视觉导航中的单目摄像机标定改进算法

在基于单目视觉的智能车自主导航系统中,摄像机标定是智能车实现安全准确视觉导航的前提和关键。研究摄像机理想模型和实际模型,提出一种改进的标定方法。结合线性模型和非线性模型的优点,在求解摄像机内外参数的过程中,先采用线性模型标定摄像机的一部分参数,进一步考虑简化畸变模型,将非线性方程组转化为线性方程组迭代求解,最终获得摄像机全部参数。该方法既保证了标定精度,又简化了复杂的摄像机实际模型。实验结果表明该方法能满足视觉导航要求。     

Obstacle avoidance algorithm for visual navigation using ultrasonic sensors and a CCD camera

An obstacle-avoidance algorithm is presented for autonomous mobile robots equipped with a CCD camera and ultrasonic sensors. This approach uses segmentation techniques to segregate the floor from other fixtures, and measurement techniques to measure the distance between the mobile robot and any obstacles. It uses a simple computation for the selection of a threshold value. This approach also uses a cost function, which is combined with image information, distance information, and a weight factor, to find an obstacle-free path. This algorithm, which uses a CCD camera and ultrasonic sensors, can be used for cases including shadow regions, and obstacles in visual navigation and in various lighting conditions. This work was presented in part at the 7th International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002     

Human navigation and mapping with a 6DOF IMU and a laser scanner

This article focuses on human navigation, by proposing a system for mapping and self-localization based on wearable sensors, i.e., a laser scanner and a 6 Degree-of-Freedom Inertial Measurement Unit (6DOF IMU) fixed on a helmet worn by the user. The sensor data are fed to a Simultaneous Localization And Mapping (SLAM) algorithm based on particle filtering, an approach commonly used for mapping and self-localization in mobile robotics. Given the specific scenario considered, some operational hypotheses are introduced in order to reduce the effect of a well-known problem in IMU-based localization, i.e., position drift. Experimental results show that the proposed solution leads to improvements in the quality of the generated map with respect to existing approaches.     

Simultaneous estimation of ego-motion and vehicle distance by using a monocular camera

Auto navigation and vehicle distance estimation are of the critical importance in intelligent vehicles. This paper proposes a novel approach to solve these two problems simultaneously by using a monocular camera. First, we introduce an incremental depth parameterized model to overcome the scale ambiguity problem in monocular vision, which differs from other parameterized models with reduced state-dimension and consistent observability. In addition, the view-field of camera is divided into static and dynamic parts so that the ego- motion and vehicle-space can be calculated simultaneously. Outdoor experiments are implemented to validate the effectiveness of the proposed approach.     

仿生机器人视觉导航研究分析

视觉导航技术是保证机器人自主移动的关键技术之一。为了从整体上把握当前国际上最新的视觉导航研究动态,全面评述了仿生机器人视觉导航技术的研究进展,重点分析了视觉SLAM(Simultaneous Local-ization and Mapping)、闭环探测、视觉返家三个关键问题的研究现状及存在的问题。提出了一个新的视觉SLAM算法框架,给出了待解决的关键理论问题,并对视觉导航技术发展的难点及未来趋势进行了总结。     

Biologically inspired visual odometer for navigation of a flying robot

Experimental research in biology has uncovered a number of different ways in which flying insects use cues derived from optical flow for navigational purposes, such as safe landing, obstacle avoidance and dead reckoning. In this study, we use a synthetic methodology to gain additional insights into the navigation behavior of bees. Specifically, we focus on the mechanisms of course stabilization behavior and visually mediated odometer by using a biological model of motion detector for the purpose of long-range goal-directed navigation in 3D environment. The performance tests of the proposed navigation method are conducted by using a blimp-type flying robot platform in uncontrolled indoor environments. The result shows that the proposed mechanism can be used for goal-directed navigation. Further analysis is also conducted in order to enhance the navigation performance of autonomous aerial vehicles.     

