A Laser Profiling Cleaning and Paint Stripping Method for Large-Area Aircraft Skin by Robot

Abstract

The present invention discloses a method for laser profiling cleaning and paint removal of large-area aircraft skins by a robot. The method includes, for irregular large-area aircraft skins with different curvatures, after determining the laser parameters for cleaning the aircraft skins, scanning their models and performing segmentation and other processing, planning the operating path of the robotic arm and programming to perform profiling cleaning on the irregular large-area aircraft skins. The method for laser profiling cleaning and paint removal of large-area aircraft skins provided by the present invention can perform laser cleaning on the convex and concave surfaces of the paint layer of large-area aircraft skins with irregular shapes and curvatures, and achieve laser profiling paint removal treatment for aircraft skins.

Description

Technical Field

[0001] The present invention relates to the technical field of laser paint removal for large-area aircraft skins, and specifically provides a method for laser profiling cleaning and paint removal of large-area aircraft skins by a robot. Background Art

[0002] During long-term service, an aircraft has to withstand the threats of severe cold and heat, wind, sun, dust, ultraviolet rays, and acid rain, which can damage the paint on the aircraft skin. Under the action of factors such as light, the paint on the aircraft skin will age faster, and even problems such as fading, scratching, and damage may occur. Therefore, it is necessary to remove the damaged paint layer and repaint it, and regularly clean the aging paint layer. Currently in China, paint removal of aircraft skins mostly uses paint removers, which are generally applied by brushing. However, this method is toxic, polluting, costly, and requires a large dosage. Traditional cleaning processes such as mechanical friction cleaning, chemical corrosion cleaning, high-strength impact cleaning, and high-frequency ultrasonic cleaning not only have a long cleaning cycle, are difficult to automate, but also have a harmful impact on the environment. Since the curvature between the head and tail of the aircraft skin is different and the shape is irregular, during the laser cleaning process, the distance between the laser and the skin, that is, the focal length, needs to be kept the same at all times to prevent excessive changes in the laser energy density, resulting in uneven cleaning effects or even damage to the base material. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for laser profiling cleaning and paint removal of large-area aircraft skins by a robot to solve the problem of laser profiling cleaning of irregular large-area aircraft skins.

[0004] To achieve the above purpose, the present invention provides the following technical solution: The method includes determining the laser parameters for cleaning the aircraft skin through experiments for irregular large-area aircraft skins with different curvatures, scanning the model and performing segmentation processing, planning the operating path of the robotic arm and programming, and performing profiling cleaning on the irregular large-area aircraft skin.

[0005] The experiment for determining the laser parameters for cleaning the aircraft skin includes the following steps:

[0006] S1. Through orthogonal experiments, different laser parameters are set for the laser to irradiate the aircraft skin base material, and the optimal laser parameters for the undamaged aircraft skin base material are obtained, including laser power, laser scanning speed, laser pulse frequency, and robotic arm speed;

[0007] S2. After step S1 is completed, the surface paint layer of the aircraft skin is irradiated with the obtained optimal laser parameters;

[0008] S3. After step S2 is completed, the surface paint layer of the aircraft skin is cleaned with the optimal parameters for different numbers of times to obtain the optimal number of cleaning times.

[0009] The laser used in step S1 is a 1064nm pulsed laser of the YDFLP series from JPT Company. The galvanometer system is a single-axis linear scan. The optimal laser parameters are a power of 50W, a frequency of 200KHz, a scan speed of 2000mm / s, a scan amplitude of 5cm, and a robotic arm speed of 2mm / s.

[0010] The scanning model and the segmentation process include the following parts:

[0011] Use a 3D scanner to obtain the point cloud file of the aircraft skin. Use Geomagic software to perform uniform sampling on the point cloud model, delete non-connected items, and delete out-of-body isolated points to obtain a polygon. Then, perform relaxation of the boundary, deletion of spikes, and mesh division on the polygon to obtain a fitted surface. Export the fitted surface to Solidworks software for segmentation. For the convex surface of the skin, use a horizontal segmentation method, and for the concave surface of the skin, use a vertical segmentation method.

[0012] For the convex surface segmentation method after processing the scanning model, for the convex surface of the model, use a horizontal segmentation method to divide the skin model into 19 curved surface areas of 100cm×5cm and 2 curved surface areas of 100cm×2.5cm.

