Method for path planning of a coating system and corresponding path planning system

Abstract

This invention relates to a path planning method for planning the movement path of an applicator relative to a component to be coated, particularly for coating automotive body components with paint, adhesive, or sealant. The method includes the following steps: setting the movement path of the applicator; setting multiple measurement points on the actual component and measuring the spatial positions of these measurement points; and correcting the movement path based on the measured spatial positions of the measurement points on the actual component. The invention proposes that correcting the movement path includes the following steps: associating the movement path with a preset mesh model of the component to be coated, the mesh model containing multiple mesh points; and adjusting the mesh model according to the measured spatial positions of the measurement points on the actual component, so that the associated movement path adjusts along with the mesh points of the mesh model. Furthermore, this invention also covers a corresponding path planning system for executing the path planning method described herein.

Description

Technical Field

[0001] This invention relates to a path planning method for planning the movement path of an applicator (e.g., a rotary atomizer, a printhead) relative to a component to be coated (e.g., a motor vehicle body component), particularly for coating motor vehicle body components with paint, adhesive, or sealant. Furthermore, this invention relates to a path planning system designed accordingly and a coating system equipped with this path planning system. Background Technology

[0002] In modern coating systems used for coating vehicle body components, rotary atomizers are often used as application devices. Guided by a multi-axis coating robot, they glide over the vehicle body component to be coated according to a pre-set coating path. The coating path traveled by the rotary atomizer relative to the vehicle body component is determined based on the geometry of the component; this process is also known as "teaching." During coating, multiple parallel coating paths are typically used, with laterally overlapping paths, ultimately forming a continuous paint film on the vehicle body component. The positioning accuracy requirements of the rotary atomizer along the parallel coating paths are relatively low because the sprayed paint stream from the rotary atomizer has indistinct spatial boundaries, meaning that the rotary atomizer is tolerant of positioning accuracy errors.

[0003] However, recently, so-called printheads have also been used as application devices. Unlike rotary atomizers, printheads do not spray a jet of paint, but rather a jet of paint with clearly defined spatial boundaries, thus forming a well-defined coating path on the component to be coated. Therefore, when using such printheads, the positioning accuracy requirements for the formed coating path are much higher than when using rotary atomizers, because printheads have less tolerance for positioning accuracy errors.

[0004] A problem arises in practical applications: the actual geometry of the vehicle body component to be coated deviates slightly from the geometry set based on the model. Furthermore, it must be considered that the vehicle body component is typically transported through the paint booth by a conveyor, which also has positioning errors. The commonly used robots and temperature effects can further contribute to these errors.

[0005] Therefore, German patent publication DE102019111760A1 discloses a path planning method for a coating system, in which the geometry of an actual motor vehicle body component is measured in a paint booth to adjust the coating path based on the measurement results. In this method, multiple measurement points are set on the motor vehicle body component to be coated, and the spatial positions of these measurement points are measured using sensors. The coating path is then adjusted based on the measured position of the measurement points.

[0006] The known path planning method works well for approximately rectangular surfaces (such as the roof and hood of a vehicle body). However, vehicle body components also have complex surfaces that are not approximately rectangular (such as fenders). When coating such curved and non-rectangular surfaces, there is still room for improvement even when using the known path planning method. Summary of the Invention

[0007] Therefore, the object of the present invention is to improve the above-mentioned known path planning method, especially to obtain better results when coating non-approximate rectangular surfaces.

[0008] This objective is achieved through the path planning method described in the independent claim.

[0009] The path planning method described in this invention is typically used to plan the movement path of an applicator relative to a component to be coated. Therefore, this invention is not limited to planning the coating path of a printhead moving relative to a vehicle body component, but is equally applicable to planning the movement path of an applicator that applies other coating agents, such as adhesives or sealants. Thus, for the coating agent to be applied, this invention is not limited to paints, but also covers other coating agents; for the component to be coated, this invention is not limited to vehicle body components, and in principle can also be used to coat other types of components.

