Experimental characterisation of Li-Po battery packs and BLDC machines for hybrid propulsion systems of lightweight UAVs

This paper deals with the design and the implementation of experiments for the performance characterisation of the main power devices of the hybrid propulsion system of a lightweight fixed-wing UAV. The basic objective of the work is to identify the parameters of the three-phase brushless DC machine (BLDCM) model and the battery pack model, up to support the development of a virtual prototype of the hybrid propulsion system, to be used for the system design and validation. In particular, the experiments are designed to identify the BLDCM model in terms of resistance, inductance, and back-electromotive force waveforms as functions of the motor angle, as well to define the parameters of the Thevenin model of the battery pack (open-circuit voltage, internal and polarization resistances, battery capacitance) as functions of battery state-of-charge and environmental temperature in the range from 0 to 49 °C.