A spraying system based on laser 3D point clouds

Abstract

This invention discloses a laser-based 3D point cloud-based spraying system. The system includes a laser 3D point cloud acquisition unit, a spraying trajectory planning unit, and a robotic spraying unit. The laser 3D point cloud acquisition unit collects data on the spraying surface of the workpiece. The spraying trajectory planning unit plans the nozzle movement trajectory. The robotic spraying unit completes the painting operation on the workpiece based on the planned nozzle movement trajectory. This invention solves the problem of point cloud data acquisition for non-standard workpieces by designing a laser 3D scanning unit. Through the trajectory planning algorithm of the spraying trajectory planning unit, it completes the planning of the spraying robot's travel trajectory and spraying direction, achieving fully automated spraying. This makes the system suitable for automated spraying operations on various non-standard workpieces by robots.

Description

Technical Field

[0001] This invention belongs to the field of automation technology, and in particular relates to a spraying system based on laser three-dimensional point clouds. Background Technology

[0002] Spray painting is a crucial process in modern industry. Traditional spray painting is typically done manually or semi-automatically, and the noise and dust from the spray booth can cause health problems for workers. Furthermore, traditional manual spray painting is inefficient, makes it difficult to guarantee paint quality, and is not conducive to saving on spray materials.

[0003] With the advent of Industry 4.0, industrial robots are playing an increasingly important role in production, replacing humans in tasks such as painting, moving, and welding.

[0004] With the development of automation, information technology, and intelligent technology, robotic automatic spraying technology has emerged. Using robotic spraying can improve product quality and production efficiency, while also reducing worker workload and protecting worker health.

[0005] Currently, industrial robots still require a lot of manual identification and teaching in spraying applications, which is not conducive to the fully automated spraying of non-standard workpieces. Spraying operations are time-consuming and costly.

[0006] Automatic spraying of non-standard workpieces of different sizes and shapes, and avoiding nozzle collisions with the workpieces, are all problems that urgently need to be solved. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of the prior art and disclose a spraying system based on laser three-dimensional point cloud. The spraying system of this invention realizes the point cloud scanning of the workpiece to be sprayed through the laser three-dimensional point cloud acquisition unit, and completes the nozzle motion trajectory planning by the spraying trajectory planning unit, thus solving the problem of automatic robotic spraying of non-standard workpieces of different sizes and shapes.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A laser-based three-dimensional point cloud-based spraying system includes a laser three-dimensional point cloud acquisition unit, a spraying trajectory planning unit, and a robotic spraying unit. The laser three-dimensional point cloud acquisition unit is used to acquire spraying surface data information of the workpiece to be sprayed. The spraying trajectory planning unit is used to plan the nozzle motion trajectory. The robotic spraying unit completes the painting operation of the workpiece to be sprayed based on the planned nozzle motion trajectory.

[0010] According to a preferred embodiment, the spray trajectory planning unit plans the nozzle motion trajectory in the following manner, specifically including: determining whether the point cloud has layers, and planning the nozzle motion trajectory for each layer.

[0011] According to a preferred embodiment, the presence of layering in the point cloud is determined as follows: Let P be the set of point clouds within the current working area. k If the current interval point cloud elevation difference is greater than the threshold z T Furthermore, there are blank areas within the preset elevation range, meaning the number of point clouds within the preset elevation range is less than the threshold n. T If the workpiece structure to be sprayed has two layers in the current area, then the workpiece structure to be sprayed has two layers.

[0012] According to a preferred embodiment, the planning of nozzle movement trajectories for each layer specifically includes:

[0013] For any layer, take the current layer point cloud set p, and use the least squares method to fit the point cloud plane Ax+By+Cz+D=0;

[0014] Let the current layer plane normal vector be (A, B, C). Then, the direction opposite to the plane normal vector is the nozzle working direction. The spray trajectory is constrained by a distance H from the plane. The nozzle motion trajectory coordinates can be obtained by solving the following equation:

[0015]

[0016] Where, x c ,y c ,z c Let x, y, and z represent the coordinates of the intersection of the normal vector and the plane, respectively, and let z represent the coordinates of the end of the spray gun. Solving the above quadratic equation will yield two valid solutions, and the coordinates of the two points correspond to two spraying points symmetrically set on the current layer plane.

