Aircraft part cross-section actual measurement point cloud bidirectional circulation sorting method

Abstract

The application discloses a kind of aviation parts section real measurement point cloud bidirectional circulation sequencing method, it mainly includes the following steps: after aviation parts section real measurement point cloud is obtained, point cloud distribution is preprocessed using genetic algorithm, in polar coordinate system, the polar radius of each node of unordered slice point set is judged one by one, bidirectional circulation sequencing is carried out by considering part section curve feature, and the final ordered point cloud processing result is obtained.This method realizes the ordered processing of part real measurement unordered point cloud based on adjusting the distribution of real measurement point cloud and considering the characteristics of aviation parts section curve, provides the basis for subsequent point cloud processing, and has practical value in aviation parts machining trajectory planning.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of robot trajectory planning, and particularly relates to a two-way cyclic sorting method for sectional measured point clouds of aviation parts. BACKGROUND

[0002] In recent years, robot intelligent machining technology has been gradually applied to the machining of parts in the fields of aviation, aerospace, etc. Aviation parts have complex shapes and various structures, and especially the parts after service have deformation and more random damage. Therefore, the initial design model cannot be used for machining path planning when the parts are repaired and machined. Therefore, point cloud collection and processing of aviation parts are prerequisites for realizing robot intelligent machining path planning.

[0003] The point cloud data obtained by scanning and collection is usually unordered point cloud. In actual production application, it needs to be ordered before the machining path curve can be obtained by connecting the cutter contact points. To solve the above technical problems, the present application proposes a two-way cyclic sorting method considering the sectional curve characteristics for the measured point cloud data of aviation parts, so as to realize the ordered processing of the measured point cloud data of parts. SUMMARY

[0004] The technical problem to be solved by the present application is:

[0005] Acquiring high-density point clouds of part surfaces is the basis for realizing robot machining trajectory planning, and the collection and processing of measured point clouds directly determine the quality and efficiency of machining path planning. In order to meet the demand of robot intelligent machining path planning of aviation parts, it is very important to order the measured point clouds.

[0006] The present application realizes the preprocessing of the distribution of measured point clouds of aviation parts based on a genetic algorithm, provides a two-way cyclic sorting method, effectively realizes the ordered processing of unordered point clouds, and provides a reference for robot intelligent machining path planning.

[0007] The technical scheme adopted by the present application is: a two-way cyclic sorting method for sectional measured point clouds of aviation parts, and the method flow is as follows:

[0008] S1, read the three-dimensional point cloud data obtained by measuring the part, and slice the data to obtain a slice point set;

[0009] S2, in a rectangular coordinate system, thinning the complete measured point cloud slice point set;

[0010] S3, using a genetic algorithm, preprocessing and analyzing the point cloud contour of the thinned point set, and rotating the complete measured point cloud slice point set to a suitable position;

[0011] S4, establishing a polar coordinate system according to the coordinate eigenvalue of the rotated slice data point set in the rectangular coordinate system; S5, pre-sorting the slice unordered point set, establishing a single linked list, and obtaining a criterion p0;

[0012] S6, taking out the head node of the pre-sorted single linked list and taking the node as the head node of a new double-direction circular linked list;

[0013] S7, sequentially reading the single linked list, judging the size relationship between the polar radius p of the current node and the current criterion p0 as the angle theta continuously increases, if the polar radius p of the current node is less than p0, taking the node out of the single linked list as a new head node and inserting it into the double-direction circular linked list representing the cross-sectional curve of the aviation part, if the polar radius p of the current node is greater than p0, taking the node out of the single linked list as a new tail node and inserting it into the double-direction circular linked list, until the judgment loop ends;

[0014] S8, inserting the remaining nodes in the single linked list into the double-direction circular linked list, comparing the polar radius p of the head node of the single linked list with the current criterion p0, if p is greater than p0, taking the single linked list out according to the current order and inserting it into the head of the double-direction circular linked list, if p is less than p0, taking the single linked list out according to the current order and inserting it into the tail of the double-direction circular linked list;

[0015] S9, modifying the predecessor pointer and successor pointer of the head and tail nodes of the double-direction circular linked list representing the cross-sectional curve of the aviation part, respectively, and completing the double-direction circular sorting of the measured point cloud of the cross section of the aviation part.

