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2016 Vol. 42, No. 8

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2016 Year 42 Volume 8 Issue E-journal
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Experimental research on vibration control of composite plate with piezoelectric networks
LI Lin, SONG Zhiqiang, YIN Shunhua, LI Chao
2016, 42(8): 1557-1565. doi: 10.13700/j.bh.1001-5965.2015.0514
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The paper mainly studies the vibration control of the plate with piezoelectric network. After giving the dynamic equations of the plate with piezoelectric network based on the homogeneous assumption, we resolved the problem that the necessary inductance in the network is too large to be realized in practice. Two kinds of simulated inductance circuit are designed. The respective vibration control effect and characteristic of the composite plate with two kinds of piezoelectric network, that is, the network only with resistors and that with resistors and inductors, are compared experimentally. Experiments prove that the electromechanical coupling dynamic equations based on the homogeneous assumption can well predict the dynamic characteristics of the plate with piezoelectric network. The coupling relationship between electrical modes and mechanical vibration modes of piezoelectric composite plate is also verified. A suggestion for determining the optimal electrical parameters to have a good effect of vibration suppression is given, which can be used as a reference for practical design of the composite plate with piezoelectric network.
Adaptive terminal sliding mode guidance law with impact angle constraint
YANG Suochang, ZHANG Kuanqiao, CHEN Peng
2016, 42(8): 1566-1574. doi: 10.13700/j.bh.1001-5965.2015.0502
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Aimed at the requirement of zero miss-distance and terminal impact angle constraint for some missiles attacking the targets, an adaptive nonsingular terminal sliding mode control algorithm based on the theories of terminal sliding mode control and finite-time control is proposed first. The algorithm avoids the singularity of terminal sliding mode control, and makes the state variables achieve the equilibrium point by improving a fast nonsingular terminal sliding mode function to construct the sliding mode surface, and employing an adaptive exponential reaching law. Then the algorithm is utilized to design the guidance law, and an adaptive nonsingular and finite-time convergent guidance law with impact angle constraint is proposed. Realizing the requirement of miss distance and attack angle of the missiles. Finite-time control theory is used to analyze the convergence of the guidance law, and proves the fast and finite-time convergence of guidance system states during the whole process. Compared with conventional nonsingular terminal sliding mode guidance law, the designed guidance law can attack the targets with less miss-distance and higher precision of expected impact angle in a shorter time. A large number of simulation experiments verify the validity of the proposed law.
Technology for power processing unit used in high power electric propulsion
LI Feng, KANG Qing, XING Jie, LI Yalin
2016, 42(8): 1575-1583. doi: 10.13700/j.bh.1001-5965.2015.0531
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Higher requirements are proposed to propulsion for space technology in new environment. As an advanced propulsion technology, electric propulsion has the virtue of high specific impulse, low launching mass and low cost. High voltage power supply is the key technology for high power and high efficiency design, since it is the main power supply for power processing unit (PPU).Application of novel power electronics technology will have a deep effect on geosynchronous orbit,geostationary earth orbit (GEO) telecommunication satellite and deep explanation. This paper focuses on PPU of 5 kW and introduces the current status and development of large power electric propulsion. The characteristics and prospects of large power and high efficiency PPU are analyzed in detail from three aspects of power electronic topology, components and control strategy. It supplies a reference for developing Chinese high voltage power supply of large power PPU.
An accurate modeling method for random drift of MEMS gyro
WANG Kedong, WU Yuxia
2016, 42(8): 1584-1592. doi: 10.13700/j.bh.1001-5965.2015.0510
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To compensate random drift in MEMS gyros, an auto-regressive moving average (ARMA) model for measured data drift was developed using time series analysis, and a new estimation method was proposed for moving-average (MA) models. The gyro noise was modeled as an ARMA with the observation noise. After the auto-regressive (AR) parameters were estimated, a more accurate estimation with a smaller variance of the MA autocovariance sequence was deduced for the residual noise by the AR filtering. The statistics were used as the input of Gevers-Wouters (GW) method to estimate MA parameters. The results of simulation prove that both the accuracy and reliability of parameter estimation are improved. The compensation experiment of MEMS gyros random drift further verifies that the proposed method is more accurate than the traditional one.
