Most view articles
2014, 42(10):1596-1603.
DOI: 10.11908/j.issn.0253-374x.2014.10.021
Abstract:
Robot technology is widely applicated in fields such as industral manufacture, medical service, exploration and exploitation, bio engineering, rescue, etc. Traditional robots have rigid underlying structures that limit their ability to interact with their environment. Soft robots are the novel bionic continuum robots, which can change their own size and shape in large range and have great potentials in the unstructured enviroment. This paper presents a review about the bionic mechaism, driving mode, modeling and control strategy for soft bodied robots. Some bottlenecks constraints and feasible solutions of soft robot technology are also summarized by means of analysis and classification. Finally, the trends in robot technology are investigated.
Robot technology is widely applicated in fields such as industral manufacture, medical service, exploration and exploitation, bio engineering, rescue, etc. Traditional robots have rigid underlying structures that limit their ability to interact with their environment. Soft robots are the novel bionic continuum robots, which can change their own size and shape in large range and have great potentials in the unstructured enviroment. This paper presents a review about the bionic mechaism, driving mode, modeling and control strategy for soft bodied robots. Some bottlenecks constraints and feasible solutions of soft robot technology are also summarized by means of analysis and classification. Finally, the trends in robot technology are investigated.
2017, 45(07):0954-0961.
DOI: 10.11908/j.issn.0253-374x.2017.07.003
Abstract:
Utilizing the powerful matrix calculating function from Matlab and the opensource characteristics from OpenSEES, this paper proposes a substructure testing system based on MatlabOpenSEES by adopting mixed programming. It introduces three basic components, which are the Matlab module, the OpenSEES numerical substructure simulation module and the interface function between Matlab and OpenSEES, and the principle of the proposed substructure system. The Matlab module is used to realize the function of solving motion equation, the loading control, and data acquisition of experimental substructure. The OpenSEES numerical substructure simulation module, which is a submodule called by Matlab module, is used to realize the numerical simulation analysis of numerical substructure. The interface is used to realize the data transmission between Matlab and OpenSEES by the text or Socket communication variables. The proposed system can be programmed on an external computer connected with the hardware I/O channel of the MTS electrohydraulic servo control system through the data acquisition card. In this way, the system can not only avoid the complex underlying programming technology of the electrohydraulic servo control system, but also reduce the requirement of system itself and finally reduce the test difficulty and cost. The test results of three largescale structure test models verify the feasibility of the proposed substructure testing system.
Utilizing the powerful matrix calculating function from Matlab and the opensource characteristics from OpenSEES, this paper proposes a substructure testing system based on MatlabOpenSEES by adopting mixed programming. It introduces three basic components, which are the Matlab module, the OpenSEES numerical substructure simulation module and the interface function between Matlab and OpenSEES, and the principle of the proposed substructure system. The Matlab module is used to realize the function of solving motion equation, the loading control, and data acquisition of experimental substructure. The OpenSEES numerical substructure simulation module, which is a submodule called by Matlab module, is used to realize the numerical simulation analysis of numerical substructure. The interface is used to realize the data transmission between Matlab and OpenSEES by the text or Socket communication variables. The proposed system can be programmed on an external computer connected with the hardware I/O channel of the MTS electrohydraulic servo control system through the data acquisition card. In this way, the system can not only avoid the complex underlying programming technology of the electrohydraulic servo control system, but also reduce the requirement of system itself and finally reduce the test difficulty and cost. The test results of three largescale structure test models verify the feasibility of the proposed substructure testing system.
2017, 45(08):1150-1159.
DOI: 10.11908/j.issn.0253-374x.2017.08.008
Abstract:
The motion planning problem of unmanned autonomous vehicle (UAV) is reviewed. UAV operates in both structured road and unstructured field with differential constraints. The problem of trajectory generation can be simplified with the differential flatness of Ackerman steering vehicle. Compared to direct trajectory generation method, pathvelocity decomposition method is more popular. Clothoids, splines and polynomial spirals are used for path generation. The two major planning algorithms of great practical significance are rapidly random tree(RRT) in the name of samplingbased and A* in the name of searchbased methods.
