Research on performance optimization method of human-machine physical interaction system considering exoskeleton wearing comfort / 生物医学工程学杂志

In order to improve the wearing comfort and bearing effectiveness of the exoskeleton, based on the prototype and working mechanism analysis of a relaxation wearable system for knee exoskeleton robot, the static optimization synthesis and its method are studied. Firstly, based on the construction of the virtual prototype model of the system, a comprehensive wearable comfort evaluation index considering the factors such as stress, deformation and the proportion of stress nodes was constructed. Secondly, based on the static simulation and evaluation index of system virtual prototype, multi-objective genetic optimization and local optimization synthesis of armor layer topology were carried out. Finally, the model reconstruction simulation data confirmed that the system had good wearing comfort. Our study provides a theoretical basis for the bearing performance and prototype construction of the subsequent wearable system.

Topological Structure and Biomechanics of Three-Dimensional Printed Height Increasing Insoles for Leg Length Discrepancy / 医用生物力学

Objective To study topological structure of a new type of three-dimensional (3D) printed height increasing insoles for leg length discrepancy (LLD) and its effect on biomechanics of lower limbs. Methods Topological structure for middle and rear part of the insole was optimized by solid isotropic microstructures with penalization (SIMP), the force was loaded and the boundary conditions were set according to force area of the insole, and the height increasing insole with thermoplastic polyurethanes (TPU) materials was printed by selected laser sintering (SLS). The insoles were used in 9 patients with LLD, visual analogue scale (VAS) and Maryland foot function scores were used to compare pain and foot function changes of patients before and after using the insole, and the 3D gait analysis system was used to compare spatiotemporal parameters and vertical ground reaction force (vGRF) of both lower limbs. Result sAfter the patient wore 3D printed insole, VAS scores decreased, Maryland foot function scores increased, vGRF of both lower limbs decreased, and the difference of cadence, stance phase and swing phase in both lower limbs decreased. Conclusions The 3D printed height increasing insole after topology optimization can improve coordination of lower limb movement, reduce ground impact, relieve pain and improve foot function, thus providing an effective personalized orthopedic plan for LLD treatment in clinic.

Research on simulation and optimal design of a miniature magnetorheological fluid damper used in wearable rehabilitation training system / 生物医学工程学杂志

The goal of this paper is to solve the problems of large volume, slow dynamic response and poor intelligent controllability of traditional gait rehabilitation training equipment by using the characteristic that the shear yield strength of magnetorheological fluid changes with the applied magnetic field strength. Based on the extended Bingham model, the main structural parameters of the magnetorheological fluid damper and its output force were simulated and optimized by using scientific computing software, and the three-dimensional modeling of the damper was carried out after the size was determined. On this basis and according to the design and use requirements of the damper, the finite element analysis software was used for force analysis, strength check and topology optimization of the main force components. Finally, a micro magnetorheological fluid damper suitable for wearable rehabilitation training system was designed, which has reference value for the design of lightweight, portable and intelligent rehabilitation training equipment.

Study on the characteristics of biology force line of proximal femur based on structural topology optimization / 生物医学工程学杂志

Internal fixator is usually adopted in the treatment of bone fractures. In order to achieve anatomical reduction and effective fixation of fractures, the placement of internal fixators should comply with the biology force line of the bone and adapt to the specific anatomical morphological characteristics of the cortical bone. In order to investigate the distribution characteristics and formation regularity of biology force line and cortical thickness of human bone, three-dimensional model of proximal femur is established by using three-dimensional reconstruction technique in this paper. The normal physiological stress distribution of proximal femur is obtained by finite element analysis under three kinds of behavior conditions: one-legged stance, abduction and adduction. The structural topology optimization method is applied to simulate the cortex of the proximal femur under the combined action of three kinds of behavior conditions, and the anatomic morphological characteristics of the proximal femur are compared. The distribution trend of biology force line of proximal femur and the characteristics of cortex are analyzed. The results show that the biology force lines of bone structure and the morphological characteristics of cortex depend on the load of human activities. The distribution trend of biology force line is related to the direction of trabecular bone and the ridge trend and firmness of cortex when bone is loaded physiologically. The proposed analytical method provides a solution to determine the biology force line of bone and the distribution characteristics of cortex. The conclusions obtained may guide the reasonable placement of internal fixator components of fracture.

