Abstract:With the development of high speed ADC and general processor with high performance, the digitalization degree of radar has reached a level much higher than before. Firstly, this paper analyzed the advantages of Digital Array Radar (DAR). Secondly, it introduced several typical DAR systems and summarized the typical architecture of DAR. Finally it introduced the development of RF direct sampling all-digital receiver, all-digital quadrature demodulation, wideband channel equalization, and the wideband signal digital beamforming technology. With the development of relevant technology, the array radar will surely develop to be digital, software defined and multifunctional.

Abstract:Reconnaissance of complex signal is an important part of the multifunctional digital array radar(MFDAR), which serves for multipurpose, including radar & communication signal reconnaissance or ESM(electronic support measurement). The real-time responsivity and flexibility are crucial for such a reconnaissance system. In this paper, we proposed a two-stage reconfigurable signal processing according to the reconnaissance characteristics of MFDAR. Then we constructed the Broadband Signal Reconnaissance Reconfigurable Computing Model(BSRRCM) based on the hybrid reconfigurable architecture to implement the processing procedures. BSRRCM describes non-identified and not unidirectional signal flow. Taking BSRRCM, we can decompose an application into a particular procedure which can be reconfigured completely and a partial reconfiguration tasks sequence, then this reconfigurable procedure and tasks sequence could be mapped on the appropriate computing platform. The BSRRCM has many merits at the same time, including flexibility, dynamic reconfigurability, multipurpose and scalability.

Abstract:Ubiquitous radar receiver generates multi-beam at the same time to monitor the area designated. It can use long-time coherent integration method to improve target detection performance. However, the crossing-beam, crossing range-cell and crossing Doppler-cell problem in long time must be solved to avoid the integration loss. A moving compensation method based on Keystone transform and Dechirping was researched in the case the crossing-beam impact can be neglected. A detecting flow for multiple targets using the Clean method was proposed. The method proposed in this paper was verified by the simulating data and the outfield experimental data processing. Results show that it can be used for target detection of ubiquitous radar.

Abstract:A joint time-space target detection and DOA estimation algorithm on ubiquitous radar is proposed. First, data received by antenna array was transformed from array space to beam space by digital beam-forming based on DFT. Then, the time domain detection was performed with the trace of covariance matrix. In the end, the direction of arrival was estimated by multistage Wiener filter. The simulation results show that the method proposed by this paper has a better performance on time domain detection and precision of DOA.

Abstract:In order to solve the problem that three-dimensional imaging result with real data of broadband mono-pulse radar cannot be displayed directly, an expressive method using visual modality in plane was studied. The visual modality in plane is the projection of target structure which was obtained by hypothetic people's eyes when they observed target according with direction of radar beam. In order to obtain the expression with visual modality in plane, firstly, the method for calculating direction of radar beam from real data was given and the necessity for obtaining the beam direction was analyzed by considering the exact estimation of target's size. Secondly, under the basis of having obtained the direction of beam, a new reference frame was formed according to the plane for projection and the method of coordinate rotation from reference frame in radar observation to new reference frame was also presented. In the end, three-dimensional imaging results of some real data for planes in civil aviation were presented with projection in reference frame in radar observation and visual modality in plane in new reference frame respectively, the comparison between two kinds of expression brings forth the value of denotation by visual modality in plane for acquisition of characteristic.

Abstract:Flexibility and simplicity are key points in designing a digital quadrature demodulator, which is an important part of wideband radar digital receiver. In this paper, we proposed a new implementation of digital quadrature demodulation based on nonuniform-sampling, which is evolved from second-order sampling and multiphase filter. The structure of nonuniform-sampling was presented, and its effectiveness was verified by simulation results. Compared with low-pass filter and multiphase filter, nonuniform-sampling obtains more optimized structure and better performance in real-time processing. This novel approach will offer potential for better resolution in designing a wideband radar digital receiver.

Abstract:An integrated recognition algorithm based on DSm theory is presented to solve target recognition problems of digital multi-purpose radar. First, various recognition results were placed in a unified frame of discernment and the classic DSm rule was applied to combine them. Then the Proportional Conflict Redistribution (PCR) rule was used to redistribute the combination results. Finally, the decision rule based on generalized basic belief assignment (GBBA) was adopted. The simulation results show that this method can avoid information loss caused by the hierarchical recognition structure, and more abundant target information is included in the fusion results.

Abstract:This paper is for the identification of the RCS sequence of the mid-course missile. On the basis of analyzing its motion and electromagnetic scattering characteristic, a new method using RCS magnitude changes with respect to the object gesture angle for inversing the mid-course object's two-dimensional length was presented. Compared with the traditional ellipse method, the new method overcomes the disadvantage of the necessity for the maximal and minimal RCS value of the object. The experiment results tested by the simulated and darkroom measurement of the representative missile object show the effectiveness of the method.

Abstract:Good anti-jamming ability is required under “Navigation Warfare”. However, radio frequency circuit is one of the key parts affecting the anti-jamming performance of GNSS receivers. According to features of the GNSS receiver on satellite, and considering both weak signal receiving and strong signal receiving, this paper analyzed the method of calculating maximum Jammer-to-Signal Ratio(JSR) J_max which the circuit can realize the gain of each circuit part, aiming at maximize JSR in the whole signal band. Further, the calculation method was simplified for a particular AGC circuit made of resistance network. Lastly, measured results were given for this kind of AGC circuit, which agrees well with the JSR target requirement 35dB. The analytical method can direct the design of not only GNSS receiver, but also various kinds of other receivers.

Abstract:Noise suppression conflicts with high accuracy in image edge detection. A multi-scale edge detection model with dominating opponent inhibition was proposed from physiological point of view. The presented model made extension of dominating opponent inhibition mechanism to processing at multiple scales. Image noise can be adaptively suppressed by dominating inhibition from the opponent path of lateral geniculate nucleus. Sharp edges were obtained through the non-linear combination of simple cell subfields. Finally multi-scale processing results were combined to obtain boundary contour. Theoretical analysis and experimental results indicate that the proposed model performs well in noise suppression and accurate edge detection through the combination of dominating opponent inhibition and multi-scale processing. Meanwhile, it is biologically plausible, simple and efficient.

Abstract:Streaming media accounts for the majority of Internet traffic. P2P is an important method for streaming media distribution on the Internet. This paper proposes an innovative implementation method of P2P Tracker named eTracker. Peer lists are reserved in the numerous distributed eTrackers which locate in the edge network. Our design not only eliminates performance bottleneck of traditional centralized Tracker, but also optimizes peer selection in P2P system through the recognition of local peers.

Abstract:After presenting the experimental and theoretical researches on whipcrack phenomenon, the current study gives a particular description of Krehl's experimental results, the whip models based on conservation of energy and based on conservation of momentum, and the current researches on this unique phenomenon. Finally, the characteristics of whipcrack were acquired, and the comparison between the whipcrack and other large flexible structures ‘swing phenomena such as the huge parachutes’ whip or the “probe-drogue” in-flight refueling system's whip showed that there was much comparability, so the study of the whipcrack phenomenon will help researchers obtain a better understanding of these phenomena.

Abstract:With the development and application of micro-satellites, proximity inspection of spacecraft has become a new area of space mission. It plays an important role in Space Situational Awareness and on-orbit servicing, ensuring broad application prospects. The current study developed a new method of guidance for proximity scanning inspection of non-cooperative space targets based on the modified artificial potential field method. First, the attractive potential function and repulsion potential function were formulated. The former, parallel to the surface of the target, guides the inspector from the initial position to the goal position. The latter, perpendicular to the surface of the target, is used to deal with the constraint conditions like image resolution, minimum angle of observation and collision avoidance constraint etc. Simulation results demonstrate that the inspector can follow the surface of the target well and conduct a coherent and stable scanning inspection. Furthermore, it requires less computational effort and is easier to realize on the inspector.

Abstract:Low-diffusion-flux-splitting scheme(LDFSS) was combined with weighted essentially non-oscillatory scheme(WENO) to form a hybrid scheme. WENO was used to the reconstruction of physical variables and LDFSS to the splitting of the flux. Riemann problems and inviscid hypersonic blunt body flow were calculated with the hybrid scheme. Also a supersonic turbulent plate boundary-layer was calculated by using hybrid LES/RANS simulation. The results showed that, compared with WENO schemes based on Lax-Fridrichs, the splitting scheme has better resolution on shock and contact discontinuity and better positivity property of scalars and robustness. In the hybrid simulation, the scheme exhibits better prediction of the fluctuating characteristics of the turbulent flow field and statistics of turbulent fluctuating velocities in the hybrid simulation.

Abstract:X-Ray pulsars/SINS integrated navigation is one of the effective means to extend the application scope of pulsars navigation, and it is also a feasible project of the application of pulsars navigation in the future. When the clock error drifts with time, the Pulsars/SINS Integrated Navigation will be affected. In this paper, the clock error is extended as the state variable, thus a new clock error control algorithm of X-Ray pulsars/SINS integrated navigation is proposed. Results show that the new algorithm can well control the clock error and guarantee the navigation precision of pulsars/SINS integrated navigation, so the new algorithm is referable to the application of navigation based on X-Ray pulsars.

Abstract:Taking Walker constellation as object, the problem of single spacecraft rendezvous with multiple constellation satellites without orbit maneuver was investigated. According to the phase homogeneous character of Walker constellation, the sufficient condition that a spacecraft rendezvous with multiple Walker constellation satellites without orbital maneuver was obtained, followed by the investigation of the problems with rendezvous number and combination of constellation satellites. Furthermore, the orbital design method that can compute spacecraft orbit analytically was presented, and the characteristic of rendezvous orbit was analyzed as well. Finally, the possibility of spacecraft rendezvous with more than three constellation satellites was discussed. The theoretical proof is provided for single spacecraft rendezvous with multiple constellation satellites without orbital maneuver by research findings.

Abstract:Considering the landing field's elastic-plastic characteristic, a model which took the capsule's vertical landing as an elastic-plastic contact problem was established. The numerical simulation indicated that the soil's bearing capability played an important role during the capsule's landing, with the same Young's modulus and Poisson's ratio: when the soil's bearing capability increases, the capsule gets bigger acceleration, less energy loss and higher bounce.

Abstract:Developing status of combustion driving high power continuous wave Deuterium Fluoride(DF) chemical laser has been briefly presented. Structure parameters of HYLTE (Hypersonic, Low Temperature) nozzle and TRIP nozzle have been comparatively analyzed. Performance difference between the two kinds of nozzles has been summarized. Based on some correlational reported test data, output transverse modes of confocal unstable resonator corresponding to typical gain coefficient distribution along the flow field have been simulated by using numerical method. Considering technical maturity and reliability, we conclude that employing HYLTE nozzle is more appropriate than TRIP nozzle in research and development of high power DF laser concerning the two hard problems: uniformity of beam spot and load of mirrors.

Abstract:The orthotropic material has been widely applied in large solid motors. In order to reduce the Von Mises strain, and greatly improve the structural integrity of solid motors, the star grain is taken as an example. The orthotropic material parameters sensitivity analysis of elastic modulus and Poisson's ratio of propellant and insulation blanket are studied. The orthotropic material parameters sensitivity coefficients of solid motor grain are obtained. The methods and conclusions are helpful for the designers, manufacturers of solid motors.

Abstract:Mesh reconstruction is the key to the numerical simulation in CFD with large scale moving boundary which contains fast and stable mesh generation arithmetic. Firstly, this framework established efficient initial triangulation arithmetic based on directional edge theory which is fit for arbitrary polygon. Then it proved the arithmetic of longest edge division matches the divergence at some time and closes down the divergence with Delaunay edge swapping. Finally, the paper optimizes mesh with vertex spring model. The results indicate the way established in this study is efficient and stable.

Abstract:The bionic underwater thruster imitating fish's undulating motion can adapt its kinematic parameters to the changing of the flux and valve signal within its hydraulic system, so that it can generate a bionic motion smoothly, fluently and continually. In the paper, flux equations of the rotatable direction valve was built, as well as the dynamic model of the valve-controlled hydraulic swaying cylinder, with which the transmission function and Bode chart were produced. Some analysis were carried out on the valve-controlled hydraulic swaying cylinder, such as the stability, the dynamic rigidity of its position, and the dynamic response velocity. The results show that the valve-controlled hydraulic swaying cylinder is a stable system, and the response speed can be optimized by adjusting its structure parameters. However, its position rigidity can be affected by the frequency of disturbing load.

Abstract:In order to obtain valid and comparable data from ALT for rolling element bearings, almost all problems which may appear in the process of ALT for rolling element bearings were investigated comprehensively. Then an orbicular method of ALT for rolling element bearing was proposed based on the existent standardizations of ALT for rolling element bearings and experience accumulated in the process of actual design and implementation. The method has complemented such omissions as pro-experiment checking, uniformity verification and signal processing which the existent standardizations and traditional life test schemes have not considered, and then formed an integral solving scheme of ALT for rolling element bearings. This scheme can be used as a guide for the design and application of ALT for rolling element bearings.

