Tạp chí Servo
Trang 10 8> U.S. $5.50 CANADA $7.00
Trang 2Let your geek shine.
Meet Pete Lewis, lead vocalist for the band Storytyme Pete recently created the RS1000,
a new personal monitor system for performing musicians It was SparkFun’s tutorials, products and PCB service that enabled him to take his idea
to market in less than a year
The tools are out there Find the resources you need to let your geek shine too
©2008 SparkFun Electronics, Inc All rights reserved.
Sharing Ingenuity
W W W S P A R K F U N C O M
Trang 3a) Science b) Technology c) Engineering d) Mathematics e) All of the above
Given a choice, middle and high school students prefer robotics among science courses
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Think Create Build Amaze Vex.
Trang 4MAARS Robots Taking Off for War
by Bryce and Evan Woolley
Rhyme of the Modern Submariner
The Greatest Playground of All
by Tom Carroll
Robots — How We’ve Built Them
Over the Years
PAGE 10
Trang 5Driving hobby servos is only one
of the tricks a CPLD can per form
In addition to turning servo rotors, you can also use a CPLD to replace a number of discreet logic ICs in your next robotic design.
Long Beach Grand Prix.
by Michael Simpson
If you’re not afraid to part with a little cash, this series will give you the choice of building either a six-
or three-wheeled robot with an onboard PC.
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Trang 6Published Monthly By
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Next Level Robotics
To an outsider looking in at
amateur robotics, it often appears
that the field hasn’t evolved much in
the past few years Certainly, there
have been evolutionary gains
Sensors are a little smaller and
smarter, and motors and controllers
are a little more powerful and
sophisticated Furthermore, there
have been a few advances in
microcontrollers, such as the
development of the Parallax Propeller,
and more powerful field
programmable gate arrays or FPGAs
Despite incremental advances in
the components we use to construct
robots, the fundamental capabilities
of carpet roamers, crawlers, and
arms haven’t changed much The
leading edge of low-cost robotics is
often represented by toys carried by
the major retail outlets So what’s it
going to take to get amateur robotics
to the next level? That is, to a level
that not only matches the capabilities
illustrated by commercial and
academic robotics, but that at least
hints at the capabilities we ascribe to
robots depicted in Star Wars and
Transformers?
First, a reality check Developing
a semi-autonomous Martian rover or
a robotic prosthetic arm for a soldier
injured in Iraq takes significant
financial resources and teams of
engineers, scientists, and machinists
So what can you do, given the
current economic environment,
to move your robot designs to the
next level?
The most fertile area in robotics
yet to be fully exploited that is within
reach of every roboticist is softwaredevelopment For example, in thearea of robot vision, there is a need
to better recognize, track, anddifferentiate objects, to read facialexpressions and gestures, and — ingeneral — to make robots moresocially adaptable If your interest isoutdoor navigation, then there is aworld of software options to explore,from GPS-based localization tonavigation with light and RF beacons
Means of providing robots with the ability to maneuver throughmazes and how to best avoid ledges and low-traction areas haveyet to be perfected
Connected to a PC, your roboticarm or vehicle with appropriatesensors can become just assophisticated as any rover developed
by NASA Of course, you can work
on challenges completely within acomputer using simulations Andthat’s an efficient, low-cost method
However, at some point you have tovalidate your work on a real robot
One thing I’ve learned over severalyears of building robots is that unless you’re working on a specifichardware specification, you’ll makemore progress in shorter time if youleave the design of the hardwareplatform to someone else and focus
on the overall functionality
For example, why spend monthsdesigning and building an arm whenyou can buy a kit from Lynxmotion
(www.lynxmotion.com) or CrustCrawler (www.crustcrawler.
com)? Even if you have to modify an
off-the-shelf arm, you’ll likely still savetime and money I’ve used variousversions of the CrustCrawler arm —
Mind / Iron
by Bryan Bergeron, Editor
Trang 7Comfortable Tactile Sensors
at Your Fingertips Literally
Pressure Profile Systems, Inc (PPS),
had just released their innovative
new wireless FingerTPS™ (Finger
Tactile Pressure Sensing) system for
immediate sale worldwide FingerTPS
sensors are soft, flexible sensors worn
on the hand that transmit accurate,
repeatable tactile force data to a PC
via wireless Bluetooth connection
FingerTPS tactile data with integrated video provides a completerepresentation of user interaction withtools, sports equipment, new productdesigns, and medical applications
"The FingerTPS concept wasoriginally funded by DARPA researchgrants to capture the forces of askilled surgeon for developingvirtual surgical simulationsystems After a decade ofnumerous iterations, we finallyhave a system that is easy touse," said Dr Jae Son, CEO
of PPS
The wireless FingerTPSsystem was unveiled to thepublic at the IVR IndustrialVirtual Reality Expo in Tokyo,Japan this last June "The wireless capability and thesimple, one-touch calibrationwere the most exciting featuresamong attending engineers andresearchers from hundreds ofleading firms," said David Ables,CTO of PPS
FingerTPS was recentlyfeatured in programming on theNational Geographic Channeland Fox Sports Net Episodes of
"SportScience" and "FightScience"
called on PPS and industryexperts to scientifically explainthe performance of world-classathletes including NFL Hall ofFame receiver Jerry Rice, NBAsharpshooter Jason Kapono, and Mixed Martial Arts legendRandy Coture
"For elite athletes like JerryRice or Jason Kapono, theirhands are their livelihood, and
they readily grasped how real-timetactile data could help evaluate and improve their performance,"explained Ables
FingerTPS systems start at a mere
$4,995 for a single-hand system withtwo sensors that are available inmultiple sizes in specialized shapes for fingers, thumbs, palms, and innerphalanges FingerTPS systems also include a video camera forsynchronized video input, software,and a reference sensor for easy, one-touch calibration
Pressure Profile Systems, Inc., wasfounded in 1996 by two graduatesfrom the Harvard University RoboticsLab Government grants and industrialsales have enabled PPS tactile sensingtechnology development for medicaldevices, industrial instruments, andconsumer electronics
For more information, visit the PPS
website at ww.pressureprofile.com.
including their latest Smart robotic arm —
as the basis for many projects that rely
on the processing power of a PC Both
CrustCrawler and Lynxmotion offer
PC-based software to control their arms,
and third party software is available,
as well
Similarly, you needn’t start your
software designs from scratch or with a
huge budget The entry-level versions of
the various Microsoft Net compilers and
the MS Robotics Studio can be freely
downloaded If you’re not a Microsoft
fan, there are dozens of software
options, from MatLab and Simulink
(www.mathworks.com) to open-source
compilers If possible, leverage what’s
been done before and move to the next
level more quickly and easily Just be sure
to return the favor and post your software
to the web – and consider sharing your
experience with SERVO readers.
I don’t want to discourage
mechanical engineers and
engineers-in-training from tackling new hardware
designs If you have a machine shop at
your disposal and the skill to use those
tools, then don’t hesitate Everyone has
different goals and ideas of what they
want to get out of robotics However, if
getting to the next level quickly on a
limited budget is your focus, then you
should at least consider focusing on the
brains — as opposed to the brawn — of
What is the maximum speed of the PPS sensors?
TactArray systems have an element-to-element scan speed of up to 10 kHz ConTacts systems have a continuous analog output allowing any sampling rate, but the sensors have a throughput of approximately 2 kHz.
Of what materials are PPS sensors made?
PPS sensors are made from conductive cloth (conformable), Kapton (industrial), Lycra (stretchable) or a combination of conductive cloth and Kapton (hybrid).
What is the smallest element size for PPS sensors?
Element sizes in TactArray sensor arrays can
be as small as 1mm x 2 mm, however, practical resolution is actually much greater PPS's pressure-sensing technology allows accurate pressure interpolation between sensing elements Single-element ConTacts sensors have been built as small as 5 mm x 5 mm.
Are PPS sensors waterproof?
PPS sensors are NOT waterproof, however, PPS can provide removable waterproof sheaths to protect the sensors or complete encapsulation for more rugged environments.
Trang 8New Hopperbot Sets Record
Mechanical jumpers are nothing
new, but one that was unveiled at
the IEEE International Conference on
Robotics and Automation appears to
have, um, leaped ahead of its
com-petitors in terms of jump distance
The tiny, 7 g mechanical grasshopper
can jump 1.4 m, which is said to be
10 times farther — relative to its size
— than any other existing jumping
robot The little bug was developed
at the Laboratory of Intelligent
Systems at the Ecole Polytechnique
Federale de Lausanne (EPFL, www.
epfl.ch), and, according to Prof Dario
Floreano, “This biomimetic form of
jumping is unique because it allows
microrobots to travel over many types
of rough terrain where no other
walk-ing or wheeled robot could go These
tiny jumping robots could be fitted
with solar cells to recharge between
jumps and deployed in swarms for
extended exploration of remote areas
on Earth or on other planets.”
The bot mimics the way fleas,
locusts, and other pests travel by
charging two torsion springs via a
small 0.6 g pager motor and a cam
To optimize jump performance, the
legs can be adjusted for jumping
force, take-off angle, and force profile
during the acceleration phase An
on-board battery allows it to make up
to 320 jumps at 3 second intervals
Down on the MEMS level, Duke
University (www.duke.edu)
researchers have been training bots to maneuver separately, withoutany obvious guidance, and assemblethemselves into organized structures
micro-The devices — which are basicallyshaped like a spatula — can displaysurprisingly flexible movements Inone experiment, two of them weretaught to pirouette to Strauss music
on a tiny “dance floor.” In the accompanying photo, four of themnumbered 1, 2, 4, and 5 (no 3 was probably somewhere being questioned by Mike Nifong), started
at the corners of a rectangle a bitsmaller than one square mm Next,two species (4 and 5) docked to formthe initial stable shape, afterwhich the others joined to formthe final assembly
The devices measure about
60 x 250 x 10 µm and drawpower from an electrified surface They take steps of only
10 to 20 nm but can make up
to 20,000 movements per second The only speculationabout practical applicationscited the ability to move aroundthe interiors of laboratory-on-a-chip devices But they’ll
probably come up with somethingmore provocative
Most subaquatic robotsneed to communicate withhuman beings from time totime, often via communicationsatellites during operation Butthe University of Washington
(www.washington.edu) is
developing fin-propelledRobofish that can skip the middle man and work cooperatively with each otheruntil their task is complete.Kristi Morgansen, UW assistantprofessor of aeronautics and
astronautics, recently ran them in aschool of three as their first majortest, in which they were programmed
to either swim all in one direction orall in different directions The latterdoesn’t sound like much of an accomplishment, being essentiallywhat would happen if you turnedthree flies loose in your living room.But bigger things are planned Theresearchers trained some live fish torespond to a stimulus by swimminginto a feeding area They discoveredthat you only have to train about athird of the fish to get the entire school
to act in unison “The fish that have astrong idea tend to dominate over those
This mechanical grasshopper can leap 27
times its body size Photo courtesy of EPFL.
