Mechanical digital design three-dimensional model building method and system

Abstract

This invention discloses a method for building a 3D model for mechanical digital design, belonging to the field of digital model generation technology. The method includes: acquiring the motion path of the mechanical design and correcting it using a curvature smoothing algorithm; determining the spatial boundary of the mechanical motion; generating a motion envelope based on the motion path and spatial boundary and performing compensation to generate the final envelope; using a tetrahedral partitioning algorithm to divide the final envelope into finite element elements and defining the shape function of each element; defining an objective function with lightweighting as the goal; constructing topology optimization constraints through the shape function; using SIMP to solve the objective function to obtain the lightweight model; and outputting the lightweight model according to a specified format for display and storage in a database. This invention effectively achieves the goals of high efficiency, accuracy, and lightweight design for complex mechanical 3D designs, improving the adaptability and flexibility of mechanical design.

Description

Technical Field

[0001] This invention relates to the field of digital model generation technology, and in particular to a method and system for building three-dimensional models for mechanical digital design. Background Technology

[0002] With the rapid development of advanced manufacturing technologies and the ever-increasing precision requirements of industrial design, computer-aided mechanical design and analysis have gradually become a key technology area. Especially in modern industry, 3D digital design technology has been widely applied in the research and development process of mechanical systems, connecting the entire process from conceptual modeling and analysis optimization to actual manufacturing. Traditional mechanical design methods rely heavily on experience and manual trial and error, while 3D digital methods, through computer modeling and simulation, can greatly improve design efficiency and accuracy, while reducing testing and manufacturing costs.

[0003] Although existing technologies have made significant progress in mechanical 3D modeling, they still have many technical bottlenecks. Existing methods often cannot universally take into account both kinematic and manufacturing process requirements, and lack flexibility in adapting to design objectives under different working conditions or boundary conditions. This makes it difficult for mechanical design to achieve an optimal balance with actual workspace constraints, motion accuracy requirements, and load-bearing capacity. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a method and system for building a three-dimensional model for mechanical digital design, which solves the problem that existing technologies cannot universally take into account both kinematic and manufacturing process requirements, and lack flexible adaptability to design objectives under different working conditions or boundary conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for constructing a three-dimensional model for mechanical digital design, comprising,

[0008] The mechanical design motion path is obtained and corrected using a curvature smoothing algorithm. The mechanical motion space boundary is determined, and a motion envelope is generated based on the motion path and space boundary. Compensation is then performed to generate the final envelope.

[0009] The final envelope is divided into finite element elements using the tetrahedral partitioning algorithm, and the shape function of each element is defined. The objective function is defined with lightweighting as the goal. Topology optimization constraints are constructed through the shape function, and the objective function is solved using SIMP to obtain the lightweight model.

[0010] After obtaining the lightweight model, output it in the specified format for display and store it in the database.

[0011] As a preferred embodiment of the mechanical digital design 3D model building method of the present invention, wherein: obtaining the mechanical design motion path and correcting it through a curvature smoothing algorithm, and determining the mechanical motion space boundary refers to generating the mechanical motion path based on the mechanical design requirements input mechanical motion requirement parameters. According to a fixed time interval motion path Discretize into a continuous point set Calculate the point set curvature at each discrete point ;

[0012] When the curvature of discrete points When the set curvature threshold is exceeded, the discrete point is taken as a high curvature point, and new path points are added around the high curvature point by cubic spline interpolation.

[0013] The discrete points after adding new path points are sorted and a new set of discrete points is output. The mechanical motion space boundary B is determined based on the set of discrete points.

[0014] As a preferred embodiment of the mechanical digital design three-dimensional model building method of the present invention, the step of generating a motion envelope based on the motion path and spatial boundary and compensating for it to generate the final envelope refers to constructing a simple initial surface by combining the minimum bounding box of the mechanical motion spatial boundary B with equidistant expansion, taking the surface points as the initial envelope points M, and calculating the minimum distance from the new discrete point set to the initial envelope points as the error function E.

