international journal of mechanical engineering and technology (ijmet… review of... ·...

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME

348

A REVIEW OF UNMANNED AERIAL VEHICLE AND THEIR MORPHING

CONCEPTS EVOLUTION AND IMPLICATIONS FOR THE PRESENT DAY

TECHNOLOGY

Mr. Abhishek S H1, Dr. C Anil Kumar

2

1PG student, Department of Mechanical Engineering, KSIT, Bengaluru, Karnataka, India

2Dean, Department of Mechanical Engineering, KSIT, Bengaluru, Karnataka, India

ABSTRACT

A new aerial platform has risen recently for military and civilian applications which

dynamically develop presently, the Unmanned Aerial Vehicle (UAV). The term “Unmanned Aerial

Vehicle” (UAV) is interchangeable with the terms “Remotely Piloted Vehicle” (RPV) and

“Remotely Operated Aircraft” (ROA). The term is also commonly used interchangeably with

“drone". The UAVs follow the laws of aerodynamics and in a larger sense, the laws of physics.

UAVs are relatively a new development and even more important, they do not have the major design

constraints associated with having a pilot on-board.

Morphing aircraft are flight vehicles that are capable of altering their shape to meet mission

changing requirements of the aircraft and to perform flight control without the use of conventional

control surfaces. Therefore, the shape characteristics of such an aircraft change in-flight to optimize

performance. This morphing is realized by monitoring the wing geometric parameters. These

parameters include the wing span, planform, aspect ratio, thickness, chord, camber, and consequently

the wing area. This paper explores the evaluation, the path and its review of recent utilization of

UAVs and their morphing concepts for the present day technology. Also it explored in detail as a

basic in UAVs and its development as miniature aircraft in the present world scenario.

Key Words: Unmanned Aerial Vehicle (UAV), Morphing aircraft, Resin Transfer Moulding (RTM)

I. INTRODUCTION

Unmanned Aerial Vehicles (UAVs for short; also known as a drone) are the logical

successors to modern aircraft and advancements in automated technology. The current generation of

UAVs is focused on wartime capabilities and reconnaissance, leaving an existing market untapped

by UAV technology: the commercial field. There are many applications for UAV technology in the

INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING

AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)

ISSN 0976 – 6359 (Online)

Volume 4, Issue 4, July - August (2013), pp. 348-356

© IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com

IJMET

© I A E M E



349

military and civilian market, from emergency response applications and media outlets to

communication technicians and horticulturalists. It is a fact, though a very simplistic fact, that

unmanned aerial vehicles (UAVs) are little aircraft, more or less. This means that the UAVs follow

the laws of thermodynamics and the laws of physics. In other words, the category of vehicles called

aircraft can be divided into two sub-categories, i.e. manned and unmanned. It is fairly common that,

under certain conditions, manned aircraft can appear strange and unusual to observers, even pilots. It

is certainly reasonable that UAVs could appear even more strange and unusual than manned aircraft.

UAVs are a relatively new development and even more important, they do not have the major design

constraints associated with having a pilot on-board.

It is worth noting that the Federal Aviation Administration (FAA), which regulates aircraft

design and operations in the United States, has stated emphatically that UAVs must meet the “rules

of the road,” essentially as do manned aircraft. The FAA standards are still being developed, but the

FAA has made it clear that they will not let aviation safety be degraded by UAVs. There will be

volumes of airspace that are at low altitude and uncontrolled where there will be reduced regulation,

much like the rules environment that applies to the operation of scale model aircraft (which may be

considered as personal UAVs). Government UAV operations can also be separated from all other air

traffic, using airspace exclusively assigned to the Government, such as restricted areas. Government

UAVs often cannot meet FAA requirements, so this concept of separation is frequently used to

prevent collisions.

