Table of Content

30 September 2007, Volume 25 Issue 5

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Articles

Differential Space-Time Block Code for Correlated MIMO Channels

QIAN Yi-qun;QIAN Ye-wang;YANG Lu-xi

2007, 25(5):  441-441 . 

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A scheme of designing differential space-time code is proposed for correlated fading MIMO channels. The design criterion is to minimize the upper bound on the average pairwise error probability of differential detection. The optimal design requires knowledge of correlation both in the transmitter and the receiver, which must be obtained numerically. By ignoring receiver correlation, the amount of feedback can be reduced and a closed-form suboptimal solution can be obtained. Simulation results show that the proposed design improves the error performance, and the suboptimal design performs close to the optimal design.

Blind Source Separation Using Adaptive Kernal Function Spatial Time Frequency Distribution

MA Ming;SHEN Yue-hong

2007, 25(5):  446-446 . 

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Blind source separation (BSS) based on spatial time frequency distribution can separate signals with different time frequency distributions. However the cross terms in the time frequency distribution affect the BSS performance, and different time frequency distributions have different abilities in reducing cross terms. While most current BSS methods are based on fixed kernel functions, we propose BSS based on adaptive time frequency kernel function to improve the performance of resisting cross terms. The proposed technique has strong ability of removing cross terms and is immune to noise. Computer simulations show that the performance of the proposed algorithm is better than that of those using Cohen class time frequency distributions in environments with or without noise.

AM Broadcasting Scheme Based on Compound Modulation

QI Chen-hao;WU Le-nan;ZHANG Shi-yuan

2007, 25(5):  451-451 . 

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A compound modulation scheme based on digital amplitude modulation broadcasting (DAMB) and very minimum additive waveform keying (VMAK) was discussed in the paper, which sufficiently utilized the limited AM bandwidth. Simulations show good BER performance of both modulation schemes under certain conditions.

A Back-Scatter Based Universal Testing System for UHF RFID

WANG Ping.;HU Ai-qun;ZHAO Hong-xin

2007, 25(5):  456-456 . 

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A universal standard testing platform is designed based on research of the back-scattering mechanism of UHF RFID systems. Techniques needed for modulation, encoding and anti-collision are studied and implemented on the platform. Power supply, signal detector, reflector and controller of the Tag is designed and discussed, and impedance of the circuits calculated and matched. Design of the reader of this platform is also presented. The system can be used as a platform for various protocols of RFID and narrow bandwidth communications.

Performance Analysis of Cluster Head Election Algorithm in LEACH

YU Lu;LIU Li

2007, 25(5):  461-461 . 

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The low energy adaptive clustering hierarchy (LEACH) protocol is an early wireless sensor network protocol. In this paper, simulation of wireless sensor networks using LEACH is given based on the sensor network simulator developed in the authors’ laboratory. The simulation focuses on the MAC layer and network layer while considering the actual hardware parameters. Performance of the cluster head election algorithm is analyzed in theory in terms of the statistic data obtained from the simulation. The advantages and disadvantages of the algorithm are presented along with an improvement mechanism.

Band-Notch for CPW-Fed Printed Monopole Antenna

YAN Xiao-rong;ZHONG Shun-shi;CHEN Kuang-da

2007, 25(5):  466-466 . 

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A compact rectangular monopole antenna fed by a tapered coplanar waveguide (CPW) with a band-notch function is proposed. A U-shaped slot is cut in the radiation patch to obtain the band-notch function and its parameters studied in detail. It is shown that the band-notched function can be realized by controlling location of the U-shaped slot. The notched band can be changed by adjusting the length and the width of the slot. Experimental results show that the proposed antenna has a stop-band of 5.07GHz to 5.85 GHz and a super- wideband characteristic, with impedance bandwidth reaching 15:1.

Frequency-Reconfigurable Antenna with Alterable Feed Configuration

DING Xiao;JIANG Xing;LI Si-min;Fang jian-gui

2007, 25(5):  469-469 . 

