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2006 Vol. 32, No. 02

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Engineering applications of structural optimization system based on Patran/Nastran
Yuan Jiajun, Chen Shenyan, Huang Hai
2006, 32(02): 125-129.
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Two satellite structures were optimized using a structural optimization system that was secondary developed on the base of the commercial finite element software Patran/Nastran. The mass of structure was taken as the objective function and frequency and stress constraints were considered in the optimization. The system provided a Patran environment for users to establish the model of problem, while Nastran was executed as structural analysis code and the optimizer was based on two-level multi-point approximation method. The designed examples were typical complex structures of spacecraft constructed by honeycomb sandwich panels, shells as well as beams with various cross-sectional types. Man-machine interactive ways were also adopted and the structural masses were obviously decreased. The work supplies useful datum for the industrial departments to improve the current designs. The results of the developed system comply well with other’s for one of the examples, and the validity of the system is further verified.
Effects of free stream on flowfield and performance of linear aerospike nozzle
Wang Changhui, Liu Yu
2006, 32(02): 130-134.
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Numerical studies on effects of free stream on flowfield and performance of aerospike nozzle were presented. Aerospike nozzle performance losses and pressure distribution along plug surface were computed and compared at four different altitudes with typical free stream Mach numbers. It is shown that aerospike nozzle performance losses caused by free stream primarily result from increase of lift body base drag and decrease of plug pressure distribution. At mid and low altitudes, thrust of lift body base and plug ramp decreases with increasing free stream Mach number. The effects of free stream on performance decrease with increasing altitude, and from a certain altitude lower than design point thrust of plug ramp is not influenced by the free stream any more. For subsonic free stream, performance losses almost linearly increase with increasing Mach number. For transonic free stream, sudden performance degradation occurs. For the further supersonic range, performance losses increase slightly with increasing Mach number.
Modeling landing signal officer for carrier approach
Shi Ming, Cui Hailiang, Qu Xiangju
2006, 32(02): 135-138.
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The landing environment of carrier-based aircraft is extremely complex. The pilot needs to get the secondary command signal from landing signal officer(LSO) for final carrier approach and landing. It is necessary to include the LSO command model in the simulation model of carrier landing approach for human pilot control. On the basis of analyzing the behaviors of the LSO in the final carrier approach, a model of LSO was presented for the digital simulation of a pilot-carrier system. Fuzzy logic laws were used to model three kinds of the behaviors of the LSO: the judgment of the distance between the aircraft and the ship, the judgment of the path deviation and the decision of the command signal sent to the pilot. A neural network model was applied to describe the LSO’s prediction of the ship motion. The rationality of the model was verified through the simulation results of carrier landing under several kinds of conditions.
Discussion of integral technique for aerodynamics calculation
Liu Jie, Zhu Ziqiang, Chen Zemin, Wu Zongcheng
2006, 32(02): 139-143.
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A method called wake integration for the aerodynamics evaluation was discussed. Based on Euler equations to get the fluid field solution, this method applies the momentum theorem to a control volume that encloses an aircraft and it is improved from the traditional far field integration method. By doing integral computation on the wake surface that is down from the aircraft and vertical to the velocity of far field, it can get the lift, induced drag, wave drag and the total drag. This method is advantaged to the aerodynamics calculation for the aircraft having the complicated configuration and it can decompose the total drag by physical causes. Consequently the designer can be aware of more details about the aerodynamics of the configuration in the design. Some methods to improve the accuracy and efficiency of wake integration were discussed. The results of the computation demonstrate that the method and improved technique are correct and useful in the aircraft design.
Inverse flight dynamics based algorithm for design of maneuvering trajectory tracker
Wang Heng, Zhang Shuguang
2006, 32(02): 144-147.
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The control architecture was constructed for maneuvering trajectory trackers, in which the inverse flight dynamics of aircraft was solved to determine the open loop command of control. Assumed that the open loop command could bring the aircraft to the neighborhood of the desired trajectory, a feedback compensation block was designed based on the nonlinear dynamic inversion theory, which is usable for both affine nonlinear systems and linear systems. Typical maneuvers were simulated to demonstrate the architecture and the accompanying algorithm, such as the conventional angle-of-attack S-turn and the post-stall Herbst maneuver. The results show that the designed maneuvering trajectory tracker is competent for both the conventional maneuvers and the post stall maneuvers, and the precision of tracking is satisfactory.
Orbital debris clouds evolution phase definition
Dong Yunfeng, Xiao Yelun, Liu Jia, Wang Ting
2006, 32(02): 148-152.
