Design Studies of an Opposed-Hemisphere Gyro Spin-Axis Gas Bearing

Abstract

An extensive analytical study has been carried out on the spiral-grooved, opposed hemisphere, self-acting gas bearing from the point of view of its application in the spin-axis suspension in inertial-grade gyroscopes. An idealized design featuring isoelasticity, zero attitude angle, and minimum compliance is established, resulting in zero compliance torque. Tolerance effects are examined. Limitation on wheel mass, on account of self-excited whirl instability, is determined, and its dependence on bearing clearance is found. Due to dynamic cross-compliance, elliptical orbital motions would be excited by linear simple harmonic forces. The elliptical orbit for a given acceleration level is characterized by its size, ratio of principal axes, orientation of the major axis, and the time phase; all of which are functions of frequency of excitation and are calculated for a range of frequencies for three typical wheel-bearing combinations. Cumulative cross-compliance torques resulting from dynamic excitation are calculated and are found to be of a similar order of magnitude as the tolerance effects.