The motion planning problem of unmanned autonomous vehicle (UAV) is reviewed. UAV operates in both structured road and unstructured field with differential constraints. The problem of trajectory generation can be simplified with the differential flatness of Ackerman steering vehicle. Compared to direct trajectory generation method, pathvelocity decomposition method is more popular. Clothoids, splines and polynomial spirals are used for path generation. The two major planning algorithms of great practical significance are rapidly random tree(RRT) in the name of samplingbased and A* in the name of searchbased methods.
2017, 45(07):1075-1082.
DOI: 10.11908/j.issn.0253-374x.2017.07.020
Abstract:
BeiDou navigation satellite system (BDS) integrates legacy PNT and authorized differential service, where differential service is provided by the satellitebased augmentation system (SBAS). The latest progress of the BDS SBAS development were introduced and the performance of pseudorange based and carrier phase based user differential positioning was evaluated. Observations of 10 stations in Chinese mainland were used. The results show that the coordinate accuracy of the pseudorange differential positioning (SBAS SPP) reaches 0.4 m, 0.3 m and 0.8 m in the North, East and Up directions respectively, which shows an improvement of 53% over the legacy SPP. For the evaluation of carrier phase based positioning, kinematic precise point positioing (SBAS PPP) was performed and compared to the kinematic PPP results based on post processing precise satellite orbits and clocks (POST PPP). The results show that the SBAS PPP kinematic coordinate estimates converge to 1 meter in 7 mins on average and the coordinate accuracy reaches 0.1 meter in horizontal and 0.2 meter in vertical component after convergence. Compared to the results of POST PPP, SBAS PPP shows better accuracy and shorter converge time, which indicates that the accuracy of BDS satellite orbits has been increased and clocks still have to be improved.
BeiDou navigation satellite system (BDS) integrates legacy PNT and authorized differential service, where differential service is provided by the satellitebased augmentation system (SBAS). The latest progress of the BDS SBAS development were introduced and the performance of pseudorange based and carrier phase based user differential positioning was evaluated. Observations of 10 stations in Chinese mainland were used. The results show that the coordinate accuracy of the pseudorange differential positioning (SBAS SPP) reaches 0.4 m, 0.3 m and 0.8 m in the North, East and Up directions respectively, which shows an improvement of 53% over the legacy SPP. For the evaluation of carrier phase based positioning, kinematic precise point positioing (SBAS PPP) was performed and compared to the kinematic PPP results based on post processing precise satellite orbits and clocks (POST PPP). The results show that the SBAS PPP kinematic coordinate estimates converge to 1 meter in 7 mins on average and the coordinate accuracy reaches 0.1 meter in horizontal and 0.2 meter in vertical component after convergence. Compared to the results of POST PPP, SBAS PPP shows better accuracy and shorter converge time, which indicates that the accuracy of BDS satellite orbits has been increased and clocks still have to be improved.
2017, 45(07):1022-1029.
DOI: 10.11908/j.issn.0253-374x.2017.07.012
Abstract:
The realizable k –ε method was used for steady simulation of external airflow of Ahmed model with different rear slant angles, and the large eddy simulation (LES) method was employed for transient simulation. Based on the pressure and velocity fluctuation distribution, Ahmed body surface pressure fluctuation level distribution and aerodynamic noise characteristics in the far field were studied. Furthermore, the relationship between wind noise radiated in the far field and aerodynamic drag was studied. The results show that there is a significant difference between model rear pressure and velocity fluctuation distribution of Ahmed model at different rear slant angles due to different flow separation pattern, which influences the noise power radiated to the far field and its distribution. Additionally, there exists a certain relationshape between noise power and aerodynamic drag. Therefore, optimizing rear slant angle is very important for rear wind noise control.
