Servo magazine 12 2007

Tạp chí Servo

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SERVO 12.2007 3

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08 Robytes by Jeff Eckert

Stimulating Robot Tidbits

10 GeerHeadby David Geer

Tortuga — From Isle of Pirates to

Underwater Spy

14 Ask Mr Roboto by Pete Miles

Your Problems Solved Here

60 Lessons From The Lab

by James Isom

NXT Packbot: Part 2

68 Robotics Resources

by Gordon McComb

Using Lasers With Your Robots

76 Appetizer by Daniel Albert

Transitioning Sequencer Using Static

Frames for Biped Control

79 Then and Nowby Tom Carroll

Servos

PAGE 79

VOL 5 NO 12

SERVO 12.2007 5

ENTER WITH CAUTION!

22 The Combat Zone

43 Spare the Rod

Spoil the Bot

by Karla Conn

Rewards and punishments can serve

as fundamental motivations for your robot to learn by.

Demonstrating Robots Task Primitives

by Alexander Skoglung and Boyko Lliev

Using imitation to teach robots isn’t as straightforward as you’d think, but it can be done.

51 Using FRAM for

Non-Volatile Storage

by Fred Eady

If EEPROM densities are too small for your robotic application and you don’t want to design in a hard drive or battery-backed SRAM, then FRAM is your answer.

Features & Projects

PAGE 14

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True Autonomy

When roboticists talk of

autonomy, it’s generally understood

that this elusive goal will be achieved

through advances in computational

methods, such as artificial intelligence

algorithms, more powerful processors,

and increasingly powerful and

affordable sensors However, achieving

truly autonomous robots will require

more than simple computational

evolution It’s a misnomer to call

a robot that can navigate a

room without human assistance

‘autonomous’ when the duration of

autonomy is limited to perhaps a half

hour because of battery life Other

than simplistic stimulus-response

BEAM robots (see Figure 1), the Mars

rovers are perhaps the best examples

of computationally and energetic

autonomous robots However, even

the rovers are controlled remotely by

scientists at NASA

The advances in battery

technology, fuel cells, and power

management chips haven’t kept pacewith computational advances inenergy management, such as behaviormodification Unfortunately, behaviortactics such as resting, altering speed

or path to reflect remaining energystores, and shutting down unnecessarysensors can only go so far in extendingthe operating time of a robot Newsources of energy must be identifiedand perfected

Although there is amplecommercial pressure to develop highercapacity energy sources and moreeffective energy management devices,there are also significant incentivesfrom the military According to theDOD, soldiers of the near future areexpected to be assisted by electronicdevices ranging from audio, video,and data communications equipment,night vision gear, and wearablecomputers, to exoskeletons And thesedevices will require an unprecedentedamount of portable power

In response to this need, theDepartment of Defense Research and

Mind / Iron

FIGURE 1 Solar powered

light-seeking BEAM robot.

Engineering Wearable Power Prize is offering $1M for the

first place winner for the best wearable electric power

system prototype The competition — which is open to

individual US citizens 21 or older — will be held in the fall of

2008 The grand prize goes to the developer of the

technically superior power vest that weighs 4 kg or less,

operates continuously for four days, and provides 20W

average and 200W peak See www.dod.mil/ddre/

prize/topic.html#7 for details on the competition.

Even if you don't take part in the competition, considerthe energy autonomy of your next robot design While youprobably don't have access to Sterling isotope thermalgenerators or other esoteric energy sources available to militaryrobotics designers, there are numerous promising technologiesthat you are free to explore One that I've followed for severalyears is illustrated by the predatory robot EcoBot II, developed

by the University of the West of England in Bristol.The EcoBot II uses a microbial fuel cell to generateelectricity from flies Bacteria in the microbial fuel cellsmetabolize sugars in the flies, releasing electrons in theprocess The robot isn't yet up to the capabilities of the

Mr Fusion Home Energy Reactor-equipped De Loreanfeatured in “Back to the Future” — top speed is 10centimeters per hour However, the EcoBot II can travelfor five days on just eight flies If you have an aversion

to flies and other decaying organic matter, you can tryyour hand at extending the basic BEAM robots,available from several vendors featured in SERVO. SV

Dear SERVO:

In reference to the September ‘07 Robytes Holy cow! $69

million for an RC airplane? Wow, where can I sign up? I think as a

tax payer I should feel screwed! Who am I? I used to fly RC planes

before I became a pilot I’ve built a four seat airplane, and been

president of an EAA (experimental aircraft association) chapter I

know a bit about what airplanes are, and what they cost

One of the members of our EAA chapter built a Lancair 4,

which would be a 300 mile per hour airplane He went top shelf

on it, and spent about $400,000 on it Sure, it only has half the

payload of the MQ-9 (1,550 lbs), but it

seems like for not a lot more, one could

build it bigger, and get the payload

Looking at an Epic Dynasty, it has

3,300 lbs payload, and is priced under $2

million; it’s capable of 340 knots The

specs might be misleading with the empty

and max takeoff weights but that is with

an interior, and equipment for people

Strip all that out and you can have a UAV

Basically, the remote control is

some extra wiring to the auto pilot

servos I am to believe that is worth 50

some million dollars?

So, maybe someone might say I am

comparing “toy” airplanes to some

commercial aircraft How about a Boeing

737? Well, right from Boeing, ready to fly,

they list at $49 million I guess a $20

million conversion would be reasonable

(probably not) But this aircraft is capable

of hauling over 30,000 lbs (about 10X the

MQ-9) It can also cruise at over 500 mph

I am very sad to hear the way things are going in the UAV market

People claim the UAVs are supposed to be cheaper andsafer, but it still takes a crew of two to fly this MQ-9, where anF-35A lightning II will only cost about $50 million and takes acrew of one It’s capable of carrying 18,000 lbs and flying pastmach 1 in a stealth mode carrying smart weapons Thismanned aircraft is clearly a more useful aircraft

Tom Brusehaver Dallas,TX

SERVO 12.2007 7

Resources

• EcoBot II — Self-sustaining killer robot creates a stink

New Scientist, September 9, 2004.

www.newscientist.com/article.ns?id=dn6366

• EcoBot II in action www.youtube.com/watch?v=1Nuw654pFbU

• BEAM Robots www.solarbotics.net; www.solarbotics.com;

www.geocities.com/SouthBeach/6897/beam2.html

• How Fuel Cells Work How Stuff Works.

www.howstuffworks.com/fuel-cell.htm

Fooling Virtual Robots

A highly abstract but interesting

concept has emerged from the University

College London (www.ucl.ac.uk),

where Dr Beau Lotto and other

researchers have been experimenting

with “virtual robots” to understand why

humans can be fooled by visual illusions

Some folks at the UCL Institute of

Ophthalmology trained artificial neural

networks (essentially, virtual toy robots

with tiny virtual brains) to “see” correctly

(i.e., as we do) They trained the virtual

critters to predict surface reflectance in a

variety of 3D scenes such as found in

nature When the bots examined a range

of grey scale illusions, they often made

the same mistakes that humans do

Among the study’s conclusions is

that “it is likely that illusions must be

experienced by all visual animals

regard-less of their particular neural

machin-ery.” For details and some entertaining

illusions, visit www.lottolab.org.

Concept Car Includes Companion Bot

At the latest Tokyo Motor Show,

Nissan (www.nissanusa.com) unveiled

the Pivo 2 electric concept car, evolvedfrom the original three-seater that firstappeared in 2005 It is mechanically asstrange as it looks, given that the wheels(each of which is powered by its ownmotor) can turn up to 90°, and the cabincan rotate 360°, so you can drive it for-ward, sideways, or backward and neverneed a reverse gear It’s powered by lithi-um-ion batteries and uses “by-wire” con-trol technologies rather than mechanicalsystems for braking and steering

But possibly the strangest feature

is the “Robotic Agent” that rides withyou everywhere you go It’s basically

a bobbling head, located near thesteering wheel, that communicateswith you in either English or Japanese

Aimed at making “every journey lessstressful,” the Agent speaks in a “cuteelectronic voice” and provides a link toeverything from basic vehicle functions

to searching for a parking spot

According to Nissan, the head cansense the driver’s mood by analyzingfacial expressions (it has digital eyesand a microphone) and deliver prepro-grammed phrases that might include

“Relax, don’t worry,” “You’ve drippedBig Mac sauce into your lap,” and “Putaway that gun.” At this point, the car is

fully functional but — alas — is still tooexpensive for the commercial market

Fortune Teller in a Bowl

Also too expensive for the mercial market but there anyway, isthe Swami Conversational Robot, avail-

com-able from Neiman Marcus (www.nei

manmarcus.com) This goes way

beyond the old mechatronic gypsy tune teller machines of penny arcadefame, although, peeping out from hisglass dome, he does bear some resem-blance to Zoltar Under the control of

for-a lfor-aptop running specifor-al AI softwfor-are,this guy generates facial expressionsusing some 30 micromotors and canwatch you via eye-mounted cameras.Apparently, you can teach him torecognize family members, havemeaningful conversations with you,and answer questions intelligently.That’s probably more than the afore-mentioned family members can do,but the catch is that this thing costsmore than my first house: $75,000

Give ‘em the Bird for Christmas

On a level that will allow it to fityour Christmas budget is Squawkers

In this image, it appears that the dark

stripes on top are darker than the

white stripes on the front of the

object But a mask placed over the

image reveals that the “white” stripes

in the foreground are exactly the

same as the “grey” ones on top.

Thanks to Beau Lotto/UCL.

Nissan’s Pivo 2 concept car Photo courtesy of Nissan Motor Company.

