Machine design , tập 83, số 11, 2011

SPECIAL FOCUS: MOTION CONTROL
June 23, 2011
A Penton Media Publication
Tune in to EngineeringTV.com

SIZING UP MOTION
TRENDS, page 44

Making
Servos
Stable

page 53

WHEN DOES IT
MAKE SENSE
TO MODIFY
STANDARD PARTS?
page 63
WORKING WITH
ROLLER PINIONS,
page 68


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VOLUME 83
ISSUE 11
JUNE 23, 2011

MOTIONTRENDS INDUSTRY FOCUS

This schematic shows a typical motion-control hierarchy with a spline interpolator feeding a PID compensator,
which provides a setpoint to the drive. In this case, the physical hardware connection is abstracted away from the
programmer. The drive command output could be written to the drive via analog or any digital network.

FEATURES

This schematic shows the same example but replaces the compensator with a state-space model, retaining the
rest of the code. In this case, the spline algorithm and communication method for sending the setpoint to the
drive are untouched. This lets the developer delve into the motion-control application at any level of interest. All
the vendor-supplied pieces including the API are retained.

Here are three trends
making waves in the
motion-control industry.

Shaping
motion control

The
Top
Three
Trends

top three trends
44 The
shaping motion control

While it’s true that the motion-control world hardly
changes at an iPhone pace, it doesn’t mean there aren’t fascinating movements afoot. And although there are a host

of interesting trends and movements worth discussing, we
will focus on three general trends:
• Motion out-of-the-box
• Power to the programmer
• Machine builders – Easing their pain

Motion out-of-the-box

As staffing levels continue to shrink at OEMs, many
machine builders are seriously questioning the long-held
belief that shopping around for every component provides
the highest value. Instead, they’re turning to out-of-thebox devices as a better way to build machines and improve
long-term value.

WANT MORE?

Here are trends making waves in
the motion-control industry.

Focus on this code image
using your smartphone and
free software from www.
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MACHINE Design.com

First, motion out-of-the-box devices combine two or

more motion-control devices into one. These can include
the controller, drive, motor, I/O, and gearhead. This concept is not necessarily new, but it’s clear its popularity is
growing fast. The packaging sector is responsible for much
of this attention.
The simplest out-of-the-box option is an integrated
motor, or smart motor. It consists of the drive electronics
coupled with the motor and often a simple motion controller. Over time, more devices such as smart actuators
have entered the fray, building on the integrated motor
concept by adding components such as gearheads and
rotary-to-linear actuation.
Another out-of-the-box motion option gaining popularity is coupling the direct-drive motor to the load without any additional components such as coupling belts or
gearheads. This stiffens the mechanical connection to the
load, effectively eliminating inertial matching, and leads to
better performance than that of traditional servosystems.
Direct-drive motors also have higher bandwidths and effectively zero backlash. Eliminating components reduces
potential failure points and lets engineers boost performance with simpler installation compared to traditional
servosystems.

JUNE 23, 2011

Engineers are also using another out-of-the-box opnew, cutting-edge machine to the market means you will
tion, namely stepper torque control. This technique inlikely have stringent weight, space, power, cost, and perforvolves operating a traditional stepmotor with classical sermance constraints that can’t be met by motion-out-of-thevocontrol methods by adding a feedback device, typically
box approaches. So a best-in-class component selection
an incremental encoder. Traditional field-oriented control
algorithms permit true torque regulation as opposed to
Authored by:
current regulation found in microstepping drives. StepBill Allai
motors are just another type of brushless motor, or what
Chairman
the industry typically refers to as a permanent-magnet

Motion Control Association
synchronous motor (PMSM), but with more poles. In
Ann Arbor, Mich.
other words, it’s a brushless motor that benefits from the
Edited by Stephen J. Mraz
same control techniques. Using PMSM control eliminates

