A method for adjusting the posture of a spine of a human body finite element model

Abstract

The present application relates to the field of vehicle passive safety collision technology, and particularly relates to a spine posture adjustment method of a human body finite element model. The spine posture adjustment method is based on a human body finite element model, establishes a hierarchical spine kinematic chain from bottom to top with a pelvis as a root component; determines joint nodes by calculating the centroid midpoint of adjacent segments, and binds each segment with a Beam unit to establish an independent local coordinate system; simulates the motion characteristics of the spine by defining a hinge with the Y-axis as the rotation axis; describes the relative motion between segments by using a three-dimensional homogeneous transformation matrix to construct a kinematics equation; develops an adjustment plug-in, and inputs an arbitrary segment rotation angle to automatically calculate and output the spatial pose of the entire spine chain. The technical scheme can accurately simulate the posture change of the human spine during the collision process to improve the accuracy of vehicle safety performance evaluation.

Description

Technical Field

[0001] This invention relates to the field of vehicle passive safety collision technology, specifically to a method for adjusting the spinal posture of a human body finite element model. Background Technology

[0002] Vehicle safety performance is a key focus for consumers and automakers. Passive safety in vehicle collisions serves as a crucial line of defense for protecting the lives of occupants, bearing the heavy responsibility of minimizing injury in the event of a collision. Among the key aspects of this field, research on human injury during a collision is paramount. Accurately understanding the injury mechanisms of different parts of the body during a collision provides a scientific basis for vehicle safety design, enabling targeted optimization of key components such as vehicle structure and restraint systems, thus allowing vehicles to better protect occupants in the event of a collision.

[0003] With the continuous advancement of computer technology and numerical simulation methods, the human finite element model has emerged. The human finite element model discretizes human tissue into a finite number of elements and uses mathematical and mechanical principles to simulate the mechanical behavior of various human tissues during a collision. It can accurately calculate key parameters such as stress, strain, and displacement of the human body under collision loads.

[0004] Compared to traditional testing methods, the human finite element model (FEM) offers several significant advantages. First, it is not constrained by ethical or experimental limitations, allowing for the simulation and analysis of various complex collision scenarios on computers, greatly reducing research costs and time. Second, the EEM provides detailed mechanical response information of internal human tissues, helping researchers gain a deeper understanding of the mechanisms and processes of injury, and providing a more accurate basis for injury prediction and assessment. Furthermore, by adjusting and optimizing the parameters of the EEM, it is possible to simulate the collision responses of individuals of different body types, ages, and genders, supporting personalized safety design.

[0005] In vehicle passive safety crash research, the human finite element model has been widely used to study the injury mechanisms of critical parts such as the spine and to optimize the design of vehicle restraint systems. As the central skeletal structure of the human body, the spine bears complex loads during a collision and is prone to severe injury. Using the human finite element model, the stress on the spine under different crash conditions can be simulated, the stress distribution and deformation of each segment of the spine can be analyzed, and the mechanisms and development of spinal injury can be revealed. Simultaneously, combined with the design parameters of the vehicle restraint system, the human finite element model can be used to evaluate the protective effect of the restraint system on the spine, providing guidance for optimizing the restraint system design and thus improving the vehicle's ability to protect the spine of occupants in collision accidents.

[0006] When performing collision analysis on a human finite element model, it is necessary to adjust the posture of the human finite element model in order to accurately simulate the human body's response in different driving postures during a collision. Precise spinal positioning is a key prerequisite for achieving this process, and its importance is reflected in several aspects.

[0007] From the perspective of collision load transmission path analysis, the spine, as a vital support structure of the human body, plays a crucial role in transmitting impact forces from the head and torso to the pelvis and lower limbs during a collision. Accurate spinal localization ensures a reasonable simulation of the collision load transmission path, allowing researchers to clearly understand the transmission process and distribution of impact forces among different parts of the body, thus providing an accurate basis for analyzing the injury risk of various parts of the body.

[0008] In calculating injury indicators, the precise location and posture of the spine directly affect the accuracy of injury assessment metrics. For example, parameters such as the curvature angle and degree of torsion of the spine are closely related to the occurrence of spinal injuries. Only through precise spinal localization can these parameters be accurately calculated, thereby assessing the risk of spinal injury during a collision and providing a reliable reference for vehicle safety design.

[0009] However, in current practice, the spinal positioning accuracy in adjusting the posture of human finite element models is insufficient to meet research requirements. This inadequate positioning accuracy directly reduces the reliability of damage prediction results. If spinal positioning is inaccurate, the collision load transfer path analysis will be flawed, and the calculation of damage indicators will lose accuracy. Consequently, vehicle safety designs based on these analyses cannot effectively reduce the risk of spinal injuries in collisions, severely impacting the effectiveness of vehicle safety design. Summary of the Invention

[0010] The purpose of this invention is to propose a method for adjusting the spinal posture of a human body finite element model. This technical solution can accurately simulate the posture changes of the human spine during a collision, thereby improving the accuracy of vehicle safety performance assessment.

[0011] To achieve the above objectives, the present invention provides a method for adjusting the spinal posture of a human finite element model, comprising,

[0012] Determine the master-slave relationship between components, and use the key reference point of the human body model as the origin of the global coordinate system to establish a spatial positioning framework. The key reference point is located at the predetermined reference position of the contact surface between the seat and the human body. Set the pelvis as the root component of the entire spinal structure, and establish the master-slave relationship between each segment of the spine from bottom to top to form a hierarchical spinal motion chain.