The Swami Conversational Robot Photo courtesy of Neiman Marcus.

by Jeff Eckert

McCaw, recommended for children over

5 years and very lonely people of all

ages Widely available on the Internet

for about $55, it talks, squawks, and is

nearly as annoying as a real parrot He

can repeat any words spoken to him,

give appropriate responses to

prepro-grammed commands, and learn new

responses Put him in dance mode, and

he will sashay to whatever music you

play or even provide his own music

In terms of mechanics, Squawkers

can move his head, flap his wings, eat a

cracker, and even give you a smooch

when you touch his beak Probably the

best feature is that he goes to sleep

when his eyes are covered or the room

gets dark You can see him at www.has

bro.com or in your local toy store.

Robot Plays the Theremin

As most readers will already know,

the theremin — invented by Leon

Theremin in 1919 — is one of the earliest

completely electronic musical instrumentsand the first to require no physical contactwith the “musician.” As far as I can verify,

it was played only by human beings untilabout 2003, when Ranjit Bhatnagar builtLev specifically for that purpose

Lev, the product of a floor lamp,some metallic junk, and a few micro-processors, has been a solo act sincethen but is now accompanied by a few

“thumpbots,” which provide a rhythmicbackground to the theremin’s notorious-

ly unappealing sound If you’re curious,

a video of the band playing a tune that

is said to be Gnarls Barkley’s “Crazy”

(but sounds more like belly dance music)

can be viewed at www.youtube.com/

watch?v=19RJEnNUg1I.

Mini Chopper Fights Fires

Most unmanned surveillance seems

to be performed by fixed-wing aircraftthese days, but the West Midlands FireService, over in Birmingham, U.K., is trying out a small chopper, which it hasdubbed the Incident Support ImagingSystem (ISIS) The device doesn’t actually put out fires, but it does providelive video from above the incident scene and aids firefighters in planning

by Microdrones GmbH (www.micro

drones.com) over in Germany.

The composite shell provides lowerweight and EMI shielding and housesinstruments that can include a GPS,accelerometers, gyroscopes, a magne-tometer, a still or video camera, and pres-sure, temperature, and humidity sensors.The unit weighs only about 2 lbs (900 g)and carries up to nearly 0.5 lbs (200 g).Depending on the payload, the four battery-powered rotors can keep it aloftfor up to 20 min In spite of the $60,000price tag, Microdrones has sold 250 ofthem 16 months after their introduction

Biped Bot Responds to PS2 Controller

Closer to home, Dallas-based

KumoTek (www.kumotek.com) is a

builder of custom and standard bots foreducation, research, entertainment, andsome industrial applications (Kumo, incase you were wondering, is Japanese for

“spider.”) The news there is the tion of the model KT-X, billed as the firstlow-cost bipedal root platform that can

introduc-be controlled via a wireless PS2 controller.The 13-in, 2.9-lb robot can walk,run, do somersaults, and stand up from

a face-up or face-down position KT-Xhas 17 degrees of freedom, is driven by

a 60 MHz HV processor, and comes with75+ preprogrammed motions As of thiswriting, the unit is still under develop-ment, but it should be commerciallyavailable “within a few months.” SV

Squawkers McCaw, the latest in

the Furreal Friends lineup.

Photo courtesy of Hasbro.

Lev the musical robot now performs

with “thumpbot” friends Shown with

a Moog Etherwave instrument Photo

courtesy of www.moonmilk.com

A special version of the MD4-200

is being evaluated for fire and rescue operations Photo courtesy

of Microdrones GmbH.

SERVO 12.2007 9

The new KT-X.

The competition is sponsored by

the Office of Naval Research

(ONR), as well as by AUVSI,

according to a Robotics@Maryland

aca-demic paper, “Tortuga: Autonomous

Underwater Vehicle,” authored by

several club members and advisors

The competition “tasks” each

robot with six challenges:

• Maintain a straight course and

head-ing through the starthead-ing gate

• Locate the flashing “start” buoy

• Ram that buoy “to free it.”

• Locate the first “orange pipeline segment.”

• Follow the orange pipeline until itmeets a second flashing buoy, which itmust also ram

• Follow two more pipelines, locate asonar beacon, and follow it to the

“treasure octagon.”

Team members based the robot’sdesign and construction on the bestpossible completion of these tasks

Tortuga Design and Construction

A serviceable aluminum chassissurrounds and supports Tortuga’smechanics, as well as an 18.5” long by8” diameter clear acrylic tube, whichhouses the watertight components.The team members selected the chassisdesign for ease of access to the robot’sfunctional parts, electronics, and other

“innards” and attachments

The robot uses an inertial navigation system (INS) to establish itslocation and maintain its heading The system is comprised of sensors,processors, and software These enablethe vehicle to establish and changelocation by adjusting its velocity

The INS includes the followinghardware and software:

1) Three magnetometers (to measurethe Earth’s magnetic field)

2) Three gyroscopes (to measure lar acceleration)

angu-3) Three accelerometers (to measure

Contact the author at geercom@alltel.net

Tortuga was the first robot that the University of Maryland entered into the Association for Unmanned Vehicles and Systems International’s (AUVSI’s) annual Autonomous Underwater Vehicle (AUV) competition, according

to Scott Watson, a University of Maryland student and Robotics Club member This is a close-up, aft (tail, stern) angle view of Tortuga

The AUV is equipped with four Seabotix thrusters (three of four are visible) to control depth, pitch, yaw, and horizontal translation, according to students who crafted the submersible robot Roll

is statically stabilized with a careful distribution of foam, small weights, and putting heavy

electronics (such as the batteries) at the bottom of the pressure hull, Watson notes

The AUV uses a MacMini to interface with all its sensors and motor controllers Photos are courtesy of Scott Watson,University of Maryland student and

linear acceleration)

4) An inertial measurement unit (IMU)

houses the aforementioned nine

sensors

5) Closed-loop controller software to

process force vector equations

The combination of sensors and

sensor data are relied on for navigation

because GPS signals don’t travel

underwater

Attaining Objectives

To get through the starting gate

properly, Tortuga uses a combination

of position confirmations from its

forward camera and output from a

nonlinear adaptive controller

A nonlinear adaptive controller

takes sensor data as input and uses it

to calculate the orientation (location,

position) of the robot and how that is

changing, according to Scott Watson,

University of Maryland student and

Robotics Club member

“It does some calculations and

then determines how best to use the

actuators available (thrusters, in our

case) to do something desirable, like

maintain heading, depth, pitch, roll,

and velocity,” explains Watson

The nonlinear aspect means that

the controller can take the many

differ-ent forces acting on the robot into

account, according to Watson If the

team could guarantee that only one

force contributed to the robot moving

up and down in the water and,

similar-ly, that only one thruster was able to

affect that up and down motion, then

the robot would only need a linear

controller, explains Watson

“But, in nature,” Watson says,

“forces tend to constructively and

destructively interfere with each

other in a way that may not be

deter-minable from the available sensors.”

The adaptive aspect means

the controller knows that the input

(parameters) it receives from the

sensors isn’t necessarily 100

per-cent accurate and that it is

permit-ted to intelligently adjust those

parameters, by use of its gramming, according to Watson

pro-“For example, it’s impossible tomeasure buoyancy or roll moments per-fectly, but an adaptive controller will, in

a sense, learn how to adjust theseparameters to more successfully controlthe vehicle by depending on sensormeasurements,” illustrates Watson

Next, we have buoy ramming

Buoy ramming sounds like fun

and, in this instance, it is a carefully culated maneuver The buoy is a flash-ing light housed in a watertight enclo-sure The robot’s task is to locate thisbuoy and run directly into it to knock itloose from its mooring, according toWatson “This demonstrates vehiclecontrol, valid image processing, and

University of Maryland student and Robotics Club member Stepan Moskovchenko submerges the watertight pres- sure hull to watch for air bubbles and water accumulation beneath the electronics and batteries.

“The first leak in the lifetime

of the robot was discovered minutes earlier due to user error with the homemade underwater FireWire connector,” says Watson.

The straps hold aluminum CNC’d end caps with piston style o-ring seals in place on an 8” diameter acrylic tube, Watson explains.

Three student team members check whether the inertial measurement unit(IMU) is level within the vehicle While hanging from the team tent at the competi-

tion in San Diego, the studentsattempt to calibrate the internalmagnetometer and tweak gains

in the controller code

“The team uses aMEMSense Nano IMU with

M i c ro - E l e c t ro - M e ch a n i c a lSystems (MEMS) technology.This affords a relatively low costand lightweight solution forinertial measurements and totrack the course of the robot,”says Watson

artificial intelligence,” explains Watson.

The robot employs two Unibrain

Fire-I cameras for object recognition

These cameras stream video via

FireWire connection to the MacMini

(1.83 GHz dual core, 2 GB RAM),

which is the robot’s onboard computer

Image processing algorithms on the

MacMini, written in C++, use the

OpenCV image processing library

to identify competition objectslike the buoy (and, of course, theorange pipelines it must follow),according to a Robotics@MarylandTortuga academic paper

The artificial intelligence comesfrom the robot’s “higher level autonomysoftware” in the robot’s hardware brain

A gigabit Ethernet tether stretches thedistance between Tortuga’s onboardMacMini computer and a com-puter on dry land “We usually

communicate with the onboard computer over a shell session, that is,over the Linux console,” says Watson.This is especially useful during testing

To aid the robot in recognizing andfollowing the pipelines, the team usescolor filters to bring out the orange,according to Watson “Then we run anedge detection algorithm that gives us

a collection of points that belong toedges in the image Finally, we feedthese points into another algorithmcalled a Hough transform, which picksout straight lines from those edgepoints,” Watson continues

“Marker dropping” is another task

in the AUVSI competition In this case,the robot drops six inch by half inch redPVC pipe sections into target boxes asmarkers at two points in the competi-tion A weight in the PVC makes sure itdrops, according to club members andstudents

Team members mount these PVCpipe sections inside Tortuga’s deploy-ment tubes, which are fitted with permanent and electromagnets to holdand deploy the markers When the robotenergizes the electromagnet, it cancelsthe permanent magnet’s magnetic field,releasing the marker over its target.The team mounted the markertubes next to the ventral video camera

in order to minimize positioning error.The ventral camera is the one onTortuga’s belly, specifically designated

to watch for targets and for the orangepipelines, according to Watson

The robot uses sound to help itlocate its “treasure” in the final task ofthe competition A sonar, seatedbeneath the octagonal treasure target,creates the sounds A three sensorhydrophone array on the robot’s sidesenses these underwater sounds like asingle microphone A series of micro-controllers and analog filters determinethe frequency and time of arrival of thesounds to pinpoint the location of thesonar, according to Watson

The external frame, made of 80/20 tubing, performed one of its design functions by protecting all the electronics and cabling during the

“jolt.” A little bit of rope and the team

is ready to go straight back to testing code to get the robot back in the water for another run, Watson exclaims!