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The antenna introduced in this paper is frequency-reconfigurable and the feed configuration can be changed, with the length of a rectangular slot being changed using an RF MEMS switch. The principle of frequency reconfigurability is analyzed both from antenna’s equivalent LC oscillation circuitry and from the changing route of resonant tank’s current. The results indicate that the antenna can operate at three frequency bands: bluetooth, DCS/GSM and GPS, all in the L/S band. Due to the same radiation mode, the radiation pattern of the antenna operating in the 3 bands is exactly the same. Changeable feed configuration using RF MEMS switch can solve the matching problem directly originating from the change of radiator structure. The results also show that the antenna has good reconfigurability and high radiation gain. The antenna can be used for multiple purposes.

Effective VLSI Architecture for Multi-level Recursive Discrete Lifting Wavelet Transform

CAO Peng;WANG Chao;LI Jie

2007, 25(5):  475-475 . 

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In this paper, a lifting-based recursive algorithm (LRA) is proposed for multi-level discrete wavelet transform (DWT) by interleaving calculation of different level DWT. As an example, we propose an architecture for multi-level 9/7 DWT with lifting scheme by using LRA.It is synthesized and implemented for Altera’s StratixⅡFPGA EP2S60 and can work under a clock frequency of 80 MHz. Performance analysis and comparison results demonstrate that the proposed architecture have good performance in terms of computing time, hardware utilization, and power consumption. Compared to other existing architectures,the hardware utilization of rate is up to 22% higher.

Hardware/Software Co-verification Environment and Co-Design Method

GAO Gu-gang;SHI Long-Xing;YANG Jun

2007, 25(5):  481-481 . 

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This paper presents a novel SoC co-verification environment based on the C simulation strategy. Using a hardware/software co-verification environment, we propose a hardware/software co-design method for computation-intensive applications. For most important verification issues of co-design, we use a hierarchical verification method. We propose a verification strategy based on a C reference model on the IP level, and co-verification based on C simulation on the system level. The design example of a low cost MPEG-4 decoder SoC is used to show validity of the method

Camera Calibration in Computer Vision Based on Artificial Neural Network

SUN Xianbin;LI Dehua;YIN Jie;XIONG Caiquan

2007, 25(5):  486-486 . 

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We combine the traditional photogrammetry calibration with neural network in this paper to overcome instability and computation complexity due to nonlinearity factors such as aberration. Calibration parameters for computer vision are obtained based on neural networks, and the unknown point world coordinates calculated with a five-step method. In traditional photogrammetry calibration, a calibration block is needed, with some control points that require accurate determination of three dimensional coordinates. To achieve high accuracy, these points must be evenly distributed in a three dimensional space, and the coordinates measured with high precision. It is difficult to make the calibration block, especially a big one. We propose to move the calibration plate along its normal direction instead of using a calibration block. The moving plate is a three dimensional block. While achieving a three-dimensional effect, it significantly increases the number of control points. Furthermore, the plate is much easier to make than a three dimensional block. Experimental results show that the proposed neural network based method with moving calibration plate can provide high accuracy and stability

Accurate Position Control of Multiple Joint Robot Driven by Ultrasonic Motors

SUN Zhi-jun;XING Ren-tao;ZHAO Chun-sheng;HUANG Wei-qing

2007, 25(5):  493-493 . 

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In this paper, according to the operating characteristics of ultrasonic motors, a new velocity-position feedback control strategy is proposed and implemented in a three-joint robot directly driven by ultrasonic motors.Results show that, the robot can achieve high positional resolution under position feedback control; however the robot will quiver due to the quick change of the speed of ultrasonic motors. The robot can operate smoothly under velocity feedback control; however the positional resolution is worse. The proposed control strategy can achieve the best performance of the robot, i.e. higher position accuracy and smooth operation.

