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    25 October 2011, Volume 39 Issue 10
    Electronics, Communication & Automation Technology
    Wu Qiong Yao Ruo-he Liu Yu-rong
    2011, 39(10):  1-6.  doi:10.3969/j.issn.1000-565X.2011.10.001
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    Proposed in this paper is a surface-potential-based drain current model for organic thin-film transistor ( OTFT) that takes into consideration the exponential distribution of the trap state density within the bandgaps. In the process of modeling,the diffusion and drift currents are approximately identified by means of the charge sheet approach. Then,a high-precision analytical solution for surface potential is presented via Taylor expansion. Moreover,the transfer and temperature characteristics of OTFT are described based on the variable-range hopping theory,i. e.,the thermally-activated tunneling mechanism of carriers between localized states. It is found that the calculation results accord well with the experimental ones,which shows that the proposed model is applicable to the circuit simulator.

    Wang Zhi-feng He Qian-hua Zhang Xue-yuan Luo Hai-yu Su Zhuo-sheng
    2011, 39(10):  7-12.  doi:10.3969/j.issn.1000-565X.2011.10.002
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    The high fidelity of recent recording and playback devices with high quality and low price make it difficult to distinguish the playback recording from the authentic speech even by auditory perception,thus causing the playback attack to pose a huge threat to speaker recognition systems. In order to solve this problem,this paper proposes a playback attack detection method based on channel pattern noise. In this method,according to the channel
    difference between the playback recording and the authentic speech,different channel pattern noises are introduced respectively for recording and playback devices in different channels and are then extracted by using the denoising filter and the statistical frame. Moreover,6-order Legendre coefficients and six statistical features are extracted from the channel pattern noise,and the support vector machine is used to establish the channel noise model to judge whether the input speech is a playback attack. Experimental results show that,by introducing the playback detector,the equal error rate of the speaker recognition system against the playback attack decreases by about 30%.

    Sun Zhong-gao Zheng Zi-wei Xu Shao-juan
    2011, 39(10):  13-18.  doi:10.3969/j.issn.1000-565X.2011.10.003
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    In order to efficiently utilize the energy in wireless sensor networks,a dual selection mechanism-based clustering algorithm ( DSMCA) effectively combining the voting mechanism with the time-driven one is proposed. In the voting process,a node casts a vote for each neighbor node with higher residual energy. The poll depends on the comprehensive evaluation value of the multiple attributes of neighbor nodes,and the weight coefficient of the multiple attributes is determined by means of the entropy weighting coefficient method. After the voting,each node maps its poll into a certain length of waiting time to participate in cluster head competition by using a conversion function. Moreover,a node with a higher poll produces a shorter time,thus being chosen as a cluster head prior to other nodes. Simulation results show that DSMCA balances the energy consumption among sensor nodes and effectively prolongs the lifetime of the sensor network.

    Zhu Xiao-ping Wang Dong Chen Yao-wu
    2011, 39(10):  19-25,31.  doi:10.3969/j.issn.1000-565X.2011.10.004
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    The real-time detection of neuronal action potentials ( namely spikes) plays an important role in the implantable brain-computer interface system. In order to implement the real-time detection and extraction of the neuronal spikes from the neural signals recorded by the real-time multi-channel neural microelectrode array,a detection method is proposed based on the lifting wavelet. In this method,the drift and noise of the neural signals are removed by using the lifting wavelet. Then,the neuronal spikes are detected via the threshold setting. Finally,the real-time parallel detection of the multi-channel neuronal spikes is realized by means of the lifting wavelet combining with the parallel and pipelined structures of FPGA. Experimental results show that,as compared with the personal computer-based detection method with the same detection results,the proposed method greatly improves the computational performance and it can achieve the parallel detection of 40 neural channels on a single FPGA chip,and that,the proposed method can not only achieve parallel real-time detection of neuronal spikes but also substantially increase the efficiency of the off-line data processing.