UM students and Robotics Club members take a moment to pose behind the

Autonomous Underwater Vehicle (AUV) they designed and built — in nine months — for

the Association for Unmanned Vehicles and Systems International annual competition.

The Maryland students ished 13th out of a field of 27 teams

fin-in this their first year, wfin-innfin-ing a

$500 prize “They are proud of their accomplishment and look forward

to spending more time developing the artificial intelligence code and refining sensor systems to better compete with more experienced teams in 2008,” Watson says.

Robotics Club member Nathan Davidge waits at Reagan National Airport with the team’s AUV robot.

All the electronics and parts for the AUV fit in the travel case on the seat to the right of Nathan “Even at the airport, the student team was working on integrating a new binary protocol for more reliable communi- cation to the motor controllers from

collecting hundreds of voltage measurements from a sensor,

averaging them together, and performing small calculations

that the main computer can ask for without worrying about

the electrical details of how it was done” is an optimization

of the architecture, as Watson explains

A sensor PCB contains most of the microcontrollers

and they have a parallel bus (8 bits wide) that coordinates

information flow and job instructions

Conclusion

AUVSI held this year’s competition July 11-15 at the

Space and Naval Warfare Systems Center TRANSDEC Facility

in San Diego, CA The University of Maryland expects to see

Tortuga or its ‘offspring’ competing again next year SV

Department of Electrical and Computer Engineering,

A James Clark School of Engineering, University of Maryland

www.ece.umd.edu Robotics@Maryland Club — http://ram.umd.edu/trac

Replacement thrusters — www.seabotix.com

AUVSI — www.auvsi.orgRESOURCES

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+656*

6SHHGVHF 7RUTXHR]LQ 6WHHO*HDUV

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6SHHGVHF 7RUTXHR]LQ 6WHHO*HDUV

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6SHHGVHF 7RUTXHR]LQ 7LWDQLXP

$//63(&,),&$7,216$792/76

Q. Do you know of any

humanoid robot kits that

cost less than a $1,000? I like

the ROBONOVA and KHR-1 body

designs with all of the motors and

flexibility, but it costs way too much

money for me I was wondering if you

happened to know of any cheaper

robots out there

— Andy Kerns

A.When it comes to fully articulated

humanoid robots, the ROBONOVA

(www.robonova.com) and the Kondo KHR-2HV (www.kondo-robot.

com or visit www.trossenrobotics.

com) can be purchased for around

$1,000 The Kondo KHR-2HV is the nextgeneration of the KHR-1 and is a littleless expensive than the KHR-1

Since humanoid robots are

becom-ing more popular,there are new robotdesigns coming outeach year A couplethat I am aware of are

the I-Sobot (www.iso

of these two robots,but from what I can see

from the videos on their websites, theyare very impressive The I-Sobot is currently available from several places,

such as Amazon (www.amazon.com).

The RoboPhilo kit should be available byDecember 2007 Table 1 shows a fewbasic specifications for these two robots.Another option to consider is the

BRAT from Lynxmotion (www.lynx

motion.com) which costs less than $300

for the basic kit This is a very basicbipedal robot kit that has a total of six servos (three for each leg) It requiresassembly and a connection with a PC

to control the robot If you add your own electronics and develop your ownwalking routines, the BRAT can becomeautonomous

For those people that want a challenging project, the BRAT is aninexpensive route to get started All ofthe parts on the BRAT are interchange-able and expandable, so at a later time,the BRAT can be reconfigured withsome additional parts to make a 17 or

19 degree of freedom robot

On the subject of reconfigurablerobot kits, you might want to take a look

at look at the Bioloid (www.tribotix.

com) robotics kit This is a very good

general-purpose robot kit which allowsyou to build many different types ofrobots, such as dogs, spiders, six-servowalkers like the Lynxmotion BRAT, andeven the big 17+ servo humanoid robots.The Bioloid robots use the Dynamixel servos, which are some of the most

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?

Figure 1 I-Sobot Figure 2 RoboPhilo.

Servos (degrees

Special Features Built-in Gyro, Voice Recognition,Speaker, Pre-programmed

Motions, Programmable

Pre-programmed Motions, Programmable

robot, you would need the

comprehen-sive kit, which has 18 servos, brackets,

and a microcontroller for controlling the

entire robot The approximate $900

price is a bit higher than the robots

previously discussed, but it has a lot of

different projects and robot designs to

build There is a beginner set which

con-sists of four servos, power supply,

micro-controller, and construction brackets

which costs about $350 that will help

you to start learning how to control the

servos and program the microcontroller

Both the BRAT and the Bioloid kits

require assembly and knowledge about

how to build and program robots

Developing walking routines on your own

can be rather challenging These kits are

not recommended for those who want a

fully functional robot right out of the box

It may take several days to weeks to get

one of these robots to do the same things

as the I-Sobot and the RoboPhilo

Q. I have been searching the

Internet for several months

looking for an inexpensive logic

analyzer My main need is for something

to analyze serial data between my laptop

and various microcontrollers I have seen

prices range from $500 to over $3,000

for the different logic analyzers, and this

is way outside my budget Do you know

of any low price logic analyzers?

— Bill T.

Salt Lake City, UT

A.It is amazing to see how much

logic analyzers cost relative to

oscilloscopes One would think

that with all of the digital electronics

in use today, there would be dozens

of low cost, budget logic analyzers

available on the market

Several months ago, I stumbled

across a very nice and inexpensive

logic analyzer from Parallax (www.

parallax.com) called the BASIC

Stamp Logic Analyzer (part #30010)

Check out Figure 5 It is a very

impressive little tool for $79 With a

sampling rate of 2Ms/s on 16 I/O

lines, it should be able to accurately

monitor all of your serial

communica-tion data with 0.5 µs resolucommunica-tion

It will store a minimum of 1 million

data points to well over 30 million data

SERVO 12.2007 15

Figure 6 BASIC Stamp 2px24 mounted

on the BASIC Stamp Logic Analyzer.

Figure 5 BASIC Stamp Logic Analyzer.

Figure 4 Bioloid humanoid configuration Figure 3 Lynxmotion BRAT.

RB.4 RB.3

RB.7 RB.6 RB.5

RC.0

RC.3 RC.2 RC.1

RC.5 RC.6 RC.4 RC.7

RA.3

RA.0

RA.2 RA.1

MCLR

OSC2 OSC1 RTCC

4 MHz

10 KΩ

+5V +5V

P1

P5 P7 P6

P3 P4 P2 P0

SIN SOUT

P12 P11 P13 P15 Vdd RES Vss

+5V

BASIC STAMP LOGIC ANALYZER (Basic Stamp not required) EXAMPLE

MICROCONTROLLER

Figure 7 BASIC Stamp Logic Analyzer wiring example.

points (the manual states that the

maxi-mum storage limit is based on how much

available RAM is on your computer) With

trigger points set at 0.8V and 1.8V, both

CMOS and TTL circuits are supported

The one requirement to use theBASIC Stamp Logic Analyzer isthat your computer must have

a USB 2.0 connection

This BASIC Stamp LogicAnalyzer is designed tomount directly under a BASICStamp microcontroller (seeFigure 6) It gets its power from thesame power supply to the Stamp, and

it will monitor all 16 of the Stamp’s I/Opins, along with the Vdd, RES, Sin, andSout pins I haven’t tried this, but the

BASIC Stamp Logic Analyzer shouldwork with other microcontrollers thatuse the same footprint

Like with all electronic circuits, theycan be used in a different applicationthan they were originally designed for.This particular logic analyzer can be used

as a stand-alone device All that isrequired is a +5V and GND power source

to the logic analyzer and wires to connect

to the signal that you want to monitor.Remember you will need to provide a common ground betweenthe BASIC Stamp Logic Analyzer andthe system under test Figure 7 shows

a simple schematic illustrating how towire the BASIC Stamp Logic Analyzer

to another microcontroller, and Figure

8 shows a photo of the setup

Figure 9 shows the graphical userinterface for the BASIC Stamp LogicAnalyzer This has some pretty power-ful features, such as setting the triggerlevels for beginning the data storage,setting the maximum data storagelength, cursors for measuring the signals, zoom in and out control, anddecoding serial, SPI, and I2C signals.Figure 10 shows you an example of theasynchronous serial data decoder

I haven’t tried testing the signalvoltage limits to the BASIC Stamp LogicAnalyzer The manual doesn’t statewhat the voltage limits are, so I wouldassume that you are limited to 0-5V signals to the logic analyzer If you havevoltages outside this range, I would recommend that you implement somesort of a voltage signal conditional thatchops/scales the voltage signals to the0-5V range Also, if you do not connectany of the unused signal pins to ground,then the signal on them will float andmay either copy an adjacent signal pin,

or bounce between logic 0 and 1.This is a pretty nice, little inexpen-sive logic analyzer, and I have used itsuccessfully to diagnose a multitude ofprojects, and reverse-engineered othersignals from other devices I wanted touse in my projects SV

Figure 8 BASIC Stamp Logic Analyzer mounted on

a Parallax Professional Development Board and

connected to an SX28 microcontroller.