[0013] For the concave surface segmentation method after processing the scanning model, for the concave surface of the model, use a vertical segmentation method to divide the skin into 19 curved surface areas of 5cm×100cm and 2 curved surface areas of 2.5cm×100cm, and then perform a 10-equal division to divide it into 210 small areas. Among them, the size of each area on the vertical boundary is 2.5cm×10cm, and the size of the remaining areas is 5cm×10cm.

[0014] For the path design method of laser cleaning the convex surface of the skin in the planned robotic arm movement path, the galvanometer scanning direction of the laser is the vertical up and down scanning direction. Each time, clean a 100cm×5cm curved surface area on the convex surface. After cleaning 10 curved surface areas of 100cm×5cm, complete the upper part cleaning of the convex surface of the skin. After flipping the skin up and down, the lower part cleaning of the convex surface of the skin can be carried out.

[0015] For the path design method of laser cleaning the concave surface of the skin in the planned robotic arm movement path, the galvanometer scanning direction of the laser is the horizontal left and right scanning direction. Each time, clean 20 curved surface areas of 5cm×10cm on the concave surface to complete the cleaning of a 100cm×10cm curved surface area. After cleaning 5 curved surface areas of 100cm×10cm, complete the upper part cleaning of the concave surface of the skin. After flipping the skin up and down, the lower part cleaning of the concave surface of the skin can be carried out.

[0016] When cleaning, the large - area aircraft skin is placed vertically both when cleaning the convex surface and the concave surface. When cleaning the convex surface, the aircraft skin is placed inside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the convex surface of the skin. When cleaning the concave surface, the aircraft skin is placed outside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the concave surface of the skin.

[0017] The operating path of the robotic arm is programmed. The program includes a positioning program and a cleaning program, both of which are programs that form a fitted curve path composed of points programmed using the PATH sub - program instruction. The sub - program consists of PTP point - to - point motion instructions, WAIT wait instructions, and LIN linear motion instructions. In the positioning program, the LIN linear motion speed is 0.1 m / s. In the cleaning program, the LIN linear motion speed is 0.002 m / s.

[0018] The beneficial effects of the present invention are:

[0019] 1. The large - area aircraft skin robot laser profiling cleaning and paint removal method provided by the present invention uses a 3D scanner to obtain the aircraft skin model and perform post - processing and segmentation. By combining the laser with the robotic arm and programming the robotic arm path, it realizes equi - focal profiling laser cleaning of the convex and concave surfaces of the irregular large - area aircraft skin. By setting the optimal laser parameters, it uses the high - density energy pulse of the laser to remove the paint layer on the skin surface to achieve the purpose of paint removal, and will not damage the substrate, which is beneficial to environmental protection. The work requirements are relatively low, which helps to save costs. It has the advantage of being able to clean the surfaces of different materials and substrates with complex shapes.

[0020] 2. The placement method of the large - area aircraft skin in laser cleaning provided by the present invention makes full use of the working space, optimizes the working path of the robotic arm, ensures the stable operation of the laser during the working process, is conducive to the balanced movement of the laser during the laser cleaning process without uneven cleaning effects, and at the same time saves the installation cost of the fixing fixture.

[0021] 3. The large - area aircraft skin robot laser profiling cleaning and paint removal method provided by the present invention uses two different cleaning path methods for the convex and concave surfaces respectively. It not only improves the cleaning efficiency but also ensures that the laser will not collide with the ground or the large - area aircraft skin during the working process, guaranteeing the equipment safety of the laser and the robotic arm. In the convex - surface cleaning path method, a curve path is adopted to ensure the continuous overlap of laser cleaning. In the concave - surface cleaning path method, a vertical straight - line path is adopted to improve the cleaning efficiency and avoid the collision of the laser with the aircraft skin. Description of the Drawings

[0022] Figure 1 is the screen of the laser control panel;

[0023] Figure 2 is an aluminum alloy substrate;

[0024] Figure 3 is the effect diagram of the convex surface material of the aluminum alloy flat plate after the test with the best laser parameters;

[0025] Figure 4 is the effect diagram after cleaning 2 times with the best laser parameters;

[0026] Figure 5 is the effect diagram after cleaning 4 times with the best laser parameters;

[0027] Figure 6 is the effect diagram after cleaning 6 times with the best laser parameters;

[0028] Figure 7 is a large-area aircraft skin with positioning labels attached;