Microassembly experiment recorded via optical microscope Image courtesy of Duke University.
Fin-propelled Robofish (shown with
a penny) is about the size of a 10 lb tuna Photo courtesy of the University of Washington.
Trang 9that don’t,” according to Morgansen.
“That has implications for what will
happen in a group of vehicles Can one
vehicle make the rest of the group do
something just based on its behavior?”
Like the live fish, the robotic ones
communicate with each other, in this
case using low-frequency sonar Test
results showed that although only about
half of the transmitted communications
actually get through, the Robofish
programming allowed them to
accom-plish their task anyway The next step
will be to let them loose in the ocean,
where they will be programmed to
trail a remote-controlled toy shark
Ultimately, they could be dispatched
to explore caves and ice-covered
waters, track whales, map regions of
pollution, or harass baby seals
Most bots walk in the rigid,
clunky movements that are typical of
industrial machinery, toy robots, and
people who buy their shoes at
Wal-Mart This differs from the much
more fluid way humans generally
move, which basically consists of
falling forward in a controlled
manner But, in pursuit of a PhD,
researcher Daan Hobbelen of theDelft University of Technology (TUDelft) has developed an advancedrobot, called Flame, that
demonstrates that a robot can behuman-like, energy-efficient, and highly stable The overall goal is toprovide insight into how people walk,which ultimately can be applied
to helping people with mobility problems via improved diagnosis andrehab Flame employs seven motors,
a balance organ, and some etary algorithms to ensure a highlevel of stability The robot can, forexample, apply the information provided by its balance organ to placeits feet slightly farther apart to prevent falling According toHobbelen, Flame’s advanced ankleshave already provided motion scientistswith advanced insight into how thecomplicated joint works For details,
propri-visit www.dbl.tudelft.nl.
LEGO’s 2008 Earth Day BuildingChallenge was to create a
MINDSTORMS NXT robot that “could
be used to help maintain a healthy,sustainable environment.” TheChampion’s Award went to DinoMartino’s TP-Bot 2008, which helpssave energy and the environment viathe efficient dispensing of toilet
paper The bot is compatible for use
by up to five different people (presumably not all at once), and itincludes a scanner (to which userspresent an access pass and a four-digit secret code) and a paperdispensing system It even monitorshow much toilet paper is left on theroll Can’t you feel the greenhousegases abating already? For info onthis and others in the winners’ circle,
visit mindstorms.lego.com/news/.
In case you missed it, the 2008inductees into the Carnegie Mellon
Robot Hall of Fame (www.robothallof
fame.org) are the Raibert Hopper,
NavLab5, LEGO® Mindstorms, and Lt.Cmdr Data The Hopper (shown in thephoto) was developed in 1983-84 forexperiments on active balance anddynamics in legged locomotion Namedfor its developer, Marc Raibert, theone-legged bot could hop in place orrun at a top speed of 2.2 m/sec (4.8mph) Congrats to all SV
R oo bb yy tt ee ss
Robot “Flame” walks like a human.
Photo courtesy of TU Delft.
SERVO 08.2008 9
The award-winning TP-Bot 2008.
Photo courtesy of LEGO.
The Raibert Hopper.
Photo courtesy of MIT.
Trang 10In 2005, I covered the SWORDS
(Special Weapons Observation
Reconnaissance Direct-action
System) maneuverable military robots,
which soldiers use as scouts and
remote weapons systems in the war in
Iraq As reported, the SWORDS iteration
of the robotic sentry is compatible
with M16s, M240s, M249s, Barrett 50
calibers, 40 mm grenade launchers, or
M202 anti-tank rocket systems
The SWORDS have many other
features including advanced sensing
The robots use these technologies
to locate enemy combatants, IEDs
(Improvised Explosive Devices), and
other hazards
The SWORDS are unmannedground vehicles (UGVs), which meansthat threats to these vehicles in theireveryday line of work don’t directlythreaten the soldiers who operatethem from a safe distance via aremote control console
Since the Defense AuthorizationBill for Unmanned Vehicles, the armedforces have been pressed to convert thevast majority of ground combat vehicles
to unmanned for this very reason
The war and the need to keep soldiers further out of risk hasbrought us to the latest evolution ofthe unmanned fighter The newlyreleased MAARS (Modular AdvancedArmed Robotic System) is the offspring of the SWORDS and
“the first fully modular groundrobot system capable of providing
a measured response includingnonlethal, less lethal, and evenlethal stand-off capabilities,” says
a June 4th media release fromQinetiQ, owner of Foster-Miller,which produced the robots
If you’ve heard references toSWORDS 2.0, these are theMAARS robots Soldiers will beable to supplement the threeexisting SWORDS robots whichare deployed in Iraq with theserobots
The Federal government andQinetiQ have been working onMAARS for 18 months to deliver
unmanned, and controlled by the soldiers themselves, according to the release
MAARS will replace SWORDS asthe core platform for building outthese kinds of systems for battlefieldtactics Because the new MAARS platform is standardized and modular,
it will make it affordable for the military to have more of the robotsand to repair them more readily.QinetiQ worked closely with themilitary to ensure that the MAARSrobot would “enhance the war fighter’scapability and lethality, extend his situational awareness, and provide allthese capabilities across the spectrum
of combat,” says Dr William Ribich,President of the Technology SolutionsGroup, QinetiQ North America
By extending the capabilities ofMAARS, soldiers can save their livesand the lives of area non-combatantsmore frequently
MAARS Mayhem
Unlike SWORDS, MAARS givesthe human operator choices forconfrontation on the battlefield Fornonlethal confrontation, a humanoperator can project their voice or asiren through mounted speakers to aperson or crowd, or emit a green pulsing laser light that is visually confusing, though harmless
When a confrontation calls for
Contact the author at geercom@alltel.net
by David Geer
MAARS Robots Taking Of f for War
SWORDS Military Robots Graduating to 2.0, MAARS Status
Here is the new MAARS robot — the larger
offspring to the SWORDS robot Four
grenade launchers, machine gun, turret,
other equipment, and tracks visible.
Trang 1140 mm “less lethal” grenade
ammunition, bean bags, smoke, star
clusters (illumination), tear gas,
pepper spray, and M240B medium
machine gun warning shots This
type of confrontation is purposed
against the enemy with the
weapons/guns pointed upward as if
to fire warning shots For lethal
firepower, MAARS weapons are
pointed directly at their targets, firing
40 mm high-explosive grenades or
400 rounds of 7.62 mm shells from
the M240B medium machine gun
Where SWORDS came with
weapons optional, MAARS come with
four grenade launchers, a machine
gun, and less lethal defenses
attached
The MAARS robot is remote
controlled to over a kilometer away
from the operator, putting a safety
buffer between the soldier-operator
and the point of immediate contact
with the aggressor This increases
the soldier’s ability to survey the war
zone, confront the aggressor from a
distance, and survive the battle
MAARS Mechanics
Foster-Miller constructed the
robot on a uni-body frame/chassiswith a simple, plug-and-play designfor quick assembly with new accessories and attachments thatmay become available The uni-bodyconstruction makes access to thebattery and electronics
easy and efficient TheMAARS has a larger payload bay areathan SWORDS, higher torque forfaster travel, andimproved brakingcapability Therobot’s remote control system isuser-friendly, intuitive, and digitalfor quick uptake bymilitary personnel
The new DigitalControl Unit (DCU)
— the remote control device the
Here is the mighty SWORD with cameras, machine gun, ammo case, tracks, antennae, and identifying US flag emblem.
This Operator Control Unit (OCU) is the
SWORD’s wireless remote control,
fitted with a hard-shell case Notice
the antenna, numerous controls for
driving and manipulating the SWORD
combat robot, and the multiple split
screens for viewing everything the
robot’s cameras pick up.
This drawing of the SWORDS robot identifies key parts
and systems, many of which are duplicated
or enhanced on the new MAARS robot.
The real ancestor of the MAARS robot is the TALON
robot for military, police, and emergency rescue From these,
Foster-Miller developed the SWORDS bots The SWORDS
originally topped out at 120 lbs., though they packed a
mighty punch through the Small Mobile Weapons Systems
(SMWS) they employed
At about $230,000 per unit, SWORDS offered front and
rear cameras with night vision, thermal vision, and wide
angle views and zoom lenses On its rugged tank tracks and
powered by a lithium ion battery, the SWORDS can run for
four hours with a maximum velocity of 5.2 mph
Soldiers can carry parts from the disassembled SWORDS
in their backpacks, transporting it from combat site to
combat site
WHERE IT ALL BEGAN
SERVO 08.2008 11
GEERHEAD
Trang 12operator uses — offers advanced
command and control capabilities and
greater situational awareness around
the robot The system gathers a large
array of situational feedback from the
battlegrounds
SWORDS laid the groundwork for
sensing battle hazards with heat, gas,
chemical, and radiation sensors These
report to the soldier wirelessly so they
know when and where it’s safe totread or what precautions to take
MAARS also uses Blue ForceTracking, a satellite and GPS trackingtechnology that informs soldiers onthe locations of friendly forces, enemyforces, and neutral areas
The MAARS robot comes with all-terrain tracks in the military style ofthe old tanks With these, it can scale
stairs It can also use wheels to travelmore quietly on other terrain, to be
“stealthier.”
