Global and robust attitude control of a launch vehicle in exoatmospheric flight

Abstract

The goal of this research is to design global and robust attitude control systems for launch vehicles in exoatmospheric flight. An attitude control system is global when it guarantees that the vehicle converges to the desired attitude regardless of its initial condition. Global controllers are important because when large angle maneuvers must be performed, it is simpler to use a single global controller than several local controllers patched together. In addition, the designed autopilots must be robust with respect to uncertainties in the parameters of the vehicle, which means that global convergence must be achieved despite of those uncertainties. Two designs are carried out. In the first one possible delays introduced by the actuator are neglected. The design is performed by using a Lyapunov approach, and the obtained autopilot is a standard proportional-derivative controller. In the second one, the effects of the actuator are considered. Then the design is based on robust backstepping which leads to a memory-less nonlinear feedback of attitude, attitude-rate, and of the engine deflection angle. Both autopilots are validated in a case study.