FAS - An au onomous sailing pla o m o
oceanog aphic missions
Jos´
e C. Al es
Depa men o Elec ical and Compu e Enginee ing
Uni e si y o Po o, Facul y o Enginee ing
Po o, Po ugal
Email: [email p o ec ed]
Nuno A. C uz
Depa men o Elec ical and Compu e Enginee ing
Uni e si y o Po o, Facul y o Enginee ing
Po o, Po ugal
Email: [email p o ec ed]
Abs ac — Sailing has been o long imes he only means o
ship p opulsion a sea. Al hough he pe o mance o a sailing
essel is well below he p esen powe d i en ships, ei he in
e ms o na iga ion speed and p edic abili y, wind ene gy is
absolu ely enewable, clean and ee. Unmanned au onomous
sailing boa s may exhibi a i ually unlimi ed au onomy and
be able o pe o m unassis ed missions a sea o long pe iods o
ime. P omising applica ions include oceanog aphic and wea he
da a collec ing, su eillance and e en mili a y applica ions. The
Mic o ansa compe i ion, launched in Eu ope in 2006, has been
a key ini ia i e o p omo e he de elopmen o obo ic unmanned
sailing boa s. Va ious ega as ha e aken place ac oss Eu ope
and he ul ima e challenge will be a ansa lan ic ace. This pape
p esen s an au onomous sailing boa de eloped a he Uni e si y
o Po o, Po ugal, wi h emphasis on he ha dwa e and so wa e
compu ing in as uc u e. This pla o m is capable o ca ying
a ew kilog ams o sensing equipmen ha can be hooked o he
boa ’s main compu e , also p o iding suppo o sho and long
ange da a communica ions.
I. INTRODUCTION
Con a y o powe d i en ships, in sailing boa s he as es
way o each a gi en des ina ion poin may be a complex pa h
ha depends on a ious pa ame e s, mainly he cu en and
u u e wind di ec ion and speed, he pe iod and heigh o he
wa es and he sailing pe o mance o he boa . In addi ion,
due o he limi ed p edic abili y o he wea he condi ions, he
bes solu ion has o be de e mined o adjus ed dynamically
du ing a jou ney.
Au opilo s ha e been used o decades o au oma ic s ee -
ing o sailing boa s and a e now an essen ial equipmen o
long sailing jou neys, specially o soli ai e sailo s. The i s
au opilo s o sailing boa s we e ully mechanical, p o iding
a closed loop con ol sys em o main ain a cons an cou se
angle ela i e o he appa en wind di ec ion. A popula
sys em, s ill in use oday by some sailo s, is he wind ane
se omechanism [1] ha has he g ea ad an age o no e-
qui ing elec ic powe o i s ope a ion. Howe e , s abili y may
be comp omised due o he a ying appa en wind di ec ion
induced by he wa es, specially in downwind legs wi h high
wa es when he absolu e boa speed can oscilla e signi ican ly.
Cu en elec onic au opilo s ely on a ious inpu da a o
s ee a sailing boa , including he heading, cou se, wind and
heeling angle. Compu e ized con ol sys ems allow he appli-
ca ion o sophis ica ed me hods like uzzy-se s [2], [3], neu al
ne wo ks [4] o o he a i icial in elligence echniques [5] as a
means o handle he s ee ing con ol much like a human does.
In addi ion o s ee ing a sailing boa o keep i in he desi ed
cou se, he con ol o sails is a key issue o maximizing i s
speed. In p ac ice, i may be impossible o cons an ly une
he sail o ollow all he luc ua ions o he appa en wind
di ec ion, mainly due o es ic ions on he powe a ailable
(ei he elec ic o human) o mo e he sails and also p ac ical
limi a ions o he speed o such adjus men s. This is e ec i e
in small dinghies whe e he sailo is con inuously con olling
he sail shee by hand bu may no be possible in la ge yach s
whe e a sail adjus men is a slow p ocess and consumes a
signi ican amoun o ene gy due o he high o ces in ol ed.
Tuning a sailing boa o minimizing he ime equi ed o
each a desi ed a ge is hus a complex ask ha in ol es
cou se planning, s ee ing con ol and sail uning. These com-
ponen s a e highly in e dependen and canno be de e mined
in ad ance du ing eal na iga ion condi ions.
Al hough p esen ly ully au onomous unmanned sailing
boa s do no i in any legal ca ego y o ship, he po en ial
hey exhibi o ca y ou unassis ed missions a sea o long
pe iods o ime may help change his scena io.
