3D printing tunnel cross-section scanning control method and system

Abstract

The application provides a 3D printing tunnel section scanning control method and system, and belongs to the technical field of tunnel engineering intelligent construction. The method comprises the following steps: acquiring tunnel rock surface measured point cloud data and a design BIM model, performing spatial registration and Boolean difference operation, and generating a deviation voxel matrix containing the normal deviation values of each spatial position; based on the normal deviation values, the tunnel rock surface is divided into a deep pit overbreak area, a conventional overbreak area and an underbreak area; for the deep pit overbreak area, a local parallel contour offset algorithm is used to generate a filling path, and a preset large layer thickness parameter is used for layer-by-layer stacking and leveling; after the deep pit overbreak is filled and leveled, for the conventional overbreak area, the target layer thickness is dynamically calculated according to the normal deviation value of the current point, and the printing head moving speed and the pumping extrusion speed are adjusted in linkage to level; when the leveling reaches the preset flatness threshold, the standard continuous slicing is switched to print the main load-bearing structure. The scheme can improve the printing quality of the tunnel secondary lining.

Description

Technical Field

[0001] This application relates to the field of intelligent construction technology for tunnel engineering, and in particular to a method and system for controlling the scanning of 3D printed tunnel cross sections. Background Technology

[0002] In tunnel secondary lining construction, traditional cast-in-place concrete technology relies on formwork trolleys and manual vibration. When faced with challenging conditions such as undulating rock surfaces and extremely uneven over- and under-excavation, quality defects often occur, including insufficient lining thickness, voids behind the lining, or concrete segregation. In recent years, 3D-printed concrete technology has been introduced into tunnel engineering, attempting to replace formwork casting with a layer-by-layer deposition method.

[0003] However, existing 3D printing tunnel cross-section scanning control technologies are mostly designed for regular geometries and adopt a global equal-thickness slicing strategy, resulting in low printing quality and hindering the practical application of 3D printed concrete technology in tunnel engineering. Summary of the Invention

[0004] The purpose of this application is to provide a 3D printing tunnel cross-section scanning control method and system to solve or alleviate the problems existing in the prior art.

[0005] To achieve the above objectives, this application provides the following technical solution: This application provides a method for controlling the scanning of 3D printed tunnel cross-sections, including the following steps: Acquire measured point cloud data of tunnel rock surface and design BIM model, perform spatial registration and Boolean difference operation to generate deviation voxel matrix containing normal deviation values ​​of each spatial location; Based on the aforementioned normal deviation value, the tunnel rock surface is divided into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone. For the deep pit over-excavation area, a local parallel contour offset algorithm is used to generate a filling path, and the filling path is stacked layer by layer with a preset large layer thickness parameter until the filling height reaches the same level as the surrounding conventional over-excavation area. After the deep pit is filled, a variable thickness slicing algorithm is used for the conventional over-excavated area. The target layer thickness is dynamically calculated based on the normal deviation value of the current point, and the print head moving speed and pump extrusion speed are adjusted in conjunction to achieve leveling. When the leveling reaches the preset flatness threshold, the printing is switched to standard continuous slicing for printing the main load-bearing structure.

[0006] Preferably, the step of dividing the tunnel rock surface into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone based on the normal deviation value specifically includes: Set a severe over-excavation threshold With slight over-excavation threshold Traverse the deviation voxel matrix and determine the deviation values ​​based on the normal values. Based on the comparison with two thresholds, the tunnel rock surface is divided into three regions: normal deviation value The area with a value greater than 0 is designated as the under-excavation area; normal deviation value Less than The independent concave area is divided into the deep pit over-excavation area; The normal deviation value is between and The area between them is designated as the conventional over-excavation zone.

[0007] Preferably, for the deep pit over-excavation area, a local parallel contour offset algorithm is used to generate a filling path, and layer-by-layer stacking and leveling are performed with a preset large layer thickness parameter, specifically including: Using the horizontal plane where the lowest point of the deep pit over-excavation area is located as the initial layer, a filling trajectory is generated by parallel offset inward according to the preset thick line width, and then stacked upward layer by layer along the depth direction according to the large layer thickness parameter. Controlling the printhead movement speed during the stacking process With extrusion flow rate Satisfying Relationship: ,in, For thicker lines, For large layer thickness parameters; When the filling height of the deep pit over-excavation area reaches a level within the preset tolerance range compared to the average height difference of the surrounding conventional over-excavation areas, the leveling of the deep pit over-excavation area is determined to be complete.

[0008] Preferably, for conventional over-excavation areas, a variable thickness slicing algorithm is used to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and to adjust the print head moving speed and pump extrusion speed in conjunction to achieve leveling, specifically including: Based on the current print position Normal deviation at point Calculate the target layer thickness using the following formula. : , in, For standard layer thickness, This is the thickness compensation coefficient; Based on the principle of volume conservation, extrusion amount satisfy: Reverse calculation of print head movement speed With pump extrusion speed The matching relationship, where, Standard line width; When the standard deviation of the normal deviation values ​​at each point of the current printed layer If the flatness is less than or equal to the preset flatness threshold, the leveling of the regular over-excavation area is considered complete.

