2005 Vol. 31, No. 09

Display Method:
Web-based collaborative process digital definition of complex mechanical product
Meng Biao, Lin Nan, Fan Yuqing, Chen Kun
2005, 31(09): 939-943.
Abstract:
Process digital definition is one of the critical tasks in process management and product definition. In order to standardize the content and methods of process digitization, the scope, the detailed content and its definition method were established based on computer aided process engineering research. In allusion to the engineering application situations, a collaborative work pattern based on Web was brought forward, and this work consummates the concept of generalized engineering dataset (GED). Then, a concurrent & collaborative working process was discussed based on GED concept linked with the apart-organization status quo inner country aviation enterprise. Process digital definition is the precondition and foundation for the transformation from digital design to digital manufacturing, and also the efficient means for a enterprise to reduce cost, eliminate waste and promote competition ability. The result of this work will be the transformation power from traditional manufacturing to digital manufacturing pattern.
Numerical simulation of wake impacting effect of axial flow compressor
Hou Anping, Xiong Jinsong, Zhou Sheng
2005, 31(09): 944-948.
Abstract:
By giving accurate inlet boundary condition of rotor to simulate the interaction between rotor and stator, the result of 3D unsteady numerical simulation to a row of rotor’s flow field can reflect the effect induced by upstream unsteady wakes. Because the number of rotor’s blades and stator’s blades is difference, traditional numerical simulation usually can’t accurately simulate the frequency of upstream unsteady excitation to downstream flow field. This difficulty can be solved by using this method. At the same time, the requirement of computational time and computational capability can be received. The result of numerical simulation to a low velocity axial flow compressor rotor shows that the aerodynamic performance of the rotor can be improved greatly if the deflected amplitude and frequency of upstream wakes were arranged reasonable. Therefore one kind of reasonable methods was presented to control and use unsteady flow in axial flow fan & compressor.
Modified PASTd algorithm and its application in large-scale adaptive antenna arrays
Lü Shanwei, He Ningrong
2005, 31(09): 949-952.
Abstract:
Projection approximation subspace tracking with deflation (PASTd) algorithm belonging to eigen-decomposition algorithm was widely used in adaptive beam forming for antenna array. However, it has been found that this algorithm can only work satisfactorily when the signal to noise level is low. In order to solve this problem, fast orthonormal PAST (OPAST)algorithm was introduced into PASTd algorithm. The modified algorithm can estimate eigenvector and eigenvalue of useful signals when the dimension of useful signals is unknown. The modified algorithm can insure the orthogonality of the eigenvectors, and the modified algorithm’s astringency is better than PASTd algorithm while the computation complexity almost remains the same. The modified PASTd algorithm combined with multiple signal classification (MUSIC) algorithm applied in large-scale adaptive arrays can restrain the interfaces in the main beam and vicinities of the main beam. The combined algorithm significantly deduces the computation cost of MUSIC and it is also very practical to form deep nulling at interfere direction.
Dynamics modeling and simulation analyzing for strapdown antenna stable platform
Zhou Ruiqing, Lü Shanwei, Liu Xinhua
2005, 31(09): 953-957.
Abstract:
In space constrained tactical missiles, the size of seeker antenna servomechanism was restricted strictly, and rate gyroscope stabilization platform failed to work very well. The strapdown stabilization technique can be applied to stabilize line-of-sight(LOS). Based on configuration feature and stabilizing principle, a complete gimbal kinematics and dynamics model of two-degree-of-freedom strapdown antenna platform was achieved via coordinate transformation. The gimbal coupling characteristics was analyzed and simulated. Analysis indicates that main differences between strapdown stabilization platform and rate gyroscope stabilization platform lies in information obtaining and control mode. The rate gyroscope platform gets stability using hardware directly, while strapdown platform bases on software compensation. Simulating also shows that coupling between gimbals and missile body is strong, which need take effect measures to isolate. While cross coupling between outer gimbal and inner gimbal is weak, which can be ignored in practice. Results obtained will be a theoretical foundation for the further study of strapdown antenna platform, and it will be a engineering design suggestion for LOS stabilized system of miniaturized seeker.
