Workpiece surface topography real-time interpolation reconstruction method based on digital twinning

Abstract

The invention belongs to the technical field of workpiece surface topography interpolation, and discloses a workpiece surface topography real-time interpolation reconstruction method based on digital twinning, which realizes point-by-point measurement and interpolation reconstruction in a workpiece machining process by constructing a digital twinning system on a numerical control machine tool. From the perspective of processing mechanism and data fusion, a material geometry removal behavior model of the digital twin system is established, and a key enabling technology of the digital twin system is formed. Mass multi-source heterogeneous data fusion is realized through circulation of energy flow, material flow and information flow in the digital twin grinding system, so that real-time symmetry between a physical system and a virtual system is kept. According to the method, high-precision real-time in-situ detection of the contour of the complex curved surface workpiece can be realized without any additional sensor equipment. By improving the detection precision and the production efficiency, the cost is reduced, the applicability is enhanced, and the method has wide application prospects in the field of workpiece machining.

Description

Technical Field

[0001] The present invention belongs to the technical field of workpiece surface morphology interpolation, and relates to a real-time interpolation and reconstruction method of workpiece surface morphology based on digital twins. Background Art

[0002] In the modern manufacturing industry, high-precision detection of workpiece surface topography is a key link to ensure product quality and performance. Especially for complex curved workpieces, the accuracy of their contours directly affects the assembly, function and aesthetics of the product. Jiang Xue et al. proposed in the document "Research on Error Compensation Strategy of Coordinate Measuring Machine-Assisted Tooling Detection" that the error of the workpiece installation process can be measured by a three-coordinate measuring machine, and Mao Anshi et al. proposed in the document "Online Detection Method of Mechanical Processing Workpiece Dimension Deviation Based on Laser Sensor" that laser sensors can be used to achieve online monitoring of workpiece errors. However, Qi Hongfang et al. pointed out in "Research on Contact Online Measurement Path Planning of Complex Curved Workpieces" that although these traditional detection methods can provide high-precision measurement results, they usually need to be tested offline after processing is completed, which not only increases the production cycle, but may also introduce new errors due to workpiece movement or reinstallation. Liu Yunqiang also mentioned in "Research on In-situ Detection Method of Workpiece Contour Error Based on Machine Vision" that these high-precision detection equipment are often expensive and complex to operate, which is a considerable economic burden for small and medium-sized enterprises. Huang Chenxiang pointed out in "Research on Workpiece Feature Detection Methods" that for some large or heavy workpieces, frequent movement and reinstallation may cause damage to the workpiece or loss of accuracy, which further increases production costs and risks.

[0003] In order to solve the above problems, the present invention proposes a real-time interpolation and reconstruction method for workpiece surface morphology based on digital twin. This method uses the control system and sensors of the CNC machine tool itself to build a digital twin system to obtain workpiece surface data in real time and perform interpolation and reconstruction without the need for additional sensor equipment, thereby achieving high-precision in-situ detection. Summary of the invention

[0004] The present invention aims to overcome the technical defects and shortcomings of existing grinding wheel detection devices, such as single applicability, low detection efficiency and poor detection accuracy, and provides an intelligent detection method for in-situ dressing contour of grinding wheels for CNC grinders. The in-situ monitoring of the dressing process is achieved through real-time power feedback of machine tool guide rail signals, and the detection requirements of grinding wheels of different shapes can be met at the same time.

[0005] The technical solution of the present invention:

[0006] A real-time interpolation and reconstruction method of workpiece surface morphology based on digital twins, such as Figure 1As shown, by establishing a virtual machining system that fully matches the actual grinding system, high-precision real-time monitoring and visual prediction of the machining state and machining effect are achieved through the combination of virtual and real, without any additional sensors. The technical solution of the present invention includes the following five steps:

[0007] S1: Building a digital twin system

[0008] A digital twin system is built on a CNC machine tool, including a real physical environment and a virtual simulation environment. The real physical environment is the CNC machine tool and the workpiece it processes, and the virtual simulation environment is a digital model corresponding to the real physical environment. The digital twin system obtains the operating data of the CNC machine tool in real time through the data acquisition module, including tool position, workpiece position, and processing parameters.

[0009] In the virtual simulation environment, the three-dimensional information of the workpiece is used to build the corresponding model file and startup file to achieve the mapping of the workpiece in the virtual simulation environment to the real environment. By continuously updating the model in the virtual simulation environment, it is kept highly consistent with the workpiece in the real physical environment.

