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Self-Identification and Balancing for AMB-Rotor System of Turbomolecular Pumps

IEEE-ASME TRANSACTIONS ON MECHATRONICS 2024年 1-10页

作者： Yin, Yifan Liu, Ximing Wang, Kun Zheng, Shiqiang Beihang Univ Sch Instrumentat & Optoelect Engn Beijing 100191 Peoples R China Beihang Univ Sch Automat Sci & Elect Engn Beijing 100191 Peoples R China

The rotor unbalance of the magnetic levitated turbomolecular pump (MLTMP) can lead to undesirable rotor synchronous vibration, and thus seriously affect the instrumentation precision in the ultra-high vacuum condition. The accurate identification and elimination of rotor unbalance is the primary issue for system stable operation at high speeds. This article proposes a method for rotor unbalance self-identification without using external information, and designs a model parameter correction procedure to improve the rotor balancing precision. First, the complex coefficient method is utilized to establish the rotor dynamic model under the regular controller, and the numerical equivalence between the correction mass centrifugal force and magnetic bearings force is used to obtain the rotor unbalance. Then, the rotor synchronous responses based on rotor radial displacement and bearing control currents are extracted through the cross-correlation algorithm. To further improve the rotor unbalance measurement accuracy, the stiffness coefficient values are also corrected by introducing virtual trial weights. Finally, the experimental results conducted on a MLTMP prototype verify the effectiveness of the proposed method in the self-identification of rotor unbalance.

关键词： Rotors Magnetic levitation Force Accuracy Vibrations Coils Mechatronics Active magnetic bearing (AMB) cross-correlation algorithm field dynamic balancing stiffness coefficients correction turbomolecular pumps

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Research on co-phasing detection of segmented mirror based on convolutioned neural networks

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OPTICS AND LASER TECHNOLOGY 2023年第1期167卷

作者： Li, Bin Yang, Akun Li, Yanbing Sun, Zhaoxiang Wu, Jian Chen, Nan Chen, Mo East China Jiaotong Univ Intelligent Electromech Equipment Innovat Res Inst Nanchang 330013 Peoples R China Xinyu Univ Sch New Energy Sci & Engn Xinyu 338004 Peoples R China Chinese Acad Sci Inst Opt & Elect Chengdu 610209 Peoples R China

To build a greater than 10 m aperture telescope, it is necessary to use the technique of segmented mirror. Although segmented mirror enables the construction of very large aperture telescopes, they also require fine cophasing of the sub-mirrors in order to achieve the imaging capability of the whole mirror with the same aperture. As a result, there is urgently necessary to develop a large range, high precision, and fast co-phasing errors measurement technique. In this paper, a new method of two-wavelength co-phasing detection based on convolutional neural network is proposed to address the problem of slow detection speeds and low accuracy in the detection of large-range co-phasing errors (piston) by the current two-wavelength co-phasing detection method based on the cross-correlation algorithm. Firstly, the co-phasing detection dataset with piston detection range [-10.5 & mu;m, 10.5 & mu;m] at wavelengths of 737 nm and 750 nm was analyzed by theory and simulation, and the rapidity and accuracy of the method of two-wavelength co-phasing detection based on convolutional neural network were verified by this dataset, and the accuracy of the training set was greater than 99.9% and the RMS value of the test sample error was 9.8 nm. This paper further discusses the tolerances for eccentricity and gap errors required for using the neural network detection method. When the gap error or eccentricity error is less than 0.2, the piston error can be directly detected using the convolutional neural network.

关键词： Segmented mirror Co-phasing errors Convolutional neural network cross-correlation algorithm

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DSM-Based Precise Pointing Angle Deviation Measurement Method for Beaconless Free Space Optical Communication

IEEE PHOTONICS JOURNAL

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IEEE PHOTONICS JOURNAL 2023年第6期15卷 1页

作者： Ao, Xueyuan Zou, Yansheng Zou, Yang Fan, Qirun Dai, Xiaoxiao Liu, Chen Yang, Qi Liu, Deming Huazhong Univ Sci & Technol Sch Opt & Elect Informat Wuhan 430074 Peoples R China Univ Sci & Technol Shenzhen Res Inst Huazhong Shenzhen 518000 Peoples R China

