The evelopment of Flapping Wings for a

Hovering Micro Air Vehicle

by

Derek John Byk

A tbesis submated in conformity withthe requirements for die degree of Masters of Appd Scierw

Graduate Deparima of Aerospace Sckixe and Eaginaring University of Toronto

3 uisitions and Acquisiis et B iognphic Services rrvkes bibliognphiques

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The Devcbpment of PLpping Wiiga for a Boveriag Mkm Air Vehick Mastcrs of Applied Scicncc, 2000

W John Bilyk

This documnt pcesents the mtbods ancl resuits of e d y experirrients, conducteci

at the University of Toronto's Ii1Stitute for Aerospace Sndies, t o w d the evebpmnt of

w b g s fbr a bovaing, ftapping-wing micro air vebick. The vehfcle envisiDrred

symmetrically actuates four whgs within a 15 cm iameter, horizontai disc, tbnistuig the

air downwacd, ushg the 'clepfing' d y n e m i c effect. The entire vehicle will fit

witbiaa 15 cmcube.

Foliowing an elementary, quasi-steady analysis to estimate the r q u g e d flapping-

ikqpency, test quipmnt was desi@ to evaIuae verious wing concepts. An empirical

test pocess &wed many wing designs to be evaiuated b u g h a wide tlapping-

hquency range and at s e d flapping ampiitudes. One year of experhentaion led to a

design capabk of geiiereting mm than 50 granrr of thrust d e coirpuming Iess than 6

W of power. This peifornmnce is comparable to the best that an unclucteci p10peIIer or

rotor of tk lp9nie! diameter wodd achieve.

I must acbwledge sevaal groups and individu&, without whom tbe

completion o f this thesis would eabcr have been impossible or much more difficuit.

1 should begin by thanking Mr. David Loewen. As tk MAV project's chief

engimer, Dave Lown p e d o d much mre thaa his dure of the nscatch. Although,

w b v e r possible in this document, 1 have given creda to Dave for both his ideas and his

hard work, 1 csmiot begin to express how indebted 1 am to him I was fbrtunate to be

involved in a project with such a thomugh. yet creative leader-

1 must also thaaL h. DeLaurier. His bands-off supmUion style gave me grrat

confiellce; somebody 1 respect& tnisted my judgement. Noaetheiess, each timt en

issue mse requiring his iuput, it becemc obvious that "Dr. D." had been cbsely

following my progress. 1 bope e>cpaicnce wl giaiit me the same wisdom.

1 wuld LiLe to thank out peitrieis at SRI I n t h n a 1 for patting us on th back

when we weren't sure Sour progcess was aequae. In particular, 1 would Iike to thaiiL

Mr. Roy Kornbluh whose input kept our erxi of the pmject on the correct course.

DAWA musi be recognzed for proMding such a fsscinathg rrsearch topic and

the fundiig to explore it.

1 mu& theak NSERC for tbe scbotsrship tha put K d Dinner on my table.

Wabout tbis m i a l recognition, tk pursuit o f my master's degree would have been a

great beidship tor both myseifand my mfe, Simimik

Finally, thaaL you, S u ~ n n a Orily you hiow what 1 was Wte, tossing and turniag

at2:am,wiilivisiotl~ofWmgactustiowchcmsdaocmginmy~ Youwete

mlmrkabIy tolaad

To my beautiflll wif,

Suuioaa Margaret Bilyk

Table of Contens

............ 2.1 Natuds SOI& ...m.m..o~.~.o.o~........o....H...m.HI..mHII..m.mmmm.H...~..H....mo. .... 2-1 ........................................................................................................ 2. 1.1 -QL of MwIa 2-1

.............................................................................................................. 2 Cmtrol of Pitcb 2-2

2.13 C l i p h g I CIapPal .................................................................................................... 2-2

2-14 Flrpping Cycle Wave Shap and Musle Duty Cycle .............. .. ....... ............................. 2-3

Frequcocy and Amplitude ............................................................................................... 2 4

h a g ~ caxiumph .................................................................................................. 2 4

Vaca< Chdan, SAAding, Pd V i i m .................... ................................ 2.7 .... CirpFhg .............. ....................-.... o................................*....... - .....................O....... 2-9

me SIUUTUiF MA VAppmucb .......w.....~-..,... ~~..-..a..a.,~........... 3-1

304 CudidrW Wh# CO-b o"oaomwoo"oo*a-~-o~ao~--aom~--"oomm~aoo-ooom-oo.oo.wmw J-7

3.4.1 S h p k Mcmkane Wmg ................... .., ............................................................... 3 - 8 3.42 RiiReinBDrcsd Manbrane Wmg ......... ...... ............ ..,. ....................................... 3-9 3.43 Camber-Ca~mlkd M e m h e Wing .,.,............... .,.,..... .............................................. 3-9 3.4.4 SpanwisaStiffcned Metubmue Wmg .................... .. .............. ........................ 3-10 3.4.5 Double Surface and Ccuqpd M i l Wmgs .......................................................... 3-1 1

4.3.1 Quasi-Stdy Fstbnatia~ of Wmg Twist fW Coaant Cr 'Ruwghout Cyck .............. ..... 4-5 4.32 Quasi-Stcady Estimath of Requwd Fhppmg Frequency for Wmg Twist Caizitent

Tbrougbout Cycle .........*..................****................*.....*....*..*.**...**......*.*.............*........*......*.......... 4-9

CL-C k Eirpc-rirlal i l g T d a HISC I ,.mmw,oo,m.,m,*woo..ooo.eoomowooooooo..m.ooao S-1

5.1 Objec8iva & Eqctirmtatbi ~ - * o w o m o - o - - - . ~ o o o - . ~ * ~ ~ a o o o o o o o 1

Tbc Trkngulr Manme Wmg ..., ,.................... .......... ....,....CU.....U....... .............. ..., 5-7 ............. W-!Wpcd Memhrne W- .,...~~.-~.tt.......................................... !M

Fikic C d Oril Wmgs..-,.. .... , ..... ....~....-.U......~...... ........................................ 5 4 1

Epr-rrkl W&I T m -@se a . . . . . . . ~ ~ ~ H . . - H H ~ ~ ~ H m . . M

vi

6J W i e h e b p w i t Tut P b ~ e e e ~ a . a a e ~ a a ~ . w w . ~ e . . e e a e * m a m a a a e a . 6 5 6.3. i Higbcr Aspact-Ratio EUipsoid Wmgs ................ ... ...... .............. ................... 6 - 5 6.3.2 A %gui Rat Plate .................................................................................... 6-7

6.3.3 SpawiSCIStiffaid W i p ......................... -... ..ti..ti................................................. 6-8 63.4 Rudimentary Flow Visualizatim ........................................................................ 6 - 1 2

6.3.5 Bi- SpnmsbStiffmd Wmgs .......................... .. .......................................... 6 - 1 4 ................. 63.6 Illustraticm of 'lhnist and Efficiency Benefits of 'ClegFling' ...........+........ 616

'13 P b III Eirpcriwitd Wiihi w ~ a a ~ e a m a ~ a w ~ ~ a ~ e ~ e a ~ e a e ~ e a e a e e ~ ~ o m a a a ~ w ~ e m ~ e e m a a a e o a m a e e 7 4

73.1 nie Switch to Caron-Fike Reinkced Pak . Obtaining a Basclint Wmg ................ ..... 7-3 . .......... 73.2 Variati01s on a Thme The 'BAT Saies of Wmgs .. ......... ........................... 7 - 7

7.33 'BAT- 12' O 'The Culminetitm of Che Y- of MAV Wmg Develo pmai t....... ................. 7-12 73.4 AttcmptoGenenrotheDesigriRoass(Kn0wl~ .,- ......................................... 7 - 1 7

f a 4 T d k d VC~&& E l b ~ ~ ~ a ~ a u a u w m m e a w e e e a ~ e e e ~ a e m e e e e e e m m o ~ ~ ~ a a a w a a m ~ ~ a a e . ~ ~ m e - w a a 7-18

................. ...........*......*....... 7.4.1 'Ouhiggd Style SeacEh YdGe T & d Vchicle .............. 7-18 7.42 'CmCPmed Scatch Ydrt' Styk Tethemi Ve&icle ......................................... .......... 7-21

Apptdl. A: A Simple Q i r C S t d y "Bluk Bos'' Acrodyndr A m i ,

A w d h C: Dib RcMw (. 'Phme 1' o l t k UTIAS M N W M D m b p r i t Rqru

List of Figures

Ck4p1cr 2 t l &~t f f

Figure 2-1 : Coiapetison o f a typical bird wing and a hummingbird wing [1] ............... -2-2 Figure 2-2: Illustration of the geaeration of 'supacirculation' using 'capfling' ............. 2-3

Figure 2-3: Insects achieve a nearly sinusoida1 flapping waveform [2] ......................... 2-4 Figure 2-4: Hummingbid flapphg fkquency and amplitude changes when d c i a l l y

loa&d with extra weight (31 ......................~.......................................................... 2.5

.................. Figure 2-5: Stiong leading edge vortex dominates dragody aerodynamics 2-8 F i g m 2-6: Clapnuig' flow visualization h m [q ................ ............................. ....... 2.9

Ck-r 3 Hg-

Figure 3-1: Early concept image of SRVUTlAS MAV in flight .................................... 3.3 Figure 3-2: Ooc-Axis Two-Hub (OATH) actuetion system as initially envisioned a d

drawn by Mr . Dan Loewen ................................................................................. 3 4

Figure 3-3: Simplined image of OATH system ............................................................ 3.5 Figure 3-4: Early concept ixnage of a T-Flex acnistion system .....................O..............e. 3 4

Figure 3-5: Trbguk-planform mm- wing concept ..........................................O. 3.8

Figure 3-6: Rib-RemIorced membrane whg concept .................................................... 3.9

Figure 3-7: Coacept image of caxnber-comioUed wing ................... ................... 3-10 Figure 3-8: Co- image of spenwise-Mened membrane wing ............................. 3-10

Ch-r 4 ~~ Figue CI : Chart of fiappmg lkquency vs . MAV nius g e d usine a tbt simple

"biack b x M appmmh dcaalbed m Appendix A.. .................................................. 4-3

Figure 4-2: Plot of mid-stroke pitch angle (relative to vertical) vs distance h m axis

.......................... ushg quasi-steady strip thcory and arsuiiptions of section 4.3.1 4-7 Fi- 4-3: View abng span of 'BAT-12' wing with twist necessary to crrate a ft

coefficient of 1 -3 at mid-stroke ushg asswaptions of section 4.3.1 ....................... 4-7 Figure 4 4 Plot of vertical t h v S. distaire h m wing root as estimateci using the strip

theory "black box" appmach ushg assumptions of section 4.3.1 ........................... 4.8 Figure 4-5: S a m as figure 4-4. but using assumptions of section 4.32 ......................... 4.9

