10.2007
VOL. 5 NO. 10
SERVO 10.2007
5
32
CAN Networking
Miniature Style
by Fred Eady
Learn everything you need to know to
code the tricky Firgelli miniature linear
actuator into the electromechanical
side of your robotic designs.
39
M-BOT
by Ron Hackett
Part 2: Take a detailed look at M-bot’s
circuitry and learn two useful yet
simple software routines.
43
Building an Android Arm
by Mark Miller
Part 1: Complete arm assembly to
begin the transformation into a
working limb.
46
NEEMO 12
by Doug Porter
Telerobotic surgery below the sea is
good practice for telerobotic surgery
in space.
48
Target Practice for
Robotics Class
by Michael Chan
Turn an old printer into a shooting
range and learn basic electronic
principles to apply in future
robot builds.
52
Build a Vex Wireless
Joystick Controller
by Daniel Ramirez
Utilize this device to bring
Hollywood-style special effects
to your next build.
61
GPS
by Michael Simpson
Part 1: A beginning look at
incorporating GPS into your
robot projects.
Features & Projects
PAGE 26
PAGE 46
TOC Oct07.qxd 9/5/2007 4:38 PM Page 5
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CONTRIBUTING EDITORS
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Pete Miles R. Steven Rainwater
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Fred Eady Doug Porter
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When it comes to robotics,
believing is seeing. Unlike scientific
areas where researchers and enthusiasts
happen upon novel processes or
compounds, robots are the product of
focused work. As such, it’s possible to
approximate the trajectory of robotics
with fairly good accuracy. My crystal
ball? Military spending. Although there
is a substantial commercial footprint in
robotics, the US military is the
traditional and largest backer of risky,
future-oriented developments.
The most accessible window into
the military’s investment in the future
of robotics is the series of DOD Small
Business Innovation Research (SBIR)
solicitations that are posted every few
months at www.acq.osd.mil/osbp/
sbir/. The SBIR program provides up
to $850,000 in early-stage R&D
funding directly to small technology
companies, including individual
entrepreneurs who form a company.
The program is competitive, with 10-
300 applicants per topic, and at most
a handful of recipients. Obviously, the
odds of eventual commercialization
are much better for a DOD-backed
robotics technology than for a robotics
project without the additional, no-
strings-attached funding.
As an example of what the DOD
funds in robotics, consider the SBIR
solicitation that closed September of
2007. Using the DOD Topics Search
Engine at www.dodsbir.net/Topics/
Default.asp, searching for “robot”
retrieved seven solicitations: one from
the Air Force, one from the Navy,
and five from the Missile Defense
Agency (MDA).
The Air Force solicitation was for
a human/machine perceptual sensing
technology to aid the wearer in
detecting an emerging threat, based
on multi-source sensor fusion. The
effect on the future direction of
robotics products is clear in this
solicitation. You can probably imagine
an urban protective suit that warns
pedestrians, cyclists, or police officers
of impending danger, whether from
motorists, potential muggers, or
simply inclement weather.
The Navy’s solicitation was for an
unmanned surface vehicle (USV)
at-sea refueling system. The goal was
to develop a refueling system that can
provide fuel for USVs with minimal
risk to personnel or the environment.
Spin-offs could one day autonomously
refuel your hybrid car — while you
drive. No need to pull over to fill up or
plug in to the power grid.
The solicitations from the Missile
Defense Agency ranged from space
component miniaturization, interceptor
algorithms, and sensor data fusion to
the application of game theory in
modeling and simulation. Space
component miniaturization, with an
emphasis on micro-electro-mechanical
systems (MEMS) and lightweight,
high-efficiency motors, has obvious
relevance to the future of robotics.
Lighter, more efficient motors will allow
for more compact robot designs,
including more compact batteries and
power supplies.
