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2015 Vol. 41, No. 2

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Volume 41 Issue22015
2015 Year 41 Volume 2 Issue E-journal
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Evaluation of ICCP algorithm for geomagnetic navigation based on hardware-in-the-loop simulation
WANG Shicheng, LÜ Zhifeng, ZHANG Jinsheng, LU Zhaoxing
2015, 41(2): 187-192. doi: 10.13700/j.bh.1001-5965.2014.0117
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The performance of geomagnetic navigation matching algorithm is influenced by many factors. However, the evaluation of algorithm is completely based on computer simulation at present, whose credibility should be validated further. The iterated closest contour point (ICCP) algorithm was studied. First, the factors were analyzed theoretically, which affect the performance of algorithm. Then, the hardware-in-the-loop simulation system of geomagnetic navigation was established. Geomagnetic field simulation environment and magnetic sensor were introduced in the system and the credibility of simulation was improved. Finally, the performance of algorithm was analyzed from measurement noise, matching length, matching region and inertial navigation system (INS) errors based on the hardware-in-the-loop simulation system. The simulation results show that anti-interference of the algorithm, determination of matching length, selection of matching region and influence of INS errors can be evaluated effectively through the hareware-in-the-loop simulation experiments. The method of hareware-in-the-loop simulation can promote the engineering process of geomagnetic navigation and ICCP algorithm.
Interval data analysis based on empirical distribution function
WANG Huiwen, WANG Shengshuai, HUANG Lele, WANG Cheng
2015, 41(2): 193-197. doi: 10.13700/j.bh.1001-5965.2014.0435
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Uniform distribution in some closed or tight interval is a basic assumption in the literature about interval data analysis, which is difficult to satisfy in real data processing. To solve this problem, the empirical cumulative distribution function (ECDF) and kernel estimation of cumulative distribution were studied, on the assumption that the date were from some continuous distribution. Based on ECDF and kernel estimation, a transformation to obtain new data was designed, which was uniformly distributed in theory. Then whether the distribution of transformed data was uniform distribution was tested. If the null hypothesis was not rejected, traditional methods in the field of interval data analysis could be utilized based on transformed data. The transform and the test were both for guaranteeing the transformed data were from some uniform distribution. Both simulation and real data example show that, the results based on ECDF and kernel estimation transformed data are more reasonable and with strong explanatory ability.
Time-varying response surface method for high-temperature structural reliability analysis
MA Xiaobing, REN Hongdao, CAI Yikun
2015, 41(2): 198-202. doi: 10.13700/j.bh.1001-5965.2014.0142
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The constitutive equation and carrying capacity of structure will change over time under high temperature conditions. The traditional structural reliability models are inefficient to solve these time-varying structural reliability problems. A time-varying response surface method with thermal response and response threshold value changing over time was proposed. The method can be used for high-temperature structural reliability analysis. Combined with Box-Behnken experimental design, a cross quadratic function of structure's basic variables and time was introduced for establishing a time-varying model of the thermal structural response. The function of structural response threshold value and time was established by using temperature as intermediate variable. The time-varying structural reliability calculation method was proposed when basic variables are normally distributed. A study case was given to demonstrate the applicability of this method and its greatly enhanced effectiveness besides accuracy.
Large scale uniform electromagnetic field simulation based on Helmholtz coil
HUANG Songtao, ZHANG Wei, ZHANG Pengfei, QI Zewu
2015, 41(2): 203-208. doi: 10.13700/j.bh.1001-5965.2014.0168
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Considering the technical requirements of the space physical environment simulation system, a square Helmholtz coil was built by a pair of axis symmetric rectangular coils which had the same turns, side length, height and thickness, based on the principle of Helmholtz coils. Combining with the constant current source and MCU control technology, the electromagnetic field simulation system was designed. Adopting finite element analysis software ANSYS Workbench, the magnetic field distribution of the square Helmholtz coil was simulated, and the emphasis of the study was on the electromagnetic field distribution of the coil X-axis, Y-axis and near the surface of the coil. Based on the analysis results, the structure parameters of the square Helmholtz coil were designed. The magnetic flux density of 12 key points was measured inside the designed coil. The results show that the magnetic flux density and uniformity of the magnetic field inside the coil could satisfy the requirements of the space environmental simulation systems.
