Parametric analysis of a sliding-mode controller to suppress drill-string stick-slip vibration
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RECENT ADVANCES IN NONLINEAR DYNAMICS AND VIBRATIONS
Parametric analysis of a sliding-mode controller to suppress drill-string stick-slip vibration Vahid Vaziri . Ibukunolu O. Oladunjoye . Marcin Kapitaniak . Sumeet S. Aphale . Marian Wiercigroch
Received: 4 November 2019 / Accepted: 16 October 2020 The Author(s) 2020
Abstract Despite a significant research effort to understand and mitigate stick-slip in drill-strings, this problem yet to be solved. In this work, a comprehensive parametric robustness analysis of the sliding mode controller has hitherto been performed. First, a model verification and extensive parametric analysis of the open-loop model is presented. This is followed by a detailed parametric analysis of the sliding-mode controller based closed-loop system for two cases, (i) an ideal actuator with no delay or constraint and (ii) a realistic actuator with delay or/and constraint. It is shown that though the proposed controller works robustly across a wide range of parameters, in the absence of delay, it fails in the presence of a delay, thereby limiting its practical application. Experimental results are included to support these claims. This work underlines the importance of including the inherent system characteristics during the control design process. Furthermore, the parametric analysis presented here is aimed to act as a blue-print for testing the efficacy of relevant control schemes to be proposed in the future.
V. Vaziri (&) I. O. Oladunjoye M. Kapitaniak S. S. Aphale M. Wiercigroch Centre for Applied Dynamics Research, School of Engineering, University of Aberdeen, Aberdeen AB24 3UE, UK e-mail: [email protected]
Keywords Drill string Stick-slip Sliding-mode control Parametric analysis Robustness Delay
1 Introduction Stick-slip vibration are characterized by phases in which a drill-bit comes to a complete standstill (stick) and phases in which a drill-bit rotates with much larger than nominal angular velocity (slip). This type of vibration often results in excessive bit wear, and is also detrimental for expensive downhole tools of a Bottom Hole Assembly (BHA) [1]. The first rigorous analysis of the stick-slip phenomena was reported in [2]. Since then, to understand this highly nonlinear phenomena, several drill-string models have been proposed in the literature. An overview of these models can be found in [3–5]. The key difference in the proposed lumped mass models is the number of degrees-of-freedom (DOF) used to establish a drill-string dynamical model, which vary from 1-DOF pendulum-type to infinite-dimensional described by partial differential equation models. The severity of stick-slip vibration has also been quantified to clearly gauge the magnitude of this problem [6–9]. As stick-slip vibration is in general detrimental to the structural health of drillstring components as well as to the bore hole stability and Rate of Penetration (ROP), devising strategies to eliminate this torsional vibration has been a key
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