Field personnel can equip therobot with a robotic arm, numerousweapons other than those described,and a broad range of sensors Therobotic manipulator arm can lift about
100 lbs By replacing the gun turretwith the arm, soldiers can readily turnthe robotic war fighter into a device foridentifying and neutralizing explosives.MAARS can also sense its environment via its seven multi-modecameras The operators can viewaction the robot views in streamingvideo The robot uses day and nightthermal vision The robot also gaugesits location and distances using a laserrange finder The soldier-operatorsknow where they are pointing therobot’s weapons in relation to therobot’s surroundings, other people,and themselves because of these cameras At about 350 lbs., the complete MAARS system is the largestmember of the TALON robots, largerthan the SWORDS
Foster-Miller has already shippedits first MAARS robot to the US military under a contract from theExplosive Ordnance Disposal/Low-Intensity Conflict (EOD/LIC) program,which is part of the CombatingTerrorism Technical Support Office(CTTSO) This is the same programthat acquired the SWORDS robots SV
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GEERHEAD
Demo video MAARS robot
www.foster-miller.com/images/ Videos/MAARS_test.avi
Fox interview about Talon (including MAARS) robots
www.myfoxboston.com/myfox/pages /ContentDetail?contentId=6692317#
Foster-Miller projects
www.foster-miller.com/lemming.htm
RESOURCES
Trang 13SERVO 08.2008 13
Trang 14This month, we have the honor of
presenting the ROV-In-A-Box Kit
from !nventivity ROV stands for
Remotely Operated Vehicle, and while
this can refer to a tethered vehicle that
tackles any sort of terrain, it very often
refers to an underwater vehicle, as was
the case with this kit After covering
the AUVSI underwater robotics
competition in 2006, we knew that
there were competitions out there
that catered to these aquatic bots,
and we thought a competition would
be a much more exciting way of
testing the robot than surreptitiously
dunking it in the community pool The
AUVSI competition, however, was
solely for autonomous robots, and aremotely operated vehicle wouldn’texactly fit into that category After abit of searching, we stumbled uponthe MATE Competition — an under-water ROV competition sponsored bythe Marine Advanced TechnologyEducation Center What’s more is thatthe international championship wassponsored by the Scripps Institute ofOceanography at our very ownUniversity of California, San Diego
Several engineering studentorganizations at UCSD are involved in
a number of design competitions, butthere was not yet a team for the MATEevent We had the kit, the opportunity,
and the onus of the home turf tage, so we really felt that the MATECompetition was an opportunity that
advan-we couldn’t pass up All advan-we had to donow was get a team together
Ocean’s Eleven and Then Some
Evan is lucky enough to be a part of UCSD’s Tau Beta Pi chapter,California Psi Tau Beta Pi is the engineering honor society and UCSD’schapter pursues excellence in engi-neering through outreach, academic,and social programs Conspicuouslymissing from TBP’s repertoire, though,was a robotics team Why a roboticsteam? Because robotics is an inter-disciplinary field that demands theeffort of engineers from every field ofstudy, and a robotics team would bemade up of the same cross sections ofengineers as Tau Beta Pi By virtue ofhis position as Publicity Officer, Evanwas able to organize meetings for arobot team and soon a group of talented engineering students hadcoalesced around our ROV in a box,and we were eager to take on thechallenge of MATE
SPECIAL EDITION:
Rhyme of the Modern Submariner
T HE ROV- IN - A - BOX IN THE BOX C OLTER (L) AND B RIAN (R) WORKING
ON THE FRAME
Trang 15great way to tackle the
challenges of the MATE
Competition The event
demands that teams complete
three underwater missions that
are part of a scenario inspired
by mid-oceanic ridge research
The first mission was to free an
OBS trapped mercilessly on the
ocean floor An OBS is an
Ocean Bottom Seismometer,
and in the game scenario, it
was placed in order to gather
information on ocean floor
seismic events like underwater
eruptions and earthquakes The good
news is that the OBS did indeed
gather the hoped for information, but
the bad news is that the OBS became
trapped in a fierce lava flow in the
process Our first mission — should we
choose to accept it — would be to
free the OBS from the lava flow
It’s basically like an episode of the
Thunderbirds, but instead of sending
puppets to save the day, we’ll be
sending in our ROV
After freeing the helpless OBS
from the ocean floor, the second
mission was to collect three samples
of the lava flow for analysis The final
mission was to take a temperature
reading from a hydrothermal vent
For the competition, the OBS is
represented by a PVC box skeleton;
the lava is represented by eight, two
pound soft dive weights; and the
hydrothermal vent is another PVC
structure spewing hot water The
mis-sions will be discussed in more detail
later, because first and foremost we
wanted to have a working platform
The ROV-in-a-box would give us a
functional ROV that could be expanded
upon to complete the missions We
wanted to finish our basic ROV before
worrying about the details of the
missions, and with that in mind, we
popped open the instruction manual
to the first step
The Life Aquatic Meets
the Life Robotic
Now that we had a team of
mechanical engineers, structural
engineers, computer science
engineers, and many more, it wastime to pop open the ROV
When we first opened it, we werereminded of our experiences at thebeginning of every FIRST build season
— we were faced with a somewhatintimidating box of loose parts
Motors, wire, PVC, and switchesabounded, and the project might haveseemed a bit overwhelming had it notbeen for the handy instruction manual
The ROV-In-A-Box K it comes with acomprehensive manual that gives easy
to read, step-by-step instructions thatare illustrated by clear pictures
The first thing that the manualwalks you through is the construction
of the frame for the ROV The PVCbits are all nicely cut and ready to go,but the kit does not include PVCcement or primer That’s nothing apreemptive trip to the hardware storewon’t fix, and the beginning of eachstep in the manual conveniently listsany additional parts required for thestep not already included in the kit
Thankfully, this list is usually veryshort, and most of the entriesare simple tools that any self-respecting tinkerer shouldhave at the ready
The PVC frame goestogether very easily, and it’s anice thing to do first because
it already gives you a sense ofthe scale of the ROV The botwas a bit smaller than we hadinitially guessed, but there’snothing wrong with that —just ask the Thunderbirds
The next step involves theinitial wiring of the motors tothe tether The tether for the
ROV is primarily made up of speakerwires, and their 50 foot length was theperfect size for the MATE Competition.The ROV kit comes with three motorsfrom Mayfair Marine: two for the rightand left thrusters, and one for the liftthruster The motors come with easy
to install couplers for small plastic propellers A soldering iron and theassociated paraphernalia is one ofthose things not included in the kit,but once again these are essentials for every robot project that roboticistsshould have in their arsenal
After preparing the motors, thenext step is to prepare the CCD cameraand LED cluster used for lighting Theunforgiving work environment faced
by the ROV requires some extra
M OUNTED MOTORS
SERVO 08.2008 15
Rhyme of the Modern Submariner
T AU B ATES AT WORK ROV- IN - A - BOX MOTORS
Trang 16Twin T Tweaks
attention that land bound bots find
unnecessary — waterproofing The
manual suggests casting the lights
and camera in resin and gives detailed
instructions on how to do just that,
but our CCD camera and LED cluster
came already cast in the kit We didn’t
mind the assistance, and we set about
tackling the next steps
The ROV-in-a-box is a humble
robot equipped with only the
essentials: three motors, the camera,
and the lights Mounting these
essentials to the frame is also done
with PVC bits After just a few quick
cuts, the ROV was starting to look like
a real robot, but the real test was still
ahead — wiring it all up
We have to say that up until the
wiring of the control box, we were
consistently impressed with thequality of the parts included inthe kit and the clarity of theinstructions that helped to put
it all together Perhaps this initial awesomeness created aharsher contrast than waswarranted when it came towiring the robot, but we have
to say at times it becamedownright inelegant For themost part, the control boxwas fine — each thruster wascontrolled with a double poledouble throw (DPDT) switch,the main power was controlled with asingle pole single throw (SPST) rockerswitch, and the kit even came withlabels for all of the switches to denotewhich motor they controlled All ofthe switches even went into a niftycontrol box that looked downrightsleek, and all of this was quite nice
The problem, we suppose, was in the wires
We have nothing against heavygauge wires They are great for whenyou are pulling a lot of amps and theirbeefiness makes them generally easier
to solder than super thin wires Whenyou have more than three 16 gaugewires going to one leg of a switch in
a crowded control box, then size canbecome a problem This might notseem so difficult if you are properlyprepared — you can twist the ends ofthe wires together and save time andenergy by soldering once where youwould have had to solder many times
The manual, however, goes through theconnections one wire at a time, andafter the fourth wire going to the same
switch leg, you begin to wonder if you’resoldering a control box or a clown car.The large gauge wires are also stifferand when it came time to close thecontrol box, it was not exactly fun.The problem with the wires could have been minimized if theinstructions had warned about theoverpopulated legs beforehand, butinstead they go through connection
by connection and by the time yourealize there’s going to be a problem,it’s already too late Some of the TBPteam members were learning how tosolder on the ROV control box, andthese complications gave them theopportunity to learn how to desolder.For all of the grief that the size
of the wires gave us, the actual electronics of the ROV were elegantlystraightforward The relatively simplewiring even made it easy for us totrack down an electrical problemusing a multimeter Our ROV onlyseemed to work intermittently, andthe rocker switch did not seem to control the main power When wehad first installed the fuse, we hadnot done it correctly; but with theaddition of a spring, everything was
in top shape Even with the ROV effectively finished, the manual continues to be useful The manualincludes an electrical schematic for the robot and an exhaustively comprehensive parts list that detailsthe cost and vendor for every item inthe kit We would like to give somewell earned kudos to the authors ofthe manual, because they really did atop notch job Congrats!
