Automatic control of drilling system

Abstract

A blasthole drill is provided with sensors for sensing the pressure (AP) applied to and through a drill bit to convey cuttings from the drill hole, the rate of rotation (N) of the drill bit, the torque (RT) required to rotate the bit, the force (FB) applied axially to the bit and the instantaneous vertical position (Y) of the bit. Output signals from the sensors are applied to a microprocessor-based controller which computes the penetration of the drill bit per revolution of the bit (P/R) and the rock specific fracture energy (Es). Using the sensed values and the computed values, the controller produces output signals to increment/decrement the force (FB) applied axially to the drill. The applied axial force is controlled such that the penetration of the bit per revolution remains substantially constant for a given range of values of the rock specific fracture energy but varies for different ranges of the rock specific fracture energy. The rate of rotation of the drill bit is controlled to a reference value. Drill vibration sensors provide further input signals to the controller and when the vibration exceeds a predetermined limit the rate of bit rotation is immediately decreased.