针对大多数同时定位与地图构建(simultaneous localization and mapping,SLAM)系统在动态场景下位姿估计不准确的问题,本文提出了一个基于语义先验的加权极线和深度约束的运动一致性检测算法,以此构建一个室内动态场景下的视觉SLAM系统...针对大多数同时定位与地图构建(simultaneous localization and mapping,SLAM)系统在动态场景下位姿估计不准确的问题,本文提出了一个基于语义先验的加权极线和深度约束的运动一致性检测算法,以此构建一个室内动态场景下的视觉SLAM系统.该系统首先对输入图像进行语义分割,获取潜在运动特征点集合;其次对图像非潜在运动区域进行特征点提取,获取帧间变换的初值,利用加权的极线约束和深度约束完成对潜在外点(如运动特征点)的二次判断,并将外点移除从而更新静态特征点集合.最后利用静态特征点集实现对相机位姿的精确求解,并作为位姿优化的初值送入后端.本文在TUM(慕尼黑工业大学)数据集上的9个动态场景序列以及波恩复杂动态环境数据集的3个图像序列上进行了多次对比测试,其绝对轨迹误差(ATE)的均方根误差(RMSE)与现有先进的动态SLAM系统DS-SLAM相比降低了10.53%~93.75%,对于平移和旋转相对位姿误差(RPE),RMSE指标最高实现73.44%和68.73%的下降.结果表明,改进的方法能够显著降低动态环境下的位姿估计误差.展开更多
The aim of this study is to propose a novel system that has an ability to detect intra-fractional motion during radiotherapy treatment in real-time using three-dimensional surface taken by a depth camera, Microsoft Ki...The aim of this study is to propose a novel system that has an ability to detect intra-fractional motion during radiotherapy treatment in real-time using three-dimensional surface taken by a depth camera, Microsoft Kinect v1. Our approach introduces three new aspects for three-dimensional surface tracking in radiotherapy treatment. The first aspect is a new algorithm for noise reduction of depth values. Ueda’s algorithm was implemented and enabling a fast least square regression of depth values. The second aspect is an application for detection of patient’s motion at multiple points in thracoabdominal regions. The third aspect is an estimation of three-dimensional surface from multiple depth values. For evaluation of noise reduction by Ueda’s algorithm, two respiratory patterns are measured by the Kinect as well as a laser range meter. The resulting cross correlation coefficients between the laser range meter and the Kinect were 0.982 for abdominal respiration and 0.995 for breath holding. Moreover, the mean cross correlation coefficients between the signals of our system and the signals of Anzai with respect to participant’s respiratory motion were 0.90 for thoracic respiration and 0.93 for abdominal respiration, respectively. These results proved that the performance of the developed system was comparable to existing motion monitoring devices. Reconstruction of three-dimensional surface also enabled us to detect the irregular motion and breathing arrest by comparing the averaged depth with predefined threshold values.展开更多
The flexural-gravity wave responses due to a load steadily moving or suddenly accelerated along a rectilinear orbit are analytically studied within the framework of the linear potential theory. A thin viscoelastic pla...The flexural-gravity wave responses due to a load steadily moving or suddenly accelerated along a rectilinear orbit are analytically studied within the framework of the linear potential theory. A thin viscoelastic plate model is used for a very large floating structure. The initially quiescent fluid in the ocean is assumed to be homogenous, incompressible, and inviscid, and the disturbed motion be irrotational. A moving line source on the plate surface is considered as a moving point in the two-dimensional coordinates. Under the assumptions of small-amplitude wave motion and small plate deflection, a linear fluid-plate coupling model is established. The integral solutions for the surface deflections and the wave resistances are analytically obtained by the Fourier transform method. To study the dynamic characteristics of the flexural-gravity wave response, the asymptotic representations of the wave resistances are derived by the residue theorem and the methods of stationary phase. It shows that the steady wave resistance is zero when the speed of moving load is less than the minimal phase speed. The wave resistances due to the accelerate motion consist of two parts, namely the steady and transient wave responses. Eventually the transient wave resistance declines toward zero and the wave resistance approaches the steady component as the time goes to the infinity. Furthermore, the effect of the strain relaxation time for this viscoelastic plate is studied and it exhibits more influence for a high-speed motion.展开更多
Generation of a depth-map from 2D video is the kernel of DIBR (Depth Image Based Rendering) in 2D-3D video conversion systems. However it occupies over most of the system resource where the motion search module takes ...Generation of a depth-map from 2D video is the kernel of DIBR (Depth Image Based Rendering) in 2D-3D video conversion systems. However it occupies over most of the system resource where the motion search module takes up 90% time-consuming in typical motion estimation-based depth-map generation algorithms. In order to reduce the computational complexity, in this paper a new fast depth-map generation algorithm based on motion search is developed, in which a fast diamond search algorithm is adopted to decide whether a 16x16 or 4x4 block size is used based on Sobel operator in the motion search module to obtain a sub-depth-map. Then the sub-depth-map will be fused with the sub-depth-maps gotten from depth from color component Cr and depth from linear perspective modules to compensate and refine detail of the depth-map, finally obtain a better depth-map. The simulation results demonstrate that the new approach can greatly reduce over 50% computational complexity compared to other existing methods.展开更多
文摘针对大多数同时定位与地图构建(simultaneous localization and mapping,SLAM)系统在动态场景下位姿估计不准确的问题,本文提出了一个基于语义先验的加权极线和深度约束的运动一致性检测算法,以此构建一个室内动态场景下的视觉SLAM系统.该系统首先对输入图像进行语义分割,获取潜在运动特征点集合;其次对图像非潜在运动区域进行特征点提取,获取帧间变换的初值,利用加权的极线约束和深度约束完成对潜在外点(如运动特征点)的二次判断,并将外点移除从而更新静态特征点集合.最后利用静态特征点集实现对相机位姿的精确求解,并作为位姿优化的初值送入后端.本文在TUM(慕尼黑工业大学)数据集上的9个动态场景序列以及波恩复杂动态环境数据集的3个图像序列上进行了多次对比测试,其绝对轨迹误差(ATE)的均方根误差(RMSE)与现有先进的动态SLAM系统DS-SLAM相比降低了10.53%~93.75%,对于平移和旋转相对位姿误差(RPE),RMSE指标最高实现73.44%和68.73%的下降.结果表明,改进的方法能够显著降低动态环境下的位姿估计误差.
