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

TL;DR

This paper compares two modeling approaches, a lumped-parameter model and finite element analysis, to understand and predict the behavior of fiber-reinforced soft robotic actuators called FREEs, highlighting their respective advantages and limitations.

Contribution

It introduces and evaluates two complementary models for FREEs, demonstrating their effectiveness and differences in predicting soft robot behavior for design and control.

Findings

Lumped-parameter model predicts FREE rotation with at most 4% error.

Finite element analysis shows material properties significantly affect FREE behavior.

Winding angle variations dramatically change the workspace of FREE modules.

Abstract

Roboticists have been seeking to address this situation in recent years through the use of soft robots. Unfortunately, identifying appropriate models for the complete analysis and investigation of soft robots for design and control purposes can be problematic. This paper seeks to address this challenge by proposing two complementary modeling techniques for a particular type of soft robotic actuator known as a Fiber-Reinforced Elastomeric Enclosure (FREE). We propose that researchers can leverage multiple models to fill gaps in the understanding of the behavior of soft robots. We present and evaluate both a dynamic, lumped-parameter model and a finite element model to extend understanding of the practicability of FREEs in soft robotic applications. The results with the lumped-parameter model demonstrate that it predicts the actual rotational motion of a FREE with at most 4% error when a closed-loop controller is embedded in the system. Additionally, finite element analysis was used to study FREE design parameters as well as the workspace achieved with a module comprised of multiple FREEs. Our finite element results indicate that variations in the material properties of the elastic enclosure of a FREE are more significant than variations in fiber properties. Finally, finite element results show that a 30-degree difference in winding angle dramatically alters the shape of the workspace generated by four FREEs assembled into a module. Concludingly, comments are made about the relative advantages and limitations of lumped-parameter and finite element models of FREEs and FREE modules in providing useful insights into their behavior.