Abstract:Usually the maintenance is characterized by maintenance personnel to repair easily or not when the aircraft have some failures during the normal service period. But, it’s hardly for aircraft to avoid the accidental and unexpected damage in the service, such as accident damage, battle damage etc. And then the recoverability is used to represent easy to repair, uneasy to repair, and recoverable when the aircraft are subject to some accidental and unexpected damage. On the basis of concepts and qualitative requirements of aircraft recoverability, this paper proposes parameters MTTRC(Mean Time to Recovery), MRCC（Mean Recovery Cost）and MWTTRC（Mean Work Time to Recovery）to characterize aircraft recoverability. Then, the significance of aircraft recoverability is discussed as well as the concept, measurement and control of aircraft operational integrity. Furthermore, the normal assessment and design methods of aircraft recoverability are put forward. Finally, a brief example of recoverability design for a monolithic backswept wing structure constructed by ribs, stringers and skins. The concept, the measurement and the design of recoverability are suitable for other equipment and devices.

Abstract:Aimed at the practical problem that the accuracy of air airborne single station passive location is limited by the error of parameter measurement, this paper presents a grid search passive location method to improve the error of phase difference. Firstly, the phase difference information is filtered out by LMS adaptive filtering, and then the positioning equation is established by using the observed phase difference according to the positioning model. Finally, the location of the radiation source target is solved by the grid search method. The target of radiation source can be located at by the method accurately under the condition of large phase difference measurement error. The simulation results show that the phase difference error filtered can be reduced to less than 0.14rad,and the positioning result is better than that of reference［17］. The positioning error is shown that within 10 degrees at the phase error, increasing the mesh resolution and extending the observation time can improve the positioning accuracy, and can verify further the necessity to obtain the accuracy, and to obtain the accurate phase difference information simultaneously.

Abstract:A nearly optimal time guidance algorithm is proposed for UAV intensive formation crossing and contesting the doorframe. Firstly, the crossing and contesting problem is described. Secondly, the guidance algorithm for single UAV crossing the doorframe is studied based on the mathematic model, which is characterized by the ability to guide the UAV onto the target point in the desired time. Finally, a crossing guidance algorithm based on flying time control and missdistance control is proposed for the crossing and contesting problem of the UAV intensive formation. The simulation results show that the proposed algorithm makes the UAV formation complete successfully the tasks, such as the cross and contest, the minimum missdistance, and the guidance time errors in the desired time, and affords the UAV formation obstacle avoidance control and collision avoidance control useful technologies.

Abstract:In order to meet the task requirements of coverage detection of interest areas in the battlefield environment, this paper proposes a multiUAV cooperative detection task allocation strategy based on regional coverage. Firstly, the target track point of the UAV in the region of interest is determined by the minimum circle coverage method. Secondly, the multiUAV collaborative task planning is carried out, and a time allocation model is further established based on the target allocation model, and then the improved gray wolf algorithm is used to solve the task assignment model, and finally the resource optimization allocation decision scheme is obtained. The simulation results show that the proposed algorithm is good at convergence speed compared with other algorithms, and is advantageous to the solution of optimal allocation of regional coverage detection resources.

Abstract:The transmitted signal of a distributed networked system needs to meet the requirements of strong diversity characteristics. The diversity characteristics between ZC sequences of the same length and different root values are determined by the root value itself and its root value difference. In this paper, the diversity characteristics of ZCOFDM signals are studied by the isomorphism between the ZC sequence and the sampling sequence of ZCOFDM signals. Combining the diversity characteristics of ZCOFDM signals and the characteristics of distributed networked systems, an optimal effective sampling length calculation algorithm is proposed. The algorithm is used to solve how the effective sampling length of the transmitted signal is determined so that the diversity characteristics of them can reach the strongest when the number of distributed network systems is limited as well as the bandwidth and time width of the transmitted signal. Combined with the time width, bandwidth range and optimal effective sampling length calculation algorithm of conventional detection signals, the parameters of the waveform are designed, and the signal processing effect of the distributed network system is simulated. The simulation results show that the ZCOFDM signals with different root values are characterized by enabling the distributed networked system to effectively separate the echo signals of the signals transmitted by each transmitting station during the echo receiving process.

