Table of Content

28 April 2020, Volume 54 Issue 4 Previous Issue    Next Issue

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Multi-Stockyard Scheduling Considering Technological Process and Combined Assembly Block MENG Lingtong, JIANG Zuhua, TAO Ningrong, LIU Jianfeng, ZHENG Hong 2020, 54 (4):  331-343.  doi: 10.16183/j.cnki.jsjtu.2020.04.001 Abstract ( 1074 )   PDF (2083KB) ( 351 )   Save In order to improve the current status of low work efficiency and high transportation costs in multi-stockyard scheduling, a multi-stockyard scheduling model was established. It aimed at the execution sequence and the procedure of incoming blocks and relocating blocks. The pursued objective was to minimize the total cost which considered the process attribute of multi-stockyard and combination of blocks. This paper compared and analyzed two approaches of incoming blocks allocation, and proposed a moving strategy between multi-stockyard of obstructive blocks. Moreover, it also improved the traditional scheduling sequence by Tabu search. Finally, the effects of stockyard occupancy rate and the comparison of various scheduling strategies on the experimental results were analyzed. The results show that the block allocation and moving strategies can effectively reduce the total cost in multi-stockyard scheduling as well as the proportion of obstructive blocks. These new strategies can effectively improve the transport efficiency. References | Related Articles | Metrics

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Curved-Surface Constant Force Tracking Based on Fuzzy Iterative Method ZHANG Tie, XIAO Meng, ZOU Yanbiao, XIAO Jiadong 2020, 54 (4):  344-351.  doi: 10.16183/j.cnki.jsjtu.2020.04.002 Abstract ( 958 )   PDF (1390KB) ( 296 )   Save Aiming at the problem that it is difficult to obtain a constant tracking force when the robot end-effector tracks the contour of a curved-surface workpiece, the contact force between robot end-effector and the curved-surface workpiece is analyzed, the mapping relationship between the normal force of the curved surface and the known sensor coordinate system is established, and a fuzzy iterative algorithm is proposed. Iterative algorithm does not need to get the advantages of the system internal transfer function, which simplifies the modeling design. Meanwhile，the fuzzy iterative algorithm compensates the robot trajectory based on the previous experimental force error and the amount of error change, which accelerates the convergence speed. The bounded convergence of fuzzy iterative algorithm is proved theoretically. The experimental results show that the fluctuation range of contact force is within ±3 N, which verifies the feasibility of this algorithm. Compared with the traditional proportional-derivative (PD) algorithm, the standard deviation of contact force of the fuzzy iterative algorithm is reduced by 42%. Compared with the iterative algorithm without fuzzy compensation, the iteration cycle is reduced at least once in the selected time periods. References | Related Articles | Metrics

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Multiuser Differential Chaos Shift Keying Scheme Based on Time Reverse ZHANG Gang, ZHAO Changchang, ZHANG Tianqi 2020, 54 (4):  352-358.  doi: 10.16183/j.cnki.jsjtu.2020.04.003 Abstract ( 953 )   PDF (1061KB) ( 302 )   Save Aiming at the problem of poor bit error performance and low transmission rate of differential chaos shift keying (DCSK), the time reverse multiuser-DCSK (TRM-DCSK) communication system is proposed. The system uses different time delays to distinguish different information time slots. In each information time slot, two-bit information signals can be transmitted by time inversion, and then the information signals of the two bits are superimposed and transmitted together as an information bearing signal. The use of time reversal can enhance the autocorrelation of chaotic signals and improve the error performance of the system. The bit error rate formula of TRM-DCSK system in additive white gaussian noise (AWGN) and Rayleigh fading channel is derived and simulated. The simulation results show that the TRM-DCSK system is significantly improved compared with the traditional multiuser DCSK system when transmitting the same number of users. References | Related Articles | Metrics

