In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign met...In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.展开更多
Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction o...Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction of the separable dictionary is a key issue for sparse representation technology. A compressive time-domain dictionary(TD) for ASC model is presented. Two-dimensional frequency domain responses of the ASC are produced and transformed into the time domain. Then these time domain responses are cutoff and stacked into vectors. These vectored time-domain responses are amalgamated to form the TD. Compared with the traditional frequency-domain dictionary(FD), the TD is a matrix that is quite spare and can markedly reduce the data size of the dictionary. Based on the basic TD construction method, we present four extended TD construction methods, which are available for different applications. In the experiments, the performance of the TD, including the basic model and the extended models, has been firstly analyzed in comparison with the FD. Secondly, an example of parameter estimation from SAR synthetic aperture radar(SAR) measurements of a target collected in an anechoic room is exhibited. Finally, a sparse image reconstruction example is from two apart apertures. Experimental results demonstrate the effectiveness and efficiency of the proposed TD.展开更多
为研究小型车和大型车两类车辆在高速公路隧道路段内的跟驰行为,本文使用“卡口相机结合激光雷达”的数据采集模式,采集广东省祈福隧道的车辆行驶轨迹,并分别提取两类车辆的跟驰轨迹数据;提出实时安全裕度偏差(Real-time Deviation of S...为研究小型车和大型车两类车辆在高速公路隧道路段内的跟驰行为,本文使用“卡口相机结合激光雷达”的数据采集模式,采集广东省祈福隧道的车辆行驶轨迹,并分别提取两类车辆的跟驰轨迹数据;提出实时安全裕度偏差(Real-time Deviation of Safety Margin,RDSM)评估车辆实时跟驰风险水平,采用模糊C-均值聚类方法将风险水平划分为无风险或低风险、中风险及高风险;从跟驰前车类型、车辆在隧道内位置、驾驶环境、当前时刻的车辆驾驶和交互状态,以及历史的车辆驾驶和交互状态这5个方面,在数据中选取26项潜在影响因素,构建两类车辆的多项Logit模型和相关随机参数Logit模型,分析和比较各项因素对两类车辆的高速公路隧道实时跟驰风险的影响,揭示影响因素的异质性。结果表明:大型车在隧道内的实时跟驰风险受到更多因素的影响;跟驰车辆与其前车的车辆类型不同时,隧道实时跟驰风险会相对降低;前车驾驶状态的波动更容易导致跟驰高风险;平均边际效应显示,相比于在隧道进口段,小型车在隧道出口段实时跟驰风险为高风险的概率增加了0.0413,大型车在隧道内部路段实时跟驰风险为高风险的概率增加了0.0155;高风险状态下的跟驰间距标准差在两类车辆中均表现出异质性。展开更多
滚动轴承是旋转机械系统的关键部件之一,其振动性能对机械设备的运行质量有重要影响。为确定轴承性能演变趋势,对轮毂轴承的全寿命周期振动时间序列进行了研究。首先,按照是否超过标定值,将轴承振动时间序列分为性能未退化和性能退化序...滚动轴承是旋转机械系统的关键部件之一,其振动性能对机械设备的运行质量有重要影响。为确定轴承性能演变趋势,对轮毂轴承的全寿命周期振动时间序列进行了研究。首先,按照是否超过标定值,将轴承振动时间序列分为性能未退化和性能退化序列,并且将其按照时间顺序等分为10个子序列;然后,采用了最大熵原理模型逐一分析了子序列,寻找了参数最早发生明显变化的序列;最后,按照时间顺序继续细分了该子序列,分析了每个子序列的参数变化趋势,并对比了参数变化序列对应的轴承服役时间。研究结果表明:通过对比映射参数、各阶原点矩、拉格朗日乘子与轴承性能变化之间的规律,可验证映射参数表征轴承性能演变的可行性;第8个子序列映射参数a减小了53.3%,映射参数b增加了43.2%;第8个子序列继续细分时,第9个子序列映射参数a减小了44.5%,映射参数b增加了38.7%;与标定失效时间(189 h 41 min)相比,采用最大熵模型可提前175 min实现对轴承的性能失效预报。采用最大熵模型可以对轴承性能进行失效预报。展开更多
In this research, effect of varying spatial orientations on the build time requirements for fused deposition modelling process is studied. Constructive solid geometry cylindrical primitive is taken as work piece and m...In this research, effect of varying spatial orientations on the build time requirements for fused deposition modelling process is studied. Constructive solid geometry cylindrical primitive is taken as work piece and modeling is accomplished for it. Response surface methodology is used to design the experiments and obtain statistical models for build time requirements corresponding to different orientations of the given primitive in modeller build volume. Contour width, air gap, slice height, raster width, raster angle and angle of orientation are treated as process parameters. Percentage contribution of individual process parameter is found to change for build time corresponding to different spatial orientations. Also, the average of build time requirement changes with spatial orientation. This paper attempts to clearly discuss and describe the observations with an aim to develop a clear understanding of effect of spatial variations on the build time for Fused Deposition Modelling process. This work is an integral part of process layout optimization and these results can effectively aid designers specially while tackling nesting issues.展开更多
基金Projects(50875090,50905063) supported by the National Natural Science Foundation of ChinaProject(2009AA04Z111) supported by the National High Technology Research and Development Program of China+2 种基金Project(20090460769) supported by China Postdoctoral Science FoundationProject(2011ZM0070) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(S2011010001155) supported by the Natural Science Foundation of Guangdong Province,China
文摘In order to optimize the embedded system implementation for Ethernet-based computer numerical control （CNC） system, it is very necessary to establish the performance analysis model and further adopt the codesign method from the control, communication and computing perspectives. On the basis of analyzing real-time Ethemet, system architecture, time characteristic parameters of control-loop ere, a performance analysis model for real-time Ethemet-based CNC system was proposed, which is able to include the timing effects caused by the implementation platform in the simulation. The key for establishing the model is accomplished by designing the error analysis module and the controller nodes. Under the restraint of CPU resource and communication bandwidth, the experiment with a case study was conducted, and the results show that if the deadline miss ratio of data packets is 0.2%, then the percentage error is 1.105%. The proposed model can be used at several stages of CNC system development.
