Parallel multi-model switched control for ship roll stabilization

This paper concerns the application of a parallel multi-model switched control (PMMSC) scheme for integrated fin and rudder roll stabilization (INFRRS). The PMMSC algorithm uses a two-level hierarchical control strategy where, at the lower level, a bank of controller pairs (fin roll and rudder roll controllers) are designed for a range of preselected operating conditions, and, at the upper level, a decision maker decides which controller pair is most suited to the prevailing conditions and ensures that the appropriate controller pair is switched into operation. A novel approach of characterizing roll angle data using power spectral density (PSD) histograms is presented. It is shown how the PSD histograms for different encounter angles exhibit sufficiently different characteristics to enable them to be used by the PMMSC algorithm to produce reliable switching between controller pairs. Simulation studies demonstrate the efficacy of the PMMSC when applied to an identified ship model.