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3rd Asian Conference on computer vision, ACCV 1998

作者： Bab-Hadiashar, Alireza Suter, David Intelligent Robotics Research Centre Department of Electrical and Computer Systems Engineering Monash University ClaytonVIC3168 Australia

ISBN: (纸本)3540639314

Robust estimators have become popular tools for solving a wide range of problems in computer vision. Despite many successes in this field, there is still a need for estimators, which are suited to specific problems such as recovering structures from multi-structural data. This paper offers an alternative approach to, and some practical insights into, the implementation of well-known rank ordering based robust estimators. The approach has been tested on synthetic and real image data for motion segmentation purposes. © 1997, Springer Verlag. All rights reserved.

关键词： Image segmentation

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Robust total least squares based optic flow computation 3rd

Robust total least squares based optic flow computation

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3rd Asian Conference on computer vision, ACCV 1998

作者： Bab-Hadiashar, Alireza Suter, David Intelligent Robotics Research Centre Department of Electrical and Computer Systems Engineering Monash University ClaytonVIC3168 Australia

ISBN: (纸本)3540639306

This paper considers the problem of finding a robust solution to the optic flow problem. The optical flow field is recovered by solving a system of over-determined linear equations with all the data matrices containing both outliers and noise. Here, we present a novel and very effective solution for this problem called weighted total least squares. The weights for this method are computed using a new robust statistical method named least median of squares orthogonal distances. Unlike the total least squares which is only robust to noise, this method is extremely robust to both noise and outliers and can tolerate up to 50% of equations in the system to be contaminated by outliers. The proposed weighting method is fast and the total computation remains inexpensive. To demonstrate the performance of the proposed algorithm, we compare the accuracy of our algorithm for computing optic flow field for a number of synthetic and real image sequences and show that the proposed method, despite being very simple and straightforward, out performs all methods used for comparison. © Springer-Verlag Berlin Heidelberg 1997.

关键词： Flow fields

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MoNiF: a modular neuro-fuzzy controller for race car navigation

MoNiF: a modular neuro-fuzzy controller for race car navigat...

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IEEE International Symposium on Computational Intelligence in robotics and Automation (CIRA)

作者： K.C. Ng R. Scorcioni M.M. Trivedi N. Lassiter Computer Vision and Robotics Research Laboratory Electrical anad Computer Engineering Department University of California San Diego CA USA

This paper characterizes how well the modular neuro-fuzzy controller, MoNiF, can perform in robotic applications by testing it in a race-car simulator. The performance of this controller is compared with that of a neural network controller (NNC) and the best programmed car (the ideal car). During the phase of learning from the ideal car, MoNiF reaches its stable performance (when it demonstrates good control) at lap 300; while the NNC requires 700 laps. Without further learning and when competing in the same learning track, MoNiF completes 20 laps of the track about 24 seconds later than the ideal car but 29 second ahead of the NNC car. However, when they all are competing in different unfamiliar tracks, MoNiF performs comparably to the ideal car, while NNC has completely lost its ability to drive. Observing the behaviors of NNC and MoNiF, we conclude that MoNiF learns to refine the output of expert rules and thus can drive in most tracks. Meanwhile NNC learns to drive in a particular track but loses its generality for other tracks. It is shown that this modular control method, equipped with the pretrained knowledge of only few simple expert rules, learns much faster than a NNC without any apriori knowledge.

关键词： Navigation Neural networks computer vision Robot vision systems Application software computer simulation Target tracking Laboratories Performance evaluation Testing

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A fast and accurate 3-D rangefinder using the Biris technology: the TRID sensor

A fast and accurate 3-D rangefinder using the Biris technolo...

