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2006 Vol. 32, No. 01

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Novel approach to improving the performance of anti-G suit for pilots
Yang Guofu, Lin Guiping, Wu Baomin, Zou Lei
2006, 32(01): 1-3.
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Pressure decrease device and pressure discharge valve were separately put between abdominal bladder and capstan bladder in capstan anti-G suit and then the pressure in the abdominal bladder was reduced to approximately 40% of the capstan pressure.The novel pressure decrease technique was applied in developing capstan anti-G suit so that the problem of tenderness on abdomen of pilots could be overcome, the comfort and +Gz protection capability for pilots were improved. Centrifuge evaluation of a new model anti-G suit with pressure decreasetechnique was undertaken and 10 male centrifuge subjects were used. The device run perfectly when the subjects were exposed to +9 G maximum profiles at acceleration onset rate 3 G/s and the average acceleration protection value of the anti-G equipment was above 3.5 G. 60 fighter aircraft aircrew comments after donning/doffing the suit show that the size of the device and discharge valve, their installation position and comfort on abdomen are acceptable. The technique is also used in developing other new capstan anti-G suits.
Numerical simulation of three dimension viscous flow of fan/compressor with tip clearance
Li Xiaojuan, Gui Xingmin
2006, 32(01): 4-7.
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A three dimension numerical simulation software named NUMECA(numerical mechanics application) was used to calculate the tip clearance flow of fan/compressor. The flow field performance under design speed condition was obtained. The results show that when back pressure of by-pass duct increases, the intensive blockage area moves upstream and towards the fan pressure surface, and twist of shock become more obvious. The efficiency and the mass flow of the by-pass duct decrease if the back pressure of the by-pass duct increases unceasingly. Atcore duct, the area influenced by tip clearance leakage flow spreads to upstream with the increase of back pressure. In the same way, the efficiency and the mass flow of the core duct decrease if the back pressure of core duct is too great. The comparison between the results and the experiments shows that the numerical simulation results of three dimension viscous flow of fan compressor with tip clearance could actually reflect the influences of leakage flows on the flow structure and parameters.
Improved star map identification algorithm based on Hausdorff distance
Quan Wei, Wang Guangjun, Fang Jiancheng
2006, 32(01): 8-12.
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To solve two problems that the identification algorithm based on Hausdorff distance have the slow recognition speed and being very sensitive for the rotation of lens of star sensor,an improved star map identification algorithm based on Hausdorff distance was proposed. In this method, vector distance was combined with scalar distance. The information of star dimensional configuration was used, and a matching model of vector distance was constructed. According to the rotation peculiarity of lens, a anti-rotation model of scalar distance was set up,the weighted factor was ascertained by testing and researching the two models, right matching and recognizing threshold was choosed, and the final optimum performance of recognition was achieved. The simulation results show that it improved algorithm not only had good identification rate and strong anti-noise characteristic of original algorithm but also had better recognition speed and good anti-rotation characteristic.It was used successfully in the actual projects.
Three-point step-by-step generating r-type adaptive grid technique
Chen Xuanyou, Dong Haitao, Lee Chunhian, Zhou Yue
2006, 32(01): 13-17.
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In order to distribute grids correctly according to certain flow parameter grads but not to increase grid number, a step-by-step generating technique for r-type three points adaptive grid was proposed based on an averaged total variation concept. By this method, the grid location could be gradually adjusted, and the adaptive grid quality could be improved and grid thread distortion could be decreased. Two test cases were given to demonstrate the effectiveness of the developed procedure, namely, the supersonic flows over a two dimensions circular cylinder and a three dimensions double ellipsoid using an Euler solver. Grid location in the two test cases was adjusted by total variation of pressure. By comparing with the results computed using original grids, it is observed that shock wave captured by adaptive grids becomes thinner, so the results obtained by the present technique do provide higher resolution.
Vibration control design and simulation method for complex structures
Luo Xiaoping, Huang Hai, Xian Kuicheng
2006, 32(01): 18-21.
