Modeling of Fluidic Prestressed Composite Actuators With Application to Soft Robotic Grippers

Soft and continuously controllable grippers can be assembled from fluidic prestressed composite (FPC) actuators. Due to their highly deformable features, it is difficult to model such actuators for large deflections. This article proposes a new method for modeling large deflections of FPC actuators called the chained composite model (CCM) to characterize the quasi-static response to an applied fluid pressure and load. The CCM divides an FPC actuator into discrete elements and models each element by a small rotation model. The strain energy of each element and the work done by pressure and loads are computed using third-order displacement polynomials with unknown coefficients; then, the total energy is minimized to calculate stable shapes using the Rayleigh–Ritz method. This study provides a set of systematic design rules to help the robotics community create FPC actuators by understanding how their responses vary as a function of input forces and pressures for a number of modeling and design parameters. Composite actuators are fabricated and a soft gripper is developed to demonstrate the grasping ability of the FPC actuators. Pneumatic pressure and end loads are applied to the composite actuators, and their responses are measured. The modeled responses of the actuators are shown to be in agreement with the measured responses.