bob手机在线登陆学报自然版

2018, 38(7): .

Abstract(696) PDF(452)

Abstract:

2018, 38(7): .

Abstract(561) PDF(383)

Abstract:

Simulation and Experimental Research on Residual Stress in Pre-Stress Turning of 20Cr₂Ni₄ Based on Equivalent Loading Theory

TANG Shui-yuan, JIAO Si-cheng, LU Ji-ping, ZHANG Cheng-yan, FAN Hong-li

2018, 38(7): 661-667. doi: 10.15918/j.tbit1001-0645.2018.07.001

Abstract(939) PDF(451)

Abstract:
In order to predict the distribution of residual stress of 20Cr₂Ni₄ steel in pre-stress turning, a 3D finite model was established based on equivalent loading theory to transfer the cutting process into a combined cycle effect of contact normal stress, tangential stress and heat flux. The shape and value of equivalent thermal-mechanical loadings were extracted from analytical model of cutting force and heat. The simulation results of residual stress distribution are basically consistent with the measured results. Analyzing and comparing the simulation results, the influences of cutting speed, feed rate and pre-stress on residual stresses distribution were studied. These results show that the effect of cutting speed on residual stresses distribution is not obvious. With the decrease of feed rate, surface residual tensile stress and the maximum compressive stress decrease accordingly. Moreover, the increase of pre-stress leads to the decrease of surface residual tensile stress and the increase of the maximum compressive stress.

Review of Temperature Dependent Performance and Temperature Compensation Control of Magnetorheological Damper

OUYANG Qing, WANG Jiong

2018, 38(7): 668-675. doi: 10.15918/j.tbit1001-0645.2018.07.002

Abstract(855) PDF(577)

Abstract:
Temperature rise effect is a significant challenge for magnetorheological fluid damper (MRD) to step in the large-scale engineering application stage from the laboratory. The temperature rise phenomenon caused in the long-term running will affect the mechanics properties and working stability of MRD. In order to find out the performance variation of the MRD under temperature rise effect and the methods to control the performance fluctuation with temperature, four aspects including the temperature characteristic of magnetorheological fluid, temperature rise theory of MRD, temperature dependent dynamic model and control algorithm were concluded and analyzed in this paper. The temperature rise of linear motion MRD was mainly discussed in this paper. Some factors that impact on MRD were comprehensively summarized from the materials, devices and systems perspective. Finally, the facing challenges and deficiencies in the temperature rise effect of MRD were also proposed.

Research on the Orientation of Hydraulic Four-Legged Robot in the Field

LIN Jun-qin, HAN Bao-ling

2018, 38(7): 676-682. doi: 10.15918/j.tbit1001-0645.2018.07.003

Abstract(790) PDF(876)

Abstract:
To make a hydraulic quadruped robot capable of following a guide effectively in the field environment, a method was proposed for the robot to estimate its relative position to the guide. Firstly, a guide sign was designed for the guide to be easy detected and recognized in the surrounding environment, for example the guide in a similar camouflage. And then a binocular vision positioning method was combined with monocular vision localization method to improve the accuracy and robustness of system positioning. The stereo vision was used to obtain the optimal estimate based on contour detection and dynamic programming, and the Newton iterative method was used to estimate the optimal pose. Finally, the effectiveness and positioning accuracy of the system were verified by the simulation experiments, and the feasibility of the system was proved by the experiments on the hydraulic quadruped robot.

Study on Active Vibration Method of Electromechanical Transmission System

HU Ji-bin, CHEN Kai, PENG Zeng-xiong, XU Zhen-yu

2018, 38(7): 683-690. doi: 10.15918/j.tbit1001-0645.2018.07.004

Abstract(751) PDF(457)

Abstract:
Based on the permanent magnet synchronous motor dynamic model (Park model), considering the influence of current injection on the electromagnetic torque of permanent magnet synchronous motor, the electromagnetic torque model of PMSM and the torsional vibration model were built for the permanent magnet synchronous motor and the mechanical rotor to solve the torsional vibration response of the external excitations. The influence of injected harmonic currents on torsional vibration was analyzed, and the active vibration condition was obtained. And finally, it was verified by a test rig. The test results show that when the harmonic current is satisfied with the active vibration condition, the torsional vibration can be reduced by the injected harmonic current.

