A Sma Elec ic Wheelchai Using UPnP
D. Cascado, S. Vicen e, J.L. Se illano, C. Amaya,
A. Lina es, G. Jiménez, and A. Ci i -Balcells
ETS Ingenie ía In o má ica. Uni e sidad de Se illa.
A . Reina Me cedes, s/n. 41012, Se illa, Spain
[email p o ec ed]
Abs ac . People wi h disabili ies in gene al, and wheelchai use s in pa icula ,
a e one o he g oups o people ha may bene i mo e om Ambien In elligen
(AmI) Sys ems, enhancing hei au onomy and quali y o li e. Howe e , cu en
wheelchai s a e usually no equipped wi h de ices capable o accessing se ices
in AmI en i onmen s. In his pape , we desc ibe how an elec ic wheelchai is
equipped wi h an UPnP based module ha allows he in eg a ion in AmI sys ems.
1 In oduc ion
Al hough he Ambien In elligen (AmI) concep is no o ien ed owa ds any pa icu-
la g oup o people, i is ob ious ha he AmI emphasis on g ea e use - iendliness,
mo e e icien se ices suppo , use -empowe men , and suppo o human in e ac-
ions [1] would be especially use ul o people wi h disabili ies and elde ly people. In
his pape , we ocus on he in eg a ion o wheelchai use s in AmI sys ems. Conside ,
o ins ance, he ollowing scena io:
A wheelchai use wi h se e al mobili y es ic ions and a mobile compu e in
his/he wheelchai en e s a building (le ’s say he ehabili a ion cen e), p o ided
wi h Ambien In elligen acili ies. As soon as he/she ge s in o he building, he Ambi-
en In elligen Sys em (AmIS) disco e s his/he p esence and he de ices announce he
se ices ha can be used, acco ding o his/he special needs (cogni i e, senso ial,
physical and communica ion abili ies), and echnological cons ain s (display esolu-
ion, oice, ex , pixel-based, bandwid h, compu ing powe , e c.).
The AmIS o e s communica ion wi h a emo e in o ma ion cen e ha appea s in
he use 's display, adap ed o his/he physical and cogni i e cha ac e is ics ( ex
menu, oice, icons…). The AmIS o e s in o ma ion abou whe e he/she is and whe e
o go om he cu en posi ion and, a e knowing whe e o go, he possibili y o a
ou e-guiding ool appea s on i s display, which he use accep s. I uses a loca ion
se ice and gi es in o ma ion ia ex messages. The use is loca ed and ecei es
his/he posi ion, oge he wi h a message o whe e o go now. The AmIS has calcu-
la ed he bes pa h o ollow, aking in o accoun he use cons ain s ( o ins ance,
a oiding s ai s, changing he iming o au oma ic doo s, e c.) and he in o ma ion o
occupa ion in he building a ha ime o day.
Finally he/she a i es a he des ina ion and he AmIS sends in o ma ion abou
wha domo ic de ices a e ins alled in he oom (and can be used). F om i s joys ick
wi h bu ons (o any o he adap ed inpu de ice), he use sends o de s o con ol
de ices o e ed by he domo ic sys em (i.e., swi ch he ligh s o o on, oll up o down
blinds, change he ele ision channel, se he empe a u e o he ai condi ioning
sys em, e c.). A e wa ds, he/she decides o lea e he building, bu his ime he ou e-
guiding ool is no employed, and he joys ick is used o guide he wheelchai o he
exi .
No e ha some cha ac e is ics o Ambien In elligen sys ems a e pa icula ly well
sui ed o people wi h mobili y es ic ions:
•Ubiqui ous access: allows access o se ices in a way ha is no es ic ed by
he loca ion o esou ces and/o he use ’s mobili y ( emo e con ol o TV, ai
condi ioning, e c.; answe ing he phone om he wheelchai , e c.).
•Con ex awa eness: apa om he ob ious use o loca ion awa eness, o he
dimensions a e use ul in ou case, pa icula ly pe sonal awa eness (dynamic
adap a ion o use needs, abili ies o p e e ences) [2].
