Welding piece precision evaluation method, device and system based on virtual assembly

Abstract

The present application belongs to the field of rail vehicles, and proposes a welding precision evaluation method, device and system based on virtual assembly. The method first obtains the point cloud model of the welding part through three-dimensional laser scanning, and assembles it with the target assembly body in the virtual environment; based on the tolerance domain extreme value analysis method, the limit working condition of the welding part within the entire allowable assembly tolerance range is simulated, and the state of the workpiece "free grinding", "grinding required" or "unqualified" can be accurately determined; for the workpiece requiring grinding, an optimal grinding amount (or differentiated grinding scheme) compatible with all assembly states is intelligently solved, and a robot integrated with force control is driven to perform high-precision adaptive grinding. The present application integrates virtual simulation, intelligent decision and physical execution closed loop, fundamentally replacing the traditional manual try-on and experience-based polishing operation mode, and realizing the full-process intelligent improvement from incoming material quality quantitative control to one-time guarantee of assembly precision.

Description

Technical Field

[0001] This invention relates to the field of rail vehicle technology, and in particular to a method, apparatus and system for evaluating the accuracy of welded parts based on virtual assembly. Background Technology

[0002] The bogie crossbeams are composed of a complex welded tube sheet structure and are the main mounting points for components of the traction and drive systems of rail vehicles. The structure is as follows: Figure 1 As shown, the main body has an H-shaped structure and includes two parallel crossbeam steel pipes, motor hanger, traction rod seat, traction rod and gearbox hanger, gearbox hanger and longitudinal auxiliary beam, etc. Among them, the longitudinal beam and motor hanger are welded components, which have been welded by the previous process before the bogie crossbeam is assembled.

[0003] Taking the motor hanger as an example (the longitudinal beam also has the following problems), the motor hanger is an irregular, semi-open, complex welded component. The three-dimensional structure is shown below. Figure 2 Due to welding deformation and the cumulative effect of tolerances in multiple processes, the accuracy of incoming materials is generally low. Traditional inspection methods are limited by the workpiece structure and can only measure individual linear dimensions by scribing. They cannot comprehensively assess the position and form tolerances of key assembly surfaces such as bevels, resulting in the true assembly accuracy only being revealed during manual trial assembly at the beam assembly stage, leading to delayed quality risks. During manual trial assembly, the position of the motor hanger is repeatedly adjusted within the deviation range of the beam assembly dimensions. While adjusting, the gap and interference with the steel pipe are observed, and interference positions are manually ground. Trial assembly and grinding operations account for 20% of the beam assembly welding time, with each beam taking up to 30 minutes, greatly reducing production efficiency. Summary of the Invention

[0004] To address the industry challenges of low precision of incoming welded parts and reliance on manual trial assembly and grinding in bogie crossbeam welding operations, the present invention aims to provide a method, device, and system for evaluating the precision of welded parts based on virtual assembly. This fundamentally eliminates manual trial assembly, improving efficiency while achieving precise and quantitative control over the quality of incoming materials.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a method for evaluating the accuracy of welded parts based on virtual assembly, comprising the following processes: A method for evaluating the accuracy of welded parts based on virtual assembly includes the following steps: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multidimensional assembly tolerance domain is established. Based on the boundary of the multidimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum clearance values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum clearance values, combined with the preset assembly clearance allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value at all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0006] In one implementation of the first aspect of the present invention, for a welded part that needs to be ground, if the maximum value of the minimum required grinding amount of all sampling points on the same surface to be evaluated is less than or equal to the minimum value of the maximum allowable grinding amount, then the optimal uniform grinding amount of the surface to be evaluated is calculated for uniform grinding; otherwise, based on the grinding requirements of each sampling point, the area is divided and a differentiated grinding scheme for different areas is generated for differentiated grinding.

[0007] As a further limitation of the first aspect of the invention, the optimal grinding amount is: the arithmetic mean of the maximum value of all minimum required grinding amounts and the minimum value of all maximum permissible grinding amounts.

[0008] As a further limitation of the first aspect of the present invention, the differentiated grinding includes: merging adjacent sampling points with similar grinding requirements into the same grinding area according to the grinding requirements of each sampling point, determining a consistent grinding amount for each area, outputting a differentiated grinding map, and performing grinding according to the differentiated grinding map.

[0009] In one implementation of the first aspect of the present invention, discrete sampling includes: For annular bevels, radial sections are generated around the axis of the annular bevel at preset angular intervals; For a straight bevel, parallel cross sections are generated at preset intervals along the extension direction of the straight bevel; On each cross section, the point on the cross section profile that is closest to the surface of the target assembly is selected as the sampling point.

[0010] In one implementation of the first aspect of the present invention, calculating the minimum required grinding amount for the i-th sampling point includes: if the minimum gap value of the i-th sampling point is less than the lower limit of the allowable range of assembly gap, then the minimum required grinding amount is equal to the lower limit of the allowable range of assembly gap minus the minimum gap value; otherwise, the minimum required grinding amount for the i-th sampling point is zero.

