Research On Life Cycle Optimization Of Coal Mine Wireless Monitoring System Based On Energy Harvesting

With the development of Internet of Things technology in mines,more and more wireless monitoring equipment and devices are installed in the coal mine roadways to meet the increasing mine safety monitoring needs.However,unlike the common roadway in coal mine,the underground working face is a space that changes dynamically with the development of mining.The wireless nodes arranged here can only be powered by batteries,and the battery can not be replaced because of the poor conditions of the nodes,which leads to the short life cycle of the wireless network.So far,there are no successful application cases in coal mine working face.Based on this,this paper studies the life cycle optimization method of underground wireless monitoring system in coal mine.It extends the life cycle of wireless nodes from two aspects: energy collection method in working face and low power routing protocol design.Firstly,this paper analyzes the environmental energy that can be used for energy harvesting.Combined with the structural characteristics of the underground working environment,a wireless network model of underground working face based on energy harvesting is proposed.The model is based on the mobile routing node arranged on the shearer gearbox as the forwarding core.The node can obtain the thermal energy of the machine surface and convert it into its own power.It can carry or forward the information of other wireless sensor nodes on the mobile path,reduce the number of multi-hop communication and the working time of the forwarding node,so as to achieve the energy balance of the whole network and prolong the life cycle of the network.Secondly,an energy harvesting device is designed for the mobile node.In this paper,a thermoelectric energy harvesting device for the surface temperature difference of downhole equipment is designed based on the thermal electric generator(TEG)and boost management module.The device is used to charge the lithium ion battery.Experimental results show that the circuit can continue energy harvesting from input sources as low as 100 mV.The stable output power of TEG can be increased by several tens of times using air cooling or water cooling.The bq25505 device is specifically designed to efficiently extract the power generated from the TEG.It can significantly increase the discharge working time of the lithium battery,and the energy conversion efficiency of the module is up to 67%.Finally,according to the structural characteristics of the underground working face,this paper designs a wireless sensor network model and proposes a clustered multi-hop routing protocol based on energy harvesting(EHCM).The routing protocol utilizes a mobile routing node capable of collecting thermal energy on the shearer,collects data of the monitoring node on the working face,and compares it with a set threshold to store or forward.Simulation results show that the protocol can effectively balance and reduce the energy consumption of network nodes;A hierarchical energy supplement model is also proposed,which can further balance the residual energy of the nodes,supplement the energy of nodes with less residual energy,avoid premature death of local nodes,and improve the life cycle of wireless sensor networks.