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A new vibration control design method based on FEM (finite element method) was proposed for structures to avoid the model error due to simplification and model reduction, in order to solve the difficulty of complex structures modeling and to improve the accuracy of the control design. The method could be implemented easily with the help of commercial FEM analysis softwares. A universal control simulation interface was established in structure analysis package PATRAN/NASTRAN environment with the programmable PCL (patran command language). The effectiveness of the method was demonstrated through the PCL simulation and experimental validation of the vibration control of a piezoelectric adaptive truss structure. The numerical result of the new technology agrees better with the experimental data when compared with Simulink simulation using simplified model. The new FEM method is proved to be more accurate and suitable for the control design simulation and evaluation of complex structures in design stage.
Optimum installation azimuth of star sensor for spacecraft celestial navigation
Song Lifang, Fang Jiancheng
2006, 32(01): 22-26.
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Starlight angular distance detected by star sensor and horizontal instrument as the observation is often used for spacecraft autonomous celestial navigation. Installation azimuth of star sensor has a significant effect to navigation precision. An investigation on autonomous celestial navigation using the starlight angular distance as the observation was presented. The effects of the installation azimuth of star sensor to the error determination were simulated using EKF(extended Kalman filter)and UKF(unscented Kalman filter)respectively. Some rules about how the installation azimuth of star sensor affects the navigation precision were summarized and some theory analyses were given. The optimum azimuth of star sensor was given and its applicability under different orbit parameters was analyzed. The simulation result indicates the optimum azimuth can be used to guide star sensor installation and star selection in the field of view. All these results also apply to the other autonomous navigation systems that use the information of starlight and horizon as their observation.
General integrative test system of unmanned aerial vehicle
Lu Aimei, Li Xinjun, He Jin, Wang Song
2006, 32(01): 27-30.
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A general integrative test system of UAV(unmanned aerial vehicle) was designed to improve the general capability of integrative test system of UAV and to increase the test system’s precision of testing. The general capability of this system was developed in aspects of design of software and hardware, the structure, and the functionality. This system adopted the VI(virtual instrument) technique. The design of hardware based on PXI(PCI extensions for instrumentation) construction and the platform of software was LabWindows/CVI. By changing the interface adaptor and the parameter settings, the system could be used in testing most subsystems of different types of UAV, such as electrocircuit, actors, engines, and so on. The system also provided an output matrix to meet the test requirements. This system was successfully used in the integrative testing of a complicated UAV.
Numerical simulation of compressible and incompressible flows in mix-compression axisymmetric supersonic inlet
Chen Bing, Xu Xu, Cai Guobiao
2006, 32(01): 31-35.
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A structure grid, multi-block computer code was developed for both compressible and incompressible flow simulations by solving the preconditioned NS(Navier-Stokes) equations with LU-SGS(lower-upper symmetric-Gauss-Seidel) implicit time integration method. The finite volume method was used to discrete the equations on the cell volume with AUSM+(P)(precondition advection upstream splitting method) or central difference scheme. The Chio-Merkle precondition matrix was adopted. Physical and mathematical mechanism of precondition method was analyzed. Computational capabilities were demonstrated through a variety of computations of typical problems in CFD(computational fluid dynamics) area, including inviscid flows in a channel with a bump and driven flows in a two-dimensional square cavity. Results show that stiffness of conventional time iterative method to low speed flows is overcome, and convergence rate is speeded up. Three-dimensional calculations were made of mix-compressed supersonic inlet flows under different flight Mach numbers, attack angles and back pressures. Results indicate that the precondition method can capture shocks accurately, and inlet performance variations characteristics agree well with the theory results.
Calculation of diffuser flow using GAO-YONG turbulence equations
Ren Xin, Gao Ge
2006, 32(01): 36-39.
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A two-dimensional incompressible diffuser flow was numerically simulated employing no staggered grid arrangement and incompressible SIMPLE method to solve GAO-YONG turbulence equations. The problem of checkerboard prediction of pressure was cured by evaluating the cell face velocities by the momentum interpolated principle. In order to improve the calculation precision, an orthogonal body fitted coordinate system was selected and a second-order QUICK discretizationfor the convective part was used. The calculation results such as velocity profiles and friction coefficients are finely close to the experimental data and better than the results of BL(Baldw-Lomax) model. It shows the GAO-YONG turbulence equations can predict the real turbulent flow with pressure gradient well without using empirical coefficients and wall functions. The calculation proves that it is important to the GAO-YONG turbulence equations for simulating adverse pressure gradient flow to introduce the effect of mean pressure gradient into energy equation which describes the characteristic length scale of the turbulent flow.