[0015] Add smoothness and thickness constraints to the error function;

[0016] Take all the envelope points on the initial surface as the initial optimization variable X, calculate the error function value for the initial optimization variable, and calculate the gradient of the objective function with respect to the current initial optimization variable using the error function value;

[0017] The initial optimization variable X is updated according to the L-BFGS algorithm update rule. Optimization stops when the convergence condition is met, and the optimized envelope points are extracted. Form an optimized envelope surface;

[0018] Calculate the mechanical speed based on the distance between discrete points. ;

[0019] And adjust the calculation gap value for the optimized envelope point;

[0020] The optimized envelope points are adjusted based on the gap adjustment value to generate the final envelope points and form the final envelope surface.

[0021] As a preferred embodiment of the mechanical digital design three-dimensional model building method of the present invention, the method involves: using a tetrahedral partitioning algorithm to divide the final envelope into finite element elements and defining the shape function of each element; calculating the curvature of the envelope points based on the final envelope surface and calculating the average curvature of all envelope points. The mesh size is adjusted using an adaptive subdivision method based on the curvature. ;

[0022] Based on grid size The geometry formed by the final envelope surface is divided into tetrahedral elements using the Delaunay triangulation method. Each tetrahedral element consists of 4 vertex nodes and 6 edges. The quality of the divided tetrahedral elements is then checked.

[0023] For each tetrahedral element, the coordinates of its four vertices are set as follows: , , as well as The nodal shape function of the tetrahedral element is defined by a linear interpolation function. .

[0024] As a preferred embodiment of the mechanical digital design three-dimensional model building method of the present invention, the following steps are taken: defining an objective function with lightweighting as the goal, constructing topology optimization constraints through shape functions, and using SIMP to solve the objective function to obtain the lightweight model, wherein an initial material density is set for each tetrahedral element. And form a unit density matrix. The objective function is defined based on the unit density matrix with lightweighting as the goal. for;

[0025] Based on node shape function Obtain the strain-displacement matrix of the tetrahedral element by taking partial derivatives. ;

[0026] The strain-displacement matrices of all tetrahedral elements are used to construct a global strain-displacement matrix P, which is then synchronously calculated based on the strain-displacement matrix of each tetrahedral element. Generate the reference stiffness matrix for each element. ;

[0027] Calculate the global stiffness matrix K based on the reference stiffness matrix;

[0028] Calculate the global load distribution F based on the shape function;

[0029] The global stiffness matrix K and global load distribution F are obtained, and the global displacement vector U is obtained by solving the finite element method.

[0030] Derive the element strain tensor from the global displacement vector U. Stress constraints are added to all tetrahedral elements;

[0031] Add volume limits simultaneously;

[0032] The SIMP method is used to minimize the objective function while satisfying stress and volume constraints. During the optimization process, the cell density is updated iteratively.

[0033] The iteration stops once the objective function converges, and a lightweight model is output based on the density obtained after iteration.

[0034] As a preferred embodiment of the mechanical digital design three-dimensional model building method of the present invention, the step of outputting and displaying the lightweight model in a specific format after obtaining the lightweight model refers to outputting the lightweight model as a STEP format three-dimensional file and displaying it to the designers.

[0035] As a preferred embodiment of the mechanical digital design three-dimensional model building method of the present invention, the storage to the database refers to storing the obtained lightweight model in the design database and allocating timestamps to generate design logs for storage.

[0036] Secondly, this invention provides a mechanical digital design three-dimensional model building system, comprising,

[0037] The design and analysis module is used to obtain the mechanical design motion path and correct it through a curvature smoothing algorithm, determine the mechanical motion space boundary, generate a motion envelope based on the motion path and space boundary, and perform compensation to generate the final envelope.

[0038] The model generation module is used to divide the final envelope into finite element elements using the tetrahedral partitioning algorithm and define the shape function of each element. The objective function is defined with lightweighting as the goal. Topology optimization constraints are constructed through the shape function. The objective function is solved using SIMP to obtain the lightweight model.

[0039] The display storage module is used to output the lightweight model in a specified format for display and store it in the database.

