement result. The visual analysis and point cloud analysis functions are fully utilized, all technical parameters of the hole to be measured are measured at one time, human operation errors caused by manual measurement conventionally measured by using a mechanical measuring tool are eliminated, and the measurement efficiency, precision and consistency of measurement results are improved.

Description

Portable aircraft curved surface skin rivet hole profile measurement system and method thereof

Technical Field

The invention relates to the technical field of aircraft skin manufacturing, relates to connection and inspection of aircraft skins, in particular to contour measurement of rivet holes on the aircraft skins, and specifically relates to a portable aircraft curved surface skin rivet hole contour measurement system and a portable aircraft curved surface skin rivet hole contour measurement method.

Background

Aircraft Skin (Aircraft Skin) is an important component of the Aircraft structure that is subjected to various loads during flight, ensuring the overall stiffness and strength of the Aircraft, while also affecting the aerodynamic performance and appearance quality of the Aircraft. The aircraft skin has the characteristics of large size, complex appearance and high surface quality requirement, and the surface of the aircraft skin is provided with complex molded surfaces such as curved surfaces, conical surfaces, spherical surfaces and the like. In order to reduce the weight of the aircraft, materials as light as possible, such as aluminum alloys, titanium alloys, composite materials, etc., are suitably used in the manufacture of the aircraft. To further reduce weight, the skin of an aircraft is typically made very thin. Such thin skins are very difficult to weld together. Moreover, in some aircraft, the fuselage is made of aluminum, so that the heat resistance is poor, and a welding process generates a large amount of heat during welding, which is obviously not suitable for the aircraft with the aluminum fuselage. In addition, the most advanced airliners internationally use composite materials in large quantities to reduce aircraft weight, which are not suitable for welding, and the interconnections of the different materials must be physically fixed. In summary, the aircraft skin is currently the best choice for connecting to each other by rivets.

The number of rivets on an aircraft is tens of thousands, up to millions. The accuracy of aircraft skin rivet assembly can affect the airflow during aircraft flight, and thus the airflow efficiency during aircraft flight. In the process of manufacturing and inspecting the aircraft skin, the machining errors of rivet holes are usually important basis for skin inspection delivery, and are visual standards for verifying that the skin meets the requirements of subsequent assembly processes. If the machining precision of the rivet hole does not meet the requirement, the flatness of the fastener is affected, so that poor assembly is caused, and even the pneumatic performance and the fuel economy of an airplane are negatively affected. For military aircraft, the assembly requirements for fasteners are higher in order to achieve better stealth and electrolyte filling of the fastener area. Therefore, the skin rivet holes, whether planar or curved, need to be measured accurately to ensure that the fastener is well assembled.

Accurate measurement of the profile of the rivet hole on the curved surface has been a difficult task. The aircraft skin surface has a large curvature and, in order to obtain accurate measurements, it is necessary to take into account the curved surface of the portion of the curved surface that is combined with the fastener. The traditional measurement mode is to use a special mechanical measuring tool for measurement, such as a socket gauge, an inside micrometer, a three-coordinate measuring machine or a standard component for contact detection. The method has the defects that the detection modes can only detect one or two parameters at a time, such as aperture, depth, central position and the like, the universality is poor, the detection efficiency is low, some important parameters such as parameter indexes of cone angle, normal vector deflection angle and the like can not be detected even, meanwhile, the position where the measuring tool is placed can influence the measurement accuracy, the measurement result is greatly influenced by human operation factors, and the measurement accuracy and consistency often cannot meet the actual measurement accuracy requirement. Therefore, how to measure the outline of the rivet hole on the curved plane skin rapidly, accurately and comprehensively is a technical problem to be solved urgently, and has important significance for improving the accuracy and efficiency of measurement, the manufacturing quality and aerodynamic performance of the plane and the like.

Disclosure of Invention

Object of the invention

Aiming at the defects and shortcomings in the prior art, the invention aims to provide a portable aircraft curved surface skin rivet hole profile measuring system and a portable aircraft curved surface skin rivet hole profile measuring method, which are used for solving the problems of low measuring efficiency, poor precision, incomplete parameters, large human error, high dependence on skills of operators and the like in the existing aircraft skin rivet hole profile measuring technology.

(II) technical scheme

In order to achieve the aim of the invention, the invention is realized by the following technical scheme:

the 1 st object of the present invention is to provide a portable measuring system for measuring the profile of rivet hole of curved skin of airplane, at least comprising a portable measuring device, the portable measuring device at least comprises a housing and a bracket fixedly arranged on the housing and integrally positioned below the housing, the bottom of the bracket is arranged on the curved skin of airplane to be measured, the invention is characterized in that: at least one line laser scanning sensor, a motion control unit, a data acquisition unit and a data processing unit are arranged in the shell, wherein:

The line laser scanning sensor is arranged on the motion control unit and is used for scanning rivet holes on the curved surface skin of the airplane to be detected and scanning to obtain outline data of the rivet holes;

the motion control unit is used for controlling the scanning position of the line laser scanning sensor and at least comprises a linear module, a servo motor and a motor encoder, wherein:

the linear module comprises at least a linear guide rail and a sliding block movable end, wherein the linear guide rail is fixedly arranged in the shell, the sliding block movable end is arranged on the linear guide rail in a linearly movable mode, and the linear laser scanning sensor is arranged on the sliding block movable end in a fixedly connected mode so as to realize linear movement and position positioning of the linear laser scanning sensor:

the servo motor is connected with the movable end of the sliding block in the linear module in a transmission way and is used for driving the movable end of the sliding block to move along the linear guide rail of the movable end of the sliding block so as to adjust the moving speed and the scanning position of the line laser scanning sensor, so that the traversing scanning of the curved surface skin of the airplane to be detected is realized and the measuring requirement of a complex curved surface is met;

the input end of the motor encoder is connected with the servo motor in a communication way and is used for detecting the rotating speed and the rotating angle of the servo motor and transmitting the rotating speed and the rotating angle data to the data acquisition unit positioned at the downstream of the motor encoder so as to perform data synchronization and coordinate transformation;

