Haji Ali Najar M., Sohrabian M., Abedi H.

The tracking sensors acting in a tracking loop as stabilizer are mounted on a two degree of freedom gyros. The gyro must align its rotor axis with the line of sight in order to remove tracking errors. The tracking precision and sensitivity are functions of the gyros performance. One of the main factors in reducing the precision and producing instabilities is nutation vibrations. This fluctuating motion, which is a dynamical inherent property of the system, is related to the gyro lateral moment of inertia, the length of gyro and its rotating speed. In order to investigate the capabilities of nutation dampers, three models are presented: a simple viscoelastic cantilever beam with a tip mass, another model of viscose liquid damper containing mercury in one ring and a third design consist of two rings, one containing mercury and the other oil. In each model presented here, the behavior of the damper and its subsystems are taking into account. The equation of motions for the dynamical motion of Gyros, are obtained using Lagrangian approach, taking into account the friction of the dampers and the interaction of the liquids with the system equations of motion. The predicted responses are used in order to compare the three models and discuss each of their advantages and disadvantages.