Feedback Control of an Exoskeleton for Paraplegics: Toward Robustly Stable Hands-free Dynamic Walking

This manuscript presents control of a high-DOF fully actuated lower-limb exoskeleton for paraplegic individuals. The key novelty is the ability for the user to walk without the use of crutches or other external means of stabilization. We harness the power of modern optimization techniques and supervised machine learning to develop a smooth feedback control policy that provides robust velocity regulation and perturbation rejection. Preliminary evaluation of the stability and robustness of the proposed approach is demonstrated through the Gazebo simulation environment. In addition, preliminary experimental results with (complete) paraplegic individuals are included for the previous version of the controller.Comment: Submitted to IEEE Control System Magazine. This version addresses reviewers' concerns about the robustness of the algorithm and the motivation for using such exoskeleton

Development and testing safe fall strategies for lower limbs exoskeletons

Loss of mobility is among the most impactful consequences of sustaining a spinal cord injury. Wheelchairs provide a considerable degree of mobility to their users, but are not without their drawbacks, most of which are caused by requiring prolonged periods of time in the sitting position. Recently, the field of lower limb exoskeletons has seen considerable developments, and the use of external power technologies has made it possible for users to walk for longer periods of time. However, current exoskeletons do not ensure balance during standing and walking conditions, which leaves their users vulnerable to situations of instability and falls. The goal of this thesis was to investigate safe fall strategies to reduce the severity of the impact in case of a loss of balance with a lower limb exoskeleton. The backwards fall scenario is examined, and a fall strategy is implemented in a simulation environment, using a combination of center of mass and hip joint angle reference signals. The results verified the model’s ability to execute the proposed strategy by following the reference signals, and the strategy was shown to result in safer falls. Further work should be conducted to test this strategy in real-life human-exoskeleton fall scenarios, and to develop strategies for other fall scenarios.Perda de mobilidade é das consequências com maior impacto na vida de quem sofre uma lesão da medula espinhal. Cadeiras de rodas providenciam um nível considerável de mobilidade aos seus utilizadores, mas trazem os seus próprios problemas, sendo que a maioria dos quais são resultantes da necessidade dos seus utilizadores permanecerem sentados durante longos períodos de tempo. Mais recentemente, a área dos exosqueletos para membros inferiores tem visto desenvolvimento notável, e o uso de fontes de energia externas tem permitido que os seus utilizadores se desloquem a pé durante intervalos de tempo maiores. Contudo, estas tecnologias ainda não garantem equilíbrio constante dos seus utilizadores durante a marcha ou em pé, o que faz com que estes estejam vulneráveis a situações de instabilidade e quedas. Esta tese teve como objetivo investigar estratégias de queda segura para reduzir a severidade do impacto em caso de uma perda de equilíbrio utilizando um exosqueleto para membros inferiores. É examinado o cenário de uma queda para trás, e é implementada uma estratégia de queda num ambiente de simulação, recorrendo a uma combinação de sinais de referência de centro de massa e ângulo da articulação da anca. Os resultados verificaram a capacidade do modelo utilizado executar a estratégia proposta ao seguir os sinais de referência, e a estratégia mostrou resultar em quedas mais seguras. No futuro, a estratégia deve ser testada em cenários reais de quedas de um exosqueleto e o seu utilizador, e devem ser desenvolvidas estratégias para os restantes cenários de queda

Robotic design and modelling of medical lower extremity exoskeletons

This study aims to explain the development of the robotic Lower Extremity Exoskeleton (LEE) systems between 1960 and 2019 in chronological order. The scans performed in the exoskeleton system’s design have shown that a modeling program, such as AnyBody, and OpenSim, should be used first to observe the design and software animation, followed by the mechanical development of the system using sensors and motors. Also, the use of OpenSim and AnyBody musculoskeletal system software has been proven to play an essential role in designing the human-exoskeleton by eliminating the high costs and risks of the mechanical designs. Furthermore, these modeling systems can enable rapid optimization of the LEE design by detecting the forces and torques falling on the human muscles