This pape in oduces he Mic o ansa compe i ion and
p esen s he ha dwa e and so wa e a chi ec u e o FAS
(FEUP1Au onomous Sailboa ), a small scale sailing boa
de eloped a he Uni e si y o Po o, Po ugal. In addi ion
o his in oduc ion, he es o he pape is o ganized as
ollows. Sec ion II p esen s he Mic o ansa con es , as a
s imuli o he de elopmen o au onomous sailing boa s. The
FAS p ojec is in oduced in sec ion III, including a b ie
p esen a ion o he cons uc ion phases and physical da a o
he cu en con igu a ion. The elec onic sys em, including
he main compu e , senso s, ac ua o s and communica ions,
is de ailed in sec ion IV, and he o ganiza ion o he so wa e
componen is p esen ed in sec ion VIII. Finally, sec ion IX
concludes he pape and discusses he u u e de elopmen s
planned o FAS .
II. THE MICROTRANSAT COMPETITION
To mo i a e he esea ch and de elopmen on au onomous
sailing boa s, a g oup o uni e si y p o esso s in he Uni ed
1Facul y o Enginee ing o he Uni e si y o Po o
Kingdom and F ance has launched, a ew yea s ago, he
Mic o ansa Challenge (www.mic o ansa .o g). This
is a compe i ion o small ully au onomous sailing boa s ha
will ha e as he ul ima e challenge a c ossing o he A lan ic
ocean.
The Mic o ansa ules a e simple: he only means o
p opulsion allowed is he wind, boa s ha e o ca y o gene a e
all he elec ic ene gy hey need and no ex e nal in e en ion
is allowed du ing he na iga ion. In addi ion, ules es ablish
a maximum boa leng h o 4 m and (o iginally) a maximum
displacemen o 40 kg. The objec i e o hese bounds was o
no ha m any o he ype o boa , in he case o an e en ual
collision a sea.
Since 2006, h ee compe i ions ha e aken place ac oss
Eu ope in es ic ed wa e s, including he i s Wo ld Robo ic
Sailing Championship in he lake Neusiedl, Aus ia, in May
2008, ha joined ou eams om Aus ia, Uni ed Kingdom,
Canada and Po ugal. These mee ings ep esen excellen op-
po uni ies o es ing he echnologies de eloped, exchange
ideas and sha e expe iences.
A. Legal issues
In spi e o he low isk o damage in a eal ship esul ing
om a collision wi h one o he Mic o ansa sailboa s, he
cu en in e na ional ma i ime law o bids he au onomous
na iga ion o such unmanned essels. Because o his, a
solu ion has s ill o be en isaged o accomplishing he ansa -
lan ic ace planned in he Mic o ansa compe i ion.
The in e na ional ules o a oiding collisions a sea (COL-
REGS) only add ess c a s unde human con ol. Cu en
echnology has no ye p o en o be capable o dealing wi h
he ambigui y o some ules unde eal si ua ions and, in some
cases, he complexi y o he p ocedu es equi ed o ollow
hem. Some ecen wo ks [6], [7] add ess he p oblem o
collision a oidance a sea, al hough a majo challenge is s ill
he di icul ies associa ed wi h he isual pe cep ion o he
local en i onmen a ound a boa .
P esen Mic o ansa pa icipan s s ill ha e no capabili y
o wa ch hei su oundings o iden i ying po en ial isks o
collision wi h o he ships. Howe e , wi h he gene aliza ion o
he AIS (Au oma ic In o ma ion Sys em) and o he elec onic
aids his may be su passed in a nea u u e by low cos and
low powe elec onics, and open oom o he inclusion o un-
manned au onomous boa s in he in e na ional sea egula ions.
III. THE FAST PROJECT
The FAS p ojec was launched a he Elec ic and Compu e
Depa men o he School o Enginee ing o he Uni e si y o
Po o, Po ugal, in he beginning o 2007, wi h he immedia e
objec i e o en e ing he Mic o ansa se ies o compe i ions.
The p ojec aimed o design and build a small-scale au-
onomous sailing boa , obus enough o wi hs and ough sea
and wind condi ions. The design leng h was se o 2.5 m, a e
scaling down in leng h and displacemen some eal oceanic
mode n sailing boa s, and keeping he displacemen no a
om he 40 kg ma k, in o de o acili a e he launch and
anspo a ion.
