Reduction of reset pulse in resonant frequency servo loop for resonant fiber-optic gyro by an auto-controlled reset technique.
Resonant fiber-optic gyro (RFOG) based on the Sagnac effect has the potential to achieve the inertial navigation system requirement with a short sensing coil. A high-accuracy resonant frequency servo loop is indispensable for a high-performance RFOG. A digital proportional-integral (PI) controller is always adopted in the resonant frequency servo loop. The resonant frequency of the optical fiber ring resonator drifts with environmental temperature changes. When the resonant frequency drift is beyond the tracking range of the resonant frequency servo loop, the digital PI controller overflows and outputs a reset signal. A large reset pulse, which is equivalent to a rotation rate error of 26°/h, has been observed at the output of the RFOG, while a long time is required for returning to the lock-in state simultaneously. To reduce the effect of the overflow resetting in the digital PI controller, an auto-controlled reset technique is proposed and experimentally demonstrated. As a result, the time for returning to the lock-in state is reduced to 5 ms from 8 s. With the integration time of 1 s, the equivalent accuracy of the resonant frequency servo loop is improved to 0.18°/h.