Servo magazine 11 2008

Tạp chí Servo

Let your geek shine.Meet Pete Lewis, lead vocalist for the band Storytyme Pete recently created the RS1000,

a new personal monitor system for performing musicians It was SparkFun’s tutorials, products and PCB service that enabled him to take his idea

to market in less than a year

The tools are out there Find the resources you need to let your geek shine too

©2008 SparkFun Electronics, Inc All rights reserved.

Hear music from Storytyme at www.storytymeband.com, or check out Pete’s RS1000 at www.rockonaudio.com

Sharing Ingenuity

W W W S P A R K F U N C O M

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Why Just Build a Robot? Be a Robot!

78 Then and Now

by Fred Eady

This circuit gives you ef fective control

of the AC power that is being applied

to your robot’s motor without having

to pamper the microcontroller.

by Michael Simpson

You’ll want to get started building this device as it will be incorporated into the Ultimate Robot Build series which picks up next month.

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I just finished listening to book

one of Kevin Anderson’s Saga of

Seven Suns, in which robots play a

central role In the story, the Klikiss

robots are highly intelligent,

multi-limbed bug-like creatures

that communicate with other robots

using digital data streams and with

humans via speech The tale

reminded me that at least one

perception of intelligent robots

revolves around the power of speech

Unfortunately, progress in

robotic speech is relatively stagnant

Speech synthesis has been a mature

technology for decades, and

advances in large vocabulary,

continuous speech recognition seems

to have hit a wall in the late 1990s

This is in part because the projected

multi-billion dollar market for PC-based speech recognitiondocument processing products nevermaterialized Today, few people eventake notice of the speech recognitionsoftware available for the PC andMac – and most hate the speechrecognition systems used by theautomated attendants employed bythe airlines and credit card industries

Despite the mystique of “AI”

surrounding speech recognition,speech recognition software that you can purchase for your PC/Macworks by simply matching spectraltemplates of sounds and using tables

of likely word sequences to buildsentences For example, if you say

“ball,” the speech recognitionsoftware would identify likely

candidates such as “ball,” “fall,” and “gall.” Now, if the

previous three words are “Johnny hit the,” the algorithm

will likely rank ball as the most probable word Current

accuracy limitations are about 97%, even with individual

training, and accuracy isn’t improved by adding

processing power or memory

The obvious limitation to current speech recognition

software is that it’s simply a replacement for the

keyboard and video display There is no underlying

intelligence or reasoning capability Of course, prototype

systems capable of reasoning have been developed in

academia, but these demonstration projects have been

limited to highly constrained domains

What we need in robotics is a system that not only

recognizes the phrase, “Johnny hit the ball,” but that can

infer with what If Johnny is playing soccer, we might

infer he hit the ball with his head If the sport is baseball,

then we might infer he used a bat Back to our needs in

robotics, the owner of a service bot should be able to

say, “Please bring me the paper” and the robot should be

able to infer that the owner is referring to the newspaper

There are also issues of image recognition, mobility, and

grasping the paper, but they all depend on the robot

understanding the need of the owner

The limitation of speech recognition in robotics then

isn’t in the ability to transform utterances into machine

readable form, but with how the computational elements

of the robot should process the machine readable words

and phrases into actionable commands So, how do you

go about accomplishing this?

It’s a non-trivial task, as a search of the IEEE literature

on Natural Language Processing will illustrate The

traditional techniques — such as Hidden Markov Modeling

— might be a bit intimidating if you don’t have a degree

in computer science However, you can get a feel for the

tools used to map out the contextual meanings of words

and phrases by working with Personal Brain You can

download the free, fully-functional personal version at

www.thebrain.com

You can use the Brain to build context maps that

show, for example, inheritance and the relationship

between various objects in your home (see Figure 1) For

your robot to bring you the newspaper, it would have to

first locate the paper, and it would help to know the

possible locations the paper might be found in the home

It would be inefficient, for example, if the robot began

digging through your clothes’ closet in search of the

newspaper, instead of on the table in your kitchen

Once you get used to working with Personal Brain,

you might want to explore other uses in robotics For

example, I keep track of my various robotic projects –

parts, suppliers, references, etc.— by creating networks

with the program In fact, the best way to build context

maps is to create explicit, detailed maps that actually help

you in everyday tasks SV

SERVO 11.2008 7

8 SERVO 11.2008

Bot Gets Bio Brain

Placing a functioning human brain

into a robot is still well within the realm

of science fiction, but some folks at

the University of Reading (www.read

ing.ac.uk) have created a biological

brain of sorts and hooked it up as a

robot controller It has been known for

some time that cultured neurons are

somewhat like ants that have been

scattered away from the anthill in that

they can no longer function as a single

unit However, when interconnected in

a culture dish, such neurons form

sim-ple networks that display spontaneous

electrical activity and can function as

memories; i.e., they can “learn” things

In this application, Prof Kevin

Warwick and associates placed the

neurons on a multielectrode array

which is a dish that employs 60

electrodes to pick up the cells’ signals

This activity is then used to control the

robot’s movement When the robot

approaches an obstacle, signals are

sent to the “brain,” and its responses

are used to drive the wheels left or

right to avoid hitting the object The

research is not aimed at creating

biomechanical robots of the future,

however Rather, according to

Warwick, “The key aim is that

eventually this will lead to a better

understanding of development and

of diseases and disorders which affectthe brain such as Alzheimer’s disease,Parkinson’s disease, stroke, and braininjury This research will move ourunderstanding forward of how brainswork, and could have a profoundeffect on many areas of science andmedicine.”

Give Us Some Skin

There’s a basic problem with creating a layer of skin for a robot Forthe skin to provide tactile feedback, itmust be able to conduct signals back

to the “brain.” And if the skin is pliableenough to bend with the bot’s move-ments, it has to be made of somethingflexible, like rubber The snag is thatrubber is a terrible conductor But nowresearchers at the University of Tokyo

(www.u-tokyo.ac.jp) say they have

developed a new, highly conductiverubber, paving the way for robots withstretchable “e-skin.”

The trick was to grind up somecarbon nanotubes, mix them with anionic liquid, and add them to the mix

The resulting material flexes like narily elastic but offers conductivityabout 570 times higher Apparently,one can use it to create elastic ICs that

ordi-can be mounted on curved surfacesand stretched up to 1.7 times theiroriginal size with no mechanical dam-age or significant change in conductivi-

ty (You can stretch the stuff more, butconductivity drops by about 50 percent

by the time you get to 2.3 times theoriginal size.) With further develop-ment of the material, bots of tomor-row may be able to feel temperatureand pressure like we do

Must Be Nuts

It isn’t immediately apparent how

students at Troy High School (www.

troyhigh.com) became concerned

about the well-being of the world’sprofessional coconut pickers, but theyare It seems that gathering nuts fromthe “tree of life” requires harvesters toclimb 100 ft trees and chop themdown with machetes, which is bothdangerous and inefficient Hence, the

“robotic tree climber,” which the students developed for the 2008Lemelson-MIT InvenTeams event Theremarkable feature of the remote-controlled device is that it can accommodate changing tree diameters, thanks to its employment

of a DryLin® QuadroSlide linear guidesystem, which was donated by igus,

Inc (www.igus.com), a manufacturer

of various motion-related componentsand machinery The developers of theclimber tell us that it will allow pickers

to scale more than 40 trees per day, asopposed to the present five to 10 Will

bbyy JJeeffff E Ecckkeerrtt

R oo bb yy ttee ss

This small mobile robot sports a

biological controller based on

cultured neurons Courtesy of

the University of Reading.

Flexible ICs may give robots a human-like sense of touch.

Courtesy of the University of Tokyo.

This climber bot could boost coconut pickers’ productivity by 800 percent.

the resulting glut of coconuts cause

a precipitous drop in the price of

coconut cream pie? Only time and

the commodity markets will tell

Heli See, Heli Do

In the past, programming robotic

helicopters has been something of a

pain, given that they must perform

some fairly complex maneuvers and

(unlike fixed-wing vehicles) are

inher-ently unstable But computer scientists

at Stanford University (www.stan

ford.edu) — tired of laboriously

pecking out source code from scratch

— have developed some AI algorithms

that allow their four-foot autonomous

helicopter fleet to teach itself to fly

The process involves both

ground-based and ‘copter-mounted

instru-ments, including accelerometers,

gyros, magnetometers, GPS receivers,

and cameras It begins with a human

using a remote control to put a vehicle

through a series of stunts and

repeating them several times The

instruments record the flight data,

which becomes the basis of the

control program But the AI system

monitors the resulting autonomous

flight data, crunches the numbers, and

relays program modifications back to

the helicopter 20 times per second,

allowing the vehicle to learn from its

mistakes and actually perform better

than under remote control

In the real world, such improved

autonomous performance could

enable these choppers to be used in

mission-critical operations such as monitoring wildfires in real time andsearching for land mines in war zones

Bots For Art’s Sake

According to Oscar Wilde, “Lifeimitates art far more than art imitateslife,“ but sometimes art imitates imitations of life, and a couple interesting works were on display thisyear Perhaps the biggest spectaclecentered around La Princesse, a 50 ft(13 m) mechanical spider created bythe French performance art company

La Machine

The spider was showcased inLiverpool, England, back in September

as part of the 2008 European Capital

of Culture celebrations In the photo,

we see it clinging to the side ofConcourse House, a derelict towerblock that was scheduled for laterdemolition.The spider was built inNantes, France, using steel and poplarwood, and complex hydraulics, taking

an entire year to construct Operated

by up to 12 people strapped to itsbody, it weighs 37 tonnes, has 50 axes

of movement, and offers seven different special effects: rain, flame,smoke, wind, snow, light, and sound

The project cost British taxpayers

£1.5 million ($2.6 million), plus thecost of treating unhinged arachnopho-bia sufferers, but at least admission tothe celebration was free

Less spectacular but (literally)creepy is Miyata Jiro, a crawlinghumanoid robot created by Japanese-born artist Momoyo Torimitsu,who now resides in New York

Miyata is a detailed and lifelikemodel of a Japanese “salaryman”

who basically crawls around onhis elbows like a soldier in thefield He has performed in NewYork, London, Paris, Amsterdam,Sydney, and Rio de Janeiro so far,evoking responses ranging fromlaughter to anger

According to Torimitsu,

“When Japan entered its high growth period in the 1960s, Japanesesociety was transformed into a

`businessman culture’ characterized byentertainment, movies, karaoke, TV,compartmentalized housing, bars, and even a sex industry that catered

to them This artwork reflects myimpression of this particular culture.”Miyata can be seen at

www.youtube.com/watch?v= glUnzzoFUxg You may mistake the

performance for just an amusing littleparody, but thankfully we have critics

to set us straight According to zing

magazine.com’s Rainer Ganahl, “The

power and success of this life-sizedcrawling doll lies in the dramatic representation of a businessman in its most humiliating position: crawling

in the street in a suit This is a stronglinguistic metaphor, as well as a psychoanalytical and a pathologicalone.” So there’s your elightenment for the month SV

R oo bb yy tt ee ss

SERVO 11.2008 9

Stanford’s AI system allows helicopters to

learn aerobatic maneuvers by “watching”

others Courtesy of Stanford University.

