Study On Accurate Positioning Theory & Technology In Mine Underground Tunnel

Adopting wireless positioning and tracking technology is the key to enrich and improve the supervision & monitoring methods, and is one of the main means to ensure the coal safety. In this dissertation, after analyzing many wireless positioning algorithms and underground channel characteristics, the underground wireless positioning & tracing algorithm is studied and analized, especially the positioning algorithms based on wideband and/or ultra-wide-band signals.Because of its multi-paths suppression peculiarities, the OFDM has been used as broadband signal for mine underground posositioning, and the frequency domain TOA and frequency-domain super-resolution TOA estimation is discussed and achieved accurately by MUSIC algorithm. In order to obtain accurate channel frequency response of OFDM signal, the transform domain channel estimation is extended to two-dimensional and given an improved interpolation method. Using multi-antenna array, a super-resolution AOA algorithm is proposed and improved by taking advantage of beamforming technology. For the positioning in blind or branched tunnel, a joint super-resolution TOA/AOA algorithm is proposed by using only one access point. Taking into account the computation of the MUSIC algorithm, it will be substituted by the Matrix-Pencil technique in super-resolution TOA and/or AOA estimation process.The nodes of UWB-based WSN in mine working faces are hardware-restrained. A compromise two-step method is proposed in time-domain for WSN node, which includes a low-speed non-correlation process and a high-speed correlation-matched filter process. The normalized-threshold in energy-acquisition and correlation-match stages are presented and discussed based on the maximum to minimum energy ratio (MMR) modele. To reduce the computation of the frequency domain TOA positioning algorithm for the UWB signals, the normalized-power-law is substituted for the MUSIC type algorithm by using iterative method to replace the singular value decomposition SVD in MUSIC.After analyzing the impacts of underground NLOS, a cost-function method is givev to identify NLOS transmission. Considering geometric characteristics of the tunnel, the simple geometric area-centroid algorithm is proposed to reduce the NLOS impacts. And then, using the GDOP to select or weight TOA measurements to reduce the impacts of NLOS transmission further. For multipath condition, the multipath-restrain performance of the TK operator is studied firstly. Then, the cross-TK energy operator and the signal similarity based on it are analysed. So, a direct TDOA estimation algorithm based on cross-TK energy operator is proposed to gain the estimated TDOA which is independent of the TOA estinmations.Of course, the underground wireless location have a lot of questions to be resolved yet, such as intrinsic safe characteristic of wireless positioning; the features of underground channel and physical make it necessary to integrate or compromise among various positioning technology; In addition, the underground need trade-offs between positioning accuracy and cost, has no industry standards or norms for underground wireless positioning unfortunately.