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2000 Vol. 26, No. 2

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Set of New Microcomputer Aided System for Comprehensively Measuring FCG
LIU Yan-li, ZHONG Qun-peng, LU Min-xu
2000, 26(2): 125-128.
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A set of new computer aided system(CAS)programmed by C+ + and developed on X86 series microcomputer for comprehensively measuring crack growth rate is briefly introduced and some part of algorithms for data process and the selection technique of load-variation are given.The CAS mentioned above can be applied to tests with different range of load ΔP and range of stress intensity factor ΔK such as constant ΔP method,constant ΔK method as well as decreasing ΔK and increasing ΔK method.Compared with other systems,the new systems can increase the measurement accuracy,shorten testing time and obtain more information. It has been successfully used in measuring corrosion fatigue crack growth rate,which shows that the system is effective in measurement and reliable in function.
Precise Estimation Method of Pseudo Random Code Delay of Spread Spectrum System in High Dynamic Environment
LI Xiao-min, LIU Hui, CHENG Lee-lung, ZHANG Qi
2000, 26(2): 129-132.
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The problems met in high dynamic environment during direct spread spectrum system measuring pseudo-random (PN) code delay are analyzed, and the effect of Doppler frequency shifted on PN code delay is studied emphatically. Carrier phase and frequency of high dynamic direct spread spectrum signal are estimated through extended Kalman filter (EKF) algorithm. The PN delay loop is adjusted through measuring the varied value of carrier phase with carrier aiding technology. The effect of Doppler shift on PN code delay is reduced through carrier aiding technology. The precise delay estimation is obtained. The dynamic tracking performance of the PN delay loop is improved.
Pspice Circuit Temperature Model of the Quantum Well Laser
YANG Wen-ge, LI Zheng
2000, 26(2): 133-136.
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By researching the temperature characteristics of the quantum well laser, the rate equation of quantum-well laser is modified, and in the rate equation, these currents which are contacted with temperature are added. These currents include radiative recombination current and nonradiative recombination current of the barriers and nonradiative recombination current and auger recombination current of the active region. With the modified rate equation, a new large-signal equivalent circuit temperature model and circuit temperature model of steady state for quantum-well laser are obtained. In the simulation, GaAS/AlGaAS quantum-well laser is adopted to analyze the temperature characteristics of laser. Finally, the results of simulation can explain the relation of the optical power, injection current and temperature.
C-R Spline Fitting Theory for the RCS Computation \=of Low-Scattering Targets
NING Huan-sheng, YANG Zhi-ling, WANG Bao-fa
2000, 26(2): 137-140.
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The geometric modelling and electromagnetic scattering characteristics of complex targets are discussed. In order to overcome the insufficiency of some other spline functions, the contour fitting of the targets was made conveniently and correctly by using Catmull-Rom spline fitting function. To the low RCS target, the effect of creeping wave is remarkable and larger than that of facets and wedges in some cases. Based on the C-R spline fitting theory, the problem of computing geodesic has been solved and a practical computing example of Low-RCS target fully proves the validity of the method by using the hybrid method of GRECO(Graphical Electromagnetic Computing) and creeping wave theory. the results can have practical engineering worth.
Adaptive Clutter Suppression for Non-Side-Looking Airborne Phased Array Radar
LI Chun-sheng, ZHOU Yin-qing
2000, 26(2): 141-144.
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The clutter suppression methods of spatial-temporal adaptive signal processing for non-side-looking airborne phased array radar is studied. On analyzing the non-side-looking spatial-temporal clutter distribution properties,three practical processors are presented based on spatial and temporal repetition structure. Spatial element repetition cascade temporal pulse repetition structure followed by adaptive processing is a practical spatial-temporal adaptive signal processing method. It can achieve sub-optimum performance by using element and pulse signal information more efficiently.
Improved AMI Code Used in Telemetry System
AMI Code, YANG Dong-kai, WEI Ke-ping
2000, 26(2): 145-148.
