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In order to solve the problem that non-line-of-sight(NLOS) interference affects wireless signal transmission in complex underground environment of coal mines, an ultra wide band(UWB) personnel positioning system in coal mine is designed. The system uses asymmetric double-sided two-way ranging algorithm with return frame mechanism for ranging without clock synchronization, which ensures the ranging precision. The positioning area is divided by the area discrimination strategy and the area correction strategy, so that the tag can only communicate with the base station in the positioning area to achieve positioning, which avoids a large number of invalid frames in the positioning process and improves the positioning efficiency. The weighted least squares method and the unscented Kalman filter joint positioning algorithm are used to solve the tag position coordinates, which improves the positioning precision. A backup power supply is configured in the base station to ensure emergency power supply in case of power failure. Two communication modes, Ethernet and LoRa, are adopted. When the Ethernet is disconnected, the ranging data is transmitted in the LoRa mode, which ensures the emergency communication of the system. The test results show that the system has high dynamic and static positioning precision and strong anti-NLOS interference capability. When the base station is powered off or the Ethernet is disconnected, the system can realize emergency communication for a period of time.

In view of the problems that RSSI positioning algorithm has large ranging error and inaccurate positioning result due to non-line-of-sight propagation of wireless signals in complex environment of underground coal mine, a mine weighted centroid positioning algorithm based on improved Gaussian mixture filter was proposed. Firstly, corresponding RSSI measurement data of unknown nodes are clustered according to the maximum expectation algorithm, and the data are divided into multiple Gaussian probability density functions models. Then, according to the characteristics of the data, the sampling data is optimized by using Akaike information criterion, and the accurate measured values are obtained. Finally, the initial coordinates of the unknown node are calculated, the error between the initial coordinates of the unknown node and the real coordinates are used as the weight factor, and the final coordinates of the unknown node are calculated combining with the centroid positioning algorithm, so as to realize target positioning. The simulation and experimental results show that the positioning algorithm can realize high precision personnel positioning in underground coal mine, and the average positioning error is 1.83 m.

In view of the problems that existing underground positioning algorithm based on UWB is complex and solution value is not global optimal, an improved trilateral positioning algorithm based on UWB was proposed. The algorithm is based on DW1000 chip and trilateral positioning algorithm, adopts bilateral two-way ranging method. Optimization objective function is set by solving the optimal solution of binary quadratic equation, and coordinate is two-dimensional, so as to reduce complexity of the algorithm. The invalid data generated in measurement process were screened out, effective search area is determined, and global traversal is conducted in the effective area to find global optimal positioning coordinates, which solves the problem that solution value is not global optimal. At the same time, in order to further improve positioning accuracy, appropriate measures are taken to increase the number of reference measurement nodes. The experimental results show that the average error of the proposed positioning algorithm is lower than that of the weighted trilateral positioning algorithm and the Taylor algorithm, and the positioning accuracy is improved obviously. Meanwhile, the algorithm has strong practicability, and measurement accuracy can be effectively improved by increasing the number of reference nodes.

In view of problems of low automation degree and high time and labor cost of static test method of mine personnel positioning accuracy, a mine personnel positioning accuracy verification system based on Hall sensing was proposed. The system uses public UDP interface to interface with different types of positioning base stations of different manufacturers, uses proprietary UDP interface to transmit related ranging messages of Hall sensing device, and uses production-consumption model to collect, parse and store communication data. The Hall ranging result is used as the reference data, and the node positioning distance information collected by positioning base station is compared in real time, so as to verify accuracy of the positioning system. The test results show that the minimum ranging error rate of the system itself is 0.80%, the maximum error rate is 3.30%, and the average error rate is 1.38%, which is much lower than the 5% error rate allowed by the personnel positioning accuracy verification system. The results of accuracy verification application example show that the system can effectively verify the accuracy of positioning system.