Non-simulation rapid calculation method for soft tissue motion deformation of human body finite element model

Abstract

The invention relates to the technical field of automobile safety, in particular to a human body finite element model soft tissue motion deformation non-simulation rapid calculation method. Comprising the steps of initializing a calculation structure, recognizing a skeleton-soft tissue common node NBS, and extracting a soft tissue inner surface node NSS, a near-end end face node NSP and a far-end end face node NSD. And extracting skeleton motion information, calculating node coordinate sets BS0 and BS1 based on the initial configuration B0 and the target configuration B1, and determining end face boundaries SP0 and SP1 and SD0 and SD1 by utilizing rigid body transformation. Calculating an initial displacement field D0, acting on the NSS to obtain an initial deformation inner surface SS1, and processing a penetration site to obtain SS2; and fixing the BS1, and optimizing the coordinates of the SS2 node to obtain SS3. And integrating the initial mark point sets SS0, SP0 and SD0 and the post-motion mark point sets SS3, SP1 and SD1, and calculating a final displacement field D1 through spatial interpolation. The technical scheme can quickly and accurately simulate the large deformation of the soft tissue involved in human motion.

Description

Technical Field

[0001] The invention relates to the technical field of automobile safety, and in particular to a non-simulation fast calculation method for soft tissue motion deformation of a human finite element model. Background Art

[0002] With the advancement of science and technology, virtual R&D and evaluation are gradually replacing traditional physical testing methods in many fields, including automotive safety. Under this trend, the human finite element model has become a mainstream tool in safety R&D due to its high degree of refinement and accuracy. Compared with traditional dummy testing, the human finite element model can more realistically simulate the human body's response in various collision scenarios, providing more reliable safety performance evaluation for automotive design.

[0003] At the same time, the rapid development of autonomous driving technology and intelligent cockpit systems is reshaping the driving state of passengers. These technologies not only improve the convenience and comfort of driving, but also make the postures of passengers inside the car more diverse, thereby further expanding the range of human postures that need to be covered by automobile safety protection design. Therefore, the automotive safety field urgently needs to establish an efficient and accurate human finite element model posture transformation / extension platform.

[0004] In the process of posture transformation of the human finite element model, the adjustment of the bone configuration is relatively simple and can be efficiently achieved through rigid body motion transformation. However, large deformation of soft tissue is a more complicated problem, which involves complex nonlinear physical processes and requires the use of finite element analysis solvers for mechanical simulation under quasi-static loading. This process is not only inefficient and time-consuming, but also often leads to problems such as motion dislocation and unit distortion, which seriously affects the bionics and numerical accuracy of the simulation results, making it difficult to meet the needs of actual engineering applications. Summary of the invention

[0005] The purpose of the present invention is to propose a method for rapid calculation of soft tissue motion deformation without simulation in a human finite element model. The technical solution can quickly and accurately simulate large deformation of soft tissue involved in human motion.

[0006] To achieve the above objectives, the present disclosure provides a method for fast calculation of soft tissue motion deformation of a human finite element model without simulation, including: Calculate the structure initialization, detect the bone-soft tissue common node set NBS, extract the inner surface node set NSS of the soft tissue node set NSOFT on the bone interface, and extract the end surface node sets NSP and NSD of the soft tissue at the proximal and distal ends; Extract the bone movement information and calculate the end surface boundary, extract the coordinate set, and extract the Cartesian coordinate sets BS0 and BS1 of the subset NBS based on the initial configuration B0 and the target configuration B1; Based on the movement relationship from B0 to B1, use the rigid body transformation method to calculate the end surface boundaries SP0, SP1 and SD0, SD1 of the proximal and distal ends of the soft tissue before and after the movement; Calculate the initial displacement field D0 based on BS0 and BS1; Apply the initial displacement field D0 to the node set NSS of the inner surface of the soft tissue to obtain the inner surface SS1 of the soft tissue after initial deformation, detect the penetration site set SS1-B1 between SS1 and the bone B1, and process each penetration site until the penetration is eliminated to obtain the new inner surface SS2 of the soft tissue; Taking BS1 as the boundary and fixing the node position of BS1, the coordinate arrangement of each node in SS2 in the three-dimensional Euclidean space is optimized to obtain the optimized inner surface SS3; Integrate SS0, SP0, and SD0 as the initial landmark set, and SS3, SP1, and SD1 as the post-movement landmark set. Use the spatial interpolation method to calculate the final displacement field D1 based on the initial landmark set and the post-movement landmark set. The final displacement field D1 is applied to the initial soft tissue node coordinate set SOFT0 to obtain the deformed soft tissue node coordinate set SOFT1.

