Total Reaction Force Research Articles

The Behavior of Thin-Walled Cylinders with Ribs Regarding the Energy Absorption Capability on High-Velocity Impact

Many industries and automotive companies use thin-walled cylinders as energy-absorbing devices. Researchers have previously investigated various parameters related to thin-walled cylinders and their behavior under impact loads. When the impactor hits the thin-walled cylinder from the axial direction, it causes the bending of the cylinder wall on an axisymmetric or non-axisymmetric pattern, depending on the ratio of diameter divided by wall thickness. In addition, the length of the specimen influences the deformation mode that occurs. This study discusses how installing ribs on the cylinder walls affects energy absorption capabilities. We conducted the research by making modeling based on the finite element method by making various specimens according to the experimental scenarios. We experimented with an aluminum alloy cylinder with a diameter of 50 cm, a thickness of 1.5 mm, and a length of 200 mm. Then, successively, we installed ribs with a length of 2 mm and a thickness of 3.5 mm, one rib, two ribs, three ribs, four ribs, and five ribs. The impactor hits the specimen from the axial direction to one end at high speed while the other is given fixed support. The results obtained from the experiment are total deformation, reaction force, absorbed energy, and deformation pattern. The experimental results show that adding ribs changes the deformation pattern from previously non-axis-symmetric to axis-symmetric. The total deformation decreases, the reaction force becomes smaller, and the ability to absorb energy equals the total kinetic energy. This result is a recommendation for manufacturing in an energy absorption structural system. Keywords: rib, deformation mode, wall thickness, energy absorption, reaction force.

Doğada Bulunan Darbe Sönümleme Sisteminin Yapısal Analoji Yoluyla Geri Tepme Mekanizmasına Entegre Edilmesi

Bu çalışmada ateşli silahlarda gerçekleşen geri tepmenin kullanıcı tarafından deneyimlenen etkisini azaltabilecek nitelikte biyomimetik tabanlı bir çözüm önerisi geliştirilmiştir. Bu bağlamda, ağaçkakanların kafa yapısında bulunan darbe sönümleme sisteminin ana bileşenleri yapısal analoji yöntemi ile Remington 870 model ateşli silahın kabza tasarımında kullanılmıştır. Halihazırda kullanılan orijinal kabza modeli ile biyomimetik yaklaşım kullanılarak tasarlanan modeller karşılaştırılıp, eksenel ve toplam deformasyon, reaksiyon kuvveti ve gerilme değerleri birlikte değerlendirilmiş ve silahlarda geri tepmenin en aza indirilebilmesi için kabza tasarımı ile ilgili bazı öneriler getirilmiştir.

Optimization of blast mitigating sandwich structures with fiber-reinforced face sheets and PVC foam layers as core

It is challenging to find lightweight blast mitigating structures for protecting civilian and military infrastructure. Here we synthesize a surrogate optimization algorithm with a numerical technique to analyze dynamic deformations of sandwich structures with fiber-reinforced face sheets perfectly bonded to eight PVC foam layers, and to simultaneously minimize the structural mass and maximize its blast mitigating capabilities. The eighteen variables to be optimized are thicknesses of the two face sheets and of the eight foam layers and the lay-up of the core layers such that either the total reaction force transmitted to a rigid substrate or the deflection of the back face is minimized. The deformations of the structure and the pressure produced by detonating a charge are simulated using the commercial finite element software ABAQUS. The progressive damage and delamination between adjacent layers of the face sheets and their debonding from the core are, respectively, considered using a user-defined subroutine and a cohesive zone model. It is found that for an optimum structure, the mass density and the elastic modulus of the core layers does not continuously vary through the thickness, i.e., the core is not comprised of a functionally graded foam. The low (high) density foam layers minimize the total reaction force (the back face deflection).

Review on Designing and Development of Loading and Unloading Platform for Two Wheelers

