Exoskeleton Technology Research Articles

Passive and Active Exoskeleton Solutions: Sensors, Actuators, Applications, and Recent Trends

Recent advancements in exoskeleton technology, both passive and active, are driven by the need to enhance human capabilities across various industries as well as the need to provide increased safety for the human worker. This review paper examines the sensors, actuators, mechanisms, design, and applications of passive and active exoskeletons, providing an in-depth analysis of various exoskeleton technologies. The main scope of this paper is to examine the recent developments in the exoskeleton developments and their applications in different fields and identify research opportunities in this field. The paper examines the exoskeletons used in various industries as well as research-level prototypes of both active and passive types. Further, it examines the commonly used sensors and actuators with their advantages and disadvantages applicable to different types of exoskeletons. Communication protocols used in different exoskeletons are also discussed with the challenges faced.

Safety in Wearable Robotic Exoskeletons: Design, Control, and Testing Guidelines

Abstract Exoskeletons, wearable robotic devices designed to enhance human strength and endurance, find applications in various fields such as healthcare and industry; however, stringent safety measures should be adopted in such settings. This paper presents a comprehensive exploration of challenges associated with exoskeleton technology, ranging from mechanical issues to regulatory and ethical considerations. The enumerated challenges include joint hyper-extension or flexion, rapid or sudden motion, misalignment, fit, and comfort issues, mechanical failure, weight and mobility limitations, environmental challenges, power supply issues, high energy consumption and regeneration, fall risk or stability concerns, sensor failures, control algorithm malfunctions, machine-learning model challenges, communication disconnection, actuator malfunctions, unexpected human–robot interactions, and regulatory and ethical considerations. The paper outlines possible risks and suggests practical solutions based on design, control, and testing methods for each challenge. The objective is to offer a guideline for developers and users, emphasizing safety, reliability, and optimal performance in the ever-evolving landscape of exoskeleton technology. The guideline covers preoperation checks, user training, emergency response, real-time monitoring, and user interaction to ensure responsible innovation and user-centricity in exoskeleton development and deployment.

Perceptions of using exoskeleton technology among physiotherapists and stroke survivors in Malaysia: a mixed methods study

Exoskeleton technology has the potential to enhance the functional abilities of individuals with upper or lower limb dysfunction, including stroke survivors. However, its adoption in Malaysia has been limited due to its restricted availability in rehabilitation centres and hospitals. In this study, we aim to explore the perceptions and opinions of physiotherapists and stroke survivors regarding exoskeleton technology, focusing on identifying desired design features and investigating their views on its use in rehabilitation. An online survey was conducted to assess the preferred features of exoskeleton technology among physiotherapists and stroke survivors. Subsequently, one-to-one online in-depth interviews were carried out with physiotherapists who had experience using exoskeleton technology. Data were analysed using descriptive, thematic, and triangulation analysis methods. The analysis included 81 survey questionnaires from physiotherapists and 122 from stroke survivors. Both groups highlighted cost-effectiveness, safety, comfort, and ease of use as key features of exoskeletons. Additional insights from in-depth interviews with five physiotherapists emphasized the importance of a user-friendly interface, adjustability, and a lightweight design. Physiotherapists also expressed that exoskeleton technology could reduce their workload, minimize musculoskeletal-related disorders, and enhance their confidence. The main desired features identified by both physiotherapists and stroke survivors for exoskeleton technology include cost-effectiveness, safety, comfort, and ease of use. Physiotherapists further viewed it as a valuable tool to alleviate their workload and reduce musculoskeletal-related disorders while boosting confidence. These findings offer valuable guidance to developers, engineers, and manufacturers in the country, aiding in the development of client-centred exoskeleton features.

