Design, Development, and Flight Test of a Small-Scale Cyclogyro UAV Utilizing a Novel Cam-Based Passive Blade Pitching Mechanism

Abstract

A cycloidal rotor is an innovative horizontal axis propulsion system, which is utilized in the present study to develop a fully-controllable flying aircraft (known as "Cyclogyro"). The present 535 gram cyclogyro uses a hybrid configuration with two cyclorotors and a horizontal tail rotor. Since a cycloidal rotor relies on cyclic blade pitching for producing thrust and also for control, designing a reliable pitch mechanism that can provide the required blade pitching kinematics (depending on the advance ratio) is extremely important. A novel blade pitch mechanism has been developed, which is passively driven by centrifugal force, and could potentially be adapted to generate the required pitching schedules for efficient operation over a range of advance ratios. A simplified flightworthy version of this mechanism was implemented in the present cyclogyro. The mechanism was able to generate the appropriate blade kinematics and the thrust required for the vehicle to hover. Also, the present mechanism is designed such that it is possible to vary both amplitude and phasing of the cyclic blade pitching. A novel control strategy was developed using blade pitch amplitude (thrust magnitude) control for roll, phasing (thrust direction) for yaw and tail rotor for pitch control. The control strategy was implemented using a three gram onboard processor, which was used to stabilize the vehicle without a pilot, through a closed-loop feedback control system. This is the first flight-capable cyclogyro reported in the literature to utilize cycloidal rotors having both pitch amplitude and phase control. The successful flight for the present vehicle also validates the flightworthiness of this completely passive pitch mechanism design, which has great potential for efficient forward flight. NOMENCLATURE µAdvance ratio V ∞ Freestream velocity Ω Rotational speed r Rotor radius 145

Design, Analysis, and Experimental Investigation of a Cyclocopter with Two Rotors

“…Eventually, a quadrotor cyclocopter, weighing approximately 12.8 kg, was demonstrated for free flight: both indoors and outdoors [13]. A team at the University of Maryland also developed a twin-rotor microaerial-vehicle-scale cyclocopter and demonstrated stable hover flight [14,15].…”

Optimal pitching schedules for a cycloidal rotor in hovering

“…Finally, another pitching profile was considered in some studies (Adams and Fagley, 2013; Adams et al , 2013): …”

“…The first term on the right hand side of equation (6) is often called zero-angle of attack profile . This type of pattern, for example, can be approximately achieved by a 3D-cam cyclorotor (3D: three-dimensional) (Adams and Fagley, 2013; Adams et al , 2013).…”

“…Cycloidal rotors for aeronautical propulsion were first introduced in the 1930s, starting with the pioneering work of Wheatley (1933; Wheatley and Windler, 1935) and later of Eastman et al (1943; Eastman, 1951). Recent years saw a rediscovery of this rather unexploited concept, documented in a diversity of experimental and theoretical works, including that of Gibbens and Boschma (1999; Boschma, 2001; Hwang (2005, 2007; Higashi, 2006; Hu et al , 2006; Iosilevski, 2003; Kim et al , 2003; Lee et al , 2014) and the thorough investigations of Benedict and co-workers (Benedict et al , 2008, 2010a, 2010b, 2011; Adams and Fagley, 2013; Adams et al , 2013). In the frame of the CROP project, a further analysis of the potentialities of the cyclogyro concept for the propulsion of manned and unmanned lightweight aircraft was undertaken, leading to the development of prototypes (Wills and Schwaiger, 2012) and numerical and analytical models (Páscoa et al , 2013; Xisto et al , 2014).…”

CFD modelling of a fan with a cycloidal rotor

“…Experimental tests were also carried out and the behaviour of the machine during flight and hovering was examined. Adams [13] developed a fully flying cyclocopter (UAV) that uses 2 cycloidal rotors for flight. To make this possible, it was necessary to significantly reduce the device mass, develop a mechanism for changing the angle of the blades and design a control system.…”