Propulsion System Modeling for Small Fixed Wing UAVs

Abstract

This paper presents a model of an electrical propulsion system typically used for small fixed wing unmanned aerial vehicles (UAVs). Such systems consist of a power source, an electronic speed controller and a brushless DC motor which drives a propeller. The electrical, mechanical and aerodynamic subsystems are modeled separately and then combined into one system model, aiming at bridging the gap between the more complex models used in manned aviation and the simpler models typically used for UAVs. Such a model allows not only the prediction of thrust but also of the propeller speed and consumed current. This enables applications such as accurate range and endurance estimation, UAV simulation and model-based control, in-flight aerodynamic drag estimation and propeller icing detection. Wind tunnel experiments are carried out to validate the model, which is also compared to two UAV propulsion models found in the literature. The experimental results show that the model is able to predict thrust well, with a root mean square error (RMSE) of 2.20 percent of max thrust when RPM measurements are available, and an RMSE of 4.52 percent without.