[0040] Thirdly, the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein when the computer program is executed by the processor, it implements any step of the mechanical digital design three-dimensional model building method as described in the first aspect of the present invention.

[0041] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program is executed by a processor, it implements any step of the mechanical digital design three-dimensional model building method as described in the first aspect of the present invention.

[0042] The beneficial effects of this invention are as follows: By obtaining the motion path of mechanical design, and using curvature smoothing correction combined with motion envelope generation to obtain the mechanical design envelope surface, this invention effectively achieves the goals of high efficiency, accuracy and lightweight design of complex mechanical three-dimensional design by simultaneously using finite element partitioning combined with lightweight target setting optimization functions and constraints, thereby improving the adaptability and flexibility of mechanical design. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart of the method for building a three-dimensional model for mechanical digital design in Example 1.

[0045] Figure 2 This is a structural diagram of the mechanical digital design three-dimensional model building system in Example 1. Detailed Implementation

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0049] Example 1, referring to Figure 1 and Figure 2 This is the first embodiment of the present invention, which provides a method for building a three-dimensional model for mechanical digital design, including the following steps:

[0050] S1. Obtain the mechanical design motion path and correct it using a curvature smoothing algorithm. Determine the mechanical motion space boundary. Generate the motion envelope based on the motion path and space boundary and perform compensation to generate the final envelope.

[0051] Specifically, the mechanical design motion path is obtained and corrected using a curvature smoothing algorithm. Determining the mechanical motion space boundary involves generating the mechanical motion path based on the input mechanical motion requirement parameters according to the mechanical design requirements. ,in , For the motion path in time coordinates and The start and end times of the movement are based on a fixed time interval. motion path Discretize into a continuous point set Calculate the point set curvature at each discrete point :

[0052]

[0053] in and For the point set of the first discrete points The first derivative of the coordinates, and For the first discrete points The second derivative of the coordinates;

[0054] When the curvature of discrete points When the curvature exceeds a set threshold, discrete points are treated as high curvature points, and new path points are added around these high curvature points using cubic spline interpolation.

[0055]

[0056] in For the j-th new path point, For the first discrete points, The total number of new path points is set based on the curvature;

[0057] After adding new path points, the discrete points are organized and a new set of discrete points is output. The mechanical motion space boundary B is determined based on the set of discrete points.

[0058]

[0059] in and These represent the minimum and maximum limits of the path on the coordinate axes, respectively.

[0060] By calculating the curvature of each discrete point, high-curvature regions on the motion path can be accurately identified, and key points can be located according to a set threshold. New path points are added in high-curvature regions using cubic spline interpolation, thereby effectively smoothing the path. The mathematical properties of spline interpolation (such as continuous second derivatives) ensure the smoothness and connectivity of the new path, avoiding geometrical abrupt changes due to the addition of points. The spline method can add key information points without destroying the overall path structure, providing accurate input for subsequent topology optimization of the finite element method. In actual mechanical motion, it can reduce vibration and deviation caused by discontinuous paths. The use of adaptive boundaries makes the generation of motion envelopes more efficient, avoids unnecessary redundant design space, and improves the finite element partitioning and optimization effect within the boundary range.

[0061] Furthermore, based on the motion path and spatial boundary, a motion envelope is generated and compensated to generate the final envelope. This involves constructing a simple initial surface using the minimum bounding box of the mechanical motion spatial boundary B combined with equidistant expansion. The points on this surface are used as the initial envelope points M. The minimum distance from the new discrete point set to the initial envelope points is calculated as the error function E.

[0062]

[0063] in The number of envelope points, For the first An initial envelope point, In order to be with the first The nearest discrete point to the initial envelope point R is the penalty weight coefficient used to balance accuracy and smoothness. R is the regularization term used to control the geometric properties of the surface, such as smoothness or curvature. To ensure the smoothness of the envelope surface, the regularization term R is typically... ,in Let S be the second-order gradient of the envelope surface, which is formed by passing through all envelope points;

[0064] To ensure the accuracy and smoothness of the generated surface, smoothness constraints and thickness constraints are added to the error function. The smoothness constraints are as follows:

[0065]

[0066] in For the envelope surface at point The external normal vector at that location, It is a constant;

[0067] The thickness constraint is:

[0068]

[0069] in and These represent the minimum and maximum design thicknesses, respectively, and D is the distance between the initial envelope point and the discrete point.

