Observer Based Path Following Control for a Stratospheric Airship with Modeling Uncertainties and Actuator Saturation

The planar path following problem for a fully-actuated stratospheric airship with modeling uncertainties and actuator saturation is investigated in this paper. Firstly, a six-DOF dynamical model of the stratospheric airship is given. Secondly, six path following errors and their derivatives for the airship are derived from the model. Thirdly, a disturbance observer is constructed to estimate unknown terms in the airship model such that a dynamic inversion control law can be designed. In consideration of saturated characteristics of the actuator, the control law is redesigned by introducing an anti-saturation dynamic compensation term. Finally, it is proved that the six path following errors can be controlled to a small neighborhood of the origin with arbitrary accuracy. Simulation results for the airship to follow a circular path are presented to verify effectiveness of the proposed method.