CN-118862675-B - Self-planning high-efficiency laser measurement method for discrete key points in complex assembly scene

Abstract

A self-planning high-efficiency laser measurement method for discrete key points in a complex assembly scene comprises the steps of firstly carrying out pre-discrimination of laser measurement sight shielding based on a point-line-plane intersection algorithm, then constructing a distributed laser measurement station position optimization layout function model, setting constraints such as a ranging range, a measuring angle range and a feasible domain by taking the minimum weighted sum of three-dimensional measurement uncertainty and key point measurement uncertainty as an objective function, solving distributed laser measurement station position coordinates and measurement tasks based on a genetic algorithm, realizing self-planning of the number, the positions and the like of measurement stations, planning a measurement sequence of the discrete key points in a large range, and solving a measurement sequence of a plurality of key points to be measured in each measurement station position based on the principle of minimum measurement path in the measurement sequence. The method can be used for the assembly process of large-scale mechanical products such as airplanes in the aerospace field, greatly improves the efficiency of key point measurement in the assembly process, and has wide application prospect.

Inventors

• ZHANG YANG
• Yan Ruidi
• LU YONGKANG
• XING HONGWEN
• WANG JIAWEI
• GUAN XIAO
• CHENG XIKANG
• LIU WEI

Assignees

• 大连理工大学

Dates

Publication Date

20260505

Application Date

20240730

Claims (1)

1. 1. A self-planning high-efficiency laser measurement method for discrete key points in a complex assembly scene is characterized by comprising the following steps: first, based on the measured line-of-sight shielding pre-discrimination of point-line-of-surface intersection Firstly, importing a model of a shielding object which is easy to cause sight shielding in an assembly site into SOLIWORKS modeling software, then exporting the model in obj format to form triangular patches of the model, obtaining triangular patches of one model each time, secondly, constructing a line segment between a key point to be tested and a measurement origin of a laser tracker, calculating the sum of three triangular areas formed by an intersection point of the line segment and a plane of the triangular patch corresponding to the shielding object and each vertex of the triangular patch, judging whether the line segment is intersected with the triangular patch, setting the coordinates of 3 vertexes of a certain triangular patch to be q 1 ＝(x 1 ,y 1 ,z 1 )、q 2 ＝(x 2 ,y 2 ,z 2 ) and q 3 ＝(x 3 ,y 3 ,z 3 respectively, setting the coordinates of the measurement origin of the key point to be tested and the laser tracker to be p a ＝(x a ,y a ,z a )、p b ＝(x b ,y b ,z b respectively), and expressing a line segment parameter equation as (1): wherein λ is a parameter; the plane equation of a triangular patch is represented by determinant (2): The lambda value of the parameter is calculated by adopting the formula (3) in the combination of the formula (1) and the formula (2), wherein C, D is that if lambda epsilon [0,1] is the process parameter ,m 1 ＝x b -x a ,m 2 ＝y b -y a ,m 3 ＝z b -z a ;, the intersection point exists between the triangular surface patch and the line segment, and the coordinate of the intersection point is calculated by the formula (1): solving the area of the model triangular surface patch, the intersection point of the line and the surface and three vertexes of the model triangular surface patch to form three triangle total areas by adopting the method (4); Wherein, S Original source is the area of the model triangular patch, S New type is the total area ,a 1 ＝x 2 -x 1 、a 2 ＝x 3 -x 1 、b 1 ＝y 2 -y 1 、b 2 ＝y 3 -y 1 、c 1 ＝z 2 -z 1 and c 2 ＝z 3 -z 1 of three triangles formed by the intersection point of the line and the plane and the vertex of the model triangular patch; If S Original source ＝S New type , the intersection point of the measuring line of sight and the triangular plane is shown to be in the triangle, namely, the intersection point is intersected, the measuring line of sight is blocked, otherwise, the measuring line of sight is not blocked; Secondly, constructing an optimization function of a measuring station of the distributed laser tracker Firstly, taking the routable range of the station position of the laser tracker, the ranging range and the angle measurement range of the laser tracker as constraints, taking the minimum weighted sum of the three-dimensional measurement uncertainty of the laser tracker and the measurement uncertainty of the key points as an objective function, taking parameters to be optimized as the quantity and the position of the station position of the laser tracker, introducing a measuring point allocation factor theta (i) to allocate measurement tasks, and constructing an optimization function of the measuring station position of the distributed laser tracker on the whole, wherein the objective function is shown in a formula (5), the measuring point allocation factor is shown in a formula (6), and the constraint function is shown in a formula (7): Wherein m is the number of measuring stations of the laser tracker, n is the number of key points, P LT,j is the j-th coordinate of measuring stations to be measured, and P i is the i-th coordinate of key points to be measured; The minimum value and the maximum value of the vertical angle are the included angle between the connecting line of the key point to be measured and the measuring origin of the laser tracker and the Z axis in the measuring coordinate system of the tracker, and l max is the maximum allowable measuring distance, epsilon x ,ε y ,ε z is the feasible area of the station position layout in the x, y and Z directions respectively; taking 1e8 as a vision shielding penalty factor for the ith control, and not shielding to be 0 when shielding; Thirdly, solving layout coordinates of measuring station based on genetic algorithm In the formula (6), theta (i) is used for distributing the key points to be measured to each measuring station according to the shortest distance principle, namely judging the distance from the key points to be measured to each measuring station, if p i is nearest to the measuring station k, theta (i) =1, otherwise 0, then adopting a genetic algorithm to optimize the number and the space position of the measuring stations in a solving formula, taking the fitness function in the algorithm as an objective function, considering that the feasible region arranged in a large aviation assembly site is not parallel to each coordinate axis, converting the three-dimensional scene to be measured into a three-dimensional space parallel to the coordinate axes for solving, and reversely converting the solved configuration parameters into an original three-dimensional space, thereby solving the final configuration parameters of the measuring stations; Fourth, measuring sequence automatic planning of discrete key points in large range Setting n key point tasks to be detected in a certain measuring station, setting G= (V p ,d p ) as a weighted graph, setting V p = {1,2,., n } as a vertex set, d p as a side length set, d i,j (d i,j ＞0,i,j∈V p as a distance between the vertexes, and adopting an optimized mathematical model as formula (8); wherein D s is the reciprocal of the total distance of each measuring point sequence, D i,j is the distance between i and j key points to be measured, a i,j is a process parameter, S is all non-empty subsets of V, S is all the number of vertexes in the weighted graph G contained in the set V; and then, establishing a key point measurement sequence planning model based on an improved genetic algorithm, reducing the optimization time through heuristic search, and finally solving a measurement sequence.