[0029] Figure 8 On the left is the effect diagram before the point cloud stage processing of skin 1, and on the right is the effect diagram after the point cloud stage processing of skin 1;

[0030] Figure 9 On the left is the effect diagram before the point cloud stage processing of skin 2, and on the right is the effect diagram after the point cloud stage processing of skin 2;

[0031] Figure 10 On the left is the effect diagram before the point cloud stage processing of skin 3, and on the right is the effect diagram after the point cloud stage processing of skin 3;

[0032] Figure 11 From left to right are the three views after the polygon stage processing of skins 1, 2, and 3;

[0033] Figure 12 is the fitting surface flow chart of the aircraft skin in the precise surface processing stage;

[0034] Figure 13 is the schematic diagram of the convex surface segmentation method of skin 1;

[0035] Figure 14 is the schematic diagram of the convex surface segmentation method of skin 2;

[0036] Figure 15 is the schematic diagram of the auxiliary line sketch in the concave surface segmentation method of the skin;

[0037] Figure 16 is the schematic diagram of the reference plane establishment in the concave surface segmentation method of the skin;

[0038] Figure 17 is the schematic diagram of the model after segmentation in the concave surface segmentation method of the skin;

[0039] Figure 18 is the schematic diagram of the convex surface cleaning path design of the skin;

[0040] Figure 19 Schematic diagram for the cleaning path design of the skin concave surface

[0041] Figure 20 Schematic diagram for the placement position of the skin and the laser scanning direction when cleaning the convex surface of the skin

[0042] Figure 21 Schematic diagram for the placement position of the skin and the laser scanning direction when cleaning the concave surface of the skin

[0043] Figure 22 For the robotic arm teach pendant

[0044] Figure 23 For the concave surface of the large - area aircraft skin 1, the left is before cleaning and the right is the comparison diagram after cleaning

[0045] Figure 24 For the convex surface of the large - area aircraft skin 2, the left is before cleaning and the right is the comparison diagram after cleaning

[0046] Figure 25 For the convex surface of the large - area aircraft skin 3, the left is before cleaning and the right is the comparison diagram after cleaning

[0047] Figure 26 For the overall view of the cleaning platform Specific implementation mode

[0048] Next, in combination with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be completely described

[0049] As Figure 1-26 shown, the present invention provides a technical solution: the method includes, for irregular large - area aircraft skins with different curvatures, determining the laser parameters for aircraft skin cleaning through experiments, scanning the model and performing segmentation processing, planning the robotic arm movement path and programming, and performing profiling cleaning on the irregular large - area aircraft skin

[0050] The experiment for determining the laser parameters for aircraft skin cleaning includes the following steps

[0051] S1. Through orthogonal experiments, different laser parameters are set for the laser to irradiate the aircraft skin substrate, and the optimal laser parameters for the undamaged aircraft skin substrate are obtained, including laser power, laser scanning speed, laser pulse frequency, and robotic arm speed

[0052] S2. After step S1 is completed, the surface paint layer of the aircraft skin is irradiated with the obtained optimal laser parameters

[0053] S3. After step S2 is completed, the surface paint layer of the aircraft skin is cleaned with the optimal parameters for different numbers of times to obtain the optimal number of cleaning times

[0054] The laser used in step S1 is a 1064nm pulsed laser of the YDFLP series from JPT Company. The galvanometer system is a single-axis linear scanning. The optimal laser parameters are power 50W, frequency 200KHz, scanning speed 2000mm / s, scanning amplitude 5cm, and the speed of the robotic arm is 2mm / s.

[0055] The scanning model and the segmentation process include the following parts:

[0056] Use a 3D scanner to obtain the point cloud file of the aircraft skin. Use Geomagic software to uniformly sample the point cloud model, delete non-connected items, and delete out-of-body isolated points to obtain a polygon. Then, perform relaxation boundary, delete spikes, and mesh division on the polygon to obtain a fitted surface. Export the fitted surface to Solidworks software for segmentation. For the convex surface of the skin, use a horizontal segmentation method, and for the concave surface of the skin, use a vertical segmentation method.

[0057] Convex surface segmentation method for the scanned model after processing. For the convex surface of the model, use a horizontal segmentation method to divide the skin model into 19 curved surface areas of 100cm×5cm and 2 curved surface areas of 100cm×2.5cm.

