Disturbance Attenuation and Pointing Control System Design for an Improved Disturbance-Free Payload Spacecraft

The low-frequency disturbances transmitted by flexible cables are difficult to be attenuated for a novel disturbance-free payload spacecraft, which decreases the payload's pointing accuracy and stability. In this research, a new spacecraft configuration with a high-precision inertial reference unit composed of capacitive sensors and a spherical test mass is proposed. The disturbance attenuation and pointing control system is subdivided into four interconnected control loops. The payload can be isolated from disturbances in the all-frequency band by the active vibration isolation control loop and the drag-free control loops, and its high-precision pointing requirement can be satisfied with the attitude pointing control loop and the attitude tracking control loop. An integrated control strategy is proposed, and the control system is decoupled into 12 single-input single-output control loops by pre-compensating, which lays the foundation for feedback design. Through the amplitude-frequency response analysis, the control bandwidth is designed according to the Proportional-Integral-Differentive control algorithm. The numerical simulations show that the disturbance attenuation performance is better than -20 dB in the all-frequency band, and the pointing accuracy and the pointing stability are better than 10(-6) deg and 10(-7) deg/s, respectively. The new spacecraft configuration and the disturbance attenuation and pointing control system provide a general technical solution for payloads with high-precision and high-stability requirements.