•”In isible” compu ing and ne wo king: allows un-no iced use moni o ing in
e ms o sa e y: alls, ca e o people who may ge los , e c. (e.g. elde ly esi-
dences).
Howe e , since many o hese people usually equi e he use o mobili y aids (like
wheelchai s) and adap ed use ’s in e aces, hese assis i e de ices should also be
in eg a ed in o he AmI sys em. Fo ins ance, i may be use ul o he handicapped o
access assis i e se ices h ough hei pe sonalized in e aces (especially in un amilia
en i onmen s). Fu he mo e, wheelchai s should be able o use and p o ide se ices
(loca ion, semiau oma ic na iga ion, e c.). Howe e , cu en wheelchai s a e usually
no equipped wi h de ices capable o accessing se ices in AmI en i onmen s. A
mos , a wheelchai use may ca y a po able compu e o a PDA o access se ices,
bu in his case, he wheelchai i sel is no in eg a ed in he AmI sys em.
In his pape , we desc ibe an elec ic wheelchai ha is equipped wi h a module
ha allows he in eg a ion in AmI sys ems. We i s desc ibe a ha dwa e module ha
se es as an in e ace be ween he wheelchai and he ex e nal de ices. In he nex
sec ions, we explain he so wa e a chi ec u e, which is based on UPnP1 (Uni e sal
Plug and Play), and we ocus on he Use In e ace so wa e. Finally, we p esen he
conclusions.
2 Ha dwa e A chi ec u e
The wheelchai used in his wo k is based on a o me p o o ype called Te anau a
[3,4,5], a low cos , ully open s ee ing sys em ha allows people wi h se e e mo o
impai men s o mo e in known en i onmen s: hospi als, schools, home, e c. Na iga-
ion is assis ed by allowing he wheelchai o ollow p ede ined pa hs (wi h acks
1 h p://www.upnp.o g
ma ked on he loo ) and also by using an in a ed-based obs acle de ec ion sys em.
As a esul , he use e o and sa e y in d i ing he wheelchai , especially in long
pa hs, is imp o ed.
So a , he majo i y o he e o s in wheelchai s ha e been o ien ed o empowe ing
he au onomous capabili ies, like obs acle a oidance, ajec o y acking, e icien
suspension o wheels o s ai -climbing capabili ies. An example o his is OMNI [31]
ha included obs acle a oidance, human-machine in e ace, high maneu e abili y and
na iga ional in elligence. Na Chai [25] is a sma wheelchai ha is able o a oid
obs acles, and o ollow a di ec ion indica ed by a use wi h emo o ano he ype o
se e e mobili y impai men . IBOT-3000 [29] was capable o climbing s ai s wi h i s
wo pai s o balanceable wheels. The Sma wheelchai o he CALL Cen e [26]
allows se e al ypes o in e ac ion modes wi h he use , acco ding o his/he disabili y
and skills. The wheelchai Te anau a was in his line o de elopmen s, being an iso-
la ed wheelchai wi hou communica ions wi h ano he de ices. In [18], a e ision o
his ype o wheelchai s can be ound.
The nex gene a ion o wheelchai s con empla es sma capabili ies o au ono-
mous ope a ion and communica ion capabili ies wi h o he sys ems (like wheelchai s,
domo ic de ices o he like). In his sense, elec ic wheelchai s ha e been used like
es beds o communica ion sys ems, like E-wheelchai [27] ha was used o p o e
he iabili y o IP 6 communica ions. The design shown in [28] used i s wi eless
communica ions o imp o e i s au onomous capabili ies ( o communica e wi h a GPS
o ob ain he posi ion o he wheelchai ).
Howe e , hese las ones we e an a emp o expanding he capabili ies o wheel-
chai s h ough communica ions, bu no o in eg a e he wheelchai in a bigge sys-
em. In his line, AmIChai [30] can use communica ions o con ol he de ices o he
en i onmen , bu en i onmen de ices can also moni o and con ol he wheelchai .
