Dynamic measurement system for lunar soil erosion process based on structured light image

Abstract

The invention discloses a lunar soil erosion process dynamic measurement system based on a structured light image, and relates to the technical field of spaceflight measurement, and the lunar soil erosion process dynamic measurement system comprises an experiment spray pipe, a simulated lunar soil container, simulated lunar soil, a structured light projector, a high-speed camera and an image calibration device; the upstream of the experimental spray pipe is connected with a gas cylinder outside the vacuum cabin through a conveying pipeline, the simulated lunar soil container comprises a side wall surface wedge, the simulated lunar soil is located in the simulated lunar soil container, the structured light projector is used for accurately projecting coded light stripe patterns onto the surface of a pit, the high-speed camera is installed above the side wall surface wedge, and the high-speed camera is connected with the simulated lunar soil container. The camera is used for shooting stripe light images of the pit surface. The whole process is recorded by using the camera, the detailed rule of pit evolution can be extracted by analyzing the radial and depth changes of the stripes on the pit surface, the image is calibrated before the experiment, quantitative analysis of the pit surface stripe image can be realized, and accurate erosion process data can be provided.

Description

Technical Field

[0001] The present invention relates to the field of aerospace measurement technology, and in particular to a dynamic measurement system for lunar soil erosion process based on structured light images. Background Art

[0002] The interaction between plumes and lunar dust has an important impact on manned space engineering, especially during the landing and takeoff phases on the lunar surface. During the landing and takeoff process of the lander, the operation of the engine forms a plume, which will have a strong comprehensive effect on the lander body through expansion and diffusion. Due to the erosion of the plume, pits will appear on the lunar surface, which may destroy the morphology of the landing support surface and threaten the stability of the lander. In addition, the reflection effect between the plume and the lunar surface becomes complicated, making the evaluation of thermal protection more difficult. Through ground simulation tests, the dynamic erosion process of the lunar surface when the engine is working can be reproduced more accurately, providing experimental results with high reference value. This not only provides a direct reference basis for the project, but also provides the necessary input conditions for the establishment and verification of the simulation model;

[0003] In previous experiments on the simulation of the evolution of lunar craters, visible light cameras were usually used to record in real time the dynamic process of crater formation when the engine was working. However, the images obtained from these experiments were mainly used for qualitative analysis, because it is difficult to use effective technical means to quantify the erosion process of the lunar soil. A major difficulty is that lunar dust images are weak texture images, and it is difficult to extract effective depth information from the images taken in the experiment. In addition, the lunar dust particles stirred up by the engine plume field diffused between the crater and the camera, causing the crater morphology to be obscured by the lunar dust, thereby reducing the clarity of the crater surface image obtained by the camera. In this regard, we proposed a dynamic measurement system for the lunar soil erosion process based on structured light images. Summary of the invention

[0004] The purpose of the present invention is to provide a dynamic measurement system of lunar soil erosion process based on structured light images to solve the problems raised in the above-mentioned background technology.

[0005] A dynamic measurement system for lunar soil erosion process based on structured light images, comprising: an experimental nozzle, a simulated lunar soil container, simulated lunar soil, a structured light projector, a high-speed camera and an image calibration device;

[0006] The upstream of the experimental nozzle is connected to the gas cylinder outside the vacuum chamber through a delivery pipeline. The simulated lunar soil container includes a side wall wedge, and the simulated lunar soil is located inside the simulated lunar soil container. The structured light projector is used to accurately project the encoded light stripe pattern onto the pit surface. The high-speed camera is installed above the side wall wedge to capture the stripe light image of the pit surface and record the evolution of the light pattern on the object surface. The image calibration device is used to calibrate the camera image taken obliquely above before the experiment. A fixed-pitch grid is set on the side of the image calibration device. The fixed-pitch grid defines the coordinate system of the calibration point. The position and spacing of the grid points are known and are used as a reference for image correction.

[0007] Preferably, during the experiment of the experimental nozzle, the gas is accelerated through the delivery pipeline, and the jet expands in a vacuum environment, simulating the plume field distribution under real conditions.