Ckapm 5 F?gms

Figure 5-1 through 5-4: Photos of the bench-top test rig ............................................... 5-3 Fi- ES: Comparison of original OATH tubes with repiacement OATH tubes ......... 5-4 Figure 5-6: Three-fiame image iliwtrathg the position of the actution bms and the

uvings as the elttic motor tunrp the crank to atuste the whgs ............................ 5.5 Figure 5-7: Photo of whig connection mchanism of origmal OATH tubes .................. 5-6 Figure 5-8: Image of &si wing design to be tested on tk bench-top test rig, a rrisapuiar-

planform membrane wing ..................................................................................... 5.8 Figure 5-9: Photo of all four of the 'firsteilipse' whgs der testhg on rig . Much damage

. . .............................................................................................................. IS evident 5-9 Fi- 5-10: Photo of Zndeip' wing mode1 afta teshg on rig ............................... 5-11

....... Figure 5-1 1: Diagram illustriiamg constmtbn of 'Mue whigs' style MAV wings 5-12 Figure 5-12: P b t o of bin 'fhtblueeI1Ppsc' style MAV wings attached to the onginil

OATH tubes of tht beacbtop test rig ................................................................. 5-13

Figure 5-13: Diagram hdhhg tk bcPdiDn of remfommg hyem of M c added to thc

%lue w@' style MAV Wnigs ...........,. ...... ~...~.~..~.t.m~~~~~.m~~~...~t..t~~~.m...~~~......~..~.~.5-l3

Figure 5-14: Illustratbn of paformaoce progress mule with the %lue wings' style ..... 5-14

Chalprcr 6 El@-

Figure 61: Photo of Spsuency - equipmnt added to bench-top test rig rnid-way h u g h Phase II.. ............................................................................................... ..62

Figure 6-2: Photo of 'BAT-12' wings (see chapter 7) a!tached to benchtop test rig using

the newer, simpler wing attacbment hubs added in Phase II .................................. 6-3 Figure 6-3: P b t o of 'higha9pectblue' whg (Scale 1:l) ................................................... 6-6

Figure 6-4: Photo of a hinged W-plate miig .................................................................. 6-7

Figure 6-5: Photo of 'desertcann' style m s ................................................................ 6 9

....................................................... Figure 6-6: Photo of whg =del 'desertcemoght' 610 Figure 6-7: Cbart of vertical thnst vs . flapping frrquency for wkg

'desertcanmiight' .................................................................................................... 6 1 1

Figure 6-8: Illustration of nmrroscopic fbw behaviour m the plant of the Wphg whgs

as observeti by the author us& a myiar tuft on a thin rod ............................... 6 1 2 Figure 69: 11lUSttELfiOn of macroscopic tbw behaviour through the plane of the tlapping

wings as observed by the author using a mylar tuft on a thin rod. .............. .......... 6-13 .................................. Figure 6-10: Photo of 'bigesertcmo' style whg (Scak 1.38.1) 614

Figure 6 1 1: P d n n s a a curves Iortbt bigdesertcarm' w h g s ................................... 6 1 5 ....................... Figure 612: Photo of bench-top test rig with only two wings attachcd 6-17

Figure 6-13: Com381jBOn of tbc thrust produced by two 'biigdeserkam' wbgs and Eour

'bigdeSeCtCIUIY)' ................................................................................... 618

F i p 6 1 4 Couparison of thc power c o d by two 'big-' whgs and feur

'bigdesertcad w i q p ......... , ........ "............................ ...................................... 619

Figure 6-15: Cornparison of the ttirust-to-pomr ratios produccd by two 'bigdeseztcam'

............................................................... wipOs a d four 'bigdesertcam' *s 6-20

Chp~sr 7FIgyrcp

Figure 7-1: Vertral stretchirig of a pboto of a cicada wing ........................................... 7.4 Figure 7-2: Photo of 'kic' wings ........................................................................... 7 4

Figure 7-3: Photo of 'BAT-OS wing on 1/4n graph peper ............................................... 7-5

Figure 7-4: Photo of 'BAT-M' whg on 1/4" graph paper ......................................O...... 7.9

Figure 7-5: Photo of 'BAT-12' wing indicating th thicbss of CFRPEEK stnrtural

mmk rn ............................................................................................................. 7-11

Figure 7-6: Highspeed video image of a p d o f cigarette d e flowiiig over a 'BAT-12'

wing ................................................................................................................... 7-13

Figure 7-7: Diagram illustmthg the fbw bebaviour assumed in tk Froude achator disc

thcov ................................................................................................................. 7-14

Figure 7-8: Graph comparing the performance of UTIAS MAV wing designs with

pmpellas or rotors .......................................................................................... 7-16

Figuns 7-9 end 7-10: Photos of oiurigget-style tdherrd vehick ................................. 7.19

Figure 7- 1 1 : fhme of a vide0 of the outrigger-styk tetbered vehicle leaving the

pd ................................................................................................................ 7-21

Figure 7-12: Tlmc images of the 'contriured scotch-yoke' type tetbered vehick .......... 7-22

Ch-8-

Figure 8-1 : Photo of travas portion of bot-wire enem>mtry ecpipmmt. ................... 8-3 Figure 8-2: Cbse-up image of hot-wke p b e aeu tbc bsnch-top test rig. ................... 3-3

............................. F 8-3: A gbw-eiigint pwcred &e-febt vthick sttaipt....... 8-5

xii

Figrne 8-4: Drawhg of a lighweight eLctric powered he-fiight vehicle design ......... 8-5

Filprrr in the Apptndiar

Tbe figures in he appendices are too numaous to iis bae. T k appendix titlcs, however, give a strong indication of wbae to nad figures nlate to a particular topic.

Chapter 1 : INTRODUCTION

f . f Pm@t Dacgmund

S k 1903, the dimnsions of the world's larger a i r d have coadinually gtom

nie upper bound of aircraft whgspan and weight bas grown h m a few metres end a

couple of hunred kiEograms befire W, to nearly 100 mties ard over 400 tonnes in

the pnsuct day. However, the bwer bound of aircraft sizes has mt seen the samt level

of 'envelope expansion'. niete are two major reasons for this bwer bound stagnation.

The fht and most important reason is tbat due to the size of people d o r automated

equipment, it bas mt been possible for an aircraft to perfomi a useful ta& with a weight

of less thaa about 25 to LOO Kg (50 to 220 lbs). Vietnam-ers drones are an example of

the bwer weight figure. A secoad raison for the bwer size boundary is the adverse

Reynolds number effats sc ia ted with steady flight et a s d size scale. It is pmbably

not coincidentai tbat the Vietnam era dro a i r c d operateci in a Reynolds number

regimc above 200,000 where airnaff lift-to-dmg ratios of 16 or more can easily be

achieved. (hum Iift-to-rag ratios directly impact the mission duration for a given

voldweight of h l . )

For the purposes of this document, a micro-air vehicle, or MAV, may k thought

of as any a i rcd tbat c m fit mthin a 15 cm cube and pafom some usefui task. Tht

micro-air vehicle (MN) concept came about duc to thc coincidental maturation of

(DARPA) bas awarded s e v d contracts in order to devebp, for tk k t tirne, very small

eaial vehicles capable of pafomiiilg a useW mil&ary a&. Iirhded among the tcams

selected to pursue tbis goal is a joint e&rt by SRI intemtbaal of Medo Park, California

and the University of Toronto lastitute for Aerospace Studies (UTIAS). nie S m

micro-air vehicle team inte& to combine the Wping-wiag propulsion eqertise of Dr.

J.D. DeLaurier's group at UTIAS with an electricaiiy actuated, aitinciai muscle

tecimobgy cunently king devebped by SRI in ordet to pmduce a hoverhg-capable,

fhpping-wing MAV. The UTIAS group's work focuses on the devebpmnt of suitable

wiags, as well as the o v d vehicle aerodynamics, while SRI concentrates effbrt on the

wing gCtUBtiOn mechaniSm, as weli as the ~ecessary electronics. This thesis documents

the important results of the frst year of the UTIM MAV wbg devebpmnt effort.

It is UIIportan to rriention that the autbior of this ocument, Derek Biyk, did mt

petsonally pediorm all of the UTIAS nscarch an devebpmcnt work discussed bnin.

Ratber, it was a team efbrt for which the project's chief research engineer, Mt. Dave

Loewen, was respoasibk for much of the work. Hence, tk autbor will try to give credit,

w k v e r possible, to the 0 t h members of tbis team.

r.2 Ru@ctOork

Two types of ptojec goals exist: q d v e and qualitafive. Quatatively, it is

obviously Unportans t h tk vehick k stable in fight. Thlp is probably a mnger

fuaction of ovedl vehicle congumtion t h whg psrsOrmence. It is alao desirable tM

tk nnnl Wmgs devebped by UTlAS be dunbk (Le. soldier-proof). It must be

remembaed ha tbe finai user ofthis technobgy wili kthe U.S. a n d fioces.

Simpcky of wing actwtbn is also importan; it WU d e SRI'S tasks easier. For

instance, one egree+Efkedom @oF) actuetion is better than two DoF, pmvided that

comparable perfoniiarioe moy be achieved. Fmally, the o d vehick must be

corducive to tbe piacement of seasors, For example, a vehicle that exhirits excessive

v i i t ion may mt albw a steady video-camaa image. These qUBLifative goals must be

kept in miid while pmuing the quantitative objectives k b w .

In the pject pioposal submitted to DAWA by SRI and UTIAS, it was wggested

tbat in order to perfonn a useful military taslr, a minimum total-vehicle msss of about 30

to 50 grams is requirrd This cange takes into consideration anticipated advances in

mim.eIectronicq the SRI electro-strictive polymer artificial muscle (EPAM) technology,

and battery enagy density. This mass target is only schievabk if the power ronsumption

of the MAV does mt exceed roughiy 5 to 6 Watts* Hence, tk first d mst important

quantitative goal of UTIAS's contr i i in to the MAV wing devebpment effort is to

p d u c e roughly 50 grenis of statr ttnust us@ only 5 Watts of power (Le. Cor hover&).

Tbe 0th important quantitative pmject goal is a b w mise emission. The iiiain

d u e of an MAV size airaaft for the military is tk dificulty the emy will have in

observing it. This advant8ge would k lost iftk MAV gave away its position audibly.

