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1998 Vol. 24, No. 5

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Design of a Digital DS/BPSK Receiver
Li Sanzhong, Zhang Qishan
1998, 24(5): 499-501.
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The design of a new digital DS/BPSK receiver is introduced and its key problems and fundmental principles involved are described in the paper.The dedicated large-scale intergrated circuit, combined with digital signal processing algorithm is adopted to implement demodulation of spread spectrum signal. It applies serial-parrallel combined PN code acquisiton, Costas phase-locked tracking loop and delay-lock tracking loop techniques. The receiver is characterized by excellent overall performance as well as flexible hardware and software interface.It can be efficiently used in multi-objects telemetry and control system based on code division multiple access.
Study of Automatic Vehicle Location and Dispatching System
Wu Shaochun, Xu Ningshou, Zhang Qishan
1998, 24(5): 502-505.
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Trunked mobile radio system has the capacity of dispatching through voice, but dose not have the capacity of location and navigation. GPS (Global Positioning System) has the capacity of location and navigation but dose not have communication links between users. So, it is of signification to realize automatic vehicle location and dispatching system, which remedy their defects and absorb their quintessence, by organically integrating trunked radio system with GPS . Based on the analysis about Motolora's SmartNet trunked radio system, the authors point out some key techniques to realize the system. Those are how to distinguish control signal and voice for establishing stable GPS data link and balance channel load etc.The experiment results have proved out our means.
GPS C/A Code Search and Implement in GPS Receiver
Sun Li, Zhang Qishan
1998, 24(5): 506-509.
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From GPS signal charcteristics,time/frequency two dimension sequential search principle is introduced in this paper.Three basic sequential search techniques and an improved search technique are compared with performances of false alarm probability,detection probability and searching rate.A digital system based on spread spectrum correlator is proposed and verified for GPS C/A code acquisition,while parameters are trade off for better performance.The improved search algorithm is adopted for shortening average acquisition time and improving acquiring reliability.It has been successfully used in digital GPS receiver.
Study of the Alogorithm for GPS Positioning and Velocity Measurement
Chang Qing, Liu Zhongkan, Zhang Qishan
1998, 24(5): 510-513.
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The mathematical models of GPS positioning and velocity measurement are given.Then the iterative algorithm for GPS positioning and velocity measurement under normal condition is discussed based on Gauss-Newton method and the solution under the condition that there are only three visible satellites of GDOP is too large is given.Finally,a complete iteration algorithm for GPS positioning and velocity measurement is obtained.This algorithm consists of two parts.In first part,the positioning solution is obtained iteratively and the satellite signal propagation time is renewed as the positioning solution is renewed in each iteration.In second part,the velocity is obtained by using the satellite signal propagation time and the normal matrix obtained in last iteration in the first part.
Space Determination of Message Buffer for LTPB Network
Xiong Huagang Li Jingsheng, Luo Zhiqiang, Zhang Qishan
1998, 24(5): 514-517.
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In a network system,overflow or overwrite of message buffer will cause missing of messages.For a timed token network,message transmission time and the message buffering space allocation in a node are very important issues on network real time capability.This paper analyses the message buffering mechanism,describes the relationship of message buffering space and message transmission bandwidth allocation,and proposes a space determination method of message buffer for LTPB network.The maximum space redundancy avoiding buffer overflow for send and receive buffers has been derived.It is found that the space of send and receive buffers is equal to the message size under condition that the message gap time is greater than message latency and node response time.
Optical Architecture Design of Time-Integrating Acoustic-Optical Correlator
Jiang Xiufu, Shao Dingrong
1998, 24(5): 518-521.
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The time-integrating acoustic-optical correlator was used to capture long codes. The additive time-integrating acoustic-optical correlator was used as the experimental model. The experimental model was devided into four parts: light source, splitter, beam expansion and detector array parts . Through the analysis and calculation for each part, the optimum experimental model was established. The experiment of time-integrating acoustic-optical correlator was finished by use this experimental model, and the result was analyzed. It is the first time the experimental model of time-integrating acoustic-optical correlator was finished in our country and at the end of this paper, the satisfied experimental results in our laboratory were given.