The input end of the data acquisition unit is in communication connection with the output ends of the line laser scanning sensor and the motor encoder, and is used for acquiring the data of the line laser scanning sensor and the motor encoder in real time and transmitting corresponding information data to the data processing unit positioned at the downstream of the data processing unit through the output ends of the data acquisition unit;

the input end of the data processing unit is in communication connection with the output end of the data acquisition unit and is used for processing various data fed back by the data acquisition unit, and the processing at least comprises data fusion, key point analysis and point cloud segmentation, filtering dimension reduction, coordinate transformation, point cloud slicing, two-dimensional point cloud array construction, normal estimation and feature extraction during operation, so that various technical parameters of rivet holes on the curved surface skin of the aircraft to be detected are obtained through analysis, and finally measurement results are output.

Preferably, a data storage unit is further disposed in the housing of the portable measuring device, and an input end of the data storage unit is connected to an output end of the data acquisition unit and an output end of the data processing unit in a communication manner, and at least scan data of the line laser scanning sensor and measurement results obtained after processing by the data processing unit are stored.

Preferably, the whole support of the portable measuring device is arranged into a three-point support structure, and the bottom of the support is arranged on the curved surface skin of the airplane to be measured so as to adapt to the curvature of the curved surface at different positions of the skin.

Preferably, the system further comprises a human-computer interaction unit and a vision sensor disposed within the housing of the portable measuring device, wherein:

the visual sensor is used for collecting images of rivet holes and surrounding areas of the aircraft curved surface skin to be tested through videos, so as to assist an operator to observe the relative position relation between the rivet holes to be tested and the line laser scanning sensor, an output end of the visual sensor is in communication connection with an input end of the data collecting unit, video stream data are collected and transmitted to the data processing unit, the image processing module arranged in the data processing unit is used for analyzing the video stream shot by the visual sensor in real time so as to extract the boundary line characteristics of the upper surface of the rivet holes and mark the positions and the sizes of the rivet holes in the images, and then the processed video stream is transmitted to the man-machine interaction unit in a feedback manner so that the operator can conveniently adjust the position of the portable measuring device, and the rivet holes to be tested are positioned in the center of a video window;

The man-machine interaction unit is used for man-machine interaction, the input end of the man-machine interaction unit is in communication connection with the output end of the data processing unit, and the man-machine interaction unit is used for carrying out data exchange with the data processing unit so that an operator can control the measuring process and check the measuring result conveniently, and the man-machine interaction unit comprises the steps of starting testing, ending testing, retesting, checking the measuring result and observing the relative position relation between a rivet hole position to be tested and the line laser scanning sensor.

Preferably, the system further comprises an inclination sensor arranged in the shell of the portable measuring device, the inclination sensor is used for detecting an included angle between the line laser scanning sensor and a rivet hole site to be measured, an output end of the inclination sensor is in communication connection with an input end of the data acquisition unit, inclination data are acquired and transmitted to the data processing unit, a corresponding inclination correction module is arranged in the data processing unit, the inclination correction module dynamically establishes a correction conversion matrix based on the inclination data, and corrects original scanning data of the line laser scanning sensor so as to eliminate data deformation in two mutually orthogonal directions of a scanning path, so that data distortion caused by angle deviation is compensated, and accuracy and consistency of the scanning data are ensured.

Further, the data processing unit performs data fusion processing on each item of data fed back by the data acquisition unit according to the following manner, specifically:

firstly, ensuring that data acquired from the line laser scanning sensor, the motor encoder and other sensors are synchronized in time through timestamp matching, and avoiding time sequence disorder of the data;

secondly, aligning the scanning data collected by the line laser scanning sensor with physical space coordinates thereof to ensure that each measuring point accurately reflects the physical position of the measuring point on the curved surface skin of the airplane and eliminates the space deviation of the data;

and then, fusing the scanning data from the line laser scanning sensor with various data acquired by the motor encoder and data acquired by other sensors to construct point cloud data.

Further, the data processing unit performs key point analysis and point cloud segmentation processing according to the following modes, specifically:

firstly, identifying and extracting key characteristic points of rivet holes on a curved surface skin of an airplane to be detected from the point cloud data, wherein the key characteristic points at least comprise edges and center points of the rivet holes;

And after the extraction and identification of key feature points are completed, the point cloud data are segmented, the point cloud data of the rivet holes and the neighborhood thereof are separated from the rest point cloud data, and the analysis area is focused on the rivet holes and the neighborhood thereof, so that the point cloud scale is reduced, and the data processing capacity is reduced.

Further, the data processing unit performs dimension reduction processing on the point cloud data by adopting a voxel grid technology, divides the space into voxels with uniform size, equally divides the space into M, N, L parts in three mutually orthogonal X, Y, Z coordinate axis directions according to the set voxel grid side length, wherein M, N, L is a positive integer greater than zero, and takes average or representative points in each voxel grid to replace all points in the voxel grid so as to simplify the point cloud data, and numbers each voxel grid, thereby reducing the scale of the point cloud data and improving the calculation speed.

