Journal of South China University of Technology(Natural Science Edition)

Research Progress of PVDF-Based Piezoelectric Tactile Sensor

LIU Yurong XIANG Yinxue

2019, 47(10): 1-12. doi:10.12141/j.issn.1000-565X.190149

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Polyvinylidene fluoride ( PVDF) piezoelectric film has wide application prospects in the fields of tactile sensors and ultrasonic transducers due to its advantages of strong flexibility，high mechanical strength，high sensitivity and wide frequency response range． Firstly，the working mechanism and manufacturing process of PVDFbased piezoelectric tactile sensor were introduced． Then，the research progress and development trend of PVDFbased piezoelectric tactile sensor were summarized from five aspects: piezoelectric properties improvement，structure optimization，device integration， flexibility and bionics． And its applications in robotic hands，minimally invasive surgery，health monitoring were also introduced in detail． Finally， the current shortcomings of the development of PVDF-based piezoelectric tactile sensor and the main research trend in the future were analyzed．

Safe Climbing of Snake-Like Robot Based on Screw and Envelope Theory

WEI Wu, ZHANG Jie, GAO Yong, et al

2019, 47(10): 13-23. doi:10.12141/j.issn.1000-565X.190019

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A new research method of spiral climbing based on screw theory and the elastic envelope for the snakelike robot with orthogonal joints was presented． Firstly， the screw theory was used to build kinematics modeling of snakelike robot to reduce the complexity of D-H modeling method． Secondly， the contact relationship between the snakelike robot and cylindrical rod during the climbing movement was analyzed based on the screw theory，and a binary images representation was proposed to reveal the elastic envelope state between snakelike robot and cylindrical rob． Finally，based on the analysis results of elastic envelope， the spiral climbing force of the snakelike robot was obtained，and then the parameter control optimization model with safe climbing force and climbing coefficient as the optimization target was proposed． The simulation results show that the climbing force and the elastic envelope state are consistent，which verifies the optimization model．

Local Path Planning Method for Unmanned Surface Vehicle Based on Image Recognition and VFH +

HONG Xiaobin WEI Xinyong HUANG Yesheng LIU Yanxia XIAO Guoquan

2019, 47(10): 24-33. doi:10.12141/j.issn.1000-565X.180592

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Aiming to solve the problem of local obstacle avoidance for unmanned surface vehicle under complex marine conditions，deep learning was introduced to deal with the vision information and completed the local path planning for unmanned surface vehicle combining with VFH + algorithm． The image semantic segmentation model with symmetrical encoder-decoder structure and faster RCNN model were used to detect water edge and identify obstacles on the surface of the water to build environment model around unmanned surface vehicle． Then local path planning method based on VFH + was brought to construct the primary histogram，binary histogram and mask histogram to compress the environment data，and a reasonable cost function was introduced to obtain the effective obstacle avoidance direction for unmanned surface water． Results of simulation experiments based on MODD dataset and obstacle avoidance experiments in real ship show that the algorithm can effectively extract the water surface image information and obtain a reasonable local path planning strategy to lead a smooth obstacle avoidance path at 10kn， which meets the obstacle avoidance requirements of unmanned surface vehicle．

A Novel Chaotic System with Multi-Wing Attractors Based on Flux-Controlled Memristor and Its Adaptive Sliding Mode Synchronization Control

XU Changbiao HE Yinghui MO Yunhui WU Xia

2019, 47(10): 34-41. doi:10.12141/j.issn.1000-565X.190153

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A novel chaotic system with multi-wing attractors was proposed based on the conjugate Lorenztype system and by introducing flux-controlled memristor． Single-wing，two-wing，three-wing and four-wing chaotic attractors can be produced by changing the system parameters． The dynamic characteristics of the system were analyzed through phase diagrams，Lyapunov exponents，bifurcation diagram，etc． An analog circuit of the system was designed and simulated by Multisim． The circuit simulation results were consistent with the results of numerical analysis，which verifies the system's chaotic behaviors and shows its implementability． Finally，an adaptive sliding mode synchronous controller was designed based on the Lyapunov stability theory，and the given signal was tracked within 0. 25s and the position parameters was identified quickly within 0. 12s by the controller．

Fast-Response Anthropomorphic Motion Control Algorithm Without Overshoot of Humanoid Manipulator Based on Prescribed Performance Function

