A pose planning method for scanning measurement of surface geometric accuracy of helicopter assembly components

Abstract

The present invention relates to a method for planning the position and posture of a scanner for the surface geometric accuracy of a helicopter assembly component, and relates to the field of laser scanning. The method comprises: decomposing a large-scale geometric feature surface in the helicopter assembly component into a plurality of small straight free-form surface features; meshing each small straight free-form surface feature and decomposing it into a plurality of sub-surfaces; determining a projection lattice; determining the minimum circumscribed rectangle of the projection lattice and performing expansion and segmentation; determining the scanner position origin and the corresponding first principal optical axis vector; determining the first position coordinates and second principal optical axis vector of the scanning position D in a workpiece coordinate system for concave features of small features in the helicopter assembly component; and determining the second position coordinates and third principal optical axis vector of the scanning position D in the workpiece coordinate system for convex features of small features in the helicopter assembly component. The above method of the present invention greatly improves the efficiency and automation of scanning inspection planning for helicopter assembly components.

Description

Technical Field

[0001] The invention relates to the field of laser scanning, and in particular to a posture planning method for scanning and measuring the surface geometric accuracy of a helicopter assembly component. Background Art

[0002] Helicopter assembly components are large in size and often consist of large surfaces (including complex combinations of curved and flat surfaces) and small features such as holes, slots, and ribs attached to these surfaces. Using laser scanners to measure these components is a highly effective method for geometric accuracy testing. However, to achieve efficient and standardized testing, it is necessary to plan and calculate a reasonable scanning pose for the laser scanner, allowing it to be held in the appropriate position and pose by a robot or tooling during the actual scanning process.

[0003] Existing scanning is usually done by hand-held or machine-held scanners, which perform multiple reciprocating carpet-style scans without reasonable planning. Although the scanning task can be completed, the efficiency is low, and some local features are sometimes not scanned in place, making the quality of the scanned point cloud uncontrollable.

[0004] Against this background, the present invention proposes a method for scanning measurement of the geometric accuracy of helicopter assembly components, which provides a high-efficiency and highly automated solution for scanning detection planning of helicopter assembly components. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for scanning measurement posture planning of the surface geometric accuracy of helicopter assembly components, which automatically calculates the scanning viewpoint and posture, provides posture drive for the scanning detection process of the laser scanner, and effectively improves the detection efficiency and the degree of automation of scanning measurement posture planning.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A method for planning the position and posture of a surface geometric accuracy scanner for a helicopter assembly component, the planning method comprising:

[0008] Decompose the large geometric features of the helicopter assembly into multiple small straight free-form surface features;

[0009] Mesh each small straight free-form surface feature and decompose it into multiple sub-surfaces;

[0010] Determining a projection lattice based on the multiple sub-surfaces;

[0011] Determining the minimum circumscribed rectangle of the projected point array;

[0012] Expanding and dividing the minimum circumscribed rectangle;

[0013] Determine the scanner position origin and the corresponding first principal optical axis vector based on the expanded and segmented minimum circumscribed rectangle;

[0014] Aiming at the concave features of small features in helicopter assembly components, the scanner laser scanning surface is abstracted into triangles;

[0015] Cover the bottom of the sunken feature in the concave feature with the laser beam, and pass the main optical axis through the center point of the upper surface of the sunken feature;

[0016] Obtaining basic position information of the concave feature;

[0017] Determine a first position coordinate and a second principal optical axis vector of a scanning posture D in a workpiece coordinate system based on basic position information of the concave feature;

[0018] For a convex feature of a small feature in a helicopter assembly component, a point on the starting end surface of the convex feature is determined and recorded as the first coordinate point;

[0019] Determine a point on the end surface of the convex feature, and record it as the second coordinate point;

[0020] Acquire basic position information of the convex feature based on the first coordinate point and the second coordinate point;

[0021] The second position coordinates and the third principal optical axis vector of the scanning posture D in the workpiece coordinate system are determined based on the basic position information of the convex feature.

[0022] Optionally, decomposing a large geometric feature surface in a helicopter assembly component into a plurality of small straight free-form surface features specifically comprises the following steps:

[0023] Performing dot matrix formation on the large-scale geometric feature surface;

[0024] Determine the UV step size;

[0025] The large profile geometric feature surface is decomposed into a plurality of small straight free-form surface features using the UV step size as a grouping condition.

