A multi-objective control approach for the synthesis of robust digital guidance laws

Abstract

This paper proposes a new approach for the synthesis of robust digital guidance laws with the objective of achieving stable and accurate missile guidance despite parametric uncertainties in the missile flight control system dynamics, prescribed limits on missile acceleration, and digital implementation at possibly slow sampling rates. The proposed approach is characterized by two consecutive steps. Firstly, a robust continuous-time guidance law is designed using mixed H2-H∞ minimization and pole placement such that the effects of noise and parametric uncertainties are attenuated. To carry out this first step of the approach, missile flight control dynamics are modelled as second-order interval transfer functions, where bounded time-varying parameters characterize the missile flight envelope. Secondly, digital redesign of the robust continuous-time missile control system (including guidance and flight control) is performed by solving an optimal control problem. The proposed global digital redesign strategy results in robust performance for the closed-loop sampled-data missile control system for a wider range of sampling rates than those obtained with currently available approaches and can be readily implemented on commercially available software by following the step-by-step procedure described in the paper. Numerical simulations consisting of a missile pursuing a manoeuvring target, described by the so-called Singer model, demonstrate the effectiveness of the proposed approach.