A review of lower-limb wearable exoskeletons for overground rehabilitation

Gait disorders are common among people with neuromuscular impairments –60% of the patients– and generally have a high impact on their quality of life . Lack of physical activity increases the risk of secondary health conditions such as respiratory and cardiovascular complications, bowel/bladder dysfunction, obesity, osteoporosis and ulcers; which can further diminish life expectancy. Therefore, walking recovery is one of the main rehabilitation priorities for patients with a neuromuscular impairment. Wearable exoskeletons are emerging as a revolutionary device for gait rehabilitation, mainly due to both the active participation required from the user promoting physical activity10 and the possibility to work as an assistive device in the community. In fact, the number of research studies during the past 10 years has shown a large increase following the general tendency of rehabilitation robotics . Although wearable exoskeletons are starting to be used in clinical practice, their efficacy is still not clear. This study provides a comprehensive overview on wearable powered exoskeletons for overground rehabilitation without body weight support in people with neuromuscular impairments.Peer ReviewedPostprint (published version

Gaussian-Process-based Robot Learning from Demonstration

Endowed with higher levels of autonomy, robots are required to perform increasingly complex manipulation tasks. Learning from demonstration is arising as a promising paradigm for transferring skills to robots. It allows to implicitly learn task constraints from observing the motion executed by a human teacher, which can enable adaptive behavior. We present a novel Gaussian-Process-based learning from demonstration approach. This probabilistic representation allows to generalize over multiple demonstrations, and encode variability along the different phases of the task. In this paper, we address how Gaussian Processes can be used to effectively learn a policy from trajectories in task space. We also present a method to efficiently adapt the policy to fulfill new requirements, and to modulate the robot behavior as a function of task variability. This approach is illustrated through a real-world application using the TIAGo robot.Comment: 8 pages, 10 figure

Robot interaction adaptation for healthcare assistance

Assitive robotics is one of the big players in the technological revolution we are living in. Expectations are extremely high but the reality is a bit more modest. We present here two realistic initiatives towards the introduction of assistive robots in real care facilities and homes. First, a cognitive training robot for mild dementia patients, able to play board games following caregiver instructions and adapting to patient’s needs. Second, we present the Robotic MOVit, a novel exercise-enabling control interface for powered wheelchair users. Instead of using a joystick the user controls the direction and speed of the powered wheelchair by cyclically moving his arms. Both robotic devices can adapt the interaction to the needs of the user and provide insightful information to researchers and clinicians.Postprint (author's final draft

Exoesqueletos robóticos para volver a caminar

Aproximadamente el 60% de los pacientes con problemas neuromusculares padecen trastornos de la marcha que, a su vez, tienen un elevado impacto en su calidad de vida.Postprint (published version

Development and preliminary evaluation of the ArmTracker: a wearable system to monitor arm activity during daily life

Peer ReviewedPostprint (published version

First steps towards accelerating the learning of using exoskeletons with immersive virtual reality

Learning to use a lower-limb wearable exoskeleton for people with spinal cord injury is time-consuming and requires effort from the user and extensive therapists’ time. In this study, we aim at exploiting visual feedback through immersive virtual reality using a head-mounted display to accelerate motor learning for the purpose of using a wearable exoskeleton with minimal supervision.Peer ReviewedPostprint (published version

Evaluation of EMG, force and joystick as control interfaces for active arm supports