[0009] Preferably, the printing of the main load-bearing structure is switched to standard continuous slices, specifically including: The algorithm of continuous spiral slicing with equal thickness is adopted. Taking the center of the tunnel cross section as the origin, the spiral path is generated by expanding circle by circle according to the polar coordinate angle increment method. Control the print head along the spiral path at a constant speed With constant Perform continuous printing and control the overlap rate between adjacent trajectories to maintain a preset overlap rate.

[0010] Preferably, the method further includes a mechanical adaptive control step implemented to address differences in the gravity environment of the tunnel cross-section, specifically including: Extract the normal vectors of each point on the current printed surface, and calculate the angle between the normal vectors and the global gravity direction vector, which is defined as the gravity deflection angle. ; According to the gravity deflection angle The tunnel cross-section is dynamically divided into three printing mechanical zones: the invert zone, the sidewall zone, and the crown zone. For the aforementioned sidewall area and arch area, mechanical compensation control for anti-slip and anti-fall is implemented.

[0011] Preferably, the mechanical compensation control for anti-slip and anti-fall measures applied to the sidewall area and the vault area includes non-orthogonal attitude offset compensation: When printing in the sidewall and vault areas, control the axial vector of the print head to generate a compensation angle. This causes the print head to be angled upwards and pressed against the previous layer of solidified concrete. The compensation deflection angle Calculate using the following formula: ,in, The angle of deflection due to gravity. This represents the attitude bias gain coefficient.

[0012] Preferably, the mechanical compensation control for anti-slip and anti-fall measures in the sidewall area and the arch crown area further includes: implementing stepped staggered slice path planning in the transition section from the arch waist to the arch crown. When generating the arch path, set the centerline of the next layer's slice path to be offset inwards towards the rock face by a preset amount. Offset The calculation formula is as follows: , in, This is the misalignment gain coefficient. This is the current printed layer thickness.

[0013] Preferably, the mechanical compensation control for anti-slip and anti-fall measures in the sidewall area and the vault area further includes adaptive rheological thin-layer rapid printing and accelerator follow-up control in the vault area: Change the current print layer thickness from the standard layer thickness. Reduce to thin layer thickness Thinning ratio satisfy: , in, This is the layer thickness reduction factor.

[0014] This embodiment provides a 3D printing tunnel cross-section scanning control system, the system being used to perform the steps of any of the methods described above, including: The generation unit is configured to acquire measured point cloud data of the tunnel rock surface and the design BIM model, perform spatial registration and Boolean difference operation, and generate a deviation voxel matrix containing the normal deviation values ​​of each spatial location. The division unit is configured to divide the tunnel rock surface into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone based on the normal deviation value; The first leveling unit is configured to generate a filling path using a local parallel contour offset algorithm for the deep pit over-excavation area, and to perform layer-by-layer leveling with a preset large layer thickness parameter until the filling height reaches the same level as the surrounding conventional over-excavation area. The second leveling and printing unit is configured to, after filling the deep pit over-excavation, use a variable thickness slicing algorithm for the conventional over-excavation area to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and adjust the print head moving speed and pump extrusion speed in conjunction to perform leveling; when the leveling reaches the preset flatness threshold, it switches to standard continuous slicing for printing the main load-bearing structure.

[0015] Beneficial effects: The solution provided in this application constructs a deviation voxel matrix characterizing the spatial distribution of over- and under-excavation on the tunnel rock surface by spatial registration and Boolean difference operation using measured point cloud and design BIM model. Based on the normal deviation value, the rock surface is scientifically divided into deep pit over-excavation zone, conventional over-excavation zone, and under-excavation zone, and differentiated collaborative control is implemented. For the deep pit over-excavation zone, a local parallel contour offset algorithm combined with large layer thickness parameters is used for layer-by-layer stacking and leveling to avoid material falling and interlayer voids caused by concrete extrusion in a suspended state. After the deep pit is filled, a variable thickness slicing algorithm is introduced for the conventional over-excavation zone. The target layer thickness is dynamically calculated based on the normal deviation value, and the print head moving speed and pump extrusion speed are adjusted in conjunction. Through the synergistic effect of the above multi-level partition slicing and parameter linkage control, the method seamlessly switches to standard continuous slicing for printing the main load-bearing structure after the leveling reaches the preset flatness threshold, ensuring the integrity, uniformity, and mechanical continuity of the lining structure. Overall, the technical solution proposed in this application can adapt to the complex geometric environment of irregular tunnel cross sections, overcome the quality defects such as insufficient lining thickness and voids behind the lining that are prone to occur in traditional 3D printing technology, and improve the printing quality and forming accuracy of tunnel secondary lining. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the method for controlling the scanning of the cross-section of a 3D-printed tunnel.

[0017] Figure 2 This is a schematic diagram of the electronic device. Detailed Implementation

[0018] Current 3D printing tunnel technology typically assumes the tunnel rock surface to be a regular geometric shape. However, the actual measured rock surface of a tunnel cross-section is usually an irregular structure with complex deviations from the design contour. When the print head reaches an under-excavated protrusion, the nozzle interferes with or even collides with the rock surface. When it reaches an over-excavated deep pit, the concrete is squeezed out in a suspended state, causing material to fall and gaps between layers. In addition, the angle between the normal direction and the direction of gravity in the tunnel cross-section changes continuously from the invert arch through the sidewalls to the arch crown. Especially in the arch crown area, the concrete is prone to tearing and falling due to the normal component of gravity before solidification. Traditional 3D printing usually uses a print head axis perpendicular to the current printing surface, making it difficult to meet the printing quality requirements in these areas.

