Conceptual Design of UAS Configurations with Dissimilar Rotors

Abstract

Three vehicle configurations: a 9 kg quadrotor bi-plane tailsitter, a 20 kg tricopter, and a 450 kg coaxial helicopter with pusher propeller are designed using the iterative rotorcraft sizing framework HYDRA, maximizing payload capacity over missions with both hover and forward flight segments. This methodology allows for vehicles to have constituent rotors of differing geometry and angular velocity, a feature that has just been implemented as a part of this work. It allows users to rapidly evaluate vehicle configurations with rotors of a wide range of size, type, and orientation with respect to the vehicle. Furthermore, HYDRA can now model the electric transmission of power to each rotor separately using individually sized motors and speed controllers according to the requirements of each rotor. Results of the sizing show that vehicle and flow-field symmetry play an important role in whether or not dissimilar rotors may be useful for a specific configuration and mission. Analysis of the coaxial helicopter with pusher propeller demonstrated that by controlling design parameters of the main rotors separately from that of the propeller, operational envelope barriers and optimal aircraft configurations can be explored more thoroughly and more quickly than before.