Determination of the shortest collision-free path for a mobile robot between start and goal positions in a workspace is central to the design of an autonomous mobile robot. The authors present a feasible path-planning algorithm which runs on the quadtree representation using a path graph. The quadtree representing the workspace is obtained from fast conversion of a real image taken through a camera on the ceiling. The quadtree integrates both obstacle regions and other regions in the workspace with its hierarchical structure in positioning. By using this hierarchical structure, the mobile robot is reduced to a point and then the forbidden regions where the robot cannot enter into are also understood in the quadtree. Hence, the algorithm can select the shortest collision-free path from the quadtree, i.e. a line between two given positions. Experimental results show that the proposed algorithm is superior to certain conventional algorithms with respect to calculation time.
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