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Two-Dimensional DOA Estimation for Multi-Hopping Signals Based on Sparse Bayes LI Hongguang, GUO Ying, SUI Ping, CAI Bin, SU Linghua 2020, 54 (4):  359-368.  doi: 10.16183/j.cnki.jsjtu.2020.04.004 Abstract ( 982 )   PDF (1428KB) ( 255 )   Save The advantages and disadvantages of the existing two-dimensional direction of arrival (DOA) estimation algorithm for frequency hopping signals are analyzed. A two-dimensional DOA estimation algorithm for frequency hopping signals based on sparse Bayesian learning is proposed. The algorithm uses the characteristics of the L-shaped array to convert the three-dimensional information of azimuth, elevation and hopping frequency into one-dimensional spatial frequency information, which reduces the length of redundant dictionary and the difficulty of sparse solution. Then, after singular value decomposition, the matrix operation dimension is reduced, and the algorithm complexity is reduced. The spatial frequency and the hopping frequency are estimated by the sparse bayes algorithm and the fast fourier transform. The spatial frequency and the hopping frequency are correctly paired by the capon spatial frequency matching algorithm to calculate the spatial angle. Finally, the azimuth and elevation angles are calculated according to the spatial angular relationship. The simulation results show that the DOA estimation performance of the algorithm is good under low signal noise ratio or low fast beat, and it is not easy to be affected by the spatial frequency interval and the coherence of the hopping signal source. References | Related Articles | Metrics

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Robust Optimization for Energy Efficiency for Secrecy MIMO SWIPT Systems YANG Guangyu, QIU Hongbing 2020, 54 (4):  369-375.  doi: 10.16183/j.cnki.jsjtu.2020.04.005 Abstract ( 889 )   PDF (854KB) ( 184 )   Save This paper investigates simultaneous wireless information and power transfer in multiple-input-multiple-output system consisting of multiple multi-antenna eavesdroppers. In the case that the channel state information of the eavesdroppers can not be accurately obtained, the objective is to maximize the worst-case secrecy energy efficiency by jointly designing the beamforming matrix, artificial noise covariance matrix and power splitting ratio subject to transmit power constraint and energy harvest constraint. Based on fractional theory, the original non-convex problem is transformed into an equivalent optimization problem in subtractive form. By means of novel equivalent transformation, the problem of coupling between multiple optimization variables is solved and then the alternating optimization is avoided. With the aid of S-procedure and first order Taylor series expansion, the non-convex problem is transformed into a convex one. Based on Dinkelbach method, a two-level optimization iterative algorithm is proposed and simulation results are provided to show the effectiveness and convergence of the proposed algorithm. References | Related Articles | Metrics

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Hybridizing Multivariate Empirical Mode Decomposition and Extreme Learning Machine to Predict Non-Stationary Processes LI Chunxiang, ZHANG Haoyi 2020, 54 (4):  376-386.  doi: 10.16183/j.cnki.jsjtu.2020.04.006 Abstract ( 1014 )   PDF (5958KB) ( 293 )   Save The lack of sensor layout and the deficiency of sensor data are the key problems in the study of wind pressure measurement. The spatial prediction of wind pressure can restore the missing data and expand the air pressure information, and help to establish the wind pressure distribution on the structure surface. In this paper, a spatial prediction algorithm based on multivariate empirical mode decomposition (MEMD) and extreme learning machine (ELM) is proposed. The MEMD method is used to decompose the multi-channel non-stationary signals. The intrinsic mode functions and the residue are obtained with the same number and similar frequency. The decomposed data are restructured by frequency and ELM is used to train the restructured data and make predictions. The effectiveness and accuracy of the algorithm are verified by simulated data from autoregressive moving average (ARMA) model and observed wind pressure data. At the same time, the least squares support vector machine using radial basis kernel function (RBF-LSSVM) and the basic ELM method are introduced as the comparison. It is proved that the prediction error of the MEMD-ELM method is smaller and the correlation with the real value is higher. The modes decomposed through MEMD preserve the correlation from origin data, so a more accurate result is obtained, which proves that MEMD-ELM is an effective multi-variety prediction method. References | Related Articles | Metrics

