Rehabilitation Exoskeleton Research Articles

Towards the Mechatronic Development of a New Upper-Limb Exoskeleton (SAMA)

Modern neuromuscular rehabilitation engineering and assistive technology research have been constantly developing in the last 20 years. The upper body exoskeleton is an example of an assistive rehabilitation device. However, in order to solve its technological problems, interdisciplinary research is still necessary. This paper presents a new three-degrees of freedom (DOF) active upper-body exoskeleton for medical rehabilitation named “SAMA”. Its mechanical structure is inspired by the geometry and biomechanics of the human body, particularly the ranges of motion (ROM) and the needed torque. The SAMA exoskeleton was manufactured and assembled into an ergonomic custom-made wheelchair in a sitting posture in order to provide portability and subject comfort during experimental testing and rehabilitation exercises. Dynamic modeling using MATLAB–Simulink was used for calculating the inverse kinematics, dynamic analysis, trajectory generation and implementation of proportional–integral–derivative (PID) computed torque control (PID-CTC). A new framework has been developed for rapid prototyping (the dynamic modeling, control, and experimentation of SAMA) based on the integration between MATLAB–Simulink and the Robot Operating System (ROS) environment. This framework allows the robust position and torque control of the exoskeleton and real-time monitoring of SAMA and its subject. Two joints of the developed exoskeleton were successfully tested experimentally for the desired arm trajectory. The angular position and torque controller responses were recorded and the exoskeleton joints showed a maximum delay of 200° and a maximum steady state error of 0.25°. These successful results encourage further development and testing for different subjects and more control strategies.

Adaptive cooperative control of a soft elbow rehabilitation exoskeleton based on improved joint torque estimation

A current challenge with robot-assisted rehabilitation is to combine the active involvement and voluntary participation of patients into the rehabilitation training process to enhance therapy outcome. This paper presents a soft elbow exoskeleton for the rehabilitation training of disabled patients. An adaptive cooperative control strategy is investigated to promote active participation based on an improved joint torque estimation method and a time-delay sliding mode control scheme. The surface electromyography signals from biceps and triceps are input into a Hill-type musculoskeletal model and a Gaussian radial basis functional network to estimate human elbow joint torque and motion intention. The joint torque estimation experiment, intention-based trajectory following experiment and patient-active free-motion training experiment are carried out by five healthy volunteers and five stroke patients to evaluate the performance of proposed control strategy. The results indicate that the proposed scheme can guarantee the joint torque estimation accuracy and position control accuracy. Moreover, it allow patients to actively dominate the training path based on their motion intention with different training intensity.

Three-Dimensional Printing Component Used in Rehabilitation Exoskeleton

This work aims to develop a light symmetrical structure that can be realized through rapid prototyping techniques. The structure must meet some restrictions imposed by possible practical applications. It must withstand a moderate load, be able to adapt to a specific external shape, be relatively light, allow the execution of some changes according to user requirements, allow execution with the help of owned equipment, and allow relatively fast production (its structure and form). The major application for which the structure is designed is that of an exoskeleton for medical rehabilitation, realized by the authors. The creation of such an exoskeleton is followed by a series of research regarding different aspects of acceptability, reliability, ease of use, and the shortcomings that such a structure can cause. In this study, the authors focused on the mechanical part of the exoskeleton realization, which would fulfill some imposed kinematic and constructive conditions.

Development of an EMG-based Elbow- Exoskeleton with Twisted String Actuation

Abstract This paper presents an exoskeleton for upper extremity rehabilitation of stroke patients. In order to make rehabilitation widely available, the goal is an inexpensive, portable, and easy-to-use therapy for paralysis of the arm. The exoskeleton is actuated by twisted string actuators (TSA). To reduce the length of the TSA a motor with hollow shaft was chosen, as this allows the string to run through the motor. The control of the exoskeleton is designed for predefined elbow flexion exercises. The start of the movement is triggered by a threshold value in the sEMG of the m. biceps brachii. To evaluate the controller, the exoskeleton performed a flexion movement (5° to 115°) in 2 s and then an extension back to 5° in the same time after a 1 s wait. To simulate different force requirements, additional weights up to 1500 g were attached. During both, the flexion and extension movement, that angle tracking error was sufficiently small and the steady state error was zero. The angular velocity of the elbow joint showed pronounced oscillations with increasing weights. The results show that TSAs can be used to actuate elbow exoskeletons. Thus lightweight, ergonomic, simple and small rehabilitation devices can now be built on this basis. The elasticity of the system must be considered in future work. sEMG must be further implemented to control more sophisticated functions of the rehabilitation device.

