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1999 Vol. 25, No. 2

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Analysis on Phase Gradient Algorithm in DiscreteDomain and Implementation
Li Liwei, Mao Shiyi
1999, 25(2): 125-129.
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Usual autofocus techniques are based on low order phase error model, and they can only estimate low order phase error, therefore they can not be fit for high resolution airborne SAR(Synthetic Aperture Radar). The PGA(Phase Gradient Autofocus) presented in this paper is uniquely not phase-error-model-based, so it has a well-deserved reputation for arbitrarily high order autofocus. This paper researches on PGA and its implementation in discrete domain, analyzes and summarizes correlative problems. Finally, some experimental results are given to compare PGA with mapdrift autofocus which is based on limited order phase error estimation.
Wavelet Analysis Theory and Application in Radar Signal Processing
Wang Zulin, Zhou Yinqing
1999, 25(2): 130-133.
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According to the features of signal to be processed, the wavelet transform is compared with short-time Fourier transform. It indicates that the wavelet transform is suitable for the processing of nonstationary and singular signal. The continuous wavelet transform, discrete wavelet transform and wavelet packet theory are reviewed in brief. Some key problems are discussed, such as sampling and fast algorithm which are essential to the application of wavelet transform. Finally, a data compression method is presented that compresses the raw SAR (Synthetic Aperture Radar) data by means of wavelet transform and vector quantizer. Compared with the traditional method, the result shows that the SAR image generated from compressed raw data has better SNR(Signal to Noise Ratio), and meanwhile the performance of wavelet transform in radar target identification and SAR image classification are also discussed.
Control Strategy and Implementation for Acquiring and Tracking GPS Signal
Sun Li, Wang Yinfeng, He Chuan, Zhang Qishan
1999, 25(2): 134-137.
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A control strategy of acquisition and tracking for code loop and carrier loop is designed to detect GPS signal. Sequential searching scheme and narrow space non-coherent digital delay locked loop assure reliable acquisition and precise tracking for code phase. Integrated algorithms of 4-quadrant frequency, cross-product automatic frequency control and Costa phase locked loop are adopted to speed up frequency acquisition and effectively track carrier frequency/phase changing, and therefore obtain better dynamic and noise performance. The control algorithms and loop parameters determination are implemented by software with inflexibility. Digital system based on spread spectrum correlator and digital signal processor proved above scheme be correct and efficient.
μ-Analysis and DFP Optimization Method of μ-Synthesis for Flight Control System
Zhang Lijun, Cheng Peng
1999, 25(2): 138-141.
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Because the result of the classical control system design is not unique,there are more than one result that satisfies the required performance.So a design result with good robust stability is selected by structured singular value analysis.This result could be regarded as a multi-target design which considers both the required performance and the robustness.Furthermore,without changing the control law, the DFP optimization method with some necessarily restricted conditions is used to minimize the structure singular value of the system by optimizing some important parameters of the control law. Consequently,a controller which not only has good robustness but also is suitable to the engineering practices is available.Finally,the effectiveness of this method is illustrated by a numerical example of a flight control system.
Analysis and Calculation of the Rotation Induced Voltage of Brushless DC Motors
Guo Hong, Wu Kai, Wang Guoliang
1999, 25(2): 142-145.
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The general calculation formulas of the rotation induced voltage of brushless DC motors are deduced systematically. Based on these formulas, the effect on the rotation induced voltage caused by the flat top width of air-gap magnetic density, the distributed winding, the short pitched winding, the fractional slot, the skewing slot and so on are studied detailedly. The essential factors of design of rotor magnet and stator winding are presented in order to ensure that the rotation induced voltage is trapezoid with the ideal flat top width.The research contents of this paper supply theoretical basis to the design of brushless DC motor of high performances and low torque ripple.
Formal Verification of Hybrid System
Gao Jianping, Chen Zongji
1999, 25(2): 146-150.
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As a case study of hybrid system, a redundancy management system in flight control system is formally investigated and its specification and verification are presented using an approach incorporating program logic into duration calculi. Firstly, the requirement with some assumptions is captured in duration calculi, then the algorithm is specified in mixed-term hybrid descriptions and a parameter selection is given. During the verification phase,the program invariant is reasoned about with Hoare logic and specified by duration formulae. Finally, the whole verification is finished in the duration calculus framework.
