Nonlinear Control For Quadrotor Unmanned Aerial Vehicles

The quadrotor unmanned aerial vehicle (UAV) is a typical underactuated system, which has less control inputs than the degrees of freedoms. Although this property can simplify the design and manufacture, it brings a great challenge to the control development. The dynamics of the quadrotor UAV also suffers from various control complexities such as: strongly coupling and nonlinearity. Besides, the quadrotor UAV is effected by the nonlinear aerodynamic drag during the flight. These dynamic uncertainties complicate the development of the controller.Due to its advantages such as vertical taking off and landing (VTOL), rapid maneuvering and precise hovering, the potential for the quadrotor UAV in civil and military applications has been well established. However, a lot of experience is required for the human pilot. High performance control laws are required for the autonomous flying control of the quadrotor UAV. Meanwhile, in consideration of the limitation of onboard actuators, the control inputs should be with some reasonable values. Recently, several literatures have proposed some new methods for the control of the quadrotor UAV, but the design of nonlinear control mechanisms for the quadrotor UAV in the presence of structural uncertainties and unknown external disturbances is still a challenging task.A further investigation on controller design for the quadrotor UAV is proposed, and several kinds of control algorithms are developed in this dissertation. In the chapter II, a new nonlinear adaptive controller is proposed for a class of quadrotor UAV, which is subjected to parametric uncertainties. The on-line parameter estimations are combined with the feedback control to develop the nonlinear adaptive regulation controller, which yields a global asymptotic regulation result for the UAV’s Cartesian position and yaw angle while keeps the closed system stable. In the chapter III, an adaptive sliding mode tracking controller is proposed for the quadrotor UAV which is subject to parametric uncertainties and external disturbances. By using Lyapunov-based stability analysis, it can be proved that the proposed control law yields a global asymptotic tracking result for the UAV’s Cartesian position and the yaw orientation. In the chapter IV, on-line parameter estimations are combined with a robust control design based on hyperbolic tangent functions to develop a new continuous and differentiable tracking controller, which yields an asymptotic tracking result for the UAV’s Cartesian position and an asymptotic regulation result for the yaw orientation. Because of the load capacity of the UAV, some high accuracy sensors may not apply to this class of aircraft. In the chapter V, an attitude and altitude output feedback tracking controller is developed, which uses only the system’s output state and yields a semi-global asymptotic tracking result. With the aid of Lyapunov-based stability analysis, Barbalat’s Lemma and vanishing perturbation theorem, the stability of the closed-loop system can be guaranteed for the proposed control strategies. Numerical simulation results are included to validate the performance of the presented control laws.