Distributed Mobile Robot Localization and Communication System for Special Interventions

Abstract

This thesis focuses on the development of a distributed mobile robot localization and communication system for special interventions like those carried out by fire-fighters in fire ground search and rescue. The use case scenario is related to the one described for the GUARDIANS EU project, where a swarm formation of mobile robots accompany a fire fighter during a rescue intervention in a warehouse. In this line, localizing the robots and the fire fighter during an indoor intervention with the presence of smoke is one of the more interesting challenges in this scenario. Several localization techniques have been developed using ultrasonic sensors, radio frequency signals and visual information. It has also been studied several communication protocols that can help to improve the efficiency of the system in such scenario and a proposal for designing a cross-layer communication platform that improves the connectivity of the mobile nodes during an intervention and reduces the number of lost data packets.

Main Contributions

The main contributions of this thesis are the following:

• • Contribution 1: Most of the literature addressing the problem of Person Following for real applications is centered on vision-based solutions. In this thesis the state of the art on Person Following is improved by designing a TDoA Radio/Sonar solution that is able to work in smoky conditions with a high reliability. This system has been tested in both, a mobile Erratic Platform, and on the GUARDIAN Robotnik platform, which has been used during the 3rd year demonstration of the FP6 GUARDIANS project.

  • Contribution 2: The system includes a module to detect the smoke density, that allows to determine in real time which is the best sensor that can provide the most accurate information for localization and navigation in every situation, and makes the system to act accordingly. This, for example, permits navigating with the laser scanner when the density of the smoke is below 25 per cent, and use only sonar and radio above this value. This multi-sensor approach for localization, as far as we know, is beyond the existing state of the art on swarm localization for interventions. The results have been obtained using paraffin smoke. It would be necessary to carry out work using more realistic smoke conditions, but that is beyond the scope of this thesis.

  • Contribution 3: The thesis proposes a communication platform based on cross-layer techniques to improve the efficiency of the system during an intervention. As the system is already calculating the node positions in real time, and this information needs to be known by every node including the base station, this information is crucial if the network protocol efficiency is to be improved. For example, knowing the position of the nodes permits extracting in real time the best route a packet must take to reach a given node, which means that the efficiency of communication layers three (network layer) and four (transport layer) is enhanced. Moreover, by using the conventional TCP/IP transport protocol it is demonstrated that the time delays become unstable, increasing their fluctuation, which is in fact not good for control systems. By looking in the scientific literature, most of the distributed robotic platforms such as ROS (Robot Operating System) and Player/Stage use TCP/IP protocol internally. In this thesis a modified version of the Bilateral Transport Protocol (BTP) is proposed, that allows a more reliable control of the system to be used through the network. As in this case the network is based on wireless techniques using a MANET (Mobile Ad-hoc Network), the original BTP protocol needs to be adapted accordingly so that it is known when the MANET changes its topology, and the transmission can be paused in this specific situation until the whole system becomes stable from the communications point of view. Using a conventional TCP/IP protocol on a MANET network means that the application would continue sending the packets even when the network is calculating its routes after the topology has been changed. This can be avoided using the proposed WBTP (Wireless Bilateral Transport Protocol) communications architecture.

Bibliographical Information

Title: Distributed Mobile Robot Localization and Communication System for Special Interventions

Author: Sales Gil, Jorge

Language: English

University: Jaume I de Castellón

Department: Ingeniería y Ciencia de los Computadores

Date of defense: 28-Oct-2011

Directors:

• • Cervera Mateu, Enric (Director)

  • Marín Prades, Raúl (Co-director)

Jury:

• • Penders, Jacques (president)

  • Sanz Valero, Pedro José (secretary)

  • Ferré Pérez, Manuel (vocal)

  • Azorín Poveda, José María (vocal)

  • Fernández Ruzafa, José (vocal)

Keywords:

Localization; Low-visibility; Smoke; Risky environment; Laser rangefinder; Ultrasound; TDoA; Communications; Network protocols; Visual servoing

Descriptors:

• • ROBOTICS

  • ARTIFICIAL VISION

  • DATA TRANSMISSION DEVICES

  • ARTIFICIAL INTELLIGENCE