Assessing network security situation quantitatively based on information fusion
WEN Zhicheng, CHEN Zhigang, TANG Jun
2016, 42(8): 1593-1602. doi: 10.13700/j.bh.1001-5965.2015.0561
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Concerning the problem that current network security situation assessment has the characteristics of single information source, limited assessment scope, not easy to build model, high time and space complexity and not high credibility, a new method of network security situation assessment is proposed based on multi-source and heterogeneous information fusion. A hierarchical naive Bayesian classifier was constructed based on the theory of Laplace's principle for smoothing parameter learning in order to optimize the result of classification and inference. The quantization for the network security situation was assessed using the method of mathematical statistics, which can generate every host security index through information fusion. The current network security situation should be understood overall and macroscopically. The feasibility and effectiveness of the proposed method for network security situation assessment are verified by the experiments in real network environment.
Information-theoretic ensemble clustering on web texts
WANG Yang, YUAN Kun, LIU Hongfu, WU Junjie, BAO Xiuguo
2016, 42(8): 1603-1611. doi: 10.13700/j.bh.1001-5965.2015.0507
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Although being extensively studied, text clustering remains a critical challenge in data mining community due to the curse of dimensionality. Various techniques have been proposed to overcome this difficulty, but the negative impact of weakly related or even noisy features is yet the hunting nightmare. Meanwhile, we should never lose sight of the explosive growth of unlimited user-generated content on social media, which is extremely sparse and poses further challenge on the efficiency issue. In light of this, a disassemble-assemble (DIAS) framework is proposed for text clustering. Simple random feature sampling is employed by DIAS to disassemble high-dimensional text data and gain diverse structural knowledge by avoiding the bulk of noisy features. Then the multi-view knowledge is assembled by fast information-theoretic consensus clustering (ICC) to gain a high-quality consensus partitioning. Extensive experiments on eight real-world text data sets are conducted to demonstrate the advantages of DIAS over some widely used methods. In particular, DIAS shows appealing merits in learning from a bulk of very weak basic partitionings. Its natural suitability for distributed computing makes DIAS become a promising candidate for big text clustering.
Comparative analysis on primary parameters of loitering munitions of different propulsion systems
HAO Feng, CHANG Min, TANG Shuo
2016, 42(8): 1612-1618. doi: 10.13700/j.bh.1001-5965.2015.0490
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As to loitering munitions, the propulsion system significantly influences design missions of flight endurance, cruising velocity, range and the mass of payloads. Based on the constraint of energy balance, the estimation formulation of loitering munitions of three types of propulsion systems is established, including electric-motor type, piston type and jet type. Then the influences of performance parameters on design missions for different types of propulsion systems are analyzed comparatively and individually by the sensitivity analysis method. The characteristics of equivalentenergy density for each kind of fuel material of three propulsion system types are compared from the perspective of energy supply to conclude the original reasons for those three types. These conclusions could provide useful guidelines for selection of propulsion systems for different military operations in the phase of preliminary design of loitering munitions.
3D obstacle avoidance method and simulation for unmanned helicopter
MENG Zhijun, PING Xueshou, CHEN Xuzhi
2016, 42(8): 1619-1626. doi: 10.13700/j.bh.1001-5965.2015.0499
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Autonomous obstacle avoidance is an indispensable ability for unmanned helicopter (UH) operating low-altitude flight. A new 3D real-time avoidance method was presented to solve UH obstacle avoidance problem in complicated environment. The vision space of sensor was divided into several unequal radii sector-shaped cylinders and cuboids distributed at the same angle, estimating the obstacle distribution based on sensor data, and UH can execute corresponding maneuver calculated by this method to avoid obstacles successfully. An originally 3D simulation method was also proposed using secondary development technology on CATIA, which can build 3D model for undiscovered environment. Combined with the obstacle avoidance method, real UH obstacle avoidance flight simulation was carried out in it. The feasibility of 3D obstacle avoidance method was validated using the proposed simulation method.
