Multivariable oscillation control of a modularized floating airport with disturbance of uncertain waves

Abstract A floating airport, flexibly connected by a series of super-scale floating bodies, faces a challenge of tight requirements on the stationarity for operations in random seas. This paper presents a model-based nonlinear control strategy for the oscillation control of the floating airport excited by uncertain waves. A configuration of controllable thrusters is elaborated. The backstepping method is employed to design the control law in conjunction with a sufficiently smooth projection operator which leads to an adaptive scheme for the disturbance estimator in tracking the actual excitations of uncertain waves. The outputs of thrusters are determined by the control law and a sequential quadratic program. The proposed approach is essentially based on the Lyapunov synthesis method and the robustness of the control is guaranteed. In the numerical case studies, the feasibility and effectiveness of the control method are demonstrated by using JONSWAP spectrum and the ITTC spectrum at different wave frequencies and angles along with a comparative study of the proportional-integral-derivative (PID) scheme. The work provides a technical solution in handling the stability control of a high-dimensional nonlinear floating system in uncertain environments.