Deformation analysis of soft Pneu-net actuators in free space with different chamber spacing

Soft pneu-net actuators (SPAs) are flexible structures, which are typically composed of elastomeric materials and capable of undergoing significant deformations. However, accurately characterizing and predicting their bending behavior remains challenging due to the distinct driving mechanisms of SPAs with different chamber spacing (DCS-SPAs). To address this problem, the paper presents a kinematic model for analyzing SPAs with varying spacing distances. The study focuses on the bending mechanisms of soft actuators with varying spacing distances, considering two scenarios: when the chamber sidewalls are in contact and when they are not during the bending expansion. A method for determining whether the chamber sidewalls are in contact is also introduced. The chamber-contact model is developed using finite strain membrane theory and finite hyperelastic cantilever beam theory. The non-contact chamber model is derived theoretically using the principle of virtual work. This model can predict the bending deformation of SPA with varying spacing distances in free space. The theoretical results are compared with experimental data and finite element analyses. The results indicate that the model accurately predicts the behavior of DCS-SPA. Errors for contact models range from 5 to 10%, while non-contact models range from 5 to 15%.