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International Conference on 3D Imaging, Modeling, Processing, Visualization and Transmission (3DIMPVT)

作者： F. Loranger D. Laurendeau R. Houde Computer Vision and Systems Laboratory (CVSL) Electrical and Computer Engineering Department Laval University QUE Canada Robotics Division Hydro-Quebec Research Institute (IREQ) Varennes Canada

In many industrial applications such as autonomous vehicle guidance and robotic manipulations, reliable 3-D informations must be extracted from the scene in order to provide a robust description of the environment in which the system evolves. This paper presents the TRID sensor, a simple, fast, robust and accurate 3-D sensing device based on the Biris technology. TRID is limited to a lateral resolution of one point. Experimental results show that an accuracy better than 0.15% can be obtained for the depth component (Z) of 3-D points at a distance of 1.3 meter from a wooden black painted beam surface with an acquisition rate of 8.5 points/s.

关键词： Robot vision systems Robustness computer vision Application software Robot kinematics Layout Cameras computer industry Costs Geometrical optics

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The geometry of visual space distortion

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International Workshop on Algebraic Frames for the Perception and Action Cycle, AFPAC 1997

作者： Fermüller, Cornelia Cheong, Loong Fah Aloimonos, Yiannis Computer Vision Laboratory Center for Automation Research University of Maryland College ParkMD20742-3275 United States Department of Electrical Engineering National University of Singapore 10 Kent Ridge Crescent 119260 Singapore

ISBN: (纸本)3540635173

The encounter of perception and action happens at the intermediate representations of space-time. In many of the computational models employed in the past, it has been assumed that a metric representation of physical space can be derived by visual means. Psychophysical experiments, as well as computational considerations, can convince us that the perception of space and shape has a much more complicated nature, and that only a distorted version of actual, physical space can be computed. This paper develops a computational geometric model that explains why such distortion might take place. The basic idea is that, both in stereo and motion, we perceive the world from multiple views. Given the rigid transformation between the views and the properties of the image correspondence, the depth of the scene can be obtained. Even a slight error in the rigid transformation parameters causes distortion of the computed depth of the scene. The unified framework introduced here describes this distortion in computational terms. We characterize the space of distortions by its level sets, that is, we characterize the systematic distortion via a family of iso-distortion surfaces which describes the locus over which depths are distorted by some multiplicative factor. Clearly, functions of the distorted space exhibiting some sort of invariance, produce desirable representations for biological and artificial systems [13]. Given that humans’ estimation of egomotion or estimation of the extrinsic parameters of the stereo apparatus is likely to be imprecise, the framework is used to explain a number of psychophysical experiments on the perception of depth from motion or stereo. © Springer-Verlag Berlin Heidelberg 1997.

关键词： Geometry

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On robust impedance force control of robot manipulators

On robust impedance force control of robot manipulators

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IEEE International Conference on robotics and Automation (ICRA)

作者： Seul Jung T.C. Hsia R.G. Bonitz Robotics Research Laboratory Department of Electrical and Computer Engineering University of California Davis CA USA

An impedance function is proposed to achieve accurate force tracking under the presence of uncertainties in robot dynamics and environment models. The new impedance function is formulated on the basis of PID control of the force tracking error which compensates for the unknown environment stiffness and position. The robot dynamics uncertainties are compensated by a simple time-delayed robust control algorithm. Stability and convergence of the control scheme are analyzed. Simulation studies with a three link rotary robot manipulator are shown. Furthermore, experimental results on a PUMA 560 arm are carried out to confirm the proposed impedance controller's performance.

关键词： Robust control Impedance Force control Robots Manipulator dynamics Uncertainty Three-term control Error correction Stability analysis Convergence

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Bounded tracking for non-minimum phase nonlinear systems with fast zero dynamics

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INTERNATIONAL JOURNAL OF CONTROL 1997年第4期68卷 819-847页

作者： Tomlin, CJ Sastry, SS Department of Electrical Engineering and Computer Sciences Intelligent Machines and Robotics Laboratory University of California Berkeley CA 94720-1770 United States

In this paper, we derive tracking control laws for non-minimum phase nonlinear systems with both fast and slow, possibly unstable, zero dynamics. The fast zero dynamics arise from a perturbation of a nominal system. These fast zeros can be problematic in that they may be in the right half plane and may cause large magnitude tracking control inputs. In this paper, we combine the ideas from some recent work of Hunt, Meyer and Su with that of Devasia, Chen and Paden on an asymptotic tracking procedure for non-minimum phase nonlinear systems. We give (somewhat subtle) conditions under which the tracking control input is bounded as the magnitude of the perturbation of the nominal system becomes zero. Explicit bounds on the control inputs are calculated for both SISO and MIMO systems using some interesting non-standard singular perturbation techniques. The method is applied to a suite of examples, including the simplified planar dynamics of VTOL and CTOL aircraft.

