Human-centered Electric Prosthetic (HELP) Hand

Through a partnership with Indian non-profit Bhagwan Mahaveer Viklang Sahayata Samiti, we designed a functional, robust, and and low cost electrically powered prosthetic hand that communicates with unilateral, transradial, urban Indian amputees through a biointerface. The device uses compliant tendon actuation, a small linear servo, and a wearable garment outfitted with flex sensors to produce a device that, once placed inside a prosthetic glove, is anthropomorphic in both look and feel. The prosthesis was developed such that future groups can design for manufacturing and distribution in India

The SmartHand transradial prosthesis

<p>Abstract</p> <p>Background</p> <p>Prosthetic components and control interfaces for upper limb amputees have barely changed in the past 40 years. Many transradial prostheses have been developed in the past, nonetheless most of them would be inappropriate if/when a large bandwidth human-machine interface for control and perception would be available, due to either their limited (or inexistent) sensorization or limited dexterity. <it>SmartHand </it>tackles this issue as is meant to be clinically experimented in amputees employing different neuro-interfaces, in order to investigate their effectiveness. This paper presents the design and on bench evaluation of the SmartHand.</p> <p>Methods</p> <p>SmartHand design was bio-inspired in terms of its physical appearance, kinematics, sensorization, and its multilevel control system. Underactuated fingers and differential mechanisms were designed and exploited in order to fit all mechatronic components in the size and weight of a natural human hand. Its sensory system was designed with the aim of delivering significant afferent information to the user through adequate interfaces.</p> <p>Results</p> <p>SmartHand is a five fingered self-contained robotic hand, with 16 degrees of freedom, actuated by 4 motors. It integrates a bio-inspired sensory system composed of 40 proprioceptive and exteroceptive sensors and a customized embedded controller both employed for implementing automatic grasp control and for potentially delivering sensory feedback to the amputee. It is able to perform everyday grasps, count and independently point the index. The weight (530 g) and speed (closing time: 1.5 seconds) are comparable to actual commercial prostheses. It is able to lift a 10 kg suitcase; slippage tests showed that within particular friction and geometric conditions the hand is able to stably grasp up to 3.6 kg cylindrical objects.</p> <p>Conclusions</p> <p>Due to its unique embedded features and human-size, the SmartHand holds the promise to be experimentally fitted on transradial amputees and employed as a bi-directional instrument for investigating -during realistic experiments- different interfaces, control and feedback strategies in neuro-engineering studies.</p

Design of a robotic hand with a biologically-inspired parallel actuation system for prosthetic applications

Trabajo presentado al 34th Annual Mechanisms and Robotics Conference celebrado en Quebec del 15 al 18 de agosto de 2010.This paper presents the design of a robotic hand for prosthetic applications. The main characteristic of this robotic hand is its biologically-inspired parallel actuation system, which is based on the behavior/strength space of the Flexor Digitorum Profundus (FDP) and the Flexor Digitorum Superficialis (FDS) muscles. The design separates the strength space of the FDS and FDP muscles into a lighter strength region where finer manipulation and general approach tasks are executed, and a higher strength region where the more robust grasps are achieved. Two parallel actuator types and kinematic structures are designed to complement the requirements of both strength space regions.This research was performed under an award/contract from Telemedicine Advanced Technology Research Center (TATRC), of the U.S. Army Medical Research and Materiel Command (USAMRMC) of the U.S. Department of Defense.Peer Reviewe

Design of a robotic hand and simple EMG input controller with a biologically-inspired parallel actuation system for prosthetic applications

This paper presents the mechatronic design of a robotic hand for prosthetic applications. The main characteristic of this robotic hand is its biologically-inspired parallel actuation system, which is based on the behavior/strength space of the Flexor Digitorum Profundus (FDP) and the Flexor Digitorum Superficialis (FDS) muscles. The design separates the strength space of the FDS and FDP muscles into a lighter strength region where finer manipulation and general approach tasks are executed, and a higher strength region where the more robust grasps are achieved. Two parallel actuator types and kinematic structures are designed to complement the requirements of both strength space regions.This unique structure is intended to be driven by electromyographical (EMG) signals captured at the surface of the skin. The direct relation between signal and actuation system lends itself well to interpreting the EMG signals from the FDP and FDS muscles into effective task execution, with the goal of helping the user to achieve a good approximation of the full capabilities associated with the human hand, without compromising strength, dexterity, appearance, or weight; which are common issues associated with prosthetic hands. The designed finger’s capability of having a strength space similar to that of the FDS and FDP muscles is validated via direct inputs from a power supply and then via a controller using an actual EMG signal input from the human forearm. The controller is a simple feed forward system at this point in the research but provides the appropriate framework to integrate more elaborate control schemes and EMG signal conditioning as this portion of the research area matures.Peer ReviewedPostprint (author’s final draft

