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The purpose of this paper is to evaluate three categories of four-degrees of freedom (4-DOFs) upper limb rehabilitation exoskeleton mechanisms from the perspective of relative movement offsets between the upper limb and the exoskeleton, so as to provide reference for the selection of exoskeleton mechanism configurations.

According to the configuration synthesis and optimum principles of 4-DOFs upper limb exoskeleton mechanisms, three categories of exoskeletons compatible with upper limb were proposed. From the perspective of human exoskeleton closed chain, through reasonable decomposition and kinematic characteristics analysis of passive connective joints, the kinematic equations of three categories exoskeletons were established and inverse position solution method were addressed. Subsequently, three indexes, which can represent the relative movement offsets of human–exoskeleton were defined.

Based on the presented position solution and evaluation indexes, the joint displacements and relative movement offsets of the three exoskeletons during eating movement were compared, on which the kinematic characteristics were investigated. The results indicated that the second category of exoskeleton was more suitable for upper limb rehabilitation than the other two categories.

This paper has a certain reference value for the selection of the 4-DOFs upper extremity rehabilitation exoskeleton mechanism configurations. The selected exoskeleton can ensure the safety and comfort of stroke patients with upper limb dyskinesia during rehabilitation training.

The purpose of this paper is to investigate the mechanical, kinematic and biological aspects that would be required for a customized upper limb exoskeleton prototype operation.

The research contained a literature survey, design, simulation, development and testing of an exoskeleton arm.

An adjustable/customizable exoskeleton arm was developed with a kinematic model to allow the desired motion. Tests were performed to determine the feasibility of the system.

The paper shows how the authors researched, designed and developed an exoskeleton arm that had similar mechanical properties to those of a biological arm. The exoskeleton must allow customization and be adaptable to the operator, without the need for major alterations.

The purpose of this review paper is to address the substantial challenges of the outdated exoskeletons used for rehabilitation and further study the current advancements in this field. The shortcomings and technological developments in sensing the input signals to enable the desired motions, actuation, control and training methods are explained for further improvements in exoskeleton research.

Search platforms such as Web of Science, IEEE, Scopus and PubMed were used to collect the literature. The total number of recent articles referred to in this review paper with relevant keywords is filtered to 143.

Exoskeletons are getting smarter often with the integration of various modern tools to enhance the effectiveness of rehabilitation. The recent applications of bio signal sensing for rehabilitation to perform user-desired actions promote the development of independent exoskeleton systems. The modern concepts of artificial intelligence and machine learning enable the implementation of brain–computer interfacing (BCI) and hybrid BCIs in exoskeletons. Likewise, novel actuation techniques are necessary to overcome the significant challenges seen in conventional exoskeletons, such as the high-power requirements, poor back drivability, bulkiness and low energy efficiency. Implementation of suitable controller algorithms facilitates the instantaneous correction of actuation signals for all joints to obtain the desired motion. Furthermore, applying the traditional rehabilitation training methods is monotonous and exhausting for the user and the trainer. The incorporation of games, virtual reality (VR) and augmented reality (AR) technologies in exoskeletons has made rehabilitation training far more effective in recent times. The combination of electroencephalogram and electromyography-based hybrid BCI is desirable for signal sensing and controlling the exoskeletons based on user intentions. The challenges faced with actuation can be resolved by developing advanced power sources with minimal size and weight, easy portability, lower cost and good energy storage capacity. Implementation of novel smart materials enables a colossal scope for actuation in future exoskeleton developments. Improved versions of sliding mode control reported in the literature are suitable for robust control of nonlinear exoskeleton models. Optimizing the controller parameters with the help of evolutionary algorithms is also an effective method for exoskeleton control. The experiments using VR/AR and games for rehabilitation training yielded promising results as the performance of patients improved substantially.

Robotic exoskeleton-based rehabilitation will help to reduce the fatigue of physiotherapists. Repeated and intention-based exercise will improve the recovery of the affected part at a faster pace. Improved rehabilitation training methods like VR/AR-based technologies help in motivating the subject.

The paper describes the recent methods for signal sensing, actuation, control and rehabilitation training approaches used in developing exoskeletons. All these areas are key elements in an exoskeleton where the review papers are published very limitedly. Therefore, this paper will stand as a guide for the researchers working in this domain.

