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

Experience of Robotic Exoskeleton Use at Four Spinal Cord Injury Model Systems Centers

Background and Purpose: Refinement of robotic exoskeletons for overground walking is progressing rapidly. We describe clinicians\u27 experiences, evaluations, and training strategies using robotic exoskeletons in spinal cord injury rehabilitation and wellness settings and describe clinicians\u27 perceptions of exoskeleton benefits and risks and developments that would enhance utility. Methods: We convened focus groups at 4 spinal cord injury model system centers. A court reporter took verbatim notes and provided a transcript. Research staff used a thematic coding approach to summarize discussions. Results: Thirty clinicians participated in focus groups. They reported using exoskeletons primarily in outpatient and wellness settings; 1 center used exoskeletons during inpatient rehabilitation. A typical episode of outpatient exoskeleton therapy comprises 20 to 30 sessions and at least 2 staff members are involved in each session. Treatment focuses on standing, stepping, and gait training; therapists measure progress with standardized assessments. Beyond improved gait, participants attributed physiological, psychological, and social benefits to exoskeleton use. Potential risks included falls, skin irritation, and disappointed expectations. Participants identified enhancements that would be of value including greater durability and adjustability, lighter weight, 1-hand controls, ability to navigate stairs and uneven surfaces, and ability to balance without upper extremity support. Discussion and Conclusions: Each spinal cord injury model system center had shared and distinct practices in terms of how it integrates robotic exoskeletons into physical therapy services. There is currently little evidence to guide integration of exoskeletons into rehabilitation therapy services and a pressing need to generate evidence to guide practice and to inform patients\u27 expectations as more devices enter the market. Background and Purpose: Refinement of robotic exoskeletons for overground walking is progressing rapidly. We describe clinicians\u27 experiences, evaluations, and training strategies using robotic exoskeletons in spinal cord injury rehabilitation and wellness settings and describe clinicians\u27 perceptions of exoskeleton benefits and risks and developments that would enhance utility. Methods: We convened focus groups at 4 spinal cord injury model system centers. A court reporter took verbatim notes and provided a transcript. Research staff used a thematic coding approach to summarize discussions. Results: Thirty clinicians participated in focus groups. They reported using exoskeletons primarily in outpatient and wellness settings; 1 center used exoskeletons during inpatient rehabilitation. A typical episode of outpatient exoskeleton therapy comprises 20 to 30 sessions and at least 2 staff members are involved in each session. Treatment focuses on standing, stepping, and gait training; therapists measure progress with standardized assessments. Beyond improved gait, participants attributed physiological, psychological, and social benefits to exoskeleton use. Potential risks included falls, skin irritation, and disappointed expectations. Participants identified enhancements that would be of value including greater durability and adjustability, lighter weight, 1-hand controls, ability to navigate stairs and uneven surfaces, and ability to balance without upper extremity support. Discussion and Conclusions: Each spinal cord injury model system center had shared and distinct practices in terms of how it integrates robotic exoskeletons into physical therapy services. There is currently little evidence to guide integration of exoskeletons into rehabilitation therapy services and a pressing need to generate evidence to guide practice and to inform patients\u27 expectations as more devices enter the market

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

Promoting inclusiveness in exoskeleton robotics: Addressing challenges for pediatric access

Pediatric access to exoskeletons lags far behind that of adults. In this article, we promote inclusiveness in exoskeleton robotics by identifying and addressing challenges and barriers to pediatric access to this potentially life-changing technology. We first present available exoskeleton solutions for upper and lower limbs and note the variability in the absence of these. Next, we query the possible reasons for this variability in access, explicitly focusing on children, who constitute a categorically vulnerable population, and also stand to benefit significantly from the use of this technology at this critical point in their physical and emotional growth. We propose the use of a life-based design approach as a way to address some of the design challenges and offer insights toward a resolution regarding market viability and implementation challenges. We conclude that the development of pediatric exoskeletons that allow for and ensure access to health-enhancing technology is a crucial aspect of the responsible provision of health care to all members of society. For children, the stakes are particularly high, given that this technology, when used at a critical phase of a child’s development, not only holds out the possibility of improving the quality of life but also can improve the long-term health prospects

Relevance of hazards in exoskeleton applications: a survey-based enquiry

Exoskeletons are becoming the reference technology for assistance and augmentation of human motor functions in a wide range of application domains. Unfortunately, the exponential growth of this sector has not been accompanied by a rigorous risk assessment (RA) process, which is necessary to identify the major aspects concerning the safety and impact of this new technology on humans. This situation may seriously hamper the market uptake of new products. This paper presents the results of a survey that was circulated to understand how hazards are considered by exoskeleton users, from research and industry perspectives. Our analysis aimed to identify the perceived occurrence and the impact of a sample of generic hazards, as well as to collect suggestions and general opinions from the respondents that can serve as a reference for more targeted RA. Our results identified a list of relevant hazards for exoskeletons. Among them, misalignments and unintended device motion were perceived as key aspects for exoskeletons' safety. This survey aims to represent a first attempt in recording overall feedback from the community and contribute to future RAs and the identification of better mitigation strategies in the field

Advanced technology for gait rehabilitation: An overview

Most gait training systems are designed for acute and subacute neurological inpatients. Many systems are used for relearning gait movements (nonfunctional training) or gait cycle training (functional gait training). Each system presents its own advantages and disadvantages in terms of functional outcomes. However, training gait cycle movements is not sufficient for the rehabilitation of ambulation. There is a need for new solutions to overcome the limitations of existing systems in order to ensure individually tailored training conditions for each of the potential users, no matter the complexity of his or her condition. There is also a need for a new, integrative approach in gait rehabilitation, one that encompasses and addresses all aspects of physical as well as psychological aspects of ambulation in real-life multitasking situations. In this respect, a multidisciplinary multinational team performed an overview of the current technology for gait rehabilitation and reviewed the principles of ambulation training