Design and Dynamic Modeling Analysis of Undulatory Propulsion Underwater Robot with Rotational Passive Degrees of Freedom in Fin Rays

Abstract

Current research on undulatory propulsion robots has predominantly centered on hydrodynamic performance simulations. However, challenges such as limited mobility and difficulties in parameter identification during underwater bio-mimetic motion remain unresolved. To address these issues, this study proposes a novel undulating fin robot featuring passive rotational joints, aiming to enhance motion capabilities and facilitate more accurate modeling. These joints enhance both the agility and stability of the robot's movements. Initially, the research develops models for the undulatory motion of the undulating fin and the rotational passive degrees of freedom in the fin rays. Based on fluid drag theory, a hydrodynamic model for undulating fin propulsion is constructed to analyze the thrust, lateral force, and lift generated at varying frequencies. Furthermore, a comprehensive dynamics model for the underwater motion of the biomimetic undulating fin robot is developed. Numerical simulations of the robot's non-steady-state motion are conducted to identify the hydrodynamic parameters of the model, thereby enabling the solution of the dynamic model. The experimental results demonstrate that the robot achieves an underwater straight-line motion speed exceeding 0.5m/s, a turning speed of approximately 45°/s, and an inclined upward motion speed of 0.21 m/s. This study provides a novel approach for the design of underwater undulating fin robots and the resolution of kinematic models for underwater robots. It is hoped that this research can contribute to the further development of undulatory propulsion robot technology.