Low noise emission should be considered a q uentaetive goal because soumi power is a

masurable property- For the nrSi year of the UTIAS MAV wing devebpment efbrt,

thiomiscgdheskenler$elyignodkdisCmaripated~becomeimportsiitasthe

Pr0.W P~gresses-

Chapter 2: Existing Literature

As a starhg point for this project, two Werent types o f existing literature were

c o d e d Scientific anci engineering lit-, such as published papers and technid

documents, are discussed in tbc nex secfion. This section, howwer, is compiled h m an

examinaion of pop& literatwe such as '~ianire books' and 'bird lovers' guides' in orda

to gain an o v d sense of the various mechanisms of flight empbyed in nature- & y o d

p o t d eaergy efficiency benents of flapping-wing fligln, a main nason for the interest

in this approach is the desire to m e a vehicle capable of king mistaken for a bird or

large k t . Dr. DeLaurier's reseerch group has fiund through previous projects that

outright feplication of bird stnrture is quite difficult. Nonctheless, the study of nature's

macroscopic aerodynamic and mechaaical pmpaties can be instnrtive.

The books that were coasuhed focus mainly on crraiurrs thet are capable of both

fornard and hovering fiight using wiqspans of no more than 15 cm. As a tesuh of this

seercb, s e v d common characteristics haw becom apparent. As weil, a few ckver

adaptations of nature bave ban identified, which, it is hoped, wiU simplify the ta& of

crestiag an efficient artificial flapping vehicle in this size ngime.

2.1 -1 Locaon of Muscles

in bth flying insects ad hummingbirds, the muscles which opaste the wngs am

located at the whg ma Tbus the hummingbird uses the wing as if it were a flem'ble but . * maniniair unit, bebg acteci upon by ody wing-mot monmts d aerodyasmic hm.

nii9iPw~tomo~otbnbrds'~wIUchincludes~mractivennisculercontrol

2-1

thugbout. This is firtunate h m an MAV point of view because it suggests tbat a

vehicle with a ghtweight (or mtrnbra) wing, wih ail lrtuasion taking place aear the

mot, is a viable flyer in this size ngime.

1 (hm AbQnda Skiodi's THE UR OF THE HUM-, 1973)

Figure 2-1: Tbli d m , f m Skutch's D e LKe of T l e H m 111, Ulpitmta tbt a l m a aii aeh.tion of a huimiogbird'r niig m u t be rppiie at the rhorLkr, wnbiry to hrger Mrdr

2.1 -2 Contrd of Pitch

Ail flyiag creaturrs at this size appear to have the abity to actively djust the

whg pitch, at least to s ~ n u degree. It has not been determined ifthis pitch adjwtment

abiiity is used d y fOr attitude control or m e r efficieiicy in the geaaation of M.

The UTIAS MAV wing devebpment effort will nced to expiore this degree-of-kdom

expaimentaily.

2.1.3 ClapFling I ClspSed

Hummingbads anci guiects fkquentiy use tbe iift edmcing effds ofthe 'chp

fhg' pkmmrmn (expiaineci in the xt figure). However, 'ciapfling' b used by

hUmmmgbirds ody wbnitky nquin a briefhurstofexapower, pedqm sugges&jng

tbat this effact is mt as energy efficient as the typicai wing rnotioa Nonetheiess, it does

albw for the generation of a e~nendous amnunt of litt in a very small spece, which

L

Clap-Fling Lift Augmentation 1. - - 2.

-XX - Wngs rnove together Air is pushed downward

t 7

F b m 2-2: ilustntion of the gentration of 'nperdrwhtki' unhg the 'chpflbg' cilie @mm by Mr. Ihvt Lanen)

buttedies. This method g e m e s the 'supercirculation' lUSt283ed in the ciepfling

picture by peeling tk wMgs apart (mich Lre peeling apsrt two sheets of paper tbat have

2.1.4 Fkpping Cyde Wave Shaw and Muscle Duty Cyde

Hummingbitds and fi& msects cycle their wngs in a mughly sinirioidal nishion.

This phemmemn will be usew fbr the design oftbe MAV since a smusoidaliy

osciltstisg lincv motion is easiiy create h m a n ehctrk-mtot dmn. Aliboughthe

finai vehicle is inteaded to use EPAM m o n , electric moton are fin mre cunvenient

for use in eatly bench-top test apparatus. One source showed tbat imects d e v e this

wave shape by se* a train of short duty-cycle electrkal impulses to the muscles [2].

Figure 2-3: hweb achieve r ncrriy riaiwid.lfhpping wavtforn iuing oaly brkf dcetrirrl impuLei to the m u e k

Whe the popular literature helps to estabiish a sense of the overaii flight

mecbanisms found in the natural world for wirigspans less than 15 cm, in g e d it does

not provide emugh detailed, n d c a l idbrmation for the initiai design of a hpping-

wuig MAV. Fortunately, there exists a substantial body of publishd biobgical and

engineering rescarh thst is applicable to the task at hPnd Many of the usefil refrences

are iisted in the uRefere~s'' ad aadibiiography". A summary of the most sqpificant

2.2.1 Frequ~ncy and Amplitude

T b e ~ b c a t ~ a ~ y o f h ~ b W w a s ~ ~ t o b e b c t m a i 8 m d 8 0

cycles per second depnding on the spff ies , with mst in the 25 to 50 range. More

miawsipg.tbcbirdsmimtPinm~ythcsuat&queacydiiriipdtypesoffliBht,mih

2 4

only a nierginsl in- in flapping kquency when tbey are artificially bded with

extra weight. The bulk of the ft force modulation in hummingbirds cornes k m

chmghg the ampiitude of the wing motion.

Aside: It should be mted h m the folbwhg figure that although the

hummingbirds used in this shdy had wingspans of 13 or 14 cm, their niess was only

about 3 or 4 grams. This initially caused the a u t h some conoem about the viability of a

50 gtam flapping vehick with a 15 cm wingspea It should also be mted tha the "stroke

amplituden presented r e k to tbe fidi angle swept by each wing rsther than the

conventional e n g i n d g dehition of amplitude, whrh would be balfof the swept

angle. For amistency, the same fidi-sweep dennition of amplitude wiii be useci in later

sections when desctr'bhg the expxhea5al work performed at UTLAS.

Wing Amplitudes and Freqwndcs of Uniaden and Heavily Laden HummingbLds

2.2.2 Energy Consumption

Perhaps the mst importaat poteatial bene& of a flapping-wing MAV over a

more conventionsl belicopter or &xi-wing design is the cmgy efficieacy. Hence, it is

desirable to obtain an esthae of the encrgy wnsumption of hummiiigbirds d o r Large

insects whe in hoverhg flight. Ideally, one could use information about the direct

mcbanical power applied by the muscles to the whgs h onier to m a h exeapokions

about the relative efficiency of flapping-wiug flight. N o d y , it is considerably easier

for the bio bgist to present information about the total energy consumption of the cteanue

lmsed on food incake or oxygen collsumptiDn. Foctunately, reknce [4] by P. Chai and

D. Mlard goes wefl beyond such rdmds.

in the experiments escri'bed in refetence [4], severai bitds h m tOur dithent

species of hummiagbad were 'obliged' to perfonn brief hovering fights, both wah an

extemal load attached and with no load. These flights were m r d e d on video and were

anal@ ushg an existing d y t i d model to provide an estimate of power

colwmptioa (Note tbst the analytical model used was 'quasi-steady' a d pmbably very

sirnilar to the simple model descri'bed in chepter 4.) The rrsults for the iargest species

( m m of about 8.4 grams) suggested a verhi-tbrust to mecbanid power ratio of about

48 g/W whcn udoaded and about 33 g/W wben iitag 23 grams (kluding tk mass of

the bird itseif). Tb Bapping equeiicies empbyed by the bids in the tm cases

averaged about 3 1 end 23 Hz mrpectively. (T& aubr wuld Le to draw k m k ' s

a#cntion to tht chart pniffncd in section 7.3.3.1, cbspbr 7 ofthis thesis. An

extrapolath of tk c h to bwer vehicle masses suggests tba these hummhgbird

thmst-to-pwer ratios rn very beiievable, considetirig tbe disc losding.)

2.2.3 Vortex Generabion, Shedding, and Viwalization

in the upcoming two years of the UTIAS MAV wing devebpment effbrt, these

three topics wiii, m doubt, be e q b d m intimate detail. For the k t year's progress,

however, it was only necessary to obtain a sense of the o d aiifbw/vortex pattems

expecte h m a thnist-gemating flapping wing.

The slliiplest and most eluciatiq paper tbat tbe author bas corn across,

discussing the vortex generation by flapping wings in hovering flight, is drence [SI by

Freymuth and Seikr. This document clearly depicts two possible combinations of wing

pitching and plmghg that may resuit in the ge-ion of a two-dimensionai 'hover-jet'

of downwardly tW air. W i these hover-jets, WU f o d voitices are present.

Reknce [5] presents images of these vortices, which have been genetated using smoke.

Most importantly, graphs are preseirted that iilUStTELte (for the 2-D case) thc relationships

of thnist coefficient (CT) to both piiching and plunging amplitude* For exampie, the

psper states t h a thmt coefficient m e r than 6.5 is possible with a peaL-to-peak

phuiging amplihde roughly equal to the chod kngth and a pitchhg amplitude (mt peak-

to-peak) around 25 degrees. In this example the pitching iags tbe pluagiag by a phase

angle of 90 degrees. AdmittedLy, it may be clifficuit to translate such values hto the 3-D

case of the MAV. Nevathcless, it pmvides a cataia sense of wbat to expcct m terms of

whg khaviour.

Whe mt directly applicable to the whg-mtion proposecl ot the SRVUTIAS

MAV concept, a nry comprebeapiw description is pmvided br tbc vortex khaviour

about a dragody's wing (in pudo-h6vering figt) in thc documwt by Dr. Iamw H.

Weygandt [q. The piipcr bluntiy illustta~es: a) the importance of a strong vortex

iuat the wing's leadhg-edge~ and b) the utility of the sbsd vortex or aft

gemration on a downseam wing. Weygandt also mntions that the ~ o ~ y ' s wings

beat in a pl- that was inciined at mughy 60 degrees to tk horizontal durhg tht

expriment he describes. Assuming quiescent beckground air, it is interesthg to mte tbat

even whik raishg the wings bachvard at 60 degrees to the horizontai, the prrseace of a

strong ieading-edge vortex on the bottom side of t& wing albws for the generation of

substantial lift. This idea is iuarated m the folbwing figure.

&mI blue a m indlcates wing vebcity

Figure 2-5: &auc r 8trmnl hding-edge vortex u n k geaemted and uhtiiacd h position by dmgonfiy nings, cvci the ipatmke may gmemte Pn: dapite the hct tbat the wiog9s attitude h n e vertical

Pahaps the mst imporiaat quaiative rrsuh of Weygdt's paper fDt UTIAS

MAV piirposes is the coiichision tbat the cormgami ierrding-edge of tht dragoafiy's wing

is inritnuncdal in tbc gmration and meinte- ofa song vortex It is inteadcd that

this concept k expbced in the second ycat of thc UTlAS MAV wing &vebpment eflltozt.

