| In order to strengthen production safety,the underground coal mine has an urgent demand for environmental monitoring,wireless voice communication and wireless video surveillance.Wireless multimedia sensor networks(WMSNs)are a new kind of sensor networks that introduce multimedia applications,such as audio,images and video,into wireless sensor networks.WMSNs have excellent multimedia perception ability,fast and convenient wireless access and flexible topology characteristics.To this end,it is proposed to structure WMSNs in underground coal mines to further improve underground coal mines environmental monitoring,wireless voice communications and wireless video surveillance capabilities to ensure the safe production of underground coal mines.This dissertation centers on the key problems like MAC layer,routing layer and application layer in WMSNs in underground coal mines.The research work involves the research on the characteristics of QoS-aware MAC protocol,differentiated services routing protocol,single video camera localization and video collaborative localization.Major work and innovative points are summarized as follows.1.The send frequency,bandwidth,delay and direction of sensing data,voice and video in underground coal mines as well as the Quality of Service(QoS)assurance requirements of network have been summarized.A QoS-aware MAC protocol based on WMSNs for underground coal mines was proposed.The different services can be implemented for sensing data,voice and video by designing different contention windows,which guarantees the QoS requirements of three kinds of multimedia services.Markov chain models of backoff series and backoff time counters for three kinds of multimedia services were established,and the performance of QoS-aware MAC protocol for saturation throughput and MAC layer access latency were analyzed.Simulations were carried out both in low load and high load conditions with the proposed QoS-aware MAC protocol.It is showed that the throughput of sensing data and voice can be increased by reducing the throughput of video services,and the delay of sensing data and voice can be reduced by increased the delay of video services.2.The services of sensing data,voice and video in underground coal mines require different QoS for transmission delay,packet loss rate and transmission energy consumption.According to the different QoS requirements a differentiated service routing protocol of WMSNs for underground coal mines was proposed.By applying linear weighted method which set different weights in normalized sub QoS evaluation function of transmission delay,packet loss rate and transmission energy consumption,the total QoS evaluation functions of three kinds of multimedia services,i.e.the services of sensing data,voice and video,are constructed respectively.According to the sequence,i.e.the sensing data service first,voice service second and video service third,by applying marking method and improved differential evolution algorithm to optimize the total QoS evaluation functions of three kinds of multimedia services respectively,the transmission path of three kinds of multimedia services are obtained.Simulation results show that three node-disjoint paths are selected with the proposed differentiated service routing protocol of WMSNs for underground coal mines which realize differentiated service and guarantee the QoS of transmission delay,packet loss rate and transmission energy consumption for three kinds of multimedia services.3.Based on WMSNs deployed in an underground coal mine,a single video camera localization algorithm was proposed to locate miners in the scene of insufficient illumination and zonal structures of underground tunnels.Cameras are deployed longitudinally along the tunnels of the zonal structure and monitor different areas of underground tunnels independently.In underground tunnels with insufficient illumination,cameras detect the miner’s head through morphological image processing and calculate mapping points of the miner’s head on the tunnel ground.A straight line between mapping point and camera vertical projection on the tunnel is established.Based on the similarity principle of triangles,according to the distance between the mapping point and the camera vertical projection on the tunnel,the height of the camera from the tunnel floor and the height of the miner,the distance of the miner from the camera vertical projection on the tunnel can be calculated.Finally,the miner’s position coordinate can be gotten by calculating the miner’s straight line and the miner’s distance from the camera vertical projection on the tunnel,so that the miner can be located in the scene of insufficient illumination and zonal structures of underground tunnels.Test was carried out in a realistic scenario of underground tunnel,which show that the average error of localization is 0.37 m with single video camera miner’s lamp localization for miners positioning.4.Based on WMSNs deployed in an underground coal mine,a miner’s lamp video collaborative localization algorithm was proposed to locate miners in the scene of insufficient illumination and bifurcation structures of underground tunnels.In bifurcation area,several camera nodes are deployed along the longitudinal direction of tunnels,forming a collaborative cluster in wireless way to monitor and locate miners in underground tunnels.Cap-lamps are regarded as the feature of miners in the scene of insufficient illumination of underground tunnels,which means that miners can be identified by detecting their cap-lamps.A miner’s lamp will project mapping points on the imaging plane of collaborative cameras and the coordinates of mapping points are calculated by collaborative cameras.Then,multiple straight lines between the positions of collaborative cameras and their corresponding mapping points are established.To find the three-dimension(3D)coordinate location of the miner’s lamp a least square method is proposed to get the optimal intersection of the multiple straight lines.The miner’s trajectory can be estimated and predicted by continuous positioning of the miner’s lamp under motion with the camera,which means that miners can be tracked.Tests were carried out both in a corridor and a realistic scenario of underground tunnel,which show that the proposed miner’s lamp video collaborative localization algorithm has good effectiveness,robustness and localization accuracy in real world conditions of underground tunnels. |
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