Development of a Simulation System with Integrated In Situ Monitoring Capabilities for the Lubrication State of Rolling Elements in Space Control Moment Gyro Bearings

As a core actuator for attitude control in spacecraft, the lubrication state of the bearing rolling elements in the Control Moment Gyro (CMG) critically determines the operational lifetime and control accuracy of the overall assembly. The complex motion patterns and unique spatial environment pose significant challenges to developing effective ground-based simulation and lubrication assessment methods. To address this, a simulation system with integrated in situ monitoring capabilities for the lubrication state of rolling elements in space CMG bearings was developed in this study. By integrating a friction force sensor, optical microscope, Raman spectrometer, and gas analyzer, the system permits the in situ, real-time monitoring of key parameters—including friction force, surface morphology evolution, tribochemical characteristics, lubricant consumption, and gas generation—while simulating rolling element motion and lubrication in a vacuum. Experimental results confirm that the system achieves a stable vacuum of 10−3 Pa within 15 min, with control accuracies for both rotational speed and loading force better than 1%. It effectively distinguishes tribological performance under different material conditions and achieves a repeatability standard deviation of the friction coefficient below 0.001, with reliable data from the in situ monitoring module. This system provides a reliable platform for investigating CMG bearing lubrication and predicting service life in vacuum.