Efficient probabilistic model checking of smart building maintenance using fault maintenance trees

Abstract

Cyber-physical systems, like Smart Buildings and power plants, have to meet high standards, both in terms of reliability and availability. Such metrics are typically evaluated using Fault trees (FTs) and do not consider maintenance strategies which can significantly improve lifespan and reliability. Fault Maintenance trees (FMTs) -an extension of FTs that also incorporate maintenance and degradation models, are a novel technique that serve as a good planning platform for balancing total costs and dependability of a system. In this work, we apply the FMT formalism to a Smart Building application. We propose a framework for modelling FMTs using probabilistic model checking and present an algorithm for performing abstraction of the FMT in order to reduce the size of its equivalent Continuous Time Markov Chain. This allows us to apply the probabilistic model checking more efficiently. We demonstrate the applicability of our proposed approach by evaluating various dependability metrics and maintenance strategies of a Heating, Ventilation and Air-Conditioning system's FMT.

Modelling Smart Buildings Using Fault Maintenance Trees

“…HVACs offer a decomposition in subsystems fitting nicely the FMT approach. The concrete model studied is taken from [5]: Fig. 1 shows a visual description of the setup.…”

“…Typically, FMT analysis is performed via statistical model checking (SMC, [19]). Analysing (smart buildings using) FMTs via probabilistic model checking (PMC) was introduced in [5]. In that work, component degradation of an HVAC is discretised in time using phases, with a stepwise degradation behaviour approximated via Erlang distributions, and using inspection and repair modules to regulate maintenance actions.…”

“…Standing on the FMT model framework introduced in [5], in the following sections we present a sequence of modelling setups which extend the central case study of that work. We enhance the modelling and analysis of the HVAC FMT by adding realistic flavours, to attune the maintenance policies towards their application in the real world.…”

“…2 presents the fundamental theoretical basis; Sect. 3 introduces the central case study, an HVAC unit, where the root HVAC model inspired in [5] is presented in Sect. 3.1; The four modelling extensions are introduced and analysed in Sects.…”

Benchmarks for cyber-physical systems: A modular model library for building automation systems

“…Interest in BAS, also colloquially known as smart buildings, is gaining rapid momentum, in particular as a means for ensuring thermal comfort ( [1]), minimising energy consumption ( [17,19]), and ascertaining reliability ( [4,20]). Quantitative models are needed to evaluate system performance, to verify correct behaviour, and to develop specific control algorithms.…”