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    25 April 2013, Volume 41 Issue 4
    Power & Electrical Engineering
    Liu Ming-bo Yuan Kang-long Yang Liu-qing Lin Shun-jiang Yang Yin-guo
    2013, 41(4):  1-7.  doi:10.3969/j.issn.1000-565X.2013.04.001
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    This paper deals with two methods for computing the stability margin of static voltage,namely the optimalpower flow method and the continuation power flow method.In the investigation,first,based on the equivalencydefinition of the two methods for determining the critical points of voltage stability,the cause of the stability margindifference between the two methods,namely,the inconformity of power flow equations,is pointed out.Then,thecomplementarity constraints describing the reactive power and the terminal voltage of generators are introduced in anew optimal power flow model,and the increase direction of the active power outputs of generators,which is thesame as that of the continuation power flow model,is adopted.Computational results on the IEEE 9-bus system,the IEEE 39-bus system and a real provincial 748-bus power system illustrate that the stability margin of the staticvoltage and the bifurcation type obtained by the optimal power flow model accord well with those obtained by thecontinuation power flow model.

    Zhang Bao-zhen Zhang Yao Lin Ling-xue Zheng Li
    2013, 41(4):  8-13.  doi:10.3969/j.issn.1000-565X.2013.04.002
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    In order to solve the partition problem of coherent generators in the dynamic equivalent method based oncoherency,an algorithm marked as PSO-FCM,namely,the fuzzy c-means clustering ( FCM) based on the particleswarm optimization ( PSO) ,is presented.In this algorithm,the cluster center is taken as a particle for encoding,and the parallel property and the global searching capacity of the PSO algorithm are applied to the optimizationthrough continuously renewing the velocity and position of the particle. Thus,the dependency of the FCM algorithmupon the initial value and the risk of falling into local optimization are overcome. Moreover,in order to evaluate theclustering validity,a validity function is constructed. Simulated results on IEEE 10-generator 39-bus system showthat the PSO-FCM algorithm is suitable for the partition of coherent generators of electric power systems in variousoperation modes because it is of simplicity,easy realization,high accuracy and high speed.

    Liu Shui-ping Liu Ming-bo Xie Min
    2013, 41(4):  14-20.  doi:10.3969/j.issn.1000-565X.2013.04.003
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    In order to overcome the limitations in voltage stability of the centralized model predictive control,a cooperatively-distributed model predictive control method based on the system partition and the predictive control modeldecomposition of voltage is constructed for large-scale power systems. In this method,a global objective cost functionis proposed with the convex combination of the objective functions of all subareas,the nodal voltage trajectory is predictedaccording to the trajectory sensitivity,and the objective cost function is transformed into a quadratic programmingfunction relevant to all control variables,thus avoiding the optimization conflicts among the subareas.Simulationson two test systems indicate that the proposed method greatly improves the calculation efficiency and achieves avoltage control performance similar to that of the centralized model predictive control.

    Li Heng-zhen Yao Si-hai Yang Kun-sheng Yang Ying Liu Gang Li Li-cheng
    2013, 41(4):  21-26.  doi:10.3969/j.issn.1000-565X.2013.04.004
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    In order to further investigate the principle of contamination deposition on electrical insulator surface,the settlement process of polluted particles on the electric insulator surface is analyzed,and a simplified model todescribe the polluted particles and the air flow field is established.Then,by adopting the hydromechanical method,the force and the motion processes of polluted particles in the air and the boundary layer are analyzed,and a motionmodel of polluted particles before their adsorption on the insulator surface is established,with the correspondingcalculation results being also discussed.It is demonstrated that the contamination deposition rate on the upper surfaceof electric insulator is greatly higher in the area with larger polluted particles,while in the area with smallerpolluted particles and stronger wind,the rate on the lower surface is greatly higher.Moreover,it is found that thepollution level of electrical insulator surface can be reduced by controlling the consistency of polluted particles witha diameter of less than 20 μm.

