Abstract:In order to obtain the influence law of structure parameters on the combustion characteristics, the numerical analysis of gaseous methane and gaseous oxygen GO₂/GCH₄ single-element splash platelet injector was investigated, and the characteristics of both chamber length and nozzle width of faceplate were studied. The chemical N-S equations were solved for the flow field, and 1-step 9-species chemical dynamic model was used to describe the reaction of methane and oxygen. The results indicate that, the characteristic velocity increases with the increase of characteristic chamber length. Under these design parameters, the corresponding value of chamber characteristic length is about 600 mm. By contrast, when the nozzle width is 0.15 mm, the mole fraction of H₂O has the biggest difference from the theoretical value; the temperatures of flow field increase at the fastest level when the nozzle width equals to 1.05 mm but increase at the slowest level when the nozzle width equals to 0.45 mm. In short, the nozzle width equals to 0.75 mm, the injector can reach the maximum combustion efficiency and the shortest combustion length compared to other cases.

Abstract:The unmanned underwater vehicle hybrid propulsion system exploits the exothermic reaction between aluminum and water which will produce high temperature, pressure steam and hydrogen mixture that can be used to drive turbine to generate power. The research shows that this system has high energy density. Three new system configurations corresponding to different working cycles were investigated respectively, and their performance parameters in terms of net power, energy density and global efficiency were discussed. The results of the simulation show that the reaction between the direct return of high temperature steam and the aluminum enhances the temperature of steam, and the system′s performance is reduced. An evaporator component and a solid heat exchanger are added into system in order to make full use of the solid product heat, and so the system performance is improved. The addition of double combustion chamber and wall cooling structure avoid the design of the high temperature compressor component on one hand, and solve the thermal protection of the combustion chamber on the other hand, which brings the improvement of the system performance. The results can provide useful information for the overall design of the unmanned underwater vehicle hybrid propulsion system.

Abstract:Taking the classic wing pylon finned store model for example, the overset grid system and CFD (computational fluid dynamics) technology were utilized to study the aerodynamic interference characteristics of the external store separation from two aspects:the interference condition simplification and the analysis of factors influencing aerodynamic interference characteristics. The predicted results of missile separation trajectory parameters and aerodynamic interference coefficients coincide well with the CTS(captive trajectory system) results, which indicates that the proposed computing method can effectively predict the separation trajectory and complex aerodynamic interference between the missile and aircraft. Based on the results of CFD numerical simulations, the missile aerodynamic interference law of separation can be obtained for different working conditions of mach number, wing angle of attack, missile angle of attack and so on. Furthermore, the incremental coefficient method with first-order heterodyne processing is also obtained to give aerodynamic interference data for the defect working condition. The proposed method can be utilized to predict the separation trajectory and to design the aerodynamic interference characteristics between the missile and aircraft, thus producing great values in practical engineering applications. 

Abstract:In order to realize intercept angle constraint and finite-time convergence when a missile intercepts a maneuvering target, a guidance model was proposed on the basis of the first-order missile dynamics. By regarding the target acceleration as unknown bounded external disturbance, and by applying the dynamic surface of nonlinear backstepping theory, a nonsingular sliding mode guidance law with missile dynamic was designed. Based on the Lyapunov stability theory, it was proved that the states of guidance system asymptotically converged to zero. Simulations on intercepting targets with constant maneuvering of low attitude and high velocity were made. Simulation results indicate that the designed guidance law can effectively reduce the influence caused by the missile dynamic delay, and the miss distance and the intercept angle error are small; by comparison with the optimal guidance law with missile dynamic and intercept angle constraint, the designed guidance law has higher guidance accuracy. 

Abstract:Regarding the influence to the inertial navigation system of missile by disturbing gravity was focused, a polynomial fitting method was used to express disturbing gravity along the trajectory, and an analytical expression for calculating the deviation from the nominal value without considering disturbing gravity was deduced based on the linear system theory and the perturbation theory. Moreover, the coupling property between disturbing gravity and apparent acceleration was considered. The apparent acceleration deviation caused by disturbing gravity was regarded as an additional term of disturbing gravity, and was corrected by iterative method. The simulation results show that the error of disturbing gravity fitting method is less than 3×10^-7m/s², and the residual error of the analytical formula considering the compensation of the apparent acceleration deviation is about 1/3 of the original method, and the computation time is only 1/10 of the numerical integration method.

Abstract:The skirt bonding properties of the composite case was analyzed by using the numerical method. The finite element model of the filament wound case was established. The contact of the skirt bonding interface was defined with the cohesive zone model. The damage failure criterion was employed and the debonding of the interface was simulated to predict the ultimate load of the skirt structure. Moreover, the distributions of the axial strain and the hoop strain on the case and the shear stress in the interface were investigated. The effects of the elastic modulus and the bonding length on the ultimate tensile load were studied. Numerical example shows that the results have a good agreement with the experimental data, which can provide validity for the present method. The proposed method can be applied to the optimal design of the skirt structure.

