Exoskeleton For Gait Rehabilitation Research Articles

Synergetic gait prediction and compliant control of SEA-driven knee exoskeleton for gait rehabilitation.

In recent years, lower limb exoskeletons have achieved satisfactory clinical curative effects in rehabilitating stroke patients. Furthermore, generating individualized trajectories for each patient and avoiding secondary injury in rehabilitation training are important issues. This paper explores the utilization of series elastic actuator (SEA) to deliver compliant force and enhance impact resistance in human-robot interaction, and we present the design of novel knee exoskeleton driven by SEA. Subsequently, the novel gait trajectory prediction method and compliant control method are proposed. The attention-based CNN-LSTM model is established to generate personalized gait trajectories for affected limbs, in which the spatial-temporal attention mechanism is adopted to improve the prediction accuracy. The compliant control strategy is proposed to nonlinearly and adaptively tune impedance parameters based on artificial potential field (APF) method, and active rehabilitation training is carried out in the coordination space to guarantee patient safety. The experimental results based on four healthy subjects demonstrated that synergetic gait prediction model could satisfactorily characterize the coordination movement with higher accuracy. The compliant control could limit the patient's movement in the safe coordination tunnel while considering personalization and flexibility.

Powered single hip joint exoskeletons for gait rehabilitation: a systematic review and Meta-analysis.

Gait disorders and as a consequence, robotic rehabilitation techniques are becoming increasingly prevalent as the population ages. In the area of rehabilitation robotics, using lightweight single hip joint exoskeletons are of significance. Considering no prior systematic review article on clinical outcomes, we aim to systematically review powered hip exoskeletons in terms of gait parameters and metabolic expenditure effects. Three databases of PubMed, Scopus, and Web of science were searched for clinical articles comparing outcomes of gait rehabilitation using hip motorized exoskeleton with conventional methods, on patients with gait disorder or healthy individuals. Of total number of 37 reviewed articles, 14 trials were quantitatively analyzed. Analyses performed in terms of gait spatiotemporal parameters like speed (self-speed and maximum speed), step length, stride length, cadence, and oxygen consumption. Improved clinical outcomes of gait spatiotemporal parameters with hip joint exoskeletons are what our review's findings show. In terms of gait values, meta-analysis indicates that rehabilitation with single hip joint exoskeleton enhanced parameters of maximum speed by 0.13 m/s (0.10-0.17) and step length by 0.06 m (0.05-0.07). For the remaining investigated gait parameters, no statistically significant difference was observed. Regarding metabolic parameters, oxygen consumption was lower in individuals treated with hip exoskeleton (- 1.23 ml/min/kg; range - 2.13 to - 0.32). Although the analysis demonstrated improvement with just specific gait measures utilizing powered hip exoskeletons, the lack of improvement in all parameters is likely caused by the high patient condition heterogeneity among the evaluated articles. We also noted in patients who rehabilitated with the hip exoskeleton, the oxygen cost was lower. More randomized controlled trials are needed to verify both the short- and long-term clinical outcomes, including patient-reported measures. Level I (systematic review and meta-analysis).

Design, control and evaluation of a treadmill-based Pelvic Exoskeleton (PeXo) with self-paced walking mode

Most gait rehabilitation exoskeletons focus only on assisting lower limb motions. However, the pelvis plays an essential role in overground ambulation. This calls for the need of gait training devices that allow full control and assistance of user’s pelvis to improve gait rehabilitation therapies of stroke survivors. This paper presents a new pelvic assistance treadmill-based exoskeleton (PeXo) for gait rehabilitation. The system includes a total of 5 actively controlled Degrees of Freedom (DOFs), plus a passive one, in order to provide all DOFs of the human pelvis. The paper describes the mechatronic design and haptic control of PeXo, and introduces a newly developed self-paced walking mode where the user can control walking speed at his/her will. The system was evaluated by means of a pilot study with a stroke survivor. Results showed PeXo can be used safely and reliably during walking activities, allowing for the natural motion of the pelvis with reduced interaction forces. However, the use of the platform reduced user’s Range of Motion at the pelvis and lower limb joints, whereas lower limb’s muscle activity increased to compensate the disturbances introduced by the platform. Nevertheless, the user reported a positive feedback when using the system, suggesting potential and promising advantages of PeXo that should be explored in a larger study in the future.

