| 1. |
- Cielniak, Grzegorz, 1975-, et al.
(author)
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Appearance-based tracking of persons with an omnidirectional vision sensor
- 2003
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In: IEEE Computer Society Conference on Computer Vision and Pattern Recognition Workshops. - : IEEE. - 0769519008
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Conference paper (peer-reviewed)abstract
- This paper addresses the problem of tracking a moving person with a single, omnidirectional camera. An appearance-based tracking system is described which uses a self-acquired appearance model and a Kalman filter to estimate the position of the person. Features corresponding to ``depth cues'' are first extracted from the panoramic images, then an artificial neural network is trained to estimate the distance of the person from the camera. The estimates are combined using a discrete Kalman filter to track the position of the person over time. The ground truth information required for training the neural network and the experimental analysis was obtained from another vision system, which uses multiple webcams and triangulation to calculate the true position of the person. Experimental results show that the tracking system is accurate and reliable, and that its performance can be further improved by learning multiple, person-specific appearance models
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| 2. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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A stereo electronic nose for a mobile inspection robot
- 2003
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In: ROSE 2003 - 1st IEEE International Workshop on Robotic Sensing 2003. - : IEEE.
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Conference paper (peer-reviewed)abstract
- This paper describes the design of a gas-sensitive system that is suitable for use on a mobile robot ("mobile nose"). The stereo architecture comprises two equivalent sets of gas sensors mounted inside separated ventilated tubes (or "nostrils"). To characterise the dynamic response, the whole system is modelled as a first-order sensor. The corresponding parameters, including the response and recovery time, can be obtained by fitting this model to the values recorded during a simple experiment described in this paper. Our experiments confirmed the suitability of the applied model and permitted a quantitative comparison of different set-ups. It is shown that using suction fans lowers the recovery time of the metal oxide gas sensors by a factor of two, while a solid separation between the tubes (a "septum") is necessary to maintain the sensitivity of the mobile nose to concentration gradients.
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| 3. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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An absolute positioning system for 100 euros
- 2003
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In: ROSE 2003 - 1st IEEE International Workshop on Robotic Sensing 2003: Sensing and Perception in 21st Century Robotics. - : IEEE.
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Conference paper (peer-reviewed)abstract
- This paper describes an absolute positioning system, which provides accurate and reliable measurements using low-cost equipment that is easy to set up. The system uses a number of fixed web-cameras to track a distinctly coloured object. In order to calculate the (x,y) position of this object, estimates calculated by triangulation from each combination of two cameras are combined, resulting in centimeter-level accuracy. Example applications, including tracking of mobile robots and persons, are described. An extended set-up is also introduced, which allows determination of the heading of a two coloured object from single images
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| 4. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Approaches to gas source tracing and declaration by pure chemo-tropotaxis
- 2003
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In: Autonome Mobile Systeme 2003. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540201427 - 9783642189869 ; , s. 161-171
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Conference paper (peer-reviewed)abstract
- This paper addresses the problem of localising a static gas source in an uncontrolled indoor environment by a mobile robot. In contrast to previous works, especially the condition of an environment that is not artificially ventilated to produce a strong unidirectional airflow is considered. Here, the propagation of the analyte molecules is dominated by turbulence and convection flow rather than diffusion, thus creating a patchy distribution of spatially distributed eddies. Positive and negative tropotaxis, based on the spatial concentration gradient measured by a pair of electrochemical gas sensor arrays, were investigated. Both strategies were implemented utilising a direct sensor-motor coupling (a Braitenberg vehicle) and were shown to be useful to accomplish the gas source localisation task. As a possible solution to the problem of gas source declaration (the task of determining with certainty that the gas source has been found), an indirect localisation strategy based on exploration and concentration peak avoidance is suggested. Here, a gas source is located by exploiting the fact that local concentration maxima occur more frequently near the gas source compared to distant regions
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| 5. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Building gas concentration gridmaps with a mobile robot
- 2004
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In: Robotics and Autonomous Systems. - : Elsevier. - 0921-8890 .- 1872-793X. ; 48:1, s. 3-16
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Journal article (peer-reviewed)abstract
- This paper addresses the problem of mapping the structure of a gas distribution by creating concentration gridmaps from the data collected by a mobile robot equipped with gas sensors. By contrast to metric gridmaps extracted from sonar or laser range scans, a single measurement from a gas sensor provides information about a comparatively small area. To overcome this problem, a mapping technique is introduced that uses a Gaussian weighting function to model the decreasing likelihood that a particular reading represents the true concentration with respect to the distance from the point of measurement. This method is evaluated in terms of its suitability regarding the slow response and recovery of the gas sensors, and experimental comparisons of different exploration strategies are presented. The stability of the mapped structures and the capability to use concentration gridmaps to locate a gas source are also discussed.
