Fabric Inflatable Soft Actuators for Soft Wearable Devices: The MOSAR Case

Abstract

This paper addresses the design, fabrication and control of Fabric Inflatable Soft Actuators (FISAs) for driving Soft Wearable Devices (SWD) for rehabilitation or assistance tasks. FISAs are integrated by a set of pneumatic chambers made of 200D TPU-nylon that create bending-extending motions using a modular assembly that allow FISAs to adapt them to any size of limb or easily replace them. Regarding FISAs fabrication, a self-hand manufacturing approach has been used for cutting, sewing, and joining them. Additionally, to evaluate FISAs operation, a Soft Exo-Sleeve called MOSAR system was manufactured to achieve elbow motion. To control their inflation-deflation process in real-time, proportional and solenoid valves have been implemented along with a Proportional-Derivative (PD) control strategy that has been embedded in the NUCLEO-STM32F767ZI™ board with rapid control prototyping. Preliminary experiments about FISA performance on the MOSAR system were carried out to measure the inflation-deflation time, Range of Motion (ROM), and output force when elbow flexion-extension occurred in a dummy limb. The results have demonstrated FISAs functionality above the exosuit since they were able to lift 1 kg with flexion of 130° in 5 s using 50 psi. Therefore, FISAs represent a feasible choice for semicircular motions in other joints such as the wrist, hand, or knee, no matter age, limb, or size, only the number of FISAs must be adjusted on the MOSAR system.

Decoupled, Wearable Soft Robotic Rehabilitation Device for the Upper Limb

“…A major benefit of these bending actuators is that the tip force of the actuator can be near-perpendicular to the axis of the body segment that it is attached to, providing much larger moment arms, which generate the desired motion more safely and efficiently. These devices use thermoplastic polyurethane (TPU)-based actuators for flexion, either by using TPU films within sewn nylon pockets [11] or by using reinforced TPU-coated Nylon fabrics [9][10] [12]. The benefits of TPU films over a moulded elastomeric design include higher working pressures and simpler construction, though the main advantage is the low mass and low volume when the actuator is deflated.…”