Topology Optimization of Bionic Porous Structure Based on Biomechanical Properties of Trabecular Bone / 医用生物力学

Objective Based on structure of animal trabecular bone, implants with porous structure were designed to describe mechanical properties of trabecular structure and explain significance of bionic trabecular porous implants in clinical treatment. Methods Based on anisotropic mechanical properties of animal trabecular bone, a porous structure was designed using the topology optimization method. The principles of partition and block reconstruction were first proposed according to bone function theory. The trabecular structure was then reconstructed based on micro-CT images. The boundary constraint and external load were applied on this model according to the respective-volume-element (RVE) method. Taking the solved mechanical properties as objective functions of optimization, the porous structure design and optimization were conducted using the variable density method and the homogenization method. Results The trabecular bone possessed the anisotropic mechanical properties. It was found that the volume fraction showed an increasing trend from the edge to the middle across the same section of trabecular bone. But there was no obvious regular pattern in Poisson’s ratio, which was evenly distributed in the range between 0.17 and 0.30. As to the values of elastic modulus and shear modulus, they were both significantly higher in the main pressure position compared with those in the other positions. After topography optimization based on these mechanical properties, the Poisson’s ratio of the optimized model was in the same range as the animal trabecular bone. The elastic modulus error was less than 14%， with the minimum being only 3%. In addition, the shear modulus error was below 8%， which ultimately complied with criteria of the original goal. Conclusions The designed porous structure based on topology optimization had the same anisotropic characteristics as animal trabecular bone, while reducing the stress concentration phenomenon, which could achieve the specific design for porous structure, thus providing a reasonable and effective method for clinical porous implants.

Numeric reconstruction of 2D cellular actomyosin network from substrate displacement

Introduction: One of the fundamental structural elements of the cell is the cytoskeleton. Along with myosin, actin microfilaments are responsible for cellular contractions, and their organization may be related to pathological changes in myocardial tissue. Due to the complexity of factors involved, numerical modeling of the cytoskeleton has the potential to contribute to a better understanding of mechanical cues in cellular activities. In this work, a systematic method was developed for the reconstruction of an actomyosin topology based on the displacement exerted by the cell on a flexible substrate. It is an inverse problem which could be considered a phenomenological approach to traction force microscopy (TFM). Methods An actomyosin distribution was found with a topology optimization method (TOM), varying the material density and angle of contraction of each element of the actomyosin domain. The routine was implemented with a linear material model for the bidimensional actomyosin elements and tridimensional substrate. The topology generated minimizes the nodal displacement squared differences between the generated topology and experimental displacement fields obtained by TFM. The structure resulting from TOM was compared to the actin structures observed experimentally with a GFP-attached actin marker. Results The optimized topology reproduced the main features of the experimental actin and its squared displacement differences were 11.24 µm2, 27.5% of the sum of experimental squared nodal displacements (40.87 µm2). Conclusion This approach extends the literature with a model for the actomyosin structure capable of distributing anisotropic material freely, allowing heterogeneous contraction over the cell extension.

Topology optimization on the configuration of titanium reconstruction plate for bridging mandibular angle defect / 医用生物力学

Objective To provide an optimization method and a basic configuration for the configuration design of mandibular defect-repair implant. Methods A topology optimization computation based on density method was adopted to make topology optimization on reconstruction titanium plate for repairing mandibular defect. Results The effects of volume fraction F and penalization factor p on the optimized configuration were compared and analyzed, respectively, and the optimum parameters were chosen to be F=0.65 and p=3.5. Using this set of parameters, optimized computation was performed on the mandibular defect-repair implant, and the three opening configuration was proved to be the basic optimization configuration. The result also showed that unilateral molar clenching had more significant effect on stress distributions in the implant as compared to incisal clenching. Conclusions A set of parameters suitable for optimizing configuration of mandibular defect-repair implant, as well as the basic configuration of optimized titanium plate were obtained, which could provide references for the design of mandibular defect-repair implant in clinic.

