Human body finite element model limb posture adjustment method

Abstract

The present application relates to the technical field of virtual simulation, and particularly relates to a human body finite element model limb posture adjustment method. The method comprises the following steps: dividing a human body finite element model into regions with joints as boundaries and creating sets; creating a hinge at a joint, the hinge being used to connect the sets on both sides of the joint and define a rotational degree of freedom; setting attribute parameters of the hinge to constrain the posture adjustment range; defining a dummy tree to establish a motion transmission hierarchical relationship between the sets of regions; calculating a target position of a sub-region node based on a target posture, connecting an initial position and the target position of the node through a spring unit, and performing pre-simulation calculation to drive the limb posture adjustment. The technical scheme can improve the universality, simplify the operation and ensure the model deformation quality.

Description

Technical Field

[0001] This invention relates to the field of virtual simulation technology, specifically to a method for adjusting the posture of the limbs of a human finite element model. Background Technology

[0002] With the development of computer-aided engineering (CAE) and virtual simulation technology, the application scenarios of human finite element models are becoming increasingly widespread in fields such as automotive safety, biomechanical analysis, and medical implant evaluation. In practical applications, for different working condition analyses (such as occupant restraint system analysis under different sitting postures or injury assessment under different fall postures), human finite element models need to present diverse postures.

[0003] However, developing high-fidelity finite element models of the human body is a very complex process, involving intricate geometric modeling, material property assignment, and mesh generation, resulting in high development costs. Therefore, in practical engineering applications, it is difficult to develop a completely new digital human body model for each specific analysis posture. This necessitates that existing general-purpose human body models possess flexible and convenient posture adjustment capabilities to adapt to changing simulation requirements.

[0004] Currently, the widely used attitude adjustment method is the pre-simulation loading method. This method typically involves establishing specific boundary conditions or applying an external force field, and then using the explicit or implicit calculation process of the finite element solver to drive the model mesh to deform and achieve the desired target attitude. While this method can achieve model deformation, it has limitations in practical operation. Different loading methods or contact definitions often need to be designed and constructed for different target attitudes, resulting in a complex operation process and insufficient versatility. When faced with the need for rapid switching between multiple attitudes, existing methods require repeated, tedious pre-processing settings, leading to low efficiency and failing to meet the requirements for efficient and standardized model pre-processing. Summary of the Invention

[0005] The purpose of this invention is to propose a method for adjusting the posture of the limbs of a human finite element model, which can improve versatility, simplify operation, and ensure the deformation quality of the model.

[0006] To achieve the above objectives, this invention proposes a method for adjusting the posture of the limbs of a human finite element model, comprising: The human finite element model is divided into regions using joints as boundaries, and sets are created accordingly. A hinge is created at the joint, which connects the sets on both sides of the joint and defines the rotational degree of freedom; Set the attribute parameters of the hinge to constrain the attitude adjustment range; Define the dummy tree and establish the hierarchical relationship of motion transmission between different region sets; The target position of the sub-region node is calculated based on the target posture. The initial position of the node is connected to the target position through a spring unit, and a pre-simulation calculation is performed to drive the limb posture adjustment.

[0007] Beneficial effects of the basic solution: This technical solution structures the complex human body model by dividing it into regions and creating sets based on joints. This division makes model management clear and facilitates subsequent independent operations and definitions for specific parts (such as the thigh, calf, etc.).

[0008] This technical solution establishes a dummy tree, clarifying the parent-child hierarchical relationship (motion transmission relationship) between different regions. This hierarchical relationship simulates the real kinematic logic of the human body (e.g., the thigh drives the lower leg), ensuring that posture adjustments conform to the physiological structure of the human body and avoiding illogical relative movements between different parts of the model.

[0009] This technical solution creates hinges at the joints and defines rotational degrees of freedom, simulating the rotational characteristics of human joints. Simultaneously, by setting the hinge's attribute parameters, the range of posture adjustment is constrained, limiting excessive bending or twisting of the limbs and ensuring that the adjusted posture remains within the reasonable range of human anatomy, thus guaranteeing the biomechanical realism of the model.

