Special Column-5G and Internet of Vehicles

Research on LTE-V scheduling method


Author:Li Yanfen,Zhu Xuetian

Author Affilications:Intelligent Network and Terminal Research Institute of China Telecom Co.,Ltd.,Beijing 102209,China

Abstract:Intelligent outgoing promotes vehicles networks from supporting on-board information services to the next generation that supports V2X services. In order to meet the development needs of Vehicles networks, the 3GPP standard has developed two communication modes, PC5 interface and Uu, for LTE-V. Combined with the characteristics of LTE-V services, this paper introduces the Mode3, Mode4 and SPS enhanced scheduling algorithms,and the advantages and disadvantages of each algorithm, which lays a foundation for the communication requirements of low-latency and high-reliability among V2V, V2I and V2P.
Key word:
SPS enhanced

Research on the compatibility between V2X Internet of Vehicles system and FSS at 6 GHz frequency band


Author:Zhang Shaowei

Author Affilications:Intelligent Network and Terminal Research Institute of China Telecom Co.,Ltd.,Beijing 102209,China

Abstract:At this stage, as China is in an important period of transformation and upgrading of manufacturing industry and innovation and development of emerging technology industries, the emerging intelligent industry V2X is increasingly receiving national attention. Based on the fifth-generation mobile communication system(5G), the compatibility between the V2X Internet of Vehicles(IoV) system and the fixed satellite service at 6 GHz is researched through the deterministic calculation, via using the communication model provided by the relevant recommendations and reports of the International Telecommunication Union(ITU). The results show that the V2X IoV system is compatible with fixed satellite service(FSS) at 6 GHz frequency band.
Key word:
Internet of Vehicles
fixed satellite service

Study on the challenge and innovation of the Internet of Vehicles enabled by operators


Author:Chen Jinghua,Bao Fengye,Jiang Yin

Author Affilications:China Telecom E-Surfing Internet of Things Technology Co.,Ltd.,Shanghai 200041,China

Abstract:This paper interprets the evolution route of network service capability provided by telecom operators in traditional Internet of Vehicles industry chain. On the basis of the development trend of future Internet of Vehicles and intelligent transportation, this paper explains the growth bottlenecks and capacity challenges faced by traditional channel service, and analyses the service capability improvement brought by 5G key technologies such as edge computing and network slicing with Internet of Vehicles. This paper also explores the innovation of Internet of Vehicles service mode and business mode that operators can carry out.
Key word:
Internet of Vehicles
network service
multi-access edge computing
network slices

Review and Comment

Overview of task scheduling algorithms in cloud computing


Author:Yang Ge1,2,3,Zhao Xin1,2,Huang Jing1,2

Author Affilications:1.College of Information Technology,Beijing Normal University(Zhuhai Campus),Zhuhai 519087,China; 2.Key Laboratory of Intelligent Multimedia Technology,Beijing Normal University(Zhuhai Campus),Zhuhai 519087,China; 3.Engineering Lab on Intelligent Perception for Internet of Things(ELIP),Shenzhen Graduate School,Peking University, Shenzhen 518055,China

Abstract:The task scheduling in cloud computing and the research status of cloud computing task scheduling algorithm are classified and summarized according to different scheduling goal. Muti-objective task scheduling algorithm can be divided into artificial bee colony algorithm, imperialist competitive algorithm, bat algorithm, cat swarm optimization algorithm. Each algorithm is analyzed and summarized in detail for the advantages and disadvantages. Each algorithm is compared. The related experiment platforms are analyzed and compared.
Key word:
cloud computing algorithm
task scheduling
multi-objective task

Artificial Intelligence

A knowledge-based dialogue system for insurance domain


Author:Dai Wentao1,Lin Shilu2,Zhu Xiaoyan1,Huang Minlie1

Author Affilications:1.Department of Computer Science and Technology,Tsinghua University,Beijing 100084,China; 2.School of Control & Computer Engineering,North China Electric Power University,Beijing 102206,China