stalling and excessive heat, common problems with tradiResources:
tional stepmotor control. And engineers can discard the
Dassault Systèmes SolidWorks Corp., www.solidworks.com
2×-torque-guardband rule of thumb for stepmotors, not
deal with PID tuning, and reduce the amount of cabling.
Delta Tau Data Systems Inc., www.deltatau.com
All of this contributes to a less costly approach than a comHochschule Esslingen, www.hs-esslingen.de
parable servo-based device.
Kollmorgen, www.kollmorgen.com
In terms of performance, this approach does away with
Mathworks, www.mathworks.com
jitter (holding-position hunting) and can boost torque by
a factor of four for servos spinning at up to 2,000 rpm. The
Motion Control Association, www.motioncontrolonline.org
idea is to merge the best attributes of stepmotor machines
National Instruments, www.ni.com
with servocontrol to get a less-expensive, better performYaskawa, www.yaskawa.com
ing motion-control system.
But there is a downside. First, suppliers of this technology tend to be single-sourced and newer players in
the industry. And although the stepmotor is just a
Advantages of out-of-the-box motion
variation of PMSM, its high pole count limits maxiEND-USER BENEFIT
RATIONALE

mum speed to approximately 2,000 rpm, as opposed
Quicker to market
Reduces design and installation time
to 10,000 rpm or higher for traditional PMSMs. FiReduces cabling and potential
Reduced maintenance
nally, some users simply have a philosophical hang
failure points
up about using stepmotors for applications tradiEliminates or significantly reduces
tionally served by servos.
Smaller size
cabinet space or factory-floor
So why aren’t all engineers jumping on the outrequirements
of-the-box bandwagon? The fact is, introducing a
JUNE 23, 2011

44

unstable servos
53 Taming
Several factors can contribute to
the likelihood of instability in an
ac drive.

settle for
63 DonÕt
standard parts

MOTION

Modifying off-the-shelf parts

or customizing from scratch
can simplify R&D and speed
production.

Don’t settle
for

standard parts

actuators that
68 Linear
keep on rolling
Roller pinions give linear
actuators precise motion control
with little to no backlash.

Modifying
off-the-shelf
parts or
customizing
from scratch
can simplify
R&D and
speed
production.

Test labs do everything from qualifying products to
evaluating performance under harsh operating conditions.

In a perfect world, no matter the application, commercial

off-the-shelf (COTS) components would provide the
exact performance required and be just the right size and
shape. In reality, almost every design involves trade-offs
and compromise. Sometimes, the process is painless,
requiring some give on low-priority parameters. Other
times, the leap is simply too big. Projects can get sidetracked as designers surf from one Web site to another or
call around for catalogs, desperately searching for products that are in the right ballpark. What’s often needed is
customization.
Engineers involved with motion-control applications
may not realize that the catalog is often only the start.
Many suppliers customize offerings to suit specific needs,
support R&D with design insights fueled by experience,

and even help with troubleshooting. Partnering with
knowledgeable vendors can improve the final product and
speed commercialization. Here’s how.

Custom brings benefits

Customization sounds time consuming and expensive,
but it doesn’t have to be. In the simplest form, customization involves a vendor modifying its COTS products to
save an OEM time, cost, and headaches.
Perhaps the most basic example is adding cables to a
motor. Many motors come with bare terminals, and users must connect the cables themselves. It’s a simple task
but not nearly as forgiving as many would like. Bend the
terminal once, it’s not a problem. Bend the terminal twice
and it often breaks. Ideally, the motor would be sent back
JUNE 23, 2011

MACHINE Design.com

63

63
Got answers? We’ve got the questions!
www.smartestdesignengineer.com
If you haven’t been there for a while, now is the time to check out the
latest questions and see who’s top on the scoreboard.
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JUNE 23, 2011

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45


Agency
Approvals
for Drives:

The SureServo family of brushless servo
systems from AutomationDirect is fully
digital and offers a rich set of features at
dynamite prices. Beginners to experienced
users can take advantage of this easy-to-use
family for as little as $965* (100W system).
* All components sold separately.

Agency
Approvals
for Systems:

Agency
Approvals
for Motors:

SureServo drives
accept a wide
range of command
sources:
•

•
•
•

• Eight standard systems
from 100 W to 3 kW
• Use with DirectLOGIC
PLCs or any other host

control
• Drives feature on-board
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All prices are U.S. list prices, AutomationDirect prices are from March 2011 Price List. The Allen-Bradley
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www.rockwellautomation.com/en/e-tools 2/22/11.

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www.automationdirect.com/servos or www.sureservo.com

RS# 103

Go online or call to get complete information,
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ON THE COVER

DEPARTMENTS

Servo-powered machine
photo courtesy of
Siemens Industry Inc.

