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2005 Vol. 31, No. 12

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Strategy of signal search and acquisition in spaceborne GPS receiver
Yang Chunbao, You Zheng, Zhang Yong
2005, 31(12): 1269-1273.
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Unaided cold start time is an important performance of spaceborne global position system(GPS) receiver. Reduction of cold start time was developed for C/A code navigation receiver on low earth orbit(LEO). The search method of frequency and code phase, signal detector and parameters select, doppler bin, and code search speed were analyzed. Doppler bin of 500 Hz and code search speed of 475 chips/s were obtained. The orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity were researched as the influential factors to doppler range. GPS satellite allocation according to statistical information of angle between GPS satellites was discussed. Analysis and simulation shows that the cold start time is reduced by 25%~30% through this GPS satellite allocation method, the influential factors of doppler range are orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity in regular order with an effect, the cold start time is reduced by 25%~40% farther considering these influential factors of doppler range.
Virtual design environments of flight control system
Qin Xudong, Chen Zongji, Gao Jinyuan, Huang Haodong
2005, 31(12): 1274-1278.
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Design-oriented virtual design environment of flight control system was established. The virtual design environment had a three-level structure. The top level was operations management based on database technology, in which product data management(PDM) systems were used to manage design documents, product configurations, workflow and design process of virtual prototype(VP). The middle level was VP technology in which VP of redundant flight control computers, sensors and actuators were provided. The bottom level was environments supporting for man-in-the-loop simulation of flight control systems. The key technology was analyzed to realize the function of each level. The parameters of virtual prototype of redundant flight control computers(RFCC-VP) were discussed. With different parameters, architecture and performance of RFCC-VP were different. Design processes of RFCC-VP were the processes to determinate the parameters of RFCC-VP. Validation of RFCC-VP was accomplished in the environments, and RFCC-VP can be built according to its major parameters such as architecture, performance and price.
Mission-based operational effectiveness evaluation model of combat aircraft
Zhang Jiankang, Cheng Long, Huang Jun, Wu Zhe
2005, 31(12): 1279-1283.
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To the combat aircraft operational effectiveness evaluation, mission effectiveness concept was presented based on combat aircraft’s different missions. With the probability analysis method, aircraft operation procedures were studied and abstracted into a group of probability values, and relevant evaluation models were built for several different typical operation procedures. These models have much more matter-of-fact significance and will be very helpful for commanders to make much reasonable and scientific mission plans and thus make much better use of combat aircraft and weapons available to implement certain mission. The new models are simple, easy understanding and conducting, their computing resources and time are more acceptable than that of traditional emulation methods while giving reasonable results with calculation accuracy close to the former. Example results show that the models are available and believable when evaluating mission-based operational effectiveness of combat aircraft, which concerns different aircraft platform with different weapon striking different target in different combat scenario.
Conforming Delaunay triangulation optimized by weighted method
Meng Xianhai, Li Jigang, Yang Qin
2005, 31(12): 1284-1288.
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As a conforming Delaunay triangulation (CDT) algorithm, Delaunay refinement method has widely application both in theory and practice. It always fails to terminate when there are some small angles intersected by input geometry constraints, so a sufficient condition for termination of Delaunay refinement method was introduced and a new conforming Delaunay triangulation algorithm was presented, which is based on Delaunay refinement method and optimized by weighted method. The algorithm imposes no angle restrictions on the input geometry domains by setting weight value to point where input constraints intersected with small angles and applying the rule of weighted Delaunay circumcircle/circumsphere claim to generate Delaunay triangular mesh, and it avoids appending any additional complex region and need not adding any Steiner points to mesh. Analysis of termination and some results applied by this algorithm were also presented. This method will be useful in the computation and analysis of complicated geometry objects.
Predications of structural weight for high aspect ratio joined-wings
Wang Xiaoni, Yu Xiongqing
2005, 31(12): 1289-1292.