Abstract:With the development of interactive intelligence technology, dialogue system becomes more and more practical. Unlike general chat-bots, the dialogue system for specific domain is a practical dialogue system with contextual reasoning and based on knowledge. The insurance domain is a typical specific domain. This paper introduces a basic construction method of the dialogue system in insurance related domain, which can help users to construct a dialogue system in a specific domain and scene quickly and practically, and has the ability of promotion and expansion.
Key word:
dialogue system
knowledge graph
semantic parsing

An SVM improvement prediction in multifactor model for stocks selection


Author:Zhang Weinan,Lu Tongyu,Sun Jianming

Author Affilications:College of Economics and Management,China Jiliang University,Hangzhou 310018,China

Abstract:In this paper, an entire multifactor model has constructed, based on financial indicators. We improve the prediction of the SVM classification in the multifactor model. The ranking method is used for data preprocessing, then SVM predicts the stock return classification. Finally, the distance from data to the hyperplane is used to improve the classification predict. With this strategy, in constituent stocks of CSI500, the portfolio gains 88.96% accumulated return from 2016Q4 to 2018Q1. Technical analysis moving average(MA) and channel breakout(CB) as trading time strategies can decrease fluctuation and drawdown. High frequent data are used to re-construct the MA strategy and get lower fluctuation. This model provides a new research perspective: SVM character is used for prediction improvement, technical analysis for strategy return.
Key word:
multifactor model
stock selection
technical analysis

Microelectronic Technology

A low-power implementation method of half-band filter


Author:Xu Peng

Author Affilications:School of Electronic Science and Engineering,University of Electronic Science and Technology of China,Chengdu 610054,China

Abstract:Half-band filters are often used to achieve 2x extraction of digital signals during digital frequency conversion. For the non-multiplier implementation structure of the decimation filter, the shifting addition is often used instead of the multiplication operation to reduce the use of hardware resources, and the multi-phase decomposition technique is used to reduce the computational complexity of the overall filtering and reduce the overall power consumption of the hardware. Based on this, this paper further proposes a low power consumption implementation method. After verifying the function correctly through Modelsim software simulation, the comprehensive results of Design Complier software show that the proposed structure effectively reduces the power consumption and area of the half-band filter compared with the traditional general shift addition architecture.
Key word:
half-band filter
low power consumption
poly-phase decomposition
digital signal processing

A large dimensional matrix chain matrix multiplier for extremely low IO bandwidth requirements


Author:Song Yukun,Zheng Qiangqiang,Wang Zezhong,Zhang Duoli

Author Affilications:School of Electronic Science and Applied Physics,Hefei University of Technology,Hefei 230009,China

Abstract:Large-dimensional matrix multiplication is often implemented by submatrix block method. The maximum size of the submatrix determines the speed of the entire matrix multiplication. Concerning the problem that the matrix size directly processed by the classical systolic structure is severely limited by the IO bandwidth, this paper proposes a large-dimensional matrix chain multiplier structure with extremely low IO bandwidth requirements, and completes the hardware design implementation and performance verification. The following is the main work of this thesis. Firstly, optimizing the data organization of matrix multiplication, realizing the input matrix size has nothing to do with IO bandwidth, and make maximum use of the internal logic and storage resources of the device. Secondly, according to the optimized data organization form, the chain multiplier hardware is designed for realizing the source data calculation and transmission overlap operation. Thirdly, the adaptability of the multiplier to the matrix scale is enhanced, and the designed chain multiplier can be configured in real time as multiple independent chains, multiple sets of operations in parallel. Lastly, completing the hardware implementation and performance test of chain multipliers of different sizes on the Xilinx C7V2000T FPGA chip. On this chip, the chain multiplier proposed in this paper supports up to 800 arithmetic units, which is 8 times the size of the classic systolic structure. In the same number of operators, the chain multiplier performance proposed in this paper uses only the classical pulsation structure to calculate the IO bandwidth of 1/8 to obtain equal performance.
Key word:
matrix multiplication
IO bandwidth

