Abstract:Two kinds of combined-cycle propulsions were studied to meet the requirement of a hypersonic vehicle that cruises at Mach number 6. One consists of T/RJ/DMSJ (turbine engine, ramjet and dual mode scramjet), while the other consists of PCT/RJ/DMSJ (pre-cooled turbine engine, ramjet and dual mode scramjet). The ranges and the flying time of the hypersonic vehicle which uses T/RJ/DMSJ and PCT/RJ/DMSJ were obtained under thrust weight ratio of 0.8 and 1.0 with a given mission. The performances of two operating mode of PCT/RJ/DMSJ were compared. Results show that the range and the flying time of the two combined-cycle propulsions are almost close. The range of PCT/RJ/DMSJ is 3.6% higher than T/RJ/DMSJ and the flying time of PCT/RJ/DMSJ is 3.8% more than T/RJ/DMSJ under thrust weight ratio of 0.8. When the thrust weight ratio is 1.0, the range and the flying time of PCT/RJ/DMSJ are 4.6% and 4.8% higher than T/RJ/DMSJ, respectively. Under the lower thrust weight ratio, the fuel consumption of the transonic flying phase is the largest part during the acceleration and climbing process. The fuel consumption of the transonic flying phase decreases as the increase of thrust weight ratio and then more fuel can be used in the hypersonic cruise and the cruise distance increases. The range increases and the flying time decreases as the increase of thrust weight ratio.

Abstract:To satisfy the requirement for autonomous scientific detection in resource constrained planetary rover exploration mission, a centralized payload control method was proposed. A novel highly integrated hardware architecture was constructed by integrating payload electronics units and traditional payload OBDH (onboard data handling) unit. The software adopted the control method based on the event table and work mode table to control the payload autonomously. Several health management measures were taken to make fault recovery and isolation according to pre-defined rules. The common control part weighs only 3 kg, and consumes 6 W power. The software supports 9 work mode tables running at the same time. Instruction executing time accuracy is better than 40 ms.The method has been applied to China first Mars exploration. Ground test results show that the method is simple, efficient and reliable, and suitable for payload control in planetary rover exploration missions with harsh resource constraints.

Abstract:In order to analyze the atomization mechanism of gas liquid swirl injector, a temporal linear stability analysis method was used to investigate the conical liquid film with coaxial annular gas flow. The dispersion equation of a conical liquid film with coaxial annular gas flow was derived and a prediction model was proposed to calculate the parameters needed in solving the dispersion equation. The results show that the film thickness at the injector exit decreases with the increase of pressure drop while the spray cone angle, liquid film velocity and liquid film axial velocity increase with the increase of pressure drop. The sinuous mode disturbance wave dominates the breakup process of conical liquid film with coaxial annular gas flow because the growth rate of sinuous wave is much larger than that of varicose wave. When the gas flow velocity is small, the increase of gas velocity reduces the relative velocity of gas and liquid, which weakens the gas liquid interaction and eliminates the growth rate and frequency of the dominant wave. Finally the breakup time and breakup length increases. However, when the gas velocity is larger than a critical value, the growth rate and frequency of the dominant surface wave increase rapidly with the increase of gas flow velocity, which in turn lowers the breakup time and breakup length immediately.

Abstract:Aiming at the design requirements of easy separation and light mass for the sabot of integrated launch projectile, an optimization design model was obtained by combining the aerodynamic calculation model by the genetic algorithm, in which the aerodynamic calculation model was established on the basis of the theory of shock and expansion wave through building the parameterized structure model for windward nest. And the discard acceleration and sabot′s mass were used as the indicators to build performance function. Taking the sabot design of armor piercing fin stabilized discarding sabot of medium caliber as an example, the proposed optimization model was used for the optimum structural design of the windward nest, and the simulation model of sabot discard based on dynamic grid technique was adopted to verify the optimality. Simulation results show that the proposed optimization design model can obtain the optimal wind′s eye of the sabot; in view of the existing armor piercing fin stabilized discarding sabot of medium caliber, the sabot structure can be further optimized to improve its rapidity.

