Ring Laser Gyroscope Path Length Control Frequency Adjustment
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Solution Overview
Problem
Ring laser gyros face accuracy degradation due to the 'lock-in' phenomenon, which existing methods like dithering only partially address, and there is a need to improve measurement accuracy by minimizing interference between path length control and dithering frequencies.
Innovation Solution
The implementation of a controller that adjusts the path length control modulation frequency based on the dither frequency to mitigate beat frequency effects, using a combination of piezoelectric actuators and transducers to induce and detect dithering, and a PLC system with mirror drives to dynamically adjust the laser path lengths within the gyroscope cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dithering is used to minimize lock-in phenomenon, then measurement reliability is improved, but measurement precision deteriorates due to beat frequency interference between dithering and path length control
Solution Approach 1:
The patent dynamically adjusts the path length control frequency based on the detected dither frequency. The controller continuously monitors the dither frequency and modifies the PLC frequency in real-time to maintain a predetermined relationship (typically a multiple or submultiple), ensuring that the system adapts to frequency variations and minimizes beat frequency interference throughout operation.
Solution Approach 2:
The patent implements a feedback mechanism where the controller detects the actual dither frequency using a frequency detector and uses this information to adjust the PLC frequency. The frequency detector receives the dither signal and provides feedback to the controller, which then modifies the PLC frequency to maintain the desired relationship, creating a closed-loop control system that actively compensates for frequency drift.
2Illumination intensity
If path length control is used to maintain peak steady state intensity, then laser beam quality is improved, but measurement precision deteriorates due to interference with dithering frequency
Solution Approach 1:
The system dynamically adjusts the PLC frequency based on the detected dither frequency to maintain a predetermined relationship between the two frequencies. This dynamic adjustment ensures that the PLC continues to maintain peak laser intensity while avoiding fixed-frequency interference with the dithering process.
Solution Approach 2:
The patent changes the PLC frequency parameter based on the dither frequency. By adjusting the frequency parameter of the PLC to maintain a specific relationship (multiple or submultiple) with the dither frequency, the system optimizes both laser intensity maintenance and measurement precision by avoiding beat frequency interference.
3Measurement precision
If fixed relationship between PLC frequency and dither frequency is maintained, then beat frequency interference is minimized, but adaptability to frequency variations deteriorates
Solution Approach 1:
The patent implements a dynamic frequency adjustment mechanism where the controller continuously monitors the dither frequency and modifies the PLC frequency in real-time. This dynamic approach maintains the predetermined relationship (multiple or submultiple) while adapting to frequency variations, combining the benefits of fixed relationship interference minimization with adaptability to frequency drift.
Solution Approach 2:
The feedback mechanism detects actual dither frequency variations and provides continuous adjustment signals to the PLC frequency controller. This ensures that the predetermined relationship between PLC and dither frequencies is maintained dynamically, allowing the system to adapt to frequency variations while minimizing beat frequency interference throughout operation.
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 enhances the accuracy of angular rotation measurements by effectively managing interference between dithering and path length control frequencies, thereby improving the overall performance of the ring laser gyroscope system.
Implementation Method 1
using a combination of piezoelectric actuators and transducers to induce and detect dithering
Implementation Method 2
using a combination of piezoelectric actuators and transducers to induce and detect dithering
Implementation Method 3
two laser beams travel in counter-rotating (i.e., opposite) directions. The laser beams create an optical interference pattern having characteristics representative of the amount by which the RLG is rotated
Implementation Method 4
a path length control (PLC) system which adjusts the path length of the laser beams within the RLG cavity to maintain peak steady state intensity/power
Data Source
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AI summary
A gyroscope system comprises a gyroscope block having a plurality of cavities and a plurality of passages that define a path; a plurality of mirrors each located in one of the plurality of cavities; at least one mirror drive coupled to one of the plurality of mirrors and configured to change a position of the respective mirror, wherein the path's length is changed by the change in the position of the respective mirror; a dither system coupled to the gyroscope block and configured to induce an angular rotation of the gyroscope block; and a controller configured to provide a dither signal indicative of a dither frequency to the dither system and a path length control (PLC) signal indicative of a PLC frequency to the at least one mirror drive. The controller is configured to calculate the PLC frequency as a function of the dither frequency.