Design of missile flight control systems using variable structure techniques

Variable Structure Control theory was extended to include simultaneous use of continuous and discontinuous control inputs. Novel methods based on linear programming were developed to blend continuous and discontinuous control inputs. Results from digital simulations of a controlled 180 degree maneuver of a hypothetical next-generation air-to-air missile model are presented to show that the proposed method provides stable, robust control over a wide range of flight conditions.; This research stems from the desire to extend the limits of present air-to-air missile maneuvering envelope to include such maneuver as extremely rapid 180 degree changes in the flight path angle. Such extreme maneuvers are not possible using only present conventional aerodynamic control. Therefore, a combination of continuous aerodynamic and discontinuous reaction jet controls is proposed.; Simulation results presented indicate that it is feasible to implement variable structure control systems with a combination of unconventional and discontinuous control sources, e.g., reaction jets, with conventional aerodynamic control surfaces. Such control system is used effectively to increase both the angle of attack envelope and the maneuverability of a mathematically modeled missile over limits dictated by aerodynamic control alone. The combination also provides vehicle controllability for phases in which the aerodynamic control surfaces become ineffective.; Various mixes of the control sources were tested to identify cases of improved missile flip-over performance. Direct use of optimal control methods to blend controls is possible by selecting the control weighting matrix appropriately. However, since no systematic approach was identified for selecting these weights, an optimal control method based on linear programming was developed. Simulations for both blended and non-blended controls are presented to show effective design improvements.; The above ideas were combined to accomplish a simulated flip-over maneuver in which the missile reverses the direction of flight. The flip-over maneuver is characterized by high pitch rates, extremely high angles of attack and loss of aerodynamic control. Results for several cases involving large variations in parameters from nominal values are presented to demonstrate enhanced performance for a single set of control gains derived for the nominal case.