Aircraft Fault Accommodation with Consideration of Actuator Control Authority and Gyro Availability

When faults of some flight actuators have occurred, an unexpected need to use larger magnitudes and higher actuation rates of fault-free actuators is often caused if fault-tolerance design is not considered. This paper presents a fault-tolerant flight control (FTFC) capable of accommodating aircraft actuator failures while respecting to the physical control authority of healthy actuators, on the basis of sliding mode (SM) and adaptive techniques. Furthermore, this paper accounts for the availability of the measured angular rate. In the presence of reliable gyro onboard, the sensed pitch rate can be applied to the developed FTFC loop. In the absence of pitch rate measurement, a SM observer (SMO) is exploited to recover the pitch rate information, while the integrated design of the SMO and FTFC is investigated. Simulation studies of a nonlinear Boeing 747 longitudinal model are conducted to manifest the effectiveness of the proposed schemes.