Modeling of a Complex-Shaped Underwater Vehicle for Robust Control Scheme

The two critical issues of robust control are stable controller synthesis and control performance guarantee in the presence of model uncertainties. Inside all robust stable solutions, small modeling parametric uncertainties lead to better performance controllers. However, the cost to develop an accurate hydrodynamic model, which shrinks the uncertainty intervals, is usually high. Meanwhile, when the robot geometry is complex, it becomes very difficult to identify its dynamic and hydrodynamic parameters. In this paper, the main objective is to find an efficient modeling approach to tune acceptable control design models. A control-oriented modeling approach is proposed for a low-speed semi-AUV (Autonomous Underwater Vehicle) CISCREA, which has complex-shaped structures. The proposed solution uses cost efficient CFD (computational fluid dynamic) software to predict the two hydrodynamic key parameters: The added mass matrix and the damping matrix. Four DOF (degree of freedom) model is built for CISCREA from CFD and verified through experimental results. Numerical and experimental results are compared. In addition, rotational damping CFD solutions are studied using STAR-CCM+ (TM). A nonlinear compensator is demonstrated to tune linear yaw model for robust control scheme.