The wheelchai is in eg a ed in he whole sys em and i is only a pa o i . Ou de el-
opmen pu sues a simila idea: being a de ice in eg a ed in a bigge sys em, bu now
he use can in e ac wi h he sys em using i s p ope wheelchai ’s adap ed in e ace.
The con ol uni o he wheelchai is composed o an embedded compu e , plus
se e al unc ional modules con olling di e en pa s o he wheelchai : powe mod-
ule, s ee ing de ice module, e c. All hese modules a e in e -connec ed by a DX se ial
bus [6], a de ac o s anda d in elec ic wheelchai s. As a esul , he wheelchai be-
comes a dis ibu ed embedded sys em whe e new unc ional modules may be con-
nec ed wi h ela i ely ew so wa e changes. Pa icula ly, in his pape we desc ibe
how a new ga eway/b idge module is inco po a ed in o he wheelchai so ha he DX
sub-sys ems can communica e wi h o he de ices in an AmI en i onmen .
The sys em a chi ec u e is shown in Fig. 2. Essen ial DX modules a e he Use
Con ol Module (UCM) and he Powe Module (PM). The UCM is no mally pa o a
con ol module (which includes a joys ick o any o he ype o speed and di ec ion
con ol), and has he unc ion o p ocessing signals om he wheelchai use and
sending ins uc ions o he o he modules. These ins uc ions and o he da a a e sen
using messages ha a e named Ne wo k Va iables (NV). The PM p o ides he con-
olled ol age o d i e he wheelchai ’s mo o (s) and ope a es he pa k b akes. These
a e modules al eady included in any DX-based wheelchai .
PM
UCM
PC I
R
DX Bus
Fig. 1. Basic p o o ype’s scheme
F om ou poin o iew, he cen al elemen is he use in e ace (UI), no included
in s anda d DX wheelchai s. The UI should ha e he ollowing cha ac e is ics:
•I should be a mobile sys em, easily handled by he use (who may no always
be sea ed in he wheelchai ) o any o he pe son ( ela i e, ca e , nu se, e c.).
•I should ha e enough esou ces (compu ing powe , memo y, sc een size,
bandwid h) o un use ul ( isual) applica ions adap ed o he use ’s needs and
p e e ences. Fu he mo e, de elopmen ki s should be a ailable in o de o
w i e applica ion-speci ic so wa e.
•I should inco po a e mul iple communica ion links, p e e ably wi eless, o al-
low ubiqui ous access o o he de ices and se ices.
Ad ancemen s in handheld de ices (such as PDAs, mobile phones and po able PCs)
a e eno mous and he e a e now comme cially a ailable de ices o accep able pe -
o mance a ela i ely low cos . In ou p o o ype, we decided o use a S ongARM®
based PDA as ou use in e ace (UI), unning unde WindowsCE® 3.0. The UI is
equipped wi h a colo sc een, as well as wi h se ial, Blue oo h and 802.11 in e aces.
Al hough usually a wi eless connec ion is mo e adequa e, some imes a simple se ial
(wi ed) link is a simple and mo e obus solu ion ( o ins ance, when he PDA is
a ached o he wheelchai ).
Ano he added elemen is he DX-B idge, a new DX module ha cap u es he Ne -
wo k Va iables (NVs) lowing h ough he DX bus. This module allows NVs ( o
ins ance, wheelchai con ol da a) o be expo ed as inpu o he use in e ace (UI),
as well as o ecei e new alues o he NVs om he UI. So a , he only allowed
way o cap u e DX da a om he bus is using a de ice named DX-KEY, p o ided by
DX
De ices
UCM
PM
DX-B idge
DX Bus
Use
In e ace
(UI)
Blue oo h
802.11
Fig. 2. Scheme o wheelchai ’s ha dwa e
Dynamic Con ols [7]. This is a DX module ha p o ides an in e ace be ween he
DX bus and an ex e nal sys em, allowing access h ough a pa allel po o DX a i-
ables. The e o e, he DX-B idge is a ha dwa e module based on a Cygnal C8051F330
mic ocon olle [8] wi h se ial and pa allel in e aces: he DX-KEY is accessed
h ough he pa allel po , and on he o he side a se ial link (RS-232, 115200bps) is
used o connec wi h he UI. As we said be o e, some imes his wi ed link is enough.
