Design And Implementation Of Environment Monitoring And Personnel Positioning System For Underground Coal Mine Based On Internet Of Things

China has an abundant of coal resources, but coal mining is mainly carried out underground, the geological condition is complicated, the production condition is harsh, which poses a huge threat to the safety of coal mine production. The existing cable monitoring system is difficult to deploy and has poor scalability, so it is difficult to monitor the whole coal mine comprehensively and effectively; the existing positioning system has low accuracy, so it's hard to timely master the distribution of miners. However, environment monitoring and personnel positioning have both great significance for the safety of coal mine production. Based on this background, this paper adopts Internet of Things (IoT) technology, puts forward an integrated kind of coal mine safety production system of environment monitoring and personnel positioning. This system is supported by mesh wireless sensor network (WSN), collects various environmental parameters, locates the miners, and transmits these to the ground monitoring and dispatching center (GMDC) via the cable optical fiber backbone network. Thereby, the functions of environment monitoring and personnel positioning are achieved, the safety of coal mine production is improved.In order to effectively monitor the underground environment, two working modes are designed:periodic inspection mode and interrupt service mode. A data gathering mechanism is put forward, which integrates in-network data aggregation and urgently transmission of overrun datum. To solve possible overtime and overrun problems during data gathering, corresponding measures are adopted. Then the environmental information could be acquired and stored automatically.Based on analysis of various wireless localization algorithms, combined with the zonal structure and the complex wireless communication condition of the coal mine, a weighted centroid localization algorithm based on Received Signal Strength Indicator (RSSI) is put forward. This algorithm obtains the path decline index dynamically, and weakens the effect of signal attenuation model, improving the location accuracy. In order to avoid communication congestion that may be caused by multiple mobile nodes in the same region locating simultaneously, a collision avoidance mechanism based on group protocol is designed, improving communication efficiency and saving network energy.Once the WSN is deployed, it works for a long time, a WSN node or a link may break down. For this reason, an integrated network management scheme is designed in four aspects, i.e. configuration management, topology management, energy management and fault management, monitoring network health. Meanwhile, in order to transfer the underground information and managing the WSN, it is necessary to communicate with the GMDC for the WSN, then a kind of interconnect between the WSN and the cable optical fiber backbone network is designed via WSN access gateway.Finally, in order to estimate the performances of the proposed environment monitoring and personnel positioning system for underground coal mine based on IoT, a series of experiments are carried out in a laboratory. The test results indicate that the proposed coal mine safety production system works well and satisfies function as expected; the designed network management scheme can timely monitor the network health; the developed WSN access gateway works stably to transfer datum. So that managers can remotely manage the WSN, effectively monitor the underground conditions and accurately locates miners.