基于遗传算法的运动物体实时识别

文章提出了一种应用遗传算法对一个已知几何模型的运动目标物体的位置与方向进行识别的方法,这种对运动目标的识别可以用于机器人手臂实时视觉伺服控制中。文章以一个三角形的物体为目标,对所提出的方法进行了仿真试验,结果证实了这种识别方法的有效性。     

基于手眼视觉的两种目标位姿测量法仿真分析

空间机器人手眼视觉系统利用合作目标物体上的合作特征点对目标物体进行位姿估计,以完成跟踪捕捉任务。针对空间机器人实时性的要求,给出了两种实时性较好的4个特征点的位姿测量算法,并且在相同仿真环境下对两种P4P位姿算法进行了分析比较。仿真结果表明:四面体体积测量的位姿测量算法对特征点的像点量化误差更加敏感,位姿测量结果偏差较大;坐标变换的位姿测量算法稳定,精度较高。后者在实际应用中,可以达到更高的精度。     

基于物体逻辑状态推理的未知物体视觉分割

为提高机器人的视觉感知能力,提出了一种新颖的基于物体逻辑状态推理的未知物体视觉分割方法.在语义层定义物体逻辑状态空间,根据机器人抓取动作反馈对物体逻辑状态进行推理.在数据层利用RGB-D摄像头采集生成场景3维着色点云,基于物体放置于支撑平面的假设,对所有可能的物体点进行空间聚类和分割,得到初始未知物体集并生成物体初始逻辑状态表示.当物体逻辑状态发生变化时,根据设定规则结合点集运算对物体点云进行重新分割,物体点云集的变化又用于指导物体逻辑状态空间的更新.在7自由度移动机械手系统上,进行了真实积木模拟环境下未知物体的视觉分割与抓取实验,实验结果证实本文方法可以有效提升机器人的视觉感知能力.     

双目立体视觉的目标识别与定位

双目立体视觉系统可以实现对目标的识别与定位.此系统包含摄像机标定、图像分割、立体匹配和三维测距4个模块.在摄像机标定部分,提出了基于云台转角的外参数估计方法.该方法可以精确完成摄像头旋转情况下外参的估计,增强了机器人的视觉功能.并利用广茂达机器人系统,基于改进的双目视觉系统进行目标识别与定位,以此结果作为依据控制机器人的手臂进行相应运动,最终实现了对目标物体的抓取,验证了提出方法的可行性.     

一种高级机器人语言中的视觉功能及其引入方法

本文讨论了一种在高级机器人语言RAPT中使用视觉信息的方法.在这个方法中,视觉 信息主要用来发现机器人工作环境中物体的预期位置与实际位置间的差异,并对机器人的动 作进行相应的调整.符号推理系统使得大量的视觉信息处理工作得以在编译阶段进行,以保 证在程序运行阶段视觉系统工作的实时性.视觉信息框架结构使得机器人系统可以充分地利 用视觉信息,以更新其有关工作环境状态的信息.     

足球机器人视觉系统光强自适应算法研究

研究足球机器人比赛问题,比赛环境的光强度变化严重影响足球机器人视觉系统的识别性能.为提高机器人视觉识别率,提出了一种基于HSI颜色空间模型的光强自适应算法.算法将比赛场地划分为若干区域,利用HSI颜色空间模型可以分离环境光强度信息的特点,在比赛中动态更新所有划分区域的HSI颜色空间,提高了机器人视觉系统对光强变化的自适应能力,实现了机器人对比赛场地信息的精确辨识.因此用算法优化机器人视觉识别系统进行仿真.结果表明,在实际比赛中,算法能够有效降低环境光强度变化,大大提高了对足球机器人视觉辨识性能.     

通用型“手—眼”式多关节机器人视觉系统物像关系的研究

本文着重研究了“手-眼”式通用型多关节机器人视觉系统中基体坐标系.物体坐标系和图象坐标系之间的关系.利用空间坐标系的投影变换和映射等方法,推导了“手-眼”式机器人系统中摄象机图象点和空间点对应的数学关系式.同时对固定式也进行了探讨.本文以多关节机器人视觉系统的实际情况为基础,在实际的机器人坐标系上导出了一个简便实用的算法,可以通过对摄象机摄取的图象中的点的坐标运算,求出其对应的空间点在机器人基体坐标中的坐标,因而能迅速准确地引导机器人根据视觉图象正确地运行到所求的空间点的位置.     

无线传感网络火灾监测与营救系统的研究

描述了一个利用安装了传感器节点的具有自动搜索路径和营救功能的机器人,通过无线传感器网络在某监测区域内完成营救工作的仿真实验;将无线传感器网络的思想应用到空间探索和灾难营救是当今世界比较关注的研究方向,人类面对很多救援工作都是无能为力,或者即使可以尝试但危险系数很大;应用机器人到人类不方便到达的区域或者危险区域完成救援工作,不仅降低了救援人员的危险系数,而且提高了工作效率.在文章中是通过利用此系统来完成救火任务的实例来介绍系统的功能和具体实现的算法,仿真表明可以满足无线传感器网络系统的实际应用.     

