IJCAS

This paper proposes a generalized three-loop autopilot topology and its optimal design methodology to control the longitudinal acceleration of missiles. The conventional control loop for the longitudinal acceleration control of missiles is a three-loop autopilot. However, it is unclear whether this topology is the optimal configuration for various control surfaces of missiles. To address this question, generalized three-loop autopilot is first acquired by taking block operation to the conventional three-loop topology. This reveals that the conventional three-loop topology consists of a full-state feedback controller with an angle-of-attack observer and an integral compensator in the outermost loop. Based on these observations, the three-loop topology can be generalized by modifying the compensator topology to optimize the performance according to different fin configurations. The control gains of the generalized three-loop topology are derived by solving the optimal output feedback control problem. To address stability issues caused by un-modeled high frequency dynamics of actuators, the weight matrices are calculated by desired phase margin and gain crossover frequency. Additionally, to ensure robustness against uncertainties, the optimal design variable of the compensator is selected based on the robust control theory. Simulation results demonstrate that the proposed technique is superior to existing methods in terms of robustness toward aerodynamic uncertainties and flexibility to achieve optimal performance regardless of the control surfaces.

Keywords: Autopilot topology, optimization, output feedback linear quadratic control, robust control.