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Damping Optimum-based Design of State Controller and Observer for Drill-String Rotary Speed Control

During petroleum drilling, the drill-string electrical drive is prone to significant torsional vibrations caused by tool vs. rock stick-slip friction and drill-string torsional compliance, which may cause mechanical failure and excessive wear of critical parts of the drilling system. Hence, the drill-string electrical drive needs to be equipped with active vibration damping functionality. This paper presents the development of a full-order state controller based on straightforward estimation of un-measurable state variables by means of state variable filtering approach, which may be well-suited for torsional vibrations active damping purposes. The effectiveness of the proposed control system design is verified by means of simulations for different drill-string configurations.