具有深度自适应估计的视觉伺服优化

在手眼机器人视觉伺服中,如何确定机器人末端摄像机移动的速度和对物体的深度进行有效的估计还没有较好的解决方法.本文采用一般模型法,通过求解最优化控制问题来设计摄像机的速度,同时,利用物体初始及期望位置的深度估计值,提出了一种自适应估计的算法对物体的深度进行估计,给出了深度变化趋势,实现了基于图像的定位控制.该方法能够使机器人在工作空间范围内从任一初始位置出发到达期望位置,实现了系统的全局渐近稳定且不需要物体的几何模型及深度的精确值.最后给出的仿真实例表明了本方法的有效性.     

基于动作选择级的多机器人协作

在多机器人环境中,由于每个机器人动作选择的重叠现象,让机器人之间的协作变得很差.提出了一个方法用于确定动作选择级别.在此基础上,可以很好地控制多机器人的协作行为的获取.首先,定义了用于动作选择级优先级的8个级别,这8个级别相应的映射到8个动作子空间.然后,利用局部势场法,每个机器人的动作选择优先级被计算出来,并且因此,每个机器人获得了各自需要搜索的动作子空间.在动作子空间中,每个机器人利用加强学习方法来选择一个适当的动作.最终,把该方法用于机器人足球比赛的机器人局部协作训练中.试验的效果在仿真和实际比赛中得到了证实.     

GA-pattern matching-based manipulator control system for real-time visual servoing

_—In robotic applications, tasks of picking and placing are the most fundamental ones. Also, for a robot manipulator, the recognition of its working environment is one of the most important issues to do intelligent tasks, since this aptitude enables it to work in a variable environment. This paper presents a new control strategy for robot manipulators, which utilizes visual information to direct the manipulator in its working space, to pick up an object of known shape, but with arbitrary position and orientation. During the search for an object to be picked up, vision-based control by closed-loop feedback, referred to as visual servoing, is performed to obtain the motion control of the manipulator hand. The system employs a genetic algorithm (GA) and a pattern matching technique to explore the search space and exploit the best solutions by this search technique. The control strategy utilizes the found results of GA-pattern matching in every step of GA evolution to direct the manipulator towards the target object. We named this control strategy step-GA-evnlution. This control method can be applied for manipulator real-time visual servoing and solve its path planning problem in real-time, i.e. in order for the manipulator to adapt the execution of the task by visual information during the process execution. Simulations have been performed, using a two-link planar manipulator and three image models, in order to find which one is the best for real-time visual servoing and the results show the effectiveness of the control method.     

利用平面单应分解实现服务机器人视觉伺服

智能空间中家庭服务机器人所需完成的主要任务是协助人完成物品的搜寻、定位与传递。而视觉伺服则是完成上述任务的有效手段。搭建了由移动机器人、机械臂、摄像头组成的家庭服务机器人视觉伺服系统,建立了此系统的运动学模型并对安装在机械臂末端执行器上的视觉系统进行了内外参数标定,通过分解世界平面的单应来获取目标物品的位姿参数,利用所获取的位姿参数设计了基于位置的视觉伺服控制律。实验结果表明,使用平面单应分解方法来设计控制律可简单有效地完成家庭物品的视觉伺服任务。     

Intelligent control of a robot manipulator by visual feedback

We present a new approach to visual feedback control using image-based visual servoing with stereo vision. In order to control the position and orientation of a robot with respect to an object, a new technique is proposed using binocular stereo vision. The stereo vision enables us to calculate an exact image Jacobian not only at around a desired location, but also at other locations. The suggested technique can guide a robot manipulator to the desired location without needing such a priori knowledge as the relative distance to the desired location or a model of the object, even if the initial positioning error is large. We describes a model of stereo vision and how to generate feedback commands. The performance of the proposed visual servoing system is illustrated by a simulation and by experimental results, and compared with the conventional method for an assembling robot. This work was presented in part at the Fourth International Symposium on Artificial Life and Robotics, Oita, Japan, January 19–22, 1999     

Uncalibrated Eye-to-Hand Visual Servoing Using Inverse Fuzzy Models

A new uncalibrated eye-to-hand visual servoing based on inverse fuzzy modeling is proposed in this paper. In classical visual servoing, the Jacobian plays a decisive role in the convergence of the controller, as its analytical model depends on the selected image features. This Jacobian must also be inverted online. Fuzzy modeling is applied to obtain an inverse model of the mapping between image feature variations and joint velocities. This approach is independent from the robot's kinematic model or camera calibration and also avoids the necessity of inverting the Jacobian online. An inverse model is identified for the robot workspace, using measurement data of a robotic manipulator. This inverse model is directly used as a controller. The inverse fuzzy control scheme is applied to a robotic manipulator performing visual servoing for random positioning in the robot workspace. The obtained experimental results show the effectiveness of the proposed control scheme. The fuzzy controller can position the robotic manipulator at any point in the workspace with better accuracy than the classic visual servoing approach.     