A qualitative study to elicit user requirements for lower limb wearable exoskeletons for gait rehabilitation in spinal cord injury

ObjectiveWe aim to determine a comprehensive set of requirements, perceptions, and expectations that people with spinal cord injury (SCI) and the clinicians in charge of their rehabilitation have regarding the use of wearable robots (WR) for gait rehabilitation.BackgroundThere are concerns due to the limited user acceptance of WR for gait rehabilitation. Developers need to emphasize understanding the needs and constraints of all stakeholders involved, including the real-life dynamics of rehabilitation centers.Methods15 people with SCI, 9 without experience with WR and 6 with experience with these technologies, and 10 clinicians from 3 rehabilitation centers in Spain were interviewed. A directed content analysis approach was used.Results78 codes grouped into 9 categories (physical results, usability, psychology-related codes, technical characteristics, activities, acquisition issues, context of use, development of the technologies and clinical rehabilitation context) were expressed by at least 20% of the users interviewed, of whom 16 were not found in the literature. The agreement percentage between each group and subgroup included in the study, calculated as the number of codes that more than 20% of both groups expressed, divided over the total amount of codes any of those two groups agreed on (≥ 20%), showed limited agreement between patients and clinicians (50.00%) and between both types of patients (55.77%). The limited accessibility and availability of lower limb exoskeletons for gait rehabilitation arose in most of the interviews.ConclusionsThe limited agreement percentage between patients and clinicians indicates that including both types of users in the design process of these technologies is important, given that their requirements are complementary. Engaging users with prior technology experience is recommended, as they often exhibit strong internal consensus and articulate well-defined requirements. This study adds up the knowledge available in the literature and the new codes found in our data, which enlighten important aspects that ought to be addressed in the field to develop technologies that respond to users’ needs, are usable and feasible to implement in their intended contexts.ApplicationThe set of criteria summarized in our study will be useful to guide the design, development, and evaluation of WR for gait rehabilitation to meet user’s needs and allow them to be implemented in their intended context of use.

Design of a Lower Limb Exoskeleton: Robust Control, Simulation and Experimental Results

This paper presents the development of a robust control algorithm to be applied in a knee and ankle joint exoskeleton designed for rehabilitation of flexion/extension movements. The goal of the control law is to follow the trajectory of a straight leg extension routine in a sitting position. This routine is commonly used to rehabilitate an injury on an Anterior Cruciate Ligament (ACL) and it is applied to the knee and ankle joints. Moreover, the paper presents the development and implementation of the robotic structure of the ankle joint to integrate it into an exoskeleton for gait rehabilitation. The development of the dynamic model and the implementation of the control algorithm in simulation and experimental tests are presented, showing that the proposed control guarantees the convergence of the tracking error.

Multi-objective Fractional Order PID Controller Optimization for Kid's Rehabilitation Exoskeleton

Fractional order Controllers have been used in several industrial cases to achieve better performance of the systems. This paper proposes a Fractional Order Proportional Integral Derivative (FOPID) controller. It is synthesized using Oustaloup approximation, and its parameters are tuned using the Genetic Algorithm (GA) optimization method. The aim is to minimize the error, the energy and the startup torques using two objective functions to improve the control performances and the robustness. The validity of the proposed controller is shown via simulation by controlling a two-link exoskeleton for children's gait rehabilitation, and the results are compared to an Integer order PID (IOPID) controller. Simulation results clearly indicate the superiority of the optimized FOPID in terms of trajectory tracking and the used torques. Moreover, the FOPID controller is tested with parameter uncertainties. Its robustness is proven against thigh and shank masses variation. Both controllers are simulated under the same frequency conditions using Simulink MATLAB R2018a.

