Single vs. Two-loop full-state multi-input multi-output missile guidance

Two types of autopilot-guidance schemes for linear quadratic multiple-input multiple- output missile systems are compared - single-loop and two-loop configurations. In both cases, all the states are fed-back into the guidance loop. In the two-loop case, the inner autopilot loop is designed separately from the outer guidance loop, where in the single- loop scheme, the guidance command is injected directly to the actuator, without a definite autopilot. It is proven that the two schemes achieve the same performance if and only if the number of guidance commands is identical to the number of available controllers. Thus, using the full-state two-loop scheme is preferred, since it ensures a stabilized airframe whether the guidance loop is active or not. The theorem and guidance laws are illustrated using a dual control missile model.