[0017] According to a preferred embodiment, the laser three-dimensional point cloud acquisition unit includes: a portal truss, a rail flatcar, and several laser scanners mounted on the portal truss; the workpiece to be coated is fixed on the rail flatcar, and the rail flatcar drives the workpiece to be coated through the portal truss, and the point cloud information of the workpiece to be coated is acquired by each laser scanner.

[0018] According to a preferred embodiment, the laser three-dimensional point cloud acquisition unit includes: a photoelectric beam switch and a rack disposed on the side of the track flatcar;

[0019] When the railcar moves toward or through the portal truss, the photoelectric photoelectric switch illuminates the rack. As the rack moves past the photoelectric photoelectric switch, it enables the switch to perform incremental encoding.

[0020] According to a preferred embodiment, during the scanning process of the laser scanner, the motion measurement resolution is improved by interpolating the motion measurement data composed of the rack and pinion switch. Specifically:

[0021] Let N0 and N0+j be the laser scanning sections of the laser scanner corresponding to the rectangular square waves generated by the i-th and i+1-th photoelectric switches, respectively. That is, the scanner scans a total of j sections in the time corresponding to the rising edges of the two rectangular square waves. Let Δx be the movement distance of the track flatcar (105) corresponding to each rectangular square wave. Then, the movement distance corresponding to each scanning section data between N0 and N0+j, that is, the x-axis movement distance, is calculated as follows:

[0022]

[0023] Where (y0, z0) are the cross-sectional coordinates obtained by the laser scanner in the j-th frame, and n is the increment of the current scan frame relative to the N0 frame.

[0024] According to a preferred embodiment, the point clouds scanned by each laser scanner are unified in coordinates using the following method, specifically including:

[0025] Let the point cloud scanned by any one of the laser scanners be the first scanner, and let the point cloud set obtained by the first scanner be P1. Let the point cloud set obtained by the second scanner, which has an overlapping area with the first scanner, be P2. Select corresponding points p1 and p2 from the point clouds of the first and second scanners, and assume that the coordinate systems of the two point clouds satisfy the relationship: p1 = R 12 p2+T 12

[0026] Among them, R 12 and T 12 These are the rotation and translation matrices for point cloud p2, i.e., the rotation and translation matrices for the same point cloud in the two point clouds via R. 12 and T 12 If the points completely overlap after rotation and translation, then the point cloud coordinates of the second scanner, based on the first scanner, are transformed as P2′=R. 12 P2+T 12 That is, after rotation and translation, P2′ and P1 are in the same coordinate system;

[0027] Therefore, through the corresponding rotation and translation matrix R 12 and T 12 Complete the coordinate system of the point cloud scanned by each laser scanner.

[0028] The aforementioned main solution of the present invention and its various further alternative solutions can be freely combined to form multiple solutions, all of which are solutions that can be adopted and are claimed by the present invention. Those skilled in the art, after understanding the solution of the present invention, will realize that there are many combinations based on existing technology and common knowledge, all of which are technical solutions to be protected by the present invention, and will not be exhaustively listed here.

[0029] The beneficial effects of this invention are:

[0030] This invention solves the problem of point cloud data acquisition for non-standard workpieces by designing a laser 3D scanning unit; through the trajectory planning algorithm of the spraying trajectory planning unit, it completes the planning of the spraying robot's travel trajectory and spraying direction, achieving the goal of fully automated spraying. This makes the system suitable for automated spraying operations on various non-standard workpieces by robots. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the laser three-dimensional scanning unit in the spraying system of the present invention;

[0032] Figure 2 This is a schematic diagram of the spraying operation in the spraying system of the present invention. Detailed Implementation

[0033] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0035] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Furthermore, it should be noted that, unless otherwise specified, the structures, connections, positions, power sources, etc. involved in this invention are all things that a person skilled in the art can know without creative effort based on the prior art.