[0019] Therefore, this embodiment provides a 3D printing tunnel cross-section scanning control method, which aims to solve the technical problems of material falling and arch tearing that occur easily in irregular tunnel cross-sections in existing 3D printing technology.

[0020] The embodiments of this application will now be described with reference to the accompanying drawings.

[0021] This embodiment provides a 3D printing tunnel cross-section scanning control method, which can be executed by an electronic device deployed on a 3D printing trolley. The 3D printing trolley is also equipped with at least a 3D laser scanner. The electronic device includes a memory and a processor, and the memory stores a computer program, such as... Figure 1 , Figure 2 As shown, when the processor executes this program, it performs the following steps: Step S1: Obtain the measured point cloud data of the tunnel rock surface and the design BIM model, perform spatial registration and Boolean difference operation, and generate a deviation voxel matrix containing the normal deviation values ​​of each spatial location.

[0022] In this embodiment, a 3D laser scanner is used to scan the 3D contour of the tunnel to obtain measured point cloud data of the tunnel rock surface. At the same time, the tunnel design BIM model is also pre-stored in the memory. After spatial registration of the measured point cloud data of the tunnel rock surface with the design BIM model, Boolean difference operation is performed to generate a deviation voxel matrix representing the spatial distribution of over-excavation and under-excavation, so as to establish a digital twin base of the tunnel.

[0023] Specifically, firstly, a 3D laser scanner is mounted on a trolley and positioned behind the tunnel face in a stable section. It then collects 3D point cloud data of the rock surface at fixed intervals along the tunnel's longitudinal direction to obtain a measured point cloud model. .

[0024] In this embodiment, the 3D laser scanner can employ phase-based or pulse-based laser scanning principles, achieving a ranging accuracy of no less than [a certain level]. The point cloud density is not less than This is to ensure the geometric resolution of subsequent Boolean difference operations. The tunnel theoretical design BIM model is imported synchronously, denoted as... The model contains three-dimensional geometric information of the inner and outer contours of the lining and the arrangement of the reinforcing bars.

[0025] Will and Spatial registration based on the iterative nearest point algorithm is performed, using the design contour as a reference to unify the coordinate system. Preferably, the registration error can be set to be controlled within a certain range. Within this period, registration is confirmed to be complete.

[0026] After registration, a spatial Boolean difference operation is performed on the two models to calculate the deviation distribution of the measured rock surface relative to the design profile, generating an over-excavation and under-excavation deviation voxel matrix. Each voxel in the matrix stores the normal deviation value at that spatial location. .

[0027] Step S2: Based on the normal deviation value, the tunnel rock surface is divided into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone.

[0028] In this embodiment, the purpose of step S2 is to perform intelligent clustering and partitioning of over-excavation and under-excavation areas based on depth gradient, including: setting a severe over-excavation threshold. With slight over-excavation threshold Traverse the deviation voxel matrix Based on the normal deviation value Based on the comparison with two thresholds, the tunnel rock surface is divided into three regions: the normal deviation value... The area with a value greater than 0 is designated as the under-excavation zone; the normal deviation value is... Less than The independent concave area is divided into the deep pit over-excavation area; the normal deviation value is between and The area between them is designated as the conventional over-excavation zone.

[0029] It should be noted that the deviation voxel matrix Each element in the database stores the normal deviation value at the spatial location of that voxel. ,like This indicates under-excavation, meaning the actual tunnel rock surface protrudes beyond the designed profile. This indicates over-excavation, meaning the rock surface is recessed outside the designed outline.

[0030] In this embodiment, two thresholds are first set. and ,in, This is a serious over-excavation threshold. This is the threshold for slight over-digging. For example, The range of values ​​is Preferred ; The range of values ​​is Preferred .

[0031] Then, based on the normal deviation value Based on the comparison with two thresholds, a region growing algorithm based on eight-neighbor connectivity is used to automatically divide the tunnel rock surface into three types of regions: the first is the under-excavation zone, i.e. In one area, the actual tunnel rock surface exceeds the design outline; the other is the deep pit over-excavation area, namely... The first is an isolated depression area, which is geometrically closed or semi-closed in shape, with a significant height difference from the surrounding rock surface, forming an island area; the second is a conventional over-excavation area, namely... The area with gentle rock surface undulations and a continuous transitional deviation from the design outline constitutes a transition zone; the remaining areas not falling into the above three categories are considered to meet the construction tolerance and are classified as standard printing areas, requiring no special treatment.

[0032] The region growing algorithm can be implemented using existing techniques and will not be elaborated here. Using a region growing algorithm based on eight-neighbor connectivity ensures the spatial continuity and boundary closure of similar regions.

[0033] In this embodiment, for the under-dug area, the obstacle avoidance polygon is generated by obtaining the convex hull shape of the area, and the printing nozzle is instructed to detour around or lift the area during the subsequent printing path design. Therefore, this area can be called the safety warning area.

