engleski

A Torque Estimator-based Control Strategy for Oil-Well Drill-String Torsional Vibrations Active Damping Including an Auto-Tuning Algorithm

Large compliance of the lengthy oil-well drill-string in combination with low tool inertia and stick-slip friction between the tool and rock bed causes the emphasized torsional vibrations of the drill-string electrical drive. In order to attenuate the torsional vibrations and improve the quality and productivity of the drilling process (i.e. rate of penetration), an automatically-tuned active damping control strategy based on drill-string torque estimation is proposed in the paper. The core of the strategy relates to a proportional-integral (PI) controller extended with a drill-string torque feedback loop, and an appropriate algorithm that prevents drill-string back-spinning for the case of limited braking power of the power converter. Finally, an auto-tuning algorithm is proposed, built around an on-line adaptive Kalman filter-based estimator of drill-string drive natural frequencies. The drill-string control strategy is verified experimentally using a drill-string hardware-in-the-loop setup under the laboratory conditions, as well as on an actual oil-drilling rig.

torsional vibration; active damping; observers; auto-tuning; Kalman filter

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