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Orbital debris clouds evolution phase was defined as sphere, spheroid, rope, spiral, spreading and shell, based on the geometry shape and debris density in the evolution from the initial breakup point to the final coverage of earth. The shape character and the key drive sources were addressed in each phase. Space craft orbital mechanics theory and research method were reviewed. The evolution dynamics principle was analyzed. The separate velocity decides the shape and size during the sphere phase. Linear relative motion differential equation can be used to reduce the debris density model. Rope and spiral is distinguished from geometry, orbital maneuver theory is used to analysis the existence of pinch point and pinch line. The orbital perturbation differences of each debris in clouds eliminate the pinch region and induce the omnibearing spreading and the final figuration of the shell. The time mark between the phases was given and calculation formula was reduced and listed. The debris clouds evolution phase was visualized through computer simulation and the phase definition rationality was verified.
Numerical investigation of dynamic stall vortex movement of different-thickness airfoils
Wang Youjin, Yan Chao, Zhou Tao
2006, 32(02): 153-157.
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Dynamic stall of NACA airfoils of three kinds of different relative thickness undergoing pitching motion at low Mach number was numerically investigated. Dual time-step approach in conjunction with lower-upper symmetric-gauss-seidel(LU-SGS) implicit method were utilized to solve the unsteady navier-stokes (NS) equations in noninertial system, and Roe scheme was brought in for space discretization, incombined with stiff moving mesh generation technology. Fully turbulent solution was adopted, by using baldwin-lomax(BL) model. The computed load hysteresis loops indicate good agreement with the experiment results,which confirms that the numerical method is effective. Through comparing and analyzing different flow fields, it is simultaneously founded that the formation and development of stall vortex passing airfoil is obvious distinct for different-thickness airfoils during light stall and deep stall.
Comprehensive evaluation model for integrative cabin environment quality of airliner
Ning Xianwen, Li Yunze, Wang Jun
2006, 32(02): 158-162.
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To study the evaluation for integrative cabin environment quality of airliner, a comprehensive evaluation model using a stratified evaluation system was proposed. Thermal environments, cabin air quality and acoustical, visual and safe environments were assumed to be the first layer of an evaluation model, while specific evaluation factors were taken as the second layer of the model. Through the method of a fuzzy comprehensive evaluation the factors of the two layers were joined together. According to the effect on the cabin environments, the weight coefficients in the second layer were confirmed and the primary result of evaluation was given by applying the fuzzy operation. The weight coefficients of the first layer were given by applying analytic hierarchy process. Then the result of comprehensive evaluation of cabin environment quality was obtained. By solving barycenter of the result of comprehensive evaluation, the question when the maximum subjection value was not applicable was solved. The feasibility and rationality of the model is substantiated through some specific cases.
Optimization designing method of wing flutter model for low-speed wind tunnel test
Lü Bin, Liu Deguang, Xie Changchuan, Yang Chao
2006, 32(02): 163-166.
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To solve the multidisciplinary problem of flutter wing model designing for low-speed wind tunnel test, which there is lots of difficulty in and expended abundant time conventionally, a design method named genetic/sensitivity-based hybrid algorithm was applied, which has very well global and local search capabilities and optimization efficiency. The theory, process and applicability of genetic/sensitivity-based hybrid algorithm were presented. The math model, based on real physical one, was modeled according the essential theory and design course of the flutter wing model designing. With the method using in design, not only the time of model designing is reduced to a great extent, but also the design precision is assured, for the error comparing result and target of model design can reach below 5% relatively. An optimization method of flutterwing model was developed and was used in many aspects of model designing, providing an efficient design method in engineering.
Thermal system analysis and calculation for extravehicular spacesuit based on human body model
Qiu Yifen, Chen Yonghua, Yuan Xiugan
2006, 32(02): 167-170.
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The characteristic of space heat exchange was introduced for extravehicular spacesuit, the heat transfer process of the thermal system was analyzed among space environment, extravehicular spacesuit and the human body, and with the help of Visual C++ 6.0 and OpenGL a three-dimension human body model was developed in which the computing results about human body surface temperature were displayed. Simulation technique of the thermal system was established with the combination of human body thermal regulation model, it was used to analyze human body thermal state under various metabolic rate, passive thermal protection conditions of spacesuit and the control of liquid-cooling and ventilation system. So the technique was used to determine the work conditions about liquid-cooling and ventilation system to assure the human bodies comfort state. Simulation results were verified by the thermal Manikin test, this issue is of important value in engineering application.
Image matching algorithm based on feature point set for satellite attitude calculation
Cai Xiaodong, Ye Peijian
2006, 32(02): 171-175.