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The joined- wing is an innovative aircraft configuration with a structural connection between the front wing and the rear wing. An approach was presented to investigate the dependences of the structural weight of a hign-aspect-ratio joined-wing on the parameters of its aerodynamic configurations. Such thedependences are essential for the priliminary deisgn of the joined-wing configuration. The approach consists of two steps. The first step is that the joined-wing structural weights were predicated by the combination of parameterized modeling of the finite element method (FEM) with structure optimization method. The second step is that the quantitative relationships between joined-wing configuration parameters and structural weights were explored using the design of experiment (DOE) method and response surfaces model. Based on this approach, the dependences of the wing structural weight of the joined-wing on the configuration parameters were obtained, which indude the span of front wing, the ratio between front wing span and rear wing span, the aspect ratio of front wing, the dihedral of front wing, the sweep of front wing, the longitudinal distance between front and rear wing, and the vertical distance between front and rear wing. The dependences obtained can be used as a guidance for the preliminary sizing of the high-aspect-ratio joined-wing configurations.
Generality analysis of the pre-corrosion influence on the fatigue life for aircraft structure
He Xiaofan, Wang Lei, Liu Wenting, Xiang Jinwu
2005, 31(12): 1293-1298.
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To analyze the influence of the different spectra loading, constant amplitude loading and crack size on the pre-corrosion influence factor (C(T)),the C(T) test assuming the fatigue life following the two-parameter Weibull distribution was proposed. The C(T) shows the pre-corrosion influence on aircraft structural life under different ground parking time is the ratio of pre-corrosion characteristic life to un-corrosion characteristic life when the pre-corrosion fatigue life located in the long life range. Assuming the slope of the Weibull distribution is material constant, and the unbiased characteristic life which was estimated with the maximum likehood estimation(MLE), the probability density function of the estimator was determined. The distribution function of the statistic C(T) was obtained, the C(T) contrast approach was proposed, and used to test the hypothesis that the C-T curve is general between different spectra loading, constant amplitude loading and crack size, the fatigue testing data shows that the C-T curve is weak-correlation with these influence factors.
Temperature field analysis for heterogeneous material piston
Wang Su, Ni Chunyang, Zhu Xinxiong
2005, 31(12): 1299-1302.
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Physical and chemical performance of heterogeneous material part exceeds homogeneous material part. Because of material distributing complexity and insufficient study for heterogeneous material, there are lots of difficult in analysis of heterogeneous material part. Theory of composite performance and ADINA-T module of finite element analysis software ADINA were used to compute and analyze temperature field and heat dissipating capacity for heterogeneous material and common piston, using the gradient aluminum matrix composite piston reinforced by ceramic fibers and aluminum matrix composite piston reinforced by ceramic fibers (no grads) as examples. The results show this method can change piston temperature distribution, reduce heat dissipation capacity and relax the stress at interface of gradient aluminum matrix composite layer reinforced by ceramic fibers and piston noumenon which caused by mismatch between different coefficients of thermal expansion, using gradient aluminum matrix composite layer reinforced by ceramic fibers.
Principle and technique of sand consolidation with novel epoxy-phenolic resins system
Gu Yizhuo, Zhang Zuoguang, Li Min, Zhang Daxing
2005, 31(12): 1303-1307.
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To solve the problem of chemical sand control in low-temperature oil wells cost-effectively, a novel sand consolidation agent was prepared with epoxy resin and phenolic resin as the primary raw material and without any other curing agents by means of the blending method. On the basis of the sand consolidation agent, a kind of resin-coated sand was developed initially. By analysis of Fourier transform infrared spectroscopy(FT-IR), the cure mechanism of resins was investigated. The results show that thesand consolidation agent can consolidate sandstone in water at 50℃ and consolidated specimens have high compression strength and permeability. As the quantity of resins is increased, the compression strength of consolidated specimens can be further increased. The resin-coated sand can consolidate with the phenolic resin as an external curing agent and the properties of consolidated specimens can satisfy use requirements. The reaction of phenolic hydroxyl and hydroxyl methyl in phenolic resin with epoxy in epoxy resin is the major mechanism of the curing reaction.