Although intended to thwart
ballistic missiles, the MDA’s solicitation
for new interceptor algorithms will
likely result in new algorithms for
robot navigation and object
avoidance, among others. Sensor
fusion has been an important topic in
robotics, ever since the introduction
of the Kalman filter in the 1960s. The
MDA’s call for more advanced, multi-
Mind / Iron
by Bryan Bergeron, Editor
Mind/Iron Continued
6
SERVO 10.2007
Mind-FeedOct07.qxd 9/6/2007 9:33 AM Page 6
sensor data fusion algorithms will
likely result in technology that will
eventually appear in commercial
robots. Furthermore, modeling and
simulation are increasingly relied on
for testing new algorithms and
platform designs before physical
robots are constructed. Advanced,
innovative models for the evaluation
and optimization of sensors have
obvious applications in the robotics
design process.
How long before the innovations
requested by the DOD leave the
laboratory or workbench to become
commercial realities? Probably years.
But there is a continuous stream of
similar DOD solicitations, dating back
decades. Many of the DOD-funded
innovations are just coming on line
now, in the form of affordable
sensors, components, and algorithms.
Even if you don’t intend to apply for
a grant, it’s fun to read through the
dozens of DOD-funded SBIR solicitations
that appear every few months, and then
try to imagine the likely effect on the
evolution of robotics.
SV
SERVO 10.2007
7
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only two Radio/Control channels for vehicles using two
separate brush-type electric motors mounted right and left
with our mixing RDFR dual speed control. Used in many
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goes straight ahead, down is reverse. Pure right or left twirls
vehicle as motors turn opposite directions. In between stick
positions completely proportional. Plugs in like a servo to
your Futaba, JR, Hitec, or similar radio. Compatible with gyro
steering stabilization. Various volt and amp sizes available.
The RDFR47E 55V 75A per motor unit pictured above.
www.vantec.com
STEER WINNING ROBOTS
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Mind-FeedOct07.qxd 9/5/2007 4:21 PM Page 7
8
SERVO 10.2007
Strength Record Set
Back in May, Germany’s KUKA
Roboter GmbH introduced Titan, which
apparently has secured (at least for now)
the title of “world’s strongest robot” in
the Guiness Book of World Records. The
machine is powered by nine motors that
give it a 1,000 kg (2,200 lb) payload
capacity, and it has a reach of 3.2 m
(10.5 ft) and a work envelope of 78 m
3
(2750 ft
3
). At full stretch, Titan reaches a
height of more than 4 m (13 ft).
According to the company, this
monster is capable of moving entire car
bodies all by itself and can withstand a
static torque of 60,000 Nm (or 44,000
ft-lb, roughly 100 times the torque
generated by your father’s Oldsmobile).
Titan is intended for various applications
in the building materials, automotive,
and foundry industries. Details are
available at ww
w.kuka.com.
Getting Into Your Head
At the other end of the spectrum
is a small bot invented by Professor
Leo Joskowicz, of the Hebrew
University of Jerusalem (www.huji.
ac.il/huji/eng/). The apparently
unnamed device was developed to
improve “keyhole” surgical procedures
in which tiny instruments are inserted
into your brain through a small hole.
Doctors already can make use of
CT or MRI images, but there is still a
risk of misdirecting the surgical instru-
ments and causing hemorrhaging or
severe neurological damage. But
Joskowicz and some associates have
developed an image-guided system
that, based on a robot that is pro-
grammed using electronic scans of the
patient, can provide better precision
and dexterity than a surgeon’s hand.
During surgery, the robot is
clamped onto the patient’s skull, after
which it automatically and accurately
positions itself with respect to surgical
targets. Once positioned, the robot
locks itself in place and serves as a
guide for insertion of a needle, probe,
or catheter to carry out the procedure.
The invention won Prof. Joskowicz
the Kaye Innovation Award (named
after and established by Isaac Kay, a
British pharmaceutical mogul).
Robot Ankle Developed
A less unsettling breakthrough
comes from Professor Hugh Herr and
his team of researchers at the MIT
Media Lab (www.media.mit.edu).
They have developed an ankle-foot
device that, driven by a small battery-
powered motor, allows amputees to
walk normally again.
In operation, the energy produced
from the wearer’s forward motion is
stored in a power-assisted spring and
then released as the foot pushes off.