[0008] Preferably, the simulated lunar soil container is made of acrylic material, which is transparent and can be clearly observed by the staff. At the same time, acrylic material is safe, durable, weather-resistant and radiation-resistant, and can be used for a long time. The tip of the side wall wedge coincides with the central cross-section of the engine, reducing the interference of the plume field on the container wall. Based on the guiding effect of the side wall wedge, the half pit formed by the lunar soil under the action of the plume is close to the complete pit shape in the actual environment.

[0009] Preferably, the simulated lunar soil is placed in a simulated lunar soil container to simulate lunar dust and is compacted. During the experiment, the plume generated by the experimental nozzle acts on the surface of the simulated lunar dust to simulate the dust reaction in a real lunar environment. The plume forms an approximately circular erosion pit on the simulated lunar dust.

[0010] Preferably, the coded stripe pattern projected by the structured light projector is encoded in the vertical direction, that is, the stripe pattern is projected horizontally, and the color of the stripe pattern changes only in the vertical direction. During the encoding process, each stripe color corresponds to the depth of the pit one by one, ensuring that the colors of stripes at different depths are unique and non-repetitive. During the actual measurement process, the positions of stripes of different colors on the surface of the pit are analyzed to accurately determine the depth information of the pit, thereby achieving a detailed analysis of the pit morphology.

[0011] Preferably, the high-speed camera can capture the stripe changes at every moment during the dynamic erosion process, and calculate the three-dimensional coordinates of the object surface based on a mathematical algorithm by analyzing the deformation degree and shape change of the pattern, thereby reconstructing the three-dimensional shape of the object and providing detailed three-dimensional data.

[0012] Preferably, before the experiment begins, the image calibration device is installed at the same position as in the formal experiment to obtain the target image to be calibrated, and a fixed-pitch grid is used as a reference for image correction. After the initial calibration image is obtained, a calibration grid is defined, and the grid matches the fixed-pitch grid of the calibration device. Through image matching, the grid points in the actual captured image are matched one-to-one with the defined calibration grid points to generate a transformation grid. The lunar erosion process obtained during the experiment is corrected by using the generated transformation grid to correct the captured image. The depth of the pit and the erosion radius information at different depths are obtained through the corrected image.

[0013] Preferably, when a specific grating pattern or stripes is projected onto the surface of an object, when the shape of the surface of the object changes, the stripes will be deformed. By analyzing the deformation of the stripes, the depth information of the surface of the object is calculated. The sinusoidal stripe projection calculation is adopted. Assume that the light intensity distribution function of the projected sinusoidal stripes is:

[0014] I(x,y)=A(x,y)+B(x,y)cos(φ(x,y))

[0015] Among them, A(x, y) is the background light intensity, B(x, y) is the contrast of the stripes, and φ(x, y) is the phase information. After the stripes are deformed on the surface of the object, the phase information of the deformed stripes captured by the camera will change. The four-step phase shift method is used, and the phase difference of each phase shift is π / 2. Four phase-shifted images are obtained, and the phase is calculated:

[0016]

[0017] Among them, I1, I2, I3 and I4 are the light intensities of the four phase-shifted images respectively. After obtaining the phase information, the depth value Z of each point on the object surface is calculated according to the calibration parameters of the system and the relationship between phase and depth. Combined with the calibration parameters of the camera's pixel coordinates, the three-dimensional coordinates of the object surface are obtained.

[0018] Preferably, the structured light projector fringe pattern is projected in a horizontal direction, and a high-precision image acquisition device is used to photograph the pit surface on which the coded stripe pattern is projected to obtain clear and complete image data. The acquired image is processed based on an image processing algorithm and analysis software to accurately identify the color information of the stripes at various positions on the pit surface.

