Global exponential angular velocity estimation of rigid-body spacecraft from quaternion and vector measurements

Two observer-based angular velocity estimation approaches for rigid-body spacecraft are presented in this paper, where quaternion and direct vector measurements are respectively adopted as available outputs. By transforming the estimation problem into the one in appropriate coordinate, the proposed observers are free from high-gain injection while being globally exponentially stable (GES) in the meantime. This unique feature is not possible in existing GES designs that are based on quaternion or vector measurements, and significantly improved performance under measurement noises are witnessed in numerical examples when compared with corresponding high-gain-based counterparts. Results in this paper also provide the first answer to the open problem on constructing truly GES angular velocity observer from vector measurements.