Based on previous research work,we present a spectrum deviation method to recognize a foreshock or generalized foreshock in this paper. The criterion to determine whether an event is a foreshock is a wide spectrum for...Based on previous research work,we present a spectrum deviation method to recognize a foreshock or generalized foreshock in this paper. The criterion to determine whether an event is a foreshock is a wide spectrum for an ordinary event,however,a moderate earthquake with foreshock or generalized foreshock has the characteristics of a narrow frequency band,and it deviates to the low frequency. It may be explained by metastable extension in the rupture source or related area of the main shock or regional fragmentation damage and crack nucleation process. The calculation results of two foreshocks,the M_S4. 7 event which occurred before the Yushu M_S7. 1 earthquake on April 14,2010 and the M_S5. 3 event which occurred before the Yutian M_S7. 3 earthquake on February 12,2014,show that the spectra of foreshocks shift,and they are quite different from the nonforeshock seismic spectrum of equivalent size. Therefore,this result can verify the validity of the spectrum deviation method.展开更多
The machining accuracy of workpiece is influenced by its orientation deviation, which is caused by the fixture-workpiece error. Based on the spatial coordinate theory, the orientation deviation of workpiece is measure...The machining accuracy of workpiece is influenced by its orientation deviation, which is caused by the fixture-workpiece error. Based on the spatial coordinate theory, the orientation deviation of workpiece is measured by using an on-machine verification system, which can take into account the errors resulting from fixture manufacturing, installation and adjustment, location and clamping of workpiece. According to the least square method, the model of orientation deviation is built to determine the relationship between the theoretical and actual coordinate systems. The influence of orientation deviation on machining accuracy is quantified, and it is shown that the orientation deviation only affects the dimensional precision and position precision, rather than shape precision. In the experiment, the compensation processing of realtime errors was conducted, and the perpendicularity and inclination errors of the tetragonal part were reduced by 38.46% and 47.06%, respectively.展开更多
This paper considers the consensus problem of a group of homogeneous agents.These agents are governed by a general linear system and can only directly measure the output,instead of the state.In order to achieve the co...This paper considers the consensus problem of a group of homogeneous agents.These agents are governed by a general linear system and can only directly measure the output,instead of the state.In order to achieve the consensus goal,each agent estimates its state through a Luenberger observer,exchanges its estimated state with neighbors,and constructs the control input with the estimated states of its own and neighbors.Due to the existence of observation and process noises,only practical consensus,instead of asymptotical consensus,can be achieved in such multi-agent systems.The performance of the achieved practical consensus can be measured by the ultimate mean square deviation of the states of agents.That performance is closely related to the observation gains of the state observers and the control gains of agents.This paper proposes a method to optimize such performance with respect to the concerned observation and control gains.That method starts with a set of feasible observation and control gains and formulates a group of linear matrix inequalities(LMIs).Solving these LMIs gives some intermediate matrix variables.By perturbing observation and control gains,and the intermediate matrix variables,the original LMIs yield another group of LMIs,which can be solved to provide a descent direction of observation and control gains.Moving along that descent direction,observation and control gains can be improved to yield better performance and work as the starting point of the next iteration.By iteratively repeating this procedure,we can hopefully improve the consensus performance of the concerned multi-agent system.Simulations are done to demonstrate the effectiveness of the proposed method.展开更多
提出一种新的基于均匀非周期B样条曲线模型的结构化道路检测算法.算法首先利用Canny边缘检测算法提取道路边缘,然后使用最小二乘法拟合道路标识线,最后利用所提取的道路标识线求取道路中央线,进而完成道路拟合.为了准确定位道路弯道位置...提出一种新的基于均匀非周期B样条曲线模型的结构化道路检测算法.算法首先利用Canny边缘检测算法提取道路边缘,然后使用最小二乘法拟合道路标识线,最后利用所提取的道路标识线求取道路中央线,进而完成道路拟合.为了准确定位道路弯道位置,算法运用最大转向偏差定位(Maximum deviation of position shift,MDPS)方法求解道路模型控制点.实验证明该算法快速、稳定、灵活,可以满足智能导航的要求.展开更多
基金sponsored by the National Key Technology Support Program of China entitled "Application of Digital Seismic Technology to Mid-and Short-term Prediction of Strong Earthquake"(2012BAK19B02-01)
文摘Based on previous research work,we present a spectrum deviation method to recognize a foreshock or generalized foreshock in this paper. The criterion to determine whether an event is a foreshock is a wide spectrum for an ordinary event,however,a moderate earthquake with foreshock or generalized foreshock has the characteristics of a narrow frequency band,and it deviates to the low frequency. It may be explained by metastable extension in the rupture source or related area of the main shock or regional fragmentation damage and crack nucleation process. The calculation results of two foreshocks,the M_S4. 7 event which occurred before the Yushu M_S7. 1 earthquake on April 14,2010 and the M_S5. 3 event which occurred before the Yutian M_S7. 3 earthquake on February 12,2014,show that the spectra of foreshocks shift,and they are quite different from the nonforeshock seismic spectrum of equivalent size. Therefore,this result can verify the validity of the spectrum deviation method.
