Spray synchronization control method and system based on workpiece three-dimensional point cloud track planning

Abstract

The present application relates to the technical field of industrial control, in particular to a showering synchronous control method and system based on workpiece three-dimensional point cloud trajectory planning, which comprises the following steps: firstly, obtaining three-dimensional point cloud data and workpiece posture data of the workpiece surface, and constructing a surface grid model; secondly, extracting surface curvature features and dividing surface areas, combining area weight and sagging risk level to generate a coating material distribution scheme; then, generating showering trajectory and flow control parameters and executing showering; finally, obtaining coating thickness data, updating showering trajectory and flow control parameters until the preset thickness requirement is met. The present application can improve showering uniformity and control stability.

Description

Technical Field

[0001] This invention relates to the field of industrial control technology, specifically to a method and system for synchronous control of spray coating based on workpiece three-dimensional point cloud trajectory planning. Background Technology

[0002] In the surface coating manufacturing process, the coating quality directly affects the uniformity of coverage, material utilization, and the consistency of subsequent finished products. Related technologies have become an important direction for the coordinated development of vision inspection and industrial control systems. Current coating control methods largely rely on preset trajectories, fixed flow rates, or manual experience corrections. When dealing with workpieces with significant surface undulations and continuously changing postures, problems such as localized drips, insufficient coverage, edge buildup, and repeated coating are prone to occur. Especially in complex surface treatments, without joint analysis of surface morphology, area, posture, and post-coating thickness, it is often difficult to achieve integrated control of trajectory generation, material distribution, and online correction, thus affecting coating stability and production cycle time. Summary of the Invention

[0003] This invention provides a method and system for synchronous control of spray coating based on workpiece three-dimensional point cloud trajectory planning, which is used to at least solve the problems of how to simultaneously take into account trajectory planning, material distribution, sagging control and thickness compliance during the spray coating process on complex surfaces.

[0004] In a first aspect, the present invention provides a method for synchronous control of spray coating based on workpiece three-dimensional point cloud trajectory planning, the method comprising: Acquire 3D point cloud data and workpiece posture data of the workpiece surface, and construct a surface mesh model based on the 3D point cloud data; The surface curvature features are extracted from the surface mesh model and the surface regions are divided. The area weight of each surface region is determined based on its area. The sag risk level of each surface region is determined based on the surface curvature features and workpiece posture data. The coating material allocation scheme is generated by combining the area weights. Based on the surface mesh model and coating material distribution scheme, generate the coating trajectory and flow control parameters, and control the coating equipment to perform coating; Acquire coating thickness data and update the coating trajectory and flow control parameters based on the coating thickness data until the coating thickness data meets the preset thickness requirements.

[0005] In one possible implementation, the process involves acquiring three-dimensional point cloud data and workpiece posture data of the workpiece surface, and constructing a surface mesh model based on the three-dimensional point cloud data. This includes: performing a three-dimensional scan of the workpiece surface to obtain raw point cloud data; acquiring workpiece posture data; denoising the raw point cloud data; and constructing a surface mesh model based on the denoised point cloud data.

[0006] In one possible implementation, surface curvature features are extracted and surface regions are divided based on a surface mesh model, including: calculating the Gaussian curvature and average curvature of each mesh cell based on the surface mesh model to obtain surface curvature features; and dividing surface regions based on the curvature continuity and spatial connectivity of adjacent mesh cells.

[0007] In one possible implementation, the area weight of a surface region is determined based on the area of ​​that surface region, including: calculating the proportion of the area of ​​each surface region in the total area of ​​the workpiece surface, as the area weight of each surface region.

[0008] In one possible implementation, generating a coating material allocation scheme includes: determining the tilt state of each surface region relative to the direction of gravity based on workpiece posture data; determining the sagging risk level of each surface region based on surface curvature characteristics and tilt state; and determining the amount of coating material allocated to each surface region based on region area weight and sagging risk level, thereby obtaining the coating material allocation scheme.

[0009] In one possible implementation, generating the coating trajectory and flow control parameters includes: generating the coating trajectory for each surface region based on the surface mesh model; and determining the flow control parameters for each surface region based on the coating material distribution scheme.

[0010] In one possible implementation, controlling the coating equipment to perform coating includes: controlling the coating equipment to move relative to the workpiece surface along the coating trajectory; and controlling the coating equipment to output coating material according to flow control parameters.

[0011] In one possible implementation, obtaining coating thickness data includes: scanning the surface of the workpiece after coating to obtain post-coating surface data; and determining the coating thickness data for each surface region based on the post-coating surface data and the surface mesh model.

[0012] In one possible implementation, updating the coating trajectory and flow control parameters based on coating thickness data includes: determining the surface area where the thickness does not meet the standard based on the difference between the coating thickness data and the preset thickness requirement; adjusting the coating material distribution scheme based on the workpiece posture data and sagging risk level corresponding to the surface area where the thickness does not meet the standard; and updating the coating trajectory and flow control parameters based on the adjusted coating material distribution scheme.

