Vibration Control of Flexible Marine Riser Systems With Input Saturation

In this paper, boundary control is designed to suppress transverse vibration of a flexible marine riser with input saturation in the ocean environment. Two cases are investigated: 1) state feedback boundary control, and 2) output feedback boundary control. In order to compensate for the input saturation, we propose an auxiliary system. First, state feedback boundary control with an auxiliary system is proposed when the boundary states of the riser can be measured. Subsequently, output feedback boundary control is developed when there are unmeasurable system states. High-gain observers are employed to estimate those unmeasurable states. Based on Lyapunov's direct method, the proposed control ensures that the deflection of the riser is uniformly bounded in the presence of the ocean disturbances. By choosing a set of appropriate parameters, numerical simulations are provided to verify the effectiveness of the proposed boundary control.