Exotendons for assistance of human locomotion

BACKGROUND: Powered robotic exoskeletons for assistance of human locomotion are currently under development for military and medical applications. The energy requirements for such devices are excessive, and this has become a major obstacle for practical applications. Legged locomotion in many animals, however, is very energy efficient. We propose that poly-articular elastic mechanisms are a major contributor to the economy of locomotion in such specialized animals. Consequently, it should be possible to design unpowered assistive devices that make effective use of similar mechanisms. METHODS: A passive assistive technology is presented, based on long elastic cords attached to an exoskeleton and guided by pulleys placed at the joints. A general optimization procedure is described for finding the best geometrical arrangement of such "exotendons" for assisting a specific movement. Optimality is defined either as minimal residual joint moment or as minimal residual joint power. Four specific exotendon systems with increasing complexity are considered. Representative human gait data were used to optimize each of these four systems to achieve maximal assistance for normal walking. RESULTS: The most complex exotendon system, with twelve pulleys per limb, was able to reduce the joint moments required for normal walking by 71% and joint power by 74%. A simpler system, with only three pulleys per limb, could reduce joint moments by 46% and joint power by 47%. CONCLUSION: It is concluded that unpowered passive elastic devices can substantially reduce the muscle forces and the metabolic energy needed for walking, without requiring a change in movement. When optimally designed, such devices may allow independent locomotion in patients with large deficits in muscle function

Elastic analysis of pressurized thick FGM cylinders with exponential variation of material properties using TSDT

AbstractIn this research, the general governing set of differential equations for axisymmetric thick FG pressurized cylinders with exponential function of material properties is derived based on third order shear deformation theory. Afterwards, a general analytical solution of governing equations based on Eigen values problems is conducted for cylinders under clamped ends condition. Furthermore, a numerical modeling is done in order to compare the results of two different solution and prove the accuracy of analysis. The displacements and stresses resulted from FEM and TSDT are depicted for a case study along the radial and longitudinal direction of the cylinder. Afterwards, the effect of internal and external pressure, FGM inhomogeneity constants and higher order approximation is investigated. The results of SDT and FEM show good agreement and prove the fact that usage of FGM cylinders causes lower values of displacements and stresses

Thermo-Elastic Analysis of Clamped-Clamped Thick FGM Cylinders by Using Third-Order Shear Deformation Theory

Abstract Using the third-order shear deformation theory (TSDT), an analytical solution for deformations and stresses of axisymmetric clamped-clamped thick cylindrical shells made of functionally graded material (FGM) subjected to internal pressure and thermal loading are presented. The material properties are graded along the radial direction according to power functions of the radial direction. It is assumed that Poisson's ratio is constant across the cylinder thickness. The differential equations governing were generally derived, making use of TSDT. Following that, the set of non-homogenous linear differential equations for the cylinder with clamped-clamped ends was solved, and the effect of loading and supports on the stresses and displacements was investigated. The problem was also solved, using the finite element method (FEM), and the results of which were compared with those of the analytical method. Furthermore, the effect of increases in the temperature gradient on displacement and stress values has been studied. Finally, in order to investigate the effect of third-order approximations on displacements and stresses, a comparison between the results of first- and third-order shear deformation theory has been made

Maximising opportunities at medical school to support a career in surgery

Introduction: During medical school, students have numerous opportunities to develop their portfolios for a career in surgery, such as undertaking additional surgical placements and participating in surgical research. However, at present, there is little guidance available for medical students on how to build a strong portfolio for the UK core surgical training application. This article outlines work undertaken to provide concise guidance to support future surgeons, via application of the competency-based CanMEDS framework to the current UK core surgical training specification. Materials and Methods: A pre-conference meeting was arranged for medical students at the Society of Academic and Research Surgeons annual conference in January 2018. Self-selected research enthusiasts from different university years discussed practical approaches to pair the CanMEDS model with the core surgical training specification, with support from the STARSurg Collaborative committee to facilitate discussion. A nominal group-based method was adopted in order to reach areas of consensus. Results: Practical tips and recommendations for each respective CanMEDS domain (communicator, collaborator, leader, health advocate, scholar, professional) were made in relation to the core surgical training specification. These included key action points and named opportunities that are currently available to UK medical students. Conclusions: A consensus approach was taken to address key areas of competence across each CanMEDS domain. This informed the development of a guidance framework to support students to develop a strong portfolio for a core surgical training application. This framework can be followed by medical students, equipping them with the skills necessary to succeed in their future surgical career.</p