[0039] Example 1:

[0040] This embodiment discloses a spraying system based on laser three-dimensional point clouds. The spraying system includes a laser three-dimensional point cloud acquisition unit, a spraying trajectory planning unit, and a robot spraying unit.

[0041] The laser 3D point cloud acquisition unit is used to acquire the spraying surface data information of the workpiece to be sprayed, the spraying trajectory planning unit is used to complete the nozzle motion trajectory planning, and the robot spraying unit completes the painting operation of the workpiece to be sprayed based on the planned nozzle motion trajectory.

[0042] Preferably, refer to Figure 1 As shown, the laser 3D point cloud acquisition unit includes: a portal truss 102, a track flatcar 105, and several laser scanners 101 mounted on the portal truss 102. The workpiece to be coated is fixed on the track flatcar 105, and the track flatcar 105 drives the workpiece to be coated through the portal truss 102, acquiring point cloud information of the workpiece through each laser scanner 101.

[0043] The workpiece is mounted on a rail flatcar 105 and the point cloud of the entire workpiece is collected by moving the portal truss 102 back and forth. The rail flatcar 105 adopts a fixed structure to support the workpiece to be sprayed, so the point cloud of the supporting structure can be removed through point cloud data preprocessing.

[0044] Preferably, the laser three-dimensional point cloud acquisition unit includes: a photoelectric beam switch 103 and a rack 104 disposed on the side of the track flatcar 105.

[0045] When the track flatcar 105 moves toward or passes through the portal truss 102, the photoelectric photoelectric switch 103 illuminates the rack 104. As the rack 104 moves past the photoelectric photoelectric switch 103, it enables the photoelectric photoelectric switch 103 to perform incremental encoding, producing an effect similar to an incremental encoder.

[0046] Preferably, the rack 104 is 2cm wide, and when the rail flatcar 105 moves along the X-axis, the photoelectric beam switch 103 outputs a rectangular square wave to measure the movement of the rail flatcar.

[0047] In a preferred embodiment, the laser 3D point cloud acquisition device can scan a maximum workpiece size of 20m×4m×4m with a measurement accuracy better than 2mm.

[0048] Furthermore, using two switching quantities to control the phase (installation position) can avoid measurement deviations caused by the flatcar retraction.

[0049] In this embodiment, the laser scanner has a scanning frame rate of 600Hz, and the flatbed carriage moves at a relatively slow speed. During the scanning process of the laser scanner 101, the motion measurement data composed of the rack 104 and the photoelectric through-beam switch 103 is interpolated to improve the motion measurement resolution. Specifically:

[0050] Let N0 and N0+j be the laser scanning sections of the laser scanner 101 corresponding to the rectangular square waves generated by the i-th and i+1-th photoelectric switches 103, respectively. That is, the scanner scans a total of j sections in the time corresponding to the rising edges of the two rectangular square waves. Let Δx be the movement distance of the track flatcar 105 corresponding to each rectangular square wave. Then, the movement distance corresponding to each scanning section data between N0 and N0+j, i.e., the x-axis movement distance, is calculated as follows:

[0051]

[0052] Where (y0, z0) are the cross-sectional coordinates obtained by the laser scanner in the j-th frame, and n is the increment of the current scan frame relative to the N0 frame. Equation (1) can effectively solve the problem of low resolution in the motion measurement of the track flatcar, that is, the motion between the rectangular square waves is regarded as uniform motion, and each scan frame is evenly distributed in the motion direction.

[0053] Let P be the 3D point cloud data acquired by a single laser scanner 101. II = 1, 2...7 (In this embodiment, seven laser scanners 101 are installed. The seven single-line laser scanners 101 are distributed around the portal truss 102 to ensure no blind spots in the tube screen. The three-dimensional point cloud of the workpiece surface is acquired by moving the track flatcar). Different laser scanners 101 use the track flatcar and scanning section data to achieve local three-dimensional scanning. Due to the randomness of the on-site installation of each laser scanner 101, the installation parameters of the installed point clouds need to be calculated to achieve the unification of point cloud coordinates and the calibration of installation parameters of multiple scanners.

