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2011 Vol. 37, No. 11

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On compressive sensing applied to SAR imaging
Xiao Peng, Li Chunsheng, Yu Ze
2011, 37(11): 1333-1337.
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State of the art radar systems apply a large bandwidth and an increasing number of channels produce huge amount of data. The data easily exceeds that be stacked in the sensor or downlinked to the ground station. In order to solve this trouble, a novel synthetic aperture radar (SAR) raw data retrieval and a corresponding pulse compression method based on compressive sensing (CS) theory were presented. Under the assumption that the observed scene shows characteristic of a sparse reflectivity distribution, traditional matched filter can be replaced by CS for pulse compression. Benefits from this substitution include much lower data amount for scenario reconstruction than traditional SAR. In this method, the pulse compressed signal was reconstructed by solving an inverse problem through a greedy pursuit. The principle and process of the algorithm were given, and the effectiveness was validated by computer simulation. The new approach greatly simplifies the radar system, effectively reduces the huge amount of data, thus shifting emphasis from expensive receiver design to smart signal recovery algorithms.
Motion blur of star image and restoration
Wu Xiaojuan, Wang Xinlong
2011, 37(11): 1338-1342.
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The impact of vehicle angular and vibrational motion on the star imaging process was researched, and the mathematical model of motion blur corresponding to various flight states was deduced and established then. On this basis, the mechanism of multiple motion blur was discussed. In order to ensure the accuracy and stability of star sensor under high dynamic conditions, a step-by-step restoration was proposed to remove the multiple blur of star image. The simulation results indicate that the star centroiding accuracy caused by vehicle motion is related with specific motion type and parameters, and the restoration method is validated by comparing the attitude estimates before and after the restoration of blurred star image.
Cooperative generation of phantom radar track using a team of ECAVS based on RGPO
Gao Bin, Mao Shiyi, Sun Jinping
2011, 37(11): 1343-1346.
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The technology of track deception for cooperative control of multiple electronic combat air vehicles(ECAVs) was analyzed by kinetics model. ECAVs were used to generate phantom radar tracks in multiple radar air defense network. Two-dimensional analyses of scenarios were provided involving single ECAV deceiving single radar and multiple ECAVs deceiving an integrated network of radars using range gate pull-off (RGPO) deception. According to the collinearity constraint request for ECAV, radar and phantom track, and through reducing finite dimensional searches to one dimensional parameter searches, the proposed algorithms were computationally attractive, and the ECAVs track programming problem under kinematic constraints can be realized real time computations amenably.
Guidance and control law design for an impulsive logic-based switching flight system
Chen Jian, Tian Yuan, Ren Zhang
2011, 37(11): 1347-1352.
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Guidance and control law design for an interceptor equipped with both aero fins and side jets was discussed. Since the aerodynamic lift force for generating available norm load is not enough at high altitude, side jets are introduced into the interceptor dynamics to increase its maneuver capability for improving the interception precision to a maneuvering target by comparison with a traditional missile equipped with only aero fins. The side-jet missile dynamics was described with a hybrid impulsive switching system model. A sliding mode guidance law and a logic-based switching function for turning on the side jets were both proposed to generate desired guidance commands. Simulations and comparisons verify that the sliding mode guidance law and logic-based switching law are sensitive to target-s maneuvering and the end-game miss distance is smaller than 0.1m which represents the interceptor directly hits and kills the target.
Tracking technique in the presence of standoff jamming
Xu Haiquan, Wang Guohong, Guan Chengbin
2011, 37(11): 1353-1358.
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In the presence of standoff jamming(SOJ), radar has low probability of target detection, which brings up the trackloss and decreases the track lifetime. Aimed at these problems, a combined target tracking approach was presented. The approach has two components: particle filter based track before detect(PF-TBD) and adaptive detection threshold selection in multiple hypothesis tracking(MHT). Track management in different region was also considered. Simulation results indicate that the approach presented takes fully advantage of TBD, meanwhile the time efficiency spent in target tracking in the whole surveillance region is considered, and it has expanded 20% of the surveillance region of radar. The resulting advantage suggests that this approach is of important reference significance for the theory and realization of tracking system in the presence of SOJ or other jamming.
