Abstract:Electromagnetic launch technology is an inevitable trend among methods of launch in the future. The principle and technology characteristics of electromagnetic launch is analyzed, three branches of electromagnetic launch technology development overseas in electromagnetic ejection, electromagnetic railgun and electromagnetic pushing were studied, and the key technology of electromagnetic launch was summarized. Furthermore, the development strategy and the extension application prospect of electromagnetic launch technology was proposed.

Abstract:For the demand of continuous energy absorption of pulsed power supply, the proposal about cycle pulse power water-cooling simulated resistance with 1.9 MA current levels was carried out. Given full consideration to the similarities between the water-cooling resistance and the actual electromagnetic emission resistance, the resistance network composed of 4×8 array of steel pipes was designed, which is convenient for realizing discharging assessment with different power combination. For the problem that 1.9 MA level current can cause too large electromagnetic force, the three-dimensional finite element model of resistance was constructed. Electromagnetic force calculation and structure analysis of resistance were implemented to ensure the stability of resistance. The analysis on resistance temperature rise with the cooling ways of natural, gale and deionized water using thermal network was implemented. The results show that the way of deionized water cooling reaches the best performance. The resistance temperature can reach initial state when pulsed power supply continuously discharges, and the maximum temperature can reach 62.5 ℃, which can satisfy the requirement of continuous discharging. A prototype of resistance was manufactured, and was used for two times discharging with 1.9 MA current. The experimental result demonstrates good agreement with the theoretical analysis. The resistance structure runs well, which verifies the correctness of theoretical analysis.

Abstract:To improve the performance of the SICEML (synchronous induction coil electromagnetic launcher), taking the launching speed and the power conversion ratio as the check mark, and taking the trigger sequence as the optimizing parameter, the mathematic model of Single-stage SICEML was established by using genetic algorithm. The best trigger situation was figure out. Validity of the result was confirmed by numeric and finite element analysis simulation system. In this way, a 2-stage and a 10-stage SICEML optimizing trigger sequences were approached and verified. To solve the inaccuracy problem of the emulate system, the situation and speed of armature were taken as the simultaneous qualification for switch trigger, and the effect of the activation switch′s random flutter to armature′s outlet speed was researched, and a best trigger sequence strategy is submitted.

Abstract:In order to investigate the law of asymmetric operation of six phase cylindrical linear induction motor and in the view of its characteristics of asymmetric operation， the magnetic motive force theory was used to deduce inductance matrix expression of pulsating magnetic field which is independent of the space position in the air gap,. The mathematical models of SCLIM in abc stationary and system simulation models which adopted the implicit trapezoidal rule were established under the Simulink environment. Simulation and experimental results of a SCLIM agree well with each other, which verifies the validity of the proposed model.

Abstract:Segment-powered switch control sensor is an important component for the segmented linear motor control system. For the problems of fault diagnosis and location, an online fault diagnosis method of switch control sensor was proposed. Sensor signal data were compressed to improve computational efficiency; the law of switch control sensor signals changing with shuttle movement was studied, and a set of standard signals were defined; a calculating method for the sensor signal difference which is considered as a quantitative indicator of similarity analysis of signal was given; this problem was represented as the search problem of directed graph and the search was narrowed to a smaller area according to the characteristics of the problem; the search algorithm was given for estimating the process of system state transition according to the metrical data of sensor signals; the fault location process was proposed on the basis of the standard signal set，then the faults were located with the estimated results of the algorithm. Three propositions were given and proved to discuss the consistency between the algorithm and the expected result. The fault diagnosis method was validated through the fault data analysis of actual prototype.

Abstract:Simplified rails and armature as straight conductor with line current, the model of electromagnetic launcher was established. The magnetic intensity of the magnetic probe coil center position was calculated by using Biot-Savart law and the principle of induction electromotive force. Under the assumption that the magnetic field is a uniform magnetic field, the electric potential of the coils was elaborated. An applied probe was designed and the model was verified by comparing with the test data. The issue that probe’s distance change and angle deflection under vibration was raised, the fault states in three groups single shot were measured and analyzed. Simulation and experimental data show that the magnetic probe do not cause failure with a small range of distance variation, while the angle deflection has an interferer on fitting velocity, with the deflection adding the fitting velocity falling.

