Considering that traditional strap-down inertial/celestial integrated navigation system (SINS/CNS) cannot accurately estimate the accelerometer bias, which can cause the divergence of navigation errors, a strap-down inertial/celestial integrated navigation method based on the stellar refraction (SINS/RCNS) was proposed. The starlight refraction angle obtained from the stellar sensor and the apparent height obtained from atmospheric refraction model were combined to inhibit the divergence of position error. A novel measurement equation based on stellar refraction was developed and the relationship between the number of used refraction stars and navigation accuracy was analyzed. When multiple refraction stars are used, the proposed method can accurately estimate the accelerometer bias so that the position errors can be inhibited completely, and its observability was analyzed. The estimation of the state of system was realized through the Kalman filter. The simulation results indicate that the precision of navigation based on the proposed method is better than that of the traditional method and inhibits the divergence of the position error effectively, which shows the validation of the proposed method.

For the problem of particles degeneration and lack of diversity in standard interacting multiple model particle filter (IMMPF) algorithm, a novel algorithm is presented, which is referred to as interacting multiple model particle filter optimization resampling (IMMPFOR) algorithm using linear optimization method in each model to improve the small-weight particles. The novelty of this algorithm lies in replacing the small-weight particles with new particles after the measurement information is received. New particles contain not only the information of the particles in the current model, but also the information of the particles in interacting models. The tracking simulation results show that the posterior probability density function of each model with newly generated set of particles accurately approximates the real state posterior probability density function, and the estimation accuracy of IMMPFOR is higher than the standard IMMPF algorithm.

Aimed at the low design precision and larger gap with actual load profile in missile life extension test, a missile vibration spectrum design based on inverse pseudo-excitation method was put forward. First, four-degree-of-freedom vibration model of missile-suspension system was established, and the system frequency response was inferred. Then, the time-domain response data was converted into the response matrix of power spectral density by means of Fourier transform, and harmonic response was constructed based on the decomposition of response matrix of power spectral density. Finally, the system excitation power spectrum was gained based on pseudo-excitation method. At the same time, the effect of response noise and system damping on identification precision was studied. The experimental results show that the inverse pseudo-excitation method has high identification precision and good robustness. When there is no noise, the identification error is 2.39%, and it reaches 3.21% when there is 30% noise. The design means of vibration spectrum is also applicable to other equipment.

The performance degradation of airborne fuel pump is nonlinear and multi-stage with stationary-accelerated-stationary degradation pattern. The existing degradation models are unsuitable for the modeling of this degradation problem in life cycle, so the signal output from the pressure sensor attached to the fuel pump is modeled based on the logistic smooth transition auto-regression (LSTAR) model. First, auto-regressive (AR) model was established for the converted pressure signal, the necessity of the LSTAR model was examined by nonlinear test, and parameters of the model was estimated by nonlinear least square method. The transfer variable was chosen by minimizing the AIC value and maximizing the goodness of fit. Adaptive test and normality test of the model have been done based on residual analysis. The results show that the LSTAR based method is superior to the AR model. The dividing of the degradation stage and the modeling problem are solved by the presented method, which lays better foundation for the prognostics and health management (PHM) of airborne fuel pump.

To improve the effect of 3D visualization for electromagnetic environment, this paper proposes a grid projecting algorithm that makes fusion of ray-casting volume rendering with isosurface rendering for electromagnetic environment. The isosurface is transformed into a layer of grid and then the grid is rendered into the image generated by ray-casting algorithm. An inerratic plane grid is projected to the sample data points with the same value in electromagnetic environment data volume, which generates the isosurface grid. Through computing the corresponding pixels of projected grid along the inverse direction of ray-casting and then generating the fusion pixels with grid color, the fusion rendering image of electromagnetic environment is carried out. When this algorithm is implemented parallel under compute unified device architecture (CUDA), the rendering effect of electromagnetic environment is improved compared with that before fusion, and the rendering efficiency is high enough to support user real-time interactive control.

The transfer of a spacecraft between coplanar orbits under continuous constant thrust with minimum fuel consumption was investigated. A control equation of the optimal trajectory, which the steering angle must satisfy, was derived by using maximum principle. Combining the control equation with dynamic equations, we establish an improved indirect method to design optimal coplanar transfer orbit and propose an approximate application method for the condition when thrust direction adjustment ability was limited. Due to avoiding solving the Lagrange costate differential equations, the improved indirect method reduces difficulty of initial value estimation and calculation a lot than traditional indirect method. Compared with Gauss pseudospectral method, the improved indirect method can get higher precision and better numerical smoothness. Simulations show that a limitation on the magnitude of the second derivative of thrust angle can improve change law of thrust angle and reduce change range of thrust angle; as to the fuel consumption, the greater the thrust magnitude is, the more the fuel consumption is, and the optimal transfer orbit can save fuel consumption a lot under a certain large magnitude of thrust.

