Friction model of a revolute joint for a precision deployable spacecraft structure

An analytical model is presented for predicting breakaway friction torque in a precision deployable spacecraft structure joint incorporating preloaded angular contact bearings. The model is based on the Todd/Johnson (1987) tribological friction model of friction within ball bearings and includes the effects of Coulombic microslippage between the bearing components and material hysteretic damping. A new nondimensional parameter is developed to quantify the effects of bearing preload, geometry, and material properties. It is analytically shown that bearing friction can be minimized for a specific bearing contact angle considering both rolling and sliding friction components. Additionally, steady-state bearing friction is calculated to vary nonlinearly with assembly preload. Analytical prediction of bearing friction is correlated with measured data. (Author)