Bionic model of natural walking posture injury of the fifth percentile female in China, model construction method, model construction system and application

Abstract

The application discloses a kind of natural walking posture pedestrian injury bionic model of Chinese fifth percentile female figure, and the pedestrian injury bionic model meets Euro NCAP pedestrian human model authentication standard, model height is 151cm, and model weight is 50.3kg, model has the anatomical structure characteristics of real human body, model has natural walking posture state, and walking posture attitude definition parameter meets Euro NCAP pedestrian human model authentication standard.The application also discloses the construction method of the above-mentioned model, model construction system;The application also discloses the method for using the above-mentioned natural walking posture pedestrian injury bionic model of Chinese fifth percentile female figure to carry out pedestrian injury mechanism research in person-vehicle collision, and carries out pedestrian injury mechanism evaluation system in person-vehicle collision.The content of the application can provide technical support for the depth analysis of person-vehicle collision accident, the formulation of person-vehicle collision safety standard and the digital evaluation of automobile safety.

Description

Technical Field

[0001] This invention belongs to the fields of human body numerical calculation model development technology and biomechanical research technology of pedestrian human body injury in human-vehicle collision safety. In particular, it relates to a biomimetic model of pedestrian injury in natural walking posture representing the fifth percentile of females in China, which meets the Euro NCAP pedestrian human body model certification requirements, as well as the model construction method, model construction system and application. Background Technology

[0002] Pedestrians are generally considered vulnerable road users due to a lack of effective protection. In addition to the high mortality rate, the high injury rate in pedestrian-vehicle collisions also has a significant impact on the injured's families and society as a whole. To provide pedestrians with a higher level of protection and effectively reduce pedestrian injuries and fatalities in pedestrian-vehicle collisions, in-depth research is needed on the damage mechanisms of human bones, internal organs, and soft tissues during pedestrian-vehicle collisions. However, cadaver experiments, animal experiments, volunteer experiments, and anthropometry testing equipment experiments are all subject to significant limitations due to ethical concerns or their own experimental conditions. The finite element method (FEM) model of the human body, due to its high biofidelity and ability to accurately calculate stress and strain changes in various human tissues, is considered one of the important tools for studying human injury. However, the several versions of the finite element model of the 5th percentile female pedestrian developed so far have been significantly simplified in terms of physiological structure, thus having certain deficiencies in biofidelity. Furthermore, existing models are based on human body dimensions from Europe and the United States, which also limits their direct application in evaluating the injury situation of pedestrians in pedestrian-vehicle collisions in my country. Therefore, developing pedestrian injury biomimetic models based on real human anatomy, especially data that conforms to Chinese anatomy, will further improve the reliability of research on pedestrian injury mechanisms and protective measures during human-vehicle collisions.

[0003] Euro NCAP Technical Bulletin Pedestrian Human Model Certification 3.0.1 (TB024) uses CAE simulation calculations based on human models with complex physiological and anatomical structures as one of the methods for vehicle evaluation. During a pedestrian-vehicle collision, the type and severity of pedestrian injury are closely related to the pedestrian's posture. Therefore, the aforementioned technical bulletin defines the posture parameters of a 5th percentile female pedestrian model in her natural gait. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a biomimetic model of natural gait injury in Chinese women at the 5th percentile of the human body model certification compliant with Euro NCAP, its construction method, and the application of the model.

[0005] In this invention, a three-dimensional reconstruction technique is employed when establishing the geometric model of the human injury biomimetic model. The geometric structure is based on the physical characteristics of female volunteers in China at the 5th percentile. The model's height is 151cm and its weight is 50.3kg, conforming to the latest human morphological statistical measurement data. The model closely approximates the anatomical features of the real human body, including all tissue structures such as the head, neck, chest, abdomen, and limbs, except for blood vessels. It possesses a high degree of biofidelity and can be used for injury simulation and mechanism analysis at the human tissue level.

[0006] Since the type and severity of pedestrian injuries are significantly influenced by pedestrian posture during human-vehicle collisions, when constructing a biomimetic model of a pedestrian's natural gait, the requirements for the fifth percentile female pedestrian model in Euro NCAP Technical Bulletin Pedestrian Human Model Certification 3.0.1 (TB024) were referenced. By adjusting the corresponding joint angles and reconstructing the mesh cells at the joint adjustment points, the posture definition parameters were made to meet the standards, thereby obtaining a biomimetic model of a Chinese fifth percentile female's natural gait injury that meets Euro NCAP pedestrian human model certification.

[0007] This invention proposes a method for constructing a biomimetic model of physical characteristics and gait impairment in Chinese women at the 5th percentile, comprising the following steps:

[0008] Step A: Construct a finite element model of human tissues and organs based on CT image information of female volunteers with the 5th percentile of physical characteristics in China;

[0009] Step B: Based on the requirements for the fifth percentile female pedestrian model in Euro NCAP Technical Bulletin Pedestrian Human Model Certification 3.0.1 (TB024), determine the posture definition parameters of the bionic model of injury of the fifth percentile female pedestrian in China with natural gait.

[0010] The posture definition parameters include: longitudinal distance between the two heels Px: 240.4mm, lateral distance between the two heels Py: 186.2mm, AC height from the ground ACz: 823.3mm, HC height from the ground HCz: 1475.5mm, distance between HC and AC in the X direction HCx: 23.5mm, right thigh angle K: 87.8°, left thigh angle L: 103.1°, right knee flexion angle G: 166.5°, and left knee flexion angle H: 17°. 4.0°, right upper arm Y-direction angle Ty: 96.8°, left upper arm Y-direction angle Uy: 71.0°, right upper arm X-direction angle Tx: 105.8°, left upper arm X-direction angle Ux: 107.7°, right elbow flexion angle V: 139.1°, left elbow flexion angle W: 153.2°; where the front-back direction of the human body is the X-direction, the left-right direction is the Y-direction, and the up-down direction is the Z-direction; AC is the midpoint of the line connecting the center points of the two acetabulum, and HC is the center of mass of the head.

[0011] The specific posture definition parameters are determined based on the range of parameters required for the model as specified in the technical announcement, while also taking into account joint range of motion. Joint range of motion refers to the arc of motion that a healthy human joint can traverse, usually expressed in angles.

