Motion control for an open-frame work-class ROV in current using an adaptive super-twisting disturbance observer

Abstract

Remotely operated vehicle (ROV) plays an important role in marine operation and maintenance for offshore facilities. Motion control design is one of the major challenges in the development of ROV, especially when the ROV is subjected to unstable sea currents, parametric uncertainty, hydraulic delay, and thrust saturations. In this study, an open-frame work-class ROV used for offshore structure surface cleaning is considered. The dynamic model of the ROV is established, based on the hydrodynamic properties obtained from CFD simulations. A sliding mode controller is designed for the ROV trajectory tracking, which is developed by the command filtered backstepping method. An adaptive super-twisting disturbance observer is employed to estimate and compensate the loading disturbances and modeling uncertainties. Stability analysis is performed and proves Lyapunov stability of the proposed controller. The effects of current, dynamics of the hydraulically-driven propellers, and thrust saturation are rigorously taken into account in this study. Various simulation cases are conducted using the Simulink software. The results have demonstrated that the superior robustness of the proposed control design against thrust saturation, modeling errors, and external disturbances.