Abstract:In order to provide a guide for specific investigations on WTBVFT(wind tunnel based virtual flight testing) techniques, the test system and key technologies of WTBVFT for the evaluation of FCS (flight control system) were analyzed. Based on the deficiencies of the traditional FCS evaluation methods, the advantages of WTBVFT for evaluation of FCS were analyzed. According to the common constitution of attitude control loop and guidance control loop used by FCS, the test system and working principle of WTBVFT for FCS evaluation were presented. The main differences between the WTBVFT system and the hardware-in-the-loop simulation system were analyzed. The key technologies of WTBVFT for FCS evaluation were also analyzed, including WTBVFT evaluation methods, aircraft model design technique, FCS modification technique, and model support technique.

Abstract:A multi-objective gliding trajectory optimization scheme was proposed for hypersonic vehicles with complicated constraints, such as aerodynamic heating, overload, dynamic pressure, control variables, waypoint, no-fly zones, and terminal states. The pole-transformed motion equations were deduced to simplify some of the constraints and to avoid the singularity of the traditional motion equations. Furthermore, the physical programming was employed to convert the multi-objective optimization problem to a single optimization objective problem considering the designer′s preference. Based on the multi-phase Gauss pseudospectral method, the optimal control problem of the single objective trajectory optimization problem was converted to a nonlinear programming problem. Results demonstrate that the algorithm can generate optimal gliding trajectories satisfying all the complicated constraints while the designer′s preference can be taken into consideration.

Abstract:In order to improve the performance of space-based missile warning system in tracking multi-target, the latitude-zone scan mode and target-group track mode were proposed for the scanner and tracker respectively. Based on these modes, the scan sensor and track sensor management algorithms were proposed. For the multi-model sensors, their working mode, the scanning frequency, the measurement error and the field-of-view differ from each other, an observation tracking Cramer-Rao formula was derived. Finally, a multi-model senor management algorithm based on the above methods was proposed. Results show that the proposed algorithm has a higher tracking accuracy for multi-target than the system in traditional working mode. 

Abstract:The design of dynamic scale model is one of the most important parts in the scale model test which is an effective approach to obtain dynamic characteristics of large launch vehicle. Taking the launch vehicle as the object, the similarity relationships for each part were derived on the basis of the structural components of the launch vehicle. Transverse dynamic similarity relationships of the launch vehicle were derived by taking advantage of the consistent similarity in respect of transverse stiffness and mass. Taking the actual processing and manufacturing conditions into consideration, the restrictions of similarity coefficient for transverse stiffness and mass were analyzed. According to the relationships and the restrictions above, a 1/5 dynamic scale model was designed and its similarity of dynamic characteristics was verified through the numerical analysis of finite element. The verification result shows that the 1/5 scale model gets a high-level similarity with the prototype in terms of dynamic characteristics, and the method can be effectively applied to the design of dynamic scale model for launch vehicle.

Abstract:In order to investigate the failure mechanism, dynamic changing law and the effect of leakage and blockage fault of spacecraft propulsion system, a dynamic simulation of some pressure-fed propulsion system was conducted based on the modular model library previously. The leakage and blockage fault of gas pressurization lines were simulated with the method of Realizable k-ε model and one-dimensional compressible duct model respectively. The leakage and blockage fault simulation for propellant lines were carried out with the finite element state-variable model and variable flow coefficient model respectively. The dynamic simulation of the propulsion system was carried out and some interesting results have been obtained as follows. Firstly, due to the leakage and blockage fault of gas pressurization lines, the pressure boost couldn′t meet the need of operational state, resulting in the propellant inadequacy and pressure drop in propellant lines. Secondly, because of the leakage and blockage fault in propellant lines, the mixture radio would deviate from the designed ones, resulting in the sliding down of the propulsion system performance. Although both of the leakage and blockage fault would make the propulsion system performance slide down, there are differences between the two faults. Firstly, due to the blockage fault, the upstream pressure of faulty component is substandard and less propellant is consumed. Secondly, due to the leakage fault, the upstream pressure of leaking object is lower than normal value and too much propellant is consumed.