The hull shape was inspi ed in he mode n acing oceanic
yach s and was de eloped wi h he ee e sion o he boa
design so wa e Del Ship (www.del ship.o g, o me
F eeShip). The ig is a s anda d Ma coni con igu a ion wi h he
head sail moun ed on a boom, as used in small adio-con olled
sailing boa s. Fo he momen , he e is no mechanism o ee
he sails, al hough his will be necessa y in he oceanic e sion
o make i capable o con olled na iga ion in a wide ange
o wind speeds. To inc ease s abili y, he boa includes a deep
keel wi h a lead ballas . Main dimensions a e p esen ed in
able I.
TABLE I
MAIN DIMENSIONS OF THE FEUP AUTONOMOUS SAILBOAT - FAST
To al leng h (LOA) 2.50 m
Leng h in he wa e line (LWL) 2.48 m
Maximum wid h (beam) 0.67 m
D a 1.25 m
Displacemen 50 kg
We ed su ace 1.0 m2
Ballas 20 kg
Sail a ea 3.7 m2
Mas heigh 3.4 m
A. Hull cons uc ion
The boa was buil by a eam o s uden s and p o esso s
o FEUP, wi h he help o a kayak builde (Elio Kayaks,
www.elio-kayaks.com) ha made some o he pa s in
composi e ma e ials. The cons uc ion s a ed in he beginning
o Ma ch 2007 wi h he assembly o a model. This was buil
s a ing om a s uc u e o plywood ames ha was co e ed
wi h a laye o s ip planking ein o ced wi h ib eglass and
polyes e esin. A e se e al i e a ions o illing and sanding
o ob ain a smoo h su ace, his ull scale model was hen used
o build a nega i e mould.
The hull was ab ica ed wi h a sandwich o unidi ec ional
ca bon ib e in he ou e laye , a low densi y 3 mm honey
comb co e in he middle and a inne laye o ib eglass. This
sandwich was hen p essed wi h acuum du ing he cu e o
he epoxy esin, ollowing he same indus ial p ocess ha is
used o build high-pe o mance and ligh weigh acing kayaks.
Addi ional ein o cemen s in plywood, ib eglass and ca bon
ib e we e added a he poin s o majo mechanical s ess: he
a achmen o he keel, he oo o mas and he main bulkheads
whe e he sh ouds connec o he hull. Figu e 1 shows key
s ages o he cons uc ion p ocess and he inal boa .
The keel was buil om a block o igid polyu e hane oam
ein o ced wi h a wood co e, shaped manually o a NACA
p o ile and hen lamina ed in acuum wi h se e al laye s o
ca bon ib e. The keel ballas was ab ica ed om se e al
laye s o a 3 mm lead shee cu o he a ious sec ions o
he bulb shape and glued oge he wi h epoxy. The udde s
we e made om a wood co e co e ed by ib eglass wi h a
s ainless s eel sha . Mas and boom a e ubes o ca bon ib e
Fig. 1. The cons uc ion o FAS : ( op-le o bo om) assembly o he
ames; s ip planking; he mould; building he hull; he inal boa .
used in compe i ion paddles and some s anda d ha dwa e o
mas s o small dinghies.
IV. ELECTRONIC SYSTEM
The elec onic sys em used in FAS is assembled wi h
a ious modules, some o hem cus om buil o his applica-
ion. These componen s a e o ganized in 5 main subsys ems:
compu ing, communica ions, senso s, ac ua o s and powe
managemen . Figu e 2 p esen s a block diag am wi h he
gene al o ganiza ion o he a ious componen s and hei
app oxima e loca ion in he hull.
The compu ing sys em is implemen ed in a small boa d
compu e based on a FPGA2 econ igu able digi al in eg a ed
ci cui [8]. The digi al sys em implemen ed on his de ice in-
cludes a 32-bi RISC mic op ocesso unning wi h a maximum
equency o 50 MHz (Mic oblaze [9]), ROM memo y holding
he boo s ap code and a ious cus om designed digi al mod-
ules ha in e ace he p ocesso wi h he senso s and ac ua o s.
The o ganiza ion, cha ac e is ics and modes o ope a ion o
his sys em a e de ailed in he nex sec ions.