[0010] According to the prior art, the path planning method of the present invention first sets the path for the subsequent movement of the applicator relative to the component to be coated.

[0011] Furthermore, according to the prior art, the path planning method of the present invention also sets multiple measurement points on the actual component, and then measures the spatial position of the measurement points on the actual component, which can be accomplished with the help of sensors.

[0012] The path planning method described in this invention also corrects the movement path based on the actual measured spatial position of the measurement points on the component to obtain the optimal coating effect.

[0013] This invention proposes representing the component to be coated as a mesh model containing multiple grid points, with the movement path associated with this mesh model. Furthermore, the path planning method of this invention adjusts the mesh model according to the measured spatial positions of the actual measurement points on the component, causing the associated movement path to adjust along with the grid points of the mesh model. Therefore, the core feature of this invention is firstly, associating the movement path with the component mesh model, so that when the mesh model is adjusted, the movement path adjusts accordingly; another core feature is that the mesh model is adjusted holistically or nearly holistically according to the measured spatial positions of the actual measurement points on the component. Preferably, the adjustment of the mesh model covers all grid points, that is, all grid points are shifted according to the measured spatial positions of the actual measurement points on the component.

[0014] The above-mentioned adjustment of the mesh model based on the measured spatial positions of the actual measurement points on the component preferably employs at least one known mathematical method for deformation / torsion of curved surfaces or computer-modeled objects. Such methods are described, for example, in the paper "A Review of Mesh Deformation Methods" by Mohamed Selim and Roy Koomullil, Volume 7, Issue 2 of the *Journal of Physical Mathematics* (DOI: 10.4172 / 2090-0902.1000181). Alternatively, another preferred approach for adjusting the mesh model based on the measured spatial positions of the actual measurement points on the component is the so-called Laplacian mesh processing algorithm, which can be found in Olga Sorkine's paper "Laplacian Mesh Processing" (European Conference on Graphics 2005, DOI: 10.2312 / egst.20051044).

[0015] It should be noted that the adjustment of the mesh model preferably covers most or even all of the area of ​​the component mesh model to be coated, that is, the position of most mesh points in the mesh model changes during the adjustment process. For example, at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or even at least 90% of the mesh points may shift during the adjustment process.

[0016] Furthermore, when adjusting the mesh model, the measured position of the measurement point is limited to a fixed point in the mesh model, while the positions of the remaining mesh points are adjusted through translation and / or interpolation. For example, if the corner point of the wheel groove of the fender of a motor vehicle body component is set as the measurement point, and the spatial position of the measurement point (i.e., all spatial directions) is completely measured, then the corresponding mesh points in the mesh model do not need to be adjusted and are limited to fixed points.

[0017] It should be noted that the number of measurement points is preferably much less than the number of grid points in the mesh model, for example, less than 5%, 1%, 5‰, or 1‰ of the number of grid points in the mesh model. Therefore, the number of measurement points can be less than 500, 200, 100, 50, 20, 10, or 5.

[0018] As mentioned above, the preset mesh model of the component to be coated can contain a large number of mesh points, which are distributed not only on the surface of the component but also inside the component. Due to the large number of mesh points, implementing the mesh model adjustment described in this invention requires a large amount of computational resources. To reduce the computational load, this invention can simplify the preset mesh model: only consider the mesh points on the surface of the component, ignoring the mesh points inside the component, to generate a simplified mesh model; then, adjustments are made based on the simplified mesh model, which has fewer mesh points, significantly reducing the computational load required for adjustment.

[0019] As explained above, the spatial position of measurement points on actual components is measured by sensors. However, in practical applications, such sensors typically cannot accurately determine the position of a measurement point in all three spatial directions; that is, the sensor measurement cannot provide position information in at least one spatial direction. In this case, adjusting the mesh model restricts the measurement point to a fixed point in the mesh model only in the spatial direction where the sensor provides position information; while in at least one spatial direction where the sensor does not provide position information, the fixed point in the mesh model can shift as the mesh model is adjusted. For example, if the edge of the roof of a motor vehicle body component is set as the measurement point, and the sensor is a distance sensor measuring perpendicular to the roof edge, then the sensor cannot provide position information along the direction of the roof edge. When adjusting the mesh model, the corresponding mesh point can shift along the direction of the roof edge.

