Navigation is one of the most important functions of the mobile robot to have. In this thesis, a navigation system for mobile robot using a rotating ultrasonic sensor was proposed. It consists of global path planner, local path planner and trajectory planner. Global path planner finds the shortest path from start point to destination with global map data using graph searching method. Local path planner makes local map between global knot points using the ultrasonic ranging system, finds obstacle free space around the robot and determines the next movement position toward the local goal while avoiding collisions with any obstacles. Trajectory planner generates the steering and driving commands for actuator to move the robot smoothly. The implementation of the system with some appropriate hardware and software was followed by an experiment in the laboratory and proved the navigation performance and the usefulness as a simple, low cost navigation system for any free ranging mobile robot with 2-dimensional mobility. And several methods to solve the inherent problem, false reflection, in using an ultrasonic sensor were proposed as further studies.