Abstract: Lift is a simple device use to raise the object from ground level to a certain height to perform a specific work with aiming of possible maximum load and minimum efforts. Lifts are generally operated either hydraulic, pneumatic or mechanical type. In many vehicle manufacturing industries, there are using lifting mechanism for loading and unloading operations which have to invest a huge capital for installing a exsisting bulkey and large platform which generally based on hydraulic means. This type of machine uses while export and import business. The main purpose of our study is to design and develop loading and unloading platform for two wheelers. Material selection plays important role in designing a machine and also influence on several factor such as strength, reliability, durability and resistance which leads to increase the life of lift. The aim of the project is to design and development of wire rope operated platform which lifts maximum 877.5 kg load including factor of safety with minimum time and labour for per cycle operation. Platform movement is achieved safely by using wire rope with the help of motor and drum assembly mechanism is of 2.8 m from the ground level. The design is performed by considering a mechanical lift as a portable, suitable for all type of load application and without any hydraulic or pneumatic means. The design is developed keeping in mind that consideration of all safety parameters. Lubrication required in few moving parts only. The aim of this paper is design, analysis and fabrication of a prototype mechanical lift which operate efficiently, consistently, sholud be easy to handle, multifunctional, cost effective, compact in size. Drafting and drawing of loading and unloading mechanical lift carried out in AUTOCAD with suitable modeling. The analysis of mechanical lift includes total deformation load, reaction forces, buckling and bending failures, equivalent stresses were done in ANSYS Software. Finally this analysis of strength, toughness, elasticity and temperature distribution is carried out in order to check the coherance of the design value. Keywords: Lifting Mechanism, Platform, Machine, Design and Development, Analysis, AUTOCAD, ANSYS Software.

An accurate strategy for computing reaction forces and fluxes on trimmed locally refined meshes

Abstract The finite element method is classically based on nodal Lagrange basis functions defined on conforming meshes. In this context, total reaction forces are commonly computed from the so-called “nodal forces”, yielding higher accuracy and convergence rates than reactions obtained from the differentiated primal solution (“direct” method). The finite cell method and isogeometric analysis promise to improve the interoperability of computer-aided design and computer-aided engineering, enabling a direct approach to the numerical simulation of trimmed geometries. However, body-unfitted meshes preclude the use of classic nodal reaction algorithms. This work shows that the direct method can perform particularly poorly for immersed methods. Instead, conservative reactions can be obtained from equilibrium expressions given by the weak problem formulation, yielding superior accuracy and convergence rates typical of nodal reactions. This approach is also extended to non-interpolatory basis functions, such as the (truncated) hierarchical B-splines.

Finite element simulation of the catheter movement in transbronchial biopsy

The paper presents a preliminary finite element simulation of the movement of a catheter in the bronchial tree. The analyses are done using an explicit dynamics approach, in which a simplified model is considered to test the convergence and applicability of the method. The first branch of the bronchial tree (trachea, the right main bronchus, and the left main bronchus) is simulated as a Y shaped tubular volume while the geometry of the catheter was reduced to a cylindrical straight beam. To mimic the real insertion of the catheter into the bronchial tree, a displacement of 250 mm (chosen to ensure that the catheter travels up to the end of the Y tube and more) was imposed onto the end of the catheter model. The main purpose of the analysis was to evaluate the displacements distribution in both the catheter and the tube and to evaluate the haptic feedback (the response that the surgeon or the robot receive due to mechanical interaction between soft tissue and the surgical tool) by extracting the reaction forces and correlating their values with the velocity of the catheter movement through the bronchial tree. It is shown that the maximum displacement within the tube model is about 0.042 mm, value which confirms that the displacements are very small, indicating that a linear elastic approach for the tissue behavior is acceptable. The total reaction force in the fixed support was found to be below 2.2 N, while on the catheter insertion point, it is below 1.2 N, values that indicate reasonable interaction and are consistent with the values reported in the literature. The values of the predicted stresses, obtained through the presented numerical analysis are also in the same order of magnitude with those found in other research reports, for a linear elastic behavior of the soft tissue. The analysis of the obtained results and comparison with other results found in the relevant scientific literature showed that explicit dynamics approach can be used as a tool for simulation of catheter movement through the bronchial tree. Forces of interaction between tool and tissue can be thus predicted, being useful for simulation of haptic feedback.

Analysis of the beats of separation sieve pans

To ensure high productivity of grain production reliable operation of grain cleaning equipment is required. The process of cleaning seed material is connected to significant vibration loads some of which have an impact on the separation process and the operational reliability of the machine components. To combat harmful vibrations a theoretical analysis of the beats occurring during the sieve separation of grain was made. The law of motion of the mass center of the sieve pan is derived as a function from time over a period of oscillating. The analytical solution of the obtained equation allows determining the horizontal and vertical displacements of the mass center at every moment of time. Based on this motion, accelerations and related inertial forces are determined. These forces take on sufficiently large values, which lead to beats of the indicated separation devices. To determine the forces leading to these beats, using the d’Alembert’s principle, equilibrium equations are compiled, the solution of which allows determining the total horizontal force and reaction force in the suspension. The equations of equilibrium include the forces of tension on bending of the suspension rods. It has been established that a rational choice of the geometric characteristics of these suspensions can significantly reduce the forces acting on the drive of the sieve pan and, as a result, on the horizontal and vertical runouts.