Implementation of Assistive Hydraulic Exoskeleton Technology for Children with Cerebral Palsy

Implementation of Assistive Hydraulic Exoskeleton Technology for Children with Cerebral Palsy

Can Exoskeletons Make Older Workers More Confident? Investigating the Impact of Exoskeletons on Aging Workers’ Self-Efficacy and Perceived Work Ability

Exoskeletons have the potential to help older workers with physical declines regain their functional capabilities and successfully meet task demands in physically demanding workplaces. This study investigated if the introduction of exoskeletons affected occupational self-efficacy and perceived work ability among manual labor workers aged 55 or older. An online survey measured changes in occupational self efficacy and perceived work ability after respondents learned about the innovative exoskeleton technology. Although it was not statistically significant, the trend showed that aging manual labor workers anticipated increased self-efficacy if exoskeletons were introduced to their workplaces. This finding suggests that exoskeletons not only help reduce injury risks and improve productivity of older workers but could also enhance their confidence at work, potentially extending their time in the workforce and improving their overall quality of life.

Recent Advances in Self-Powered Wearable Flexible Sensors for Human Gaits Analysis.

The rapid progress of flexible electronics has met the growing need for detecting human movement information in exoskeleton auxiliary equipment. This study provides a review of recent advancements in the design and fabrication of flexible electronics used for human motion detection. Firstly, a comprehensive introduction is provided on various self-powered wearable flexible sensors employed in detecting human movement information. Subsequently, the algorithms utilized to provide feedback on human movement are presented, followed by a thorough discussion of their methods and effectiveness. Finally, the review concludes with perspectives on the current challenges and opportunities in implementing self-powered wearable flexible sensors in exoskeleton technology.

Torque Detection Using EMG Signals for Different Walking Speed of a Person

This paper analyses the different walking speed of a person for torque detection by using the Electromyography (EMG) signals. EMG measures electrical activity and the muscle response to a nerve stimulation. The reduced ability to move due to variation in tendon structured muscle in lower limb joints of legs affects the overall activity of the human lifecycle. This defect makes it difficult to move causing severe pain resulting in disability. In order to overcome this problem, exoskeleton technology is implemented where Electromyography (EMG) signals are collected from electric impulse generated during the muscle movements. From these electric impulses, the torque present in EMG signals are detected and classified accordingly. The first step consists of pre processing EMG signals using Infinite Impulse Response (IIR) filter. Secondly features are extracted from pre processed signals by using Continuous Wavelet Transform (CWT) methods and classified using Convolutional Neural Networks (CNN) classifier. From this classification, the rotational movement of muscles named torque in processed EMG signal is detected. Form detected torque, the normal muscle system and problematic muscle system are differentiated

Active self-powered human motion assist system

Harvesting human energy currently occurs to power wearable devices or monitor human signs, these applications make the energy harvester less applicable to and seldom used for assisting human motion. However, there is a high demand for using such collected energy with the assistance of human motion. This paper presents a novel energy harvester that is designed to collect negative work, assist human motion, and realize self-powering. An active self-powered human motion assist system (HMAS) is developed. The system consists of a human motion assist device, a flexible rack, an electronic circuit module, and a supercapacitor. The HMAS can collect negative work from the human body, provide the user with additional motion assistance, and reduce stamina consumption. A series of experiments verify that HMAS has a high negative work collection power and a high energy conversion efficiency. The average output power is 0.93 W measured by the negative work collection test bed at a simulated knee bend angle of 40° and a frequency of 2 Hz. The energy conversion efficiency is up to 48.2%. Human motion assistance experiments verify that HMAS can provide volunteers with up to 2.57% assisting moment and minimize the metabolic cost of volunteers by 6.07% compared to without wearing HMAS. This research work is proposed to contribute to the development of active self-powered exoskeleton technology. This technology can be practically applied in the fields of rehabilitation therapy, logistics transportation, and military combat.

