A Calibration Method for the Errors of Ring Laser Gyro in Rate-Biased Mode

Area of Science:

• * Inertial Navigation Systems (INS)
• * Optical Gyroscopes
• * Sensor Performance Evaluation

Background:

• * Ring Laser Gyros (RLGs) operate in mechanically dithered or rate-biased modes.
• * Mode switching is instruction-driven, impacting inertial navigation system (INS) performance.
• * Understanding RLG behavior in rate-biased mode is critical for accurate INS.

Purpose of the Study:

• * To evaluate the performance of RLGs in rate-biased mode.
• * To develop and validate a calibration method for RLGs in rate-biased mode.
• * To present a method for calculating Angle Random Walk (ARW) in rate-biased mode.

Main Methods:

• * An RLG-based Inertial Measurement Unit (IMU) was mounted on a dual-axis turntable.
• * The turntable provided a constant angular velocity to simulate rate-biased operation.
• * A novel calibration technique was applied to assess scale factor error, misalignments, and constant bias.

Main Results:

• * Differences in scale factor between modes were minimal (3.5–9 ppm).
• * Constant biases varied between modes (0.011–0.020 °/h), indicating mode-specific characteristics.
• * Angle Random Walk (ARW) in rate-biased mode was approximately one-third of that in mechanically dithered mode.

Conclusions:

• * RLGs exhibit distinct performance parameters in rate-biased mode compared to mechanically dithered mode.
• * The proposed calibration method effectively characterizes RLG errors in rate-biased operation.
• * Rate-biased mode offers significantly reduced ARW, enhancing navigation accuracy.