Variable Rotor Speed Trim and Interactional Aerodynamics for Quadcopter UAS

Abstract

Variable rotor speed trim analysis for the SUI Endurance quadcopter has been successfully performed using the high-fidelity HPCMP CREATETM-AV Helios rotorcraft analysis and simulation framework. In forward flight, the 2DOF vehicle trim is applied using Helios/RCAS loose coupling, and the resulting Helios vehicle loads show marginal differences with the test data. The trimmed mean rotor speed and differential rotor speed are found moderately different from the test data. The 3DOF vehicle trim is explored to understand the effects of trim with fuselage pitch attitude as an additional trim variable. The effects of aerodynamic interactions are examined systematically using four CFD models: the isolated forward and aft rotor models, the model with all the rotors but without fuselage, and the full vehicle model. It is found that the forward rotor-to-aft rotor interaction is the most significant. In addition, the interaction on the forward rotors is found beneficial, whereas the interaction on the aft rotors degrades rotor thrust.