[0012] Step C: Based on the posture definition parameters in Step B, determine the joints that require angle adjustment and set marker points at the selected joints. According to the magnitude of the joint adjustment, divide the joints requiring angle adjustment into primary joints with larger adjustment ranges and secondary joints with smaller adjustment ranges. The primary joints refer to the shoulder, elbow, hip, and knee joints, and the secondary joints refer to the wrist and ankle joints. Temporarily remove muscles, ligaments, fat, and skin tissue from the model's limbs. Divide the temporarily removed upper limbs into the upper arm, forearm, and hand, using the elbow crease as the boundary; divide the lower limbs into the thigh, calf, and foot, using the popliteal fossa as the boundary. In the model, only the skeletal structure of the limbs is retained; the rest of the body remains unchanged.

[0013] The marker points are located at the shoulders, wrists, ankles, and the junction of the abdomen and buttocks on both sides of the body. The marker points are used for positioning, which can quickly and accurately reconnect previously removed muscles, ligaments, fat, and skin tissue to the limb bones after the joint angle adjustment is completed.

[0014] Step D: Use the "delete-rebuild mesh cell method" to adjust the angles of the main joints, in the order of hip, knee, shoulder, and elbow.

[0015] During joint adjustment, the horizontal axis of the rotation center at the acetabulum, knee joint, shoulder joint, and elbow joint of the model is defined as the rotation axis. According to the parameter requirements of each posture definition in step B, the lower limb rotates around the rotation axis at the acetabulum, the lower leg rotates around the rotation axis at the knee joint, the upper limb rotates around the rotation axis at the shoulder joint, and the lower arm rotates around the rotation axis at the elbow joint.

[0016] Based on the established markers, the removed limb muscles, ligaments, fat, and skin tissue are reconnected to the limb skeleton of the model after the main pose adjustment. Specifically, the upper arm uses markers at the shoulder, the lower arm and hand uses markers at the wrist, the thigh uses markers at the junction of the abdomen and buttocks, and the lower leg and foot uses markers at the ankle. At this point, mesh cells exhibiting interference due to joint adjustments are clearly visible, and these interference mesh cells are deleted. Mesh reconstruction is then performed at the deleted mesh cell locations based on the actual physiological structure of the human body, filling in the missing mesh cell areas.

[0017] Step E: Adjust the angles of the accessory joints using the "forced mesh element displacement method", in the order of wrist joint and ankle joint.

[0018] When adjusting the wrist and ankle joints, the "Motion" command (BOUNDARY PRESCRIBEDMOTION RIGID keyword) in Ansa software is used to apply velocity to the joints whose angles need adjustment, causing forced displacement. The "Node Constraint" command (BOUNDARY SPC NODE keyword) is used to fix nodes that do not need to move. Then, the Ls-Dyna software solver is submitted for calculation, causing displacement of the accessory joints to achieve angle adjustment. Once the accessory joint reaches the position corresponding to the required angle, the joint angle adjustment is complete. The solver calculation is stopped, and the adjusted .k file is exported. This .k file and the original model .k file are imported into Primer software. The "Node Input" command (NODE INPUT keyword) is used to replace nodes in the original model .k file with data from the adjusted model .k file to achieve the model's accessory joint angle adjustment. Finally, the mesh elements are checked and optimized.

[0019] Mesh element quality checks primarily include metrics such as Jacobian, warpage, twist, aspect ratio, and the presence of negative volume. The mesh elements are checked using the "Quality Criteria" module in the Ansa software. The standards are set as follows: Jacobian greater than 0.3, warpage less than 50°, twist less than 60°, and aspect ratio less than 8°. For non-compliant mesh elements, initial optimization is performed using the "Fix Quality" command to better meet the actual needs of the model. A manual review is then conducted based on this optimization.

[0020] The forced displacement refers to fixing the position nodes of the mesh cells that do not need to be displaced, and applying velocity to the mesh cell regions that need to be displaced to generate displacement, so that the joints that need to be adjusted reach the specified angle.

[0021] Step F: Construct a finite element model of the shoe based on the foot dimensions obtained in Step E. The shoe model consists of two parts: the sole and the upper. The geometry of the sole is derived from the schematic diagram of the sole in the national standard GB / T 38018—2019 "Test Methods for Fatigue Resistance of Footwear Soles," and adjusted in conjunction with the foot structure of the pedestrian model. The sole thickness is set according to the specifications in Euro NCAP Edamestrian Human Model Certification 3.0.1 (TB024). The upper is constructed based on the foot of the pedestrian model. A stable connection is achieved between the shoe and the pedestrian's foot, resulting in a bionic model of natural gait injury for a Chinese woman at the 5th percentile of the Euro NCAP pedestrian anthropometric model certification.

[0022] The biomimetic model of gait impairment of the fifth percentile female pedestrian in China proposed in this invention conforms to Euro NCAP pedestrian anthropometric model certification. It meets the various posture definition parameters of the fifth percentile female pedestrian gait model in the Euro NCAP TB024 certification technical report, as shown in Table 1 below:

[0023] Table 1. Posture definition parameters of the 5th percentile female pedestrian model with natural gait.

[0024]

[0025] This invention also proposes a biomimetic model of natural gait injury of the 5th percentile female in China, constructed using the above-mentioned method for constructing a biomimetic model of natural gait injury of the 5th percentile female in China, which conforms to Euro NCAP pedestrian human body model certification.

[0026] This invention also proposes a method for studying the injury mechanism of pedestrians in human-vehicle collisions using a biomimetic model of the natural gait of a Chinese woman at the 5th percentile of the human body model certification conforming to Euro NCAP. The method specifically includes the following steps:

[0027] Step 1: Import the biomimetic model of the natural gait injury of a Chinese woman at the 5th percentile of the human body model certification that meets Euro NCAP standards, along with a finite element model of the front structure of a certain car and a ground finite element model, into the Hypermesh software.

[0028] Step II: Fix the finite element model of the front structure of a certain car and the ground finite element position in Step I.

