Soft Robotic Fish with Anisotropic Bimorph Actuators: A Nonlinear Dynamic Approach

This study presents a nonlinear dynamic analysis of an anisotropic bimorph dielectric elastomer actuator (DEA) designed for soft robotic applications. By reinforcing the elastomer with soft fibers, the drawbacks of isotropic DEAs are addressed, improving their actuation capabilities. Experimental stress relaxation tests at varying temperatures were conducted to determine viscoelastic properties, including shear moduli and relaxation time. The actuator’s thermo-electro-visco-hyperelastic behavior is modeled using the Gent hyperelasticity framework alongside a newly formulated relaxation model. The governing equation of motion is derived via the Euler-Lagrange principle and solved numerically using MATLAB and Simulink. The influence of taper ratio and temperature on dynamic responses is examined. Results indicate that increasing taper ratio enhances stretch and deflection due to reduced stiffness and natural frequency. Frequency spectrum analysis reveals nonlinear interactions, with phase portraits and bifurcation diagrams demonstrating quasi-periodic behavior. These findings contribute to optimizing DEA performance in soft robotic applications.