Linear Quadratic Integrated vs. Separated Autopilot-Guidance Design

Three types of guidance systems are studied. The first type is a separated two-loop autopilot guidance law that assumes spectral separation between the guidance and the flight control. However, separation may not hold close to interception, requiring possibly an integrated design of guidance and control. Using the integrated approach, two different guidance law types can be used to improve the end-game performance. The first one is the integrated single-loop guidance law, where the coupling between flight control and guidance loops is taken into account in the derivation process. The second type is the integrated two-loop autopilot guidance law. In this case, the autopilot loop is designed separately from the guidance one, but all the states are fed-back into the guidance loop. The performance of the three guidance laws is evaluated and compared via a single-input single-output test case. It is shown that the integrated two-loop autopilot-guidance law can manipulate the inner autopilot dynamics, resulting in the same performance as the integrated single-loop guidance law. In addition, it is shown that the performance of the separated guidance law is inferior to that of the integrated laws.