[0007] Beneficial effects of the basic scheme: This method avoids the complex iterative solution process in traditional finite element analysis by directly calculating the displacement field and optimizing the coordinates, thereby significantly improving the calculation efficiency. By extracting key nodes (such as NBS, NSS, NSP, NSD) and end surface boundaries (SP0, SP1, SD0, SD1), the amount of calculation is reduced, making the entire deformation calculation process faster.

[0008] The rigid body transformation method is used to calculate the end face boundary, which can accurately reflect the position change of the bone during the movement, and provide a reliable basis for the subsequent displacement field calculation and coordinate optimization. Through penetration detection and iterative processing, it is ensured that the soft tissue and the bone do not penetrate during the movement, the physical consistency of the model is maintained, and the accuracy of deformation calculation is improved. The singularity problem of interpolation calculation caused by the displacement field step induced by the slip of the bone-soft tissue interface is solved, and the physical fidelity of the deformation displacement field is improved.

[0009] The coordinate optimization process takes into account multiple factors such as shape matching, face flipping and mesh quality. The optimized soft tissue inner surface SS3 is obtained through the optimization algorithm, which further improves the mesh quality and robustness of the model. The spatial interpolation method can smoothly transition the displacement field and reduce errors and instability factors in deformation calculation.

[0010] The present invention can complete the simulation of soft tissue deformation based on skeletal movement in the shortest time, enabling the human finite element model to have the pre-processing efficiency at the level of a dummy model and the deformation bio-fidelity at the level of real human movement, and solve the problem of displacement field discontinuity caused by interface contact deformation coupling, avoiding the distortion of deformation mode and abnormal unit distortion, which seriously affects the accuracy of simulation results. In addition, this method is not only suitable for the calculation of soft tissue motion deformation in the human finite element model, but can also be extended to the deformation analysis of other biomechanical models or engineering structure models. By adjusting and optimizing the parameters in the algorithm, it can adapt to the calculation requirements of different precision and complexity.

[0011] As an implementable preferred solution, it is characterized in that the rigid body transformation method adopts the Rodrigues equation.

[0012] As an implementable preferred solution, it is characterized in that the calculation of the initial displacement field D0 includes the following contents: Based on BS0 and BS1, the deformation displacement field of the intermediate node is calculated using the spatial interpolation method, which is recorded as the initial displacement field D0.

[0013] As an implementable preferred solution, it is characterized in that the spatial difference method for calculating the initial displacement field D0 and the final displacement field D1 adopts a thin plate spline and / or Kriging method based on radial basis functions.

[0014] As an implementable preferred scheme, it is characterized in that the coordinate arrangement of each node in SS2 in the three-dimensional Euclidean space is optimized, and the optimization functions used include shape matching penalty function terms, face flipping penalty function terms and mesh quality regularization terms; an optimization algorithm is used to solve the optimization function to obtain the optimized soft tissue inner surface SS3.

[0015] As an implementable preferred scheme, it is characterized in that the shape matching penalty function term is the Chamfer distance between SS2 and SS3; the face flipping penalty function term is used to detect whether the dihedral angles along the edges of adjacent faces on the triangular surface structure have a step jump exceeding a threshold between SS2 and SS3; the mesh quality regularization term is the mean square error of the edge lengths in SS3 or the conformal measure of the angles within each face.

[0016] As an implementable preferred solution, it is characterized in that the penetration site set SS1-B1 between SS1 and the skeleton B1 is detected, and each penetration site is processed, including the following contents: Detect the set of segment nodes penetrated by the bone in SS1. For each penetration site, translate the corresponding node in the opposite direction of the penetration along the normal direction of the SS1 surface, and the displacement is a certain proportion of the penetration depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a logical diagram of a method for rapid calculation of soft tissue motion and deformation without simulation in a finite element model of the human body.

[0018] Figure 2 This is a conceptual diagram illustrating the computational process and node set. DETAILED DESCRIPTION

[0019] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings. It will be understood that the specific embodiments described herein are only partial embodiments of the present invention, which are only used to explain the present application, rather than to limit the present application. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects. The same reference numerals appearing in the drawings of the following embodiments represent the same features or components, which can be applied to different embodiments.