[0010] This technical solution employs a method that connects the initial and target positions of nodes using spring elements and performs pre-simulation calculations. Essentially, this is a soft-driven physical process. Compared to directly forcibly moving node coordinates (rigid body displacement), this method better handles the deformation of the finite element mesh, avoiding problems such as mesh distortion, penetration, or volume lock caused by forced stretching. It utilizes the tension of springs to guide the limbs to the target position, resulting in smooth and natural deformation of muscles and soft tissues, thus helping to ensure the quality and computational stability of the finite element model after positioning.

[0011] This technical solution utilizes a dummy tree function to determine the target positions of limbs in real time. Combined with a computationally driven automatic adjustment process, it replaces the inefficient traditional method of manually adjusting node coordinates one by one. From target position calculation to pre-simulation driving, the entire process has clear logic and automation potential, shortening model preprocessing time and improving work efficiency.

[0012] As a feasible and preferred option, a hinge is created at the joint, including: The rotation center is determined based on the shape of the bone at the joint, and a first local coordinate system and a second local coordinate system are created with the rotation center as the origin. The first local coordinate system and the second local coordinate system are used to control two collection regions on both sides of the joint. Create beam elements that coincide with the first local coordinate system and the second local coordinate system respectively, and assign the beam elements to the corresponding sets respectively; The hinge is defined at the center of rotation according to the joint type, and the beam units on both sides of the joint are used as the connecting bodies of the hinge.

[0013] As a feasible preferred solution, the beam element adopts rigid material properties, and the starting node of the beam element is the joint rotation center point, and the ending node is a node generated by offsetting a preset distance along the local coordinate system axis.

[0014] As a feasible preferred embodiment, a hinge is defined at the center of rotation according to the joint type, including: For a single-degree-of-freedom joint, define a single-degree-of-freedom hinge, which releases only the rotational degree of freedom about the specified axis and constrains the remaining degrees of freedom; For multi-degree-of-freedom joints, define multi-degree-of-freedom hinges, release multiple rotational degrees of freedom and constrain translational degrees of freedom.

[0015] As a feasible preferred embodiment, the property parameters of the hinge are set, including: Set the translational and rotational stiffness of the hinge; Set the minimum and maximum values ​​of the joint rotation angle as the soft limit range.

[0016] As a feasible and preferred option, a dummy tree is defined, including: Define the human torso as the root node; Each region of the limbs is defined as a child node at a different level according to its anatomical connection. A subordinate relationship between the parent region and the child region is established so that the child region moves when the parent region moves, and the child region rotates relative to the parent region through a hinge.

[0017] As a feasible and preferred approach, calculating the target position of sub-region nodes based on the target pose includes: Obtain the initial position, joint rotation center, rotation angle, and rotation axis unit vector of the key nodes in the sub-region; Based on the initial position, rotation center, rotation angle, and rotation axis unit vector, the target position of the key node after rotation is calculated using the Rodriguez rotation formula.

[0018] As a feasible and preferred solution, the initial and target positions of the nodes are connected by spring units, and pre-simulation calculations are performed to drive limb posture adjustment, including: Select several key nodes on the sub-region set and record their initial positions; Create auxiliary nodes at the calculated target locations; Create a spring unit to connect the key node and the auxiliary node, and set the spring stiffness coefficient; Through pre-simulation, the traction force of the spring unit is used to move the sub-region node from the initial position to the target position, thereby realizing the positioning of the limb posture.

[0019] As a feasible preferred solution, several key nodes are selected on the sub-region set, including nodes on the mesh surface of the limb end and the middle of the limb as control points, and multiple spring elements are evenly arranged on the surface of the sub-region.

[0020] As a feasible and preferred approach, the human finite element model is divided into regions using joints as boundaries, and a set is created, including: Determine the joint position as the dividing line; Select nodes and cells containing bone and surrounding soft tissue and skin meshes, and create independent region sets according to limb segments. The selection of these sets is accurate to the mesh layer at the joint interface. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating a method for adjusting the posture of the limbs in a human finite element model.

[0022] Figure 2 This is a schematic diagram of the right upper arm and right lower arm area.

[0023] Figure 3 This is a schematic diagram of the local coordinate system at the right elbow joint.

