Abstract:The parameterized analysis model for a composite material central bearing column shell satellite platform was established using FEM software, and the analysis model for central composite column shell was then simplified according to the calculated vibration modes of the satellite platform. The central shell's structural optimization was performed under several design constraints, such as strength, displacement, vibration and buckling. Some design scenarios were calculated and compared, and the work done in this paper will be of reference value for structure design related.

Abstract:Based on the finite element method, the strength and stiffness of spacesuit hatch closure under internal pressure are calculated. The optimization model of the hinges configuration is established to reduce residual internal force of the hinges. An improvement configuration of the hinges is obtained. The results demonstrate that the optimal configuration of the hinges of the irregular shaped pressure vessel can reduce the residual internal force as a result of the structural plastic deformation.

Abstract:The Hamiltonian dynamic model of distributed satellite system(DSS)relative motion under earth oblateness perturbation was introduced, and the Hamilton's equation of DSS relative motion was also obtained. Aiming at solving relative two-point boundary value problems of DSS under earth oblateness perturbation, a shooting method based on solving generating function was proposed. High precision formation adjusting problems of DSS under earth oblateness perturbation was calculated. Results demonstrate that the algorithm has high computational efficiency and can avoid the problem of dimension disaster.

Abstract:A two-stages successive genetic algorithm was used to optimize the scheduling of TT&C (Tracking Telemetry and Command) resource from space and land. Because the object was somewhat separable, the scheduled time windows were separated into two sections. After the population from first section was evolved, the gained optimized solution was combined with the second section, and then the evolution of second phase goes further. For lessening the local searching limitation, virtual time windows were set with some probability in the fitness computation process of first phase, which could retain the individuals that might be the component of overall optimization solution. Simulation demonstrates the proposed method can get good solution at the cost of less time.

Abstract:Satellite and ground station time synchronization is the key technology of navigation satellite system. Two-way time comparison method between satellite and ground station clocks can improve the accuracy of satellite and ground station time synchronization effectively. By analyzing the influence of satellite-to-ground station range variation on two-way time comparison, which is the source of hundred nanoseconds error, a method of observe data differential correction was presented. Numerical simulation performed later shows that this method can reach the level of nanosecond precision.

Abstract:A low-cost small solid launcher using both lateral jets and gird fins for its attitude control purpose was designed. According to the layout of the vehicle, this paper designed a cold separation scenario to which a close-loop attitude control scheme is introduced. Based on the description of the separation process, dynamic and kinematic equations were built. Meanwhile the ejector piston model, retro-rocket model, aerodynamic model and attitude control model were also established. The collision detection method was discussed and Monte Carlo simulation was introduced to deal with the uncertainties. Simulation results show that the proposed project can not only reduce the attitude deflection of the vehicle but also avoid interstage collision, so it provides a possible choice for the stage separation of this type of vehicles.

Abstract:The method to design lunar free-return trajectory and hybrid trajectory was studied. The sectional perturbational high precision dynamical model was established, then the search variables, target parameters and differential correction algorithm were designed, and a nominal free-return trajectory was searched out, which was validated and three-dimensionally simulated by STK. In addition, the error transfer was analyzed. The paper described a typical design procedure of hybrid trajectory which combines free-return trajectory and non-free-return trajectory, and simply analyzed the advantages and disadvantages of it. The method and conclusions in the paper can be applied to conceptual design of manned lunar landing mission and trajectory design of the later stage of China Lunar Exploration Program, as well as trajectory design of micro lunar probe launched together with other spacecrafts.

Abstract:Moisture measurement, shear strength testing and morphology observation of glass fiber reinforced epoxy resin composites (GF/E-51) specimen immersed in water were carried out in this paper. Experimental results show that the maximum moisture content of the specimen in water of 50℃ was increased by 145% than that in water of 30℃, while the diffusivity coefficient increased by 47.6% and the average water absorbing rate increased by 300%. Increasing temperature accelerated the transformation of water absorbing process from the Fick law based to the No-Fick law based. Increasing pressure, however, decreased the process as the pressure restrains the swelling of the GF/E51 in water. Sixty days after the specimen was immersed in water, the shear strength of all specimen will reach the minimum values while the shear strength of the specimen in water of 5atm and 30℃ is 3.97% higher than that of the specimen at 1atm and 30℃， and 5.17% higher than that of the specimen at 1atm and 50℃, respectively.

