Three-Dimensional Optimal Trajectory Tracking Control of Underactuated Autonomous Underwater Vehicles Using Double Closed-Loop Control

In this paper, a double closed-loop control method is proposed for three-dimensional optimal trajectory tracking control of underactuated autonomous underwater vehicles (AUVs), Firstly, a five-degree-of-freedom mathematical model of under-actuated AUV is established. Secondly, an output redefinition method is adopted to solve underactuated control problem. On this basis, a backstepping method is utilized to design the outer-loop controller where virtual velocity is derived using the error between input and output of the system. Next, an adaptive dynamic programming method is used to design the inner-loop controller, where the performance index function containing the disturbance upper bound is set, and a neural network is employed to solve the Hamilton-Jacobi-Bellman equation online. Finally, the Lyapunov theorem is used to establish that all signals of the closed-loop system are uniformly ultimately bounded. Simulation results demonstrate the effectiveness of the proposed method.