8 EDITORIAL
College classes for the wealthy

10 EDITORIAL STAFF
12 LETTERS
18 SCANNING FOR IDEAS
Transporter moves heavy loads across factory floors
Probe detects temperature of corrosive exhaust gases

22 REPORTER’S NOTEBOOK
34 LOOKING BACK
40 ADVANCED MANUFACTURING
Product-analytics software boosts
advanced manufacturing

42 BERKE ON SAFETY
Inconvenient lockout/tagout likely gets ignored

73 ORR ON ENGINEERING
Betrayed by technology!

Editorial content is indexed in the Applied Science
Technology Index, the Engineering Index, SciSearch
and Research Alert. Microfilm copies available from
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74 PRODUCT SPOTLIGHT
Gears & gearmotors

78
84
85

86
87

For customized article reprints and permissions
please contact: Penton Reprints, 1-888-858-8851,
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EDITOR’S WEB PICKS

Conveyor blog

RS# 105

6

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JUNE 23, 2011

Dorner Manufacturing has
launched its Conveyor blog
(www.blog.dornerconveyors.
com). Experts post on topics such
as conveyor designs, unique
applications, maintenance, and
material handling in packaging,
food, automation, medical, and
other industries. Readers can voice
opinions, ask questions, and get
immediate feedback.

Motion-control
handbook
The new Animatics catalog offers
engineering details on servomotors,
communication protocols, cables,
and connectors, as well as linearharmonic drives and belt-slide
systems. It includes updates on
recent motion-control advances
and helps designers select, connect,
and get products up and running.
Request or download a copy at
www.animatics.com.

Switch finder

Power-drain challenge

EAO’s Web site (www.eao.
com) helps users sort through
components such as illuminated
pushbuttons, indicators, key
switches, emergency-stop
switches, and membrane-type
human-machine interfaces. Users
can simultaneously search multiple
criteria, including type, positions,
protection class, and current
rating, as well as application and
market segment. Other features
include a product configurator and
3D drawings.

A dead mobile phone is
inconvenient, to say the least. So
Nokia’s Power Drain Challenge
seeks new, radical ideas to solve
mobile power problems and
extend a cell phone’s battery
life. Submissions to date include
external power packs, fuel cells, and
solar, kinetic, and bike chargers. The
contest runs through August 1 and

offers prizes for winning entries.
Learn more at www.ideasproject.
com/community/challenges/gear_
power.


RS# 106


EDITORIAL
College classes
for the wealthy
With summer in full swing, let’s reflect a bit on summer
jobs. Back in the early 1970s, I landed a job one summer
assisting industrial electricians. We spent most of our time wiring machines
that were to be installed on automotive assembly lines. The most vivid recollection I have of that summer was the paycheck. We worked a lot of hours, so
we ended up making time-and-a-half and even double-time pay. By the time
I headed back to college, I had earned enough to pay for my next three semesters with a little left over.
My experience that summer wasn’t unique. Several of my classmates had
summer employment that paid for much or all of their next-year’s tuition.
And this was at a school considered to be among the top five U. S. engineering
colleges.
Fast forward to today. Summer jobs that will pay for more than a year’s worth
of tuition at a major school are few and far between. In a nutshell, tuition costs
have risen dramatically, a fact well understood by parents with college-age kids.
Pay scales for jobs within reach of college students just haven’t kept up.
Consider what it now costs to educate a student for one year at a good engineering school. At Purdue University, the annual in-state tuition alone runs
$9,070. Supplies and room and board are extra. Purdue students who don’t
happen to reside in Indiana get a tuition bill for $26,622. Aspiring engineers at
Georgia Tech pay an annual in-state tuition of $8,716 and an out-of-state tab of

$26,926.
To pull off a feat similar to my own in the 1970s, today’s college kids would
have to find a three-month, 58-hour/week summer job paying north of
$13/hour. Those paying out-of-state tuition would need better than $38/hour
to accomplish the same thing. A point that also helps illuminate this situation is
the current U. S. minimum wage of $7.25/hour. Back in the 1970s, the minimum
wage was below $3/hour. My base rate that summer so long ago was above minimum wage, but not by much.
This analysis explains why many college students finish four years of school
with both a degree and a large student loan debt. I believe it also helps show why
a significant number of engineering students abandon the engineering field and
opt for careers in finance. Consider that entry-level engineering jobs pay in the
$60,000 range. For analytical jobs in finance, the entry level is around $90,000,
sometimes with a shot at bonuses that can equal that figure. When you are starting a career with fistful of IOUs, that kind of money talks.
And finally there’s this: Efforts to encourage kids toward engineering careers
get a lot of press these days. It is a safe bet that most U. S. engineers come from
middle-class backgrounds. But a college education increasingly looks out of
reach for many kids from middle-class homes. So despite a lot of chest thumping
by politicians about the need to reinvigorate manufacturing and boost exports,
the high cost of a higher education makes it unlikely this will ever happen.
— Leland Teschler, Editor

Congratulations to the May
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EDITORIAL STAFF

Solar panel
positioning
to 0.0006”?
No problem.

