Helicopter equipment fastener maintenance space evaluation method based on three-dimensional projection

Abstract

The invention provides a fastener maintenance space evaluation method based on three-dimensional projection, and the method comprises the steps: 1, constructing a three-dimensional projection surface of each part of a helicopter based on a helicopter three-dimensional mathematical model; step 2, based on an image edge feature extraction algorithm, extracting edge position information of airborne equipment fasteners and adjacent parts on each three-dimensional projection plane; 3, calculating the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent part based on the edge position information of the airborne equipment fastener and the adjacent part on each three-dimensional projection plane; 4, based on the type of the airborne equipment fastener, the three-dimensional projection plane of the helicopter component and the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component, constructing a maintenance space evaluation correlation matrix of the airborne equipment fastener and the adjacent component; and 5, obtaining an airborne equipment fastener maintenance space evaluation conclusion based on the airborne equipment fastener and adjacent part maintenance space evaluation correlation matrix.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of maintainability analysis and evaluation of general quality characteristics of helicopters, and particularly relates to a helicopter equipment fastener maintenance space evaluation method based on three-dimensional projection. BACKGROUND

[0002] Modern helicopters usually have the ability to perform different tasks in different climates and different geographical conditions, and are often equipped with a large number of on-board task devices with complex architecture and advanced performance. Limited by the structural characteristics of the helicopter, the effective installation space left for the on-board device is very limited. Therefore, when the on-board device is arranged, not only the maintenance space of the fastener of the on-board device needs to be considered, but also the space utilization efficiency needs to be considered.

[0003] How to effectively evaluate the maintenance space of the fastener of the on-board device so that the layout of the on-board device meets the disassembly and assembly requirements of the fastener and maximizes the saving of the limited space on the helicopter is an important issue in the maintainability design of the helicopter.

[0004] At present, the evaluation method of the maintenance space of the helicopter device is to use a digital mockup, and evaluation personnel rely on personal experience to analyze and give evaluation conclusions. Since there are many on-board devices on the helicopter and the layout on the helicopter is complex, the analysis coverage of the fastener maintenance space is poor, the analysis time is long, and the accuracy is poor, which leads to the fact that the evaluation conclusions of the fastener maintenance space of some on-board devices are inconsistent with the actual situation, seriously affecting the work efficiency of the field maintenance, and increasing the difficulty of the maintenance work. SUMMARY

[0005] The purpose of the application is to solve the problems of poor analysis coverage, long analysis time and poor accuracy of the existing maintenance space evaluation method, and to provide a helicopter on-board equipment fastener maintenance space evaluation method based on three-dimensional projection. Based on the equipment digital mockup, at the initial stage of development, based on the fastener maintenance space and the three-dimensional projection correlation model, and the LRU maintenance space three-dimensional projection evaluation matrix, the LRU fastener maintenance space is evaluated.

[0006] The application provides a fastener maintenance space evaluation method based on three-dimensional projection, which comprises the following steps: Step 1: based on the three-dimensional digital mockup of the helicopter, a three-dimensional projection surface of each component of the helicopter is constructed; Step 2: based on an image edge feature extraction algorithm, edge position information of the fastener of the on-board device and adjacent components in each three-dimensional projection surface is extracted; Step 3: based on the edge position information of the fastener of the on-board device and adjacent components in each three-dimensional projection surface, the minimum distance from the edge of the fastener of the on-board device to the edge of the adjacent component is calculated; Step 4: constructing a correlation matrix between the airborne equipment fastener and the adjacent component maintenance space evaluation based on the type of the airborne equipment fastener, the three-dimensional projection plane of the helicopter component, and the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component; Step 5: obtaining a conclusion of the airborne equipment fastener maintenance space evaluation based on the correlation matrix between the airborne equipment fastener and the adjacent component maintenance space evaluation.

[0007] Preferably, the three-dimensional projection plane of the helicopter component includes a top view projection plane, a front view projection plane, and a side view projection plane.

[0008] Preferably, the three-dimensional projection plane of the helicopter component has projection information of each component of the helicopter, which is characterized by an information matrix, i.e., Q n = [ O n , F n , S n ]……………………………………(1) In the formula, Q n represents the projection information of the nth component of the helicopter, n = 1, 2, 3, … n N , N is the maximum number of components of the helicopter; O n represents the projection information of the three-dimensional numerical model of the component n in the top view projection plane; F n represents the projection information of the three-dimensional numerical model of the component n in the front view projection plane; S n represents the projection information of the three-dimensional numerical model of the component n in the side view projection plane.