[0058] Concave surface segmentation method for the scanned model after processing. For the concave surface of the model, use a vertical segmentation method to divide the skin into 19 curved surface areas of 5cm×100cm and 2 curved surface areas of 2.5cm×100cm, and then perform a 10-equal division to divide it into 210 small areas. Among them, the size of each area on the vertical boundary is 2.5cm×10cm, and the size of the remaining areas is 5cm×10cm.

[0059] Laser cleaning path design method for the convex surface of the skin. The galvanometer scanning direction of the laser is the vertical up and down scanning direction. Each time, clean a 100cm×5cm curved surface area on the convex surface. After cleaning 10 curved surface areas of 100cm×5cm, complete the upper part cleaning of the convex surface of the skin. After turning the skin upside down, the lower part cleaning of the convex surface of the skin can be carried out.

[0060] Laser cleaning path design method for the concave surface of the skin. The galvanometer scanning direction of the laser is the horizontal left and right scanning direction. Each time, clean 20 curved surface areas of 5cm×10cm on the concave surface to complete the cleaning of a 100cm×10cm curved surface area. After cleaning 5 curved surface areas of 100cm×10cm, complete the upper part cleaning of the concave surface of the skin. After turning the skin upside down, the lower part cleaning of the concave surface of the skin can be carried out.

[0061] The placement position of the large-area aircraft skin. When cleaning the convex and concave surfaces, the skin is placed vertically. When cleaning the convex surface, the aircraft skin is placed inside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the convex surface of the skin; when cleaning the concave surface, the aircraft skin is placed outside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the concave surface of the skin.

[0062] Programming the operating path of the robotic arm. The program includes a positioning program and a cleaning program, both of which are programs that form a fitted curve path composed of points programmed using the PATH subroutine instruction. The subroutine consists of PTP point-to-point motion instructions, WAIT wait instructions, and LIN linear motion instructions. In the positioning program, the LIN linear motion speed is 0.1 m / s, and in the cleaning program, the LIN linear motion speed is 0.002 m / s.

[0063] The following combines specific cases to elaborate in detail on the large-area aircraft skin robot laser profiling cleaning and paint removal method provided by the present invention:

[0064] The skin material used in the experiment is a 2A12 aluminum alloy substrate. The convex paint layer is the topcoat H06-3 and the primer S04-60 layer of paint, and the concave paint layer is TB06-9.

[0065] In the ablation threshold experiment of the aluminum alloy substrate, a flat 2A12 aluminum alloy material was used to explore the laser parameters.

[0066] As Figure 1 shown, the adjustable range of the laser power is 20 - 100 W, the adjustable range of the frequency is 20 - 200 KHz, the adjustable range of the scanning speed is 200 - 20000 mm / s, the adjustable range of the scanning amplitude is 1.9 - 190 mm, and the focal length is 285 mm; the frequency, scanning speed, scanning amplitude, and power are adjusted through the control panel to set the laser parameters in the experiment. The robotic arm moves horizontally in a straight line, and the laser galvanometer scans in the vertical up and down direction. The flat aluminum alloy material is clamped by a fixture. After turning on the laser, the robotic arm drives the laser to move horizontally and maintains a distance of 285 mm from the test plate to complete a cleaning experiment.

[0067] For the ablation threshold experiment of the aluminum alloy substrate, four factor levels of power, frequency, scanning speed, and robotic arm speed are respectively selected for an orthogonal experiment, with a total of 9 groups.

[0068] After initially screening out the laser parameters that do not damage the substrate, an exploration experiment on the laser cleaning parameters for paint removal on the convex and concave surfaces is carried out.

[0069] Table 1 Parameter settings for the orthogonal experiment group of the ablation threshold of the aluminum alloy substrate

[0070]

[0071] The results obtained after all groups of orthogonal tests show that the substrates of groups 1-6 are not damaged, while those of groups 7-9 are damaged. On this basis, the power is further adjusted to conduct cleaning tests at powers of 50, 52, and 55 W.

[0072] After the laser parameter tests with a frequency of 100 KHz, a scanning speed of 5%, and a power of 55 W, the substrate is damaged; after the tests with a frequency of 100 KHz, a scanning speed of 10%, and a power of 55 W, the substrate is still damaged; after the tests with a frequency of 200 KHz, a scanning speed of 10%, and a power of 55 W, the substrate is damaged; after the tests with a frequency of 200 KHz, a scanning speed of 38%, and a power of 55 W, the substrate is damaged; after the tests with a frequency of 200 KHz, a scanning speed of 30%, and a power of 52 W, the substrate is damaged.

