Welcome to Journal of Beijing Institute of Technology

2015 Vol. 24, No. 4

Engineering Mechanics
Triaxial high-gaccelerometer of microelectro mechanical systems
HE Xu, ZHANG Zhen-hai, LI Ke-jie, LIN Ran
2015, 24(4): 427-431. doi:10.15918/j.jbit1004-0579.201524.0401
Abstract:
A triaxial high-gaccelerometer of microelectro mechanical systems(MEMS) has a structure of multi-chips combination and will be used in aerospace field, civil and military fields. The accelerometer can measure the acceleration of the carrier. The chips with island-membrane structures on its back surfaces are made by MEMS dry processing. The chip is reasonable and can work well under high impact load; Titanium alloy base is also stronger in high shock environment, these are proved by finite element analysis. Finally, the MEMS combined triaxial high-gaccelerometer is validated by high impact calibration experiments in order to get a key performance index, including range, sensitivity and transverse sensitivity and so on. These data can satisfy the need of design but some problems remain, these will be eliminated by improvement of the processing technology and materials.
Dynamic modeling and simulation for the rigid flexible coupling system with a non-tip mass
LI Cui-chun, MENG Xiu-yun, LIU Zao-zhen
2015, 24(4): 432-440. doi:10.15918/j.jbit1004-0579.201524.0402
Abstract:
The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate system, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are established. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays: the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can't be offered. First, the mass at non-tip position is incorporated into the continuous dynamic equations of the system by use of the Dirac function and the Heaviside function. Then, based on the conclusions of orthogonalization about the normal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that: dynamic stiffening is included in the first-order model established in this paper, which indicates the dynamic responses of the rigid flexible coupling system with large overall motion accurately. The results also show that the mass has a softening effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.
Mechanical Engineering
Multi-constrained model predictive control for autonomous ground vehicle trajectory tracking
GONG Jian-wei, XU Wei, JIANG Yan, LIU Kai, GUO Hong-fen, SUN Yin-jian
2015, 24(4): 441-448. doi:10.15918/j.jbit1004-0579.201524.0403
Abstract:
A multi-constrained model predictive control (MPC) algorithm for trajectory tracking of an autonomous ground vehicle is proposed and tested in this paper. First, to simplify the computation, an active steering linear error model is applied in the MPC controller. Then, a control increment constraint and a relaxing factor are taken into account in the objective function to ensure the smoothness of the trajectory, using a softening constraints technique. In addition, the controller can obtain optimal control sequences which satisfy both the actual kinematic constraints and the actuator constraints. The circular trajectory tracking performance of the proposed method is compared with that of another MPC controller. To verify the trajectory tracking capabilities of the designed controller at different desired speed, the simulation experiments are carried out at the speed of 3m/s, 5m/s and 10m/s. The results demonstrate the MPC controller has a good speed adaptability.
Estimating the clutch transmitting torque during HEV mode-switch based on the Kalman filter
WU Xue-bin, ZHANG Xin, CHEN Hong-wei, YANG Meng
2015, 24(4): 449-457. doi:10.15918/j.jbit1004-0579.201524.0404
Abstract:
A power train dynamics model of a coaxial parallel hybrid electric vehicle (HEV) was built for different clutch operating states. With the state vector constituted by the motor rotation speed and the clutch transmitting torque at two successive time steps, a discrete state space model for estimating the clutch transmitting torque was built, and the Kalman filtering algorithm was used to estimate the clutch transmitting torque. The Matlab/Simulink was employed to simulate the clutch transmitting torque for two mode-switch processes. Estimation errors were analyzed through comparing the estimated and simulated values of the clutch torque. Impact of the noise covariance and the sample time on clutch torque estimation errors were explored. The results show that the developed estimation method can be used to estimate the clutch transmitting torque for HEV with good accuracy. The results are useful for torque direct control of automatic diaphragm clutches.
Optimal tracking control for automatic transmission shift process
WAN Guo-qiang, LI Ke-qiang, PEI Ling, HUANG Ying, ZHANG Fu-jun
2015, 24(4): 458-465. doi:10.15918/j.jbit1004-0579.201524.0405
Abstract:
In order to improve the shift quality, a linear quadratic optimal tracking control algorithm for automatic transmission shift process is proposed. The dynamic equations of the shift process are derived using a Lagrange method. And a powertrain model is built in the Matlab/Simulink and verified by the measurements. Considering the shift jerk and friction loss during the shift process, the tracking trajectories of the turbine speed and output shaft speed are defined. Furthermore, the linear quadratic optimal tracking control performance index is proposed. Based on the Pontryagin's minimum principle, the optimal control law of the shift process is presented. Finally, the simulation study of the 1-2 upshift process under different load conditions is carried out with the powertrain model. The simulation results demonstrate that the shift jerk and friction loss can be significantly reduced by applying the proposed optimal tracking control method.
