Multi-field coupled dynamic modeling of hard-magnetic beams interacting with fluid and its application to a magnetic-driven biomimetic jellyfish robot

Hard-magnetic materials have emerged as a promising candidate for developing a magnetic-driven biomimetic jellyfish robot, due to their powerful and versatile actuation mechanism. However, in an interdisciplinary context, there is a critical absence of dynamical modeling approaches that can accurately capture the bidirectional coupling between the fluid and hard-magnetic beam that possesses large displacements and large deformations induced by the external magnetic field. The present work focuses on the development of a novel multi-field coupled dynamical modeling method of a hard-magnetic soft beam interacting with fluid and its application to the magnetic-driven biomimetic jellyfish made of a curved hard-magnetic soft beam. The soft jellyfish-like robot is modeled using the absolute nodal coordinate formulation to capture the rigid-flexible coupling effect caused by large displacements and deformations. The magnetic actuation force is derived through the magnetic potential energy that is related to the deformation gradient. The interaction between the fluid and jellyfish robot is effectively handled by the immersed boundary method, while the hydrodynamics is well tackled by the lattice Boltzmann method. A new semi-implicit co-simulation scheme is proposed for the bidirectional fluid-structure interaction. Numerical simulations show that the biomimetic jellyfish robot can swim underwater effectively with the designed external magnetic field and the swimming orientation can also be changed by controlling the direction of the magnetic field. This work is expected to guide researchers to better understand the swimming mechanism of the magnetic-driven biomimetic jellyfish, thus contributing to its structural design and locomotion control for various applications.