Howe e , in o de o p o ide a wi eless link, we also use a comme cial se ial-
Blue oo h module ha wo ks unde he RFCOMM p o ile (Se ial Cable Emula ion).
DX-Key Cygnal
µcon olle
RS-232
Blue oo h
con e e
Pa allel
In e ace
Se ial
In e ace
DX Bus
Fig. 3. Ha dwa e in he DX-B idge
The DX-B idge has wo ope a ion modes: d i ing, and domo ic modes. In he d i ing
mode, he DX-B idge simply cap u es he commands (NVs) sen by he Use Con ol
Module (UCM) and hen i deli e s hese commands o he Powe Module (PM). These
commands a e deli e ed wi hou any changes, so he wheelchai ope a ion is no di e -
en om a s anda d manually ope a ed wheelchai . In he domo ic mode, he DX-B idge
cap u es he commands sen by he UCM and hen i deli e s hese commands o he
use in e ace-UI. In his way, hese commands a e no longe used o con ol he wheel-
chai , bu hey a e in e p e ed by he UI as commands o con ol a domo ic sys em o he
like. Ob iously, he domo ic mode canno be used unless he wheelchai has eached a
secu e s a e, a oiding dange ous si ua ions o he use .

PM
DX- B idge UCM
PM
DX-B idge UCM
Na i
g
a ion
mode
Domo ic
mode
Fig. 4. Ope a ion modes o DX-B idge
The use o he wheelchai UCM o con ol a domo ic sys em has wo main ad an-
ages: i s , he use is p obably used o handling he con ol de ice (e.g. joys ick) o
d i e his/he wheelchai , and he e o e he/she would p obably lea n o use he ex e -
nal de ices mo e easily. And second, since he UCM would p obably be adap ed o
he use ’s needs and/o di icul ies, we ha e an adap ed con ol de ice o domo ic
sys ems “ o ee”. This is a key ques ion because wi h his solu ion, he cos o do-
mo ic sys ems does no depend on he use ’s physical and/o cogni i e abili ies.
Finally, al hough i canno be conside ed as an ope a ion mode, he DX-B idge
may be used by he UI o se new alues o some DX a iables. Fo ins ance, i an
ex e nal se ice p o ides posi ioning and loca ion in o ma ion, hese da a can be sen
o an op ional assis ed na iga ion DX module.
PM
UCM
PC IR
DX-B idge
UI
Blue oo h
802.11
Fig. 5. Final a chi ec u e o he wheelchai
3 UPnP A chi ec u e
As we said be o e, he wheelchai mus be capable o ob aining in o ma ion om he
en i onmen , o ins ance posi ioning in o ma ion o he lis o a ailable de ices
and/o se ices, and he domo ic sys em (o he like) mus be capable o ob aining
in o ma ion om he wheelchai (like o de s o he di e en de ices o he oom).
Connec ion be ween hese de ices can be implemen ed in se e al ways: in a ed
ca ds, adio communica ion sys ems, o e en wi ed connec ions. In ou sys em, com-
munica ions a e cen e ed on he use in e ace (UI), which should be able o commu-
nica e ac oss he e ogeneous and dynamically changing links and ne wo ks. Fo in-
s ance, he UI would be able o communica e wi h da a ne wo ks, In e ne Access
Poin s, domo ic buses like EHS (a Powe line-like bus used o he con ol o home
de ices) [9], e c. Wi eless pe sonal (e.g. Blue oo h) and local (e.g. Wi-Fi) a ea ne -
wo ks now pe mi low-cos comme cial solu ions o his ype o communica ion, bu
he e a e s ill open p oblems like e icien oaming, eachabili y, in e mi en ailu es,
aul ole ance, secu i y, e c.
