A method for online monitoring and self-correction of coating quality for automotive plastic parts

Abstract

This application provides a control method for online monitoring and self-correction of the coating quality of automotive plastic parts, relating to the field of automotive parts processing technology. The method includes the following steps: obtaining the theoretical slot position of the adapter post based on the coating information of the workpiece; determining whether there are target sections on the actual surface that do not match the theoretical arc surface; if so, obtaining the first correction sequence corresponding to each target section, including multiple horizontal displacement points passed by the nozzle during horizontal movement within the target section, and the first displacement deviation corresponding to each horizontal displacement point; after inserting the adapter post into the theoretical slot position, controlling the nozzle to perform coating operations along the horizontal movement path, and executing the corresponding first correction sequence within each target section to ensure that the nozzle and the actual surface of the area to be coated always maintain a preset constant distance. This application can identify surface deviations online and autonomously correct the coating trajectory, overcoming the limitations of purely mechanical structures in adapting to certain special workpieces.

Description

Technical Field

[0001] This application relates to the field of automotive parts processing technology, specifically to a method for online monitoring and self-correction of the coating quality of automotive plastic parts. Background Technology

[0002] In the field of automotive plastic trim coating, existing technologies typically employ fixed-path translational coating devices. However, for workpieces with arched surfaces (such as rearview mirror baffles), this method can lead to uneven coating due to inconsistent distances between the nozzle and the workpiece surface, affecting oxidation resistance and aesthetics. Therefore, a patent application (application number 202321954968.9) was filed to achieve synchronized distances between the nozzle and various parts of the workpiece surface. This is achieved by using a power component to drive the moving component and nozzle horizontally. The movement of the adapter column within the slot adjusts the curvature of the adapter arc plate to ensure it matches the workpiece surface. A spring applies upward pressure to the telescopic column and rollers, causing the adapter arc plate, with the same curvature as the workpiece surface, to compress and limit the rollers. This synchronizes the vertical movement of the connecting column and nozzle, ensuring equal distances between the nozzle and various parts of the workpiece, resulting in more uniform coating.

[0003] However, there are key issues in the use of this device: the wear and tear of injection molds after long-term use and the difference in shrinkage rate of material batches can cause local curvature deviations (local depressions) on the surface of the workpiece to be sprayed for the same model. This causes a structural mismatch between the theoretical arc surface of the original matching arc plate and the actual surface, resulting in poor adaptability of the device for spraying. The spraying uniformity in the depressed area with deviation is inconsistent with that in the normal area, which affects the spraying quality of plastic parts. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, this application aims to provide a control method for online monitoring and self-correction of the coating quality of automotive plastic parts, based on an automotive plastic trim coating device. The device includes a coating box, an adapter component, a moving component, and a nozzle. The adapter component matches the workpiece surface by means of the curvature of the adapter arc plate. The moving component drives the nozzle to rise and fall synchronously with the adapter arc plate through springs and telescopic columns, so as to realize online identification of surface deviations and autonomous correction of the coating trajectory, thereby breaking through the adaptability bottleneck of pure mechanical structures.

[0005] The control method includes the following steps:

[0006] Based on the spraying information of the workpiece to be sprayed, the theoretical slot position of the adapter column is obtained; the spraying information includes the workpiece type and the area to be sprayed; the theoretical slot position corresponds to the theoretical arc surface of the adapter arc plate;

[0007] Determine whether the target segment exists on the actual surface. The target segment is a segment on the actual surface that does not match the theoretical arc surface. The actual surface is the surface of the area to be coated on the workpiece.

[0008] If so, then obtain the first correction sequence corresponding to the target segment. The first correction sequence includes multiple horizontal displacement points passed by the nozzle during horizontal movement within the target segment, and the first displacement deviation corresponding to each horizontal displacement point.

[0009] After the adapter post is inserted into the theoretical slot, the nozzle is controlled to perform spraying operations along the horizontal movement path, and the corresponding first correction sequence is executed in the target section so that the nozzle and the actual surface of the area to be sprayed always maintain a preset constant distance.

[0010] According to the technical solution provided in this application, determining whether there is a target segment on the actual surface that does not match the theoretical arc surface includes the following steps:

[0011] Scan along the horizontal movement path of the area to be sprayed to obtain the first curvature dataset of the actual surface;

[0012] Using the theoretical arc surface as a reference surface, the first curvature dataset is discretized to divide it into several detection segments;

[0013] Calculate the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each detection segment. If the first deviation value corresponding to at least one detection segment is greater than the preset curvature tolerance threshold, it is determined that there is a target segment on the actual surface that does not match the theoretical arc surface.

[0014] According to the technical solution provided in this application, after calculating the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each of the detection sections, the method further includes the following steps:

[0015] The detection segment whose first deviation value is greater than the preset curvature tolerance threshold is designated as the primary abnormal segment.

[0016] Curvature continuity analysis is performed on adjacent primary anomaly sections to calculate the rate of curvature change between adjacent detection points;

[0017] If the rate of change of curvature is greater than the first rate of change, then it is determined that there is a curvature abrupt change boundary;

[0018] Based on the spatial distribution characteristics of the curvature abrupt change boundary, N or more consecutive primary anomalous segments with the same curvature deviation are merged into the same target segment.

[0019] According to the technical solution provided in this application, before controlling the spray head to perform spraying operations along the horizontal movement path after the adapter post is inserted into the theoretical slot position, the following steps are also included:

[0020] The nozzle is controlled to move horizontally without load, and the verification arc curve of the path taken by the nozzle is obtained; wherein, during the horizontal movement of the nozzle without load, the corresponding first correction sequence is not executed and the nozzle does not spray paint.