    Ouyang Sen Shi Yi-li Liu Yang
    2013, 41(4):  27-32,46.  doi:10.3969/j.issn.1000-565X.2013.04.005
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    In order to effectively evaluate the power quality of regional power grids,a dynamic evaluation algorithmbased on the vertical and horizontal scatter degree method,which makes full use of the current and historical dataand reflects the overall level of the evaluated objects in a certain period,is proposed.In the investigation,the synthesizedweights of power quality indexes are determined via the vertical and horizontal scatter degree method andthe sequence-relation analysis,in which the objective weights are used to highlight the overall differences of theevaluated objects and the subjective weights are used to reflect the expert experience.Then,by linearly weightingeach index,the evaluation value of power quality in each period is obtained for each evaluated object. Moreover,the least variance method is employed to compute the sum of the evaluated power quality in each period for a regionalnetwork; therein the time degree is adjusted to emphasize the current and the historical data. The performance ofthe proposed algorithm is finally verified by a case study on the power quality of a power supply bureau.

    Zhang Zhi-guo Xie Yun-xiang Yuan Zhao-mei
    2013, 41(4):  33-38.  doi:10.3969/j.issn.1000-565X.2013.04.006
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    In order to fully reveal the circuit characteristics of the parallel resonant converter with capacitive outputfilter,the principle of the two operational modes of the converter is analyzed and the corresponding mathematicalmodels are constructed.Then,the circuit characteristics of the converter in the two operating modes are discussedand a linear variation of the input current is revealed when the equivalent output voltage is less than the input one.Finally,some expressions are deduced to design circuit component parameters,and a design method is proposed toobtain component parameters meeting the application requirements of the parallel resonant converter.Simulated resultsindicate that the above analysis and the proposed design method are both correct.

    Zhang Wen Xue Jia-xiang
    2013, 41(4):  39-46.  doi:10.3969/j.issn.1000-565X.2013.04.007
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    In order to avoid the performance degradation of EMI filters with PCMC Boost converters under peak current-mode control and to guarantee the stability and robustness of the cascaded system,the state-space averagingmethod is used to construct a small-signal model of the converter for obtaining the transfer function set of such parametersas impedance.Then,a PI controller,whose loop gain is of a control bandwidth of 4 kHz and a phase marginof 67°,is designed.Moreover,an EMI filter corresponding to the noise suppression stipulated by relevantstandards is designed with Matlab,with its stability being evaluated by the graphical impedance ratio and theNyquist stability validation. Finally,a closed-loop cascaded system for simulation and modeling is constructed.Simulated and experimental results indicate that the designed EMI filter can not only suppress the noise current tothe acceptable level stipulated by EMC standard but also guarantee the stability and dynamic performance of thecascaded system. It is thus concluded that the cascaded approach is effective in the application of PCMC Boost converters.

    Du Qun-gui Zou Jie-hui Chen Shui-jin Gao Jun-ling
    2013, 41(4):  47-53.  doi:10.3969/j.issn.1000-565X.2013.04.008
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    In order to effectively calculate the electricity-generating performance parameters of semiconductor thermoelectricgenerator units,the existing calculation model based on constant material properties is analyzed,and anew model based on variable material properties,which includes the procedures of solving the temperature distributionof semiconductor particles and calculating the material parameters as well as the electricity-generating performanceparameters,is proposed.Then,the two models respectively based on constant and variable material propertiesare used to calculate the performance parameters of a semiconductor thermoelectric generator unit in various workingconditions.The results are finally compared with those of ANSYS simulation. It is found that the proposed modelbased on variable material properties is superior to that based on constant material properties because it greatlyreduces the calculation error.