Real-Time Frequency and 2-D Angle Estimation Method with Sub-Nyquist Sampling
Si Deyi Le Qiang, Shen Shituan, Li Jingwen
1998, 24(5): 522-524.
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A method is proposed to estimate real-time frequency and azimuth and elevation angles of arrival with parallel uniform linear arrays and elements output signal delay.The method uses PRO-ESPRIT algorithm in DFT beam-space.It can estimate the frequency and angles with sub-Nyquist sampling.The analog frequency is estimated by general eigenvalue in the direct method.The alias zone of frequency can be determined by the estimation of analog frequency.Then,the digital frequency is estimated,and the analog frequency is calculated by digital frequency in the indirect method.The variance of the frequency estimates of indirect method is more little than that of the direct method.Simulations are presented demonstrating the capabilities of the method.
Characteristics of the Inclined Narrow-Slot on a Sectoral Waveguide
Gao Wenjun, Lü Shanwei, Xiao Wei
1998, 24(5): 525-528.
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According to the continuative condition of the tangential fields on the slot aperture which is the inclined narrow-slot on the broadwall of a sectoral waveguide,the moment method is used to calculate the magnetic current coefficient and distribution.Then the scattering field,the scattering parameter and the equivalent impedance are obtained.Leting only the TE-11 dominant mode propagates in the waveguide,the scattering parameters and the normalized equivalent series impedance in the X-band are computed.The basis disigned the slot antenna and the slot array is offered.
Intelligence Control Based on Self-Correcting Fuzzy-Neural Networks for Brushless DC Motor Drive
Fan Zhengqiao, Li Chengjun
1998, 24(5): 529-532.
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It presents a self-correcting fuzzy-neural networks controller (SCFNNC) to realize the requirement of the start,regulating the speed,resisting disturbance and the brake for brushless DC motor.The SCFNNC implements good controlling rules by the method of regulating self-conrrecting gain parameters for the system.The paper emphatically develops designing method of self-correcting gain parameters,the design of fuzzy controller and the method to realize the rules of fuzzy control by artificial neural networks etc.The self-correcting gain parameters depend on expected values of the overshoot,steady-state error and dynamic velocity-drop for the system.According to systematic requirement fuzzy controller is designed,suitable rule table of fuzzy control is also determined,which is used to training neural networks.In order to reaching optimal performances complex control of combining self-correcting fuzzy-neural networks with Bang-Bang and proportional control is applied.It is shown by digital simulation that the system with SCFNNC has excellent dynamic and static performances,good robustness and ability for resisting disturbance.
Methods of Analysis Failure of Squeeze Film Damper
Liu Fangjie
1998, 24(5): 533-537.
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The methods of analysis failures of squeeze film damper are emphasis on expounded.First, the studies of squeeze film damper of the principal aeroengine manufacture factories in the international have been introduced. It is not only to help the envelopment of squeeze film damper for China but also it raises an inspiration that is to research the failure of squeeze film damper should be based on the collocations of synthetical parameters. Thus the bearing parameter B and unbalance eccentricity ratio U are used as the elementary parameters to detail the methods of analysis failures. There are two cases to define the failure . One is the rotor system can not to strit over the critical speed ,and the other is arising the bistable characteristic. The data and character diagram of unable to strid over critical speed ,and three typical bistable curves have been presented.
Effect of Radar Cross Section on Aircraft Survivability
Ma Dongli, Zhang Kao
1998, 24(5): 538-541.
