Robust pseudo-linearising autopilot for a quasi-linear parameter varying missile model

Abstract

A sideslip velocity autopilot is designed for a model of a tactical missile and robust stability of the closed-loop system investigated. The tail-controlled missile in the cruciform fin configuration is modelled as a second-order quasi-linear parameter-varying system. This nonlinear model is obtained from the Taylor linearised model of the horizontal motion by including explicit dependence of the aerodynamic derivatives on a state and external parameters. The autopilot design is based on input-output pseudo-linearisation, which is the restriction of input-output feedback linearisation to the set of equilibria of the nonlinear model. The design makes Taylor linearisation of the closed-loop system independent of the choice of equilibria. Simulations for constant lateral acceleration demands show good tracking with fast response time. Parametric stability margins for uncertainty in the controller parameters and aerodynamic derivatives are analysed using quadratic Lyapunov approach.