Minimum Drag Control Allocation

Continued research into the direct control allocation problem with rate limiting has led to consideration of a modified problem in which control generated drag is considered as a fourth objective (in addition to the 3 moments). This allocation scheme uses the controls' effectiveness in generating moments as well as their effectiveness in generating drag to obtain an admissible solution in moment space while, simultaneously, driving the controls toward their minimum drag configurations. The control allocation algorithm was tested in a non-linear, six degree of freedom simulation of an F-18. Also implemented in the simulation were a maneuver generator and a dynamic inversion control law to provide the moment inputs to the allocator. The simulation results show that while minimum drag allocation is not an optimization algorithm, it continuously drives the controls toward their minimum drag configurations while satisfying the control law moment demands during maneuvers. It is also shown that in non-maneuvering flight, the allocation scheme actually achieves a minimum drag configuration.