The communica ions sec ion includes a con en ional WiFi
ou e (LinkSys WRT54GC), GSM modem (Siemens MC35),
IRIDIUM SBD modem (model 9601) and a adio con ol
ecei e . All hese componen s a e in eg a ed as OEM modules
and can be swi ched on and o unde con ol o he so wa e
unning in he compu ing sys em. The WiFi ou e p o ides
a con enien da a link o sho ange communica ion wi h a
pe sonal compu e , mainly o so wa e de elopmen , debug
and con igu a ion pu poses. The adio con ol ecei e allows
a o ally manual con ol o he sailboa using a ou -channel
p opo ional adio-con ol ansmi e . While in sea missions,
small olume communica ions a e done by sho da a mes-
sages h ough a GSM modem and a IRIDIUM SBD modem.
While he GSM ne wo k is only a ailable wi hin a ew miles
om sho e, he IRIDIUM sa elli e se ice gua an ees wo ld
wide co e age.
Senso s include he wind ane and anemome e , boom
posi ion, digi al compass (Honeywell HMR3300), GPS (uBlox
RCB-4H), inclinome e , ol age moni o s, ambien ligh sen-
so , in e io empe a u e and a se o wa e senso s dis ibu ed
is a ious places inside he hull. The wind ane and boom
posi ion indica o we e cus om buil wi h a magne ic ield
di ec ion senso om Aus ia Mic o Sys ems (AS5040). This
chip measu es he o ien a ion o he magne ic ield c ea ed by
a small magne placed close o i s case and p o ides 10 bi
measu es wi h 1 deg ee o accu acy. The chip was embedded
in epoxy esin and is hus comple ely isola ed om he wa e .
The wind speed senso is a con en ional cup o o ac ua ing
a hall-e ec swi ch.
The sailboa includes only h ee ac ua o s: wo s anda d
high-powe RC se os p o ide independen con ol o he wo
udde s and a DC gea ed mo o con ols simul aneously he
shee s o bo h sails. The in e io layou has oom o a second
DC mo o o allow independen con ol o he wo sails o o
p o ide some mechanism o educing he sail a ea. These DC
mo o s a e s anda d window mo o s used in ca s. Al hough his
ype o mo o and he associa ed gea box is known o i s low
e iciency, hey a e ex emely obus and once posi ioned and
unpowe ed he gea box na u ally locks he mo o ’s sha . As
he sail angle only needs o be adjus ed o se a new cou se o
when he wind di ec ion changes signi ican ly, his ep esen s
an impo an sa ing o elec ic ene gy when compa ing o
o he combina ions mo o -gea box ha would need powe o
2Field-P og ammable Ga e A ay
Fig. 2. The o ganiza ion o he FAS elec onic sys em and i s dis ibu ion inside he hull.
eac o he o ce o he sail shee .
Finally, he powe managemen sec ion includes a 45 Wp
sola panel (Sola a SM160M), and a comple e ba e y powe
solu ion wi h wo 95 W h Li-ion ba e ies, ba e y cha ge and
managemen module and a ul a e iciency powe supply.
V. THE COMPUTING PLATFORM
The compu e boa d used in FAS is a comme cial sys em
om Suzaku (SZ130 [8]), buil a ound a Xilinx FPGA, model
Spa an3E S1200. The boa d includes 32 MB o SDRAM,
8 MB o SPI lash memo y, se ial in e ace and E he ne
po implemen ed by a dedica ed chip ex e nal o he FPGA.
A o al o 86 digi al I/O pins a e a ailable o he use
applica ion, di ec ly connec ed o FPGA inpu /ou pu pins and
dis ibu ed in edge connec o s a ound he boa d. The FPGA
is only pa ially occupied by he base p ojec (p ocesso and
essen ial pe iphe als), lea ing oughly mo e han 1 million
equi alen logic ga es a ailable o he use sys em. Figu e 3
depic s he o ganiza ion o he SZ130 boa d and he e e ence
p ojec implemen ed in he FPGA ha is included wi h he
de elopmen ki .
The sys em uns uCLinux (www.uclinux.o g), a e -
sion o he popula Linux ope a ing sys em ha has been
simpli ied and adap ed o embedded applica ions unning
in p ocesso s wi h no memo y managemen uni (MMU).
The ope a ing sys em p o ides an in e ac i e command line
console h ough a s anda d RS232 po , a s uc u ed ile
sys em, mul i asking and basic TCP/IP se ices (FTP, HTTP
and TELNET).