The realizable k –ε method was used for steady simulation of external airflow of Ahmed model with different rear slant angles, and the large eddy simulation (LES) method was employed for transient simulation. Based on the pressure and velocity fluctuation distribution, Ahmed body surface pressure fluctuation level distribution and aerodynamic noise characteristics in the far field were studied. Furthermore, the relationship between wind noise radiated in the far field and aerodynamic drag was studied. The results show that there is a significant difference between model rear pressure and velocity fluctuation distribution of Ahmed model at different rear slant angles due to different flow separation pattern, which influences the noise power radiated to the far field and its distribution. Additionally, there exists a certain relationshape between noise power and aerodynamic drag. Therefore, optimizing rear slant angle is very important for rear wind noise control.
2017, 45(07):1053-1060.
DOI: 10.11908/j.issn.0253-374x.2017.07.017
Abstract:
A simplified model of envelope HAVC load prediction for individual building was proposed, in which the number of input parameters was reduced to six, and prediction accuracy guaranteed. This building thermal dynamic model was established with the open source library of Buildings Modelica Library developed by Lawrence Berkeley National Laboratory. The linear aggregation method was used to reduce the order of simplified model, in order to accelerate calculation. This simplified model makes possible the fast calculation of HVAC load for each individual building, and hence provides the method basis to expand to the regional scale simulation. Finally, discussion was conducted to expand the method in regional dynamic load prediction in the future.
A simplified model of envelope HAVC load prediction for individual building was proposed, in which the number of input parameters was reduced to six, and prediction accuracy guaranteed. This building thermal dynamic model was established with the open source library of Buildings Modelica Library developed by Lawrence Berkeley National Laboratory. The linear aggregation method was used to reduce the order of simplified model, in order to accelerate calculation. This simplified model makes possible the fast calculation of HVAC load for each individual building, and hence provides the method basis to expand to the regional scale simulation. Finally, discussion was conducted to expand the method in regional dynamic load prediction in the future.
2017, 45(07):1000-1008.
DOI: 10.11908/j.issn.0253-374x.2017.07.009
Abstract:
A refined etype fastener model based on its real size was established and nonlinear contact and restraints were used to deal with the interaction between the components of the fastener. The modal shapes and harmonic response characters of the fastener, in both unrestraint and service status, were analyzed using the timefrequency responses analytical method. Besides, the main cause for fastener fracture was revealed and compared with the field test results. This research shows that the first and second resonance frequencies of fasteners in unrestraint and service status (808 Hz~812 Hz, 869 Hz and 410 Hz~420 Hz, 530 Hz) agree with the test section corrugation frequencies, which is the main cause leading to fasteners fracture. An effective way to reduce or avoid fastener fracture is to change the running speed of the train. To avoid the resonant response, it is recommended to control the traveling speed under 80 km?h-1 after calculation.
A refined etype fastener model based on its real size was established and nonlinear contact and restraints were used to deal with the interaction between the components of the fastener. The modal shapes and harmonic response characters of the fastener, in both unrestraint and service status, were analyzed using the timefrequency responses analytical method. Besides, the main cause for fastener fracture was revealed and compared with the field test results. This research shows that the first and second resonance frequencies of fasteners in unrestraint and service status (808 Hz~812 Hz, 869 Hz and 410 Hz~420 Hz, 530 Hz) agree with the test section corrugation frequencies, which is the main cause leading to fasteners fracture. An effective way to reduce or avoid fastener fracture is to change the running speed of the train. To avoid the resonant response, it is recommended to control the traveling speed under 80 km?h-1 after calculation.
2017, 45(07):0941-0947.
