This study is focused on a novel approach to perform underwater robot localization using sonar sensors. The approach is divided in three main steps. First, the sonar data is used to build probabilistic point clouds. Second, these point clouds are registered and a pose graph is constructed. Finally, the pose graph is optimized and a globally consistent map is built. The experimental results evaluate the proposal using real data gathered by an Autonomous Underwater Vehicle.
Publication type: Conferences
The Time Sensitive Networking (TSN) Task Group has been working on describing a set of standards that will provide enhanced capabilities to standard Ethernet. Specifically, they work to provide Ethernet with real-time, reliability and reconfiguration capacities. Nevertheless, this set of standards (commonly referred to as TSN) does not cover some reliability aspects that are relevant for the correct operation of critical distributed control systems. Thus, in this work we present a first proposal of a highly reliable architecture and a set of mechanisms based on TSN to support the real-time and reliability requirements of these critical systems.
Critical Adaptive Distributed Embedded Systems (ADESs) are nowadays the focus of many researchers. ADESs are envisioned to dynamically modify their behavior to support changes of their real-time and dependability requirements at runtime as the conditions of the environment in which they operate vary. To provide ADESs with an adequate communication infrastructure, our research group proposed the Flexible-Time-Triggered-Replicated Star (FTTRS). FTTRS provides highly reliable communication services on top of Ethernet, while keeping the adaptivity benefits that the FlexibleTime-Triggered (FTT) communication paradigm offers from a real-time perspective. This paper formally verifies, by means of model checking, the correctness of the mechanisms FTTRS includes to enforce consistent changes of the communication scheduling at runtime.
Adaptive systems, apart from fulfilling some functional requirements, can modify their behaviour autonomously and dynamically to cope with new operational requirements or conditions. The DFT4FTT project aims at providing a self-reconfigurable infrastructure that can support distributed applications with real-time, reliability and adaptivity requirements. This paper describes the architecture and the set of mechanisms that make it possible to: monitor the environment and the system itself, decide when a new configuration is needed, decide on a new valid configuration
and apply said configuration. Finally, note that this self-reconfiguration capabilities are not only interesting from a functional perspective, but from a reliability perspective as new we can implement dynamic fault-tolerance mechanisms. In this regard, DFT4FTT implements a N-Modular Redundancy scheme with spares, that increases the system reliability if it is used from the very beginning of the mission.
TSN is a set of technical standards developed by IEEE to provide Ethernet with flexibility, real-time and reliability services. For these reasons, TSN represents an appealing technology for the networks of Cyberphysical Systems. Nevertheless, TSN does not cover some reliability aspects that are important to reach the reliability levels required by certain Cyberphysical Systems. Specifically, TSN does not devise any time redundancy mechanisms in the layer 2 to tolerate temporary faults in the channel. Thus, we proposed a time redundancy mechanism, called Proactive Transmission of Replicated Frames, to increase the reliability of TSN-based networks. In this work we describe two previous designs
of PTRF and we present a new design. We also describe the simulation model used to compare the designs. Specifically, we carried out exhaustive fault injection to validate the mechanism and a case study to compare the three designs.
Cyber-Physical Systems (CPSs) usually execute critical applications, which imposed the use of specialised networks due to their high reliability and hard real-time requirements. There is a growing interest in developing CPSs capable of adapting to unpredictable changes in the environment without jeopardising their correct operation. Ethernet is an appealing technology to build the networks of future adaptive CPSs, due to the advantages in bandwidth, cost and internet compatibility offered. Ethernet lacks real-time, reliability and flexibility services. Thus, the IEEE Time-Sensitive Networking task group are developing a set of standards (commonly referred to as TSN) to provide Ethernet with said services. Nevertheless, TSN’s reliability services are not enough for some highly-critical applications. Thus, we proposed a mechanism to tolerate temporary faults in the Layer 2 of TSN-based networks. In this work we propose to mix time and spatial redundancy over a TSN-based network to increase its reliability while reducing resource consumption.
This paper presents the design of Xiroi: a modular Autonomous Surface Vehicle (ASV) built to guarantee a stable and continuous Acoustic Communication Link (ACL) between an underwater vehicle and a remote computer, either located on the shore or on a support vessel. The ASV is commanded to automatically ensure a close distance for the ACL by following the submarine platform when underwater, and keeping a safety distance when it surfaces.
The platform can be operated in the following ways: (i) Autonomous Underwater Vehicle (AUV) tracking, where the vehicle is required to track a moving frame (e.g. the AUV) without the need to know the actual position of the platform, (ii) path following, where the objective of the vehicle is to achieve a number of waypoints in a time window and (iii) station keeping, where the vehicle holds its GPS position regardless of the wind or water currents.
This paper describes the architecture and mechanisms proposed in the context of the DFT4FTT project for implementing Adaptive Distributed Embedded Systems (ADESs), that is, distributed systems with real-time, dependability and adaptivity requirements. The focus is on the reconfiguration strategies that allow, not only to change the system behaviour, but to improve its tolerance to permanent hardware faults.