ZHAO Jing WANG Yan CHEN Yuqing

2019, 47(10): 42-50. doi:10.12141/j.issn.1000-565X.180499

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In order to ensure safety in the process of interaction between people and the manipulator and acquire the fast response without overshoot， the traditional PID control was improved by introducing the prescribed performance control，and a fast humanoid motion control algorithm without overshoot for the manipulator was proposed． Based on PID control， the algorithm utilizes the prescribed performance control to make the convergence speed and overshoot of control errors satisfy the preset conditions，and make the control error converge to a preset relatively small area， so as to control the steady and dynamic performance of the system ( including overshoot and convergence speed， etc. ) ． The analysis results of modeling and simulation of spatial three joints manipulator show that the proposed prescribed performance PID control has the advantage of fast response and no overshoot comparing with the traditional PID control． Thus，the control algorithm suits to anthropomorphic manipulator motion control． Finally，the validity of the algorithm was verified by the prototype experiment of Dobot robot with 4 degrees of freedom．

Kinematic Analysis of Hybrid Automatic Drilling and Riveting Machine with Redundant Degree of Freedom

CHEN Wenliang WANG Hui WANG Min PAN Guowei

2019, 47(10): 51-59. doi:10.12141/j.issn.1000-565X.180551

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A unified kinematic model and forward and reverse solution problem of automatic drilling riveting machine with redundant degrees of freedom and serial-parallel structure was studied，in order to improve the quality and efficiency of automatic drilling and riveting for aircraft panel assembly． Based on the equivalent transformation method defined by the coordinates，the moving platform and static platform of the parallel part were equivalently inverted． And based on the virtual branching method and the D-H method，the closed-chain kinematic model of the automatic drilling riveting machine was established． Thus the analytical solution of the positive solution of the kinematic position was obtained． According to the characteristics that the automatic drilling riveting machine owns redundant degrees of freedom and hybrid structure，the‘step-bystep’decoupling strategy of the kinematic inverse solution was proposed． Finally，the case study shows that the position average error and the normal average error between the actual pose and the target pose of the automatic riveting machine are 0. 13191mm and 0. 16842°，respectively，which verified the correctness of the method．

A Discrete Flower Pollination Algorithm for Solving Double-Layer Corridor Allocation Problem

GUAN Chao ZHANG Zeqiang LI Yunpeng JIA Lin

2019, 47(10): 60-74. doi:10.12141/j.issn.1000-565X.180388

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Considering the situation that facilities are distributed into multilayers space，a double layer corridor allocation problem was proposed，and the mixedinteger nonlinear programming model was built for this problem． Based on the discrepancy of feasible solutions and complexity of the issue，a discrete flower pollination algorithm was proposed． By redefining the pollination process，the random search process that sets the problem size as the search depth was taken as the global search． In the local optimization stage， the individual updated itself via the exchange pair by following the optimal solution． In order to improve the performance of the algorithm， the thresholds were set in the global search stage to actualize variable neighborhood search by mutating the individual that was in the local optimum，and another threshold was set to improve the efficiency of the solution． The effectiveness of the algorithm was validated by comparing the results that are gotten from two algorithms via solving the 38 benchmark instances． Finally， the improved flower pollination algorithm was applied to solve the corridor allocation problem， and the contrast experiments illustrate that the proposed algorithm possesses more advantages both in quality and efficiency．

Performance Improvement Technology for Serial Acquisition Card Based on Time Stamp Compensation

ZHONG Senming LIU Guixiong WU Jiajian HUANG Jian

2019, 47(10): 75-80. doi:10.12141/j.issn.1000-565X.190064

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Restricted by the serial acquisition principle of serial acquisition card，the time stamps of each channel are inconsistent during multi-channel acquisition． To solve this problem，a performance improvement technology for serial acquisition card based on time stamp compensation was proposed and a mathematical model of multi-channel time stamp compensation algorithm was established． Formulas of multi-channel time stamp compensation and multi-channel synchronous acquisition value estimation were derived． The method can improve the data synchronization performance of each channel through the software processing algorithm without changing the serial acquisition card，and obtain the data equivalent to the parallel acquisition card． The example calculation and application show that the performance improvement technology for serial acquisition card based on time stamp compensation is practical and effective for synchronous realtime acquisition．

Stress Analysis of Continuously Welded Rail of Ballastless Tracks on Simply Supported Girder Bridges with Different Spans

DAI Gonglian GE Hao ZHENG Rongrong CHEN Guorong

2019, 47(10): 81-92. doi:10.12141/j.issn.1000-565X.180597

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Based on the principle of bridgetrack interaction，the formula of multispan simply supported bridgetrack interaction considering nonlinear resistance was deduced and compared with the finite element ( FE) method to research the continuously welded rail ( CWR) stress of different ballastless tracks on multispan simply supported girder bridges． Different ballastless track models on simply supported girder bridges with standard span of 32m were established，and the rail additional stress distribution and its stable maximum value were analyzed considering the coupled effect of measured temperature and brake flexural force． Meanwhile， the influences of structural parameters such as span number of simply supported bridges，pier top stiffness and fastener resistance on the stress of CWR were also discussed． The results show that for girder bridges with standard span of 32m， the rail maximum additional stress tends to remain unchanged with the increase of the number of the bridge span，and the unchanged value is less than the norm limit; for the simply supported bridge with ballastless track，its span number is not limited by the rail additional stress; for the unitslab and double-block ballastless track， the change of pier stiffness has little effect on the rail additional stress when the pier top stiffness is greater than 2000kN/cm． Small resistance fasteners

are not recommended for ballastless track on multispan simply supported bridge．

Local Stability Performance of Arch Components of Underground Supporting Structure with Corrugated Steel Webs