Research on Mechanism of Imitating-Human Intelligent Control Triple-Inverted Pendulum
Zhang Feizhou, Chen Weiji, Shen Chengzhi
1999, 25(2): 151-155.
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Based on the mechanism of acrobatic erecting poles, this paper makes use of phase plane method and human controlling experience, puts forward an obvious imitating-human intelligent control method used to control one stage inverted-pendulum which combines qualitative analysis and quantitative estimation, and then abstracts controlling rules of one stage inverted-pendulum. By introducing "equivalent cart" concept, the analytical method is readily extended from one stage inverted-pendulum control system to double-inverted pendulum system, triple-one and even more. The theoretical analysis is the same as the test result. So the qualitative method used to analyze inverted-pendulum based on phase plane is feasible.
Robust Detection in Multisensor Data Fusion
Su Huimin, Zhang Minglian
1999, 25(2): 156-159.
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Robust detection problem is presented in this paper. The design of optimal decision rules in detection problems requires the knowledge of the conditional probability distributions of the observations given by each hypothesis. In many applications, however, the probability distributions are not specified completely. In these cases, the problem could be solved to find least favorable distributions. In the view of data fusion, the decentralized detection is better in information transmission and fault tolerance properties of the system. Finally,the data compression for multisensor system is discussed when N sensors work at different sampling rate.
Posterior Ellipsoids Conditional Filtering Method of Stochastic System
Wu Sentang
1999, 25(2): 160-162.
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In the case of unknown control vectors, unknown distribution and parameters of system state and that of stochastic interference existing in stochastic system, based on posterior ellipsoids approximation principle, an ellipsoids conditional filtering method of stochastic system is developed in this paper to ensure that the soluted ellipsoids sequence is the minimum ellipsoids sequence consisting of system state estimation field. This method is one of the effective ways in solving state statistics of stochastic system when the prior statistics information is not enough.
Theoretical Analysis of a Kind of Hydraulic Active Filter
Li Yunhua, Jiao Zongxia, Wang Zhanlin
1999, 25(2): 163-166.
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Aiming at the problems existing in traditional passive hydraulic filter, a concept of hydraulic filter with active control is presented. Based on its simple operation principle, the theoretical analysis for a kind of active control hydraulic filter with static pressure balance and variable chamber, driven by double accumulator-piezoelectric crystal, is carried out, and its attenuating principle is understood. In order to describe the united operating characteristics of hydraulic system composed of pump, pipe line and load, the accurate mathematical models of pump and load, and the matching method between pump and load are put forward.Finally, the selection method of the control law for achieving the desirable vibration absorption behavior is proposed considering hydraulic supply characteristics and hydraulic load characteristics reasonably.
Experiment Study on Combined Fatigue of Turbine Disc Fir-tree　Slots at Elevated Temperature
Hou Guicang, Wang Rongqiao, Yan Xiaojun, Nie Jingxu
1999, 25(2): 167-170.
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Based on a practical problem of the teeth crack breakdown of a turbine disc at elevated temperature, an experiment and theoretical study on L-HCCF (Low and High Cycle Combined Fatigue) of fir-tree slot is carried out.The major cause of the fracture is the interreaction of high and low cycle fatigue. Further studies including contrast experiments of light and serious corrosion disc slot are also conducted. Major service factors are successfully simulated and the experiment results show obvious fatigue failure feature which is identical with that in service. A new designed test system, achieving low and high cycle noninterfering loading, high frequency induction local heating ,and the control of high cycle vibration frequency and amplitude,and the crack propagation real-time detection,is established for all above purpose. This investigation is very helpful in establishing the failure standards of turbine disc's slot with corrosion.
Analysis of Active Aeroelastic Wing Technology
Yang Chao, Chen Guibin, Zou Congqing
1999, 25(2): 171-175.
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Based on aerosevorelasticity technology, active aeroelastic wing technology (also called active flexible wing technology) was discussed. Active aeroelastic wing technology was advanced technology of aircraft design to improve performance from a lot of cases. The main design concept and characteristic, key technology (mathematics model of aerosevorelasticity system, integrated design, analysis method for stability, and design of active control system), difference to classical wing design, and functions for future aircraft were analyzed. The design with integrated multidisciplinary in the technology was showed mainly and was important to the research person for future aircraft design.
