Wireless Sensor Network for Underground Mining Services Applications

Backdrop Of Wsn

Wireless Sensor Network (WSN) is a technology which offers several potential advantages in mining and related industries. It goes without saying that environmental monitoring mainly in underground coal mines, comprising the galleries with lengths of several kilometers and widths of several meters, has always been a critical task to ensure safe working conditions. Further, this antagonistic milieu due to presence of numerous toxic and inflammable gases, dust, moisture and water makes it desirable to sense the underground environment closely for safety reasons. In addition to that, the danger and threat of fall of roof and side galleries make the environment more challenging. Thus, it is required to collect the sample data at a number of strategic places to acquire a full-scale monitoring of underground geotechnical and environmental parameters to warn the miners before the fall of roof or side gallery takes place or amount of toxic and inflammable gases reaches beyond their threshold limit. Obviously it needs a large number of sensing devices. The present practices of underground environment monitoring are usually performed either in a sparse way or manually. The sensing devices may be connected through cable to central processing unit placed at remote and safer place or surface. But it calls for a huge amount of cable deployment throughout the underground galleries which can pose difficulty for laying out the cable in hostile environment as well as high maintenance cost. On the other hand, the cable has to be extended every time because when the face of the mine advances, the more sensing devices are required to be deployed. In view of this, wireless system finds an opportunity (Murphy & Parkinson, 1978; Fiscor, 2008; Bandhyopadhyay et al., 2010). However, due to the uneven and crisscross path of the galleries, the direct wireless communication channels between sensing devices and the central processing unit is somehow intricate. Therefore, WSNs gets an advantage to be employed in this hostile environment (Li & Liu, 2007; Zhao et al. 2013) . WSNs utilize multi-hop routing for data gathering in which each sensor node performs the task of data collection as well as transmission throughout the network (Bhattacharjee et al., 2012; Sohraby et al., 2007). Further, WSN holds the promise of delivering a smart communication paradigm and have better compatibility with various gas and geotechnical sensors. It enables to set up an intelligent network capable of handling critical applications that evolve from the requirement of day to day underground mining operations. The different module consisting of a WSN node is shown in Figure 1 (Kumar et al., 2010; Sohraby et al., 2007).

Figure 1.

Functional Block Diagram of WSN Node

WSN node consists of a combination of sensors, processing unit that may be microprocessor/microcontroller or tiny battery driven computers, wireless transceivers/radio and a power supply unit. The system on chip (SoC) may also be used in which microcontroller and radio are embedded on the single chip (Bandhyopadhyay et al., 2010). The prime function of processing unit is to transfer the sensor data following the communication protocol with the help of wireless transceiver module. A suitable signal conditioning is being done for further processing of the output signal. The basic logical topologies used in WSNs are flat/unstructured, chain-based, clustered-based and tree-based. Each topology has its own advantages and disadvantages for underground environment depending upon the geological conditions and utilities. However, a single network may consist of several network topologies.