Abstract:Regarded as the launch object of EM (electromagnetic) energy weapon, the hypervelocity ILP (integrated launch projectile) has a lot of scientific problems different from those caused from traditional artillery. The theoretical and experimental results of EM launch ILP at home and aboard in recent years were summarized, and the basic theory and key technologies faced right now were analyzed. In addition, the solutions to these problems are put forward to provide some references to the subsequent research on EM launch ILP.

Abstract:The optimization model of topology is a kind of important model in network, which can effectively optimize the overall link performance of the system. In Ethernet topology of electromagnetic launch system, some nodes and links are overloaded, once the blockage occurred, the performance of the key links in the network can be affected. To solve this problem, a multi-objective programming model for optimizing Ethernet topology was established and the genetic algorithm based on genetic ring operation was designed to solve the model. The simulation was carried out to obtain the optimal Ethernet topology. Default parameters of corresponding network nodes in the practical system were modified through simulation and calculation. The result shows that the model and the algorithm can effectively balance load, reduce conflict rate and optimize the topology without changing the physical link by adding cost, which is of universal significance to electromagnetic launch system.

Abstract:By simplifying the rail as a Bernoulli-Euler beam fixed on the elastic support under moving loads and obtaining the equivalent stiffness of the elastic support through the finite element model, the critical velocity of the launcher was derived. Dynamic contact force between the armature and the rail and the distribution of stresses and strains were obtained from electromagnetic-structural-motion multi-physics field coupling dynamic model by using hybrid finite-element/boundary-element method. The measuring data of fiber Bragg grating strain sensors on the back of rails were used to verify the dynamic response and analyze armature stability. For the typical 30 mm × 30 mm rectangular caliber launcher, analysis and test results show that the electromagnetic extrusion force of the C-type armature on the rail reaches the peak value at the beginning of the flat-top and gradually decreases as time goes on; the stress waves caused by armature passing are easily resonant with the reflected stress waves in the rail in the high-speed stage, in which the stress exerted on the rail is the most severe and the stress concentration level is about 2.44 times that in the initial region; when the armature operates in the high-speed region, there will be a vibrating phenomenon which will lead the asymmetry of loads on the upper and lower rails. These results have guiding significance for analyzing dynamic response characteristics of internal ballistic process and design launcher.

Abstract:The flight ballistic of the EML (electromagnetic launch) projectile was simulated. Based on the establishment of a rigid body six degree of freedom flight external ballistic model, the time-frequency analysis and eddy current analysis method were adopted to establish the EMdynamic coupling model for the analysis of muzzle disturbance caused by the interior vibration, and the dynamic grid technology was used to establish the EM-aerodynamic coupling model for the analysis of aerodynamic disturbance brought by sabot discard. Thereby, the flight trajectory model of EML projectile was obtained. Taking the IAT-HVP designed by the advanced technology research institute of University of Texas as an example, the influence of the muzzle disturbance on the velocity and aerodynamic characteristics of the projectile was simulated and analyzed when the projectile leaves the muzzle at 1117 m/s with 0° angle of fire, and the 200 m exterior trajectory of the projectile was obtained. Simulation results show that 24% deviation of the drop point relative to idea ballistic are caused by the disturbance of the integrated projectile in the muzzle, in which the maximum is caused by the muzzle vibration, and secondly the sabot discard.

Abstract:Focused on the voltage drop and energy loss of metallized film pulse capacitor in actual use, which leads to the decreases of stored energy and energy density of pulsed power supply during the long voltage holding process after charging, based on the experimental data of a high voltage and high capacity pulse capacitor and the relationship between conductivity characteristics, self-healing characteristics, polarization characteristics and energy loss, the quantitative relationship between conductivity and voltage drop was derived and the conductivity measurement was carried out, the quantitative relationship between self-healing and voltage drop was derived and the life test was conducted, the quantitative relationship between relaxation polarization and voltage drop was described and the simulation was completed. The results show that the proportions of dielectric leakage, self-healing and relaxation polarization in voltage drop are 29.6%, 11.75% and 58.35%, respectively. The main factor which leads to voltage drop is relaxation polarization.

Abstract:Based on the derivation of analytical formulae for electromagnetic force and thermal stress, ANSYS finite-element simulation software was used to analyze the electromagnetic-temperature-structure coupling of copper skin at the fixed top and bottom end surface. The distribution of thermal stress and the total stress and strain were obtained. The structure of reactor was further optimized, and the optimum design of the reactor was determined by taking the structural strength requirements and the temperature requirements into consideration. The credibility of simulation and design solution was verified by carrying out a test.

