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2020, 40(4): .

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2020, 40(4): .

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A Review of Methods for HRRP Target Automatic Recognition

HAN Lei, YAO Lu

2020, 40(4): 351-361,381. doi:10.15918/j.tbit1001-0645.2019.057

Abstract(1213) PDF(423)

Abstract:
Radar high resolution range profile (HRRP) target automatic recognition is a hot research field in radar target recognition in recent years. Based on the research status of HRRP automatic recognition methods at home and abroad, firstly, two problems that need to be solved at present were pointed out: the recognition of non-cooperative targets and the acquisition of classified hyperplanes. Secondly, three focuses about the problems were proposed: research on SNR’s mismatch, research on a small number of incomplete samples and research on classification hyperplane acquisition methods. Then the research ideas of each research focus were divided detailedly, including removal of noise components, feature extraction, support vectors, etc. and the the research status of each idea was summarized. Finally, the research status of the three focuses was summarized and the future development direction of the three focuses was pointed out.

Dynamic Response of Thin-Walled Cylindrical Shells Suffering Impact Loading

LI Jin-zhu, QI Kai-li, YUAN Ting, WU Hai-jun, HUANG Feng-lei

2020, 40(4): 362-368. doi:10.15918/j.tbit1001-0645.2019.139

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Abstract:
To investigate the dynamic mechanical response characteristics, failure modes, and energy absorption characteristics of thin-walled metal structures under impact loading, the cylindrical shells were impacted by dropping hammer at different velocities. The deformation modes and the axial shortening rates of cylindrical shells with different materials under the same impact conditions were obtained. The effects to energy absorption and axial shortening rates of impact velocity and ratio of diameter to thickness were also analyzed. The results show that the axial shortening rate of thin-walled cylindrical shells increases with the increase of impact velocity and ratio of diameter to thickness. The energy absorption capacity increases with the increase of impact velocity due to strain rate effect. The average post-buckling load under dynamic impact condition is much larger than the theoretical load under quasi-static condition, which is related not only to the diameter, thickness and material properties of shells, but also to the impact velocity. To absorb the impact energy of the A6060 aluminum alloy through non-axisymmetric buckling and folding deformation applies to thin-walled structural parts.

Automatic Calibration of JWL Parameters for DNAN/RDX Melt-Cast Explosive Using LS-OPT Software

ZHOU Lin, LIU Kai, ZHANG Xiang-rong, MIAO Fei-chao, YAN Bo, BAI Yu-qi

2020, 40(4): 369-374. doi:10.15918/j.tbit1001-0645.2019.286

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The state equation of detonation product is an important method for estimating the working capacity of explosives. In order to fit the parameters of JWL state equation, experiments on flyers driven by explosives were conducted by using copper and tungsten, two metals with large impedance differences. The parameters of the JWL state equation of DNAN based melt-cast explosives (DNAN/RDX 40/60) under the condition of tungsten flyer were calibrated by trial and error method and LS-OPT software automatic calibration. The error of the calculated curve obtained by trial and error method was 16.86% compared with that of the experimental curve, and the error of automatic calibration was 3.04%. The parameters obtained by automatic calibration were used to simulate the process of driving the copper flyer, and the experimental curves were compared with those of the copper flyer. The error was 4.60%. The research shows that the LS-OPT software automatic calibration method can be used to calibrate the parameters of the JWL state equation of DNAN based melt-cast explosives. Compared with the traditional fitting method, it can avoid a lot of manual calculations and obtain more accurate results.

Experimental Study on Terminal Demolition Lethality of Reactive Fragments

ZHAO Hong-wei, YU Qing-bo, DENG Bin, CUN Hui

2020, 40(4): 375-381. doi:10.15918/j.tbit1001-0645.2019.092

Abstract(864) PDF(314)

Abstract:
Aiming at the terminal demolition lethality of reactive fragments, the ability of perforation, ignition and detonation for reactive fragments were investigated by experiments in this paper. The result showed that a reactive fragment weighting 2.5 g could perforate the 8 mm-thick LY12 hard aluminum under the collision velocity of 870 m/s, forming penetration holes of a diameter about 1.6~2.0 times diameter of the fragment on target plates. The reactive fragment weighting 10 g could ignite aviation kerosene in the fuel tank shell of 10 mm-thick LY12 hard aluminum at a velocity of more than 800 m/s. Furthermore, it could also detonate the warhead charge after perforating through the 6 mm-thick A3 steel plate at a velocity of more than 960 m/s. Therefore, it can be learned through the analysis of the perforation ability of reactive fragments that reactive fragments perforating a certain thickness of target plates can reliably reach its initiation threshold and ignite fuel or detonate charge.

Improving the Accuracy of Static Defect Analysis Based on Symbolic Execution

WANG Mei-lin, ZHANG Yi-ni, LI Ming-yue, Shao Shuai, LIU Shi-run

2020, 40(4): 382-385,395. doi:10.15918/j.tbit1001-0645.2017.383

Abstract(1014) PDF(297)

Abstract:
Static analysis is an effective way of detecting defects and improving the quality of software codes. However, without running the programs, it can not collect runtime information, so the accuracy of its analysis result is low, i.e. there are false positives. Symbolic execution method can collect data flow information through simulating the execution of the target program, thereby increasing the accuracy of static analysis. In order to improve the accuracy of static analysis results, this paper designed and developed a defect detection tool ABAZER-SE, which was built on the GCC abstract syntax tree and combined symbolic execution and static analysis techniques. The tool was applied on the Toyota ITC benchmark and the experimental results show that it can improve the accuracy of static defect analysis.

Roll Control of Course Correction Fuze for Dual-Spin Projectile with Fixed-Canards

ZHANG Xin, YAO Xiao-xian

2020, 40(4): 386-395. doi:10.15918/j.tbit1001-0645.2019.090

Abstract(1064) PDF(376)

Abstract:
In order to solve the input disturbance and model uncertainty problems of the roll channel of the course correction fuze (CCF) for dual-spin projectile with fixed-canards, a two-degree-of-freedom roll channel control method based onH_∞loop shaping was proposed. Through the modeling of electrical and mechanical systems of the CCF, the calculation method of the electromagnetic control torque of the actuator was researched. Based on theoretical analysis and experimental test, the modeling method of the aerodynamic torque and the rolling damping torque of the CCF were studied, and then the roll channel control model was obtained. A two-degree-of-freedom roll channel controller based onH_∞loop shaping was designed to control the roll angle of the CCF. Hardware-in-the-loop simulation experiments show that it is feasible to establish the roll channel control model by analyzing the electrical and mechanical systems of the CCF, and the designed roll channel controller can achieve accurate roll angle control.

Low-Impact Contact Study Based on Fuzzy Weighed Control of Sliding-Mode and State Feedback for Pneumatic Servo Welding Gun

WANG Tao, WANG Shao-ning, WANG Bo, ZHU Ai-dong

2020, 40(4): 396-400. doi:10.15918/j.tbit1001-0645.2018.454

Abstract(902) PDF(284)

Abstract:
It is expected to reduce the velocity and the impact of the contact, which is significance to improve the efficiency and quality of welding. Sliding-mode control can reduce contact force, but it takes long time. In this paper, a fuzzy weighed control method between sliding-mode and state feedback was used to reduce the contact force and electrode operating time for pneumatic servo welding gun. Firstly, the sliding mode switch function and sliding mode control law were designed based on a system model. Then, a state feedback controller was designed by means of pole assignment, and a fuzzy weighted controller was designed based on fuzzy control for sliding mode and state feedback. Finally, the proposed control strategy was verified by experiments. Results show the effectiveness of the designed controller, being better than other controller.

Kinematics Analysis and Gait Planning of the Quadruped Robot Leg Mechanism

MA Guang-ying, LIU Run-chen, CHEN Yuan, GAO Jun, XU Pi-bing

2020, 40(4): 401-408. doi:10.15918/j.tbit1001-0645.2019.013

Abstract(1209) PDF(340)

Abstract:
In order to improve the carrying capacity and operation stability of the foot robot, a quadruped robot based on 3UPR parallel mechanism was proposed and its motion performance was analyzed. Analyzing the degree of freedom of the robot structure based on the spiral theory, and performing kinematics analysis for the robot leg mechanism based on a position reversal model, the drive feed amount and drive speed were obtained. Comparing the data of ADAMS simulation with theoretical calculation results, the correctness of the model was verified. The singularity was analyzed based on the velocity Jacobian matrix, and the diagonal gait planning on the robot was carried out according to the trajectory of the single leg. The results show that, the mechanism possesses three degrees of freedom, including the rotation in theXandZdirections and the movement in theYdirection. There is no any singular positions in the mechanism movement, showing better motion performance. The gait simulation results show that the robot can achieve smooth motion on the flat ground with a forward speed of 135 mm/s.

Point Cloud Registration Method Based on Key Point Extraction with Small Overlap

LU Jun, SHAO Hong-xu, WANG Wei, FAN Zhe-jun, XIA Gui-hua

2020, 40(4): 409-415. doi:10.15918/j.tbit1001-0645.2018.476

Abstract(1190) PDF(342)

Abstract:
The ICP registration algorithm has high requirements for the initial position of point clouds and low registration ability for point clouds with low overlapping rate.To solve these problems, a point cloud registration method based on feature matching of key points was proposed.A key point extraction algorithm based on the differences of mean values of multiscale weighted normal projection was designed, and then key points were characterized by SHOT descriptors.Fusing of geometric consistency and RANSAC algorithm, the mismatched point pairs were removed in the matching process, and the correspondences between key points were optimized.The transformation matrix was obtained by using singular value decomposition, cloud rough registration was completed, and fine registration was performed by using ICP.The experiment results show that the key point extraction algorithm proposed in this paper can effectively extract points with obvious changes in the surface of the point cloud.And using SHOT descriptor to characterize the key points can complete registration of point cloud data quickly and accurately.At the same time, for the point cloud with low overlapping rate, the proposed method also has better registration effect.

Quantitative Research on GPS Position Errors in an East-North-Up Coordinate System

GUO Yan-bing, MIAO Ling-juan, LI Chuan-jun, ZHANG Xi

2020, 40(4): 416-420. doi:10.15918/j.tbit1001-0645.2019.105

Abstract(875) PDF(335)

Abstract:
The current quantitative analysis of GPS position errors using pseudoranges is still not accurate enough. Therefore, in this paper, GPS position errors in an east-north-up local topocentric coordinate system were further analysed in two scenarios. Firstly, using all visible satellites for positioning, the expressions of GPS position errors were modified by setting corresponding parameters for different latitudes. Secondly, four optimum satellites were selected for positioning, the expressions for GPS position errors were first derived for a more practical situation. On this basis, the interrelationships between various position errors were established for the above two scenarios, respectively. It was designed that, if the standard deviation of a user ’s pseudorange errorσ_UREwas known, the standard deviations of GPS position errors could be estimated more accurately according to the proposed formulas. The accuracy of the proposed formulas was verified using a SPIRENT satellite signal simulator, generating realistic satellite signals at the equator,45° north latitude and the north pole respectively.

Non-Rigid and Large Displacement Optical Flow Based on Descriptor Matching

WANG Guang-long, TIAN Jie, ZHU Wen-jie, FANG Dan

2020, 40(4): 421-426,440. doi:10.15918/j.tbit1001-0645.2019.023

Abstract(998) PDF(327)

Abstract:
In order to solve the arithmetic problem of non-rigid and large displacement optical flow, an improved arithmetic was proposed based on descriptor matching for optical flow. In the method, a novel data term was put forward firstly to adaptively select invariable hypothesizes for each pixel. And then, the traditional isotropic smoothness term was optimized to be the anisotropic one for the optical flow estimation of image details. Furthermore, the descriptor matching was applied to optical flow fields, taking advantage of the robust ability of descriptor matching to produce some large displacement correspondences and the ability of dense optical flow. At last, a quantitative analysis of the approach was performed on MPI Sintel.The results show that the proposed method can realize accurate estimation of non-rigid and large displacement optical flow. And the method is superior to LDOF with a relative gain of 18.9% for AAE and 21.9% for AEPE in market_5.

ArUco-SLAM: a Monocular SLAM System Based on ArUco Landmark Array

XING Bo-yang, PAN Feng, FENG Xiao-xue

2020, 40(4): 427-433. doi:10.15918/j.tbit1001-0645.2019.026

Abstract(1452) PDF(333)

Abstract:
Accurate mapping algorithm is the core of ArUco landmark array localization. Most of the existing mapping algorithms based on offline processing or manual calibration behave inefficiently and time-consuming. In addition, the existing online mapping algorithms can though guarantee real-time performance, but show low accuracy, large cumulative error and sensitive to false detection. In order to overcome those shortcomings, a monocular ArUco-SLAM algorithm was proposed based on parallel mapping and synchronization optimization in this paper. Firstly, the closure principle of coordinate transformation was used to build and correct the global map online. And then, a linearity optimization algorithm was used to minimize the projection error in the corners and to achieve global optimization for key frame of the map. A synchronization optimization algorithm was used to match the online map and optimized map, and to reduce the cumulative error of the global map. Finally, several contrast experiments with other mapping systems were carried out. The experimental results show that the proposed system can not only establish high-precision map, but also realize online mapping and real-time camera localization.

An Acceleration Control Method with Three Variable Controller

WANG Shou-kun, HU Xiao-yu, SHI Ming-xin, YUE Bin-kai

2020, 40(4): 434-440. doi:10.15918/j.tbit1001-0645.2019.031

Abstract(956) PDF(327)

Abstract:
Electrical driven shaking tables possess the merits of being clean and easy to install. In order to implement acceleration replication control of the electrical driven shaking tables, a simplified model of the electrical driven mechanicals was established. A three variable controller was adopted both in the Matlab/Simulink environment and the physical system to carry out simulation and experimental study. The simulation and experimental results show that, the three variable controller can expand the bandwidth of the acceleration response of the electrical driven shaking table. Finally, acceleration road spectrum replication experiments were carried out with TVC and realized higher-precision acceleration road spectrum replication control.

Trajectory Design and Simulation of Space-Based Surveillance Controlled Flying Around for GEO Slow-Spinning Space Target

ZHANG Yang, GAN Qing-bo, FU Jiang-liang, LI Zi-shen, YUAN Hong, XIONG Yao

2020, 40(4): 441-447. doi:10.15918/j.tbit1001-0645.2018.534

Abstract(928) PDF(324)

Abstract:
A method of controlled flying around of space-based surveillance was proposed to observe continuously the specific surface of GEO slow-spinning space target. Firstly, a relative motion model of target and space-based platform was established. And then, analyzing the expected relative orbit model of arbitrary spin axis, a single cycle controlled flying around model and a multi-cycle spiral approaching controlled flying around model were designed. Time constrained multi-pulse control was used to realize controlled flying around. Finally, the controlled flying around orbit with different flying radius, different number of pulses and different flying periods was simulated and analyzed to provide and verify a multi-cycle spiral approaching controlled flight strategy. The results show that, by mapping the attitude changes of GEO slow-spinning space target to the design of relative controlled flying around orbit, the continuous surveillance of the specific surface can be realized. The simulation results and conclusions can provide a significant reference for engineering application.

The Geometric Approach of Riccati Equations

AUNG Naing Win, CAO Yue-qi, ZHANG Shi-qiang, SUN Hua-fei

2020, 40(4): 448-451. doi:10.15918/j.tbit1001-0645.2019.028

Abstract(1288) PDF(332)

Abstract:
In this paper, the concept of optimal control for linear system, as well as the classical Riccati equation was introduced first. Then four kinds of Riemannian metrics were presented to obtain the geodesic distances on symmetric positive definite matrix manifold. At last, solving the corresponding Riemannian gradient, the new methods were provided for solving the Riccati equations.

A New Remapping Method to Suppress Velocity Nonphysical Propagation

WANG Cheng, LI Hao, LI Tao, JIA Zu-peng

2020, 40(4): 452-460. doi:10.15918/j.tbit1001-0645.2019.134

Abstract(1109) PDF(391)

Abstract:
The severe numerical dissipative phenomenon exists in the multi-material arbitrary Lagrange-Euler (ALE) method with original remapping algorithm when strong discontinuities and large deformations are simulated. In order to improve reliability of calculation results and robustness of the algorithms, it is necessary to use repeated re-mapping technique. Through some numerical tests and analysis with the traditional remapping technique, it was found that the numerical dissipation meets with nonphysical velocity. Then, an improved remapping method was presented, which not only restores the spatial distribution of the physical field but satisfies mass conservation, momentum conservation and energy conservation. Thus the new method shows more accuracy and reliability for the numerical simulation of hydrodynamic problems such as strong discontinuities, high density-ratio, high pressure-ratio, and strong shocks.

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