Modelling and control of an buoyancy driven airship. (Modélisation et Commande d'un Dirigeable Propulsé par la Force de Flottabilité)

A new concept of airship without thrust, elevator or rudder is considered in this thesis. It is actuated by a moving mass and a mass-adjustable internal air bladder. This results into the motion of the center of gravity and the change of the net lift. The development of this concept of airship is motivated by energy saving. An eight degrees-of-freedom complete nonlinear mathematical model of this airship is derived through the Newton-Euler approach. The interconnection between the airship’s rigid body and the moveable mass is clearly presented. The dynamics in the longitudinal plane is analyzed and controlled through a LQR method, an input-output feedback linearization, and the maximal feedback linearization with internal stability. Thanks to maximal feedback linearization, an efficient nonlinear control is derived. In this process, modelling, analysis, and control are solved for special cases of the airship, which become gradually closer to the most general model. The most constrained special case reduces to a two degree-of-freedom system. It is shown that the basic properties of this two DOF mechanical system remain instrumental for the analysis and synthesis of advanced airship models. These properties are far from being obvious from the most complex model. Through a singular perturbation approach, the superposition of the two control actions in the longitudinal plane and in the lateral plane is shown to achieve the control of the dynamics in three dimension.