Abstract:High-capacity energy storage generator can work as pulse power supply for large pulse power load through inverter after the energy storage generator′s output rectified. The loaded ability and reliability of system can be improved effectively with energy storage generators working in parallel operation. Reasonably distributing the output power of energy storage generators working in parallel operation with different speed can effectively improve the performance of system. Therefore, it is necessary to design a kind of excitation control algorithm with power regulation function. The power feed-forward control was introduced on the basis of voltage and current closed-loop control, the relationship between load power and excitation current was deducted and the feed-forward control parameters were solved, and according to the energy storage generator initial speed, the load power distribution algorithm was designed. Simulation test results show that the power feed-forward control plays a leading role in excitation control, which can control the energy storage generator′s output power and increase the excitation current response speed, and can inhibit the disturbance of load power on excitation system effectively. 

Abstract:In order to effectively study the discharge performance of pulsed power supply for electromagnetic launch, provide technical support for electromagnetic launch and reduce the cost of research and development, the related modeling and simulation work of electromagnetic launch process needs to be studied. A mathematical model for the actual physical process of the projectile was established, a circuit model of the pulsed power source was set up, and the discharge system of pulsed power supply was studied by using the method of combination of these two models. Furthermore, the simulation model of pulsed power supply discharge system based on the multi physical phenomena in transmit process was proposed. The effectiveness of the proposed method was verified by experiments, which lays a foundation for the discharge research of pulsed power supply.

Abstract:A harmonic suppression method with multi-mode fuzzy hysteresis control was proposed for the rapid increase problem of grid harmonics in large-rate rapid charging of battery for electromagnetic launch. Based on the timing series topology of the hybrid energy storage system for electromagnetic launch, the special application conditions and largerate charging strategy of the battery were explained. The topology of the battery charging was introduced, and the source, characteristics and causes of the harmonics were clarified. Based on the analysis of the harmonic characteristics of a single charger, the distribution of harmonic voltage and current of the power grid under different charging currents and the number of chargers were studied. The multi-mode control method and its switching criteria were designed. The simulation model of the charger, instantaneous reactive power detection, harmonic suppression and multi-mode control were established. Simulation and experimental data show that the multi-mode control method can quickly suppress the harmonic abrupt increase of the large-scale start, stop and fluctuation of the chargers, and the compensation effect satisfies the national standards.

Abstract:With the development of the electromagnetic launch technology, the energy storage system has become an important part of electromagnetic launch system. Taking the power and energy demand as the traction, and the volume weight fitness of the energy storage system as the optimal target, the demands of battery were studied. By comparing the existing kinds of batteries and taking safety, power density, energy density and cycle life into consideration, the lithium battery was selected as the candidate for electromagnetic launch system. Research on circuit topology to satisfy current and voltage demands from different equipment, the battery groups can realize serial-parallel conversion in this circuit topology. It is necessary to keep consistency between the battery groups for realizing the parallel connection of them. So the estimation of SOC (state of charge) was needed and the balance of battery groups was also needed. Aimed at solving the difficulty of SOC accuracy under the condition of short pulse, high rate and continuous discharging, the battery pack was taken as the research object and a dynamic identification method was employed to estimate the SOC of batteries. Unbalance happens as battery groups are connected in parallel, because there is discordance between battery groups, which will lead to limits for some groups. Therefore, a balance method is put forward to solve this problem.

Abstract:The transient image of the liquid jet in supersonic crossflow was obtained by microphotography method and the spatial resolution was 1.57 μm/pixel. The evolution of the surface wave was phenomenologically analyzed. The 3D flow field and liquid column structure were numerically investigated through volume of fluid method and the gasliquid interaction was discussed accordingly. The primary breakup of liquid jet experiences two physical processes: the column breakup and the surface breakup. The column breakup is dominated by RT instability from gasliquid acceleration while the surface breakup is dominated by KH instability from gasliquid shearing. The oscillation of the local pressure around the jet surface should be the main mechanism of the generation and evolution of the surface wave. The recirculation flow generates leeward the jet column since the interaction of the supersonic flow and the continuous liquid column. Therefore, the spray near the bottom wall contains two portions: the shearing spray from the surface breakup and the transporting spray through the recirculation flow.