[0009] Preferably, the adjacent component refers to the six components closest to the airborne equipment fastener in the left, right, top, bottom, front, and rear directions.

[0010] Preferably, the step 3 includes: calculating the shortest image distance D Omin between the airborne equipment fastener and the adjacent component in the top view projection plane based on the edge position information of the airborne equipment fastener and the adjacent component in each three-dimensional projection plane; determining the top three-dimensional projection coefficient λ O of the helicopter component; ​Based on the oblique three-dimensional projection coefficient λ of the helicopter component O and the shortest image distance D Omin , the shortest physical distance λ of the fastener in the oblique projection plane from the adjacent component is obtained O D Omin .

[0011] Preferably, the step 3 comprises: Based on the edge position information of the fastener and the adjacent component of the airborne equipment in each three-dimensional projection plane, the shortest image distance D of the fastener in the front projection plane from the adjacent component is calculated Fmin ; The front three-dimensional projection coefficient λ of the helicopter component is determined F ; Based on the front three-dimensional projection coefficient λ of the helicopter component F and the shortest image distance D Fmin , the shortest physical distance λ of the fastener in the front projection plane from the adjacent component is determined F D Fmin .

[0012] Preferably, the step 3 comprises: Based on the edge position information of the fastener and the adjacent component of the airborne equipment in each three-dimensional projection plane, the shortest image distance D of the fastener in the side projection plane from the adjacent component is calculated Smin ; The side three-dimensional projection coefficient λ of the helicopter component is determined S ; Based on the side three-dimensional projection coefficient λ of the helicopter component S and the shortest image distance D Smin , the shortest physical distance λ of the fastener in the side projection plane from the adjacent component is determined S D Smin .

[0013] Preferably, the step 4 comprises: Based on the shortest physical distance and the reference value, the correlation factor is determined d ij ; wherein the reference value is a value determined based on the type of the fastener of the airborne equipment; Based on the correlation factor d ij , the correlation matrix of the maintenance space evaluation of the fastener and the adjacent component of the airborne equipment is constructed.

[0014] Preferably, the step 5 comprises: Based on the correlation factor in the correlation matrix of the maintenance space evaluation of the fastener and the adjacent component of the airborne equipment, the space coefficient is calculated; Based on the spatial coefficient, a maintenance evaluation conclusion of the airborne equipment fastener is obtained.

[0015] The present application has the following technical effects: The maintenance space evaluation method based on three-dimensional projection of the present application, by constructing three-dimensional projection information of the helicopter components, obtaining edge position information of the projection image based on image edge feature extraction algorithm, then establishing a correlation model of fastener and adjacent component maintenance space evaluation, obtaining the maintenance space evaluation conclusion of the airborne equipment fastener. Through traversal, full coverage of the maintenance space evaluation of all components fasteners of the helicopter can be realized, the evaluation time is greatly shortened, and the maintenance space evaluation accuracy is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A flow chart of the helicopter airborne equipment fastener maintenance space evaluation method based on three-dimensional projection provided by the embodiment of the present application. DETAILED DESCRIPTION The present application proposes a helicopter airborne equipment fastener maintenance space evaluation method based on three-dimensional projection, aiming at the problems of poor analysis coverage, long analysis time and poor accuracy of the existing maintenance space evaluation method. Based on the equipment digital mockup, at the initial development stage, based on the correlation model of fastener maintenance space and three-dimensional projection, and the LRU maintenance space three-dimensional projection evaluation matrix, the LRU fastener maintenance space evaluation is realized.

[0017] The fastener maintenance space evaluation method based on three-dimensional projection provided by the present application, the method comprises: Step 1: based on the three-dimensional model of the helicopter, constructing the three-dimensional projection plane of each component of the helicopter; Step 2: based on the image edge feature extraction algorithm, extracting the edge position information of the airborne equipment fastener and the adjacent components in each three-dimensional projection plane; Step 3: based on the edge position information of the airborne equipment fastener and the adjacent components in each three-dimensional projection plane, calculating the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component; Step 4: based on the type of the airborne equipment fastener, the three-dimensional projection plane of the helicopter component and the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component, constructing a correlation matrix of the maintenance space evaluation of the airborne equipment fastener and the adjacent component; Step 5: based on the correlation matrix of the maintenance space evaluation of the airborne equipment fastener and the adjacent component, obtaining the maintenance space evaluation conclusion of the airborne equipment fastener.

[0018] The step 1 comprises: Further, the three-dimensional projection plane of the helicopter component can be divided into: a top view projection plane, a front view projection plane and a side view projection plane.