Simulation and optimization of liquid propellants rocket engine for system design
Zheng Yuntao, Tong Xiaoyan, Cai Guobiao, Chen Jun
2006, 32(01): 40-45.
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The system simulation model and the relevant multi-objective optimization model were established for a type of liquid propellants rocket engine. A system simulation procedure was programmed. Design parameters of system were optimized owing to different optimization objectives on iSIGHT software platform. A type of hybrid algorithm, which combined the multi-island genetic algorithm and the sequential quadratic programming algorithm, was used to find global optimum in given design space during the optimization procedure. Weight model of single gas generator cycle system was established. Main components weights were concerned in optimization because of their influence on system performance. The optimization design variables were the combustor pressure, mixture ratio, and the outlet pressure of pipe. The optimization objectives were engine specific impulse, payload, engine weight, engine density specific impulse, flight speed at shutting down and engine compositive density. The effects of combustion chamber pressure and mixture ratio on engine performance were analyzed based on simulation.
Components parameterization in helicopter conceptual design
Lu Xinlai, Liu Hu, Wu Zhe
2006, 32(01): 46-49.
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To satisfy the requirement of rapid modeling in helicopter conceptual design, a method was brought forward for classifying helicopter components on the basis of object-oriented technique, and a computer aided helicopter conceptual design system was developed. By applying NURBS(non-uniform rational B-spline) surfaces and feature-based components modeling technique, parametric modeling of helicopter concepts belonging to different types was realized. In particular, by taking the design parameters into account, the patameters describing rotor blade, blade tip, rotor hub and fairing were proposed, and ducted tail rotor was modeled by breaking it into several continual segments. Two design concepts generated with this system were finally presented as examples to validate the convenience andeffectiveness of the proposed methods, which formed the bases for such further work as concept performance analysis and optimization.
Application of novel method of digital to frequency conversion in Coriolis mass flowmeter
Zheng Dezhi, Fan Shangchun, Xing Weiwei
2006, 32(01): 50-52.
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A new data transforming method of D/F(digital to frequency conversion) was adopted to export frequency in the novel digital Coriolis mass flowermeter. The frequency output was completed by the crystal and the FPGA(field programmable gate arrays) together with the DSP(digital signal processing). The influence of V/F(voltage to frequency conversion method) in the traditional analog Coriolis mass flowmeter was avoided, for example, the conversion precision was not high, temperature excursion and the circuits were more complex. And the frequency output was not whole period because of the frequency update, which influenced the frequency output result. The experimental results show that the transforming method of digital to frequency conversion has high conversion precision and realizes the whole period frequency output. In addition, it also has not the temperature excursion of the voltage to frequency conversion method. The circuits are simple and seamless to connect with digital circuit. Thus the method is well worthy applying in digital system.
Architecture of software GPS receiver and implementation of its acquisition algorithm
Zhao Yun, Zhang Qishan
2006, 32(01): 53-56.
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The design architecture of the software GPS (global positioning system) receiver in accordance with the current development level of the involved hardware technology was proposed, in order to develop the software radio technology application to designing and performing the GPS receiver. The requirements of the signal acquisition algorithm for the software GPS receiver were analyzed. The circular correlation algorithm was presented and employed as the signal acquisition algorithm, which was more suitable for the software GPS receiver compared to the conventional approaches for the traditional GPS receivers. The corresponding signal acquisition program was implemented in the Matlab simulation environment. The GPS satellite C/A-code signal collected data was used to test the implemented acquisition algorithm. The primary test results show that this acquisition algorithm can provide the software GPS receiver with fast signal acquisition performance without sacrificing signal detection sensitivity; i.e. it is a suitable and efficient acquisition algorithm for the software GPS receiver.
Fuzzy AHP and its application in effectiveness evaluation for radar netting
Gao Bin, Lü Shanwei
2006, 32(01): 57-60.
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Difficulties in evaluating effectiveness and selecting an optimum scheme for radar netting arise as a result of the different goals involved and the large number of attributes considered. Our approach was based upon a fuzzy extension of the AHP (analytic hierarchy process), which was applied to the effectiveness evaluation for radar netting. The evaluation index hierarchy for radar netting’s effectiveness evaluation was presented, and some definitions of the interval judgment matrix were introduced. The methods of calculating weight-vector or comprehensive evaluation value of interval judgmentmatrix were summarized generally. Utilizing the probability distribution method, the ordering of chief combination weights was investigated for the lowest level according to the highest level. Fuzzy AHP was applied based on interval judgment matrix,and the fuzzy judgment model was set up for radar netting’s effectiveness evaluation. The practical example shows practicability of the method and the results can help commanders improve accurate and scientific decision in deploying radar netting.