Abstract:In order to reduce the size of coolant supply system of opposing jet in hypersonic vehicles, the fuel gas generating with solid fuel was adopted as an opposing jet. The RANS (reynolds-average navier-stokes) equations coupled with the Menter′s SST (shear stress transport) model was employed to solve the opposing jet flow field of hypersonic hemisphere model. The typical results have been validated with experiments performed in the literature. The influence of the high temperature fuel gas on the hemisphere model thermal protection characteristics was analyzed with different flying condition. Results show that the high temperature fuel gas weakens the heat flux reduction of opposing jet, but the peak heat flux exhibits a prominent reduction in contrast to that without injection.The cooling efficiency can be strengthened by increasing the jet pressure. With a reasonable jet pressure, the similar cooling efficiency can be obtained compared with that of the normal coolant and it does not result in additional mass flux. Moreover, the three solid fuel and its combustion temperature are listed. For high Mach flying which is higher than 6, the solid fuel can provide required jet temperature for opposing jet thermal protection system.

Abstract:The governing equations using primitive properties of pressure, velocity and temperature as dependent variables, but constructed in the conservative form can be applied for calculating solutions for steady state problems. When the method was recently used to simulate a canonical shock-tube problem, however, overshoot of temperature was observed after the shock. Moreover, the errors cannot be eliminated by using fine grid, high spatial order of accuracy or any alternative inviscid fluxes schemes that are available, implying the numerical discrepancy may be caused by the method itself. Numerical analysis was conducted on the method using the one-dimensional Euler equations as the model equation system. It can be shown that the numerical error specifically arises from the discretized time terms. A dual-time-looping technique was developed to address the issue. It used conservative variables in physical-time derivatives while primitive variables for pseudo-time terms. An inner iteration procedure within two adjacent physical-time steps were driven until a steady state was reached. The resulting governing equation converged to the corresponding conservative form in time, and the time-accurate solution was recovered.

Abstract:The problem of any selected position hovering control of uncontrolled tumbling satellite was researched. A three-dimensional relative motion equation of arbitrary eccentricity was established in the target orbital coordinate system, and the attitude motion characteristics of the uncontrolled tumbling satellite were analyzed. The hovering problem was decoupled into two-dimensional fuzzy control problem of three channels, and the Mamdani fuzzy controller was designed with the channel x as an example. Determining the corresponding fuzzy subset, membership function and fuzzy control rule table, the fuzzy was solved by using the area center method. The control performance of the designed fuzzy controller was verified by numerical simulations.

Abstract:It is focused on CE-4 lunar orbit duel micro satellites mission for super-long wave astronomy. Under the strict resource constraints, the lunar orbit micro-nano satellites have very limited communication bandwidth. In order to maximize valuable scientific data, a method of in-orbit signal preprocessing was presented: the digital down conversion method was used to build the ultra-narrowband filter, which significantly reduces the data rate. The ultra-narrowband filtering scheme can perform comb filtering by increasing the down-conversion filter channels. The ultra-narrowband filter scheme simulations on the field programmable gate array show that the key technical indicators such as flatness and linear phase meet the requirements, and the data rate can be reduced by more than 10³ times compared with original data rate under the circumstances of the sampling rate is 80 MSPS with baseband bandwidth is 1 kHz.

Abstract:In order to obtain the theoretical model of the axial residual velocity of PELE (penetration with enhanced lateral efficiency projectile) under the condition of vertical penetration, the plane shock wave theory was used to analyze the mechanism of PELE vertical penetrating metal thin target. According to the penetration model of the flat head projectile, the energy loss during the penetration of PELE was divided into the following parts: the energy obtained by the annular plug block corresponded to the outer shell and the inner core, the increased internal energy of the outer casing and inner core, the shear energy dissipated in the outer casing. Based on the principle of energy conservation, the theoretical model of axial residual velocity after PELE vertical penetrating thin metal targets was obtained. To verify the rationality and accuracy of the theoretical model, the corresponding experiments were designed to verify the results. The results show that the calculated results coincide well with the experimental results under different conditions. Therefore, the theoretical model of axial residual velocity of PELE vertical penetrating thin target can provide guidance and reference for engineering application.

Abstract:In order to solve effectively many shortcoming of traditional load design, a threesection method, namely segment stiffness, segment mass and segment aerodynamics, for the load design of aircraft was presented. The method approximates the actual mass distribution and aerodynamic load distribution of the aircraft. For a simplified aircraft, the modal parameters and the section load were calculated by using the threesection method, the theoretical method and the masspartition method. The results show, the threesection method and the theoretical method are consistent with the model parameters and the calculation principle, which largely can be considered as a method, so their modal parameters and the section load are identical. The load of the left and right section of the masspartition method is pretty inconsistent, and it is not in accordance with the actual load condition. In a word, the threesection method can get a more real and reasonable section load distribution, and the engineering application is simple, reasonable and reliable. At the same time, the method can reduce the design difficulty of missile load and structure.

