Visible Light-Based Synchronization Method for Acoustic Positioning in Underground Mines

The underground mining environment is one of the most hazardous for workers. Monitoring the miner's location precisely is essential for the miner's safety in this situation. Roof collapses, toxic gas releases and crashes of vehicles in mines are some of the factors that make this occupation more hazardous to human life than others. In order to determine the location of miners, however, a positioning system must be accurate and precise. The synchronization signal between transmitters and receivers is crucial in emergency situations. By using the synchronization signal, it is possible to prevent both data loss and misinterpretation. This article describes a method for combining visible light with an acoustic-based 2D positioning system. The developed proof-of-concept makes use of loudspeakers and a microphone as an acoustic transmitter and receiver, respectively. In addition, LED and LDR are used as transmitter and receiver for visible light. Using a timer circuit, synchronization has been achieved, and the transmitters are turned on sequentially using time division multiplexing. For the safety of miners, the system establishes the viability of using visible light as a synchronization signal and locates the miner with an error of ± 3 cm.