Simplified controller for three wheeled omni directional mobile robot

This paper presents the work on developing a controller for the three wheeled omni-directional mobile robot for the operation on a flat terrain. Central to a robot base are omni-directional wheels. In addition to providing traction normal to the rotor axis like an ordinary wheel, they are capable of sliding parallel to the rotor axis without much friction. We have designed and implemented a robot utilizing three omni-directional wheels mounted 120° apart. Trajectory of the robot is specified as the time variation of the position coordinates and the orientation of the robot with respect to a fixed frame. The trajectory is dictated by the speeds of the three omni-directional wheels. Been a holonomic robot, the designed robot can achieve any continuous trajectory. The trajectory is planned on the fixed world frame. Then, it is transformed to the time-varying robot body frame. The velocities of the wheels are computed with respect to the body frame. A PID controller is utilized for the control of each parameter. Consequently, several PID controllers are employed for trajectory control. The MATLAB® SIMULINK® platform is used to develop the kinetic model of the system. The designed robot has been implemented in hardware.