DOI: 10.11908/j.issn.0253-374x.2017.07.001
Abstract:
The simulation of random traffic load is the foundation and crux of load assessment and performance evaluation of bridges. The current traffic simulation based on the Monte Carlo method is inappropriate for describing the dynamic evolution of traffic on microscopic scales within a relatively long span, while the singlecell method based on cellular automaton (CA) remains to be improved concerning precision. In the singlecell method, a car is simulated by a single cell, which could not consider the influence of axle load and exerts a limit on enhancement of simulation precision. In this paper, based on the current CA, a model is proposed to simulate an axle by a cell and to simulate a car by a number of consecutive cells, which is defined as multicell cellular automaton (MCA). It verifies the mathematical model with realistic traffic and its load data. It is demonstrated that the parameters of traffic flow and traffic load, such as traffic volume, time headway, velocity and weight of simulated traffic are reproduced accurately by the multicell method. With the distribution load, bearing shear and midspan moment in a simply supported girder with a length of 1 000 meters set as indexes respectively, the statistics analysis of the load response characteristics of simulated and realistic data is conducted. The result indicates that the relative errors of simulated data of the MCA model to realistic data are within 5%. When MCA is applied, the precision of load response can be increased from the correlated error of less than 17% in the traditional singlecell method to a relatively high precision.
The simulation of random traffic load is the foundation and crux of load assessment and performance evaluation of bridges. The current traffic simulation based on the Monte Carlo method is inappropriate for describing the dynamic evolution of traffic on microscopic scales within a relatively long span, while the singlecell method based on cellular automaton (CA) remains to be improved concerning precision. In the singlecell method, a car is simulated by a single cell, which could not consider the influence of axle load and exerts a limit on enhancement of simulation precision. In this paper, based on the current CA, a model is proposed to simulate an axle by a cell and to simulate a car by a number of consecutive cells, which is defined as multicell cellular automaton (MCA). It verifies the mathematical model with realistic traffic and its load data. It is demonstrated that the parameters of traffic flow and traffic load, such as traffic volume, time headway, velocity and weight of simulated traffic are reproduced accurately by the multicell method. With the distribution load, bearing shear and midspan moment in a simply supported girder with a length of 1 000 meters set as indexes respectively, the statistics analysis of the load response characteristics of simulated and realistic data is conducted. The result indicates that the relative errors of simulated data of the MCA model to realistic data are within 5%. When MCA is applied, the precision of load response can be increased from the correlated error of less than 17% in the traditional singlecell method to a relatively high precision.
2013, 41(6):953.
DOI: 10.3969/j.issn.0253-374x.2013.06.025
Abstract:
In view of the needs of e-commerce website for recommendation system, user interest is divided into long-term interest and short-term interest, furthermore, based on long-term interest and short-term interest, a way to describe user’s preferences is proposed. Utilizing the data from the web server database, using unsupervised learning, user’s registration information can be fully mined to abstract user’s long-term interest. Based on vector mapping, both the records data and content data on the server log is analyzed to abstract user’s short-term interest. Moreover, the rough profile presenting user’s preferences can be modified by dealing with user’s feedback, and that makes updating user’s preferences profile possible. Case analysis illustrates to a certain extent this method is reasonable and feasible.
In view of the needs of e-commerce website for recommendation system, user interest is divided into long-term interest and short-term interest, furthermore, based on long-term interest and short-term interest, a way to describe user’s preferences is proposed. Utilizing the data from the web server database, using unsupervised learning, user’s registration information can be fully mined to abstract user’s long-term interest. Based on vector mapping, both the records data and content data on the server log is analyzed to abstract user’s short-term interest. Moreover, the rough profile presenting user’s preferences can be modified by dealing with user’s feedback, and that makes updating user’s preferences profile possible. Case analysis illustrates to a certain extent this method is reasonable and feasible.
2017, 45(07):1091.
DOI: 10.11908/j.issn.0253-374x.2017.07.022
Abstract:
A controllingactivity based model was proposed to estimate the construction duration of terminal megaprojects from the consulting achievements of project timecontrolling for more than ten airport megaprojects in China (2000—2016). First, typical construction sequences of controlling activities for each possible critical path were determined, and the distributions of nonoverlapping time between controlling activities were fitted. After that, based on fitting the duration distributions of four possible critical paths, a model for predicting the duration of terminal building was proposed and applied to three completed terminals. The results show that the proposed model reasonably predicts the construction duration for the case projects. Compared to traditional risk planning methods, the model proposed simplifies the complex work.
