Theoretical Model for Dynamic Analysis of Soft Eel Robot’s Underwater Motions Based on Mechanics of Multibody System

Soft robotics has posed unique challenges in dynamic analysis and motion control, particularly in contrast to conventional rigid robots. This paper introduces a theoretical approach for evaluating the dynamic behavior of an underwater soft eel robot - our previous soft robot design. Based on the concept of a pseudo-rigid-body model, we propose an equivalent dynamic model for the eel robot, converting its flexible body into an assembly of traditional rigid links and joints. Subsequently, utilizing the mechanics of multibody system dynamics, we derive explicit dynamic equations governing the underwater locomotion of the eel robot. The configuration parameters and external forces of the dynamic model are determined. Then the dynamic equations are solved with different scenarios to explore the effect of pneumatic pressure frequency and amplitude on the robot’s dynamic response. The theoretical calculations are compared with preliminary experimental results, demonstrating the robustness and reliability of the proposed dynamic model. This dynamic model is expected to become a valuable approach for the analysis and control of soft eel robots and diverse soft robotic systems.