[0013] Secondly, the present invention provides a spray coating synchronization control system based on workpiece three-dimensional point cloud trajectory planning, used to implement a spray coating synchronization control method based on workpiece three-dimensional point cloud trajectory planning. The system includes: The data modeling module is used to acquire 3D point cloud data and workpiece posture data of the workpiece surface, and to construct a surface mesh model based on the 3D point cloud data. The risk allocation module is used to extract surface curvature features and divide surface regions based on the surface mesh model, determine the area weight of each surface region based on its area, determine the sagging risk level of each surface region based on the surface curvature features and workpiece posture data, and generate a coating material allocation scheme by combining the area weights. The trajectory control module is used to generate the coating trajectory and flow control parameters based on the surface mesh model and coating material distribution scheme, and to control the coating equipment to perform coating. The thickness update module is used to acquire coating thickness data and update the coating trajectory and flow control parameters based on the coating thickness data until the coating thickness data meets the preset thickness requirements.

[0014] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: By employing 3D point cloud modeling and surface curvature analysis techniques, material allocation for surface regions was achieved; by using attitude data and sagging risk joint judgment techniques, differentiated control of coating risks in different regions was realized; and by using coating thickness detection and trajectory and flow closed-loop update techniques, dynamic correction of the coating process was achieved, reducing sagging, missed coating, and material waste. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of the method of the present invention; Figure 2 This is a diagram showing the module composition of the system of the present invention. Detailed Implementation

[0016] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0017] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0018] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0019] Workpiece 3D point cloud trajectory planning refers to the process of acquiring 3D spatial information of a workpiece surface through visual inspection and generating an executable motion trajectory based on the workpiece surface's geometric contour, surface undulations, and spatial orientation. This technology essentially belongs to spatial path planning technology that combines visual inspection with industrial control systems. Its core lies in transforming discretely sampled surface point information into continuous, controllable trajectory information, ensuring that the equipment's motion path corresponds to the actual surface morphology of the workpiece. In surface treatment, processing control, and automated coating technologies, workpiece 3D point cloud trajectory planning is not only used to determine the range of motion and direction of travel but also provides a geometric basis for region division, parameter matching, and process control. Based on this, this invention further integrates workpiece 3D point cloud trajectory planning with material distribution, attitude analysis, and thickness feedback in the coating process to construct a complete technical solution for synchronous control of coating.

[0020] like Figure 1 As shown, a method for synchronous control of spray coating based on workpiece 3D point cloud trajectory planning is presented. The method includes: Acquire 3D point cloud data and workpiece posture data of the workpiece surface, and construct a surface mesh model based on the 3D point cloud data; After the workpiece enters the coating station, the surface to be coated is first scanned from multiple perspectives using a 3D scanning device to acquire 3D point cloud data reflecting the surface's spatial contour. Simultaneously, workpiece attitude data is acquired by an attitude acquisition unit located at the fixture or turntable end. The 3D point cloud data and workpiece attitude data are then unified into the same station coordinate system. The 3D point cloud data undergoes basic processing, removing obvious outliers and invalid points. A surface mesh model is then constructed based on the processed point connections. This surface mesh model characterizes the local morphology and overall boundary of the workpiece surface and serves as the geometric basis for subsequent surface region division, coating trajectory generation, and coating thickness comparison.

[0021] Acquire 3D point cloud data and workpiece posture data of the workpiece surface, and construct a surface mesh model based on the 3D point cloud data, including: performing 3D scanning of the workpiece surface to obtain raw point cloud data; collecting workpiece posture data; denoising the raw point cloud data; and constructing a surface mesh model based on the denoised point cloud data.

[0022] In one embodiment, the process of acquiring three-dimensional point cloud data and workpiece posture data of the workpiece surface, and constructing a surface mesh model based on the three-dimensional point cloud data, can be implemented as follows: After the workpiece is fixed on a rotatable fixture, a three-dimensional scanning device is activated to continuously scan the workpiece surface. The three-dimensional scanning device can be a structured light scanner or a line laser scanner, and the output raw point cloud data includes at least the spatial coordinate information of each sampling point.

