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

Physical Diagnosis and Rehabilitation Technologies

The book focuses on the diagnosis, evaluation, and assistance of gait disorders; all the papers have been contributed by research groups related to assistive robotics, instrumentations, and augmentative devices

A knee brace design to reduce the energy consumption of walking

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 51-52).Recent research into the mechanics of walking indicates that a quasi passive wearable device could be created which dramatically reduces the metabolic energy used in walking especially when the wearer is carrying additional torso weight. Target population groups include military personnel who must carry heavy battle packs and body armor, hikers, letter carriers, and the quasi disabled. This latter group includes a significant fraction of the elderly who have reduced leg strength and/or higher weight torsos. The device is called PUUMA, an acronym for Personal Unpowered Universal Mobility Assistant. Though walking has been studied extensively, there appears to be a limited understanding of the interplay between the kinetic and potential energy of the torso when driven by legs that can store and release energy. This thesis introduces a simplified model which enables simulation of the entire walking process including the epoch following heel strike. One simulation goal was to explore the knee spring properties which enable lossless walking. Simulations show that there are two knee spring configurations which allow for lossless walking. It is also shown that the percentage of kinetic energy transferred to a knee spring can be a significant fraction of the torso kinetic energy.(cont.) PIJUMA's basic idea is the incorporation of torsion springs at the knee joints which absorb torso kinetic energy following heel strike and then release that stored energy later in the step. An application of the capstan effect is introduced which enables a practical implementation of two knee spring configurations. In particular, the design allows the thigh and shank to be dynamically coupled to a microprocessor controlled knee spring thereby allowing both unimpeded leg swing and kinetic energy transfer to the knee spring. Another use of the capstan effect is introduced which allows for a microprocessor controlled brake that can freeze the knee at its maximum torsion and then release it later in the walking cycle. A design is shown which embodies the architectural ideas created. Several of the key components were designed, prototyped and tested.by Matthew R. Carvey.S.B

Advances of Italian Machine Design

This 2028 Special Issue presents recent developments and achievements in the field of Mechanism and Machine Science coming from the Italian community with international collaborations and ranging from theoretical contributions to experimental and practical applications. It contains selected contributions that were accepted for presentation at the Second International Conference of IFToMM Italy, IFIT2018, that has been held in Cassino on 29 and 30 November 2018. This IFIT conference is the second event of a series that was established in 2016 by IFToMM Italy in Vicenza. IFIT was established to bring together researchers, industry professionals and students, from the Italian and the international community in an intimate, collegial and stimulating environment

Design of a wearable active ankle-foot orthosis for both sides

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Biomateriais, Reabilitação e Biomecânica)Portugal is the west European country with the highest rate of stroke-related mortality, being that, of those who suffer cerebrovascular accidents, 40% feature an impairment which can manifest itself through motor sequelae, namely drop foot. An ankle-foot orthosis is often recommended to passively accommodate these motor problems; however, active/powered exoskeletons are also a suitable solution for post-stroke patients. Due to the high complexity of the human ankle joint, one of the problems regarding these active devices is the misalignment occurring between the rehabilitation device and the human joint, which is a cause of parasitic forces, discomfort, and pain. The present master dissertation proposes the development of an adjustable wearable active ankle-foot orthosis that is able to tackle this misalignment issue concerning commercially available lower limb orthotic devices. This work is integrated on the SmartOs – Smart, Stand-alone Active Orthotic System – project that proposes an innovative robotic technology (a wearable mobile lab) oriented to gait rehabilitation. The conceptual design of a standard version of the SmartOs wearable active orthosis was initiated with the analysis of another ankle-foot orthosis – Exo-H2 (Technaid) – from which the necessary design changes were implemented, aiming at the improvement of the established device. In order to achieve a conceptual solution, both the practical knowledge of the Orthos XXI design team and several design methods were used to ensure the accomplishment of the defined requirements. The detailed design process of the standard SmartOs wearable active orthosis prototype is disclosed. With the purpose of validating the design, the critical components were simulated with the resources available in SolidWorks®, and the necessary CAD model’s adaptations were implemented to guarantee a reliable and safe design. The presented design is currently set for further production in Orthos XXI, followed by the mandatory mechanical tests.Portugal é o país da Europa ocidental com maior taxa de mortalidade por acidente vascular cerebral (AVC), sendo que, dos que sofrem acidentes vasculares cerebrais, 40% apresentam uma deficiência que pode manifestar-se por sequelas motoras, nomeadamente o pé pendente. Uma ortótese do tornozelo é recomendada frequentemente para acomodar passivamente esses problemas motores; no entanto, exoesqueletos ativos são também uma solução adequada para pacientes pós-AVC. Devido à alta complexidade da articulação do tornozelo humano, um dos problemas associados a esses dispositivos ativos é o desalinhamento que ocorre entre o dispositivo de reabilitação e a articulação humana, que é uma causa de forças parasitas, desconforto e dor. A presente dissertação de mestrado propõe o desenvolvimento de uma ortótese ativa do tornozelo ajustável e vestível, que seja capaz de resolver esse problema de desalinhamento relativo aos dispositivos ortóticos de membros inferiores disponíveis comercialmente. Este trabalho está integrado no projeto SmartOs - Smart, Stand-alone Active Orthotic System - projeto que propõe uma tecnologia robótica inovadora (wearable mobile lab) direcionada para a reabilitação da marcha. O projeto conceptual de uma versão padrão da ortótese ativa vestível do projeto SmartOs foi iniciado com a análise de outra ortótese do tornozelo – Exo-H2 (Technaid) - a partir da qual foram implementadas as alterações de projeto necessárias, visando o aprimoramento do dispositivo estabelecido. Para se chegar a uma solução conceptual, tanto o conhecimento prático da equipa de projeto da Orthos XXI como os diversos métodos de projeto foram utilizados para garantir o cumprimento dos requisitos definidos. O processo do desenho detalhado da versão padrão da ortótese ativa SmartOs será também divulgado. Com o objetivo de validar o projeto, os componentes críticos foram simulados com os recursos disponíveis no SolidWorks® e as adaptações necessárias do modelo CAD foram implementadas para garantir um projeto fidedigno e seguro. O projeto apresentado está atualmente em preparação para produção na empresa Orthos XXI, depois do qual se seguem os ensaios mecânicos obrigatórios

