A lunar soil erosion process dynamic measurement system based on structured light images

Abstract

The application discloses a lunar soil erosion process dynamic measurement system based on a structured light image, and relates to the field of aerospace measurement technology.The system comprises an experimental nozzle, a simulated lunar soil container, simulated lunar soil, a structured light projector, a high-speed camera and an image calibration device.The experimental nozzle is connected with a gas cylinder outside a vacuum cabin through a conveying pipeline at an upstream side.The simulated lunar soil container comprises a side wall surface bevel.The simulated lunar soil is arranged in the simulated lunar soil container.The structured light projector is used for accurately projecting an encoded light stripe pattern onto a crater surface.The high-speed camera is arranged above the side wall surface bevel and used for shooting a stripe light image of the crater surface.The application records the whole process by using a camera, and can extract detailed rules of crater evolution by analyzing radial and depth changes of the stripe on the crater surface.The image is calibrated before the experiment, quantitative analysis of the crater surface stripe image can be realized, and accurate erosion process data can be provided.

Description

TECHNICAL FIELD

[0001] The application relates to the field of aerospace measurement technology, and particularly relates to a lunar soil erosion process dynamic measurement system based on a structured light image. BACKGROUND

[0002] The interaction between plume and lunar dust has an important influence on manned space engineering, especially in the landing and take-off stages on the moon surface. The plume formed by the engine working during the landing and take-off process of the lander will have a strong comprehensive effect on the lander body after expansion and diffusion. Due to the erosion effect of the plume, craters will appear on the moon surface, which may destroy the shape of the landing support surface, and then threaten the stability of the lander. In addition, the reflection effect of the plume and the moon surface becomes complex, which makes the evaluation of the force and heat protection more difficult. Through the ground simulation test, the dynamic erosion process of the moon surface during the engine working can be reproduced more accurately, and experimental results with high reference value can be provided. This not only provides a direct reference basis for engineering, but also provides necessary input conditions for the establishment and verification of the simulation model.

[0003] In the previous lunar crater simulation evolution experiment, a visible light camera is usually used to record the dynamic process of crater formation during the engine working. However, the images obtained by these experiments are mainly used for qualitative analysis, because it is difficult to use effective technical means to quantitatively analyze the erosion process of the lunar soil. One of the main difficulties is that the lunar dust image belongs to a weak texture image, 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 diffuse between the crater and the camera, which causes the crater shape to be blocked by the lunar dust, and then reduces the clarity of the crater surface image obtained by the camera. To this end, the application provides a lunar soil erosion process dynamic measurement system based on a structured light image. SUMMARY

[0004] The application aims to provide a lunar soil erosion process dynamic measurement system based on a structured light image to solve the problems in the background technology.

[0005] A lunar soil erosion process dynamic measurement system based on a structured light image comprises 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 experimental nozzle is connected with a gas cylinder outside the vacuum chamber through a conveying pipeline upstream, a simulated lunar soil container includes a side wall inclined wedge, simulated lunar soil is located inside the simulated lunar soil container, a structured light projector is used to accurately project an encoded light stripe pattern onto the crater surface, a high-speed camera is installed above the side wall inclined wedge and is used to shoot a stripe light image of the crater surface, record the evolution of the light pattern on the object surface, an image calibration device is used to calibrate the camera image shot obliquely above before the experiment, a fixed-pitch grid is arranged on the side of the image calibration device, the fixed-pitch grid defines a coordinate system of the calibration points, the positions and pitches of the grid points are known and are used as a reference for image correction.

[0007] Preferably, during the experiment, the gas is accelerated through the conveying pipeline, the jet flow expands in the vacuum environment, and the plume field distribution under the real condition is simulated.

[0008] Preferably, the simulated lunar soil container is made of acrylic material and is transparent, so that the staff can clearly observe, at the same time, the acrylic material has safety, durability, weather resistance and anti-radiation ability, and can be used for a long time; the tip of the side wall inclined wedge coincides with the center section of the engine, reducing the interference of the plume field on the container wall, and based on the guiding action of the side wall inclined wedge, the half crater formed by the lunar soil under the action of the plume is close to the complete crater shape in the actual environment.