Synthesis and electrochemical performance of lithium-rich cathode material
WEI Xin, ZHANG Shichao, LIU Guanrao, YANG Puheng, MENG Juan, LI Honglei
2016, 42(8): 1627-1631. doi: 10.13700/j.bh.1001-5965.2015.0505
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Lithium-rich cathode material Li1.2Mn0.54Ni0.13Co0.13O2 has been synthesized by sol-gel method followed by a high-temperature calcination process at 800℃ and 900℃ (signed as S8 and S9, respectively). The structure, morphology and electrochemical properties of as-synthesized materials are characterized in detail. Electrochemical test results show that sample S9 has higher discharge capacity, better cyclic stability and smaller charge transfer resistance. Sample S9 delivers the initial charge capacity of 345.0 mA·h·g-1 and the initial discharge capacity of 273.9 mA·h·g-1 at 0.1C (25 mA·g-1) with a coulombic efficiency of 79.4%. The discharge capacity is 173.3 mA·h·g-1 at 1 C after 30 cycles, remaining 92.1% of initial discharge capacity (188.1 mA·h·g-1). The results indicate that the ordering between lithium and transition metal cations in their respective layers needs a higher calcination temperature in spite of the formation of the R-3m layered phase at 800℃. It is helpful to effectively improve the electrochemical properties.
Combustion performance and range of coal-based Fischer-Tropsch aviation fuel
ZHOU Guanyu, WANG Hongbo, WANG Zhichao, YANG Xiaoyi
2016, 42(8): 1632-1638. doi: 10.13700/j.bh.1001-5965.2015.0527
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Aviation alternative fuels play an important role in energy security and environmental protection. Coal-based Fischer-Tropsch synthetic fuel was chosen to experimentally study its basic combustion performance and evaluate the influence of flight range compared to theretical study. A B737-800 with two CFM56-7B engines was chosen to evaluate flight range in full envelope range in a civil aircraft typical mission. The study results show that the coal-based Fischer-Tropsch synthetic fuel has lower density and higher calorific value than petroleum-based aviation kerosene. The evaluation results show that the coal-based Fischer-Tropsch synthetic fuel's lower density and higher calorific value lead to its range shortened by 2.1%. Although Fischer-Tropsch synthetic fuel's combustion boundary is narrower, it performs better in ignition and coking than petroleum-based kerosene. The results obtained has certain directive significance to the practical application of the Fischer-Tropsch alternative fuel.
Impact of channel curvature on microgravity membrane gas-liquid separation performance
ZHANG Wenwei, KE Peng
2016, 42(8): 1639-1648. doi: 10.13700/j.bh.1001-5965.2015.0533
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The simulation research on the performance of microgravity membrane gas-liquid separation is of great significance for the design and optimization of gas-liquid separation technology. The Eulerian two-fluid model with an interface probability approximation method is introduced for the computability of multi-scale gas-liquid interface problem at inlet boundary in microgravity (inlet flow pattern problem), and the momentum source method is proposed for multi-scale geometric problem at membrane boundary. The model and the method provide a valid entry and permeable boundary for the simulation study. The influence of channel curvature on the membrane separation performance with typical operating parameters is studied, and the influence mechanism is analyzed in the view of flow morphologies and force contributions. The results show that the membrane separation performance reduces with channel curvature increasing, and the influence is related to inlet gas phase volume fraction; straight channel is suitable for membrane static gas-liquid separator.
