Drag Free and Attitude Control System design for gravitational wave detection satellites

This paper focuses on the Drag-Free and Attitude Control System (DFACS) design for space-based gravitational wave detection missions. First, based on the stringent scientific requirements, the control objectives and the operation scheme in science mode are formulated. Second, the environmental and actuation noises acting on the spacecraft are modeled in the frequency domain using transfer functions, and a complete dynamical model of the spacecraft with two test masses is established. To address the strong couplings inherent in this system, a decoupling procedure is performed, resulting in single-input single-output (SISO) control loops. Subsequently, for each loop, sensitivity and complementary sensitivity functions are constructed according to the control objectives, and a H∞ suboptimal control problem is formulated within the frequency domain framework. Considering that solar radiation pressure (SRP) dominates in the ultralowfrequency band of the deep-space environment, an additional feedforward compensation channel is introduced on top of the traditional H∞ controller to pre-cancel the induced forces and torques, thereby alleviating the burden on the control loops, releasing robustness margins and improving the overall control performance. Simulation results demonstrate that the proposed DFACS effectively suppresses environmental disturbances and actuator noises, ensuring that both the residual accelerations of the test masses and the inter-satellite pointing errors satisfy the stringent scientific specifications, thus verifying the effectiveness and superiority of the proposed control scheme.