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

[0010] Preferably, the encoded stripe pattern projected by the structured light projector is vertically encoded, that is, the stripe pattern is projected horizontally, and the color of the stripe pattern changes only in the vertical direction, in the encoding process, each stripe color corresponds to the crater depth one by one, ensuring that the stripe color of different depths is unique and not repeated, in the actual measurement process, the position of the stripe of different colors on the crater surface is analyzed to accurately determine the depth information of the crater, and detailed analysis of the crater shape is realized.

[0011] Preferably, the high-speed camera can capture the change of the stripe at each moment in the dynamic erosion process, the deformation degree and shape change of the pattern are analyzed, the three-dimensional coordinates of the object surface are calculated based on a mathematical algorithm, so as to reconstruct the three-dimensional shape of the object and provide detailed three-dimensional data.

[0012] Preferably, the image calibration device is installed at the same position as in the formal experiment before the experiment starts to obtain the image of the target to be calibrated, and a fixed pitch grid is used as a reference for image correction. After obtaining the initial calibration image, 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 one-to-one corresponding to the defined calibration grid points, and a transformation grid is generated. For the lunar surface erosion process obtained during the experiment, the generated transformation grid is used to correct the captured image. Through the corrected image, the depth of the crater and the erosion radius information at different depths are obtained.

[0013] Preferably, a specific grating pattern or stripe is projected onto the surface of the object. When the shape of the object surface changes, the stripe will deform. By analyzing the deformation of the stripe, the depth information of the object surface is calculated. Using the sine stripe projection calculation, the light intensity distribution function of the projected sine stripe is:

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

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

[0016]

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

[0018] Preferably, the stripe pattern of the structured light projector is projected in the horizontal direction. Based on high-precision image acquisition equipment, the crater surface with the encoded stripe pattern is captured to obtain clear and complete image data. Based on image processing algorithms and analysis software, the color information of the stripe at each position on the crater surface is accurately identified.

[0019] Preferably, the acrylic material has a light transmittance of greater than 92%, and when the plume is ejected and rushes towards the lunar soil, the lunar soil particles are originally in a relatively disordered state, and under the pushing force of the plume impact, movement, rolling and recombination occur, and the natural diffusion path of the lunar soil particles is changed in the presence of the side wall inclined wedge, so that the lunar soil particles are orderly gathered and accumulated in a specific direction under the guidance of the inclined wedge slope, and gradually form a concave pit embryo with different shapes.

[0020] Compared with the prior art, the beneficial effects of the present application are:

[0021] The present application uses a programmable projector to project a stripe-shaped light beam from the side of the lunar soil container, and different heights of the stripes present different colors, and when the engine is working, the center of the nozzle coincides with the side wall of the lunar dust to form a half-pit, and the stripe light beam projected from the side will be projected on the inner wall of the pit, and as the erosion proceeds, pits of different depths will be illuminated by stripes of different colors, and a camera records the whole process, and by analyzing the radial and depth changes of the stripes on the pit surface, the detailed rules of pit evolution can be extracted, and the image is calibrated before the experiment, so that quantitative analysis of the stripe image on the pit surface can be realized, and accurate erosion process data can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0022] Fig. 1 It is a schematic diagram of the overall structure of the present application;

[0023] Fig. 2 It is a 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 inclined wedge; 601, fixed-pitch grid. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] Please refer to Figs. 1-2 The present application provides a technical solution: a lunar soil erosion process dynamic measurement system based on structured light images, which comprises: 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 experimental nozzle 1 is connected to a gas cylinder outside the vacuum chamber via 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 surface of the pit. The high-speed camera 5 is installed above the side wall wedge 201 to capture the stripe light image of the pitted 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 taken from the obliquely above before the experiment. The side of the image calibration device 6 is provided with a fixed spacing grid 601. The fixed spacing grid 601 defines the coordinate system of the calibration points. The position and spacing of the grid points are known and used as a reference for image correction.