Leland E. Teschler, Editor,

Kenneth J. Korane, Managing Editor,


MATERIALS

SENIOR EDITORS

Jessica Shapiro,


Leslie Gordon,
Stephen J. Mraz

MANUFACTURING

AUTOMOTIVE &
NEWS FEATURES

Leslie Gordon,

Kenneth J. Korane,


Stephen J. Mraz,


CAD/CAM

MECHANICAL

Leslie Gordon,


Kenneth J. Korane,

Jessica Shapiro,


ELECTRICAL, ELECTRONICS
Robert J. Repas, Jr.,


EDITORIAL PRODUCTION

FASTENING, JOINING

Denise Greco,
Editorial Production Manager

Jessica Shapiro,


Randall L. Rubenking, Art Director

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RS# 111


LETTERS
Stop the whining
Jobs have dried up … some have
gone offshore … the government
isn’t helping …woe is me. That’s
what a lot of the letters in your
magazine seem to say (“Engineering’s Downside,” April 21). So? Get
off your duff, use those engineering
skills you supposedly have, and go
to work for yourself. Design a product. Provide a service. Build it in your
garage. Start small and build it up.
Stop feeling sorry for yourself.
I’m 75 with a high-school education (graduated in ‘53 when it was
possible to get a good, rounded
education), and I immediately
started my own business at 18 and
failed just about as quickly. Serial
entrepreneurs simply move on and

work on the next challenge.
I am currently working seven
days a week (and falling behind with
orders) making a product (patent
pending) that had not been updated
or revised in the last 500 years.

When the going gets tough, the
tough get going.
Lee Marshall
It would have been helpful if a sheet
of absorbent paper toweling could
have been bound into the magazine
in the letters’ section recently. As it
was, I had to scramble to find my
personal “crying towel” upon reading the plight of these engineers.
As for the editor ial (G ood
Enough for Government Work,”
April 19), I have never worked on
a government contract that didn’t
need a correction to the designs or

specifications provided by all those
government workers.
Richard Distel

Outsourcing debate
Outsourcing is a bad idea and could
only work if you believe a nation as
large and diverse as the U. S. can

survive and grow using a servicebased economy (“Thinking About
Outsourcing Product Development?” April 5). If a company does
not have the knowledge of how to
develop its own products, what differentiates it from any other com-

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RS# 113


LETTERS
pany? Know-how, the ability to do
what needs to be done, is probably
the most valuable asset an organization has. We devalue this asset at
our own peril.
Louise Kitchner
Thank you for your comment. I think
what is often misunderstood is the
difference between core technology
that every company should certainly
retain internally, and noncore engineering functions. For example, designing a plastic component is not a
core technology. Sure, it may be part
of a larger system, but executing a design is something that specialists can
do faster and better in many cases.
When looked at this way, a company
does not give up anything regarding
the core knowledge of its products.
This is what we see in our business
and we view our role as maximizing

a company’s internal talent and resources by shedding noncore activities. — Jorg Lorscheider

So goes Germany
At least we in Germany are trying
to find a way to a future without
nuclear power. Not only because of
the dangers from the power plants
but also because of the nuclear
waste which will become more and
more difficult to handle. We feel
responsible for our country, our
resources, and our children. Sustainability is what we reach for. This
does not mean closing one nuclear
power plant and building two coal
power plants. We have a long-term
energy plan. It is a strategy for the
next 10, 20, 50, and 100 years. This
is foresight, a goal.
And we have started tackling
that goal with concretely defined
milestones. One very important
point is to raise the efficiency and
to save energy. Energy that does
not have to be produced is the
cleanest and safest.
I am very proud to live in a country where people accept their re-

sponsibilities for their country and
act accordingly. We are on the way.
What about you?

