Fiber Optic Gyroscope Automatic Gain Control Loop Stabilization
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Solution Overview
Problem
Fiber optic gyroscope systems face issues with saturation and nonlinearities due to limited loop bandwidth and finite analog-to-digital converter input range, especially when using high-amplitude dither signals, leading to inadequate deadband suppression and residual dither problems.
Innovation Solution
An automatic gain control system that stabilizes the fiber optic gyroscope loop gain by filtering and multiplying the output signal with a calibration reference signal to produce a gain error signal, which is then used to adjust the gain, allowing for the use of low-amplitude dither signals and eliminating perturbation signals from the output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-amplitude dither signal is used to break up the deadband, then deadband suppression is improved, but saturation and nonlinearities occur due to limited loop bandwidth and finite analog-to-digital converter input range
Solution Approach 1:
The patent changes the amplitude parameter of the dither signal from high to low, and introduces a gain adjustment mechanism that dynamically modifies the dither signal amplitude based on loop conditions, allowing sufficient deadband suppression without causing saturation
Solution Approach 2:
The patent implements a feedback mechanism where the dither signal amplitude is automatically adjusted based on loop performance metrics, ensuring optimal deadband suppression while preventing saturation through continuous monitoring and adjustment
2Reliability
If the loop bandwidth is increased to handle large dither amplitudes, then saturation is reduced, but the system becomes more sensitive to high-frequency noise and the complexity increases
Solution Approach 1:
The patent makes the dither signal amplitude dynamic rather than fixed, allowing it to adapt to changing loop conditions and bandwidth constraints, thereby avoiding saturation without requiring a permanently increased loop bandwidth
3Measurement precision
If the dither frequency is increased to be at least ten times the sampling frequency, then deadband suppression is improved, but residual dither problems occur if there are not precisely an integer number of dither cycles in the sampling period
Solution Approach 1:
The patent adjusts the dither frequency parameter to achieve a precise integer relationship with the sampling frequency, eliminating spectral leakage and residual dither while maintaining effective deadband suppression
Solution Approach 2:
The patent employs periodic dither action with a frequency carefully selected to complete an integer number of cycles within each sampling period, ensuring complete cancellation of dither residuals while maintaining deadband suppression effectiveness
Data Source
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AI summary
An automatic gain control system for a fiber optic gyroscope control loop (13) includes an adjustable gain applied to the gyro output signal. A calibration signal is injected into the fiber optic gyroscope control loop (13). A compensation loop (42) receives signals output from the control loop (13) and also receives calibration signals. The compensation loop (42) processes the calibration signal to produce a compensation signal that is combined with signals output from the control loop (13) to provide a compensated fiber optic gyroscope output signal. An automatic gain control loop (51) is connected between the compensation loop (42) and the adjustable gain applied to the fiber optic gyroscope output signal. The automatic gain control loop includes a gain error demodulator (50) that multiplies the compensated fiber optic gyroscope output signal and the compensation signal together to produce a gain error signal used to control the adjustable gain to stabilize the gyro control loop gain.