Overcoming Hydrophobia
The ROV-in-a-box is an elegantlysimple machine Everything wenttogether so easily that it seemed thatthere had to be more to it There wasactually more to it — waterproofing Intruth, though, there was not that muchwaterproofing to be done The resincastings kept the camera and lightssafe, and the motors were designedfor underwater applications (perhapspumping, as the 500 GPH label might
ROV CAMERA AND LIGHT
T SUKASA (L) AND E RIC (R) WORK
ON THE TETHER
ROV CONTROL BOX
Trang 17Rhyme of the Modern Submariner
points for waterproofing were the
electrical connections, of which there
were not too many There were four
connections between the camera, light,
and tether, and six connections between
the motors and the tether The kit
pro-vided ample materials for waterproofing
in the way of epoxy and self-vulcanizing
rubber tape A couple layers of each
did the trick, even though the tape was
not exciting as we had anticipated
given the name — apparently the
vulcanization is pretty low key
Our previous description may have
made the construction of the ROV
seem like a breeze but, in fact, it took
several weeks of meetings So when it
finally came time to test the bot, it
was very climactic Our first tests were
to see if the motors all functioned
properly, and they spun the propellers
so quickly that we were eager to see
how zippy the bot would be in the
water It was also exciting to see the
light turn on, but we had to find a
monitor so we would check the
camera We didn’t have any extra
monitors sitting around, so eventually
we hooked it up to the television in
our dorm room (the ROV comes with
an RCA plug for output to a monitor)
The camera was downright
impressive It was black and white, but
the resolution was excellent and the
LED cluster provided perfect lighting
We have worked on other robots with
cameras like the POB robot, but the
acuity of the ROV would impress any
optometrist
Adventures With a
Laundry Cart
Everything on the ROV worked
like a charm on the safety of dry
ground, and despite these
encourag-ing signs we have to admit that we
were a little apprehensive about
putting it in the water At first, we
wanted to test the robot in one of
UCSD’s on-campus pools, but it
turned out to be a hassle to
reserve the time and space Plan B
was pretty much what you might
expect If we couldn’t test the
ROV in a pool, we’d go with the
next best thing — a laundry cart
It might sound like a wackyidea, but the residential life office
of our beloved Warren Collegehas large plastic laundry carts forstudents to cart stuff around in(probably laundry, most of thetime) It was a bit awkward tomake the request to our collegeresidential life if we could use alaundry cart to fill up with waterand test a robot in it, but thank-fully they are very accommodating
of our robot related idiosyncrasiesand gave us the go ahead to giveour ROV some swimming lessons
The small scale of the ROV madetesting in the laundry cart a lot lessawkward than it might sound Beforetaking the plunge, we equipped thebot with an ROV’s equivalent of floaties — floral Styrofoam that wasincluded in the kit
Our moment of truth turned out
to be a moment of triumph, becausethe ROV worked in the water so wellthat it seemed like a fish out of water before We had to adjust thebuoyancy with some rebar for ballastand more Styrofoam for balance, butafter just a few tries we had an ROVsitting serenely in the water with neutral buoyancy The kit also includesStyrofoam bits to adjust the buoyancy
of the tether, which led us to conclude that the folks at !nventivityreally did think of everything
Southern California Fly-Of f
Until now, the MATE Competitionhad been only a far-off goal, but
shortly after our laundry cart adventure we had to meet a deadlinethat had the potential of disqualifying
us from the competition Our teamwas registered for the internationalchampionship, and the MATE organization required that all teamsregistered for the championship prove they have a working robotbeforehand To do so, we had
to attend the closest regional competition to undergo a simple safetyinspection and to show that our ROVcould ascend, descend, and move forward, backwards, left, and right.The closest regional for our teamwas actually at UCSD, held at theCanyonview West Pool in our veryown Warren College We showed up
to the regional with confidence — therobot certainly wasn’t finished, butafter our laundry cart test we weresure it could handle the qualifying test.Our little ROV had no problempassing the test, and it was exciting togive the little bot a chance to run free
in a big pool It was also exciting to
Trang 18Twin T Tweaks
see the other teams there Some were
there to qualify like us, but others
were there to compete in the regional
The MATE Competition has two
competition classes: the Ranger class
for high school teams; and the
Explorer class for university teams and
qualified high schools The Southern
California Regional was actually a
Ranger class competition, and we
were categorically impressed by the
sophisticated robots built by the
teams The missions for the Ranger
class were slightly different than those
for the Explorer class, but it was still
exciting to see the creative ideas that
teams came up with to pick up the
crabs that their missions demanded
As for the other Explorer teams, it
seemed that our little ROV was certainlythe smallest of the bunch But onceagain we wouldn’t let that discourage
us — remember the Thunderbirds Otherteams had sophisticated control stationsstocked with monitors and videogame controllers, and there were plen-
ty of colorful ROVs that prowled thepool with ease We looked forward togetting to know more about our competition at the InternationalChampionship, but before that wehad our own ROV to finish
So Long and Thanks for All the Fish
The Southern California Regionalwas an exciting competition that
inspired us to do our best
to add the mechanismsand sensors necessary totransform the ROV-in-a-boxinto a truly competitiverobot To finish, we neededmore motors, a tempera-ture sensor, and someother miscellaneous materials, but unfortunatelythe kit would no longer be
of help — the only partsleft in the kit were someextra Styrofoam bits andsome battery connectorsthat we had to ignore in favor of thelug connectors demanded by the competition The ROV-in-a-box wasactually inspired by an ROV competi-tion — the National UnderwaterRobotics Challenge, held in Chandler,
AZ The pool next door was a lot closer than Arizona, so unfortunately
we couldn’t make it out to NURC Itwas at least nice to know that our little ROV-in-a-box had a competitivestreak !nventivity also shows somegreat community involvement by being
an active supporter of NURC, the MATE Organization, and even FIRST Robotics
UCSD’s Tau Beta Pi members alsohave a competitive streak, and afterfinishing the ROV-in-a-box they wereeager to go off script We would all getour chance to be creative, because wehad to design and build mechanismscapable of freeing the OBS, retrieving thedive weights, and taking the temperaturereading But there’s so much more tocome than additional mechanisms —total redesigns, technical reports,scavenging from other robots, and theclimactic International Championshipall await in the exciting conclusion inthe next Twin Tweaks! SV
S OUTHERN C ALIFORNIA R EGIONAL L ETTING THE ROV ROAM
RReeccoom mm meennddeedd W Weebbssiit teess
Trang 20Q.Our club is making a club robot based on the
Atmel ATMEGA168 About half of the members
use either Mac OS X or Linux, not Windows What
can we use to program our robots that isn’t Windows only?
A.Many fellow robot makers out there know that I am
a Mac fan and go out of my way to do just what you
are asking about Sometimes there is no choice and
for that, I have a Windows laptop BUT, in this case you
do indeed have an option: avr-gcc Avr-gcc is gcc, the
open source C and C++ compiler of choice for many
environments, customized for AVR programming This
environment can be used on Windows (usually Winavr),
Linux, and the Mac OS In this column, I’m going to detail
where to find the parts, how to install them, and how to
configure it all to program your robots These packages
usually want OS X 10.3.9 minimum; I recommend 10.4
(Tiger) to play in (Mostly because that is what I used —
that and Leopard — so I know that it works.)
Setting up a Mac to program
AVR microControllers
There are three pieces of the puzzle that you will
need to get:
1) Macpack AVR: This is avr-gcc and has all kinds of utilities
and goodies Top onthe list is avrdude,one of the most popular AVR programmer programs You canfind this Mac-friendlyinstall package here:
www.obdev.at/
products/avrmac pack/download-de.
recent version It will come in a “dmg” package
2) Eclipse Europa for C/C++ programming This is a based IDE that can be customized for just about anything.Like gcc, it too is open source based You can find the latest
Java-here: www.eclipse.org/downloads/ Get the one for
C/C++ development This will be a gzip’d tarball (in theUNIX parlance) that your computer will know about
3) AVR plug-in for Eclipse This customizes the Eclipse IDEfor use with the AVR toolchain You can find it here:
http://avr-eclipse.sourceforge.net/ I got the plug-in
directly from the web page; they tell of a way to get it fromEclipse too, but call me cautious, I went for the sure thing
Installing Macpack AVR
To install Macpack AVR, simply double-click on thedownloaded file; in my case, it was called AVRMacPack-20080514.dmg It will mount a drive called AVRMacPack
on your desktop; in there, you’ll find a readme file and aninstall package Read the former and double-click on the latter to install avr-gcc (see Figure 1)
The installer is very nicely done and, of course, youmust enter your admin password since this is going to beinstalled in UNIX system directories In this case, in/usr/local/AVRMacPack You are now delving into the realm
of command line interfaces, so take a deep breath and look
in your Applications/Utilities folder and find “Terminal.”Install it on your dock; you’re going to be using it a bunchnow Avr-gcc, via AVR MacPack, has the version 3 and version 4 compilers Lots of the new work is being done inversion 4, but some like to use version 3 I recommend thatyou just issue this command on the command line in yourterminal “avr-gcc-select 4” and use the latest Figure 2shows how this dialog might look Remember, all of this isfree, so you won’t get much hand-holding as you do with afull-fledged IDE, but we’re not done setting up Let’s waituntil we get Eclipse and the AVR plug-in installed before we
Tap into the sum of all human knowledge and get your questions answered here! From software algorithms to material selection, Mr Roboto strives to meet you where you are — and what more would you expect from a complex service droid?
Trang 21Installing Eclipse Europa
When you have downloaded the Eclipse install
package, you’ll see that it isn’t the friendly type of
Macintosh installer It is a gnu zipped tarball Not to
worry, your Mac can handle this package easily Move
the install file to your Applications directory and
double-click on it After you double-double-click the install file, a couple
of windows will pop up and then go away When those
are all done, you will have an Eclipse directory in your
Applications directory Inside there you will find the
Eclipse program You will want to have easy access to
this program if you do a lot with robotics, so drag the
Eclipse icon on to your dock next to your Terminal icon
Installing the Eclipse AVR Plug-in
We have two ways we can install the AVR plug-in
One is to take the file that we’ve just downloaded and
unzip it in the Eclipse directory by moving the file to the
Eclipse directory and double-clicking on it This is the direct,
brute force method If you have Eclipse running, then
restart it after you unzip the file
The second way is for you to use Eclipse itself to install
the plug-in Since you’ve just seen the brute force method —
which is easy, let’s look at the elegant way — through the
Eclipse IDE Click on the Eclipse globe on your dock (you did
put it there, right?) and wait for it to start When it first
comes up, you will see the screen shown in Figure 3 asking
you where to put the workspace files It usually wants to
put them in the Documents folder; I have no objection,
so just press OK
Next, navigate to Help-> Software Updates -> Find and
Install as shown in Figure 4 to get to the Feature Updates
dialog and click the Search for new features to install
button, then click Next Click the New Remote Site button
and fill in the dialog box as shown in Figure 5
There are lots of Next, Finish, and I Accept type of
buttons to push; remember to actually select the plug-in
when you see its checkbox on the screen! When you have
navigated this endless selection of screens, licenses, and
warnings about unsigned downloads and hit your final
finish button, you will see the window as in Figure 6
Whew! Now restart Eclipse and let’s get to work!
Using avr-gcc, Eclipse, and the
AVR plug-in to write your code
I’ve written a toy program that blinks some LEDs on
one of my educational robot boards All this program will
do is blink two LEDs alternately This article isn’t about how
to write AVR programs — you can learn that anywhere (if
enough ask, I’ll be happy to write such an article) — but
how to use this set of tools on your Mac to do it, so I’m
not going to explain the code beyond using the tools to
write, compile, and download it Now, let’s create an AVR
robot project!
Creating a Project
Navigate the File -> New -> C Project and fill in the
Project name asshown in Figure 7
Note that the AVRCross TargetApplication is automatically chosen We’ll usejust that; pressNext to set everything up You will get a configurations screen thatshows a Debug and RELEASE configuration We’ll take thedefaults, but before we’re done here, click the AdvancedSettings button so that we can choose our processor andclock speed This window will look like Figure 8
SERVO 08.2008 21
Figure 2 Avr-gcc configure example.