[0070] Using all envelope points on the initial surface as initial optimization variables X, calculate the error function value for the initial optimization variables, and then use the error function value to calculate the gradient of the objective function with respect to the current initial optimization variables:

[0071]

[0072] in The error function value of the initial optimization variable. For gradient;

[0073] This gradient includes the gradient of the trajectory fitting error and the gradient of the regularization error, which are discretized using the difference form of the finite element mesh gradient, as follows:

[0074] Gradient of trajectory fitting error:

[0075]

[0076] The gradient of the regularization error:

[0077]

[0078] The initial optimization variable X is updated according to the L-BFGS algorithm update rule. Optimization stops when the convergence condition is met, and the optimized envelope points are extracted. Form an optimized envelope surface;

[0079] Calculate the mechanical speed based on the distance between discrete points. :

[0080]

[0081] in For time intervals;

[0082] And adjust the calculation gap value for the optimized envelope point:

[0083]

[0084] in The basic gap value (set according to manufacturing tolerance, initial value is set to 0.5 mm). For speed compensation coefficient, For discrete points The gap value;

[0085] The optimized envelope points are adjusted based on the gap adjustment value to generate the final envelope points and form the final envelope surface:

[0086]

[0087] in This is the final envelope point.

[0088] The error function combines the minimum distance from the discrete point set to the envelope point as a measure of fitting accuracy, and then superimposes a regularization term to strongly constrain smoothness. This not only optimizes the surface geometry but also avoids the local abrupt change problem in simple fitting methods. Through adjustable penalty weight coefficients, different priority envelope generation schemes can be selected according to the application scenario. For example, in automated production, accuracy is prioritized, while in mold design, surface smoothness is more important. Smoothness constraints suppress local discontinuities on the surface by limiting the change of the normal vector of the envelope surface, significantly improving the practical applicability of the envelope surface in processing. Combined with thickness constraints, it can ensure that the generated envelope surface has higher consistency while meeting the requirements of mechanical strength and stiffness, avoiding the occurrence of weak areas. The combination of the two constraints provides an initial model with uniform quality for subsequent finite element meshing and topology optimization, improving the efficiency of the overall optimization link. The introduction of gap adjustment values ​​and speed-based compensation coefficients can dynamically respond to changes in the speed of the motion path and compensate for deviations in manufacturing. This dynamic adjustment mechanism is particularly suitable for the surface design of complex mechanical motion and can effectively reduce the generation of mismatched areas after processing.

[0089] S2. Use the tetrahedral partitioning algorithm to divide the final envelope into finite element elements and define the shape function of each element. Define the objective function with lightweight as the goal, construct topology optimization constraints through the shape function, and use SIMP to solve the objective function to obtain the lightweight model.

[0090] Specifically, the final envelope is divided into finite element elements using a tetrahedral partitioning algorithm, and the shape function of each element is defined. The curvature of the envelope points is calculated based on the final envelope surface, and the average curvature of all envelope points is calculated. The mesh size is adjusted using an adaptive subdivision method based on the curvature. :

[0091]

[0092] in and For control parameters;

[0093] Based on the mesh size l, the geometry formed by the final envelope surface is divided into tetrahedral elements using the Delaunay triangulation method. Each tetrahedral element consists of 4 vertex nodes and 6 edges. The quality of the divided tetrahedral elements is then checked.

[0094] For each tetrahedral element, the coordinates of its four vertices are set as follows: , , as well as The nodal shape function of the tetrahedral element is defined by a linear interpolation function. :

[0095]

[0096] in , as well as The tetrahedral element is the first The coordinates of each node, , , as well as The coefficients of the shape function are obtained by solving using the coordinates of the element nodes:

[0097]

[0098] in The volume of the tetrahedral element is calculated using the vertex coordinates of the tetrahedron, where j, k, and l are the indices of the remaining nodes.