[0010] The five-dimensional architecture of the digital twin machine tool established by the present invention mainly includes physical entity PE, virtual entity VM, service SS, twin data DD, and links CN between the components, which can be expressed as:

[0011] CNCGM-DT={PE,VM,SS,DD,CN} (1)

[0012] The virtual entity can describe the geometric information of the tool system, including the initial geometry and the machining geometry. The initial geometry represents the original shape of the workpiece and tool, including the arc radius of the tool, the geometric dimensions of the cutting edge, the diameter and length of the workpiece, etc. The machining geometry reflects the changed geometry. During the grinding process, the feed rate, grinding depth and grinding time determine the material removal value, and the spindle speed and feed rate determine the wear scar spacing, which in turn determines the wear scar morphology. The established virtual entity model can be expressed as:

[0013]

[0014] Among them, R s v w a p etc. respectively represent the relevant parameters of the tool system: R s is the grinding wheel radius, v w a p are the parameters such as feed speed and grinding depth. h θh and others represent the relevant geometric parameters of the workpiece system: R his the residual height of the wear scar on the workpiece surface, θ is the angle between the grinding point and the contact point of the grinding wheel, and h is the distance between the grinding points. dx and dz represent the influence of environmental factors on the tool system, dx is the disturbance of the environment on the tool system in the x direction, and dz is the disturbance of the environment on the tool system in the z direction.

[0015] When h>2R s And a p <R s Sometimes:

[0016] R h =a p (3)

[0017] At this time, the grinding pattern cannot completely cover the workpiece surface, that is, the quality of the product cannot be controlled. Based on this, the overlap rate K is defined s =Removal volume / total volume=Removal volume / (Removal volume+Residual height volume) to characterize the processing quality of the material:

[0018]

[0019] By definition, the higher the overlap, the more fully the material is processed:

[0020]

[0021] When 0<h≤2R s Sometimes:

[0022]

[0023] when a p ≤R h Same as formula 5 and formula 6. When R h <a p When ≤R, we have formula 7:

[0024]

[0025] in

[0026]

[0027] As the grinding depth increases, the material undergoes elastic deformation-plastic deformation-material removal. When the material undergoes plastic deformation, the actual cutting depth will change. The main consideration is the impact of plastic deformation on the surface morphology of the material. When the actual grinding point deviates from the theoretical grinding point due to elastic-plastic deformation, the two adjacent grinding points (x a ,z a ,c a ) and grinding point (x b ,z b ,c b) between the i-th actual grinding point coordinates (x i ,z i ,c i ):

[0028]

[0029] where h a are two adjacent grinding points (x a ,z a ,c a ) and grinding point (x i ,z i ,c i ) in the X direction, h b are two adjacent grinding points (x i ,z i ,c i ) and grinding point (x b ,z b ,c b ), and h(F,E,ΔR) represents the influence of grinding force, material properties and grinding wheel radius change on h.

[0030]

[0031] where h b+ ,h b- They represent the size of the deviation distance in the X direction under dx and dz disturbances respectively, and A, C, and Ψ are the corresponding parameter calculation symbols respectively.

[0032] S2: Real-time point-by-point measurement

[0033] During the workpiece processing, the CNC machine tool's own control system is used to obtain the position information of the contact point between the tool and the workpiece in real time. The encoder, sensor and other equipment of the CNC machine tool are used to accurately record the coordinates of each processing point, including the position information of the X-axis, Z-axis and C-axis.

[0034] Combined with the real-time position feedback signal and power signal of the machine tool in the machine tool coordinate system, the surface processing state of the workpiece is judged by the change of the time domain signal of the X, Z, and C axes in the machine tool coordinate system, and then the real-time grinding state of the workpiece is obtained. The real-time position signal of the machine tool can be expressed as:

[0035]

[0036] Among them, x instruction , z instruction , c instruction are the command positions of the XZC coordinates in the NC program after being discretized by the machine tool NC program, and x actual , z actual , c actualThey are the actual positions of the XZC coordinates in the machine tool coordinate system during grinding, and the difference between them is x pe , z pe , c pe These are the influences on the three coordinates X, Z and C during the grinding process.

