Comparative assessment on ramp and bias voltage variations of closed loop interferometric fiber optic gyroscope

Abstract

Background/Objectives: The main objective of this paper is to perform a comparative discussion in gyro parameters for three cases: (i) V2π (vary) & Vπ/2 (constant), (ii) Vπ/2 (vary) and Vπp (constant) and (iii) both Vπp and Vπ/2 are varying simultaneously. Methods/Statistical Analysis: Fibre optic gyroscope has to be operated in closed-loop approach to achieve the inertial-grade-performance. The Closed-Loop Interferometric Fibre Optic Gyroscope (CLIFOG) system depends upon ramp voltage (Vπp of IOC) and square-wave biasing signal frequency (fbias). The digital-phase-ramp-function is used as feedback to system and makes gyro to null condition. The biasing signal voltage (Vπ/2) is 1/4th of ramp voltage (Vπp). If there are any variations in ramp and biasing signal voltages, then it introduces variations in gyro performance. Results: The ramp voltage (Vπp) and square wave biasing signal voltage (Vπ/2) is increased from 1% to 10%, decreased to 1% to 10% and performed the various tests for three cases. From results, it was noted that: (i) When V2π is varying and Vπ/2 is kept constant, the scale-factor change is increasing as the error in the signal voltage is also increases. (ii) When V2π is kept constant and Vπ/2 is varying, the change in scale-factor is very minute and maintains the scale-factor linearity. (iii) While varying both V2π and Vπ/2 voltages simultaneously, the device is not responding accordingly as the error is increasing and also scale-factor is out of range subsequently. The effects on the CLIFOG system are described with the derived values in terms of bias and scale-factor. The gyro performance is very sensitive with respect to Vπp variations and the percentage error is high in gyro output, but very less effect due to Vπ/2 variations when the ramp voltage (V2π) is constant. Conclusion/Application: The Closed Loop Interferometric Fiber Optic Gyroscope (CLIFOG) system requires a proper resetting of ramp voltage (V2π) in order to avoid the bias and scale factor instabilities.