Numerical Analysis of Optimal Control on Composite Plate Deformation
Fang Youliang, Wu Zhe
1999, 25(2): 176-179.
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Kirchoff hypothesis is applied to laminate plate with induced strain actuators. Piezoelectric patch is bonded to its surface or embedded within the laminate. Using plate element, FEM(Finite Element Method) for laminate plate with induced strain actuators is proposed. Considering the control matrix, which is gotten from applied voltage to laminate plate, the needed applied voltage is given for any plate shapes using optimization algorithms. Numerical example is presented. Comparison between experiments and FEM is shown up in this paper. Three solutions of unconstrained optimization, constrained optimization and optimization considering energy consumption,are given.
Waverider Configuration Design
Wang Zhuo, Qian Yiji
1999, 25(2): 180-183.
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The computation of generating waverider configurations using the theories of conical flow field,OC(Osculating Cone) and OA (Osculating Axisymmetric) flows are presented. Investigation shows that the method of using conical flow field theory is relatively simple and the lift-to-drag ratio of the configuration generated is high. But the inlet flow field is not quite uniform and thus it is not beneficial to the engine. The inverse design of using OA and OC theories accompanied with the inverse characteristic method can get the most universal waverider configurations and improve the inlet flow field quality and the volume efficiency effectively. Additionally, these methods have high speed of computation,which is quite promising for the integration design and optimization process later.
Methods for Estimating Parameters in Random Model ofFatigue Multi-Crack Propagation
Zhang Jianyu, Fei Binjun, Zhao Libin
1999, 25(2): 184-187.
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Methods, which are used to evaluate correlation parameters in fatigue multi-crack propagation random model using test data, were established. Taking advantage of the existed single-crack propagation test data, the parameter estimation method was established by using non-complete test data for analyzing the probability damage tolerance with multi-crack structure.Two cases (complete test data-far parallel crack and complete test data-near crack) were discussed to analyze the parameter estimation method as stated above by using least square method.At the same time, the extreme cases of crack propagation test were considered.Finally, a parameter estimation method whose estimation results inclined to conservative condition in the case of non-complete test data-near crack was developed.
Reliability Analysis Models for Multi-Crack Structure
Zhang Jianyu, Fei Binjun, Zhao Libin
1999, 25(2): 188-191.
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Reliability analysis models for multi-crack structure are established in this paper. These models are based on the FMPRM(Fatigue Multi-crack Propagation Random Model) and can be used to evaluate the multi-crack structural reliability. The structural reliability is the probability that the multivariate random variability controlling the crack propagation falls into a range from the equal-life curved surface(curve) to the coordinate surface(axis). It's equal to the integrity of the probability density function of the multivariate random variability in the same range. Three models are established corresponding to different conditions: CIRM(Complete Integral Reliability Model) for simple case, SSRM(Simplistic Series Reliability Model) for complex structure with small difference to each crack propagation behavior and MSSRM(Modified Simplistic Series Reliability Model) for complex structure with large difference to each crack propagation behavior. Finally, two illustrative examples are presented along with the FMPRM to illustrate the reliability.
Optimum Association of Difference Schemes
Zhuang Damin, Yuan Xiugan
1999, 25(2): 192-196.
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The selection of the finite difference schemes for the convective and diffusion terms of the governing equations of fluid flow has great influence on the computational stability, accuracy and time. In this paper, various combinations of difference schemes, including Central difference, Up-wind, Hybrid, PLDS, QUICK and OPTIMAL, are used to compute the turbulent flow in 3-D room for comparing the stability, accuracy and computational time. A new conception thus obtained reflects in the following aspects. The local use of Up-wind method can eliminate the oscillation of the solution when Reynolds equation is applied in Central difference. Besides, the combination of QUICK and Up-wind method is also proposed to solve the problem that the solution of κ,ε equations diverges when QUICK method is used.
Analysis on Evaluation Method of Handling Qualities of Pilot and Aircraft System
Xu Zhongxiang, Qu Xiangju
1999, 25(2): 197-200.
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The closed-loop system of pilot-aircraft is studied,which is made up of the structural model of human pilot and the equivalent longitudinal model of aircraft. Based on evaluation function of the pilot work load proposed by Hess,the pilot opinion rating of the handling qualities is calculated for two controlled elements, the effects of the command signal, the atmospheric disturbance, the remnant of the human pilot ,the changing of the pilot model parameters on the pilot opinion rating of aircraft handling qualities are analysed to understand completely and expose the essence of the evaluation of the handling qualities proposed by Hess.
