Deterministic Response Prediction of Wave-induced Vessel Motions

Demanding marine operations require a high level of safety. Examples of such operations are offshore lifting operations by floating vessels, gangway landing on offshore wind structures, helicopter landings, subsea installations operations, towing of large structures, and various ship-to-ship operations. For operational intelligence, real-time environmental monitoring and forecasting are essential for planning and execution of demanding marine operations as well as optimizing DP operations and ship voyages. The most challenging part of environmental monitoring and forecasting is real-time estimation and prediction of wave-induced vessel motions. Enabling such functionality will be essential as an onboard decision support tool. In this thesis, two different real-time deterministic prediction algorithms for wave-induced response prediction are investigated. The first method is based on the Fourier transform, using a phase-resolved reconstruction of the measured wave field to predict the spatio-temporal wave elevation and from this the wave-induced motions through known Response Amplitude Operators. The second method is based solely on the measured vessel motion and its autocorrelation function to predict future motion. For the purpose of evaluating the prediction methods, high-fidelity 6 \acrfull{dof} low-speed simulation models of \acrfull{rvg} and the model-scale vessel \acrfull{csad}, subject to first- and second-order wave loads, are developed to simulate vessel motions. The first simulation model is a state-space formulation of the Cummins equation, while the second is a frequency-independent manuevering model. The results of this study demonstrate that deterministic prediction of wave-induced vessel motions can be achieved by using either of the proposed algorithms. Additionally, the prediction methods' limitations are discussed. Lastly, it is discussed how the simulation platform developed and published can be used as a cornerstone in future research and development of marine control and decision support systems.