基金Project(NCET-11-0866)supported by Education Ministry's new Century Excellent Talents Supporting Plan,China
文摘Parameter estimation of the attributed scattering center(ASC) model is significant for automatic target recognition(ATR). Sparse representation based parameter estimation methods have developed rapidly. Construction of the separable dictionary is a key issue for sparse representation technology. A compressive time-domain dictionary(TD) for ASC model is presented. Two-dimensional frequency domain responses of the ASC are produced and transformed into the time domain. Then these time domain responses are cutoff and stacked into vectors. These vectored time-domain responses are amalgamated to form the TD. Compared with the traditional frequency-domain dictionary(FD), the TD is a matrix that is quite spare and can markedly reduce the data size of the dictionary. Based on the basic TD construction method, we present four extended TD construction methods, which are available for different applications. In the experiments, the performance of the TD, including the basic model and the extended models, has been firstly analyzed in comparison with the FD. Secondly, an example of parameter estimation from SAR synthetic aperture radar(SAR) measurements of a target collected in an anechoic room is exhibited. Finally, a sparse image reconstruction example is from two apart apertures. Experimental results demonstrate the effectiveness and efficiency of the proposed TD.
文摘为研究小型车和大型车两类车辆在高速公路隧道路段内的跟驰行为,本文使用“卡口相机结合激光雷达”的数据采集模式,采集广东省祈福隧道的车辆行驶轨迹,并分别提取两类车辆的跟驰轨迹数据;提出实时安全裕度偏差(Real-time Deviation of Safety Margin,RDSM)评估车辆实时跟驰风险水平,采用模糊C-均值聚类方法将风险水平划分为无风险或低风险、中风险及高风险;从跟驰前车类型、车辆在隧道内位置、驾驶环境、当前时刻的车辆驾驶和交互状态,以及历史的车辆驾驶和交互状态这5个方面,在数据中选取26项潜在影响因素,构建两类车辆的多项Logit模型和相关随机参数Logit模型,分析和比较各项因素对两类车辆的高速公路隧道实时跟驰风险的影响,揭示影响因素的异质性。结果表明:大型车在隧道内的实时跟驰风险受到更多因素的影响;跟驰车辆与其前车的车辆类型不同时,隧道实时跟驰风险会相对降低;前车驾驶状态的波动更容易导致跟驰高风险;平均边际效应显示,相比于在隧道进口段,小型车在隧道出口段实时跟驰风险为高风险的概率增加了0.0413,大型车在隧道内部路段实时跟驰风险为高风险的概率增加了0.0155;高风险状态下的跟驰间距标准差在两类车辆中均表现出异质性。
文摘滚动轴承是旋转机械系统的关键部件之一,其振动性能对机械设备的运行质量有重要影响。为确定轴承性能演变趋势,对轮毂轴承的全寿命周期振动时间序列进行了研究。首先,按照是否超过标定值,将轴承振动时间序列分为性能未退化和性能退化序列,并且将其按照时间顺序等分为10个子序列;然后,采用了最大熵原理模型逐一分析了子序列,寻找了参数最早发生明显变化的序列;最后,按照时间顺序继续细分了该子序列,分析了每个子序列的参数变化趋势,并对比了参数变化序列对应的轴承服役时间。研究结果表明:通过对比映射参数、各阶原点矩、拉格朗日乘子与轴承性能变化之间的规律,可验证映射参数表征轴承性能演变的可行性;第8个子序列映射参数a减小了53.3%,映射参数b增加了43.2%;第8个子序列继续细分时,第9个子序列映射参数a减小了44.5%,映射参数b增加了38.7%;与标定失效时间(189 h 41 min)相比,采用最大熵模型可提前175 min实现对轴承的性能失效预报。采用最大熵模型可以对轴承性能进行失效预报。
文摘In this research, effect of varying spatial orientations on the build time requirements for fused deposition modelling process is studied. Constructive solid geometry cylindrical primitive is taken as work piece and modeling is accomplished for it. Response surface methodology is used to design the experiments and obtain statistical models for build time requirements corresponding to different orientations of the given primitive in modeller build volume. Contour width, air gap, slice height, raster width, raster angle and angle of orientation are treated as process parameters. Percentage contribution of individual process parameter is found to change for build time corresponding to different spatial orientations. Also, the average of build time requirement changes with spatial orientation. This paper attempts to clearly discuss and describe the observations with an aim to develop a clear understanding of effect of spatial variations on the build time for Fused Deposition Modelling process. This work is an integral part of process layout optimization and these results can effectively aid designers specially while tackling nesting issues.