Herman Hellstern

For the safety expert
At our company, we use several
safety devices on machinery. Often
two such devices are used at the
same time, including pull backs,
light curtains, palm buttons, and
guards. My concern is that we are
looking at a new press brake that
uses a safety feature consisting of
three laser beams placed about the
tooling tip. It senses objects and is
programmable. We have asked for
literature on the equipment, but I
would also prefer third-party information or safety reviews.
Have you seen any information on
this feature or its ability to keep workers safe? Is there a database available
of case files? How can we get access?
Any thoughts to a best practice for

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Pneumatic Actuators

Compact Modules

Custom Handling System

Pickin’ n placin’
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you up to 80% on the manpower, money, engineering and integration challenges
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RS# 115


LETTERS
searching this kind of data?
Chris Bunten
I am not familiar with this guarding
system. If I were in your place, I would:
1. Contact the company and ask
for a copy of their hazard-analysis
and safety-studies reports. Be wary
if they are not willing to share this
information with you.
2. Contact OSHA and ask if they
know of this safety system and any
problems it might have.
3. Have your corporate attorney
check to see if this device has been
involved in any lawsuits. The lawyer should have contacts with the
plaintiff bar which keeps this type of
information.
4. Perform your own hazard analysis study of this device.
5. Be aware of the differences between machine guards and machine
guarding devices. All of the safety
devices you mention rely on people

using them properly. This leaves a lot

Zero backlash

of room for human error.
6. If this device is programmable,
make sure any hazard analysis looks
at the worst possible scenario. I am
always concerned about programmable devices in that they may be
programmed for maximum production rather than maximum safety.
7. Make sure anyone who leads
your safety investigation is a qualified safety expert, knowledgeable in
machine guarding, and, hopefully,
has a Certified Safety Professional
(CSP) rating.
— Lanny Berke

Professors being honest
Your editorial (“Bad Advice Online,”
May 4) reminded me of the time
I attended a conference at Purdue University as an editor, and a
bunch of professors assumed I was
one of them.
About 10 of us went out for pizza
and beer, and I heard stories that
would curl your hair. They talked
about grantsmanship and how

“good” professors can make two to
three times their salaries from government grants. Plus, no one in government ever reads these studies, so

professors only need to ensure that
when anyone opens the study, they’ll
read something that sounds professorial. And a rule of thumb is that
the size of the study (in pounds) is
directly related to the dollar amount
of the grant.
The professors also spoke favorably of using grad students as slaves.
In fact, they said the only two forms
of slavery left in this country are grad
students and interns. Another rule of
thumb they discussed was that no
professor worth his salt teaches any
more than he absolutely has to, especially undergrad classes. That’s why
teaching assistants (grad students)
were invented.
And to these professors, “peer
review” meant: “Don’t criticize my
paper and I won’t criticize yours.”
Rich Merritt

Put some teeth

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length, load capacity and zero backlash performance. Not to
mention it’s also extremely quiet, 99% efficient, and so
refined it can run without lubrication. Replace inferior rack
and pinion, ball screw and belt drive technologies with
higher performance and lower maintenance solution.
RS# 116

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Call 800.843.7445


[ MOTOR TRUTH #2 ]

Can I really save
money by installing
a smaller motor?
The truth? You just might be able to. If you look at
your entire drivetrain, you’ll probably find that if you
replace inefficient components (which can waste

up to 50% of the energy they use), you’ll be able
to install a new, smaller, high-efficiency DR motor
and still get the power output you need.
And, you’ll save energy at the same time, because
your current oversized motors may be wasting
energy to overcome the inefficiencies of your
entire drivetrain.
SEW’s new DR motor series is specifically designed
to work with a total system, including our helical
bevel gearboxes and electronic drives, to provide
you with maximum energy savings. Get the
whole story and learn how the DR motors are
the newest piece of the energy savings puzzle
at sewmotortruth.com.

sewmotortruth.com

RS# 117


SCANNING FOR IDEAS
Edited by Stephen J. Mraz

Transporter moves heavy
loads across factory floors
Transporters from Wheelift Systems, Waverly, Iowa
(www.wheelift.com), can move hundreds of tons of
equipment or machinery across almost any type
of floor, including ramps and in-floor rails. And for
heavier or larger loads, up to four transporters can be

ganged together, using onboard lasers to maintain
predetermined separations and distances. Each set of
two-wheeled, omnidirectional load modules — and
a transporter can have up to 20 of them — supports
up 30,000 lb and carries its own electric motor. But
operators have the option of powering the onboard
generator using a diesel engine, LP gas, or bypassing
the generator in favor of a power cord and electricity
LPG or diesel
engine

