Obstacle Avoidance System Design and Path Planning for An Unmanned Vehicle
Date Issued
2012
Date
2012
Author(s)
Chien, Mao-Yu
Abstract
The main purpose of this paper is to integrate GPS recievers, electronical compass, stereo camera, ultrasonic sensors, and dynamic system, developing a PC-based unmanned vehicle system for outdoor navigation. The main system comprises three parts: main station, reference station, and the vehicle. GPS signals received by reference station and vehicle are utilized to determine the position of the vehicle by Carrier Smoothed Code method. Electronical compass senses the heading angle of vehicle. Stereo camera and ultrasonic sensors are employed to detect obstalces, and obstalce-avoiding action is taken if obstacles exist. Main station monitors the motion of the vehicle, and the information is exchanged via wireless network.
SRI Stereo Engine(API) and the concept of “grids” are utilized to determine the relative distance between the vehicle and obstalces. Once the positions of obstacles are known, a path along which the vehicle can avoid those obstacles is decided by Rapidly-Exploring Random Tree method. Six ultrasonic sensors are assembled and controlled through FPGA board, and a rule-based system is utilized to deal with the data collected by ultasonic sensor system, determining the corresponding linear velocity and angular velocity output in order to avoid nearby obstacles.
An operation flow is developed to integrate these obstacle avoidance modes, making the vehicle choose the proper mode. Besides, the vehicle is able to switch from one mode to another correctly. Experimental results described in this thesis proves that the proposed navigation and control methodolgy are feasible.
Keywords: Rapidly-Exploring Random Tree, Obstacle Avoidance for Navigation System.
Subjects
Rapidly-Exploring Random Tree
Obstacle Avoidance for Navigation System
Type
thesis
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