Sliding-Mode Disturbance Observer-Based HOFA Predictive Control of Spacecraft Flying-Around

On the basis of high-order fully actuated (HOFA) system theory, this research is devoted to a flying-around problem of spacecraft with lumped disturbances under a sight coordinate system, where the lumped disturbances are used to represent the total impacts of the model uncertainties and external disturbances. Following the HOFA system theory, a nonlinear HOFA system model is exploited to establish the relative dynamical model of spacecraft flying-around under the sight coordinate system, such that the flying-around mission can be equivalent to a tracking control problem. A sliding-mode disturbance observer-based HOFA (SMDOB-HOFA) predictive control method is proposed to handle this problem. Specifically, a HOFA sliding-mode disturbance observer is designed to estimate and compensate for the lumped disturbances. Then, an incremental HOFA prediction model including the errors of disturbance estimation is developed with the help of Diophantine Equation to construct the multi-step ahead predictions. Based on these predictions, an objective function involving the tracking control performance can be minimized to obtain an optimal tracking controller for the realization of flying-around mission. The capability of SMDOB-HOFA predictive control is verified via a flying-around experiment of air-bearing spacecraft (ABS) simulator in a desired circular orbit.