Research on an indirectly driven servo system for CMG frameworks based on dual-angle-sensor technology

Abstract

As the core actuator for spacecraft attitude control, the precision of the control moment gyroscope (CMG) frame servo system directly affects the attitude stability of the spacecraft. Addressing the performance degradation caused by nonlinear factors—such as flexibility, transmission errors, and backlash—introduced by harmonic reducers in indirect-drive systems, this paper presents a series of studies. First, a system dynamics model incorporating transmission stiffness, damping, and backlash characteristics is established based on Lagrange’s equations. The impact of the harmonic reducer on the frame system control is analyzed through simulations, revealing that lower transmission stiffness and larger errors lead to poorer steady-state accuracy. To address this issue, a control strategy based on dual-angle sensors is proposed. By constructing a dual closed-loop feedback system and introducing an inner velocity loop on the motor side, the angular velocity fluctuations of the improved system are significantly reduced under various stiffness and disturbance conditions (with the root mean square deviation decreasing by approximately four orders of magnitude), thereby substantially enhancing the system’s robustness and dynamic response performance. Furthermore, the proposed scheme is experimentally validated on a physical test platform. This research provides both a theoretical foundation and an engineering reference for the design of high-precision CMG frame servo systems.