Design optimization of a small quadrotor's electrical propulsion system

Abstract

This thesis presents an approach for the optimization of the propulsion system of an unmanned lightweight quadrotor by introducing rotor aerodynamics and identifying methods to improve the electrical propulsion system (EPS), hence improving its performance and efficiency. Since the rotor is the main component to generate thrust, a numerical model based on the combined momentum and blade element theory is presented to aid in the design and/or selection of the optimum rotor. In order to validate this numerical model and to benchmark the different system solutions, a propulsion test bench was built to collect experimental data from a series of tests carried out in the lab. Rotors of 11 and 13 inches of diameter and of different brands were tested under the same environmental conditions with rotational velocities ranging from 4000 to 8000 rpm in hover situation. The measured thrust and power were compared to the theoretical thrust output and required power, and the average discrepancy between both results was estimated to be 4.6% in terms of thrust and to 24.3% in terms of power. The design and optimization of the EPS is an iterative procedure; consequently, an optimization workflow method is proposed, since propulsion improvements mainly depend on the optimum combination of the propeller, motor and battery.