| In China coal is primary energy, limited by complex terrain of coal mines, coalmine accidents occur frequently. The defects and deficiencies of existing coal minesafety monitoring system, has become bottlenecks which restricts development of minesafety, it is very necessary to design a set of mine safety comprehensive monitoringsystem which can meet requirement of coal mine. In recent years wirelesscommunication technology and Wireless Sensor Network(WSN) technology developedrapidly, which has provided technical basis for research and development of nextgeneration coal mine safety comprehensive monitoring system. As WSN have thecharacteristics of flexible structure, self-organizing, multi-hop and so on, which issuitable for bad environments, it becomes an effective tool to make up deficiencies ofcurrent coal mine safety monitor system.In this paper221coal mine serious accidents happened in China between April2003and December2009has been analyzed, and the statistic analysis has been carriedout for cause of each accident. With these actual accident data, according to the analysison necessary condition lead to coal mine accidents, the incredibility models of fourtypical coal mine accidents: gas explosion, coal and gas outburst, roof accidents,flooding accident are built with Analytical Hierarchy Process (AHP) method. Based onanalysis of mine accident incredibility factors and incorporated the state of coal minesafety monitoring system and developing trends of WSN technology, a WSN based coalmine safety comprehensive monitoring system solution is proposed，which is composedby five parts: sensing and detection system, security information network andcommunication system, safety information management system, safety warningdecision and decision support system and rescue information assurance system. Thenthe research on WSN node localization technology and routing technology, which aretwo key support technologies of coal mine WSN system has been carried on. Finallybased on theoretical studies, a WSN positioning prototype system is designed andimplemented with CC2430/CC2431node, and performance of improved RSSIlocalization algorithm, proposed in this paper has been test under simulatedunderground environment with the prototype system. The researches and mainachievements around these elements are as follows:1. According to static node self-localization problem of underground WSN,through the annalyse on the traditional RSSI localization algorithm, the path lossexponent(PLE) often is assigned a fixed empirical value, which can not reflect theactual tunnel environmental impact on the wireless signal, it is reason that lead to lowposition accuracy and considerable positioning error under the underground environments. In this paper combine with deployment characteristics of beacon node intunnel, a dynamic PLE calculation method, which takes distance and correspondingRSSI between adjacent beacon nodes into account to calculate actual path lossparameter in the tunnel is proposed, on this basis the improved RSSI localizationalgorithm suit for coal mine tunnel environment is proposed. Simulation results showthat effect of proposed method is more precise than tridational RSSI algorithm undersame environment and can meet requirements of underground person position.2. Affect by bad conditions of underground and limited energy of nodes,underground WSN nodes often occur failure, which lead to the problem of insufficientnode coverage in tunnel. When it happened blind node can not collect enoughlocalization auxiliary information and can not locate its position, on this condition theblind node needs more auxiliary information to locate its position. Limited by narrowand closed underground space, localization result can only fall within this enclosedspace, furthermore the information of nodes deployment and network connectivity canhelp to eliminate some redundant localization results. On this basis, a server-sidegeographic information based aided localization method is proposed. According todifferent beacon node coverage degree during underground node localization process,by means of underground geographic information and node deployment information themethod can assist the blind node to locate its position and improve blind nodelocalization accuracy in case of insufficient beacon node coverage. The simulationresults show effectiveness of aided localization method.3. According to mobile node self localization problems of underground WSNs,through analyse on moving process of mobile node, it has been found that affected bydeployment characteristics of underground beacon node, during the moving process theCentroid of one hop adjacent beacon node of mobile node, which can be perceived bymobile node, always keep same moving trend with mobile node, and its position is alsocloser to position of mobile node. So if mobile node localization algorithm takes sampleat the position near Centroid, success rate of sampling will greatly improve. On thisbasis, a Monte Carlo Centroid-Box (MCCB) localization algorithm is proposed.Simulation results show that MCCB algorithm is more suitable for mobile nodelocalization within the underground tunnel than Monte Carlo Localization (MCL)algorithm and Monte Carlo Localization Boxed(MCB) algorithm.4. According to routing problems of node within underground tunnel, through theanalysis on three application scenarios characteristics of underground tunnel WSN:Linear, Mesh and Group type, corresponding routing strategy is proposed. For theLinear type scenarios as monitor area is often long and narrow, a position based clusterrouting (PBCR) protocol suit for strip WSN is proposed, which divided the strip WSNinto many belt-shaped region clusters and elected the cluster head through the positionand the cluster head chain is set up as the backbones of the strip WSN to forward thedata of nodes. For the Mesh type scenarios a dynamic Minimum Energy Relay Routing (DMERR) algorithm is proposed, which can dynamically adjusts communicationdistance of beacon node to reduce energy consumption of beacon node in datatransmission. For Group type scenarios a position estimate based multi-hop routing(PEBHR) protocol is proposed, which makes mobile node to assume primary dataforwarding task to reduce the load of beacon node and prolong network lifetime.Simulation experiments show that the validity of these three algorithms, which can meetrouting requirements of different scenarios. |
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