Neuromusculoskeletal modeling-based evaluation of physical treatment outcomes: Assessing how an exoskeleton rehabilitation treatment affects people with PD

Neuromusculoskeletal modeling-based evaluation of physical treatment outcomes: Assessing how an exoskeleton rehabilitation treatment affects people with PD

Flatness tracking control scheme of rehabilitation exoskeleton robot with dynamic uncertainties

Artificial limbs are new robotic devices created to help stroke victims in the rehabilitation process. In this article, we focus our work on applying passive, active or assistive control strategies to provide a physical assistance and rehabilitation by a 7-degree-of-freedom exoskeleton robot with nonlinear uncertain dynamics and unknown bounded external disturbances due to the robot user’s physiological characteristics. The flatness controller combined with time-delay estimation is designed for the 7-degree-of-freedom exoskeleton robot called ETS-MARSE (Ecole de Technologie Supérieure—Motion Assistive Robotic-exoskeleton for Superior Extremity) in order to ensure a passive rehabilitation exercises with a high level of tracking accuracy and robustness against the uncertainty constraints. The stability analysis of such systems is proven using the Lyapunov–Krasovskii functional theory. This approach is illustrated by experimental results with healthy human to highlight the efficiency of the suggested controller scheme.

The Wearable Lower Limb Rehabilitation Exoskeleton Kinematic Analysis and Simulation.

In recent years, due to the increase in the incidence of traffic accidents, the number of people with limb injuries has also increased. At the same time, among the aging population, neurological diseases or cardiovascular and cerebrovascular diseases have caused many people to have limb hemiplegia. It has been clinically proven that the use of rehabilitation equipment can help patients with limb injuries to restore limb motor function. This paper takes wearable lower limb rehabilitation exoskeleton as the research object, and its main contents are mechanical structure design, kinematics analysis, gait planning, virtual prototype simulation, and experimental verification and analysis. Based on the physiological characteristics of human body and the principle of comfortable and reliable wearing, this paper designs wearable exoskeleton for lower limb rehabilitation. Firstly, the physiological structure characteristics and movement mechanism of human lower limbs were studied and analyzed. By referring to the rotation range and height and size of each joint of human lower limbs, the overall scheme of wearable lower limb rehabilitation exoskeleton was designed and the degree of freedom was allocated. At the same time, Solidworks was used to establish a three-dimensional model. On the basis of a 3D model, a kinematics model was established, and the forward kinematics solution was obtained by using homogeneous coordinate transformation. Since the inverse kinematics solution was relatively complicated, the inverse kinematics solution was conducted in this paper according to the geometric relations of the joints of the lower limbs. Kinematics analysis of the exoskeleton structure of wearable lower limb rehabilitation was carried out to lay a theoretical foundation for gait planning. The off-line gait planning was carried out by using the method based on ZMP stability criterion, and the gait planning was divided into five stages: squat, start, middle step, stop and rise, and the motion trajectory of the center of mass and ankle joint was planned. Based on the inverse kinematics formula, the function of the change of joint angle with time in walking process is derived. The virtual prototype is established in ADAMS, and the simulation of virtual prototype is carried out by using the function of gait planning's joint angle and time. The correctness of structural design and gait planning was verified by measuring the trajectories of the centroid and ankle joints in each gait stage and the functional relationship between the rotation angle of each joint and time. Then, using a 3D dynamic capture system to capture the human lower limb motion trajectory of each joint, each joint trajectory data output, using the MATLAB software to output data, gets the joint trajectory change over time function curve and is used to verify feasibility and applicability of human gait planning. Through the research and analysis of the joints of the lower limbs of the human body, it can be concluded that the hip joint and the knee joint have 3 degrees of freedom, respectively, and the knee joint has 1 degree of freedom.