[0034] Step S3: For the deep pit over-excavation area, a local parallel contour offset algorithm is used to generate a filling path, and the path is stacked layer by layer with a preset large layer thickness parameter to level it until the filling height reaches the same level as the surrounding conventional over-excavation area.

[0035] After completing the division of the three types of areas, this embodiment implements an island-style leveling and slicing stage, namely the macro-leveling stage, for the isolated areas of deep pit over-excavation. This includes: using the horizontal plane where the lowest point of the pit bottom of the deep pit over-excavation area is located as the initial layer, generating a filling trajectory by parallel offset inward according to a preset coarse line width, and stacking it layer by layer upward along the depth direction according to the large layer thickness parameter; during the stacking process, controlling the movement speed of the print head. With extrusion flow rate Satisfying Relationship: ,in, For thicker lines, The maximum layer thickness parameter is used; when the filling height of the deep pit over-excavation area reaches the average height difference with the surrounding conventional over-excavation area within the preset tolerance range, the leveling of the deep pit over-excavation area is considered complete.

[0036] The above process breaks away from the traditional full-section circumferential slicing logic. For each independent island region, a local parallel contour offset algorithm is used to generate the filling path, with its outer contour as the boundary. Specifically, the horizontal plane where the lowest point of the pit bottom of the island region is located is taken as the initial layer, and the parallel contour offset algorithm is used to generate the filling path for this layer. Then, the filling path is generated along the Z-axis (depth direction) according to the maximum layer thickness. Stacking upwards layer by layer, each layer generates a parallel profile offset path until the fill height reaches the same level as the surrounding conventional over-excavation area.

[0037] In this embodiment, the initial layer inward offset distance is first considered. , To create a thicker line width, an initial layer fill trajectory is generated; then, using this trajectory as a reference, the line is further offset inwards. Generate the second layer trajectory, and simultaneously adjust according to the large layer thickness parameters. Stack them layer by layer upwards along the depth direction, and so on, until the entire island area is covered.

[0038] As an example, The range of values ​​can be set to Preferred , The range can be set to Preferred .

[0039] After each layer of trajectory is generated, the trolley's control system receives the generated trajectory and drives the robotic arm to move the print head above the isolated area. The concrete extruder, operating at slow speeds, then performs localized, layer-by-layer stacking within the pit. The extrusion flow rate of the print head... With printhead movement speed Satisfying Relationships For example, The range of values ​​is Preferred .

[0040] Through the above process, the deep pit can be filled with the maximum material filling rate in a short time, making the outermost surface of the isolated area level with the surrounding conventional over-excavated area, laying the foundation for the subsequent global transition.

[0041] When the filling height of the isolated area reaches a difference from the average height of the conventional over-excavation area within the preset tolerance range (e.g.) When the depth is within 1 / 3 of the specified value, the leveling of the over-excavated area of ​​the deep pit is considered complete.

[0042] Step S4: After the deep pit is filled, for the conventional over-excavated area, a variable thickness slicing algorithm is used to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and the print head moving speed and pump extrusion speed are adjusted in conjunction to level the surface; when the leveling reaches the preset flatness threshold, the process is switched to standard continuous slicing for printing the main load-bearing structure.

[0043] After the deep pit is filled, the rock surface becomes a gently undulating continuous curved surface. At this point, the non-planar variable thickness transition slicing stage, or Meso-leveling stage, is entered into the conventional over-excavation transition zone. A variable thickness slicing algorithm is introduced, and the printing layer thickness is no longer a global constant, but is dynamically calculated based on the normal distance of the current point from the theoretical design surface.

[0044] In one specific embodiment, step S4 includes the following sub-steps: Based on the current print position Normal deviation at point Calculate the target layer thickness using the following formula. : , in, For standard layer thickness, This is the thickness compensation coefficient; for example, The range of values ​​is Preferred And satisfy the constraints. , The minimum printable layer thickness is generally taken as... , The maximum printable layer thickness is generally taken as... This formula ensures that the layer thickness is increased at pits to fill depressions, and that the layer thickness is reduced at protrusions to avoid interference.

[0045] At the same time, based on the calculated continuously varying layer thickness Real-time reverse calculation of printhead movement speed With pump extrusion speed The matching relationship. Based on the principle of volume conservation, the extrusion amount satisfy: Reverse calculation of print head movement speed With pump extrusion speed The matching relationship, where, For standard line width, exemplarily, The range of values ​​is Preferred Under the condition that the rated flow rate of the pumping system is constant, and It is inversely proportional, that is, the potholes Increase, system decrease And improve simultaneously This increases the extrusion amount per unit length; the protrusion... Reduce, system improve and reduce This reduces the amount extruded per unit length. In practice, the above-mentioned linkage control logic can be implemented through a PLC to achieve an adaptive effect where the material moves slower and extrudes more in uneven areas, and moves faster and extrudes less in raised areas.

[0046] When the standard deviation of the normal deviation values ​​at each point of the current printed layer If the flatness is less than or equal to the preset flatness threshold, the leveling of the regular over-excavation area is considered complete.