High-precision method of detecting motion straightness based on plane mirror interference
DENG Yong-jun, ZHANG Zhi-jing, JIN Xin, XU Zhi-yao, SUN Hong-chang
2015, 24(4): 466-470. doi:10.15918/j.jbit1004-0579.201524.0406
Abstract:
A high-precision method of detecting motion straightness was proposed based on the principle of plane mirror interference after analyzing the motion straightness error of a linear stage. Detection experiments were carried out and the motion straightness errors were separated by the linear regression method. Finally, linear measurement uncertainty of the detection method was estimated. The results showed that this detection method was simple and accurate, and was especially suitable for precision detection of motion straightness error in the small travel movement of ultra-precision machining.
Analysis of stress-magnetic coupling effect in weak magnetic environment
QIU Zhong-chao, ZHANG Wei-min, GUO Yan, DUBOV A A
2015, 24(4): 471-477. doi:10.15918/j.jbit1004-0579.201524.0407
Abstract:
Metal magnetic memory (MMM) signals are difficult to be analyzed due to noise interference, which limits its practical engineering application. A method of improving the magnetic signals is proposed in this paper by placing the excitation device which generates a weak external magnetic field about 100 A/m. The effect of the external magnetic field on the magnetic signals is studied using both finite element method (FEM) and uniaxial tensile tests. Comparison of the test data with the simulation ones of stress-magnetic coupling shows that the magnetic signals are strengthened and the measurement sensitivity of the detection system is greatly improved through the external magnetic excitation. Moreover, the FEM result has a good agreement with the testing results of No.20 steel plate. The proposed method has laid a foundation for further practical engineering application.
Inter-limb and intra-limb coordination control of quadruped robots
LI Hua-shi, HAN Bao-ling, LUO Qing-sheng
2015, 24(4): 478-486. doi:10.15918/j.jbit1004-0579.201524.0408
Abstract:
To realize the coordinated and stable rhythmic motion of quadruped robots (QRs), the locomotion control method of QRs based on central pattern generator (CPG) was explored. In traditional control strategies based on CPG, few CPG models care about the intra-limb coordination of QRs, and the durations of stance phase and swing phase are always equal. In view of these deficiencies, a new and simpler multi-joint coordinated control method for both inter-limb and intra-limb was proposed in this paper. A layered CPG control network to realize the locomotion control of QRs was constructed by using modified Hopf oscillators. The coupled relationships among hip joints of all limbs and between hip joint and knee joint within a limb were established. Using the co-simulation method of ADAMS and MATLAB/Simulink, various gait simulation experiments were carried out and the effectiveness of the designed control network was tested. Simulation results show that the proposed control method is effective for QRs and can meet the control requirements of QRs' gaits with different duty factors.
Effect of rifle bullet parameters on the penetration into ballistic gelatin
LIU Su-su, XU Cheng, CHEN Ai-jun, LI Hong-kui
2015, 24(4): 487-493. doi:10.15918/j.jbit1004-0579.201524.0409
Abstract:
To understand the effects of the rifle bullet parameters on the bullet-gelatin interaction quantitatively, a finite element model of bullet penetrating gelatin was set up and computational results are compared with experimental ones. The penetration of the rifle bullet into the gelatin was simulated by the nonlinear finite element method. The quantitative analysis of the changes in the gelatin interaction with the rifle bullet were conducted by changing the bullet parameters, such as attack angle on gelatin, initial velocity, warhead's tip and location of mass center of bullet. Results demonstrate that with the increase of the attack angle, instable moment of the bullet moves forward,the length of narrow wound channel shortens,and when penetration is completed diameters of temporary cavities increase, the gelatin energy and energy transmission ratio increases; With the increase of the impact velocity, instable moment of the bullet moves forward, the maximum forces acting on the gelatin and the gelatin energy increase remarkably; the length of narrow wound channel shortens, diameters of temporary cavities increase when penetration is completed, the gelatin energy and energy transmission ratio increase; The warhead's tip and location of mass center have a influence on the instable moment of the bullet and length of the narrow wound channel. The instable moment delays and narrow wound channel increases when the warhead's tip flattens. The instable moment moves forward a little and the narrow wound channel shortens a little when location of mass center moves back.