[0029] Step III: Place the pedestrian injury bionic model described in Step I on the front side of the car's front-end structure using "move" and "rotate" commands. When determining the pedestrian's position, ensure that the perpendicular line from the car's center point to the ground lies within the plane of the human coronal plane passing through the pedestrian's head centroid. This determines the pedestrian's position in the X direction. Next, determine the pedestrian's position in the Z direction based on the height of the pedestrian's head centroid. Then, adjust the pedestrian model's position in the Y direction by translation, ensuring that the pedestrian walking posture model is as close as possible to the car's front-end structure while preventing contact.

[0030] Step IV: Check and adjust the pedestrian injury biomimetic model and vehicle front-end structure model described in Step III to ensure that there is no mesh penetration or interference.

[0031] Step V: Set boundary conditions for the pedestrian injury biomimetic model and the car front structure model, including: setting surface-to-surface contact between the pedestrian injury biomimetic model and the car front structure model to ensure effective contact between the models and normal force transmission; setting surface-to-surface contact between the shoe finite element model and the ground finite element model; and setting a gravity field between the pedestrian injury biomimetic model (including the shoe model) and the car front structure finite element model.

[0032] Step VI: Set the initial velocity for the front-end structure model of the car and conduct a human-vehicle collision simulation test.

[0033] Step VII: Analyze the kinematic and biomechanical parameters of the head, neck, chest, abdomen, and limbs of the pedestrian injury biomimetic model output from the simulation experiment in Step VI. Compare the kinematic trajectories of different body parts with the corresponding data reference channels to assess the kinematic response trend of the pedestrian injury biomimetic model of the fifth percentile female physical characteristics in China during a human-vehicle collision. Compare the damage observation parameters of different tissues with the preset and reasonable damage thresholds for the corresponding body parts. Combine this with stress and strain contour maps of the tissue parts to comprehensively analyze the injury mechanism of the fifth percentile female physical characteristics pedestrian in China.

[0034] Step VIII: Examine the energy changes in the simulation experiment and quantitatively determine the rationality of the experimental results from the perspective of energy changes. The main items to be checked include total energy, hourglass energy, contact energy, and mass gain rate.

[0035] Generally, total energy refers to the sum of all energies involved in a system during a simulation experiment, including internal energy, kinetic energy, and slip interface energy. When checking the total energy, it is necessary to accumulate the energy states of the system at different times and ensure that the total energy is conserved. If the total energy is conserved, it indicates that the energy model and calculations of the simulation experiment are reasonable.

[0036] The hourglass energy refers to the energy change in a certain part of the system, usually representing the energy flow or transfer within the system. When checking the hourglass energy, it is necessary to focus on the energy changes in a specific area or component to ensure that energy flows and transforms within the system in the expected manner.

[0037] Contact energy refers to the energy exchange between different parts of a system. In simulation experiments, contact energy between different components may be transferred through collisions, friction, and other means. Checking contact energy requires ensuring that the energy exchange conforms to physical laws and does not lead to abnormal energy loss or increase.

[0038] The mass increase rate refers to the ratio of the increase in model mass during the simulation experiment to the initial mass of the model.

[0039] The simulation test results are considered reasonable when the total energy and mass increase rate vary within a certain threshold range, the ratio of hourglass energy to total energy and the ratio of contact energy to total energy do not exceed the preset threshold, and all of the above conditions are met simultaneously.

[0040] The present invention also proposes a model building system for implementing the above-mentioned model building method. The model building system includes: a mesh cell deletion module, a local adjustment module, a mesh cell forced displacement module, and a mesh cell checking and optimization module.

[0041] The Delete Mesh Cell module is used to identify and delete mesh cells at major joints that need to be deleted due to angle adjustments;

[0042] The local adjustment module is used to adjust the main joint angles and reconstruct the mesh cells at the joints after adjustment.

[0043] The mesh element forced displacement module is used to adjust the angle of the auxiliary joints through forced displacement.

[0044] The Mesh Cell Inspection and Optimization module is used for inspecting the quality of the mesh after joint angle adjustments and optimizing low-quality mesh cells.

[0045] This invention also proposes an evaluation system for pedestrian injury mechanisms in human-vehicle collisions using a biomimetic model of the natural gait injury of the fifth percentile female in China. The pedestrian injury mechanism evaluation system includes: a fixing module, an adjustment module, a loading module, an evaluation module, and an inspection module.

[0046] The fixing module is used to fix the position of the vehicle model and the ground model;

[0047] An adjustment module is used to place a pedestrian injury bionic model of the 5th percentile female physical characteristics in China with a natural walking posture in front of the vehicle and adjust the position of the pedestrian injury bionic model relative to the vehicle.

[0048] The loading module is used to apply corresponding constraints and contact conditions to the vehicle model, ground model, and pedestrian injury biomimetic model. A gravity field is applied throughout the entire test environment. Based on the test conditions, an initial collision velocity or velocity variation curve is applied to the vehicle model.

[0049] The evaluation module is used to output the kinematic and biomechanical parameters of the pedestrian injury biomimetic model and to conduct a comprehensive evaluation study on the pedestrian injury mechanism based on the data.

[0050] The inspection module is used to check the energy changes during the experiment to determine the rationality of the simulation results.

[0051] The beneficial effects of this invention include: the biomimetic model of injury of the fifth percentile female pedestrian in China with natural gait, which conforms to Euro NCAP pedestrian anthropometric model certification, fills the gap in the field of constructing biomimetic models of injury of the fifth percentile female pedestrian in China that conforms to natural gait standards and Chinese anthropometric features and has detailed anatomical structure. The above model can be used for pedestrian-vehicle collision simulation calculation and injury analysis at the human tissue level.

[0052] The present invention proposes a biomimetic model of pedestrian injury based on the natural gait of a woman in China, which is compliant with Euro NCAP pedestrian anthropometric model certification and represents the physical characteristics of the 5th percentile of women in China. Compared with the 5th percentile female pedestrian models developed abroad, this model is more consistent with the human anthropometric characteristics of the 5th percentile of women in my country. It also has more detailed anatomical structural features that are more consistent with the real human body. The constructed tissues and organs are more detailed, including all tissue structures of the head, neck, chest, abdomen, and limbs except for blood vessels. Compared with the previously developed models that greatly simplified the human body structure, the model described in this invention can more realistically simulate the interactions between bones, between bones and muscles, between muscles, between internal organs, and between soft tissues during a human-vehicle collision.