[0047] Specifically, the Meso-leveling stage continues until the overall flatness of the current printed layer reaches a preset threshold, which is the standard deviation of the normal deviation at each point on the printed surface. Characterization, exemplarily, when The leveling process is considered complete upon completion.

[0048] After the bottom layer has undergone macro-leveling and meso-leveling processes and meets the flatness requirements, the printing mode is adjusted to switch to standard continuous slicing for printing the main load-bearing structure. Specifically, this involves automatically switching to the standard layer continuous spiral slicing stage, also known as the micro-printing stage. This includes: using a constant-thickness spiral continuous slicing algorithm, with the center of the tunnel cross-section as the origin, expanding the spiral path circle by circle according to the polar coordinate angle increment method to generate a spiral path; controlling the print head to move along the spiral path at a constant... With constant Perform continuous printing and control the overlap rate between adjacent trajectories to maintain a preset overlap rate.

[0049] In other words, the micro-printing stage employs a constant-thickness spiral continuous slicing algorithm, with the print head maintaining a constant layer thickness along the circumferential direction of the tunnel cross-section. With constant linewidth Perform continuous spiral printing, maintaining the distance between adjacent spiral tracks. The preset overlap ratio forms the secondary lining of the main load-bearing structure.

[0050] Furthermore, the spiral path is generated using an angle increment method based on polar coordinates, with the center of the tunnel cross-section as the origin, expanding counterclockwise in successive loops, with a constant radial step distance between loops: ,in, The overlap rate has a range of values. Preferred .

[0051] In this embodiment, by acquiring measured point clouds and performing spatial registration and Boolean difference operations with the design BIM model, a deviation voxel matrix that accurately represents the spatial distribution of over-excavation and under-excavation on the tunnel rock surface is constructed. Based on the normal deviation value, the rock surface is scientifically divided into deep pit over-excavation zone, conventional over-excavation zone, and under-excavation zone, and differentiated collaborative control is implemented. Specifically, for the deep pit over-excavation zone, a local parallel contour offset algorithm combined with large layer thickness parameters is used for layer-by-layer stacking and leveling. After the deep pit is filled, a variable thickness slicing algorithm is introduced for the conventional over-excavation zone. The target layer thickness is dynamically calculated based on the normal deviation value, and the printing head moving speed and pump extrusion speed are adjusted in conjunction. Through the synergistic effect of the above-mentioned multi-level partition slicing and parameter linkage control, 3D printing technology can highly adapt to the complex geometric environment of irregular tunnel cross-sections, overcome the quality defects such as insufficient lining thickness, back voids, and concrete segregation that are prone to occur in traditional 3D printing technology, improve the printing quality and forming accuracy of tunnel secondary lining, and is expected to promote the practical application of 3D printed concrete technology in complex tunnel engineering.

[0052] In one embodiment of the present invention, based on geometrically adaptive slicing, a mechanical adaptive control step is further included to address the differences in gravity environment across the tunnel cross-section. Specifically, this includes: extracting the normal vectors of each point on the current printed surface, calculating the angle between the normal vectors and the global gravity direction vector, and defining it as the gravity deflection angle. According to the aforementioned gravity deflection angle The tunnel cross-section is dynamically divided into three printing mechanical zones: the invert zone, the sidewall zone, and the crown zone. For the sidewall and crown zones, anti-slip and anti-fall mechanical compensation controls are implemented. Furthermore, the anti-slip and anti-fall mechanical compensation controls include non-orthogonal attitude offset compensation: during printing in the sidewall and crown zones, the axial vector of the print head is controlled to generate a compensation angle. This causes the print head to be angled upwards and aligned with the previous layer of solidified concrete for compression; the compensation angle... Calculate using the following formula: ,in, The angle of deflection due to gravity. This represents the attitude bias gain coefficient.

[0053] In one embodiment of the present invention, for the sidewall area and the arch crown area, mechanical compensation control for anti-slip and anti-fall is performed, which also includes implementing stepped staggered slice path planning in the transition section from the arch waist to the arch crown: when generating the arch crown path, the center line of the slice path of the next layer is set to be recessed inward by a preset amount towards the rock wall. Offset The calculation formula is as follows: , in, This is the misalignment gain coefficient. This is the current printed layer thickness.

[0054] The following details the mechanical adaptive control mechanism implemented based on differences in the gravity environment.

[0055] First, a gravity deflection field mapping and collapse risk classification model is established. The establishment of this model further includes the following sub-steps: Extracting the normal vector of each point on the current printing surface during the Meso-leveling or Micro-printing stage. And calculate its relationship with the global gravity direction vector. The included angle , This is called the gravitational deflection angle; according to The size of the tunnel cross-section dynamically divides it into three mechanical zones: the first is the invert zone, i.e. In the first area, the printed surface faces upwards, and the angle between the direction of gravity and the normal to the printed surface is small. Gravity is beneficial for concrete compaction and density. The second area is the sidewall area, i.e. The printing surface in this area is approximately vertical, and gravity generates a significant component force tangentially to the printing surface, causing the uncured concrete to slide down the wall surface; the third is the arched area, i.e. The area was printed with the printing surface facing down, and gravity generated a tearing force in the normal direction of the printing surface, causing the concrete to fall.

[0056] The aforementioned partitions are dynamically updated as the printing surface progresses layer by layer, ensuring real-time mechanical control.

