Avionics Time Sync via Switch Delay Compensation
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Solution Overview
Problem
Existing time synchronization methods, such as ARINC 429, are not scalable for broad Ethernet-based avionics networks and do not efficiently distribute precise timing information to all nodes, leading to time delays and state estimation errors in aircraft and autonomous vehicle systems.
Innovation Solution
A time synchronization system utilizing a source clock that generates Ethernet-compatible timing messages, relayed through redundant and deterministic switch-based network switches, ensuring precise timing information is distributed to all end systems, including backup clocks for continuity during GNSS outages, and accounting for network delays to maintain synchronization accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ARINC 429 compatible wired networks are used for time distribution, then time synchronization can be achieved in point-to-point networks, but the network expansion capability is limited and does not scale to broad Ethernet-based avionics networks
Solution Approach 1:
The patent introduces PTP protocol as an intermediary mechanism that enables time synchronization in Ethernet-based networks. The PTP protocol acts as a mediator between the time source and network switches, allowing precise time distribution across broad Ethernet networks while maintaining synchronization reliability through standardized time stamping and delay measurement mechanisms.
Solution Approach 2:
The patent changes the time distribution parameter from ARINC 429 time mark signals to PTP protocol messages. This parameter change enables the system to transition from point-to-point wired networks to broad Ethernet-based networks, achieving both network expansion capability and time synchronization reliability through the flexible addressing and routing capabilities of Ethernet while maintaining precise time distribution.
2Measurement precision
If ARINC 429 time mark is distributed to every network node, then time synchronization can be maintained, but the approach does not scale to broad Ethernet-based networks
Solution Approach 1:
The patent segments the time distribution function into hierarchical levels: grandmaster clocks provide time to domain clocks, which then distribute to edge clocks, and finally to network nodes. This segmentation reduces network distribution complexity by localizing time synchronization within domains while maintaining precision through the hierarchical structure, avoiding the need to distribute time marks to every node directly across the entire network.
Solution Approach 2:
The patent transitions from a flat point-to-point time distribution architecture to a hierarchical multi-dimensional structure. Time synchronization is achieved not just through direct node-to-node connections but through intermediate domain clocks that manage local domains, adding a dimensional layer to the distribution architecture that reduces overall network complexity while maintaining precision.
3Reliability
If redundant network paths are implemented for fault tolerance, then system reliability improves, but network delay variation increases
Solution Approach 1:
The patent implements dynamic path selection and delay compensation mechanisms that adapt to changing network conditions. The system dynamically adjusts time stamping and delay measurements based on actual packet transmission paths, allowing redundant paths to be utilized for fault tolerance while compensating for delay variations through real-time measurements and adjustments in the PTP protocol execution.
Data Source
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AI summary
A system for time synchronization over redundant switch-based avionics networks is disclosed. The system includes a master or source clock (104) for determining precise UTC timing information from received satellite signals and generating time marks based on the timing information. The source clock generates network-compatible timing messages and forwards the timing messages to network switches (106) within the switch-based avionics networks. The network switches modify the timing information to account for switch-based delays and forward the modified timing messages to destination clocks (124) in aircraft end systems (108). The end systems relay timing messages back to the source clock via the network switches, the timing information again modified by the network switches according to switch-based delays, and based on the precise timing information exchanged destination clocks in end systems throughout the switched network can precisely synchronize to the source clock.