A. Visser

VLAM-G: A Grid-based virtual laboratory

The Grid-based Virtual Laboratory AMsterdam (VLAM-G), provides a science portal for distributed analysis in applied scientific research. It offers scientists remote experiment control, data management facilities and access to distributed resources by providing cross-institutional integration of information and resources in a familiar environment. The main goal is to provide a unique integration of existing standards and software packages. This paper describes the design and prototype implementation of the VLAM-G platform. In this testbed we applied several recent technologies such as the Globus toolkit, enhanced federated database systems, and visualization and simulation techniques. Several domain specific case studies are described in some detail. Information management will be discussed separately in a forthcoming paper.

Towards heterogeneous robot teams for disaster mitigation: Results and performance metrics from RoboCup rescue

There are disclosed benzothiadiazinyl and quinazolinyl substituted carboxylalkyl dipeptides, wherein the benzothiodiazinyl or quinazolinyl portions are joined to the dipeptide portions by an aminocarbonyl group. Compounds of this invention are useful as antihypertensive agents, in the treatment of congestive heart failure and in the treatment of glaucoma. In addition, compounds of this invention have diuretic activity.

A Scalable Hybrid Multi-robot SLAM Method for Highly Detailed Maps

Recent successful SLAM methods employ hybrid map representations combining the strengths of topological maps and occupancy grids. Such representations often facilitate multi-agent mapping. In this paper, a successful SLAM method is presented, which is inspired by the manifolddata structure by Howard et al. This method maintains a graph with sensor observations stored in vertices and pose differences including uncertainty information stored in edges. Through its graph structure, updates are local and can be efficiently communicated to peers. The graph links represent known traversable space, and facilitate tasks like path planning. We demonstrate that our SLAM method produces very detailed maps without sacrificing scalability. The presented method was used by the UvA Rescue Virtual Robots team, which won the Best Mapping Award in the RoboCup Rescue Virtual Robots competition in 2006.

Evaluating maps produced by urban search and rescue robots: lessons learned from RoboCup

This paper presents the map evaluation methodology developed for the Virtual Robots Rescue competition held as part of RoboCup. The procedure aims to evaluate the quality of maps produced by multi-robot systems with respect to a number of factors, including usability, exploration, annotation and other aspects relevant to robots and first responders. In addition to the design choices, we illustrate practical examples of maps and scores coming from the latest RoboCup contest, outlining strengths and weaknesses of our modus operandi. We also show how a benchmarking methodology developed for a simulation testbed effortlessly and faithfully transfers to maps built by a real robot. A number of conclusions may be derived from the experience reported in this paper and a thorough discussion is offered.

Optical dephasing in organic glasses between 0.3 and 20 K. A hole-burning study of resorufin and free-base porphin

Abstract Spectral holes have been burnt in the S 1 ←S 0 0-0 transition of resorufin in polymethylmethacrylate (PMMA) and glycerol, and of free-base porphin (H 2 P) in PMMA and polyethylene (PE). The holewidths follow a T 1.3 dependence over almost two orders of magnitude in temperature and extrapolate to the fluorescence lifetime-limited value of each guest when T →0. The discrepancy between the holewidths of resorufin in glycerol presented here and those reported in the literature are attributed to burning fluences. Photon-echo and hole-burning results are compared. Optical dephasing data are interpreted in terms of low-frequency localized phonon modes and are critically discussed.

Including communication success in the estimation of information gain for multi-robot exploration

This article investigates the effect of incorporating knowledge about the communication possibilities in an exploration algorithm used to map an unknown environment. The mission is to explore a hypothetical disaster site with a small team of robots. The challenge faced by the robot team is to coordinate their actions such that they efficiently explore the environment in their search for victims. The coordination can only be optimal when the robots share the same map. With a limited communication range the map cannot be shared in all circumstances. This article concentrates on the effect of a distributed map, where each robot has only has knowledge of a part of the global map and has no guaranteed connection to the other robot or the operator.

Balancing the information gain against the movement cost for multi-robot frontier exploration

This article investigates the scenario where a small team of robots needs to explore a hypothetical disaster site. The challenge faced by the robot-team is to coordinate their actions such that they efficiently explore the environment in their search for victims.

A low-cost pose-measuring system for robot calibration

To maintain robot accuracy, calibration equipment is needed. In this paper we present a self-calibrating measuring system based on a camera in the robot hand plus a known reference object in the robot workspace. A collection of images of the reference object is obtained. Using image-processing, image-recognition and photogrammetric techniques, the positions and orientations of the camera are computed. The essential geometrical and optical camera parameters can be derived from the redundancy in the measurements. From each image the positions of markers on the reference object are extracted and the individual markers are identified. The camera positions for all images plus the parameters of the camera are solved together in a non-linear least-squares fitting procedure. Experimental results for this low-cost measuring system are presented.

An appearance-based visual compass for mobile robots

Localization is one of the most important basic skills of a mobile robot. Most approaches, however, still rely either on special sensors or require artificial environments. In this article, a novel approach is presented that can provide compass information for localization, purely based on the visual appearance of a room. A robot using such a visual compass can quickly learn a cylindrical map of the environment, consisting of simple statistical features that can be computed very quickly. The visual compass algorithm is efficient, scalable and can therefore be used in real-time on almost any contemporary robotic platform. Extensive experiments on a Sony Aibo robot have validated that the approach works in a vast variety of environments.

RoboCup Rescue Robot and Simulation Leagues

The RoboCup Rescue Robot and Simulation competitions have been held since 2000. The experience gained during these competitions has increased the maturity level of the field, which allowed deployin ...