Modern Defense Technology

Simulation of High Dynamic GPS Anti⁃Jamming Algorithm

Jia-xin CHEN, Bai-chun LI

2022, 50(1): 33-40. doi:10.3969/j.issn.1009-086x.2022.01.005

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For the anti-jamming problem of global positioning system（GPS） receiver in high dynamic environment， We studies the received signal model of equidistant linear array and the basic principle based on covariance matrix expansion， and simulates and analyzes the effect of two classical anti-jamming algorithms based on covariance matrix expansion： Mailloux algorithm and Zatman algorithm in high dynamic environment. Through Matlab simulation， the results show that compared with the conventional method， Mailloux method and Zatman method can effectively widen the null formed from the interference direction when the array element is an equidistant linear array， which can improve the anti-jamming effect in high dynamic environment and enable the receiver to capture satellite signal.

Wind Resistance of Fixed⁃Wing UAV Path Tracking

Xuan-bing LIU, Shao-lei ZHOU, Zhi-cai XIAO, Ya-hui QI, Fei-yang DAI

2022, 50(1): 41-47. doi:10.3969/j.issn.1009-086x.2022.01.006

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As a new type of military equipment， unmanned aerial vehicle（UAV） has a wide range of operational applications. The path tracking performance and anti-jamming capability of UAV are the guarantee of its safe completion of flight missions. With the increasingly complex operational environment of modern war ， UAV flight will face greater challenges. In order to solve the problem that the fixed-wing UAV is seriously affected by wind disturbance during flight， a path tracking method with wind resistance is designed. The nonlinear guidance principle is used to track the path， and the static deviation between the flight path and the expected path is eliminated by introducing feedback. Finally， the feasibility and effectiveness of the proposed method are verified by simulation.

Calculation Analysis of the Distance Between Planned Waypoints of the Ship⁃to⁃Land Cruise Missile

Yan SHI, Hang SUN, Yun-ge CHEN, Jue WANG

2022, 50(1): 48-53. doi:10.3969/j.issn.1009-086x.2022.01.007

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In view of the fact that the ship-to-land cruise missile's flight path needs to refer to the approximate geodesic route， the calculation method of geodesic distance between two points in space， which is easy to program and has improved accuracy， is put forward on the basis of fully considering the planning process of the missile's path from sea to land. Based on the calculation of the parameters of the earth ellipsoid model considering the altitude， the calculation formula of space waypoint considering the altitude is re-derived by using the Bowring inverse solution formula. The relevant calculation examples show that this method can improve the accuracy of distance calculation and is easy to be implemented in engineering.

Research on Rules for Reconnaissance Area Planning of Communications Countermeasure Drone Swarms

Jun-yi CHEN, Jian YANG

2022, 50(1): 54-59. doi:10.3969/j.issn.1009-086x.2022.01.008

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Reconnaissance area planning is the primary task for communications countermeasure reconnaissance of smart drone swarms. The ability to properly plan the reconnaissance area is critical to the accomplishment of the communication countermeasure reconnaissance task. By researching the reconnaissance area planning allocation and dynamic adjustment process， combining the combat principles of communication countermeasures and relevant military experience， the behavior rules， judgment rules and strategy rules for reconnaissance area planning of communication countermeasures drone swarms are collated and summarized， and the use of the rules is suggested and specific application scenarios are conceived.

A Multi-Channel Synchronization Method for Phased Array Radar

Sheng⁃xiang ZHU, Min HE, Zhi⁃yi HE, Jia⁃xin WANG

2022, 50(1): 60-66. doi:10.3969/j.issn.1009-086x.2022.01.009

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The multi-channel mode of phased array radar increases the degree of freedom and improves performance of the system. To solve the synchronization problem of the radar， a multi-channel synchronization method for phased array radar is proposed. It uses the synchronization trigger mode for single clock chip. The delay values of multiple synchronization signals of the clock chips are adjusted accurately. An adaptive sample window center adjustment method is proposed for multiple high speed analog to digital converters. This method is used for actual radar products. Test results have demonstrated the effectiveness of the approach to implement multi-channel synchronization for phased array radar.

Research on Tracking and Filtering Method of Ballistic Target

Zhao-qiang SUN, Wei WEI, Zhi-gui WANG, Yan CHEN

2022, 50(1): 67-73. doi:10.3969/j.issn.1009-086x.2022.01.010

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The method of tracking filter of ballistic target is summarized. The key points， advantages and disadvantages of the extended Kalman filter （EKF）， conversion measurement Kalman filter （CMKF）， ballistic EKF （BEKF）， and ballistic unscented Kalman filter （BUKF） are analyzed. The efficacy of the four filtering methods is further verified using simulated ballistic data. The filtering precision， tracking performance of different filters for reentry target are compared and the effect of ballistic coefficient and measure error on filter performance is analyzed. The method of forming covariance of measure error is proposed， which improves adaptability and precision of filter. Several problems that should be considered when choosing and designing target tracking filter methods are proposed to provide reference and bases for the selection and desing of radar filtering methods.

Bayesian Evaluation Method for Detection Efficiency of Early Warning Detection System Based on Knowledge Graph

Bo-wen YUAN, Feng ZHU, Zhao-peng LIU, Li-wei WANG, Run-yu HUANG

2022, 50(1): 74-80. doi:10.3969/j.issn.1009-086x.2022.01.011

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In war， early warning and detection system as a typical complex system， the effective evaluation of its detection effectiveness has always been an important practical problem that needs to be studied and solved. The limitations of traditional effectiveness evaluation methods are break- throughed. On the basis of analyzing the basic principles of knowledge graph technology and Bayesian evaluation method， a new method of detection efficiency evaluation of early warning detection system based on their comprehensive application is proposed. The knowledge graph is constructed by using expert knowledge and experimental data， and the Bayesian network method is further used to implement knowledge reasoning， so as to realize the evaluation of system detection efficiency. The effectiveness of the proposed method by constructing specific combat scenarios is verified， and the evaluation of the proposed method based on deduced data is analyzed.

Analysis on the Research Status and Development Trend of Military Camouflage Technology

Wan-li ZHENG, Ping YANG, Shao-qiang YAN, Feng-xuan WU, Song YAN

2022, 50(1): 81-86. doi:10.3969/j.issn.1009-086x.2022.01.012

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With the advances in reconnaissance and reconnaissance-strike integrated technology， the transparency of the battlefield in modern warfare is increasing. The survival of military targets faces serious threats， and camouflage protection is an important prerequisite to ensure the survival on the battlefield. The inception， emergence， development and maturing of camouflage technology applications are reviewed； summarizes the research status of certain camouflage technologies such as stealth， sheltering， disruptive pattern-making， and faking. The analysis suggests that future camouflage technologies may incorporate multispectral compatibility， intelligent adaptation， and integrated designs. The paper provides important and valuable references to the R&D of military target camouflage technologies.

Study on Patriot Weapon System Maintenance Support of the U.S. Military

Xi-xuan FENG, Xiao-qiang TIAN

2022, 50(1): 87-93. doi:10.3969/j.issn.1009-086x.2022.01.013

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The United States and other military powers regard missile weapon system maintenance and support as one of the key contents of annual defense spending， and maintenance and support has become one of the important businesses for foreign military enterprises to expand the military industry chain and ensure enterprises to obtain continuous income. Patriot weapon system is the main combat equipment of U.S. military air defense， and the study of its maintenance and support can reveal the maintenance and support status of U.S. military missile weapon system. The main methods of Patriot weapon system maintenance support and its future development trends of the Patriot missile two-stage maintenance system and Army life extension program are analyzed， which has important reference value for continuously improving the maintenance support level of missile weapons system in our army.

Study on the Characteristics of Asymmetrical Ventilated Cavitating Flows

Lei HUANG, Han⁃rui HUANG, Xiao⁃wang LI, Yuan SI, Lei DUAN

2022, 50(1): 94-101. doi:10.3969/j.issn.1009-086x.2022.01.014

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The asymmetric medium distribution of ventilated cavitating will affect their hydrodynamic force and then the cavitating stability control. In recent years， the understanding of the flow characteristics is relatively limited. The flow characteristics of asymmetric ventilated cavity is demonstrated by experimental and numerical methods. The results show that the asymmetric flow leads to the formation of asymmetric wet zone. On the basis of different flow media， asymmetric wetted region can be compartmentalized into transparent gas zone， water vapor mixing zone and wetted zone. As the boundary of water vapor mixing zone develops from incident flow axis to back flow axis， the relatively high pressure decreases， cavity thickness increases， the way that the liquid entering into the cavity is gradually transformed from the axial direction to the circumferential direction， and the area of water vapor mixing increases. In the water-gas mixture flow， with the liquid layer formed along the circumferential direction developing to the back flow axis， a low speed， high pressure and water vapor mixing area is formed at the back flow axis. Furthermore this area has enhanced turbulent characteristics accompanied by large shedding of cavitating vortex.

Research on Self⁃Tuning and Optimization of Speed Loop Controller Parameters in Servo System

Fang⁃jun LI, Sheng⁃jie WANG

2022, 50(1): 102-108. doi:10.3969/j.issn.1009-086x.2022.01.015

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In order to avoid the tedious parameter tuning process， a self-tuning and optimization method for the speed loop controller parameters based on inertia identification is proposed. The design rules of the speed loop controller parameters are analyzed with the frequency method. The inertia is identified with recursive least square method with a forgetting factor. The controller parameters optimization is performed using the variable step iterative algorithm designed in this paper. Simulation results show that using the recursive least square method with a forgetting factor can effectively identify the moment of the inertia of a motor. Speed loop controller parameters， which are optimized by the method proposed， can provide the system good dynamic response and robustness.

Mission Capability and Denial Distance Analysis of Small Reconnaissance UAVs

Pei HUANG, Guo-hui CAO, Hai-jing ZHANG, Jun-jie ZHANG

2022, 50(1): 1-6. doi:10.3969/j.issn.1009-086x.2022.01.001

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With the rapid development of unmanned aerial vehicle（UAV）， UAVs have been widely used in civil and military fields. Small UAVs with “low flight height， slow flight speed and small dimensions” characteristics are especially convenient and flexible to use and relatively inexpensive. They can be used for reconnaissance， surveillance，suicide attack and other task purposes， posing a serious threat to daily air defense security and important assets protection. The main threat patterns of the small reconnaissance UAV and payload capabilities are analized. The denial distance requirements to small UAVs are also proposed， which can provide reference for anti-UAV system development .

Summary of Equipment System Contribution Rate Evaluation

Min DU, Zhong-hua CHENG, En-zhi DONG

2022, 50(1): 7-18. doi:10.3969/j.issn.1009-086x.2022.01.002

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With the in-depth application of equipment systematized combat mode in military activities， its advantages have been highly concerned by the world's military powers. As an important index to measure the advantages and disadvantages of equipment systematized construction and combat application， the contribution rate of equipment system has become a research hot topic in the current military science. The current status of research on evaluation needs， evaluation theory and evaluation methods of equipment system contribution rate at home and abroad is systematically sorted and summarized ，and summarized the problems existing in the research results， and provides guidance for the future research on equipment system contribution rate. The summary of equipment system contribution rate evaluation has certain guiding significance for the research of equipment system contribution rate.

Study on Motion Instability and Disability Characteristics of Rotor UAV Under Extreme Wind Speed

Qun LIU, Zhao YANG, Chuan-xia ZHOU

2022, 50(1): 19-24. doi:10.3969/j.issn.1009-086x.2022.01.003

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Wind resistance is the key to determine the application scope and survival capacity of UAV（unmanned aerial vehicle）. This paper takes a rotor UAV as the research object， and makes use of wind tunnel test equipment and binocular vision non-contact measurement system to conduct fine measurement and research on the instability characteristics （attitude or speed） and the disability of each component under the extreme wind speed of UAV. The critical instability conditions and characteristics of the rotor UAV and the disability characteristics of vulnerable parts are obtained. The results show that speed of 17 m/s is the critical instability wind speed of UAV， and the UAV is 40° angle of attack backward. When the wind speed is 28 m/s， the UAV power system will stop. When the wind speed reaches 34 m/s， the rotor is almost free of deformation. From the view of using wind field to destroy UAV， the most easy way is instability to fall， the second is to destroy the power system， and the most difficult is to damage the rotor.

An Aerial Forensic Target Detection Algorithm Based on RetinaNet and SE Fusion

Ke LIU, Guang-yu PAN, Da-guo ZHENG, Jiao-jiao GU, Chun-ying MENG

2022, 50(1): 25-32. doi:10.3969/j.issn.1009-086x.2022.01.004

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Aiming at the lack of automated and intelligent forensics methods in the aviation reconnaissance and evidence collection， an aviation forensics target detection algorithm based on the fusion of RetinaNet and SE is proposed to solve the problem of large changes in target scale and imbalance in data collection. The performance is further improved by introducing an attention mechanism through the SE （squeeze-excitations） module. The feature pyramid network（FPN） can effectively deal with the problem of large changes in target scale， Focal Loss can effectively deal with the imbalance of categories in dataset， the SE module introduces a channel attention mechanism to strengthen the feature map， and can further use the extracted channel correlation to enhance effective features and suppress ineffective features. Through simulation experiments， it is verified that the algorithm can improve the accuracy of target detection with a small amount of calculation increased， further enhance the characterization ability of the model， and effectively improve the efficiency of target detection， which can provide a reference for related engineering applications.

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