Additional mechanical energy is provided
for momentum. According to Herr, “This
design releases three times the power of
a conventional prosthesis to propel you
forward and, for the first time, provides
amputees with a truly humanlike gait.”
And he should know, being a
double amputee who tested his own
invention. Herr created the device
under the auspices of the Center for
Restorative and Regenerative Medicine
(CRRM), a collaborative research
initiative that includes the Providence
VA Medical Center, Brown University,
and MIT. Commercial versions may be
available by the summer of next year.
Bluegill Inspires UAV Design
Also from MIT, over in the Bio-
Instrumentation Systems Laboratory
(bioinstrumentation.mit.edu), is a
robotic fin design that someday could
be used to propel UAVs in functions
ranging from ocean floor mapping to
surveying shipwrecks, as well as mili-
tary tasks such as mine sweeping and
harbor inspection. An underwater bot
KUKA’s Titan is billed as the world’s
largest and strongest six-axis
industrial robot. Photo courtesy
of the KUKA Robot Group.
Professor Joskowicz demonstrates
equipment for probing your brain.
Photo courtesy of Hebrew University
of Jerusalem. Photo by Sasson Tiram.
The MIT Media Lab’s powered
ankle-foot prosthesis in action.
Photo by Webb Chappell.
by Jeff Eckert
Robytes
Robytes.qxd 9/5/2007 2:42 PM Page 8
driven by fins could prove to be more
maneuverable and energy efficient
than its propeller-driven counterparts.
The researchers picked the bluegill
sunfish because of its unusual swim-
ming motion, in which it generates a
constant forward thrust without creat-
ing backward drag. The latest design is
based on a flexible polymer
that repli-
cates two critical motions: the forward
sweep and the simultaneous
cupping of
the upper and lower fin edges.
When an electric current is run
across the base of the fin, it sweeps
forward, just like the fish. When the
direction of the current is changed,
the fin curls to create the cupping
action. Future research will focus on
other aspects of the sunfish’s move-
ment, including interactions between
its fins and body.
Robotic Punk Music
His real name is Jay Vance, but
he goes by the moniker of JBOT
when performing with his “band,”
Captured! By Robots (C!BR).
According to the official story, JBOT
spent a few years playing in some
awful ska groups but back in the late
‘90s decided to build his own backup
band. He collected some scrap
metal, pulleys, and pneumatic
actuators, and the result was
DRM-
BOT0110, GTRBOT666, AUTOMATOM,
TAWHNN, SOTAWHNN, and the
Headless Hornsmen.
C!BR’s 10-year anniversary spring
tour ended in June, but presumably the
act will go on the road again someday.
In the meantime, you can hear sam-
ples, watch video clips, and even buy
CDs at www.capturedbyrobots.com.
But be warned that, with tunes like
“Torture,” “I Hate Your Techno,” and “I
Just Peed Your Waterbed,” this ain’t
exactly Peabo Bryson. It’s more like
Chuck E. Cheese from Hell.
Walking on Water — Almost
Apparently, there is this thing
called a basilisk lizard, a member of
the iguana family, that hangs out in
Central and South America eating
insects, plants, and small vertebrates.
Its main claim to fame is that it can
flap its web-like feet up to 10 times per
second, which allows it to walk (run,
actually) on water for distances of up
to 20 m (~66 ft); hence the nickname
“Jesus lizard.”
Now some students at the
Carnegie-Mellon NanoRobotics Lab,
working with Professor Metin Sitti, are
attempting to build a robotic version
on the theory that a bot that can
travel across water without being
submersed may offer more efficient
movement by eliminating viscous drag.
It’s still in the prototype stage,
but you can monitor the critter’s
progress and even see videos at
nanolab.me.cmu.edu/projects/wat
errunner/.
SV
Robytes
A bluegill sunfish swims in a
laboratory tank near a prototype
of a robotic fin it inspired.
Photo by Donna Coveney.
Four-legged prototype of the
“Jesus lizard.” Photo courtesy of
Carnegie-Mellon NanoRobotics Lab.
JBOT and the band: not everyone’s cup of hemlock.