    Gao Jun-ling Du Qun-gui Shi Gui-ju
    2013, 41(4):  54-57.  doi:10.3969/j.issn.1000-565X.2013.04.009
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    The maximum output power of a thermoelectric module ( TEM) can be estimated according to the opencircuit voltage and the short circuit current under certain temperature difference. As there are two switch modes,namely the mode from open to short circuit and the mode from short to open circuit,there may exist two groups ofopen circuit voltage and short circuit current.Consequently,under identical temperature difference,the maximumoutput powers of TEM in the two modes are different from each other,and the difference varies with the temperaturegap between the hot and the cold sides.This paper deals with such power difference based on theoretical analysisand points out that the power difference is due to the variable electromotive potential caused by the current varyingwith the switch mode.Moreover,a computation method to reduce the power difference is put forward.Experimentalresults show that the proposed method greatly improves the estimation accuracy of maximum output power of TEM.

    2013, 41(4):  58-62,70.  doi:10.3969/j.issn.1000-565X.2013.04.010
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    In this paper,the diffused combustion flame linearly moving in different conditions was analyzed by experimentsand was numerically simulated and compared using the software of Fluent.The results show that themovement of fire greatly influences the combustion flame. For example,at a wind speed of 0m/s,the flame movesto the contrary direction of the fire source movement,with a deflection angle increasing with the fire speed.At thefire speed of 0. 36,0. 44 and 0. 55m/s,the flame deflection angle respectively reaches 36°,47°and 60°.Underthe action of wind and car movement with the same relative speed,the flames deflect to the same direction but exhibitdifferent shapes,and the cobbustion flame in a absolute rest condition is of a lower combustion temperaturebecause it dissipates more heat energy.Moreover,it is found that,as compared with the combustion flame in absoluterest condition,the flame in relative rest condition has a shape deviation to the contrary movement direction ofthe fire source and a higher combustion temperature.According to the above-mentioned statements,it is concludedthat the diffusion combustion flame with mobile source cannot be simply analyzed with the concept of relative motiondue to the great difference in the intrinsic influence and the flame shape.

    Traffic & Transportation Engineering
    Li Hai-jian Dong Hong-hui Jia Li-min Xu Dong-wei Hu Yue
    2013, 41(4):  63-70.  doi:10.3969/j.issn.1000-565X.2013.04.011
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    This paper deals with the layout of sensors in traffic networks,a key problem related to the economicbenefit of intelligent transportation system ( ITS) . In the investigation,first,a new measure describing the spatialcharacteristics of traffic information is used to construct a maximum integrated value model ( MIVM) based on thegame between the maximum information value and the minimum investment cost of sensors,and the model is solvedby constructing a directed graph and by making use of the shortest path algorithm ( SPA) of the directed graph.Then,the model parameters are analyzed and the corresponding mathematical methods to describe and calibrate theparameters are presented.Moreover,in order to simplify the problem,a simplified model based on the MIVM isgiven and the relationship between the sensor number and the integrated value is determined.Finally,a case studyon Beijing 3rd Ring Road is performed,with the optimal section sensor number and the best sensor spacing beingdetermined as 142 and about 676 m,respectively.The results indicate that,as compared with the widely-appliedgraph theory models,the MIVM helps to obtain not only the optimal sensor number but also the optimal location ofeach sensor. Besides,from the calibration results of model parameters in different conditions,it is found that theMIVM can be universally applied because it can be easily used for different cities,roads and sensor types.

    Wu Wei-tiao Shen Lü-ou Jin Wen-zhou
    2013, 41(4):  71-76.  doi:10.3969/j.issn.1000-565X.2013.04.012
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    Pacey's platoon dispersion model is based on the assumption that the speed of vehicles follows the normaldistribution spreading from the minus infinity to the positive infinity.However,this assumption cannot properly reflectthe actual traffic situation.In order to solve this problem,based on the field data,a more practical platoondispersion model is constructed under the assumption that the speed follows the truncated lognormal distribution rangingfrom the minimum speed to the free flow speed.Then,a piecewise function is developed to describe the platoondispersion as it moves to the downstream intersection and to reveal the relationship between the flow distributionmoving to the downstream intersection and that leaving the upstream intersection. Finally,by taking the signalcoordination control of an adjacent intersection as a case,the distribution mode of platoon flow is discussed accordingto the measured data,and the validity of the proposed model is verified by a comparison between the proposedmodel and the Robertson model.

