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Localized measurement of image fractal dimension using gabor filters

Journal of Visual Communication and Image Representation 1991年第2期2卷 114-128页

作者： Super, Boaz J. Bovik, Alan C. Department of Computer Sciences The University of Texas at Austin Austin TX 78712 United States Laboratory for Vision Systems Department of Electrical and Computer Engineering The University of Texas at Austin Austin TX 78712 United States

We present a method for making accurate, optimally localized measurements of the fractal dimension of images modeled as locally fractal Brownian surfaces. Fractal Brownian surfaces are good models for the multiscale and irregular image textures arising from natural scenes and for elevation maps of terrain. 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 at every point in the image. We also introduce a variational technique for enforcing a smoothness constraint on the computed fractal dimension function. This technique is implemented using an iterative relaxation algorithm. We demonstrate the method on synthetic images, real images of natural textures, and U.S. Geo-Data digital elevation maps of real terrain. We discuss the ways in which real images depart from the fractal Brownian surface model. © 1991.

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Nonlinear analog networks for image smoothing and segmentation

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Journal of VLSI Signal Processing 1991年第1-2期3卷 53-68页

作者： Lumsdaine, A. Wyatt Jr., J.L. Elfadel, I.M. Research Laboratory of Electronics Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge 02139 MA United States

Image smoothing and segmentation algorithms are frequently formulated as optimization problems. Linear and nonlinear (reciprocal)resistive networks have solutions characterized by an extremum principle. Thus, appropriately designed networks can automatically solve certain smoothing and segmentation problems in robot vision. This paper considers switched linear resistive networks and nonlinear resistive networks for such tasks. Following [1] the latter network type is derived from the former via an intermediate stochastic formulation, and a new result relating the solution sets of the two is given for the "zero temperature" limit. We then present simulation studies of several continuation methods that can be gracefully implemented in analog VLSI and that seem to give "good" results for these nonconvex optimization problems. © 1991 Kluwer Academic Publishers.

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On force-tracking impedance control of robot manipulators

On force-tracking impedance control of robot manipulators

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IEEE International Conference on robotics and Automation (ICRA)

作者： T.A. Lasky T.C. Hsia Robotics Research Laboratory Department of Electrical Engineering and Computer Science University of California Davisburg CA USA

A reference force-tracking impedance control system is proposed, consisting of a conventional impedance controller in the inner-loop and a trajectory modifying controller in the outer-loop for force-tracking. The design of the outer-loop is presented and the stability of the two-loop control system is analyzed. A computationally efficient control algorithm for the inner-loop is suggested. Simulation results are presented. The controller is able to achieve excellent position and force-tracking with unknown environment stiffness and the presence of a burr on the tracking surface.< >

关键词： Force control Robot control Control systems Robot kinematics Manipulator dynamics Surface impedance Friction Velocity control Automatic control Algorithm design and analysis

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Robot performance measurement and calibration using a 3D computer vision system

Robot performance measurement and calibration using a 3D com...

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IEEE International Conference on robotics and Automation (ICRA)

作者： B. Preising T.C. Hsia Biomedical Engineering Graduate Group Graduate Division University of California슠Davis Davis CA USA Robotics Research Laboratory Electrical Engineering and Computer Science University of California Davis Davis CA USA

The use of a single-camera 3D computer vision system as a position sensor in order to perform robot calibration is examined. A vision feedback scheme, termed vision-guided robot control (VRC), that can improve the accuracy of a robot in an online iterative manner is described. This system demonstrates the advantage that can be achieved by a Cartesian space robot control scheme when end-effector position and orientation are actually sensed instead of calculated from the kinematic equations. The viability of using a vision system for robot calibration is demonstrated by experimentally showing that the accuracy of a robot can be drastically improved. The vision system can also be used to determine the repeatability and accuracy of a robot in a simple, efficient, and quick manner. Experimental work with an IBM electric drive robot and the proposed vision system produced a 97- and 145-fold improvement in the position and orientation accuracy of the robot, respectively.< >