Joint-Angle Adaptive Coordination Control of a Serial-Parallel Lower Limb Rehabilitation Exoskeleton

A serial–parallel lower limb rehabilitation exoskeleton can achieve a kinematic function similar to that of the human lower limb. Based on this bionic structure, joint-angle coordination is needed for model-based control. Because the kinematics of the parallel mechanism is difficult to solve, real-time attitude control of the task space cannot be realized. Moreover, owing to structural errors and parameter uncertainty, accurate modeling cannot be realized, which causes difficulties in system control. Therefore, based on existing modeling methods, adaptive control of a serial–parallel lower limb rehabilitation exoskeleton is proposed. The sensor of the parallel mechanism can realize accurate perception of the attitude, and the controller is designed to solve the control problem of the task space of the parallel component. A radial basis function neural network adaptive controller is used to compensate for the uncertainty and external disturbance of the model. Experiments were conducted to verify the effectiveness of the dynamic modeling and control system.

AGREE: an upper-limb robotic platform for personalized rehabilitation, concept and clinical study design.

Rehabilitation exoskeletons can supplement therapist-based training allowing post-stroke patients to perform functional, high-dosage, repetitive exercises. The use of robotic devices allows providing intense rehabilitation sessions and permits clinicians to personalize the therapy according to the patient's need. In this work, we propose an upper-limb rehabilitation system developed within the AGREE project. The platform relies on a four degrees-of-freedom arm exoskeleton, capable of assisting state-of-the-art rehabilitation exercises under different training modalities while behaving transparently to user-generated and therapist-applied forces. The system is provided with a LEDs-matrix mat to guide patients during reaching tasks with visual feedback, an EMG reader to evaluate the patient's involvement during the therapy, and several software tools to help clinicians customize the treatment and monitor the patient's progress. A randomized controlled pilot study aimed at evaluating the usability and the effectiveness of the AGREE rehabilitation platform to improve arm impairment after stroke is currently ongoing.

Feedback-Error Learning for time-effective gait trajectory tracking in wearable exoskeletons.

The use of exoskeletons in gait rehabilitation implies user-oriented and efficient responses of exoskeletons' controllers with adaptability for human-robot interaction. This study investigates the performance of a bioinspired hybrid control, the Feedback-Error Learning (FEL) controller, to time-effectively track user-oriented gait trajectories and adapt the exoskeletons' response to dynamic changes due to the interaction with the user. It innovates with a controller benchmarking analysis. FEL combines a proportional-integral-derivative (PID) feedback controller with a three-layer neural network feedforward controller that learns the inverse dynamics of the exoskeleton based on real-time feedback commands. FEL validation involved able-bodied subjects walking with knee and ankle exoskeletons at different gait speeds while considering gait disturbances. Results showed that the FEL control accurately (tracking error <7%) and timely (delay <30 ms) tracked gait trajectories. The feedforward controller learned the inverse dynamics of the exoskeletons in a time compliant for clinical use and adapted to variations in the gait trajectories, such as speed and position range, while the feedback controller compensated for random disturbances. FEL was more accurate and time-effective controller for tracking gait trajectories than a PID control (error <27%, delay <260 ms) and a lookup table feedforward combined with PID control (error <17%, delay >160 ms). These findings aligned with FEL's time-effectiveness favors its use in wearable exoskeletons for repetitive gait training.