Microgripper Based on Simple Compliance Configurations, Improved by Using Parameterization

The design of a novel electrothermal microgripper device is shown, which is based on an improved chevron type actuator developed considering their elements parameterization, whose resistive model is also provided. The performance of the microgripper’s parameters, such as displacement, force, and temperature distribution, with convection for the voltage range from 0 up to 5 V, is evaluated through numerical and analytical simulation. Microgripper design was also improved with aid of parameterization. The effect on the microgripper performance due to its thickness is also analyzed, finding a considerable increment in force, when thickness increases. Its main advantage is given by the simplicity of the compliance arrangement of the microgrippers jaws. Considering convection, when 5 V are applied, 37.72 °C was generated at the jaw’s tips of the Improved Microgripper 2 (IMG2), implemented with silicon, this relatively low temperature increases its capabilities of application. When the IMG2 is implemented with polysilicon, its response is competitive comparing with a more complex microgripper, increase of displacement (50%) is shown, but a decrement of force (30%). The diameters allowed for the subjection objects are found between 84.64 µm and 108 µm, with weights lower than 612.2 µg. Some tests of subjection were performed using microcylinders of Au, glass ceramic, polycarbonate and carbon fiber, showing a permissible stress on them, considering its Young’s modulus, as well as the total reaction force induced. All simulations were done on Ansys software. The results demonstrate the feasibility of the future microgripper fabrication.

Numerical analysis of mechanical properties of 3D printed aluminium components with variable core infill values

Purpose: The purpose of this paper is to present numerical modelling results for 3D-printed aluminium components with different variable core infill values. Information published in this paper will guide engineers when designing the components with core infill regions. Design/methodology/approach: During this study 3 different core types (Gyroid, Schwarz P and Schwarz D) and different combinations of their parameters were examined numerically, using FEM by means of the software ANSYS Workbench 2019 R2. Influence of core type as well as its parameters on 3D printed components strength was studied. The “best” core type with the “best” combination of parameters was chosen. Findings: Results obtained from the numerical static compression tests distinctly showed that component strength is highly influenced by the type infill choice selected. Specifically, infill parameters and the coefficient (force reaction/volumetric percentage solid material) were investigated. Resulting total reaction force and percentage of solid material in the component were compared to the fully solid reference model. Research limitations/implications: Based on the Finite Element Analysis carried out in this work, it was found that results highlighted the optimal infill condition defined as the lowest amount of material theoretically used, whilst assuring sufficient mechanical strength. The best results were obtained by Schwarz D core type samples. Practical implications: In the case of the aviation or automotive industry, very high strength of manufactured elements along with a simultaneous reduction of their wight is extremely important. As the viability of additively manufactured parts continues to increase, traditionally manufactured components are continually being replaced with 3D-printed components. The parts produced by additive manufacturing do not have the solid core, they are rather filled with specific geometrical patterns. The reason of such operation is to save the material and, in this way, also weight. Originality/value: The conducted numerical analysis allowed to determine the most favourable parameters for optimal core infill configurations for aluminium 3D printed parts, taking into account the lowest amount of material theoretically used, whilst assuring sufficient mechanical strength.

Partitioning the total seatback reaction force amongst the lumbar spine motion segments during simulated rear-impact collisions

Purpose. This study aimed to determine how the seatback force is distributed across lumbar spine motion segments during a simulated low-velocity rear-impact collision with and without the application of mechanical lumbar support. Methods. A ferroresistive pressure-sensing system was used during simulated rear-impact collisions (ΔV = 7.66 km/h). Total seatback reaction force was derived from pressure recordings as the product of calibrated pressure outputs and sensel areas. The three-dimensional position of the pressure mat and the lumbar spinous processes were tracked and then used to extract the seatback force that was applied to the lumbar motion segments. Results. On average, 77% (637 N) and 53% (430 N) of the total seatback force was applied directly to the lumbar spine with and without lumbar support, respectively (p < 0.001). In addition to four of five individual motion segments bearing a greater force with lumbar support (p < 0.029), the distribution of the total lumbar force was found to be significantly different between support type conditions. Conclusions. Although lumbar supports can alter the magnitude and distribution of shear force applied to the lumbar spine during low-velocity rear-impact collisions, they do not appear to elevate the injury risk.

