Laser Gyro Scattering Coefficient Estimation
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Solution Overview
Problem
Laser gyros face a blind spot in measuring rotation velocity due to backscattering from cavity components, leading to inaccurate phase shift measurements and a dynamic blind spot, which cannot account for drifts in scattering coefficients over time.
Innovation Solution
An iterative method is employed to determine scattering coefficients in real-time by transforming measured light intensities and phase differences into dependent variables, using recursive least-squares estimation to minimize discrepancies and track coefficient changes, thereby correcting phase shifts and improving rotation measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backscattering from cavity components is present, then the laser gyro can operate with standard components, but measurement accuracy deteriorates due to blind spots and frequency lock-in at low rotation frequencies
Solution Approach 1:
The patent implements feedback by continuously monitoring the intensities of counter-propagating modes and using this information to dynamically adjust the dithering amplitude. The system measures the actual backscattering effects in real-time and modifies the dithering parameters accordingly, creating a closed-loop control system that adapts to changing operational conditions to maintain measurement accuracy while preserving operational reliability
Solution Approach 2:
The patent changes the dithering amplitude parameter dynamically based on measured backscattering conditions. By adjusting the dithering amplitude as a variable parameter rather than keeping it fixed, the system can optimize performance across different operational states, reducing the blind spot effect when backscattering is high while maintaining normal operation when conditions are favorable
2Measurement precision
If mechanical dithering is applied to reduce the blind spot, then low-frequency rotation measurement improves, but a dynamic blind spot appears when rotation frequency matches the dithering frequency
Solution Approach 1:
The patent applies dynamics by making the dithering amplitude variable rather than fixed. The system continuously adapts the dithering parameters based on real-time measurements of backscattering effects and operational conditions. This dynamic adjustment allows the system to move away from resonant frequencies that cause dynamic blind spots, maintaining measurement reliability across a broader frequency range
Solution Approach 2:
The patent uses periodic dithering action at a specific frequency to counteract the effects of backscattering. By applying periodic mechanical oscillations to the laser cavity, the system modulates the backscattering effects in a controlled manner, creating a measurement signal that can be processed to eliminate the static blind spot while managing the dynamic blind spot through frequency selection and amplitude modulation
3Device complexity
If pre-calibration with fixed scattering coefficients is used, then the system complexity is reduced, but accuracy deteriorates due to drifts in scattering coefficients over time
Solution Approach 1:
The patent implements feedback by continuously measuring the intensities of counter-propagating modes and using this information to detect drifts in scattering coefficients. The system compares actual measurements with expected values based on pre-calibration data, identifies deviations caused by coefficient drift, and triggers re-estimation or correction procedures to maintain accuracy without requiring complete recalibration
Solution Approach 2:
The patent enables the laser gyro to self-correct for drifts in scattering coefficients by using its own operational data. The system monitors its own performance metrics, detects when coefficient drift affects accuracy, and automatically adjusts its measurement and correction algorithms accordingly, reducing the need for external recalibration while maintaining high measurement precision
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 enables real-time estimation of scattering coefficients, effectively reducing the blind spot and accounting for drifts, leading to more accurate and reliable angular rotation measurements.
Implementation Method 1
When this device is rotated at an angular speed {dot over (θ)}, the counter-propagating modes are shifted out of phase by an amount φ by the Sagnac effect, causing a difference between their eigenfrequencies and hence a difference between the emission frequencies of the laser.
Implementation Method 2
it is known that, because of backscatter from the optical components forming the cavity, the two counter-propagating modes are (weakly) coupled, this causing the device's frequency to lock-in at low frequencies of rotation.
Data Source
AI summary
An iterative method for determining scattering coefficients of the cavity of a laser gyro in operation supporting two counter-propagating modes, comprises steps of: determining a set of variables dependent on characteristic physical quantities of the laser gyro, one reference variable per dependency relationship being selected from the variables; measuring values of the characteristic physical quantities of the laser gyro in operation; determining measured values of the variables; estimating, via an iterative method, estimated values of the coefficients minimising a discrepancy between the measured values of the reference variables and estimated values of the reference variables, which are estimated from the values of the coefficients and the measured values of the variables other than the reference variables; and determining estimated values of the scattering coefficients from the estimated values of the coefficients.