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For assisting the daily lives of the elderly or patients with abnormal walking by hemiplegia, wearable robots which are constructed with relatively soft materials such as cable-driven method are being actively developed and partially commercialized. The main advantage is that the flexible power transmission system could distribute the inertia of the distal area, which is essential for stabilizing the gait balance. However, in flexible power transmission system, it has disadvantage that it cannot directly measure the tension applied to the patients. Therefore, tension measurement device on the assisting point is required for generating precise assistance on the patients. But adding the tension measuring device is challenging because it increases complexity and inertia. The main factor for inaccurate force transmission is the unpredictable friction from the transmission cable's varying curvature in human motion. In this paper, a methodology of design and control of reaction force-based series elastic actuator is proposed to generate the precise assistive force at the actuating module while maintaining the overall weight small. The mechanical elements of Series Elastic Actuator are designed with the optimal specifications required for stroke patient assistance. The compactness and weight reduction are also guaranteed by designing the mechanical elements with optimal specifications, which enables assisting the patients with minimal gravitational load. Furthermore, periodic friction compensation is done through experiments by using feedforward compensator, which adjusts the corresponding loss, linked with the estimated gait phase. Therefore, even in the presence of friction loss in the cable, application of precise torque at the end-effector became possible. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a clothing-type platform of wearable robots for industrial workers who usually lift loads to prevent accidents and increase their work efficiency. First, fabrics were selected through test analyses of the elongation recovery rate and tensile strength. Second, a suit-type platform embedded with electrostatic clutch band actuators was prototyped and measured the friction force, and a washing dimension change rate of the test with the platform was conducted. Third, clothing pressures were measured after the developed prototype was worn, using an air injection sensor system at nine points and with four motions. Next, subjective clothing pressure and satisfaction surveys were conducted. The study produced four major results: (a) the selected fabrics and the prototype with the electro)static clutch actuator met the performance requirements; (b) the greatest clothing pressure occurred at the back, back waist, and back knee, where actuators were connected, and the clothing pressure was sufficient for positional stability; (c) the subjective pressure was different in each section from the actual clothing pressure measurement; and (d) participants were satisfied with the developed prototypes, and they showed willingness to purchase them. The results can help developers of wearable robots increase comfort and user satisfaction. [ABSTRACT FROM AUTHOR]

Soft wearable robots are attracting immense attention owing to their high usability and wearability. In particular, studies on soft exosuits have achieved remarkable progress. Walking is one of the most basic human actions in daily life. During walking, the ankle joint has considerable influence. Therefore, an exosuit design paradigm having a light and simple structure was developed with the goal of fabricating a soft exosuit that supports the ankle. The new exosuit matches the performance of existing exosuits while being as comfortable as everyday wear. A walking test through a combination with a mobile actuator system, which can maximize these advantages, was also conducted. The combination with the mobile system demonstrates the potential of using the new ankle exosuit as inner wear that maximizes the advantages of a lighter and simpler design. The exosuit design paradigm could serve as an effective guideline for manufacturing assistive exosuits for various body parts in the future. [ABSTRACT FROM AUTHOR]

An FDA-approved soft wearable robot, the Myosuit, which was designed to provide hip and knee extension torque has recently been commercialized. While studies have reported reductions in metabolic costs, increased gait speeds, and improvements in clinical test scores, a comprehensive analysis of electromyography (EMG) signals and joint kinematics is warranted because the recruitment of appropriate muscle groups during physiological movement patterns facilitates effective motor learning. Here, we compared the lower limb joint kinematics and EMG patterns while wearing the Myosuit with that of unassisted conditions when performing level overground and incline treadmill gait. The level overground gait sessions (seven healthy subjects) were performed at self-selected speeds and the incline treadmill gait sessions (four healthy subjects) were performed at 2, 3, 4, and 5 km/h. In order to evaluate how the user is assisted, we conducted a biomechanical analysis according to the three major gait tasks: weight acceptance (WA), single-limb support, and limb advancement. The results from the gait sessions suggest that Myosuit not only well preserves the users' natural patterns, but more importantly reduce knee extensor demand during the WA phase for both level and incline gait. [ABSTRACT FROM AUTHOR]