Robotics continues to be a popular medium for artists, as demonstrated

by Miyata Jiro, the robotic Japanese businessman.

La Princesse, a giant mechanical spider.

10 SERVO 11.2008

The Self-Reassembling robot is a

precursor to modular,

self-configuring robots of the future,

which are envisioned with many

thousands of parts and modules that configure themselves for varying applications or — as in this case —reassemble all their parts after separation by explosion

In this experiment, the goals ofthe robot are to perform a task, suffer

an explosion, reassemble itself, andcontinue the original task from where

it left off

The robot is designed to disassemble along specific, preselectedlines or weakest links between themodules in a structured fashion Byensuring that the robot separates atthese “bonds” between the modules,the robot absorbs the shock and disassembles at points where it iscapable of reassembling

The self-assembly of the robot ispart of a larger plan for self-repair.This type of self-repair involves diagnosis of the problem/breakpoints, a plan for re-assembly, and

an execution of that plan, according

to Yim

Diagnosis

The robot uses sensors to determine that it is no longer connected to itself The robot consists

of clusters of modules According toJimmy Sastra, the clusters are connected to each other at certainmodules — using magnets Each module face — which is connected toanother module face — has two IR

Contact the author at geercom@alltel.net

by David Geer

A Self-Reassembling Robot

Ever seen a robot torn apart only to put itself back together? Jimmy Sastra, a student in the Modular Robotics Lab at the University of Pennsylvania has He helped create it As with most scientific endeavors, the Robotic Self-Reassembly After Explosion (SAE) project was

a solution to a problem: how to get a robot to reassemble itself after ‘disassembly’ by

‘explosion’ (“Towards Robotic Self-Reassembly After Explosion,” the Modular Robotics Lab, University of Pennsilvania, Mark Yim, et.al.) Jimmy Sastra, a named author on the paper and research student at the University, calls an explosion “the rapid randomized disassembly of

a system from a high-energy event.” As shown in the video linked here with, the explosion

is the separation of the robot as students kick it apart, separating it into three parts.

This cluster of five modules shows the camera module attached, top-side.

Close-up of cluster with camera module.

(infrared) pairs: one is an emitter and

one is a detector

The pairs check to see whether

they can communicate with the set of

pairs on the other module facing

them If they can’t communicate with

each other, they know they have been

“exploded” (disconnected from each

other) The IR pairs also inform themodules as to who their neighboringmodules are

Each cluster consists of five modules screwed together Each module in a cluster also uses IR pairs

to determine which module is itsneighbor Each cluster talks to itselfusing a CANbus, which is a global bus connecting the internal microcontrollers

Planning and Execution

Each module in the robot contains a microcontroller that controls the angle of the module

Each of three camera modulesemploys a vision localization processor The camera module alsocontains a communications unit

The camera module includes a

three-axis accelerometer so that it mayknow its orientation; whether it isstanding or lying down “After we kickthe robot to explode it, it might beupside down Using the accelerome-ter, it will self-right the cluster or theentire robot as needed It needs toself-right in order to locomote to connect to the other clusters,”

explains Sastra

Each of three clusters has an additional stand-alone controller that communicates with the micro-controllers in the camera modules.Each microcontroller runs its ownstate machine (software), according toSastra If the robot is fully assembled,

it walks If it is assembled, one of thethree stand-alone controllers in one ofthe three clusters will become themaster controller over the other clusters and control the walking task

As the robot walks, it uses its IR

By the time this is published,Jimmy Sastra and the self-reassembling robot team will haveattended the Wired NextFest at which they planned to demo therobot “It’s a well attended event,”

comments Sastra

The robot is a collaboration ofvarious labs at the University ofPennsylvania, including CJ Taylor’s lab, which worked on the vision technology and Mark Yim’s lab, whichworked on the modular robotics

Other researchers involved

in the project include BabakShirmohammadi, Michael Park, andMichael Dugan, all of the University

of Pennsylvania Sastra notes thatwhile there are about eight differentmodular robotics labs around theworld, the robot from the University

of Pennsylvania is a very unstructureddemonstration of the technology, and it uses a high impact means ofdisassembling Probably the closest

to this robot is in a lab in Japan,called the Entran robot, which canalso self-assemble

More Entertainment Than A Political Debate!

SERVO 11.2008 11

GEERHEAD

Three separated clusters attempting to

locate each other and re-join.

Two clusters making ground toward each other.

Two clusters even closer The third cluster is shown in the background.

Three clusters re-united into a

single robot.

The single robot returns to its original

activity: walking.

sensors to check whether the clusters

are all connected If they are, it will

continue walking If at any point itdetermines that it is disconnectedfrom the other clusters, each clusterbegins searching for the others Thisbecomes an independent task of eachmaster controller in each cluster Atthis point, the robot is essentially a

distributed system and each clusterwill circle until it locates another.When any two clusters see eachother (the camera of one sees theflashing LEDs of the other, and viceversa), they start moving toward each other As part of the re-assemblyprocess, each cluster needs to localizethe other clusters so they can talk toeach other The blinking LEDs enableeach cluster to ID the others becausethey use different blink patterns.Once the clusters recognize eachother, they come together so thatthey can dock at their ajoining modules, which use magnetic faces,

as previously mentioned

Conclusion

This technology is just the beginning of robots that can quickly re-assemble once they have literally been blown apart into manypieces SV

GEERHEAD

Video demo, self re-assembling robot,

separated, then reconstructing itself

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

12 SERVO 11.2008

Since I like to group similar topics with the questions in this

column, the theme this month seems to be motor controls.

Q.Hey, could something like a relay board be used

for driving really big honking motors with PWM?

I have eight relays, and (unless I’m confused) you

can make an H-bridge out of four, so it seems like you could

use this as a dual H-bridge motor driver if you wanted, and

have your motor power completely separated from your logic

circuitry Or is this nonsense?

- Joe in Fort Collins

A.In reality, you don’t need so many relays to make a

reversible motor controller If you design a motor

controller that is just all relays, you would only need

two relays if one of them is a DPDT (double dole, double

throw) One example of this type of driver is shown in Figure

1 There are only two speeds with this type of a driver: ON

and OFF Diodes D1 and D2 shunt the CEMF, often called

Back EMF to the relay coil and not to the transistors Diodes

D3 and D4 try to keep those voltage spikes out of your

power supply The odd looking diodes D5 and D6 are transient voltage suppressors (TVS) that protect the transistors from excessive voltage spikes between the collector and emitter The values of all of these diodes andtransistors depend upon the current that you are runningthrough your relays; more current = bigger relays = moredrive current to turn on their coils This type of motor controller is pretty common in older “BattleBot” style vehicles It is simple, rugged, and high powered We call itthe “Bang! Bang!” motor controller because it has littlefinesse It literally bangs the motor on and off It works, but

it ain’t pretty With a little more effort, we can create a moreuseful motor controller that can handle very large loads andhave variable speeds, as well Usually, our robot motor controllers are H-bridges that use transistors to choose thedirection of current flow through our motors, and from thatthe motor direction However, high powered H-bridges areexpensive and need proper care and feeding If we use aMOSFET and single DPDT relay, we can create very high current motor drivers for very little cost Figure 2 shows justsuch a motor controller This particular motor driver is limited

to eight amps because that

is the current limit of thetransformer The MOSFET iscapable of handling over 30amps Note that this designuses opto-isolators to protectthe rest of our robot fromunfriendly voltage and current spikes from themotor controller The relayhas the usual CEMF diodeand the MOSFET is protected

by a TVS, as well Anothernotable design characteristic

is the zener diode on thegate of the MOSFET This is

to protect the MOSFET fromhaving the gate ring at a

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?

higher voltage than the Vgs rating of the device Ringing

can occur on any MOSFET that is driving a high Vds (Voltage

across the drain and source of the MOSFET) Even if the

MOSFET has a voltage rating of 60V, the Vgs will typically be

much less than that The resistor R4 is used to bleed off the

voltage at the gate of the MOSFET which will speed up its

switching time The PWM frequency here is limited by the

opto-isolator transition speeds The advantage of this type of

MOSFET/relay motor driver compared to the relay only driver

is that you can PWM the MOSFET and get variable speeds If

you are driving large currents, however, it is a good idea to

turn the PWM off before switching motor directions to avoid

arcing on your relay contacts

Q.I’ve heard that PID is hard to implement but that it

makes your motors run better Is this true?

- Don

A.Hmmm, I guess this depends on your definition of

difficult There have been many articles written about

PID algorithms, and if you have read some of them

you could come away with the idea that PID is horrifically

complex and difficult to implement Really, this is not

generally true Sure, some of the very fancy algorithms that

need to run super fast for super accurate motor controls can

be very hairy indeed But most of that complexity comes

from the need to have high accuracy for special applications

We can implement PID in our robot motors with a minimum

of complexity because we would be happy with just getting

constant speeds that don’t depend much on battery levels

Before we continue, some definitions are in order for the

elements of a PID algorithm

Proportional: We will apply a correction that is

proportional to the difference between the speed we aregoing now and the speed we want to be going In otherwords, if we want to be going 500 RPM and we are going

100 RPM, we will have a larger P term than if we wanted to

go 500 RPM and we were already going 400 RPM

Integral: We will add a correction every time we are not

going the speed that we want to be going This element ofthe PID algorithm is usually the one that is misunderstood.With this element, we will accumulate an error term everycycle of the PID where our speed is not where we want it to

be Sometimes the P error term will not be large enough toreach our terminal speed Over time, the I error term will getlarger and force a greater error correction to eventuallyoccur This is a very handy error term for making smooth corrections to large error terms This term should be keptsmall relative to the other PID elements

Derivative: The P and I elements have been driving us

onward to our terminal speed goal As we approach ourgoal, someone needs to start applying the brakes so that wedon’t overshoot the target This is what the D term will do

As the motor speed gets closer to the terminal value that wewant, the D term will start supplying a negative correction toslow the acceleration down so that we won’t overshoot ourtarget speed (by much) This term will be larger than the Iterm, but still smaller than the P term This term is arrived

at by subtracting the last error from the current error.Eventually (we hope), the current error will be smaller thanthe last error and this term will get increasingly more negative

Error: This is the name given to the difference between

the terminal (target) speed and the current speed

Correction: This is the PWM value that we will give the

motors to tell them to speed up or slow down

So, here is how a PID loop is calculated and used

SERVO 11.2008 15

Figure 2 MOSFET and

relay motor driver.