[0057] Then, for the sidewall area and the vault area, mechanical compensation control for anti-slip and anti-fall is performed, including implementing non-orthogonal printhead attitude offset compensation based on the component of gravity.

[0058] It should be noted that in traditional 3D printing, the print head axis is always perpendicular to the printing surface, that is, the print head axis is perpendicular to the normal vector. Overlap. In this embodiment, anti-slip attitude offset control is achieved through non-orthogonal printhead attitude offset compensation. That is, during printing in the sidewall area and the arch area, the printhead axial vector is set. Generate a compensation deflection angle This means that the nozzle is no longer perpendicular to the rock surface, but is angled upwards to squeeze the upper layer of solidified concrete, in order to reduce the risk of slippage and fall in the sidewall area and the arch area.

[0059] Among them, the compensation deflection angle The calculation formula is as described above. For example, the attitude bias gain coefficient... The range of values ​​is Preferred This formula ensures that at the starting position of the sidewall zone... hour ,along with Increase to the vault area hour, Reaching the maximum value By performing forward and inverse kinematics calculations using a multi-axis robotic arm, the compensated nozzle axial direction is... Converted into joint angles of the robotic arm The target value drives the robotic arm to adjust its posture, thereby increasing the normal component of the extrusion pressure. Actively counteract the tangential component of gravity acting on the concrete. The material is pushed in and pressed firmly against the rock wall. During the attitude adjustment process, the position of the robotic arm's end effector remains along the preset slicing path, with only the attitude shifting, ensuring that the path accuracy is not affected.

[0060] In traditional slicing, the centerlines of the upper and lower paths completely coincide, and the integrity between layers relies solely on material bonding force, making them prone to overall slippage under the influence of the tangential component of gravity. In one embodiment of this invention, to further resist interlayer slippage, the solution also includes implementing a stepped staggered slicing path planning in the transition section from the arch waist to the arch crown: when generating the arch crown path, a preset inward offset is set for the centerline of the next layer's slicing path towards the rock wall. Offset The calculation formula is as follows: , in, This is the misalignment gain coefficient. This is the current printed layer thickness.

[0061] For example, the misalignment gain coefficient The range of values ​​is Preferred This formula ensures that in the sidewall zone... hour ,along with Increase to the vault area, Gradually increasing in size. The formed cross-section exhibits a microscopic inverted stepped interlocking structure, with the lower surface of the upper concrete layer embedded in the groove formed by the upper surface of the lower concrete layer, significantly increasing interlayer friction and mechanical interlocking force. When hour, Reaching its maximum value, approximately That is, the interlayer misalignment is about half the layer thickness, forming a stable mechanical interlock.

[0062] This embodiment introduces an inward offset when generating the arch path using the slicing algorithm. This causes the centerline of the slice path in the next layer to no longer coincide with the centerline of the previous layer, but to recede towards the rock wall, thereby resisting interlayer slippage.

[0063] Furthermore, in the vaulted area, to address the most severe risk of fall, adaptive rheological thin-layer rapid printing and accelerator follow-up control are implemented, namely: Change the current print layer thickness from the standard layer thickness. Reduce to thin layer thickness Thinning ratio satisfy: , in, This is the layer thickness reduction factor.

[0064] For example, the layer thickness reduction factor The range of values ​​is Preferred .when hour, That is, the thickness of the thinnest part of the vault is half the thickness of the standard layer, for example from... Thin to Thin-layer printing increases the heat dissipation area of ​​a single layer, accelerates the release of heat of hydration and temperature uniformity, thereby shortening the initial setting time.

[0065] At the same time, the current gravitational deflection angle The accelerator addition valve, output as a control variable to the concrete pumping equipment, specifies the instantaneous addition ratio of the accelerator. Calculate using the following formula: , in, Add a scale to the baseline, with a range of values, for example, set to... Preferred ; This is the gain coefficient of the accelerator, and its value range is, for example, set to... Preferred .

[0066] Based on the above formula, when hour, To achieve the maximum addition ratio, this linkage control enables slow-setting self-leveling of the base plate and instant-setting without falling off of the arch: inverted arch area hour, The concrete is kept within a relatively long workable time to facilitate self-leveling and air bubble removal; sidewall area Increase As the curing time increases linearly, the setting time gradually decreases; vault region maximum, At its maximum, the concrete reaches initial setting quickly after extrusion, which helps it resist gravity-induced falls.

[0067] In summary, the method provided in this embodiment, through a three-level progressive strategy of macro-leveling, meso-leveling, and micro-printing, transforms complex over- and under-excavated cross-sections that traditional equal-thickness slicing cannot handle into a flat substrate that can be printed layer by layer. This avoids mechanical interference between the print head and the under-excavated rock surface, and eliminates suspended extrusion and material fall at over-excavated deep pits. In terms of mechanical adaptability, the printing quality is improved through four-dimensional synergy of gravity-biased field mapping, non-orthogonal attitude offset, stepped staggered slicing, and accelerator follow-up control. In addition, variable-thickness slicing and island filling strategies improve material utilization. In conclusion, this solution provides a complete, executable, and scalable technical solution for intelligent tunnel construction through the cross-integration of multiple technologies from geometry, robot kinematics, and materials rheology.