This boa d cons i u es a con enien pla o m o building a
digi al in eg a ed sys em ha combines a ha dwa e/so wa e
coope a i e app oach. In addi ion o a con en ional mic op o-
cesso , a sys em may include i ually any cus om designed
digi al ci cui ha may i in o he FPGA’s ee esou ces,
combining sequen ial so wa e execu ion wi h pa allel cus om
p ocessing ca ied ou by dedica ed ha dwa e modules. By
mo ing in o cus om ha dwa e some o he p ocessing and
in e acing unc ions o a sys em, he compu ing load o he
Fig. 3. O ganiza ion o he Suzaku SZ130 single boa d compu e .
cen al mic op ocesso may be signi ican ly alle ia ed. Besides
simpli ying he de elopmen o he so wa e, his app oach
also allows o educe he p ocesso ’s clock equency wha
impac s in he o e all powe consump ion.
A. FPGAs
The compu ing sys em designed o FAS is based on a
FPGA (Field-P og ammable Ga e A ay), p o iding a lexible
econ igu able compu ing pla o m [10]. This solu ion allows
he in eg a ion o almos all he equi ed digi al elec onics
in o a single chip and simpli ies signi ican ly he design o he
con ol so wa e, emo ing om he cen al mic op ocesso
he low-le el in e acing and da a p ocessing asks.
FPGAs a e comme cial in eg a ed ci cui s ha can be
con igu ed by he end use o implemen any a bi a y dig-
i al sys em. The common con igu a ion echnology used in
p esen FPGAs is based on SRAM and p o ides a i ually
in ini e numbe o e-con igu a ions in e y sho imes ( ens
o hund eds o milliseconds). The s a e o he a FPGA
de ices o e capaci ies equi alen o a ew millions o logic
ga es, and include on-chip s a ic RAM exceeding 10 Mbi ,
dedica ed unc ional blocks op imized o signal-p ocessing
applica ions, gigabi anscei e s and, in some amilies, em-
bedded high-pe o mance p ocesso s. Fu he mo e, he digi al
sys ems implemen ed in such de ices can un wi h clocks o a
ew hund eds o MHz and exceed one housand inpu /ou pu
pins a ailable o he use applica ion. This is now a ma u e
digi al echnology ha o e s lexible single chip pla o ms
o a ge ing complex and high-pe o mance digi al sys ems
wi hou incu ing in he high cos s and long u na ound imes
o silicon ab ica ion.
Ano he in e es ing a ac i e o FPGA echnology is he
abili y o quickly modi y he digi al sys em implemen ed in
he chip. Di e en p e-compiled con igu a ion iles can eside
in low cos o -chip lash memo ies (o e en ha d disk) and
loaded on eques in o he FPGA o con igu e a comple ely
di e en sys em. Some FPGA amilies e en allow pa ial
econ igu a ions wi hou dis u bing he es o he chip. This
is pa icula ly in e es ing in applica ions whe e he p ocessing
equi emen s may a y along he unning ime depending on
ex e nal s imuli o ope a ing condi ions.
B. So wa e de elopmen
The so wa e o his boa d is de eloped in ANSI C and
compiled wi h a cus omized e sion o gcc. The de elopmen
o p og ams o un on he uCLinux ope a ing sys em can make
use o he mos common Linux s anda d lib a ies, including
TCP/IP communica ion, ile I/O and ile sys em managemen .
The compila ion is done on a con en ional Linux machine and
ans e ed o he Suzaku boa d ia FTP o h ough he RS232
se ial in e ace.
The uCLinux ile sys em is locally s o ed in he lash mem-
o y and loaded in o a segmen o he SDRAM (con igu ed as a
RAM disk) du ing he boo p ocess. Du ing applica ion de el-
opmen , e alua ion and debug, he suppo o he uCLinux
ope a ing sys em is a con enien solu ion because i eases
he implemen a ion o ne wo k communica ion p ocesses, ile
managemen and mul i asking o di e en p og am’s pa s.
Howe e , o applica ions equi ing low powe consump ion,
unning on he op o an ope a ing sys em may ep esen a
signi ican o e head in e ms o ene gy consump ion. This
pla o m suppo s easily bo h implemen a ions ha s ill ha e
o be e alua ed.
C. Ha dwa e de elopmen
The de elopmen o he digi al sys em implemen ed in
he FPGA is done wi h he EDK/ISE so wa e ools om
XILINX. The XILINX EDK (Embedded De elopmen Ki ) is
a design ool ha builds a combined ha dwa e/so wa e design,
a ge ed o a XILINX FPGA-based boa d. The ha dwa e pa is
assembled wi h p e-designed pa ame izable modules (mic o-
p ocesso , SDRAM in e ace, USART, e c.) and use designed
componen s. The so wa e pa is buil as a C p og am ha
will be la e embedded wi h he FPGA con igu a ion da a. The
ISE ool sui e pe o ms he comple e digi al design low o
XILINX FPGAs and ansla es he ci cui models p oduced by
EDK in o he inal da a ile (bi s eam) used o con igu e he
FPGA.
