The performance of the integer-ambiguity decorrelation algorithm in the Global Navigation Satellite System (GNSS) directly affects the accuracy and the efficiency of the solution of integer ambiguity.In order to improve the efficiency of the integer-ambiguity decorrelation algorithm, a method was proposed to organize the diagonal elements of the ambiguity covariance matrix in ascending order at first, then reorganize the diagonal elements of the transformation matrix in descending one, thus to improve the termination conditions of the existing algorithm, and improve the effect of decorrelation solution and the ambiguity search efficiency.The numerical simulation results show that, compared with the decorrelation algorithm based on diagonal ascending order and the iterative algorithm, the algorithm proposed here has obvious advantages on decorrelation performance in high-dimensional data space, which is suitable for the integer ambiguity solution of multi-satellite navigation system.

To solve such problems in infrared image pedestrian detection as lack of image details, low detection accuracy and the difficulty in extracting the feature information, an infrared image pedestrian detection algorithm based on the improved SSD algorithm was proposed.Depthwise Separable Convolution (DSC) method was used to reduce the number of parameters and calculation costs of the network in feature extraction, and improve the real-time performance.The SENet module was embedded in the network, and the weight of each feature channel was reassigned, so that the network could better target the pedestrians. Since the space ratio of the pedestrian target is relatively stable, the Default Boxes value was set by using cluster analysis algorithm, so as to improve pedestrian detection effects.Experimental results showed that, the proposed algorithm performed better than the VSSD algorithm.The precision ratio and the recall ratio reached 91.7% and 84.8% respectively, and the real-time performance of the algorithm was also greatly improved.

In view of the problem of how to use and deploy the search force in the on-call search method of multi-layered array, the array deploying, array monitoring and the relationship between them are taken into comprehensive consideration.The concept of the maximum controllable bounding array of on-call search is proposed, and its parameter model is constructed.The model for locating the awaiting-airspace/airport is established for the anti-submarine patrol aircraft.The steps of the planning and preparing of on-call search are given, which provides a theoretical and methodological basis for carrying out on-call search with anti-submarine patrol aircraft.

To eliminate the stripes of Remote Sensing Image (RSI), which is easy to cause blur or loss of detail, the direction and structure characteristics of clean image and stripes are analyzed and studied, a stripe separation method for RSI is proposed.For the stripes, the sparse structure feature is characterized by the group sparsity and smoothness of the stripes, the characteristic constraints are realized by combining the L2, 1 norm of stripe and L0 norm of the gradient along the direction of stripe.For clean image, the edge continuity is constrained by L1 norm.Considering the non-convexity of the constraint model, the algorithm based on Proximal Alternating Direction Method of Multipliers (PADMM) is used to solve the constraint model fast.Experimental results of simulation data and actual data show that the proposed algorithm can effectively remove the stripes and preserve the details of the original image efficiently, which fully verifies the feasibility and reliability of the algorithm.

Aiming at the problem that the effect of variational Bayesian adaptive Kalman filtering will be affected when the noise statistical characteristics in the linear Gaussian state space model are time-varying, an improved algorithm based on the principle of strong tracking is proposed.The measurement noise model is selected as the inverse Wishart distribution, the system state and time-varying measurement noise covariance are taken as the parameters to be estimated, and variational Bayesian approach is used for their recursive estimation.The optimum estimation result of the measurement noise covariance is then taken as a time-varying parameter and introduced into the sub-optimal fading factor based on the strong tracking principle, to improve the correction accuracy of the covariance of state prediction.Simulation results show that:1) The improved algorithm can track the measurement noise covariance adaptively in the linear Gaussian system with time-varying noise, and effectively overcome the influence of time-varying noise covariance;and 2) The convergence speed and accuracy of the estimated results are greatly improved.

With the advantages of low cost and high bandwidth, the airborne short-range data communication system is becoming more and more important for the digital communication between digital aircraft and ground systems.Based on avionics system engineering method, the requirements on function, performance and interfaces of the airborne short-range data communication system were defined.The logical architecture was designed through function flow block diagram method;and the physical architecture was designed by using integrated and modular method.A system prototype was developed based on ARINC600 standard, and a system verification environment was set up including airborne and ground system simulations.The verification result shows that the system design can meet the requirements, and the research result supplies a reference for the avionics system designers.

Aiming at the problem that the noise reduction effect of fault signal is not ideal by only using SVD or morphology, an SVD noise reduction method based on multiscale morphology was proposed.Firstly, based on the principle of SVD noise reduction, the matrix was reconstructed by using the circulant matrix method.Secondly, considering that the effective order size of the reconstructed signal matrix may affect the denoising effect, and based on the MMRR singular value ratio method, the ratio between the adjacent feature extremums is used as the objective function for estimating the effective order, determining the significant figure of the singular value, and restoring the signal.Finally, an SVD filter based on multi-scale morphology was designed, the appropriate structural elements were selected, and the morphological opening and closing operations were adaptively combined.The simulation results show that the improved method can significantly improve the signal-to-noise ratio, and effectively filter out the impact signal and white noise in the fault signal.Compared with the single SVD or morphological noise reduction method, it has stronger anti-noise ability and has certain engineering application value.