Stability of Mina v2 for Robot-Assisted Balance and Locomotion

The assessment of the risk of falling during robot-assisted locomotion is critical for gait control and operator safety, but has not yet been addressed through a systematic and quantitative approach. In this study, the balance stability of Mina v2, a recently developed powered lower-limb robotic exoskeleton, is evaluated using an algorithmic framework based on center of mass (COM)- and joint-space dynamics. The equivalent mechanical model of the combined human-exoskeleton system in the sagittal plane is established and used for balance stability analysis. The properties of the Linear Linkage Actuator, which is custom-designed for Mina v2, are analyzed to obtain mathematical models of torque-velocity limits, and are implemented as constraint functions in the optimization formulation. For given feet configurations of the robotic exoskeleton during flat ground walking, the algorithm evaluates the maximum allowable COM velocity perturbations along the fore-aft directions at each COM position of the system. The resulting velocity extrema form the contact-specific balance stability boundaries (BSBs) of the combined system in the COM state space, which represent the thresholds between balanced and unbalanced states for given contact configurations. The BSBs are obtained for the operation of Mina v2 without crutches, thus quantifying Mina v2's capability of maintaining balance through the support of the leg(s). Stability boundaries in single and double leg supports are used to analyze the robot's stability performance during flat ground walking experiments, and provide design and control implications for future development of crutch-less robotic exoskeletons

Empowering and assisting natural human mobility: The simbiosis walker

This paper presents the complete development of the Simbiosis Smart Walker. The device is equipped with a set of sensor subsystems to acquire user-machine interaction forces and the temporal evolution of user's feet during gait. The authors present an adaptive filtering technique used for the identification and separation of different components found on the human-machine interaction forces. This technique allowed isolating the components related with the navigational commands and developing a Fuzzy logic controller to guide the device. The Smart Walker was clinically validated at the Spinal Cord Injury Hospital of Toledo - Spain, presenting great acceptability by spinal chord injury patients and clinical staf

Robotic Rehabilitation Devices of Human Extremities: Design Concepts and Functional Particularities

International audienceAll over the world, several dozen million people suffer from the effects of post-polio, multiple sclerosis, spinal cord injury, cerebral palsy, etc. and could benefit from the advances in robotic devices for rehabilitation. Thus, for modern society, an important and vital problem of designing systems for rehabilitation of human physical working ability appears. The temporary or permanent loss of human motor functions can be compensated by means of various rehabilitation devices. They can be simple mechanical systems for orthoses, which duplicate the functions of human extremities supplying with rigidity and bearing capacity or more complex mechatronic rehabilitation devices with higher level of control. We attempt to cover all of the major developments in these areas, focusing particularly on the development of the different concepts and their functional characteristics. The robotic devices with several structures are classified, taking into account the actuation systems, the neuromuscular stimulations, and the structural schemes. It is showed that the problems concerning the design of rehabilitation devices are complex and involve many questions in the sphere of biomedicine, mechanics, robot technology, electromechanics and optimal control. This paper provides a design overview of hardware, actuation, sensory, and control systems for most of the devices that have been described in the literature, and it ends with a discussion of the major advances that have been made and should be yet overcome