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An improved AMI code being suitable for telemetry system is proposed. It is realized through inserting redundancy Bit into the binary data stream to be synchronized rapidly and steadily. It has no long continuous zeroes. Its properties are analyzed, such as code efficiency, error Bit rate, power spectrum, the acquisition probability of the first frame marker. This type of code has the similar power spectrum to the original AMI code, and though its code efficiency decreases, rapid synchronization will avoid losing data and increase the credibility of data. In addition, the implementation of this code is described in detail.
Hybrid Petri Nets and Analysis of Its Reachability
LI Hui-feng, ZHOU Rui, CHEN Zong-ji
2000, 26(2): 149-152.
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Hybrid system is a type of sophisticated system which consists of interactive discrete event dynamic systems and continuous variable dynamic systems. A new type of hybrid Petri net is proposed, which can not only describe and analyze deterministic discrete events, but also deal with the concurrent problem concerning discrete events or continuous evolution. If the hybrid net is simplified properly, the timed Petri net model and logic Petri net model of the original system can be obtained. Therefore, the objective systems could be researched under the same theoretic framework in DES, RTDES and HS respectively. In addition, an algorithm is presented in order to compute the set of reachable states in hybrid system.
Aircraft Engine On-Line Wear Monitor Based on Isotope X-Ray Fluorescence Method
YUAN Mei, Lü Jun-fang, CHEN Xing-lu, ZHANG Jiang-ping
2000, 26(2): 153-155.
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An OLWM(On-Line Wear Monitor) of aircraft engine based on IXRF(Isotope X-Ray Fluorescence) method is illustrated. The lubrication oil of running engine has plenty of wear debris. IXRF method can detect the composition and content of different metal on-line, according to the principle that different metals radiate different length of X-ray. One advantage of this technique is that it can make the test rapid, reliable and contactless. The experimental results indicate that OLWM can examine the concentration of Fe and Cu in oil on time. The study and application of this method can make early failure prediction of engine and avoid serious fault.
Real-Time Distributed Simulation of Aircraft Anti-Skid Control System
ZHAO Hai-ying, WANG Zhan-lin, QIU Li-hua
2000, 26(2): 156-159.
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Firstly,the work fundamentals of anti-skid braking system have been analyzed in detail. The mathematical model of the system has been set up. On the basis of it, the simulation research was made to the system by adopting the real-time distributed simulation system. It has also given the structure scheme of the real-time distributed system and discussed the questions of simulation algorithm, the selection of simulation step, and so on. The simulation result under the circumstances of dry and wet runway of a certain aircraft anti-skid braking system has been analyzed. The experiment verified that the real-time distributed system possessed the advantages of good realtime distinction,strong processing ability, and so on.
Scheme Analysis of Fly-by-Light of Airborne Actuation Systems
QI Xiao-ye, FU Yong-ling, WANG Zhan-lin, WANG Yi-qun
2000, 26(2): 160-163.
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An overview is given of the FBL(Flight By Light) scheme currently developed for airborne actuation systems. After paralleling the benefits of FBL with demands of the flight control system of future aircraft, the necessity of developing FBL technology is pointed out. Considering the present status of technology and the level of researches on FBL in our country, and balancing the pros and cons of analog and digit FBL schemes, a kind of quasi-digit FBL scheme is put forward. The schematic circuit diagram of V/F-E/O and O/E-F/V conversion of this scheme is illustrated, which has been demonstrated in laboratories. The frequency bandwidth of the conversion component reaches 500Hz. The preliminary experiment shows that this quasi-digit FBL scheme can meet the needs of future flight control systems and is a reasonable transition to the digit FBL scheme.
Robust Controller Design and Research on Airplane Anti-Skid System
ZHAO Hai-ying, WANG Zhan-lin, QIU Li-hua
2000, 26(2): 164-166.
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Firstly, the system has been analyzed in detail and the mathematical model has been given. The second problem is how to improve the robustness of the system. When the airplane is running on the runway, the tyre/runway characteristic will be disturbed by various time-variant or uncertain factors, such asthe airplane velocity, the various road surface condition of dry, wet or ice, and so on. In addition, when setting up the mathematical model of system, some certain modeling errors may be produced. The control effect will descend obviously when the system is influenced by the disturbances. So, in the view of all the disturbances discussed above, a control method based on robust adaptive filter has been put forward. The simulation has been made by exerting various disturbances to the system. The simulation result has demonstrated that this method is effective in improving the robustness of the system.