16 SERVO 11.2008

Read your chosen feedback value and subtract it from

your desired terminal value This is called the error term You

can get this any way you want — via wheel encoder, motor

back EMF readings, or anything else you wish to use It will

be: error = (desired speed – current speed)

Calculate your P term It will be: kP * (error term) =

Vproportional

Calculate your I term It will be: kI * SUM(all past error

terms) = Vintegral

Calculate your D term It will be: kD * (current error –

last error) = Vderivative

Calculate your Correction term It will be: Vproportional

+ Vintegral + Vderivative Note that Vderivative will most

likely be a negative term

Apply your correction term to your PWM setting; this

will set the voltage to the motor

A PID algorithm will have terms that are used to multiply

times the error term These terms will supply the gain of the

term Think of them as amplifiers for the error term in the

PID algorithm Typically, they are denoted with a lower case

k In order of our definition above, they are kP, kI, and kD

You’ve probably heard the term “tuning a PID loop.” This is

the process of tweaking the three terms above to give your

PID algorithm the response you desire

That isn’t so scary, is it? There are more sophisticated

ways to calculate these values and come up with proper

corrections that will work with your PWM generation, but

careful selection of your PID gains will allow your loop (called

a loop because you do it over and over again) to return sane

values Your friendly neighborhood SERVO Magazine website

has a C program written in CCS PCM for the PIC16F73

microcontroller that allows you to play with your PID

algorithm to see what gain values cause what responses

You can download this program at www.servomagazine.

com under Mr Roboto as picpid.zip

I’ll describe the various functions of this demonstration

code first Picpid will allow you to control the speed and

direction of a DC motor through a serial interface at 115200

baud You are free to choose your favorite processor, but I

recommend that you use one that has a hardware PWM, as

well as a hardware USART, so that your PID algorithm can

run as fast as it can in the background This program does

not use interrupts to take the error term; it simply operates

at a sample rate of every 5 ms

To do the best job with a PID algorithm, you should

have the sample rate repeat at a constant rate so your error

terms will be proportional to both the time they are taken

and the error value that you get Picpid is simply an example

program that will allow you to play with PID values to see

what effects they have on your hardware

Picpid uses the ADC hardware to measure the CEMF (or

back EMF) of the DC motor to determine how fast it is

spinning This isn’t incredibly accurate, but it requires no

other sensors to be used beyond that required to get the

voltage from the motor wires Listing 1 shows the GetError()

function which reads that back EMF Feel free to modify this

to get your quadrature readings instead (Listing 1, 2, and 3

are available on the website, as well.) Here, in this function,

you should scale your readings to allow them to match

up with your PWM settings I’m using a 10 bit PWM in the PIC hardware, so I scaled my readings up by two to getbetter response

Note that new settings are only sent to the programwhen you press the L key This allows you to set severalattributes before the motor has to respond to them

Picpid is a very simple PID implementation, but it works.There are bugs in it, such as interesting motor behavior atboundary conditions that I didn’t test and correct for Since Ichose to use 16-bit signed calculations, the resolution isn’t asgreat as it could be, but again, it works Experiment with thesettings to see what happens You may wish to change theprogram to make it implement a positional servo mechanisminstead of one controlling motor speed It can be done!

I will leave this as an exercise for the student You toocan implement PID in your motors quite easily However, Icaution you — a PID algorithm of sufficient sample speed will take over your microcontroller if it is a low speed device I recommend that you implement PID on a dedicatedmicrocontroller and talk to it via a serial connection like thisone or SPI or even I2C so that your main computer can set its “mind” to higher things that you want your robot to

be doing

I hope that you’ve learned something this month

As usual, I can be reached for questions, comments, and criticisms at roboto@servomagazine.com and I’ll be happy

to work on it! Until next time, keep on building thoserobots! SV

signed long getError()/* Find the difference between where we want to be andwhere we are */

{signed long error;

unsigned int16 ma,mb;

setup_ccp1(CCP_OFF); //Turn off PWMdelay_us(500); //wait for steady stateset_adc_channel(0); //get fwd side voltagedelay_us(20);

email: sales@crustcrawler.com

1SORC Technologies, LLC (pronounced “one source”)

announces the release of its premiere product, the

KicCrab walking crab robot kit This kit is one of the

most complete robot kits on the market today,

combining the three basic components of robotics

(mechanical engineering, electronics, and programming)

to create the ultimate robotics experience for both the

advanced and beginner robotics enthusiast

The KicCrab is based on the popular three motor

walker design and utilizes tiny R/C airplane servos which

can be precisely positioned for controlled walking

Many hours have gone into the design to make it

both appealing and functionally balanced for great

performance All structural components are cut from

light but durable expanded PVC plastic

Kits are available in four colors: red, yellow, green,

and blue The functional electronic circuit board is

printed on colored boards to match the crab colors

When complete, the circuit board becomes the curved

shell of the crab, giving it a unique character while

maintaining a robotic look This versatile board is also

equipped with extra ports for the addition of an IR

demodulator for remote control, I2C peripherals, IR

sensors, tactile sensors, temperature sensors, and

light sensors, as well as a modulated IR output for

communications with other crabs or for annoying your

family by changing the channels on your TV

The KicCrab offers USB programming via onboard

USB to TTL conversion It also has a state-of-the-art

onboard Lithium Polymer battery charging circuit that

charges and manages the KicCrab’s battery using PC

power through the USB connection The kit includes the

battery, which should last the lifetime of the robot

The KicCrab also includes the KicChip™ processor

and the intelligently designed KicStudio™ programming

environment This system provides an outstanding

solution for those who haven’t yet mastered the skills ofprogramming Using a flowchart-style programming interface, even the most inexperience programmer can

be using his KicCrab in no time The chip can also beprogrammed in the Basic language for the more experienced programmer Those wishing to learn Basiccan program using the flow chart style and watch as it’stranslated to Basic in real time

The assembly of this kit requires a skill level of 5 andtherefore may not be suitable for children under the age

of 15 Kits are available online for $79.95

For further information, please contact:

New Robotics Curriculum

Innovation First, Inc (www.innovationfirst.com), and Autodesk, Inc (www.autodesk.com), have

teamed up to offer a new robotics curriculum package

It is primarily intended for classroom use, but it includessome features that should make it appealing to thehome hobbyist, as well Autodesk has been around for years, providing 2D and 3D design software to manufacturing, construction, and other markets, and itscontribution is based on the Autodesk Inventor package,which is used by many professional robotics engineers.Innovation First is kicking in its VEX Robotics system,which is already used in more than 2,000 classrooms.The result is the new VEX Classroom Lab Kit, which

“provides a custom solution for robotics education that

is flexible enough to be applied at multiple grade levels,including secondary and post-secondary.”

The basic $699 package contains a set of 17 units,each of which contains a separate lesson, concept, andactivity For a list of included hardware and options, visit

www.vexrobotics.com/vex-education.shtml.

The Lab Kits make it easy to bring VEX Robotics intothe classroom while making budgets go farther Turn-keybundles of essential classroom equipment make it easy

to order while saving money The Classroom Lab Kitwhich is ideal for two to five students This bundleincludes everything needed to design, build, power, andoperate robots Increase the challenge level by addingexpansion kits for advanced sensors, drive systems, and pneumatics For larger classes, add kits for every

additional two to five students.

Bundled kits are ideal for the beginning VEX

Robotics engineering lab and include popular accessory

items Turn-key discounted bundle includes:

• Protobot Robot Kit

• Microcontroller

• Transmitter and Receiver

• Additional Servo

• Bumper Switch Kit

• Limit Switch Kit

• Advanced Gear Kit

• Chain and Sprocket Kit

• PWM Cable Bundle

• (4) Safety Glasses

• Inventor’s Guide

• Tank Tread Kit

• Booster Kit w/Additional Metal, Gears, and Hardware

• 7.2V Robot Battery and Charger

• 9.6V Transmitter Battery and Charger

For further information, please contact:

New Line of Wheels and Hubs

BaneBots has a newly released line of wheels and

hubs specifically designed to

provide a simple, lightweight,

durable, low cost method of

mount-ing a wheel on just about any small

motor or shaft Constructed of a

thermoplastic rubber tread bonded

to a polypropylene core, they

provide excellent traction

The wheels are available in

eight different sizes ranging from a

small 1-3/8” diameter (weighing

only 1/4 oz) up to a relatively

large 4-7/8” diameter Treads are

available in various durometers

including soft 30 Shore A green

tread, medium 40 Shore A orange

tread, and relatively hard 50 Shore

A blue tread

Standard low profile hubs and

bushings are available supporting

shaft sizes from 2 mm upto 1/2”

in both drive wheel and caster

applications Wheels can be mounted one, two, or eventhree wide Mounting two or three wheels to the samehub gives the flexibility of creating wider tread or mixingdifferent durometers

Custom hub solutions are available subject to minimum quantity orders (typically starting at 500)

For further information, please contact:

WHEELS

Is your product innovative, less expensive, more functional, orjust plain cool? If you have a new product that you would

like us to run in our New Products section, please email

a short description (300-500 words) and a photo of yourproduct to:newproducts@servomagazine.com

Show Us What You’ve Got!