[0013] Determine the joint nodes of the spinal segment, take the midpoint of the centroid of the upper and lower surfaces of the adjacent spinal segment to obtain the joint nodes, and form a spinal kinematic chain with the joint nodes and the corresponding spinal segment.

[0014] Establish kinematic control connections for the spinal segments, create and bind Beam elements for each root component and slave component, and establish an independent local coordinate system for each Beam element; define rotational hinges, determine the coordinate axis of the relative motion of the spinal segments, set it as the Y-axis, and simulate the motion characteristics of the spine through preset hinge parameters;

[0015] Establish the kinematic equations of the spinal segments, model the spine as a series structure of spinal segments and joint nodes, control the relative motion between the spines through rotational hinges, and use a three-dimensional homogeneous transformation matrix to describe the relative motion between each spinal segment.

[0016] Automatic spinal posture adjustment control: Construct a spinal posture adjustment plugin, input the rotation angle of any spinal segment, complete the posture adjustment calculation of the spinal chain, and output the spatial position and orientation of the spinal segment.

[0017] Beneficial effects of the basic scheme: This method establishes a master-slave relationship with the pelvis as the root component and the spinal segments from bottom to top, forming a hierarchical kinematic chain. Its core advantage lies in constructing a rigid reference logic where the next level is the benchmark of the previous level, thus avoiding the attitude drift problem caused by the confusion of the reference system in traditional models.

[0018] Using the key reference point of the seat-human contact surface as the origin of the global coordinate system, combined with the positioning of the root components of the pelvis, a fixed benchmark matching the real sitting posture scenario is provided for the entire spinal motion chain, ensuring that the posture adjustment of all spinal segments revolves around the physiological center of the human sitting posture, rather than free movement without reference.

[0019] The posture adjustment of each level of the spine (such as the lumbar, thoracic, and cervical vertebrae) is based on the directly connected next level of the spine. For example, the rotation of the cervical spine is based on the top of the thoracic spine, and the rotation of the thoracic spine is based on the top of the lumbar spine. This hierarchical control logic can effectively avoid the problem of error backtracking and accumulation in the traditional serial model, ensuring the accuracy of posture adjustment of each segment and ultimately achieving precise control of the entire spinal posture.

[0020] By combining the design of joint node definition, single-axis rotation hinge and biomechanical parameter constraints, the spinal motion simulation is made to better fit the physiological structure and biomechanical characteristics of the human body, solving the pain points of excessive idealization of motion and large differences from the real human body in traditional finite element models.

[0021] Using the midpoint of the centroid of the upper and lower surfaces of adjacent spinal segments as the joint node, this positioning method closely matches the actual location of the intervertebral disc in the human spine (located between two vertebral bodies), ensuring the accuracy of the anatomical anchor point of the spinal kinematic chain and providing a basic framework that conforms to human structure for subsequent motion simulation.

[0022] The coordinate axis for the relative motion of the spinal segments is set as the Y-axis (corresponding to the main physiological motion directions of the human spine, such as flexion, extension, and lateral flexion). The motion characteristics of the real spine are simulated by preset hinge parameters. Constraints can effectively prevent the model from exhibiting motions beyond the physiological range (such as excessive lumbar extension or excessive cervical rotation), making the spinal motion more in line with the laws of human anatomy.

[0023] Improved biomechanical consistency: By introducing parameters based on human biomechanics, the relative motion between spinal segments can not only be correct in posture but also in mechanical properties. For example, when simulating sitting posture adjustment, the stress and deformation patterns of the spine in the model can be consistent with the biomechanical response of the real human spine, providing reliable model support for subsequent applications such as sitting comfort analysis and spinal stress assessment.

[0024] By encapsulating the attitude control logic into an independent plugin, the extremely simple interactive process of "input angle → automatic recursion → output attitude" significantly reduces the threshold for using finite element models, while improving the real-time performance and integration flexibility of attitude adjustment.

[0025] Users only need to input the target rotation angle of any spinal segment, and the plugin can automatically complete the upward transmission of angle (such as the rotation of the lumbar spine will drive the coordinated adjustment of the thoracic and cervical spine) and the downward transmission and update of posture (such as the adjustment of the cervical spine angle will simultaneously correct the spatial position of its top node). There is no need for manual calculation and adjustment of each segment, which greatly reduces the operation steps and time cost of posture optimization, and is especially suitable for scenarios that require frequent adjustment of sitting posture.

[0026] Strong real-time performance and easy integration: The plug-in encapsulation decouples the posture control logic from the core calculation module of the finite element model. It can be quickly embedded into different human finite element models and can also interface with external software such as seat design and human-computer simulation. Moreover, the logic of automatic recursive calculation can achieve millisecond-level response through algorithm optimization, which meets the application scenarios with high timeliness requirements such as real-time sitting posture simulation and dynamic posture adjustment.

[0027] As a feasible preferred approach, the articular nodes are obtained by taking the midpoint of the centroids of the upper and lower surfaces of adjacent spinal segments, including the following:

[0028] For each pair of adjacent spinal segments, calculate the centroid coordinates of their upper and lower surfaces in three-dimensional space, and take the midpoint of these two centroids as the joint node.

[0029] As a feasible preferred solution, a rotational hinge is defined, the coordinate axis of the relative motion of the spinal segments is determined and set as the Y-axis, and the motion characteristics of the spine are simulated by preset hinge parameters, including the following:

[0030] Two nodes with coincident spatial coordinates on the Y-axis are selected on the Beam element of adjacent spinal segments as the rotation center of the rotation hinge. The preset hinge parameters include initial stiffness, motion damping and angle limit.

