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Building hierarchical solid models from sensor data

IEEE International Conference on robotics and Automation (ICRA)

作者： S. Aubry V. Hayward Computer Vision and Robotics Laboratory McGill Research Center for Intelligent Machines McGill University Montreal QUE Canada

ISBN: (纸本)0818619384

The authors consider the problem of aggregating the geometrical information provided by sensors such as range finders, and its applications to scene modeling. The information consists of collections of three-dimensional surface points that form a discrete subspace of the objects-to-free-space boundaries within the world to be modeled. The ultimate goal is to obtain a valid surface model which can in turn be transformed into an efficient volumetric representation for solid-interference-detection algorithms. This representation should achieve search efficiency, compactness, and parallelism. The authors first introduce such a volumetric representation which uses a tetrahedrization of space. Then they show that surface connectivity is a nontrivial and essential element of a valid representation. To that end, they introduce a formal graph-theoretic definition for model validity which they use to guide the process of aggregating the different views. Finally, the topological problems posed by objects nonhomeomorphic to spheres, such as multiholed tori, are introduced.< >

关键词： Solid modeling Robot kinematics Orbital robotics Intelligent sensors Intelligent robots Interference Path planning Manipulators Detectors computer vision

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An expert system for circuit board repair

An expert system for circuit board repair

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IEEE Pacific Rim Conference on Communications, computers and Signal Processing

作者： N. Ling M.E. Malowany A.S. Malowany McGill Research Centre for Intelligent Machines McGill University Montreal QUE Canada Computer Vision and Robotics Laboratory McGill University Montreal QUE Canada

Using a hierarchical approach, an expert system for performing circuit board repair tasks within a robotic workcell has been developed. The new circuit board repair system is rule-based and includes a nonmonotonic inference engine using forward chaining and nonblocking functions, a database describing a robotic workcell, and rule sets into which repair tasks are implemented. Parallel-processing capability is achieved by using nonblocking functions. Action synthesis is based on matching rules to the given database. The system was programmed in Common LISP on a SUN 3 workstation under UNIX BSD version 4.3 and on a dedicated Symbolics 3600 LISP machine. The development, implementation, and testing of the circuit board repair system are described.< >

关键词： Expert systems Printed circuits Robots Databases Circuit testing Engines Circuit synthesis Sun Workstations System testing

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Mean field theory and MT neurons

Mean field theory and MT neurons

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IEEE International Conference on Systems, Man and Cybernetics

作者： A. Dobbins S.W. Zucker Computer Vision and Robotics Laboratory Department of Electrical Engineering McGill University Montreal QUE Canada Canadian Institute for Advanced Research Montreal QUE Canada

The problem of obtaining reliable estimates of the optic flow field and its variation is discussed. It is argued that circuitry in the middle temporal (MT) visual area is arranged to provide mean field approximations of the optical flow field, that is, the maximal neighborhood over which the local field can be well-approximated as uniform, parallel translation. In addition, the way the mean field approximation varies with neighborhood size and position is informative about the variation of the flow field. It is shown how receptive fields can be synthesized to represent the first-order differential information about the flow field. The same ideas are applicable to the binocular disparity vector field, and lead one to predict the existence of extrastriate neurons that are specialized for the local shear and stretch of the disparity and motion vector fields.< >

关键词： Neurons Image motion analysis Circuits computer architecture computer vision Robot vision systems Laboratories Shape Optical devices Retina

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A digital signal processor network for robot axis control

A digital signal processor network for robot axis control

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IEEE Pacific Rim Conference on Communications, computers and Signal Processing

作者： N. Ling A.S. Malowany McGill Research Center for Intelligent Machines McGill University Montreal QUE Canada Computer Vision and Robotics Laboratory McGill University Montreal QUE Canada

A distributed control system built using a local area network of digital signal processor based controllers is described. By coordinating the single-loop controllers, the system allows the partitioning of different tasks on separate microcomputers and offers the advantages of expandability and modularity. Different strategies can be implemented by downloading of software in this distributed control system. Although the architecture of this control system is designed for robot control, the system is generally and fully programmable and does not assume any manipulator characteristics. AT&T DSP32 32-bit, 16-MHz digital signal processors are used in this design. Simulation of the control system software is tested on an IBM-AT with the AT&T DSP32 development tools, and these results are presented.< >

关键词： Digital signal processors Robot control Control systems Distributed control Robot kinematics Local area networks Process control Microcomputers computer architecture Manipulators

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Kinematics of common industrial robots

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robotics and Autonomous Systems 1988年第2期4卷 169-191页

作者： Lloyd, John Hayward, Vincent Computer Vision and Robotics Laboratory McGill Research Centre for Intelligent Machines McGill University MontréalQuébec Canada

An approach to finding the solution equations for simple manipulators is described which enhances the well known method of Paul, Renaud, and Stevenson, by explicitly making use of known decouplings in the manipulator kinematics. This reduces the set of acceptable equations from which we obtain relationships for the joint variables. For analyzing the Jacobian, such decoupling is also useful since it manifests itself as a block of zeros, which makes inversion much easier. This zero lock can be used to obtain a concise representation for the forward and inverse Jacobian computations. The decoupling also simplifies the calculations sufficiently to allow us to make good use of a symbolic algebra program (MACSYMA) in obtaining our results. Techniques for using MACSYMA in this way are described. Examples are given for several industrial manipulators. © 1988

关键词： Kinematics

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SAGE: A decision support system for the sequencing of operations within a robotic workcell