Description

Self-planning high-efficiency laser measurement method for discrete key points in complex assembly scene Technical Field The invention belongs to the field of large-size/digital measurement, and relates to a self-planning high-efficiency laser measurement method for discrete key points in a complex scene. Background In-situ assembly driven by digital measurement has become one of the mainstream manufacturing modes of large aircraft parts, and measurement accuracy, efficiency and reliability directly affect assembly quality and efficiency. For example, accurate transfer and evaluation of geometric measurement data in aircraft assembly is a key to ensuring assembly accuracy and shortening assembly time. However, the key points (positioning points, datum points and the like) on the aircraft parts are often large in distribution range, discrete in spatial distribution and serious in-site vision shielding, and high-precision, high-efficiency and high-reliability measurement of the series of key points faces serious challenges. The conventional field measurement technology often needs to rely on manual experience to carry out measurement station layout, whether the measurement sight is blocked or not is difficult to judge in advance, the condition that the measurement station is temporarily supplemented due to the fact that the measurement sight is blocked easily occurs, meanwhile, the measurement sequences of a plurality of measurement targets also completely depend on personal experience, the problem of low-efficiency measurement of missing measurement, heavy measurement and backward measurement easily occurs, in addition, the measurement precision of the laser tracker is related to the distance and the angle, and the measurement precision cannot be ensured by experience layout. In summary, a self-planning high-efficiency measurement method for complex assembly sites must be explored to ensure the measurement accuracy, efficiency and reliability of key points. In a laser tracker station planning method based on combined measurement and a patent number CN202011243780.4, a laser tracker station planning method based on combined measurement is disclosed, and the method plans the placement position and the gesture of a laser tracker by a planned T-Scan scanning track. In the patent 'space measurement accessibility simulation analysis and arrangement method of laser tracker and IGPS', patent number CN202210363899.8, a space measurement accessibility simulation analysis and arrangement method of laser tracker and IGPS is disclosed, the method judges the accessibility of measurement points by simulating and analyzing the difference between the measured distance and the theoretical distance, and searches the position of the laser tracker which can be measured by all measurement points through gridding search. The method is only suitable for combined measurement of the laser tracker and the T-Scan, and can only find the station positions of the laser tracker which enable all measurement points to be measurable, the whole measurement precision of the laser tracker during multi-station measurement is not considered, and the problem of discrete key point measurement task allocation and measurement sequence planning is not studied. Therefore, the invention provides a self-planning high-efficiency laser measurement method for discrete key points in a complex scene, which realizes self-planning and full-coverage measurement of multiple measurement stations and has good universality and wide application prospect. Disclosure of Invention The invention discloses a self-planning high-efficiency laser measurement method for discrete key points in a complex scene. The method comprises the steps of firstly carrying out pre-discrimination of laser measurement sight shielding based on a point-line-plane intersection algorithm, secondly constructing a distributed laser measurement station position optimization layout function model, setting constraints such as a ranging range, a measuring angle range and a feasible domain by taking the minimum sum of weights of three-dimensional measurement uncertainty and key point measurement uncertainty as an objective function, solving distributed laser measurement station position coordinates and measurement tasks based on a genetic algorithm, realizing self-planning of the number, the positions and the like of measurement stations, finally planning a measurement sequence of discrete key points in a large range, and solving a measurement sequence of a plurality of key points to be measured in each measurement station position based on the principle of minimum measurement paths in the measurement sequence. The invention changes the traditional mode of manual experience station layout, solves the problems of undetected measurement, insufficient measurement and low efficiency, and has wide application prospect. The technical scheme of the invention is as follows: The self-planning high-efficiency las