Inertial Measurement Unit Characterization via Allan Variance
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Solution Overview
Problem
Current methods for characterizing inertial measurement units for navigation purposes are complex and time-consuming, requiring integration into a navigation unit and execution of calibration and alignment algorithms, which does not provide a simple or rapid characterization of their measurement precision.
Innovation Solution
A method involving maintaining the inertial measurement unit centered on a fixed point to obtain accelerometric and angular signals, processing these signals to project the specific force vector in an inertial frame, calculating the Allan variance, and comparing it to reference data, allowing for direct characterization of the unit's performance without needing navigation algorithm processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inertial measurement unit is integrated into a navigation system and navigation algorithms are executed for characterization, then comprehensive IMU characterization is achieved, but the process becomes complex and time-consuming
Solution Approach 1:
The patent extracts the essential characterization function from the complete navigation system by isolating the IMU on a stable platform. Instead of requiring full navigation algorithm execution, the method extracts only the necessary measurements (accelerometric and angular signals) while eliminating complex navigation processing, achieving comprehensive characterization through simplified direct analysis of Allan variance on raw sensor data
Solution Approach 2:
The characterization process is segmented into independent sensor analyses. Each accelerometer and angular sensor is characterized separately through individual Allan variance calculations on their respective signals, allowing comprehensive IMU characterization to be achieved through composition of individual sensor results rather than requiring integration into a complete navigation system
2Ease of manufacture
If traditional Allan variance analysis is performed on each sensor separately on a stable platform, then individual sensor characterization is achieved, but overall IMU characterization remains incomplete
Solution Approach 1:
The patent merges individual sensor characterization results into comprehensive IMU performance evaluation. By combining the Allan variance analyses of all accelerometers and angular sensors while accounting for their spatial relationships and error correlations, the method achieves complete IMU characterization that maintains both simplicity and accuracy
Data Source
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AI summary
Disclosed is a method for characterising an inertial measurement unit comprising a block carrying at least one accelerometer having a sensitive axis positioned according to an axis of a measurement reference frame and at least one gyrometer arranged to determine an orientation of the measurement reference frame relative to an inertial reference frame, the method comprising the steps of: - keeping the inertial measurement unit centred on a point that is fixed in relation to the ground in a predetermined environment in order to obtain image accelerometer signals of at least one component of the specific force vector in the measurement reference frame and image gyrometer signals of at least one component of the instantaneous rotation of the measurement reference frame relative to an inertial reference frame; processing the signals to obtain data representative of a projection of the specific force vector in the inertial reference frame after compensating for the Earth's rotation; calculating the Allan variance based on this data and comparing it with reference data.