Redundant Bus Fault Detection Using Timer-Based Monitoring
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Solution Overview
Problem
Current fault detection methods in redundant bus systems for building automation fail to provide sufficient information for identifying and correcting faults, particularly in high-safety-class systems like 'class X' where propagation delays complicate simple logic solutions, and additional data is needed to aid first responders and maintenance personnel during emergencies.
Innovation Solution
Implementing a method using timers to monitor redundant communication buses, ensuring at least one data path exists from a controller, with four timing parameters (power up/cold start reset, periodic activity, valid bit time, and maximum pathway delay) to detect and annunciate faults, and provide additional information for fault correction and risk identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple combinatorial logic is used to process redundant received data lines, then the system complexity is reduced, but the propagation delay variations in redundant pathways make the logic infeasible
Solution Approach 1:
The patent replaces complex combinatorial logic with timer-based measurement systems. Instead of using logic circuits to compare redundant data lines, the system uses timers to measure propagation delays and detect faults. This substitution of mechanical/logic systems with timing measurement systems resolves the contradiction by making the solution feasible despite propagation delay variations.
Solution Approach 2:
The patent changes the detection parameter from logical comparison to temporal measurement. By measuring propagation delays in nanoseconds and comparing them against expected values, the system can detect faults without requiring complex logic to synchronize redundant pathways. This parameter change makes the system robust to propagation delay variations.
2Device complexity
If current simple fault detection methods are used, then the system complexity is minimized, but additional information for fault correction and emergency response is not provided
Solution Approach 1:
The patent segments the redundant bus system into multiple monitorable sections by implementing timers at different locations (FACU and remote peripherals). Each timer measures local propagation delays and can independently detect faults in its section. This segmentation allows the system to provide detailed fault location information while keeping each individual monitoring function relatively simple.
Solution Approach 2:
The patent implements feedback mechanisms where timers continuously monitor propagation delays and provide feedback about system health. When a fault is detected, the system can annunciate the fault condition and potentially trigger corrective actions. This feedback approach provides valuable information for fault correction without requiring overly complex detection systems.
3Length of moving object
If propagation delays of five nanoseconds per meter or more are present in redundant pathways, then real-world cable lengths are accommodated, but simple logic solutions cannot arrive at desired logic levels within the bit time
Solution Approach 1:
The patent substitutes logic-based synchronization with timer-based measurement. Instead of using logic circuits that assume simultaneous arrival of signals, the system uses timers to measure and accommodate the actual propagation delays caused by cable lengths. This substitution allows the system to work correctly with real-world cable lengths of five nanoseconds per meter or more.
Solution Approach 2:
The patent implements preliminary timing measurements during system operation to establish expected propagation delay values. By measuring propagation delays in advance and storing them as reference values, the system can later compare actual measurements against these references to detect faults. This preliminary action allows the system to accommodate variable cable lengths without complicating the logic operations.
Data Source
AI summary
A system and method for an approach of detecting faults in a redundant bus system based upon four timers.