Design of unmanned aerial vehicles

• Κύριος συγγραφέας: Επίσκοπος, Ιωάννης
• Άλλοι συγγραφείς: Episkopos, Ioannis
• Γλώσσα: English
• Έκδοση: 2022
• Θέματα: Tail-sitter; Vertical takeoff and landing; Unmanned aerial vehicles; Multicopters; Αεροσκάφος ουραίας έδρασης; Κάθετη απογείωση και προσγείωση; Μη επανδρωμένα αεροχήματα; Ελικόπτερα με πολλαπλούς έλικες

Contrary to conventional aircraft design, the design of Unmanned Aerial Vehicles (UAVs) with Vertical Takeoff and Landing (VTOL) capabilities lacks a standardized, coherent methodology of development. This thesis aims to develop such a methodology for two different configurations and apply it for numerous unmanned aerial vehicle instances of various scales, purposed for aerial firefighting. A literature survey on firefighting aircraft and VTOL UAVs indicates that the water quantities required in firefighting correspond to aircraft of significantly greater size than any non-military drone. The survey also shows that the basis of firefighting aviation is the ability of heavy cargo transport. These observations function as guidelines for the early conceptual design procedure called “sizing”. Sizing refers to the use of mission requirements and statistical data on existing aircraft to approximate the aircraft’s weight and size. The procedure is conducted on three scales of each configuration, for payload capacities that collectively range from 100 to 2,000 kilograms. Elements from conventional airplane and helicopter design are combined to initially produce a total of six VTOL, firefighting UAVs of various sizes that use a plethora of propulsion systems. The configurations studied and sized are the tail-sitter and the multicopter. Tail-sitters are fixed-wing aircraft capable of hovering vertically, with their tail facing the ground, hence their name. Multicopters are rotorcraft powered by more than two lift-generating motors. The sizing of the electric multicopters results in an extreme scaling rate with respect to endurance, which is confirmed by a direct comparison of a petroleum-powered and an electric large-scale multicopter with the same mission requirements. A brief literature survey reveals that the low energy density of batteries compared to hydrocarbons is the main explanation. Our attempt to further upscale the multicopters for improved firefighting capacity produces a 27-ton quadcopter matching the capabilities of the S 64 Aircrane heavy-lift helicopter. Each VTOL configuration has its own inherent issues requiring attention. The tail-sitter configuration instigates stability problems during flight, takeoff, and landing, which directly affect tail size and landing gear placement. The multicopters’ entirely vertical operation is highly energy consuming, leading to increased weight.