Abstract:According to the working characteristics of SpaceWire network in hotspot communication mode, the buffer allocation algorithm was studied. The definition of uniform communication mode and hotspot communication mode were given; the calculation method of full-load probability and the average delay of nodes in the network were deduced, and the key communication nodes in the network were calculated; the buffer allocation algorithm for SpaceWire network was derived. Then, the SpaceWire communication model was established by using the Opnet network simulation platform, and the key performance indexes of the different communication modes were simulated before and after adopting the buffer optimization strategy. The study results show that, in the hotspot communication mode, the buffer allocation algorithm reduces the average delay of the network system under the same total resource. The performance of the SpaceWire network is optimized.

Abstract:A numerical predictor corrector guidance with environmental parameter online identification was proposed for boosting glide missile. Comprehensive environment parameter was introduced in gliding phase concerning both atmospheric density and aerodynamic parameter influence. Extend Kalman filter was used to identify the comprehensive parameter online. Based on identification results, gradual fading-memory recursion least square method was used to build identification model of environment parameter. And the model was gradually revised based on the updated identification. Longitudinal and lateral guidance laws were designed. Drop point was estimated based on the identification model to limit the influence of environmental disturbance. The guidance simulations were carried out with atmosphere density and aerodynamic disturbance. The results demonstrate the identification model can predict the environment parameters accurately and the guidance method has enough robustness to environmental disturbance.

Abstract:In order to increase the connect reliability between the core stage and the boosters of the launch vehicle, the boosters with large fineness ratio can use hyper-static strap-on style. However, it may increase the analysis difficulty of the dynamic characters. Therefore, the dynamic model of booster with hyper-static strap-on style was established, and the bi-linear stiffness spring was employed to simulate the strap-on equipment. The dynamic response of the booster by the radial impulsion will be researched. The responses, including generalized displacements, frequency and the internal force will be compared with the static strapon style. Research results can provide reference and theoretical support for the engineering application.

Abstract:Solar power is normally the only persistent power for satellites, so the energy supply problem of onboard devices is more difficult than that of the terrestrial networks. To fit the special architecture of satellite networks, the capacitated multi-commodity minimum cost flow model with constrained link capacity was modified and extended. Meanwhile, based on the multi-coverage scheme and traffic distribution patents in satellite networks, the existing heuristic algorithms were improved to turn off the unnecessary satellites, up-down links and inter-satellite links for energy saving. Under the constraints of link utilization and routing hops increasing ratio, the closing ratios of the three parameters are up to 59%, 61% and 72% respectively, and the total energy saving ratio can be up to 65% in simulation.

Abstract:Space-time coding techniques are used to mitigate cross-correlation in the multiple-input multipleoutput radar. However, the imaging algorithms based on the conventional space-time coding schemes cannot accurately compensate the range-azimuth coupling, which limits the ability to handle the radar data acquired at high squint angles. To avoid the above drawback, a space-time coding scheme combined with ωK algorithm was proposed. In the space-time decoding processing, the modified decoding matrix and Stolt mapping operation were introduced to achieve the bulk focusing and differential focusing simultaneously, and the range-azimuth coupling could be accurately compensated. Theoretical analysis and simulation results show that the high quality imaging in the case of high squint angles can be achieved by the proposed scheme, and the cross-correlation interference can be canceled.

Abstract:Antenna beam steering along azimuth of sliding spotlight SAR(synthetic aperture radar) system was accomplished by step steering scan in practical operation. However, this scanning method may cause the paired-echo in the image of sliding spotlight SAR. To analyze the reason of pairedecho, the step steering scan model of sliding spotlight SAR was established. And the relationship in quantitatively between beam stepped steering and both amplitude and position of paired-echo by Tyler series expanding and Fourier series were calculated out. The theory analysis and signal simulation indicate that the model demonstrates the phenomenon well, and the model provides the theory basis for the design of the sliding spotlight SAR beam steering scan parameters.

Abstract:In order to make the process of CSAR (circular synthetic aperture radar) imaging more efficient, a fast time-domain CSAR imaging method was presented. The proposed method was based on the circular aperture of the CSAR model, and the full aperture was divided into several sub-apertures; those sub-apertures were processed by the fast factorized back projection algorithm to get their corresponding sub-images; the final focused image was obtained by the coherent interpolation of the sub-images from the polar coordinate to the global coordinate system. Some key problems in the algorithm realization, such as coordinate transformation, error control and computation efficiency, were analyzed in detail. Experiments results based on the simulated data and real data were given to prove the validity of the proposed method. The proposed method has the advantages of improving imaging extension and lowering computational complexity.

