A method and system for generating a flexible structure dynamics model with modal description

Abstract

A flexible structure dynamics model generation method and system containing modal description relate to the field of multi-body dynamics simulation. The method solves the problems of insufficient processing capacity of existing software for multi-flexible body units and complex node constraints, low model construction automation degree and the like. The method automatically reads geometric information, modal data, unit type and constraint definition in the modal neutral file through a modal neutral file analysis module, completes classification analysis and key parameter extraction of multi-flexible body constraints, establishes a flexible body unit database relying on a flexible body unit and constraint processing module, determines the connection relationship and force transmission path among different units through topological structure analysis, processes self-defined constraints to realize automatic mapping and collaborative calculation of constraint relationship among different unit types, and finally generates a flexible body dynamics model and integrates multiple solving algorithms for dynamics calculation by a model construction and calculation module, and outputs simulation results such as displacement, stress and strain.

Description

Technical Field

[0001] This invention relates to the field of multibody dynamics simulation technology, specifically to a method and system for generating dynamic models of flexible structures with modal descriptions. Background Technology

[0002] In the field of multibody dynamics simulation, flexible body models described by modal parameters are widely used as an important carrier of flexible body data. However, current software has many problems in processing modal neutral file models and flexible body constraints. On the one hand, existing software has limited ability to handle various flexible body elements and complex node constraints, and most only support a few standard constraint types, which cannot meet the simulation requirements of complex multibody dynamics systems. On the other hand, the process of reading data from modal neutral files and constructing a constrained flexible body model has a low degree of automation and relies heavily on manual operations, resulting in low simulation efficiency and making it difficult to achieve high-precision and high-efficiency multibody dynamics simulation analysis. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of existing software in handling multiple flexible body elements and complex node constraints, as well as the low degree of automation in model construction. To address these issues, this invention proposes a method and system for generating dynamic models of flexible structures with modal descriptions. The invention achieves these technical problems through the following technical solutions: Option 1: This invention proposes a method for generating dynamic models of flexible structures with modal descriptions, the method comprising the following steps: Step 1: Read the modal neutral file, automatically identify and parse the geometric information, modal data, element type and constraint type in the file, classify and parse standard constraints and custom constraints, and extract key constraint parameters; Step 2: Establish a flexible body element database to store the mechanical properties and calculation methods of different element types; determine the connection relationship and force transmission path between the modal description flexible body and the large deformation cable, beam, plate and shell flexible body elements through topology analysis; handle custom constraints to realize automatic mapping and collaborative calculation of constraint relationships between different element types; Step 3: Based on the geometric information, modal data, element types, and constraint definitions in the file parsed in Step 1, as well as the custom constraint relationships processed in Step 2, a dynamic model of the flexible structure is generated using a parametric modeling engine; at least one solution algorithm is integrated, and the corresponding algorithm is selected to perform dynamic calculations on the constructed model, outputting simulation results of displacement, stress, and strain; Step 4: Present the output displacement, stress, and strain simulation results as the motion and stress state of the flexible body through a visualization interface for analysis and model optimization.

[0004] Furthermore, a preferred embodiment is provided, wherein in step 1, the modal neutral file is read, and the constraint type in the file is automatically identified and parsed as follows: The modal neutral file includes the node coordinates, mass properties, mode shape matrix, frequency information, and constraint association data of the flexible body; during the analysis process, the constraint types are automatically identified, including RBE2 rigid constraints, RBE3 flexible constraints, and custom multi-point constraints.

[0005] Furthermore, a preferred embodiment is provided, in which step 1 further includes the standardization and reorganization of the geometric information, modal data, element type and constraint type in the parsing file, and the construction of a model configuration file containing the flexible body topology, physical properties and dynamic characteristics.

[0006] Furthermore, a preferred embodiment is provided, wherein in step 2, the connection relationship and force transmission path between the modal description flexible body and the large deformation cable, beam, plate, and shell flexible body elements are determined through topological analysis, and custom constraints are processed to achieve automatic mapping and collaborative calculation of constraint relationships between different element types. The topology analysis is based on graph theory, using flexible body element nodes as topological vertices and constraint relationships as topological edges to identify the connection topology and force transmission paths between elements. The automatic constraint mapping includes mapping the constraint nodes of the modal description flexible body to the constraint marker points of cable, beam, plate, and shell elements, realizing the transmission and coordination of constraint parameters under different element types.

