Adaptive Fuzzy Integral Sliding Mode Control Application to the Launch Vehicle’s Orbital Injection Problem

This paper presents an application of adaptive fuzzy integral sliding mode control to the longitudinal attitude tracking problem of satellite launch vehicles. A direct adaptive Fuzzy control law is set to be the equivalent part in the sliding mode control expression. This equivalent part strives to imitate a perfect feedback linearization of the vehicle’s longitudinal attitude dynamics by approximating the unknown functions in the vehicle s model. The singleton control action of the fuzzy control law is set to be an adjustable parameter, and the adaptive mechanism is augmented to tune this parameter with respect to the changing environment in order to reduce the residual error between fuzzy control and feedback linearization control. The adaptation mechanism is designed based on Lyapunov principle, and it guarantees asymptotic stability of the closed loop system. The reaching (switching) part of the sliding mode control law attempts to constrain the system’s state to remain on the sliding surface. An external guidance loop is designed to reshape the reference attitude profile online in order to attain desired orbital altitude and injection angle. To analyze the controlled ascent flight trajectory, a nonlinear 3 Degrees of Freedom numerical simulation model is developed for a four stage Launch Vehicle, and performance evaluation of the proposed control system is conducted on the model in the presence of model parametric uncertainties and external disturbances.