Guidance synthesis for evasive maneuver of anti-ship missiles

Abstract

In this dissertation, a guidance synthesis method for anti-ship missiles to enhance their survivability against ship-borne CIWS(Close-In Weapon System) is investigated. Using CFSQP(C code for Feasible Sequential Quadratic Programming) and CEALM(Co-Evolutionary Augmented Lagrangian Method), direct optimization techniques, an optimal control problem to minimize time-varying weighted sum of the inverse of aiming errors of CIWS is solved. The optimal evasive trajectory exhibits sinusoidal acceleration commands, resulting in barrel-roll type evasive maneuvers. Inspired by the optimization results, 3-dimensional biased PNG laws to induce a barrel-roll maneuver during the homing phase are proposed. First, a biased PNG with a constant barrel-roll frequency is introduced. Another proposed BPNG has a time-varying barrel-roll frequency in order to use all possible energy of the missile. Capturability of the proposed guidance laws are proved by using the Lyapunov stability theory. In the capturability analysis, it is noted that a bias term of the BPNG perpendicular to the missile velocity vector and the LOS vector does not affect the capturability of the BPNG. In the case of the BPNG with a constant barrel-roll frequency, a proper choice of the barrel-roll direction guarantees that the missile altitude can be made lower bounded. Performance of the proposed guidance laws is compared with conventional PNG via simulations. The proposed guidance laws provide an effective evasive maneuver against the CIWS, while homing to the target. The evasion performance of the proposed guidance laws is close to the results of the optimal control problem.