Bases of Judging the Failure of Squeeze Film Damper
LIU Fang-jie
2000, 26(2): 167-170.
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If the design of squeeze film damper is not properly,it will be causing the failure of its functions. There are two cases of failure of the elastic support-squeeze film damper:one is the bistable character being take place,the other is unable to stride over the critical state,i.e.,the amplitude of the rotor system has been increasing with the rotating speed increasing. Two diagrams of judging the failures have been established. One is the bistable region diagram. Provided the data of the bearing parameter cooperated with the unbalance ratio do not be selected in that region,the bistable character will not be arising. The other is the failure boundaries diagram of attenuating vibration. Provided the above-mentioned data do not be selected at the side of failure boundaries,that will not be causing the phenomenon of unable to stride over the critical state. The result of experiment proves that the above conclusions are correct. This is observed from both positive and negative respect. By experiment, the excellent functions of attenuating vibration of squeeze film damper have also been affirmed still further.
Experimental Study on the Flow Patterns of a Simplified Aircraft Model at High Angles of Attack
WANG Jin-jun, XUE Qi-zhi, BAI Tao, FENG Ya-nan
2000, 26(2): 171-173.
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The dye-injection flow visualization technique has been used to study the changes of flow patterns for a simplified aircraft model with the variation of angles of attack and the incoming flow velocity in a water tunnel. In this experiment, the changes of flow patterns do not have essential difference at several incoming flow velocities, but the variation of the relevant angles of attack occurs indeed, which means that there exists the Re-dependence. Moreover, for the scatter of the experimental pitch-up moment curve in the case of natural transition, the explanation has been made. α=35° corresponds the start of asymmetric breakdown of the strake vortex and α=70° is the critical point of the flow forth and back in the up wind side of the nose.
Method for Predicting Rotor Vortex Wake and Downwash Velocity Field
CAO Yi-hua
2000, 26(2): 174-177.
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An analytical method for predicting rotor vortex wake in low speed and hovering flight is described to investigate the motion of the helical tip vortex. Beginning with the prescribed wake model, a Semi-Empirical Correction for the vortex core effect on rotor wake is made and free wake calculation is carried out. Then on the condition of circulation and wake geometry convergence, the rotor thrust is calculated to satisfy convergence criterion of thrust. Finally, as an example of its engineering application, the calculated downwash velocity field along the rocket launch line is presented and simply analysed. In terms of theory, the calculating method developed here may provide referable basis for further studying the formation mode of the tip vortex and vortex core interior structure. Also the method is practical for predicting rotor induced flow field in engineering applications.
Design and Analysis Expert System of Airplane Structure Durability
ZHAO Yao-wu, LIU Xiao-dong, JIANG Dong-bin, LIU Wen-ting, WANG Fan
2000, 26(2): 178-181.
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In order to satisfy the need of rapid development of modern airplane design,the development process of expert system is presented for airplane structure durability design and analysis with Visual C+ + language. This expert system includes knowledge base formed by organizing existed expert's knowledge and expert's experience, experiment database on the basis of many kinds of material experiment, and calculation model formed by calculation manner of original design and analysis. This expert system realizes the normalization of durability design and analysis, and is applied in certain model airplane durability evaluation. This paper presents the system organization structure, its functions and also shows an example and gives the conclusion.
Numerical Prediction of Moduli of 3-D and 4-step Braided Composites
LIU Zhen-guo, LU Meng, MAI Han-chao, LU Zi-xing, FENG Zhi-hai
2000, 26(2): 182-185.
