Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve...Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.展开更多
High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system suc...High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.展开更多
The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of diffe...The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of different diameters casting shadows onto the same plane is identical. Using AutoCAD to get the shadow of a general object of revolution, it only needs to take a series of circles along the axis of symmetry and get their corresponding shadows of ellipses, drawing an envelope to cover all these silhouettes results in the required overall shadow. Then the discrete points of shadow contour line are projected back onto the original object surface, shadow on the object is obtained altogether.展开更多
in the design of civil and water conservancy projects, the identical slope suffice isfrequently used. Its mathematical model may be formulated as an envelope of a cone when itS vertexmoves along the cylindrical helix....in the design of civil and water conservancy projects, the identical slope suffice isfrequently used. Its mathematical model may be formulated as an envelope of a cone when itS vertexmoves along the cylindrical helix. According to the principle of conStrUcting the envelope curves of afamily of circles, the parametric equstion for the identical slope surface is established. The parametricform makes it most convenient to draw the contour lines and grade lines, and is well suited toproduce indexed projection of identical slope surface in civil and water conservancy projects.展开更多
利用希尔伯特(Hilbert)变换能够得到电力系统振荡中电流信号包络线的特点,根据系统正常运行、纯振荡以及振荡中再故障情况下包络线的不同变化趋势,采用两相电流包络线之差的突变量作为判别量,提出了一种新型的振荡中再故障判别元件,该...利用希尔伯特(Hilbert)变换能够得到电力系统振荡中电流信号包络线的特点,根据系统正常运行、纯振荡以及振荡中再故障情况下包络线的不同变化趋势,采用两相电流包络线之差的突变量作为判别量,提出了一种新型的振荡中再故障判别元件,该判别元件的计算精度不受电力系统振荡时频率变化的影响。大量 ATP 仿真证明了该元件在纯振荡过程中能够可靠不误动,并且可以快速有效地识别系统振荡中发生的各种故障。而且,文中采用的算法实现方便,计算量小,具有在工程中良好的实际应用价值。展开更多
基金National Science and Technology Major Project of China(No.2016ZX04003001)
文摘Dynamic envelope curve is a significant parameter to assess the running safety of high-speed trains.Up to now the method based on binocular stereo vision is the only way available to measure the dynamic envelope curve of a train,the speed of which is over200km/h.Nevertheless the method has two limitations,one is large field-〇f-view(FO V),the other is calibration time.Hence portable calibration equipment,easy-t〇-build target and rapid calibration algorithm are required to complete the calibration.In this paper,a new rapid on-site calibration method with large FOV based on binocular stereo vision is proposed.To address these issues,a light target has been designed,the rail coordinate system(RCS)is represented by40fixed retroreflective points on the target,and they are utilized to calibrate the parameters of two cameras.In addition,two cameras merely capture a single image of the target simultaneously,and the intrinsic and extrinsic parameters of the cameras can be calculated rapidly.To testify the proposed method,the experiments have been conducted and the results reveal that the accuracy can reach+1mm,which can meet the measurement requirement.
基金National Science and Technology Major Project(No.2016ZX04003001)
文摘High-speed vehicle dynamic envelope curve is defined as the maximum limit outline affected by a variety of adverse factors while the train is running. Considering the difficulties in the current measurement system such as complicated calibration process,cumbersome aided-instruments,strict limitation of working distance, this paper carries out an optical method in which two high-speed cameras with variable-zoom lenses are adopted as binocular stereo sensors of measurement system and a high-ac-curacy 3D target with fast reconstruction is designed. The intrinsic parameters of the sensors and the relative positions between coordinate systems are solved by the method of colinearity constrained optimization algorithm. The calibration process is easy to operate and the device is also of portability. Most importantly, the severe working distance limitation between sensors and measured body is solved, enhancing the adaptability of measurement system to environment. Experimental results show that when the sensors are in the range of 8 -16 m away from the measured body, system accuracy can reach up to ±0. 5 mm, which meets the requirements to measure the dynamic envelope curve of high-speed vehicle.
文摘The shadow of a circle casting on a unparallel plane is an ellipse, the shadow algorithm involves a perspective affine transformation. Under commonly used light, the transformation matrix for parallel circles of different diameters casting shadows onto the same plane is identical. Using AutoCAD to get the shadow of a general object of revolution, it only needs to take a series of circles along the axis of symmetry and get their corresponding shadows of ellipses, drawing an envelope to cover all these silhouettes results in the required overall shadow. Then the discrete points of shadow contour line are projected back onto the original object surface, shadow on the object is obtained altogether.
文摘in the design of civil and water conservancy projects, the identical slope suffice isfrequently used. Its mathematical model may be formulated as an envelope of a cone when itS vertexmoves along the cylindrical helix. According to the principle of conStrUcting the envelope curves of afamily of circles, the parametric equstion for the identical slope surface is established. The parametricform makes it most convenient to draw the contour lines and grade lines, and is well suited toproduce indexed projection of identical slope surface in civil and water conservancy projects.
文摘利用希尔伯特(Hilbert)变换能够得到电力系统振荡中电流信号包络线的特点,根据系统正常运行、纯振荡以及振荡中再故障情况下包络线的不同变化趋势,采用两相电流包络线之差的突变量作为判别量,提出了一种新型的振荡中再故障判别元件,该判别元件的计算精度不受电力系统振荡时频率变化的影响。大量 ATP 仿真证明了该元件在纯振荡过程中能够可靠不误动,并且可以快速有效地识别系统振荡中发生的各种故障。而且,文中采用的算法实现方便,计算量小,具有在工程中良好的实际应用价值。
