Adaptive Control for Test Mass Capture and Drag-Free Mode in Drag-Free Satellite

In space-borne gravitational wave detection missions, drag-free satellites are essential for achieving high-precision interferometric measurements. This paper aims to develop nonlinear control schemes for test mass capture and drag-free mode to achieve stringent ultra-quiet-stable requirements. The nonlinear dynamics model is reformulated within the Lagrangian framework, without relying on the skew-symmetric property. An adaptive controller is proposed for capture phase, addressing uncertain parameters in the actuator matrix. The proposed controller directly compensates for uncertain parameters in the nonlinear system without skew-symmetric property. Based on two sliding surfaces defined for the sensitive and insensitive axis, an adaptive controller is designed for drag-free mode subject to uncertain parameters and time-varying disturbances. Finally, numerical simulations are conducted to verify the effectiveness of the proposed controllers.