Localization techniques of mobile objects in coal mines:challenges, solutions and trends

The precise object localization system is a fundamental infrastructure for the safe and effective production in coal mines. Authors analyzed the key problems faced by the localization of mobile objects in coal mines,such as road- way characteristics,excavation equipment,multipath features,multi-site interferences and error accumulations. The ma- instream methods of range measurement,including RSSI,TOA / TDOA and AOA / DOA,were summarized. The authors also discussed the common position computation methods and specialized position computation methods based on the particular surroundings of roadway,respectively. The representatives of the former are least square,maximum likeli- hood,cost function and fingerprint methods,and the distance-constraint method and the joint distance measuring meth- od based on electromagnetic wave and ultrasonic wave are two typical examples of the latter. Then analyzed the optimi- zation methods of localization results,including the identification and suppression of NLOS in coal roadway,the real- time computation of path loss exponent and the optimization techniques assisted by space information. Besides,the au- thors proposed the development trend of localization framework based on internet of coal things. With the idea that everything is connected with each other, one can work out better distance measuring technologies, position estimating methods and result optimizing algorithms. The paper strived to clarify the technology levels and development venation of the localization of mobile objects in coal mines and analyze the influential factors of localization precision in de- tailed.