Mitigation of torsional vibrations in drilling systems: A robust control approach

Thijs Vromen, Cam Hing Dai, Nathan van de Wouw, Tom Oomen, Patricia Astrid, Apostolos Doris, Henk Nijmeijer

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)

Abstract

Stick-slip vibrations decrease the performance, reliability, and fail safety of drilling systems. The aim of this paper is to design a robust output-feedback control approach to eliminate torsional stick-slip vibrations in drilling systems. Current industrial controllers regularly fail to eliminate stick-slip vibrations, especially when multiple torsional flexibility modes play a role in the onset of stick-slip vibrations. As a basis for controller synthesis, a multimodal model of the torsional dynamics for a real drill-string system is employed. The proposed controller design strategy is based on skewed-μ DK iteration and aims at optimizing the robustness with respect to uncertainty in the nonlinear bit-rock interaction. Moreover, a closed-loop stability analysis for the nonlinear drill-string model is provided. This controller design strategy offers several benefits compared with existing controllers. First, only surface measurements are employed, therewith avoiding the need for down-hole measurements. Second, multimodal drill-string dynamics are effectively dealt with in ways inaccessible to state-of-practice controllers. Third, robustness with respect to uncertainties in the bit-rock interaction is explicitly provided and closed-loop performance specifications are included in the controller design. Case study results confirm that stick-slip vibrations are indeed eliminated in realistic drilling scenarios using the designed controller in which state-of-practice controllers fail to achieve this.

Original languageEnglish
Pages (from-to)249-265
JournalIEEE Transactions on Control Systems Technology
Volume27 (2019)
Issue number1
DOIs
Publication statusPublished - 2017

Keywords

  • drilling systems
  • output feedback
  • robust control
  • stick-slip oscillations

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