Redundant Signal Comparison With Delay Compensation Circuits
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Solution Overview
Problem
Conventional signal comparison mechanisms in functional safe systems suffer from false alarms and loss of availability due to different signal latencies in redundant signal paths, especially in high-speed applications where signals change rapidly over time.
Innovation Solution
A delay compensation circuit is employed to align measurement signals from different signal paths by compensating for propagation delays, using techniques such as trigger timing adjustments and filter circuits, including FIR filters and Kalman filters, to ensure accurate comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diverse signal paths are used for functional safety comparison, then diagnostic coverage is improved, but signal latency differences cause false alarms
Solution Approach 1:
The patent applies preliminary action by introducing delay compensation circuitry that pre-adjusts signals with different propagation delays before they reach the comparison stage. By measuring and compensating for latency differences in advance, the system ensures that signals from diverse paths are time-aligned when compared, preventing false alarms while maintaining the diagnostic benefits of path diversity
Solution Approach 2:
The patent changes the time parameter of signals by introducing variable delay elements that adjust signal timing based on measured propagation delays. This parameter adjustment allows signals from different paths to be synchronized in time, enabling accurate comparison while preserving the use of diverse signal paths for improved diagnostic coverage
2Adaptability or versatility
If diverse signal paths are used with different sampling times, then signal path diversity is improved, but timing alignment between signals deteriorates
Solution Approach 1:
The patent employs feedback mechanisms where the system continuously monitors the timing relationships between signals from diverse paths and dynamically adjusts delay compensation parameters. This feedback loop ensures that even when sampling times differ, the system maintains optimal timing alignment by adapting to actual signal propagation characteristics in real-time
Solution Approach 2:
The patent introduces dynamic delay adjustment mechanisms that can adaptively change signal timing based on observed propagation delays and sampling rate differences. This dynamic approach allows the system to maintain timing alignment across diverse signal paths with different characteristics, preserving both path diversity and temporal coherence
3Device complexity
If simple comparison mechanisms are used, then implementation complexity is reduced, but false alarms increase due to latency differences
Solution Approach 1:
The patent introduces delay compensation circuitry as an intermediary component between signal paths and the comparison mechanism. This intermediary layer handles the complex timing adjustment tasks, allowing the core comparison logic to remain simple while effectively addressing latency differences. The intermediary absorbs the complexity of delay measurement and compensation, preventing false alarms without complicating the fundamental comparison operation
Data Source
AI summary
Methods and apparatuses for comparing redundant signals in functional safe systems are provided, including methods for mitigating differing signal path delays and for signal weighting of the redundant signals are proposed. An Apparatus includes a first signal path for a first measurement signal of a physical quantity, the first signal path having a first signal propagation delay; a second signal path for a second measurement signal of the physical quantity, the second signal path having a second signal propagation delay different from the first signal propagation delay; a delay compensation circuit configured to compensate for a difference between the first and second signal propagation delays to generate delay-compensated first and second measurement signals; and comparison circuitry configured to compare the delay-compensated first and second measurement signals.