Modeling and simulation of the second feedback loop for fiber optic gyroscope

Abstract

Current research on modeling of fiber optic gyroscope (FOG) is mainly concentrate on single digital closed loop FOG under square-wave modulation and demodulation. Little work has been done in modeling and simulation of the second feedback loop of FOG under four-state modulation and demodulation. However, the second feedback loop is very important in improving FOG performance. In order to improve the accuracy and stability more efficient, it’s essential to modeling and does simulation of the second feedback loop for fiber optic gyroscope especially in the field of high precision application. There are three major contributions in this paper. Firstly, the physical model of digital closed loop fiber optic gyroscope is built and the scale factor error of FOG due to gain error is derived in theory. The gain error including half-wave voltage change and driver circuit gain change are mainly caused by temperature fluctuation in practical environment. To solve this problem, the second feedback loop based on four-state modulation and demodulation method is provided, and the control model of this method is then set up theoretically by means of transfer function. In the end, simulation of the second feedback loop of FOG is performed by Labview to demonstrate the efficiency of this method. According to our theoretical analysis of the control model and the simulation result, this method can track and compensate the variation of driver circuit gain and half-wave voltage in real-time. Therefore, the nonlinear error of FOG scale factor is reduced by the control of the second feedback loop, which leads to improvement of FOG accuracy.