[0073] When testing under the laser parameters of a frequency of 200 KHz and a power of 50 W, the substrate is not damaged at any scanning speed.

[0074] Through comparison of multiple groups of tests, the power parameter is the most important parameter in the exploration of the ablation threshold test. At a power of 50 W, laser cleaning can be carried out on the aluminum alloy substrate without damage. The aluminum alloy substrate is as Figure 2 shown.

[0075] After obtaining the ablation threshold of the aluminum alloy, the parameters of groups 4-6 in the orthogonal table are used to conduct cleaning tests on the paint layer to obtain the best cleaning parameters.

[0076] After conducting laser cleaning tests on the convex surface of the aircraft skin (topcoat H06-3, primer S04-60) with the parameters of groups 4-6, the effects are as Figure 3 shown. 1 is the effect after the test with group 4 parameters, 2 is the effect after the test with group 5 parameters, and 3 is the effect after the test with group 6 parameters. Among them, the test parameters with a power of 50 W, a frequency of 200 KHz, a scanning speed of 2000 mm / s, and a robotic arm speed of 2 mm / s have the best effect.

[0077] Tests on the number of cleaning times are carried out under the laser parameters of a power of 50 W, a frequency of 200 KHz, a scanning speed of 2000 mm / s, and a robotic arm speed of 2 mm / s. Cleaning tests are carried out 2, 4, and 6 times respectively. The effect after cleaning 2 times is as Figure 4 shown, the effect after cleaning 4 times is as Figure 5 shown, and the effect after cleaning 6 times is as Figure 6 shown.

[0078] When the number of cleaning times is 6 times, the cleaning effect of the surface paint layer is better. After obtaining the best number of cleaning times as 6 times, the determined number of cleaning times is the laser cleaning times for the aircraft skin.

[0079] Before scanning the skin model, prepare the work. Place three large irregular aircraft skins with different curvature shapes vertically and flat on the ground, and paste positioning labels on their surfaces respectively. The skin with the positioning label pasted is as Figure 7 shown. The positioning label can ensure the continuity of scanning and the accuracy of capturing point clouds during the 3D scanning process. Use Tianyuan handheld 3D laser scanner to scan and obtain the 3D point cloud data files of the three aircraft skins respectively.

[0080] The 3D point cloud data files of aircraft skins 1, 2, and 3 before and after processing are as Figure 8-10 shown. In the point cloud stage, use Geomagic software to delete out-of-body isolated points and non-connected items, and then perform noise reduction and uniform sampling processing. The positioning label of the circular hole can be seen in the point cloud model in the figure, and hole filling processing needs to be carried out in the polygon stage later.

[0081] In the polygon stage, as Figure 11 shown, it is necessary to perform relaxation boundary, delete spikes, reduce noise, select some depressions to delete features on the model, and then use the network doctor for processing. Further processing is required in the precise surface stage later.

[0082] After the skin is processed in the precise surface stage, after performing steps of dividing the mesh → constructing the grille → fitting the surface, the solid file model can be exported. The fitting surface process is as Figure 12 shown.

[0083] Import the processed model into Solidworks software to split the convex surface model. For the convex surface of the model, adopt the horizontal splitting method to split the skin model into 19 curved surface areas of 100 cm × 5 cm and 2 curved surface areas of 100 cm × 2.5 cm.

[0084] Taking skin 1 as an example, the specific process is as follows: Set the coordinate origin and coordinate system of the aircraft skin model, create a reference plane with the top of the skin model as the plane, move the skin model 5 cm in the +Y axis direction each time, and use the reference plane to split it once after each movement to obtain the split model, as Figure 13 shown.

[0085] Since the model of skin 2 consists of multiple surface patches after being processed in Geomagic software, multiple surface patches appear and cannot be merged after export. Therefore, when splitting, use 20 planes parallel to the top of the model to split the model, and the distance between every two adjacent planes is 5 cm. The splitting schematic diagram is as Figure 14 shown.

[0086] Since the model of skin 3 also consists of multiple surface patches after being processed in Geomagic, multiple surface patches appear and cannot be merged after export. Therefore, the splitting method is the same as that of skin 2.