Free-chattering fractional order sliding mode control of integrated electro-hydraulic servo pump
YANG Rongrong, FU Yongling, WANG Yan, WANG Deyi, GUO Jianwen, ZHANG Ling
2016, 42(8): 1649-1658. doi: 10.13700/j.bh.1001-5965.2015.0495
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Thanks to the special structure with the same rotor and housing shared by higher degree integrated servo motor and pump, integrated electro-hydraulic servo pump (IEHSP) has significant advantages in aspects of size, noise, efficiency, etc., and it has good application prospect. To improve IEHSP's speed regulation performance and anti-disturbance ability, a novel fractional order sliding mode controller (NFOSMC) is designed. First, the controller provides the system with more degrees of freedom because of introduction of fractional order calculus. Second, aimed at chattering problem of traditional sliding mode control, it is ensured that the fractional order integral action of switching term is included directly in the proposed controller, so that free-chattering sliding control can be achieved by utilizing its filtering property. Meanwhile, the finite time convergence stability is proved via Lyapunov theorem in presence of internal and external disturbance. Besides, the range of order for fractional order is extended due to the high order fractional differential term avoidance. To further enhance the ability of anti-disturbance, fractional order disturbance observer (FODOB) is proposed for observation and compensation of internal and external disturbance, so the response speed and stiffness of the controller is enhanced effectively. By comparison with PI, counterpart integer order sliding mode controller (IOSMC) and conventional fractional order sliding mode controller (CFOSMC), the simulation results indicate that NFOSMC based on FODOB can effectively improve the performance of speed tracking and the ability of disturbance rejection, and the effect of chattering elimination is remarkable.
Rendering algorithm with color coherence for dynamic electromagnetic environment
FENG Xiaomeng, WU Lingda, YU Ronghuan
2016, 42(8): 1659-1666. doi: 10.13700/j.bh.1001-5965.2015.0503
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After studying the existing state of the art, we firstly propose an rendering algorithm with color coherence for dynamic electromagnetic environment. The definition of color coherence for rendering is that the same value in different data frames corresponds to the same color and the change of colors in different rendered images follows the changing data. Based on the definition, the algorithm of rendering static electromagnetic environment is improved to render dynamic electromagnetic environment with color coherence kept. If needed, the relationship between mapping data and colors is edited by user interaction or the principles defined for the algorithm to follow the change of data. The experimental results show that the dynamic electromagnetic environment can be rendered with color coherence kept by the algorithm and the change of data is shown in the rendering images, which is helpful for user to understand the electromagnetic environment. Furthermore, parallel implementation of the algorithm using compute unified device architecture gets a high efficiency, which is good for using it.
Method of time-to-go estimation based on predicted crack point
LI Yuan, ZHAO Jiguang, BAI Guoyu, YAN Liang
2016, 42(8): 1667-1674. doi: 10.13700/j.bh.1001-5965.2015.0509
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Aimed at the different characters of the head-pursuit and head-on interception flight trajectory, the time-to-go (TGO) estimation methods are designed. According to the prediction of the crack point for the interceptor and target, the influence of different launch conditions on the precision of TGO estimation is decreased. At first, the linear proportional navigation motion equation is transformed, and the first order differential equation about the distance between interceptor and target is obtained. Based on the predicted crack point, the error for the integration result caused by the different initial launch angles is corrected. Then the TGO analytical expressions of two interception models are obtained. Compared with the existing three methods, the simulation result verifies the real time performance and the estimation precision of the proposed method which is able to optimize the guidance performance effectively.
Condition prediction of liquid propellant rocket engine based on process neural networks
NIE Yao, CHENG Yuqiang, WU Jianjun
2016, 42(8): 1675-1681. doi: 10.13700/j.bh.1001-5965.2105.0521
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Aimed at the problem of liquid propellant rocket engine condition prediction, a double parallel feedforward discrete process neural network (DPFDPNN) model based on extreme learning (EL) algorithm is proposed. The discrete process neural network (DPNN), which was trained via off-line data, is firstly adopted to make prediction of liquid propellant rocket engine condition. In order to improve the accuracy and efficiency of the DPNN for condition prediction, the weights connecting the hidden layer and output layer are then directly updated by the EL algorithm based on recursive algorithm with the real data stream. The corresponding computational steps are given and the DPNN with weights update is compared with the DPNN without weights update by predicting the lift of oxygen turbo pump. The result shows good accuracy and adaptibility of the DPNN with weights update and this work provides an effective way to solve the problem of liquid propellant rocket engine condition prediction.