Figure 9 BASIC Stamp Logic Analyzer software.

Figure 10 Asynchronous

serial data decoder.

For those of you who are interested

in further reading on a similar topic,

Nuts & Volts (www.nutsvolts.com)

will be featuring a project in theJanuary 2008 issue on a Low Cost

Know 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

Beard-Eaves Memorial Coliseum, Auburn University, Auburn, AL

Regional BEST teams from multiple states compete

in this regional championship

www.southsbest.org

Penn State Abington, Abington, PA

The Penn State Abington Robo-Hoop is anautonomous robot basketball event in which robotsmust pick up foam balls and shoot or dunk theminto a basket

www.ecsel.psu.edu/~avanzato/robots/con tests/robo-hoops

Ja nua r y 2 008

25-27 TechFest

Indian Institute of Technology, Bombay, India

Lots of events for autonomous and remote controlled robots including standard Micromouseand several events unique to TechFest: Pixel, acontest for vision-equipped bipeds; Full Throttle:Grand Prix, remote-controlled, internal combustionpowered cars race on a concrete track; Vertigo, aremote-controlled robot and an autonomousrobot must work together to move blocks around;Prison Break, remote-controlled robot mustclimb out of a pit and survive a fall to escaperobot-jail; U-571, an obstacle avoidance contestfor underwater robots

http://techfest.org/competitions/department

Feb ruar y

24-28 APEC Micromouse Contest

Austin Convention Center, Austin, TX

Amazingly fast little autonomous robot critters race

to solve a maze If you’ve neverseen one of these events, go seethis one You won’t believe howfast these things are

www.apec-conf.org

28-Mar 2 Pragyan

National Institute of Technology, Trichy, India

Events in this competition includestandard Micromouse and Sym-Bot, a contest in which aremote controlled robot mustguide an autonomous robot tothe starting line of a course —then the autonomous robot mustcomplete the course by itself

www.pragyan.org/08/home/

Send updates, new listings, corrections, complaints, and suggestions to: steve@ncc.com or FAX 972-404-0269

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Featured This Month

26 Advanced Materials in Insect

Armor by Kevin Berry

27 Armor Considerations in

Large Robots

by Paul Ventimiglia

Events

29 Results and Upcoming

Armor is a subject all combat robot builders willhave an opinion on Manyhave written in detail aboutthe theory of robot armormaterials, with formulae andspecification tables galore

All of this is must-readmaterial if you plan to survive in this sport

With so many edgeable people offeringarticles containing suchdetailed material science, I

knowl-think this article needs to focuselsewhere Instead of trying to tell you what you should do and offering mathematical reasoning, Iwill simplify the issue, based on

my experiences, to the game ofRock/Paper/Scissors

Rock

Rock is solid, it’s hard, it doesn’t bend Rock is strong.Traditionally, a robot builder looking to fend off all attacks will

FEATHER WEIGHT ARM R

● by James Baker

As we do periodically (sorry — pun alert), this month’s Combat Zone departs from our usual format to focus on a topic of interest to all builders

— armor From my own experience and that of many other veterans, this

is the single most misunderstood area when new builders attempt their first bot SERVO put out a call to the community, asking for tips and techniques from builders on this tough subject (sorry, the puns just keep

on a'coming) Four builders answered the call, and we hope their thoughts will be useful to all builders, new or veteran.

Combat Zone is meant to be a resource to the robot fighting community.

We welcome builder’s stories, requests for topics of interest, build reports, and feedback on how to make this even more useful — Kevin Berry

SERVO 12.2007 23

build their machines with heavy,

thick, solid armor This is especially

true at the moment in the

feather-weight class in the UK We currently

have a very high number of robots

built using Hardox, a very strong

wear resistant steel

One example of the rock

solution is my own featherweight,

“Unity” which is a zero compromise

armored steel tank without weapons

and with moderate drive power My

teammate has a similar robot called

“Bloody-L” machined from a solid

billet of high-grade aluminium with

stainless steel skin

It is obvious where the

advan-tages and disadvanadvan-tages lie with

these All but the most extreme of

spinning weapons are unable to even

scratch the outside, but inside the

components are shaken to pieces

The rock is very good against

crush-ing, cuttcrush-ing, and piercing weapons,

but the solid robot transmits impacts

from spinning and impact weapons

directly to the components inside,

causing unseen failures

Having heavy armor also reduces

the other capabilities of the robot,

such as reduced speed or lacking

weapons, which means it can be less

than exciting in rock vs rock fights

When rock breaks, it usually breaks

badly, leaving distorted, sharp

sections of very visible damage

Paper

Paper is light It’s flexible, and

easy to cut and shape Paper absorbs

energy The analogy of the paper

robot is not one built of cardboard,

but one of deformable materials such

as polycarbonate, polypropylene,

HPDE, wood, or even rubber The

characteristics of the paper robot are

the opposite of the rock By allowing

the energy from the opposing

weapon to deform and damage the

armor, almost all of the energy is

used up or displaced, leaving less to

rattle the internal components

This type of armor works very

well against axes or impact weapons,but does not do very well against crushing, cutting, or piercingweapons Because of the relativelight weight of this type of armor,more weight can be allocated todrive power and weapons, makingfor fast and exciting fights, taking small amounts of damageconstantly, but sometimes ending incatastrophic failure

The paper robot (how strangedoes that term sound?) is usually a

crowd pleaser It is also easy to workwith, allowing new builders to getinto the sport without spending afortune on tools and metalworkingequipment I run a number of robotswith chassis and armor made entirely of plastic, which I found hasanother, often overlooked advantage

— I can keep my antenna inside the robot as it is transparent to radiosignals

or penetration, but paper-like in its energyabsorption capabilities

It is a middle ground,giving good levels ofprotection against alltypes of weapons, butstill being more vulnera-

ble than a zero compromise solution.Rubber mounted steel, for exam-ple, fits this description Titanium isalso a good example of scissors-typearmor It is very resistant to cutting,but flexes well to absorb energy.Titanium is not the indestructiblematerial many people think, but it is avery good compromise betweenstronger, heavy steels and light plas-tics It is expensive and hard to workwith, but in the featherweight class, it

is common and works very well Myheavyweight robot “Wheely BigCheese” is made entirely of titanium,

as is the featherweight version Therereally is nothing like it for solving somany problems with just one product.Aluminium is also a scissors type

— more paper than rock — but weuse it very effectively in our heavy-

The spinning disk weapon that tore Bloody-L’s

stainless steel armor destroyed itself doing so.

Edgehog uses sacrificial armor that takes

a lot of visible damage, but saves the internals from shock damage.

Building a robot from titanium gives excellent strength and energy absorption, but they are expensive and hard to build.

Let me ask you: Would you walk

into a hail storm without any sort

of protection/armor for your body? I

am going to guess not unless, of

course, you want to get pelted todeath So, would you create a combat robot without armor, which

is going to face other robots that are

armed to the teeth with variousdestructive weapons that are capable of ruining the creation thattook you so many hours to build?Again, I would hope that theanswer to that would be no.Armor is one of the most critical aspects you must accountfor when you are designing yourcombat robot If you do not havearmor of some sort, what is going

to protect the expensive and critical places inside your robotfrom being destroyed by youropponents? In this article, I will

weight robot “Edgehog” The armor

takes a lot of damage, but keeps the

opponent’s axes from doing internal

damage We have many aluminium

featherweights who require a lot of

repairing after events, but they work

very well

Rock Beats Scissors

Beats Paper Beats

Rock

It is a very black and white subject, or so it would seem from

what I have written so far You can

have indestructible robots that

cannot beat anyone (as they have no

available weight left) or awesome

weapons on fragile robots that fall

apart with the slightest impact, or

you can spend a fortune on middle

ground materials and machining Ofcourse, it is never really black andwhite What happens if we put heavysteel under polycarbonate, or havestainless steel parts of the robot,with aluminium elsewhere?

A hybrid robot made of lightmaterials, using heavy, strong materi-als in specific areas, is one solution

Laminate armor — using layers of ferent types of material — can haveadvantages, as well Bonding theselayers can help them; sometimesthey work better if not bonded

dif-One very cheap solution toimproving the capability of yourarmor is to correctly shape it

Crushers love a flat lid, spinners lovevertical sides and catching edges

Shape your armor to maximize itsnatural properties If it needs to flex,

give it room to do so If itmust not bend, support itproperly Slope as manysides as possible If youhave thick, super strongarmor all around yourobot, do you need internal structure at all?Why not put teeth on thearmor and spin it?

Armor is a subjectthat should be given as muchthought as weapons or drive There

is no perfect solution Some peoplechoose to turn their armor intoweapons, such as ram-bots or shellspinners Others have armor as anafterthought, relying on huge offen-sive weapons to ward off attackers.Whatever you choose to do, itwill always be a compromise, unlessyou live in the UK right now We justhad our weight limit raise from 12 kg(26.4 lbs) to 13.6 kg (30 lbs) to meetthe American standard, so all of ourweapon-focused robots can have 1.6

kg of extra armor, and our less rock-bots can have 1.6 kg ofweapons Does that make them allscissors now? Then, I guess it’s time

weapon-to build a new 30 lb rock or paperrobot SV

ARM R GUIDELINES

● by Chad New

Even super strong ram-bots like Unity take damage sometimes.