Figure 3 Workspace dialog.
Figure 4 Get a plug-in.
Figure 5 Install the AVR plug-in.
Trang 22In Figure 8, you see that I’ve selected the processortype and the clock speed Study your product document foryour chosen AVR microcontroller carefully to select its clockspeed and other settings we’ll discuss later I selected theAVR Target Hardware to set these features If you look atthe Environment selection (after you click on the triangle toopen the C/C++ Build category), you’ll see that the IDE hasalready found your AVR MacPack directory and has seteverything up for us! Totally cool! We’re ready to make aprogram and project.
When we created our project, a folder was createdcalled Documents/Workspace/Tiny26 Here, you can drop
or create your C files for your projects If you copy filesthere, go to the Eclipse IDE in the Explorer Window andright-click on the project — in this case, Tiny26 — selectRefresh, and the project will pick up the files If you aremaking new files, then just remember to save them there.When you have everything ready to go, it is time to buildyour project At this time, the Debug configuration isn’tall that useful since it doesn’t create a hex file So, makesure you are using your Release configuration To do this,navigate Project -> Build Configuration -> Set Active ->Release
To build, you can navigate Project -> Build All, use the
<propeller> B hot key, or press the Build All icon on thetoolbar (looks like a page with 1s and 0s on it.) If there areany problems in the build, the errors will show up in theConsole window at the bottom of the IDE window To go
to the error line in your source code, click on the Problemswindow and double-click on the error; the IDE will take you
to the line See Figure 9 for a condensed view of the IDEand those tabs
You’ll note a tab called AVR Device Explorer; this is
a very nice utility that shows you all of the hardware registers, I/O ports, and interrupt sources and their namesfor your chosen microcontroller
Programming a Microcontroller
I’ve reached the end of my allotted space now In mynext installment, I will show you how to configure a programmer board — an AVRISP 2 to be specific — to program your microcontroller, and how to add a tool toyour Eclipse IDE to program at a press of a button SV
Figure 9 The Eclipse IDE window.
Figure 6 Install complete.
Figure 8 Configure microcontroller settings.
Figure 7 Start a project.
Trang 23SERVO 08.2008 23
Trang 24Know of any robot competitions I’ve missed? Is your
local school or robot group planning a contest? Send an
email to steve@ncc.com and tell me about it Be sure to
include the date and location of your contest If you have a
website with contest info, send along the URL as well, so we
can tell everyone else about it
For last-minute updates and changes, you can always
find the most recent version of the Robot Competition FAQ
at Robots.net: http://robots.net/rcfaq.html
— R Steven Rainwater
Aug uss tt
9 RoboCountry
Takamtsu City, Kagawa, Japan
ROBO-ONE style humanoid robot combat
www.dragoncon.org
TBA DPRG Robot Talent Show
The Science Place, Dallas, TX
Autonomous robots demonstrate their talents
TBA Robots at Play
City Square, Odense, Denmark
Robots compete to demonstrate playfulness andinteractivity
www.robotsatplay.dk
Sep ttemb err
6 ROBO-ONE Helper Robot Project
Kawasaki City, Japan
Teleoperated robots compete at performingcommon household tasks
http://getrobo.typepad.com/getrobo/2008/
05/new-helper-robo.html or
www.robo-one.com/robo_help/robo_help html
17 Powered by Sun
Ostrava, Czech Republic
Just as the name suggests, this is a competition ofsolar-powered robots
http://napajenisluncem.vsb.cz
18-19 Korea Intelligent Robot Contest
POSTECH Gymnasium, Pohang City, Korea
This competition includes several events forgeneral-purpose intelligent robots and oneevent for specialized cleaning robots
http://irc.piro.re.kr
20 Robotour
Prague, Czech Republic
Autonomous robots must navigate in a park
www.robotika.cz
20-21 RoboCup Junior Australia
Scitech Museum, Perth, Australia
Events include robot dance, robot rescue, androbot soccer
www.robocupjunior.org.au
27 Elevator:2010 Climber Competition
To be announced (see website for updates)
Autonomous climber robot must ascend a scalemodel of a space elevator using power beamedfrom the base
www.elevator2010.org
Send updates, new listings, corrections, complaints, and suggestions to: steve@ncc.com or FAX 972-404-0269
Trang 2529 Microtransat Challenge
Viana do Castelo, Portugal
This event is a transatlantic autonomous robot sailboat race
www.microtransat.org
TBA BotTrot 4Bottle Race
To be announced (see website for updates)
Robot must navigate a figure-8 course Video ofrobot completing the course must be submitted
by the contest date for judging
www.botmag.com/articles/06-10-07_4bottle_
robot_race.shtml
TBA Robothon
Seattle Center, Seattle, WA
Events include Robo-Magellan, MicroMouse, Line
Following (two categories), Line Maze, WalkingRobot Race, Mini Sumo, and 3 kg Sumo(autonomous and RC)
www.robothon.org
Occ tto berr
24-26 Critter Crunch
Hyatt Regency Tech Center, Denver, CO
Robot combat — 2 lbs and 20 lbs eventcategories Autonomous and Remote-Control.Starting size of 12” x 12” x 12” Expansion duringevent okay Weight limit of 20 lbs Power sourcemust meet OSHA requirements for indoor use.Awards for 1st, 2nd, and 3rd place, as well as
“amusing and arbitrary accomplishments.”
www.milehicon.org/critrule.htm
SERVO 08.2008 25
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Trang 26Micro Metal Gearmotor Bracket
Pololu introduces its
compact bracket for
convenient mounting of
the popular Sanyo-style
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metal gearmotors The
plastic brackets are custom
made to securely hold the
metal gearmotors in place
while enclosing the otherwise
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for easy installation
For further information, please contact:
Solar-Breeze Intelligent Solar
Robot Pool Skimmer
is the first of its kind,
hoping to bring pool
owners on board with
the idea of having
“greener” pools Solar-Breeze uses a unique solar-power
system that allows it to skim your pool surface all day
while the sun is shining, collecting debris from the pool
surface and preventing it from sinking to the bottom
Since it keeps dust and debris from sinking to the
bottom of the pool, the time required to run the pool
pump is significantly reduced, thus making pools cleaner
and clearer, so pool pump usage should go down A
Chemical Dispenser (for commercial solid pool chemical
tablets) is included in the Solar-Breeze design since
dispensing chlorine or clarifiers evenly and randomly overthe surface makes the chemicals far more efficient thanwhen spread by other means
Mr Clock Radio
Mr Clock Radio —manufactured by GeeWizEntertainment — is the world’s firstanimated talking robotic clockradio Press the snooze button and
he will tell you the current time,
or press the fortune teller button and ask him a questionabout your future Mr ClockRadio has working eyes, a multi-directional motorized head, as well as a motiondetector Aside from AM/FM radio, Mr Clock Radio canalso play music from other devices using the MP3 playerjack and it comes with 50 different wake-up shows.For further information on either of these two products, please contact:
LEGO® Education WeDo
LEGO Education — The LEGO Group’s educational division
— introduces LEGO® Education WeDo™, a new productthat redefines classroom robotics, making it possible forprimary school students 7-11 years of age to build andprogram their own solutions Bridging the physical worldrepresented by LEGO models, and the virtual worldrepresented by computers and programming software,LEGO Education WeDo provides a hands-on, minds-onlearning experience that actively involves young students
in their own learning process and promotes children’screative thinking, teamwork, and problem-solving skills
“Building upon our successful 10-year history ofbringing educational robotics to middle, high school, anduniversity classrooms with the award-winning LEGO MIND-STORMS toolset, we are excited to extend this expertise
to benefit an even younger audience,” said Jens Maibom,vice president of LEGO Education “With a progressivelycompetitive global economy, we know it is imperative to
RobotShop, Inc
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Trang 27provide even younger children and their teachers with
curricular-relevant, easy-to-implement educational materials
to spark children’s interest in all manner of subjects.”