Furthermore, the data processing unit performs dimension reduction processing on the point cloud data according to the following voxel grid technology, so that the data quantity is reduced and the calculation efficiency is improved while the key geometric information of the data is not lost, and the method specifically comprises the following steps:

firstly, the data processing unit calculates the maximum values of X, Y, Z on three coordinate axes according to the point cloud data coordinate set X _max 、Y _max 、Z _max And minimum valueX _min 、Y _min 、Z _min The range of the point cloud data on each coordinate axis is determined, and a foundation is provided for subsequent space grid division;

secondly, calculating the side length of the minimum bounding box of the point cloud according to the maximum value and the minimum value of the point cloud data on three coordinate axes X, Y, ZL _x 、L _y 、L _z The minimum bounding box is a minimum cubic space defined around the point cloud data for defining an overall spatial range of the point cloud data:

then, the side length of the voxel small grid is set ascellThe X, Y, Z three coordinate axes are equally divided intoM、N、LThe minimum bounding box is divided intoM×N×LEach voxel small grid represents a small region in the point cloud data:

then numbering each small voxel grid and marking as%i,j,k) The voxel small grid to which each data point in the point cloud data belongs is determined through numbering:

finally, on the basis of the voxel grids, calculating the gravity center of each voxel small grid, replacing all points in the voxel small grid with the gravity center to simplify the point cloud data, and if the gravity center does not exist, selecting the data point closest to the theoretical gravity center in the voxel as a representative:

wherein,C _ijk 、P _i 、Krepresenting the center of gravity, data points and points, respectively, of the voxel small grid.

Further, the data processing unit performs coordinate transformation according to the following manner to correct the scan data, and eliminates scan deformation caused by possible inclination angle between the laser scan sensor and the measured rivet hole, specifically:

firstly, three coordinate systems are established, namely a system coordinate systemSSensor coordinate systemTHole coordinate systemPWherein the system coordinate systemSIs a coordinate system fixed on a measuring system, and a sensor coordinate systemTIs a coordinate system fixed on an on-line laser scanning sensor and a hole coordinate systemPThe coordinate system is fixed on the measured rivet hole, and the relative position and direction relation among the three coordinate systems are described through a conversion matrix;

secondly, according to the inclination angle of the line laser scanning sensor obtained by measurementθCalculating a sensor coordinate systemTCoordinate system of systemSConversion matrix betweenM _TS ：

Then, calculating a hole coordinate system according to the shape of the rivet hole to be measuredPCoordinate system of systemSConversion matrix betweenM _PS ：

Wherein the parameters area,b,c,d,e,f,g,h,iIs a constant determined according to the geometric parameters of the rivet hole to be measured;

then, each original scanning point in the point cloud data is converted by using a conversion matrixT(x,y,z) From a sensor coordinate systemTConversion to hole seatLabel system PThereby eliminating scan distortion:

finally, outputting the corrected scan dataP(x',y',z') Accurate geometric information is provided for subsequent analysis and measurement to ensure that the scan data geometrically accurately reflects the actual morphology of the rivet hole.

Further, the data processing unit performs point cloud slicing and builds a two-dimensional point cloud array according to the following manner, and divides the three-dimensional point cloud into the two-dimensional point cloud array to improve the analysis speed, specifically:

firstly, determining one or more reference planes in three-dimensional point cloud data based on the geometric features of an aircraft curved surface skin or the positioning of rivet holes, and taking the reference planes as the references of point cloud slices;

secondly, dividing the three-dimensional point cloud along the direction perpendicular to the reference plane by taking the reference plane as a benchmark so as to form a series of two-dimensional point cloud layers, wherein the point cloud data contained in each two-dimensional point cloud layer represents a section with a specific depth in an original three-dimensional space;

and then, carrying out noise reduction and/or feature enhancement image processing operation on each two-dimensional point cloud layer so as to improve the usability of data and the accuracy of analysis.

Further, the data processing unit performs normal estimation according to the following manner, specifically:

Firstly, the data processing unit constructs a local point set of each point by searching adjacent points in a set radius aiming at each point or a selected key point set in point cloud data;

secondly, for each point and a local point set thereof, three eigenvalues and corresponding eigenvectors are obtained by calculating covariance matrixes and performing singular value decomposition;

then, selecting a feature vector with the minimum feature value as a normal vector of the local point set, wherein the normal vector is perpendicular to a best fit plane where the local point set is located;

then, the normal vector direction is adjusted according to the viewpoint position, so that the connecting line included angle between the normal vector direction and the viewpoint is smaller than 90 degrees;

and finally, repeating the steps for all points or selected key point sets in the point cloud data to obtain a group of normal vectors which are used as normal estimation results of the point cloud data.

Furthermore, the data processing unit performs feature extraction according to the following manner, and analyzes various technical parameters of the tested rivet hole by utilizing boundary analysis, dotted line and circle feature extraction technology, wherein the technical parameters are specifically as follows:

firstly, for each tested rivet hole, the data processing unit identifies and extracts the outline of the rivet hole through a boundary analysis technology, wherein the outline comprises key points representing the edges of the rivet hole in the identification point cloud data, and the geometric outline of the rivet hole is constructed according to the key points;

Then, analyzing symmetry and linear characteristics of the rivet hole by utilizing a dotted line characteristic extraction technology, revealing structural details of the rivet hole to be tested by analyzing a linear mode in a point cloud, determining center, diameter and roundness parameters of the rivet hole by utilizing a circular characteristic extraction technology for the circular or approximately circular rivet hole, and analyzing depth and curved surface characteristics of the rivet hole to be tested by combining previous normal estimation data, wherein the method comprises the steps of estimating depth profile and internal surface structure of the rivet hole;

and finally, integrating all the extracted characteristic data to form comprehensive technical parameter analysis of the tested rivet hole.