Abstract:The stress image method and the perfect matching layer method were used to deal with the boundary problem of shallow water ship seismic wave field simulation. The algorithm fully considers the shallow water environment and the excitation mechanism of the seismic wave. Based on the first-order velocity-stress equation, staggered grid finite difference method was taken to discretize the equations. The stress mirror method was applied to deal with free surface of seawater and air. The split boundary perfectly matched layer method was applied to deal with the boundary of the computing area. The parallel and inclined seafloor seismic wave fields were computed. The results before and after were compared, which shows that if the boundary is not treated, serious reflection would cover up the original wave field characteristics, but after the treatment, each case of wave field wave line and wave propagation rules are quite clear. So this method completely conforms to the shallow water ship seismic wave field numerical simulation requirements.

Abstract:In order to decrease the computation complexity of the spoofing detection methods for antenna-array GNSS(global navigation satellite system) receivers, a spoofing detection method before signals despreading was proposed. The correlation difference of signal and noise on different antenna elements was used in signal power estimation. Then the spoofing was differentiated according to the estimated signal power. Simulation result indicates the effectiveness of the proposed method and the reduction of computation complexity.

Abstract:In order to improve the operation reliability of oscillator, a novel radiation-hardened-by-design VCO (voltage-controlled-oscillator) using interleaved structure was presented. The VCO consists of multi-stage delay cells which apply interleaved structure and can complete majority decision voter, so it is tolerant to single-event transient effect. Additionally, the VCO can generate symmetric multi-phase output as no additional module for majority decision voter is needed to be introduced in it. The radiation-harden differential VCO was implemented in a 130 nm bulk complementary metal oxide semiconductor process. Simulation results show that, when deposited charges range from 100 fC to 800 fC, the maximum phase displacement generated by a single simulated ion strike for the proposed VCO output is less than 0.35 rad.

Abstract:The large-capacity data storage device of spacecraft mainly adopts the solid-state storage based on NAND Flash chip. However, due to data bit error caused by the single event upset of the space environment and the threshold voltage deviation during memory operation, the data reliability of the storage device is reduced. According to the physical structure and data structure of the NAND Flash chip, an error detection and correction coding design with RS(256,252)+LDPC(8192,7154) cascade encoder circuit was proposed, for improving the error tolerance of data storage devices. Moreover, the method for circuit realizing of the coding algorithm was optimized. The results of modeling simulation and the ground system testing prove that the solid-state storage controller system has the advantages of low hardware consumption, low power consumption and high reliability. In addition, the total capacity of the storage system reaches 512 Gb, and the effective data throughput is 700 Mb/s, which can meet the design requirements of large-capacity data control and high-data throughput for solid state storage controller of spacecraft.

Abstract:The ADMM (alternating direction method of multipliers) with appropriate parameters plays a successful role in solving linear inverse problems (including image restoration). But the results obtained by ADMM are sensitive to the choices of the penalty parameter, and this bad robustness brought some troubles in its applications. Based on a scheme of choosing the penalty parameter adaptively, a RADMM (robust ADMM) was proposed to tackle this shortcoming. Through analyzing optimization conditions and convergence of RADMM, we can conclude that the adaptive control of the penalty parameter provides good robustness, faster speed of convergence and better solution. And the experiments show that, in the application of image restoration based on the Parseval tight frame, the RADMM is robust to the choices of the penalty parameter, outperforms the ADMM, and is far superior to other alternative state-of-the-art methods.

Abstract:The conventional vector field method is very susceptible to unsteady wind disturbances in the handling of UAV (unmanned aerial vehicle) curved path following problems, which increases the tracking error. Therefore, many methods use the inertial coordinate system of a vehicle (the ground speed and the course) instead of the body coordinate system (the airspeed and the yaw angle) to improve the wind resistance. However, this method can only handle the wind disturbances with constant amplitude and direction, which is an ideal assumption in actual flight. In order to overcome these deficiencies, an integrated vector field method was proposed for actively cancelling unsteady wind disturbances using the integral of side-offsets for the curved path following of a fixed-wing UAV. According to the curvature of the desired path and the path angle, the curved path following strategy was designed on the basis of the state information of the vehicle itself, and the Lyapunov theory was used to prove that the proposed method can ensure the global asymptotic stability of the closedloop system. Finally, the wind tracking performance of the proposed method was verified through the high performance hardware-in-the-loop simulation system.