Cold-flow tests on 1-cell 2D linear plug nozzle
Liao Yunfei, Liu Yu, Wang Changhui
2005, 31(09): 958-962.
Abstract:
To know more altitude compensation and base characteristics of plug nozzle, cold-flow tests on 1-cell 2D linear plug nozzle, which utilize high pressure air as propellant were conducted. The effects on 1-cell 2D linear plug nozzle of base wall and base bleed ratio were studied. The pressure distribution on plug was also studied. The results indicate that the performance of plug nozzle can be increased 2%~7% without base wall at low altitude. The bleed can increase base pressure and decrease the variety of thrust which be caused by changing from open base to close base. It is found that 1% to 1.5% base bleed ratio is the optimum value range and the performance of plug nozzle would be decreased if base bleed ration is more than that range. The maximum nozzle efficiency of all of plug nozzle tested here are more than 99%, some of them are nearly 100%. It has good altitude compensation.
Simulation of effect of air-to-air missile on operational effectiveness of fighter
Liu Xingwei, Zhu Rongchang, Xiang Jinwu
2005, 31(09): 963-965.
Abstract:
Effect of quantity, performance and flexibility of air-to-air missile on airfight effectiveness was analyzed, and effective manner to use air-to-air missile in air action was discussed to improve fighter’s survivability and its airfight effectiveness. Three degrees of freedom particle kinetic equations were employed to model the missile’s motion, and typical trace of missile was partitioned into three different phases: breaking, parting, and contacting. Meanwhile, the different requirements of the missile trace were given in each phase; the characteristics of the missile radar cross section(RCS)were also taken into account in the simulation analysis. One-one airfight pattern was used to simulate a Mirage2000 vs. a F16 under circumstances of high altitude middle distance, different amounts of air-to-air missiles, various opportunities to launch missile, et al. Results show that fighter’s velocity, disengagement angle and missile’s velocity significantly affect the operational effectiveness of fighter.
Half-scan mode for industrial CT
Fu Jian, Lu Hongnian
2005, 31(09): 966-969.
Abstract:
Industrial computed tomography (ICT) adopts generation III scan mode to execute the rapid test of objects. However, generation III has the small filed of view limited by the length of the detector. It is difficult to test the large objects rapidly. In order to realize the rapid ICT test of large objects, a scan mode called half-scan was discussed and its filter back-projection (FBP) reconstruction algorithm was deduced. This algorithm firstly modified the fan-beam projection data acquired by half-scan into the in-completed parallel-beam data at 0°~360° with the rebin reconstruction principle of fan-beam generation III CT. Then the completed parallel-beam data at 0°~180°was created with the symmetry of parallel-beam. Finally CT reconstruction was executed with parallel-beam reconstruction algorithm. The validity of half-scan mode was verified by the results of computer simulation and experiments. Analysis shows that the effective scan field of view can be improved more than 80% compared with that of generation III.
Optimal low-IF quadrature architecture for microwave amplitude and phase receivers
Dong Yuliang, He Guoyu
2005, 31(09): 970-974.
Abstract:
To solve the problem of frequency offset out of intermediate frequency(IF) bandwidth for microwave and millimeter wave amplitude and phase receivers, an optimal architecture of low-IF quadrature receiver combining with double-sideband suppressed-carrier(DSBSC) was presented. The frequency error canceling method was employed to achieve stable low-IF signal, which excluded the frequency offset from microwave local oscillator and kept the phase relationship between two input signals. Its two IF channels are asymmetric in that one of them was pre-modulated by a sine wave generated by a crystal oscillator. The canceling process was fulfilled by an analog multiplier and a quadrature demodulator at the first IF. Differing from frequency error track, it avoid spurious modulation and complexity caused by phase-locked loops. Its performances, including error and correctionof I/Q imbalance, were analyzed. A practical microwave receiver based on this architecture was outlined. The results of performance test and practical application show high sensitivity and accuracy of the receiver, characterized by simplified circuits, low cost and miniaturization.