No e ha i is no only a p oblem o in e connec i i y o in e ac ions a he in e -
ne wo king le el, bu also o in e ac ion among de ices a highe le els: con ol, con-
igu a ion and in o ma ion sha ing in di e en o ma s, impo /expo se ices, e c.
Among he di e en communica ion a chi ec u es a ailable (Juni, UPnP, HAVi), as
discussed in [10], we conside ha UPnP is a good choice o implemen ing ou com-
munica ion sys em. UPnP is a ligh weigh se o p o ocols o ex end he Plug & Play
concep s o ne wo k de ices, and i suppo s all men ioned unc ions including he
dynamic connec ion o a de ice o a ne wo k, se ices o e ing and disco e y, e e y-
hing based on a uni ied desc ip ion o unc ions and a ibu es o se ices h ough
XML (eX ended Ma k-up Language) documen s [11]. UPnP is capable o wo king
wi h sca ce esou ces and un eliable connec ions (de ices can suddenly appea and
disappea ), and a u he eason o choose UPnP is ha he e a e a la ge numbe o
a ailable SDKs o se e al pla o ms and ope a ing sys ems [12,13]. Fu he mo e,
he e a e wo ac o s ha make UPnP especially a ac i e om ou poin o iew: one
is he use o open and s anda d p o ocols; second is he use o he IP p o ocol a he
lowes le el.
Indeed, IP p o ocol has demons a ed i s success in he in e connec ion o he e o-
geneous de ices (a good example is he In e ne ). Mos de ices can be connec ed
h ough a backbone IP ne wo k while seconda y, maybe simple , de ices (e.g. sen-
so s) may be connec ed using non-IP communica ions. In his case, a ga eway is used
o in e connec IP and non-IP sub-ne wo ks. Fo ins ance, in ou p o o ype, we need
ga eways o in e connec he IP backbone ne wo k o he DX bus (a non-IP con ol
ne wo k). Fu he mo e, UPnP ope a es wi h a se o exis ing and well- es ed p o ocols
and only needs an au o-IP ne wo k o unning. UPnP wo ks in a dis ibu ed philoso-
phy, and classi ies de ices in o wo oles: con ol poin s o clien s, and hos de ices o
se e s o se ices. Howe e , almos all UPnP de ices implemen bo h clien and
se e unc ionali ies, so pee o pee communica ions a e possible.
Fo he wheelchai o be in eg a ed in o an AmI en i onmen , he wheelchai mus
expo in o ma ion, ac ing as a hos de ice: we need o know he posi ion o he joy-
s ick, i any bu on o he console was p essed, he ba e y s a us, and so on. On he
o he hand, he wheelchai also needs o ac as a con ol poin (clien ): i has o know
i s loca ion in o de o know how o ge o ano he oom/place, selec ing he ou e
om a map, e c. All hese in o ma ion/se ices a e supplied om o he de ices (se -
ices) in he ne wo k. Since no only he wheelchai , bu also he domo ic sys em and
mos o he elemen s o he AmI sys em ge in o ma ion om o he de ices, con ol
poin s mus be implemen ed on hem.
The ole o he use in e ace (UI) is o se e as an in e ace be ween he wheel-
chai and hese UPnP se ices. All de ices implemen ing UPnP se ices (hos de-
ices) should be connec ed by means o a backbone IP-based ne wo k. In ou sys em,
since he wheelchai is a mobile sys em, and se ices should be accessed "on he
mo e", we use an IP wi eless ne wo k (802.11b/g [14]).
Among he many di e en hos de ices ha may be p esen in an AmI sys em, we
iden i y he ollowing o ou scena io (see Fig. 6):
•Moni o ing: expo s wheelchai ’s s a us a iables (i.e.: joys ick posi ion) and i
is implemen ed in he wheelchai ’s ga eway h ough se ial (o Blue oo h) in e -
ace and he DX B idge.
•Map s o ing: a small p ocesso wi h an associa ed memo y o s o ing and ead-
ing maps. This de ice can be in a ixed place o he building.