Effects of wing planform on aerodynamics force production of stroking model insect wing
Mou Xiaolei, Sun Mao
2011, 37(11): 1359-1364,1371.
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The effects of wing planform (shape and aspect ratio) on the aerodynamic force production of model insect wings in stroking motion were investigated, using the method of computational fluid dynamics. Ten respective insect wings were considered, they were the wings of fruit fly, cranefly, dronefly, hoverfly, ladybird, bumblebee, honeybee, lacewing (forewing), hawkmoth and dragonfly (forewing).The main results are as following. The force will be increased as the radius of the second moment of wing area is increased, but it has only minor effects on the force coefficients when the velocity at the radius of the second moment of wing area is used as the reference velocity. The force coefficients vary slightly, when aspect ratio increasing from 2.8 to 5.5. The reduction of 3-dimensional flow effects and the shedding on part of the leading-edge vortices (LEV) cancel each other, resulting in only minor change of the force coefficients.
Singular perturbation midcourse guidance law based on dynamic inversion for air-to-air missile
Qiao Qingqing, Chen Wanchun
2011, 37(11): 1365-1371.
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A near optimal midcourse guidance law incorporating a linear combination of flight time and terminal specific energy as the performance index was derived using singular perturbation theory and dynamic inversion. Missile state functions were put into three time-scale system according to the time constants of state variables. The reduced-order model consists of down range, cross range and specific energy dynamic. Optimal solution of reduce-order system, so called outer solution of original system, was obtained using optimal control theory. Dynamic inversion was applied to boundary layer correction for a close-loop controller. The performance of the controller could be regulated in accordance with different requirement of rise, cruise and descent stage or other instance. Simulation result shows that this guidance law satisfies requirements on trajectory smoothness, flight time and terminal specific energy. At the end of midcourse stage, missile heading error was small enough to ensure smooth transition from midcourse guidance stage to terminal guidance stage.
Fault detection of dual redundant actuation system based on the fault modeling
Fu Yongling, Pang Yao, Liu Hesong, Zhang Ye
2011, 37(11): 1372-1377.
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In order to solve the problem of fault diagnosis of dual redundant actuation system characterized by complicated structure, a fault diagnosis method based on reverse-reasoning of fault models was proposed. With all the failure mechanism of different components considered, the typical fault models of close-loop system were established through fault injection. It was revealed that how these faults led to degradation of system performance or even total failure. According to the simulation results, the fault diagnosis method was established through classifying and reverse-reasoning of observed abnormalities and some faults were evaluated quantitatively using mathematical formulas. This fault diagnosis method covers all the components of the system. Moreover, it can not only locate the failure part of system rapidly, but also can identify and quantify the faults. Furthermore, the algorithm is easy to realize in project.
Method of TDOA multi-station passive location based on weighted matrix
Chang Xiaoming, Zhang Xiaolin, Zhang Qiang
2011, 37(11): 1378-1383.
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Passive location technology has been applied broadly these years. Taylor expansion method was commonly used by the traditional multi-station passive location system. A new method of time difference of arrival(TDOA) passive location with multi-station based on weighted matrix was presented. When the stable carrier being included in a target-s emission signal, the noise characteristics equations was analyzed using the conventional time-domain correlation method after the carrier was tracked. The model was constructed with the weighted matrix of the distance difference observations among a number of stations, thus the high accuracy location being obtained by employing the weighted matrix. From the simulation, it can be proved that under the same condition, the position results using presented method are more accurate than the traditional Taylor expansion method, improved by about 30% in best cases. This method is an effective method for multi-station passive location, particularly for mobile observation stations.
Electromagnetic interference caused by aerospace explosives
Cao Jingyang, Xie Shuguo, Su Donglin, Ma Zhichao
2011, 37(11): 1384-1387,1394.
