Introducing Simulation Middle Size: A New Soccer

League to RoboCup

Mansour Jamzad and Mahdi Asadpour

Sharif University of Technology

Department of Computer Engineering

Azadi Ave. Tehran, Iran.

Abstract. There is a big difference between Simulation League and Middle Size

League in RoboCup, that is, a program written for the former can not be easily

transferred to the latter. Since the ﬁnal aim is real robotics, in this paper we sug-

gest a new match for RoboCup Soccer which can ﬁll this gap. We designed and

implemented a Modeled Robot Soccer Server most like Middle Size RoboCup

that contains a Soccer Field, Ball, Referee, etc. Each participated team should

provide not only his robots controller program but also the hardware model of

own robots in VRML97 format, using which our system will model a simulation

version of them. As an implementation of our ideas, we modeled and simulated

two teams of soccer robots and present the set up method for the match between

them. According to these setups, two teams will play and the scores are calculated

by the automated referee.

1 Introduction

RoboCup soccer competition is divided into two categories: Real Robots and Simula-

tion. The main goal of any simulation as a testbed is to facilitate the trial and evaluation

of ideas that have promise in the real world [1]. But there is a big difference between

the style of simulation league and the real robot league, so that a program written for

the former can not be easily transferred to the latter.

In this paper, we will introduce a new league for RoboCup that we call Simulation

Middle Size. In this new league we can use the advantages of the simulation soccer

league. In addition it gives many advantages to researchers to model real robots, add

new parts and capabilities to them, design advanced software algorithms and actually

see the result of implementation of these algorithms on the simulated robots. We believe

that this league can ﬁll the big gap between simulation league and real robot league, so

that the programs developed for the new league can be easily ported to real robots.

For this new league, each team should provide his robots controller program and

also the hardware model of own robots in VRML97 format. Using these data our system

enables the simulated robots to play soccer according to middle size league rules. We

have modeled and simulated two teams of robots and in this paper we present the set up

method for the match.

The rest of this paper is organized as follows: In next section, we present the reasons

for introducing a new league, in section three we introduce elements of this new league.

Jamzad M. and Asadpour M. (2005).

Introducing Simulation Middle Size: A New Soccer League to RoboCup.

In Proceedings of the 1st International Workshop on Multi-Agent Robotic Systems, pages 122-131

DOI: 10.5220/0001193501220131

 SciTePress

In section four we describe how to set up a competition between two teams of modeled

robots. In the conclusion section we discuss the limitations and present our suggestions

for the future works.

2 A New League Can Be a Solution

Fig.1. (a) A typical view of a Simulation League (b) One snapshot of robots in a Real Robots

League.

The main differences between Simulation and Middle Size leagues can be listed as

follows:

1. An important part of the real robot soccer is how to recognize the environment el-

ements and their positions according to soccer ﬁeld; participated teams generally

use real time machine vision algorithms for this purpose. But in simulation league,

there is a Soccerserver which provides the ﬁeld, ball and players position informa-

tion [6].

2. In real robot league, a robot may be damaged during the game, impose serious

damage to others, or it may not work properly due to hardware or software failures.

However, in simulation league such failures are either not considered or might be

of limited importance.

3. There has been many advances in designing and implementing new ideas in simula-

tion league that are based on AI methods and multiagent systems. But in real robot

league, due to the construction problems and limits in implementation of advanced

algorithms, its speed of progress is somehow limited.

However, although the 3D Simulation League provides a 3D shape for robots and

the ball movement in 3D space, but the users can not model their own robots in this

environment. In addition it can not provide any solution for the above mentioned limi-

tations.

We have a clear goal in RoboCup, that is to make robots that can win the human

soccer champion team by 2050. Having a look at the present leagues, we see a great

progress in designing and implementing ideas based on AI, multiagent systems, includ-

ing cooperative behavior, path planning, team work, etc that can be easily implemented

in soccer simulation league. On the other hand there are many limitations in imple-

menting most advanced methods used in simulation league in middle size. The reason

is due to the hardware and mechanical limitation of robots. If we continue the leagues

as they are, by the time that we could build better robots, we might face some serious

limitations, that is we might not be able to apply the advanced software algorithms on

those robots.

