Nonlinear suboptimal control of fully coupled non-affine six-DOF autonomous underwater vehicle using the state-dependent Riccati equation

This work considers a general fully coupled autonomous underwater vehicle (AUV) for applying nonlinear suboptimal control. In most cases, AUV models are nonlinear and affine in control, especially without modeling rudders and fins. The aim of this work is to address the challenges of nonlinear non-affine AUVs for implementing the controllers, as this aspect of control design has received little attention in this field of research. The NPS Ills a well-known AUV that is often mentioned in research on nonlinear, non-affine modeling. This model is considered for applying the state-dependent Riccati equation (SDRE) controller with a non-affine structure for point-to-point motion that generates a suboptimal path. Furthermore, the control, design and simulation results are provided without any simplification or decoupling of the entire system. The design approach of this paper is implemented on NPS II; nonetheless, this point of view can be actualized on any AUV using the same technique. (C) 2014 Elsevier Ltd. All rights reserved.