Nonlinear trajectory tracking control of underactuated AUVs using the state-dependent Riccati equation (SDRE) with parameter perturbation

This paper deals with a novel direct state-dependent Riccati equation (SDRE) controller designed for trajectory tracking of underactuated autonomous underwater vehicles (AUVs) in the presence of parameter perturbation. Despite the traditional SDRE regulator control, the proposed closed-loop SDRE controller design chiefly consists of two parts. First, by selecting a virtual reference point in front of the AUV system as the tracking output, the error variable control model in the earth-fixed reference frame is described. Second, the position errors are driven to the origin by introducing an integral model of first-order fed by the tracking error. The main advantage of the proposed control scheme is that the controller has a unified structure. Moreover, the algorithm is able to provide robustness with parameter perturbation because of its intrinsic robustness capability. Within the SDRE framework, the asymptotic stability of the closed-loop tracking system is also guaranteed. The robustness and effectiveness of the proposed methodology are verified by performing simulation experiments on an underactuated AUV.