A method for measuring the bore diameter of a gun barrel

Abstract

This invention provides a method for measuring the bore caliber of a gun barrel. The specific process is as follows: Based on the inner wall contour image of a standard ring gauge, a three-dimensional laser point cloud of the standard ring gauge is obtained; a point P is randomly selected in the three-dimensional laser point cloud, and multiple planes containing point P are created to intersect the three-dimensional laser point cloud; for each intersecting elliptical cross-section, the point with the largest distance from point P is selected, and multiple selected points form a point set N; the point with the smallest distance from point P in the point set N is obtained, and the smallest distance is used as the pixel distance of the standard ring gauge, and the physical distance corresponding to a single pixel is calculated; based on the bore image of the gun barrel, its three-dimensional laser point cloud is obtained, and the point cloud of the plane containing the point with the smallest distance in the bore image of the gun barrel is obtained for curve fitting, and the diameter of the inscribed circle of the curve is calculated; based on the physical distance corresponding to a single pixel and the pixel diameter of the inscribed circle of the bore, the inner diameter of the bore is calculated, thereby realizing the measurement of the bore caliber.

Description

Technical Field

[0001] This invention relates to a method for measuring the bore diameter of a gun barrel, belonging to the field of weapon design measurement technology. Background Technology

[0002] With the rapid development of electromagnetic rail technology, the online measurement methods based on the internal surface structure dimensions of electromagnetic rail launchers have not yet been discussed and studied in depth. Equivalent evaluation methods for characteristic parameters such as the transverse diameter and axial straightness of the irregular, non-referenced internal cavity structure of electromagnetic rail launchers need to be developed to meet the needs of life assessment and engineering design of electromagnetic rail launcher tubes.

[0003] In the assessment and diagnosis of damage to elongated cavities, inner diameter measurement is one of the important indicators for evaluating their structural errors. Measuring the internal geometry parameters mainly involves measuring the three-dimensional dimensions and structure of the barrel, providing a basis for quality control before shipment. During use, periodic inspection of the barrel's inner diameter can assess its lifespan and ensure safety. Therefore, it is necessary to study the diagnostic assessment of the inner surface diameter of elongated cavities with large length-to-diameter ratios, such as electromagnetic railguns, and to propose an efficient, high-precision, and simple method for measuring and assessing the inner diameter of elongated cavities.

[0004] Quantitative measurement of internal diameter can be categorized into contact measurement and non-contact measurement based on whether the probe of the measuring device directly contacts the internal cavity. Contact measurement is mainly used for static testing of various types of artillery, with representative devices including coordinate measuring machines (CMMs) and mechanical star-shaped diameter gauges. Non-contact measurement is primarily based on photoelectric principles, with optical measurement methods including optical star-shaped diameter gauges, optical triangulation, binocular intersection measurement, optical sectioning, phase measurement, and digital holography. Contact measurement is generally less efficient and may cause additional damage to the internal surface of the cavity. The development of photoelectric technology in non-contact measurement methods has greatly enriched traditional internal cavity detection methods, and CCD sensors are widely used in the field of non-contact internal cavity measurement.

[0005] Chinese patent application CN202010732339.6 discloses a method and apparatus for measuring the rifling inner diameter of a gun barrel. The method utilizes an image acquisition device to capture images of the emitted light spots of an indicator optical fiber moving along the barrel's axial direction. The barrel's inner diameter is then measured using image processing and fitting algorithms. The measuring apparatus mainly includes a measuring vehicle unit, a control computer, and a measuring control box. The measuring vehicle unit is installed inside the barrel and can move within it. It is equipped with an image acquisition device, a light source, and an indicator optical fiber. The image acquisition device captures images of the emitted light spots of the indicator optical fiber. However, this method uses a mechanical contact measurement method, which can cause some damage to the inner wall of the barrel, resulting in a relatively large measurement error.

[0006] Chinese patent application publication number CN202310301696.0 discloses a method for detecting the diameter of a gun barrel. This method requires adjusting the barrel angle to ensure a horizontal arrangement, installing a gun inner diameter measuring instrument, and using displacement and tilt sensors to collect the axial displacement length of the top column. The axial displacement length is then calculated, processed, and converted to determine the corresponding gun inner diameter. The measuring instrument is pushed along the gun's axial direction by a push rod, and the inner diameter at various locations within the gun is recorded and displayed in real time via a display module. However, this invention involves a bulky measuring device and a complex measurement method.