[0099] By calculating the average curvature of the envelope points and adaptively adjusting the mesh size based on curvature, fine meshes can be generated in high-curvature regions, thereby improving the accuracy of stress and deformation calculations in these critical areas. In low-curvature regions where high-density meshes are not required, using larger mesh sizes significantly reduces computational load and avoids unnecessary resource waste. In extremely high curvature or large surface change paths (such as sharp transition regions), adaptive meshing can effectively avoid analysis errors caused by overly coarse meshing, improving the overall smoothness of the mesh and element quality. Delaunay meshing, based on geometric characteristics, optimizes the shape of elements during the meshing process, avoiding the generation of distorted tetrahedrons (such as sharp and non-convex shapes), thereby improving mesh consistency and the accuracy of finite element solutions. Through triangulation that conforms to mathematical optimality, the side length and angle of each element can be automatically adjusted, reducing the need for manual local processing and improving the automation of mesh generation for complex geometries. Utilizing the analytical form of shape functions provides a foundation for the stiffness matrix and mass matrix of elements in subsequent finite element calculations, avoiding instability problems that may be caused by strong nonlinear calculations.

[0100] Furthermore, with lightweighting as the objective, a target function is defined, topology optimization constraints are constructed using shape functions, and the objective function is solved using SIMP to obtain the lightweight model, which sets an initial material density for each tetrahedral element. , 0≤ ≤1, its value is between 0 (no material) and (Completely filled material) between them, forming a unit density matrix. The objective function is defined based on the unit density matrix with lightweighting as the goal. for:

[0101]

[0102] in Let V be the total volume of all tetrahedral elements, and V be the integration variable.

[0103] Based on node shape function Obtain the strain-displacement matrix of the tetrahedral element by taking partial derivatives. :

[0104]

[0105] in , as well as Let n be the partial derivative of the shape function with respect to geometric coordinates in the element coordinate system, and n be the number of nodes in the quadrilateral element.

[0106] The strain-displacement matrices of all tetrahedral elements are used to construct a global strain-displacement matrix P, which is then synchronously calculated based on the strain-displacement matrix of each tetrahedral element. Generate the reference stiffness matrix for each element. :

[0107]

[0108] Where T is the transpose operation and E is the material elasticity matrix, which depends on the Young's modulus and Poisson's ratio of the material;

[0109] Calculate the global stiffness matrix K based on the reference stiffness matrix:

[0110]

[0111] Where A is the number of tetrahedral units. For the first The density of tetrahedral elements, where p is the penalty factor;

[0112] Calculate the global load distribution F based on the shape function:

[0113]

[0114] in This is the load density vector (volume force, calculated from density and gravitational acceleration).

[0115] The global stiffness matrix K and global load distribution F are obtained, and the global displacement vector U is obtained by solving the problem using the finite element method.

[0116]

[0117] Derive the element strain tensor from the global displacement vector U. Stress constraints are added to all tetrahedral elements:

[0118]

[0119] in For material element stress, The Young's modulus of the material. The minimum yield stress;

[0120] Add volume limits simultaneously:

[0121]

[0122] in The maximum volume of material allowed to be retained in the design;

[0123] The SIMP method is used to minimize the objective function while satisfying stress and volume constraints. During the optimization process, the cell density is iteratively updated:

[0124]

[0125] in For the first The iteration of the ... Material density of a tetrahedral unit Step size factor;

[0126] The iteration stops once the objective function converges, and a lightweight model is output based on the density obtained after iteration.