[0031] As a feasible and preferred solution, automatic spinal posture adjustment control includes inputting the target angle, determining the angle limit, calculating the posture position, global posture coupling, creating spring units, calculating the target posture, and updating the target posture.

[0032] As a feasible and preferred approach, establishing the kinematic equations of the spinal segment includes single-segment posture update expressions, comprising the following:

[0033] Joint rotation matrix:

[0034]

[0035] in, Indicates the first The angle of rotation of the vertebral column around the Y-axis;

[0036] Translation vector of the spinal segment:

[0037]

[0038] in, Indicates from arrive distance, This indicates the position of the articular node in the i-th spinal segment;

[0039] Then the first The local homogeneous transformation matrix of the section is:

[0040]

[0041] in, This represents the i-th spine.

[0042] As a feasible and preferred approach, establishing the kinematic equations of the spinal segment also includes a recursive expression for the overall posture, including the following:

[0043] Let the pelvis be The initial orientation is the identity matrix:

[0044]

[0045] Then the first The global pose of each spine is:

[0046]

[0047] The coordinates of the spine after posture adjustment are obtained.

[0048] As a feasible and preferred solution, the posture update control logic of the spinal posture adjustment plugin also includes angle limit judgment. If the input angle exceeds the preset maximum limit, the angle will be automatically adjusted to the maximum limit before subsequent calculations are performed.

[0049] As a feasible preferred solution, the posture update control logic of the spinal posture adjustment plugin also includes creating spring units, automatically identifying three nodes with greater rigidity on each segment of the spine, calculating the node positions corresponding to the target posture based on the posture coupling results, and then creating spring units through the initial nodes and target nodes to pull the spine to the final position.

[0050] As a feasible and preferred solution, the posture update control logic of the spinal posture adjustment plugin also includes target posture calculation, outputting the target posture calculation file and automatically submitting it to DYNA for calculation via a bat file; after the calculation is completed, the coordinates of the spinal target posture nodes are written to the corresponding file, and the file is imported into the initial model to update the global position of the nodes.

[0051] As a feasible preferred solution, the posture update control logic of the spinal posture adjustment plugin also includes target posture update, which imports the target posture node coordinate file into the initial model and updates the global position of the nodes to the target posture position. Attached Figure Description

[0052] Figure 1 This is a logical schematic diagram of a spinal posture adjustment method based on a human finite element model according to the present invention.

[0053] Figure 2 This is a schematic diagram of the key structures of the spine.

[0054] Figure 3 This is a schematic diagram of the spinal kinetic chain.

[0055] Figure 4 A schematic diagram of the posture update control logic for the spinal posture adjustment plugin.

[0056] Figure 5 This is a schematic diagram of the electronic device structure according to an embodiment of the present invention.

[0057] The attached figures indicate the following: electronic device 500, processor 501, communication interface 502, memory 503, and bus 504. Detailed Implementation

[0058] 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.

[0059] 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.

[0060] The present invention will now be described in further detail with reference to the accompanying drawings.

[0061] Reference Figure 1 A method for adjusting spinal posture using a human finite element model is proposed. By constructing a master-slave nested posture control chain, combined with joint motion parameter constraints based on human biomechanics and modular posture control plugins, the method achieves efficient and accurate adjustment of spinal posture, including the following steps.

[0062] Step S100, determining the master-slave relationship between components, including:

[0063] Step S101: Establish a spatial positioning framework. Use the H-point of the human body model as the origin of the global coordinate system, and establish the spatial positioning framework based on this. The H-point is a key reference point in the human body model, usually located at a specific position on the contact surface between the seat and the human body, used to determine the relative position of the human body in the vehicle.

[0064] Step S102: Set the root component and master-slave relationship, and set the pelvis as the root component of the entire spinal structure.

[0065] The segments of the spine are arranged in a hierarchical, top-bottom order according to anatomical structure: the spinal segment closest to the pelvis acts as the subordinate component of the pelvis, while simultaneously serving as the root component of the adjacent spinal segment above it, thus forming a hierarchical spinal motion chain. For example, the L5 segment of the lumbar spine is a subordinate component of the pelvis, the L4 segment is a subordinate component of L5 and the root component of L3, and so on down to the C1 segment of the cervical spine. This "root-subordinate" nested relationship ensures that the overall spinal movement is based on the pelvis, avoiding positioning confusion caused by independent movements of multiple components. The overall structure of the spine in the human model is as follows: Figure 2 As shown.

[0066] Step S200, determine the articular nodes of the spinal segment, including:

[0067] Step S201, Joint Node Determination Method: The joint node is determined by the centroid coordinates of the upper and lower surfaces of adjacent vertebrae. Specifically, for each pair of adjacent vertebral segments, the centroid coordinates of their upper and lower surfaces in three-dimensional space are calculated, and the midpoint of these two centroids is taken as the joint node. For example, for the L4 and L5 lumbar segments, the centroid coordinates of the lower surface of L4 and the upper surface of L5 are calculated first, and then the midpoint of these two centroids is taken as the L4-L5 joint node.