Advancing the Underactuated Grasping Capabilities of Single Actuator Prosthetic Hands

The last decade has seen significant advancements in upper limb prosthetics, specifically in the myoelectric control and powered prosthetic hand fields, leading to more active and social lifestyles for the upper limb amputee community. Notwithstanding the improvements in complexity and control of myoelectric prosthetic hands, grasping still remains one of the greatest challenges in robotics. Upper-limb amputees continue to prefer more antiquated body-powered or powered hook terminal devices that are favored for their control simplicity, lightweight and low cost; however, these devices are nominally unsightly and lack in grasp variety. The varying drawbacks of both complex myoelectric and simple body-powered devices have led to low adoption rates for all upper limb prostheses by amputees, which includes 35% pediatric and 23% adult rejection for complex devices and 45% pediatric and 26% adult rejection for body-powered devices [1]. My research focuses on progressing the grasping capabilities of prosthetic hands driven by simple control and a single motor, to combine the dexterous functionality of the more complex hands with the intuitive control of the more simplistic body-powered devices with the goal of helping upper limb amputees return to more active and social lifestyles. Optimization of a prosthetic hand driven by a single actuator requires the optimization of many facets of the hand. This includes optimization of the finger kinematics, underactuated mechanisms, geometry, materials and performance when completing activities of daily living. In my dissertation, I will present chapters dedicated to improving these subsystems of single actuator prosthetic hands to better replicate human hand function from simple control. First, I will present a framework created to optimize precision grasping – which is nominally unstable in underactuated configurations – from a single actuator. I will then present several novel mechanisms that allow a single actuator to map to higher degree of freedom motion and multiple commonly used grasp types. I will then discuss how fingerpad geometry and materials can better grasp acquisition and frictional properties within the hand while also providing a method of fabricating lightweight custom prostheses. Last, I will analyze the results of several human subject testing studies to evaluate the optimized hands performance on activities of daily living and compared to other commercially available prosthesis

Study of composite elastic elements for transfemoral prostheses: the MyLeg Project

In this thesis, the work on the design and realization of a semi-active foot prosthesis with variable stiffness system is presented. The final prosthesis was the result of a path started by the design of the elastic composite elements of an ESR prosthesis, a passive prosthetic device, generally prescribed to amputees with K3 and K4 of level of ambulation. The design of both the ESR prosthesis and the final variable stiffness prosthesis was carried out using a new systematic methodology of prosthesis design. This methodology has been developed and then presented in the same thesis by the author. Modelling and simulation techniques are illustrated step by step. With the variable stiffness prosthesis, the aim is to allow future users to perform more daily activities without being restricted by the conditions of the ground. It has been chosen to develop a semi-active prosthesis rather than a bionic foot for two main reasons: a bionic foot may be too expensive for most future users; and a bionic foot may be undesirable for too much weight; the much weight can be due to the motor and batteries, in addition to the structure that will certainly be much more complex than the structure of a semi-active prosthesis. To investigate the effectiveness of the variable stiffness, human subjects with amputees will be carried out

Study of design issues in a prototype lower-limb prosthesis - proof-of-concept in a 3D printed model