Exact trajectory tracking control of automatic landing
Che Jun, Zhang Xinguo
2005, 31(09): 975-979.
Abstract:
The problem of trajectory exact output tracking of non-minimum phase aircraft plant in automatic landing process was studied. The characteristic of aircraft automatic landing process was analyzed. Combined with a feedback controller, the stable inversion control method was adopted to design the automatic landing control law of a commercial jet airplane. The stable inversion calculated the desired control input and desired state trajectory according to nominal aircraft plant model, and the feedback controller deals with the parameter uncertainties of aircraft plant and external disturbance. Based on the relative degrees of aircraft plant, the smooth landing trajectory was also designed to satisfy the comfortable requirement of commercial jet airplane. The simulation results showed that the automatic landing control law had exact output tracking ability, and the automatic landing process met federal aviation administration (FAA) requirements for the category III precision approach landing. The internal dynamic of aircraft was stable and bounded.
Active control of dynamic response of a piezoelectric adaptive truss structure: modeling and experiment
Duan Yong, He Linshu
2005, 31(09): 980-984.
Abstract:
An active control method of a piezoelectric flexible adaptive truss structure was presented to develop high performance structural systems with dynamic vibration, which can be used with smart actuators and sensors to control the shape and suppress the vibration of the flexible adaptive truss structure. The piezoelectric adaptive truss structure was composed of piezoelectric ceramic sensors, actuators, and flexible beams. An active vibration control of piezoelectric flexible adaptive truss structure in space was developed by the method of an improved integral plus double integral force feedback under measuring the displacement, using the mechanical-electro coupled theory of the adaptive structure. An active vibration control system for the piezoelectric flexible adaptive truss structure was set up for real-time computer active vibration control experimental tests. The experiment results show that the dynamic performance of the truss structure can be easily improved and the control system has good dynamic behavior to uncertainties and disturbance inputs.
Space heat flux calculation of extravehicular space suit
Qiu Yifen, Yuan Xiugan, Chen Yonghua
2005, 31(09): 985-988.
Abstract:
Space radiation heat transfer and heat flux through extravehicular spacesuit must be solved for the design of the spacesuit passive thermal protection. Characteristic of space heat exchange and performance of the vacuum shielding thermal insulation layer for the extravehicular spacesuit were analyzed, four typical position relations among spacesuit, earth, airship, and the solar direction were given, space external radiation heat flow of the spacesuit was analyzed under each of the four conditions, a method of calculating the space heat flux was established, then the maximum calculated heat gain and the maximum heat loss were solved. The final computation results indicate that the capability of the passive thermal protection for the spacesuit has immense influence on space heat flux. The spacesuit thermal insulation is most important to reduce the heat flux, and the ratio of the spacesuit surface solar absorptivity to emissivity should be properly reduced for fear of larger leakage heat flow from the spacesuit.
Using neural network inverse control system to improve the performance of turbo decoding
Dong Zhenghong, Zhou Hui, Zhu Renfeng
2005, 31(09): 989-993.
Abstract:
To solve inverse decoding model problem of turbo codes, an adaptive inverse turbo decoding model was proposed, based on neural network nonlinear filter. Desired coefficients attenuation of cross-entropy (CE) was gotten by using optimal constant scaling factor with statistical principle. The auto-regressive exogenous input (NARX) neural network was trained to build the mapping model between the input and output of turbo inverse decoding all round by the desired coefficients attenuation. Compared with the nonlinear inverse control system nonlinear structure based,the proposed adaptive inverse model with linear structure has simpler structure, less computation. Simulations show that when the signal to noise ratio (SNR) is greater than 0 dB,the inverse model algorithm converges rapidly and stably with computational error being within a minimal bound. The proposed adaptive inverse model for turbo decoding has agreement with turbo decoding mechanism and provides a new way to improve the performance of turbo decoding.
