Robust composite control design of drag-free satellite with Kalman filter-based extended state observer for disturbance reduction

Abstract

For future space-based gravitational wave detectors, drag-free control is one of the core technologies to achieve ambitious ultra-quiet-stable requirements. Generally, the high performance of such a drag-free satellite is severely limited by the intrinsic nonlinearities, various noise and limited bandwidth. To overcome these limitations, a dual-loop drag-free control scheme with the merits of simple structure and tuning method is proposed. First, a special combination of Kalman filter (KF) and extended state observer (ESO) is applied in the inner-loop to perform disturbance reduction. The KF serves as noise filtration, while the ESO accepts the filtered measurement signals to achieve better online reconstruction of states and lumped disturbances. Then, GS/T mixed sensitivity H∞ controllers are adopted in the outer-loop to stabilize the test masses in the cage center. The controllers are tuned based on the sensitivity function and complementary sensitivity function specifications to enhance robustness. Finally, a simulation considering various disturbance models is built to test the effectiveness of the control system. A comparison between three types of controllers reveals the advantages of the proposed method in terms of the disturbance attenuation and control performance.