Abstract:The equations describing the relative dynamics was established by using a modified polar coordinate. The capture region of the typical guidance law for intercepting the hypersonic target was derived, and the optimal intercept geometry which is the zero effort miss steering was derived. The missile speed, the missile height, the characteristics of seeker and terminal capture region were analyzed. Then, the influence factors, application, features of handover window and calculation flow were analyzed. Taking the pure proportional navigation guidance law as an example, the mid-course and terminal guidance handover window and the zero effort interception handover region were described quantitatively. Finally a simulation was performed to verify the feasibility of the handover window.

Abstract:Aimed at the changing progress that sabot moves from contacting to the projectile′s body to doing 6-DOF(degree of freedom) motion revolving around sabot′s centroid, a simulation model for sabot′s discard based on motion separation and coupling the fluid control equation and 6-DOF equation by using dynamic mesh was proposed. Taking APFSDS (armor piercing fin stabilized discarding sabot) for example, this model was used to simulate the sabot′s discard under different Mach numbers and analyze the variations of dynamic coefficients of sabot and projectile body. Simulation results show that the bigger the discard Mach number is, the closer to projectile′s body the sabot′s trajectory is, and also the shorter the discard time is, but the further the discard distance is. The validity of the proposed sabot′s discard simulation model was verified by a comparison with the experiment data. 

Abstract:A method of measuring the relative pose of satelliterocket separation based on vision was presented. For the camera parameters were known, the camera was installed on the carrier rocket, and more than six cooperation signs were fixed on the satellite. The cameras can take pictures of the cooperation signs in real time. Based on the basic principle of monocular vision pose estimation, the relative pose relationship between satellite and rocket was solved by combining efficient perspectivenpoint with orthogonal iteration. The simulation experiment and the semiphysical simulation experiment prove the feasibility and accuracy of the proposed method.

Abstract:The models of attitude movement were established in order to study the influence factors of ATEA(average torque equilibrium attitude) of the space station. The influence of the air torque on the ATEA(average torque equilibrium attitude) of the space station was analyzed. The models of dynamic and control of the space station were established. A typical proportion derivative controller was used. Groups of 24 ATEA were separately obtained under two conditions. The results show that the air torque exhibits a significant influence on ATEA. In order to keep the ATEA of the space station, periodicity of control torque need to be provided. The momentum unloading and accumulating effects of the space station induced by air torque cannot be neglected.

Abstract:The viscoelastic Poisson′s ration master curve of solid propellant was established on the basis of the time-temperature equivalence principle and WLF equation, and then the viscoelastic constitutive model of solid propellant was proposed. The viscoelastic constitutive model in incremental form was deduced on the basis of the incremental finite element method and by adopting the fully explicit integration method. The constitutive model was realized in finite element software by using the consistent tangent stiffness acquired according to the programming rules of user subroutine in MSC.Marc. The stress-strain mechanical response of solid propellant grains was analyzed by using the viscoelastic and the elastic Poisson′s ration under solidification process and ignition pressurization process. Furthermore, the effects of different kind of Poisson′s rations on the stress-strain field were compared. The method and result can provide a reference for the structural integrity analysis of engine grain.

Abstract:To solve the high dynamic pressure testing problem while ballistic missile is in flight testing with high-altitude launch site, a test trajectory design method for simulating high dynamic pressure condition was proposed. Firstly, aimed at the actual characteristics of launch site, the dynamic model of wreckage reentry and the impact area boundary model were established. Then, the high dynamic pressure simulated condition was transferred to a process constraint, and a powered phase united optimization strategy was proposed. Based on the adaptive simulated annealing algorithm, three test trajectories meeting different high dynamic pressure simulated conditions and all constraints were designed separately, meanwhile the impact area adjusted program was generated correspondingly, and its feasibility was demonstrated. Results illustrates that the maximal dynamic pressure occurs in the first stage, the maximal negative angle of attack in the first stage contributes to improve the maximal dynamic pressure greatly; the warhead impact point constraint of test trajectory can be guaranteed by adjusting launching azimuth and the pitch program angle of the second and the third stage at the same time.

Abstract:Dynamics model of the stratospheric airship during floating was established, and the model was linearized using linear perturbation theory based on the assumption which the flight altitude is constant. A flexible leaderfollower formation control method for stratospheric airships based on path following was proposed, in which the leader and followers track the reference trajectory respectively through velocity and heading control. Linear formation and circular control of three stratospheric airships were simulated and the simulation results show that the control accuracy of the path following method is high while the formation can operate stably, and the collision among airships can be avoided.