    2013, 41(4):  77-82.  doi:10.3969/j.issn.1000-565X.2013.04.013
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    By introducing the concept of group clustering degree in the group dynamics theory,some formulas arededuced to calculate the clustering degree at adjacent intersections.Then,by controlling the subarea border andsetting the constraint conditions for subarea division,a layered substep strategy of subarea division for traffic controlis developed and a subarea division model based on the group dynamics theory is established.Moreover,the completeacquiring process of optimal subarea division is presented,and the subarea division schemes are comprehensivelyanalyzed and evaluated with the intersection group clustering algorithm.Example results indicate that the proposeddivision method of coordinated control subareas based on the group dynamics theory is effective because it decreasesthe total number of vehicle stops as well as the stop delay in road networks.

    Zhang Min-jie Xu Jian-min Cai Yan-guang
    2013, 41(4):  83-89,95.  doi:10.3969/j.issn.1000-565X.2013.04.014
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    In order to seek an effective method of traffic coordination control for road networks,the traffic behaviorsat intersections are analyzed based on the macroscopic transmission model via a gridding procedure,and a newmacroscopic simulation model is constructed to fast evaluate control schemes.Then,by taking the optimal trafficrunning as the objective,a bi-level programming model for traffic coordination control is proposed.Moreover,bycombining the macroscopic simulation model with the proposed bi-level model,a method of traffic coordination controlbased on the improved macroscopic traffic model is presented.The method is finally tested on a virtual networkwith three different traffic demands,and the results are compared with those of the Transyt-7F method.It is foundthat the proposed method is feasible and is superior to the Transyt-7F method especially in the high demand scenario.

    Wang Zi-jia Chen Feng Shi Zhong-heng
    2013, 41(4):  90-95.  doi:10.3969/j.issn.1000-565X.2013.04.015
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    The micro-simulation of pedestrians has become a major tool of facility layout assessment and evacuationevaluation for the places with dense pedestrian flow such as a subway station.The social force model,which is formulatedfrom the aspect of force exerted on pedestrians,helps to obtain both the motion and the force states of pedestrians,and demonstrates various self-organization phenomena without setting complex walking rules.In order toovercome the high complexity of algorithm and the blindfold moving of pedestrian particles in the social force model,this paper introduces the Gear's predictor-corrector method and the linked-list cell algorithm in molecular dynamics,and presents an improved model and the corresponding object-oriented programming implementation frameworkbased on the perceiving and decision-making method of Agent.Then,with the help of the ellipse element modelingthe pedestrian body,the parameters including the pedestrian body,the movement and the model itself are calibrated,and the Agent-pedestrian interaction method as well as the corresponding algorithm,which takes into considerationthe density scanning /turning,the varied interaction strength and the collision prediction /avoidance,designed.Finally,the modified model is programmed with VC++ 2008 and the one-direction and bi-direction pedestrian simulationsof subway passageway are performed.The results indicate that the linked-list cell algorithm greatly saves thesimulation time and that the modified model helps to achieve prominent lane formation and reveal the pedestriandensity-flow relationship which agrees well with that derived from field study.

    Yuan Miao-miao Zhang Xiao-ning Chen Wei-qiang Zhang Shun-xian
    2013, 41(4):  96-101.  doi:10.3969/j.issn.1000-565X.2013.04.016
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    Presently,it is not reached consensus for asphalt mittures fatigue failure criterion. In this paper,based onthe dissipated energy method,the relative change rate of dissipated energy is put forward to characterize the damageaccumulation in the fatigue test process of asphalt mixtures,and the catastrophe point of the relative change ratebased on variable step is taken as the fatigue failure criterion of asphalt mixtures,with a theoretical proof being alsopresented.Then,with the help of this criterion,the feasibility of the proposed prediction model of fatigue performance,which is independent of the load control mode,is verified.

