Browsing by Author "Pérez-Collazo, Carlos"

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    Adaptative Integral Sliding Mode Based Course Keeping Control of Unnamded Surface Vehicle
    (Journal of Marine Science and Engineering, 2022, 10, 68, 2022) González-Prieto, José Antonio; Pérez-Collazo, Carlos; Sing, Yogangh
    This paper investigates the course keeping control problem for an unmanned surface vehicle (USV) in the presence of unknown disturbances and system uncertainties. The simulation study combines two different types of sliding mode surface based control approaches due to its precise tracking and robustness against disturbances and uncertainty. Firstly, an adaptive linear sliding mode surface algorithm is applied, to keep the yaw error within the desired boundaries and then an adaptive integral non-linear sliding mode surface is explored to keep an account of the sliding mode condition. Additionally, a method to reconfigure the input parameters in order to keep settling time, yaw rate restriction and desired precision within boundary conditions is presented. The main strengths of proposed approach is simplicity, robustness with respect to external disturbances and high adaptability to static and dynamics reference courses without the need of parameter reconfiguration.
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    OrthoSpar, a novel substructure concept for floating offshore wind turbines: Physical model tests under towing conditions
    (Ocean Engineering 245 (2022) 110508, 2022) Büttner, T.; Pérez-Collazo, Carlos; Abanades, J.; Hann, M.; Harper, P.; Greaves, D.; Stiesdal, H.
    An important condition of any port-assembled floating offshore wind turbine concept is the de-ballasted trans-port stage. As the hydrostatic and dynamic stability may vary greatly from the operational condition, it needs to be carefully investigated in early stages of the design-phase. In this work, physical modelling of the transport of the de-ballasted OrthoSpar device was carried out to determine roll and pitch RAOs, as well as load charac-teristics of the towing line. Towing was simulated with a stationary model being subjected to currents. To examine the influence of wave direction, a range of model orientations towards the incident waves were tested in still water and together with the simulated towing state. Roll and pitch motions were found to be highly dependent on the wave frequency and a result of a low damping ratio. The towing load amplitude was found to be influenced by the towing direction regarding the wave direction.