Wearable exoskeletons to support ambulation in people with neuromuscular diseases, design rules and control

Neuromuscular diseases are degenerative and, thus far, incurable disorders that lead to large muscle wasting. They result in constant deterioration of activities of daily living and in particular of ambulation. Some common types include Duchenne muscular dystrophy, Charcot-Marie-Tooth disease, polymyositis and amyotrophic lateral sclerosis. While these diseases individually have a low rate of occurrence and are mostly unknown to most people, collectively they affect a significant part of the population. About 1 person in 2000 suffer from neuromuscular diseases, which means an approximate total of 370â000 people over the European continent. Recent technology breakthroughs have made possible the realization of advanced powered orthotics, which are commonly called exoskeletons. The most advanced devices have successfully been able to support patients in walking despite a debilitating condition such as complete spinal cord injury. Such technology could be ideal for people with mid-stage neuromuscular diseases as it provides more mobility and independence. This work investigates the definitions and requirements that would need to be fulfilled for any proposed orthotic device to assist people living with neuromuscular diseases. To define the needs of patients with neuromuscular disease, a large literature review is conducted on gait compensation patterns. The research also includes the data collection of experimental gait measurements from fourteen people with heterogeneous neuromuscular diseases. Conclusions show that orthotics for people with neuromuscular diseases require tunable assistance at each joint and a collaborative control strategy in order to let the user control motion. Eventually, most people may not be able to use crutches. A full lower limb exoskeleton, AUTONOMYO, is designed, realized and evaluated. A particular attention is put on the optimization of the actuator and transmission units. In order to reduce the effects of inertia and weight of those units, a design is explored with actuation remotely located from the joints. The transmission is realized by custom cable wire and pulley systems, combined with standard planetary gears. The dynamics of different coupling between the hip and the knee flexion/extension joints are explored, and their benefits and tradeoffs analyzed. A novel control strategy based on a finite-state active impedance model is designed and implemented on the AUTONOMYO device. The controller consists of three states of different active impedances mimicking a visco-elastic behavior. The switching condition between states is uniquely based on the hip flexion velocity to detect the user intent. The performance of the strategy regarding the detection of intention and the modulation of the assistance is evaluated on a test bench and in real conditions with healthy pilots and with a person with limb girdle muscular dystrophy. The preliminary results are promising since all pilots (including the one with muscular dystrophy) are able to initiate and terminate assisted walking on demand. They are all able both to walk with a good stride rate and to reach moderate velocities. Healthy pilots are able to ambulate alone with the exoskeleton, while the pilot with muscular dystrophy requires human assistance for the management of balance.

Neuroprosthetics to support impaired hand functions: A multidisciplinary approach combining brain-machine interfaces and wearable exoskeletons

Luca Randazzo

Neuroprosthetics, the discipline that aims at interfacing neural systems to artificially engineered devices, has witnessed in recent years important advancements towards the ultimate goal of augmenting and restoring human functions through technology and artificial systems. Research in this field covers a wide range of efforts, from advancing our basic understanding of the neural processes involved into human sensory, motor and cognitive functions, to developing artificial intelligence algorithms for their decoding, to the physical interfacing between artificial devices and the human nervous system and biomechanics. Ultimately, this discipline aims at fusing these systems in order to restore, replace and rehabilitate lost and impaired functions due to motor disabling conditions or traumatic accidents. In this thesis, I present a multidisciplinary approach that aimed at developing a neuroprosthesis for the assistance and restoration of hand functions impaired by neurological disorders or traumatic accidents, such as cerebrovascular accidents and spinal cord injuries. These efforts encompassed the conceptualization and development of a robotic hand exoskeleton and brain-machine interface (BMI) algorithms for its control. Specifically, this thesis focused on the design, development and testing of (i) a novel mechatronic hand exoskeleton to assist hand motions within domestic and clinical settings, (ii) non-invasive BMI approaches based on electroencephalography (EEG) to decode neural correlates of intended hand movements, and on (iii) the closed-loop integration of the proposed exoskeleton and BMI for the sake of providing continuous feedback about ongoing neural modulations through hand motions and to trigger sensorimotor rehabilitation within clinical scenarios. Results showed that the proposed mechatronic system can successfully control hand opening and closing within a fully wearable, portable and lightweight package. The system was tested with users who suffered from motor disabling impairments, showing that it could help them in performing several activities of daily living for the first time since their accidents. From a brain-machine interfacing perspective, this work shows how imagined hand movements can be decoded, through EEG, in parallel with exoskeleton-induced motions, with important implications for the development of more embodied human-machine interaction protocols. Finally, this work shows how the closed-loop control of exoskeleton motions by means of the decoded ongoing neural activity enhances the discriminability of sensorimotor neural patterns and improves the performance of the brain-machine control channel. Overall, the results presented here represent important advancements within the field of neuroprosthetics, with interesting implications for the development of assistive exoskeletal technologies and non-invasive brain-machine interfaces aimed at controlling such systems in clinical or domestic settings, for both assistive and neurorehabilitative purposes.

