Design of nonsaturating guidance systems

Design of nonsaturating guidance systems is considered. Assuming linearized kinematics, a proportional navigation guidance model is introduced. The missile guidance loop discussed contains nonlinearities such as limited missile maneuverability, limited acceleration command, and constrained measured line-of-sight angular rate. A novel approach, based on input-output stability, renders design guidelines that assure operation in the nonsaturating region, given the missile-target maneuver ratio. These guidelines yield a proportional-navigation-based guidance law that assures zero miss distance for any bounded target maneuver. It is shown that if the total dynamics of the guidance loop is designed to be positive real, and the effective proportional navigation constant is chosen to be a simple function of the maneuver ratio, no saturation shah occur. The illustrative examples validate the analysis and show that the new guidance law is robust enough to guarantee a significant performance improvement even if the design guidelines are somewhat loosened.