It has been clinically proven that exoskeletons are effective self-training rehabilitation or daily living assistance devices for patients with hand dysfunctions. However, exoskeleton-assisted hand exercises with high degrees-of-freedom are considered as challenging tasks because the digit space, especially the thumb, cannot accommodate enough actuators. In this article, we report a tendon-driven soft hand exoskeleton with a hybrid configuration for thumb actuation. The soft hand exoskeleton system uses the least number of actuators to realize full degrees-of-freedom actuation for all digits. It is tested on a stroke patient with hemiplegia and a healthy subject. The experimental results show that the hand exoskeleton could assist the stroke patient to accomplish various training tasks, such as thumb encircling, grasping, pinching, releasing, and writing. It was found that digit trajectories and joint angle changes of the stroke patient were close to those of the healthy subject. Especially, the range of motion of the stroke patient shows significant improvement with the hand exoskeleton assistance compared to that without the hand exoskeleton assistance. The research in this article paves the way to develop fully actuated soft hand exoskeleton that can be eventually integrated with an electroencephalogram or electromyography for self-training rehabilitation or daily living assistance. [ABSTRACT FROM AUTHOR]

Tendon-driven soft wearable robots should be simple, compact, and safe because they are worn on the human body and interact directly with the human. Here, unlike rigid robots, wire pre-tension should be removed at the end-effector due to the inherent characteristics of the soft robot. In this article, for a stable and compact actuation system without pretension, a linear actuator called a slider-tendon linear actuator is proposed. The proposed actuator is designed to make a linear motion using a tendon, as compared to other linear transmissions, such as ball screw or lead screw transmissions. By using the proposed design method that uses a tendon, the actuator size was reduced to 23.6% of the size of an actuator that uses a ball screw; this is because the tendon can endure high tensile force with a small cross-section area. Furthermore, this article proposes a robot design methodology to locate the robot mechanism in the actuator, rather than in the end-effector. The proposed actuator is designed to contain a fast-connection and stroke-amplified under-actuation mechanism. In the proposed method, not only is the complexity and size of the worn part reduced, but its performance is also improved. Finally, by applying this actuator to a specific wearable robot, this paper verifies that the proposed actuator sufficiently satisfies the requirements of the wearable robot. [ABSTRACT FROM AUTHOR]

This study introduces a wearable soft knee exoskeleton that aids active knee motions during walking. It is mainly driven by vacuum-actuated rotary actuators. In this paper, the overall design of the exoskeleton is introduced. Moreover, the design of the vacuum-actuated rotary actuator is introduced, and the correspondence among the interior air pressure, rotation angle and output force of the actuator under a vacuum condition and during the transition from the vacuum to an equal atmospheric pressure condition were studied. Then, the corresponding relations among the pressure, angle and torque of the actuator were obtained to construct a knee torque model. Furthermore, we introduced in detail the control system of the exoskeleton, including a gait estimation model and knee torque model. The control system analysed knee angle information measured by IMUs and the air pressure of the actuators measured by air pressure sensors. Then, by the calculations performed by both the gait estimation model and knee torque model, the corresponding commands for the aerodynamic switch, pressures and air flow rates were determined. According to the commands, a micro air pump and valves provided quantitatively positive or negative pressure for the actuators to generate gait-consistent auxiliary torques, stretching torques and bending torques that were able to meet the needs of the knee during walking. Finally, a cardiopulmonary exercise test was used to quantitatively evaluate the exoskeleton. The results show that under the same load condition, the metabolic cost of walking is reduced by an average of 6.85% when the exoskeleton is worn.