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| 6. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Creating gas concentration gridmaps with a mobile robot
- 2003
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In: Proceedings. - New York, USA : IEEE. - 0780378601 ; , s. 118-123
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Conference paper (peer-reviewed)abstract
- This paper addresses the problem of mapping the features of a gas distribution by creating concentration gridmaps from the data collected by a mobile robot equipped with an electronic nose. By contrast to metric gridmaps extracted from sonar or laser range scans, a single measurement of the electronic nose provides information about a comparatively small area. To overcome this problem, a mapping technique is introduced that uses a Gaussian density function to model the decreasing likelihood that a particular reading represents the true concentration with respect to the distance from the point of measurement. This method is evaluated in terms of its suitability regarding the slow response and recovery of the gas sensors. The stability of the mapped features and the capability to use concentration gridmaps to locate a gas source are also discussed.
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| 7. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Detection and Localization of an Odour Source by an autonomous mobile Robot
- 2002
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In: Robotik 2002. - Dusseldorf, Germany : V D I-V D E - VERLAG GMBH. - 3180916796 ; , s. 689-694
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Conference paper (peer-reviewed)abstract
- This paper presents studies concerning the use of an electronic nose on an autonomous mobile robot. In particular experiments were introduced in which a mobile robot generates two dimensional concentration maps of a known target gas in an unventilated room. It was shown that these concentration maps are clearly related to the position of the odour source. Moreover our results show that if accurate localization of the odour source itself is desired one has to consider weak air currents which usually occur even in closed unventilated rooms (often caused by convection).
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| 8. |
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| 9. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Experiences using gas sensors on an autonomous mobile robot
- 2001
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In: Proceedings of EUROBOT 2001, 4th European workshop on advanced mobile robots. ; , s. 1-8
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Conference paper (peer-reviewed)abstract
- This paper reports on experiences concerning the deployment of gas sensors on an autonomous mobile robot. It particularly addresses the suitability of the developed system to localize a distant odour source. First experiments were undertaken in which the robot was ordered to move along different weakly ventilated corridors, while keeping track of its center (framing a '1D' scenario). The measured sensor values show evident peaks that roughly indicate the location of the odour source, if the robot moves with a speed not too low. In this case the system proved to be well suited to detect even weak odour sources. Otherwise the observed course of the received values show many peaks hardly correlated with the location of the odour source. Several investigations were performed to clear up this behaviour but it is still not possible to make concluding statements about the reasons. Finally the setup to perform experiments in a '2D' scenario is described and concerning results of first investigations are presented. It was shown that the utilized system is also capable of detecting a distant odour source in a 2D environment and that the somewhat harder localization task has to account for some weak airflow even in closed, unventilated rooms.
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| 10. |
- Lilienthal, Achim J., 1970-, et al.
(author)
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Experimental analysis of gas-sensitive Braitenberg vehicles
- 2004
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In: Advanced Robotics. - Oxfordshire, United Kingdom : Taylor & Francis. - 0169-1864 .- 1568-5535. ; 18:8, s. 817-834
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Journal article (peer-reviewed)abstract
- This article addresses the problem of localising a static gas source in an indoor environment by a mobile robot. In contrast to previous works, the environment is not artificially ventilated to produce a strong unidirectional airflow. Here, the dominant transport mechanisms of gas molecules are turbulence and convection flow rather than diffusion, which results in a patchy, chaotically fluctuating gas distribution. Two Braitenberg-type strategies (positive and negative tropotaxis) based on the instantaneously measured spatial concentration gradient were investigated. Both strategies were shown to be of potential use for gas source localisation. As a possible solution to the problem of gas source declaration (the task of determining with certainty that the gas source has been found), an indirect localisation strategy based on exploration and concentration peak avoidance is suggested. Here, a gas source is located by exploiting the fact that local concentration maxima occur more frequently near the gas source compared to distant regions
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