Digital model driven multi-mechanical-arm additive manufacturing process planning method and system

Abstract

The invention belongs to the technical field of additive manufacturing, and discloses a multi-mechanical-arm mixed machining path planning method and system driven by a digital model, and the method comprises the steps: modeling a machining tool and a to-be-machined part, and obtaining a path point set; traversing and searching a path point set, judging whether the surface where each path point is located intersects with each surface on the machining tool model, setting the path points during intersection as interference path points, and otherwise, taking the path points as machining path points; marking path points between the starting path point and the interference path points as task subsets; performing variable attitude search based on TCP position invariance on the interference path points until motion interference is eliminated, and updating attitude information to a path point set; and performing backward recursive search on any interference path point until the next interference path point is searched, and decomposing and defining the printing task between the two interference path points as additive and subtractive manufacturing switching sub-tasks. According to the invention, the rapidity, the accuracy and the processing quality of the hybrid processing system can be ensured.

Description

Technical Field

[0001] The present application belongs to the field of additive manufacturing technology, and more specifically, to a digital model-driven multi-robotic arm additive manufacturing process planning method and system. Background Art

[0002] Metal additive manufacturing technology has a natural advantage in processing complex parts, and it is easier to achieve rapid prototyping of parts with complex geometric features. Since the surface roughness of the molded parts based on additive manufacturing based on deposition energy methods such as high-energy beams is usually poor, and there are problems such as low processing accuracy and uneven material deposition leading to large residual stress, grinding finishing and sandblasting, shot blasting and other processes are often used after additive manufacturing to improve the processing accuracy and surface roughness of parts. Processing path planning is a key link in data preparation before composite manufacturing, which directly affects the quality and performance of the part surface. When the part structure is relatively simple, CAM software can be used to plan the processing path as a whole; when the part structure is complex, it is difficult to support direct planning of its processing path. Therefore, the existing path planning methods have problems such as complex methods, low processing efficiency, processing accuracy is limited by the model slicing accuracy, and are not suitable for multi-axis processing path planning. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of this application is to provide a multi-robot hybrid processing path planning method driven by a digital model, aiming to solve the problems of inefficiency, low precision and low processing quality existing in the existing path planning methods.

[0004] To achieve the above objectives, the present application provides a multi-robot hybrid machining path planning method driven by a digital model, comprising the following steps:

[0005] S1: Modeling a machining tool to obtain a machining tool model; Modeling a part to be machined to obtain a part model, and using a set of surface vertices on the part model as a path point set;

[0006] S2 traverses and searches the path point set, and determines whether the surface where each path point is located intersects with the surfaces on the processing tool model. If so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C. j ;

[0007] S3 uses the zero space control method to perform a variable posture search based on the TCP position unchanged on the interference path point until the motion interference is eliminated, and then updates the posture information of the interference path point to the path point set to obtain a new path point set;

[0008] S4 starts from any interference path point in the new path point set and searches backward recursively until the next interference path point is found. The printing task between the two interference path points is decomposed into an additive and subtractive manufacturing switching subtask C. j+1 ;

[0009] S5 repeats step S4 until all subtask decomposition results are output to obtain a process planning strategy for the multi-robot hybrid machining system.

[0010] This application reconstructs the outer contour of additively manufactured parts through three-dimensional vision, and uses this as feedback data to generate grinding processing parameters, thereby forming a closed-loop control mechanism that integrates the "model-decision-feedback-processing-evaluation" process, while ensuring the speed, accuracy and processing quality of the hybrid manufacturing system.

[0011] Furthermore, in step S1, a polygon with n vertices is used to simplify the laser directed energy deposition head and the grinding tool head, and the end center point of each processing tool model is taken as the TCP position.

[0012] Furthermore, in step S1, the part is modeled using a finite element analysis method, a triangular mesh is used for discretization to obtain a part model, and a set of all triangular face vertices on the part model is used as a path point set.

[0013] Furthermore, in step S2, the path point set is traversed and searched to determine whether the triangle face where each path point is located intersects with each surface on the processing tool model.

[0014] Furthermore, in step S2, the intersection judgment method is: perform intersection calculation on all the outer surfaces of the processing tool and the triangular facet where the current path point is located: if an intersection line is returned, it is judged that the two are intersected, otherwise it is judged that they are not intersected.