Abstract:Based on the ANSYS software, the structural analysis of a kind of 1500kW large-scale composite wind turbine blade which applied in GL3A wind farm was carried out. The analysis results show that the vibration modes of this blade are mainly presented as first flapwise mode and first edgewise mode, the frequencies of the vibration are respectively 0.86Hz and 1.59Hz. At the action of ultimate flapwise loads, the FEM analysis results show that the blade tip deformation is 8.445m, while the blade tip deformation of the full scale blade under static test is 8.12m, so the deviation between the calculated and tested value of the blade tip deformation is only 3.8%. Moreover, the calculated maximum tensile stress and the compressive stress are 228MPa and 201MPa, while the tested tensile strength and compressive buckling strength of the glass-fiber/epoxy composite are 720MPa and 380MPa, respectively. Consequently, the percentages of the calculated maximum stress and the tested ultimate strength are respectively 31.7% and 52.9%.

Abstract:Aiming at image with high noise, a fast clustering segmentation approach combining peak testing is proposed in this paper. Two-dimension histogram was converted into one-dimension with parallel projection segmentation algorithm. Peak testing algorithm was used to test the clustering result of the pixels in noisy image. Parallel width in projection model was adjusted according to the testing result. As the histogram is approximated by double-peak distribution, noisy image can be segmented with weighted Fuzzy c-Means clustering algorithm. Experimental results proved that the proposed approach is fast and effective.

Abstract:FMA(Fused Multiply-Add) with high precision is required in high performance microprocessors. A new 10 stages pipelined architecture of 128bit FMA is proposed. In this architecture, multiply, adder, LZA(Leading Zero Anticipator) and normalization with large width data-paths were partitioned and optimized carefully to balance the latency at every pipeline stage. After designed and synthesized with SMIC 0.13μm technology, the frequency of the FMA can reach 465MHz, which is about 130% better than previous 128bit FMA. Furthermore, its frequency can reach 1.075GHz with TSMC 65nm technology, which basically meets the requirements of the high performance computation.

Abstract:Based on the BiCR algorithm, s-BiCR algorithm　is proposed to solve nonsymmetric linear systems. Firstly, the basic computation frame for the s-BiCR was given by introducing the fundamental principle　in the new method and the solution approach to the parameters. Next, according to the analysis of the characters of the sequences of residual vectors and direction vectors, an approach is deduced to reduce computational volume for the parameters so that a more effective advanceds-BiCR is designed. Finally, the　correctness ofs-BiCR is proved, that is, the ith approximate solution froms-BiCR is equal to the isth approximate solution from BiCR. In addition, by performance analysis, the number of both synchronous communication and accessing memory fors-BiCR is less than the one for BiCR so the algorithm here　has better parallel feature and data locality. The effectivity and validity ofs-BiCR have been confirmed by experiments.

Abstract:Based on Bayesian theorem, a method is proposed to estimate the unknown parameters of Lorenz chaotic system using Markov Chain Monte Carlo (MCMC) method. Firstly，the posterior probability density function for unknown parameters is deduced. Secondly, taking the posterior probability as the invariant distribution, the Adaptive Metropolis algorithm is used to construct the Markov Chains. Thirdly, the converged samples are used to calculate the mathematic expectation of the unknown parameters. The results of numerical experiments show that the parameters estimated by the new method have high precision and the noise is filtered effectively from observations at the same time.

Abstract:A novel knowledge-aided reduced rank (RR) space time adaptive processing (STAP) method is proposed in this paper. Firstly, a clutter model was constructed by a priori knowledge such as flying parameters, radar system parameters, mapping and terrain parameters. Secondly, the clutter was performed via the pre-whiten processing of the constructed clutter model. Finally, RR STAP method was used to suppress the residual clutter. The simulation results show the KA-RR method is more robust in nonhomogeneous clutter environment compared with conventional RR STAP method.

Abstract:Due to the rapid increase in the amount of available video data, there has been a growing demand for efficient methods to understand and manage the data at the semantic level. In this paper, the V-OWL is proposed with extensions to OWL, which can describe complex video content including temporal-spatial and uncertain relationships. The B-Graph description model based on Bayesian Net is proposed to map the concepts and relationships in V-OWL ontology into the nodes and edges in B-Graph. Video semantic content can be discovered automatically by using existing training and reasoning methods of Bayesian Net. Results from experiments show that V-OWL has achieved good description of complex video content, and satisfactory precision and recall of high level semantic content detections.

Abstract:Costas loop is usually used in navigation receiver as carrier tracking loop, so many analyses have been made about coastas loop. Traditional analysis is based on unitary signal power multiplicative detector, and the loop bandwidth is considered constant no matter what the signal to noise ratio is. In this paper, two kinds of phase detectors are precisely modeled and analyzed. The pll thermal noise formula is given and proved by simulation. If the signal to noise ratio is lower than 4dB, the performances of the two detectors are almost the same, the signal to noise ratio threshold of tracking is almost the same. The results of this paper can be used to design the satellite navigation receiver.

Abstract:Radar word is a fixed arrangement of finite number of pulses that can reflect the work modes and threat levels of hostile multi-function radars. To deal with the problem of radar words extraction with reference to dropped pulses and false pulses, this paper proposes a new extracting method based on three-level matching (TLM) algorithm, which can first perform a coarse search by identifying the radars from the radar template library that have character parameters similar to those present in the deinterleaved pulse stream of the emitter, and then make use of the technology of pulse pairing and sequence cross correlation for precise identification. A number of simulations are presented to demonstrate the radar words extracting capability of the TLM algorithm. Simulation results show that the proposed algorithm can not only extract the radar words correctly, but also have better adaptability to noisy environment.

Abstract:A hybrid technique combining the Pseudo-Spectral Time-Domain method with the Finite-Volume Time-Domain method is presented to solve 3-D mixed-scale problems, which contain both electrically large and relatively homogeneous regions and electrically small fine details in computational electromagnetics. FVTD is suitable for electrically small problem but suffers from large numerical errors for electrically large-scale regions. The PSTD method, on the other hand, is accurate and efficient for regions with large and relatively homogeneous materials, but is low in efficiency for electrically small structures. The hybrid method overcomes disadvantages and unites advantages of either method mentioned and is potentially more useful. A least square based quadratic polynomial reconstruction method is developed for FVTD to reduce the reflection brought by the boundary of the algorithms, then an overlapping grids scheme and a no overlapping grids scheme are presented. Numerical examples demonstrate that the method proposed enjoys high level of precision and strong capability in region analysis.

Abstract:A lower bound on the error rate of linear binary block codes (under maximum likelihood decoding) over BPSK-modulated AWGN channels is proposed in the current study. The essence of the optimization to the lower error rate bound is to optimize the lower bound on the union probability of finite events. Combined with the optimizing rule of the improved Dawson-sankoff bound, we obtain the judge rule of the redundant error events and obtain the calculation expression about lower bound of SER which solely depends on the Hamming weight enumerator function of the code and the signal-to-noise ratio (Eb/N0). The algorithm can get the tighter lower bound and has lower complexity than the de Caen's kind bound and the KAT kind bound, which has been proved by the numerical results applying to LDPC codes and the others.

Abstract:In order to enhance the angle measurement accuracy in passive radar seeker (PRS) restrained by weight volume, a novel Extended Kalman Filter (EKF) using missile-to-target relative state is proposed in this paper. Missile-to-target relative position was described by several relative state variables, including range, line-of-sight azimuth and elevation angle. Missile-to-target relative motion model was then established by using velocity measurement of Inertial Navigation system (INS). This approach can fully take advantage of onboard INS information, thus offering favorable PRS measuring error suppressing. It has practical application in enhancing missile strike precision, attacking performance as well as the ability of anti-target losing. The approach proposed is validated by the simulation in a representative scenario.

Abstract:A method based on quasi-static and Multi-level Fast Multi-pole Algorithm (MLFMA) is introduced to compute the micro-Doppler echo by motion body targeting with arbitrary shape. The joint time frequency analysis algorithm is used to calculate some typical motion's micro-Doppler echo. Furthermore, efforts were made to extract the instantaneous frequency and then compare it with the point target's instantaneous frequency in accord with the same micro-motion. The results indicate that they share the same trend and the current method is efficient.

Abstract:In order to monitor the condition of a liquid rocket engine turbopump in the case of lacking fault samples and prior knowledge about fault modes, and to eliminate the false alarms caused by sensor faults, a novelty detection method based on one-class support vector machine (OCSVM) is introduced. An OCSVM is trained on the basis of normal samples, and is used as turbopump condition monitor. Another OCSVM is trained on the basis of sensor fault samples and is used as sensor fault detector. Turbopump condition monitor detects whether novel events may occur, while sensor fault detector identifies whether novel events detected are caused by sensor faults. The validity of this turbopump condition monitoring and sensor fault recognition method is verified with historical test data.