    Chen Jing-yun Liu Jia-yin Li Yu-hua Zhou Chang-hong
    2013, 41(4):  102-106.  doi:10.3969/j.issn.1000-565X.2013.04.017
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    The fatigue cracking law of asphalt mixture slabs is investigated based on the APA ( Asphalt PavementAnalyzer) fatigue test,and the representativeness of specimen geometry to actual pavement structure is improved byadjusting the width-span ratio of asphalt mixture specimens. In the investigation,first,unaged,short-term agingand long-term aging slab specimens are respectively fabricated and loaded with a cyclic moving wheel to generatebidirectional bending stress in the opposite-edge supported slab. Then,the deflections of the specimens are measured,the development of fatigue crack is observed,Finally,the fatigue life of specimen is determined at the time itfails.By these fatigue tests,the cracking propagation of a finite-width slab with inherent local defects and underbidirectional bending stress is revealed.The results indicate that the crack tip vertically propagates from the slabbottom to the top and presents a length increase in the horizontal direction at the bottom,and that the crack development,the crack pattern and the deflection curve of the slab specimens are all different from those of beam specimens.

    Qiu Zhi-xiong Li Zhi Li Dong-hai Zhang Xiao-ning Liu Tao
    2013, 41(4):  107-112.  doi:10.3969/j.issn.1000-565X.2013.04.018
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    The research on the meso-structure of asphalt mixture helps to describe the anti-slide structure and itsevolution more comprehensively and accurately and solve the prominent problem of how to design durable and structure-rich asphalt-layer material in lack of high-quality anti-slide stone material.In this paper,four kinds of denseskeleton asphalt mixtures GAC-13 with non-continuous gradation are designed,and a test device for rub evaluationis developed to simulate the traffic load and environment.Then,by analyzing the specimens in different rub stageswith high-accuracy industry CT scan,a method,which adopts the affecting-zone depth and the decay rate to evaluatethe anti-slide properties of meso-structure of asphalt mixture,is put forward.The results show that GAC-13 with acomplete granular gap of 2.36mm helps to obtain more ideal anti-slide structure.

    Wang Yi-min Zou Chao Gao Shui-qin
    2013, 41(4):  113-118,126.  doi:10.3969/j.issn.1000-565X.2013.04.019
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    In order to explore the long-term performance of the geogrid-reinforced soil retaining walls and the softsoil ground under combined action,the creep properties of the geogrid and the soft soil were investigated throughcreep tests,and a constitutive model considering the creep effect was established based on experimental results.Then,a case study on a geogrid-reinforced soil retaining wall built on soft soil ground was performed by using the finiteelement method,and the long-term deformation performance of the wall considering the creep effect of reinforcementmaterial was analyzed.The results show that ( 1) the proposed numerical model is effective in simulatingthe long-term creep behaviors of the reinforced soil retaining wall on soft soil ground; ( 2) the lateral displacementof the reinforced wall gradually increases with time and becomes larger at the central part but smaller at the twoends of the wall; ( 3) with the prolonging of time,the position of maximum lateral displacement along the wall becomeshigher; and ( 4) due to the influence of foundation deformation,the positions of maximum tension and strainof each geogrid layer are different from the Rankine failure surface stated by the current design theory.In addition,the distribution law of geogrid tension and strain along the wall at different times,which is obtained by numericalsimulation,provides some references for the design of reinforced soil retaining walls on soft soil ground.

    Wang Shuo Su Yu-min Du Xin
    2013, 41(4):  119-126.  doi:10.3969/j.issn.1000-565X.2013.04.020
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    In order to accurately estimate the hydrodynamic characteristics of planing crafts,the high-speed sailing ofplaning crafts in calm water and in regular head waves was numerically simulated with multiple degrees of freedom byperforming resistance model experiments and seakeeping model experiments.In the simulation,the RANSE VOF solverwas adopted and the trimming mesh technique as well as the integral dynamic mesh method was employed.Theresults were then compared with the experimental data to verify the accuracy of the simulation.It is found that theadopted computational fluid dynamics technique helps to accurately and efficiently simulate the sailing attitude andhydrodynamic characteristics of high-speed planing crafts in calm water and in waves,and that the simulation providesa credible reference for the design of planing crafts.