Abstract:In order to improve the mixing performance of fan bypass and CDFS (core driven fan stage) bypass, a innovative configuration of FVABI (front variable area bypass injector) with jet mixing enhancement was proposed. Numerical simulation was performed to investigate mass flow rate characteristic, flow mixing and total pressure loss of FVABI configuration with lobed mixer. Compared with the baseline configuration, the predictions are discussed and several conclusions can be summarized. Firstly, the significant improvement in fan bypass mass flow rate is achieved by jet mixing enhanced configuration at high back pressure operating point. Secondly, the performance is not degraded at low back pressure operating situation, but the total pressure loss is decreased at high back pressure operating point. Finally, the characteristic length of stream-wise vortex is the key to improve mixing performance, and the optimization of lobed mixer is available to match further structural requirement of adjust configuration.

Abstract:The back electromotive force of the non-contact actuator in a disturbance-free-payload spacecraft can cause the coupling between payload module and support module, hence can be detrimental to the precise pointing of payload module. To analyze its effect, a coupling dynamics model was established for the disturbancefreepayload spacecraft. In consideration of the cubic architecture disturbance-free-payload-interface, this dynamics model was developed by a combination of the Newton-Euler method with the Lagrange formulation. The output force of the non-contact actuator was derived, which was introduced into the dynamics model of the payload module platform, then the coupling dynamics model with the back electromotive force was obtained. Considering the harmonic vibration caused by the static and dynamic unbalance of the flywheels as the disturbance torque, an on-orbit pointing model for the disturbance-free-payload spacecraft was established in Simulink. The simulation results illustrate that the larger value of the back electromotive force coefficient will cause larger effect on payload module.

Abstract:Based on the traditional 1553B data bus protocol, a new protocol with plug and play features was designed by adding remote terminal EDS (electronic data sheet) and procedure of transferring EDS. According to this protocol, the plug and play resolution of 1553B bus controller was designed, including constructing a bus list algorithm with the remote terminals plug in，management data structure, and dynamic operation and control bus list method. The constructing bus list algorithm uses remote terminal EDS to analyze, calculate and transform an old bus list to a new one, to satisfy remote terminals′ communication requirements. A management data structure is used for analyzing and storing bus list information during initialization phase， to increase efficiency of operation control and data exchanging. Dynamic operation and control bus list method adopts main bus list with plug in messages method. The timeliness and use cases of the resolution were evaluated. The results show that its time of bus cycle and time of remote terminal plugged into the system can be accepted. The resolution can remain stable in the communication process, and provide flexibility for plug and play needs. In CCSDS-SOIS architecture, 1553B data bus is one of the subnetworks on the bottom layer. With plug and play features, it can be extended to support constructing plug and play system in higher layer.

Abstract:In order to realize the real-time and embedded operation of the model, a lightweight convolution neural network structure was proposed. By using a smaller filter size and introducing depthwise separable convolution, a large number of model parameters can be subtracted and the nonlinear capability can be improved. The sub-pixel convolution was introduced at the end of the network, then the mapping was learned directly from the original low-resolution image (without interpolation) to the high-resolution one, the cost is 1/k² as much as before (k is the magnification factor). Experimental results on Set5 show that the proposed model is more than 25.8 times faster than the classical super resolution reconstruction algorithm and can run in real-time on a common GPU; and the proposed method with only 35% parameters of SRCNN(super resolution convolution neural network), improves the PSNR(peak signal to noise ratio) with value of 0.17 dB.

Abstract:Aiming at the problems such as neglecting the dynamic changes in the conventional missile attacking envelop solution, a missile attack envelop classification model based on deep belief network was proposed. The missile attack envelop was divided into five parts according to the relationship between missile hits and target maneuvers. By analyzing the situation parameters which affect the attack result of air-to-air missile, a missile attack prediction model was constructed. In the experiments, the reconstruction error and the test error rate were used to determine the network structure. Through extracting data layer by layer, the features of parameters were analyzed and the approaches of fine-tuning data sampling were discussed. Back propagation network and support vector machine were selected for classification comparison experiments. The results show that the deep belief network performs better than the other two algorithms in speed and prediction accuracy and the presented method is of great practical value.

