Abstract:The basic principle, representative methods, and state-of-the-art research of the sub-module related research within the general framework of cooperative maneuvering flight planning from single UAV (unmanned aerial vehicle) maneuvering flight to multi-UAV cooperative planning were introduced. It mainly included real-time navigation map construction, discrete-space path planning, continuous-space trajectory planning, hybrid planning based on discrete-space and continuous-space, and multi-courses/trajectories cooperative planning. The next research directions were proposed based on the major technologies of the planning framework.

Abstract:Aiming at the problem of occlusion and confusion targets recognition for UAV (unmanned air vehicle) under small sample conditions, a target recognition model integrating self-attention mechanism and few-shot learning was proposed. On the basis of using the idea of meta learning to obtain the ability of few-shot learning, the self-attention mechanism to learn the context dependence between the internal parts of the target was introduced into the model, so as to enhance the target representation ability and solve the problem of insufficient effective features in the case of occlusion and confusion. In order to verify the effect of the model, the occlusion and confusion target datasets were constructed by further processing the reference datasets and UAV aerial photography data, and different occlusion degrees and background confusion rates were set. Through the verification on different datasets and compared with the deep learning model, the proposed model is proved to possess higher learning efficiency and recognition accuracy.

Abstract:In order to improve the efficiency of the UAV (unmanned aerial vehicle) swarm in cooperative search for moving targets, a UAV swarm cooperative search method was proposed on the basis of the moth pheromone courtship mechanism. According to the courtship behavior of moth in choosing flight direction by pheromone, a wind direction model in pheromone map and a moth pheromone courtship model were established. Considering the constraint of collision avoidance between UAV swarm, a map from moth pheromone courtship mechanism to UAV swarm distributed cooperative search was proposed, and the specific implementation process was given. Simulation results show the effectiveness and stability of the proposed method in solving the cooperative search problem of single moving target, and the outdoor flight experimental results verified the feasibility of the proposed method in practice.

Abstract:The autonomous obstacle avoidance of UAV (unmanned aerial vehicle) is the basis of completing complex tasks, and the obstacle avoidance performance directly affects the efficiency of UAV performing tasks. Aiming at the obstacle avoidance problem of UAV with external disturbance, a design method of anti-disturbance and obstacle avoidance guidance law based on model prediction was proposed. The disturbance observer was designed to estimate the external disturbance in the system dynamics, and the auxiliary guidance law was designed based on Lyapunov function method to establish the stability constraints. Combining the first two with MPC (model predictive control), the relationship between UAV and obstacles was considered in the MPC optimization solution, and the horizontal linear velocity and yaw angular velocity commands were solved according to the designed guidance law to realize the obstacle avoidance of UAV. The numerical simulation and physical flight verification of the proposed obstacle avoidance guidance law show the effectiveness of the proposed method.

Abstract:In order to solve the problem of low computing speed in the process of state transition in the analytical modeling of UAV (unmanned aerial vehicle) swarm operation, a fourth-order Runge-Kutta method based on the row compressed storage was proposed. The UAV swarm operation process was divided into three stages according to the UAV swarm operation style, and continuous time Markov chain model was established for the state transition process of UAV swarm operation in stages. In the meantime, taking the reliability of UAV swarm to complete combat mission as the solving index, the fourth-order Runge-Kutta method was used to solve the Markov model, and the method based on row compressed storage was used to optimize the solving rate owing to the sparsity feature of the rate transfer matrix. Simulation results show that the established continuous time Markov chain model has better effectiveness and feasibility than other models. At the same time, compared with other algorithms, the proposed algorithm has higher computing speed and better reliability requirements to meet the accuracy of results, which further shows the superiority of it.

Abstract:When the robot is running in a complex environment with densely distributed obstacles, the DWA (dynamic window approach) algorithm is prone to obstacle avoidance failure or unreasonable planning. In this regard, an improved DWA planning algorithm based on MOPSO(multi-objective particle swarm optimization) was proposed. Based on the establishment of multi obstacle environment coverage model, a method was put forward for judging obstacle-dense areas in complex environments. And the original DWA algorithm was improved by optimizing the sub-evaluation functions. On these basis of the improved MOPSO algorithm, the adaptive change of DWA weight coefficients were transformed into a multi-objective optimization problem. According to the requirements of path planning, the safety distance and speed can be set as the optimization goals, moreover, the corresponding multi-objective optimization model was established. The results of a series of simulations show that this method enables the robot to effectively pass through the dense area of obstacles while taking account of the safety and speed of operation, and has better path planning effect.