In the other hand, many research groups who are interested in middle size, but be-

cause of the high cost of purchasing real robots, or difﬁculties in constructing own ro-

bots, the number of teams that have been participated in middle size league are limited.

The trend in recent years shows that there might not be much change in this regard.

Therefore, in order to speed up many research ideas in related ﬁelds, the need for a

Simulation Middle Size league seems to be a reality.

In this new league, two teams of modeled robots can play according to middle size

league rules. Each team should provide the model of his robot(s) in VRML97

format

and also its controller program using which the server will model a simulation version

of them. At this stage the server will arrange a match between these two teams in an

environment similar to that of middle size league.

We highly recommend the reader to look at the movies in the web page of this paper

(http://sina.sharif.edu/∼jamzad/robocup.html

). These movies show the matches played

in the new league environment. Also, the controller programs source codes (in C/C++

language) are ready to download from this web page.

All our design and implementations were done using Webots

, a commercial mobile

robot simulation software that provides a rapid prototyping environment for modeling,

programming and simulating mobile robots. Using the libraries of this software one can

transfer his control programs to several commercially available real mobile robots[3].

The reason that at this stage we have used Webots, was because we were familiar

with its usage in mobile robots applications. But, there are other simulations tools such

as Player/Stage which is an open source, that can be used for this purpose, or even

a group of researches might develop a special purpose simulations tool for RoboCup

environment.

However, although most middle size teams might have their own simulation soft-

ware tools, but such tools are limited to test some speciﬁc functionality of their robots.

In addition due to the hard schedule of most teams in developing practical software and

hardware and also mechanical ﬁx ups, there is very limited time left for testing many

available methods and new ideas, for example, path planning, cooperative behavior,

distributed AI, etc, on real robots.

Virtual Reality Modeling Language, version 97: Most 3D modeling software, like 3D Studio

Max, Maya, AutoCAD or Art Of Illusion, include the VRML97 export feature.

http://www.cyberbotics.com

3 Elements of Simulated League

Elements of this new league and its rules are based on Middle Size League. Its most

important rules are listed in the web page of this paper, [11]. The complete middle size

league rules is available in [2].

3.1 The Field of Play

As shown in ﬁgure 2, the color of the ﬁeld surface is green. Dimensions of the ﬁeld is

rectangular and marked with white lines.

Fig.2. Top view of the ﬁeld of play with white lines, yellow and blue goals, goal area, corner

ﬂagposts, safety boundaries, etc.

A goal area is deﬁned at each end of the ﬁeld and cylinders are used instead of

ﬂagposts. As you see in the ﬁgure 2, the corner cylinders are painted in the same color

as the nearest goal. A wall is placed around and behind the goal and the interior of one

goal is blue, the other is yellow. The exterior of the goal, the goalposts and the crossbar

are painted white.

3.2 The Ball

The ball is spherical and its color is red, as is shown in ﬁgure 3 in front of the robots.

3.3 Players

A match is played by two modeled teams, each consisting of not more than six players

including a goalkeeper. The maximum difference of number of players between the two

teams starting a match is deﬁned as 1, if the team with less robots has 4 or more players.

Each Player/Robot carries the markers, which include Color Markers and Number

Markers. The color marker is one of the two predetermined ofﬁcial colors. The ofﬁcial

colors are with RGB

(0, 255, 255) for blue robots and with RGB(255, 220, 130) for

yellow robots, painted in ﬁgure 4.

Red, Green and Blue color numbers

Fig.3. The yellow team: player and goalkeeper plus the ball and number markers above each

robot.

Also each robot carries a number marker. The number 1 is reserved for goalkeepers

(as shown on top of robots in ﬁgure 3).

Fig.4. The used colors in this match.

3.4 The Referee

In this league, two referees control each match: Automated Referee and Human Referee.

Rules Judged by The Automated Referee The Automated Referee is a controller/supervisor

program that manages the game. It does the following tasks:

1. Starts the game.

2. Assigns blue or yellow color to one team randomly. The blue team starts the match.

3. Imports the model of robots to game and load their controllers programs.

4. Acts as timekeeper and keeps a record of the match.

5. When a team scores, the referee performs a number of tasks. It updates the score

(showing in the top of simulation scene), moves the ball to the center mark and

moves the players to start predeﬁned positions.

