Application of H-infinity control to missile guidance and control

Abstract

This paper presents a missile guidance law designed using the u,-synthesis. Namely the guidance law design problem is solved as a robust controller design problem for a homing system, where the plant is composed of missile airframe/autopilot dynamics, linearized kinematic and geometric relations between the missile and target, and seeker dynamics. As for uncertainties, measurement noise, target maneuver, varying missile-target relative distance, and time delay are taken into account. The obtained high-order controller is reduced to a lower-order one by pole-zero cancellation, balanced realization, and elimination of fast modes. Miss distances are computed through computer simulation where nonlinearities of geometric and kinematic relations are taken into account. The results of Monte Cairo simulation and covariance analysis are compared to those of the proportional navigation guidance law (PNG) and suboptimal guidance law (SOG). The simulation study reveals that the //-control-based guidance law (MUG) is generally superior to PNG and almost equivalent to SOG in miss distance, and that MUG commands less acceleration. A problem with the design is weight selection. Its performance strongly and sensitively depends on the weights used in the u-synthesis. It turns out that the frequency characteristics of a finally obtained guidance law are very close to those of SOG.