SERVO 12.2007 25

explain what I believe

to be the most

critical aspects of your

armor configuration; for

instance, the type, how

you mount it, its shape,

and attachments By

the end of this article, it

is my hope that you will

be able to utilize this

information and improve the

armor-ing techniques on your robots

Mounting

We will start with mounting

because I believe this to be one of

the most important aspects of your

entire armor layout You can have

the best and most expensive armor

ever created, but unless you mount it

correctly, it will be useless If you

have an armor ‘shell’ that mounts to

the base plate or frame, you need to

have very strong attachment points

If your 1/4” titanium shell is held

onto your 1/4” titanium base plate

by 1/8” aluminum brackets, there is a

good chance that it will be torn off

or bent in short order

Consider the forces involved in

the class that you are going to enter

Use appropriate sized hardware that

won’t distend under high loads and

consider using armor mounts that

are just as strong as the armor itself

You might also want to consider

shock mounting your armor Shock

mounting usually involves rubber of

some sort which provides a cushion

When it’s impacted, it allows some

of the force to be absorbed into

the mounts

If your robot’s armor is the

frame itself, you need to plan for the

armor getting bent and damaged

Allow tolerance for components

to work even with a damaged

frame/armor panel Consider

layering the outer area with

UHMW or even a thin shock

mounted strip of metal to shield the

important pieces

Type

The type of armor that you aregoing to use depends on the goal ofyour robot If you want a robot that

is going to be able to withstandattacks from the most destructivecompetitors, then you are obviouslygoing to need strong and thickarmor that is mounted very securely

to the frame If weight is not a concern, you might as well use cheapmetal such as steel; many robotshave even used wood as armor withpositive results

If your robot uses a weapon, youwill likely not have the weight to allocate towards an impenetrablesetup such as steel You may have toconsider materials that are able toabsorb shock well or have a highstrength-to-weight ratio Materialssuch as UHMW, aluminum, and titanium work well in this instance

Shape

I believe that a robot’s armorshould be built around the chassis

Once you have decided the basic bits

of your robot, you need to begin tothink about how you are going toarmor it Are you going to bolt

it flush onto the frame, bend apiece of plastic around thewhole thing, or perhaps evenuse a shaped piece of wood toprotect the robot?

When you design yourarmor, you also need to keepthe shape of it in mind Why

mount it vertically which givesspinning robots a wonderful surface

to grip and impact on when youcan design your armor with aslope so that the angles will help todissipate some of the force (whichwill give you a distinct advantagewhen facing your opponents)? Try

to design your armor so that it willaid your design Do not think of it

as something that has to be onlydefensive If possible, attempt toincorporate it into the offense side

of your bot

Attachments

If after you have completed yourrobot and you find that you haveweight left over, you might want toconsider making some attachmentsfor weapons that you might face.Even if you don’t have extra weight,

it might be worth it to take off awheel, lose a motor, or cut back

on the batteries to give you theadvantage of some added armor

If you are going to fight a horizontal spinner, you might want

to add extra armor at the height ofthe blade That way, it will be less

Rocket, a 60 lb launch bot, uses

its shape, shock mounting,

and attachments to protect

itself from opponents.

Get Flippen, an ant weight, uses the shape

of its armor to keep damage to a minimum.

A great example of what can happen

to even the best designed robots if the mounting is not strong enough.

Our team, Legendary Robotics, has

built (or done major upgrades to)

almost 50 insect class bots (150

gram, one pound, three pound, or

six pounds), and their armor has run

the gambit We’ve had bots with no

armor (all offense), ones mostly

made of armor (all defense), and

many in between

Until the advent of major spinners in the last few years, we had

great success with 1/8” aluminum,

which was easy to work, absorbed

hits well, and was inexpensive Once

ant or beetle spinners started cutting

through it, however, we knew we

had to move to something else In

this sport, you either stay ahead of

the “death spiral,” or it screws you

into the ground

At one event, we were talkingwith Team Barracuda about their

antweight, Flounder It was made of

a novel carbon fiber honeycomb

Exhibiting the sportsmanship thatdefines our sport, they directed us totheir favorite bot supply place, AcmeIndustrial Surplus in Sanford, FL

(www.acmeindustrialsurplus.com

) Well, we hit the mother lode

Besides the CF honeycomb, they alsocarry a Kevlar honeycomb material,

in thicknesses from 3/32” to 1” Infact, they have aluminum honey-comb in all kinds of various sizes

We knew we just had to build a bot

out of this stuff!

Babe The Blue Bot, anantweight, was our first (and mostsuccessful) build Using this material,along with titanium from Titanium

Joe (www.titaniumjoe.com), we

developed a bot that has survivedbattles with some of the Southeast’s(and Texas’, as well) most viciousspinners

Our strategy was to combinethe chassis and armor, using a fairlyclassic wedge/box design The topand bottom are just the rawKevlar, while the sides have a layer

of 0.014” titanium over them.This light, stiff, strong material left

us plenty of weight for a 0.040”titanium plow

We started with spacer/screwsinks/corner braces made of wood,but after having several split by amassive hit from superspinnerPirhana, we upgraded those toUHMW (also from Acme) All cutswere made with hand tools TheKevlar cuts well with a hack saw orcoping saw, and the titanium withsnips The plow, of course, was harder to work, but by wearing out ahacksaw blade, it was done by hand also The Kevlar basically workslike plywood, except it takes hits

likely to rip through and damage

your armor If you are fighting a

vertical, think about a wedge of

some sort, or the ever-popular “keep

away” stick which can be used for

just about any type of spinner The

point is that anything you can add

for a specific opponent is something

that will give you an advantage; try

to allocate weight for attachments

mind that offense and defense are bothhuge factors for the success of yourrobot Again, take note of how you willmount your armor, what type of armoryou are going to use, the shape of it,and perhaps some special attachments

to better equip yourself against certainrobots If you do all of this, chances areyour robot will be in much better shape

at the end of an event! SV

ADVANCED MATERIALS

IN INSECT ARM R

● by Kevin Berry

Babe’s top shows Pirhana damage, while the bottom exhibits the

results of a 30 second ride on SWARC’s kill saw. Battered but functional, Babe’s aluminum bracket, zip tie, and UHMW spacer construction provides nine ounces for motors, battery, ESC, and receiver.

SERVO 12.2007 27

There are some nasty weapons

found in today’s combat robots,

especially in the 120 lb-340 lb weight

classes If your armor isn’t up to the

task, you will not only lose the

match, but your expensive robot

innards will be defenseless Having

the proper armor for a match is

just as important as having that

killer weapon, and often it is more

important

Know Your Constraints

To maximize your chance of

success, you must plan ahead carefully You should first decide howmuch weight you have allottedfor armor The most importantdesign factor is surface area; inorder to maximize protection,you must minimize surfacearea If you reduce the length

or width of an armor pane,then you can increase thethickness of that piece whilekeeping the weight constant

Remember, your robot should nothave to be taller than the largest

extremely well

We bought some 5/8”

thick material for our

light-weight, and plan to layer

some 0.030” titanium over

that (if we ever get it

finished) We’ve also used

this 3/32” as the chassis for

our beetle John Henry, and it’s

proven just as tough in the beetle

class with 0.018” titanium overlay

We’ve seen the carbon fiber

honey-comb used in antweights as well,

and it seems to perform just fine

When we bought it, the 3/32”

ran about 10¢ per square inch, or

about $5 for Babe The 0.014”

titani-um ran about $1 for every six

square inches, or about $18

The plow, made from 0.040”

costing about $1 for every four

inches, cost around $3 So, our

chassis and armor cost $26 Of

course, we bought the material

in bigger sheets, but with

thrifty layout, we use every

possible bit with no waste

Table 1 shows sizes, material,

and weight for all six pieces

I strongly recommend thisapproach for any small bot, andwould like to see someone experiment in a mid-sized machine

Babe has survived dozens of nastybattles, and while sometimes losingthese fights — and often parts — hersoft creamy center has never been

violated Knock on wood (or maybeKevlar)! SV

ARMOR CONSIDERATIONS

IN LARGE ROB TS

● by Paul Ventimiglia

While the 0.040” titanium plow is

barely scratched, the thinner

0.012” does get a bit dinged up.

No marks or penetration to the

Kevlar underneath, however.

“Exploded view” of Babe’s side construction When using wooden spacers, this was how

it looked coming out of the arena, also!

Front view shows the plow attachment The screws are left

a bit loose so it “bounces” over arena irregularities.

Heavyweight Verbal Abuse illustrates the rubber shock mounting technique where its armor will attach to all sides.

Photo courtesy of Dick Stuplich.

Material Size (in) Weight (oz)

component inside!

Always consider the application

of what you are designing You

might not be able to predict what

each of your opponents will look

like at an event, but you know

historically what types of robots have

competed This is an area to take

some design risks in how you choose

to distribute your allocated weight

For example, “there are many

heavy-weight spinners, but almost no

hammer or crushing weapons.”