[0020] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of the present invention should have the common meanings understood by those skilled in the art in the art to which the present invention belongs.

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings: Reference Figure 1 and Figure 2 , a fast calculation method for soft tissue motion deformation of human finite element model without simulation, including: Step S100, computing structure initialization, includes the following contents: Step S101, detecting the bone-soft tissue common node set NBS, where the NBS nodes are the connection points between bones and soft tissues and remain relatively fixed during movement.

[0022] Step S102, extracting the inner surface node set NSS of the soft tissue node set NSOFT on the bone interface. The NSS nodes constitute the inner surface of the soft tissue, and its deformation will directly affect the overall shape of the soft tissue.

[0023] Step S103 , extracting the end surface node sets NSP and NSD of the soft tissue at the proximal end and the distal end, wherein the NSP node and the NSD node define the boundary conditions of the soft tissue and are used to determine the overall motion range of the soft tissue.

[0024] Step S200, extracting bone motion information and calculating end surface boundaries, includes the following contents: Step S201, extracting a coordinate set, based on the initial configuration B0 and the target configuration B1, extracting a Cartesian coordinate set of a subset NBS, denoted as BS0 and BS1, respectively, to reflect the position change of the bone during the movement process.

[0025] Step S202, calculate the end surface boundary: based on the motion relationship from B0 to B1, use rigid body transformation methods such as Rodrigues equation, Euler angle, quaternion, etc. to calculate the end surface boundaries SP0, SP1 and SD0, SD1 of the proximal / distal end surface of the soft tissue before and after the movement, which are used for subsequent spatial interpolation calculations.

[0026] Step S300, calculate the initial displacement field, based on BS0 and BS1, use the radial basis function based thin plate spline and / or Kriging method and other spatial interpolation methods to calculate the intermediate node deformation displacement field, recorded as the initial displacement field D0. According to the movement information of the bones, the deformation of the soft tissue is preliminarily estimated.

[0027] Step S400, initial deformation and penetration detection, includes the following contents: Step S401 : Apply the initial displacement field D0 to the soft tissue inner surface node set NSS to obtain the soft tissue inner surface SS1 after initial deformation.

[0028] Step S402, based on the position and connection relationship of the B1 node, detect the penetration site set SS1-B1 between SS1 and the skeleton B1, that is, detect the set of segment nodes in SS1 penetrated by the skeleton. For each penetration site, translate the corresponding node in the opposite direction of the penetration along the normal direction of the SS1 surface, and the displacement is a certain proportion of the penetration depth.

[0029] Then the penetration is re-detected and the above process is iterated until the penetration is eliminated. At this time, the current node coordinate set of NSS is recorded as the new soft tissue inner surface SS2, so as to ensure that the soft tissue and the bone do not penetrate during the movement and maintain the physical consistency of the model.

[0030] Step S500, coordinate optimization and mesh quality tuning, includes the following contents: Step S501, SS2 takes BS1 as the boundary, fixes the node position of BS1, optimizes the coordinate arrangement of each node in SS2 in the three-dimensional Euclidean space, and obtains the optimized inner surface SS3. The optimization variables and optimization function construction include the following contents: The variables to be optimized are the Cartesian coordinates of each node in SS2, and the new coordinate set constitutes the new inner surface configuration SS3; Shape matching penalty function items, such as calculating the Chamfer distance between SS2 and SS3 (i.e., the degree of deviation between the initial shape and the optimized shape in space), are used to ensure that the surface shapes before and after optimization maintain sufficient similarity.

[0031] The face flip penalty function item detects whether the dihedral angles along the edges of adjacent faces on the triangular surface structure have a step jump exceeding the threshold between SS2 and SS3. For example, if the dihedral angle changes by more than 90°, a larger penalty function value is assigned to avoid the occurrence of mesh face folding or flipping.

[0032] Mesh quality regularization terms, such as the mean square error of the edge lengths in SS3 or the conformal measure of the angles within each face (for example, calculating the sum of the squares of the differences between the initial shape and the target shape on the triangle mesh), are used to improve the uniformity and conformality of the mesh displacement field during the optimization process and avoid excessive shape distortion of the triangular elements.

[0033] In step S502, an optimization algorithm is used to iteratively solve the above-mentioned shape matching, face flipping and mesh quality optimization functions, and the node coordinates are updated to obtain the inner surface SS3 of the soft tissue that is consistent with the shape of the SS2 surface and has high mesh quality, so as to solve the mesh quality loss caused by the local translation of the node in step S400 and improve the robustness of the model.