[0054] The point clouds scanned by each laser scanner 101 were unified in coordinates using the following method, specifically including:

[0055] Taking any one of the laser scanners 101 as the first scanner, let the point cloud set obtained by the first scanner be P1, and let the point cloud set obtained by the second scanner with an overlapping area be P2. Select the corresponding points p1 and p2 in the point clouds of the first and second scanners, and assume that the coordinate systems of the two point clouds satisfy the following relationship:

[0056] p1 = R 12 p2+T 12 (2)

[0057] Among them, R 12 and T 12 These are the rotation and translation matrices for point cloud p2, i.e., the rotation and translation matrices for the same point cloud in the two point clouds via R. 12 and T 12 If the points completely overlap after rotation and translation, then the point cloud coordinates of the second scanner, based on the first scanner, are transformed as P2′=R. 12 P2+T 12 That is, after rotation and translation, P2′ and P1 are in the same coordinate system.

[0058] Therefore, through the corresponding rotation and translation matrix R 12 and T 12 The coordinate system of the point clouds scanned by each laser scanner 101 is completed. After rotation and translation, the coordinates of the point clouds of each scanner are completely unified to the preset coordinate system, with no misalignment between point clouds and complete structural information of the scanned object.

[0059] Spraying operations such as Figure 2 As shown, the spraying area covered by the spraying robot is an isosceles triangle. During the spraying operation, the paint sprayed from the nozzle must be perpendicular to the upper surface of the workpiece, with a preset spraying height H. Let P be the point cloud set of the workpiece after removing the supporting structure. Along the X-axis, the point cloud data is extracted segment by segment to calculate the spraying trajectory.

[0060] Preferably, the spraying trajectory planning unit plans the nozzle motion trajectory according to the following method, specifically including: determining whether the point cloud has layers, and planning the nozzle motion trajectory for each layer.

[0061] Specifically, the presence of layering in a point cloud is determined as follows:

[0062] Let P be the set of point clouds within the current working area. k P k ={p i ∈P|x∈[x i x i+1 The method shown in equation (3) is used to determine whether the point cloud has upper and lower layers (the tube screen has L-shaped pillars):

[0063]

[0064] That is, if the elevation difference of the point cloud in the current interval is greater than the threshold z T And within the preset elevation range [z i ,z j There are blank areas within the range, meaning the number of point clouds within the preset elevation interval is less than the threshold n. T If the workpiece structure to be sprayed has two layers in the current area, then the workpiece structure to be sprayed has two layers.

[0065] Preferably, the planned nozzle movement trajectory for each layer specifically includes:

[0066] For any layer, take the current layer point cloud set p, and use the least squares method to fit the point cloud plane Ax+By+Cz+D=0;

[0067] Let the current layer plane normal vector be (A, B, C). Then, the direction opposite to the plane normal vector is the nozzle working direction. The spray trajectory is constrained by a distance H from the plane. The nozzle motion trajectory coordinates can be obtained by solving the following equation:

[0068]

[0069] Where, x c ,y c ,z c Let x, y, and z represent the coordinates of the intersection of the normal vector and the plane, respectively, and let z represent the coordinates of the end of the spray gun. Solving the above quadratic equation will yield two valid solutions, and the coordinates of the two points correspond to two spraying points symmetrically set on the current layer plane.