Experimental investigation on the effects of the height of distant canard wing of a forward-swept configuration
Zhan Jingxia, Wang Jinjun
2005, 31(09): 994-998.
Abstract:
Force measurement in a low speed wind tunnel was conducted to investigate the effects of the height of a distant canard wing on the longitudinal aerodynamic characteristics of a forward-swept configuration. The Reynolds number is about 1.44×105 based on the average chord length of forward-swept main wings. The results indicate that it is more favorable for the lift characteristic to equip a lower canard wing away from a greater forward-swept main wing, and the canard wing below the main forward-swept wing also slows down the stalling of theconfiguration. Canard wing increases lift coefficient with the penalty of the increase of drag coefficient. The increase of drag coefficient is significant at higher angles of attack. An upper canard, which is in the vicinity height of forward-swept main wing, could improve the maximum lift-to-drag ratio. Much more increase of maximum lift-to-drag ratio can be obtained with a forward-swept main wing with a small sweepback angle leading edge.
Identification system to dynamic characteristics of on-orbit space vehicles
Zhao Shougen, Cheng Wei, Sun Guojiang, Tang Yingqian
2005, 31(09): 999-1003.
Abstract:
Based on the structure identifiability, some frequency-domain technologies using the free dynamic response of the structure were discussed. Including the hardware system which consists of the sensors, The data acquisition equipments, the computers and the identification software which was developed using the C+ + language and the assembly language, an identification system which was used to identify dynamic characteristics of an on-orbit space vehicle had been developed, and also a test certification system was designed to verify the reliability of the system and the identification algorithm. The test certification system consisted of a twin-beam which was weakly coupled through a flexible beam between the two beams, and could obtain several concentrated low-frequency modals. The specific dynamic characteristics which the on-orbit space vehicles had under zero-gravity conditions in space could be simulated. The test results show that the system is reliable and the precision of the identification algorithm can meet the design aims.
Experiment of heat transfer within a rotating ribbed serpentine passage in unsteady cases
Deng Hongwu, Tao Zhi, Xu Guoqiang, Ding Shuiting
2005, 31(09): 1004-1008.
Abstract:
Experiments were conducted to study the heat transfer characteristics of a rotating ribbed square serpentine passage for unsteady cases. Abundant experimental data were obtained to investigate the variation of heat transfer coefficient at different engine working conditions, such as mass flux and rotational speed. For unsteady cases, the convective heat transfer was affected by the cross-stream secondary flow caused by unbalance distribution of the Corilis, the buoyancy and the angular acceleration forces. Effects of angular acceleration force increase heat transfer coefficients on leading surface and decrease the coefficients on trailing surface in radial outward passage flow for the accelerating rotation system; Reverse conclusions can be obtained for the case of decelerated rotation system. It is shown that the fluctuations of heat transfer coefficients occur mainly at the moment when the work conditions vary under unsteady cases. The fluctuations of heat transfer coefficients mainly occur at the moment when the work conditions change, though long exists of the walls temperatures variation. An interesting phenomenon was also observed that there exists a hysteresis of Nu number ratio when the variation of rotational speed completes a cycle.
Numerical simulation of stationary plasma thruster plume
He Bijiao, Zhang Jianhua, Cai Guobiao
2005, 31(09): 1009-1013.
Abstract:
Using 2D axisymmetrical model, a hybrid particle-fluid model was used to model plasma dynamics of the stationary plasma thruster (SPT) plume, which includes the particle in cell (PIC) method and the direct simulation Monte Carlo (DSMC) method. The randomly sampled frequency (RSF) method was applied to solving the collision process between the atoms and the ions. Three different computational conditions were contrasted, which are ways of charge assignment, models of electron moving and setting of the SPT outlet parameters. The ion current density and the ion density of the computations were compared with these of the experiments results at 0.1 m, 0.5 m and 1.0 m to the SPT exit. The present result shows that the computations, including the ion density near the thruster axis and the ion current density, satisfactorily agree with the experiments by charge assignment for linear weighting in 2D, electron moving for constant entropy model, and setting outlet parameters of the thruster by experiments.