[0127] By constructing the element strain-displacement matrix and then progressively building the global strain-displacement matrix and global stiffness matrix from the element matrix, the coordination between elements can be ensured, avoiding the global performance degradation caused by local performance optimization in traditional methods. Linearization of the strain-displacement matrix can improve the overall calculation accuracy, especially in lightweight design, where changes in system performance are more accurate and reliable. At the same time, it makes the optimization have good preservation characteristics. Stress constraints can effectively prevent high stress points in local areas from exceeding the allowable range of material strength, thereby ensuring the service life of the optimization model and reducing the risk of failure. By transforming the iterative update of material density into a mathematical optimization process through the SIMP method, the globally optimal density distribution can be found systematically, significantly reducing trial and error time. The combination of penalty factors and volume constraints makes the optimization results have high-precision material distribution rationality, while meeting the actual needs of manufacturing processes.

[0128] S3. After obtaining the lightweight model, output it in the specified format for display and store it in the database;

[0129] Specifically, after obtaining the lightweight model, outputting it in a specified format means outputting the lightweight model as a STEP format 3D file and presenting it to the designers.

[0130] Furthermore, storing to the database refers to storing the obtained lightweight model in the design database and assigning timestamps to generate design logs for storage.

[0131] This embodiment also provides a mechanical digital design 3D model building system, including:

[0132] The design and analysis module is used to obtain the mechanical design motion path and correct it through a curvature smoothing algorithm, determine the mechanical motion space boundary, generate a motion envelope based on the motion path and space boundary, and perform compensation to generate the final envelope.

[0133] The model generation module is used to divide the final envelope into finite element elements using the tetrahedral partitioning algorithm and define the shape function of each element. The objective function is defined with lightweighting as the goal. Topology optimization constraints are constructed through the shape function. The objective function is solved using SIMP to obtain the lightweight model.

[0134] The display storage module is used to output the lightweight model in a specified format for display and store it in the database.

[0135] This embodiment also provides a computer device applicable to the mechanical digital design three-dimensional model building method, including: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the mechanical digital design three-dimensional model building method proposed in the above embodiment.

[0136] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0137] This embodiment also provides a storage medium storing a computer program, which, when executed by a processor, implements the method for building a three-dimensional model of mechanical digital design as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0138] In summary, this invention obtains the motion path of mechanical design, uses curvature smoothing correction combined with motion envelope generation to obtain the mechanical design envelope surface, and simultaneously sets optimization functions and constraints through finite element analysis combined with lightweight objectives, effectively achieving the goals of high efficiency, accuracy and lightweight design of complex mechanical three-dimensional designs, and improving the adaptability and flexibility of mechanical design.

[0139] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing a three-dimensional model for mechanical digital design, characterized in that: include, The mechanical design motion path is obtained and corrected using a curvature smoothing algorithm. The mechanical motion space boundary is determined, and a motion envelope is generated based on the motion path and space boundary. Compensation is then performed to generate the final envelope. The final envelope is divided into finite element elements using the tetrahedral partitioning algorithm, and the shape function of each element is defined. The objective function is defined with lightweighting as the goal. Topology optimization constraints are constructed through the shape function, and the objective function is solved using SIMP to obtain the lightweight model. After obtaining the lightweight model, output it in the specified format for display and store it in the database; The process of using the tetrahedral partitioning algorithm to divide the final envelope into finite element elements and defining the shape function of each element includes: calculating the curvature of the envelope points according to the final envelope surface and calculating the curvature average of all envelope points adjusting the grid size l according to the curvature by using adaptive subdivision method Based on the mesh size l, the geometry formed by the final envelope surface is divided into tetrahedral elements using the Delaunay triangulation method. Each tetrahedral element consists of 4 vertex nodes and 6 edges. The quality of the divided tetrahedral elements is then checked. For each tetrahedral element, the coordinates of its four vertices are set as follows: , , as well as The nodal shape function of the tetrahedral element is defined by a linear interpolation function. ; The objective function is defined with lightweighting as the goal, topology optimization constraints are constructed through shape functions, and the lightweight model is obtained by solving the objective function using SIMP. This involves setting an initial material density for each tetrahedral element. And form a unit density matrix. The objective function is defined based on the unit density matrix with lightweighting as the goal. ; Based on node shape function Obtain the strain-displacement matrix of the tetrahedral element by taking partial derivatives. The strain-displacement matrices of all tetrahedral elements are used to construct a global strain-displacement matrix P, which is then simultaneously calculated based on the strain-displacement matrix of each tetrahedral element. Generate the reference stiffness matrix for each element. ; Calculate the global stiffness matrix K based on the reference stiffness matrix; Calculate the global load distribution F based on the shape function; The global stiffness matrix K and global load distribution F are obtained, and the global displacement vector U is obtained by solving the finite element method. Derive the element strain tensor from the global displacement vector U. Stress constraints are added to all tetrahedral elements; Add volume limits simultaneously; Minimizing the objective function based on satisfying stress and volume constraints using the SIMP method In the optimization process, the unit density is iteratively updated; The iteration stops once the objective function converges, and a lightweight model is output based on the density obtained after iteration.

