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Use your hand as a 3-D mouse, or, relative orientation from extended sequences of sparse point and line correspondences using the affine trifocal tensor 5th

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5th European Conference on Computer Vision, ECCV 1998

作者： Bretzner, Lars Lindeberg, Tony Dept. of Numerical Analysis and Computing Science KTH StockholmS-100 44 Sweden

ISBN: (纸本)3540645691

This paper addresses the problem of computing three-dimensional structure and motion from an unknown rigid configuration of point and lines viewed by an affine projection model. An algebraic structure, analogous to the trilinear tensor for three perspective cameras, is defined for configurations of three centered affine cameras. This centered affine trifocal tensor contains 12 non-zero coefficients and involves linear relations between point correspondences and trilinear relations between line correspondences. It is shown how the affine trifocal tensor relates to the perspective trilinear tensor, and how three-dimensional motion can be computed from this tensor in a straightforward manner. A factorization approach is also developed to handle point features and line features simultaneously in image sequences. This theory is applied to a specific problem in human-computer interaction of capturing three-dimensional rotations from gestures of a human hand. Besides the obvious application, this test problem illustrates the usefulness of the affine trifocal tensor in a situation where sufficient information is not available to compute the perspective trilinear tensor, while the geometry requires point correspondences as well as line correspondences over at least three views. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Tensors

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Scaling the dynamic approach to autonomous path planning: Planning horizon dynamics

Scaling the dynamic approach to autonomous path planning: Pl...

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15th International Joint Conference on Artificial Intelligence, IJCAI 1997

作者： Large, Edward W. Christensen, Henrik I. Bajcsy, Ruzena GRASP Laboratory University of Pennsylvania 3401 Walnut Street Philadelphia PA 19104-6228 United States Centre for Autonomous Systems Dept. Numerical Analysis and Computing Science Kungliga Tekniska H gskolan S-100 44 Stockholm Sweden

In the dynamical systems approach to robot path planning both sensed and remembered information contribute to shape a nonlinear vector field that governs the behavior of an autonomous agent. Such systems perform well with partial knowledge of the environment and in dynamically changing environments. Nevertheless, it is a local heuristic approach to path planning, and it is not guaranteed to find existing paths. We describe a method of adjusting the spatial resolution of the planner using a dynamical system that operates at a faster time scale than the planning dynamics. This improves the system's ability to utilize both sensed and remembered information, and to solve a larger range of problems without resorting to global path planning.

关键词： Motion planning

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Combinatorial geometry for shape representation and indexing

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International Workshop on Object Representation in Computer Vision II, ECCV 1996

作者： Carlsson, Stefan Dept. of Numerical Analysis and Computing Science Royal Institute of Technology StockholmS-100 44 Sweden

ISBN: (纸本)3540617507

Combinatorial geometry is the study of order and incidence properties of groups of geometric features. Ordering properties for point sets in 2-D and 3-D can be seen as a generalization of ordering properties in 1-D and incidences are configurations of features that are non-generic such as collinearity of points. By defining qualitative shape properties using combinatorial geometry we get a common framework for metric and qualitative representations. Order and incidence form a natural hierarchy together with metric representations in terms of increasing abstraction Metric==>Order==>Incidence The problem of recognition can be structured in a similar hierarchy ranging from the recognition of specific objects from specific viewpoints, using calibrated cameras to that of calibration free, view independent recognition of generic objects. Order and incidence relations have invariance properties that make them especially interesting for general recognition problems. We present an algorithm for 3-D object hypothesis generation from single images. The combinatorial properties of triplets of line segments are used to define an index to a model library. This library consists of line segment triplets for object model views. Every indexing of a model triplet by an image triplet is accumulated into a matching matrix between image and model line segments. From this matrix we can evaluate the strength of an hypothesis that a specific object is present. © Springer-Verlag Berlin Heidelberg 1996.

