控制力矩陀螺(CMG)是重要的空间执行机构, 受柔性转子和外框架耦合运动影响, 高速轴承容易因滚动体异常滑动发生润滑失效和磨损, 引起CMG微振动。为揭示CMG高速滚动体空间运动特性, 该文考虑轴承接触与润滑状态、柔性转子、框架-轴承-转子耦合效应等因素, 基于有限单元法建立了CMG非线性动力学模型, 分析了转子柔性特征对CMG高速滚动体接触与空间运动特性的影响, 进一步搭建了CMG高速滚动体运动原位测量实验台, 基于双目视觉技术实现了滚动体空间运动测量, 验证了CMG动力学模型的正确性。研究表明, 转子柔性会改变径向力和力矩的分布, 影响滚动体的接触行为, 减小滚动体俯仰角, 增大滚动体与内滚道的旋滚比。

Objective: The control moment gyroscope (CMG) is a crucial actuator for spacecraft, such as space stations and high-resolution satellites, enabling attitude regulation and pointing control. The CMG offers high efficiency and generates significant output torque. It mainly consists of a high-speed rotor, a low-speed gimbal, and bearings. Microturbulence within the CMG, which limits the precision of spacecraft attitude control, arises from the flexible characteristics of the high-speed rotor and bearing wear failure. High-speed bearings, commonly used in spaceflight, operate under challenging conditions of time-varying load and speed, making them prone to wear and lubrication failure due to anomalous ball sliding. This is a major contributing factor to CMG failure and micro-vibration. Therefore, this study develops a CMG dynamics model that accounts for rotor flexibility, the coupling effect between the gimbal, bearing, and rotor, and bearing contact behavior. The model can be used to analyze the motion state of the balls and investigate the ball sliding mechanism. Methods: The flexible shaft in the CMG is modeled as a Timoshenko beam unit, and a finite element dynamics model of the rotor is constructed, considering the rotor's flexible deformation, gyroscopic effect, and unbalanced forces and moments. According to the cylindrical coordinate system of the bearing, a set of dynamic equations is developed for the balls, raceways, and cage. The mass and gyro matrices are derived through the calculation of the kinetic energy of the CMG system using the Lagrange method. The nonlinear dynamics equations of the system are then obtained by coupling the bearing dynamics equations with the flexible rotor dynamics equations. In this model, the time-varying high-speed bearing support stiffness allows for real-time coupling between bearing analysis and system dynamics. An experimental platform is established for in-situ measurement of high-speed ball motion in the CMG, and binocular vision technology is employed to track the spatial motion of the balls. The model's accuracy is validated through experimental results. Results: The model is further used to investigate the effect of rotor flexibility on the balls' behavior. Both low-frequency and high-frequency fluctuations define the dynamic response of a high-speed bearing's rolling element in a CMG. The variation period is half of the gimbal rotation period, and the low-frequency variations are mostly influenced by the gyroscopic torque generated by the gimbal rotation. High-frequency fluctuations are mainly influenced by rotor speed and bearing parameters, manifesting as the cage characteristic frequency. When rotor flexibility is considered, the gyroscopic moment is converted into a greater radial force. This change alters the dynamic behavior of the balls in both the "load-bearing" and "non-load-bearing" zones of the bearing, leading to more significant variations in the balls' contact force with the raceway and the contact angle. When rotor flexibility is considered, the spin-to-roll ratio of the inner raceway increases, and the pitch angles of the balls are smaller than those with a rigid rotor. Conclusions: This study develops a CMG dynamics model that incorporates rotor flexibility, gimbal-bearing-rotor coupling effect, and balls' contact behavior to reveal the spatial motion characteristics of the high-speed bearing balls in the CMG. An experimental platform for in-situ measurement of high-speed ball motion in the CMG is constructed, and the ball's motion is measured using binocular vision technology. The accuracy of the theoretical model is confirmed. To further understand the spatial motion dynamics of the rolling body and explore bearing wear inhibition techniques, the impact of rotor flexibility on rolling body motion is also examined.