[0016] Further, in step S2, the method for thinning the complete measured point cloud slice point set is grid thinning sampling on the collected point cloud coordinates, and the grid size is selected according to the overall size of the point cloud and the sampling density.

[0017] Further, in step S3, the point cloud contour preprocessing analysis specifically includes: obtaining the thinned point cloud contour by solving the shortest scheme connecting each point according to a genetic algorithm, finding the maximum and minimum values x max , x min , y max , y min , and rotating the thinned point set with the center of the point ((x max +x min ) / 2, (y max +y min ) / 2), rotating the complete measured point cloud slice point set to a suitable position according to the rotation effect, and completing the point cloud contour preprocessing analysis.

[0018] Further, in step S4, the method for establishing the polar coordinate system is to find the maximum and minimum values of the x and y directions of the slice point set in the rectangular coordinate system, and mark them as x max, x min , y max , y min , x max +(x max -x min ) / 2,(y max +y min ) / 2) as the pole point, an polar coordinate system is established.

[0019] Further, in step S5, the preordering method is specifically that, according to the polar axis, a preordering is performed from small to large, a single linked list is established with the point of the smallest angle θ as the head node.

[0020] Further, in step S5, the method for obtaining the criterion ρ0 is that, the polar radius ρ0 of the head node of the single linked list at this time is recorded as the criterion.

[0021] Further, in step S7, the selection method of the current criterion ρ0 is that, when step S4 is executed, the bidirectional circular linked list only receives a new head node and a new tail node, and whenever the new head node and the tail node are generated, the average of the polar radii of the new head node and the tail node is taken as the new criterion ρ0.

[0022] Further, in step S7, the loop end criterion is that, after the new criterion ρ0 is obtained, whether step S7 is looped is confirmed by judging whether the tail node of the single linked list is inserted into the bidirectional circular linked list, if the tail node of the single linked list is not taken out and inserted into the bidirectional circular linked list, step S7 is repeatedly executed, if the tail node of the single linked list is taken out and inserted into the bidirectional circular linked list, step S7 is exited and step S8 is executed. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Method flowchart of the present application

[0024] Figure 2 Actual point cloud thinning result

[0025] Figure 3 Effect after rotation of the thinned point set

[0026] Figure 4 Effect before and after rotation of the unordered part slice point set

[0027] Figure 5 Ordering result of the part single layer slice point set DETAILED DESCRIPTION

[0028] The present application is further described below in combination with the drawings and specific embodiments, and the following embodiments do not constitute a limitation on the present application.

[0029] The present method can be applied to the ordering processing of the cross section of the actual point cloud of the aviation part, and when specifically implemented, reference is made toFigure 1 Based on the part measured point cloud data, considering the part measured point cloud distribution and the cross-sectional curve characteristics, the unordered point cloud is ordered by using a bidirectional circular sorting method, and finally a closed part cross-sectional curve is obtained. In this embodiment, the single-layer grinding processing path planning of the aircraft engine blade is taken as an example to perform point cloud sorting processing on the measured point cloud.

[0030] The technical scheme adopted by the application is a kind of aviation part cross-section measured point cloud bidirectional circular sorting method, and the method flow is as follows:

[0031] S1, read the three-dimensional point cloud data obtained by measuring the part, and slice the data to obtain a slice point set;

[0032] S2, in the rectangular coordinate system, the complete measured point cloud slice point set is thinned;

[0033] S3, using genetic algorithm, the point cloud contour preprocessing analysis is carried out on the thinned point set, and the complete measured point cloud slice point set is rotated to the appropriate position;

[0034] S4, in the rectangular coordinate system, according to the coordinate characteristic value of the rotated slice data point set, the pole point is established and the polar coordinate system is established;

[0035] S5, the slice unordered point set is pre-ordered, a single linked list is established, and the criterion ρ0 is obtained;

[0036] S6, the head node of the pre-ordered single linked list is taken out and taken as the head node of the new bidirectional circular linked list;

[0037] S7, the single linked list is read in order, as the angle θ increases, the polar radius ρ of the current node and the current criterion ρ0 are judged point by point, if the polar radius ρ of the current node is less than ρ0, the node is taken out from the single linked list as the new head node and inserted into the bidirectional circular linked list representing the cross-sectional curve of the part; if the polar radius ρ of the current node is greater than ρ0, the node is taken out from the single linked list as the new tail node and inserted into the bidirectional circular linked list, until the judgment loop ends;

