Abstract:In this paper, taking the large aspect ratio wing as a research object, and combined with the geometric nonlinear structure finite element modeling method and the nonlinear aerodynamic calculation technology, a interpolation method is proposed to solve the geometically nonlinear aeroelastic problem. Taking a scaled model of solar UAV wing as an example, the calculation and analysis and experimental research are carried out. The resuts show that the nonlinear flutter solution obtained by the method in this paper is basically the same as that obtained by the conventional method. By so doing, not only the calculation efficiency is doubled, but also the serious calculation deviation may be avoided in the conventional method, which may result from the unreasonable setting of the calculation working condition.

Abstract:Flight data is a typical time series whose random noise and complex deformation cause the difficulty of sub-sequence similarity query. For this reason, a similarity query method for flight data time series sub-sequences based on pathologic matching of DTW is proposed. Firstly, boundary curves are built up and down by using query sequence sample sets. Simultaneously, lower bounding distance is proposed with a proof correctness to build lower bounding algorithm for filtrating subsequences to increase efficiency. Then, the invalid subsequence field is recognized and deleted for determining the valid subsequence field of matching by pathologic matching of DTW. The results show that the proposed method can accurately find similarity sub-sequences，and the start stop time deviation can be controlled in less than 3 seconds, meeting the actual needs of aircraft flight action query.

Abstract:Aimed at the problems that the fitting method is limited by the system model and the model order in establishing a small deviation state variable model of aircraft engine, a method based on multiple-improved-chaotic fruit fly optimization algorithm (MICFOA) is proposed. Firstly, the method is divided into two sub-processes: first thing is to optimize the system matrix, input matrix, and to find the optimal results, and then is to optimize the output matrix and the transfer matrix. Simultaneously, work is done according to the principle that the SVM's dynamic response is consistent with the nonlinear model's, fitness functions are constructed that are unaffected by the variable value domain. Secondly, synergisitic sub-population strategy and chaos mapping strategy are introduced into FOA to improve the diversity of fruit fly populations by using the adaptive adjustment strategy introduced to balance the relationship between global search and local search to avoid premature convergence. Finally this method is used to establish a turbo-shaft engine's SVM, and to design LQ/H∞ disturbance-rejection controller. The simulation results show that MICFOA can improve the accuracy of 5-10 orders of magnitude compared with FOA, the SVM has good dynamic and static performance, and the newly built model is consistent with the nonlinear model.

Abstract:In the process of the rocket silo launching, the rock particles on launching site move toward the silo and may impact the rocket having out just in time under the action of high-speed airflow. In order to predict the damage of rocket skin, the model of vertically impact of rock particle on a thin plate is established by LS-DYNA, and the dynamic response of the skin is analyzed. The effects of stringer structures and rock particle velocity, volume and shape on the deformation of the skin are discussed. The results show that under the impact of rock particle, the elastic deformation of the rocket skin mainly occurs and the plastic deformation occurs in local areas，and the depth of the permanent depression is from 1 mm to 5 mm. The deformation displacement of the rocket skin is approximately proportional to the impact velocity and volume of the rock particle, and the damage caused by the cuboid rock particle is less than that of the sphere particle. The stringer structures can improve the impact resistance of the skin in a certain extent.

Abstract:What is the most important is to separate the scatterers and keep their own phases simultaneously in the research of three-dimensional (3D) interferometric imaging for space micro motion target, however, when the pulse repetition frequency (PRF) does not satisfy the needs of the Nyquist Sampling Theorem, the image processing based method can't effectively separate the scatterers. Therefore, a 3D interferometric imaging method based on sparse dictionary decomposition is proposed. The method can be used to separate each of the scatterers from echo data directly. First of all, according to the characteristics of target echo signal, an over-complete sparse dictionary is constructed, and then the echo is decomposed by using sparse decomposition algorithm to get the sub-echoes of each scatterer. Secondly, by means of time-frequency analysis and its performance of phase preservation, the micro motion curves of each scatterer are obtained, and the interferometric phase differences in the time-frequency plane are extracted. Finally, according to the relationship between interference phase differences and coordinates, the 3D imaging of space spinning target is constructed. The simulation results show that when PRF is greater than 0.25 times of Nyquist frequency, the proposed method can effectively achieve the 3D imaging of space spinning target.

Abstract:Aimed at the problems that the degree of freedom in the current nested MIMO array (Multiple-Input Multiple-Input Multiple Output Multiple Array) is limited, an optimized nested array is proposed, i.e. to optimize the nested MIMO array design. This method not only retains the original advantage of nested MIMO array design-closed expression with array element position and degree of freedom, but also greatly improves the array aperture and degree of freedom (DOF). Firstly, the optimized nested array is used as the transmitting and receiving arrays, and then the difference between the MIMO arrays is processed to obtain the difference array of array elements. By properly designing the array spacing of the transmitting and receiving arrays, a non-porous difference matrix can be obtained. When the total number of array elements is given, by analyzing the characteristics of the array structure, the best array element number of the transmitting and receiving arrays can be obtained. The simulation experiments show that compared with the nested MIMO array design, the proposed method can effectively expand the array aperture, increase the degree of freedom, and increase the DOA estimation accuracy of the MIMO radar under condition of non increasing the number of actual array elements.

Abstract:In order to reduce the wave path difference, a Cross-eye jamming structure is proposed based on forwarding path optimization. An interference signal propagation path model is established by analyzing Cross-eye signal propagation path. Under condition of radar arrival direction deviating the perpendicular bisector of Cross-eye jamming antenna, through changing the location of double loops crossing receiving antenna and transmitting antenna, the phase changes caused by wave path-difference when interference distance is far away could be reduced and Cross-eye interference effect could be improved. The following conclusions are demonstrated by the simulation results: the farther the distance between Cross-eye jamming structure and radar is, the smaller the wave path difference is; the bigger the angle of radar incoming wave direction measured from the perpendicular direction of the Cross-eye jamming structure is, the smaller the wave path difference is; the wave path difference can be ignored when the Cross-eye jamming structure based on forwarding path optimization is far away from the jammed radar (r>3 km), where the phase difference satisfies the jamming requirement.

Abstract:In the presence of main-lobe interference, the main-lobe offset comes out on the adaptive pattern by eigen-projection matrix preprocessing. Aimed at the problem that the fixation of coefficient is difficult to determine in the traditional main-lobe shape-preserving method of diagonal loading technique, an improved ridge regression estimation based on HKB algorithm is proposed. The load can be determined adaptively according to the data received. The new diagonal loading coefficient is obtained by replacing the minimum variance cost function of the residual vector with the error absolute value function when performing the ridge regression estimation. At the same time, the improvement of the proposed method for the adaptive antiinterference total effect pattern is studied. For the obvious deterioration of the sidelobe performance, the improvement of the total effect pattern is studied in combination with the proposed method. The simulation results demonstrate that the proposed method is correct and effective, and not only can effectively solve the mainlobe offset problem of the pre-processed pattern, but also improve the side-lobe performance of the total effect pattern.

Abstract:A phase shifter is a kind of functional device used to regulate the phase of guiding wave output signal, and is widely used in beam formation network, phase modulator, phased array antenna and other electronic, radar and communication systems, and has the most direct impact on the performance of related systems. Therefore, it is very important to design a practical microwave phase shifter with high performance, stability, miniaturization and low cost to meet the future development needs. In order to solve the bottleneck of current technology development and realize relevant technical innovation, it is necessary to comprehensively analyze the technical overview, advantages and disadvantages and development status of various phase shifters, accurately sort out the future development trend of phase shifters, and better integrate the latest academic research progress in related fields into the design of phase shifters. Based on the goal mentioned above, the development of phase shifter, the ferrite phase shifter, PIN diode phase shifter, MEMS phase shifter, ferroelectric phase shift principle and performance index of the phase shifter are analyzed separately in systematic summary based on BST ferroelectric material phase shifter microwave circuit design, and combined with the related technical trend, some prospects for the development of BST ferroelectric phase shifter are made to a certain extent.

Abstract:Although the zero crossing detection algorithm is being applied widely in frequency estimation of a single sinusoid for its low computation and for the convenience of realization，the zero crossing method is easily effected by the stochastic noise in the frequency estimation performance. In order to solve this problem, a new method is presented based on moving window data and zero crossing detection. Firstly, the multi-groups moving window data are obtained from the observation data; Secondly, the pre-estimated frequency values are obtained by using the zero crossing detection algorithm in multi-groups moving window data; Then, the outliers of frequency values are removed by threshold processing. Finally, the average value is confirmed as an estimated result. A series of frequency estimation factors are discussed in detail, such as data length, slipping times, adjoining sliding point number and sampling frequency. The result shows that the proposed method can improve the performance of frequency estimation. And the new method is feasible.

