Air Muscle.pdf

7/27/2019 Air Muscle.pdf

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[2008]

Air Muscles
http://opt/scribd/conversion/tmp/scratch8980/www.techalone.com


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Air Muscles

Contents

Title Page

Abstract 4

Introduction 5

History 5

Construction 6

Working 6

Theoretica !ode "#sti$ation o% %rictiona e%%ects &0

'yna$ic (ro)erties &*)eri$enta resuts &&

+)erationa Characteristics &2

,)eci%ications %or ,hado- Air !usces &.

'i%%erences %ro$ )neu$atic cyinders &4Ad/antages o% Air !usces &5

'isad/antages &5

A))ications &6Hu$anoid obots &6

Arti%icia i$bs &"

The 'e*terous hands &"

1urther de/eo)$ents &8

Concusion &

e%erences 20

(ubished (a)ers 203ooks 2&

Websites 2&

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Air Muscles

About

This is a se$inar to)ic use%u %or $echanica engineering students

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Abstract

Air $usce is essentiay a robotic actuator -hich is re)acing the con/entiona )neu$atic

cyinders at a ra)id )ace 'ue to their o- )roduction costs and /ery high )o-er to -eight ratio

as high as 400& the )re%erence %or Air !usces is increasing Air !usces %ind huge

a))ications in biorobotics and de/eo)$ent o% %uy %unctiona )rosthetic i$bs ha/ing su)erior

controing as -e as %unctiona ca)abiities co$)ared -ith the current $odes This )a)er

discusses Air !usces in genera their construction and )rinci)e o% o)eration o)erationa

characteristics and a))ications

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Introduction

obotic actuators con/entionay are )neu$atic or hydrauic de/ices They ha/e

$any inherent disad/antages ike o- o)erationa %e*ibiity high sa%ety re7uire$ents and high

cost o)erationa as -e as constructiona etc The search %or an actuator -hich -oud satis%y a

these re7uire$ents ended in Air !usces They are easy to $anu%acture o- cost and can be

integrated -ith hu$an o)erations -ithout any arge scae sa%ety re7uire$ents 1urther $ore they

o%%er e*tre$ey high )o-er to -eight ratio o% about 400& As a co$)arison eectric $otors ony

o%%er a )o-er ration o% &6& Air !usces are aso caed !cibben actuators na$ed a%ter the

researcher -ho de/eo)ed it

History

It -as in &58 that H9ayord in/ented a )neu$atic actuator -hich:s origina

a))ications incuded a door o)ening arrange$ent and an industria hoist ;ater in &5

-hich -oudcontract -hen e*)anded radiay This coud actuay be considered as a biorobotic actuator as it

o)erates a$ost si$iar to a bioogica $usce

Air !usce ,che$atic? !cibben !ode

The current %or$ air $usces -ere de/eo)ed by the 3ridgestone Co$)any

%a$ous %or its tires The )ri$ary $ateria -as rubber ie the inner tube -as $ade %ro$ rubber

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Hence these actuators -ere caed @ubbertuators: These de/eo)$ents took )ace around

&80s

;ater in &0s ,hado- obotic Co$)any o% the nited ingdo$ began

de/eo)ing Air !usces These are the $ost co$$ony used air $usces no- and are associated

-ith a$ost a hu$anoid robotic a))ications -hich -ere de/eo)ed recenty A)art %ro$

,hado- another co$)any caed The !erin Hu$ani%or$ de/eo)s air $usces %or the sa$e

a))ications athough their design is so$e-hat di%%erent %ro$ the ,hado- $usces

Construction

The Air !usce consists o% an inner rubber tube -hich is o%ten $ade %ro$ )ure rubber

ate* It is surrounded by a braided $esh

Air $usce construction [,hado- air $usce .0$$]

The header at each end o% the $usce consists o% an Au$iniu$ ring and a

'erin )astic bung -ith a %e$ae thread This thread can be used as a $eans o% attach$ent and

to ao- air into or out o% the $usce The $usce is su))ied -ith t-o 'erin %ittings aso