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Simulative experiments on the ground were carried out to measure the radiation by chemical explosion of aerospace explosives in stage separation and evaluate the impaction on the electronics in the rocket. Electromagnetic pulses by different explosives were captured by a rod antenna and measured by a real time analyzer. The results show that radiation increases as the energy of the explosion. When using a mild linear shaped charge,considerable pulses were recorded in dozens of milliseconds after the separation, with the frequencies around megahertz and magnitude about several V/m on single frequency. Electromagnetic environment inside and outside the rocket were recorded and compared by simple dipoles, and current pulses induced on the circuits inside the rocket were also measured. The conclusion could direct the anti-interference design on the inner electronics of launch vehicle.
Satellite attitude determination algorithm of model error robustness
Wei Mingkun, Yang Jing
2011, 37(11): 1388-1394.
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A new high-precision star sensor/gyro attitude determination algorithm based on nonlinear predictive filter (NPF) and second-order divided difference filter was presented. In this algorithm, model error was estimated by NPF, and the state was estimated via second-order divided difference filter by using compensated system model. While it is difficult to obtain the accurate dynamic model of attitude determination system, extended Kalman filter (EKF) treated uncertain model error as zero-mean white noise might cause low precision of state estimation even to divergence. The proposed method solved such problem. The nonlinear model was the second-order approximation while using second-order divided difference filter without calculating the partial derivatives of system model, and then attitude estimation with high precision was obtained. Simulation results show that the proposed method estimates and compensates the model error in real-time effectively and improves the estimation precision, also the filter period influences the precision slightly. The effectiveness and the robustness of the proposed method are proved.
Improved analysis method of risk priority number
Chen Zhengping, Fu Guicui, Zhao Youhu
2011, 37(11): 1395-1399.
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Aiming at the defect of traditional risk priority number(RPN) method in process failure modes and effects analysis(PFMEA),the reasons of the defect thoroughly were analyzed, and a new RPN ranking method based on cost and probability was presented which is combined qualitative analysis with quantitative analysis. In the qualitative analysis , which is based on the estimation of severity ranking in the traditional risk priority number method, the severity ranking of the process failure mode was estimated. In the quantitative analysis, it used the expected cost caused by the failure mode as the risk priority number. The improved RPN method uses the quantitative numbers to make the ranking result of the RPN more objective and accurate. Finally, the new RPN method was applied to the PFMEA of the filter assemblage of a module in the modern radar, and a great result is obtained.
Tactical data link system with low-density parity-check code scheme
Li Hang, Chen Wei
2011, 37(11): 1400-1403,1409.
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In information warfare, military combat capability can be improved by tactical data link system of which coding is one of crucial techniques of the transmission reliability. A new type of tactical data link system was proposed employing low-density parity-check (LDPC) code scheme, which is a new set of codes for communication systems demanding intensive reliability. The sum-product algorithm of the LDPC code scheme was introduced and the transmission model was described. Then the link performance of the system within the fix frequency over additive white Gaussian noise (AWGN) channel was analyzed. Simulation results with Monte-Carlo method show that the LDPC code scheme can decrease the bit error rate of the tactical data link system effectively. The results also showe that the LDPC-coded data link system achieves better performance than joint tactical information distribution system (JTIDS), which employe Reed Solomon codes as channel coding scheme, over AWGN channel and Rayleigh fading channel. LDPC codes, serving as the alternative codes for channel coding technique, provide possible solutions to enhance the transmission reliability of tactical data link system.
Experiments of combined heat transfer in leading of blades at rotating state
Gu Zhenpeng, Deng Hongwu, Tao Zhi, Zhu Jianqin
2011, 37(11): 1404-1409.