    2011, 39(10):  26-31.  doi:10.3969/j.issn.1000-565X.2011.10.005
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    In order to compensate the interference from the phase noise ( PHN) of local oscillators in orthogonal frequency division multiplexing ( OFDM) systems,an iterative algorithm for PHN estimation and equalization is proposed based on the interpolation of estimated common phase error ( CPE) . In this algorithm,based on the slowgoing characteristic of PHN between neighbor symbols,PHN is estimated by acquiring the interpolation of the CPE
    estimation. Then,with the estimated PHN as the initial value,the iterative estimations of PHN and data symbols are jointly carried out,thus recovering the modulation symbols. Simulated results show that,as compared with the conventional method based on the CPE coefficient,the proposed algorithm is of better BER ( Bit Error Ratio) performance and lower complexity at the same iterative number. In addition,the proposed algorithm without iteration is superior to the simple non-iteration CPE correction one in terms of BER performance,especially in the environments with severe PHN.

    Chen Jian-zhong Liang Chang-hong Chen Jia Deng Kun
    2011, 39(10):  32-36,73.  doi:10.3969/j.issn.1000-565X.2011.10.006
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    In order to improve the design efficiency of microwave bandpass filters,an optimization design method is proposed based on the parameter extraction and the space mapping. In this method,first,the Cauchy-TLS ( Total Least Squares) method is used to obtain the rational fraction models of the filters. Next,by using these models,a fast convergent objective function is constructed to extract the equivalent circuit parameters. Then,according to the
    principle of the space mapping,the problem of solving the optimal physical dimension of the filter is transformed into a quadratic constrained optimization model,and the corresponding solution is used to guide full-wave simulation of the filters. Finally,a dual-mode circular-waveguide filter is designed and machined,and its optimal physical dimension with ideal response is achieved after six iterations. It is found that the measured results accord well with the simulated ones.

    Li Meng Wang Dao-bo Sheng Shou-zhao
    2011, 39(10):  37-43.  doi:10.3969/j.issn.1000-565X.2011.10.007
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    In this paper,a multi-heuristic ant colony optimization algorithm is proposed for the route planning of the unmanned aerial vehicle ( UAV) in complex environments. In the algorithm,the distance and the threat distribution between the current UAV position and the candidate one,as well as between the candidate position and the target one,are designed as the multi-heuristic information in the state transition of ants to guide their search behaviors. Moreover,the convergence of the ant colony optimization algorithm is analyzed,and the route smoothing and online route replanning methods are presented respectively for the unfeasible route and the pop-up threats in the task region. Simulation results show that the proposed methods can effectively enhance the route planning ability of the ant colony optimization algorithm and improve the speed and precision of the convergence,thus achieving the optimal route.

    Wang Nian Ding Ye-bing Tang Jun Bao Wen-xia
    2011, 39(10):  44-49.  doi:10.3969/j.issn.1000-565X.2011.10.008
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    In this paper,a new mean-shift target tracking algorithm is proposed to improve the kernel function bandwidth-adaptive ability of the traditional one. First,the probability density of the eigenvalue of the target color is derived by employing the kernel function. Next,a distribution image of the target probability density is projected on the new optimal location of the target in the current video frame. Then,according to the zeroth-order moment of
    the probability density distribution,the width of the tracking window in the next frame is adjusted. Thus,the adaptive bandwidth of kernel function is achieved. Finally,the ellipse parameters derived by means of the moment operation are adopted to lock the tracking target,thus achieving the target position in space,scale and direction in a complex background. Face-tracking experimental results show that,as compared with the conventional algorithm,the proposed one can achieve real-time scaling and locking of the target and estimate the target attitude,and that,it is superior to the Cam Shift algorithm in terms of resistance to the interference of similar color.

