Stability and Control of a Coaxial Quadcopter with Rotor-On-Rotor Interactional Aerodynamics

This article focuses on the integration of generalized rotor-on-rotor interactional aerodynamics models in state-variable form within flight dynamics simulations of multi-rotor unmanned aircraft systems, and on their subsequent linearization. The aircraft chosen for this investigation is a resupply coaxial quadcopter. Upon trimming the flight dynamics simulation in hover, linearized models of the dynamics are extracted. Models with and without interference are compared to isolate the role of interactional aerodynamics on this configuration. Model-order reduction methods are used to guide the development of linearized models that are tractable for flight control design while still capturing the effect of rotor-on-rotor interactions on the vehicle flight dynamics. Dynamic inversion based model-following flight control laws based on these reduced-order linearized models are developed and tested on the models with and without the interference. The results indicate that, for the coaxial quadcopter configuration studied, rotor-on-rotor interactions mostly affect trim (steady-state) predictions rather than the overall flight dynamics.