[0021] Based on the verified arc curve and the theoretical arc curve corresponding to the theoretical arc surface, determine whether the theoretical slot position is reliable;

[0022] The control nozzle performs spraying operations along a horizontal movement path, including the following steps:

[0023] If so, control the nozzle to perform the spraying operation along the horizontal movement path.

[0024] According to the technical solution provided in this application, if the actual surface has a target segment that does not match the theoretical arc surface, the following steps are also included:

[0025] Determine the location range of the target segment on the horizontal movement path;

[0026] Determine whether the position range maps to the two end regions of the adapter arc plate, wherein the two end regions of the adapter arc plate are the ranges along its length direction that are more than a preset distance threshold from the center point;

[0027] Obtaining the first corrected sequence corresponding to the target segment includes the following steps:

[0028] If not, obtain the first corrected sequence corresponding to the target segment.

[0029] According to the technical solution provided in this application, after determining whether the position range maps to the two end regions of the adapting arc plate, the method further includes the following steps:

[0030] Obtain all first displacement deviations in the first correction sequence corresponding to the target segment;

[0031] Each of the first displacement deviations is determined to be whether it exceeds the safe displacement threshold, which is the maximum compensation displacement that the spring can allow under the premise of ensuring reliability and not causing plastic deformation;

[0032] Executing the corresponding first correction sequence within the target segment includes the following steps:

[0033] If none of the first displacement deviations exceed the safe displacement threshold, then the corresponding first correction sequence is executed within the target segment.

[0034] According to the technical solution provided in this application, after determining whether each of the first displacement deviations exceeds a preset safe displacement threshold, the method further includes the following steps:

[0035] If at least one of the first displacement deviations exceeds the safe displacement threshold, the horizontal displacement point corresponding to the first displacement deviation exceeding the safe displacement threshold is marked as a displacement point to be corrected.

[0036] The first displacement deviation corresponding to all the displacement points to be corrected in the first correction sequence is corrected to the safe displacement threshold to obtain the second correction sequence corresponding to the target segment;

[0037] After the adapter post is inserted into the theoretical slot, the nozzle is controlled to perform spraying operations along the horizontal movement path, and the corresponding second correction sequence is executed in the target section.

[0038] According to the technical solution provided in this application, executing the corresponding first correction sequence within the target segment includes the following steps:

[0039] The linear actuator installed on the side wall of the receiving column is controlled to perform the corresponding displacement of the first displacement deviation when the nozzle moves to each of the horizontal displacement points.

[0040] According to the technical solution provided in this application, after determining that the actual surface has a target segment, the method further includes the following steps:

[0041] Determine whether there is a curvature abrupt boundary within the target segment;

[0042] Obtaining the first corrected sequence corresponding to the target segment includes the following steps:

[0043] If not, obtain the first corrected sequence corresponding to the target segment.

[0044] According to the technical solution provided in this application, after determining whether there is a curvature abrupt boundary within the target segment, the method further includes the following steps:

[0045] If there is a curvature change boundary within the target section, redundant displacement points will be added at the curvature change boundary.

[0046] Based on the number of redundant displacement points added and the first displacement deviation of the horizontal displacement points before and after the curvature change boundary, the second displacement deviation of the redundant displacement points is calculated.

[0047] The third correction sequence corresponding to the target segment is formed by the first displacement deviation at each of the horizontal displacement points and the second displacement deviation at each of the redundant displacement points in sequence.

[0048] Compared with existing technologies, the beneficial effects of this application are as follows: This application automatically identifies mismatched sections (target sections) caused by production errors or process improvements (such as newly added grooves) by comparing the matching degree between the theoretical arc surface and the actual surface, and generates a first correction sequence including the first displacement deviation of multiple horizontal displacement points within the target section. Compared with fixed mechanical fitting methods, it can compensate for local deformation in real time, enabling the nozzle to dynamically track surface depressions or grooves, thus improving the spacing control accuracy. In addition, there is no need to replace the fitting arc plate or adjust the slot position. The same device can be used to accommodate multiple batches of error workpieces and improved products. For workpieces with local depressions, this method can reduce the re-spray rate and reduce equipment modification costs. Through the constant spacing control of this application, overspray waste of paint is reduced, spraying material consumption is reduced, and defects such as drips and dry spraying caused by sudden changes in spacing are avoided, significantly improving the spraying quality. Attached Figure Description

[0049] Figure 1 A flowchart of the online monitoring and self-correction control method for the coating quality of automotive plastic parts provided in this application;

[0050] Figure 2 A schematic diagram of the automotive plastic trim spraying device provided in this application;

[0051] Figure 3 This is a structural schematic diagram of the spray box provided in this application;

[0052] Figure 4 Provided for this application Figure 3 A partial schematic diagram of part A in the middle;

[0053] Figure 5 This is a schematic diagram of the spring provided in this application.