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Transient experiment was performed to study the heat transfer characteristic of impingement cooling with outflow film in the leading of turbine blades at rotating state. And, the effect of Coriolis forces and centrifugal forces on combined heat transfer effectiveness was discussed. The Reynolds number based on the inlet velocity of the impinging jet and hole diameter is 4 000. The Rotation number is from 0 to 0.139. Experiments' results show that the heat transfer effectiveness decreases with the Rotation number increasing. The average Nusselt number on the impingement face decreases 33%, and the average Nusselt number on the pressure face and the suction face decreases 20.5% and 7.5%, respectively. The effect of Coriolis forces enhance the spreading rate of the jet flow, which is mostly factor that result in heat transfer characteristic down. The effect of Coriolis forces together with centrifugal forces arouses the difference of heat transfer on pressure face and suction face at rotating state, and the average Nusselt number on the suction surface was larger than that on the pressure surface. The presence of the film holes changes the flow structure and gathers head the heat transfer effectiveness of films'border area.
Wear condition prediction of hydraulic pump
Ge Wei, Wang Shaoping
2011, 37(11): 1410-1414.
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Wear is a typical progressive failure of aero hydraulic pump. It is difficult to measure wear loss. To solve precision wear condition prediction problem, multi-dimensional support vector machine (SVM) prediction method was proposed, based on theoretical basis of SVM applied to time series prediction, multi-dimensional data decomposition and phase space reconstruction. The inner relationship of time series can be mined and reflected more effectively by this method. Oil-return flow was chosen to reflect the wear condition of hydraulic pump and was decomposed into trend data and random data. Multi-dimensional SVM was applied to predict oil-return flow of the aero hydraulic pump one-step ahead and multi-step ahead with grid search optimization method. The results show that multi-dimensional SVM model has higher prediction precision and is very suitable for long-term forecasting compared with the predicted results of traditional SVM.
Safety simulation applying Stateflow technology
Wang Bei, Zhao Tingdi
2011, 37(11): 1415-1420.
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The accident-process oriented safety simulation method was proposed to ensure the safety of high risk systems, as well as explore the movement during the accident evolution and emergency treatment. The modeling and simulation method was designed upon the principle of finite state machine and the technology of Stateflow. By this method, the modeling and simulation of process logic and continues mechanism in hybrid system can be achieved. Then the simulation result can reflect the system characteristic of state transforming and man-machine communicating, and the mechanism in the accident process, accordingly, the quantitative support can be provided for the emergency treatment decision-making. Finally, the model design and simulation experiment for the typical accident process in some product were implemented, and the validity and rationality of this proposed method were validated by the result.
Analysis of features of particulate matters emitted from engine fueled with petroleum coke slurry
Xiang Liming, Li Xinghu
2011, 37(11): 1421-1424.
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Scanning electron microscope, X-ray energy dispersive spectroscopy and thermal gravimetric analyzer were used to detect the surface structure, chemical component and combustion characteristics of petroleum coke particulate matter (PM) samples and PM samples from the exhausts of engine fueled with petroleum coke slurry (PCS) and No. 0 diesel fuel respectively. The results show that PM samples from PCS array sparsely, but PM samples from diesel array closely, cohering mutually. The diameter of PM from PCS is somewhat bigger than that of petroleum coke PM, but in some sort smaller than that of PM from diesel. The superficial major element contents of PM from PCS, such as C, O and S element, are close to those of PM from diesel. But the C and S element contents of PM from PCS are lower than those of petroleum coke, and O element content is higher than that of petroleum coke. The volatile component concentration of PM from PCS is higher than that of petroleum coke, but lower than that of PM from diesel. The fixed carbon content of PM from PCS is lower than that of petroleum coke, but higher than that of PM from diesel. The ignition temperature and burnout temperature of fixed carbon content of PM from PCS and diesel are similar, but both are higher than those of petroleum coke.
Effect of mix milling on the microstructure and surface modification of YAl2 particles
Zhang Xin, Wu Guoqing, Ling Zhaohua, Huang Zheng
2011, 37(11): 1425-1428.
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A homogeneous distribution of ultrafine YAl2 particles in YAl2/Mg mixture was obtained by mix-milling method. The effect of milling on the microstructure of YAl2 particles and the dispersion of YAl2 particles in the mixture were investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDAX) and transmission electron microscope (TEM) techniques. The results show that with increasing milling time, YAl2 particle size decreases, and the amount of particle sharp corners is significantly reduced. After 20 h of milling, YAl2 particles have a nearly spherical shape with an average size of approximately 1.5 μm. YAl2 particles are coated by elemental magnesium, and distribute uniformly in YAl2/Mg mixture through ball milling.