[0011] In one implementation of the first aspect of the present invention, calculating the maximum allowable grinding amount of the i-th sampling point includes: if the maximum gap value of the i-th sampling point is less than or equal to the upper limit of the allowable range of assembly gap, then the maximum allowable grinding amount is equal to the upper limit of the allowable range of assembly gap minus the maximum gap value; otherwise, the maximum allowable grinding amount of the i-th sampling point is zero.

[0012] Secondly, the present invention provides a welding precision evaluation device based on virtual assembly.

[0013] A welding component accuracy evaluation device based on virtual assembly, comprising: The tolerance domain construction and simulation module is configured to: establish a multi-dimensional assembly tolerance domain based on the floating tolerance of the assembly position of the welded part relative to the target assembly; and determine multiple extreme assembly conditions and perform virtual assembly simulation based on the boundary of the multi-dimensional assembly tolerance domain. The gap analysis module is configured to: perform discrete sampling on the surface to be evaluated of the welded part under various extreme assembly conditions to obtain multiple sampling points; based on the distance between the sampling point and the surface of the target assembly, obtain the minimum and maximum gap values ​​of each sampling point under different extreme assembly conditions; and calculate the minimum required grinding amount and the maximum allowable grinding amount of each sampling point based on the minimum and maximum gap values ​​and the preset assembly gap allowable range. The decision-making module is configured as follows: if the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value of all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0014] Thirdly, the present invention provides a welding accuracy evaluation system based on virtual assembly.

[0015] A precision evaluation system for welded parts based on virtual assembly, comprising: A three-dimensional data acquisition unit is used to acquire three-dimensional point cloud data of the welded parts; The positioning and clamping unit includes a tooling platform with a positioning device and a clamping mechanism, used for rough positioning and clamping of welded parts; The grinding unit includes a force-controlled actuator for performing grinding operations; Robots, including robotic arms, are used to carry 3D data acquisition units to acquire 3D point cloud data or switch grinding units to perform grinding operations. The coordinate calibration unit is used to establish a unified spatial coordinate system for scanning and grinding. The main control unit is communicatively connected to the three-dimensional data acquisition unit, the positioning and clamping unit, the grinding unit, the robot, and the coordinate calibration unit, respectively, and is used to drive the collaborative work of each unit according to the virtual assembly-based welding part accuracy evaluation method of the first aspect of the present invention.

[0016] In one implementation of the third aspect of the present invention, the coordinate calibration unit includes three reference spheres arranged in a non-collinear manner in the positioning and clamping unit. The robot end effector contacts and measures at least four non-coplanar points on the surface of each reference sphere, calculates the coordinates of the centers of the three reference spheres in the robot base coordinate system Base_CS, and then establishes the user's actual coordinate system User_CS according to preset geometric rules based on the coordinates of the centers of the three reference spheres, and calculates the coordinate transformation matrix T from User_CS to Base_CS. When the robot carries a laser scanner to scan the welded parts, it simultaneously scans three reference spheres on the tooling platform; The industrial control computer performs fitting calculations on the scanned reference sphere point cloud to obtain the center coordinates of the three reference spheres in virtual space. Based on the center coordinates, a user virtual coordinate system User_CS' is established according to the same geometric rules as the User_CS coordinate system. The coordinates of each sampling point and the grinding position are determined based on the user virtual coordinate system User_CS'. The robot transforms the coordinates of the grinding position to the robot base coordinate system Base_CS according to the coordinate system transformation matrix T.

[0017] Fourthly, the present invention provides a computer device, comprising: a processor and a computer-readable storage medium; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for evaluating the accuracy of welded parts based on virtual assembly, which is the first aspect of the present invention.

[0018] Fifthly, the present invention provides a computer-readable storage medium storing a computer program adapted to be loaded by a processor and executed by the method for evaluating the accuracy of welded parts based on virtual assembly, which is a first aspect of the present invention.

[0019] In a sixth aspect, the present invention provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the welding precision evaluation method based on virtual assembly of the first aspect of the present invention.

[0020] The beneficial effects of the present invention are as follows: This invention innovatively proposes a method for evaluating the accuracy of welded parts based on virtual assembly, which realizes accurate evaluation of the incoming material accuracy of complex welded parts. By using three-dimensional laser scanning of incoming materials and virtual assembly, it solves the problem of unpredictable assembly interference and accurately determines the quality status of the workpiece as "useable directly without grinding", "useable after grinding" or "unqualified and requires rework".

[0021] This invention employs a globally optimal grinding amount decision method and a tolerance domain extreme value analysis strategy. During virtual assembly, it uses multi-condition constraints to simulate the assembly state within the entire assembly dimensional tolerance range, calculates the optimal grinding amount and grinding position, and ensures that subsequent manual assembly at any position within the assembly dimensional tolerance range is qualified.

