A method for realizing simulation of a deformation motion component for digital twinning

Abstract

The application discloses a kind of deformation motion component simulation implementation methods for digital twin, it is characterized by: first, standard parameter numerical model is preprocessed, to provide model basis for motion simulation;Second, according to the reconstruction of skeleton chain model based on root skeleton ID, from single chain to double chain;Third, in the twin system, the flexible track model is driven to produce deformation based on bidirectional chain transmission model, and finally the installation of track is completed;Fourth, after the completion of track installation, the position coordinates of each vacuum chuck are read and stored, and based on curve or surface fitting algorithm, the coordinate information is fitted as the trajectory control curve or surface of motion component, so as to determine the pose of motion component.The application greatly reduces the workload of developing twin system for different products.

Description

Technical Field

[0001] This invention relates to a method for simulating deformable motion components in digital twins, particularly to equipment such as flexible tracks that adhere to product surfaces through component deformation, and to a method for realizing the deformation motion and moving components within a digital twin system. Specifically, addressing the problem that simulations of such equipment, often using a single digital model for each product, fail to reflect the actual installation and use of the equipment and do not meet the requirements of digital twins for the entire manufacturing process, this invention provides a solution for realizing deformable motion components in digital twins. This solution can be used to visualize the deformation process of flexible components in a digital twin system and to generate deformable motion components online. Background Technology

[0002] In practical manufacturing fields such as aerospace assembly, intelligent equipment with deformable kinematic pairs, such as flexible tracks, is often used. To solve the simulation problem of such equipment, most current methods adopt the approach of building a digital model for each product, which cannot reflect the actual installation and use of the equipment and does not meet the requirements of digital twins for the entire manufacturing process. Therefore, how to handle intelligent equipment with deformable kinematic pairs is also a key problem that needs to be solved. This involves two aspects: first, how to realize the visualization and control of the deformation process of flexible components in the twin system; second, how to realize the online generation of deformable kinematic components.

[0003] Currently, common methods for visualizing the deformation of flexible components include:

[0004] The first method simulates flexible fabric for character clothing. This physically based fabric simulation is only effective for skinned meshes and can achieve random fluttering effects for models such as flags, clothes, and hair. However, this solution struggles to achieve precise interactive control of deformation motion and cannot meet the real-time control requirements for precise deformation motion of some components in industrial applications.

[0005] The second approach involves defining a mesh component for the model, which includes geometric information such as the model's vertices, triangles, and normals. This approach provides a solution for deforming components by controlling the mesh vertices. This method can be applied to deformation problems involving small areas and a small number of vertices with clear movement patterns. However, for components with large-area deformation, due to the complexity of the components and the large number of vertices, it is difficult to find a common movement pattern for each vertex, thus making it impossible to accurately control the deformation movement of components with large-area deformation.

[0006] The third approach considers an animation perspective. This involves pre-creating the component's deformation animation in animation software such as Blender or 3ds Max and importing the animation into the simulation platform. The platform then controls the animation's playback timing based on trigger states. This method can be applied to offline simulations of some known deformation animations, but it struggles to meet the real-time control requirements of digital twins.

[0007] The solutions mentioned above cannot meet the requirements for visualizing the large-area deformation of flexible components in intelligent equipment with deformable kinematic pairs, nor can they enable the online generation of deformable kinematic components. Therefore, it is necessary to implement a simulation method for deformable kinematic components in digital twins, which can be used to address the challenges of visualizing the deformation process of flexible components in twin systems and enabling the online generation of deformable kinematic components. Summary of the Invention

[0008] The purpose of this invention is to address the problems of visualizing the deformation process of flexible components and generating deformable motion components online in digital twin systems, and to develop a method for simulating deformable motion components in digital twins.