In free space optical (FSO) communication, acquisition, tracking and pointing (ATP) is the key technology to maintain a high-quality FSOlink. Specifically, the detection of pointing angle deviation greatly affects the performance of ATP, especially under weak receiving power. However, the separated beacon laser beam commonly used in ATP will increase the structural complexity of the terminal such as the size, weight, and power. It is unwanted in some limited applications such as satellite. To improve the pointing accuracy with weak signal in beaconless FSO communication, we propose a delta-sigma enabled beaconless cross-correlation (CCR) method with four-quadrant detectors. In the proposed method, a low-frequency sine analog signal for CCR calculation is modulated into a 1-bit digital signal by delta-sigma modulation and then inserted into the communication data as a training sequence. The root means square error (RMSE) of the pointing angle deviation measurement is 14.17 mu rad with the incident optical power of-40 dBm. Compared with the direct intensity method, of which RMSE is 67.61 mu rad, the proposed method can effectively improve the pointing accuracy with weak power without a beacon laser in FSO communication.

关键词： Four-quadrant detector pointing angle deviation measurement beaconless free space optical communication cross-correlation algorithm delta-sigma modulation

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Adaptive large-scale particle image velocimetry method for physical model experiments of flood propagation with complex flow patterns

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MEASUREMENT 2022年 198卷

作者： Hou, Jingming Yang, Lu Wang, Xinhong Chai, Jie Zhang, Zongxiao Li, Xuan Shao, Jianbin Du, Ying'en Bai, Ganggang Xian Univ Technol State Key Lab Ecohydraul Northwest Arid Reg China Xian 710048 Shaanxi Peoples R China Northwest A&F Univ Yangling 712100 Shaanxi Peoples R China

This work presents an Adaptive Large Scale Particle Image Velocimetry method (ALSPIV), which measures surface velocity of a physical model experiment with complex flow pattern. In the experiment, the eleven low-cost, high-resolution surveillance cameras are adopted to achieve a large-scale flow field in real time. The lenses of them are shined perpendicularly on water surface to minimize perspective distortion. A camera calibration method is also designed to enhance measurement accuracy. In addition, an adaptive cross-correlation algorithm can contribute to cross-correlation and a lower signal-to-noise ratio. Finally, an experimental method is employed to verify the ALSPIV method's accuracy, and the surface velocity distributions under three different steady flows are measured to demonstrate its applicability. Results show that the method is demonstrated to be a low-cost and automatic flow diagnostic tool and an accurate means of measuring surface velocities in the physical model experiments of flood propagation with complex flow patterns.

关键词： ALSPIV Complex flow patterns cross-correlation algorithm Physical model experiment Surface velocity measurement

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Optimization in PIV algorithm for visualizing vortices in bubble wake

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FLOW MEASUREMENT AND INSTRUMENTATION 2022年 86卷

作者： Ye, Xinwei Niu, Xiaojing Tsinghua Univ Dept Hydraul Engn State Key Lab Hydrosci & Engn Beijing Peoples R China Tsinghua Univ Dept Hydraul Engn Beijing 100084 Peoples R China

The PIV (Particle image velocimetry) is the most commonly used method for flow field observation because of its high efficiency and non-interference to the flow field. This study aims to clarify the optimal parameter conditions used in the cross-correlation algorithm of PIV for flow fields with vortices. The influence factors on the error of the cross-correlation algorithm are analyzed and discussed using a synthetic flow field, including the seeding conditions, the velocity gradient and vortex size. It is confirmed that the minimum particle number density per interrogation window is about 10, which generally limits the minimum size of the window. For a vortex, when the vortex size is fixed, the velocity gradient corresponding to the characteristic velocity both controls the lower and upper limitation of window size. For a relatively small vortex, generally a window not larger than the vortex size is asked. Then, a strategy to improve the observation based on the existing equipment is discussed and applied to visualize a rising bubble wake based on LIF (Laser-induced fluorescence) images.

关键词： PIV cross-correlation algorithm Vortex Error analysis Bubble

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A New Method of Eddy Current Impedance-Extracting and Hardness-Classifying for Valves

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IEEE ACCESS 2020年 8卷 46781-46794页

作者： Hu Pengfei Xie Qingsheng Huang Haisong Guizhou Univ Minist Educ Key Lab Adv Mfg Technol Guiyang 550025 Peoples R China Guizhou Prov Inst Metro Log Testing Guiyang 550003 Peoples R China

