Model of noise and instability sources of a ring monoblock gyro
Various systems operating on different physical principles are applied as gyroscopic sensors of modern high-precision aircraft strapdown inertial navigation systems. The most widespread in the world are laser gyroscopes implementing the Sagnac effect and differing in design and technological versions. Commercially available inertial navigation systems employ two types of such gyroscopes: ring gas and fiber-optic. Relatively recently, a novel design, occupying an intermediate place between ring gas and fiber-optic gyroscopes, appeared in the group of laser gyroscopes. This unit was called a “ring monoblock gyroscope with the semiconductor laser diode”. The vital difference of this unit consists in the presence of the polyhedral optical monobloc with the triangular optical scheme with open channels, placed inside the unit. The problem of the bidirectional optical signal formation form the laser diode is solved by the original resonator-splitter design. With this, the semiconductor laser diode is placed inside the gyroscope optical scheme. The ring mode of the optical signal is realized by the mirror system. Information retrieval about the navigation object angular velocity is performed by dynamic interference pattern processing from the gyroscope output. The new design and technological solution of the gyroscopic sensor requires its error knowledge based on the corresponding generalized noise and error sources mathematical model. The article examines the triangular optical monoblock diagram of a laser gyro with high symmetry relative to the axis “resonator-beam splitter - interference mixer - photo detector” to evaluate potential noise and instabilities. This optical scheme was not analyzed earlier due to the fact that the ring gas laser gyroscopes were unclaimed. Estimates of the given design and technological solution potentialities as a sensitive element of the aircraft inertial navigation system were obtained. The article demonstrates that the optical system possesses the internal mutual phase modulation presence, and compensation of the internal temperature gradients of the object under study exists as well. The developed structure of the ring monoblock gyroscope is recommended as high precision, thermally stable ring monoblock gyroscope with laser semiconductor diode for the aircraft strapdown inertial navigation systems. The design and technological solution specifics of the sensor may be the basis while solving the problems on sensitive elements of the inertial navigation system backing-up.