“…The navigation problem is usually expressed mathematically as the 'Piano Mover's Problem' (Canny, 1985), also referred to as the 'Routing' (Cesarone andEman, 1988 andRichbourg et al, 1987), 'Find path' (Brooks, 1982 andBrooks andLozano-Ptrez, 1983), 'Path Planning' (Bao and Lin, 1988;Kambhampati and Davis, 1986;Montgomery et al, 1987 andThorpe, 1984), 'Motion Planning' (Schwartz and Sharir, 1988), 'Collision Avoidance' (Hong and Mauceri, 1986) problem and so on. After all, these problems are dealing with finding the safest (some also achieve shortest) path automatically for the moving object, within a known (have the map in advance) or unknown (gathering information step by step from sensor device) territory which might be a two-dimensional plane or three-dimensional space, and the obstacles might be movable or immovable.…”