6. When the ball goes out of the ﬁeld, the referee moves the ball to a proper position.

7. Finishes the game and saves the result of game to a storage ﬁle.

Rules Judged by The Human Referee The Human Referee sets up a match ﬁrstly.

During the match, some errors may occur for the league system, in the other word, there

are some fouls like ”obstruction” which are difﬁcult to judge automatically. To resolve

such situations, the human referee is allowed. Other responsibilities are when intention-

ally blocking the movement of other players, inappropriate behavior and blocking the

goal with too many players [6].

4 How to Setup a Match

In this section, we mention the way of setting up the match from the ground up. Figure

5 shows a scene of match between two teams.

Fig.5. One scene of the match including images, at the right side, which were captured by each

robot camera.

Before setting up a competition, two participated teams should provide their robots

models and controlling programs.

We modeled and simulated two teams of robots to show:

1. The ability to construct complex and impressive robots, and

2. To provide a good sample for enthusiastic researchers to use it as it is or modify it

as desired.

To run a simulation in Webots, you need three things:

1. Deﬁne a 3D virtual world containing one or more 3D virtual robots to be saved as

a .wbt ﬁle.

2. Write C/C++ or Java programs to control each robot called Controller Program,

and optionally, a supervisor program to control the simulation.

3. Use Webots to run simulations for your robots and controllers [5].

4.1 An Example of How Teams Participate in The League

For the ﬁrst team participated in our league, the Arvand robots are selected. Arvand

is the name of robots designed and constructed by Sharif CE team for playing in the

middle size league [9]. Two different types of robots were made, players and the goal-

keepers. These robots showed a high performance in Robocup-99: became champion

[7].

Arvand Players We modeled the players as below (see ﬁgure 6):

1. The front camera captures an image in the ﬁeld of view of 90 degrees (1.57 radians)

with size of 64 × 64 pixels (used the Camera node of Webots).

2. The kicker kicks the ball (used the Servo node of Webots).

3. Two servo motors for each wheel for driving left/right and forward/backward (used

the Servo node of Webots). The combination of drive units movement and proper

settings provides the robot with continuous rotational move around any point [7].

4. Castor wheel is used for balancing the robot (used the Solid node of Webots).

5. Communication between robots by Emitting and Receiving messages (used the

Emitter and Receiver nodes of Webots).

The controller program of this robot is a simple image processing algorithm that

recognizes the ball and opponent goal positions. Its C source code is freely available at

[11].

We use three copies of this robot plus a goalkeeper for establishing a team.

Fig.6. A simulation model of Arvand player plus its goalkeeper robot and the match ball: team

color markers and number markers are included.

Arvand goalkeeper We modeled the goalkeeper as below (see ﬁgure 6):

1. Front camera is similar to the player one.

2. Two castor wheels is similar to the player one.

3. Two servo motors for each wheel, similar to the player one but are used for driving

according to the goal line.

The controller program of the goalkeeper recognizes the ball position and tries to

prevent the ball from passing over the goal line. You can ﬁnd some sample codes for

this goalkeeper in [11].

4.2 The Needed Settings

After you constructed

all the robots, you must observe the following settings before

competition:

1. Prepare two copies of your team; one with blue marking, and one with yellow

marking.

2. Choose the DEF name

of B

for robots in blue team, and so on for Y

3. Export

the VRML97 model of your robots to ﬁles b

.wbt for the robots of blue

team and y

.wbt for the robots of yellow team which n indicates the number mark

of that robot. Number 1 is reserved for goalkeepers.

4. You should deliver b

.wbt, y

.wbt and controller programs in a folder with your

team name.

4.3 The Match Routine

When two teams deliver the needed ﬁles to human referee,

1. He records the names of two teams.

2. He runs the simulation program.

3. The automated referee select one of teams as the starter (blue team) randomly.

4. It imports b

.wbt ﬁles of starter team and y

.wbt ﬁles of other one to the soccer

ﬁeld.