[0023] To minimize occlusion effects, point clouds can be collected after the workpiece has rotated at two or more different angles using the fixture. These multiple collections are then stitched together in the same coordinate system to form a complete raw point cloud. Simultaneously, an attitude sensor is installed at the fixture end to collect real-time data on the workpiece's rotation around each axis, generating workpiece attitude data corresponding to the scanning time. This workpiece attitude data characterizes the current orientation of the workpiece surface relative to gravity. Therefore, after collection, the workpiece attitude data is correlated with the raw point cloud data using timestamps or sampling numbers, allowing geometric and attitude information to be used in the same processing flow. After the raw point cloud data is formed, denoising is performed. Denoising includes removing isolated points, eliminating outliers exceeding neighborhood distance thresholds, and filling and smoothing missing points in localized areas. Isolated point removal removes scattered points caused by scanning reflections, edge jitter, or environmental interference; outlier removal preserves the true contour of the workpiece surface; and point filling and smoothing maintain surface continuity for subsequent mesh reconstruction. After obtaining the denoised point cloud data, triangular facets are connected based on the spatial adjacency relationship between adjacent points to form a surface mesh model composed of vertices, edges, and triangular facets.

[0024] For areas with significant surface curvature changes, the local mesh density can be increased; for areas with relatively flat surfaces, a larger patch size can be used. The completed surface mesh model not only preserves the workpiece surface's shape boundary and local undulation information, but also provides a unified geometric basis for subsequent extraction of surface curvature features, surface region division, and generation of coating trajectories.

[0025] The surface curvature features are extracted from the surface mesh model and the surface regions are divided. The area weight of each surface region is determined based on its area. The sag risk level of each surface region is determined based on the surface curvature features and workpiece posture data. The coating material allocation scheme is generated by combining the area weights. After the surface mesh model is constructed, surface curvature features reflecting local undulations and overall transition relationships are extracted from it. Surface regions are then divided based on the continuity of curvature changes and mesh connectivity. Once the surface regions are determined, the area percentage of each region on the workpiece surface is calculated to obtain the region area weights used to characterize the region coverage requirements. Subsequently, the surface curvature features are jointly analyzed with workpiece attitude data to determine the sagging risk level of each surface region under the current attitude. Finally, the region area weights are combined to generate a coating material allocation scheme, providing a region-level basis for subsequent coating trajectory planning and flow control.

[0026] The surface curvature features are extracted and the surface regions are divided according to the surface mesh model, including: calculating the Gaussian curvature and average curvature of each mesh unit according to the surface mesh model to obtain the surface curvature features; and dividing the surface regions according to the curvature continuity and spatial connectivity of adjacent mesh units.

[0027] In one embodiment, surface curvature feature extraction and surface region segmentation are primarily used to transform discrete meshes into region cells that can directly participate in coating control. The new limitation of this embodiment compared to the previous step is that it no longer merely uses the surface mesh model as a geometric display result, but further extracts curvature information reflecting the degree of local bending from each mesh cell, and utilizes the geometric continuity between adjacent mesh cells to form stable surface region boundaries.

[0028] In practice, triangular facets or mesh vertices are used as basic computational units. The normal variations and spatial relationships of adjacent units around each basic unit are read. For each basic unit, Gaussian curvature and mean curvature can be calculated using local fitting or neighborhood difference methods commonly used in discrete surface processing. Gaussian curvature reflects whether the location is flat, convex, concave, or saddle-shaped, while mean curvature reflects the strength of the overall curvature at that location. After calculation, Gaussian curvature and mean curvature are saved together as surface curvature features in the mesh attributes. Subsequently, region growth is performed on all mesh units. During region growth, the starting unit is a mesh unit with relatively stable curvature changes, and the growth expands outwards along adjacent edges. When the Gaussian curvature variation, mean curvature variation, and normal angle of adjacent mesh units are all within a preset range, the adjacent mesh units are merged into the same surface region. When there is a significant curvature abrupt change, excessive normal variation, or no direct connectivity between meshes, the expansion in the current direction is stopped, and that point is taken as the boundary of the adjacent surface region. For areas with holes, sharp corners, or incomplete scanning, boundary repair can be performed first, followed by region division to avoid incorrect region splitting due to data breakage. The surface regions obtained in this way retain the true surface undulations of the workpiece while avoiding overly fragmenting the originally continuous spraying surface, thus facilitating subsequent organization of material usage and planning of coating paths according to regions.

[0029] For large, flat areas, the area division results are usually more complete; for edge transition areas, groove areas, or boss areas, the area division results can form clearer local boundaries, which can make subsequent risk assessment and material allocation closer to the actual surface condition of the workpiece.

[0030] The area weight of a surface region is determined by the area of ​​that surface region, including: calculating the proportion of the area of ​​each surface region in the total surface area of ​​the workpiece, which is used as the area weight of each surface region.

[0031] In one embodiment, the process of determining the area weights of different regions further incorporates area quantization constraints compared to surface curvature feature extraction and surface region segmentation. The purpose of introducing this constraint is to ensure that subsequent material allocation is not only based on changes in surface shape, but also reflects the objective requirements of different surface regions for coverage area.