[0019] Preferably, the light transmittance of the acrylic material is greater than 92%. When the plume is ejected and rushes towards the lunar soil with energy, the lunar soil particles are originally in a relatively disordered state. Under the impetus of the plume impact force, they move, roll and rearrange themselves. The existence of the oblique split of the side wall changes the natural diffusion path of the lunar soil particles, so that under the guidance of the oblique split slope, they gather and accumulate in an orderly manner in a specific direction, gradually forming the prototypes of pits of various shapes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention utilizes a programmable projector to project a striped light beam from the side of a lunar soil container. Stripes of different heights appear in different colors. When the engine is working, the center of the nozzle coincides with the side wall of the lunar dust to form a semi-pit. The striped light beam projected from the side will be projected onto the inner wall of the pit. As erosion proceeds, pits of different depths will be illuminated by stripes of different colors. The camera records the entire process. By analyzing the radial and depth changes of the stripes on the pit surface, the detailed laws of the pit evolution can be extracted. The image is calibrated before the experiment, which can realize quantitative analysis of the stripe image on the pit surface and provide accurate erosion process data. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 Schematic diagram of the image correction device.

[0024] In the figure: 1. Experimental nozzle; 2. Simulated lunar soil container; 3. Simulated lunar soil; 4. Structured light projector; 5. High-speed camera; 6. Image calibration device; 201. Side wall oblique wedge; 601. Fixed spacing grid. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1-Figure 2 The present invention provides a technical solution: a dynamic measurement system of lunar soil erosion process based on structured light images, comprising: an experimental nozzle 1, a simulated lunar soil container 2, simulated lunar soil 3, a structured light projector 4, a high-speed camera 5 and an image calibration device 6;

[0027] The upstream of the experimental nozzle 1 is connected to the gas cylinder outside the vacuum chamber through a delivery pipeline. The simulated lunar soil container 2 includes a side wall wedge 201. The simulated lunar soil 3 is located inside the simulated lunar soil container 2. The structured light projector 4 is used to accurately project the encoded light stripe pattern onto the pit surface. The high-speed camera 5 is installed above the side wall wedge 201 to capture the stripe light image of the pit surface and record the evolution of the light pattern on the surface of the object. The image calibration device 6 is used to calibrate the camera image taken obliquely from above before the experiment. A fixed-pitch grid 601 is set on the side of the image calibration device 6. The fixed-pitch grid 601 defines the coordinate system of the calibration points. The position and spacing of the grid points are known and are used as a reference for image correction.

[0028] The present application is connected to the gas cylinder outside the vacuum chamber through a delivery pipeline, which can accurately control the gas-related parameters entering the experimental system, such as the gas flow and pressure, so as to create an experimental environment that meets specific requirements, which is helpful to simulate some real conditions involving gas effects that may exist on the lunar surface. For example, it can provide a reliable condition basis for studying the impact of gas on the lunar surface under a specific gas environment. The oblique split structure changes the layout and display angle of the simulated lunar soil to a certain extent, making it convenient to observe the changes in the simulated lunar soil during the experiment from different directions. Whether observing the evolution of the surface light pattern or the changes in its physical form through optical equipment, there are more suitable observation angles. The high-speed camera has a high shooting frame rate and resolution, and can clearly capture the details of the streak light image, and even the slightest change in the light pattern will not be missed, so that subsequent image-based analysis and modeling work can be based on accurate and detailed image data, thereby improving the reliability of the entire experimental results.

[0029] Experimental Nozzle 1 During the experiment, the gas is accelerated through the delivery pipeline, and the jet expands in a vacuum environment, simulating the plume field distribution under real conditions.

[0030] In this application, on the moon, the plume field generated by the spacecraft engine is developed in a vacuum environment. After the gas is accelerated through the delivery pipeline through the experimental nozzle, the jet expands in a vacuum environment, which can simulate the actual distribution of the plume field very realistically. For example, when the lunar probe is landing or taking off, the impact of the plume field formed by the airflow ejected by its engine on the surrounding lunar soil and lunar topography can be studied through this simulation experiment, thereby helping scientists to better understand and predict the specific circumstances of the effect of the plume field in actual lunar missions.

[0031] The simulated lunar soil container 2 is made of acrylic material, which is transparent and allows staff to observe clearly. At the same time, acrylic material is safe, durable, weather-resistant and radiation-resistant, and can be used for a long time. The tip of the side wall wedge 201 coincides with the central cross-section of the engine, reducing the interference of the plume field on the container wall. Based on the guiding effect of the side wall wedge 201, the half pit formed by the lunar soil under the action of the plume is close to the complete pit shape in the actual environment.

