One of the most significant goals in coal mining technology research is the automation of underground coal mining machinery. A current challenge with automating underground coal mining machinery is measuring and maintaining a coal mining horizon. The coal mining horizon is the horizontal path the machinery follows through the undulating coal seam during the mining operation. A typical mining practice is to leave a thin remnant of coal unmined in order to maintain geological stability of the cutting face. If the remnant layer is too thick, resources are wasted as the unmined coal is permanently unrecoverable. If the remnant layer is too thin, the product is diluted by mining into the overburden and there is an increased risk of premature roof fall which increases danger. The main challenge therefore is to develop a robust sensing method to estimate the thickness of thin remant coal layers. This dissertation addresses this challenge by presenting a pattern recognition methodology to estimate thin remnant coal layer thickness using ground penetrating radar (GPR). The approach is based upon a novel feature vector, derived from the bispectrum, that is used to characterise the early-time segment of 1D GPR data. The early-time segment is dominated by clutter inherent in GPR systems such as antenna crosstalk, ringdown and ground-bounce. It is common practice to either time-gate the signal, disregard the clutter by rendering the early-time segment unusable, or configure the GPR equipment to minimise the clutter effects which in turn reduces probing range. Disregarding the early-time signal essentially imposes a lower thickness limit on traditional GPR layer thickness estimators. The challenges of estimating thin layer thickness is primarily due to these inherent clutter components. Traditional processing strategies attempt to minimise the clutter using pre-processing techniques such as the subtraction of a calibration signal. The proposed method, however, treats the clutter as a deterministic but unknown signal with additive noise. Hence the proposed approach utilises the energy from the clutter and monitors change in media from subtle changes in the signal shape. Two complementary processing methods important to horizon sensing have been also proposed. These methods, near-surface interface detection and antenna height estimation, may be used as pre-validation tools to increase the robustness of the thickness estimation technique. The proposed methods have been tested with synthetic data and validated with real data obtained using a low power 1.4 GHz GPR system and a testbed with known conditions. With the given test system, it is shown that the proposed thin layer thickness estimator and near-surface interface detector outperform the traditional matched filter based processing methods for layers less than 5 cm in thickness. It is also shown that the proposed antenna height estimator outperforms the traditional height estimator for heights less than 7 cm. These new methods provide a means for reliably extending layer thickness estimation to the thin layer case where traditional approaches are known to fail.

Coherent plane-wave compounding (CPWC) ultrasound is an important modality enabling ultrafast biomedical imaging. To perform CWPC image reconstruction for a stratified (horizontally layered) medium, one needs to know how the speed of sound (SOS) varies with the propagation depth. Incorrect sound speed and layer thickness assumptions can cause focusing errors, degraded spatial resolution and significant geometrical distortions resulting in poor image reconstruction. We aim to determine the speed of sound and thickness values for each horizontal layer to accurately locate the recorded reflection events to their true locations within the medium. Our CPWC image reconstruction process is based on phase-shift migration (PSM) that requires the user to specify the speed of sound and thickness of each layer in advance. Prior to performing phase-shift migration (one layer at a time, starting from the surface), we first estimate the speed of sound values of a given layer using a cosine similarity metric, based on the data obtained by a multi-element transducer array for two different plane-wave emission angles. Then, we use our speed estimate to identify the layer thickness via end-of-layer boundary detection. A low-cost alternative that obtains reconstructed images with fewer phase shifts (i.e., fewer complex multiplications) using a spectral energy threshold is also proposed in this thesis. Our evaluation results, based on the CPWC imaging simulation of a three-layer medium, show that our sound speed and layer thickness estimates are within 4% of their true values (i.e., those used to generate simulated data). We have also confirmed the accuracy of our speed and layer thickness estimation separately, using two experimental datasets representing two special cases. For speed estimation, we used a CPWC imaging dataset for a constant-speed (i.e., single-layer) medium, yielding estimates within 1% of their true values. For layer thickness estimation, we used a monostatic (i.e., single-element) synthetic-aperture (SA) imaging dataset of the three-layer medium, also yielding estimates within 1% of their true values. Our evaluation results for the low-cost alternative showed a 93% reduction in complex multiplications for the three-layer CPWC imaging dataset and 76% for the three-layer monostatic SA imaging dataset, producing images nearly similar to those obtained using the original PSM methods. / Graduate

The technological advancement in electrical machinery represents the need to understand the lubricant behaviour in the electrical environment. As shaft voltages are unavoidable in electrical machinery, developing new grease formulations and studying their performance against electric loads is required. The thesis aims to design, develop, install and validate a novel test machine to study grease performance under the influence of electric currents. The system aims to supply damaging electric currents through the bearing, but that was not possible to accomplish due to miscalculations. The test machine is designed to carry out experiments using angular contact bearings. The experiments were performed with four greases, Lithium-complex and polypropylene-based, of high and low base-oil viscosity, respectively. The study compares the frictional moments and self-induced temperatures in the bearings with and without the influence of electric currents. Along with the frictional moment measurements, the lubricant film thickness was estimated using the “electrical-capacitance” method to monitor the status of the lubricant inside the bearing in real-time. The test machine is limited to speeds up to 3600 rpm, and the project lays out a foundation for research in film thickness estimation in rolling element bearings. As a part of the thesis, new slip rings were specified to facilitate the test machine to perform studies at higher speeds up to (17000rpm). / De tekniska framstegen inom elektriska maskiner representerar behovet av att förstå smörjmedlets beteende i den elektriska miljön. Eftersom axelspänningar är oundvikliga i elektriska maskiner krävs utveckling av nya fettformuleringar och studier av deras prestanda mot elektriska belastningar. Avhandlingen syftar till att designa, utveckla, installera och validera en ny testmaskin för att studera fettprestanda under påverkan av elektriska strömmar. Systemet syftar till att leverera skadliga elektriska strömmar genom lagret, men det var inte möjligt att åstadkomma på grund av felberäkningar. Testmaskinen är designad för att utföra experiment med vinkelkontaktlager. Experimenten utfördes med fyra fetter, litiumkomplex- och polypropenbaserade, med hög respektive låg basoljeviskositet. Studien jämför friktionsmomenten och självinducerade temperaturer i lagren med och utan påverkan av elektriska strömmar. Tillsammans med mätningarna av friktionsmomentet uppskattades smörjmedelsfilmtjockleken med hjälp av metoden "elektrisk kapacitans" för att övervaka statusen för smörjmedlet inuti lagret i realtid. Testmaskinen är begränsad till hastigheter upp till 3600 rpm, och projektet lägger en grund för forskning inom filmtjockleksuppskattning i rullager. Som en del av avhandlingen specificerades nya släpringar för att underlätta för testmaskinen att utföra studier vid högre hastigheter upp till (17000rpm).