[0026] Optionally, determining the projection point array based on the multiple sub-surfaces specifically includes the following steps:

[0027] Assume that there are n points on the subsurface, and each point A i The coordinates of the points are recorded as (x, y, z, i, j, k);

[0028] A dot matrix is ​​determined based on the n points, and the dot matrix is ​​recorded as A={A1, A2, ..., A n};

[0029] Calculating the center of gravity of the lattice;

[0030] Determining a fitting plane passing through the center of gravity;

[0031] Projecting the point array on the sub-surface perpendicularly to the fitting plane to obtain the coordinates of any projection point;

[0032] Based on the coordinates of the arbitrary projection points, a projection point matrix is ​​determined.

[0033] Optionally, determining the minimum bounding rectangle of the projected point array specifically includes the following steps:

[0034] Create a new temporary coordinate system on the projection plane;

[0035] Calculate the transformation matrix Q;

[0036] Determine the coordinate matrix Q' of the projection point matrix in the temporary coordinate system based on the transformation matrix;

[0037] Get the maximum and minimum xy coordinates in the coordinate matrix Q' min , x max ,y min ,y max ;

[0038] Based on the x min , x max ,y min ,y max Determine the coordinates of the four vertices of the minimum enclosing rectangle;

[0039] Obtain the maximum and minimum values ​​of the xyz coordinates in the coordinate matrix Q';

[0040] Determine the coordinates of four boundary points based on the maximum and minimum values ​​of the xyz coordinates;

[0041] Determine the coordinates of the four boundary points in the original workpiece coordinate system {workCoo} based on the coordinates of the four boundary points;

[0042] A minimum circumscribed rectangle is determined based on the four vertex coordinates and the coordinates of the four boundary points in the original workpiece coordinate system {workCoo}.

[0043] Optionally, expanding and dividing the minimum bounding rectangle specifically includes the following steps:

[0044] Expanding the minimum circumscribed rectangle outward by a preset distance;

[0045] Assume that the length of the long side of the minimum circumscribed rectangle is a, the length of the short side is b, the distance the long side extends outward is h, the distance the short side extends outward is w, and the area is divided with s as the unit distance to obtain the number of long side divisions m, the number of short side divisions n, and mn sub-scanning areas.

[0046] Optionally, determining the scanner position origin and the corresponding first principal optical axis vector based on the expanded and segmented minimum circumscribed rectangle specifically includes the following steps:

[0047] Based on mn sub-scanning areas, with the boundary point as the starting point, the center of the segmented area in the pth row and qth column is defined as C' on the temporary coordinate system. pq ;

[0048] Based on the C' pq Calculate the coordinate C in the original workpiece coordinate system {workCoo} pq ;

[0049] Define the actual reference distance of the scanner as sd;

[0050] Based on the coordinate C pq The actual reference distance is sd to calculate the position coordinates of the scanner position origin and the first principal optical axis vector,

[0051] Optionally, the position coordinates of the scanner origin are expressed as:

[0052]

[0053] in, Indicates the origin coordinates of the scanner position, C pq represents the center of the segmented area under the original workpiece coordinate system {workCoo, sd represents the actual reference distance of the scanner, Indicates the direction of optical axis loss;

[0054] The expression of the first principal optical axis vector is:

[0055]

[0056] in, Represents the coordinates of the first principal optical axis vector.

[0057] Optionally, the basic position information of the concave feature includes the coordinates of the four vertices of the lower surface of the rectangular depression, the coordinates of the center of the rectangle, the depression height, and the normal vector of the bottom surface of the depression toward the outside of the component entity.

[0058] Optionally, the expression of the first position coordinate is:

[0059]

[0060] Among them, D xyz 凹 represents the first position coordinate, A represents the middle point between any two lower surface vertices m and n, sd represents the actual reference distance of the scanner, and C represents the center point of the upper surface of the concave feature. Represents the vector from point A to point C;

[0061] The expression of the second principal optical axis vector is:

[0062]

[0063] Among them, D ijk 凹 represents the second principal optical axis vector, Represents the vector from point C to point A.

