Rolling and swaying motion estimation for a mobile robot by using omnidirectional optical flows

Described here is a method for estimating rolling and swaying motions of a mobile robot using optical flow. We have proposed an image sensor with a hyperboloidal mirror for the vision-based navigation of a mobile robot. Its name is HyperOmni Vision. The radial component of optical flow in HyperOmni Vision has a periodic characteristic. The circumferential component of optical flow has a symmetric characteristic. The proposed method makes use of these characteristic to estimate robustly the rolling and swaying motion of the mobile robot. Correspondence to: Y. Yagi e-mail: y-yagi@sys.es.osaka-u.ac.jp     

流体运动估计光流算法研究综述

对流体图像序列进行运动分析一直是流体力学、医学和计算机视觉等领域的重要研究课题。从图像对中提取的密集精确的速度矢量场能够为许多领域提供有价值的信息,基于光流法的流体运动估计技术因其独特的优势成为一个有前途的方向。光流法可以获得具有较高分辨率的密集速度矢量场,在小尺度精细结构的测量上有所改进,弥补了基于相关分析法的粒子图像测速技术的不足。此外,光流方法还可以方便的引入各种物理约束,获得较为符合流体运动特性的运动估计结果。为了全面反映基于光流法的流体运动估计算法的研究进展,本文在广泛调研相关文献的基础上,对国内外具有代表性的论文进行了系统阐述。首先介绍了光流法的基本原理,然后将现有算法按照要解决的突出问题进行分类：结合流体力学知识的能量最小化函数,提高对光照变化的鲁棒性,大位移估计和消除异常值。对每类方法,从问题解决过程的角度予以介绍,分析了各类突出问题中现有算法的特点和局限性。最后,总结分析了流体运动估计技术当前面临的问题和挑战,并对未来基于光流法的运动估计算法的研究方向和研究重点进行了展望。     

Fast optical flow using 3D shortest path techniques

Optical flow or image motion estimation is important in the area of computer vision. This paper presents a fast and reliable optical flow algorithm which produces a dense optical flow map by using fast cross correlation and 3D shortest path techniques. Fast correlation is achieved by using the box-filtering technique which is invariant to the size of the correlation window. The motion for each scanline or each column of the input image is obtained from the correlation coefficient volume by finding the best 3D path using dynamic programming techniques rather than simply choosing the position that gives the maximum cross correlation coefficient. Sub-pixel accuracy is achieved by fitting the local correlation coefficients to a quadratic surface. Typical running time for a 256×256 image is in the order of a few seconds on a 85 MHz computer. A variety of synthetic and real images have been tested, and good results have been obtained.     

Attitude estimation and control of a 3-DOF lab helicopter only based on optical flow

This paper proposes an attitude estimation method based on optical flow to solve the attitude tracking control problem for a three degree-of-freedom (3-DOF) lab helicopter. First, the relationship between optical flow and the motion of a general unmanned aerial vehicle is derived from the transformation between the image coordinate frame and the world coordinate frame. Then, an expression for the angular velocity of the 3-DOF helicopter is deduced only based on optical flow, and the attitude information is acquired by solving nonlinear equations. Finally, using visual feedback, a linear quadratic regulation (LQR) controller is designed for hovering and tracking, which consists of a feedforward controller and a LQR state feedback controller. Closed-loop experimental results on the lab helicopter demonstrate the effectiveness of the proposed estimation and control methods.     

高炉炉喉煤气流形态三维模型重建

高炉炉喉煤气流分布是表征高炉生产状况的重要因素且无法直接检测;本文提出一种基于炉顶摄像检测的高炉炉喉煤气流形态三维模型重建方法.首先建立检测系统的硬件结构,其次对煤气流形态图像预处理后,采用边缘检测算法提取图像特征,并提出基于方向链码的边缘跟踪算法,计算煤气流形态的图像坐标;最后结合摄像机内部参数并利用坐标系三维变化关系以及坐标映射关系,计算煤气流形态在三维空间的坐标,从而重建煤气流形态的三维模型.通过仿真对比高炉布料后煤气流形态发展的4个阶段的三维模型变化,估计气流形态的变化,从而估计高炉内部的煤气流分布状况,对指导高炉布料操作以及高炉稳顺运行奠定了基础.