Solid rocket engine skirt end face butt joint hole position information detection method

Abstract

The invention discloses a method for detecting position information of a butt joint hole of a skirt end face of a solid rocket engine, and the method comprises the steps: 1, installing a tool on the butt joint hole of the skirt end face, and completing the laser scanning of the skirt end face and a cylinder segment which is about 200mm around the skirt; the tool is conical, the tail end of the tool is provided with threads, the tool can be directly installed on a skirt end face threaded hole, and the axis of the conical face is coaxial with the axis of the threaded hole. 2, performing preliminary optimization on the three-dimensional point cloud model obtained by scanning, then eliminating errors caused by noisy points by using a filtering model combining a system filtering algorithm and a moving least square method, and finally completing overall optimization of the point cloud data; 3, packaging the optimized model by using a triangle principle, carrying out reverse modeling on the packaged three-dimensional model, and extracting to-be-detected data by using the reverse regularized model and the three-dimensional point cloud model; according to the invention, detection of position information of butt joint holes of skirt end surfaces of various models of solid rocket engines including large diameters can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of intelligent detection, and in particular relates to a method for detecting position information of a butt hole on a skirt end face of a solid rocket engine. Background Art

[0002] The docking holes on the skirt end of a solid rocket engine are evenly distributed on the front and rear skirt end surfaces of the solid rocket engine skirt. They play a key role in installing solid rocket engine components and connecting engine stages. The accuracy of the holes affects the performance of the engine to a certain extent.

[0003] Solid rocket engines have a complex structure, and most of the processes are operated by a large number of people, which is very costly. In terms of detection, in the development and production of solid rocket engines, most dimensions are detected by calipers, three-coordinate measuring instruments, laser trackers, etc., and the skirt end of the solid rocket engine faces the docking hole, which plays a key role in the connection. The angle and pitch circle of the skirt end of the engine with a smaller barrel diameter can be detected by three-coordinate measuring after the installation of the tooling, but the cost of using three-coordinate measuring for slightly larger diameters is extremely high and difficult to implement. Usually, such dimensions are usually guaranteed by the process, and sometimes a model is used for trial installation, but there is no effective means to obtain such dimensions.

[0004] At present, the patents that have been applied for involve the reconstruction and intelligent detection of three-dimensional point clouds and internal surfaces and components that are usually solved by solid rockets. For example, Chinese patent application CN202110593376.8 discloses a method for measuring the inner cavity volume of a solid rocket engine, and Chinese patent application CN202311450761.2 discloses a method for detecting metal parts of a solid rocket engine based on three-dimensional laser scanning. Neither of them involves effective detection of surface connection holes of skirt ends of solid rocket engines of various sizes, and the above inventions are difficult to solve the problems described in this article. Summary of the invention

[0005] In view of this, the present invention provides a method for detecting the position information of the butt holes on the skirt end of a solid rocket engine, which can detect the position information of the butt holes on the skirt end of various types of solid rocket engines including those with large diameters.

[0006] The technical solution for implementing the present invention is as follows:

[0007] A method for detecting position information of a butt hole on a skirt end of a solid rocket engine comprises the following steps:

[0008] Step 1: Install the tooling on the butt hole of the skirt end surface, and complete the laser scanning of the skirt end surface and the tube section of about 200mm around the skirt; the tooling is conical, with a thread at the tail end, and can be directly installed on the threaded hole of the skirt end surface, and the axis of the cone surface is coaxial with the axis of the threaded hole;

[0009] Step 2: After preliminary optimization of the 3D point cloud model obtained by scanning, a filtering model combining the system filtering algorithm and the moving least squares method is used to eliminate the errors caused by noise points, and finally complete the overall optimization of the point cloud data;

[0010] Step 3: Encapsulate the optimized model using the triangle principle, perform reverse modeling on the encapsulated 3D model, and use the reversed regularized model and the 3D point cloud model to extract the data to be tested.

[0011] Furthermore, in step one, the position of the tracker used for laser scanning is determined according to the diameter of the solid rocket engine. When the diameter is less than 1m, the tracker is 3m away from the front skirt. When the diameter is between 1m and 2m, the tracker is 4m away from the front skirt. When the diameter is greater than 2m, dual trackers are used, and the tracker is 4m away from the front skirt. The center viewpoint of the tracker coincides with the center of the solid engine skirt end surface. During scanning, the barrel section at least 200mm from the skirt end surface is completely scanned.