[0064] Optionally, the expression of the second position coordinate is as follows:

[0065]

[0066] Among them, D xyz 凸 represents the second position coordinate, B1 represents a point on the starting end surface of the convex feature, B2 represents a point on the ending end surface of the convex feature, sd represents the actual reference distance of the scanner, and θ represents the angle between the scanner and the convex feature. is the unit direction vector from B1 to B2, Indicates that any two points P1 and P2 are selected from the projection point set, and the vector And normalize the resulting vector;

[0067] The expression of the third principal optical axis vector is as follows:

[0068]

[0069] Among them, D ijk 凸 represents the third principal optical axis vector, B1 represents a point on the starting end surface of the convex feature, and D is the scanning posture of the scanner in space. Represents the vector from point B1 to point D.

[0070] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0071] The above method in the present invention can realize automatic scanning pose planning for large surfaces and small features attached to the surfaces, and can effectively solve the problem of scanning and detection planning for the geometric accuracy of the helicopter assembly process. This method only needs to input UV segmentation parameters and import the geometric model of the scanned object to realize automatic calculation of the scanning pose and generate a scanning pose set, which greatly improves the efficiency and automation level of scanning and detection planning of helicopter assembly components. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0073] Figure 1 This is a flow chart of the method for planning the position and posture of a scanner for the surface geometric accuracy of a helicopter assembly component according to the present invention;

[0074] Figure 2 This is a schematic diagram of a large-scale exploded view of a helicopter assembly component of the present invention;

[0075] Figure 3 This is a schematic diagram of the surface meshing of the present invention;

[0076] Figure 4 This is a schematic diagram of the plane and curved surface fitting of the present invention;

[0077] Figure 5 Schematic diagram of the projection dot matrix on the fitting plane of the present invention;

[0078] Figure 6 Schematic diagram of the minimum circumscribed rectangle of the projection dot matrix of the present invention;

[0079] Figure 7 This is a schematic diagram of the expanded segmentation of the present invention;

[0080] Figure 8 This is a schematic diagram of the classification of small features of the present invention;

[0081] Figure 9 This is a schematic diagram of a standard rectangular sunken cross section of the present invention;

[0082] Figure 10 This is a schematic diagram of the laser scanning format of the scanner of the present invention;

[0083] Figure 11 This is a schematic diagram of the standard concave feature scanning plan of the present invention;

[0084] Figure 12 This is a schematic diagram of the rib feature scanning planning of the present invention;

[0085] Figure 13 Schematic diagram of the rib scanning motion sequence of the present invention. DETAILED DESCRIPTION

[0086] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0087] The purpose of the present invention is to provide a method for planning the position and posture of a surface geometric accuracy scanner of a helicopter assembly component.

[0088] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0089] Figure 1 This is a flow chart of the method for planning the geometric accuracy of the scanner position of the helicopter assembly component of the present invention, as shown in FIG. Figure 1 As shown, the planning method of the present invention specifically includes two parts. The first part is aimed at large-scale surface features in helicopter assembly components, and the second part is aimed at common small features such as bosses, holes, seams, ribs, sinks, etc.

[0090] For large surface features in helicopter assembly components:

[0091] Step 1: Decompose the large surface geometric features in the helicopter assembly into multiple small straight free-form surface features.

[0092] The large-scale surface features are read from the 3D model of the helicopter assembly component using the geometric information extraction interface of UG NX. The total UV length of the large-scale surface of the helicopter assembly component is obtained using the surface UV parameter reading interface. Given that the large-scale surface of the helicopter assembly component is too large, it is difficult for the laser scanner to complete the entire scan at one scanning station and multiple station transfers are required. Therefore, the present invention proposes a surface rasterization grouping method to decompose the large surface into multiple small straight free-form surface features.

[0093] The specific process is: after rasterizing the surface, use the UV step size as the grouping condition, input the UV step size, and divide the surface into blocks. Suppose it is divided into n blocks, such as Figure 2 As shown, to determine the attribution information of the entire surface lattice in these block areas, the entire surface lattice can be divided into n groups, which can be expressed as:

[0094] A={{A group1},{A group2},{A group3},…,{A groupn}}.

[0095] Step 2: Mesh each small straight free-form surface feature and decompose it into multiple sub-surfaces.

