Adaptive sliding-mode-backstepping trajectory tracking control of underactuated airships

The problem of trajectory tracking control for an underactuated stratospheric airship with model parameter uncertainties and wind disturbances is addressed in the paper. An adaptive backstepping sliding-mode controller is designed from the airship nonlinear dynamics model. The proposed controller has a two-level structure for trajectory guidance, tracking and stability, and the developed controller, based on nonlinear adaptive sliding-mode backstepping method, provides airship attitude and velocity control for the entire flight process. Furthermore, an active set based weighted least square algorithm is applied to find the optimal control surface inputs and the thruster commands under constraints of actuator saturation. The closed-loop system of trajectory tracking control plant is proved to be globally asymptotically stable by using Lyapunov theory. By comparing with traditional backstepping control and PID design, the results obtained demonstrate the capacity of the airship to execute a realistic trajectory tracking mission under two cases of lateral- and roll- underactuations, even in the presence of aerodynamic coefficient uncertainties, and wind disturbances

Robotic Airship Trajectory Tracking Control Using a Backstepping Methodology

Abstract-This paper considers the design of a novel closedloop trajectory tracking controller for an underactuated robotic airship having 6 degrees of freedom (DOF) and 3 controls, on forward, yaw and pitch motions using two side thrusters. A backstepping methodology is adopted as a design tool, since it is suitable for the cascaded nature of the vehicle dynamics. It also offers design flexibility and robustness against parametric uncertainties which are often encountered in aerodynamic modeling and air stream disturbances. Indeed, in our simulations we assume a 10% error in all dynamic parameters and yet the controller performs position, orientation, linear and angular velocities tracking successfully. We also impose an additional air stream disturbance and the controller corrects the vehicle's trajectory successfully too