Abstract:In order to comprehensively verify the fault detection algorithm in the ducted rocket rapidly, a simulation platform based on system configuration switch method was built, which can simulate various fault mode for ducted rocket. Based on the simulation platform, the ducted rocket ignite fault model, pressure sensor fault model, device interface model and fault detection algorithm model which have a same interface and system configuration with the aircraft engine controller, etc. were built. Compared with the fault detect result of mathematical model and engine control system under a same fault mode, the fault detection algorithm in the engine control system can be verified rapidly. Taking the fault simulation of nozzleless booster ignition as an example, the modeling, the test, the verification, and the process of analysis were narrated. In addition, it is also applicable to the fault simulation and verification of the shutdown of nozzleless booster, the open of air inlet cover, the ignition of gas generator, and fault tolerant control of gas flow, which has strong universality, and can greatly reduce the time cost on system development and verification, and it has a strong applied value.

Abstract:A system design method for SpaceWire router based on SRAM FPGA(fieldprogrammable gate array) was proposed to improve its reliability and availability. The router was hardened by system level triple modular redundancy; and the dynamic partial scrubbing technique based on bitstream relocation was adopted to repair the faulty module in case of soft errors. Meanwhile, a real-time state synchronization approach based on present input and healthy state was introduced to synchronize the repaired module′s state with the other modules′ after scrubbing. Hence the router is capable of error masking and selfhealing. The proposed design method was implemented and verified on the Xilinx Virtex-5 FPGA develop kit ML507. Experimental results show that the reliability and availability of the router are increased significantly. And the router′s real-time performance is satisfactory, such that it can offer normal service during the entire work process, without any interruption or delay in system functionality. Meanwhile, the amount of memory required is reduced to one-third of the original amount as a result of adopting the bitstream relocation technique, and the failure probability of the original bitstream is also greatly reduced.

Abstract:In order to study the effects of the airborne ballistic characteristics of wake simulation rockets on the simulated wake area, the exterior ballistic model of the rocket projectile, the space motion differential equation of the resistance plate and the engine, the force model of the connecting rope were established. The differential equations of space motion in the whole process of uncontrolled flight, air steering, air separation and unfolding of the detonating cable were obtained. The whole trajectory of the tail-flow-simulated-rocket was simulated and analyzed. The effect of different initial firing elements on the air trajectory of the detonating cable was emphatically analyzed. The influence of initial launch angle, the number of pulse tubes, the ignition time and the rocket separation time on simulated wake generation region were investigated. The simulation results show that the range and maximum shot height of the rocket projectile are relatively reasonable when the initial launch angle is 15 degrees. The angle of the rocket′s air steering depends on the total impulse of the pulse engine and has nothing to do with the ignition time. The effect of air separation time on the water foaming area of the detonating cord is not obvious. Air steering and separation should be completed as soon as possible when the steering requirements and the requirements of the foamed area are met.

Abstract:In order to improve the wear resistance and corrosion resistance of the soft copper substrate, the protective multi-layer diamond-like carbon film on the copper substrate was prepared by the pulsed laser deposition. The silicon carbide / diamond-like carbon cyclic layer was used to avoid the accumulation of internal stress in the diamond-like carbon layer and to reduce the risk of rupture of the functional diamond-like carbon layer. The individual silicon carbide layer reduced the hardness difference between the soft copper substrate and the hard diamond-like carbon layer. The titanium layer made the copper substrate combined with the upper silicon carbide layer firmly. Experimental tests show that the protective multi-layer diamond-like carbon film can adhere firmly on the copper substrate, and can be tested by heavy friction and adhesive adhesion as stipulated in the MIL-48497A and the temperature impact test by GJB150.5A-2009. At the same time, it can withstand the corrosion of weak alkali solution; the friction coefficient of the protective film is low and below 0.093, and the wear resistance is good for 2 hours. The multi-layer technics can be used as anti-wear film for mechanical tools in the corrosive environments after being improved for different substrates.

Abstract:Based on the correlation approach in uniform turbulence, the formula of propeller broadband noise in non-uniform turbulence was deduced to analyze the unsteady noise problem of propeller. For uniform turbulence, the ten-bladed propeller model was used, and the calculated result was compared with the experiments data, which shows a good agreement. For non-uniform turbulence, the results show that the degree of non-uniformity have no effect on the position of the peak in sound spectrum which depends on the blade frequency, but it can change the degree of hump in blade frequency. Finally the effects of skew angle to propeller noise in uniform and non-uniform turbulence were studied，and the results show the skew angle of blade can reduce the noise spectrum of propeller in turbulence.