A controllingactivity based model was proposed to estimate the construction duration of terminal megaprojects from the consulting achievements of project timecontrolling for more than ten airport megaprojects in China (2000—2016). First, typical construction sequences of controlling activities for each possible critical path were determined, and the distributions of nonoverlapping time between controlling activities were fitted. After that, based on fitting the duration distributions of four possible critical paths, a model for predicting the duration of terminal building was proposed and applied to three completed terminals. The results show that the proposed model reasonably predicts the construction duration for the case projects. Compared to traditional risk planning methods, the model proposed simplifies the complex work.
2017, 45(07):0978-0984.
DOI: 10.11908/j.issn.0253-374x.2017.07.006
Abstract:
In this paper, flume model test on local scour around piles embedded in composite sand was performed, and comparisons and discussions of such predictions of local scour depth in current China and America were also made. The test results show that the scoring progress is slow because the main scoured parts are coarse sand in the early stage. However, in the later stage, as the fine sand becomes the main scoured parts, the progress is faster. The upperlayer coarse sand can help to keep the lowerlayer fine sand from being scoured, and the thicker the coarse sand layer was slower than the fine sand will be scoured. The present design codes of China and USA both work well, but these codes often lead to a much exaggerated results. Therefore, to reflect the effects of the coarse sand on the fine sand, the scour depth should be reduced.
In this paper, flume model test on local scour around piles embedded in composite sand was performed, and comparisons and discussions of such predictions of local scour depth in current China and America were also made. The test results show that the scoring progress is slow because the main scoured parts are coarse sand in the early stage. However, in the later stage, as the fine sand becomes the main scoured parts, the progress is faster. The upperlayer coarse sand can help to keep the lowerlayer fine sand from being scoured, and the thicker the coarse sand layer was slower than the fine sand will be scoured. The present design codes of China and USA both work well, but these codes often lead to a much exaggerated results. Therefore, to reflect the effects of the coarse sand on the fine sand, the scour depth should be reduced.
2017, 45(07):0962-0969.
DOI: 10.11908/j.issn.0253-374x.2017.07.004
Abstract:
In this paper, the monotonic directshear tests composed of eleven C80 and four C40 concrete pushoff specimens were conducted. The failure patterns of specimens, loadslip relation curves, and loadrebar strain relation curves were obtained. The experimental results were analyzed in terms of concrete strength, interface shear rebar strength, and interface types. Afterwards, 32 sets abroad results of interface shear capacity were compared with calculated values using relevant standards at home and abroad. It is found that two failure patterns occur, specifically the interface shear failure and concrete punch failure. The load of C80 specimens with rough interfaces at their first peaks are lower than those of C40 specimens. Moreover, the load values of specimens with shear keys are larger than those with rough interfaces, and the load increases with interface rebar strength. The ratio of capacity calculated by JGJ 1 and test results is between 0.33 and 0.72. Compared with MC2010, ACI318 and EN1992, JGJ 1 is more conservative. Based on the test results, regression analysis was finished and a modification suggestion calculation formula aimed at interface between high strength concretes was presented.
In this paper, the monotonic directshear tests composed of eleven C80 and four C40 concrete pushoff specimens were conducted. The failure patterns of specimens, loadslip relation curves, and loadrebar strain relation curves were obtained. The experimental results were analyzed in terms of concrete strength, interface shear rebar strength, and interface types. Afterwards, 32 sets abroad results of interface shear capacity were compared with calculated values using relevant standards at home and abroad. It is found that two failure patterns occur, specifically the interface shear failure and concrete punch failure. The load of C80 specimens with rough interfaces at their first peaks are lower than those of C40 specimens. Moreover, the load values of specimens with shear keys are larger than those with rough interfaces, and the load increases with interface rebar strength. The ratio of capacity calculated by JGJ 1 and test results is between 0.33 and 0.72. Compared with MC2010, ACI318 and EN1992, JGJ 1 is more conservative. Based on the test results, regression analysis was finished and a modification suggestion calculation formula aimed at interface between high strength concretes was presented.
2017, 45(07):1030-1036.