LEGO Education WeDo encourages teachers to issue
curriculum-based challenges for students to solve
Working in teams, children invent their own solution by
building a LEGO model and programming it to perform a
certain task Cause and effect learning is enhanced by
the models remaining tethered to a computer; similar to
scientists in working labs, children can test and adjust
their programming in real time After reflecting on what
did and did not work, students can consult with peers,
adapt programming, adjust models, or begin again
Newly-designed software developed by National
Instruments makes programming easy and intuitive and
students quickly learn that they can solve real-world
challenges by tinkering with building and programming
Developed to cover a broad range of curriculum
areas, WeDo sample topics include Language and Literacy:
narrative and journalistic writing, storytelling, interviewing
and interpreting; Mathematics: measuring time and distance,
adding, multiplying, estimating, using variables; Science:
transmission of motion, working with simple machines,
gears, levers and pulleys; Technology: programming,
using software media and creating a working model
The complete LEGO WeDo package includes:
• 158 brightly colored LEGO elements, including gears
and levers
• One LEGO USB hub connects directly to a Mac/PC
laptop, desktop, OLPC XO, or Intel Classmate computer to
allow control of hardware input (tilt and motion sensors)
and output (motor), thereby bringing models to life
• One motor, one motion sensor, and one tilt sensor
• Drag-and-drop, icon-based software that provides an
intuitive and easy-to-use programming environment
suitable for beginners and experienced users alike
• CD-Rom provides up to 24 hours of instruction
Teacher notes and glossary are also included
For further information, please contact:
New Power ful, Versatile, and
Easy-to-Use Motor Controller
The CS110100 from A-WIT Technologies is a
multi-functional, high-current two-axis motor driver
with motion control It features on-board, over-current
protection and over-temperature protection Maximum
DC current per motor channel is 10A For DC motors
with incremental encoder feedback, the CS110100 is
able to drive the motor in velocity mode or position
mode For DC motors without encoder feedback, theCS110100 is able to drive the motor via PWM The on-board motion processor allows users to changemotion control parameters, such as PID parameters,motor configuration, etc
The motor controller has three operating modes: UARTMode — the CS110100 is able to interface with a hostcontroller, such as the C Stamp (sold separately) via theserial port In this mode, the CS110100 will receive ATcommands sent from the host controller to change its speed,position, etc; I2C Mode — the CS110100 is able to interfacewith the host controller via an I2C port The I2C address isselectable from 0x70 to 0x7E The host controller is able tocontrol the CS110100 by I2C commands; Radio Control PWMMode — the CS110100 can be connected to RC receiversdirectly so that the motor speeds can be controlled bythe RC remote
controller In this mode, users may choose to run the twomotors under coordinated mode or independent mode.This mode is especially useful in building RC remoterobots Some technical specifications are:
• Power Supply Voltage: 7V-24V
• Power Consumption: 2W (without motors)
• Processor Speed: 40 MHz
• On-Board Motion Control for brushed DC Motors (Velocity Mode, Position Mode)
• On-Board MOSFET PWM drivers
• Able to drive Two DC motors at the same time
• MAX DC Current Per Motor = 10A
• PEAK DC Current Per Motor = 20 A
• On-Board fan for efficient heat dissipation
• Protection for Reverse Polarity, Over-Current, andOver-Heating
• Controllable by RC Servo PWM pulses directly
• Controllable by a serial interface
• Controllable by an I2C interface
• User can control the PWM output to the motors directly
• Switching power supply for lowest battery powerconsumption
A-WITTechnologies, Inc
Website: www.LEGO.com
The LEGO Group
Trang 28Featured This Month:
Mall of America Rotunda
Rumble by Aaron Nielsen
ROBOT PROFILE – Top
Ranked Robot This Month:
33 Touro by Kevin Berry
For many builders, combatrobotics is about pushing theengineering envelope You know,how many extra volts can wehammer through the systembefore it flames out? But since Iprimarily work with studentrobotics programs, I have takenthis concept in a different direction Given the pressure onschool budgets these days, I havebecome adept at “pushing theeconomic envelope.” That is, howtiny a budget, how minimal theshop access, how few work hours can still translate into an
effective fighting machine?Ladies and gents, I think wehave an answer With our latestbuild, I believe we have attainedclose to Absolute Zero onresources, and still cooked up a
30 pounder that went 2-2 in itsdebut competition
I have been teaching a middle school level robotics program for years, where webuild one and three pound combat machines It’s an after-school program, so when I proposed doing a bigger build Iknew we would only have a total
of about 15 workhours Also, the Tech
Ed teacher whohoped to help me hadother commitments,
so there would effectively be noaccess to the schoolshop Fortunately, Ihad a great volunteerassistant, and a talented bunch ofkids sign up; all
Trang 29SERVO 08.2008 29
veterans of my small robot classes,
some of them also having
experience on my Destination
Imagination teams
The first session I tossed out a
bunch of stuff from my workshop:
cordless drills, cordless screwdrivers,
Barbie Jeep gearboxes with and
without removal of the final gear
for a “speed hack.” I had the kids
weigh them, and test the amp
draw running free and at stall They
liked the standard Barbie gearboxes,
which was fortunate as I had a box
full of them
Next, I had them draw up some
materials stats, such as weighing
and measuring various thicknesses
of plywood, aluminum, Lexan, and
foam; and calculating how heavy
a robot would be if it were made
of each material and had some
plausible dimensions for this project
I suggested a simple pushy/wedge
bot for a first build and at the end
of session 1, we had a shopping list
It helps a great deal to have a
workshop full of junk The expensive
components such as speed
controllers and batteries were all
lying around from years of previous
projects In fact, I had built
something very much like the kids’
design a few weeks earlier when
the high school drama department
needed a robotic goat on rather
short notice
Speed controllers are kind of
the soul of a robot That being the
case, it appears that some Eastern
religions are correct about
reincarnation, as electronics for this
project had lived previous lives as
everything from the 340 pound
“Newton’s Claw” down to the candy
delivering “Pumpkin Bot” that
scared my trick-or-treaters a few
years back
Our basic drive system was a
pair of Barbie Jeep gearboxes,
hubbed to eight inch rubber wheels
that were about a buck at the local
surplus shop We added a pair of
7.2 volt R/C car batteries wired in
series for 14.4 volts; a mild over-volt
for the motors but no problem for
the Victor 883 speed controllersthat I pulled out of RoboGoat
One of the kids brought a bigslab of half-inch plywood that made
up the basic frame and base armor
I tossed in a broken snow shovelblade for the pusher
So far, not much ground breaking technology, but a serviceable machine We did get abit more creative with the secondaryarmor, which was a tricky composite
of dense foam, 1/32” Lexan in twolayers, and plenty of Gorilla Tape Infact, two rolls of this stuff at about
5 bucks each were the singlebiggest expense of the project
The new machine — dubbedSUMO for its final pudgy look —was controlled with a 75 MHz
JR receiver and an IMX mixer forsimpler handling
With time to spare, we actuallystarted a second 30 pounder, with
a working name of NSP (No SpareParts) This was to have a similardrive system and an active weapon
But alas, with two sessions to
go a problem arose Spring arrived
Middle school boys are not the mostfocused primates on their best days,and warm weather, track practice,and the attire of middle school girlsall became major distractions So,
we scrapped NSP at the half-builtstage and upgraded SUMO a bit
Basically, we ended up swapping in 24 volts’ worth of NiCdbatteries, which made SUMO a veryeffective pusher
In actual combat, lessons were
— as usual — quickly learned The
“close enough” fit between the axle
and shaft collar proved to be notquite close enough, and we lost onematch when one hub slipped offthe output gear of the gearbox Thedesign was a bit tight, making emergency repairs difficult Thiscould have been avoided, as wewere four pounds underweight
(Note to self: Next time, bring anaccurate scale The one from theschool nurse’s office must havebeen jumped on too often.)The composite armor provedmore than sufficient against flail and blade, and with some additionalrefinements will make more
appearances in future projects
The kids all had a fun time, andthe relative success of the project islargely a tribute to their outstandingdriving skills
Total out-of-pocket costs came
in under $40, which at just over adollar a pound must be some kind
of record True, you could claim that
we cheated by raiding my robotgraveyard/workshop But I suspectthat with a bit of eBay trolling anddumpster diving, it would be possible
to do the entire project includingelectronics and radio equipment forsomewhere around $150
SUMO’s drivetrain The build team pauses for a photo-op.
SUMO the pushybot.
Trang 30All in all, a fun project, with lots
of opportunity for creative tinkering
and for on-the-fly troubleshooting
and repair And at this kind of price,something very possible on a widerbasis Without an active weapon,
we could have just as easily fought
in the school parking lot as in anexpensive arena SV
Results May 4 –
Jun 15, 2008
SRJC Day Under The Oaks was
held May 4th in Santa Rosa, CA
Fifteen bots were registered
Presented by SRJC Robotics Club
Robots Live presented an event
May 17th–18th at the NationalSpace Center in Leicester, England
CCR Memorial Day Qualifier was
held May 24th in Greensboro,
NC Sixteen bots were registered
Presented by Carolina Combat
Robots
2008 Fighting Robots UKFeatherweight Championshipswere held May 24th–25th inBirmingham, England Presented
in Guildford,England Forty two bots wereentered Presented by RoamingRobots
Upcoming Events for Aug-Sept 2008
HORD Fall 2008 will be held bythe Ohio Robot Club in
Strongsville, OH
on September13th Go to
www.ohio robotclub.org
for more details
Ashow at Midlands MCM Expowill be in Telford, Shropshire,England on September 13th–14th
Go to www.robotslive.co.uk for
more details
Ashow at the Huddersfield Sport Centre will be held onSeptember 20th–21st in
Huddersfield, West Yorkshire,England Go to
www.robotslive.co.uk for more
details
RobotCombat 2008will be held byWestern AlliedRobotics inSeattle, WA on September 21st Go
to www.westernalliedrobotics.
com for more details SV
In the post-televised robotic combat
era, it’s good to see the sport
can still draw a standing room only
crowd Such was the case at the
Rotunda Rumble held at the Mall of
America in Minneapolis, MN, wherethere were at times four floors ofspectators cheering for more
The event, sponsored bySynergy Robotics Entertainment and
the Midwest Robotics League, washeld on April 26th and 27th, and itwas divided into two major classes:student and professional Beyondthat, there was the usual weight
Trang 31class spread starting with the cute
‘n cuddly ant weights (one pound)
and ending with the “that just
might rip your leg off”
feather-weights (30 pounds) As for fight
structure, the 15 pound student
Battle Bots IQ (BBIQ) class fought
in classic bracket style, while the
remaining classes fought round
robin
Taking center stage was the
BBIQ half of the tournament where
teams of students — some coming
from as far as Williams, AZ —
displayed their prowess in
mathematics, science, and
engineering by vigorously applying
it to their opponents in the form of
stored kinetic energy When
comparing the tournament
designations of “student” versus
“professional,” one might be tempted
to assume that the “student” class
was somehow inferior That would
be the thought of someone about
to be resoundingly beaten by
something conceived of, designed,
and built by a 10th grader
Even the schools that opted tostick to the “classic” concepts ofrobot combat (wedges and bricks)managed to bring something new
to the table Billet — a simple brickbot to the untrained eye — featuredmagnets to increase its tractiveeffort Another bot — dubbedCatapult — boasted the most JamesBond worthy weapon What I mean
is they opted to forgo poweringtheir flipper with a mere tank of airand instead chose to mount a complete working air compressorright on the robot so they couldrecharge on the go Frankly, I stillhave no idea how that whole apparatus worked, but it did Eitherway, enough about the event Let’stalk about results
The ant weight battles wereless of a tournament and more of aone-on-one brawl for supremacybetween ANTI (vertical spinner) andthe peculiarly named UnderWHERE(horizontal spinner) It was a friendly
rivalry, and there were only two ofthem; thus, they opted to pummeleach other on an exhibition basis.Moving on to the beetleweights (three pounds), third placewent to Rampage Productions’
wedge bot, Screw U, which mightnow hold the title of “bot namethat gets the most snickers whenannounced over the PA.” Secondplace went to Team Bobbing forFrench Fries’ wooden wonder, BoxyBrown, a wooden box with a dowel
on the front and a driver with anaffinity for trash picking After Boxytook a bit of a beating from the firstplace finisher, his driver disappearedfor a bit and, upon his return,proudly declared he had found aplastic bottle in the trash and commenced attaching it to theremains of his bot’s keep-away-stick.First place went to team Python and their bot, Strychnine, which can be best described as threepounds of precision machined, barspinning death
SERVO 08.2008 31
Humdinger versus Pox Guess which
of these bots is having a bad day?
Studley Do-Right versus a distressing
amount of kinetic energy (Murder-Go-Round).
SUMO and Edge of Madness pause to ponder one another.
ANTI versus UnderWHERE — two tiny brushless spinners enter.
Only one leaves.