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Simplified Procedure for Seismic Response Analysis of the Latticed Arch Under Bi-Directional Earthquake Excitations QU Yang, LUO Yongfeng, ZHU Zhaochen, HUANG Qinglong 2020, 54 (4):  387-396.  doi: 10.16183/j.cnki.jsjtu.2020.04.007 Abstract ( 939 )   PDF (3764KB) ( 240 )   Save The deformation pattern of the large-span latticed arch under the bi-directional earthquake excitation was predefined and expressed as the linear combination of displacements of the dominant vibration modes. Based on the load pattern derived from the deformation pattern, a nonlinear pushover analysis was carried out to establish an equivalent single degree of freedom (ESDF) system. Then, the responses of the ESDF system were solved by response history analysis method. Finally, the target point of the structure was found so that the seismic responses of the overall structure were obtained accordingly. Since the two components of ground motion inputs were transformed, a simplified procedure for seismic response analysis of the large-span latticed arch under bi-directional earthquake excitations was proposed. The seismic responses of a latticed arch model under a series of bi-directional earthquake waves in firm and soft sites were obtained by the simplified procedure. Compared with the results given by response history analysis, the nodal displacements and the extreme stress of elements are consistent in trends and distributions, with relative errors about 15.1%, 12.5% and 16.6% respectively, and 25% computing consumption. References | Related Articles | Metrics

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Analytical Solution for Rigid Retaining Structure Under Asymmetric Excavation in Cohesionless Soil FAN Xiaozhen, XU Haiming, XU Changjie, FANG Tao, TAN Yong 2020, 54 (4):  397-405.  doi: 10.16183/j.cnki.jsjtu.2020.04.008 Abstract ( 1142 )   PDF (1185KB) ( 279 )   Save Common design methods of retaining structure cannot be suitable in the design of asymmetric foundation pit. In view of the increasingly common asymmetric excavation, a calculation method of earth pressure considering displacement is presented to modify the mode of earth pressure acting on retaining structures. Based on the obtained earth pressure mode, the force of the whole structure system is analyzed, and the analytical solution of rigid retaining structure with bracing under asymmetric excavation is derived. The influences of the internal friction angle of soil, bracing stiffness and asymmetric degree on the insert ratio of retaining structure are analyzed. The results show that the calculated insertion ratio of classical equivalent beam method is unsafe, for the reason that this method adopts the limit equilibrium earth pressure theory. And the unsafe degree of the calculation result is more serious when the friction angle of the soil is relatively small. The insertion ratio of the shallower side is more sensitive to the asymmetric excavation than that of the deeper side. Compared with the common design method which only considers the single side, the proposed method can effectively save the project cost. The verification of the test data shows that the presented solution can be used for the calculation and design of single-strut retaining structure under asymmetric excavation. References | Related Articles | Metrics

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Field Test and Numerical Simulation for the Dynamic Response of Low-Strain Testing on Static Drill Rooted Pile XIAO Si, WANG Kuihua, ZHANG Rihong, WANG Mengbo 2020, 54 (4):  406-412.  doi: 10.16183/j.cnki.jsjtu.2020.04.009 Abstract ( 1134 )   PDF (5770KB) ( 353 )   Save In order to investigate the effect of cemented soil on dynamic response of static drill rooted pile, field tests and numerical simulation methods were employed. At first, field tests were performed to acquire the time domain curves of pile by low-strain testing, indicating that the amplitude and the arrival time of the reflected signal from pile tip were both affected by the cemented soil. Then, the shear moduli of cemented soil in different ages were obtained by bending element test. Afterwards, a three-dimensional finite element numerical model was established based on the tests on cemented soil, focusing on the amplitude of the reflected signal and wave velocity. After that, a comparison between the results of field tests and numerical simulation was presented, demonstrating good agreement. Finally, a parameter study for the effect of soil’s modulus was presented. The above research indicated that the modulus of cemented soil influenced both the amplitude of the reflected signal and the wave velocity of the pile. The numerical model could well simulate the dynamic response of the pile in low-strain test, and could be used for further research. The modulus of surrounding and base soil had no influence on the wave velocity of the pile. References | Related Articles | Metrics

