Tactical missile autopilot design using nonlinear control

In this dissertation, a nonlinear autopilot design for a medium range bank to turn air-to-air missile is presented. The key to the autopilot design is the decoupling of the missile maneuvers into lateral and longitudinal components and performing them sequentially while maintaining zero sideslip angle. The resulting missile motion consists of a series of changes in angle of attack and changes in bank angle performed at zero angle of attack. The missile is always returned to zero angle of attack before performing a roll maneuver. This maneuver redefinition results in strictly planar motion, reducing the required rudder and the required structural mass by minimizing lateral translational accelerations. Furthermore, this redefinition permits the use of two single input single output autopilots for control, a pitch autopilot to command changes in angle of attack, and a roll autopilot to command changes in bank angle. The control degrees of freedom not necessary to meet the tracking requirements are used to stabilize the resulting zero dynamics. Variable structure control laws with time varying gains and bandwidths are used to make the autopilots more robust to parameter uncertainties and to variations in initial conditions. Command filtering is employed to reduce the time required to complete the desired maneuvers by defining smooth reference trajectories with desired time response properties. The complete autopilot is then evaluated using a nonlinear simulation, and it is shown that the resulting missile performance meets the requirements for the air to air mission. Finally, conclusions about the effectiveness of the design and alternate applications for the design methodologies are discussed.