[0028] This application connects to gas cylinders outside the vacuum chamber via delivery pipelines, enabling precise control of gas-related parameters entering the experimental system, such as gas flow rate and pressure. This creates an experimental environment that meets specific requirements, facilitating the simulation of real-world conditions involving gas interactions on the lunar surface. For example, it provides a reliable basis for studying the impact of gas on lunar regolith under specific gas environments. The wedge structure alters the layout and display angle of the simulated lunar regolith to some extent, allowing for observation of changes in the simulated lunar regolith from different directions. Whether observing the evolution of surface light patterns or changes in physical morphology through optical equipment, more suitable observation angles are available. The high-speed camera has a high frame rate and resolution, clearly capturing details of the striped light images, even subtle changes in light patterns. This ensures that subsequent image-based analysis and modeling can be built upon accurate and detailed image data, improving the reliability of the overall experimental results.

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

[0030] On the Moon, the plume field generated by spacecraft engines unfolds in a vacuum environment. By accelerating the gas through the delivery pipeline via an experimental nozzle, the jet expands in a vacuum environment, which can simulate the distribution of this real plume field in a very realistic way. For example, the impact of the plume field formed by the airflow ejected by the engine of a lunar probe on the surrounding lunar soil and lunar surface topography during landing or takeoff can be studied through this simulation experiment, thereby helping scientists to better understand and predict the specific situation of the plume field in actual lunar missions.

[0031] The material of the simulated lunar soil container 2 is acrylic material, which is transparent, so that the staff can clearly observe the real-time state change of the simulated lunar soil under various experimental conditions. At the same time, the acrylic material has safety, durability, weather resistance and anti-radiation ability, which can be used for a long time. The tip of the side wall inclined wedge 201 coincides with the center section of the engine, reducing the interference of the plume field on the container wall. Based on the guiding effect of the side wall inclined wedge 201, the half crater formed by the lunar soil under the action of the plume is close to the complete crater shape in the actual environment.

[0032] The staff can directly observe the real-time state change of the simulated lunar soil under various experimental conditions through the container, without the need for additional tools such as complex endoscopic equipment. This greatly facilitates the monitoring work during the experiment, allowing the displacement of lunar soil particles, changes in the accumulation shape, and various subtle phenomena of interaction with other objects to be captured in a timely manner. This helps to accurately record the experimental conditions. The weather resistance and anti-radiation ability of the acrylic material enable it to maintain its performance stability in such relatively complex simulated environmental conditions, without 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 crater on the simulated lunar dust.

[0034] By placing the simulated lunar soil in the container to simulate lunar dust and compacting it, and then using the plume generated by the experimental nozzle to act on its surface, the scene of the interaction between the spacecraft engine plume and lunar dust in the real lunar environment can be simulated very realistically.

[0035] The coded fringe pattern projected by the structured light projector 4 uses vertical direction coding, i.e. the fringe pattern is projected horizontally. The color of the fringe pattern changes only in the vertical direction. In the coding process, each fringe color corresponds to the crater depth one by one, ensuring that the color of the fringe with different depths is unique and not repeated. In the actual measurement process, the position of the fringe with different colors on the crater surface is analyzed to accurately determine the depth information of the crater, realizing detailed analysis of the crater shape.

[0036] By making each fringe color correspond to the crater depth one by one and ensuring that the color of the fringe with different depths is unique and not repeated, when analyzing the fringe on the crater surface, as long as the color of the fringe is determined, the corresponding crater depth value can be directly and accurately obtained. This clear correspondence avoids ambiguity and polysemy, greatly improving the accuracy of depth measurement. Compared with some methods that rely on rough estimation or indirect calculation of crater depth, more accurate depth data can be obtained, providing a reliable basis for subsequent detailed analysis of the crater shape.

[0037] The high-speed camera 5 can capture the change of the stripe at each moment in the dynamic erosion process. By analyzing the deformation degree and shape change of the pattern, the three-dimensional coordinates of the object surface are calculated based on a mathematical algorithm, thereby reconstructing the three-dimensional shape of the object and providing detailed three-dimensional data.

