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This paper presents the synthesis of a research on dynamic positioning systems (DPS) for semisubmersible platforms, that included both analytic-computational and experimental parts. Firstly it is presented an overview of the mathematical models used for simulation of the vehicle motion in the horizontal plane. The theoretical treatment of the control problem and its implementation Is also focused. Two different schemes were used to get the controller, one of them is fully original in DPS applications. After that, the control system prototype construction is briefly presented. The evaluation of the control system performance may be done by the analysis of computer simulation and experimental trial results. The trials were carried out in the towing tank of Berlin Technical University, using a propelled aluminium model of a semlsubmersible platform equiped with the I control system prototype developed by the authors.

This paper completes an exploration analysis of onshore ballast water treatment alternatives at major ports. The authors had presented results for option (1) ballast water treatment onshore installed in two iron ore ports in 2012 applying the discrete events simulation model. Now, two more options are presented: (2) mobile and (3) desalination reception facilities. The previous simulation model developed called TRANSBALLAST, was adapted to consider these two new alternatives. This model was applied to the same ports presented in 2012 and this evaluation also includes one more port with 50 million tons annually (Mta) of iron ore transport capacity. The results uncovered that for (2) there is an increase of 1.90 days on the average waiting time of ships that moored at Port 1. In (3), the average waiting time and berth occupation rates were observed to remain the same presented in (1). One of the major differences between the systems consists in catching sea water to increase the desalination plant operational capacity. Among those three onshore ballast water treatment alternatives, (2) does not impact port terminals infrastructure. Additionally, option (2) could be offered to ports users as a ballast water treatment service and ship-owners might not need any onboard ballast water treatment system. (3) Might be feasible to ports regions without enough water supplies solving two issues: transfer of invasive species from ballast water and water recycling.Este ensayo realiza un análisis exploratorio de alternativas de tratamiento de agua de lastre en tierra en puertos principales. Los autores habían presentado resultados para la opción (1) del tratamiento en tierra de agua de lastre instalado en dos puertos de minerales de hierro en 2012 aplicando el modelo de simulación de eventos discretos. Ahora, se presentan dos opciones adicionales: (2) móvil e (3) instalaciones de recepción de desalinización. El modelo de simulación anterior desarrollado que se denominó TRANSBALLAST, fue adaptado para considerar estas dos nuevas alternativas. Este modelo fue aplicado a los mismos puertos presentados en 2012 y esta evaluación también incluye un puerto adicional de 50 millones de toneladas al año (Mta) de capacidad de transporte de minerales de hierro. Los resultados concluyeron que para (2) hay un aumento de 1.90 días de promedio de tiempo de espera de naves que atracaron en el Puerto 1. En (3), el tiempo de espera promedio y las tasas de ocupación de atraque fueron observadas para mantenerse igual que las presentadas en (1). Una de las principales diferencias entre los sistemas consiste en atrapar agua de mar para aumentar la capacidad operacional de la planta de desalinización. Entre esas tres alternativas de tratamiento de agua de lastre, (2) no tiene un impacto en la infraestructura de los terminales de puertos. Adicionalmente, la opción (2) puede ser ofrecida a usuarios de puertos como un servicio de tratamiento de agua de lastre y los propietarios de naves podrían no necesitar ningún sistema de tratamiento de agua de lastre...