5. Places the players to start predeﬁned positions.

6. Kick off the match.

7. During the match, two teams compete with each other, and

8. Referees do their tasks respectively.

9. After the game ﬁnished, the automated referee shows the game result as seen in

ﬁgure 7, and also saves it in a log ﬁle.

Modeling the hardware and writing controller program

DEF is a ﬁeld deﬁned in each node of Webots

By using ”Export” item in Webots software

Fig.7. At the end of match, the automated referee shows/saves the match result.

5 Conclusion

In this paper we suggested to start a new league called Simulation Middle Size. Not

only it can use the advantages of the simulation soccer league, but also it gives many

advantages to researchers such as modeling their real robots, adding parts and capa-

bilities to them, designing advance software algorithms and studying how they will be

implemented on their modeled robot.

As a result the researches can evaluate the performance of such algorithms in shorter

period of time with higher accuracy.

We believe that if the suggested league is presented as a new match in RoboCup, we

will see a high improvement in the real robots league. We can design our robots in such

a way that certain algorithms that have proven to be efﬁcient in the simulation, could be

easily applied on them.

We conclude that our suggestion can be improved as follows:

1. The rules that are not currently applied in Middle Size e.g. Offside, Penalty Kick

[2], can be applied here to evaluate its practical effectiveness.

2. Such league can easily be set up for Small Size and Humanoid RoboCup.

3. In order to evaluate the performance of algorithms on real robots, we can program

a fault injection mechanism to be added to hardware and mechanical parts of the

simulated robots. These faults can be injected with the predeﬁned probabilities dur-

ing the match. At the end of a match, the overall performance evaluation will be

informed to each team.

4. The image acquisition of Webots provides noise free images. That is, we can always

get the exact predeﬁned ﬁxed colors for corner ﬂagposts, land marks, robots, etc.

However, in order to have a realistic simulation of the robot vision system, we can

introduce a new option for adding noise and degradation to the images.

5. At this stage the match is setup as a local game. Therefore, there are restrictions

on programming languages used by teams. To solve this problem, the match can

be carried out in a client-server style and using communication via UDP/IP (or

TCP/IP).

Acknowledgment

The authors would like to thank Masoud Asadpour from EPFL university (Switzer-

land), Olivier Michel from Cyberbotics Ltd. and all members of Sharif CE Middle Size

RoboCup team for their sharing of knowledge and cooperation.

References

1. P. Stone and M. Veloso, Multiagent Systems: A Survey from a Machine Learning Perspective,

Journal of Autonomous Robots, Vol. 8, No. 3, pp 345-383, 2000.

2. MSL Technical Committee, Middle Size Robot League Rules and Regulations for 2004, Draft

Version pre-8.2, May 18, 2004.

3. Olivier Michel, WebotsTM: Professional Mobile Robot Simulation, Journal of Advanced Ro-

botics Systems, Vol. 1, No. 1, pp 39-42, 2004.

4. Itsuki Noda, Soccer server : a simulator of robocup, Proceedings of AI symposium 95, pp

2934. Japanese Society for Artiﬁcial Intelligence, December 1995.

5. Cyberbotics Ltd., Webots 4.0.5 User Guide, 2004.

6. Mao Chen et al., Users Manual RoboCup Soccer Server version 7.07, 2001.

7. Mansour Jamzad et al., ARVAND: a Soccer Player Robot, AI Magazine, Vol. 21, No.3, pp

47-51, Fall 2000.

8. Mansour Jamzad et al., A Goal Keeper for Middle Size RoboCup, Lecture Notes in Artiﬁcial

Intelligence: RoboCup-2000: Robot Soccer World Cup IV, pp 583-586, Springer 2001.

9. Mansour Jamzad et al., A Fast Vision System for Middle Size RoboCup, RoboCup-2001:

Robot Soccer World Cup V, Peter Stone, et al (Eds), Springer, pp. 76-85, 2001.

10. Mahdi Asadpour, Simulating ARVAND Middle Size Soccer Player Robot with Webots, BS

thesis, Sharif University of Technology, Department of Computer Engineering, Feb 2005.

11. http://sina.sharif.edu/∼jamzad/robocup.html

12. http://www.cyberbotics.com

13. http://www.robocup.org