Pipeline spraying robot: structure and pose adjustment
CHEN Youdong, JI Xudong, TANG Wei
2015, 41(2): 209-215. doi: 10.13700/j.bh.1001-5965.2014.0163
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To meet the demand of large allotype pipelines inner wall spraying, a pipeline spraying robot with series and parallel structure was designed, which consisted of a support platform and a series manipulator. The support platform was modeled by geometric method. The manipulator was analyzed by D-H method. Based on the robot model, inverse equations were obtained. After the robot was positioned initially, the robot and pipeline poses were measured by laser tracker. The adjustments were calculated by the inverse equations. According to the adjustments, the robot was adjusted so that the axis of the pipeline coincided with the axis of the spray gun. Through the implemented by the manufacturing plant, the effectiveness of the pipeline spray robot and the method of the pose adjustment were confirmed, and the results show that the robot can improve the efficiency and the quality of spray.
Principle of plane display interface design based on visual search
FAN Xiaoli, ZHOU Qianxiang, LIU Zhongqi, XIE Fang
2015, 41(2): 216-221. doi: 10.13700/j.bh.1001-5965.2014.0087
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Pilots monitor all kinds of instrument information by visual searching during flight. This process was studied to explore the effects of time pressure and search difficulty on visual searching, aiming to provide scientific basis for the ergonomic design of display interface of aircraft cockpit. A visual searching program was designed to simulate the display interface. Before conducting formal experiment, the classified ranges of time pressure and searching difficulty were evaluated by pre-experiment. Using SPSS 19.0, analyses such as double factor variance analysis, simple main effect, and regression analysis were conducted on the response correct rate and response time obtained by the formal experiment. The following conclusions were obtained, different levels of time pressure and search difficulty all have significant effect on the response accurate rate; search difficulty has obvious effect on the response time which has a linearly increasing relationship with distractor number; under high correct rate situation, that is within the human cognitive abilities, time pressure haven't such effect on the response time. In ergonomical study of display interface in plane cockpit, good match of time pressure and searching difficulty could obtain better searching performance.
Numerical simulation of individual components of pitch-damping coefficient sum
XI Ke, YAN Chao, HUANG Yu, WANG Wen, YUAN Wu
2015, 41(2): 222-227. doi: 10.13700/j.bh.1001-5965.2014.0094
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An approach for predicting the direct damping derivatives that formed the pitch-damping sum was presented. Application of the technique was made to the axisymmetric projectile configuration as well as the non-axisymmetric winged vehicle. The plunging derivatives and pitch-damping sum were obtained using forced heave and angular motions that excited the different angular rates under the basis of Etkin's unsteady aerodynamic model. The numerical calculation method of pitch damping derivatives was studied. The investigations of HBS and Basic Finner standard model and Hyflex show that the predicted pitch-damping coefficient sum obtained by adding the individually determined coefficients is in excellent agreement with the pitch-damping coefficient sum predicted by forced angular motions and with experimental data, and the variation of the damping derivative components with the location of gravity center is also consistent with the theoretical prediction. As for winged vehicle, the plunging derivative plays a leading role in the pitch-damping coefficient sum in the supersonic region.
Application of UKF parameter estimation in the three-body Lambert problem
ZHANG Hongli, LUO Qinqin, HAN Chao
2015, 41(2): 228-233. doi: 10.13700/j.bh.1001-5965.2014.0120
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A new algorithm based on unscented Kalman filter (UKF) parameter estimation was proposed for the fast and efficient solution of the three-body Lambert problem. The algorithm was divided into two steps, guessing the initial solution and searching the exact solution. The initial solution of the three-body Lambert problem was generated using the two-body model of the Earth-Moon system. Then the two-point boundary value problem corresponding to the original three-body Lambert problem was converted to a parameter estimation problem. Through solving the converted problem using UKF, the converged exact solution was found. The algorithm was based on the theory of probability, so the derivation of the gradient matrixes required by traditional numerical methods was omitted. Moreover, the demand for the accuracy of the initial solutions for the three-body Lambert problem was modified. Therefore, the difficulty of solving the three-body Lambert problem was greatly reduced. Numerical examples indicate that the algorithm is of high efficiency and robustness and obtains a larger convergence domain compared with the differential-correction method and the second order differential-correction method.