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The parameterized modeling technology for three dimensionally and 4-step braided composites is studied. First, the ""-type model of a representative unit cell is presented for FEM numerical prediction, which more really simulates the inner meso-structures of the materials because of considering the interactions of them. Then, the boundary conditions and constrain conditions of the unit cell model are discussed and the longitudinal and transverse elastic moduli and Poisson-s ratio of the materials are obtained by FEM calculation. Finally, the predicted results are compared with those of experiments, and it is showed that they are in good agreement with each other.
Influence of Grid Structure on the Euler Solution
LI Jin, ZHU Zi-qiang, WU Zong-cheng, CHEN Ze-min
2000, 26(2): 186-189.
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Using two types of patched grids, the influence of grid structure on the Euler solution of the flow around a wing with aileron deflection is discussed. One type is a partially discontinuous grid (PDG) and the other is a completely continuous grid (CCG). Van Leer's flux-vector splitting scheme and Jameson's central difference scheme are used respectively in PDG and CCG as the numerical methods to solve the Euler equations. Numerical results show that the two grids, CCG and PDG, have their own advantages and disadvantages respectively. Even though the useful results can be obtained in both grids,a suitable grid structure must be chosen depending on the flow and geometry to obtain better results efficiently.
Generation of the 2D Unstructured Grids and the Euler Solution on It
WANG Ping, ZHU Zi-qiang
2000, 26(2): 190-193.
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Computational unstructured grid is generated by advancing front method, and the structured background gird is obtained by using multigrid technique to solve the Poisson equation. A new method of boundary discretization is presented for generating the initial fronts, and a novel data structure—Array Linked List is proposed to store the grid data. The Euler equations on unstructured grid are solved by cell-centered scheme of finite volume method. Numerical examples show that the correlation of the computational results with experimental data is favorable and the need of N-S equations solver is obvious for both case of airfoil in transonic flow and multi-element airfoil in subsonic flow.
2D Multiblock and Parallel Method to Solve Transonic Euler Equations
Lü Xiao-bin, ZHU Zi-qiang
2000, 26(2): 194-197.
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Two-dimensional domain decomposition method and parallel computing method are applied to solve Euler equations on networked computers. The Van Leer-s Flux-Vector-Splitting method is applied. All the variables are stored in one-dimensional order, so the domain decomposition can be made arbitrarily. Non-reflection boundary conditions, conservative interface boundary condition and "First-In First-Out" synchronization strategy are applied. Two examples of different decomposition show that efficiency of various types of decomposition does not decrease by using conservative interface boundary condition given by the present paper. Influencing factors on increasing parallel performance are discussed. Examples show that the higher speedup ratio can be reached if the overhead ratio of communication over computing is smaller when parallel computing load maintains balanced well.
Assessments of Air-to-Surface Operational Effectiveness for Aircraft during Combat Sortie
MA Dong-li, HAN Ying
2000, 26(2): 198-200.
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Operational effectiveness analysis of aircraft is one of the important research texts on military equipment. The determining methods of accessible zone of airborne air-to-surface missile and first attacking probability are described. The mathematical models are established to describe operational effectiveness of a single and a group aircraft attacking targets during combat sortie. The calculating methods of the probability that a target is killed and the probability that an aircraft is killed in the phase of attack are presented. The formulas to be used to calculate the average killed number of targets for one aircraft and the probability that a group aircraft is killed during combat sortie are deduced. The foundation has been established for assessments of multistep air-to-surface attacking action.
Model for Speech Recognition Based on Multiple Time Scale Features
HAN Jiang, YIN Bao-lin
2000, 26(2): 201-205.
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The model explicitly models the correlation among successive frames of speech signals in segment scale by using segmental features representing contours of spectral parameters. By using the proposed segmental feature dependent non-stationary time series model, the new model not only achieves the modeling of correlation between different scale features but also implicitly models the correlation among neighboring frames in frame scale via parametric mean trajectory function. A modified Viterbi algorithm based on joint statistical distance of multiple time scale features is proposed, and a algorithm based on the maximum likelihood criteria for estimating the model parameters is also proposed in the training. Experimental results show that the new model achieves better performance than the standard HMM and the trended HMM.
Implementation of Dual Languages Specification for Idea of Separation of Concern with OOD
SUN Wen-yan, XIONG Zhang, SONG Jing-min
2000, 26(2): 206-209.