Assessment of an arm-support exoskeleton on physical demands, task performance, and usability during simulated agricultural tasks

This laboratory-based study aimed to determine whether an arm-support exoskeleton (ASE) would be an effective intervention to reduce the physical strain associated with manual agricultural work. Twenty-four (gender-balanced) participants performed pruning and harvesting tasks (at four different heights: knee, elbow, shoulder, and overhead), lifting/lowering, and Timed Up & Go (TUG) tasks with and without an ASE. During these tasks, muscle activity (in the upper trapezius, anterior deltoid, biceps brachii, and erector spinae), task completion time, perceived exertion, and usability were assessed. The results indicated a significant reduction (31.7%–60.2%) in muscle activity, particularly in the upper trapezius and anterior deltoid, when using the ASE during tasks at shoulder work height or above. However, there was an observed increase in muscle strain in the erector spinae, suggesting potential risk to the lower back. Given these findings, a more rigorous evaluation of ASEs in agricultural tasks should be pursued before implementing exoskeletons in agricultural tasks to avoid unintended health hazards. Relevance to industryA relatively new application of exoskeleton technology, extensively studied in fields like rehabilitation, manufacturing, and the military, is its use in agriculture. This study details the physical requirements of specific tasks to offer insights into the challenges that exoskeleton technologies for agriculture may encounter.

Estimating human joint moments unifies exoskeleton control, reducing user effort.

Robotic lower-limb exoskeletons can augment human mobility, but current systems require extensive, context-specific considerations, limiting their real-world viability. Here, we present a unified exoskeleton control framework that autonomously adapts assistance on the basis of instantaneous user joint moment estimates from a temporal convolutional network (TCN). When deployed on our hip exoskeleton, the TCN achieved an average root mean square error of 0.142 newton-meters per kilogram across 35 ambulatory conditions without any user-specific calibration. Further, the unified controller significantly reduced user metabolic cost and lower-limb positive work during level-ground and incline walking compared with walking without wearing the exoskeleton. This advancement bridges the gap between in-lab exoskeleton technology and real-world human ambulation, making exoskeleton control technology viable for a broad community.

Soft Hand Exoskeletons for Rehabilitation: Approaches to Design, Manufacturing Methods, and Future Prospects

Stroke, the third leading cause of global disability, poses significant challenges to healthcare systems worldwide. Addressing the restoration of impaired hand functions is crucial, especially amid healthcare workforce shortages. While robotic-assisted therapy shows promise, cost and healthcare community concerns hinder the adoption of hand exoskeletons. However, recent advancements in soft robotics and digital fabrication, particularly 3D printing, have sparked renewed interest in this area. This review article offers a thorough exploration of the current landscape of soft hand exoskeletons, emphasizing recent advancements and alternative designs. It surveys previous reviews in the field and examines relevant aspects of hand anatomy pertinent to wearable rehabilitation devices. Furthermore, the article investigates the design requirements for soft hand exoskeletons and provides a detailed review of various soft exoskeleton gloves, categorized based on their design principles. The discussion encompasses simulation-supported methods, affordability considerations, and future research directions. This review aims to benefit researchers, clinicians, and stakeholders by disseminating the latest advances in soft hand exoskeleton technology, ultimately enhancing stroke rehabilitation outcomes and patient care.

Investigation of the Effectiveness of the Robotic ReStore Soft Exoskeleton in the Development of Early Mobilization, Walking, and Coordination of Stroke Patients: A Randomized Clinical Trial

Medical robotics nowadays can prevent, treat, or alleviate numerous severe conditions, including the dire consequences of stroke. Our objective was to determine the effect of employing a robotic soft exoskeleton in therapy on the development of the early mobilization, gait, and coordination in stroke patients. The ReStore™ Soft Exo-Suit, a wearable exosuit developed by a leading company with exoskeleton technology, was utilized. It is a powered, lightweight device intended for use in stroke rehabilitation for people with lower limb disability. We performed a randomized clinical intervention, using a before–after trial design in a university hospital setting. A total of 48 patients with a history of stroke were included, of whom 39 were randomized and 30 completed the study. Interventions: Barthel Index and modified Rankin scale (mRS) patients were randomly assigned to a non-physical intervention control (n = 9 of 39 completed, 30 withdrew before baseline testing), or to a high-intensity agility program (15 sessions, 5 weeks, n = 30 completed). The main focus of assessment was on the Modified Rankin Scale. Additionally, we evaluated secondary factors including daily life functionality, five dimensions of health-related quality of life, the Beck depression inventory, the 6 min walk test (6MWT), the Berg Balance Scale (BBS), and static balance (center of pressure). The Robot-Assisted Gait Therapy (ROB/RAGT) program led to significant improvements across various measures, including a 37% improvement in Barthel Index scores, a 56% increase in 10 m walking speed, and a 68% improvement in 6 min walking distance, as well as notable enhancements in balance and stability. Additionally, the intervention group demonstrated significant gains in all these aspects compared to the control group. In conclusion, the use of robotic therapy can be beneficial in stroke rehabilitation. These devices support the restoration and improvement of movement in various ways and contribute to restoring balance and stability.

