The DelFlyBradshaw, Nancy L., and David Lentink. "Aerodynamic and structural dynamic identification of a flapping wing micro air vehicle." AIAA conference, Hawaii. 2008.Lentink, D. "Exploring the biofluiddynamics of swimming and flight." Wageningen University and Research Centre, Wageningen (2008).
/ref>de Croon, G.C.H.E.; de Clercq, K.M.E.; Ruijsink, R.; Remes, B.; de Wagter, C. (1 June 2009). "Design, aerodynamics, and vision-based control of the DelFly". International Journal of Micro Air Vehicles 1 (2): 71–97. doi:10.1260/175682909789498288.
/ref>Lentink, David, Stefan R. Jongerius, and Nancy L. Bradshaw. "The scalable design of flapping micro-air vehicles inspired by insect flight." Flying insects and robots. Springer Berlin Heidelberg, 2010. 185-205.
/ref>^ de Croon, G.C.H.E.; de Weerdt, E. ; De Wagter, C. ; Remes, B.D.W. ; Ruijsink, R. (April 2012). "appearance variation cue for obstacle avoidance". Robotics, IEEE Transactions on 28 (2): 529–534. doi:10.1109/TRO.2011.2170754. is a fully

controllable Controllability is an important property of a control system, and the controllability property plays a crucial role in many control problems, such as stabilization of unstable systems by feedback, or optimal control. Controllability and observabi ...

camera-equipped flapping

wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...

Micro Air Vehicle A micro air vehicle (MAV), or micro aerial vehicle, is a class of miniature UAVs that has a size restriction and may be autonomous. Modern craft can be as small as 5 centimeters. Development is driven by commercial, research, government, and mil ...

Ornithopter An ornithopter (from Greek ''ornis, ornith-'' "bird" and ''pteron'' "wing") is an aircraft that flies by flapping its wings. Designers sought to imitate the flapping-wing flight of birds, bats, and insects. Though machines may differ in form, th ...

developed at th
Micro Air Vehicle Lab of the Delft University of Technology
in collaboration wit
Wageningen University
The DelFly project focuses on fully functioning systems and follows a

top-down approach Top-down and bottom-up are both strategies of information processing and knowledge ordering, used in a variety of fields including software, humanistic and scientific theories (see systemics), and management and organization. In practice, they c ...

toward ever smaller and more autonomous flapping wing MAVs. The DelFly Micro with its 10 cm wing span and 3.07 grams is the smallest free flying controllable flapping wing MAV equipped with a

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

and video transmitter. Smaller flapping wing MAVs exist, but then without an onboard camera. In particular, a hobbyist from Albany NY, built a flapping wing MAV of 920 mg and just 60mm wing span, which i
the world's smallest free flying flapper till date
The 28 centimeter 16 gram DelFly II was capable of vertical take-off and landing and demonstrated simplified forms of autonomous flight, mainly using off-board processing. The DelFly Explorer measures 28 centimeter while weighing 20 grams and is equipped with a miniature stereo vision system for autonomous flight in buildings.

The DelFly Nimble is a very agile, tailless flapping wing MAV. It steers by modifying the motions of its wings, which allows it to perform high-speed maneuvers such as 360-degree flips. One of its uses is in studying insect flight; mimicking the extremely fast escape maneuvers of fruit flies revealed a new aerodynamic mechanism that helps to make rapid banked turns. The startup compan
Flapper Drones
is developing a commercial version of the DelFly Nimble for applications within the entertainment sector (drone shows, festivals, theme parks).

History

The DelFly project started in 2005 as a Design Synthesis Exercise for a group of Bachelor of Science students at the Faculty of Aerospace Engineering of the

TU Delft Delft University of Technology ( nl, Technische Universiteit Delft), also known as TU Delft, is the oldest and largest Dutch public technical university, located in Delft, Netherlands. As of 2022 it is ranked by QS World University Rankings among ...

. The flapping wing design was mentored b
Wageningen University
the remote control and micro camera integration b
Ruijsink Dynamic Engineering
and the real-time image processing by the TU Delft. The result of this exercise was the ''DelFly I'', a 50 cm

wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the other wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingspan of ...