[0015] Furthermore, step S3 also includes the following steps: using a zero-space control method to perform kinematic modeling on the processing robot so that the joint velocity is within the zero space of the Jacobian matrix.

[0016] Furthermore, the kinematic model expression of the processing robot is:

[0017]

[0018]

[0019] Among them, ε is the velocity vector, matrix J is the Jacobian matrix of the robot, q = [q1…q n ] T is the vector composed of the robot arm joint variables, q nis the nth variable, T is the transposed matrix, I is the standard unit matrix, is the angular velocity vector of the joint.

[0020] According to another aspect of the present invention, there is provided a system capable of implementing any of the above multi-robot hybrid machining path planning methods, comprising:

[0021] A modeling module, used to model the laser directed energy deposition head and the grinding head respectively to obtain corresponding processing tool models; and also used to model the part to be processed to obtain a part model, and use the set of surface vertices on the part model as a path point set;

[0022] The judgment module is used to traverse and search the path point set, and judge whether the surface where each path point is located intersects with each surface on the processing tool model: if so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C j ;

[0023] A posture change search module is used to use a zero space control method to perform a posture change search based on a TCP position invariance on the interference path point until the motion interference is eliminated, and then update the posture information of the interference path point to the path point set to obtain a new path point set;

[0024] The subtask decomposition module is used to recursively search backwards with any interference path point in the new path point set as the starting point until the next interference path point is found, and the printing task between the two interference path points is decomposed into the additive and subtractive manufacturing switching subtask C j+1 ; Repeat the recursive search steps until all subtask decomposition results are output to obtain the process planning strategy for the multi-robot hybrid machining system.

[0025] According to another aspect of the present invention, there is also provided a processing system which can apply a process planning strategy planned by a multi-robotic arm hybrid processing path planning method as described in any of the foregoing items, including a laser directed energy deposition subsystem, a non-metallic extrusion subsystem, and a grinding and cutting subsystem, all of which use robotic arms as mobile carriers.

[0026] Furthermore, the laser directed energy deposition subsystem is equipped with a powder feeding laser directed energy deposition unit, the non-metal extrusion subsystem is equipped with an extrusion type non-metal wire printing unit, and the grinding and cutting subsystem is equipped with a grinding tool unit.

[0027] Furthermore, the grinding and cutting subsystem is also provided with a line laser sensor, and the robotic arm in the grinding and cutting subsystem is used to guide the line laser sensor to perform reverse reconstruction to obtain point cloud data of the surface contour of the printed part, and generate process parameters of the grinding and cutting process based on the point cloud data.

[0028] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0029] (1) The multi-robot hybrid machining path planning method driven by a digital model provided in the present application determines the interference path points and machining path points by judging whether the surfaces of the machining tool model and the part model intersect, and plans the machining sequence by traversing and searching the path point set using the Newton iteration method, thereby decomposing the tasks of the additive and subtractive machining sequence into multiple subtasks; by optimizing the work node selection problem during the alternating machining of the additive process and the subtractive process, it is ensured that the system requires the shortest machining time while the hybrid machining task is completed, and provides a systematic, precise, dynamic adjustment and task decomposition optimization method to achieve an efficient, accurate and adaptable hybrid machining system process planning strategy.

[0030] (2) The processing system of this application combines metal additive manufacturing with subtractive manufacturing processes such as grinding and shot peening in a hybrid manufacturing system, integrating their advantages. It not only integrates the technical advantages of additive manufacturing such as short processing cycle and high material utilization rate, but also has the unique advantages of subtractive manufacturing systems such as high dimensional accuracy and low surface roughness. The same-platform hybrid manufacturing method also avoids the limitations of the two processing methods and realizes their complementary advantages, that is, while ensuring the rapid manufacturing of complex structural parts, it also ensures their extremely high processing accuracy and surface quality.

[0031] (3) The processing system of the present application reconstructs the external contour of the additively manufactured part through three-dimensional vision, and uses this as feedback data to generate grinding processing parameters, thereby forming a closed-loop control mechanism that integrates the "model-decision-feedback-processing-evaluation" process, while ensuring the speed, accuracy and processing quality of the hybrid manufacturing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process flow of the multi-manipulator hybrid processing path planning method driven by a digital model provided in Example 1 of the present application;

[0033] Figure 2 It is a schematic diagram of a laser directed energy deposition head and a grinding tool head modeling model provided in Example 1 of the present application;

[0034] Figure 3 It is a schematic diagram of a parts model provided in Example 1 of the present application;

[0035] Figure 4 is a schematic diagram of the outer surface of the processing tool model provided in Example 1 of the present application;

[0036] Figure 5 It is a schematic diagram of the structure of a multi-manipulator processing system provided in Example 3 of the present application;

[0037] Figure 6 It is a schematic diagram of the processing flow of the multi-robotic arm processing system provided in Example 3 of the present application.

