A Semi-physical Model of Closed-loop IFOG and Ways to Improve the Dynamic Performance

Abstract

Dynamic performance is an important indicator of fiber optic gyroscopes, indicating the gyroscopes tracking ability in the state of large angular acceleration, such as overload, swaying, vibration. The Interferometric Fiber Optic Gyroscopes(IFOG) is based on the Sagnac effect and has the characteristics of nonlinearity, input saturation and time delay, etc. In general the IFOG’s closed-loop system is approximated as a linear system for modeling and analysis. This linear model is just suitable for the IFOG working in a static or uniform motion. In high dynamic conditions, the IFOG tracking error will appear strong nonlinearity and even become zero, which cannot be simply treated as linear model. Based on the analysis of the high dynamic tracking error characteristics of the IFOG, a semi-physical simulation method is proposed which can simulate the dynamic working environment of the IFOG under laboratory environment conditions. By equivalent external excitation to −π ~ +π phase, an arbitrary angular acceleration input is achieved. Comparing the external excitation and the IFOG output, the IFOG’s Dynamic response capability is truly reflected. Simulation show that it is beneficial in three aspects for improving the IFOG’s tracking ability. Firstly, reduce the delay time which is produced by data processing in the processor, Improve the rapidity of the IFOG’s response; Secondly, A dynamic modulation depth which is proportional to the tracking error technology can be implemented. Thirdly, the system feedback gain is combined of a optimal static gain and a optimal dynamic gain, which is decided by the tracking error.