Development of a Coal-Rock Interface Sensor (Phase 2)

摘要

Research under Phase II was performed to develop prototype horizon sensor technology and evaluate the technology in an underground coal mine. The horizon sensor technology is based upon the propagation of electromagnetic (EM) waves through layers of natural media with contrasting electric parameters (dielectric constant and conductivity). The EM wave launching antenna input terminal admittance depends on the thickness and contrast of the natural media layers. A loop antenna operated at its resonant frequency exhibits an input admittance that is most sensitive to changes in thickness and electrical parameters. The sensor measures the antenna input admittance in a Maxwell bridge and a microcomputer is used to compute the real-time admittance. Changes in admittance are used to generate control signals that tell the shearing machine operator if the cutting drum should be lowered or raised to maintain the desired uncut coal thickness. Field evaluation indicated that the sensor could detect uncut coal thickness changes in an actual underground coal mine.