[0032] In practice, after the surface area is divided, all triangular facets contained in each surface area are first read. The area of ​​each triangular facet can be directly calculated based on the spatial coordinates of its three vertices. Then, the areas of all triangular facets within the same surface area are summed to obtain the area of ​​that surface area. The total surface area of ​​the workpiece is obtained by summing the area areas of all surface areas. To avoid fixture-obstructed surfaces, non-coating surfaces, or surfaces prohibited from being covered by the process from entering the statistical range, facets that do not participate in coating can be filtered out before calculating the area, based on the workpiece process boundaries, and only the areas to be coated are counted. After the area calculation is completed, the area area of ​​each surface area is divided by the total surface area of ​​the workpiece to obtain the corresponding area weight. The area weight is used to reflect the proportion of the surface area in the overall surface to be coated. Surface areas with larger areas usually bear greater basic coverage requirements, while surface areas with smaller areas but concentrated shape variations reflect more local fine coverage requirements. To ensure the stability of the subsequent allocation process, the area weights can be normalized so that the sum of the area weights of all surface areas remains one.

[0033] If certain surface regions are too small and formed by mesh noise or boundary debris, a minimum region threshold can be set after area statistics. This allows the excessively small surface regions to be merged into adjacent surface regions with similar curvature characteristics, and the region area weights can then be recalculated. Through this process, the region area weights not only have a clear geometric origin but can also directly participate in subsequent material allocation calculations. This ensures that the material allocation results simultaneously consider both the region coverage and local surface features, avoiding the neglect of basic coverage requirements for large areas when allocating materials solely based on curvature characteristics.

[0034] The process of generating a coating material allocation scheme includes: determining the tilt state of each surface region relative to the direction of gravity based on workpiece posture data; determining the sagging risk level of each surface region based on surface curvature characteristics and tilt state; and determining the amount of coating material allocated to each surface region based on region area weight and sagging risk level, thus obtaining the coating material allocation scheme.

[0035] In one embodiment, the process of generating the coating material distribution scheme further incorporates attitude constraints and risk constraints compared to the aforementioned process. The purpose of introducing these constraints is to unify the surface shape, area, and current orientation of the workpiece into the same distribution logic, avoiding the situation where material distribution is based solely on static geometric results and fails to reflect the actual flow trend during coating.

[0036] In practice, the tilt of each surface region relative to the direction of gravity is first determined based on the workpiece posture data. The average normal of the surface region can be used as the representative direction of that surface region, and then the orientation relationship of the surface region in the current station is calculated by combining it with the workpiece posture data. For surface regions with a large angle between the average normal and the direction of gravity, the flow tendency of the coating material in the tangential direction of the surface is more obvious; for surface regions with an average normal close to vertically upward, the material is more likely to remain locally. Subsequently, the tilt state and surface curvature characteristics are analyzed together to determine the sagging risk level. Specifically, a graded judgment method can be adopted: when the average curvature of the surface region is large, there is a clear transition between concave and convex areas, and the tilt degree is large, the surface region is judged as a high sagging risk area; when the curvature change is moderate and the tilt degree is moderate, it is judged as a medium sagging risk area; when the curvature change is gentle and the tilt degree is small, it is judged as a low sagging risk area.

[0037] To facilitate subsequent calculations, different risk correction coefficients can be pre-set for different sagging risk levels. The area weight and the risk correction coefficients are then used together to calculate the amount of coating material allocated to each surface area. The amount of coating material allocated to each surface area can be determined using the following formula:

[0038] in, For the first The amount of coating material allocated to each surface area This refers to the total amount of material applied to the workpiece surface. For the first The area weight of each surface region For the first Risk correction coefficient corresponding to each surface area This represents the total number of surface areas.

[0039] After obtaining the coating material allocation for each surface area using this method, a complete coating material allocation scheme is formed. The coating material allocation scheme can at least include surface area identification, area weight, sagging risk level, and corresponding material allocation amount. For areas with high sagging risk, the material allocation amount can be appropriately reduced to avoid localized material accumulation; for surface areas with low sagging risk and large areas, the material allocation amount can be maintained at a higher level to ensure basic coverage requirements. The resulting allocation scheme has a clear calculation basis and can be directly used as input for subsequent coating trajectory planning and flow control.

[0040] Based on the surface mesh model and coating material distribution scheme, generate the coating trajectory and flow control parameters, and control the coating equipment to perform coating; After the surface mesh model and coating material distribution scheme are determined, corresponding coating trajectories and flow control parameters are generated according to the surface regions, and the coating equipment is driven to perform coating. Specifically, the trajectory direction is first determined based on the boundary range, spatial orientation, and coverage direction of each surface region. Then, the material output demand per unit time is determined by combining the material distribution amount corresponding to each surface region, forming flow control parameters that correspond one-to-one with the trajectory position. Subsequently, the coating equipment is controlled to move relative to the workpiece surface along the predetermined trajectory, and the coating material is output synchronously according to the flow control parameters, ensuring that the material supply to different surface regions corresponds to the trajectory operation process.