Dissertação de Mestrado Integrado em Engenharia Biomédica Ramo de Biomateriais, Reabilitação e BiomecânicaThe amputation of one or both lower limbs, which can be brought on by trauma, diabetes, or other vascular diseases, is an increasingly common occurrence, especially due to the increase in the number of cases of diabetes in the developed world. In Portugal alone 1300 amputations each year are attributed to diabetes. These amputations severely impact the mobility, self-esteem, and quality of life of the patients, a situation that can be alleviated via the installation of a lower limb prosthesis. Sadly, these prostheses are not yet capable of completely emulating a sound limb in an affordable fashion. In this dissertation, state-of-the-art research was carried out regarding the mechanics of human gait, both healthy and prosthetic. An investigation regarding the state-of-the-art research was also carried out regarding lower-limb prostheses, their evolution, mechanics, and prospects, as well as additive manufacturing techniques, and how they can be crucial to the development of affordable prostheses. Special attention was provided to the study of the leading edge of prostheses research, namely active prostheses, capable of generating and introducing energy into the human gait, rather than simply acting as passive devices. This dissertation follows up on previous work carried out in the BioWalk Project of Universidade do Minho’s BiRDLab: “Prosthetic Devices and Rehabilitation Solutions for the Lower Limbs Amputees”. This work consisted of the development of an active lower-limb prosthesis prototype, with the goal of providing an affordable, but functional, prosthesis for future testing with patients. However, the resulting prototype was laden with issues, such as excessive weight and an underpowered motor. As such, this work set out to identify these issues, design, implement and test modifications to the prosthesis to produce a satisfying prototype. Given the limited resources and facilities available, it was decided to work on a smaller model prosthesis installed in a bipedal robot, the DARwIn-OP, using it as proof-of-concept for modifications to be implemented in the BiRDLab prosthesis. Modifications were successfully implemented, chiefly among them a planetary gear-based reductor and a novel attachment mechanism built using additive manufacturing techniques. It is possible to conclude that there is a great potential in the implementation of additive manufacturing techniques in the development of affordable prosthesis.A amputação de um ou ambos os membros inferiores, que pode ser causada por trauma, diabetes, ou outras doenças vasculares, é um evento cada vez mais frequente, especialmente devido ao aumento do número de casos de diabetes no mundo desenvolvido. Em Portugal, 1300 amputações são atribuídas aos diabetes todos os anos. Estas amputações influenciam negativamente a mobilidade, autoestima e qualidade de vida dos pacientes, mas estes efeitos podem ser minimizados através da instalação de uma prótese de membro inferior. Infelizmente, estas próteses ainda não são capazes de emular completamente um membro saudável de forma económica. Nesta dissertação, um estado da arte do caminhar humano foi realizado, tendo em atenção o funcionamento deste, quer em sujeitos saudáveis ou amputados. Um estado da arte também foi realizado relativamente às próteses de membros inferiores, a sua evolução, funcionamento, e perspetivas futuras, e também relativamente a técnicas de fabrico aditivas e a forma como estas podem ser aplicadas em próteses acessíveis. Tomou-se atenção especial ao estudo das próteses ativas, capazes de gerar e introduzir energia no caminhar, ao invés das próteses passivas tradicionais. Esta dissertação baseia-se em trabalho prévio ao abrigo do projeto BioWalk do laboratório BiRDLab da Universidade do Minho: “Dispositivos prostéticos e soluções de reabilitação para amputados dos membros inferiores”. Este trabalho consistiu no desenvolvimento de um protótipo de prótese de membro inferior ativa, com o objetivo de criar uma prótese de baixo custo para testes em pacientes. No entanto, o protótipo produzido possuí vários problemas, tais como peso excessivo e um motor subdimensionado. Assim sendo, este trabalho propôs-se a identificar estes problemas e a desenhar, implementar, e testar modificações. Tendo em conta os limitados recursos disponíveis, decidiu-se trabalhar numa prótese modelo mais pequena, instalada num robô bipedal, o DARwIN-OP, e a usá-la para testar modificações a implementar na prótese do BiRDLab. As modificações foram implementadas com sucesso, especialmente um redutor de engrenagens planetárias e um novo método de conectar a prótese, usando técnicas de fabrico aditivas

