Single versus two-loop full-state guidance and control

Full-state approach to designing nonlinear autopilot and guidance systems with bounded controls (servo command or acceleration command) is presented. Two types of full-state architectures are considered: full-state single-loop and full-state two-loop. In the full-state single-loop case, the guidance command is injected directly to the actuator, whereas in the full-state two-loop case, it is the input to the autopilot loop. It is proven that the two full-state architectures are equivalent for nonlinear systems for any cost function if there is a unique mapping from the servo command and state sets into the guidance command set. This result encourages the use of the full-state two-loop architecture over the full-state single-loop one because it ensures a stabilized vehicle if the guidance loop is inactive. The theorem and guidance laws are illustrated via a dual-control missile in an endo-atmospheric interception scenario.