A Review on the Rehabilitation Exoskeletons for the Lower Limbs of the Elderly and the Disabled

Effectiveness of a passive military exoskeleton in off-loading weight during static and dynamic load carriage: A randomised cross-over study

BACKGROUND

Load carriage imposes high physical stresses on the human body, increasing the risk of injuries. This study assessed the effectiveness of a passive military exoskeleton in off-loading the weight placed on the body during heavy load carriage under static standing and dynamic walking conditions.

METHODS

Eight full-time regular personnel of the Singapore Armed Forces enrolled in the study. Static loading tests included nine trials of 10-s quiet standing while carrying different loads (0-55 kg) with and without the exoskeleton. For dynamic loading, participants walked on a treadmill on flat, inclined, and declined surfaces while carrying two different loads (25 kg, 35 kg) with and without the exoskeleton. In-shoe normal ground reaction forces (GRF) were recorded during quiet standing and treadmill walking. Differences in total force with and without the exoskeleton during static loading were compared using Wilcoxon one-sample signed ranked tests against zero (no weight off-load) as a reference. Statistical parametric mapping test was used to compare the walking in-shoe GRF-time series with and without exoskeleton use for each load and surface condition.

RESULTS

Exoskeleton use was effective in off-loading loads of 2.3-13.5 kg during static quiet standing but the response varied substantially across loads and among the participants. Statistical analysis revealed no meaningful differences in the walking in-shoe GRF with and without exoskeleton use. The results were largely consistent across flat, inclined, and declined surfaces, and both 25-kg and 35-kg loads.

CONCLUSIONS

The passive military exoskeleton was effective in off-loading some load from the human body during static quiet standing but not dynamic walking on flat and sloped surfaces. The varied response across loads and participants calls for better design and fitting of the military exoskeleton to individual users.

The impact of assistive living technology on perceived independence of people with a physical disability in executing daily activities: a systematic literature review

PURPOSE

People with physical disabilities often require lifetime support and experience challenges to maintain or (re)define their level of independence. Assistive living technologies (ALT) are promising to increase independent living and execution of activities of daily living (ADL). This paper provides a systematic literature review that aims to analyse the present state of the literature about the impact of ALT on perceived independence of people with a physical disability receiving long-term care.

MATERIALS AND METHODS

Databases Embase, Medline, and Web of Science were searched for eligible studies from 2010 or later.

RESULTS

Nine studies were included, of which seven qualitative, one quantitative, and one mixed methods. Quality was generally high. ALT enabled participants to execute ADL. We found six themes for the impact of ALT on perceived independence: feeling enabled, choice and control, feeling secure, time alone, feeling less needy, and participation.

CONCLUSIONS

ALT appears to impact perceived independence in many ways, exceeding merely the executional aspect of independence. Existing research is limited and quite one-sided. More large-scale studies are needed in order to inform care organisations how to implement ALT, especially considering societal developments and challenges impacting long-term care.

Design and motion control of exoskeleton robot for paralyzed lower limb rehabilitation

Introduction

Patients suffering from limb movement disorders require more complete rehabilitation treatment, and there is a huge demand for rehabilitation exoskeleton robots. Flexible and reliable motion control of exoskeleton robots is very important for patient rehabilitation.

Methods

This paper proposes a novel exoskeleton robotic system for lower limb rehabilitation. The designed lower limb rehabilitation exoskeleton robot mechanism is mainly composed of the hip joint mechanism, the knee joint mechanism and the ankle joint mechanism. The forces and motion of the exoskeleton robot were analyzed in detail to determine its design parameters. The robot control system was developed to implement closed-loop position control and trajectory planning control of each joint mechanism.

Results

Multiple experiments and tests were carried out to verify robot's performance and practicality. In the robot angular response experiments, the joint mechanism could quickly adjust to different desired angles, including 15°, 30°, 45°, and 60°. In the trajectory tracking experiments, the exoskeleton robot could complete tracking movements of typical actions such as walking, standing up, sitting down, go upstairs and go downstairs, with a maximum tracking error of ±5°. Robotic wearing tests on normal people were performed to verify the assistive effects of the lower limb rehabilitation exoskeleton at different stages.

