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Industrial Metrology 1990年第3期1卷 261-274页

作者： Soucy, M. Laurendeau, D. Poussart, D. Auclair, F. Computer Vision and Digital Systems Laboratory Department of Electrical Engineering Laval University Que. GIK 7P4 Canada

In active laser range finders, the position of the center of gravity of the imaged laserspot is used in triangulation computations for the recovery of range data. The computation of reliable range data thus depends on the accurate estimation of the position of the center of gravity of the imaged spot on the image plane. It is often assumed that the intensity profile of the spot is a 2-D gaussian. However, when the laser is scanned over a surface with variable reflectance properties, the intensity profile on the image plane is no longer gaussian near reflectance discontinuities. The assumption of a 2-D gaussian can thus cause an interpretation error that is reflected in the accuracy of the computed range values. This paper presents a model for the description of the behaviour of the position of the center of gravity of the image of a laser spot when it crosses over a reflectance discontinuity. The intensity of the laser spot is assumed to be a 2-D gaussian distribution and the reflectance discontinuity is an ideal step function. The model states that the interpolation error is proportional to the integral of the variance of the imaged spot. The interpolation error is defined as the difference between the center of gravity of the 2-D gaussian on a scan line and the actual position of the center of gravity of the imaged spot over the discontinuity. Simulations show the behaviour of the interpolation error near the discontinuity. Experiments with a He-Ne laser crossing over a reflectance discontinuity confirm the validity of the model. © 1990 Elsevier Science Publishers B.V.

关键词： center of gravity Laser range finder reflectance discontinuity

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An intelligent path planning system for robot navigation in an unknown environment

An intelligent path planning system for robot navigation in ...

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Mobile Robots IV 1989

作者： Luo, Ren C. Pan, Tai-Jee Robotics and Intelligent Systems Laboratory Department of Electrical and Computer Engineering North Carolina State University RaleighNC27695-7911 United States

In this paper, a novel approach to solve the mobile robot path planning problem in an unknown environment is presented. Inherently, the obstacle information from robot perception is contaminated with uncertainties, and thus, the acquired obstacle knowledge for path planning needs to be updated dynamically. Therefore, the development of an adaptive path planning scheme capable of determining a desired path with uncertain, and incomplete obstacle knowledge is necessary. We use the concept of traversability vectors to analyze the spatial-relations between the robot and obstacles in the task environment. Then, these analyzed relations are used to determine the obstacles that must be bypassed by the robot, and the ways to bypass them. Dynamically changing obstacle knowledge can be accommodated by replanning the path at the time when a change is reported. The proposed scheme can work very efficiently since because of the elimination of an exhausted search process that is often required in previous approaches. We implement a computer program to simulated the proposed planning scheme. A graphical representation for robot motions guided by the planned paths is illustrated to show the feature of the presented work. © 1990 SPIE. All rights reserved.

关键词： Motion planning

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Intelligent motion control system for autonomous vehicles operating in a factory floor

Intelligent motion control system for autonomous vehicles op...

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1990 IEEE International Workshop on Intelligent Motion Control, IMC 1990

作者： Luo, Ren C. Pan, T.J. Aras, C.M. Robotics and Intelligent Systems Laboratory Department of Electrical and Computer Engineering North Carolina State University University RaleighNC27695 United States

To improve the performance of autonomous vehicles operating in a factory environment, it is important to develop an intelligent planning system to avoic. vehicle collisions as well as to design a good path network which can minimize the congestion problem. Given a path network, the collision problem can be eliminated by velocity planning for vehicles. To achieve this, we first represent each vehicle as an intersection of time varying half-planes. Then, we use traversability vectors method to predict vehicle collisions along their paths. Once a collision is predicted, time constraints on lower-priority vehicles are registered on a constraint map which shows time instances when the path is obstructed. Velocity planning is then accomplished ty a search on the map. To solve the congestion problem, we must reduce the average waiting time of vehicles. We use a queueing network model to evaluate the average waiting time for different path network configurations. As a result. the network that yields the best performance is selected. © 1991 IEEE.

关键词： Autonomous vehicles

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Surface reconstruction based on descripions of cross-sectional contours

Surface reconstruction based on descripions of cross-section...

