We present a robot control system for known structured environments that integrates robust reactive control with reasoning-based execution monitoring. It provides a robot with a powerful method for dealing with situations that were caused by the interaction with humans or that are due to unexpected changes in the operating environment. On the reactive level, the robot is controlled using a hierarchy of low-level behaviours. On the high level, a logical representation of the world enables the robot to plan action sequences and to reason about the state of the world. If the execution of an action does not have the expected effect, high-level reasoning allows the robot to infer possible explanations and, if necessary, to recover from the failure situation. For the robot to act optimally, the discrepancies between the internal world model and the real world have to be detected and corrected. The proposed system obtains new information about the world by executing sensing actions (active perception) and by sensory interpretation during the robot's operation. It also takes into account temporal information about changes in the environment. All updates of the world model are performed in a way that the changes are consistent with an underlying action theory. Having implemented the proposed system on a common mobile robot platform, we demonstrate the value of intelligent execution monitoring by means of two realistic office delivery scenarios.

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For the past three years, we have been running an experiment in web-based interaction with an autonomous indoor mobile robot. The robot, Xavier, can accept commands to travel to different offices in our building, broadcasting camera images as it travels. The experiment, which was originally designed to test a new navigation algorithm, has proven very successful, with over 30,000 requests received and 210 kilometers travelled, to date. This article describes the autonomous robot system, the web-based interfaces, and how they communicate with the robot. It highlights lessons learned during this experiment in web-based robotics and includes recommendations for putting future mobile robots on the web.

Research on execution monitoring in its own is still not very common within the field of robotics and autonomous systems. It is more common that researchers interested in control architectures or execution planning include monitoring as a small part of their work when they realize that it is needed. On the other hand, execution monitoring has been a well studied topic within industrial control, although control theorists seldom use this term. Instead they refer to the problem of fault detection and isolation (FDI). This survey will use the knowledge and terminology from industrial control in order to classify different execution monitoring approaches applied to robotics. The survey is particularly focused on autonomous mobile robotics. © 2005 Elsevier B.V. All rights reserved.

In this paper we present a model-free execution monitor for behavior-based mobile robots. By modelfree we mean that the monitoring is based only on the actual execution, without involving any predictive models of the controlled system. Model-free monitors are especially suitable for systems where it is hard to obtain adequate models. In our approach we analyze the activation levels of the di#erent behaviors using a pattern recognition technique. Our model-free execution monitor, which is realized by radial basis function networks, is shown to give a high performance in several realistic simulations.

In this paper, we are interested in the design and the experiment of a control architecture for an autonomous outdoor mobile robot which mainly uses vision. We focus on the design of a mechanism that permits the dynamic selection and firing of perception processes. We propose an hybrid architecture that uses an attention mechanism which controls the robot environment awareness while managing the computational resources and allowing a fair reactivity. We describe its implementation and experimentation on a robot in an outdoor environment. Keywords: Robot control architecture, perception, attention, resource management. 1. INTRODUCTION In the last decade, behavior-based robotic has gained much interest in the international research community. Purely reactive at its beginning, it has evolved to incorporate more deliberative behaviors. Robots constructed with this approach have begun to show interesting performances in uncertain or unpredictable environments where deliberative knowledge...

Monitoring plan preconditions can allow for replanning when a precondition fails, generally far in advance of the point in the plan where the precondition is relevant. However, monitoring is generally costly, and some precondition failures have a very small impact on plan quality. We formulate a model for optimal precondition monitoring, using partially-observable Markov decisions processes, and describe methods for solving this model effectively, though approximately. Specifically, we show that the single-precondition monitoring problem is generally tractable, and the multiple-precondition monitoring policies can be effectively approximated using single-precondition solutions. 1

We present a robot control system that integrates robust reactive control with e#cient reasoning about actions and execution monitoring. On the reactive level, the robot is controlled using a hierarchy of low-level behaviors. On the high level, a logical representation of the world enables the robot to reason about the state of the world and to plan action sequences. If the execution of an action fails, probabilistic information on the state of the world based on the robot's sensors are used to update the logic-based representation of the world. High-level reasoning then allows to infer possible explanations and to recover from the failure situation. The proposed system is evaluated using a set of realistic o#ce-delivery scenarios.

This paper presents the results of a short study on the nature and challenges of the "Assessment Problem," and the approaches applicable to the solution of the problem. This study was performed as a task within the DARPA's JFACC project, in February-March of 1999, primarily in several brainstorming sessions conducted by the authors

Problem: To be useful, autonomous mobile robots need to be able to reliably achieve high-level tasks,such as deliverying mail or patrolling buildings. Our work focuses on both the overall software architecture that can be used for such robot systems and the specific algorithms to achieve reliable, high-speed navigation.Our extensive experience over the years in testing the Xavier robot and in extending its capabilities has validated, to a large extent, our overall approach. Impact: The world is on the verge of a revolution in the use of autonomous mobile robots in offices,homes, stores, hospitals, etc. However, commercially viable applications need robots that can achieve tasks autonomously, without tedious (and often error prone) human control. Having reliable autonomous robotsystems that are easy to maintain and extend will go a long way towards making this a reality.