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Gray scale and geometry feature approaches were integrated. Feature point set was selected according to local texture energy distribution and geometry constraint of feature point set was utilized to construct templates describing the holistic feature of the image. A stepped refining image matching algorithm was introduced. Coarse searching was performed first by feature point set registration, thereafter fine searching and angle correction was processed so that the object translation and rotation in the real-time image can be obtained. Compared with traditional image registration methods, this algorithm can enhance the matching speed while maintaining high matching precision with rotation invariance and noise depression capability. The application of such algorithm is verified by simulated experiments.
Parameter influence analysis of free-wake numerical method
Zeng Hongjiang, Hu Jizhong
2006, 32(02): 176-180.
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The parameter influence of rotor free-wake method was presented, including blade discrete segments, vortices grid density and wake length. Several areas were made from blade root to blade tip. The inside area was segmented coarsely but the tip area was segmented more densely. The segment density of inside area has lower influence on the numerical result than that of tip area. Vortices were used to model unsymmetrical aerofoil. The density of vortices can affect the numerical result obviously. Proper density is needed and too dense vortices grid can not improve the accuracy of numerical result. For the hover and low speed flight state, 9 loops of wake is enough to get accurate numerical result, and for climb and high speed flight state 7 loops of wake is enough. The influence of time cost of these parameters was also discussed and wake length has the most influence.
General-utility testing path model of switches for ATE and application
Zhao Ruixian, Meng Xiaofeng, Wang Guohua
2006, 32(02): 181-185.
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In order to solve the questions such as searching testing path, judging testing path conflict and managing testing path of switches during the course of programming testing programs (TP) of automation testing equipment (ATE), a general-utility testing path model of switches was brought forward, the model general description and interlink algorithm for much more switches connecting were presented, and the material application methods of the model was introduced. The automated searching of optimum testing path and judging of testing path conflict are realized, the fault of testing path can be isolated well and TP are not related to the material path hardware by the model means. Accordingly the general-utility and replantability of TP are improved, and the workload of programming TP is reduced.
Visual computation of glint error for complex targets
Fang Ning, Ning Huansheng, Wang Baofa
2006, 32(02): 186-189.
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The glint error is one of the important error sources in radar tracking on extended target. In practise, the lose-possibility has been risen greatly in teams of the glint error of the scattering wave in radar tracing and guiding system. So the research of glint error can improve the accuracy of tracing target. The visual method was developed to compute the glint error of complex targets by the phase gradient method in GRECO(graphical electromagnetic computing) system in high frequency region. This method made each pixel of screen as one scatter center of target and the number of scatter centers was greatly increased to the pixel level, then the result accuracy was improved and the visual computation course was implemented. The glint result of the two-ball target model wascompared with the measured result and proved its validity. Meanwhile, the complex target glint was also proposed in this visual platform. And, the lose-possibility of an traced missile was also given.
Fault-tolerance operation of brushless DC motor for flight control
Zhou Yuanjun, Dong Huifen, Wang Ziqiang
2006, 32(02): 190-194.
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The operation of a brushless DC motor with dual-windings for the flight control system was described. The dual-channels electro-mechanical actuator (EMA) is composed of the motor, the fault-tolerance operation mode can be obtained when any channel is failure. The mechanical characteristic, power losses and allowed torque of the motor were analyzed at two cases of normal and fault-tolerance operation modes. From the experimental mechanical characteristics curve, it can be obtained that the no load speeds of two operation modes are same under the same voltage, but the speed drop in the case of the fault-tolerance operation is greater than the normal operation because of the load. Holding the power loss not changed in the case of fault-tolerance operation, the motorallowed current is 1.4 times of the rated current and the allowed torque is 0.7 times of the rated torque, these were validated by the temperature experimental data. The balance control of the dual-windings operation and the control method of the fault-tolerance operating were researched, the dynamic characteristic of the fault-tolerance operation was simulated.
Theory analysis and experiment of random modulation in FOG
Zhang Xi, Pan Xiong
2006, 32(02): 195-198.
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Bias stability is an important performance of gyro. But in digital closed loop fiber optical gyro(FOG), it is influenced extremely by the electrical crosstalk in the electronics. Output drift can be reduced by using random modulation.The crosstalk of square wave modulation and random modulation was analyzed through fast Fourier transformation(FFT). When square wave modulation is used, the crosstalk result has the same square wave frequency with the photodetector analog output. So it can not be filtered in the gyro electronic and bias error arises in output. Further more , it causes the output dependence on the light intensity. When random modulation is used, the crosstalk result has different frequency with the photodetector analog output, so the output of FOG has more stablity. The random modulation point is -3π/2,-π/2,π/2,3π/2, which is the most sensitive point. The modulation wave has even harmonious of square wave frequency. Experimental results indicate that bias error can be restrained and the bias stability of output increased when random modulation is used in digital closed loop FOG.
