| In this thesis, a novel hybrid unmanned aerial vehicle (UAV) concept and a computational framework to optimize and test its performance is developed. This UAV, called the Blended-wing-body Integrated Tilt-arm UAV or BITU, is capable of transitioning in-flight between VTOL, hover, and fixed-wing-like forward flight, as well as to other flight states in-between. The overall configuration comprises a blended-wing-body (which facilitates desirable weight distribution and flight efficiency), with two rotor arms mounted at the two wing tips using span-wise shafts; the arms can rotate about the span-wise axis, and each contains two propellers at its two ends. The computational framework for conceptual design comprises mass, inertia, and aerodynamic analysis and mission-performance optimization. Preliminary dynamics-controls and structural analysis was performed (by other researchers) in a parallel effort to complement this design framework. Here, Vortex Lattice Method is used to perform the aerodynamic analysis. The lift and drag forces computed are used to estimate the forward flight range and endurance (assuming battery-powered flight), by leveraging typical momentum theory formulations. One of the design goals of BITU is to leverage its hybrid capability to survive and perform in diverse environmental conditions unlike traditional multi-rotor and fixed-wing UAV. As an initial investigation of this capability, different wind scenarios are considered during performance optimization w.r.t. two different mission profiles. Uncertainties associated with wind conditions are addressed by taking a typical and worst case scenario perspective, and introducing carefully tailored redundancies during the modeling and optimization formulation process. Optimization of BITU geometry and component choices is performed using a mixed-integer Particle Swarm Optimization algorithm, with the aim to separately maximize forward-flight range and hovering endurance, subject to various aerodynamic and geometric constraints. The optimization converges to noticeably distinct designs under calm, windy, and stormy wind scenarios, with flight ranges going from ~40-150 km. These studies resulted in a trade-off design that balances performance and reliability, and will serve as the baseline for further dedicated multi-disciplinary optimization, fabrication, and flight testing of BITU in the near future. |