[0007] Currently, there are very few practical devices and mature methods for measuring the inner diameter of electromagnetic rail launcher tubes. Existing methods are cumbersome to operate and have low measurement accuracy. There is an urgent need for a flexible, fast, and efficient method for measuring the inner diameter of launcher tubes. Summary of the Invention

[0008] To achieve the above objectives, the present invention provides a method for measuring the bore diameter of a gun barrel. This method involves selecting a point cloud plane and then performing curve fitting to ultimately measure the bore diameter. This method is applicable to the measurement of bore diameters of various internal cavities with large length-to-diameter ratios, such as electromagnetic launcher barrels, gun barrels, and narrow pipes.

[0009] The technical solution for implementing the present invention is as follows:

[0010] A method for measuring the bore caliber of a gun barrel, the specific process of which is as follows:

[0011] I. Obtain the three-dimensional laser point cloud of the standard ring gauge based on the inner wall contour image of the standard ring gauge;

[0012] 2. Take any point P in the three-dimensional laser point cloud, and create multiple planes containing point P that intersect with the three-dimensional laser point cloud; for each intersecting elliptical cross section, select the point with the largest distance from point P, and the multiple selected points form a point set N; obtain the point with the smallest distance from point P in the point set N, use the smallest distance as the pixel distance of the standard ring gauge, and calculate the physical actual distance corresponding to a single pixel;

[0013] III. Obtain the three-dimensional laser point cloud based on the image of the gun barrel bore;

[0014] Fourth, based on the three-dimensional laser point cloud, obtain the point with the minimum distance in the barrel bore image according to the method in step two, perform curve fitting on the point cloud of the plane where the minimum distance point is located, and calculate the diameter of the inscribed circle of the curve.

[0015] 5. Based on the actual physical distance corresponding to the single pixel and the diameter of the inner circle pixel of the bore, calculate the inner diameter of the barrel bore, thereby realizing the measurement of the bore diameter.

[0016] Furthermore, the standard ring gauge inner wall contour image and the gun barrel inner bore image of the present invention are captured by a high-resolution camera. The standard ring gauge and the gun barrel inner bore are fixed in the same position on the camera worktable, and the camera moves along the same path during the shooting.

[0017] Furthermore, the process of obtaining the three-dimensional laser point cloud of the standard ring gauge described in this invention is as follows: first, the image captured by the camera is distorted, then noise reduction filtering and grayscale binarization are performed, then pixel threshold determination is performed, that is, the point cloud of the illuminated area is extracted by a preset threshold, and finally, three-dimensional point cloud modeling is performed based on the extracted point cloud.

[0018] Furthermore, the specific process of step two in this invention is as follows:

[0019] 201. Take any point P in the three-dimensional laser point cloud of the standard ring gauge, and construct any plane containing the point. The intersection of the plane with the three-dimensional laser point cloud array will result in an elliptical cross section.

[0020] 202. Select the points on the elliptical cross section that are furthest from the initially chosen point P, and use them as a subset for later use;

[0021] 203. Repeat steps 201 and 202 multiple times to summarize all spare subsets into a total set N;

[0022] 204. In the summative set N, select the point with the smallest distance from the initial randomly selected point, and take the smallest distance as the pixel distance of the inner diameter of the measured standard ring gauge.

[0023] 205. Based on the known inner diameter of the standard ring gauge and the distance between its measured pixels, calculate the actual physical distance corresponding to a single pixel.

[0024] Furthermore, the present invention sets the size of the total set N, and stops repeating steps 201 and 202 when the number of spare subsets reaches N.

[0025] Furthermore, in this invention, the physical distance d corresponding to a single pixel is defined, and the inner diameter R for calculating the bore caliber of the gun barrel is defined as follows:

[0026] R = R p *d

[0027] Among them, R p It is the pixel diameter of the inscribed circle inside the barrel.

