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95 results on '"Zhao, Changhai"'

1. Automatic compensation system for eccentricity error of absolute optical encoder.

Author

Zhao, Changhai, Wan, Qiuhua, and Liang, Lihui

Abstract

Eccentric error is a vital part of high-precision optical encoder error. An automatic error compensation system is designed to lower the eccentric error of the encoder. On the periphery of the fan-shaped code path of the traditional encoder disk, a set of radial code paths is drawn. This radial code path is composed of several concentric circles with alternating light and dark lines. The direction of the radial code path is perpendicular to the direction of the fine code path. When the encoder rotates, the eccentricity of the encoder disk is measured by the moiré fringe signal output from the radial code channel. Based on the eccentricity error compensation algorithm, the eccentricity error of the encoder disk is compensated in real time to enhance the accuracy of the encoder. The experimental results of an encoder show that the mean square error of the encoder before the eccentricity error compensation is 21.25 arc seconds, and it is 3.66 arc seconds after compensation by this algorithm. The algorithm can significantly compensate the error caused by the eccentricity of the encoder and greatly improve the accuracy of the encoder. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Analysis and Elimination of Grating Disk Inclination Error in Photoelectric Displacement Measurement

Author

Yu, Hai, Wan, Qiuhua, Liang, Lihui, and Zhao, Changhai

Abstract

As core elements of photoelectric displacement measurement, installation coaxiality and rotation parallelism are the main factors affecting measurement accuracy. When there is a processing error or an offset in the installation process of structural elements, the plane of the grating disk will be tilted, which seriously affects the accuracy of angular displacement measurements. In this study, error caused by inclination of the grating disk was analyzed and a method to eliminate this error presented. First, an error model was established by analyzing the mechanism of measurement error caused by grating disk tilting, analysis showed that the error caused by grating disk tilt showed a “double cycle” fluctuation in the circle. Then, by using “double cycle” fluctuation, a method for eliminating errors was presented. Finally, the validity of the proposed theory and method was verified by simulation and experimentation. To eliminate errors, angular displacement measurements needed to be made using at least three reading heads to produce a mean. In these experiments, when the grating disk was tilted, the error was perfectly eliminated using three reading head measurements. The experimental results verified the validity of the proposed theory, which provided a theoretical basis for improving the displacement measurement accuracy.

Published
2024
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5. Parallel Kirchhoff Pre-Stack Depth Migration on Large High Performance Clusters

Author

Li, Chao, Wang, Yida, Zhao, Changhai, Yan, Haihua, Zhang, Jianlei, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Wang, Guojun, editor, Zomaya, Albert, editor, Martinez, Gregorio, editor, and Li, Kenli, editor

Published
2015
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9. A Parallel Algorithm of Kirchhoff Pre-stack Depth Migration Based on GPU

Author

Wang, Yida, Li, Chao, Tian, Yang, Yan, Haihua, Zhao, Changhai, Zhang, Jianlei, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Kobsa, Alfred, Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Sun, Xian-he, editor, Qu, Wenyu, editor, Stojmenovic, Ivan, editor, Zhou, Wanlei, editor, Li, Zhiyang, editor, Guo, Hua, editor, Min, Geyong, editor, Yang, Tingting, editor, Wu, Yulei, editor, and Liu, Lei, editor

Published
2014
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26. High precision angular displacement measurement based on self-correcting error compensation of three image sensors

Author

Yu, Hai, Wan, Qiuhua, Lu, Xinran, Zhao, Changhai, and Liang, Lihui

Abstract

As the feedback link of a numerical control system, the measurement accuracy of absolute angular displacement measurements directly affects the control performance of a numerical control system. In previous research, angular displacement measurements based on dual image sensors can achieve higher measurement performance. However, the elimination of harmonic error by the dual image sensor is still limited. For this reason, this paper proposes an image-type angular displacement measurement method based on self-correction error compensation of three image sensors. First, the mathematical model of harmonic error is established, and the shortcomings of using dual image sensors to compensate the error are analyzed. Then, a high precision angular displacement measurement method based on three image sensors is proposed. Finally, the self-correction error compensation method of three image sensors is applied to the angular displacement measurement system, and the measurement performance is verified. The experimental results show that a measurement accuracy of 1.76^′′ can be achieved on the circular grating with a diameter of 96 mm. In contrast, the dual image sensor can only achieve a measurement accuracy of 2.88^′′. It is concluded that the odd number of image sensors can achieve higher measurement accuracy than the even number. This research lays a foundation for the realization of high precision image angular displacement measurement.

Published
2022

33. Fto Deficiency Reduces Anxiety- and Depression-Like Behaviors in Mice via Alterations in Gut Microbiota

Author

Sun, Lijuan, primary, Ma, Lanjing, additional, Zhang, Haohao, additional, Cao, Ying, additional, Wang, Chenchen, additional, Hou, Nannan, additional, Huang, Niu, additional, von Deneen, Karen M., additional, Zhao, Changhai, additional, Shi, Yupeng, additional, Pan, Yan, additional, Wang, Meixia, additional, Ji, Gang, additional, and Nie, Yongzhan, additional

Published
2019
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42. Discussion on key factors of PS-wave Kirchhoff time migration

Author

Zhao Changhai, Qian Zhongping, Yue Yubo, Shi Yunyan, and Wang Shihu

Subjects
Data processing, Operator (computer programming), Flow (mathematics), Computer science, Aperture, Calculus, Linear interpolation, Algorithm, Convolution, Image (mathematics), Interpolation
Abstract

PS-wave Kirchhoff time migration is a crucial step in the converted wave data processing flow. However, because of the different propagation mechanisms of downing-going P-waves and up-going S-waves, its implementation is quite different from that of PP-wave migration. In order to obtain an optimal image, we discuss several important technical issues of PS-wave Kirchhoff time migration, including amplitude weighting, operator anti-aliasing and migration aperture selection, and propose to use cubic convolution interpolation method to calculate the parameters at fine image grids so as to eliminate the influence of non-smoothness caused by traditional linear interpolation method on the migration operator. Tests on real datasets demonstrate the validity of our method.

Published
2015

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