Flexible network system for wearable computing using conductive fabric

Flexible network system for wearable computing using conductive fabric

著者 Akita Junichi, Shinmura Toru, Murakami Tomomichi, Yao Mariko, Toda Masashi journal or

publication title

Proceedings ‑ IEEE International Conference on Mobile Data Management 2006

page range 1630637

year 2006‑05‑01

URL http://hdl.handle.net/2297/3528

Using Condutive Fabri

JunihiAkita Toru Shinmura

TomomihiMurakami MarikoYao

KanazawaUniversity

Kakuma,Kanazawa, Japan

akitais.t.kanazawa-u.a.jp

Masashi Toda

Future University-Hakodate

116-2Kamedanakano, Hakodate, Japan

todafun.a.jp

1. Introdution

Aording to the drasti development of omput-

ersand network systems, anewparadigmof omput-

ingsystem,thewearableomputingsystemsisreently

widelystudied[1,2℄. Usersaninstallthedevies,suh

asomputers,sensorsanddisplays,ontheirwear,and

theintegratedsystemofthesedeviesenablesthenovel

usageofomputing.

The ommon fats in wearable omputing systems

aresummarizedasfollows.

Alot ofdeviesexistonthewear.

Thedeviesneedtoommuniateeahother.

Thedeviesrequirethepower.

There aretwopossiblephysial methodologiesforim-

plementation of system onguration; the wired and

thewirelesssystems.

Inthewiredsystem,thedeviesareonnetedeah

other by wires whih provide both powersupply and

ommuniation hannels. The wired systems essen-

tiallyhaveaproblemin wiring. It isaburdenforthe

usertoinstallthewiresatinitial,anditismoreserious

andfataltoarrangethephysiallayoutofthedevies,

sinetheompliatedwires existonthewear.

Inthe wireless system,the ommuniationsamong

devies are arried out by the wireless hannels (ra-

dio,infraredandsoon). Therefore,theprobleminthe

wiredsystemsaresolvedandusersaninstallandar-

rangethelayoutofdeviesmoreexibly. However,the

wirelesssystemshaveanotheressentialproblem;power

supplyproblem. Allthedeviesrequirethepowersup-

ply for their operations, but in the wireless system,

therearenopowersupplyablesfordevies. Thebat-

teryoperationisoneofthesolutionsforpowersupply,

the nite battery life. This batteryproblem beomes

fatalespeially whenwearableomputingsystemsare

extended,sineasthenumberofthedeviesinreases,

itbeomesdiÆulttomaintainthebatteriesofsomany

deviesforalongperiod ofoperationtime.

As desribed above, the wearable omputing sys-

temsrequirethepowersupplyandtheommuniation

network,whileneither theonventional wirednorthe

wirelesssystemsannotompletelyprovidethemwith

keepingtheexibilityofinstallingandarranginglayout

ofdevies.

We've been developing a new arhiteture of ex-

ible network infrastruture for wearable omputing

systems using ondutive fabri, whih is named as

\TextileNet[3,4℄." TextileNetprovidesallthedevies

installedonthewearbothsuÆientpowersupplyand

ommuniation hannels, while keeping the exibility

of installing and arranging layout of devies. Users

aninstalltheadequatedeviesaordingtotheappli-

ations ofTextileNet, andsuÆienteletri powerfor

operation as well as ommuniation hannels an be

suppliedtothedeviesatthesametime. Asdesribed

here, TextileNet is expetedto beome an infrastru-

tureforanykindofwearableomputingsystems,whih

isessentialforfurtherdevelopmentandspreadofwear-

ableomputingsystemin apersonalusage.

Inthispaper,wedesribetheideaandimplementa-

tionofoutTextileNetsystemaswellasitsevaluation.

2. Related Works

Therearesomerelatedworksonnetworksystemfor

wearableomputingsystemusingondutivefabris.

`NetworkedVest'[5℄ usesondutivefabri forboth

sidesofthewear,andthedeviesattahedonthisvest

have DC-PLC (Power Line Communiation) modem

Although the attahed devies an be supplied suÆ-

ientpower,ommuniationsignalsarebroadastedto

whole thewearasanalogsignals,andtherearenoar-

bitration mehanisms implemented for point-to-point

ommuniation. The details of eletriharateristis

aredisussedandevaluated,butitannotprovidethe

wideband-widthofommuniationhannels.

