A mathematical model of the propeller pitch change mechanism for the marine propulsion control design

The paper is mainly focused on the mathematical model of the control pitch mechanism for a marine controllable pitch propeller (CPP), able to perform the propeller blade position change and to give a proper information about the oil pressures, produced inside the CPP hub. In fact, too high pressures can be responsible for the mechanism failure, then they should be always under examination by the ship automation. With regard to the traditional representation of the few spindle torque data reported in literature, in the proposed mathematical model the transportation inertial forces and the Coriolis inertial forces acting on the propeller blade are evaluated taking into account the yaw motion of the ship, the propeller speed (including shaft accelerations and decelerations) and the blade turning during the pitch change. On the basis of the introduced procedure, it is developed the CPP model which is part of an overall propulsion simulator, representing the dynamic behaviour of a twin-screw fast vessel. The aim of the work is to represent the ship propulsion dynamics by time domain simulation, on the ground of which the automation designers can develop and test several propulsion control options. A brief description of the simulation approach adopted for the vessel crash stop is illustrated at the end of this paper. In particular, the propulsion control action is studied taking into account machinery performance and constraints, including also the control pitch mechanism feedback in terms of allowable forces and pressures.