Intelligent precise control technology of fully mechanized top coal caving face

The electro-hydraulic control system for the supports of the fully mechanized top coal caving face has achieved a regular and memorized top coal caving,which cannot adapt to the changes in the geological conditions of roof coal,and it is difficult to guarantee mining rate and coal quality. Through introducing the comprehensive monito- ring technology and equipment for the coal mining process,a real-time monitoring of the changes in the roof coal seam before,during and after coal mining,and an accurate control of the coal mining process are proposed to achieve an op- timal balance of improving the mining rate and coal quality. Firstly,the technical difficulties of coal mining process monitoring are analyzed. The visual imaging signals are severely attenuated due to coal rock dust brought by coal min- ing. Secondly,the signal processing time for assessing the proportion of coal rock caving according to the coal mining data is in the order of seconds,which meets the requirement of real-time control for “closing window whenever seeing rock” decision. According to the coal mining process,different sensing technologies and equipment are used in three- phases:“before coal mining,during coal mining,and after coal mining”. Before coal mining,a penetrating radar in- stalled at the front of the roof beam of the bracket is used to measure the thickness of roof coal as the amount of coal. The 3D radar installed between canopy and shield beam scans the caved coal space,measures the remaining roof coal volume,and compares it with the pre-caved coal volume benchmark to determine when the coal mining process ends. After coal caving,the coal volume and coal rock ratio caved on the rear scraper conveyor will be identified to improve the robustness of coal rock detection. The radar that measures the thickness of coal seam before coal mining can use ultra-wideband wireless pulse signals,which can penetrate 3 to 6 m of coal seam,and the accuracy of measuring the thickness of coal seam reaches centimeter level. The dynamic change of the amount of roof coal is detected by laser ra- dar or millimeter-wave radar which can meet the requirements of space measurement accuracy. The coal rock is identi- fied after coal caved by using a high-definition and wide dynamic camera supplemented by a dust-permeable light source. Then the coal and rock gray convolution is used to calculate the coal rock mixing ratio parameter to determine the overall digital quantification of three processes of coal decentralization,mixed rock decentralization and full rock decentralization,realizing real-time feedback control and accurate coal placement. Through a technical integration to three-phases before,during,and after coal mining,the corresponding sensor equipment is developed,and the measure- ment data is transmitted to the workface automation system in real time. After the data analysis,calculation and intelli- gent processing of the automation system,the coal mining control decision data are sent to the hydraulic support elec- tro-hydraulic control system to realize the size and closing control of the coal opening of the corresponding support. The field industrial test of the intelligent caving face with conditions has verified that the monitoring of the entire process before,during and after the coal mining is implemented,and the switch of the coal caving window is controlled in real time. The surface monitoring center has achieved the intelligent mining goal of unmanned operation at the underground mine workface.