Lateral Acceleration Flight Control for a Quasi-Linear Parameter Varying Missile Model Via Pseudolinearisation

Abstract

A lateral augmented acceleration 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 (sideslip velocity) and external parameters (longitudinal velocity and roll angle). The autopilot design is based on input-output pseudolinearisation, 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. Thus, if the operating points are in the vicinity of the equilibria, then only one linear model will describe closed-loop dynamics, regardless of the rate of change of the operating points. 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.