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Sensorless Brushless DC Motor Drive for Frequently Startup
Zhou Genfu,Wu Zhigan,Ying Jianping The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Electrical Mach Vol.b5 No.1
This paper develops a sensorless BLDCM drive for frequently startup. The position information is based on detecting the zero-crossing point of the BEMF that can be directly obtained from the terminal voltage of the floating phase without voltage-dividing and filtering. As a result, this approach makes it possible to detect the rotor position over a wide speed range, especially at a lower speed. A fast startup procedure is also discussed because the induced BEMF signals are not present when motor is at rest. Experimental results shows that the schemes implemented are feasible and the performance achieved are satisfactory.
Reconfigurable Optical Delay Lines Based on Single Folded Waveguides
Linjie Zhou,Tong Ye,Jianping Chen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.42
We propose a novel single folded waveguide-based reconfigurable optical delay line. Due to waveguide self-coupling, light travels back and forth along the waveguide, forming resonances. With two phase shifters embedded in the waveguide, resonance modes and coupling can be conveniently controlled. Under proper phases, the delay line can be reconfigured to perform various types of delays. In particular, when the resonance input and mutual coupling strengths are properly matched, the group delay dispersion can be significantly reduced, favoring an optical signal delay with low distortion. The group delay can be continuously tuned at low tuning power by changing the phases.
Evaluation of Regional Climate Simulations over the CORDEX-EA-II Domain Using the COSMO-CLM Model
Weidan Zhou,Jianping Tang,Xueyuan Wang,Shuyu Wang,Xiaorui Niu,Yuan Wang 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.2
The COSMO-CLM (CCLM) model is applied to perform regional climate simulation over the second phase of CORDEX-East Asia (CORDEX-EA-II) domain in this study. Driven by the ERAInterim reanalysis data, the model was integrated from 1988 to 2010 with a high resolution of 0.22o. The model’s ability to reproduce mean climatology and climatic extremes is evaluated based on various aspects. The CCLM model is capable of capturing the basic features of the East Asia climate, including the seasonal mean patterns, interannual variations, annual cycles and climate extreme indices for both surface air temperature and precipitation. Some biases are evident in certain areas and seasons. Warm and wet biases appear in the arid and semi-arid areas over the northwestern and northern parts of the domain. The simulated climate over the Tibetan Plateau is colder and wetter than the observations, while South China, East China, and India are drier. The model biases may be caused by the simulated anticyclonic and cyclonic biases in low-level circulations, the simulated water vapor content biases, and the inadequate physical parameterizations in the CCLM model. A parallel 0.44o simulation is conducted and the comparison results show some added value introduced by the higher resolution 0.22o simulation. As a result, the CCLM model could be an adequate member for the next stage of the CORDEX-EA project, while further studies should be encouraged.
A New Approach for SINS Stationary Self-alignment Based on IMU Measurement
Jiangbin Zhou,Jianping Yuan,Xiaokui Yue 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-
For the poor observability of azimuth misalignment angle and east gyro drift rate of the traditional initial alignment, a bran-new SINS stationary fast self-alignment approach is proposed. By means of analyzing the characteristic of the strapdown inertial navigation system (SINS) stationary alignment seriously, the new approach takes full advantage of the specific force and angular velocity information given by inertial measurement unit (IMU) instead of the mechanization of SINS. Firstly, coarse alignment algorithm is presented. Secondly, a new fine alignment model for SINS stationary self-alignment is derived, and the observability of the model is analysed. Then, a modified Sage-Husa adaptive Kalman filter is introduced to estimate the misalignment angles. Finally, some computer simulation results illustrate the efficiency of the new approach and its advantages, such as higher alignment accuracy, shorter alignment time, more self-contained and less calculation.
Valley V² Control Technique for Switching Converters with Fast Transient Response
Guohua Zhou,Jianping Xu,Jin Sha,Yanyan Jin 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Valley V² control technique for switching converters is proposed in this paper. By utilizing output voltage ripple as pulse-width modulation ramp and valley voltage of output voltage ripple as additional control variable, valley V² control technique provides faster load transient response than conventional current-mode control techniques. Steady-state and transient performances of switching converters with valley V² control, peak V² control, and current-mode control are compared and verified by experimental results.
Improvement of the Multiple Image Encryption Capacity Using QR Code as a Data Container
Xing Bai,Jianping Hu,Sheng Yuan,Jinchao Wang,Jing Wang,Xin Zhou 한국광학회 2020 Current Optics and Photonics Vol.4 No.4
An image encryption scheme based on the quick response (QR) code as a data container has aroused wide interest due to the lossless recovery of the decrypted image. In this paper, we apply this method to multi-image encryption. However, since the decrypted image is affected by crosstalk noise, the number of multi-image encryptions is severely limited. To solve this problem, we analyzed the performance of QR code as a data container, and processed the decrypted QR code using the proposed method, so that the number of multi-image encryptions is effectively increased. Finally, we implemented a large image (256 × 256) encryption and decryption.
Xi Zhang,Jianping Xu,Jiahui Wu,Bocheng Bao,Guohua Zhou,Kaitun Zhang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.
Asymmetrical Pulse-Width-Modulated Full-Bridge Secondary Dual Resonance DC-DC Converter
Chen, Zhangyong,Zhou, Qun,Xu, Jianping,Zhou, Xiang The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6
A full-bridge secondary dual-resonant DC-DC converter using the asymmetrical pulse-width modulated (APWM) strategy is proposed in this paper. The proposed converter achieves zero-voltage switching for the power switches and zero-current switching for the rectifier diodes in the whole load range without the help of any auxiliary circuit. Given the use of the APWM strategy, a circulating current that exists in a traditional phase-shift full-bridge converter is eliminated. The voltage stress of secondary rectifier diodes in the proposed converter is also clamped to the output voltage. Thus, the existing voltage oscillation of diodes in traditional PSFB converters is eliminated. This paper presents the circuit configuration of the proposed converter and analyzes its operating principle. Experimental results of a 1 kW 385 V/48 V prototype are presented to verify the analysis results of the proposed converter.