The heat release rate of single lithium-ion battery measured by the commonly used experimental method is not able to reflect the heat losses caused by the domino effect and the intermittent changes during the transfer process of a large number of lithium-ion batteries within the air transport package. This paper, instead, proposes a method of equivalent analysis for the heat release rate of lithium-ion battery based on domino effect. Namely, the domino effect and the surface temperature of each battery after the thermal runaway of typical 18650 lithium-ion battery in 3×3 configuration were analyzed with the help of independently designed experimental platform. Using FLUENT to use the standard 18650 lithium-ion battery heat release rate curve for the same experimental conditions of lithium-ion battery thermal runaway simulation. Then dichotomy was used to revise the standard heat release rate to accord the surface temperature of the lithium-ion battery in simulation and in experiment to obtain equivalent heat release rate curve of lithium-ion battery to apply to further simulation. It turned out that the maximum temperature of each battery and the time to reach maximum temperature coincided with the experimental data, verifying the reliability of the revised equivalent heat release rate model. This method can be applied to obtain heat release rate of various types of lithium-ion batteries in different amount of package, therefore guiding the fire prevention and control project in the air transport of lithium-ion battery in practice.

Aimed at the situations of the spreading and moving dynamics behavior of the droplet that plays an important role in industrial production and microfluidic chips, an elastic planar model based on the theory of ultrasonic travelling wave was proposed. The droplet on the elastic glass surface was driven by ultrasonic travelling wave generated by the inverse piezoelectric effect of piezoelectric ceramic. The droplet model was built with multi-physics field software COMSOL. Firstly, through the analysis of the ultrasonic travelling wave, the feasibility of the model was verified. During the period of 0 to 60 ms, the droplet behaves a shrinking-spreading sinusoidal oscillation motion driven by ultrasonic travelling wave. Then, the internal flow structure inside the droplet was also investigated. When the droplet radius spreads to the maximum and begins to shrink, the velocity inside the contact surface between the droplet and the substrate changes first. It shows that the change of the velocity field inside the droplet plays an important role in the motion of the contact line. There is a similar elliptic vortex in the flow field inside the droplet, which illustrates that the droplet motion is not a simple translation induced by shrinking-spreading, but a forward movement with rolling. Finally, we studied the dependency of the moving velocity of the droplet on the parameters (driving voltage, driving frequency and dynamic viscosity) via simulations. The results show that the moving velocity of the droplet is significantly influenced by the dynamic viscosity.

Vanadium (V) is identified as a promising candidate of the structural materials in fusion reactors. Experimental results have demonstrated that the impurity oxygen (O) has great influence on the structure and mechanical properties of V. Employing a first-principles method based on the density functional theory, we study the stability and diffusion property of impurity O as well as its interaction with defect vacancy in V. O atom is energetically favorable to occupy the octahedral insterstitial site with the solution energy of -4.942 eV. The intrinsic optimal diffusion route of O in the interstitial site is octahedral insterstitial site→tetrahedral insterstitial site→octahedral insterstitial site, and the diffusion activation energy is calculated to be 1.728 eV. The diffusion coefficients of O at the different temperature are systematically analyzed. We demonstrate that there is the strong attractive interaction between O and vacancy in V. The trapping energies of one and two O atoms are-0.484 eV and -0.510 eV, respectively. With the increase of the number of O atoms, the trapping energy of the third O becomes the positive value of 0.382 eV, meaning that vacancy cannot bind the additional O atom again. Thus, one vacancy can accommodate as many as two O atoms. It is revealed that the "O₁-vacancy" and "O₂-vacancy" clusters are easily formed in V. The current results can provide a very useful reference for V as a candidate structural material in a fusion reactor.

To implement multi-parametric sensitivity analysis and multi-parametric classification of air-breathing hypersonic vehicle and reduce the complexity of design, parameterized shape generation of air-breathing hypersonic is performed. First, the orthogonal design of experiment is used to generate the sample; then the high-precision aerodynamic performance calculation is implemented by the computational fluid dynamics (CFD); finally, parameter sensitivity analysis of aerodynamic performance by the method of variance analysis is carried out. Multi-parametric sensitivity analysis of aerodynamic performance on complex geometries is completed with the small sample size of the experiment. The results show that the sensitivity of multi-parameter to aerodynamic performance of aircraft and the influence rules of aerodynamic performance can be obtained correctly. Besides, the better aircraft geometry can be selected by experiment samples and is of great significance for optimization design and ground experiments.