Soft wearable robots are attracting immense attention owing to their high usability and wearability. In particular, studies on soft exosuits have achieved remarkable progress. Walking is one of the most basic human actions in daily life. During walking, the ankle joint has considerable influence. Therefore, an exosuit design paradigm having a light and simple structure was developed with the goal of fabricating a soft exosuit that supports the ankle. The new exosuit matches the performance of existing exosuits while being as comfortable as everyday wear. A walking test through a combination with a mobile actuator system, which can maximize these advantages, was also conducted. The combination with the mobile system demonstrates the potential of using the new ankle exosuit as inner wear that maximizes the advantages of a lighter and simpler design. The exosuit design paradigm could serve as an effective guideline for manufacturing assistive exosuits for various body parts in the future.

An FDA-approved soft wearable robot, the Myosuit, which was designed to provide hip and knee extension torque has recently been commercialized. While studies have reported reductions in metabolic costs, increased gait speeds, and improvements in clinical test scores, a comprehensive analysis of electromyography (EMG) signals and joint kinematics is warranted because the recruitment of appropriate muscle groups during physiological movement patterns facilitates effective motor learning. Here, we compared the lower limb joint kinematics and EMG patterns while wearing the Myosuit with that of unassisted conditions when performing level overground and incline treadmill gait. The level overground gait sessions (seven healthy subjects) were performed at self-selected speeds and the incline treadmill gait sessions (four healthy subjects) were performed at 2, 3, 4, and 5 km/h. In order to evaluate how the user is assisted, we conducted a biomechanical analysis according to the three major gait tasks: weight acceptance (WA), single-limb support, and limb advancement. The results from the gait sessions suggest that Myosuit not only well preserves the users’ natural patterns, but more importantly reduce knee extensor demand during the WA phase for both level and incline gait.

With the ongoing research on soft robots, the performance of soft actuators needs to be enhanced for more wide robotic applications. Currently, most soft robots based on pneumatic actuation are capable of assisting small systems, but they are not fully suited for supporting joints requiring large force and range of motion. This is due to the actuation characteristics of the pneumatic artificial muscle (PAM); they are relatively slow, inefficient, and experience a significant force reduction when the PAM contracts. Hence, we propose a novel PAM based on a spring-frame collateral compression mechanism. With only a single compressed air source, the external mesh-covered and inner spring-frame actuators of the proposed PAM operate simultaneously to generate considerable force. Additionally, the design of the internal actuator within the void space of PAM reduces the air consumption and consequently improves the actuator’s operating speed and efficiency. We experimentally confirmed that the proposed PAM exhibited 31.2% greater force, was 25.6% faster, and consumed 21.5% lower air compared to the conventional McKibben muscles. The performance enhancement of the proposed PAM improves the performance of soft robots, allowing the development of more compact robots with greater assistive range.

Control of a Bowden-cable transmission requires dealing with varying frictional nonlinearity of the cable, which varies as the bend angle of the cable changes and degrades the performance of the output tension control if not compensated for. This article proposes a novel method of compensating for the changing nonlinearity of the Bowden cable. The method enables controlling the tension of a Bowden cable without directly measuring the output tension. The output tension differs from the input tension because of friction along the cable, which changes with the cable's bend angle. The bend angle can be estimated by using a Bowden-cable Angle (BoA) Sensor and the input tension of the actuation wire to compensate for the friction change. Friction compensation allows for feedforward control of the output tension of the Bowden-cable transmission despite the varying shape of the cable. The results show that the control error of the output tension decrease from 5.21 to 0.50 N when the bend angle of the Bowden cable change from 0° to 400°. The proposed control method can be fully embedded into a Bowden-cable system without redesigning the original device, minimizing the complexity and size of the actuation system. A Bowden-cable implementing the proposed control method is demonstrated with a soft wearable robotic hand. [ABSTRACT FROM AUTHOR]

