Operational stability control of a linear actuator in the telescope tracking mechanism based on a robust disturbance observer

Before the TianQin mission is implemented in 2035, it still faces many scientific and technological challenges. One of these is the breathing angle changes between the TianQin constellation. Adjusting optical components using the telescope tracking mechanism to actively compensate for angle changes is a key factor for normal gravitational wave detection. As the driving device of the telescope tracking system, the linear actuator has its tracking error and operational stability directly determining whether the telescope tracking mechanism’s pointing jitter meets the TianQin mission’s requirements. However, factors such as nonlinear friction force, sensor measurement errors, and environmental noise significantly degrade the actuator's tracking accuracy and operational stability, necessitating the development of high-precision control strategies to effectively suppress these disturbances. In this article, we propose a composite control method to improve the linear actuator’s operational stability. Firstly, modeling and identification were conducted based on the experimental setup of the linear actuator drive system, and the main disturbance noise was analyzed and measured. Secondly, to suppress the linear actuator, a high-performance robust disturbance observer (DOB) was introduced into the feedback control system. Finally, the proposed method was validated using the linear actuator drive system experimental setup. The experimental results demonstrate that the proposed method significantly enhances the transient performance and trajectory tracking performance of the linear actuator. When ω is 0.00001, the linear actuator achieves an operational stability of 1.2 nm/Hz 1/2 @ 10 mHz. This meets the stability requirements for the linear actuator in the gravitational wave telescope tracking mechanism.