High-speed PCB circuit power integrity simulation analysis


Author:Meng Xiangsheng,Che Kai,Li Xiaofeng,Li Jiufa,Li Suxuan,He Xueqin

Author Affilications:College of Electrical and Information Engineering,Hubei Automotive Industry Institute,Shiyan 442002,China

Abstract:Aiming at the increasingly complicated high-speed PCB power supply voltage fluctuation problem, a method based on PDN(Power Distribution Network) and target impedance co-simulation design is proposed for the 1.15 V power network. PI(Power Integrity) was studied. Mainly involved in two aspects:(1)DC analysis, by widening the copper area, reducing the return path and other measures to reduce the 1.15 V voltage drop from 9 mV to 2.5 mV, the temperature from 1.3 ℃ to 0.1 ℃, DC current density from 91.340 3 A/mm2 drops to 82.393 5 A/mm2;(2)AC analysis, from the resonance distribution and PDN input impedance analysis, add 22 μF decoupling capacitor at the 987.34 MHz resonance point to build a decoupling network to remove the risk point. The simulation results show that the method effectively reduces the risk of potential voltage fluctuation and target impedance mismatch in high-speed PCB circuits, thus improving the stability and reliability of the power system.
Key word:
power integrity
target impedance

A 6.4 ppm/℃ and low power consumption bandgap voltage reference


Author:Pan Hongze1,Wang Dongxing1,Song Mingxin2

Author Affilications:1.School of Sciences,Harbin University of Science and Technology,Harbin 150080,China; 2.Hainan University,Haikou 570228,China

Abstract:This paper proposed an innovative CMOS bandgap reference with both low current consumption and high precision over a wide temperature range. The proposed bandgap reference was designed using a standard 0.18 μm CMOS technology. The high precision method can make impedance varied with temperature. While the temperature is rising, the increased impedance can compensate the nonlinear of Vbe. And by improving the structure of conservative bandgap reference, current consumption was extremely shrunk. Measured results have shown the temperature coefficient is 6.4 ppm/℃ over a wide range of -40 ℃~150 ℃. The total power consumption is 1.2 μW while the voltage supply is 5 V.
Key word:
bandgap reference
low current consumption
high precision
varied impedance

A hardware Trojan attack protection method for CGRCA configuration bitstream


Author:Liu Min1,Yan Yingjian1,Nan Longmei1,2

Author Affilications:1.The PLA′s Information Engineering University,Zhengzhou 450001,China; 2.State Key Laboratory of Applied Integrated Circuits and Systems,Fudan University,Shanghai 200433,China

Abstract:A protection method based on authentication and encryption hardware security engine is proposed as the reconfigurable device configuration bitstream is vulnerable to hardware Trojan attacks. Firstly, the security threats of system are analyzed in detail and the possible hardware attack process and implantation method for unencrypted original configuration flow are proposed, via researching on the structure and configuration process of coarse-grained reconfigurable cryptographic array(CGRCA). Aiming at the attack process, a protection method based on advanced CCM authentication and encryption is proposed. The method partially encrypts and authenticates the original configuration bitstream in software, and uses a dual security engine for decryption and authentication on the hardware to ensure the integrity and authenticity of the configuration bitstream. The experimental results show that the protection method can protect the configuration bit stream by protecting the configuration flow from potential hardware Trojan attack threat with small area and time overhead.
Key word:
hardware Trojan protection
coarse-grained reconfigurable cryptographic array
configuration bitstream protection
dual hardware security engine

Measurement Control Technology and Instruments

Design of portable multi-channel high precision acquisition system based on FPGA


Author:Wang Wei1,Lu Xiangyu2,Zhang Qiuyun1,Yu Hengsong3

Author Affilications:1.School of Information Engineering,Southwest University of Science and Technology,Mianyang 621000,China; 2.Key Laboratory of Aerodynamic Noise Control,China Aerodynamic Research and Development Center,Mianyang 621000,China; 3.School of National Defense of Science and Technology,Southwest University of Science and Technology,Mianyang 621000,China