Detection and tracking for robotic visual servoing systems

Robot manipulators require knowledge about their environment in order to perform their desired actions. In several robotic tasks, vision sensors play a critical role by providing the necessary quantity and quality of information regarding the robot's environment. For example, “visual servoing” algorithms may control a robot manipulator in order to track moving objects that are being imaged by a camera. Current visual servoing systems often lack the ability to detect automatically objects that appear within the camera's field of view. In this research, we present a robust “figureiground” framework for visually detecting objects of interest. An important contribution of this research is a collection of optimization schemes that allow the detection framework to operate within the real-time limits of visual servoing systems. The most significant of these schemes involves the use of “spontaneous” and “continuous” domains. The number and location of continuous domains are. allowed to change over time, adjusting to the dynamic conditions of the detection process. We have developed actual servoing systems in order to test the framework's feasibility and to demonstrate its usefulness for visually controlling a robot manipulator.     

Neural network Reinforcement Learning for visual control of robot manipulators

It is known that most of the key problems in visual servo control of robots are related to the performance analysis of the system considering measurement and modeling errors. In this paper, the development and performance evaluation of a novel intelligent visual servo controller for a robot manipulator using neural network Reinforcement Learning is presented. By implementing machine learning techniques into the vision based control scheme, the robot is enabled to improve its performance online and to adapt to the changing conditions in the environment. Two different temporal difference algorithms (Q-learning and SARSA) coupled with neural networks are developed and tested through different visual control scenarios. A database of representative learning samples is employed so as to speed up the convergence of the neural network and real-time learning of robot behavior. Moreover, the visual servoing task is divided into two steps in order to ensure the visibility of the features: in the first step centering behavior of the robot is conducted using neural network Reinforcement Learning controller, while the second step involves switching control between the traditional Image Based Visual Servoing and the neural network Reinforcement Learning for enabling approaching behavior of the manipulator. The correction in robot motion is achieved with the definition of the areas of interest for the image features independently in both control steps. Various simulations are developed in order to present the robustness of the developed system regarding calibration error, modeling error, and image noise. In addition, a comparison with the traditional Image Based Visual Servoing is presented. Real world experiments on a robot manipulator with the low cost vision system demonstrate the effectiveness of the proposed approach.     

Vision-based integrated system for object inspection and handling

Image-based effector servoing is a process of perception–action cycles for handling a robot effector under continual visual feedback. This paper applies visual servoing mechanisms not only for handling objects, but also for camera calibration and object inspection. A 6-DOF manipulator and a stereo camera head are mounted on separate platforms and are steered independently. In a first phase (calibration phase), camera features are determined like the optical axes and the fields of sharp view. In the second phase (inspection phase), the robot hand carries an object into the field of view of one camera, then approaches the object along the optical axis to the camera, rotates the object for reaching an optimal view, and finally the object shape is inspected in detail. In the third phase (assembly phase), the system localizes a board containing holes of different shapes, determines the hole which fits most appropriate to the object shape, then approaches and arranges the object appropriately. The final object insertion is based on haptic sensors, but is not treated in the paper. At present, the robot system has the competence to handle cylindrical and cuboid pegs. For handling other object categories the system can be extended with more sophisticated strategies of the inspection and/or assembly phase.     

Visual servoing of redundant manipulator with Jacobian matrix estimation using self-organizing map

Vision based redundant manipulator control with a neural network based learning strategy is discussed in this paper. The manipulator is visually controlled with stereo vision in an eye-to-hand configuration. A novel Kohonen’s self-organizing map (KSOM) based visual servoing scheme has been proposed for a redundant manipulator with 7 degrees of freedom (DOF). The inverse kinematic relationship of the manipulator is learned using a Kohonen’s self-organizing map. This learned map is shown to be an approximate estimate of the inverse Jacobian, which can then be used in conjunction with the proportional controller to achieve closed loop servoing in real-time. It is shown through Lyapunov stability analysis that the proposed learning based servoing scheme ensures global stability. A generalized weight update law is proposed for KSOM based inverse kinematic control, to resolve the redundancy during the learning phase. Unlike the existing visual servoing schemes, the proposed KSOM based scheme eliminates the computation of the pseudo-inverse of the Jacobian matrix in real-time. This makes the proposed algorithm computationally more efficient. The proposed scheme has been implemented on a 7 DOF PowerCube? robot manipulator with visual feedback from two cameras.     

Improved eye-vergence visual servoing system in longitudinal direction with RM-GA

Visual servoing is a control method to manipulate the motion of the robot using visual information, which aims to realize “working while watching.” However, the visual servoing towards moving target with hand–eye cameras fixed at hand is inevitably affected by hand dynamical oscillation. To overcome this defect of the hand–eye fixed camera system, an eye-vergence system has been put forward, where the pose of the cameras could be rotated to observe the target object. The visual servoing controllers of hand and eye-vergence are installed independently, so that it can observe the target object at the center of camera images through eye-vergence function. In this research, genetic algorithm (GA) is used as a pose tracking method, which is called “Real-Time Multi-step GA(RM-GA),” solves on-line optimization problems for 3D visual servoing. The performances of real-time object tracking using eye-vergence system and “RM-GA” method have been examined, and also the pose tracking accuracy has been verified.