A stability monitoring and advisory system for small ships

Considering the loss of lives and money as a result of marine accidents, the importance of reducing or preventing capsizing of small boats is clearly evident. The research described in this thesis addresses the development of a monitoring and advisory system for the safety of fishing vessels. This system uses environmental information obtained from a number of sensors and proposes corrective action based on a rule-base derived from experiments, theoretical research and human expertise. Improvements in computer technology and the low prices of measurement equipment facilitates the integration of a system based on off-the-shelf devices and subsystems such as a ship's radar system to measure wave properties. The thesis demonstrates that such off-the-shelf devices and subsystems can be used with special purpose software developed to produce a low cost, intelligent safety monitoring and advisory system. This monitoring system is designed based on the following requirements : • The system should measure the minimum amount of data. In order to make system practical and least costly, the equipments already existing onboard should be used. • The system should not interfere with the operation of the ship, since anything interfering with operation is expected to be discarded by the captain or crew. In view of the need for the evaluation of wave parameters at a fast rate, in the order of 30 - 60 seconds, for input into the advisory system, two new techniques (Boxing and thinning techniques) have been developed. Reasonable agreement has been found between these two techniques and conventional techniques, such as Fourier transforms. A fuzzy expert system has been developed as a decision making process for the monitoring and advisory system. Rules forming the basis for the advisory system are presented. An advantage of this modular structure is that new rules may be easily appended to the existing rule-base in view of further knowledge gained through interviewing experts, experiments or theoretical developments. Finally, feasibility of this approach has been demonstrated through numerical simulations of various sea conditions on a range of ship forms.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat