Robust Fault-Tolerant Dynamic Positioning of Marine Surface Vessels With Prescribed Performance

This paper is concerned with the problem of fault-tolerant dynamic positioning (DP) for the marine surface vessels with sensor faults and unknown dynamics as well as random disturbances. It is anticipated that the requisite performance for the faulty system still holds, especially for the post-fault phrase, which remains open in the literature. In this paper, a fault-tolerant prescribed performance control approach is put forward to solve the problem. It achieves DP with the prescribed speed and accuracy in the sense that the DP errors evolve within the preselected performance envelops whenever the sensor faults happen. It is also inherently robust against the unknown vessel dynamics and ocean disturbances. Thus, the common assumptions on the partially known vessel nonlinearities and the differentiable disturbances are eliminated. On the other hand, there is no need for disturbance estimation, parameter identification, function approximation, fault detection, fault isolation or fault estimation, yielding a control simplicity. Finally, a pair of comparative simulations on Cybership II are carried out to validate the feasibility and advantage of the proposed approach.