[0053] This invention proposes a posture adjustment method for a biomimetic model of pedestrian injury in a natural gait, representing the 5th percentile female physiology in China and conforming to Euro NCAP pedestrian anthropometric certification standards. This method combines the commonly used "delete-rebuild mesh element method" with the "forced mesh element displacement method." During the adjustment of accessory joint angles, the tedious work of large-scale mesh element deletion and reconstruction required by the "delete-rebuild mesh element method" is eliminated. The "forced mesh element displacement method" only requires local mesh element quality checks and optimizations after mesh element displacement, thus improving the efficiency of adjusting the model's posture. The application of this biomimetic model of pedestrian injury in a natural gait, representing the 5th percentile female physiology in China and conforming to Euro NCAP pedestrian anthropometric certification standards, in the study of pedestrian injury mechanisms in human-vehicle collisions makes the human-vehicle collision simulation research process more standardized, efficient, systematic, and reasonable.

[0054] The innovative methods of this invention mainly include the following five aspects: (1) A biomimetic model of pedestrian injury in a natural walking posture, representing the physical characteristics of the fifth percentile of Chinese women, was constructed in accordance with Euro NCAP pedestrian human body model certification. By applying the above model to carry out human-vehicle collision simulation tests, the kinematic and biomechanical responses of the pedestrian model can be output, and in-depth analysis of human kinematics and injuries can be carried out at the level of the entire pedestrian and at various tissue levels such as the head, neck, chest, abdomen, and limbs. (2) A method for efficiently and quickly determining the mesh units to be deleted due to posture adjustment is proposed when adjusting from a pedestrian standing posture model to a natural walking posture model using the "delete-rebuild mesh unit method". That is, during the posture adjustment process, secondary tissues (muscles, ligaments, fat, skin) are temporarily removed from the limbs, leaving only the skeletal parts. After the joint adjustment is completed, the temporarily removed parts are reconnected to the bones, and the mesh units that cause interference at this time are deleted. This method can effectively avoid blindly deleting mesh units during the posture adjustment process, thereby increasing unnecessary workload, while ensuring that the model after posture adjustment has a high degree of biofidelity. (3) A "forced mesh element displacement method" was proposed for adjusting joints with small adjustment angles during pedestrian posture adjustment, in order to avoid the complex operations of mesh element deletion and reconstruction in the traditional "delete-rebuild mesh element method" and improve the efficiency of model posture adjustment. (4) A method was proposed to quickly determine the pedestrian position in the process of studying the pedestrian injury mechanism in human-vehicle collisions by using a biomimetic model of natural walking posture representing the fifth percentile female physical characteristics in China that conforms to Euro NCAP pedestrian anthropometric model certification. This method simplifies the complex problem of determining the pedestrian's position in the X, Y, and Z directions. After determining the feature plane and feature points, only a translation operation is required in one direction, reducing the blindness in determining the pedestrian position and improving the accuracy and efficiency of the work. (5) A method was proposed to use a biomimetic model of natural walking posture representing the fifth percentile female physical characteristics in China that conforms to Euro NCAP pedestrian anthropometric model certification to study the pedestrian injury mechanism in human-vehicle collisions. In particular, most current judgments on the rationality of simulation test results are concentrated in the qualitative judgment stage, that is, mainly based on the output animation, which is highly subjective. This invention proposes to apply energy change to further examine the rationality of simulation test results, that is, to conduct quantitative analysis from the perspective of energy change. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1This invention provides a flowchart of the construction method and application of a biomimetic model of pedestrian injury representing the 5th percentile female physical characteristics in China, conforming to Euro NCAP pedestrian anthropometric model certification.

[0057] Figure 2 This is a schematic diagram illustrating the posture definition of a female pedestrian's natural gait model at the 5th percentile in Euro NCAP Pedestrian Human Model Certification 3.0.1 (TB024). The abbreviations in the diagram are as follows: HCz – HC height above the ground, ACz – AC height above the ground, HCx – distance between HC and AC in the X-direction, T – right upper arm angle, U – left upper arm angle, V – right elbow flexion angle, W – left elbow flexion angle, K – right thigh angle, L – left upper thigh angle, G – right knee flexion angle, H – left knee flexion angle. The X-direction represents the forward / backward direction, the Y-direction represents the left / right direction, and the Z-direction represents the up / down direction; AC is the midpoint of the line connecting the centers of the two acetabulum fossae, and HC is the center of mass of the head.

[0058] Figure 3 This is a schematic diagram of a biomimetic model of pedestrian injury in a natural gait, representing the fifth percentile female physical characteristics in China, which conforms to Euro NCAP pedestrian anthropometric model certification in this invention; wherein (a) is an anterior coronal view and (b) is a left sagittal view.

[0059] Figure 4 This is a schematic diagram of a female pedestrian at the fifth percentile in an embodiment of the present invention standing in front of the front structure of a vehicle.

[0060] Figure 5 This is a schematic diagram of the motion trajectory of the fifth percentile female pedestrian's head centroid HC according to an embodiment of the present invention; where (a) is the motion trajectory in the X direction and (b) is the motion trajectory in the Z direction.

[0061] Figure 6 This is a schematic diagram of the motion trajectory of the center point of the T12 vertebra (twelfth thoracic vertebra) of a female pedestrian in the fifth percentile of this invention; where (a) is the motion trajectory in the X direction and (b) is the motion trajectory in the Z direction.

[0062] Figure 7 This is a schematic diagram of the movement trajectory of AC, the midpoint of the line connecting the center points of the two acetabular fossae of a female pedestrian in the fifth percentile of this invention; where (a) is the movement trajectory in the X direction and (b) is the movement trajectory in the Z direction.

[0063] Figure 8 This is a schematic diagram illustrating the relationship between the contact time and contact force between a female pedestrian and a vehicle at the fifth percentile of this invention.