Abstract:FFD (free-form deformation) technique was applied to achieve the parameterization of RAE2822 transonic airfoil. Then the method of DoE (design of experiment) was used to obtain the sample values of design parameters by CFD (computational fluid dynamics) numerical simulation. Lastly, the optimization analysis was carried out by using the Kriging surrogate model and MIGA, NLPQL optimization algorithm. The CFD values with optimized design parameters were regarded as the final results. The results show that the FFD parametric method can directly realize deformation on airfoil mesh. Compared with original airfoil, the lift-to-drag ratio of optimized airfoil increases by 57.2%, therefore, the proposed method is feasible and effective.

Abstract:With the ionospheric electron density profiles derived from the COSMIC radio occultation mission during 2010 to 2014, the qualities of these profiles were checked comprehensively using four quality control parameters which consider only the profile′s own characteristics. The spatial and temporal distributions of the qualities of the profiles were analyzed accordingly. It is found that the qualities of the profiles are the highest over the high-latitude regions, followed by the low-latitude regions and the lowest over the mid-latitude regions. This may be due to the existence of the equatorial anomaly of the electron density distribution near the magnetic equator. The seasonal variation of the qualities of the profiles is distinct, which shows a significantly higher rejection ratio in winter and spring than in summer and autumn over both of the two hemispheres. In addition, the rejection ratio of the profiles is significantly lower in daytime than in nighttime, and it has great changes occurring at twilight demarcations. The peak electron densities and the corresponding peak heights derived from the qualified profiles are significantly higher over magnetic equator than over other regions, which shows a “double hump” phenomenon.

Abstract:In order to verify the rationality of flexible object deformable model, the force-deformation model validation system was established, which consists of wireless data transceiver platform based CC2531, force sensor measuring platform, and displacement measurement platform based FALCON hand controller. The relationship between interactive force and deformation in the elastic deformation experiment and impaling experiment with the experimental object of fresh pig liver was studied. Based on the data of force and deformation, the parameters were confirmed and amended. The simulation results show that the characteristic of force and deformation is consistent with actual measurement. The proposed system can be utilized for verifying general deformable models, which will lead to more applications in haptic based medical simulation.

Abstract:The stratospheric airship has the potential as large observation area, long drift time, and better efficiency. It is expected in many different applications, such as reconnaissance and surveillance. The imaging difference between the stratospheric airship SAR (synthetic aperture radar) and the airplane SAR was compared. Aimed at the redundant pulse repetition frequency and the large-amplitude low-frequency trajectory deviation, an optimization scheme was proposed and verified by simulation. The simulation result shows that the proposed optimized motion compensation method can eliminate the influence of motion error for the stratospheric airship effectively.

Abstract:Once clutter training samples mix with interfering targets, the clutter suppression performance by space-time adaptive processing will decline. In order to solve the problem, a robust training samples detection method based on target knowledge and partly sparse recovery was proposed. Firstly, the object region in unit to be detected was locked. Then the sparse complete base was obtained by covering the whole angleDoppler plane. After that, the corresponding object region in sparse complete base by transformation matrix was hollowed out to obtain the super resolution clutter space-time spectrum, which helps to estimate the clutter covariance matrix. Finally, the method was combined with the generalized inner product method to realize non-homogeneous training sample detection. Compared with GIP (generalized inner product) method, the proposed method can detect interfering targets in different intensity. Simulation analysis demonstrates that the test statistics of the proposed method have excellent discrimination validity, and can drastically eliminate interfering targets, thus improving the target detection performance of STAP (space-time adaptive processing).

Abstract:The underwater vibration response of cylindrical shell with different ribs and bulkheads arrangement was calculated by using the finite element method and the boundary element method. By means of the wavenumber spectrum method, the vibration and sound radiation of structural waves with different wave numbers were quantized in combination with the acoustic radiation efficiency of the regular wave of a shell. Based on the vibration theory of periodic and aperiodic structure, the mechanism of influence of the ribs and bulkheads arrangement on the vibration and sound radiation characteristics of cylindrical shell was revealed. Through the study it can be found that the shell with aperiodic ribs and bulkheads has better underwater vibration characteristics, which are more affected by the circumferential vibration of shell. And the acoustic radiation characteristics of a shell with aperiodic ribs and bulkheads are not necessarily better than those of a cylindrical shell with periodic ribs and bulkheads.

Abstract:The hysteresis model of giant magnetostrictive actuator, considering the hysteresis loss and dynamic stress, can comprehensively reveal the electric, magnetic, mechanical and thermal multi-field coupling effect. It is often, however, difficult to accurately identify the nonlinear model by the experiment. The intelligent IWO (invasive weed optimization) with a fierce competition mechanism and strong search ability is very suitable for solving the problem of multi-objective physical parameters identification. Nevertheless, the number of seeds is linearly generated in traditional IWO and the distribution variance is lack of adaptability as well, which greatly affects the algorithm convergence speed and model recognition accuracy. Therefore, an improved algorithm with nonlinear propagation and distribution was proposed and applied to the model parameters identification of giant magnetostrictive actuator. The experiment exhibits that the improved algorithm has stronger noise suppression ability, which can accurately identify the physical parameters of the hysteresis nonlinear model with noise signal, and the errors between model predictions and experimental data are much smaller, thus the identified parameters can make the hysteresis nonlinear model comprehensively describe the actuator multi-field coupling mechanism and dynamic characteristics.