WU Lili YU Yaqian Lǚ Bufan

2019, 47(10): 93-104. doi:10.12141/j.issn.1000-565X.180589

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The model tests of a new type of arch components of underground supporting structure with corrugated steel webs were carried out to study the local stability performance． The model tests included six semicircular arch supports models，and the effects of width to thickness ratio of the flange and height to thickness ratio of the web on the local stability of corrugated steel webs were analyzed． Then the local buckling performance of the test bracket was calculated and analyzed by finite element software ANSYS，at the same time，compared with the test results． Finally， the elasto-plastic local buckling numerical analysis of arch structure was conducted． The results show that the local stability capacity of the arch component greatly increased with the decrease of the width to thickness ratio of the flange，and the local buckling of flange can lead to the increase of global deformation of the component and then cause the global buckling of the arch component． The local stability capacity of the arch component also increased with the increase of the height to thickness ratio of the web． The local buckling of the webs may lead to the local buckling of the flange，which induce larger deformation and speed up the global buckling of the component． The experiment results of the support were in good agreement with the results of the finite element model，so the finite element model was verified． The increase of web height and thickness， flange width or thickness can increase the local stability capacity of corrugated steel webs． With the increase of the arch angle ( rise to span ratio) ， the local buckling capacity of the flange decreases gradually， the arch angle has little effect on the local stability bearing capacity of corrugated steel webs．

Improved Method of Calculating the Influence of Foundation Pit Excavation on Adjacent Single Pile#br#

SHI Chenghua LIU Jianwen WANG Zuxian PENG Limin YANG Gaoshang

2019, 47(10): 105-113. doi:10.12141/j.issn.1000-565X.180629

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The construction of foundation pit adjacent to the pile foundation of a building will cause additional deformation and internal force of the pile foundation，which will affect the safety and applicability of the upper building． In view of the current theoretical research on this problem， the elastic foundation beam method is widely adopted，which simplified the pile as an Euler-Bernoulli beam resting on the Winkle foundation or Pasternak foundation． However， this method is unable to account for the shearing effect of the pile and the unevenness of the soil parameters along the pile caused by excavation． So an improved twostage analytical method was proposed，seeing existed piles as Timoshenko beams resting on the Vlazov foundation and considering both the bending and shearing effects． The results were compared with the existing research results and field monitoring data． The results show that the calculation method can accurately and effectively analyze the mechanical response of adjacent single pile under the influence of foundation pit excavation． At the same time，the selection of foundation model and the influence of shear effect of pile foundation are discussed and analyzed． It is concluded that the parameters determination of Vlazov foundation model has more theoretical basis and the model is more in line with engineering practice; and with the increase of pile diameter， the shear effect of pile foundation has a significant impact on the internal force of pile foundation．

Welding Residual Stress Simulation and Experimental Verification in Beamto-Column Joints of Q345B Steel

LI Wanrun ZHANG Guangli LIU Yufei FANG Zhao LI Aiqun DU Yongfeng

2019, 47(10): 114-123. doi:10.12141/j.issn.1000-565X.190044

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The welding residual stress of beamto-column joints was simulated by finite element software in order to study the distribution of welding residual stress in beamto-column joints，and the experimental verification was carried out． Firstly，a stochastic thermodynamic model for the whole welding process of beamto-column joints was established to analyze the welding temperature field of beamto-column joints． Secondly，the distribution of welding residual stress of beamto-column joints was analyzed by indirect thermalstructural coupled analysis． Finally，the welding residual stress of beamto-column joints was measured by the blind hole method and compared with the simulation． The results show that due to the far distance between the upper and lower flange welds and the existence of process holes， the interaction between the welds is very small，and the welding residual stresses of the two welds are basically the same; owing to the close distance between the web welds and the great interaction between the two welds， the distribution of the residual stresses of the two welds is inconsistent; in the weld toe area of beamto-column joints， the distribution of residual stresses in the upper and lower flanges of beams is basically the same， the equivalent residual stresses are“V”type distribution， the horizontal， longitudinal and normal residual stresses are basically“M”type distribution，while the stress distributions of the two welds in the web of beams are obviously different，and the reason is that the two welds of web have mutual influence during welding．