[0022] This invention enables adaptive automatic grinding of incoming welded parts. It scans and acquires actual three-dimensional data for each workpiece, identifies manufacturing errors in each workpiece through virtual assembly, and outputs adaptive grinding instructions. During grinding, the grinding force is sensed in real time by a force control sensor, thus achieving adaptive automatic grinding.

[0023] This invention can provide guidance for process optimization. By analyzing the trends and patterns of virtual assembly results from a large amount of scanning data, it can generate corresponding process optimization suggestions, providing support for process optimization. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a schematic diagram of the crossbeam structure mentioned in the background art of the present invention, wherein: 101, crossbeam steel pipe; 102, motor hanger; 103, traction rod seat; 104, traction rod and gearbox hanger; 105, gearbox hanger; 106, longitudinal auxiliary beam; Figure 2 This is a three-dimensional structural diagram of the motor hanger mentioned in the background section of this invention; Figure 3 This is a schematic diagram of a welding precision evaluation system based on virtual assembly, provided as an exemplary embodiment of the present invention, wherein: 1. Robot; 2. Laser scanner; 3. Laser tracker; 4. Fixed reference sphere group; 5. Positioning fixture platform; 6. Tool quick change device; 7. Force-controlled grinding head; 8. Gripping fixture; 9. Barcode scanning device; 10. Industrial computer; 11. Robot controller; Figure 4 A schematic diagram illustrating the working method of a weldment accuracy evaluation system based on virtual assembly, provided as an exemplary embodiment of the present invention; Figure 5A schematic diagram illustrating the creation of a uniform cross-section of an arc bevel, provided as an exemplary embodiment of the present invention; Figure 6 A schematic diagram illustrating the creation of a uniform cross-section with a straight bevel, provided as an exemplary embodiment of the present invention; Figure 7 A schematic diagram of a welding accuracy evaluation method based on virtual assembly provided as an exemplary embodiment of the present invention; Figure 8 A schematic diagram of a weldment accuracy evaluation system based on virtual assembly, provided as another exemplary embodiment of the present invention; Figure 9 A schematic diagram of a computer device provided for another exemplary embodiment of the present invention. Detailed Implementation

[0026] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] This invention innovatively proposes a welding component precision evaluation system based on virtual assembly, using a motor hanger as an example. First, a point cloud model of the welding component is acquired through 3D laser scanning, and then assembled with a crossbeam steel pipe in a virtual environment. Next, based on the tolerance domain extreme value analysis method in tolerance analysis, multiple working condition floating constraints are adopted during virtual assembly. The assembly precision of the incoming material is comprehensively evaluated within the assembly tolerance domain, accurately determining the quality state of the workpiece: "ready to use without grinding," "requires grinding," or "unqualified and requires rework." For workpieces requiring grinding, the optimal grinding amount and position are intelligently calculated to ensure all assembly states are qualified. Finally, based on the optimal grinding amount and position, precise adaptive automated grinding is achieved, solving the problems of difficult-to-accurate evaluation of the incoming material precision of complex welding components and unpredictable assembly interference. This fundamentally eliminates manual trial assembly, improving efficiency while achieving precise and quantitative control of incoming material quality.

[0028] Specifically, such as Figure 3 As shown, the adaptive precision evaluation system for incoming welding parts provided by the present invention includes: a robot 1, a laser scanner 2 (i.e., a three-dimensional data acquisition unit), a laser tracker 3, a fixed reference sphere group 4 (i.e., a coordinate calibration unit), a positioning fixture platform 5 (i.e., a positioning clamping unit), a tool quick change device 6, a force-controlled grinding head 7 (i.e., a grinding unit), a gripping fixture 8, a barcode scanning device 9, an industrial control computer 10 (i.e., a main control unit), and a robot controller 11.

[0029] In this implementation, preferably, the robot is a six-degree-of-freedom articulated robot with a repeatability accuracy better than 0.1mm. It is responsible for carrying the laser scanner 2, the force-controlled grinding head 7, and the gripping fixture 8 to complete the scanning, grinding, and gripping of the workpiece.

[0030] In this implementation, preferably, the laser scanner 2 is mounted on the flange at the end of the robot 1, and a high-precision line laser scanner is used, with scanning accuracy and resolution better than 0.03mm, to acquire the three-dimensional point cloud data of the motor mount.

[0031] In this implementation, preferably, the laser tracker 3 tracks the spatial position of the scanner in real time during the scanning process, and associates the local point cloud data scanned at different positions and angles with a unified global coordinate system to ensure the accurate stitching of the model as a whole.

[0032] In this implementation, preferably, the fixed reference sphere group 4 includes three reference spheres made of stainless steel or ceramic. The surfaces of the spheres are affixed with reflective markers for easy scanner identification. They are mounted on the tooling platform near the edge via strong magnetic bases, arranged in a non-collinear "triangular" distribution. This serves as the reference for coordinate transformation between the robot system and the virtual assembly environment.

[0033] In this implementation, preferably, the positioning fixture platform 5 uses a positioning device and a clamping mechanism to roughly clamp the motor hanger, with a repeated clamping position accuracy of ±5mm.

