Modeling of a Thick Cylindrical Pneumatic Leg for a Soft Parallel Robot

Soft manipulators have experienced a significant development over the past few years thanks to their versatility, compliance, and safety. Soft manipulators made of hyperelastic materials present a modeling challenge due to their combined geometric and material nonlinearity, alongside their leveraged compliance. This paper considers a thick cylindrical pneumatic actuator in the context of a soft parallel robot. The input pressure and the external axial force to which it is subjected are modeled. The analytical solutions for these models are then derived using the Yeoh strain energy density function. The advantage of using the Yeoh material model is guaran-teeing the existence of an analytical solution regardless of the material used for the fabrication of the cylindrical actuator. The accuracy of the models is evaluated using Finite Element Analysis, and a sensitivity analysis is also carried out to test their robustness. Finally, experimental results are provided and the importance of the material characterization is highlighted. The purpose of this work is to lay the foundation for future studies in modeling a soft parallel robot with three soft thick cylindrical “legs”.