    Dong Lei-lei Zhang Qi Huang Yi
    2013, 41(4):  127-131,141.  doi:10.3969/j.issn.1000-565X.2013.04.021
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    In this paper,first,the relationship between the dynamic response of the deepwater riser and the significantwave height is deduced under a linear assumption,and a correction is further made to allow for nonlinearity.Then,the dynamic response of the riser is obtained by employing the time-domain scaling method,based on whicha global fatigue analysis is performed. Finally,the results are compared with those obtained by the accurate calculationmethod. It is shown that ( 1) the power-law scaling approach achieves a fatigue life more acceptable in industrywhile the linear scaling approach is more conservative; ( 2) the proposed method takes into consideration thesystem nonlinearity implicitly and helps to obtain accurate results with less computational effort,so that it is suitablefor the initial assessment of riser fatigue and the sensitivity analysis of predicted fatigue life to key input parameters;and ( 3) the proposed method is also suitable for the fatigue evaluation due to its conservatism guaranteed by thescaling from large to small significant wave heights.

    Physics
    Lu Yi-gang Li Yue-jia
    2013, 41(4):  132-136.  doi:10.3969/j.issn.1000-565X.2013.04.022
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    Based on the single-bubble and double-bubble ultrasonic cavitation noise models derived respectivelyfrom the single-bubble and double-bubble dynamic equation and from the Lighthill equation,the effects of the initialbubble radius,the double-bubble distance,the sound pressure amplitude,the sound frequency and the bifrequencyultrasound on the cavitation noise are analyzed via Matlab programming.Calculated and analytical resultsshow that ( 1) under the same initial conditions,the peak of the double-bubble cavitation noise is much higher thanthat of the single-bubble one,which means that the single-bubble and double-bubble cavitation noise curves are differentform each other; ( 2) the initial radius,the sound pressure amplitude,the sound frequency and the bifrequencyultrasound all affect the single-bubble cavitation noise,especially the former two; ( 3) the cavitation noisereaches the maximum when the pressure amplitudes in the two components of the bifrequency ultrasound are equal;and ( 4) the initial radius and the sound pressure amplitude influence the double-bubble cavitation noise significantlywhile the effects of the sound frequency and the bifrequency ultrasound are almost ignorable.

    Liu Jin-mei Qiu Shui-sheng
    2013, 41(4):  137-141.  doi:10.3969/j.issn.1000-565X.2013.04.023
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    In this paper,a new three-dimension chaotic system is constructed by adding an absolute item in thesystem,and the dynamic properties of the new system are investigated.Then,by virtue of the chaos theory and thenumerical simulation,the equilibrium point,the Lyapunov dimension,the Poincaré section,the largest Lyapunovexponent spectrum and the bifurcation diagram of the system are analyzed.It is indicated that the proposed threedimensionautonomous system exhibits chaotic features in a wide parameter range and is of fractional dimension,multiple unstable equilibrium points and layered Poincaré mapping.Moreover,Owing to its complex dynamic properties,the system can generate four-wing chaotic attractors.

    Chen Guo-hua Liang Jun Wang Xin-hua
    2013, 41(4):  142-146.  doi:10.3969/j.issn.1000-565X.2013.04.024
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    In this paper,the acoustic emission source with slewing ring is roughly located via a linear time-difference-of-arrival ( TDOA) location method. Then,in order to overcome the low precision resulting from the threshold-based TDOA estimation and improve the location accuracy of acoustic emission source,a correction signal isconstructed,and the corresponding smooth pseudo Wigner-Ville distribution ( SPWD) is calculated to obtain a correctionvalue of the threshold-based TDOA.The results show that the corrected TDOA helps to improve the locationaccuracy of the acoustic emission source with slewing ring,with a maximum absolute error decreasing from 23.63mmto 11.57mm.

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