Computational issues in autonomous control of unmanned air vehicles

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Title: Computational issues in autonomous control of unmanned air vehicles
Author: Holsapple, Raymond
Abstract: In this work , we investigate just a few of the many computational issues involved in achieving autonomous control of unmanned air vehicles (UAVs ) . Of the many techniques used for UAV control , this research is vision based . We seek autonomous control and obstacle avoidance using a sequence of images from a camera . With the use of a camera , one part of this process is image processing , but it is not discussed here . We instead investigate several of the 'post processing of the image' issues . Image processing seeks to determine the flow of the image in the image plane . Using two consecutive images , image motion vectors are computed for a given collection of pixel position vectors . We describe two methods used to recover the linear and angular velocity that the UAV (camera ) underwent between the two camera frames . The only information needed is the pixel position vectors , the image motion vectors , and the speed of the UAV . The two methods discussed are the continuous eight -point algorithm and a direct minimization of a cost function . Without access to real data taken from a camera undergoing a known motion , we test the algorithms on random synthetic data and compare the results to the initial known linear and angular velocity . The linear and angular velocity signals being computed may be noisy ; as such , we also investigate a nonlinear observer to filter the possible noisy signal and test this observer on the equations of motion of a rigid body undergoing rotations and translations . As solving the observer equations involves numerical integration , we also investigate variable step -size selection methods for implicit integration schemes . The minimization of an efficiency function is the basis for the selection of the step -sizes for implicit Runge -Kutta and Runge -Kutta -Nyström methods . The methods are tested on three well -known examples from the literature . Finally , we consider the topic of obstacle avoidance . A novel approach based on Lyapunov theory is used to steer a UAV away from obstacles detected by the camera . We test the algorithm on a UAV simulation evolving in a two -dimensional space .
URI: http : / /hdl .handle .net /2346 /18314
Date: 2006-08

Citation

Computational issues in autonomous control of unmanned air vehicles. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /18314 .

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