[0034] In this implementation, preferably, the tool quick-change device 6 is used to cooperate with the robot to automatically and quickly switch end tools such as laser scanners, force-controlled grinding heads, and gripping fixtures.

[0035] In this implementation, preferably, the force-controlled grinding head 7 is installed on the end flange of the robot and is responsible for executing the grinding instructions (grinding position and grinding amount) output by the virtual assembly. It is equipped with a force sensor, which can detect the contact force between the grinding tool and the workpiece surface in real time and feed the signal back to the robot control system for feedback compensation, so as to ensure constant grinding pressure and stable material removal.

[0036] In this implementation, preferably, the gripping fixture 8 is installed on the end flange of the robot to enable the robot to grip the workpiece for loading, scanning, and unloading.

[0037] In this implementation, preferably, the scanning device 9 is used to read the QR code on the workpiece label, obtain information such as the incoming material model and production number, and transmit it to the industrial control computer, and associate it with the corresponding workpiece's scanned point cloud data and accuracy evaluation results.

[0038] In this implementation, preferably, the industrial control computer 10 has built-in software modules for point cloud processing, virtual assembly, and coordinate transformation, which are responsible for performing core calculations such as point cloud denoising, virtual assembly, tolerance domain analysis, grinding decision generation, and transformation between robot coordinate system and virtual assembly coordinates.

[0039] In this implementation, preferably, the robot controller 11 serves as the robot motion control unit, and receives feedback signals from the force sensor during the grinding process, outputs instructions to the robot, and realizes closed-loop control of constant force grinding.

[0040] The working method of the above system is as follows: Figure 4 As shown, the process includes the following: S401: Calibration (required only for the first measurement or when the position of the reference sphere changes).

[0041] A high-precision contact probe is installed at the robot's end effector. The human operator teaches the robot to select at least four non-coplanar contact points on the surface of each reference sphere. The software first calculates the coordinates of the centers of the three reference spheres in the robot's base coordinate system (Base_CS), and then uses these coordinates to establish the user's actual coordinate system (User_CS). Subsequently, the robot software can calculate the coordinate transformation matrix T from User_CS to Base_CS.

[0042] S402: Loading materials.

[0043] The robot uses a gripper to pick up the motor mount from the storage and transportation fixture. First, it moves to the QR code vision inspection device to identify the QR code label on the workpiece and obtain the current workpiece number. Then, it places the motor mount on the positioning fixture, which automatically clamps and fixes it.

[0044] S403: Laser scanning.

[0045] The robot holds a laser scanner to perform laser scanning on the motor mount according to a preset path. At the same time, it is linked with a laser tracker to track the spatial position of the laser scanner in real time and perform global spatial positioning, acquire workpiece point cloud data and transmit it to the industrial control computer.

[0046] S404: Point cloud noise reduction.

[0047] Isolated noise points and irrelevant point clouds (such as tooling platforms and positioning fixtures) are removed from the initial point cloud data. After denoising, only the point cloud of the motor mount and the reference sphere group are retained. This process is completed by industrial computer point cloud processing software.

[0048] S405: Establish geometric features.

[0049] Import the motor mount point cloud (containing three reference spheres) into the virtual assembly software. Based on the assembly requirements of the motor mount and steel pipe in the process document, fit and construct the geometric features of the relevant assembly reference surface and the center of the reference sphere.

[0050] S406: Establish a user virtual coordinate system.

[0051] Using the center features of three reference spheres, and following the calibration method in S401, a user virtual coordinate system User_CS' is established in the virtual assembly environment. The grinding position information output after virtual assembly is based on this coordinate system.

[0052] S407: Virtual assembly, analysis and automated grinding.

[0053] Since the outer surface of the crossbeam steel pipe has undergone precision machining with a machining accuracy within 0.1mm, and the actual object is highly consistent with the CAD theoretical model, in order to save system resources and improve the operation cycle, the crossbeam steel pipe entity is not scanned. Instead, the steel pipe theoretical CAD model and the motor hanger point cloud are used for assembly. The detailed assembly analysis method will be introduced in the next chapter. If grinding is required after assembly analysis, the grinding amount and grinding position information will be output. The grinding position coordinates are based on User_CS' in S406.

[0054] The virtual assembly output grinding position coordinates are transformed into coordinates in the robot's base coordinate system using the transformation matrix T. The robot holds the force-controlled grinding head to the corresponding position to grind the workpiece assembly surface. Different contact forces are selected according to the amount of grinding, and the actual contact force between the grinding head and the workpiece surface is monitored in real time by the force sensor. The signal is fed back to the robot control system for motion compensation to ensure that the grinding pressure is constant.

[0055] S408: Material feeding.

[0056] Once the tooling fixture receives the completion signal, it releases the clamping mechanism, and the robot uses the gripper to pick up the motor hanger from the positioning fixture and place it in the finished storage area.