[0028] Beneficial effects:

[0029] First, this invention uses a standard ring gauge as a reference to calculate the actual physical distance corresponding to a single pixel. Through multiple distance calculations, curve fitting is performed based on the calculation results to calculate the diameter of the inscribed circle of the curve, thereby realizing the measurement of the bore diameter. This method is applicable to the measurement of the bore diameter of various bore cavities with large length-to-diameter ratios, such as electromagnetic launcher barrels, artillery barrels, and narrow pipes.

[0030] Secondly, based on the model of three-dimensional cloud point data of the inner bore of an electromagnetic orbital launcher, this invention proposes a definition of the diameter of the irregular cavity of the launcher and provides a new method for measuring the diameter of the inner cavity of the launcher. This method involves taking any point P in the three-dimensional laser point cloud and creating multiple planes containing point P that intersect with the three-dimensional laser point cloud. For each intersecting elliptical cross section, the point with the largest distance from point P is selected, and multiple selected points form a point set N. The point with the smallest distance from point P in the point set N is obtained, and the plane point cloud containing the point with the smallest distance is subjected to curve fitting, and the diameter of the inscribed circle of the curve is calculated. This method can achieve online measurement of the inner cavity parameters of the launcher without the need for multi-axis precise coincidence required by conventional inner diameter measurement.

[0031] Third, the measurement method of this invention is simple and easy to implement, the measurement process is flexible and efficient, it is highly practical, and has a wide range of application prospects.

[0032] Fourth, based on a model using three-dimensional cloud point data of the bore of an electromagnetic railgun, a definition of the aperture of an irregular cavity in an electromagnetic railgun is proposed, and a new method for measuring the aperture of the launcher's bore is given. This method can solve the problem of multi-axis coincidence assumptions in the diagnostic measurement methods of the bore of electromagnetic railguns or traditional artillery, and has significant application value in electromagnetic railguns of various sizes and platforms, as well as in various artillery equipment. Attached Figure Description

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] Figure 1 This is a schematic flowchart of a method for measuring the bore diameter of an electromagnetic rail launcher provided by the present invention.

[0035] Figure 2 In the method for measuring the bore diameter of an electromagnetic orbiter provided by the present invention, a schematic diagram of an elliptical cross section obtained by intersecting a plane at any point P in the point cloud with the original point cloud array is provided.

[0036] Figure 3 This invention provides a method for measuring the bore diameter of an electromagnetic launcher, which includes a schematic diagram of curve fitting and inscribed circle calculation of the irregular point cloud cross-section of the electromagnetic launcher's inner cavity. Detailed Implementation

[0037] To better describe the purpose and advantages of the present invention, the invention will be further elaborated below in conjunction with the accompanying drawings and implementation process.

[0038] This invention provides a method for measuring the bore caliber of a gun barrel, such as... Figure 1 As shown, the method includes the following steps:

[0039] Step 1: Obtain the 3D laser point cloud of the standard ring gauge based on the inner wall contour image of the standard ring gauge;

[0040] The inner wall contour image of a standard ring gauge with a known inner diameter, captured by a high-resolution camera, is used as the processing object. The three-dimensional laser point cloud of the standard ring gauge with a known inner diameter is obtained through image processing. Based on the three-dimensional point cloud model of the standard ring gauge with a known inner diameter, it is used as a processing object to perform subsequent steps.

[0041] The above-mentioned 3D point cloud model generation process is as follows: The standard ring gauge inner wall contour image is processed to extract the point cloud coordinate model. This image processing method is mature and reliable, and has been verified through extensive testing. The image processing flow includes image input, distortion correction, noise reduction filtering, grayscale binarization, pixel threshold determination, and 3D point cloud modeling. Distortion correction uses the Zhang Zhengyou calibration method, noise reduction filtering uses Gaussian filtering, grayscale binarization is achieved by converting the color image to a grayscale image, and pixel threshold determination is performed by extracting the point cloud of the illuminated area using a preset threshold.

[0042] Step 2: Take any point P(x,y) in the 3D laser point cloud of the standard ring gauge. Construct a plane Ax + By + C = 0 containing point P. The plane intersects this plane with the 3D laser point cloud array of the standard ring gauge to obtain an elliptical cross-section. All points on this cross-section form a set M, as shown below. Figure 2 As shown.

[0043] Step 3: Calculate the distance between all points in set M and point P, and select the point Q on the elliptical cross-section that has the largest distance from point P. i (x i ,y i ), calculate the maximum distance D i Add to set N i ,like Figure 2 As shown.