[0054] The text labels in the image represent:

[0055] 1. Spraying box; 11. Inlet; 12. Outlet; 13. Adapter block; 14. Placement slot; 2. Transport assembly; 3. Power assembly; 31. Support column; 32. Lead screw; 33. Slider; 41. Adapter column; 42. Adapter arc plate; 5. Through slot; 6. Card slot; 71. Receiving column; 72. Telescopic column; 73. Roller; 74. Spring; 75. Connecting column; 8. Spray nozzle. Detailed Implementation

[0056] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0057] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0058] Example 1

[0059] As mentioned in the background section, in view of the problems in the prior art, this application proposes an automotive plastic trim spraying device, such as... Figure 2-5 As shown, it includes:

[0060] The spray box 1 contains a transport component 2, a power component 3, an adapter component, a moving component, and a spray head 8. The left and right sides of the spray box 1 are provided with an inlet 11 and an outlet 12, respectively. The front of the spray box 1 is also provided with a placement groove 14, a through groove 5, and a locking groove 6 extending to the back. The placement groove 14 is located below the through groove 5 and the locking groove 6, and the front and rear ends of the slider 33 are respectively adapted to and locked inside the placement groove 14. The locking groove 6 is located at the bottom of the through groove 5, and the inner wall of the locking groove 6 is designed to be inclined. The two ends of the adapter post 41 are respectively adapted to and locked inside the locking groove 6.

[0061] The top of the inner wall of the spray box 1 is also glued with an adapter block 13. The bottom of the adapter block 13 is pressed and contacted with the top of the adapter arc plate 42. The adapter block 13 is made of rubber block.

[0062] The power assembly 3 consists of a support column 31, a lead screw 32, and a slider 33. The support column 31 and the lead screw 32 are fixedly installed on the front and rear sides of the spray box 1 in sequence, and the slider 33 is slidably installed on the outer surface of the support column 31 and the lead screw 32.

[0063] The movable component is fixedly installed on the top of the slider 33. The movable component includes a receiving column 71, a telescopic column 72 movably sleeved on the inner wall of the receiving column 71, and a spring 74 movably sleeved on the outer surface of the telescopic column 72. The spring 74 is installed by fixing its top end to the upper cover or inner flange of the receiving column 71 and its bottom end to the side lug of the telescopic column 72. A roller 73 is fixedly connected to the top of the telescopic column 72, and a connecting column 75 is fixedly connected to the bottom of the telescopic column 72. The bottom of the connecting column 75 is fixedly connected to the nozzle 8. The receiving column 71 is fixedly installed on the top of the slider 33, and the top of the roller 73 is in contact with the bottom of the adapter component.

[0064] The adapter assembly consists of two symmetrically distributed adapter posts 41 on the left and right. An adapter arc plate 42 is movably fitted on the outer surface of the two adapter posts 41. The adapter arc plate 42 is arched and made of stainless steel. The bottom of the adapter arc plate 42 is in contact with the roller 73. The adapter posts 41 are adapted to be inserted into the inner wall of the spray box 1. The spring 74 is stretched inside the receiving post 71. The rebound force of the roller 73 is equal to the sum of the reaction force from the adapter arc plate 42 and the weight of the nozzle 8.

[0065] Accordingly, when slider 33 moves horizontally, nozzle 8 will precisely rise and fall, its movement trajectory completely replicating the arched curvature of the bottom of fixed arc plate 42. This allows the nozzle to uniformly spray the automotive plastic trim below along the set arc path during its movement.

[0066] Example 2

[0067] Based on Example 1, this example proposes a method for online monitoring and self-correction of the coating quality of automotive plastic parts, such as... Figure 1 As shown, the control method includes the following steps:

[0068] S1. Based on the spraying information of the workpiece to be sprayed, the theoretical slot 6 position of the adapter column 41 is obtained; the spraying information includes the workpiece type and the area to be sprayed; the theoretical slot 6 position corresponds to the theoretical arc surface of the adapter arc plate 42.

[0069] Specifically, the information to be painted includes the workpiece type, which includes different types of automotive plastic trim parts such as car bumpers, interior panels, and rearview mirrors. The area to be painted refers to the specific part of the plastic part that needs to be painted. Based on this information, the operator, using experience (first, establishes a database storing the theoretical slot positions of the adapter post 41 corresponding to different workpiece types and their areas to be painted; when the workpiece type and area to be painted are entered, the system can retrieve the corresponding theoretical slot positions of the adapter post 41 by querying the database. For example, for a bumper of a specific car model, the area to be painted is the side, and the database has pre-recorded the specific slot number or coordinate position of the adapter post 41 in this case), can obtain the theoretical slot position of the adapter post 41 corresponding to the workpiece to be painted.

[0070] S2. Determine whether the target segment exists on the actual surface. The target segment is a segment on the actual surface that does not match the theoretical arc surface. The actual surface is the surface of the area to be sprayed on the workpiece.

[0071] Furthermore, determining whether the actual surface has a target segment that does not match the theoretical arc surface includes the following steps:

[0072] Scan along the horizontal movement path of the area to be sprayed to obtain the first curvature dataset of the actual surface;

[0073] Specifically, a high-precision 3D laser scanner or other equipment with surface contour detection capabilities is used to scan the actual surface along a pre-planned horizontal movement path along the area to be coated. During the scanning process, the equipment collects the coordinate information of each point on the actual surface in real time, and converts this coordinate information into corresponding curvature data through a specific algorithm, ultimately forming the first curvature dataset.

[0074] Optionally, a specific algorithm is as follows: Collect the coordinates of three points: Within the detection area, take three consecutive scanning points: point A(x1,y1,z1), point B(x2,y2,z2), and point C(x3,y3,z3), and calculate the side length of the triangle: (The same applies to the other sides BC and AC). Calculate the area of ​​the triangle (Heron's formula): Where S represents the area of ​​the triangle, p represents the semi-perimeter, calculated as p = (AB + BC + AC) / 2, and the circumcircle radius R = (AB × BC × AC) / 4S; the actual curvature is the reciprocal of the circumcircle radius R. The coordinates of each point on the actual surface can be converted into corresponding actual curvature data using the above algorithm.

