Abstract:Since aircraft survivability evaluation is necessary and it is fuzzy and uncertain, a new evaluation method based on interval number was proposed. The index system for aircraft survivability evaluation was constructed by susceptibility, vulnerability and combat capability, the interval weights were calculated based on interval-based analytic hierarchy process and information entropy, the evaluation model of aircraft survivability was established based on weight coefficient. In the end, a numerical example was given. Calculation results show that the method is effective and feasible.

Abstract:The mode of a certain type aeroengine turbine blades under the condition of operating regime is analyzed by using the finite elements analysis (FEA) software ANSYS in consideration of influence factors from centrifugal field, aerodynamic field, temperature and thermal field separately. It is found that centrifugal field and temperature field are the main factors influencing the natural frequency by comparing the frequencies and mode shapes with those of stationary ones at room temperature. But they have less influence on the blades' mode shapes. And then, thermal-structure coupling modal analysis of the blades is conducted in consideration of the effects of centrifugal field and temperature field simultaneously. At the same time, natural frequencies and mode shapes of the blades are obtained in working condition. The conclusion obtained in this paper is of great significance and engineering practical value to the design, retrofit and use of aeroengine blades.

Abstract:By using the commercial CFD software Fluent 6.3, the three-phase (water, air, vapour) flow field with natural cavitation was established. The UDF was used to resolve and control the missile's movement. It realized the numerical calculation of unsteady high-speed water-entry flow field, which consider natural cavitation as well as the missile's multiple degree of free movement. The Mixture was adopted as the multi-phase model; and the stand [WTBX]k-ε[WTBZ] model was used as the turbulence model; and SIMPLE and Standard were used as pressure-velocity coupling method and discretizaion method respectively. The Layering was adopted as the dynamic mesh updating method and the UDF can output the parameters real time. In this paper, the missile high-speed water-entry flow field with 20° angle was simulated and analyzed, and the influence of the thrusting force on cavity development and the missile hydrodynamics were gained.

Abstract:Aimed at the problem that airport pavement roughness evaluation indexes and standards fail to make strict distinction between the two different slipping speeds of aircraft respectively on runway and taxiway in existing standard, taking three-meter wavelength as the most disadvantageous wavelength to airport pavement, and taking 0.40g as a discomfort evaluation standard on the basis of airplane speed representative value on the taxiway and on runway of airport rand A and rand B, this paper analyzes the dynamic response of pavement under the action of aircraft by using software ADAMS. The analyzed results show that allowable roughness of taxiway pavement is 57 mm and runway for airport class A is 12 mm, for class B is 19 mm. The analytic results indicate that the allowable roughness is rather closely related with the airplane slipping speed than the airport classification.

Abstract:This study focuses on nonlinear behavior of aeroelasticity and dynamic elastic load of vertical tail on fighter aircraft in a state of transonic speed. A time domain coupled CFD/CSD strategy is introduced and a method of calculating elastic load is presented by using this strategy. The analysis is based on numerical results of flutter boundary of 0°sideslip angle under different mach numbers and unsteady aeroelastic load at 0.9 Mach、sideslip angle of 2°and 10°, and the effect of rudder on flutter is detected. Dynamic responses of inertial load and elastic load are also available.

Abstract:In order to solve the problem that the use of the existing automatic test equipment can not conduct the task of fault diagnosis very well, a design plan of fault diagnosis software system is proposed. Firstly, a fault diagnosis system framework and information model are given out. Then, taking electron warfare equipment complex test and fault diagnosis system in a certain type of aircraft as example, the function module design is described and a software system framework is built up. And this design plan is applied successfully to an electron warfare equipment complex test and fault diagnosis system in a certain type of aircraft, and good results are achieved, which shows that the plan is effective.

Abstract:A comprehensive evaluation index system is established according to the plan-development characteristics of Air and Missile Defense warhead. Utility function and expert evaluation methods are introduced to quantify uniformly the quantitative index and the qualitative index, the big difference in dimension of significance of evaluation index, evaluation with different dimension and different index are solved. And then, a model of integrated evaluation for developing plan of air defense and antimissile warhead is put forward based on the gray clustering theory, the clustering weight of the evaluation index is ascertained and calculated by using of the Delphi Method and the Analytic Hierarchy Process. The evaluations for the superior and interior of developing plan are realized by calculating and comparing the decision-making measures of all plans. The rationality of the model is verified through example analysis.

