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2009 Vol. 35, No. 7

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Unsteady drag measurements for flow over a circular disk
Hu Ye, Wang Jinjun
2009, 35(7): 783-785.
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Unsteady drag measurementsw ere conducted in a low speed wind tunnel to investigate the drag of the circular disk which was normal to the flow. The circular disk was interfered by an upstream two-dimensional rod in the horizontal symmetry plane of the disk in the Reynolds number range from 0.44×105 to 2.74×105 based on the disk diameter. The results indicate that the mean drag coefficient of the circular disk does not depend on the Reynolds number which was tested in present study, no matter there is an interference rod upstream of the circular disk or not Meanwhile, the interference rod leads to decrease of the mean drag coefficient and increase of the drag fluctuation of the circular disk. The increment value of the drag fluctuation increases rapidly, when the Reynolds number is beyond 1.84×105. By the frequency analysis, the dominate frequency of the disk drag without the interference rod corresponds to the antisymmetric fluctuation frequency induced by the helical vortex structure(the Strouhal number is 0.135).
Bayes comprehensive assessment of reliability for binomial products by using test information of similar product
Yang Jun, Huang Jin, Shen Lijuan, Zhao Yu
2009, 35(7): 786-788.
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For reliability assessment of binomial products, the history sample and the current sample often follow different populations, which have remarkable effect on reliability assessment. The similarity degree between the history sample and the current sample were studied by similar system analysis, and their similarity degree was denoted by inheritance factor. Then, the history posterior was obtained from the history sample and the innovation posterior was given by the non-informative prior, which reflect the history information of similar products and the current test information respectively; the complex posterior was obtained from the history posterior and the innovation posterior via inheritance factor, and statistical inference was made on the basis of the complex posterior. This method makes full use of information of similar products and emphasizes the particular characteristic of the evaluated product.
Architecture of software-based GNSS signal simulator and implementation of its IF signals generation
Zhao Yun, Kou Yanhong, Huang Zhigang, Zhang Qishan
2009, 35(7): 789-793.
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The software-based global navigation satellite systems(GNSS) signal simulator would be an enormous asset for the efficient development of GNSS receivers, due to its flexible structure, the possibility for easy updates and changes and low cost. A hybrid GPS/Galileo intermediate frequency(IF) software-based signal simulator was proposed. The architecture and implementation description for it are included. This hybrid IF signal simulator consists of the following main parts, i.e. GPS/Galileo satellite constellation simulation, receiver trajectory generation, propagation and disturbance channel (including the ionosphere model, the troposphere model, the multi-path model and etc.), and GPS/Galileo IF signals generation. Meanwhile, the hybrid GPS/Galileo IF signal generator was presented in detail, which provides the following signals: GPS L1 C/A, Galileo E1 CBOC(composite binary offset carrier), Galileo E5a and E5b signals. Finally, the power spectral density (PSD) curves for the IF signals obtained with the hybrid signal simulator were given. From the PSD point of view, the implementation of the hybrid signal simulator was validated.
Modeling design of general purpose ATE
Shen Li, Shen Shituan
2009, 35(7): 794-798.
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Aiming at the problems in the modeling design of general purpose automatic test equipment(ATE) and in order to satisfy the requirement of the model of ATE , a integrated ATE model was presented based on signal. The ATE hardware and unit under test(UUT) are both made models. A basal signal model was established based on test foundation framework(TFF).The device driver model based on signal was proposed. The UUT model was proposed based on the thought of integrating test and diagnosis. The route model was pointed out based on the thought of sharing information between models and the thought of describing route with logic switch. This model gave direction to the resource allocation, instrument-s interchangeability, the automatic generation of test program set(TPS) and fault diagnosis. So the use of the model can quicken the design process greatly and reduce the cost greatly.
Simulation of liquid slosh in braking process of tank truck
Liu Kui, Kang Ning
2009, 35(7): 799-803.
