Spatial Path Following Control of an Autonomous Underactuated Airship

This paper studies the spatial path following control of an autonomous underactuated airship in the presence of model uncertainties and external disturbances. Firstly, the nonlinear dynamics model, kinematics model and path following error dynamics model are given. And the control objective is formulated. Then, an adaptive backstepping sliding mode controller is designed. Besides, to overcome the disadvantage of dependence on the accurate vehicle model, a nonlinear disturbance observer (NDOB) is adopted to estimate the attack and sideslip angular velocities. In addition, when backstepping technique is uesd, the complex analytic computation of command derivative is required to be known. To handle this problem, a sliding mode differentiator is implemented to generate the command derivatives. Finally, the closed loop stability for the system is proved using Lyapunov stability theory. Numerical simulations are given to demonstrate the effectiveness of the proposed method.