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Radar cross section (RCS) of an aircraft is one of the important influences on aircraft survivability. A computational method for the probability that an aircraft survives hostile air-defense system consisting of early warning radar, interceptor and surface-to-air missile has been developed in this paper. The method includes calculation of the probability of detection, the probability of hit and the probability of kill. The influence of the pattern propagation factor and atmospheric loss and the influence of signal-to-noise radio on miss distance are considered in calculating the probability of detection and the probability of hit, respectively. The effect of RCS on aircraft's survivability is analyzed by the calculation. The results show that reduction of aircraft's RCS can remarkably reduce the probability of detection, and decrease the maximum intercept distance when interceptor and surface-to-air missile intercept penetrating aircraft. In order to enhance the aircraft survivability, its RCS must be reduced．
RCS Analysis of Bomb-Fins
Li Jing, Wu Zhe, Li Tian
1998, 24(5): 542-545.
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This paper analyzes the difference of corner reflection effect between bomb-fins and ordinary rectangular corner reflector , and derives the formula of RCS of the corner reflection effect of bomb-fins for engineering calculating using equivalent-section-method, and the formula is verified by means of calculating the scatter property of bomb-fins synthetic model. And the reflecting coefficient is induced to the RCS formula of polygon plate covered wiith radar absorption material (RAM), two coefficients are used to express the two times of absorption/reflection effect of the corner reflection;And finally the scatter property of the model covered with RAM is calculated with this reflection-coefficient-method.
Effect of Material Nonlinearity on Progerssive Damage of Laminated Composites
Xu Chengdong, Hua Yu, Li Zhengneng, He Qingzhi
1998, 24(5): 546-548.
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A nonlinear finite element program in terms of the nonlinear shear stress-shear strain relation proposed by Hahn and Tsai is used to simulate the progressive damage of laminated composites with a circulor hole subjected to remote tensile loading.Stress,strain and ultimate strength of laminates are analyzed by this program.Compared with the experimental data in earlier paper,the nonlinear approch is more accurate than the linear approach,especially for orthotropic laminate.The parametric study manifests that the variance of nonlinearity coefficient has more serious effect on orthotropic plate than on quasi-isotropic plate.
Calculation Research of the Radar Cross Section
Xue Xiaochun, Yang Bin
1998, 24(5): 549-551.
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The paper focus on tests on electromagnetics field and Radar Cross Section (RCS) with densified grid provided by the flux-splitting method.It separated the representative value into positive and negative part in order to hold down the allowance errows respectively.For the purpose of optimization design computation,the time-domain scheme is applied to calculate RCS,the final results agree satisfitorily compareing with previous results.
Compression of Composite Honeycomb Core Sandwich Panels after Low Velocity Impact
Cheng Xiaoquan, Kou Changhe, Li Zhengneng
1998, 24(5): 551-554.
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Compressive tests after low velocity impact were carried out on Nomex honeycomb core sandwich specimens. Some methods were used to study the cause of damage development when the specimens were compressed to fail: X ray, deply, and visual inspection. Compressive failure mechanism was analyzed. The results showed that the residual compressive strength decreased while impact energy increased. The compressive failure of Nomex honeycomb core sandwich specimen was controlled by the front facesheet.The loads that caused the front facesheets to buckle was close to the load that made the planes fail. The glass cloth on surface not only could reduce impact damage, but also could show the damage within the plane on the surface so that it could been found easily.
Prediction of the Compressive Strength for Composite Honeycomb Core Sandwich Panels after Low Speed Impact
Kou Changhe, Cheng Xiaoquan, Li Zhengneng
1998, 24(5): 555-558.
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Based on the experimental study of compressive failure mechanisms on composite honeycomb core sandwich panels after low speed impact before, a equivalent delamination was used to replace the low speed impact damage of Nomex honeycomb core sandwich panels in this paper. It was postulated that the edge of sublaminate formed by the equivalent delamination is clamped. The load on which the sublaminate buckled was considered to be compressive failure load. Comparing the results of theory with experiment, it showed that the method of equivalent damage could be used to predict the residual compressive strength of honeycomb core sandwich panels, in the case that the facesheet of sandwich panels had no obvious cracks after low speed impact.
Structural Optimization Based on Envelope Function and Two-Level Approximation Concepts
Chen Shaojun, Xia Renwei
1998, 24(5): 559-562.
