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This paper presents a review of research work done on various aspects of control system approaches of unmanned surface vehicle (USV) in order to improve the course keeping performance. Various methods have been used to produce a course keeping control system for manoeuvring system of USV. However, the review reveals that the adaptive backstepping control system is a powerful tool for the design of controllers for nonlinear systems or transformable to form a tight feedback parameter. It is very suitable for the automated control system of USV in relative motion that involves the disturbances from waves and wind. Fuzzy logic control also had been suggested as an alternative approach for complex systems with uncertain dynamics and those with nonlinearities. This method does not rely on the mathematical models, but the heuristic approach. Further studies may be conducted to combine the control method approach mentioned above to develop a real time system with robust control laws to the motions of a USV in waves, usually at a specific speed, including station keeping or heading in sinusoidal and irregular waves.

Waste heat recovery from shipboard machineries could be a potential source for heat treatment of ballast water. Similar to a shipboard schematic arrangement, a laboratory-scale engine-heat exchanger set-up harvesting waste heat from jacket water and exhaust gases was erected to test the level of species' mortalities. Mortalities were also assessed under experimental conditions for cultured and natural plankton communities at laboratory level. Effect of pump impellers on species' mortalities were also tested. Exposures between 60°C and 70°C for 60 sec resulted in 80-100% mortalities. Mortalities due to pump impeller effects were observed in the range of 70-100% for zooplankton. On the laboratory-scale arrangement, >95% mortalities of phytoplankton, zooplankton and bacteria were recorded. It was demonstrated that the temperature of tropical sea waters used as secondary coolant can be raised to cause species' mortalities, employing engine exhaust gases. The results also indicated that pump impeller effects will enhance species' mortalities. The limitations of the shipboard application of this method would be the large ballast volumes, flow rates and time for treatment.

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