Abstract:For the formation tracking problem for swarm systems, an optimal control method with linear quadratic regulator performance index was put forward.Establish the mathematical description of the formation tracking problem and design a formation tracking control protocol. Necessary and sufficient conditions for swarm systems with formation tracking were obtained and the stability of the system was analysed by using the second method of Lyapunov.Topology conditions of the control protocol which can minimize linear quadratic regulator performance index were obtained and the formation tracking algorithm was designed.A numerical simulation was provided to illustrate the effectiveness of the control method.

Abstract:To study the influence of lunar soil parameters on the airbag buffer performance, a lunar landing airbag was designed according to the landing conditions of “Chang′e 3” probe, and then an airbag dynamic model considering the characteristics of lunar soil was established based on the crushable foam model. The airbag cushioning process under different lunar soils was analyzed, and it is found that the softer the lunar soil, the smaller the payload impact acceleration, but the airbag will sink into the lunar soil, which is not conducive to venting and affects its cushioning effect. Therefore, three indicators of airbag peak pressure, payload maximum acceleration, and payload maximum drop height were used to evaluate the airbag cushioning performance comprehensively, and the influence law of lunar soil parameters was quantitatively studied. Results show that the lunar soil density and shear modulus, as well as the yield parameters a₀ and a₁, have a significant influence on the cushioning performance, with a positive effect on the first two indicators and a negative effect on the latter one. Further research reveals that the relationship between each of the four lunar soil parameters and the three cushioning performance indicators is an exponential function.

Abstract:High-frequency attitude vibration usually exceeds the measurement frequency range of spaceborne gyroscopes and star sensors,resulting in a decrease in the accuracy of satellite attitude determination. Thus,a method for high-frequency attitude determination based on the regular attitude sensors was proposed. The key idea is that the high-frequency attitude of the spacecraft was sparse in the frequency domain and can be recovered from the normal-sampling-rate measurements. In this method, the normal-sampling-rate attitude sensors and indirect Kalman filters were used to estimate attitude. The filters′ estimation results were merged, and the high-frequency attitude was recovered from the merged data using the compressive sampling algorithm. The effectiveness of the method was verified by simulation experiments.

Abstract:A target staring adaptive attitude control method was designed, which could achieve staring at the target in the presence of the unknown target′s position and camera parameters. Based on the kinematic equation, the estimated parameters were extracted and linearized. A potential function with respect to unknown parameters was introduced to meet the demand for the rank of the parameter matrix. A self-updating principle of parameters was adopted to estimate the parameters on line, and accordingly, the adaptive control method was proposed. Based on the Lyapunov stability theory and Barbalat′s lemma, it was proved that the error between the target imaging position and the desired imaging position could asymptotically converge to zero. Simulation results reveal that the adaptive controller can effectively achieve staring observation for deep space targets with the uncertainties of the target position and the camera parameters.

Abstract:The numerical simulation method was used to carry out a systematic study on the roll control of the flying wing using the trailing-edge CC(circulation control) jet at a wide speed range (Ma为0.145～0.7), and was compared with the configuration controlled by classical control surfaces. Research focuses the electromagnetic stealth characteristics, the roll control characteristics and their flow physics, and the impacts of the bleed air. Results show that as the Mach number increases, the roll control capability of the CC jet decreases due to the weakening of entrainment and blocking effects. However, the CC jet enhances the stealth performance at specific azimuth ranges remarkably. Moreover, it requires less bleed air, induces less thrust loss, and has a high control efficiency factor (aerodynamic moment coefficient produced per unit of additional drag coefficient). In conclusion,the trailing-edge CC jet is a highly promising roll control device for a flying wing.

Abstract:In order to improve the autonomy of gliding guidance for complex flight missions, a multi-constrained intelligent gliding guidance strategy based on optimal guidance and RL (reinforcement learning) was proposed. Three-dimensional optimal guidance was introduced to meet the terminal latitude, longitude, altitude and flight-path-angle constraints. A velocity control strategy through lateral sinusoidal maneuver was proposed, and an analytical terminal velocity prediction method considering maneuvering flight was studied. Aiming at the problem that the maneuvering amplitude in velocity control cannot be determined offline, an intelligent parameter adjustment method based on RL was studied. This method designed a state space via terminal velocity and an action space with maneuvering amplitude. In addition, it constructed a reward function that integrated the terminal velocity error and gliding guidance tasks, and used Q-Learning to achieve the intelligent adjustment of maneuvering amplitude. The simulation results show that the intelligent gliding guidance method can meet various terminal constraints with high accuracy, and can improve the autonomous decision-making ability under complex tasks effectively.