[0037] Based on this, the real-time position signal of the machine tool can be converted into spatial coordinates:

[0038]

[0039] In order to achieve point-by-point measurement, the point-by-point measurement mode can be set in the control system of the CNC machine tool. By controlling the tool to move on the workpiece surface, the position information of each contact point can be recorded in real time. At the same time, by controlling the tool feed speed and cutting depth, the accuracy and reliability of the measurement can be guaranteed.

[0040] S3: Data interpolation processing

[0041] The point-by-point measurement data obtained is usually sparse. In order to reconstruct the complete morphology of the workpiece surface, data interpolation processing is required. Data interpolation processing includes selecting a suitable interpolation method and setting reasonable interpolation parameters. The resolution of the real-time morphology fitting of the workpiece is proposed by establishing a digital twin system:

[0042]

[0043] Where R path is the resolution in the machining path direction, R ⊥path is the resolution perpendicular to the machining path, feed is the feed rate, and f is the sampling frequency. By selecting a suitable sampling frequency, nanometer-level resolution can be easily achieved, while the resolution perpendicular to the machining direction is significantly related to the process parameters.

[0044] Common interpolation methods include linear interpolation, quadratic interpolation, cubic interpolation, etc. According to the shape and precision requirements of the workpiece, a suitable interpolation method is selected. The present invention establishes a real-time interpolation algorithm based on the tool-workpiece contact model, and can establish an improved fitting algorithm under given process parameters. In order to improve the fitting accuracy and make the fitting resolution in two directions not too different, the number of interpolation times can be selected according to formula 14, and the surface of the workpiece is subjected to data-mechanism-based surface microscopic interpolation fitting by adopting the interpolation fitting algorithm.

[0045]

[0046] Where n is the number of interpolation times, R tar For the ideal resolution, R is usually taken tar =[R path ,R ⊥path ] minBased on this, the interpolation algorithm can be adjusted according to the shape fitting accuracy requirements to further improve the fitting of the workpiece surface shape.

[0047] By adjusting the interpolation parameters, the interpolation results can be optimized and the accuracy and efficiency of reconstruction can be improved.

[0048] S4: Surface topography reconstruction

[0049] After data interpolation, a complete set of data points on the workpiece surface is obtained. Using these data points, the morphology of the workpiece surface is reconstructed in a virtual simulation environment. The reconstruction process includes steps such as generating a three-dimensional mesh model, calculating the surface normal vector, and performing smoothing.

[0050] When generating a 3D mesh model, adjacent data points are connected according to the interpolation results to form a triangular or quadrilateral mesh. When calculating the surface normal vector, the position information of the mesh vertices is used to calculate the normal vector of each vertex for subsequent lighting and rendering processing. When smoothing, the position of the mesh vertices is adjusted to make the surface smoother and in line with the shape characteristics of the actual workpiece.

[0051] S5: High-precision real-time in-situ detection

[0052] After the reconstruction is completed, the surface morphology of the workpiece in the virtual simulation environment is compared with the workpiece in the real physical environment. The control system of the CNC machine tool is used to obtain the position information of the tool in real time and compare it with the model in the virtual simulation environment to determine whether the tool collides or deviates from the workpiece surface.

[0053] By continuously adjusting the tool position and processing parameters, the contact point between the tool and the workpiece surface is kept within the predetermined error range. At the same time, the real-time feedback function of the digital twin system is used to monitor the error changes during the processing in real time and make compensation adjustments to achieve high-precision real-time on-site detection.

[0054] Beneficial effects of the present invention: The present invention proposes a real-time interpolation and reconstruction method for the workpiece surface morphology based on digital twins, which realizes point-by-point measurement and interpolation reconstruction during the workpiece processing process by constructing a digital twin system on a CNC machine tool. From the perspective of processing mechanism and data fusion, a material geometry removal behavior model of the digital twin system is established, forming a key enabling technology for the digital twin system. Massive multi-source heterogeneous data fusion is achieved through the flow of energy flow, material flow and information flow in the digital twin grinding system to maintain real-time symmetry between the physical system and the virtual system. The method can detect the contour of complex curved workpieces in real time with high precision without the need for any additional sensor equipment. By improving detection accuracy and production efficiency, reducing costs and enhancing applicability, the present invention has broad application prospects in the field of workpiece processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of the real-time interpolation and reconstruction method of workpiece surface morphology based on digital twins.

[0056] Figure 2 It is a schematic diagram of the interference removal between the workpiece and the tool during the machining process, where a) is a schematic diagram of the wear mark formation process on the workpiece surface; b) is the workpiece surface formation process when the wear mark residual height is greater than the grinding depth; c) is the workpiece surface formation process when the wear mark residual height is less than the grinding depth; d) is the influence of plastic deformation on the grinding morphology; e) is the grinding morphology interpolation algorithm considering plastic deformation and external disturbance.

[0057] Figure 3 Schematic diagram of real-time interpolation and reconstruction of workpiece surface morphology based on the digital twin system, where a) represents the overall path of the workpiece surface based on the digital twin real-time data before interpolation; b) represents the workpiece surface path after interpolation of the digital twin path driven by data and mechanism; c) is the distribution of a part of the workpiece surface morphology data points intercepted from the path after interpolation.

[0058] Figure 4 It is the real-time interpolation and reconstruction result of the workpiece surface morphology based on digital twin during the grinding process.

[0059] Figure 5 It is the real-time interpolation and reconstruction result of the workpiece surface morphology based on digital twin under different end face grinding processes. a)-f) represent the real-time interpolation results of the surface morphology of the corresponding processes at different times under end face grinding.

[0060] Figure 6 It is a comparison between the real-time interpolation and reconstruction results of the workpiece surface morphology based on the digital twin and the actual processing results of the workpiece, where a) represents the real-time interpolation and reconstruction results of the workpiece surface morphology based on the digital twin; b) is the actual processing effect of the workpiece surface morphology. DETAILED DESCRIPTION

[0061] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0062] Example

[0063] A real-time interpolation and reconstruction method for workpiece surface morphology based on digital twins, the steps are as follows:

[0064] S1: Building a digital twin system

[0065] A digital twin system is built on a CNC machine tool, including a real physical environment and a virtual simulation environment. The real physical environment is the CNC machine tool and the workpiece it processes, and the virtual simulation environment is a digital model corresponding to the real physical environment. The digital twin system obtains the operating data of the CNC machine tool in real time through the data acquisition module, including tool position, workpiece position, and processing parameters.

[0066] In the virtual simulation environment, the three-dimensional information of the workpiece is used to build the corresponding model file and startup file to achieve the mapping of the workpiece in the virtual simulation environment to the real environment. By continuously updating the model in the virtual simulation environment, it is kept highly consistent with the workpiece in the real physical environment.

[0067] The five-dimensional architecture of the digital twin machine tool established by the present invention mainly includes physical entity PE, virtual entity VM, service SS, twin data DD, and links CN between the components, such as Figure 1 As shown, it can be expressed as:

[0068] CNCGM-DT={PE,VM,SS,DD,CN} (15)

[0069] Virtual entities can describe the geometric information of the tool system, including the initial geometry and the machining geometry. The initial geometry represents the original shape of the workpiece and tool, including the arc radius of the tool, the geometric dimensions of the cutting edge, the diameter and length of the workpiece, etc. The machining geometry reflects the changed geometry. During the grinding process, the feed rate, grinding depth and grinding time determine the material removal value, the spindle speed and feed rate determine the wear scar spacing, and then determine the wear scar morphology, such as Figure 2 As shown. The established virtual entity model can be expressed as:

[0070]

[0071] Among them, R s v w a p etc. respectively represent the relevant parameters of the tool system: R s is the grinding wheel radius, v w a p are the parameters such as feed speed and grinding depth. h θh and others represent the relevant geometric parameters of the workpiece system: R h is the residual height of the wear scar on the workpiece surface, θ is the angle between the grinding point and the contact point of the grinding wheel, and h is the distance between the grinding points. dx and dz represent the influence of environmental factors on the tool system, dx is the disturbance of the environment on the tool system in the x direction, and dz is the disturbance of the environment on the tool system in the z direction.

[0072] like Figure 2 As shown in (a), when h>2R s And a p <R s Sometimes:

[0073] R h =a p (17)

[0074] When 0<h≤2Rs Sometimes:

[0075]

[0076] when a p ≤R h Same as formula 17 and formula 18.

[0077] As the grinding depth increases, the material undergoes elastic deformation-plastic deformation-material removal. When the material undergoes plastic deformation, the actual cutting depth will change. The main consideration is the impact of plastic deformation on the surface morphology of the material. When the actual grinding point deviates from the theoretical grinding point due to elastic-plastic deformation, the two adjacent grinding points (x a ,z a ,c a ) and grinding point (x b ,z b ,c b ) between the i-th actual grinding point coordinates (x i ,z i ,c i ):

[0078]

[0079] where h a are two adjacent grinding points (x a ,z a ,c a ) and grinding point (x i ,z i ,c i ) in the X direction, h b are two adjacent grinding points (x i ,z i ,c i ) and grinding point (x b ,z b ,c b ), and h(F,E,ΔR) represents the influence of grinding force, material properties and grinding wheel radius change on h.