Fatigue crack propagation behavior in typical corrosion environments is the precondition of damage tolerance design for metallic structures in aircraft; therefore, in order to determine corrosion fatigue crack propagation behavior, fatigue tests were performed on three categories of aluminum alloys (i.e., 2E12-T3, 2E12-T42 and 7050-T7451) in two kinds of corrosion environments (3.5wt% NaCl solution and fuel tank ponding) under constant amplitude loading. Corrosion fatigue crack propagation properties in different corrosion environments were analyzed and compared with each other, and the interaction mechanisms between corrosion and fatigue were deduced from fractographic studies by using SEM analysis. It is showed that the effect of fuel tank ponding on fatigue crack propagation behavior is more significant than that of 3.5wt% NaCl solution, and aluminum alloys 2E12-T3 and 2E12-T42 hold superiority over aluminum alloy 7050-T7451 in corrosion fatigue crack propagation behavior. Corrosion crack propagation is enhanced due to the hydrogen embrittlement effect and anodic dissolution mechanism.

Missile countermeasure optimization problem for fighter aircraft was studied. The missile countermeasure optimization was modeled as a sequential decision-making problem under uncertainty, and a Markov decision process (MDP) based approach was proposed. First, the engagement process was divided into several phases, and these phrases were marked by states. Electronic counter measures (ECM) and strategic maneuvers were treated as actions. Then, the state transition probability was used to reflect the uncertainty of each action, and average occupancy of "hit" state and "search" state was used to evaluate the aircraft survivability under different policies. Finally, the policy iteration algorithm was used to get the optimal policy, which maps the optimal action to be taken in each state. Simulation indicates that the aircraft survivability decreases as time goes on; the proposed MDP-based approach can effectively improve the aircraft survivability; one-step optimization is useless for the aircraft survivability and the influence of the state transition should be considered from the view of long-time horizon.

For repair optimization of system with periodic inspection, we need to not only consider the system reliability information, but also make full use of the inspection data and optimize the inspection period. A multi-state parallel repairable system was taken as the research object, and the system inspection and repair optimization were realized considering the imperfect inspection and imperfect repair with the objective of reducing operation cost rate. System reliability model was established by non-homogeneous Markov chains, and Monte Carlo simulation was carried out for system degradation, detection and repair. Particle filter was used for fusing the system model and inspection data, and the residual life of the system was estimated. Life related thresholds used for triggering repairs were set, and simulation results of the expecting cost rate were used as the objective function for a genetic algorithm to achieve optimization of the inspection period and the thresholds. It is proved that this method can effectively overcome the inspection error and achieve the optimization of system repair and inspection.

Aimed at the outstanding issue of angular velocity extraction from useless information, which is caused by gradient hot phase of traditional interference grating gyro, a multiple weak links fan shaped superfluid interference grating gyro structure without gradient hot phase was proposed, and the accuracy and sensitivity performance of the gyro was intensively studied. First, on the basis of gradient hot phase mechanism, the equal adjacent interference loop area structure without gradient hot phase was designed. Second, the mathematical model of the gyro was established, and the sensitive process of angular velocity was verified. Finally, the performance of angular velocity detection range and sensitivity was analyzed: the impact of sensitive area, membrane area, Josephson frequency, and numbers of micropore and weak link on angular velocity range was explored. The ultrahigh-precision and ultrahigh-sensitivity of this structure are proved by comparing simulation results.

For the combustor based on full-height swept strut coupled with cavity, the experiments were conducted under clean air conditions and the inlet air was preheated by storage heater. Liquid kerosene was used as fuel and was injected by stages from the wall and strut. The effect of equivalence ratio of wall injection on the static pressure distribution and combustion performance was studied by experiments and one-dimensional analysis. The results show that as the equivalence ratio of strut was constant, with the increasing of wall injection equivalence ratio, the peak static pressure increased, and the position of the lifting of pressure was moved upward. When the total equivalence ratio reached 1.1, an inlet unstart occurred. One-dimensional analysis shows that the Mach number decreased below 1 in the strut area, then reached 0.5 in cavity and finally back to more than 1 in diverging area of outlet. The combustor worked in subsonic mode. In the combustion performance aspect, increasing of wall injection equivalence ratio ledes to increase of total pressure recovery coefficient, increase of total temperature at exit, but reduction of combustion efficiency.