Discussion

The experimental results indicated that the exoskeleton robot has excellent reliability and practicality. The application of this exoskeleton robotic system will help paralyzed patients perform some daily movements and sports.

Modeling and Analysis of Foot Function in Human Gait Using a Two-Degrees-of-Freedom Inverted Pendulum Model with an Arced Foot

Gait models are important for the design and control of lower limb exoskeletons. The inverted pendulum model has advantages in simplicity and computational efficiency, but it also has the limitations of oversimplification and lack of realism. This paper proposes a two-degrees-of-freedom (DOF) inverted pendulum walking model by considering the knee joints for describing the characteristics of human gait. A new parameter, roll factor, is defined to express foot function in the model, and the relationships between the roll factor and gait parameters are investigated. Experiments were conducted to verify the model by testing seven healthy adults at different walking speeds. The results demonstrate that the roll factor has a strong relationship with other gait kinematics parameters, so it can be used as a simple parameter for expressing gait kinematics. In addition, the roll factor can be used to identify walking styles with high accuracy, including small broken step walking at 99.57%, inefficient walking at 98.14%, and normal walking at 99.43%.

Review of adaptive control for stroke lower limb exoskeleton rehabilitation robot based on motion intention recognition

Stroke is a significant cause of disability worldwide, and stroke survivors often experience severe motor impairments. Lower limb rehabilitation exoskeleton robots provide support and balance for stroke survivors and assist them in performing rehabilitation training tasks, which can effectively improve their quality of life during the later stages of stroke recovery. Lower limb rehabilitation exoskeleton robots have become a hot topic in rehabilitation therapy research. This review introduces traditional rehabilitation assessment methods, explores the possibility of lower limb exoskeleton robots combining sensors and electrophysiological signals to assess stroke survivors' rehabilitation objectively, summarizes standard human-robot coupling models of lower limb rehabilitation exoskeleton robots in recent years, and critically introduces adaptive control models based on motion intent recognition for lower limb exoskeleton robots. This provides new design ideas for the future combination of lower limb rehabilitation exoskeleton robots with rehabilitation assessment, motion assistance, rehabilitation treatment, and adaptive control, making the rehabilitation assessment process more objective and addressing the shortage of rehabilitation therapists to some extent. Finally, the article discusses the current limitations of adaptive control of lower limb rehabilitation exoskeleton robots for stroke survivors and proposes new research directions.

Design and Optimization of Lower Limb Rehabilitation Exoskeleton with a Multiaxial Knee Joint

To facilitate rehabilitation training for patients, we proposed the implementation of an anthropomorphic exoskeleton structure that incorporates a variable instantaneous center of rotation (ICR). This design considers the variability in knee ICR among individuals, resulting from the irregular form of the human knee joint, and leverages a double-degrees-of-freedom (2DOF) five-bar mechanism to adapt to these differences. The walking gait of the human lower limb and the corresponding knee ICR were measured and calculated using an optical 3D motion capture system. The optimal dimension parameters of the five-bar mechanism were then obtained through the optimization of human movement position inputs and rod length constraints to minimize the error in knee ICR, gait angle, and ankle trajectory between the human and the exoskeleton. Finally, we established an exoskeleton prototype to conduct relevant experimental tests. The experiment results showed that the average errors of knee ICR trajectory, hip angle, knee angle, and ankle trajectory were 5.52 × 10-4 m, 0.010 rad, 0.014 rad, and 1.57 × 10-3 m, respectively. The experimental results demonstrated that the exoskeleton's movement trajectory was close to the human's, reducing the human-mechanism interaction force and improving patient comfort during rehabilitation training.

A User-Friendly Nonmotorized Device for Ankle Rehabilitation

The ankle is formed by several joints, and it is the union of the lower leg with the foot. Its main function is to perform dorsiflexion and plantar flexion movements. Many people are affected by ankle problems. These problems can be due to simple factors, but they can also be a sign of a more serious impairment that can lead to the need for ankle rehabilitation. Thus, this paper presents a novel, fairly simple nonmotorized device for ankle rehabilitation. The design of the novel device is based on the crank–rocker mechanism, activated by the patient’s upper limb, allowing the execution of the ankle flexion range. The dimensions of the device were found using a differential evolution algorithm considering the ankle movement limits, the link stress, and singularity configurations. Graphic simulations were performed to validate the mathematical model. A prototype was constructed, and the angular ankle movement was verified. The device is easy to operate and low-cost, and in the future, it may be a tool for ankle rehabilitation.

