Map construction and localization using Lego Mindstorms NXT

Maps are very useful for understanding unknown places before visiting them as maps represent spatial relationships between various objects in a region. Using robots for map construction is an important field these days as robots can reach places which may be inaccessible to human beings. This paper presents a method to use the data obtained from a single ultrasonic sensor mounted on a robot, to construct a map and localize the robot within that map. Map of the previously unknown environment is created with the help of a mobile robot, built using Lego Mindstorms NXT assembled in a modified TriBot configuration. The robot is equipped with an ultrasonic sensor and is controlled from a computer system running a MATLAB program, which communicates with the NXT over a USB or Bluetooth connection and performs complex calculations that are not possible for the NXT itself. After the map construction, the robot finds its position in the map by using a particle filter. Implementation has been done in MATLAB programming environment using RWTH – Mindstorms NXT Toolbox and has been successfully tested for map construction of a room and localization within that room with the use of a TriBot.