Abstract:In order to further improve the DOA estimation accuracy of coherent signals, a modified algorithm based on main feature vectors is proposed. First, the main eigenvectors corresponding to the signal subspace are selected, and the inverse conjugate transformation is performed to obtain the augmented main feature eigenvectors. Then, the linear prediction equation is constructed, and the weighted least squares method is used to solve the polynomial coefficients in the prediction equation. Finally, the DOA of the signals is obtained by finding the root of the polynomial. The modified algorithm overcomes the weakness of PUMA algorithm under conditions of the deteriorated severely performance and the completely cohered signals, and is good in performance. It’s no matter whether the signals are completely coherent or partially coherent. The maximum number of the resolvable signals are improved. The high precision can be obtained when the signaltonoise ratio is low and the number of snapshots is small. Compared with the PUMA algorithm, when the signal is partially coherent, the root mean square error of the proposed algorithm is reduced by about 0.2°; When the signal is completely coherent, the root mean square error is reduced by about 0.8°.The performance of the algorithm is verified by comparison with various decoherence algorithms.

Abstract:

Abstract:Target RCS fitting extrapolation is one of the effective means to save storage space of target RCS database. In this paper, based on the target echo data obtained by FEKO and the classical spectral estimation algorithm, a frequency full angle extrapolation of RCS of a typical missile warhead target is performed. First, based on the simulation data of 1~2 GHz, the parameters of the GTD (geometric theory of diffraction) scattering center model is extracted. Secondly, the RCS of the warhead target at 3 GHz and 4 GHz is extrapolated by using the proposed method. Finally, the extrapolated data are compared with the data obtained by FEKO, and the accuracy and the reliability of the extrapolation method proposed are verified. The simulation results show that the extrapolation results and the simulation results of FEKO are a highly similarity on the overall trend and at the strong scattering points, which can also be used to effectively describe the scattering characteristics of radar targets. The proposed method provides a theoretical support for RCS frequency full angle extrapolation and has a wide application in military.

Abstract:In view of the complexity of node selection and migration at platform dynamic defense, a single stage static game strategy is designed based on the system prior information. Through analyzing from the principle of dynamic platform defense, a single stage static game model is constructed by combining the needs of the defense under conditions of game relationship between the two parties and complete information condition, and a process of the key parameters of the attack and defense utility and the complete information game is proposed. The demo and the simulation results show that after 1000 times of attack-defense game experiments, the actual revenue of the defense is , and the actual revenue of the attacker is , showing that the proposed strategy can effectively intercept cyber attacks, and the expected revenue of the defense is , the deviation between the actual revenue and the expected revenue is about 1.8%. The revenue of the new strategy is much higher than that of the undifferentiated migration strategy. The single-stage static game strategy based on the system prior information can solve the problems of high cost, unbalanced defense budget and effective node migration in the traditional platform dynamic defense.

Abstract:Aimed at the problem that the traditional characteristic parameters have difficulty in characterizing the specific characteristics of complex system radar signals, a specific emitter identification algorithm based on deep belief network feature extraction is proposed on account of the deep feature extracting and highdimensional data processing ability of deep belief network. Firstly, a DBN model based on multilayer restricted Boltzmann machine is established. Then, unsupervised extraction of pulse envelope frontier is realized via deep belief network. After that, the model parameters are finetuned with label data in a supervised way to complete the training. Finally, the pulse envelope frontier features of the unknown source signals are input to realize the radar specific emitter identification. Compared with the traditional algorithm, the novel algorithm can adaptively extract from deep pulse features, and can also reduce the process of feature extraction to the dependence on human experiences. The experimental results show that the proposed algorithm provides satisfactory performance of pulse envelope feature extraction and higher recognition accuracy. The validity and application value of the algorithm are verified.

Abstract:Aimed at the problem that the clutter suppression performance of multipleinput multipleoutput radar spacetime adaptive processing technology is greatly degraded when the training samples are in jam, a jamming detection method is proposed. This method firstly uses the regularized FOCUSS algorithm to estimate the spacetime power spectrum of each atom. Next, the spectrum threshold is set to pick up atoms with large values. Then, the scanning band is determined to scan the spacetime twodimensional plane. Finally, according to the ratio of the maximum number of atoms entering the scanning band to the total number of atoms, a determination can be made whether there is jamming in the training sample. The simulation results show that this method can effectively detect the jamming in the training samples, and the clutter suppression performance of spacetime filter can be guaranteed by using the training samples selected by this method.

Abstract:Locally repairable code (LRC) is a new family of erasure codes to reduce the repair bandwidth during recovering the lost data in distributed storage systems. Dependent on the characters of different distance and the parity check matrices of binary optimal codes, a method is presented to construct evendistance LRCs from odddistance LRCs, and some new LRCs with good properties are obtained by puncturing strategy. By using these two methods, four classes of LRCs (length n≤24, dimension k≥8 and distance 6≤d≤8)attained to the C-M bound are constructed. There is much in these methods of constructing LRCs that optimal LRCs with higher distance over binary field and general fields can be made use of.