Operational control based on environmental detector for floating LNG connection system during side-by-side offloading operation

This paper addresses the dynamic positioning problem for Liquefied Natural Gas (LNG) carrier with unknown shielding effect via a sea state detector and robust control design. First, to deal with the shielding effect existing between LNG facility and LNG carrier, sea state detector is developed to estimate the variation of wave force on the LNG carrier. In addition, the wind drag coefficients can be obtained adaptively to achieve feedforward control. Then, to guarantee a safe operation, a robust constrained control with prescribed performance is proposed considering actuator dynamic. Further, once a large wave force is identified in the detector, Neural Network compensator will be activated in the controller. Lyapunov analysis is conducted to ensure the boundedness of all the closed-loop states. Finally, the feasibility of the theoretical results is demonstrated by simulation studies.