[0080]

[0081] where h b+ ,h b- They represent the size of the deviation distance in the X direction under dx and dz disturbances respectively, and A, C, and Ψ are the corresponding parameter calculation symbols respectively.

[0082] S2: Real-time point-by-point measurement

[0083] During the workpiece processing, the CNC machine tool's own control system is used to obtain the position information of the contact point between the tool and the workpiece in real time. Through the encoder, sensor and other equipment of the CNC machine tool, the coordinates of each processing point are accurately recorded, including the position information of the X-axis, Z-axis and C-axis. By controlling the tool to move on the workpiece surface, the position information of each contact point is recorded in real time. In order to ensure the accuracy and reliability of the measurement, a reasonable feed speed and cutting depth can be set to avoid excessive errors during the measurement process.

[0084] Combined with the real-time position feedback signal and power signal of the machine tool in the machine tool coordinate system, the surface processing state of the workpiece is judged by the change of the time domain signal of the X, Z, and C axes in the machine tool coordinate system, and then the real-time grinding state of the workpiece is obtained. The real-time position signal of the machine tool can be expressed as:

[0085]

[0086] Among them, x instruction , z instruction , c instruction are the command positions of the XZC coordinates in the NC program after being discretized by the machine tool NC program, and x actual , z actual , c actual They are the actual positions of the XZC coordinates in the machine tool coordinate system during grinding, and the difference between them is x pe , z pe , c pe These are the influences on the three coordinates X, Z and C during the grinding process.

[0087] Based on this, the real-time position signal of the machine tool can be converted into spatial coordinates:

[0088]

[0089] In order to achieve point-by-point measurement, the point-by-point measurement mode can be set in the control system of the CNC machine tool. By controlling the tool to move on the workpiece surface, the position information of each contact point can be recorded in real time. At the same time, by controlling the tool feed speed and cutting depth, the accuracy and reliability of the measurement can be guaranteed.

[0090] S3: Data interpolation processing

[0091] Use programming software such as MATLAB and Python to implement data interpolation processing. According to the shape and accuracy requirements of the workpiece, select the appropriate interpolation method and interpolation parameters. Import the point-by-point measurement data into the programming software, perform interpolation calculations, and obtain a complete set of data points on the workpiece surface. The point-by-point measurement data obtained is usually sparse. In order to reconstruct the complete morphology of the workpiece surface, data interpolation processing is required. Data interpolation processing includes selecting a suitable interpolation method and setting reasonable interpolation parameters. Establish a digital twin system and propose the resolution of real-time morphology fitting of the workpiece:

[0092]

[0093] Where R path is the resolution in the machining path direction, R ⊥path is the resolution perpendicular to the machining path, feed is the feed speed, and f is the sampling frequency. By selecting a suitable sampling frequency, nanometer-level resolution can be easily achieved, while the resolution perpendicular to the machining direction is significantly related to the process parameters. As shown in Table 1, it can be found that the feed amount per revolution of the workpiece under different process parameters is significantly different. The feed amount per revolution under end face grinding is 60μm, while the feed amount per revolution under cylindrical grinding is 300μm. This means that the resolution in the feed amount direction per revolution during cylindrical grinding is 300μm; although it can be achieved by adjusting process parameters such as reducing the feed speed and increasing the spindle speed, it will inevitably affect the processing quality of the product.

[0094] Table 1 Processing parameters

[0095]

[0096] According to the fitting algorithm proposed in the previous section, an improved fitting algorithm under given process parameters can be established, such as Figure 3 As shown in Figure 2, a part of the path is randomly intercepted on the cylindrical workpiece. According to Formula 23, it can be found that when the sampling frequency is 500Hz, the resolution in the path direction is 0.5μm, while the resolution perpendicular to the path direction is only 300μm. In order to improve the fitting accuracy and make the fitting resolution in the two directions not too different, the interpolation times can be selected according to Formula 24, and the surface microscopic interpolation fitting based on data-mechanism can be performed on the workpiece surface by adopting the interpolation fitting algorithm described in the previous section.

