Abstract:To set up the accurate mathematical model of airplane synchronous generator is the key technology for AVR dynamic performance test. Dealing with the application background of AVR dynamic performance test, a novel idea of setting up the non-linear model of synchronous generator using the modularization method is proposed. A wavelet neutron network model of the impact load and impact unload characteristics of synchronous generator is set up based on WNN. The accuracy of this model is verified using the pre-distributed verification data, and the model for AVR dynamic performance test is feasible.

Abstract:The aircraft typical mission profile is chosen from its actual flight data. Through the pretreatment of flight data, rain-counting method and linear cumulative theory, effective loads are extracted and converted into standard cycles，then the profile is divided into four parts to analyze the fatigue damage. The statistical result shows that the fatigue lives of the aircraft right and left engine are submitted to Weibull distribution, but solo-engine is greatly different in fatigue damage. In typical mission section, difference in the take-off and the cruise subsection can reach to 3～4 times, and landing subsection even reach to 10 times for the engines in the same side of different aircraft, however the difference of the fatigue damages for the left-side and the right-side engines in the same aircraft is rather small. The statistical results show that engine fatigue damages are submitted to Weibull distribution. Through implementing single aero-engine life surveillance, flight training can be arranged advisably and engine service life can be prolonged effectively.

Abstract:In order to study the influence of nozzle length and divergence angle on shock wave focusing detonation ignition and thrust of the 2-stage PDE resonator, a group models with a variety of nozzle lengths and divergence angles are studied by numerical simulation. Analytical results in a run indicate that the effect of nozzle length and divergence angle on jet collision and detonation initiation is very feeble. The average pressure and impulse on unit area of resonator is enhanced and times of shock wave focusing in the nozzle is increased as the nozzle length grows, though the frequency of shock wave focusing is decreased. The axial average pressure and impulse on unit area of nozzle wall is increased as the nozzle divergence angle grows, however, the frequency of shock wave focusing is almost unchanged. In consideration of the composite action of the resonator and the nozzle, the nozzle with a divergence angle of 45°presents the best 2-stage PDE performance.

Abstract:To forecast the fault and carry out condition-based maintenance for weapon system, the prognostic method based on Genetic Neural Network (GNN) is studied. The genetic algorithm is improved by adopting real coding, adaptive crossover rate and mutation rate, also the learning algorithm of neural network's weight is ameliorated with the improved genetic algorithm, and the genetic neural network is obtained. The genetic neural network is trained by the detected data of equipments, and then is used to predict the degenerating trend of the characteristic parameters of the equipments. The predicting example shows that the use of the improved neural networks can achieve fault prediction before the time point of faults respectively, and the predicting accuracy and the predicting performance of the genetic neural networks are greatly improved compared with those of the basic neural network, which can enhance the supporting capability of the weapon equipment and realize condition-based maintenance.

Abstract:The application of PHM can greatly help improve the dependability, the efficiency of maintenance, the advance of fault diagnosis and the capacity of fault tolerance of power system of More-Electric Aircraft. Since the traditional use of PHM in power system of More-Electric Aircraft is the concentrated project, in which the power system is looked as a segment system of aircraft function management area, the equipments have no PHM and the signals of the equipments are given to the PHM of function management district, which can not fulfill the needs of complicated power system. Based on analyzing the augmented-FMEA and sorting the faults, this paper designs a focus-distributing PHM system, adopts the augmented-FMEA and the prognosticating model of the fuzzy comprehensive evaluation and finally combines the power system PHM with the aircraft PHM properly. All the tasks done in this paper are of some practical value and thinking innovation, which decide the direction for the research and development of power system PHM.

Abstract:Automatic target recognition (ATR) using Synthetic Aperture Radar (SAR) imagery is investigated in this paper. According to the imaging model of SAR image, a SAR ATR based on fusion of target contour and shadow contour is proposed. Firstly, this paper presents a SAR image segmentation method based on marker-controlled, by using which the target contour and the shadow contour of SAR image are obtained. Then, fusion recognition is performed by using these two kinds of contours. The effectiveness of the proposed algorithm is verified by experimental results on MSTAR. The experiments verify that the fusion of these two kinds of contours contains not only the structural information of target but also the height information of SAR target. Compared with the feature of the target contour or the shadow contour when they are used separately，the feature of the fusion of them is more steady.