Structure Design of Automotive B-Pillar Based on Tailor-Welded Blank Technology

WANG Deng-feng, CAI Ke-fang, ZHANG Shuai, MA Ming-hui

2018, 38(7): 691-697,708. doi: 10.15918/j.tbit1001-0645.2018.07.005

Abstract(1077) PDF(764)

Abstract:
A tailor-welded blank technology was used to perform the integrated design of structure and material for B-pillar. To meet the collision performance, the intrusion displacement and invasion speed of B-pillar were controlled under lightweight design. Based on the C-NCAP, a finite element model of the side collision system was built and verified. A parametric model of B-pillar was built based on the mesh morphing technology. On the basis, three structural design variables and two material type design variables were defined. Then, setting the mass, maximum intrusion displacement and maximum invasion speed of the middle of B-pillar as the multi-objectives, the maximum intrusion displacement and maximum invasion speed of the upper and lower of B-pillar as constrains, the radial basis function (RBF) surrogate model and non-dominated sorting genetic algorithm (NSGA-Ⅱ) were applied to perform the multi-objective optimization design of B-pillar. The Pareto front was obtained and some compromise solutions were discussed to verify the effectiveness of structure design of B-pillar.

State Parameter Estimation of Distributed Drive Electric Vehicle Based on Adaptive Unscented Kalman Filter

WANG Zhen-po, XUE Xue, WANG Ya-chao

2018, 38(7): 698-702. doi: 10.15918/j.tbit1001-0645.2018.07.006

Abstract(927) PDF(508)

Abstract:
A vehicle state parameter estimation algorithm based on adaptive unscented Kalman filter (AUKF) was proposed to estimate vehicle state parameters accurately. Taking a nonlinear three freedom vehicle model as object, the fuzzy control algorithm and the unscented Kalman filter algorithm were combined to realize the adaptive adjustment of the system measurement noise. The sensor information about steering wheel angle, longitudinal acceleration and lateral acceleration were synthesized to realize the estimation of side slip angle and yaw rate. CarSim and Matlab/Simulink were used to establish the distributed driving electric vehicle model and the effectiveness of the algorithm was verified by simulation. The results show that the adaptive unscented Kalman filter is more effective and accurate than the unscented Kalman filter to estimate the parameters of the vehicle. In the double lane conditions, side slip angle estimation accuracy is improved by 6.7%, and the yaw rate estimation accuracy is improved 4.8%.

Multi-Living Agent System Oriented Quantitative Method and Planning Based on Complex Multi-Stage Tasks

WANG Yue, WU Jian-guang, HU Jin, JIA Li-juan

2018, 38(7): 703-708. doi: 10.15918/j.tbit1001-0645.2018.07.007

Abstract(852) PDF(470)

Abstract:
Multi-living agent theory has been a powerful tool for complex information system, where system living degree is an important index. With the boom of "Internet +", the tasks achieved by complex information system always possess the characteristics as high complexity, multi-stage feature variation, etc. To adapt to these features, a multi-living agent system oriented quantitative and planning method was proposed for complex multi-stage tasks, in which a system service model was built, service living degree was calculated, and a service strategy was designed based on stochastic service system theory. Results show that, the proposed method can solve the living degree quantization problem for multi-living agent system in the condition of weak prior information, validating its usefulness in practical situation.

Mechanism Modeling and Verification of Receiver with In-Band Dual-Frequency Blocking Jamming

WANG Ya-ping, WEI Guang-hui, LI Wei, PAN Xiao-dong, SHANG Zai-fei, WAN Hao-jiang

2018, 38(7): 709-714. doi: 10.15918/j.tbit1001-0645.2018.07.008

Abstract(890) PDF(416)

Abstract:
The reason of blocking jamming in-band is that the useful signals are buried in interfering signals and can not be detected due to adaptive gain adjustment of some kind receiver. In order to predict the survivability of frequency equipment in battlefield environment, a prediction model was deduced for the dual-frequency interference condition, taking the useful signal gain as standard and adapting the working principle of the general receiver. Taking a certain type of communication station as an example and the bit error rate as the criterion of interference, a single-product sensitivity test method and a dual-frequency interference sensitivity test method were developed for a communication station. The correctness of the interference prediction model was verified with the test data.

Perceptual Contrast Metric for Visible and Infrared Gray Fusion Images

GAO Shao-shu, ZHANG Xiao-dong, JIN Wei-qi

2018, 38(7): 715-720. doi: 10.15918/j.tbit1001-0645.2018.07.009

Abstract(984) PDF(478)

Abstract:
To evaluate the fusion image quality scientifically for fusion technology research and equipment applications, image contrast was taken as an important quality metric of dual-band gray fusion images. To solve the problem in the existing contrast metrics, unconsidering human visual system and affecting coherence between the predictions and the human perceptions, an objective perceptual contrast metric was proposed based on isotropic local contrast model as well as the introduction of the human luminance masking effect. The simulated gray images and the observer evaluation scores for 15 groups of real scene gray fusion images were used to test the proposed model. Experimental results show that the proposed perceptual contrast metric is more closely matched to the human vision perception than existing methods and can evaluate the dual-band gray fusion image perceptual contrast effectively.