D. FPGA econ igu a ion
When he sys em is powe ed up, he FPGA chip is con ig-
u ed wi h da a s o ed in he lash memo y. Once he con ig-
u a ion is comple ed (wi hin less han 1 second) he sys em
implemen ed in he FPGA s a s wo king and he Mic oblaze
mic op ocesso uns he code s o ed in e nally in he FPGA
memo ies. I he s a up o he uCLinux is enabled, hen a
boo loade is execu ed o ins all he ile sys em image in o a
i ual RAM disk, s a ing hen he ope a ing sys em ke nel.
The comple e boo p ocess, om powe -up o sys em idle
s a e, akes only app oxima ely 42 s, unning he Mic oblaze
a 50 MHz.
The econ igu a ion o he FPGA can be done easily unde
con ol o so wa e. Unde uCLinux, he sec ion o he lash
memo y ha holds he FPGA con igu a ion da a can be e-
w i en om a egula ile s o ed in he ile sys em, using one
applica ion included in he dis ibu ion. The unning so wa e
applica ion can hus choose a digi al sys em om a ba ch o
p e-buil FPGA con igu a ions, copy i o he lash memo y
and issue a eboo command o es a he sys em wi h a
comple ely di e en digi al sys em in he FPGA.
This unique ea u e o FPGA-based sys ems allows o
change he digi al ci cui played by he FPGA, acco ding
o di e en p ocessing needs ha may be d i en by se e al
ac o s (eg. he a ailabili y o ene gy, en i onmen al condi ions
o unc ion o execu e). This is no ye being exploi ed in FAS ,
al hough i may be a good s a egy o educing he ene gy
consump ion.
VI. THE FAST COMPUTING SYSTEM
The FAS compu ing sys em is implemen ed in he FPGA
o he Suzaku boa d. Besides he cen al Mic oblaze p ocesso ,
he sys em includes a ious dedica ed con olle s o in e ac-
ing he senso s and ac ua o s used in he sailboa , some o
hem associa ed wi h cus om compu ing modules. Figu e 4
p esen s he gene al o ganiza ion o he sys em.
Fig. 4. Simpli ied iew o he o ganiza ion o he FAS compu ing
sys em implemen ed in he FPGA. All he senso s and ac ua o s a e
accessed by he mic op ocesso ia dedica ed in e aces. The wo
shaded blocks a e s anda d se ial po con olle s implemen ed as
p e-buil modules om he Xilinx EDK lib a y.
The global s a egy adop ed du ing he design o his sys em
was o c ea e a se o au onomous in e aces capable o

deli e ing o he so wa e he da a e ie ed om he senso s
in a o ma easy o be used by he so wa e con ol sys em.
Besides he implemen a ion o he senso ’s speci ic in e ace
p o ocols, his includes pa sing messages om he senso s,
da a il e ing, and con e sion o uni s. Simple sliding window
a e aging il e s ha e been implemen ed o he wind senso s
and he inclinome e , al hough he e is enough oom o include
highe quali y il e ing app oaches coupled o he in e acing
modules.
The access o he pe iphe als om he Mic oblaze is done
h ough a po expande . This module uses only one pai o 32-
bi memo y-mapped bidi ec ional po s and makes a ailable
o he es o he ci cui a se o 16 ou pu and inpu s po s
(32-bi each).
A. In e aces wi h senso s
The wind di ec ion in e ace eads he AS5040 senso
sampled a 50 Hz and a e aged using a sliding window il e o
64 samples ( he boom posi ion senso is in e aced by ano he
ins ance o his module). The ou pu o he so wa e domain
is an in ege in he ange [-180,+180] and he ze o e e ence
can be co ec ed wi h a alue p e-loaded in o he ha dwa e
in e ace. The wind speed senso in e ace coun s he numbe
o 10 KHz clock pe iods du ing one e olu ion o he cup o o ,
con e s o kno s and ou pu s an a e age alue compu ed by
a simila sliding window mean il e .
To measu e he heel angle a ound he whole 360 deg ee
ange, a wo-axis accele ome e is used as an inclinome e .