[0020] Furthermore, the path planning method can be performed either within or outside the coating system, such as in the body shop of a motor vehicle manufacturing plant. Therefore, measurements of the component to be coated do not need to be taken in the paint booth where the component will be coated later.

[0021] The path planning method of the present invention has been described above without coating the component. However, the present invention also covers a coating method: first, the path planning method is executed, and then the component is coated according to a set movement path.

[0022] It should be noted that the relative movement of the applicator with respect to the component to be coated can be achieved in various ways. In one embodiment of the invention, the component to be coated is stationary during coating, and the applicator (e.g., a print head) is driven by a manipulator (e.g., a coating robot) along a movement path. Alternatively, in another embodiment of the invention, the applicator is stationary, and the component to be coated is driven by a manipulator, moving relative to the stationary applicator along a movement path. In yet another embodiment, both the applicator and the component to be coated move during the relative movement.

[0023] The aforementioned manipulator is preferably a coating robot, such as an articulated arm robot with multiple movable axes, wherein the articulated arm robot may optionally move along linear axes. Alternatively, the coating robot may also employ a parallel motion structure, although this structure is less commonly used. Furthermore, the manipulator may not be a robot in the strict sense, but rather a motion machine with at least one linear axis. Such motion machines are well known in coating systems and are also referred to as top-mounted machines (i.e., having a horizontal linear axis) or side-mounted machines (i.e., having a vertical linear axis).

[0024] As mentioned above, the path planning method of this invention can be performed outside the coating system, such as at a measurement station or body shop in a motor vehicle manufacturing plant. The components are then coated within the coating system (e.g., a paint booth) of the motor vehicle manufacturing plant. The coating path determined during the path planning process can be transferred from the measurement station to the coating system, preferably bound accordingly to the corresponding component.

[0025] Alternatively, the path planning method and the actual coating method can be performed in the same coating station (e.g., a spray booth).

[0026] The sensor used to measure the component to be coated can be mounted on the manipulator. During coating, the manipulator moves the applicator, and the sensor moves along with it.

[0027] This invention is particularly advantageous for applicators (e.g., printheads) that use virtually no overspray and spray a spatially narrow beam of coating agent, with an application efficiency of at least 80%, 90%, 95%, or 99%. When using such applicators, the requirements for applicator positioning accuracy and preset movement path accuracy are much higher than when using atomizers. However, the invention is not limited to printheads; atomizers (e.g., rotary atomizers) can also be applied.

[0028] Furthermore, the present invention also covers a path planning system suitable for performing the path planning method described herein.

[0029] The path planning system of the present invention first includes a manipulator, such as a multi-axis coating robot.

[0030] Furthermore, the path planning system of the present invention includes a sensor for spatially measuring the component to be coated.

[0031] Furthermore, the path planning system of the present invention includes a control unit for controlling the manipulator and querying the sensors. The control unit is designed to control the manipulator and query the sensors, causing the path planning system to execute the path planning method and / or coating method of the present invention.

[0032] The robot, manipulator, and sensors are preferably arranged together in the coating workshop of the automotive manufacturing plant. For example, as briefly mentioned above, the sensors can be driven by the manipulator and move together with the applicator.

[0033] For sensors, it should be specified that they may include, for example, light-cutting sensors, cameras, and / or illumination units.

[0034] Other preferred embodiments of the present invention are described in the dependent claims, or in the detailed description of preferred embodiments of the present invention below in conjunction with the accompanying drawings. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the principle of the path planning method described in this invention.

[0036] Figure 2 This is a detailed schematic diagram showing the adjustment of the mesh model based on the spatial location of the measurement points.