[0009] The technical solution of this invention is:

[0010] A method for simulating deformable and moving parts for digital twins, characterized by:

[0011] First, the standard industrial model is preprocessed to provide a model foundation for subsequent deformation control. Specifically, this includes the following three steps: First, the 3D digital model is discretized and its format converted. Second, the vertices of the discretized model are grouped using a skeletal binding technique. A bone chain with parent-child relationships is established from left to right, with a specific location on the model as the starting point of the root bone and a specific feature dimension of the model as the length of each bone segment. Each bone segment corresponds to a part on the model that contacts other components. To facilitate bone movement control, each bone segment is assigned an ID, ranging from 0 to n from left to right. Third, appropriate colliders are added to each bone segment, and mesh colliders are added to components that have contact with the deformable part. Collision detection is used to determine whether the contacting parts of the deformable part at the corresponding segment have touched the contacting parts of the product to be processed, thus determining whether the deformable part has reached the working position.

[0012] Second, the skeletal chain inheritance relationship is reconstructed online, changing from a single chain to a double chain, providing the correct chain transmission structure for the bending deformation of deformable parts. Specifically, the deformable part, starting from the first contact part it touches on the product during installation, sequentially adheres to the product surface in a bidirectional chain diffusion. Corresponding to the skeletal chain model mentioned above, this requires the bone corresponding to the first vacuum suction cup adhering to the skin to be the root bone (assuming its ID is r). This root bone should have two child bone chains, left and right. Based on the skeletal chain model constructed in the first part, the following adjustments are made: the right bone of the root bone (bones with IDs r+1 to n) meets the required inheritance relationship and can be directly used as the right child bone chain of the root bone. However, the inheritance relationship of the left bone (bones with IDs r-1 to 0) is completely opposite, requiring reconstruction of the left bone chain. To avoid the generation of wave bending effect, a bone space loading bone scheme is adopted, and the inheritance relationship of the bone space is constructed to generate a new bone space chain, which serves as the left child bone chain of the root bone.

[0013] Third, the deformation of deformable components is controlled by a program within the twin space. Specifically, after the contact parts corresponding to the root skeleton are attached to the product component, the ID of the skeleton to be moved is transferred to both sides as r-1 and r+1. When the suction cup with ID r-1 is attached to the surface, it continues to be transferred forward to the skeleton with ID r-2. Similarly, when the suction cup with ID r+1 is attached to the surface, it continues to be transferred forward to the skeleton with ID r+2, and so on, performing a bidirectional chain transfer on the skeletons to be moved on both sides until the vacuum suction cups corresponding to the skeletons with ID 0 and ID n are attached to the product component.

[0014] Fourth, online generation of deformable moving parts. Specifically, after the deformable part is fully attached to the product, the coordinate information of the contact positions of each contacting part can be obtained. This set of coordinate information is stored from left to right, and based on curve or surface fitting algorithms, the coordinate information is fitted into a trajectory control curve or surface of the moving part. Specifically, for parts with curved motion, a piecewise polynomial curve Curve(U) that can be controlled by a parameter U can be generated based on the Hermite curve interpolation algorithm. Any point P on the curve can be represented as a function of U, P = (X(U), Y(U), Z(U)). Differentiating this function with respect to U yields another Hermite curve, Tangent(U). The function value of this curve represents the shear at the corresponding point. In the twin system, the pose of the moving part along the deformable part can be determined based on these two curves. The Curve(U) curve is used to determine the position of the moving part, and the Tangent(U) curve is used to determine the attitude of the moving part.

[0015] The beneficial effects of this invention are:

[0016] This invention solves the problems of visualizing the deformation process of flexible components and online generation of deformable moving parts in digital twin systems. It utilizes skeletal rigging technology to group and control model vertices, employs collision detection technology for real-time qualitative monitoring of the deformation state of each segment of the model, and transmits the motion state of each bone segment in the skeletal chain through a bidirectional chain. Based on curve or surface fitting algorithms, the coordinate information is fitted into the trajectory control curve or surface of the moving part, thereby achieving the visualization of the deformation motion of flexible components and the definition of the trajectory of deformable moving parts in a digital twin system. This solution has the following significant advantages:

[0017] First, this method provides a set of visualization and control methods for the deformation motion of flexible components in a digital twin system. It can dynamically display the deformation animation of the model in real time in the twin system. This technology can more realistically restore the on-site work preparation status and process, and provide technical support for training and twinning.

