Abstract:A variable-bandwidth design method based on the principle of energy equivalence was proposed for the random vibration environmental test condition of launch vehicles. By adopting the fractional octave frequency band data processing method and keeping the RMS (root mean square) in every frequency band identical with the one of the original power spectral density, the exorbitant RMS problem of the traditional constant-bandwidth random vibration environmental test condition was avoided. To validate the capability of the method, the random vibration simulations of a typical pipeline were conducted. The results indicate that the method is able to assess the product effectively rather than excessively. The proposed variable-bandwidth design method offers an efficient alternative for the conditions design in the random-vibration environment test of launch vehicles.

Abstract:In the ignition state, the SRM (solid rocket motor) grain with wall pouring is in the state of superimposed pressure, while the circumferential direction of SRM inner bore is under tensile strain. It is urgent to carry out related research on the failure mechanism of propellant under superimposed pressure. The mechanical behavior of solid propellant under coupling effect of superimposed pressure, temperature and strain rate was investigated through uniaxial tensile tests at different pressure, temperature and strain rates using self-developed superimposed pressure loading system. According to the mechanical response characteristics of the propellant under superimposed pressure, the failure modes of the propellant under superimposed pressure were further studied by means of meso-scale mechanical simulation. At the same time, the morphologic sectional features of the propellant specimens were analyzed by means of scanning electron microscope test. The failure mechanism of the propellant under superimposed pressure was found out by means of combining test and simulation. The results show that the damage interfaces of propellant decrease significantly under superimposed pressure, and with the increasing of superimposed pressure, the damage form of propellant changes from particle dewetting dominated to particle breakage dominated.

Abstract:Compared with the traditional gunpowder bullets, electromagnetic launch bullets have the advantages of high muzzle velocity and long fire range. However, the bullet shape is no longer axisymmetric because of the armature groove at the tail, resulting in unique aerodynamic characteristics. Based on the three-dimensional unsteady Navier-Stokers equation, the aerodynamic characteristics of electromagnetic projectile were analyzed by using the sliding grid technique. Results show that for the hypervelocity spinning electromagnetic projectile, the Magnus effect comes from the interaction of shock layer distortion and the upwind area variation of the armature arm. The aerodynamic force and the moment varies periodically with the roll angle due to the periodic variation of the upwind area of the armature arm, and the Magnus moment reaches the minimum and the maximum at the roll angle of 45° and 135°, respectively. The influence of the armature arm groove is remarkable, which not only worsens the Magnus effect (increased by more than 50% at 135°), but also makes the pressure center move forward periodically (the absolute forward amount is up to 5%). Furthermore, with the increase of spinning speed, the increase of the Magnus moment and the pressure center move-forward effect become more and more significant, which is harmful to the dynamic stability of the projectile.

Abstract:Double two-body model is the fundamental conception model for solving Earth-Moon transfer orbit. The traditional approaches use the latitude and longitude of entry point on the sphere of influence to describe double two-body model, while in this paper a geometrical representation method of double two-body model by using parameters in orbital plane of flight trajectory was proposed. The search space on three-dimensional sphere was reduced to be a two-dimensional circle formed by tangent of the orbital plane and the sphere of influence, the shape parameter of Earth-Moon transfer orbit can be efficiently solved by one-parameter Brent root-finding algorithm and Lambert theory. In order to avoid double calculation, the orbital multivariate search problem calculated by the transfer orbit window was decoupled into two sub-problems, the transfer orbit shape parameter solution problem and the transfer orbital plane space orientation problem, which reduce the solution dimension of the problem, The two-stage method with parallel computing was approached in order to make full use of the nowadays computational power of multi-core computer. The simulation results show that the new parallel double two-body model with the use of geometrical section of orbital plane can be successfully applied to the analysis of the Earth-Moon transfer orbit from space elevator.