[0087] In the method for dividing the concave surface of the skin, for the concave surface of the model, a vertical division method is adopted. The skin is divided into 19 curved surface areas of 5 cm × 100 cm and 2 curved surface areas of 2.5 cm × 100 cm, and then divided into 210 small areas by 10 equal divisions. Among them, the size of each area on the vertical boundary is 2.5 cm × 10 cm, and the size of the remaining areas is 5 cm × 10 cm.

[0088] Import the model into the Solidworks software. Before dividing the concave surface of the skin model, draw an auxiliary line sketch. First, establish an auxiliary line sketch in the way of offset on the curved surface, using the left and right 2 vertical boundaries of the skin as the offset objects, and offsetting once every 5 cm at both the upper and lower ends to obtain the auxiliary lines for establishing the reference planes, as Figure 15 shown.

[0089] On the basis of establishing the auxiliary lines, establish reference planes in the vertical direction for the model. Select two line segments on the same straight line of the upper and lower sides and the curved boundary where the line segments intersect, and establish a reference plane every 5 cm along the edge part, establishing 20 reference planes with a 5 cm interval, as Figure 16 shown.

[0090] On the basis of the vertical reference planes, divide the aircraft skin. After division, continue to establish 10 horizontal reference planes in the vertical direction and continue to divide 10 times. After the division of the concave surface of the model is completed, as Figure 17 shown.

[0091] For the method of designing the laser cleaning path for the convex surface of the skin, the dividing line in the divided model is the walking path of the robotic arm. The starting position of the laser is the left end of the first dividing line from top to bottom after the skin is divided. The galvanometer scanning direction of the laser is the vertical up and down scanning direction. Each time, a curved surface area of 100 cm × 5 cm on the convex surface is cleaned. After cleaning 10 curved surface areas of 100 cm × 5 cm from top to bottom, the upper part of the convex surface of the skin is cleaned. The cleaning route of the convex surface of the skin is as Figure 18 shown.

[0092] For the method of designing the laser cleaning path for the concave surface of the skin, the vertical dividing line in the divided model is the walking path of the robotic arm. The starting position of the laser is the upper end of the first vertical dividing line from left to right after the skin is divided. The galvanometer scanning direction of the laser is the horizontal left and right scanning direction. Each time, 20 curved surface areas of 5 cm × 10 cm on the concave surface are cleaned to complete the cleaning of a curved surface area of 100 cm × 10 cm. After cleaning 5 curved surface areas of 100 cm × 10 cm from top to bottom, the upper part of the concave surface of the skin is cleaned. The cleaning route of the first 100 cm × 10 cm curved surface area of the concave surface of the skin is as Figure 19 shown.

[0093] Before the large-area aircraft skin cleaning test begins, its placement position needs to be designed according to the working space of the robotic arm and the rotation limit conditions of each axis of the robotic arm.

[0094] To prevent the skin from deforming and causing a change in curvature when placed horizontally, if the skin is placed horizontally, the laser on the robotic arm will tilt during the cleaning process, which is not conducive to the stability of the robotic arm's movement. When cleaning the convex and concave surfaces, the skin is placed vertically. In the vertical placement state of the skin, the laser always rotates horizontally during the movement of the robotic arm without tilting, thus ensuring the stability of the robotic arm's movement and making full use of the working space of the robotic arm.

[0095] When cleaning the convex surface of the skin, the aircraft skin is placed inside the robotic arm, the concave surface of the skin faces the base of the robotic arm, and the direction of the laser is towards the convex surface of the skin. As Figure 20 shown, 1 the scanning direction of the laser is vertical, 2 the laser output direction is towards the convex surface of the skin, and 3 the direction of the laser handle part is horizontal.

[0096] When cleaning the concave surface of the skin, the aircraft skin is placed outside the robotic arm, the concave surface of the skin faces the base of the robotic arm, and the direction of the laser is towards the concave surface of the skin, as Figure 21 shown, 1 the scanning direction of the laser is horizontal, 2 the laser output direction is towards the concave surface of the skin, and 3 the direction of the laser handle part is vertical.

[0097] The robotic arm movement programming can be carried out through the teach pendant. The teach pendant is as Figure 22 shown. In the programming of the robotic arm movement path, the instruction programming method is used, and the PTP, LIN, WAIT, and PATH instructions are used to implement different functions. Among them, the function of the PTP instruction is point-to-point movement according to the axis coordinates, the function of the LIN instruction is linear movement along the trajectory, and the speed and acceleration between two points can be set through programming. The speed range of the robotic arm is 0.001m / s - 2m / s. The waiting function in the movement program can use the WAIT instruction to pause the movement of the robot according to the programmed time. The PATH instruction can form a subprogram path point group from the points in the linear movement, so as to fit a complex curved path.