[0070] The spraying trajectory and spraying direction parameters obtained by solving equation (4) are sent to the robot spraying unit, and the robot spraying unit automatically realizes the spraying operation.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A spraying system based on laser three-dimensional point clouds, characterized in that, The spraying system includes a laser 3D point cloud acquisition unit, a spraying trajectory planning unit, and a robotic spraying unit. The laser 3D point cloud acquisition unit is used to acquire the spraying surface data information of the workpiece to be sprayed, the spraying trajectory planning unit is used to complete the nozzle motion trajectory planning, and the robot spraying unit completes the painting operation of the workpiece to be sprayed based on the planned nozzle motion trajectory. The spraying trajectory planning unit plans the nozzle motion trajectory in the following way, specifically including: determining whether the point cloud has layers, and planning the nozzle motion trajectory for each layer; Determine whether a point cloud has layers using the following method: Let the set of point clouds within the current working range be . If the current interval point cloud elevation difference is greater than the threshold Furthermore, there are blank areas within the preset elevation range, meaning the number of point clouds within the preset elevation range is less than the threshold. If the workpiece structure to be sprayed has two layers in the current area, then the workpiece structure to be sprayed has an upper and lower layer structure. The specific nozzle movement trajectories planned for each layer include: For any layer, take the point cloud set of the current layer. The point cloud plane was obtained by fitting using the least squares method. ; Let the normal vector of the current layer plane be... If the plane normal vector is reversed, then the nozzle's working direction is determined. The spray trajectory is constrained by a distance H from the plane. The nozzle's motion trajectory coordinates can be obtained by solving the following equation: in, x c ,y c ,z c Let x, y, and z represent the coordinates of the intersection of the normal vector and the plane, respectively, and let z represent the coordinates of the end of the spray gun. Solving the above quadratic equation will yield two valid solutions, and the coordinates of the two points correspond to two spraying points symmetrically set on the current layer plane.

2. The spraying system as described in claim 1, characterized in that, The laser three-dimensional point cloud acquisition unit includes: a portal truss (102), a track flatcar (105), and several laser scanners (101) mounted on the portal truss (102). The workpiece to be coated is fixed on the rail flatcar (105), and the rail flatcar (105) drives the workpiece to be coated through the portal truss (102), and the point cloud information of the workpiece to be coated is obtained by each laser scanner (101).

3. The spraying system as described in claim 2, characterized in that, The laser three-dimensional point cloud acquisition unit includes: a photoelectric beam switch (103) and a rack (104) disposed on the side of the track flatcar (105). When the railcar (105) moves toward or through the portal truss (102), the photoelectric photoelectric switch (103) illuminates the rack (104). When the rack (104) moves past the photoelectric photoelectric switch (103), the photoelectric photoelectric switch (103) is able to perform incremental encoding.

4. The spraying system as described in claim 3, characterized in that, During the scanning process of the laser scanner (101), the motion measurement resolution is improved by interpolating the motion measurement data composed of the rack (104) and the photoelectric through-beam switch (103). Specifically: Let the first and The laser scanning section of the laser scanner (101) corresponding to the rectangular square wave generated by the photoelectric through-beam switch (103) is as follows: and That is, the total number of scans performed by the scanner during the time corresponding to the rising edges of the two rectangular square waves. Each cross section; let the track flatcar (105) travel distance corresponding to each rectangular square wave. Then for and The movement distance corresponding to each scan section data point, i.e., the x-axis movement distance, is calculated as follows: in, Let J represent the cross-sectional coordinates obtained by the laser scanner in the j-th frame. For the current scan frame relative to The increment of frames.

5. The spraying system as described in claim 2, characterized in that, The point clouds scanned by each laser scanner (101) were unified in coordinates using the following method, specifically including: Taking any one of the laser scanners (101) that scans the point cloud as the first scanner, let the set of point clouds obtained by the first scanner be . Let the point cloud set obtained by the second scanner, which has an overlapping area with the first scanner, be denoted as . Select corresponding points from the point clouds of the first and second scanners. and Let the coordinate systems of the two point clouds satisfy the following relationship: in, and Point clouds The rotation and translation matrix, that is, the rotation and translation matrix of the same point cloud in two point clouds, through and If the points completely overlap after rotation and translation, then the point cloud coordinates of the second scanner, based on the first scanner, are transformed as follows: That is, after rotation and translation transformation and In the same coordinate system; Thus, through the corresponding rotation and translation matrices and Complete the coordinate system of the point cloud scanned by each laser scanner (101).

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