Development of a novel ground simulator reproducing drag-free control

Space gravitational-wave detection requires the precise control of the relative positions between the satellite-internal test mass and the satellite body at nanometer-level precision. Furthermore, the satellite platform is required to provide an "ultra-stable and ultra-quiet" scientific experimental environment. Drag-free control is a key technology for achieving such an "ultra-stable and ultra-quiet" satellite experiment platform in space gravitational wave detection. This study focuses on the "Taiji" mission and proposes a novel semi-physical simulation platform to validate drag-free control technology on the ground. The platform integrates a quasi-zero-stiffness motion platform and a suspension torsion pendulum system to model satellite dynamics and replicate the motion of test masses along sensitive axes. This study proposes a finite-frequency-domain disturbance-rejection drag-free controller based on generalized Kalman-Yakubovich-Popov (GKYP) theory. Numerical simulation results show that within the drag-free control frequency band, the control accuracy and disturbance-rejection capabilities of this controller are superior to those of both the H_∞ and PID controllers. Experiments were conducted to verify the drag-free controller using two test masses arranged at a 60° angle on the semi-physical simulation platform. The results demonstrate that the performance of the GKYP controller is superior to the H_∞ and PID controllers, thus validating the effectiveness of the proposed drag-free control method. This study provides a reference for the design of drag-free controllers for gravitational wave detection in space.