This paper aims to propose a novel system design and control algorithm of lower limb exoskeleton, which provides walking assistance and load sharing for the wearer.

In this paper, the valve-controlled asymmetrical hydraulic cylinder is selected for driving the hip and knee joint of exoskeleton. Pressure shoe is developed that purpose on detecting changes in plantar force, and a fuzzy recognition algorithm using plantar pressure is proposed. Dynamic model of the exoskeleton is established, and the sliding mode control is developed to implement the position tracking of exoskeleton. A series of prototype experiments including benchtop test, full assistance, partial assistance and loaded walking experiments are set up to verify the tracking performance and power-assisted effect of the proposed exoskeleton.

The control performance of PID control and sliding mode control are compared. The experimental data shows the tracking trajectories and tracking errors of sliding mode control and demonstrate its good robustness to nonlinearities. sEMG of the gastrocnemius muscle tends to be significantly weakened during assisted walking.

In this paper, a structure that the knee joint and hip joint driven by the valve-controlled asymmetrical cylinder is used to provide walking assistance for the wearer. The sliding mode control is proposed to deal with the nonlinearities during joint rotation and fluids. It shows great robustness and frequency adaptability through experiments under different motion frequencies and assistance modes. The design and control method of exoskeleton is a good attempt, which takes positive impacts on the productivity or quality of the life of wearers.

The purpose of this paper is to present the control methods of the exoskeleton robotic arm for stroke rehabilitation.

The robotic arm is driven by the pneumatic muscle actuators. The control system provides independent control for the robot. The joint axes of the robotic arm are arranged to mimic the natural upper limb workspace.

Findings are the classification of training modes and control methods of rehabilitation training, and the characters of both the instant spasm and the sustaining one.

This paper is a preliminary step in the control system and the kinematical characteristics should be analyzed to achieve high precision of movement.

Based on a hierarchical structure, the control system allows the execution of sequence of switching control methods: position, force, force/position and impedance. Patient‐active‐robot‐passive and patient‐passive‐robot‐active (PPRA) training modes are also presented in this paper. In PPRA mode, the robotic arm can provide pre‐specified resistances on the patient's arm. Both instant and sustaining spasms are taken into account for safety.

The purpose of this paper is to improve the problem of kinematics incompatibility of human–exoskeleton in the existing rigid lower-limb exoskeleton (LLE).

In this paper, following an introduction, the motion characteristics of the human knee joint and the design method of the exoskeleton were introduced. A kinematics model of the LLE based on cross-four-bar linkage was obtained. The structural parameters of the LLE mechanism were optimized by the particle swarm optimization algorithm. The predefined trajectories used in the optimization process were derived from the ankle joint, not the instantaneous center of rotation of the knee joint. Finally, the motion deviation of the optimization result was simulated, and the human–exoskeleton coordination experiment was designed to compare with the traditional single-axis knee joint in terms of comfort and coordination.

The lower limb exoskeleton mechanism obtained in this paper has a good tracking effect on human movement and has been improved in terms of comfort and coordination compared with the traditional single-axis knee joint.

The customized exoskeleton design method introduced in this paper is relatively simple, and the obtained exoskeleton has better movement coordination than the traditional exoskeleton. It can provide a reference for the design of lower limb exoskeleton and lower limb orthosis.

In certain industrial operations, workers are required to stand for a prolonged duration. This leads to muscular fatigue in the legs, posing a threat to the productivity and well-being of the workers. This paper aims to address this problem of women in the clothing industry with an exoskeleton designed for lower extremities and improve productivity.

Ulrich’s product design approach has been followed with suitable modifications. The methodology involves a study to justify the need for this product and terminating at the physical and virtual evaluations of the product. Required anthropometric parameters are considered along the design process.

The exoskeleton discussed in this paper is an innovative product made of Aluminium 6061 alloy. During the simulation phase of the product, total von-mises stresses to a part bearing 1 leg were 31.5 MPa, 94.7 MPa and 284 MPa for aluminium, SS308 and springs, respectively. These values are below the yield limit by a great margin. Based on a user survey of this product, 72% of the targeted customers were interested in buying. Also, comparing electromyography (EMG) mean value of the voltage between workers’ leg with and without exoskeleton revealed that there was an improvement in the voltage by 2.5% when exoskeleton was used.