[0007] Furthermore, a preferred embodiment is provided, wherein the solution algorithm in step 3 includes a linear solution algorithm and a nonlinear solution algorithm, and the dynamic calculation is performed using the modal synthesis method or the generalized coordinate order reduction method.

[0008] Option 2: A system for generating dynamic models of flexible structures with modal description, the system comprising: The modal neutral file parsing module allows users to read modal neutral files, automatically identify and parse the geometric information, modal data, element types, and constraint types in the files, classify and parse standard constraints and custom constraints, and extract key constraint parameters. The flexible body and constraint processing module is used to establish a flexible body element database to store the mechanical properties and calculation methods of different element types; it determines the connection relationship and force transmission path between the modal description flexible body and the large deformation cable, beam, plate and shell flexible body elements through topology analysis, processes custom constraints, and realizes automatic mapping and collaborative calculation of constraint relationships between different element types; The model building and calculation module is used to generate a dynamic model of a flexible structure based on the geometric information, modal data, element types and constraint definitions in the file parsed by the modal neutral file parsing module, as well as the custom constraint relationships processed by the flexible body element and constraint processing module. It integrates at least one solution algorithm, selects the corresponding algorithm to perform dynamic calculations on the constructed model, and outputs simulation results of displacement, stress, and strain. The interaction and visualization module is used to present the output displacement, stress, and strain simulation results of the flexible body in the form of a visual display interface, which is used for analysis and optimization of the model.

[0009] Furthermore, a preferred embodiment is provided in which the constraint processing module supports cross-element constraint coupling modeling between modal description flexible bodies.

[0010] Furthermore, a preferred embodiment is provided in which the interaction and visualization module further includes steps for rendering cloud maps, replaying animations, and exporting data from simulation results, thereby realizing quantitative analysis and iterative optimization of the motion and stress state of the flexible body.

[0011] Option 3: A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method described in Option 1.

[0012] Option 4: A computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the method described in Option 1.

[0013] The advantages of this invention are: The present invention discloses a method for generating dynamic models of flexible structures with modal descriptions. By accurately identifying geometric and modal data through a modal neutral file parsing module and combining it with the automatic mapping between flexible body elements and constraint processing modules, it can efficiently construct cross-type constraint relationships between modal description models and flexible body elements such as beams, plates, and shells. This solves the problem of constraint nonlinearity and modal order reduction coupling, ensures the accuracy of topology identification and constraint transfer in multi-flexible body systems, and improves the simulation accuracy of model dynamic characteristics.

[0014] The present invention provides a method for generating dynamic models of flexible structures with modal descriptions. This method addresses the challenge of integrating constraints of multiple flexible bodies with modal descriptions, and proposes a unified solution method for cross-type constraints. By integrating coordinate system transformation, quaternion and vector operations, it achieves accurate and rapid constraint integration dynamic modeling of modal models, rigid bodies and flexible bodies.

[0015] This invention is also applicable to applications such as automatic mapping and collaborative solution calculation of constraint relationships between different units. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for generating a dynamic model of a flexible structure with modal description, as described in Embodiment 1.

[0017] Figure 2 This is a flowchart of the modal description model file parsing process described in Implementation Method 1.

[0018] Figure 3 This is a flowchart of the cross-unit constraint dynamics modeling process described in Implementation Method 1.