The 2 nd invention of the present invention is to provide a method for measuring the profile of a curved skin rivet hole of an aircraft, using the portable system for measuring the profile of a curved skin rivet hole of an aircraft provided by the 1 st invention, wherein the method comprises at least the following steps:

SS1, placing a portable measuring device on a to-be-measured curved surface of an aircraft curved surface skin;

SS2, adjusting the position of the measuring device through the video window to enable the hole site to be measured to be positioned at the center of the video window;

SS3, starting a line laser scanning sensor and a servo motor, and controlling the scanning position of the laser scanning sensor through the servo motor to perform scanning;

SS4. Collecting the data of the line laser scanning sensor and the motor encoder in real time, and processing the data, wherein the processing operation at least comprises data fusion, key point analysis and point cloud segmentation, filtering dimension reduction, coordinate transformation, point cloud slicing, two-dimensional point cloud array construction, normal estimation and feature extraction;

and SS5. Outputting the measurement result and storing the measurement result.

Preferably, in step SS4, the processing operation specifically includes:

SS41. Data fusion, the data of each item of feedback that the data acquisition unit transmits are carried on the data fusion processing, and construct the point cloud data accordingly;

SS42. Analyzing key points and dividing point cloud, focusing an analysis area to a rivet hole and a neighborhood thereof, and reducing the scale of the point cloud;

SS43, filtering and dimension reduction, namely equally dividing X, Y, Z three coordinate axes into M, N, L parts according to a set voxel small grid side length cell, numbering each voxel small grid, and further reducing the scale of point cloud so as to improve the calculation speed;

SS44, coordinate transformation, eliminating scanning deformation caused by possible inclination angle between the laser sensor and the rivet hole to be measured, correcting scanning data;

SS45, slicing the point cloud, constructing a two-dimensional point cloud array, and dividing the three-dimensional point cloud into the two-dimensional point cloud array so as to improve the analysis speed;

SS46. Normal estimation, the preparation phase of the subsequent feature analysis;

SS47 feature extraction, the technical parameters of rivet holes are analyzed by utilizing boundary analysis, dotted line and circle feature extraction technology.

Preferably, in the SS41, the data fusion process is performed on each item of data fed back by the data acquisition unit in the following manner, which specifically includes:

Preferably, in the SS42, the key point analysis and the point cloud segmentation process are performed as follows:

Preferably, in the SS43, the point cloud data is subjected to the dimension reduction processing as follows:

SS431 calculating the maximum values of X, Y, Z coordinate axes according to the coordinate set of the data point cloud dataX _max 、Y _max 、Z _max And minimum valueX _min 、Y _min 、Z _min The range of the point cloud data on each coordinate axis is determined, and a foundation is provided for subsequent space grid division;

SS432 calculating the side length of the minimum bounding box of the point cloud according to the maximum value and the minimum value of the point cloud data on three coordinate axes X, Y, ZL _x 、L _y 、L _z The minimum bounding box is a minimum cubic space defined around the point cloud data for defining an overall spatial range of the point cloud data:

SS433 set the side length of the voxel small grid ascellThe X, Y, Z three coordinate axes are equally divided intoM、N、LThe minimum bounding box is divided into m×n×l voxel small grids, each representing a small region in the point cloud data:

SS434 numbering and marking each voxel small grid as @ i,j,k) The voxel small grid to which each data point in the point cloud data belongs is determined through numbering:

SS435, on the basis of the voxel grids, calculating the gravity center of each voxel small grid, replacing all points in the voxel small grid with the gravity center, simplifying the point cloud, and if the gravity center does not exist, selecting the data point closest to the theoretical gravity center in the voxel as a representative:

Preferably, in the SS44, coordinate transformation is performed to correct scan data, so as to eliminate scan deformation caused by possible inclination angles between the laser scan sensor and the rivet hole to be measured, specifically:

firstly, three coordinate systems are established, namely a system coordinate systemSSensor coordinate systemTHole coordinate systemPWherein the system coordinate systemSIs a coordinate system fixed on a measuring system, and a sensor coordinate systemTIs fixed on-line laser scanning sensingCoordinate system on the device, hole coordinate systemPThe coordinate system is fixed on the measured rivet hole, and the relative position and direction relation among the three coordinate systems are described through a conversion matrix;

secondly, according to the inclination angle of the line laser scanning sensor obtained by measurement θCalculating a sensor coordinate systemTCoordinate system of systemSConversion matrix betweenM _TS ：

then, each original scanning point in the point cloud data is converted by using a conversion matrixT(x,y,z) From a sensor coordinate systemTConversion to an aperture coordinate systemPThereby eliminating scan distortion:

Preferably, in the SS45, the point cloud slicing and the two-dimensional point cloud array construction are performed in the following manner, and the three-dimensional point cloud is divided into the two-dimensional point cloud arrays to improve the analysis speed, specifically:

Preferably, in the SS46, the normal estimation is performed as follows:

Preferably, in the SS47, feature extraction is performed in the following manner, and each technical parameter of the measured rivet hole is analyzed by using boundary analysis, dotted line and circle feature extraction technology, specifically:

(III) technical effects

Compared with the prior art, the portable airplane curved surface skin spot facing contour measuring system and the portable airplane curved surface skin spot facing contour measuring method are disclosed. The beneficial effects are as follows:

(1) The invention has the advantages of portability and convenience, fully utilizes the functions of visual analysis and point cloud analysis, completes all technical parameters of the hole to be measured by one-time measurement, eliminates human operation errors caused by manual measurement which is conventionally measured by a mechanical measuring tool, and improves the efficiency, the precision and the consistency of measurement results.

(2) The invention combines various analysis technologies and means such as image analysis, high-precision laser scanning, point cloud segmentation, point cloud reconstruction, feature extraction and the like, effectively reduces the complexity of data and improves the efficiency of data processing. In particular, the method and the device for reducing the dimension of the point cloud data by voxel grid technology remarkably reduce the data quantity, improve the calculation speed and simultaneously reserve the key geometric information of the data. This is particularly important when processing large-scale point cloud data, and can greatly improve overall processing efficiency.