[0038] S8, the remaining nodes in the single linked list are inserted into the bidirectional circular linked list, the polar radius ρ of the head node of the single linked list is compared with the current criterion ρ0, if ρ>ρ0, the single linked list is taken out in the current order and inserted into the head of the bidirectional circular linked list, if ρ<ρ0, the single linked list is taken out in the current order and inserted into the tail of the linked list; S9, the predecessor pointer and the successor pointer of the head and tail nodes of the bidirectional circular linked list representing the cross-sectional curve of the aviation part are modified respectively, and the aviation part cross-sectional measured point cloud bidirectional circular sorting is completed.

[0039] Further, in step S2, the method of thinning the complete measured point cloud slice point set is to perform grid thinning sampling on the collected point cloud coordinates, and the grid size is selected according to the overall size of the point cloud and the sampling density. In this embodiment, the thinning grid size is set to 3mm*3mm.

[0040] Further, in step S3, the point cloud contour preprocessing analysis is specifically to obtain the thinned point cloud contour as shown in FIG. 6 by solving the shortest scheme connecting each point according to a genetic algorithm, and to find the maximum and minimum values x Figure 2 , y max , y min , y max , y min of the thinned point set x max , x min and y max , y min , and to rotate the thinned point set with the point ((x max +x min ) / 2, (y max +y min ) / 2) as the rotation center, to rotate the complete measured point cloud slice point set to a suitable position according to the rotation effect, and to complete the point cloud contour preprocessing analysis. In this embodiment, the leaf basin direction of the measured point cloud slice point set is roughly directed to the positive direction of the x-axis of the rectangular coordinate system through coordinate rotation, and the thinned point set is rotated as shown in FIG. 7, and the effects before and after the rotation of the complete point cloud slice point set are shown in FIG. 8. It can be seen that the node data in the slice point set at this time is in a disordered state. Figure 3 Figure 4

[0041] Further, in step S4, the method of establishing the polar coordinate system is to find the maximum and minimum values of the x and y directions of the slice point set in the rectangular coordinate system, and to record them as x max , x min , y max , y min , and to establish the polar coordinate system with the point (x max +(x max -x min ) / 2, (y max +y min ) / 2) as the polar point.

[0042] Further, in step S5, the method of preordering is specifically to perform a preordering from small to large according to the polar axis ordering, to take the point with the smallest angle θ as the head node, and to establish a single linked list.

[0043] Further, in step S5, the method of obtaining the criterion ρ0 is to record the polar radius ρ0 of the head node of the single linked list at this time as the criterion.

[0044] Further, in step S7, the selection method of the current criterion ρ0 is that each time the step S4 is executed, the double-direction circular linked list only receives a new head node and a new tail node, and each time a new head node and a tail node are generated, the polar radius mean value of the new head node and the tail node is taken as a new criterion ρ0.

[0045] Further, in step S7, the loop end criterion is that after the new criterion ρ0 is obtained, whether the step S7 is looped is confirmed by judging whether the tail node of the single linked list is inserted into the double-direction circular linked list, if the tail node of the single linked list is not taken out and inserted into the double-direction circular linked list, the step S7 is repeatedly executed, if the tail node of the single linked list is taken out and inserted into the double-direction circular linked list, the step S7 is exited and the step S8 is executed.

[0046] According to the steps S1-S9, the point cloud data obtained by slicing the aviation part is adjusted and sorted, and the sorting result of the point cloud double-direction circular sorting algorithm considering the curve characteristics of the airfoil is as shown in the drawing. Figure 5 The result can be used as the single-layer grinding processing path of the airfoil, and after the measured point cloud is sliced and sorted for multiple times, the final grinding path is obtained by superimposing the paths of each layer, and the robot processing trajectory planning is realized.

[0047] The application adopts a double-direction circular sorting method for the cross-section measured point cloud of an aviation part, uses the genetic algorithm to pre-process the distribution of the measured point cloud, considers the curve characteristics of the part cross-section to establish a polar coordinate system, takes the polar radius of each node as a criterion, and uses the double-direction circular sorting method to sort the unordered point cloud.