[0057] In step S407 of this implementation method, due to tooling positioning errors and manual operation errors, under existing manual assembly conditions, the assembly dimensions cannot be maintained at a constant value, but fluctuate within ±0.5mm of the reference value. Therefore, based on the concept of tolerance analysis, floating constraints are adopted during virtual assembly. By constructing a tolerance domain and performing extreme value analysis on the boundaries, the worst assembly conditions are simulated, the incoming material accuracy is comprehensively evaluated, and the optimal grinding amount that covers all possible assembly states is calculated. This ensures that manual assembly at any position within the assembly tolerance domain guarantees acceptable gaps and prevents grinding. The detailed process is as follows: S407-1: Tolerance Domain Analysis.

[0058] Since the assembly clearance is affected by the Y-axis (along the steel pipe spacing direction) and Z-axis (height) assembly dimensions, and is independent of the X-axis (along the steel pipe length direction) dimensions, only the Y-axis and Z-axis dimensions need to be considered in the tolerance domain analysis. Both fluctuate within ±0.5mm of their respective reference values, together forming a two-dimensional rectangular tolerance domain. For any point on the assembly surface, all its possible assembly positions fall within this rectangular tolerance domain. The goal of incoming material quality assessment is no longer to ensure that the workpiece is assembled correctly in a certain ideal position, but rather to ensure that it is assembled correctly throughout the entire tolerance domain.

[0059] S407-2: Extreme value analysis.

[0060] Consider any point on the bevel of the motor mount. Since its assembly clearance changes monotonically with the assembly dimensions (i.e., the clearance increases when the assembly dimensions increase and decreases when the assembly dimensions decrease), the maximum and minimum clearances for this specified point must occur at the four corner points (extreme values) of the rectangular tolerance domain. Therefore, during virtual assembly, applying dimensional constraints according to the following four extreme value conditions sequentially will cover all cases within the tolerance domain: ①Working condition A: Y_min, Z_min; ②Condition B: Y_min, Z_max; ③ Working condition C: Y_max, Z_min; ④ Operating condition D: Y_max, Z_max; Where Y_min and Y_max are the lower and upper limits of the assembly dimensions in the Y direction, respectively, and Z_min and Z_max are the lower and upper limits of the assembly dimensions in the Z direction, respectively.

[0061] To examine the clearance under the four extreme conditions mentioned above, a series of analysis points Pi were obtained by uniformly and discretely sampling the bevel surface. The clearance at each point was then evaluated. The specific method for creating point Pi is as follows: ① For the arc bevel of the motor mount, along the radial direction of the steel pipe and with the axis of rotation of the steel pipe as the axis of rotation, create N uniform cross sections at equal angles, such as... Figure 5 As shown. After the cross-section is created, select the point Pi (or the point closest to the steel pipe) at the front edge of the bevel on each cross-section in sequence.

[0062] ② For the straight bevel of the motor hanger, create it at equal intervals along the length of the steel pipe, such as... Figure 6 As shown, after the cross-section is created, select the point Pi (or the point closest to the steel pipe) at the front edge of the bevel on each cross-section in turn.

[0063] Under four working conditions (A, B, C, and D), the distance between Pi and the surface of the crossbeam steel pipe is measured to obtain the minimum distance Gap_min_i and the maximum distance Gap_max_i, which correspond to the minimum and maximum gap values, respectively. Gap_min_i may be negative, indicating that interference has occurred at that point.

[0064] In the above expression, i = 1, 2, 3, ..., N, where N is the number of analysis points sampled on a certain assembly surface.

[0065] S407-3: Solving for the optimal grinding amount.

[0066] Under the above four extreme conditions, for each analysis point Pi, calculate its minimum required grinding amount G_min_i and maximum allowable grinding amount G_max_i. The specific method is as follows: E is defined as the lower limit of the clearance allowable value, and F is defined as the upper limit of the clearance allowable value. Both are known parameters required by the process. In this example, E=1mm and F=3mm.

[0067] The calculation method for G_min_i is as follows: if the minimum gap value of Pi, Gap_min_i < E, then G_min_i = E - Gap_min_i; if Gap_min_i ≥ E, then G_min_i = 0.

[0068] The calculation method for G_max_i is as follows: if the maximum gap value of Pi, Gap_max_i, is less than or equal to F, then G_max_i = F - Gap_max_i; if Gap_max_i > F, it means that the gap exceeds the upper limit under a certain working condition, and grinding is not allowed at this point under this working condition, so G_max_i = 0.

[0069] For any point Pi on the bevel assembly surface, the safe grinding window is [G_min_i, G_max_i]. To maximize the uniformity of the bevel angle after grinding, uniform grinding across the entire bevel is preferred. The problem then becomes whether there exists a uniform grinding amount G_uni that satisfies the following for any point Pi on the bevel assembly surface: max(G_min_i)≤P≤min(G_max_i).

[0070] If max(G_min_i)≤min(G_max_i), it means that G_uni exists. To improve the robustness of the system, the optimal grinding amount G_best is taken as the midpoint of this range, that is, G_best=[max(G_min_i)+min(G_max_i)] / 2, which means that the bevel is uniformly ground according to G_best for the entire range, and any assembly within the tolerance domain is qualified.