Abstract:The pressure and temperature of air flow can be increased by aero engine, so the application of aero engine in supersonic ejector system is possible. The effects of air source on ejector performance and the effects of bleeding on aero engine performance were analyzed. And 3 types of aero engine layout in supersonic ejector system were presented. According to the requirements of a supersonic ejector system, the performance parameters of all 3 types of aero engine layout were calculated. The calculation results indicate that when the pressure of the upstream gas is 0.044×10⁵ Pa and 0.029 3×10⁵ Pa, aero engine can directly discharge the upstream gas or be used as the driving gas source for the supersonic ejector system by reasonable selecting the engine layout and working parameters.

Abstract:Aiming at the problem of excessive vibration of the multi-rotor drone, which causes instability of flight state, the vibration reduction analysis work was carried out based on finite element simulation technology and experimental methods. Through frequency analysis, the reason of excessive vibration was determined to be resonance caused by coupling of natural frequency and excitation frequency,and the mode shape corresponding to the resonance frequencies were the first-order waving, the first-order swing and the second-order swing mode shapes. An optimization design method for optimizing the cross-sectional shape of the drone was proposed. Without adding extra weight, the corresponding frequency points of the first-order waving mode, the first-order swing mode, and the second-order swing mode have been increased by 37.23%, 22.47% and 18.43%, respectively. Simulation experiments prove that the proposed vibration reduction analysis and optimization design method can provide references for design work of drones.

Abstract:The deep space impact load is of great significance to the detection of the internal material composition and structural characteristics of small celestial bodies. Therefore, based on considering the characteristics of the variable section of EFP (explosively formed projectile) and the differentiation of the BAD (behind-armor debris),a spatial distribution model for BAD formed by the perforation of variable cross-section EFP through the target was established. Under the condition that the target thickness is 30 mm to 70 mm and the EFP speed is 1 650 m/s to 1 860 m/s, the model can quantitatively predict the relationship between the velocity, mass, quantity and spatial position of each debris in the BAD cloud.The results indicate that the relative velocity increases by a linear function with the increase of the relative spatial position, the relative mass and the relative number increase by a power function with the increase of the relative spatial position.

Abstract:Based on the regenerative cooling technology of liquid rocket engine, the flow distribution characteristics of Z-type parallel channels were studied by numerical simulation method. The effects of channel number, channel section shape and entrance confluence structure on the flow distribution characteristics were analyzed. The results show that the non-uniformity coefficient of flow distribution decreases from 2.59% to 0.5% with the increase of the number of channels in the regenerative cooling system. Increasing the number of channels under the same flow area can effectively ensure the uniformity of flow distribution. The channel section shape has little influence on the non-uniformity coefficient of flow distribution, which is mainly reflected in the flow velocity distribution and heat transfer area in the channel, and the heat transfer effect of the trapezoidal configuration is better than that of the rectangular configuration. The entrance confluence structure is beneficial to the uniform of flow distribution. The research has a certain reference significance for the structural design of regenerative cooling channel.

Abstract:For the problem of the performance of many existing efficient sorting algorithms depends heavily on the parameters from external input, such as clustering number and clustering tolerance, the parameterless clustering algorithm DSets-DBSCAN was applied to the radar signal sorting, and a parameterless radar signal pulse clustering algorithm was presented. The proposed algorithm could automatically cluster without relying on any parameter settings. Firstly, the algorithm input was the pairwise similarity matrix processed by histogram equalization, which made the Dsets(dominant sets) algorithm independent of any parameters. Then, the input parameters of DBSCAN were given adaptively according to the obtained ultra-small cluster. Finally, the cluster was extended by DBSCAN. Simulation results show that the proposed method is effective in sorting radar pulse descriptors without parameters. And the clustering accuracy of radar signals is higher than 97.56% in the case of the false pulse ratio (false pulse/radar pulse) is lower than 80%.

Abstract:Aiming at the active angle deception decoys that may appear in the process of high-altitude and high-speed target detection, a comprehensive and theoretical analysis of the dynamics characteristics was presented, the dynamics equation of active decoy was derived, and the conservation of mechanical energy and moment of momentum of the decoy were analyzed. Theoretical analysis and simulation experiments show that the dynamic characteristics of the azimuth active decoy with fixed angle deception are completely consistent with the real target, and it is impossible to distinguish the true from the false in dynamics. In addition, other angle deception active false targets do not meet the elliptic orbit characteristics of high-altitude high-speed targets and the law of conservation of dynamics. This difference can be used to identify the false targets in the data processing layer.

