Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 6 Articles
A 4 Ã?â?? 4 matrix model with three degrees of freedom is proposed as a means for controlling microvibrations and applied to\r\nan electromagnetic isolator. The model was derived from an assumption based on small- and low-frequency vibrations. The\r\ncoordinates of the 3 DOF was composed of the 4 variables, representing a vertical position, pitch, roll, and a proof term. The\r\ncoordinates were calculated from the 4 position sensors in the isolator and formulated into a 4 Ã?â?? 4 matrix, which possesses\r\ninversive full rank. The electro-magnetic isolator was built for a simulated machine in semiconductor manufacturing and consisted\r\nof a heavy surface plate, sensors, amps, a controller, and air springs with electromagnets. The electromagnets are installed in a\r\npneumatic chamber of the individual air spring. The performance of the 3 DOF model was experimented and compared with that\r\nof a 1 DOF model in an impact test. The settling time in the result was reduced to 25%....
Compressed sensing or compressive sampling is a recent theory that originated in the applied mathematics field. It suggests a robust\r\nway to sample signals or images below the classic Shannon-Nyquist theorem limit. This technique has led to many applications,\r\nand has especially been successfully used in diverse medical imaging modalities such as magnetic resonance imaging, computed\r\ntomography, or photoacoustics. This paper first revisits the compressive sampling theory and then proposes several strategies to\r\nperform compressive sampling in the context of ultrasound imaging. Finally, we show encouraging results in 2D and 3D, on highand\r\nlow-frequency ultrasound images....
This paper describes a cumulative harmonic analysis (CHA) that replaces the stepwise time window function of Berman and\r\nFincham�s cumulative spectral analysis with a spectral accumulation function, thereby enabling a new structural health monitoring\r\nmethod. CHA estimates and visualizes system damping conditions without the need of transient-vibration records. The damping\r\nconditions are closely related to the spectral distribution around the dominant spectral peaks due to structural resonance. This\r\ntype of spectral distribution can be visualized with CHA even within a short interval of random vibration samples. The effect of\r\nCHA on monitoring the damping conditions was reported by the authors in a previous study. In the current study, the authors\r\nconfirmed the usefulness of CHA for structural condition monitoring by conducting scale-model experimen...
We introduce a multiengine speech processing system that can detect the location and the type of audio signal in variable noisy\r\nenvironments. This system detects the location of the audio source using a microphone array; the system examines the audio first,\r\ndetermines if it is speech/nonspeech, then estimates the value of the signal to noise (SNR) using a Discrete-Valued SNR Estimator.\r\nUsing this SNR value, instead of trying to adapt the speech signal to the speech processing system, we adapt the speech processing\r\nsystem to the surrounding environment of the captured speech signal. In this paper, we introduced the Discrete-Valued SNR\r\nEstimator and amultiengine classifier, usingMultiengine Selection orMultiengineWeighted Fusion. Also we use the SI as example\r\nof the speech processing. The Discrete-Valued SNR Estimator achieves an accuracy of 98.4% in characterizing the environment�s\r\nSNR. Compared to a conventional single engine SI system, the improvement in accuracy was as high as 9.0% and 10.0% for the\r\nMultiengine Selection and MultiengineWeighted Fusion, respectively....
Machine condition monitoring and diagnosis have become increasingly important, and the application of these processes has\r\nbeen widely investigated. The authors previously proposed a stepwise diagnosis method for a beam structure. In that method,\r\nthe location of the abnormality is first estimated using the force identification approach, and then the cause of the abnormality is\r\nidentified. In this study, the stepwise diagnosis method was improved specifically for rotating machinery. The applicability of the\r\nproposed method was checked by using the experimental data. In the case of a rotor system with unbalance, it was shown that\r\nthe location of the abnormality and its severity could be identified, and, in the case of a rotor system with stationary rubbing, the\r\nlocation of the abnormality could be accurately identified. Therefore, it was confirmed that the proposed diagnostic method is\r\nfeasible for actual application....
Because of the density mismatch between the decoupler and surrounding fluid, the decoupler of all hydraulic engine mounts\r\n(HEM) might float, sink, or stick to the cage bounds, assuming static conditions. The problem appears in the transient response of\r\na bottomed-up floating decoupler hydraulic engine mount. To overcome the bottomed-up problem, a suspended decoupler design\r\nfor improved decoupler control is introduced. The new design does not noticeably affect the mechanism�s steady-state behavior,\r\nbut improves start-up and transient response. Additionally, the decoupler mechanism is incorporated into a smaller, lighter, yet\r\nmore tunable and hence more effective hydraulic mount design. The steady-state response of a dimensionless model of the mount\r\nis examined utilizing the averaging perturbation method applied to a set of second-order nonlinear ordinary differential equations.\r\nIt is shown that the frequency responses of the floating and suspended decoupled designs are similar and functional. To have a more\r\nrealistic modeling, utilizing nonlinear finite elements in conjunction with a lumped parameter modeling approach, we evaluate\r\nthe nonlinear resorting characteristics of the components and implement them in the equations of motion....
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