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The liquid sloshing in braking process of tank truck was simulated by volume of fluid (VOF) model. The forces and their locations of a single room and weight distribution of a truck were calculated. The reliability of the calculation method was validated by comparing with experimental results. The results show that the maximum of Fx (force in direction x), Fy(force in direction y) and C (The ratio of weight acting on the front axle and rear axle) increase as the deceleration increases without a baffle. When the liquid filling ratio increases, the maximum of Fx increases firstly and decreases afterwards, the maximum of Fy increase, and C increases in the starting and ending period of braking process and decreases during the period around 1 s. When there is a baffle, as the area of the baffle becomes bigger, the maximum of Fx, Fy and C decreases.
Application and analysis of formation satellites cluster orbit transfer based on genetic algorithm
Li Jingsheng, Deng Zhongmin
2009, 35(7): 804-806.
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Orbit transfer of formation satellites was a potential way for future spacecrafts. The Lambert maneuver problem of formation satellites with initial and target positions was studied. Relative motion model including central orbit elements and perturbation was set up using Gim-Alfriend matrix, and an impulse thrust control strategy for coordinated formation keeping on transfer orbit was designed. Genetic algorithm (GA) was applied to optimize the maneuver of formation satellites, with the goal to minimize the total fuel consumption, or weighted index which concerns the fuel consumption and time duration. Factors affecting fuel consumption were analyzed. Simulation results indicate that GA is available to solve the maneuver problem of formation satellites.
Synthesis and atomic oxygen resistance of phosphorus-containing polyimide
Su Yingxia, Wang Kai, Zhan Maosheng
2009, 35(7): 807-811.
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A series of phosphorus-containing polyimide films were synthesized by a self made phosphorus-containing diamine, bis( m -aminophenyl)phenylphosphine oxide (DAPPO). The atomic oxygen (AO) resistance testes of films were carried out using a ground-based atomic oxygen effects simulation facility of Beijing University of Aeronautics and Astronautics. The effects of phosphorus content on the morphology and structure evolvement of polyimide films were investigated using a field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectrometer (XPS) respectively. The results indicate that the Kapton and Upliex-R films were seriously damaged and formed lots of hill structure, but a phosphorus-rich layer was formed on the film based on the DAPPO after AO exposure, which decreased the erosion rate and obviously improved the AO resistance of the phosphorus-containing polyimide films, when the DAPPO content was 5.47% by weight, the erosion rate of phosphorus-containing polyimide film after 20 hour-AO exposure was only 13% and 20% of the Kapton and Upliex-R films.
Numerical investigation of film cooling effectiveness over rotating curved surfaces:blowing ratio and curvature effect
Wu Hong, Meng Henghui, Zhao Zhenming, Wu Hongwei
2009, 35(7): 812-816.
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Numerical method was conducted to investigate film cooling performance over different rotating surfaces. Compared different models, the influences of curve and blowing ration were obtained with different conditions. The results show that: more film cooling effectiveness is obtained in low blowing ratio, and less effectiveness is occurred in high blowing ratio; For convex surfaces, the increasing curvature radius bring less efficiency; and while for concave surfaces, the increasing curvature radius create more efficiency; The increasing Rotation number weakens curvature effect on convex surfaces, while strengthens curvature effect on concave surfaces.
Tentative of reliability integrated assessment method based on exponential regression model
Wan Bo, Fu Guicui, Yao Jun
2009, 35(7): 817-820.
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The multi-regress-analysis reliability assessment method was built based on the exponential regression model with environmental severe degree factor, environmental integrated factor and technique state of the product factor, which aims at the less information because of the fewer ones for testing in the development process of military products for reliability assessment. The method can estimate the reliability parameters using performance test, environmental test and reliability test data of products in development. In this method, the conversion of life data under different environments is avoided and the regression parameters will be calculated to give the pertinent reliability parameters, which is quite different from the classic reliability integrated assessment method.
Design optimization of satellite platform considering multiple structural cases
Zhou Zhicheng, Qu Guangji, Huang Hai
2009, 35(7): 821-823.
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The engineering system of structural optimization for spacecraft(ESSOSⅡ) was applied in the optimization design of a complicated satellite structure, in which the minimum weight was taken as the objective, the layer thicknesses of composite laminate panels as the design variables, and the frequencies and stresses under two structural cases of being launched (furled) and working in orbit (deployed) as the constraints. Based on finite element models of these two structural cases, twol-evel multi-point approximation method was adopted in optimum solution and in each optimization iteration finite element analyses were performed for both structural case models. Compared with the primal design, structural weight decreases obviously after optimization, and all constraints under furled and deployed structural cases were satisfied, which provide a basis for the engineering department to improve the primal design and meanwhile also show the effectiveness of ESSOSⅡ.