DOI: 10.11908/j.issn.0253-374x.2017.07.013
Abstract:
Based on a retrofitted twocylinder diesel engine, combined with a selfdesigned intake and direct high temperature water injection system, the knock condition existed in internal combustion rankine cycle engine have been investigated at a high compression ratio and high oxygen fraction. The results show that compared with air intake, the knock occurred results in a high oxygen faction and the knock intensity (KIA) calculated from incylinder pressure Fourier transfer and bandpass filtering reaches 0.26 MPa. The knock frequency is controlled by utilizing a suitable direct water injection strategy and the combustion stability is sustained. Meanwhile, the injected high temperature and pressure water evaporate after heat absorption, which improves system thermal efficiency effectively.
Based on a retrofitted twocylinder diesel engine, combined with a selfdesigned intake and direct high temperature water injection system, the knock condition existed in internal combustion rankine cycle engine have been investigated at a high compression ratio and high oxygen fraction. The results show that compared with air intake, the knock occurred results in a high oxygen faction and the knock intensity (KIA) calculated from incylinder pressure Fourier transfer and bandpass filtering reaches 0.26 MPa. The knock frequency is controlled by utilizing a suitable direct water injection strategy and the combustion stability is sustained. Meanwhile, the injected high temperature and pressure water evaporate after heat absorption, which improves system thermal efficiency effectively.
2017, 45(07):1016-1021.
DOI: 10.11908/j.issn.0253-374x.2017.07.011
Abstract:
A mathematical equation system was derived based on the Lagrange method for wind vane electric double inertia vibrator fatigue loading system, and thus a electromechanical coupling equation of the system was built. Using the small parameter cycle average method, the approximate analytic system vibration was derived for coupling process synchronization stability conditions. The influencing factors on the motor load torque in the process of system operation were obtained, and the mechanism of system coupling was revealed. On this basis, a simulation model was established to numerically simulate system frequency characteristic, and the vibration characteristics of blade under different loading frequencies were obtained. Experimental study on system frequency characteristics, main resonance electromechanical coupling characteristics, and control synchronization verifies the correctness of the mathematical model and simulation model and the feasibility of the control, providing reference for engineering application of fatigue loading system and test.
A mathematical equation system was derived based on the Lagrange method for wind vane electric double inertia vibrator fatigue loading system, and thus a electromechanical coupling equation of the system was built. Using the small parameter cycle average method, the approximate analytic system vibration was derived for coupling process synchronization stability conditions. The influencing factors on the motor load torque in the process of system operation were obtained, and the mechanism of system coupling was revealed. On this basis, a simulation model was established to numerically simulate system frequency characteristic, and the vibration characteristics of blade under different loading frequencies were obtained. Experimental study on system frequency characteristics, main resonance electromechanical coupling characteristics, and control synchronization verifies the correctness of the mathematical model and simulation model and the feasibility of the control, providing reference for engineering application of fatigue loading system and test.
2017, 45(07):0970-0977.
DOI: 10.11908/j.issn.0253-374x.2017.07.005
Abstract:
A field monitoring program was performed to measure the steel strain in segments of a shield tunnel deeply buried with high pore water pressure of Nanjing Metro Line 3 project. Concerning the nonlinear properties of concrete and segment joint of tunnel, an improved algorithm was proposed to compute the internal forces of deeply buried shield tunnels under high water pressures based on three existing reverse calculation methods, and the results were compared to the ones computed in structural design. The results show that the improved algorithm can reflect the actual stress state of segments, especially the lining of shield tunnels deeply buried with high pore pressure; the distribution of internal forces calculated in design is almost equal to the one computed by the improved algorithm, but there are some quantitative discrepancies; the axial forces of segments and joints calculated in structural design are approximately half of the backcalculation results; the bending moments of segments calculated by the proposed algorithm are close to the results of the modified routine method at the bottom of the tunnel while approximate the results of the beamspring model at the roof and haunch of the tunnel, and the bending moments of segment joints are greater than the results of the beamspring model. The insights provided from this study can contribute to the improvement of largesection shield lining design.