Aeroservoelastic stability analysis of non-linear structure
Liu Deguang, Li Chaohui
2006, 32(01): 61-64.
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The real aeroservoelastic systems usually have various nonlinear factors, which may induce unnegligible effects on the characteristics of the systems. A frequency-domain method was applied to analyze the aeroservoelastic stability on nonlinear structures with gap. In the equations of motion of the aeroservoelastic system, the nonlinear structural stiffness was transformed to the quasi-linear equivalent stiffness by using the describing function method. The stability and stable margin of the aeroservoelastic system were analyzed by Nyquist method in linear control theory. Numerical calculations were conducted on a controlled wing with flapping gap and rotating gap. The results indicate that the flapping gap is the major factor which affects the stability, and the bigger the flapping gap is, the worse the stability of the system gets.
Knowledge fusion based on D-S evidence theory and its application
Han Liyan, Zhou Fang
2006, 32(01): 65-68.
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Knowledge fusion is a new concept proposed at the end of last century. The fused knowledge is referred as method, experience and idea as well as data and information. A new knowledge fusion method based on D-S(Dempster-Shafer) evidence theory was presented and applied to corporate failure prediction. There were three steps in the method: mathematic modeling, knowledge fusing and discriminating. The implementation of these steps was developed. The information entropy theory was employed to determine the basic probability assignment of knowledge. The knowledge fusing equation was induced following D-S evidence combination rule. A concise discriminating regulation was proposed to analyze the fusion result. The data of two listed companies was used to show the validity of the presented method. The results indicate this method can reduce the uncertainty of the prediction model effectively.
Realization of single side working mode of active magnetic bearings
Xing Tao, Zhang Qingchun, Li Guodong, Liang Yingchun
2006, 32(01): 69-73.
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It is difficult to provide an accuracy model for an AMB(active magnetic bearing) system due to the strong nonlinearity among magnetic force, the currents flowing in the coils and the displacements between the rotor and the AMBs. The bias currents in the coils increase the system power loss. For AMBs, higher stiffness and system stability in a larger displacement range could not be achieved at the same time. Magnetic force was considered as a controlled object and a component named magnetic force component with magnets and power amplifiers included was built to avoid nonlinearity of the model for the AMB system. With a base current of 0.2 A in the coils, high bearing stiffness was obtained when single side working mode of AMBs was achieved. To achieve higher stiffness and stability in a larger range at the same time, a fuzzy control method was used. Simulations and experiments show that a more accurate AMB model can be obtained with magnetic force component used; System power loss is reduced when single side working mode of AMBs is achieved and higher stiffness and stability in a larger range are achieved at the same time with the fuzzy control method used.
Design of buffer architecture for multi-media stream microprocessor
Wang Guang, Shen Xubang
2006, 32(01): 74-78.
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The characteristics of media processing applications are poorly matched to conventional microprocessor architectures. The growing processor-memory performance gap was solved. The communication bottlenecks of traditional microprocessor, which is used for media processing application, were discussed. It was concluded that the traditional Cache architecture does not adapt to the modern media processing application by analyzing the characteristics of Cache memory. Some current schemes used to solve the communication bottlenecks were discussed. A new architecture design of pyramid memory hierarchy was brought forward, which substituted the larger stream register files for Cache as the medial buffers and could adapt to media processing applications. This architecture provided a three-tiered parallel data bandwidth hierarchy, including memory bandwidth, global register bandwidth, and local register bandwidth, with a ratio of 1∶16∶256. With this bandwidth scaling, the bandwidth requirements of satellite remote sensing image pretreatment may be efficiently matched.
Focusing ultrasonic levitation
Pan Xiangsheng, Xing Lihua, Li Xun, Zhang Deyua
2006, 32(01): 79-82.
