METHOD FOR DYNAMICALLY MEASURING DEFORMATION OF ROTATING-BODY MOLD

Abstract

A method for dynamically measuring deformation of a rotating-body mold, including: (S1) subjecting an overall outer surface of the rotating-body mold to three-dimensional measurement to acquire an initial point cloud data; (S2) shooting, by a multi-camera system, the mold from different angles to obtain three-dimensional coordinates of marking points and coding points on the overall outer surface of the rotating-body mold; (S3) rotating the mold, and repeatedly photographing the marking points and the coding points on the mold surface under different angle poses; and calculating three-dimensional coordinates of the marking points and the coding points; and (S4) predicting a point cloud data of the outer surface under different angle poses based on a conversion relationship among the marking points to analyze a deformation degree of the mold during a rotation process.

Claims

1. A method for dynamically measuring deformation of a rotating-body mold, comprising: (S1) subjecting an overall outer surface of the rotating-body mold to three-dimensional measurement to acquire an initial point cloud data; (S2) shooting, by a multi-camera system, the rotating-body mold from different angles to obtain three-dimensional coordinates of marking points and three-dimensional coordinates of coding points on the overall outer surface of the rotating-body mold; (S3) rotating the rotating-body mold, and repeatedly photographing the marking points and the coding points on the mold surface under different angle poses; and calculating three-dimensional coordinates of the marking points and three-dimensional coordinates of the coding points; and (S4) predicting a point cloud data of the outer surface under different angle poses based on a conversion relationship among the marking points to analyze a deformation degree of the rotating-body mold during a rotation process.

2. The method of claim 1, wherein the step (S1) is performed through steps of: (S11) pasting the coding points on the mold surface and cylindrical surfaces of chucks on both sides of the rotating-body mold at a certain density, and pasting the marking points randomly on the mold surface; wherein the coding points are configured for construction of a global coordinate system and a data alignment reference; and the marking points are configured for sampling increase and subsequent conversion and calculation of a surface data; (S12) placing a reference ruler and a benchmark; taking multiple sets of overlapping photos using MaxShot, and performing three-dimensional calculation of the coding points via image triangulation to establish a measurement coordinate system; and (S13) measuring a three-dimensional point cloud data P.sub.1={p.sub.1, p.sub.2, . . . , p.sub.m} of the overall outer surface of the rotating-body mold through binocular C-Track transformation using MetraScan.

3. The method of claim 1, wherein the step (S2) is performed through steps of: (S21) planning a plurality of stations for photogrammetry followed by photographing; wherein each of the plurality of stations is configured to contain as many marking points as possible; and adjacent stations are configured to contain at least four common marking points; (S22) recognizing coding marks in images respectively taken in the plurality of stations; (S23) subjecting images with the same coding mark to matching; unifying the images into a photogrammetric coordinate system using the coding marks; and obtaining an exterior orientation element of each image; (S24) based on known exterior orientation elements of the images, subjecting other non-coding mark points to correspondence points matching using an epipolar matching method; and (S25) calculating the three-dimensional coordinates of the marking points through bundle adjustment to obtain data t.sub.1={t.sub.1_1, t.sub.2_1, . . . , t.sub.n_1} of a total of n marking points in a first pose.

4. The method of claim 1, wherein the step (S3) is performed through steps of: rotating the rotating-body mold, and repeating the step (S2) to shoot and calculate marking point data t.sub.2={t.sub.1_2, t.sub.2_2, . . . , t.sub.n_2}, . . . , t.sub.i={t.sub.1_i, t.sub.2_i, . . . , t.sub.n_i} under different angle poses, wherein i is the number of poses corresponding to a rotation angle.

5. The method of claim 1, wherein the step (S4) is performed through steps of: (S41) based on a rigid-body transformation of coding points on a chuck, unifying marking point data under multiple angles into the same coordinate system; (S42) calculating a transformation relationship between marking points adjacent to outer surface points under multiple angle poses to reversely obtain a three-dimensional coordinate of the outer surface under a corresponding pose; and (S43) analyzing the deformation degree of the rotating-body mold during the rotation process based on three-dimensional coordinates of the outer surface under multiple angle poses.

6. The method of claim 5, wherein the step (S41) is performed through steps of: (S411) recognizing the coding points on cylindrical surfaces of chucks on both sides in a captured image; and (S412) taking marking point data t.sub.1={t.sub.1_1, t.sub.2_1, . . . , t.sub.n_1} measured for the first time as a reference to calculate a rotation matrix among coordinates of the coding points with the same serial number; and subjecting data obtained under different angle poses to alignment; wherein the marking point data after alignment are s.sub.1={s.sub.1_1, s.sub.2_1, . . . , s.sub.n_1}, s.sub.2={s.sub.1_2, s.sub.2_2, . . . , s.sub.n_2}, . . . , s.sub.i={s.sub.1_i, s.sub.2_i, . . . , s.sub.n_i}; and s.sub.1=t.sub.1.