Symplectic weighted discontinuous Galerkin method with minimal phase-lag
ZHU Shuai, ZHOU Gang, LIU Xiaomei, WENG Shilie
2016, 42(8): 1682-1690. doi: 10.13700/j.bh.1001-5965.2015.0523
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Symplectic finite difference method (FDM) can keep the symplectic structure, and finite element method (FEM) can keep the symplectic structure as well as energy conservation for linear Hamiltonian systems. However, symplectic FDM and FEM still have phase errors for the numerical solution, so, the computational accuracy is not very well in time domain analysis. Symplectic weighted discontinuous Galerkin method with minimal phase-lag (WDG-PF) is proposed for Hamiltonian systems. This method is symplectic and can highly decrease the phase error, compared to traditional method for Hamiltonian systems. Meanwhile, WDG-PF can keep the conservation of energy as well as the symplectic structure of Hamiltonian systems. WDG-PF can solve the phase-lag problem of continuous Galerkin method, and WDG is symplectic by the technique of weight. Compared to symmetric symplectic(FSJS) algorithm, Runge-Kutta-Nystrom(SRKN) and symplectic partitioned Runge-Kutta (SPRK) methods which are aimed at increasing the accuracy of phase error, WDG-PF ismuch more accurate and increase the energy accuracy of Hamiltonian systems, tremedously. The phase error and Hamiltonian function error almost achieve the accuracy of computer. WDG-PF has the ultraconvergence point in each element. Especially, for the systems with high and low frequency signals, and seldom has a method can simulate the high and low frequency signals with a fixed time step, WDG-PF can effectively simulate the high and low frequency signals with large time step. The numerical experiments show its validity.
Tube numerical controlled bending quality prediction based on machine learning
GE Yulong, LI Xiaoxing, LANG Lihui, CHENG Pengzhi
2016, 42(8): 1691-1697. doi: 10.13700/j.bh.1001-5965.2015.0493
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Wrinkle and over thinning, as well as inevitable spring-back, may occur along with the tube numerical controlled (NC) bending process, which have strong impacts on forming quality. As the bending processing is a complex non-linear system, it is hard to compute the result theoretically. Besides, finite element simulation is a time-consuming method for industry.To predict the forming quality of the NC bending, a rapid method based on the machine learning method and finite element modeling is raised. To apply the method, the first step is to build the finite element model of tube bending and make simulations whose process parameters are selected randomly as samples.After extracting experimental data, a radius basis function (RBF) neural network and a support vector machine (SVM) are built to predict thinning, spring-back and wrinkle separately.New instances are taken to verify the prediction method. The results show that the machine learning method can reliably predict the large diameter thin-walled tube NC bending quality and improve the efficiency of part forming process design.
Highly maneuvering hypervelocity-target tracking algorithm based on ST-SRCKF
FANG Jun, DAI Shaowu, XU Wenming, ZOU Jie, Wang Yongting
2016, 42(8): 1698-1708. doi: 10.13700/j.bh.1001-5965.2015.0494
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The movement model of highly maneuvering hypervelocity-target is difficult to construct accurately, and the existence of bad measurements in tracking process may lead to filtering divergence. In order to deal with these problems, a tracking algorithm applicable to highly maneuvering hypervelocity-target is proposed. This algorithm derives a new strong tracking square-root cubature Kalman filter (ST-SRCKF) structure from the orthogonality principle, and introduces multiple fading factors. The solution and function position of fading factors are both different from original ST-SRCKF. According to the statistical characteristics of innovation that the trace of innovation covariance matrix is in a chi-square distribution, a modified CS-Jerk model is constructed. The model describes target movement more accurately. When the modified CS-Jerk model is combined with the modified ST-SRCKF, highly maneuvering hypervelocity-target is tracked with high precision. Simulation results show that the modified algorithm has better tracking performance for highly maneuvering hypervelocity-target.