Using that assumption, I am making

a potentially risky tradeoff as I shift

weight from my top/bottom armor

to the rest of my robot

Importance of Shape

When designing your armor,look at the most powerful robots

that exist and ask yourself, “Do I feel

comfortable letting them hit each

part of my robot?” At a minimum,you should plan to receive an attackfrom a horizontal spinner such asMegabyte or Last Rites, a hammerrobot such as The Judge, and a vertical disk spinner such asNightmare The energy of thoseattacks can be deflected if yourarmor is sloped at an angle

Megabyte, Last Rites, andBrutality have all placed holes in the1/2 inch thick steel arena bumpers

Does that mean your robot musthave better than 1/2 inch steel armoreverywhere? No — of course not — it

is all about the shape of your armor

Thin aluminum and plastic caneasily render a spinning weapon useless if it is mounted at a low angle(below 30 degrees) to the floor

Similarly, having a one inch thicksteel front bumper will do you nogood if a spinner can “catch” onto itsedge Often an entire armor panelcan be torn off from a solid hit That

is why the corners of your robot arethe most vulnerable area; any seam

or edge can be caught by agood spinner

Material Selection

The most common robotarmor materials are alu-minum, steel, polycarbonate,and titanium Your budget

and tools will often be the mainlimiting factor in your selectionprocess

Steel offers the best protectionfor your dollar Mild steel (such as1018) offers good strength andcomes in any shape and size Highcarbon steels (such as 4130 and toolsteels) have the added advantage ofthe ability to be hardened, becomingmany times stronger and harder

to penetrate

A simple steel wedge is yourbest chance of fending off that bigspinning weapon, but plan to have it

at least 3/16 inch thick at a lowangle, and almost 3/8 inch thick asthe wedge approaches 45 degrees.For armor in less vulnerable areas,you can get away with 1/4 inch thickness, if you don’t mind a fewlarge gashes and holes

Aluminum is the most

common-ly used robot building material Itcomes in a variety of alloys; 6061 hasabout half the strength of mild steel,but that comes at about a third ofthe weight More exotic alloys such

as 7075 obtain similar strengths tomild steel, but they can be veryexpensive Additionally, the strongeraluminum will generally fail in a brittle way by cracking, but 6061 is asofter metal that will bend

Polycarbonate (or Lexan) is a surprisingly resilient material It is one

of the lightest materials you can usefor armor, and is available in sheets

up to about one inch thick Although

it has low strength in tension and it

The 1/4 inch steel wedge is being welded

upside-down to steel hinges on WPI’s

winning middleweight entry at BotsIQ 2006.

Note the use of many large fasteners.

Photo courtesy of Paul Ventimiglia.

The 340 lb robots from Robogames

2007 The Judge tries to sentence Ziggy who has added additional shock-mounted panels by removing the side armor just for this fight.

Photo courtesy of Brian Benson.

The 120 lb robots from Robogames 2007 Subzero shows off its shock-mounted armor and titanium wedge deflecting the hits from the drum of Touro Photo courtesy of Brian Benson.

can be cut fairly easily, it performs

well during impact forces This is due

to its ability to flex and still return to

its original shape

Some care must be taken when

designing to use polycarbonate

however, because it is prone to

cracking in areas such as sharp

corners and near holes Additionally,

this plastic does not block radio

waves, and it can give your robot a

nice look because it is transparent

Titanium offers the highest

strength-to-weight ratio of these

materials, but with a very costly price

tag Alloys such as 6AL-4V have more

strength than many steel alloys

Super heavyweights such as Ziggy

and The Judge are clad in titanium all

around; it is necessary to keep their

weight down while covering theirlarge surface areas I personally donot feel it is worth the price to usetitanium armor in the large classes,

so instead I try and allow extraweight to use steel

Mounting Your Armor

If your armor is rigidly secured toyour frame by welds or bolts, it willresist bending well The front of yourrobot will take the most abuse, souse the largest and highest qualityfasteners you can find Reinforce alllong spans with gussets and multipleattachment points If armor panelsare mounted on hinges, make surethey are steel, and bigger than youthink is necessary (I use 1/4 inch

thick walled, 5/8 inch pin steelhinges on Brutality.)

Alternatively, many buildersswear by “shock-mounting” theirarmor Large rubber washers ormetal studs encased in rubber completely isolate an armor panelfrom a robot’s frame By using thistechnique, the energy of an impact ismore slowly absorbed and thereforeyour robot will not be damaged

as easily I prefer to save weight overall by making my frame a part ofthe armor

Whatever you choose, ber to make it easily repairable orbring spares Steel can always bewelded at an event, but good luckgluing back together your shatteredpolycarbonate! SV

remem-Table 1

Material Density (lbs/in^3) Best Used For Other Notes

Mild Steel 0.284 Front wedge, high impact areas, sides Easily machined and welded; welded

with MIG and TIG.

High Carbon Steel 0.284 Front wedge, high impact areas Has to be machined in annealed state;

must be hardened for best results.

6061 Aluminum 0.098 Sides, top, bottom Easily machined, difficult to weld in

thicknesses above 3/8 inch.

7075 Aluminum 0.098 Sides, top, bottom Easily machined, cannot be welded.

Polycarbonate 0.043 Top, sides against non-spinners Very easily machined, should not be

tapped; mount with bolts and washers Titanium 0.161 Works well in all areas Difficult to machine, welds only with

TIG and heavy shielding.

details Results are as

● 1 lb Antweight Class — 1st: Melty

B 2.0, Spam Butcher; 2nd: Baby

Blaster, Ghetto Logic Robotics; 3rd:Green Hornet, Robo-Yasha

Roaming Robots held an event inPortsmouth at the MountbattenCentre on 10/6-7/2007 Go to

EVENTS

Results and Upcoming Events

SERVO 12.2007 29

more details.

RoboCore was held in Brazil on

10/6-7/2007 Go to

details Results are as follows:

● Middleweight — 1st: Touro, Team

RioBotz; 2nd: Orion, Team Triton;

3rd: Team ThunderRatz

● Hobbyweight (12 lb) — 1st:

Puminha, Team RioBotz; 2nd:

Butcher, Team Uai!rrior; 3rd: Team

Botville

Upcoming Events for

December 2007 and

January 2008

BotsIQ Boston Regional, “Rumble

At The Rock,” will be presented

by: BotsIQ Boston in Plymouth,

MA on 12/1/2007 Go to

www.botsiq.org for more details.

The Plymouth North andPlymouth South High SchoolEngineering Teams in cooperationwith BOTSIQ and The BostonTooling and Machining Association,will host a 15 lb BOTSIQ RobotCombat Competition at theEngineering Lab at Plymouth NorthHigh School — 41 Obery Street,Plymouth, MA

Wreck-The-Halls will be

present-ed by Carolina CombatRobots in Greensboro, NC, on

150 g Fairyweight to the 120 lbMiddleweights

RoboChallenge will present theirThinktank Christmas SpecialDecember 28th and 29th inBirmingham, England Go to

· 2 Serial Ports including Bi-Directional USB

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More New Products on the way!

It is the voice for the Heathkit HERO

1 and HERO Jr robots, the RB5X

robot, some arcade games, and

several other devices Many will always

remember hearing this chip asking if

“Dr Falken” would like to play a game

of chess in the classic “War Games”

movie The SC-01 had a long run, but

these days they are getting hard to

find I was concerned about this and

wanted to ensure there was some sort

of replacement option that would be

available for the future

Finding a suitable replacement for

this chip proved to be an interesting

project It highlightsthe many differentproblems that come up

in the robotics hobby

What seemed at first to

be a very straightforwardendeavor ended up covering a lot ofground I’ll try to review all the ups anddowns and share some knowledgealong the way

Currently, there is no direct drop-inreplacement for the SC-01 speechsynthesizer, so I decided to go aboutcreating one At least a hybrid onefor now!

The Language Barrier

First, let me start with how the SC-01 generates its speech Somespeech chips (or modules) accept regular ASCII text strings and others actlike a sound recorder which play back

The SC-01 speech chip

was one of the most

popular speech chips in

use during the ‘80s

The SC-01 speech chip

was one of the most

popular speech chips in

use during the ‘80s

b y R o b e r t D o e r r

SERVO 12.2007 31

stored phrases The SC-01, however, is a

phoneme based synthesizer which

builds words from small sound

fragments called phonemes With this in

mind, I looked to see what other phoneme-basedspeech chips are out there

After looking at the fewavailable chips, it seemedthat the closest matchwould be the SpeakJet(SpeakGin) chip Although

it too is phoneme based,that is about all it has incommon with the SC-01chip (except that they areboth in DIP packages)

In the SC-01, there are

64 of these phonemesdefined The SpeakJet has 72 (allo-phones) plus a variety of sound effects

The first part of the project was to see

if this idea had merit and was possible

All of the codes for each phoneme aredifferent for each chip I went throughand made a lookup table for what Ithought would be a good mapping

of each SC-01 phoneme to SpeakJetallophone With this conversion table

in hand, I had some speech stringsfrom the HERO 1 that I ran through the table

Initially, I had a SpeakJet wired up

to an old Handyboard for testing I thentook the translated string of phonemecodes and with an Interactive ‘C’ program, sent them all to the SpeakJet.The results of that first test were inspiring and showed that this could be

a viable option Some of the wordssounded exactly the same while othersneeded work (More to follow )

The original SC-01 chip.

