1、A Coal Mine Environmental Monitor System with Localization Function Based on ZigBee-CompliantPlatform Dongxuan Yang College of Computer and Information Engineering Beijing Technology and Business University Beijing, China Yan Chen College of Computer and Information Engineering Beijing Technology an
2、d Business University Beijing, China Kedong Wang College of Computer and Information Engineering Beijing Technology and Business University Beijing, China AbstractThis paper describes and implements a new type ofcoal mine safety monitoring system, it is a kind of wireless sensornetwork system based
3、 on ZigBee technology. The system consistsof two parts underground and surface. Wireless sensor networksare constituted by fixed nodes, mobile nodes and a gateway inunderground. PC monitoring software is deployed in the surface.The system can not only gather real-time environmental data formine, but
4、 also calculate the real-time location of mobile nodesworn by miners. Keywords： ZigBee； localization； wireless sensor networks； coalMine I.RESEARCH STATUS As an important energy, coal plays a pivotal role in the economic development. Coal mine monitoring system, is the important guarantee for coal m
5、ine safety and high efficiency production 1. In order to ensure the safe operation, the installation of environment monitoring node in tunnels to real-time detection is very important. However, commonly used traditional monitoring node wired connection to obtain communication with the control system
6、, this node exist wiring difficulties, expensive and other shortcomings. In contrast,wireless sensor node can be easily with current mine monitoring network connection, and good compatibility,facilitate constituted mine gas monitoring network, to suit various size of mine applications. Since wireles
7、s nodes are battery powered, so completely out of the shackles of the cable,shorten the construction period can be arranged at any time where the need to use. The ZigBee wireless communication technology is used inthis coal mine environmental monitor system. This is a newshort-range, low complexity,
8、 low power, low data rate, low-cost two-way wireless communication technology 2. Now,wireless sensor network product based on ZigBee technologyare quantity and variety, but the real product can be applied inunderground environments of special sensor node is very few3. The sensor node that we designe
9、d in the system is trulyable to apply to in-well environment, it through the wirelesssensor node security certification. At the same time, due to thespecial nature of the wireless network is that it can spread the wireless signal, we can easily locate staff for coal mine safetymonitoring provides mo
10、re protection 4. II.SYSTEM ARCHITECTURE This system is a comprehensive monitoring system whichis combined with software and hardware. Hardware partincludes wireless mobile nodes and fixed nodes which weredeployed in the underground tunnel, the main function of themis to collect coal mine environment
11、 data and require personslocation. Software part refers to the PC monitoring softwarewhich is designed in VC+ is used to summarize and displaythe data of each node. Monitoring node is divided into mobilenodes and fixed nodes； they are using ZigBee protocol forwireless transmission of data. Because t
12、he fixed node is alsousing wireless data transmission method, so its deployed in theunderground roadway becomes very convenient. As the mobilenode is carried by the miner, it must be using wirelesstransmission method. This allows the mine to form a topologyof ZigBee wireless sensor network. The fixe
13、d node in wirelesssensor network is router device and the mobile node carried byminer is the end device. Normally, the router of ZigBeenetwork has no sensor equipment； it is only responsible fordata forwarding. But considering the practical application, webelieve that add sensor devices on the route
14、r will be better onmonitoring underground coal mine environment. So in ourdesign, the router also has an environment monitoring functionwhich is usually designed in end device. Fixed node will sent received data from mobile node to thegateway, then the gateway transmits data to monitor computerthrou
15、gh RS232 or optical fiber. The PC monitor software in thecomputer will process all data and display them in avisualization window. The PC software also calculates eachmobile nodes real-time location through the specificlocalization algorithm, according to the received signal strength(RSSI) obtained
16、from mobile nodes. III.NODE DESIGN Since the ZigBee wireless network platform sold on presentmarket was designed for the general environment, for specialunderground so they are not suitable for the environment. Therefore, we need to customize the system for undergroundenvironment whit a special hard
17、ware circuit. Node photo areshown in Fig. 1 Then wireless microcontroller CC2530 chip is the coreprocessor of the node device, it can constitute a ZigBeenetwork with very few peripheral circuits. The CC2530 is anIEEE 802.15.4 compliant true System-on-Chip, supporting theproprietary 802.15.4 market a
18、s well as the ZigBee, ZigBeePRO, and ZigBee RF4CE standards. Unlike other wirelesschip, CC2530 built-in 8051 monolithic integrated circuitskernel, therefore we no longer need to use a single MCU tocontrol the circuit, and this save us a lot of cost 5. A. Mobile Node The mobile node is the end device
19、 of a ZigBee network thatcan be carried by miner； it should be a portable and low powerconsumption node. So the mobile node we designed is only assmall as a mobile phone, and it is by built-in lithium ion batterypower supply. In power loss, the core processor CC2530 is alow power consumption chip, w
20、hen it is in the sleep mode, itonly need to use less then 1uA work current. In order to reducepower consumption as much as possible on the display, a100*32 pixel matrix with no backlighting LCD screen wasused. The batterys capacity of the mobile node is 1500mAh,so it is enough to meet the miners lon
21、g hour works in theunderground. The battery charge management chip is TP4057,the maximum charge current can up to 500Ma. Figure 1.Node photo. The mobile node circuit includes the gas concentrationsensor MJ4.0 and temperature sensor PT-1000. As far as weknow, many wireless sensor platforms use the di
22、gital typesensor. The communication between the digital sensor and theMCU need strict timing requirements. But considering theactual application, the wireless MCU usually has a real-timeoperating system in general, if we use the microcomputer tosimulate the strict timing, it will affect the real-time of wholeoperating system. These two sensors output analog signals notdigital signals. Only input this signal into a differentialamplifier, can we get an appropriate signal that can beconverted to a digital signal by an ADC mode within theCC2530 chip. In order to facilitate the