Performance Analysis on Hot-Air Anti-Icer of Airplane Engine Inlet
Chang Shinan, Han Fenghua
1999, 25(2): 201-203.
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Two patterns of air plane engine inlet hot-air anti-icer are introduced in this paper,one is circumferential anti-icer,the other is double skin corrugated chord direction anti-icer.Based on the thermal analysis of the two anti-icers,the heat transfer performance and temperature field of ice protected surface are compared.The results indicate that the structure of frontal anti-icer affects anti-icing effectiveness obviously for a hot-air anti-icing system,the double skin chord direction anti-icer is more efficient,but under the normal conditions,a circumferrential anti-icer can attain the goal of ice protection and its structure is more simple,so it is more practical.
Studies on the Product Data Management Based on Web
Chu Xingjun, Fan Yuqing
1999, 25(2): 204-207.
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A methodology which aims at developing the framework of PDM(Product Data management) based on Web is proposed,while the features and disadvantages of conventional PDM system are analysed. The unique scenario of building enterprise-level application, provided by Internet/Intranet technology including three-tier Client/Server architecture, TCP/IP network,database and distributed technology, gives us a promising way to develop and realize a new adaptive PDM system. At the same time, the underlaid data mode and organization for new framework are given. Based on the framework drawn from an example, it can improve the development and research of PDM greatly.
Analysis of Algorithms for Calculating Job Shop Scheduling Problem's Makespan
Wei Youshuang, Han Limin
1999, 25(2): 208-211.
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JSSP(Job Shop Scheduling Problem) is a well-known NP-hard problem. In this paper the JSSP is divided into two parts: one for calculating the makespan, the other for finding a scheduling which has the minimum makespan. Up to now the papers published are all focused on how to find an algorithm for finding the schedule that has minimum makespan quickly. Seldom papers talk about a related topic, that is the algorithm for calculating the makespan.Several algorithms are shown and discussed for that purpose in detail.The experimental result shows that there is a big difference among the speed of these algorithms. The analysis also indicates that the difference realization of algorithms may cause different result, even the wrong result. From the experiment and analysis, it can be seen that the speed of parallel simulation clock advance algorithm is the fastest. It is very useful for some iterative algorithm such as genetic algorithm for finding the schedule that has minimum makespan.
Computer-Aided Analysis for the Application of the Control Charts
Xu Zhe, Duan Xiaojiang
1999, 25(2): 212-215.
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Making use of the control charts to monitor the manufacturing process, to investigate what kind of state the process is and to find out whether the process capability is appropriate or not, it realizes the preventative ideas. Designing the control charts and judging the manufacturing process states by hand is troublesome, that is to say, it is difficult to use the control charts in actual field. Computer-aided system for the control charts is accurate, convenient, fast and efficient. The software—Quality Control Simulation System, which can be used in actual field and for a computer-aided teaching software,is designed and developed.
Study on the Existence and Uniqueness of G-K System in Multilateral International Comparison
Bai Manying, Ren Ruoen
1999, 25(2): 216-220.
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In studying international comparison problem, the famous G-K systemic technique is always used by economic experts. However, whether this method has the unique positive solution or not is the problem economists have been debating at all times.This problem is discussed far and wide in this paper which is based on other research works, and six equivalent conditions are obtained of which the G-K systemic technique has the unique positive solution in the purchasing power parity multilateral international comparison.This paper also points that the conclusion about this problem is mistaken in prasada's literature. In addition, this paper discusses the self-building problem of the unique positive solution of G-K system, and presents corresponding economic explanations.
Some Weighted Inequalities on Polyharmonic Operators and Applications
Guo Dinghui
1999, 25(2): 221-224.
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This work is devoted to weighted inequalities on polyharmonic operators and their applications to the critical exponent problems of semilinear polyharmonic operator with Dirichlet boundary value conditions. Some newer weighted inequalities on polyharmonic operator are obtained. By applying these new weighted inequalities to the critical exponent problems, it obtains a preferable necessary condition for nontrivial radial solutions of the critical exponent problems of semilinear polyharmonic operator with Dirichlet boundary conditions existing. This preferable necessary condition extends the scope in which the critical exponent problems has nontrivial radial solutions to two times of that in Bernis' paper.