520 W 67th St.

Loveland, CO 80538 970•461•8880 Fax: 970•461•8771

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Website: www.innovationfirst.com www.autodesk.com

Innovation First, Inc

and Autodesk, Inc

SERVO 11.2008 19

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

N ove mberr

1 Bloomington VEX Tournament

Ivy Tech Community College, Bloomington, IN

Events include Top-It-Off-2, Pythagorean-2, VEXTractor Pull, and a CAD Design Contest

http://robotics.bloomington.googlepages.com

Indian Trails Public Library, Overland, MO

This year’s ROBOMO will include demonstrations

of mini-Sumo, line-following, mini-Magellan, androbot soccer All robots are welcome There will be door prizes and a Chinese food buffetafterwards

Ontario Science Centre, Toronto, Ontario, Canada

Lots of events including Mini-Sumo, full sizeSumo, fire-fighting robots, line-following, a

walking robot race, Photovore, Search and Rescue,and an Art and Innovation contest

www.robotgames.ca

24 Hawaii Underwater Robot Challenge

Kahanamoku Pool, UoH at Manoa, Honolulu, HI

Timed, multitasking tethered mission

TBA South’s BEST competition

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

Different each year, see website for details The listed date is for the state-wide championshipcontest A month earlier, the various teams haveregional contests and the winners go on to compete at the state-wide competition BEST

is very similar to the FIRST contest except that inthe BEST event, teams of students build robotsfrom standardized kits with only minimal guidancefrom their corporate sponsors

www.southsbest.org/ or www.bestinc.org/

Decc embe rr

4-31 ROBOEXOTICA

Museumsquartier, Vienna, Austria

Robots are tested on serving cocktails, mixingcocktails, bartending conversation, lightingcigarettes/cigars, and other achievements inelectronic cocktail culture

www.roboexotica.org/en/acra.htm

Tallinn University of Technology, Tallinn, ESTONIA

www.robotex.ee

Kuala Lumpur, MALAYSIA

www.iroc.org or www.iiu.edu.my/ICOM/2008

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

20 SERVO 11.2008

The folks at Inertia Labs may have

forever earned a celebrated place

in the memory of combat

robotics fans with their formidable

and uplifting creations like Toro, but

Alexander Rose and Reason Bradley

have also put their energies into other,

less destructive projects One of their

new endeavors at Inertia Labs is as a

designer and distributor for the new

quad motor Surveyor SRV-1Q from

Surveyor Labs — a nifty little treaded

robot outfitted with a high quality

camera Perhaps the most distinctive

detail about the SRV-1Q is that it

allows you to do your surveying

autonomously or over a wireless

network How cool is that? With that

most tantalizing detail about the

Surveyor robot and its capability to be

controlled wirelessly over the Internet,

we were excited to see what this web

savvy robot had to offer

Let Your Robot

Do the Walking

The Surveyor robot can be

acquired in pre-assembled form, or

it can be bought as a kit that needs

to be put together We received the

already built version, but we also

received the base kit so that we couldmake another bot Two bots in onearticle is a bit too crowded, so theproject base will have to wait foranother month

At first blush, it is evident that theSurveyor is one sophisticated bot Thetough rubber treads give the bot arugged feel, and the solid frame constructed from thick plastic andmachined aluminum is like ChuckNorris walking into High Tea The elegant exterior hides four DC gear-motors with a 100:1 gear reductionthat gives the robot both hefty torqueand considerable zippiness The robot

is also quite well equipped in the sensor department A high qualitycamera takes center stage on the face

of the bot, and it is flanked by laserpointers for range finding And in case those sensors don’t make the botaware enough for you, the fancy printed circuit boards (PCBs) haveports for additional sensors like ultrasonic range finders

The robot comes with an antennaand a charger that imbues it with overfour hours of battery life A clearlylabeled switch at the back of the botlabeled ON, OFF, and CHARGE is also

a comforting sight The robot radio is

Lantronix Matchport 802.11b/g WiFi,and the robot can be teleoperatedfrom a distance of 100 m indoors,and up to 1,000 m with a line ofsight The bot makes use of three layers of PCBs (Figures 2, 3, and 4),but with the plastic headpiece holdingdown the camera, the lower boardsare fairly difficult to reach That, however, shouldn’t be a major concern The topmost PCB on a fancyred wafer is what will intrigue mosttinkerers, because it is this board that possesses the spare ports foradditional sensors and other flights

of fancy And to top it all off, the redPCB is graced by the presence of anice Blackfin processor

One Fish, Two Fish, Red Fish, Blackfin

The Blackfin processor fromAnalog Devices debuted circa 2001,and it is designed specifically to support open source operatingsystems like Linux This is great newsfor tinkerers of a programming persuasion, but the descendant of theSHARC processor has something tooffer to more mechanical hobbyists,

as well The Blackfin was designed to

SERVO 11.2008 21

F IGURE 1.T HE S URVEYOR

THIS MONTH:

Surveyor’s Travels

Twin T Tweaks

create a platform where applications

including sound, video, and signal

processing could be integrated

without sacrificing the performance of

any single application A project that

combines video and other signal

processing sounds a lot like a camera

toting robot – how fortuitous! And to

top it all off, the Blackfin cuts through

the waters of signal processing with

the utmost energy efficiency

The Blackfin processor on the

SRV-1Q handles the camera (Figure 5),

which is an Omnivision OV9655 1.3

megapixel sensor For those of us that

don’t structure our thoughts with spec

numbers, that basically means that

the bot is outfitted with a nice color

camera The SRV-1Q seems to be

nothing but quality through and

through, and you get what you pay

for The bot comes with a price tag of

a little under $500, which really seems

quite reasonable given the caliber of

the robot A fine chassis, robust

motors, a stunning camera, an able

processor, and more software than

one could shake the proverbial stick at

all seem like excellent justifications for

something that is a much better use

of one’s money than the newest gaming console

My Robot is More Well-Traveled than Your Robot

We were eager to test out thecapabilities of the SRV-1Q, but theidea of tackling a robot without thecomfort of a software CD did seem alittle daunting We wanted to get anidea of the bot’s capabilities and limi-tations before we tackled it ourselves,

so we looked to the place where anyroboticist would look if they were inthe same situation – Australia!

A fun showcase of the Surveyorrobot’s abilities comes from a somewhat unexpected place – thefolks at the Australian branch of theenergy company British Petroleum

The BP Explorer is a website thatallows users from all over the world

to drive a Surveyor robot around adiorama of a cityscape and the surrounding countryside Not only isthis a cool way to

demonstrate the wireless capabilities

of the Surveyor, but there is alsosomething intangibly empoweringabout controlling a robot that lives inanother continent The project alsoearns kudos for the camera on theSurveyor, which gives a clear color picture of the surroundings that isdetailed enough to read model billboards scattered around the environment that offer clues to asecret message

Why would these intrepid bots begiven a playground by an energy company, anyway? Apparently, thedemonstration is meant as a way tospotlight the company’s environmen-tal initiatives The SRV-1Qs in the BPExplorer all run off of batteries thatare charged with BP solar panels Forthat reason, the bots only run duringthe daytime (in Australia)

When the website debuted, thelittle bots were so popular that thewaiting time to use one of the fivewas several hours When we surfedthe website, however, there was nowait time at all and we were able todrive around at our leisure After acouple of rounds, we felt that wehad become sufficiently acquaintedwith our robot’s Australian cousins,

so we turned back to the home frontwith renewed excitement and pride

in the capabilities of therobot

We personally think

it is a great thing to seethe adventuresome bot involved in the environmental cause,especially when it takesthe form of a fun andinteractive game

Surveyor’s Travels

Even Robots can have

Dog Day Afternoons

After our international adventure,

we were even more excited to tackle

our SRV-1Q Even with the SRV-1Q in

pre-built form, there is some minimal

assembly required All you need to do

it attach the antenna to the bot, and

while this might sound like a trivial

task it turned into something much

more dramatic Normally, the antenna

should just screw into place near the

stern of the robot, but our parts had a

bit of a compatibility problem (Figure

6) The connector on the antenna and

the connector on the bot were both

male, with the connector pins to

prove it It was only a minor setback,

and after a quick trip to our favorite

electronics shack we were ready to

proceed We acquired a male-to-male

connector (Figure 7), but we hoped

that the extended length of the

connection wouldn’t interfere with the

bot’s nifty treads

To begin the process, we screwed

the new connector into the one on

the antenna When we weren’t sure if

it was fitting nicely, we unscrewed the

male-to-male connector, and we were

surprised to see the pin from the

antenna come with it

And with that, our problem had

been solved, and the antenna screwed

onto the robot just as it should have

We were assured by the folks at

Surveyor labs that this mix-up only

occurred in a small number of kits,

but if you were to run across one of

them you can perform a much quickerfix than the one we did The pin inthe connector on the antenna cameout so easily because the connectorwas socketed and it wasn’t soldered

to a wire Since this is the case, someneedle-nosed pliers can be used tosimply extract the pin with no illeffects With the assembly of therobot finally finished, we let the littlebot charge up its Li-poly battery packbefore we made our first attempt atteleoperation

Smooth Teleoperator

Don’t be fooled into thinking thatthe SRV-1Q doesn’t come with anygoodies just because it doesn’t comewith a CD The bot comes equippedwith some handy firmware that makeswireless operation over the computer

a snap To get everything fully ured, you’ll have to visit the Surveyor

config-website (www.surveyor.com) The

Surveyor website provides clear andconcise instructions on how to getstarted with your bot There are aplethora of software applications tochoose from, but we went with thehighly recommended Java console

The Java console can be downloadedfor free, and after the generic installation procedure you’ll have ascreen pop up as in Figure 8

After opening the console, thenext task was to connect to therobot’s wireless network (Figure 9)

An “SRV1” network convenientlypopped up, and connecting was no

problem After we were connected,the mysterious purple smear on theJava console was replaced by animage of our dorm room desk Whilethis might seem random, it wasbecause the robot was looking at ourdesk Before we could officially get toplaytime, we had to configure theMatchport connection for easy access.This actually involves a somewhatlengthy process, but roboticists arecarefully guided through the stepswith generous screenshots and cleardirections

With all of the network nuts andbolts taken care of, we were ready toget going (Figure 10) Some of thecontrols on the Java console are prettystraightforward Directional arrowscontrol the basic movements, while afamiliar red octagon causes the bot tofreeze in its tracks Some controls,however, are a bit more enigmatic.Buttons labeled fast and slow can control the motor speed of the robot,and the different sized rectangles onthe right side of the console canchange the resolution of the screen.Don’t think that you could get a hugescreen for nothing though – there’s acorresponding trade-off in frame rate

In addition to the screen with the terious button, the command promptwindow also pops up with the Javaconsole (Figure 11), and it provideseven more enigmatic feedback that issure to delight programmers

mys-Driving around our own SRV-1Qwas quite like our experience with theAustralian robot, but without the lag

SERVO 11.2008 23

F IGURE 8

F IGURE 9

F IGURE 10

time The scenery of the miniature

cityscape was replaced by the scenery

of our dorm room The quality of the

camera image was stunning, and the

treaded robot was also deceptively

zippy One important caveat, however,

is that the robot will continue to move

in the direction specified until another

command is given We figured that

the driving would be like that of the

Australian bot – pressing a directional

button would cause the bot to move

in that direction for a time proportional

to the time that the button was

pressed This was not the case, and

the unexpected learning curveball

caused the over-eager robot to

crash into a wall Thanks to its robust

construction, no damage was

inflicted, but we were more careful

from then on out

After a bit of practice, the driving

becomes a bit more intuitive, but

slower motor speed is definitely

helpful for navigating obstacle-laden

areas and for enjoying the scenery

The frame rate of the camera is also

admirable, because it is good enough

so that surveying your space doesn’t

become a motion sickness inducing

blurry mess

The robot even has a built-in

software module that allows several computers to view the output fromthe camera, so your robot can have anice audience as it surveys the land

