Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi University, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2023
Thesis Language: English
Student: Sami ARSLAN
Principal Supervisor (For Co-Supervisor Theses): Tuğba Selcen Navruz
Co-Supervisor: İres İskender
Open Archive Collection: AVESIS Open Access Collection
Abstract:
The increasing demand for leadership in the socio-military sector has led to a growing focus on the integration of new, compact concepts into UAVs. Advancements in power electronics, motor drives, and material science have enabled the development of more efficient systems, which aligns with a otable trend in UAVs. The conversion of conventional mechanisms to compact electromagnetic systems, making Starter/Generator structures play a crucial role. The Starter/Generator serves two functions: acting as both the primary drive mechanism for initiating the piston engine and supporting the propulsion system in motor mode, while in generator mode, it charges the electronic system battery once the engine is running. Innovative progress in high energy density rare-earth magnets has also facilitated the development of magnetic couplers, enabling magnetically insulated, contactless power transmission between the shafts of the piston engine and the Starter/Generator. This thesis focuses on the development and application of a novel, highly efficient, high-speed, double stage direct-drive magnetically coupled Starter/Generator, referred to as double stage DCSG. The aim is to provide a hybrid propulsion system for mini/small scale piston-engined surveillance UAVs, ultimately enhancing safety, reliability, usability, endurance, and flight time. The Starter/Generator is an inner-runner permanent magnet brushless synchronous machine, with specifications of 1 kW at 4500 rpm for motor mode and 1.25 kW at 5500 rpm for generator mode. The analytical design model efficiency of the Starter/Generator is 84%. However, through tuning with RMxprt sensitivity analysis, the efficiency is increased to 87%. Further evolutions are achieved through Maxwell 2D/3D FEA and optimizations, resulting in an efficiency of 90%. The magnetic couplers employed in the system adopt a radial synchronous magnetic coupler topology, while meeting stringent torque requirements of 6 N.m and 12 N.m. The coupler efficiency reaches 93.8% at the maximum operating speed and critical angle, and 96.9% at the minimum torque angle and minimum operating speed. By implementing the DCSG in designated mission zones, the UAV propulsion efficiency has been improved from 20% to 45% in cruising. As a result, the flight time has increased by 24%. The absolute error rates are determined to be 13% for the 2D and 6% for the 3D.
Key Words : Hybrid UAV, magnetic coupler, piston engine, Starter/Generator