Working

The inner rubber tube is in%ated by entering air at a )ressure usuay i$ited to .5 bar

The $o/e$ent o% this tube is constrained by the braid When the tube gets in%ated it e*)eriences

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Air Muscles

a ongitudina contraction This -oud create a )u at both ends o% the tube suay one end o%

the tube -i be attached to so$e-here so that %orce can be a))ied %ro$ one end This )u -hen

e%%ecti/ey utoised coud )ro/ide the necessary $otion The -orking o% the Air !usce cosey

rese$bes that o% the natura $usce and hence the na$e !usce gi/en to it aong -ith Air The

%igure beo- sho-s the )hysica a))earance o% the $usce at di%%erent stages o% its -orking

Air !usce at di%%erent stages

Theoretical Model

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sing conser/ation o% energy and assu$ing the actuator $aintains dB d( e7ua to ero

reasonabe %or actuators buit -ith sti%% braid %ibers that are a-ays in contact -ith the inner

badder the tensie %orce )roduced can be cacuated %ro$

Where

( ? the in)ut actuation )ressure

dB ? the change in the actuator:s interior /ou$e

d; ? the change in the actuator:s engthBb ? the /ou$e occu)ied by the badder

dW ? the change in strain energy density=change in stored energyDunit /ou$e>

1fdescribes the u$)ed e%%ects o% %riction arising %ro$ sources such as contact bet-een

the braid and the badder and bet-een the %ibers o% the braid itse% Eegecting the second and

third ter$s on the right hand side o% abo/e e7uation and assu$ing the actuator $aintains the

%or$ o% a right circuar cyinder -ith an in%initesi$ay thin badder yieds kno-n soutions The

soution to the second ter$ on the right side o% the e7uation is based on a non?inear $aterias

$ode de/eo)ed by !ooney and i/in in the &40:s and &50:s )ro)osed a reationshi)

bet-een stress =F > and strain =G > gi/en by F dW dG -here W is the strain

energy density %unction sing the assu$)tions o% initia isotro)y and inco$)ressibiity W can

be described as a %unction o% t-o strain in/ariants =I&andI2>

-here Cijare e$)irica constants +ny t-o !ooney?i/in constants =C&0&&84 k(a

and C0&&05" k(a> -ere necessary %or accurate resuts -ith the natura ate* rubber badder

ho-e/er other $aterias $ay re7uire additiona constants 1or the case o% the !cibben

actuator the e*)eri$enta $ethods re7uired to deter$ine these constants are dra$aticay

si$)i%ied because the !cibben actuator:s strain in/ariants constrained by braid kine$atics

are neary the sa$e as the strain in/ariants %or unia*ia tension This %ortuitous reationshi)

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ei$inates the need %or $uti?a*ia testing that -oud other-ise be necessary ,o/ing e7uation a

using the non?inear !ooney?i/in $aterias $ode resuts in a !cibben actuator $ode

-hose structure is ao-ed to de%or$ as -e as store eastic energy in a non?inear %ashion This

$ode is gi/en by

-hereF$ris the )redicted %orce and )ara$eters N Lo B, andRoare sho-n in %igure & and

%igure 2 3adder thickness is denoted by to and is used in the badder /ou$e cacuation &

re%ers to the actuator:s ongitudina stretch ratio and is gi/en by

& ;iD ;o -here Li is the actuator:s instantaneous ength andLo is the origina resting state

ength

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1igure &

1igure 2

!cibben actuators are %abricated %ro$ t-o )rinci)e co$)onents an in%atabe inner badder $ade o% a

rubber $ateria and an e*terior braided she -ound in a doube hei* At a$bient )ressure the actuator is at

its resting ength =%igure &> As )ressure increases the actuator contracts )ro)ortionay unti it reaches its

