Towards Untethered Soft Pneumatic Exosuits Using Low-Volume Inflatable Actuator Composites and a Portable Pneumatic Source

The application of pneumatic soft robots is limited by factors such as operational pressure and air flow rates. Pneumatic soft robots are typically tethered in nature due to the high energy costs for actuation as well as the lack of portable pneumatic sources capable of providing high pressures and air flow rates. This work presents a low-volume inflatable actuator composite (IAC) designed to reduce energy costs of actuation and a portable pneumatic source to overcome the aforementioned issues towards untethered applications. The pressure-deflection characteristics of the fabricated IAC are compared with those of a completely fabric-based beam using experimental results and finite element analysis. FEM models of IACs with varying volumes are generated and actuation speeds are measured using a pressure step response test. The force output and hysteresis of the actuator are studied. The developed portable pneumatic source is capable of generating a pressure and flow rates of 0.131 MPa and 21.45 standard litres per minute (SLPM), respectively. The IACs and portable pneumatic source are integrated with a soft exosuit to assist knee extension, and the integrated system is evaluated with three healthy participants for incline walking. A reduction of muscle activities in the Vastus Lateralis muscle group is observed for all the three participants when the exosuit is active.