Complex equipment development project characters of high risk and many research units result in risk transmission in the development process. To solve the risk source identification problem, a risk source identification method was proposed based on association rule (AR) and decision making trial and evaluation laboratory (DEMATEL). The association rules between risk type and risk factors were solved firstly, and then the interaction of the risk sources was obtained, both with data mining method. Finally, each risk source's relevant parameters were obtained through DEMATEL. Besides, a case was analyzed and the risk sources identification was completed by AR-DEMATLE method on a stage of the data stored in the database of a research unit. The identification result shows that the risk sources corresponding to various risk types and the risk sources leading to risk transmission easily.

In order to improve the safety of low altitude flight for the helicopter with tail rotor, an alternative anti-torque device has been proposed by using the flow control technology of the cross flow fan. Wind tunnel tests show that the device has the characteristics of lateral force. At the same time, the numerical simulation calculation method of the device has been established. It is concluded that the influence of the cross flow fan rotating speed, the rotor down wash flow and the front flying flow on the aerodynamic characteristics of the anti-torque device is great. The source of the force of the anti-torque device is analyzed. It is proved that the lateral force can be controlled by controlling the speed of cross flow fan and this device can be used as anti-torque device for helicopter.

Signal detection is the key technology for the high precision of laser Doppler velocimetry (LDV) system. In order to achieve the accurate detection of the weak Doppler signal in LDV, we carried out a band-stop filtering toward the Doppler signal on the ground of the statistical characteristics of the noise in frequency domain. Combined with the constant false alarm rate (CFAR) detection technology of radar, an algorithm of adaptive threshold detection based on the sum of unit square in frequency domain is proposed so as to address the difficulty in signal detection within the atmosphere of low signal noise ratio (SNR), improving the detection performance and decreasing the probability of false alarm. Compared with the fixed threshold through simulations and experiments, this algorithm boasts the advantage of complete detection under the circumstance of SNR -12 dB while maintaining a relatively lower false alarm rate and simple operation as well as great applicability.

Faster-than-Nyquist (FTN) signaling is a transmission method with high bit density and inevitable inter-symbol interference. Based on soft output Viterbi algorithm (SOVA), a low complexity receiver for FTN was introduced. The number of comparison in the backtracking process was adjusted by the result of survivor path and competitive path, and was reduced during the process. In application, a fixed backtracking length was searched and defined by statistical value, which was shorter than that in SOVA. The presented method reduces the complexity and time delay in the FTN signal detector. Without deteriorating bit error rate (BER), the number of comparison operations is reduced by 2/3, the number of registers is reduced by more than 50%, and the system delay is reduced by more than 50%.

The working condition of reinforced concrete (RC) structures in coastal chloride environment combined load effects and environmental effects and there would be a different degree of damage due to load effects in normal conditions. In order to simulated that working condition in laboratory, different loads of 0.3P_u, 0.4P_u, 0.5P_u, 0.6Pu and 0.7P_u (P_u is the ultimate load of beam under monotonic loading) were applied on RC beam specimens to induce varying degrees of damage. Subsequently, beam specimens were placed in an automatic sprinkler device to simulate seawater wet-dry cycles. After 120 wet-dry cycles, monotonic loading test and chloride concentration test were conducted on RC beams. The test results show that the yield load, ultimate load and ductility of specimens decrease with the increase of initial damage load amplitude. When the initial load is 0.4P_u, the decrease of yield load and ultimate load is 10.4% and 7.9% respectively, compared with control group. With the damage increasing, the yield load and ultimate load decrease constantly. When the initial load is 0.7P_u, a great degeneration of mechanical performance occurs and the decrease of yield load and ultimate load is 33.7% and 32.4% respectively. The results of chloride concentration test show that the chloride ion content of concrete in tension area is higher than that in compression area. When the initial load is below 0.5P_u, the chloride ion content in steel position is below 0.1% and has no significant changes. When the initial load is 0.7P_u, the chloride ion content increases significantly and the maximum value is up to 0.14%. Thus, the initial damage combined with seawater wet-dry cycles has a great impact on degradation of mechanical performance and durability of RC beams.

Aimed at the analysis of comprehensive combat effectiveness for cooperative guidance & control of missile autonomous formation, the conception of cooperative guidance & control level (CGCL) for missile autonomous formation was introduced, an analytical model of comprehensive combat effectiveness for missile autonomous formation was established by combining analytic hierarchy process (AHP) with the ADC effectiveness evaluation model. The cooperative penetration probability, successful handoff probability, hitting probability and damage probability of missile member in the formation were analyzed in a typical combat scenario, the combat ability and characteristics of missile autonomous formation were fully considered, and the validity of the model was analyzed and verified using a missile autonomous formation attack-defense confrontation simulation system. This model provides a fast and reliable calculation method for quantitatively analyzing comprehensive combat effectiveness of missile autonomous formation.

