To improve the accuracy of passive localization of multiple Unmanned Aerial Vehicles (UAVs) in collaborative tracking, a closed-loop optimal control method is proposed based on analysis of the optimal station arrangement modes and Time Differences of Arrival (TDOA) measurements.First, the expression of Geometrical Dilution of Precision (GDOP) is derived.Then, simulation analysis is made to the influence of different observation station arrangement modes on GDOP under the constraints of UAV characteristics, communication range and safe distance.Three conclusions are summarized, and the optimal arrangement for single target is proposed.Finally, based on Extended Information Filter (EIF) and two-dimensional distribution model, the closed-loop optimal control method is used to solve the collaborative tracking of multiple UAVs with TDOA measurements.Simulation results indicate that, through the proposed method, the observation stations can implement target tracking collaboratively according to the optimal station location, and the accuracy of target localization is improved.

ADS-B has a wide working range, and when it is applied to the collision-avoidance system in aviation, it builds a protective zone outside the previous collision-avoidance zone to avoid any collision from happening in advance, which further improves the performance of the collision-avoidance system.The detection of route conflicts is the premise of avoiding collision in advance, and the relevant algorithms are complex.To solve the problem, an algorithm of route conflict detection was proposed based on time-axis mapping.First, this algorithm interpreted route conflict as an issue of calculating the conflict intervals on the X, Y and Z axis respectively.Then, the conflict intervals on the X, Y and Z axis were mapped onto the time axis to get the conflict time periods.Finally, the intersection of the three conflict time periods was calculated to determine the route conflict.In the simulation, a detection test for the route conflicts of the invading aircrafts was conducted in the ATC collision-avoidance area within 100 nautical miles of the ADS-B working range.The results showed that only 1‰ of the invading aircrafts were in conflict, which was close to the volume ratio between the ATC collision-avoidance area and the 100 nautical miles of the ADS-B working range.Therefore, the correctness of the algorithm is proved.

Based on the characteristic analysis of images under deep space background, a new method for dim target detection under deep space background was proposed based on topological invariance.Firstly, the image matching method based on topology invariance was adopted to match the sequential images with the first-frame image as baseline.Then, the background of the sequential images was removed.Finally, the method of Hough transform was used to detect the dim target in the image, so as to obtain target information.In order to verify the effectiveness of the proposed method, a series of semi-simulating sequential images were made by using the STK software, and an experiment was carried out.The results showed that:1) The detection ability of the proposed algorithm exceeds that of SMP and SBV;and 2) The computational efficiency of the proposed algorithm is equal to that of the SMP algorithm, and is higher than that of the SBV algorithm.

The attitude of the aircraft is controlled based on the theory of fault-tolerant control and integral sliding mode control to make it fault-tolerant.Taking a class of nonlinear system with uncertainties and possibility of actuator faults as the aircraft model, an integral sliding mode controller was designed for the system, which can keep an ideal control performance even in the case of actuator faults.For comparison, the controller was also designed for the system based on Lyapunov′s direct method and sliding mode control theory respectively.Simulation was made in the presence or absence of actuator faults, to observe the effects of the three kinds of control methods on the state variables, and to compare the chattering condition under normal sliding mode control and integral sliding mode control.The results show that integral sliding mode control performs better in control effect and chattering reduction.

In order to build the kinematics and dynamics models of the reentry segment of a nonlinear and multi-constrained gliding aircraft, the multi-interval hp adaptive pseudo-spectral method is used to optimize the reentry trajectory of the aircraft, and the optimal control quantity is obtained.The quantity is further solved, the optimal control signal of the aircraft is obtained, and the tracking control of the rolling channel of the gliding aircraft is performed.The simulation results show that the system can identify the control signal and effectively realize the attitude tracking, making the aircraft reenter the flight along the optimal trajectory.

