Look-Ahead Radar and Horizon Sensing for Coal Cutting Drums

Safe and efficient coal extraction requires advanced radar subsystems that can be mounted on cutting drums of coal mining machines. A look-ahead radar (LAR) must solve the radio geophysics problem of transmitting an electromagnetic (EM) wave through at least 6.1 m (20 ft) of coal to detect an air- or water-filled void. An up- or down-looking radar must determine the distance to the coal bed sedimentary rock boundary. The reflected EM wave from the void or boundary rock must be processed in real time in the radar electronics to determine the physical distance to the void or coal bed boundary. The distance determination requires the in situ measurement of the coal electrical conductivity or relative dielectric constant. Up or down (horizon) sensing enables selective cutting near the undulating sedimentary rock boundaries of the coal bed to address coal quality and ground control issues. Both sensors require subsystems for dynamic electric power generation, real-time measurement of antenna rotation angle, detection of weak coal-boundary reflected EM waves concurrently with the suppression of the significant larger first air-coal reflected wave, processing to determine distance through coal, and RF modem transmission of measured data from the cutting drum to the body of the mining machine and along the segmented or coiled-tubing drill pipe. This paper describes the development of the GPR subsystems and field test results.