Abstract:The radar waveform design for weak target detection in interference and channel noise is considered. Based on the principle of maximizing the SINR, combined with the advantages of the phase-modulate method and the Optimum Transmit-receive Design method (OTRD), a synthesized waveform design method based on phase modulate and OTRD is put forward. Through the simulation, a larger SINR is obtained compared to the previous two methods, the effect is particularly obvious for weak target detection in strong interference, consequently, the function of radar detection is promoted obviously.

Abstract:A new guidance algorithm with threat avoidance ability and target sighting restraint is proposed for traditional staged guidance method lack of threat avoidance ability. Firstly, mathematic model of guidance is established based on relative velocity vector, second, the path restraint model is established based on threat avoidance, and guidance terminal restraint for target sighting is given. Value function is established based on rapidity, economical control and guiding precise, optimal control model for attack guidance is constructed with nonlinear boundary restraint, state restraint and path restraint. Gauss Pseudo spectral Method (GPM) is adopted to transform the problem into nonlinear programming problem. Simulation result shows, this new guidance algorithm is effectively for threat avoidance and the missile launch requirement is well satisfied by air combat requirement.

Abstract:Aimed at the planning problem of terminal attack for TV guidence missile, a terminal planning algorithm is put forward based on a particle colony algorithm. Firstly, factors those have influence on the entrance aim angle of missile at the end are analyzed, and a restrained model of entrance angle is established. An optimization guide line of entrance angle is proposed, and an optimization model of terminal planning is built up based on a particle colony algorithm. At last, simulation and analysis are carried out, the results show that the use of this algorithm can obtain a rapid convergence and find the optimization guide line value and angel can be obtained. The validity of each model is verified adequately, and this provides an effective means for the campaign use and planning of TV guidence missile.

Abstract:New Problems such as redundancy bispectrums, cross-items and possess too high feature dimension still arise though the existing methodes of bispectrum feature extraction can meet the needs of signal classification and recognition at present. A new bispectrum cascade feature extraction method is proposed. Firstly, the bispectrum is converted to gray image, and the amplitude of bispectrum is denoted by gray value. Secondly, the bispectrum cascade feature is extracted based on image processing technique. The gray level co-occurrence matrix (GLCM) cascade feature can specify the bispectrum image texture information of radar emitter signal. Finally, the comparative experiment is made. The result shows that the GLCM features are superior to Hu-invariant moment features greatly in the aspect of performing radar signal classification and recognition.

Abstract:The application of OFDM in troposcatter communication can enlarge the tropo communication capacity. Meanwhile, Inter Carrier Interference (ICI) of OFDM system is the major drawback to degrade OFDM system performance. As a result, the multi-antenna diversity techniques are introduced and the OFDM with Maximal Ratio Combining (MRC) diversity under tropo fading channel is investigated. Firstly, the tropo channel model is established, then, system ICI is investigated. OFDM system with MRC diversity under tropo channel is investigated, and the system SER is derived. Simulation results show that ICI can degrade the SER performance and introduce symbol error floor while multi-antenna diversity can solve the problem above. When normalized Doppler spread equals 0.02 and signal to noise ratio equals 20dB, dual diversity can decrease SER by two orders of magnitude and triplex diversity with four orders of magnitude.

Abstract:When the eigenvalue decomposition(EVD) algorithm is used to estimate the basic function for transform domain communication systems(TDCS) under the asynchronous condition, the eigenvector got by the algorithm is fuzzy, thus degrading the system performance. A synchronous method of basis function is proposed to solve this problem. Based on a detailed study of the EVD algorithm, the relational expression of the data sampling delay and the eigenvalue of self-covariance matrix is deduced, and then a maximum likelihood(ML) estimation algorithm of the synchronization parameter is obtained. According to the norm-equivalence theorem, the frobenius norm is introduced in the problem of finding the largest eigenvalue in ML estimation algorithm, so the algorithm complexity is reduced. The simulation results show that the frobenius norm-based algorithm has the same performance as the largest eigenvalue-based algorithm but it only requires a less calculating time, and its estimation accuracy is in direct proportion to the signal-to-noise ratio(SNR). When the estimated basic function remains fuzzy under the asynchronous condition, the reception performance of the system can be improved by the use of basic function after synchronization.

Abstract:In order to realize the representation of perceptual information of terrain space environment for UCAV cognitive navigation, a method is proposed to construct place cells based on IHDR tree. SURF algorithm is used to extract high robustness feature points in environment, the landmarks' information are combined by the description vector of feature point and its position in geographic space, so the training samples are obtained, and the double clustering of landmarks' information is achieved according to the IHDR algorithm, and the leaf nodes of clustering are regarded as place cells to represent the terrain space environment. Finally, the place cells are constructed .The simulation results show that the place cells constructed by this method can represent the terrain space environment effectively, and have the ability of recognizing terrain space environment under condition of certain noise interference.

