The Omni Directional Wheel is a kind of wheel that can freely role in more than one direction. It is popular for mobile robots such as junior soccer robots, small size robots, and middle size robots since it does not need to rotate first for moving from one point to another in a straight path. It has some extra wheels along its circumstance which allows the wheel roll laterally in addition to the normal rotation. In RoboCup competition such as middle size league MSL, the time of reaching for the ball for a robot is extreme importance. The faster it gets the ball, the more chances it has to score a goal. Using an Omni Directional Wheel can help very much to get this goal. By using Omni Directional Wheel one can change a non-holonomic robot to a holonomic one. The non-holonomic robots are slower than holonomic one since it has 2 degrees of freedom. These freedoms are moving forward/backward and rotating. By using Omni Directional Wheel in a robot it can rotate and move in every desired direction without the need to change the direction of the wheels.
One of the most important applications of Omni Directional Wheels is in robots, especially robots used in RoboCup challenges. RoboCup is a scientific competition. It is designed and held to develop lots of fields like mobile autonomous robotic, soccer robots, electronics, robot wheels, image processing and etc. The RoboCup competitions help the development of lots of kinds of robots as robotic soccer players and rescue. In order to let the robots move on a solid surface, there are several ways. The most popular ones are using wheels and legs. Because of the attractive mechanisms of wheels in robots, it is the most useful one. In football and soccer robots, wheels are interesting because they help the robot to have a sufficient speed and it is mechanically attractive. Moreover, control of wheels in soccer robots are easier. So the wheels are the first solution for moving the robots in the middle size league.
In using Omni Directiona Wheels for moving robots there some challenges which should be solved. One is the number of wheels that should be specified. One of the most popular methods is using 3 Omni Directional Wheels which controlled by different motors. It helps robots such as junior soccer robots, small size robots, and middle size robots to move efficiently in any direction. There are some different ways to optimally control an Omni directional robot which the physical and theoretical bases for control approaches of an n-wheeled control are the same. Some of the robotic team leaders have written papers in this field. Most of them are presented in the RoboCup International Symposium and IEEE Robotics and Automation Society. It seems that one of the most important challenges in controlling a robot with Omni Directional Wheel is to detect and control of the slip and motor failure. But there is some practical solution for these challenges in the papers.