The output SINR of the existing MIMO radar beamforming algorithms may decrease greatly due to the large mismatch of the joint steering vector.To solve this problem, an algorithm using iterative robust Capon beamforming for MIMO radar is proposed.Considering the transceiver array structure of MIMO radar, the mismatch error model is analyzed in theory at first.Based on this, we point out the limitations of the big-uncertainty-set algorithm.Then, an algorithm using small uncertainty sets to constraint large mismatch is proposed.The proposed algorithm iterates over the estimated joint steering vector until meeting the designed termination conditions.Compared with the previous algorithms, the proposed method can acquire a more accurate estimation of the joint steering vector.Simulation experiments show that the proposed algorithm presents outstanding performance in improving the output SINR and has strong robustness in the case of large mismatch.

This paper focuses on threat assessment of aerial target under uncertain environment.First, the problem of uncertain information is solved by using fuzzy neural networks.In the environment with less threat target information, the wavelet neural network is used to enhance the self-learning ability of the network and the threat factors are analyzed.The Fuzzy Wavelet Neural Network (FWNN) in the uncertain environment is established to achieve the target threat evaluation.For the uncertainty of the initial parameters, the consequent parameters of each fuzzy rule are updated by using the particle swarm optimization algorithm and the BP algorithm to achieve the purpose of improving the evaluation effect.The simulation results show that:Compared with the fuzzy wavelet neural network, the stability of the system is improved, the convergence speed is accelerated, and the prediction accuracy is enhanced.

The path planning of large-scale Multiple Traveling Salesman Problem (MTSP) is one of the key technologies in multi-UAV cooperative combat.In cooperative search, multiple UAVs set out from the same depot to scout the suspicious targets nearby.To finish the search task as soon as possible, we build a MTSP model and put forward an optimized algorithm, which combines the clustering algorithm with the genetic algorithm.First, the large-scale MTSP is divided into multiple separate TSPs by using the K-means clustering algorithm.Second, we optimize the genetic algorithm, take in the 2-opt algorithm as the optimization operator, redesign the selection operator and the crossover operator, and solve the multiple TSPs separately.Simulations have verified the rationality of the new algorithm.The comparison between the new algorithm and traditional grouping genetic algorithm shows that the new algorithm has higher computational efficiency and can get more reliable results, especially for solving the large-scale MTSP.

Due to the interference of the external complex environment on the observations of integrated navigation, the filtering accuracy may be degraded.This paper proposes a robust Kalman filter based on modified Rodrigues parameters.The proposed algorithm can suppress the disturbance of observations using modified Rodrigues parameters and Huber robust filtering strategy.In the integrated SINS/GPS navigation test, contrast is made to the filtering algorithm based on unscented quaternion estimator, the filtering algorithm based on modified Rodrigues parameters and their robust forms.The results prove that the proposed algorithm is valid with lower calculation cost and better robustness.

According to the characteristics of controllable muzzle velocity of the new shipboard gun, a method for calculating the firing data based on maximum hitting probability is proposed.The projectile muzzle velocity is added as a new firing data element of the shipboard gun with controllable muzzle velocity.When striking the sea target within visual range, there is a nonlinear relationship between the hitting probability and projectile muzzle velocity.The model of projectile exterior ballistic trajectory and the equation for solving hit problem are established for calculating the trajectory.Based on the concept of golden section, the projectile muzzle velocity is obtained through dichotomy.Constrained by the condition of maximum hitting probability, the method can calculate the firing data of the new-energy shipboard gun weapon effectively.

The influences of disturbing gravity on trajectory can′t be ignored when the missile is gliding at supersonic speed in near space.A three degree-of-freedom trajectory model was established considering the earth′s flattening factor and rotation.The disturbing gravity is calculated by using the spherical harmonic function method, and the variation tendency of the disturbing gravity and the landing point deviation under different-order coefficient are analyzed for the skipping-gliding trajectories with fixed-initial flight height and speed.At the same time, under the fixed-order disturbing gravity, the influence of disturbing gravity on the accuracy of the landing point under different shooting angles and different initial flying heights of skipping-gliding trajectory is analyzed respectively.The simulation results show that:1) The maximum deviation of the drop point caused by the disturbing gravity under different shooting angles of skipping-gliding trajectory is more than 4900 meters, and the deviation decreases with the reduction of the initial height of the ballistic trajectory;and 2) When the order of the disturbing gravity exceeds 360, the drop point deviation tends to be consistent, and the calculation results are reliable.Therefore, under the actual combat background, it is necessary to consider the influence of disturbing gravity on the hitting precision of the missile.Under the condition of meeting the operational requirements, it is possible to reduce the initial height of the skipping-gliding trajectory to reduce the impact of the disturbing gravity on the precision of the landing point.