2. The mechanical digital design three-dimensional model building method of claim 1, wherein: The process of obtaining the mechanical design motion path and correcting it using a curvature smoothing algorithm, and determining the mechanical motion space boundary, refers to generating the mechanical motion path based on the mechanical design requirements and inputting mechanical motion requirement parameters. According to a fixed time interval motion path Discretize into a continuous point set Calculate the point set curvature at each discrete point ; When the curvature of discrete points When the set curvature threshold is exceeded, the discrete point is taken as a high curvature point, and new path points are added around the high curvature point by cubic spline interpolation. The discrete points after adding new path points are sorted and a new set of discrete points is output. The mechanical motion space boundary B is determined based on the set of discrete points.

3. The mechanical digital design three-dimensional model building method of claim 2, wherein: The process of generating a motion envelope based on the motion path and spatial boundary and then compensating to generate the final envelope refers to constructing a simple initial surface by combining the minimum bounding box of the mechanical motion spatial boundary B with equidistant expansion, using the surface points as the initial envelope points M, and calculating the minimum distance from the new discrete point set to the initial envelope points as the error function E. Add smoothness and thickness constraints to the error function; Take all the envelope points on the initial surface as the initial optimization variable X, calculate the error function value for the initial optimization variable, and calculate the gradient of the objective function with respect to the current initial optimization variable using the error function value; The initial optimization variable X is updated according to the L-BFGS algorithm updating rule, and the optimization is stopped when a convergence condition is met, and the optimized envelope point is extracted An optimized envelope surface is formed Calculating mechanical motion speed from discrete point distances ; And adjust the calculation gap value for the optimized envelope point; The optimized envelope points are adjusted based on the gap adjustment value to generate the final envelope points and form the final envelope surface.

4. The mechanical digital design three-dimensional model building method of claim 3, wherein: The phrase "after obtaining the lightweight model, output and display it in a specified format" refers to outputting the lightweight model as a STEP format 3D file and displaying it to the designers.

5. The mechanical digital design three-dimensional model building method of claim 4, wherein: The term "store to database" refers to storing the obtained lightweight model in the design database and assigning timestamps to generate design logs for storage.

6. A mechanical digital design three-dimensional model building system based on the mechanical digital design three-dimensional model building method of any one of claims 1-5, characterized in that: include, The design and analysis module is used to obtain the mechanical design motion path and correct it through a curvature smoothing algorithm, determine the mechanical motion space boundary, generate a motion envelope based on the motion path and space boundary, and perform compensation to generate the final envelope. The model generation module is used to divide the final envelope into finite element elements using the tetrahedral partitioning algorithm and define the shape function of each element. The objective function is defined with lightweighting as the goal. Topology optimization constraints are constructed through the shape function. The objective function is solved using SIMP to obtain the lightweight model. The display storage module is used to output the lightweight model in a specified format for display and store it in the database. 7.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is characterized in that: When the processor executes the computer program, it implements the steps of the mechanical digital design three-dimensional model building method according to any one of claims 1 to 5.

8. A computer readable storage medium having stored thereon a computer program, characterized in that: When the computer program is executed by the processor, it implements the steps of the mechanical digital design three-dimensional model building method according to any one of claims 1 to 5.

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