The intermittent connection（IC）of the field-bus in networked manufacturing systems is a common but hard troubleshooting network problem,which may result in system level failures or safety issues.However,there is no ...The intermittent connection（IC）of the field-bus in networked manufacturing systems is a common but hard troubleshooting network problem,which may result in system level failures or safety issues.However,there is no online IC location identification method available to detect and locate the position of the problem.To tackle this problem,a novel model based online fault location identification method for localized IC problem is proposed.First,the error event patterns are identified and classified according to different node sources in each error frame.Then generalized zero inflated Poisson process（GZIP）model for each node is established by using time stamped error event sequence.Finally,the location of the IC fault is determined by testing whether the parameters of the fitted stochastic model is statistically significant or not using the confident intervals of the estimated parameters.To illustrate the proposed method,case studies are conducted on a 3-node controller area network（CAN）test-bed,in which IC induced faults are imposed on a network drop cable using computer controlled on-off switches.The experimental results show the parameters of the GZIP model for the problematic node are statistically significant（larger than 0）,and the patterns of the confident intervals of the estimated parameters are directly linked to the problematic node,which agrees with the experimental setup.The proposed online IC location identification method can successfully identify the location of the drop cable on which IC faults occurs on the CAN network.展开更多
The porosity of carbon fiber reinforced polymer（CFRP） workpiece is tested by ultrasonic in pulse-echo mode.When the ultrasonic frequency is close to the resonant frequency of the workpiece,the resonance will occur a...The porosity of carbon fiber reinforced polymer（CFRP） workpiece is tested by ultrasonic in pulse-echo mode.When the ultrasonic frequency is close to the resonant frequency of the workpiece,the resonance will occur along the thickness direction.If the CFRP workpiece contains voids,the resonant frequency will decrease.The result of ultrasonic testing experiment clearly draws the conclusion that the center frequency of the backscattered signal spectrum declines with increasing porosity.Based on the above theory and conclusion,the three-dimensional（3D） voids identification and location method is established.Firstly,the ultrasonic signals are collected and the center frequencies of the backscattered signal spectra are calculated.Then the C-scan of center frequency is generated to identify the voids.At last the B-scan of center frequency for the region containing voids is generated to determine the depth of the voids.The experimental results show that,by using this method,the voids in the CFRP workpiece can be identified and pinpointed.展开更多
Understanding the characteristics of passenger vehicle use is the prerequisite for effective urban management.However,it has been challenging in the existing literature due to the lack of continuously observed data on...Understanding the characteristics of passenger vehicle use is the prerequisite for effective urban management.However,it has been challenging in the existing literature due to the lack of continuously observed data on passenger vehicle use.Thanks to the advances in data collection and processing techniques,multi-day vehicle trajectory data generated from volunteered passenger cars provide new opportunities for examining in depth how people travel in regular patterns.In this paper,based on a week’s operation data of 6600 passenger cars in Shanghai,we develop a systematic approach for identifying trips and travel purposes,and classify vehicles into four categories using a Gaussian-Mixed-Model.A new method is proposed to identify vehicle travel regularities and we use the Z Test to explore differences in travel time and route choices between four types of vehicles.Wefind that commercially used vehicles present high travel intensity in temporal and spatial aspects and the use intensity in elevated roads is higher for household-used commuting vehicles than semi-commercially used vehicles.The methodologies and conclusions of this paper may provide not only theoretical support for future urban traffic prediction,but also guidance for employing customized active traffic demand management measures to alleviate traffic congestion.展开更多
基金Supported by National Natural Science Foundation of China(Grant No51005205)Science Fund for Creative Research Groups of Nationa Natural Science Foundation of China(Grant No.51221004)+1 种基金Nationa Basic Research Program of China(973 Program,Grant No.2013CB035405)Open Foundation of State Key Laboratory of Automotive Safety and Energy,Tsinghua University,China(Grant No.KF13011)
文摘The intermittent connection（IC）of the field-bus in networked manufacturing systems is a common but hard troubleshooting network problem,which may result in system level failures or safety issues.However,there is no online IC location identification method available to detect and locate the position of the problem.To tackle this problem,a novel model based online fault location identification method for localized IC problem is proposed.First,the error event patterns are identified and classified according to different node sources in each error frame.Then generalized zero inflated Poisson process（GZIP）model for each node is established by using time stamped error event sequence.Finally,the location of the IC fault is determined by testing whether the parameters of the fitted stochastic model is statistically significant or not using the confident intervals of the estimated parameters.To illustrate the proposed method,case studies are conducted on a 3-node controller area network（CAN）test-bed,in which IC induced faults are imposed on a network drop cable using computer controlled on-off switches.The experimental results show the parameters of the GZIP model for the problematic node are statistically significant（larger than 0）,and the patterns of the confident intervals of the estimated parameters are directly linked to the problematic node,which agrees with the experimental setup.The proposed online IC location identification method can successfully identify the location of the drop cable on which IC faults occurs on the CAN network.
基金Funded by the National Natural Science Foundation of China(No.51075358)Zhejiang Key Discipline of Instrument Science and Technology(No.JL130112)Zhejiang Natural Science Foundation(No.LQ12E05018)
文摘The porosity of carbon fiber reinforced polymer（CFRP） workpiece is tested by ultrasonic in pulse-echo mode.When the ultrasonic frequency is close to the resonant frequency of the workpiece,the resonance will occur along the thickness direction.If the CFRP workpiece contains voids,the resonant frequency will decrease.The result of ultrasonic testing experiment clearly draws the conclusion that the center frequency of the backscattered signal spectrum declines with increasing porosity.Based on the above theory and conclusion,the three-dimensional（3D） voids identification and location method is established.Firstly,the ultrasonic signals are collected and the center frequencies of the backscattered signal spectra are calculated.Then the C-scan of center frequency is generated to identify the voids.At last the B-scan of center frequency for the region containing voids is generated to determine the depth of the voids.The experimental results show that,by using this method,the voids in the CFRP workpiece can be identified and pinpointed.
基金supported by the project of the National Natural Science Foundation of China(No.71734004)。
文摘Understanding the characteristics of passenger vehicle use is the prerequisite for effective urban management.However,it has been challenging in the existing literature due to the lack of continuously observed data on passenger vehicle use.Thanks to the advances in data collection and processing techniques,multi-day vehicle trajectory data generated from volunteered passenger cars provide new opportunities for examining in depth how people travel in regular patterns.In this paper,based on a week’s operation data of 6600 passenger cars in Shanghai,we develop a systematic approach for identifying trips and travel purposes,and classify vehicles into four categories using a Gaussian-Mixed-Model.A new method is proposed to identify vehicle travel regularities and we use the Z Test to explore differences in travel time and route choices between four types of vehicles.Wefind that commercially used vehicles present high travel intensity in temporal and spatial aspects and the use intensity in elevated roads is higher for household-used commuting vehicles than semi-commercially used vehicles.The methodologies and conclusions of this paper may provide not only theoretical support for future urban traffic prediction,but also guidance for employing customized active traffic demand management measures to alleviate traffic congestion.