视觉—惯性导航定位技术研究进展

视觉—惯性导航定位技术是一种利用视觉传感器和惯性传感器实现载体的自定位和周围环境感知的无源导航定位方式,可以在全球定位系统（global positioning system,GPS）拒止环境下实现载体6自由度位姿估计。视觉和低精度惯性传感器具有体积小和价格低的优势,得益于二者在导航定位任务中的互补特性,视觉—惯性导航系统（visual inertial navigation system,VINS）引起了极大关注,在移动端的虚拟现实（virtual reality,VR）、增强现实（augmented reality,AR）以及无人系统的自主导航任务中发挥了重要作用,具有重要的理论研究价值和实际应用需求。本文介绍视觉—惯性导航系统,总结概括该系统中初始化、视觉前端处理、状态估计、地图的构建与维护以及信息融合等关键技术的研究进展。对非理想环境下及基于学习方法的视觉—惯性导航定位算法等热点问题进行综述,总结用于算法评测的方法及标准数据集,阐述该技术在实际应用中所面临的主要问题,并针对这些问题对该领域未来的发展趋势进行展望。     

使用单目视觉的移动机器人导航方法

机器视觉与机器人的结合是未来机器人行业发展的一大趋势。在移动机器人的避障导航方案中,使用传统的传感器存在诸多问题,且获取的信息有限。提出一种基于单目视觉的移动机器人导航算法,在算法应用中,如果使用镜头焦距已知的相机,则无需对相机标定。为降低光照对障碍物边缘检测的影响,将机器人拍摄的彩色图像转换到HSI空间。采用canny算法对转换后的分量分别进行边缘检测,并合成检测结果。通过阈值处理过滤合成边缘,去除弱边缘信息,提高检测准确度。采用形态学处理连接杂散边缘,通过区域生长得到非障碍区域,并由几何关系建立图像坐标系与机器人坐标系之间的映射关系。利用结合隶属度函数的模糊逻辑得出机器人控制参数。实验结果表明,对图像颜色空间的转换降低了地面反光、阴影的影响,算法能有效排除地面条纹等的干扰并准确检测出障碍物边缘,而模糊逻辑决策方法提高了算法的鲁棒性和结果的可靠性。     

Indoor navigation of a non-holonomic mobile robot using a visual memory

When navigating in an unknown environment for the first time, a natural behavior consists on memorizing some key views along the performed path, in order to use these references as checkpoints for a future navigation mission. The navigation framework for wheeled mobile robots presented in this paper is based on this assumption. During a human-guided learning step, the robot performs paths which are sampled and stored as a set of ordered key images, acquired by an embedded camera. The set of these obtained visual paths is topologically organized and provides a visual memory of the environment. Given an image of one of the visual paths as a target, the robot navigation mission is defined as a concatenation of visual path subsets, called visual route. When running autonomously, the robot is controlled by a visual servoing law adapted to its nonholonomic constraint. Based on the regulation of successive homographies, this control guides the robot along the reference visual route without explicitly planning any trajectory. The proposed framework has been designed for the entire class of central catadioptric cameras (including conventional cameras). It has been validated onto two architectures. In the first one, algorithms have been implemented onto a dedicated hardware and the robot is equipped with a standard perspective camera. In the second one, they have been implemented on a standard PC and an omnidirectional camera is considered.

Rotation estimation for mobile robot based on single-axis gyroscope and monocular camera

The rotation matrix estimation problem is a keypoint for mobile robot localization, navigation, and control. Based on the quaternion theory and the epipolar geometry, an extended Kalman filter (EKF) algorithm is proposed to estimate the rotation matrix by using a single-axis gyroscope and the image points correspondence from a monocular camera. The experimental results show that the precision of mobile robot s yaw angle estimated by the proposed EKF algorithm is much better than the results given by the image-only and gyroscope-only method, which demonstrates that our method is a preferable way to estimate the rotation for the autonomous mobile robot applications.     

Simultaneously learning to recognize and control a low-cost robotic arm

In this paper, we present a visual servoing method based on a learned mapping between feature space and control space. Using a suitable recognition algorithm, we present and evaluate a complete method that simultaneously learns the appearance and control of a low-cost robotic arm. The recognition part is trained using an action precedes perception approach. The novelty of this paper, apart from the visual servoing method per se, is the combination of visual servoing with gripper recognition. We show that we can achieve high precision positioning without knowing in advance what the robotic arm looks like or how it is controlled.     

基于多传感器信息融合的移动机器人导航综述

综述了自主式移动机器人导航技术,对其中的同步定位与地图创建、路径规划以及多传感器信息融合等技术进行了详细的分析,并从基于地图、基于环境和基于行为3个方面全面地阐述了移动机器人路径规划技术的研究现状.对当前的研究热点SLAM技术、遗传算法和基于行为的规划算法等进行了较为详细的介绍和分析.同时,展望了移动机器人导航技术的发展趋势.     

