Design and Experiments of a Nonlinear Observer System for Spaceborne Synthetic Aperture Radar States Detection During Microgravity Simulation

This article proposes a nonlinear observer system for spaceborne synthetic aperture radar during ground microgravity simulation provided by an active gravity offloading system. Through dynamic analysis of the microgravity simulation process, the nonlinear coupling relationship is clarified, a state observer system which integrates a position, velocity subsystem along with a nonlinear disturbance observer is proposed to indirectly obtain the radar’s states using only the gravity offloading system’s sensors. Numerical simulations, platform experiments demonstrate that the proposed observer system outperforms the traditional unscented Kalman filter method. The experimental results show that the root-mean-square errors of joint position, velocity, and torque observation results are reduced by 35%, 65%, and 49%, respectively.