The marine systems simulator state-space model representation for dynamically positioned surface vessels

摘要

This paper presents a nonlinear state-space model suitable for numerical simulation and ship motion control system testing for dynamic positioning (DP) operations. This model represents a typical application of the tools included in the Marine Systems Simulator (MSS), and illustrates the modeling philosophy of the MSS. This simulator is a Matlab®/Simulink®-based toolbox specially developed at The Norwegian University of Science and Technology (NTNU) for education, rapid prototyping and evaluation of marine control systems. The model presented here is based on results of standard potential theory tools, which are used to obtain radiation and wave excitation forces. The fluid memory effects associated with the radiation forces are expressed as a reduced-order state-space model. This is a key issue, which allows one to replace the traditional low-/wave-frequency motion superposition principle by a unified state-space model in body-fixed coordinates. The resulting model is suitable for simulation of marine operations requiring station-keeping and low-speed ship manoeuvring in a seaway, and can incorporate viscous forces, wave drift, current loads, wind loads, multi-body interactions, and ship motion control systems.