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Time-Varying Reliability of Rust Cracking Model Based on Initial Defect ZHANG Qiang, LU Zhaohui, ZHAO Ran, LUN Peiyuan 2020, 54 (4):  413-420.  doi: 10.16183/j.cnki.jsjtu.2020.04.010 Abstract ( 851 )   PDF (1099KB) ( 292 )   Save In this paper, the prediction model of rust expansion time of concrete structures with the consideration of initial defects is established based on the theory of fracture mechanics. The limit state function of structure life prediction is established and an analysis method of time-dependent reliability based on three-order moment method is developed. The results show that compared with Monte-Carlo method, this method reduces the calculation time and improves the analysis efficiency when the calculated results are more consistent with each other. Among the parameters of concrete materials, the failure probability of concrete structure is the most sensitive to the randomness and uncertainty of cover thickness and less sensitive to the probability distribution type of random variables. References | Related Articles | Metrics

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Vessel Traffic Flow Prediction Based on CFA-GRNN Algorithm XUE Han，SHAO Zheping，PAN Jiacai，ZHANG Feng 2020, 54 (4):  421-429.  doi: 10.16183/j.cnki.jsjtu.2020.04.011 Abstract ( 938 )   PDF (934KB) ( 440 )   Save In order to provide the maritime department with the scientific and accurate prediction of the essel traffic flow, this paper proposes an algorithm based on the cultural firefly algorithm (CFA) to optimize the generalized regression neural network (GRNN) to predict vessel traffic flow. This paper introduces the statistial method of fairway traffic flow based on automatic indentity system (AIS). Fast rejection test and cross stand test are used to judge whether the ship track passes through the observation line of a certain cross section of the channel. The latitude and longitude data in the AIS data is converted to the Mercator plane coordinate system. The realization principle of GRNN is studied. CFA takes the output mean square error of GRNN as fitness function. Its encoding takes the weight value in the input and hidden layers, the weight value in the hidden layer and the output layer, the threshold of the hidden layer and the threshold of the output layer. Its evolutionary goal is to get the most suitable and optimal structure of GRNN. With the statistics and pretreatment data collected from AIS, the CFA-GRNN is used to predict the vessel traffic flow, and the experimental results and errors are analyzed. The results show that CFA-GRNN has better generalization performance and higher accuracy of the prediction results than GRNN and firely algorithm-GRNN, and is not easy to fall into local optimum. This study is of theoretical and practical significance for forecasting and analyzing ship traffic flow. References | Related Articles | Metrics

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Analysis and Simulation of Frequency Characteristic Based on Optimal Objective Parameter in Magnetically-Coupled Resonant Wireless Power Transfer System FAN Xingming,JIA Erju,GAO Linlin,ZHANG Weijie,JIAO Ziquan,ZHANG Xin 2020, 54 (4):  430-440.  doi: 10.16183/j.cnki.jsjtu.2020.04.012 Abstract ( 1015 )   PDF (2367KB) ( 309 )   Save Magnetically coupled resonant wireless power transfer (MCR-WPT) has the advantages such as mid-range and high efficiency and shows great application potential. In this technology, the change of frequency has an important impact on the transmission performance of the system. Therefore, the analysis of frequency characteristics is of great significance to improve the performance of the system. The increase of resonant topological strategy is sending terminal, resulting from the variation of loads and transmission distance, is analyzed theoretically through the reflect impedance theory taking coil resistance into account in four topological structures. It is found that series-series topological structure has the most stable frequency property. Besides, this paper researches the relationship between optimal operating frequency and variations of loads, transmission distance in the desiable and undesiable cases by means of multual inductance theory. Modeling and analysis in MATLAB environment verify the correctness of the above theory. The interpolation method and the polynomial fitting are used to simulate and analyze the optimal operating frequency of transmission efficiency under ideal state. The results show that spline interpolation and 8th order polynomial fitting are the best, which can provide some references for improving the accuracy of frequency control in the later period. References | Related Articles | Metrics