基于EKF的全景视觉机器人SLAM算法

研究全景视觉机器人同时定位和地图创建（SLAM）问题。针对普通视觉视野狭窄, 对路标的连续跟踪和定位能力差的问题, 提出了一种基于改进的扩展卡尔曼滤波（EKF）算法的全景视觉机器人SLAM方法, 用全景视觉得到机器人周围的环境信息, 然后从这些信息中提取出环境特征, 定位出路标位置, 进而通过EKF算法同步更新机器人位姿和地图库。仿真实验和实体机器人实验结果验证了该算法的准确性和有效性, 且全景视觉比普通视觉定位精度更高。     

全景图像拼接的网络化感知节点自主定位系统

分析网络化感知系统节点定位问题的特殊性,针对深空探测环境未知的问题,提出利用全景图像重合度来修正信号衰减模型,提高测距精度;提出一种修正的高精度节点自主定位算法来解决多移动节点协同定位问题,该算法是把切圆法引入到基于全景图片重合度的RSSI修正定位方法中。当多个感知节点定位时,根据视距近似原则选择定位锚节点来进行H-CM算法,仿真结果表明该定位方案可以有效提高感知节点的定位精度。     

中央民族大学信息工程学院，北京100081

分析网络化感知系统节点定位问题的特殊性,针对深空探测环境未知的问题,提出利用全景图像重合度来修正信号衰减模型,提高测距精度;提出一种修正的高精度节点自主定位算法来解决多移动节点协同定位问题,该算法是把切圆法引入到基于全景图片重合度的RSSI修正定位方法中。当多个感知节点定位时,根据视距近似原则选择定位锚节点来进行H-CM算法,仿真结果表明该定位方案可以有效提高感知节点的定位精度。     

基于全景视觉的移动机器人同步定位与地图创建研究

提出了一种基于全景视觉的移动机器人同步定位与地图创建（Omni-vSLAM）方法．该方法提取 颜色区域作为视觉路标;在分析全景视觉成像原理和定位不确定性的基础上建立起系统的观测模型,定位出 路标位置,进而通过扩展卡尔曼滤波算法（EKF）同步更新机器人位置和地图信息．实验结果证明了该方法在 建立环境地图的同时可以有效地修正由里程计造成的累积定位误差．     

基于全景视觉的移动机器人地图创建与定位

提出一种高效的基于全景视觉的室内移动机器人地图构建和定位方法. 该方法充分利用全景视觉系统视野广阔、获取环境信息完整的特点, 根据全景图像生成环境描述子; 利用上述环境描述子描述环境, 创建拓扑地图, 将地图表示为环境描述子的集合. 在此基础上, 提出一种基于贝叶斯理论的定位方法, 根据当前全景摄像头的观测值, 利用已生成的地图完成状态跟踪, 全局定位和“绑架”定位. 最后通过实验验证了该方法的有效性, 并给出了计算成本分析.     

基于全景视觉与里程计的机器人自定位方法研究

通过分析全景视觉与里程计传感器的感知模型的不确定性，提出了一种基于路标观测的移动机器人自定位算法. 该算法利用卡尔曼滤波器，融合多种传感器在不同观测点获取的观测数据完成机器人自定位．与传统的、采用单一传感器自定位的方法相比，它利用视觉和里程计的互补特性，提高了自定位的精度．实验结果证明了上述方法的有效性．     

一种鲁棒高效的足球机器人自定位方法

为了解决中型组比赛环境下的足球机器人自定位问题,本文提出一种新的基于全向视觉的自定位方法,该定位方法首先从全景图像中提取出场上白线的对应点,并将其作为机器人的观测信息,然后计算观测信息与静态地图的匹配误差,且根据匹配误差的大小决定是否重新选取主位姿,最后利用梯度优化算法修正主位姿,并以主位姿信息作为定位结果,仿真结果说明了该定位方法的有效性.     