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The technique of ultrasonic levitation has a wide application in the containerless processing and manufacturing of materials and the status simulation of space on the Earth. Taking advantage of the principle of ultrasonic focusing, a single axis ultrasonic levitation system was set up with the radiator designed into a concave circular one so as to improve the system’s capability of levitation. The distributions and characteristics of the sound field were investigated theoretically. The further research based on the numerical analysis was also conducted. Three sorts of ultrasonic levitation configurations were fabricated and a series of experiments were carried out consequently. The results show that the capability of levitation is directly proportional to the curvature radius of the radiator, as well as the distance between it and the reflector. And the results also proved that the performance of the focusing ultrasonic levitation system is higher than that of the conventional one.
Numerical simulation of consumable-rod’s thermal-mechanical behavior in friction surfacing
Liu Xuemei, Zhang Yanhua
2006, 32(01): 83-87.
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By finite element method and rigid-viscoplastic model, the coupling of 3-D temperature field and deformation field of consumable-rod during friction surfacing process was simulated. Temperature change and deformation of consumable-rod were analyzed. The factors influencing temperatures were discussed. Temperature change of consumable-rod was measured by thermocouple. It was showed in the simulation results that the temperature increase rate at friction interface was higher at first, then became lower. Once the friction system became quasi-steady, the temperature here would be stable approximately. Special temperature gradient was found at consumable-rod’s bottom end. The friction interface firstly became viscoplastic and then deformed. The largest effective strain existed near the center of the bottom of the circle. The simulation results are consistent with experiments, reappearing temperature change and deformation of consumable-rod during friction surfacing. The results can be helpful in the study of process mechanism and supplying the theoretical guide to choose key technical parameters in engineering practice.
FEM simulation for residual stress in quenched aeronautics aluminum alloy thick-plate based on rolled residual stresses distribution
Zhao Lili, Zhang Yidu
2006, 32(01): 88-91.
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The residual stresses of 7075 aluminum alloy thick-plate in the process of rolling and quenching was simulated by using highly non-liner software MSC.Marc and elas-plastic large deformation FEM methods. In addition, the residual stresses of rolling, temperature rising-preservation-falling were simulated respectively, and the influence of rolling stress and temperature rising-preservation stress towards quenching stress were studied too. The result shows that in small reduction case, the whole rolling stress is smaller than quenching stress; the rolling stress decreases when temperature rising-preservation and increases rapidly when quenching, the last stress remained is quenching stress. The influence of rolling stress towards quenching stress is little, but quenching stress totally changes the original rolling stress.
Geometrical characteristics of structural model for 3-D braided composites
Lu Zixing, Yang Zhenyu, Liu Zhenguo
2006, 32(01): 92-96.
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It has significant effects on the FEA(finite element analysis) results of the mechanical properties of braided composite to set up a reasonable structural model of 3-D(three-dimension)braided composite. The braided composite after molding was taken as a study object. According to the experimental result and former research, a new model of representative volume elements for FEA of braided composite was proposed. The new model truly reflected the braided manner, coinciding with the actual configuration of the 3-D and four-direction braided composites. On the basis of the new model, the relationship between the braiding parameter and the parameters of unit model was derived and the volume fraction of fibers in this representative volume element was calculated. By studying the geometrical characteristics of the braided composite, it indicates that if the volume fraction of yarn, the radius of yarn bundle and the number of yarns in a yarn bundle are invariable, the pitch length and thickness of composites will increase and decrease respectively with the increase of braiding angle, and the volume fraction can reach as much as 68% theoretically.
Experiment on structural formation and mechanism of strength increasing of stabilized soil
Ning Jianguo, Huang Xin
2006, 32(01): 97-102.
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For the hardening process of the stabilized soil, a new structural model of stabilized soil was proposed that the structure formation of stabilized soil included soil particle cementing and pore filling. Based on the new structural model, when silt was used for soil sample and cement for hardening agent, the results show that the theoretical calculations of hardening agent contents used for cementing soil particle and filling pore are identical with those derived from experiment in the structure formation of stabilized soil. Some experimental results can be interpreted by the new structural model, such as the relationship between the mechanism of the strength increase and hardening agent contents of the stabilized soils. Through substituting expansive material for the cement contents used for filling pore in the above-mentioned hardening agent and increasing/decreasing the cement content, the role of soil particle cementing and pore filling to the structure formation was validated. And it was proposed that pore filling was critical to the strength increase of the stabilized soil.