[0097]

[0098] Where n is the number of interpolation times, R tar For the ideal resolution, R is usually taken tar =[R path ,R ⊥path ] minBased on this, the interpolation algorithm can be adjusted according to the shape fitting accuracy requirements to further improve the fitting of the workpiece surface shape.

[0099] like Figure 3 (b) and (c) show the distribution of data points on the cylindrical surface after interpolation, where the asterisks are the original data and the solid points are the interpolated data points. By adjusting the interpolation parameters, the interpolation results can be optimized and the accuracy and efficiency of reconstruction can be improved.

[0100] S4: Surface topography reconstruction

[0101] After data interpolation processing, a complete set of data points on the workpiece surface is obtained. These data points are used to reconstruct the morphology of the workpiece surface in a virtual simulation environment. The reconstruction process includes steps such as generating a three-dimensional mesh model, calculating the surface normal vector, and performing smoothing. Using three-dimensional modeling software or special surface reconstruction software, a three-dimensional mesh model is generated based on the interpolation results. The surface normal vector is calculated and smoothed to obtain a three-dimensional model that conforms to the shape characteristics of the actual workpiece. When generating a three-dimensional mesh model, adjacent data points are connected according to the interpolation results to form a triangular or quadrilateral mesh. When calculating the surface normal vector, the position information of the mesh vertices is used to calculate the normal vector of each vertex for subsequent lighting and rendering processing. When smoothing, the position of the mesh vertices is adjusted to make the surface smoother and conform to the shape characteristics of the actual workpiece.

[0102] like Figure 4 The figure shows the real-time monitoring process of a single end face part during grinding. It can be found that material removal begins when the grinding wheel contacts the workpiece at point A, and the workpiece surface is gradually formed. The method described in the previous section is used to fit the workpiece surface morphology in real time. It can be found that as the grinding progresses, the workpiece surface gradually shows the corresponding grinding effect. The fitted surface morphology also reflects the change of real-time load, and finally the end face workpiece grinding is completed at point E.

[0103] Through the above process, it can be found that the digital twin model established by the present invention can realize real-time monitoring of the product grinding process, and can accurately reflect the causes and impacts of the current errors.

[0104] S5: High-precision real-time in-situ detection

[0105] Set up a real-time detection mode in the control system of the CNC machine tool. Obtain the tool position information in real time and compare it with the model in the virtual simulation environment to determine whether the tool collides or deviates from the workpiece surface. According to the comparison results, adjust the tool position and processing parameters to achieve high-precision real-time in-situ detection.

[0106] By continuously adjusting the tool position and processing parameters, the contact point between the tool and the workpiece surface is kept within the predetermined error range. At the same time, the real-time feedback function of the digital twin system is used to monitor the error changes during the processing in real time and make compensation adjustments to achieve high-precision real-time on-site detection.

[0107] In addition, the digital twin system established by the present invention can not only realize the real-time monitoring of the processing of a single workpiece, but also realize the real-time morphology fitting results of the workpiece during the continuous processing of multiple steps, such as Figure 5 The figure shows the real-time processing effect of the end face blank under different processes. It can be found that the change of real-time load has a greater impact on the surface accuracy of the workpiece; and as the grinding progresses, the surface shape and accuracy of the workpiece processed area are gradually improved, and can be displayed in real time through the digital twin system. The predicted morphology and actual morphology of the workpiece are shown as follows: Figure 6 As shown in (a) and (b), the two are very consistent, indicating that the real-time fitting method proposed in the present invention can effectively realize the real-time fitting of the workpiece surface morphology.

[0108] The technical effects of the present invention are mainly reflected in the following aspects:

[0109] 1. Improve detection accuracy

[0110] By building a digital twin system, point-by-point measurement and interpolation reconstruction can be achieved during the workpiece processing process, and high-precision surface morphology data can be obtained without additional sensor equipment. Compared with traditional detection methods, the detection accuracy of the present invention is higher and can meet the high-precision detection requirements of complex curved surface workpieces.

[0111] 2. Improve production efficiency

[0112] By using the CNC machine tool's own control system and sensors, real-time point-by-point measurement and in-situ detection can be achieved without interrupting the processing flow for scanning. At the same time, through data interpolation processing and surface morphology reconstruction, the complete morphology of the workpiece surface can be quickly obtained, improving production efficiency.

