Optimization of Multirotor UAV Endurance

Abstract

Advancements in the technology of electric motors, batteries and control modules have facilitated a steep increase in the interest of small battery-powered multirotor aircraft. Unmanned areal vehicles (UAV) of this type are mechanically simple, robust, have high maneuverability and a compact size due to their propulsion system. A critical issue in the design process is the UAV’s limited flight time, or endurance, due to inefficiencies and a relatively low endurance to weight ratio. This thesis gives an overview of the factors that influence endurance, defines analytical models for the estimation of endurance and analyses the impact of propeller diameter, configuration and battery size for a 25 kg maximum take-off weight UAV. The endurance is found to be sensitive to all three factors. A case analysis is performed to compare a set of design options to the existing "Staaker BG-200" UAV produced by Nordic Unmanned AS, and improvement recommendations are presented. The maximum estimated endurance increase found is 61%, resulting in an endurance of 96 minutes and 36 seconds.This design is estimated to have a 91% increase in UAV length and a 52% decrease in payload capacity. A more practical design was recommended, with 23% increased endurance and $1892 decreased propulsion system cost compared to the Staaker BG-200 UAV.