[0064] Figure 9This is a Von Mises stress cloud diagram of the long bones of the lower limb of a female pedestrian in the fifth percentile of this invention; where (a) is the femur, and (b) is the tibia and fibula. The upper limit of the legend values ​​in the figure is the maximum Von Mises stress value appearing in the long bones. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0066] The pedestrian injury biomimetic model used in this invention, representing the 5th percentile female physical characteristics in China and conforming to Euro NCAP pedestrian anthropometric model certification standards, features a more detailed anatomical structure that closely resembles the real human body. It includes all bones, internal organs, muscles, ligaments, fat, and skin tissues, with shared nodes connecting these tissues to ensure effective force transmission. The adjustment of the natural gait posture of the 5th percentile female pedestrian in this invention is based on a finite element model rather than a geometric model. This invention fills a gap in the field of constructing 5th percentile female pedestrian injury biomimetic models that conform to natural gait standards and Chinese anthropometric characteristics, and possess detailed anatomical structures. It can be used to study the injury mechanisms of small-statured female pedestrians in human-vehicle collisions.

[0067] The content of this invention can provide technical support for in-depth analysis of human-vehicle collision accidents, formulation of human-vehicle collision safety standards, and digital evaluation of vehicle safety.

[0068] This invention proposes a method for constructing a biomimetic model of pedestrian injury representing the 5th percentile of female physical characteristics in China, conforming to Euro NCAP pedestrian anthropometric model certification standards. For example... Figure 1 As shown, the construction method of the present invention includes the following steps:

[0069] Based on CT images of female volunteers at the 500th percentile in China, 3D geometric models of various tissues and organs were obtained using Mimics software. Further smoothing and leveling of the extracted 3D geometric models were performed in Geomagic software, which divided the models into surface patches, generated grids, and fitted surfaces. Then, in Hypermesh software, the fitted surfaces were used to mesh the tissue and organ geometric models, assigning properties and materials to them to construct finite element models of human tissues and organs.

[0070] Based on the Euro NCAP technical bulletin Pedestrian Human Model Certification 3.0.1 (TB024), which requires the determination of posture definition parameters for a bionic model of the natural gait impairment of the 5th percentile female pedestrian in China, such as... Figure 2 As shown, Figure 2 The diagram illustrates the specific correspondence between different posture definition parameters and human postures.

[0071] Based on the magnitude of joint adjustment, the joints requiring angle adjustment are divided into primary joints with larger adjustment ranges and secondary joints with smaller adjustment ranges. The primary joints refer to the shoulder, elbow, hip, and knee joints, while the secondary joints refer to the wrist and ankle joints. The "delete-rebuild mesh element method" is applied to adjust the angles of the primary joints, and the "forced mesh element displacement method" is applied to adjust the angles of the secondary joints.

[0072] During the adjustment of major joints, when adjusting the hip joint, the midpoint of the acetabular fossa on both sides is selected as the axis of rotation. The midpoint of this line is used as the reference point for rotation. The lower limb is rotated around the axis of rotation to adjust the angle of the left and right thighs. When adjusting the knee joint, the midpoint of the intercondylar fossa on both sides is selected as the axis of rotation. The midpoint of the axis of rotation is used as the reference point for rotation. The lower leg is rotated around the axis of rotation to adjust the flexion angle of the left and right knee joints. When adjusting the shoulder joint, the midpoint between the supraglenoid and infraglenoid tubercles of the scapula on both sides is selected as the axis of rotation. The midpoint of the axis of rotation is used as the reference point for rotation. The upper limb is rotated around the axis of rotation to adjust the angle of the left and right upper arm. When adjusting the elbow joint, the line connecting the midpoints of the trochlear portions of the humerus on both sides is selected as the axis of rotation. The midpoint of the axis of rotation is used as the reference point for rotation. The forearm is rotated around the axis of rotation to adjust the flexion angle of the left and right elbows.

[0073] During the adjustment of accessory joints, a velocity is applied to the joint whose angle needs to be adjusted, causing it to undergo forced displacement, and the angle of the accessory joint is calculated. When adjusting the ankle joint, the line connecting the medial malleoli of both sides is selected as the axis of rotation, and the center point of the axis of rotation is used as the reference point for rotation, and the foot is rotated around the axis of rotation. When adjusting the wrist joint, the line connecting the midpoints of the caudal styloid processes of both sides is selected as the axis of rotation, and the center point of the axis of rotation is used as the reference point for rotation, and the hand is rotated around the axis of rotation.

[0074] In addition, it is necessary to delete and reconstruct the meshes involved in interference, and to perform quality checks and optimizations on the mesh cells to ensure that the parameters in the mesh cell quality check better meet the actual needs of the model. The checked indicators include Jacobian, warpage, twist, aspect ratio, and the presence of negative volume phenomena; among these,

[0075] The Jacobian is a metric used to characterize the shape transformation of mesh cells. For 3D mesh cells, the Jacobian is a 3×3 matrix that describes the mapping transformation of mesh cells from the original coordinate space to the physical space. In mesh quality checks, it is necessary to ensure that the Jacobian value is greater than or equal to zero; otherwise, it indicates that the mesh cells are reversed or flipped.

[0076] Skewness is a metric used to measure the non-uniformity of angles within a mesh cell. For 3D mesh cells, skewness is typically expressed as the difference between the maximum and minimum interior angles of a given angle. A larger skewness value indicates greater angular variation within the mesh cell, which may lead to instability or decreased accuracy in numerical calculations.

[0077] Distortion is an index used to describe the degree of distortion in the shape of mesh elements. The distortion index can be compared with the ideal shape of the mesh element based on the vertex position. A larger distortion value indicates that the shape of the mesh element is more distorted, which may affect the accuracy of the simulation results.

[0078] Aspect ratio refers to the ratio of the lengths of the sides of a mesh cell. In a two-dimensional mesh, the aspect ratio is usually the ratio of the length of the longest side to the length of the shortest side of the mesh cell. A large aspect ratio indicates that the mesh cells are very long and thin or very flat, which may increase numerical calculation errors.

