Locating Tennis Balls with RFID
If you
wanted to build a device, a robot device, not much larger than a robot vacuum
cleaner, that would collect and return tennis balls, how would you do this?
The ‘Hawk-Eye’
system, familiar to watchers of professional sports, does an
excellent job of using video imagery and statistics to calculate a best guess location for a tennis ball in relation
to the boundary lines.
 |
| from UC Berkeley |
And more
than once, university students have built bumbling
robots that rely on a variety of remote and local video, computing
and robotic systems, to find and retrieve balls. At a rate of about one a
semester.
Could a video system, some modern software and
a radio controlled (‘RC’) car be fused together with some odds and ends into a
better than bumbling system for ball retrieval? One that coaches might want to
use?
 |
| Tony |
I skype
my mate Tony, who has a lot of RC stuff and a lot of experience with software
as well.
“Forget
video,” he says, “You want to use RFID.”
“I’ve
been trying it out on the cars, and it’s pretty good.”
“Radio-frequency
identification (RFID)
uses electromagnetic fields to automatically identify and track tags attached
to objects.” – Wikipedia. Today, the market for RFID is around
USD10 billion annually and growing. It’s the technology in that device the toll
company expects you to attach to the windscreen of your car, for example. It’s
in clothes – clothing companies are in trouble for tracking the movement of
customers by tracking the movements of tags in the clothes they buy. It’s in
event tickets, in every kind of proximity card. All over the place. It’s often
a transmitter about the size of a grain of rice, worth between 5c and 15c a
unit.
 |
| some of Tony's cars |
I have a
few concerns about RFID I’d like to discuss with Tony, but it’s too late. I’ve
fired up his enthusiasm and he’s gone, out to the shed to get a car and some
RFID tags and have a play with it all in the backyard at home.
So what
are my concerns? Pretty obvious ones – how’s it going to work, and how much
will it cost? And has someone already done this?
Let’s
start with the last question. Time to engage the inter-bubble.
 |
| Wallace E. Bolden Jr. |
In 2012,
Wallace Bolden applied for a US patent for a system that would
track balls using RFID. His application includes some pictures of how the
system works. I am sure though, that he’s not actually built a working version
of this system. Don’t you have to do that if you’re making a patent
application? “You can’t patent an idea”, right? So I look him up in the bubble,
so I can ask him directly, and guess what! A friend of mine is a contact of a
contact of his on LinkedIn. We’re so close. So I decide to leverage our
LinkedIn (three degrees of separation) connection – I email my friend and ask
him to introduce me to his contact so his contact can introduce me to Wallace
so I can ask him if he’s actually built a working device or if it’s some kind
of ambit claim ripe for reverse engineering once someone else builds a working
system and he wants to sue them for patent infringement. In a nice way though.
Two weeks
later, and my friend (well I thought he was my friend) still hasn’t responded.
Perhaps he’s not as enthusiastic about the power of (yet another social
network, this one called) LinkedIn as I am.
But
that’s okay, because in the meantime, I’ve broadened my search, and come up
with a load of sites citing various systems using RFID to
locate, in particular, golf balls. Ominously, ‘Radar Golf Inc.’, the one time
lead innovator in the field, seems to not exist anymore.
Following
these leads through I eventually fix on something solid. At the ‘Fraunhofer Institute’ in Germany, they’ve got
RFID working in numerous sporting applications. A collaboration with Adidas has
produced systems actually being used by a German soccer team. RFID tags on
balls and monitors placed around goals can determine with
never-before-ascertainable accuracy whether or not the ball has actually
crossed the goal line. And other applications tied more directly to team
performance. Other systems are being trialed in rugby and ice hockey, and
discussions are under way with skiing, basketball and golf entities.
The guys
at the institute who are heading up this work, their email addresses and phone
numbers are right there on the net, so I bang off an email, without even
cross-referencing LinkedIn.
And get
no reply.
From the
German guys that is.
On the
other hand, I’m hearing a lot from Tony, who thinks the idea is a goer, and is
urging me to assert some kind of intellectual property right over the whole
concept (perhaps I’ll ask Bolden if he has a friend like Tony if and when we
ever actually catch up).
Tony’s
telling me the system he’s thinking of is going to work just fine. I ask him
how he thinks the tags will attach to tennis balls. He’s assumed I’ve got that
bit sorted out. I point out that if we want to use RFID with the balls, we’re
going to have to get the tags inside the balls somehow. He agrees we have to do
that. I also express concerns about the rapid acceleration a tennis ball
undergoes, being thumped really hard with a bat designed for thumping it really
hard.
