Advanced control for fault-tolerant dynamic positioning of an offshore supply vessel

The paper presents a solution to guarantee a fault-tolerant robust control for the dynamic positioning of an over-actuated offshore supply vessel. Fault detection is obtained by a combination of two model-based techniques: the parity space approach and the Luenberger observer. The dynamic positioning system is provided by a bank of reconfigurable Discrete-Time Variable-Structure Controllers (DTVSC), selected by a supervisor, based on a fault isolation logic. The control system is combined with a wave compensation based on a Multi-rate Extended Kalman Filter (MREKF). The proposed solution is compared with a standard Proportional-Integral-Derivative (PID) control system and a passive nonlinear wave filter to assess its robustness to input disturbances and uncertainties in the model parameters. The simulation tests developed for a scale model of an offshore supply vessel show that, in the case of actuators faults, dynamic positioning is guaranteed by the proposed solution.