[0079] Negative volume refers to the phenomenon where a mesh element has a negative volume. In 3D meshes, a negative volume indicates that the mesh element's face is facing incorrectly or that the mesh element is reversed. Negative volume can lead to numerical calculation errors, therefore such mesh elements must be excluded during mesh quality checks.

[0080] In this invention, the standards for setting the inspection indicators are: Jacobian greater than 0.3, warpage less than 50°, twist less than 60°, and aspect ratio less than 8°.

[0081] When constructing the finite element model of the shoe, the shoe model consists of two parts: the sole and the upper. The geometry of the sole is derived from the schematic diagram in the national standard GB / T 38018—2019 "Test Methods for Fatigue Resistance of Footwear Soles," and adjusted based on the size and structure of the pedestrian model's foot. The sole thickness at the heel is 26mm, conforming to the Euro NCAP Pedestrian Human Model Certification 3.0.1 (TB024) requirement of 20-30mm for the heel sole thickness. Then, the upper is constructed based on the pedestrian model's foot. The sole model uses solid element meshes, while the upper uses shell element meshes. In Hypermesh software, the "Constrianed > Tied" keyword is used to select the left and right sole elements as principal faces and the left and right feet of the pedestrian model as secondary faces, respectively, to achieve a stable connection between the shoe and the pedestrian's foot. Finally, a bionic model of natural gait injury for a Chinese woman at the 5th percentile of the Euro NCAP pedestrian human model certification is obtained.

[0082] The present invention provides a biomimetic model of natural gait injury in Chinese women at the 5th percentile, conforming to Euro NCAP pedestrian anthropometric model certification. Figure 3 As shown, the model has more detailed anatomical features that are more consistent with the real human body. The model represents the human body structure through units and / or nodes with mechanical properties. It can be used to calculate the kinematic and biomechanical response parameters of small-statured female pedestrians in human-vehicle collisions under their natural walking posture. It can be used to study the injury mechanism of small-statured female pedestrians in human-vehicle collisions at the whole person and tissue levels.

[0083] like Figure 4 As shown, the biomimetic model of the injury of a Chinese woman with the fifth percentile of physical characteristics and natural gait, which conforms to Euro NCAP pedestrian anthropometric model certification, was placed on the front side of the front structure of an SUV and a human-vehicle collision test was conducted to study the injury mechanism of a Chinese woman with the fifth percentile of physical characteristics and natural gait.

[0084] The constructed biomimetic model of pedestrian injury with natural gait, representing the fifth percentile of female vital signs in China, was imported into Hypermesh software along with the finite element model of the front structure and ground of an SUV. The front structure parameters of the SUV were: spoiler ground clearance 289.1 mm, bumper width 70.0 mm, hood front edge height 904.1 mm, and vehicle weight 1823.4 kg. The positions of the SUV front structure finite element model and the ground finite element model were fixed, and the pedestrian model with natural gait, representing the fifth percentile of female vital signs in China, was placed in front of the SUV front structure using "translation" and "rotation" commands. The right side of the pedestrian model was defined as the impact side. When determining the pedestrian's position, ensure that the perpendicular line from the center point of the car to the ground lies within the plane of the human coronal plane passing through the centroid of the pedestrian's head. This determines the pedestrian's position in the X direction. Next, determine the pedestrian's position in the Z direction based on the height of the centroid of the pedestrian's head. Then, adjust the pedestrian model's position in the Y direction by translation, so that the pedestrian walking posture model is as close as possible to the front structure of the car while ensuring that it does not come into contact with the front structure of the car. Finally, check and adjust any mesh penetration and interference phenomena between the pedestrian walking posture model and the front structure of the vehicle.

[0085] Boundary conditions were set for the pedestrian injury biomimetic model of the 5th percentile female physical characteristics in China with a natural gait and the finite element model of the SUV front-end structure. Surface-to-surface contact was established between the pedestrian model and the SUV front-end structure model to ensure effective force transmission. Surface-to-surface contact was also established between the shoe finite element model and the ground finite element model. The friction coefficient between the vehicle and the outer surface of the pedestrian model was set to 0.3, and the friction coefficient between the shoe and the ground was set to 0.58. A gravity field was established for the pedestrian model (including the shoe model) and the SUV front-end structure model. An initial velocity of 40 km / h was set for the SUV front-end structure finite element model, and a pedestrian-vehicle collision simulation test was conducted.

[0086] The kinematic and biomechanical parameters of the head, neck, chest, abdomen, and limbs of the biomimetic model of the injury of the fifth percentile female pedestrian with a natural gait in China were output. The motion trajectories of the output feature points at different locations were compared with the corresponding data reference channels to evaluate the kinematic response trend of the biomimetic model of the injury of the fifth percentile female pedestrian with a natural gait in China during a human-vehicle collision. The injury observation parameters of different locations were compared with the injury thresholds of the corresponding locations, and the injury mechanism of the fifth percentile female pedestrian in China was comprehensively analyzed by combining the stress and strain cloud maps of the tissue locations. Table 2 shows a comparison of some head injury observation parameters and thresholds of the fifth percentile female pedestrian in China during the human-vehicle collision test. In the simulation test results, the maximum Von Mises stress, intracranial pressure, brain shear stress, and maximum principal strain of brain tissue all exceeded the thresholds, indicating a high risk of head injury for the pedestrian.

[0087] Table 2. Comparison of observation parameters and thresholds for head injuries among female pedestrians at the 5th percentile.

[0088]

[0089]

[0090] like Figure 5-7 The figure shows the motion trajectory of human characteristic points (center of mass of the head, center of T12 vertebra, and midpoint of the line connecting the centers of the two acetabular fossae). The simulation results all fall well into the reference channel, indicating that the biomimetic model of natural gait injury of a Chinese woman at the fifth percentile of the human body, which conforms to Euro NCAP pedestrian human body model certification, has a high degree of biosimulation.

[0091] like Figure 8 As shown, the human-vehicle contact force reaches its peak of 17.40 kN at approximately 11 ms.

