Stefan Gaechter - Academia.edu (original) (raw)

Papers by Stefan Gaechter

Research paper thumbnail of Berührungslose Distanzmessung - ein Technologieüberblick

Research paper thumbnail of Vector Quantization - Modeling the Computational Complexity of Unconstrained Vector Quantization

Vector quantization, as an image compression method requires considerable computational complexit... more Vector quantization, as an image compression method requires considerable computational complexity. The following report examines this complexity for the unconstrained vector quantization method, in especially for the partial search algorithm.

Research paper thumbnail of Gachter Vector Quantization MatLab Files

Research paper thumbnail of Cognitive spatial representations for mobile robots-perspectives from a user study

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their ability to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical concept oriented representation of space that is based on objects. This work attempts to provide a "cognitive" validation to the proposed representation and also looks into ways of enhancing it. This is done by means of an elaborate user study experiment. Analysis of the data obtained from the user study provides a human perspective to the robotics problem. This work also attempts to put forward a more generic methodology in order to develop such a representation, to be able to map the robots sensory information to increasingly abstract concepts that describe the semantics of the space the robot inhabits. The work itself is aimed at radically improving the degree of spatial awareness of state-of-the-art robot systems. Thus, the theme of the work is -representation for spatial cognition.

Research paper thumbnail of Optimization of the magnetic levitation process by iterative feedback tuning

Research paper thumbnail of Functional Object Classification

Research paper thumbnail of A Hierarchical Concept Oriented Representation for Spatial Cognition in Mobile Robots

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their abilities to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is compatible to humans. The work presented here is oriented in this direction. It suggests a hierarchical, concept oriented, probabilistic representation of space for mobile robots. A salient aspect of the proposed approach is that it is holistic - it attempts to create a consistent link from the sensory information the robot acquires to the human-compatible spatial concepts that the robot subsequently forms, while taking into account both uncertainty and incompleteness of perceived information. The approach is aimed at increasing spatial awareness in robots.

Research paper thumbnail of Dynamic Analysis and Levitation Test in 1kWh Class Flywheel Energy Storage System

Proceeding of 7th International …, 2003

Research paper thumbnail of Incremental Object Part Detection with a Range Camera

Autonomous Systems Lab, Swiss Federal Institute …, 2006

This report presents an object part detection method using a particle filter. The method is adapt... more This report presents an object part detection method using a particle filter. The method is adapted to a range camera that provides 3D information with a high data rate. However, the data is affected by considerable measurement noise and distortion. Thus, the range data is quantized to cope more efficiently with the high data volume and segmented into primitive parts with morphological operators to assure processing speed. Measurement noise, outliers and segmentation errors are handled with a particle filter used here as a soft decision tree to detect object parts over several fames.

Research paper thumbnail of Mirror Design for an Omnidirectional Camera with a Uniform Cylindrical Projection when Using the SVAVISCA Sensor

Research Reports of CMP, OMNIVIEWS Project, …, 2001

OpenGrey. Open System for Information on Grey literature in Europe. ... Help. Search. XML. To cit... more OpenGrey. Open System for Information on Grey literature in Europe. ... Help. Search. XML. To cite or link to this reference: http://hdl.handle.net/10068/335818. Title : Mirror Design for an Omnidirectional Camera with a Uniform Cylindrical Projection when Using SVAVISCA Sensor. ...

Research paper thumbnail of Object classification based on a geometric grammar with a range camera

… and Automation, 2009 …, 2009

This paper proposes an object classification framework based on a geometric grammar aimed for mob... more This paper proposes an object classification framework based on a geometric grammar aimed for mobile robotic applications. The paper first discusses the geometric grammar as a compact representation form for object categories with primitive parts as its constituent elements. The paper then discusses the object classification implemented as parsing of primitive parts. In particular, two approaches are discussed that constrain the search space in order to render the parsing of the primitive parts practical. The two approaches are experimentally verified, first, for a generic object category of chair applied to real range images acquired with a range camera mounted on a mobile robot and, second, for multiple generic object categories applied to synthetic range images. The experimental results show the practicability of the framework.

Research paper thumbnail of Motion Detection as an Application for the Omnidirectional Camera

… of Cybernetics, Faculty Electrical Engineering Czech …, 2001

Research paper thumbnail of Structure Verification toward Object Classification using a Range Camera

Intelligent autonomous systems, 2008

This paper proposes an incremental object classification based on parts detected in a sequence of... more This paper proposes an incremental object classification based on parts detected in a sequence of noisy range images. Primitive parts are jointly tracked and detected as probabilistic bounding-boxes using a particle filter which accumulates the information of the local structure over time. A voting scheme is presented as a procedure to verify structure of the object, i.e. the desired geometrical relations between the parts. This verification is necessary to disambiguate object parts from potential irrelevant parts which are structurally similar. The experimental results obtained using a mobile robot in a real indoor environment show that the presented approach is able to successfully detect chairs in the range images.