[0019] Clearly, the spatial information of each component of the helicopter can be represented by an information matrix. That is: Q n = [ O n , F n , S n ]………………………………(1) In the formula, Q n The number of helicopters n Spatial information of each component (structural part, airborne equipment, or fastener) (n=1,2,3,… N ), N This represents the maximum number of helicopter components. O n Indicates components n The projection information of the three-dimensional digital model on the top-view projection plane; F n Indicates components n The projection information of the three-dimensional digital model onto the frontal projection plane; S n Indicates components n The projection information of the three-dimensional digital model on the side-view projection plane.

[0020] Furthermore, the projection information of the component includes: the center coordinates of the image, edge features, etc.

[0021] Preferably, step 2 includes: Furthermore, adjacent components of airborne equipment refer to the six components that are closest to the airborne equipment in six directions: left, right, above, below, front, and rear.

[0022] Furthermore, the Canny operator is used for airborne equipment fasteners. n Images of the component and its adjacent parts in a three-dimensional projection plane O n , F n , S n Process them to extract their binary edge images E On , E Fn , E Sn .

[0023] Furthermore, the Canny operator mainly includes four steps: Gaussian filtering, gradient calculation, nonmaximum suppression, double thresholding, and hysteresis connection.

[0024] Further, the airborne equipment fastener n is projected onto the image plane O n The pixel value at pixel coordinate x , y ) is I ( x , y ), and the value after Gaussian filtering of I ( x , y ) is I smooth ( x , y ), and the filtered image is I n Then we have: ……………………………………(2) In equation (2), k is the kernel radius, and 5x5 kernel is selected here; G ( i , j ) is a two-dimensional Gaussian function, and we have: ……………………….(3) In equation (3), is the standard deviation of the Gaussian function, which is used to control the smoothing strength.

[0025] Further, the Sobel operator is used to calculate the gradient amplitude I n The gradient amplitude x ( y , M ) and direction θ x ( y , x ) at pixel coordinate y , then we have: , …………(4) ……………………(5) ……………(6) , …………………(7) To simplify the calculation, the gradient direction θ is usually quantized to 0°, 45°, 90°, and 135° four main directions.

[0026] Further, to ensure that the image In The edge width is single pixel, non-maximum suppression is taken, and the edge is refined by keeping the local maximum in the gradient direction. For the image I n At the pixel point at coordinate x , y , let the gradient amplitude of the adjacent pixel in the gradient direction θ x , y be d tmp1 and d tmp2 (through linear interpolation): if M ( x , y ) ≥ max( d tmp1 , d tmp2 ), then I smooth ( x , y ) is unchanged, otherwise it is suppressed to 0, i.e. I smooth ( x , y ) = 0, and the edge image I n of the image is finally obtained.

[0027] Further, the image is subjected to double-threshold processing and lag connection, a high threshold T high and a low threshold T low are set, and the pixel value of the image is classified: if M ( x , y ) ≥ T high , it is a strong edge; if T high > M ( x , y ) ≥ T low , it is a weak edge; if M ( x , y ) < 0 T low , it is a non-edge. The high threshold T high is generally obtained adaptively according to the Otsu method, and the low threshold T low = 0.5 Thigh .

[0028] Furthermore, Convert to binary edge image E On , E On In pixel coordinates ( x , y The pixel value at ) E ( x , y If an image edge pixel is characterized as a strong edge or a connected weak edge (a connected weak edge is one that is connected to a strong edge through an 8-neighborhood check), then let... E ( x , y )=255; otherwise, let E ( x , y)= 0.

[0029] Obviously, the above steps can be used to calculate the fasteners of airborne equipment. Q n Top-view projection image of the component and its adjacent parts O n 、 Viewing the projection surface F n Side view projection surface S n of Binary edge image E On , E Fn , E Sn 。

[0030] Preferably, step 3 includes: Furthermore, through traversal, the computer-mounted device fasteners Q n Binary edge image in the top-view projection plane E On Binary edge image of adjacent components in the top-view projection plane E Oleft , E Oright , E Ofront , E Oback Distance D O Then the minimum value D Omin Fasteners Q n The shortest image distance to adjacent components in the top-view projection plane, λO D Omin Fasteners Q n The shortest physical distance to adjacent components in the top-view projection plane, λ O λ is the top-view three-dimensional projection coefficient of the helicopter component. O ∈[0,1].

