Finite frequency domain H_∞ hybrid control design of drag-free spacecraft with model-based generalized extended state observer

For the drag-free spacecraft on the space-borne gravitational wave detection mission, the drag-free control scheme is considered one of the core technologies to achieve the ultra-quiet-stable control requirements in the measurement bandwidth (MBW). This high-precision control performance is constrained by actuation noises, measurement noises, environmental disturbances, and the limited control bandwidth. In order to address these difficulties, a finite frequency domain double closed-loop control (DCC) framework with the parameter design method is proposed in this paper. First, a model-based generalized extended state observer (MGESO) framework is proposed. This framework integrates plant estimation and disturbance estimation components to accurately estimate those disturbances and noises with lower orders. Then, based on the MGESO framework, the DCC framework is proposed for drag-free control. Within the control structure, the performance specifications can be directly divided into the inner and outer loop performances, which reduces the complexity of the parameter tuning. Subsequently, a finite frequency domain parameter tuning method for the DCC framework is provided, leveraging the generalized Kalman-Yakubovich-Popov (GKYP) lemma. The introduction of the sensitive frequency domain as a design constraint can result in a reduction of control expenditures. Finally, the effectiveness and superiority of the DCC structure are verified in the drag-free spacecraft hardware-in-loop experiment platform.