Aircraft Sensor Fault Detection Using AC Superposition
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Solution Overview
Problem
Aircraft sensors face challenges in detecting faults without increasing measurement error or uncertainty, as current non-destructive testing methods can introduce errors and make fault conditions less conspicuous.
Innovation Solution
The system employs an alternating current source with a phase offset to minimize direct current across sensors, using filters to isolate and rectify alternating current components, allowing for error detection with reduced impact on measurement accuracy. This involves a high-pass or band-pass filter to separate AC from DC, converting AC to DC for error threshold comparison, and using capacitors to reduce AC to a trickle current for minimal error imposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-destructive testing is applied to detect sensor faults, then fault detection capability is improved, but measurement error and uncertainty increase
Solution Approach 1:
The patent applies periodic alternating current at specific frequencies (e.g., 60 Hz) to the sensor circuit during testing. This periodic action allows the test signal to be distinguished from the sensor's normal DC output through frequency separation, enabling fault detection without permanently altering the sensor's measurement capability. The alternating nature of the test current allows it to be filtered out after testing, preserving the sensor's original measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary alternating current signal that serves as a mediator between the test objective and the sensor measurement system. This AC test signal acts as a temporary intermediary that can be superimposed on the sensor circuit, used for fault detection through frequency-based separation, and then removed without affecting the sensor's normal DC measurement function.
2Reliability
If direct current is applied across sensors for testing, then fault detection is enabled, but measurement accuracy deteriorates
Solution Approach 1:
Instead of applying direct current for testing, the patent employs periodic alternating current at frequencies distinct from the sensor's measurement bandwidth. This periodic testing current can be easily separated from the sensor's DC measurement signal using frequency-based filtering, enabling fault detection while preserving measurement accuracy by not introducing DC offset or drift into the measurement circuit.
Solution Approach 2:
The patent changes the electrical parameter being used for testing from direct current to alternating current at specific frequencies. This parameter change allows the test signal to be differentiated from the sensor's normal measurement signal through frequency separation, enabling accurate fault detection without degrading the sensor's measurement precision for its intended DC measurement function.
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 approach enables effective fault detection in aircraft sensors with reduced measurement errors, allowing for timely adjustments in vehicle control and maintaining accurate environmental parameter readings by isolating and analyzing AC changes indicative of faults like corrosion or breakage.
Implementation Method 1
The system includes an AC source for superimposing an alternate signal to the DC signal generated by the thermocouple
Implementation Method 2
The signal at the output of the thermocouple is then split into a direct and an alternate component
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Disclosed is an aircraft sensor fault detection system. The system includes a sensor system (102) having a sensing apparatus (102) to measure a parameter of an environment and a measurement circuit coupled to the sensing apparatus. The system includes a source of alternating current (120) connected to the sensor system. The system further includes an alternating current measurement system that measures alternating current passing through the sensor system (105) and indicates an error when a threshold based on a change in impedance of the sensing apparatus is exceeded.