Abstract:In order to achieve cooperative attack of multiple missiles, the impact time and impact angle control guidance-law with field-of-view limit was proposed. A new impact time and impact angle control guidance-law was derived by adding two biases to proportional navigation, and the stability is analyzed by the Lyapunov theory. The guidance process with seeker field-of-view limit was designed by dividing angle control bias term into three stages for the reason that the seeker look angle may overstep the field-of-view and lose the target. Simulation results show that the seeker look angle is limited within the view field of the seeker and multiple missiles at different positions attack the target at a specific angle at the same time, achieving the cooperative attack effect under the designed guidance-law.

Abstract:Due to the long transmission distance and low power, satellite navigation receivers may not be able to demodulate the message normally in the complex environment. Error correction encodings were commonly used in the navigation message design to improve demodulation performance. With the improvement of technology, more powerful error-correction codes have been adopted in the modernization of GNSS (global navigation satellite system). BDS (BeiDou navigation satellite system ) new signals will adopt M-ary LDPC (low density parity check) encoding. Based on the principle of M-ary LDPC codes, the software simulation and hardware test results of M-ary LDPC codes on BDS were presented. Results show that the 64-ary LDPC codes have high coding gain, and they can outperform about 0.4~0.8 dB over their binary counterparts, which will greatly improve the demodulation performance under harsh environment. The results can provide reference for the development of BDS new receivers.

Abstract:With the wide applications of the global navigation satellite system, the security problem of it has gradually become the focus of attention. In order to detect the induced spoofing, the most covert spoofing technology for satellite navigation systems, a combo-signal model which processes two satellite navigation signals simultaneously was proposed. Based on this signal-processing model, a method to detect induced spoofing signals was proposed. Then the detection threshold of the method was analyzed. An experiment with the BeiDou B1I and B1C signals and a software receiver implementing this combo-signal model was used to verify this method. The experimental results show that this method can effectively detect the induced spoofing. The statistics of the detection probability are consistent with the analysis.

Abstract:In the code delay lock loop of GNSS receiver, the false-lock problem of binary offset carrier signal was caused by its multi-peak characteristic for the present multipath mitigation technique. An optimal discriminator curve design technique was proposed by using the least squares method combined with the truncated singular value decomposition. As a result, the local code correlation reference waveforms which have no ambiguity points in tracking the BOC signals can be derived. The simulation results show that the proposed method can realize coherent and non-coherent binary offset carrier signal discriminators without false lock points. Generally, there is a performance degradation in the tracking jitter. However, there are performance promotions for the BOC(1,1) signal, which has a 8.184 MHz front-bandwidth, with 61.8% increase in the multipath error envelope area, and 4 to 5 dB increase in the tracking precision compared with W2 waveform. Thus, the selection of waveform parameters involves a trade-off between the tracking ambiguity and tracking performances obtained under multipath and thermal noise conditions.

Abstract:Aimed at the problems of traditional assessment methods, such as the subjectivity of determining the weights, the weak ability of processing big data and the lack of feature extraction ability, an improved air combat situation assessment method based on VAE (variational autoencoder) and clustering algorithm was proposed. Firstly, according to the characteristic of continuity of situation changes, a situation classification method based on time period data was proposed, and the situation of both sides was divided into four categories. Then, on the basis of VAE, a VAE-WRBM-MDN feature extraction model was proposed, which used the MDN (mixed density network) to optimize VAE feature extraction capability as well as the similarity of generated data, and to optimize initial weights of the network with WRBM (weighted uncertainty restricted Boltzmann machines). Finally, the extracted features were input into two typical clustering algorithms for clustering, and then the situational function and actual battlefield conditions were used to modify the clustering results, so as to forming a correct situation classification criteria. In the process of experiments, the optimal parameters adjustment, key feature extraction, clustering and correction were performed. Experimental results show that the model classification accuracy rate and the model runtime both meet the application requirements. In addition, the assessment results of the example are consistent with the actual situation. Therefore, the proposed method is of practical value.