Research paper thumbnail of Cognitive spatial representations for mobile robots-perspectives from a user study

IEEE Int. Conf. on Robotics and …, 2007

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their ability to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical concept oriented representation of space that is based on objects. This work attempts to provide a "cognitive" validation to the proposed representation and also looks into ways of enhancing it. This is done by means of an elaborate user study experiment. Analysis of the data obtained from the user study provides a human perspective to the robotics problem. This work also attempts to put forward a more generic methodology in order to develop such a representation, to be able to map the robots sensory information to increasingly abstract concepts that describe the semantics of the space the robot inhabits. The work itself is aimed at radically improving the degree of spatial awareness of state-of-the-art robot systems. Thus, the theme of the work is -representation for spatial cognition.

Research paper thumbnail of FAST RANGE IMAGE SEGMENTATION FOR INDOOR 3D-SLAM

6th IFAC Symposium on Intelligent …, 2007

Real-time 3D localization and mapping is eventually needed in many service robotic applications. ... more Real-time 3D localization and mapping is eventually needed in many service robotic applications. Toward a light and practical SLAM algorithm, we focus on feature extraction via segmentation of range images. Using horizontal and vertical traces of the range matrix, 2D observed polygons are considered for calculation of a one-dimensional measure of direction, called Bearing Angle (BA). BA is the incident angle between the laser beam and edges of the observed polygon by the scanner in the selected direction. Based on this measure, two different approaches to range image segmentation, region-and edge-based, are proposed and evaluated through a set of standard analysis. It is experimentally shown that for navigation applications, edge based approaches are more efficient. Extensive tests on real robots prove BA-based segmentation is successful for SLAM.

Research paper thumbnail of Incremental object part detection toward object classification in a sequence of noisy range images

Robotics and Automation, …, 2008

This paper presents an incremental object part detection algorithm using a particle filter. The m... more This paper presents an incremental object part detection algorithm using a particle filter. The method infers object parts from 3D data acquired with a range camera. The range information is uniquely quantized and enhanced by local structure information to partially cope with considerable measurement noise and distortion. The augmented voxel representation allows the adaptation of known track-before-detect algorithms to infer multiple object parts in a range image sequence. The appropriateness of the method is successfully demonstrated by an experiment.

Research paper thumbnail of Results on Range Image Segmentation for Service Robots

Computer Vision Systems, …, 2006

This report presents an experimental evaluation of a plane extraction method using various line e... more This report presents an experimental evaluation of a plane extraction method using various line extraction algorithms. Four different algorithms are chosen, which are well known in mobile robotics and computer vision. Experiments are performed on two sets of 25 range images either obtained by simulation or acquired by a proprietary 3D laser scanner. The segmentation outcome of the simulated range images is measured in terms of an average segment classification ratio. Moreover, the speed of the method is measured to conclude on the suitability for service robot applications.

Research paper thumbnail of Mirror design for an omnidirectional camera with a space variant imager

Research paper thumbnail of A comparison of line extraction algorithms using 2D range data for indoor mobile robotics

Autonomous …, 2007

This paper presents an experimental evaluation of different line extraction algorithms applied to... more This paper presents an experimental evaluation of different line extraction algorithms applied to 2D laser scans for indoor environments. Six popular algorithms in mobile robotics and computer vision are selected and tested. Real scan data collected from two office environments by using different platforms are used in the experiments in order to evaluate the algorithms. Several comparison criteria are proposed and discussed to highlight the advantages and drawbacks of each algorithm, including speed, complexity, correctness and precision. The results of the algorithms are compared with ground truth using standard statistical methods. An extended case study is performed to further evaluate the algorithms in a SLAM application.

Research paper thumbnail of Cognitive maps for mobile robots - an object based approach

Robotics and Autonomous …, 2007

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their abilities to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical probabilistic representation of space that is based on objects. A global topological representation of places with object graphs serving as local maps is proposed. The work also details the first efforts towards conceptualizing space on the basis of the human compatible representation so formed. Such a representation and the resulting conceptualization would be useful for enabling robots to be cognizant of their surroundings. Experiments on place classification and place recognition are reported in order to demonstrate the applicability of such a representation towards understanding space and thereby performing spatial cognition. Further, relevant results from user studies validating the proposed representation are also reported. Thus, the theme of the work is -representation for spatial cognition.