Synthesis of the array’s amplitude and phase pattern using genetic algorithm
Lü Shanwei, Han Yanju, Wang Wei
2005, 31(09): 1014-1017.
Abstract:
The element excitation relationships were analyzed respectively when the array patterns are symmetric, real or symmetric and real. Then genetic algorithm(GA) was introduced, and it was applied to synthesize array patterns. GA is an adaptive and global optimizing probability search method.It directly uses the objective function as search message.So GA can synthesize not only amplitude but also phase by designing the objective function correctly. It is fit for the conditions that need to compensate amplitude and phase and optimize multi-objective. At last, GA was proved to be valid and flexible through synthesizing flatbeam power pattern and the square of secant pattern which is used for the parabolic antenna’s initial feed.These two simulation examples imply that making best use of patterns’ real or symmetric characters in GA can reduce optimizing parameters and accelerate convergence speed. It also suggests that combining GA with traditional pattern synthesis method will farther reduce the evolution generations, which are needed to get the best solution.
Transfer function model on X-ray digital radiography system
Liang Lihong, Lu Hongnian
2005, 31(09): 1018-1021.
Abstract:
Currently, industry X-ray digital radiography system based on the amorphous silicon X-ray flat-panel detector is the latest test technology. The system transfer function, namely point spread-function (PSF) consists of system geometry dispersion caused by nonpiont-source, scintillator screen dispersion and aperture sampling of detector pixels. The intensity distribution of X-ray penetration field was analyzed at each segment. The mathematical model of system PSF and modulation transfer function (MTF) was established by means of Gassian function which is the mathematic expression to describe the transfer behavior of each compose segment of the system PSF. So the system approximating effective bandwidth was achieved from half-wave width of the system PSF. In the case of the digital radiography system based on PaxScan2520 flat-panel detector; the experiment which validates the mathematical model is simply appropriate to estimate resoluble minimum detail of work-piece tested by the system and provide theoretic foundation for industry X-ray radiography.
Organization mode of NC workshop in network manufaturing
Lin Nan, Meng Biao, Fan Yuqing, Chen Kun
2005, 31(09): 1022-1026.
Abstract:
Based on the analysis of the basic characters and connotations of network manufacturing, an enterprise running mode oriented to networking manufacturing system was put forward. Some problems existing in organization mode were discussed according to the reseach in a large scale aviation enterprise NC workshop. A fractal organization model adaptive to networking & agile manufacturing was put forward based on the theories of fractal enterprise and independent manufacturing island. According to the original production mode and product speciality in the NC workshop, an improved method to organize manufacturing cells and production lines based on the group technology was put forward. Some rules of how to build up organization oriented to product process and how to execute support service in workshop were studied as well. The mode, the methods and rules have the adaptability to traditional discrete manufacturing enterprise and have been successfully adopted by the NC workshop.
Method of damage mechanics to determine the p-S-N curve of material
Bai Zhaoyu, Meng Xianhong, Zhang Xing
2005, 31(09): 1027-1030.
Abstract:
High reliability is required in the structures of aero planes, it is necessary to determine the probability fatigue curves of materials. It is well known that it is very expensive and takes numerous time to obtain probability fatigue curves by fatigue tests. Due to this situation, by means of the method of damage mechanics, for the first time a p-S-N curve can be determined according to its median S-N curve and the corresponding fatigue data. The result shows that the fatigue strength and the fatigue life decrease greatly with the increase of the survival probability. This conclusion was obtained from the fatigue tests of metals, so this method can be used under this condition. However, it can be also extended to some new kinds of composite materials. In addition, it should be indicated that the confidence will be higher with a larger sample. The significance of this method is that median fatigue tests can be used to replace probabilistic fatigue tests in order to draw p-S-N curves. Thus the time and the cost of fatigue tests will be reduced greatly.
Effect of plenum chamber total pressure on arcjet thruster operation
Xiao Yingchao, Tang Haibin, Liu Yu
2005, 31(09): 1031-1035.