Industrial practitioner's perception on the application of exoskeleton system in automotive assembly industries: A Malaysian case study

The automotive industry is a key manufacturing industry for the Malaysian economy, where manual jobs and task are still common. Hence, Work-related Musculoskeletal Disorders (WMSD) is a common type of injury among workers. Exoskeleton system has gained global traction as a possible solution to reduce the risk of MSD among workers. Nonetheless, the application of exoskeleton in the automotive industry in Malaysia remains unknown. As such, this study attempts to provide insight into the industry's perception on the potential of exoskeleton application within the context of Malaysian automotive assembly sector. Therefore, a total of 52 management level respondents from various manufacturers participated in this study. It is found that, although the technology seems to be relatively new and disruptive, the respondents have a positive perception towards it with an acceptance rate of 86.5%. Cost of implementation exoskeleton technologies seems to be primary concern from the respondents, other concern such as maintenance cost and ease of application into existing application is also highlighted.

Evaluation of EMG patterns in children during assisted walking in the exoskeleton.

While exoskeleton technology is becoming more and more common for gait rehabilitation in children with neurological disorders, evaluation of gait performance still faces challenges and concerns. The reasoning behind evaluating the spinal locomotor output is that, while exoskeleton's guidance forces create the desired walking kinematics, they also affect sensorimotor interactions, which may lead to an abnormal spatiotemporal integration of activity in particular spinal segments and the risk of abnormalities in gait recovery. Therefore, traditional indicators based on kinematic or kinetic characteristics for optimizing exoskeleton controllers for gait rehabilitation may be supplemented by performance measures associated with the neural control mechanisms. The purpose of this study on a sample of children was to determine the basic features of lower limb muscle activity and to implement a method for assessing the neuromechanics of spinal locomotor output during exoskeleton-assisted gait. To this end, we assessed the effects of a robotic exoskeleton (ExoAtlet Bambini) on gait performance, by recording electromyographic activity of leg muscles and analyzing the corresponding spinal motor pool output. A slower walking setting (about 0.2 m/s) was chosen on the exoskeleton. The results showed that, even with slower walking, the level of muscle activation was roughly comparable during exoskeleton-assisted gait and normal walking. This suggests that, despite full assistance for leg movements, the child's locomotor controllers can interpret step-related afferent information promoting essential activity in leg muscles. This is most likely explained by the active nature of stepping in the exoskeleton (the child was not fully relaxed, experienced full foot loading and needed to maintain the upper trunk posture). In terms of the general muscle activity patterns, we identified notable variations for the proximal leg muscles, coactivation of the lumbar and sacral motor pools, and weak propulsion from the distal extensors at push-off. These changes led to the lack of characteristic lumbosacral oscillations of the center of motoneuron activity, normally associated with the pendulum mechanism of bipedal walking. This work shows promise as a useful technique for analyzing exoskeleton performance to help children develop their natural gait pattern and to guide system optimization in the future for inclusion into clinical care.