[0068] Based on the same inventive concept, this embodiment also provides a 3D printing tunnel cross-section scanning control system, which is used to perform the steps of the method described in any of the above embodiments, including: The generation unit is configured to acquire measured point cloud data of the tunnel rock surface and the design BIM model, perform spatial registration and Boolean difference operation, and generate a deviation voxel matrix containing the normal deviation values ​​of each spatial location. The division unit is configured to divide the tunnel rock surface into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone based on the normal deviation value; The first leveling unit is configured to generate a filling path using a local parallel contour offset algorithm for the deep pit over-excavation area, and to perform layer-by-layer leveling with a preset large layer thickness parameter until the filling height reaches the same level as the surrounding conventional over-excavation area. The second leveling and printing unit is configured to, after filling the deep pit over-excavation, use a variable thickness slicing algorithm for the conventional over-excavation area to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and adjust the print head moving speed and pump extrusion speed in conjunction to perform leveling; when the leveling reaches the preset flatness threshold, it switches to standard continuous slicing for printing the main load-bearing structure.

[0069] The 3D printing tunnel cross-section scanning control system provided in this embodiment can realize the steps and processes of the 3D printing tunnel cross-section scanning control method provided in any of the above embodiments, and achieve the same technical effect, which will not be described in detail here.

[0070] It should be noted that the method provided in this application can be applied to Figure 2 Among the electronic devices shown, the electronic devices may be, but are not limited to, mobile terminals such as mobile phones, tablets, handheld computers, and personal digital assistants (PDAs), smart home devices such as smart TVs and smart cameras, wearable devices such as smart bracelets, smartwatches, and smart glasses, or other computer devices such as desktop, laptop, notebook, ultra-mobile personal computer (UMPC), netbook, and smart screen.

[0071] like Figure 2 As shown, the electronic device 200 may include one or more of the following components: a processor 201, a memory 203, a communication interface 202, and a communication bus 204. The memory 203 can be connected to the processor 201 via the bus 204. The bus can transfer data between the processor 201 and the memory 203. The bus can be divided into an address bus, a data bus, a control bus, etc.

[0072] Processor 201 may include one or more processing cores. Processor 201 can connect to various parts within the electronic device 200 using various interfaces and lines. It performs various functions and processes data by running or executing instructions, programs, code sets, or instruction sets stored in memory 203, and by calling data stored in memory 203. For example, processor 201 may include an application processor (AP), a modem processor, a CPU, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic array (PLA), and / or a neural network processing unit (NPU). The CPU primarily handles the operating system, user interface, and applications; the GPU is responsible for rendering and drawing the content to be displayed; the NPU implements artificial intelligence (AI) functions; and the modem handles wireless communication. Different processing units can be independent devices or integrated into one or more processors. For example, the multiple processing units shown above are all integrated into a single SoC, or the AP is a separate semiconductor chip, while other processing units are integrated into a single SoC. This application does not limit this to any particular type.

[0073] The memory 203 may include random access memory (RAM), read-only memory (ROM), or non-transitory computer-readable storage medium. The memory 203 can be used to store instructions, programs, code, code sets, or instruction sets. The memory 203 may include a program storage area and a data storage area. The program storage area may store instructions for implementing an operating system or instructions for at least one function, such as a 3D printing tunnel section scanning control method. The data storage area may store data created based on the use of the electronic device 200, such as input data for numerical solutions.

[0074] In addition, those skilled in the art will understand that the structure of the electronic device 200 shown in the above figures does not constitute a limitation on the electronic device 200. The electronic device may include more or fewer components than shown, or combine certain components, or have different component arrangements. For example, the electronic device 200 may also include components such as a microphone, speaker, radio frequency circuit, sensor, audio circuit, power supply, and Bluetooth module, which will not be described in detail here.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for controlling the scanning of a 3D printed tunnel cross-section, characterized in that, Includes the following steps: Acquire measured point cloud data of tunnel rock surface and design BIM model, perform spatial registration and Boolean difference operation to generate deviation voxel matrix containing normal deviation values ​​of each spatial location; Based on the aforementioned normal deviation value, the tunnel rock surface is divided into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone. For the deep pit over-excavation area, a local parallel contour offset algorithm is used to generate a filling path, and the filling path is stacked layer by layer with a preset large layer thickness parameter until the filling height reaches the same level as the surrounding conventional over-excavation area. After the deep pit is filled, a variable thickness slicing algorithm is used for the conventional over-excavated area. The target layer thickness is dynamically calculated based on the normal deviation value of the current point, and the print head moving speed and pump extrusion speed are adjusted in conjunction to achieve leveling. When the leveling reaches the preset flatness threshold, the printing is switched to standard continuous slicing for printing the main load-bearing structure.

2. The method according to claim 1, characterized in that, Based on the normal deviation value, the tunnel rock surface is divided into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone, specifically including: Set a severe over-excavation threshold With slight over-excavation threshold Traverse the deviation voxel matrix and determine the deviation values ​​based on the normal values. Based on the comparison with two thresholds, the tunnel rock surface is divided into three regions: normal deviation value The area with a value greater than 0 is designated as the under-excavation area; normal deviation value Less than The independent concave area is divided into the deep pit over-excavation area; The normal deviation value is between and The area between them is designated as the conventional over-excavation zone.

