Modeling and Calibration for Dithering of MDRLG and Time-Delay of Accelerometer in SINS

At present, the design and manufacturing technology of mechanically dithered ring laser gyroscope (MDRLG) have matured, the strapdown inertial navigation systems (SINS) with MDRLG have been widely used in military and business scope. When the MDRLG is working, high-frequency dithering is introduced, which will cause the size effect error of the accelerometer. The accelerometer signal has a time delay relative to the system, which will cause the accelerometer time delay error. In this article, in order to solve the above-mentioned problem: (1) we model the size effect error of the mechanically dithering of the MDRLG and perform an error analysis for the size effect error of the mechanically dithering of the MDRLG; (2) we model the time delay error of accelerometer and perform an error analysis for the time delay error of accelerometer; (3) we derive a continuous linear 43-D SINS error model considering the above-mentioned two error parameters and expand the temperature coefficients of accelerometers, inner lever arm error, outer lever arm error parameters to achieve high-precision calibration of SINS. We use the piecewise linear constant system (PWCS ) method during the calibration process to prove that all calibration parameters are observable. Finally, the SINS with MDRLG is used in laboratory conditions to test the validity of the calibration method.

Self-Alignment/Navigation Performance Analysis in the Accelerometer Resonance State Generated by Dither Motion of Ring Laser Gyroscope in Laser Inertial Navigation System

In this paper, we theoretically analyzed the self-alignment/navigation performance in the accelerometer resonance state generated by dither motion of ring laser gyroscope in LINS and verified it through simulation. As a result of analysis, it is confirmed that the amplitude of the accelerometer measurement amplified in the accelerometer resonance state is decreased in the process of sampling per the navigation calculation period and that frequency is changed by the aliasing effect too. It was also analysed that the attitude error in self-alignment is determined by the amplitude/frequency of the accelerometer measurement, the gain of the self-alignment loop, and the velocity and position error in the navigation is determined by the amplitude/frequency/phase error of the accelerometer measurement. This analysis and simulation results show that the self-alignment and navigation performance is not be degraded only when the amplification factor of the accelerometer measurement in the accelerometer resonance state is 3 or less

Noise Reduction Method for the Ring LaserGyro Signal Based on Ceemdan and the Savitzky–Golay Algorithm

The ring laser gyro signal contains complex noise components, affecting the system’s measurement accuracy. It is an engineering problem worthy of study to find an effective method to reduce the noise in the sampling signal and improve the system’s accuracy. In order to reduce various noises of the ring laser gyroscope and improve its measurement accuracy, a noise reduction method combining complete ensemble empirical mode decomposition with adaptive noise and the Savitzky–Golay algorithm is proposed. First, the measured samples are mode decomposed, and the concept of weighted-permutation entropy is introduced to distinguish the noisy modes. Then, the Savitzky–Golay algorithm is used to process the noisy modes, and finally, the signal is reconstructed. Simulated test signal and actual gyro signal are used to test, and compared with the EMD noise reduction method, each indicator is improved. The paper proposes a new noise reduction method for the laser gyro signal, and introduces weighted-permutation entropy to analyze the dividing point. The test data show the effectiveness of the method.

Monitoring Local Earthquakes in Central Italy Using 4C Single Station Data

In this study, performed on a set of twenty-two earthquakes that occurred in central Italy between 2019 and 2020, we will explore the possibility to locate the hypocenter of local events by using a ring laser gyroscope observing the vertical ground rotation and a standard broadband seismometer. A picking algorithm exploiting the four components (4C) polarization properties of the wavefield is used to identify the first shear onset transversely polarized (SH). The wavefield direction is estimated by correlation between the vertical rotation rate and the transverse acceleration. The picked times for Pg and Sg onsets are compared to the ones obtained after manual revision on the GIGS station seismometer. The results are compared with the location provided by the national monitoring service of the INGV.

Analysis of the possibility for optical path full automation when working with a ring laser gyroscope

The key features of the focusing modes of optical mirrors are considered; two focusing modes are developed and two algorithms for the implementation of these modes at the operator’s workplace are described. Keywords gyroscopic devices; ring laser gyroscope; operator’s workplace; control of the mirror optical purity; scattering of particles; optical path