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2019, 39(8): .

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2019, 39(8): .

Abstract(532) PDF(354)

Abstract:

Technology of a Composite Recoil Reduction of the Small Caliber Automatic Gun

XIAO Jun-bo, YANG Guo-lai, LI Hong-qiang, SONG Jie, QIU Ming, LIAO Zhen-qiang

2019, 39(8): 771-776. doi:10.15918/j.tbit1001-0645.2019.08.001

Abstract(1238) PDF(524)

Abstract:
A complex reducing recoil technology was put forward, which combines a high-efficient muzzle brake and a time-delay nozzle flow anti-recoil device with a new damping adjustable high energy absorbing buffer, to effectively reduce the recoil of the small caliber automatic gun firing continuously. A complex rigid-flexible-coupling mathematical model for simulating recoil of the automatic gun was set up. Through the simulation analysis, the calculation result curve was basically consistent with the experimental curve. The test data show that the complex reducing recoil technology can effectively make automatic gun recoil significantly reduced. Therefore, the complex reducing recoil technology will provide a theoretical basis and application reference for future research on the low recoil firing of a small caliber automatic gun.

Control Effect Analysis of Dual-Spin Projectile Based on Modified Mass Point Trajectory Model

MA Guo-liang

2019, 39(8): 777-783. doi:10.15918/j.tbit1001-0645.2019.08.002

Abstract(806) PDF(445)

Abstract:
An analysis method was proposed to investigate control effect of a class of fixed canard dual-spin projectile based on mass point modified trajectory model. With the roll angle of forward body regarded as control input, 6 DOF exterior ballistic model was constructed in the earth fixed coordinate system. Yaw of repose equations were derived for constant canard roll angle, and mass point modified trajectory model was obtained. Calculation formulas of range correction acceleration and cross range correction acceleration were presented, and the definition of the dominant correction coefficient was proposed. Influence of the dominant correction coefficient on correction direction and correction distance was investigated, and the results show that coefficient was one of the key factors for determining the control effect of fixed canard dual-spin projectile. Simulation examples demonstrate that the angle of attack can be approximated by yaw of repose, and position results are close for 6 DOF exterior ballistic model and mass point modified trajectory model.

Trajectory and Cavitation Characteristics of High-Speed Projectiles at Small Angle of Water Entry

XIAO Hai-yan, LUO Song, ZHU Zhu, YU Yong

2019, 39(8): 784-791. doi:10.15918/j.tbit1001-0645.2019.08.003

Abstract(899) PDF(569)

Abstract:
The cavitation phenomena and ballistic characteristics of high-speed rotating projectiles entering the water with a small angle were numerically studied. The VOF multiphase model was introduced to capture the vacuole interface and the free liquid surface. The Schnerr-Sauer cavitation model was used to simulate the generation and evolution of cavitation process. The motion of the missile was calculated by the overset mesh technique and the six-degree-of-freedom algorithm. Then the trajectory characteristics, cavitation evolution and hydrodynamic properties of projectile were studied in the process of small angle water entry. The bouncing and fluttering phenomenon of the high-speed spinning projectile with small water entry angle was preliminarily explored. The results showed that when the initial launching angle was too small, the posture of the projectile tended to change greatly, the asymmetric shape of the vacuole and the large wet area of the projectile caused the moving body to receive large fluid dynamics and moments; the motion of the projectile was unstable and resulted in the bouncing and fluttering phenomena. The analysis shows that the projectile is easy to get wet with too small water entry angle. The wetting of the projectile has a great influence on the hydrodynamics and the motion state of the projectile. The asymmetric wetting of the projectile is an essential factor for the instability of super-cavitation projectiles.

