Equivalent-input-disturbance based rotating control of drill-string in compound directional drilling process subject to coal seam variation

Abstract

Coal seam variations in coal mine drilling can cause fluctuations in feed speed and rotational speed of the rotary head (ROR), reducing the performance of compound directional drilling control systems. This paper addresses these issues by considering the change in intrinsic specific energy caused by coal seam variations as a disturbance. An equivalent-input-disturbance (EID) based control system is designed to mitigate these effects. An axial-torsional coupled dynamic model of the drill-string system is developed, and EID and improved EID estimators are used to suppress the impact of bit–rock interaction. Field data from a gas extraction borehole is used to validate the effectiveness of the drill-string dynamics model. Simulation results demonstrate that the proposed control system surpasses the PI control system, the disturbance observer-based control system, and the active disturbance rejection control system. Specifically, the feed speed overshoot is reduced from 73%, 47%, and 46% to 33%, with settling time reduced from 3 s, 1.7 s, and 1.8 s to 1.5 s. The ROR overshoot decreases from 54%, 49%, and 43% to 11%, and settling time from 4.7 s, 3.1 s, and 2.8 s to 2.3 s. Additionally, feed speed and ROR fluctuations are minimized to 0.2% and 0.1%, respectively, demonstrating superior performance.