MEMS Gyrocompass Rotation Fitting for Rate Drift Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gyrocompassing systems suffer from systematic errors due to varying rate drifts among gyroscopes, which cannot be effectively mitigated by existing methods, leading to inaccuracies in determining the true north direction, especially in time-sensitive applications.
Innovation Solution
A method is employed to fit Earth rate responses of a gyroscope array as a function of rotation angle and time, individually fitting rate drifts of each gyroscope using algorithmic processes to correct for systematic errors, utilizing a matrix equation for polynomial or exponential functions to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If integration time is increased to reduce angular random walk error, then measurement precision improves, but rate drift causes larger systematic errors
Solution Approach 1:
The patent segments the total integration period into multiple shorter measurement intervals, taking measurements at different rotation angles throughout the period. This allows the system to capture Earth rotation rate information at multiple points without requiring a single long integration, thereby reducing the impact of rate drift while maintaining precision through statistical combination of multiple measurements.
Solution Approach 2:
The patent performs preliminary characterization of rate drift behavior by measuring the gyroscope output at multiple rotation angles during a warm-up period or initial operation. This preliminary data is used to fit a rate drift model (polynomial or exponential) that is then applied to correct subsequent measurements, allowing the system to compensate for rate drift effects without extending integration time.
2Measurement precision
If multiple gyroscopes are used to mitigate rate drift effects, then north angle accuracy improves, but device complexity increases
Solution Approach 1:
The patent combines measurements from multiple gyroscopes arranged in a carousel configuration, where each gyroscope measures Earth rotation rate at a different fixed rotation angle. By merging these measurements and fitting them to a sinusoidal model representing Earth's rotation, the system achieves improved accuracy through diversification of measurement perspectives while managing complexity through a standardized array architecture.
3Measurement precision
If rate drift fitting is performed for each gyroscope individually, then systematic error mitigation improves, but computational complexity increases
Solution Approach 1:
The patent employs a universal rate drift fitting approach where the same mathematical model (polynomial or exponential function) is applied to all gyroscopes in the array. This universal model is fitted to the combined measurements from all gyroscopes simultaneously, rather than fitting separate models to each gyroscope individually. This reduces computational complexity while maintaining the ability to correct systematic errors through the shared fitting process.
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 effectively mitigates systematic errors caused by rate drifts, allowing for shorter integration times and improved accuracy in determining the north angle, reducing device warm-up time and power consumption.
Implementation Method 1
Measuring horizontal rotation rate of the Earth reveals the direction to the geographic (true) north. This is called gyrocompassing, or north finding.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a MEMS gyrocompass, a method performed by the MEMS gyrocompass and a computer program product. The MEMS gyrocompass mitigates systematic error in determination of a north angle. The MEMS gyrocompass comprises at least one MEMS gyroscope having a sense axis within a reference plane. Samples from an output of the at least one MEMS gyroscope are obtained in at least two angles of rotation about an axis perpendicular to the reference plane. First fit coefficients are determined by fitting samples obtained from each individual MEMS gyroscope with first fitting functions determined as function of time. Second fit coefficients are determined by fitting components of earth rotation rate projected on the reference plane based on samples obtained by all of the at least one MEMS gyroscope, which fitting is performed with a second fitting function determined as a function of rotation angle of the at least one MEMS gyroscope with respect to a reference angle. The north angle is determined as an angle between the reference angle and true north based on the second fit coefficients.