Abstract:To solve the problem of the exponential growth of the Gaussian mixture components for estimating the state of the non-Gaussian system with the Gaussian mixture model, a cluster-fusion algorithm based on the similarity distribution criterion was proposed. According to that criterion, the Gaussian components were then clustered into different Gauss clusters based on the optimal confidence interval, derived by minimizing the extended integral square error cost function. Meanwhile, to avoid the reuse of the cross components, the local nearest neighbor approach was introduced to re-allocate these cross ones. Then, the components in the clusters were merged by the multielement mergence method to keep with the unbiased property, which can decrease the number of the mixture components sharply. The results show that the proposed algorithm can not only reduce the running time, but also guarantee the tracking performance with a proper confidence interval.

Abstract:For studying how to select the algorithm parameters, which are wavelet basis, wavelet coefficient processing method and threshold calculation method respectively, in stationary wavelet denoising algorithm to obtain the optimal denoising performance. The denoising performance under different parameters, the selection of orthogonal filter banks and the wavelet coefficients processing method in stationary wavelet denoising algorithm were proposed and compared. The results show that: compared with other filter banks, the filter bank corresponded to Daubechies wavelet basis can achieve a better denoising performance; the soft thresholding method should be selected for processing wavelet coefficient in low signal noise ratio condition, and the hard thresholding method should be utilized when signal noise ratio is high; when using the thresholding method to process the wavelet coefficients, the threshold value should be calculated by the sqtwolog method in low signal noise ratio condition, and rigrsure method should be adopted when the signal noise ratio is high.

Abstract:In order to optimize the performance of graphene electroacoustic transducer, the research on the electroacoustic mechanism of graphene thermoacoustic sound device and graphene electrostatic sound device was conducted. Through theory modeling and analysis, the influence of structural parameters such as size, thickness and stress of graphene film on the frequency response characteristics of two kinds of electroacoustic transducers was obtained. Finally, a batch of electroacoustic transducers with different structural parameters were designed and fabricated. The performance test and comparison analysis of these devices show that the thickness of graphene film has a significant influence on the sound pressure of the thermoacoustic transducer, that is, the thinner the film is, the larger the sound pressure of the electroacoustic transducer is. The electrostatic transducer is influenced by the radius, thickness and stress of graphene film, that is, the corresponding film with larger radius, thinner thickness and smaller stress of the electrostatic transducer will have a wider frequency bandwidth. This research can lend support for the optimizing selection of graphene electroacoustic transducer, the optimizing design of structural parameters and the improvement of the device′s sound performance.

Abstract:In order to improve the computational stability and accuracy of the acoustic wavenumber integration propagator matrix approach, the automatic selection algorithm for maximum truncate wavenumber based on predictor-corrector theory was proposed. The algorithm has the advantages of simple, reliable and small computational load. The test results of acoustic spherical wave in free space show that the stability of propagator with the order of bottom to top is relatively poor, the non-physical divergence of the wavenumber kernel function is easy to appear above the sound source, so it was necessary to use different truncate wavenumbers at different depths to calculate the correct result; while the calculation stability and precision of propagator with the order of bottom to source and top to source respectively reach higher levels.

Abstract:Oxygen concentration and seawater conductivity are important factors affecting the corrosion behavior in seawater, and these two factors mainly depend on salinity and temperature of seawater. The model of impressed current cathodic protection and corrosion electrostatic field was established by using the boundary element method. The effects of oxygen concentration, seawater conductivity and diffusion coefficient of oxygen on the corrosion related electrostatic field of the ship at different seawater temperatures were studied. The results show that the peak value of the corrosion electrostatic field decreases with the increase of temperature. When the output current of the two pairs of anodes are 13.5 A and 8 A, respectively, the hull and the rudder are in overprotection at low temperatures and underprotection at high temperatures accordingly, but the propeller and the shaft get perfect protection at all temperatures.

Abstract:The prediction of remaining useful life for T/R module is significant for equipment support personnel to master current health status of equipment and to improve the level of repair and maintenance. The fault characteristics of T/R module were analyzed and the indices reflecting the degradation process of T/R module were screened out, the remaining life prediction result of T/R module was obtained by calculating the remaining life information and weight of each index. The practicability and effectiveness of the prediction method were demonstrated by experimental example analysis and comparison. The results can provide theoretical guidance for predicting the remaining life of electronic equipment, and it is significant for planning maintenance resources reasonably and improving battle effectiveness of equipment.