What Happens When Pneu-Net Soft Robotic Actuators Get Fatigued?

TL;DR

This study investigates fatigue effects in pneu-net soft robotic actuators through finite element modeling and experiments, revealing how performance degrades with cyclic high-angle bending, informing adaptive control strategies.

Contribution

It combines FEM modeling with experimental validation to quantify fatigue effects in soft actuators, highlighting performance decline over cyclic use.

Findings

FEM models predict initial performance with ~96% accuracy.

Fatigue reduces performance to about 80% after repeated cycles.

Fatigue causes deviation from ideal actuator behavior.

Abstract

Soft actuators have attracted a great deal of interest in the context of rehabilitative and assistive robots for increasing safety and lowering costs as compared to rigid-body robotic systems. During actuation, soft actuators experience high levels of deformation, which can lead to microscale fractures in their elastomeric structure, which fatigues the system over time and eventually leads to macroscale damages and eventually failure. This paper reports finite element modeling (FEM) of pneu-nets at high angles, along with repetitive experimentation at high deformation rates, in order to study the effect and behavior of fatigue in soft robotic actuators, which would result in deviation from the ideal behavior. Comparing the FEM model and experimental data, we show that FEM can model the performance of the actuator before fatigue to a bending angle of 167 degrees with ~96% accuracy. We also show that the FEM model performance will drop to 80% due to fatigue after repetitive high-angle bending. The results of this paper objectively highlight the emergence of fatigue over cyclic activation of the system and the resulting deviation from the computational FEM model. Such behavior can be considered in future controllers to adapt the system with time-variable and non-autonomous response dynamics of soft robots.