[0038] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: A-directed energy deposition head model; B-grinding tool model; C-triangular face; D-intersection line; s1-side surface of directed energy deposition head; s2-side surface of the upper end of directed energy deposition head; s3-bottom surface of directed energy deposition head. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0040] Example 1

[0041] This embodiment provides a multi-manipulator hybrid machining path planning method driven by a digital model. Figure 1 As shown, the method specifically comprises the following steps:

[0042] S1 models the laser directed energy deposition head and the grinding tool head respectively to obtain the corresponding processing tool models; models the part to be processed to obtain the part model, and uses the set of surface vertices on the part model as the path point set.

[0043] Specifically, Figure 2 As shown, a polygon with n vertices is used to simplify the modeling of the laser directional energy deposition head and the grinding tool head. The working principle of the simplified modeling in this embodiment is: the symmetrical three-dimensional model of the gun body is projected on a plane, and then the projected shape is represented by a polygon with n vertices. To obtain the directional energy deposition head model A and the grinding tool model B, since both are mostly symmetrical structures, the end center points of the directional energy deposition head model A and the grinding tool model B are taken as their respective working path point contact positions (TCP, (Tool Center Point)). In this embodiment, the working path point contact positions of each processing tool model are TCP1 and TCP2 respectively.

[0044] like Figure 3As shown, the aforementioned part model is meshed by finite element method, and a triangular mesh is used for discretization to obtain the part model during the modeling process, and the set of all triangular facet vertices on the part model is used as a path point set, and C in the figure is one of the triangular facets. The remaining steps of modeling the part by finite element method are well known to those skilled in the art and will not be repeated here.

[0045] S2 traverses the path point set to determine whether the surface where each path point is located intersects with the surfaces on the processing tool model: if so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C j .

[0046] Specifically, the criteria for determining the intersection relationship between faces are as follows:

[0047] Take all external faces of the machining tool model, such as Figure 4 The three surfaces shown in s1, s2, and s3 in the left figure. Compare each surface with the triangle patch where the current path point is located ( Figure 4 The intersection operation is performed by using Boolean operations: Figure 4 If the intersection line D is returned as shown in the middle right figure, it is judged that the two intersect, that is, there is interference between the processing tool model and the current path point, and the point is confirmed as an interference path point; if not, the current path point is judged to be a normal processing path point and stored in the current task subset C j middle.

[0048] S3 uses the zero space control method to search for the interfering path points with a variable posture based on the unchanged TCP position until the motion interference is eliminated, and then updates the posture information of the interfering path points to the path point set to obtain a new path point set.

[0049] The above-mentioned posture change search process also includes kinematic modeling of the processing robot used in this embodiment, so that the joint velocity of its mechanical arm is within the null space of the Jacobian matrix. The kinematic model expression of the processing robot is:

[0050]

[0051]

[0052] Among them, ε is the velocity vector, matrix J is the Jacobian matrix of the robot, q = [q1…q n ] T is the vector composed of the robot arm joint variables, q n is the nth variable, T is the transposed matrix, I is the standard unit matrix, is the angular velocity vector of the joint.

[0053] S4 starts from any interference path point in the new path point set and recursively searches backward until the next interference path point is found. The printing task between the two interference path points is decomposed into the additive and subtractive manufacturing switching subtask C j+1 .

[0054] Specifically, the original interference path point P i Recursively search backward for the starting point until the next path point P where motion interference occurs k , decompose the printing task between two interfering path points into {P i …P k} and define it as the additive and subtractive manufacturing switching subtask C j+1 .

[0055] S5 repeats step S4 until all subtask decomposition results are output to obtain a process planning strategy for the multi-manipulator hybrid processing system, and subsequent processing robots perform processing tasks according to the process planning strategy.

