Recursion Based Control and Separation Sliding Manifold Based Control of Under-Actuated 4-DOF Autonomous

Underwater vehicles are now mainly researched using the 6-DOF equations of motion. The research on 4-DOF Autonomous Underwater Vehicles (AUV) for small Underwater Vehicles regularly focuses on fully actuated control algorithms. Research on underactuated systems has been conducted frequently for surface ships, while 4-DOF underactuated AUV using a nonlinear control system has received little attention. Little research focuses on devices with quadrotor UAV configuration, also known as QUV, but evaluations have yet to be conducted to advise on which controller to use for different cases. Therefore, in this article, the authors focus on building a control algorithm for an AUV object that lacks a typical recursive executive structure, which is the Backstepping controller when dividing the 4-order strict backpropagation nonlinear system into subsystems to design feedback controllers and Lyapunov control functions for each subsystem. Using this same approach, the authors built a controller that combines Backstepping controller and Hierarchical Sliding Mode Controller (HSMC). This is the guiding premise for research on improving the quality of 4-DOF AUV control before comparing and evaluating the two controllers for specific cases. Newly proposed algorithms and stability analyses are based on Lyapunov's theory, and an evaluation survey is carried out through simulation by Matlab software.