Abstract:The distribution of solar radiation intensity on the upper surface of the stratospheric airship is an important factor affecting the output performance of photovoltaic arrays. In order to analysis the influence of the dynamic change of the flight attitude of the stratospheric airship on its upper surface solar radiation intensity distribution characteristics and establish a calculation model of interactive coupling between the airship dynamics model and the solar radiation physical model was established. By using this mode, a certain airship example was calculated, the solar radiation intensity distribution on the upper surface of the stratospheric airship was also proposed under flight yaw and pitch angle change, and the characteristics of solar radiation intensity affected by airship flight attitude. The result can be used to guide the optimized layout and array configuration of the solar array on the stratospheric airship.

Abstract:At present, the optimal design of linear pyrotechnic separation device mostly depends on experiments, which is not only costly but also low efficient. Herein, a numerical model was developed with arbitrary Lagrangian-Eulerian method for a typical linear pyrotechnic separation device. The numerical model was validated via pyrotechnic separation experiments and photonic Doppler velocimetry, and it was found to have reasonable accuracy. The model was applied to study the mechanical mechanism of the transient separation process of the pyrotechnic separation device. The influence of multiple factors on the critical characteristic parameters was also studied quantitatively, such as effective plastic strain of the key areas of the device. It is found that the linear density of the detonating cord and the bottom radius of the v-notch of the separation plate have significant influence on the separation process. In addition, the material of the protection plate, the angle of the v-notch and the dimension of the rectangular notch of the separation plate also have a certain influence on the separation process, however, the influence is less than that exerted by the linear density of the detonating cord and the bottom radius of the v-notch. The study can provide a foundation for optimal design of the typical linear pyrotechnic separation device.

Abstract:Aiming at the problem of signal detection in small sample and nonhomogeneous clutter, a matrix information geometric detector based on manifold filter was proposed. The signal detection problem was transformed into a geometric problem on the matrix manifold. The correlation of each sample data was modeled as a Toeplitz positive definite matrix. On the basis, each matrix was replaced by a weighted smoothing filter of its surrounding matrices. The weighted smoothing filter removed part of the clutter energy and improved the discrimination between the target and the clutter. The geometric mean of a set of secondary sample data was calculated. By comparing the distance between the matrix under test and the geometric mean matrix with the detection threshold, the signal detection was realized. Simulation results demonstrate the superiority of the detection performance of the proposed method in small sample and nonhomogeneous clutter compared with adaptive matched filtering.

Abstract:Aiming at the problem of task offloading failure caused by the excessively fast vehicle moving in the Internet of vehicles, an effective task offloading risk assessment model was designed, and a dynamic task offloading scheme based on joint resource allocation was proposed. Time, energy consumption, and risk were jointly modeled as system utility, and the system utility was maximized through joint optimization of offloading decision and resource allocation. The optimization problem was formulated as a mixed integer nonlinear programming. Convex optimization techniques were used to solve the computational resource allocation problem under a given offloading decision, power allocation was optimized through fractional programming technology. The simulation analyzes the impact of vehicle mobility on system utility, and the rationality of the proposed scheme is proved.

Abstract:A set of electromagnetic radiation measurement devices based on short-wave omnidirectional antennas and ultra-wideband omnidirectional antennas was designed to measure the electromagnetic radiation generated by TNT explosions, and the data was processed to obtain electromagnetic radiation characteristics.The results show that the explosive mass has a significant effect on the time domain characteristics of the electromagnetic radiation generated by the explosion. The greater the mass, the shorter the delayed response of the electromagnetic signal, the longer the duration, and the earlier the peak time. 60 kg TNT explosion generated electromagnetic radiation signal frequency is mainly concentrated below 100 MHz, the most concentrated energy is in the 0～50 MHz band, the explosive composition has the largest effect on the spectrum distribution, and the electromagnetic radiation spectrum distribution generated by different components of the explosive explosion has obvious specificity. Electromagnetic radiation intensity generated by dynamite explosion shows a strong correlation with the distance from the burst center. The intensity decreases with the distance increasing, and the magnitude of the decrease is large. Charge configuration and detonation mode will change the geometric movement pattern of the explosive during the explosion process, resulting in the non-uniformity characteristics of the explosion electromagnetic radiation propagation.