Ekonomicky dostupný aktivní exoskeleton pro dolní končetiny pro paraplegiky

After a broad introduction to the medical and biomechanical background and detailed review of orthotic devices, two newly developed lower limbs exoskeletons for paraplegics are presented in this study. There was found out the main challenges of designing devices for paraplegic walking can be summarized into three groups, stability and comfort, high efficiency or low energy consumption, dimensions and weight. These all attributes have to be moreover considered and maintained during manufacturing of affordable device while setting a reasonable price of the final product. A new economical device for people with paraplegia which tackles all problems of the three groups is introduced in this work. The main idea of this device is based on HALO mechanism. HALO is a compact passive medial hip joint orthosis with contralateral hip and ankle linkage, which keeps the feet always parallel to the ground and assists swinging the leg. The medial hip joint is equipped with one actuator in the new design and the new active exoskeleton is called @halo. Due to this update, we can achieve more stable and smoother walking patterns with decreased energy consumption of the users, yet maintain its compact and lightweight features. It was proven by the results from preliminary experiments with able-bodied subjects during which the same device with and without actuator was evaluated. Waddling and excessive vertical elevation of the centre of gravity were decreased by 40% with significantly smaller standard deviations in case of the powered exoskeleton. There was 52% less energy spent by the user wearing @halo which was calculated from the vertical excursion difference. There was measured 38.5% bigger impulse in crutches while using passive orthosis, which produced bigger loads in upper extremities musculature. The inverse dynamics approach was chosen to calculate and investigate the loads applied to the upper extremities. The result of this calculation has proven that all main muscle groups are engaged more aggressively and indicate more energy consumption during passive walking. The new @halo device is the first powered exoskeleton for lower limbs with just one actuated degree of freedom for users with paraplegia.První část práce je věnována obsáhlému úvodu do zdravotnické a biomechanické terminologie a detailnímu souhrnnému představení ortopedických pomůcek. Následně jsou představeny dva nově vyvinuté exoskelety aplikovatelné na dolní končetiny paraplegiků. Bylo zjištěno, že hlavní úskalí konstrukčního návrhu asistenčních zařízení pro paraplegiky lze shrnout do tří hlavních skupin, jako první je stabilita a komfort, druhá je vysoká účinnost a nízká energetická náročnost uživatele a do třetí lze zahrnout rozměry a hmotnost zařízení. Toto všechno je navíc podmíněno přijatelnou výslednou cenou produktu. Nový ekonomicky dostupný exoskelet pro paraplegiky, který řeší problematiku všech tří zmíněných skupin je představen v této práci. Hlavní myšlenka tohoto zařízení je postavena na mechanismu HALO ortézy. HALO je kompaktní pasivní ortéza s mediálním kyčelním kloubem umístěným uprostřed mezi dolními končetinami. Speciální mediální kyčelní kloub je kontralaterálně propojen s kotníkem soustavou ocelových lanek což zajištuje paralelní polohu chodidla se zemí v každém okamžiku chůze a navíc asistuje zhoupnutí končetiny. Tento mediální kyčelní kloub je redesignován a v novém provedení je vybaven jedním aktuátorem, nové řešení aktivního exoskeletu dostalo název @halo. Díky tomuto vylepšení lze dosáhnout stabilnější a plynulejší chůze s výrazně redukovanou energetickou náročností uživatele přičemž dochází k zachování nízké hmotnosti a kompaktnosti zařízení. Toto bylo dokázáno během předběžných experimentů se zdravými subjekty, během kterých byla testována aktivní chůze se zařízením vybaveným odnímatelnou pohonnou jednotkou a pasivní chůze se stejným zařízením bez této aktivní jednotky. Nadměrné naklánění se během chůze ze strany na stranu a nadměrná výchylka pohybu těžiště těla ve vertikálním směru byly sníženy o necelých 40% s velmi významně menšími standardními odchylkami v případě chůze s pohonem. Z rozdílu výchylky pohybu těžiště těla ve vertikální poloze bylo vypočítáno snížení energetické náročnosti uživatele o 52% při chůzi s aktivní konfiguraci @halo. Při pohybu s pasivní ortézou byl naměřen o 38,5% větší reakční silový impuls v berlích, což znamená nárůst zátěže pro svalový aparát horních končetin. Pro podrobné vyšetření zátěže ramenních kloubů byl aplikován model inverzní dynamiky. Výsledek tohoto výpočtu jednoznačně indikuje agresivnější a hlubší zapojení všech svalových skupin ramenního kloubu a tím vyšší spotřebu energie uživatelem během pasivní chůze. Nové asistenční zařízení @halo je prvním exoskeletem svého druhu pro paraplegiky s jediným poháněným stupněm volnosti.354 - Katedra robotikyvyhově