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

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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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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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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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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Biorthogonal quincunx Coifman wavelets

Biorthogonal quincunx Coifman wavelets

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IEEE International Conference on Image Processing

作者： Dong Wei B.L. Evans A.C. Bovik Laboratory for Vision Systems Department of Electrical and Computer Engineering University of Technology Austin TX USA

We define and construct a new family of compactly supported, nonseparable two-dimensional wavelets, "biorthogonal quincunx Coifman wavelets" (BQCWs), from their one-dimensional counterparts using the McClellan transformation. The resulting filter banks possess many interesting properties such as perfect reconstruction, vanishing moments, symmetry, diamond-shaped passbands, and dyadic fractional filter coefficients. We derive explicit formulas for the frequency responses of these filter banks. Both the analysis and synthesis lowpass filters converge to an ideal diamond-shaped halfband lowpass filter as the order of the corresponding BQCW system tends to infinity. Hence, they are promising in image and multidimensional signal processing applications. In addition, the synthesis scaling function in a BQCW system of any order is interpolating (or cardinal), which has been known as a desired merit in numerical analysis.

关键词： Filter bank Signal synthesis Image reconstruction Passband Frequency Image converters H infinity control Multidimensional signal processing Numerical analysis

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GMA Welding Process Regulation via Hierarchical GPC with Assured Stability

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IFAC Proceedings Volumes 1997年第3期30卷 221-226页

作者： S.G. Tzafestas E.J. Kyriannakis Intelligent Robotics and Automation Laboratory National Technical University of Athens Department of Electrical and Computer Engineering 15773 Zografou Campus Athens Greece

This paper deals with the regulation of the thermal characteristics of Gas Metal Arc (GMA) welding. A previously developed model is used for the open loop predictions. At the first level of the hierarchy, a parameterized Generalized Predictive Control (GPC) algorithm is selected among other control techniques, due to its robustness against modeling errors and parameter variations. A coordinator, at the second level of the hierarchy, specifies a set of reliable values for the parameters of GPC, so that stability is assured. A representative set of simulation results is included, along an evaluation of the advantages and limitations of the proposed hierarchical GPC technique.

关键词： Predictive control Hierarchical structures Regulation Stabilization Arc welding

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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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Two-stage neural network for volume segmentation of medical images

Two-stage neural network for volume segmentation of medical ...

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International Conference on Neural Networks

作者： M.N. Ahmed A.A. Farag Computer Vision and Image Processing Laboratory Department of Electrical Engineering University of Louisville Louisville KY USA

We present a system to segment and label CT/MRI brain slices using feature extraction and unsupervised clustering. In this technique, each voxel is assigned a feature pattern consisting of a scaled family of differential geometrical invariant features. The invariant feature pattern is then assigned to a specific region using a two-stage neural network system. The first stage is a self-organizing principal components analysis (SOPCA) network that is used to project the feature vector onto its leading principal axes found by using principal components analysis. This step provides an effective basis for feature extraction. The second stage consists of a self-organizing feature map (SOFM) which will automatically cluster the input vector into different regions. The optimum number of regions (clusters) is obtained by a model fitting approach. Finally, a 3D connected component labeling algorithm is applied to ensure region connectivity. Implementation and performance of this technique are presented. Compared to other approaches, the new system is more accurate in extracting 3D anatomical structures of the brain, and can be adapted to real-time imaging scenarios.

关键词： Neural networks Image segmentation Biomedical imaging Feature extraction Principal component analysis Computed tomography Magnetic resonance imaging Brain Labeling Clustering algorithms

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An invariant pulse-coder for 2-D shape recognition

An invariant pulse-coder for 2-D shape recognition

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International Conference on Information, Communications and Signal Processing

作者： N. Rishikesh Y.V. Venkatesh Computer Vision and Artificial Intelligence Laboratory Department of Electrical Engineering Indian Institute of Science Bangalore India

We present some novel schemes for (i) pulse coding for invariant representation of shape; and (ii) a neural architecture for recognizing the encoded shape. The proposed shape encoder utilizes the properties of complex logarithmic mapping (CLM) which transforms rotation and scaling (in its domain) to shifts (in its range). In order to handle this shift, in an attempt to provide increased speed of operation, the encoder converts the CLM output to a sequence of pulses. These pulses are fed to a novel multilayered neural recognizer which (i) invokes template matching with a distinct architecture; and (ii) achieves robustness (to noise and shape deformation) by virtue of its overlapping strategy for code classification. The proposed encoder-recognizer system, which is hardware implementable by a high-speed electronic switching circuit, and can add new shapes on-line to the existing ones, is illustrated by examples.

关键词： Pulse shaping methods Shape Pattern recognition Encoding Fires computer vision Artificial intelligence Laboratories computer architecture Noise robustness

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