Real-Time Ethernet Protocol Reducing Cycle Time to 4 μs
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Solution Overview
Problem
Current real-time Ethernet protocols are limited by cycle times of around 30 μs, which are insufficient for applications requiring shorter control cycles, such as milling or computer numerical control machines, and do not guarantee deterministic data delivery or sequence in industrial automation systems.
Innovation Solution
A new real-time Ethernet protocol that reduces frame length, interframe gap, and dynamically switches between frame forwarding modes, enabling a control cycle time of 4 μs or less for up to 4 Ethernet devices by using frame-based digital communications, and includes start-up frames for network initialization and data exchange frames without source or destination addresses, allowing for user-modifiable network parameters and error handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard Ethernet protocols are used, then compatibility and ease of operation are improved, but cycle time and real-time performance deteriorate (30 μs or more)
Solution Approach 1:
The protocol is segmented into distinct phases: start-up phase for network initialization and data exchange phase for actual communication. This segmentation allows optimization of each phase independently, enabling ultra-short cycle times during data exchange while maintaining standard Ethernet compatibility during initialization.
Solution Approach 2:
The protocol dynamically changes key parameters including frame length (reduced to minimal size), interframe gap (reduced to 960 ns), and forwarding mode (switched between store-and-forward and cut-through). These parameter changes enable the system to achieve 4 μs cycle time while maintaining Ethernet compatibility.
2Loss of time
If frame length and interframe gap are reduced, then cycle time is improved (to 4 μs or less), but frame structure complexity increases
Solution Approach 1:
The protocol implements dynamic switching between different frame forwarding modes (store-and-forward and cut-through) based on network conditions and data requirements. This dynamic adaptation allows the system to optimize cycle time by selecting cut-through mode when speed is critical, while maintaining robustness by switching to store-and-forward when needed.
Solution Approach 2:
Network parameters including frame structure, forwarding modes, and timing parameters are pre-configured during the start-up phase. This preliminary configuration eliminates the need for complex real-time negotiations during data exchange, simplifying the operational frame structure while achieving ultra-short cycle times.
3Reliability
If deterministic real-time communication is achieved, then reliability is improved, but protocol complexity increases
Solution Approach 1:
The protocol implements self-service mechanisms where each device autonomously manages its transmission timing and frame forwarding based on pre-configured parameters. Devices independently determine when to transmit and how to forward frames without complex centralized control, achieving deterministic delivery while keeping individual device complexity low.
Solution Approach 2:
The protocol uses periodic time slots for data exchange between master and slave devices. Each device has predetermined transmission windows, creating a rhythmic, predictable communication pattern that ensures deterministic delivery without requiring complex real-time arbitration or scheduling algorithms.
4Productivity
If cycle time is reduced to 4 μs or less, then productivity is improved, but manufacturing precision requirements increase
Solution Approach 1:
The protocol replaces mechanical timing mechanisms with electronic timestamping and hardware-based timing circuits. Precise time measurement is achieved through electronic counters and timestamps rather than mechanical clocks, enabling 4 μs or less cycle times with the required timing precision for industrial control applications.
Data Source
AI summary
A real-time Ethernet (RTE) protocol includes start-up frames originated by a master device for network initialization including a preamble, destination address (DA), source address (SA), a type field, and a status field including state information that indicates a current protocol state that the Ethernet network is in for the slave devices to translate for dynamically switching to one of a plurality of provided frame forwarding modes. The start-up frames include device Discovery frames at power up, Parameterization frames that distribute network parameters, and Time Synchronization frames including the master's time and unique assigned communication time slots for each slave device. After the initialization at least one data exchange frame is transmitted exclusive of SA and DA including a preamble that comprises a header that differentiates between master and slave, a type field, a status field excluding the current protocol state, and a data payload.