Optimal Design of Integrated Missile Guidance and Control

Tactical ballistic missiles (TBM) target may experience severe spiral maneuvers as they reenter the earth's atmosphere due to a configurational asymmetry. To hit these targets, the interceptor must possess extremely fast maneuver response characteristics. Before 10 secs to go optimal integrated guidance and control (OIGC) is slightly better than a conventional autopilot. From 2 to 10 secs OIGC is much better than a conventional autopilot in closing up trajectories. However, with 2 secs to go, OIGC uses up full authority and with the aerodynamic surfaces alone may not catch the tactical ballistic missile target. Therefore, there is a need for thrusters. In this paper, a blending mechanism of optimal integrated guidance and control (OIGC) and fuzzy logic controlled thruster is developed for a skid-to-turn missile to improve the missile interception performance. OIGC is an innovative approach to designing guidance and control laws. The OIGC approach combines the guidance law and autopilot designs into one framework so that the end-game parameters can be accounted for in the control gains. This design augmentation has the merits of optimizing the interactions between the guidance dynamics and control dynamics, leading to a reduced miss distance. Fuzzy logic control is used to determine the magnitude and direction of the thrust. As a result, the blending control of the OIGC controlled aerodynamic surface and the fuzzy logic controlled thruster is specifically investigated. A 6DOF nonlinear missile model is derived and established. The simulation results demonstrate a substantially improved miss distance performance for the blending OIGC controlled aerodynamic surfaces and fuzzy logic controlled thrusters over that of a conventional guidance and control design in the presence of a spirally maneuvering target. The results also show that the miss distance for the blending approach remains insensitive to increasing target maneuvers, while the miss distance for a conventional guidance and control system increases significantly with the motion of a maneuvering target. This feature is critical for the interception of a spiraling target.