$a*i$ay contracted state at $a*i$u$ )ressure =%igure 2> The a$ount o% contraction is described by the

actuator:s ongitudina stretch ratio gi/en by & Li Lo -hereL is the actuator:s ength and subscri)t i re%ers

to the instantaneous di$ension and the subscri)t o re%ers to the origina resting state di$ension

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Air Muscles

#sti$ation o% 1rictiona #%%ects

The third ter$ on the right o% e7uation are)resents these %rictiona osses -hich are a %unction o%

=1> braid $ateria =2> badder $ateria =3> )ressure and => actuator ength In ieu o% a $ode

that incor)orates a %unction %or each o% these -e ha/e taken the inter$ediate ste) o% u$)ing a

o% these e%%ects into a singe )ara$eter = Ff> as a si$)e %unction o% )ressure Anaysis o% the

e*)eri$enta data and theory )redictions =F$r> suggests a inear %or$ gi/en by

Ff mP J b

-here m and b are e$)iricay deter$ined constants The actuator $ode -hich no- incudes

the geo$etry o% the braid and badder the $ateria )ro)erties o% the badder and a ter$ %or

%rictiona e%%ects =a three ter$s o% e7uation a> is gi/en by

F F$rKFf

A co$)arison o% this $ode /ersus e*)eri$enta resuts %or the argest actuator =no$ina braid

dia$eter o% &?&D4 in> is )resented in %igure .5 The %igure sho-s a reasonaby cose %it %or each

o% the %our acti/ation )ressures tested ,i$iar resuts -ere obtained %or the t-o s$aer actuators

=no$ina braid dia$eters o% L and &D2> but are not sho-n

1igure .

!yna"ic Pro#erties

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Air Muscles

To $easure the %orce?/eocity )ro)erties o% the !cibben actuator a series o% e*)eri$ents -ere

conducted -ith the a*ia?torsiona 3ioni* =!T, ,yste$s Cor) !innesota ,A> tensie

testing instru$ent Actuators o% three sies -ere constructed and tested #ach e*)eri$ent

$easured the %orce out)ut at a constant )ressure o/er the contraction range at /arious /eocities

+ne end o% the actuator -as rigidy attached to the oad ce -hie the other end -as $o/ed in

res)onse to the instru$ent:s digita controer ,te) /eocity )ro%ies -ere a))ied such that one

end o% the actuator -as ra)idy acceerated and hed to a constant /eocity unti the end o% the

actuator:s -orking ength -as reached In)ut ste) /eocity )ro%ies tested incuded & &0 25 50

&00 &50 200 250 and .00 $$Ds %or concentric contractions and & &0 25 50 &00 and &50

$$Ds %or eccentric contractions ) to 500 $$Ds is )ossibeM ho-e/er instantaneous %uctuations

in /eocity o% &5 )ercent -ere $easured during trais at 500 $$Ds The $agnitude o% these

%uctuations decreased at o-er /eocities and -as ess than )ercent at .00 $$Ds and 6 )ercent

at 200 $$Dsec This ano$ay is thought to arise %ro$ the hydrauic )u$)

#*)eri$enta esuts

The e*)eri$entay $easured out)ut %orce o% a singe !cibben actuator )otted as a %unction

o% both ength and /eocity is sho-n in %igure 4 The resuts sho-n are %ro$ an actuator -hose

no$ina braid dia$eter -as L inch and constructed -ith a natura ate* badder The actuator

)ressure -as 5 bar and the origina resting state ength o% the actuator -as &80 $$ The out)ut

%orce is ceary a %unction o% ength but not o% /eocity ,i$iar resuts -ere obtained at o-er

)ressures and -ith the other t-o sied actuators but are not sho-n

1igure 4

$#erating Characteristics

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Air Muscles

The characteristics o% !usces as gi/en by the ,hado- obotic co$)any

45 N load

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Air Muscles

%#eci&ications &or a ty#ical Air Muscle 'the %hado( co"#any)

!ia"eter Weight Pull '3*+ bar) Ma,i"u" #ull -ength

.0 $$ 80 g .5 kg "0 kg 20 $$ =stretched>

stretched %or$

These $easure$ents are taken -hen the $usce is %uy stretched out under a oad o% at east