UAVs are even more varied in their physical characteristics than are manned aircraft. Their

size widely varies with wingspans ranging from 7 inches to 13 ft [1]. Mini-UAVs in the current field

have wingspans ranging from 21 inches to 10 ft. These UAVs can be remotely controlled or can fly

autonomously based on pre-programmed flight plans. They carry a variety of payloads including

infrared cameras, television cameras and jamming electronics. UAVs are of growing interest to

military operations, but they can also be used in a variety of civilian applications. Potential military

applications for mini-UAVs include local reconnaissance, target identification, post-strike battle

damage assessment, electronic warfare (including radar jamming) and combat search and rescue.

Potential civilian applications include monitoring traffic, inspection of oil pipelines or power-lines,

border surveillance, killing harmful insects, surveying wildlife, real estate photography, monitoring

concentrations in chemical spills and more [2].

II. HISTORY

1922 – First Launch of an unmanned aircraft (RAE 1921 Target) from an aircraft carrier (HMS

Argus).

1924 – First successful flight by a radio controlled unmanned aircraft without a safety pilot on-board;

performed by the British RAE 1921 Target 1921, which flew 39 minutes.

1933 – First use of an unmanned aircraft as a target drone; performed by a Fairey Queen for gunnery

practice by the British Fleet in the Mediterranean.

1944 – First combat use of an unmanned aircraft (German Fi-103 “VI”) in the cruise missile role and

U.S. Navy TDR- 1 attack drone in the strike role, dropping 10 bombs on Japanese gun positions on

Ballale Island.

1946 – First use of unmanned aircraft for scientific research; performed by a converted Northrop P-

61 Black Widow for flights into thunderstorms by the U.S. Weather Bureau to collect meteorological

data.

1955 – First flight of an unmanned aircraft designed for reconnaissance; performed by the Northrop

Radio-plane SD-1 Falconer/Observer, later fielded by the U.S. and British armies.



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1960 – First free flight by an unmanned helicopter; performed by the Gyrodyne QH-50A at NATC

Patuxrnt River, Maryland.

1998 – First trans-Atlantic crossing by an unmanned aircraft; performed by the Insitu Group’s

AerosondeLaima between Bell Island, Newfoundland, and Benbecula, Outer Hebrides, Scotland.

2001 – First trans-Pacific crossing by an unmanned aircraft; performed by the Northrop Grumman

Global Hawk “Southern Cross II” between Edwards AFB, California, and RAF Edinburgh,

Australia.

COUNTRIES DEVELOPING UAV IN LARGE QUANTITY The two main countries involved in UAV development are the USA and Israel both these

countries are the world leaders in UAV design.

� The USAF tends to classify their main operational UAVs using the RQ abbreviation.

� The prefix IAI (Israel Aircraft Industry) is used for the majority of the UAVs that Israel

produces.

� These two main countries then sell these developed UAVs to other world countries,

depending on their needs. As some counties need then for reconnaissance while other need

them for battle purposes.

� Not only there is interest in battle UAVs, but there is also a commercial interest for non-

military UAVs. This commercial interest has lead to private developers in different countries

designing and developing UAVs.

� Australian aerospace industry has been developing UAVs since the early 1950s. The

development of UAVs in recent years has assisted the Australian army in surveillance and

coast watch.

III. Classification of UAVs

UAV became one of the branches of military and civil technics which dynamically develops

presently. Due to the fact that the development of UAVs, much momentum is filled with modern

aviation science and technology, the main emphasis of this theory should be made to develop models

and methods of system integrators designing unmanned systems and their effective use for different

people’s economic and military tasks. The first stage of development of any theory is a unified

terminology and classification of research and development. Consider the example of the

classification of UAVs as shown in table. 3.1 for such basic parameters such as take-off weight and

range and fig. 3.1 shows the current U.S. operational UAVs.

Table 3.1: Classification of UAVs defined by Unmanned Vehicle System (UVS) [4]

UAV

Category Range(km)

Flight

Altitude (m)

Endurance

(hour)

Max.