Dynamic force equalization for dissimilar redundant actuator system
FAN Dianliang, FU Yongling, GUO Yanqing, ZHOU Guozhe
2015, 41(2): 234-240. doi: 10.13700/j.bh.1001-5965.2014.0121
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With the development of key technologies about more/all electric aircraft (MEA/AEA), the dissimilar redundant actuator system (DRAS) which consists of power-by-wire actuators, EMA and EHA, indicates the trend of more-electric-aircraft. First of all, the construction and the working principle of the dissimilar redundant actuator system were described. The force fighting model within dissimilar redundant actuator system was built up. The mechanism of dynamic force fighting was introduced. Three kinds of dynamic force equalization for eliminating dynamic force fighting, such as trajectory pre-compensator strategy, force fighting feedback with PID compensator strategy, EHA force/EMA position strategy were put forward and theoretically discussed. Finally, a comparative simulation was exhibited for the three control strategies, and a detailed analysis of the simulation result was provided within the two aspects of the pursuit dynamics and the rejection dynamics of the dissimilar redundant actuator system. The results provide theoretical basis for the design and force equalization of the dissimilar redundant actuator system.
Comfort evaluation for aircraft seat cushion based on finite element model
LI Xianxue, DING Li, WANG Xingwei, WEI Shihua, ZHOU Qianxiang, HU Huimin
2015, 41(2): 241-245. doi: 10.13700/j.bh.1001-5965.2014.0122
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The comfort of pilot's seat is highly demanded and the sitting pressure is a very important index to evaluate the seat comfort. A human-seat cushion finite element model including the pelvis was built to simulate the pressure distribution in the human-seat cushion interface and interior the human body, and finally to evaluate the comfort of the plane's seat. The simulation and experiment results were compared to verify the validity of the model, after that simulation under different overload accelerations was performed. By an analysis of the pressure distribution and maximum pressure, the simulation and experiment results are highly consistent and the maximum pressure is linearly dependent with the overload acceleration. The results show that the human-seat cushion model is validated and can be used to evaluate the comfort of different seat cushions under different overload accelerations.
Real-time scheduling for models in computer generated forces
WU Yulin, GONG Guanghong, LI Ni
2015, 41(2): 246-251. doi: 10.13700/j.bh.1001-5965.2014.0093
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The computer generated forces (CGF) based on time-stepped simulation suffered from the problem of real-time performance during time advancing through run-time infrastructure (RTI). A new simulation framework was proposed which separated time advancing from execution of CGF models by different threads. The simulation time was synchronized with local clock and advanced through RTI in a separate thread. Furthermore, a new static scheduling algorithm was proposed to manage the execution of periodic simulation models. Based on the load balancing strategy, the algorithm generated a scheduling table in accordance with time step of system and execution periods of models. Specifically, the algorithm involved three procedures, allocated simulation nodes for pre-deployed simulation entities, generated initial scheduling table for model components and adjusted the table for created or deleted entities during runtime. The experimental results show that the time advancing method meets the real-time requirement and the scheduling algorithm provides good performance in terms of overhead and processor utilization.
Cooperative weapon-target assignment based on multi-objective discrete particle swarm optimization-gravitational search algorithm in air combat
GU Jiaojiao, ZHAO Jianjun, YAN Ji, CHEN Xuedong
2015, 41(2): 252-258. doi: 10.13700/j.bh.1001-5965.2014.0119
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An air combat weapon-target assignment (WTA) model based on multi-objective decision theory with a hybrid evolutionary multi-objective optimization algorithm solver was proposed. Air combat is a multi-stage process of attack-defense countermeasure, existing WTA models are based on disposable fully allocated assignment without considering the missile consumption, which does not conform to the actual air combat process. The minimum of total expected remaining threats and total consumption of missiles were selected as two objectives functions of the multi-objective decision model, with the premise of reaching damage threshold. The hybrid multi-objective discrete particle swarm optimization-gravitational search algorithm (MODPSO-GSA) was proposed to handle the model, which possesses stable global search capacity and promises to converge to Pareto frontier. A Pareto optimal solution set with damage threshold met can be obtained, which offers decision reference to the commander. Simulation results verify that the model is of advantage and the proposed MODPSO-GSA is effective.
