Summary form only given. A fuzzy mobile robot area filling system designed to traverse the entire unknown environment is described in this paper. Such a system has a variety of applications such as vacuuming, lawn-mowing, polishing, crop harvesting, etc. In particular, it is also suitable for performing waste cleanup in hazardous environments where the area is inaccessible to humans. This also implies that the robot must be able to complete the cleaning task in unknown environments. The area filling system detects and follows the wall of an enclosed area. The coordinates of the boundary of the area are recorded upon completing the wall-following action. The bounded area is then partitioned into overlapping parallel tracks with the two end points lying on the boundary recorded. By passing along those tracks one by one, the whole area can be covered.