Time-Triggered Life-Sign Message Failure Detection in System-of-Systems
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Solution Overview
Problem
Current methods for detecting failures in constituent systems within a system of systems are hindered by high error detection latency due to the use of event-driven communications systems lacking global time, leading to prolonged downtime and increased accident risks in systems like moving vehicles.
Innovation Solution
Implementing a time-triggered communications system with global time synchronization for the creation, transmission, and receipt of life-sign messages, ensuring precise timing and minimizing latency by setting timeouts based on global time progression, thereby reducing the interval between error occurrence and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If event-driven communications system is used without global time, then system autonomy and flexibility are maintained, but error detection latency increases to over 400 μs
Solution Approach 1:
A global time reference acts as an intermediary between distributed constituent systems, providing a common temporal framework that enables synchronized error detection without requiring complex inter-system coordination. The global time reference mediates the timing relationships between message creation, transmission, and timeout events across all systems.
Solution Approach 2:
The timeout value is predetermined based on the maximum expected message transmission time calculated from global time references. This preliminary determination of timeout parameters eliminates the need for dynamic adjustment and reduces detection latency by preparing the detection mechanism in advance with optimal timing parameters.
2Reliability
If timeout value is increased to accommodate event-driven message transmission variations, then message delivery flexibility is maintained, but error detection latency increases
Solution Approach 1:
The timeout parameter is optimized by calculating it as the sum of maximum message creation time and maximum transmission time, both derived from global time references. This parameter optimization achieves the minimum necessary timeout value that still accommodates normal transmission variations, thereby minimizing error detection latency while maintaining system reliability.
3Reliability
If a priori synchronization of message creation, transmission, and receipt times is implemented, then error detection latency is reduced to under 30 μs, but system complexity increases due to global time requirement
Solution Approach 1:
The global time reference serves multiple functions simultaneously: it synchronizes message creation times across constituent systems, determines transmission timing, establishes receipt time expectations, and provides the basis for timeout calculations. This multi-functionality reduces the need for separate synchronization mechanisms for each timing aspect.
Data Source
AI summary
A process to detect a failure of a constituent system (110 . . . 113) in a system of systems (1) consisting of a number of constituent systems (111 . . . 113) which exchange messages through a communications system (120), in which every constituent system (111 . . . 113) has a global time with a known granularity g, and at least one constituent system creates, at periodic creation times (210, 211) determined a priori from the progression of the global time, a time-triggered life-sign message, the time of transmission (211, 221) of this life-sign message in the time-triggered communications system (120), determined a priori from the progression of the global time, is synchronized with the creation time of this life-sign message, and the time of receipt (212, 222) of this life-sign message, determined a priori from the progression of the global time, is synchronized with the timeout time point (213, 223), determined a priori from the progression of the global time, of a monitor (130) of this life-sign message monitoring the arrival of the life-sign message, wherein an error message is triggered at the timeout time point if no life-sign message has arrived at the expected time of receipt (222).