Finite-time attitude controller design via dual-loop control strategy

Abstract

In this paper, a finite-time attitude control scheme based on the dual-loop framework is proposed for rigid spacecraft in the presence of inertia uncertainties, external disturbances, bounded angular velocity, and control input saturation. The control law was designed based on a dual-loop structure. First, a hyperbolic tangent function was used to design the virtual angular velocity command, which serves as the control input of the outer loop system to stabilize the attitude under angular velocity constraints. Second, a smooth function was used to approximate the saturation and an auxiliary system was constructed to compensate for the effects of actuator saturations. A finite-time control law was designed to track the limited command of the outer loop under the disturbance and control input constraints in the inner loop. The stability of the closed-loop system during saturation is thus guaranteed, and the tracking error converges to zero after controller parameters are selected appropriately. A numerical example illustrates the effectiveness of the proposed attitude controller.

Dynamic infinity‐norm constrained control allocation for attitude tracking control of overactuated combined spacecraft

“…Besides input saturation, angular velocity constraint has also been considered in some literature. Under angular velocity constraints, a virtual angular velocity command used to stabilise the attitude was designed by a hyperbolic tangent function [30]. Based on a two‐loop structure, Li et al [31] stabilised the attitude under angular velocity constraints by designing an outer‐loop control law.…”