Background:\ud The performance capabilities and limitations of control interfaces for the operation of active movement-assistive devices remain unclear. Selecting an optimal interface for an application requires a thorough understanding of the performance of multiple control interfaces. \ud \ud Methods:\ud In this study the performance of EMG-, force- and joystick-based control interfaces were assessed in healthy volunteers with a screen-based one-dimensional position-tracking task. The participants had to track a target that was moving according to a multisine signal with a bandwidth of 3 Hz. The velocity of the cursor was proportional to the interface signal. The performance of the control interfaces were evaluated in terms of tracking error, gain margin crossover frequency, information transmission rate and effort. \ud \ud Results:\ud None of the evaluated interfaces was superior in all four performance descriptors. The EMG-based interface was superior in tracking error and gain margin crossover frequency compared to the force- and the joystick-based interfaces. The force-based interface provided higher information transmission rate and lower effort than the EMG-based interface. The joystick-based interface did not present any significant difference with the force-based interface for any of the four performance descriptors. We found that significant differences in terms of tracking error and information transmission rate were present beyond 0.9 and 1.4 Hz respectively. \ud \ud Conclusions:\ud Despite the fact that the EMG-based interface is far from the natural way of interacting with the environment, while the force-based interface is closer, the EMG-based interface presented very similar and for some descriptors even a better performance than the force-based interface for frequencies below 1.4 Hz. The classical joystick presented a similar performance to the force-based interface and holds the advantage of being a well established interface for the control of many assistive devices. From these findings we concluded that all the control interfaces considered in this study can be regarded as a candidate interface for the control of an active arm support

Comparing walking with knee-ankle-foot orthoses and a knee-powered exoskeleton after spinal cord injury: a randomized, crossover clinical trial

Recovering the ability to stand and walk independently can have numerous health benefits for people with spinal cord injury (SCI). Wearable exoskeletons are being considered as a promising alternative to conventional knee-ankle-foot orthoses (KAFOs) for gait training and assisting functional mobility. However, comparisons between these two types of devices in terms of gait biomechanics and energetics have been limited. Through a randomized, crossover clinical trial, this study compared the use of a knee-powered lower limb exoskeleton (the ABLE Exoskeleton) against passive orthoses, which are the current standard of care for verticalization and gait ambulation outside the clinical setting in people with SCI. Ten patients with SCI completed a 10-session gait training program with each device followed by user satisfaction questionnaires. Walking with the ABLE Exoskeleton improved gait kinematics compared to the KAFOs, providing a more physiological gait pattern with less compensatory movements (38% reduction of circumduction, 25% increase of step length, 29% improvement in weight shifting). However, participants did not exhibit significantly better results in walking performance for the standard clinical tests (Timed Up and Go, 10-m Walk Test, and 6-min Walk Test), nor significant reductions in energy consumption. These results suggest that providing powered assistance only on the knee joints is not enough to significantly reduce the energy consumption required by people with SCI to walk compared to passive orthoses. Active assistance on the hip or ankle joints seems necessary to achieve this outcome.Peer ReviewedPostprint (published version

Immediate Biomechanical Effects of Providing Adaptive Assistance With an Ankle Exoskeleton in Individuals After Stroke

Recent studies on ankle exoskeletons have shown the feasibility of this technology for post-stroke gait rehabilitation. The main contribution of the present work is a comprehensive experimental analysis and protocol that focused on evaluating a wide range of biomechanical, usability and users’ perception metrics under three different walking conditions: without exoskeleton, with an ankle exoskeleton unpowered, and with an ankle exoskeleton powered. To carry out this study, we developed the ABLE-S exoskeleton that can provide time-adapted ankle plantarflexion and dorsiflexion assistance. Tests with five participants with chronic stroke showed that walking with the ABLE-S exoskeleton significantly corrected foot drop by 25 % while reducing hip compensatory movements by 21 %. Furthermore, asymmetrical spatial gait patterns were significantly reduced by 51 % together with a significant increase in the average foot tilting angle at heel strike by 349 %. The total time to don, doff and set-up the device was of 7.86 ± 2.90 minutes. Finally, 80 % of the participants indicated that they were satisfied with their walking performance while wearing the exoskeleton, and 60 % would use the device for community ambulation. The results of this study add to the existing body of evidence supporting that ankle exoskeletons can improve gait biomechanics for post-stroke individuals.Peer ReviewedPostprint (published version