Trang 32Jumping up to the 15 poundBBIQ class, the rule for the day was
vertical spinning egg beaters rule,
with one exception That exception
was third place finisher No Remorse
from Valley Middle School in Apple
Valley, MN No Remorse was a
wedge bot that proudly proclaimed
it had no regrets (except perhaps
not finishing first or second) The
story behind second and first place
is a little more amusing Chucker,
from St Cloud Technical College in
Minnesota, and Humdinger 2, from
Buffalo High School (also in
Minnesota) were both armed with
egg beaters and spent the duration
of the Rotunda Rumble putting
various items, including themselves,
into low orbit Interesting fact: The
creators of Chucker and Humdinger
2 used to be on the same team
Thus, when they both found their
way to the finals, the ensuing battle
was the robotic equivalent of
Obi-Wan Kenobi facing off with Anakin
Skywalker It was three minutes of
sheer pandemonium to see who
was stronger in the force, but the
results showed that Humdinger 2
was the master and, as such,walked away with $2,500 in merchandise (including a GEARS kitdonated by GEARS) for first place
Chucker would have to content himself with being the apprentice
Since they were able to make itthrough the entire BBIQ tournament
on Saturday, there was a secondBBIQ tournament on Sunday foranyone who could still cobbletogether a working robot Takinghome first place ($200) and somevindication for Saturday was noneother than Chucker In second wasUppercut built by John GlennMiddle School in Maple Wood, MN
In an honorable third was DeathStar deployed by PACT CharterSchool in Ramsey, MN (I’d trot out
another Star Wars metaphor, but
I’m afraid we used them all up inthe last paragraph.)
Among the 30 pound big boys
of the event, third place went toTeam Nerd Academy and theirwood, plastic, shovel, Gorilla Tapecomposite push bot, SUMO (SeeTim Wolter’s build report on SUMO
in this month’s Combat Zone.) In
second was team RampageProductions’ Whop Rivet, an articulated flail spinner And bringing home first place and $500
in prizes was veteran driver DickStuplich from Team Killerbotics andhis wedged-wonder, Pyromancer Even more impressive was thatPyromancer was fighting with theproverbial arm behind the back, asthe flame based weaponry, and,consequently, his flamethrower wasnot allowed at the Mall of America
If anyone happens to think that’ssilly, I would like to point out twothings One, every other store in theMall of America sells 100% cottonshirts Two, 100% cotton shirts burnquite well (Your honor, the defenserests.)
All in all, it was an impressiveevent which boasted an excellentturnout in terms of both buildersand bot watchers Better still, plansare in the works for a similar eventnext year We’re looking forward
to it SV
All the pictures were taken by Deb Holmes
of the Midwest Robotics League.
The power switch is one of the
most overlooked yet critical
parts of a combat robot
Paraphrasing the Robot Fighting
League rule set, all robots musthave an easily accessible power
● by Chad New
PARTS IS PARTS:
P wer Switches
Trang 33achieving third place Afterwards,
it won Brazil’s III Winter Challenge
and VI Robocore ENECA – both in
2006 In 2007, Touro won a
RoboGames gold medal and kept
both Brazilian competition titles
TOP RANKED ROBOT THIS MONTH
Touro flips Orion 3 during the
2007 Winter Challenge final match.
Photo courtesy of Robocore.
switch that can be used to turn on
and off the robot safely, quickly,
and easily
During the mad dash of event
preparation, builders often neglect
this critical component I have seen
dozens of fights lost due to a power
switched being tripped during a
hard hit, links falling out because
of poor design and placement,
and even fights lost simply because
of not turning the switch to the full
on position
Given the importance of this
component, it should be factored
into your robot’s design previous to
the final hours of your build Power
switches can be made very simple
or complex; what you decide to go
with will depend mainly on available
space and budget
It is my opinion that the two
best options for a power switch are
a removable power link which any
builder should be able to easily
make, or the Team Whyachi ready —
made power switch line
A removable power link is easily
made by creating an open on the
negative side of your main power
line which can be closed by inserting
the plug, thus completing the circuit
and turning the robot on Turning
the robot off is as simple as yanking
the plug out which puts the open
back onto the line The link can be
made of whatever youwant I find, however,it’s easiest to use a set
of Deans Ultra Plugs
I simply wire the femaleend into the power anduse the male end as the plug; that’s it Thisswitch should cost youless than $5
The other option is
to buy a ready-made switch fromTeam Whyachi They are made verysolidly featuring a UHMW body withcopper contacts inside which youare able to make and break contactwith by adjusting an internal screw
Loosening the screw turns the robot
on while tightening breaks the copper contact and shuts the poweroff They also come in a
variety of sizes to fityour needs If you havethe budget for this item,then it may be a soundinvestment of about $50
No matter whatpower switch option youdecide to go with, the
most important thing is to put someforethought into it
Be sure to consider its placement so you have easy access to it and so it is protectedfrom your opponents Rememberthat one shot to this part can takeyou out of the match, so treat
it well SV
PHOTO 1 A Team Whyachi power switch Simply insert the wrench and turn on or off.
PHOTO 2 A removable link made from Deans Ultra connectors A simple, easy, and cheap solution to your power switch needs.
● by Kevin Berry
Trang 34walls and 8 mm (approx 5/16”)
thick top and bottom
● Drive: Two MagMotor S28-150s
and Team Whyachi TWM3M
gearboxes
● Wheels: Two Colson 6” x 1.5”
tread, mounted on aluminum
hubs
● Configuration: Two wheel drive
with tank mixing
● Drive ESC: Two IFI
Victor HV-36s
● Drive batteries: Two
24 VDC, 3,600 mAhBattlepacks
● Weapon: 12 kg
(26.5 lb) 304 stainlesssteel drum, with two1” x 1” S7 tool steelteeth and 1.5”
● Weapon ESC: Team Whyachi C1
Contactor trigged by custom-madeelectronics
● Armor: 3 mm (approx 1/8”)
6Al-4V titanium with Kevlar underneath; also 5 mm (approx.3/16”) 304 stainless steel
● Radio system: Spektrum DX6
● Future plans: Work hard to stay
on top
● Design philosophy: As a rule of
thumb, the design is as simple aspossible; our goal was to build acompact, strong, and reversiblerobot After 2006, it has undergoneminor revisions to become evenmore simple and powerful
● Builders bragging opportunity:
We don’t like to brag, we like to seeour robots in action!
● Future plans: Four wheel drive
version SV
All fight statistics are courtesy of BotRank
(www.botrank.com) as of June 14, 2008.
Event attendance data is courtesy of
BotRank and The Builders Database (www.
buildersdb.com) as of June 14, 2008.
Touro’s inside
Photo courtesy of RioBotz.
Weight
Class Bot Win/Loss Weight Class Bot Win/Loss
150 grams VD 26/7 150 grams Micro Drive 7/1
1 pound Dark Pounder 44/5 1 pound Dark Pounder 23/3
1 kg Roadbug 27/10 1 kg Roadbug 11/4
3 pounds 3pd 48/21 3 pounds Limblifter 12/1
6 pounds G.I.R 17/2 6 pounds G.I.R 11/2
12 pounds Solaris 42/12 12 pounds Surgical Strike 17/7
15 pounds Humdinger 2 29/2 15 pounds Humdinger 2 29/2
30 pounds OffensiveTotally 43/13 30 pounds Billy Bob 12/4
30 (sport) Bounty Hunter 9/1 30 (sport) Bounty Hunter 9/1
60 pounds Wedge of Doom 43/5 60 pounds Texas HEAT 11/4
120 pounds Devil's Plunger 53/15 120 pounds Touro 10/0
220 pounds Sewer Snake 43/12 220 pounds Sewer Snake 11/5
340 pounds SHOVELHEAD 39/15 340 pounds Ziggy 3/0
390 pounds MidEvil 28/9 390 pounds MidEvil 3/0
Rankings as of June 14, 2008
History Score is calculated by perfomance
at all events known to BotRank
Current Ranking is calculated by performance at all known events, using data from the last 18 months
History Score Ranking Touro – Currently Ranked #1
Historical Ranking: #7 Weight Class: 120 lb Middleweight Team: RioBotz
Location: Rio de Janeiro — Brazil
BotRank Data Total Fights Wins Losses
Lifetime History 16 14 2 Current Record 10 10 0
Photo courtesy of Robocore.
Trang 35CONFERENCE & EXPO , 08
NOV 18-19, 2008
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Join the International Technical Design and Development
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QValuable networking opportunities that put you in touch with peers, industry experts and up-and-coming talent
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For Information on Sponsorship and Exhibiting Opportunities , contact Ellen Cotton at ecotton@ehpub.com
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Listing as of July 7, 2008 For a current list of participating companies, please visit
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Plus
Trang 36My first serious hobby servo controller was built
around an LM556 dual timer IC with a potentiometer
at the end of a joystick acting as the hobby servo
controller input After discovering PIC microcontrollers,
my next generation of hobby servo controllers got a bit
more flexible as I could control the hobby servo PWM
signal — and thus the servo itself — with both firmware
PHOTO 2 This is the real McCoy There are other XC2C64A programming alternatives However, this CPLD and FPGA programming device is fully supported by the Xilinx ISE WebPACK firmware generation package You can purchase this tool
The hobby servo is an amazing device The typical hobby servo is a collection of plastic or
metal gears driven by a DC motor, which is under the control of a specialized motor driver IC and a feedback potentiometer Back in the day, one would find hobby servos in most every model airplane and model boat If you really put a brain cell to it, radio-controlled model
planes, cars, and boats are actually specialized types of robots that depend greatly on the controlled motion provided by a hobby servo Hobby servos don’t care who drives them as long as they are driven with a specifically
timed PWM signal So, it’s not so strange
that the ubiquitous hobby servo has
rotated its way into today’s
microcontroller-controlled robotic ramblers.
PHOTO 1 This Xilinx CPLD development board contains everything you need to put the XC2C64A
on the air The idea is to put down and test your XC2C64A design on this board before building up the final hardware that will be dedicated to your XC2C64A project.
