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

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

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

"I will never forget the emotion of my first steps […]," were the words of Fran?oise, the first user during initial trials of the exoskeleton ATALANTE [1]. "I am tall again!" were the words of Sandy (the fourth user) after standing up in the exoskeleton. During these early tests, complete paraplegic patients dynamically walked up to 10 m without crutches or other assistance using a feedback control method originally invented for bipedal robots. As discussed in "Summary," this article describes the hardware (shown in Figure 1) that was designed to achieve hands-free dynamic walking, the control laws that were deployed (and those being developed) to provide enhanced mobility and robustness, and preliminary test results. In this article, dynamic walking refers to a motion that is orbitally stable as opposed to statically stable

Projeto mecânico de um exoesqueleto com atuação no quadril

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2019.Neste trabalho foi desenvolvido o projeto mecânico de um exoesqueleto com atuação no quadril. Tal modelo vem como uma opção viável para tratamentos clínicos de reabilitação em indivíduos com lesões medulares, principalmente em métodos aliados com eletroestimulação funcional. O projeto é baseado no modelo autoral Exosuit EMA (Freire et al, 2018) e apresentado como uma opção de otimização e evolução do mesmo. O novo modelo foi desenvolvido para atender os requisitos mecânicos de um usuário-padrão em uma marcha de reabilitação. O exoesqueleto foi projetado para permitir a fixação e verticalização do usuário enquanto controla ativamente os movimentos do quadril durante a marcha do usuário, dando sustentação para que um protocolo de eletroestimulação funcional atue nos músculos agonistas das juntas do joelho e tornozelo. Todos os sistemas do exoesqueleto foram projetados levandose em consideração os critérios de resistência estática e à fadiga, bem como o critério de rigidez. Ao final deste trabalho é apresentado o projeto global da nova Exosuit EMA e os desenhos técnicos de fabricação respectivos a cada um dos componentes mecânicos do exoesqueleto.This work developed the mechanical project of a rehabilitation exoskeleton with active actuation in the hip joint. This model comes as a complementary tool for rehabilitation such as FES-based therapy for SCI patients. The project is based in the EMA Hip Exosuit exoskeleton model developed by Freire et al (2018), with the purpose of optimizing and evolving the previous model. The new model was designed to fully comply with the needs of a rehabilitation gait for a standard user model while concurrently controlling hip motion. The exoskeleton project aims to support the user in the upright position during gait while it simultaneously controls the movements of the hip joint. In that way, the system provides the proper conditions for a FES protocol in the lower-leg muscles that are the motion source of the knee and ankle joints. All the systems of the Exosuit underwent static, fatigue and stiffness modelling in order to fulfill the needs for failure prevention. At the end of this work is presented the global project of the new EMA Exosuit as well the CAD fabrication technical drawings of all the designed exoskeleton mechanical systems

Identification of Motion Controllers In Human Standing And Walking

The method of trajectory optimization with direct collocation has the potential to extract generalized and realistic motion controllers from long duration movement data without requiring extensive measurement equipment. Knowing motion controllers not only can improve clinic assessments on locomotor disabilities, but also can inspire the control of powered exoskeletons and prostheses for better performance. Three aims were included in this dissertation. Aim 1 was to apply and validate the trajectory optimization for identification of the postural controllers in standing balance. The trajectory optimization approach was first validated on the simulated standing balance data and demonstrated that it can extract the correct postural control parameters. Then, six types of postural feedback controllers, from simple linear to complex nonlinear, were identified on six young adults’ motion data that was collected in a standing balance experiment. Results indicated that nonlinear controllers with multiple time delay paths can best explain their balance motions. A stochastic trajectory optimization approach was proposed that can help finding practically stable controllers in the identification process. Aim 2 focused on the foot placement control in walking. Foot placement controllers were successfully identified through the trajectory optimization method on nine young adults’ perturbed walking motions. It was shown that a linear controller with pelvis position and velocity feedback, suggested by the linear inverted pendulum model, was not sufficient to explain their foot placement among multiple walking speeds. Nonlinear controllers or more feedback signals, such as pelvis acceleration, are needed. Foot placement control was applied on a powered leg exoskeleton to control its legs’ swing motion. Two healthy participants were able to achieve stable walking with the controlled exoskeleton. v Results suggested that the foot placement controller helped decelerate the swing motion at late swing. In Aim 3, the trajectory optimization method was used to identify joint impedance properties in walking. Results of the synthetic study showed that relatively close impedance parameters can be identified. Then, a preliminary study was done to identify the ankle joint impedance properties of two participants at two walking speeds. The identified impedance properties were close to previous studies and consistent between different participants and walking speeds

