• control laws
• hybrid electric propulsion
• modelling
• performance
• simulation
• Unmanned Aerial Vehicle

UAVs performances during rapid climb in a hot day are typically limited by the engine overheating. This implies the necessity of alternating climb phases with levelled flight phases to permit the engine to cool down. One of the basic objectives of this MSc Thesis is to evaluate the design feasibility of hybrid propulsion systems for low-weights UAVs that integrate the conventional internal combustion engine with the electric generator temporarily working as motor (i.e. during climb), by focusing attention on characterising the system dynamics during transition.
With reference to the engine and generator data of a modern low-weight UAV, the dynamic models of the propulsion systems are developed for both conventional and hybrid configurations and the system control laws are designed to fulfil the dynamic performance requirements during climb.
Once selected the most suitable strategy for controlling the electric motor when boosting the propulsion power, a complete model of the hybrid propulsion system is developed, and a commands management logics is preliminary designed to control the transition from conventional to “booster” configuration and way back.
Simulations demonstrate that the hybrid propulsion system improves the transient performances of the UAV during climb and that an opportune management of the transition between propulsive configurations can strongly enhance overall system performance.