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This paper focusses on the hydrodynamic performance of an unmanned vehicle system, consisting of a remotely operated underwater vehicle (ROV) that has to be launched and recovered autonomously from an Autonomous Surface Vehicles (ASV). The hydrodynamic model of the ASV/ROV coupled system is described in detail and solved numerically. The paper seeks to assess the overall performance of the ASV/ROV system, including the stability of the ASV, the ROV tidal current capacity and the required power of the launch and recovery winch system. The results demonstrate that this ASV/ROV system can complete the launch, holding and recovery tasks meeting stability for the given winch power requirements. The tidal current capacity of the ROV decreases with a larger target water depth. The maximum ROV umbilical tension is observed during steep wave instances when the ROV is in proximity to the ASV. A down-control force is demonstrated to be a suitable solution to limit the maximum tension within the umbilical rated force limits. This paper presents the methods and considerations for working towards a fully autonomous ASV/ROV system capable of autonomous inspection and maintenance missions. The work will be useful for practitioners and researcher working on autonomous offshore systems. • A nonlinear model is promoted to evaluate the coupled effects caused by the system integration of an ASV/ROV system. • The numerical model is validated by the sea trial data. • The environment capacity of the ASV/ROV system is discussed. • Two winch control methods are compared. [ABSTRACT FROM AUTHOR]

This paper uses a fully nonlinear model to comprehensively explore the coupled effects caused by the system integration between an offshore wind turbine and a heaving buoy wave energy converter. Parameters of the study include the pitch motion of wind turbine, the tension on the mooring line, the contact pressure between these two devices, and the energy absorbed by power take-off (PTO) system. Results demonstrated that the buoy stabilises/reduces the pitch motion of wind turbine when its metacentric height is positive. A buoy with a negative metacentric height will increase the pitch amplitude of wind turbine and the tension of the mooring line, which is undesirable. The relative vertical motion between heaving buoy and spar could buffer their maximum contact pressure. The Coulomb PTO could offer a higher peak output power of WEC than the linear PTO. The relationship between contact pressure and WEC peak power is quantified to inform the PTO design. The wind/wave device is evaluated at a representative site with suitable wind and wave conditions off the US West Coast. The WEC does significantly reduce the wind turbine pitch motion by at least 60%/50% for the modelled average/max wave conditions with increased power production (14%/80%). • A nonlinear model is promoted to evaluate the coupled effects caused by the system integration of an OWT/WEC device. • Three heaving buoys and two types of PTO have been integrated into an OWT. • The motion of OWT, the tension, the contact pressure, and the energy absorption have been systematically discussed. • The field study based on the west costa of US is conducted. [ABSTRACT FROM AUTHOR]