[0018] Second, this method provides an online means of generating the deformed state of flexible components, thereby avoiding the work of modeling equipment specifically for a particular product, thus forming a general method for defining equipment motion models, which greatly reduces the workload of developing twin systems for different products.

[0019] Third, this method uses skeletal binding to group the vertices of the discretized model. Therefore, it is not necessary to process the massive vertex data in the twin system. This will reduce a lot of tedious calculations, save a lot of memory and computational consumption, and make it possible to display the deformation and motion of flexible parts in the twin system in real time.

[0020] Fourth, this method uses a curve or surface fitting algorithm to fit the coordinate information of the contact positions of each contacting part online to obtain the motion trajectory of the moving part, thereby realizing the motion simulation of the deformable part after deformation online.

[0021] Finally, this method can dynamically adjust the pose of devices and products based on online data, thus providing a method for digital twins. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method for implementing deformable moving parts for digital twins according to the present invention.

[0023] Figure 2 This is a schematic diagram of the parameter model of the present invention.

[0024] Figure 3 This is a schematic diagram of the discretization model of the present invention.

[0025] Figure 4 This is a schematic diagram of the skeletal binding model of the present invention.

[0026] Figure 5 This is a schematic diagram of the wave bending effect on the left side of the present invention.

[0027] Figure 6 This is a schematic diagram showing the installation of the flexible track drilling equipment of the present invention.

[0028] Figure 7 This is a schematic diagram of n Hermite curve segments of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] like Figure 1-7 As shown.

[0031] A simulation method for deformable motion components based on digital twins, taking a flexible track drilling system as an example, includes the following steps:

[0032] First, the digital model of the equipment to be deformed needs to be preprocessed. Taking a flexible track equipment system as an example, it includes the following three steps: The first step is to discretize and convert the format of the three-dimensional digital model, and to perform parameterized industrial model (such as...) Figure 2 As shown, a mosaic subdivision operation is performed. Specifically, for the flexible track model, subdivision processing yields a discretized model (such as...). Figure 3 (As shown); The second step is to group the vertices of the discretized model. This can be done using a skeletal binding function. Vertices are grouped and controlled via bones. The leftmost end of the model is taken as the starting point of the root bone, and the horizontal dimension of the vacuum suction cup is used as the length of each bone segment. A bone chain with parent-child relationships is established from left to right. Each bone segment in the chain is associated with a corresponding vacuum suction cup on the model. To facilitate bone movement control, each bone segment is assigned an ID, ranging from 0 to n from left to right. The basic idea of ​​skeletal binding is to bind the model vertices to bones. When the bones are driven to move, the vertices move, thus achieving the deformation movement of the track. A schematic diagram of the skeletal binding model is shown below. Figure 4 As shown, since the vacuum suction cup can be considered a rigid part and its deformation is not considered, it is necessary to manually brush the weights when binding the bones so that each bone strictly controls one suction cup. The third step is to add colliders to the model. Specifically, since the size of each suction cup is known, a spherical collider (the spherical collider has the highest computational efficiency) can be added to each bone segment to surround the corresponding vacuum suction cup. The shape of the skin surface is determined according to the specific workpiece, so a mesh collider can be used on the skin to improve the suction cup adsorption accuracy.

