AMLCD Fault Detection via Embedded Carryover Pixel Comparison
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Solution Overview
Problem
Existing fault-tolerant large area Active Matrix Liquid Crystal Displays (AMLCDs) for aircraft cockpits face challenges in detecting faults within the display system and its video path, leading to potential information loss and operator-dependent visual inspection, which can render misleading or invalid information to pilots.
Innovation Solution
A fault detection system that embeds an encoded carryover pixel (COP) within the digital video stream and uses a timing and control unit to compare the sent and received COP data, as well as a PASS/FAIL bit from cascaded shift registers, to automatically mitigate faults without operator intervention by switching to a known good display or video source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simple redundancy is used to achieve fault tolerance, then the display system can continue operation after a fault, but information loss occurs and operator intervention is required
Solution Approach 1:
The system embeds carryover pixel (COP) data in advance within the video stream before transmission to the display. These COPs serve as preliminary test data that will be used to detect faults, allowing the system to proactively identify issues before they result in information loss or require operator intervention.
Solution Approach 2:
The system establishes a feedback loop where the display controller receives the embedded COP data from the video stream, processes it through the display system, and then compares the received COP data with the originally embedded COP data. This feedback mechanism automatically detects faults and enables corrective action without operator intervention, preventing information loss while maintaining reliability.
2Device complexity
If visual inspection by operator is used to detect faults, then no additional detection circuitry is needed, but operator intervention is required and faults may not be detected in time
Solution Approach 1:
The display system performs self-diagnosis by automatically detecting faults through the embedded COP mechanism. The system serves itself by embedding test data, processing it through the display chain, and comparing results to detect faults without requiring external operator inspection. This maintains simplicity while eliminating the need for operator intervention.
Solution Approach 2:
The automatic feedback loop between the video processor and display controller enables the system to self-detect faults by comparing embedded COP data with received COP data. This feedback mechanism replaces manual visual inspection with automated detection, reducing device complexity while improving operational ease by eliminating the need for operator intervention.
3Reliability
If COP data is embedded in the video stream for fault detection, then automatic fault detection is achieved, but the video stream requires additional data processing
Solution Approach 1:
The system merges the fault detection function with the existing video stream by embedding COP data within the same data channel. Instead of creating a separate detection system, the fault detection capability is combined with the video transmission path, allowing automatic fault detection while utilizing the existing video processing infrastructure with minimal additional complexity.
Solution Approach 2:
The video stream serves multiple functions: it carries both the actual video information and the embedded COP test data simultaneously. This multi-functionality allows the same processing path to handle both display content and fault detection, achieving automatic fault detection without requiring separate dedicated processing channels, thereby limiting the increase in device complexity.
Data Source
AI summary
A fault detection system is provided for a display system including an AMLCD. A video processor embeds encoded fault detection data within the digital video stream that is sent directly to the AMLCD. The fault detection data is embedded in such a manner that it is not displayed by the AMLCD. The fault detection data in the digital video stream received by the AMLCD is detected by the AMLCD and is then sent back to the video processor. The video processor compares what was sent with what is received to determine whether there is a difference which may be indicative of a fault in the AMLCD or the path of the digital video stream. As an additional check, the AMLCD may send timing error data to the video processor indicating whether the AMLCD is working properly. The video processor generates and outputs a fault flag to initiate a corrective action if a fault is detected in the AMLCD and/or the path of the digital video stream.