Inertial Unit Comparison via Specific Force Filtering
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Solution Overview
Problem
Existing methods for comparing inertial units used in navigation systems face challenges due to errors in both short-term and long-term data, particularly when combining data from units with different performance characteristics, which affects the accuracy and reliability of navigation data.
Innovation Solution
A method is developed to compare inertial units by filtering and normalizing specific force measurements using a rotation matrix, low-pass filtering, and downsampling, allowing for improved reliability in orientation estimation between units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If navigation data from two inertial units with different performance characteristics are compared directly, then short-term precision can be maintained, but long-term accuracy deteriorates due to cumulative errors
Solution Approach 1:
The method applies preliminary low-pass filtering and downsampling to the specific force measurements before comparison. This preprocessing action removes high-frequency noise and prepares the data for reliable long-term comparison, enabling both short-term precision and long-term accuracy to be achieved simultaneously
Solution Approach 2:
The method changes the temporal parameters of the measurements by applying low-pass filtering (modifying frequency content) and downsampling (changing sampling rate). These parameter transformations allow the system to maintain short-term precision while improving long-term reliability by eliminating cumulative errors
2Productivity
If navigation data from two inertial units are compared without filtering, then comparison speed is maintained, but measurement reliability deteriorates due to noise and errors
Solution Approach 1:
The low-pass filtering and downsampling are performed as preliminary actions before the comparison operation. This preprocessing reduces the data volume and eliminates noise, thereby improving both reliability and processing efficiency in subsequent comparison steps
Solution Approach 2:
The method extracts only the relevant low-frequency components of the specific force measurements through low-pass filtering, discarding high-frequency noise. This extraction process improves measurement reliability while maintaining processing speed by focusing only on essential information
3Reliability
If specific force measurements are filtered with long duration, then measurement reliability is improved, but response time deteriorates
Solution Approach 1:
The method applies partial filtering by selecting a filtering duration that is sufficient to improve reliability for the specific application requirements, rather than using excessive filtering. The downsampling factor is also optimized to achieve the necessary reliability without excessive processing time
Solution Approach 2:
The filtering parameters (duration and cutoff frequency) are optimized to achieve the desired balance between reliability and response time. By adjusting these parameters, the system can adapt to different operational requirements without sacrificing either reliability or timeliness
Data Source
AI summary
A method for comparing two inertial units that are integral with a carrier in positions spaced apart from each other and that each comprise three angular measurement sensors and three accelerometer sensors mounted according to the axes of a measurement reference frame unique to each inertial unit, the method comprising the steps of: - over a predefined time period, measuring a specific force and rotations respectively with the accelerometer sensors and the angular measurement sensors of each inertial unit, - correcting a leverage effect to return the reference frames to a same origin, - reconstituting an inertial reference frame of each inertial unit from the measured specific force and the rotations, - comparing the inertial reference frames to determine a discrepancy between them.