Methods and strategies of object localization

An important property of an intelligent robot is to be able to determine the location of an object in 3-D space. A general object localization system structure is proposed, some important issues on localization discussed, and an overview given for current available object localization algorithms and systems. The algorithms reviewed are characterized by their feature extracting and matching strategies; the range finding methods; the types of locatable objects; and the mathematical formulating methods

Range data processing: representation of surfaces by edges

Journal ArticleRepresentation of surfaces by edges is an important and integral part of a robust 3-D model based recognition scheme. Edges in a range image describe the intrinsic characteristics about the shape of the objects. In this paper we present three approaches for detecting edges in 3-D range data. The approaches are based on computing the gradient, thresholding, thinning and fitting straight lines or curves; fitting 3-D lines to a set of points, and detecting changes in the direction of unit normal vectors on the surface. These approaches are applied locally in a small neighborhood of a point. The neighbors of a 3-D point are found by using the k-d tree algorithm. As compared to previous work on range processing, the approaches presented here are applicable not only to sensor range data corresponding to any one view of the scene, but also to 3-D model data obtained using the Computer-Aided Geometric Design (CAGD) techniques, and to 3-D model built using the sensor data such as the data obtained by combining several views of an object. We present several examples where the data is synthetically genetrated, obtained from CAGD methods or obtained from a laser scanner. A comparison of the techniques is presnted

Tele-Autonomous control involving contact

Object localization and its application in tele-autonomous systems are studied. Two object localization algorithms are presented together with the methods of extracting several important types of object features. The first algorithm is based on line-segment to line-segment matching. Line range sensors are used to extract line-segment features from an object. The extracted features are matched to corresponding model features to compute the location of the object. The inputs of the second algorithm are not limited only to the line features. Featured points (point to point matching) and featured unit direction vectors (vector to vector matching) can also be used as the inputs of the algorithm, and there is no upper limit on the number of the features inputed. The algorithm will allow the use of redundant features to find a better solution. The algorithm uses dual number quaternions to represent the position and orientation of an object and uses the least squares optimization method to find an optimal solution for the object's location. The advantage of using this representation is that the method solves for the location estimation by minimizing a single cost function associated with the sum of the orientation and position errors and thus has a better performance on the estimation, both in accuracy and speed, than that of other similar algorithms. The difficulties when the operator is controlling a remote robot to perform manipulation tasks are also discussed. The main problems facing the operator are time delays on the signal transmission and the uncertainties of the remote environment. How object localization techniques can be used together with other techniques such as predictor display and time desynchronization to help to overcome these difficulties are then discussed

Integration of range images from multiple viewpoints into a particle database

Thesis (M.S.V.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1989.Includes bibliographical references (leaves 118-122).by Paul Michael Linhardt.M.S.V.S

View generated database

This document represents the final report for the View Generated Database (VGD) project, NAS7-1066. It documents the work done on the project up to the point at which all project work was terminated due to lack of project funds. The VGD was to provide the capability to accurately represent any real-world object or scene as a computer model. Such models include both an accurate spatial/geometric representation of surfaces of the object or scene, as well as any surface detail present on the object. Applications of such models are numerous, including acquisition and maintenance of work models for tele-autonomous systems, generation of accurate 3-D geometric/photometric models for various 3-D vision systems, and graphical models for realistic rendering of 3-D scenes via computer graphics

Integration of 3D vision based structure estimation and visual robot control

Enabling robot manipulators to manipulate and/or recognise arbitrarily placed 3D objects under sensory control is one of the key issues in robotics. Such robot sensors should be capable of providing 3D information about objects in order to accomplish the above mentioned tasks. Such robot sensors should also provide the means for multisensor or multimeasurement integration. Finally, such 3D information should be efficiently used for performing desired tasks. This work develops a novel computational frame wo rk for solving some of these problems. A vision (camera) sensor is used in conjunction with a robot manipulator, in the frame-work of active vision to estimate 3D structure (3D geometrical model) of a class of objects. Such information is used for the visual robot control, in the frame-work of model based vision. One part o f this dissertation is devoted to the system calibration. The camera and eye/hand calibration is presented. Several contributions are introduced in this part, intended to improve existing calibration procedures. This results in more efficient and accurate calibrations. Experimental results are presented. Second part of this work is devoted to the methods of image processing and image representation. Methods for extracting and representing necessary image features comprising vision based measurements are given. Third part of this dissertation is devoted to the 3D geometrical model reconstruction of a class o f objects (polyhedral objects). A new technique for 3D model reconstruction from an image sequence is introduced. This algorithm estimates a 3D model of an object in terms of 3D straight-line segments (wire-frame model) by integrating pertinent information over an image sequence. The image sequence is obtained from a moving camera mounted on a robot arm. Experimental results are presented. Fourth part of this dissertation is devoted to the robot visual control. A new visual control strategy is introduced. In particular, the necessary homogeneous transformation matrix for the robot gripper in order to grasp an arbitrarily placed 3D object is estimated. This problem is posed as a problem of 3D displacement (motion) estimation between the reference model of an object and the actual model of the object. Further, the basic algorithm is extended to handle multiple object manipulation and recognition. Experimental results are presented

Proceedings of the NASA Conference on Space Telerobotics, volume 1

The theme of the Conference was man-machine collaboration in space. Topics addressed include: redundant manipulators; man-machine systems; telerobot architecture; remote sensing and planning; navigation; neural networks; fundamental AI research; and reasoning under uncertainty

Automated Assembly Using Feature Localization

Automated assembly of mechanical devices is studies by researching methods of operating assembly equipment in a variable manner; that is, systems which may be configured to perform many different assembly operations are studied. The general parts assembly operation involves the removal of alignment errors within some tolerance and without damaging the parts. Two methods for eliminating alignment errors are discussed: a priori suppression and measurement and removal. Both methods are studied with the more novel measurement and removal technique being studied in greater detail. During the study of this technique, a fast and accurate six degree-of-freedom position sensor based on a light-stripe vision technique was developed. Specifications for the sensor were derived from an assembly-system error analysis. Studies on extracting accurate information from the sensor by optimally reducing redundant information, filtering quantization noise, and careful calibration procedures were performed. Prototype assembly systems for both error elimination techniques were implemented and used to assemble several products. The assembly system based on the a priori suppression technique uses a number of mechanical assembly tools and software systems which extend the capabilities of industrial robots. The need for the tools was determined through an assembly task analysis of several consumer and automotive products. The assembly system based on the measurement and removal technique used the six degree-of-freedom position sensor to measure part misalignments. Robot commands for aligning the parts were automatically calculated based on the sensor data and executed