[0012] Furthermore, the system filtering algorithm first needs to use the kd-tree structure to perform point cloud topology and establish a k-nearest neighbor neighborhood set, and then remove the coarse error points of the point cloud set through statistical filtering. In order to eliminate small errors and improve the accuracy of the cone structure, the system uses the moving least squares method after filtering to smooth the noise points confused in the point cloud, and finally achieve overall point cloud optimization.

[0013] Furthermore, in the reverse modeling process in step three, the optimized point cloud data is first meshed, and then the skirt end face, the 200 mm shell barrel section and the skirt end face are modeled using reverse technology, and other areas do not need to be modeled.

[0014] Furthermore, the optimized point cloud model is aligned with the reverse modeling model. The 200mm barrel section and the skirt end face are used as the reference for alignment. Then, the corresponding features related to the three-dimensional point cloud are extracted through the various features on the reverse three-dimensional model for size extraction, so as to achieve rapid detection of the empty position information of the skirt end face of the solid rocket engine.

[0015] Beneficial effects:

[0016] 1. The present invention can efficiently and accurately extract spatial information such as the spatial angle and pitch circle of the solid rocket engine skirt end surface butt hole, and can cover rocket engines with diameters ranging from hundreds of millimeters to thousands of millimeters. The present invention has a fast detection speed and a wide coverage range.

[0017] 2. The only hardware equipment required for the present invention is a laser scanner, and this type of laser scanner can be used in a mobile manner, has flexible usage scenarios, and is low in cost. It does not require the high cost of a large three-coordinate measuring machine, and does not require the construction of a separate testing room with a harsh environment.

[0018] 3. The detection method described in the present invention can be carried out at the solid rocket engine assembly site, which can avoid the extra manpower, material resources and time caused by transportation, and has a high tolerance for environmental requirements, and can be carried out in many occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of the method for detecting the position information of the butt hole on the skirt end of a solid rocket engine. DETAILED DESCRIPTION

[0020] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0021] The present invention provides a method for detecting position information of a butt hole on a skirt end of a solid rocket engine. Figure 1 This is a flow chart of a method for detecting the position information of the docking holes on the skirt end of a solid rocket engine. The detection method specifically includes tooling preparation, engine status confirmation, scanner preparation, tooling installation, scanner placement, scanning of the area to be scanned, completion of scanning, preliminary data optimization, point cloud optimization based on system filtering, reverse modeling, and data extraction.

[0022] Based on the confirmation of the engine status, before implementing the entire detection method, it is necessary to confirm the solid rocket engine's placement position, diameter, docking hole diameter, surrounding environment and other conditions to ensure the preparation of the tooling, the preparation and placement of the scanner. The tooling preparation described in the present invention includes the design of the tooling, and the design and manufacture of special tooling according to the solid engine diameter and the size of the docking hole on the skirt end face (the tooling needs to be designed for the first time, and the subsequent detection of the same or similar models can directly use this set of tooling). The tooling is conical, and the diameter of the large end of the cone is one percent of the diameter of the barrel section. The tail end is threaded and can be directly installed on the threaded hole on the skirt end face. The axis of the cone is coaxial with the axis of the threaded hole, and the axial extraction of the threaded hole can be converted into the extraction of the cone axis.

[0023] After the tooling is fully prepared, it can be installed directly and installed on the docking hole of the skirt end face of the solid rocket engine. After the engine status is confirmed, the scanner can be prepared and placed. At this time, the laser scanner tracker can be placed at the front and rear skirts of the engine. When the engine diameter is less than 1m, the tracker is 3m away from the front skirt. When the diameter is between 1m and 2m, the tracker is 4m away from the front skirt. When the diameter is greater than 2m, a double tracker is used, and the tracker is 4m away from the front skirt. The center viewpoint of the tracker should coincide with the center of the end face of the solid engine skirt. Therefore, when the engine is placed higher or lower, the tracker angle should be set reasonably to meet the above requirements. The steps for scanning the rear skirt are the same as those for the front skirt.