Your Telepresence

is Requested

For those who can study a robot’sbehavior like a patient naturalist anddetermine how the bot could beimproved, the Surveyor website alsooffers the source code for the Javaconsole (which is open source) Thesite even encourages tinkerers to messaround with the code and share theirimprovements In addition to the Javaconsole, there is also a Python console(also open source, of course), and thewebsite has links to all of the mostpopular third party software likeRoborealm and Microsoft RoboticsStudio The popular platformRoborealm can be acquired for free

at www.roborealm.com The

down-load was quick and painless, and soon

we were ready to see what else theSRV-1Q had to offer (Figure 12)

The Roborealm program sports aninterface that looks fairly intimidating,even if only because it has such aplethora of options for image

processing There are options for edgeand blob detection, and also a myriad

of other things to keep even the mosttechnical of tinkerers occupied fordays on end Some of the options givesome quite interesting images, fromthe minimalistic skeleton to the unflat-tering Sobel edge convolution (Figure13) to the trippy Canny edge detectionmethod (Figure 14) You can even turnthe object of your robot’s attentioninto a cartoon using the whimsicalKuwahara variance filter (Figure 15).For all of those folks unfamiliarwith the refined mathematical techniques of image processing (ourselves included), the numerousmethods presented by Roborealm are

a great motivation for some

intellectu-al development You can drag yourcursor over each option for a verybrief description, but this will probablyonly serve to whet your intellectualappetite

You’ll be asking yourself why theSobel edge convolution creates such ascary picture, and a little research willreveal that the Sobel method analyzesthe image gradient and takes theareas of highest gradient as the likelyedges of the image Then, you have

to look up what an image gradient is,and you’ll find out that it is a gradualblend of colors that changes in discretizable steps from low values(white) to high values (black) of color.Then you’ll want to learn about thetrippy Canny method, and the wonderful floodgates of curiosity willhave been officially opened After anexciting whitewater ride, you’ll findthat you are much more well-versed

in the subtleties of image processingthan you were before

But just in case image processing

isn’t your cup of tea, the Surveyor

can also run autonomously using

interpreted C programming Programs

are stored in Flash memory There are

special robot commands and the

protocol is also available on the

website The robot-specific commands

even include those for a “wander

mode” and a “swarm mode.” There

are entertaining videos on the website

that demonstrate these And, as you

might have guessed, there is also

sample code that can be acquired

through the website, and — by

extension — the community of SRV-1Q

users that frequent it

Open Source

Opening Doors

Perhaps the most exciting things

about the SRV-1Q are the possibilities

In the space of this article, we have

hardly even scratched the surface of

this bot It can run autonomously, it

can archive the video it takes, you can

even get a bunch of SRV-1Qs together

to make a swarm The bot can be

expanded with more sensors, and it

can even be given “stereo vision” with

the addition of another camera Hacks

like stereo vision and other things that

score highly on the cool factor scale

are all shared on the Surveyor Labs

website, and a Robot User Forum

encourages hackers and hobbyists to

share their latest projects

All of the possibilities are made

reachable because the bot is open

source Not only can tinkerers mess

around with the source code, but

schematics and other diagrams of the

robot are also freely available Users

can even download a Solidworks

3D model of the SRV-1Q from the

website so they can truly get an idea

of how this robot has progressed from

design to reality The open sourcementality seems to have been trulyadopted by the folks at Surveyor, withall of the shared software, hacks, andenthusiasm for creating a better andmore interesting product

The Surveyor Labs website features a link to a video about theGoogle Lunar X Prize that talks aboutthe new contest to send a robot tothe moon tasked with photographing

the Lunar Lander With all of thepromise shown by the SRV-1Q and theimpressive community that is growingaround it, we wouldn’t be surprised tosee a robot like it end up on themoon someday SV

Special T Thanks t to

Zander Rose and Reason Bradley

of Inertia Labs and Howard Gordon

of Surveyor Labs.

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Featured This Month:

Features

26 BUILD REPORT:

30 Pound Combat Robot

— Mitch by Ray Billings

28 MANUFACTURING:

Even More Things to

Consider When Building a

Fighting Robot by Mike Jeffries

33 PARTS IS PARTS:

Chain Length Calculator

and Chain Path Visualizer

by Charles Guan — Team Test Bot

ROBOT PROFILE – Top

Ranked Robot This Month:

34 Limblifter by Kevin Berry

26 SERVO 11.2008

Frequently at events, I aminundated with questions onhow to get started in combatrobotics I’m always honored bythe requests, and enjoy theenthusiasm that potentially newbuilders bring to the sport Butdue to the violent nature of some of my more high-powered creations, I always feel hesitant totell a 10-year-old how to build aheavyweight spinner! I usuallyrecommend something simpler tostart out with — like a wedge —but up until recently, I didn’t have

an example of my own to display

Well, all that changedfor the RoboGamesevent this year

Introducing TeamHardcore’s first wedgebot: Mitch

Mitch was createdalmost completely fromoff-the-shelf parts and,although there weresome areas that weremachined specifically forassembly, there is no

reason this bot couldn’t havebeen built with a simple drillpress, or even a hand drill andbasic hand tools Most of thematerial used was inexpensive,

as well And the best part: Thismachine was very effective, winning the 30 pound division atthe 2008 RoboGames event;going undefeated in the class

I started out with four of thebasic 20:1 36 mm planetary gearmotors from Banebots They areonly 1.5” tall, allowing me to create a very low profile robotand still have decent power

SERVO 11.2008 27

Paired with the new wheels

that Banebots just

released, this made for a

relatively inexpensive and

responsive drivetrain I also

used the bearing blocks

that Banebots sells to

support the drive shafts I

ended up shortening the

output shafts of the gear

motors about half an inch

to fit into this design The

wheels extend out both the

bottom and top equally, allowing

the bot to drive inverted

For battery power, I wanted

something simple and didn’t want

to overvolt the motors too much

Overvolting is a very common

method for improving the power

output of a DC motor, and frequently

combat builders will double (or

more) the rated voltage of a motor

to get maximum power But I

wanted this machine to be

dependable, with the least amount

of maintenance needed as possible

For that reason, I went with some

four cell lithium polymer batteries,

for 14.8 volts The motors are rated

for 12V, so I felt this was a good

compromise between reliability and

power I used a pair of 2200 mAh

batteries from Hobby City

For speed control, I used the

standard for most of the larger

weight categories: the Victor 883

units from IFI Robotics Since these

are rated for 60 amps continuous at

24 volts, I felt I could run them at

the lower voltage (and probably

nowhere near the maximum amps)

without the fans This was necessary

due to the extremely low clearance

inside the bot There were few

problems with this setup,

although we never actually

stalled the drivetrain, which I

suspect would be an issue if

this ever happened I may

consider making some kind of

custom fan arrangement in thefuture Radio control was provided

by a Spektrum DX6 transmitter coupled with the BR6000 receiver

A 2.4 GHz system such as theSpektrum (or some other non-frequency dependant system) is arequirement for combat events atthe RoboGames Many competitionsstill allow the 75 MHz systems, sothis isn’t mandatory everywhere, but

if you are new to this sport andwant to get equipment that you will

be using for the foreseeable future,

I highly recommend some form ofspread spectrum system Make sureyou get a receiver that correctly failsafes on all channels, such as theBR6000 There are some systemsthat only failsafe on the throttlechannel The remaining electronics

in the system are a small batteryeliminator circuit from Park, and thesmallest main power switch sold byTeam Whyachi A list of the partsused is included here

The front and side rails are 2”

tall by 1” thick 6061 aluminum Icould afford to use such thick material since the bot was going to

be very compact and I would not

have to worry about weight Theback rail in Mitch was actually 1”thick UHMW, although there wouldhave been no reason I couldn’t haveused more of the aluminum in itsplace The truth is, I had the UHMWlaying around Sometimes the right part is whatever junk you have

on hand!

Top and bottom plates are identical, and were made from 1/4”Lexan This was also a matter ofconvenience, since it was also mate-rial I had on hand I had consideredusing some thinner titanium in constructing the top and bottomplates, but the Lexan made for aquick and easy build For the finalcombat-ready machine, I ended upmaking an extra titanium plate toplace on top of the top Lexan plate

to protect the internals I machined

in a 25” recess around the inside ofthe frame rails, so that the top andbottom panels were set into therails This was the only step thatrequired any fancy machining equipment, but could have easily

This is the view of the shock mounting from the underside I used three rubber standoffs on each end These really helped a lot to isolate the bot from the big hits, and I credit a great deal of our success with Mitch to these isolators. This is an overhead view of the bot with the titanium panel removed.

The bolt holes for the motors were

countersunk This certainly isn’t required,

since the clearance top and bottom was

more than sufficient for the bolt heads to

stick out I simply didn’t want an opponent

to be able to “catch” a bolt head that was

attached to the motor/gearbox assembly

and possibly damage it.

This is a view of the interior with all panels removed, showing the layout You can pretty much see all of the components The block of foam towards the top houses the receiver and battery eliminator.

28 SERVO 11.2008

been avoided if needed You could

simply use 1.5” tall aluminum for

the frame rails, and made the top

and bottom plates match theexterior dimensions The only critical dimension was to makesure the distance from the top tobottom plates was 1.5” to correspond to the height of themotors and bearing blocks

Available on the SERVO website

(www.servomagazine.com) are

the AutoCAD drawings (and PDFfiles for those without access toAutoCAD) with the specifications onMitch’s construction, not includingthe wedge mounts With 1” thickaluminum across the front andsides, there is plenty of opportunity

to mount a wedge in almost anyfashion you would like I am

providing these as a guide

to making a simple andeffective combat robotwhich you can copy exactly or modify as yousee fit The frame and drivetrain minus thewedge weighs in at about 15 pounds, givingplenty of weight for any extras youmay feel like adding Our wedgeweighed in at ~12 pounds, giving

us a combat weight of slightly lessthan 27 pounds.The wedge onMitch is constructed of 25” 4130steel, which was cut and weldedinto the final shape A big part ofMitch’s success is due to the shockmounting I used for the wedge Awedge that is more than 1/3 thebot’s weight is obviously substantialfor the class, but the shock mountsreally helped isolate the chassis ofthe bot from the big hits from allthe nasty spinners in the 30 poundweight class The rubber isolatorsare the only item I cannot find you

a link to the exact part I used Ibought these surplus years ago andlike most surplus items, once theyare gone you can never find themagain McMaster-Carr sells manyrubber isolation mounts though, soyou can find similar items, such astheir part #9376K39 Mitch proved

to be a tough little machine, andwas a blast to build and drive Topspeed was manageable at around

8 mph, and was easily controlled Ifyou have any questions on the partsand materials used, I can be reached

at ray@hardcorerobotics.com SV

In previous issues of SERVO, I’ve

talked about weapon and drive

systems in robot combat There are

a lot of important things to consider

that don’t fit under either of thoseumbrellas but still merit considera-

MANUFACTURING:

Even More Things to C nsider When Building a Fighting Robot

● by Mike Jeffries

A more close-up view of the speed controllers.