Trang 37and a potentiometer As time passed, PICs got more
sophisticated and began to include on-chip PWM
subsystems that could be programmed to effortlessly
service a hobby servo while doing other things at the same
time This month, we’re going to add yet another hobby
servo controller type to our list This hobby servo controller
variant is based on a Xilinx XC2C64A CPLD If you are CPLD
challenged, fear not The April and May 2008 issues of
Nuts and Volts contain introductions to CPLD hardware and
firmware In fact, we are going to “reuse” that Nuts & Volts
64A CPLD hardware in this month’s discussion There are
lots of details we need to cover So, let’s get started
Doing Some Servo Math
The typical radio-controlled servo system consists of a
transmitter, a receiver and multiple servos Most advanced
microcontrollers that contain on-chip PWM subsystems only
provide up to two independently controlled PWM output
channels If you only need to control a couple of hobby
servos and your selected microcontroller can drive its PWM
outputs independently, you’re covered However, if you
need to drive a greater number of hobby servos, you’re
going to need some help That’s where the 64A
CoolRunner-II CPLD comes in
In the pages of those issues of Nuts & Volts that I
steered you to earlier, we built up the basic CPLD hardware
configuration you see in Photo 1 exactly as it is represented
in Schematic 1 The pinned-out CoolRunner-II CPLD is
programmed via its JTAG port using a Xilinx-compatible
CPLD programming device To raise the chances of project
success, I like to use the official programming tools offered
up by the manufacturer For the 64A, those programming
tools include the free Xilinx ISE WebPACK CPLD/FPGA
firmware generation tool and the Platform Cable USB
hardware programming tool shown in Photo 2
A microcontroller uses its system clock to assist in the
generation of PWM signals We’ll also need a clock source
to lock in the PWM signal that the 64A will be sourcing to
the hobby servos The LTC6900 is configured as a 1 MHz
clock source that can have its output frequency divided by
10 or by 100 with the positioning of a jumper Our hobby
servo application will utilize the undivided 1 MHz clock
signal To get 1 MHz out of the LTC6900’s OUT pin, we
must ground the DIV pin (pin 4) with a jumper The 1 MHz
output jumper configuration and the LTC6900 along with
its supporting circuitry are shown from a lizard’s viewpoint
in Photo 3
We need to drive our hobby servos with a
positive-going pulse every 16 to 30 ms or so The positive-positive-going
pulse width must be able to be varied between a minimum
of 1 ms and a maximum of 2 ms within the 20 to 30 ms
window With a center servo rotor position represented by
a 1.5 ms pulse width, it’s rather obvious that we must use
microsecond-based pulse widths to be able to better position
the servo rotor within its bounds of travel Microsecond
timing falls into our lap here as each tick of our 1 MHzclock is 1 microsecond (1.0 µs) in length
Now that we have a solid timebase figure of 1 µs towork with, let’s assign bits fields to our pulse widths thatcorrespond to their numeric size At a minimum, we’ll need to generate a 16 ms control pulse window whichmust contain a positive-going servo positioning pulse with
a minimum pulse width of 1 ms and a maximum pulsewidth of 2 ms:
16 ms = 16,000 µs = 0x3E80 µs = 0b0011111010000000 µs
1 ms = 1000 µs = 0x3E8 µs = 0b001111101000 µs
2 ms = 2000 µs = 0x7D0 = 0b011111010000 µs
Instead of using ABEL as we did in our Nuts and Volts
CPLD introduction, the programming language of choice forthis project will be Verilog Verilog is very much like C and isvery easy for most anyone to pick up and run with Verilogsupports numbers up to 32 bits in length Judging from ourbinary breakdown of the pulse widths, by stripping off theleading zeros of the most significant bytes of each pulsewidth bit field we can easily represent our largest pulsewidth number (16 ms) with 14 bits All of the rest of our pulse width values (including the 2 ms servo positioning pulse) can be represented with a maximum of
11 binary digits
Every 16 ms servo control pulse window must beginwith a positive-going servo control pulse, which we knowcan vary anywhere between 1 ms and 2 ms We can easilywrite some 64A code to produce the timing necessary torealize a 16 ms servo control pulse window However, fromexperience I know that we must generate extra code toreload the 16 ms value into the servo control pulsecounter at the end of every 16 ms timing period Ourcoding chore would be a little easier and the code flowmade easier to follow if we could eliminate the necessity to
SERVO 08.2008 37
PHOTO 3 The LTC6900’s undivided output frequency is determined by the value of resistor R18 Utilizing the LTC6900 is a really neat way to put a highly stable and programmable frequency source in a tight space.
The CPLD Servo Driver
Trang 39reload the servo control pulse counter value We can follow
the easier coding path by selecting a servo control pulse
window time that lies on a power of two boundary The
power of two timing method allows the servo control
pulse counter to run continuously and reset itself without
intervention
Ultimately, we want the servo control pulse counter to
roll over to zero and restart the servo control pulse width
timing period automatically The closest power of two
boundary value that meets our 16 ms servo control pulse
window timing limitation is 0x4000 Thus, we will assign a
bit pattern that will allow our servo control pulse counter to
count from 0x0000 to 0x3FFF and roll over to 0x0000 Our
selection of 0x4000 as the servo control pulse window
count provides a 16.384 ms control pulse window If we
find that we need more time to service more servos, we
could multiply our servo control pulse window time by two
and use 0x8000 as our servo control pulse count value
Counting from 0x0000 to 0x7FFF would yield a 32.768 ms
servo control pulse window
From what I have read, 40 ms is the typical minimum
servo control pulse window used by RF-based hobby servo
systems and is mandated by the FCC (Federal
Communications Commission) to limit interference We can
service a bunch of hobby servos in a 40 ms window Let’s
go with the 32.768 ms servo control pulse window for
now If necessary, we can always scale the pulse window
time back to 16.384 ms with the flip of a bit Here’s the
32.768 ms servo control pulse window bit pattern:
32,768 µs = 0x8000 µs = 0b1000000000000000 µs
We will count from 0x0000 to 0x7FFF and roll over
If that doesn’t compute, remember that we clock on zero
and the zero clock counts as one clock pulse So, we’ll need
15 bits — not 16 bits — for our 32.768 ms servo control
pulse counter
Transposing the Servo Math
The idea is to plant the servo position pulse (1 ms to
2 ms) at the beginning of the 32.768 ms servo control
pulse window Let’s begin by putting some code together
that will center the servo rotor:
module rcservo(
input clk_1mhz,
output reg pwm_out
);
Verilog is module based Our rcservo Verilog module
has an input and an output The output is registered,which means it has the ability to emulate a flip-flop
A registered Verilog component also has the means
of holding a value just as a D flip-flop can on itscomplementary Q and outputs The input signal — whichhas defaulted to a Verilog type of wire — is derived fromour LTC6900 1 MHz clock output Verilog wires cannot holdvalues and can only be driven by an external force such as
a register or the output of a gate Basically, a Verilog wire
is just like the copper wire you use to connect electroniccomponents
Next, let’s associate our pulse width numeric valueswith some human-readable names using the Verilog keyword parameter Verilog parameters are equivalent to
So, adding 500 µs (0.5 ms) to the minimum servo positionpulse width with the servo_vector value of 500 will give usthe 1.5 ms centering pulse we are looking for
We calculated that we would need a total of 15 bits toimplement our 32.768 ms servo control pulse window.Here’s the Verilog instantiation of our 15-bit servo controlpulse register, which we will call window_32ms:
If you lay down a “1” for every bit position in the window_32ms register (bits 14 through 0), you’ll end upwith 0x7FFF hexadecimal, or 0b111111111111111 binary.When the window_32ms register contains 0x7FFF and isincremented, it will roll over to zero So far, so good We’ve served up the potatoes Now, let’s bring the meat
to the table:
always @(posedge clk_1mhz) begin
window_32ms <= window_32ms + 1;
pwm_out <= (window_32ms <
(servo_vector + minpulsewidth));
end endmodule
The Verilog always @(posedge clk_1mhz) statementdoes exactly what it says Every time the positive edge ofthe LTC6900-provided 1 MHz clock occurs, everythingbetween the begin and end block delimiters is executed.The Verilog endmodule keyword signals the end of thercservo module
The always @(posedge clk_1mhz) block statement is
SERVO 08.2008 39
< SCHEMATIC 1 The electronic playground is contained
within U1, the Xilinx XC2C64A U2 is a 1 MHz clock source
that can be divided by 10 and 100 with the movement of
a jumper The LEDs and switches are here because the
XC2C64A is part of a XC2C64A development board design.
The CPLD Servo Driver
Trang 40similar to a while(1) C loop that runs continuously Verilog
always blocks run freely and are triggered every time the
condition in the always block sensitivity list is met In the
rcservo module we’ve just coded, the Verilog always block’s
sensitivity list contains a trigger for every positive edge
(posedge) of the incoming 1 MHz clock signal (clk_1mhz)
That equates to the always block’s code between the
Verilog begin and end block delimiters executing every
microsecond
The “<=” Verilog operator in our always loop code tells
us that the logic associated with this operator is clocked,
which means all of the statements using a “<=” operator
are termed “unblocked” and execute in parallel If you’re
having trouble with this concept, think of a bunch of D
flip-flops with all of their clock lines tied to the same clock
source When clocked, every D flip-flop will switch its D
input to the Q output ously So, everything to the right
simultane-of the “<=” operator will executeand the results will end up to the left of the “<=” operatorbeginning with every positiveedge of the 1 MHz clock Thewindow_32ms <= window_32ms+ 1; Verilog statement is veryeasy to understand as everymicrosecond we are incrementingthe count that is being held within the 15-bit window_32msregister
The pwm_out <=
(window_32ms < (servo_vector + minpulsewidth)); Verilogstatement takes a bit more thought Associate logically highwith Boolean TRUE and logically low with Boolean FALSE asyou sound it out:
The pwm_out output pin is logically high as long
as the window_32ms register count is less than the servo_vector value plus the minimum servo position pulse width value
We know that we want to generate a 1.5 ms servoposition pulse with our rcservo Verilog module So, let’ssound out the pwm_out <= (window_32ms < (servo_vector+ minpulsewidth)); Verilog statement again, but this timewe’ll sound it out mathematically:
When the window_32ms register value is less than
1500 decimal, the pwm_out pin is logically high When the window_32ms register value is greater than 1500 decimal, the pwm_out pin is logically low The window_32ms versus servo position value comparison is made at every rising edge of
SCREENSHOT 1 This pulse width
is right on the money Upon sensing this signal, the rotor of
my JR Sport SM8 hobby servo snapped to the central position.
SCREENSHOT 2 My JR Sport SM8 hobby servo didn’t chatter while under the control of this 32.768
ms servo control pulse window timing The 4.8 volt SM8 ran well using the XC2C64A’s 3.3 volt I/O supply voltage However, I’m sure you’ll get the most out of the SM8 with a +5.0 volt servo supply Note the rising-edge-to-rising-
The CPLD Servo Driver