关键词： Nonlinear control systems

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Probabilistic octree modeling of a 3D dynamic environment

Probabilistic octree modeling of a 3D dynamic environment

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IEEE International Conference on robotics and Automation (ICRA)

作者： P. Payeur P. Hebert D. Laurendeau C.M. Gosselin Computer Vision and Digital Systems Laboratory Department of Electrical and Computer Engineering Laval University Sainte Foy QUE Canada Computer Vision and Digital Systems Laboratory Department of Mechanical Engineering Laval University Sainte Foy QUE Canada

Probabilistic occupancy grids have proved to be very useful for workspace modeling in 2D environments. Due to the expansion of computational load, this approach was not tractable for mapping a 3D environment in real applications. In this paper, the original occupancy grid scheme is revisited and a generic closed-form function is introduced to avoid numerical computation of probabilities for a range sensor with Gaussian error distribution. Occupancy probabilities are computed and stored in a multiresolution octree for improved performance and compactness. Occupancy models are built in local reference frames and linked to a global reference frame through uncertain spatial relationships that can be updated dynamically. This scheme is used for building a 3D map in a telerobotic maintenance application of electric power lines where perturbations may cause motion of object assembly.

关键词： Layout computer vision Grid computing Spatial resolution Robotic assembly Solid modeling Bayesian methods Digital systems Mechanical engineering Distributed computing

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Determining the skeletal description of sparse shapes

Determining the skeletal description of sparse shapes

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IEEE International Symposium on Computational Intelligence in robotics and Automation (CIRA)

作者： R. Singh V. Cherkassky N.P. Papanikolopoulos Artificial Intelligence Robotics and Vision Laboratory Department of Computer Science University of Minnesota Minneapolis MN USA Department of Electrical Engineering University of Minnesota Minneapolis MN USA

A variety of techniques in machine vision involve representation of objects by using their shape skeleton. In this paper we present a method to obtain the skeletal shape of binary images in the presence of both boundary noise and noise occurring inside object regions. We propose to obtain the skeletal shape of such images by a modified version of the Kohonen self-organizing map, implemented in a batch processing mode. The modifications allow the map to adapt to the input shape distribution. At each iteration, a competitive Hebbian rule is used to progressively compute the Delaunay triangulation of the shape. Information from the triangulation augments the map topology to yield the final skeletal shape. The batch mode implementation of the self-organizing process, allows our approach to compare very favourably, in terms of computational time, with the traditional flowthrough implementations. Encouraging experimental performance has been obtained on a variety of shapes under varying signal to noise ratios.

关键词： Shape Noise shaping Skeleton Intelligent robots Machine vision computer vision Noise level Noise figure Machine intelligence Robot vision systems

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3D reconstruction of the human jaw from a sequence of images

3D reconstruction of the human jaw from a sequence of images

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Conference on computer vision and Pattern Recognition (CVPR)

作者： M. Ahmed S. Yamany E. Hemayed S. Ahmed S. Roberts A. Farag Computer Vision and Image Processing Laboratory Department of Electrical Engineering University of Louisville Louisville KY USA

A novel approach is proposed to obtain a record of the patient's occlusion using computer vision. Data acquisition is obtained using intra-oral video cameras. The technique utilizes shape from shading to extract 3D information from 2D views of the jaw, and a novel technique for 3D data registration using genetic algorithms. The resulting 3D model can be used for diagnosis, treatment planning, and implant purposes. The overall purpose of this research is to develop a model-based vision system for orthodontics to replace traditional approaches. This system will be flexible, accurate, and will reduce the cost of orthodontic treatments.

关键词： Image reconstruction Humans computer vision Data acquisition Cameras Shape Data mining Genetic algorithms Implants Machine vision

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