Abstract:For the problem in the mission design demands, the influence of the drag mode on the deployment property of the space net system was investigated. The dynamic model was set up and verified by ground test result. Evaluation criterion of space net system was set up to meet the mission demands and the impact that the drag mode brought in was studied through a finite element method. The simulation models, in which mass of the net and initial projection energy were kept the same, were built based on the finite segment approach for four and six points drag modes. Simulation result of the evaluation criterion indicates that the system flight performance indexes and the dynamic evaluation criterions are improved in the six points drag mode, the energy utilization rate and system reliability, however, show minor decrease.

Abstract:Based on the variance-based global reliability sensitivity index, new regional and parametric sensitivity indices were defined respectively to measure how the sensitivity indices of the whole inputs change when the distribution range of one input is changed or its variance is decreased. Then these two proposed indices were described by PCC (Pearson correlation coefficient) between the unconditional failure indicator and its pick-frozen replication. Based on the transformation, two methods based on PCC were proposed to compute the proposed regional and parametric sensitivity indices. One method was based on Monte Carlo method and iterating sampling, whereas the other one was based on IS (importance sampling) and reusing the samples without extra computational cost, so the computational efficiency of the second method was much higher. The feasibility of the proposed regional and parametric indices, the accuracy and high efficiency of the proposed methods were demonstrated by the results of several examples.

Abstract:Based on the demand of the spacecraft protection against the orbital debris, numerical simulation of a new designed stuffed corrugation-cored sandwich under hypervelocity impact was carried out. The hypervelocity impact process was obtained, and thereby the perforation of the sandwich and the characteristics of the debris cloud were analyzed. It can be seen that the phenomenon of stuffed corrugation-cored sandwich under hypervelocity impact is similar to that of Whipple structure, but the head velocity of the debris cloud is lower and the expansion velocity and expansion angle is larger. With the impact velocity increasing from 3 km/s to 10 km/s, the size of the sandwich perforation increases accordingly and the shape of the perforation becomes more irregular. Furthermore, the epoxy stuffed in the sandwich absorbs most impact energy of the debris while the front plate and the corrugation core absorb less energy. The research can provide some references for the design of orbital debris shield.

Abstract:To improve the navigation accuracy of airship in the disturbance environment of wind field, a navigation algorithm with anti-interference of wind field was studied. Based on building up an error constraints model of the airship velocity in wind field disturbance, a constraints unscented Kalman filter algorithm which resists wind field disturbance was designed. The error constraint vector of airship velocity was determined. To decrease the impact of wind field on positional accuracy of airship, the velocity error was estimated and compensated by the combination of unscented Kalman filter and error constraint vector. The state estimation value of proposed algorithm was proved to be unbiased, and the covariance was less than that of the standard unscented Kalman filter. The proposed algorithm was applied to SINS/CNS/SAR integrated navigation system and conducted simulation, and was compared with the adaptive extended Kalman filter and robust adaptive unscented Kalman filter. The simulation results show that not only the filter performance of the proposed constraints unscented Kalman filter was much better than those of adaptive extended Kalman filtering and robust adaptive unscented Kalman filter, but also the impact of wind filed on positional accuracy of was reduced and the navigation accuracy of airship was improved effectively.

Abstract:The image system design for sounding rockets faced many difficulties, such as the limited telemetry bandwidth, multiple camera channels and a limited size, therefore an appropriate image capture and compression system based on ADV212 was proposed. The images were compressed as JPEG2000 standard which support both lossless and high ratio compression, so acceptable quality images can be transmitted through the limited-bandwidth telemetry channel. An effective channel switching and interrupt processing method suitable for on-board design was proposed. The image data was transmitted by assembly line based on pingpong operation and sent to the telemetry module on sounding rocket via two real-time channels and one buffering channel. The images compression scheme, which support both dynamic frame frequency and dynamic compression ratio, was proposed to deal with the limited telemetry bandwidth. The whole system was controlled by a Virtex-4 FPGA(field programmable gate array), and images were decoded by ADV7182 and compressed by ADV212. The realtime data transfer was approached by SRAM(static random access memory), while the buffering data transfer was approached by SDRAM(synchronous dynamic random access memory). The suitable choices of compression filter and wavelet transformation level for CCD(change-coupled device) images were analyzed through experiments by comparing PSNR(peak signal to noise ratio) between images. This image compression system fully satisfies the image monitor mission of space environment vertical exploration sounding rocket.

Abstract:Due to the big difference between the velocities of the transmitter and the receiver, the working mode should be reasonably designed to realize high resolution and extended scene in SA-BiSAR (spaceborne/airborne bistatic synthetic aperture radar system). Based on the ratio of the beam width to the velocity, a scheme for the computation of integration time and azimuth coverage of SA-BiSAR was described. A classification of bistatic SAR(synthetic aperture radar) configurations was introduced in terms of the antenna footprints′ size and the velocities. At the same time, accurate effect of the initial footprints offset on the image performance in azimuth direction was obtained. Simulation results validate that the proposed method can be well used for footprint synchronization error analysis and SA-BiSAR system design.

Abstract:As for nonlinear/non-Gaussian information processing problems in navigation systems, a kind of adaptive integrated navigation system was established on the basis of the modified traditional nonlinear Kalman filter by utilizing self-organization algorithm, neural network and genetic algorithm. Applying self-organization algorithm with redundant trends, Volterra neural network and genetic algorithm, the nonlinear prediction model of navigation system error was built. Then, predicted values of navigation errors were obtained using the established error model. Comparing the predicted values with the estimated values by Kalman filtering algorithm, the difference between them, functioning as an indicator of the divergence of Kalman filter, was formulated. The modification of nonlinear Kalman filter was made and a novel technology of navigation error compensation was thus developed on the basis of adaptive control methods. Applying traditional and modified Kalman filtering algorithms respectively, the semi-physical simulation study based on the navigation system KIND-34 was carried out. The analyzed results indicate that the accuracy of error estimation and compensation in navigation systems is improved by using the modified nonlinear Kalman filter, and thus the ability of self-adaption and fault tolerance are enhanced in integrated navigation systems.

Abstract:DOA (direction-of-arrival) discrimination is one of the most effective spoofing detection methods. There are two forms of DOA, one is the carrier phase single difference and the other is the carrier phase double difference. However, the carrier phase single difference cannot be used in the motion vector, and the carrier phase double difference will be ineffective in detecting single spoofing signal or multi-elements spoofing transmitter. In order to solve this problem, a method based on the inertial assisted three elements antenna was introduced. This method was applied to motion vectors, the motion vectors using this method can detect the spoofing only by means of moving a distance during a certain time. This method not only can be effective for several spoofing signals from the same antenna, but also can detect single spoofing signal or multi-elements spoofing transmitter with strong ability. The proposed spoofing detection method was verified to be effective through theoretical analyses and simulation tests. The results indicate that the longer the displacement distance of the receiver antenna is, the better the spoofing detection performance of the proposed method is; the closer to spoofer from the receiver antenna is, the better the spoofing detection performance of the proposed method is; the more vertical between DOA and antenna displacement direction is, the better the spoofing detection performance of the proposed method is.

Abstract:The statistical property of monopulse ratio was derived under the condition of single target and multiple unresolved targets. According to the inherent difference, the multiplicity detection algorithm was proposed using complex monopulse ratio. Taking two targets as an example, the detection performance was presented by Mont Carlo simulations, with respect to the SNR (signal to noise ratio), the angle interval and the complex amplitude ratio. Some meaningful conclusions are inferred qualitatively. When one target predominates, the detection performance is low. As for two comparative targets, the detection performance is improved with the increase of the phase difference. This algorithm can eliminate the outliers of estimated angle effectively and can lay the foundation for the resolution and measurement process of multiple targets.

Abstract:The research of influence on TDICCD camera′ s imaging geometric quality can contribute to improving quality by advancing the design requirements of the platform. The quantitative relation of the platform attitude error and the imaging geometric quality based on the image point displacement was studied. The model of imaging parameters′ error caused by attitude error was built, including the error of image motion velocity, the drift angle correction and integral time. The relation between imaging parameters′ error and image motion combined with the strict geometric imaging model was deduced. The quantitative model of the geometric quality indexes under the influence of image motion was established, including angle distortion, length distortion, pixel resolution and positioning accuracy. The perfectly quantitative chain from attitude error to geometric quality indexes was created. The simulation experiment was conducted and the results indicate that the main influencing factor of geometric quality is the error of yaw angle.

Abstract:In order to lower the error floor of LDPC (low-density parity-check) codes, a new class of APPS-LDPC (arithmetic progression and partition shift LDPC) codes was proposed. The APPS-LDPC codes are based on cycle path description theory with arbitrary code length, code rate, column weight. The girth of their Tanner graph is at least eight. Cyclic shift coefficients can be described in simple analytic expressions to reduce required memory usage. The simulation results show that the proposed APPS-LDPC code (496,248) gets a coding gain of 1.9 dB at least compared to the PEGLDPC (progressive edgegrowth LDPC) code at BER (bit error rate) 10^-5. And at high signal to noise ratio region, the gap between two decoding curve increases gradually. Besides, APPS-LDPC code (6144, 5376) whose column degree is 3 gets a coding gain of 0.25 dB at least compared to the PS-LDPC code at BER 10^-8, and there′s no obvious error floor phenomenon when the signal to noise is above 4.6 dB. The performance of the proposed algorithm also outperforms the 4-girth or the 6-girth PEG-based LDPC codes, especially in error floor region. The time-consuming and complexity for constructing an APPS-LDPC code also show some advantages over PS-LDPC code and PEG-LDPC code. And through trapping sets searching method based on Tanner graph, there is no small trapping set composed by cycle 8 in (496,248) APPS-LDPC code, which demonstrates the reduction of the error floor.

Abstract:The direction of arrival (DOA) of multiple targets was acquired by solving non-liner correlation equations involving acoustic pressure and particle velocity with quantum particle swarm algorithm. In order to improve the precision, the DOA tracks of multiple targets were fitted with the method of least squares, the prediction model was found and then the DOA tracks were optimized by Kalman filter. The results indicate that the DOA of multiple targets can be resolved with the single vector hydrophone and the results should be expressed by statistic characteristics. The maximum number of unknown sources is 7. As the number increases, the DOA error is more serious. When the signal to noise ratio is higher, the resolution ratio and precision are also higher and the deviation is smaller. More importantly, the precision of DOA can be improved effectively by the method of data fitting and the Kalman filter. 

Abstract:The existing intersession network coding mechanisms almost unanimously adopt “τ-interval-notification”, which is used to determine the coding opportunities, and its overhead has not been analyzed. In the current study, its communication overhead and its impacts on coding opportunity and throughput were analyzed, and an adaptive reception report sending mechanism called AR²SM (Adaptive Reception Reports Sending Mechanism) was proposed. In AR²SM, the interval of broadcasting reception reports is determined adaptively according to the traffic of local network, and the reception reports carry the packets overheard in the last 2 intervals. As a result, the size of reception report and the frequency of sending reception report were both reduced on the condition of guaranteeing the coding opportunity. According to the simulator results in network simulator, the proposed mechanism reduces the overhead of transmitting the reception reports, and achieves higher throughput than the “τ-interval-notification” mechanism.

Abstract:To analyze the throughput of streaming application systems, it is necessary to model the periodic static order schedule into the synchronous dataflow graph. The throughput analysis efficiency depends on the size of the dataflow graph and the modeling time. To improve the throughput analysis efficiency, a schedule-aware dataflow model and its modeling method were proposed on the basis of the homogeneous synchronous dataflow graph. By exploiting the structure of the application model and the periodic static order schedule, the task number, edge number and initial token number were reduced. Besides, the throughput of the model can be analyzed using available analyzing methods. Experimental results show that the proposed modeling method outperforms the available methods, with the throughput analysis being optimized efficiently.