[0038] Based on the stripe change information captured by the high-speed camera, the three-dimensional coordinates of the object surface are calculated by using a mathematical algorithm, and then the three-dimensional shape of the object is reconstructed. This enables researchers to obtain the overall shape information of the object surface, and is no longer limited to the previous two-dimensional image or simple partial measurement to roughly infer the shape of the object. Instead, a complete and accurate three-dimensional model can be obtained, which clearly presents the ups and downs, unevenness and spatial relationship details of each part of the object surface, thereby providing strong support for accurately grasping the overall shape change of the object before and after erosion.

[0039] The image calibration device 6 is installed at the same position as in the formal experiment before the experiment starts to obtain the image of the target to be calibrated. The fixed pitch grid 601 is used as a reference for image correction. After obtaining the initial calibration image, a calibration grid is defined, which matches the fixed pitch grid of the calibration device. Through image matching, the grid points in the actual photographed image are one-to-one corresponding to the defined calibration grid points, and a transformation grid is generated. The transformation grid is used to correct the images obtained during the experiment process. Through the corrected images, the depth of the crater and the erosion radius information at different depths are obtained.

[0040] During the experiment, due to the influence of factors such as shooting angle and camera lens optical properties, the images obtained by shooting often have a certain degree of distortion, which may cause the shape and size information of the object in the image to deviate. By using the fixed pitch grid as a reference through the image calibration device, the transformation grid is generated to correct the image, which can effectively eliminate the influence of these distortions, making the image more truly reflect the actual lunar surface erosion situation. For example, the image that is originally stretched and deformed at the edge due to the wide-angle effect of the lens can be restored to the appearance close to the real scene after correction, thereby ensuring the accuracy of the crater depth and erosion radius information obtained based on the subsequent image analysis.

[0041] When a specific grating pattern or stripe is projected onto the object surface, the stripe will be deformed when the shape of the object surface changes. By analyzing the deformation of the stripe, the depth information of the object surface is calculated. The sine stripe projection calculation is adopted, and the light intensity distribution function of the projected sine stripe is set as:

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

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

[0044]

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

[0046] The 4-fringe pattern of the structured light projector is projected in the horizontal direction. Based on high-precision image acquisition equipment, the concave surface on which the coded fringe pattern is projected is photographed to obtain clear and complete image data. Based on image processing algorithms and analysis software, the color information of the fringe at each position on the concave surface is accurately identified.

[0047] The present application uses high-precision image acquisition equipment to photograph the concave surface on which the coded fringe pattern is projected, which can capture the rich and detailed information of the concave surface to the greatest extent. High precision means high resolution, low noise and good color restoration ability, so that clear fringe pattern images can be obtained, and the situation that the fringe is difficult to distinguish due to image blur does not occur.

[0048] The light transmittance of the acrylic material is greater than 92%. When the plume is ejected and carries energy to the lunar soil, the lunar soil particles are originally in a relatively disordered state. Under the pushing force of the plume impact, movement, rolling and recombination occur. The existence of the side wall inclined wedge 201 changes the natural diffusion path of the lunar soil particles, so that they are orderly gathered and accumulated in a specific direction under the guidance of the inclined wedge slope surface, and gradually form a concave embryo with different shapes.

Claims

1. A lunar soil erosion process dynamic measurement system based on structured light images, characterized in that, The utility model relates to a kind of experimental nozzle, simulation lunar soil container, simulation lunar soil, structured light projector, high-speed camera and image calibration device. The upstream of the experimental nozzle (1) is connected with gas cylinder outside vacuum chamber through conveying pipeline, the simulation lunar soil container (2) includes side wall surface bevel (201), the simulation lunar soil (3) is located in the inside of simulation lunar soil container (2), the structured light projector (4) is used to accurately project the coded light stripe pattern on the concave surface, the high-speed camera (5) is installed above the side wall surface bevel (201), for shooting the stripe light image of being concave surface, record the evolution of light pattern on object surface, the image calibration device (6) is used to calibrate the camera image shot obliquely above before experiment, the side of image calibration device (6) is provided with fixed pitch grid (601), fixed pitch grid (601) defines the coordinate system of calibration point, the position and interval of grid point are known, as reference for image correction; The tip of the side wall surface bevel (201) coincides with the center section of the engine, reducing the interference of plume field on the container wall, based on the guiding effect of the side wall surface bevel (201), the half concave formed by the lunar soil under the action of plume is close to the complete concave morphology in actual environment; The coded stripe pattern projected by the structured light projector (4) uses vertical direction coding, that is, stripe pattern horizontal projection, the color of stripe pattern changes only in vertical direction, in the coding process, each stripe color corresponds to the depth of concave one by one, ensuring that the color of stripe of different depth is unique and not repeated, in actual measurement process, the position of stripe of different color on concave surface is analyzed to accurately determine the depth information of concave, realizing detailed analysis on concave morphology. In the experimental process, the gas is accelerated through the conveying pipeline, and the jet expands in the vacuum environment to simulate the plume field distribution under real conditions.