`Push&Pin'system[6℄aimsatthenetworksystemon

apairofondutivesurfae,inludingondutivefab-

ri wear aswell asthewall, but it employs1-Wire[7℄

system for physial implementation. In the 1-Wire

system's speiations, the exibility of network on-

guration is limited as master-slavearhiteture, and

the ommuniation speed isasslowasapproximately

1200[bps℄,thatisnotfastenoughforpratialwearable

omputingsystems.

`PinPlay' system[8℄ also uses a pair of ondutive

surfaefor powersupplyin order to build distributed

omputing systems, but the ommuniations among

deviesareimplementedbywirelessmanner.

C.Randelletal.[9℄implementsthewearwithapair

ofondutivefabriforpowersupply,eletro-magneti

detetor, and thermalsourefordisplay,but there no

implementationonnetworkingsystem.

3. Implementation of TextileNet

TextileNet system desribed in this paper has the

followingfeatures omparedwith theexisting systems

basedonthenewlydevelopediruitry.

Cable-free

Comfortablewearwithondutivefabri

Freeinstallationonthewearbypins

Highommuniationability(Point-to-point)

Highpowersupplyability(3W)

3.1. Condutive fabri and wear

Wehavedevelopedeletriondutivewearforthe

TextileNet systemasshown in Fig.1. This wear on-

sists of three layers; the ondutive fabri for both

outer sides of the wear with one insulator fabri be-

tweenthem. These threelayersoffabrisaresewnby

usingaonventionalsewingmahine. Condutivefab-

riemployedhereisaprodutfortheeletro-magneti

shieldloth whosesurfaeresistaneisabout0.5/sq.

This ondutivefabri is made of meshed ondutive

thread,anditis adequateforomfortablet,whih is

Figure 1. Developed wear using conductive fabric.

Power Supply Unit Communication Unit

CL CP

SWp S W d

Figure 2. Circuit architecture of data commu- nication and power supply unit of TextileNet.

The evaluation of the eletroni harateristis of

this wear inluding in the pratial situations is de-

sribedin setion4.

3.2. Communiation unit andpower supply

unit

The 1-Wire system[7℄ is a wiring system using a

pair of ables whih provide power supply and om-

muniationhannels. Inthe1-Wiresystem'sspeia-

tions,theexibilityofnetworkongurationislimited

as master-slave arhiteture, and the ommuniation

speedisasslowasapproximately1200[bps℄,thatisnot

fastenoughforpratialwearableomputingsystems.

Fromtheappliation point ofview,the deviesat-

tahedonthewearshould bephysially smallenough

to suit the omfortable wearable omputing applia-

tion. In order to implement suh small ommunia-

tion devies, weemployed the DC-based arhiteture

for power supply with oasional pull-down strategy

forommuniation. Wenewlydesignedthepowersup-

plyandommuniationiruitarhitetureusingapair

ｔ V

t0 VH

VL

"0" "1"

Vref

Figure 3. Voltage wave of developed Tex- tileNet system.

(a) (b)

Figure 4. Developed communication unit(a) and power supply unit(b).

powersupplyunit, theommuniationunits installed

ontheTextileNet,andapairofeletrodesasthesur-

faesofthewear.

Theenergysuppliedfromthepowersupply(thebat-

teryonnetedtothepowersupplyunit)ishargedin

thepowerapaitor,C

P

at eah ommuniationunit,

and thevoltageof the surfaeofthe wear, V

L is on-

trolledtokeepapproximately15Vbythepowersupply

unit asshownin Fig.3. Whenoneof theommunia-

tionunitsstartstosendsomedata, V

L

ispulled-down

to low voltage of 0V for a ertain moment, T

0 , and

alltheommuniationunits ontheTextileNet reeive

this data of `0' simultaneously. At this moment, the

powersupply unit detets this drop of V

L

and turns

the pull-up swith o. This pull-up swith is again

turned on after a ertain termof T

1

, where T

0

<T

1 ,

in ordertoontinuepowersupplytoeahdevie. The

energyofommuniationunitsforthetermofV

L

=0

issuppliedbythepowerapaitor,C

P

ineahommu-

niationunit. Thedataof`1'anberepresentedasthe

highV

L

,anddatatransmissionanbeinitiatedbythe

startbitastherst`0',asaonventionalasynhronous

serialommuniation.