[0071] If max(G_min_i)>min(G_max_i), it means that the uniform grinding amount G_uni does not exist, and differential grinding is required for each point on the bevel assembly surface.

[0072] S407-4: Grinding decision generation and incoming material accuracy assessment.

[0073] The calculation based on the above method for determining the optimal grinding amount yields the following four results: ① Qualified: If the minimum gap value Gap_min_i and the maximum gap value Gap_max_i of any point Pi both fall within the allowable range [E,F] of the assembly gap, it indicates that no grinding is required. Assembly at any position within the tolerance domain is qualified and belongs to high-quality incoming materials. Grinding is not required and the materials can be released directly. ② Uniform grinding: If max(G_min_i)≤min(G_max_i), it means that there is a uniform grinding amount, G_uni and an optimal grinding amount, G_best. Then the system outputs a uniform grinding map with the grinding amount being G_best and the grinding position being the entire range of the bevel. ③ Differentiated Grinding: If max(G_min_i) > min(G_max_i), it indicates that there is no uniform grinding amount that ensures the gaps at all points are within the assembly tolerance range, and differentiated grinding is required. Based on the grinding requirements of each sampling point, adjacent sampling points with similar requirements are merged into the same grinding area, and a consistent grinding amount is determined for each area to generate a differentiated grinding map. Grinding is then performed according to this map. For example, in area P on the bevel assembly surface, the grinding amount is 1.3 mm, and in area Q on the bevel assembly surface, the grinding amount is 0.8 mm. ④ Non-conforming: If there are some points G_min_i > G_max_i, it indicates that after grinding, the clearance in any state cannot be guaranteed to be qualified within the assembly tolerance domain. It needs to be returned to the previous process for adjustment, or accepted with a compromise, and manually assembled and ground by the assembly personnel.

[0074] S407-5: Recommendations for process optimization.

[0075] By analyzing the trends and patterns in a large amount of scanning data, process optimization suggestions can be generated. For example, if a lot of uniform grinding is found, it indicates that there is a systematic dimensional deviation in the incoming material rather than random deformation, and it is recommended that the upstream process adjust the welding reference of the welded parts; if a lot of local differential grinding is found, it indicates that there is a regular local deformation in the incoming material, and it is recommended to optimize the control of welding deformation, or optimize the process yield according to the different grinding conditions of different parts; if a lot of non-conforming conditions are found, it indicates that there is a conflict between the dimensional tolerance allocation and the clearance requirements, and it is necessary to optimize the design or process dimensional chain from blanking to welding, or optimize the assembly clearance requirements.

[0076] Based on the above entity system, Figure 7A method for evaluating the accuracy of welded parts based on virtual assembly is shown, applicable to processing terminals or industrial control computers, including the following process: S701: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multi-dimensional assembly tolerance domain is established. Based on the boundary of the multi-dimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. S702: Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum gap values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum gap values, combined with the preset assembly gap allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. S703: If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value of all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0077] Meanwhile, based on the aforementioned entity system, Figure 8 A virtual assembly-based welding precision evaluation system is shown, which can be deployed on a processing terminal or industrial control computer, including: The tolerance domain construction and simulation module 801 is configured to: establish a multi-dimensional assembly tolerance domain based on the floating tolerance of the assembly position of the welded part relative to the target assembly; and determine multiple extreme assembly conditions and perform virtual assembly simulation based on the boundary of the multi-dimensional assembly tolerance domain. The gap analysis module 802 is configured to: perform discrete sampling on the surface to be evaluated of the welded part under various extreme assembly conditions to obtain multiple sampling points; obtain the minimum and maximum gap values ​​of each sampling point under different extreme assembly conditions based on the distance between the sampling point and the surface of the target assembly; and calculate the minimum required grinding amount and the maximum allowable grinding amount of each sampling point based on the minimum and maximum gap values ​​and the preset assembly gap allowable range. The decision-making module 803 is configured to: if the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is determined to be unqualified; if the minimum gap value of all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is determined to be qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is determined to require grinding.

[0078] It is understood that the aforementioned units can be individually or entirely merged into one or more other units, or some of the units can be further divided into multiple functionally smaller units. This achieves the same operation without affecting the technical effects of the embodiments of the present invention. The aforementioned units are based on logical functional division. In practical applications, the function of one unit can be implemented by multiple units, or the function of multiple units can be implemented by one unit. In other embodiments of the present invention, the system may also include other units. In practical applications, these functions can also be implemented with the assistance of other units, and can be implemented collaboratively by multiple units.

[0079] According to another embodiment of the present invention, the system of this embodiment can be constructed by running a computer program (including program code) capable of performing the steps involved in the corresponding method of the present invention on a general-purpose computing device, such as a computer, which includes processing elements and storage elements such as a central processing unit (CPU), random access memory (RAM), and read-only memory (ROM). The computer program can be recorded on, for example, a computer-readable recording medium, loaded into the aforementioned computing device through the computer-readable recording medium, and run therein.