Non-probabilistic reliability analysis of active control system for structural vibration
LI Yunlong, WANG Xiaojun, HUANG Ren
2015, 41(2): 259-266. doi: 10.13700/j.bh.1001-5965.2014.0133
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To solve the reliability problem of active control system of structural vibration, considering the uncertainties in controlled structure, reliability analysis of the active control system for structural vibration based on non-probabilistic reliability model was studied. The uncertain parameters were expressed in the form of interval number or vector. Calculation method of responses of the closed-loop system with interval parameters was proposed based on interval mathematics. Combined with the non-probabilistic reliability model, non-probabilistic reliability analysis method, which requires the bounds of the uncertainties rather than the probability density function, was established for active vibration control systems. This reliability analysis approach had certain theoretical significance for reliability analysis of open-loop system, closed-loop control system and reliability-based controller design. The results of numerical examples demonstrate the effectiveness of the proposed method and the applicability for complex structures compared with the Monte Carlo method that can be taken as the benchmark of accuracy for judgment.
Near field image reconstruction algorithm of synthetic aperture radiometer based on partial differential equations
YAO Xianxun, SHANG Xiaozhou, MIAO Jungang, LI Zhiping
2015, 41(2): 267-272. doi: 10.13700/j.bh.1001-5965.2014.0135
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Since the Fourier imaging theory of the synthetic aperture interferometric radiometer (SAIR) is unavailable under near field conditions, a nontrivial numeric image reconstruction algorithm based on the local adaptive partial differential equations (PDE) was proposed. Based on the prior information of the desired brightness temperature distribution, an isotropic diffusion was applied at the image background areas to denoise, whereas adaptive diffusion was performed at image target areas to maintain image edges. It was demonstrated by near-field simulation that this algorithm is effective in lowering the image reconstruction errors caused by visibility measurement noise. Imaging experiments were conducted on the two-dimensional 8 mm band SAIR BHU-2D-U, and the advantages of this method were proved.
Fast satellite selection method for integrated navigation systems
HUO Hangyu, ZHANG Xiaolin
2015, 41(2): 273-282. doi: 10.13700/j.bh.1001-5965.2014.0138
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On the basis of the relationship between the number of the selected satellites and geometry dilution of precision (GDOP) and navigation computation, a genetic algorithm (GA)-based fast satellite selection method named fast genetic satellite selection method (FGSSM) was proposed. In this method, firstly the initial number of selecting satellites and GDOP threshold was decided according to the precision of user's requirement. And then the initial population of satellite selection solutions was constructed. Under the condition that evolution algebra limit is less than 1, the initial solution was obtained by selection, crossover and mutation operation. Whether the initial solution was optimized based on the principles of GDOP minimum was determined by the relationship between the GDOP of the initial solution and the GDOP threshold. The optimization terminates until the termination condition was satisfied and final solution was obtained. The experiment results show that, the method can satisfy GDOP of the solution at the request of 2.5 to 6 within an evolutionary, with no less than 92.45% probability, at the same time it can effectively reduce more than 54.75% of the navigation computation.
Configuration and mathematical modeling for advanced three-axis centrifuge system
CHANG Le, LIU Zhenghua, WEN Nuan, WU Sentang
2015, 41(2): 283-288. doi: 10.13700/j.bh.1001-5965.2014.0148
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The traditional centrifuge system usually uses a high speed, high precision single-axis rotator system to achieve one-way precise simulation of unidirectional centrifugal acceleration in a broad range. Nowadays, in order to realize immense three-axis normal overload of an aviation apparatus in three dimensions, an advanced three-axis centrifuge system was proposed. The high precision three-axis rotator was composed of a foundation and three rotational axes. It succeeded in simulating normal acceleration overload by regulating speed of outer axis, and precise position control of inner and middle axis. Based on the configuration above, a mathematical model of a three-axis centrifuge system was built; related kinematics simulation and theoretic calculation were analyzed. Given the three directions overload of x,y,z, offset angle of internal axis, middle axis and rotation speed of outer axis was solved inversely by means of the force-balance equation. In the end, through the analysis of dynamics simulations, correctness and effectiveness of the new centrifuge system configuration were validated further.