    Cheng Hong Gong Yan-yan Zhang Quan-bing Zhang Wei
    2011, 39(10):  50-54.  doi:10.3969/j.issn.1000-565X.2011.10.009
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    In order to solve such problems existing in the traditional information divergence algorithm as the inconsistence of object image sizes and the low accuracy of the depth recovery in non-contiguous areas,a new information divergence algorithm is proposed based on space-variant window. In this algorithm,first,the homography matrix between two original defocused images is calculated. Then,by using this homography matrix,the original images are rectified to obtain new defocus images of the same size. Moreover,the depth of non-contiguous area is estimated through the space-variant window structure. The simulated and real-image experimental results show that the proposed algorithm can avoid the smoothing depth in discontinuities and improve the precision.

    Computer Science & Technology
    Peng Li-min Xiao Wen-jun
    2011, 39(10):  55-60.  doi:10.3969/j.issn.1000-565X.2011.10.010
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    In DHT-based structured P2P ( Peer to Peer) networks,load imbalance occurs owing to the non-uniform distribution of objects stored at peer nodes,the heterogeneity nature of node capabilities and the dynamic characteristics of P2P networks. In order to solve this problem,a hierarchical load balancing model based on binary trees is established on the hypercube DHT overlay networks. The proposed model is used to collect the load and capacity information of nodes,develop the load balancing strategy and transfer the overloaded loads. In this model,by using the balancing domain,load balancing can be implemented in a parallel and distributed way. Simulation results show that the proposed scheme can achieve preferable load balancing in the environment of dynamic P2P networks.

    Li Guang-song Jiang Qi Ma Jian-feng
    2011, 39(10):  61-67.  doi:10.3969/j.issn.1000-565X.2011.10.011
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    In order to meet the security and efficiency requirements of the access in 3G Network and WLAN ( Wireless Local Area Networks) integrated networks,a localized authentication protocol is proposed based on the roaming ticket. With the aid of the media-independent information service,the mobile user adopting the proposed protocol can find neighbor WLANs,from which one possible target network is chosen in advance. Then,the mobile user requests a roaming ticket for the target network from his home network. As a result,when the mobile user is entering the target network,a fast and safe authentication can be achieved by using the corresponding ticket. Finally,the security of the proposed protocol is verified through the Canetti-Krawczyk model. Simulated results show that the protocol costs less time and needs less message passing.

    Bi Sheng Zhuang Zhong-jie Min Hua-qing
    2011, 39(10):  68-73.  doi:10.3969/j.issn.1000-565X.2011.10.012
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    In order to achieve a good walking pattern of biped robots,a multi-objective optimal method for the gait planning is proposed,with the stability,the mobility and the energy of the robot as the research focuses. In this method,the basic gaits are generated based on the inverted pendulum. Then,Pareto optimal solutions based on the basic gaits are obtained in the feasible region by means of the improved strength Pareto evolutionary algorithm ( SPEA2) and the penalty function method. Finally,after the walking simulation through Matlab 6.5,some gaits are generated and are then used in SCUT-I Humanoid Robot,thus obtaining a stable walking pattern with an average velocity of 0. 26m/s.

    Miao De-cheng Xi Jian-qing Jia Lian-yin Liu Yong
    2011, 39(10):  74-78.  doi:10.3969/j.issn.1000-565X.2011.10.013
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    Considering the status quo of formal language researches both at home and abroad,this paper preliminarily investigates the mathematic model of formalization specification description language for formal system and establishes an algebraic model of formal language. Moreover,the concept of language reuse is presented based on the software reuse and transformational semantics methods,and a formal language family model is set up according to the hierarchical design principle of software engineering. In this model,the degree of the abstract expression of software specification
    for the complex formal system is described at different levels,which is suitable for the deve-lopment and testing of complex formal systems. Besides,the inherent relationship among the language models in the language family model is deeply analyzed based on the category theory,so as to provide a convenient and efficient theoretical framework for formal language models.