(3) Compared with the traditional mechanical measuring tool or contact type detection method, the non-contact type measurement technology has the advantages that the influence of human factors in the measurement process is eliminated, the measurement precision and the degree of automation of measurement are improved, and the non-contact type measurement technology has important significance for improving the rapid detection of rivet holes and improving the flatness of aircraft skin riveting.

Drawings

FIG. 1 is a schematic diagram of a portable aircraft curved skin rivet hole profile measurement system of the present invention;

FIG. 2 is a flow chart of a method for measuring the profile of a rivet hole of a curved skin of a portable aircraft;

FIG. 3 is a schematic flow chart of the measuring method of the present invention;

FIG. 4 is a schematic diagram of a coordinate system of the present invention;

FIG. 5 is a schematic diagram of a line laser scanning analysis of the present invention;

FIG. 6 is a schematic diagram of the measured parameters of the present invention.

Detailed Description

For a better understanding of the present invention, the following examples are set forth to illustrate the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of the invention. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention. 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 following describes the structure and technical scheme of the present invention in detail with reference to the accompanying drawings, and an embodiment of the present invention is given.

Example 1:

referring to fig. 1, the portable aircraft curved surface skin rivet hole profile measuring system provided by the embodiment of the invention at least comprises a portable measuring device, wherein the portable measuring device comprises a shell and a bracket, and is used for supporting a line laser sensor to measure, the position of the sensor can be adjusted according to specific measurement requirements, so that the measuring precision and the comprehensiveness are ensured, and the bracket of the portable measuring device for supporting the sensor is designed to adopt a 3-point supporting structure so as to adapt to different curved surface curvatures of the aircraft curved surface skin to be measured because the measured surface is of a curved surface structure. A line laser scanning sensor, a motion control unit, a data acquisition unit and a data processing unit are arranged in a shell of the portable measuring device, wherein:

The line laser scanning sensor is arranged on the motion control unit and is used for scanning the rivet hole of the curved surface to be detected and acquiring the contour data of the rivet hole; because the requirement (45-90 degrees) of the line laser profile sensor on the incident angle is considered, the line laser profile sensor is preferably installed obliquely so as to improve the accuracy and the integrity of the detection hole;

the motion control unit comprises a linear module, a servo motor and an encoder and is used for controlling the scanning position of the linear laser sensor so as to realize the traversal scanning of the curved surface to be detected, wherein:

the linear module at least comprises a linear guide rail and a sliding block movable end, the linear guide rail is fixedly arranged in the shell, the sliding block movable end is arranged on the linear guide rail in a linear movement mode, and the linear laser sensor is fixedly connected to the sliding block movable end of the linear module so as to realize linear movement and position positioning of the linear laser scanning sensor;

the servo motor is connected with the sliding block movable end in the linear module in a driving way and is used for driving the sliding block movable end to move along the linear guide rail of the sliding block movable end and then driving the line laser scanning sensor to move so as to control the scanning position of the line laser scanning sensor and realize the traversal scanning of the curved surface skin of the airplane to be detected;

the input end of the motor encoder is in communication connection with the servo motor and is used for detecting the rotating speed and the rotating angle of the servo motor and transmitting the rotating speed and the rotating angle data to a data acquisition unit positioned at the downstream of the motor encoder so as to perform data synchronization and coordinate transformation.

The input end of the data acquisition unit is in communication connection with the output ends of the line laser scanning sensor and the motor encoder, and is used for acquiring the data of the line laser sensor and the motor encoder in real time and transmitting the data to the data processing unit through the output ends thereof so as to perform real-time processing and analysis.

The input end of the data processing unit is in communication connection with the output end of the data acquisition unit and is used for processing various data fed back by the data acquisition unit, such as data obtained by scanning a processing line laser sensor, so as to analyze and obtain various technical parameters of rivet holes on the curved surface skin of the aircraft to be detected and output measurement results.

In the preferred embodiment of the invention, a data storage unit is also arranged in the shell of the portable measuring device, and the data storage unit is used for storing scanning data and measuring results and can store the data as electronic files so as to facilitate subsequent analysis, display and sharing.

In a preferred embodiment of the invention, the system further comprises a human-computer interaction unit and a visual sensor disposed within the housing of the portable measuring device, wherein: the visual sensor is used for collecting images of rivet holes and surrounding areas on the curved surface skin of the aircraft to be tested in a video mode, so that an operator is assisted in observing the relative position relation between the rivet holes to be tested and the line laser scanning sensor, the output end of the visual sensor is in communication connection with the input end of the data collecting unit, video stream data are collected and transmitted to the data processing unit, the image processing module arranged in the data processing unit is used for analyzing video streams shot by the camera in real time to extract surface boundary line characteristics of the rivet holes and mark the positions and the sizes of the rivet holes in the images, and then the processed video streams are transmitted to the man-machine interaction unit in a feedback mode, so that the operator can conveniently adjust the positions of the portable measuring device, and the rivet holes to be tested are located in the center of the video window; the man-machine interaction unit is used for man-machine interaction, the input end of the man-machine interaction unit is in communication connection with the output end of the data processing unit, and the man-machine interaction unit is used for carrying out data exchange with the data processing unit so that an operator can control the measuring process and check the measuring result conveniently, and the man-machine interaction unit comprises the steps of starting testing, ending testing, retesting, checking the measuring result and observing the relative position relation between the hole site and the line laser scanning sensor.