This ci cui ou pu s wo PWM signals wi h a pulse wid h
p opo ional o he accele a ion along each axis. The du a ion
o each pulse is measu ed by digi al ci cui s based on coun e s
and con e ed o he heel angle.
The magne ic compass p o ides 8 eads pe second wi h he
heading, oll and pi ch angles in ASCII o ma , as a iable
sized messages. This in e ace is done by a small cus om
con olle ha implemen s a pa se o he messages ecei ed
om he compass and pe o ms he con e sion o bina y. The
GPS in e ace is buil wi h independen ini e s a e machines
o ex ac ing he ele an da a (la /lon, speed, ime, cou se
and s a us) om he di e en bina y messages ou pu om
he GPS.
The in e ace wi h he adio-con ol ecei e is done by 4
ins ances o he same con olle , one o each channel o he
adio. The s anda d con ol signal used in RC ecei e s and
se os is a 50 Hz digi al signal, whe e he high ime de ines
he posi ion o he se o ( anging om 0.8 ms o 2.2 ms). Each
ecei e module measu es he high ime o he co esponding
channel and con e s i o a wo’s complemen 10 bi in ege :
ze o means he con ol s ick a he middle, +511 is ull igh
( ull on ) and -512 is ull le ( ull ea ). One addi ional
module moni o s con inuously he signal ecei ed om adio
channel 1, looking o 8 consecu i e alid pulses (c i e ia
o alid pulses is equency be ween 45 Hz and 55 Hz and
high ime be ween 0.5 ms and 2.5 ms) o asse a adio
p esen signal. This no i ies he es o he sys em ha he
RC ansmi e is in ange and ansmi ing co ec da a.
TABLE II
SUMMARY OF THE FPGA SPARTAN 3E 1200 OCCUPATION
4-inpu LUTs 7314 (42%)
Flip- lops 3997 (23%)
Occupied slices 4730 (54%)
LUTs used as ou e- h u 324 (1.8%)
LUTs used as SRAM 256 (1.5%)
LUTs used as shi - egis e s 796 (4.6%)
Block RAMs 14 (50%)
Dedica ed mul iplie s 8 (28%)
Equi alen ga e coun 1078257
B. Ac ua o s
The se o mo o s con olle s ecei e a 10-bi wo’s comple-
men numbe and gene a e he 50 Hz s anda d se o con ol
signal, acco ding o he iming e e ed abo e. Fo he momen ,
only wo se os a e being used o he wo udde s. A
ha dwa e mul iplexe selec s he sou ce o da a ha is ou ed
o hese se os: his can be he ou pu o he RC channel 1
(co esponding o he le - igh joys ick) o he da a sen by
he so wa e applica ion unning on he p ocesso .
The sail shee o bo h sails is commanded by he same
DC mo o linked o a mul i- u n po en iome e o posi ion
eedback. This mo o is con olled by a PWM modula o ha
ecei es om he so wa e a signed 8 bi alue ha ep esen s
he desi ed speed o he mo o . This in e ace includes a low-
pass il e applied o he inpu da a, o a oid high accele a ions
ha would esul in high cu en d aw.
VII. FPGA IMPLEMENTATION
Cu en design, as ep esen ed in igu e 4, uses less han
50% o he XC3S1200E FPGA esou ces and, acco ding o
he implemen a ion epo s gene a ed by he Xilinx ools,
co esponds app oxima ely o 1 million equi alen logic ga es.
All he modules un wi h he maximum clock equency o
50 MHz allowed o he Mic oblaze p ocesso , al hough mos
o hem may ope a e wi h much lowe clock equencies. Ta-
ble II summa izes he occupa ion o he FPGA esou ces (LUT
s ands o Look-up able and is he elemen a y con igu able
block in Spa an 3E FPGA: a 16 bi SRAM implemen ing any
4-inpu combina ional logic unc ion).
A. Powe consump ion issues
Elec ic powe consump ion is one o he g ea conce ns in
an au onomous sailboa . Fo a small boa , he only easonable
sou ces o elec ic ene gy o long e m na iga ion a e pho-
o ol aic panels and wind u bines. Bes solu ion would be a
combina ion o bo h bu , as a as we know, he comme cially
a ailable wind gene a o s a e oo la ge and hea y o ou
sailboa . In bo h cases, he a ailabili y o ene gy always
depends on he wea he condi ions which ha e a high deg ee
o unce ain y. The elec onic sys em mus consume he lowes
possible ene gy and whene e possible adap i s beha iou o
he powe budge a ailable a each s age.