Estimation for detection probability of infrared point target under complex backgrounds
Mao Xia, Chang Le, Diao Weihe
2011, 37(11): 1429-1434.
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The detection probability of infrared(IR) imaging system for point target will always be affected by complex backgrounds, but present methods can not be applied in the condition of complex backgrounds. Beginning from the model of operating distance of IR imaging system for point target, the relationship between detection probability, signal-to-noise ratio(SNR) and operating distance was analyzed, the estimation method under single background was gained. Then through the gray-to-radiance function of IR imaging system, the background-s IR radiance with its gray-value information was calculated. At last, the esimation method for single background was improved and the method for estimating the detection probability of infrared point target under complex background was proposed. The experimental results demonstrated that this method could effectively estimate the detection probability of IR imaging system under complex background in practical applications.
Pulse phase thermography chirp Z transform
Ma Shuohan, Ma Qishuang
2011, 37(11): 1435-1439,1445.
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In order to solve the problem of insufficient frequency resolution, occurring at the infrared detection data processing by the pulse phase thermography (PPT), a new frequency domain transform method was proposed. The fast Fourier transform (FFT) was utilized to choose the narrow frequency band included within the characteristic frequency, this band was processed by the chirp Z transform (CZT), the refined frequency structure was obtained. The clear amplitude and phase image sequences were reconstructed from the pixel-by-point analysis results. Without increasing the sampling time, a higher frequency resolution was achieve than the one of the PPT. Through the comparison of the detection signal from an aluminum material specimen, the results show that the algorithm can effectively refine the selected frequency band, get more precise characteristic frequency and effectively reduce the spectral leakage errors.
Afterbody/nozzle optimal design of hypersonic vehicle
Gan Wenbiao, Yan Chao
2011, 37(11): 1440-1445.
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Through combining design of experiment (DOE), surrogate models with genetic algorithms, modified optimization method was built,which was applied in the integrated design of afterbody/nozzle of a hypersonic vehicle．The sequential global surrogate models were developed to satisfy the computational demand. The issue of modifying genetic algorithms included the real number coding,niche technique and multi-objective class&rank skill.In the optimization question, precise computational fluid dynamics(CFD) were used, thrust and lift were used as the performance objects,moment were used as constrain ,and the Pareto front was gotten. After the optimization, the thrust and lift force of the nozzle has a great improvement．As a method,this algorithm can be applied in the optimization design with a more complex flow model．
Two-axes mechanism for satellite antenna disturbance characteristics simulation and experiment
Wu Shijian, Cheng Wei
2011, 37(11): 1446-1450,1455.
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The micro-disturbance of satellite antenna is a key factor which will affect the accuracy of satellite attitude control. The satellite disturbance modeling is aimed for obtaining the disturbance characteristics and then adopting corresponding control methods and isolation systems to restrain it. On account of the influence of both the antenna structure-s nature mode and the stepper motor to the satellite body disturbance, the satellite antenna structure-s disturbance math model was built. Based on the model simulation was calculated and an experiment was designed to test the disturbance. Comparing the simulation and experiment results the math model is correct and reliable and it-s a reference and a consult to the influence of the antenna to the pointing control precision and stability of the satellite
Scalar multiplication algorithm of ECC based on precomputation and periodicity
Zhang Xiaoqiang, Zhu Guiliang, Wang Weiping, Wang Mengmeng
2011, 37(11): 1451-1455.
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Based on the binary method, non-adjacent form (NAF) method, etc., a new scalar multiplication algorithm was proposed, which uses the periodicity of based point and the precomputation mean. Meanwhile, the steps of new algorithm were given. The periodicity of based point and the coefficient of scalar multiplication determine performing the operation of scalar multiplication directly or computing its inverse element. The precomputation mean can void a quantity of repeat computation during the encryption and decryption processes of elliptic curve cryptosystem (ECC). To verify the correctness of new algorithm, a concrete experiment was offered with an elliptic curve, whose key length is 192 bit. The experimental results and algorithm analyses show that comparing with binary and NAF methods, although the new algorithm requires a little extra space to store precomputed points, it does not need the operation of point doublings and reduces the operation times of point addition. Therefore, the new algorithm can improve the efficiency of scalar multiplication sharply. The research achievement is significant for completing the theory of ECC and accelerating its application in practice.