Abstract:A mathematical model which displays the relation between the vibro-acoustic modulation index and the crack contact area was developed. Based on the analysis of crack faces response to the resultant of applied load and plasticity induced crack closure stress, a procedure of on-line approximating the opening and closure stress was proposed. To study the performance of this measuring method experimentally, the on-line vibro-acoustic modulation tests were carried out on a central cracked aluminum alloy fatigue sample. Analysis of the experimental results suggests that the vibro-acoustic modulation technology is not only capable of measuring the fatigue crack opening and closure stresses, but also capable of analyzing the crack closure behavior, even for physically short cracks.

Abstract:Considering the factors such as commutation process, residual energy of muzzle and Joule loss of resistance, the equivalent circuit model was established, and the efficiency of conventional helical launcher and a novel helical launcher was analyzed by theoretical, numerical and experimental methods, respectively. The results show that the Joule heat loss is the largest, followed by the magnetic energy loss of commutation, while the muzzle residual magnetic energy loss is minimal. The energy conversion efficiency of the launcher can be effectively improved by reducing the resistance, increasing the mutual inductance gradient, reducing the number of turns in the stator coil unit, and increasing the operating current, etc. However, larger armature coil turns will also bring greater magnetic energy of commutation and muzzle magnetic energy loss, resulting in barrel erosion or even damage, energy release and low efficiency. Besides, the theoretical efficiency of the helical launcher is higher than the one of the railgun under constant current operating mode. The theoretical efficiency of the novel helical launcher is close to 100%, which is expected to be implemented in the case of superconductivity or lower resistance in the future.

Abstract:The network security testbed mapping problem was formally defined and a new mapping heuristics based on K -partition was presented. The insight of the heuristic is that the tightly connected nodes of the logic topology should be mapped in the same switch in order to save more network resources. This novel mapping determines the initial state by greedy method, and moves nodes according to the defined cost function. The iteration partition of subgraph is in progress until that the number of subgraph nodes is not more than the port capacity of the physical switch. The problem that the result is influenced by the random initial partition in K-L partition is resolved by the K -partition mapping heuristics. The experiment result shows that the runtime is far less than the genetic algorithm, and the proposed algorithm can find near-optimal solutions in shorter period.

Abstract:In order to analyze the effect of armature′s velocity and quality changing on the accumulated thermal energy of rail, the thermal field model of rail was established and the rail temperature variation was calculated. Compared with the experimental results measured by FBG (fiber Bragg grating) temperature sensors, the correctness of the model and the measurement results were verified. On this basis, three types of experiments were designed to analyze the differences accumulated from the thermal energy on rail under different velocity, quality and the same energy level in different velocity. Experimental conclusions can provide valid references for determining the interval between two launches and designing the cooling system.

Abstract:On the basis of signal flow graph, the method of loop analysis was put forward to study the mechanism of velocity vector instability and its stable control. The signal flow graph of the longitudinal dynamics was established, and the convergence theorem of loop was proved. On this basis, through theoretic analysis, the reasons of velocity vector instability at different levels were obtained, and the velocity and flight path′s instability expressions were obtained too. In addition, it was also shown that the drag-velocity curve, the track angle-velocity curve, the polar curve and the drag-coefficient curve possess mutual backside area and frontside area, and the drag-velocity curve′s slope is proportional to the track angle-velocity curve′ s. The conclusions about the velocity vector′s stability critical condition, convergence expressions and stability mechanism under APCS (approach power compensation system) were obtained, and the comparison results about control performance between velocity constant APCS and angle-of-attack constant APCS were obtained through theoretic analysis and simulation.

Abstract:To guarantee the detection accuracy and viability of the single observer, a trajectory optimization method of the single observer with the battlefield threats′ constraint was proposed. The threatened factors in battlefield were analyzed, and the quantitative model between the battlefield threats and the trajectory of the observer was obtained. On that basis, considering both the accuracy and the threats extent of the trajectory, the accuracy score function and the threats score function were built, respectively. Then, the course choice function was constructed, and the different trajectories of the observer were evaluated. Simulation results show that the proposed method can avoid the threats effectively and improve the detection accuracy as well; the accuracy and reliability of single-observer bearings-only detection in battlefield can be guaranteed through the method.