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Decision Support Systems 1988年第3期4卷 329-343页

作者： Freedman, P. Malowany, A. Computer Vision and Robotics Laboratory McGill Research Centre for Intelligent Machines McGill University Montréal Que. Canada

This paper describes a new approach to decision support based on logic programming. SAGE, Sequence Analysis by Graphical Evaluation, is a both a logic framework and a set of Prolog programs to express and then solve the problem of repetitive sequencing of operations within a robotics workcell. We create a Timed Petri Net from the user description consisting of the initial state of the workcell, plus the operations to be performed. Each operation is defined by (i) the command to be executed, (ii) a list of enabling conditions, (iii) a list of changes made to the state of the workcell by executing the command, and (iv) its relative integer duration. After some preliminary analysis, this net is used to generate the Task Space of all feasible time histories of workcell events. Repetitive sequences of all the workcell operations are then constructed from cycles in the Task space. From the feasible sequences thus identified, the time-optimal one is selected. SAGE clearly demonstrates both the power of symbolic expression, and the power of pattern matching as a basis for decision support systems. © 1988.

关键词： Petri Nets Prolog robotics

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Planning collision-free trajectories in time-varying environments: a two-level hierarchy

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The Visual computer 1988年第5期3卷 304-313页

作者： Kant, Kamal Zucker, Steven W. Computer Vision and Robotics Laboratory McGill Research Centre for Intelligent Machines McGill University Montréal Québec Canada

We propose a two-level hierarchy for planning collision-free trajectories in time varying environments. Global geometric algorithms for trajectory planning are used in conjunction with a local avoidance strategy. Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles. Essentially, the robot has a global geometric planner that provides a coarse global trajectory (the path and velocity along it), which may be locally modified by the low-level local avoidance module if local sensors detect any obstacles in the vicinity of the robot. This hierarchy makes effective use of the complementary aspects of the global trajectory planning approaches and the local obstacle avoidance approaches. © 1988 Springer-Verlag.

关键词： Obstacle avoidance Path planning robotics Trajectory planning Velocity planning

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A biologically motivated approach to early visual computations: orientation selection, texture, and optical flow 4th

A biologically motivated approach to early visual computatio...

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4th International Conference on Pattern Recognition, 1988

作者： Zucker, Steven W. Computer Vision and Robotics Laboratory McGill Research Centre for Intelligent Machines McGill University MontréalQC Canada The Canadian Institute for Advanced Research Canada

ISBN: (纸本)9783540190363

The problem of curve detection decomposes naturally into two stages: (i) inferring the (discrete) trace and tangent to the curve;and (ii) finding integrals through the resultant tangent field. Orientation selection is the term used by physiologists for the first of these stages;i.e., for the process of extracting the tangents to piecewise smooth curves from a two-dimensional image. We present an analysis of the orientation selection process from a computational perspective that is strongly influenced by various biological constraints. As such, it provides both a solid foundation for curve detection algorithms within computer vision systems and illustrates the insights that can be gained by analyzing biological vision systems. Formal extensions to the algorithm can also be posed that provide further insight into texture and optical flow. © 1988, Springer-Verlag.

关键词： Optical flows

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On describing a robotic scene

On describing a robotic scene

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Intelligent Robots and computer vision VI 1987

作者： Hayward, Vincent Aubry, Stéphane Computer Vision and Robotics Laboratory McGill Research Center for Intelligent Machines 3480 University Street MontréalQCH3A 2A7 Canada

The focus of this article is the presentation of the issues involved in the design of a system able to automatically or semi-automatically construct a global, world-centered model of an industrial scene. In a robotic context, the uses of such a model could be the detection and prevention of collisions, and the interactive off-line programming of manipulators. More generally, such a model can be useful for a variety of automation tasks, including graphic simulation and machining operations sequencing. We first review range acquisition and solid modelling techniques in light of' their respective appropriateness to the above problem. Then we explain how the process of constructing a scene differs from both object recognition and image processing, since we are a priori not interested in isolating distinguishing features of objects but rather in faithfully describing entire scenes. We also discuss how the merging of the several views of the scene is a central element of the scene acquisition process and how great care must be exercised in order to maintain connectivity consistency. Finally, we show that data acquisition, solid modelling as well the actual process of constructing the scene are closely interrelated and that these three issues, all of which are necessary components of the scene description process, should not be considered independently of each other. © 1988 SPIE. All rights reserved.

关键词： Manipulators

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A hybrid to range image detection

A hybrid to range image detection

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International Conference on Pattern Recognition

作者： N. Yokoya M. Levine Electro Technical Laboratory Tsukuba Ibaraki Japan Computer Vision and Robotics Laboratory Computer Vision and Robotics Laboratory McGill Research Centre for Intelligent Machines McGill University Montreal QUE Canada

An approach to the problem of range image segmentation is described. It is a hybrid of region- and edge-based approaches. It is assumed that the range image of an object, which may be constructed of both curved and planar surfaces, is divided into surface primitives which are homogeneous in their intrinsic differential geometric properties and do not contain discontinuities in either depth or surface orientation. The method is based on the computation of the Gaussian and mean curvatures from which a curvature sign map is computed. Two initial edge-based segmentations are also computed from the partial derivatives and depth values. One detects jump edges while the other highlights roof edges. The three image maps are then combined to produce the final range image segmentation. Experimental results for both synthetic and real range data of polyhedral and curved objects have proved the usefulness of the approach. Results for the real data are given.< >

关键词： Surface fitting Smoothing methods Shape Image analysis Pixel Geometry

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