[0068] Specifically, in the finite element model of the human body, the geometry of each spinal segment is represented by its three-dimensional mesh. The upper and lower surfaces are defined as follows: the lower surface is defined as the geometric plane at the bottom of the spinal segment, typically facing the adjacent lower spinal segment; the upper surface is defined as the geometric plane at the top of the spinal segment, typically facing the adjacent upper spinal segment. In the finite element model, the upper and lower surfaces are typically composed of a set of coplanar nodes, which can be automatically identified using geometric analysis tools.

[0069] For the upper and lower surfaces of each spinal segment, calculate their centroid coordinates in three-dimensional space. The specific calculation formula is as follows:

[0070] Assume the surface consists of N nodes, and the coordinates of each node are... Then the centroid coordinates The calculation formula is:

[0071]

[0072]

[0073]

[0074] The centroid coordinates of each surface can be obtained using the above formula.

[0075] To determine the joint nodes, the midpoint of the centroid coordinates of the upper and lower surfaces of adjacent spinal segments is taken as the joint node. For example, the centroid of the lower surface of the L4 lumbar segment... The centroid of the upper surface of segment L5 is given by the following formula.

[0076]

[0077]

[0078]

[0079] Using the above method, the upper and lower surfaces and centroid coordinates of spinal segments can be accurately determined, thus providing a basis for the definition of joint nodes.

[0080] Step S202: The spinal kinetic chain structure is constructed, consisting of joint nodes and spinal segments. The core function of the joint nodes is to achieve posture matching between the spine and pelvis, and between spinal segments, by adjusting their relative positions. All joint movements must strictly adhere to human biomechanical constraints to ensure that the movement state conforms to the physiological limits of the human body.

[0081] For example, the range of motion of joint nodes cannot exceed the flexion, extension, and rotation angles of the human spine within its normal physiological range. The core function of joint nodes is to achieve postural matching between the spine and pelvis, and between spinal segments, by adjusting relative positions. All joint movements must strictly adhere to biomechanical constraints to ensure that the movement conforms to the body's physiological limits. For example, the range of motion of joint nodes cannot exceed the flexion, extension, and rotation angles of the human spine within its normal physiological range. (Spinal kinetic chain reference) Figure 3 As shown.

[0082] Step S300, establish spinal segment kinematic control connections, including:

[0083] Step S301, Construct Beam elements and local coordinate system: Create corresponding Beam elements for each root component and slave component, and bind them to the corresponding components.

[0084] An independent local coordinate system is established for each Beam element, and the relative motion between the master and slave components is identified through two different local coordinate systems. For example, for two adjacent spinal segments A and B, A is the root component and B is the slave component. Local coordinate systems are established for the Beam elements corresponding to A and B respectively, and the relative motion between A and B is determined by the relative relationship between these two local coordinate systems.

[0085] Beam elements are finite element types used to simulate the mechanical behavior of slender structures. In this embodiment, they are used to represent the connection relationships between spinal segments.

[0086] Beam element definition and node selection:

[0087] First, using the joint node as the origin, construct a Beam element parallel to the Y-axis (in the opposite direction of the main motion). Second, referencing the global coordinate system of the human model, determine the directions of the X and Z axes, and construct Beam elements parallel to the X and Z axes respectively, using the joint node as the origin. Bind these three Beam elements as a whole to the main component. Similarly, using the above three Beam elements as references, create three Beam elements with the same coordinate positions but different node IDs, and bind these Beam elements to the slave components.

[0088] For two adjacent spinal segments A and B, A is designated as the root component and B as the slave component. Local coordinate systems are created for A and B using three Beam elements. The relative motion between the master and slave components is determined by the relationship between the two local coordinate systems. Specifically, the local coordinate system of the master component A is defined as the reference coordinate system. The local coordinate system of the slave component B is rotated or translated relative to the local coordinate system of A. By calculating the rotation matrix and translation vector between the two local coordinate systems, the motion state of the slave component B relative to the master component A can be obtained.

[0089] The relative motion between master and slave components can be identified in the following ways:

[0090] Rotational motion:

[0091] The rotation matrix between the two local coordinate systems Calculate the rotation angle and direction of component B relative to main component A. Rotation matrix. The calculation formula is:

[0092]

[0093] in, The angle is the rotation angle.

[0094] Translational motion:

[0095] The translation distance from component B to main component A is calculated using the translation vector \(d\) between the two local coordinate systems. The formula for calculating the translation vector \(d\) is:

[0096]

[0097] in, These represent the translation distances along the X, Y, and Z axes, respectively.

[0098] Using the above method, an independent local coordinate system can be established for each Beam unit, and the relative motion between the master and slave components can be identified by the relative relationship between the two local coordinate systems.

[0099] Step S302: Define the rotational hinge and determine the coordinate axis for the relative motion of the spinal segments, setting it as the Y-axis. Each Beam unit bound to the master and slave components on this coordinate axis contains two nodes, and the spatial coordinates of the corresponding two nodes completely coincide. The rotation center of the rotational hinge is defined through this coincident node. For example, on the Beam units of two adjacent spinal segments, two nodes located on the Y-axis are selected respectively, ensuring that the spatial coordinates of these two nodes are the same. This node is used as the rotation center of the rotational hinge.

[0100] The specific implementation method is as follows:

[0101] Beam element node definition: Between two adjacent spinal segments (such as L4 and L5 of the lumbar spine), the Beam element is used to simulate the connection relationship between spinal segments. The Beam element consists of two nodes: one node is located on the upper surface of the master component (such as the L5 segment); the other node is located on the lower surface of the slave component (such as the L4 segment).