实时、鲁棒的移动机器人自主跟随算法

本文提出一种实时、鲁棒的机器人自主跟随算法.该算法先通过基于SIFT(Scale Invariant Feature Transform)的目标识别算法识别衣服图案,定位人的位置,再利用CAMSHIFT(Continuously Adaptive Mean shift)颜色跟踪算法在全景图像中实时跟踪衣服颜色,对人进行跟踪,同时通过全景成像模型定位人的相对位置,规划机器人的运动.实验表明,该算法稳定可靠,能主动寻找被跟踪对象,跟随速度快,定位精度也较可靠.     

无线传感器网络中一种自适应定位算法的实现

本文基于应用,采用事件触发机制,融合了两种已有的无线传感器网络节点自定位算法:质心算法和Dv-Hop算法,提出了一种自适应分级定位算法.该算法根据触发事件的级别使用循环求精的方法,使得定位结果满足不同的应用需求,实现了定位精度和能源开销的较好平衡.仿真实验结果显示,该算法能够满足不同的应用需求.     

全景摄像系统中展开图像的电子稳像方法研究*

深入分析和研究了全景图像的解算算法与稳像的实现方法,提出了全景摄像系统的稳像方法——基于灰度投影的电子稳像算法。该系统的硬件由全景装置、CCD、图像采集卡和计算机构成,软件编程基于DirectShow平台,通过VC++实现。通过对结果的分析表明,该算法的设计具有快速、准确的特征,是实现全景摄像系统的电子稳像的一种切实可行的方法。     

Robust and real-time self-localization based on omnidirectional vision for soccer robots

Self-localization is the basis to realize autonomous ability such as motion planning and decision-making for mobile robots, and omnidirectional vision is one of the most important sensors for RoboCup Middle Size League (MSL) soccer robots. According to the characteristic that RoboCup competition is highly dynamic and the deficiency of the current self-localization methods, a robust and real-time self-localization algorithm based on omnidirectional vision is proposed for MSL soccer robots. Monte Carlo localization and matching optimization localization, two most popular approaches used in MSL, are combined in our algorithm. The advantages of these two approaches are maintained, while the disadvantages are avoided. A camera parameters auto-adjusting method based on image entropy is also integrated to adapt the output of omnidirectional vision to dynamic lighting conditions. The experimental results show that global localization can be realized effectively while highly accurate localization is achieved in real-time, and robot self-localization is robust to the highly dynamic environment with occlusions and changing lighting conditions.     

Robust omnidirectional mobile robot topological navigation system using omnidirectional vision

Robust topological navigation strategy for omnidirectional mobile robot using an omnidirectional camera is described. The navigation system is composed of on-line and off-line stages. During the off-line learning stage, the robot performs paths based on motion model about omnidirectional motion structure and records a set of ordered key images from omnidirectional camera. From this sequence a topological map is built based on the probabilistic technique and the loop closure detection algorithm, which can deal with the perceptual aliasing problem in mapping process. Each topological node provides a set of omnidirectional images characterized by geometrical affine and scale invariant keypoints combined with GPU implementation. Given a topological node as a target, the robot navigation mission is a concatenation of topological node subsets. In the on-line navigation stage, the robot hierarchical localizes itself to the most likely node through the robust probability distribution global localization algorithm, and estimates the relative robot pose in topological node with an effective solution to the classical five-point relative pose estimation algorithm. Then the robot is controlled by a vision based control law adapted to omnidirectional cameras to follow the visual path. Experiment results carried out with a real robot in an indoor environment show the performance of the proposed method.     

Robust place recognition based on omnidirectional vision and real-time local visual features for mobile robots

Topological localization is especially suitable for human–robot interaction and robot’s high level planning, and it can be realized by visual place recognition. In this paper, bag-of-features, a popular and successful approach in pattern recognition community, is introduced to realize robot topological localization. By combining the real-time local visual features proposed by ourselves for omnidirectional vision and support vector machines, a robust and real-time visual place recognition algorithm based on omnidirectional vision is proposed. The panoramic images from the COLD database were used to perform experiments to determine the best algorithm parameters and the best training condition. The experimental results show that the robot can achieve robust topological localization with high successful rate in real time by using our algorithm.     