Tony
confuses acceleration with velocity, and tells me that the maximum velocity of
a tennis ball is about 240km/h. I’m trying to explain that going from high
speed in one direction, a lot of force is applied to a tennis ball to get it to
accelerate extremely rapidly in the opposite direction. But it’s too late.
Tony’s gone, back to the test site (his backyard and shed), where he’s
assessing how accurately he can ascertain the location of an RFID tag on an RC
car traveling at more than 200km/h.
There’s
an audible doppler effect in the tone of the little car’s motor, as it shoots
past the phone, and I duck involuntarily and wait for the crash.
A little
while later, Tony wanders back over to the phone, and says he thinks there
might be something in what I was saying about rapid decceleration (instant really). Says he’s had a few
red wines this evening.
“Oh by
the way,” he says, “You know I was at that concert too, the one you wrote about a few weeks ago?”
“And
Sue,” he says, referring to his wife, “Was too, though I didn’t know her then.
But we bought tickets.”
A few
people have been telling me they were at the concert too, all of them stressing
that they bought and paid for their tickets. Only one of them though able to
recall more detail than me about the actual performance.
Anyway.
I’ve been
thinking a little more about Tony’s proposal that we use RFID, and I can think
of several different tennis scenarios where the technology might be applied:
1.
At the
professional level: a working RFID system could outperform the ‘Hawk-Eye’
system – could in fact replace the human line call system entirely. Hawk-eye
has limitations – speed, accuracy, infrastructure and price. An RFID system
would be less defined by these limitations.
2.
At the
coach level: and this is where I originally envisaged the technology being
applied, a ‘robot ball boy’ that works with a coach while he’s giving a lesson,
to collect and return balls.
3.
At the
personal level: for about $80 you can buy a system to help you locate your
possessions using RFID. You attach a tag to your item, and when you need to,
use a ‘direction finder’ to point you towards it. A similar system could track
down those balls the kids hit over the fence, lose in the bushes, etc.
The ITF
(International Tennis Federation) website clearly defines the properties of a tennis ball, and nothing suggests
that an intra-ball infrastructure supporting components of an RFID location tag
system contravenes any of their criteria.
It all
seems reasonable. Why haven’t the Germans emailed me to say they think so too?
I decide to call them and find out – perhaps my emails all ended up in the junk
mail.
The first
two days I call, no-one answers. But on the third day:
 |
| René Dünkler |
I’m
talking to René Dünkler at the institute. We talk for about twenty
minutes, during which it becomes increasingly clear to me that he has actually
received and read my email, and ignored it. Setting this aside, we have a good
discussion about the application of the technology to tennis. Dünkler is
clearly proud of the work they’ve done in other sports, and the collaboration
with Adidas.
Dünkler
describes my thinking about RFID and tennis as an ‘interesting project’ that
the institute would like to take on. He thinks it would be possible but
problematic to use RFID to locate tennis balls. The problems link not to the
ability of the technology to quickly and accurately locate balls, but to
attaching the tag (or tags) to the ball. Tennis balls are empty inside, and
undergo rapid acceleration.
We agree
it’s a line of thought worth pursuing but one that would require the
participation of a tennis ball manufacturer, not to mention substantial
funding.
But think
for a minute: tennis balls is big business, and all the manufacturers make a
very similar product. Incorporating RFID technology into tennis balls would
substantially differentiate one manufacturer’s product from the others, at
least until the others catch up.
 |
| an Adidas 'tennis ball' |
Which
manufacturer? Back to the bubble I go. While looking for contact information
for manufacturers, I find that Adidas released a ‘tennis ball’ in August 2016,
alongside images of tennis balls with Adidas logos. Ultimately I realise
the Adidas ‘tennis ball’ is actually the name of a green shoe cross-promoted by
an American rapper, and that none of the Adidas-logoed balls are actually an
Adidas product.
Nevertheless,
Adidas is a sports manufacturer with a technological bent, they make balls, and
they have established links with the Embedded Systems folk at Fraunhofer. It’s
worth a look.
 |
| not an Adidas tennis ball |
The
inter-bubble throws up Jon Werner – Innovation Explorer at Adidas in the USA –
as a good person to talk to. So how do I track him down? The corporate website
is clearly going to be no help. I find him on LinkedIn, where he’s left
‘contact info’. One of the contacts is the Adidas website, but the other
suggests Twitter. His Twitter profile describes him as ‘friend to all (unless
you are evil)’. So I message him, and get a message back that says since he
doesn’t ‘follow’ me on Twitter, I can’t message him. So I tweet, a few tweets
because it doesn’t fit in one, roughly: ‘Hi friendly Jon. Wanted to chat about
RFID and tennis balls, but can’t message you, so I’m sending these tweets.