A field monitoring program was performed to measure the steel strain in segments of a shield tunnel deeply buried with high pore water pressure of Nanjing Metro Line 3 project. Concerning the nonlinear properties of concrete and segment joint of tunnel, an improved algorithm was proposed to compute the internal forces of deeply buried shield tunnels under high water pressures based on three existing reverse calculation methods, and the results were compared to the ones computed in structural design. The results show that the improved algorithm can reflect the actual stress state of segments, especially the lining of shield tunnels deeply buried with high pore pressure; the distribution of internal forces calculated in design is almost equal to the one computed by the improved algorithm, but there are some quantitative discrepancies; the axial forces of segments and joints calculated in structural design are approximately half of the backcalculation results; the bending moments of segments calculated by the proposed algorithm are close to the results of the modified routine method at the bottom of the tunnel while approximate the results of the beamspring model at the roof and haunch of the tunnel, and the bending moments of segment joints are greater than the results of the beamspring model. The insights provided from this study can contribute to the improvement of largesection shield lining design.
2017, 45(07):1069-1074.
DOI: 10.11908/j.issn.0253-374x.2017.07.019
Abstract:
The relationships between vehicles, such as position, velocity and distance, are the main cantonments of microtraffic flow parameters. These parameters are important to unmanned driving, intelligent traffic, etc. A novel method was proposed for microtraffic flow extraction from mobile laser scanning data. Based on the mobile sectional laser scanning data, a threshold was selected to segment and classify the original point cloud into different vehicles. Then, the quadratic polynomial weighting method was used to extract the feature point from vehicle’s point cloud. The distance and velocity parameters were then computed from adjacent vehicles or adjacent sections. Finally, an experiment was conducted in Shanghai Yan’an elevated road to verify the traffic flow parameter extraction method from mobile laser scanning data. The results show that such parameters could be easily and accurately calculated. The average distance error of directly front or behind car is about 0.058 m and its average velocity error is about 1.62 km?h-1. The average distance error of sideward car is merely 0.100 m, and its average velocity error is about 1.29 km?h-1.
The relationships between vehicles, such as position, velocity and distance, are the main cantonments of microtraffic flow parameters. These parameters are important to unmanned driving, intelligent traffic, etc. A novel method was proposed for microtraffic flow extraction from mobile laser scanning data. Based on the mobile sectional laser scanning data, a threshold was selected to segment and classify the original point cloud into different vehicles. Then, the quadratic polynomial weighting method was used to extract the feature point from vehicle’s point cloud. The distance and velocity parameters were then computed from adjacent vehicles or adjacent sections. Finally, an experiment was conducted in Shanghai Yan’an elevated road to verify the traffic flow parameter extraction method from mobile laser scanning data. The results show that such parameters could be easily and accurately calculated. The average distance error of directly front or behind car is about 0.058 m and its average velocity error is about 1.62 km?h-1. The average distance error of sideward car is merely 0.100 m, and its average velocity error is about 1.29 km?h-1.
2017, 45(07):0948-0953.
DOI: 10.11908/j.issn.0253-374x.2017.07.002
Abstract:
To investigate the effect of the concrete shear keys at abutment on transverse seismic reaction of a short and medium span continuous girder bridge, a finite element model was built based a continuous girder bridge. The effects of peak strength of the concrete shear keys at abutment on transverse seismic reaction of a continuous girder bridge were analyzed using the nonlinear time history method. The results show that when the peak strength of the concrete shear key at abutment increases, the shear demand of the top of abutment increases while the displacement demand of bearing at pier decreases, but the decrease amplitude declined to zero. A reasonable selection of the peak strength of the concrete shear key at abutment can effectively reduce the displacement demand of bearing at the pier, and avoid the severe seismic damage on the abutment.