Abstract:In order to meet the high-speed, parallel and high-precision data acquisition of the multi-point sensitive pressure sensor signals on the surface of the rotor blade, and with the functions of program-controlled gain amplification and anti-aliasing filtering, a portable multi-channel high precision front-end acquisition system with FPGA as the core control unit is designed. The measured signals are processed by signal conditioning and filtering module to improve the quality, and then collected by ADC sampling module, and finally the acquired data are transmitted to the main control board for analysis and processing through SPI bus in real time,achieving synchronous and high-precision acquisition of multi-channel signals. The test results show that the system has stable performance, in small signal acquisition under large interference environment, the amplitude accuracy can attain 0.1%, the spurious-free dynamic range can reach up 60 dBc. The system utilizes a portable design, small size, low cost, strong scalability, and has a good application value.
Key word:
multichannel acquisition

Design of multi-channel data acquisition system based on FPGA in rotating environment


Author:Yi Zhiqiang,Han Bin,Xian Long,Li Wei

Author Affilications:School of Information Engineering,Southwest University of Science and Technology,Mianyang 621010,China

Abstract:In order to meet the real-time and high-precision multi-channel acquisition requirements of a large rotating machinery equipment in the monitoring process, this paper proposes a design scheme of multi-channel vibration signal acquisition and detection system based on FPGA. The system adopts the master/slave FPGA architecture and realizes the 128-channel parallel real-time data acquisition function with a sampling frequency of 100 kHz in the strong noise environment. Then, by designing a random resonance signal detection system with adjustable parameters, the signal-to-noise ratio of the signal is improved and the accuracy of the system detection in the rotating environment is enhanced. The test shows that the system has good real-time performance, stability and effectiveness.
Key word:
rotating machinery
data acquisition
stochastic resonance

Communication and Network

An improved weighted centroid location algorithm based on fingerprint quantization


Author:Gao Yuan1,Yang Yuan2

Author Affilications:1.Xuzhou College of Industrial Technology,Xuzhou 221000,China; 2.School of Instrument Science and Engineering,Southeast University,Nanjing 210096,China

Abstract:An improved weighted centroid location algorithm based on fingerprint quantization is proposed to solve the problem of large interference and low positioning accuracy in indoor personnel positioning signals. In the ZigBee communication environment, the fingerprint database is established by collecting the actual measured values. In the quantization domain, the quantized distance and the quantized RSSI value are obtained according to the RSSI value received by the unknown nodes. The quantized distance and the quantized error are taken as the weight parameters. The improved intersection triangle weighted centroid algorithm is further used to locate the unknown nodes. The experimental results show that the algorithm can effectively avoid the theoretical error caused by serious signal attenuation and improve the positioning accuracy.
Key word:
weighted centroid

Implementation of BRNs routing protocol based on YunSDR-Y450


Author:Ren Neng

Author Affilications:Department of Electronic Engineering,Tsinghua University,Beijing 100089,China

Abstract:The barrage relay networks(BRNs) is a new multi-hop self-organizing network routing protocol proposed by the tactical Internet. The protocol utilizes the broadcast characteristics of the wireless network to implement routing and data transmission, and has the characteristics of low overhead, low latency and high robustness. It can adapt to a complex and varied network environment. This paper completed the development and testing of routing protocols based on the YunSDR-Y450 RF communication hardware. The implementation scheme is based on the time division multiple access technology and the autonomous cooperative technology, and completes the establishment of the control barrage region by transmitting routing control messages(requests and replies). The node processes the key values in the routing control message, and then determines the local transmission attribute in the control barrage region, thereby completing the routing process. Messages can be transmitted quickly in a control barrage region, and the delay depends mainly on the physical transmission speed.
Key word:
barrage relay networks
self-organizing network communication
routing protocol development

Design and implementation of SPCB-based processor directly connected low delay PCS