[0075] Using the theoretical arc surface as a reference surface, the first curvature dataset is discretized to divide it into several detection segments;

[0076] For example, taking equal intervals as an example, the first curvature dataset is divided into segments of 10mm each, thus dividing the continuous first curvature data into several detection segments. Each detection segment contains curvature information of the corresponding 10mm length of the actual surface area.

[0077] Calculate the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each detection segment. If the first deviation value corresponding to at least one detection segment is greater than the preset curvature tolerance threshold, it is determined that there is a target segment on the actual surface that does not match the theoretical arc surface.

[0078] Specifically, for each detection segment, a corresponding geometric formula is used (derived from the curvature data within the detection segment; specifically, the actual curvature data of points A, B, C, D, E, and F within the detection segment are obtained through the aforementioned specific algorithm, and then expressed using the formula). The actual radius of curvature is obtained, where R 实际 Q represents the actual radius of curvature of the detection section.A To Q F The actual radius of curvature is calculated by taking the actual curvature data of each point within the detection section. Simultaneously, based on the mathematical model of the theoretical curved surface, the theoretical radius of curvature at the corresponding location is calculated. The difference between the two is then calculated, i.e., the first deviation value. A preset curvature tolerance threshold can be set according to actual production requirements and empirical values, for example, 0.3mm. If the first deviation value of any detection section is greater than 0.3mm, it is determined that there is a target section on the actual surface that does not match the theoretical curved surface.

[0079] This implementation method is based on a comparative analysis of the curvature of actual and theoretical curved surfaces. Curvature data of the actual surface is acquired through scanning, and then discretized and compared with the curvature of the theoretical curved surface. Since curvature reflects the degree of surface bending, when the actual curvature radius deviates significantly from the theoretical curvature radius, it indicates that the actual surface and the theoretical curved surface have inconsistent shapes at that location, i.e., there is a mismatched target segment. This curvature-based comparison method can more accurately detect differences in surface shape and, compared to simple distance comparison, can more sensitively detect subtle surface deformations or unevenness.

[0080] S3. If so, obtain the first correction sequence corresponding to the target segment. The first correction sequence includes multiple horizontal displacement points passed by the nozzle during horizontal movement within the target segment, and the first displacement deviation amount corresponding to each horizontal displacement point.

[0081] Specifically, once an area is identified where the deviation between the actual surface and the theoretical curved surface exceeds the allowable range, it is directly marked as a target segment by color coding or a special identifier. Since the horizontal displacement points are known and pre-set, these preset, evenly distributed horizontal point data are directly invoked. For each target segment, based on these known horizontal displacement points, the displacement adjustment amount required for the nozzle 8 to maintain a preset constant distance from the actual surface at each point is calculated. This positional adjustment amount is the first displacement deviation amount corresponding to that horizontal displacement point. Using 3D scanning data, the actual surface and the theoretical curved surface are compared. At each horizontal displacement point, the vertical distance difference between the actual surface and the theoretical curved surface is calculated, i.e., the height deviation value. For example, if there are 10 horizontal displacement points in a target segment, by comparison, it is calculated that at the first horizontal displacement point, the actual surface is 0.8 mm lower than the theoretical curved surface, and at the second horizontal displacement point, the actual surface is 0.5 mm lower than the theoretical curved surface, and so on. For example, a target section has 7 evenly distributed horizontal displacement points. When the nozzle 8 is at the first horizontal displacement point, the first displacement deviation corresponding to the first horizontal displacement point is calculated based on the deviation between the actual surface and the theoretical arc surface of the target section. The nozzle 8 and the first horizontal displacement point on the actual surface maintain a preset constant distance consistent with other areas. The same process is applied to the second horizontal displacement point, and so on. A corresponding first displacement deviation is determined for each horizontal displacement point, thereby forming a complete first correction sequence for the target section.

[0082] S4. After the adapter post 41 is inserted into the theoretical slot 6, the nozzle 8 is controlled to perform spraying operation along the horizontal moving path, and the corresponding first correction sequence is executed in each target section so that the nozzle 8 and the actual surface of the area to be sprayed always maintain a preset constant distance.

[0083] Specifically, during actual spraying operations, the adapter post 41 is manually or through automated mechanical devices accurately inserted into the previously obtained theoretical slot 6 position. Then, the spraying device is started, and the nozzle 8 begins spraying according to the preset horizontal movement path. When the nozzle 8 moves to the target section, the system automatically calls the corresponding first correction sequence, and adjusts the position of the nozzle 8 in real time according to the horizontal displacement point and the corresponding first displacement deviation in the first correction sequence.

[0084] The technical principle is described as follows: This control method is based on feedback control and adaptive adjustment. First, based on the known information of the workpiece to be coated, the theoretical coating parameters and positions are determined (i.e., the theoretical slot 6 position of the adapter column 41 and the corresponding theoretical arc surface). However, considering that the coating surfaces of some batches of workpieces may have production errors, or that some positions may not match the original arc surface of the adapter arc plate 42 after process improvements (this solution only applies to the case of surface concavity, because the upper end is interfered with by the adapter arc plate, so the telescopic column cannot compensate for the convexity upwards), a purely mechanical automotive plastic trim coating device cannot achieve uniform coating in this case. At this time, by comparing the actual surface with the theoretical arc surface, the mismatched target sections are identified. Then, for these target sections, adaptive adjustment is performed using a pre-calculated first correction sequence. The setting of the horizontal displacement point is to precisely control the position of the nozzle 8 within the target section, and to achieve targeted correction of deviations at different positions, so as to ensure that the nozzle 8 and the workpiece surface always maintain a preset constant distance, ensuring the consistency of coating quality.

