MEMS Gyrocompass Drift Fitting for Faster North Angle Determination
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Solution Overview
Problem
Gyrocompassing systems suffer from systematic errors due to rate drift in MEMS gyroscopes, which are not effectively mitigated by existing methods, leading to inaccurate north angle determination and prolonged integration times.
Innovation Solution
A method and apparatus that utilize a MEMS gyrocompass with multiple gyroscopes arranged such that their sense axes form a zero vector sum, and employ fitting functions to individually address rate drifts of each gyroscope as a function of time, determining fit coefficients to calculate the north angle accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long integration times are used to reduce systematic error in north angle determination, then measurement precision improves, but loss of time increases
Solution Approach 1:
The patent replaces the conventional mechanical approach of extending integration time to reduce error with a mathematical signal processing method. By fitting gyroscope output data to a polynomial function and calculating north angle from fitted coefficients, the system achieves accurate north angle determination without requiring long integration periods, thus resolving the contradiction between measurement precision and time loss.
Solution Approach 2:
The patent changes the parameter of integration time from long to short while maintaining or improving measurement precision. This is achieved by transforming the measurement approach from direct integration to polynomial fitting, where the order of the polynomial and the integration duration become adjustable parameters that can be optimized for both accuracy and speed.
2Measurement precision
If polynomial fitting is applied to mitigate rate drift effects, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent replaces complex hardware-based drift compensation mechanisms with a software-based polynomial fitting algorithm. This substitution reduces the need for additional sensors or complex mechanical stabilization systems, achieving improved measurement precision through computational methods rather than physical complexity.
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 drift, allowing for accurate north angle determination with shorter integration times and reduced warm-up times, improving the overall performance and accuracy of gyrocompassing systems.
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.
Implementation Method 2
determining second fit coefficients by fitting components of earth rotation rate projected on the reference plane based on samples obtained from all of the at least one MEMS gyroscope
Data Source
AI summary
A MEMS gyrocompass and method are provided to mitigate systematic error in determination of a north angle. The MEMS gyrocompass includes one or more MEMS gyroscopes having a sense axis within a reference plane. Samples from an output of the 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 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 the MEMS gyroscopes, which fitting is performed with a second fitting function determined as a function of rotation angle of the 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.