Abstract:
Thermodynamic disasters (fires and explosions) are the most serious disaster in coal mine, so it is necessary to establish a fire characteristic parameter monitoring system for monitoring. At present, the goaf wireless communi-cation monitoring system has the problem that the communication equipment is limited due to the goaf collapse, and the fire characteristic parameters cannot be monitored stably. In order to improve the stability of the wireless communication monitoring system, the reasons for the limited wireless penetration communication in the goaf environment are analyzed, and the antenna performance of the communication equipment is confirmed to be an important factor of the shadow communication performance after the goaf collapse. Three key technologies for improving the stability of wireless penetration communication are further studied: antenna environment adaptation, antenna performance detection and automatic optimization of communication parameters. In order to improve the adaptability of the antenna environment, a reconfigurable antenna is designed to ensure that the adaptive antenna can maintain high radiation efficiency under different environments such as unburied and buried. A performance detection method based on return loss detection is applied, which can directly measure and evaluate the antenna performance at fixed transmission frequency. The automatic optimization of communication parameters can be carried out according to the working environment, such as adjusting the transmission power and spread spectrum factor of LoRa, so as to balance the power consumption and performance of the communication system. Finally, a set of communication equipment was designed with optimized antenna to enhance the stability of wireless penetration communication. Ground and underground tests in coal mines were conducted on the communication equipment with and without antenna optimization. The ground test results show that the performance of the optimized wireless communication equipment is superior to that of the unoptimized equipment in different burial medium test environments, and it can meet the stable communication requirement within 10 m. The actual underground test results indicate that this research technology can effectively adapt to the situation where the monitoring of fire characteristic parameters in the goaf is restricted after the goaf collapses. It can significantly enhance the communication signal strength and achieve stable communication within 10 m even when buried in the actual goaf, ultimately achieving stable monitoring of fire characteristic parameters in the goaf.