[0033] Second, after the track-feeding process is completed, the skeleton chain needs to be reconstructed based on the first suction cup adsorbed on the workpiece. Specifically, the skeleton corresponding to the first vacuum suction cup adsorbed on the skin is taken as the root skeleton (assuming its ID is r). This root skeleton should have two child skeleton chains, left and right. Based on the skeleton chain model constructed in the first part, the following adjustments are made: the right skeleton of the root skeleton (the skeleton with IDs r+1 to n) meets the required inheritance relationship and can be directly taken as the right child skeleton chain of the root skeleton. However, the inheritance relationship of the left skeleton (the skeleton with IDs r-1 to 0) is completely reversed, and the left skeleton chain needs to be reconstructed. However, directly reversing the parent-child relationship will produce a wave-like bending effect (such as...). Figure 5 As shown in the diagram, the reason is that the pivot of each bone segment is at the head of the bone. When the parent-child relationship is reversed, it is desired to rotate with the tail of the bone as the pivot. However, in reality, the pivot of the bone cannot and will not change. If no other measures are taken, the above-mentioned wave bending effect will occur. To avoid this phenomenon, a bone space loading scheme is adopted. An empty object is created at the tail of each bone as the bone space of that bone, and the inheritance relationship of the bone space is constructed to generate a new bone space chain, which serves as the left child bone chain of the root bone.

[0034] Third, based on the bidirectional chain transmission model, the bending of the flexible track is controlled programmatically within the twin system. Specifically, two shaping parameters, a left vertex LID and a right vertex RID, are created to store the currently moving bone IDs on the left and right sides. The bone with ID LID rotates counterclockwise around the Z-axis, and the bone with ID RID rotates clockwise around the Z-axis. Initially, LID = r - 1 and RID = r + 1. When the left bone completes a collision, LID is decremented by 1, and when the right bone completes a collision, RID is incremented by 1, until the vacuum suction cups corresponding to the bones with IDs 0 and n are both attached to the skin surface, thus completing the installation of the flexible track drilling equipment (e.g., ...). Figure 6 (As shown).

[0035] Fourth, online construction of the deformation kinematic pairs. Specifically, after the flexible track is fully adsorbed onto the workpiece surface, the coordinate information of each vacuum chuck can be obtained. This coordinate information of the chuck is stored from left to right, and a piecewise polynomial curve Curve(U) that can be controlled by a parameter U is generated based on the Hermite curve interpolation algorithm. The specific Hermite curve interpolation algorithm is as follows:

[0036] The Hermite curve is a cubic curve, which ensures the continuity of the second derivative at the junction point when the two Hermite curves are connected, while avoiding curve oscillations and excessive computation caused by excessively high degree curves. A typical cubic parametric equation can be expressed as:

[0037]

[0038] In equation (11), u is a position parameter on the curve, and its geometric meaning is the percentage of the arc length of a point on the curve relative to the starting point to the entire curve segment. When u changes from 0 to 1, the point moves from the starting point of the curve to the ending point of the curve. and These are the vector coefficients of the parametric equations, which are row vectors containing x, y, and z components. Next, we will assign geometric meaning to this set of vectors; one possible choice is to use the position vectors of the curve's endpoints. and and the shear loss at both ends and Boundary conditions and Substituting into equation (11), we can solve for:

[0039]

[0040] Substituting equation (12) into equation (11), we obtain a new curve equation:

[0041]

[0042] Therefore, data points are given. The equation of each Hermite curve segment can be derived. From these n+1 points, n Hermite curve segments can be obtained (e.g., ... Figure 7 As shown), it is represented as

[0043] From equation (13), the i-th curve segment can be obtained. The expression is as follows:

[0044]

[0045] in, and These are data points and The shear rate, u, ranges from 0 to 1.

[0046] But the coefficients in equation (14) and Often the information is unknown, therefore constraints need to be added to determine it. and In fact, it is also necessary to impose constraints on the equations to ensure that all curve segments are second-order continuous:

[0047]

[0048] Solving equations (14) and (15) simultaneously yields:

[0049]

[0050] By replacing the values ​​of i from 1 to n-1 in equation (16), we can obtain the following matrix equation:

[0051]

[0052] Now we need to determine and One approach is for the designer to directly provide the cutoff values ​​at the start and end points. Another approach is to treat the start and end points as free ends, which is equivalent to the second derivative of the Hermite curve at the start and end points being zero. Therefore, the following constraint equations can be obtained:

[0053]

[0054] By combining equations (14) and (18), we can obtain:

[0055]

[0056] Combining equations (16) and (19), we obtain the following matrix equation:

[0057]

[0058] The n+1 unknowns are obtained by solving the n+1 equations in equation (20).