This paper emphasizes, for the first time – the necessity of an exoskeleton indigenized for the Indian population and the process of realizing it by designing an exoskeleton.

Upper-limb joint kinematics are highly complex and the kinematics of rehabilitation exoskeletons fail to reproduce them, resulting in hyperstaticity and human–machine incompatibility. The purpose of this paper is to design and develop a compatible exoskeleton robot (Co-Exos II) to address these problems.

The configuration synthesis of Co-Exos II is completed using advanced mechanism theory. A compatible configuration is selected and four passive joints are introduced into the connecting interfaces based on optimal configuration principles. A Co-Exos II prototype with nine degrees of freedom (DOFs) is developed and still owns a compact structure and volume. A new approach is presented to compensate the vertical glenohumeral (GH) movements. Co-Exos II and the upper arm are simplified as a guide-bar mechanism at the elevating plane. The theoretical displacements of passive joints are calculated by the kinematic model of the shoulder loop. The compatible experiments are completed to measure the kinematics of passive joints.

The compatible configuration of the passive joints can effectively reduce the gravity influences of the exoskeleton device and the upper extremities. The passive joints exhibit excellent compensation effect for the GH joint movements by comparing the theoretical and measured results. Passive joints can compensate for most GH movements, especially vertical movements.

Co-Exos II possesses good human–machine compatibility and wearable comfort for the affected upper limbs. The proposed compensation method is convenient to therapists and stroke patients during the rehabilitation trainings.

This paper aims to design and control of a novel compact transportation system called the “wearable vehicle”. The wearable vehicle allows for traversing all types of terrains while transporting one's luggage in a comfortable and efficient manner.

The proposed design consists of a lower limb exoskeleton carrying two motorized wheels and two free wheels installed alongside its feet. This paper presents a detailed description of the system with its preliminary design and finite element analysis. Moreover, the system has been optimally designed to decrease wearable vehicle’s total weight, consequently leading to a reduction in motor size. Finally, two controllers have been designed to achieve stable operation of the wearable vehicle while walking. A PD controller with gravity compensation has been designed to ensure that the wearable vehicle tracks human motion, while a PID controller has been designed to ensure that the zero moment point is close to the center of the system’s support polygon.

Experimental tests were carried out to check the wearable vehicle concept. The obtained results prove the feasibility of the proposed wearable vehicle from the design, dynamics and control viewpoints.

This proposed wearable vehicle’s purpose is for traveling faster with less effort than normal walking. When a human comes across a flat open ground, the wearable vehicle can be used as a vehicle. However, when a human enters crowded traffic, an unstructured area or other obstacles like stairs, the vehicle can be switched into walking mode.

The wearable vehicle has seven DOFs exoskeletons, two motorized wheels, two free wheels and a foldable seat. It is used as a vehicle via its motorized and free wheels to travel fast with minimal effort. In addition, the human can switch easily into walking mode, if there is unstructured terrain to be traversed. Furthermore, an illustration of system's mechanisms and main feature parameters are presented to become acquainted with the ultimate benefits of the new system.

This paper aims to get rid of the traditional basic principle of using the motor as the variable stiffness drive source, simplify the structure of the exoskeleton and reduce the quality of the exoskeleton. This paper proposes to use shape memory alloys (SMA) as the variable stiffness drive source.

In this study, SMA is used to construct the active variable stiffness unit, the Brinson constitutive model is used to establish a dynamic model to control the active variable stiffness unit and the above active variable stiffness unit is used to realize the force control function and construct a lightweight, variable stiffness knee exoskeleton.

The dynamic model constructed in this paper can preliminarily describe the phase transformation process of the active variable stiffness unit and realize the variable stiffness function of the knee exoskeleton. The variable stiffness exoskeleton can effectively reduce the driving error under the high-speed walking condition.

The contribution of this paper is to combine SMAs to construct an active variable stiffness unit, build a dynamic model for controlling the active variable stiffness unit and construct a lightweight, variable stiffness knee exoskeleton.