The Research Of Fiber-optic Gyro North-finding System

Rapid and high-precision north-finding technology based on the fiber-optic gyroscope (FOG) and accelerometer play an important role in providing accurate positioning for the modern weapons systems and civil survey. Compared with the conventional mechanical gyro, the FOG has many advantages, such as high sensitivity, wide dynamic range, low-cost etc. It is especially suitable for the north-finding system reseach of miniaturization, high precision, low cost. So, the paper designs and developes a north-finding system composed by a uniaxial FOG and a uniaxial accelerometer based on these factors.Base on full understanding of the development course of gyro north-finding system and development and application of FOG, the paper analyses the main properties and measuring principle of FOG, and studies deeply principle and several common coordinate system of the north-finder composed of uniaxial FOG and uniaxial accelerometer. At the same time, the paper puts forward several north-finding schemes. Through comparison of different north-finding schemes, the efficient and suitable four-position north-finding algorithm is selected.According to design requirements of the system, this article introduces the whole designing scheme of north-finder. For the method, choosing appropriate FOG and accelerometer, the paper designs corresponding signal collection circuit in accordance with the features of output signal firstly. Meanwhile, the signal of accelerometer is flitered by second-order low-pass filter and is transformed by AD transform chip. Then, taking minimum system of FPGA as a core, the main control circuit is made up and the related NiosⅡsoft nuclear is configured. Finally, the north-finding algorithm process of the whole system is designed and the corresponding software program is programmed according to north-finding mechanism and data preprocessing method. Thus, the article completes the basic design of the system.This paper analyses and summarizes the impact for north-finding accuracy of the system by studying error sources. On the one hand, FOG error model is established adopting the ALLAN variance, which helps FOG to make analysis of various error coefficients of its output characteristic. Meanwhile, ALLAN variance curve of fiber optic gyroscope is mapped in the paper. On the other hand, the original output signal of sensors is processed by means of eliminating the rough error and smooth filtering, and improving the application accuracy of FOG. Finally, based on testing environment providing in the lab, a debugging tool of host computer is designed for system debugging and performance test of FOG north-finder. The FOG north-finder designed in the paper meets the design requirements, which has been validated by many times experiment, such as many experiments are conducted under the condition of in the same azimuth and different attitude and the north-finding repetitive experiments are based on the four different positions.