[0032] The staff of this application can clearly observe the real-time state changes of the simulated lunar soil under various experimental conditions directly through the container without the aid of complex endoscopic equipment or additional tools. This greatly facilitates the monitoring work during the experiment and can timely capture the displacement of lunar soil particles, changes in stacking morphology, and various subtle phenomena of interaction with other objects, which helps to accurately record the experimental conditions. The weather resistance and radiation resistance of acrylic materials enable them to maintain their own stable performance under such relatively complex simulated environmental conditions, and will not experience material aging, brittleness, or reduced transparency due to long-term exposure to these factors.

[0033] The simulated lunar soil 3 is placed in the simulated lunar soil container 2 to simulate lunar dust and is compacted. During the experiment, the plume generated by the experimental nozzle 1 acts on the surface of the simulated lunar dust, simulating the dust reaction in the real lunar environment. The plume forms an approximately circular erosion pit on the simulated lunar dust.

[0034] The present application places simulated lunar soil in a container to simulate lunar dust and compacts it, and then uses the plume generated by an experimental nozzle to act on its surface. This can extremely realistically simulate the scene of interaction between spacecraft engine plumes and lunar dust in a real lunar environment.

[0035] The coded stripe pattern projected by the structured light projector 4 is encoded in the vertical direction, that is, the stripe pattern is projected horizontally, and the color of the stripe pattern changes only in the vertical direction. During the encoding process, the color of each stripe corresponds to the depth of the pit one by one, ensuring that the colors of stripes at different depths are unique and non-repetitive. During the actual measurement process, the positions of stripes of different colors on the surface of the pit are analyzed to accurately determine the depth information of the pit, thereby achieving a detailed analysis of the pit morphology.

[0036] The present application makes each stripe color correspond to the pit depth one by one, and ensures that the colors of stripes of different depths are unique and non-repetitive. In this way, when analyzing the stripes on the pit surface, as long as the color of the stripes is determined, the corresponding pit depth value can be directly and accurately obtained. This clear correspondence avoids ambiguity and ambiguity, greatly improves the accuracy of depth measurement, and can provide more accurate depth data compared to some methods that rely on rough estimation or indirect inference of pit depth, providing a reliable basis for subsequent detailed analysis of pit morphology.

[0037] The high-speed camera 5 can capture the stripe changes at every moment during the dynamic erosion process, and calculate the three-dimensional coordinates of the object surface based on mathematical algorithms by analyzing the deformation degree and shape changes of the pattern, thereby reconstructing the three-dimensional shape of the object and providing detailed three-dimensional data.

[0038] This application is based on the stripe change information captured by a high-speed camera, and uses mathematical algorithms to calculate the three-dimensional coordinates of the object's surface, and then reconstruct the object's three-dimensional shape. This enables researchers to obtain all-round morphological information on the object's surface. They are no longer limited to roughly estimating the shape of the object through two-dimensional images or simple partial measurements. Instead, they can obtain a complete and accurate three-dimensional model that clearly presents the ups and downs, unevenness, and detailed features of the spatial relationship between various parts of the object's surface, providing strong support for accurately grasping the overall morphological changes of the object before and after erosion.

[0039] Before the experiment begins, the image calibration device 6 is installed at the same position as in the formal experiment to obtain the target image to be calibrated. A fixed-pitch grid 601 is used as a reference for image correction. After the initial calibration image is obtained, a calibration grid is defined, which matches the fixed-pitch grid of the calibration device. Through image matching, the grid points in the actual captured image are matched one-to-one with the defined calibration grid points to generate a transformation grid. The captured image of the lunar erosion process obtained during the experiment is corrected using the generated transformation grid. The depth of the pit and the erosion radius information at different depths are obtained through the corrected image.