关键词： Measurement Calibration Robot vision systems Robot sensing systems Orbital robotics Machine vision Robot control computer vision Sensor systems Feedback

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AN ADAPTIVE SCHEME FOR ROBOT JOINT TRAJECTORY GENERATION

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JOURNAL OF ROBOTIC SYSTEMS 1990年第6期7卷 881-895页

作者： HSIA, TC GUO, ZY LI, L Robotics Research Laboratory Department of Electrical Engineering and Computer Science University of California Davis Davis CA 95616

It has been shown recently that robot inverse kinematic transformation can be easily carried out by using a nonlinear dynamic system called “joint space command generator.” In this paper, an adaptive version of the command generator is proposed. The main feature of this command generator is that the inverse Jacobian is estimated on-line (using least-squares algorithms), thus the explicit form of the inverse Jacobian is not required. Since the Jacobian is dependent on the end-effector orientation representation, the adaptive command generator is then inherently flexible in accommodating any choice of orientation representation during Cartesian trajectory planning. The only knowledge required is the forward kinematics of the robot. Thus inverse kinematic transformation of robot trajectories can be carried out with a minimum amount of kinematic information. Extensive simulation studies of the proposed scheme have been carried out which showed that the adaptive command generator is computationally feasible and highly accurate. Different orientation representations have been tested with equal success. Some typical simulation results are presented to illustrate the performance of the adaptive command generator.

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SENSORS AND INTERFACING IN robotics AND MANUFACTURING

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robotics AND computer-INTEGRATED MANUFACTURING 1990年第3-4期7卷 243-253页

作者： JAMSHIDI, M CAD Laboratory for Systems/Robotics Department of Electrical and Computer Engineering University of New Mexico Albuquerque NM 87131 U.S.A.

Sensing is one of the most essential aspects of any robotic application, be it manufacturing or any automated process. Robotic sensors can be divided into two classes of " internal " and " external ". Examples of the first group are position or velocity, while the second group includes proximity, touch, or vision to name a few. The other important problem in manufacturing is interfacing with the environment within a cell. The object of this tutorial paper is to survey the two issues of "sensing" and "interfacing" in robotics and manufacturing.

关键词： Robots, Industrial

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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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Behaviour of the center of gravity of a reflected gaussian laser spot near a surface reflectance discontinuity

Industrial Metrology

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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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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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A 1024-ELEMENT HIGH-PERFORMANCE SILICON TACTILE IMAGER

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IEEE TRANSACTIONS ON ELECTRON DEVICES 1990年第8期37卷 1852-1860页

作者： SUZUKI, K NAJAFI, K WISE, KD Sensor Research Laboratory Microelectronic Research Laboratories NEC Corporation Limited Sagamihara Japan Center of Integrated Sensors and Circuits Solid State Electronics Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

A 32*32-element capacitive silicon tactile imager, for use in precision robotics applications where high density and high resolution are important, is discussed. The silicon chip measures 1.6 cm*1.6 cm, and is organized in an X-Y matrix of 1024 capacitor elements on 0.5-mm centers. The process uses two boron diffusions (deep and shallow) followed by a silicon-to-glass electrostatic bonding step and subsequent unmasked wafer dissolution. This results in a thick center plate for the sense capacitor supported by thinner beams. Only four noncritical masking steps for silicon and two for glass are required. A measured force sensitivity of 0.27 pF/gmf/element, temperature sensitivity of less than 3o p.p.m./ degrees C, and maximum operating force of approximately=1 gm/element has been obtained. A discrete data acquisition system used with the device offers over 6 b of force resolution, and the imager can be read at a rate of 15-20 mu s/element, offering an effective frame rate of 5.1 ms.< >

关键词： Silicon Force measurement Image resolution Electrostatic measurements Capacitors Robots Semiconductor device measurement Boron Diffusion bonding Wafer bonding

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