Schematic for

The Protocol Barrier

Now that the SpeakJet could sound

like the good old SC-01 (provided the

right codes were fed into it), the next

step was handling the protocol it uses

to talk to the host These days, a lot of

peripheral devices can be told what to

do using a single serial line with perhaps

a handshaking line or two

The SC-01 and many earlier

devices are from when most peripheral

devices were parallel based The SC-01

accepts six parallel bits of phoneme

data, two bits of inflection data, and

has a couple control lines to latch the

data and acknowledge (busy) that it

was received This added one more

thing to deal with for a translator The

SpeakJet, on the other hand, expects

to receive all the allophones sent as a

serial data stream

Too Much Power

Another oddity about the SC-01 is

its source of power Instead of just +5V

that most devices seem happy with,

this chip was commonly run at +12V

Even so, it had a nice feature in that

the data lines had 5V compatible

inputs to make it easy to interface to

standard 5V systems A hybrid module

would also need an onboard 5V

regulator to bring the supply down to a

safe level

Enter the Translator

To fit in with the idea of drop-in

replacement for the SC-01, the whole

thing had to plug into the odd 22-pin

DIP socket and act just like an SC-01

Lately, I’ve been working with the

Parallax SX series of microcontrollers

and found that the SX28 was ideal for

this project The translator program

was written in SX/B (BASIC compiler)

to make it easy for everyone reading

this article to follow the code The

SX28 acts as the hardware protocol

translator, phoneme translator, and

handles all the handshaking signals In

order to do this, it must:

• Accept the parallel phoneme and

pitch data meant for the SC-01

• Acknowledge to the hostthat it was received

• Perform a lookup todetermine what the equiv-alent SpeakJet phonemeshould be

• Send any special codes

to the SpeakJet

• Send the new phoneme

to the SpeakJet (if buffer isnot too full)

• Set the acknowledge line high to signalthat host can send another phoneme

The Hardware

To jumpstart the project, thiswhole prototype was built upon anSX28 protoboard that Parallax offers Itcontains a SX28AC/SS-G surface mountchip, voltage regulator, prototype area,and a header for the programmingadapter Programming the SX serieschips also requires the use of an SX-Key

or SX-Blitz The ability to quickly Flashthe SX28 processor with new versions

of the translator code really helpedspeed the development process along

The SX28 is available in both a 28-pin SSOP package and a 28-pin DIPpackage An important point to note isthat pins 1 through 14 are not the same

on both package styles Make sure tonote which package is used in anyschematic that uses the SX28 chip! Carehas to be taken when

switching package styles toensure the wiring is correct

In the example schematic,

a surface mount SX28SSOP package was used

The SX28 chip sitsbetween the 22 pin SC-01socket and the SpeakJetchip to translate all the signals The only exception

is the voice out signalwhich the SpeakJet

handles and goes out through pin 21

of the 22 pin socket Port A of theSX28 handles the serial data to andalso gets the status back from theSpeakJet Port B is used to get thestrobe from the host since that portcan generate interrupts This will allowfor an alternate version of the transla-tor to be written as interrupt driven

A portion of port B can also act as ananalog converter and that pin is wired topin 16 (MCRC) of the 22 pin SC-01 socket It can eventually look at the riginal SC-01 timing signal and adjust the translation speed accordingly Theremaining pins on port B are used to getconfiguration information from a DIPswitch Port C is used to get the phonemeand inflection data from the host

To ensure the serial timing to theSpeakJet would be accurate, a 4 MHzresonator is used Although the internal

RC clock of the SX28 is fine for manyprojects, an external resonator or crystalshould be used when timing is critical

SERVO 12.2007 33

The custom DIP adapter.

Original SC-01 amp board with the DIP adapter replacing the SC-01 microchip.

Issues That Came

Up (and were

overcome)

As a real world test, I pulled out the

genuine SC-01 chip from the Speech

board of my HERO 1 robot and plugged

in my translator gadget

The original power source for this

prototype originated fromthe supply pin of the SC-01socket The HERO 1 can shutdown parts of itself to savepower and as a result thepower on the speech boardwould cycle on and off this12V supply whenever therobot tried to talk It alsomade downloading newtranslator program code achore since the board wouldnormally be off

As a temporary solution, I suppliedpower to the prototype board from the+5V connection on the HERO 1 bread-board The amplifier section on the HERO

1 speech board would still power up anddown to save power Later, the 5V regula-tor will take the 12V from pin 1 on the 22pin socket for power so that all the con-nections are directly to the SC-01 socket

The default behavior of the SpeakJet

is to announce ‘READY.’ It is also whatthe HERO 1 says when you first powerhim up When the power was firstapplied, it would say READY but it wasmisleading I knew it wasn’t going to bethat easy! It only did it the first time itwas powered up and following that, all itmade was a sort of sick ‘Ehhh’ soundrepeating a bit before going silent

Well, that isn’t supposed to pen! It was pretty obvious what wasgoing on with the READY announce-ment, so I took another look at thesource code I found a typo for the vari-able name used for the index to look

hap-up the SpeakJet allophone in the table

As a result, it was always pointing tothe first phoneme in the table (thathappens when your index is always 0)

so that explained it I fixed that andstarted to hear a few new phonemes

I could make out some of thephonemes and portions of words but itwas way off I knew that the lookuptable would need work but thought “Ican’t be that far off!” A little trou-

bleshooting work quickly uncoveredwhat had happened I had used a 22 pinDIP socket to make the plug-in adapter

to go into the original SC-01 socket The

guessed what had happened

Two of the six data leads used tosend the phoneme data to the SC-01

on my custom connector had foldedunder instead of going into their appropriate pins in the socket below.That left two of the six data bits used

to select a phoneme open and in afloating state Usually when something

is open it floats high, so it meant thatsome phonemes would never be usedand other incorrect ones would beselected in their place! Once that wasfixed, it started to sound a lot better.The robot would speak a portion

of what it was supposed to but would

be truncated before it could finish TheSC-01 would accept a single phoneme

at a time and would be ready to acceptthe next while speaking so the speechwould be continuous This ended upbeing another issue

The SpeakJet is nice enough tooffer a 64 byte buffer for incomingcommands/allophones The robotwould send along all its phonemeswhich were being buffered by theSpeakJet Once transferred, the robotwould assume the speech was doneand shut down power to the speechboard, shutting off the sound amplifier.(Hmm, that’s a problem!)

To confirm that was the case, I threw

in a small delay after each phoneme wasreceived and sent over to the SpeakJet Itdefinitely showed this was it and thenbrought up the issue of how to deal with

it The SpeakJet provides a few ing signals It can signal if it’s ready, it cantell you if it is actively speaking, and it cantell you if the 64 byte buffer is half full.Unfortunately, it has no easy way of letting you know when there is only onebyte left in the buffer

handshak-This is something that would havebeen extremely useful in its role ofimpersonating an SC-01 Instead ofsending all it could take and using thebuffer half full as a handshaking signal,

I wanted to spoon-feed the chip andprovide it the allophone codes one at atime so I would know about when itwould be done I did try using thespeaking line as the handshake, but theproblem was there ended up being a

www.robotworkshop.com

Author’s website, home for the HERO

robots and vintage robot Guru

(Pre-programmed SX28 chips with

resonator available here).

www.parallax.com

Provider of the SX series processors.

Offers free software development

References

would either take too much or too little.

Unfortunately, none were just right

Luckily, an elegant little solution hit

me Why not just go ahead and send

codes to the SpeakJet using the buffer

half full as a throttle Then as a way to

sync up the timing, I could use the

Speaking handshake line whenever the

SC-01 was sent a pause or a STOP It just

so happens that the convention used in

the HERO 1 is such that all the speech

sent to the speech board ends with a

STOP to ensure the board would finish

speaking before it was powered off This

was PERFECT! An audible pause between

phonemes might normally be a problem,

but if the phoneme was a silent one,

then no one would notice This is just

what I needed to make it work on HERO

1 and it got around the power issue

After that, some more work went

into the translation table for the SC-01

phonemes to SpeakJet allophones Extra

code was added to consider the two

inflection bits If they changed state from

the last phoneme, then the program will

send out a code to the SpeakJet to

change its inflection to improve the

emulation It’s still not perfect, but keeps

getting better with each revision

One of the last minute additions

into the code was to send a small

pause phoneme to the SpeakJet when

everything was first powered up

Without this, the first phoneme that

was translated and sent to the

SpeakJet was garbled Adding that

delay cleared up the problem and now

everything sounds just as expected

The Extras

Finally — just for fun — I wanted to

use some of the extra features of the

SpeakJet and put a few of the extra

unused pins on the SX28 chip to good

use One of the unused bits on port

B (RB.5) can send debugging info

to a serial port for monitoring the

translation process A small DIP switch

was added to configure the way the

translation is handled Alternately,

instead of a DIP switch, an output port

on the robot or another device could

be used to control these settings

In the example program provided,

DIP switch 1 is used to enable R2/Bio

sounds instead of regular SC-01phoneme translation, DIP switch 2enables extra status info to be sent outthe debug port, and DIP switch 3enables a small section of code to ini-tialize a fresh SpeakJet chip by disablingits startup READY announcement

Now, by merely flipping a DIPswitch, I can have HERO speak just likeR2D2 since it translates real phonemes toequivalent R2 sounds I don’t know if thereal R2 would understand it but everyonethat hears it seems to like it! So, not onlywill this project effectively emulate an SC-01, but also adds value by leveragingsome extras within the SpeakJet

Ideas for Improvement

• Better matching of audio output circuitry here

• Monitor RC circuit that sets SC-01timing and adjust overall timing ofemulation

• Tweak phoneme lookup table

• Add another mode to enable morespecial SpeakJet features like soundeffects

• Make another version to translate

from the SC-02 (SSI263) to the SpeakJet

It should be noted that either theSpeakJet or SpeakGin chips can be usedinterchangeably as the target speechchip with this project For those thatmay not be aware, these two devicesare actually the exact same chip The co-developers decided to pursue differentmarkets and each have their own brandname for this particular speech chip.Eventually, this can all be put on alittle hybrid module as a nice tidy plug-in replacement package For those

of you interested in trying out thetranslator yourself, preprogrammedSX28 chips with a resonator will beavailable from the author SV

SERVO 12.2007 35

Robert has been working on personal robots since building one of the early HERO 1 robot kits when they came out He enjoys repairing/rebuilding/ upgrading all the robots from that era It can be challenging at times, but it is rewarding to keep these old robots going.

About the Author

The source code for the translator isavailable on the SERVO website at

www.servomagazine.com.

