Multimodal hybrid powerplant for unmanned aerial systems (UAS) robotics

Abstract

Most UAS propulsion systems currently utilize either Internal Combustion Engines (ICE) or Electric Motor
(EM) prime movers. ICE are favoured for aircraft use due to the superior energy density of fuel compared to
batteries required for EM, however EM have several significant advantages. A major advantage of EM is that
they are inherently self starting have predictable response characteristics and well developed electronic control
systems. EMs are thus very easy to adapt to automatic control, whereas ICE have more complex control
response and an auxiliary starting motor is required for automated starting.
This paper presents a technique for determining the performance, feasibility and effectiveness of powerplant
hybridisation for small UAS. A Hybrid Powerplant offers the possibility of a radical improvement in the
autonomy of the aircraft for various tasks without sacrificing payload range or endurance capability. In this
work a prototype Aircraft Hybrid Powerplant (AHP) was designed, constructed and tested. It is shown that an
additional 35% continuous thrust power can be supplied from the hybrid system with an overall weight penalty
of 5%, for a given UAS.
Dynamometer and windtunnel results were obtained to validate theoretical propulsion load curves. Using
measured powerplant data and an assumed baseline airframe performance characteristic, theoretical endurance
comparisons between hybrid and non-hybrid powerplants were determined. A flight dynamic model for the
AHP was developed and validated for the purposes of operational scenario analysis. Through this simulation it
is shown that climb rates can be improved by 56% and endurance increased by 13%.
The advantages of implementing a hybrid powerplant have been baselined in terms of payload range and
endurance. Having satisfied these parameters, a whole new set of operational possibilities arises which cannot
be performed by non-self-starting ICE only powered aircraft. A variety of autonomous robotic aircraft tasks
enabled by the hybrid powerplant is discussed.