[0031] Furthermore, through traversal, the computer-mounted device fasteners Q n Binary edge image in the frontal projection plane E Fn Binary edge image of adjacent components in the frontal projection plane E Fup , E Fdown , E Fleft , E Fright Distance D F Then the minimum value D Fmin Fasteners Q n The shortest image distance to adjacent components in the frontal projection plane, λ F D Fmin Fasteners Q n The shortest physical distance to adjacent components in the frontal projection plane, λ F λ is the orthographic 3D projection coefficient of the helicopter component. F ∈[0,1].

[0032] Furthermore, through traversal, the computer-mounted device fasteners Q n Binary edge image in the side-view projection plane E Sn Binary edge image of adjacent components in the side view projection plane E Sup , E Sdown , E Sfront , E Sback Distance D S Then the minimum value D Smin Fasteners Q n The shortest image distance to adjacent components in the side-view projection plane, λ S D Smin Fasteners Q n The shortest physical distance to adjacent components in the side-view projection plane, λ Sλ is the side view three-dimensional projection coefficient of the helicopter component S ∈[0,1].

[0033] The projection coefficient λ is the cosine value of the included angle between the projection direction of the helicopter and the surface normal vector of the component. When the included angle is 0 degrees, λ takes 1, and when the included angle is 90 degrees, λ takes 0.

[0034] Preferably, the step 4 comprises: Further, the helicopter component fastener types are divided into the following 3 categories: category I, hexagonal type fastener; category II, internal hexagonal type fastener; category III, cross and straight type fastener.

[0035] Further, the maintenance space evaluation correlation matrix of the on-board equipment fastener and the adjacent component in the three-dimensional projection plane is constructed.

[0036] To represent the spatial relationship between the on-board equipment fastener and the adjacent component, the physical distance of the fastener and the adjacent component in the top view projection plane, the front view projection plane, and the side view projection plane can be used to represent. Therefore, for the target on-board equipment fastener Q n The maintenance space evaluation is constructed by constructing the component fastener Q n The shortest physical distance of the adjacent component in the three-dimensional projection plane PT Q That is: …………………………………………(6) In the formula: correlation factor d ij is a Boolean quantity ( i =1,2,3; j =1,2,3); P 1 is the I type fastener, P 2 is the II type fastener, P 3 is the III type fastener; T O is the top view projection, T D front top view projection, T S is the side view projection.

[0037] Further, for the I type fastener, when λ O D Omin ≥2A, d 11 =1, otherwise, d 11 =0, where A is the bolt head width; when λ F D Fmin >55mm, d12 = 1, otherwise, d 12 = 0; when λ S D Smin > 70mm, d 13 = 1, otherwise, d 13 = 0. The reference values 2A, 55mm, 70mm are determined by considering the tool operation space, hand accessibility and other factors of the Class I fastener.

[0038] Further, for the Class II fastener, d 21 = 0; when λ F D Fmin > 55mm, d 22 = 1, otherwise, d 22 = 0; when λ S D Smin > 70mm, d 23 = 1, otherwise, d 23 = 0. The reference values 55mm, 70mm are determined by considering the tool operation space, hand accessibility and other factors of the Class II fastener.

[0039] Further, for the Class III fastener, d 31 = 0, d 33 = 0; when λ F D Fmin > 300mm, d 32 = 1, otherwise, d 32 = 0. The reference value 300mm is determined by considering the tool operation space, hand accessibility and other factors of the Class III fastener.

[0040] Preferably, the step 5 comprises: Further, by calculating the space coefficient of each class of fastener, the maintainability evaluation conclusion of the fastener of the airborne equipment is given.

[0041] Further, for the Class I fastener, the space coefficient α I is the sum of the three-dimensional space related factors, i.e. α I = d 11 + d 12 + d 13When α I The fastener maintenance space is evaluated as qualified when n = 3, otherwise unqualified.

[0042] Further, for the fastener of type II, the space coefficient is α II is the sum of the three-dimensional space correlation factors, i.e. α II = d 21 + d 22 + d 23 When n = 2, the fastener maintenance space is evaluated as qualified, otherwise unqualified. α II

[0043] Further, for the fastener of type III, the space coefficient is α III is the sum of the three-dimensional space correlation factors, i.e. α III = d 31 + d 32 + d 33 When n = 1, the fastener maintenance space is evaluated as qualified, otherwise unqualified. α III

[0044] Further, when all the fasteners of the airborne equipment are evaluated as qualified, it indicates that the maintenance space of the target fastener meets the requirements, otherwise, the maintenance space requirements are not met, and the design needs to be changed.