In a preferred embodiment of the present invention, the system further includes an inclination sensor disposed in the housing of the portable measuring device, the inclination sensor is used for detecting an angle between the laser scanning sensor and the rivet hole site to be measured, an output end of the inclination sensor is communicatively connected to an input end of the data acquisition unit, and then the inclination data is acquired and transmitted to the data processing unit, a corresponding inclination correction module is disposed in the data processing unit, and the inclination correction module dynamically establishes a correction conversion matrix based on the inclination data, and corrects the original scanning data of the laser scanning sensor, so as to eliminate data distortion in two mutually orthogonal directions of the scanning path, to compensate data distortion caused by the angle deviation, and ensure accuracy and consistency of the scanning data.

In the portable aircraft curved surface skin rivet hole profile measuring system, the data processing unit is a core part of the system and is used for processing data obtained by scanning a line laser sensor and outputting a measuring result. Specifically, the data processing unit processes key point analysis and point cloud segmentation, data fusion, filtering dimension reduction algorithm, coordinate transformation, point cloud slicing, two-dimensional point cloud array construction, normal estimation and feature extraction.

By analyzing the line laser profile sensor and the shape to be detected, the whole measurement system will involve 3 coordinate systems: system coordinate systemSSensor coordinate systemTCoordinate system of parts (holes)P. In some embodiments, as shown in fig. 4 and 5, the pose relationship between the line laser sensor and the rivet hole to be measured has a certain uncertainty due to the placement of the portable measuring device on the surface of the curved surface structure. When the laser line of the line laser contour sensor forms an included angle with the surface to be measured, the detection contour of the line laser contour sensor is deformed, and as a result, the X direction is enlarged, the Y direction is distorted, and the Z direction (height direction) is unchanged. Therefore, a conversion relation among 3 coordinate systems needs to be established, when a measurement included angle exists, X and Y-direction data of measurement data need to be corrected, and a correction conversion matrix is dynamically established according to the inclination angle of the sensor; and a correction unit is arranged in the system and used for correcting the possible included angle between the line laser sensor and the rivet hole to be measured, and a correction conversion matrix is dynamically established according to the inclination angle of the sensor.

Example 2

As shown in fig. 2 and 3, the present embodiment provides an aircraft curved skin rivet hole profile measuring method, using the portable aircraft curved skin rivet hole profile measuring system provided in the above embodiment 1, the method includes at least the following steps when implemented:

SS3, starting a line laser scanning sensor and a servo motor, and controlling the scanning position of the laser scanning sensor through the servo motor to perform scanning; after the scanning is finished, an analysis flow is started, and the rapid and automatic detection of the spot facing contour degree of the aircraft skin is realized through technologies such as image analysis, line laser scanning, point cloud construction, rapid point cloud segmentation, point cloud feature extraction and the like, wherein the measurement of the coaxiality of a large diameter, a small diameter, a nest depth, a nest axis and a hole axis of the spot facing is realized (as shown in fig. 6).

SS4, collecting and processing the data of the line laser sensor and the motor encoder in real time, including data fusion, key point analysis and point cloud segmentation, filtering dimension reduction, coordinate transformation, point cloud slicing, two-dimensional point cloud array construction, normal estimation and feature extraction;

and SS5. Outputting the measurement result, outputting the measurement result to a human-computer interaction interface, and storing the measurement result in a storage unit.

In a preferred embodiment of the present invention, the processing operation in step SS4 specifically includes the following sub-steps:

SS41. Data fusion, the data acquisition unit transmits each item of data fed back, such as the data scanned by a line laser sensor, to form point cloud data;

In a further preferred embodiment of the present invention, the above substep SS41 specifically comprises the following steps: firstly, the time stamp matching ensures that the data collected from a line laser scanning sensor, a motor encoder and other sensors are synchronized in time, so that the time sequence disorder of the data is avoided; secondly, aligning scanning data collected by a line laser scanning sensor with physical space coordinates of the scanning data so as to ensure that each measuring point accurately reflects the physical position of the measuring point on the curved surface skin of the aircraft and eliminate the space deviation of the data; and then, fusing the scanning data from the line laser scanning sensor with various data acquired by the motor encoder and data acquired by other sensors to construct point cloud data.

In a further preferred embodiment of the present invention, the above substep SS42 specifically comprises the following steps: firstly, identifying and extracting key characteristic points of rivet holes on a curved surface skin of an airplane to be detected from point cloud data, wherein the key characteristic points at least comprise edges and center points of the rivet holes; after the extraction and identification of key feature points are completed, the point cloud data are segmented, the point cloud data of the rivet holes and the neighborhood thereof are separated from the rest point cloud data, and the analysis area is focused on the rivet holes and the neighborhood thereof, so that the point cloud scale is reduced, and the data processing amount is reduced.

In a further preferred embodiment of the present invention, the above substep SS43 specifically comprises the following steps:

SS431 obtaining the maximum value X of X, Y, Z on three coordinate axes according to the coordinate set of the data point cloud data _max 、Y _max 、Z _max And a minimum value X _min 、Y _min 、Z _min The range of the point cloud data on each coordinate axis is determined, and a foundation is provided for subsequent space grid division;

SS432 find the side length L of the minimum bounding box of the point cloud according to the maximum and minimum values on three coordinate axes of X, Y, Z _x 、L _y 、L _z The minimum bounding box is the minimum cubic space defined around the point cloud data, defining the overall spatial range of the point cloud data:

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SS433. Set up voxel small grid side length cell, equally divide X, Y, Z three coordinate axes into M, N, L, then the minimum bounding box is divided into m×n×l voxel small grids, each representing a small region in the point cloud data:

SS434 numbering small grids for each voxeli,j,k) The voxel small grid to which each data point belongs is determined through numbering:

SS435, calculating the gravity center of each voxel small grid on the basis of the voxel grid, replacing all points in the voxel small grid with the gravity center, and simplifying the point cloud;

wherein C is _ijk 、P _i K represents the center of gravity, data point and number of points, respectively, of the voxel small grid.

