Determining the Direction of True Meridian by Micromechanical Gyro

Abstract

© 2020 IEEE. The gyrocompassing method based on the parametric excitation of micromechanical gyro (MMG) is proposed. The incoherent mode of parametric excitation of MMG mounted on a horizontal base is considered. A feature of this mode is the presence of "strong resonance", which enhances the amplitude of oscillations of the rotor with respect to its resonance value, and "weak resonance", which reduces its amplitude of oscillations. The vibrational shape of the rotor is not preserved in this mode, and instead of harmonic vibration with one spectral component, there is a complex vibration (observed as a quasi-harmonic vibration) consisting of two spectral components with a slight difference in their frequencies. Thus, the rotor vibrations have the shape and frequency of the generated oscillations of the beats. This behavior of the gyroscope is associated with a change in its damping coefficient. Fluctuations of this coefficient with the beat frequency lead to a periodic change in the steepness of the phase-frequency characteristic of the MMG and, accordingly, to the oscillation of the measuring axis of the device regarding its original direction, approximately perpendicular to the direction of the true meridian. Metrological accuracy of the measurer reached by using the amplitude and phase gyrocompassing methods.