Thefuntionsrequiredforeahommuniationunit

are (1)power regulation, (2)one bit transmission by

pull-downswith,and(3)datareeive,whihenablesto

implementthesmallsizeoftheommuniationdevie.

Figure 4(a) shows a developed ommuniationdevie

whosesizeis20mm20mm,andithasthepowersup-

non-conductive layer

component B conductive layer C component A

conductive layer D component B' conductive cloth

communication module

anode(+)

cathode(-)

Figure 5. Structure of electric contact.

Table 1. Devices used in the evaluation exper- iment of TextileNet.

Data

Devie Funtion Communiation

#0 photosensor `0'or`1'todevie#2

#1 photosensor `0'or`1'todevie#2

#2 LEDdisplay datafromdevie#0&#1

#3 PCinterfae oneharatertodevie#4

#4 LEDdisplay datafromdevie#3

opedpowersupplyunit. Theommuniationspeedof

thisprototypedeviesisdesignedtobeome9600[bps℄

in orderto keeptheenoughmarginof operation. The

developedprototypesystemofTextileNethastheom-

muniationabilityofonebytebroadasting,andarbi-

tration of data transmission and error orretion an

be implemented by the higher protool layers in our

future work.

Boththeommuniationunitsandthepowersupply

unit should be eletrially onneted to both side of

thewearbystiking. Figure5showsastrutureofthe

developedontat. Theunit isontatedtothe outer

side of the wear by the eletrode of the unit, and to

the inner side of the wear by the pin with insulator

andsnap.

3.3. Operation of TextileNet system

We arried outthe evaluation operationof the de-

velopedTextileNetsystem. We'vebuiltvedeviesus-

ing theommuniationunitsasshownin Tab.1. Two

photosensorsdetetthehangeofbrightness,andsend

theinformationtotheLEDdisplaydevie. Thehange

of thebrightness on eah photo sensor is reeted to

the red and the green LEDs on the LED display de-

vie. ThePConnetiondevie reeivestheharater

of `0' to `9'from thePC using EIA232,and the data

issentto theLEDnumerialdisplaydevie todisplay

it. These deviesare installedonthe TextileNetwear

asshownin Fig.6,andwehaveonrmedtheyareop-

erational. Thedevies are alsoin operationwhen the

Figure 6. Test usage of

.

4. Evaluation of wear

Wehaveevaluatedtheeletriharateristisofthe

developedwearwithondutivefabriinthepratial

situations.

Theeletriresistaneofthesurfaeandtheapai-

tanebetweenbothsurfaesofthewearweremeasured

byLCRmeter(HewletPakard4284A).

Themaximumeletriresistanewasapproximately

18[℄ when dry, whih is the resistanebetweenboth

sleeves of thewear. The eletri resistanedereased

to approximately1/3when wet,asin rain. Thus, the

maximum resistane in the pratial situation is ex-

petedtobe18[℄.

Themaximumapaitanebetweenbothsidesofthe

wear was approximately 9[nF℄ when dry. The maxi-

mumapaitaneinreasedupto 22[nF℄when wet by

sweat. Thus, themaximumapaitaneintheprati-

alsituation isexpetedtobe22[nF℄.

Theupperlimitofommuniationspeedin thede-

veloped ommuniation unit determined by the time

onstantof harge and disharge. Based on themea-

suredresistaneandapaitaneatpratialonditions

desribed above, the upper limit of the ommunia-

tionspeedisexpetedtobeupto1/(18[℄22[nF℄)=

2.5[Mbps℄in theworstaseofpratialsituation, dry

surfaeand wetbysweat.

5. Conlusion

Inthispaper,wedesribedtheidea,andimplemen-

tation of anew exible network arhiteture whih is

named as TextileNet. We also desribed the experi-

mental results of its evaluation. It has the merits of

high apability of ommuniation and power supply,

aswell asaexibility ofdevie layoutand simpleir-

uitarhiteture. Wedevelopedtheprototypesystem

onthewearasanexample,andevaluatedtheiropera-

tionsinthedevelopedTextileNetsystem.

ThedevelopedTextileNetsystemisexpetedtobe-

lem andwireompliationproblemhavebeensolved.

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