[0098] Under the PTP instruction movement, the robot will move to the target point along the fastest trajectory. The fastest trajectory is usually not the shortest trajectory and is therefore not a straight line. Due to the rotational movement of the robot's axis, the arc trajectory will be faster than the straight line trajectory. However, the first movement in the program during programming must be a PTP movement because only in this movement are the status and steering evaluated.

[0099] Under LIN linear motion, the robotic arm moves along a linear trajectory. The robotic arm moves uniformly from the starting point to the target point in the set posture. In LIN linear motion, the trajectory of the robotic arm is the line segment between the set starting point and the ending point, and the trajectory during the motion is predictable.

[0100] The program includes a positioning program and a cleaning program, both of which are programs that use PATH subroutine instructions to program points to form a fitted curve path. The subroutine consists of PTP point-to-point motion instructions, WAIT wait instructions, and LIN linear motion instructions. In the positioning program, the LIN linear motion speed is 0.1 m / s. In the cleaning program, the LIN linear motion speed is 0.002 m / s.

[0101] In the programming of the skin position positioning program, the points using the PATH subroutine form a fitted curve path for the positioning program of the aircraft skin. The starting instruction is the PTP motion instruction to determine the initial position of the first point. After arrival, the WAIT instruction is called to wait for 5 seconds, so that the laser switch can be turned on during this period, and the position of the laser under low power and whether the focal length from the laser lens to the skin to be cleaned is 285 mm can be checked. When using the positioning program, the point-to-point linear speed is 0.1 m / s for quick positioning. After walking through the positioning program and measuring the distance from the lens to the skin in manual mode, the positioning of the skin placement position is completed.

[0102] In the cleaning program of the skin, the PTP instruction is used for the first running point, and the point running speed is set to 0.1 m / s to quickly position the laser. Starting from the second linear motion point position, a 100-cm curved path composed of more than 200 points at about 5 mm intervals is formed. The speed is set to 2 mm / s, which is the actual experimental robotic arm running speed, for laser cleaning. After completing the curved path fitted by all the point groups of the PATH instruction, the cleaning ends.

[0103] The test process for cleaning a large area of aircraft skin is as follows: First, set the laser parameters in the laser panel to a power of 50 W, a frequency of 200 KHz, a scanning speed of 2000 mm / s, and a scanning amplitude of 5 cm. After completing the laser parameter setting, move the laser position near the skin to be cleaned.

[0104] Select the skin cleaning program, run the program to the preparatory position of the PTP point in manual mode. After reaching the PTP starting point, switch the mode to automatic mode. In automatic mode, press the start arrow, and then turn on the laser. After the 5-second waiting time set by the WAIT wait instruction has passed, start the LIN linear motion point group part in the PATH subroutine. At this time, the laser on the robotic arm starts to run along the pre-planned path.

[0105] After the path movement is completed, the robotic arm program stops, the laser is turned off, and the cleaning of the large-area aircraft skin is completed.

[0106] Due to the still limited working space of the robotic arm, the curved surface cleaning of some areas of the skin was carried out in the experiments. The concave surface cleaning experiment was carried out on the aircraft skin 1, and the convex surface cleaning experiments were carried out on the aircraft skins 2 and 3. Before and after the concave surface cleaning of the aircraft skin 1 are as Figure 23 shown, before and after the convex surface cleaning of the aircraft skin 2 are as Figure 24 shown, and before and after the convex surface cleaning of the aircraft skin 3 are as Figure 25 shown.

[0107] The cleaning platform is as Figure 26 shown. In the experiment of cleaning the large-area aircraft skin, the laser parameters are power 50w, frequency 200KHz, scanning speed 2000mm / s. During the cleaning process, the speed of the robotic arm is 2mm / s, and the number of cleaning times is 6 times.