Error Correction for Source of Time Domain Antenna Planar Near-Field Measurement

CAO Meng, XUE Zheng-hui, CAI Hong-wei, ZHU Ruo-qing

2018, 38(7): 721-725,732. doi: 10.15918/j.tbit1001-0645.2018.07.010

Abstract(931) PDF(401)

Abstract:
A correction method for source stability error in time domain antenna planar near-field test was proposed. Firstly, a reference channel was built for error correction to analyze the items included in source error. Then, considering two methods for near-field reconstruction and near/far-field translation in time domain measurement, methods called time domain-frequency domain combining correction and time domain correction were developed respectively, which could correct error in sampling signal caused by stability error of source. Finally, practical measurements were implemented for the method. Results show that, the modified frequency-domain pattern and the time domain waveform are in better agreement with the reference results, which proves the correctness of the two correction methods.

Jointly Estimation for Delay,Doppler and Channel Parameters in the DS-CDMA Systems

DU Chang-hao, HAN Hang-cheng, AN Jian-ping

2018, 38(7): 726-732. doi: 10.15918/j.tbit1001-0645.2018.07.011

Abstract(1537) PDF(354)

Abstract:
In this paper,the problem of estimating the large Doppler frequency offset,delay,and channel parameters in the asynchronous band-limited long-code-based uplink of direct sequence-code division multiple access (DS-CDMA) system was considered.The receiving signal model was established that was shaping by square root-raised cosine wave as two parts,one was composition of guide pilot and Doppler,the other was including the delay and complex gain of the multiple channel.Then proposed an unstructured indirect estimating algorithm,that used wave matched-least squares and multiple grade grid searching based on pilot assistance to estimate Doppler and used wave matched greed to estimate the others parameters.The simulation results based on Monte Carlo method show that the model and methods proposed perform well upon the scenario of the large Doppler frequency offset.

High Throughput Parallel Decoding Method for Serial Concatenated Convolutional Codes Based on CCSDS Standard

LI Lin-tao, LIU Hao, ZHANG Shu-yi, LIU Yuan-an

2018, 38(7): 733-738. doi: 10.15918/j.tbit1001-0645.2018.07.012

Abstract(806) PDF(389)

Abstract:
According to serial concatenated convolutional codes(SCCC) adaptive coded modulation scheme defined in the consultative committee for space data systems (CCSDS) standard, Log-MAP algorithm and Max-Log-MAP algorithm with multiplicative correction were analyzed and compared in the decoding performance and implementation complexity. On the basis of these studies, a parallel decoding method with low complexity and high coding gain was proposed in this paper. Furthermore, a general and parallel decoding structure, supporting a variety of coded modulation schemes, was provided. Finally, based on FPGA hardware platform, a high-speed, parallel and high-throughput SCCC decoder was designed for eight coded modulation schemes. The testing result indicates that the maximum throughput can be up to 300 Mbit/s.

Joint Estimation and Compensation of IQ Imbalance and Carrier Frequency Offset in MB-OFDM UWB Receiver

REN Shi-jie, AN Jian-ping, XU Zhan, BU Xiang-yuan

2018, 38(7): 739-743,765. doi: 10.15918/j.tbit1001-0645.2018.07.013

Abstract(957) PDF(408)

Abstract:
Studying the influence of IQ imbalance and carrier frequency offset (CFO) on the system performance in multi-band orthogonal frequency division multiplexing ultra wideband (MB-OFDM UWB) receiver, a joint estimation and compensation method of IQ imbalance and CFO was proposed in time domain and frequency domain. First, three repeat preambles were used to estimate and compensate the CFO and IQ imbalance in time domain. Second, pilots of data unit were used to estimate and compensate the residual IQ imbalance in frequency domain. The simulation results show that the method can overcome the influence of IQ imbalance and CFO, when CFO is 40 PPM, IQ imbalance factor is g=1.1 and θ=10°, the IQ imbalance and CFO can be compensated. The design method is of high accuracy, and is suitable for long symbol MB-OFDM UWB system.