[0102] The two nodes of a Beam element are located above and below the joint node, respectively, and aligned along the Y-axis. Specifically: for the master component (such as segment L5), the Beam element's node is located below the joint node; for the slave component (such as segment L4), the Beam element's node is located above the joint node.

[0103] In finite element modeling, the two nodes of the Beam element in the master-slave component need to be completely coincident in spatial coordinates to ensure the uniqueness and accuracy of the rotation center of the rotational hinge. The specific operation is as follows:

[0104] The Beam element nodes of the main component and the Beam element nodes of the slave component have completely identical coordinates in the X and Z directions; in the Y direction, the coordinates of the two nodes can be slightly offset to reflect the hierarchical relationship between the upper and lower segments, but in actual modeling, the Y coordinates of the two nodes are usually set to the same value to satisfy the coincidence condition.

[0105] The rotation center of the rotating hinge is defined by the coincident nodes of the master and slave Beam units. The rotational hinge moves along the Y-axis, allowing rotational movements (such as flexion, extension, and lateral flexion) between spinal segments around the Y-axis, while restricting degrees of freedom in other directions. This design ensures that the biomechanical characteristics of spinal movement are consistent with the movement patterns of the real human spine.

[0106] Joint nodes are determined by the midpoint of the centroids of the upper and lower surfaces of adjacent spinal segments (such as the L4-L5 joint node), and the coincident nodes of the Beam element are spatially aligned with the joint nodes. The coincident nodes of the Beam element serve as the rotation centers of the rotational hinges, working in conjunction with the joint nodes to ensure that the motion simulation between spinal segments conforms to human anatomy and biomechanics.

[0107] Step S303, motion parameter control, simulating spinal motion characteristics through preset hinge parameters, including:

[0108] The initial stiffness is matched to the elastic properties of the intervertebral discs of the spine. Through experimental measurements or by referring to relevant literature data, parameters such as the elastic modulus of the intervertebral discs under different stress conditions are determined and used as the initial stiffness in the rotating hinge. Specifically, the compressive stiffness of the lumbar intervertebral discs under different axial pressures is obtained through experimental measurements. Experiments typically use mechanical testing equipment to apply axial pressure to the intervertebral discs and record the deformation, calculating the compressive stiffness using stress-strain curves. Based on existing research on the mechanical properties of lumbar intervertebral discs, a compressive stiffness value within the physiological range of the human body is selected. In the finite element model, the compressive stiffness value from the experiments or literature is assigned to the stiffness parameters of the rotating hinge, and its rationality is verified through simulation. If the simulation results are consistent with the experimental data, the setting of the stiffness value is confirmed to be reasonable. In this embodiment, the compressive stiffness of the lumbar intervertebral disc under axial pressure is set to 1314 N / mm.

[0109] Motion damping simulates energy dissipation during spinal movement. It considers energy loss due to tissue friction, fluid flow, and other factors during spinal movement, and simulates this process by setting an appropriate damping coefficient. Specifically, the damping coefficient is calculated by experimentally measuring the energy dissipation characteristics of the human spine during movement. Experiments typically employ dynamic mechanical testing, recording the energy loss of the spine during movement and calculating the damping coefficient using kinematic equations. In this embodiment, the damping coefficient during spinal movement is 133.6 – 905.3 N·s / m to reflect energy dissipation.

[0110] Simulation calibration involves setting the range of damping coefficients within the finite element model based on the dynamic characteristics of spinal motion. Simulation analysis verifies whether the model's motion response matches the motion characteristics of the real human body. If the simulation results meet expectations, the damping coefficient setting is confirmed to be reasonable. Specifically, based on human anatomical data, the maximum flexion and extension angles of the lumbar spine within the normal physiological range are determined. This data typically originates from medical imaging studies (such as MRI or CT scans) or human biomechanical experiments. In the finite element model, the maximum flexion and extension angles of the lumbar spine are set using the angle limiting function of the hinge. The angle limits can be achieved through hinge rotation range constraints. Simulation analysis verifies whether the model's motion range conforms to the anatomical data. If the simulation results are consistent with the reference data, the angle limit setting is confirmed to be reasonable. In this embodiment, based on the normal physiological range of motion of the human spine, while also considering the mesh quality of the human finite element model after posture adjustment, the maximum flexion angle of the L5 lumbar spine is set to 16°, and the maximum extension angle to 9°.

[0111] Angle Limitation: Based on anatomical data, the maximum angle thresholds for flexion, extension, and rotation are set to ensure that the movement does not exceed the biomechanical safety range.

[0112] The motion characteristics of the spine are simulated using the aforementioned preset hinge parameters. The specific implementation method is as follows:

[0113] A rotational hinge is defined on the Beam element of adjacent spinal segments, and parameters such as compressive stiffness, damping coefficient, and angle constraint are assigned to the hinge. The rotation center of the rotational hinge is the coincident node of the Beam element.

[0114] Based on the stiffness, damping, and angular constraints of the rotating hinge, kinematic equations for the spinal segments are established. These kinematic equations describe the relative motion between spinal segments using a three-dimensional homogeneous transformation matrix.

[0115] The preset hinge parameters are substituted into the kinematic equations, and the calculations are performed using finite element simulation software (such as LS-DYNA). During the simulation, the motion characteristics of the spinal segments (such as flexion-extension and lateral flexion) are controlled by the parameters of the rotating hinge.

[0116] By comparing simulation results with experimental or anatomical data, we can verify whether the model's motion characteristics conform to the biomechanical laws of the real human body.