2.2.4 ClapFling

nie iitt enbanchg phenomtnon of 'clapflhg' (descriibed in section 2.1.3) was

first poposecl in a 1973 papa by T. Weis-Fogh [7]. Siace this tirne, s e v d papen have

ken pubshe iscussing the n d s of this thcory. (3 fpu th .k importance in the

Metatute is the discussion of the leading-edge vortex, kludhg the rate at which it is

g d and its bcation with respect to the wing. in rekace [8] by Spedding and

hhworthy, for example, a chart U proMded which details average ft coefficients and

jmwer co~lsumption obtainsd during a series of expaimnts in which flat piates were

mtated apart as i f in th f h g portion of a 'clapfling' action. The average Cr dues

obiained were several timcs greata thgn the CL- tbet o ~ e would expect h m similer

aufoils in steady ow. Regardless of tk exact increase, the scientific teiahirr &!Mely

suggesis tba the 'clapfling' type whg interference effects nmy be used to substantially

1st MAV

Chapter 3: The SWUTlAS MAV Approach

It is apparent h m the previous cbepta that therr are a muititue of ways in

whrh nature hss tackled the issue of flight wahm a 15 cm wingspaa Because the

expected mass of the complete MAV is anticipated to be many times heavier th^ bu&

and msects of the same size, an ordrigbt copy of one of nature's flight ~ilbe(:hanisms is not

suitable. Thus, at the beginning of the pmject, the SRVUTIAS team had an abundance of

pssible fhpping-hg flight concepts to c b s e hm, aorie of which wouid be

signifcanly based on an existhg system. This chapter wiU, as biefly as possible,

present the general MAV configuration decideci upoa by the SRVUTIAS team and wiii

attempt to elwidate the nssonhg thet led to this arrangement. The chapter wiil continue

by discussing the muhitude of actuation and wing concepts avaiiable. Finally, the last

section wii i coacisely describe the o v d methodobgy used in the nrst year of the

UTlAs MAV wing design effort.

3. f A Four WIng HoMng Unit - *Th. Doubk Hummingbird8* Ahhough mst sma birds are &le of hoverhg flight for bief bursts of up to a

few seconds, the hummingbird is the oniy b i i capabk of sustainhg homing fiight until

its e m g y is depleted ( d c h , iacidentally, is about hafan hour). As a rrsuli, w h t

was decickd to pursue an MAV design whose dominant fght mode woukl be hovetiLIg,

the hummingbird niinrrslly came to min. The hummingbird aise ofsCred a cue as to b w

M grrms of mass (the anticipeted naal MAV mass) m*ght efficiently be supported using

flipp'ig-wiqg hoverhg with a wingspm of only 15 cm. Whcn attificially bakd wiih

extra mass (as descr i i m rrf-ace [4a or w k n rccelaatiqg rapidly h m a pack tbe

hummingbird inCreeses tk ampiitue of its wing motion substantUy, d is beiieved to

be making use of tht 'clepfling' pbeaomemn d i s c d in t& pmious chspter*

Ifsomcbclaptliiig'isgood,ism>rebmei? Thisisthefhtquestionposdbythe

remthg SRYUTIAS initial MAV design comept in the iiiUStf8tjOn bebw. This four-

wing design seeks to double thc number: of 'clapfling' actions perfbrmed by the wings

in cach bpping cyck This design is atttactive kcsuse tbe wings ed only swap a

niaety-degne arc and the 'clepfling' phemmmn (which gf&y edmms Ut) occurs

apptied to a unit mth any numkr of wings. Although the fbur-wisg unit is anticipateci to

be a simplet design ta&, it is unerstood that m certain situatBons tht abity to appear

mm bird-ke couid be desirable. (Note: It should be remembed tba ai tbe required

flapping fkque~~;ies, four whgs would iikely be mdisthguisliable h m two M e the

MAV is in flight.)

Beyond the increased oppommities for %.clapfhg', t h are 0th advarmges to

this fiapping-wing MAV design. Most mtably, due to the synimary of the design, the

aerodynamic and ineitial forces are belaaced Hence, the vehick sbould be latnally

viiration fke in flight. (h may still be vertical oscilations due to variations in l i fk

tiwugh the fiapping cycle.) The reader wiJl notice in the concept image that the wings

are placed near the top of the MAV. It is anticipateci tha by placing the centre of gravity

weli k k w the wbgs, the vehicle will be stabilized in a hoverhg attaude. For eviations

h m pure hoverhg flight, or to make incremental attitu& and position ajustments,

control fins are aded to the aft poriion of the vehicle, protnidirig into the slipaream of

the thnisting wings.

n#e are many possile actuation mechanisms for -hg t& MAV wings.

However, it mrist be remcmbed tbat whcnal devebpment work is cornplete, thc nnal

MAV wbg irhiator is intcnded b bc tht EPAMs king rrseaichcd by SRI. As a rrsult,

only wiag achiation schemes that can be d y adapted to these ertif9cY maiscles have

ken considerd Pmented m the EDiioWmg subsections are thc scnia5joncoircpte tba

are eiievd to have ttU mst p i o h duriqg tk design pbase of tk SRVUTlAS M A . . For tbt frst yeat of tk proces, only Jmsie dcgrresMeedorn acuahncowepts were

considerad. It was desmd to mvestigate solely the 8Ct\18ti011 of the wings within tbeu

fhpping pia. Active wing pitch coritroi, etc,, was not expiorrd in the hope thiit passive

am~iastic wing tmstiqg would d c e (see also section 3.3).

3.2.1 The On&4xis Two-Hub (OATH) Flapping Unit

The idea cumntly king pursued is to use two hubs thst are fiee to mwe about

the same axis. For a four-wing tlapper, each hub is wxmcted to two wings. The two

hubs will move exactly oppsite one am& m a cycle (approx. sinusoid) such that each

wing will sweep bck and forth o v a nearly 90 degrees. As the wings change -ion

(tmce per cycle), two pairs of wings will execute a 'clepfling' mtion.

Figam 3-2: Image of

ifa two-wing fiapper were desired, ePch hub would conct to only one whg,

which would sweep over aearly 180 degrres. In this case, 'clegfling' again murs twi

pet cyck but involves only OIE pair of wiogs each tirne. The elegance of tht OATH

design is th:

a) It aiiows the development of a singie design that wili acconmiodate eitha two

wings or f8ur simply by adjusting the sweep angle (Le. amplitude).

b) It WU probably allow Br the entire large-scak flapping motion to be actuated

by one or two idependent sets of EPAMs (ehbough Som conhol functions may need

their own ariincial muscles).

3 . 2 . Potentiul Incorporation of an OATH T'ype Napping Actturtor into a Flyng

MAV

Us@ an OATH type flapper design presents the option of actuating the main

flapping mtion of the wiags by wing only two EPAMs. One end ofeach acniator wouki

Two EPAM Actuation Unit

be anchorcd to a single hard point. The 0th end of each is comvded to either end of a

line thes bops mund a puiley. This idea is iiiuptrated in the hgmm This concept is

widely variable i~ form and able to accommodete various EPAM stniin Limas by simply

adjustiag tbe size of the pulley. hxesthgly, both whg hubs could be actuated by a

single two-EPAM unit of this type by addmg a second Lme and puiley. Further, by

eddiiig otber smsli pulleys, the EPAM's could be placed in any convenient location

within tk h l a g e of tbe MAV.

For fuithet insight into how the OATH system m y k hoorpomed hto flying

MAV package, see tbe 'tethend vehicle' descriptions in chapter 7.

3.2.2 The Thorax Flexing (l-Flex) Flapping Unit

Many nsem use a tlapping mechanism that is fsr simpler in concept thao the OATH

system dacribed above. The insects have a 'split thorax' that is contracted by U i t d

muscles. By attachhg the wings to the qlit in the thorax, thty fiap with each muscle

wntrection (see diagram). Ahhough tbe T-Fiex design uses Wer parts a d is simpla

to m b t a d , the aigiwering challenges involved are anticipateci to be gnater. This

design should be pursucd when thc correct ftapping waveforms and EPAM strrngths

bave been determined using the OATH system,

3.3 PHch Conm

As stated above, the nrst year of tbe UTIAS wing devebpmcn eart

e o p w ~ e d on wing esigns that conforni to efficient (or at kast effective) airfail

shapes hughout the flapping cycle solely as a resuit of passive deformation due to

aerodynamic Io&. Should some active control of wing pitch becom nccessary, it will

be explod at a later date. For example, one mi@ consder a rnuiiahirr . adaptation of

one of the main 8Ct118tor mchanisms descnii in t& previous section Whether active

pitch control is d e s i d for eitber iacrecisrd efficieacy or control the author suggests thai

the mre elegant 'active cambetantro' mahod d e s c f l i in 3.4.3 k expioreci before

resortmg to the more 'brute force' actm pitching conoept.

3.4 Candllckm m g Conmpb

At the beginning of the UTIAS MAV wing evebpmnt efirt, several general

wing concepts wwe king considered. Som of these types have since been tntd and

bave either been eveloped furthet or dropped h m thc wing design program bascd on

kir initial Paa,mmce. In the foUowing subscctions, tk methcmetrally hclined

might consider the pmente wing CO- hyouts as akin to 'eigenvectors' wahui

'MAV wing design space'; actuai conswted wings have tended to be hybnd

combinatio11~ of tbese types,

3.4.1 Simple Membrane Wng

At the begllming of the devebpment efirt (mugbly in September of 1998) tht

siinple membrane wing was anticipated to k the b l i n e by which other whg

candidates wod k judgd A mmbane wing is iightweight, simple to wirrinrt, and

has been pmriously researched to some degree. Hen, more cornplex wings need to

demastrate s u b e i a n t i a l ~ ~ k n e b to justif;/ tbe incrrssed weight a d

comtrwtbn effort. Through exphentai evaluation, it bas since ken determhed that

this simplest of wing designs is not very effective for the MAV use considere.

However, a wing type that is effectivey a hybrid of the 'simple membrane M g ' and the

'niceinforceci mm- wing' has shom much promise.

Note thst ifit w a e desireci to actively control the pitch of this type of wing with

respect to the MAV body, an actuator would Likely have to be added to each wing mot.

Triangular Pianforni - Membrane Wing

3.4.2 Ribdeinfarwd Membrane Wing

By stiffening the me- wing wih iightweight ribs, a mre efficient airfoil

shape may be obtallisd. In the year of Uie UTIAS w i design etlbrt, a pure 'ni

reinforced mmbra' style wing was mt teste& but a hybcid whg horporating some

chordwise membmm reinforcement has shown eiicouraghg resdts. I f active pitch

conhol of this type of wing were Qsited, an acniator would need to be d e d at the mot.

Figure 3-6: Rib-rrhlorrcd membrane wing concept dnwing rhowing rehHve poiitbi of ral l kadiog edge and chordivhc Mkners.

