Vision-Based Control and Flight Optimization of a Rotorcraft UAV

• Main Author: Hubbard, David Christian
• Format: Others
• Published: BYU ScholarsArchive 2007
• Subjects: Computer Vision; Real Time; Rotorcraft; Helicopter; UAV; Computer Sciences
• Online Access: https://scholarsarchive.byu.edu/etd/1198; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2197&context=etd

A Rotorcraft UAV provides an ideal experimental platform for vision-based navigation. This thesis describes the flight tests of the US Army PALACE pro ject, which implements Moravec's pseudo-normalized correlation tracking algorithm. The tracker uses the movement of the landing site in the camera, a laser range, and the aircraft attitude from an IMU to estimate the relative motion of the UAV. The position estimate functions as a GPS equivalent to enable the rotorcraft to maneuver without the aid of GPS. Flight tests were performed with obstacles and over concrete, asphalt, and grass in daylight conditions with a safe landing area determined by a separate method. The tracking algorithm and position estimation performance are compared to GPS. Accurate time synchronization of the inputs to the position estimation algorithm directly affect the closed-loop stability of the system, proportional with altitude. By identifying the frequency response of each input and adding filters to delay some of the inputs, the closed-loop system maintains stable flight above 18 m above ground, where the system was unstable without the additional filters.