Reconstruction of inner surface with data points acquired by structured light scanning
Li Zhang, Zhou Fuqiang, Zhang Guangjun
2006, 32(02): 199-203.
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A method for reconstructing the inner surface with feature data points acquired by structured light scanning was proposed. Feature data points acquired by structured light scanning are accurate and the distribution density of those data points is nonuniform. Some redundancy points on the measuring direction were removed by sub-sampling and the new points on the scanning direction were added by interpolating. Then the primitive surface of the measured object was reconstructed using the local tangent plane methods with those of preprocessed data points. One local tangent plane for the neighborhood point set of a certain point was constructed and the primitive surface could be approximated by the tangent plane cluster. Based on extracting the isosurface through Marching cubes algorithm, the initial meshes were obtained and the meshes were optimized through an energy function. Then the smooth surface was obtained through Loop subdivision method. It shows that this method can be used for effectively implementing the reconstruction of the inner surface with the nonuniform data points acquiring by structured light scanning.
Mechanism and suppression of extraneous torque of motor driver load simulator
Li Chenggong, Jin Hongtao, Jiao Zongxia
2006, 32(02): 204-208.
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Based on an introduction to the mechanical structure and operating principle of the load simulator drived by the direct current torque motor, a mathematical model of the actuating mechanism of the electrical loading system was founded and was expressed by means of block diagram. The mechanical characteristic of the direct current torque motor and the operating range were studied. The production mechanism of the extraneous torque during the start-up, operating mode and reversing of the motor-drive load simulator was analyzed. A method of feedforward compensating the extraneous torque based on the principle of structure invariance was promoted. The result of the simulation shows theoretically that the feedforward compensating can reduce the interference caused by the extraneous torque effectively. The feasibility and effectivity of the method are also proved by experiments.
Algorithm for delay constraints optimal path calculation
Zhang Tao, Liu Zhongkan, Zhang Jun
2006, 32(02): 209-213.
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As one of the most challenging problems in the QoS Routing and traffic engineering, the problem of delay constraints optimal path calculation has the non-polynomial(NP) complete complexity. The algorithm which is proposed in literature has some problem, such as not getting optimal path and being very hard complexity etc. So a delay constraints optimal path (DCOP) algorithm which can solve this problem well was proposed. By reduced the search region of the algorithm, the efficiency of algorithm can be improved effectively and an optimal loop-less path can be gotten. The self-adapting parameter design is adopted in this algorithm toimprove the adaptability on the network scale and the changing of complicated service. Using extensive simulations on random graphs and random assigned link weights, the huge improvement in complexity of the new algorithm is tested. The test also indicate that the algorithm has more adaptability and more practicability.
Wavelet and nonlinear model based borescope image compression
Ding Peng, Ma Qishuang, Li Changyou, Yao Hongyu
2006, 32(02): 214-217.
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The borescope image quality around edges is very important to the fault diagnostic of aeronautic engine. And inside the turbofan engine, the borescope image often has complex edges and textures. To achieve high compression ratio without losing of the edge and texture information, a kind of image compression method with emphasis on edges and textures was presented. First, it used wavelet transform in order to obtain a set of biorthogonal subclasses of images. Second, multiscale Canny edge detector was used to locate the edge. Third, the AOI(area of influence) was set by contour plus profile model, witch was an edge nonlinear represent and modeling method. Finally, by rate control, different image quality was obtained in different areas of the image, like ROI(region-of-interest) coding of JPEG2000. Test result shows, comparing with general image compression method, at different compression ratio, PSNR(peak signal to noise ratio) has all gotten lightweight raise, and the visual perception around edges is also better than the general method.
Maximal frequent itemsets mining algorithm based on effective pruning mechanisms
Chen Peng, Lü Weifeng
2006, 32(02): 218-223.
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The maximal frequent itemsets mining problem was studied and an algorithm based on pruning itemset lattice effectively was proposed. The itemset lattice tree data structure was adopted to translate maximal frequent itemsets mining into the process of depth-first searching the itemset lattice tree. One of the key measures to promote performance of the algorithm is to prune the itemset lattice tree while traversing it. Three properties of itemset lattice tree were given and three pruning mechanisms, direct superset pruning, indirect superset pruning and transaction sets equivalence pruning, were proposed based on them respectively to prune the infrequent nodes and their extension nodes to reduce the number of nodes while traversing the itemset lattice tree. Test results indicate that all the three pruning mechanisms can reduce the search space effectively and the transaction sets equivalence pruning has the best effect on performance of the algorithm. Test results also indicate that performance of the algorithm is related to denseness of the datasets.
