Precision Instrumentation and Measurement

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Authors: Qian Cheng Zhao, Chang You Lu, Qiao Xu, Geng Huang
Abstract: The important parts of a screw compressor are the two rotors. At present, generally use a CMM to check the form and other parameters of the rotors to ensure its function. Among the all geometrical parameters of a rotor, the form of traverse section profile is the most important one. In the process of measurement, the key technology problem is the probe radius correction because of the complexity of 3D helical surface. When the nominal values of the rotors are unknown, the radius correction is more difficult than that is known. This paper presents a method to evaluate the precision of measuring screw rotors by simulation. Suppose a referenced helical surface, first select the probe ball radius and sampling density, calculate the coordinate values of the probe ball centers along a fixed plane, then calculate the values of measured contour by radius correction, finally compare the reconstructed contour with the referenced surface to evaluate the selected measuring parameters such as probe ball radius, sampling density, the algorithm of radius correction and so on. This simulation process is necessary for actually measuring a screw rotor.
Authors: Chuan Jun Liao, Shuang Fu Suo, Wei Feng Huang
Abstract: Acoustic emission (AE) techniques are put forward to monitor rub-impacts between rotating rings and stationary rings of mechanical seals by this paper. By analyzing feature extraction methods of the typical rub-impact AE signal, the method combining of wavelet scalogram and power spectrum is found useful, and can used to attribute the feature information implicated in rub-impact AE signals of mechanical seal end faces. Both simulations and experimental research prove that the method is effective, and are used successfully to identify the typical features of different types of rub-impacts of mechanical seal end faces.
Authors: Ping Yu Zhu, Hong Yan Zeng, Yuan Bao Leng, Ji Ming Ma
Abstract: In this study we analyze the signal in measurement system with distributed optical fiber sensors. The display signal is defined by the user not for general custom. The data of for-processing-part are processed regularly, which directly provides results for the user from the monitoring system. These results go into the next step to add environmental parameters, which includes weather, special events and season information. Information fusion and matching operation of the result and environment information enhances the accuracy of hidden hazard early warning.
Authors: Yu Chuan Lin, Long Jeng Lee, Shenq Tsong Chang, Yu Cheng Cheng, Ting Ming Huang
Abstract: This article reports an accurate analysis approach of finite element modeling and optical modeling. It has been used for design and analysis of many opto-mechanical systems such as large telescopes and laser systems. The approach is to represent mirror surface deformation derived from finite element analysis (FEA) by Zernike polynomials, such that the impact of deformation on optical system performance can be evaluated by optical design and analysis program. The methodology of shell-based and solid-based finite element modeling and the comparison of their results have been described in this paper. The result shows that the deformation of the light-weighted mirror designed by this approach fulfills the requirements of optical design. The simulation results of shell based FE model are in good agreement with those of solid based FE model.
Authors: Syh Shiuh Yeh, Jin Tsu Sun
Abstract: Static friction generally exists in feed drive servomechanisms and usually affects the motions of CNC machine tools. In this study, the breakaway experiment is applied to measure the static friction of a feed drive servomechanism generally used in CNC machine tools, and the spectral analysis using the fast Fourier transformation algorithm is applied to analyze the frequency characteristics of the obtained static friction. Several experiments were carried out on a three-axis CNC milling machine so as to illustrate the feasibility of the developed measurement and analysis methods. The experimental results indicate that the static friction of a feed drive servomechanism is clearly position-dependent and the physical interaction of the mechanical parts in the transmission system used by the feed drive servomechanism significantly affects the characteristics of the static friction.
Authors: Jing Wang, Te Fang Chen, Cai Lun Huang, Qian Cheng Zhao
Abstract: In condition monitoring of train, because of load change, speed fluctuation and other effect factors, it may cause vibration frequency spectrum migration. If using the common vibration signal acquisition and spectral analysis method to this fault, there will be a result of characteristic spectral smearing, which will lead to misdiagnosis or missed diagnosis. To solve this problem, the vibration mechanism of spectrum-varying fault was discussed. This paper studies a pulse-triggered sampling method of integral periodic signal, the equal angle re-sampling method and other appropriate signal processing method. The feasibility and validity of this method and technology has been verified by the application in Liuzhou Railway Bureau .
Authors: Kuan Fang He, Ping Yu Zhu, Xue Jun Li, D.M. Xiao
Abstract: Distributed optical fiber sensing technology in the dam safety monitoring has been applied. The most typical application is the Swiss distributed optical fiber DiTeSt-STA202 analyzer. The instrument can simultaneously measure the distribution of thousands of points in a fiber strian and temperature, and it is suitable for measurement of objects up to several kilometers, but it’s functions limit to the data acquisition and the most primitive conversion of the strain and temperature without the deeper data processing functions, and the interface is less of user-friendly nature and poor adaptability. In this paper, The secondary development of DiTeSt-STA202 is done by Delphi and ADO technology based on analysis of the data storage types and formats. The data processing and analysis system is achieved in an efficient and accurate way.
Authors: Kuan Fang He, Ji Gang Wu, Xue Jun Li
Abstract: According to the soft-switching pulsed SAW (Submerged arc weld) weld power supply based on the double closed-loop constant current control mode, a small signal mathematic model of main circuit of soft-switching SAW inverter was established by applying the method of three-terminal switching device modeling method, and the mathematic model of double closed-loop phase-shift control system circuit was established by applying the method of state-space averaging method. Dynamic performance of the inverter was analyzed on base of the established mathematic model, and the tested wave of dynamic performance was shown by experimentation. Research and experimentation show that relation between structure of the power source circuit and dynamic performance of the controlling system can be announced by the established mathematic model, which provides development of power supply and optimized design of controlling parameter with theoretical guidance.
Authors: Guang Hui Li, Gui Ling Jiang, Ping Yu Zhu
Authors: Z.J. Wen, Ping Yu Zhu, X.P. Zhang, H.C. Liu
Abstract: A new state space model of multi-operational machining processes is presented for dimensional variation propagation, transformation and accumulation based on perturbation vectors (PV). Taking perturbation vectors (PV) for state vectors of part geometric variaton and the fixture variations for input vectors, the perturbation homogeneous transformation (PHT) is applied to analyze and derivate datum-induced deviation, re-location deviation, fixture error and machining error, and a state space model of variation propagation in multi-operational complicated machining processes is developed. Furthermore, a three-operation machining process of cylinder is given to illustrate the method presented. With the results of calculation and simulation, it is verified that the proposed model is effective and useful.

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