Physical system modeling and optimized control strategy of 6-DOF vessel motion simulator based on MBD and LBM

Under the wave-coupling effects, vessels experience six-degree-of-freedom (6-DOF) complex and extreme motions. Vessel motion simulators replicate wave-induced vessel motions for dynamic inspection of shipboard equipment, which requires integrated models, input diversity, and motion control accuracy. This paper establishes an integrated physical system model for the vessel motion simulator with a Stewart mechanism based on kinematic and dynamic analyses. It integrates a multi-body dynamics (MBD) model, an input and inverse kinematic system model, a sensor system model, and a control system model. The Lattice-Boltzmann method (LBM) is used for computational fluid dynamics (CFD) simulation of a vessel in waves, and 6-DOF vessel motions are predicted for the simulator inputs under multiple sea states. Furthermore, a fuzzy PID controller with fuzzy rules optimized by the genetic algorithm (GA) is proposed and its control performance, including the motion accuracy, robustness, and stationarity, is evaluated. The simulation and test analyses show that the physical system model can accurately simulate vessel motions and GA-fuzzy PID controller improves the control performance.