Toward Avoiding Misalignment: Dimensional Synthesis of Task-Oriented Upper-Limb Hybrid Exoskeleton

One of the primary reasons for wearable exoskeleton rejection is user discomfort caused by misalignment between the coupled system, i.e., the human limb and the exoskeleton. The article focuses primarily on the solution strategies for misalignment issues. The purpose of this work is to facilitate rehabilitative exercise-based exoskeletons for neurological and muscular disorder patients, which can aid a user in following the appropriate natural trajectory with the least amount of misalignment. A double four-bar planar configuration is used for this purpose. The paper proposes a methodology for developing an optimum task-oriented upper-limb hybrid exoskeleton with low active degrees-of-freedom (dof) that enables users to attain desired task space locations (TSLs) while maintaining an acceptable range of kinematic performance. Additionally, the study examines the influence of an extra restriction placed at the elbow motion and the compatibility of connected systems. The findings and discussion indicate the usefulness of the proposed concept for upper-limb rehabilitation.

Assessment of Soft Actuators for Hand Exoskeletons: Pleated Textile Actuators and Fiber-Reinforced Silicone Actuators.

Soft robotic approaches have been trialed for rehabilitation or assistive hand exoskeletons using silicone or textile actuators because they have more tolerance for alignment with biological joints than rigid exoskeletons. Textile actuators have not been previously evaluated, and this study compares the mechanical properties of textile and silicone actuators used in hand exoskeletons. The physical dimensions, the air pressure required to achieve a full bending motion, and the forces generated at the tip of the actuator were measured and compared. The results showed that the construction method of the silicone actuators is slower than the textile actuators, but it generates better dimensional accuracy. However, the air pressure required for the actuators to generate a full bending motion is significantly lower for textile actuators, and the blocking force generated at that pressure is 35% higher in the textile actuators. There are significant differences across all variables compared, indicating that actuators constructed using pleated textile techniques have greater potential for the construction of an exoskeleton for hand rehabilitation or assistance.

Design and analysis of a lightweight lower extremity exoskeleton with novel compliant ankle joints.

The exoskeleton for lower limb rehabilitation is an uprising field of robot technology. However, since it is difficult to achieve all the optimal design values at the same time, each lower extremity exoskeleton has its own focus. This study aims to develop a modular lightweight lower extremity exoskeleton (MOLLEE) with novel compliant ankle joints, and evaluate the movement performance through kinematics analysis. The overall structure of the exoskeleton was proposed and the adjustable frames, active joint modules, and compliant ankle joints were designed. The forward and inverse kinematics models were established based on the geometric method. The theoretical models were validated by numerical simulations in ADAMS, and the kinematic performance was demonstrated through walking experiments. The proposed lower extremity offers six degrees of freedom (DoF). The exoskeleton frame was designed adjustable to fit wearers with a height between 1.55m and 1.80m, and waist width from 37cm to 45cm. The joint modules can provide maximum torque at 107Nm for adequate knee and hip joint motion forces. The compliant ankle can bear large flexible deformation, and the relationship between its angular deformation and the contact force can be fitted with a quadratic polynomial function. The kinematics models were established and verified through numerical simulations, and the walking experiments in different action states have shown the expected kinematic characteristics of the designed exoskeleton. The proposed MOLLEE exoskeleton is adjustable, modular, and compliant. The designed adjustable frame and compliant ankle can ensure comfort and safety for different wearers. In addition, the kinematics characteristics of the exoskeleton can meet the needs of daily rehabilitation activities.

Exoskeletons in MS rehabilitation are ready for widespread use in clinical practice: Commentary

Exoskeletons in MS rehabilitation are ready for widespread use in clinical practice: Commentary

Exoskeletons in MS rehabilitation are ready for widespread use in clinical practice: Yes

Exoskeletons in MS rehabilitation are ready for widespread use in clinical practice: Yes

NESM-γ: An Upper-Limb Exoskeleton With Compliant Actuators for Clinical Deployment

This letter describes the design and characterization of an upper-limb exoskeleton for post-stroke rehabilitation. The platform interacts with the shoulder and elbow of the user through four active joints, driven by series elastic actuators (SEAs) with custom springs to achieve compactness and ease of maintenance. The exoskeleton adopts a passive kinematic chain for aligning the user's and robot joints’ rotation axes, and a quick flipping mechanism to enable dual-side use. The pole-placement method based on the dynamic model of the SEA was used to design the low-level controller, to guarantee torque control precision and stability. The joint load due to the robot's gravity is counteracted by using a feed-forward gravity compensation algorithm. Experimental characterization demonstrates the torque control bandwidth up to 10 Hz and highly transparent behavior of the joints (namely, close to null parasitic impedance) at least up to 2 Hz, showing suitability for rehabilitation purposes.