[0108] So far, although the present invention has been shown and described in detail with respect to a plurality of exemplary embodiments, those skilled in the art can make various variations, modifications or substitutions to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for laser profiling cleaning and paint removal of large-area aircraft skins by a robot, characterized in that: The method includes determining the laser parameters for aircraft skin cleaning through experiments for irregular large-area aircraft skins with different curvatures, scanning the model and performing segmentation processing, planning the operating path of the robotic arm and programming, and performing profiling cleaning on the irregular large-area aircraft skin. The scanning the model and performing segmentation processing includes the following steps: obtaining the aircraft skin point cloud file using a 3D scanner, uniformly sampling the point cloud model using Geomagic software, deleting non-connected items, and deleting outlier points to obtain a polygon, then performing relaxation boundary, deleting spikes, and dividing the mesh on the polygon to obtain a fitted surface, exporting the fitted surface to Solidworks software for segmentation, using a horizontal segmentation method for the convex surface of the skin and a vertical segmentation method for the concave surface of the skin; the specific horizontal segmentation method for the convex surface of the skin is: dividing the convex surface skin of the model into 19 curved surface areas of 100 cm × 5 cm and 2 curved surface areas of 100 cm × 2.5 cm; the specific vertical segmentation method for the concave surface of the skin is: dividing the concave surface skin of the model into 19 curved surface areas of 5 cm × 100 cm and 2 curved surface areas of 2.5 cm × 100 cm, and then performing a 10-equal division to divide it into 210 small areas, where the size of each area on the vertical boundary is 2.5 cm × 10 cm, and the size of the remaining areas is 5 cm × 10 cm; for the path design method of laser cleaning the convex surface of the skin in planning the operating path of the robotic arm, the galvanometer scanning direction of the laser is the vertical up and down scanning direction, and each time it cleans a 100 cm × 5 cm curved surface area on the convex surface. After cleaning 10 curved surface areas of 100 cm × 5 cm, the upper part of the convex surface of the skin is cleaned. After turning the skin upside down, the lower part of the convex surface of the skin can be cleaned; for the path design method of laser cleaning the concave surface of the skin in planning the operating path of the robotic arm, the galvanometer scanning direction of the laser is the horizontal left and right scanning direction, and each time it cleans 20 curved surface areas of 5 cm × 10 cm on the concave surface to complete the cleaning of a 100 cm × 10 cm curved surface area. After cleaning 5 curved surface areas of 100 cm × 10 cm, the upper part of the concave surface of the skin is cleaned. After turning the skin upside down, the lower part of the concave surface of the skin can be cleaned.

2. A laser profiling cleaning and paint stripping method for a large-area aircraft skin robot according to claim 1, characterized in that: The experiment for determining the laser parameters for aircraft skin cleaning includes the following steps: S1. Through orthogonal experiments, set different laser parameters for the laser to irradiate the aircraft skin substrate, and obtain the optimal laser parameters for the undamaged aircraft skin substrate, including laser power, laser scanning speed, laser pulse frequency, and robotic arm speed; S2. After step S1 is completed, irradiate the aircraft skin surface paint layer with the obtained optimal laser parameters; S3. After step S2 is completed, clean the aircraft skin surface paint layer with the optimal parameters for different numbers of times to obtain the optimal number of cleaning times.

3. A laser profiling cleaning and paint removal method for a large-area aircraft skin robot according to claim 2, characterized in that: The laser used in the step S1 is a 1064nm pulsed laser of the YDFLP series from JPT Company. The galvanometer system is a single-axis linear scan. The optimal laser parameters are a power of 50W, a frequency of 200KHz, a scanning speed of 2000mm / s, a scanning amplitude of 5cm, and a robotic arm speed of 2mm / s.

4. A laser profiling cleaning and paint stripping method for a large-area aircraft skin robot according to claim 1, characterized in that: When cleaning, the large-area aircraft skin is placed as follows: when cleaning the convex and concave surfaces, the skin is placed vertically. When cleaning the convex surface, the aircraft skin is placed inside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the convex surface of the skin; when cleaning the concave surface, the aircraft skin is placed outside the robotic arm, with the concave surface of the skin facing the base of the robotic arm and the laser direction facing the concave surface of the skin.

5. A laser profiling cleaning and paint removal method for a large-area aircraft skin robot according to claim 1, characterized in that: The program for programming the running path of the robotic arm includes a positioning program and a cleaning program, both of which are programs that form a fitting curve path composed of points programmed using the PATH subroutine instruction. The subroutine consists of the PTP point-to-point motion instruction, the WAIT wait instruction, and the LIN linear motion instruction. In the positioning program, the LIN linear motion speed is 0.1m / s, and in the cleaning program, the LIN linear motion speed is 0.002m / s.

Images