Speeding up soft pneumatic actuators through pressure and flow dynamics modeling and optimization

Abstract

Soft pneumatic actuators (SPAs) possess the potential to be used in various scenarios due to the softness of their compositional materials to generate various modes of motion. The actuation frequency of SPAs is commonly in the range of 0-4 Hz, limiting their applications only to normal-speed tasks. To reveal the key affecting factors to the actuation speed and further optimize an SPA's response speed for more dynamic applications, a predictive model of the whole pneumatic supply system (PSS) that takes the pressure and flow dynamics into consideration is needed. In this work, we introduce a comprehensive pressure and flow dynamic model of high-speed PSSs and SPAs. Here, the PSS is regarded as a compressed air source and a volume-fixed reservoir that are connected by a tube. The pressure and flow dynamic is modeled by correcting the adiabatic model to account for real heat exchange, and considering the assumptions of steady state of the gas flow through an orifice and the one dimensional unsteady gas flow in the tube. After calibration and validation with experiment results, we investigated the key affecting factors of PSSs on the attainable frequency of the SPA, which provides the design guidelines for the high-speed PSSs. Results show that the PSS with pure helium is dramatically faster than that with air. Finally, we present a demonstration of a helium-PSS actuated fiber-reinforced, bending SPA that achieves high frequency of up to 39 Hz in its blocked force.