Design of Nonlinear Optimal Controller for moving of Underwater Vehicle in Depth Channel by using Gradient Descent Method with Systematic Step Selection

This paper proposes the design of a nonlinear optimal controller for a submarine with nonlinear model with six degrees of freedom (6-DOF). The control aims includes achieving system stability، reaching the submarine to a desirable point at the end of the maneuver، and choosing the optimal path that are accessible by solution of optimal cost function. The novelty of this paper is the systematic step selection in the gradient descent algorithm that has increased the rate of convergence beyond two times rather than fixed step algorithm. Finally، via some simulations، the robust performance of the designed controller for moving in different depths with considering of parametric uncertainty has been confirmed.