ADAPTIVE FUZZY SLIDING MODE CONTROL: APPLICATION TO SATELLITE LAUNCH VEHICLE'S ATTITUDE CONTROL

This paper presents a control design approach for attitude tracking of Satellite Launch Vehicles (SLVs) based on adaptive fuzzy sliding mode control (AFSMC) with integral sliding mode switching surfaces. The AFSMC strives to enforce feedback linearization of the vehicle's attitude dynamics by approximating the unknown functions in a prescribed feedback linearization control law. The hitting (switching) control part of the AFSMC law works to compensate for the approximation error between ideal feedback linearization control and AFSMC. The outputs of the AFSMC laws for the roll, pitch, and yaw channels are singleton control actions that are chosen to be adjustable parameters. The adaptive mechanism is based on Lyapunov stability principle, which aims to estimate the adjustable AFSMC parameters and the bounds of estimation errors, such that asymptotic stability of the closed-loop system is guaranteed. An external guidance loop is designed for online reshaping of the reference pitch and yaw attitude profiles, such that the desired orbital parameters are attained. To analyse the ascent flight trajectory, a six degrees of freedom (DOFs) mathematical model is developed for a four-stage SLV. Numerical simulations are conducted on six DOFs simulator for performance evaluation of AFSMC control in presence of parametric variations and external disturbances.