Anti-atomic oxygen properties of silicone coating modified by nano-ZnO
Wang Jing, Li Weiping, Chen Yichi, Zhu Liqun
2009, 35(7): 824-827.
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To improve the anti-atomic oxygen properties of silicone coating, nano-ZnO modified by silane coupling reagent was filled in the silicone resin and nano-ZnO/silicone composite coating on polyimide film was obtained. Polyimide with and without nano-ZnO/silicone coating was exposed to atomic oxygen(AO) in a ground-based AO effect simulation facility. The modified nano-ZnO particles were uniformly distributed within the silicone coating so that micro-cracks occurred during film-forming of the silicone were eliminated effectively. The AO experiment results indicate that polyimide is significantly eroded which is characterized by substantial weight loss and change of surface morphologies; nano-ZnO/silicone coatings exhibit excellent properties for anti-atomic oxygen effects with little variation in weight or morphology. The anti-oxygen properties of the coatings were improved along with the increase of nano-ZnO content.
BOC signal multi-path mitigation technique based on wavelet analysis
Zhu Di, Shen Gongxun
2009, 35(7): 828-832.
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Satellite navigation receives requires to tracking code phase of satellite-s signals precisely because it affects the precision of pseudo-range directly. However, the multi-path effect introduces quite big errors to the traditional delay locked loop(DLL)-based estimators. An algorithm of multi-path mitigation by the method of wavelet analysis was proposed. The algorithm was formulated in detail. Simulation shows that it greatly improves the estimation performance of code phase compared with narrow correlator and double delta technique. Under certain extreme condition, this technique is equivalent to correlator method when Harr wavelets are adopted. The computation complexity is much lower than multipath mitigating technique(MMT) technique which is based on mostly likelihood method.
Denoising of micro-CT image based on improved NL-means algorithm
Li Baolei, Yang Min, Li Junjiang
2009, 35(7): 833-837.
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Micro-CT(computed tomography)is based on microfocus X-ray source and the ray dose is low. So the noise level of micro-CT image is big and denoising of the CT image is very necessary. The current main denoising methods for CT image and their advantages and disadvantages were summaried. The NL(nonlocal)-means algorithm was described. According to the experiment result, the disadvantage of NL-meas algorithm that artificial artifact will be introduced in smooth region of CT image was analyzed. Based on the shortage of the NL-means algorithm, gradient information of image was introduced in the original algorithm and the improved algorithm was put forward. The improved algorithm keeps the excellent denioising function and the artificial artifact was restrained effectively. The detail contrast can be also enhanced. The availability of the improved algorithm was validated by the experiment result.
Experimental investigation of rotation number effect on film cooling over a convex surface
Zhao Zhenming, Wu Hongwei, Ding Shuiting, Xu Guoqiang
2009, 35(7): 838-841.
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Experimental study was conducted to investigate the influence of rotation number ( Rt=ωD/u ∞) on the film cooling performance over a convex surface. Measurements of film cooling effectiveness η ad and heat transfer coefficient h f were presented for single film hole. Thermochromic liquid crystal (TLC) was used to obtain the temperature distributions on the curved surface. The results show that ① an obviously deflection occurs under the rotating condition;② with the increase of rotation number, the film cooling effectiveness decrease while the heat transfer coefficient increase;③ a reattachment phenomenon can be observed in the rotating condition.
Multichannel reservation MAC protocol for mobile ad hoc networks
Xing Xiaoqin, Liu Kai
2009, 35(7): 842-847.
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A novel multichannel reservation multiple access (MRMA) protocol was presented for efficient channel sharing in mobile ad hoc networks. It employed request-to-send (RTS) and clear-to-send (CTS) dialogue on a common channel and flexibly selected conflict-free traffic channel to accomplish the transmission of data packet based on a novel channel selection scheme. The acknowledgment (ACK) packet for the data packet transmission was replied to the sender over another common channel, which effectively eliminated the influence of exposed terminal problem, and the spatial reuse of the same channel was extended to communication pairs even within 2-hops. In addition, the influence of hidden terminal problem was greatly reduced because most of possible packet collisions on a single channel were avoided due to traffic load balance on multiple channels. Finally, performance comparison of the proposed protocol with the IEEE 802.11 RTS/CTS protocol was provided, and simulation results show that it outperforms the IEEE 802.11 RTS/CTS protocol on total channel utilization and average packet delay.