[0041] Generate coating trajectory and flow control parameters, including: generating coating trajectory for each surface region based on the surface mesh model; and determining flow control parameters for each surface region based on the coating material distribution scheme.

[0042] In one embodiment, the coating trajectory and flow control parameters are not generated using a uniform setting for the entire workpiece, but are instead constructed separately for each surface region and then spliced ​​together into a complete execution sequence. The purpose of this approach is to ensure that different curved surface regions have independent constraints in terms of coverage direction, movement distance, and material supply, avoiding uneven coating in localized areas caused by using the same set of parameters for smooth and transitional regions. Specifically, the boundary points, center positions, and local normal distributions of each surface region in the surface mesh model are first read.

[0043] For large, continuous surface areas, it is preferable to arrange the trajectory along the long side of the area or along the direction of gentle curvature change to make the coverage transition between adjacent trajectories more stable. For surface areas with obvious boundary transitions, many local protrusions, or deep grooves, the surface area is further divided into several trajectory sub-segments, and the start point, end point, and extension direction of each trajectory sub-segment are determined to reduce abrupt coverage changes caused by the trajectory crossing areas with drastic shape changes. When generating the trajectory, several trajectory baselines that are basically parallel to the main direction of the area can be established within the surface area first. The trajectory baselines are reference lines used to determine the movement path of the coating equipment. Then, the trajectory baselines are shifted to both sides according to the preset trajectory spacing to obtain the coating trajectory covering the entire surface area.

[0044] The trajectory spacing can be determined based on the surface area width and spray width. If there are narrow corners or irregular boundaries at the edge of the surface area, an edge correction trajectory is added outside the main trajectory to ensure that the boundary position is completely covered. After the trajectory is generated, the flow control parameters corresponding to each surface area are determined according to the coating material distribution scheme. Specifically, the material distribution amount of each surface area can be read first, and then combined with the total length of all coating trajectories in that surface area, the average material output level that the surface area should maintain during the execution can be calculated. For surface areas with long trajectory lengths but low material distribution amounts, the flow control parameters are set to a smaller value; for surface areas with moderate trajectory lengths and high material distribution amounts, the flow control parameters are set to a larger value.

[0045] If the same surface area contains both a main trajectory and an edge correction trajectory, the flow control parameters can be reduced separately for the edge correction trajectory to prevent excessive material accumulation at the edges. Once the flow control parameters are determined, each coating trajectory and its corresponding flow control parameters are written into the control sequence according to the execution order, forming a trajectory parameter table that can be directly sent to the coating equipment. The trajectory parameter table can include at least the surface area number, trajectory number, trajectory start point, trajectory end point, trajectory direction, and flow control parameters. In this way, the geometric information in the surface mesh model is transformed into an executable motion path, and the material requirements in the coating material allocation scheme are transformed into executable material output instructions. This allows trajectory planning and flow setting to be completed within the same process, facilitating continuous and stable execution by the subsequent coating equipment.

[0046] Controlling the coating equipment to perform coating includes: controlling the coating equipment to move relative to the workpiece surface along the coating trajectory; and controlling the output of coating material by the coating equipment according to the flow control parameters.

[0047] In one embodiment, the execution process of the coating equipment is not simply moving along a predetermined path, but rather the trajectory movement and material output are linked and controlled in the same time sequence. The purpose of this is to ensure that when the coating equipment moves to the corresponding position in space, it can synchronously output the amount of material matching that position, avoiding local accumulation, interrupted spraying, or coverage gaps caused by moving before or after material output.

[0048] In practice, the trajectory parameter table is first loaded into the control unit, which then parses each coating trajectory sequentially according to its trajectory number. For each coating trajectory, the control unit first drives the motion mechanism to move the nozzle above the trajectory start point, then adjusts the relative distance between the nozzle and the workpiece surface to position the nozzle in the set working position. Once the nozzle is in position, the feeding mechanism is activated to enter the material discharge state. Subsequently, the motion mechanism drives the nozzle to move continuously relative to the workpiece surface along the trajectory direction, while the feeding mechanism outputs coating material according to the corresponding flow control parameters.

[0049] The motion mechanism can be a linear module, a robotic arm, or a combination of a turntable and a slide. The feeding mechanism can be a metering pump, a pressure feeding unit, or an electrically controlled valve unit. Regardless of the structure, the execution logic remains consistent: the movement and discharging processes occur synchronously. After one coating trajectory is completed, the control unit first stops material output, then moves the nozzle away from the end point of the current trajectory and switches to the starting position of the next coating trajectory. If the distance between two adjacent coating trajectories is small, a continuous lane-changing method can be used to complete the switch; if there is a significant height or direction difference between two adjacent coating trajectories, the position is first retracted and then repositioned to avoid material being dragged into non-target areas during the switch.