Author:Wu Jianxiao1,2,Wang Peng3,Wu Tao1,Gao Peng1,Chen Wentao4,5

Author Affilications:1.Shanghai Advanced Research Institute,Chinese Academy of Sciences,Shanghai 200120,China; 2.University of Chinese Academy of Sciences,Beijing 100049,China; 3.School of Computer Engineering and Science,Shanghai University,Shanghai 200444,China; 4.Shanghai Si-future Electronics & Technology Co.,Ltd.,Shanghai 201411,China; 5.State Key Laboratory of Mathematical Engineer and Advanced Computing,Wuxi 214125,China

Abstract:SERDES(serial de-serialization) technology has become the mainstream physical layer specification of high-speed interface due to its high transmission rate and strong capacity of resisting disturbance. However, the upper PCS(physical coding sublayer) needs to set elastic buffering, code, encode and do other functions, so the system transmission delay is high. SERDES cannot be directly applied to delay sensitive applications such as processor direct connection. This paper introduces a design of PCS architecture based on synchronous phase compensation buffer(SPCB), which can be applied to delay sensitive SERDES transmission system. This architecture features high throughput and ultra-low latency. With a custom SPCB, the transmission reception path delay is about 10 ns at 32 Gb/s per lane, which is about half of the typical PCS delay in the industry, reaching the level of Intel(QPI) and AMD(HT) interface. This PCS architecture can be realized through 28 nm/16 nm/7 nm chip manufacturing tech, and has been applied to a variety of domestic processor.
Key word:
synchronous phase compensation buffer(SPCB)
low delay
processor direct connection

Computer Technology and Its Applications

A mixed single image motion deblur method


Author:Wang Siyu,Li Liangrong,Gu Ping,Li Zhen

Author Affilications:College of Big Data and Information Engineering,Guizhou University,Guiyang 550025,China

Abstract:The blind recovery of images is a difficult problem in the field of digital image processing. Researching the restoration of motion blurred images,a hybrid single image motion deblur method is proposed. Firstly, the PSF is estimated, then the latent image is evaluated by PSF and original blurred image, and the edge restoration, fuzzy kernel estimation and deconvolution are iterated several times. The adaptive unblind deconvolution method is used to obtain high quality deblurred image. Finally, compared with the experimental results of two classical algorithms, Wiener Filter and Lucy Richardson, the experimental results show that the proposed algorithm has strong ability to maintain details and better deblurring effect.
Key word:
motion blur
image restoration
edge restoration
fuzzy kernel estimation

Underwater polarization image restoration based on Laplacian algorithm


Author:Li Lei1,2,Guo Tiantai1,Pan Sunqiang2,Chen Huan2,Zhao Jun1,Kong Ming1

Author Affilications:1.China Metrology University,Hangzhou 310000,China;2.Zhejiang Institute of Metrology,Hangzhou 310000,China

Abstract:In order to solve the problem of underwater image quality degradation in the process of ship navigation,the image contrast enhancement technology and image enhancement algorithm based on polarization imaging were studied. In this technique, different angle fusion images are decomposed into multi-scale Pyramid image sequences based on polarization information. Gaussian convolution and Laplacian Pyramid algorithm are used for image fusion. Compared with the wavelet transform image fusion algorithm, it can be concluded that the SNR and SSIM values of underwater images are improved obviously. Experiments show that with attenuation coefficient of 2.1, the underwater imaging distance of the underwater polarization system reaches 6 m in the seawater environment, can clearly identify the objects and their characteristics in the water, and the system operates stably.
Key word:
underwater laser imaging
polarization imaging
Laplacian algorithm
image fusion

Nonlinear fitting comparison of capacitive displacement sensors


Author:Zhang Han1,Bo Hanliang2,Wang Shuai1,Yang Wenlong1,Fu Yifan1

Author Affilications:1.National Computer System Engineering Research Institute of China,Beijing 100083,China; 2.Institute of Nuclear and New Energy Techgology,Tsinghua University,Beijing 100084,China

