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

Studies on gait control using a portable pneumatically powered ankle-foot orthosis (PPAFO) during human walking

A powered ankle-foot orthosis (AFO) can be very useful for people with neuromuscular injury. Control of powered AFOs will be more efficient to provide assistance to individuals with lower limb muscle impairments if we can identify different gait events during walking. A walking or gait cycle can be divided into multiple phases and sub-phases by proper gait event detection, and these phases/sub-phases are associated with one of the three main functional tasks during the gait cycle: loading response, forward propulsion, and limb advancement. The gait cycle of one limb can also be characterized by examining the limb’s behavior over one stride, which can be quantified as 0% to 100% of a gait cycle (GC). One easy approach to identify gait events is by checking whether sensor signals go above/below a predetermined threshold. By estimation of a walker’s instantaneous state, as represented by a specific percentage of the gait cycle (from states 0 to 100, which correlate with 0% to 100% GC), we can efficiently detect the various gait events more accurately. Our Human Dynamics and Controls Laboratory previously developed the portable pneumatically powered ankle-foot orthosis (PPAFO), which was capable of providing torque in both plantarflexion and dorsiflexion directions at the ankle. There were three types of sensor attached with the PPAFO (two force sensitive resistors and an angle sensor). In this dissertation, three aspects of effective control strategies for the PPAFO have been proposed. In the first study, two improved and reliable state estimators (Modified Fractional Time (MFT) and Artificial Neural Network (ANN)) were proposed for identifying when the limb with the PPAFO was at a certain percentage of the gait cycle. A correct estimation of percentage of gait cycle will assist with detecting specific gait events more accurately. The performance of new estimators was compared to a previously developed Fractional Time state estimation technique. To control a powered AFO using these estimators, however, detection of proper actuation timing is necessary. In the second study, a supervised learning algorithm to classify the appropriate start timing for plantarflexor actuation was proposed. Proper actuation timing has only been addressed in the literature in terms of functional efficiency or metabolic cost during walking. In this study, we will explore identifying the plantarflexor actuation timing in terms of biomechanics outcomes of human walking using a machine learning based algorithm. The third study investigated the recognition of different gait modes encountered during walking. The actuation scheme plays a significant role in walking on level ground, stair descent or stair ascent modes. The wrong actuation scheme for a given mode can cause falls or trips. A gait mode recognition technique was developed for detecting these different modes by attaching an inertial measurement unit and using a classifier based on artificial neural networks. This new algorithm improves upon the current one step delay limitation found as a drawback of a previously developed technique. Overall, this dissertation focused on addressing some important issues related to control of powered AFO that ultimately will help to assist people wearing the device in daily life situations during walking. The proposed approaches and algorithms introduced in this dissertation showed very promising results that proved that these methods can successfully improve the control system of powered AFOs

Design of actuation system and minimization of sensor configuration for gait event detection for Gen 3.0 Portable Powered Ankle-Foot Orthosis (PPAFO)

