Evaluation of Two Complementary Modeling Approaches for Fiber-Reinforced Soft Actuators

Robots are increasingly used in a wide range of applications. We, as humans, still find it challenging to work in proximity to robots due to safety concerns. In recent years, roboticists have been seeking a solution to this challenge through soft robots. Unfortunately, it is often challenging to find the optimal model to fully investigate and analyze the behavior of a soft robot. This paper seeks to address this challenge by proposing two complementary modeling techniques for a particular type of soft robotic actuator known as Fiber Reinforced Elastomeric Enclosures (FREEs). We propose that designers can leverage multiple models to fill the gaps in the understanding of soft robots. We develop and test both a dynamic lumped-parameter model and a finite element model in an attempt to understand the practicability of FREEs for use in a soft robotic arm. The resulting insights enabled us to investigate the controllability of FREEs using the dynamic model, and its design parameters and workspace via the finite element model. The results from the lumped-parameter model allowed us to make simplifying assumptions that led to the development of a model-driven controller for a single FREE, although extending this model for a module of multiple FREEs can be challenging. This provided motivation for the development of a finite element model for single and multiple FREE configurations. Our findings indicate that the material properties and winding angles greatly influence FREEs' extension, rotation, and force and moment generation. Overall, both models efficiently predict the behavior of FREEs. Employing two modeling approaches enabled us to fully investigate behavior, whereas neither model individually significantly demonstrates the complete range of FREE capabilities.