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Functional safety communication for distributed control system: Experimental evaluation of the OPC UA safetys
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School of Electrical Engineering |
Master's thesis
Electronic archive copy is available via Aalto Thesis Database.
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Mcode
Language
en
Pages
70
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Abstract
As Industry 4.0 drives the migration toward network-centric architectures, ensuring functional safety in Distributed Control Systems (DCS) becomes increasingly critical. OPC UA Safety offers a promising solution for vendor-independent safety communication; however, its performance on resource-onstrained embedded platforms remains largely unexplored. This thesis presents a systematic evaluation of the OPC UA Safety protocol on an embedded real-time platform, specifically targeting the Xilinx ZCU102 MPSoC.
To assess the protocol’s viability, a comprehensive test framework was devel-
oped, incorporating automated configuration and the PREEMPT_RT patch to ensure deterministic timing. The study conducted extensive performance benchmarking, executing one million test samples per configuration to measure OPC UA Safety Stack Request-Response Round Trip Time (UAS ReqRes RTT), jitter, and system resource usage (CPU/RAM).
The calibration results demonstrate that the PREEMPT_RT patch significantly enhances system determinism, reducing the 90th percentile of OS scheduling latency from 710 μs to 33 μs.
Experimental results further reveal that CycleTime is the dominant factor influencing UAS ReqRes RTT distribution, with larger CycleTime resulting in significantly higher stability and tighter clustering. In contrast, the Publishing Interval shows a secondary impact, primarily affecting extreme tail latencies, while SPDU (Safety Protocol Data Unit) payload size difference demonstrates minimal influence. Furthermore, footprint analysis indicates a clear correlation: CPU usage increases with higher-frequency operations (smaller CycleTime and Publishing Interval), yet remains within efficient limits, averaging below 12% for all test cases. Meanwhile, RAM usage demonstrates exceptional stability across all configurations, staying within the range of 3.3% to 3.5%.
Overall, this research validates the feasibility of deploying OPC UA Safety on embedded systems over standard Ethernet. The findings provide a practical performance model and essential guidance for selecting communication parameters in next-generation industrial safety applications.
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Supervisor
Manner, JukkaThesis advisor
Dán, GyörgyZeng, Yanghang