AVLC retransmission mechanism simulation based on adaptive channel estimation algorithm
GAO Lin
2015, 41(2): 289-295. doi: 10.13700/j.bh.1001-5965.2014.0152
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Aviation VHF (very high frequency) link control (AVLC) is the data link service protocol of VHF data link mode 2 (VDL2) which will be the next generation civil aviation dada link. To increase the AVLC retransmission control efficiency and reduce the mistaken retransmission possibility, the adaptive surveillance frame delivery algorithm was proposed based on channel estimation. VDL2 architecture was established with physical layer, data link layer and sub-network layer on OPNET platform. By dynamic process modeling, AVLC model was built. Contrast simulation was carried out through setting up models of none surveillance frame, surveillance frame delivery static algorithm and adaptive algorithm respectively. Experimental results show that surveillance frame retransmission control has validity in improving VDL2 performance and the adaptive algorithm has superiority over the static algorithm. Experimental results also show that the proposed algorithm can increase the throughput and lessen the packet delay efficiently, as well as enhance the system stability under wide reasonable coefficient range.
Real-time de-noising of PWM switching amplifier current in magnetic bearing
TANG Enqiong, FANG Jiancheng, HAN Bangcheng
2015, 41(2): 296-301. doi: 10.13700/j.bh.1001-5965.2014.0154
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As the traditional digital low-pass filter has difficulty in balancing the de-noising performance and the bandwidth of the system in de-noising process of the amplifier current, the real-time de-noising method based on lifting wavelet transform was proposed. Firstly, the dB4 lifting wavelet algorithm combined with sliding data window, symmetry boundary expansion and mandatory noise reduction with threshold value was adopted to achieve the real-time de-noising of the amplifier current. Secondly, the suitable wavelet decomposition layers were chosen according to the relation between wavelet decomposition layers and cut-off frequency. The experiment results show that the proposed method can not only reduce the current noise effectively, but also affect the bandwidth and response speed little, and is suitable for the magnetically suspended high-speed rotor system which has high requirements for real-time, signal-to-noise ratio and robustness.
Accelerated image classification algorithm based on naive Bayes K-nearest neighbor
ZHANG Xu, JIANG Jianguo, HONG Richang, DU Yue
2015, 41(2): 302-310. doi: 10.13700/j.bh.1001-5965.2014.0471
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Naive Bayes nearest neighbor (NBNN) classification algorithm possesses merits of avoiding feature quantization and image-to-class distance measurement, but it faces limitation of slow speed and low classification accuracy. To address the problem, a naive Bayes K-nearest neighbor classification algorithm was presented, where K-nearest neighbor searched by fast library for approximate nearest neighbors(FLANN) was employed and the influence of background information was removed. In order to improve the running speed and reduce memory cost, feature selection was included for reducing feature number of test and training images. And an attempt was tried to balance the contradictory between classification accuracy and classification time by reducing feature number of test image and training images simultaneously. The algorithm retains merits of original NBNN algorithm and requires no parameter learning process. Experimental results verify the correctness and effectiveness of the algorithm.
Effects of delamination on compressional properties of composite laminate
ZHOU Rui, GUAN Zhidong, JIA Yunchao, WANG Kailun, ZHANG Chenqian
2015, 41(2): 311-317. doi: 10.13700/j.bh.1001-5965.2014.0116
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Compressional behaviors of composite laminates were experimentally investigated based on three measuring methods, Shadow Moiré measurement, strain measurement on the surface of laminates and C-scan together with multi-stage loading. Laminates with artificial delamination of various depths, sizes and quantities were studied. The buckling of sub-layer, the extension of delamination and the instability phenomena during the experiments were observed, compared and connected. Three different modes of the extension of delamination were summarized based on the experimental results. The mechanisms of the buckling of sub-layer, the instability of the laminates, etc. were analyzed based on the three modes. The critical buckling stress, the final failure stress and the delamination extension extent through the vertical direction were compared and combined with the experimental phenomenon to analyze the effects of delamination on compressional properties of composite laminate systematically. The results can provide guidance for the damage tolerance designing of composite structures.