Abstract:With the widespread use of PMBLDCM（permanent magnet brushless direct current motor）, high-power, high-capacity drive technology is one of its research direction. The parallel operation of drivers can effectively expand the drive system’s capacity, but the way is easy to introduce the circulate current. In order to restrain the circulate current, the system including separate direct current power supply for two paralleled inverters that feed the PMBLDCM was analyzed and the character of the system’s circulate current was inferred. The control structure based on the circulate current feedback was put forward. The control structure only needs to control one inverter. Simulation results represent that the control structure can make two direct current supplies that have different amplitudes feed the load, and suppress the circulate current, which achieves a separate power supply brushless direct current motor with drivers in parallel.

Abstract:A truncation function-based finite-time sliding mode control strategy was presented to address the robust control problem of the second-order nonlinear uncertain system. The advantages of the proposed method are as follows: the system states will converge to zero at the desired finite time; the controlled system is globally robust against external disturbance and parameter variation; the system response can be analytically expressed; the system performance can be tuned by selecting different truncation function. Simulation results validate the effectiveness of the proposed method.

Abstract:In order to improve the usability of PRTH (portable rope-track hoist), the friction-based PRTH lifting capacity was studied. The influence of tension at the end of the rope, wrap angle and relative size on the friction between the wheel and the rope was experimentally studied by using the control variant method. The results show that: the friction increases with the increase of the three factors, but the trend is slowed down; the coefficient of static friction decreases with the increase of the end tension and the wrap angle and tends to be stable, and it increases with the relative size of the wheel to the rope and converges to a constant. The effects of wrap angle and end tension on the friction were demonstrated to be identical to each other, the size effect of wheel-rope friction was found, and a new lifting capacity model on wheel-rope friction was established with the three factors. The model is the sublation of Euler formula, deepens the understanding of the friction law between the wheel and the rope, and is of great significance to the miniaturization and lightweight design of PRTH.

Abstract:For inner pressure tank, with the comparison of stress variation of pressure tank frames at two different forms of connection, the influence of different loading conditions on deformation and stress characteristics of the tank shell plate was analyzed. The results show that for different connection forms, the best angle β between the section changing location and the tank top plate exists with each form. In the circumferential range, different schemes mainly affect the tank top plate longitudinal stress and the circumferential stress of the frame and rib is affected by the β values.

Abstract:Aiming at the QoS(quality of service) and delay problems of aeronautic Ad Hoc network under high load, a DQM transmission mechanism was proposed(dynamic QoS of multi-channel MAC). On the basis of multi-channel detection statistics and the priority mechanism, the DQM optimized the network traffic via shutting down the low-priority traffic in the high-load network timely to ensure the low-latency transmission of high-priority traffic. The traffic prediction model was used to estimate the network traffic. Combined the particle swarm optimization algorithm, the DQM could find the optimal priority threshold and guarantee the access rate of highpriority services. Simulation results prove that the DQM maintains an optimized network traffic by adaptively controlling channel access in high-load network. Thus, the access rate of high-priority services reaches above 99%, which helps to solve the QoS and latency issues associated with high traffic in the air data link.

Abstract:In terms of the reliability analysis of ultimate longitudinal strength of naval ships in-service based on the data of pitting corrosion recorded, the non-probabilistic reliability analysis theory was introduced. A new method to analyze the ultimate longitudinal strength reliability under the present condition was put forward for hull structures，the non-probabilistic reliability analysis model was established, and the application of non-probability reliability method on condition assessment of hull structure was analyzed. Results show that the proposed theory overcomes the defects that relied too much on the corrosion sample library， the consequence tends to be more realistic than the deterministic method, and the non-probabilistic reliability analysis theory has a good application prospect for condition assessment of naval ships.

Abstract:Considering the connections between frame and skin of composite rudder, two types of T connections were designed to test the ultimate load carrying capacity when suffering to wave load. According to the load characteristics of structure, a typical local experimental model was extracted, and the load equivalence method was proposed as well. The difference of load characteristics of two types of T connections was compared, and the effect of span on initial stiffness, ultimate failure load and ultimate bearing moment were studied. The results show that type A has obvious initial failure, but the ultimate failure load is larger than that of type B, the ultimate bearing moment does not change with the span, and can be evaluation criterion for different span and different types of T connections. The evaluation method for bearing capacity of T connections was proposed based on the experimental results, load equivalent method and shrinkage principle.

Abstract:Parameter sensitivity analysis of nuclear reactor passive system is the main part of uncertainty analysis for passive system reliability. There are drawbacks for correlation coefficient to describe the parameter sensitivity of success criteria of passive system physical progress. So an iterative method was proposed, the method took account of correlation coefficient and partial correlation coefficient for input parameters, success criteria and correlation coefficient between parameters comprehensively, and the validity and practicability of the method were verified by a specific case. It is suitable for iterative method to analyze partial correlation of success criteria, to recognize more accurate sensitivity parameters and to provide reference for improving reliability of passive system physical process.