3. The method according to claim 1, characterized in that, For the over-excavated deep pit area, a local parallel contour offset algorithm is used to generate a filling path, and the path is leveled layer by layer using a preset large layer thickness parameter. Specifically, this includes: Using the horizontal plane where the lowest point of the deep pit over-excavation area is located as the initial layer, a filling trajectory is generated by parallel offset inward according to the preset thick line width, and then stacked upward layer by layer along the depth direction according to the large layer thickness parameter. Controlling the printhead movement speed during the stacking process With extrusion flow rate Satisfying Relationship: ,in, For thicker lines, For large layer thickness parameters; When the filling height of the deep pit over-excavation area reaches a level within the preset tolerance range compared to the average height difference of the surrounding conventional over-excavation areas, the leveling of the deep pit over-excavation area is determined to be complete.

4. The method according to claim 3, characterized in that, For conventional over-excavation areas, a variable thickness slicing algorithm is used to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and to adjust the print head moving speed and pump extrusion speed in conjunction to achieve leveling. Specifically, this includes: Based on the current print position Normal deviation at point Calculate the target layer thickness using the following formula. : ， in, For standard layer thickness, This is the thickness compensation coefficient; Based on the principle of volume conservation, extrusion amount satisfy: Reverse calculation of print head movement speed With pump extrusion speed The matching relationship, where, Standard line width; When the standard deviation of the normal deviation values ​​at each point of the current printed layer If the flatness is less than or equal to the preset flatness threshold, the leveling of the regular over-excavation area is considered complete.

5. The method according to claim 4, characterized in that, Switching to standard continuous slice printing for the main load-bearing structure includes: The algorithm of continuous spiral slicing with equal thickness is adopted. Taking the center of the tunnel cross section as the origin, the spiral path is generated by expanding circle by circle according to the polar coordinate angle increment method. Control the print head along the spiral path at a constant speed With constant Perform continuous printing and control the overlap rate between adjacent trajectories to maintain a preset overlap rate.

6. The method according to any one of claims 1 to 5, characterized in that, The method also includes a mechanical adaptive control step implemented to address differences in the gravity environment of the tunnel cross section, specifically including: Extract the normal vectors of each point on the current printed surface, and calculate the angle between the normal vectors and the global gravity direction vector, which is defined as the gravity deflection angle. ; According to the gravity deflection angle The tunnel cross-section is dynamically divided into three printing mechanical zones: the invert zone, the sidewall zone, and the crown zone. For the aforementioned sidewall area and arch area, mechanical compensation control for anti-slip and anti-fall is implemented.

7. The method according to claim 6, characterized in that, For the aforementioned sidewall and vault areas, mechanical compensation control for anti-slip and anti-fall measures is implemented, including non-orthogonal attitude offset compensation: When printing in the sidewall and vault areas, control the axial vector of the print head to generate a compensation angle. This causes the print head to be angled upwards and pressed against the previous layer of solidified concrete. The compensation deflection angle Calculate using the following formula: ,in, The angle of deflection due to gravity. This represents the attitude bias gain coefficient.

8. The method according to claim 6, characterized in that, For the aforementioned sidewall and arch areas, mechanical compensation control for anti-slip and anti-fall measures is implemented, which also includes: implementing stepped staggered slice path planning in the transition section from the arch waist to the arch crown. When generating the arch path, set the centerline of the next layer's slice path to be offset inwards towards the rock face by a preset amount. Offset The calculation formula is as follows: ， in, This is the misalignment gain coefficient. This is the current printed layer thickness.

9. The method according to claim 6, characterized in that, The mechanical compensation control for anti-slip and anti-fall measures applied to the sidewall area and the arch area also includes adaptive rheological thin-layer rapid printing and accelerator follow-up control in the arch area: Change the current print layer thickness from the standard layer thickness. Reduce to thin layer thickness Thinning ratio satisfy: ， in, This is the layer thickness reduction factor.

10. A 3D printing tunnel cross-section scanning control system, characterized in that, The system is used to perform the steps of the method according to any one of claims 1 to 9, including: The generation unit is configured to acquire measured point cloud data of the tunnel rock surface and the design BIM model, perform spatial registration and Boolean difference operation, and generate a deviation voxel matrix containing the normal deviation values ​​of each spatial location. The division unit is configured to divide the tunnel rock surface into a deep pit over-excavation zone, a conventional over-excavation zone, and an under-excavation zone based on the normal deviation value; The first leveling unit is configured to generate a filling path using a local parallel contour offset algorithm for the deep pit over-excavation area, and to perform layer-by-layer leveling with a preset large layer thickness parameter until the filling height reaches the same level as the surrounding conventional over-excavation area. The second leveling and printing unit is configured to, after filling the deep pit over-excavation, use a variable thickness slicing algorithm for the conventional over-excavation area to dynamically calculate the target layer thickness based on the normal deviation value of the current point, and adjust the print head moving speed and pump extrusion speed in conjunction to perform leveling; when the leveling reaches the preset flatness threshold, it switches to standard continuous slicing for printing the main load-bearing structure.

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