Centering behavior with a mobile robot using monocular foveated vision

A system for corridor following based on properties of the human visual system is presented. The robot extracts image features using an interest operator to compute sparse optical flow induced by the translatory motion of the robot. The available status information from the robot is used to compensate for the known rotatory movement of the image. Control of the robot is done by transforming the optical flow to ego-motion complex log space. The difference between the median flow extracted from the left and right peripheral visual areas is used to control the heading of the robot. Forward velocity is controlled by trying to keep the perceived optical flow constant.     

低成本组合导航系统滤波算法的研究

本文将扩展卡尔曼滤波(EKF)应用于GPS/DR组合导航系统中,以解决系统观测方程的非线性问题。同时,针对组合导航系统松组合和紧组合不同组合方式对导航精度的影响进行了详细的比较,并对仿真结果进行了分析,从整体上给出一种最优的组合方式。仿真结果证明,基于EKF方法的GPS/DR组合导航采用紧组合方式具有更高的定位精度,系统获得更良好的性能。     

捷联惯导互补滤波姿态融合算法设计

为了满足低成本、高性能的载体测姿需求,针对MEMS器件漂移导致载体姿态无法准确测量的问题,提出了一种基于方向余弦矩阵（DCM）更新的多轴显式互补滤波载体姿态估计算法。利用陀螺仪和辅助传感器的噪声所处频段互补的特点,运用互补滤波进行信息融合,发挥各个传感器的优点,提升系统的姿态测量精度。分别以三轴转台与实验车辆为验证平台,设计了静态与动态实验。实验结果表明,该姿态融合算法能够稳定输出高精度的姿态信息,抑制陀螺漂移导致的姿态发散,有效提高载体姿态的测量精度,满足捷联惯导系统的测姿需求。     

A variant of navigation of a mobile robot with the help of a camera

The navigation problem for a mobile robot in indoor environment is considered. A camera, rigidly attached to the object and observing markers placed on the ceiling, is the main source of navigation data. Additional data are provided by odometry devices and is processed by an algorithm based on approximate integration of the equations of nonholonomic constraints.     

Ranging-aided relative navigation of multi-platforms

This paper proposes a relative attitude and distance estimation algorithm based on pairwise range measurements between vehicles as well as inertial measurement of each platform. The solution of Wahba''s Problem is introduced to compute the relative attitude between multi-platforms with the sampled pairwise ranges, in which the relative distance estimation is derived and the estimation error distributions are analyzed. An extended Kalman filter is designed to fuse the estimated attitude and distance with the inertial measurement of each platform. The relative poses between platforms are determined without any external aided measurement. To show this novelty, a real testbed is constructed by our research lab. And the experiment results are positive.     

Design and testing of a low-cost robotic wheelchair prototype

Many people who are mobility impaired are, for a variety of reasons, incapable of using an ordinary wheelchair. In some instances, a power wheelchair also cannot be used, usually because of the difficulty the person has in controlling it (often due to additional disabilities). This paper describes two low-cost robotic wheelchair prototypes that assist the operator of the chair in avoiding obstacles, going to pre-designated places, and maneuvering through doorways and other narrow or crowded areas. These systems can be interfaced to a variety of input devices, and can give the operator as much or as little moment by moment control of the chair as they wish. This paper describes both systems, the evolution from one system to another, and the lessons learned.     

Learners' evaluation of a navigation support tool in distance education

Abstract   This article investigates the usability of a navigation support tool, which guides learners by generating advice on the next best step to take in a self-study e-learning course. The article draws on log data and responses from online questionnaires to provide insights into learners' evaluation of the tool, their adherence to the advice and their expectations of self-efficacy. The theoretical underpinnings of the work are described together with the experimental set-up. Results show that more than half of the learners in the experimental group adhered to the advice and held the opinion that the advice stimulated them to proceed with the course. Learners expressed a need to know what the advice was based on which can be seen as an essential element in future development of the tool.     

火星探测器转移轨道的自主导航方法

本文针对转移轨道火星探测器对自主导航的迫切需求,提出了一种基于小行星和X射线脉冲星交互观测的自主导航方法,并结合工程任务对上述量测信息的获取方式和获取条件进行了研究,仿真结果表明,与单独基于小行星或单独基于X射线脉冲星观测的自主导航系统相比,该方法不仅可获得更高的导航精度,为转移轨道中途修正提供准确的轨道信息,且工程实现简单,是一种可行的转移轨道火星探测器自主导航方案,可为我国火星探测器自主导航系统的设计提供参考.