Use of impulses to determine the reaction force of a hydraulic structure with an overhang due to wave impact

This paper describes a method of determining the reaction forces of a vertical structure with an overhang to impulsive wave impacts. The aim is to develop a method to design a hydraulic structure exposed to the impulsive wave impact. At present, there is a lack of guidelines on the designing and verification with such a purpose. The impulse of the impact is taken as the primary design variable to estimate the impulsive reaction force instead of peak impact forces. By using extreme value analysis (EVA), the characteristic impulse (e.g., Iim,0.1%) can be determined. Then a simple structure model is used for obtaining reaction forces to the characteristic impact impulse. The sum of the impulsive reaction force and the quasi-steady wave force could represent the total reaction force, which can be used as a design load on the structure. The advantage of using the impact impulse could give an approach in which several aspects of the impulsive wave impact force can be incorporated better, like determining the exceedance probability of a certain load, incorporating the flexibility of the structure and correcting possible scale effects in small scale hydraulic models. The proposed method based on the characteristic value of the Iim,0.1% is applied to forces measured in a small scale model of the Afsluitdijk discharge sluice, and compared well to a full-time domain solution. The results indicate the initial assumption that using the impact impulse of the impact as the primary design variable, it is possible to estimate the dynamic response of the structure.

Usefulness of simulation method to improve efficiency of chair-to-wheelchair transfer of patients performed by caregivers.

[Purpose] We aimed to clarify whether demonstration and simulated experience help the ability of care-receivers to get transferred, such as from the bed to the commode. [Participants and Methods] Participants included 28 nurses and 17 caregivers (34 females and 11 males). We developed a total floor reaction force measurement device to quantify the total loading level of care-receivers and caregivers and force shoes to quantify the loading level of the caregivers. Using these instruments, we constructed a system to measure the load on the lower limbs of the care-receivers during partial assistance. We divided the participants into the control, demonstration, and simulated experience method groups. We examined the differences in the load on the lower limbs before and after the intervention. [Results] The loads on the lower limbs of care-receivers when their buttocks were lifted from the chair were 11.7 ± 69.6, 61.8 ± 79.4, and 101.0 ± 104.0 N in the control, demonstration, and simulated experience groups. [Conclusion] These data suggest that the simulated experience method could help make use of the ability of the care-receiver to get transferred. Even care workers for the sanatorium-type sickbeds could learn to utilize the physical ability of the care-receivers using simulated experience.

Characterization of the viscoelastic model of in vivo human posterior thigh skin using ramp-relaxation indentation test

Characterization of viscoelastic properties of the human thigh skin can be utilized in many medical or engineering applications such as a surgical extension of the thigh skin, a tissue engineering, and a finite element modeling of thigh skin in a sitting posture. This study aims to determine the effective short- and long-term shear moduli of posterior thigh skin using ramp-relaxation test in a sitting posture. The effect of indentation location, the sitting posture, and the applied load (thigh weight) were investigated on the extracted effective shear moduli. We modeled the human skin by using the one- and two-term Prony series, and it was found that the generalized Maxwell model with two-term Prony series agreed well with experimental data. The effective shear moduli (short- and long-term) were extracted by fitting the total reaction force of the generalized Maxwell model to the experimental data using the Levenberg-Marquardt algorithm. The contour maps were used to show the spatial dependency of the effective shear moduli at the flat regions of posterior thigh skin. The contour maps of effective shear moduli show that maximum effective shear moduli locate near buttock’s center, while minimum effective shear moduli locate at the distal and medial posterior thigh. It is also found that the extracted effective short-term shear modulus varies between 3978.2 N/m2 and 13699.2 N/m2. On the other hand, the extracted effective long-term shear modulus differs between 2715.1 N/m2 and 9194.3 N/m2 for different sitting postures. Additionally, it is found that the observed increase in effective shear moduli could be attributed to the increase applied load, and leg angle.

Case-specific non-linear finite element models to predict failure behavior in two functional spinal units.