Abstract:In order to evaluate the effectiveness of pulse laser experiment aiming at the single event effect of SoC(System on Chip), an experiment system was established based on a 65 nm SoC. The methods of coordinate setting, focusing on source and compensation about ΔZ on flip chip integrated circuit were proposed and employed. Pulsed laser tests were carried on static random access memory, register file, RapidIO and Dice flip-flop. The results indicate that SRAM is the most sensitive area and the results on these modules are consistent with the corresponding results under heavy-ion experiment. Therefore, the pulse laser is suitable for single-event effect researches on large-scale integrated circuit designed with nanometer technology. 

Abstract:The request processing of ternary optical computer lacked reasonable systematic standard and system for performance evaluation. Therefore, a four-stage service model was built based on complex queuing systems includingM/M/1、M/M/n、M^X/M/1和M/M^B/1. Meanwhile, strategy and algorithm of instant-scheduling and end-scheduling were proposed in detail. Based on different queuing systems, the calculation method of receiving time, preprocessing time, operating time and transmitting time of the request were discussed, and the final response time was obtained. Finally, the models of two strategies were verified by simulation experiments. Results show that the end-scheduling strategy is superior to the instant-scheduling strategy.

Abstract:Unmanned ground vehicle swarm was proposed to monitor the process of reentry vehicle landing, and then the techniques about intelligent swarm self-organizing strategy were researched. Swarm behavior patterns about unmanned vehicle swarm collaboratively monitoring the process of reentry vehicle landing were designed and the swarm self-organizing strategy based on cooperative game was presented for the swarm aggregation behavior in the process of collaborative monitoring. Each agent regards achieving swarm aggregation and saving energy as top goal and carries out the gaming. The particle swarm optimization was used to program the local path thus the aggregation behavior was realized. Simulation experiment proves the effectiveness of the autonomous aggregation strategy.

Abstract:A friction torque analysis model of seeker servo mechanism including thermal coupling deformation was established. The influence of changing environment temperature on geometry parameters and friction torque of angular contact bearing was mainly studied. Taking mirror-type seeker as an example, its friction torque was calculated and analyzed by using the proposed calculation model. Results show that the grease viscosity is the main cause for the dramatic rise of the friction torque with the decreasing of the temperature, while the thermal deformation has a small impact on it. Based on the electrical method, an experimental system for friction torque measurement was established. And a rapid temperature experiment chamber was used to simulate environment temperature. Theoretical calculation results and experimental results were compared and analyzed. Experiments prove that the results of friction torque experiment agree with the theoretical model calculation.

Abstract:The influence of speed and air flow on the flat gas reservoir law of drag reduction was investigated by an experiment of plate with air injection, and the air layer formation in different groove configuration was observed by an underwater imaging system. The results show that the grooves increase the resistance of the plate without air; the resistance of flat plate can be reduced with the injection of air, and there is an optimal air flow; the optimal air flow decreases with the rise of the groove depth, and the absolute drag reduction rate decreases with the increase of the speed; the configuration of the groove is an effective measure to maintain the stability of the plat bottom surface air layer; the appropriate groove configuration significantly improves the flow field at the bottom of the flat plate and increases the effect of the flat drag reduction with air injection; the absolute drag reduction rate reaches more than 40% under the optimal air flow when the Fr is 0.119.

Abstract:Production rate of important reactants was calculated through grimech 3.0 mechanism in methane oxidation. A sensitivity analysis was employed to determine important elementary reactions in oxidation. A reduced kinetics mechanism for lean methane oxidation was built, including 16 species and 31 steps. Simulation results based on the reduced mechanism were compared with the calculation results of grimech 3.0. The reduced mechanism is suitable for lean fuel condition at an equivalence ratio lower than 0.2.