I have used some zip strips to try to manage

the mess of wires that invariably comes

from wiring a bot Don’t be afraid to tie

down everything that you think will move

around Nobody will ever give you a bad

time after you’ve won a match and tell you

that you have too many wire ties!

For a simple, quick, and cheap locating method for the wheels, I simply stacked washers on each side of the wheel This kept the wheel centered in the wheel opening, but allowed some side to side movement of the wheel on the axle.

The wheels from Banebots get fantastic traction, but they are very soft rubber and wear quickly Buy spares!

Parts List

• Drive motors http://banebots.com/pc/MP-36XXX-545/MP-36020-545

• Wheels http://banebots.com/c/WHB-KS3-298

• Bearing blocks http://banebots.com/pc/MOTOR-ACC/PB-S3751-BB

• Batteries www.hobbycity.com

• Speed controllers www.robotmarketplace.com/products/IFI-V883.html

• Power switch www.teamwhyachi.com/MS1.htm

• BEC www.robotmarketplace.com/products/0-PBEC1.html

• Radio www.robotmarketplace.com/products/0-SPM6600.html

tion when building your bot.

Car vs Tank Steering

Most robots use tank steering,

which is where each side of the

drive system can go forward or

backward independently allowing

the robot to go forward, backward,

or turn in place Car steering works

just the way it sounds The robot

will drive like a large, metal

remote-controlled car One common point

of confusion in tank steering is

turning while reversing With the

way tank steering works, when

you’re turning left from standing

still, the right side wheels are going

forward and the left side wheels are

going backward When you’re

turning left while moving forward,

the right side wheels are spinning

faster than the left side in the

forward direction When going in

reverse, however, the left wheels are

spinning faster backwards than the

right, causing it to rotate to the left

while moving to the right

External vs Internal

Wheels

Internal wheels are better

protected and able to be supported

on both sides External wheels willprevent the robot from being hung

up on a competitor’s armor if it gets lifted off the ground Externalwheels can be hit easily by theopposing robot’s weapons and are subject to many more directimpacts Which option is bestdepends on both the design of therobot and which features are mostimportant to it

Belts, Chains, and Gears

You’ve got to get the powerfrom your motors to your wheelsand weapons somehow Belts,chains, and gears are your threeoptions if the motor can’t have thewheel or weapon attached directly

to it

Belts are fairly lightweight and

can transmit power over large gaps

There are multiple types of belts tochoose from but most use tensionand friction to provide enough grip

on the pulleys on each side of thesystem to transmit power

Chains are stronger and heavier

than belts, but serve essentially the same function as belts They

transmit power from one shaft toanother over a gap Chains need to

be aligned more precisely than beltsdue to their inflexibility If they arenot aligned well, the chain is likely

to fall off or break

Gears require the highest

precision of the three options andare also able to be the most efficient They are not, however,able to span the same distancesthat belts or chains can Tight toler-ances and proper pitch selection can result in a nearly indestructiblepower transfer system, however, ifthe pitch is too small or the gearsare too loose or tight, you’re justasking for catastrophic failure

Chassis

At the core of every competitiverobot is a strong chassis It doesn’tmatter how powerful your spinningweapon is or how high your armcan flip other robots if the chassiscan’t handle the forces that act on

it both internally and externally Asmall number of construction methods make up the majority ofcombat robot chassis today

The first method is to usesquare, tubular, or right angle metal

SERVO 11.2008 29

Beta uses chain drive to

power its electric hammer.

Sewer Snake has external wheels.

Checkmate uses a strong baseplate

for component mounting.

Crocbot uses car style steering to maneuver in the arena.

beams to form a strong skeletal

chassis Armor and components are

then mounted to the chassis This

arrangement allows for easy

replacement of damaged armor and

components, and easy access at any

angle The main downside of this

type of chassis is that unless it’s very

carefully designed it will be heavier

than the other chassis styles

The second type of chassis usesthe frame itself as armor Instead of

working like a skeleton, this chassis

functions more like the shell on a

crab A strong outer body with rigid

internal supports holds all the parts

and provides for a very strong

defense This style tends to belighter than a skeletal chassis butoften leads to difficulty in replacing

These are only a few of themost popular chassis styles Thereare more options of varying complexity and many hybrids of the three mentioned that have seensuccess in robot combat

Armor

Choosing the right armor isoften the difference between winning and losing in robot combat

Do you go with the stronger, heavier steel? Do you choose thelight, but easily cut polycarbonate?

Perhaps aluminum or titaniumarmor is a better fit for the job.You are not limited to a singlechoice in armor Often robots will

be heavily armored in areas thebuilders think will be subject to themost stress and have somethingthat acts essentially as a dust coverfor less vital areas When choosingwhich material, how much, andwhere, you should look at therobots you’ll likely face If there arevery few robots with hammerweapons, top armor is less of a priority With most arenas in usetoday, there isn’t much need forthick bottom armor unless it is astructural part of your robot.Layering different materials canwork very well in robot combat.Having a thin layer of a materialresistant to cutting over a thickerimpact resistant material that cutseasily can act to minimize the negatives while keeping weight andcosts low SV

All photos courtesy of BuildersDB

OH, on September

13th Twenty-three

bots were entered

Upcoming Events Nov-Dec 2008

RoamingRobots willhold an event

in Maidstone,England onNovember 22nd

Antweight Benelux Championshipwill be held by Dutch RobotGames in the Netherlands on

30 SERVO 11.2008

Storm II has internal wheels.

Tillah uses belts to power its spinning drum.

Village Idiot has a

skeletal chassis.

Totally Offensive uses gears to drive around the arena.

November 1st, and a large

bot event will be held on

November 6th

Robots Live willhold events atReading on November

15th, and Birmingham on November

22nd Please go to www.robots

live.co.uk for more details SV

What’s the second

longest-running robotic combat

competition ever? It’s neither

BattleBots nor Robot Wars In

fact, you have probably never

even heard of it It’s the Robot

Battles series of events, which

held its first tournament in 1991

and has been held every year

since then at the Dragon*Con

sci-fi and fantasy convention

every Labor Day weekend in

Atlanta, GA What has kept it

going all these years is its complete

disregard for everything a

mainstream robot combat

competition holds dear

The MC of the event is a former

radio disc jockey and newspaper

editor that occasionally makes fun

of the audience (which has a

disturbingly high proportion of

Stormtroopers) The tournament

itself is half robots and half stand-up

comedy The atmosphere is relaxed,

and matches are often re-run just

because the builders or audience

members feel like it The essence

of Robot Battles is that of robot

combat before the glamour of

cameras, cash prizes, and minor

pop culture icons

There are two separate

tournaments at Robot Battles

The main tournament

happens on Labor Day

Monday — the last day of the

convention — and is for 12

pound and 30 pound robots

The tournament is

double-elimination, and each match

is best-two-out-of-three Leave

your high-energy kinetic

weapons at home, because thefights are open-air on a raised stage, sumo style That means gooddriving far outweighs your weaponchoice, and a fair percentage ofmatches are actually decided whenone robot simply careens off thestage Robot MicroBattles, whichbegan in 2003, caters to the smallest combat classes: the one-pounders and three-pounders Thistournament is enclosed-arena andwith the full set of Robot FightingLeague-approved weaponry allowed

The level of destruction and energy

is much higher The audience lovesshredded parts, flying sparks, and

especially when one robot runshead-on into the floor hazard (agrinder-powered spinning rubberwheel with gratuitous protrusions)and is subsequently sprayed acrossthe arena

For the 2008 event, 29 little

‘bots fought at MicroBattles and 20large robots competed at the maintournament The record number

of small ‘bots necessitated runningthe tournament single-elimination,instead of the usual double in order

to fit the event within its given timeslot The audience packed bothevents to standing-room-only levels,and the convention twice closed thelarge ballroom in which the maintournament was held because the

Thirty pound robots Jaws (right) and Vorpal Bunny Foo-Foo (left) ensnare their weapons.

Überclocker (left) and Poulan Rouge (right) tangle in the 30 pound elimination rounds.

32 SERVO 11.2008

number of people watching had

exceeded the hotel’s fire code limit

The MicroBattles event onSunday saw the first irreparable

arena damage at any Robot Battles

event, when the spinning wheel

hazard was sheared off in the

three-pound class Battle Royale A

solid slam by three-pounder Cloud

of Suspicion broke the mounting

hub off the wheel, sending it

bouncing around the arena floor

Builders and audience alike were

stoked, and the combat arena goes

back to the shop for a completely

new arena hazard to be debuted

later this year In a move that

straddled the point intersection

between confidence, arrogance, and

insanity, Cloud of Suspicion’s builder

strapped six pounds of dead weight

on top of his robot and returned

Monday to fight in the 12 pound

division

This year’s event also saw the

introduction of a new design to thecombat stage The open stageformat of the competition isparticular well-suited to a grabber-lifter type design; one which canmanipulate the opponent by holding

it completely off the floor, notmerely breaking its traction Yet, for as long as the event has run,nobody has built such a machine

This year, two grabber-lifter robotsentered into the 30 pound class:

Jaws, from Team Stingray, and myown entry, Überclocker Jaws didwell, advancing through the loser’sbrackets after losing its first round

to the eventual 30 pound classchampion Due to some poor design

on my part, Überclocker wasplagued with mechanical problems,and I had to repair the bot quiteliterally after every match Despitelosing after the first round, it wasable to put on a good show for theaudience by performing a few body

slams on opponents

The perennial winners returnedagain this year, with the 12 poundclass final match a repeat of lastyear’s Dale’s Homemade Robotsswept all the categories at theMonday tournament, except for the

12 pound Battle Royale Other historically successful teams including Blade Robotics and EvilRobotics also placed Here’s the list

of champions and runners-up:

• First place 1 lb class: Gilbert, TeamMeatheads

• Second place 1 lb class: MisdirectedPedestrian, Team Meatheads

• First place 3 lb class: NuclearKitten 5, Team Test Bot

• Second place 3 lb class: Ringo,Evil Robotics

• First place 12 lb class: Omegaforce

2, Dale’s Homemade Robots

• Second place 12 lb class: NicoleRichie, Team Shenanigans

MC Kelly Lockhart

entertains the crowd

at the Robot Battles

Tournament on

Monday.

Overthruster knocks Jaws off the stage using its innovative automatic flipper mechanism, moving on to take the 30 pound division championship.

The small arena is enclosed

by 1/4” polycarbonate sheet and features drop-out pits and

a spinning wheel hazard.

A clean gash in a 1 lb robot’s titanium front plow.

SERVO 11.2008 33

● by Kevin Berry

PARTS IS PARTS:

Chain Length Calculat r

and Chain Path Visualizer

An endless source of information

on bot building is the RFL forum

on Delphi Forums (www.chief

delphi.com/media/papers/1598).