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Sensing and Reconstruction of Three-Dimensional Objects and Scenes 1990

作者： Kim, Yonghoon Luo, Ren C. Robotics and Intelligent Systems Laboratory Department of Electrical and Computer Engineering North Carolina State University RaleighNC27695-7911 United States

Surface reconstruction from cross-sectional contours has become increasingly important in medical image applications. In this paper, a method of reconstructing the surface of an object based on the descriptions of cross-sectional contours has been developed. Each cross-sectional contour is first partitioned into convex/concave segments based on the relative locations of points on the contour. Each segment of the contour is then described by a parametric cubic polynomial, and the boundary is recovered based on the description. A matching technique incorporating possible deformations between adjacent cross-sections is used to obtain the correspondence between adjacent cross-sectional contours. Once the correspondence is established, the surface between correspondent segments of adjacent crosssectional contours is reconstructed by a traditional triangulation technique. As the reconstruction is based on the shape of the cross-sections, the reconstructed surfaces are more close to that of the original object. © 1990 SPIE. All rights reserved.

关键词： Surface reconstruction

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3D object recognition using a mobile laser range finder

3D object recognition using a mobile laser range finder

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1990 IEEE International Workshop on Intelligent Robots and Systems, IROS 1990

作者： Luo, Ren C. Scherp, Ralph S. Robotics and Intelligent Systems Laboratory Department of Electrical and Computer Engineering North Carolina State University RaleighNC27695-7911 United States

The objective of this paper is to present a 3D object recognition system with emphasis on an optimum placement strategy for a mobile 3D range sensor. The theoretical aspects leading to the development of the 3D sensor placement paradigm are presented and described. In this paper we use a triangulation type laser range finder in which a CCD based imaging device is utilized to view a plane of laser light bounced from a sweeping mirror. The sensor characteristics are described and modeled. A set of criteria for use in constraining the. possible sensor site location for future scans is presented. These constraint conditions are essential to drive the actual sensor placement algorithm for 3D object recognition. © 1990 Institute of electrical and Electronics Engineers Inc.. All rights reserved.

关键词： Laser mirrors

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BUILDING EFFICIENT AND FLEXIBLE FEATURE-BASED INDEXES

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INFORMATION SYSTEMS 1990年第6期15卷 653-662页

作者： JEA, KFJ LEE, YC Robotics Research Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States Current affilation: Cell Communications Research United States Current affilation: AT and T Bell Laboratories U.S.A.

If database management systems are to play an important role in CAD/CAM technologies, building engineering indices must be a primary task even though it is beyond conventional database practice. Information regarding design semantics or functionalities is often embedded in the geometric description of design objects, and is therefore not directly available for indexing. Presented in this paper is an efficient and flexible indexing mechanism for retrieving design objects that possess similar design features as described by the user. The underlying database is composed of rotational objects represented by constructive solid geometry (CSG). Although domain-specific representation schemes and algorithms are involved, the main objective of this paper is to emphasize the importance of engineering indices and to illustrate the effort required to build as well as to use such indices.

关键词： engineering DATABASE MANAGEMENT engineering INDEXES FEATURE EXTRACTION CONSTRUCTIVE SOLID GEOMETRY MULTIPLE KEY ACCESS PATTERN MATCHING DESIGN RETRIEVAL

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Optimally localized estimation of the fractal dimension

Optimally localized estimation of the fractal dimension

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Curves and Surfaces in computer vision and Graphics 1990

作者： Super, Boaz J. Bovik, Alan C. Department of Computer Sciences University of Texas at Austin AustinTX78712 United States Laboratory for Vision Systems Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78712-1084 United States