Study bone density changes in femoral head with avascular necrosis cystic degeneration using adaptive bone remodeling theory / 医用生物力学

Objective To explore the effect of avascular necrosis cystic degeneration on distribution of bone density. Methods Based on the bone reconstruction model of Weinans and Huiskes, bone density distribution in normal femoral head and in femoral head with avascular necrosis cystic degeneration were calculated by finite element analysis. Results (1) The medial system of lamellae, lateral system of lamellae, intertrochanteric arch and Ward's triangle were generated on the normal proximal femur under simulation. (2) If a primary cystic degeneration occurred, a secondary cystic area would appear below the primary one and its bone density would decrease dramatically with the primary cystic area increased. Cystic degeneration would also change the femoral bearing truss system. Conclusions (1) Wolff’s law on bone remodeling is consistent with modern topology optimization theory. (2) If cystic degeneration appeared due to avascular necrosis of the femoral head, it should be treated timely to prevent the secondary cystic degeneration and collapse of the femoral head.

Síntesis topológica de mecanismos flexibles para aplicaciones biomédicas / Topology synthesis of feasible for biomedical applications

Los mecanismos flexibles son dispositivos mecánicos diseñados para transformar desplazamientos, fuerzas o energía a través de la flexibilidad de sus elementos estructurales. Sus ventajas frente a los mecanismos de eslabones rígidos con juntas pinadas los convierten en una alternativa viable para el diseño de BioMEMS, ya que son sistemas que requieren alta precisión de movimiento a escalas de tamaño muy reducidas. El diseño de mecanismos flexibles puede realizarse con el empleo de técnicas de optimización estructural, es la optimización topológica la más empleada. En investigaciones previas se desarrolló un nuevo método de optimización topológica inspirado en el proceso de regeneración ósea conocido como el Método de los autómatas celulares híbridos, el cual demostró su aplicabilidad y eficiencia computacional en la síntesis topológica de estos dispositivos. El objetivo de este artículo es extender el método a la síntesis de mecanismos flexibles para aplicaciones biomédicas, específicamente, para el diseño de una micropinza para manipulación de fibroblastos. La topología óptima obtenida corresponde con los diseños referidos en otras investigaciones. Los resultados permiten llevar a cabo la manufactura del dispositivo gracias a que no presentan juntas de facto o patrones de tablero de ajedrez, que son errores típicos en la solución de problemas de optimización topológica mediante otros métodos de solución

Feasible mechanisms are mechanical devices designed to transform displacements, strengths or energy through flexibility of its structural elements. Its advantages versus rigid links mechanisms with pinnate joints becoming a viable alternative for the BioMES design since they are systems requiring high movement accuracy at very reduced scale level. The feasible mechanisms design may be carried out using structural optimization techniques where that of topology type is the more used. In prior researches we developed a new topology optimization method inspired in the bone regeneration process known as the Method of hybrid cellular automaton, which showed its applicability and computer effectiveness in the topology synthesis of these devices. The aim of present paper is to spread the method to feasible mechanisms synthesis for biomedical publications, specifically, for the design of a microclamp for the fibroblasts management. Optimal topology achieved is in correspondence with the designs mentioned in other researches. Results allow to carry out the manufacture of this device because of they haven't de facto joints or patterns in chessboard, which are typical errors to solve the topology optimization by means of other solutions methods

The optimal design of connectors in all ceramic fixed partial dentures manufactured from alumina tape / 대한치과보철학회지

STATEMENTS OF PROBLEM: All ceramic fixed partial denture cores can be made by the slip casting method and the advanced alumina tape method. The fracture resistance of these core connector areas is relatively low. PURPOSE: The purpose of this study is to standardize the appropriate volumetric figure and location of the connectors in the alumina core fabricated in alumina tape to be used in fixed partial dentures by way of topology optimization. MATERIAL AND METHOD: A maxillary anterior three-unit bridge alumina core with teeth form and surrounding periodontal apparatus model was used to ultimately design the most structurally rigid form of the connector. Loadings from a 0 degree, 45 degrees and 60 degrees to the axis of each tooth were applied and analyzed with the 3-D finite element analysis method. Using the results from these experiments, the topology optimization was applied and the optimal reinforcement layout of connector was obtained and the detail shape in the fixed partial denture core was designed. RESULTS: The modified prosthesis with the form of a bulk in the lower lingual surface of the connector in the event, reduced the stress concentration up to 20% in the 3-D FEA. CONCLUSION: The formation of a bulk in the lower lingual connector area of an alumina core for a fixed partial denture decreases the stress to a clinically favorable measure but does not harm the esthetic point of view. This result illustrates the possibility of clinical application of the modified form designed by the topology optimization method.