Optimization of Hybrid Electric Vehicle Power System Using Fuzzy Logic Control

ZHOU Chun-guo;LIU Hong-zhao;LI Xin;CUI Ya-hui

2007, 25(5):  500-500 . 

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We study multi-target optimization of the power system of hybrid electric vehicles aimed at fuel saving and emission minimization. A fuzzy logic control strategy is used to realize different control targets. The structure chart and inference rule of the fuzzy logic control system is established, with emphasis on the discussion of the fuzzy control method and process. Two operation modes are simulated with the software, under ordinary electric control and fuzzy logic control, respectively. Curves of SOC change are obtained. Comparison between the control effects indicates that the fuzzy logic control strategy is suitable for the control of hybrid electric vehicles.

Compensation for Coning Error of Pure Filtered Angular Rate Input

ZENG Qing-hua;LIU Jian-ye;ZHU Yan-hua;LAI Ji-zhou

2007, 25(5):  505-505 . 

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To improve the precision of fiber optic gyro strapdown inertial navigation system (FOG SINS), a cone-error compensation algorithm with pure filtered angular rate input is proposed. From the different coning effects of the physical quantity before and after filtering, the rule of coning error is analyzed. Combined with the angular increment algorithm using angular rate, compensation coefficients and the dominant terms of the coning error compensation algorithm in SINS with pure filtered angular rate input are derived. Results of simulation with the characteristics of real FOG IMU indicate that the proposed coning compensation algorithm is two or three orders better in precision than the traditional attitude algorithm. Coning compensation with pure filtered angular rate input is closer to the actual system. It has theoretical and practical values for improving attitude accuracy of SINS made up of angular rate gyros.

Automatic-Extraction of Wavelet Energy Features for Rotor Fault Signals

DENG Yan;CHEN Guo

2007, 25(5):  510-510 . 

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A new method based on wavelet transform is proposed to extract rotor fault signal energy features automatically. The method is motivated by multi-frequencies analysis and the scaling transform theory is applied to resample the original signal at certain time interval. The re-sampled signal is decomposed into a predefined layer with wavelet transform, and the energy features of the frequency band are acquired. It can eliminate the effect of rotor speed and sampling frequency on the distribution of wavelet analysis frequency band. Energy features of the frequency band have unified physical meanings. In a simulation setup of the ZL-3 multi-function rotor, we simulate 128 samples including 4 kinds of common rotor faults, namely, imbalance, rub-impact, oil whipping and misalignment, extract the samples’ energy features, and construct integrated neural networks to recognize the samples’ faults. The results show validity of the proposed method.

Experimental Study on Frequency-Domain Characteristic of Surge

CAO Ju-jinag;LI Yan;SUN Tao

2007, 25(5):  516-516 . 

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This paper studies dynamic pressure signals from the state far from surge to the state of fully developed surge in the centrifugal compressor using a correlation integral method to quantify various stages in the surge development. The measured data in the transitional stage and the surge stage are analyzed using FFT to obtain the exact frequency of surge and its precursor with high-resolution spectrum. Variation of the spectrum peak with time in the fixed zoom region is obtained through a continuous spectral analysis. It is illustrated that the dominant frequency in the transitional stage and the surge stage fluctuates mildly around these two frequencies.

Simulated Annealing with Sorting for Gate Assignment in Hub Airport

CHEN Xin;LU Xun;ZHU Jin-fu

2007, 25(5):  520-520 . 

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It is important to reduce transfer time in hub airports with real-time gate assignment. However, the gate assignment problem (GAP) is an NP-hard problem, and traditional heuristic algorithms do not provide satisfactory solutions. We propose a new simulated annealing algorithm integrated with a sorting strategy to resolve the GAP. An initial solution is obtained through sorting each gate preference value and flight load factor. An optimal solution is then obtained using the traditional simulated annealing algorithm. Case studies show the simulated annealing algorithm with a prior sorting process can provide better results than the traditional simulated annealing algorithm. Computation efficiency is also better than CPLEX with an acceptable convergence rate. The proposed algorithm provides a new ways to resolve the GAP in hub airports.


