Design Of Data Acquisition System For IFOG Vibration Test

The vibration characteristic of fiber optic gyroscope (FOG) is an important part of dynamic characteristics and an important indicator to measure the performance of FOG In theory,compared with traditional gyroscope, the solid-state and no moving parts characteristics make FOG have advantages of impact resistance and vibration resistance, but in fact, the elastic-optical effect in fiber will cause nonreciprocal phase shift when FOG work in impact and vibration environment and reduce the precision and stability of FOGSo far, the solutions of FOG vibration problem mainly have concentrated on curing fiber ring and electric light pieces pigtail, improving loop control and avoiding mechanical resonance and so on, these measures can effectively keep vibration error in the range of error permission. Because the filter in FOG can not completely eliminate the vibration component of FOG original output data, the improper sample frequency can cause spectrum aliasing phenomenon in FOG vibration test and influence the analysis and judgment of the vibration characteristics of FOG. To solve this problem,this paper designs a new data acquisition system to avoid the spectrum aliasing effecting on the accuracy of the vibration characteristics of FOG test.Firstly, this paper introduces the principle, structure, function and application of FOG The vibration characteristics and testing methods of the interferometric digital closed-loop FOG are described in detail and the key factors of affecting the vibration characteristics test are pointed out. Content mainly includes the vibration of FOG, the method of FOG vibration test and analysis on the effect of the axial and transverse stress of the optical fiber on FOG accuracy under vibration condition and proposing two effective measures to inhibit the vibration effect on FOG accuracy.After that, the analysis and study of the spectrum aliasing in interferometric digital closed-loop FOG test are introduced. Based on the power spectrum analysis of eight sets FOG output data under different vibration frequencies, the composition characteristics of the FOG data were obtained. By setting different sampling frequency, we verify the spectrum aliasing, and analysis the mechanism of the spectrum aliasing and the effect on the FOG vibration test.Then,a data acquisition hardware system based on FPGA was designed to inhibit the spectrum aliasing and the data processing program is written in VHDL language to obtain FOG output data in the vibration test. The system collects FOG original data with 8-bit data parallel transmission, by setting appropriate sampling links to eliminate the sampling frequency and vibration frequency aliasing. The data containing real vibration components will be acquired, transmitted and stored in the PC, which can be used for the following-up analysis and judgment of FOG vibration characteristic.Finally, this paper tests and verifies the validity of the data acquisition system. FOG vibration test is performed by using the designed data acquisition system. A conclusion is drawn by comparing the simulation and experimental results that the system can effectively inhibit spectrum aliasing phenomenon in FOG vibration test and improve the test accuracy,which provide an effective basis for FOG vibration characteristics analysis and judgment.