Observer-Based Attitude Control for Reusable Launch Vehicle with Input Constraints

This paper investigates the attitude tracking control problem of a reusable launch vehicle(RLV) in cases of inertia uncertainties, external moment disturbances and input constraints. The controller design is based on synthesizing the extended state observer (ESO) into a back-stepping control technique. In order to improve the system robustness, a finite-time ESO (FTESO) is proposed. This will estimate the total disturbances and is equipped with a controller. The dynamic surface control (DSC) technique is used to avoid the increasing complexity problem when compute virtual command derivatives and the adaptive law is applied to estimate the bound of observer error. A new auxiliary variable vector mainly driven by error states between the actual control input and the desired control input is integrated to compensate for the saturation effect. Thus the control strategy characterized by shorter saturation time is successfully proposed as total disturbances and input constraints considered simultaneously. Following this, the finite-time stability of the closed-loop system is proved within the Lyapunov theory framework. Several simulations are then investigated to illustrate the effectiveness of the proposed constrained attitude control scheme.