[0059] Therefore, after obtaining the position coordinates of each suction cup after the deformation motion ends, a set of Hermite curves can be constructed based on this algorithm, and a cubic polynomial parametric equation array can be used to store this set of curves. Since the parameter u of each Hermite curve ranges from 0 to 1, a single floating-point number U can be used as the overall position parameter of this set of piecewise curves. Here, U can be expressed as U = N + u, where the integer part N of U represents the equation of the Nth curve (0 ≤ N ≤ n and N is an integer), and the fractional part u represents the position parameter of the Nth equation (0 ≤ u < 1). In this way, a given U can uniquely correspond to a coordinate point on the piecewise curve.

[0060] The kinematic pairs constructed based on this algorithm depend on the position coordinates of each suction cup. Therefore, when the flexible track is laid on the skin surface with different curvatures, the position of each suction cup will change according to the skin contour, thereby realizing the flexibility of the curved kinematic pairs, that is, deformable kinematic pairs, which is more in line with the digital twin requirements of the entire manufacturing process.

[0061] In particular, in practical implementation, the model discretization process in the first step can also be performed using traditional finite element software.

[0062] The parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A method for realizing simulation of a deformation motion component oriented to digital twinning, Its features are as follows: First, the standard industrial model is preprocessed to provide a model basis for subsequent deformation control; second, the bone chain inheritance relationship is reconstructed online, changing from a single chain to a double chain, providing the correct chain transmission structure for the bending deformation of the deformable parts; third, the deformation of the deformable parts is controlled by the program in the twin space; specifically, after the contact part corresponding to the root bone is adsorbed onto the product part, the ID of the bone to be moved is transmitted to both sides as r-1 and r+1. When the suction cup with ID r-1 is adsorbed onto the surface, it continues to be transmitted forward to the bone with ID r-2. Similarly, when the suction cup with ID r+1 is adsorbed onto the surface, it continues to be transmitted forward to the bone with ID r+2, and so on, to perform bidirectional chain transmission of the bones to be moved on both sides until the vacuum suction cups corresponding to the bones with ID 0 and ID n are adsorbed onto the product part; Fourth, online generation of deformable moving parts; after the deformable part is completely attached to the product, the coordinate information of the contact position of each contacting part is obtained, and this set of coordinate information is stored from left to right. Based on the curve or surface fitting algorithm, the coordinate information is fitted into the trajectory control curve or surface of the moving part; for the part with curved motion, a piecewise polynomial curve Curve(U) controlled by a parameter U is generated based on the Hermite curve interpolation algorithm. Any point P on the curve is represented as a function of U P = (X(U), Y(U), Z(U)). The derivative of this function with respect to U yields a Hermite curve Tangent(U). The function value of this curve represents the shear of the corresponding point. In the twin system, the pose of the moving part along the deformable part is determined based on these two curves. The Curve(U) curve is used to determine the position of the moving part, and the Tangent(U) curve is used to determine the attitude of the moving part.

2. The method of claim 1, wherein: The preprocessing includes the following three steps: First, the 3D digital model is discretized and its format converted. Second, the vertices of the discretized model are grouped using a skeletal binding technique. A bone chain with parent-child relationships is established from left to right, with a specific location on the model as the starting point of the root bone and a specific feature dimension of the model as the length of each bone segment. Each bone segment corresponds to a part on the model that contacts other components. To facilitate bone movement control, each bone segment is assigned an ID, ranging from 0 to n from left to right. Third, appropriate colliders are added to each bone segment, and mesh colliders are added to components that have contact with the deformable part. Collision detection is used to determine whether the contacting part of the corresponding segment of the deformable part has touched the contacting part of the product to be processed, thus determining whether the deformable part has reached the working position.

