Output-constrained fixed-time control for autonomous ship landing of helicopters

In this paper, we consider a fixed-time autonomous ship landing control design for helicopters subject to asymmetric output constraints, model uncertainties and external perturbations. By incorporating a universal barrier function into the backstepping design, an output-constrained fixed-time control algorithm is proposed, where a new adaptive estimation method is introduced to compensate the effects resulting from uncertainties and disturbances. To avoid crash and overcome the limitation of the helicopter's under-actuated property, the whole landing operation is completed in a dual-phase landing sequence with two controllers, which are both designed based on the output-constrained fixed-time control algorithm. The proposed control strategy guarantees that the tracking and landing errors converge into a small neighborhood of zero in a fixed settling time without violating the constraint requirement. Numerical comparative simulations are executed to further verify the prominent control performance.