关键词： Indexing (of information)

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All bits in ax + b mod p are hard: Extended abstract 16th

All bits in ax + b mod p are hard: Extended abstract

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16th Annual International Cryptology Conference, CRYPT0 1996

作者： Näslund, Mats Dept. of Numerical Analysis and Computing Science Royal Institute of Technology StockholmS-100 44 Sweden

In this paper we show that for any one-way function f, being able to determine any single bit in ax + b mod p for a random Ω(|x|)-bit prime p and random a, b with probability only slightly better than 50% is equivale... 详细信息

ISBN: (纸本)3540615121

关键词： Computers

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Genetic programs and co-evolution: Developing robust general purpose controllers using local mating in two 2-dimensional populations 4th

Genetic programs and co-evolution: Developing robust general...

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International Conference on Evolutionary Computation - 4th International Conference on Parallel Problem Solving from Nature, PPSN 1996

作者： Ronge, Andreas Nordahl, Mats G. Studies of Artificial Neural Systems Dept. of Numerical Analysis and Computing Science Royal Institute of Technology StockholmS-100 44 Sweden Institute of Theoretical Physics Chalmers University of Technology GothenburgS-412 96 Sweden Santa Fe Institute 1399 Hyde Park Road Santa FeNM87501 United States

ISBN: (纸本)354061723X

A co-evolutionary approach for developing programs for controlling a very simple "robot-like" simulated vehicle is presented. The main goal is to find programs that can generalize and solve other similar problems. Good results are achieved by coevolving the test cases and the simulated vehicles and using locality in both the reproduction and evaluation phases. The fitness of a controller is determined by its performance in competition with its neighbours in the test case population. The fitness of a test case is similarly determined through competition with its neighbours in the controller population. The co-evolved controllers are more robust and general than a simple hand-designed algorithm or controllers evolved using a fixed training set. © 1996, Springer-Verlag. All rights reserved.

关键词： Controllers

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Universal hash functions and hard core bits

Universal hash functions and hard core bits

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International Conference on theTheory and Applications of Cryptographic Techniques, EUROCRYPT 1995

作者： Näslund, Mats Royal Institute of Technology Dept. of Numerical Analysis and Computing Science StockholmS-100 44 Sweden

ISBN: (纸本)3540594094

In this paper we consider the bit-security of two types of universal hash functions: linear functions on GF[2n] and linear functions on the integers modulo a prime. We show individual security for a l l bits in the first case and for the O(1og n) least significant bits in the second case. Both types of functions are shown to have O(log7a) simultaneous secure bits. For the second type of functions, primes of length D(n) are needed. Together with the Goldreich-Levin theorem, this shows that all the common types of universal hash functions provide so called hard-core bits. © Springer-Verlag Berlin Heidelberg 1995.

关键词： Hash functions

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AUTONOMOUS LEARNING WITH COMPLEX DYNAMICS

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INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS 1995年第1期10卷 119-153页

作者： LILJENSTROM, H SANS—Studies of Artificial Neural Systems Dept. of Numerical Analysis and Computing Science Royal Institute of Technology S-100 44 Stockholm Sweden Phone: 8-790 6909 Fax: 8-790 0930.

Traditionally, associative memory models are based on point attractor dynamics, where a memory state corresponds to a stationary point in state space. However, biological neural systems seem to display a rich and complex dynamics whose function is still largely unknown. We use a neural network model of the olfactory cortex to investigate the functional significance of such dynamics, in particular with regard to learning and associative memory. The model uses simple network units, corresponding to populations of neurons connected according to the structure of the olfactory cortex. All essential dynamical properties of this system are reproduced by the model, especially oscillations at two separate frequency bands and aperiodic behavior similar to chaos. By introducing neuromodulatory control of gain and connection weight strengths, the dynamics can change dramatically, in accordance with the effects of acetylcholine, a neuromodulator known to be involved in attention and learning in animals. With computer simulations we show that these effects can be used for improving associative memory performance by reducing recall time and increasing fidelity. The system is able to learn and recall continuously as the input changes, mimicking a real world situation of an artificial or biological system in a changing environment. (C) 1995 John Wiley & Sons, Inc.

关键词： Learning systems

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Response properties of a population of neurons.

