Application of a model-based nonlinear attitude control for quadrotor UAVs

A quadrotor, a UAV equipped with four rotors, has an advantage of its maneuver, and has been used for various purposes. For this advantage, many researchers have studied a quadrotor's operation. An attitude control system for a quadrotor is one of the most important parts in order to improve the quadrotor's performance. This thesis developed a quadrotor testbed and applied a model-based nonlinear attitude control, originally designed for a space craft, to the quadrotor. In order to implement a nonlinear attitude control system, the dynamic model of the quadrotor is studied and the quadrotor's physical properties are characterized based on the model. Then, stability and agility of the nonlinear attitude control are validated by both simulations and experiments and its performance is compared with one of an conventional PID attitude control. Finally, this thesis proposes a computationally-e cient position estimator for the quadrotor's operation. The position estimator detects visual markers of an image from the camera, and computes the quadrotor's position. The position estimator was also evaluated by experiments