While a mcmbrane wing is automatidy cambere by the aerodynamic bads, the

incIusion of a bi-miphhg EPAM acniatot, as h m in tk diesram, albws a

modulation of th wing sbqe, end hena thc M. This simple addition might eliminstc

the ed iDr a more compiicated wing-mot actutor to contml pkh. (For more

inhmtion on the 'bi-moiphmg EPAM' coacept, aee dxence [9].)

Bimorphing EPAM M 1 Figure 3-7: Concept mage of ambelc~~ntrolcd whg, The -ber & adjutcd by joMg the radial rt i i l i tr i , with a bi-morpliig EPAM tbrt a n fom m arc when bad ia rpplkd

3.4.4 SpanwiwStkM Memkrim Wng

This type of whg is typical of tbat hund on many inset% and is a nasonable

stnranal approximation to the most outboard portion of a birc's wing. The ides is to

design the in-flight eirfoil shape by choosiiig tbe chodwise distriidmion of spanwise

bending stiBLiiess (Le. remove the single spar a d replace it with pcecisely distncbuted

Membrane Wing - Spanwise Saffeners

This type of wing would be ideaily suited to the bi-mrphing EPAM acaiation

system d e s c r i i above. ExperimecatPI evaliiatinn of thip wing type withou EPAM

actuPtion (see cbapter 6) sbowed it to k a very robust design. Unfortunately, ,these

wings tendeci to coiiwuae a s i s n i f i a n t amount of power. Expianations for thip are

discussed in section 6.3.5.

3.4.5 Double Surface and Cmgated Airfbil Wmgs

AU of the previous wing types listed use only thin airfoils (with perbaps a small

amount of thiclmss to acconmpdate the sinictural compoiwnts). However, there may be

mnt in exploring a few double sinfsce &oh. The possible bencfits of this type of

wing (dependhg on Reynolds-numbet effects) are that a) durhg each flapping motion,

flow over the wiag might separate later and re-attach eark than tbe fbw over thin

airfoi1 wings, and b) a cerhh amount ofleaing edge suctioa might k gemratd

Simatly, ad- corrugation or largescale surfsce roughDess mar the M i n g -

edge of the wing may have the effect of ntaining a iarge, strong L.E. vortex as discussed

in reference [6].

3.5 Th. OwmII UTlUS MAY Wlng O.vrkg-t -mach

The MAV devebpment program at UTIAS bas pmeeded in he fbbwing way:

Caadidete wing esigns were constnicted and evaiuated eqmhmmly on a bety:h-top

testhg rig actusted by an electroc-motor drive system (see chipiet 5). Data h m the wing

testshas beeausedto spcifiltheactuaiionreqybmn~ssothnaniaaimEPAM

flqping ammion system may be devebped y SRI M e wing nsearch contibtiris at

m.

For the next tWD yeam of the project, 0th aqects of the MAV aetodynamics (Le. otha

than wings) wi k rwearchod as the wing @m approaches acceptable leveis.

Stabity and coatiiol in both hoverhg and translationai flight will beoom important

topics, but bave not been addressecl in the eerly MAV wing design efforts at UTIAS.

Chapter 4: A Sfarting Point

4 . Th.LogkaIApptwch

The devebpmait of an dyt ica i metho for determining appropriate MAV wing

properties is weii beyond tk scope of this thesis. Irdeed, the complexity of such a higidy

UllSfeady, aeroelastic, inverse wingdesign algorithm for anaiyticaiiy isolating a ar

optimum wing would kely require s e v d years of tesearch and devebpmnt by m n

then one talenteci person. As a rrwih, the UTIAS MAV wing devebprnent team (which

for the nrst year of the program consisted of Dr. DeMer, Mr. Dave Loewen a d the

author, Derek Biiyk) chose to pursue a more pragmaic design mcthodobgy. Many sets

of simple, eady comtructed wiqs of diverse physical pro- wouki k

expcrimentally evaluated in order to devebp an intuitive understandiag of the

rekionships involved nce 'reasonable' whg pmpatiw had been isolated, this

enpirical design approach would be refned to systemafidy isolete a 'near~ptimai'

whg design (for SRVUTIAS MAV purposes). Using optimization terminobgy, this

second stage of the pocess involves a mugh detcrmmetion of thc petformance sensitivity

with respect to s d changes in design variables in (wbat is hoped to be) the vicinity of

the &bal minimum. It is intende that subssquent years of tbc project k devoted to

r e f i g the design fiirther thugh the impleumtatbn of anaiytical mDdels.

Despite the boedly emompassing approach ckxi'bed in tlr pmious pnragmph,

somc W estimates were m s a r y befire e>rpaimntai work couid even kgin For

exampie, if itwaeestmilited(tbr0uphroughcal~~~) tbatthtwingswoukihaveto

flapatcquarciescbseto 1H&thewingtcst-~wouldedtobeconsiderablymon

mbusttban ifthe Bspping fhquency wae near 10 H i Hence, the Eolbwing two secfions

detail s o m t simpk "back of the envebpe" appmximatioas devebped by the author in thc

ntst m i a h of th pmject in orda to prrdict the test equipmnt requirements.

In order to determine an 'orda of mgdude' estiriaate of the flappuig equency

require, two very simple quasi-steady approaches wen taken. (Note thas the author uses

the term 'quasi-steady' to hply tha steady-state aerodynamic assumptions are applied to

au inherently unsteady problem)

The nrst mthod is termeci the Black box" epproach because it simply presums

that thugh some u h o w n mchanism, the MAV is pushing downwad enough air to

support its own weight. W of the moVmg air is coiistrallied to p a s through a circle of 15

cm diamter (the 'disc a m ' of the wings) so that the Fmude actuator disc thcory may k

useci to predjct the flow vebcty tbrough the plane of the *S. (In a subsequent d o n ,

it wiii e shown eqerhentaliy that this aswimption is mt measonable.) Reference [IO]

provicies a more detailed p m t a t b n of this theory. It is mw Msualtzcd I tbet *s an

pked into this presuppose Bow. Wrig pLanf0rx.n ena, flapping amplihide, and

spanwise bcation of the aeroynamic centre of pnssiirr (wkn flapping) mwt be

spccincd Most signiticantly, the wings arr presumed to bave the abiiity to geacrate

given 'time-awmgeci coefficients of Lift end drag' when king depped. (This average CL

concept was hund in some of the bummingbird references such as [3], [4] end [Il]).

Resolving the litt and drag focces to obtain thrust, we nmy mw determine tk tLpphg

~uet~:yte~uiredtogarrate1&~tce~thebckbox"wasorigmillyp#wncdto

appiy to tk air. F M y , by tyiag wtiDus rez~sonebk values of 'average CL' ancl wing

a m , an 'order of rilegnaude' e s t h a t h of -mg muency is obtallwd A numerical

example ushg this method and fiutbet expiadon about the himent assumptiOm an

prrscnte in Appendix A.

Tbe fobwing figure, conswted ushg t& "black-box? approach, illustrates tbet

depcnding upon tk fiaal MAV m a s ard the whg poperius selectedfachieved, a

flapping ikqueiicy between roughly 30 Hz and 70 Hz wl be required to suppod an

MAV of 40 to 50 $rams total mess.

4.3 Q u m b ~ s m p An-&

A second mthod of gethg order of miignihde estimates f ir the tequired wing

anci test equipment pmpertus can be devebped by extendhg the %la& box" appmach

d e s c r i i above. in a matmer sllnilar to the pnviou metb, t& Froue actuator isc

theory is used to detennine the macroscopic &DW field t k the wings would geacrate if

suppotthg a given weight in hoverhg flight. Tbt quasi-steady strip mehd Mers h m

the "black box9' mthod by requiring tliat the span of the wings (of b w n planform) be

divideci iuto discrete chordwise strips and th& the flapping motion k divickd hto

iscrete time steps. nie coefficients of Lift and drag may now be specied at each

spanwise location, for each time step (and, therefore, phase angle of the flappiiig cycle).

Similar to the previous methocl, the nsultllig ff force may then k averaged over a cyck

to determine whet tlapping frquency is requed for the average resolved vertical thrust

component to quai the MAV weight.

Uiifomiiiately, the process d e s c l l i in the prrcsding paragraph is hwed; d e

the "black box" approwh, in which average CL values may k spccifed, this mthod

requires a CL at each Iocation for each step. However, when this mthod was devebped

in the early months of the MAV project, m experimentai evidence existed to jus-

guessing how thc Lift hrce was distriied throughout the flapping cycle. Nonethekss,

author pafDrme the calculsth by pmgranmiing a sprradsheet. However, an attempt

bas been niede to iaclude enough information in the description above and in tbe

subsections k b w for tbe reader to ce-construct this 'quasi-steady strip appmacb' if

desid.)

4.3.1 QuasMteady E s t i ~ o n s of Wing Twist for Constant CL Throughout

Cycle

ui steady aerodynamicq the coefficient of Liff is cornpod of the angle of attack

(a) d p l i e d by the lift curve sbpe (Ch). The author di not expect the Ch concept to

lx appiicabk to the M N wings (which, it was miagmad might draw theh lift largely

h m leding edge vortces). Nonetheles, it was thought that this mthod might prove

usefui in giviag an estimate of what tk wings' twist woud have to k (through the

flapping cycle) if they pmduced A in the same mannet as a propeler - through steady,

attacbed h w .

For the sake of coqmison, an example is p e r f ~ r d here using the wing

plantbrm of the 'BAT-12' wings (which the reader wl becom fiuniliar with in chapter

7). In order to estmiete the C h ofthe wings, they were treated as thin, flat piate whgs of

the sam aspect ratio. Using a lift cwve sbpe of 2% for a 2-D fat phe, Cr, was f o d

h m the wei-knom equtttjon:

mughly 5.8. Thus, Ch nr 4.67. In k t , the resubg Ch for neerly ali fasile wing

planforms (for the SRVUTIAS MAV) is m the range h m about 4.5 to 4.9. Hence, for

the purposes ofthis simple analysis, usiag a CL= value of 4.67 broacy reprments ai i

rrasonable wing designs. For simplicity, ail of tbe chodwise stnps will be assi@ this

same CL= value, regardless of the spanwise bcation. Wi the wings fapping at a given

ftaluency and amphide, the dowdhnrpt air and the wing flapping speed (at each step in

the flapping cycle) are added (as vectors) to determine the net air vebcity with respect to

the wings. Finally, an iterative ptocess is undertaken to determine the a wng twist

distriadion at aii points in the cycle tbat r d in a) nccessary thrust to support the

vehicle (ad hence cause the dculated ownwash), and b) a consitant CL.