SERVO 10.2007
9
Robytes.qxd 9/5/2007 2:42 PM Page 9
10
SERVO 10.2007
N
icholas McMahon — a current
engineer at iRobot (where he is
proudly working on the iRobot
Packbot project) — took a few minutes
to fill in the details about his roof-
inspecting electro-mechanization.
Robotic Goals,
Rooftop Got-yas
Roboticists are problem-solvers.
They solve problems of physics, physi-
cal mechanics, electronics, and robotics
to create moving solutions to seeming-
ly immovable problems.
A key challenge for Nick and partner
Sam Feller was to create a robot that
could perform practical, quality roof
inspections while maintaining balance
and mobility in an environment of steep
inclines and treacherous twists and turns.
The duo had to design the robot
around maintaining stability and traction
on steep surfaces (i.e., 45-degree slopes),
according to McMahon. The stability
problem required a low center of gravity.
The roboticists used CAD modeling
techniques and live testing scenarios
to design and validate the robot’s low
center of gravity. In order to be a suit-
able replacement for human inspectors,
the robot must not tip or get hung up
in this most inhibitive of environments.
Traction was another matter. The
traction problem meant experiment
upon experiment with varying materi-
als of differing levels of friction to
create wheel surfaces that would
maintain contact with the roofing. Not
just any material would do.
“We started with traditional convey-
or belt material. Other candidates were
Scotch Brite pads and various foams and
rubbers. We settled on EPDM (ethylene
Contact the author at geercom@alltel.net
by David Geer
Robot Roof Inspector
Holds its Footing
Former Worcester Polytechnic Institute (WPI, Worcester, MA) students Nick McMahon and
Sam Feller designed and built a roof inspection robot to help keep flesh and blood roof
examiners from precarious and injurious positions. (Both McMahon and Feller graduated
from WPI this year with Bachelor of Science degrees in Mechanical Engineering.)
The roof inspection robot (top-side, on faux roof). At the bottom, see if you can
find the pan/tilt X10 camera. Can you find the potentiometer in the center?
Can you tell which way it is going? Which way is it looking right now?
According to former WPI
student and now graduate Nick
McMahon, he and former student
Sam Feller learned how robotics rely
on software engineering, mechanics,
and electronics to work properly.
They also learned about time
management, team work, and
working with customers to get their
input. Travelers Insurance, their
customer for this robot research,
sponsored the roof robot project,
McMahon explained.
LESSONS LEARNED
Geerhead.qxd 9/5/2007 2:44 PM Page 10
GEERHEAD
propylene diene monomer) rubber,”
says McMahon. EPDM has several
properties including density, durability,
and resistance to abrasion.
McMahon and Feller used force
gauges and friction testing to “calcu-
late the coefficient of friction on
asphalt shingles” to determine the best
material for the job from among all
the candidates.
The roboticists attempted to add
to the surface area of the wheel that
would actually make contact with the
roof by using substrates — layers of
material — on the wheels.
“In theory, surface area doesn’t
matter in friction calculations,” says
McMahon, “but we found that the
more weight you have per area, the
more likely the shingle is to fall apart
from the rotation of the wheels.”
Spreading out the contact area helps
spread the weight of the robot across
more area so the shingles don’t crack.
“Peak” Navigation
Performance
Talk about difficult terrain — the
robot would need to straddle roof peaks
and negotiate the valleys between them
without getting stuck or leaving hidden
places it couldn’t reach to inspect. The
first part was resolved by leaving the
underbody of the robot open to
allow for “the cresting of peaks,”
according to McMahon.
The body of the robot
uses a special joint that
allows it to drive onto one
plane of the roof from
another plane and sit half
on one at one angle and
half on another at another
angle, if necessary.
Basically, the front and
back of the robot are divided
into two independent seg-
ments that can turn up and
down and left and right to
navigate the planes of a roof
where they meet without
the wheels or other parts of
the robot getting hung up. “So, it can
operate on two planes without losing
contact with the roof,” says McMahon.
The robot’s controls allow each
wheel to move at the speed necessary
to maintain its “rolling contact” with
the roof, dependent upon the angle of
the wheel joint. This arrangement
avoids loss of traction and roof
damage simultaneously. The operator
uses command and control and a video
camera to inspect the roof and to drive
the robot around.
