PLC-Controlled Redundant Link Switching in Flat Ethernet Networks
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Solution Overview
Problem
Flat network architectures in industrial automation systems lack effective redundancy management, leading to increased complexity and costs when attempting to enhance connectivity between control and device networks, particularly due to the risk of broadcast storms and the need for intelligent routing protocols like Spanning Tree Protocol.
Innovation Solution
A daisy chain loop topology is implemented with a primary and secondary PLC connected via a dedicated link, where the secondary PLC logically enables and disables Ethernet ports of switches to manage redundancy, reducing the need for complex protocols and equipment by allowing failover without introducing additional network complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flat network architecture is used to maintain simplicity and transparency, then ease of operation is improved, but redundancy and reliability deteriorate
Solution Approach 1:
The system pre-configures a secondary PLC in standby mode with all necessary communication pathways and control logic ready before failure occurs. When the primary PLC fails, the secondary PLC can immediately take over without requiring complex real-time reconfiguration or protocol negotiations, thus maintaining ease of operation while ensuring reliability through predetermined redundancy
2Reliability
If additional connections are added to improve redundancy, then reliability is improved, but device complexity increases
Solution Approach 1:
The secondary PLC is integrated into the existing flat network architecture using the same communication protocols and infrastructure as the primary PLC. Both PLCs share the same network switches and communication pathways, merging redundancy functionality into the existing structure rather than adding separate redundant systems. This approach improves reliability through duplication of critical components while avoiding the complexity increase that would result from hierarchical structures or specialized routing protocols
3Reliability
If Spanning Tree Protocol is implemented to prevent broadcast storms, then reliability is improved, but device complexity and costs increase
Solution Approach 1:
The patent extracts the loop prevention function from complex protocols like Spanning Tree and implements it through a simpler mechanism: the secondary PLC actively monitors the network for broadcast storms and dynamically disables its Ethernet port when loops are detected. This approach maintains reliability by preventing broadcast storms while avoiding the complexity and computational overhead of implementing full Spanning Tree Protocol in network switches
Data Source
AI summary
A control device having an integrated switch and being configured to logically enable and disable an Ethernet port of the integrated switch. Further disclosed is a device network consisting of at least two field devices, a primary control device and a primary switch, a secondary control device and a secondary switch, which are connected in a daisy chain loop topology. And wherein the secondary control device is configured to logically enable and disable an Ethernet port of the secondary switch. Further disclosed is a flat network consisting of such a device network. Further disclosed is a method for controlling a redundant connection in a flat network, consisting of detecting failure of the primary control device, initiating failover, enabling the Ethernet port of the secondary switch, and disabling the Ethernet port of the primary switch.