Abstract:For the numerical simulation method of the dynamic launching in electromagnetic rail launcher, a discrete formulation of three dimensional transient eddy problem for electromagnetic rail launcher considering dynamic launching was established, based on the magnetic vector A and the time integrated electrical scalar potential V, combined by using nodal element method and the moving coordinate frame to deal with the motion. The corresponding three dimensional magneticthermal coupled model was formed finally by using the governing equation for thermal field. The dynamic launching process of an electromagnetic rail launcher was simulated by the finite element model. Numerical analysis results of FEM (finite element method) code and the experiment results were compared and analyzed. The characteristic of thermal field distribution for launcher and the variation of inductance gradient with time were obtained by the model. Results show that the magnitudes of the pulsed current, muzzle current, and muzzle velocity have good correspondence with measure dates respectively, which has verified the correctness of the FEM code.

Abstract:Aircraft arresting gear is a vital safety device for the airfield to ensure normal landing and block the aircrafts which are accidentally out of runway. According to the condition that the mechanical arresting gear used at the present stage cannot meet the arresting needs of future carrier aircraft types, a kind of electromagnetic arresting gear with arresting electric motor as energy absorption components was put forward. A model of electromagnetic arresting gear considering the effects of kink wave was built. The closedloop control algorithm of electromagnetic arresting gear was designed and was validated by simulation.

Abstract:Traditional space debris removal technology with chemical fuel is costly, and it is difficult to be implemented. An innovative method, which is based on ground electromagnetic launch technology, was proposed to remove the space debris. The projectile was launched to the space utilizing ground electromagnetic launch technology which is effective with low cost, and then the particle cloud was released out, which can make the debris can go out of its orbit. The debris was removed by the friction effect during falling out of orbit. As eliminating chemical propellant, which accounts for the majority of the cost, the proposed strategy utilizing ground electromagnetic launch technology to remove the space debris provides an effective and low cost method for space debris removal.

Abstract:Air-breathing scramjet propulsion is the basis of air-breathing solar thermal propulsion technology. How to design an ideal air-inlet is crucial for the propulsion system. By taking advantage of the common method, the DSMC(direct simulation Monte Carlo) on rare-field gas dynamics research, was made to simulate two kinds of air-inlets, which obtained a lot of air parameters such as temperature, density, coefficient of flow and velocity. Then it selected a better air-inlet shape from comparison and treated the shape as a basic air-inlet shape in airbreathing solar thermal propulsion system. It lays a foundation for the design, computation, analysis and optimization on the whole system.

Abstract:High noise and complicated errors caused by low-cost MIMU (micro-electro-mechanical system-based inertial measurement unit, MEMS-based IMU) have caused its stochastic modeling challenge, which may undermine the performance of inertial-based integrated navigation. In order to achieve accurate MEMS-based navigation, a stochastic modeling method called auto-regressive moving-average model for low-cost MEMS-based inertial sensors was proposed on the basis of time series analysis theory. This model was then expanded into the state variables of the conventional Kalman filter to establish the system dynamic equation and observation equation and to estimate the zero-bias online. Field test results indicate that the proposed algorithm can not only realize a highly accurate autonomous navigation for lowcost MIMU, but also provide reliability to the MIMU/GNSS integrated system. 

Abstract:The initial and boundary condition, the hydrodynamic force on the cylinder surface and the cylinder response equations with shear flow were derived based on the stream function-vorticity equations in the exponential-polar coordinates attached on the moving cylinder. The whole evolutions of cylinder starting from rest and then undergoing development and vibration steady were calculated and discussed. The development process of separation vortexes, the deformation and shift of drag-lift phase diagram and the variation of cylinder vibration and equilibrium position were described. Moreover, the steady condition of vortex-induced vibration with the shear rate K was investigated. The results show that the symmetrical flow field will be broken due to the background vorticity generated by the shear flow which also causes the increase of upper vortex strength and the decrease of lower vortex strength. The vortex street inclines toward the lower side and the inclination of vortex streets increase with the increasing shear rate K. So does the shift of pressure curves which leads to the increase of absolute value of lift, the amplitude and the shift of cylinder.