Powered ankle-foot orthoses (AFOs), which are capable of providing assistive torque at the ankle joint, have significant potential as both assistance and rehabilitation devices. Technology advancements have led to great progression in the development of powered AFOs. Our group had developed the Portable Powered Ankle-Foot Orthosis (PPAFO) that was capable of providing bidirectional assistive torque at the ankle joint. Two generations of the PPAFO were previously developed. Both designs used two different off-the-shelf rotary actuators. This thesis consists of two studies focusing on the development of a new compact higher torque actuation system and the identification of a minimum sensor configuration for gait event detection for a powered AFO. Study 1 presents the design and evaluation of a new actuation system for the PPAFO (Generation 3.0). The actuation system utilized two dual-action linear actuators and a customized gear train. Compared with the previous designs, it generated higher torque and power while providing a thinner lateral profile. The new design had a total weight of (680g) and was capable of generating 32 Nm torque and 110 W power. While running under the same torque and power level as the previous designs, the new design offered better longevity (42.9% and 81.4% increases in normalized run time for test bench emulation and treadmill walking). Although the overall weight of the new actuation system had a 20% increase compared with previous design, it could generate 166.7% more torque and 120% more power, which will enable us to test the system at various torque and power settings. Study 2 investigated the minimum sensor configuration for detecting gait events. Knowledge of the expected orientation and behavior of a limb as related to specific events during the gait cycle (or state timing as a function of the percentage of the gait cycle, % GC) is essential to allow appropriate control of a powered AFO. A total of five sensors were selected (two force sensitive sensors, one ankle angle sensor, and two inertial measurement units (IMU)). The performances of selected sensor configurations were quantified and compared through state-based and event-based approaches in terms of gait state estimation and gait event detection timing, respectively. Gait data were collected from five healthy subjects while walking on a treadmill wearing the Gen 3.0 PPAFO. Results indicated that, while single IMU configurations (located on the shank or foot) both outperformed all other configurations (mean state estimation error: < 2% GC; mean event detection timing error: < 23 ms), the shank IMU was able to detect more gait events than the foot IMU. Since more detectable events could improve the system's robustness (i.e., adjusting to variable speeds) by updating estimation more frequently, a single shank IMU configuration was recommended for powered AFO applications

Rehabilitation Engineering

Population ageing has major consequences and implications in all areas of our daily life as well as other important aspects, such as economic growth, savings, investment and consumption, labour markets, pensions, property and care from one generation to another. Additionally, health and related care, family composition and life-style, housing and migration are also affected. Given the rapid increase in the aging of the population and the further increase that is expected in the coming years, an important problem that has to be faced is the corresponding increase in chronic illness, disabilities, and loss of functional independence endemic to the elderly (WHO 2008). For this reason, novel methods of rehabilitation and care management are urgently needed. This book covers many rehabilitation support systems and robots developed for upper limbs, lower limbs as well as visually impaired condition. Other than upper limbs, the lower limb research works are also discussed like motorized foot rest for electric powered wheelchair and standing assistance device

On improving control and efficiency of a portable pneumatically powered ankle-foot orthosis

Ankle foot orthoses (AFOs) are widely used as assistive and/or rehabilitation devices to correct gait of people with lower leg neuromuscular dysfunction and muscle weakness. An AFO is an external device worn on the lower leg and foot that provides mechanical assistance at the ankle joint. Active AFOs are powered devices that provide assistive torque at the ankle joint. We have previously developed the Portable Powered Ankle-Foot Orthosis (PPAFO), which uses pneumatic power via compressed CO2 to provide untethered ankle torque assistance. My dissertation work focused on the development of control strategies for the PPAFO that are robust, applicable to different gait patterns, functional in different gait modes, and energy efficient. Three studies addressing these topics are presented in this dissertation: (1) estimation of the system state during the gait cycle for actuation control; (2) gait mode recognition and control (e.g., stair and ramp descent/ascent); and (3) system analysis and improvement of pneumatic energy efficiency. Study 1 presents the work on estimating the gait state for powered AFO control. The proposed scheme is a state estimator that reliably detects gait events while using only a limited array of sensor data (ankle angle and contact forces at the toe and heel). Our approach uses cross-correlation between a window of past measurements and a learned model to estimate the configuration of the human walker, and detects gait events based on this estimate. The proposed state estimator was experimentally validated on five healthy subjects and with one subject that had neuromuscular impairment. The results highlight that this new approach reduced the root-mean-square error by up to 40% for the impaired subject and up to 49% for the healthy subjects compared to a simplistic direct event controller. Moreover, this approach was robust to perturbations due to changes in walking speed and control actuation. Study 2 proposed a gait mode recognition and control solution to identify a change in walking environment such as stair and ramp ascent/descent. Since portability is a key to the success of the PPAFO as a gait assist device, it is critical to recognize and control for multiple gait modes (i.e., level walking, stair ascent/descent and ramp ascent/descent). While manual mode switching is implemented on most devices, we propose an automatic gait mode recognition scheme by tracking the 3D position of the PPAFO from an inertial measurement unit (IMU). Experimental results indicate that the controller was able to identify the position, orientation and gait mode in real time, and properly control the actuation. The overall recognition success rate was over 97%. Study 3 addressed improving operational runtime by analyzing the system efficiency and proposing an energy harvesting and recycling scheme to save fuel. Through a systematic analysis, the overall system efficiency was determined by deriving both the system operational efficiency and the system component efficiency. An improved pneumatic operation utilized an accumulator to harvest and then recycle the exhaust energy from a previous actuation to power the subsequent actuation. The overall system efficiency was improved from 20.5% to 29.7%, a fuel savings of 31%. Work losses across pneumatic components and solutions to improve them were quantified and discussed. Future work including reducing delay in recognition, exploring faulty recognition, additional options for harvesting human energy, and learning control were proposed