What Goes Up .
Into every roboticist’s life, a few parts
must fall, smash, crack, bang, and bend.
McMahon and Feller tested the
robot’s maneuverability and center of
gravity on an 8’ x 8’ test roof built
inside a WPI lab. The test roof had
the necessary 45-degree slope and a
right-angle section to test the “valley
traversing” capabilities.
The two young scientists drove the
robot in every possible orientation and
angle to test the limits of its configura-
tion and software code, according to
McMahon. Of course, robots seldom
score 100 the first time around.
Too fast a speed or too twisted a
turn and off the makeshift roof the
robot flew. “For instance, as it went
around the corner, the body would
twist and the center of gravity would
move causing the whole robot to fall
over and off of the roof. No significant
SERVO 10.2007
11
WPI students conduct MQPs or Major Qualifying Projects in
their Senior year at WPI. This is an example of a WPI search and
rescue robot project. Here, the robot is seeking out the candle.
Take a look at the WPI search and rescue robot
on a test rescue mission.
Here is a side angle. Why is it looking to its rear?
Geerhead.qxd 9/5/2007 2:45 PM Page 11
12
SERVO 10.2007
damage ever occurred but we had
some bent parts that needed to be
straightened out,” says McMahon.
McMahon also recounts how the
robot would literally try to destroy
itself. This flaw required adjustments
around potentiometer feedback.
This particular potentiometer
tracks body rotation angle. On rare
occasions, the feedback signals looped.
The robot, responding to the feedback,
went into convulsive joint oscillations,
gyrating its two halves continually until
the roboticists reset it.
This happened at varying points in
the testing phase for different reasons.
In the beginning, the potentiometer
wasn’t properly secured to the joint it
was measuring. When the potentiome-
ter slipped, the software code would
use the misguided feedback to try to
keep the joint in position, oscillating the
joint, according to McMahon. “Other
times, bits of phantom code would
cause the joint motor to suddenly come
on full power and slam the two body
halves together,” McMahon explains.
Parts and
Configuration
Unique to the
Problem at Hand
For the roof robot construction,
McMahon and Feller used leftover win-
dow motors from FIRST competition
robot projects, a McMaster-Carr gear
motor, and IFI Victor speed controllers.
The motors are Nippon Densos,
like those shipped with the FIRST
robotics competition kits, according to
McMahon. “We chose them because
they suited our power and speed
requirements,” comments McMahon.
McMahon and Feller bought a
generic 12V motor with gear reduction
to drive that infamous joint in the cen-
ter of the robot. The motor drives the
two halves of the robot mechanically
when the wheels don’t get traction,
explains McMahon.
The Victor speed controllers also
come from the FIRST robotics competi-
tion kit and control the speed of the
wheel motors.
The two roboticists also used
potentiometers, encoders, and Sharp
IR sensors for edge detection.
The potentiometer tracks the joint
position. This information helps the
wheels to each move at the right
speed to maintain contact with the
roof. The encoders are actually beam
interrupters modified to read the speed
of each wheel independently.
The robot feeds the encoder infor-
mation back to the microcontroller. The
microcontroller uses software to make
sure the wheels don’t slip and that
each wheel is powered at the right
time to keep them touching the
surface, according to McMahon.
The Sharp IR sensors reflect a
beam off the surface of the roof and
back to the sensor. When the sensor
doesn’t see its reflection, it knows it
has reached the edge of the roof and
the robot stops so as not to fall off.
“All of the mechanical pieces were
designed and fabricated by us in the
school’s machine shops,” says McMahon.
These include chassis panels, motor
mounts, joint parts, the “belly pan” and
the “pan tilt tower” used for the camera,
according to McMahon. “Everything is
held together with threaded fasteners,”
he adds.
McMahon and Faller also used an
X10 camera for the video and a VEX
microcontroller for the robot’s brain.
