Proceedings of the ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering OMAE2018 June 17-22, 2018, Madrid, Spain OMAE2018-77859 CONTROLLER ANALYSIS IN REAL-TIME HYBRID MODEL TESTING OF AN OFFSHORE FLOATING SYSTEM Stefan A. Vilsen Centre for Autonomous Marine Operations- and Systems (NTNU AMOS) Department of Marine Technology NO-7491 Trondheim, Norway SINTEF Ocean P.O. Box 4762 Torgard, NO-7465 Trondheim, Norway Email: stefan.vilsen@sintef.no Thomas Sauder Centre for Autonomous Marine Operations- and Systems (NTNU AMOS) Department of Marine Technology NO-7491 Trondheim, Norway SINTEF Ocean P.O. Box 4762 Torgard, NO-7465 Trondheim, Norway Email: thomas.sauder@ntnu.no Martin Føre Centre for Autonomous Marine Operations- and Systems (NTNU AMOS) Department of Engineering Cybernetics NO-7491 Trondheim, Norway SINTEF Ocean P.O. Box 4762 Torgard, NO-7465 Trondheim, Norway Email: martin.fore@sintef.no Asgeir J. Sørensen Centre for Autonomous Marine Operations- and Systems (NTNU AMOS) Department of Marine Technology NO-7491 Trondheim Norway Email: asgeir.sorensen@ntnu.no ABSTRACT This paper presents an experimental study using Real-Time Hybrid Model (ReaTHM) testing of a moored floating cylindrical buoy, conducted in a wave basin. ReaTHM testing is a method for studying the dynamics of marine structures by partitioning the system into numerical and physical substructures that are then coupled in real-time using a control system. In this study, the floating cylinder buoy is modelled physically, and the mooring system modelled numerically. In this paper, the effect of selected controller parameters on the performance of the control system is studied, for both wave frequency and low-frequency ranges. The architecture/design of the control system is presented in the first part of the paper, while results from experimental tests with wave excitation on the physical substructure are presented in the second part of the paper. 1 Introduction The design processes for marine structures often requires model-scale testing to study complex hydrodynamic phenom- ena which are difficult to represent analytically or numerically (e.g. nonlinear wave loads, slamming or viscous effects). How- ever, limitations arise when considering systems/structures in very deep water or with large geometric extent, such that scal- ing with conventional scaling methods becomes infeasible due to the high scaling ratio required [1]. Hybrid model testing methods have been suggested as a potential solution to mitigate such challenges, where the sys- tem under consideration is separated into physical and numeri- cal substructures that are interconnected through a control sys- tem [2]. The method is inspired by similar methods developed and used in the civil engineering community [3] and automo- 1 Copyright c  2018 by ASME