The vertical guidance of longwall coal cutting machines (shearers), using a novel method of measuring machine position relative to the coal seam, is considered. Coal is a stratified sedimentary rock made up of horizontal layers of material with different physical properties, in particular hardness. A cutting pick mounted on the periphery of a rotating shearer drum will experience variations in cutting force as it passes through the various layers of the coal. The pattern of forces experienced as the drum rotates will be unique and if the drum is displaced in the vertical sense relative to the seam, then the force pattern will be similarly displaced. Therefore comparison of pick force patterns can form the basis for a drum position measurement system. An experimental trial was conducted to assess the viability of this concept. The results of the trial showed that it was possible to detect and measure changes in the vertical position of a shearer cutting drum, when cutting an artificial 'coal' face. On-line measurement of drum position was used to satisfactorily control a shearing machine. The effects of the pick force data signal to noise ratio, on the accuracy of the measurement system employed was considered by simulation, The minimum signal to noise ratio of data which could be used to give acceptably accurate results was determined. Simulation has been used to compare the operation of a proposed 'pick force' based control system with that of an existing guidance system. The results show the systems perform in a similar manner. The effect of time delay in the measurement of position by pick force analysis, on control was also studied to determine the maximum acceptable lag.
|Date of Award||1984|