[0024] Figure 4 This is a schematic diagram of the spring in the right arm. Detailed Implementation

[0025] To make the technical solution and advantages of this application clearer, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are only some embodiments of the present invention, and are only used to explain this application, not to limit it. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated; they can be combined with each other to achieve better technical effects. The same reference numerals appearing in the accompanying drawings of the following embodiments represent the same features or components, and can be applied to different embodiments.

[0026] Furthermore, unless otherwise defined, the technical or scientific terms used in this invention description shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings.

[0028] Reference Figure 1This disclosure proposes a method for adjusting the posture of limbs in a human finite element model, which involves importing an existing human finite element model. This model should be a three-dimensional mesh model including bones, soft tissues, and skin. In this embodiment, HyperMesh software is preferably used, but ANSA software can also be used.

[0029] To facilitate subsequent operation and management, a preliminary cleaning and geometric check of the model is required before starting posture adjustment to ensure that the mesh quality meets the requirements of simulation calculation (such as Jacobian ratio, warpage, etc., are all within a reasonable range). The model used in this embodiment is a fine finite element model reconstructed based on real human CT data. Its upper limb part includes the humerus, ulna, radius, and the surrounding muscles, fat, and skin layers.

[0030] It includes the following steps.

[0031] Step S1, Model Segmentation, Planning, and Creation: The human body model primarily adjusts its posture through joint rotation; therefore, it needs to be segmented into different areas, using joints as boundaries. This process can be represented by creating a set for areas such as the upper arm and lower arm, for example... Figure 2 As shown. During the positioning process, each area is treated as a whole and its position is modified accordingly.

[0032] Taking the upper right arm as an example, the implementation details include: Determine the boundaries to identify the positions of the shoulder, elbow, and wrist joints. The center of rotation of the shoulder joint is located at the junction of the humeral head and the glenoid cavity of the scapula; the center of rotation of the elbow joint is located at the junction of the distal humerus and the proximal ulna.

[0033] The model is divided into regions based on the above dividing lines, and sets are created.

[0034] Select the nodes and elements containing the mesh of all soft tissues and skin around the humerus and upper arm to create an upper arm assembly. To ensure a smooth boundary transition during subsequent rotations, the assembly should be selected precisely down to the mesh layer at the joint interface. Name the selected elements "Right_Upper_Arm". This assembly will be used as a whole for subsequent position changes.

[0035] Select the nodes and units containing the ulna, radius, and all soft tissue and skin meshes around the lower arm to create a lower arm assembly. Note that units within the elbow joint capsule should be categorized as belonging to the upper arm or treated separately according to the actual anatomical structure; in this embodiment, they are categorized as belonging to the rigid connection portion of the upper arm assembly. Name the selected units “Right_Lower_Arm”.

[0036] Select the hand bones and related soft tissue mesh, create a hand collection, and name it "Right_Hand".

[0037] Through the above operations, the upper limbs of the human model are logically divided into three independent sets of regions, laying the foundation for adding hinges and establishing hierarchical relationships in the future.

[0038] Step S2, creating the hinge at the joint, includes: Step S21: Define the local coordinate system for hinge rotation and create the hinge. In this embodiment, HyperMesh is used in conjunction with the LS-dyna processor to create the hinge.

[0039] Specifically, a suitable center of rotation is determined by the shape of the bones at the joint. For the elbow joint, by observing the geometry of the olecranon fossa of the ulna and the trochlea of ​​the humerus, a geometric center point located on the anterior side of the distal end of the humerus and close to the axis of rotation is fitted as the center of rotation of the elbow joint. For the shoulder joint, the center of rotation is determined at the geometric center of the humeral head.

[0040] A first local coordinate system and a second local coordinate system are created with the center of rotation as the origin. The origins of both coordinate systems are in the same position, but they belong to two separate set regions on either side of the joint, and are used to control these two set regions. The creation process is illustrated using the elbow joint as an example. (Refer to...) Figure 3 ,include: Create a first local coordinate system with the center of rotation of the elbow joint as the origin. The Z-axis points along the axis of the humerus towards the proximal end of the upper arm (towards the shoulder); the X-axis is perpendicular to the Z-axis and points forward of the body (determined according to anatomical posture); the Y-axis is determined according to the right-hand rule. This coordinate system is used to control the upper arm alignment.