Abstract:Considering the vessel environmental constraints and the requirements of pulsed load, it is necessary to rationally select and configure the ESD(energy storage device) to improve the performance of the vessel integrated power system. For this reason, based on the weighted minimal module ideal point method and analytic hierarchy process, a performance evaluation function of ESD was proposed, and the optimal configuration was carried out with this function. The proposed function fully considers the system requirements and pulse load characteristics, and takes the ESD volume, weight, and economy as the main components of the evaluation function. At the same time, it takes power, energy, voltage, and state of charge as constrains to establish an optimal configuration model. The differential evolution algorithm was adopted to solve it. The proposed model was solved and calculated with the example of high performance lithium battery and supercapacitor. The results show that lithium battery has better performance and are more suitable for integrated power system under the given weight. Besides, the guiding configuration scheme was given.

Abstract:Aiming at the problem that the carrier vibration of underwater detection system interferes with the micro-Doppler spectrum of target echo signal, the approximate multiplicative expression of interference was derived from the basic principle of interference generation. With obtaining vibration interference data, an interference suppression algorithm for multiplicative interference was proposed. Meanwhile, the error caused by the approximate algorithm was analyzed according to the approximate conditions when the multiplicative expression of interference was derived. Simulation results show that the proposed method can effectively suppress the interference which is derived from vibration of underwater acoustic detection system and imposed on the micro-Doppler spectrum, and the algorithm error can be ignored generally.

Abstract:In practical applications, the traditional Whitt passive point target calibration algorithm often leads to the problem of incorrect solution of polarimetric distortion matrix, which makes it impossible to calibrate the polarimetric distortion correctly. To solve this problem, on the basis of analyzing the cause of failure in solving the distortion matrix of the commonly used Whitt algorithm, a new polarimetric calibration method using 22.5° dihedral was proposed, including a new calibrator set, a preprocessing procedure for measured polarimetric scatter matrix and a new eigenvalue match rule, which could prevent wrong eigenvalue match result and thus wrong calibration result effectively. Simulation results verify its effectiveness and robustness.

Abstract:In order to improve the detection ability of weak ship shaft-rate electric field in the background of marine environment electric field, the ALE (adaptive line enhancement) based on incremental meta-learning IDBD (incremental delta-bar-delta) algorithm was proposed to improve the traditional LMS (least mean square) algorithm. The proposed algorithm was used to process the measured shaft-rate electric field signal data generated by the ship scale model. The results show that the algorithm can effectively separate the weak shaft-rate electric field signal from the broadband background noise under the condition of low SNR(signal-to-noise ratio). Compared with the ordinary ALE algorithm, the proposed algorithm has a more significant effect in improving the SNR of the signal, and has a faster convergence speed and a smaller steady-state error, which greatly improves the ability to test shaft-rate electric field of the ship.

Abstract:In the complex electromagnetic environment of the battlefield, satellite navigation receivers are susceptible to EMI (electromagnetic interference) and cannot be positioned. In response to this phenomenon, a method for evaluating the EMI situation of satellite navigation receivers based on unmanned aerial vehicle′s environmental perception was proposed. When the navigation receiver was not interfered, the characteristic parameters of the EMI and the receiving state of the navigation receiver were used as the input of the prediction. When the receiver tracking loop was lost, the effect threshold was used as the observation target value to establish the XGBoost prediction model. On this basis, the rank of the EMI situation of the navigation receiver was given, and the situation assessment method of the navigation receiver under single-source or dual-source were proposed. Compared with the prediction methods of Gaussian processes for regression and support vector regression, the results show that the XGBoost method has the better prediction accuracy. According to this prediction method, the comprehensive utilization of the technology schemes and the tactical schemes is beneficial to improving the adaptability of unmanned aerial vehicles in complex electromagnetic environments.

Abstract:Aiming at the problem of cooperative airspace configuration of early warning aircrafts and jammers in offensive operations, and on the premise that early warning aircraft and jammers can ensure their safe and effective implementation of aerial target perception and long-distance support jamming operations, the decision-making models of airspace configuration of early warning aircraft, airspace configuration of jammers, target angle estimation model and optimal decision-making model of cooperative airspace configuration were constructed based on the electromagnetic interference between them, in addition, a collaborative effectiveness evaluation model was proposed. Combined with the proposed algorithm process, the location relationship of the cooperative airspace configuration of early warning aircraft and jammers was simulated and analyzed according to the attack angle and the vertical pattern factor of jammers, and the optimal airspace configuration of early warning aircraft and jammers in cooperative operation was obtained, which has certain practical significance.