Purpose-centered design of rehabilitation robots: a case study of a hand exoskeleton for assessing spasticity

Hand exoskeletons offer promising solutions for hand function rehabilitation. Despite considerable research on novel exoskeleton technologies and the commercial availability of many hand exoskeletons, most hand exoskeletons can only perform motor training and assistance, rather than treatment or diagnosis of hand diseases. This limitation is also observed in other rehabilitation robots. Designing a rehabilitation robot for medical purposes necessitates the integration of existing technologies, tailored to the symptoms, clinical conditions, and management methods of the target disease. To facilitate such design, this study presents a design strategy for rehabilitation robots that assist in the therapy and assessment of specific diseases. The strategy first systematically gathers prior medical and engineering knowledge on the management of the target disease and clarifies comprehensive design requirements, including medical goals and user needs. Next, modified Quality Function Deployment (QFD) and Theory of Inventive Problem Solving (TRIZ) methods are used to identify the core requirements and the optimal design scheme based on existing technical solutions. Lastly, the optimal design scheme is prototyped, tested, and refined iteratively until the product satisfies the design purpose. As an illustrative case study of this design strategy, the design of a hand exoskeleton for assessing hand spasticity is discussed. This strategy is adaptable for designing hand exoskeletons for other diseases or developing other types of rehabilitation robots, thereby extending the potential of rehabilitation robots in diagnostic and therapeutic applications.

A COMPARATIVE ANALYSIS OF LOWER LIMB EXOSKELETON GAIT CONTROL SYSTEMS

The complexities associated with lower limb exoskeleton control systems stem from the dynamic and non-linear nature of human movement. Gait control, in particular, re-quires intricate coordination of joints and muscles, demanding precise adjustments to ac-commodate variations in walking speed, terrain, and user preferences. Additionally, the diverse physical characteristics among users, such as weight, height, and muscle develop-ment, introduce parametric uncertainties that amplify the challenge of designing control systems that can adapt seamlessly to individual differences. Addressing these complexities involves an advanced and multi-level control approach. In the pursuit of effective control strategies, a non-linear mathematical model for a single-leg lower limb exoskeleton is de-rived, considering mechanical and electromechanical components. Тhe gait control sys-tems of a lower limb exoskeleton were investigated, emphasizing the development of vari-ous control strategies, including proportional derivative (PD), PD with gain scheduling, hy-brid adaptive, and adaptive controllers with gain scheduling. The article ends with a com-prehensive comparative analysis of the developed controllers, presenting the integral abso-lute errors (IAE) during exoskeleton walking in both load and no-load conditions to evalu-ate their productivity, efficiency, and adaptability. Extensive testing was conducted using a physical test model representing the exoskeleton of the lower limbs. During a series of ex-periments, the functionality and operability of each control system were evaluated in vari-ous scenarios. The results of these tests give valuable information about the strengths and weaknesses of various control strategies, contributing to the development of lower limb exoskeleton technology.

Biomechanical Analysis and Mobility Improvement of Auxiliary Mobile Equipment

As an advanced auxiliary mobile device, exoskeleton booster has attracted wide attention in the field of rehabilitation and life assistance. Through biomechanical analysis, this paper discusses the effect of exoskeleton booster on user mobility. Using biomechanical tools such as kinematics, dynamics and muscle mechanics, this paper deeply studies the influence of exoskeleton booster in different motion States, and verifies its biomechanical effect through simulation and experiment. Firstly, this paper analyzes the influence of exoskeleton booster on gait from the perspective of kinematics. The research shows that the exoskeleton booster can improve the walking efficiency of users by optimizing the step size and step frequency. The precise adjustment of joint motion by intelligent control system enables exoskeleton to better adapt to the gait characteristics of different users. Secondly, through dynamic analysis, this paper deeply studies the influence of exoskeleton on joint torque. The exoskeleton is designed to apply appropriate torque at key joints to help users complete the movement. The synergistic effect of this moment not only reduces the muscle burden of users, but also improves the stability of joints and reduces the risks in sports. In terms of improving mobility, exoskeleton technology can significantly improve the gait of patients in rehabilitation training, which is helpful to improve the balance ability of patients. The improvement effect of exoskeleton technology directly affects the quality of daily life of patients. This biomechanical effect provides strong support for the extensive application of exoskeleton technology in rehabilitation, sports assistance and daily life.

