Research Of IFOG Modulation And Closed-loop Control Technology

Driven by the application of telecommunication, research on solid-state semiconductor,light source, low-loss optical fiber and detector has been made great achievements since1970s.Thus, fiber-optic gyroscope(FOG) whose theory basis is based on sagnac effect can beput into reality. FOG is a new kind of all-solid inertial instrument, with large dynamic range,short startup time,high reliability, long life,etc., its accuracy can cover from the tracticallevel to strategic level, and is widely used in aircraft navigation, missile guidance in militaryfield as well as the vehicle navigation, robot control, drilling inclinometer in civil areas. FOGhave obvious advantages compared to traditional gyro and has become the preferred supplierin the inertial navigation system.Firstly,the paper analyses interferometric fiber-optic gyroscope(IFOG),focusing onmodulation method and its implement including the sine wave modulation,analog sawtoothmodulation, triangle wave modulation, two-state-square-wave modulation, four-statesquare-wave modulation,double-square-wave modulation. Built a basic model for FOG withverilog HDL, which include a clock controller, A/D timing controller, demodulation and filtermodule, square wave generator, feedback of D/A and2PI voltage controller.Subsequently, the first closed-loop and second closed-loop of FOG is designed. What’smore, the basic principle of light source, detector and Y waveguide is analyzed. And then, thedetection circuit board of IFOG is designed and put into reality. Meanwhile, the reset errormodel of eight half-wave voltage fluctuation and its compensation algorithm is illustrated.The second closed-loop is design in the way of controlling the reference voltage of thefeedback D/A by another D/A chip.Although the double closed loop control design of detection circuit can meet therequirement of low precision fiber optic gyro, but in the implementation process willencounter bias is too large, the dead zone problem, measuring range’s short. At the end of thepaper, research on improving fiber optic gyro bias stability, eliminating the dead zone,expanding the scope of measurement is done, according to GJB2426-2004test methodstipulated in the acquisition of the fiber optic gyroscope scale factor data and zero biasstability analysis. The experimental results show that, performance indexes meet the designexpectations, confirmed the rationality and feasibility.