Ficção científica e medicina: elaborando uma framework para auxiliar o desenvolvimento de artefactos médicos

With technological advances, the human being becomes more and more reliant on technology. We use technology to work, to improve our social experiences, to learn, among many other activities. Medicine is no exception to this. It is common to hear about concepts originated on Science Fiction coming to life in areas such as spatial exploration or even communication. It is important to realise how Science Fiction helps teams working in those domains, as well as understand what consumers expect for the future. However, we rarely hear about Science Fiction directly influencing Medicine. Has this field also benefited from Science Fiction to create new or enhanced existing artifacts? This literary and cinematic genre pushes the boundaries of what is thought "possible" by idealizing artifacts that go beyond what is conceivable in their time. It is an outlet for those who want to imagine what the future might hold, without forgetting to distinguish the possible or plausible from the fantastical. In this dissertation, we go through how Science Fiction can be used as a guide to developing Medical Artifacts, as well as devise a framework that has the potential to help their developers make more informed decisions about the characteristics of those artifacts. MADIS - Medical Artifact Design Inspired by Science Fiction - is a framework that incorporates the knowledge acquired during the research and interviews with medical professionals to create a tool which supports the development of Medical Artifacts through the lens of Science Fiction.Com o avanço tecnológico, o ser humano torna-se cada vez mais dependente da tecnologia. Usamo-la para trabalhar, para melhorar a nossa experiência social, para aprender, etc. e a medicina não é uma exceção. É comum ouvirmos falar de conceitos originários da Ficção Científica ganharem vida em áreas como a exploração espacial ou até a comunicação, e ver como ajuda as equipas a saber o que os consumidores esperam do futuro. No entanto, raramente ouvimos falar da sua influência nas tecnologias que nos mantêm vivos. Terá sido a medicina também beneficiado dos mundos de Ficção Científica na criação ou aperfeiçoamento dos seus artefactos? Este género literário e cinematográfico supera as barreiras do que é pensado como “possível” ao idealizar artefactos que vão para além do que é concebível no seu tempo. É um escape para aqueles que querem imaginar o que o futuro nos espera, sem esquecer de distinguir o possível ou plausível do fantástico. Nesta dissertação, vamos ver como a Ficção Científica pode ser usada como um guia para desenvolver artefactos médicos, bem como elaborar uma framework para ajudar os seus criadores a tomar decisões mais informadas. MADIS - Design de Artefactos Médicos Inspirados pela Ficção-científica - é uma framework que incorpora o conhecimento adquirido durante a pesquisa e as entrevistas feitas a profissionais médicos para criar uma ferramenta que suporta o desenvolvimento de Artefactos Médicos através da Ficção Científica.Mestrado em Comunicação Multimédi

A Meta-Study and Content Analysis of Science Fiction in Computer Science Research

Ph.D

7-degree-of-freedom hybrid-manipulator exoskeleton for lower-limb motion capture

Lower-limb exoskeletons are wearable robotic systems with a kinematic structure closely matching that of the human leg. In part, this technology can be used to provide clinical assessment and improved independent-walking competency for people living with the effects of stroke, spinal cord injury, Parkinson’s disease, multiple sclerosis, and sarcopenia. Individually, these demographics represent approximately: 405 thousand, 100 thousand, 67.5 thousand, 100 thousand, and 5.9 million Canadians, respectively. Key shortcomings in the current state-of-the-art are: restriction on several of the human leg’s primary joint movements, coaxial joint alignments at the exoskeleton-human interface, and exclusion of well-suited parallel manipulator components. A novel exoskeleton design is thus formulated to address these issues while maintaining large ranges of joint motion. Ultimately, a single-leg unactuated prototype is constructed for seven degree-of-freedom joint angle measurements; it achieves an extent of motion-capture accuracy comparable to a commercial inertial-based system during three levels of human mobility testing