The d~~ process was performed assudg an MAV niass of 50 g. The

resulting 'propellet-Wre-wing' twist approximation is shown in figure 4-2 for the wings at

mid-stmke, tlspping at 50 Hz, geacrating 50 granis of thrust with the 'BAT-12' wing

PH=

As one might expect, tk aeroelasticaiiy deformeci shape of the reai 'BAT-12'

wings were observecf to k quite different h m tbat predicted in fi- 4-2 and 4-3 whcn

producing comparable vertical tbnist.

O 1 2 S 4 S 7 8 Dbbirrea eom &b of bLWn (cm)

Figure 4-2: Pbt of mi-ohokc wing pitch in* (dative to vertical) vb diibnce fmm ut of rotation riing quukteady rriip tbwy 6bkk-bs' ippmch u daeribed above. Conditku: 50 gram MAV tahi mms, constant cadackmt of iift of

Perhaps more mterrsting and more appiicable, tbe striptheory app~ach may also

be used to roughiy esthate the verticai tlnist d i s t r i i n abng tk whg's span. For tbt

same conditions as desc t i i a h , the tbmt pronks at s e v d points throughout the

flapping cyck were calculated and are displayed in he folbwiiig chart.

F l y c 4-4: Pbt of vc-1 thmat (rrintive udh) W. d h c e h m wing mot rn crtimatd uaing the EMp tbcory Wack-oxm appmach for the m r conditjoiu u wd in fIgum 4-2 and 4-3. kbeb on euh tint indiate phrw and, in bppiog w b In the above figrm. two pmpaiks strmd out. FLai, despite tbe highiy appioximate

impottame of tk ouiboard portion of the wing in ge- nist Sceoad, br the

constant lift-coe5cient case, positive tbriua is gcirriitcd ai ai spanwise W M n s , at ail

tintes in the &apping cycle.

4.3.2 Quasi-Steady Esimaon of Required Flapping Fmqwncy for Wing Twia

Constant Thmughout Cycle

Ushg the Lift c u m sbpe approsch disc& in 32.1, it is aheniatively possible

to estimate the flspping firesuency repuired to support the M N ' S weight if the wing

twist is specifed. For simpcity, this anaiysis was p e r f o d for a wing tbat niaintainaa

constant spanwise twisthg distribution for each haif of a iap cycle. (Tht is, the wing's

shape is &Id constant as it aps in one directioa As it flsps back in the other direction,

the twisting amplitude is similar but opposite in direction)

Presented here is an example thet was examiasd using the stripappmach

spreadshen For further simplicity, imagine that the wing is a flat plate tba is albwed to

pivot about the kading edge. As a resuit, tk wing wil i mt only have a constant twist

angle bughout the hpping cycle, but the twist angle WU also be constant abng the

span. Again, the 'BAT-12' planhm Born chepter 7 will k a s d . In orda to treat

this smiation as t d y quasi-steady, oiw would ideally maintain non-stalled fbw on tk

whg by specifying a niiurllnum Mt coefficient of less t b about I .1 at aU spsulwise

bcatbns at aii times. (The 1.1 figure is representajnte of a 'typical' airfoi1 et this

Reynolds number regimc.) However, as a way of compwhg agahst tk constant CL case

preseated abow, the nipx CL will be specined as 1.3. A Ch of 4.67 will again be uscd

Through itcraiion it may be detemllncd tbat i f t k aetodyiipmics are steady, the tbnira

requited to W tk MAV's weight wiU k geaerated wah tk whgs pivothg 65.56

(to clrh side of verticai) a d tlipphg at a fkquency ofabout 65 H z The mticai

~pnk8bcbwbythe~nfir~~ue11~yincrrace~0mprrrcitothe

cOristamCL case:

Figure CS: Pbt o l v e ~ c a l thrirt (rthtive udb) va d b c e fimm h g mot a~ atiuted mbg the 8t!ip thcory Ybhck.box* appmach. Conditionr irc apeciiled in the cbart titk

The most substantial chqge in the wrtical thnist pmnks is the preseiice of

negative thnist durhg parts of thC -mg cyck. Beause the mode1 assumes tbat the

d o w n d fbw of air is always present (as nceded to support the MAV weight), the high

"ng pitch angles (relative to vertical) tbat are needed fot the fbw to rrniain uastaiied at

mid-mke becorne a hiadrance at thc beginning and end of each aroke. (With no wing

motion due to -hg, the Qmrmirdly fbwmg ait wouki ha thc whgs at nwly 65

degrees, pishiog them d o m )

It is m w obvious tba d h u g h thcsc simpie q&steady mtbDds bave th& uses,

t k y provicie only very rough estimates.

Chapter 5: Exprimerital Wing Teeting, Phase I

The process of building9 tes@, edustiiig and improvhg MAV whg designs in

the fint year of tht wing devebpment efirt at UTIAS can be broken hto three distinct

phases. Durhg 'Phase 1', initial e>

Figure 51: Side vbn of bencbtop Figure 5-2: Fnnt view of eneh-top tut 4-w ri6

Figure 5-5: Cornpariroi of the originil kich-top t a mig OATE hba (u useai in P b w I) with tk rrphcemcnt tubu (addd in P h i c IL).

The 04 mechanism wocks in the Qbwirig muim: The inm bras tube is

roughiy 1 1 ineks bng. The outer tube is about 5 inches bng d sits near tht top end of

the inner tube such thet the bottoxn of tk outer tuk is at the same kight as the midie of

the inna tube. At tk top of each of tbe tubes, an 'actmhn h' is attsched which is

intended to transfirmtbc linecir motions of a puSad into tub rotation. Tbt p&tOdS

are attacheci to a aanlr on an e W motor such tiiat tbey exprie= a ncat s b i d a l

osciiatian and, b e , tk aiba m m kck a d &rth m a ncrrly sBruoibl ishioa Note

tliat1&actuatjonbragirrpMoppoBacoatamtbersuchtbit,6erex~tzlpie.whentht

pu&-rods are pushhg, the imm-tube rotates chhivise (as seen h m above) and tht

F m Si: Thme ihme image igp8tntirg tb pwidkn of the u8uaon LON and t h e ~ u t h e d r c M c m o t o r ~ m s t e c ~ t o a d u a t o t b w i ~ ~

oriened so that when the actuation horns are in tbc 'neutrai' position (180 dcgrees

opposie), t& wings of the oiiianibe's hub are otiente et 90 dcgrres to the wings of the

inm tube's hub. Thus, powerhg the el& mtor causes the wiiig positions to rotate

and flap against onc another. Each of the wings will ahmate between flapping against

thewuigtobleAd@p@egsmstthe*toitsrfeht. Tbefhppingamplitudeis

adjusted by choosing m n g severai push-rod wmwction points on the actuatbn borne.

The enth 'modified-OATH' flapping mecbanism described above is supporteci by a

wood and aluminum fiam, whkh can be c0~ected to the corner of a workbench. As a

resuit, the wings fhp in an environment that has my M e d y i i a m i c obrbnrtion (Le.

interference with the h w ) .

Figure 5-7: Photo of onghi l OATE hab am ricd in Phuc 1 of UTlAS MAV wiig devebpment clkrt Baialy v&ibk in aii byt air the abb hto wbich the wing coucet. A rwec to t moldtd h m 3M'r DP-JZO eposy & on 8 k mot of the bbic

Fmm thc images of tbc bench-top m cig (figures 5-1 to 5-!i), o may mti thet

Each ahiminum d e v e r is uislnimented with strain gauges. This part of tbe rig is

are applying k i r b a h to the achiation homs normal to the dirrctiDn of th-

masunment, the thrust dues an mt inueaced by tht fapping 8Ctuatio1~

T b tbnist data was c o i i d electronicaliy by a Fluke 'NetDAQ' data acquisition

system connecteci to a laptop PC computer. For Pbase 1 of tbe wing testiq, the flapphg

hquency was detenniried manually by djustiiig the fbhing rate of a strobe light unSil

the wings appead to be standhg di. As a resut, duchg this nrsi phase of

expaimeasation, it was necessary to take thcust and frequemy data at several discrete

kqueiries an then interpolete. in Phases II a d (aee chapters 6 and 7), as the

equipmen was graddy upgrsded to include eiectronic puency m8sutement, it

bccame possible to record a cuntinuous thnrn W. equency cum.

Finally, for c a l i i n of the stmin gauges, an electtonic scale was placed under

the bench-top test rig before each set of tests. With tk test rig operaing at a b w

Wphg fkquency (Le. genemthg appmximately zero UguQs bllt eliminating stak

fiction), a verticai force was apped between the elect~onic scale and the bottom s t r h

gauged cant i levd eam o f the test rig. By qxathg this test severai times while

iimmenting thc vertical fi,=, a cali'bration c m was obtained which abwed the

amplifiecl main-gauge bridge cirait voltage to be converted imo verticai tbrust. This

poadureisalsolusatedinAppcidixB.

gluing two 1 mm diawer carbon-fibre iods together et a right aagle (see photo bebw).

A 'connecter' was added to the root of t& leadiiig-edge carbon mi so tbat it codd be

connectai to tk hubs of the benchtop test rig. comvetor was mided h m 3M's

DP-420 epoxy. The same connecter mold was used on di subaquent wings in P h 1.)

A biaagulat piece of 0.004 mm thick aiuminkd mylar was glued amss both carboa

members.

Udommately, the qualitative pertomme of this 6rst whg design was

unacceptaIe. In k t , m matter how East t h wings were @ped (wahin the limits of the

beacb-top test rig), the m y k was hardly Sffied and m dowrdraft of air could k feit.

Thecefore, it wari decidecl to not wllect aa for a pbt of v a t r d thust W. hquency for

thiswing.

Fiprc S-8: Image of llnj whg dci ip to k tgtcd on the enebtop test riL, i Mryihr pbdorm m w b n i e wing.

f l e m i . For the simple m w n tbat it CO& k eady ami @My constrpcted h m

nimiat mkrhds, the author bcicated the ovai plaafonnhg show beiow. This wing

is constnicted by bendmg a 0.8 mm diimcta polystyre rod to form the whg's curved

perimctcr and ghhg it onto a sbca of ahiminacd myiar with cyanoacrylate glue. A 25

mm kiigth of 1 mm diamaer carbon-are mi was addcd to tbe wing root so tbat a

connecter muid be adQd It sbould be mte that the wing sbape used hcrr (d adopted

for several folbw-on wing designs) was based on an arbitrary cuMinrre of the

polystyre tods that seemd to keep the mylar taut. The entire wing ana is aft of the

test cig comector to aibw the wing to k twisted by both the hertiai and aemdyaamic

bads eacountered whiie fiapping. One mi@ thhic of tbese wings as an adaptation of the

simple membra whgs (discusse in chapter 3) that albws mre of the membrane to be

piaced near the tip.