Take-off

Weight (kg)

Example

Micro <10 250 1 <5 Wasp III

Mini <10 150 – 300 <2 <30 Raven

Medium Range 70 – 200 5000 6 – 10 1250 Sky Spirit

Medium Altitude

Long Endurance >500 14000 24 – 48 1500 Predator

High Altitude

Long Endurance >2000 20000 24 – 48 12000

Global

Hawk



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Fig. 3.1: Current U.S. Operational UAVs [3]

IV. MATERIALS

Recent UAV combat successes and US military plans for a multi-billion dollar UAV fleet by

2013 have made composites – intensive UAVs a key growth market for advanced materials. UAVs

are no longer simple and inexpensive. Use of lightweight advanced composites is essential in

increasing UAV flight time. Lear Astronics Corp Development Sciences Centre’s composite

capabilities for the design and fabrication of UAVs include high molecular weight polyethylene, S-

glass (magnesia-alumina-silicate glass with high tensile strength), high electrical resistivity glass (E-

glass), aramid, quartz, bismaleimide and graphite fibres reinforcing epoxy, polyester, vinyl ester,

phenolic and polyimide resins. Composite processing methods include compression moulding, resin

transfer moulding (RTM), prepreg lay-up, wet lay-up and convolute winding with oven or autoclave

curing. These advantages of composites over metals are important in UAVs:

� low weight and excellent corrosion resistance;

� high resistance to fatigue;

� reduced machining;

� a very low thermal expansion reducing operational problems in high altitude flight.

However, composites also have disadvantages compared to metals:

� Higher cost;

� Relative lack of established design criteria;

� Degradation of structural properties at high temperature or when wet;

� Poor energy absorption and resulting impact damage in hard landings;

� The need for lightning strike protection;

� The expensive and complicated inspection procedures needed.



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For weight reasons, aluminium is the only metal used in UAVs. Use of composites can

reduce overall UAV weight by 15-45% depending on the extent of composite use. Above a 50%

weight reduction requires improvements in composite economics at the moment. Composites have

been used in modest load-bearing components such as elevators, which comprise about 20% of

aircraft weight. For further weight reduction, composites must be used in higher load-bearing

components such as the tail, wing and fuselage. Organic fibres offer high strength and low weight

and are used more in UAVs than ceramic and metallic fibres. Graphite (>95% carbon) and carbon

(93- 95% carbon) fibres are the most commonly used. Glass fibre is used occasionally for its low

cost and is likely to be more common in civilian than military UAVs due to the former’s less

rigorous operating conditions. Typical damage to composites that needs to be detected both after

fabrication and after UAV flight are: cracks and delaminations in the skin; debondings between skin

and core; and defects in the core (crushing), of which only a small part is visible from the outside.

Ultrasonic detection can indicate internal defects. Detection of damage is essential to proper UAV

maintenance and long service life.

V. MORPHING AIRCRAFT

Morphing aircraft are flight vehicles that are capable of altering their shape to meet changing

mission requirements of the aircraft and to perform flight control without the use of conventional

control surfaces. Therefore, the shape characteristics of such an aircraft change in-flight to optimize

performance. This morphing is realized by monitoring the wing geometric parameters. These

parameters include the wing span, planform, aspect ratio, thickness, chord, camber, and consequently

the wing area. Aircraft morphing research is generally conducted for benefits including the

improvement of the versatility of a given airframe by improving the performance for multiple flight

regimes, the replacement of conventional control mechanisms, the increase of cruise efficiencies and

the reduction of structural vibration.

The research on morphing UAVs has experienced over recent decades increasing

investigations in both military and civilian domains for applications including surveillance, attack,

fire detection, and traffic monitoring. Subsequently, the NASA morphing project [11] focused on

developing novel applications for smart materials and inventing methods for applying those materials

to aircraft. Additionally, the Morphing Aircraft Structure (MAS) program [12] aimed to design and

build active, variable geometry wing structures with the ability to morph in-flight. Furthermore, the

US Air Force’s Adaptive Versatile Engine Technology (ADVENT) program [13] supplied inlet,

engine and exhaust technologies to optimize propulsion system performance. This increasing interest

in morphing structures is the result of their significant advantages over conventional UAV structures.