7. The method of claim 5, wherein the step (S42) is performed throughs steps of: (S421) finding k neighboring marking points {(s.sub.1_1, s.sub.2_1, . . . , s.sub.k_1), (s.sub.1_2, s.sub.2_2, . . . , s.sub.k_2), . . . , (s.sub.1_i, s.sub.2_i, . . . , s.sub.k_i)} of outer surface points p.sub.j in an initial station in a marking point data set {s.sub.1, s.sub.2, . . . , s.sub.i}; (S422) calculating three-dimensional coordinates of points on the outer surface of the rotating-body mold at a second station, expressed as p.sub.j_2=p.sub.j_1+(θ.sub.1(s.sub.1_2−s.sub.1_1)+θ.sub.2(s.sub.2_2−s.sub.2_1)+ . . . +θ.sub.k(s.sub.k_2−s.sub.k_1))/k; wherein θ.sub.k is a weight of each neighboring marking point; and the closer a marking point is to p.sub.j_1, the greater its weight is; and (S423) repeating the step (S422) to calculate a three-dimensional coordinate set P.sub.1, P.sub.2, . . . , P.sub.i of the outer surface under multiple angle poses.

8. The method of claim 5, wherein the step (S43) is performed through steps of: (S431) calculating a distance between surface points of adjacent stations, wherein a distance between P.sub.1 and P.sub.2 is d.sub.1, a distance between P.sub.2 and P.sub.3 is d.sub.2, and so on, and a distance between P.sub.i_1 and P.sub.i is d.sub.i-1; and a distance array is expressed as d={d.sub.1, d.sub.2, . . . , d.sub.i-1}; and (S432) calculating an average value and a variance of the distance array d={d.sub.1, d.sub.2, . . . , d.sub.i-1} to evaluate the deformation degree of the rotating-body mold.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is flowchart of a method for dynamically measuring deformation of a rotating-body mold according to an embodiment of the present disclosure;

[0043] FIG. 2 is a flowchart of step (S1) according to an embodiment of the present disclosure;

[0044] FIG. 3 is a flowchart of step (S2) according to an embodiment of the present disclosure;

[0045] FIG. 4 is a schematic diagram of a rotating-body mold according to an embodiment of the present disclosure;

[0046] FIG. 5 is a flowchart of step (S4) according to an embodiment of the present disclosure;

[0047] FIG. 6 is a flowchart of step (S41) according to an embodiment of the present disclosure;

[0048] FIG. 7 is a flowchart of step (S42) according to an embodiment of the present disclosure; and

[0049] FIG. 8 is a flowchart of step (S43) according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0050] This application will be described in detail below with reference to the accompanying drawings and embodiments.

[0051] To measure a surface of the mold and analyze the influence of its deformation on the forming of composite components, this disclosure provides a method for dynamically measuring and analyzing deformation of a rotating-body mold (as shown in FIG. 4), which is mainly shown in FIG. 1.

[0052] This disclosure provides a method for dynamically measuring deformation of a large-size rotating-body mold, which includes the following steps.

[0053] (S1) An overall outer surface of the rotating-body mold is subjected to three-dimensional measurement to acquire an initial point cloud data.

[0054] (S2) A multi-camera system shoots the rotating-body mold from different angles to obtain three-dimensional coordinates of marking points and three-dimensional coordinates of coding points on the overall outer surface of the rotating-body mold.

[0055] (S3) The rotating-body mold is rotated and the marking points and the coding points on the mold surface under different angle poses are repeatedly photographed, and then the three-dimensional coordinates of the marking points and the three-dimensional coordinates of the coding points are calculated.

[0056] (S4) A point cloud data of the outer surface under different angle poses is predicted based on a conversion relationship among the marking points to analyze a deformation degree of the rotating-body mold during a rotation process.

[0057] The application of the technical solutions provided herein can effectively realize the dynamic measurement and deformation analysis of the rotating-body mold.

[0058] In this embodiment, as shown in FIG. 2, the step (S1) is performed through the following steps.

[0059] (S11) The coding points are pasted on the mold surface and cylindrical surfaces of chucks on both sides of the rotating-body mold at a certain density. The marking points are randomly pasted on the mold surface, where the coding points are configured for construction of a global coordinate system and a data alignment reference and the marking points are configured for sampling increase and subsequent conversion and calculation of a surface data.

[0060] (S12) A reference ruler and a benchmark are placed. Multiple sets of overlapping photos are taken using MaxShot. Three-dimensional calculation of the coding points is performed via image triangulation to establish a measurement coordinate system. (S13) A three-dimensional point cloud data P.sub.1={p.sub.1, p.sub.2, . . . , p.sub.m} of the overall outer surface of the rotating-body mold is measured through binocular C-Track transformation using MetraScan.

[0061] In this embodiment, as shown in FIG. 3, the step (S2) includes the following steps.