Effects of airflow split and primary holes arrangement on lean blowout limits of combustor with dual-axial swirlers
Xie Fa, Huang Yong, Miao Hui, Chen Haigang
2011, 37(11): 1456-1460.
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An experimental research was conducted for the effect of the variations of dome air entry areas and the arrangement of primary holes on the lean blowout (LBO) limits of a single dome rectangular model combustor with dual-axial swirl cups. The experimental results show that the variations of air entry areas into the swirlers will have great effect on the LBO performance of the combustors. Increasing the air entry area into the primary swirler by 20% will improve the combustor lean blowout limits about 11.8%, and increasing the air entry area into secondary swirler by 20% will improve the combustor lean blowout limits about 16.6%. On the contrary, the decrease of the air entry areas of the swirlers will deteriorate the LBO performance. Besides, the arrangement of primary holes has little effect on the combustor LBO limits.
Risk assessment and sensitivity analysis of detector safety landing
Li Tao, Yang Jun, Fei Simiao
2011, 37(11): 1461-1464.
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Safe landing of detector is the key of planetary exploration, but the success probability of landing is still low, and the study of landing risk is very important in practical engineering. The detector-s structure and landing way were analyzed, and the main influence factors of the safety landing were concluded, then the criterions of safe landing were given. Based on Monte Carlo theory, the planet surface landform and detector landing way were simulated, and the probability of safety landing under blind landing was given by simulation method.Furthermore, consider the detector size and landing area, the sensitivity analysis of the probability of safety landing was carried out, and the results show that the detector size has significant influence on the probability of safety landing.
Finite element model updating of airplane wing based on Gaussian radial basis function response surface
Qin Yuling, Kong Xianren, Luo Wenbo
2011, 37(11): 1465-1470.
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The benchmark finite element model(FEM) of the airplane wing was constituted using the three-dimensional solid element SOLID45 in ANSYS, and the uniform design method was employed to group the structure parameters to calculate the corresponding modal frequencies of each set of parameters, then the Gaussian radial basis function(RBF) response surface was constituted, the coefficients of which were fitted by the least square method(LSM), and the fitting precision was evaluated. The non-updated FEM was obtained by adding perturbation to the structure parameters of the benchmark FEM, and the fitness function was constituted based on the difference between the modal frequencies of the benchmark FEM and the Gaussian radial basis function(RBF) response surface, which guided the particle swarm optimization(PSO) algorithm with chaos-search mechanism to search for the perturbation of the structure parameters, the optimal solution was substituted into the non-updated FEM and then the updated FEM was obtained, the validity of the updated FEM is approved by comparing the similarity of the modal frequencies of the updated FEM and the benchmark FEM in and out of the test range.
Analysis of electromagnetic radiation for airborne very-low-frequency (VLF) dual trailing antenna in half-space
Wu Longgang, Su Donglin, Chen Jiajia, Wu Nankai
2011, 37(11): 1471-1474.
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Electromagnetic radiation characteristics of an airborne very-low-frequency (VLF) dual trailing antenna in the half-space (a space including air and seawater) were studied. The airborne VLF dual trailing antenna models in half-space were established and calculated by finite element method (FEM). The influences of the half-space to antenna radiation patterns were investigated using numerical results. In addition, through shifting feed locations (i.e., changing the ratio of long antenna and short antenna), variation trends of antenna characteristic parameters in half-space, including antenna input impedance and radiation efficiency were obtained. Good agreements of simulation results and the corresponding data announced by american naval and air development center were achieved, which validates the effectiveness and reliability of the proposed method and results. The achievements provide significance to the airborne VLF dual trailing antenna design in the future.

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