Informatics and Electronic Engineering
Factor-graph-based iterative channel estimation and signal detection algorithm over time-varying frequency-selective fading channels
ZHAO Hong-jie, WU Nan, WANG Hua, LI Zhi-xin, KUANG Jing-ming
2015, 24(4): 494-500. doi:10.15918/j.jbit1004-0579.201524.0410
Abstract:
The problem of soft-input soft-output (SISO) detection for time-varying frequency-selective fading channels is considered. Based on a suitably-designed factor graph and the sum-product algorithm, a low-complexity iterative message passing scheme is proposed for joint channel estimation, equalization and decoding. Two kinds of schedules (parallel and serial) are adopted in message updates to produce two algorithms with different latency. The computational complexity per iteration of the proposed algorithms grows only linearly with the channel length, which is a significantly decrease compared to the optimal maximum a posteriori (MAP) detection with the exponential complexity. Computer simulations demonstrate the effectiveness of the proposed schemes in terms of bit error rate performance.
Multi-subpulse process of large time-bandwidth product chirp signal
ZHANG Hong-gang, FAN Hua-yu, HE Shao-hua, LIU Quan-hua
2015, 24(4): 501-507. doi:10.15918/j.jbit1004-0579.201524.0411
Abstract:
To prevent the long-time coherent integration and limited range window stumbling blocks of stretch processing and reduce computational complexity, a novel method called multi-subpulse process of large time-bandwidth product linear frequency modulating (LFM) signal (i.e. chirp) is proposed in this paper. The wideband chirp signal is split up into several compressed subpulses. Then the fast Fourier transform (FFT) is used to reconstruct the high resolution range profile (HRRP) in a relative short computation time. For multi-frame, pulse Doppler (PD) process is performed to obtain the two-dimension range-Doppler (R-D) high resolution profile. Simulations and field experimental results show that the proposed method can provide high-quality target profile over a large range window in a short computation time and has the promising potential for long-time coherent integration.
Radial-curve-based facial expression recognition
YUE Lei, ZHANG Chao, ZHAO Shan-yuan, DU Bu-zhi
2015, 24(4): 508-512. doi:10.15918/j.jbit1004-0579.201524.0412
Abstract:
A fully automatic facial-expression recognition (FER) system on 3D expression mesh models was proposed. The system didn't need human interaction from the feature extraction stage till the facial expression classification stage. The features extracted from a 3D expression mesh model were a bunch of radial facial curves to represent the spatial deformation of the geometry features on human face. Each facial curve was a surface line on the 3D face mesh model, begun from the nose tip and ended at the boundary of the previously trimmed 3D face points cloud. Then Euclid distance was employed to calculate the difference between facial curves extracted from the neutral face and each face with different expressions of one person as feature. By employing support vector machine (SVM) as classifier, the experimental results on the well-known 3D-BUFE dataset indicate that the proposed system could better classify the six prototypical facial expressions than state-of-art algorithms.
Generalized ionospheric dispersion simulation method for wideband satellite-ground-link radio systems
ZHOU Yang, ZHENG Zhe, WU Si-Liang
2015, 24(4): 513-518. doi:10.15918/j.jbit1004-0579.201524.0413
Abstract:
A generalized ionospheric dispersion simulation method is presented to verify and test wideband satellite-ground-link radio systems for dispersion robustness. In the method, ionospheric dispersive effects on wideband radio waves are modeled as an allpass nonlinear phase system, thus greatly decreasing the need for signal priori information. To accurately simulate the ionospheric dispersion and reduce the implementation complexity, the system is decomposed into three new allpass subsystems: with a linear phase passing through zero frequency, a constant phase, and a nonlinear phase with zero-offset and quasi-parabolic form respectively. The three subsystems are implemented respectively by the combination of integer-interval delay and fractional delay filter, digital shifting phase and the complex-coefficient finite impulse response (FIR) filter. The ionospheric dispersion simulation can be achieved by cascading the three subsystems in a complex baseband and converting the frequency to a radio frequency. Simulation results show that the method has the ability to accurately simulate the ionospheric dispersion characteristics without knowing the signal priori information and has a low implementation complexity.
Fast Chinese syntactic parsing method based on conditional random fields
HAN Lei, LUO Sen-lin, CHEN Qian-rou, PAN Li-min
2015, 24(4): 519-525. doi:10.15918/j.jbit1004-0579.201524.0414
Abstract:
A fast method for phrase structure grammar analysis is proposed based on conditional random fields (CRF). The method trains several CRF classifiers for recognizing the phrase nodes at different levels, and uses the bottom-up to connect the recognized phrase nodes to construct the syntactic tree. On the basis of Beijing forest studio Chinese tagged corpus, two experiments are designed to select the training parameters and verify the validity of the method. The result shows that the method costs 78.98.ms and 4.63.ms to train and test a Chinese sentence of 17.9 words. The method is a new way to parse the phrase structure grammar for Chinese, and has good generalization ability and fast speed.
