Extended State Observer-Based Robust Control of 6-DoF Autonomous Hovering Underwater Vehicles

In this paper, a robust control based on extended state observer is designed for a six-degree-of-freedom (6-DoF) autonomous hovering underwater vehicle. The control scheme considers four main challenges of multi-degree-of-freedom underwater vehicle: nonlinearity, modeling uncertainty, coupling, and external disturbance. A 6-DoF extended state observer is developed to deal with modeling uncertainty and external disturbance, and to estimate unmeasured or immeasurable linear velocity and angular velocity for real-time nonlinear compensation. Then a robust controller is introduced to further deal with modeling uncertainty and coupling. Finally, compared with PID and active disturbance rejection control, the simulation results show that the proposed method has good coupling motion suppression ability and robustness to modeling uncertainty and external disturbance.