We present a method for making accurate measurements of the instantaneous fractal dimension of (1) images modeled as fractal Brownian surfaces, and (2) images of physical surfaces modeled as fractal Brownian surfaces. Fractal Brownian surfaces have the property that their apparent roughness increases as the viewing distance decreases. Since this true of many natural surfaces, fractal Brownian surfaces are excellent candidates for modeling rough surfaces. To obtain accurate local values of the fractal dimension, spatio-spectrally localized measurements are necessary. Our method employs Gabor filters, which optimize the conflicting goals of spatial and spectral localization as constrained by the functional uncertainty principle. The outputs from multiple Gabor filters are fitted to a fractal power-law curve whose parameters determine the fractal dimension. The algorithm produces a local value of the fractal dimension for every point in the image. We also introduce a variational technique for producing a fractal dimension function which varies smoothly across the image. This technique is implemented using an iterative relaxation algorithm. A test of the method on 50 synthetic images of known global fractal dimensions shows that the method is accurate with an error of approximately 4.5% for fractal Brownian images and approximately 8.5% for images of physical fractal Brownian surfaces. © 1990 SPIE. All rights reserved.

关键词： Gabor filters

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Image reconstruction based on human and monkey cone mosaics

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Journal of Visual Communication and Image Representation 1990年第2期1卷 137-152页

作者： Costaridou, Lena Stefanou, Spyros Hirsch, Joy Orphanoudakis, Stelios Image Analysis and Computer Vision Laboratory Institute of Computer Science Foundation of Research and Technology-Hellas Heraklion Crete Greece Department of Ophthalmology and Visual Science Yale University New Haven CT United States Image Analysis and Computer Vision Laboratory Institute of Computer Science Foundation of Research and Technology-Hellas Heraklion Crete Greece Departments of Diagnostic Imaging and Electrical Engineering Yale University New Haven CT United States

The image reconstruction capacity of the actual foveal cone sampling mosaics of an adult monkey and human is investigated through computer simulations. A retinocortical mapping model in which positions are known and disorder is compensated (DC) has been implemented using classical Whittaker-Kotelnikov-Shannon (WKS) reconstruction theory and a two-dimensional hexagonal tessellation technique that maps the cone lattice onto a perfectly hexagonal grid. The DC model has been compared with a retinocortical mapping model in which cone positions are also known but position disorder is uncompensated (DU) in the reconstruction process. A control model has also been implemented using WKS reconstruction based on sampled data obtained with simulated perfectly hexagonal lattices whose Nyquist limits are equivalent to those of the human and monkey lattices. Quantitative comparisons of these models are based on the RMS error per pixel between the original and reconstructed images. Results of these simulations demonstrate a pronounced superiority of the DC over the DU model. The results of these simulations, which use "biologically correct" sampling lattices, document a potential image reconstruction advantage when foveal cone positions are known. © 1990.

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On reducing compensator bandwidth of LQG/LTR control: an H∞- optimization approach

On reducing compensator bandwidth of LQG/LTR control: an H∞...

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American Control Conference (ACC)

作者： K. C. Han T. C. Hsia Robotics Research Laboratory Department of Electrical Engineering and Computer Science University of California Davis CA 95616 Robotics Research Laboratory Department of Electrical Engineering and Computer Science University of California Davis CA USA

Due to lack of robustness, the Linear Quadratic Gaussian (LQG) approach to the design of control systems is enhanced by Loop Transfer Recovery (LTR) techniques. However, the robustness is recovered with the price paid to the unduly large or infinite bandwidth of the compensator. Such compensators are undesirable because plant output measurement noise is greatly amplified so as to degrade the system performance. A simple method is presented for reducing compensator bandwidth by H ∞ - optimization of a stable function which combines the usual sensitivity function difference with a weighted closed-loop transfer function from noise to plant input. An example is given to show the improvement achievable by this new design method.

关键词： Bandwidth Noise robustness Robust control Control systems Noise measurement Degradation System performance Optimization methods Transfer functions Noise reduction

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Review of the four parameter controller approach for FDI problems

Review of the four parameter controller approach for FDI pro...

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IEEE International Symposium on Intelligent Control (ISIC)

作者： C.A. Jacobson K.P. Valavanis Robotics Laboratory Department of Electrical and Computer Engineering Northeastern University Boston MA USA

A summary of fault detection and isolation methodologies used to accommodate system actuator and sensor failures is given. The four-parameter controller for failure diagnostic problems is described in detail. Applicat... 详细信息

关键词： Fault detection Sensor systems Acoustic sensors Failure analysis Actuators Open loop systems Control systems Jacobian matrices Robot sensing systems Laboratories

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