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An efficient solution method for structural optimization is proposed by coordinated use of mathematical transformation, two-level approximation concepts and dual theory. At first the original multi-constraint structural optimization problem is converted into a single-constraint optimization problem by using envelope function which is then approximated by a new two-point approximation function proposed in this paper, and then a corresponding high accuracy approximation problem is constructed. The solution of the approximation problem is obtained by two-level strategy and dual theory. Theory and computation examples have shown that the main advantages of methods developed in the paper are the generality in use and the efficiency in computation, which are particularly important for large scale problems with complicated functions in engineering.
Applications of Inverse Flight Dynamics
Zhang Shuguang, Fang Zhenping, Wang Yong
1998, 24(5): 563-566.
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Two computational techniques for inverse fight dynamics, namely derivation-iteration and integration-iteration techniques, are investigated.The application of inverse dynamics to determine control power requirements for post-stall maneuvering is researched, and a maneuvering flight trajectory based algorithm is provided, which lays a numerical foundation for simplifying design criteria for post-stall aircraft.With the model of inverse dynamics employed, a flight control mode for the outermost loop of the control system, named maneuver generator, is designed to follow desired complicated maneuvering flight trajectories.An example of rapid heading-reversal maneuver and other numerical simulations show the feasibility of the algorithm and the design idea.
Implementation of Data Management Method Oriented Engineering Design
Cai Yunhong, Fan Yuqing, Wang Deng
1998, 24(5): 567-570.
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This paper aims at providing a product data management method oriented engineering design by describing its implementation in the Pressure Vessel CAD system(PVCAD). By this method,a CAD system can efficiently manage and automaticly visit those product data in normal engineering design.It comprehensively describes the data classification,expressive form,data structure and implementation method for the model of product data in the system.
Study on Tool Wear Monitoring Based on Milling Force
Li Jinsong, Chen Dingchang
1998, 24(5): 571-574.
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Based on the milling experiment,the characteristics included in milling force and concerning the conditions of tool wear was analyzed,the influence on cutting force spectra for cutting regime was analyzed,and the comparison among the effect to conditions of tool wear for components of cutting force was made . Through the analysis to the milling force spectra,it indicated that: 1)the radial force spectra is more sensitive to the conditions of tool wear,2)there is characteristic band in cutting force spectrum,which has close relation with the conditions of tool wear and is out of the relation to the cutting regime . And through the analysis to cutting force in time domain,the relationship between the conditions of tool wear and the components ratio of radial force and tangential force was discussed.
Comparing Two Regression Methods Based on Different Principal Components
Wang Huiwen, Yang Xianglong
1998, 24(5): 575-578.
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This paper deals with the comparing two regression methods based on different principal components.The principal components acquired by principal component analysis are the best summery of the information in the independent variables' system,but generally they are short of the explanatory capability to the dependent variable.However the components acquired by using PLS regression can not only summarize the independent variables well,but also they have the best explanation to the dependent variable.Moreover,the interference from invalid information is eliminated at the same time.
Scheduling Model and Resource Pricing in Multi-Stage Manufacturing Systems
Huang Haijun, Xu Gang
1998, 24(5): 579-583.
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This paper presents a scheduling model of multi-stage manufacturing systems with multiple job classes and variable production capacity constraints at workstations. The model aims to minimize the total cost which is the sum of all costs incurred in holding, processing and schedule delay over the whole study horizon. On the basis of analyzing optimality conditions, the prices of production capacities or resources are derived and explained in economic meaning. It is shown that the model can be transferred into an equivalent static minimum cost network flow problem over a space-time network which is a temporal expansion of the base workstation network. An adapted network approach based on the Frank-Wolfe algorithm is proposed to solve the equivalent problem and tested on a numerical example.
Traveling Waves of the Cahn-Hilliard Equation
Liu Shenquan, Lu Qishao, Wang Qi
1998, 24(5): 584-587.