[0117] Step S400: Establish the kinematic equations of the spinal segments. This is done by modeling the spine as a series structure of spinal segments and joint nodes, and controlling the relative motion between the spinal segments through rotational hinges. To accurately obtain the coordinate position of the spine after posture adjustment, a three-dimensional homogeneous transformation matrix is ​​used to describe the relative motion between each spinal segment. The specific derivation process is as follows:

[0118] Single-segment pose update expressions include:

[0119] Since the joint only rotates around the Y-axis, the rotation matrix is:

[0120]

[0121] in, Indicates the first The angle of rotation of the vertebral column around the Y-axis.

[0122] Obtain the rotation angle of the i-th vertebral segment around the Y-axis. :

[0123] Rotation angle The rotation angle is calculated by the user input or the control logic of the spinal posture adjustment plugin. For example, the user can input a target rotation angle for a certain spinal segment (such as L3 of the lumbar spine rotating 10° around the Y-axis), and the plugin will automatically calculate the rotation angles of other spinal segments according to the master-slave relationship.

[0124] If the input angle exceeds the preset biomechanical angle limit (e.g., the maximum flexion angle of L5 lumbar spine is 16°), the plugin will automatically adjust the angle to the maximum allowed value.

[0125] Translation vector of the spinal segment:

[0126]

[0127] in, This represents the position of the joint node of the i-th spinal segment. The joint node is determined by the midpoint of the centroid of the upper and lower surfaces of the adjacent spinal segments. Indicates from arrive The distance is calculated using the following formula:

[0128]

[0129] in, and Joint nodes and The three-dimensional coordinates.

[0130] Then the first Local homogeneous transformation matrix of the section for:

[0131]

[0132] in, This represents the i-th spine.

[0133] The local homogeneous transformation matrix describes the motion state of the i-th vertebral segment relative to its parent node (such as the pelvis or the next level vertebral segment), including rotation and translation.

[0134] The global pose describes the position and orientation of the i-th spinal segment in the global coordinate system, and is calculated recursively. The calculation formula is as follows:

[0135] The recursive expression for the overall attitude:

[0136] Let the pelvis be The initial orientation is the identity matrix:

[0137]

[0138] Then the global pose of the i-th spine for:

[0139]

[0140] The above formula allows for the accurate determination of the spine's coordinate position after posture adjustment. The recursive expression for the overall posture starts from the global root component and traces upwards through the posture transformations of all subordinate components within that segment, recursively updating the global position of all subordinate segments. Specifically, starting from the pelvis (root component), the global posture of each spinal segment is calculated sequentially. Based on the global posture matrix, the translation and rotation information of the i-th spinal segment can be extracted, thereby determining its position and posture in the global coordinate system.

[0141] Ultimately, the coordinate positions and posture information of all spinal segments will be integrated and output as the adjusted spinal posture.

[0142] Step S500, automatic spinal posture adjustment control, refer to Figure 4 ,include:

[0143] To achieve efficient and automated spinal posture adjustment, a spinal posture adjustment plugin based on the spinal kinematic chain was constructed. This plugin, based on the spinal kinematic chain composed of the pelvis, spinal segments, and joint nodes, encapsulates a set of posture update control logic. By inputting the rotation angle of a single spinal segment, it can automatically complete the posture adjustment calculation for the entire spinal chain and output the spatial position and orientation of all spinal segments, achieving rapid response and dynamic reconstruction of the human spinal spatial state. The posture update control logic flow is as follows:

[0144] Enter the target angle, which is the rotation angle of a specific spinal segment. For example, enter a 10-degree rotation of the L3 segment around the Y-axis.

[0145] Angle limit judgment: Determine whether the input angle is within the preset limit range. If it is within the limit, proceed directly to the next step. If it exceeds the limit, automatically adjust the input angle to the maximum limit and proceed to the next step. For example, the preset maximum limit for the L3 segment of the lumbar spine to rotate around the Y-axis is 15 degrees. If the input angle of 10 degrees is within the limit, proceed directly to the next step.

[0146] The attitude and position calculation starts from the global root component and traces upwards to the attitude transformation of all subordinate components of that segment, recursively updating the global position of all subordinate segments; for example, starting from the pelvis, based on the input L3 segment rotation angle, the global positions of the upper spinal segments such as L2 and L1 are updated sequentially.

[0147] Global pose coupling couples the spine as a global position updated from the component, calculating the final global position of the spine. The specific steps are as follows:

[0148] Starting with the pelvis (root component), initialize its global position as the origin of the global coordinate system, that is:

[0149]

[0150] The global position of each spinal segment is calculated sequentially according to the hierarchical relationship of the spinal segments (from bottom to top). For the i-th spinal segment, its global position is obtained by multiplying the global position of its parent node (such as the pelvis or the next level spinal segment) by its own local homogeneous transformation matrix:

[0151]

[0152] in, It is the local homogeneous transformation matrix of the i-th vertebral segment, containing its rotation angle and translation vector about the Y-axis.

[0153] The global position information of all spinal segments is integrated to ensure that the position and orientation of each segment are updated based on the global position of its parent node. This hierarchical update method ensures the overall motion consistency of the spinal chain.

[0154] After updating the global position of all spinal segments, the global position information of the entire spinal chain is integrated to obtain the final global position of the spine. This includes: the three-dimensional coordinate position of each spinal segment; the rotation angle and direction of each spinal segment; and the relative position and orientation relationships between adjacent spinal segments.

