Experimental verification of drill string vibration suppression using an adaptive self-tuning controller

Abstract

Drill bit whirl is a common phenomenon in rotary drilling rigs. It causes severe drill collar damage and borehole enlargement, leading to an irrevocable decrease in drilling efficiency. The majority of the research in this field concentrates on designing new drill bits or placing shock absorbers near the bottom hole assembly to minimize the damage caused by drill bit whirling. However, practically, vibrations in rotary drilling are minimized by tuning the upper rotary table speed or varying the weight on drill bit. This work explores the design and implementation of an adaptive controller to minimize vibrations of drill bits, particularly bit whirl. The developed controller achieves the vibration mitigation by varying the upper rotary speed. Moreover, the developed control law takes into account the vibrational frequencies and critical operating speeds of the drill string, thus also being capable of avoiding resonant vibrations. Experimental results are provided to prove the vibration mitigation capability of the developed controller.