Evaluating Optimality in the Control of Wearable Robotic Devices

Lower-limb wearable robots, such as prostheses and exoskeletons, have the potential to fundamentally transform the mobility of millions of able-bodied and disabled individuals during work, recreation, and/or rehabilitation. Researchers have developed high-performance robotic devices that are lightweight and autonomous, yet we have not seen their widespread adoption as clinical or commercial solutions. One major factor delaying the dissemination of this technology is that our control of these devices remains limited, especially outside controlled laboratory settings. While many adaptive control strategies have been proposed and tested for wearable robotic systems, it is still an open question as to how to provide users with optimal assistance. This is a challenge because a clear definition of 'optimal assistance' has not yet been established, due to the various goals of assistive devices and the complex interactions between robotic assistance and human physiology. Furthermore, it has been difficult to move these systems outside the laboratory environment due to constraints imposed by tethered hardware and sensing equipment, as well as the difficulty associated with quantifying non-steady-state activities. To address this challenge, the goal of the work presented in this dissertation is to further our understanding of how to provide users with optimal assistance from robotic exoskeletons and prostheses outside the laboratory environment. The first theme of this dissertation is the translation of experimental methods (e.g., human-in-the-loop optimization) and measurement tools outside the laboratory environment. The second theme is the evaluation of context-specific objectives for the optimization of wearable robotic devices (e.g., metabolic cost, user preference) in clinical and research settings. This dissertation comprises four primary projects. First, I evaluated the impact that changing the power setting of the BiOM commercial powered ankle prosthesis has on the metabolic cost of transport of individuals with transtibial amputation. This work informs clinical tuning and prescription practices by revealing that, to minimize their metabolic energy consumption, individuals require a higher power setting than the setting chosen by the prosthetist to approximate biological ankle kinetics. Second, I investigated an alternative method for estimating instantaneous metabolic cost using portable wearable sensors. The goal of this project was to accurately estimate instantaneous metabolic cost without relying on indirect calorimetry, and thus enable the use of human-in-the-loop optimization algorithms outside the laboratory environment. I utilized linear regression algorithms to predict instantaneous metabolic cost from physiological signals, and systematically compared a large set of signals to determine which sensor signals contain the highest predictive ability, robust to unknown subjects or tasks. In the third project, I built upon this work and demonstrated that including the derivatives of physiological signals in the linear regression algorithm could improve both the speed and accuracy of instantaneous metabolic cost prediction from portable sensors. Finally, I investigated user preference as an objective for the control of lower-limb robotic exoskeletons. In this work, I demonstrated that exoskeleton users can quickly and precisely identify unique preferences in the characteristics of their ankle exoskeleton assistance in two dimensions simultaneously, and that preference changes with speed, exposure, and prior experience. These results provide insight into how users interact with exoskeletons, and establish important benchmarks for researchers, designers, and future consumers. Together, these four projects evaluate the notion of optimality in the control of wearable robotic systems and lay the foundation for translating optimization protocols outside the laboratory environment.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/169808/1/kaingr_1.pd