The size of a device and its adaptability to human properties are important factors in developing a wearable device. In wearable robot research, therefore, soft materials and tendon transmissions have been utilized to make robots compact and adaptable to the human body. However, when used for wearable robots, these methods sometimes cause uncertainties that originate from elongation of the soft material or from undefined human properties. In this research, to consider these uncertainties, we propose a data-driven method that identifies both kinematic and stiffness parameters using tension and wire stroke of the actuators. Through kinematic identification, a method is proposed to find the exact joint position as a function of the joint angle. Through stiffness identification, the relationship between the actuation force and the joint angle is obtained using Gaussian Process Regression (GPR). As a result, by applying the proposed method to a specific robot, the research outlined in this paper verifies how the proposed method can be used in wearable robot applications. This work examines a novel wearable robot named Exo-Index, which assists a human’s index finger through the use of three actuators. The proposed identification methods enable control of the wearable robot to result in appropriate postures for grasping objects of different shapes and sizes.

Tendon drives are widely used in robotics. The compliance of the tendon in such drives suits them for soft robots, including soft wearable robots, but several issues impede their use. Generally, the tendon should always maintain tension to prevent derailment from the spool. However, in soft robots, tendon tension induces high friction forces owing to the absence of ball bearings. Because the kinematics of the soft robot is basically nonlinear and changed by the deformation of the structure, the kinematic difference between the soft structure and the spool causes derailment of the tendon. Moreover, continuously maintained tension in soft wearable robots causes safety issues. The linear actuator can be an option. However, the need to increase the length of the linear actuator to accommodate the excursion length of its tendon is a barrier to its use in small-scale applications. To preclude this issue, a slack-enabling actuator that employs a spool is proposed. The space efficiency of the spool enables the mechanism to be small, and a one-way clutch applies unidirectional friction force to the tendon to tighten the tendon around the spool. This paper describes the design concept for the slack-enabling mechanism, its design optimization, and system identification for force control. [ABSTRACT FROM PUBLISHER]

With the ongoing research on soft robots, the performance of soft actuators needs to be enhanced for more wide robotic applications. Currently, most soft robots based on pneumatic actuation are capable of assisting small systems, but they are not fully suited for supporting joints requiring large force and range of motion. This is due to the actuation characteristics of the pneumatic artificial muscle (PAM); they are relatively slow, inefficient, and experience a significant force reduction when the PAM contracts. Hence, we propose a novel PAM based on a spring-frame collateral compression mechanism. With only a single compressed air source, the external mesh-covered and inner spring-frame actuators of the proposed PAM operate simultaneously to generate considerable force. Additionally, the design of the internal actuator within the void space of PAM reduces the air consumption and consequently improves the actuator's operating speed and efficiency. We experimentally confirmed that the proposed PAM exhibited 31.2% greater force, was 25.6% faster, and consumed 21.5% lower air compared to the conventional McKibben muscles. The performance enhancement of the proposed PAM improves the performance of soft robots, allowing the development of more compact robots with greater assistive range. [ABSTRACT FROM AUTHOR]

The size of a device and its adaptability to human properties are important factors in developing a wearable device. In wearable robot research, therefore, soft materials and tendon transmissions have been utilized to make robots compact and adaptable to the human body. However, when used for wearable robots, these methods sometimes cause uncertainties that originate from elongation of the soft material or from undefined human properties. In this research, to consider these uncertainties, we propose a data-driven method that identifies both kinematic and stiffness parameters using tension and wire stroke of the actuators. Through kinematic identification, a method is proposed to find the exact joint position as a function of the joint angle. Through stiffness identification, the relationship between the actuation force and the joint angle is obtained using Gaussian Process Regression (GPR). As a result, by applying the proposed method to a specific robot, the research outlined in this paper verifies how the proposed method can be used in wearable robot applications. This work examines a novel wearable robot named Exo-Index, which assists a human's index finger through the use of three actuators. The proposed identification methods enable control of the wearable robot to result in appropriate postures for grasping objects of different shapes and sizes. [ABSTRACT FROM AUTHOR]