A novel mobile robot localization approach based on topological maps using classification with reject option in omnidirectional images

Mobile robot localization, which allows a robot to identify its position, is one of main challenges in the field of Robotics. In this work, we provide an evaluation of consolidated feature extractions and machine learning techniques from omnidirectional images focusing on topological map and localization tasks. The main contributions of this work are a novel method for localization via classification with reject option using omnidirectional images, as well as two novel omnidirectional image data sets. The localization system was analyzed in both virtual and real environments. Based on the experiments performed, the Minimal Learning Machine with Nearest Neighbors classifier and Local Binary Patterns feature extraction proved to be the best combination for mobile robot localization with accuracy of 96.7% and an Fscore of 96.6%.     

The study of path error for an omnidirectional home care mobile robot

The first objective of this research was to develop an omnidirectional home care mobile robot. A PC-based controller controls the mobile robot platform. This service mobile robot is equipped with an “indoor positioning system” and an obstacle avoidance system. The indoor positioning system is used for rapid and precise positioning and guidance of the mobile robot. The obstacle avoidance system can detect static and dynamic obstacles. In order to understand the stability of a three-wheeled omnidirectional mobile robot, we carried out some experiments to measure the rectangular and circular path errors of the proposed mobile robot in this research. From the experimental results, we found that the path error was smaller with the guidance of the localization system. The mobile robot can also return to its starting point. The localization system can successfully maintain the robot’s heading angle along a circular path.     

Localization of mobile robots with omnidirectional vision using Particle Filter and iterative SIFT

The Scale Invariant Feature Transform, SIFT, has been successfully applied to robot localization. Still, the number of features extracted with this approach is immense, especially when dealing with omnidirectional vision. In this work, we propose a new approach that reduces the number of features generated by SIFT as well as their extraction and matching time. With the help of a Particle Filter, we demonstrate that we can still localize the mobile robot accurately with a lower number of features.     

Omnidirectional vision scan matching for robot localization in dynamic environments

The localization problem for an autonomous robot moving in a known environment is a well-studied problem which has seen many elegant solutions. Robot localization in a dynamic environment populated by several moving obstacles, however, is still a challenge for research. In this paper, we use an omnidirectional camera mounted on a mobile robot to perform a sort of scan matching. The omnidirectional vision system finds the distances of the closest color transitions in the environment, mimicking the way laser rangefinders detect the closest obstacles. The similarity of our sensor with classical rangefinders allows the use of practically unmodified Monte Carlo algorithms, with the additional advantage of being able to easily detect occlusions caused by moving obstacles. The proposed system was initially implemented in the RoboCup Middle-Size domain, but the experiments we present in this paper prove it to be valid in a general indoor environment with natural color transitions. We present localization experiments both in the RoboCup environment and in an unmodified office environment. In addition, we assessed the robustness of the system to sensor occlusions caused by other moving robots. The localization system runs in real-time on low-cost hardware.     

改进SIFT用于全景视觉移动机器人定位

经典SIFT算法的计算量比较巨大,在应用到图像匹配中,尤其是多地图检索的图像匹配定位中时不能满足系统实时性的要求。可用于全景视觉传感器图像的改进SIFT算法,在不改变原算法匹配稳定性的基础上,通过修改原算法的采样规则,同时针对对复杂和简单两种情况下的图像采用不同的采样方式,使系统基本可以达到实时的效果。结果表明,改进算法可以实现高效、准确的定位。     

An efficient similarity metric for omnidirectional vision sensors

This paper presents an efficient metric for the computation of the similarity among omnidirectional images (image matching). The representation of image appearance is based on feature vectors that include both the chromatic attributes of color sets and their mutual spatial relationships. The proposed metric fits well to robotic navigation using omnidirectional vision sensors, because it has very important properties: it is reflexive, compositional and invariant with respect to image scaling and rotation. The robustness of the metric was repeatedly tested using omnidirectional images for a robot localization task in a real indoor environment.