Nonlinear Robust Control of an Highly Manoeuvrable Missile

Various controllers are developed in order to test them on the missile airframe and make a comparison of the simulation results obtained.
The aim is to show how a systematic nonlinear robust control design can outperform the classic LTI techniques, as well as more recent techniques like feedback linearization. More particular: this thesis is about control design based on the Lyapunov function: all the techniques presented here are based on Lyapunov direct criterion.
Lyapunov based design does not take into account directly the fact that the system may have some uncertain terms, but achieve global asymptotic stabilization on the base of the knowledge of a nominal model. Therefore, the control laws developed in this chapter are not "robust" from the theoretical point of view. Nevertheless, they can be made less sensitive to parameter variations making some peculiar modications, which in simulation will show up an increased level of robustness if compared to the standard design.
From all the Lyapunov based approaches we have chosen the backstepping one, due to the fact that it is really suitable for the missile dynamical model structure. Furthermore, it is a very exible approach that can be re-used in many situations and can be easily modied to improve performance and robustness. As a matter of fact, we will make two useful modications of the standard backstepping design in order to decrease its sensitivity to parameter variations: 1) the use of a non-quadratic control Lyapunov function in the recursive process; 2) the use of integral action.
It is important to stress since now that backstepping is an energetic approach, and this, as we shall underline various times during this work, gives to it a basic level of intrinsic robustness.