IMAGE PROCESSING APPLIED TO A ROBOTIC FOOTBALL TEAM Carlos Machado, Sérgio Sampaio, Fernando Ribeiro Grupo de Automação e Robótica, Industrial Electronics Department, University of Minho, Campus de Azurém, 4800 Guimarães, PORTUGAL fernando@dei.uminho.pt http://www.robotica.dei.uminho.pt/ Abstract Autonomous mobile robots are ever increasing their number of different applications, even in ludic applications or in sports. In the last few years, several robotic football competitions have been organised with participating teams from all over the world. This paper describes a team of Autonomous Mobile Robots which play football, developed by the Group of Automation and Robotics at the Industrial Electronics department (School of Engineering) of the University of Minho, in Guimarães (Portugal). In these competitions each team is free to use and/or build all the different electronics, sensory systems, playing algorithms, etc. as far as they cope with the rules imposed by the organisation. From every team new ideas emerge, sometimes the most incredible ones, but proving in the end that they work. These competitions proved to be very fruitful scientifically as well as very mediatic. INTRODUCTION Following a participation in other football competition, this team decided to increase reliability of these robots as well as implementing new improvements. The mechanics needed rebuilding and the software needed to cope with communication between the robots. Also some rules demanded some changes in the software and game tactics. Basically, the robots are typical ones with two motors/wheels with a differential type steering control. Each robot has a standard personal computer inside and some electronics to read the wheels movement (through encoders). Instead of using several different sensors increasing electronics complexity, this team decided to use only one major sensor and invest some time on it: a vision system with a small colour camera. The main feature of this team consists of an innovative image processing system developed on purpose for this robots. In order to see the whole field, this vision system uses a convex mirror placed at the top of the robot looking downwards with the video camera looking upwards, towards the mirror. With this technique, the robots can see all around themselves with a top view, which means continuous vision of the ball, goals and other robots. All the image processing algorithms were developed from scratch. With this vision system, all the information necessary for the game is read avoiding though other sensors. Collision detection was an important aspect taken into consideration and is achieved also with image processing. ROBOTS DESCRIPTION The team is made up of four equal robots (with a small difference only to the goal keeper later described). Even the software running on each robot is the same. This way standardisation was achieved which means that they should behave the same.