[0155] By comparing the updated spine pose with the target pose, the final global position is verified to meet expectations. If deviations exist, the input parameters (such as rotation angle) can be further adjusted and the calculation recalculated.

[0156] A spring element is created to automatically identify three relatively rigid nodes on each segment of the spine. Based on the attitude coupling results, the node positions corresponding to the target attitude are calculated. Then, a spring element is created using the initial and target nodes to pull the spine to its final position. For example, three relatively rigid nodes are selected on the L3 segment of the lumbar spine. Based on the calculated target attitude node positions, a spring element is created to pull the L3 segment to the target position. The specific implementation method is as follows:

[0157] In finite element models, the nodal stiffness of spinal segments is typically determined by the material properties and geometry surrounding the nodes. Nodes with higher stiffness are usually located in the vertebral body portion of the spinal segment, as the vertebral body is the primary load-bearing structure of the spine.

[0158] By analyzing the mesh distribution and material properties of the finite element model, three nodes with high rigidity on each spinal segment were identified. The specific method is as follows: Nodes located near the geometric center of the spinal segment and uniformly distributed were selected. Nodes located in high-rigidity regions (such as the vertebral body) were preferentially selected. Nodes in stress concentration areas were selected based on anatomical characteristics.

[0159] The attitude coupling results provide the position and attitude information of the spinal segments in the global coordinate system. For each spinal segment, given its global position and attitude, the node position corresponding to the target attitude can be calculated using the following formula:

[0160]

[0161] in, These are the global coordinates of the node under the target's pose; It is the global pose matrix of the i-th spinal segment; It is the initial position of the node in the local coordinate system.

[0162] Spring elements are created using initial nodes and target nodes. Initial nodes refer to the original positions of the three most rigid nodes on the spinal segment before attitude adjustment. These node positions are stored in global coordinates within the finite element model. Target nodes refer to the new positions of the corresponding nodes calculated based on the attitude coupling results after attitude adjustment.

[0163] In the finite element model, spring elements are used to apply force or displacement to achieve posture adjustment of the spine. For each spinal segment with three rigid nodes, spring elements are created separately, connecting the initial node and the target node.

[0164] The spring stiffness coefficient is set according to the biomechanical characteristics of the spine to ensure that the applied force can pull the node from the initial position to the target position. The preload of the spring is calculated based on the displacement difference between the initial and target positions.

[0165] The implementation steps are as follows:

[0166] Create spring elements: In the finite element model, create a spring element for each rigid node and connect the initial node and the target node.

[0167] Apply force or displacement through the spring unit to gradually move the node from the initial position to the target position.

[0168] Iterative calculations are performed using a finite element solver (such as LS-DYNA) until the node positions converge to the target positions.

[0169] In finite element simulation, the force applied by spring elements causes the spinal segments to gradually adjust their posture until they reach the target position. The solver iteratively calculates the displacement, velocity, and acceleration of the nodes until the convergence condition is met.

[0170] After the calculation is complete, the coordinate information of all nodes in the target pose is output to a file. This coordinate information is then imported into the initial model to update the spine's pose, completing the pose adjustment.

[0171] The target pose is calculated, and the calculated target pose file is output and automatically submitted to DYNA via a batch file. After the calculation is complete, the coordinates of the spine target pose nodes are written to the corresponding file to record the target pose information.

[0172] The target attitude calculation file is a text file containing the spine mesh model, spring elements, material properties, element properties, and control card parameters, typically stored in .dyn or .k format. This file defines the initial position of the finite element model and the spring elements created to adjust to the target position, and can be directly submitted to DYNA for calculation.

[0173] This uses a batch file (.bat) to automatically submit DYNA calculations. The batch file contains a series of commands to start the DYNA solver and load the target attitude calculation file. The path to the generated target attitude calculation file and the solver parameters are written into the batch file. Running the batch file automatically starts the DYNA solver and performs the calculations.

[0174] The specific process of DYNA calculation:

[0175] DYNA automatically reads the target pose calculation file using batch processing code, extracting the nodal coordinates, element definitions, material properties, boundary conditions, and control cards of the spine model. The batch processing code is as follows:

[0176] @echo off

[0177] cd / d "path to the folder containing the target attitude calculation files"

[0178] set DYNA_PATH="DYND solver installation path"

[0179] set INPUT_FILE="path to target attitude calculation file"

[0180] pushd "output file path"

[0181] %DYNA_PATH% i=%INPUT_FILE% ncpu=number of compute nodes memory=size of memory accessed

[0182] Popd

[0183] After the calculation is complete, the DYNA solver outputs the results to a specified file (such as output.dyn), which includes the coordinates and attitude information of all nodes in the target spinal pose.

[0184] Record the target pose information and extract the coordinate information of all nodes in the spine target pose from the DYNA output file. Write the extracted node coordinate information into an intermediate file (such as target_pose.txt) for later import into the initial model. Import the node coordinate information from the intermediate file into the initial finite element model to update the spine pose and complete the pose adjustment.

[0185] The target pose update involves importing a file containing the target pose node coordinates into the initial model and updating the global position of the nodes to the target pose position, thereby achieving automatic adjustment of the spinal pose.

[0186] This application also provides a spinal posture adjustment system based on a human finite element model, which utilizes the aforementioned spinal posture adjustment method based on a human finite element model.

[0187] This application embodiment also provides an electronic device 500 that utilizes the aforementioned method for adjusting spinal posture using a human finite element model. The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps of the aforementioned method for adjusting spinal posture using a human finite element model. In this application embodiment, the processor is the control center of the computer method and can be a physical machine processor or a virtual machine processor.