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A new idea of formal specification named "separation of concern" has been discussed. The dual languages technique based on this idea has also been analyzed. Compared with traditional single language technique, "separation of concern" and dual languages techniques are more suitable to represent the distributed multimedia systems. Combined with the application of OOD(Object Oriented Design) in formal specification of distributed multimedia system, a scheme building on ground of LOTOS/QTL (or Esterel/QL) and adopting the idea of OOD has been given. This method can be used to construct time model and synchronization model in distributed multimedia systems.
Evaluation Method for Projects of Product Conceptual Design
HAN Xiao-jian, DENG Jia
2000, 26(2): 210-212.
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Evaluation method for projects of product conceptual design is an important gist for acceptant decision-making of design process. Using method and theory of fuzzy mathematics and making various fuzzy information to numerical value, projects of conceptual product are evaluated in ration. By establishing evaluated system of design project and degree of subjection of various evaluated indexes,considering method of weight of various indexes, a fuzzy integrated evaluation method of project of product conceptual design is presented. So, a formalized,scientific gist of reasoning decision-making is presented for product conceptual design. In the meanwhile, a good base of automatization of product design process is founded.
PC/DSP Based Open System Architecture Intelligent Machining Module
LIU Qiang, Yusuf Altintas
2000, 26(2): 213-217.
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The structure and functions of open system architecture intelligent machining module(OSA-IMM) are investigated based on PC and DSP. The key strategies to realize the openness of the system are discussed. The signal processing network(SPN), reentrant plug in module(PIM), script command file(SCF) and standard function library(SFL) for intelligent control/monitoring of machining process are used to make OSA-IMM open and intelligent. Two experiment systems based on the OSA-IMM platform, the adaptive control system and the on-line flank wear estimation using artificial neural network for turning operations, have been implemented for testing OSA-IMM. The experiments have demonstrated that OSA-IMM is characterized by satisfactory open system architecture and powerful real-time ability, as well as intelligent computations. Based on the platform of OSA-IMM, the control/monitoring systems for different objectives in the machining processes can be configured conveniently.
Mechanism Analysis and Empirical Study of Second Mover Advantage of Imitative Innovation
YUAN Zhi-shan, GAO Yuan-yang, CHEN Liang-you
2000, 26(2): 218-220.
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It is true that the second mover has the advantage over the first mover on certain condition. The single or multi-product growth pattern of imitative innovation project with R&D increasing was founded by analyzing the quantity relationship between the R&D input accumulation and project output. The contribution of the accumulation input of the R&D to the output of the imitative innovation project was specified. It was pointed out that the key of triggering second mover advantage over first mover was the continual R&D input. Especially, the continual and stable increase depended on the exploitation of the variety and series of the imitative innovation products.
Analysis of Growth Pattern in Typical Imitative Innovation Institution
YUAN Zhi-shan, GE Zi-gan, CHEN Liang-you
2000, 26(2): 221-223.
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Based on the analysis of the actual statistical data of the product values of five representative imitative innovation projects in time sequence, the growth pattern of the imitative innovation project in the representative aeronautical institution (BIAM) was set up. The model was checked with the actual data. Therefore, the growth dynamics of the imitative innovation project in the aeronautical institution was recognized. It is found that the increase trend of the ratio value of the imitative innovation project income to the total project accords with the Logistic or Comperz curves.
Three Parts about Cooperated Software Development Activity Management
CHEN Qian, LIU Hui, FENG Yun-cheng, DAI Gui-liang, ZHANG Chang-chun
2000, 26(2): 224-227.
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For cooperated software development activity management based on network, following contents are researched: how to build a cooperated working environment between developer teams and develop a software management information system of supporting activity management, how to give a task partition and how to manage tasks which will be cooperated by developers on network. Furthermore,three models for three sections of cooperated software development activity management are given: software component model(SCM),relation model(RM) and task model(TM). Then, it describes SCM using software component, discusses RM using the principle: "Who should close the door he is last one of leaving room",analyses TM using task division method.
