A Unified Conceptual Framework for Aerodynamic and Rigid-Body Modeling of Multirotor UAVs

Abstract

Traditional UAV modeling often treats rigid-body dynamics and aerodynamic effects as decoupled phenomena, a simplification that fails during high-speed transitions or aggressive maneuvers. This paper proposes a Unified Conceptual Framework (UCF) that bridges the gap between classical robotics and high-fidelity aerodynamics. By integrating Blade Element Momentum Theory (BEMT) directly into the Newton-Euler equations of motion, the framework enables a state-dependent representation of rotor-to-rotor interference, fuselage drag, and non-linear lift-drift characteristics. The architecture is built upon a modular “Force-Moment Manifold” that maps the vehicle’s instantaneous linear velocity, angular rates, and rotor speeds to a continuous field of aerodynamic perturbations. Unlike static lookup tables, the UCF introduces a dynamic coupling where the vehicle’s motion alters the local inflow velocity at each rotor disk, which in turn modifies the resultant forces acting on the airframe. Furthermore, the framework establishes a standardized mathematical nomenclature and a hierarchical coordinate transformation system to maintain consistency across diverse multirotor configurations, from quadrotors to over-actuated octorotors. By providing a rigorous theoretical foundation, this paper enables the development of “physics-aware” simulators capable of predicting edge-of-the-envelope behaviors, such as vortex ring state, without the computational burden of full CFD. This unified approach is presented as a prerequisite for the next generation of robust control systems and high-fidelity digital twins in the Urban Air Mobility (UAM) sector.