[0050] For multiple coating trajectories within the same surface area, they are typically executed from the inside out or from one side to the other to ensure consistent material coverage. The execution order between different surface areas can be arranged according to their spatial location and material distribution. For example, higher-level areas can be executed first, followed by lower-level areas, to reduce interference from the material in the previous area to the next. During execution, the control unit continuously records the trajectory completion status and material output status. When a nozzle is detected not in position, abnormal material output, or trajectory interruption, the current trajectory execution is paused, and execution resumes from the interruption point or is re-executed after the anomaly is resolved. After the entire execution process is completed, an initial coating result corresponding to the surface area distribution is obtained, providing a basis for subsequent coating thickness detection and trajectory updates.

[0051] Acquire coating thickness data and update the coating trajectory and flow control parameters based on the coating thickness data until the coating thickness data meets the preset thickness requirements.

[0052] After the coating process is completed, the workpiece surface is re-scanned to obtain post-coating surface data reflecting the current coating state. This post-coating surface data is then registered with the previously established surface mesh model to determine the coating thickness data for each surface region. After obtaining the coating thickness data for each surface region, it is compared with the preset thickness requirements to identify surface regions where the thickness does not meet the standard. Based on the workpiece posture data and sagging risk level corresponding to these surface regions, the coating material allocation scheme is adjusted. The coating trajectory and flow control parameters are then updated according to the adjusted coating material allocation scheme, and supplementary coating is performed until the coating thickness data meets the preset thickness requirements.

[0053] Obtaining coating thickness data includes: scanning the surface of the workpiece after coating to obtain post-coating surface data; and determining the coating thickness data for each surface region based on the post-coating surface data and the surface mesh model.

[0054] In one embodiment, the process of acquiring coating thickness data is performed after the initial coating is completed. The added limitation compared to the previous stage is the introduction of a correspondence between post-coating surface data and the surface mesh model, used to convert the initial coating results into thickness information that can be used for subsequent adjustments. The purpose of this processing is to ensure that subsequent trajectory updates and flow rate updates are based on actual detection results, rather than simply continuing to coat based on the initial allocation results.

[0055] In practice, after the workpiece completes the current round of coating, the nozzle discharge is stopped, and the nozzle or scanning head is removed from the workpiece surface to avoid residual material affecting the detection accuracy. Then, the scanning device is activated to scan the coated workpiece surface to obtain post-coating surface data. The scanning device can continue to use the structured light scanner or line laser scanner used in the initial modeling stage, or it can be an independent scanning device positioned at the inspection station. To ensure a one-to-one correspondence between the detection data and the initial geometric model, the post-coating surface data is first converted to a station coordinate system consistent with the surface mesh model after acquisition. After coordinate unification, the post-coating surface data and the surface mesh model are registered. Registration can be performed using a reference feature point alignment method or an iterative alignment method based on the overall contour, as long as the post-coating surface data and the surface mesh model coincide under the same spatial reference.

[0056] After registration, the corresponding post-coating surface data is extracted according to the boundary range of each surface region in the surface mesh model. For each surface region, the reference position of each mesh cell in that region before coating is read, and then the corresponding current position in the post-coating surface data is read. By comparing the distance difference between the two in the surface normal direction, the local coating thickness at that position is determined. After summing the local coating thicknesses at each position, the average thickness, maximum thickness, and minimum thickness of each surface region can be obtained, and complete coating thickness data can be formed accordingly. To avoid interference from local splashes, edge burrs, or scanning shadows on the thickness results, the post-coating surface data can be smoothed before thickness calculation, and outliers that deviate significantly from the thickness level of the neighborhood can be removed. For areas with small scanning blind zones, the thickness results can be supplemented by interpolation of nearby positions; for areas with large scanning blind zones, they are retained as areas to be retested to avoid using unreliable data in subsequent adjustments. After the above processing, the coating thickness data is no longer limited to single-point detection, but is established in correspondence with the surface area and surface mesh model. This allows for accurate reflection of the actual coverage status of different surface areas after the initial coating, and provides a basis for subsequent judgment on whether the thickness meets the standard and in which areas supplementary coating is needed.

[0057] The coating trajectory and flow control parameters are updated based on the coating thickness data, including: determining the surface area where the thickness does not meet the standard based on the difference between the coating thickness data and the preset thickness requirement; adjusting the coating material distribution scheme based on the workpiece posture data and sagging risk level corresponding to the surface area where the thickness does not meet the standard; and updating the coating trajectory and flow control parameters based on the adjusted coating material distribution scheme.

[0058] In one embodiment, the process of updating the coating trajectory and flow control parameters based on coating thickness data further incorporates closed-loop correction compared to the thickness detection process. The added limitation is that instead of directly repeating the coating process based on the detection results, it first identifies surface areas where the thickness does not meet the standard, then adjusts the coating material allocation scheme accordingly based on workpiece posture data and sagging risk level. Subsequently, it only updates the coating trajectory and flow control parameters for the areas requiring correction. The purpose of this approach is to ensure that supplementary coating has clear regional boundaries and parameter guidelines, avoiding repeated coverage of already compliant areas.