Application of wearable sensors in actuation and control of powered ankle exoskeletons: a Comprehensive Review

Powered ankle exoskeletons (PAEs) are robotic devices developed for gait assistance, rehabilitation, and augmentation. To fulfil their purposes, PAEs vastly rely heavily on their sensor systems. Human–machine interface sensors collect the biomechanical signals from the human user to inform the higher level of the control hierarchy about the user’s locomotion intention and requirement, whereas machine–machine interface sensors monitor the output of the actuation unit to ensure precise tracking of the high-level control commands via the low-level control scheme. The current article aims to provide a comprehensive review of how wearable sensor technology has contributed to the actuation and control of the PAEs developed over the past two decades. The control schemes and actuation principles employed in the reviewed PAEs, as well as their interaction with the integrated sensor systems, are investigated in this review. Further, the role of wearable sensors in overcoming the main challenges in developing fully autonomous portable PAEs is discussed. Finally, a brief discussion on how the recent technology advancements in wearable sensors, including environment—machine interface sensors, could promote the future generation of fully autonomous portable PAEs is provided

serial and parallel robotics: energy saving systems and rehabilitation devices

This thesis focuses on the design and discussion of robotic devices and their applications. Robotics is the branch of technology that deals with the design, construction, operation, and application of robots as well as computer systems for their control, sensory feedback, and information processing [1]. Nowadays, robotics has been an unprecedented increase in applications of industry, military, health, domestic service, exploration, commerce, etc. Different applications require robots with different structures and different functions. Robotics normally includes serial and parallel structures. To have contribution to two kinds of structures, this thesis consisting of two sections is devoted to the design and development of serial and parallel robotic structures, focused on applications in the two different fields: industry and health