[0048] The application has the advantages of simple principle, reliable result, efficient conversion of unordered point cloud into ordered point cloud, and specific application in the field of robot processing path planning of aviation parts considering the distribution of the measured point cloud and the curve characteristics of the cross-section.

Claims

1. A bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections, the method flow of which is as follows: S1. Read in the 3D point cloud data obtained from the actual measurement of the part, and slice the data to obtain the slice point set; S2. Thinning of the complete measured point cloud slice point set in a rectangular coordinate system; S3. Using a genetic algorithm, perform point cloud contour preprocessing analysis on the thinned point set, and rotate the complete measured point cloud slice point set to a suitable position. S4. In a rectangular coordinate system, determine the poles and establish a polar coordinate system based on the coordinate characteristic values ​​of the rotated slice data point set. S5. Pre-sort the unordered point set of the slice, establish a singly linked list, and obtain the criterion ρ0. S6. Take out the head node of the pre-sorted singly linked list and use that node as the head node of the new doubly linked circular list. S7. Read the singly linked list sequentially. As the angle θ increases, check the relationship between the polar radius ρ of the current node and the current criterion ρ0. If the polar radius ρ of the current node is less than ρ0, remove the node from the singly linked list as the new head node and insert it into the doubly linked circular list representing the cross-sectional curve of the component. If the polar radius ρ of the current node is greater than ρ0, remove the node from the singly linked list as the new tail node and insert it into the doubly linked circular list until the cycle ends. S8. Insert the remaining nodes in the singly linked list into the doubly linked circular list. Compare the polar radius ρ of the current head node of the singly linked list with the current criterion ρ0. If ρ>ρ0, remove the singly linked list in the current order and insert it into the head of the doubly linked circular list. If ρ<ρ0, remove the singly linked list in the current order and insert it into the tail of the list. S9. Modify the predecessor and successor pointers of the head and tail nodes of the doubly linked circular list representing the blade curve, respectively, to complete the bidirectional circular sorting of the measured point cloud of the aerospace component cross-section.

2. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The point cloud thinning method in step S2 is to perform grid thinning sampling on the collected point cloud coordinates, and the grid size is selected based on the overall size of the point cloud and the sampling density.

3. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The point cloud contour preprocessing and analysis method in step S3 is as follows: A genetic algorithm is used to find the shortest path connecting all points to obtain the thinned point cloud contour; then, the maximum and minimum values ​​x' of the thinned point set in the x and y directions are found. max 、x' min y' max y' min , with point ((x' max +x' min ) / 2,(y' max +y' min ) / 2) Rotate the sparse point set with the rotation center, and rotate the complete measured point cloud slice point set to a suitable position according to the rotation effect.

4. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The method for establishing the polar coordinate system in step S4 is as follows: in the rectangular coordinate system, find the maximum and minimum values ​​in the x and y directions of the slice point set, and denote them as x and y respectively. max x min y max y min , with point (x max +(x max -x min ) / 2,(y max +y min Let ) / 2) be the pole, and establish a polar coordinate system.

5. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The pre-sorting method in step S5 is to perform a pre-sorting from small to large according to the polar axis sorting, and establish a singly linked list with the point with the smallest angle θ as the head node.

6. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The method for obtaining the criterion ρ0 in step S5 is to record the polar radius ρ0 of the head node of the singly linked list at this time as the criterion.

7. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, The method for selecting the current criterion ρ0 in step S7 is as follows: each time step S7 is executed, the doubly linked circular list only receives a new head node and a new tail node. Whenever a new head or tail node is generated, the average polar radius of the new head and tail nodes is calculated as the new criterion ρ0.

8. The bidirectional cyclic sorting method for measured point clouds of aerospace component cross-sections according to claim 1, characterized in that, In step S7, the loop termination criterion is as follows: after obtaining the new criterion ρ0, the loop termination of step S7 is confirmed by determining whether the tail node of the singly linked list has been inserted into the doubly linked list. If the tail node of the singly linked list has not been removed and inserted into the doubly linked list, step S7 is repeated; if the tail node of the singly linked list has been removed and inserted into the doubly linked list, step S7 is exited and step S8 is executed.

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