[0041] Create a second local coordinate system with the rotation center of the elbow joint as the origin. The initial direction of the second local coordinate system is the same as that of the first local coordinate system, but logically it belongs to the lower arm set. This coordinate system is used to control the lower arm set.

[0042] Step S22: Create two sets of beam elements that coincide with the positions of the two local coordinate systems (i.e., the shape of the beam elements is consistent with the coordinate systems), including: Create material properties: In the software, create a rigid material, set its density to the average density of human bones, and set its elastic modulus to a high value to ensure its rigidity.

[0043] Create the properties of the beam element and assign them to the rigid material described above.

[0044] Generate beam elements: Upper Arm Beam Element: Create a beam element at the rotation center of the elbow joint. The starting node of this beam element is the rotation center of the elbow joint, and the ending node is a node offset by a certain distance (e.g., 50mm) along the Z-axis of the coordinate system. The cross-sectional shape of this beam element is defined as circular with a radius of 5mm (adjustable as needed for visualization). This beam element is assigned to the Right_Upper_Arm collection.

[0045] Create another beam element at the rotation center of the elbow joint. The starting node of this beam element is also the rotation center of the elbow joint, and the ending node is a node offset 50mm along the Z-axis of the coordinate system (towards the distal end of the lower arm). Assign this beam element to the Right_Lower_Arm set.

[0046] The main function of the beam element is to connect the components on both sides of the joint. Subsequently, only the rotation of the beam element needs to be controlled to control the corresponding entire area. The angle of hinge rotation can be observed in real time through the geometric shape consistent with the coordinate system.

[0047] Step S23, define the hinge at the joint rotation center according to the location and requirements, including: Define single-degree-of-freedom hinges (elbow and knee joints), where the elbow and knee joints primarily perform flexion and extension movements. Their rotational axes should be perpendicular to the plane formed by the upper and lower arms. In the local coordinate system, this is typically specified as the Y-axis or X-axis (depending on the coordinate system definition above). Let's assume the rotational axis is set to the Y-axis here. Constrain the other five degrees of freedom (three translational and two rotational), releasing only the rotational degree of freedom about the Y-axis.

[0048] In this embodiment, HyperMesh is used in conjunction with the LS-DYNA processor to define a single-degree-of-freedom hinge. Enter the “Analysis” -> “Joints” interface. Select “Revolute Joint” (i.e., revjoint). Select the upper arm beam element (or the rigid body element it contains) as “Body A”, and select the lower arm beam element as “Body B”.

[0049] Define a multi-degree-of-freedom hinge (shoulder joint, hip joint), where the shoulder and hip joints are ball-and-socket joints with three rotational degrees of freedom. Therefore, constrain the three translational degrees of freedom and release the three rotational degrees of freedom.

[0050] Step S3, hinge attribute settings: Define the CONSTRAINED_JOINT_STIFFNESS_GENERALIZED keyword to set the parameters of the rotary hinge, so as to simulate the biomechanical characteristics of the joint and control the range of attitude adjustment.

[0051] In the HyperMesh card editor, taking the elbow joint's revjoint as an example, make the following settings: Stiffness settings: Since the primary purpose of this embodiment is attitude adjustment (positioning) rather than precise collision biomechanical response, the stiffness setting is mainly to prevent joint penetration and instability during attitude adjustment.

[0052] Set the translational stiffness to a large value to simulate the rigid connection of the hinge.

[0053] Set the rotational stiffness. To simulate the passive resistance of soft tissue, a non-zero stiffness can be set, for example, the elbow flexion-extension stiffness can be set to 50 N·mm / deg. If only pure rigid rotation is required, it can be set to a minimum value or zero, relying on subsequent limit control.

[0054] Set the joint friction coefficient. In a purely positioning scenario, the friction coefficient can be set to 0. To simulate active muscle torque, this parameter or subsequent applied force can be adjusted. In this embodiment, it is set to 0.

[0055] Setting the rotation angle range (soft limit) provides a direct constraint for posture control. For the elbow joint, the normal range of flexion and extension is approximately 0° (fully extended) to 145° (fully flexed).

