Unmanned Aerial Vehicles: Embedded Control

Chapter 10

Vision-Based Position Control of a Two-Rotor VTOL Mini UAV ¹

10.1. Introduction

The development of mini UAVs and micro UAVs has recently motivated new research areas in different disciplines, such as electronics, mechanics, aeronautics, automatic control just to mention a few. Such vehicles have great potential for search and rescue missions, homeland security, real-time forest fire monitoring, surveillance of sensitive areas (borders, ports, oil pipelines), remote sensing, etc. Accurate navigation and efficient control of the vehicle are essential to successfully accomplish such missions. Furthermore, small UAVs impose weight and size constraints which exclude the use of heavy sensors. Light sensors are usually less accurate and therefore suitable estimation and control algorithms should be developed, since the performance of the closed-loop control system will be as good as the quality of the feedback sensor signal.

Inertial sensors, gyroscopes and accelerometers, provide rotational velocity and linear acceleration respectively. The numerical integration of these signals can provide the attitude, translational position and velocity of the vehicle. These measurements are valid only for a short period of time, since the signal drifts due to inherent noise and bias. Thus, for a reliable attitude measurement, a fusion between accelerometers and gyroscopes is needed. Concerning the position, the GPS is fused with inertial sensors (INS) to provide periodic corrections, in ...