A Hyperstable Model-Following Flight Control System Used for Reconfiguration Following Aircraft Impairment

Techniques have been developed for remixing the commands issued by flight control laws that assume unimpaired operation. This approach allows impairments to be accommodated that previously were not. This increase in fault tolerance does not decrease reliability because no additional hardware is installed on the aircraft. Instead, previously existing redundant control surfaces are used to greater advantage. A recent effort has focused on an implicit approach as opposed to a previously mechanized explicit approach. The implicit approach, which is termed Hyperstable Model-Following Flight Control (HMFC), is estimated to be an order-of-magnitude smaller in size than the explicit approach, which is termed the Control Reconfiguration Feature (CRF). This reduction in size is accomplished without a loss in performance. In fact, performance can be increased because the reduced complexity allows a higher iteration rate and, hence, reduced reconfiguration time. Furthermore, HMFC will successfully reconfigure under conditions for which the CRF will not, while possessing robustness with respect to disturbances and unmodeled states. The completion of the HMFC system design constitutes an advance in the simplicity and comprehensiveness of reconfigurable flight control systems.