A recent thread had a great

discussion about a software tool —

Dr Joe’s Chain Length Calculator,

and the accompanying Chain Path

Visualizer This handy tool lets a

builder input sprocket and chain

data (up to 12 sprockets!) and out

pops the geometry to build the rig

The Excel front end drives a macro

called Goal Seek, that does loops of

“what if” analysis to optimize the

design The outputs and a graphic

visualize the answer, while the raw

outputs are on other tabs

I haven’t built any chain driven

mechanisms myself that would

require this level of calculations,

but according to the folks on both forums (RFL/Delphi andCheifdelphi), it’s both useful andaccurate

Dr Joe Johnson, the creator,has a few comments worth noting:

“This is a tool I use to get my chain adjuster travels right and to give my “gut” a chance to “see” the chain path before I commit to it in metal It is not a perfect

tool It does not have any way to enter a slider, for example.

Here is how I use it most often:

1) I lay out my chain path (counte-clockwise order around the chain).

2) I move my “idler” up and down (or left and right) the amount I plan to build in to my adjuster so that I can tell if I can actually tighten the chain.

Alternatively, I use it to see if I can swap sprockets and still tighten

my chain with the different ratio (this is a non-obvious calculation

at times).” SV

• First place 30 lb class:

Overthruster, Dale’s Homemade

Robots

• Second place 30 lb class: Scimitar,

Blade Robotics

For 2009, the Robot Battles

main tournament is moving to a

larger ballroom to handle the

increasingly large audience With

Dragon*Con hosting a Robotics

program track specifically to

introduce more people to robots

and robot fighting, the competition

is only going to grow larger and

more intense So, if you’re tired of

the same old arena, consider

coming to Atlanta over Labor Day

weekend 2009 and checking out

not only the Robot Battles

competition, but Dragon*Con as a

whole If you are already attending

the Con, and have(somehow) missed usfor the past 18 years,then you know what to

do next year Here’ssome resource links toget you started:

• www.robotbattles.

com is the event’s

website Look here forthe rules, photo galleries, and onlinecommunity Make sure

to join the email list!

• www.dragoncon.org is the

website of the hosting convention,Dragon*Con, your one-stop shopfor any sort of science fiction,comics, fantasy, role-playing, anime,subcultures, and much more

As a bit of interesting trivia: Theoldest robot fighting competition —Critter Crunch — began in 1987 atthe MileHiCon in Denver, CO RobotBattles is a direct descendant ofCritter Crunch, with almost identicalrule sets SV

Dr Joe’s Chain Path Visualizer.

Überclocker holds Scimitar perilously

close to the stage’s edge.

150 grams VD 26/7 150 grams Micro Drive 10/3

1 pound Dark Pounder 44/5 1 pound Dark Pounder 23/3

3 pounds 3pd 48/21 3 pounds Limblifter 12/1

6 pounds G.I.R 17/2 6 pounds G.I.R 11/2

12 pounds Solaris 42/12 12 pounds Surgical Strike 19/7

15 pounds Humdinger 2 29/2 15 pounds Humdinger 2 29/2

30 pounds Helios 31/6 30 pounds Billy Bob 12/4

30 (sport) Bounty Hunter 9/1 30 (sport) Bounty Hunter 9/1

60 pounds Wedge of Doom 43/5 60 pounds K2 14/2

120 pounds Devil's Plunger 53/15 120 pounds Touro 14/2

220 pounds Sewer Snake 46/13 220 pounds Original Sin 12/5

340 pounds SHOVELHEAD 39/15 340 pounds Ziggy 6/0

390 pounds MidEvil 28/9 390 pounds MidEvil 3/0

Top Ranked Combat Bots

History Score Ranking Limblifter – Currently Ranked #1

Historical Ranking: #6 Class: 3 pound Beetleweight Team: Team GuavaMoment Builder(s): Brendan McClure Location: Edmonton, Alberta, Canada

BotRank Data Total Fights Wins Losses

Limblifter has competed at

Kilobots X, WBX-IV, Kilobots XI,

and WBX-3 Details are:

● Overall configuration: Four wheel

drive with lifting arm that can

go 360 degrees around the

● Wheels: 2” Lectra Lite flites.

● Drive ESC: 2x Banebots 3-9 ESC.

● Drive batteries: 1320 mAh 7.4V

Banebots gearmotor, RS-385 motor

● Weapon controller: Banebots

5-18 ESC

● Armor: 1/8” 6061 Aluminum,

1/4” UHMW-PE

● Radio system: Futaba 8U.

● Future plans: 60 lb version of

Limblifter

● Design philosophy: Know your

strengths and weaknesses, andbuild accordingly

● Builders bragging opportunity:

#1 ranked Beetleweight onBotRank.com! SV

Photos and information are courtesy of Dennis Beck All fight statistics are courtesy

of BotRank (www.botrank.com) as of

September 14, 2008 Event attendance data

is courtesy of BotRank and The Builder’s

Database (www.buildersdb.com) as of

September 14, 2008.

WAR has much of what you

expect — flying shrapnel,

destruction, winners and losers, but

unlike real war, Western Allied

Robotics competitions are always

good natured fun The organization

currently has a 12 x 16 foot steel

and polycarbonate arena capable of

containing powerful 30 lb robots,

but WAR had a much simpler start

A lot of early BattleBot builders

came out of the Pacific Northwest

After the first season of BattleBots

appeared on TV, a dedicated fan

contacted several local builders to put

on a robot demonstration at a regional

science fiction convention The builders

had a great time showing off their

robots and talking to people who were

interested in getting involved Near

the end of the show, Brett Dawson

of team UVGScorpion brought out

two small robots and put them on

the ground One was a four-wheel

wedge and the other was a horizontal

spinner He needed someone to drive

the wedge robot so he handed the

controls of the wedge over to me

Over the next five minutes, Brett and

I battled it out with cheering crowds

As Brett schooled me on the fine

arts of robot destruction, it was

clear from the crowd’s reaction that

the robots did not need to be big to

generate the same excitement we

had experienced at BattleBots

A small scale fighting robot

com-petition was scheduled for April 2002

at Gasworks Park in Seattle Brett built

a 6 x 6 foot wood arena with

polycar-bonate walls to contain the robots

Having an actual arena to compete

in made the event more than just talk

or a dream; it solidified things and the

race was on to design and build an

effective robot for the competition

Computer scientists, artists,

teachers, and students made up the

group Only about half of the original

competitors had ever built or competed

with robots before Making things

even more challenging, robots had

to weigh one pound or less This was

a few years before cheap, reliablespeed controllers that would fit intosuch small robots became readilyavailable Even the experiencedbuilders had to figure out how tomake these things powerful but small

Luckily, there was an activeonline community to provide adviceand guidance to anyone who wasinterested in building People workedmodifying RC toys and co-optingmotors and electronics from RC air-planes and cars to build their creations

Well over a dozen robots competed

in the first event with robots thatranged from remote control rats thatcould only turn left, to powerfulspinner and wedge robots that weresolidly built The first event was such

a solid hit with builders that everyonewanted to do it again, and soon

No one is sure of how the term

“War Lord” came about, but it wasthe title thrust upon whoever represented WAR with the largerRobot Fighting League The firstWar Lord was Mike Morrow ofTeam Juggerbot He helped organize WAR’s participation in theDavinci Days festival in Corvallis, OR

The robots fit right in with the kinetic sculptures and creativelyengineered machines that drove thetheme of the festival WAR heldanother successful antweight competition Crowds were alsoentertained by robots ranging from

60 to 340 pounds holding strations by pushing each otheraround and attacking large objectslike washing machines Becausethere was no large arena to containthe robots, no actual fighting was allowed at the festival, but afterwards a few of the competitorsgathered at a remote parking lotand had a street fight with some ofthe less hazardous bots

demon-One of WAR’s strengths as an

organization is that so many peoplehave stepped up to handle the events.For years, Dylan Feral-McWhirter ofTeam Evil Squirrel was the standingWar Lord and managed the arenalogistics Adam Conus of TeamWildcard and Scott Ferguson ofTeam Whoopass held events in theirbackyards and the term BotBQ wascoined to refer to fun with equalparts robot fighting and grilled hotdogs As the events, robots, andarena have gotten bigger, biggervenues have been needed

Rob Purdy of Team Gausswavehas grown WAR to the next level

as an organization In 2006, WARbecame a branch of the SeattleRobotics Society The alliance madesense given that Bill Bottenberg ofTeam Crash was running a robotclass with young kids to get themexcited about science, engineering,and learning about how thingswork As the new War Lord, Robalso drove larger competitionswhere hundreds of spectators couldenjoy the show, like at the CenterHouse at Seattle Center and in association with large hobby shows

As the organization has grown,

so have the robots In the early days,only the one pound antweight classwas supported Now the focus islargely on the three poundBeetleweight and 12 pound Hobbyweight classes, although one poundrobots still compete Whether large orsmall, these events have brought theregional robot building communitytogether and entertained thousands

of people Where will WAR go fromhere? It’s hard to say, but as thesport continues to change, WAR will be up to the challenge SV

● by Robert Farrow

SERVO 11.2008 35

36 SERVO 11.2008

If you visit a robot club or any

robotic function for that matter, it

is likely that you will meet someone

who is interested in humanoid robots

Often, these enthusiasts are not

par-ticularly interested in building robots

that perform useful tasks Instead, they

wish to build a robot that looks and

moves like a real person They may or

may not want to endow their creation

with artificial intelligence (AI), but they

nearly always want to create the

illusion of life

My interest in robotics has always

been very diversified and I too have

always been fascinated with the idea

of creating the illusion of life Perhapsthat was a motivating factor that pushed

me towards another of my hobbies —ventriloquism It occurred to me thatthe techniques used in puppet con-struction might be of interest to manyhobbyists interested in animatronics

A typical ventriloquist puppet iscarved from wood or molded from someform of composite material such asplastic wood or papier-mâché In eithercase, the head cavity must be openenough to add mechanisms such aspulleys and levers to control the move-

ment of the mouth and otheroptional features such as movingeyes, eyebrows, and eyelids

If we are creating a roboticpuppet, the head must containall the moving parts found in

a standard puppet plus appropriate actuators (motors

or solenoids) to effect themovements Since I wantedthe puppet to appear life-like,

it was important to animatesome body movements inaddition to the facial features

In order to simplify the programming aspects of theproject, servo motors were

used as actuators This meant that theoverall size and weight of the puppethad to be kept to a minimum Keepingthe puppet small was no bother To thecontrary, it was actually very intriguing.Normally, a ventriloquist’s puppet has

to be big enough so that a hand can

be placed inside it to perform themanipulations With a small puppet,everyone would know it was not beingcontrolled in the normal manner.The puppet’s head in this project

is smaller than normal and it has tocontain even more mechanisms than

a standard puppet If the head wasmade from wood or composite materi-als, the required wall thickness wouldreduce the size of the head cavityeven further, adding to the problem.One solution is to use a plastic headfrom a doll or holiday decoration Thethin plastic shell would provide themaximum interior space