[0096] After step 1, the large geometric surface features in the helicopter assembly are segmented into multiple small straight free-form surface features. The present invention proposes a surface rectangular region segmentation algorithm for the small straight free-form surface features, thereby solving and calculating the scanning position origin and main optical axis vector of the laser scanner in space, thereby solving the scanning measurement pose planning of the large-scale surface decomposition of the helicopter assembly component. The specific process is as follows:

[0097] Surface lattice

[0098] The same surface rasterization method based on UV step length is used to read the total length of the surface in UV direction, and then take points with equal step lengths in the U and V directions, so as to network the surface and decompose it into multiple sub-surfaces, such as Figure 3 As shown in the figure, current surfaces are all equations with U and V as independent variables, commonly known as parametric surfaces. For a surface with a boundary, both U and V have a maximum and minimum value. The UV step size is determined by dividing U and V into N equal parts from the maximum to the minimum value, thus dividing a surface into many smaller pieces.

[0099] Step 3: Determine a projection point matrix based on the multiple sub-surfaces.

[0100] Step 3 is the lattice fitting projection:

[0101] Assume that there are n points on the surface, and each point A i is a 6-DOF coordinate point (x, y, z, i, j, k), then the lattice can be expressed as:

[0102] A={A1,A2,...,A n}

[0103] Calculate the representative point of the lattice (i.e. the center of gravity), which can be expressed as:

[0104]

[0105] in: That is, directly take the mean of each dimension.

[0106] According to the point-normal equation of the space plane, there is a fitting plane passing through this point, such as Figure 4 It can be expressed as:

[0107]

[0108] The points on the surface lattice are projected vertically onto the fitting plane, and the position coordinates of any projection point are recorded as The position coordinates of the projected point are Because the projection point to the projected point is perpendicular to this plane, according to the vertical constraint condition, it is easy to know that and Requirements:

[0109]

[0110]

[0111] Further solve the coordinates of any projection point:

[0112]

[0113]

[0114]

[0115] The projection lattice is obtained as Figure 5 , expressed as:

[0116] B={B1,B2,B3,…,B n}

[0117] Step 4: Determine the minimum bounding rectangle of the projected point array.

[0118] Next, we need to find the minimum bounding rectangle of all the projected points on the fitting plane. To simplify the calculation, we can create a temporary coordinate system directly on the projection plane so that the z coordinates of all points are consistent, thus achieving dimensionality reduction.

[0119] The specific steps are: first select two points P1 and P2 in the projection point set to obtain the vector And unitize to get The normal vector of the plane, i.e. (i, j, k) is By the definition of the right-hand system, we get Then the transformation matrix from the workpiece coordinate system {workCoo} to the newly created temporary coordinate system on the projection plane is:

[0120]

[0121] Suppose the matrix composed of all points on the plane is Then the coordinate matrix Q' of the projection point set in the newly created temporary coordinate system is:

[0122] Q′=QG

[0123] To find the minimum enclosing rectangle of a point set in two-dimensional space, we only need to take the maximum and minimum values ​​x in the xy coordinates of all points in the set. min , x max ,y min ,y max, then the coordinates of the four vertices of the minimum circumscribed rectangle of the point set are:

[0124]

[0125] In Q', find the maximum value of the xyz coordinate according to the above method (the z coordinate is consistent in the new temporary coordinate system), find the coordinates of the four boundary points, and set them as Since n1, n2, and n3 are a set of orthogonal bases, G must be reversible. Then the coordinates of the four boundary points in the original workpiece coordinate system {workCoo} are:

[0126] J=J'G -1

[0127] This gives the circumscribed rectangle as Figure 6 shown.

[0128] Step 5: Expand and segment the minimum bounding rectangle.

[0129] Assume that the area of ​​the scanning irradiation format on the plane is approximately s×s area. To ensure that all areas are scanned completely, the circumscribed rectangle is extended outward by a certain distance. Assume that the four boundary points of the circumscribed rectangle are as follows: Figure 7 As shown, let the length of the long side be a, the length of the short side be b, the distance the long side extends outward be h, the distance the short side extends outward be n, and the division is performed with s as the unit distance.