Novel Design and Implementation of a Knee Exoskeleton for Gait Rehabilitation with Impedance Control Strategy

Novel Design and Implementation of a Knee Exoskeleton for Gait Rehabilitation with Impedance Control Strategy

Synthesis of a six-bar mechanism for generating knee and ankle motion trajectories using deep generative neural network

Robotic exoskeletons have demonstrated their effectiveness in post-stroke gait rehabilitation therapy. Nevertheless, further research is being conducted to improve existing rehabilitation exoskeletons in terms of ease-of-use and innovative design. Previously, the adaptation of linkage-based mechanisms for rehabilitation exoskeletons has been considered an option. However, finding linkage parameters that will produce the required gait trajectories using a linkage-based exoskeleton, is quite challenging. It is furthermore challenging to obtain parameters of a linkage-based mechanism designed for a gait rehabilitation task that has to produce two trajectories (for knee and ankle joints) simultaneously. In this work, we propose Deep Generative Neural Networks (DGNN) to obtain a set of optimal dimensions and parameters for the Stephenson III six-bar linkage-based gait exoskeleton. The proposed methodology demonstrates high efficacy in determining the linkage parameters for various target trajectories. The proposed framework, once trained, can accurately predict mechanism parameters to achieve two joint trajectories simultaneously. Subsequent to developing the model, walking trajectories from healthy human subjects are given to the model to determine the optimal linkage dimensions of the gait rehabilitation exoskeleton. The proposed model can be used to assist designers in quickly determining the optimized linkage dimensions of linkage-based mechanisms that can provide various target trajectories.

Analyzing Classification Performance of fNIRS-BCI for Gait Rehabilitation Using Deep Neural Networks.

This research presents a brain-computer interface (BCI) framework for brain signal classification using deep learning (DL) and machine learning (ML) approaches on functional near-infrared spectroscopy (fNIRS) signals. fNIRS signals of motor execution for walking and rest tasks are acquired from the primary motor cortex in the brain’s left hemisphere for nine subjects. DL algorithms, including convolutional neural networks (CNNs), long short-term memory (LSTM), and bidirectional LSTM (Bi-LSTM) are used to achieve average classification accuracies of 88.50%, 84.24%, and 85.13%, respectively. For comparison purposes, three conventional ML algorithms, support vector machine (SVM), k-nearest neighbor (k-NN), and linear discriminant analysis (LDA) are also used for classification, resulting in average classification accuracies of 73.91%, 74.24%, and 65.85%, respectively. This study successfully demonstrates that the enhanced performance of fNIRS-BCI can be achieved in terms of classification accuracy using DL approaches compared to conventional ML approaches. Furthermore, the control commands generated by these classifiers can be used to initiate and stop the gait cycle of the lower limb exoskeleton for gait rehabilitation.

Analysis and Evaluation of a Quasi-Passive Lower Limb Exoskeleton for Gait Rehabilitation

Lower extremity exoskeletons can assist with performing particular functions such as gait assistance, and physical therapy support for subjects who have lost the ability to walk. This paper presents the analysis and evaluation of lightweight and adjustable two degrees of freedom, quasi-passive lower limb device to improve gait rehabilitation. The exoskeleton consists of a high torque DC motor mounted on a metal plate above the hip joint, and a link that transmits assistance torque from the motor to the thigh. The knee joint is passively actuated by spring installed parallel with the joint. The action of the passive component (spring) is combined with mechanical output of the motor to provide a good control on the designed exoskeleton while walking. The results show that muscles' efforts on both the front and the back sides of the user's leg were decreased when walking using the exoskeleton with the motor and spring.

Design and Implementation of a Robotic Hip Exoskeleton for Gait Rehabilitation

In this paper, a four degrees-of-freedom robotic hip exoskeleton was proposed for gait rehabilitation. The robotic hip exoskeleton was designed with active flexion/extension and passive abduction/adduction at each hip joint to comply with the movement of the thigh. Due to each user’s different lower limbs characteristics and unknown torques at hip joints, model-free linear extended state observer (LESO)-based controllers were proposed for rehabilitation gait control. The prototypes of the robotic hip exoskeleton and controller designs were validated and compared through walking and ascending rehabilitation experiments. Additionally, a motion captured system and EMG signals were used to investigate the walking assistance of the robotic hip exoskeleton.

Efficacy of robotic exoskeleton for gait rehabilitation in patients with subacute stroke : a systematic review.

