Combined Analytical-FE Modeling of the Deformation Mechanisms and Forces in Soft PneuNets Bending Actuators

We consider the mechanical behavior of soft pneumatic network bending actuators (PneuNets) consisting of a series of chambers made of elastomeric material and fixed to an inextensible bottom layer. The pressure-induced bending angle in free space, as well as the contact force between the actuator tip and an external rigid obstacle are modeled with combined analytical-Finite Elements (FE) approach. We propose two distinct mechanisms for free-end bending, namely, bending of the bottom layer, and bending due to the contact forces between inflated membranes of neighboring chambers. It is found that the main contribution to the total free-end bending angle comes from bending of the inextensible layer, as opposed to bending entirely due to membrane-membrane interactions. It is also found that the pressure-induced contact force between the actuator tip and an obstacle is solely due to the membrane force of the chamber at the actuator's free end and the related moments. The model predictions are compared to FE simulations and experimental data obtained from testing of an in-house fabricated prototype.