•Loca ion: o e s a posi ioning se ice, maybe ou -doo s posi ioning (like a GPS
de ice a ached o he wheelchai ), o in-doo s posi ioning [15].
•Domo ic: o e s as a se ice he kind o ope a ions ha may be pe o med wi h
he associa ed domo ic de ices, ells which a e he a ailable de ices a a speci ic
oom. An UPnP con ol poin a ached a he same domo ic se ice’s hos de ice
can ead he s a us o he wheelchai o gene a e an ala m in he domo- ic sys em
i he ba e y is low o can ead he posi ion o he joys ick o using i as an in-
pu de ice o handle a g aphical in e ace o any domo ic de ice.
4 The Use In e ace (UI)
In his sec ion, we desc ibe he implemen a ion o he UPnP hos de ice in he use
in e ace (UI). This desc ip ion se es as an example, since all hos de ices can be
implemen ed in a simila way. The UI has been implemen ed o e a S ongARM®-
based PDA equipped wi h se ial, Blue oo h and 802.11b in e aces. The la e is used
o suppo ing UPnP ac i i y, as desc ibed in he p e ious sec ion. We use an unde -
eques p o ocol implemen ed ad hoc, ha wo ks as ollows. The UI pe iodically
sends a se o inqui y ames o he DX sub-sys em o know wha he alues o he
DX a iables a e. When he mic o-con olle in he DX-B idge (see sec ion 2) e-
cei es an inqui y ame, i e u ns he alue o he inqui ed a iable. We p e e ed his
simple solu ion because he Cygnal mic o-con olle used in he DX-B idge is no
powe ul enough o suppo he UPnP s ack. Howe e , we could ha e implemen ed an
UPnP DX a iable se ice a an inc eased cos and complexi y.
The UPnP so wa e in he UI uns as an applica ion o e WindowsCE® 3.0. Basi-
cally, he applica ion con ains wo p o ocol s acks: Se ial communica ion s ack and
UPnP s ack (see Fig. 7). The o me implemen s he communica ions p o ocol be-
ween he DX-B idge and he UI. This p o ocol is e y simple; i only needs PHY and
MAC laye s, including some e o co ec ion capabili ies like ame e ansmission.
O e hese wo laye s, a laye named DX a iable s o e is implemen ed in o de o
gua an ee he consis en s o ing o alues (no e ha hese DX a iables a e " e-
sou ces" accessed bo h by he Se ial Communica ion S ack and by he highe laye , so
his laye has o cope wi h he consis en use o hese sha ed esou ces). On op o
bo h s acks is he UPnP se ice laye , which implemen s wo h eads: a DX inqui y
loop ( ha ga he s DX a iables om he DX a iable s o e laye ) and he UPnP p oc-
essing h ead ( esponsible o ga he ing all he UPnP eques s and gene a ing he ap-
p op ia e esponses). DX inqui y loop no i ies when a DX a iable changes in o de
o no i y his change o he UPnP clien s connec ed o he se ice.
Fig. 6. UPnP se ices (S), Con ol Poin s (CP) o UPnP a chi ec u e. Do s indica e da a lows.
The main ask o UPnP s ack is he implemen a ion o he UPnP se ice. This is
composed o a se o ac ions (me hods) and s a us a iables ha he UPnP clien (con-
ol poin ) can in oke a any ime.
Se ice’s s a us a iables a e all he DX a iables ha a e desi ed o be moni o ed:
joys ick posi ion; bu on, ba e y, DX con ol uni and se ial communica ion s a us,
and so on. The UPnP Moni o ing Se ice main ains an inqui y loop esponsible o
holding he la es alues o hese a iables. On he o he hand, hese se ices’ s a us
a iables can be ead by o he UPnP de ices in he IP ne wo k unde demand ( his is
he de aul mode) o by a change no i ica ion e en . Unde his la e mode, he clien
ecei es an e en e e y ime he DX a iable changes. When his e en occu s, he
clien ecei es he a iable name and alue.