Aircraft Fuel Valve Position Compensation for Accurate Flow Control
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Solution Overview
Problem
Existing fuel flow measurement systems in jet engines suffer from inaccuracies due to errors in FMV position calculations, which affect engine operability and require costly high-precision sensors and uniform LVDT error distribution across channels, increasing costs and weight.
Innovation Solution
Utilizing calibration resistors with position sensors to derive delta curves that compensate for measurement discrepancies, allowing for accurate fuel flow calculation without the need for high-precision LVDT sensors and uniform LVDT error distribution, thereby reducing operational margins and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision LVDT sensors are used to measure FMV position, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a copy of the measurement system with two independent measurement channels instead of relying on a single high-precision sensor. Each channel has its own LVDT sensor with potentially different error characteristics, and the system processes both measurements to achieve accurate fuel flow calculation without requiring either individual sensor to be highly precise.
Solution Approach 2:
The patent transforms the problem from measuring absolute FMV position accurately to measuring the difference between two FMV position measurements. By changing the measurement parameter from absolute position to differential position, the system can tolerate larger individual measurement errors while maintaining accurate fuel flow calculation.
2Measurement precision
If uniform LVDT error distribution is required across channels, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent explicitly accepts and utilizes the asymmetric nature of LVDT errors across different channels rather than requiring uniform error distribution. The system is designed to handle channels with different error characteristics, transforming a manufacturing constraint into a design feature that simplifies production while maintaining measurement accuracy through differential measurement.
Solution Approach 2:
By implementing two independent measurement channels with potentially different error profiles, the system creates redundancy that allows accurate fuel flow calculation without requiring uniform manufacturing precision across all sensors. The differential approach cancels out individual channel errors.
3Measurement precision
If additional high-precision sensors are added to compensate for measurement errors, then measurement precision is improved, but weight increases
Solution Approach 1:
The patent uses existing LVDT sensors in a differential configuration rather than adding new high-precision sensors. By copying the measurement function across two channels and processing the difference, the system achieves accurate fuel flow measurement without the weight penalty of additional high-precision sensing hardware.
4Reliability
If operational margins are increased to account for measurement errors, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent uses dual-channel measurement to directly calculate accurate fuel flow without requiring large operational margins. The differential measurement approach provides inherent error compensation, allowing the system to maintain both high reliability and high productivity by eliminating the need for conservative margin-based corrections.
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
Enhances fuel flow calculation accuracy and reduces operational margins by compensating for measurement errors, providing a low-cost solution that maintains engine performance without the need for additional sensors, thus optimizing engine efficiency and reducing weight.
Implementation Method 1
This measurement is affected by a certain error
Implementation Method 2
a variable capacitor for providing a feedback signal
Data Source
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AI summary
Based upon measured resistances, a first delta curve and second delta curve are selected. A first fuel valve position (FVP) is received from a first position sensor (102), and the first FVP is applied to the first delta curve to obtain a first offset. A second FVP is received from a second position sensor (104), and the second FVP is applied to second delta curve to obtain a second offset. The first offset is applied to the first measured FVP to obtain the first compensated FVP and the second offset is applied to the second measured FVP to obtain the second compensated FVP. The first compensated FVP and the second compensated FVP are correlated to obtain a final compensated FVP, which is applied to a desired fuel valve position to obtain a final fuel valve position.