A method to improve the modulation depth servo accuracy of an integrated fiber-optic gyroscope using the Bouc-Wen model

Abstract

The development of integrated fiber-optic gyroscopes using piezoelectric modulation (PEM) represents a significant advance in the field of fiber-optic gyroscopes. However, the hysteretic creep nonlinearity of Piezoe-lectric Transducer (PZT) affects the modulation depth monitoring and leads to a drift of its resonant frequency. The accuracy of the PEM's closed-loop feedback signal determines the open-loop gyroscope's accuracy. However, the hysteresis deteriorates the controller phase and the gain margin, inducing the fluctuation of the amplitude of each harmonic wave, which undoubtedly increases the difficulty of the closed-loop feedback control of the modulator. This paper proposes a method to quantify the high-frequency hysteresis nonlinearity of PZT, combining the advantages of feedforward compensation and feedback closed-loop. Feedforward compensation is used to reduce the hysteresis nonlinearity of PEM, reduce the interference of the nonlinear phase shift to zero drift, and increase the control accuracy of feedback control to PEM under temperature disturbance.