[0019] Figure 4 This is a schematic diagram of the satellite model with flexible attachments as described in Implementation Method 1. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0021] Implementation Method 1, see [link] Figures 1 to 4 This embodiment describes a method for generating dynamic models of flexible structures with modal descriptions. The aim of this embodiment is to efficiently and accurately construct the constraint relationships between the modal description model and flexible body elements such as large-deformation cables, beams, plates, and shells, achieving constraint parameter transfer and coordination across element types. When dealing with constraint nonlinearity and modal order reduction coupling problems, it achieves efficient and automatic identification of multi-flexible-body constraint topology. The method specifically includes: First, the modal neutral file is parsed to extract key information describing the flexible body model, including: nodal spatial coordinates, mass distribution at each node, mode shapes, and frequencies. The parsed information is then standardized and reorganized to construct a model configuration file containing the flexible body's topology, physical properties, and dynamic characteristics. This allows for rapid loading of the flexible body model and subsequent multi-flexible-body constraint integration modeling and calculation. Specifically, the following steps are included: (1) Input modal files (.mnf / .mbs) and determine the type by the "FLEXMNF" identifier in the file header; (2) Initialize the data structure and allocate memory to store parameters such as node coordinates, mass matrix, and mode shapes; (3) Traverse the file sub-items, identify and extract the multi-flexible body identifiers, including: component ID and unit type label; (4) Read node-level data: parse node coordinates node by node. Mass (m), inertial parameters (Jxx, Jyy, Jzz); (5) Read modal level data: Extract the first N modal frequencies (ω1, ω2…ω n ), mode matrix .

[0022] Based on the principle of modal superposition, at any point of a flexible body position vector It can be decomposed into two parts: rigid body motion and elastic deformation.

[0023] The rigid body's motion components are determined by the translation of its center of mass and its rotation, i.e.:

[0024] in The rotation transformation matrix from the body coordinate system to the inertial system (derived from the attitude angles) (Derivation) For point The position vector in the undeformed connected coordinate system can be obtained from the initial coordinates of the nodes of the modal description model.

[0025] Elastic deformation components are described by modal superposition:

[0026] In summary, the complete expression for the position vector is:

[0027] For position vectors Regarding the time derivative, decompose the velocity of rigid body motion into the velocity of elastic deformation:

[0028] in , The rigid body angular velocity antisymmetric matrix is ​​derived from the flexible body kinetic energy. Includes the kinetic energy of rigid body motion and the kinetic energy of elastic deformation, and is obtained by integrating the kinetic energy of a point mass. have to:

[0029] Expand and utilize modal orthogonality Simplifying, we can obtain kinetic energy expressed in terms of generalized velocity:

[0030] Generalized coordinates Generalized mass matrix satisfy:

[0031] elastic potential energy Caused by modal deformation, based on the MNF modal stiffness matrix The following expression exists:

[0032] The flexible body element and constraint processing module enables cross-type flexible body connections and constraint transfer. In multi-flexible body constraint integrated modeling, cross-type flexible body connections and constraint transfer are crucial for ensuring model accuracy and associativity. Specifically, it includes the following steps: (1) Constraint activation determination and initialization: Check constraint activation flags; if not activated, skip the calculation. Initialize the coordinate system transformation matrix. Integrate the rotation relationship between the local coordinate system and the volume coordinate system of the modal model, and clear the constraint residual vector to zero. Ready to receive constrained contributions;

[0033] in: The rotation composite matrix of two coordinate systems , It is a rotation matrix.

[0034] Read the rotation quaternions of the modal description model constraint node marker1 and the rigid / flexible element constraint node marker2. If the quaternion is non-zero, perform nested cross product and conjugate operations to construct the rotation constraint relationship; Marker-dominated rotational speed deviation

[0035] Rotational velocity deviation dominated by rigid / flexible bodies

[0036] in: , This is the intermediate term of the rotational deviation. The coordinate rotation quaternion for marker1. The coordinate rotation quaternion for marker2. The quaternion for the coordinate rotation of the constraint nodes of the model to which marker1 belongs. The coordinate rotation quaternion for the rigid / flexible body to which marker2 belongs. The conjugate of the quaternion for the coordinate rotation of marker1. The conjugate of the quaternion for rotating the coordinates of marker2.

[0037] (3) Perform translational constraint calculations. When the marker point moves with the parent body, it is necessary to combine centripetal acceleration, Coriolis acceleration, and translational acceleration. The velocity and position vectors of the constraint nodes in the modal description model are:

[0038] The velocity and position vectors of the constrained nodes in the flexible element are:

[0039] in: This is the local angular velocity vector of the constraint node of the model to which marker1 belongs. This is the local angular velocity vector of the rigid / flexible body to which marker2 belongs. This is the local position vector of marker1. The second time derivative at marker1 position. The second time derivative at marker1 position. This is the local position vector of marker2. The second time derivative at marker2 position. This is the second time derivative at marker2.

