Robustness of a Variable Structure Control System for Maneuverable Flight Vehicles

One of the key issues related to design of supermaneuverable missiles is precise control during rapid maneuvers. An autopilot synthesis for a marginally stable air-to-air missile with the inclusion of on/off reaction jets to supplement pitch control provided by the elevators is presented. The proposed control method is an extension of variable structure control theory to include simultaneous use of continuous and discontinuous actuators. Stability and robustness issues are addressed, and autopilot synthesis is then carried out. A blending of aerodynamic and propulsive controls is also introduced, based on linear programming that optimizes continuous and discontinuous control, into a single input at low angles of attack. Results from digital simulation of a controlled 180-deg maneuver of a hypothetical next-generation air-to-air missile model show that the proposed method provides stable and robust control over a wide range of flight conditions.