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International journal of neural systems 1993年第1期4卷 1-13页

作者： Ekeberg, O. SANS-Studies of Artificial Neural Systems Dept. of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden

This work is concerned with the question of how a population of neurons responds to tonic and transient synaptic input from other similar populations. Because of the methodological problems involved in measuring and manipulating the firing properties of a large set of real neurons simultaneously, another strategy is used here: the experiments are made as a series of simulations using a population of realistic model neurons. The steady state response of this particular model neuron is found to be similar to that used in abstract nonspiking models. The transient response, however, reveals that even though each individual neuron simply changes its frequency moderately, the population can respond quickly and with damped oscillations. These oscillations are due to spike synchronization caused by systematic phase shifts induced by synchronous changes in the input.

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Integrating task-directed plaiming with reactive object recognition 12

Integrating task-directed plaiming with reactive object reco...

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Intelligent Robots and Computer Vision XII: Algorithms and Techniques 1993

作者： Dickinson, Sven Stevenson, Suzanne Amdur, Eugene Tsotsos, John Olsson, Lars Department of Computer Science University of Toronto 6 King's College Rd. TorontoONM5S1A4 Canada Computational Vision and Active Perception Laboratory Dept. of Numerical Analysis and Computing Science Royal Institute of Tecimology StockholmS-10044 Sweden

We describe a robot vision system that achieves complex object recognition with two layers of behaviors, performing the tasks of planning and object recognition, respectively. The recognition layer is a pipeline in which successive stages take in images from a stereo head, recover relevant features, build intermediate representations, and deposit 3-D objects into a world model. Each stage is an independent process that reacts automatically to output from the previous stage. This reactive system operates continuously and autonomously to construct the robot's 3-D model of the environment. Sitting above the recognition pipeline is the planner which is responsible for populating the world model with objects that satisfy the high-level goals of the system. For example, upon examination of the world model, the planner can decide to direct the head to another location, gating new images into the recognition pipeline, causing new objects to be deposited into the world model. Alternatively, the planner can alter the recognition behavior of the pipeline so that objects of a certain type or at a certain location appear in the world model. © 1993 SPIE.

关键词： Pipelines

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MODELING THE DYNAMICS OF OLFACTORY CORTEX USING SIMPLIFIED NETWORK UNITS AND REALISTIC ARCHITECTURE

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International Journal of Neural Systems 1991年第1N02期2卷 1-15页

作者： Hans Liljenström Division of Chemistry and Chemical Engineering California Institute of Technology USA Present address: Dept. of Numerical Analysis and Computing Science Royal Institute of Technology S-100 44 Stockholm Sweden

This report describes a three-dimensional computer model of the olfactory cortex developed for the study of cortical oscillations and their biological significance. The model was designed with the intention of investigating the relative role of network circuitry and network unit properties, resulting in a model complexity between simple Hopfield nets and detailed realistic simulations. Network connections are essentially the same as in a detailed simulation of the olfactory (piriform) cortex by Wilson and Bower (1989), but the network units are here modeled with continuous output functions and single compartments. It is shown that the present model is capable of reproducing all major results of the more complex model, corresponding to spatiotemporal patterns found in the actual cortex (Freeman 1975). This indicates that action potentials and the geometry of cells are not needed per se for explaining certain cortical activities. In contrast, connections between units, in particular feedforward and feedback inhibitory loops and long-range, excitatory-excitatory connections, are found to be crucial for the dynamical behavior of this system. The model describes intrinsic oscillatory properties of olfactory cortex and reproduces response patterns associated with a continuous random-input signal and with a shock pulse given to the cortex. In the latter case, waves of activity move across the model cortex in a way similar to the detailed simulations by Wilson and Bower, and consistent with corresponding global dynamic behavior of the functioning cortex. For a constant random input, the network is able to oscillate with two separate frequencies simultaneously, purely as a result of its intrinsic network properties. A delicate balance between inhibition and excitation, in terms of connection strength and timing of events, is necessary for coherent frequency and phase of the oscillating neural units. The analytical equations used in this model seem an adequate representation

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