Abstract:Aiming at the relationship between capacitance and displacement of the rod position indicator sensor when the control rod drops, the data of the control rod are calibrated in four different working conditions at the horizontal position. One half of the maximum and minimum capacitance values obtained from the calibration are taken as the fitting values. The data are fitted by cubic spline interpolation, least square method and BP neural network method respectively, and then the data are fitted by using the method of cubic spline interpolation, least square method and BP neural network. The original data obtained under four working conditions are interpolated and observed errors are analyzed. The results of MATLAB fitting show that cubic spline interpolation has a good effect.
Key word:
capacitive displacement transducer
cubic spline interpolation
nonlinear fitting

A correction method of spin-stabilized satellites attitude control based on infrared benchmark


Author:Zhou Jinbiao1,2,Li Yonggang2,Guo Libing2,Li Xiangming2,Mao Wen2

Author Affilications:1.Trainee Team 2 of the 49th Joint Operational Command Training Course of National Defense University,Beijing 100091,China; 2.China Satellite Maritime Tracking and Control Department,Jiangyin 214431,China

Abstract:Aiming at the problem that there is a large deviation of the spin-stabilized satellite using infrared benchmark for attitude controlling, the control theory of isoclinic angle is described firstly, the difference between the solar reference and infrared benchmark on attitude controlling is analyzed,the main cause leading to the large deviation using infrared benchmark is also explained. A method of execution angle compensation and correction is put forward finally. Verified by simulation, the control precision is improved effectively after execution angle correction.
Key word:
attitude contro
execution angle correction
infrared ground reference

Application of machine vision in capacitor appearance defect detection


Author:Yu Yang,Chen Zuozheng,Chen Zhuyang,Shen Weijun

Author Affilications:Jiangsu University of Technology,Changzhou 213001,China

Abstract:The traditional capacitor appearance defect detection adopts manual detection, which has low efficiency, high error rate and high cost. In order to overcome the shortcomings of manual detection and improve the automation of capacitor production, a machine vision based capacitor defect detection system is designed. Firstly, the image is collected, pre-processed, and matched to the capacitor area. Then the threshold segmentation is used to detect the defects of the overflow and epoxy surface pores. The template matching is used to detect the characters and the shell damage defects. Finally, to meet the testing requirements of different standards,the Blob analysis is used to extract the defect features and set the threshold parameters. According to the experimental results of the prototype, the detection system greatly improves the detection efficiency and accuracy.
Key word:
machine vision
capacitance appearance
defect detection
threshold segmentation
template matching

Embedded Technology

Design of missle-borne SAR signal processing system based on FPGA and DSP


Author:Chen Yong1,2

Author Affilications:1.School of Physics and Electronics Electrical Engineering,Huaiyin Normal University,Huai′an 223300,China; 2.School of Electronic and Optical Engineering,Nanjing University of Science and Technology,Nanjing 210094,China

Abstract:A missile-borne SAR(synthetic aperture radar) signal processing system based on the hardware structure of the cooperative processing of FPGA and DSP is presented in this paper in view of the heavy calculation and the poor real time performance. The XC2VP30 of Xilinx company and TMS320C6416 of TI company is used to realize the preprocessing of echo data and the processing of imaging algorithm respectively. The system improved the efficiency of image processing and solved the problems of parallelism and speed. The feasibility of the system is verified by the orbital experiment in the field.
Key word:
synthetic aperture radar
signal processing

Power Management

A control method for interleaved Boost PFC converter


Author:Lin Anna,Xie Yunxiang

Author Affilications:School of Electric Power,South China University of Technology,Guangzhou 510640,China

