In recent years there has been a rapid growth in the application of miniature UAVs to monitoring our environment. The majority of this monitoring is for either ecological reasons or to provide improved security during times of natural disaster. A miniature UAV entrusted with a mission must follow either a pre-planned or a real-time defined trajectory. The ability of such a UAV to track the desired trajectory closely is critical. The main focus of this work is to contribute to the synthesis of guidance/piloting control laws which provide enhanced performance over an enlarged flight domain and mission set. From a control viewpoint, miniature UAVs represent often unstable, highly nonlinear dynamic systems, whose physical parameters are usually only partially known. They are also subject to strong atmospheric perturbations which provides further complications. In this respect, the work of this dissertation focuses on the synthesis of nonlinear control laws (feedback linearization, differentially flat control, backstepping) and their enhancement using adaptive control theory. The main case study of this dissertation is that of a quadrotor helicopter, a type of vehicle with an interesting flight envelope including : vertical takeoff and landing, stationary flight and, most importantly, maneuverability even at low speed. The flight dynamics of the vehicle have been modeled and the parameters of the model analysed in order to develop a control structure, the performance of which has been assessed using a number of simulations.
Contribution to the synthesis of guidance and piloting laws for mini UAVs