Abstract:To solve the problem of radiation-source target localization for a single UAV(unmanned aerial vehicle) in an urban environment, a new trajectory optimization algorithm for bearings-only target localization based on the environment prediction method was proposed. Interacting multiple model methods coupled with the extended Kalman filter was used to estimate the target localization in the line-of-sight and non-line-of-sight mixed environment. Based on the estimated target location and urban geographic information system, the electromagnetic signal occlusion region and the multipath interference region were calculated by using the line of sight tracking method. Under the framework of receding horizon method, the UAV prediction trajectory was generated, so as to maximize the Fisher information matrix determinant as the orientation positioning evaluation criterion. Considering the influence of building obstacles and their occlusion and reflection effects in the localization process, the UAV was controlled to choose the optimal heading flight.The numerical simulation results show that the trajectory optimization algorithm enables the UAV to perform high-precision bearings-only target localization in the complex environment containing obstacles, signal occlusion, and multipath interference. The algorithm provides a new way to solve the problem of bearings-only target localization for single UAV in an urban environment.

Abstract:In view of the wide demand for precision positioning in the ocean and the high cost of traditional precision positioning services, it was proposed to use BeiDou short-message equipment to transmit navigation observation data, combined with real-time data products, to achieve low-cost centimeter-level precise relative positioning in the ocean. In order to overcome the shortcomings of low transmission frequency of short messages, for the first time, the two technologies of fusion spatial relative positioning and precise point positioning were used to encrypt coordinates outside the minute interval, avoiding the accumulation of errors in the encrypted coordinates of the traditional time-relative method. Simulation experiments were carried out based on static and dynamic ocean observation data. Results show that the new method can achieve centimeter-level positioning in both horizontal and vertical directions, and the results show that the new method is not sensitive to the length of time interval.

Abstract:The real-time performance of each node in one cluster varies greatly due to different configurations and the job running on it. To improve the cluster performance, NPARSA (node real-time performance adaptive cluster resource scheduling algorithm) was proposed. The real-time performance of a cluster node was represented by its configuration (such as the number of its CPU cores,the speed of CPU, memory capacity, and disk capacity) and the real-time state parameters (such as the residual of CPU, memory, and disk). NPARSA chose the attribute weights for a node according to the type of the job to be handled, and assigned nodes with higher priority to the job. Virtual machine experiments and physical cluster experiments prove the effectiveness of NPARSA. Compared with Spark′s default scheduling algorithm,the algorithm that does not consider the job type and node matching, and the algorithm that uses the degree of job and node matching difference as the basis for resource allocation, NPARSA can improve the performance of a cluster and shorten the execution time of user jobs.

Abstract:Aiming at the global task planning problem of large-scale heterogeneous UAV (unmanned aerial vehicle) swarm, a task planning method based on balanced clustering market auction mechanism was proposed. Scene of completing tasks by collaborative UAVs was analyzed, and a task planning model with high generality was established by combining the advantages of task clustering and UAV coalition. Considering the demand for load balance of UAVs, a new balanced clustering market auction algorithm which comprehensively considers the travel consumption and task consumption was established by integrating and improving the K-means algorithm and market auction mechanism. The balance parameter was introduced into the auction process. By solving the traveling salesman problem to modify the balance parameter, the total cost was continuously reduced while ensuring the load balance. The simulation results show that the task planning method using balanced clustering market auction mechanism can complete the complex task planning of heterogeneous UAV swarm in a short time, ensures the load balance of UAV coalitions, and has good performance in total cost and total time, exhibiting certain practical application value.

Abstract:In order to reasonably choose a sample condition which supports efficient intelligent diagnosis, and to overcome the problems of too many weights and weak local information extraction capability of intelligent traditional BP (back propagation) network, an open-circuit faults diagnosis method based on CNN(convolutional neural network) was studied. Moreover, by taking the typical three-phase two-level inverter as the specific object, the advantages of the CNN method on network weights number, network training stability and diagnosis effects under different conditions of sample durations and training sample numbers over the BP network method were analyzed quantitatively. Results show that the CNN method can build a deeper network model with much less weights than the BP network method, and it can achieve efficient and accurate model training and diagnosis with shorter and less samples.

