(A) practical optimal guidance scheme under impact angle and terminal acceleration constraints

Abstract

This thesis proposes a practical optimal guidance law that can handle terminal angle and acceleration constraints, at the same time providing robustness against uncertainty in autopilot dynamics. Building upon a well-established linear-quadratic optimal guidance framework, we first derive an energy-minimizing guidance scheme that nullifies terminal acceleration, termed Optimal Guidance Law with Impact Angle and Terminal Acceleration constraints(OGL-IATA). Then, a practical modification to OGL-IATA is proposed to deal with the stability degradation of OGL-IATA due to unmodeled high-order autopilot dynamics. The modification primarily features feedback of pseudo-acceleration that is computed by passing the true acceleration signal through approximate missile dynamics

this simple modification is demonstrated to improve the stability margin of the guidance loop. Numerical examples on nonlinear engagement kinematics demonstrate the performance and the robustness characteristic of the proposed practical guidance scheme. The degree of freedom of optimal guidance design is extended by time-to-go weighted control energy cost function. The effects of autopilot dynamics error on the stability of guidance is analyzed through an analytical method, and the performance is compared by numerical nonlinear simulations.