Acco ding o ou i s es ima es, he compu ing sys em will
accoun o mo e han 50% o he o al ene gy consumed by all
he elec ic componen s, assuming a con inuous ope a ion wi h
he maximum powe consump ion measu ed o he p esen
con igu a ion. This ep esen s ap oxima ely 560 mA o he
3.3 V supply (1.85 W), including he GPS, digi al compass
and he wind senso s.
VIII. THE CONTROL SOFTWARE
The con ol so wa e uns on he op o he uCLinux
ope a ing sys em as a se o p ocesses communica ing by UDP
socke s. The so wa e a chi ec u e ies o mimic he command
hie a chy ha exis s is eal boa s, associa ing o a p ocess
(so wa e applica ion) a key ope a ional ask ha exis s in a
eal boa . Each le el ecei es commands (as UDP packe s)
om a highe hie a chical le el and sends o de s o he lowe
le el applica ions.
P esen ly he so wa e componen is composed o 5 appli-
ca ions ha implemen he main 5 asks: ha dwa e in e ace,
helm, sail, skippe and logge . The ha dwa e in e ace imple-
men s all he communica ion wi h he boa ’s senso s, ac ua o s
and con igu a ion pa ame e s. The helm is esponsible o
con olling he udde s, acco ding o he p og ammed con ol
algo i hms and o de s ecei ed om he highe hie a chy ( he
skippe ). The commands suppo ed by his module include
keeping a gi en heading o cou se, main aining he angle o
he appa en wind and pe o ming he basic maneu e s o
acking o gibing. The sail applica ion con ols he posi ion
o sails acco ding o he wind speed and di ec ion and a se
o decision ules ha de ine he bes sail angle. Au oma ed
unc ions embedded in his module include easing he shee
when he heel angle is g ea e han a ce ain alue and ease
comple ely he sail shee when he boa is capsized. The
skippe is p esen ly he highe le el con ol p ocess. I has
access o all he in o ma ion collec ed om he senso s h ough
he ha dwa e in e ace bu he commands o he ac ua o s a e
only sen h ough he helm and sail p ocesses. This module
is esponsible o deciding he cou se o ake o each a gi en
poin , when o ack o gibe, o when swi ch be ween he
manual and au onomous con ol mode. Finally, he logge
is a lis en only applica ion ha in e oga es all he o he
applica ions o collec a se o ele an da a in a log ile. This is
specially impo an du ing he de elopmen and debug phases.
IX. CONCLUSIONS
This pape p esen ed an au onomous unmanned sailing
boa ha was de eloped in he Facul y o Enginee ing o
he Uni e si y o Po o, Po ugal, o en e he Mic o ansa
compe i ion. This boa p o ides an e icien sailing pla o m
wi h i ually unlimi ed au onomy, capable o pe o ming
unassis ed missions on he ocean o long pe iods o ime.
The boa can ca y a ew kilog ams o addi ional equipmen
and i includes a cus om designed compu e sys em ha can
be easily in e aced o a wide a ie y o addi ional senso s o
ac ua o s.
The compu ing sys em includes a RISC mic op ocesso
unning a simpli ied e sion o he Linux ope a ing sys em,
su ounded by se e al cus om designed pe iphe als ha in-
e ace he p ocesso wi h he senso s and ac ua o s used
in he sailboa . The ha dwa e econ igu abili y ea u e o
he FPGA de ice used in his de elopmen enables a sho
design i e a ion and allows as econ igu a ions o he unning
ha dwa e. This may be exploi ed o minimizing he ene gy
consump ion by adap ing he con ol and compu ing logic
ci cui s o he speci ic equi emen s o na iga ion unde gi en
wind and sea condi ions.
Al hough p esen ly he in e na ional ules do no allow he
au onomous na iga ion o unmanned sailboa s, such pla o ms
may be a aluable esou ce o se e al applica ions domains.
The gene aliza ion o low cos elec onic su eillance and
iden i ica ion sys ems, such as he AIS in use oday in comme -
cial ships, may open oom in a nea u u e o include obo ic
boa s as legal essels in he in e na ional na iga ion ules.
ACKNOWLEDGEMENTS
The au ho s would like o hank he Depa men o Elec-
ical and Compu ing Enginee ing (DEEC) o he Facul y o
Enginee ing o he Uni e si y o Po o, Po ugal (FEUP), o
he inancial suppo o his p ojec .
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