[0037] Figure 3A schematic diagram illustrating the principle of simplifying the mesh model of motor vehicle body components to reduce the computational load of mesh model adjustments.

[0038] Figure 4A This is a highly simplified schematic diagram of the coating system described in this invention, which can execute the path planning method described in this invention.

[0039] Figure 4B for Figure 4A A magnified partial view. Detailed Implementation

[0040] The following text combines Figure 1 Describe the implementation method.

[0041] In step S1, a mesh model of the vehicle body component to be coated is set, which may be generated, for example, by a CAD system (CAD: Computer-Aided Design).

[0042] Furthermore, measurement points are set on the actual component, and the reference positions of these measurement points can be obtained, for example, from the mesh model in step S1. Subsequently, the spatial positions of these measurement points are measured by sensors, and in step S2, the deviation between the measured spatial positions of the measurement points and the preset reference positions in the mesh model is determined.

[0043] In step S3, the set mesh model is adjusted using the deviation between the measured spatial position and the reference position. The mesh model adjustment in step S3 employs the known "Laplace mesh processing" algorithm, described in Olga Sorkine's paper "Laplace Mesh Processing" (European Conference on Computer Graphics 2005). The following text combines... Figure 2 The detailed diagram further illustrates the adjustment process.

[0044] In step S4, the set mesh model is combined with the preset movement path, and the segments of the movement path are assigned to the mesh model.

[0045] In step S5, the assigned path segment and corresponding part of the mesh model are combined with the adjusted mesh model to adjust the movement path. It should be noted that the movement path is associated with the mesh model, so when the mesh model is adjusted in step S3, the movement path is adjusted accordingly.

[0046] The following text elaborates Figure 2 The diagram shows a detailed illustration of mesh model adjustments.

[0047] In step S3.1, the unadjusted preset mesh model of the component is read and converted into an expression describing the local geometry. This process adopts the "Laplacian operator and surface differential expression" method described in Section 2 of the article "Laplacian Mesh Processing" above.

[0048] In the next step S3.2, the displacement values ​​of the measurement points (i.e., the deviation between the reference position of the measurement points and the actual spatial position) are introduced to reconstruct the mesh model, so that the displacement of the measurement points corresponds as closely as possible to the local geometry. This process corresponds in principle to the "mesh editing and shape interpolation" method described in Section 4 of the article "Laplace Mesh Processing" above.

[0049] Figure 3 The left side shows a complex mesh model 1 of a motor vehicle body component to be coated, which contains a large number of mesh points. Adjusting the mesh model as described in this invention requires significant computational resources. Therefore, the complex mesh model 1 is converted into a simplified mesh model 2. The simplified mesh model 2 significantly reduces the number of mesh points, thus significantly reducing the computational load required for adjusting the mesh model as described in this invention.

[0050] Figure 4A and Figure 4B This is a highly simplified schematic diagram of the coating system described in this invention. The system includes a multi-axis coating robot 3, which guides a printhead 4 to move on a vehicle body component 5 to coat the vehicle body component 5. Furthermore, the coating robot 3 also guides a sensor 6 to move together with the printhead 4 on the vehicle body component 5 to measure the spatial position of measurement points on the vehicle body component 5.

[0051] Sensor 6 and coating robot 3 are connected to robot controller 7. Robot controller 7 controls coating robot 3 and queries sensor 6. Robot controller 7 has a built-in program that executes the path planning method described in this invention when the program runs.

[0052] This invention is not limited to the preferred embodiments described above, but encompasses all variations and modifications that utilize the core concept of this invention and fall within its scope of protection. In particular, this invention claims that the subject matter and technical features of the dependent claims are independent of the referenced claims, and especially independent of the protection of the technical features of the independent claims. Therefore, this invention includes multiple independently protected technical solutions.