Abstract:Aiming at the lack of load power prediction function in electric drive armored vehicles leading to the lag of control action, a real-time energy management strategy with higher load power prediction accuracy was proposed. Based on analyzing the whole vehicle′s structure, each power source′s mathematical model was established using theoretical analysis and data fitting methods. Combining the two forecasting methods of auto regressive integrated moving average model and adaptive Markov chain, a combination forecasting method of non-stationary trend load power was designed. Under the framework of nonlinear model predictive control, a multi-objective optimization function was constructed, and the sequential quadratic programming method was utilized to solve the optimal control command in real-time in the finite time domain. The multi-power source was optimized and coordinated. Relying on the hardware-in-the-loop simulation platform, multi-road driving experiments were carried out, and energy management control effects with or without power prediction method were compared. The results show that the improved real-time energy management strategy has good predictability for future load power. It can significantly optimize the coordinated control process of multiple power sources, improve vehicle fuel economy, stabilize bus voltage and battery state of charge. Moreover, it has specific reference significance in engineering application scenarios under traditional model predictive control.

Abstract:In order to scientifically predict the electromagnetic force performance of the electric-controlled booster pump high-speed solenoid valve for the ultra-high pressure common rail system, the response surface method was used to construct the electromagnetic force prediction model to achieve efficient prediction and optimization of its performance. A three-dimensional finite element simulation model of the high-speed solenoid valve for the electric-controlled booster pump was established and verified by experiments. Based on the idea of experimental design, key factors such as drive current, working air gap, armature thickness, number of coil turns, main magnetic pole radius, and orifice radius were selected. 54 sets of sample points of electromagnetic force numerical test research program were developed through the response surface method. The electromagnetic force prediction model was constructed. After R test, and the simulation test verifies that the electromagnetic force prediction model has a maximum error of 1.3%, indicating that the model can accurately predict the electromagnetic force of the electric-controlled booster pump high-speed solenoid valve and provide a theoretical basis for the design and optimization of the ultra-high pressure common rail system control system.

Abstract:The core actuator in a strong electromagnetic shock environment is the coil. In addition to ensuring the electromagnetic characteristics of the coil in a strong magnetic environment, it is also necessary to ensure that the coil support has adequate mechanical characteristics. On the basis of the completed magneto-electric design of the coil, the finite element calculation model of the overall system of the coil support structure was established based on the three-dimensional structure drawing of the coil, the material configuration, the mass distribution, the connection method between the components and the coil fixation method, etc. The numerical calculation analysis of the static force and stability of the coil support system was carried out and the strength of the coupling was checked to provide a reference basis for the coil support structure. The design and analysis of the overall mechanical structure of the coil used in the practical large-scale strong magnetic shock system is relatively new, and the simulation calculation process is strictly in accordance with the actual size of the construction, with a high degree of consistency, providing a solid foundation for the subsequent construction of the strong magnetic environment generator.

Abstract:In order to assure the transport airworthiness of large rubber container, the design of the landing impact test system was carried out according to the Civil Aviation Administration of China on the emergency landing overload requirements for transport category aircraft. The impact platform was simulated and verificated, the waveform generator was simulated and designed, the pendulum system and guiding mechanism were designed, while the landing impact test system was constructed. The payload reaches nearly 20 t, and the maximum impact load reaches 400 t. The large rubber container was selected as a typical air cargo for emergency landing test verification. The results show that the waveform of the impact test is approximately triangular wave, which is simular to the waveform of the simulation curve. The overload peak is 1.54g laterally and 3.06g, 9.02g, 16.20g heading respectively. The maximum error with the target peak is less than 3%, and the corresponding time of the peak is more than 50 ms. The test system meets the design requirements. The system will be used for the development of airlift platform,which is great significance to ensure flight safety, reduce development risk and improve the airworthiness of airlift platform.