A Unified Conceptual Framework for Hydrodynamic and Rigid-Body Modeling of Unmanned Underwater Vehicles

Abstract

Accurate modeling of Unmanned Underwater Vehicles (UUVs) requires integrating rigid-body dynamics with complex hydrodynamic forces arising from fluid-structure interactions in marine environments. This paper proposes a unified conceptual framework that combines 6-DOF rigid-body equations with hydrodynamic models accounting for added mass, drag, lift, and wave-induced forces. The framework introduces a modular “Force-Moment Manifold” that maps the vehicle’s velocity, angular rates, and control inputs to hydrodynamic loads, incorporating nonlinear effects such as vortex shedding and flow separation. Unlike traditional decoupled approaches, this framework dynamically couples vehicle motion with local fluid conditions, enabling more accurate prediction of UUV behavior during maneuvers and in turbulent currents. A standardized coordinate transformation system is established to maintain consistency across different vehicle configurations, from torpedo-shaped AUVs to multi-thruster ROVs. The framework supports scalable fidelity, allowing researchers to balance computational complexity with model accuracy for simulation and control design. This conceptual foundation facilitates the development of physics-aware simulators and robust controllers, essential for precise navigation and manipulation tasks in challenging underwater environments.