[0044] In this step, the point with the largest distance from point P is selected from set M. This is to determine the major axis length of the elliptical cross-section of any point cloud passing through point P. The distance between point P and the point in set M with the largest distance from P is the major axis length of the elliptical cross-section. The larger the major axis distance, the larger the angle between the selected elliptical cross-section and the ideal cross-section (i.e., the inner bore diameter cross-section); the smaller the major axis distance, the smaller the angle between the selected elliptical cross-section and the ideal cross-section (i.e., the inner bore diameter cross-section). When the angle approaches 0, the major axis distance of the elliptical cross-section is approximately equal to the diameter of the inner bore diameter cross-section.

[0045] Step 4: Repeat steps 2 and 3. The number of repetitions is set according to actual needs. The more iterations, the greater the accuracy of the final result. Apply this to all subsets N. i The total set N is obtained by induction.

[0046] Each repetition of steps two and three in this process is equivalent to re-selecting an ellipse for calculation, resulting in multiple repetitions of selection.

[0047] Step 5: In set N, select the point Q that has the smallest distance from the initially chosen point P. min The corresponding minimum distance D min The pixel distance is used as the inner diameter of the measured standard ring gauge.

[0048]

[0049] Step 6: Using the known inner diameter G of the standard ring gauge and the measured pixel distance D... min Find the physical distance d corresponding to a single pixel.

[0050] d = G / D min

[0051] Step 7: Obtain the three-dimensional laser point cloud based on the image of the gun barrel bore;

[0052] In this embodiment, the gun barrel is an electromagnetic railgun. The inner wall contour image of the electromagnetic railgun, captured by a high-resolution camera, is used as the processing object. Existing techniques are employed for image processing (including distortion correction, filtering and noise reduction, grayscale binarization, pixel thresholding, and 3D point cloud modeling) to obtain the 3D laser point cloud of the electromagnetic railgun's inner cavity. The 3D laser point cloud of the electromagnetic railgun's inner cavity is used as another processing object in this embodiment.

[0053] Step 8: Based on the three-dimensional laser point cloud of the electromagnetic rail launcher, following the steps 2 to 5, obtain the point with the minimum distance in the inner cavity image of the electromagnetic rail launcher, that is, obtain the point cloud model of the irregular cross section of the launcher cavity.

[0054] Step 9: Perform curve fitting on the point cloud of the irregular cross-section of the inner cavity to obtain the fitting curve of the transmitter's inner cavity insulation support and track, and calculate the inscribed circle A, i.e., the pixel diameter R of the inscribed circle. p ,like Figure 3 As shown.

[0055] Currently, in military standards, the diameter of the irregular cross-section of an electromagnetic railgun's bore is conventionally defined as the diameter of the largest inscribed circle within that cross-section. This invention adopts this definition, using the diameter of the largest inscribed circle from the fitted curve of the irregular cross-section as the launcher's bore size.

[0056] Step 10: Obtain the pixel diameter R of the inscribed circle within the electromagnetic transmitter cavity obtained in Step 9. p The actual physical distance d corresponding to a single pixel obtained in step six can be used to obtain the true physical distance R of the electromagnetic orbiter's aperture.

[0057] R = R p *d

[0058] This application provides a method for measuring the inner bore diameter of an electromagnetic rail launcher based on a 3D modeling point cloud of the inner bore. Combining image processing and 3D point cloud extraction techniques, the pixel distance of the inner diameter is calculated from the acquired 3D modeling point cloud. Then, the inner diameter is measured using a standard ring gauge with a known diameter to obtain the physical distance corresponding to each pixel. Finally, the inner diameter of the electromagnetic rail launcher is calculated by fitting and inscribed in a circle.

[0059] As an improvement to the method for measuring the bore diameter of an electromagnetic orbital launcher according to the present invention, the smaller the axial distance of the collected launcher bore profile section, the denser the processed laser point cloud, and the higher the accuracy of the final bore diameter. Furthermore, the image processing algorithm can be improved to obtain a more accurate point cloud model, and the subsequent curve fitting and inscribed circle fitting algorithms can be iteratively optimized.