[0040] Construct the constraint transfer matrix by transposing the transformation matrix between the marked points and the volume:

[0041] After transforming the local accelerations of m1 and m2 to the local coordinate system of m2, the difference is calculated to obtain the initial acceleration deviation vector:

[0042] in: It is the final transformation matrix. It is the local to global coordinate system rotation matrix of marker2. It is the local → global coordinate system rotation matrix of the rigid body to which marker2 belongs. It is the local → global rotation matrix of the node to which marker1 belongs. It is the marker1 modal description model that constrains node velocity. The marker2 flexible element constrains the node velocity.

[0043] (4) Calculate the absolute position difference of the marker points Speed ​​difference Acceleration difference

[0044] in: This is the absolute position of marker1. This is the absolute position of marker2. For the speed of marker1, For the speed of marker2, For the acceleration of marker1, This is the acceleration of marker2.

[0045] Combine the rotational constraint contribution (quaternion operation result) with the translational constraint contribution ( , (etc.) superimposed onto the system residual vector .

[0046]

[0047]

[0048]

[0049] in: Contribution matrix to combined centripetal acceleration, This is the supplementary contribution vector of centripetal acceleration to position deviation. This is the antisymmetric matrix of the local angular velocity of the rigid body. The second derivative term of the rotational deviation. The core formula is

[0050] in: For the six first derivative cross terms ( , , , , ) Position Second Derivative Deviation The core formula is:

[0051] The relative position vector is used to describe the positional relationship between two things, and its expression is:

[0052] The first-order time derivative of the relative position vector, i.e., the rate of change of relative position with time, is expressed as:

[0053] The second-order time derivative of the relative position vector reflects the time-varying coupled acceleration effect of attitude and position, and its expression is:

[0054] Relative rotation is represented using unit quaternions, and its relative attitude is described by quaternion product operations, expressed as:

[0055] The first-order time derivative of the relative rotation quaternion, reflecting the instantaneous rate of change of attitude over time, is expressed as:

[0056] The second-order time derivative of the relative rotation quaternion, reflecting the time-varying angular acceleration transmission effect, is expressed as:

[0057] To uniformly represent position and rotation constraints, the aforementioned relative constraint variables are stacked according to their dimensions to construct a constraint vector C.

[0058] in: The x / y / z components are relative positions. Let e1 / e2 / e3 be the e1 / e2 / e3 components of the relative rotation quaternion.

[0059] For each component Constrained residuals:

[0060] The constraint equations for the rigid connection in step (4) above are:

[0061] The hinge constraint equation is:

[0062] For the connection between two external modal flexible bodies, the constraint types already defined in the original model are preferentially used, such as RBE2 (rigid beam element constraint) and RBE3 (flexible beam element constraint). The constraint equations for the flexible connection between the two modal description flexible bodies are as follows:

[0063] In the formula, These are the node positions of the two modal models. To correspond to the mode shape, These are the corresponding modal coordinates.

[0064] Taking a rigid connection constraint as an example, the Jacobian matrix expansion is:

[0065] In the formula,

[0066] For custom constraints, semantic analysis and pattern matching algorithms are used to extract constraint-related parameters, such as connection point coordinates, stiffness coefficients, and damping coefficients. The transformation of constraints in the modal description model from local coordinates to global coordinates satisfies:

[0067] In the formula, Based on The rotation matrix, It is a translation vector.

[0068] The dynamic modeling is performed using the Lagrange equations as follows:

[0069] Topology analysis algorithms are used to determine the connection relationships and force transmission paths between different flexible body elements. For constraints composed of multiple flexible body elements, the constraint relationships are analyzed, and complex constraints such as nonlinear elastic constraints are transformed into software-computable mathematical models, enabling automatic mapping and collaborative solution calculation of constraint relationships between different elements.