[0062] (S21) A plurality of stations are planned for photogrammetry followed by photographing, where each of the plurality of stations is configured to contain as many marking points as possible. Adjacent stations are configured to contain at least four common marking points.

[0063] (S22) Coding marks in images respectively taken in the plurality of stations are recognized.

[0064] (S23) Images with the same coding mark are subjected to matching. The images are unified into a photogrammetric coordinate system using the coding marks. An exterior orientation element of each image is obtained.

[0065] (S24) Based on known exterior orientation elements of the images, Other non-coding mark points are subjected to correspondence points matching using an epipolar matching method.

[0066] (S25) The three-dimensional coordinates of the marking points are calculated through bundle adjustment to obtain data t.sub.1={t.sub.1_1, t.sub.2_1, . . . , t.sub.n_1} of a total of n marking points in a first pose.

[0067] In this embodiment, the step (S3) is performed through the following step.

The rotating-body mold is rotated and the step (S2) is repeated to shoot and calculate marking point data t.sub.2={t.sub.1_2, t.sub.2_2, . . . , t.sub.n_2}, . . . , t.sub.i={t.sub.1_i, t.sub.2_i, . . . , t.sub.n_i} under different angle poses, where i is the number of poses corresponding to a rotation angle.

[0068] In this embodiment, as shown in FIG. 5, the step (S4) is performed through the following steps.

[0069] (S41) Based on a rigid-body transformation of coding points on a chuck, marking point data is unified under multiple angles into the same coordinate system.

[0070] (S42) A transformation relationship between marking points adjacent to outer surface points under multiple angle poses is calculated to reversely obtain a three-dimensional coordinate of the outer surface under a corresponding pose.

[0071] (S43) The deformation degree of the rotating-body mold is analyzed during the rotation process based on three-dimensional coordinates of the outer surface under multiple angle poses.

[0072] In this embodiment, as shown in FIG. 6, the step (S41) is performed through the following steps.

[0073] (S411) The coding points on cylindrical surfaces of chucks on both sides are recognized in a captured image.

[0074] (S412) Marking point data t.sub.1={t.sub.1_1, t.sub.2_1, . . . , t.sub.n_1} measured for the first time is taken as a reference to calculate a rotation matrix among coordinates of the coding points with the same serial number. The data obtained under different angle poses is subjected to alignment, where the marking point data after alignment are [0075] s.sub.1={s.sub.1_1, s.sub.2_1, . . . , s.sub.n_1}, [0076] s.sub.2={s.sub.1_2, s.sub.2_2, . . . , s.sub.n_2}, . . . , s.sub.i={s.sub.1_i, s.sub.2_i, . . . , s.sub.n_i}; and s.sub.1=t.sub.1.

[0077] In this embodiment, as shown in FIG. 7, the step (S42) is performed through the following steps.

[0078] (S421) k neighboring marking points {(s.sub.1_1, s.sub.2_1, . . . , s.sub.k_1), (s.sub.1_2, s.sub.2_2, . . . , s.sub.k_2), . . . , (s.sub.1_i, s.sub.2_i, . . . , s.sub.k_i)} of outer surface points p.sub.j in an initial station in a marking point data set {s.sub.1, s.sub.2, . . . , s.sub.i} are found.

[0079] (S422) Three-dimensional coordinates of points on the outer surface of the rotating-body mold at a second station is calculated, expressed as p.sub.j_2=p.sub.j_1+(θ.sub.1(s.sub.1_2−s.sub.1_1)+θ.sub.2(s.sub.2_2−s.sub.2_1)+ . . . +θ.sub.k(s.sub.k_2−s.sub.k_1))/k, where θ.sub.k is a weight of each neighboring marking point. The closer the marking point is to p.sub.j_1, the greater its weight is.

[0080] (S423) The step (S422) is repeated to calculate a three-dimensional coordinate set P.sub.1, P.sub.2, . . . , P.sub.i of the outer surface under multiple angle poses.

[0081] In this embodiment, as shown in FIG. 8, the step (S43) is performed through the following steps.

[0082] (S431) A distance between surface points of adjacent stations is calculated, where a distance between P.sub.1 and P.sub.2 is d.sub.1, a distance between P.sub.2 and P.sub.3 is d.sub.2, and so on, and a distance between P.sub.i_1 and P.sub.i is d.sub.i-1. A distance array is expressed as d={d.sub.1, d.sub.2, . . . , d.sub.i-1}.

[0083] (S432) An average value and a variance of the distance array d={d.sub.1, d.sub.2, . . . , d.sub.i-1} are calculated to evaluate the deformation degree of the rotating-body mold.

[0084] Described above are merely preferred embodiments of the disclosure, which are not intended to limit the scope of the application. It should be understood that any replacements, modifications and changes made by those skilled in the art without departing from the spirit of this application shall fall within the scope of this application defined by the appended claims.