PIRF-Nav 2.0: Fast and online incremental appearance-based loop-closure detection in an indoor environment

This paper presents a fast and online incremental solution for an appearance-based loop-closure detection problem in a dynamic indoor environment. Closing the loop in a dynamic environment has been an important topic in robotics for decades. Recently, PIRF-Nav has been reported as being successful in achieving high recall rate at precision 1. However, PIRF-Nav has three main disadvantages: (i) the computational expense of PIRF-Nav is beyond real-time, (ii) it utilizes a large amount of memory in the redundant process of keeping signatures of places, and (iii) it is ill-suited to an indoor environment. These factors hinder the use of PIRF-Nav in a general environment for long-term, high-speed mobile robotic applications. Therefore, this paper proposes two techniques: (i) new modified PIRF extraction that makes the system more suitable for an indoor environment and (ii) new dictionary management that can eliminate redundant searching and conserve memory consumption. The results show that our proposed method can complete tasks up to 12 times faster than PIRF-Nav with only a slight percentage decline in recall. In addition, we collected additional data from a university canteen crowded during lunch time. Even in this crowded indoor environment, our proposed method has better real-time processing performance compared with other methods.     

SIFT在行星表面探测器视觉导航系统中的应用

介绍了行星探测器自主导航系统的相关背景,讨论了行星探测器自主视觉导航系统算法的主要目的和传感器信息融合的必要性,并就此引入了尺度不变特征变换(SIFT)的相关理论分析.对SIFT方法提出了改进,从而改善了算法的效果.最后给出了三维重建和目标追踪的实验结果.     

基于校准靶的C形臂相机模型自动校准方法

根据校准靶标志点影像的特点,提出一种自动的离线C形臂相机模型校准方法。应用聚类算法实现标志点信息的自动识别,通过行列索引表简化标志点网格姿态的识别,自动建立标志点在影像坐标系和空间坐标系下坐标的对应关系,经几何变形校正后,实现C形臂相机的校准。实验数据证明,该方法具有良好的鲁棒性,误差小于1 mm,可应用于基于术中C形臂X线影像的手术导航系统。     

特种电动机高压阀门准确制动的仿真计算

对于特种异步电动机拖动的高压阀门 ,切断电动机交流供电电源后 ,在电机的定子绕组中通入适当的直流电流 ,产生直流磁场 ,使电机进行能耗制动 ,让阀心和电机转子的能量 ,包括动能消耗在转子的绕组中 ,达到准确停车的目的。介绍了这一过程的计算机仿真计算     

High power pulsed lasers

Pulsed high power lasers can deliver sufficient energy on inertial fusion time scales (0.1–10 ns) to heat and compress DT fuel to fusion reaction conditions. Several laser systems have been examined for application to the fusion problem. Examples are Ndglass, CO₂, KrF, and I₂, etc. A great deal of developmental effort has been applied to the Ndglass laser and the CO₂ gas laser systems. These systems now deliver >10⁴ kJ and >20×10¹² W to inertial fusion targets. The Nova Ndglass laser is being constructed to provide >200 kJ and >200×10¹² W of 1 m radiation for fusion experimentation in the mid-1980s. For inertial fusion target gain, >100 times the laser input, it is expected that the laser must deliver 3–5 MJ of energy on the 10–20 ns time scale. This paper reviews the developments in laser technology and outlines approaches to construction of a 3–5 MJ driver.     

Fusion Innovative Confinement Concepts: 2004

This paper summarizes recent progress in fusion Innovative Confinement Concepts (ICC) as reported at the 2004 ICC Workshop held May 25–28, 2004 in Madison, Wisconsin. This was the third in an annual series of workshops on this topic. The purpose of these workshops is to provide a forum for those who are thinking and working beyond what is considered to be the current state of understanding of fusion concepts.     

最小阶时分滤波器及其在运载体对准中的应用

设计一种时分降低滤波器用来进行运载体惯导系统的动态对准和传递对准，假定运载体惯导系统已标定的。在运载体水平直线运动的短时间内，两个二阶滤波以时分工作方式估计平台水平失调角，在消除水平失调角后，运载体在垂直与当地垂线的水平面内机动，此时用一个三阶（或四阶）滤波器来估计方位失调角，另外，在本文中给出该滤波器的数据压缩算法，来提高估计精度。     

A Method of Determining the Axes of a Three-Component Magnetometer Sensor with Respect to the Axes of the Navigation System of a Ferromagnetic Mobile Object

A method of determining the orientation of the axes of a three-component magnetometer sensor with respect to the axes of the navigation system of a ferromagnetic mobile object is considered, which eliminates the effect of the magnetization of the object on the determination of the angular position of the axes of the sensor with respect to the axes of the navigation system.     

GNSS/SINS/视觉导航鲁棒算法

全球导航卫星系统(Global Navigation Satellite System,GNSS)、捷联惯性导航系统(Strapdown Inertial Navigation System,SINS)和视觉传感器优势互补,3者信息融合可获得高精度、无漂移的导航定位信息.针对GNSS／SINS／视觉融合导航易受运动速度、光照变化、遮挡等影响导致定位精度和鲁棒性降低问题,本文在图优化框架的代价函数中加入SoftLOne鲁棒核函数,设置量测值粗差检验程序,降低离群点带来的负面影响.进一步,对量测值计算残差进行卡方检验,对超限残差降权处理,提高系统精度和鲁棒性.实验结果表明,本文算法较不施加鲁棒核函数、不采用异常值剔除策略和卡方检验的传统算法,以及加入其他鲁棒核函数的算法精度更高、鲁棒性更好,能够较大程度提升GNSS／SINS／视觉导航定位精度和鲁棒性,在大尺度环境下,未出现较大漂移误差,绝对位姿均方根误差0.735 m,绝对位姿误差标准差0.336 m.