A Systematic Method for Constrained Attitude Control under Input Saturation

Abstract

In this paper, the constrained attitude control prob-lem with a prescribed performance requirement is investigated, and a systematic method involving the synthesis of path planning, prescribed performance design, and tracking control with inherent saturation is proposed. The overall works are based on attitude rotational matrix and its equivalent vector description. In the path planning phase, both the solid constraints, referring to the forbidden region where the sensitive instrument is strictly prohibited, and the soft constraints, referring to a designable margin of safety are considered. Then a centric reference trajectory outside the soft constraints is established according to a gradient-base algorithm. To formulate the reference trajectory, a motion planning method is employed to establish the ideal angular velocity constrained by the maximum affordable control torque. In the prescribed performance design phase, the performance boundary tube is generated to avoid any potential invasion caused by the attitude tracking error. Finally, in the controller design phase, inherent input saturation is considered and a magnitude-constrained controller is proposed. When the proposed controller is exerted on the system, closed-loop system stability is achieved and the spacecraft is always kept outside the solid constraints. The effectiveness of the proposed method is verified through numerical simulations.