I found a Halloween prop thatwas the perfect size, but (as youwould expect) it had a ghoulish lookthat was not appropriate I usedepoxy putty to fill in unsightly wrinkles, alter the lips, add teeth, andlift the cheeks Epoxy putty is as easy

to work with as clay — but for only 10

or 15 minutes — so don’t try to do too

much at once Figure 1 shows the

altered head before painting

The back of the head was cut

away to allow easy access to the

inside Magnets were epoxied in

appropriate positions (on both pieces)

to hold the cut piece in place and still

allow easy removal for repairs

Figure 2 shows the interior of the

head, which contains three miniature

servos: one for the mouth, one for the

eyes, and one for the eyebrows The

details of how you mount your servos

depends on the features you want and

the space available in your puppet’s

head It is also important to realize

that you can purchase servos in various

sizes with a wide variety of torque,

speed, and noise levels, so consider

your needs carefully

Most of the bell

cranks, disconnects, and

other apparatus I use are

mechanisms designed for

model airplane

construc-tion and can be found in

many hobby stores Your

local hardware store can

also be a great source for

small pulleys, lazy-susan

bearings, and such

of a hole because the opposing rotationalmotions can cause binding The use ofthe bell crank in Figure 2 allows themotor to be mounted away from theeyes This can be very advantageouswhen working in a confined space

The puppet’s body is shown inFigure 4 and is constructed primarilyfrom wood Padding may be needed

to make the body look more naturalunder the clothes His full height is

28 inches The legs are made fromPVC pipe One leg of the pants ispulled up to show the pipe

Figure 5 shows how the head ismounted on a hinge to allow a forward tilt under control of the neck-mounted servo The lazy-susanbearing gives the head the ability torotate The neck is connected to aservo mounted in the body using ashort piece of rubber hose The flexibility of the hose connection prevents binding by allowing fortwisting and bending (much like

SERVO 11.2008 37

FIGURE 2 The interior of the head is

cramped The miniature servos shown

move the eyes and eyebrows Notice

the magnets on each side.

FIGURE 3 A puppet’s eyes are easily motorized for computer control.

FIGURE 4 The puppet’s body

is hinged to allow side-to- side tilt The legs are made from PVC pipe.

FIGURE 5 The head is hinged to tilt forward and mounted on a lazy- suzan bearing to handle rotation.

38 SERVO 11.2008

universal joints on an automobile

driveshaft) while ensuring a secure

connection The body is hinged to the

hips allowing a small side-to-side tilt

Figure 6 shows how the servo is

mounted to control this movement

The connecting rod passes through a

hole in the bottom of the body and

connects to an eye-bolt in the hip

surface Figure 6 also shows a Parallax

USB servo controller that will be

dis-cussed later The arms aren’t functional

in a true robotic sense, but the pull of

a string creates just enough movement

to add to the illusion of life

Figure 7 shows the fully clothed

and painted puppet Fake fur from a

cloth store was used for hair The USB

cable for the servo controller, as well

as a power cable are run down the

puppet’s leg and extend from the

bot-tom of the pants to make connections

//——Constants COMMS_PORT = 1 JOYSTICK_PORT = 1 //==================================================================== MainProgram:

GoSub Instructions GoSub SetUp GoSub Initialize GoSub Start_Control GoSub FinishUp Exit

//==================================================================== Read_Joystick:

GetButton btn

if btn == Buttons[0] then n=MsgBox(I_M)

if btn == Buttons[1] then Quit = true joystickE JOYSTICK_PORT,jvalue

while !Quit GoSub Read_Joystick //—-check buttons first (special movement combinations

if jb == B_Yes then GoSub Yes_Combo \ continue

if jb == B_No then GoSub No_Combo \ continue

if jb == B_Combo1 then GoSub Combo1 \ continue

if jb == B_Combo2 then GoSub Combo2 \ continue //—-then move all motors based on joystick’s position GoSub HeadR_Movements

GoSub HeadT_Movements GoSub Arms_Movements GoSub Brows_Movements GoSub Eyes_Movements GoSub Mouth_Movements GoSub Torso_Movements wend

Return //==================================================================== Yes_Combo:

//—-Yes comination movement

m = “Yes”

xyText 0,100,m+spaces(20),””,20,fs_Bold ramping = HeadTRamping

channel = HeadTChannel for i = 1 to 3

nn = 750

a = char(channel)+char(ramping)+char(nn&255)+char((nn >> 8)&255) SerOut “!SC”,a,char(13)

delay 500

nn = 950

a = char(channel)+char(ramping)+char(nn&255)+char((nn >> 8)&255) SerOut “!SC”,a,char(13)

delay 500 next Return //==================================================================== HeadR_Movements:

//—-rotate the head ramping = HeadRRamping channel = HeadRChannel

if HeadRTime < Timer() rHeadR =random(HeadRRandomness)-HeadRRandomness/2 HeadRTime = Timer()+1000 // random movement every 1000 mseconds endif

nn = HeadRLowLimit+round(jr*(HeadRHighLimit-HeadRLowLimit))+rHeadR

a = char(channel)+char(ramping)+char(nn&255)+char((nn >> 8)&255) SerOut “!SC”,a,char(13)

Return //====================================================================

FIGURE 9 Partial listing of the Real_Puppet.BAS

program for controlling the puppet.

FIGURE 6 The body is hinged at the

hips and moved with a servo The

Parallax servo controller simplifies

the controlling program.

FIGURE 7 The complete puppet looks

very lifelike when being manipulated

with the joystick.

easy while being hidden from view.

The clothes for a small puppet are

not easy to find An outfit for a 12-18

month old child was tailored and

modi-fied to give it the correct proportions

The features on this puppet allow

for a variety of emotions When the

puppet lowers his eyebrows, for

example, he looks mad Raising the

eyebrows while keeping the mouth

open will express surprise

In order to make control of the

puppet as intuitive as possible, all the

movements on the puppet were

associated to similar movements

on an extended joystick Figure 8

summarizes these movements

Some of the puppet’s actions are

provided automatically by the computer,

thus making the manipulation easier

for the user Buttons on the extended

joystick, for example, can be

pro-grammed to provide specific movements

for the arms, or head movements for

yes and no All of these motions could

be created by controlling the puppet

manually with the joystick, but

preprogrammed movements can have

pre-selected servo speeds and limits so

that the automated movements can

be as lifelike as possible Furthermore,

the arms, head, and body all havesmall random movements pro-grammed into them even when thepuppet is not being controlled Thissimulates life-like restless shuffling

At this point, we are ready to create the program to bring the puppet to life We used RobotBASICbecause it has the ability to read andwrite to all the ports on a PC (parallel,serial, and USB) A Parallax USB multi-

servo motors controller www.Parallax.

com) makes it easy to control the

servos because it will simultaneouslymove the servos using the positionsand speeds requested by the controller program and maintain thosepositions without further intervention

The RobotBASIC program reads thejoystick and then commands the servomotor controller module to position themotors accordingly, reflecting the posi-tioning of the joystick and/or buttonpresses The program is too long to listhere in full, but the listing in Figure 9

shows a representative sample of some

of the subroutines You can download

the full program from www.Robot

BASIC.com It is well commented so

it should be easy to follow the logic.The techniques demonstrated inthis article can be valuable in a widevariety of projects Even this projectitself can be the starting point for furtherideas For example, instead of usingthe humanoid form as a manually controlled puppet, you could place itunder automatic computer control Ifyou combine voice synthesis and voicerecognition with the puppet’s ability tosimulate emotions, it is easy to imagine

an amusing interactive robotic display

Of course, the techniques shownhere can be utilized in robotic projectsinvolving humanoid forms and otheranimatronic characters Constructingyour own computer-controlled puppetallows you to have the features youwant along with the ability to control

it as you see fit SV

SERVO 11.2008 39

JOYSTICK ACTION

• Twisting the stick

• Moving the stick forward/backward

• Moving the stick left/right

• POV hat left/right

• POV hat forward/backward

• Trigger (firing) button

PUPPET MOVEMENT

• Rotates the puppet’s head

• Tilts head forward/backward

• Tilts the body left/right

• Moves the eyes left/right

• Moves the eyebrows up/down

• Opens the mouth

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FIGURE 8 An extended joystick provides

control of the puppet’s functions.

40 SERVO 11.2008

It is often desirable to be able to control a motor’s speed

and direction I’ll bet that most of you have experience

with controlling the speed of a standard brushed DC motor

The first brushed DC motor speed control circuit that comes

to my mind is shown in Schematic 1A and consists of a PIC

microcontroller squirting a PWM (Pulse Width Modulation)

signal into the gate of a MOSFET whose job it is to switch

current to a brushed DC motor Adding a trio of MOSFETs

in Schematic 1B forms an H-bridge configuration that allows

us to change both the speed and the direction of thebrushed DC motor with a few bits of PIC I/O

Can you conjure up a similar circuit in your mind’s eyefor a simple AC motor speed control? I see a PIC microcon-troller punching an optoisolated DIAC (short for the words

DIode AC Switch) triggering a TRIAC, which is controlling

the flow of AC voltage to an AC motor (Schematic 1C) Theproblem with the DIAC/TRIAC motor circuit is that the DIACand a series resistor have all of the “control” and that control is very limited Another problem with the AC motorcontrol circuit I’ve envisioned lies in the need to provide aseparate DC power supply for the PIC microcontroller What

Electric motors come in a seemingly

endless variety of shapes and sizes If you’re

into robots and mechanical devices that

move about freely, DC (Direct Current)

motors capable of operating on battery

power are almost always your most

practical motor choice However, not every

robot created by man or alien is a fully

mobile Robby running around on forbidden

planets If your robot is a stationary

collection of nuts and volts that’s at home

working next to a wall outlet, you may

be able to use the advantages of an AC

(Alternating Current) power source to drive

your mechanical animal’s motors.

Schematic 1A The duty cycle of the PWM signal that

is applied to the gate of the MOSFET determines the speed of the motor In this case, the duty cycle percentage (0% to 100%) is directly proportional to

the speed of the motor shaft.

Schematic 1C This is about as simple as it gets for

AC motor control Fact is, we don’t have much

“control” here as the DIAC break over voltage characteristics and the value of the resistor between

MT2 and the DIAC determine the TRIAC’s

DC motor The PWM signal is applied to one of the diagonally opposing MOSFETs while the other associated diagonally opposing MOSFET is held in

an energized state.