It should be noted that if a centroid does not exist, all points within the voxel small grid are replaced with data points within the voxel small grid that are closest to the calculated centroid.

In a further preferred embodiment of the present invention, the above substep SS44 specifically comprises the following steps:

firstly, three coordinate systems are established, namely a system coordinate systemSSensor coordinate systemTHole coordinate systemPWherein the system coordinate systemSIs a coordinate system fixed on a measuring system, and a sensor coordinate systemTIs a coordinate system fixed on an on-line laser scanning sensor and a hole coordinate system PThe coordinate system is fixed on the measured rivet hole, and the relative position and direction relation among the three coordinate systems are described through a conversion matrix;

In a further preferred embodiment of the present invention, the above substep SS45 specifically comprises the following steps: firstly, determining one or more reference planes in three-dimensional point cloud data based on the geometric features of an aircraft curved surface skin or the positioning of rivet holes, and taking the reference planes as the references of point cloud slices; secondly, dividing the three-dimensional point cloud along the direction perpendicular to the reference plane by taking the reference plane as a reference to form a series of two-dimensional point cloud layers, wherein the point cloud data contained in each two-dimensional point cloud layer represents a section with a specific depth in an original three-dimensional space; and then, carrying out noise reduction and/or feature enhancement image processing operation on each two-dimensional point cloud layer so as to improve the usability of data and the accuracy of analysis.

In a further preferred embodiment of the present invention, the above substep SS46 specifically comprises the following steps: firstly, a data processing unit constructs a local point set of each point by searching adjacent points in a set radius aiming at each point or a selected key point set in point cloud data; secondly, for each point and a local point set thereof, three eigenvalues and corresponding eigenvectors are obtained by calculating covariance matrixes and performing singular value decomposition; then, selecting a feature vector with the minimum feature value as a normal vector of the local point set, wherein the normal vector is perpendicular to a best fit plane where the local point set is located; then, the normal vector direction is adjusted according to the viewpoint position, so that the connecting line included angle between the normal vector direction and the viewpoint is smaller than 90 degrees; and finally, repeating the steps for all points or selected key point sets in the point cloud data to obtain a group of normal vectors which are used as normal estimation results of the point cloud data.

In a further preferred embodiment of the present invention, the above substep SS47 specifically comprises the following steps: firstly, for each tested rivet hole, the data processing unit identifies and extracts the outline of the rivet hole through a boundary analysis technology, wherein the outline comprises key points representing the edges of the rivet hole in the identification point cloud data, and the geometric outline of the rivet hole is constructed according to the key points; then, analyzing symmetry and linear characteristics of the rivet hole by utilizing a dotted line characteristic extraction technology, revealing structural details of the rivet hole to be tested by analyzing a linear mode in a point cloud, determining center, diameter and roundness parameters of the rivet hole by utilizing a circular characteristic extraction technology for the circular or approximately circular rivet hole, and analyzing depth and curved surface characteristics of the rivet hole to be tested by combining previous normal estimation data, wherein the method comprises the steps of estimating depth profile and internal surface structure of the rivet hole; and finally, integrating all the extracted characteristic data to form comprehensive technical parameter analysis of the tested rivet hole.

The object of the present invention is fully effectively achieved by the above-described embodiments. Those skilled in the art will appreciate that the present invention includes, but is not limited to, those illustrated in the drawings and described in the foregoing detailed description. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims

1. The utility model provides a portable aircraft curved surface covering rivet hole profile measurement system, includes a portable measuring device at least, portable measuring device includes a shell and a fixed setting on the shell and wholly is located the support of shell below, the bottom of support sets up on the aircraft curved surface covering that awaits measuring, its characterized in that: at least one line laser scanning sensor, a motion control unit, a data acquisition unit and a data processing unit are arranged in the shell, wherein:

the linear module at least comprises a linear guide rail and a sliding block movable end, wherein the linear guide rail is fixedly arranged in the shell, the sliding block movable end is arranged on the linear guide rail in a linearly movable mode, and the line laser scanning sensor is arranged on the sliding block movable end in a fixedly connected mode so as to realize linear movement and position positioning of the line laser scanning sensor;

the input end of the motor encoder is connected with the servo motor in a communication way and is used for detecting the rotating speed and the rotating angle of the servo motor and transmitting the rotating speed and the rotating angle data to the data acquisition unit positioned at the downstream of the servo motor so as to perform data synchronization and coordinate transformation;

2. The portable aircraft curved skin rivet hole profile measurement system according to claim 1, wherein a data storage unit is further disposed in the housing of the portable measurement device, and an input end of the portable measurement device is communicatively connected to the output ends of the data acquisition unit and the data processing unit, and at least stores scan data of the line laser scanning sensor and measurement results obtained after processing by the data processing unit.

3. The portable aircraft curved skin rivet hole profile measurement system according to claim 1, wherein the portable measurement device is integrally provided with a three-point support structure, and the bottom of the portable measurement device is arranged on the aircraft curved skin to be measured so as to adapt to the curved curvature of the skin at different positions.

4. The portable aircraft skin rivet hole profile measurement system of claim 1, further comprising a human-machine interaction unit and a vision sensor disposed within the housing of the portable measurement device, wherein:

5. The portable aircraft curved skin rivet hole profile measurement system according to claim 4, further comprising an inclination sensor arranged in the housing of the portable measurement device, wherein the inclination sensor is used for detecting an included angle between the line laser scanning sensor and a rivet hole to be measured, an output end of the inclination sensor is in communication connection with an input end of the data acquisition unit, and then the inclination data acquisition is transmitted to the data processing unit, a corresponding inclination correction module is arranged in the data processing unit, and the inclination correction module dynamically establishes a correction conversion matrix based on the inclination data, corrects original scanning data of the line laser scanning sensor to eliminate data deformation in two mutually orthogonal directions of a scanning path, compensates data distortion caused by angle deviation, and ensures accuracy and consistency of the scanning data.