Abstract:Feature extraction and evaluation is the basis of detection and prognosis. Aiming at tooth breakage in 2K-H planetary gear sets, damage model of planetary gear sets was developed. After the analysis of simulation signals, features based on sidebands around dominant frequency, wavelet transform and EMD were presented and valuated with two samples consistency check. Then the features extracted in the above were verified by simulation signal and test data. Validation results show that the features are promising and the feature based on sideband around dominant frequency is the best one to detect damage for 2K-H planetary gear sets.

Abstract:A novel numeric method for the planar space manipulators joint trajectory optimization problem was proposed based on the wavelet collocation. Based on the interval spline wavelet according with its derivation algorithms, the approach expanded the state and control variables via cubic spline wavelet decomposition, and then the trajectory optimization problem was translated to nonlinear programming problem with wavelet coefficient being parameters. The wavelet advantageous properties of compact representation could inherently make it efficiently and accurately capture the discontinuities. The novel approach was demonstrated by a typical space manipulators joint trajectory optimization problem, and the optimal results show that out approach is efficient and accurate.

Abstract:The use of damping system can significantly reduce the shock and vibration experienced by inertial measurement unit (IMU), and improve the measurement accuracy and the final navigation result. Firstly, modal analysis of IMU damping system was studied using finite element software Patran/Marc and the damping system main modal frequencies and shapes were obtained. Secondly, the influence on the modal analysis imposed by three key factors, such as temperature, axes-compression and radial-compression of damping rubber module, were analyzed with the simulation method. Then an optimized design of an IMU damping system was presented. The results show that the parameters in the damping system can be adjusted by changing the structure parameters, and the application demand of dither laser gyro INS are satisfied.

Abstract:With a deep analysis of the signal characteristics of CDMA receiver on unideal power control instance, the current research deduced the receiving signal model of multi-cell. Furthermore, the research presented the asynchronous multi-user detection method based on FastICA, which is naturally near-far and multiple-access interference resistant. The simulation results show that: this method has less iterative time, small computational complexity and good performance of multi-user detection, which can enhance the capability of multi-user receiver and is very suitable for asynchronous multi-user detection on unideal power control.

Abstract:The credibility is the lifeline for warfare simulation. To execute verification, validation and accreditation (VV&A) is an important approach to insure the credibility of warfare simulation system all the life circle. A proper method is the precondition for credibility evaluation. On the basis of analysis and comparison with existing evaluation methods, the subject integrated judgment method was put forward, aiming at the characteristics of giving prominence to the function of subject matter expert (SME) in the credibility evaluation for warfare simulation. Furthermore, a method of quantitative weights calculating based on SME was designed as the focal part of the research. These methods were applied in credibility evaluation of the warfare simulation system. The practice shows that the research is highly effective for complex system simulation, such as warfare simulation system.

Abstract:To solve the problem of fault-tolerant control for saturating system, a design method was presented to estimate the attraction domain of the saturating system with constraints of D-stability. Based on the volume of the invariant set and the reference set, two sufficient conditions were given to optimize the fault-tolerant invariant set. To solve the BMI resulting from the optimization problems, an algorithm was provided by constructing proper objective functions which incorporate the LMI, and turning the BMI to the nonlinear programming problems. The simulation results verified the effectiveness of the proposed approach.

Abstract:Aimed at trajectory tracking of robot manipulators without velocity information, the current study proposed an output feedback PD control without measuring joint velocities dispense with model. The developed controller and observer were based on a Fuzzy-Basis-Function-Network, which were employed to approximate nonlinear functions in the dynamics of controller and estimate velocity of joints. All parameters of the fuzz-basis-functions and weights could be tuned online by commix arithmetic, and no offline learning phase was needed. The observer and controller require no model knowledge of robot manipulators, including inertia matrix. This control scheme is easy to be used in project by introducing PD controller. According to the standard Lyapunov theorem extension, all signals in the closed-loop are uniformly ultimately bounded(UUB). The simulation of two-link robot manipulators results show that the presented method is effective.

Abstract:Geomagnetism aided inertial navigation system for unmanned aerial vehicles was studied. An analysis was presented for the whole magnetic matching process. “One-dimension matching” concept was first used and analyzed in view of its feature space, similarity metric, search space and search strategy, upon which a framework for matching methods study was built. Through simplification of inertial computational process, one-dimension magnetic matching can be considered as an affine transformation problem with compensation. A contour constraint based iterative coarse fine two-stage matching method was proposed to get the best transformation parameters, in which global search ability and localization precision were both considered. Simulation and real experiment results show the improvements in matching precision, speed and adaptability.