These wings, b w n as 'firsteiiipse', were the nnt wings to k successWy tested

on the bench-top test rig. Tht tiapping-amplitude d fbr these tests was mughly 80

degreesattheroot(alth0ughthetip swepttbroughafiill90degreesdueto miig

deformation under the fhpping bads). Note that this amplitude was chosen because,

when testing began, it was believed tbat a root flapping amphde of a fidi 90 de-

would be most desirable. 80 degrces was as cbse to 90 as the bench-top test rig would

albw before the wing mots hpacted. In Pbase 1 all whig experiments were conducted

with the four wings each flapping over 80 egrees (Ml-sweep angle) mil the Ibric

c o v d wing designs were evaluated (see 5.3.3).

Aahough the 'fkstellipse' wings broke diiriag testing' and only three data points

were colected for the &rut W. fiesuency cunie with a max thnist of only 12 gram

when Dapped at atarly 19 Hz (see Appendix C, figure C-3), these whgs nnally provided

som numeric data The wings did mt survive long emugh to albw an accurate visuai

inspection of th& efommiion d e r the inertial and mdynamic fiapping bads.

The 'firsteliipse' wings were fobwed by the Yndellipse' d e l This mode1

used tbe semc principle except tbat the polystyrene tods w m ghwd to a BLaps-fibre

reidbrced sheet of cl- myiar ushg epoxy.

The 'lndellipse' moGl wings pan>rmcd even more poorly ien the 'nrsteilipse' mode1

with a niax tlepping ftepuency of 14 Hz end a total lift of only 7 gmms of thruat (see

Appendix C, figure C4). Thc maia diff ince, howevet, is tbat the Mure modt bad

changed h m a tearng of tbe mylar to destniction of tk sunoundhg polystyrene fram

( ~ e e figure 5-10).

In orda to evebp some degree of MAV wiag coastnrtion inhiaion, tbe aidhor

ad Dave Loewen dccided to continue coaPtnrimg and evolving wings of this germai

dupe (an ovai ot egg-sbape) mil it was cl= that tht design had ken exhwsted. niy

tbcnwouldUrnextwingdesignconceptbeattempted

over the polystyre ih end hned bacL oato hl The 25 mm kagth of 1 mm

diametercarbonrodandhub~~orwenIdenticaltothose~hthegmious~

u~lsuccesshi designs except that the cerbon rod was bondecl to the polystyrene by first

wrapping the two togeth in sing then cos- them in CA (cyano8ctylate) glue. For a better undastaadmg of tbe hbric-covered whg constmdbn, examine tbe diegram

Faire 5-11: Migram ULutntbg utmction of $bhw winp' 8tyk MAV wiip This germai wing style was a f f i n a t e l y b w n as 'blue wings' because of tk

blue fibric used in kir constmtion. Many SUCCeSSiVe improvements were medc to this

'blue whg' CO-. Ratkr thaa to nmmtomusly desCrri each successive change, it

&tailed apprgciation of the wing perfbrmance of each ggmroiion of blue whgs is

Fipire 512: Photo of four 6ihtbhaai&pe' atyk MAV whgs r#Kkd to the o r l g u l OATH t u b of the bench-top tm rb.

The pertiormance of this mode1 was sllnar to tbc earer Wed eiiipsoid wuhg

mernpts. However, by graduaily adding further reinforcing layers of &bric to criticai

areas of the wing, considerable persDcxnance iacrrases were realized. The anas to which

these fiirther fhric layers were added are depicted in 6gure 5-13 bebw.

hcrease with frequency uat a maximum tbrust d u e was rrachrd. Increasing the

At fkst, the auuior and Dave h w e n eiiiaiaiiud the idea that the thmst measurement

portion of the rig was expiencing aome brm of rrsoaaiice to accomt for this peak.

excessively. In fim above the max-thtvst @phg fkque~~y, die tips of the w i q s were

virtuay horizontal (and, hence, had an aagk of attack close to pro). Further iaacases

to the bending and tomional stiffiiess of the wings ( thugh the eddition of Mt hyers

of fabrc at key bcations) caud the maximum thnist frrquency to incrase and the max

'reinfot~edstrongblue' wing depicted bebw which was capable of produchg roughly 40

Vartical Thru8t va. Fnquency Cuwo8 of Thne %lue wlnga' SCyh YAV Wing Deabna

It must be mentioned that the aiipping amplitude used hr teshg tes 'blue wings'

stylewasabout70degreesrathntban8Odegrres. Whcsettingupfbrexprimentswith

this design, the author trird flapping tb rig at the bwer anplihde setting of 70 degrees

(which tbe rig bsd k e n equippcd fbr sime it was buiit). It was mticed that the wing tip

contiiruadtoOapovathefull90&gneatcdueto&flec~n&the~flappiiigbeds

However, signincantly less noise and v i i n existed, probably iadicatiq that the 80

degree root apping amplitude hsd ecaielly been smacking together the stiffwing mots

of opposiiig whgs duhg each 'clap' portion of the apphg cycle. Perbsps this had

contnbute to the pmious wing Wures. The initial thrust target or the project was 50

grams. Only two ( d e and shple) whg concepts bad thus fiu been testeci d the

a b i i t o goduce roughiy4 gramsofthrust badalrredy beendemoi3strated. Thug, it

was It that thc primary goal of Phase 1, to prove tbat tbe pmject thmst met of 50

grannr was a ceasonabk pa, bad ken achieved Not bng aiter complethg tht test run

of 'reinfbrcedstrongblue' the a u t h sccidentally glucd soiid the entm OATH nrchanism

oftbetestrig. Thiswtakaia9anomn,ditwasdecidedtoceasethePheseItesting

h orda to pp for a somewhat more thomugh and mise empirical pn>cess in wbat

would kcome Phase II of UTIAS's MAV wing evebpment effort,

Chapter 6: Experimental Wing Testing, Phase II

The nrSt phase of the TAS MAV wing devebpen program was Cnide a d

praginatic. It sought only to pmve b t dcient thnist might be geaeraicd by a

hover@, Oapping-whg h4AV to support its own aiibiipaed mass of 50 grams. nie

second phase of wing devebpment bed dEenit goais. The first new objective was to

e q m d the wing performaiiw envebpe, h0pefbl.l~ exceediDg the 50-gram t q e t thrust

value. In so &hg, it was hoped that the UTIAS groups wuid kani to construct wings

tbat c o u operate at signincantiy higher fiapping hquencies. (It simuici be noted tbat

tbe EPAM &ciai muscies being devebped by SRI have a higher 'weight-specifc

power' wfm higber flapping bque~~~ies are us+d, that is, high fiequency cequires bwer

musck nniss for similar power outpuSI) The second objective of Pbaae II was to explorr

several omr wiag design concepts. The fiaal goal was to expard the test equipment

capabiiity to include input pwer xmaswment.

Aithough the secon pbase tests woui be more stnrnned and i n f i , d v e than

the ' s h in the ark' of Phase I, 1&n was m w a pressing need to have som i n t e

and meaningfi paS0fm~11l~e numbers. (Co nhuatbn of tbe pmject fnding fbr

s u b q m t yean depeDded upon a micw by DAWA representatives, which

co~esponed with the d of Phase II.) T b resui was tba tk OTIAS p u p o h b d

to mve on to w, mon immeviEatciy pcomising design iders rathcr tban to M y expbze

mme 'teserrrch rich' aveIIues,

Several ahetations to the test equipment took place d u h g Pliise [I. Tht nrSt

signifiatut cbaqe was an electmnic tlapping-firesuer~y meter. This device, construded

by Rambod Larjiaiii (a PhD shdeat in Dr. DeLaurier9 research group), of two

megnets placed on the crank of the bench-top test dg 's hpping motor, a 'Hall-effect'

sensor, a d some eieetronic circuitry. A pboto of the unit is shown bebw. The e u h r

does mt hiow the details of tk citcuihy. However, the basic principle of operation is

thus: Tbe Hall4kt sarior outputs a brf vo-e puise each t h OIE of tbe megzets

elctroaieally, the strobe ght was still u d 60r most tests to visually obsme the wing

obvious thst the existllig wing-connection huh on the bench-top test rig were hadequate.

At about the sam ime, i was discovmd that the bras tubwithin-tube OATH hppimg

meclienism (sa chapter 5) bad a resoiiairt aCquency that wuid be enoountered with the

new, bigher fkquex~y wing desi-. Dave Loewen thus undertook a sustantial effort to

upgrade the test rig. When wmpleted, the OATH kass nibw hd ban upsized to O.D.'s

of 3/16'' (0.476 cm) and 7/32'' (0.556 cm), eliminetiiig the monance problem The wing

attachment hubs were replaced with a considerably simpler and more robust system of

using a single machine tmew to press the wisg mt sgaiast a ncw aat-plate hub design

(see photo bebw). Collsequently, the moideci DP-420 epoxy conctor on tht wing mot

was npbced with a small flat phte h u g h which the machine sam must pass.

The final upgrade @rrned on the benchtop test rig mis the addition of a very

low vaiue mistor in saies with the electric motor, which actustes the wngs. By ushg

thc NetDAQ to record the voltage across the tesistor a d the voltage across the eiectric

motor, it is possible to detemine the electrical powa input to the mtor ushg the

If one uses an el& motor wbse efficiency is hiown, one may actuate the rig at a

given firesuency both with d without mn$s to obtain the mechanical power used by the

wings:

PMh(wmp) = q-r x ( ~ m w r a k n n g s ) P~kc(mnvmgs) 1 Tht only outsianding variable in ths mechaaical power equation is the rrarismission

efficiency (q-). ne rrm~t note that 'PEImIko*,' accounts h r the power rquired ta

actuate the transmission while the ' qKe' accoaccoim*r for additionai frictionai bsses

as a d of incrrased loading of the aansmission when the wings are king actuated.

'ftdurr$' is aswimd to be W h or hi* when aii four wings are king actuated kcause

the forces on the test a's actuation huba are neary baliiicbd; only the fictionai bads on each end of the push-COdS are substantiaiy increased (see figures 5-1 thugh 5-6 in

cbapter 5 for photos containhg the pusbtods).