Network topology optimization of supply chain information systems
XU Na, PENG Su-ping
2015, 24(4): 526-533. doi:10.15918/j.jbit1004-0579.201524.0415
Abstract:
Network topology optimization has been widely researched. Since market competition has gradually developed into competition among the supply chain information systems, the network topology optimization of supply chain information systems has been in urgent need. However, the network topology optimization of supply chain information systems is still in its early stages and still has some challenges. So a description of typical seven network topologies for various supply chain information systems has been given. The generic characteristics of each network topology can be summarized. To analyze the optimization of network topology optimization of supply chain information systems, a numeric model has been established based on these general characteristics. A genetic algorithm is applied in the network topology optimization of supply chain information systems model to achieve the minimum cost and shortest path. Finally, our experiment results are provided to demonstrate the robustness and effectiveness of the proposed model.
Effect of dual annealing upon photovoltaic properties of polymer solar cells based on poly (3-hexylthiophene)
LI Chang, XUE Wei, ZHANG Ting, YU Zhi-nong, JIANG Yu-rong
2015, 24(4): 534-539. doi:10.15918/j.jbit1004-0579.201524.0416
Abstract:
A dual annealing method comprised of toluene vapor treatment and post thermal annealing was employed to fabricate polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and -phenyl-C61-butyric acid methyl ester (PCBM) film. It is found that the P3HT crystallinity and chain ordering can be dramatically enhanced by this annealing process as compared with the films treated merely with solvent vapor annealing, which is verified by a higher X-ray diffraction intensity peak and clearly visible fibrillar crystalline domains of P3HT. The result suggests that a favorable equilibrium condition was established by dual annealing in the morphology reorganization. Due to the morphological improvement of active layer, the dually annealed PSCs show better overall performances, with a mean power conversion efficiency of 4.06% and an increase in each electrical parameter, than any solely annealed ones.
Spatial heterodyne spectroscopy for space-based measurements of atmospheric CO2
YE Han-han, WANG Xian-hua, LI Zhi-wei, WEI Qiu-ye, SHI Hai-liang, XIONG Wei
2015, 24(4): 540-545. doi:10.15918/j.jbit1004-0579.201524.0417
Abstract:
To reduce the error from measurement and retrieval process, a new technology of spatial heterodyne spectroscopy is proposed. The principle of this technology and the instrument spatial heterodyne spectrometer (SHS) are introduced. The first application of this technology will be for CO2measurements from space on a high spectral observation satellite. The outstanding measurement principle and the priority of combination of retrieval algorithm and three channels (O2A-band, CO21.58. μ m and 2.06. μ m bands) are theoretically analyzed and numerically simulated. Experiments using SHS prototype with low spectral resolution of 0.4.cm-1are carried out for preliminary validation. The measurements show clear CO2absorption lines and follow the expected signature with theory spectrum, and the retrievals agreed well with GOSAT CO2products, except a small bias of about 4×10-6. The results show that the ability of spatial heterodyne spectroscopy for CO2detecting is obvious, and SHS is a competent sensor.
Force-feedback based active compliant position control strategy for a hydraulic quadruped robot
WANG Li-peng, WANG Jun-zheng, MA Li-ling, CHEN Guang-rong, YANG Chao-feng
2015, 24(4): 546-552. doi:10.15918/j.jbit1004-0579.201524.0418
Abstract:
Most existing legged robots are developed under laboratory environments and, correspondingly, have good performance of locomotion. The robots' ability of walking on rough terrain is of great importance but is seldom achieved. Being compliant to external unperceived impacts is crucial since it is unavoidable that the slip, modeling errors and imprecise information of terrain will make planned trajectories to be followed with errors and unpredictable contacts. The impedance control gives an inspiration to realize an active compliance which allows the legged robots to follow reference trajectories and overcome external disturbances. In this paper, a novel impedance force/position control scheme is presented, which is based on Cartesian force measurement of leg's end effector for our hydraulic quadruped robot The simulation verifies the efficiency of the impedance model, and the experimental results at the end demonstrate the feasibility of the proposed control scheme.
Application of fuzzy cognitive map in information intelligent push
ZHANG Jia, XU Sheng-li, DENG Fang
2015, 24(4): 553-557. doi:10.15918/j.jbit1004-0579.201524.0419
Abstract:
Since computer system functions are becoming increasingly complex, the user has to spend much more time on the process of seeking information, instead of utilizing the required information. Information intelligent push technology could replace the traditional method to speed up the information retrieval process. The fuzzy cognitive map has strong knowledge representation ability and reasoning capability. Information intelligent push with the basis on fuzzy cognitive map could abstract the computer user's operations to a fuzzy cognitive map, and infer the user's operating intentions. The reasoning results will be translated into operational events, and drive the computer system to push appropriate information to the user.