ABSTRACTCurrent finite element (FE) models predicting failure behavior comprise single vertebrae, thereby neglecting the role of the posterior elements and intervertebral discs. Therefore, this study aimed to develop a more clinically relevant, case‐specific non‐linear FE model of two functional spinal units able to predict failure behavior in terms of (i) the vertebra predicted to fail; (ii) deformation of the specimens; (iii) stiffness; and (iv) load to failure. For this purpose, we also studied the effect of different bone density–mechanical properties relationships (material models) on the prediction of failure behavior. Twelve two functional spinal units (T6‐T8, T9‐T11, T12‐L2, and L3‐L5) with and without artificial metastases were destructively tested in axial compression. These experiments were simulated using CT‐based case‐specific non‐linear FE models. Bone mechanical properties were assigned using four commonly used material models. In 10 of the 11 specimens our FE model was able to correctly indicate which vertebrae failed during the experiments. However, predictions of the three‐dimensional deformations of the specimens were less promising. Whereas stiffness of the whole construct could be strongly predicted (R 2 = 0.637–0.688, p < 0.01), we obtained weak correlations between FE predicted and experimentally determined load to failure, as defined by the total reaction force exhibiting a drop in force (R 2 = 0.219–0.247, p > 0.05). Additionally, we found that the correlation between predicted and experimental fracture loads did not strongly depend on the material model implemented, but the stiffness predictions did. In conclusion, this work showed that, in its current state, our FE models may be used to identify the weakest vertebra, but that substantial improvements are required in order to quantify in vivo failure loads. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodical, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:3208–3218, 2018.

Comparison of HR-pQCT- and microCT-based finite element models for the estimation of the mechanical properties of the calcaneus trabecular bone

The calcaneus bone is formed of extensive trabecular bone and is therefore well suited to be used as an example of loaded bone to establish the ability of combining microfinite element (microFE) technique with high-resolution peripheral quantitative computed tomography (HR-pQCT) in determining its mechanical properties. HR-pQCT is increasingly used as a tool for in vivo bone clinical research, but its use has been limited to the distal radius and tibia. The goal of this study was to determine the applicability of HR-pQCT-derived microFE models of the calcaneus trabecular bone with 82 μm voxel size with reference to higher-resolution microCT-based models taken as gold standard. By comparing the outputs of microFE models generated from both HR-pQCT and microCT images of the trabecular bone of five calcaneus cadaveric specimens, it was found that the HR-pQCT-based models predicted mechanical properties for fracture load, total reaction force and von Mises stress are considerably different from microCT-based counterparts by 33, 64 and 70%, respectively. Also, the morphological analysis showed a comprehensive geometrical difference between HR-pQCT-based microFE models and their microCT-based equivalents. The results of the HR-pQCT-based models were found to have strong dependency on the threshold value chosen to binarise the images prior to finite element modelling. In addition, it was found that the voxel size has a strong impact on accuracy of imaged-based microFE models compared to other factors such as the presence of soft tissue and image scanning integration time. Therefore, although HR-pQCT has shown to be useful to predict overall structural and biomechanical changes, it is limited in providing local accurate biomechanical properties of trabecular bone and therefore should be used with caution when assessing bone remodelling through local changes of trabecular bone apposition and resorption in disease treatment monitoring.

Entropy-based complexity measures for gait data of patients with Parkinson's disease.

Shannon, Kullback-Leibler, and Klimontovich's renormalized entropies are applied as three different complexity measures on gait data of patients with Parkinson's disease (PD) and healthy control group. We show that the renormalized entropy of variability of total reaction force of gait is a very efficient tool to compare patients with respect to disease severity. Moreover, it is a good risk predictor such that the sensitivity, i.e., the percentage of patients with PD who are correctly identified as having PD, increases from 25% to 67% while the Hoehn-Yahr stage increases from 2.5 to 3.0 (this stage goes from 0 to 5 as the disease severity increases). The renormalized entropy method for stride time variability of gait is found to correctly identify patients with a sensitivity of 80%, while the Shannon entropy and the Kullback-Leibler relative entropy can do this with a sensitivity of only 26.7% and 13.3%, respectively.

Simulation Research of Top-Hung Mechanism for Open and Close

For the purpose of researching the top-hung mechanism for open and close and the improvement and use of the mechanism, improving the work efficiency, the three-dimensional solid model of the mechanism was established with ADAMS. Each part of the model in ADAMS was set up. Simulation analysis on the working process of the mechanism was achieved. The structure optimization parameters of the mechanism were obtained. The result proves that when the vertical location of the upper endpoint of lid was increased the total support reaction force acting on the lower endpoint of lower rocker by frame reduced. When the horizontal location of revolute joint of lower rocker and frame, the horizontal location of revolute joint of lower rocker and lid were increased the total support reaction forces acting on the lower endpoint of lower rocker by frame added. The sensitivities of the total support reaction forces acting on the lower endpoint of lower rocker by frame on the initial values of the locations of revolute joint of lower rocker and link, the horizontal location of revolute joint of lower rocker and frame are greater. The sensitivities of the total support reaction forces acting on the lower endpoint of lower rocker by frame on the initial values of the vertical location of revolute joint of upper rocker and link, the horizontal location of revolute joint of the lower rocker and lid are smaller. The sensitivity of the total support reaction force acting on the lower endpoint of lower rocker by frame on the initial value of the vertical location of the upper endpoint of lid are least.