Abstract:Shape-based approximation is an effective method for the low-thrust trajectory design. However, the vast majority of methods assume that the motion trajectory is a specific shape, and there is no constraint on the thrust acceleration. In this representation, according to the issue of low-thrust spacecraft rendezvous, a new method for transfering trajectory design was proposed. Based on the polar coordinates, the trajectory design was successfully turned into solving polynomial coefficients problem through three degrees of freedom motion model built by introduced polynomial function. Meanwhile, the dynamic characteristics of the trajectory as well as the constraint equations were deduced. Subsequently, the optimal polynomial coefficients were solved by the approach of sequential quadratic programming. This method can not only solve problems with a greater number of free parameters, but also meet the thrust acceleration constraints. The simulation has confirmed that this method is accuracy and availability. It can provide a certain technical reference for the trajectory design and fuel consumption estimation during the preliminary stage.

Abstract:In order to investigate the dynamic characteristics and influence factors of reciprocating pump, a modular model library of the RPFPS (reciprocating pump-fed propulsion system) was established. The modular model library was built on the basis of lumped parameter approximation and the dynamic simulation of the work process for RPFPS was carried out on the basis of the AMESim system. The effects of initial pressure of accumulator, equivalent volume of pipeline under gas generator and number of nozzles on the dynamic characteristics of reciprocating pump were studied. Results have been obtained as follows: due to the bigger initial pressure of accumulator, less time was used to start the reciprocating pump, but the regulation ability of accumulator was weaker; it would take less time to start the reciprocating pump because of larger equivalent volume of pipeline under gas generator, but it would also lead to the increase of pressure fluctuation; the greater the number of nozzles, the lower the pressure fluctuation in gas generator, and the more time of reciprocating pump to start because of the slower pressure increasing speed.

Abstract:An anti-rendezvous evasion maneuver method was proposed in order to escape from the spacecraft that has autonomous approaching ability. A bearing-only relative navigation model was built and the definition of absolutely non-observable maneuver was proposed. After some algebra, it was proved that the absolutely non-observable maneuver is non-existent. Based on that, an object function using vector multiplication was designed to find the minimum of measurement difference during the evasion. An optimization model was established and the variable bound was given so that the minimum of the object function could be obtained by the Genetic Algorithm. The numerical simulation was conducted with different maneuver impulse. The result shows that the proposed method can minimize the measurement difference between evasive maneuver adopted and evasive maneuver ignored. The method presented offers a new viewpoint for evasion maneuver research.

Abstract:The sparse reconstruction is one of the key factors in compressive sensing theory. In order to apply sparse reconstruction to compressive imaging process of star tracker in an effective way, the effect of sparse reconstruction on star image was analyzed from the perspectives of star image error and star feature error. For the problem of image error, PSNR（peak signal-to-noise ratio） evaluation index was employed to observe reconstruction quality of star image under different reconstruction algorithm and diverse compression ratio. For the problem of feature error, firstly, the influential mechanism of sparse reconstruction on star feature was analyzed theoretically; and then the evaluation index of reconstruction error of star feature was proposed to investigate the reconstruction error of star centroid, brightness and number. Result shows that, the star image can obtain higher reconstruction quality than the common image with the same reconstruction condition under diverse compression ratio of selected algorithm, and the reconstructed star can keep its features for attitude determination to a large extent. The conclusion proves the validity of attitude estimation by using the reconstructed star image, verifies the feasibility of applying compressive sensing to star tracker and provides the practical foundation for compressive imaging of star tracker.

Abstract:Aiming at the multi-constraint terminal guidance of hypersonic vehicle, a novel 3D (three-dimensional) nonlinear adaptive terminal guidance law was proposed to resolve the problems of channel coupling, parameter perturbation and model mismatching. For the integrality and concision in model description, a 3D guidance reference model and its corresponding practical guidance system were both constructed on the basis of the concepts about line-of-sight twist and its rate. In order to guarantee the robustness and adaption, a 3D nonlinear adaptive guidance law was deduced on the basis of the adaptive control theory. The stability of this guidance law was proved through mathematical deduction. With this novel guidance law, the channel coupling, parameter perturbation and model mismatching problems were avoided and the multiconstraint of terminal guidance was satisfied as well. The validity of this guidance law was also validated through simulation experiments.