The VEX masterminds the edge
sensing, course of direction, velocity,
and joint angle; it also negotiates
command and control instructions from
a human operator. The pan/tilt tower
forms the foundation for the X10
camera. This makes it possible for the
operator to maneuver the camera, to
catch every glimpse of the roof for a
thorough inspection.
Nickel metal
hydride batteries power the robot, giv-
ing it an hour’s worth of locomotive
and inspection capabilities.
The robot is currently sitting in
storage at WPI where it can be used
for parts for future Major Qualifying
Projects (MQPs); MQPs are WPI’s
moniker for senior design projects.
SV
GEERHEAD
Worcester Polytechnic Institute
www.wpi.edu
First college major in
Robotics Engineering
www.wpi.edu/News/Releases/20067
/rbemajor.html
WPI Robotics Engineering
www.wpi.edu/Academics/Majors/RBE
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Geerhead.qxd 9/5/2007 2:55 PM Page 12
Full Page.qxd 9/4/2007 4:07 PM Page 13
14
SERVO 10.2007
Q
. H
ere is a tough question for
you to chew on. I have seen
you write articles about the
PS2 controller and the bluetooth
modem from SparkFun, but can you
make the PS2 controller a wireless
controller using these two parts? Right
now, I have a regular Futaba R/C
controller to drive my robot around, but
it doesn’t have any switches for turning
on lights and sounds. The PS2 con-
troller has 12 buttons for turning things
on and off and two joysticks for driving
my robot. Can you help me here?
— Will Harrison
A
. Sounds like you have a fun
robot project, and converting a
Playstation 2 controller into a
wireless controller isn’t that difficult,
especially if you are using the
BlueSMiRF Bluetooth serial modem
from SparkFun Electronics (www.
sparkfun.com). There are two
different things that you have to build:
a serial interface for the Playstation 2
controller and a serial interface for
your robot.
In the January ‘07 issue of SERVO
Magazine, I showed how to interface a
regular wireless Playstation 2 controller
to a BASIC Stamp from Parallax
(www.parallax.com). This may be the
simplest way to go since all you would
need is one of the wireless PS2
controllers, such as the Madcatz
(www.madcatz.com) or the PS2
robot controller from Lynxmotion
(www.lynxmotion.com), a microcon-
troller, and a controller interface cable.
(I included the above reference for
anyone who may have missed that
issue of SERVO Magazine.)
I am going to do something a little
different here. In the previous article,
the communication timing between
the wireless PS2 controller and the
BASIC Stamp needed to be at high
speeds, which limited the selection of
the BASIC Stamps to their faster
processors.
For this article, I am going to
make the PS2 interface using a Scenix
SX-28 microcontroller (www.para
llax.com/SX), mainly because it is
faster than the BASIC Stamp (up to 75
MHz), and it uses the SX/B program-
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?
by
Pete Miles
Our resident expert on all things
robotic is merely an Email away.
roboto@servomagazine.com
S
X28A
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RC.0
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RC.7
RA.3
RA.0
RA.2
RA.1
MCLR
OSC2
OSC1
RTCC
4 MHz
+9V FOR VIBRATION MOTOR POWER
NOT CONNECTED
ACKNOWLEDGE
Vdd (+3V to +5V)
ATTENTION
CLOCK
GROUND
COMMAND
DATA
LYNXMOTION PS2 CONTROLLER ADAPTER
CABLE. AS VIEWED FROM THE FEMALE END
GREEN
BROWN
ORANGE
BLACK
YELLOW
RED/SHIELD
BLUE
VIOLET
N/C
DATA
CMD
ATTN
CLOCK
Vdd
GND
+9V
ACK
4.7 KΩ 4.7 KΩ
10KΩ
+5V
+5V+5V
BA
S
I
CS
TAMP
2
FAMILY
P6
P7
VSS
P4
P5
P13
P9
P8
P10
P11
P15
P14
RES
VDD
+5V
VIN
P3
P2
P1
P0
ATN
VSS
SIN
SOUT
220 Ω
Figure 1. Playstation 2 controller interface hardwired to a BASIC Stamp for testing.
MrRoboto.qxd 9/5/2007 2:38 PM Page 14
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