Abstract:Aimed at the problem that the decision threshold is difficult to precisely set and the complexity of hard decision is high, a new method of power spectrum flip to generate basis function is proposed based on the sampling and estimates of electromagnetic environmental and the environmental spectrum flip is used to construct basis function's amplitude spectrum. In this way, lots of the threshold setting and decision steps are eliminated, thus greatly reducing the computational complexity in the communication system. Furthermore, compared with the traditional ‘0’ and ‘1’ hard decision method, the new method can be used to generate the basis function with more frequency components and a better correlation performance because the jammed band is not discarded completely. Simulation results show that the new method of generating basis function in power spectrum flip can reduce the computational complexity of the communication system and simultaneously improve the correlation performance of the basis function, which provides a new way of thinking for the in-depth study of TDCS.

Abstract:Aimed at the slow matching speed of SIFT feature matching method in searching the whole database of feature points for matching points, an improved matching method of searching between the layers of the pyramid is proposed for improving the speed of SIFT matching. First, according to the feature points in different layers of the pyramid, the feature points are divided into different sets. Then a layer set in the input image pyramid is chosen to search for the similar layer in the template image pyramids, and then the similarity between input image pyramid and the template pyramid is determined. Finally, the matches are found between the similar layers. The chosen layer in the input image pyramid is from the bottom of the pyramid to the top of the pyramid. By so doing, the time of searching for similar layer is shorten. Compared with the original algorithm, this algorithm has the same rotational stability. This algorithm and the original algorithm are applied to the actual image registration respectively, the results show that the matching speed is 3.2 times as fast as the original matching speed and the correct matching rate is increased by 10.3% in visual image registration. In infrared image registration the matching speed is 1.4 times as fast as the original matching speed and the correct matching rate reaches 100%.

Abstract:Pulse waveform design problems of cognitive ultra wide band (CUWB) are studied, and a method of optimized combination Morlet wavelet is proposed. On the basis of characteristic analysis in time and frequency domain of Morlet, the design steps of the method are worked out. Firstly, the value area of wavelet stretching factor is acquired by the use of dichotomy method under the action of power spectrum density (PSD) met the needs of FCC spectral mask. Then, optimized weight is searched by designing programmable logistic language so as to get combined UWB pulse with high frequency spectrum efficiency. In consideration of authorized frequency band detected by cognitive user, band-stop filter is designed for suppressing narrow band interference, thus CUWB pulse waveform is got by making UWB pulse pass the designed filter. The simulation shows that the proposed method is susceptible to realization and operation, the designed waveform has good autocorrelation character and high spectrum utilization ratio, which provides a new thought for waveform design of CUWB.

Abstract:Aimed at the problem that the navigation devices fail to access the network and the navigation devices communication format in confusion in the process of designing the intelligent navigation device remote monitoring system, a special navigation device interface system is designed to make navigation equipment able to access the internet based on the idea of networking and taking the embedded microprocessor as the master chip. Through the development of a unified navigation device output information protocol, the data format of navigation device is standardized. The experimental circuit is utilized to test the interface system, and the hardware and software flow chart are discussed in detail. Experiments show that the interface system enables the navigation devices to access network and the problems of navigation devices communication format confusing are solved.

Abstract:Aimed at studying the effect of thread pitch and clearance on self-loosening of bolted joints, this paper builds up a three dimensional FEA model of bolted joints in which thread is taken into consideration, and the simulation of self-loosening of bolted joints under transverse vibration is conducted based on the Newmark algorithm. Then the effect of thread pitch and different clearance on self-loosening of bolted joints is analyzed. The results show that the preload of bolted joints with coarse thread pitch falls faster than the preload of bolted joints with fine thread pitch, and the slippage of bolted joints with coarse pitch is acuter than the slippage of bolted joints with fine pitch, thus the self-loosening of bolted joints with fine thread pitch is more difficult to happen; and the larger clearance of bolted joints, the more rapidly the preload falls and the acuter the slippage is. The self-loosening of bolted joints with larger clearance is easier to happen.

Abstract:In this paper, a method of evaluating the metal structure safety of aging aircraft is researched. The index system of safety evaluation is built based on load factors, environment factors and material factors. Then the weights of the indexes are analyzed on rough set, and the model of safety evaluation is built. Finally, the analysis is performed by taking a certain type of aircraft for example. The result shows that the subscribed method is effective in safety evaluation for metal structure safety of the aging aircraft.