[0092] like Figure 9 As shown, in the pedestrian-vehicle collision, the maximum Von Mises stress of the femur was 115.0 MPa, exceeding the injury threshold of 114 MPa; the maximum Von Mises stress of the tibia and fibula was 124.8 MPa, exceeding the injury threshold of 98.2 MPa. Simultaneously, mesh cell deletion was observed, indicating that the simulation predicted fractures of the long bones of the lower limbs in pedestrians.

[0093] Table 3 shows the energy changes in the simulation experiment. Total energy refers to the sum of internal energy, kinetic energy, and sliding interface energy during the simulation experiment. Hourglass energy refers to the energy generated by adding an hourglass during the experiment. Contact energy refers to the energy generated by contact during the experiment. Mass increase rate refers to the ratio of the increase in model mass during the simulation experiment to the initial model mass. Parameters such as total energy, hourglass energy, contact energy, and mass increase rate can be directly obtained from the simulation experiment result output file. The formula for calculating the total energy change rate is: 1 - (Minimum total energy / Maximum total energy).

[0094] The simulation results are considered reasonable when the total energy and mass increase rate vary within a certain threshold range, and the ratios of hourglass energy to total energy and contact energy to total energy do not exceed the thresholds. The thresholds used in Table 3 are derived from Euro NCAP Pedestrian Human Model Certification 3.0.1 (TB024). Comparison with these thresholds demonstrates the reliability of the simulation results from an energy change perspective.

[0095] Table 3. Comparison of Energy Changes and Thresholds in Simulation Experiments

[0096]

[0097] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A method for constructing a biomimetic model of physical characteristics and gait impairment in Chinese women at the 5th percentile, characterized in that, The construction method includes the following steps: Step A: Construct a finite element model of human tissues and organs based on CT image information of female volunteers with the 5th percentile of physical characteristics in China; Step B: Based on the requirements for the fifth percentile female pedestrian model in Euro NCAP Technical Bulletin Pedestrian Human Model Certification 3.0.1 (TB024), determine the posture definition parameters of the bionic model of injury of the fifth percentile female pedestrian in China with natural gait. Step C: Based on the posture definition parameters in Step B, determine the joints whose angles need to be adjusted, and set marker points at the selected joints; the joints whose angles need to be adjusted are divided into primary joints and secondary joints; the primary joints refer to the shoulder joint, elbow joint, hip joint, and knee joint, and the secondary joints refer to the wrist joint and ankle joint; In step C, after setting the marker points, temporarily remove the muscles, ligaments, fat, and skin tissue from the model's limbs. Divide the temporarily removed upper limbs into two parts: the upper arm, forearm, and hand, with the elbow crease as the boundary. Divide the lower limbs into two parts: the thigh, calf, and foot, with the popliteal fossa as the boundary. In the model, only the skeletal structure is retained in the limbs, and the rest of the body remains unchanged. Step D: Use the "delete-reconstruct mesh unit method" to adjust the angles of the main joints, in the order of hip joint, knee joint, shoulder joint, and elbow joint; identify and delete the muscle, ligament, fat, and skin tissue mesh units in the model that cause interference due to joint adjustment; reconstruct the mesh based on the real physiological structure of the human body; fill in the deleted mesh unit locations; and reconnect the removed limb muscles, ligaments, fat, and skin tissue with the limb bones of the model after posture adjustment. In step D, after the posture adjustment is completed, the removed muscles, ligaments, fat, skin tissue and bones are reconnected according to the established marker points to determine the mesh cells in the model that cause interference due to joint adjustment. In step D, during joint adjustment, the horizontal axis of the rotation center of the model at the acetabulum, knee joint, shoulder joint, and elbow joint is defined as the rotation axis. According to the posture parameter requirements of each part, the lower limb rotates around the rotation axis at the acetabulum, the lower leg rotates around the rotation axis at the knee joint, the upper limb rotates around the rotation axis at the shoulder joint, and the lower arm rotates around the rotation axis at the elbow joint. Step E: Use the "forced mesh element displacement method" to adjust the angles of the accessory joints, in the order of wrist joint and ankle joint; force the mesh elements of the bones, muscles, ligaments, fat, and skin tissue of the joints to be adjusted to the specified positions; Step F: Construct a finite element model of the shoe based on the foot size obtained in Step A, and connect it to the foot of the model. Finally, obtain a bionic model of pedestrian injury with a natural walking posture that meets the Euro NCAP pedestrian anthropometric model certification standards and represents the physical characteristics of the fifth percentile female in China.

2. The construction method as described in claim 1, characterized in that, In step E, the method for forcing mesh cell displacement is as follows: fix the position nodes of mesh cells that do not need to be displaced, apply velocity to the mesh cell region that needs to be displaced to generate displacement, so that the joint that needs to be adjusted reaches the specified angle. The angle adjustment of the accessory joints is obtained through calculation.

3. The construction method as described in claim 1, characterized in that, In step B, the posture definition parameters include: longitudinal distance between the two heels Px: 240.4mm, lateral distance between the two heels Py: 186.2mm, AC height from the ground ACz: 823.3mm, HC height from the ground HCz: 1475.5mm, distance between HC and AC in the X direction HCx: 23.5mm, right thigh angle K: 87.8°, left thigh angle L: 103.1°, right knee flexion angle G: 166.5°, and left knee flexion angle H. : 174.0°, right upper arm Y-direction angle Ty: 96.8°, left upper arm Y-direction angle Uy: 71.0°, right upper arm X-direction angle Tx: 105.8°, left upper arm X-direction angle Ux: 107.7°, right elbow flexion angle V: 139.1°, left elbow flexion angle W: 153.2°; where the front-back direction of the human body is the X-direction, the left-right direction is the Y-direction, and the up-down direction is the Z-direction; AC is the midpoint of the line connecting the center points of the two acetabulum, and HC is the center of mass of the head.

4. The construction method as described in claim 1, characterized in that, In step C, the markers are set at the two shoulders, two wrists, two ankles, and the junction of the abdomen and buttocks on both sides of the body; the upper arm uses the markers at the shoulders, the lower arm and hand uses the markers at the wrists, the thigh uses the markers at the junction of the abdomen and buttocks, and the lower leg and foot uses the markers at the ankles.

