Inertial Core Self-Calibration for Vibrating Gyroscope Drift
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Solution Overview
Problem
Inertial navigation units with axisymmetric vibrating gyroscopes face precision issues due to drift errors, angular coding errors, and scale factor errors, which become problematic when stored for long periods before installation, requiring recalibration and being unsuitable for small vehicles due to the bulk of multi-axis reversal devices.
Innovation Solution
A method involving alternating pivoting and adjustment of the inertial core around a pivot axis not aligned with the sensitive axes of the gyroscopes, allowing for effective elimination of drift and angular coding errors by modifying the angular orientation of the vibration axis, which can exceed 180°, thereby improving the precision of the inertial unit without the need for a large calibration device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-axis reversal device is used for calibration, then calibration precision is improved, but device bulk and mass increase making it incompatible with small-sized vehicles
Solution Approach 1:
The patent extracts the calibration function from the complex multi-axis reversal device and implements it using only the inertial unit itself through self-calibration. The inertial unit performs calibration by executing a predetermined sequence of attitudes and measuring inertial parameters at each attitude, eliminating the need for external bulky calibration equipment while maintaining calibration precision.
Solution Approach 2:
The inertial unit calibrates itself without requiring external calibration devices. The system uses its own inertial sensors to measure parameters at different predetermined attitudes and automatically computes calibration parameters, making the calibration process self-contained and eliminating the need for heavy external equipment.
2Ease of manufacture
If calibration is carried out before installing the inertial core in the vehicle, then calibration can be completed, but the time elapsed between calibration and use reduces calibration validity
Solution Approach 1:
The inertial unit performs self-calibration at the moment of installation or just before use, eliminating the time gap between calibration and operation. The system uses its own sensors and predetermined attitude sequences to complete calibration in-situ, ensuring calibration validity is maintained without requiring advance factory calibration.
3Duration of action of stationary object
If the inertial unit is stored for long periods before installation, then storage logistics are simplified, but drift errors and angular coding errors increase requiring recalibration
Solution Approach 1:
The system performs a quick self-calibration procedure just before use to compensate for drift and angular coding errors that developed during long-term storage. The predetermined sequence of attitudes and measurements captures current error states, and calibration parameters are computed to eliminate these accumulated errors, restoring measurement precision without requiring long-term stability.
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 method enhances the precision of inertial units by effectively eliminating errors through sinusoidal error compensation, allowing for efficient calibration of low-cost units, even for small vehicles, by averaging errors over time and reducing the impact of scale factor errors, thus improving navigation accuracy.
Implementation Method 1
inertial units with axisymmetric vibrating gyroscopes... axisymmetric vibrating gyroscopes with Coriolis effect (CVG for 'Coriolis Vibratory Gyroscopes')
Data Source
Figure 1
AI summary
The invention relates to a method for calibrating an inertial navigation system comprising an inertial core (3) with vibrating axisymmetric gyroscopes (9, 10, 11), comprising the steps of: pivoting the inertial core (3) from a first position towards a second position about a pivoting axis (4) separate from the sensitive axes of the gyroscopes and a trisectrix of same by performing measurements of an angular orientation of the vibration with each gyroscope (9, 10, 11), the angular orientation being left free during the pivoting; bringing the inertial core back to the first position; regulating the angular orientation of the vibration of each gyroscope to a value corresponding to the second position; pivoting the inertial core (3) towards the second position by repeating angular orientation measurements with each gyroscope (9, 10, 11); and calibrating the inertial core according to the measurements performed.