This study addresses the challenge of simulating ground scattering characteristics in equivalent irradiation tests for radio detectors. By combining electromagnetic modeling with experimental validation—including drone-carried detection and sliding rail tests—the scattering properties of bare soil surfaces in the K, Ka, and V bands and their effect on millimeter-wave detector performance are systematically analyzed. By employing Monte Carlo methods and Gaussian rough surface modeling, we compared the radar cross-section (RCS) and echo signals of corner reflectors of different sizes against real ground responses. Experimental results show that a corner reflector no smaller than 14 cm closely matches the RCS characteristics of actual ground across multiple bands and reliably triggers the detector, meeting equivalence requirements. This work provides practical guidance for selecting equivalent targets and supports calibration and performance evaluation of millimeter-wave detectors in complex terrain.

Aiming at the problem of low distance accuracy of the harmonic distance determination method in the practical application of frequency modulation fuze,a differential frequency signal processing method is designed based on fast Fourier transform(FFT)and constant false alarm rate(CFAR)theory,with a two-dimensional fast Fourier transform(2D-FFT)method and frequency domain two-dimensional constant false alarm rate(2D-CFAR)adaptive detection method as the core.To reduce the impact of noise on the frequency modulation fusion,this approach transforms a one-dimensional differential frequency signal into a two-dimensional matrix,applies 2D-FFT transformation to produce a two-dimensional distance velocity frequency domain,and removes static clutter.The filtered two-dimensional frequency domain is used to extract the distance and velocity of the target using 2D-CFAR.The performance of the system is verified by simulation.According to the research findings,at a jamming-to-signal ratio of 15 dB,the relative error of the velocity measurement is 0.004 and the relative error of the differential frequency signal processing system is 0.033.The system has high real-time performance and can accurately output the initiation signal within 10.26 μs.The proposed method can obtain the target distance and speed accurately and in real time when the frequency modulation fuze and the ground target intersect at high speed,and improve the anti-sweep jamming ability of the frequency modulation fuze.

The spatial location of fuze detonation point is crucial for evaluating the working condition and improving the performance of fuze. Considering the observation safety, the non-contact long-distance accurate measurement technology is essential. In this paper, we propose a method that takes the sensor data of optics, spatial attitude and GPS as input and outputs the spatial position of the fuze detonation point. The proposed method consists of two steps. First, an object detection algorithm with post-processing algorithm is proposed to obtain rich information of the target. The algorithm achieves high-accuracy detection by introducing powerful backbone, attention mechanism, group convolution, and improved multi-scale feature fusion. Second, a Variational Auto-Encoder (VAE) algorithm model improved by dense connection structure and multiple source heterogeneous sensor information fusion structure is proposed as the position regression algorithm. It receives the status information of the observer camera and the output of the object detection algorithm, and then outputs the three-dimensional coordinates of the explosion point. Finally, method validation and performance analysis are realized through virtual scene simulation. Experiment results show the superiority of the proposed object detection algorithm over other typical algorithms on explosion flare detection, with its Average Precision (AP) of 0.889. The positioning error of the spatial location method is 0.896 m, while that of the binocular stereo vision method is 2.863 m. Therefore, the proposed target spatial location method is proved to be effective and accurate.

Radio frequency interference (RFI) significantly hampers the target detection performance of frequency-modulated continuous-wave radar. To address the problem and maintain the target echo signal, this paper proposes a priori assumption on the interference component nature in the radar received signal, as well as a method for interference estimation and mitigation via time–frequency analysis. The solution employs Fourier synchrosqueezed transform to implement the radar’s beat signal transformation from time domain to time–frequency domain, thus converting the interference mitigation to the task of time–frequency distribution image restoration. The solution proposes the use of image processing based on the dual-tree complex wavelet transform and combines it with the spatial domain-based approach, thereby establishing a dual-domain fusion interference filter for time–frequency distribution images. This paper also presents a convolutional neural network model of structurally improved UNet++, which serves as the interference estimator. The proposed solution demonstrated its capability against various forms of RFI through the simulation experiment and showed a superior interference mitigation performance over other CNN model-based approaches.

