Design and Development of a Lightweight Ankle Exoskeleton for Human Walking Augmentation

RESUMÉ La plupart des exosquelettes motorisés de la cheville ont une masse distale considérable, ce qui limite leur capacité à réduire l’énergie dépensée par l’utilisateur durant la marche. L’objectif de notre travail est de développer un exosquelette de chevilles avec le minimum de masse distale ajoutée comparé aux exosquelettes motorisés de chevilles existants. Aussi, l’exosquelette doit fournir au moins 50 Nm de support au couple de flexion plantaire. L’exosquelette développé dans le cadre de ce mémoire utilise deux câbles Bowden pour transmettre la force mécanique de l’unité d’actionnement attachée à la taille aux deux tiges en fibre de Carbonne attachées à la botte de l’utilisateur. Quand les deux tiges sont tirées, ils génèrent un couple qui supporte le mouvement de flexion plantaire à la fin de la phase d’appui du cycle de marche. Une pièce conçue sur mesure et imprimé en plastique par prototypage rapide a été attachée au tibia pour ajuster la direction des câbles. Une étude d’optimisation a été effectuée pour minimiser la masse des tiges limitant ainsi la masse distale de l’exosquelette (attaché au tibia et pied) à seulement 348 g. Le résultat principal obtenu à partir des tests de marche est la réduction de l’activité des muscles soléaire et gastrocnémien du sujet par une moyenne de 37% et 44% respectivement lors de la marche avec l’exosquelette comparée à la marche normale. Cette réduction s’est produite quand l’exosquelette a fourni une puissance mécanique de 19 ± 2 W avec un actionnement qui a commencé à 38% du cycle de marche. Ce résultat démontre le potentiel de notre exosquelette à réduire le cout métabolique de marche et souligne l’importance de réduire la masse distale d’un exosquelette de marche.----------ABSTRACT Most of powered ankle exoskeletons add considerable distal mass to the user which limits their capacity to reduce the metabolic energy of walking. The objective of the work presented in this master thesis is to develop an ankle exoskeleton with a minimum added distal mass compared to existing autonomous powered ankle exoskeletons, while providing at least 50 Nm of assistive plantar flexion torque. The exoskeleton developed in this master thesis uses Bowden cables to transmit the mechanical force from the actuation unit attached to the waist to the carbon fiber struts fixed on the boot. As the struts are pulled, they create an assistive ankle plantar flexion torque. A 3D-printed brace was attached to the shin to adjust the direction of the cables. A design optimization study was performed to minimize the mass of the struts, thereby limiting the total added distal mass, attached to the shin and foot, to only 348 g. The main result obtained from walking tests was the reduction of the soleus and gastrocnemius muscles activity by an average of 37% and 44% respectively when walking with the exoskeleton compared to normal walking. This reduction occurred when the exoskeleton delivered a mechanical power of 19 ± 2 W with an actuation onset fixed at 38% of the gait cycle. This result shows the potential of the proposed exoskeleton to reduce the metabolic cost of walking and emphasizes the importance of minimizing the distal mass of ankle exoskeletons

Steering natural dynamics to yield energy efficient, stable, and agile legged locomotion

We investigate how natural dynamics can yield stable, agile, and energy efficient robotic systems. Firstly, we cover a design with a single passive rolling element to stabilize frontal plane dynamics for a 3D biped walking across a range of forward velocities and/or step lengths. We examine aspects of the non-linear dynamics that contribute to the energy efficiency and stability of the system through simulations. Secondly, we examine switching controllers that allow for agile foothold selection in 5-link walkers. We leverage dynamic programming and discretization of the reachable space to walk across intermittent footholds. We utilize our meshing techniques to quantify stability and agility of these switching controllers. Finally, we provide experimental data on the effect of extra mass and power on humans at a variety of locations and forward velocities. This allows robot and exoskeleton designers to optimize for energy performance by understanding mass placements and power densities required for high performing legged locomotion. Finally, we present experimental data for an exoskeleton capable of assisting across running and walking speed

Exoskeletons to enhance human capabilities and support rehabilitation: a state of the art

El presente artículo presenta una revisión bibliográfica sobre el diseño de exoesqueletos y las diferentes aplicaciones que estos pueden tener en la vida humana. Se exponen diferentes desarrollos, resaltando las partes más importantes de cada uno y prestando especial atención al área de la ingeniería electrónica presente en estas estructuras. Además, se realiza un agrupamiento de los diseños, dependiendo de la zona corporal para la cual se ha construido el exoesqueleto o de la finalidad del estudio realizado. Finalmente, se presentan desarrollos y estudios que buscan utilizar las señales mioeléctricas como parte fundamental del sistema exoesquelético.This paper presents a literature review about exoskeletons and their applications in human life. Different developments highlighting the most important parts of each of them, and paying particular attention to the area of electronic engineering related to these structures, are shown. Also, a grouping of the different kinds of structures is made depending on the area of the human body to which the exoskeleton was intended to or depending on the purpose of the research. Finally, various studies and developments which use mioelectric signals as a fundamental part of the system are presented

Gait analysis for designing a new assistive knee brace

Assistive knee brace is a species of wearable lower extremity exoskeletons. In this research, an assistive knee brace was developed by integrating a multifunctional actuator with a custom-made knee-ankle-foot orthosis. In the study, the location of the actuator is moved up to the lateral side of the hip, instead of knee joint. Waist belt and shoulder belt are appended on the knee brace. This paper aimed to improve the design of the assistive knee braces through gait analysis. By walking with the knee braces, the spatial and temporal gait parameters, joint kinematics and joint kinetics parameters were evaluated, and the changes from normal walking were compared as well. The experimental results showed that walking with the developed knee brace provided minimal hindrance to the wearer. © 2011 IEEE