Audio similarity measure based on distance correlation image
Li Chao, Xiong Zhang, Zhu Chengjun
2006, 32(02): 224-227.
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Similarity measure is one of the keys of content-based audio analysis. Traditionally, statistic methods are used for accomplishing the aim. But it is hard to represent the results in a visual way and it shows very weak relationship with semantic layer. An image segmentation-based method was introduced to partly solve the problem. Features were extracted respectively to form a so-called feature space. The distance correlation images were calculated by comparing the feature vectors. A maximal similar direction was estimated by segmentation on the image to calculate local similarity and global similarity. Experiment was also provided. The method was proved to be suitable for applications like clip searching in digital broadcasting stream.
Real-time solution for Cyber data acquisition simulation system in petroleum industry
Li Wei, Wang Lei
2006, 32(02): 228-232.
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In order to reserve the valuable software and hardware fruits of the Cyber data acquisition system,the method of software simulation was adopted to build a simulation system on a modern high performance hardware platform．Petroleum industry’s Cyber data acquisition simulation system was modeled by taking individual real devices as fundamental items and it shaped an architecture which contained a instruction-set simulator as a core,a communication bus simulation module as a bridge that connected each device simulation module．In order to meet the deadline of simulation system,its real-time performance was analyzed at length according to the average performance requirement and the worst performance requirement,and serveral performance parameters were extracted,then a real-time solution which based on a real-time operating system RTLinux was provided to solve the real-time communication problem between the simulation system and the real data acquisition devices．
Research on mechanism of actuated active reflectors for FAST
Lu Zhen, Yang Guang, Wang Qiming, Nan Rendong
2006, 32(02): 233-238.
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A new type of actuate mechanism for the active reflector of FAST(five-hundred-meter aperture spherical telescope) radio telescope was proposed so that one can overcome the deficiency of original actuate mechanism. The mechanism was utilized to prevent from the sideslip in the margin cell of the active reflector, and to promote the mechanical efficiency and reliability, and to reduce the cost of manufacture and operate. The core of the improvement is so-called Sarrus linkage that can produce perfect translational motion without any sideslip. The kinematical analysis was made to demonstrate the feasible of the prototype, and the force analysis indicates that the system has sufficient strength and stiffness. The prototype operation and simulation prove that one can prevent any sideslip of the reflector’s units based on the new type actuate mechanism, even in the base slope of 45°. The issuers of being improved point out, which are essential for the design and manufacture of the real system.
Hermite method convergence analyses and improvement
Wang Ruiqiu, Bian Yongmei, Chen Wuyi
2006, 32(02): 239-243.
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To make multi-points tangent contact machining have higher computational efficiency, an improved algorithm based on Hermite method was proposed. Theoretical analyses were given on the convergence of the improved algorithm, and the constraints for local convergence of the new algorithm were also derived. Then the formula of steffensen accelerated iterative method was applied on the algorithm. Another novel algorithm called iterative method of undetermined coefficient based on trial method was developed. The results show that the improved algorithm based on Hermite method acts as a linear convergence method, while the iterative method of undetermined coefficient algorithm has the same convergence speed with square convergence method approximately. Then it can meet the demand for the tool path generating computation of general sculpture surface by combining all the above-mentioned algorithms applied on them.
Time-frequency characteristics research for pressure waves of fuel injection system of diesel engine
He Yongling, Yan Zhiqiang
2006, 32(02): 244-248.
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In research of pressure wave of fuel injection system of diesel engine, with Wigner-Ville distribution, the time-frequency characteristics of pressure wave in fuel injection system of a diesel engine under condition of liquid-gas tow-phase flow was analyzed. The comparison of its results with the results of wavelet function analysis was made. The results show that using Wigner-Ville distribution the energy density of pressure wave of fuel injection system in time and frequency field can be better described and the change of frequency of this unstable signal with time can be better reflect. When long living time cavitation existed in fuel injection system, the energy density of pressure wave, which included some high frequency energy besides low frequency energy in this energy, concentrates mostly on the first pressure wave and there is not any high frequency energy in the second pressure wave. When short living time cavitation existed in fuel injection system, frequency of first pressure wave is low and the energy density is high. And there is some high frequency energy in the second pressure wave.

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