[0130] Step 6: Determine the scanner position origin and the corresponding first principal optical axis vector based on the expanded and segmented minimum circumscribed rectangle.

[0131] After the segmentation is completed, the number of long side segmentations is:

[0132]

[0133] The number of short side divisions is:

[0134]

[0135] Therefore, the entire extended rectangle is divided into mn sub-scanning areas, with the boundary point as the starting point, and the center of the segmented area in the pth row and qth column is defined as C' in the above temporary coordinate system. pq , after calculation and deduction, the coordinates of this center can be obtained as:

[0136]

[0137] The coordinates in the original workpiece coordinate system {workCoo} are:

[0138] C pq =C' pq G -1

[0139] Define the scanning distance, that is, the actual reference distance of the scanner as sd (ScanningDistance), then the scanner position origin posP mapped to this area pq The position coordinates are:

[0140]

[0141] The principal optical axis vector (i.e., the first principal optical axis vector) is uniformly:

[0142]

[0143] After the mathematical calculations are completed, the surface information is processed by the algorithm to obtain the planned scanner position origin and the corresponding main optical axis vector.

[0144] For common small features

[0145] For common small features such as bosses, holes, seams, ribs, and depressions, if they are located above the main feature, i.e., the large-scale surface, then based on the main feature, the present invention divides the small features into three categories: ① convex features, such as bosses, ribs, etc.; ② concave features, such as holes, seams, etc.; ③ mixed features, i.e., a mixed form of the above two types, such as Figure 8 As shown, the left side is a convex feature, the middle side is a concave feature, and the right side is a mixed feature.

[0146] Factors that lead to incomplete scanning of small features include the following: the acquisition laser light path cannot cover the area to be acquired due to occlusion of elements in the concave and convex features; the acquisition laser light path cannot illuminate the acquisition area due to viewing angle problems; the acquisition laser has an inappropriate reference distance, that is, the distance between the scanning laser and the workpiece surface.

[0147] The following methods can be used to solve the problem of incomplete acquisition: ① Change the incident direction of the acquisition light; ② Change the acquisition angle of view; ③ Change the acquisition reference data. Therefore, this invention proposes a scanning planning method for simple concave and convex features. The following uses the example of a rectangular depression in a concave feature and a rib in a convex feature to introduce this scanning planning method:

[0148] The specific introduction of the rectangular sink in the concave feature is as follows:

[0149] Step 7: For the concave features of the small features in the helicopter assembly components, the scanner laser scanning surface is abstracted into triangles.

[0150] Step 8: Cover the bottom of the sunken feature in the concave feature with the laser format, and pass the main optical axis through the center point of the upper surface of the sunken feature.

[0151] Step 9: Obtain the basic position information of the concave feature.

[0152] Step 10: Determine the first position coordinates and the second principal optical axis vector of the scanning posture D in the workpiece coordinate system based on the basic position information of the concave feature.

[0153] like Figure 9 Shown is a rectangular depression feature tFea 下陷 In this algorithm, the scale of small features is assumed to be much smaller than the area that the scanner can scan, and the scanner laser scanning area is abstracted as follows: Figure 10 shown.

[0154] Cover the bottom of the sunken feature with the laser beam and pass the main optical axis through the center of the sunken upper surface, such as Figure 11 As shown, the ultimate goal is to solve the position origin of the scanner in space and its second principal optical axis vector D. Before solving point D, it is necessary to obtain a certain amount of basic position information of the sink feature, including the coordinates of the four vertices of the lower surface of the rectangular sink, the coordinates of the center of the rectangle, the sink height, and the normal vector of the bottom surface of the sink facing the outside of the component entity, which can be expressed as:

[0155]

[0156] center=(x c ,y c ,z c )

[0157] h = height of the sag

[0158]

[0159] A is the midpoint between any two vertices of the lower surface m and n, B is the coordinate of the center of the rectangle, and C is the center point of the sunken upper surface, then BC = h, and

[0160]

[0161] After calculation, we get:

[0162]

[0163] Easy to know Then the position coordinates of the scanning posture D in the workpiece coordinate system are:

[0164]

[0165] The principal optical axis vector is:

[0166]

[0167] Similarly, the remaining three scanner origins and their corresponding principal optical axis vectors can be calculated for the remaining three sides of the rectangle, completing the scanning pose calculation for this small feature. For cylindrical depressions, the cylinder can be fitted into a rectangular depression, and then the scanning pose planning can be performed according to the above algorithm.