Generation method of walsh function based on balanced matching property
Guo Jia, Yang Dongkai, Li Shujian, Shao Dingrong
2009, 35(7): 848-851.
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Balanced matching property is a new property of Walsh function sequence and is equal to its orthogonality. Using balanced matching property and the concept of linear space in Galois field, a generation method of orthogonal function sequence was produced, and this method only need compute two matrixes products in Galois field. In addition, the orthogonal function sequences generated by this method satisfy an important property—multiplication theorem, and constitute the Abel group to its multiplication. Under the specific condition, this method also generates Walsh function sequence of the different serial number. Finally, a new Walsh function generator was designed by using the generation method produced.
Fractal characterization of uniformity of discrete phase in nanocomposites
Nie Peng, Wang Xinxin, Gao Ji, Zhang Kaifeng
2009, 35(7): 852-855.
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The traditional method to evaluate uniformity of discrete phase in polymer nanocomposite is deficient. A quantitative description method was proposed to evaluate uniformity of filling particles in polymer nanocomposite. The method is based on the mathematical model of fractals theory and takes the TEM(transmission electron microscope) image of polymer nanocomposite as the research object. An evenly distributed dispersed phase of the mathematical model was established by using a natural sub-fractal dimension formed by discrete objects. Then, the polymer nanocomposite TEM image was processed with image processing. Circles were drawn with different radius and with the TEM image-s centroid as the circle center. The particle counts and gyration radius were extracted from the circles of the different radius and made coordinates of linear fitting in bi-logarithm. The reciprocal value of the linear slope just is uniformity parameter, which can be used as the evaluating indicator to evaluate the uniformity. The method was applied to describe the polymer-nano-particle composites, and the feasibility of the evaluating was verified.
Lateral and directional flight qualities of the saucer-shaped aircraft
Wang Linlin, Gao Ge
2009, 35(7): 856-859.
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The saucer-shaped aircraft is a novel aircraft adopting blend-wing-body configuration. The linear perturbation theory based on the classic flight dynamics was used to analyze the lateral and directional flight qualities of the saucer-shaped aircraft under low speed conditions, and the time-domain method was applied on the lateral and directional mode. The lateral and directional flight qualities were given by simulation. The aerodynamic characteristics of the saucer-shaped aircraft, the conventional aircraft and the flying wing aircraft were also contrasted to discuss their similarities and differences. The results show that the saucer-shaped aircraft exhibits superior flight qualities and excellent comprehensive performances.
Design and dynamic simulation of hydraulic system for AT
Wang Shuhan, Xu Xiangyang, Liu Yanfang, Peter Tenberge
2009, 35(7): 860-864.
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A new hydraulic system in AT was designed. The parameters of every valve was designed by theoretical calculation. The dynamic simulation model of hydraulic system of AT was established by ITI-SimulationX. Simulation results and theoretical design results were compared to confirm the simulation model. Every valve-s dynamic characteristic in hydraulic system was simulated. The simulation results of pressure and flow of system pressure valve, shifting manipulations, torque converter and lubrication system were analyzed. The dynamic simulation method would be very helpful during the course of designing and analyzing the performance of system pressure valve and further optimization design. The theoretical design method and dynamic simulation model will be feasible for the real industrial applications. The research results can be used in design and optimization of hydraulic system.
Two impulses transfer trajectory design for Sun-Earth libration point missions
Li Mingtao, Zheng Jianhua, Yu Xizheng, Gao Dong
2009, 35(7): 865-868.
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Two impulses transfer trajectory design based on the least differential corrections method was studied, differential correction equation with the altitude and the flight path angle constraints was concluded, and the convergence of the method was discussed. Halo orbit around the L1 libration point of the Sun-Earth system was taken as the objective orbit, two impulses transfer trajectory was designed in the framework of the circular restricted three-body problem. Effect of Halo orbit insertion (HOI) point and amplitude was studied in a systematic way, a strategy for the selection of HOI point was given, and the fast transfer trajectory for emergency was also studied. Numerical simulation shows that the proposed method is very effective, and transfer trajectory with moderate flight time can be obtained by choosing points on the near Earth side of Halo orbit as HOI point.
