A model to represent loss of control effectiveness in an aircraft is developed by analyzing physical faults in the hydraulically-driven control surfaces. A hybrid fault-tolerant control system (FTCS) that combines the merits of passive and active FTCSs is proposed to accommodate this kind of partial actuator failures. The hybrid FTCS is able to first slow down the rate of fault induced system deterioration with minimal fault information so that the fault detection and diagnosis (FDD) schemes can have additional time to achieve more accurate fault diagnosis. Once the correct fault information is obtained, the hybrid FTCS can counteract the faults effectively through an optimal reconfigurable controller. Depending on the availability of actuator redundancies, the passive FTCS and the reconfigurable controller are designed in the framework of linear matrix inequality (LMI) approach. Case studies of an aircraft subject to different degree of loss of control effectiveness have been carried out to prove the effectiveness of this new approach to FTCS.
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