Considering the uncertain parameters in the model of the trajectory tracking and controlling of quad-rotor aircrafts, an adaptive control algorithm is proposed based on the contraction theory and the backstepping method.Firstly, the contraction theory based on differential geometry is introduced, and the dynamic model of the quad-rotor aircraft is given.Then, the adaptive contraction backstepping control method is proposed for tracking the desired trajectory of the aircraft.Finally, the incremental stability of the system is analyzed, and it is proved that the error of the system is converged.The simulation results of Integral Backstepping (IB) and Adaptive Contraction Backstepping (ACB) show that, the aircraft system using the proposed control algorithm has higher robustness, and can implement trajectory tracking more accurately.

For the class of uncertain nonlinear systems with external disturbance in the big initial state, a nonlinear term with adjustable index is added into the traditional terminal sliding mode control, and a new fixed-time nonsingular terminal sliding mode control method is proposed.The traditional linear sliding mode, Terminal Sliding Mode (TSM) and Fast Terminal Sliding Mode (FTSM) are all special cases of the new sliding mode;and it is proved that the new sliding mode converges in fixed time when N>1.An analytic expression of the upper bound of the convergent time is obtained, which is independent of the initial state.It is proved that the scheme is superior to FTSM, and the influence of parameter selection on convergence speed and convergence time is further analyzed and the rule is summarized.Based on Lyapunov stability theory, a nonsingular fixed-time sliding mode controller is constructed for second-order nonlinear system, and it is proved that the control error can converge to any small closed ball at fixed time.Simulation results of quad-rotor aircraft attitude control have demonstrated the superiorities, such as faster convergent speed, stronger robustness and smaller steady error.

In order to quantitatively analyze the sensitivity of early-warning aircraft based cooperative midcourse-guidance accuracy to errors, the acquisition probability under cooperative midcourse-guidance is modeled.Firstly, the feasibility of cooperative midcourse guidance scheme based on early warning aircraft is analyzed.Secondly, the calculation process of midcourse guidance command is analyzed according to the guidance scheme, and the model for midcourse-guidance command calculation is established.Then, five error sources affecting cooperative midcourse guidance are analyzed, and each error is modeled, which is then added to the midcourse-guidance command calculation model.Monte Carlo method is used to calculate the acquisition probability of cooperative midcourse guidance.Finally, based on Monte Carlo model, the sensitivity of acquisition probability of cooperative midcourse guidance to errors is analyzed by orthogonal experiment method.According to variance analysis results and the differences between guidance performance of early warning aircraft and fighter aircraft, it is concluded that the urgent task of realizing early-warning aircraft based midcourse guidance is to improve the radar search cycle and the height measurement accuracy of the early warning aircraft.

When the UAV performs target tracking, there is a high demand on the real-time performance of the algorithm in the process of obtaining the distance between the UAV and the target.In consideration of the demand, a binocular stereoscopic vision ranging method based on the combination of Matlab toolbox and OpenCV vision library is proposed.The method uses the Matlab toolbox to perform binocular calibration on the camera, and then imports the calibration result into the OpenCV-based stereo matching BM algorithm for subse-quent ranging processing.Through experiments, it is verified that the proposed method has high accuracy and excellent real-time performance, which can meet the ranging requirements of UAV dynamic tracking.

A specific definition of ship heave movement is given, and an error model of heave measurement is established, based on which a heave filter is designed to realize low-frequency attenuation and quadratic integral of a specific band.Detailed analysis is made to the error characteristics, and the influence of each error source on measurement results is presented. An adaptive algorithm is proposed for estimating the state of wave motion in real time, i.e., the average amplitude and dominant frequency of the wave, based on which the parameter of the filter is obtained to minimize the error.Simulation is made to verify the measurement algorithm.The result shows that:Compared with the traditional digital high-pass filter, the adaptive algorithm performs better in real-time and accurate measurement.

In order to extract and detect the Frequency Hopping(FH) signals in communication confrontation under fixed-frequency interference, a method based on local adaptive threshold is proposed.On the basis of Short Time Fourier Transform (STFT), a suitable local adaptive threshold value is obtained to eliminate the effects of fixed-frequency interference and to extract the frequency hopping signals.Furthermore, the signals can be detected by using the difference between the signals and Gaussian noise on continuity.Simulation results show that this algorithm can detect the frequency hopping signals effectively with low computational complexity and high reliability when the Interference to Signal Ratio（ISR） is 10 dB whether there is frequency collision (The hopping signal has the same frequency as the interference frequency) or not.

The tracking accuracy of high-precision photoelectric stability platform system is susceptible to friction torque and nonlinear interference.The additive decomposition theory is used to decompose the photoelectric stability platform system into the main system and the auxiliary system.An acceleration-based fractional-order PID control method is adopted for the main system to ensure the tracking accuracy of the visual axis.To the auxiliary system, a design method of fractional-order disturbance observer based on velocity signal is proposed.By using the characteristics that the fractional-order can be arbitrarily selected within the real number field, interference suppression and estimation compensation can be better solved to ensure the stability of the visual axis.A fractional-order sliding mode compensator is designed based on the fractional-order theory to further compensate for the unknown interference in the auxiliary system.The finite time convergence theory and the Lyapunov theory are used to prove that the system can achieve stability in a finite time.The experimental results show that, by using the method, the photoelectric stability platform system has high tracking accuracy for moving targets.