[0080] Figure 9 A computer device is shown, which includes a processor 901, a communication interface 902, and a computer-readable storage medium 903. The processor 901, communication interface 902, and computer-readable storage medium 903 can be connected via a bus or other means.

[0081] The communication interface 902 is used to receive and send data. The computer-readable storage medium 903 can be stored in the memory of the electronic device. The computer-readable storage medium 903 is used to store computer programs, which include program instructions. The processor 901 is used to execute the program instructions stored in the computer-readable storage medium 903.

[0082] The processor 901 is the computing and control core of electronic devices. It is suitable for implementing one or more instructions, specifically for loading and executing one or more instructions to achieve corresponding methods or functions.

[0083] Processor 901 is configured to perform the following procedure: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multidimensional assembly tolerance domain is established. Based on the boundary of the multidimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum clearance values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum clearance values, combined with the preset assembly clearance allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value at all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0084] This invention also provides a computer-readable storage medium, which is a memory device in an electronic device for storing programs and data. It is understood that the computer-readable storage medium here may include both built-in storage media in the electronic device and extended storage media supported by the electronic device. The computer-readable storage medium provides storage space for storing the processing system of the electronic device.

[0085] Furthermore, this storage space also contains one or more instructions suitable for loading and execution by the processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory; alternatively, it can also be at least one computer-readable storage medium located remotely from the aforementioned processor.

[0086] In one embodiment, the computer-readable storage medium stores one or more instructions; the processor loads and executes the one or more instructions stored in the computer-readable storage medium to perform the following process: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multidimensional assembly tolerance domain is established. Based on the boundary of the multidimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum clearance values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum clearance values, combined with the preset assembly clearance allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value at all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0087] The present invention also provides a computer program product or computer program comprising computer instructions stored in a computer-readable storage medium. A processor of an electronic device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the electronic device to perform the following process: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multidimensional assembly tolerance domain is established. Based on the boundary of the multidimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum clearance values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum clearance values, combined with the preset assembly clearance allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified; if the minimum gap value at all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, the welded part is deemed qualified and does not require grinding; if the minimum gap value at any sampling point is less than the lower limit of the allowable range of assembly gap, the welded part is deemed to require grinding.

[0088] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed in this invention can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can implement the described functions using different methods for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0089] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of the present invention is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in or transmitted through a computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic cable, digital cable) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can access or a data processing device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive), etc.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the accuracy of welded parts based on virtual assembly, characterized in that, The process includes the following: Based on the floating tolerance of the assembly position of the welded part relative to the target assembly, a multidimensional assembly tolerance domain is established. Based on the boundary of the multidimensional assembly tolerance domain, multiple extreme assembly conditions are determined and virtual assembly simulation is performed. Under various extreme assembly conditions, discrete sampling is performed on the surface of the welded part to be evaluated to obtain multiple sampling points. Based on the distance between the sampling point and the surface of the target assembly, the minimum and maximum gap values ​​of each sampling point under different extreme assembly conditions are obtained. Based on the minimum and maximum gap values, combined with the preset assembly gap allowable range, the minimum required grinding amount and the maximum allowable grinding amount of each sampling point are calculated. If the minimum required grinding amount at any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified. If the minimum gap value of all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, then the welded part is deemed qualified and does not require grinding. If the minimum gap value at any sampling point is less than the lower limit of the assembly allowable range, then the welded part is determined to need grinding.

2. The method for evaluating the accuracy of welded parts based on virtual assembly as described in claim 1, characterized in that, For welded parts that need to be ground, if the maximum value of the minimum required grinding amount of all sampling points on the same surface to be evaluated is less than or equal to the minimum value of the maximum allowable grinding amount, then the optimal uniform grinding amount of the surface to be evaluated is calculated for uniform grinding. Otherwise, based on the grinding requirements of each sampling point, the region is divided, and a differentiated grinding scheme is generated for different regions to carry out differentiated grinding.

3. The method for evaluating the accuracy of welded parts based on virtual assembly as described in claim 2, characterized in that, The differentiated grinding includes: merging adjacent sampling points with similar grinding requirements into the same grinding area according to the grinding requirements of each sampling point, determining a consistent grinding amount for each area, outputting a differentiated grinding map, and performing grinding according to the differentiated grinding map.

4. The method for evaluating the accuracy of welded parts based on virtual assembly as described in claim 2, characterized in that, The optimal grinding amount is the arithmetic mean of the maximum value of all minimum required grinding amounts and the minimum value of all maximum allowable grinding amounts.

5. The method for evaluating the accuracy of welded parts based on virtual assembly as described in any one of claims 1-4, characterized in that, The discrete sampling includes: For annular bevels, radial sections are generated around the axis of the annular bevel at preset angular intervals; For a straight bevel, parallel cross sections are generated at preset intervals along the extension direction of the straight bevel; On each cross section, the point on the cross section profile that is closest to the surface of the target assembly is selected as the sampling point.