[0188] Reference Figure 5 The electronic device 500 includes at least one processor 501, at least one communication interface 502, at least one memory 503, and at least one bus 504. The bus 504 is used for communication between these components, the communication interface 502 is used for signaling or data communication with other node devices, and the memory 503 stores machine-readable instructions executable by the processor 501. When the electronic device 500 is running, the processor 501 communicates with the memory 503 via the bus 504. When the machine-readable instructions are invoked by the processor 501, they execute the steps of the spinal posture adjustment method based on a human finite element model as described above.

[0189] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor of an electronic device, can implement the steps of a method for adjusting the spinal posture of a human finite element model as described above.

[0190] Those skilled in the art will understand that implementing all or part of the process in a spinal posture adjustment method based on a human finite element model can be accomplished by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium. When executed, the program can include the processes of various embodiments of the spinal posture adjustment method based on a human finite element model. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0191] The above content is merely an embodiment of the present invention. Commonly known structures and characteristics of the solutions 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 prior art 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 this solution based on the guidance provided in this application and their own capabilities. Some typical well-known structures or systems 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. These should also be considered within the scope of protection of the present invention, and 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 spinal posture using a human finite element model, characterized in that, include: Determine the master-slave relationship between components, and use the key reference point of the human body model as the origin of the global coordinate system to establish a spatial positioning framework. The key reference point is located at the predetermined reference position of the contact surface between the seat and the human body. Set the pelvis as the root component of the entire spinal structure, and establish the master-slave relationship between each segment of the spine from bottom to top to form a hierarchical spinal motion chain. Determine the joint nodes of the spinal segment, take the midpoint of the centroid of the upper and lower surfaces of the adjacent spinal segment to obtain the joint nodes, and form a spinal kinematic chain with the joint nodes and the corresponding spinal segment. Establish kinematic control connections for the spinal segments, create and bind Beam elements for each root component and slave component, and establish an independent local coordinate system for each Beam element; define rotational hinges, determine the coordinate axis of the relative motion of the spinal segments, set it as the Y-axis, and simulate the motion characteristics of the spine through preset hinge parameters; Establish the kinematic equations of the spinal segments, model the spine as a series structure of spinal segments and joint nodes, control the relative motion between the spines through rotational hinges, and use a three-dimensional homogeneous transformation matrix to describe the relative motion between each spinal segment. Automatic spinal posture adjustment control: Construct a spinal posture adjustment plugin, input the rotation angle of any spinal segment, complete the posture adjustment calculation of the spinal chain, and output the spatial position and orientation of the spinal segment.

2. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that: The articular nodes are obtained by taking the midpoints of the centroids of the upper and lower surfaces of adjacent spinal segments, including the following: For each pair of adjacent spinal segments, calculate the centroid coordinates of their upper and lower surfaces in three-dimensional space, and take the midpoint of these two centroids as the joint node.

3. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, Define a rotational hinge, determine the coordinate axis for the relative motion of the spinal segments (set as the Y-axis), and simulate the spinal motion characteristics using preset hinge parameters, including the following: Two nodes with coincident spatial coordinates on the Y-axis are selected on the Beam element of adjacent spinal segments as the rotation center of the rotation hinge. The preset hinge parameters include initial stiffness, motion damping and angle limit.

4. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, Automatic spinal posture adjustment control includes inputting the target angle, judging the angle limit, calculating the posture position, global posture coupling, creating spring units, calculating the target posture, and updating the target posture.

5. The method for adjusting the spinal posture of a human finite element model according to claim 2, characterized in that, Establishing the kinematic equations for the spinal segment includes single-segment posture update expressions, including the following: Joint rotation matrix: in, Indicates the first The angle of rotation of the vertebral column around the Y-axis; Translation vector of the spinal segment: in, Indicates from arrive distance, This indicates the position of the articular node in the i-th spinal segment; Then the first The local homogeneous transformation matrix of the section is: in, This represents the i-th spine.

6. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, Establishing the kinematic equations for the spinal segment also includes recursive expressions for the overall posture, including the following: Let the pelvis be The initial orientation is the identity matrix: Then the first The global pose of each spine is: The coordinates of the spine after posture adjustment are obtained.

7. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, The posture update control logic of the spinal posture adjustment plugin also includes angle limit judgment. If the input angle exceeds the preset maximum limit, the angle will be automatically adjusted to the maximum limit before subsequent calculations are performed.

8. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, The posture update control logic of the spinal posture adjustment plugin also includes creating spring units, automatically identifying three nodes with greater rigidity on each segment of the spine, calculating the node positions corresponding to the target posture based on the posture coupling results, and then creating spring units through the initial nodes and target nodes to pull the spine to the final position.

9. The method for adjusting the spinal posture of a human finite element model according to claim 1, characterized in that, The posture update control logic of the spinal posture adjustment plugin also includes target posture calculation, outputting the target posture calculation file and automatically submitting it to DYNA for calculation via a bat file; after the calculation is completed, the coordinates of the spinal target posture nodes are written to the corresponding file, and the file is imported into the initial model to update the global position of the nodes.

10. The method for adjusting the spinal posture of a human finite element model according to claim 9, characterized in that, The posture update control logic of the spinal posture adjustment plugin also includes target posture update, which imports the target posture node coordinate file into the initial model and updates the global position of the nodes to the target posture position.

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