Optimizing control of a two-span rotor system with magnetorheological fluid dampers
XING Jian, HE Li-dong, WANG Kai, HUANG Xiu-jin
2015, 24(4): 558-565. doi:10.15918/j.jbit1004-0579.201524.0420
Abstract:
A control system aims at vibration reduction in a two-span rotor system with two shear mode magnetorheological (MRF) dampers is designed. A finite element model of the MRF damper-rotor system is built and used to analyze the rotor vibration characteristics. Based on Hooke and Jeeves algorithm and the numerical simulation analysis, an optimal appropriate controller is proposed and designed. Experimental results show that rotor vibration caused by unbalance is well controlled (first critical speed region 37%, second critical speed region 42%). To reflect advantages of optimizing strategy presented and validate the intelligent optimization control technology, detailed experiments were developed on a two-span rotor-vibration-control platform. The influence on accuracy, rapidity and stability of optimizing control for rotor vibration are analyzed. It provides a powerful technical support for the extension and application in target and control for shafting vibration.
Similarity matrix-basedK-means algorithm for text clustering
CAO Qi-min, GUO Qiao, WU Xiang-hua
2015, 24(4): 566-572. doi:10.15918/j.jbit1004-0579.201524.0421
Abstract:
K-means algorithm is one of the most widely used algorithms in the clustering analysis. To deal with the problem caused by the random selection of initial center points in the traditional algorithm, this paper proposes an improvedK-means algorithm based on the similarity matrix. The improved algorithm can effectively avoid the random selection of initial center points, therefore it can provide effective initial points for clustering process, and reduce the fluctuation of clustering results which are resulted from initial points selections, thus a better clustering quality can be obtained. The experimental results also show that theF-measure of the improvedK-means algorithm has been greatly improved and the clustering results are more stable.
Chemical Engineering and Materials Science
Influence of shear sensitivities of steel projectiles on their ballistic performances
WANG Lin, HU Xian-feng, CHENG Xing-wang
2015, 24(4): 573-578. doi:10.15918/j.jbit1004-0579.201524.0422
Abstract:
In ballistic penetration, a main failure mode for a projectile is adiabatic shear localization which results in macro cracks developing along ASBs which lead to the fracture of projectile. In this paper, the adiabatic shear sensitivity and ballistic performances of two high strength steels, 30CrMnSi and 35CrWMo, with similar static mechanical properties were investigated. Split Hopkinson Pressure Bar (SHPB) for compression loading and ballistic experiments above the velocity of 1.000.m/s against thick concrete targets were performed. The SHPB and ballistic experimental results showed that the 30CrMnSi steel exhibits more adiabatic shear sensitivity, compared with the 35CrWMo steel. Even though these two steels have similar static mechanical properties, the 35CrWMo steel projectile exhibits better penetration performance than the 30CrMnSi projectile due to different adiabatic shear sensitivities.
Nano-silica particles enhanced adsorption and recognition of lysozyme on imprinted polymers gels
ZHAO Wen-tao, XUE Bin, CHEN Zhen-he, YANG Shu, ZHANG Xin, SUN Li-quan, LUO Ai-qin
2015, 24(4): 579-586. doi:10.15918/j.jbit1004-0579.201524.0423
Abstract:
Molecular imprinting technology has a great potential to be used in protein separation and purification. In this work, lysozyme imprinted polyacrylamide gel was prepared with silica particles as a sacrificial template to generate macro-porosity for fast adsorption. The adsorption equilibrium time and adsorption capacity were 9.h and 56.mg/g respectively, which was 2.h less and 2.3-fold more than polymers without the sacrificial template. In order to test molecular imprinting polymers (MIPs)'selectivity, bovine serum albumin (BSA) was chosen as interferent for binary adsorption tests. In addition, the adsorption selectivity was further investigated using different molar ratios of lysozyme to BSA with fixed total concentration of proteins, as well as using various total concentrations of proteins with an equimolar ratio of lysozyme to BSA. It has been proven that the total concentration of proteins should be larger than 1.5×10-7.mol/mL, when the molar ratio of BSA to Lyz is 1:1, in order to effectively separate Lyz from the binary protein mixture. The macro-porous lysozyme molecularly imprinted polymers have less adsorption time, larger adsorption capacity, and better imprinting effect.
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