These advantages comprise the increase in the capability and versatility of the aircraft. According to

MAS, such an aircraft is a multi-role platform that firstly, changes its state substantially to adapt to

mission changing requirements. Secondly, it provides a superior system capability in term of an

optimal performance into a single system with a low turning radius, long endurance, increased

payload, and high speed. This is not possible without the wing reconfiguration. Finally, it uses a

design that integrates innovative combinations of advanced materials, actuators, flow controllers and

mechanisms to achieve the state change. By wing morphing, the author refers to a planform that is

able to transform smoothly its shape or any other characteristic affecting significantly its

aerodynamic properties. It is evident that a conventional aircraft has a wing matching the mission it

is dedicated to. As a general observation, the concept of morphing wings is inspired from birds; but

also from bats at its early stage as illustrated by the flying machines of Clement Ader [14] depicted

by fig. 5.1.



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Fig. 5.1: Ader’s Eole – a shape changer

in 1890 [14]

Fig. 5.2: Eagles in various wing

configurations [15]

In fact, birds are able to adapt their wings to the conditions that need to be met at a given

time. Thus, they can fold their wings tightly to dive for a prey or fully extend them to glide; thus

saving energy as it can be seen in fig. 5.2. Additionally, they use the camber and wing twist to

control their flight. By changing the area of the wing, birds and other flying insects are able to alter

the lift generated.

Compared to conventional aircraft, morphing aircraft become more competitive as more

mission tasks or roles are added to their requirements. As indicated in fig. 5.3, designing and

building aircraft shape changing components is not new. In the past, aircraft have used variable

sweep, retractable landing gear, retractable flaps and slats, and variable incidence noses. However,

recent work in smart materials and adaptive structures has led to a resurgence of interest in more

substantial shape changes, particularly changes in wing surface area and controlled airfoil camber.

The Hypercomp/NextGen design, shown in fig. 5.4, used substantial in-plane shape changes and

surface area reduction to transform the wing from an efficient, high-aspect-ratio loiter shape to an

efficient, swept, reduced-wing-area transonic, low altitude dash shape.

Fig. 5.3: Morphing Aircraft Design

Components

Fig. 5.4: Next Gen Morphing Design



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There are four main configurations that morphing aircrafts should be able to perform in order

to keep the optimized shape for the best performance possible: loiter, dash, manoeuvre and cruise

which is shown in fig. 5.5.

Fig. 5.5: Standard, Loiter, Dash and Manoeuvre

Standard configuration is the best configuration for cruising which depends on the cruise

altitude and cruise speed. Loiter configuration is used for flight stages like surveillance thus low

speeds; in general the wing must have high aspect ratio, i.e., large span and small chord. Dash

configuration is indicated for high speeds; the span is small, the wing is swept and is tapered.

Manoeuvre configuration is appropriated for manoeuvres; small span and large chord and slightly

swept. The aim of these companies is to build a UAV for multiple flight conditions. Numerous wing

parameters such as aspect ratio, wing span, sweep angle and chord change during the flight, allowing

the wing to change its shape.

Lockheed Martin is developing a folding wing: the fully extended configuration is for

loitering and the folded configuration for dashing. The wing is able to fold 130º into the fuselage

shown fig. 5.6, [16].

Fig. 5.6: Lockheed Martin’s Morphing Aircraft

Variable-span morphing wings were studied in Virginia Polytechnic Institute and it has been

found that this morphing not only improves the aircraft’s performance at different flight conditions,

but also improves the roll control, when compared to conventional roll controls. This research was

conducted to apply these wings to a cruise missile. Even so they found that, when the wing is fully

extended instability problems such as flutter are likely to happen sooner (fig. 5.7).



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Fig. 5.7: Variable Span Morphing Wing Fig.5.8: Raytheon Morphing Wing Design

Fig. 5.8 shows the Raytheon telescoping wing design in its morphed and unmorphed

configurations. This design addresses a unique challenge since the wing loading is large (of the order

of 250 pounds per square foot) and the available volume for actuators and support structure is small.

