Designing of Three-dimensional Robust Guidance Law Using Adaptive Dynamic Programming with Input Saturation Constraint

In this paper, a three-dimensional robust guidance law for a surface to air missile considering actuator saturation and first order dynamic for autopilot system has been designed in order to enhance the performance of defense systems. To attain this goal, first, modeling of the system in 3D spherical coordination using engagement basics has been derived and after that, appropriate cost function for collision of missile and target considering actuator constraints and in absence of target maneuver information has been formulated. Hamilton-Jacobi-Isaacs (HJI) differential equation inequality should be solved according to robust control literature for achieving guidance law which unfortunately does not have closed form solution in our case study problem. Therefore, to overcome this challenge, using adaptive dynamic programming theory for solving acquired HJI, algorithm for designing robust guidance law has been presented. Simplification solving of differential inequality and also guaranteeing robustness of the controller are the most important feature of the proposed algorithm. Numerous simulations for targets with different maneuvering capabilities and comparison of the proposed method with conventional augmented proportional navigation, show effectiveness of designed 3D robust guidance law.