Asymptotic Solutions, Bifurcations and Chaosof Slow-Varying System
Gan Chunbiao, Lu Qishao
1999, 25(2): 225-228.
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A non-linear system with slow-varying parameters is dealt with.By using perturbation theory,the asymptotic expressions of periodic solutions are obtained and compared with the numerical results. By the phase portraits, power spectrum analysis, bifurcation diagram and computation of the largest Lyapunov exponent,the process from period-doubling bifurcations to chaos is studied. It is shown that, following the variation of the system's small parameter, the motion of the system becomes chaotic through a similar bifurcation as that in the Lorenz model. Moreover, it is not difficult to find that the system is more tractable than the Lorenz model and the analytic form of the symmetric periodic solutions can be got easily.
New Symmetrically Loading Epicyclic Traction Drive Reducer
Yan Deyuan, Guo Jingjing
1999, 25(2): 229-231.
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A new symmetrically loading epicyclic traction drive reducer is introduced. It has advantage of high drive ratio of other epicyclic gears. It loads three epicyclic gears and two steel tapers and drives through traction oil. It has more work surfaces and higher drive ratio. Its contact stress is decreased because the same curved surfaces is used at the contact region. It has simpler structure, easier making and installation,lower noise than ordinary gear drive. Especially, unlike ordinary epicyclic gear, its installation will not be limited by the number of gears.
Study of Reliability and Maintainability and Supportability Effectiveness Model
Kang Rui, Zhang Guodong, Lü Chuan
1999, 25(2): 232-234.
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This work analyzed the definition of system effectiveness and its affected factor, presented the concept of reliability and maintainability and supportability effectiveness, established a new synthetic parameter RMS effectiveness for reliability and maintainability and supportability design and analysis, introduced two typical equation of RMS effectiveness for the repairable system and unrepairable system during mission time. Based on the parameter, a synthetic design and analysis procedure for reliability and maintainability and supportability is presented finally.
Adaptive Extended Kalman Filter Model for Integrated Land Vehicle Navigation system
Fang Jiancheng, Shen Gongxun, Wan Dejun
1999, 25(2): 235-239.
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An adaptive extended Kalman filter model and its algorithm for GPS/DR integrated navigation system in land vehicles are proposed.By using the adaptive extended Kalman filter model and algorithm,the positioning accuracy of the vehicular integrated navigation system is greatly improved. An effective method, in which the performance of the model designed for GPS/DR integrated navigation systems can be antomatically regulated by changing the [WTHX]Q[WTBZ] and [WTHX]R[WTBZ] in terms of the value of PDOP, is firstly presented.The systems can be adapted for different situations of land vehicle navigation, and possesses smart characteristics. The efficiency of the adaptive extended Kalman filter is verified by computer simulation and experimental results.
Research of Effect of Missile Main Parameters on the Clobber Probability
Zhou Tao, Zhou Huizhong
1999, 25(2): 240-243.
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This work studies the probability of clobber(Pc) of a cruise missile's low height terrain following flight. It deduces the computation method of the clobber probability, puts forward a set of practical formulas for computing the probability of clobber, while taking the influences of both the random input of terrain and the random interference of wind at low height, and the characteristically long-time very low height terrain following flight of missile into consideration. Using them and taking the parameters a24 and Kh as an example, under given condition, the correlative curve of the parameters and the probability of clobber is worked out, the parameters' influence on the probability of clobber is analysed. The conclusion is that, to co-ordinate the parameters such as a24 and Kh can reduce the clobber probability effectively, and at the same time enhance the warring capability of the cruise missiles.
Numerical Simulation of Atomic Oxygen Action on Spacecraft Surface Material
Cai Guobiao, Zhu Chengmin, Sun Bing
1999, 25(2): 244-248.
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This paper introduced the influence of the LEO(Low Earth Orbit) environments to spacecraft surface material and the evaluating technology about the lifetime of the spacecraft surface material in LEO.This work numerically simulate the action of atomic oxygen on polyimide with or without coated layer both in LEO and ground experiment environments. The results compare very well with the LDEF results. As a result, the present work provides a good guideline to the design of spacecraft.

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