Abstract
The positioning technology to find shallow underground vibration sources based on a wireless sensor network is receiving great interest in the field of underground position measurements. The slow peaking and strong multi-waveform aliasing typical of the underground vibration signal result in a low extraction accuracy of the time difference and a poor source-positioning accuracy. At the same time, the transmission of large amounts of sensor data and the host computer’s slow data processing speed make locating a source a slow process. To address the above problems, this paper proposes a method for high-precision time-difference measurements in near-field blasting and a method for its hardware implementation. First, based on the broadband that is typical of blast waves, the peak frequency of the P-wave was obtained in the time–frequency domain, taking advantage of the difference in the propagation speed of the P-wave, S-wave, and the surface wave. Second, the phase difference between two sensor nodes was found by means of a spectral decomposition and a correlation measurement. Third, the phase ambiguity was eliminated using the time interval of the first break and the dynamic characteristics of the sensors. Finally, following a top-down design idea, the hardware system was designed using Field Programmable Gate Array(FPGA). Verification, using both numerical simulations and experiments, suggested that compared with generalized cross-correlation-based time-difference measurement methods, the proposed method produced a higher time-difference resolution and accuracy. Compared with the traditional host computer post-position positioning method, the proposed method was significantly quicker. It can be seen that the proposed method provides a new solution for solving high-precision and quick source-location problems, and affords a technical means for developing high-speed, real-time source-location instruments.
Highlights
Shallow subsurface distributed source localization involves a large number of sensor nodes that are buried at different depths in an underground near-field monitoring area, where a wireless sensor network is built up in a self-organized and multi-hop mode, which works in a collaborative way to sense, monitor, collect, process, and transmit the vibration signal generated from the source
This technology mainly relies on the deep seismic location method to construct, from the differences in time of the the vibration vibration signal reaching the nodes, i.e., using time difference of arrival (TDOA)-based source location equations
To address problems in TDOA-based shallow subsurface vibration source location, such as low time-difference measurement accuracy and poor real-time performance, this paper proposed a new method for time-difference measurement that was based on phase-difference information
Summary
High-Precision Time-Difference Information and Implementation of Its Hardware Circuit. National Key Laboratory of Electronic Measurement Technology, North University of China, Taiyuan 030051, China. Received: 29 September 2019; Accepted: 18 November 2019; Published: 20 November 2019
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