    Hou Ai-min Hao Zhi-feng Hu Chuan-fu Lu Hai-peng
    2011, 39(10):  79-83.  doi:10.3969/j.issn.1000-565X.2011.10.014
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    The two important methods of distinguishing undirected graph isomorphism,namely the canonical labeling algorithm and the vertex partition algorithm,both have their own disadvantages. Specifically,the former can not work for those graphs which cannot be canonically labeled,and,this latter has to backtrack and try again and again,which results in exponential time cost. For any two isomorphic undirected graphs,new supergraphs can be
    constructed by adding a new vertex and its incident edges to each graph. The supergraphs are isomorphic if and only if ths neighbors of the new vertexes preserve the isomorphic relation in the original isomorphic graphs. Based on this necessary and sufficient condition,a candidate set of isomorphic functions is selected with the help of an efficient necessary condition. Then,by distinguishing the supergraph isomorphism according to the subgraph isomorphism,a fast algorithm without backtracking is proposed to reduce the time cost and guarantee the distinguishing results.Theoretical and experimental results on some real cases demonstrate that the proposed algorithm is effective.

    Liang Huo-min Xiao Wen-jun Wei Wen-hong
    2011, 39(10):  84-89.  doi:10.3969/j.issn.1000-565X.2011.10.015
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    CayDHT is a constant-degree structured peer-to-peer overlay network based on Cayley graph,and it is very efficient in accurate single keyword search but does not support complex searches with unrestricted form. In this paper,by analyzing the topological properties of CayDHT,a virtual tree-based complex search ( VTCS) algorithm is proposed,which needs no maintenance of the extra tree structure and can obtain the address of the next hop only according to the parameters inside the messages. Theoretical analyses indicate that the proposed algorithm can complete the search without redundant messages within O( logN) hops. Simulation results show that VTCS is more reasonable than Flooding and RW.

    Su Jin-dian Yu Shan-shan
    2011, 39(10):  90-95.  doi:10.3969/j.issn.1000-565X.2011.10.016
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    As the coinductive data types in the framework of the category theory can be regarded as the carriers of final coalgebras for some coalgebraic functors,this paper presents the coalgebraic descriptions of the coinductive data types in programming languages from the viewpoint of the category theory and proposes the definitions and coalgebraic calculation laws of corecursion operations based on the finality of final coalgebras. Meanwhile,bifunctors and type functors are used to abstractly describe parametric coinductive data types,and such calculation laws on type functors as unit and fusion ones are put forward via natural transformations. It is proved that these laws can be used to simplify the calculations on coinductive data types,thus improving the dynamic behavior description ability of programming languages for various data types.

    Traffic & Transportation Engineering
    Cao Bao-gui Yang Zhao-sheng
    2011, 39(10):  96-99,131.  doi:10.3969/j.issn.1000-565X.2011.10.017
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    In order to overcome the shortcomings of current car-following models,a novel optimal velocity ( desired velocity) function is proposed and an improved car-following dynamic model is established based on the“stimulusresponse” pattern. Then,the stability of this model is analyzed by using the Lyapunov stability theory on motion. Finally,the parameter calibration and application verification of the improved model are performed by using the
    measured data. The results show that the theoretical results of the improved model accord well with the experimental data in terms of starting acceleration,approximately uniform speed and deceleration,without unrealistic acceleration which occurs in other models.

    Li Yi-shun Xu Jian-min Lu Kai
    2011, 39(10):  100-104.  doi:10.3969/j.issn.1000-565X.2011.10.018
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    Based on the fact that the area-based congestion pricing may well restrict cars from running into urban centers and park and ride ( P&R) can encourage passengers to choose public transportation without affecting the convenience of driving,this paper establishes a network equilibrium model combining these two schemes which can effectively relieve the traffic congestion in big cities. Then,this model is used to analyze the mixed travel behaviors of cars and buses. Moreover,a modified Gini coefficient is proposed to evaluate the social and spatial equity with the help of the combination measures. Finally,some tests are conducted in the city of Guangzhou,China. The results show that,by using the proposed combination model, the total user benefit is less than that obtained by means of single area-based congestion pricing,while the social and spatial equity is much better,and that,as compared with single P&R,the adoption of the proposed combination model can increase the total user benefit without significant
    influence on the social and spatial equity.

