Evaluation of Fiber-Reinforced Modular Soft Actuators for Individualized Soft Rehabilitation Gloves

Abstract

Applying soft actuators to hand motion assist for rehabilitation has been receiving increasing interest in recent years. Pioneering research efforts have shown the feasibility of soft rehabilitation gloves (SRGs). However, one important and practical issue, the effects of users’ individual differences in finger size and joint stiffness on both bending performance (e.g., Range of motion (ROM) and torque) and the mechanical loads applied to finger joints when the actuators are placed on a patient’s hand, has not been well investigated. Moreover, the design considerations of SRGs for individual users, considering individual differences, have not been addressed. These, along with the inherent safety of soft actuators, should be investigated carefully before the practical use of SRGs. This work aimed to clarify the effects of individual differences on the actuator’s performance through a series of experiments using dummy fingers designed with individualized parameters. Two types of fiber-reinforced soft actuators, the modular type for assisting each joint and conventional (whole-finger assist) type, were designed and compared. It was found that the modular soft actuators respond better to individual differences set in the experiment and exhibit a superior performance to the conventional ones. By suitable connectors and air pressure, the modular soft actuators could cope with the individual differences with minimal effort. The effects of the individualized parameters are discussed, and design considerations are extracted and summarized. This study will play an important role in pushing forward the SRGs to real rehabilitation practice.

Numerical and experimental assessment of tilted-helical fiber orientation effects on deformation of pneumatic soft actuators

“…They find applications in human motion assistive devices, bioengineering instruments, and wearable devices. Compared to traditional robotic actuators, they are cost-effective and can achieve fast and complex movements [16][17][18][19]. The complex motions and material nonlinearities of these actuators make their characterization and prediction challenging.…”

Neural Network-Based Active Load-Sensing Scheme and Stiffness Adjustment for Pneumatic Soft Actuators for Minimally Invasive Surgery Support

“…Soft actuators can self-adjust their stiffness and are ideal for dealing with unstructured environments or interacting with humans because their softness allows them to deform around their surroundings. Soft actuators are also commonly employed in different fields, such as rehabilitation [ 8 , 9 , 10 , 11 , 12 , 13 ] and MIS instruments [ 14 , 15 ]. In numerous applications, a pneumatic soft actuator is expected to have a small size, low hardness, large bidirectional bending angle and low stiffness, hence, minimizing the damage of surgical instruments to the surrounding tissues.…”

Finger Joint Stiffness Estimation with Joint Modular Soft Actuators for Hand Telerehabilitation

“…Firstly, a whole-finger soft actuator with a single-pocket structure with multiple air chambers connected to each other, such as the SECA, is not suitable for home environments because it requires high air pressure to achieve high bending performance [17,19,20]. Secondly, this type of actuator has only one pneumatic input and cannot support individual joints.…”

“…Finally, it is costly to customize the actuator for each patient. Yun et al and Kokubu et al developed joint modular soft actuators that are divided into parts corresponding to each finger joint [20,21]. By using spacers to connect each actuator, the actuators can accommodate differences in the length of the user's fingers without changing the dimensions of the actuator.…”

“…This enables personalized customization at a low cost. In addition, the actuator does not require high air pressure because it transmits force better than a whole-finger soft actuator does [20]. Based on these considerations, the joint modular soft actuator can be considered a suitable soft actuator for use in a telerehabilitation environment because it provides high bending performance with minimal energy and can accommodate individual differences with minimal effort.…”