Design of a algorithm of mapping from phase to sine amplitude in DDS of a GPS signal simulator system
Zhu Yuhong, Zhang Qishan, Chang Qin
2005, 31(12): 1308-1311.
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Based on trigonometric identities, Sunderland technique is a effective compression algorithm for mapping from phase to sine amplitude in ROM-based direct digital frequency synthesizers(DDS)design. A modification based on Taylor-series linear interpolation method was proposed to provide additional improvements in compression efficiency. Their effect on distortion and trade-offs were investigated, and spurious were identified by using fast Fourier transform algorithm (FFT). A computer program was created to simulate and optimize the effects of the memory compression and algorithmic techniques on the output spectrum of the DDS with the help of matlab computing tool. The subjected multiplierless architecture was then implemented in a Xilinx’s field programmable gate array (FPGA). Simulation results show that the proposed techniques is effective, and the digital output of the designed DDS which using this compression technique has the worst case spurious about -90 dB. A 80 MHz DDS was developed and used successfully in a actual projects of a GPS signal simulator system.
High accuracy coning compensate algorithm by angular velocity
Wei Xiaohong, Zhang Chunxi, Zhu Kuibao
2005, 31(12): 1312-1316.
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Traditional coning compensation algorithm error greatly increased while angular velocity signal was algorithm input. Considering the direct angular velocity signal output from fibre optic gyroscope (FOG), a novel coning compensation algorithm was introduced and it need input angular velocity signal. In the attitude updating period, the expression of the angular velocity output from FOG was educed by the output signal from FOG. Combining the rotation vector differential equation, the new algorithm expression was deduced. The new algorithm was optimized by the least arithmetic excursion error. These motions, regular forward and rotation motion, coning motion and the coning motion with noise, were test input. Compared with custom algorithms, the new algorithm performance is better in computing time and computing accuracy. Also the new algorithm expression conveniences attitude error compensation. The introduction of the new algorithm is a new idea to calculate attitude error compensation of FOG strapdown inertial navigation (SINS) under the condition of high dynamic angular motion.
Adaptive threshold method for real-time audio segmentation
Li Chao, Xiong Zhang, Xue Ling, Liu Yun
2005, 31(12): 1317-1321.
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Content-based audio analysis has become an interesting direction for many researchers. Deep analysis on audio signal segmentation was reviewed. Conventionally, automatic segmentation can be implemented by calculating some audio features like short-term energy, amplitude, fundamental frequency or others, in time-domain or frequency-domain, via referencing to several constant thresholds established in advance. But these methods were found lack of reliability in such applications, because of the complexity of real-time audio signals, together with the fluky changing of environment and various models of acquiring devices. An adaptive threshold adjusting method based on background learning was introduced. On condition of real-time environment, a so-called environment factor was computed iteratively through background learning, and then it was used as a measure to control the fluctuating of real thresholds. To make a balance between efficiency and precision, a state table was introduced to help judging on the types of audio clips. Validity of the methods was proved by a group of experiments.
Thermally-induced birefringence of polarization optical fiber on gyro
Li Jing, Lin Heng
2005, 31(12): 1322-1326.
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To solve the performance labefaction problem of fiber-optic gyroscope (FOG) when its temperature changed, modes coupling caused by thermally-induced refractive index of highly birefringent optical fiber was analyzed to be the main reason of limitting the precision of gyro in theory. Finite element method was used to calculate stress distributing. Based on the stress state of high or low temperature, the variational instance of birefringence was conjectured respectively. Six typical temperature points were selected as work condition to calculate thermal stress. The result shows that thermal-induced birefringence variations reduces accordingly based on different temperature, tallying the experimentation well from the extinction ratio. The result indicates double-coated optical fiber loop changes its birefringence at temperature range , for the expanding coefficient of fiber dismatching that of the framework and glue. Thermally-induced birefringence is 1×10-4 at 60℃, the same order with its own birefringence of 5.5×10-4, and it deteriorates the polarization in optical fiber and decrease gyro precision furthermore.
