Analysis of a Limit Cycle Induced by Gimbal Friction of a CMG

Abstract

The purpose of this research is to analyze the characteristics of a limit cycle occurring in the spacecraft attitude when CMGs are used as attitude control actuators. A limit cycle represents the oscillations that may arise from a nonlinear element in a nonlinear system. In a spacecraft system equipped with CMGs, the gimbal friction is a nonlinear element that can induce a limit cycle. In this study, the characteristics of the limit cycle are analyzed 1) by modeling the gimbal friction as static and dynamic frictions, and 2) as based on a describing function of the gimbal friction. The validity of the analytical solution was subsequently verified via numerical simulation and hardware experimentation.