Stroke is the most common cause of disability in Western Countries. It can lead to loss of mobility, capability to walk and ultimately loss of independence in activities of daily living (ADL). Several rehabilitative approaches have been proposed in these years. Robot-assisted gait rehabilitation (RAGT) plays a crucial role to perform a repetitive, intensive, and task-oriented treatment in stroke survivors. However, there are still few data on its role in subacute stroke patients. The aim of the present study was to assess the efficacy of RAGT for gait recovery in subacute stroke survivors. Systematic review with meta-analysis. The setting of the study included Units of Rehabilitation. The analyzed population was represented by subacute stroke patients. PubMed, Scopus, Web of Science, CENTRAL, and PEDro were systematically searched until January 18, 2021, to identify randomized controlled trials (RCTs) presenting: stroke survivors in subacute phase (≤6 months) as participants; exoskeleton robots devices as intervention; conventional rehabilitation as a comparator; gait assessment, through qualitative scales, quantitative gait scales or quantitative parameters, as outcome measures. We also performed a meta-analysis of the mean difference in the functional ambulation category (FAC) via the random effect method. Out of 3188 records, 14 RCTs were analyzed in this systematic review. The 14 studies have been published in the last 14 years (from 2006 to 2021) and included 576 stroke survivors, of which 306 received RAGT, and 270 underwent conventional rehabilitation. Lokomat robotic system was the most investigated robotic exoskeleton by the RCTs included (N.=9), albeit the meta-analysis demonstrated a non-significant difference of -0.09 in FAC (95% CI: -0.22.0.03) between Lokomat and conventional therapy. According to the PEDro scale, 11 (78.5%) were classified as good-quality studies, two as fair-quality studies (14.3%), and one as poor-quality study (7.1%). Taken together, these findings showed that RAGT might have a potential role in gait recovery in subacute stroke survivors. However, further RCTs comparing the efficacy of RAGT with conventional physical therapy are still warranted in the neurorehabilitation field. This systematic review provides information on the efficacy of RAGT in allowing subacute stroke patients to perform high-intensity gait training with a lower physical burden on PRM professionals.

Design and Preliminary Assessment of a Passive Elastic Leg Exoskeleton for Resistive Gait Rehabilitation

This article aimed to develop a unique exoskeleton to provide different types of elastic resistances (i.e., resisting flexion, extension, or bidirectionally) to the leg muscles during walking. We created a completely passive leg exoskeleton, consisting of counteracting springs, pulleys, and clutches, to provide different types of elastic resistance to the knee. We first used a benchtop setting to calibrate the springs and validate the resistive capabilities of the device. We then tested the device's ability to alter gait mechanics, muscle activation, and kinematic aftereffects when walking on a treadmill under the three resistance types. Benchtop testing indicated that the device provided a nearly linear torque profile and could be accurately configured to alter the angle where the spring system was undeformed (i.e., the resting position). Treadmill testing indicated the device could specifically target knee flexors, extensors, or both, and increase eccentric loading at the joint. Additionally, these resistance types elicited different kinematic aftereffects that could be used to target user-specific spatiotemporal gait deficits. These results indicate that the elastic device can provide various types of targeted resistance training during walking. The proposed elastic device can provide a diverse set of resistance types that could potentially address user-specific muscle weaknesses and gait deficits through functional resistance training.

Offline ANN-PID Controller Tuning on a Multi-Joints Lower Limb Exoskeleton for Gait Rehabilitation

This paper presents Artificial Neural Network (ANN) as an optimization tool in tuning Proportional-Integral-Derivative (PID) controller's gain of a multi-joints Lower Limb Exoskeleton (LLE) for gait rehabilitation. The interest in wearable post-stroke and spinal cord injury rehabilitation devices such as LLE has been increasing due to the demand for assistive technologies for paralyze patients and to meet the concerns in the increasing number of ageing society. The dynamic of three degree of freedom LLE was determined using Euler-Lagrange equation, and PID parameters were initially tuned using the Ziegler-Nichols (ZN) method. The paper compares different ANN-based algorithms in tuning PID controller's gain for LLE applications. The method compared and evaluated with other methods and dynamic systems in the literature. ANN-based algorithms, Gradient Descent, Levenberg-Marquardt, and Scaled Conjugate Gradient, are utilized for PID tuning of each joint in the LLE model. The result shows faster convergence and improves step response characteristics for each controlled joint model. The overshoot values found to be 0.3126%, 0.6335%, and 0.2619% compared to the ZN method with 10.5582%, 15.1643%, and 11.8511% for hip, knee, and ankle joints, respectively. It can be ascertained that the PID controlled of LLE has been optimally tuned significantly by different ANN methods, which reduced its steady-state errors.

