This paper studies the attitude-tracking control problem of spacecraft considering on-orbit refuelling. A time-varying inertia model is developed for spacecraft on-orbit refuelling, which actually includes two processes: fuel in the transfer pipe and fuel in the tank. Based upon the inertia model, an adaptive attitude-tracking controller is derived to guarantee the stability of the resulted closed-loop system, as well as asymptotic convergence of the attitude-tracking errors, despite performing refuelling operations. Finally, numerical simulations illustrate the effectiveness and performance of the proposed control scheme.

Purpose This paper aims to address the spacecraft attitude control problem using hybrid actuators in the presence of actuator saturation, uncertainties and faults, inertia uncertainties and external disturbances. Design/methodology/approach A hybrid actuator configuration is used where thrusters are engaged for rapid attitude maneuvers, while reaction wheels (RWs) are used for fine pointing. Findings The key advantages are two-fold: a finite-time high-level controller is designed to produce the three-axis virtual control torques; an online robust control allocation (RobCA) scheme is proposed to redistribute virtual control signals to the actuators with taking into account the actuator saturation, uncertainties and faults; and the RobCA scheme allows a smooth switch between thrusters and RWs, which handles the inaccuracy problem of thrusters and saturation problem of RWs. Practical implications An online RobCA algorithm is designed that maps the total control demands onto individual actuator settings and allows a smooth switch between thrusters and RWs. Simulation results show the effectiveness of the proposed control strategy. Originality/value This work may be used on modern space missions, which impose higher requirements on smooth switching of spacecraft thrusters and RWs.

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