Access
panels

19-in.
height

from the factory’s electrical subsystem. The load modules can spin 360°, letting the transporter move in any
direction at any time, even diagonally. And the operator need only tell the transporter where to go and onboard controls handle steering for each load module.
Hydraulics power the load-leveling feature on the
load modules to keep cargo level. Hydraulics also let
the load modules raise the transporter by 8 in. This
should let the 19-in.-tall vehicle drive under heavy,
bulky loads, then lift them. The headless version of the
transporter is low profile, while the vehicle can also be
equipped with a headboard.
RS# 401

480-V,
three-phase

generator

30,000-lb capacity,
omnidirectional
load modules
(up to 20 on a
transporter)

Electronic
controls

Control
screen

Emergency
stop

Wireless
controller

Hydraulics for
Laser beam
independent fluid measures separation
suspensions and
from other
load leveling
transporters being
teamed together

75-ft backup

cord for 480-V
power

LPG
gas

NEW! 13.56 MHz RFID System
utilizes high-frequency technology
Allows for the integration of all tags complying
with the requirements of the ISO/IEC 15693 standard
• Read/write modules can be connected directly to an RS485 field bus
• A network of up to 253 read/write modules may be created
• By means of a USB adaptor, up to 10 read/write modules can be directly
addressed physically from a control console
• The physical address of a specific read/write module is determined by means
of a selector built into the device
• Demo program provides you with an introduction to the system
Contrinex Inc.
Old Saybrook, CT 06475
Toll free: (866) 289-2899

Fax: (860) 388-3574
E-mail:
www.contrinex.com

Visit our Design Site at www.contrinex.com

18

MACHINE Design.com

JUNE 23, 2011

RS# 118


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RS# 119


SCANNING FOR IDEAS

Probe detects temperature of
corrosive exhaust gases
The EGT Diesel & Biofuel Exhaust Gas temperature sensor

from The Sensor Connection, Troy, Mich. (www.
thesensorconnection.com), features a noncorrosive
sensing tip that withstands sulfuric exhaust gases from
burning biofuels and diesel fuels. An ungrounded
Type K thermocouple measures temperatures
from –148 to 2,372°F (–100 to 1,300°C). Errors are
±0.4% of the reading. The probe comes with a
6-ft double-jacketed Teflon cable overbraided
in steel for abrasion resistance. This cable
can be optionally extended to 12 or
25 ft. The probe measures 0.187 in. in
diameter and includes an adjustable
stainless-steel compression fitting
for mounting it to most dieselengine exhausts. The sensor
sheath can be either straight
or have a 90° bend to
accommodate tight
spaces.
RS# 402

Heavy-duty
spring for
flexible strain
relief

High-temperature
potting compound
withstands long-term
temperature cycling.

Corrosionresistant 316
stainless steel

Inconel sheathing
withstands
temperatures to
2,280°F.

MgO insulation

Ungrounded enclosed
sensing tip protected
against sulfuric
exhaust gases.

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RS# 120
20

MACHINE Design.com

JUNE 23, 2011


Keep Your Machine Running!
Festo’s VTUB pneumatic manifold is not only
reliable, but is also very easy to maintain.
Designed for corrosion resistance, your machine
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Go to: festo.com/us/addedvalue

Global manufacturer of process control and factory automation solutions
RS# 121

For more information:
Call: 1-800-Go-Festo
1-800-463-3786
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REPORTER’S NOTEBOOK
Formula One race cars get faster thanks to
particle-image velocimetry and CFD

A Formula One race car sits in one of
Toyota Motorsport’s state-of-the-art
wind tunnels in Cologne, Germany.
Image Credit: Toyota Motorsport

