Prescribed performance based sliding mode path-following control of UVMS with flexible joints using extended state observer based sliding mode disturbance observer

The accuracy and stability of an underwater vehicle manipulator system (UVMS) are essential for performing underwater tasks. However, exogenous disturbance and unmodeled dynamics will lead to poor UVMS performance in terms of degraded transient behavior and large steady-state errors. In this paper, the path following problem with prescribed performance of a UVMS with flexible joints is addressed. First, a terminal sliding mode control scheme with prescribed performance is presented along with a novel extended state observer (ESO) based sliding mode disturbance observer (SMDO). The proposed controller simplifies the parameter tuning process by ensuring the predefined system behaviors of interest right after the design. Subsequently, a path following scheme is designed for the UVMS such that the position of both base vehicle and robot arms can converge to the specified path in 3-D space. Finally, numerical simulations and comparisons are conducted to show the effectiveness of the proposed method in terms of trajectory tracking in the presence of environmental disturbances and modeling uncertainties.