Abstract:Due to its accidental, sudden and regional characteristics, the simulation of GNSS navigation signals under ionospheric scintillation is difficult to be implemented accurately. The ionospheric scintillation time-series generation method based on Gamma distribution and zero-mean Gaussian distribution was proposed. With the NSS8000, a multi-system navigation signal simulator developed by our department, the hardware architecture of BeiDou navigation signal simulation under ionospheric scintillation was given. Then based on this, by intermediate frequency signal sampling and software receiver processing, the impact of ionospheric scintillation on BeiDou receiver tracking loops was analyzed. The results indicate that the code tracking error can reach 0.05 chips when the phase scintillation index is 0 and amplitude scintillation index is 0.9, while the carrier tracking error can reach 15 degrees when the amplitude scintillation index is 0 and the phase scintillation index is only 0.5, which the carrier tracking loops is almost loss of lock.

Abstract:In the diagnosis of large-scale mechanic-electronic-hydraulic control system, and for the mathematical model was hard to build and the historic fault data was short, a hybrid fault diagnosis method based on virtual prototyping and PNN (probabilistic neural network) was proposed. Virtual prototyping was first built and its credibility was validated. On this basis, fault injection and simulation were conducted to obtain fault data, which was then extracted as fault features and trained by PNN to form diagnosis knowledge library. A case study of steering system was presented to verify the correctness of the proposed method, which shows that the accuracy of fault detection and isolation is high and the rate of false/missing alarm is low. The proposed method may bring a novel idea for the fault diagnosis of large-scale and complicated mechanic-electronichydraulic control system.

Abstract:Local feature extraction plays an important role in related point cloud applications. Therefore, an EPFH (extended point feature histograms) descriptor for the local feature representation of 3D point cloud was proposed. Each point pair was represented by several invariant pairwise point attributes. Then, a local reference frame was defined for a keypoint and the neighboring points of the keypoint were transformed into the local reference frame. These pairwise points attributing between the neighboring points and the keypoint were accumulated into several subfeatures in a set of subspaces. These subfeatures were finally concatenated and compressed into an overall feature descriptor. The EPFH descriptor was tested by a popular publicly available Bologna dataset and was compared with several existing methods. Experimental results show that the proposed EPFH method outperforms several existing methods under different levels of noise and point cloud resolutions.

Abstract:As the targets in the same beam are close to each other, it is difficult to resolve them via traditional techniques. Furthermore， it also brings difficulty in detecting and tracking. The problem of resoling two targets in the same beam was studied with array radar. An echo model of two unresolved targets with array radar was established. An improved angle estimation method was proposed based on the maximum likelihood estimation principle. In consideration of the convergence speed and estimation accuracy, the LevenbergMarquardt method was applied to obtain the maximum likelihood estimation of target direction. The simulation results prove that the method performs well in several aspects, including smaller estimation error and computational cost.

Abstract:To deal with the problem of radar emitter recognition caused by parameter complexity and agility of muti-function radars in electronic intelligence reconnaissance field, a new recognition model based on deep restricted Boltzmann machine was proposed. The model was composed of multiple restricted Boltzmann machine. A bottom-up hierarchical unsupervised learning was used to obtain the initial parameters, and then the traditional back propagation algorithm was conducted to fine-tune the network parameters, and the Softmax was used to classify the results at last. Simulation and comparison experiment shows that the proposed method has the ability of extracting the parameter features and recognizing the radar emitters, and it has strong robustness as well as high recognition rate.

Abstract:There are two important characteristics for missile plume in infrared multispectral imagery: one is the gray-scale difference caused by strong infrared radiance; and the other one is the unique spectral signature feature. However, the classical single-band detection technology only uses the first characteristic, and the multispectral detection technology which has been developed in recent years only uses the second characteristic. In order to fully exploit the characteristics of missile plume, three detection algorithms were proposed by combining the single-band and multispectral detection technology. The advantages and disadvantages of the three algorithms were discussed in detail in the aspects of detection performance, computational complexity and robustness. Experiments on synthetic infrared multispectral imagery demonstrate a better performance of the combined algorithms when compared with single-band or multispectral detection algorithm.

Abstract:A novel communication system based on orthogonal frequency and code division multiplexing was proposed for precise time measurement in the fading channel, and a novel iterative algorithm was proposed to improve the performance caused by the fading channel and phase noise without reducing the maximum unambiguous time. In the scheme, the coefficients of fading channel and the phase noise were jointly estimated with the time delay. It is shown both by theory and computer simulations that the proposed scheme can effectively mitigate the time estimation error caused by fading channel and phase noise.

Abstract:IFFT(inverse fast Fourier transform) technique is usually used in high resolution radar imaging with stepped frequency signal. However, due to the high side-lobes introduced by IFFT, the weak scatters or small targets may be covered by the range side-lobes of the strong scatters, which limit its application in the strong clutter environment. In order to suppress the high range sidelobes, APC (adaptive pulse compression) algorithm based on MMSE (minimum mean square error) has been proposed in recent years. Based on the model of APC algorithm, the APC algorithm of stepped frequency signal for stationary and moving target was detruded. Simulation results show that the APC algorithm has a better side-lobe suppression effect when compared with the IFFT method and the windowed processing, and it can detect weak scatter or small target in the neighborhood of the strong one better.

Abstract:In order to achieve the continuous and dynamic monitoring of physiological signals, such as the pulse wave, the respiratory wave and the blood pressure, a wearable health monitoring body area network system based on piezoelectric film sensors was made. Using the sensors attached into the stretchy fabric (For example, belt and wristband), the system can receive physiological signals such as pulse wave and respiratory wave. A condition recognition algorithm was proposed to distinguish conditions such as lying, standing, sitting, walking, running and sleeping by analyzing the geometric features of the respiratory signals received from piezoelectric film sensors. Taking advantage of the relationships between pulse wave translation time and blood pressure to calculate diastolic blood pressure and systolic blood pressure of user, the pressure-free blood pressure measurement was achieved. The nodes communicated with each other through Bluetooth. The data were displayed on the wearable display devices and mobile devices. The system realized continuous and dynamic monitoring of physiological signals, such as the pulse wave, the respiratory wave, the blood pressure.

Abstract:To weaken the strength of the signals, a prediction method was presented. The electric field signal was decomposed into a low frequency signal and several high frequency signals. The high frequency part was predicted with auto regressive prediction model and the low frequency part was predicted with GM(1，1) model. The prediction result was the superimposition of the respective prediction. Based on the measurement at sea, the simulation results show that the prediction error of the electric field can be controlled within 20% of the amplitude of the signal.

Abstract:To effectively reduce or hedge the development risk of weapon equipment for smooth project progress, a comprehensive assessment method based on SPA(set pair analysis) theory and LS-SVM (least square support vector machine) method was proposed for weapon equipment development. Firstly, according to the specific characteristics of weapon equipment development, the weapon equipment development risk assessment index system was established. Secondly, on the basis of this, the concept of connection degree and set pair in SPA theory was introduced to construct the training samples and test samples. Finally, through the obtained samples, LSSVM was trained and tested to get the assessment model and to produce the assessment result. An example analysis shows that the proposed method has many advantages in simple implement, combining the qualitative analysis and the quantitative analysis, easy understanding. The assessment results are more close to the actual development. It has important practical significance to improve the risk management and decisionmaking level of weapon equipment development project.

Abstract:Aiming at the problem that the underwater small platform cannot locate the low-frequency near-field target, a cooperative localization algorithm using multiple vector hydrophones was proposed. The hydrophones were regarded as different observation points, and then the azimuth angles of target connected to different observation points were estimated respectively on the basis of the array manifold characteristics of hydrophones. According to these azimuths, the location of near-field target was realized by using the orthogonal vector method. This algorithm avoids the multi-dimensional search process and reduces the calculation. The simulation results show that this algorithm can locate the nearfield target accurately and improve the location accuracy effectively.

Abstract:A dual-band circularly polarized patch array using a sequential-phase feeding network was presented. The array includes four metal patches and a metal square ring. Each rectangle patch was cut in diagonal corners, and was excited by feeding lines on the edge. The feeding lines are microstrip which are connected to the middle metal square ring. In addition, four patches are rotated arrangement. The middle mental square ring is not only a feeding network which provides increasing phase for circularly polarization, but also a radiator which enhances the performance of the array. With this feeding way, the patch array just has single-layer substrate and it is compact. In addition, it radiates circularly polarized patterns in two working bands. Through fabrication, test and measurement, the -10 dB impedance bandwidth of the patch array is 5.17 GHz～5.59 GHz and 5.99 GHz～6.27 GHz. The measured 3 dB AR bandwidth is 5.19 GHz～5.49 GHz and 6.1 GHz～6.18 GHz. 