Adaptive estimation of attitude and angular velocity of malfunctioned satellites for on-orbit servicing

Abstract

Estimating the attitude and angular velocity of a malfunctioned satellite is one of the key technologies to achieve robotic on-orbit servicing, which is a challenging space activity. In this paper, a new method of estimating attitude parameters for target satellite by using stereo-vision system is proposed. First, two sets of vectors are constructed according to the feature point coordinates in target frame and stereo-vision system frame respectively, and then the relative attitude between the target and the servicer is determined through QUEST algorithm. Secondly, a new nonlinear estimator is proposed to estimate the attitude and inertial angular momentum of the target and the angular velocity is computed according to the estimated angular momentum and attitude. The stability of the estimator is proved by using the LaSalle’s invariance principle. Thirdly, a switch rule and an adaptive regulating rule are proposed to improve the estimation performance. The former decides when to switch from the rough estimator to the precise one. The latter regulates the gain dynamically in order to reduce the influence of the varying stereo-vision noise in the precise estimating procedure. Finally, numerical simulations and an experiment are carried out to verify the validity of the proposed method.