Comparative Results on Stabilization of the Quad-rotor Rotorcraft Using Bounded Feedback Controllers

In the recent years autonomous flying vehicles are being increasingly used in both civil and military areas. With the advancement of the technology it has become possible to test efficiently and cost-effectively different autonomous flight control concepts and design variations using small-scale aerial vehicles. In this paper the stabilization problem of the quad-rotor rotorcraft using bounded feedback controllers is investigated. Five different types of nonlinear feedback laws with saturation elements, previously proposed for global control of systems with multiple integrators, are applied and tested to control the quad-rotor rotorcraft roll and pitch angles. The results obtained from autonomous flight simulations and real time experiments with the Draganflyer V Ti four-rotor mini-rotorcraft are analyzed with respect to the structural simplicity of the control schemes and the transient performance of the closed-loop system.