Subjective Evaluation of the Effect of Exoskeleton Robots for Rehabilitation Training

Recently, the interest in the lower-limb exoskeleton robot is increasing within rehabilitation practice. While research on advancing the gait rehabilitation exoskeleton robot (ER) is being actively conducted from a technical point of view, studies evaluating usability and user value of ERs are insufficient. In this study, an evaluation tool was developed and verified, and an evaluation of an ER-based rehabilitation training program was conducted using the evaluation tool. A total of 102 rehabilitation patients (51 using ER and 51 under the existing training program [ETP] without robots) and 38 therapists participated in this experiment. The ER used in this study was Exowalk (HR-02, HMH Co. Ltd, South Korea). As a result of the study, the usability of the ERs consists of trust and overall satisfaction. The patient group using the ER showed statistically higher trust and overall satisfaction scores than the patient group with the ETP. On the other hand, the user value of the ER includes self-direction and security. The self-direction score of the patients using the ER was significantly higher than that of the patients with the ETP, but the security score showed the opposite tendency. This study is unique in that measures were developed to evaluate the usability and user value of the gait rehabilitation ER, especially for the Exowalk, verified by various user groups, and statistically analyzed to be used as a reference for the design of usability and user value in other gait rehabilitation ERs.

Generation of a gait pattern for a lower limb rehabilitation exoskeleton

In this article, a simple prototype and control system of a lower limb exoskeleton driven by stepper motors was proposed. To study kinematic parameters of the device, a general, three-dimensional simulation model of the exoskeleton was developed. Moreover, a gait pattern was modeled for hip, knee, and ankle joints. It represents sagittal plane angular positions of joints during normal gait and consists of three piecewise-defined sine-square-based functions. It is based on the experimental gait data recorded with an optoelectronic motion capture system for a healthy subject walking on a treadmill. Although the developed pattern is intended to be implemented in a control system of a lower limb exoskeleton for gait rehabilitation, it can be used to control bipedal robots as well. Last but not least, the control approach was tested with the exoskeleton prototype.

Fuzzy logic compliance adaptation for an assist-as-needed controller on the Gait Rehabilitation Exoskeleton (GAREX)

Assist-as-needed control strategy is an emerging approach to improve the effectiveness of gait rehabilitation training. We have proposed a pneumatic muscle (PM) driven Gait Rehabilitation Exoskeleton (GAREX) implemented with a multi-input–multi-output (MIMO) sliding mode control system to actively adjust the assistance level provided during gait rehabilitation. To realize the assist-as-needed control strategy, a specific algorithm is imperative to assess the active participation or effort of wearers and adapt the amount of assistance accordingly. We sought to establish a fuzzy logic compliance adaptation (FLCA) controller to form a novel cascade control system. We evaluated the feasibility of implemented FLCA controller on the performance of adjusting the compliance of GAREX’s knee joint according to the online assessment of the wear’s active participation level once in every gait cycle. Using controlled, treadmill-based walking tests involved three healthy subjects, we demonstrate that FLCA controller could effectively distinguish the capability/effort levels of wearers and enable the exoskeleton to adapt the knee joint compliance accordingly. Obtained results reveal that FLCA controller can collaborate well with MIMO sliding mode controller in a system and indicate the novel method of realizing assist-as-needed concept with the pneumatic muscle powered mechanisms.

Implementing the exoskeleton Ekso GTTM for gait rehabilitation in a stroke unit – feasibility, functional benefits and patient experiences