[0053] Beneficial effects of the invention The path planning method described in this invention is particularly advantageous for path planning on complex surfaces (such as fenders and vehicle body components with roof cutouts), significantly improving the path point positioning accuracy of the adjusted coated path. Sensors cannot measure directional displacement components (e.g., along the edge direction) and do not incorporate displacement or deformation into the mesh model.

[0054] List of reference numerals 1 Complex Mesh Model 2. Simplified Mesh Model 3 Coating Robots 4 printheads 5 Motor vehicle body components 6 sensors 7 Robot Controller

Claims

1. A path planning method for planning the movement path of an applicator (4) relative to a component (5) to be coated, particularly for coating a motor vehicle body component (5) with paint, adhesive or sealant, comprising the following steps: a) Set the movement path of the applicator (4); b) Set multiple measurement points on the actual component (5) and measure the spatial position of the measurement points on the actual component (5); and c) Based on the measured spatial position of the measurement points on the actual component (5), correct the movement path. Its features are, The method includes the following steps for correcting the movement path: d) Associate the movement path with a preset mesh model (1, 2) of component (5), the mesh model containing multiple mesh points; and e) Adjust the mesh model (1, 2) according to the measured spatial position of the measurement point on the actual component (5) so that the movement path associated with it is adjusted together with the mesh points of the mesh model (1, 2).

2. The path planning method according to claim 1, characterized in that, a) Adjust the mesh model (1, 2) of component (5) according to the Laplace mesh processing algorithm; and / or b) The adjusted distribution of the grid models (1, 2) covers most of the area of ​​the grid models (1, 2), specifically covering at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of all grid points of the grid models (1, 2); and / or c) During the adjustment of the mesh models (1, 2), the measured positions of the measurement points are limited to fixed points in the mesh models (1, 2), and the positions of the remaining mesh points in the mesh models (1, 2) are adjusted, in particular, by translation and / or interpolation; and / or d) The number of measurement points is significantly less than the number of grid points in mesh models (1, 2), particularly less than 5%, 1%, 5‰, or 1‰ of the number of grid points in mesh models (1, 2); and / or e) The number of measurement points is less than 500, 200, 100, 50, 20, 10 or 5.

3. The path planning method according to any one of the preceding claims, characterized in that, a) The preset mesh model (1) includes not only the mesh points on the surface of the component (5), but also the mesh points inside the component (5); b) By considering only the mesh points on the surface of component (5), the pre-defined mesh model (1) is converted into a simplified mesh model (2); and c) Adjust the simplified grid model (2) according to the actual measured position of the measurement point.

4. The path planning method according to any one of the preceding claims, characterized in that, a) Measure the spatial position of the measuring point on the actual component (5) using the sensor (6); b) The sensor (6) cannot measure the spatial position of the measurement point on the actual component (5) in all spatial directions, and has no position information in at least one spatial direction; c) When adjusting the mesh model (1, 2), the measured spatial position of the measurement point is limited to the fixed point of the mesh model (1, 2), and the positions of the other mesh points of the mesh model (1, 2) are adjusted; d) The spatial positions of the fixed points in the mesh models (1, 2) are fixed only in the spatial direction in which the sensor (6) provides position information; and e) The fixed point of the grid model (1, 2) can be shifted in at least one spatial direction in which the sensor (6) does not provide position information during the adjustment of the grid model (1, 2).

5. The path planning method according to any one of the preceding claims, characterized in that, The path planning method is performed outside the coating system, particularly in the body shop of a motor vehicle manufacturing plant.

6. A coating method for coating a component (5) with a coating agent, particularly coating a motor vehicle body component (5) with a paint, adhesive, or sealant, comprising the following steps: a) Performing the path planning method according to any one of the preceding claims to determine a movement path; and b) The applicator (4) is driven by the manipulator (3) to move along a defined movement path relative to the component (5) to be coated, and the component (5) is coated by the applicator (4).

