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.
This master thesis presents the development, analysis and comparison of different heave compensator methodologies for drill string.Firstly, a review of previous studies about the subject is presented. Next, is presented a study of drill string modelling. Following the studies, a methodology to design a passive heave compensator is develop and validated by using a small scale prototype. In order to obtain higher levels of attenuation, active heave compensators are designed.Hence, the study of observers, estimators and filters, such as Kalman filter is developed. Three methodologies of active controls are presented, pole placement, pole placement with disturbance rejection using flatness and backstepping robust control. Finally, numerical simulations results are presented and analysed.
Heave compensator is a system that mitigates transmission of heave movement from vessels to the equipment in the vessel. In drilling industry, a heave compensator enables drilling in offshore environments. Heave compensator attenuates movement transmitted from the vessel to the drill string and drill bit ensuring security and efficiency of the offshore drilling process. Common types of heave compensators are passive, active and semi-active compensators. This article presents 4 main points. First, a bulk modulus analysis obtains a simple condition to determine if the bulk modulus can be neglected in the design of hydropneumatic passive heave compensator. Second, the methodology to design passive heave compensators with the desired frequency response. Third, four control methodologies for semi-active heave compensator are tested and compared numerically. Lastly, we show experimental results obtained from a prototype with the methodology developed to design passive heave compensator.
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