6. The method for evaluating the accuracy of welded parts based on virtual assembly as described in any one of claims 1-4, characterized in that, Calculate the first The minimum amount of grinding required for each sampling point includes: if the first sampling point... If the minimum gap value of the first sampling point is less than the lower limit of the allowable range of the assembly gap, then the minimum required grinding amount is equal to the lower limit of the allowable range of the assembly gap minus the minimum gap value; otherwise, the first... The minimum grinding amount required for each sampling point must be zero.

7. The method for evaluating the accuracy of welded parts based on virtual assembly as described in any one of claims 1-4, characterized in that, Calculate the first The maximum allowable grinding amount for each sampling point includes: if the first sampling point... If the maximum gap value of a sampling point is less than or equal to the upper limit of the allowable range of the assembly gap, then the maximum allowable grinding amount is equal to the upper limit of the allowable range of the assembly gap minus the maximum gap value; otherwise, the maximum allowable grinding amount is equal to the upper limit of the allowable range of the assembly gap minus the maximum gap value. The maximum allowable grinding amount for each sampling point is zero.

8. A welding precision evaluation device based on virtual assembly, characterized in that, include: The tolerance domain construction and simulation module is configured to: establish a multi-dimensional assembly tolerance domain based on the floating tolerance of the assembly position of the welded part relative to the target assembly; and determine multiple extreme assembly conditions and perform virtual assembly simulation based on the boundary of the multi-dimensional assembly tolerance domain. The gap analysis module is configured to: perform discrete sampling on the surface to be evaluated of the welded part under various extreme assembly conditions to obtain multiple sampling points; obtain the minimum gap value and maximum gap value of each sampling point under different extreme assembly conditions based on the distance between the sampling point and the surface of the target assembly; and calculate the minimum required grinding amount and maximum allowable grinding amount of each sampling point based on the minimum gap value and maximum gap value, combined with the preset assembly gap allowable range. The decision-making module is configured to determine that if the minimum required grinding amount for any sampling point is greater than its maximum allowable grinding amount, the welded part is deemed unqualified. If the minimum gap value of all sampling points is not less than the lower limit of the allowable range of assembly gap, and the maximum gap value is not greater than the upper limit of the allowable range of assembly gap, then the welded part is deemed qualified and does not require grinding. If the minimum gap value at any sampling point is less than the lower limit of the assembly allowable range, then the welded part is determined to need grinding.

9. A precision evaluation system for welded parts based on virtual assembly, characterized in that, include: A three-dimensional data acquisition unit is used to acquire three-dimensional point cloud data of the welded parts; The positioning and clamping unit includes a tooling platform with a positioning device and a clamping mechanism, used for rough positioning and clamping of welded parts; The grinding unit includes a force-controlled actuator for performing grinding operations; The robot includes a robotic arm, which is used to carry a three-dimensional data acquisition unit to acquire three-dimensional point cloud data or switch a grinding unit to perform grinding operations. The coordinate calibration unit is used to establish a unified spatial coordinate system for scanning and grinding. The main control unit is communicatively connected to the three-dimensional data acquisition unit, the positioning and clamping unit, the grinding unit, the robot, and the coordinate calibration unit, and is used to drive the collaborative work of each unit in accordance with the virtual assembly-based welding part accuracy evaluation method according to any one of claims 1-7.

10. The weldment accuracy evaluation system based on virtual assembly as described in claim 9, characterized in that, The coordinate calibration unit includes three reference spheres, which are arranged in a non-collinear manner on the tooling platform of the positioning and clamping unit. The robot carries a contact probe to contact and measure at least four non-coplanar points on the surface of each reference sphere, calculates the coordinates of the centers of the three reference spheres in the robot's base coordinate system Base_CS, and then establishes the user's actual coordinate system User_CS according to preset geometric rules based on the coordinates of the centers of the three reference spheres, and calculates the coordinate transformation matrix T from User_CS to Base_CS. When the robot carries a 3D data acquisition unit to scan the welded part, it simultaneously scans three reference spheres on the tooling platform; The main control unit performs fitting calculations on the scanned reference sphere point cloud to obtain the center coordinates of the three reference spheres in virtual space. Based on the center coordinates, a user virtual coordinate system User_CS' is established according to the same geometric rules as the User_CS coordinate system. The coordinates of each sampling point and the grinding position are determined based on the user virtual coordinate system User_CS'. The robot transforms the coordinates of the grinding position to the robot base coordinate system Base_CS according to the coordinate system transformation matrix T.

11. A computer device, characterized in that, include: Processor and computer-readable storage media; A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program, which, when executed by the processor, implements the method for evaluating the accuracy of welded parts based on virtual assembly as described in any one of claims 1 to 7.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program adapted to be loaded by a processor and executed as described in any one of claims 1 to 7, for evaluating the accuracy of welded parts based on virtual assembly.

13. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method for evaluating the accuracy of welded parts based on virtual assembly as described in any one of claims 1 to 7.

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