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More on the NEMA

0183 Protocol

Back in Part 1, we looked at the

GSV and GSA NEMA commands

While those commands are invaluable

for determining your GPS lock status,

they won’t yield any positional

data, which you will need in order to

generate a nifty plot like that of Figure

1 Let’s take a look at two additional

commands:

• GGA: Time, Position, Fix Type

• RMC: Time, Date, Position, Course, Speed

Remember you can download acomplete NEMA 0183 reference

$GPGSV,3,1,12,20,00,000,,10,00, 000,,25,00,000,,27,00,000,*79

The message name — which isalso referred to as the option —comprises the characters just following the $GP Each data element is separated by a comma

The data elements are terminated

by the * character, followed by thechecksum There is an eight-bitXOR of each character between the

last two characters in the message are

a hex representation of the calculatedchecksum

GGA: Global Positioning System Fixed Data

• Field 1, UTC Time in the format of hhmmss.sss

• Field 2, Latitude in the format of ddmm.mmmm

• Field 3, N/S Indicator (N=North, S=South)

• Field 4, Longitude in the format of dddmm.mmmm

• Field 5, E/W Indicator (E=East, W=West)

• Field 6, Position Fix Indicator (0=No Fix, 1=SPS Fix, 2=DGPS Fix)

• Field 7, Satellites Used (0-12)

• Field 8, Horizontal Dilution of Precision

• Field 9, MSL Altitude

• Field 10, MSL Units (M=Meters)

• Field 11, Geoid Separation

• Field 12, Geoid Units (M=Meters)

• Field 13, Age of Diff Correction in seconds

by Michael Simpson

FIGURE 1

• Field 7, Speed over ground in knots

• Field 8, Course over ground in

degrees

• Field 9, Date in the format of ddmmyy

• Field 10, Magnetic Variation in degrees

• Field 11, Mode (A=Autonomous,

D=DGPS, E=DR)

Both the GGA and RMC fields will

give you the Longitude and Latitude,

but only the GGA will report the

Altitude and Fix Type The RMC

command will report your course and

speed So, it’s clear that we need to

parse both of these commands to

gain all the information

Data Logger

To help you understand the GGAand RMC commands a little better,let’s start out by building a data logger Data loggers are invaluablebecause they let you collect test datathat you can later use to help youtest and refine your projects withouthaving to resort to field tests

As shown in Figure 2, the datalogger is straightforward I have

included both PC andPocket PC versions that will handle allthe modules and receivers discussed inthis series You select the device usingthe Device menu shown in Figure 3.This will set the correct baud rate andenable special setup commands neededfor the Etek and Copernicus modules.You start the data collection byhitting the start button shown inFigure 4 The program will then openthe com port indicated and initializethe GPS module, if needed Collecteddata will be saved to the file indicated

If you want to save the file into thesame directory as the GPSDataLoggerprogram, precede the filename with adecimal point as shown in Figure 4

As data is collected and saved, it isalso parsed The NEMA commandsGGA, GSV, GSA, and RMC are allparsed The pertinent information is

FIGURE 5

FIGURE 6FIGURE 4

SERVO 12.2007 37

displayed on the form as shown in Figure

5 The actual number of bytes captured

and saved will also be displayed If

you see the captured number go up

but none of the data fields are updated,

you have selected the wrong device

Data Plotter

You will want to view the data

you collected I have created two

programs to allow you to do just that

The GPSLogDisplay program shown inFigure 6 will display all the pertinentinformation You select the log filecaptured with the GPSDataLoggerprogram by selecting the File Menu asshown in Figure 7

You have the option of displayingthe data as fast as your computer canprocess the data, or in real time bysetting the RealTime menu shown in

Figure 8 When in real time,the data will be processedbased on the UTC time stamp

in the message What theprogram does is look for differences in the seconds inthe UTC field When it sees adiscrepancy, it delays the program for one second.For actual plotting, youcan use the program calledGPSLogPlot shown in Figure 9.This program will allow you toplot your actual trip By default,the program sets the scale to

200 This divides plot points by

200, thus shrinking the plot tofit on the display You canchange this using the settingsmenu When plotting short distances, use a smaller scale.When you start the plot,the first valid point becomesthe reference starting pointthat will be — by default — thecenter point on the display.You can change this point bychanging the Start x and Start

y points in the settings menu.The actual plot area is a 1000

x 1000 grid You can changethe view of this grid by usingthe small pad on the formshown in Figure 10 The center button will center theview to its default

The plots shown in Figure

11 were all captured with theGPSDataLogger and my pocket PCusing the BT359W shown in Figure 12.This is the most accurate GPS I haveever owned The main reason I have notshowcased it in this series is that it is aBluetooth only receiver You can use thesame interface program as the HoluxGPSLim236 Unlike the GPSLim236, theBT359W does supports WAAS

GPS Parsing Software

While I have included thecompiled version of the pro-grams presented in this article, Ihave also included the source

Function Variable Populated

procGGA

GGA_UTCTime GGA_Latitude GGA_NS GGA_Longitude GGA_EW GGA_FIX GGA_FIXtxt GGA_Sats GGA_HDOP GGA_AltValue GGA_AltUnit GGA_Sep GGA_SepUnits GGA_Age GGA_Diff

procRMC

RMC_UTC RMC_Status RMC_Latitude RMC_NS RMC_Longitude RMC_EW RMC_SOG RMC_COG RMC_Date RMC_Variation RMC_Mode

procGSV

GSV_SATSINVIEW GSV_NOM GSV_MSG GSV_SATIDS(x) GSV_SATELE(x) GSV_SATAZ(x) GSV_SATSNR(x) When GSV_NOM = GSV_MSG then all data has been

collected At that point you should set GSV_NOM = 0

procGSA GSA_SATMODEGSA_SATCOUNT

roll their own Each of the programs

parse the GGA, RMC, GSV, and GSA

NEMA commands The main NEMA

processor function is called ProcNEMA

This function calls four functions to

handle the parsing of these commands

Each function populates a set of global

variables as shown in Table 1 These

variables map to the fields in the NEMA

specification One exception is the

GGA_FIXtxt variable, which contains an

actual description of the FIX type

Take a look at the Dispit function

shown in Program Snippet This

is the heart of the GPSLogDisplay

program This function is called

when the Start button is pressed The

function opens the log file you have

selected, then enters a processing

loop In each iteration of the loop,

the abort button is checked and a line

of data is retrieved from the log file If

the end of the file is reached or the

‘———————————————

‘Get and display the data

‘———————————————

func Dispit() dim tstr as string dim newtime as string dim oldgpstime as string FormMenu(0,0,0,””) FormButton(Disp_Start,-1,-1,-1,-1,”Abort”)

‘First Open the File

if FileOpen(1,gfname,Open) = 0 then msgbox(“Unable to open file: “+gfname,0,”Open File”) FormMenu(0,0,1,””)

FormButton(Disp_Start,-1,-1,-1,-1,”Start”) exit()

FormMenu(0,0,1,””) FormButton(Disp_Start,-1,-1,-1,-1,”Start”) exit()

endif

if FileEOF(1) = 1 then FileClose(1) Print “End of Data”

FormMenu(0,0,1,””) FormButton(Disp_Start,-1,-1,-1,-1,”Start”) exit()

GSV_MSG=0

if GGA_Fix <> 0 then Formlabel(Disp_Longitude,-1,-1,-1,-1,GGA_Longitude+GGA_EW) Formlabel(Disp_Latitude,-1,-1,-1,-1,GGA_Latitude+GGA_NS) Formlabel(Disp_Alt,-1,-1,-1,-1,GGA_AltValue+GGA_AltUnit) Formlabel(Disp_Course,-1,-1,-1,-1,RMC_COG)

Formlabel(Disp_Speed,-1,-1,-1,-1,Format(float(RMC_SOG * 1.1508),”.0”)+” mph”)

else Formlabel(Disp_Longitude,-1,-1,-1,-1,””)

abort button is hit, the file is closed

and the function exits Each line

retrieved from the log file is passed to

the procNEMA function and only

when a GGA message is received does

the display get updated

The plotit function in theGPSLogPlot program is very similar tothe dispit function, with the exception

of how the GPS information is sented The plotit function uses a spe-cial command built into the Zeus lan-guages called GPSCVTLongitudedecand GPSCVTLatitudedec to convertthe GPS positional string data to aninteger value in degrees * 100000

pre-This is a whole number that can beused for plotting

One final variation of the dispitfunction is the StartCapture functionused in the GPSDataLogger program Inthis function, a com port is opened andits parameters are

set based onthe actual device

selected The function also calls varioussetup functions to place the device intothe correct mode when needed Instead

of calling the procNEMA function directly, data from the device is added

to a global variable called rxdat when

it is received A call is then made to a function called procdata This functionpulls a single line (one at a time) fromthe rxdat variable and passes them tothe procNEMA command as before

Sending Log Data

Plotting and displaying data iscool to play with, but the main reason

we want to capture the data is so that

we can simulate an actual GPS ule or receiver I have included a pro-gram called GPSLogOutput shown inFigure 13 GPSLogOutput allows you

mod-to play back the captured log data mod-to

a serial port The program looks andoperates much like the GPSLogDisplayprogram, but also sends a copy of thecaptured data to a serial com port.You select the com port via theSettings menu shown in Figure 14.You can also set the baud rate andflag the data to be sent in real time

Using the Log Data with a Microcontroller

Next month, when we start

to interface the GPS modules

to a microcontroller, theGPSLogOutput program will beindispensable In addition to

your PC, you willneed a DiosPro

‘—- Used for realtime display option strif oldgpstime <> newtime then oldgpstime = newtime

if realtime = 1 then pause(1000) endif

endif

goto loop

endfunc

SERVO 12. 2007 27

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