SAR Image Denoising Based on Similarity Validation and Patch Ordering in NSST Domain

LIU Shuai-qi, HU Qi, LI Zhe, AN Yan-ling, LI Peng-fei, ZHAO Jie

2018, 38(7): 744-751. doi: 10.15918/j.tbit1001-0645.2018.07.014

Abstract(997) PDF(656)

Abstract:
In order to overcome the shortcoming of traditional synthetic aperture radar(SAR)image denoising algorithm in non-local transform domain without considering the patch relationship,a new SAR image denoising algorithm in non-subsampled shearlet transform(NSST)domain was proposed based on similarity validation and patch ordering.Firstly,the density distribution of distances between similar patches of SAR image in the NSST domain was constructed.Then,the patches with lower similarity were removed according to the similarity between the patches.Finally,SAR image was denoised by combining the patch ordering and the optimal one-dimensional filter.The experimental results show that,compared with other transform domain algorithms,the equivalent numbers of looks in this algorithm can increase by 6.92 on average,and the edge preservation index is close to 1.And the unassisted measure of quality can reduce by 2.51 on average.The algorithm can better maintain the image edge and texture information,and improve the visual effect of the image.

Design and Implement on Monopulse Radar Signal Preprocessing System Base on FPGA

LIU Guo-man, HAN Hai-yue

2018, 38(7): 752-758. doi: 10.15918/j.tbit1001-0645.2018.07.015

Abstract(1291) PDF(395)

Abstract:
Monopulse radar signal preprocess is very important in signal preprocess, but monopulse radar signal preprocess requires large amount of computation with fixed algorithm structure relatively. To solve the problem, a field programmable gate array (FPGA) was used to realize the preprocessing system. Firstly, sampling three channel IF signal, and the sampled data were respectively used for down conversion to obtain the baseband digital signal. Considering a variety of patterns of the signal, and a lot of resources in pulse compression, a pulse compression module was used to complete the processing of three signals of different modes. Then a test signal was generated with FPGA and input to the ADC to realize the loopback test. Finally, the processing result and simulation result were compared and analyzed. The consistent results show that the design of the system is reasonable and feasible.

A New Method for Performance Evaluation of Pulsed Interference Based on Wigner-Ville Distribution

YANG Jie, XU Jing-ying, ZHI Ru-xin, HAN Bing-yang

2018, 38(7): 759-765. doi: 10.15918/j.tbit1001-0645.2018.07.016

Abstract(1310) PDF(363)

Abstract:
To evaluate pulse interference performance in digital communication countermeasure, a new parameter measuring the average effective correlation power density between the target signal and the interfering signal was presented based on the time-frequency analysis tool, Wigner-Ville distribution, making use of the abruptness of the pulsed interference and the non-stationarity brought by the frequency offset and the phase offset of its carrier. Simulation results in typical communication systems show that the new parameter is capable of effectively reflecting the relation between pulsed interference performance and SIR (signal to interference ration), and correctly distinguishing interfering pulses with pulse widths smaller and larger than one information bit. The proposed method is directly applicable to pulsed interferences with different formats and can effectively analyze pulsed interference performance even where the communicating side and the interfering side are hidden to each other.

Effect of Simulated Microgravity on Hepatic CYP1A2 in Rats

LI Yu-juan, LI Pan-pan, SUN Xin-xin, LI Yong-zhi, WANG Jia-ping

2018, 38(7): 766-770. doi: 10.15918/j.tbit1001-0645.2018.07.017

Abstract(783) PDF(453)

Abstract:
To provide basic research data for understanding the changes of metabolic enzymes under weightlessness, the effect of simulated microgravity on hepatic CYP1A2 in rats was investigated. After the rats are tail suspended for 3, 7, 14 and 21 days, the protein expression, mRNA expression and the CYP1A2 activity were detected by western-blot, Q-PCR and HPLC-UV methods. Compared with the control group, the expression of CYP1A2 protein decreases significantly (p<0.05) in the 3 d tail suspended (TS) rats, but increases significantly (p<0.05) in the 7 and 14 d TS rats. The expression of protein decreases slightly (p> 0.05) in the 21 d TS rats. The mRNA expression and activity of CYP1A2 increase significantly (p<0.05) in 3, 7 and 14 d TS rats and increase slightly (p> 0.05) in 21 d TS rats compared with the control group. The 14 d simulated group has the most significant effect on the expression and the activity of hepatic CYP1A2 in rats. All the indices in 21 d TS rats show the tendency to the control group level. This study provides basic research data for understanding changes of metabolic enzymes and drug safety of astronauts under the microgravity condition.

Submission System

Author Related

Writing Norms

Links

2018 Vol. 38, No. 7

Archive