Experimental Results of Transient Variable Speed Rotor Performance for Small UAS Propulsion Scalability

This paper is the first of two, detailing a Department of the Army funded research effort that experimentally measured the transient response of different small UAS (sUAS) rotor-motor configurations used for quadcopter applications, in order to predict the effect of scalability on the transient response. The researchers constructed an electric VTOL (eVTOL) test stand capable of measuring several aspects of electric rotor-motor performance. Experiments were conducted using seven different variable-speed rotor-motor configurations during both ramp-up and coast-down conditions between different electrical throttle settings. The results concluded that the coast-down transient was more significant than the ramp-up transient. eVTOL configurations responded differently to rotor transients compared to rotors powered by air-breathing powerplants, where rotor inertia is the predominant variable. Results show that in addition to rotational inertia, other variables influence the transient response and must be taken into account.