Ship´s roll stabilization by anti-roll active tanks

This paper examines the control of the heeling angle of a ship in still waters based on the utilisation of anti-heeling tanks operated by pressurized air. The proposed objective attempts to reduce the list angle to a null value during the loading process in a fast ferry ship. A nonlinear adaptive controller has been designed as a means of counteracting the parameter inaccuracies that are involved in the nonlinear model. These are the linear and quadratic damping coefficients and the size of the cargo that is being handled. The design is based on a relatively new methodology, the backstepping procedure. With the objective of reducing the number of sensors a model reference based nonlinear observer has been introduced. The controller thus designed provides a robust control system under parametric uncertainties and state variable errors. The designed control implies an improvement on the actual systems based on the PID control implemented under programmable logic controllers (PLCs).