Abstract:A kind of radar echo simulator hardware architecture based on PC and FPGA is proposed, it is extensible, programmable and suitable for upgrading, and the ballistic missile echo is generated based on such simulator. This paper builds up a ballistic model and an echo signal model on ballistic missile, the model-based analysis is presented and the analyses of the echo simulator and simulation signal source's test results are done. The result shows that the simulator can precisely and effectively simulate and generate ballistic missile echo signal.

Abstract:In order to use parabolic antenna to generate scanning beams, excitations of the feeding array are adjusted. Single-feed parabolic antenna patterns are calculated using PO, and based on this, the excitation coefficients of the array are optimized by solving the least-squares problem and the antenna pattern is synthesized efficiently to control the side-lobe level and cross-polarized components, and to scan the beam direction. Numerical simulation results are given to verify the feasibility of this method.

Abstract:Considering that the existing methods of evaluation of air attack threat against target is not fully ideal, a new method of evaluation of air attack threat against target based on interval numbers TOPSIS is proposed. A criterion system of evaluating air attack threat against target is founded and a standardization approach to the index value of evaluating the threat against target in the form of interval numbers is presented. The calculation steps for solving the index weight is given based on the optimization idea and using the concept of deviation degree and ideal value when the index value is an interval number and the index weight is unknown, which conquers the subjectivity of the former methods. Then the mathematical model for evaluating the threat against target by interval numbers TOPSIS is established. Finally, a numerical example of evaluating the air attack threat against target is given to show the rationality and effectiveness of the method.

Abstract:The ghost problem exists in multi-DF station multi-target passive cross-location under complicated environment. The number of ghost is increased rapidly and the correct association is more difficult along with the increasing DF station and target. Aimed at this problem, two algorithms of eliminating ghost based on redundant information are presented. By associating data with azimuth angle or TDOA redundant information selectively, high computation burden can be avoided effectively when associating directly with azimuth angle data of all DF stations, based on ensuring certain association probability. Computer simulations show that these two algorithms are effective. Because of using additional TDOA redundant information, the correct association probability of eliminating ghost algorithm based on TDOA redundant information is higher than that of eliminating ghost algorithm based on azimuth angle redundant information when the TDOA error is lower than 0.5ms.The eliminating ghost algorithm based on TDOA redundant information is more adapted to the occasion with high TDOA precision、low space between targets, and big DF error.

Abstract:The estimation of flight state for guided projectiles is one of the most critical techniques in obtaining precise trajectory parameters. When Kalman filtering is used, the system model deviation may cause reduction of the filtering accuracy significantly. In this paper the foregoing problem is investigated by taking a type of fin-stabilized projectiles with low spin speed as object. An Extended Point-Mass Model (EPMM) is proposed. Based on the EPMM and radar detecting system, the state equation and measurement equation are established respectively. The effect of model deviation on the filtering performance is analyzed via numerical simulation, thus a new scheme of estimation of flight state is proposed based on the process noise control. The results indicate that the negative influence is overcome effectively by adopting this scheme. The estimation error of lateral range for projectiles can be reduced more than 50% at least and the increase of computation burden is fairly small. Some results concluded are useful for further research.

Abstract:A new Ad hoc routing algorithm combining the dynamic source routing (DSR) protocol with the position prediction-based clustering algorithm is presented in this paper. In the algorithm the prediction-based algorithm is used to detach the different clusters, and to pass a reasonable position judgment based on actual needs and implement environmental, the same treatment is done aimed at the dynamically wireless network environment, by the way, the members in clusters do not need the routing function. Location information acquirement in this algorithm is from GPS or self-localization algorithm, the cluster heads run DSR protocol serves as a router, which makes the communications of different cluster members depend on the head of various clusters, thus greatly reducing the redundancy of the routing information. The simulation results suggest that the algorithm is good in packet deliver ratio and low in average delay.

Abstract:This paper proposes a new method of spot detection and tracking for the sake of reducing the effect of atmospheric turbulence on the level of atmospheric wireless laser communication link APT subsystem and enhancing the robustness of spot detection algorithm in strong noise. In this method the sequence information distributions are adopted as the detection and tracking characteristic parameters to fit the circle centre and estimate the spot energy centre according to the fitting equation, i.e. to make the MSE minimum by following the principles of the least squares. The use of this method can play a strong role in compensating the obstruction of atmospheric turbulence and background to effectively restrain the detection error in a small range, and has a strong aim at the strong turbulence environment, which provides an effective solution to the atmospheric turbulence for the level of wireless laser communication link. In this method the equalization time-domain means with robustness is used to avoid the difficult problem of over-strong noise led into by the turbulence. This paper performs an analysis of the advantages and disadvantages of this method from the perspective of engineering and at the same time makes a prospect for the bottlenecks.