[0040] During the experiment of this application, due to the influence of multiple factors such as the shooting angle and the optical characteristics of the camera lens, the images captured often have a certain degree of distortion, which may lead to deviations in the shape and size information of the objects in the image. The image calibration device uses a fixed-pitch grid as a reference to generate a transformation grid to correct the image, which can effectively eliminate the effects of these distortions and make the image more realistically reflect the actual lunar erosion situation. For example, an image that was originally stretched and deformed at the edges due to the wide-angle effect of the lens can be restored to its appearance close to the real scene after correction, thereby ensuring the accuracy of the pit depth and erosion radius information subsequently obtained based on image analysis.

[0041] When a specific grating pattern or stripes is projected onto the surface of an object, the stripes will deform when the shape of the object surface changes. By analyzing the deformation of the stripes, the depth information of the object surface is calculated. The sinusoidal stripe projection calculation is used, and the light intensity distribution function of the projected sinusoidal stripes is assumed to be:

[0042] I(x,y)=A(x,y)+B(x,y)cos(φ(x,y))

[0043] Among them, A(x, y) is the background light intensity, B(x, y) is the contrast of the stripes, and φ(x, y) is the phase information. After the stripes are deformed on the surface of the object, the phase information of the deformed stripes captured by the camera will change. The four-step phase shift method is used, and the phase difference of each phase shift is π / 2. Four phase-shifted images are obtained, and the phase is calculated:

[0044]

[0045] Among them, I1, I2, I3 and I4 are the light intensities of the four phase-shifted images respectively. After obtaining the phase information, the depth value Z of each point on the object surface is calculated according to the calibration parameters of the system and the relationship between phase and depth. Combined with the calibration parameters of the camera's pixel coordinates, the three-dimensional coordinates of the object surface are obtained.

[0046] The 4-stripe pattern of the structured light projector is projected in the horizontal direction. The pit surface projected with the coded stripe pattern is photographed based on the high-precision image acquisition equipment to obtain clear and complete image data. The collected image is processed based on the image processing algorithm and analysis software to accurately identify the color information of the stripes at various positions on the pit surface.

[0047] This application uses high-precision image acquisition equipment to photograph the pit surface on which the coded stripe pattern is projected, which can capture the rich and detailed detail information of the pit surface to the greatest extent. High precision means high resolution, low noise and good color reproduction capabilities, so that a clear stripe pattern image can be obtained, and there will be no situation where the stripes are difficult to distinguish due to blurred images.

[0048] The light transmittance of acrylic material is greater than 92%. When the plume is ejected and rushes towards the lunar soil with energy, the lunar soil particles are originally in a relatively disordered state. Under the push of the plume impact force, they move, roll and rearrange themselves. The existence of the side wall oblique wedge 201 changes the natural diffusion path of the lunar soil particles, so that under the guidance of the oblique wedge slope, they gather and accumulate in an orderly manner in a specific direction, gradually forming the prototypes of pits of various shapes.

Claims

1. A dynamic measurement system for lunar soil erosion based on structured light images, characterized in that: include: Experimental nozzle (1), simulated lunar soil container (2), simulated lunar soil (3), structured light projector (4), high-speed camera (5) and image calibration device (6); The upstream of the experimental nozzle (1) is connected to a gas cylinder outside the vacuum chamber through a delivery pipeline. The simulated lunar soil container (2) includes a side wall wedge (201). The simulated lunar soil (3) is located inside the simulated lunar soil container (2). The structured light projector (4) is used to accurately project the encoded light stripe pattern onto the pit surface. The high-speed camera (5) is installed above the side wall wedge (201) and is used to capture the stripe light image of the pit surface and record the evolution of the light pattern on the object surface. The image calibration device (6) is used to calibrate the camera image captured obliquely from above before the experiment. A fixed-pitch grid (601) is arranged on the side of the image calibration device (6). The fixed-pitch grid (601) defines the coordinate system of the calibration points. The positions and spacings of the grid points are known and are used as a reference for image correction.

2. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: During the experiment of the experimental nozzle (1), the gas is accelerated through the delivery pipeline, and the jet expands in a vacuum environment, simulating the plume field distribution under real conditions.

3. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: The simulated lunar soil container (2) is made of acrylic material, which is transparent and can be clearly observed by the staff. At the same time, the acrylic material is safe, durable, weather-resistant and radiation-resistant, and can be used for a long time. The tip of the side wall wedge (201) coincides with the central cross section of the engine, reducing the interference of the plume field on the container wall. Based on the guiding effect of the side wall wedge (201), the half pit formed by the lunar soil under the action of the plume is close to the complete pit shape in the actual environment.

4. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: The simulated lunar soil (3) is placed in a simulated lunar soil container (2) to simulate lunar dust and is compacted. During the experiment, the plume generated by the experimental nozzle (1) acts on the surface of the simulated lunar dust to simulate the dust reaction in a real lunar environment. The plume forms an approximately circular erosion pit on the simulated lunar dust.

5. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: The coded stripe pattern projected by the structured light projector (4) is coded in the vertical direction, that is, the stripe pattern is projected horizontally, and the color of the stripe pattern changes only in the vertical direction. During the coding process, the color of each stripe corresponds to the depth of the pit one by one, ensuring that the colors of stripes at different depths are unique and non-repetitive. During the actual measurement process, the positions of stripes of different colors on the surface of the pit are analyzed to accurately determine the depth information of the pit, thereby achieving a detailed analysis of the pit morphology.

6. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: The high-speed camera (5) can capture the stripe changes at every moment in the dynamic erosion process, and calculate the three-dimensional coordinates of the object surface based on a mathematical algorithm by analyzing the deformation degree and shape change of the pattern, thereby reconstructing the three-dimensional shape of the object and providing detailed three-dimensional data.

7. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 1 is characterized in that: Before the experiment begins, the image calibration device (6) is installed at the same position as in the formal experiment to obtain the target image to be calibrated. The fixed-pitch grid (601) is used as a reference for image correction. After the initial calibration image is obtained, a calibration grid is defined, which matches the fixed-pitch grid of the calibration device. Through image matching, the grid points in the actual captured image are matched one-to-one with the defined calibration grid points to generate a transformation grid. The lunar surface erosion process obtained during the experiment is corrected using the generated transformation grid to correct the captured image. Through the corrected image, the depth of the pit and the erosion radius information at different depths are obtained.

8. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 6 is characterized in that: When a specific grating pattern or stripes is projected onto the surface of an object, the stripes will deform when the shape of the object surface changes. By analyzing the deformation of the stripes, the depth information of the object surface is calculated. The sinusoidal stripe projection calculation is used, and the light intensity distribution function of the projected sinusoidal stripes is assumed to be: I(x,y)=A(x,y)+B(x,y)cos(φ(x,y)) Among them, A(x, y) is the background light intensity, B(x, y) is the contrast of the stripes, and φ(x, y) is the phase information. After the stripes are deformed on the surface of the object, the phase information of the deformed stripes captured by the camera will change. The four-step phase shift method is used, and the phase difference of each phase shift is π / 2. Four phase-shifted images are obtained, and the phase is calculated: Among them, I1, I2, I3 and I4 are the light intensities of the four phase-shifted images respectively. After obtaining the phase information, the depth value Z of each point on the object surface is calculated according to the calibration parameters of the system and the relationship between phase and depth. Combined with the calibration parameters of the camera's pixel coordinates, the three-dimensional coordinates of the object surface are obtained.

9. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 5 is characterized in that: The structured light projector (4) projects the fringe pattern in the horizontal direction, and uses a high-precision image acquisition device to photograph the pit surface on which the coded fringe pattern is projected to obtain clear and complete image data. Based on an image processing algorithm and analysis software, the acquired image is processed to accurately identify the color information of the fringe at each position on the pit surface.

10. The dynamic measurement system of lunar soil erosion process based on structured light images according to claim 3 is characterized in that: The light transmittance of acrylic material is greater than 92%. When the plume is ejected and rushes towards the lunar soil with energy, the lunar soil particles are originally in a relatively disordered state. Under the impetus of the plume impact force, they move, roll and rearrange themselves. The existence of the side wall slope (201) changes the natural diffusion path of the lunar soil particles, so that under the guidance of the slope, the lunar soil particles gather and accumulate in a specific direction in an orderly manner, gradually forming a number of pit prototypes with different shapes.

Images