[0113] 3. Reduce costs

[0114] The detection method of the present invention does not require additional sensor equipment, thereby reducing the detection cost. At the same time, by improving the detection accuracy and production efficiency, the scrap rate and rework rate are reduced, further reducing the production cost.

[0115] 4. Strong applicability

[0116] The detection method of the present invention is suitable for high-precision detection of various complex curved surface workpieces. By adjusting the interpolation method and parameters, it can adapt to workpieces of different shapes and precision requirements. At the same time, by using the real-time feedback function of the digital twin system, the error changes in the processing process can be monitored in real time, and compensation adjustments can be made to improve the applicability and flexibility of the detection.

[0117] Based on the hybrid drive method proposed in the present invention, the processing state in the grinding process can be monitored in real time through the digital twin grinding system, and the workpiece morphology can be estimated in real time, realizing the visual prediction of the workpiece processing accuracy. On this basis, the source of the processing error can be traced, and the cause of the workpiece error can be clarified, providing a theoretical basis for further improving product accuracy and improving product quality. The results show that the real-time monitoring of the grinding state by the digital twin method established by the present invention has the advantages of high accuracy, strong reliability, and convenient implementation.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A real-time interpolation and reconstruction method for workpiece surface morphology based on digital twin, characterized in that: The steps are as follows: S1: Build a digital twin system A digital twin system is built on a CNC machine tool, including a real physical environment and a virtual simulation environment; the real physical environment is the CNC machine tool and the workpiece it processes, and the virtual simulation environment is a digital model corresponding to the real physical environment; the digital twin system obtains the operating data of the CNC machine tool in real time through the data acquisition module, including the tool position, workpiece position and processing parameters; In the virtual simulation environment, the three-dimensional information of the workpiece is used to build the corresponding model file and startup file to achieve the mapping of the workpiece in the virtual simulation environment to the real environment; by continuously updating the model in the virtual simulation environment, it is kept highly consistent with the workpiece in the real physical environment; The five-dimensional architecture of the digital twin machine tool is established, including the physical entity PE, the virtual entity VM, the service SS, the twin data DD and the links CN between the components, which can be expressed as: CNCGM-DT={PE,VM,SS,DD,CN} (1) The virtual entity describes the geometric information of the tool system, including the initial geometry and the machining geometry; the initial geometry represents the original shape of the workpiece and tool, including the arc radius of the tool, the geometric dimensions of the cutting edge, the diameter and length of the workpiece; the machining geometry reflects the changed geometry; In the grinding process, the feed speed, grinding depth and grinding time determine the material removal value, the spindle speed and feed speed determine the wear scar spacing, and then determine the wear scar morphology; the established virtual solid model is expressed as: Among them, R s 、v w 、a p Respectively represent tool system related parameters: R s is the grinding wheel radius, v w 、a p are feed speed and grinding depth respectively; R h , θ, and h represent the geometric parameters of the workpiece system: R h is the residual height of the wear scar on the workpiece surface, θ is the angle between the grinding point and the contact point of the grinding wheel, and h is the distance between the grinding points; dx and dz represent the influence of environmental factors on the tool system, dx is the disturbance of the environment on the tool system in the x direction, and dz is the disturbance of the environment on the tool system in the z direction; When h>2R s And a p <R s Sometimes: R h =a p (3) At this time, the grinding pattern cannot completely cover the workpiece surface, that is, the quality of the product cannot be controlled. Based on this, the overlap rate K is defined s =Removal volume / total volume=Removal volume / (Removal volume+Residual height volume) to characterize the processing quality of the material: By definition, the higher the overlap, the more fully the material is processed: When 0<h≤2R s Sometimes: when a p ≤R h Same as formula (5) and formula (6); when R h <a p When ≤R, we have formula (7): in, As the grinding depth increases, the material undergoes elastic deformation-plastic deformation-material removal in succession; when the material undergoes plastic deformation, the actual cutting depth will change, mainly considering the influence of plastic deformation on the surface morphology of the material; when the actual grinding point deviates from the theoretical grinding point due to elastic-plastic deformation, the two adjacent grinding points (x a ,z a ,c a ) and grinding point (x b ,z b ,c b ) between the i-th actual grinding point coordinates (x i ,z i ,c i ): Among them, h a are two adjacent grinding points (x a ,z a ,c a ) and grinding point (x i ,z i ,c i ) in the X direction, h b are two adjacent grinding points (x i ,z i ,c i ) and grinding point (x b ,z b ,c b ), h(F,E,ΔR) represents the influence of grinding force, material properties