[0034] Step S600, calculating the final displacement field, includes the following contents: Step S601, integrating SS0, SP0, SD0 as an initial landmark point set, and SS3, SP1, SD1 as a post-movement landmark point set.

[0035] Step S602, using a thin plate spline, Kriging or other spatial interpolation method, the deformation displacement field is calculated based on the initial landmark point set and the landmark point set after movement, recorded as the final displacement field D1; and the final soft tissue deformation result is obtained based on the optimized soft tissue inner surface and end surface boundary information.

[0036] Step S700 , applying the final displacement field D1 to the initial soft tissue node coordinate set SOFT0 to obtain the deformed soft tissue node coordinate set SOFT1 .

[0037] The above are the steps of a fast calculation method for large deformation of soft tissue that does not rely on simulation and numerical simulation. The obtained SOFT1 is the set of node coordinates after the soft tissue is deformed under given bone motion conditions.

[0038] The above contents are only embodiments of the present invention. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or the priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for the ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the patent. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. A fast calculation method for soft tissue motion deformation of human finite element model without simulation, characterized by: include: Calculate the structure initialization, detect the bone-soft tissue common node set NBS, extract the inner surface node set NSS of the soft tissue node set NSOFT on the bone interface, and extract the end surface node sets NSP and NSD of the soft tissue at the proximal and distal ends; Extract the bone movement information and calculate the end surface boundary, extract the coordinate set, and extract the Cartesian coordinate sets BS0 and BS1 of the subset NBS based on the initial configuration B0 and the target configuration B1; Based on the movement relationship from B0 to B1, use the rigid body transformation method to calculate the end surface boundaries SP0, SP1 and SD0, SD1 of the proximal and distal ends of the soft tissue before and after the movement; Calculate the initial displacement field D0 based on BS0 and BS1; Apply the initial displacement field D0 to the node set NSS of the inner surface of the soft tissue to obtain the inner surface SS1 of the soft tissue after initial deformation, detect the penetration site set SS1-B1 between SS1 and the bone B1, and process each penetration site until the penetration is eliminated to obtain the new inner surface SS2 of the soft tissue; Taking BS1 as the boundary and fixing the node position of BS1, the coordinate arrangement of each node in SS2 in the three-dimensional Euclidean space is optimized to obtain the optimized inner surface SS3; Integrate SS0, SP0, and SD0 as the initial landmark set, and SS3, SP1, and SD1 as the post-movement landmark set. Use the spatial interpolation method to calculate the final displacement field D1 based on the initial landmark set and the post-movement landmark set. The final displacement field D1 is applied to the initial soft tissue node coordinate set SOFT0 to obtain the deformed soft tissue node coordinate set SOFT1.

2. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 1, characterized in that: The rigid body transformation method uses the Rodrigues equation.

3. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 1, characterized in that: Calculate the initial displacement field D0. Includes the following: Based on BS0 and BS1, the deformation displacement field of the intermediate node is calculated using the spatial interpolation method, which is recorded as the initial displacement field D0.

4. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 3, characterized in that: The spatial difference method for calculating the initial displacement field D0 and the final displacement field D1 adopts the thin plate spline and / or Kriging method based on radial basis function.

5. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 1, characterized in that: The coordinate arrangement of each node in SS2 in three-dimensional Euclidean space is optimized. The optimization functions used include shape matching penalty function term, face flipping penalty function term and mesh quality regularization term. The optimization function is solved by using the optimization algorithm to obtain the optimized soft tissue inner surface SS3.

6. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 1, characterized in that: The shape matching penalty function term is the Chamfer distance between SS2 and SS3; the face flipping penalty function term is used to detect whether there is a step jump exceeding the threshold between SS2 and SS3 of the dihedral angles along the edges of adjacent faces on the triangular surface structure; the mesh quality regularization term is the mean square error of the edge lengths in SS3 or the conformal measure of the angles within each face.

7. The method for rapid calculation of soft tissue motion deformation of a human finite element model without simulation according to claim 1, characterized in that: Detect the penetration site set SS1-B1 between SS1 and bone B1, and process each penetration site, including the following: Detect the set of segment nodes penetrated by the bone in SS1. For each penetration site, translate the corresponding node in the opposite direction of the penetration along the normal direction of the SS1 surface, and the displacement is a certain proportion of the penetration depth.

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