Tim BEDFORD, Professor
Department of Management Sciences
University Associate Principal (Vice President)
for Research and Innovation
University of Strathclyde, UK
"Requisite Reliability Modelling
in Complex Engineered Systems"
Complex engineered systems underpin many of the essential components of modern society. The reliability of these systems is therefore essential to operate those components efficiently and safely. In this presentation I shall look at how reliability modelling can support different levels of decision making for such systems and the challenges in designing approaches which are useful for practitioners and decision-makers.
The challenge for reliability modelling in complex engineered systems is often two-fold. The system itself is by definition complex, with many interacting subsystems and components, many different mechanisms that could lead to failure and degraded function of those components, and multiple ways in which the system as a whole can operate at different levels of quality or effectiveness. The second challenge is that people interact with the system in multiple ways, as operators, users, and maintainers, planners and regulators, placing different types of demands on the systems and making decisions which impact the state of the system.
The notion of a requisite model was introduced by the Operational Researcher Larry Phillips, who defined it as follows: A requisite decision model is defined as a model whose form and content are sufficient to solve a particular problem. The model is constructed through an interactive and consultative process between problem owners and specialists (decision analysts).
While many mathematical reliability challenges do not require us to use the idea of requisite modelling, those involving the study of complex engineered system most certainly do. At Strathclyde we have worked on a number of complex modelling situations where important choices have to be made about the way the real world system is represented in order to ensure that it represents the impact of a specific range of options of interest to the decision maker.
The processes involved in developing such modelling approaches in our contexts include:
We shall discuss approaches to requisite modelling in complex engineered systems, using examples from work carried out at the University of Strathclyde including power stations, wind farms and electricity networks. This work has been carried out with a number of colleagues including Lesley Walls, Euan Barlow, Matthew Revie, Athena Zitrou, Junchi Tan, Abby Colson, Keith Bell, John Quigley, Babakalli Alkali.
- Judicious selection of black box and white box modelling elements to avoid complexity where possible but to explicitly model features of importance to gain decision makers trust
- Representation of uncertainty, differentiating between aleatory and epistemic uncertainties
- Selection of intermediate and outcome metrics.
- Understanding of the role of loadings and environment in short and longer term condition, and of partial operation.
- Understanding the role of operators, users, maintainers etc, and the key drivers in their decision making.
- Understanding the impact of regulation and higher level business policies on the operation of the system and on data collected for the system.
- Obtaining appropriate data from empirical, analogy and expert data sources
Tim Bedford is Professor of Decision and Risk Analysis at the University of Strathclyde working at the Department of Management Science in Strathclyde Business School. He is also the University Associate Principal (Vice President) for Research and Innovation.
He studied mathematics at Warwick University where he obtained BSc, M.Sc. and Ph.D. degrees. He holds an Honorary Doctorate in recognition of his work in risk analysis, from the Faculté Polytechnique de Mons, and has been elected a Fellow of the Royal Society of Edinburgh, Scotland’s National Academy. He held a fellowship at King's College Cambridge moving later to Delft University of Technology before going to Strathclyde.
Prof Bedford has been active in various professional societies, amongst others the European Safety and Reliability Association and the Dutch Reliability Society, of which he was Chair. He has been Chair of the Committee of Professors of Operational Research, the network of UK OR Professors and was a member of the Board of Directors of the European Safety Reliability and Data Association ESReDA. He has been elected a Fellow of the UK Safety and Reliability Society and of the Institute for Mathematics and its Applications. He was awarded the Donald Julius Groen prize for 2009 by the IMechE Safety and Reliability Group, and in 2013 was awarded the Lloyds Risk Prize for work on Societal Risk. He has co-chaired major international conferences including MMR2007, EURO2015 and ESREL2016.