Algorithm of radar-IFF correlation in back-to-back configuration
Yan Hongxing, Wang Xiaobo, Wang Guohong, Wang Chenxi
2009, 35(7): 869-872.
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To solve the problem of radar-IFF correlation in back-to-back configuration, an algorithm was discussed, mainly including time-alignment between radar tracks and identification friend or foe(IFF) points, construction of discriminate functions, choice of the decision-making rule, and computation formula of decision thresholds. Moreover, the problem of ambiguity was also discussed. Simulation results in four typical conditions show that, with the greater ratio of target interval to range from target to radar, the better performance is; when it comes to target cross, the closer to the crossing, the worse the correlation is; when target maneuvering, time registration realized by track smoothing better than track predicting, while, in other conditions, the correlation results produced by these two methods are similar. Moreover, the correlation performance obtained in north east down(NED) coordinate system is almost the same as that in polar coordinate system. There, n/m logic should be chosen as 2/3 or 3/4 in order to promise both the missing correlation probability of friendly target and the false correlation probability of unknown target are low.
Fuzzy-PID control method of vehicular DYC
Wang Weida, Ding Nenggen, Xu Xiangyang, Zhang Wei
2009, 35(7): 873-876.
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Direct yaw-moment control (DYC) is a very important methodology of enhancing the vehicle stability, and its research is of great significance for improving the active safety of vehicle. Based on the in-depth study of the vehicular handling dynamics and the advanced control theories, a fuzzy-PID controller with intelligent integral module was designed and applied for the DYC control. The vehicular dynamic model reflecting the basic dynamic characters of steering situation and the fuzzy-PID controller with intelligent integral module was established and simulated in the circumstance of Simulink. The simulation results validate the feasibility and effectiveness of this control algorithm, and indicate that it can realize perfect control of DYC. This control strategy is of a good prospect in this field.
3D data registration method for vision measurement
Xie Guanghui, Sun Junhua, Yang Zhen, Zhang Guangjun
2009, 35(7): 877-881.
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A 3D data registration method was proposed for vision measurement using mark points as global measurement control points. Mark points were attached to the measured objects and one or more baseline rulers were put in the measured area. The images of mark points and the baseline rulers were captured by a digital camera from different viewpoints, by which the coordinate frame transformations between viewpoints were estimated. Using the stereo vision model, the local coordinates of the mark points were determined, and then converted at the global coordinate frame, forming the global measurement control points. Scanning different parts of the object at different positions, the vision sensor obtained the coordinates of some mark points in the local coordinate frame of the sensor. The transformation from the local to the global coordinate frame was computed using at least three non-collinear mark points, thus the 3D data acquired by the sensor at different positions were integrated into the global coordinate frame. The proposed method is convenient and applicable in field measurements. Experimental results show that the registration error in x, y, z axis are 0.03mm, 0.02mm, 0.07mm respectively.
Visual aid for teleoperation applied to satellite on-orbit self-servicing
Zhang Guoliang, Liu Hong, Jiang Zainan, Wang Jie
2009, 35(7): 882-886.
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To overcome effect of time delay on space robot teleoperation, a novel method of vision aid for teleoperation applied to satellite on-orbit self-servicing was presented. A vision-based shared control scheme was designed and implemented to deal with data transmission delay. The scheme consists of free space control and auto visual servo control. In the process of free space control, 3D graphic prediction simulation and real feedback video stream make teleoperator achieve the best telepresence experience. In the process of auto visual servo control, the visual servoing of redundant features eliminates system dependency on calibration accuracy and improves system intelligence. Finally, a typical satellite servicing experiment demonstrates the effectiveness of this method.
Cooperative trajectory planning for UAV towards moving target aground
Zeng Jia, Shen Gongzhang, Xia Jie, Yang Lingyu
2009, 35(7): 887-890.
