The Dragonfly Flight Envelope and its Application to Micro UAV Research and Development

2014

Journal of Aircraft

This paper explores the energetics, efficiency, and performance of flapping-wing actuation. The system-level consequences of energy-saving resonant mechanisms across the full flight envelope of hover, maneuver, and glide of flapping-wing systems is analyzed. A review of the extent to which resonant mechanisms are employed in a dragonfly and how useful they are to a maneuvering flapping-wing micro air vehicle system shows that the value of resonance is limited. It is shown that employing resonant elastic mechanisms in real-world configurations on an aerodynamically efficient flyer could produce insignificant energy savings. This number is further reduced by at least 14% across the operational flapping frequency band of a dragonfly, suggesting that resonance is not the major driver for aerodynamically efficient flyers such as the dragonfly. Using a simple harmonic oscillator as a simplified model, a significant reduction of approximately two to three times in maneuvering limits is demonstrated for a system employing elastic elements. In systems with elastic storage, aeroelastic instabilities leading to reductions in maximum glide speed are possible, especially for aerodynamically dominated systems. It is concluded that the system-level cost of implementing resonant mechanisms indicates against resonance in hover being a primary factor in the design of a dragonfly or dragonfly-inspired aircraft. Nomenclatureof the wing, m D = drag, N E = energy, J E A = aerodynamic energy, J F = actuator torque, N · m H r = vertical force in the local frame of reference, N H r;vert = vertical force in the global frame of reference, N I = inertia, kg · m 2 K = spring constant, N · m∕rad K h = translational stiffness, N∕m K ϕ = torsional stiffness, N · m∕rad L = lift, N P = time-averaged power, W r = radius from wing root, m S = wing area, m 2 s = semispan, m T = flapping-wing period, s U = critical velocity, m∕s V = tangential velocity, m∕s α = angle of attack, rad β = stroke plane angle, rad ζ = damping ratio Θ = change in angle of attack, rad λ = − B 2I τ = torque, N · m Φ = full stroke flapping angle, rad ϕ = flapping angle, rad ϕ proj = flapping angle projected onto vertical plane, rad ω d = damped natural frequency, rad∕s ω n = natural frequency, rad∕s

Section: Discussionmentioning

confidence: 98%

Section: Dragonflymentioning

confidence: 98%

Section: Maneuverabilitymentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Systems-Level Analysis of Resonant Mechanisms for Flapping-Wing Flyers

Kok

2014

Journal of Aircraft

“…Dragonflies in particular are able to take-off and land vertically, fly backwards and sideways and accelerate rapidly. [3][4][5][6] Such a versatile range of motion expands the mission envelope of the aircraft system, making it worth investigating.…”

Section: Introductionmentioning

confidence: 99%

A low-cost simulation platform for flapping wing MAVs

Kok

2015

SPIE Proceedings

This paper describes the design of a flight simulator for analysing the systems level performance of a DragonflyInspired Micro Air Vehicle (DIMAV). A quasi-steady blade element model is used to analyse the aerodynamic forces. Aerodynamic and environmental forces are then incorporated into a real world flight dynamics model to determine the dynamics of the DIMAV system. The paper also discusses the implementation of the flight simulator for analysing the manoeuvrability of a DIMAV, specifically several modes of flight commonly found in dragonflies. This includes take-off, roll turns and yaw turns. Our findings with the simulator are consistent with results from wind tunnel studies and slow motion cinematography of dragonflies. In the take-off mode of flight, we see a strong dependence of take-off accelerations with flapping frequency. An increase in wing-beat frequency of 10% causes the maximum vertical acceleration to increase by 2g which is similar to that of dragonflies in nature. For the roll and yaw modes of manoeuvring, asymmetrical inputs are applied between the left and right set of wings. The flapping amplitude is increased on the left pair of wings which causes a time averaged roll rate to the right of 1.76rad/s within two wing beats. In the yaw mode, the stroke plane angle is reduced in the left pair of wings to initiate the yaw manoeuvre. In two wing beats, the time averaged yaw rate is 2.54rad/s.

Three biomimetic flight control sensors

International Journal of Intelligent Unmanned Systems

2014

Self Cite

Purpose – Insects depend on the spatial, temporal and spectral distribution of light in the environment for navigation, collision avoidance and flight control. The principles of insect vision have been gradually revealed over the course of decades by biological scientists. The purpose of this paper is to report on bioinspired implementations and flight tests of these sensors and reflexes on unmanned aerial vehicles (UAVs). The devices are used for the stabilization of UAVs in attitude, heading and position. The implementations were developed to test the hypothesis that current understanding of insect optical flight control systems is feasible in real systems. Design/methodology/approach – Design was based on behavioral and anatomical studies of insects. The approach taken was to test the designs in flight on a UAV. Findings – The research showed that stabilization in attitude, heading and position is possible using the developed sensors. Practical implications – Partial alternatives to magnetic, inertial and GPS sensing have been demonstrated. Optical flow and polarization compassing are particularly relevant to flight in urban environments and in planetary exploration. Originality/value – For the first time the use of multispectral horizon sensing, polarization compassing and optical flow-based heading control have been demonstrated in flight.