Satisfying Terminal Angular Constraint Using Proportional Navigation

Abstract

Classical proportional navigation guidance (PNG) law achieves only a set of impact angles against a non-stationary non-maneuvering target for values of navigation constant (N) greater than a minimum allowable value. For achieving impact angles outside the capture region of classical PNG an orientation guidance command is proposed. The orientation guidance command is again PNG with the navigation constant being a function of initial engagement geometry parameters. It is proven that following the orientation trajectory the interceptor can switch to PNG with N = 3 and intercept the target with the desired impact angle. The guidance law is also presented in feedback implementable form for realistic engagements. Simulations are carried out for kinematic and realistic interceptor models separately. Results show successful achievement of all possible impact angles for planar surface-to-surface engagements and all impact angles in a deterministic set for planar air-to-surface engagements. Results for a maneuvering target and for the interceptor with autopilot lag show low impact angle errors with no errors in miss distance.