    2011, 39(10):  105-110.  doi:10.3969/j.issn.1000-565X.2011.10.019
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    In order to improve the allocation and installation specifications of traffic signal lights for road,the conflict matrix of various vehicle flows at T-intersections is proposed based on right-of-way rules,and then two models of the traffic capacity and the average vehicle delay at one unsignalized intersection are obtained according to the gap acceptance and queuing theories. Then,from the viewpoint of traffic efficiency,the average vehicle delay is taken as the discriminant index to describe the relationship between the difference of the average vehicle delay before and after the signal setting and the movement volume. Finally,the critical traffic volumes for the signal setting under specific conditions are achieved via the optimal control pattern with lower delay.

    Bie Yi-ming Wang Dian-hai Zhao Ying-ying Duan Yu-zhou Song Xian-min
    2011, 39(10):  111-118.  doi:10.3969/j.issn.1000-565X.2011.10.020
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    In order to reduce the bus delay due to the meeting of several buses from different phases at an intersection with arterial coordination,a multiple-phase bus signal priority ( MPBSP) strategy without damaging the coordination of green wave band is proposed. In this strategy,“proximity principle”is presented to settle the conflicts among priority requests for multiple phases and determine the optimal priority sequence. Then,a multiple-phase bus
    priority control procedure is established. As the bus with highest priority may belong to different phases,the green extension and the green-early-start are adopted to respectively establish the coordination phase and non-coordination phase BSP( Bus Signal Priority) algorithms. Finally,by taking two neighboring intersections on arterial roads in a city as case studies,the effectiveness of the proposed strategy is verified through VAP in VISSIM. In addition,the MPBSP strategy is compared with the non-BSP and single phase BSP ones. It is found that the MPBSP strategy can reduce all the bus delays of road networks more efficiently and limit the increase of average delay of general traffic.

    2011, 39(10):  119-126.  doi:10.3969/j.issn.1000-565X.2011.10.021
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    By analyzing the nonlinear influence of ship speed on fleet planning decision,the mathematical functions are deduced to describe the relationships between the ship speed and three parameters,namely,the round voyage time,the voyage cost,and the ship allocation. On the basis of these functions,a mixed integer nonlinear model for fleet planning is established. Then,according to the characteristics of the nonlinear model,a hybrid particle swarm optimization algorithm is designed by combining the feasibility rule-based update strategy with the local search technique of simulated annealing. Finally,the nonlinear model is compared with the linear one by performing simulations for a shipping enterprise. The results show that the nonlinear model can simultaneously solve the problems of fleet investment,ship allocation and ship speed,and that the corresponding optimal solution accords well with the practical application.

    Power & Electrical Engineering
    Zhang Yong-jun Huang Hui Liu Yang-hai Chen Zhi-feng
    2011, 39(10):  127-131.  doi:10.3969/j.issn.1000-565X.2011.10.022
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    In this paper,the existing lightning strike protection problems of distributed hydropower grid are analyzed in terms of grid-connected hydropower lines,hydropower stations and customers,and the lightning strike risk composition and risk sharing differences between grid-connected hydropower lines and normal ones are presented. Then,the lightning strike risk index is proposed. Moreover,a lightning strike risk evaluation model for the power
    grid with distributed hydropower is established,which considers the lightning strike exposure,the probability of line failure,and the losses. Finally,this model is used for evaluating Shaoguan power grid which contains various hydropower stations. It is found that lightnig risks mainly occcur on the grid-connected hydropower lines rather than the normal ones,and that lightning strikes may result in high power failure and severe waste of renewable resources. The paper points out that such lightning strike risks can only be avoided by building smart distribution grids and enhancing the electricity market. To this end,several measures to reduce lightning strike risks are also proposed.

    Wang Shuang Liu Ming-bo Hu Bo Xie Min
    2011, 39(10):  132-138.  doi:10.3969/j.issn.1000-565X.2011.10.023
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    In this paper,the design method of an emergency voltage controller for the power systems containing wind farms is presented based on the nonlinear model-predictive control theory. In this method,a receding dynamic optimization model is proposed based on the quasi-steady-state approximate models of power systems. Then,the proposed model is described as an optimal control problem with continuous and discrete time differential-algebraic equations,with the purpose to achieve voltage deviation and control cost minimization. Moreover,Radau collocation method is used to convert the proposed model into a nonlinear programming problem which can be solved by using the optimization solver IPOPT through the modeling software AMPL. Finally,the effectiveness of the proposed method is verified on the modified New England 10-machine 39-bus system.

