Redundant Capacitive Touch Screen Cross-Diagnostics
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Solution Overview
Problem
Current capacitive touch screen systems lack high diagnostic coverage and redundancy, which is critical in applications requiring continued performance in the event of partial failure, such as commercial aviation and military applications.
Innovation Solution
A touch screen system with an advanced cross-sensing and monitoring technique using two independent capacitive touch screen channels, each divided into a capacitive sub-grid, allowing for cyclic testing of the capacitive grid and enhanced diagnostic coverage without additional external elements, achieving fully redundant touch sensing and high diagnostic coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard capacitive touchscreen is used, then the device structure remains simple, but the diagnostic coverage and reliability are insufficient for safety-critical applications
Solution Approach 1:
The capacitive grid is divided into two independent capacitive sub-grids, each processed by a separate channel with its own sensor controller and microcontroller unit. This segmentation allows each channel to independently sense and process touch inputs, providing redundancy and enhanced diagnostic coverage without requiring completely separate physical touchscreens.
Solution Approach 2:
Each channel is designed to perform multiple functions: normal touch sensing, self-diagnostics of its own channel, and cross-diagnostics of the other channel. The first channel can detect touches on the first capacitive sub-grid and also test the second channel by sending stimuli signals to the second capacitive sub-grid, and vice versa. This multi-functionality achieves full redundancy without proportionally increasing system complexity.
2Reliability
If redundant touch sensing is implemented using two independent capacitive touchscreens, then reliability improves, but the device complexity and cost increase significantly
Solution Approach 1:
Two independent processing channels are merged into a single capacitive touchscreen structure. The first channel processes signals from the first capacitive sub-grid while the second channel processes signals from the second capacitive sub-grid. Both channels share the same physical touchscreen surface, reducing overall system complexity compared to using two completely separate touchscreens while maintaining full redundancy.
Solution Approach 2:
Each channel is capable of self-diagnostics, where the first channel can test itself by monitoring its own capacitive sub-grid and the second channel can test itself similarly. Additionally, the channels perform cross-diagnostics where the first channel tests the second channel and vice versa. This self-service capability reduces the need for external testing equipment and simplifies the overall system architecture.
3Reliability
If cross-sensing and monitoring is implemented, then diagnostic coverage increases, but the processing complexity and computational requirements increase
Solution Approach 1:
The cross-diagnostics are performed cyclically rather than continuously. The first channel tests the second channel at periodic intervals by sending stimuli signals, and the second channel tests the first channel similarly. This periodic action reduces computational burden compared to continuous monitoring while maintaining adequate diagnostic coverage for safety-critical applications.
Solution Approach 2:
Stimuli signals act as intermediaries in the cross-diagnostics process. Instead of directly comparing complex touch patterns, the channels use simplified stimuli signals to test each other's response. This intermediary approach reduces processing complexity by transforming complex diagnostic tasks into simpler signal transmission and detection operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly improves diagnostic coverage and reliability, enabling the capacitive touch screen system to function safely and accurately even in the event of channel failures, suitable for functional safety implementations.
Implementation Method 1
Using the mutual capacitance principle, the capacitive grid and the whole chain of touch sensing, i.e. the channel, can be tested cyclically
Implementation Method 2
the first channel is tested by the second channel by sending a stimuli signal to the second capacitive sub-grid from the second channel and by retrieving a first test position by the first channel by detecting change in the electrical field in the first capacitive sub-grid
Data Source
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AI summary
A touch screen system (TSS) comprising: a touch screen (TS); capacitive grid (CG) associated with the touch screen and comprising a first capacitive sub-grid and a second capacitive sub-grid; a first channel (CI) controlling the first capacitive sub-grid; a second channel (C2) controlling the second first capacitive sub-grid; wherein the first channel and the second channel are configured to get respectively a first touch position and a second touch position after a touch input on the touch screen, wherein the first channel and the second channel are configured to test respectively the second channel and the first channel by sending a stimuli signal respectively to the first capacitive sub-grid and to the second capacitive sub-grid, wherein at least one of the first channel and the second channel determine a consolidated touch position by correlation of the first touch position and the second touch position.