VI. DISTINGUISHING CHARACTERISTICS OF A UAV

The fundamental aspects that distinguish UAVs from other types of small unmanned aircraft

(such as models) include the operational purpose of the vehicle, the materials used in its manufacture

and the complexity and cost of the control system. A model aircraft is used for sport and the pleasure

of flying it. The only exception to this is the use of a model aircraft for training purposes. This is

only a limited use utilised at the beginning of a pilot’s training. If a model is used for commercial

gain or payment, it is then being operated as a UAV and aviation regulations need to be considered.

The materials used in UAV manufacture are high tech composites delivering maximum strength at a

low density to increase performance. These are expensive materials and are not used in models and

recreational aircraft where balsa wood and basic plastics are the primary materials used and not

composites due to the cost. Control systems employed for UAVs enable greater performance

characteristics to suit its mission aspect. Autopilot systems, radio-controlled and high complicated

control systems, help operate the UAVs during missions. However the operational requirements of

model aircraft are less complicated than that of a UAV and thus radio controlled system are used,

without implementing the use of autopilot and other complicated engineering systems. Reliability of

UAVs is essential, not only for completing a mission successfully, but also to ensure that the cost of

the mission does not exceed projected funding. However model aircrafts are not completing

missions, whereby reliability is essential. Therefore, the reliability of a UAV is much more

significant than that of a model aircraft, due to the mission aspect and cost involved.

VII. CONCLUSION

Performance, characteristics and mission aspects have resulted in many different types of

UAVs being researched and developed. With all these new and varied UAVs now in service,

improved classification methods need to be developed so the correct UAV can be chosen for the

right mission. When classifying UAVs using their performance, characteristics such as weight,

range, endurance, altitude, payload and wing loading will help determine what the UAV is used for.

Thus, a UAV can be designed from data given to suit its necessary mission. Once the mission aspect

has been determined for a given UAV, its required performance, characteristics and mission aspects

can be found to suit its mission criteria. Further, this paper will help as a reference for a future

review of recent utilization of UAVs for designers and manufacturers.



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REFERENCES

Books

[1] Cambone S. A., Krieg K., Pace P., and II L. W. “Unmanned Aircraft Systems Roadmap 2005-

2030”. Technical Report, Office of the Secretary of Defence, 2005.

[2] Huber A. F. I. “Death by a Thousand Cuts: Micro-Air Vehicles (MAV) in the Service of Air

Force Missions”. Technical Report, Air War College, US Air Force, April 2001.

[3] “The Impact of Unmanned Aerial Vehicles on the Next Generation Air Transportation

System: Preliminary Assessment”, UAV National Task Force, October 22, 2004.

Proceedings Papers [6] "RQ-11 Raven". Army-technology.com. Retrieved 2013-08-12.

[11] R.W. Wlezein, G.C. Horner, A.R. McGowan, S.L. Padula, M.A. Scott, R.J. Silox, and J.O.

Simpson, “The Aircraft Morphing Program”, AIAA-98-1927.

Thesis [16] D. A. Neal III, “Design, Development, and Analysis of a Morphing Aircraft Model for Wing

Tunnel Experimentation”, University of Virginia, April 2006.

Journal Papers [10] John K. Borchardt, “Unmanned Aerial Vehicles Spur Composites Use”, Elsevier Ltd., 0034-

3617/04, April 2004.

Web site [4] Unmanned Vehicle Systems International web site, “http://www.uvs-international.org/”, as

accurate of May 15th

, 2007.

[9] International Defense Magazine,

“http://defense-update.com/products/s/sky_spirit.htm”, Retrieved 2013-08-10.

[12] DARPA, “http://www.darpa.mil/dso/archives/mas”, 2013-08-10.

[13] Defense Industry Daily, “http://www.defenseindustrydaily.com/the-advent-of-a-better-jet-

engine-03623”, 2013-08-13.

[14] “http://www.flyingmachines.org/ader.html”, 2013-08-14.

[15] Aerospace Consulting DrorArtzi, “www.dror-aero.com/index.htm”, 2013-08-14.

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