50E and a )ressure o% 0 bar

Hoe N Hoe ,)acing 20$$

Tota !usce ;ength 250$$

Acti/e ;ength 2.0$$

& The Hoe?Hoe s)acing is the distance bet-een the hoes in the %ittings at either end o% the $usce This is

adOustabe as the %ittings can be

scre-ed in or out They can aso be re$o/ed entirey creating a $ore co$)act $usce se an !&0 scre-

instead and re$e$ber to use

(T1# ta)e to ensure a good sea

2 The Tota !usce ;ength is the ength o% the -hoe $usce e*cuding the %ittings. The Acti/e ;ength is the ength o% the )art o% the $usce -hich contracts under )ressure and does not

incude the headers

These $easure$ents are taken -hen the $usce is )ressurised to .bar -ith a oad o% 50E

Hoe N Hoe ,)acing 2&0$$

Tota !usce ;ength &"0$$

Acti/e ;ength &50$$

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Air Muscles

Contracted %or$

!i&&erences &ro" #neu"atic cylinders

The Air !usce is a o- )ressure actuator -ith a set o% o)erationa %eatures uni7ue in the

%ied o% robotics and auto$ation

a)? %"ooth .erk &ree "otion%ro$ start to %inish due to the co$)ete ack o% stiction the %eature

o% standard actuators -hich )roduces the characteristic Oerk so -e kno-n in air o)erated

de/ices

b) / Co"#liance ? Athough they can )roduce the %orce needed to $o/e a %unction the Air

!usce -i aso yied -hen an obstace is encountered thus )re/enting da$age to the obOect

and the PAr$P ? a distinct ad/antage -here robots $i* -ith hu$ans

c) / -ight (eight? The $aterias %ro$ -hich the Air !usce is $ade are non?$etaic and gi/e

it a reati/ey high )o-er?to?-eight ratio ? a critica %eature in choosing an actuator %or a $obie

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Air Muscles

Ad0antages o& Air Muscles

(o-er to -eight ratios in e*cess o% & kWDkg by -ay o% co$)arison eectric dri/es ty)icay has

so$e &00 WDkg

A /arying %orce?dis)ace$ent reation at constant gas )ressure contrary to )neu$atic cyinders

-hich resuts in a $usce?ike beha/iorM an adOustabe co$)iance due to gas co$)ressibiity

and the dro))ing %orce?dis)ace$ent characteristics

A $a*i$u$ dis)ace$ent or stroke o% u) to 50Q o% initia ength

The absence o% %riction and hysteresis as o))osed to other ty)es o% (A!s

The abiity to o)erate at a -ide range o% gas )ressures and thus to de/eo) both /ery o- and

/ery high )uing %orces

The )ossibiity o% direct connection to a robotic Ooint i. e. -ithout ha/ing to use any gears

because o% their high out)ut %orces at a s)eeds

,o$e o% the ad/antages s)et out by the shado- co$)any ty)ica to their )roducts are?

-ight(eight? Air !usces -eigh as itte as &0 g$ ? )articuary use%u %or -eight?

critica a))ications

-o(er Cost ? Air !usces are chea)er to buy and insta than other actuators and

)neu$atic cyinders

%"ooth / Air !usces ha/e no RstictionR and ha/e an i$$ediate res)onse This resuts in

s$ooth and natura $o/e$ent

le,ible? Air !usces can be o)erated -hen t-isted a*iay bent round a corner and

need no )recise aigning

Po(er&ul? Air !usces )roduce an incredibe %orce es)eciay -hen %uy stretched

!a"#ed? Air !usces are se%?da$)ening -hen contracting =s)eed o% $otion tends to

ero> and their %e*ibe $ateria $akes the$ inherenty cushioned -hen e*tending

Co"#liant? 3eing a so%t actuator Air !usces syste$s are inherenty co$)iant

&&icient? a $usce ength can be $aintained -ith $ini$a energy in)ut

ast ?%u contraction can be achie/ed in ess than one second %ro$ rest

!isad0antages

The %orce -hich can be a))ied is ony tensie in nature 1or both kinds o% %orcesadditiona $echanis$s are re7uired