Current strategies for regenerative therapy of spinal cord injury

Spinal cord injury (SCI) is a leading cause of death and severe disability amongst young people. The incidence of SCI is 0.6–1.0 per 10,000 individuals. Unfortunately, there are no effective methods of restoring locomotor function for individuals with severe SCI. To address this issue, exoskeleton technology controlled using BCI is actively being developed for prosthetic locomotion. Despite the lack of encouraging data for severe spinal cord injuries, regenerative technologies continue to hold promise for spinal cord repair. The limited options for regenerating the central nervous system in humans necessitate creating new sources of neural stem cells for regeneration. Reprogramming autologous somatic cells neurologically can effectively serve as such a source [1]. Nevertheless, the constitution of neuroglial progenitors, which are necessary for regenerating damaged axons of the pyramidal tract, still requires clarification [2]. Some interesting efforts are underway to directly reprogram glial cells in situ using a variety of biotechnological approaches [3]. Overcoming or preventing the formation of a harsh scar tissue at the injury site is the key obstacle to successful regeneration therapy for SCI. Various scaffolds are being developed to facilitate axon regeneration, and several gene therapy agents are being tested to either knock down scar formation factors or activate extracellular matrix remodeling and reparative regeneration. Neuromodulation shows promise for SCI treatment. Studies indicate that epidural stimulation of the L2-S1 spinal cord in humans and mammals activates SPG neurons, aiding spinal walking generator functions. A potentially successful treatment approach involves scaffolds with reprogrammed cells and neuromodulation [4].

Applied Exoskeleton Technology: A Comprehensive Review of Physical and Cognitive Human–Robot Interaction

Exoskeletons and orthoses are wearable mobile systems providing mechanical benefits to users. Despite significant improvements in the last decades, the technology is not fully mature to be adopted for strenuous and non-programmed tasks. To accommodate this insufficiency, different aspects of this technology need to be analysed and improved. Numerous studies have tried to address some aspects of exoskeletons, e.g. mechanism design, intent prediction, and control scheme. However, most works have focused on a specific element of design or application without providing a comprehensive review framework. This study aims to analyse and survey the contributing aspects to this technology’s improvement and broad adoption. To address this, after introducing assistive devices and exoskeletons, the main design criteria will be investigated from both physical Human-Robot Interaction (HRI) perspectives. In order to establish an intelligent HRI strategy and enable intuitive control for users, cognitive HRI will be investigated after a brief introduction to various approaches to their control strategies. The study will be further developed by outlining several examples of known assistive devices in different categories. And some guidelines for exoskeleton selection and possible mitigation of current limitations will be discussed.

Tracking Control for a Lower Extremity Exoskeleton Based on Adaptive Dynamic Programing.

The utilization of lower extremity exoskeletons has witnessed a growing presence across diverse domains such as the military, medical treatment, and rehabilitation. This paper introduces a novel design of a lower extremity exoskeleton specifically tailored for individuals engaged in heavy object carrying tasks. The exoskeleton incorporates an impressive 12 degrees of freedom (DOF), with four of them being effectively controlled through hydraulic cylinders. To achieve optimal control of this intricate lower extremity exoskeleton system, the authors propose an adaptive dynamic programming (ADP) algorithm. Several crucial components are established to implement this control scheme. These include the formulation of the state equation for the lower extremity exoskeleton system, which is well-suited for the ADP algorithm. Additionally, a corresponding performance index function based on the tracking error is devised, along with the game algebraic Riccati equation. By employing the value iteration ADP scheme, the lower extremity exoskeleton demonstrates highly effective tracking control. This research not only highlights the potential of the proposed control approach but also showcases its ability to enhance the overall performance and functionality of lower extremity exoskeletons, particularly in scenarios involving heavy object carrying. Overall, this study contributes to the advancement of lower extremity exoskeleton technology and offers valuable insights into the application of ADP algorithms for achieving precise and efficient control in demanding tasks.