Abstract:With the deepening of the research on anti-encirclement strategy of underwater vehicles, the encirclement of underwater vehicles has been more and more difficult. For this reason, a multi-layer annular ambush capture model was constructed and a task assignment method based on the capture task was designed, so that the underwater vehicle can make full use of its own characteristics to complete the task better. At the same time, considering that the energy consumption in the system is uneven with the passage of time in the capture process, an energy balance method was proposed to balance the energy consumption of the system. Experiments show that the proposed task allocation method based on the energy balance strategy of multi-layer annular capture model can effectively improve the success rate of capture and prolong the life of the system.

Abstract:Remote sensing data, as national fundamental and strategic resources, plays an important role in economy, state security, environment protection and ecology. Since remote sensing data have been widely used in various industries, there is a large amount of data requests from different users, demanding a lot of valuable EOS (earth observation resources). On one hand, users′ data requests increase constantly. On the other hand, EOS resources are always limited. Our objective is to ease the contradiction between a large amount of users′ requests and limited EOS resources. The key idea is to merge identical or similar users′ requests in order to reduce the total number of requests, and then to use requirement forecasting and requirement mining technology to improve requirement fusion efficiency. It is high likely that different users may share identical or similar data requests, since users may show concerns about the same area of the earth over the same time range.

Abstract:In order to eliminate the ambiguity in the land cover classification of LiDAR point cloud by using the image texture, the texture feature of point cloud based on the searching structure of KD tree and the gray level co-occurrence matrix were proposed, which represents the distribution of attribute values of points and their surrounding neighborhood points. The influence of the parameters, such as search neighborhood, moving step and gray-level, on the texture features of point cloud was analyzed. Using the support vector machine classification method, it was verified that the texture feature of point cloud can effectively assist the elevation and intensity to improve the results of the land cover classification. In addition, the results demonstrated that the land cover classification under the constraint of the texture features of point cloud has higher accuracy than that under the constraint of the rasterbased image texture features, and the texture features of point cloud perform outstandingly in distinguishing tiny land objects and separating the water and land. These excellent characteristics of the texture features of point cloud can contribute significantly to the refined classification of coastal LiDAR data, the construction of highprecision DEM in coastal zone and the extraction of coastlines.

Abstract:ISRJ(interrupted-sampling repeater jamming) is an effective method to wideband imaging radar. According to the basic principle of ISRJ, when the jamming with conventional uniformly repeater is applied to wideband imaging radar, a string of uniformly spaced artificial scatters are overlain on the high resolution range profile. The artificial scatters′ characteristic of being uniformly spaced goes against with the camouflage of jamming signal. In order to solve this problem, based on the conventional ISRJ, a new jamming method using interrupted-sampling un-uniformly repeater, in which the main purpose was broken the uniformly spaced of artificial scatters, was put forward, and the effect of the new jamming method was also analyzed. Finally, by means of simulation, it is found that the new jamming method can promote jamming effect to wideband imaging radar.

Abstract:In order to describe the maintenance activities for the phased array radar′s antenna system, a time based maintenance model that “T/R unit can not be restored to as good as new” under the foundation of reliability was built. Firstly, the antenna′s construction parameters under the T/R unit failure in series were analyzed and the threshold value of failure T/R unit was determined. Then in view of the fact that“T/R unit can not be restored as good as new”, a maintenance model that minimizes the average cost per unit time under the restriction of antenna′s operational availability was established by introducing failure rate increasing factor. Finally, the marginal efficiency analysis algorithm was applied to achieve the optimized maintenance cycle and service group. Several examples are given to verify that the model excludes the restriction of “T/R unit cannot be restored to as good as new”, which are more in accordance with the actual situation and will provide the theoretical foundation for preventive maintenance policy.

Abstract:Accelerated degradation testing has been widely used to investigate the reliability of long lifetime products, including rubber seals. The test results at higher stress levels were extrapolated to the normal stress level in the accelerated degradation testing. For an accurate product reliability evaluation, the failure mechanism under accelerated stresses should be consistent with the mechanism under normal conditions. Based on the likelihood ratio test, an identification method and a flow chart were proposed. For describing the mechanism consistency and variation, log-linear and non-log-linear acceleration models were suggested, and the mixed-effects model was introduced to depict the degradation process. According to the judgment between the consistency and variation of acceleration model parameters, the identification was completed. The simulation test and the real test show that this method can identify the mechanism variation of rubber seals. Moreover, the stress boundary for consistent mechanism is found by the identification method.

