bob手机在线登陆学报自然版

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2022, 42(10)

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2022, 42(10): 1-2.

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Numerical Study on Transition Reversal of Hypersonic Cone Boundary Layer

LEI Juanmian, CAO Jiawei

2022, 42(10): 991-1001. doi:10.15918/j.tbit1001-0645.2021.224

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In order to study the transition reversal phenomenon in the transition of the hypersonic boundary layer, based on the Reynolds average N-S equation, the flow around a hypersonic cone was numerically simulated with a γ transition model, obtaining the changing law of the transition position of the cone boundary layer with the attack angle and the bluntness of the head, and analyzing the flow mechanism of the transition and reversal phenomenon of the cone boundary layer. The results show that, when the bluntness of the cone head increases to a certain value, the transition position of the cone boundary layer presents a reversal phenomenon, i.e. the windward surface advances and the leeward surface delays with the increase of the angle of attack. And when the attack angle reversal phenomenon occurs in the cone boundary layer transition, the friction coefficient on the windward surface is significantly greater than that of the leeward surface, and the friction change is greater before and after the transition, so as to pay attention on the thermal protection of the windward surface. Under the condition of zero angle of attack, the transition position of the cone boundary layer can show an "N" type reversal phenomenon with increasing the bluntness of the cone head gradually from a very small value. When the bluntness of the cone head increases to a certain value, the transition reversal phenomenon of the boundary layer occurs, may be caused by the significant increase in the height of the entropy layer after the head shock.

Dynamic Characteristics of Underwater Explosion Bubble near Rigid Cylinder

LI Yikai, XI Ru

2022, 42(10): 1002-1008. doi:10.15918/j.tbit1001-0645.2021.254

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To study the dynamic characteristics of underwater explosion bubbles near a rigid cylinder, a numerical model was established based on the Navier-Stokes equation combined with the volume of fluid method (VOF) to capture the gas-liquid two-phase interface, Using capacitor discharge to generate underwater explosion bubbles and using a high-speed camera to record the pulsation of the bubbles, some experiments were carried out. The experimental results were compared with the numerical simulation results to verify the validity of the numerical model. The numerical simulation results provide detailed information of the flow field of the interaction between the bubble and the rigid cylinder. The results show that the bubble pulsates near the rigid cylinder can make the fluid medium on the surface of the rigid cylinder form a velocity gradient, and the fluid layer with higher velocity can make the bubble form different bubble shapes. Finally, a dimensionless parameter was defined to characterize the relative distance between the bubble and the rigid cylinder, and the influence of the distance parameter on jet impact pressure, maximum jet velocity and bubble core movement was studied. The results show that, with the increase of the distance parameter, the jet impact pressure gradually decreases, and the maximum jet velocity inside the bubble increases first and then decreases, the deviation of the bubble core decreases with the increase of the distance parameter.

Effect of Projectile Oblique Penetrating into Multi-Layered Thin Concrete Slabs on Attitude Deflection

CHENG Lirong, WANG Dewu, HE Yuanji, ZHAO Hongwei, YANG Jie, DENG Bin

2022, 42(10): 1009-1016. doi:10.15918/j.tbit1001-0645.2021.299

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To solve the problem of attitude deflection appeared in projectile oblique penetrating into multi-layered thin concrete slabs, a finite element analysis model and relevant analytical method were proposed for projectile attitude deflection. Firstly, the effect of projectile shape parameters on the rate of angular change was studied for the penetration of the single-layered concrete slab. And then, the attitude deflection trend was analyzed for the penetration of the multi-layered concrete slabs. The research results show that a stable trajectory can be got when a projectile shape with blunt, high length–to-diameter ratio and expanded tail is used to penetrate into multi-layered thin concrete slabs. To arrange a scaling test for the validation of attitude deflection performance, the proportions on thickness of slabs, floor height should be made the same with the length of projectile, making all physical quantities equivalence such as resistance and moment in the movement of scaled projectile.

Experiments on the Resistance Mechanism of Low-Hardness Polyurea/Steel Composite Structures Penetrated by High-Velocity Fragments

MAO Liuwei, WAN Changzhao, CHEN Changhai, CHENG Yuansheng

2022, 42(10): 1017-1025. doi:10.15918/j.tbit1001-0645.2021.219

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To explore the resistance mechanism of low-hardness polyurea/steel composite structures (PSCSs) penetrated by high-velocity fragments, ballistic tests were carried out. Failure modes and ballistic resistances of PSCSs were analyzed, and were compared with those of monolithic steel plates. On the basis of stress waves, ballistic resistance mechanisms of PSCSs were probed. Results show that the front polyurea layers mainly exhibit shearing plugging under high-velocity penetration by fragments, while the failure modes of rear steel layers change from shearing plugging to petalling. Under the same total areal density, the whole ballistic resistance of PSCSs is lower than that of monolithic steel plates, but the ballistic resistance efficiency of rear steel layers is promoted due to the influence of front polyurea layers. The whole ballistic resistance of PSCSs first decreases and then increases, instead of constantly decreasing, as the areal density ratio of front polyurea layer to rear steel layer increases. For a PSCS, the rear steel layer is its main energy absorption component.

Disperse Characteristic of Behind-Armor Debris Formed by Explosively Formed Penetrator Vertically Penetrating Steel Target

XING Boyang, ZHAO Jianxia, CHEN Liang, HU Aiqian, ZHU Fulin, LIU Jianlu, GUO Rui, HOU Yunhui

2022, 42(10): 1026-1033. doi:10.15918/j.tbit1001-0645.2021.304

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In order to predict the debris distribution in tank quantificationally by initial condition before explosively formed penetrator (EFP) attacks a target, so as to optimize and upgrade the target attack strategy, by adopting numerical simulation verified by experimental data was adopted, behind-armor debris (BAD) formed by EFP penetrating steel target was investigated, the relationship between the amount of BAD and disperse angle was analyzed, the connection between the above-mentioned relation and impact velocity (1700～1900 m/s), thickness of target (30～70 mm), the source of debris (EFP or target) was built. Results indicate that debris distribution could be predicted by initial condition quantificationally and credibly, accumulated amount of BAD generated by EFP and target increases in the manner of Weibull distribution as disperse angle increases.

Theoretical and Orthogonal Analysis on Trunconical Hypercumulation Shaped Charge Structure

GE Chao, QU Zhuojun, WANG Jin, ZHOU Sheng, HU Die, YU Qingbo

2022, 42(10): 1034-1041. doi:10.15918/j.tbit1001-0645.2021.248

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To meet the purpose of design and application of trunconical hypercumulation shaped charge structure, a theoretical model describing the formation of hypercumulation jet was established. By comprehensively considering key parameters such as liner, explosive, shell and stand-off, a dimensionless theoretical model of the main parameters affecting the forming characteristics of hypercumulation jet was proposed. By means of orthogonal design and numerical simulation, effects of liner cone angle, liner thickness, additional body thickness, additional body edge projection length and stand-off on the main indexes of jet were studied, and the primary and secondary relationship of the five key factors were obtained.

Extreme Learning Machine Based on State Transition Algorithm

ZOU Weidong, LI Yuxiang, XIA Yuanqing

2022, 42(10): 1042-1050. doi:10.15918/j.tbit1001-0645.2021.302

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In order to solve the problems of extreme learning machine (ELM), occupying more computing resources and low accuracy during model training, an extreme learning machine based on the state transition algorithm (STA) was proposed to improve the calculation efficiency of the algorithm and the accuracy of the model. Taking advantage of the global search feature of the state transition algorithm, the algorithm was arranged to solve the linear equations, obtain the output weight matrix of the extreme learning machine and complete the modeling. Compared with extreme learning machine and other mainstream algorithms on classification and regression data sets, the proposed algorithm can realize high model accuracy with fewer hidden layer nodes and achieve better learning accuracy. The high-performance modeling method can make up for the deficiencies of the extreme learning machine.

Variable Step Size LMS Algorithm Based on Inverse Hyperbolic Tangent Function

HUO Yuanlian, AN Yaqi, GONG Qi, LIAN Peijun

2022, 42(10): 1051-1058. doi:10.15918/j.tbit1001-0645.2021.257

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Aiming at the problem that the fixed-step least mean square (LMS) algorithm could not meet the requirements of low steady-state error and fast convergence speed at the same time, a variable-step LMS algorithm was proposed based on the inverse hyperbolic tangent function. Utilizing the inverse hyperbolic tangent function, the algorithm was arranged to construct the non-linear function relationship between the step size and the error signal, so as to replace the fixed step size in the LMS algorithm and realize the dynamic adjustment of the step size factor. In this paper, the influence of the parametersα,βandγin the new variable step size function on the performance of the algorithm was discussed in detail, and the performance of the algorithm was compared with several other newer variable step size algorithms. The simulation results show that the proposed algorithm takes into account the contradiction among convergence speed, steady-state error and tracking performance, and present excellent performance in system identification, sinusoidal signal denoising and adaptive linear prediction.

Overview on Event-Triggered Consensus of Multi-Agent Systems

ZHANG Dong, MA Suhui, LÜ Shi, WANG Mengyang, TANG Shuo

2022, 42(10): 1059-1072. doi:10.15918/j.tbit1001-0645.2021.222

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Event-triggered consensus control is an effective method to solve the communication resource consumption problem for multi-agent systems (MASs) consensus. Firstly, a basic framework of MASs event-triggered consensus was established. Then the domestic and foreign research progress on MASs event-triggered consensus issue was reviewed, including four aspects: event-triggered mechanisms and its design strategies, influence factors, Zeno behavior and application of event-triggered consensus. Finally, some challenging issues were put forward for future research.

PMSM Current Robust Incremental Predictive Control

ZHANG Shuo, SUN Yonglu, ZHAO Mingwei, ZHOU Ying

2022, 42(10): 1073-1079. doi:10.15918/j.tbit1001-0645.2021.296

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The traditional deadbeat current predictive control of permanent magnet synchronous motor heavily depends on motor parameters, causing the control performance degraded seriously, the current unconformity and harmonic content increase with motor parameter change. To solve the problem of parameter disturbance in the traditional deadbeat current predictive control, a deadbeat predictive current control (DPCC) method was proposed based on the incremental model of Luenberger observer. Firstly, based on the original deadbeat current predictive control model, an incremental model was derived to eliminate the influence of flux linkage change in current predictive control. Secondly, in order to eliminate the influence of inductance change on the effect of current predictive control, the Luenberger observer was introduced and an incremental model with Luenberger observer was established. Finally, the effectiveness of the proposed method was verified by Simulink simulation and experiments.

Multidisciplinary Modeling and Optimization of Direct-Driving Electro-Hydrostatic Actuator

TAN Cao, LI Bo, YU Peng, LU Jiayu, LIU Yongteng, SUN Zhaoyue

2022, 42(10): 1080-1088. doi:10.15918/j.tbit1001-0645.2021.266

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To meet the increasingly stringent requirements of automobiles on execution components of control-by-wire system, a kind of high-power density moving coil linear actuator was proposed to directly drive the piston of the hydraulic pump, thereby realizing the direct-driving electro-hydrostatic actuator (DEHA) with servo control of the actuator volume, and effectively shortening the path of power transmission. A multidisciplinary simulation model of DEHA with electromagnetic, mechanical, hydraulic and control coupling was established, the algorithm based on sliding mode and active disturbance rejection control for direct-driving piston motion was designed, and the influence of structural parameters, such as the diameter of the ball seat of the check valve core, the diameter of the valve core ball, the spring rate, and the spring preload, on the performance of DEHA was analyzed. Taking the dynamic response time of DEHA as target, the structural parameters of the check valve were optimized by genetic algorithm. Simulation and experimental results verify the effectiveness of the DEHA built model and optimization: when the trajectory of the plunger is the typical operating condition with a frequency of 20 Hz and an amplitude of 5 mm, the response time of DEHA moving 20 mm is less than 0.2 s.

A RBF-FOC System for Robotic Arm PMSM

TANG Xiaogang, YANG Guangyu, HUAN Hao, YU Haoyuan, LI Keying

2022, 42(10): 1089-1096. doi:10.15918/j.tbit1001-0645.2021.267

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In order to solve the problems of the conflict of high precision and fast response, and stability of robotic arm servo control in a dynamic environment, several measures were proposed. Firstly, taking the permanent magnet synchronous motor (PMSM) as the study object, a radial basis function (RBF) field-oriented control (FOC) system was developed to improve the controller structure, to overcome the integral hysteresis of the PI controller and to improve the response speed of the system. And then, a supervised learning method was used to solve the instability problem of neural network in the control system. An online learning method was applied to improve the adaptability of the control system in a dynamic environment. The experiment results show that the proposed methods can effectively improve the stability of the RBF-FOC system, the dynamic response speed and anti-interference ability of the PMSM.

Research on Microwave Imaging Technology of Stroke Detection Based on Improved Contrast Source Inversion Algorithm

LIU Heng, WANG Ruoxuan

2022, 42(10): 1097-1104. doi:10.15918/j.tbit1001-0645.2021.306

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In order to improve the speed and accuracy of brain imaging, an improved contrast source inversion algorithm based on fast conjugate gradient iteration（FCG-CSI）was proposed for microwave imaging of hemorrhagic stroke. A microwave detection simulation system for cerebral apoplexy was established based on COMSOL and MATLAB software to carry out microwave imaging on the brain model. The simulation results show that FCG-CSI algorithm can effectively image blood clots in the brain, and the location error of imaging is only 0.54 cm.

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2022 Vol. 42, No. 10

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