Unmanned Aerial Vehicles: Embedded Control

Chapter 11

Optic Flow-Based Vision System for Autonomous 3D Localization and Control of Small Aerial Vehicles ¹

11.1. Introduction

Recent advances in cost effective inertial sensors and accurate navigation systems, such as the GPS, have been key determinants of the feasibility of UAV systems. Milestones in manned and unmanned aircraft have been achieved using conventional navigation sensors such as standard IMUs for orientation, GPS for position, pressure sensors for altitude sensing, radar, ultrasound and laser range finder for obstacle detection. Our particular interests, however, involve small and micro UAVs flying close to the ground in cluttered environments like urban and indoor environments. Therefore, GPS information may not be available. Furthermore, the substantial weight and energy constraints imposed by small and micro UAVs preclude the use of conventional sensors. On the other hand, visual sensors are passive, lightweight and can provide rich information about the aircraft self-motion and surroundings structure. Therefore, computer vision can be used for autonomous localization, which is a crucial step for small aerial robots control and guidance. However, the design of a reliable vision system for aerial vehicles has many unsolved problems, ranging from hardware and software development to pure theoretical issues, which are even more complicated when applied to small flying machines operating in unstructured environments. Moreover, the difficulty found when using ...