Modeling of a Non-Rigid Passive Exoskeleton-Mathematical Description and Musculoskeletal Simulations

There is a growing application of passive exoskeletons in the industrial sector with the purpose to reduce the incidence of work-related musculoskeletal disorders (MSDs). Nowadays, while many passive shoulder exoskeletons have been developed to support overhead tasks, they present limitations in supporting tasks such as load lifting and carrying. Further developments are therefore needed to have a wider application of these devices in the industrial sector. This paper presents a modelling procedure of a passive non-rigid exoskeleton for shoulder support that can be used to evaluate the device in its development phase. The modelling began with the definition of the equations to describe the exoskeleton kinematics and dynamics to obtain the support force profile provided by the device over the shoulder flexion angle. A musculoskeletal simulation software was then used to evaluate the effect of the device on the human body. The computed support force profile is in agreement with the purpose of the device, with the maximal support force obtained for a shoulder flexion angle of 85–90°. The maximum support force value had the same magnitude as the one reported by the device user manual (3.5 kg). In particular, for a determined exoskeleton configuration, the maximum support force value computed was 34.3 N, equal to the reported by the manufacturer. The subsequent musculoskeletal simulation showed the ability of the device to reduce the muscular activation of agonist muscles such as the anterior deltoid (−36.01%) compared to the case when the exoskeleton is not used. The musculoskeletal results showed a positive effect of the device on the joint reaction forces at the glenohumeral joint with a reduction up to 41.91%. Overall the methodology and the mathematical model proposed can be used to further develop these devices, making them suitable for a wider range of tasks.

Lower Limb Exoskeleton Sensors: State-of-the-Art

Due to the ever-increasing proportion of older people in the total population and the growing awareness of the importance of protecting workers against physical overload during long-time hard work, the idea of supporting exoskeletons progressed from high-tech fiction to almost commercialized products within the last six decades. Sensors, as part of the perception layer, play a crucial role in enhancing the functionality of exoskeletons by providing as accurate real-time data as possible to generate reliable input data for the control layer. The result of the processed sensor data is the information about current limb position, movement intension, and needed support. With the help of this review article, we want to clarify which criteria for sensors used in exoskeletons are important and how standard sensor types, such as kinematic and kinetic sensors, are used in lower limb exoskeletons. We also want to outline the possibilities and limitations of special medical signal sensors detecting, e.g., brain or muscle signals to improve data perception at the human-machine interface. A topic-based literature and product research was done to gain the best possible overview of the newest developments, research results, and products in the field. The paper provides an extensive overview of sensor criteria that need to be considered for the use of sensors in exoskeletons, as well as a collection of sensors and their placement used in current exoskeleton products. Additionally, the article points out several types of sensors detecting physiological or environmental signals that might be beneficial for future exoskeleton developments.

Editorial for the Special Issue on Physical Diagnosis and Rehabilitation Technologies

Recently, physical diagnosis and human motion analysis have become active research topics in bioelectronics, and they have a broad range of applications, such as pathology detection, rehabilitation, prosthesis design, biometric identification, and humanoid robotic locomotion [...]

Assistive Mobility Control of a Robotic Hip-Knee Exoskeleton for Gait Training

In this paper, we present an assistive mobility control for a robotic hip-knee exoskeleton intended for gait training. The robotic hip-knee exoskeleton is designed with an active flexion/extension and a passive abduction/adduction at each hip joint and an active flexion/extension at each knee joint to comply with the movement of lower limbs. While facilitating walking with the robotic exoskeleton, model-free linear extended state observer (LESO)-based controllers are proposed for gait control, in which the LESO is used to deal with each user's different lower limb parameters and unknown exerted torques. Walking and ascending experiments were conducted to evaluate the performance of the proposed methods, and the results are shown with respect to walking parameters. Moreover, a preliminary study for an extended application to the recovery of normal gaits that relieves the freezing of gait (FOG) in Parkinson's disease (PD) patients is also investigated in the paper.