Abstract:Fluid interface instability seriously affects the performance of ICF (inertial confinement fusion) capsule implosion, doped CH plastic or Be (Beryllium) ablator is generally employed in ICF capsule. The RM(Richtmyer-Meshkov) instability occurs when the radiation-generated shock penetrates the rippled inner surface of ablator. In order to explore the resistance ability to RM instability with Be or CH plastic as ablator, theoretical analysis and numerical simulation were carried on the evolution of RM instability. Theoretical analysis indicates that the linear growth rate of RM instability depends on the radiation temperature, the wavelength，the initial amplitude of perturbation and the density of ablator. The hydrodynamics process of high temperature (above 100 eV) blackbody spectrum X-ray ablating rippled interface of Be/Foam and CH/Foam target is simulated by a radiation hydrodynamic code. Simulation results show that the Be ablator with higher density has stronger resistance ability to RM instability than CH plastic ablator. The results are useful for capsule design in inertial confinement fusion.

Abstract:Testability is crucial for the enhancement of system maintainability, and testability growth can promote the testability metric of the system to satisfy the design requirements by a series action of identifying and correcting the testability design defects. The test resources allocating problem arising in delay fix based testability growth was studied and modeled, considering that whether there are constrains on the growth object and growth test cost or not. A Lagrangian relaxation algorithm and local search hybrid optimal algorithm were applied to solve this problem. Simulation results show that the proposed model is feasible for the test resources allocating problem in testability growth test, and the hybrid optimal algorithm can promise the effectiveness and accuracy to the integer programming problem.

Abstract:In order to implement the automatic generation of binary decision diagram (BDD) for phased mission system reliability analysis, a universal approach for establishing BDD reliability model was proposed. A nested BDD data structure named BDD_Element was defined, and the approaches of BDD description and storage were given. Algorithms for transforming AND Gate, OR Gate and k/n Gate into BDD models were proposed. The BDD model for reliability analysis of phased mission system was constructed in 2 steps: based on the logic gate transforming algorithms, structure functions of the component logic relationship were transformed into phase BDD models; based on the BDD manipulation rules, phase BDD models were integrated together. By analyzing the reliability of satellite attitude adjustment mission, it shows that this approach can be effectually applied in the reliability analysis of phased mission system.

Abstract:Nuclear security is an important part of national security. To deal with the lack of quantitative methodologies in the current researches, the GMCR（graph model for conflict resolution） was adjusted and applied to games analysis for nuclear crisis. Firstly, the analysis framework, the related definitions and the matrix representation approaches were proposed. Secondly, the conflict model was calibrated based on the history background of the Sino-Soviet nuclear crisis in 1969, and the evolution of game state was unveiled by using matrix analysis algorithms. Thirdly, two parameters of conflict model were introduced, namely game policy and military capability, and the sensitivity analysis for their influence to stability results was researched. Fourthly, coalition analysis methodologies were utilized to identify the potential alliances of decision makers and its impact on national relation evolution. Finally, relevant conclusions and decision suggestions of nuclear security were summarized based on the analysis results of the conflict model. Results show that the GMCR is suitable for investigating nuclear crisis and the strategy matching with military capability play a key role in game evolution.

Abstract:A method to estimate submarine′s strongly nonlinear motion and hydrodynamic performance during emergency ascent was presented. RANS equations and VOF (volume of fluid) model were applied for simulation cases. The oblique towing experiments with different pitch and yaw angles were calculated numerically to verify the effectiveness of the method and obtain the proper application range for a fully appended Suboff model. Therefore, the emergency ascent process of submarine was simulated with integral dynamic mesh strategy, and the time parameters and the detail flow information of submarine under 6DOF (six degree of freedom) motion were obtained. Numerical simulation results show that the method can reasonably describe the motion law for submarine′s emergency ascent and is feasible and powerful in the research about the multi degree of freedom motions and hydrodynamic characteristics of the submarine′s ascent.