Abstract:In order to solve the problem that the traditional truth discovery algorithm cannot be applied to text data directly, a truth discovery algorithm(NN_Truth) for text data based on deep neural network was proposed. For the features of multifactorial property of text answers, the diversity of word usages, and the sparsity of the text data, the “source-answer” vector was used as the network input, and the truth vector was recognized as the network output. The relationship between answers from each source could be unsupervised learned according to general hypothesis of truth discovery, and finally obtained the truth. The experiment results show that the proposed algorithm is suitable for text data truth discovery, and it is better than the retrieval methods and traditional truth discovery algorithm.

Abstract:Existing convolutional neural networks, which are used for radio frequency fingerprints recognition, process time-sequenced IQ (in-phase and quadrature) signals as images directly, resulting in low recognition accuracy and high computation complexity. IQCNet(convolutional neural network structure based on IQ correlation features), an efficient convolutional network structure, was proposed. IQCNet firstly extracted IQ correlation features and time domain features, then obtained the average value of each channel features through adaptive average pooling, and finally used only one fully connected layer for classification. Experimental results under a variety of channel conditions show that IQCNet improves recognition accuracy greatly with lower computation complexity compared with traditional convolutional neural networks.

Abstract:Aimed at the problem of weak radar echo of small unmanned aerial vehicle targets and difficult target detection. Long-term coherent integration method under the LFMCW(linear frequency modulation continuous wave) radar was studied. By deriving the expression of LFMCW radar echo, an Radon-Fourier transform implementation method based on Chirp-Z transform of time-domain beat signal was proposed. The computational complexity of this method was evaluated and compared with the method implemented in frequency domain. Simulation and measured data verified the effectiveness of this algorithm for the coherent integration of weak targets under LFMCW radar.

Abstract:In view of the shortcomings of limited terminal battery capacity and low energy efficiency in the existing research on CR-NOMA (cognitive radio non-orthogonal multiple access) networks, a relay was used to assist users in transmission, and a method of simultaneous transmission of wireless information and energy was introduced. Under the constraints of user service quality and minimum energy capture, the sub-user transmission energy efficiency expression was derived. The non-convex objective function was transformed into three convex single-objective problems of optimizing relay transmission power, relay power allocation and receiver power allocation by fractional programming method. Using function monotonicity, golden section algorithm, Lagrangian dual algorithm and multi-objective joint optimization algorithm for optimization, the global optimal solution was obtained to maximize the transmission energy efficiency of the secondary user system. The complexity of the adopted algorithm was analyzed.The simulation results show that compared with the traditional OMA (orthogonal multiple access) scheme, while the system spectrum utilization was improved, the sub-user transmission energy efficiency has been improved by 47%.

Abstract:In order to reduce the subjective one-sided influence of empowerment process of the traditional hierarchical analysis method, a comprehensive AHP(analytic hierarchy process) and Arena simulation modeling technology was proposed to evaluate the efficiency of the allocation of UAV(unmanned aerial vehicle) training resources. Based on flight training process analysis, the factors influencing the efficiency of training resource allocation and efficiency evaluation index were determined, a hierarchical comprehensive evaluation system was established, and the comprehensive evaluation steps of AHP-Arena were summarized. Arena modeling software was used to realize the dynamic simulation system of the training process and verify the validity, the single-variable numerical simulation method and the mean variance decision-making method were used to complete the objective empowerment of the influencing factors, and the comprehensive evaluation coefficient was obtained by linear weighting comprehensive method, so as to implement resource allocation efficiency evaluation and selection of the optimal program.The practical application shows the effectiveness of the method. Meanwhile, this method can be extended to other similar training processes, and can also provide references for other multi-factor multi-indicator evaluation decision-making processes.

Abstract:Few quantitative models can be found amenable to the quantitative evaluation of social work, which motivates the presented work. Moreover, a few related existing works suffer from no suitable indicator system and high expenses of time and money. To overcome these limitations, a real-time quantitative evaluation model using the Internet open-source big data was developed, a target indicator system was established, the rapid computation methods of each criterion were proposed, and a prototypical software system was designed and implemented. Case studies on selected social work were conducted, and the work performance of the 14 cities belonging to a certain province in China was evaluated. Results achieved were largely consistent with the subjective feelings of many respondents and relevant official assessment, which validated the efficiency and rationality of the proposed model.