Experimental Study on Fatigue Damage of Sandstone Based on NMR and Acoustic Emission

REN Song, WANG Xiao-shu, GAO Si-xian, OUYANG Xun, XIE Kai-nan

2019, 39(8): 792-799. doi:10.15918/j.tbit1001-0645.2019.08.004

Abstract(803) PDF(415)

Abstract:
In order to evaluate the long-term stability and safety of engineering rock mass scientifically, cyclic loading and unloading test was carried out on saturated sandstone. Acoustic emission technology and nuclear magnetic resonance analysis technology were used to explore the macroscopic and microscopic deformation and fatigue damage evolution law. The conclusions are as follows:under cyclic loading, the distribution law of sandstone's acoustic emission energy was consistent with the development law of axial cumulative residual deformation and the variation law of the stress-strain curve hysteresis loop. They all reflected the rock' gradual deterioration to damage under repeated stress. During rock fatigue damage, the power law characteristics of acoustic emission energy had scale invariance in time series, and the medium-term power index could effectively represent the energy distribution of the whole process. According to the result ofT₂spectrum, the ratio of the fine fracture to the larger fracture volume was defined asK₂. During the cycle,K₂was always increasing. WhenK₂dropped sharply, the sandstone showed symptoms of destruction; the AE and NMR characteristics of the specimen could reflect the cracks in the internal pores of the rock, and the results are consistent, which indicates rock damage is the overall fatigue damage caused by local deformation accumulation.

Numerical Calculation of Dynamic Response for Bending Members Under Gas Explosion

SUN Song, WANG Ming-yang, QIU Yan-yu, GAO Kang-hua

2019, 39(8): 800-807. doi:10.15918/j.tbit1001-0645.2019.08.005

Abstract(925) PDF(510)

Abstract:
Gas explosion in building structures often presents the characteristics of long duration, small peak overpressure and multiple pressure peaks. Based on the equivalent single-degree-of-freedom method, the numerical calculation method of structural dynamic response under gas explosion was derived by the matrix of load and resistance and its accuracy and validity was verified by comparing experimental data. The results show that:compared with the actual gas explosion, the simplified explosion load will underestimate structural vibration displacement due to ignoring the change of load rate, and the existence of damping will reduce this calculation error. The longer the load duration of the same peak value is, the larger the deformation energy acting on the structure will be, thus the maximum amplitude and residual deformation of structural vibration will increase. Both the initial velocity and displacement will increase the vibration deflection and residual deformation of the structure. The initial velocity is equivalent to the additional impulse load on the structure, while the initial displacement is equivalent to the external static load on the structure.

Shock Dynamic Response Reduction Method of Surface Ship Basement by Impedance Method

DONG Jiu-ting, LIU Jian-hu, WANG Jun, LI Hai-tao, LIU Guo-zhen, GAO Tao

2019, 39(8): 808-812,824. doi:10.15918/j.tbit1001-0645.2019.08.006

Abstract(819) PDF(335)

Abstract:
Equipment will cause spectrum dip effect under underwater explosion. In order to study the influence of installed equipment on shock environment, the impedance of basement and equipment were calculated by frequency response analysis of ABAQUS. And then the relationship between basement response and impedance was obtained by a simplified dynamic model of equipment-basement. Based on the difference between steady state response and transient response, a reduction formula to describe how installed equipment affects shock environment of basement was developed. The results show that the reduction formula based on impedance better agrees better with experiment data in most areas than other reduction formulas.

Research on Dual-Arms Inspection Robots Walking Along Transmission Line

WEI Yong-le, FANG Li-jin

2019, 39(8): 813-818. doi:10.15918/j.tbit1001-0645.2019.08.007

Abstract(769) PDF(327)

Abstract:
To solve some problems such as force unbalance of walking-wheels and easy to get off line existing in traditional dual-arms inspection robot walk along transmission line, the walking-wheels' force models of traditional dual-arms inspection robot and dual-arms inspection robot with flexible-cable were established respectively. Compared with traditional dual-arms inspection robot, the two walking-wheels' force of robot with flexible-cable were more balance and walking-wheel couldn't get off line with line angle increasing. Walking wheels' force conditions of two kinds of robots walking along line were simulated based on virtual prototype technology with the same parameters. Simulation results show that traditional robot would walk with single arm while line angle gradually increased to 28°, yet robot with flexible-cable still walked with two arms while line angle gradually increased to 37°. Therefore, the structural design of dual-arms inspection robot with flexible-cable has obvious advantages in walking along line, and it has stronger adaptive capacity for long-span transmission line with the bigger angle.

Mixed Weighted Feature Method for Human Eye Detection

WANG Jian-zhong, ZHANG Guang-yue, WANG Hong

2019, 39(8): 819-824. doi:10.15918/j.tbit1001-0645.2019.08.008

Abstract(990) PDF(527)

Abstract:
Eye gaze targeting technology based on eye movement tracking can free target tracking and aiming control of unmanned weapons from the need for limbs and make it possible to "attack whatever is seen", which is an important control mode of unmanned weapons in the future. A mixed weighted feature method was proposed in this paper. Human eye region detection was obtained through Gabor operator filtering, integral graph calculation, introducing local region variance as weight to weight mixed feature codes and combining it with cascade classifier training. The experimental results show that the method in this paper is better than the commonly used Haar-like and LDP methods, and the false detection rate shows a downtrend with the increase of series. This method can enhance the detection rate of human eyes and reduce false detection rate, providing a possible technical way to meet the requirements of real-time and accuracy of unmanned weapon eye gaze targeting.

A Probability-Based Fast Blind Rendezvous Channel-Hopping Algorithm in Cognitive Radio Sensor Networks

TAN Long, ZHANG Xiao-qi, LI Jian-zhong

2019, 39(8): 825-832. doi:10.15918/j.tbit1001-0645.2019.08.009

Abstract(827) PDF(280)

Abstract:
To solve the limitation of common control channel in cognitive radio sensor networks (CRSN), a simple and fast channel hopping algorithm SRA (sender-receiver-X) was proposed based on the traditional Rendezvous mechanism for reducing channel conflicts and improving the spectral adaptability of sensor nodes without using common control channels. In the SRA, node states were assorted into sending and receiving states firstly. And then, the channel hopping sequence was generated to realize the communication between nodes by adjusting the step size and the probability parameters. Finally, some theoretical and experimental analyses were carried out. Results show that, the algorithm can effectively solve the bottleneck problem of common control channel in CRSN, support symmetric and asymmetric models, satisfy multi-user/multi-hop application scenarios and realize guaranteed Rendezvous. Compared with other related algorithms, the SRPX algorithm is superior on maximum time to Rendezvous (MTTR) and average time to Rendezvous (ATTR).

Experimental Study on Sleep Stages Based on Normal Inverse Gaussian and Characteristic Contribution

YOU Yu-yang, YOU Shu-kai, GAO Jian-kai, YANG Zhi-hong

2019, 39(8): 833-838. doi:10.15918/j.tbit1001-0645.2019.08.010

Abstract(869) PDF(301)

Abstract:
An experimental framework based on normal inverse Gaussian and feature contribution was proposed for automatic classification of sleep stages. Features were extracted from the sleep EEG (electroencephalo-graph) signals. The signals were decomposed by tunableQ-factor wavelet transform (TQWT). The normal inverse Gaussian parameters were extracted from the TQWT sub-bands. The important features were selected and ranked according to the contribution degree based on the SVM model; according as the selected features of high contribution, the results of different classifiers were compared afterwards. A multi-classifier based automatic sleep staging algorithm was then designed. Results show that, the accuracy of sleep staging can reach 89.88% according to the validation on sleep-EDF dataset from PhysioBank. Compared with the single classifiers, the accuracy of staging can be improved greatly. Therefore, the proposed method is of great value for the clinical diagnosis and researches of sleep disorders.

Suboptimal Midcourse Trajectory Modification for Hypersonic Target Interception

ZHOU Jin, WANG Hua-ji, ZHAO Wei, ZHANG Da-yuan, LEI Hu-min

2019, 39(8): 839-845. doi:10.15918/j.tbit1001-0645.2019.08.011

Abstract(973) PDF(298)

Abstract:
Aimed at the hypersonic interception combat demand caused by the rapid developments of the near space vehicles, a suboptimal midcourse trajectory modification algorithm was designed based on model predictive static programming(MPSP).Firstly, analyzing the optimum conditions at the handover moment between the midcourse and terminal guidance, the zeroing effort interception condition was deduced according as the interceptor and target velocity ratio and their velocity heading angles. Secondly, introducing the proportional navigation as the terminal guidance law, the capture region of the terminal guidance was analyzed for the cases where the interceptor failed to satisfy the zeroing effort interception condition. The structure of the capture region was built in the plane composed of the interceptor and target velocity heading angles, serving as the constraints for the interceptor at handover moment. Thirdly, the Gauss pseudospectral method (GPM) was used to get the nominal optimal trajectory, satisfying the zeroing effort interception condition and the MPSP was introduced to modify the trajectory, considering the capture region constraints. Finally, the simulations were carried out to testify the rationality and effectiveness of the proposed method.

Optimization of VMD Parameters and Its Application in Bearing Fault Feature Extraction

ZHANG Dong-liang, LI Shuai-wei, HUANG Xin-yu, CHEN Pu

2019, 39(8): 846-851. doi:10.15918/j.tbit1001-0645.2019.08.012

Abstract(839) PDF(447)

Abstract:
To solve the problems existing in the swarm optimization algorithm, such as the low efficiency in searching the modal number and quadratic penalty parameters for the variational mode decomposition, a signal pretreatment method was proposed for fast local mean empirical mode decomposition. The number of modal was estimated according to the similarity coefficient criterion, and the penalty parameter was selected with the multi-evaluation factors. In order to reduce the influences of high natural frequencies band on results of VMD, the signal was reconstructed based on autocorrelation energy function to reduce the influence of noise and high frequency band. Simulation test and real data analysis of bearing fault were carried out to compare the parameter selection effect with swarm optimization algorithm and VMD modal selection effect based on similar center frequency. The results show that this method can extract early weak fault characteristic frequencies of bearings effectively.

Research on ADRC-Based Trajectory Linearization Control of Hypersonic Reentry Vehicle

ZHANG Hui-ping, YU Yue, WANG Hong-lun

2019, 39(8): 852-858. doi:10.15918/j.tbit1001-0645.2019.08.013

Abstract(948) PDF(448)

Abstract:
Based on the kinematic model of hypersonic reentry vehicle, coupling effects between three channels were comprehensively analyzed, including kinematics coupling, inertial coupling, aerodynamic coupling and control coupling. To solve the attitude tracking problem of the strong coupling system, ADRC(active disturbance rejection control)-based trajectory linearization controllers were designed based on time-scale separation and singular perturbation theory for attitude and angular rate loops respectively. During design process, decoupling mechanism of ADRC-based trajectory linearization control were analyzed fully from perspective of feedforward, feedback, disturbance estimation and compensation. The simulation results show the correctness of the decoupling mechanism analysis and excellent decoupling effects of ADRC-based trajectory linearization control possesses, being suited to design controller for strong coupling systems.

Zhang's Camera Calibration Method Based on Circular Array Calibration Board

WANG Shou-kun, ZHAO Jin-zhi, JIANG Ming, WANG Hao-tian, ZHANG Yi-ding

2019, 39(8): 859-863. doi:10.15918/j.tbit1001-0645.2019.08.014

Abstract(992) PDF(406)

Abstract:
A Zhang's camera calibration method based on circular array calibration board was proposed. Firstly,using the Daheng mercury series camera to take photos to the different directions and different attitudes circular features calibration board,the shoots were carried out for 20 times. And a sub-pixel edge extraction algorithm was used to extract the edge of the feature in the image field of view. Then the received closed features were conditionally restricted respectively on circularity, eccentricity and convexity to extract the circular features in the images satisfied the requirements. Finally, the camera calibration was performed by mapping the pixel coordinates of the circular feature points on the calibration board to the world coordinates. Experiments results show that the average re-projection error of the center point coordinates of the circular featurecan be below 0.007 pixels, proving the feasibility of this algorithm.

Tightly-Coupled UWB/AHRS Integrated Navigation Based on Improved Strong Tracking Filter

ZHENG Shu-hua, LU Dong-yuan, WANG Xiang-zhou, LIU Peng

2019, 39(8): 864-869. doi:10.15918/j.tbit1001-0645.2019.08.015

Abstract(720) PDF(353)

Abstract:
For the positioning problem of vehicle in the occluded environment, a tightly coupled positioning method was proposed based on improved strong tracking filter for ultra wideband (UWB) and attitude and heading reference system (AHRS). In the method, the threshold was used to identify the UWB ranging anomaly value and eliminate its influence. A strong tracking filter (STF) algorithm was applied to the data fusion of the tightly coupled system, and the algorithm was improved by combining the positioning model to improve the stability of the algorithm and the estimation accuracy of the observed noise. The simulation and test results show that, the proposed method can provide accurate positioning information of vehicles in complex conditions. Compared with the single positioning of UWB and the use of several nonlinear filtering algorithms, the system has stronger robustness, higher positioning accuracy, and has strong practicality.

A Fast Method for Hyperspectral Image Subpixel Mapping Based on Maximum a Posteriori and Total Variation Estimation

HU Zhong-kai, GAO Kun, DOU Ze-yang, ZHOU Ying-jie, GONG Xue-mei

2019, 39(8): 870-875. doi:10.15918/j.tbit1001-0645.2019.08.016

Abstract(1128) PDF(655)

Abstract:
To solve the ill-posed pr oblem of spectral unmixing in hyperspectral subpixel mapping applications, the maximum a posteriori estimation (MAP) spectral unmixing model combined with spatial distribution prior total variation (TV) was improved to ensure the scalability of the algorithm and the uniqueness of the solution. At the same time, in order to solve the cumbersome problem caused by the inherent nonlinear characteristics of TV prior, a fast algorithm was proposed to transform the original complex nonlinear operation into several simple operations with closed solutions. To solve the sub-problem respectively, a fast iterative shrinkage threshold algorithm (FISTA) and the split Bregman algorithm were utilized. The results show that the proposed new method can maintain the consistent mapping accuracy of the traditional gradient descent method, and can increase the iteration speed by more than 10 times, providing higher computational efficiency.

Analysis and Evaluation of System Effectiveness of Flamethrower

WU Yu, BI Peng-yu, JIN Qing-jun, REN Xiu-juan, YAO Wei-zhao

2019, 39(8): 876-880. doi:10.15918/j.tbit1001-0645.2019.08.017

Abstract(985) PDF(343)

Abstract:
Flaming combat is a short-distance combat pattern that causes destruction by using flame jet, playing a unique fire support role in modern wars. But the inherent defect of powder flamethrower on duty makes it unable to meet the actual need of flexible fighting in future combat. Therefore, the design idea of a new type flamethrower was put forward, and ADC model analysis method was established. Through the setup of usability, credibility, and capacity matrices, a system effectiveness analysis model was built for powder flamethrower on duty and the new-type flamethrower, to compare and analyze system effectiveness of the two types of flamethrower. The result shows that the new-type flamethrower has a conspicuous advantage in integral systematic effect and use preservation. The establishment of the ADC model of the flamethrower provides theoretical basis for the demonstration and development of the new-type flamethrower on the foundation of the quantized analysis of the system effectiveness of the flamethrower.

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