Hybrid finite difference schemes without free parameters
WANG Lai, WU Songping
2015, 41(2): 318-322. doi: 10.13700/j.bh.1001-5965.2014.0134
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A new algorithm was proposed to calculate the weights of sub-schemes in hybrid compact-WENO (weighted essentially non-oscillatory) schemes. It used smoothness indicators of the stencils of hybrid schemes as variables to work globally. The new weight algorithm employed none freely user-defined parameter, making the hybrid schemes more robust and applicable. Two different 5th order upwind compact schemes were coupled with a 5th order WENO-Z scheme respectively. The new algorithm maked the transition between two sub-schemes more smoothly. Generally, WENO-Z could preserve the accuracy at critical points while compact schemes were less dissipative in smooth area. Thus, these hybrid schemes with new algorithm maintained high resolution and high order of accuracy qualities and shock-capturing abilities. Numerical tests were taken upon benchmarks of hyperbolic equations to test performances of these two hybrid schemes between the new weight algorithm and a typical one. Numerical results demonstrate that the new parameter-free weight algorithm performs well.
Fast similar face retrieval based on mobile platform
DENG Jiankang, YANG Jing, WANG Meng, LIU Qingshan
2015, 41(2): 323-330. doi: 10.13700/j.bh.1001-5965.2014.0460
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The problem of similar face retrieval on the mobile platform was studied. For the mobile terminal, sparse constrained cascade regression model was utilized to align the face image accurately, which could not only select the robust features, but also compress the model size to about 5% compared to the original size. Then high-dimensional texture features were extracted around some specific landmarks, and compressed by sparse projection. For the server side, shape and texture features were cascaded to retrieve similar faces efficiently. Faces with similar facial shape were selected by sparse shape reconstruction, and similar faces were finally selected by sparse texture reconstruction. On the Samsung smart phone of Note 3, the alignment time for each face image was about 10 ms. On the extended labeled face in wild (LFW) database, the retrieval time was about 1.5 s and the size of the whole model was only 5.4 MB. Extensive experiments show that the proposed alignment method is accurate and fast with compact model size. Similar face retrieval is efficient and the results are consistent with human visual perception.
Vernier ranging method for pulse radar based on motion constraints
CHEN Hao, GUO Junhai, QI Wei
2015, 41(2): 331-336. doi: 10.13700/j.bh.1001-5965.2014.0095
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Traditional pulse radar Vernier ranging method has the problem of coupled ambiguity in resolving the ambiguity of Doppler phase and velocity. To solve this problem, the motion constraint of target was applied into Vernier ranging and a new motion constraint Vernier ranging method was proposed. Accumulating a period of measurement data, an unscented Kalman filter was used to estimate radial velocities with higher accuracy. The high accuracy velocities were used to resolve the velocity ambiguity to startup the Vernier ranging. The radial velocity of next time period was accurately estimated through UKF forecast on the Vernier range, and the velocity ambiguity of next period was resolved. The coupling filter that could resolve phase ambiguity and velocity ambiguity was built, and the random errors of pulse radar radial range data were greatly eliminated using this new Vernier ranging method. Simulations of high-speed aircraft in boost phase and measured data of pulse radar prove that, this motion constraint Vernier ranging method greatly reduces the random error of radial range from meters to decimeters.
Property evaluation on turbulence models calculation in hypersonic heat transfer simulation
ZHANG Xiang, YAN Chao
2015, 41(2): 337-342. doi: 10.13700/j.bh.1001-5965.2014.0109
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Factors that influence the prediction accuracy of hypersonic heat transfer simulation under turbulence were studied with the double ellipsoid model by the means of computational fluid dynamic. Four popular turbulent models, which include the Baldwin-Lomax(BL) model, the Spalart-Allmaras(SA) model, the Wilcox k-ω model and the Menter shear-stress transport(SST) model, were employed in the study of heat transfer simulation, their performances were assessed, the dependence of heat transfer on grid Reynolds number was assessed. Besides, the connection between sweep angle and the heat in stagnation point was established by simulation with seven different sweep angles in blunt fin. The results indicate that the Two equation model, especially the SST model, is more suitable for the heat transfer simulation in reattaching flow than the One equation model and the Zero equation model. The results also show that the maximum heat of blunt fin varies non-monotonic with the sweep angle and reaches a peak value when the sweep angle is about 22°.