3. The method of claim 1, wherein: The online reconstruction of the skeletal chain inheritance relationship starts from a contact part that the deformable component first touches on the product during installation, and then spreads outwards in a bidirectional chain to adsorb onto the product surface. Corresponding to the skeletal chain model, the first bone adsorbed onto the skin is the root bone (assuming its ID is r). This root bone should have two child bone chains, left and right. Based on the skeletal chain model constructed in the first part, the following adjustments are made: the right bone of the root bone (bones with IDs r+1 to n) meets the required inheritance relationship and can be directly used as the right child bone chain of the root bone. However, the inheritance relationship of the left bone (bones with IDs r-1 to 0) is completely opposite, and the left bone chain needs to be reconstructed. To avoid the wave bending effect, a bone space loading bone scheme is adopted, and the inheritance relationship of the bone space is constructed to generate a new bone space chain, which serves as the left child bone chain of the root bone.

4. The method of claim 1, wherein: The deformation of deformable components controlled by the program in the twin space refers to the following: after the contact parts corresponding to the root bones are adsorbed onto the product component, the ID of the bones to be moved is transferred to both sides as r-1 and r+1. When the suction cup with ID r-1 is adsorbed onto the surface, it continues to be transferred forward to the bone with ID r-2. Similarly, when the suction cup with ID r+1 is adsorbed onto the surface, it continues to be transferred forward to the bone with ID r+2, and so on, performing a bidirectional chain transfer on the bones to be moved on both sides until the vacuum suction cups corresponding to the bones with ID 0 and ID n are both adsorbed onto the product component.

5. The method of claim 1, wherein: The Hermite curve described is a cubic curve, which ensures the continuity of the second derivative at the connection point when the two Hermite curves are connected, while avoiding curve oscillations and excessive computation caused by excessively high curve degrees. The cubic parametric equation is as follows: In formula (11), and are the vector coefficients of the parametric equation, are row vectors with x, y, z components, and the following gives the geometric meaning to this set of vectors, using the position vectors of the two endpoints of the curve and and the tangent vectors T0 and T1 of the two endpoints Substitute the boundary conditions and into formula (11), and the solution is obtained: Substituting equation (12) into equation (11), we obtain a new curve equation: Thus, the data points The equation of each Hermite curve is found; from the n+1 points, n Hermite curves are found, denoted as From equation (13), the i-th curve segment can be obtained. The expression is as follows: in, and These are data points and The shear loss, u, ranges from 0 to 1; But the coefficients in equation (14) and Constraints need to be added to find the answer. and The value of is used to impose constraints on the equation to ensure that all curve segments are second-order continuous: Solving equations (14) and (15) simultaneously yields: Replacing the values ​​of i from 1 to n-1 in equation (16) yields the following matrix equation: Sure and The method is to directly provide the shear at the start and end points or treat the start and end points as free ends, which is equivalent to the second derivative of the Hermite curve at the start and end points being 0. Therefore, the resulting constraint equation is: Combining equations (14) and (18), we get: Combining equations (16) and (19), we obtain the following matrix equation: The n+1 unknowns are obtained by solving the n+1 equations in equation (20). After the deformation motion ends and the position coordinates of each suction cup are obtained, a set of Hermite curves are constructed based on the algorithm, and a cubic polynomial parametric equation array is used to store this set of curves. Since the position parameter u of each Hermite curve ranges from 0 to 1, a single floating-point number U is used as the overall position parameter of this set of piecewise curves. Here, U = N + u, where the integer part N represents the equation of the Nth curve (0 ≤ N ≤ n and N is an integer), and the fractional part u represents the position parameter of the Nth equation (0 ≤ u < 1). In this way, a given U can uniquely correspond to a coordinate point on the piecewise curve.

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