Algorithm of conflict probability prediction for the case of trajectory change
Deng Wei, Zhang Jun, Wu Xian, Wang Gang
2005, 31(12): 1327-1331.
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An algorithm of conflict prediction available for the condition of trajectory change was put forward concerning the problem of how to detect the latent conflict between airplanes in flight efficiently. It calculates the conflict probability to realize the conflict prediction due to the uncertainty of actual trajectory positions. Ameliorated from the prediction algorithm which is only applicable for flight along straight-line fairway, it made the best use of intent information provided by ADS-B to compute the trajectory change point and trajectory change angle, calculated the error covariance matrix of the changed trajectory by matrix transforming, and simplified the expression of the increased error by approximating all angle conditions into two entries: small change angle and huge change angle to ultimately get the conflict probability. The monte-carlo simulation results testify the veracity and precision of the algorithm, the comparison with the algorithm for straight-line fairway indicates the adaptability to more complicated environments.
Multi-screen display calculation method of GRECO for complex targets
Zhang Yunfei, Ma Jun
2005, 31(12): 1332-1336.
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Graphical electromagnetic computing (GRECO) is an effective method of predicating the radar cross section(RCS) of complex targets, but there must beforehand be a model file from which the shape parameter can be easily obtained. Based on the GRECO, the model file generated by several commercial shaping software could be converted to the type fitting for the RCS calculation by means of the commercial software RHINO. The processing method of data had a wide use and may not delimit any details of model. The multi-screen display calculation methodwas used to improve the precision of calculation when predicting the RCS of electrically large and full size targets. By using display list technology of OpenGL, the program expended less time than before. A simple approach was also presented by which the scattering source of targets can be analyzed expediently. The good agreement between the calculating results of our method and that of plate-edge method indicates that this method possesses practical value in engineering.
Circuit functional reliability simulation based on grid
Sun Yufeng, Yang Libo, Zhao Guangyan
2005, 31(12): 1337-1341.
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The functional reliability simulation (FRS) is an advanced integrative simulation and analysis technology in reliability by integrating functional simulation with reliability analysis of system. The architecture and functions and mostly realization methods were discussed, such as failure modeling, virtual failure rejection, simulator integration, failure automatic criterion about FRS. In order to resolve the problems about simulation time and data storage, a new architecture was put forward, which is based on the grid technology, and the related service of simulation, analysis, data management and so on was represented. The grid provides a virtual capability of computing and storage. The new architecture shortens the simulation time and realizes the distributed data storage. The Tyrensgrid circuit functional reliability simulation(TG-CFRS) system was produced based on the idea, which makes the Tyrensgrid as the grid platform and PSpice as the simulation kernel and proves the availability of the new architecture.
Taylor series expansion method for vibration system with fuzzy parameters
Qiu Zhiping, Liu Zhengquan
2005, 31(12): 1342-1346.
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To study the eigenvalues problem of vibration structure with fuzzy parameters, the Taylor series expansion method was proposed. Based on the property of membership level, the uncertain fuzzy parameters were expressed in the interval forms, and accordingly the fuzzy finite element equilibrium equation could be expressed by interval finite element equilibrium equation. The Taylor series expansion method was used to compute the eigenvalues interval sets of interval finite element equilibrium equation for the purpose of calculating the eigenvalues variety range of vibration structure with fuzzy parameters. The fuzzy result sets of eigenvalues could be constructed by interval result sets gained from computing the interval finite element equilibrium equation under every α-level through fuzzy decompose theorem. Consequently the variety range of natural frequencies can be obtained concerning vibration structures with fuzzy parameters and establish the foundation for fuzzy reliability evaluation. A numerical example is considered to illuminate the practicability of the method presented.