[0168] The detailed description of the ribs in the convex feature is as follows:

[0169] Step 11: For a convex feature of a small feature in a helicopter assembly component, determine a point on the starting end surface of the convex feature and record it as the first coordinate point.

[0170] Step 12: Determine a point on the end surface of the convex feature and record it as the second coordinate point.

[0171] Step 13: Obtain basic position information of the convex feature based on the first coordinate point and the second coordinate point.

[0172] Step 14: Determine the second position coordinates and the third principal optical axis vector of the scanning posture D in the workpiece coordinate system based on the basic position information of the convex feature.

[0173] For convex features, a rib feature tFea distributed on the main feature 筋 For example, when planning a local scan, its cross-sectional scale is assumed to be much smaller than the area that the scanner can scan, while its length scale is of the same order of magnitude as the scanning area scale. Figure 12 , B1 is a point on the starting end surface of the rib, B2 is a point on the ending end surface of the rib, sd is the scanning reference distance, and D is the scanning position of the scanner in space. is the amount mentioned in step 4, is the unit direction vector from B1 to B2, defined θ is customized The angle with B1D represents the angular relationship between the scanner and the rib.

[0174] Before solving the coordinates of the scanner scanning posture D, it is necessary to know the coordinates of B1, B2 and the appropriate angle θ. Then the position coordinates of D (i.e., the second position coordinates) are:

[0175]

[0176] The third principal optical axis vector is:

[0177]

[0178] Similarly, the scanner posture on the end face side can be obtained, and the scanner posture in the other direction can be obtained by taking π-θ as θ. Finally, according to Figure 13Sequential scanning can clearly traverse all areas of the entire rib. For convex features with a large comprehensive scale, the above method can also be used for scan planning to find the scanner pose between two surfaces.

[0179] After the above steps, the scanning pose set of the large surface of the helicopter assembly component and the small features on the surface can be obtained, thereby completing the scanning planning of the helicopter assembly component.

[0180] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0181] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for planning the position and posture of a scanner for the surface geometric accuracy of a helicopter assembly component, characterized in that: The planning method includes: Decompose the large geometric features of the helicopter assembly into multiple small straight free-form surface features; Mesh each small straight free-form surface feature and decompose it into multiple sub-surfaces; Determining a projection lattice based on the multiple sub-surfaces; Determining the minimum circumscribed rectangle of the projected point array; Expanding and dividing the minimum circumscribed rectangle; Determine the scanner position origin and the corresponding first principal optical axis vector based on the expanded and segmented minimum circumscribed rectangle; Aiming at the concave features of small features in helicopter assembly components, the scanner laser scanning area is abstracted into triangles; The laser scanning surface is covered with the bottom of the sunken feature in the concave feature, and the main optical axis passes through the center point of the upper surface of the sunken feature; Obtaining basic position information of the concave feature; Determine a first position coordinate and a second principal optical axis vector of a scanning posture D in a workpiece coordinate system based on basic position information of the concave feature; For a convex feature of a small feature in a helicopter assembly component, a point on the starting end surface of the convex feature is determined and recorded as the first coordinate point; Determine a point on the end surface of the convex feature, and record it as the second coordinate point; Acquire basic position information of the convex feature based on the first coordinate point and the second coordinate point; The second position coordinates and the third principal optical axis vector of the scanning posture D in the workpiece coordinate system are determined based on the basic position information of the convex feature.

2. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 1, wherein: Decomposing the large geometric feature surface of the helicopter assembly into a plurality of small straight free-form surface features specifically comprises the following steps: Performing dot matrix formation on the large-scale geometric feature surface; Determine the UV step size; The large profile geometric feature surface is decomposed into a plurality of small straight free-form surface features using the UV step size as a grouping condition.

3. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 1, wherein: Determining the projection point array based on the multiple sub-surfaces specifically includes the following steps: Assume that there are n points on the subsurface, and each point A i The coordinates of the points are recorded as (x, y, z, i, j, k); A dot matrix is ​​determined based on the n points, and the dot matrix is ​​recorded as A={A1, A2, ..., A n }; Calculating the center of gravity of the lattice; Determine a fitting plane passing through the center of gravity; Projecting the point array on the sub-surface perpendicularly to the fitting plane to obtain the coordinates of any projection point; Based on the coordinates of the arbitrary projection points, a projection point matrix is ​​determined.

4. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 1, wherein: Determining the minimum circumscribed rectangle of the projected point array specifically includes the following steps: Create a new temporary coordinate system on the projection plane; Calculate the transformation matrix Q; Determine the coordinate matrix Q' of the projection point matrix in the temporary coordinate system based on the transformation matrix; Get the maximum and minimum xy coordinates in the coordinate matrix Q' min , x max ,y min ,y max ; Based on the x min , x max ,y min ,y max Determine the coordinates of the four vertices of the minimum enclosing rectangle; Obtain the maximum and minimum values ​​of the xyz coordinates in the coordinate matrix Q'; Determine the coordinates of four boundary points based on the maximum and minimum values ​​of the xyz coordinates; Determine the coordinates of the four boundary points in the original workpiece coordinate system {workCoo} based on the coordinates of the four boundary points; A minimum circumscribed rectangle is determined based on the four vertex coordinates and the coordinates of the four boundary points in the original workpiece coordinate system {workCoo}.

5. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 4, characterized in that: Expanding and dividing the minimum bounding rectangle specifically includes the following steps: Expanding the minimum circumscribed rectangle outward by a preset distance; Assume that the length of the long side of the minimum circumscribed rectangle is a, the length of the short side is b, the distance the long side extends outward is h, the distance the short side extends outward is w, and the area is divided with s as the unit distance to obtain the number of long side divisions m, the number of short side divisions n, and mn sub-scanning areas.

6. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 5, characterized in that: The method of determining the scanner position origin and the corresponding first principal optical axis vector based on the expanded and segmented minimum circumscribed rectangle specifically includes the following steps: Based on mn sub-scanning areas, with the boundary point as the starting point, the center of the segmented area in the pth row and qth column is defined as C' on the temporary coordinate system. pq ; Based on the C' pq Calculate the coordinate C in the original workpiece coordinate system {workCoo} pq ; Define the actual reference distance of the scanner as sd; Based on the coordinate C pq The actual reference distance sd is used to calculate the position coordinates of the scanner position origin and the first principal optical axis vector.

7. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 6, wherein: The expression of the position coordinates of the scanner position origin is: in, Indicates the origin coordinates of the scanner position, C pq Indicates the center of the segmented area under the original workpiece coordinate system {workCoo}, sd indicates the actual reference distance of the scanner, Indicates the direction of optical axis loss; The expression of the first principal optical axis vector is: in, Represents the coordinates of the first principal optical axis vector.

8. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 1, wherein: The basic position information of the concave feature includes the coordinates of the four vertices of the lower surface of the rectangular depression, the coordinates of the center of the rectangle, the depression height, and the normal vector of the bottom surface of the depression facing outside the component entity.

9. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 8, wherein: The expression of the first position coordinate is: Among them, D xyz 凹 represents the first position coordinate, A represents the middle point between any two lower surface vertices m and n, sd represents the actual reference distance of the scanner, and C represents the center point of the upper surface of the concave feature. represents the vector from point A to point C; The expression of the second principal optical axis vector is: Among them, D ijk 凹 represents the second principal optical axis vector, Represents the vector from point C to point A.

10. The method for positioning and planning a surface geometric accuracy scanner for a helicopter assembly component according to claim 1, characterized in that: The expression of the second position coordinate is as follows: Among them, D xyz 凸 represents the second position coordinate, B1 represents a point on the starting end surface of the convex feature, B2 represents a point on the ending end surface of the convex feature, sd represents the actual reference distance of the scanner, and θ represents the angle between the scanner and the convex feature. is the unit direction vector from B1 to B2, Indicates that any two points P1 and P2 are selected from the projection point set, and the vector And normalize the resulting vector; The expression of the third principal optical axis vector is as follows: Among them, D ijk 凸 represents the third principal optical axis vector, B1 represents a point on the starting end surface of the convex feature, and D is the scanning posture of the scanner in space. Represents the vector from point B1 to point D.

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