To guarantee high availability, automation systems must be fault-tolerant. To this end, they must provide redundant solutions for the critical parts of the system. Classical fault tolerance patterns such as standby or N-modular redundancy provide system stability in the case of a fault. Fault tolerance is subsequently degraded or, depending on the number of deployed replicas, often even unavailable until the system has been repaired.We introduce a combination of a component-based framework, redundancy patterns, and a runtime manager, which is able to provide fault tolerance, to detect host failures, and to trigger a reconfiguration of the system at runtime. This combined solution maintains system operation in case a fault occurs and automatically restores fault tolerance. The proposed solution is validated using a case study of an industrial distributed automation system. The validation shows how our solution quickly restores fault tolerance without the need for operator intervention or immediate hardware replacement while limiting the impact on other applications.
When an emergency occurs within a building, it may be initially safer to send autonomous mobile nodes, instead of human responders, to explore the area and identify hazards and victims. Exploring all the area in the minimum amount of time and reporting back interesting findings to the human personnel outside the building is an essential part of rescue operations. Our assumptions are that the area map is unknown, there is no existing network infrastructure, long-range wireless communication is unreliable and nodes are not locationaware. We take into account these limitations, and propose an architecture consisting of both mobile nodes (robots, called agents) and stationary nodes (inexpensive smart devices, called tags). As agents enter the emergency area, they sprinkle tags within the space to label the environment with states. By reading and updating the state of the local tags, agents are able to coordinate indirectly with each other, without relying on direct agent-to-agent communication. In addition, tags wirelessly exchange local information with nearby tags to further assist agents in their exploration task. Our simulation results show that the proposed algorithm, which exploits both tag-to-tag and agent-to-tag communication, outperforms previous algorithms that rely only on agent-to-tag communication.
Building automation systems (BAS) are technologies which automatically control building appliances based on specialized algorithms to achieve predefined goals, such as optimising user comfort or regulating energy consumption. Normally, they are configured during deployment as a one-time effort by technicians with expert knowledge and tools. However, the dynamic nature of the environment and the preferences of occupants calls for the need of frequent reconfigurations, which is often impractical and expensive to implement. As a solution, we propose a novel BAS design which considers user-based information such as user preferences and feedback in order to continuously reconfigure itself, as opposed to static configurations. This high-level information is then adopted by a software framework based on multi-agent systems (MAS) that applies the PROSA reference model [9] to dynamically control the building. Under this framework, every room in the building is automated by a dedicated agent, acting as a software mediator between the appliances and its occupants, with the aim of maximising the result of a utility function taking into account power optimisation, user comfort, and environment dynamics. The proposed approach has been implemented in a real office environment, and we discuss our design to improve user experience a BAS deployment.
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