[0085] In a preferred embodiment, after calculating the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each of the detection segments, the method further includes the following steps:

[0086] The detection segment whose first deviation value is greater than the preset curvature tolerance threshold is designated as the primary abnormal segment.

[0087] Specifically, detection segments with a first deviation value greater than a preset curvature tolerance threshold are directly selected and marked as primary abnormal segments. For example, if five detection segments have a first deviation value greater than the preset 0.5mm threshold, then these five detection segments are identified as primary abnormal segments.

[0088] Curvature continuity analysis is performed on adjacent primary anomaly sections to calculate the rate of curvature change between adjacent detection points;

[0089] Specifically, for adjacent primary anomaly sections, their adjacent detection points are first determined. Then, the curvature data of these two adjacent detection points are obtained. The curvature change rate is calculated using the formula: Curvature change rate = (Curvature of the next detection point - Curvature of the previous detection point) / Distance between the two points. For example, for two adjacent detection points of two primary anomaly sections, the curvature of the previous point is 0.02, the curvature of the next point is 0.08, and the distance between the two points is 5mm, then the curvature change rate = (0.08 - 0.02) / 5 = 0.012.

[0090] If the rate of change of curvature is greater than the first rate of change, then it is determined that there is a curvature abrupt change boundary;

[0091] Specifically, the calculated rate of change of curvature is compared with a pre-set first rate of change. The first rate of change can be set based on actual production experience and the requirements for product surface quality, for example, 0.01. If the calculated rate of change of curvature is greater than 0.01, it is determined that there is a curvature abrupt change boundary between these two adjacent detection points.

[0092] Based on the spatial distribution characteristics of the curvature abrupt change boundary, N or more consecutive primary anomalous segments with the same curvature deviation are merged into the same target segment.

[0093] Specifically, all primary anomalous segments are traversed, and the distribution of curvature abrupt change boundaries among them is observed. Simultaneously, the direction of curvature deviation for each primary anomalous segment is determined (whether it is greater than or less than the theoretical radius of curvature). When N or more consecutive primary anomalous segments (N can be set according to the actual situation, such as 3) are found to have the same curvature deviation direction, and there are no curvature abrupt change boundaries between them, or the curvature abrupt change boundaries are within a reasonable range, these primary anomalous segments are merged into a single target segment. For example, if there are 4 consecutive primary anomalous segments, all of which have actual radii of curvature greater than the theoretical radius of curvature, and all of which have curvature change rates less than the first rate of change, then these 4 primary anomalous segments are merged into a single target segment.

[0094] This implementation method is based on the analysis of the curvature continuity and deviation direction of primary anomaly sections. By studying the rate of curvature change between adjacent detection points, it is possible to determine whether the surface curvature change is smooth, thereby identifying the curvature abrupt change boundary. Continuous primary anomaly sections with the same curvature deviation are merged because these regions have similar curvature characteristics. They may be mismatched with the theoretical arc surface due to the same reason (such as mold manufacturing errors). Merging them into a single target section facilitates more efficient and accurate subsequent correction operations.

[0095] In a preferred embodiment, before controlling the spray head 8 to perform spraying operations along the horizontal movement path after the adapter post 41 is inserted into the theoretical slot 6, the following steps are further included:

[0096] Control the nozzle 8 to move horizontally without load, and obtain the verification arc curve of the path taken by the nozzle 8; wherein, during the horizontal movement of the nozzle 8 without load, the corresponding first correction sequence is not executed and the nozzle 8 does not spray paint.

[0097] Specifically, before the formal spraying operation, the moving component of the spraying device is activated, controlling the nozzle 8 to move unloaded along a preset horizontal movement path. During the movement, position sensors installed on the nozzle 8 or the moving component collect the position information of the nozzle 8 in real time. Based on this position information, a curve of the path traversed by the nozzle 8 is plotted, i.e., a calibration arc curve. For example, the position sensor collects the coordinates of the nozzle 8 every 0.1 seconds, and connecting these coordinate points forms the calibration arc curve.

[0098] Based on the verified arc curve and the theoretical arc curve corresponding to the theoretical arc surface, determine whether the position of the theoretical slot 6 is reliable;

[0099] Specifically, the obtained verification arc curve is compared with the theoretical arc curve pre-calculated based on the theoretical slot 6 position and the theoretical arc surface. A curve fitting degree analysis algorithm can be used to calculate the fitting degree between the two curves. If the fitting degree is higher than a pre-set standard value (e.g., 90%), the theoretical slot 6 position is considered reliable; otherwise, the theoretical slot 6 position may be deviated from its intended direction. For example, if the curve fitting degree analysis algorithm calculates a fitting degree of 92% between the verification arc curve and the theoretical arc curve, and since 92% is greater than 90%, the theoretical slot 6 position is determined to be reliable.

[0100] The control nozzle 8 performs spraying operations along a horizontal movement path, including the following steps:

[0101] If so, control the nozzle 8 to perform spraying operations along the horizontal movement path.

[0102] Specifically, once the position of the theoretical slot 6 is determined to be reliable, the painting system of the spraying device is started, while the nozzle 8 is kept moving along the preset horizontal movement path to begin the formal spraying operation.

