Papers by Keyword: Signal-Analysis

Abstract: In order to find the machine fault and take adaptive measures to deal with it accurately and in time for machine equipment fault diagnosis, a portable data-acquisition and signal analysis instrument based on Qt is introduced, which plays an important role in mechanical industry. Qt is a tool which is used to build multi-platform graphical interface in the way of "written once, compiled anywhere”. The factors which make Qt outstanding in most programming tools are the availability of source code, help documentation and high-class technical support and so on. In this paper, how to develop the software of portable data-acquisition and signal analysis instrument is discussed in detail.

Abstract: A misalignment rotor-bearing systems is studied as an object. Comparing two kinds of vibration characteristics of 0 torque excitation and linear torque excitation. The experimental data are analyzed by FFT and wavelet. Conclusion is obtained. Certain torque excitation can control oil whirl to a certain extent. On the other hand, linear torque excitation can increase degree of misalignment.

Abstract: Magnetic Suspension Flywheel (MSFW) is regarded as a promising attitude control actuator for the ultra-precision and long life-span spacecraft. The output vibration of an operating MSFW is an important criterion to evaluate the system’s performance. Based on the dynamics model of rotor with the residual imbalances and the transfer functions of the controller, the restoring electromagnetic forces and torques for the suspension of the rotor is calculated. Then a testing rig was designed to measure the displacements, currents and vibration outputs of the MSFW. The vibrations of the basement caused by reactions of the restoring forces and torques are calculated. In the end, the displacements, currents and vibrations of the operating MSFW are measured to evaluate the performance of the MSFW.

Abstract: Tidal bore is a series of waves propagating upstream as the tidal flow turns to rising. The Qiantang Bore has aroused the curiosity of scientists and tourists all over the world in the past centuries as a strong turbulent bore. We consider here tidal bore impact measurements, recorded in the Qiantang River using pressure transducers. Based on the empirical mode decomposition (EMD) algorithm, a signal processing method for impact test due to the Qiantang Bore is proposed. As a self-adaptive approach, EMD method can be used to decompose the local characteristics of the no-stationary and nonlinear signals into several fluctuations and trend items with different time scales step by step. The separation of the quasi-static and dynamic pressures is conducted by using the empirical mode decomposition method.

Abstract: With piezoelectric acceleration sensor, charge voltage filter amplifier, data acquisition card, PC and vibration experiment table for hardware development platform, and LABVIEW for software development platform, virtual instrument technology was applied to the design of mechanical vibration test system. This test system mainly consists of data acquisition, time domain analysis, amplitude domain analysis, frequency domain analysis, time-frequency analysis module. Experimental results indicate: The system not only can perform real-time data acquisition of multiple channels signal, waveform display, data storage, signal analysis, playback measurement and output printing etc, but also has good expansibility, high speed, high accuracy and friendly interface. It is suitable for engineering personnel and laboratory use.

Abstract: The vibration phenomenon of pipeline for conveying liquid and gas is very common. Based on the feature of pipeline vibration and multi-resolution of wavelet, this paper has mainly simulated the vibration signal of pipeline and made muti-scale analysis of the signal. At the same time, this paper points out that the selected frequency band which causes the vibration can be found out, by using frequency spectrum analysis of pipeline vibration signal, combined with Fast Fourier Transform (FFT).So this paper shows that the processing way of pipeline vibration signal based on wavelet transform is available.

Abstract: By taking full advantage of the technologies of data acquisition, signal analysis and processing and fault diagnosis, this thesis carries out a research on the realization method of mine hoist bearing condition monitoring and fault diagnosis. Firstly, this thesis takes a technical analysis for rolling bearing. Secondly, based on determining the overall framework and using a virtual instrument software (Labview), it carries out a program development of the system. The developed system not only integrates the functions of traditional instruments, but also describes the bearing states and the types of bearing failure accurately according to the running status of the monitored bearings. It provides technical support for the mine hoist repair and maintenance and scientific protection for its safe running.

Abstract: Basing on the analysis of Mine Hoist working condition, Research on fault diagnosis system for Mine Hoist was introduced, including detailed introduction of its functions, composition and work principles. According to its application, it shows that fault diagnosis and monitoring technology to ensure that the equipment can run in good conditions so as to reduce unplanned downtime and help to reduce maintenance costs.

Abstract: The path of tire pattern’s impact on interior noise and vibration was analyzed. The same type tires with six kinds of different tread pattern were selected as the investigating subjects, and the interior measuring points’ vibration and noise signals of different tires were measured under full load condition. The basic theory of Wavelet Transform (WT) and its signal reconstruction principle were researched, and 1/3 octave Morlet wavelet was induced and analyzed. The vibration and noise signals of measuring points were transformed by using 1/3 octave Morlet wavelet, distribution features of vibration and noise signals of six tires with different tread pattern were made a comparison in time domain and frequency domain, and the distinct results of different tires were achieved. The advantage of WT in the aspect of time-frequency analysis for time domain signal is revealed.

Abstract: This paper discussed on an application of the statistical based analysis approach on fatigue failure of carbon steel. A new statistical based method known as Integrated Kurtosis-based Algorithm for Z-filter (I-kaz) and the quadratic mean were used in this fatigue failure assessment. Fatigue tests were performed according to the ASTM E466-96 standard with the attachment of a strain gauge to the tested specimen. Test was performed at a constant loading leading to the collection of strain data throughout the test. A fatigue based data acquisition system was used in this work. All obtained data were analysed using specific software. Fatigue failure behaviour was observed through the strain signal analysis to investigate significant correlation between I-kaz coefficient, root mean square value and the fatigue failure behaviour. It was found that I-kaz coefficient and root mean square value are proportional to life cycle.