In order to improve the anti-interference performance and precision of Sparse Fourier Transform (SFT) time delay estimation algorithm under low SNR conditions, a new SFT time delay estimation algorithm is proposed based on Generalized Second Cross Correlation (GSCC).The new algorithm performs the SFT operation on the signal, and then adds the GSCC algorithm improved by least squares fitting.The algorithm rapidly processes the signal while suppressing the interfering noise at the same time.In this way, the performance of the time delay estimation algorithm is improved.Simulation tests and field data verification both indicate that the improved algorithm has satisfying anti-interference performance and estimation precision.

Aiming at the problem of point cloud registration under different angles of view, a registration method based on the Improved Dynamic Differential Evolution(IDDE) algorithm is proposed.Firstly, Principal Component Analysis(PCA) is used to estimate the curvature and normal vector of the point cloud, and the average angle between the normal vectors of each point and its k-nearest neighbors is calculated.Subsequently, the first feature point extraction is conducted by the first feature parameter constructed by the curvature and the average normal vector angle, and the second feature point extraction is conducted by the second feature parameter constructed by curvature.Finally, according to the acquired feature point cloud, the registration parameter is calculated by the IDDE algorithm based on the coupled-optimal ordering mutation proposed in this paper, thus the initial registration result can be obtained, and the fine registration is achieved by an improved iterative closest point algorithm.Experiment shows that the proposed registration algorithm has the advantages of short registration time and high registration accuracy.

Fog droplet particles have severe absorption and scattering effects on infrared radiation.Researching its attenuation characteristics is important for improving the performance of weapons in fog.Based on the CART software, the Beer-Lambert law, the Mie scattering theory and the spectral distribution function of the particle group of fog droplets, the transmittance of infrared radiation through the fog particle group was calculated.The attenuation characteristics of infrared radiation in advection fog and radiation fog were analyzed respectively.Taking the 1.064 μm near-infrared radiation, 3.8 μm mid-infrared radiation, and 10.6 μm far-infrared radiation in the light fog environment as the example, and by use of the field data from three Chinese regions, the effects of visibility, transmission distance, the wavelength of the incident light, and the transmittance in clear atmosphere on the overall transmittance of advection fog and radiation fog were analyzed.The results show that:1) Under the condition of light fog, the attenuation in radiation fog is less than that in advection fog;and 2) The 10.6 μm far-infrared radiation has satisfying transmission performance, on which the regional atmospheric parameters have great influence.

To overcome the complicated nonlinearity such as friction, clearance and coupling and the uncertainties such as time-varying of parameter existed in the servo simulated loading system for Gun Control Systems (GCS), an adaptive sliding mode control strategy based on RBF neural network is proposed.To the uncertainties such as parameter time-varying in the system, RBF neural network is used to approach uncertain parts adaptively.Then, a dynamic adjustment approach of the switch gain RBF neural network is used to dynamically adjust the switching gain of the switching function, which enhances the dynamic performance of the system.An adaptive law is derived by using Lyapunov theory to estimate neural network weights and unknown functions online and ensure the stability of the system.Simulation results show that this control strategy can not only effectively suppress the external disturbances, but also has a rapid responding speed, which ensures the control precision and robustness when the system is loading in static or dynamic state.