New frequency domain adaptive filtering algorithm
Pu Xiaolin, Li Jingwen
2005, 31(12): 1347-1350.
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After analyzing existing adaptive algorithms,a new frequency adaptive algorithm was proposed which can achieve faster convergence speed under the color noise background. It uses the Newton-type algorithm searching the performance surface and uses the similar structure of recursive least-squares (RLS) adaptive filtering algorithm. The time domain quasi-Newton adaptive algorithm to the frequency domain was applied by using fast fourier transform (FFT), and the whole calculating duration according to the parallel method using in fast block least mean square(FBLMS) adaptive filtering algorithm. Because of changing the format of the input signal and the coefficients of the gain-matrix, the speed ofthe recursive procession convergence and the efficiency of the signal procession were increased. Additive computer simulation results present the comparison of the adaptive system identify effect after using LMS algorithm, QN algorithm and the new algorithm respectively, which is separately passed the same hamming window with the white noise and color noise inputs. The results indicate the new algorithm can be efficiently applied to adaptive filtering with color noise.
Effects of thickness and environmental factors on conductivity of composite coatings
Song Wenbo, Li Huanxi, Lü Mingyun, Wu Zhe
2005, 31(12): 1351-1354.
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To provide information for the manufacture and application of digital processing frequency selective surface(FSS), the properties of two conductive composite coatings consisting of silver flakes and resin matrix were contrastively investigated. With environmental accelerated test, attention was focused on the effects of environmental factors including temperature, humidity and corrosive atmosphere on their adhesion, microstructure and conductivity. Variation of their surface resistance was measured by bridge method,and their microstructure and pattern change of section and surface were observed before and after environmental test with SEM. The over-all properties of the polyurethane matrix composite coating is better than that of the epoxy resin matrix coating for the two coatings containing silver flakes. The effects of environmental factors on conductivity of the two coatings are obvious, though no appreciable influence on adhesion can be identified in experimental scope and parameter variation range. The negative effect of environmental factors on conductivity is attributed to the micro-damages occurred within the microstructures of the coatings.
Robust PID control for a class of nonlinear systems
Liao Daozheng, Zhang Minglian
2005, 31(12): 1355-1357.
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A robust control design method was proposed for a class of nonlinear systems with uncertainty. The controller was composed of a proportional integral differential (PID)controller and a robust compensator. The whole design was divided into two steps. A PID controller was developed based on the linear nominal model of the plant. On the basis of the developed PID controller, a robust compensator was given to compensate for the bad influence resulted from the system parameter perturbation, the unknown external disturbance , the model error because of linearization and so on. The compensating control law was derived by Lyapunov stability theory, as a result, the stability of the closed loop system was guaranteed despite the uncertainty, the robustness of the system was improved accordingly. Applying the proposed control method to the tracking control of an inverted pendulum, the results of numerical simulations show the validity of this scheme.
Influence of damping characteristics to landing gear shimmy
Xiang Jinwu, Yang Dongmei
2005, 31(12): 1358-1362.
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A linear shimmy analysis model was used ,which includes the elasticity of strut, the elasticity of damper linkage system, tire deflection, structure weight, vertical loads and wheel gyroscopic couple. With the method of sensitivity analysis,research on tire-yaw shimmy and structural-torsion shimmy was made separately. The three key landing gear structural parameters including trail, bending stiffness and torsional stiffness of damper linkage on aircraft wheel shimmy were investigated thoroughly. The investigation took the coupling effects among different parameters into consideration and calculated the sensitivity of damping to parameters’ variety ,and the effects of damping characteristics to shimmy was attained. The results supply a new idea for the design of aircraft and for the safe maintenance of operational ones to prevent the occurrence of shimmy.

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