Abstract:In order to solve the problem of complexity of zero-crossing detection and distortion of input current waveform, a novel control method is proposed for interleaved Boost PFC converter operates in critical conduction mode. This method is based on a new switching voltage detection circuit. By detecting the drain-source voltage of MOS transistor, the zero crossing signal is obtained through the comparator, and switch achieves zero voltage switching or valley switching, which greatly reduces the switching loss. Adopting the switch conduction time compensatory strategy, it improves the average inductor current and distortion of input current waveform caused by resonance between inductance and parasitic capacitance of MOS transistor. Finally, an 800 W prototype is built and experimental results show the efficiency and feasibility of this method.
Key word:
Boost PFC
critical conduction mode
zero crossing signal
zero voltage switching

Design of cooling system in space solar array simulator


Author:Zhang Jian1,2,Wang Zicai1,Zhang Hua2,Zhang Donglai3

Author Affilications:1.School of Astronautics,Harbin Institute of Technology,Harbin 150001,China; 2.Shenzhen Academy of Aerospace Technology,Shenzhen 518057,China; 3.School of Mechanical Engineering and Automation,Harbin Institute of Technology(Shenzhen),Shenzhen 518055,China

Abstract:For the high power solar array simulator, the requirements such as high power, miniaturization and modularization are higher. In this paper the total power of the simulator is 2.4 kW with the chassis height is no more than 2U. The forced air cooling is adopted. The modular structure is used in the forced cooling system according to the electrical connection requirement. The chassis is divided into three parts, the linear, the multilevel and the Vicor module. And the independent cooling air duct system is set up for each part. The contractile air duct of the multilevel and the Vicor part are optimized mainly. The forced air cooling system with the optimization design can satisfy the high power density requirements of the simulator. The maximum case temperature of the components can be controlled under 88 ℃, and all the devices in the simulator can work safely and reliably. The results are verified by both finite element simulation and thermal test.
Key word:
forced air cooling
cooling system
air duct optimization

Reliability analysis of cooling fans and their impact on UPS system


Author:Sun Haihua

Author Affilications:Zhejiang Post and Telecommunication College,Shaoxing 312000,China

Abstract:The heat generated in the operation of UPS system is dissipated by cooling fans. Compared with natural convection cooling, the cooling effect of fan is better, and the temperature in the system can be reduced up to 30 ℃. The expected life of electronic components requires extensive modeling, laboratory testing and field verification. In UPS system, if the fan fails, the velocity of air flow used for forced cooling air will decrease, and the temperature of components in the system will rise. In order to achieve the expected life of UPS system, periodic maintenance and replacement of cooling fans are needed. This paper briefly discusses the effect of temperature on insulation aging, the difference between natural convection and forced convection, the reliability modeling of cooling fans and how periodic maintenance improve the reliability of UPS system.
Key word:
cooling fans
UPS system reliability
expected life

Research on photovoltaic grid-connected inverter control by predictive current


Author:He Songyuan,Sha Guorong

Author Affilications:Nanjing Institute of Industry Technology,Nanjing 212013,China

Abstract:A kind of control method which is suitable for photovoltaic grid-connected is introduced in this paper. It can solve the problems of the parameters set difficult and the system static error of the PI control method. For the shortcomings of static error of traditional PI control, the system adopts deadbeat control adjustment based on predictive current method and analyses the control delay of inductance parameters. The control method can effectively reduce total harmonic distortion. Feasibility and correctness of the improvement program are verified by simulation and experimental results.
Key word:
photovoltaic gird-connected
predictive current

Design of 200 W full digital switching power supply


Author:Rao Gang,Wang Wei

Author Affilications:College of Machinery and Automation,Wuhan University of Science and Technology,Wuhan 430081,China

Abstract:By using a bridgeless PFC and a half-bridge LLC resonant converter as the main conversion topology of the digital switching power supply, the all-digital control PFC and DC-DC converter based on the STM32 series of microcontrollers, firstly the digital switching power supply scheme is compared, and then the overall scheme of 200 W digital switching power supply is expounded, and the bridgeless PFC and half-bridge LLC converter of digital switching power supply are systematically studied.
Key word:
bridgeless PFC
LLC resonant circuit
STM32 series microcontroller
full digital control