A strap is a frequently utilized component for securing wearable robots to their users in order to facilitate force transmission between humans and the devices. For the appropriate function of the wearable robot, the pressure between the strap and the skin should be maintained appropriately. Due to muscle contraction, the cross-section area of the human limb changes according to the movement of the muscle. The cross-section area change causes the change in the pressure applied by the strap. Therefore, for a new strap design to resolve this, it is necessary to understand the shape change characteristics of the muscle where the strap is applied. In this paper, the change in the circumference of the thigh and the calf during walking was measured and analyzed by multiple string pot sensors. With a treadmill and string pot sensors using potentiometers, torsion springs, and leg circumference changes were measured for different walking speeds and slopes. And, gait cycles were divided according to a signal from the FSR sensor inserted in the right shoe. From the experimental results, there were changes in the circumference of about 8.5mm and 3mm for the thigh and the calf, respectively. And we found tendencies in various walking circumstances such as walking speed and degree of the slope. It is confirmed that they can be used for estimation algorithms of gait cycles or gait circumstances.

As the aging of society continues to accelerate, the number of elderly patients is increasing, as is the demand for manpower to care for them. In particular, there is an urgent need for bedridden patient care. However, limitations in the supply of human resources have caused an increase in the burden for care. In particular, nursing personnel often experience inconvenience and difficulties owing to the great deal of effort required to transfer a patient from bed to wheelchair, or vice versa. The most difficult process during the patient transfer is inserting the sling under the patient. Aiming to solve this problem, a mechanical Growing Sling was devised. The proposed sling adapts a growing mechanism comprising a low-friction fabric and steel shafts, and the sling is inserted under the patient by towing the steel shafts with cables connected to a motor. For the comfort and safety of the sling insertion, the required towing force was analyzed to find the minimum diameter of the shaft. The results from experimental evaluations using the proposed sling verified that it can be inserted under the patient without moving the patient, and with an acceptable level of pressure being applied to the patient.

In this study, a new type of sling for assisting bedridden patients is developed using a pneumatic growing mechanism. Growing Sling focuses on minimizing the labor input of the caregivers by automating the sling insertion and retraction process while maintaining safety and comfort. Improvements over the typical growing mechanism were made by reinforcing the sling with shafts and filament tape for restricting the height of the sling to ensure its design purpose. Analysis of forces exerted on the structure was made to interpret the driving power of the automated insertion process and to ensure the structural integrity of components. Experiments on materials and prototype devices were conducted to determine the quantitative load that the sling needs to endure and what type of material is suitable for fabrication. Further, we propose a fabrication process for the Growing Sling, including its dimensions, and validate the performance of the fabricated prototype.

This paper presents the development of a polymer-based tendon-driven wearable robotic hand, Exo-Glove Poly. Unlike the previously developed Exo-Glove, a fabric-based tendon-driven wearable robotic hand, Exo-Glove Poly was developed using silicone to allow for sanitization between users in multiple-user environments such as hospitals. Exo-Glove Poly was developed to use two motors, one for the thumb and the other for the index/middle finger, and an under-actuation mechanism to grasp various objects. In order to realize Exo-Glove Poly, design features and fabrication processes were developed to permit adjustment to different hand sizes, to protect users from injury, to enable ventilation, and to embed Teflon tubes for the wire paths. The mechanical properties of Exo-Glove Poly were verified with a healthy subject through a wrap grasp experiment using a mat-type pressure sensor and an under-actuation performance experiment with a specialized test set-up. Finally, performance of the Exo-Glove Poly for grasping various shapes of object was verified, including objects needing under-actuation.

A soft wearable robot with a tendon drive is a promising technology that enables a wearable robot to be compact and lightweight. A soft tendon routing system was previously proposed to apply a tendon drive to a soft wearable robot. In this study, a slack enabling mechanism was proposed to increase the efficiency and guarantee the safety of the soft tendon routing system. The proposed mechanism eliminates the pre-tension of the tendons and minimizes the friction induced by the pre-tension, which causes inefficiency and a lack of safety. Furthermore, the slack enabling mechanism mechanically prevents the derailing of the tendon from the spool. In order to verify the benefits of the proposed mechanism, a prototype was built and tested on the Exo-Glove, which is a soft wearable robot for the hand. The experiment results showed that the prototype could completely remove the pre-tension, whichproposed to apply a tendon drive to a soft wearable robot. In this study, a slack enabling mechanism was proposed to increase the efficiency and guarantee the safety of the soft tendon routing system. The proposed mechanism eliminates the pre-tension of the tendons and minimizes the friction induced by the pre-tension, which causes inefficiency and a lack of safety. Furthermore, the slack enabling mechanism mechanically prevents the derailing of the tendon from the spool. In order to verify the benefits of the proposed mechanism, a prototype was built and tested on the Exo-Glove, which is a soft wearable robot for the hand. The experiment results showed that the prototype could completely remove the pre-tension, which allowed the Exo-Glove to function well with the prototype.

A soft wearable robot, which is an emerging type of wearable robot, can take advantage of tendon-driven mechanisms with a Bowden cable. These tendon-driven mechanisms benefits soft wearable robots because the actuator can be remotely placed and the transmission is very compact. However, it is difficult to compensate the friction along the Bowden cable which makes it hard to control. This study proposes the use of a position-based impedance controller, which is robust to the nonlinear dynamics of the system and provides compliant interaction between robot, human, and environment. Additionally, to eliminate disturbances from unexpected tension of the antagonistic wire arising from friction, this study proposes a new type of slack enabling tendon actuator. It can eliminate friction force along the antagonistic wire by actively pushing the wire while preventing derailment of the wire from the spool.

Tendon-driven mechanisms are one of the most popular mechanisms for transmitting force and power from a distance. The energy efficiency of a tendon-driven system can be improved if it can maintain the actuation force while not moving, without mechanical work. This can be achieved by using a brake. A brake without an additional actuator is preferred for achieving compactness of the entire system. We present a novel passive brake mechanism - the capstan brake, which consists of a capstan, rollers, and one-way clutches. The friction between the capstan and tendon amplifies a small resisting force (originating from an inactivated motor) to gain enough brake force. Because no additional actuator is involved, no energy is consumed to generate the brake force. In addition, the one-way clutch enables the capstan to rotate in the winding direction. Therefore, the brake force is only exerted when needed, and the performance of the entire device does not decrease owing to the use of the capstan brake. The brake force of the system is limited to handling the safety issues. If the external load exceeds the maximum brake force, the brake becomes back-drivable again. The limit level can be controlled by changing the number of times the tendon is wound around the capstan. Another issue for a tendon-driven system is that the tendon escapes from a spooler when the tendon does not maintain proper tension. By implementing the rollers with the capstan brake, the tendon cannot escape from a spooler even though the tendon is not pulled by an external load in all actuating situations. The performance of the proposed brake mechanism was evaluated through several tests. The results showed that the capstan brake is suitable to be applied to the wearable robotic hand, which is one of the prospective applications of the brake. The force loss caused by the brake was negligible and the brake operated properly even though the tendon was not pulled by an external load in all actuating situations.