Decoupling design and control of a spaceborne ultra–stable platform for vibration isolation and precise steering

Abstract

This study concerns the problems of system coupling and large payload mass ratio and designs a spaceborne ultra–stable platform (SUSP) to isolate the payload from the satellite vibration and accomplish high–precision payload steering. First, the dynamic equilibrium of the SUSP and vibration transfer functions are determined. The decoupling condition is then derived to make the coupled vibration transfer functions equal to zero, and the SUSP multi–input multi–output (MIMO) system is decoupled into six single–input single–output (SISO) subsystems. Consequently, the natural frequency matrix can be easily designed to guarantee the vibration isolation performance and obtain identical feedback gain values. Subsequently, a steering controller based on a nominal system simplified by decoupled dynamic equilibrium was designed. The impact of a large payload mass ratio was estimated and eliminated by the improved disturbance observer (IDO) in the steering controller. After rigid–flexible coupling dynamic modeling and analysis, two simulation stages were implemented. The results of the isolation stage exhibit a –40 dB/dec roll–off of the vibration disturbance and a coupled response reduction of approximately –20 dB. The payload tracking error of the isolation–steering integrated stage is reduced to 0.13″ (0.1° circular trace), and the isolation performance is further improved.