[robocup-nao] ball decision for 2010

[Oskar von Stryk]

Hi Tekin,

As you probably know, the RoboCup Humanoid KidSize League uses
an orange standard tennis ball.

To my (limited) knowledge, the standard data for tennis balls are
- diameter: between 6.35 und 6.67 cm
- weight: between 56.7 und 58.5 g

The data you mention for an orange street hockey ball
(65mm in diameter and 55g weight) matches the
above data of an orange tennis ball pretty well.

Therefore I was wondering about the following:

1) Why did you select a hockey and not a tennis ball
 	as it is used in the Humanoid KidSize League?

2) Did you compare the performance of the hockey ball
 	with a tennis ball on a RoboCup soccer field?
 	And, if so, what were the results?

 	(Besides size and weight, tennis balls must satisfy certain
 	back-bouncing abilities from the ground and will probably
 	behave differently than hockey balls in robot soccer.)

3) If teams order a standard orange street hockey ball from
 	a store which does not give the precise diameter
 	and weight of the ball, which range of variation
 	in size and weight must be expected?

 	From a quick internet search it seems that there
 	is more variation in street hockey balls than
 	in tennis balls. I found: diameter 6.35-7cm, weight: up to 85g.

 	A weight difference between 55g and 85g can make
 	an enormous difference to the robot performance (e.g.
 	when kicking the ball)!

 	In the Standard Platform League where only software should count
 	I would expect also a standard ball that teams can, e.g.,
 	remotely participate in local RoboCup Open competitions.
 	With a large variation in ball weight, this will be difficult.

Thanks for your time and efforts.

Best regards,
Oskar

On Fri, 11 Dec 2009, Tekin Mericli wrote:

> Hi Olivier and Markus,
>
> Although it is possible to find hockey balls with other colors and patterns,
> the orange ones are pretty common. Amazon website was just an example, but
> you should be able to find it in other (online) stores as well. As I already
> mentioned, different members of the committee from all around the world
> including the US and Europe were able to order these balls and test them
> before we announced the decision.
>
> You might want to check this store; they seem to ship internationally:
>
> http://www.hockeymonkey.com/hockey-a-r-balls-accessorie.html
>
> Cheers,
>
> Tekin
>
>
>
> On Fri, Dec 11, 2009 at 3:16 PM, Olivier Michel <
> Olivier.Michel at cyberbotics.com> wrote:
>
>> Hi Markus,
>>
>> As suggested by Tekin, I believe street hockey balls are pretty
>> standard. I ordered some from here in Switzerland:
>> http://www.chip-hockeyshop.com/product.php?productid=283&cat=0&page=1
>> I guess they are the same color, size, weight (and hence behavior) as
>> the one mentioned by Tekin, am I right?
>>
>> -Olivier
>>
>> Markus Bader wrote:
>>> Hi
>>>
>>> Amazon.com does not ship this ball to Europe and it is not available
>>> on amazone.co.uk nor amazon.de, ...
>>> It it possible to setup a list and to bring multiple packages to the
>>> workshop to Paris?
>>>
>>> Greetings
>>> Markus (Austrian-Kangaroos)
>>>
>>> 2009/12/11 Tekin Mericli <tekin.mericli at boun.edu.tr>:
>>>
>>>> Dear all,
>>>>
>>>> Since the official ball that we use in our games is no longer available
>> in
>>>> the market, we needed to make a decision about which ball to use for
>> 2010.
>>>> After some discussion and tests with various balls, we decided that a
>> street
>>>> hockey ball will be the best choice since it is available in the market,
>> has
>>>> standard dimensions and colors, and rolls straighter compared to the old
>>>> official ball. Here is an example of the candidate ball:
>>>>
>>>>
>> http://www.amazon.com/Mylec-Weather-Bounce-Hockey-Orange/dp/B002LBDA30/ref=sr_1_18?ie=UTF8&s=sporting-goods&qid=1259775748&sr=8-18
>>>>
>>>> It is 65mm in diameter and it weighs 55g.
>>>>
>>>> You can assume that this ball will be used in the league for 2010.
>>>>
>>>> Best regards,
>>>>
>>>> Tekin Mericli
>>>>
>>>> On behalf of the SPL Technical Committee
>>>>