A constant parameter time-domain simulator for a tugboat with forward-speed dependent hydrodynamics and speed control

The stability of the tugboats in waves is critical in the wet-towing transportation operation. However, most recent research primarily focuses on optimising vessel shapes and predicting speed using machine learning models. To investigate the challenge of nonlinear motion responses and precise numerical assessments of the vessel during moving forward in waves, this study presents a state-space model (SSM) based simulator. The model is the Sequence Quadratic Programming (SQP) algorithm based on the modified hydrodynamic coefficient to consider the motion responses of the tugboat moving in waves. Initially, stability analyses are simulated in HydroD software to ensure the safety of the tugboat in the process of moving. The SQP algorithm is considered to calculate and optimise the forward speed of the tugboat under wave action. Additionally, the corrected hydrodynamic coefficients according to the speed of the tugboat are used in the SSM, the motion responses calculated through the constant parameter time-domain model in the time-domain analysis. Finally, the results from this simulator are compared with that of the professional simulation software, AQWA and OrcaFlex. The methodology and procedure are contributing to validating and improving engineering practice.