Abstract:BPSK-PM is a modulation mechanism in which BPSK is used as its sub-carrier modulation mode and PM as its main-carrier modulation mode. This mechanism makes the spectrum of the modulated telemetry signal separate from that of carrier signal, while the residual carrier can be applied in A/V measuring and tracking. This paper firstly introduces the BPSK-PM modulation mechanism and analyzes the spectrum characteristics of its modulation signal, and then proposes a mid-frequency digital reception and carrier acquisition scheme according to the specific application. The carrier acquisition scheme is divided into a frequency searching part based on FFT and a frequency tracking part based on digital frequency-lock loop technology, which are analyzed in details. Finally, this paper shows a practical application of the carrier acquisition scheme, and the effectiveness of the scheme has been preliminarily verified in the Martian deep-space exploration of China.

Abstract:Identity-based multi-recipient signcryption (IDMRSC) is an extension of identity-based signcryttion. At first, a new IDMRSC algorithm is proposed based on bilinear pairings and its security and efficiency are analyzed. The result shows that the algorithm is provable secure in the random oracle model. Furthermore, the algorithm is significantly efficient and of low computation cost and communication overhead, and is very suitable for secure communication in Ad hoc networks. Finally, the method of using IDMRSC algorithm to deal with malicious nodes in Ad hoc networks is expounded. This IDMRSC algorithm can meet the high level secure requirement in practical application and therefore, is of a certain practical value in application.

Abstract:In traditional pulsed eddy current (PEC) nondestructive testing (NDT) technique usually a reflection-type probe is used, which consists of a pancake exciting coil for generation of incident magnetic field and a pick-up coil or a solid-state magnetic field sensor for detecting the perturbed magnetic field. However, due to the restriction of the traditional structure of PEC probes, the incident magnetic field generated by the excitation coil is much stronger than the eddy current induced magnetic field, thus reducing the detection sensitivity, and a reference signal must be subtracted from total transient response signal to get the flaw information, the process of difference may bring errors. A new PEC sensor is proposed, which, in crack defect quantification, does not need the difference processing by changing the distribution of exciting magnetic field with a rectangular exciting coil. The principle of the new sensor is analyzed first, and then, the performance of the sensor is verified by the method of combining simulation with experiment together, the agreement in experiment with theory shows that the present sensor is effective.

Abstract:Aimed at the complicated structure and remarkable rigidity of the process of flight line maintenance, a process optimization method based on modular theory is proposed. According to the theory of modular evolvement, the modular trend of flight line maintenance is demonstrated. The programming course and symbol description of modular process is educed. Process activities are identified by work break down structure. The association among maintenance activities is depicted by combining with graph structure model，and a reasonable maintenance module k-division is realized by the optimization algorithm of DSM model. The process optimization model of small outfield/big infield maintenance is educed from a quantitative view. Finally, a new method of resource optimization and flexibility improvement is established.

Abstract:On the basis of concepts of skew symmetric -cyclotomic coset and skew asymmetric coset pair, and their properties deeply studied, and methods determined, a maximal design distance of BCH codes with length contained in its Hermitian dual is studied. Thus, such an unsolved problem for maximal design distance of BCH codes with length is solved, upper bound of maximal design distance of BCH codes previously known is improved, and a new upper bound picked up is sharp. By utilizing these Hermitian dual containing non-narrow-sense BCH codes, many new quantum codes with good parameters are constructed, these new quantum codes are better than that constructed from narrow-sense BCH codes in the literature.

Abstract:The differential transform method used for solving the approximation analytic solution of the unconstrained optimal control problem is established. According to the state equation, costate equation and governing equation in the set of Hamilton regular equations, we first construct the differential transform form based on initial value or terminal station, by which the optimality condition is transformed into a corresponding algebraic equation, furthermore, the approximation analytic solution of the optimal control problem is obtained. In addition, to the nonlinear optimal control problem which is complex in structure, in particular condition, the discreteness set of algebraic equations can be constructed in light of the principle of approximation by interpolation and the differential transform method to obtain its approximation analytic solution. By using this method, the initial-boundary value problem of the differential equation and the complex system of the functional optimization problems are converted into algebraic equations which facilitate getting the solution, also are simple, feasible and easy to realize. Finally, the effectiveness of this method is verified by numerical examples.