EPFL2018

mano: A Wearable Hand Exoskeleton for Activities of Daily Living and Neurorehabilitation

Inaki Asier Iturrate Gil, Serafeim Perdikis, Luca Randazzo

Hand sensorimotor impairments are among the most common consequences of injuries affecting the central and peripheral nervous systems, leading to a drastic reduction in the quality of life for affected individuals. Combining wearable robotic exoskeletons and human-machine interfaces is a promising avenue for the restoration and substitution of lost and impaired functions for these users. In this study, we present a novel hand exoskeleton, mano, designed to assist and restore hand functions of people with motor disabilities during activities of daily living (ADL) and in neurorehabilitative scenarios. Compared to state-of-the-art devices, our system is fully wearable, portable and minimally obtrusive on the hand. The exoskeleton can actively control flexion and extension of all fingers, while allowing natural somatosensorial interactions with the environment surrounding the users. We evaluated the device from four different perspectives. A mechanical characterization, showing that the exoskeleton can cover more than 70% of healthy hand workspace and it can achieve forces at the fingertips sufficient for ADL. A functional characterization, where we showed how two users who suffered from spinal cord injuries were able to perform several ADL for the first time since their accidents. Thirdly, we evaluated the system from a neuroimaging perspective, showing that the device can elicit EEG brain patterns typical of natural hand motions. We finally exemplified the control of the hand exoskeleton within an exemplar framework, a brain-machine interface scenario, showing how motor intention can be successfully decoded for a continuous control of the device. Overall, our results showed that the device represents an ecological solution for use both in ADL and in scenarios aimed at promoting sensorimotor recovery.

Ieee-Inst Electrical Electronics Engineers Inc2018

Control Strategies for Lower-limb Exoskeletons: from Full Mobilization to Assistance of Balance

Romain Pierre François Baud

Bipedal locomotion is a remarkable feature of humans. This skill is necessary for the activities of daily living. Unfortunately, many people only partially benefit from it or miss it entirely because of a disability. This may result in a slower gait, less endurance before pain or exhaustion, inability to climb stairs, or even the permanent use of a wheelchair. This may make reaching remote places difficult, prevents from practicing some sportive activities, and limit the chances of social interaction. Robotic exoskeletons have been introduced recently to assist the gait. The control of such devices should be addressed with care, because of the interaction with the human user, which makes part of the system unpredictable or at least difficult to model. This PhD thesis report explores the broad range of existing control methods that are currently disseminated in the literature. All these references have been sorted with a novel classification that categorizes the subparts of an algorithm, instead of considering the entire one. This rational overview contribute to understanding what was already tried, and what is missing to the state of the art. Then, the developed modular control platformis described. This platform allowed sharing electronicmodules and software between all the devices and provided a consistent and efficient development experience. It could handle all eight exoskeletons of the laboratory, even though their hardware was never the same. Fully embedded and with a convenient development interface, it allowed testing efficiently in the field. The case of the fullmobilization for paraplegic users was tackled with the exoskeleton TWIICE, intended for personal use. A controller based on operating modes was implemented and allowed its user to walk again and overcome many types of obstacles of daily living, autonomously. This controller made TWIICE the current best performer for the "Powered Exoskeletons Race" category of the CYBATHLON competition, able to overcome all the six obstacles. A variant, WIITE, enabled another paraplegic user to practice ski touring in snowy mountains. This showed a use-case with a similar handicap, but a totally different need. TWIICE is sagitally constrained, is actuated at the hip and knee joints only and has a locked ankle, to be lightweight and cost-effective. Crutches are then required to maintain the user’s balance, which prevents using the arms for interaction with the surrounding environment. A controller performing dynamic balance with such hardware would be too complicated and probably not robust enough. A suggested acceptable trade-off was to let the user use freely his arms for interactions only while standing still and use normally the crutches while walking. The controller was biologically inspired, from healthy participants trying to keep standing dynamically in a passive constraining exoskeleton, called INSPIIRE. Dynamic standing balance control was successfully assessed with a complete paraplegic user wearing TWIICE. Finally, partial assistance techniques have been investigated. First, in running using SPRIINT, a unilateral hip orthosis to assist a transfemoral amputeed user. Second, the endurance augmentation in walking was also studied with HiBSO, a bilateral hip exoskeleton. A novel assistance controller was developed, able to immediately assist, from the beginning of the first step.

EPFL2020