Multi-pulse width modulation control technology for an underground inclination correction hydraulic control system

Based on continuous adjustment of the underground inclination correction force in a pulse width modulation AADDS (Automaic Anti-Deviation Drilling System) automatic vertical drilling tool to address problems such as pulse width modulation induced significant fluctuation of the inclination correction force and instable relative orientation of a well's inclination, the optimization of the continuous control of the underground inclination correction force of this drilling tool is investigated. Two-position two-way electromagnetic valves in a hydraulic control system undergo multiple on/off controls (i.e., multi-pulse width modulation) in a drill rod rotational cycle T (i.e., a modulation cycle) without changing the existing structure, components and parameters of the drilling tool. The system inclination correction cylinder discharges the oil volume obtained in a cycle T multiple time instead of once. Additionally, a spring energy accumulator is added to leverage automatic conversion between hydraulic energy and elastic potential energy to effectively improve the stability of the inclination correction cylinder pressure and inclination correction force. Multi-pulse width modulation parameters are obtained via a mathematical model of a hydraulic control system. When the drill rod rotating speed is 65 r/min and its cycle is 0.923 s, the inclination correction hydraulic control system test shows that the fluctuation amplitude of the inclination correction cylinder modulation pressure via three-pulse width modulation with a spring energy accumulator is only 30% of the value of that via a single pulse width modulation. (paper)