Clock Synchronization in Railway Distributed Controllers
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Solution Overview
Problem
Current railway systems face challenges in ensuring rapid response times while maintaining security, particularly in distributed systems like CBTC, which require synchronized operations between platform screen doors and train control systems.
Innovation Solution
Implementing a synchronization method that synchronizes local clocks within the controller's processing chains using a global clock, reducing asynchronism and latency through redundant processing chains and secure clock mechanisms, ensuring timely and secure operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a distributed system is used to manage railway operations, then system versatility and automation are improved, but asynchronism between local clocks increases response time variability
Solution Approach 1:
The patent introduces a global clock as an intermediary time reference that mediates between multiple local clocks in the distributed system. Each processing chain uses its local clock but references the global clock to determine common time intervals, reducing asynchronism while preserving distributed automation.
Solution Approach 2:
The patent changes the time parameter representation by introducing a common local time interval derived from the global clock. This allows processing chains to operate with synchronized time references, reducing response time variability without eliminating distributed operation.
2Device complexity
If local clocks are used in processing chains, then system complexity is reduced, but asynchronism between clocks reduces measurement precision
Solution Approach 1:
The patent segments the timekeeping function into two parts: local clocks continue to operate independently for timing processing chains, while a global clock provides periodic synchronization references. This segmentation maintains low complexity at the local level while improving precision through global coordination.
Solution Approach 2:
The global clock performs preliminary synchronization by establishing a common local time interval before processing chains execute their operations. This preliminary time reference reduces asynchronism without requiring complex real-time synchronization mechanisms.
3Reliability
If security margins are increased to ensure safety, then system reliability is improved, but response time increases
Solution Approach 1:
The patent applies partial synchronization by using the global clock to establish a common time interval for critical security functions while allowing local clocks to operate independently for non-critical operations. This partial application of synchronization provides sufficient security for safety-critical functions without unnecessarily increasing response time for all system operations.
Data Source
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AI summary
The present invention relates to a method for synchronizing a system comprising redundant processing chains, the method comprising providing a first instant by the global clock for each processing chain, converting the first instant into the first local instant for each processing chain, implementing the same series of operations on the same input data on each processing chain from the first local instant, incrementing the second local clock specific to each processing chain to obtain a second local instant, calculating the local time interval defined as the difference between the second local instant and the first local instant, comparing the calculated local time intervals to determine a local time interval common to a majority of processing chains.