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The asymptotic perturbation method is used to deal with the Cahn-Hilliard equation and obtain the inner and outer solutions of traveling waves. The two solutions are matched into one solution of the equation. The feature of the method not only matches the inner and outer solutions of the higher order partial differential equation, but also satisfies the boundary condition and initial condition. After a long time evolution, the solutions of the Cahn-Hillard equation have the structures of traveling waves as the limit states. The result in this paper can explain the theoretic and numerical simulation results of the Cahn-Hillard equation. The property of model fits well with that of the equation.
Algorithm of Movie Transit Intersection Survey Via the Least Square Estimation
Yan Shoufeng, Lü Fenghai, Liu Zhongkan
1998, 24(5): 588-591.
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A method based on the least square estimation for movie transit rendezvous survey is proposed. In conventional direct algorithm. It is not easy to control the switching time of two equation. This new method is an iterative algorithm, it can obtain the moving object' spatial location at anytime used the redundant data of three transit and avoid the question of two equation'switch. Theoretical analyses and numeric simulations in the new choice of stations have shown that this method possesses the advantages in computation and the fast convergence rate.Compare with the conventional direct method.It can improves the measure precision of radar etc.
Modal Bifurcations and Stability Analysis of a Nonconservative Nonlinear Coupled System
Gan Chunbiao, Lu Qishao, Huang Kelei
1998, 24(5): 592-595.
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This paper deals with a coupled nonlinear Van der Pol oscillator system with linear coupled elastic term,the dissimilar modes and their bifurcations have been discussed by modal analysis.Moreover,the stabilities and the superposition of the dissimilar modes have also been analyzed theoretically and numerically.It is shown that the modal superposition can effectively simulate the system's attenuation effects,the theoretical results are compared with the numerical ones,it is found that there exit very small errors between each other.However,when the parameter of the system passes through some value,the Hopf bifurcation takes place and a stable limit cycle arises in the modal equation of the system,and as a result,the modal superposition lose its efficacy,especially in their phase positions.
Ion Beam Modification of Ti-Alloys
Hu Zhengqiong, Zhang Ying, Wang Yihua
1998, 24(5): 596-598.
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Titanium alloys are very useful in area of aeronautics and astronautics.They have good performance of light weight,high intensity and corrosion resistance,but have poor wear resistance.In order to improve their abrasion resistance,the specimens of TC4,TA7 titanium alloys were titanium-plated by sputtering,and then Ti atoms were implanted into the surface of specimens by (N++N+2) ion beam.On the basis of the above ion implantation,some specimens were implanted by C+ ion beam additionally.The results of tests of friction and wear shows that the coefficient of kinetic friction of specimens is decreased by 64%~77%,and the wear rate of specimens is decreased by 22%~48%.The measurement of microhardness show that the surface microhardness of specimens is increased by a factor of 0.3~1.4.After ion implantation,the mechanical performance are improved effectively.Analysis of X-ray photoelectron spectroscopy shows that the metal compounds of TiO2,TiN and TiC were formed in the layer of Ti-alloys,which are the primary factor of decreasing the friction coefficient and increasing the wear resistance.For the specimens of additional C+ ion implantation,the mechanical performance can not improve more than other,the reason will be analyzed later.
Motion of Microwave Plasma Electrons in the Action of Magnetic Field
Song Ruan, Cheng Xianan, Qi Xianglin
1998, 24(5): 599-602.
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In rectangular microwave resonator, under the action of high frequency electro-magnetic field and inhomogeneous static magnetic field, the electron cyclotron resonance motion of the plasma electrons have been studied. Writing out the Newton equations of motion of the electrons and by using the numerical method, the trajectory and the behavier of the motion of the electrons were computed and drawn out by computer. The energy of the electrons were also computed. Form the computed results,the characteristics of the motion and the energy absorbed by the electrons were analyzed.
Closed-Form Displacement Analysis of a Planar Fifth-Class Group with Lower Pairs
Han Lin, Liao Qizheng, Liang Chonggao
1998, 24(5): 603-606.