[0056] In the keyword card, set the minimum rotation angle to 0 degrees and the maximum rotation angle to 145 degrees.

[0057] Set limit transition ranges and forces, such as applying exponentially increasing restoring forces at the boundaries, to prevent computational overflow.

[0058] For the sphjoint of the shoulder joint, stiffness and limit ranges in three rotational directions need to be set separately, while also following anatomical constraints (such as the angle ranges of abduction, adduction, internal rotation, and external rotation).

[0059] Step S4: Define the DUMMY TREE. The DUMMY TREE defines the hierarchical relationship between the regions and establishes the hierarchical structure of motion transmission.

[0060] In this embodiment, the construction logic of DUMMY TREE is as follows: Establish the highest level region: Define the human torso as the highest level, denoted as PARENTS (root node).

[0061] Define sub-region hierarchy: The trunk (root) comprises four primary subregions (CHILDS): left upper arm, right upper arm, left thigh, and right thigh. This embodiment focuses on the right upper arm.

[0062] The right upper arm (first-level sub-region) contains a second-level sub-region (CHILDS): the right forearm.

[0063] The right forearm (secondary sub-region) contains a tertiary sub-region (CHILDS): the right hand.

[0064] In this embodiment, in the LS-DYNA keyword file (.k file) or the corresponding HyperMesh interface, through... Use the DATABASE_HISTORY_NODE or a dedicated DUMMY TREE definition card to build this tree structure.

[0065] Specifically, the Parent ID of the right upper arm is defined as the rigid body ID of the torso, and the Child ID is defined as the rigid body ID of the right forearm.

[0066] When the parent region (such as the torso) moves, the child region (such as the right upper arm) follows suit; relative motion occurs when the hinge drives the child region to rotate relative to the parent region. For example, when the elbow joint hinge rotates, it is the child region (right forearm) that rotates relative to the parent region (right upper arm).

[0067] Step S5, regarding the definition and calculation of the simulated spring, addresses the issue that when directly rotating the joints of a human model using a DUMMY TREE, the subcutaneous soft tissue mesh at the joints is prone to misalignment, distortion, or penetration. This invention solves this problem by defining a spring connecting the initial and target positions and performing pre-simulation posture adjustment. (Refer to...) Figure 4 ,include: Selecting key nodes: Select several key nodes on the right forearm set. Typically, nodes at the end of the arm (wrist) and the mid-forearm mesh surface are selected as control points. Let's assume the center point on the back of the wrist is selected as node P.

[0068] Record the initial position: Record the spatial coordinates (x, y, z) of node P, which is the initial position.

[0069] Determine the target position and its connection to the spring: Based on the posture requirements (such as elbow bending at 90 degrees), calculate the target position that node P should theoretically reach.

[0070] Create a spring element, connect one end to node P, and the other end to an auxiliary node created at the target location.

[0071] Set spring properties: Assign the spring a large stiffness coefficient so that it generates sufficient tension during the simulation to pull node P to move towards the target position.

[0072] Repeat this process to evenly distribute multiple springs on the surface of the right forearm (as shown in the diagram). Figure 4As shown in the figure, this creates a cable pulling effect, ensuring the stability of the positioning process.

[0073] Step S52, calculation of the target location of the sub-region node, includes: Given the initial position of a point in a subregion Center of rotation (joint hinge point) The distance from this point to the center of rotation Rotation angle and the unit vector of the rotation axis .

[0074] Calculate the vector from the center of rotation to the initial point:

[0075] Verify distance, point P The distance d from the center of rotation C is:

[0076] This distance should remain constant during the rotation.

[0077] Rotated vector The calculation formula is:

[0078] in: It is the dot product (scalar):

[0079] It is the cross product (vector):

[0080] Expand Quantity:

[0081]

[0082]

[0083] Target location :

[0084] therefore:

[0085]

[0086]

[0087] The initial position P is connected to the target position P′ using a spring, and the limbs are located through pre-simulation.