Abstract:In order to improve the energy dissipation performance of the filament wound composite solid ball structure element, the maximization of the SEA（specific energy absorption）and the minimization of the IPF (impact peak force) of the structure element were chosen as the evaluation indexes. Based on the crashworthiness performance of the initial design scheme, the ratio of height to diameter for core cylinder，centrifugal rate of spherical core and filament winding thickness ratio and winding angle of composite surface were chosen as optimal design variables to establish a multi-objective optimization model．The multi-objective optimization model was decomposed into two single-objective optimization models by the hierarchical progressive optimization method. The finite element software Abaqus was adopted to compute the impact responses of the structure element with different design parameters．Furthermore, an approximate objective function was constructed with the radial basis functions，the optimal design was performed in two stages by using the second generation non-dominated sorting genetic algorithm．After the optimization，the ideal and optimal structure element was obtained for crashworthiness and energy absorption．Further experimental studies and failure modes analysis show the effectiveness of the optimization model and the improvement of the energy dissipation performance of the structure element.

Abstract:A tensor decomposition based clustering method was proposed for heterogeneous information in networks. This clustering method can cluster multiple types of objects and rich semantic relationships simultaneously. The multi-types of information objects in networks were modeled as a high-dimensional tensor, and the rich semantic relationships among different types of objects were modeled as elements in the tensor. Based on an effective tensor decomposition method, the multi-types of objects were partitioned into different clusters simultaneously. The experimental results on both synthetic datasets and real-world dataset show that the proposed clustering method can deal with the heterogeneous information in networks well, and can outperform the state-of-the-art clustering algorithms.

Abstract:A multi-attribute game theoretic model was proposed to address a two-stage attack-defense resource allocation problem. That is, under limited resources, the defender first allocates different types of safeguard measures among possible targets, against which the attacker chooses a combination of threats and targets to attack. The proposed model, using game theory, was used to determine the optimal resource allocation for both the defender and attacker. The results can minimize the loss for the defender while maximizing the utility for the attacker. In addition, some lemmas were given on the basis of the particularities of this solving model. An illustrative example was studied to verify the feasibility of the proposed model and the accuracy of the lemmas, which can provide decision support for the resource allocation process.

Abstract:In order to deal with the difficulty of technical risk direct measurement and the strong subjectivity for model parameter setting, the TRL (technology readiness level) as a standard method, was applied for evaluating the condition and the difficulty of technology realization. The quantitative relations were built by system representation with matrix and relation inference between the TRLs of all subsystems and the dynamic parameters of system process model. Then the uncertainties of schedule and cost beyond tolerable range were evaluated by the indirect method of system process modeling and simulation for the technical risk assessment of complex system development. Additionally, to improve the system resolution for analysis, the multi-resolution modeling method is designed to update the assessment continuously and to improve the analytical resolution along with system evolution.

Abstract:A ground impact test of space net was designed and conducted. Then the simulation of ground test was established and the comparisons of ground test and simulation results were analyzed. The impact force and tether tension of space net during impact process were investigated based on the simulation. The results show that: the simulation results agree well with the ground test results, which indicates the reliability of simulation model; the constraining tension of space net during impact process can well make the space net close up and wrap the target; the flexibility of space net can well mitigate the impact response and the tethers in impact area are more likely to fracture during impact process.

Abstract:In order to solve the influence of the satellite position error on the pulsar position error estimation results, an augmented estimation algorithm for the pulsar position error with satellite position error was proposed. In order to satisfy the observability conditions and ensure the lowest possible number of matrix operations, the algorithm used the satellite's position error scalar as the augmented state. Combined with the basic principle of the pulsar position error estimation, the state equation and the observation equation of the augmented algorithm were deduced again. Furthermore, the theoretical analysis proved the observability of the algorithm. The simulation results show that when the position error of the satellite causes the estimation of the traditional algorithm to deviate greatly, the algorithm can still guarantee the 0.01 mas accuracy of right ascension and 0.3 masaccuracy of declination. The position errors in different directions have less effect on the accuracy of the estimation results.

Abstract:A novel satellite scheduling framework based on the divide and conquer principle was proposed. Under this framework, an ant colony optimization algorithm was employed to distribute observation tasks to different satellite orbits. Then, an adaptive simulated annealing algorithm was designed to solve the satellite observation problem involved in each orbit. According to the feedback on the scheduling results at each orbit, the task distribution schema was adjusted. This process was repeated until the termination condition was met. To improve the efficiency of the algorithm, the domain knowledge of the satellite scheduling problem was considered into the heuristic information model of the ant colony optimization algorithm. Next, two neighborhood structures were designed in the simulated annealing algorithm. In addition, the dynamic selection strategy was used to choose the most appropriate neighborhood search structure. Extensive experiments show that the proposed method can reduce the problem complexity effectively, especially in solving the large-scale satellite observation scheduling problems, which exhibits extraordinary performance.