All Optical Real Time Three Dimensional Color Image Optical Fiber Sensor
LI Ying-zi, ZHANG Jia-hua
2000, 26(2): 228-230.
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The resolving power of optical fiber image transmission (OFIT) is studied, and a solution is provided in view of the problems coming up from that. Both the working principles and experimental outcome are introduced. The result shows that three-dimensional color image optical-fiber sensor which takes neutral photon as information-carrier instead of electron has the functions of real-time intussusception and transmission, as well as visualizing the colorful cubic target in time. Both its immunity to the effects of electromagnetic interference and capability of hiding itself are excellent. It is predicted that the system will become an important complement of the aeroplane-carried visual image electric system in the time of emergent power failure or in an electronic war.
Approximate Limit Sampling Data Using Fuzzy-Tree Model
MAO Jian-qin, ZHANG Jian-gang, DAI Ji-yang, WEI Ke-hui
2000, 26(2): 231-234.
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A linear binary fuzzy tree structure approach, i.e. Fuzzy-Tree model, is proposed for complex nonlinear system modeling. In comparison with some other modeling approaches, such as ANFIS and Neural Network model, the proposed model is of less computation, higher accuracy, especially insensitivity to high dimension. It is proved that for any square integrated continuous function, there always exists a Fuzzy-Tree model to approximate it arbitrarily. Fuzzy-Tree model simulates the layered decision-making and piece-wise linearized processing procedure for solving complex problems. A numerical solution was given to show the approach.
Bifurcation of a Quadratic Integrable System under Quadratic Conservative Perturbations
PENG Lin-ping
2000, 26(2): 235-238.
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The question on bifurcation of limit cycles in quadratic conservative perturbations of a quadratic integrable system is discussed. As a result of conservative perturbations, the first order Melnikov function for a perturbed system is identically equal to zero, so the second order Melnikov function has to be considered. The perturbation parameters which make no use in the first order Melnikov function may be important in the second order Melnikov function. Hence perturbed systems are more complicated. With the help of the formula for the second Melnikov function and theoretical analysis, the following result is obtained: if the first order Melnikov function for a perturbed system is identically equal to zero, and the second order Melnikov function for the perturbed system is not identically equal to zero, the system has at most two limit cycles.
Static Shape Control of Adaptive Structure Using Composite Laminated Piezoelectric Element
TANG Ji-ye, HUANG Hai, XIA Ren-wei, HUANG Hai-bo
2000, 26(2): 239-243.
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The static shape control of composite plate adaptive structure was studied. Using the piezoelectric composite laminated plated element, the displacement sensitivity matrix was established. Then,the optimal control equations were derived from the sensitivity matrix. If there were same number of controlled displacements and actuators,the voltage of actuators could be obtained precisely by calculating linear equations. When the number of actuators was less,optimal methods were used,and the equations could be solved to achieve the optimal shape control of adaptive structure. Numerical example were given to compare the different control situations, and the results showed the efficiency of the method and the importance of actuators placement.
Solar Panel Substrate Planeness Measuring System
FANG Jian-cheng, ZHU Shi-ping, ZHOU Rui, YU Wen-bo, SHEN Gong-xun
2000, 26(2): 244-248.
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A solar panel substrate planeness non-contact system is presented, which employs optical triangulation method and bases on virtual precise benchmark. By means of declinate optical triangulation measuring instrument structure which is firstly proposed, the measured area and resolution of this measuring system are greatly increased, and the high accuracy non-contact measurement of the planeness of a large area plane is realized. On the basis of a new modeling method of virtual precise measuring benchmark and measurement error compensation technique, the measuring system can accurately measure the solar panel substrate planeness on a non-precision plate. In addition, in order to lay a theoretic foundation for optimization design of the laser spot, the relationship between measuring laser spot positioning accuracy and the shape, size and energy distribution of spot image, is analyzed deeply. The actual measurement results show that the measurement accuracy 0.02mm(RMS) can be obtained when a solar panel substrate (2581mm×1755mm) planeness is measured by using of this measuring system.

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