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Air Muscles

The e%%iciency o% Air !usces is not as good as eectric $otors

Its tota dis)ace$ent is ony about 20Q to .0Q o% its initia ength

1riction bet-een the netting and the tube eads to a substantia hysteresis in the %orce?

ength characteristicsM this ob/iousy has an ad/erse e%%ect on actuator beha/ior and

necessitates using co$)e* $odes and contro agorith$s

ubber is o%ten needed to a/oid the tube %ro$ bursting this co$es at the cost o% a high

threshod )ressureSty)icay about 0 k(a Sthat has to be o/erco$e in order to start

de%or$ing the rubber $ateria and beo- -hich the actuator -i si$)y not o)erate

ubber de%or$ation ike any $ateria de%or$ation needs energy this -i o-er the

%orce out)ut o% this ty)e o% $usce u) to 60Q

A##lications

Hu$anoid robots

The $aOor a))ication o% Air !usces is in the %ied o% hu$anoid robots As these

actuators neary rese$be the characteristics o% actua skeeta $usces they can )er%or$ a /erity

o% %unctions as is )er%or$ed by the hu$an hand Cou)ed -ith the i$)e$entation o% neuranet-orks and )o-er%u )recise sensors they are ca)abe o% high end a))ications such as

asse$bing o% /ery $inute co$)onents etc

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Air Muscles

Hu$anoid robot $anu%actured by ,hado- robotic co$)any

Arti%icia i$bs

Arti%icia i$b de/eo)ed at the bio robotics ;ab ni/ersity o% Washington

At the bio robotic ab o% uni/ersity o% Washington the i$b as sho-n %igure -as de/eo)ed The

$aOor re7uire$ents o% their research tea$ -ere

& Continuous and e*tended o)eration %or about 8?&0 hours

2 ;o- -eight

. uieter o)eration

4 ser satis%action

5 Eo $aintenance or o- e/es o% $aintenance

To satis%y a the %ore $entioned re7uire$ents to be satis%ied a research tea$ $ight s)end

years 3ut )artiay these %eats -ere acco$)ished The %igure gi/en beo- iustrates this

!erin Hu$ani%or$ Air !usces attached to hu$an hand



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Air Muscles

The 'e*terous hands

The de*terous hand -as de/eo)ed by the ,hado- robotic co$)any The hands

o)erate Oust ike hu$an hands -ith %i/e %ingers It is )o-ered by 28 Air !usces The sie is

a$ost sa$e as hu$an hands as they cosey %it into a hu$an hand The %igure sho-n iustrates

this %act

The $usce can )er%or$ any %unction the hu$an hand )er%or$s 3esides it is e7ui))ed to s-i/e

its %ingers It $akes use o% 28 Air $usces %or these $o/e$ents The hu$an hand has 24

$usces The additiona %our in case 'e*terous hands due to the s-i/eing $otion

urther de0elo#"ents

The (eated (neu$atic Air !usces [((A!s] As a resut gro-ing research in

the %ied o% Air !usces another /ariant caed )eated )neu$atic air $usces -ere de/eo)ed

(eated )neu$atic arti%icia $usces are strong and ight-eight actuators that )er%or$ /ery -e

in )osition contro and other auto$ation and robotic tasks They are easy to use re7uire no

gearing and are easy to connect and re)ace A high degree o% )ositioning accuracy is

acco$)ished -ith the$ and this Oust by using o%%?the?she% )ressure reguating ser/o?/a/es

together -ith si$)e (I contro techni7ues 1urther$ore they can easiy be $ade to ha/e a so%t

touch so as not to da$age %ragie obOects or to e%%ect a sa%e $an?$achine interaction 3ecause o%

their inherent characteristics ((A!s are suitabe %or )o-ering -aking and running $achines

Autono$ous $achine o)eration can then be guaranteed in a nu$ber o% -ays e. g.by using on?

board s$a sie interna co$bustion engines

,o$e o% the stated ad/antages o% ((A!s are?

