惯性技术课件光纤陀螺哈工大版全.ppt

Lecture 14 -- Fiber Optic Gyro To improve the accuracy and linearity of the FOG, a servo amplifier and a phase transformer are introduced to provide a feedback, thus forming a closed loop. Let’s look at the mechanism. The output from the detector is demodulated by PSD, and is then amplified by the servo amplifier. Then it is used to drive the phase transformer PT, which produces a phase shift det(theta). The amplitude of det(theta) is such that it cancels the det(phi) caused by the input angular rate OMG. As a result, the output of PSD is kept near zero. Instead, the det(theta) from PT is chosen as the output of FOG. The advantage of using such feedback is that, by canceling the output from the detector using det(theta) produced by PT, the operational point of the FOG is always near to its zero point, where the FOG has the best accuracy and linearity. Finally, I’d like to say something about another type of FOG, namely, resonant FOG. In terms of principle, resonant FOG is more like a laser gyro. Because, like laser gyro, such type of FOG utilizes the resonance of laser beams. The difference is that, first, the resonance is produced in the fiber coils; and second, the laser is generated from the outside, not inside the coils. The laser from the outside source LR is split by the haft-reflective mirror SL. And we have two beams, which enter the fiber coils from the two sides, and come out from the opposite sides respectively. Today, we would discuss another type a optical gyro -- fiber optic gyro (FOG). Compared with laser gyro, FOG can better meet the requirements of SINS. Like laser gyro, operation of FOG is also based on Sagnac effect. But, unlike laser gyro, the laser used in FOG are from an outer source, and the light are transmitted by optic fiber. The virtues of FOG are: cheap, small and light. The development of FOG can be summarized as follows: 1967, the concept of FOG was proposed by Pircher and Hepner 1970s, optic fiber, the most important co