Demand and Application of Aero-spare Parts Based on Generalized Renewal Process

CHEN Feng-teng;ZUO Hong-fu;NI Xian-cun

2007, 25(5):  526-526 . 

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In view of the 6 types of performance failure rate of aerial equipment, we establish corresponding fault distribution models to meet and predict the demand of aero-spare parts. Considering the degree of repairing, we analyze the failure data by applying a generalized renewal process and estimate the parameter values of repair degree. We then calculate the average failure number of non-repairable and repairable parts in a Monte Carlo simulation. Finally we compare the results of perfect repair and general repair with an example. The presented method is more reasonable than previous ones with prospect of practical applications.

Prediction of Fretting Fatigue Life of Dovetail Joint under LCF

GU Yuan-xing;WEN Wei-dong;CUI Hai-tao

2007, 25(5):  531-531 . 

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A factor of friction power is considered during fatigue, and a new model for predicting fretting fatigue life under low cycle load is presented based on a nominal stress method. For dovetail joint, the problem of elastic contact is solved using the finite element method. Distribution of contact stress and contact status of dovetail joint are obtained, and the location of fretting fatigue crack predicted. With the stress field and contact status of the location,low cycle fatigue(LCF) of the joint can be predicted. Some parameters in the model are evaluated in theoretical analysis and experiment. Experimental results presented in the literature are used to show validity of the proposed model.

Relaxation of Semi-online Model

LUO Run-zi;SUN Shi-jie

2007, 25(5):  535-535 . 

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In this paper, we introduce relaxation of a semi-online model and discuss a new semi-online relaxation model: known largest job interval. We investigate P2|known largest job interval| Cmax problem and P2|known largest job interval| Cmin problem, respectively. For these two problems, we present an algorithm called PInterval, and derive its tight competitive ratios. We also discuss characteristics of these two problems and competitive ratio of the LS algorithm.

Generation of MDA-based Fuzzy Ontology

TANG Xinxiang;MIAO HuaiKou

2007, 25(5):  541-541 . 

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This paper presents an approach to Model-Driven Architecture-based fuzzy ontology generation. This method extends ontology definition metamodel to fuzzy ontology definition metamodel(FODM) , creates a fuzzy ontology modeling language(FOML) to represent visual fuzzy ontology and generates mappings between FOML and FODM,FODM and fuzzy ontology web language (FOWL) . By using the mapping between FOML and FOWL, we can easily generate corresponding OWL documents from ontology models created by FOML. This method enables us to generate fuzzy ontology efficiently.

Joint Detection with Delay Coding for Multi-user MIMO MC-CDMA Systems

XIA Fei;FENG Guang-zeng

2007, 25(5):  544-544 . 

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In this paper, a joint detection (JD) technique with delay coding is used for the downlink of multi-user MIMO MC-CDMA systems. Compared with VBLAST downlink signal detection, JD detection provides better performances and can be applied in case the number of receiving antennas is less than transmitting antennas. The paper also studies bit error rate of the system using Alamouti coding with two transmitters and two receivers.

Damping Coefficient of Platform-Tank Stabilizer

YU Li-jun;JIN Hong-zhang;WANG Hui;LIANG Li-hua

2007, 25(5):  547-547 . 

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The method for simulating parameters of ship’s roll equation with the platform is analyzed. The mathematical model of ship-tank system is studied based on this principle, and its damping moment coefficient obtained. The damping coefficient of platform-tank model is calculated with a reduced scale. Additionally, aiming at the characteristic of platform without damping item, the function of the physical system is derived. Simulation curves are analyzed and the statistical data compared. The results show that output of the platform-tank model is consistent with that of the ship-tank model.