Modelling Smart Buildings Using Fault Maintenance Trees

Abstract

Increasingly many industrial spheres are enforced by law to satisfy strict RAMS requirements-reliability, availability, maintainability, and safety. Applied to Fault Maintenance Trees (FMTs), formal methods offer flexible and trustworthy techniques to quantify the resilience of (abstract models of) systems. However, the estimated metrics are relevant only as far as the model reflects the actual system: Refining an abstract model to reduce the gap with reality is crucial for the usefulness of the results. In this work, we take a practical approach at the challenge by studying a Heating, Ventilation and AirConditioning unit (HVAC), ubiquitous in smart buildings. Using probabilistic and statistical model checking, we assess RAMS metrics of a basic fault maintenance tree HVAC model. We then implement four modifications augmenting the expressivity of the FMT model, and show that reliability, availability, expected number of failures, and costs, can vary by orders of magnitude depending on involved modelling details.

Quantifying the impact of resource redundancy on smart city system dependability: a model-driven approach

“…Kharchenko et al [20] presented a control system for smart buildings that incorporates a three-level architecture for the building automation system, encompassing FPGA, communication, and management components. Abate et al [1] applied quantitative model checking to analyze the Fault Maintenance Tree (FMT) of a Heating, Ventilation, and Air-Conditioning (HVAC) unit in a smart building. Specifically, they modeled the FMT using continuous-time Markov chains and priced time automata.…”

“…Previous research has not comprehensively addressed the crucial aspect of dependability in the context of smart cities, specifically in analyzing multiple sub-architectures concurrently. Most studies have focused on smart buildings, examining automation mechanisms and Internet of Things (IoT) sensor communication [20,1,4,32,39]. Only one paper has explored the topic of smart surveillance [17].…”

Rare event simulation for non-Markovian repairable fault trees

“…Since the number of states (i.e. system configurations) is exponential in the number of tree elements, analysing large trees remains a challenge today [26,1]. Moreover, numerical methods are usually restricted to exponential failure rates and combinations thereof, like Erlang and acyclic phase type distributions [40].…”

“…Now, if a clone observes a new head (HH), this is even more promising than H, so the splitting can be repeated. If we make 5 copies of the HH clone, then observing three heads in any of these copies counts as 1 35 = 1 7 • 1 5 . Alternatively, observing tails as second flip (HT ) is less promising than heads.…”

“…Our approach can converge to precise estimations in increasingly reliable systems. This method has four advantages over earlier analysis methods for rfts-which we overview in the related work section 6namely: (1) we are able to estimate both the system reliability and availability;…”