Please drop me a line when you have a minute. Surely there’s a better way to
communicate than this?’ I stare at the screen waiting for the immediacy of (yet
another social network, this one called) Twitter to take effect. For about a
minute I do that, then head off on a different tangent when nothing
happens.
I'd never
actually bothered to ask tennis coaches if they’d like a robotic ball boy. I
call one coach I know, and email another. Matt McDonald, the professional at
Red Hill Tennis Club wants one, wants to order one now. I explain to him that I
need to get a tennis ball manufacturer on board. He gives me his contacts at
Babolat and urges me to follow up. The other coach, Mark Fabian, is not a full
time professional, more a roving consultant. He says he wouldn’t buy a robot,
as he’s not based anywhere he could keep it..But he's sure that clubs would definitely
want them. He starts giving me reasons why coaches would love them – allows
coaches to spend more time coaching, keeps parents and other ball collectors
off the court (but especially parents), could be integrated with a tennis ball
machine to keep the balls coming, etc.
Okay, so
there’s a market for the coaching/club level product, if it costs no more than
a few thousand dollars and works properly and reliably. That’s important. Now
I’ve got to get a manufacturer on board, one prepared to work with Fraunhofer
to turn my idea into reality. This idea has two parts – one is building the
ball-with-RFID, the other is building the systems to track it, to varying
degrees of sophistication – personal, club and professional, with club level
the main focus.
Tony’s
back. He thinks we should go it alone. He starts telling about the various
factories in India making tennis balls for international brand names. (I’m in
India, Tony’s in Australia.)
Tony is
listing all the Indian cities with tennis ball factories when my desktop tells
me Jon Werner sent me a personal message via Twitter 22m ago. Sorry Tony, gotta
go, I’m 22m behind the green ball.
 |
| Jon Werner |
Werner
and I spend 15m sending PMs back and forth via Twitter. To cut to the chase,
Werner sees this idea as something that’s going to come of age simultaneous
with an RFID internet of things that will itself explode on the world once
mobile phones include an RFID tracker. Werner has locked onto my third,
personal, application for RFID in tennis balls – helping individuals locate
their tennis balls, at the court, or even in the shed, house, or car, depending
how errant or disorganised that individual is. He thinks this day is
precipitant now that Qualcomm (a phone components manufacturer) has purchased
NXT (a maker of other types of electronic components) in a deal worth $47
billion. But he doesn’t think it’s something Adidas is very interested in.
However, he also revs me up, telling me if I have an idea, I should ‘go for
it’. The little I know of entrepreneurialism suggests that having a good team
is critical to success.
Tony and
I are not a good team. Tony’s now giving me instructions derived from
GoogleMaps on the most sensible route to the tennis ball factory closest to
where I live in Delhi, two and a half hours away in a city called Meerut. The instructions,
nuanced to account for varying traffic conditions, suggest I leave home at
4.30am.
“Oh by
the way,” he says, “I’m sending you a surprise.”
I can’t
wait.
But I’ll
have to, and use the interim to call Matt McDonald’s mate Alex at Babolat. They’re
a casual lot at Babolat – don’t even use surnames. I talk to Alex for a while.
He’s a bit mystified by the whole story and my motivation, a little bit
sceptical. But he asks me to put the detail in an email and promises he’ll move
it on to the relevant product development person at Babolat, and that I should
hear back in the not-too-distant future. I don't.
Tony’s
back.
“Did you
see it?” he asks.
Did I see
what?
"The
RC car on your front verandah."
There is,
in fact, an RC car on the front verandah.
“Do you
mean the one with ‘RFID Tennis ball project experimental vehicle #1’
stencilled on it?”
“Are
there two RC cars on your verandah?” he asks, rhetorically.
Tony
explains that the little vehicle navigated its entire journey from Canberra to
Delhi, in less than a blog’s breath, relying solely on RFID signals. Which I
find hard to believe.
"Now,”
he says, “Are you ready for your surprise?”
The car
on my verandah isn’t surprise enough?
A tennis ball impacts with my forehead. I recover from the shock, just in time to duck as
the car fires a second furry green cannonball, and then a third, and
…
“TONY
!!!!”
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