Novel coal gangue mixing ratio sensing technique based on synthetic parity-time symmetry

In the process of comprehensive mechanized caving coal mining, the monitoring technology for coal gangue mixing ratios at coal discharge outlets has long relied on manual experience judgment, lacking automated monitoring methods. This has led to widespread over-discharge or under-discharge phenomena during coal release, severely affecting mining efficiency and quality. To address this technical challenge, this paper innovatively designs and develops an integrated sensing monitoring system based on the PT symmetry principle. By constructing a three-coil LC resonant circuit system, we utilize the high-sensitivity characteristics of third-order PT symmetry at exceptional points (EP) to achieve stable monitoring of resonant frequency variations. Experimental results show that the sensitivity enhancement factor of the synthetic third-order PT system reaches up to 1.8 times that of second-order systems, effectively detecting frequency differences caused by changes in coal gangue mixture dielectric constants. Based on this, we establish a quantitative relationship model between coal gangue ratios and resonant frequencies, enabling precise determination of mixing ratios. Additionally, combining synthetic dimension theory, we design a sensing system with PT symmetric circuit architecture, achieving high-sensitivity monitoring of minute gangue ratio variations. This sensing monitoring system not only significantly reduces equipment size but also demonstrates excellent detection accuracy and stability. It provides reliable technical support for improving coal quality and achieving automated mining in coal mine working faces, playing a significant role in advancing intelligent development in the coal industry.