Robots with Omnidirectional Wheels

Omnidirectional wheels have become popular and choose to develop for mobile robots, because they allow them to drive on a straight path from a given location on the floor to other places without having to rotate first. Moreover, the movement of translational along any desired path can be combined with a rotation, so the robot arrives to its destination at the correct angle.

Mostly omnidirectional wheels based on the same general principle; the wheel can slide frictionless in the motor axis direction while the wheel proper provides traction in the direction normal to the motor axis. In order to achieve this, the wheel is built using smaller wheels attached along the periphery of the main wheel. The kind of wheel that is using in RoboCup is small size and middle size omnidirectional robot since 2002. The wheel is a variation of the Swedish wheels, which use rollers with a rotation direction which is neither parallel nor perpendicular to the motor axis.

Two or more omnidirectional wheels are used to drive a robot movement each wheel provides traction in the direction parallel to the floor and normal to the motor axis. The forces provide and add up a translational and a rotational motion for the robot. If it were possible to mount two orthogonally oriented omnidirectional wheels right under the center of a robot with a circular base, then driving the robot in any desired direction would be trivial. To give the robot a speed, with respect to a Cartesian coordinate system attached to the robot, each wheel would just have to provide one of the two speed components.

Since the motors and wheels need some space, this simple arrangement is not possible. The wheels are usually mounted on the periphery of the chassis. It is also easier to cancel any rotational torque which could make difficult to drive the robot on a straight path. The popular configurations of omnidirectional robots are three and four-wheeled.