Dynamic modeling and simulation analysis of robot driver's mechanical legs
LIU Kunming, XU Guoyan, YU Guizhen
2016, 42(8): 1709-1714. doi: 10.13700/j.bh.1001-5965.2015.0519
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In order to improve the design efficiency of the robot driver, the dynamic analysis and modeling of the robot's mechanical legs are carried out, and furthermore, a collaborative simulation platform of the robot and vehicle is built. The mechanical leg dynamic model is made up of mechanical structure and servo motor, and the simulation model was built by ADAMS and MATLAB/Simulink; then the vehicle model was built by CarSim while the electromechanical co-simulation model "robot driver-vehicle" was built based on the closed-loop speed control in Simulink. Simulation results show that the dynamic model of mechanical leg has good dynamic response; in addition, the electromechanical co-simulation model is able to complete the basic speed tracking simulation experiment so as to provide a virtual prototyping model to improve the mechanical structure and control strategy.
Angular momentum management of space station based on pole placement
DANG Qingqing, JIN Lei, XU Shijie
2016, 42(8): 1715-1723. doi: 10.13700/j.bh.1001-5965.2015.0535
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For the problem that gravity-gradient torque and other disturbance torques can cause the accumulation of control momentum gyros (CMG) angular momentum when space station operates in inertial frame. Gravity-gradient torque is used for torque equilibrium attitude. An angular momentum management controller based on pole placement is proposed. First, the linearized model of space station in inertia frame is established and the infeasibility of the pitch axis direction of angular momentum management is proved. So we decouple the pitch axis and the roll/yaw axis, and do not constrain the angular momentum of CMG in pitch axis. The disturbance rejection filters are introduced to suppress the disturbance's impact on attitude in pitch axis. In orbit plane, to limit the cyclic disturbance's impact on roll/yaw axis and the secular disturbance's impact on the angular momentum of CMG, other disturbance rejection filters are introduced. Then, feedback controllers in pitch and row/yaw axis are developed based on linear quadratic regulators (LQR) with pole placement respectively. This algorithm is developed to place the closed-loop poles to the left side of complex plane imaginary axis based on the system performance requirements without choosing weight matrix. Finally, the simulation results demonstrate the validity of the proposed algorithm.
Correlation loss caused by GNSS receiver front-end processing for strong signals
PAN Hongchen, KOU Yanhong
2016, 42(8): 1724-1730. doi: 10.13700/j.bh.1001-5965.2015.0518
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In the applications of global navigation satellite system (GNSS) signal quality monitoring and GNSS radio frequency (RF) signal simulator test, the power of the desired GNSS signal usually goes much higher above the noise floor. This paper investigates the correlation power loss of binary phase shife keying (BPSK) and binary offset carrier (BOC) signals caused by band-limiting, sampling and quantization (BSQ) processing under strong signal conditions. Firstly, the correlation power loss caused by band-limiting and sampling without quantization is studied, and then the loss caused by quantization and sampling without band-limiting is analyzed. Consequently the desired signal correlation loss under corresponding conditions is theoretically derived, and the optimal step size of the uniform quantizer with different quantization bit numbers is determined. Finally, for the combined effect of BSQ on the signal correlation power, Monte Carlo simulations are conducted to analyze the normalized correlator power with the configurations of different bandwidths and quantization bit numbers of a GPS L1 C/A receiver, from which a method of fitting an analytical expression of correlation power loss by using the simulation results is explored to simplify the analysis.