6.3.1 Higher Aspect-Ratio EYipsoid Wngs

Because of the importance of hi* flappiag-hquencies to EPAM efficiency

(sat 6.1 ebove), the first whg expetiments o f t b phase of the UTIAS MAV wing

evebpment effort sought simply to adep the reiatively successfid 'blue wing' design of

'Phase 1' to operate m a bigher flapphg-kquency regim. At the same time, it was

desired to expbre the durability and bngevity of this design. (The nader sbould mt get

the impression tk either the author or Dave Lawen were 'hug up' on this firsi

rnarginaiiy acceptable wing design. Rather, because this wing conoept was a known

staaiag point, it was hoped that smali alterations to wing propertYs would reveal

quaiitative tnads that couid be apped to future wing esigm) In ' P b 1' it was

explained tha by adding firrtbet layen of reinforcing fbric, tbe maximum tbrust

pCOducedbyt&'blucwings'wesh~aswastbemcucimumtlinist~ueocy.

bstea of continuhg this trend, which had aiready rrsulted in wings whose mess

approacbe 1 gram each, f was decideci to try a sborter chord msion of the sam basic

shape. (This nsulted in a higher aspect-ratio wing, since aii wing sets buib fbr this

propCt span 6 inches h m tip to tip w h munted on the test rig). The subseqrnrn wbg,

name 'hisbespectb1ue' is pictured on tht iwxt page. It bad beea anticipateci tbat

decreas~iechord~Pbout4w.miuldhavctheeffeftofiancaPingthe~~at

whrh the whg achieved the maximum tbnist. In otda to evaliate the test npcliiabiiay,

the durabay a d bngevity of the coristn#ion mahDdq and tk mateds empbyed in

the 'Mue wing' style of wing, a total of 8 'higbaspccblue' whgs mn constnrtcd (Le.

two compw sets of fiUr).

6 5

one set of fout wiogs, folbwed by two test runs with the second set. Q kt, due to a

with these wiags wen wnducfed st a flapping amplitude of 70 degmes.

The nsults were both enwuragiiig and disoourag* (sa figure D-2 in Appendix

D). First, it was arouraging to see that the shortet chord did pu& tk operatiiig

ficquency of these wings higher (as prcdicted). In fact, tk bench-top test rig (which ha

aot yet unergo the upgmdes descriibed in section 6.2) could mt dely fap tht wiilgs

much fster than 30 Hz; it could mt be detennined ifa 'msximum-tbnist' tlapping

hquency existed for the 'highqectblue' style of h g s . The ody cataPay is tbat

duriag two of tbe ~JM, the wbgs g e d roughiy 40 grenrr of tbmt when flapped at

about 30 HZ

Unfomiaately, amthCr tnid is apparent; tbe wings tige @Idy. A carrful

e Yaminnrinn of fi- D-2 shows tbat fat each d v e test of a given set of wings, the

a i t in tbni s tv~ .~~t11~yc iavc ipsh i&dsgMly~totbek~ . subssquent

d*itnrtMcvaliiiitinnoftk tcatcdwhgs nvealed tbattk poiustyrr= md(tbattT,~ltl~

t b t p ~ r m s b s p e o f t b t w 0 q g s ) w a r b e i a g b s n t m d ~ b y t h c ~ . Thus,

6-6

aithough the 1 mm &meter polystyre mds appcar to have appmxhately the correct

beadiag stifnless to be used for MAV Bappkg-wings, and are quite ghs. they are mt

adequately durable. One furtha mte about tk resuits in figure D-2 is m m positive:

Despite the kt tbat thes 'highappectbiue' wings were aii txmuhmd individuaiiy and

by han, the paformance of the nrs5 set tested was quite simar to the performance of

the second set tested. (This is perticularly true with the nrst rn of each set, befOre any

'aging' hd o c c d ) .

6.3.2 A Hinged Flat Plate

F i i y , it was tirne to begin explorhg some o k r wing design ~OaCeptSe The

~ x t design consisteci of a 5.5 cm bag, 1 mm diameter carbon-fibre rod oonnected to the

test rig hub via a DP-420 moled epoxy wmtor. By ushg appropriately simi plsstic

tubhg (as suppiied with 'WD-40' caas), a Bet plate of bedsa-wood was m b e d in such a

Figmre 61: Pbob of i hingd fit-phtt wing ir ovigbdy colutrpcta by Mr. Ihve L4Dewca Scrlc of photo ipprn*te~ 1:l.

kss thau 90 egrees to begin). The p M r m shPpc of tbt balsa-wd was chosen by

Dave Lomn such tbat whcn Ospping, as two wings canie togciba m the intended 'clap

fling' shbn, most of the ailing edge of each of tht two w h g s would corn into contact

withitsco-

No numaicai rrsults could be obtaine h m this wiug style: When tleppod on tbe

bench-top test rig, the rig shook vioiently and made considerable mise (prompthg an

unmdiate shutdown). Several fhpping amptudes wre attempted, as was trimmmg tbe

trailing edge of the wings to Metent sbapes. The smrr v i i i o n , the author bclieves,

was a r e d of the balsa plate impacthg the 'T-stopper' hvice per Bapping-eycle on esch

wing. It should be noted that m si@cant domiward mvement of air could be felt

when these wings were flapped. A decision was mede to explore this concept fiirther

when a m e r intuitive undeffiandin$ of ot&r MAV wing coaEepts bad ken obtained.

As an uiidagraduae 4' year tbesis pmject, tbe author rmdatook an eirpaimntal

examimtion of the lift aad drag of a bng-extinct glEding reptiie whose wings bosely

resembled the 'spanwisestiffened' mmbra whg concept iscussed in cbapter 3. The

author d e d that construction of the whgs for the wind-tunnel mode1 of the extuict

reptile was quite snsighdorward. It was decideci to try constmcting a highly sUapMed

vasion of this type n>r evahistion as an MAV wing.

Tbt resuitiiig spanwise-Mened mmbraat wiogs k c k the lesson of aection

6.3.1; aii s m c h d me- would k made of carbodibre or steel (piano wice) 6 r

d d i . ~one~~~~ewahthefewwiiig&~aaemptcdso~,t&CWlfhDr

anci D m Loewen bad devebped an 'intuaive sense' of bow flexible an MAV wing

wouldhveto beinoidatogeneratesigdhntW mtbedesircdBiippingncqueaCy

regime. Atta a few pmious attempts d e in wings which were obviously nit too

stiff, the 'desertcarno' wings pictured bebw were coastnictad. The whgs bave a 4 cm

bng, 1 mm diamet csrboa-fibre rod adiilg as a rigid lePdiiig edge for the inboard

podon of the wing. Four piano-wke tods of 0.5 mm diameter are u d to pmvide

spanwise stif&ess to a membrane msde h m one iaya of beige packing tape and a thin

layer of clear mylar. Tbe carbon d piano-wire rods are potted in epoxy between two

thiil, triarigular carbon-fibre plates mat thc wing mot. AU of the 'struchiral' m m b are

sadwictied between the packing tape and the mylar. (The 'desertauam' name was

applied to this styk of wing because of tbe packing tape's beige cobur.)

of Hz, thse wiags gmrated only about 28 greme of trust (see figure D-3 in

Appendix D). (Note: Wre iileLPig tbe thomugh test rig mdScaiom outlincd m

'desetlcamo' w h g s were nui up to 40 Hz several tims and the only damage that

o c c d was brralrege of tbe moldeci DP-420 connecter tbat anchod the wing to the

bench-top test rig hub. In b t , had the comrctors mt hicen, it is lrtly that the

'desertctmm' wirigs wod have witbstood considerably higba Iispping &eque~~:ies*

V W y , the 'desertcam' style w h g s did mt behave exady as intadcd V a y

M e aeroelastic deformation was obBewed, probaMy due to tbe use of excessively thick-

gauge pisno-W. In fct, the author found it mcndible tbat the wings gerwiatad es

much thrust as they did given that, w&n fiapped at high spee, they appeared to k flat

plates aesrly aligned with the flapping axis (wah perbeps 8 de- of whg twist at the

tip). Unfomiristely, no pbotodvideos were taken of this bebaviour.

Because the 'esertcam' spanwise-stiffened wings were so resilient, it was

decided ttiet this concept should be expiored furiher, but ushg a lighter gauge of pieno

wire (0.4 mm diamRter) and a slightiy different trailing edge shepe. The resuhing

'desertcamoght' wing is pictcmd klow.

less tban 35 grams of th- were geacratod with these wiqp at a bpping ftesuency of

about 45 Hz (see cbart kbw). Unlike the previous 'desertcarno' r e d t s , bowever, the

tbnrPt W. &equency cum for the 'desert~911~1ligh' wings has a positive second

derivative in tbe 40 Hz range. In otha wofds. d fbque~~:y Ui~re8ses would p d u c e

messive thnist boosts. UnfortunateEy, the existmg bench-top test rig was riot capable of

reaching higher fhpping equencies. Thris, Dave hewen began designhg the test-rig

upgrades described in section 6.2.

F i g m 17: C h e of vcrtial tLrat vr. !bppiy n#laency for wbg modd ' d c r ~ ~ ~ o ~ t ' . Fhpphg . a p W e w u 72 depeu. The mdcr L eiunged to corn& igmre M of Appcidix D k 8 more hibomve vcniia et- chait.

6.3.4 Rudimentary Flow Wsualizaton

During the time tbat Mr. LoeMn was prepeting the new rig design, the a u h r

tooktbe oppoiiunily to attempt a vay nadimentary, baverageci Bow vbmbtion

ushg a thin mylar tuft on the end of a 0.5 mm diamta d The tuft was positioned in

various spots s u r r o e the apping 'de~erfcamlight' wings uatil an o v e d sense of

t&e fiow pattem was es&blisbed. From this Ilifofmation, the author geamed two

orthogonai views of the fbw behaviour: fbw in the plane of tht wings a d fbw through

the plone of the wings (see figures 6-8 and 6 9 bebw).

Figure 64: mPrtn8ion a l macrr#eopic tbn khvkv ia (Lc plue of the Ilipphg wiqp aa akewa by the amthot uly a myht ha on # t h ml.

Figure 6-9: iRurtmtion of macroraplc Ibn k l iv iour throagh the phne of tht flappbg wng as obaeived by the uithor u ~ i y mmyhr hiil: on a thin rod

An importani remit om this basic tbw visualization 8pproach can be descri i

in the fiiiowing way: in ordcr for the flapping wings of the SRVUTIAS MAV design to

through the plane of the flapping w h g s behaves, m a qU81if8five khion, iike the flow

thugh a ppeUer or rotor. in fct, the fbw pattern illustrateci m figures 6-8 and 6-9 is

very simar to wbat one might aad in the presellce of a htlicopter's rotors in hoverhg

flight or a ppeUer gemating tatic thnrit That is an intbw of air b m both above

and in the p h of thc flapping wings. Tbe air ejected h m the bomm of the disc of

propeiiedrotor type flow is kimd in the ana in which the wings are coming togaha and

apert Inthesedarras.tbefbwmvrsradiallyoutward8ndishigblytirtbulent~

0.3.5 Bigger Spanwi-ned Wings

With the bench-top test rig upgrades completed (as desc r i i in section 6.2), it

was again possible to continue expadhg the MAV whg performance envelope. Taking

into account the lessons of the most recent spanwisestiffened wing design

('desrtamlight'). the concept was mDdjfled in an attempt to design whgs that muid

geiwrate sienificant tbnist in the 40 to 50 Hz flapping-equency regime. It was decided

that the best way to achieve this aim was to iiirrease the chord of the 'desatcamoli*'

style wings. In so