Vehicle Gateway Clock Synchronization Across Fieldbus Systems
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Solution Overview
Problem
Current vehicles lack the ability to determine the exact age of data exchanged across different bus systems, such as FlexRay, making it impossible to precisely measure latency in data transmission, which hinders the implementation of time-critical vehicle functions.
Innovation Solution
A gateway and node system that synchronizes clocks across different bus systems using the Precision Time Protocol (PTP) and generates timestamps to enable accurate determination of data age, allowing for reduced data overhead and efficient synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data is exchanged across different bus systems (e.g., FlexRay to CAN), then data exchange between systems is enabled, but the ability to determine the exact age of exchanged data is lost
Solution Approach 1:
The gateway acts as an intermediary between different bus systems, implementing a timestamp mechanism that preserves timing information across protocol boundaries. The gateway receives data with timestamps from one bus system and forwards it to another bus system, maintaining the timing reference through the translation process.
Solution Approach 2:
Timestamps are generated at the source node before data leaves the first bus system, and this timing information is preserved and transmitted through the gateway to the second bus system. This preliminary tagging of data with timing information enables later determination of data age regardless of the bus system boundaries crossed.
2Device complexity
If clocks in different nodes are not synchronized, then device complexity is reduced, but latency measurement becomes impossible
Solution Approach 1:
The system implements a timestamp feedback mechanism where senders attach timestamps to data packets, and recipients use these timestamps to calculate transmission latency. This feedback loop provides timing information without requiring complex continuous clock synchronization between all nodes.
Solution Approach 2:
Instead of synchronizing clock frequencies and phases across all nodes (which would be complex), the system changes the approach by using discrete timestamp parameters at specific events (data transmission moments). This transforms the continuous clock synchronization problem into discrete timing markers that are easier to implement and measure.
3Measurement precision
If timestamps are added to every data message, then data age can be determined precisely, but data overhead increases
Solution Approach 1:
The timestamp functionality is extracted as a separate, optional field in the data message structure. Rather than embedding timing information in every aspect of the protocol, the timestamp is taken out as a distinct element that can be added or removed based on whether timing measurement is needed for that particular data exchange.
Data Source
AI summary
A gateway for a vehicle communication system is configured to forward a payload message from a first node of a first fieldbus system to a second node of a second fieldbus system, wherein the first and the second fieldbus systems are different. The gateway is configured to synchronize a first clock in the first node with a second clock in the second node.