The design of a dynamic positioning (DP) system is a challenging task with several technical fields involved in the problem solution. Numerical simulation is a powerful tool to aid the designer during the system development and to speed up the design process. This paper presents the simulation methodology adopted to design and test the DP system for a vessel with a standard propulsion configuration. Simulation results and sea trial measurements are compared to illustrate the reliability of the proposed simulation platform.

Heading and speed control for a patrol vessel is addressed by using simple PID regulators. The selection of the PID parameters for both controllers is accomplished by using decoupled linearized model of the original motion equations and LMIs as a design tool. The effectiveness of the resulting controllers is validated on the original dynamic equations and with the presence of external disturbances such as wind, waves, and current.

Autonomous ships represent one of the new frontiers of technological innovation in marine engineering, which demand the development of innovative control systems to guarantee efficient and safe navigation of vessels. A convenient control system should be able to command the several actuators installed on board in different conditions—for instance, during oceanic navigation, harbor approach, narrow channels, and crowed areas. Such tasks are accomplished by different switching controllers for high and low speed motion, which have to be orchestrated to ensure an effective maneuvering. An approach to the design of hierarchies of controllers for maneuvering and navigation of ships equipped with a standard propulsion configuration in both blue and narrow water is proposed. Different levels of control, from global to local, are defined and integrated to steer the vessel in such a way to increase the maneuvering capability in various scenarios.

Intelligent and/or autonomous vehicle technologies are rapidly growing to meet the needs of marine safety and transport efficiency. One of the requirements to manage autonomous vehicles includes the integration between route planning and automatic motion control. In the authors' opinion, the latter could be sketched in three different layers: obstacle detection, planning and actuation. Moreover, the three layers should be able to interact in real-time. Dealing with such a challenging task, one of the best techniques to develop and test the logic is the use of the time-domain simulation. In the present work, a simulation model, integrating a path planning algorithm in the presence of obstacles with a track keeping controller, is developed. The path planning is based on a modified version of the Rapidly-exploring Random Tree (RRT*) algorithm. The track keeping is based on the Line-of-Sight (LOS) waypoints navigation for underactuated vessels. To achieve more reliable results, a detailed ship simulation model is used as a benchmark. Different scenarios and navigation modes are successfully tested, and the results are presented and analysed.

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Waste Heat Recovery (WHR) marine systems represent a valid solution for the ship energy efficiency improvement, especially in Liquefied Natural Gas (LNG) propulsion applications. Compared to traditional diesel fuel oil, a better thermal power can be recovered from the exhaust gas produced by a LNG-fueled engine. Therefore, steam surplus production may be used to feed a turbogenerator in order to increase the ship electric energy availability without additional fuel consumption. However, a correct design procedure of the WHR steam plant is fundamental for proper feasibility analysis, and from this point of view, numerical simulation techniques can be a very powerful tool. In this work, the WHR steam plant modeling is presented paying attention to the simulation approach developed for the steam turbine and its governor dynamics. Starting from a nonlinear system representing the whole dynamic behavior, the turbogenerator model is linearized to carry out a proper synthesis analysis of the controller, in order to comply with specific performance requirements of the power grid. For the considered case study, simulation results confirm the validity of the developed approach, aimed to test the correct design of the whole system in proper working dynamic conditions.

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