[0070] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention, and the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. This is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0071] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for generating a dynamic model of a flexible structure containing modal description, characterized in that, The method includes the following steps: Step 1: Read the modal neutral file, automatically identify and parse the geometric information, modal data, element type and constraint type in the file, classify and parse standard constraints and custom constraints, and extract key constraint parameters; Step 2: Establish a flexible body element database to store the mechanical properties and calculation methods of different element types; determine the connection relationship and force transmission path between the modal description flexible body and the large deformation cable, beam, plate and shell flexible body elements through topology analysis; handle custom constraints to realize automatic mapping and collaborative calculation of constraint relationships between different element types; Step 3: Based on the geometric information, modal data, element types, and constraint definitions in the file parsed in Step 1, as well as the custom constraint relationships processed in Step 2, a dynamic model of the flexible structure is generated using a parametric modeling engine; at least one solution algorithm is integrated, and the corresponding algorithm is selected to perform dynamic calculations on the constructed model, outputting simulation results of displacement, stress, and strain; Step 4: Present the output displacement, stress, and strain simulation results as the motion and stress state of the flexible body through a visualization interface for analysis and model optimization.

2. The method for generating a dynamic model of a flexible structure with modal description according to claim 1, characterized in that, In step 1, the modal neutral file is read, and the constraint types in the file are automatically identified and parsed as follows: The modal neutral file includes the node coordinates, mass properties, mode shape matrix, frequency information, and constraint association data of the flexible body; during the analysis process, the constraint types are automatically identified, including RBE2 rigid constraints, RBE3 flexible constraints, and custom multi-point constraints.

3. The method for generating a dynamic model of a flexible structure with modal description according to claim 1, characterized in that, Step 1 also includes standardizing and reorganizing the geometric information, modal data, element types, and constraint types in the parsed file to construct a model configuration file containing the flexible body topology, physical properties, and dynamic characteristics.

4. The method for generating a dynamic model of a flexible structure with modal description according to claim 1, characterized in that, Step 2 involves determining the connection relationships and force transmission paths between the modal description flexible body and the large deformation cable, beam, plate, and shell flexible body elements through topological analysis, and handling custom constraints. The method for automatically mapping and co-calculating constraint relationships between different element types is as follows: The topology analysis is based on graph theory, using flexible body element nodes as topological vertices and constraint relationships as topological edges to identify the connection topology and force transmission paths between elements. The automatic constraint mapping includes mapping the constraint nodes of the modal description flexible body to the constraint marker points of cable, beam, plate, and shell elements, realizing the transmission and coordination of constraint parameters under different element types.

5. The method for generating a dynamic model of a flexible structure with modal description according to claim 1, characterized in that, The solution algorithms described in step 3 include linear and nonlinear solution algorithms, and the dynamic calculation is performed using the modal synthesis method or the generalized coordinate order reduction method.

6. A system for generating dynamic models of flexible structures with modal description, characterized in that, The system includes: The modal neutral file parsing module allows users to read modal neutral files, automatically identify and parse the geometric information, modal data, element types, and constraint types in the files, classify and parse standard constraints and custom constraints, and extract key constraint parameters. The flexible body and constraint processing module is used to establish a flexible body element database to store the mechanical properties and calculation methods of different element types; it determines the connection relationship and force transmission path between the modal description flexible body and the large deformation cable, beam, plate and shell flexible body elements through topology analysis, processes custom constraints, and realizes automatic mapping and collaborative calculation of constraint relationships between different element types; The model building and calculation module is used to generate a dynamic model of a flexible structure based on the geometric information, modal data, element types and constraint definitions in the file parsed by the modal neutral file parsing module, as well as the custom constraint relationships processed by the flexible body element and constraint processing module. It integrates at least one solution algorithm, selects the corresponding algorithm to perform dynamic calculations on the constructed model, and outputs simulation results of displacement, stress, and strain. The interaction and visualization module is used to present the output displacement, stress, and strain simulation results of the flexible body in the form of a visual display interface, which is used for analysis and optimization of the model.

7. The flexible structure dynamics model generation system with modal description according to claim 6, characterized in that, The constraint processing module supports modal description of cross-element constraint coupling modeling between flexible bodies.

8. The flexible structure dynamics model generation system with modal description according to claim 6, characterized in that, The interaction and visualization module also includes steps for rendering cloud maps, replaying animations, and exporting data from simulation results, enabling quantitative analysis and iterative optimization of the motion and stress state of the flexible body.

9. A computer storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-5.

10. A computer device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the method of any one of claims 1-5.

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