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Air Muscles

A $a*i$u$ dis)ace$ent or stroke o% u) to 50Q o%

initia engthM

The absence o% %riction and hysteresis as o))osed to other ty)es o% (A!

The )eated )neu$atic Air !usces

Conclusion

#/en thoughAir !usces are not ca)abe o% o%%ering an e*tre$ey -ide

range o% o)erations but in the case o% arti%icia egs hu$anoid robots etc they o%%er a -ide range

o% )ossibiities With %urther de/eo)$ents in neura net-orks and sensor e7ui)$ents it $ightbe )ossibe re)ace an entire i$b %or an a$)utee and %unction nor$ay ike a natura i$b

-oud do The ony dra- back ies in de/eo)ing a co$)ete theoretica $ode %or cacuating the

characteristics such as %atigue etc esearch is aso directed to-ards substituting %or Air -ith

nitrogen or other gases %or $a*i$u$ e%%iciency and better da$)ing

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Air Muscles

e&erences

(ubished (a)ers [source The internet]

Measure"ent and Modeling o&

Mc4ibben Pneu"atic Arti&icial Muscles

Ching/Ping Chou

5lake Hanna&ord

'e)art$ent o% #ectrica #ngineering

1T?&0ni/ersity o% Washington,eatte Washington 8&5

Pleated Pneu"atic Arti&icial Muscles6 Co"#liant obotic Actuators

rank !A!78 !irk -58 5.9orn :-%T8 onald :A7 HAM

BI


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Air Muscles

(hone 66?"445?&60& 1a* 66?"42&?2&5#$ai -suntonU$edicine)suacth

%atha#orn -aksanacharoen

!echanica #ngineering 'e)art$ent

ing !ongkut:s Institute o% Technoogy Eorth 3angkok&5&8 (ibusongkra$ d 3angsue 3angkok THAI;AE' &0800

(hone 662?&.?2500 1a* 66?2586?54$ai ,T;Uk$itnbacth

Arti&icial Muscles6 Actuators &or 5iorobotic %yste"s

?lenn 4enneth 4lute

A dissertation sub$itted in )artia %u%i$ent o% the

re7uire$ents %or the degree o%

'octor o% (hioso)hy ni/ersity o% Washington &

atigue Characteristics o& Mc4ibben Arti&icial Muscle Actuators?lenn 4* 4lute

'e)art$ent o% 3ioengineering

ni/ersity o% Washington,eatte WA 8&5?"62

gkuteUu-ashingtonedu5lake Hanna&ord

'e)art$ent o% #ectrica #ngineeringni/ersity o% Washington

,eatte WA 8&5?2500bakeUee-ashingtonedu

htt)DDrcsee-ashingtoneduD3;D

Accounting &or lastic nergy %torage in

Mc4ibben Arti&icial Muscle Actuators

?lenn 4* 4lute

'e)art$ent o% 3ioengineeringgkuteUu-ashingtonedu

5lake Hanna&ord

'e)art$ent o% #ectrica #ngineering

bakeUee-ashingtoneduni/ersity o% Washington

,eatte WA 8&5?2500htt)DDrcsee-ashingtoneduD3;D

3ooks

Ad0anced Mechanics o& %olids

- % %rinath

Tata !c9ra-?Hi (ubishing Co$)any ;i$ited Ee- 'ehi

A Te,t 5ook o& Metallurgy and Material %cience$ P 4hanna

'han)at ai (ubications Ee- 'ehi

Websites

---shado-orguk

---br-ashingtonedu---robotstoreukco$

---kisuiuceduhtt)DDtea$ski)rorg

htt)DDbioroboticsc-ruedu

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Air Muscle.pdf

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