Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 6 Articles
Condition-based monitoring (CBM) has advanced to the stage where industry is now demanding machinery that possesses\r\nself-diagnosis ability. This need has spurred the CBM research to be applicable in more expanded areas over the past decades.\r\nThere are two critical issues in implementing CBM in harsh environments using embedded systems: computational efficiency\r\nand adaptability. In this paper, a computationally efficient and adaptive approach including simple principal component analysis\r\n(SPCA) for feature dimensionality reduction and K-means clustering for classification is proposed for online embedded machinery\r\ndiagnosis. Compared with the standard principal component analysis (PCA) and kernel principal component analysis (KPCA),\r\nSPCA is adaptive in nature and has lower algorithm complexity when dealing with a large amount of data. The effectiveness of\r\nthe proposed approach is firstly validated using a standard rolling element bearing test dataset on a personal computer. It is then\r\ndeployed on an embedded real-time controller and used to monitor a rotating shaft. It was found that the proposed approach\r\nscaled well, whereas the standard PCA-based approach broke down when data quantity increased to a certain level. Furthermore,\r\nthe proposed approach achieved 90% accuracy when diagnosing an induced fault compared to 59% accuracy obtained using the\r\nstandard PCA-based approach....
This paper has proposed an automatic precise alignment coupling algorithm of planar optical waveguide devices based on\r\npolynomial fitting, and the experiment shows that for 1 Ã?â?? 8 planar optical waveguide splitter, the time it takes for alignment is within\r\n2.5 min and for 1 Ã?â?? 16 planar optical waveguide splitter, the required time is within 3 min. For 1 Ã?â?? 8 planar optical waveguide splitter,\r\nmany repeated experiments can guarantee that the insertion loss of the device channels is less than 10.5 dB, with the maximum\r\nuniformity of 0.67 dB; for 1 Ã?â?? 16 planar optical waveguide splitter, many repeated experiments can guarantee that the insertion\r\nloss of the device channels is less than 13.7 dB, with the maximum uniformity of 0.66 dB. The alignment velocity, precision, and\r\nreliability of this algorithm are all greatly increased....
This survey addresses the existing state of knowledge related to vision-based mobile robots, especially including their background\r\nand history, current trends, and mapless navigation. This paper not only discusses studies relevant to vision-based mobile robot\r\nsystems but also critically evaluates the methodologies which have been developed and that directly affect such systems....
The large generator faults are mostly from the stator insulation, which is aged by exposure to a combination of thermal, electrical,\r\nmechanical, and harsh environment stresses. Condition evaluation of stator insulation is an important measure of ensuring the\r\nsafe operation and extending the remaining life of large generator. In this paper, a diagnosis method based on the partial discharge\r\n(PD) measurement was used for the condition evaluation of the stator insulation. The statistical parameters of partial discharge\r\nphase resolved distribution were proposed to assess the aging condition of stator insulation. A partial least square (PLS) approach\r\nwas used to explore and extract relationships between the statistical parameters of partial discharge distribution with physical\r\nproperties and performance such as electrical breakdown strength. Results of the PD testing and statistical analysis show that the\r\nstatistical parameter Sk extent of partial discharge distribution changes much more remarkably with the aging time than do the\r\nother parameters.Thestatistical parameter Sk can be considered as a potential indicator of stator insulation aging.The PLS approach\r\ncan effectively assess the stator insulation aging condition and can provide a predictive capability for the stator insulation diagnosis....
Amulticriteria decision-makingmodel was proposed in order to acquire the optimumone among different product design schemes.\r\nVIKOR method was introduced to compute the ranking value of each scheme. A multiobjective optimization model for criteria\r\nweight was established. In this model, projection pursuit method was employed to identify a criteria weight set which could\r\nkeep classification information of original schemes to the greatest extent, while PROMETHEE II was adopted to keep sorting\r\ninformation. Dominance basedmultiobjective simulated annealing algorithm (D-MOSA) was introduced to solve the optimization\r\nmodel. Finally, an example was taken to demonstrate the feasibility and efficiency of this model....
Experiments are performed in a dense-phase pneumatic conveying system of pulverized coal, and electrostatic signals and coal\r\nparticle distribution images over cross-section of the pipeline at superficial gas velocities of 5.7 m/s, 6.9 m/s, and 8.1 m/s are obtained\r\nthrough use of electrostatic sensor arrays (ESA) and electrical capacitance tomography (ECT), respectively. In combination with\r\nECT imaging results, the output signals of the ESA are analyzed by FFT and approximate entropy method. Results show that\r\ncharacteristic of particles motion and its change with increasing superficial gas velocity are different in the dense and dilute phase\r\nregion of the pipe. With increasing the superficial gas velocity, the peak frequency of the electrostatic signal increases linearly in\r\ndense-phase region, while that in dilute phase region is nonlinear, implying that the increase of the axial particles velocity is the\r\nmain dynamic change, while in dilute phase regions, the particles velocity fluctuation in the radial direction cannot be ignored.\r\nThe ApEn value of the electrostatic signal in dense phase region is larger than that in dilute phase region. When the ApEn value\r\ndifference of the electrostatic signals is smaller, the pulverized coal particles are better suspended....
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