Research paper thumbnail of Berührungslose Distanzmessung - ein Technologieüberblick

Research paper thumbnail of Vector Quantization - Modeling the Computational Complexity of Unconstrained Vector Quantization

Vector quantization, as an image compression method requires considerable computational complexit... more Vector quantization, as an image compression method requires considerable computational complexity. The following report examines this complexity for the unconstrained vector quantization method, in especially for the partial search algorithm.

Research paper thumbnail of Gachter Vector Quantization MatLab Files

Research paper thumbnail of Cognitive spatial representations for mobile robots-perspectives from a user study

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their ability to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical concept oriented representation of space that is based on objects. This work attempts to provide a "cognitive" validation to the proposed representation and also looks into ways of enhancing it. This is done by means of an elaborate user study experiment. Analysis of the data obtained from the user study provides a human perspective to the robotics problem. This work also attempts to put forward a more generic methodology in order to develop such a representation, to be able to map the robots sensory information to increasingly abstract concepts that describe the semantics of the space the robot inhabits. The work itself is aimed at radically improving the degree of spatial awareness of state-of-the-art robot systems. Thus, the theme of the work is -representation for spatial cognition.

Research paper thumbnail of Optimization of the magnetic levitation process by iterative feedback tuning

Research paper thumbnail of Functional Object Classification

Research paper thumbnail of A Hierarchical Concept Oriented Representation for Spatial Cognition in Mobile Robots

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their abilities to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is compatible to humans. The work presented here is oriented in this direction. It suggests a hierarchical, concept oriented, probabilistic representation of space for mobile robots. A salient aspect of the proposed approach is that it is holistic - it attempts to create a consistent link from the sensory information the robot acquires to the human-compatible spatial concepts that the robot subsequently forms, while taking into account both uncertainty and incompleteness of perceived information. The approach is aimed at increasing spatial awareness in robots.

Research paper thumbnail of Dynamic Analysis and Levitation Test in 1kWh Class Flywheel Energy Storage System

Proceeding of 7th International …, 2003

Research paper thumbnail of Incremental Object Part Detection with a Range Camera

Autonomous Systems Lab, Swiss Federal Institute …, 2006

This report presents an object part detection method using a particle filter. The method is adapt... more This report presents an object part detection method using a particle filter. The method is adapted to a range camera that provides 3D information with a high data rate. However, the data is affected by considerable measurement noise and distortion. Thus, the range data is quantized to cope more efficiently with the high data volume and segmented into primitive parts with morphological operators to assure processing speed. Measurement noise, outliers and segmentation errors are handled with a particle filter used here as a soft decision tree to detect object parts over several fames.

Research paper thumbnail of Mirror Design for an Omnidirectional Camera with a Uniform Cylindrical Projection when Using the SVAVISCA Sensor

Research Reports of CMP, OMNIVIEWS Project, …, 2001

OpenGrey. Open System for Information on Grey literature in Europe. ... Help. Search. XML. To cit... more OpenGrey. Open System for Information on Grey literature in Europe. ... Help. Search. XML. To cite or link to this reference: http://hdl.handle.net/10068/335818. Title : Mirror Design for an Omnidirectional Camera with a Uniform Cylindrical Projection when Using SVAVISCA Sensor. ...

Research paper thumbnail of Object classification based on a geometric grammar with a range camera

… and Automation, 2009 …, 2009

This paper proposes an object classification framework based on a geometric grammar aimed for mob... more This paper proposes an object classification framework based on a geometric grammar aimed for mobile robotic applications. The paper first discusses the geometric grammar as a compact representation form for object categories with primitive parts as its constituent elements. The paper then discusses the object classification implemented as parsing of primitive parts. In particular, two approaches are discussed that constrain the search space in order to render the parsing of the primitive parts practical. The two approaches are experimentally verified, first, for a generic object category of chair applied to real range images acquired with a range camera mounted on a mobile robot and, second, for multiple generic object categories applied to synthetic range images. The experimental results show the practicability of the framework.

Research paper thumbnail of Motion Detection as an Application for the Omnidirectional Camera

… of Cybernetics, Faculty Electrical Engineering Czech …, 2001

Research paper thumbnail of Structure Verification toward Object Classification using a Range Camera

Intelligent autonomous systems, 2008

This paper proposes an incremental object classification based on parts detected in a sequence of... more This paper proposes an incremental object classification based on parts detected in a sequence of noisy range images. Primitive parts are jointly tracked and detected as probabilistic bounding-boxes using a particle filter which accumulates the information of the local structure over time. A voting scheme is presented as a procedure to verify structure of the object, i.e. the desired geometrical relations between the parts. This verification is necessary to disambiguate object parts from potential irrelevant parts which are structurally similar. The experimental results obtained using a mobile robot in a real indoor environment show that the presented approach is able to successfully detect chairs in the range images.