CAD/CAE/CAM expert system of cathode design of turbine blades in electrochemical machining
Li Zhiyong, Zhu Di
2006, 32(01): 103-107.
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ECM(electrochemical machining) is one of the main machining methods of the aero-engine blades production. However, the tool cathode design is very difficult, which limits the applications of ECM in modern industries. To solve the difficulties in automation of the tool cathode design of aero-engine blades in ECM, a specialized expert system of computer aided cathode design for aero-engine blades in ECM was developed on the basis of electrochemical machining foundational theories. The basic structure, module components and work principle of this expert system were discussed in detail. The finite element cathode design arithmetic based on the mathematics model of actual electric field distribution in electrode gap in ECM process was proposed. The experiments for verifying the machining accuracy of the design cathode were developed. The experimental results demonstrate that this cathode design expert system has high design accuracy and excellent operating stability.
Parameter design for power train and simulation of dynamic performance of electrical vehicles
Ji Fenzhu, Gao Feng, Wu Zhixin
2006, 32(01): 108-111.
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The method and principle of parameters design for electromotor, the ratio of power train and batteries' capacity of electric vehicles(EVS) were explored and discussed. Based on some types of EVS, the parameters of power train of EVS were selected and designed reasonably. A performance simulation model of dynamic power train system in whole vehicle and key parts, such as electromotor, cells and retarder were developed utilizing the EVS dynamic simulation soft of advanced vehicle simulator (ADVISOR). Then the dynamic performance of EVS was simulated. Simulation result indicates that the dynamic performances of lithium cells EVS, including acceleration performance, grade ability, the maximum speed of the vehicle, retaining distance and etc. are satisfied to the demands of designing guide line. So the correctness and validity of the simulation model are demonstrated.
Operational availability demonstration of military airplane based on simulation
Jiao Jian, Wang Zili
2006, 32(01): 112-116.
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Operational availability (AO) is an important top parameter of military airplane RMS(reliability, maintainability and supportability). In order to obtain reasonable and valid AO, based on characters of demonstration stage, a simulation model using Monte-Carlo method and queue theory was constructed by integrating the mission requirements, initial operations and support concept of military airplane and RMS data from similar systems. The sample methods of mission start, failure time and repair time were analyzed, and the sample formulas were presented. The model requires military airplane RMS data and operation maintenance scheme as input data, and calculates iteratively a family of relative curves between AO and RMS parameters. Based on analyzing the curves synthetically, the reasonable results could be obtained. The algorithm processes of reliability simulation and relative formulas were presented, and the method was verified by a case as well. The simulation model has general-duty character and can be used for different parameters demonstration by modifying the statistical formulas.
Quantitative assessment approach of RET based on interference model
Yao Jun, Cao Xinkuan, Jiang Tongmin
2006, 32(01): 117-120.
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RET(reliability enhancement testing) is the most advanced technology in western countries. RET’s concept, process and stress limit classification were introduced. The basic theory of RET was explained. Interference model was introduced into RET, to settle the problem that RET couldn’t be analyzed quantitatively. The failure mechanism occurred in RET was analyzed by using interference model. Because the test stress was higher than the operation stress limit of product, almost all products in RET failed. By analyzing the interdependence between the operating stress found in RET and the stress in actual operation environment, the formula for reliable probability was deduced based on interference model. Then an example was given to explain this approach’s feasibility. RET could improve the reliability of products by improving the quality of design and manufacturing process. By using the interference model and the deuced formula, two ways of improving the reliability of products were analyzed. And also the basic principle of RET was explained based on the model.
Reliability of space flexible mechanisms
Zhang Jianguo, Su Duo
2006, 32(01): 121-124.
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The dynamics differential equations of flexible kinetic mechanisms were established on the basis of using the floating coordinate system and mode flexibility according to the kinetic reliability characters of the flexible bodies on space applications. The integral and iteration algorithm was applied in the solving of dynamics equations. The reliability analysis and simulation methods of kinetic mechanisms were studied, which included the first-order second-moment method and the hi-efficient response surface method. Especially, the applicability of this method on the space flexible mechanism kinetic reliability was analyzed. The kinetic reliability analysis and simulation were successfully provided to the deployable space mechanisms on the basis of flexible multi-body dynamic modeling, using ADAMS and self-developed software S RSM (sequence response surface method).

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