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In contrast to the most existing unmanned aerial vehicle (UAV) cooperative trajectory planners that are suitable for stationary targets, a novel decentralized cooperative trajectory planning method for UAV towards moving target aground was proposed. The decentralized cooperative trajectory planning scheme was given and the time advancing mechanism by alternation of self-planning and synchronized-planning was adopted to match the constraints of information transfer interval. The heuristic information function suitable for moving target aground was constructed to enhance the UAV trajectory feasibility. The heuristic search algorithm was used to generate the trajectory segments, which make UAV reacting to target movement aground. The decentralized computing method for cooperative variable was designed to reduce the cooperative computing. The simulation results show that the method could generate the real time three-dimensional cooperative trajectory for UAV towards moving target aground via information transfer and decentralized computing, which meets the real time application requirement.
Geomagnetic mapping and validity estimation
Huang Xuegong, Fang Jiancheng, Liu Gang, Jiang Yanwei
2009, 35(7): 891-894.
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One of the key technologies of geomagnetic matching navigation is looking for high accuracy geomagnetic map. Based on introducing the principles of four kinds of interpolation methods (inverse distance to a power method, Kriging method, modified Shepard-s method and radial basis function method), the data of geomagnetic survey was used, and a region where the survey points were uniform was selected. Geomagnetic maps were created by all the interpolation methods, and cross-validation was used to estimate the methods. The results show that the geomagnetic map created by radial basis function method has little "bull-s-eyes", the contour is much smoother, and its standard deviation is much less than other methods, the standard error and the mean deviation is the minimum. The interpolation precision with radial basis function method is high, so the geomagnetic map created by the method better reflects the regional distribution of the earth-s magnetic field.
New product conceptual design scheme generation method based on ontology mapping
Bi Luyan, Jiao Zongxia, Fan Shengtao
2009, 35(7): 895-898.
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The ontology and ontology mapping technology were introduced into the conceptual design schema generation field. A new conceptual design scheme generation method based on ontology mapping was proposed to solve the problems of design knowledge reuse difficulty and low accuracy in conceptual design scheme generation because of different knowledge description approaches in traditional conceptual scheme generation methods.The proposed method constructed product design knowledge database in the way of ontology-based knowledge presentation and product conceptual design schema satisfying the design requirement was found in the product design knowledge database through the ontology mapping algorithm.Finally, the correctness and validity of the new scheme generation method were tested and verified through the drive device of crane lifting mechanism design example.
Technology of light-weight design for wire-winding prestressed cylinder structure
Li Huili, Lang Lihui, Jiao Wei, Su Huaizhong
2009, 35(7): 899-903.
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Based on the iso-shear stress theory a light-weight wire-winding prestressed working cylinder for isostatic pressing equipment was designed through application of the multi-island genetic algorithm. A light-weight design model was defined. The maximum inner pressure in the cylinder was 300MPa and the minimum inner diameter was 500mm. Within these specifications the weight of the design was minimized. The weight of the conventional design is 9.03 tons, and the weight of the optimized design is 8.53 tons, corresponding to a 5.5% reduction. It was verified by an expert system and CAE software that the optimized cylinder has the necessary strength, rigidity and stability and that the inner diameter is greater than 500mm after prestressed. As it was proved, the design is reasonable and the muti-island genetic algorithm is an structural optimization method which gives a fast convergence. This method can also solve the weight-optimization problems of isostatic pressing equipment for extra-high pressure.
Performance analysis and improved method for airborne three-channel SAR/GMTI system
Shi Hongyin, Zhou Yinqing, Chen Jie
2009, 35(7): 904-908.
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A comprehensive performance analysis method of three-channel SAR(synthetic aperture radar) GMTI(ground moving target indication) was presented after analyzing the theory of conventional three channel SAR ground moving target indication methods. The main error factors such as velocity variety of radar platform, receiver channel mismatch, clutter internal motion and system noise were considered in this method and the detection performance of each error factor affect on was analyzed too. The shortcoming of conventional three channel SAR/GMTI methods is that the performance of minimum detectable velocity, ambiguous speed and blind-speed simultaneously can-t be improved to meet the requirements of the system. The improved method solves the problem without increasing receiving channels by rearranging the transmitting and receiving antennae. Theoretical analysis and simulation results show the validity of this scheme.

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