[0103] This implementation method is based on a comparison between the no-load movement path of the nozzle 8 and the theoretical path. If the theoretical slot 6 is accurately positioned, then the no-load movement path of the nozzle 8 should be close to the theoretical curvature curve. By comparing the fit between the two curves, it is possible to indirectly determine whether the position of the theoretical slot 6 is correct. This is because the position of the theoretical slot 6 determines the position of the adapting arc plate 42, which in turn affects the initial position and movement path of the nozzle 8. If the theoretical slot 6 is incorrectly positioned, the actual movement path (verification curvature curve) of the nozzle 8 will deviate significantly from the theoretical curvature curve.

[0104] In a preferred embodiment, if the actual surface has a target segment that does not match the theoretical arc surface, the method further includes the following steps:

[0105] Determine the location range of the target segment on the horizontal movement path;

[0106] Determine whether the position range maps to the two end regions of the adapter arc plate 42. The two end regions of the adapter arc plate 42 are the ranges along its length direction that are more than a preset distance threshold from the center point.

[0107] Obtaining the first corrected sequence corresponding to the target segment includes the following steps:

[0108] If not, obtain the first corrected sequence corresponding to the target segment.

[0109] Specifically, obtain the horizontal coordinate boundary and extract the coordinate values ​​of the starting and ending points of the target segment in the horizontal movement direction (X-axis). For example, if the target segment covers a horizontal path from X=550m to X=580m, then the position range is [150, 350]. Map to the spraying device coordinate system: Convert the workpiece coordinates to the spraying box coordinate system (e.g., ...). Figure 2-5 (As shown), ensure physical alignment with the adapter arc plate 42. Optionally, the preset distance threshold is 1 / 6 of the total length of the adapter arc plate 42.

[0110] For example, the length of the adapting arc plate 42 is 600m. The range of each end being more than 100m from the center point is called the two-end region. That is, the area measured 100m from each end is the two-end region. If the right end region of the arc plate is X=[500,600], then the horizontal path covered by the target segment from X=550m to X=580m belongs to the right end region of the adapting arc plate 42, and it is determined that the position range is mapped to the two-end region of the adapting arc plate 42. If the left end region of the arc plate is X=[0,100], and the horizontal path covered by the target segment is from X=200m to X=270m, then it is determined that the position range is not mapped to the two-end region of the adapting arc plate 42, and the acquisition process of the first correction sequence can be executed.

[0111] This embodiment takes into account the unique properties of the mechanical structure. When the roller 73 moves to both ends of the arc plate, the spring 74 is stretched to the maximum deformation state due to the reduction of the arc height. If the first correction sequence is executed in the area at both ends, it is very likely that the spring will be stretched again at a certain point. Therefore, active pull-down correction is disabled in the area at both ends of the arc plate (high-risk area of ​​the spring) to avoid overload failure of the spring 74.

[0112] Furthermore, after determining whether the position range maps to the two end regions of the adapting arc plate 42, the method further includes the following steps:

[0113] Obtain all first displacement deviations in the first correction sequence corresponding to the target segment;

[0114] Each of the first displacement deviations is determined to be whether it exceeds the safe displacement threshold, which is the maximum compensation displacement that the spring can allow under the premise of ensuring reliability and not causing plastic deformation;

[0115] Specifically, each horizontal displacement point has a corresponding safe displacement threshold. For each adapter arc plate 42 and spring 74, each horizontal displacement point has a corresponding deformation of spring 74, which can be obtained by measuring the displacement of telescopic column 72 relative to receiving column 71 in real time using a laser displacement sensor. The safe displacement threshold corresponding to that point can be obtained by subtracting the deformation at that point from the maximum elongation of spring 74. For example, if the current deformation of spring 74 is 3mm at a horizontal displacement point, and the maximum elongation of spring is 10mm, then the safe displacement threshold corresponding to that horizontal displacement point is 7mm.

[0116] Executing the corresponding first correction sequence within the target segment includes the following steps:

[0117] If none of the first displacement deviations exceed the safe displacement threshold, then the corresponding first correction sequence is executed within the target segment.

[0118] Specifically, a safe displacement threshold database can be obtained before spraying begins using the method described above. This database includes multiple horizontal displacement points and the corresponding safe displacement threshold for each horizontal displacement point. The safe displacement threshold database is retrieved and iterated through. The first displacement deviation of each horizontal displacement point is compared with the corresponding safe displacement threshold. After comparing them one by one, it is determined whether all first displacement deviations do not exceed the safe displacement threshold. If they do not exceed the threshold, it means that the corresponding first correction sequence can be executed.

[0119] In this embodiment, in areas where there is a risk of tensile failure at both ends of the arc plate, it is first determined whether adding downward pull will cause the spring 74 to fail. If it is determined that it will not cause the spring 74 to fail, then the additional tension is added to reduce the risk of spring 74 failure.

[0120] Furthermore, after determining whether each of the first displacement deviations exceeds a preset safe displacement threshold, the method further includes the following steps:

[0121] If at least one of the first displacement deviations exceeds the safe displacement threshold, the horizontal displacement point corresponding to the first displacement deviation exceeding the safe displacement threshold is marked as a displacement point to be corrected.

[0122] The first displacement deviation corresponding to all the displacement points to be corrected in the first correction sequence is corrected to the safe displacement threshold to obtain the second correction sequence corresponding to the target segment;

[0123] After the adapter post 41 is inserted into the theoretical slot position, the nozzle 8 is controlled to perform spraying operation along the horizontal moving path, and the corresponding second correction sequence is executed in the target section.