Online control of a mobility assistance smart walker

Dissertação de mestrado integrado em Engenharia BiomédicaThis work presents the NeoASAS project that was developed at the Bioengineering Group, Consejo Superior de Investigaciones Cientificas (CSIC) in Madrid. Further, it continued with adaptations and improvements at Minho University with the Adaptive System Behavior Group (ASBG) in Guimarães, being designated by ASBGo Project. These developments include the conceptual design, implementation and validation of Smart Walkers with a new interface approach integrated into these devices. This interface is based on a joystick and it is intended to extract the user’s movement intentions. It was designed to be user-friendly and efficient, meeting usability aspects and focused on a commercial implementation, but not being demanding at the user cognitive level. Considering the ASBGo walker, the overall assemblage, mechanical adjustments, electronics and computing have been performed. First, a review about the mobility assistive devices is presented, specially focused on Smart Walkers. Despite the intensive research, in current literature, there are not many works providing a "point of the situation", and explaining the role that robotics can play in this domain. Healthy users performed preliminary sets of experiments with each walker, which showed the sensibility of the joystick to extract command intentions from the user. These signals presented a higher frequency component that was attenuated by a Benedict-Bordner g-h filter, considering the NeoASAS walker and by a Butterworth circuit, considering the ASBGo walker. These methodologies offer a cancelation of the undesired components from joystick data, allowing the system to extract in real-time user’s commands. Based on this identification, an approach to the control architecture based on a fuzzy logic algorithm was developed, in order to allow the control of the walkers’ motors. In addition, a set of sensors were integrated on the walker for safety reasons: an infrared sensor to detect if the user is falling forwards; two force sensors to make sure that the user is properly grabbing the hand support; and two force sensors in the support forearms to verify if the user is with his forearms properly supported. This will make sure that the device stops when one of these situations happens. Thus, an assistive device to provide safety and natural manoeuvrability was conceived and offers a certain degree of intelligence in assistance and decision-making. These results will be used to advance towards a commercial product with an affordable cost, but presenting high reliability and safety. The motivation is that this will contribute to improve rehabilitation purposes by promoting ambulatory daily exercises and thus extend users’ independent living.Este trabalho apresenta o projecto NeoASAS desenvolvido no Grupo de Bioengenharia, do Consejo Superior de Investigaciones Cientificas (CSIC) em Madrid. Este teve continuidade com adaptações e melhorias na Universidade do Minho com o grupo Adaptative System Behaviour (ASBG) em Guimarães, sendo designado por projecto ASBGo. Estes desenvolvimentos incluem o projecto concetual, implementação e validação de andarilhos inteligentes com uma nova interface integrada nestes dispositivos. Esta interface é baseada num joystick e tem como objetivo a extração de intenções de comando do utilizador, sendo intuitiva e eficiente. Atende a aspectos de usabilidade e está focada numa aplicação comercial, não sendo exigente a nível cognitivo. Considerando o andarilho ASBGo, foi realizada a construção deste, bem como, ajustes mecânicos, eletrónicos e programação. É apresentada uma revisão sobre os dispositivos de assistência à marcha, tendo especial enfoque os andarilhos. Apesar da intensa investigação, na literatura não existem trabalhos que apresentem o ponto de situação desta área, bem como o seu papel na robótica de reabilitação. Depois foram realizados testes com utilizadores, mostrando a sensibilidade que o joytick tem na identificação de inteções de comando do utilizador. Além disso, os sinais apresentam uma componente de alta frequência que foi atenuada, no caso do NeoASAS, com um filtro g-h Benedict-Bordner, e no caso do ASBGo, através de um filtro Butterworth implementado em hardware. As metodologias apresentadas oferecem um cancelamento componentes indesejáveis, permitindo ao sistema a extração das intenções de comando do utilizador em tempo real. Desta forma, uma arquitetura de controlo baseada em fuzzy logic foi desenvolvida de maneira a fornecer uma assistência segura ao utilizador, através do controlo dos motores. Foram também integrados um conjunto de sensores no andarilho por razões de segurança: um sensor infravermelho para detetar a queda frontal do utilizador, dois sensores de força nos apoios de mão para detetar se o utilizador está a agarrá-los, e dois sensores de força nos suportes de antebraço para certificar que o utilizador está devidamente apoiado. Assim, foi concebido um dispositivo que garante a segurança do utilizador e oferece um certo grau de inteligência e tomada de decisão. Estes resultados serão utilizados para a criação de um produto comercial com custo acessível, mas com alta confiabilidade. A motivação deste trabalho reflete-se na contribuição que este dispositivo terá na melhoria da reabilitação e desenvolvimento de dispositivos ambulatórios para promover exercicios diários, e melhorar a vida dos utilizadores

Assessment of human kinematic performance with non-contact measurements for tele-rehabilitation

&nbsp;Aging of population is challenging the traditional rehabilitation services for various movement disorders. In the foreseeable future, tele-rehabilitation will be a contributive factor for the well-being of the older generation. This research has tackled a series of problems in developing an automated assessment tool for human kinematic performance in tele-rehabilitation with optoelectronic bio-kinematic motion capture devices and preliminarily confirmed its applicability