The calibration process for a single-axis Fiber Optic Gyroscope (FOG) involves several critical steps to ensure its accuracy and reliability, particularly in applications such as aerospace and defense [citation:2]. Below are the key stages of this calibration process:
Initial Setup
- Reference Value Establishment: The output of the FOG is compared against a known reference value to determine its accuracy. This involves setting up a reference source that provides precise angular measurements .
- Environmental Stabilization: The FOG and the reference apparatus are placed in a controlled environment to minimize the impact of temperature fluctuations and other environmental factors on the calibration results .
Data Acquisition
- Static and Dynamic Testing: Data is collected under both static (non-rotating) and dynamic (rotating) conditions. The sensor's response over a period is observed and recorded.
- Rotational Calibration: The FOG is subjected to precise rotational movements. This phase involves rotating the FOG around the axis, both clockwise and counterclockwise, to capture its response to known angular velocities.
Error Analysis
- Bias Instability Measurement: The gyroscope's output is analyzed to identify any bias instabilities—constant errors that affect the gyroscope's readings over time.
- Scale Factor Determination: The scale factor, which converts the gyroscope's electrical output to angular velocity, is calculated by comparing the FOG's output to the reference values.
- Misalignment and Nonlinearity Detection: Any misalignment or nonlinearities in the FOG's response are identified and quantified.
Calibration Algorithm Application
- Error Compensation Models: Calibrated mathematical models are applied to compensate for identified errors such as bias, scale factor, misalignment, and nonlinearity.
- Periodic Rotation Method: A method that involves modulating certain device errors by periodic rotation to further refine the error compensation model and improve navigation accuracy.
Performance Validation
- Validation Tests: The FOG is subjected to further tests after calibration to validate the effectiveness of the error compensation algorithms. These tests ensure that the gyroscope meets required performance criteria under different operational conditions.
- Real-time Adjustment Verification: The ability of the FOG to maintain accuracy in real-time applications is verified, often through a series of dynamic tests that simulate actual operational environments.
Final Adjustments and Documentation
- Fine-tuning: Any necessary fine-tuning is performed based on the validation test results to ensure optimal performance.
- Calibration Documentation: The calibration results, including the methods and adjustments made, are thoroughly documented. This documentation is crucial for future reference and verification purposes.
By following these steps, single-axis Fiber Optic Gyroscopes can be calibrated to provide highly accurate and reliable angular measurements, which are essential for precise navigation and control in various high-performance applications .