Depth control of ROVs using time delay estimation with nonsingular terminal sliding mode

In this paper, a nonsingular terminal sliding mode (NTSM) control method based on time delay estimation (TDE) is proposed and investigated for the depth control of remotely operated vehicles (ROVs). The complex dynamics is approximately compensated by TDE leading to an attractive model-free nature, which is more suitable for practical applications than other model-based methods. Furthermore, the NTSM manifold based on nonlinear error dynamics can ensure better control performance than the traditional sliding mode (SM) manifold with linear error dynamics. Stability of the closed-loop system is analyzed using Lyapunov theory. Finally, the faster convergence and higher tracking accuracy compared with traditional TDE method with linear error dynamics are verified through simulation.