This paper describes a new method of eddy current impedance extraction and hardness classification for valves, which is used in online classification. A finite element simulation is conducted to estimate the base magnetic response in specimens with various initial permeabilities, and a scatter diagram between the hardness calibration and initial permeability is plotted experimentally;thus, the hardness classification model is obtained by using the initial permeability as the intermediate variable. A lock-in amplifier is commonly used to measure the amplitudes of impedance components in conventional eddy current testing. This study replaces the lock-in amplifier with a cross-correlation algorithm with the objective of integrating the impedance processing with the subsequent classification. Moreover, an incremental and decremental support vector machine is used to classify the valve specimens based on the extracted impedance due to its demonstrated excellent performance for both linearly separable and nonlinearly indivisible problems. The cross-correlation algorithm and the incremental and decremental support vector machine are implemented on a field-programmable gate array, which has the advantage of parallel processing and can satisfy the online requirements. A comparison with the traditional impedance comparison method shows that the proposed method not only is suitable for online hardness classification but also achieves good performance in correlating impedance amplitude changes caused by a temperature increase of the coil and various heat treatment conditions with the hardness values.

关键词： Eddy current testing finite element model cross-correlation algorithm incremental and decremental support vector machine impedance extraction hardness classification

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Hyperspectral image-based analysis of thermal damage for ex-vivo bovine liver utilizing radiofrequency ablation

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SURGICAL ONCOLOGY-OXFORD 2021年 38卷 101564-101564页

作者： Aref, Mohamed Hisham Aboughaleb, Ibrahim H. Youssef, Abou-Bakr M. El-Sharkawy, Yasser H. Mil Tech Coll Biomed Engn Dept Cairo Egypt Cairo Univ Syst & Biomed Engn Dept Giza Egypt

Background & objective: Thermal ablation is the predominant methodology to treat liver tumors for segregating patients who are not permitted to have surgical intervention. However, noticing or predicting the size of the thermal strategies is a challenging endeavor. We aim to analyze the effects of ablation district volume following radiofrequency ablation (RFA) of ex-vivo liver exploiting a custom Hyperspectral Imaging (HSI) system. Materials and methods: RFA was conducted on the ex-vivo bovine liver at focal and peripheral blood vessel sites and observed by Custom HSI system, which has been designed to assess the exactness and proficiency using visible and near-infrared wavelengths region for tissue thermal effect. The experiment comprised up to ten trials with RFA. The experiment was carried out in two stages to assess the percentage of the thermal effect on the investigated sample superficially and for the side penetration effect. Measuring the diffuse reflectance (R , d) of the sample to identify the spectral reflectance shift which could differentiate between normal and ablated tissue exploiting the designed cross-correlation algorithm for monitoring of thermal ablation. Results: Determination of the diffuse reflection (R , d) spectral signature responses from normal, thermal effected, and thermal ablation regions of the investigated liver sample. Where the ideal wavelength range at (600-640 nm) could discriminate between these different regions. Then, exploited the converted RGB image of the HS liver tissue after RFA for more validations which shows that the optimum wavelength for differentiation at (530-560 nm and 600-640 nm). Finally, applying statistical analysis to validate our results presenting that wavelength 600 nm had the highest standard deviation (delta) to differentiate between various thermally affected regions regarding the normal tissue and wavelength 640 nm shows the highest (delta) to differentiate between the ablated and normal regions. Concl

关键词： Liver tumor Hyperspectral imaging Radiofrequency thermal Ablation cross-correlation algorithm Liver tissue thermal Effect Spectral signature

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Study on the co-phasing simulation and experimental of segmented mirror based on broadband light

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Optica Acta: International Journal of Optics 2024年第1-3期71卷

作者： Bin Li Yinling Liu Akun Yang Nan Chen Jian Wu Mo Chen a Intelligent Electromechanical Equipment Innovation Research Institute of East China Jiao-tong University Nanchang People’s Republic of China b Institute of Optics and Electronics Chinese Academy of Sciences Chengdu People’s Republic of China

At present, the co-phasing detection algorithms for segmented mirrors struggle to balance the measurement range and accuracy. This paper proposes a coarse co-phasing measurement method using the incoherent properties of a broadband (400–800 nm) light source combined with the incoherence of two semicircular diffraction patterns of visible light as a template to detect the piston error, and a narrowband algorithm for fine co-phasing measurement. The diversity factors between template patterns and actual diffraction patterns can be calculated by the cross-correlation algorithm. This proposed method addresses long measurement time caused by low target flow rate and is characterized by wide measurement range, high precision and high energy utilization. The method is theoretically researched and simulated and an experimental system which was constructed to verify the effectiveness of this method achieves 15 nm detection accuracy, and the measurement range using the proposed method can match the measurement range of the actuator.