[0045] The present application is based on the maintenance space evaluation method of three-dimensional projection, the three-dimensional projection information of the helicopter component is constructed, the edge position information of the projection image is obtained based on the image edge feature extraction algorithm, then the correlation model of the fastener and the adjacent component maintenance space evaluation is established, and the maintenance space evaluation conclusion of the fastener of the airborne equipment is obtained. Through traversal, the full coverage of the fastener maintenance space evaluation of all components of the helicopter can be realized, the evaluation time is greatly shortened, and the maintenance space evaluation precision is improved.​​

Claims

1. A method for evaluating fastener repair space based on three-dimensional projection, characterized in that, The method includes: Step 1: Based on the helicopter's 3D digital model, construct the 3D projection surfaces of each component of the helicopter; Step 2: Based on the image edge feature extraction algorithm, extract the edge position information of the airborne equipment fasteners and adjacent components on each three-dimensional projection plane; Step 3: Based on the edge position information of the airborne equipment fastener and adjacent components on each three-dimensional projection plane, calculate the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component; Step 4: Based on the type of the airborne equipment fastener, the three-dimensional projection surface of the helicopter component, and the minimum distance from the edge of the airborne equipment fastener to the edge of the adjacent component, construct a correlation matrix for the maintenance space evaluation of the airborne equipment fastener and the adjacent component; Step 5: Based on the correlation matrix of the maintenance space evaluation of the airborne equipment fasteners and adjacent components, the maintenance space evaluation conclusion of the airborne equipment fasteners is obtained.

2. The method according to claim 1, characterized in that, The three-dimensional projection surfaces of the helicopter components include a top-view projection surface, a front-view projection surface, and a side-view projection surface.

3. The method according to claim 2, characterized in that, The three-dimensional projection surface of the helicopter components displays projection information for each component, which is represented by an information matrix. Q n = [ O n , F n , S n ]……………………………………(1) In the formula, Q n The number of helicopters n Projection information of each component, n=1,2,3,… N , N This represents the maximum number of helicopter components. O n Indicates components n The projection information of the three-dimensional digital model on the top-view projection plane; F n Indicates components n The projection information of the three-dimensional digital model onto the frontal projection plane; S n Indicates components n The projection information of the three-dimensional digital model on the side-view projection plane.

4. The method according to claim 3, characterized in that, The adjacent components refer to the six components that are closest to the fasteners of the airborne equipment in six directions: left, right, above, below, front, and rear.

5. The method according to claim 4, characterized in that, Step 3 includes: Based on the edge position information of the airborne equipment fasteners and adjacent components on each three-dimensional projection plane, the shortest image distance D between the airborne equipment fasteners and adjacent components in the top-view projection plane is calculated. Omin ; Determine the top-view three-dimensional projection coefficient λ of helicopter components O ; Based on the top-view three-dimensional projection coefficient λ of the helicopter component O and the shortest image distance D Omin The shortest physical distance λ between the fastener and adjacent components in the top-view projection plane is obtained. O D Omin .

6. The method according to claim 5, characterized in that, Step 3 includes: Based on the edge position information of the fasteners and adjacent components of the airborne equipment on each three-dimensional projection plane, the shortest image distance D between the fastener and the adjacent component in the frontal projection plane is calculated. Fmin ; Determine the frontal three-dimensional projection coefficient λ of the helicopter component F ; Based on the orthographic three-dimensional projection coefficient λ of the helicopter component F and the shortest image distance D Fmin The shortest physical distance λ between the fastener and adjacent components in the frontal projection plane is obtained. F D Fmin .

7. The method according to claim 6, characterized in that, Step 3 includes: Based on the edge position information of the fasteners and adjacent components of the airborne equipment on each three-dimensional projection plane, the shortest image distance D between the fastener and the adjacent component in the side view projection plane is calculated. Smin ; Determine the side-view three-dimensional projection coefficient λ of the helicopter component S ; Based on the side-view three-dimensional projection coefficient λ of the helicopter component S and the shortest image distance D Smin Determine the shortest physical distance λ between the fastener and adjacent components in the side view projection plane. S D Smin .

8. The method according to claim 7, characterized in that, Step 4 includes: Based on the shortest physical distance and the reference value, determine the relevant factors. d ij The reference value is determined based on the type of fastener used in the airborne equipment. Based on the aforementioned relevant factors d ij A correlation matrix was constructed to evaluate the maintenance space of airborne equipment fasteners and adjacent components.

9. The method according to claim 8, characterized in that, Step 5 includes: Based on the correlation factors in the correlation matrix of the maintenance space evaluation of the airborne equipment fasteners and adjacent components, the space coefficient is calculated; Based on the aforementioned spatial coefficient, the maintainability assessment conclusions for the airborne equipment fasteners are obtained.

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