[0124] Specifically, if the first displacement deviation exceeds the safe displacement threshold, the displacement point to be corrected is marked, and the point exceeding the limit is added to the set to be corrected. A second correction sequence is generated: the first displacement deviation of the displacement point to be corrected in the original first correction sequence is replaced with the safe displacement threshold, so that while ensuring that the spring 74 does not fail, it is pulled down as much as possible, so that the nozzle 8 and the actual surface maintain a preset constant distance as much as possible. This embodiment prioritizes mechanical protection; exceeding the limit displacement means that the spring 74 may fail, and forcibly cutting off the displacement can avoid structural damage.

[0125] In a preferred embodiment, executing the corresponding first correction sequence within the target segment includes the following steps:

[0126] The linear actuator installed on the side wall of the receiving column 71 is controlled to perform the corresponding displacement of the first displacement deviation when the nozzle 8 moves to each of the horizontal displacement points.

[0127] Specifically, the linear actuator is a miniature servo cylinder with a built-in displacement sensor, installed laterally on the outer wall of the receiving column 71, and the push rod axis of the linear brake is parallel to the telescopic column 72. Figure 2-5 The push rod end of the linear actuator (in the Y-axis direction) is connected to the lateral lug of the telescopic column 72 via a universal hinge (to avoid interfering with the axial movement of the spring 74). The linear actuator only activates auxiliary compensation when the spring compensation margin is insufficient, and its output force is always coordinated with the spring deformation direction.

[0128] Specifically, when the nozzle 8 moves to each horizontal displacement point, the system sends a control signal to the linear actuator installed on the side wall of the receiving column 71 according to the first correction sequence calculated in the previous step. After receiving the signal, the linear actuator controls its output terminal to drive the connecting column 75 to move a corresponding distance according to the displacement command in the signal (corresponding to the first displacement deviation at each horizontal displacement point in the first correction sequence), so that the nozzle 8 reaches the target position.

[0129] This embodiment uses a linear actuator to precisely control the adjustment of the nozzle 8 position to ensure the preset distance between the nozzle 8 and the workpiece surface.

[0130] In a preferred embodiment, after determining that the target segment exists on the actual surface, the method further includes the following steps:

[0131] Determine whether there is a curvature abrupt boundary within the target segment;

[0132] Obtaining the first corrected sequence corresponding to the target segment includes the following steps:

[0133] If not, obtain the first corrected sequence corresponding to the target segment.

[0134] Furthermore, after determining whether there is a curvature abrupt boundary within the target segment, the method further includes the following steps:

[0135] If there is a curvature change boundary within the target section, redundant displacement points will be added at the curvature change boundary.

[0136] Based on the number of redundant displacement points added and the first displacement deviation of the horizontal displacement points before and after the curvature change boundary, the second displacement deviation of the redundant displacement points is calculated.

[0137] The third correction sequence corresponding to the target segment is formed by the first displacement deviation at each of the horizontal displacement points and the second displacement deviation at each of the redundant displacement points in sequence.

[0138] Specifically, redundant displacement points are additional horizontal displacement points added at curvature change boundaries when there are curvature change boundaries within the target section, in order to smoother the transition of nozzle 8 position adjustment. These points are used to more precisely adjust the nozzle 8 position in the curvature change region to ensure a smooth change in the distance between the nozzle 8 and the workpiece surface. For example, when a curvature abrupt change boundary is identified at 250 mm, two redundant displacement points are inserted between the adjacent original displacement points before and after the abrupt change point. Specifically, the points 250.33 mm and 250.67 mm are inserted between 250 mm and 251 mm. The compensation amount of the redundant points is calculated (using a progressive method) to obtain the compensation amount of the original points on both sides of the abrupt change boundary: the front point (250 mm) needs to be pressed down by 0.6 mm, and the back point (251 mm) needs to be pressed down by 1.8 mm. Since there are two redundant points ((1.8-0.6) / 3=0.4, each redundant point increases by 0.4), the second displacement deviation of the redundant point closer to the front point is 0.6+0.4=1, and the second displacement deviation of the redundant point closer to the back point is 0.6+0.4+0.4=1.4.

[0139] Specifically, the first displacement deviation calculated at each horizontal displacement point within the original target section and the second displacement deviation at each newly calculated redundant displacement point are arranged sequentially according to the horizontal displacement order. This is used to refine the position adjustment of the nozzle 8 in the curvature abrupt change region by adding redundant displacement points in the target section with curvature abrupt change boundary. This ensures that the distance between the nozzle 8 and the workpiece surface can smoothly transition when passing through the curvature abrupt change region, avoiding spraying quality problems caused by abrupt distance changes. This is based on the refined processing of complex surface shapes (with curvature abrupt changes) to meet the requirements of high-precision spraying.

[0140] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A control method for online monitoring and self-correction of the coating quality of automotive plastic parts, based on an automotive plastic trim coating device, the device comprising a coating box (1), an adapter component, a moving component, and a nozzle (8), wherein the adapter component consists of two symmetrically distributed adapter columns (41), and an arched adapter plate (42) is movably fitted on the outer surface of the two adapter columns (41), and the bending curvature of the adapter plate (42) matches the surface of the workpiece; the moving component drives the nozzle (8) to rise and fall synchronously with the arched curvature at the bottom of the adapter plate (42) via a spring (74) and a telescopic column (72); characterized in that, The control method includes the following steps: Based on the spraying information of the workpiece to be sprayed, the theoretical slot position of the adapter column (41) is obtained; the spraying information includes the workpiece type and the area to be sprayed; the theoretical slot position corresponds to the theoretical arc surface of the adapter arc plate (42); Determine whether the target segment exists on the actual surface. The target segment is a segment on the actual surface that does not match the theoretical arc surface. The actual surface is the surface of the area to be coated on the workpiece. If so, then obtain the first correction sequence corresponding to the target segment. The first correction sequence includes multiple horizontal displacement points that the nozzle (8) passes through during the horizontal movement within the target segment, and the first displacement deviation corresponding to each horizontal displacement point. After the adapter column (41) is inserted into the theoretical slot, the nozzle (8) is controlled to perform spraying operation along the horizontal moving path, and the corresponding first correction sequence is executed in the target section so that the nozzle and the actual surface of the area to be sprayed always maintain a preset constant distance.

2. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 1, characterized in that: Determining whether the actual surface has a target segment that does not match the theoretical arc surface includes the following steps: Scan along the horizontal movement path of the area to be sprayed to obtain the first curvature dataset of the actual surface; Using the theoretical arc surface as a reference surface, the first curvature dataset is discretized to divide it into several detection segments; Calculate the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each detection segment. If the first deviation value corresponding to at least one detection segment is greater than the preset curvature tolerance threshold, it is determined that there is a target segment on the actual surface that does not match the theoretical arc surface.

3. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 2, characterized in that: After calculating the first deviation value between the actual radius of curvature and the theoretical radius of curvature in each of the detection sections, the method further includes the following steps: The detection segment whose first deviation value is greater than the preset curvature tolerance threshold is designated as the primary abnormal segment. Curvature continuity analysis is performed on adjacent primary anomaly sections to calculate the rate of curvature change between adjacent detection points; If the rate of change of curvature is greater than the first rate of change, then it is determined that there is a curvature abrupt change boundary; Based on the spatial distribution characteristics of the curvature abrupt change boundary, N or more consecutive primary anomalous segments with the same curvature deviation are merged into the same target segment.

4. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 1, characterized in that: Before controlling the spray head (8) to perform spraying operations along the horizontal movement path after the adapter post (41) is inserted into the theoretical slot position, the following steps are also included: Control the nozzle (8) to move horizontally without load, and obtain the verification arc curve of the path taken by the nozzle (8); wherein, during the horizontal movement of the nozzle (8) without load, the corresponding first correction sequence is not executed and the nozzle does not spray paint. Based on the verified arc curve and the theoretical arc curve corresponding to the theoretical arc surface, determine whether the theoretical slot position is reliable; The control nozzle (8) performs spraying operations along a horizontal movement path, including the following steps: If so, control the nozzle (8) to perform spraying operations along the horizontal movement path.

5. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 1, characterized in that: If the actual surface has a target segment that does not match the theoretical arc surface, the following steps are also included: Determine the location range of the target segment on the horizontal movement path; Determine whether the position range is mapped to the two ends of the adapter arc plate (42). The two ends of the adapter arc plate (42) are the ranges along its length direction that are more than a preset distance threshold from the center point. Obtaining the first corrected sequence corresponding to the target segment includes the following steps: If not, obtain the first corrected sequence corresponding to the target segment.

6. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 5, characterized in that: After determining whether the position range maps to the two end regions of the adapter arc plate (42), the following steps are also included: Obtain all first displacement deviations in the first correction sequence corresponding to the target segment; Each of the first displacement deviations is determined to be whether it exceeds the safe displacement threshold, wherein the safe displacement threshold is the maximum compensation displacement that the spring (74) can allow under the premise of ensuring reliability and not causing plastic deformation; Executing the corresponding first correction sequence within the target segment includes the following steps: If none of the first displacement deviations exceed the safe displacement threshold, then the corresponding first correction sequence is executed within the target segment.

7. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 6, characterized in that: After determining whether each of the first displacement deviations exceeds a preset safe displacement threshold, the method further includes the following steps: If at least one of the first displacement deviations exceeds the safe displacement threshold, the horizontal displacement point corresponding to the first displacement deviation exceeding the safe displacement threshold is marked as a displacement point to be corrected. The first displacement deviation corresponding to all the displacement points to be corrected in the first correction sequence is corrected to the safe displacement threshold to obtain the second correction sequence corresponding to the target segment; After the adapter column (41) is inserted into the theoretical slot, the nozzle (8) is controlled to perform spraying operation along the horizontal moving path, and the corresponding second correction sequence is executed in the target section.

8. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 1, characterized in that: Executing the corresponding first correction sequence within the target segment includes the following steps: The linear actuator installed on the side wall of the receiving column (71) is controlled to perform the corresponding displacement of the first displacement deviation when the nozzle (8) moves to each of the horizontal displacement points.

9. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 1, characterized in that: After determining that the target segment exists on the actual surface, the following steps are also included: Determine whether there is a curvature abrupt boundary within the target segment; Obtaining the first corrected sequence corresponding to the target segment includes the following steps: If not, obtain the first corrected sequence corresponding to the target segment.

10. The online monitoring and self-correction control method for the coating quality of automotive plastic parts according to claim 9, characterized in that: After determining whether there is a curvature abrupt boundary within the target segment, the method further includes the following steps: If there is a curvature change boundary within the target section, redundant displacement points will be added at the curvature change boundary. Based on the number of redundant displacement points added and the first displacement deviation of the horizontal displacement points before and after the curvature change boundary, the second displacement deviation of the redundant displacement points is calculated. The third correction sequence corresponding to the target segment is formed by the first displacement deviation at each of the horizontal displacement points and the second displacement deviation at each of the redundant displacement points in sequence.

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