Analysis of the dead zone is among the intensive studies in a closed-loop fiber optic gyroscope. In a dead zone, a gyroscope cannot detect any rotation and produces a zero bias. In this study, an analysis of dead zone sources is performed in simulation and experiments. In general, the problem is mainly due to electrical cross coupling and phase modulation drift. Electrical cross coupling is caused by interference between modulation voltage and the photodetector. The cross-coupled signal produces spurious gyro bias and leads to a dead zone if it is larger than the input rate. Phase modulation drift as another dead zone source is due to the electrode contamination, the piezoelectric effect of the LiNbO3 substrate, or to organic fouling. This modulation drift lasts for a short or long period of time like a lead-lag filter response and produces gyro bias error, noise spikes, or dead zone. For a more detailed analysis, the cross-coupling effect and modulation phase drift are modeled as a filter and are simulated in both the open-loop and closed-loop modes. The sources of dead zone are more clearly analyzed in the simulation and experimental results.
In this paper, The flight data processing system was designed for multiple target flight test. For flight data processing, multiple target grouping, data fusion processing, and data slaving processing were performed and, as a data fusion filter, centralized, and federated Kalman filters were designed. A centralized kalman filter was modified in order to improve the vehicle's low altitude measurement using radar's SNR and estimation process. From the testing of multiple target missile, it confirmed flight trajectory measurement was improved in low altitude area and the beginning stage of vehicle.
Gyroscope's deadzone is a region where can not detect the rate even though the actual rotation is applied. This paper analyzed the cause of deadzone by modeling/simulation and introduced pulse dithering method to overcome. From the testing of 3-axis fiber optic gyro system using 900m fiber, it confirmed deadzone could be effectively eliminated by combination of three factors, dither amplitude, dither frequency, and gyro loop gain.
We studied the design of fiber optic gyroscope that enables to sense high rotation by extending the limit of rotation sensibility of fiber optic interferometer. Based on the digital serrodyne modulation technique, the signal processing of fiber optic gyroscope was designed and the prototype fiber optic gyroscope showed the high rotation sensibility up to ยฑ3000[deg/sec] and scale factor performance of about 150 [ppm] by the experiments. Accordingly, we confirmed that the design of fiber optic gyroscope was valid for high rotation.
The amplitude error of phase modulator used in closed-loop fiber optic gyroscope has occurred by the temperature dependency of the electro-optic coefficient, and also can be due to the square-wave dither signal which is generally applied for eliminating the deadzone. This error can cause bias drift and scale factor error. This paper analyzes the temperature dependency of the modulation amplitude and the relationship with the scale factor of the gyroscope, and deals with an amplitude control method. The error calculation logic considering the dither signal is implemented on the signal processing module. The result of experiments from a prototype gyroscope shows the effect of the modulation amplitude control and a considerable improvement on performances.
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