Fuzzy time-variant reliability analysis of mechanical structure based on generalized degradation
SUN Xuan, ZHANG Jianguo, WANG Pidong, PENG Wensheng
2016, 42(8): 1731-1738. doi: 10.13700/j.bh.1001-5965.2015.0528
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The character that the specimen number of on-orbit mechanical products in space is small leads to the fuzziness of relative parameters and the dynamic degraded failure criterion. The existing fuzzy reliability model mainly aims at static problems, which cannot describe the time-variant and fuzzy problem. This paper proposes a fuzzy time-dependent reliability modeling and analysis method which is based on the interference model of generalized stress-strength and takes account of the fuzziness of both variables and failure criterion at the same time. First, fuzzy criterion can be transferred into random variables equivalently. Then the theory of cut set in fuzzy math can be used to deal with the fuzzy random variables, and thus the fuzzy time-variant reliability model is built. After that, a new method (FPHI2) is presented, based on the method of PHI2 which is a tool for time-variant reliability computation based on the outcrossing approach, to compute the fuzzy time-variant reliability. In the end, a numerical case and an engineering case are provided to verify the feasibility of the proposed method.
Simulation test platform of electrostatic damage based on three-dimensional field-and-road coordinated method
ZHANG Xin, BAI Chaoping
2016, 42(8): 1739-1746. doi: 10.13700/j.bh.1001-5965.2015.0529
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The electrostatic discharge has been taken as one of the main reasons for failures of electronic equipments, so electronic products are always tested to examine the antistatic ability in the process of development. However, the test is limited by high cost of expense, poor repeatability and damage on equipments. In this situation, the problems can be solved by building a simulation test platform of electrostatic damage based on three-dimensional field-and-road coordinated method. The platform is based on the computer simulation technology (CST) software and the results can be calculated through the electrostatic discharge gun module, tested equipment module, simulation parameter setting module and data output and processing module with the finite integration time domain solver. By using the platform, a data transmission equipment was tested with an 8 kV voltage touching input and then the conducted and radiated interference were analyzed with the results of surface currents and magnetic field distribution. Through building the simulation test platform of electrostatic damage, the purpose of repeatability and no damage of testing is achieved and the engineering guidance is meaningful.
Influence of inconsistence of GNSS anti-jamming antenna array on MUSIC algorithm
YU Lihong, QIN Honglei, LI Wutao, LANG Rongling
2016, 42(8): 1747-1754. doi: 10.13700/j.bh.1001-5965.2015.0497
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Suffering from the errors of antenna array elements such as radio frequency (RF) amplifier and analog to digital converter (ADC), global navigation satellite system (GNSS) anti-jamming antenna array has channel inconsistence inevitably. Firstly, the influences of the amplitude and phase inconsistence of channel on multiple signal classfication (MUSIC) anti-jamming algorithm are analyzed with the subspace theory of matrix. Theoretical analyses and experimental results indicate that in the case of single interference, the amplitude inconsistence decreases the nulling depth of antenna array pattern generated by MUSIC algorithm, but does not influence the nulling direction, while the phase inconsistence affects both the nulling depth and direction of the antenna array pattern. In the case of multiple interferences, the amplitude inconsistence influences both the depth and direction of nulling in antenna array pattern; the phase inconsistence of channel influences both the depth and direction of nulling in antenna array pattern of MUSIC algorithm. When the channel inconsistence changes slowly, before using array pattern to evaluate the performance of the MUSIC algorithm, the array pattern should be calibrated by measuring the deviation matrix of the channel amplitude and phase. Then, the experimental analyses on the influences of the inconsistence are carried out by simulation, and the results of the experimental analyses are consistent with those of the theoretical analyses.