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The closed-form displacement analysis of one kind of planar fifth-class groups with 8 links and 12 lower pairs is solved by the method of combining vector with complex number. First, the vector equations are established according to different loops. Then the equations are changed into the form of complex number. The problem is reduced to a single unknown equation after algebraic elimination. The input-output equation, which is proved to be a 42th degree polynomial equation, is obtained. It shows that this construction of fifth-class group has 42 structures. Last, a numerical example is studied. Four real roots are listed. The symbolic computation is carried out by computer algebra system Mathematica.
Research on Dynamic Optimization Control of Redundant Manipulators
Chen Weihai, Zhang Qixian, Yang Zongxu, Li Jian
1998, 24(5): 607-610.
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Stability and end state self-motion are important and difficult points. To solve these difficulties that exist in dynamic optimization of redundant manipulators, this paper deeply researched the inner relation and contradictory conflict between the dynamic optimization and the joint velocities, a new idea to raise the general quality of dynamic optimization by means of optimizing joint velocities is presented; A scheme resulted from adjusting joint velocity homogeneous item in real-time is developed to effectively improve stability and joint velocities at end of motion to be near zero; Computer simulations verified the proposed approach to be very useful and efficient.
ANN Based Expert System and Its Application to Fault Diagnosis
Luo Dehan, Chen Weihai
1998, 24(5): 611-614.
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Fault diagnosis of complex devices has become an issue of very importance in modern industrial process automation. Many methods about fault diagnosis were presented in last 30 years, and intelligent diagnostic methods have been rapidly developed in recent years. Their applications, however, are limited due to their inherent defects in some fields. In this paper, a new intelligent diagnostic model which combines Artificial Neural Networks (ANN) with Expert System (ES) is developed. The architecture of its hardware and software are discussed. Its knowledge base, and knowledge acquisition are studied. The hybrid reasoning mechanism and layered diagnosing strategy are proposed. The diagnostic expert system based on the new model has been built for MK9-5 machines fault diagnosis. It has been shown that the new intelligent diagnostic expert system based on ANN has higher effect and liability than the common diagnostic expert system does. It is expected to be further developed and improved in order to apply it in practice.
Direct Digital Synthesizer (DDS) and Performance Analysis
Gao Zexi, Gao Cheng
1998, 24(5): 615-618.
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This paper introduces the composition, operational principle and performance of DDS, and uses signal theory and method to analyze the effect of phase noise, spurious noise and digital phase truncation error on output wave form and the effect of DAC non-linearity on spectrum purity in detail. Analysis formula and correspondence curve in question are also provided. The conclusion is some instructive to increase the quality of DDS output signal.
Close-Loop FOG Self-Diagnosing and Application in RSDIMU
Yang Yuanhong, Ma Jing
1998, 24(5): 619-622.
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The loop characteristic of close-loop interferometer fiber optic gyroscope(I-FOG) was studied first and its self-diagnosing capability has been reveal. A new type FOG with self-diagnosability has been gotten and used in a redundant strapdown inertial measure unit (RSDIMU), and a new fail tolerance algorithm has been designed for this unit too. In this algorithm, both the output and the state information of this FOG were induced, so that the information redundancy at the instrument grade has been realized and the fail tolerance capability was improved from fail operate(FO)-fail operate(FO)-fail safe(FS) to FO-FO-FO-FO-FS. Using Markov reliability evaluation mode, the reliability was calculated, compared with the old system, the reliability was improved greatly.
Model of Rain-Flow Real-Time Counting Method
Yan Chuliang, Zhuo Ningsheng, Gao Zhentong
1998, 24(5): 623-624.
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This paper presents a new model of rain-flow real-time counting method.It has the advanges such as counting easily,not needing the whole loading-time course.And it is also not necessary to readjust or modify the loading-time course.The field loading-time course of the model can be counted directly.The model surmounts the limitation of the previous counting model.It doesn't need the second stage counting.The above research results have been applied to the data treatment of loading-spectra for the plane engine,the fighter plane and the war tank.

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