Sonar based systematic exploration method for an autonomous mobile robot operating in an unknown environment

A new systematic exploration method is addressed that permits a mobile robo t to effectively acquire the information on an unkown environment without w asting time. The algorithm is composed of following three modules: the firs t is the decomposition of a workspace into several sub-nodes by employing t he concept of Quadtree. These nodes are chosen as sub-goals to be reached s uccessively. The second is that controls the robot to follow the boundaries of objects in the environment in order to reach each sub-goal avoiding the situation of the robot entering a local minima. Here we utilize the imagin ary distance forces exerted by objects. The third is the node conditions fo r estimating the map quality for each node, which enables the robot to remo ve sufficiently informed nodes from the Quadtree. Two conditions are define d for the estimation of the map quality; entropy and maximum level of Quadt ree. The proposed approaches were successfully implemented to our mobile ro bot equipped with sonar sensors for constructing a sonar map of an unknown environment in a real world.