To investigate the effect of the concrete shear keys at abutment on transverse seismic reaction of a short and medium span continuous girder bridge, a finite element model was built based a continuous girder bridge. The effects of peak strength of the concrete shear keys at abutment on transverse seismic reaction of a continuous girder bridge were analyzed using the nonlinear time history method. The results show that when the peak strength of the concrete shear key at abutment increases, the shear demand of the top of abutment increases while the displacement demand of bearing at pier decreases, but the decrease amplitude declined to zero. A reasonable selection of the peak strength of the concrete shear key at abutment can effectively reduce the displacement demand of bearing at the pier, and avoid the severe seismic damage on the abutment.
2017, 45(07):1037-1043.
DOI: 10.11908/j.issn.0253-374x.2017.07.014
Abstract:
Based on the reference relation between piston velocity and piston position in the stable operation stage of the linear engine/generator system, a trajectory tracking control strategy based on PI controller was proposed. A system Simulink model was established which was verified to be accurate by experiment. Simulation results show that when fuel injection quantity fluctuates or misfire happens, the proposed control strategy makes the piston trajectory go back to the reference trajectory within one cycle, realizing an effective and prompt control over piston motion.
Based on the reference relation between piston velocity and piston position in the stable operation stage of the linear engine/generator system, a trajectory tracking control strategy based on PI controller was proposed. A system Simulink model was established which was verified to be accurate by experiment. Simulation results show that when fuel injection quantity fluctuates or misfire happens, the proposed control strategy makes the piston trajectory go back to the reference trajectory within one cycle, realizing an effective and prompt control over piston motion.
2017, 45(05):0617-0624.
DOI: 10.11908/j.issn.0253-374x.2017.05.001
Abstract:
With the developments of past 30 years, people working in the civil engineering area have stand on an very important historical node: to establish the third generation design theory of structures. This paper briefly addresses the historic clues of the first and second generations of structural design theory and discusses the basic contradictions associated with the second generation of structural design theory. The characteristics typically featured by the third generation of structural design theory is then illustrated and basic framework are proposed as well. It is point out that the theory of solid mechanics, the modern numerical computational methods and probability density evolution theory consist of the three milestones of the third generation design theory of structures. The primary objective of the third generation of structural design theory is to achieve the global reliability design of structures in its life cycle such that a scientific quantification description can be drawn upon the global safety and service reliability of engineering structures. Ongoing work towards completely building up the third generation of structural design theory is outlined.
With the developments of past 30 years, people working in the civil engineering area have stand on an very important historical node: to establish the third generation design theory of structures. This paper briefly addresses the historic clues of the first and second generations of structural design theory and discusses the basic contradictions associated with the second generation of structural design theory. The characteristics typically featured by the third generation of structural design theory is then illustrated and basic framework are proposed as well. It is point out that the theory of solid mechanics, the modern numerical computational methods and probability density evolution theory consist of the three milestones of the third generation design theory of structures. The primary objective of the third generation of structural design theory is to achieve the global reliability design of structures in its life cycle such that a scientific quantification description can be drawn upon the global safety and service reliability of engineering structures. Ongoing work towards completely building up the third generation of structural design theory is outlined.
2017, 45(04):0544-0553.
DOI: 10.11908/j.issn.0253-374x.2017.04.012
Abstract:
As the upgraded system of traditional cruise control, the adaptive cruise control (ACC) system can improve the driving comfort and safety. The development stages of ACC system were explicated in this paper. The latest research achievements of ACC system in recent years were discussed in detail from the aspects of environmental perception, tracking behavior of driver, vehicle dynamic modeling, ACC system control algorithm, and function extension of ACC. Based on these achievements, the common problems of ACC were summarized and some viewpoints on the trend of the future developments were given.
As the upgraded system of traditional cruise control, the adaptive cruise control (ACC) system can improve the driving comfort and safety. The development stages of ACC system were explicated in this paper. The latest research achievements of ACC system in recent years were discussed in detail from the aspects of environmental perception, tracking behavior of driver, vehicle dynamic modeling, ACC system control algorithm, and function extension of ACC. Based on these achievements, the common problems of ACC were summarized and some viewpoints on the trend of the future developments were given.