Research paper thumbnail of Cognitive spatial representations for mobile robots-perspectives from a user study

IEEE Int. Conf. on Robotics and …, 2007

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their ability to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical concept oriented representation of space that is based on objects. This work attempts to provide a "cognitive" validation to the proposed representation and also looks into ways of enhancing it. This is done by means of an elaborate user study experiment. Analysis of the data obtained from the user study provides a human perspective to the robotics problem. This work also attempts to put forward a more generic methodology in order to develop such a representation, to be able to map the robots sensory information to increasingly abstract concepts that describe the semantics of the space the robot inhabits. The work itself is aimed at radically improving the degree of spatial awareness of state-of-the-art robot systems. Thus, the theme of the work is -representation for spatial cognition.

Research paper thumbnail of FAST RANGE IMAGE SEGMENTATION FOR INDOOR 3D-SLAM

6th IFAC Symposium on Intelligent …, 2007

Real-time 3D localization and mapping is eventually needed in many service robotic applications. ... more Real-time 3D localization and mapping is eventually needed in many service robotic applications. Toward a light and practical SLAM algorithm, we focus on feature extraction via segmentation of range images. Using horizontal and vertical traces of the range matrix, 2D observed polygons are considered for calculation of a one-dimensional measure of direction, called Bearing Angle (BA). BA is the incident angle between the laser beam and edges of the observed polygon by the scanner in the selected direction. Based on this measure, two different approaches to range image segmentation, region-and edge-based, are proposed and evaluated through a set of standard analysis. It is experimentally shown that for navigation applications, edge based approaches are more efficient. Extensive tests on real robots prove BA-based segmentation is successful for SLAM.

Research paper thumbnail of Incremental object part detection toward object classification in a sequence of noisy range images

Robotics and Automation, …, 2008

This paper presents an incremental object part detection algorithm using a particle filter. The m... more This paper presents an incremental object part detection algorithm using a particle filter. The method infers object parts from 3D data acquired with a range camera. The range information is uniquely quantized and enhanced by local structure information to partially cope with considerable measurement noise and distortion. The augmented voxel representation allows the adaptation of known track-before-detect algorithms to infer multiple object parts in a range image sequence. The appropriateness of the method is successfully demonstrated by an experiment.

Research paper thumbnail of Results on Range Image Segmentation for Service Robots

Computer Vision Systems, …, 2006

This report presents an experimental evaluation of a plane extraction method using various line e... more This report presents an experimental evaluation of a plane extraction method using various line extraction algorithms. Four different algorithms are chosen, which are well known in mobile robotics and computer vision. Experiments are performed on two sets of 25 range images either obtained by simulation or acquired by a proprietary 3D laser scanner. The segmentation outcome of the simulated range images is measured in terms of an average segment classification ratio. Moreover, the speed of the method is measured to conclude on the suitability for service robot applications.

Research paper thumbnail of Mirror design for an omnidirectional camera with a space variant imager

Research paper thumbnail of A comparison of line extraction algorithms using 2D range data for indoor mobile robotics

Autonomous …, 2007

This paper presents an experimental evaluation of different line extraction algorithms applied to... more This paper presents an experimental evaluation of different line extraction algorithms applied to 2D laser scans for indoor environments. Six popular algorithms in mobile robotics and computer vision are selected and tested. Real scan data collected from two office environments by using different platforms are used in the experiments in order to evaluate the algorithms. Several comparison criteria are proposed and discussed to highlight the advantages and drawbacks of each algorithm, including speed, complexity, correctness and precision. The results of the algorithms are compared with ground truth using standard statistical methods. An extended case study is performed to further evaluate the algorithms in a SLAM application.

Research paper thumbnail of Cognitive maps for mobile robots - an object based approach

Robotics and Autonomous …, 2007

Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, a... more Robots are rapidly evolving from factory work-horses to robot-companions. The future of robots, as our companions, is highly dependent on their abilities to understand, interpret and represent the environment in an efficient and consistent fashion, in a way that is comprehensible to humans. The work presented here is oriented in this direction. It suggests a hierarchical probabilistic representation of space that is based on objects. A global topological representation of places with object graphs serving as local maps is proposed. The work also details the first efforts towards conceptualizing space on the basis of the human compatible representation so formed. Such a representation and the resulting conceptualization would be useful for enabling robots to be cognizant of their surroundings. Experiments on place classification and place recognition are reported in order to demonstrate the applicability of such a representation towards understanding space and thereby performing spatial cognition. Further, relevant results from user studies validating the proposed representation are also reported. Thus, the theme of the work is -representation for spatial cognition.