Frans van der Klip
	Mark's site Webots contest y z w

Webots Judo contest

During development of my control program for the "Robot Judo contest" of Cybertronics, I made some items that I like to share (even with competitors). I joined medio Septembert, and submitted my first robot controller program to the match end September 2003. During the course of the contest I will find out more, and put it either here or in the WIKI pages <<add link>> for the Joduka Contest .

Some of the information can be found in on the WIKI pages for this contest. There all competitors and the contest organisation can share information.
( If you don't know WIKI, that take a look at it. It is a web site where many people can contribute to the contents of the web site using an on-line web page editor. Very nice for a group of people wanting to share information, like the patricipants of this contest.)

The main source of information is off course the Webots Contest web site. There you can see the current score board in The Hall Of Fame, or you can see the life match going on each working day on 14:00 Western European time (GMT+1 during winter time / daylight savings time).
When you download the special 3D viewer applet, you can even see the match in 3D. You can also download recordings of earlier match rounds and see them in the 3D viewer.

The robot-judoka

The contestants must each make a control program for the robot and upload it to the match server of Cybertronics. Every working day a match is held. Two robots control programs are loaded, and they compete against each other for the best of 5 sets, with a maximum set time of 2 minutes.The robot at the first place on the last round (30 April 2004, or 1 May?) wins the prize.

The robot is a walking (you can crawl of course) robot with 2 legs, 2 arms, a head, a low-resulotion camera, a distance sensor, and a gyro compass. The control program must be written in Java™, and uses the Webots library routines to control the robot in the Webots simulator.
The robot model is provided by Cybertronics and cannot be changed: all contenders have the same "hardware", it is up to their own program how good their robot performs. Contenders can download the free demo version of Webots (Windows or Linux), with which they can test their program in their own environment. (With Java and the free Webots demo, competing does not cost you any extra investment, but a flat-rate internet connection would be very economic).
A competing robot can be download (the compiled version that is, not the source code) to hold a test match. And the replay files of each match can be donwloaded too, so that you can analyse the actual matches with the provided 3D contest player in your own environment.

The judoka must make the opponent fall. But it is not quite so easy to make a bi-ped robot walk. Several competitors have problems of just staying up by themself.

The contest rules are quite simple and the game looks more like karate, sumo, or boxing then judo. I have not yet seen any robot actually trying to perform a real judo technique.

For leg movement studies - a 2D cardboard model of a leg

(sept 2003)
I created a simple model to study the possible movements of the robot leg. In a side-view picture of the robot leg, the several parts of the leg were "exploded" at the joints. The drawing contains the separate parts of the leg with the rotation points of the joints clearly marked. On one of the sides of each joint, a circular dial is draw, so you can see the angle that two joining parts of the leg make.

How to put it together

1. Print the drawing. I advise beter (coated of photo paper) or thicker (120 gr) paper, because we are going to glue it. You could use fancy stuff like self-adhesitive paper. Use plastic sheets or transparancys for an even more durable print.
   If you click the image, a bigger version of the image is shown. Store that one on your ouwn computer and print it.
2. Glue the print on a sturdy background. I used cardboard. But you could even use thin plywood or even sheet metal.
3. Cut (or saw) out the leg parts around the edges.
4. Drill or punch small holes through the centre points of the joints.
5. Put the corresponding joints over each other with the part with the dial on top
6. Connect each joint together with anything that allows free, but not too smooth, rotation of the parts.
   I used small M3 screws, with a small ring on both sides of the cardboard to protect it against wearing out too soon. Also I put a little drop of glue on the nut to fixate it (it tends to get loose when you move a leg joint, even with the rings)

Now you can move your robot leg, and find out what things are possible. Below you can see a foto of my first-made leg.

Of course, this is only a 2D model from the side of a leg. But that movement is very important to walk, and even to remain standing up. (When you fall down, you loose).

The joint structure of the Judoka robot

(2 October 2003)
The robot has 21 joints, 5 sensors (a camera and a distance sensor on the head, 2 touch sensors below the feet, and a GPS device (for this contest) returning only rotation angles). The definition robot model itself is not very easy to read, as it is in VRML language. Therefore I took 2 screenshots and added markers (showing the axis of rotation) for each joint and sensors. You see below a small version of this drawing. A larger copy suitable for printing (2351x1621, 86 kB, PNG format) is available (click the image).

In case you need better scaling of leters and lines (not of the background robot image), there is a version in EMF (Enhances Window MetaFile) format, size 956 kB. If you have problems reading a file or need another format, you can e-mail me