[0059] In practice, the average thickness of each surface area is first compared with the preset thickness requirement. If the average thickness of a surface area is lower than the preset lower limit, or if there are continuously distributed local locations within the surface area that are lower than the preset lower limit, then the surface area is determined to be a surface area with insufficient thickness. If the average thickness of a surface area is within the allowable range, the original trajectory and flow rate settings are maintained, and no further coating is applied to that surface area. After the surface area with insufficient thickness is determined, the workpiece posture data and sagging risk level corresponding to that surface area are read. If the surface area is still a high sagging risk area under the current posture, the coating material distribution scheme is adjusted by reducing the amount of material output per replenishment, while increasing the number of trajectories or reducing the trajectories spacing during trajectory updates, so that the material is replenished to the target thickness in a more gradual manner; if the surface area is a low sagging risk area, the material distribution amount corresponding to that surface area can be directly increased, and the original trajectory direction is maintained during trajectory updates, with only local flow rate control parameters increased. For surface areas in the medium-risk sagging zone, the material distribution can be slightly increased and the track spacing can be slightly reduced simultaneously to achieve a balance between coverage efficiency and sagging control.

[0060] After the coating material distribution scheme is adjusted, a supplementary coating trajectory is regenerated for the surface area where the thickness does not meet the standard, and the corresponding flow control parameters are updated simultaneously. The updated supplementary coating trajectory prioritizes covering areas with low thickness, and then smoothly connects with adjacent areas that have met the standard to avoid creating new thickness abrupt changes. After the supplementary coating is completed, the workpiece surface is scanned again and the coating thickness data is recalculated. If the re-obtained coating thickness data still does not meet the preset thickness requirements, the above identification, adjustment, and update process is repeated; if all the re-obtained coating thickness data meets the preset thickness requirements, the current round of closed-loop adjustment ends. Through this process, a continuous correspondence is formed between the coating thickness detection results, workpiece posture, sagging risk judgment, and trajectory and flow update, enabling the coating process to have a repeatable closed-loop correction capability.

[0061] like Figure 2 As shown, a synchronous control system for spray coating based on workpiece 3D point cloud trajectory planning is used to implement a synchronous control method for spray coating based on workpiece 3D point cloud trajectory planning. The system includes: The data modeling module is used to acquire 3D point cloud data and workpiece posture data of the workpiece surface, and to construct a surface mesh model based on the 3D point cloud data. The data modeling module mainly consists of a 3D acquisition unit, a posture acquisition unit, and a modeling processing unit. The 3D acquisition unit can use a structured light camera, a line laser scanner, or an industrial vision camera to acquire 3D point cloud data of the workpiece surface; the posture acquisition unit can use a tilt sensor, an inertial measurement unit, or an encoder mounted on the fixture end to acquire workpiece posture data; the modeling processing unit can use an industrial computer, an edge controller, or an embedded processor to perform denoising, registration, and mesh reconstruction on the 3D point cloud data to form a surface mesh model.

[0062] The risk allocation module extracts surface curvature features from the surface mesh model and divides the surface into regions. It determines the area weight of each region based on its area and, based on the surface curvature features and workpiece posture data, determines the sagging risk level of each surface region. Finally, it generates a coating material allocation scheme by combining the area weights. The risk allocation module mainly consists of a processing unit and a data storage unit, typically deployed in an industrial computer, industrial control host, or a control platform with graphics processing capabilities. The processing unit reads the surface mesh model and workpiece posture data, performing curvature feature extraction, surface region division, region area statistics, sagging risk level determination, and coating material allocation scheme generation. The data storage unit stores mesh data, region parameters, risk levels, and material allocation results. This module is essentially a computational hardware unit oriented towards process decision-making.

[0063] The trajectory control module generates the coating trajectory and flow control parameters based on the surface mesh model and coating material distribution scheme, and controls the coating equipment to perform the coating process. The trajectory control module mainly consists of a trajectory planning unit, a motion control unit, and a material supply control unit. The trajectory planning unit, typically implemented by an industrial controller or motion control card, generates the coating trajectory and flow control parameters based on the surface mesh model and coating material distribution scheme. The motion control unit drives the robotic arm, linear module, turntable, or nozzle movement mechanism, causing the spray head to move relative to the workpiece surface along the planned trajectory. The material supply control unit controls the metering pump, solenoid valve, proportional valve, or pressure supply device to output the coating material at the set flow rate. This module is the core execution hardware of this system.