Abstract:
To investigate effect of plenum chamber total pressure on arcjet thruster operation, numerical simulation of operation under various plenum chamber total pressures was performed on the basis of mechanism analysis on its operation and modeling for chemical non-equilibrium flow and steady state electromagnetic field within it. Various flow mechanisms and interactions between electromagnetic field and high temperature ionized gas were covered in the fluid dynamic and electromagnetic equations, and various impact reactions were taken into account in the chemical dynamics model. Non-oscillatory and non-free-parameters dissipative (NND)finite difference scheme (a total variation diminishing scheme) with second order accuracy was adopted to solve the fluid dynamic equations, a finite rate chemical reaction model was developed to calculate ingredient producing rate, and an ADI over relaxation iteration technique was used to solve the electromagnetic discretized equations. Parameter distributions within the thruster and its macroscopical performance were presented. The investigation shows that plenum chambertotal pressure has multifarious effects on arcjet thruster operation, and both specific impulse and thrust efficiency can be improved by increasing it befittingly under steady arc.
Design and realization of multiplex telemetry signal simulate source based on CompactPCI bus
Feng Wenquan, Zhang Xiaolin
2005, 31(09): 1036-1039.
Abstract:
Performace of compact peripheral component interconnect (CompactPCI )bus and other industrial buses were compared and analyzed, some key technolgies in research and implementation of multiplex telemetry signal simulate source based on CompactPCI bus were introduced, the software interface of simulate source were also described. The general testing environment of the satellite test control system, which based on CompactPCI bus, need generate a large amount of simulation signals from sensors as the source of remote sensing. So it is difficult to achieve 128 ways DA output on single 6U CompactPCI board, if still using traditional sampling circuit and the DA integrated mode. Based on the 8-channel 10bits serial bus controlled DA chip AD5318 produced by analog devices company, it realizes the direct communication between CompactPCI interface chip through simple interface circuits, greatly reducing the amounts of devices on the board and finishing 128-routed output. At the same time, this design also implements a 16 bits AD cored high accuracy feedback loop on the board, dynamically monitoring and regulating each output channel, guaranteeing the DA precision and validating the performance of telemetering collection system.
Design and implementation on UDDI-based application service center
Ma Xiaoxuan, Huai Jinpeng, Wang Zhihu
2005, 31(09): 1040-1044.
Abstract:
Web Service is the key technical foundation of Web-based distributed computing and application at present. Universal description, discovery and integration(UDDI) is the key technical standard of Web service, which provides the standard of Web service’s register and discovery and solves the problem of Web service’s description, publication and discovery. UDDI specification only offers standard interface and data structure, has no clear definition and implementation mechanism on the security and management of UDDI registry. On the basis of Web service and UDDI technical analysis, UDDI-based application service center (ASC) was designed and implemented.ASC consisted of ASC client, ASC server and ASC administration console, which supported Web service’s publication, discovery and management operation. According to practical requirement, publisher assertion relation match arithmetic was designed and implemented, UDDI’s application program interface was extended, security and management function was provided, therefore a application service registry system was built which had stronger security and apt management.
Simulating turntable control system with neural network
Pei Zhongcai, Yin Li, Wang Zhanlin
2005, 31(09): 1045-1048.
Abstract:
To solve the turntable uncertain partial load and friction disturbance, a turntable control system was designed with neural-proportion-integral-differential (PID) theory. Because of the learning capacity of neural network, the control system showed adaptive capacity to the load disturbance. The basic theory of a self-adaptive PID controller based on back propagation (BP) neural network was described, The mathematic model of the turntable position control system was set up. A thorough analysis on the system was given by simulation and experiments. The simulation and experiment results prove that the turntable with neural-PID controller shows good track performance and capacity against the load disturbance, but the traditional PID controller hasn’t. The neural-PID system can regulate the PID parameters dynamically by self-learning to fit for the load changes and makethe PID parameters regulation become easier. The controller has a simple structure and can be easily realized in engineering. The results show the effectiveness of the control algorithm.