Adaptive Robust Finite-Time Nonlinear Control of a Typical Autonomous Underwater Vehicle With Saturated Inputs and Uncertainties
Fatemeh Sedghi, Mohammad Mehdi Arefi, Ali Abooee, Okyay Kaynak
Abstract
The problem of finite-time path following control for a typical 6-DOF (degree of freedom) autonomous underwater vehicle (AUV) subjected to parametric and modeling uncertainties, disturbances and unknown saturation nonlinearities is studied and discussed in this article. For the mentioned AUV, finite-time control inputs are designed based on innovative terminal sliding surfaces and several finite-time adaptation laws. By means of the designed adaptation laws, the unknown physical parameters of AUVs, the unknown upper bound of uncertainties, and an unknown parameter of input saturation are estimated. By using the Lyapunov stability theorem, it is proven that designed control inputs are able to ensure and provide the practical finite-time stability for the closed-loop AUV system. Furthermore, it is mathematically demonstrated that the tracking errors (defined for the path following problem of the AUV) converge to the vicinity of zero within an adjustable finite time. Finally, the efficacy of the suggested control scheme is demonstrated by the hardware-in-the-loop OPAL real-time test.