Fault Tolerant Sliding Mode Control Schemes With Aerospace Applications

The thesis concerns the theoretical development and implemantation of sliding mode schemes for fault tolerant control. The theoretical ideas developed in the thesis have been applied to aerospace systems. In particular, actuator and sensor fault tolerant control schemes have been developed for a high fidelity full nonlinear model of a Boeing 747 aircraft which is a widely researched testbed in the open literature. A key development in this thesis considers sliding mode control allocation schemes for fault tolerant control based on integral action and a model reference framework. Unlike many control allocation schemes in the literature, one of the main contributions of this thesis is the use of actuator effectiveness levels to redistribute the control signals to the remaining healthy actuators when faults/failures occur. A rigorous stability analysis and design procedure is developed from a theoretical perspective for this scheme. A fixed control allocation structure is also rigorously analyzed in the situation when information on actuator effectiveness level is not available. The proposed scheme shows that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. A design of an adaptive gain for the nonlinear component of the sliding mode controller for handling faults is also described. The later chapters of the thesis present the results obtained from real time hardware implementations of the controllers on the 6-DOF SIMONA flight simulator at Delft University of Technology as part of the GARTEUR AG16 programme. The schemes have been evaluated by experienced pilots and the results have shown good performance in both nominal and failure scenarios. A reconstruction of the Bijlmermeer ELAL 1862 scenario on SIMONA using one of the controllers shows that a safe flight and landing is possible with significant reduction in pilot workload when compared with the classical controller.