针对环境复杂的工业现场中自主定位精度低、适应性差的问题,提出一种结合人工信标和视觉的同时定位与地图构建(Simultaneous localization and mapping,SLAM)的双相机定位系统。人工信标无需覆盖全空间布置,无需具备ID信息,通过两台相...针对环境复杂的工业现场中自主定位精度低、适应性差的问题,提出一种结合人工信标和视觉的同时定位与地图构建(Simultaneous localization and mapping,SLAM)的双相机定位系统。人工信标无需覆盖全空间布置,无需具备ID信息,通过两台相机分别拍摄信标及运行视觉SLAM算法完成全空间定位,利用信标定位算法恢复单目SLAM的尺度不确定因子并且建立起两种定位算法坐标系之间的关系,因此当相机视场由信标组成的控制场覆盖范围外再次移回其覆盖范围内时,可通过SLAM算法得到的系统位姿初值实现信标和像点的快速匹配,从而再次精确定位。将双相机定位系统安装在可穿戴的头盔上,测量人员头戴头盔便可实现高精度定位。分析了双相机头盔定位系统的工作原理,并进行了试验验证。试验结果表明,该方法精度较高、适应性强,可满足在信标无法全空间覆盖的复杂工业环境下的自主定位需求。展开更多
The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied th...The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied the erosion-deposition pattern of the entire Yangtze Estuary. An alternation between erosion and deposition was found during the past 65 years, which was in correspondence to the alternation between flood and dry periods identified by multi-year average duration days of high-level water flow (defined as discharge ≥ 60,000 m<sup>3</sup>/s, namely, D<sub>≥60,000</sub>) from the Yangtze River Basin. A quantitative relationship was further developed between the erosional/depositional rate of the Yangtze Estuary and the interpreting variables of yearly water discharge, D<sub>≥60,000</sub> and yearly river sediment load, with contributing rates of 1%, 59% and 40%, respectively. Mechanism behind the alternate erosion and deposition pattern was analyzed by examining residual water surface slope and the corresponding capacity of sediment transport in flood and dry periods. In flood periods, a larger discharge results in steeper slope of residual water level which permits a greater capacity of sediment transport. Therefore, more bed materials can be washed to the sea, leading to erosion of the estuary. In contrast, flatter slope of residual water level occurs in dry periods, and deposition dominates the estuarine area due to the decreased capacity of sediment transport and the increased backwater effect of flood-tide. Coastal dynamics and estuarine engineering projects alter the local morphological changes, but slightly affect the total erosional/depositional rate of the whole estuarine region. Heavy sedimentation within the Yangtze Estuary after the impoundment of the Three Gorges Dam can be attributed to the reduced occurrence frequency of flood years due to water regulation by the dam, and largely (at least 36%-52%) sourced from the sea. Deposition is still possible to occur in the Yangtze Estuary in the future, because the multi-year average D<sub>≥60,000</sub> is unlikely to exceed the critical value of 14 days/yr which corresponds to the future equilibrium state of the Yangtze Estuary, under the water regulation of the large cascade dams in the upper Yangtze. Nevertheless, the mean depositional rate will not surpass the peak value of the past years, since the total sediment load entering the Yangtze Estuary has presented a decreasing trend.展开更多
文摘针对环境复杂的工业现场中自主定位精度低、适应性差的问题,提出一种结合人工信标和视觉的同时定位与地图构建(Simultaneous localization and mapping,SLAM)的双相机定位系统。人工信标无需覆盖全空间布置,无需具备ID信息,通过两台相机分别拍摄信标及运行视觉SLAM算法完成全空间定位,利用信标定位算法恢复单目SLAM的尺度不确定因子并且建立起两种定位算法坐标系之间的关系,因此当相机视场由信标组成的控制场覆盖范围外再次移回其覆盖范围内时,可通过SLAM算法得到的系统位姿初值实现信标和像点的快速匹配,从而再次精确定位。将双相机定位系统安装在可穿戴的头盔上,测量人员头戴头盔便可实现高精度定位。分析了双相机头盔定位系统的工作原理,并进行了试验验证。试验结果表明,该方法精度较高、适应性强,可满足在信标无法全空间覆盖的复杂工业环境下的自主定位需求。
基金Youth Project of National Natural Science Foundation of China,No.41601275Open Research Fund of Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province,No.2019SS06Scientific Research Key Project in Hunan Province Education Department,No.2014A006。
文摘The morphological changing trend of the Yangtze Estuary, the largest estuary of Asia, has become a focus of research in recent years. Based on a long series of topographic data from 1950 to 2015, this paper studied the erosion-deposition pattern of the entire Yangtze Estuary. An alternation between erosion and deposition was found during the past 65 years, which was in correspondence to the alternation between flood and dry periods identified by multi-year average duration days of high-level water flow (defined as discharge ≥ 60,000 m<sup>3</sup>/s, namely, D<sub>≥60,000</sub>) from the Yangtze River Basin. A quantitative relationship was further developed between the erosional/depositional rate of the Yangtze Estuary and the interpreting variables of yearly water discharge, D<sub>≥60,000</sub> and yearly river sediment load, with contributing rates of 1%, 59% and 40%, respectively. Mechanism behind the alternate erosion and deposition pattern was analyzed by examining residual water surface slope and the corresponding capacity of sediment transport in flood and dry periods. In flood periods, a larger discharge results in steeper slope of residual water level which permits a greater capacity of sediment transport. Therefore, more bed materials can be washed to the sea, leading to erosion of the estuary. In contrast, flatter slope of residual water level occurs in dry periods, and deposition dominates the estuarine area due to the decreased capacity of sediment transport and the increased backwater effect of flood-tide. Coastal dynamics and estuarine engineering projects alter the local morphological changes, but slightly affect the total erosional/depositional rate of the whole estuarine region. Heavy sedimentation within the Yangtze Estuary after the impoundment of the Three Gorges Dam can be attributed to the reduced occurrence frequency of flood years due to water regulation by the dam, and largely (at least 36%-52%) sourced from the sea. Deposition is still possible to occur in the Yangtze Estuary in the future, because the multi-year average D<sub>≥60,000</sub> is unlikely to exceed the critical value of 14 days/yr which corresponds to the future equilibrium state of the Yangtze Estuary, under the water regulation of the large cascade dams in the upper Yangtze. Nevertheless, the mean depositional rate will not surpass the peak value of the past years, since the total sediment load entering the Yangtze Estuary has presented a decreasing trend.
