| Fuzzy logic is a logical system which is much closer to human thinking and natural language than traditional logical systems. Furthermore, fuzzy logic is capable of expressing and manipulating imprecise, vague, and ill-defined quantities in a systematic manner. These features make it possible to use fuzzy logic in autonomous navigation algorithms for mobile robots. The resulting fuzzy logic-based navigation algorithms can endow a robot with the ability of emulating humanoid behavior when coping with a large amount of uncertainty in real-world environments.; Based on the observation of the behavior of human beings in dynamic environments, three fuzzy autonomous robot navigation algorithms are proposed in this thesis. The direction-based fuzzy reactive algorithm combines information about obstacles and the goal position together and gives the final steering direction which is safe, in the sense of avoiding collisions, and desired, in the sense of seeking the goal. The fuzzy-Braitenberg navigation strategy takes advantage of the essential characteristics of a differential drive robot and combines fuzzy logic with the ideas of Braitenberg vehicles, taking into account obstacle repulsion and goal attraction to set the speeds for the motors. In the layered goal-oriented fuzzy motion planning algorithm, information about the global goal and the long-range sensory data are used by the first layer of the planner to produce an intermediate goal, referred to as the way-point, that gives a favorable direction in terms of seeking the goal within the detected area. The second layer of the planner takes this way-point as a subgoal and, using short-range sensory data, guides the robot to reach the subgoal while avoiding collisions. Systematic procedures of the design and implementation of the three algorithms are addressed. The resulting navigation algorithms are implemented on a real mobile robot, the Koala, and extensively tested in various environments. Experimental results are presented which demonstrate the effectiveness and success of the proposed fuzzy navigation systems. |