2. The system according to claim 1, wherein, The simulation lunar soil container (2) is made of acrylic material, which is transparent for clear observation by the staff, and has safety, durability, weather resistance and radiation resistance for long-term use.

3. The system according to claim 1, wherein, The simulation lunar soil (3) is placed in the simulation lunar soil container (2) to simulate lunar dust and compact, in the experimental process, the plume generated by the experimental nozzle (1) acts on the surface of simulation lunar dust, simulates the dust reaction under the real lunar environment, and the plume forms an approximately circular erosion pit on the simulation lunar dust.

4. The system according to claim 1, wherein, The high-speed camera (5) can capture the change of stripe at each moment in dynamic erosion process, calculate the three-dimensional coordinates of object surface based on mathematical algorithm by analyzing the deformation degree and shape change of pattern, thereby reconstructing the three-dimensional morphology of object, and provide detailed three-dimensional data.

5. The system according to claim 1, wherein, ​ 6. The system according to claim 1, wherein, The image calibration device (6) is installed at the same position as in the formal experiment before the experiment starts to obtain the image of the target to be calibrated, and a fixed pitch grid (601) is used as a reference for image correction. After obtaining the initial calibration image, a calibration grid is defined, which matches the fixed pitch grid of the calibration device. Through image matching, the grid points in the actual photographed image are one-to-one corresponding to the defined calibration grid points, and a transformation grid is generated. The transformation grid is used to correct the images obtained during the lunar surface erosion process. Through the corrected images, the depth of the craters and the erosion radius information at different depths are obtained.

7. The system according to claim 6, wherein, When a specific grating pattern or stripe is projected onto the surface of an object, the stripe will deform when the shape of the object surface changes. By analyzing the deformation of the stripe, the depth information of the object surface can be calculated. Using the sine stripe projection calculation, the light intensity distribution function of the projected sine stripe is: ； Where A(x, y) is the background light intensity, B(x, y) is the contrast of the fringe, The phase information is obtained. After the fringe on the object surface is deformed, the phase information of the deformed fringe captured by the camera changes. Using the four-step phase shift method, the phase difference of each phase shift is π / 2. Four images after phase shift are obtained. The phase is calculated. ； where I1, I2, I3, and I4 are the light intensities of the four phase-shifted images. After obtaining the phase information, the depth values Z of each point on the object surface are calculated based on the system calibration parameters and the relationship between phase and depth. Combined with the calibration parameters of the camera pixel coordinates, the three-dimensional coordinates of the object surface are obtained.

8. The system according to claim 1, wherein, The structured light projector (4) projects the stripe pattern in the horizontal direction. Based on high-precision image acquisition equipment, the crater surface with the projected coded stripe pattern is photographed to obtain clear and complete image data. Based on image processing algorithms and analysis software, the color information of the stripe at each position on the crater surface is accurately identified.

9. The system according to claim 3, wherein, The light transmittance of the acrylic material is greater than 92%. When the plume is ejected and carries energy to the lunar soil, the lunar soil particles, which were originally in a relatively disordered state, move, roll, and recombine under the impact of the plume. The existence of the side wall inclined wedge (201) changes the natural diffusion path of the lunar soil particles, causing them to order and accumulate in a specific direction under the guidance of the inclined wedge slope, gradually forming a series of crater embryos with different shapes.

Images