Radiator threat evaluating method based on rough set and information entropy
FAN Xiangyu, WANG Hongwei, SUO Zhongying, CHEN You, YANG Yuanzhi
2016, 42(8): 1755-1761. doi: 10.13700/j.bh.1001-5965.2015.0663
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In order to meet the need of threat ranking arithmetic of air radar emitter in complex electronic environment, the rough set theory is introduced into radar radiator threat evaluation. A self-contained data processing model for computing threat metric values is established to realize the quantitative representation of the radiator threat degree, thus allowing evaluating the threat degree of emitter straightforward. The information entropy is applied to determine the attribute with the maximal weight instead of decision one, solving the decision-making problem when there is no prior knowledge, which can be used to extend the range of application of classical rough set. This model is based on data-boost method to acquire the radiator threat metric values directly, which is easily realized and has favorable time-efficient feature. The method reduces the demand of system for prior information and avoids the effect introduced by subjective assignments. The simulation results show that the method has good ability to accomplish target threat assessment fleetly and exactly.
Object contour extraction based on image feature analysis
WANG Tian, ZOU Zilong, QIAO Meina
2016, 42(8): 1762-1768. doi: 10.13700/j.bh.1001-5965.2015.0491
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Contour analysis and extraction is the fundamental problem in computer vision, and the research about it plays an important part in complex scene analysis and comprehension. In this paper, an algorithm for analyzing indoor scene images is studied. Based on the image features extracted from the images, the objects in the indoor scenes are segmented, and further the contours of the objects are extracted. Based on the globalized posterior probability of a boundary (gPb) method for the contour extraction on the RGB image, we introduce the depth information to enhance the performance of contour extraction on RGB-D data of indoor scenes. By combining multi-scale cues, the multi-scale posterior probability (mPb) and spectral posterior probability (sPb) are obtained. The mPb and sPb results are summed and weighted to get the gPb information. Then, the gPb information is processed by ultrametric contour and watershed algorithm, and the contours of the indoor scene objects are gained. The experiments presented in this paper are run on the general RGB-D dataset. The experimental results show that our method can extract the distinct contours of indoor objects.
Simulation and analysis of active cancellation stealth based on LFM wave
BIAN Xiaochen, HUANG Peilin, JI Jinzu
2016, 42(8): 1769-1776. doi: 10.13700/j.bh.1001-5965.2015.0492
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Abstract:
Active cancellation stealth technology is gaining increasing attention due to its wide applicability, flexibility and its effect which has nothing to do with the shape of the target. A kind of active cancellation system based on linear frequency modulated (LFM) wave was proposed for its technical requirements such as rapid response and low-delay. The phase and frequency of the sampling incident wave were modulated and transmitted, so the synthetizing output of cancellation and original wave are decreased. The electromagnetism principle of active cancellation technology is discussed. The effect of cancellation between plane wave and cylinder wave was simulated based on the scattering source of the ideal electrically conducting infinite cylinder. The conclusion is that the effect of cancellation is influenced by the angle of view and the intersection angle of the two waves and the best result is obtained when the angle is 0°. The output formula of the output signal is derived and the simulation is carried out using MATLAB. Simulation results show that the effect of cancellation is decided by the division of repeating time delay and pulse width, and the width of the output signal is decided by the bandwidth.
Dynamic surface control for quadrotor unmanned air vehicle
FANG Xu, LIU Jinkun
2016, 42(8): 1777-1784. doi: 10.13700/j.bh.1001-5965.2015.0498
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Abstract:
A dynamic surface control method is proposed to control position and attitude of quadrotor unmanned air vehicle (UAV) against its characteristics of underactuation. Considering that velocity and angular velocity are hard to measure, we design a high-gain observer for UAV to estimate velocity and angular velocity. Compared with backstepping approach, the design of dynamic surface control is more concise. Dynamic surface control eliminates the problem of "explosion of complexity" by introducing filter. Traditional time scale separation principle cannot prove the stability of whole system. By introducing the dynamic surface control method, it is shown that the control strategy can guarantee semi-global stability of the closed-loop system and arbitrarily small tracking error by adjusting the controller parameters. The stability of whole system is also given. Simulation results indicate that the proposed control system can achieve accurate tracking control for quadrotor UAV.

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