Bio-inspired friction switches: adaptive pulley systems

Frictional influences in tendon-driven robotic systems are generally unwanted, with efforts towards minimizing them where possible. In the human hand however, the tendon-pulley system is found to be frictional with a difference between high-loaded static post-eccentric and post-concentric force production of 9-12% of the total output force. This difference can be directly attributed to tendon-pulley friction. Exploiting this phenomenon for robotic and prosthetic applications we can achieve a reduction of actuator size, weight and consequently energy consumption. In this study, we present the design of a bio-inspired friction switch. The adaptive pulley is designed to minimize the influence of frictional forces under low and medium-loading conditions and maximize it under high-loading conditions. This is achieved with a dual-material system that consists of a high-friction silicone substrate and low-friction polished steel pins. The system, designed to switch its frictional properties between the low-loaded and high-loaded conditions, is described and its behavior experimentally validated with respect to the number and spacing of pins. The results validate its intended behavior, making it a viable choice for robotic tendon-driven systems.Comment: Conference. First submission, before review

Numerical-experimental characterisation of a hand prosthesis: pilot project built by additive manufacturing

Dissertação de mestrado integrado em Engenharia Biomédica (especialização em Biomateriais, Reabilitação e Biomecânica)The loss of one hand affects significantly the level of autonomy and the ability to carry out activities of daily living, work and social activities. Since the dawn of humanity, the use of prostheses has been used to compensate for this loss. Despite technological advances in the manufacture of prostheses, hand prostheses currently marketed have a high cost, making access impossible for many users. One alternative to these prostheses is produce them by fused filament fabrication, allowing for the improvement of low-cost prosthetic hands. A powerful tool that allows making accurate predictions of the mechanical behaviour of discrete and continuous media is the finite element method. The simulation of grip movements of a hand prosthesis pro totype using this method was used in the present study, whose objective is the numerical and experimental characterisation of this prototype. In the context of this work, the numerical model that aims to obtain the deformed configuration of the prosthesis in the regions of contact with an object was successfully obtained. The displacement, strain and stress fields in critical regions of the prosthesis are relevant and were consistent with the mechanism kine matics. Moreover, the characterisation of the material constituting the prosthesis (polylactic acid) implies the 3D printing of specimens with different processing conditions, four filament orientations and two infill percentages. Mechanical tests were performed, namely three-point bending and uniaxial tensile tests, as well as the respective numerical simulations. The results obtained demonstrated high reproducibility for the different processing conditions with a clear differences between them. The modulus of elasticity and Pois son’s ratio determined were always higher for the specimens printed with a 100% infill than for those with 30%. Regarding the orientations, no significant trend was observed. The mechanical responses obtained through numerical simulations were very close to the ones obtained experimentally.A perda de uma das mãos afeta significativamente o nível de autonomia e a capacidade de realizar atividades diárias, de trabalho e sociais. Desde os primórdios da humanidade que se recorre à utilização de próteses para compensar essa perda. Apesar dos avanços tecnológicos no fabrico de próteses, as próteses de mão comercializadas atualmente têm um custo elevado, inviabilizando o acesso a vários utilizadores. Uma alternativa a estas próteses é a sua produção através do fabrico de filamentos fundidos, permitindo aprimorar mãos prostéticas de baixo custo. Uma ferramenta poderosa que permite realizar previsões precisas do comportamento mecânico de meios discretos e contínuos é o método dos elementos finitos. A simulação de um movimento de preensão de um protótipo de prótese da mão utilizando este método foi empregue no presente estudo, cujo objetivo é a caracterização numérica e experimental desse protótipo. No contexto deste trabalho, a modelação numérica que visa obter a configuração deformada da prótese nas regiões de contacto com um objeto, foi obtida com sucesso. Os campos de deslocamento, deformação e tensão em regiões críticas da prótese são relevantes e apresentaram-se coerentes com a cinemática do mecanismo. Além disso, a caracterização do material que constitui a prótese (poliácido lático) compreen deu a impressão 3D de provetes combinando diferentes condições de processamento, quatro orientações do filamento e duas taxas de enchimento. Foram realizados ensaios mecânicos, nomeadamente de flexão em três pontos e uniaxiais de tração, bem como as respetivas simulações numéricas. Os resultados obti dos demonstraram elevadas reprodutibilidade para as diferentes condições de processamento com uma clara diferença entre estas. O módulo de elasticidade e coeficiente de Poisson determinados foram sempre superiores para os provetes impressos com uma taxa de enchimento de 100% face aos de 30%. Relativa mente às orientações, não foi verificada nenhuma tendência significativa. As respostas mecânicas obtidas através das simulações numéricas encontraram-se bastante próximas dos resultados experimentais