Robust Iterative Learning Control Algorithm for Lower Limb Rehabilitation Proactive Human-robot Collaboration

At present, the motion control algorithms of lower limb exoskeleton robots have errors in tracking the desired trajectory of human hip and knee joints, which leads to poor follow-up performance of the human-machine system. Therefore, an iterative learning control algorithm is proposed to track the desired trajectory of human hip and knee joints. In this paper, the experimental platform of lower limb exoskeleton rehabilitation robot is built, and the control system software and hardware design and robot prototype function test are carried out. On this basis, a series of experiments are carried out to verify the rationality of the robot structure and the feasibility of the control method. Firstly, the dynamic model of the lower limb exoskeleton robot is established based on the structure analysis of the human lower limb; secondly, the servo control model of the lower limb exoskeleton robot is established based on the iterative learning control algorithm; finally, the exponential gain closed-loop system is designed by using MATLAB software. The relationship between convergence speed and spectral radius is analyzed, and the expected trajectory of hip joint and knee joint is obtained. The simulation results show that the algorithm can effectively improve the gait tracking accuracy of the lower limb exoskeleton robot and improve the follow-up performance of the human-machine system.

Development of an Exoskeleton Platform of the Finger for Objective Patient Monitoring in Rehabilitation.

This paper presents the application of an adaptive exoskeleton for finger rehabilitation. The system consists of a force-controlled exoskeleton of the finger and wireless coupling to a mobile application for the rehabilitation of complex regional pain syndrome (CRPS) patients. The exoskeleton has sensors for motion detection and force control as well as a wireless communication module. The proposed mobile application allows to interactively control the exoskeleton, store collected patient-specific data, and motivate the patient for therapy by means of gamification. The exoskeleton was applied to three CRPS patients over a period of six weeks. We present the design of the exoskeleton, the mobile application with its game content, and the results of the performed preliminary patient study. The exoskeleton system showed good applicability; recorded data can be used for objective therapy evaluation.

Review of Key Technologies for Developing Personalized Lower Limb Rehabilitative Exoskeleton Robots

Review of Key Technologies for Developing Personalized Lower Limb Rehabilitative Exoskeleton Robots

A Framework for Determining the Performance and Requirements of Cable-Driven Mobile Lower Limb Rehabilitation Exoskeletons.

The global increase in the number of stroke patients and limited accessibility to rehabilitation has promoted an increase in the design and development of mobile exoskeletons. Robot-assisted mobile rehabilitation is rapidly emerging as a viable tool as it could provide intensive repetitive movement training and timely standardized delivery of therapy as compared to conventional manual therapy. However, the majority of existing lower limb exoskeletons continue to be heavy and induce unnecessary inertia and inertial vibration on the limb. Cable-driven exoskeletons can overcome these issues with the provision of remote actuation. However, the number of cables and routing can be selected in various ways posing a challenge to designers regarding the optimal design configuration. In this work, a simulation-based generalized framework for modelling and assessment of cable-driven mobile exoskeleton is proposed. The framework can be implemented to identify a ‘suitable’ configuration from several potential ones or to identify the optimal routing parameters for a given configuration. For a proof of concept, four conceptual configurations of cable-driven exoskeletons (one with a spring) were developed in a manner where both positive and negative moments could be generated for each joint (antagonistic configuration). The models were analyzed using the proposed framework and a decision metric table has been developed based on the models’ performance and requirements. The weight of the metrics can be adjusted depending on the preferences and specified constraints. The maximum score is assigned to the configuration with minimum requirement or error, maximum performance, and vice versa. The metric table indicated that the 4-cable configuration is a promising design option for a lower limb rehabilitation exoskeleton based on tracking performance, model requirements, and component forces exerted on the limb.