Aiming at the problems of slow response speed, poor anti-jamming ability and large overshoot in traditional PID control system of quadrotor aircraft, the Model Algorithmic Control (MAC) is introduced into the traditional PID control system to improve the dynamic and static performance of the control system.The incomplete differential PID controller is combined with the MAC controller to form a cascade closed-loop control system.The incomplete differential PID controller is used as the inner loop control to realize the attitude control of roll angle and pitch angle.The MAC is used as the outer loop control to realize the control of position and yaw angle.The simulation results show that the method has smaller overshoot, faster response speed and smoother response curve than the traditional PID control.

Firstly, the attitude dynamic model of the fixed-wing UAV under ideal conditions is given, and then, the UAV attitude controller is designed based on the dynamic inverse method.But the controller above is not suitable for the UAV model under actual conditions, because there is a certain offset between the actual model and the ideal model, which is model uncertainty.Moreover, there are also some external disturbances in the actual situation.Therefore, the fuzzy neural network is combined with the original UAV attitude controller to compensate for the model uncertainty and external disturbances existed in the operation of the UAV.

In needs of stray light suppressing and system volume compression, a compact system of off-axis three-mirror structure with secondary imaging and real exit pupil is designed.A method of constructing the initial structure of the off-axis three-mirror optical system with secondary imaging is given.The optical system is optimized with freeform surfaces based on the initial structure, and the off-axis three-mirror optical system with the focal length of 130 mm, F-number of 1.3, the linear FOV of 5°×0.1° is designed.The system imaging quality is close to the diffraction limit, the system has the characteristics of stray light suppressing with secondary imaging and real exit pupil, and the 100% cold stop efficiency can be realized theoretically.The system is compact with the super-little F-number of 1.3 and can be applied to such military fields as aviation and aerospace detection where there are high demands of stray light suppressing.

For the detection of concealed objects, radar technology is commonly used at present and ground penetrating radar, wall penetrating radar and other technologies have also been developed.Millimeter wave can be used for imaging and has certain penetration capability.The millimeter wave radiometer can work all-weather day and night.What‘s more, the detection system is relatively small in size, low in cost and convenient to use, which makes it more and more attractive.In this paper, a radiometric imaging system is used for shallow-buried metal object detection, the region growing method is used for extracting the interested single target, and the center of the target is calculated based on its radiation temperature.Experimental result shows that, the method can detect the shallow-buried metal targets and extract the interested single target and its characteristics, which can be used for further application.

In order to improve the disturbance suppression capability of lightweight airborne photoelectric stabilized platform, a stable control loop was designed based on Disturbance Observer (DOB) and Stribeck model.At first, the stability loop of airborne photoelectric stabilized platform was modeled, the sources of disturbance were analyzed, and the compensation scheme was determined.Then, Stribeck friction compensator and DOB were integrated based on the traditional stability loop, and the feasibility of improving the stability accuracy was verified by simulation.The results show that:1) Under sinusoidal disturbance of 5 Hz/0.12°, the stability accuracy of the visual axis is improved by nearly 5 times, which suppressed the phenomenon of low-speed creeping effectively; 2) The root mean square value of velocity tracking error was decreased from 0.31 （°）/s to 0.07 （°）/s;and 3) The isolation of different-frequency disturbances was obviously improved.

The damage power of the warhead can be judged by making calculation and visualized simulation to the designed warhead and the shooting range parameters.Digital simulation is made to the static blasting process of the warhead in corresponding shooting range by using the theoretical model.Unity3D technology and simulation data are used for creating the mathematical model of the static-blasting field and the 3D scenethus to realize numerical fitting of the simulation data and 3D model animationand enable the users to observe a multi-viewscalable physical process of the static-blasting field in 3D scenes.The analysis of system simulation experiment results show thatthe fitting of system numerical calculation and 3D visual model animation has good effectsand the user interaction experience is satisfyingwhich can provide a basis for making power evaluation to the design and experiment of complex fragment warhead.

To solve the problem of frame angular velocity extracting in a semi-strapdown stabilized platform, a velocity measurement scheme is proposed based on nonlinear tracking differentiator, which can avoid the error amplification caused by conventional differential velocity measurement, and can solve the problem of phase delay caused by nonlinear tracking differentiator by using a predictive compensation method.The digital simulation and experimental results show that the nonlinear tracking differentiator can accurately extract the angular velocity signals from the frame angular position signals.The experimental results show that the semi-strapdown stabilized method based on the nonlinear tracking differentiator can isolate the low-frequency angular disturbances as well as the direct stability method does, which proves the feasibility and effectiveness of application of the nonlinear tracking differentiator in the semi-strapdown stabilized platform.