When the electromagnetic rail launcher accelerates the projectile, the inner bore of the track is in a harsh environment such as high temperature, high pressure and high current, which will cause irreversible and cumulative structural damage on the surface of the inner bore. It is important to study the damage image of the inner cavity of the electromagnetic rail transmitter for evaluating the durability and life decay of the tube. In this paper, a new measuring structure is designed according to the special cavity structure of electromagnetic orbital transmitter with large aspect ratio and special shape. It can be equipped with a micro-multi-camera array to obtain high definition image of the inner cavity. The image detection system in the cavity of the electromagnetic track transmitter is composed of ARM master, micro-multi-camera combination module, laser ranging module and motion mechanism, and upper computer which is composed of wireless control and image data fusion. According to the characteristics of ring stitching and parallel fusion of multi-camera images in this paper, an optimal stitching algorithm is proposed, which mainly includes SIFT feature extraction, BBF feature matching, RANSAC screening optimization, image transformation mapping, in-out edge fusion and image stitching. The experimental results show that this method can obtain high resolution inner surface image and achieve better image Mosaic effect.

The detection performance of radar is significantly impaired by active jamming and mutual interference from other radars. This paper proposes a radio signal modulation recognition method to accurately recognize these signals, which helps in the jamming cancellation decisions. Based on the ensemble learning stacking algorithm improved by meta-feature enhancement, the proposed method adopts random forests, K-nearest neighbors, and Gaussian naive Bayes as the base-learners, with logistic regression serving as the meta-learner. It takes the multi-domain features of signals as input, which include time-domain features including fuzzy entropy, slope entropy, and Hjorth parameters; frequency-domain features, including spectral entropy; and fractal-domain features, including fractal dimension. The simulation experiment, including seven common signal types of radar and active jamming, was performed for the effectiveness validation and performance evaluation. Results proved the proposed method’s performance superiority to other classification methods, as well as its ability to meet the requirements of low signal-to-noise ratio and few-shot learning.

High-Power Microwave (HPM) is an emerging technology formed by the development of electrotechnology, traditional microwave, plasma physics, and other related fields, which has very important applications in the military field. With the formal entry of the HPM weapon into the battlefield, it is of great practical significance to study the HPM effects in susceptible electronic systems such as the detector. To objectively evaluate the ability of a certain type of millimeter-wave proximity detector to resist HPM electromagnetic pulse jamming, an HPM irradiation system for the proximity detector was constructed, and a method of real-time storage of proximity detector output potentials using a compact online recording device has been provided. Based on that, the paper carries out the HPM irradiation test of the K-band proximity detector and enriches the means of irradiation effect data recording for small electronic devices.

This paper used Ls-Dyna to simulate the measurement process of the differential probe in the time-domain transient magnetic field, then figure out the displacement-time and velocity-time data measured by the differential probes. There is a variation in the equivalent measurement position of the differential probes by comparing the displacement data of the probes with the corresponding simulation values. From the simulation results. In the previous phase of the armature acceleration, the probe displacement deviates significantly from the simulated value; with the increase of the armature velocity, this value fluctuates; at the telophase of acceleration, the displacement difference is negligible. The equivalent displacement deviation of the corresponding simulation value shows positive and negative fluctuations based on the displacement difference of adjacent probes. Excluding extreme cases, the absolute value of the deviation is within 5%; at the acceleration telophase, it is within 2%. This deviation makes the output of the differential probes inaccurate in the time domain, which is significant for the related experiments when measuring the transient information of the armature motion in the electromagnetic launch by the differential probe.

电磁轨道发射器内表面二维图像可直观反映内膛损伤情况,包括损伤规模、颜色和细节纹理等,可通过获取内表面二维图像来进行内腔损伤评估.针对单台微型相机拍摄的局部图像视野狭窄,获取的内腔图像存在大量相似纹理的问题,提出一种多相机融合的电磁轨道发射器内表面图像采集方法,使用广角相机标定微型相机阵列之间的单应性关系,实现局部相似纹理图像的图像拼接,解决高相似纹理造成基于特征提取的图像拼接算法的误匹配率高的问题.经实验验证,该方法可获取内表面高清晰度图像,并实现较好的图像拼接效果.

The inner bore damage affects the launch performance and service life of electromagnetic railgun launcher. Detection and observation of railgun inner bore damage contribute to the study on mechanism and development rules of railgun damage. This paper analyzes five types of typical railgun inner bore damage. Based on the detection requirement for the damages, this paper proposes an automated damage detection system for the inner bore of electromagnetic railgun launcher consisting of data acquisition device and detection algorithms. The proposed device can step inside the inner bore of the railgun launcher to take photos of the inner bore surface automatically. We use the images obtained by the proposed device to build a data set for the training and verification of the detection algorithms. The object detection algorithm You Only Look Once v5 (YOLOv5) is utilized to achieve the rapid detection of railgun inner bore damages. We introduce the adaptive data augmentation and the focal loss to balance out the uneven category distribution of our data set. The result proves that our YOLOv5 model reaches the state-of-the-art level in the railgun inner bore damage detection task, with its mean Average Precision (mAP) of 0.659 and detection speed of 47.6 frames per second (fps). We choose Segmenting Objects by Locations v2 (SOLOv2) to extract the shape of the damage, with the Average Precision of 0.631. We further achieve damage statistics and the model visualization of damage distribution. The experimental results show that the proposed detection system meets the requirements of rapid detection and accurate feature extraction. It provides researchers with an approach for the study of railgun inner bore damage mechanism.

In this paper, we measured the armature velocity of an experimental electromagnetic launcher by B‐dot method and analyzed the change of the armature's average speed. The electromagnetic gun launching process was also simulated by Ansoft Maxwell simulation software. The launch current is used as the model's excitation which means that the current in the model is the same as the rail current. Ansoft Maxwell's 3D model can accurately simulate the launching process, in theory. We found that there was an unexpected rise during the real launching process. The phenomenon can be discovered in the following several experiments. We analyzed several possible causes such as the inductive gradient change, rail broken and inaccurate measurement of B‐dot probe. The inductive gradient is an important parameter in the launching process and can affect the armature speed. After checking the measurement problem, we also found that the wave form of the output signal from the probe where the unexpected change occurred was normal but the amplitude was very small. The measurement method was proved correct. The rise of average inductance gradient leads to the unexpected increase in average speed and the small signal. Furthermore, the physical reason for the change of inductance gradient should be the change of current distribution. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

In order to evaluate the electromagnetic launch effectiveness and understand the corrosion damage of the electromagnetic launcher, it is necessary to master the magnetic field data in the bore. At present, there is no related research on the measurement of the bore magnetic field of the electromagnetic launcher. Therefore, a small-scale projectile-borne measuring apparatus based on B-dot probe is developed in this paper. This apparatus uses FPGA as the core. Through the static magnetic field measurement experiment, the data of the induced voltage and the induced magnetic field can be obtained. The projectile-borne magnetic field measuring apparatus designed in this paper can accurately measure the bore magnetic field of the electromagnetic launcher, which lays the foundation for further analysis of the influence of the electromagnetic field in the bore on the launch effect and investigation of the corrosion damage of the electromagnetic launcher.

When the electromagnetic rail gun accelerates the armature, the rail is in a harsh condition of high temperature, high pressure and powerful current which will cause a series of grooving phenomenon. In order to detect the inner bore profile, we developed a measuring device using laser triangulation method and basically realized the measurement of the inner bore profile measurement. However, except for the translation and deflection errors, we found that the actual measurement cross-section would be rotated due to the unsteady movement compared with the ideal section. In addition, the previous calibration needs a high-resolution image sensor to get deflection information, it means high cost. In this paper, we analyzed the 3 kinds of deviations and provide a method to calibrate the rotation error using a calibration block. An improved calibration system was designed in low cost and experiment verified the feasibility of the calibration method. The calibration system can be divided into 3 parts, the outside global laser light provides a constant central position, a distance detecting device with a cone laser generator and an inside calibration block. After experiment, the calibration method was effective and the deviation of the profile can be corrected.

In the process of electromagnetic launching, there is much inner damage containing wear, corrosion, gouging, and transition in the rail. After several launchings, the damage has an enormous influence on the accuracy of launching and rail lifetime. In order to protect the rail and research on the damage mechanism, this paper provides an insight into the methods of measuring the inner bore of the electromagnetic rail launcher based on the optical vision measurement principle. Applying this optical method, the apparatus is designed and divided into three subsystems. These three subsystems provide global alignment information, the axial depth information, and inner surface profile information respectively. In this way, the 3D model of the rail can be precisely rebuilt. The feasibility of the method was confirmed in the experiment. And this method may have significant implications for the further research on the online measurement of electromagnetic rail launchers. (C) 2019 Elsevier Ltd. All rights reserved.

Spark gap switches with three electrodes and thyristor switches were used in the pulsed power supply system of the electromagnetic launcher. Electromagnetic field radiation from switches could cause electromagnetic interference damage to the devices. In order to analyze the problem, electromagnetic field radiation waveforms around two typical switches were measured by the B-dot. Based on the wavelet analysis method, time–frequency characteristics of the radiation field are compared for the two types of switches. The results represent that the maximum frequency of the thyristor switches’ signal is much lower than that of the spark gap switches’ signal, according to the frequency distribution. The turn-on time of the spark gap from the initial triggering time to the main discharge time is 0.024 ms'C and the variation is limited to less than 0.008 ms. The maximum frequency duration is about 0.005 ms, and the variation is limited to less than 0.003 ms. The maximum signal amplitude of thyristor switches is lower than that of spark gap switches. The comparison and results will benefit the compatibility design of the system.

The purpose of this article is to find a general parameter that can closely link the research of different-caliber electromagnetic (EM) railguns. In this article, an approximate field scaling method for EM rail launchers is proposed under the condition of matching the dynamic parameters of the projectile, which provides guidance for a suitable subscale test of an EM railgun. Through theoretical analysis and formula derivation, the concept of "rail-armature linear resistance density" is put forward. It is defined as: the contact resistance per unit length along the moving direction of the armature on the contact surface between the armature and the rail of the EM railgun. Through multiple launching tests and calculation of the rail-armature linear resistance density for different-caliber launchers, the rail-armature linear resistance density can be used as a characteristic parameter for the sliding electrical contact performance of the EM railgun in the case of linear current density approximation.

Electromagnetic disturbance in the course of rail-gun launching has great influence on the launching process and staff. Based on the magnetic force measured at the startup acceleration and separation stages, the corresponding magnetic field can be calculated. The magnetic field at different positions and heights near the rail gun is analyzed and compared. The results show that the position of the armature has great influence on the magnetic field. The maximum value of the instantaneous magnetic field should be located in the middle of the rail gun. At the same position, the magnetic field decays rapidly with the increase of height. The electromotive force waveforms are analyzed by using the wavelet transform; the analysis shows that the wavelet transform can reveal the time-frequency energy distribution of the electromotive force more accurately and clearly. The research of this paper has a guiding significance to the shielding design of magnetic field of the electromagnetic rail gun, and will promote the development of rail guns.

There are much inner damage consisting of wear, corrosion, gouging, and transition in the process of electromagnetic launch. In order to study damage mechanism, it is essential to detect the bore profile of electromagnetic rail-gun. In this paper, the inner surface profile detector is developed for measurement damage location and shape of electromagnetic rail-gun. The detector which uses the way of laser triangle consists of laser generator, image collector, main control circuit, and mechanical structure. Using field programmable gate array as the main control chip, the collected graphics are processed. The photoelectric measuring method used in this instrument has the characteristics of high accuracy, non-contact and on-line measurement. It can also provide the result of fixed-point measurement and the image of the cross section of any position of the tube being measured. Through the comparison of the ideal contour and the measured profile of the electromagnetic rail-gun, the damage profile can be obtained. In the experiment, the object is a barrel of electromagnetic rail-gun with a length of 6 m, height of 40 mm, and width of 30 mm. Finally, we can get 2-D and 3-D bore profiles of the launcher.

In this paper, based on the advantages of artificial neural network, such as good tolerance of data noise, strong ability of nonlinear mapping, multi-dimensional input variables, fast operation, low error, etc., a method of using artificial neural network for data prediction is proposed for the research of rail-gun. The results show that it is feasible to use the Back Propagation Neural Network, the Radial Basis Function Neural Network and the General Regression Neural Network to realize the method of prediction and simulation of the rail-gun current and the armature speed curve through relevant parameters. The General Regression Neural Network has superiority in error performance and time cost of neural network training and simulation. (C) 2018 Published by Elsevier Ltd.