关键词： Segmented mirrors cross-correlation algorithm phase detection broadband light

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Quantitative characterization of the interfacial roughness and thickness of inhomogeneous coatings based on ultrasonic reflection coefficient phase spectrum

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NDT & E INTERNATIONAL 2019年 102卷 16-25页

作者： Ma, Zhiyuan Luo, Zhongbing Lin, Li Krishnaswamy, Sridhar Lei, Mingkai Dalian Univ Technol NDT & E Lab Dalian 116024 Peoples R China Northwestern Univ Ctr Smart Struct & Mat Evanston IL 60208 USA Dalian Univ Technol Sch Mat Sci & Engn Surface Engn Lab Dalian 116024 Peoples R China

Aim at nondestructively characterizing the interfacial roughness of coatings, ultrasonic reflection coefficient phase spectrum (URCPS) as a function of interfacial roughness is derived based on the phase screen approximation theory [1]. For inhomogeneous coatings, the attenuation coefficient alpha(f) shows a non-negligible effect on the URCPS. The relationship of alpha(f) on frequency f is used to decouple the URCPS. The constructed URCPS is used to determine the interfacial roughness and thickness of specimens through a two-parameter inversion utilizing the cross-correlation algorithm. The effects of the coating inhomogeneity (such as porosity) on the roughness measurement are analyzed through numerical calculation. A series of simulations with interfacial roughness from 6.2 to 12.7 mu m indicate that measurement errors of the thickness are all less than 8.0%. The relative errors of the measured roughness of models without porosity and models with the porosity of 3% are less than 11.8%. For the models with porosity 5%, when the roughness is larger than 10.3 mu m, the relative error is still larger than 11.7%. Ultrasonic experiments were carried out on a tungsten carbide (WC-Ni) coating utilizing water immersion, flat transducer. The WC-Ni coating, with unknown interfacial roughness, was sprayed on a stainless steel using the high-velocity oxygen fuel (HVOF) method. Experimental results show that the interfacial roughness of specimen obtained by the proposed ultrasonic measurement are in good agreement with that of SEM observations, the absolute error of the measured roughness is less than 1.4 mu m and the relative error was less than 11.0%.

关键词： Ultrasonic Phase spectrum WC-Ni coating Interfacial roughness cross-correlation algorithm

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Identification of the Velocity, Thickness, and Interfacial Roughness of Coating Using Full Time-Domain URCPS: cross-correlation-Based Inverse Problem

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JOURNAL OF NONDESTRUCTIVE EVALUATION, DIAGNOSTICS AND PROGNOSTICS OF ENGINEERING SYSTEMS 2019年第1期2卷 011008页

作者： Ma, Zhiyuan Lin, Li Jin, Shijie Lei, Mingkai Dalian Univ Technol NDT&E Lab Dalian 116024 Peoples R China Dalian Univ Technol Sch Mat Sci & Engn Surface Engn Lab Dalian 116024 Peoples R China

Aiming at characterizing interfacial roughness of thin coatings with unknown sound velocity and thickness, we derive a full time-domain ultrasonic reflection coefficient phase spectrum (URCPS) as a function of interfacial roughness based on the phase screen approximation theory. The constructed URCPS is used to determine the velocity, thickness, and interfacial roughness of specimens through the cross-correlation algorithm. The effect of detection frequency on the roughness measurement is investigated through the finite element method. A series of simulations were implemented on Ni-coating specimens with a thickness of 400 mu m and interfacial roughness of 1.9-39.8 mu m. Simulation results indicated that the measurement errors of interfacial roughness were less than 10% when the roughness satisfies the relationship of Rq = 1.6-10.0%lambda. The measured velocity and thicknesses were in good agreement with those imported in simulation models with less than 9.3% error. Ultrasonic experiments were carried out on two Ni-coating specimens through a flat transducer with an optimized frequency of 15 MHz. Compared with the velocities measured by time-of-flight (TOF) method, the relative errors of inversed velocities were all less than 10%. The inversed thicknesses were in good agreement with those observed by optical microscopy with less than 10.9% and 7.6% error. The averaged interfacial roughness determined by the ultrasonic inversion method was 16.9 mu m and 30.7 mu m, respectively. The relative errors were 5.1% and 2.0% between ultrasonic and confocal laser scanning microscope (CLSM) method, respectively.

关键词： ultrasonic phase spectrum interfacial roughness inverse problem cross-correlation algorithm

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