International Journal of Micro Air Vehicles

Editor-in-Chief: Dr. Mark Reeder
published quarterly • ISSN 1756-8293 • 2012 journal prices/format options
2012 is volume 4

The demand for small unmanned air vehicles, commonly termed micro air vehicles, is rapidly increasing. Driven by applications ranging from civil search-and-rescue missions to military surveillance missions, there is a rising level of interest and investment in better vehicle designs, and miniaturized components are enabling many rapid advances.

The need to better understand fundamental aspects of flight for small vehicles has spawned a surge in high quality research in the area of micro air vehicle, or MAV research. These aircraft have a set of constraints which are, in many ways, considerably different from that of traditional aircraft and are often best addressed by a multidisciplinary approach.

Fast-response non-linear controls, nano-structures, integrated propulsion and lift mechanisms, highly flexible structures, and low Reynolds aerodynamics are just a few of the important considerations which may be combined in the execution of MAV research.

The role of the International Journal of Micro Air Vehicle Research is to provide the scientific and engineering community with a resource dedicated to publishing high-quality technical articles summarizing both fundamental and applied research in this field.

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abstracts from the first issue

Multi-Objective Topology Optimization of Wing Skeletons for Aeroelastic Membrane Structures

Bret Stanford and Peter Ifju University of Florida, Gainesville, FL, 32607
Corresponding Author Email Address: bstan@ufl.edu

This work considers the multi-objective aeroelastic optimization of a membrane micro air vehicle wing through topology optimization. The low aspect ratio wing is discretized into panels: a two material formulation on the wetted surface is used, where each panel can be membrane (wing skin) or carbon fiber (laminate reinforcement). An analytical sensitivity analysis of the aeroelastic system is used for the gradient-based optimization of aerodynamic objective functions. An explicit penalty is added, as needed, to force the structure to a 0-1 distribution. Pareto trade-off curves are constructed by considering convex combinations of two disparate lift, drag, or pitching moment-based objective functions. The general relationship between spatial stiffness distribution (wing topology) and aerodynamic performance is discussed, followed by the Pareto optimality of the computed designs over a series of baseline wing structures. The work concludes with an experimental validation of the superiority of select optimal designs.

Parameter studies in periodic and transient airfoil pure-plunge at low Reynolds Number

Unsteady airfoil aerodynamics is seeing a resurgence of interest beyond its classical foundations, especially at low Reynolds numbers, for applications to miniature unmanned aircraft and to understanding animal flight. The abstraction of the rigid 2D airfoil oscillating harmonically or in steps/ramps is a useful approximation for maneuvering flight, for gust response, and for flapping-wings in natural or manmade fliers. In contrast with the more traditional applications of helicopter blades and gust response of manned aircraft, the dimensionless rates for micro-flier applications are much higher and the boundary layer physics is perhaps different. The usual low-Reynolds number issues of laminar separation and vortex shedding are further complicated by the length and time scales of the imposed motion. We compare results from particle image velocimetry and dye injection in a water tunnel with two CFD solutions, for a set of high-frequency (k = pfc/U = 3.93) pure-plunge, cases. For high reduced frequencies we find little dependency on Reynolds number, evidently because the vortex shedding is dominated by motion-induced pressure gradients. Periodicity is strong, as established from comparison of instantaneous vs. phase-averaged PIV. For this condition, induced angles of attack are large enough to cause vortex shedding, but not a detached coherent leading edge vortex, in contradistinction with oft-cited results in classical dynamic stall. We observe that periodicity in the flowfield is established after 1-2 plunge periods after startup. We trace the evolution of the wake from the traditional "planar", at very low reduced frequency, through the aforementioned high-frequency case. Amplifying on prior results, we find that when varying reduced frequency and amplitude such that their product is constant (thus, Strouhal number is constant), that Strouhal number governs the topology of the wake, whereas the wake characteristic dimension depends on reduced amplitude of oscillation.

On the Birth of Micro Air Vehicles

Thomas J. Mueller, Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana, USA, 46556

The history of micro air vehicles really began with the development of model airplanes in
the 19th century and the development of radio controlled model airplanes in the 20th
century. The improvement in propulsion systems from rubber bands to liquid fuel
internal combustions engines and later battery powered electric motors made it possible
to produce longer and longer flights. The development of miniature radio receivers
and control components in the 1990s also had a large impact on the ability to design a
very small flying vehicle. Once the aerodynamics and control of small aircraft models
with a mass less that 100 grams were better understood, the micro-air-vehicle was born.
This paper traces the history of these events.

A Fixed-Wing Biplane Micro-Air Vehicle for Low-Speed Missions

Chinnapat Thipyopas and Jean-Marc Moschetta

Practical MAV recognition missions to be conducted in an outdoor urban environment simultaneously require the capability of both dashing to escape enemy fire and slowly loitering over a target in order to capture and transmit clear images to the ground station. Since they intrinsically offer better payload and endurance capabilities than rotorcraft of equal size, fixed-wing MAVs are considered as promising platforms to start with. The objective of the present study was to investigate the possibility to develop a fixed-wing MAV which could both perform rapid translations and low-speed flights through urban canyons. A low-speed wind tunnel campaign was conducted so as to compare several powered configurations including monoplane, biplane and tandem wing combinations. Since the experimental setup allowed for separate forces measurements of the wing and the propulsion set, the wing-propeller interaction was analyzed. It was observed that a positive-stagger biplane configuration powered by counter-rotating propellers placed in pusher position provided the best trade-off between high-speed performances and a low-speed capability with a limited electric consumption. Consequently, a 30cm-span MAV biplane prototype, named TYTO-30, equipped with a 110g-payload which includes a video camera, navigation and autopilot system has been designed and successfully flight tested.

Flight Dynamics of Flapping-Wing Air Vehicle

Roman Y. Krashanitsa, Dmitry Silin, and Sergey V. Shkarayev, University of Arizona, Tucson, Arizona, 85721, USA

Gregg Abate, Air Force Research Laboratory, Munitions Directorate, Eglin AFB, FL 32542-6810, USA

The research and development efforts presented in this paper address the flight dynamics of a flapping-wing air vehicle (ornithopter). The 74-cm wing span ornithopter was equipped with the automatic control system that provides the stability augmentation and navigation of the vehicle, and flight data acquisition. Wind tunnel tests were conducted with the control surfaces fixed in neutral position and flapping motion of the wings activated by a motor at a constant throttle setting. Coefficients of a lift, drag, and pitching moment were determined at a free stream velocity of 7.2 m/sec and the angle of attack varied from 0 to 40 degrees. In addition, variations of derivatives of aerodynamic coefficients with the freestream velocity were investigated. A series of flight tests were conducted with fixed controls demonstrating ornithopter stability in all axes. Proportional control laws were programmed into the autopilot for the closed-loop controls. A number of test flights of the autonomous ornithopter were conducted with the telemetry acquisition. During the autonomous flights, the autopilot performed waypoint and altitude navigation demonstrating stable performance.

International Journal of Micro Air Vehicles

abstracts from the first issue

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