Abstract:Equipment Maintenance Support System (EMSS) is a class of complex dynamic system. How to effectively analyze and construct simulation model for EMSS is a problem. Firstly，a two-layers framework named “physical layer—operation layer” framework is presented to analyze the EMSS in detail. Secondly, the concept of Object is extended to Stochastic Service Resource Management Object (SSRMO) to model the physical layer of EMSS. Thirdly, a modeling approach based on UML dynamic modeling technique for the operation procedure of EMSS is presented and the operation procedure model is further decomposed into the operation rules of SSRMO. Finally, a detailed simulation experiment nearly including all the important aspects of EMSS is designed and conducted. The results have revealed the integrality of the two-layers analyzing method and the feasibility of SSRMO in modeling the physical resource and the artificial rules.

Abstract:The detection of plane landmarks from airborne Lidar points cloud data is considered the key technology for mapping and guidance. Traditional plane detection algorithm based on 3D Hough transform using polar coordinate suffers inconsistent space segmentation problem which causes apex phenomenon when normal of plane is vertical to ground. The new 3D Hough transform is presented with dual space segmentation, utilizing two orthogonal polar coordinates to segment half unit sphere into Gaussian grid. This algorithm can avoid space inconsistent problem. Simulation and real data processing result indicate that the new algorithm can detect plane landmarks effectively without increasing calculation amount.

Abstract:Slow Tool Servo diamond turning is capable of effectively generating freeform optical surfaces or rotationally non-symmetric surfaces. However, many error sources, such as geometric and thermal errors of machine tool, and the forced vibration, dominate machining accuracy. In order to enhance fabricate accuracy, machining error compensatory approach was studied. Zernike polynomials are powerful in analyzing the relationship between the surface figure and the optical performance. So machining error was analyzed by Zernike polynomial fitting procedure, and the error compensation algorithm based on tool path correction was constructed. Experiments show that the slow tool servo diamond turning method can generate freeform optical surface, while the compensation method can obviously improve the machining accuracy.

Abstract:In order to simulate seafloor reverberation time series in the case of monostatic, the mixed model method is presented, using the point-scatterer model method and the patch-scatterer model method alternately. This method can not only overcome computational errors caused by the Gaussian distribution assumption in the patch-scatterer model method, but also decrease computational complexities of the point-scatterer model method. In order to simulate narrowband reverberation time series easily, the simulation method designed based on simulating reverberation complex envelop, which is feasible for any sampling frequency. Finally, the validity of the simulation method is verified by the simulation test.

Abstract:The basic way to realize reusability, share and interoperability in M&S is standardization. A number of open standards have been proposed to solve interoperable problems in their own domain, which promotes the development of simulation technology. Many researches have been done about the specification and application of the standards themselves. What has rarely done is the establishment of a wide-reaching demonstration or test environment within which the mutually supporting (and possibly conflicting) capabilities of the various standards can be put on display for evaluation and education. First, five emerging open standards (MDA, BOM, SRML, MSDL, C-BML) were selected and described, then an XMSF case was given and the integration and analysis of the five standards were elaborated. Finally, the effect of “taking open standards together” was deduced and summarized, which might benefit the present simulation industry.

Abstract:Spectrum shifting method is a new kind of high resolution imaging technology. The influence of the moving error and the field's noise, which may appear in practical application, has been discussed by simulation method combining theoretical derivation. Research shows that it can achieve the best effect with three times of scanning only. In the presence of system error or random error, the quality of processed image will decline along with the increase of scanning times. So the imaging result and velocity are not contradictory in this technology. Furthermore, the quality requirement to stripe field is not strict. Generally, the effect of processed image using noisy stripe field whoes SNR is from 15dB to 20dB is very close to the ideal effect.

Abstract:The paper proposes a new approach of beam combination, in which the feasibility of volume Bragg gratings as the laser beam guiding device was analyzed. Based on Kogelnik's theory of coupled waves, the wavelength selectivity and angular selectivity of volume Bragg gratings were emphatically discussed. The experimental fabricating process was reported in detail. Two different wavelength lasers beam combination and two same wavelength lasers beam combination were performed. As a result, the feasibility of Bragg grating for beam combination was verified. In order to be used conveniently in practical operation, the special angle is taken into account. The optical path will be improved and the theoretic calculation also be simplified. The beam combination efficiency will be greatly improved.

Abstract:Dither signal removal is the important work of mechanical dithered ring laser gyro (MDRLG) signal processor. In view of the limitation of present dither signal removal method in fast tracking use, a new method combining dither stripper with FIR filter is proposed in this paper. Results show that the dither signal in gyro count can be attenuated about 75dB after dither stripper, which can be used in the situation that real time angular rate output is needed. The residual dither signal and high frequency noise can be removed by FIR low pass filter，then the performance is improved under the condition of short time delay.