Background Reports on the implementation of exoskeletons for gait rehabilitation in clinical settings are limited. Objectives How feasible is the introduction of exoskeleton gait training for patients with subacute stroke in a specialized rehabilitation hospital? What are the functional benefits and the patient experiences with training in the Ekso GTTM exoskeleton? Design Explorative study. Methods During an 18 months inclusion period, 255 in-patients were screened for eligibility. Inclusion criteria were; walking difficulties, able to stand 10 min in a standing frame, fitting into the robot and able to cooperate. One-hour training sessions 2–3 times per week for approximately 3 weeks were applied as a part of the patients’ ordinary rehabilitation programme. Assessments: Functional Independence Measure, Motor Assessment Scale (MAS), Ekso GTTM walking data, patient satisfaction and perceived exertion of the training sessions (Borg scale). Results Two physiotherapists were certified at the highest level of Ekso GTTM. Twenty-six patients, median age 54 years, were included. 177 training sessions were performed. Statistical significant changes were found in MAS total score (p < 0.003) and in the gait variables walking time, up-time, and a number of steps (p < 0.001). Patients reported fairly light perceived exertion and a high level of satisfaction and usefulness with the training sessions. Few disadvantages were reported. Most patients would like to repeat this training if offered. Conclusions Ekso GTTM can safely be implemented as a training tool in ordinary rehabilitation under the prerequisite of a structured organization and certified personnel. The patients progressed in all outcome measures and reported a high level of satisfaction. Implications for rehabilitation The powered exoskeleton Ekso GTTM was found feasible as a training option for in-patients with severe gait disorders after stroke within an ordinary rehabilitation setting. The Ekso GTTM must be operated by a certified physiotherapist, and sufficient assistive personnel must be available for safe implementation. Patients' perceived exertion when training in the Ekso GTTM was relatively low. The patients expressed satisfaction with this training option.

Synchronous Position and Compliance Regulation on a Bi-Joint Gait Exoskeleton Driven by Pneumatic Muscles

A previously developed pneumatic muscles’ (PMs) actuated gait exoskeleton (with only knee joint) has been demonstrated in achieving appropriate actuation torque, range of motion (ROM), and control bandwidth for task-specific gait training. While the adopted multi-input–multi-output (MIMO) sliding mode (SM) strategy has preliminarily implemented simultaneous control of the exoskeleton’s angular trajectory and compliance, its efficacy with human users during gait cycles has not been investigated. This article presents an improved bi-joint gait rehabilitation exoskeleton (BiGREX) with integrated human hip and knee joints. The results with 12 healthy subjects demonstrated that the system’s compliance can be effectively adjusted while guiding the subjects walking in predefined trajectories. Note to Practitioners —This article was motivated by achieving compliant interaction between PM-actuated exoskeletons and human when conducting task-specific gait training. Due to the intrinsic nonlinearity of PM, it is challenging to establish a mathematical model to precisely predict real-time compliance of the powered joints. This article suggests a new strategy that adopts the average pressure of flexor and extensor PMs as the feedback to synchronously realize the joint position control and compliance regulation. A novel experimental approach was adopted to validate the system capability on adjusting the compliance from human users’ perception. This article provides a new insight between the controlled PM pressure and the desired joint compliance, which would be essential for the future design of PM-actuated exoskeletons.

A new lower limb portable exoskeleton for gait assistance in neurological patients: a proof of concept study

BackgroundFew portable exoskeletons following the assist-as-needed concept have been developed for patients with neurological disorders. Thus, the main objectives of this proof-of-concept study were 1) to explore the safety and feasibility of an exoskeleton for gait rehabilitation in stroke and multiple sclerosis patients, 2) to test different algorithms for gait assistance and measure the resulting gait changes and 3) to evaluate the user’s perception of the device.MethodsA cross-sectional study was conducted. Five patients were recruited (4 patients with stroke and 1 with multiple sclerosis). A robotic, one-degree-of-freedom, portable lower limb exoskeleton known as the Marsi Active Knee (MAK) was designed. Three control modes (the Zero Force Control mode, Mode 1 and Mode 3) were implemented. Spatiotemporal gait parameters were measured by the 10-m walking test (10MWT), the Gait Assessment and Intervention Tool (G.A.I.T.) and Tinetti Performance Oriented Mobility Assessment (gait subscale) before and after the trials. A modified QUEST 2.0 questionnaire was administered to determine each participant’s opinion about the exoskeleton. The data acquired by the MAK sensors were normalized to a gait cycle, and adverse effects were recorded.ResultsThe MAK exoskeleton was used successfully without any adverse effects. Better outcomes were obtained in the 10MWT and G.A.I.T. when Mode 3 was applied compared with not wearing the device at all. In 2 participants, Mode 3 worsened the results. Additionally, Mode 3 seemed to improve the 10MWT and G.A.I.T. outcomes to a greater extent than Mode 1. The overall score for the user perception of the device was 2.8 ± 0.4 95% CI.ConclusionsThe MAK exoskeleton seems to afford positive preliminary results regarding safety, feasibility, and user acceptance. The efficacy of the MAK should be studied in future studies, and more advanced improvements in safety must be implemented.