[0056] The process planning method provided in this embodiment has the advantages that: the method simplifies the complex kinematic calculation process, decomposes the printing task by determining the interference path points, and thus forms a reasonable and feasible processing strategy.

[0057] Example 2

[0058] This embodiment provides a system capable of implementing the multi-robot hybrid processing path planning method as described in Embodiment 1, including:

[0059] A modeling module is used to model the laser directed energy deposition head and the grinding tool head respectively to obtain corresponding processing tool models; it is also used to model the part to be processed to obtain a part model, and use the set of each surface vertex on the part model as a path point set;

[0060] The judgment module is used to traverse the path point set and judge whether the surface where each path point is located intersects with the surfaces on the processing tool model: if so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C j ;

[0061] The variable posture search module is used to use the zero space control method to perform variable posture search based on the TCP position invariance on the interfering path points until the motion interference is eliminated, and then update the posture information of the interfering path points to the path point set to obtain a new path point set;

[0062] The subtask decomposition module is used to recursively search backwards from any interference path point in the new path point set as the starting point until the next interference path point is found. The printing task between the two interference path points is decomposed into the additive and subtractive manufacturing switching subtask C. j+1 ; Repeat the recursive search steps until all subtask decomposition results are output to obtain the process planning strategy for the multi-robot hybrid machining system.

[0063] Example 3

[0064] This embodiment provides a processing system, such as Figure 5 As shown, it is a schematic diagram of the structural model of the system, which can apply the process planning strategy planned by the multi-robot hybrid processing path planning method provided in any of the previous embodiments. The processing system includes a laser directed energy deposition subsystem, a non-metallic extrusion subsystem and a grinding and cutting subsystem, all of which use robots as mobile carriers.

[0065] The aforementioned laser directed energy deposition subsystem is equipped with a powder feeding laser directed energy deposition unit, the non-metal extrusion subsystem is equipped with an extrusion type non-metal wire printing unit, and the grinding and cutting subsystem is equipped with a grinding tool unit.

[0066] The aforementioned grinding and cutting subsystem is also equipped with a line laser sensor. The robotic arm in the grinding and cutting subsystem is used to guide the line laser sensor to perform reverse reconstruction to obtain point cloud data of the surface contour of the printed part, and generate process parameters for the grinding and cutting process based on the point cloud data.

[0067] The processing flow chart of the processing system provided in this embodiment is as follows Figure 6 As shown. First, the functions under the part configuration are designed and modeled by computer software and converted into an STL model. The STL model is sliced ​​isometrically to obtain a set of two-dimensional layered contour curves, in which the corresponding filling path is set and the G-code code is generated. Since the G-code code cannot be directly read by the robot controller, it is necessary to convert the G-code code including the processing information into an executable program for the robot printing, such as the Rapid program, through code translation. The robot performs 3D printing based on laser directional energy deposition or wire heating and melting extrusion process according to the calibration results to obtain the parts after additive manufacturing. Since the surface quality of robot 3D printed parts is usually poor and it is difficult to obtain a standard grinding processing path, a line laser sensor is also introduced into the processing system. The line laser sensor is guided by the robot arm for reverse reconstruction to obtain the point cloud data of the surface contour of the printed part. At the same time, the point cloud data is iteratively registered with the point cloud of the standard design model to calculate the removal amount distribution of the printed part and generate the process parameters of the grinding removal process.

[0068] In summary, this embodiment reconstructs the outer contour of the additively manufactured part through three-dimensional vision, and uses this as feedback data to generate grinding processing parameters, thereby forming a closed-loop control mechanism that integrates the "model-decision-feedback-processing-evaluation" process, while ensuring the speed, accuracy and processing quality of the hybrid manufacturing system.

[0069] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0070] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0071] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0072] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0073] In the description of the present application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0074] In addition, references throughout this specification to "one embodiment"; "one embodiment", "an example" or similar language indicate that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment"; "in one embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0075] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0076] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A multi-manipulator hybrid machining path planning method driven by a digital model, characterized in that: The following steps are involved: S1: Modeling a machining tool to obtain a machining tool model; Modeling a part to be machined to obtain a part model, and using a set of surface vertices on the part model as a path point set; S2 traverses and searches the path point set, and determines whether the surface where each path point is located intersects with the surfaces on the processing tool model. If so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C. j ; S3 uses the zero space control method to perform a variable posture search based on the TCP position unchanged on the interference path point until the motion interference is eliminated, and then updates the posture information of the interference path point to the path point set to obtain a new path point set; S4 starts from any interference path point in the new path point set and searches backward recursively until the next interference path point is found. The printing task between the two interference path points is decomposed into an additive and subtractive manufacturing switching subtask C. j+1 ; S5 repeats step S4 until all subtask decomposition results are output to obtain a process planning strategy for the multi-robot hybrid machining system.