[0064] The thickness update module acquires coating thickness data and updates the coating trajectory and flow control parameters based on this data until the coating thickness meets the preset thickness requirements. The thickness update module mainly consists of a thickness detection unit, a data comparison unit, and a parameter update unit. The thickness detection unit can use a laser displacement sensor, line scan profilometer, structured light detector, or other non-contact detection device to acquire coating thickness data. The data comparison unit analyzes the detection results against the preset thickness requirements and the previous surface mesh model to identify areas where the thickness does not meet the standard. The parameter update unit re-corrects the coating trajectory and flow control parameters based on the analysis results and sends the updated control parameters to the trajectory control module. This module corresponds to the closed-loop detection and feedback hardware section.

[0065] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects.

[0066] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for synchronous control of spray coating based on workpiece three-dimensional point cloud trajectory planning, characterized in that, The method includes: Acquire three-dimensional point cloud data and workpiece posture data of the workpiece surface, and construct a surface mesh model based on the three-dimensional point cloud data; The surface curvature features are extracted and the surface regions are divided according to the surface mesh model. The area weight of each surface region is determined according to its area. The sagging risk level of each surface region is determined according to the surface curvature features and the workpiece posture data. The coating material allocation scheme is generated by combining the area weight. Based on the surface mesh model and the coating material distribution scheme, a coating trajectory and flow control parameters are generated, and the coating equipment is controlled to perform coating. Acquire coating thickness data, and update the coating trajectory and flow control parameters based on the coating thickness data until the coating thickness data meets the preset thickness requirements.

2. The method according to claim 1, characterized in that, Acquire 3D point cloud data and workpiece orientation data of the workpiece surface, and construct the surface mesh model based on the 3D point cloud data, including: Perform a 3D scan of the workpiece surface to obtain the original point cloud data; Collect workpiece posture data; The original point cloud data is denoised, and the surface mesh model is constructed based on the denoised point cloud data.

3. The method according to claim 1, characterized in that, Extracting the surface curvature features based on the surface mesh model and dividing the surface region includes: The surface curvature characteristics are obtained by calculating the Gaussian curvature and average curvature of each grid cell based on the surface grid model. The surface region is divided according to the curvature continuity and spatial connectivity of adjacent grid cells.

4. The method according to claim 3, characterized in that, Determining the area weight of the region based on the area of ​​the surface region includes: Calculate the proportion of the area of ​​each surface region in the total surface area of ​​the workpiece, and use it as the area weight of each surface region.

5. The method according to claim 4, characterized in that, Generating the coating material distribution scheme includes: The tilt state of each surface region relative to the direction of gravity is determined based on the workpiece posture data; The sag risk level of each surface region is determined based on the surface curvature characteristics and the tilt state. The amount of coating material allocated to each surface area is determined based on the area weight and the sag risk level, thus obtaining the coating material allocation scheme.

6. The method according to claim 1, characterized in that, Generating the coating trajectory and the flow control parameters includes: The coating trajectory corresponding to each of the surface regions is generated based on the surface mesh model; The flow control parameters for each of the surface regions are determined according to the coating material distribution scheme.

7. The method according to claim 6, characterized in that, Controlling the coating equipment to perform coating includes: The coating equipment is controlled to move relative to the workpiece surface along the coating trajectory; The coating equipment is controlled to output coating material according to the flow control parameters.

8. The method according to claim 1, characterized in that, Obtaining the coating thickness data includes: The surface of the workpiece after coating is scanned to obtain post-coating surface data; The coating thickness data for each of the surface regions is determined based on the post-coating surface data and the surface mesh model.

9. The method according to claim 8, characterized in that, Updating the coating trajectory and the flow control parameters based on the coating thickness data includes: The surface area where the thickness does not meet the standard is determined based on the difference between the coating thickness data and the preset thickness requirement; The coating material distribution scheme is adjusted based on the workpiece posture data corresponding to the surface area where the thickness does not meet the standard and the sagging risk level. The coating trajectory and flow control parameters are updated according to the adjusted coating material distribution scheme.

10. A synchronous control system for spray coating based on workpiece three-dimensional point cloud trajectory planning, used to implement the synchronous control method for spray coating based on workpiece three-dimensional point cloud trajectory planning as described in any one of claims 1-9, characterized in that, The system includes: The data modeling module is used to acquire three-dimensional point cloud data and workpiece posture data of the workpiece surface, and to construct a surface mesh model based on the three-dimensional point cloud data. The risk allocation module is used to extract surface curvature features and divide surface regions according to the surface mesh model, determine the area weight of the surface regions according to the area of ​​the surface regions, determine the sagging risk level of each surface region according to the surface curvature features and the workpiece posture data, and generate a coating material allocation scheme by combining the area weight. The trajectory control module is used to generate the coating trajectory and flow control parameters according to the surface mesh model and the coating material distribution scheme, and to control the coating equipment to perform coating. The thickness update module is used to acquire coating thickness data and update the coating trajectory and the flow control parameters according to the coating thickness data until the coating thickness data meets the preset thickness requirements.

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