Flight Performance Of A Multirotor Unmanned Aerial Vehicle With Digital Displacement Hydrostatic Transmission

Abstract

This paper summarises the development of a hybrid multirotor UAV which uses a Digital Displacement® hy-drostatic transmission. The design of Flowcopter’s FC-100 demonstrator UAV is presented, along with a sum-mary of the concept and the modelling equations of the propulsion system. Focus is placed on gaining a critical physical understanding of the rotor aerodynamic performance through experimental characterisation. To iso-late the influence of interactional aerodynamic effects between rotors and with the airframe, the experimental campaign comprises testing at different levels; a single fixed-pitch rotor in static and translational flight condi-tions, and flight testing of the full-scale demonstrator UAV. The analysis of the aerodynamic ground effect demonstrates a greater effect than an equivalent helicopter. Test data shows a negligible effect on lift efficiency when hovering at wind speeds up to 11.2 m/s. Translational flight tests at airspeeds of up to 18.2 m/s demon-strate an increase in lift efficiency at lower speeds. An outlook towards future testing and development is presented.