When using airborne optoelectronic platforms for “air-to-air” target tracking, the tracking effect is always affected by the environment and it is easy to lose the completely-sheltered target.Based on the traditional CamShift algorithm, a dynamic target tracking and trajectory prediction algorithm based on multi-feature fusion and relative Kalman model is proposed.In target template construction, the method of fusing the color, texture and gradient features is adopted to improve model description.During the tracking period, the dynamic update of feature templates is introduced to ensure the long-term stability of the algorithm.In the case of complete occlusion, the Kalman models are established respectively for background center and the difference between the flight target and the center point through the secondary occlusion judgment method, which greatly decreases the probability of misjudgment and frame loss.Experimental results show that the proposed algorithm has high accuracy, fine real-time performance and stability.

Based on time stamp alignment and fault diagnosis technology,this paper designs an integrated navigation system to meet the actual requirements of the quad-rotor aircraft when executing tasks.The system is equipped with MEMS accelerometer and gyroscope,MEMS barometer and GPS sensor.First,a predictor is designed to align the time stamp of the GPS data,so as to synchronize the GPS data with the Inertial Navigation System (INS) data.Second,the measured data (from GPS and barometer) and the INS data are used for fault diagnosis,so as to prevent the jump of the measured data and the continuous increasing of the error of INS data.Finally,an extended Kalman filter based on time stamp alignment and fault diagnosis is used to design the integrated navigation system,so as to estimate the position and velocity of the quad-rotor aircraft.

To overcome the shortcomings of the traditional document methods used in the design of the integrated avionics fire control system,with the aid of the model-based system engineering theory,a method for object-oriented graphic system design based on Rhapsody is proposed.The specific design procedure and implementation steps are given.Taking a typical combat process of a certain aircraft for instance,this paper studies the application scenario and usage of various legends in the design of Rhapsody graphic system in detail,connects the legends in each designing stage with each other through function transference,and works out a complete design method for complex system.This method can realize the iteration optimization of the system,reduce workload and shorten the development cycle,which can serve as a reference for the graphic design of complex systems in the future.

The technological advancement in optical fabrication and testing has exploited a new field for the application of freeform surfaces.Based on the requirements of volume compression and performance promotion for space optics,an initial configuration of a compact,off-axis,three-mirror optical system is presented.The three mirrors are folded,which greatly compresses the volume.In addition,since the nodal aberration theory has laid a theoretical foundation for the application of freeform surfaces,two Zernike polynomial surfaces are adopted in the optimization process.With the verification of a designed example,it can be found that the final optical system possesses the advantages of compact structure,wide field-of-view and small F number,while the optimization process based on this design method can converge to the expected result with a fast speed.

A linear active disturbance rejection controller was designed for the trajectory tracking control system of a quad-rotor UAV to reduce the effects of parameter variations and external disturbances.The Linear Active Disturbance Rejection Controller (LADRC) can well overcome the problems of strong coupling,model uncertainty,and external disturbances.In this paper,the quad-rotor UAV trajectory tracking control system is divided into two loops:the outer loop uses a simple PD controller,and the inner loop uses a linear active disturbance rejection controller.The trajectory tracking experiment was performed on the linear active disturbance rejection control system on the simulation platform,and it was compared with the traditional PID control system.Simulation results show that the linear active disturbance rejection controller not only accurately estimates and compensates the internal/external disturbances,but also implements the quad-rotor flight control with robustness under the condition of dynamic parametric uncertainties.The controller meets the design requirements of fast attitude maneuver and high stability,and shows a superior performance to PID controller.

In the tilting process of the three-rotor UAV,the rotational inertia of the body along each axis direction will change as the nacelle angle of the engine changes.In order to realize the precise control of the three-rotor UAV in the tilting transitional mode,it is necessary to study the changes of the rotational inertia during the tilting process and to build a suitable mathematical model.By analyzing the changes of the position of the gravity center of the three-rotor UAV in its tilting process,the basic principle and experimental method of the torsion pendulum are used to analyze the rotational inertia of the aircraft under the condition of different nacelle angles.The relationship between the rotational inertia and the nacelle angle is obtained,which has laid a theoretical foundation for the modeling of the rotary three-rotor UAV in the tilting process.