Two reconfigurable flight-control design methods: Robust servomechanism and control allocation

Two methods are discussed for design of reconfigurable night-control systems when one or more control surfaces are jammed. The first is a robust servomechanism control approach, which is a generalization of the classical proportional-plus-integral control to multi-input/multi-output systems. The second proposed method is a control-allocation approach based on a quadratic programming formulation. The formulation is formally analyzed, and a globally convergent fixed-point iteration algorithm is used to make onboard implementation of this method feasible. The two methods are applied to reconfigurable entry night control design for the X-33 vehicle, Nonlinear sis-degree-of-freedom simulations demonstrate simultaneous tracking of angle-of-attack and roll-angle commands during control surface failures. The control-allocation method appears to offer more uniform and good performance at the expense of modestly higher computation requirement.