Missile sliding mode guidance law based on extended state observer
ZHANG Yao, GUO Jie, TANG Shengjing, MA Yueyue, SHANG Wei
2015, 41(2): 343-350. doi: 10.13700/j.bh.1001-5965.2014.0127
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Based on the technology of extended state observer (ESO), a novel missile sliding mode guidance law was derived to intercept maneuvering target. According to relative movement between missile and target in the process of interception, the difficult question was effectively settled that too large overload was required during terminal intercepting phase, which was addressed by currently estimating and dynamically compensating to target acceleration via ESO. Thus, the goal of precision against target was achieved. Moreover, accounting for the autopilot as second-order dynamics in simulation, three simulation experiments of different interception strategies, which included head-on interception, tail-chase interception and head-pursuit interception, were investigated in the two kinds of cases of intercepting periodic maneuvering target and aperiodic maneuvering target. Compared with sliding mode guidance law based on finite time convergence, the results show the strong robustness and validities of the proposed sliding mode guidance law based on ESO in the terminal interception guidance.
Optimization of repair level considering maintenance effectiveness
FAN Jiujiu, GUO Linhan, YANG Yi, MA Lin
2015, 41(2): 351-357. doi: 10.13700/j.bh.1001-5965.2014.0139
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Level of repair analysis (LORA) is an important method of maintenance decision for establishing system of operation and maintenance in the equipment development period, but it can not decide the spares inventory at each location in repair network. To this end, compared with traditional research, a jointly optimization method of LORA and spares inventory considering maintenance time in equipment support system was proposed and systematically analyzed. Thus the objective function and modeling condition of LORA optimization model were decided, and then the transferring and coupling relations of random variables such as number of failures sent to repair, spares demand, spare backorders etc., in support organization of multi echelon and multi station, were resolved. Maintenance time parameter was introduced into traditional quantitative level of repair analysis and joint optimal model combining level of repair and spare stock was established. Meanwhile, efficient convex optimization algorithm with multi-variable was designed by analyzing the characteristic of optimization problem, which was highly effective when applied to complicated support system of multi-echelon, multi-station and multi-spare. Finally, an application case of optimization method was established and the correctness of algorithm and model were verified by simulation, which provides a feasible optimization method for carrying out LORA.
Rapid design algorithm for intercept missile trajectory
WANG Bei, ZHOU Tao, DONG Changhong
2015, 41(2): 358-363. doi: 10.13700/j.bh.1001-5965.2014.0143
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Traditional optimization algorithm always needs iterative calculation and consumes long time when it is used to solve the problem of intercept trajectory design under the multi-constraints condition. In view of this disadvantage, a rapid trajectory design algorithm for intercept missile was proposed. The new algorithm was based on the nonlinear fit technique of artificial neural network. First, a sample was calculated offline through a general optimization algorithm. The target position and the optimized flight procedure parameters in the sample were trained to fit the input-output mapping. Then the optimal flight procedure parameters could be calculated fast in the condition that the target position was given, and the goal of improving the trajectory design efficiency was achieved. Applying this algorithm to intercept trajectory design, while ensuring good hit accuracy, the calculation time is greatly reduced compared with the traditional algorithm, and it improves the timeliness of intercept trajectory design. The numerical simulation demonstrates the effectiveness of the algorithm proposed.
Morphing technology for Chinese characters based on skeleton graph matching
LIU Min, ZHAN Huanian, LIANG Xiaohui, HU Jiajia
2015, 41(2): 364-368. doi: 10.13700/j.bh.1001-5965.2014.0469
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Automatically shape morphing for Chinese characters represented in different writing stages is a challenging task. A novel method was proposed to solve this problem. Specifically, the source and target Chinese characters were decomposed to corresponding components. And then, the components were decomposed to strokes which were used to construct the graph pattern, and the stroke path similarity graph matching method was applied to establish an accurate correspondence between two graph patterns. Finally, according to the matching results, isomorphic triangulations were established for the source and target Chinese characters contours, and morphing animations were generated by using as-rigid-as-possible shape interpolation to the isomorphic triangulations. In the experiment, the stroke path similarity graph matching method was compared with two existing methods, and some morphing animations were also presented. The experimental results show that the proposed method can produce correct correspondence between Chinese characters from different writing stages, and generate smooth deformation animations.

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