Contract-based design for robust networked control systems in industrial automation

Ensuring real-time constraints for industrial distributed control systems remains challenging, particularly for models such as IEC 61499 that prioritise functionality and device mapping over network communication and formal timing guarantees. This can lead to performance degradation and safety hazards. Our approach formally enhances the definition of the logical messages and introduces a systematic methodology for mapping a message to physical channels that represent the communication protocol. Thereby, this work enables precise timing verification and deterministic execution. Our approach enforces controlled message transmission and synchronisation through the utilised communication protocol and contract-based design to determine a feasible communication schedule. Using virtual integration testing, we verify network communication timing across three refinement steps, demonstrating scalable contract reuse and addressing challenges for timing constraints in the case of closed-loop control. Key contributions of this work are (1) a formal definition of messages, (2) a systematic mapping strategy to ensure deterministic communication, (3) enhanced synchronisation mechanisms, (4) explicit scheduling enforcement, and (5) a case study demonstrating how the proposed modelling approach enables verification of distributed systems. By integrating timing verification at design time, our approach mitigates the impact of non-determinism and communication delays, reduces redesign efforts, and improves the reliability of industrial distributed control systems while ensuring compliance with strict timing constraints in industrial automation.