5. A method for studying the pedestrian injury mechanism in human-vehicle collisions using a biomimetic model of pedestrian injury based on the physical characteristics of the 5th percentile female in China constructed according to any one of claims 1-4, characterized in that... The pedestrian injury bionic model meets the Euro NCAP pedestrian human body model certification standards. The model is 151cm tall and weighs 50.3kg. The model has real human anatomical structure features and a natural walking posture. The walking posture definition parameters meet the Euro NCAP pedestrian human body model certification standards. The posture definition parameters include: longitudinal distance between the two heels Px: 240.4mm, lateral distance between the two heels Py: 186.2mm, AC height from the ground ACz: 823.3mm, HC height from the ground HCz: 1475.5mm, distance between HC and AC in the X direction HCx: 23.5mm, right thigh angle K: 87.8°, left thigh angle L: 103.1°, right knee flexion angle G: 166.5°, and left knee flexion angle H: 174°. 0°, Right upper arm Y-direction angle Ty: 96.8°, Left upper arm Y-direction angle Uy: 71.0°, Right upper arm X-direction angle Tx: 105.8°, Left upper arm X-direction angle Ux: 107.7°, Right elbow flexion angle V: 139.1°, Left elbow flexion angle W: 153.2°; Wherein, the front-back direction of the human body is the X-direction, the left-right direction is the Y-direction, and the up-down direction is the Z-direction; AC is the midpoint of the line connecting the center points of the two acetabulum, and HC is the center of mass of the head; The method specifically includes the following steps: Step 1: Import the bionic model of a pedestrian with a natural gait, representing the 5th percentile female physical characteristics in China, which meets the Euro NCAP pedestrian anthropometric model certification standards, along with a finite element model of a car's front-end structure and a ground finite element model, into the Hypermesh software. Step II: Fix the finite element model of the front structure of a certain car and the ground finite element position from Step I; Step III: Place the pedestrian injury bionic model described in Step I in front of the front structure model of the car; when determining the pedestrian's position, ensure that the perpendicular line passing through the center point of the car and the ground lies in the plane of the human coronal plane passing through the centroid of the pedestrian's head, thereby determining the pedestrian's position in the X direction. Then, determine the pedestrian's position in the Z direction based on the height of the centroid of the pedestrian's head. Then, adjust the position of the pedestrian model in the Y direction by translation, so that the pedestrian walking posture model is as close as possible to the front structure of the car while ensuring that it does not come into contact with the front structure of the car. Step IV: Check and adjust the pedestrian injury biomimetic model and vehicle front-end structure model described in Step III to ensure that there is no mesh penetration or interference. Step V: Set boundary conditions for the pedestrian injury biomimetic model and the car front-end structure model; Step VI: Set the initial velocity for the front-end structure model of the car and conduct a human-vehicle collision simulation test; Step VII: Perform a comprehensive analysis of the kinematic and biomechanical parameters of the pedestrian injury biomimetic model output from the simulation experiment in Step VI to determine the pedestrian injury situation; Step VIII: Examine the energy changes in the simulation experiment to determine the reasonableness of the experimental results.

6. A model building system for implementing the method as described in any one of claims 1-4, characterized in that, The model building system includes: a mesh cell deletion module, a local adjustment module, a mesh cell forced displacement module, and a mesh cell inspection and optimization module; The mesh cell deletion module is used to identify and delete mesh cells at major joints that need to be deleted due to angle adjustments; The local adjustment module is used for adjusting the main joint angles and reconstructing the mesh cells at the joints after adjustment. The grid unit forced displacement module is used to adjust the angle of the auxiliary joint through forced displacement; The inspection and optimization module is used for inspecting the quality of the mesh after joint angle adjustment and optimizing low-quality mesh cells.

7. A biomimetic model of pedestrian injury based on the natural gait of a Chinese woman at the 5th percentile, constructed using the method described in any one of claims 1-4, characterized in that... The pedestrian injury bionic model meets the Euro NCAP pedestrian human body model certification standards. The model is 151cm tall and weighs 50.3kg. The model has real human anatomical structure features and a natural walking posture. The walking posture definition parameters meet the Euro NCAP pedestrian human body model certification standards. The posture definition parameters include: longitudinal distance between the two heels Px: 240.4mm, lateral distance between the two heels Py: 186.2mm, AC height from the ground ACz: 823.3mm, HC height from the ground HCz: 1475.5mm, distance between HC and AC in the X direction HCx: 23.5mm, right thigh angle K: 87.8°, left thigh angle L: 103.1°, right knee flexion angle G: 166.5°, and left knee flexion angle H: 174°. 0°, Right upper arm Y-direction angle Ty: 96.8°, Left upper arm Y-direction angle Uy: 71.0°, Right upper arm X-direction angle Tx: 105.8°, Left upper arm X-direction angle Ux: 107.7°, Right elbow flexion angle V: 139.1°, Left elbow flexion angle W: 153.2°; Wherein, the front-back direction of the human body is the X direction, the left-right direction is the Y direction, and the up-down direction is the Z direction; AC is the midpoint of the line connecting the center points of the two acetabulum, and HC is the center of mass of the head.

8. A system for evaluating pedestrian injury mechanisms in human-vehicle collisions using a biomimetic model of pedestrian injury based on the 5th percentile female physical characteristics in China, characterized in that... Using the research method described in claim 5, the pedestrian injury mechanism evaluation system includes: a fixing module, an adjustment module, a loading module, an evaluation module, and an inspection module; The fixing module is used to fix the positions of the vehicle model and the ground model; The adjustment module is used to place a pedestrian injury bionic model with the natural walking posture of the fifth percentile female physical characteristics in China in front of the vehicle and adjust the position of the pedestrian injury bionic model relative to the vehicle. The loading module is used to apply corresponding constraints and contact conditions to the vehicle model, ground model and pedestrian injury bionic model, apply a gravity field in the entire test environment, and apply an initial collision speed or speed change curve to the vehicle model according to the test conditions. The evaluation module is used to output the kinematic and biomechanical parameters of the pedestrian injury biomimetic model and to conduct a comprehensive evaluation study on the pedestrian injury mechanism based on the data. The inspection module is used to check the energy changes during the experiment in order to determine the rationality of the simulation test results.

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