[0024] After completing the preliminary preparations, further scan the parts to be scanned, and completely scan the point clouds of the front skirt and the barrel section about 200mm away from the front skirt. The tooling on the threaded hole needs to be completely scanned. The point cloud file required for this invention requires the end face of the engine skirt, the barrel section 200mm away from the skirt end face, and the tooling installed on the skirt end face docking hole. After completing the scanning of the point clouds of the above parts, delete the redundant point clouds, and use the scanning software system to preliminarily optimize the data. When scanning large-sized objects, many noise points will be generated on the surface of the point cloud model, especially at the junction of the two surfaces. The filtering model based on the combination of the system filtering algorithm and the moving least squares method can solve this problem to a large extent. The point cloud data is encapsulated using the principle of triangulation to form a grid file, and the grid file is used for reverse modeling. During modeling, the length of the barrel section is defined as 200mm, and the skirt end face and the tooling installed on the end face are reverse modeled according to the actual shape of the point cloud.

[0025] The optimized point cloud model is aligned with the reverse modeling model, and the 200mm barrel section and the skirt end face are used as the reference for alignment. Then, the corresponding features related to the 3D point cloud are extracted through each feature on the reverse 3D model for size extraction, so as to achieve rapid detection of the solid rocket motor skirt end face butt position information. After the reverse model and the point cloud model are aligned, data can be automatically extracted to improve efficiency.

[0026] The present invention realizes the detection of the position information of the docking holes on the skirt end faces of various types of solid rocket engines, including those with large diameters, through tooling design, scanning process writing, optimization of point cloud filtering algorithm, and reverse modeling of the model. Experimental verification and practical application have shown that the present invention can quickly and accurately detect the position information of the docking holes on the skirt end faces of various types of solid rocket engines, including the pitch circle diameter, the angle between each threaded hole, the angle between the threaded hole and the quadrant line, etc. The detection accuracy meets the design requirements, and the detection efficiency of the docking hole position information on the skirt end faces of small-diameter solid rocket engines is improved by more than five times, achieving a breakthrough in the detection of the docking hole position information on the skirt end faces of large-diameter solid rocket engines from process assurance to quantitative detection.

[0027] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting position information of a butt hole on a skirt end of a solid rocket engine, characterized in that: The following steps are involved: Step 1: Install the tooling on the butt hole of the skirt end surface, and complete the laser scanning of the skirt end surface and the tube section of about 200mm around the skirt; the tooling is conical, with a thread at the tail end, and can be directly installed on the threaded hole of the skirt end surface, and the axis of the cone surface is coaxial with the axis of the threaded hole; Step 2: After preliminary optimization of the 3D point cloud model obtained by scanning, a filtering model combining the system filtering algorithm and the moving least squares method is used to eliminate the errors caused by noise points, and finally complete the overall optimization of the point cloud data; Step 3: Encapsulate the optimized model using the triangle principle, perform reverse modeling on the encapsulated 3D model, and use the reversed regularized model and the 3D point cloud model to extract the data to be tested.

2. The method for detecting the position information of the butt hole of the skirt end of a solid rocket engine according to claim 1, characterized in that: In step one, the position of the tracker used for laser scanning depends on the diameter of the solid rocket engine. When the diameter is less than 1m, the tracker is 3m away from the front skirt. When the diameter is between 1m and 2m, the tracker is 4m away from the front skirt. When the diameter is greater than 2m, dual trackers are used, and the tracker is 4m away from the front skirt. The center viewpoint of the tracker coincides with the center of the solid engine skirt end surface. When scanning, the barrel section at least 200mm from the skirt end surface is completely scanned.

3. The method for detecting the position information of the butt hole of the skirt end of a solid rocket engine according to claim 1, characterized in that: The system filtering algorithm first needs to use the kd-tree structure to perform point cloud topology and establish a k-nearest neighbor neighborhood set, and then remove the coarse error points of the point cloud set through statistical filtering. In order to eliminate small errors and improve the accuracy of the cone structure, the system uses the moving least squares method after filtering to smooth the noise points confused in the point cloud, and finally achieve overall point cloud optimization.

4. The method for detecting the position information of the butt hole of the skirt end of a solid rocket engine according to claim 2 or 3, characterized in that: During the reverse modeling process in step three, the optimized point cloud data is first meshed, and then the skirt end face, 200mm shell section and skirt end face are modeled using reverse technology. No other areas need to be modeled.

5. The method for detecting the position information of the butt hole of the skirt end of a solid rocket motor as claimed in claim 4, characterized in that: The optimized point cloud model is aligned with the reverse modeling model, and the 200mm barrel section and the skirt end face are used as the reference for alignment. Then, the corresponding features related to the 3D point cloud are extracted through the various features on the reverse 3D model for size extraction, so as to achieve rapid detection of the solid rocket engine skirt end face docking position information.

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