Abstract:A parameter estimation algorithm based on data assistance is proposed to estimate the parameter estimation problem of single channel cofrequency mixed signal with fixed frame length and frame synchronization sequence in noncooperative satellite communication. First, the algorithm estimates the frame length and the beginning position of the frame head and extracts the frame synchronization data to construct the auxiliary function. After correlating with mixed signals, the interference term is removed, and the precise estimation of frequency offset is obtained by peak search. The auxiliary function is used to simplify the mixed signal, and then the initial information of the signal is extracted based on the maximum likelihood estimation theory. Finally, the estimation of the signal frequency offset and the initial phase of the signal is realized. Based on algorithm research, the modified Cramer-Rao bound for parameter estimation of single-channel cofrequency mixed signals is derived, which provides a theoretical basis for the performance analysis of the algorithm. The simulation results show that when the frame synchronization signal reaches a certain number, the variance of frequency offset is 10-7, and the initial phase variance is 10-3.The performance of the algorithm is close to the MCRB theory.

Abstract:In consideration of the problem in applying Kalman filter when time varying noise covariance matric of measurement and process are neither known, a new adaptive filter was purposed by Variational Bayesian(VB) approach. This filter overcame two key problems as following: first, relative transfer probability was proposed as realizing to promote the performances of steady state precision and dynamic respond simultaneously, by designing the heuristic adaptive window for noise estimation, according to the conjugate posterior distribution of measurement and process noise; second, the serious offset of the estimation value of noise covariance matric under single time scale was notable reduced by designing the approach which estimated the covariance matric under double time scales. The simulations proved that this method could track the noise statistics feature quickly without losing estimation precision.

Abstract:In order to judge the state of secondorder chaos system more accurately and efficiently, in this paper, starting from the characteristic of Duffing oscillator and using the intensity of Poincare section points as the criterion of chaotic state, a quantitative description has been developed to distinct the state of chaotic by constructing a function. The method is mainly according to different periodic characteristic of second-order chaotic system showing in specific conditions. To obtain the Poincare section points, the system output is sampled as a constant period, which is all just the same to the period of the driving force. Based on the calculation to the deviation's mean square value of a fixed number of adjacent sampling points, this method indicates concentrate degree of the sampling points' distribution quantificationally. Then through the further experiment, an appropriate threshold can be determined and the chaotic state can be judged. The method directly uses the basic characteristics of chaos as the criterion to realize the chaotic state judgment from the system Poincare section's point, greatly reducing the computation complexity, weakening the effect of the machine error when computer numerically is calculating and the detection accuracy is increasing. The result shows that the sampling time is shortened, thus shortening the time of decision and improving the efficiency of decision. Through conducting an experiment by using the Duffing oscillator driven by Second order periodic force as an example, an anticipative conclusion is reached to prove the feasibility of the theory. By reproducing the experiments of former theory, and compared this theory to the former, this theory has higher accuracy and efficiency.

Abstract:Aimed at the problems that in distributed state estimation systems, the fusion methods are often employed to systematically combine multiple estimates of the state into a single, more accurate estimate, and if the correlation structure is unknown, conservative strategies are typically pursued with less accurate, an inverse covariance intersection fusion robust steady-state Kalman filter is proposed to gain more accurate estimate. As a major advantage of the novel approach, the fusion results prove to be more accurate than those provided by the well-known covariance intersection method. The geometric interpretation of the accuracy relations is given based on the covariance ellipses. A Monte-Carlo simulation example for a two-sensor system shows that its actual accuracy is close to that of the optimal Kalman fuser with known cross-covariance.

Abstract:Firstly, this paper proposes a novel protocol based on distributed PID control law and introduces a descriptor method to transform the differential equations of the closed systems into a descriptor model, transforming the consensus problem into an asymptotic stability problem. And then a Lyapunov-Krasovskii functional is constructed and the parameters of the consensus protocol are given based on the linear matrix inequality(LMI). The simulations show that if the topology contains a globally reachable node, through selecting appropriate PID parameters, the MAS can achieve consensus, and the uncertain parameters will cause bad effect to the trajectories of the systems. Compared with the PD-Control-Based consensus protocol, the proposed protocol makes the swarm systems converge faster, and the robustness stronger.

Abstract:On the basis of thoroughly analyzing the microwave curing process of glass fiber epoxy composites, this paper combines with electromagnetic, heat transfer and cure reaction kinetics theories, to build a three-dimensional coupled model of electromagnetic field, temperature field and cure degree field, and the model includes two internal heat sources. Based on this model, the simulation of microwave curing process of glass fiber epoxy NOL ring is realized, and the simulation results are compared with the traditional thermal curing process. The comparative studies show that the microwave curing method shortens the time for the composite to reach the curing temperature , and reduces the gradient of cure degree distribution in the composite NOL ring and effectively improves the uniformity of cure compared with conventional thermal curing method. The realization of numerical simulations on microwave curing processes of epoxy composites could provide a feasible method for the study of microwave curing technique.