7. The coating method according to claim 6, characterized in that, a) During the relative motion, the component to be coated (5) remains stationary, and the applicator (4) is driven by the manipulator (3) along the moving path; or b) During the relative motion, the applicator (4) remains stationary, while the component (5) to be coated is driven along the movement path by the manipulator (3); or c) During the relative motion, the applicator (4) is driven by the manipulator (3), and the component (5) to be coated also moves.

8. The coating method according to any one of claims 6 to 7, characterized in that, a) The manipulator (3) is for the coating robot (3), in particular: a1) As an articulated arm robot, the coating robot (3) has multiple movable axes, wherein the articulated arm robot can selectively move along linear axes; a2) A coating robot with a parallel motion structure (3); or b) The manipulator (3) is a moving machine having at least one linear axis, particularly a top-mounted or side-mounted machine.

9. The coating method according to any one of claims 6 to 8, characterized in that, a) The path planning method is performed at least in part at a vehicle manufacturing plant measurement station outside the coating system, particularly in the vehicle manufacturing plant body shop; and b) The component (5) is then coated in the coating system of the motor vehicle manufacturing plant.

10. The coating method according to claim 9, characterized in that, The adjusted mesh model (1, 2) and / or the adjusted coating path are transmitted from the measuring station to the coating system and bound to the corresponding component (5).

11. The coating method according to any one of claims 6 to 8, characterized in that, The path planning method is performed within the coating system of the motor vehicle manufacturing plant, and the coating of component (5) is also performed within the coating system.

12. The coating method according to claim 11, characterized in that, The sensor (6) used to measure the component (5) to be coated is attached to the manipulator (3) and is driven by the manipulator (3) to move along the moving path together with the applicator (4).

13. The coating method according to any one of claims 6 to 12, characterized in that, a) The applicator (4) is an applicator (4) with minimal overspray, which, unlike the atomizer, does not atomize the coating agent but sprays a spatially narrow stream of coating agent, particularly for the printhead, and especially with an application efficiency of at least 80%, 90%, 95% or 99%; or b) The applicator (4) is an atomizer, particularly a rotary atomizer.

14. A path planning system for planning the movement path of an applicator (4) guided by a manipulator (3) during the coating of a component (5), particularly for coating a motor vehicle body component (5) with a paint, adhesive, or sealant, comprising: a) Manipulator (3), particularly for multi-axis coating robot (3); b) Sensor (6), used for spatial measurement of the component (5) to be coated; and c) Control unit (7) for controlling the operator (3) and querying the sensor (6). Its features are, d) The control unit (7) controls the manipulator (3) and queries the sensor (6) to cause the path planning system to perform the path planning method according to any one of claims 1 to 5 and / or the coating method according to any one of claims 6 to 13.

15. The path planning system according to claim 14, characterized in that, The manipulator (3) and the sensor (6) used to measure the component (5) to be coated are arranged in the coating workshop or body shop of the motor vehicle manufacturing plant.

16. The path planning system according to claim 14 or 15, characterized in that, The sensor (6) used to measure the component (5) is mounted on the manipulator (3) and is driven by the manipulator (3) to move together with the applicator (4) on the surface of the component (5) to be coated.

17. The path planning system according to any one of claims 14 to 16, characterized in that, a) The sensor (6) includes: a1) Optical section sensor; and / or a2) Camera; and / or a3) Lighting unit; b) Applicator (4): b1) refers to an atomizer, specifically a rotary atomizer; or b2) is an applicator (4) with minimal overspray, which, unlike an atomizer, does not atomize the coating agent but instead sprays a spatially narrow beam of coating agent; and / or c) The coating agent is a paint, adhesive, or sealant; and / or d) The component to be coated (5) is a motor vehicle body component (5); and / or e) The manipulator (3) is for the coating robot (3), in particular: e1) As a coating robot (3) of a multi-joint arm robot, it has multiple movable axes, wherein the articulated arm robot can optionally move along a linear axis; e2) A coating robot with a parallel motion structure (3); or f) The manipulator (3) is an automatic motion machine having at least one linear axis, particularly an overhead or side-mounted machine.

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