文摘The aim of this study is to propose a novel system that has an ability to detect intra-fractional motion during radiotherapy treatment in real-time using three-dimensional surface taken by a depth camera, Microsoft Kinect v1. Our approach introduces three new aspects for three-dimensional surface tracking in radiotherapy treatment. The first aspect is a new algorithm for noise reduction of depth values. Ueda’s algorithm was implemented and enabling a fast least square regression of depth values. The second aspect is an application for detection of patient’s motion at multiple points in thracoabdominal regions. The third aspect is an estimation of three-dimensional surface from multiple depth values. For evaluation of noise reduction by Ueda’s algorithm, two respiratory patterns are measured by the Kinect as well as a laser range meter. The resulting cross correlation coefficients between the laser range meter and the Kinect were 0.982 for abdominal respiration and 0.995 for breath holding. Moreover, the mean cross correlation coefficients between the signals of our system and the signals of Anzai with respect to participant’s respiratory motion were 0.90 for thoracic respiration and 0.93 for abdominal respiration, respectively. These results proved that the performance of the developed system was comparable to existing motion monitoring devices. Reconstruction of three-dimensional surface also enabled us to detect the irregular motion and breathing arrest by comparing the averaged depth with predefined threshold values.
基金Project supported by the National Natural Science Foundation of China(Grant No.11472166)the State Key Laboratory of Hydraulic Engineering Simulation and Safety at Tianjin University(Grant No.HESS-1506)the National Key Basic Research Development Program of China(973 Program,Grant No.2014 CB046203)
文摘The flexural-gravity wave responses due to a load steadily moving or suddenly accelerated along a rectilinear orbit are analytically studied within the framework of the linear potential theory. A thin viscoelastic plate model is used for a very large floating structure. The initially quiescent fluid in the ocean is assumed to be homogenous, incompressible, and inviscid, and the disturbed motion be irrotational. A moving line source on the plate surface is considered as a moving point in the two-dimensional coordinates. Under the assumptions of small-amplitude wave motion and small plate deflection, a linear fluid-plate coupling model is established. The integral solutions for the surface deflections and the wave resistances are analytically obtained by the Fourier transform method. To study the dynamic characteristics of the flexural-gravity wave response, the asymptotic representations of the wave resistances are derived by the residue theorem and the methods of stationary phase. It shows that the steady wave resistance is zero when the speed of moving load is less than the minimal phase speed. The wave resistances due to the accelerate motion consist of two parts, namely the steady and transient wave responses. Eventually the transient wave resistance declines toward zero and the wave resistance approaches the steady component as the time goes to the infinity. Furthermore, the effect of the strain relaxation time for this viscoelastic plate is studied and it exhibits more influence for a high-speed motion.
文摘Generation of a depth-map from 2D video is the kernel of DIBR (Depth Image Based Rendering) in 2D-3D video conversion systems. However it occupies over most of the system resource where the motion search module takes up 90% time-consuming in typical motion estimation-based depth-map generation algorithms. In order to reduce the computational complexity, in this paper a new fast depth-map generation algorithm based on motion search is developed, in which a fast diamond search algorithm is adopted to decide whether a 16x16 or 4x4 block size is used based on Sobel operator in the motion search module to obtain a sub-depth-map. Then the sub-depth-map will be fused with the sub-depth-maps gotten from depth from color component Cr and depth from linear perspective modules to compensate and refine detail of the depth-map, finally obtain a better depth-map. The simulation results demonstrate that the new approach can greatly reduce over 50% computational complexity compared to other existing methods.
