Redundant Packet Forwarding via Switcher Unit for EtherCAT Networks
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Solution Overview
Problem
Existing redundant EtherCAT network systems face challenges in supporting both redundancy and Distributed Clock (DC) synchronization without significant modifications to the master device, and they experience processing complexity and jitter due to the need for packet duplication and topology changes during synchronization updates.
Innovation Solution
The implementation of a switcher unit, either embedded in a slave or as a separate device, between the master's redundant port and the last slave, which detects a circulating bit to switch between terminating and transfer modes, allowing for seamless distributed clock synchronization and maintaining network connectivity even after a failure, without requiring changes to the master device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant network topology with ring configuration is implemented, then network reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the redundant network into two independent subsequences after a connection break, with each subsequence managed by a respective embedded slave. This segmentation allows independent handling of each path, reducing the complexity of managing the entire redundant network as a single complex system.
Solution Approach 2:
The patent introduces an intermediary mechanism where embedded slaves act as mediators between the master and the network segments. The embedded slaves handle clock synchronization and packet forwarding independently, reducing the complexity burden on the master device while maintaining network reliability.
2Measurement precision
If Distributed Clock synchronization is implemented in redundant topology, then synchronization precision is improved, but processing complexity increases
Solution Approach 1:
The patent segments the clock synchronization process into independent operations for each subsequence. Each embedded slave performs DC synchronization independently for its connected slaves, avoiding the need for complex centralized synchronization management and reducing processing complexity while maintaining precision.
Solution Approach 2:
The patent performs preliminary clock synchronization setup during network initialization, establishing reference clocks and synchronization parameters before actual data transmission begins. This preliminary action simplifies ongoing synchronization operations and reduces real-time processing complexity.
3Reliability
If packet duplication is performed for redundancy, then network reliability is improved, but productivity decreases
Solution Approach 1:
The patent implements dynamic packet forwarding where packets are routed through different paths based on real-time network conditions and failure states. This dynamic approach eliminates the need for continuous packet duplication, improving productivity while maintaining reliability through adaptive routing.
Solution Approach 2:
The patent extracts the packet duplication function from the master device and implements it selectively at embedded slaves only when needed for redundancy. This selective extraction reduces unnecessary processing overhead and improves overall network productivity while maintaining reliability.
4Adaptability or versatility
If topology changes are made during synchronization updates, then adaptability is improved, but loss of time increases
Solution Approach 1:
The patent performs topology change preparation in advance by pre-configuring alternative paths and synchronization parameters. When updates are needed, the system can switch to pre-prepared configurations without time-consuming real-time calculations, reducing time loss while maintaining adaptability.
Solution Approach 2:
The patent implements periodic synchronization updates at optimized intervals, combining multiple updates into single topology changes when possible. This periodic approach balances adaptability with time efficiency, avoiding excessive topology changes while ensuring network synchronization remains current.
Data Source
AI summary
A master device has a slave port and a redundant slave port for communicating with slaves according to a network protocol, e.g. EtherCAT, via data packets including a circulating bit. The slaves are arranged in a sequence starting at the slave port, and are connected via a communication medium. A respective slave in the sequence detects whether the connection to its processing receiver is lost, and, if so, internally transfers any data packets from its forwarding arrangement to its processing arrangement, while setting the circulating bit. The master device has a switcher unit coupled to the redundant slave port and a last slave in the sequence. The switcher unit transfers data packets from the switcher receiver to the switcher transmitter, and detects whether a circulating bit is set. If so, the unit switches off said transferring and switches on a connection between the redundant slave port and the switcher for transferring replicated packets to the sequence. Advantageously, the system enables hot plug-in and also distributed clock synchronization, and reduces the processing requirements of the master device.