Bjarne Johansson's PhD Defense

2025/09/02

Bjarne Johansson , ARRAY PhD student will defend his PhD thesis on 6th November 2025 at 13:15 in Västerås Campus

Title:

Revisiting Spatial Redundancy in Industrial Controller Architectures: A Network-Centric Perspective

Date and time: November 6th, 2025 13:15

Room: Kappa (Västerås Campus)

Opponent:

Associate Professor Thilo Sauter, University for Continuing Education Krems, Austria

Committee:

Professor Ahlem Mifdaoui, University of Toulouse, France;

Professor Luis Almeida, University of Porto, Portugal,

Professor Paul Pop, Technical University of Denmark, Denmark.

Abstract:

Automation solutions are omnipresent in modern society as a part of the infrastructure that provides utility services such as water and power. At the core of these systems is the controller, a specialized computer designed to operate in harsh environments where unplanned downtime can be costly. High-quality hardware, software, and spatial redundancy (i.e., hardware multiplication) are commonly employed to mitigate disruptions.

Industrial control systems are evolving into more interconnected and interoperable architectures, marking a shift toward network-centric designs where the network, rather than the controller, becomes the central part of the system. Concepts traditionally associated with information technology, such as edge and cloud computing, containerization, and orchestrators, are entering the operational technology domain. New standards, such as OPC UA, with its information model and communication protocols, are gaining traction to facilitate interoperability.

This evolution presents redundancy challenges, such as adapting failure detection and state transfer mechanisms needed by standby redundancy to a network context, and opportunities, such as utilizing systems previously confined to the information technology domain. This shift toward a network-centric control system architecture is the overarching motivation for this thesis's revisit of spatial redundancy.

Specifically, this thesis investigates orchestrator-aided failure recovery as a complement to traditional redundancy. It also proposes a failure detection mechanism that maintains consistent control during network partitioning between redundant controllers. The thesis also examines the behavior of OPC UA PubSub in a standby redundancy context. It introduces a method for processing priority based on information embedded in incoming network frames. Additionally, the thesis proposes an architecture that enables the distribution of redundancy-related state data. It also investigates checkpointing solutions and communication protocols to identify a suitable mechanism for transferring state data between redundant controllers.