A hydropneumatic heave compensation system and a semi-active control are proposed according to the requirements drilling offshore of 6 km deep. The goal of this semi-active control is to maintain an acceptable performance of the system when the drill string mass changes, which also changes the performance of the hydropneumatic system. The control action is executed just by a servo valve, which modifies the system damping to optimize the compensator performance. This servo valve is the only moving part of the control system and therefore, this system is more robust regarding mechanical/ electrical failures and it has low consumption energy. The results show a satisfactory frequency response of semi-active control when the drill string mass is changed.
This paper presents a backstepping approach for an active heave compensator actuated by a double acting cylinder. For practical applications, is desired to stabilize the system around the equilibrium point when subjected to unknown external disturbances. Knowing the governing equations, a robust backstepping control design is proposed by introducing a well-defined smooth function and using a Nussbaum function together with a Kalman filter-based disturbance estimator. The efficiency of the proposed control scheme is demonstrated through numerical simulations and compared with related works.
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