[0060] As another improvement to the method for measuring the bore diameter of an electromagnetic rail launcher according to the present invention, the method can also utilize three-dimensional point cloud models of several standard ring gauges with known different inner diameters to evaluate the uncertainty of the bore diameter measurement of the electromagnetic rail launcher in reverse. The physical actual distances corresponding to single pixels in the point cloud models of several standard ring gauges with known different inner diameters are compared, and the standard deviation of their measured values ​​is used as the evaluation metric for the bore diameter measurement uncertainty.

[0061] This invention provides a method for measuring the inner bore diameter of an electromagnetic rail launcher. This method can measure the inner bore diameter of the launcher based on the three-dimensional laser point cloud of the inner bore image. This method does not require the triaxial coincidence assumption required by traditional inner bore measurement. The measurement method is simple and easy to implement. It can effectively measure the pixel size and actual physical size of the inner bore diameter of the electromagnetic rail launcher. It is suitable for post-processing of images containing the inner bore cavity contour obtained by image acquisition equipment, and there are no specific restrictions on the shape and contour of the inner bore cavity.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that improvements or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0064] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring the bore caliber of a gun barrel, characterized in that, The specific process is as follows: I. Obtain the three-dimensional laser point cloud of the standard ring gauge based on the inner wall contour image of the standard ring gauge; 2. Take any point P in the three-dimensional laser point cloud, and create multiple planes containing point P that intersect with the three-dimensional laser point cloud; For each intersecting elliptical cross section, select the point with the largest distance from point P, and multiple selected points form a point set N; obtain the point with the smallest distance from point P in the point set N, use the smallest distance as the pixel distance of the standard ring gauge, and calculate the physical actual distance corresponding to a single pixel. III. Obtain the three-dimensional laser point cloud based on the image of the gun barrel bore; Fourth, based on the three-dimensional laser point cloud, obtain the point with the minimum distance in the barrel bore image according to the method in step two, perform curve fitting on the point cloud of the plane where the minimum distance point is located, and calculate the pixel diameter of the inscribed circle of the curve.

5. Based on the actual physical distance corresponding to the single pixel and the diameter of the inner circle pixel of the bore, calculate the inner diameter of the barrel bore, thereby realizing the measurement of the bore diameter.

2. The method for measuring the bore diameter of a gun barrel according to claim 1, characterized in that, The standard ring gauge inner wall contour image and the gun barrel inner bore image were captured using a high-resolution camera. The standard ring gauge and the gun barrel inner bore were fixed in the same position on the camera worktable, and the camera moved along the same path during the shooting.

3. The method for measuring the bore diameter of a gun barrel according to claim 1, characterized in that, The process of obtaining the three-dimensional laser point cloud of the standard ring gauge is as follows: First, the image captured by the camera is distorted, then noise reduction filtering and grayscale binarization are performed, then pixel threshold determination is performed, that is, the point cloud of the illuminated area is extracted by a preset threshold, and finally three-dimensional point cloud modeling is performed based on the extracted point cloud.

4. The method for measuring the bore diameter of a gun barrel according to any one of claims 1-3, characterized in that, The specific process of step two is as follows:

201. Take any point P in the three-dimensional laser point cloud of the standard ring gauge, and construct any plane containing the point. The intersection of the plane with the three-dimensional laser point cloud array will result in an elliptical cross section.

202. Select the points on the elliptical cross section that are furthest from the initially chosen point P, and use them as a subset for later use; 203. Repeat steps 201 and 202 multiple times to summarize all spare subsets into a total set N; 204. In the summative set N, select the point with the smallest distance from the initial randomly selected point, and take the smallest distance as the pixel distance of the measured standard ring gauge inner diameter; 205. Based on the known inner diameter of the standard ring gauge and the distance between its measured pixels, calculate the actual physical distance corresponding to a single pixel.

5. The method for measuring the bore diameter of a gun barrel according to claim 4, characterized in that, Set the size of the total set N. When the number of spare subsets reaches N, stop repeating steps 201 and 202.

6. The method for measuring the bore diameter of a gun barrel according to claim 4, characterized in that, Let the physical distance d corresponding to a single pixel be defined, and let the inner diameter R for calculating the bore diameter of the gun barrel be defined as follows: R=R p *d Among them, R p It is the pixel diameter of the inscribed circle inside the barrel.

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