Consider the Formula One (F1) race car. Rather than
just running on simple oval tracks and always turning
left, F1s race on closed tracks — sometimes even on
blocked-off city streets — and drivers must quickly
brake, corner right or left, and accelerate along
straightaways. Motorsports engineers thus try to optimize F1 aerodynamics for these tricky conditions. The
vehicle’s complex design, along with constantly changing regulations, makes aerodynamics an evolving
challenge, says Frank Michaux,
aerodynamic engineer at Toyota
Resources:
Motorsport in Germany.
Tecplot, www.tecplot.com
The open-wheel design of
Toyota Motorsport, www.
F1s disrupts airflow, creating
toyota-motorsport.com
wakes behind the front wheels,
which, while local, can affect the
entire vehicle’s performance, explains Michaux. The
cars also sport airfoils that generate downforce while
also reducing drag.
To get a handle on normally hidden aerodynamic
effects, Toyota Motorsport engineers rely on a wind
tunnel equipped for particle-image velocimetry
(PIV). Technicians feed PIV data into Tecplot 360, a

stand-alone computational fluid-dynamics (CFD) postprocessor. This lets researchers quickly correlate PIV
results with CFD simulations — both measured and
rendered by Tecplot software.
Toyota’s full-scale wind tunnel includes a “seeding”
generator (a pressurized vessel), CCD digital camera,
high-power laser, an optical device that converts a la22

MACHINE Design.com

JUNE 23, 2011

ser beam into a sheet of light, and dedicated software.
For PIV tests, engineers position the camera at 90º
to the plane of the flow field they want to examine.
The generator floods the tunnel with tiny particles of
di-ethyl-hexyl-sebacat (DEHS), which have nearly the
same density as air. The particles don’t affect airflow
because they simply float.
Engineers then turn off all tunnel lights. A moving
belt under the vehicle spins the wheels for more realistic load conditions. Air in the tunnel is accelerated
to travel 50 m/sec. Next, researchers illuminate the
portion of interest with a laser, converted via optics
to a 2D plane of light. The camera takes two black and
white snapshots of the plane every 10 to 20 msec —
the white DEHS particles contrast well with the black
background — making up a dataset. A complete data
collection comprises 300 datasets, each containing
the X, Y position of the measured point and its velocity.
“Understanding the wake behind the front wheel
is important because it must be calibrated to get

the best performance out of the F1,” says Michaux.
“Because the front wheel is completely exposed to
the air, wind hitting the wheel produces a weak velocity component in the wind behind it. Ideally, this
airflow should not hit other parts of the car, so we try
to move it as far outboard as possible. For example,
we might use PIV to measure a wheel’s wake to see
if changing the shape of the front wing endplate
moves the wake in a positive or negative direction.”
The front wing endplate helps generate downforce.


REPORTER’S NOTEBOOK
With low pressure under the wing
and high pressure on top of it,
air is forced from the top to the
bottom. The endplate partially
blocks this flow, thus boosting
downforce.
PIV builds data files — basically just text and numbers —
but they aren’t useful until engineers can see them, says Mike
Peery, CEO of Tecplot Inc., Bellevue, Wash. “Engineers must understand the phenomena qualitatively — that is, what is in the
flow field: Is it a vortex, a wake, a
combination, and are they interacting or not? They also must understand things quantitatively.
Tecplot 360 can, for instance,
generate a profile across the PIV
field to extract vorticity.”
Vorticity is local rotation of the
fluid and is generally visible. For
example, it’s sometimes possible
to see vortices at the wing tips of

airplanes when they fly through a
cloud.
F1 aerodynamic studies typically use experimental data from
PIV, computational results from a
CFD package, and a CFD postprocessor such as Tecplot 360. Preprocessing involves CAD software
(either as a stand-alone package
or as geometry-building capabilities in a CFD package) to generate
a geometry and mesh generator

(in the CFD software) to get a
computational grid of millions of
finite volumes. The postprocessor’s
job is to accurately approximate
the governing differential equations — Navier-Stokes equations
for the F1, with variations for compressible and incompressible flow
— and generate an approximate
solution.
Most commercial CFD packages
contain their own postprocessors,
says Peery. “But one advantages of
being stand-alone is that the postprocessor can read in all kinds of
data, whether it’s from Ansys, Fluent, CFX, or CD-adapco, or even
experimental data.”

Toyota Motorsport engineers
can compare, say, a contour of a
vorticity magnitude in the cross
plane from the PIV data to what
is coming out of the CFD code.
“Because they are both surfaces,

the software can also interpolate
the field data from one set, say
the computational slice, into a PIV
slice,” says Peery. “Thus, everything
is on the same grid. The software
computes the differences and
then displays them, giving quantitative values for where the PIV and
the CFD data differ and by how
much. This, in turn, lets engineers
build increasingly exact CFD models of the entire car.” MD

makes perfect sense to choose over Pneumatics
6 GOOD REASONS:
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RS# 122
JUNE 23, 2011

MACHINE Design.com

23