Ultra Wideband Radar Technology and Signal Processing Methods for the Multiphase Flow Monitoring and Tunnel Boring Operations
Creators: Sabzevari, Fatemeh Modares
Publisher: name: University of Alberta Library
Year: 2024

<p>Ultra-wideband (UWB) radar technology can provide solutions for many existing challenges in the industry. In this research, we tackle three existing problems in the oil industry and tunnel construction operations. First, microwave imaging and associated signal processing techniques are proposed for multiphase flow monitoring and metering in oil and gas pipes. A high-resolution image of the pipe cross-section has been generated using UWB synthetic aperture radar (SAR) technique. The image is then used to estimate the area of each phase by identifying and extracting its edges. Individual phase volume is estimated based on the corresponding area and the flow speed. Additionally, a generalized impulsization technique is presented and applied to reconstruct a sharp image and to reduce the error in flow area estimation. Furthermore, a novel technique to enhance the detectability of weak targets is proposed. Finally, a sectional image reconstruction technique is also applied to improve the stratified flow&#39;s imaging and metering. All the proposed techniques are evaluated through experiments.<br>
Secondly, the feasibility of applying the UWB radar technology to probe the tunnel face for buried objects or hidden man-made obstacles is investigated. In this study, different buried objects extracted from tunnel construction projects in Edmonton area are considered and characterized by radar techniques. The electrical properties of buried objects, which include the dielectric constant and loss tangent, are measured and compared to the vector network analyzer dielectric probe measurements. Then, based on its dielectric constant, the buried object is determined. By using a low-power UWB radar, the depth of the buried object from the surface of the tunnel face and its thickness are extracted. In addition, three different pipes containing various fluids are buried in the sand, and the fluids&#39; relative permittivity and loss tangents are estimated. These measurements distinguish the sewer pipes from oil pipes. This study demonstrates the capability of UWB radar technology for acquiring online geological conditions in tunnel construction operations.<br>
Then, with the motivation of automating the future ground-penetrating radars (GPR) or tunnel boring machines (TBM), the reconstructed images of the buried objects are classified into three categories, i.e., boulder, cutter head tooth, and wrench by a deep convolutional neural network. When the model is trained, the effect of the SAR system polarization on the image feature extraction is studied. Moreover, the speed of model training and the classification accuracy across different SAR system polarizations are investigated, and it is shown that the classification accuracy improves by 13.3$\%$ due to the inclusive feature of the quad-pol images.<br>
n a real tunnel construction site, large boulders, metal objects, or hidden pipes can hamper the TBM during the excavation operation. In this research, the feasibility of microwave radial imaging by UWB SAR technique is studied through finite difference time domain (FDTD) simulations. In this modeling, a sensor array is placed along the spokes of a wheel that mimics a TBM, and the data is collected at different angles. Then, the image reconstruction process is proposed based on the time domain global back projection. In this study, the effect of the sensor arrangement, the range and cross-range resolution, and the proposed method&#39;s effectiveness for imaging the hidden object at the wheel&#39;s margin are investigated and presented. These results confirm the proof of concept and lead us to the next stage of this research.<br>
Lastly, a modified Kirchhoff&#39;s migration technique for near-field imaging using the UWB radar transceiver is presented. In the near-field region, the velocity of the pulse propagation is a function of the distance and angle. The proposed technique compensates for this non-uniform propagation velocity. It is shown that the conventional Kirchhoff technique is not successful in focusing the target&#39;s image in the near-field; however, the modified Kirchhoff technique results in the focused image of the target with the correct position. </p>