[0088] The above content is merely an embodiment of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can improve and implement the present invention based on the guidance provided in this application and their own capabilities. Typical well-known structures or operating methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for adjusting the posture of the limbs of a human finite element model, characterized in that, include: The human finite element model is divided into regions using joints as boundaries, and sets are created accordingly. A hinge is created at the joint, which connects the sets on both sides of the joint and defines the rotational degree of freedom; Set the attribute parameters of the hinge to constrain the attitude adjustment range; Define the dummy tree and establish the hierarchical relationship of motion transmission between different region sets; The target position of the sub-region node is calculated based on the target posture. The initial position of the node is connected to the target position through a spring unit, and a pre-simulation calculation is performed to drive the limb posture adjustment.

2. The method for adjusting the posture of limbs in a human finite element model according to claim 1, characterized in that, Create hinges at the joints, including: The rotation center is determined based on the shape of the bone at the joint, and a first local coordinate system and a second local coordinate system are created with the rotation center as the origin. The first local coordinate system and the second local coordinate system are used to control two collection areas on both sides of the joint. Create beam elements that coincide with the first local coordinate system and the second local coordinate system respectively, and assign the beam elements to the corresponding sets respectively; The hinge is defined at the center of rotation according to the joint type, and the beam units on both sides of the joint are used as the connecting bodies of the hinge.

3. The method for adjusting the posture of limbs in a human finite element model according to claim 2, characterized in that, The beam element uses rigid material properties. The starting node of the beam element is the joint rotation center point, and the ending node is a node generated by offsetting a preset distance along the local coordinate system axis.

4. The method for adjusting the posture of limbs in a human finite element model according to claim 2, characterized in that, The hinge is defined at the center of rotation according to the joint type, including: For a single-degree-of-freedom joint, define a single-degree-of-freedom hinge, which releases only the rotational degree of freedom about the specified axis and constrains the remaining degrees of freedom; For multi-degree-of-freedom joints, define multi-degree-of-freedom hinges, release multiple rotational degrees of freedom and constrain translational degrees of freedom.

5. The method for adjusting the posture of limbs in a human finite element model according to claim 1, characterized in that, The properties of the hinge are set, including: Set the translational and rotational stiffness of the hinge; Set the minimum and maximum values ​​of the joint rotation angle as the soft limit range.

6. The method for adjusting the posture of limbs in a human finite element model according to claim 1, characterized in that, Define a dummy tree, including: Define the human torso as the root node; Each region of the limbs is defined as a child node at a different level according to its anatomical connection. A subordinate relationship between the parent region and the child region is established so that the child region moves when the parent region moves, and the child region rotates relative to the parent region through hinges.

7. The method for adjusting the posture of limbs in a human finite element model according to claim 1, characterized in that, Calculate the target position of sub-region nodes based on the target pose, including: Obtain the initial position, joint rotation center, rotation angle, and rotation axis unit vector of the key nodes in the sub-region; Based on the initial position, rotation center, rotation angle, and rotation axis unit vector, the target position of the key node after rotation is calculated using the Rodriguez rotation formula.

8. A method for adjusting the posture of limbs of a human finite element model according to claim 1 or 7, characterized in that, By connecting the initial and target positions of the nodes through spring units, pre-simulation calculations are performed to drive limb posture adjustment, including: Select several key nodes on the sub-region set and record their initial positions; Create auxiliary nodes at the calculated target locations; Create a spring unit to connect the key node and the auxiliary node, and set the spring stiffness coefficient; Through pre-simulation, the traction force of the spring unit is used to move the sub-region node from the initial position to the target position, thereby realizing the positioning of the limb posture.

9. The method for adjusting the posture of limbs in a human finite element model according to claim 8, characterized in that, Several key nodes are selected on the sub-region set, including nodes on the mesh surface of the limb end and the middle of the limb as control points, and multiple spring elements are evenly arranged on the surface of the sub-region.

10. The method for adjusting the posture of limbs in a human finite element model according to claim 1, characterized in that, The human finite element model is divided into regions using joints as boundaries, and sets are created, including: Determine the joint position as the dividing line; Select nodes and cells containing bone and surrounding soft tissue and skin meshes, and create independent region sets according to limb segments. The selection of these sets is accurate to the mesh layer at the joint interface.

Images