Abstract:A speed control strategy based on integral sliding-mode was proposed to solve the problems such as poor control, large fluctuation and slow dynamic response of the output speed of servo motor system; the load torque observer was designed to resolve the load disturbance in the control process; the permanent magnet synchronous motor speed control model was established on the basis of the Simulink; the test system of motor was built to test and verify the steady-state performance and dynamic performance of the control system respectively. Experimental results show that, compared with the traditional proportion integration differentiation control and the ordinary SMC(sliding mode variable structure control), the designed control strategy can improve the robustness and rapidity of the system significantly and the chattering phenomenon of SMC control can be inhibited.

Abstract:At a certain frequency or in a band, one or several acoustic radiation modes which make a major contribution to the acoustic potential energy are defined as DARMs (dominant acoustic radiation modes) of coupling enclosure. The determination of DARMs is of virtual importance, and it directly affects the effect of active structural acoustic control. However, the current determination methods either one-sidedly emphasize the effect of radiation efficiency while ignoring the impact of modal amplitude, or require the knowledge of structural modes which was difficult to be extracted in engineering applications. To overcome these problems, comprehensively by the means of computation and testing, and fully considering both radiation efficiency and modal amplitude, a method based on “primary election-reservation-posteriori correction” was proposed to determine DARMs in coupling enclosure, and an experimental research was performed to verify the effectiveness and feasibility of the proposed method. Results show that the proposed method can accurately identify DARMs and does not require the knowledge of structural modes throughout the process, so it can be used to guide the selection of control objective or reconstruct the acoustic potential energy of coupling enclosure.

Abstract:In order to study the failure mechanism of large warship broadside protective liquid cabin, the scaled model of warhead and two kinds of liquid cabin structure, including exposure model and airtight model, were designed based on the bearing characteristics of the liquid cabin. The combined damage experiment of high-velocity fragment and shock wave under warhead close explosion, including two kinds of posture, were performed. According to the damage of liquid cabin model after test, the failure mechanism of front plate and back plate of liquid cabin under typical load was analyzed, and the failure mode and mechanism of liquid cabin structure was summarized and analyzed. The result shows that the high-velocity fragment is the main defensive object of protective liquid cabin, the drag and cavitation of fragment are the main stage of liquid cabin deformation and fracture, and the shock wave and cavitation squeezing pressure caused by penetration of fragment cluster into liquid cabin structure are the major load, which make structure deform and damage.

Abstract:Electro-hydraulic steering gear system adopted variable frequency speed control strategy, has a characteristic of obvious linear spectrum noise, and it is difficult to attenuate with the changing working condition. Combined with the principle of the electro hydraulic steering mechanism of double redundancy pump source, a pressure ripple control strategy based on the auxiliary pump source confluence was proposed, and it only changed the control system. The theoretical analysis indicates that the pressure ripple of odd harmonics can be attenuated when the two pump sources rotate at the same speed, and the initial phase difference at half cycle. Thus, the master slave synchronization control strategy was adopted, and the corresponding hardware was configured. With the method applying to actual steering gear system, the structure vibration on the pedestal can reduce 3~5 dB, and the first order line spectrum can attenuate 23 dB.

Abstract:Aiming at the inherent characteristics of complicated structure, multiple fault types and system uncertainty of marine main power plant, a quantitative algorithm for fault isolation and parameter estimation based on bicausal BG (bond graph) was developed. Based on sensor configuration scheme, the system bicausal BG model was built. By analyzing the model causal path, the system ARRs (analytical redundancy relations) were derived and the fault signature matrix was obtained. The LFT (linear fractional transformation) BG model was developed for fault simulation. Through coupling LFT and bicausal BG models, the fault isolation and parameter estimation of marine main power plant were realized and the effectiveness was validated by MATLAB/Simulink software. Results show that the bicausalled BG helps to simplify ARRs deviation, and the fault isolation and parameter estimation can be effectively realized and the fault status can be tracked and predicted by analyzing the element constitutive equation of bicausalled BG.

Abstract:Considering the highdynamics, incomplete information and uncertainty of massive operations, on the basis of the analysis and induction of a methods was proposed to solve the problem of dynamic weapon target assignment, a comprehensive mathematical of dynamic game based on both sides was made in structure, a phased solution was provided based on Nash equilibrium algorithm and Pareto optimization. The results validate that combining the mathematical model with the game theory method can effectively deal with the problem of dynamic weapon target assignment efficiently.