An adaptable mathematical model for integrated navigation systems
The project has been directed towards improving the accuracy and safety of marine navigation and ship handling, whilst contributing to reduced manning and improved fuel costs. Thus, the aim of the work was to investigate, design and develop an adaptable mathematical model that could be used in an integrated navigation system (INS) and an automatic collision avoidance system (ACAS) for use in marine vehicles. A general overview of automatic navigation is undertaken and consideration is given to the use of microprocessors on the bridge. Many of these systems now require the use of mathematical models to predict the vessels' manoeuvring characteristics: The different types and forms of models have been investigated and the derivation of their hydrodynamic coefficients is discussed in detail. The model required for an ACAS should be both accurate and adaptable, hence, extensive simulations were undertaken to evaluate the suitability of each model type. The modular model was found to have the most adaptable structure. All the modular components of this model were considered in detail to improve its adaptability, the number of non-linear terms in the hull module being reduced. A novel application, using the circulation theory to model the propeller forces and moments, allows the model to be more flexible compared to using traditional B-series four-quadrant propeller design charts. A new formula has been derived for predicting the sway and yaw components due to the propeller paddle wheel effect which gives a good degree of accuracy when comparing simulated and actual ship data, resulting in a mean positional error of less than 7%. As a consequence of this work, it is now possible for an ACAS to incorporate a ship mathematical model which produces realistic manoeuvring characteristics. Thus, the study will help to contribute to safety at sea.