, 21

gram The gram (originally gramme; SI unit symbol g) is a Physical unit, unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram. Originally defined as of 1795 as "the absolute weight of a volume of pure wate ...

s flapping wing MAV equipped with a camera. The DelFly I was able to fly both fast and perform slow hovering flight while providing reasonably stable camera images. In 2007, the DelFly II was created: a 28 cm wing span 16 gram flapping wing MAV equipped with onboard camera. This version was not only smaller, but it had a much broader flight envelope ranging from 7 m/s forward flight to near hovering flight and even backward flight at -1 m/s. In contrast to the DelFly I, the DelFly II could take-off and land vertically. The flight time of the DelFly II was around 15 minutes. The DelFly II was followed in 2008 by the DelFly Micro, a 10 cm wing span, 3.07 gram flapping wing MAV, also equipped with camera. The DelFly Micro is fully steerable with 3 controls for the throttle, elevator and rudder. Given the limited onboard energy, the flight time of the DelFly Micro was around 2 to 3 minutes. The DelFly Micro featured in the Guinness book of records 2009 as the smallest airplane in the world equipped with a camera. The DelFly participated in the 2005, 2007, 2008, 2010 and 2013 editions of the Micro Air Vehicle Competitions and was the first vehicle to demonstrate fully autonomous indoor flight. The DelFly Explorer was created in 2013. It has a stereo vision system that allows autonomous obstacle avoidance even in unknown and unprepared environments. The DelFly Nimble, presented in 2018, is the first tailless DelFly. It is much more agile than earlier designs; it can hover and fly in any direction up until 7 m/s in forward flight. It has a relatively simple design and is based on commercially of the shelf components and 3D printed parts. In 2019, a technological spinoff of the Delft University of Technology '
Flapper Drones
'' developing a commercial version of the DelFly Nimble was founded.

Influence

The DelFly is based on scaling relations for the aerodynamic design of flapping wings, which were discovered in the Dickinson lab at Caltech in collaboration with Wageningen University. Earlier research in the Dickinson lab also inspired The

Robobee RoboBee is a tiny robot capable of partially untethered flight, developed by a research robotics team at Harvard University. The culmination of twelve years of research, RoboBee solved two key technical challenges of micro-robotics. Engineers i ...

, both the Robobee and the DelFly design originated from research with robot models of flying insects.Lentink, David. "Biomimetics: Flying like a fly." Nature (2013). The DelFly influenced the

TechJect Dragonfly UAV The Dragonfly is a failed crowdfunding project that was to build a miniaturized four-winged ornithopter UAV designed by TechJect. The Dragonfly supposedly was designed for: aerial photography, interactive gaming, autonomous patrolling for security ...

and

FlyTech Dragonfly The Flytech Dragonfly is a remote-controlled flying toy manufactured by WowWee. The Dragonfly has been incorrectly billed as the world's first commercially available RC ornithopter (flapping wing aircraft). It was actually preceded by several othe ...

among many others refer to DelFly developments.

Design challenges

The design of autonomous, light-weight, less than 20 grams flapping wing MAVs poses challenges in various domains, including

materials Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologic ...

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

control Control may refer to: Basic meanings Economics and business * Control (management), an element of management * Control, an element of management accounting * Comptroller (or controller), a senior financial officer in an organization * Controllin ...

aerodynamics Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...

computer vision Computer vision is an interdisciplinary scientific field that deals with how computers can gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to understand and automate tasks that the hum ...

and

artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech re ...

. All these domains feed into each other. For example, studies on the design and aerodynamics of the wings have enhanced the efficiency of flight and the amount of generated lift. This allows for a larger payload to be taken on board, such as more onboard sensors and processing. In turn, such onboard processing can be used to perform automatic maneuvers in a wind tunnel, helping to create better models the DelFly and its low Reynolds

Applications

Flapping wing MAVs have a natural appearance and are inherently safe by means of their low weight and low speeds of the wings. This makes them particularly suitable for indoor flight, also in the presence of humans. Further, flapping wing MAVs can be used as (

augmented reality Augmented reality (AR) is an interactive experience that combines the real world and computer-generated content. The content can span multiple sensory modalities, including visual, auditory, haptic, somatosensory and olfactory. AR can be de ...

) toys, but other possible applications include

inspection An inspection is, most generally, an organized examination or formal evaluation exercise. In engineering activities inspection involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity. ...

of indoor industrial structures or

video streaming Video on demand (VOD) is a media distribution system that allows users to access videos without a traditional video playback device and the constraints of a typical static broadcasting schedule. In the 20th century, broadcasting in the form of o ...

of the crowd during indoor events. The DelFly flies well indoors with the air conditioning turned off, and outdoors under very low wind conditions. The exceptional flight capabilities of the DelFly Nimble, combined with its inherent safety and natural appearance, opened up new applications within the entertainment sector. The startup compan
Flapper Drones
is developing the technology further for drone shows during concerts, festivals and within theme parks.

References

{{reflist 2013 robots Unmanned aerial vehicles of the Netherlands Robotic animals Ornithopters Audiovisual introductions in 2005 Micro robots Aerial photography