基金Supported by National Natural Science Foundation of China (No.50975200)
文摘The machining accuracy of workpiece is influenced by its orientation deviation, which is caused by the fixture-workpiece error. Based on the spatial coordinate theory, the orientation deviation of workpiece is measured by using an on-machine verification system, which can take into account the errors resulting from fixture manufacturing, installation and adjustment, location and clamping of workpiece. According to the least square method, the model of orientation deviation is built to determine the relationship between the theoretical and actual coordinate systems. The influence of orientation deviation on machining accuracy is quantified, and it is shown that the orientation deviation only affects the dimensional precision and position precision, rather than shape precision. In the experiment, the compensation processing of realtime errors was conducted, and the perpendicularity and inclination errors of the tetragonal part were reduced by 38.46% and 47.06%, respectively.
基金The work of W.Zheng and Q.Ling was partially supported by the National Natural Science Foundation of China(No.61273112)the National Key Research and Development Project(No.2016YFC0201003).The work of H.Lin was partially supported by the National Science Foundation(Nos.NSF-CNS-1239222,NSF-CNS-1446288,NSF-EECS-1253488).
文摘This paper considers the consensus problem of a group of homogeneous agents.These agents are governed by a general linear system and can only directly measure the output,instead of the state.In order to achieve the consensus goal,each agent estimates its state through a Luenberger observer,exchanges its estimated state with neighbors,and constructs the control input with the estimated states of its own and neighbors.Due to the existence of observation and process noises,only practical consensus,instead of asymptotical consensus,can be achieved in such multi-agent systems.The performance of the achieved practical consensus can be measured by the ultimate mean square deviation of the states of agents.That performance is closely related to the observation gains of the state observers and the control gains of agents.This paper proposes a method to optimize such performance with respect to the concerned observation and control gains.That method starts with a set of feasible observation and control gains and formulates a group of linear matrix inequalities(LMIs).Solving these LMIs gives some intermediate matrix variables.By perturbing observation and control gains,and the intermediate matrix variables,the original LMIs yield another group of LMIs,which can be solved to provide a descent direction of observation and control gains.Moving along that descent direction,observation and control gains can be improved to yield better performance and work as the starting point of the next iteration.By iteratively repeating this procedure,we can hopefully improve the consensus performance of the concerned multi-agent system.Simulations are done to demonstrate the effectiveness of the proposed method.
文摘提出一种新的基于均匀非周期B样条曲线模型的结构化道路检测算法.算法首先利用Canny边缘检测算法提取道路边缘,然后使用最小二乘法拟合道路标识线,最后利用所提取的道路标识线求取道路中央线,进而完成道路拟合.为了准确定位道路弯道位置,算法运用最大转向偏差定位(Maximum deviation of position shift,MDPS)方法求解道路模型控制点.实验证明该算法快速、稳定、灵活,可以满足智能导航的要求.
