Look Angle Constrained Impact Angle Control Based on Proportional Navigation

Abstract

Two guidance schemes for nonlinear impact angle control against stationary ground targets are presented to address the issue of the look angle constraint. The guidance laws utilized are the unbiased and biased pure proportional navigation laws, for which the necessary analytical solutions are derived. The logic is based on switching action, where the navigation gain and/or the bias is switched when proper conditions for the terminal phase are achieved. The solutions of the nonlinear optimal control problem for selected engagement geometries are obtained to serve as benchmarks. The results imply that it may be possible to approach the performance of the optimal solution if the biased proportional navigation is employed as the midcourse guidance law. The implementation of the proposed schemes is expected to be straightforward because problematic inputs such as time-to-go are not required.