Advanced Materials Research Vols. 301-303

Abstract: The magnetic levitation system is nonlinear and inherently unstable. In order to improve its anti-interference performance and its loading capacity, a robust H_∞ controller is designed based on the H_∞ theory. The selection of the weighting function matrix is discussed for both the sensitivity and the complementary sensitivity of the H_∞ controller. Simulation and experimental results show that the H_∞ controller works effectively with excellent precision and robustness.

Abstract: A new real time inversion method is proposed for calculating multi-wavelength laser atmospheric aerosol extinction coefficients’ profile. The real-time data of atmospheric aerosol extinction coefficients’ profile measured by 0.532μm lidar is utilized together with complex aerosol model of Fascode. The unique features of this method are discussed in detail. Atmospheric aerosol extinction coefficients inversely calculated by this method compared with real time measurements data. The results show that it is feasible to inversely calculate the infrared atmospheric propagation with reasonable accuracy. The real time atmospheric correcting model is established by the method for extinction coefficients at different wavelengths without absorption of water vapor.

Abstract: An experimental study of low velocity impact (LVI) was carried out on 2D carbon fabric reinforced silicon carbide (C/SiC) ceramic matrix composites. The C/SiC composite specimens were impacted by using a free-drop impact machine at different energy levels ranging from 1J to 9J and acoustic emission (AE) technique was used to detect the damage process. The results indicated that AE signals could evaluate the LVI damage behaviors of C/SiC composites from the different aspects. By comparing impact load process with AE hits and AE amplitude, the damage process could be determined. In the loading stage, matrix cracking mainly occurred in the composites; when impact load reached peak load, delamination and fiber fracture started to produce; in the unloading stage, the damage modes were mainly delamination and matrix cracking. AE event count fractions could quantify the main damage modes at different impact energy levels. At lower impact energy, matrix cracking was the main damage mode; when impact energy were between 3J and 6J, delamination and matrix cracking became the main damage modes; at higher impact energy, fiber fracture was the main damage mode.

Abstract: Core analysis is one of the most necessary means to recognize the geological characteristics of reservoirs. Recently, the oil and gas exploration of particular lithology such as volcanic, conglomerate, mud and carbonate rocks continued to make new breakthroughs. As a result, core analysis for particular lithology reservoir rock is increasingly significant. However, conventional methods of core analyzing have great limitations on particular lithology due to the complex chemical components and variable physical status. In order to obtain accurate experimental data and understand the seepage law of particular lithology, advanced core analysis methods are developed through the application of computed tomography (CT). Through the application of nondestructive CT testing for inner construction of core, and the establishing of CT evaluation criterion for the heterogeneity of particular lithology, the goals of analyzing the features and growth of holes and fractures in core and heterogeneity of core are archived. The evaluation criterion is composed by qualitative evaluation and quantitative evaluation, and gives the corresponding evaluation method and formula. The evaluation criterion provides the basis for CT analysis of particular lithology. The application of CT analysis for 211 cores of particular lithology shows: 1) Most conglomerates develops gravel-edge fractures, growth of the fractures is proportional to the level of gravel and inverse proportional to the degree of compaction. Holes in conglomerate are mainly corroding holes between gravel. The growth of holes is related to the composition of cement and compaction. With the lower gravel level, the number of holes and fractures decline. 2) Most volcanic rocks develop holes; some of them develop big holes or lots of holes. Several volcanic samples contain micro-fractures. The growth of holes and fractures in different volcanic rock categories are equivalent, but the type of holes and fractures are different. This research has opened new experimental means for cores of particular lithology. By increasing the skills of core analysis, this research has increased people’s knowledge of reservoir of particular lithology, and means a lot to oil and gas exploration and development.

Abstract: Colorimetry is commonly used to measure the surface temperature as true one when the surface emissivity is constant. That is, the target is regarded as greybody. But in fact, most materials are not greybody. Spectrum emissivity has to do with wavelength and temperature. And in the most case, it is difficult to assure the exact values of the emissivity .This makes the relative error of the temperature big. Therefore, it is necessary to modify the emissivity response of radiation pyrometer. The factor influencing the spectrum was researched through the application of least square method to create the relationship of spectrum emissivity with wavelength and temperature, at last mathematic model was established which provided numerical correction of infrared two-color thermometry.

Abstract: A finite-time speed tracking control for a permanent-magnet synchronous motor (PMSM) is presented. The proposed control scheme depends on finite-time convergence of a fractional power differential equation. A continuous feedback controller for a PMSM is constructed based on the double integrator form of PMSM with a tricky coordination transformation. The simulation results show its efficiency.

Abstract: There are uncertainties such as randomicity, vagueness, gray, unsureness in the factors of comprehensive evaluation of rock burst risks due to the complexity of the geological conditions and deficiency of experimental data. In this paper, we apply the mathematic theory of blind information to the comprehensive index method for the assessment of rock burst risks, use blind data to express the uncertainty of the risk index, and put forward blind data form of the comprehensive index. Meanwhile, by use of blind data algorithms, we compute the reliability value in different numerical value intervals of comprehensive index, which consequently provide more comprehensive evidence to judge the rock burst risk levels and overcome the problem of absolutization in traditional methods. The case analysis indicates that the apply for blind data in rock burst evaluation can consider influential factors better and obtain more reliable results. In conclusion, it is a new way of evaluating the rock burst more comprehensively and scientifically.

Abstract: Microwave emissions at various frequencies are known to contain information on atmospheric chemistry. Information about water vapor is of great interest at 183.31GHz. Interferometric synthetic aperture radiometer avoids the disadvantages of manufacturing and carrying large antennas at the expense of complexity. This paper has discussed the design of the 183.31GHz interferometer system with two elements based on imaging theory and retrieving algorithm of two-dimensional synthetic aperture radiometer. And then several important experimental results are presented.

Abstract: For the detection of the broken-bar fault of rotor in motors, a traditional method is frequency spectrum analysis for the stator current. However, the frequency components representative of the rotor fault can be easily submerged by the fundamental frequency, so that the detections results are inaccurate. In this paper, the stator current will be decomposed and reconstructed, after that the fast Fourier transform can be applied to the frequency spectrum analysis. It eliminates the influence that the fault characteristic components are flooded by the basic frequency components. The experiment result shows that the existence of a slight fault in rotor can be detected. The method has a good theoretical and engineering application.

Abstract: This paper mainly introduces the development process of energy-efficient of non-invasive motor for on-line monitoring system based on reasoning model. In addition, the function , composition and commissioning of shis system is introduced. In this system, in order to collect and analyze status recording of the motor running, operating parameters of motor speed, torque and power factor, efficiency are estimated on-line by using motor stator current signal feature analysis technology. In the paper, air-gap torque method is used to non-invasive electromotor for efficiency computation. The designing process of software for On-line monitoring system is shown as: Firstly, monitor motor’s operating parameters on-line, then, motor energy management is supported by the analysis of monitoring recording. At the same time, construct communication network for motor monitoring by using wireless communication technology about efficiency curve of industry motor. This system has the advantages of monitoring precision, easy installation, low costs, especially suitable for monitoring and energy management of efficiency for small and medium-sized motor, and it has been used widely in industrial production.