Anti-Disturbance Control for Tethered Aircraft System With Deferred Output Constraints

In this paper, we investigate the peaking issue of extended state observers and the anti-disturbance control problem of tethered aircraft systems subject to the unstable flight of the main aircraft, airflow disturbances and deferred output constraints. Independent of exact initial values, a modified extended state observer is constructed from a shifting function such that not only the peaking issue inherently in the observer is circumvented completely but also the accurate estimation of the lumped disturbance is guaranteed. Meanwhile, to deal with deferred output constraints, an improved output constrained controller is employed by integrating the shifting function into the barrier Lyapunov function. Then, by combining the modified observer and the improved controller, an anti-disturbance control scheme is presented, which ensures that the outputs with any bounded initial conditions satisfy the constraints after a pre-specified finite time, and the tethered aircraft tracks the desired trajectory accurately. Finally, both a theoretical proof and simulation results verify the effectiveness of the proposed control scheme.