Incorporating Heterogeneity and Subjective Evaluation into Travel Mode Choice

2019, 47(10): 124-129,150. doi:10.12141/j.issn.1000-565X.180460

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Travelers' evaluation on travel mode and heterogeneity of travelers have significant impacts on travelers' choice of travel mode． These impact on travel mode choice were analyzed with the latent-class conditional logit model． Through the confirmative factor analysis，travelers' latent psychological variables，that is，subjective evaluation of travel mode's comfort and reliability，were obtained． The similarities and dissimilarities of in-vehicle time of value，comfort evaluation and reliability evaluation between different latent classes were analyzed by incorporating these latent psychological variables into the latent-class conditional logit model． The study shows that travelers could be divided into two subgroups ( class 1 and class 2) ． On choosing travel mode，travelers in class 1 consider the comfort and reliability of travel mode and have a low value of travel time; while travelers in class 2 don't consider comfort and reliability of travel mode，and have a higher value of travel time than travelers in class 1． The estimated willingto-pay can be used in planning and evalution of the public transportation．

Impact Effect of Aerodynamic Loads on High-Speed Trains When Entering into Tunnel Under Crosswinds

DENG E YANG Weichao ZHANG Pingping

2019, 47(10): 130-138. doi:10.12141/j.issn.1000-565X.190008

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A 3D CFD numerical model of tunneltrain-air was built to analyze the transient change characteristics of the aerodynamic loads of each carriage when a HST enters tunnel and the corresponding change of the running postures of each carriage，considering the unsteady compressible turbulent characteristics of the flow field when a highspeed train ( HST) enters into tunnel． The corresponding change mechanisms were uncovered from the perspective of flow field． The impact effect of aerodynamic loads on the carriage was discussed． The main conclusions are as follows: ( 1) The five aerodynamic loads of each carriage show remarkable sudden change characteristics，and accordingly，all carriages show instantaneous deflection and‘nodding’and other behaviors． ( 2) The great difference in longitudinal pressure difference between the two sides of the carriage is the fundamental reason of the sudden unloading of side force and rolling moment and the sudden increase of yawing moment． ( 3) Crosswind is the main factor that causes the impact strength of aerodynamic loads on the carriage to rise remarkably． ( 4) The safety coefficient of the head carriage is the key to control the traffic safety of the whole train．

Safety Design Method of Long Slope Downhill Slope Based on Temperature Increase of Brake Drum

ZHANG Chi HOU Yudi QIN Jihan ZHANG Hong

2019, 47(10): 139-150. doi:10.12141/j.issn.1000-565X.190077

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A safety combined design method of longitudinal slope based on the temperature rise of truck brake drum was studied in order to improve the driving safety level of continuous downhill driving on expressway and to alleviate the contradiction between road and vehicle in China． Six-axis semitrailer were taken as the leading truck，and the brake heating model was constructed by theoretical analysis method． The accuracy of the model was verified by the real vehicle test． The downhill distance when the brake drum temperature reaches 200 ℃，the temperature of the slope bottom and the temperature rise rate were selected as the analysis indexes to analyze the combined design method of the longitudinal slope，based on the analysis of the correlation between the accident rate of truck and the temperature rise of the brake drum． The results show that，considering the temperature rise of brake heating，the continuous downhill should be designed and optimized safely from three aspects: transition slope setting，difference control of adjacent slope segments and slope length combination，supplemented by protective measures and traffic management measures． Reasonable transition slope setting is beneficial to relieve the temperature rise of brake heating，but the cooling effect of transition slope is limited． The infinite reduction of slope not only can't help to reduce the temperature of brake heating，but also increases the length of the route． It is advisable to control the slope value reasonably according to the critical slope index． The slope difference of adjacent slope section should not be too large，designing longitudinal alignment as far as possible with the small slope difference of the longitudinal slope combination． It is advisable to control the slope difference according to the average longitudinal slope and the maximum slope difference regression equation． And the slope length combination form of long gentle slope and short steep slope should be adopted． Thus can to the greatest degree minimizes the continuous downhill of the lorry brake hub over 200℃， improving the safety of the lorry downhill．

Redistribution Method for Slack Time of Flight Based on Propagated Delay#br#

GAO Qiang ZHOU Tan CHEN Xin

2019, 47(10): 151-156. doi:10.12141/j.issn.1000-565X.180471

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Slack time in flight schedule is redundancy time for flight turnaround． If slack time is too long，it is a waste of resource，such as planes，crews and time． Slack time is a significant method to absorb delay in actual operation． If it is too long， the propagated delay will be serious． A propagated delay tree with initial flight as the root was built to conduct dynamic research on the propagated process to solve the optimization of slack time． An optimization model of slack time redistribution was built，which has the advantages of certainty and linear easy to solve． Experimental results based on actual operation data of an airline show that the proposed model could reduce propagated delay by 28% without increasing costs while slightly changing the original fleet and crew schedule．

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