Fault Tolerant Vehicle Time Synchronization via Ignition Cycle Switching
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Solution Overview
Problem
Current time synchronization systems in vehicle networks, particularly in autonomous vehicles and Advanced Driving Assistance Systems, fail to account for conditions like primary grand leader clock failures and subsequent recoveries, leading to potential inaccuracies in sensor data timestamping and application execution.
Innovation Solution
A fault-tolerant time synchronization system that includes a primary grand leader clock and a standby grand leader clock, with a processor programmed to synchronize time follower clocks based on ignition cycles and link availability, using multiple time domains to ensure continuous accurate synchronization and minimize time discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single primary grand leader clock is used for time synchronization, then the system structure is simple, but the system fails to account for clock failures and recoveries leading to synchronization inaccuracies
Solution Approach 1:
The system pre-establishes a standby grand leader clock that is ready to take over if the primary clock fails. The standby clock is continuously synchronized with the primary clock and maintains readiness to assume the leader role without interruption, enabling fault tolerance before failures occur.
Solution Approach 2:
The standby grand leader clock is a replica of the primary clock, maintaining the same synchronization functionality and timekeeping capabilities. This copy allows the system to continue operating with accurate time synchronization even when the primary clock fails, by switching to the standby copy.
2Reliability
If the time follower clock switches to standby grand leader clock upon primary failure, then continuous synchronization is maintained, but time discontinuities may occur if the primary clock recovers quickly
Solution Approach 1:
The system continuously monitors the operational status of the primary grand leader clock and uses this feedback to determine when to switch to the standby clock and when to switch back. The feedback mechanism includes detecting failure conditions and recovery conditions, enabling intelligent switching decisions that maintain both continuity and accuracy.
Solution Approach 2:
The synchronization system dynamically adjusts its configuration based on real-time clock status. The processor can switch between primary and standby clocks, and between different time domains, based on the operational conditions, enabling the system to adapt to changing circumstances and maintain optimal performance.
3Measurement precision
If the system monitors for ignition cycle changes to determine clock switching, then time continuity is maintained, but the complexity of monitoring and decision-making increases
Solution Approach 1:
The system uses the vehicle's existing ignition cycle information, which is already being tracked by the vehicle's control systems, to determine when to switch between time domains. This self-service approach leverages existing data without requiring separate monitoring infrastructure.
Solution Approach 2:
The ignition cycle monitoring serves multiple purposes: it tracks vehicle operational state, determines appropriate time domain switching, and provides a reference for synchronization decisions. This multi-functionality reduces the need for separate dedicated monitoring systems.
Data Source
AI summary
A system for synchronization of multiple clocks in a vehicle network includes a processor that is programmed to synchronize a time follower clock to a primary grand leader clock. The primary grand leader clock is monitored and the time follower clock is synchronized to a standby grand leader clock upon a failure of the primary grand leader clock. The time follower clock is synchronized to the primary grand leader clock if a new ignition cycle has occurred between a failure of the primary grand leader clock and a recovery after failure of the primary grand leader clock. The time follower clock continues to be synchronized to the standby grand leader clock if a new ignition cycle has not occurred between the failure of the primary grand leader clock and the recovery after failure of the primary grand leader clock.