2. A multi-manipulator hybrid machining path planning method driven by a digital model as claimed in claim 1, characterized in that: In step S1, a polygon with n vertices is used to simplify the laser directed energy deposition head and the grinding tool head, and the end center point of each processing tool model is taken as the TCP position.

3. The multi-manipulator hybrid processing path planning method driven by a digital model as claimed in claim 1, characterized in that: In step S1, the part is modeled using a finite element analysis method. During the modeling, a triangular mesh is used for discretization to obtain a part model, and a set of all triangular facet vertices on the part model is used as a path point set.

4. A multi-manipulator hybrid machining path planning method driven by a digital model as claimed in claim 3, characterized in that: In step S2, the path point set is traversed and searched to determine whether the triangular facet where each path point is located intersects with each surface on the processing tool model.

5. The multi-manipulator hybrid processing path planning method driven by a digital model as claimed in claim 1, characterized in that: In step S2, the intersection judgment method is: perform intersection calculation on all the outer surfaces of the processing tool and the triangular facet where the current path point is located: if an intersection line is returned, it is judged that the two are intersected, otherwise it is judged that they are not intersected.

6. The method for multi-manipulator hybrid machining path planning driven by a digital model as claimed in claim 1, characterized in that: Step S3 also includes the following steps: using the zero space control method to perform kinematic modeling on the processing robot so that the joint velocity of its robot arm is within the zero space of the Jacobian matrix.

7. A multi-manipulator hybrid machining path planning method driven by a digital model as claimed in claim 6, characterized in that: The kinematic model expression of the processing robot is: Among them, ε is the velocity vector, matrix J is the Jacobian matrix of the robot, q = [q1…q n ] T is the vector composed of the robot arm joint variables, q n is the nth variable, T is the transposed matrix, I is the standard unit matrix, is the angular velocity vector of the joint.

8. A system capable of implementing the multi-manipulator hybrid processing path planning method as described in any one of claims 1 to 7, characterized in that: include: A modeling module, used to model the laser directed energy deposition head and the grinding tool head respectively to obtain corresponding processing tool models; It is also used for modeling the part to be processed to obtain a part model, and taking a set of surface vertices on the part model as a set of path points; The judgment module is used to traverse and search the path point set, and judge whether the surface where each path point is located intersects with each surface on the processing tool model: if so, the path point is set as an interference path point; if not, the path point is used as a processing path point; and the path points between the starting path point of each search and the confirmed interference path point are marked as task subset C j ; A posture change search module is used to use a zero space control method to perform a posture change search based on a TCP position invariance on the interference path point until the motion interference is eliminated, and then update the posture information of the interference path point to the path point set to obtain a new path point set; The subtask decomposition module is used to recursively search backwards with any interference path point in the new path point set as the starting point until the next interference path point is found, and the printing task between the two interference path points is decomposed into the additive and subtractive manufacturing switching subtask C j+1 ; Repeat the recursive search steps until all subtask decomposition results are output to obtain the process planning strategy for the multi-robot hybrid machining system.

9. A processing system, characterized in that: The process planning strategy planned by the multi-robot hybrid processing path planning method as described in any one of claims 1 to 7 can be applied, including a laser directed energy deposition subsystem, a non-metallic extrusion subsystem, and a grinding and cutting subsystem, all of which use robots as mobile carriers.

10. The processing system according to claim 9, characterized in that: The laser directed energy deposition subsystem is equipped with a powder feeding laser directed energy deposition unit, the non-metallic extrusion subsystem is equipped with an extrusion type non-metallic wire melt deposition printing unit, and the grinding and cutting subsystem is equipped with a grinding unit; preferably, the grinding and cutting subsystem is also provided with a line laser sensor, and the robotic arm in the grinding and cutting subsystem is used to guide the line laser sensor to perform reverse reconstruction to obtain point cloud data of the surface contour of the part after printing, and generate process parameters of the grinding removal process based on the point cloud data.

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