Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast trac...Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast track and simply-supported beam are combined with each other,was established.The laws of the track stress,the pier longitudinal stress and the beam-track relative displacement were analyzed.The results show that reducing the longitudinal resistance can effectively reduce the track stress and the pier stress of the continuous beam,and increase the beam-track relative displacement.Increasing the rigid pier stiffness of continuous beam can reduce the track braking stress,increase the pier longitudinal stress and reduce the beam-track relative displacement,Increasing the rigid pier stiffness of simply-supported beam can reduce the track braking stress,the rigid pier longitudinal stress and the beam-track relative displacement.展开更多
To better understand the crustal deformation of the South China Sea Basin, we produce a mechanically consistent 2-dimensional model for observing regional velocity field in the South China Sea (SCS). We studied the do...To better understand the crustal deformation of the South China Sea Basin, we produce a mechanically consistent 2-dimensional model for observing regional velocity field in the South China Sea (SCS). We studied the dominating regional tectonic stress field by geodetic measurements and finite element analysis, the spatial variations of velocity field and strain field, and relative movements among different blocks, using a 2-dimensional model describing crustal deformation of the South China Sea Basin. Strain results show that the SCS is extending at present. The western part of SCS is opening gradually in NW- SE direction from its northern margin to the south, but the eastern part of SCS is opening gradually from its central part to the north and south. In addition, we analyzed the plate kinematics to the deformation of the SCS, using a two-dimensional finite element model. Our simulations results are well explained by available geodetic data. The movement of SCS is resulted from interactions among Indian Plate, Pacific Plate, Philippine Sea Plate, and Eurasian Plate.展开更多
Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking (RVD) for an unmanned spacecraft or for guiding the chaser docking with an uncooperative target.The inherent teleopera...Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking (RVD) for an unmanned spacecraft or for guiding the chaser docking with an uncooperative target.The inherent teleoperation time delay is a rigorous problem,especially when the chaser is teleoperated on the ground.To eliminate the effect of time delay,a new approach for teleoperation RVD is studied.The characteristics of teleoperation RVD are analyzed by comparisons with the teleoperation robot and with manually controlled RVD;the relative motion of the chaser is predicted based on the C-W equation;and the processed measure information with time delay through the Kalman filter is utilized to correct the current prediction.Experimental results verify that the approach produces an 18% enhanced success rate of teleoperation RVD compared with direct visual feedback,and consumes less time and fuel.The developed approach also solves the time delay problem effectively.Teleoperation RVD using this method can be applied as a useful backup for autonomous RVD.展开更多
This paper considers the problem of optimal multi-objective trajectory design for autonomous rendezvous. Total velocity cost and relative state robustness of close-looped control are selected as the objective function...This paper considers the problem of optimal multi-objective trajectory design for autonomous rendezvous. Total velocity cost and relative state robustness of close-looped control are selected as the objective functions. Based on relative dynamics equations, the state equations and measurement equations for angles-only relative navigation between spacecraffs are set forth. According to the method of linear covariance analysis, the close-looped control covariance of the true relative state from the reference relative state is analyzed, and the objective functions of relative state robustness are formulated. Considering the total velocity cost and the relative state robustness, the multi-objective optimization algorithm of NSGA-II is employed to solve this multi-impulsive rendezvous problem. Lastly, the validity of the objective functions and the covariance results are demonstrated through 1 00 times Monte Carlo simulation.展开更多
基金Project(50678176) supported by the National Natural Science Foundation of China
文摘Based on the construction bridge of Xiamen-Shenzhen high-speed railway(9-32 m simply-supported beam + 6×32 m continuous beam),the pier-beam-track finite element model,where the continuous beam of the ballast track and simply-supported beam are combined with each other,was established.The laws of the track stress,the pier longitudinal stress and the beam-track relative displacement were analyzed.The results show that reducing the longitudinal resistance can effectively reduce the track stress and the pier stress of the continuous beam,and increase the beam-track relative displacement.Increasing the rigid pier stiffness of continuous beam can reduce the track braking stress,increase the pier longitudinal stress and reduce the beam-track relative displacement,Increasing the rigid pier stiffness of simply-supported beam can reduce the track braking stress,the rigid pier longitudinal stress and the beam-track relative displacement.
基金Supported by the National Basic Research Program of China (973 Program) (No. 2007cb411702)
文摘To better understand the crustal deformation of the South China Sea Basin, we produce a mechanically consistent 2-dimensional model for observing regional velocity field in the South China Sea (SCS). We studied the dominating regional tectonic stress field by geodetic measurements and finite element analysis, the spatial variations of velocity field and strain field, and relative movements among different blocks, using a 2-dimensional model describing crustal deformation of the South China Sea Basin. Strain results show that the SCS is extending at present. The western part of SCS is opening gradually in NW- SE direction from its northern margin to the south, but the eastern part of SCS is opening gradually from its central part to the north and south. In addition, we analyzed the plate kinematics to the deformation of the SCS, using a two-dimensional finite element model. Our simulations results are well explained by available geodetic data. The movement of SCS is resulted from interactions among Indian Plate, Pacific Plate, Philippine Sea Plate, and Eurasian Plate.
文摘Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking (RVD) for an unmanned spacecraft or for guiding the chaser docking with an uncooperative target.The inherent teleoperation time delay is a rigorous problem,especially when the chaser is teleoperated on the ground.To eliminate the effect of time delay,a new approach for teleoperation RVD is studied.The characteristics of teleoperation RVD are analyzed by comparisons with the teleoperation robot and with manually controlled RVD;the relative motion of the chaser is predicted based on the C-W equation;and the processed measure information with time delay through the Kalman filter is utilized to correct the current prediction.Experimental results verify that the approach produces an 18% enhanced success rate of teleoperation RVD compared with direct visual feedback,and consumes less time and fuel.The developed approach also solves the time delay problem effectively.Teleoperation RVD using this method can be applied as a useful backup for autonomous RVD.
基金supported by the National Natural Science Foundation of China (Grant No. 10902101)
文摘This paper considers the problem of optimal multi-objective trajectory design for autonomous rendezvous. Total velocity cost and relative state robustness of close-looped control are selected as the objective functions. Based on relative dynamics equations, the state equations and measurement equations for angles-only relative navigation between spacecraffs are set forth. According to the method of linear covariance analysis, the close-looped control covariance of the true relative state from the reference relative state is analyzed, and the objective functions of relative state robustness are formulated. Considering the total velocity cost and the relative state robustness, the multi-objective optimization algorithm of NSGA-II is employed to solve this multi-impulsive rendezvous problem. Lastly, the validity of the objective functions and the covariance results are demonstrated through 1 00 times Monte Carlo simulation.