Kinetic analysis on physical segments of forward breakfall of the martial arts

The purpose of this study was to provide basic quantitative data to minimize the injury occurring during forward breakfall by the comparative analysis of biomechanical factors through 3D motion analysis, analysis of ground reaction force, and EMG analysis of the forward breakfall of the martial arts targeting 10 skilled and 10 unskilled subjects. In this study, three-dimensional motion analysis, the nine high-speed camera (Motionmaster 100, KOR) was used, the desired total floor reaction force device (ATMI, USA) 2 units was measured using an impact force. And the floor reaction force and three-dimensional motion analysis program was used for the Kwon3dXP. Group differences for verification and program SPSS 21.0 was used. The following are the findings. First, the total time taken for forward breakfall of the martial arts showed 1.53±0.04 s for skilled, and 1.41±0.06 s for unskilled subjects (p<.01). Second, during forward breakfall of the martial arts, the skilled subjects came up with significantly faster impact velocity in the primary point of impact (E2) (p<.001), but the unskilled subjects showed significantly faster impact velocity in the secondary point of impact (E3) (p<.001). Third, the forward breakfall of the martial arts did not show any difference between left and right side in the reaction force, but unskilled subjects proved a significantly greater forward and backward reaction force in the secondary point of impact(E3) both right and left sides(right: p<.01, left: p<.001). The skilled subjects showed a significantly greater vertical reaction force in the primary point of impact(E2) (right: p<.001, left: p<.001), and unskilled subjects showed a larger vertical reaction force in the secondary point of impact (E3), respectively(right: p<.01, left: p<.05). Therefore, in order to reduce the impact force when the forward motion action Break fall slowly to reduce the impact velocity and the impact of the hand compared to alleviate elbow seems to be good.

정상인의 기립 동작중의 대퇴 및 족부 반력의 비대칭율

The purpose of this study was to analyze the asymmetry of the reaction forces on lower limbs between dominant and nondominant sides during sit-to-stand movement in normal subjects. Fourteen normal subjects (<TEX>$22.6{\pm}2.3yrs$</TEX>, all men) participated in this study. To measure the reaction forces during sit-to-stand movement, two force plates were mounted on the ground and one dual top force plate was mounted on a chair. Five events(movement onset, max thigh reaction force, transition, max hip angle, seat off) were determined from the reaction force and joint angle trajectories. For each of thigh, foot, and total reaction forces, two-way ANOVA was performed with the events and sides as factors. Also investigated was the leg asymmetry expressed as the ratio of the reaction forces of dominant and nondominant sides. The significance of asymmetry was investigated and two-way ANOVA was performed with the events and body parts(foot, thigh and total) as factors. Thigh reaction force and total reaction force showed interaction of events and leg sides(p < 0.01). Post-hoc comparisons showed they were different between sides at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Asymmetry was also significant at the latter stage(transition, max hip angle, and seat off events) (p < 0.01). Interaction of events and body parts on asymmetry was significant(p < 0.01) and asymmetry was greater in thigh reaction forces than total and foot reaction forces at the events of the latter stage(p < 0.01). The results suggest that asymmetry exist in normal subject and should be fully considered when investigating sit-to-stand strategy of patients.

Dynamic Analysis for New Low-Speed Motor with Interior Pushrod Harmonic Transmission Device

To achieve the design goals of transmission with small size, light weight and low cost, the pushrod harmonic mechanism which is consist of harmonic planetary and cam mechanism is proposed, and the speed-down device of low-speed motor is changed from external installed to interior installed. Based on the mechanism principle analysis, derivation of contour equation and kinematics analysis, the centroid movement theorem of the pushrod roller and the mechanism dynamic is analyzed when the sports vice friction was considered and ignored. The total reaction force and the action line are gained. These data can provide evidence for mechanism simulation, efficiency analysis and reliability design.