The stability and controllability characteristics of flying wings are much different from those of conventional airplanes. This difference is prevalent in crosswind take-off and landing. To ensure flight safety in these circumstances, this paper conducts calculation and analysis of trim and response characteristics in crosswind take-off and landing for flying wings. From these, the differences between flying wings and conventional airplanes are derived, with the conclusion that the roll-over is the most serious problem for flying wings taking off or landing in crosswinds. The control efficiency requirements of innovative control surfaces on flying wings during take-off and landing are analyzed based on the control surfaces' control and usability characteristics. Two control strategies commonly applied to flight in crosswind conditions are simulated and compared; a suitable one for flying wings is proposed.

A two-phase optimization method for layup design of composite frame for satellite antenna is introduced to improve the structural dynamics performance of the composite frame. Phase Ⅰ focused on generating a new ply layout by optimizing the ply orientation angle and stacking sequences, while the number of plies is the upper bound of the constraints. The objective of the first phase was to maximize the fundamental frequency of the frame. Design variables were n-nary codes which were mapped to continuous variables. The optimization model of phase Ⅰ was solved by the particle swarm optimization (PSO) algorithm. Phase Ⅱ aimed to reduce the number of plies for the ply layout optimized in phase Ⅰ. A multi-objective topology optimization model was built to minimize the mass of the frame and maximize the fundamental frequency. The optimization model was solved by the non-dominated sorting genetic algorithm Ⅱ (NSGA-Ⅱ). To verify the feasibility of optimization method, the example of a frame of large satellite antenna was conducted. The result shows that the two-phase optimization can effectively reduce the mass of the frame of large satellite antenna and also improve the fundamental frequency.

Paraffin actuators have attracted a great deal of attention in the field of aerospace non-pyrotechnic actuators. The current aerospace paraffin actuator usually employs an elastic squeeze boot to push the actuator rod to move, which causes the disadvantages of large friction force and small force output. Motivated by these issues, a piston-type paraffin actuator has been developed in this paper. The actuator effectively enlarges the area that the liquid paraffin can apply pressure on, which greatly enhances the output driving force. The reset function and sealing performance have also been ensured by introducing a double-sealing design and a reset spring. In order to verify the proposed paraffin actuator, a prototype was fabricated. Validation experiments including friction force test, functional test, and life test have been performed. The results show that the reset spring with a designed force range of 85-165 N can successfully overcome the system friction force and push the piston to move, so as to ensure the auto-reset function. Under a rated power of 40 W (rated voltage 12 V), the output displacement of the actuator is 6.9 mm, the response time is 20 min, and the output force is more than or equal to 300 N. Life test shows that the actuator can function 100 times or more, and the output displacement is very stable (around 7 mm). Excellent sealing performance of the actuator has also been proven, since no paraffin leakage has been observed even after 100 times of actuation.

In applications of computer aided design and reverse engineering, for the data of point clouds without any topology information, we propose an effective smoothing and enhancing algorithm for point clouds based on empirical mode decomposition (EMD). First, the input signal of EMD is computed via the inner product of Laplacian vector and point's normal. For the input signal, the extreme points are extracted, and then the upper and lower envelopes are calculated by considering the extreme points as interpolating points. Second, in order to achieve feature preserving EMD signal decomposition, the sharp feature points are detected and considered as constrains in envelope computing. In this way, the over smoothing effect of traditional EMD algorithm can be effectively overcome. Finally, we can obtain the intrinsic mode function (IMF) and the residue by iteratively subtracting the mean of upper and lower envelops from the input signal in each iteration. Based on the multi-scale decomposition, different filter operators are designed to achieve point clouds smoothing and enhancing. Experimental results show that satisfactory smoothing and enhancing results of point clouds are obtained by the proposed novel EMD-based algorithm and EMD can be effectively extended to point clouds, which expands the application range of EMD in three-dimensional geometry processing.

Compared with traditional "rigid" robots, soft robots inspired by biology have been of particular interest to the robotic communities due to their inherent compliance and safety. However, the actuation and control of the soft actuators for such soft robotics are still lacking of theoretical investigation. For these issues, a pneumatic actuator was designed to achieve compliant motions for use in soft robots. The mathematical model was then developed based on the analysis of its structure and bending principle utilizing the geometric analysis and the principle of virtual work. The model were finally validated by finite element model and prototype experiments, and can be used for the future design and control of soft robotic actuators.