Localization and Navigation of Autonomous Systems in Complex Scenarios

Author - A. Benini

Abstract - Autonomous systems represent a promising evolving area, in particular with respect to research in artificial and embedded systems.

In the European Industry, many solutions of autonomous systems focused on solving a very specific problem are available, but the majority of these solutions, however, is proprietary. While maintaining the property of a particular technology ensures a position in the market, on the other hand this becomes very costly especially in long term. Due to the proliferation of proprietary solutions, the Robotic Industry presents a high degree of fragmentation, which cause a slowdown in the development of new systems, especially nowadays, where an even more increasing number of applications of robotic systems comes. Most of the issues that must be addressed in the development of Autonomous Systems are common to all areas of applications: These problems relate, for example, the localization in indoor/outdoor environments, the ability to avoid obstacles, the ability to make simple decisions based on the occurrence of certain events. It is therefore clear that having a framework of tools that solves common problems in all areas of application, and from which is possible to start for the development of new particular systems used for certain tasks, produces a remarkable advantage. Therefore, in order to become competitive in a highly dynamic market it is necessary to fill some gaps that currently slow down the diffusion of autonomous systems, such as:

The lack of platforms for the integration of components from various technology suppliers
The unavailability of high-performance embedded platformsThe absence of a framework of methodologies are just some of the obstacles to overcome.
In this context, the European Project R3-COP (https://artemis-ia.eu/project/14-r3cop.html), made possible by funds of the ARTEMIS Joint Undertaking as well as different National Funding Authorities and thanks to the collaboration of 27 partners from different European Countries, aims to advance over the state of the art providing a contribution from both perspectives: Technology and Methodology. In particular, it aims to propose new technologies and methodologies that enable the production for the European Industry of advanced, robust, autonomous and cooperating robotic systems at a reduced cost.

This Thesis has been developed in the context of the R3-COP Project, in order to overcome some of the addressed problems, and provides a contribution in both directions: Technology and Methodology.

Concerning the technology, the developed algorithms, based on variants of the Kalman Filter, demonstrate the ability to leverage the latest technologies radio belonging to the IEEE 802.15.4a Standard (Ultra Wide Band and Chirp Spread spectrum) in indoor localization. Going more in detail, a Localization System for Unmanned Ground Vehicle (UGV) based on Nanotron Chirp Spread Spectrum (CSS) Real Time Localization System is proposed. The Nanotron RTLS Kit provides a system for ranging especially in outdoor environments using a proprietary ranging technology called Symmetrical Double-Sided Two Way Ranging (SDS-TWR). This technique tries to overtake the limitations of the classical Received Signal Strength Indication (RSSI) (e.g., Wi-fi mapping) that does not ensure good performance especially in structured environments. The set of these devices allows to create a Wireless Sensor Network (WSN) that is suitable for cooperative tasks where the data link is fundamental to share data and support the relative localization. The proposed algorithm allows to model the bias of ranging data considering also the faults in the measurements in order to have a more reliable position estimation when ranging data are not available. The management of fault measurements allows also to reduce the errors on ranging when there is not Line of Sight between the anchors and the tag, in which situation the performances of the system decreases. Furthermore, a Localization Algorithm for Unmanned Aerial Vehicle (UAV) based on UbiSense Ultra Wide Band (UWB) is presented: The proposed solution allows to use a low-cost Inertial Measurement Unit (IMU) in the prediction step and the integration of vision-odometry for the detection of markers nearness the touchdown area. The ranging measurements allow to reduce the errors of inertial sensors due to the limited performance of accelerometers and gyros. The obtained results show that an accuracy of 15 cm can be achieved.

Concerning the methodology, the second part of this Thesis presents a 3D Simulation Environment for the prototyping and validation of cooperative tasks for unmanned systems as part of the framework of methodologies addressed by the R3-COP project. The proposed Simulation Environment, provides also the possibility to convert the control software from Simulated Scenario into real application using the tools provided by MatLab/Simulink. Some example of use of the developed Simulation Environment, such as formation control of many UAVs using Networked Decentralized Model Predictive Control, and mission management, using Finite State Machines and cooperation among autonomous agents realized through exchange of information, are explained. All the developed systems have been focused on the Final Air-Borne Demonstrator of the R3-COP Project in which the Autonomy and the Cooperation between the mobile agents have been proved. The results of the research have been successfully reviewed and published into international conferences and journal and applied in the Final Air-Borne Demonstrator of the R3-COP Project.

The full text is available on UNIVPM Openarchive.