    Liu Zhi-peng Wen Fu-shuan Gerard Ledwich
    2011, 39(10):  139-145.  doi:10.3969/j.issn.1000-565X.2011.10.024
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    The under-frequency load shedding ( UFLS) is considered as the last effective remedial measure against a severe frequency decline of a power system.Aiming at this issue,an optimal UFLS strategy considering distributed generator ( DGs) and load static characteristics is proposed based on the frequency and its change rate. This strategy consists of several basic rounds and a special round. In the basic rounds,the system emergency can be alleviated by quickly shedding some loads runs by runs according to the feedback control law. In the special round,by optimizing the output power of DGs and adjusting some loads,the system security can be regained and the corresponding ope-rating parameters can be optimized. Finally,the effectiveness of the proposed optimal UFLS strategy is verified with the modified IEEE 37-node test feeder as an example.

    Sun Yue Yang Fang-xun Dai Xin
    2011, 39(10):  146-151,164.  doi:10.3969/j.issn.1000-565X.2011.10.025
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    When wireless power transfer is used to realize the randomly-distributed multi-load real-time power supply in a space,the transfer space scale is restricted and the transfer efficiency is low. In order to solve these problems,a framework for wireless power transfer networks is proposed in this paper. Based on the topology of wireless power transfer networks,a mathematical model of the network is established to ensure high power transfer efficiency and to simultaneously implement wireless power transfer in a certain range through relay stations. Moreover,the system model of power transfer based on magnetic resonant coupling is set up and the characteristics of the transfer efficiency are discussed. In addition,according to the dynamic updating mechanism of pheromone,the ant colony algorithm is improved to control its premature convergence and ensure fast and comprehensive search in the feasible field. Simulated results confirm the feasibility of the improved ant colony algorithm in constructing wireless power transfer networks.

    Yang Tong-guang Jiang Xing-hua Fu Qiang
    2011, 39(10):  152-156.  doi:10.3969/j.issn.1000-565X.2011.10.026
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    During the fault diagnosis of asynchronous motor based on stator current signals,the fault feature frequency component of broken bar always hides behind the fundamental component in the spectrum of the stator current. In order to solve this problem,a novel fault diagnosis method for the broken bar of speed sensorless induction motor is proposed based on the vector control. In this method,the reactive power is constructed by using the cross production of the rotor back electromotive force and the current vector,and then the corresponding reactive power spectrum is analyzed,with the characteristic frequency 2sf as the fault diagnosis criterion for the broken bar. Meanwhile,the reactive power is used to identify the speed and correct the magnetic field orientation,thus eliminating the impacts of the stator resistance and integral term of the traditional model reference adaptive system speed identification equation of stator flux. Experimental results demonstrate that the proposed method is effective in the fault diagnosis of broken bars,and that it can improve the speed identification accuracy as well as the vector control performance.

    Li Ji-fang Han Jin-gang Tang Tian-hao
    2011, 39(10):  157-164.  doi:10.3969/j.issn.1000-565X.2011.10.027
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    As model analysis is the basis of the switching converter research,a switching system-based unified model is proposed according to the hybrid system theory,which is suitable for DC-AC and various types of DC-DC switching converters. Then,the construction method of Lyapunov function is proposed based on the parameter matrix of the unified model and the system switching laws are put forward by constructing this function. Meanwhile,the system stability under the proposed switching laws is analyzed and a general approach and some specific steps for the unified modeling are summarized. Finally,some simulations are carried out by establishing models for the DC-AC and three-level Buck-type DC-DC converters,and the rationality of the established models and the effectiveness of the modeling method and steps are both verified.

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