Modeling of 3D Printed Soft Pneumatic Actuators

Soft Pneumatic Actuators (SPAs) have a simple structure of inner chambers that can be deformed to generate force when pressurized. Additive Manufacturing (AM) has been used to enhance SPAs by leveraging design freedom and customization for specific tasks. This study aims to develop a Finite Element Method (FEM) model to simulate a generic 3D-printed bellow SPA performing planar bending motion under pressure. The model, which can be used with different SPA design parameters, evaluates properties such as bending angle and exerted forces. The performance of a bellow SPA is influenced by factors such as its main dimensions, material, operating pressure, and chamber shape. This study considered three main contributors to bending behavior: wall chamber thickness, the number of bellow segments, and operating pressure. Various configurations were 3D-printed in Thermoplastic Polyurethane (TPU) and tested using a physical rig. FEM analyses were conducted within Ansys 2019 using static structural analysis. The second-order Ogden model was chosen for the hyper-elastic material according to reference [1]. Material parameters were identified for limited configurations through an optimization process that minimized the bending angle error. Other actuator configurations were simulated using various sets of parameters and compared with physical test results. The results showed a valid approximation across different actuator configurations. This study has developed an effective methodology to simulate the behavior of a generic 3D-printed TPU bellow SPA with a satisfactory level of approximation.