6. The portable aircraft curved skin rivet hole profile measurement system according to claim 5, wherein the data processing unit performs data fusion processing on each item of data transmitted and fed back by the data acquisition unit in the following manner, specifically:

7. The portable aircraft curved skin rivet hole profile measurement system according to claim 6, wherein the data processing unit performs key point analysis and point cloud segmentation processing according to the following manner, specifically:

8. The portable aircraft curved surface skin rivet hole profile measurement system according to claim 6, wherein the data processing unit performs dimension reduction processing on the point cloud data by adopting a voxel grid technology, divides a space into voxels with uniform size, equally divides the space into M, N, L parts in three mutually orthogonal X, Y, Z coordinate axis directions according to a set voxel grid side length, wherein M, N, L is a positive integer greater than zero, and takes an average or representative point in each voxel grid to replace all points in the voxel grid so as to simplify the point cloud data, and numbers each voxel grid, thereby reducing the scale of the point cloud data and improving the calculation speed.

9. The portable aircraft curved skin rivet hole profile measurement system according to claim 8, wherein the data processing unit performs dimension reduction processing on point cloud data according to the following voxel grid technology, and reduces data volume and improves calculation efficiency while ensuring that key geometric information of the data is not lost, specifically:

firstly, the data processing unit calculates the maximum values of X, Y, Z on three coordinate axes according to the point cloud data coordinate setX _max 、Y _max 、Z _max And minimum valueX _min 、Y _min 、Z _min The range of the point cloud data on each coordinate axis is determined, and a foundation is provided for subsequent space grid division;

secondly, calculating the side length of the minimum bounding box of the point cloud according to the maximum value and the minimum value of the point cloud data on three coordinate axes X, Y, ZL _x 、L _y 、L _z The minimum bounding box is the minimum cubic space defined around the point cloud data, and is used forIn defining the overall spatial range of point cloud data:

then numbering each small voxel grid and marking as% i,j,k) The voxel small grid to which each data point in the point cloud data belongs is determined through numbering:

10. The portable aircraft curved skin rivet hole profile measurement system according to claim 6, wherein the data processing unit performs coordinate transformation to correct scan data, eliminating scan distortion due to possible tilt angles between the laser scan sensor and the rivet hole under test, in particular:

11. The portable aircraft curved skin rivet hole profile measurement system according to claim 6, wherein the data processing unit performs point cloud slicing and two-dimensional point cloud array construction in the following manner, and divides the three-dimensional point cloud into the two-dimensional point cloud array to improve the analysis speed, specifically:

12. The portable aircraft curved skin rivet hole profile measurement system of claim 6, wherein the data processing unit performs normal estimation in the following manner:

13. The portable aircraft curved skin rivet hole profile measurement system according to claim 12, wherein the data processing unit performs feature extraction in a manner that utilizes boundary analysis, dotted line and circle feature extraction techniques to analyze various technical parameters of the measured rivet hole, specifically:

14. A portable aircraft curved skin rivet hole profile measurement method, using the portable aircraft curved skin rivet hole profile measurement system of claim 5, characterized in that the method comprises at least the following steps when implemented:

and SS5. Outputting the measurement result and storing the measurement result.

15. The method for measuring the profile of a rivet hole in a curved skin of an aircraft according to claim 14, wherein in the step SS4, the processing operation specifically includes:

16. The method for measuring the profile of the rivet hole of the curved skin of the portable airplane according to claim 15, wherein in the SS41, data fusion processing is performed on each item of data transmitted and fed back by the data acquisition unit according to the following manner, specifically:

17. The method for measuring the profile of the rivet hole of the curved skin of the portable airplane according to claim 15, wherein in the SS42, the key point analysis and the point cloud segmentation are performed as follows:

18. The method for measuring the profile of the rivet hole of the curved skin of the portable airplane according to claim 15, wherein in the SS43, the dimension reduction processing is performed on the point cloud data according to the following manner:

SS431 calculating X, Y, Z three data according to the coordinate set of the data point cloud dataMaximum value on coordinate axisX _max 、Y _max 、Z _max And minimum valueX _min 、Y _min 、Z _min The range of the point cloud data on each coordinate axis is determined, and a foundation is provided for subsequent space grid division;

SS434 numbering and marking each voxel small grid as @i,j,k) The voxel small grid to which each data point in the point cloud data belongs is determined through numbering:

19. The method for measuring the profile of the rivet hole of the curved surface skin of the portable airplane according to claim 15, wherein in the SS44, coordinate transformation is performed to correct scan data and eliminate scan deformation caused by possible inclination angles between the laser scan sensor and the rivet hole to be measured, specifically:

20. The method for measuring the profile of the rivet hole of the curved surface skin of the portable airplane according to claim 15, wherein in the SS45, the point cloud slicing and the two-dimensional point cloud array construction are performed in the following manner, and the three-dimensional point cloud is divided into the two-dimensional point cloud array to improve the analysis speed, specifically:

21. The method for measuring the profile of a rivet hole in a curved skin of a portable aircraft according to claim 15, wherein the SS46 performs normal estimation by:

22. The method for measuring the profile of the rivet hole of the curved surface skin of the portable airplane according to claim 15, wherein the SS47 performs feature extraction in the following manner, and uses boundary analysis, dotted line and circle feature extraction technology to analyze various technical parameters of the rivet hole to be measured, specifically: