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2020, 40(7): .

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2020, 40(7): .

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Simulation Analysis on Testing Characteristics of Typical Planar Eddy Current Stress Sensors

LI Jian-wei, ZHANG Wei-min, GAO Xuan-yi

2020, 40(7): 691-696. doi:10.15918/j.tbit1001-0645.2019.111

Abstract(1777) PDF(1873)

Abstract:
In measuring stress using eddy current, characteristics of eddy current sensors are very important in selecting the appropriate sensor. The characteristics of six planar eddy current stress sensors (circular, elliptical, rectangular, Archimedes spiral, rectangular spiral, and meandering winding magnetometer, MWM) were compared through simulation. An aluminum 6063-T83 plate was used as a sample. Taking the change of electrical conductivity as the simulation parameter of the stress change, taking the induced voltage of the detecting coil as the analysis object, the simulation comparison of the sensor characteristics was carried out from two aspects, the stress measurement sensitivity and the stress direction sensitivity. Results show that, the sensitivities of the six sensors vary with exciting frequency and space between sensor and sample, possessing nearly the same patterns. When there is only single exciting unit in the sensors, the rectangular sensor is the best of all sensors in induced voltage, sensitivity, and ability to distinguish the direction of stress. When there are multiple exciting units, the MWM sensor is the best of those, and the circular sensor and Archimedes spiral sensor nearly could not distinguish the direction of stress. Finally, the abilities to distinguish the stress direction of rectangular and MWM sensors were verified experimentally.

Multi-Parametric Vibration Characteristics of Noncircular Face Gear Based on Harmonic Balance Method

LIU Da-wei, LIU Zhi-jia, LÜ Zhen-zhen

2020, 40(7): 697-704. doi:10.15918/j.tbit1001-0645.2019.164

Abstract(1613) PDF(1777)

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Considering the time-varying instantaneous center, meshing stiffness and static transmission error, a dimensionless dynamic model of the gear was established based on elastic rotational angle separation method. A multi-term harmonic balance method (HBM) was applied to obtain the approximate analytic solution of the gear under compound excitations composed of the instantaneous center and meshing stiffness. The effects of the system parameters on the dynamic response and the sensitivity of the parameters were analyzed emphatically. Results show that there exist multi-frequency harmonic components in the gear dynamic responses; the vibrational amplitudes grow with different tendencies as the rotational speed, the eccentricity, the error, the amplitude ratio of the meshing stiffness and the load torque increase; and every parameter of the gear has a greater influence on the sensitivity of itself and others.

Analysis on the Torsional Stiffness for Push-Rod Teeth Transmission with Pin Gear

FEI Yu, LI Hua, XIE Chao, YAO Jin, HUANG Bin-hong

2020, 40(7): 705-710. doi:10.15918/j.tbit1001-0645.2019.052

Abstract(1737) PDF(1759)

Abstract:
In order to study the torsional stiffness of push-rod teeth transmission with pin gear and influencing factors of the torsional stiffness, the formulas for calculating the meshing force and torsional stiffness were derived based on the deformation coordination method. By means of an example analysis, the variation law of the meshing force between the push-rod tooth and the pin, the variation law of the torsional stiffness of push-rod teeth transmission with pin gear were analyzed. The influence of the structural parameters of push-rod teeth transmission with pin gear on the torsional stiffness was discussed. The research results show that: there is the least meshing forces at the top and the root of the push-rod tooth profile, and there is the largest meshing force in the middle of the tooth profile; the torsional stiffness of push rod teeth transmission with pin gear fluctuates little; the eccentricity of generator and the number of pins have great influence on the torsional stiffness; the radius of pin and the radius of pin gear have little influence on the torsional stiffness; the influence of generator ’s radius on the torsional stiffness can be neglected. The research results can provide theoretical basis for tooth profile modification and parameter selection of the push-rod teeth transmission with pin gear.

Influence of Thermal and Mechanical Properties of Coating on Gun Barrel Life

GENG Xue-hao, ZHOU Ke-dong, HE Lei, LI Jun-song, WU Qi-jun

2020, 40(7): 711-718. doi:10.15918/j.tbit1001-0645.2019.170

Abstract(1629) PDF(1810)

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To analyze the influence of coating material properties on gun barrel life, applying synthetically the theories of coating shear failure mechanism and fatigue cumulative damage, a life prediction model was proposed based on the theories of coating shearing failure and fatigue cumulative damage. Taking the small caliber gun barrels coated with Cr, Ta and Si₃N₄ceramic respectively as study objects and 10-round burst shot firing as the process period, their near-wall temperature field, stress field and barrel life were numerically analyzed based on finite difference method, and the influence of coating properties on barrel life was analyzed. The results show that, the thermal diffusivity, the influence factorηand the crackedL/hratio of coating are the key properties for barrel life. And the crackedL/hratio of coating can bring a significant influence on interface shear stress and barrel life, and the coating with larger crackedL/hratio can reduce the interface shear stress effectively during firing and then improve the barrel life.

Experimental Research on Electronic Control Lubrication System for Aviation Two-Stroke Direct Injection Engine

WU Hao, ZHANG Fu-jun, WANG Zheng-kai, GAO Hong-li

2020, 40(7): 719-724. doi:10.15918/j.tbit1001-0645.2019.100

Abstract(1662) PDF(1774)

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According to the structural and performance requirements of the aviation two-stroke direct injection engine, an intelligent lubrication system was developed by taking a certain type of electronically controlled lubrication oil pump as the core actuator. The working principle of this oil pump was analyzed, a specialized drive-feedback system was designed and the experimental research on the characteristics of the pump oil was conducted. Aiming at the actual needs of the engine, the matching calculation of the lubricating oil quantity was completed before carrying out the engine bench tests. The uniformity of the lubricating oil of different cylinders was detected. Results show that, the effective oil-pumping pulse duration of the oil pump is 16~30 ms, the lubrication system can meet the lubrication requirements of the two-stroke direct injection engine, and the pumping-oil uniformity is satisfactory.

A Stiffness Prediction Model for Fiber Reinforced Plastic Coil Spring

CHEN Xiao-kai, LI Chao

2020, 40(7): 725-730. doi:10.15918/j.tbit1001-0645.2019.046

Abstract(1620) PDF(1819)

Abstract:
A general form of stiffness prediction model was built for fiber reinforced plastic coil spring, and a finite element modeling method was presented for finite element without considering the mesh or node number. Based on the theory of composite laminates, the equivalent shear modulus of laminates was derived and used to establish a stiffness prediction model for fiber reinforced plastic coil spring, being applicable for arbitrary ply angle. In order to avoid the difficulties in coordinating the direction between the element coordinate systems and spring helix, a novel finite element modeling method was presented to design the laminating directly without considering the mesh. The comparison between stiffness prediction model and the experiment result in reference shows that the accuracy of the prediction model is better than the prediction model in the reference. Considering the various combination of composite material and ply angle, a comparative analysis between the prediction model and the finite element model was conducted. The results show that the error between the prediction results and the FEA results are small, which indicate the effectiveness of the proposed model.

Numerical Study on the Inducer Cavitation in Cryogenic Fluids

PAN Jun-yi, WANG Guo-yu, XIAO Lei, HUANG Biao, FAN Ya-ding

2020, 40(7): 731-737. doi:10.15918/j.tbit1001-0645.2019.097

Abstract(1684) PDF(1793)

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In order to investigate the cavitation performance of inducer with cryogenic fluids, the cavitating flows inside an inducer with liquid nitrogen was simulated. In the numerical method, a FBM turbulence model with the rotational correction and Singhal cavitation model with the thermal correction were applied. The numerical method was verified by the general agreement between the numerical results and experimental data. The results show that, with the decreasing cavity number, three typical cavitation pattern in inducer can be observed, namely no-cavitation, gap cavitation, and back-flow vortex cavitation. The critical point for different cavitation stages will not change with the temperature changing(77.5 K≤T≤83 K). The cavity volume inside inducer increased at first and then decreased with the increasing temperature of liquid nitrogen. This is because the Weber number dominates the development of cavitation at low temperature while thermal effects aren't remarkable. As temperature increases, thermal effects dominates the cavitation dynamics, which suppresses the development of cavitation, while the thermal effects becomes more and more significant when the temperature is higher and the cavitation is highly suppressed.

A Bank-Address-Based Method for Conflict Delay Analysis and Optimization of IABA Bus

WANG Bo, TANG Jie, ZHANG Rui

2020, 40(7): 738-745. doi:10.15918/j.tbit1001-0645.2019.024

Abstract(1681) PDF(1758)

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In order to reduce the worst-case response time (WCRT) of hard real-time tasks for critical transaction in the Internet of things applications, a framework for bank conflict optimization was proposed based on access address of tasks was proposed. The framework was arranged to improve WCRT for hard real-time tasks in two aspects. Firstly, taking the access cache address of tasks as the reference factor to constrain the bank conflict conditions, the worst case execution time (WCET) could be constringed by introducing the access address constraints. Secondly, based on the distribution character of access cache address to optimize the address mapping, the conflict delay time of running tasks could be reduced. Experiments show that, the proposed approach can improve the average delay estimation value up to 18.15% and reduce the conflict delay time by about 20%.

An Automatic Sleep Staging Method Based on CNN-BiLSTM

LUO Sen-lin, HAO Jing-wei, PAN Li-min

2020, 40(7): 746-752. doi:10.15918/j.tbit1001-0645.2019.041

Abstract(2082) PDF(1836)

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To solve the problems, including the manual dependence in the extraction of sleep staging features, difficult identification to the timing pattern in long-term correlated data, and the inaccuracy of EEG timing data staging in the model, and so on, an automatic sleep staging method based on CNN-BiLSTM was proposed. Firstly, the original data was over-sampled with improving the MSMOTE algorithm to form the class equilibrium data. And then the advanced features were expressed by CNN and fed to BiLSTM to explore the dependency relationship between sleep stages, so as to realize the automatic learning and sleep cycle determination of sleep data staging characteristics. The experimental results on the Sleep-EDF open data set show that the classification accuracy of the CNN-BiLSTM model can reach 92.21%. The improved over-sampling technique of MSMOTE can alleviate the problem of inaccuracy in the determination of sleep stage. In the case of unbalanced class of original data set, automatic sleep data staging is realized, which can effectively improve the accuracy of sleep staging model, possessing a certain practical value.

The Design and Evaluation of Abnormal Event Generation System for Autonomous Driving Algorithms

MAO Ting, LIANG Wei

2020, 40(7): 753-759. doi:10.15918/j.tbit1001-0645.2019.025

Abstract(1807) PDF(1837)

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Evaluating the response of autonomous driving algorithms to abnormal traffic events acts an important application value. However, generating abnormal traffic events in the real world is costly and risky. In this paper, a method was proposed to generate abnormal traffic events for the evaluation of autopilot algorithms. The method was arranged to automatically generate five kinds of abnormal traffic events. And a Driving Strategy Evaluation System was established to realize the evaluation of the autopilot algorithm. An imitation learning autopilot algorithm based on a deep network was evaluated by the proposed system in order to verify the validity of the generated abnormal traffic events. The experimental results show that the generated abnormal traffic events can more comprehensively evaluate the performance of the autonomous driving algorithm.

A STA/LTA Based Pipeline Leak Detection Method

WANG Gui-yu, FANG Rui, SUN Kai, LI Hong-yan, WANG Hao-yu

2020, 40(7): 760-764. doi:10.15918/j.tbit1001-0645.2019.168

Abstract(1763) PDF(1780)

Abstract:
A method, combing the STA/LTA method in seismic identification with the negative pressure detection, was studied and applied to oil pipeline leak detection. According to the signal similarity of seismic first arrival and negative pressure produced in oil pipeline leak, the STA/LTA method was used to capture and extract the arrival time of negative pressure wave precisely. By obtaining the time delay between the stations on the two sides of the pipe, the position of leak could be calculated. Studied results indicate that, STA/LTA method can not only effectively recognize the leak signal, but also can reduce the computational complexity in the signal processing, such as the wavelet analysis. The experimental results show the superiority of the STA/LTA method, that it can recognize the negative pressure wave effectively.

A Fast Modular Inversion Architecture over GF(2^m) Based Modifiedx^2ⁿUnits

LI Jia-kun, LI Zhe, ZHANG Jing-qi, GAO Wei

2020, 40(7): 765-770. doi:10.15918/j.tbit1001-0645.2018.313

Abstract(1774) PDF(1758)

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A high-speed hardware architecture was presented to implement modular inversion operations for the field of elliptic curve cryptograph (ECC) in the paper. Two hardware architectures based on Itoh-Tsujii algorithm (ITA), Least-Cock-Cycle-ITA (LCC-ITA) architecture and high-speed-ITA (HS-ITA) architecture, were built and implemented on Xilinx Virtex-5. In the architectures, power operations and multiplications were simplified into non-iterative logic to speed up modular inversion operations. The test results show that the operating frequencies of both architectures are higher than the work before. LCC-ITA architecture takes nine clock cycles to complete a modular inversion operation with the operating frequency 126.1 MHz over GF(2¹⁶³), while HS-ITA architecture takes 20 cycles with the operating frequency 177.6 MHz over GF(2¹⁹³).

Frequency Domain Calibration and Uncertainty Evaluation in GTEM Cell

YAN Xue-fei, LIU Wei-dong, WANG Jia, OU Yuan, SHI Gen-zhu

2020, 40(7): 771-777. doi:10.15918/j.tbit1001-0645.2018.333

Abstract(1585) PDF(1769)

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The frequency domain calibration method of pulsed electric field was studied and its uncertainty was evaluated. According to the calibration requirement of pulsed electric field, a frequency domain calibration system based on GTEM cell was established. Through simulation and experiment, the uncertainty of standard electric field produced in GTEM cell and the uncertainty of interaction between sensor and standard electric field were analyzed. Synthesizing the uncertainties, the total uncertainty of the calibration was 4.45% when the confidence probability is more than 95%. Based on this, a three-dimensional pulsed electric field was calibrated in frequency domain. The calibration results show that the sensor has a relatively flat amplitude frequency response in 10 MHz~1 GHz. The research in this paper can provide a certain reference value for analyzing the frequency domain calibration of electric field sensors.

Design and Implementation of Code-Aided Carrier Phase Synchronization for High-Order Modulations

SHI De-sheng, WU Nan, WANG Hua, LIANG Tao, KUANG Jing-ming

2020, 40(7): 778-783. doi:10.15918/j.tbit1001-0645.2018.685

Abstract(1544) PDF(1804)

Abstract:
In this paper, a novel code-aided maximum-likelihood (ML) carrier phase synchronization algorithm was introduced. The mean square error (MSE) of the phase estimation and the impact to the bit error rate (BER) performances were evaluated via simulations. An embedded structure of LDPC code-aided carrier phase synchronization algorithm was proposed based on FPGA to enable joint iteration between phase synchronization and decoding, to reducing the complexity and delay of the algorithm. The algorithm was implemented based on Xilinx Kintex-7 FPGA platform. The test results show that the BER performances of the proposed algorithm are very close to that of the ideal synchronization scenarios. The proposed algorithm outperforms the data-aided algorithm, it can achieve about 0.7~0.9 dB SNR gap.

Discussion on the Convergence of Circuit Simulation Based on WDF Theory

YAN Su, LEI Lei, ZHONG Shun-an

2020, 40(7): 784-789. doi:10.15918/j.tbit1001-0645.2019.032

Abstract(1923) PDF(1775)

Abstract:
Compared with the existing mature simulation technology of Cadence, the theoretical simulation technology based on wave digital filter (WDF) showed a non-convergence phenomenon in the simulation process of some analog circuits. In this paper, a variety of circuit structures composed of resistors, capacitors and inductors were simulated in Matlab and Cadence simulation environments. The simulation results were compared and analyzed. Finally, three optimization schemes were proposed to overcome the non-convergence phenomenon with WDF theoretical simulation technology.

Optimization of Energy Transfer Efficiency for Pulsed Power Supply

XIONG Shi-cheng

2020, 40(7): 790-796. doi:10.15918/j.tbit1001-0645.2018.098

Abstract(1701) PDF(1082)

Abstract:
In this paper,the optimization of sequential discharge was taken as the study object for a pulsed power supply system in electromagnetic launch.In order to improve the launching efficiency of the projectile with fixed mass and velocity,a sequential optimization method was proposed based on pattern search.Firstly,taking the initial charging voltage and discharge time sequence of the pulse capacitor bank as the optimization parameters,the multi objective problem was transformed into a single objective optimization problem by the constraint model method.And then,an iterative pattern search algorithm was used to optimize the problem,obtaining the required optimal results.Finally,the results were analyzed and compared with the results published in other literature.Results show that,the launch performance can be improved,validating the feasibility of the proposed method.And the results of actual emission experiment show that,the efficiency of this method can be increased by 7%.

Design and Implementation of a Runtime-Configurable Two-Dimensional CFAR Processor

GAO Wei, YANG Hao, JIANG Rong-kun, XIE Fang, ZHOU Zhe, WANG Xiao-hua

2020, 40(7): 797-802. doi:10.15918/j.tbit1001-0645.2018.517

Abstract(1840) PDF(1792)

Abstract:
A hardware architecture of runtime-configurable two-dimensional constant false alarm rate (CFAR) processor was proposed based on FPGA to improve the algorithm speed for multi-scenario. This processor was designed to implement four pipeline architecture operations, cell averaging (CA), greatest of (GO), smallest of (SO) and ordered statistics (OS), for two-dimensional rectangular window (2D-RW) detectors. Also, controlling correlative parameters, this processor could make the reference window size, guard window size and detector type configurable. Test results show that, for 256×512 points data, the computation time of each detector in the processor is less than 3ms, and the relative error of detection threshold is no more than 0.1%, validating its better detection ability for two-dimensional radar data.

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