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The purpose of this study is to simulate the different walking adaptation strategies and their impact on muscle activities while changing the anchor point position of an exosuit in hip extension assistance motion. In particular, muscle activation and metabolic power consumption are assessed at varying levels of assistive force actuation that alters the position of anchor points. OpenSim software was used to perform simulations of 10 elderly subjects at comfortable gait speed while varying the anchor point positions of the thigh. Compared to unassisted gait, the extension assistance at placements below 40% (proximal) requires an increase in metabolic cost to maintain gait characteristics. At 40%, energy consumption corresponds to unassisted gait. From 50% proximal to distal positions, a reduction in metabolic cost is observed, with a minimum at 80%. The variation of the metabolic cost at different positions of the anchor point is reflected in the muscular activities, with an increase when the cable is placed below 40% of the total length of the thigh and a decrease from this position onwards. The activation level and metabolic cost exerted by the hip flexors and extensors muscles may be optimized during the exosuit actuation. The dynamics of the muscles spanning joints not actuated by the exosuit are not influenced by the actuation. The results and analysis provide information to optimize actuation profiles in the design of exosuits to assist gait for older adults and, thus, promote active aging and improving rehabilitation routines. [ABSTRACT FROM AUTHOR]

This document is an editorial titled "Rehabilitation robotics: challenges in design, control, and real applications, volume II." It discusses the field of rehabilitation robotics, which combines knowledge from various disciplines to develop devices that aid in rehabilitation. The editorial highlights the shift from rigid, clinical-centric solutions to more adaptable and user-centric approaches, such as soft, lightweight, and fully wearable devices. The document also mentions advancements in design, control, and simulation techniques, as well as the integration of rehabilitation devices into everyday living environments. The editorial concludes by summarizing the six articles included in the second volume of the research topic, which cover various aspects of rehabilitation robotics, including lower limb exoskeletons and reinforcement learning control. The article discusses various aspects of developing rehabilitation robots, emphasizing interdisciplinary collaboration and user involvement in the design process. It also highlights the potential of biomechanical models, simulation techniques, and advanced control strategies in improving rehabilitation outcomes. The article concludes by discussing future directions in rehabilitation device design, including portable devices, biosignal feedback, and personalized interventions. [Extracted from the article]

The design of walking-assistance exosuits is becoming increasingly popular among those who aim at developing a light, affordable and wearable system. They are indeed an alternative to traditional exoskeletons, which tend to be bulkier and more expensive. The main advantages of exosuits, as opposed to exoskeletons, are their lower weight and price, as well as their increased wearability and kinematic compatibility with the user. Thus, it is key to optimize their design and, particularly, the number of actuators and the actuation scheme. One of the current, common ways to achieve better designs, is to conduct a Principal Component Analysis (PCA) on some of the involved variables to reduce their dimensionality and thus, simplify the actuation system. The goal of this paper is to analyze the different variables upon which PCA can be conducted and propose the resulting actuation schemes, comparing the results and determining the best design approach for the design of a synergy-based, gait-assistance exosuit. The study focuses on both postural and dynamic synergies to optimize their design. Here, both synergy types are reviewed from a design perspective, yielding different design criteria following a PCA-based study, each with their own set of advantages and disadvantages. Thus, the design of cable-driven exosuits is optimized via analysis of gait parameters related with its actuation, such as joint torque or cable extensions. Kinematics or postural synergies lead to a higher cumulative variance of the first principal component and the transmission system is simpler than the ones obtained through dynamic synergies. [ABSTRACT FROM AUTHOR]

With ever-rising population comes a corresponding rise in people with mobility issues who have difficulty handling tasks in their daily lives. Such persons could benefit significantly from an active movement assistance device. This paper presents the design of a lower-limb exosuit designed to provide the wearer with useful gait assistance. While exoskeletons have existed for a while, soft exoskeletons or exosuits are relatively new. One challenge in the design of a gait-assistance device is the reduction of device weight. In order to facilitate this, the concept of kinematic synergies is implemented to reduce the number of actuators. In this prototype, the exosuit can actuate the hip, ankle, and knee of both legs using just one single motor, and a transmission system consisting of gears and clutches. The implementation of these synergies and their advantages are detailed in this paper, as well as preliminary tests to assess performance. This was performed by testing the exosuit worn by a subject on a treadmill while taking EMG readings and measuring cable tension produced. Significant reductions by up to 35% in certain muscle activations were observed, demonstrating the validity of this prototype for gait assistance. [ABSTRACT FROM AUTHOR]

When designing any rehabilitation, sportswear or exoskeleton device the mechanical behaviour of the body segment must be known, specifically the skin, because an excessive tissue strain may lead to ulceration and bedsores. To date, it is not known if the kinematic variability between subjects have an effect on the skin strain field, and therefore, in the design and manufacturing of rehabilitation products, such as orthoses. Several studies have analysed the skin deformation during human motion, nevertheless, the comparison between the skin strain field in different subjects during normal or pathological gait has not been reported yet. This work presents a comparison of skin strain analysis for different gait patterns to study the differences between people and, specifically, if it is possible to standardize the orthotic design between subjects with the same gait disorder. Moreover, the areas with relatively minimum strain during the ankle-foot motion are compared to improve the design of structural parts of rehabilitation devices. In this case, a validated 3D digital image correlation system has been used for this purpose combined with strain ellipse theory. The results demonstrate variations in the skin strain field between subjects with the same pathology and similarities between subjects with normal gait. However, more studies and experiments are necessaries to validate this hypothesis and also to test it between different gait pathologies. [ABSTRACT FROM AUTHOR]

AbstractExosuits for the lower limb have developed rapidly as an affordable, light, and more cost-effective alternative to the bulkier, traditional exoskeletons. The synergy-based approach aims at further emphasizing such advantages, providing even lighter and cheaper solutions, thanks to its reduction in actuators and the subsequent simplification of the actuation unit. In this paper, a design approach based on dynamic synergies is proposed to reduce the number of required actuators, thus decreasing the price and weight of walking-assistance exosuits. Also, in this work, we propose a methodology to calculate motor torque output and cable forces during assisted gait. Mechanical designs for the actuation unit are proposed along with experimental and computer-based testing and simulation. Lastly, actuation units with one and two motors are studied and compared, regarding control, mechanical complexity, and metabolic cost reduction. The results show that dynamic synergies can indeed contribute to the design of these assistive devices, with its own set of advantages and disadvantages when compared to the previously proposed postural synergies: while the latter led to a higher cumulative variance of the first principal component and the transmission system is simpler, control may be more unpredictable and forces upon the system, harder to estimate. With dynamic synergies, more related to muscle synergies, metabolic benefit on users may be more significant. [ABSTRACT FROM AUTHOR]

A novel, synergy-based design for lower-limb, gait assistance exosuits is proposed in this paper. The general design philosophy is followed by the mathematical model that leads to the exosuit's actuation system design from a certain set of postural synergies, which may reduce the number of total required actuators and, thus, the overall system weight and price. Cable extensions are chosen as the design variable upon which the principal component analysis is performed, given the high resulting cumulative variance that is obtained with few principal components. Expressions for the pulley radii are then derived and a general exosuit design is proposed, along with a novel transmission system that can combine any number of actuators to follow the gait movements from a synergy perspective. A basic testbench is also presented with such a transmission system implemented and an empirical set of results are shown with a varying number of actuators, proving that cable extensions and synergy-based design provide an excellent solution when reducing the number of actuation units in a walking-assistance exosuit. [ABSTRACT FROM AUTHOR]