Inertial Reference System Alignment Using FFT Vibration Filtering
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Solution Overview
Problem
Inertial reference systems, such as those used in helicopters, face challenges in timely alignment due to vibrations during the rotor spool-up phase, which can slow down the convergence of alignment and affect navigation accuracy.
Innovation Solution
A processing system is employed to identify and filter out vibration frequencies from inertial measurements using techniques like Fast Fourier Transform and notch filters, allowing for reduced vibration effects and aiding in the initial alignment of the inertial reference system with respect to reference axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the inertial reference system performs alignment during rotor spool-up, then the system can provide navigation measurements, but vibrations slow down the convergence to alignment state
Solution Approach 1:
The patent extracts and removes vibration components from the accelerometer measurements by transforming the data into the frequency domain using Fast Fourier Transform, identifying vibration frequencies, and attenuating those specific frequency components. This separates the harmful vibration signals from the useful navigation measurements, allowing alignment to proceed despite ongoing rotor spool-up operations.
Solution Approach 2:
The patent introduces an intermediary processing system that acts as a mediator between the vibrating inertial reference system and the alignment algorithm. This processing system applies Fast Fourier Transform and frequency-domain filtering to isolate and remove vibration effects, providing cleaned measurements to the alignment process without requiring the vibrations to stop.
2Measurement precision
If vibration filtering is applied to improve alignment accuracy, then navigation solution accuracy improves, but processing complexity increases
Solution Approach 1:
The patent replaces complex mechanical vibration isolation systems with computational signal processing methods. Instead of using physical dampers or isolation mechanisms, the system uses Fast Fourier Transform and digital filtering algorithms to remove vibration effects from the measurements, achieving vibration mitigation through software rather than hardware complexity.
Solution Approach 2:
The patent changes the domain in which vibration filtering is performed by transforming measurements from the time domain to the frequency domain using Fast Fourier Transform. This parameter change allows for more efficient and targeted removal of vibration components at specific frequencies, improving filtering effectiveness while managing processing complexity through mathematical transformation rather than complex temporal filtering.
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 faster and more accurate alignment of inertial reference systems by mitigating the impact of varying vibrations, improving navigation solution convergence and accuracy during startup.
Implementation Method 1
A processing system is employed to identify and filter out vibration frequencies from inertial measurements using techniques like Fast Fourier Transform
Implementation Method 2
A processing system is employed to identify and filter out vibration frequencies from inertial measurements using techniques like Fast Fourier Transform and notch filters
Data Source
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AI summary
Systems and methods for inertial reference system alignment are provided. In certain embodiments, a system comprises an inertial reference system, the inertial reference system providing motion measurements; and a processing system coupled to receive the motion measurements from the inertial reference system. Further, the processing system is configured to execute instructions that direct the processing system to identify one or more frequencies in the spectrum of the motion measurements that are associated with vibrations; attenuate the motion measurements at the one or more frequencies; and use the attenuated measurements to aid in the production of navigation information.