Published on June 2012 | Marine Salvage, Marine Hydrodynamics, Control Systems

A new ship recovery concept and design using adaptively controlled buoyancy systems

In this paper, attention is placed on the salvage of a sunken ship resting on the seafloor by introducing a new design concept based on the adaptively-controlled buoyancy (gas-inflating) systems. A mathematical model describing a ship rigid-body motion in a vertical diving plane accounting for the heave and pitch degrees of freedom will be presented and analyzed with respect to both hydrostatic and hydrodynamic loads. A new design approach is implemented by integrating a fuzzy logic algorithm with the sliding mode controller to bring together the advantages of both controllers. An adaptive fuzzy sliding-mode control strategy (Conventional or Two input fuzzy sliding mode controller and Single input fuzzy sliding mode controller) ensuring a safe and stable ascending ship dynamics will be presented along with the discussion of a practical aspect of automatic controller design regulating the gas inflating flow rate. Computational simulations with a series of parametric studies based on an experimental ship model will be carried out to show the effectiveness of the proposed adaptive fuzzy sliding mode controllers and its comparative performance with conventional sliding mode controller. It is found that both fuzzy sliding mode controllers show about 30 % of improvement in tracking performance over the conventional controller in which single input fuzzy sliding mode controller is the optimum choice due to less tuning effort and computational time.