and grinding wheel radius on h, h b+ ,h b- They represent the magnitude of the deviation distance in the X direction under dx and dz disturbances, respectively, and A, C, and Ψ are the corresponding parameter calculation symbols; S2: Real-time point-by-point measurement During the workpiece processing, the CNC machine tool's own control system is used to obtain the position information of the contact point between the tool and the workpiece in real time; the encoder and sensor of the CNC machine tool record the coordinates of each processing point, including the position information of the X-axis, Z-axis and C-axis; Combined with the real-time position feedback signal and power signal of the machine tool in the machine tool coordinate system, the surface processing state of the workpiece is judged by the change of the time domain signal of the X, Z, and C axes in the machine tool coordinate system, and then the real-time grinding state of the workpiece is obtained; the real-time position signal of the machine tool is expressed as: Among them, x instruction 、z instruction 、c instruction are the command positions of the XZC coordinates in the NC program after being discretized by the machine tool NC program, and x actual 、z actual 、c actual They are the actual position of the XZC coordinate in the machine tool coordinate system during grinding, and the difference between the command position and the actual position x pe 、z pe 、c pe They are the influences of the three coordinates X, Z and C during the grinding process; Based on this, the real-time position signal of the machine tool is converted into spatial coordinates: In order to achieve point-by-point measurement, a point-by-point measurement mode is set in the control system of the CNC machine tool. By controlling the tool to move on the workpiece surface, the position information of each contact point is recorded in real time. At the same time, the feed speed and cutting depth of the tool are controlled to ensure the accuracy and reliability of the measurement. S3: Data interpolation processing The point-by-point measurement data obtained are relatively sparse. In order to reconstruct the complete morphology of the workpiece surface, data interpolation processing is required; data interpolation processing includes selecting the interpolation method and setting the interpolation parameters; establishing a digital twin system and proposing the resolution of the real-time morphology fitting of the workpiece: Among them, R path is the resolution in the machining path direction, R ⊥path is the resolution perpendicular to the machining path, feed is the feed speed, and f is the sampling frequency. The nanometer-level resolution is achieved by selecting the sampling frequency, while the resolution perpendicular to the machining direction is significantly related to the process parameters. A real-time interpolation algorithm based on the tool-workpiece contact model is established, and an improved fitting algorithm under given process parameters is established; in order to improve the fitting accuracy, the interpolation times are selected according to formula (14), and the surface microscopic interpolation fitting of the workpiece surface is performed based on data-mechanism by adopting the interpolation fitting algorithm; Where n is the number of interpolation times, R tar For the ideal resolution, take R tar =[R path ,R ⊥path ] min ; Based on this, the interpolation algorithm needs to be adjusted according to the shape fitting accuracy to further improve the fitting of the workpiece surface shape; By adjusting the interpolation parameters, the interpolation results are optimized to improve the accuracy and efficiency of reconstruction; S4: Surface topography reconstruction After data interpolation processing, a complete set of data points on the workpiece surface is obtained; using these data points, the morphology of the workpiece surface is reconstructed in a virtual simulation environment; the reconstruction process includes generating a three-dimensional mesh model, calculating the surface normal vector, and performing smoothing processing; When generating a 3D mesh model, adjacent data points are connected according to the interpolation results to form a triangular or quadrilateral mesh; when calculating the surface normal vector, the position information of the mesh vertices is used to calculate the normal vector of each vertex for subsequent lighting and rendering processing; when smoothing, the position of the mesh vertices is adjusted to make the surface smoother and in line with the shape characteristics of the actual workpiece; S5: High-precision real-time in-situ detection After the reconstruction is completed, the surface morphology of the workpiece in the virtual simulation environment is compared with the workpiece in the real physical environment. The position information of the tool is obtained in real time by using the control system of the CNC machine tool, and compared with the model in the virtual simulation environment to determine whether the tool collides with or deviates from the workpiece surface. By continuously adjusting the position of the tool and processing parameters, the contact point between the tool and the workpiece surface is kept within the predetermined error range. At the same time, the real-time feedback function of the digital twin system is used to monitor error changes during the processing process in real time, and compensatory adjustments are made to achieve high-precision real-time in-situ detection.

2. The method for real-time interpolation and reconstruction of workpiece surface morphology based on digital twin according to claim 1 is characterized in that: The interpolation methods include linear interpolation, quadratic interpolation and cubic interpolation.

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