Fault Detection/Isolation and Fault Tolerant Control for Hypersonic Vehicle

The scramjet-powered air-breathing hypersonic vehicle (HSV) presents a more efficient and affordable way of achieving space routine and intercontinental travels. However, to maintain sustainable and safe hypersonic flight is a very challenging task due to strong coupling effects, the variable operating conditions and possible failures of the system components.;In order to develop effective reconfiguration control approaches to address the tracking control task of the air-breathing HSV subject to possible sensor/actuator failures, we studied three algorithms based on the current fault detection and isolation, gain-scheduling and switching control techniques.;In this thesis, we start with the fault detection and isolation (FDI) problem for faulty linear parameter-varying (LPV) systems subject to disturbances and propose a observer-based solution by using multiobjective optimization techniques. To simply the design process, a general faulty LPV system will be constructed from standard LPV description by converting actuator/system component faults into sensor faults at first. Then a bank of LPV FDI filters will be designed to identify each fault. Each FDI filter could generate a residual signal to track individual fault with minimum error and suppressing the effects of disturbances and other fault signals. The design of FDI filters will be formulated as multiobjective optimization problems in terms of linear matrix inequalities (LMIs) and can be solved efficiently.;Then in the second part of this thesis, we study a robust fault-tolerant control (FTC) problem for linear systems subject to time-varying actuator and sensor faults. The faults under consideration are loss of effectiveness in actuators and sensors. Base on the estimated faults from a fault detection and isolation (FDI) scheme, robust parameter-dependent FTC will be designed to stabilize the faulty system under all possible fault scenarios. The synthesis condition of such a FTC control law will be formulated in terms of linear matrix inequalities (LMIs) and can be solved efficiently by semi-definite programming.;Finally, we propose a switching fault-tolerant control (FTC) approach for linear systems subject to time-varying actuator and sensor faults. The faults under consideration include effectiveness loss and outage of actuators and sensors. All possible fault scenarios are categorized to different fault cases according to fault type and location. For each case, a parameter-dependent (or constant gain) FTC will be designed to stabilize the faulty system with optimal controlled performance. The synthesis of such a local FTC control laws can be accomplished using standard LPV control techniques. To achieve both local optimal performance and switching stability, Youla parameterizations of individual local FTCs are derived and applied to the feedback system. The switching stability of multiple closed-loop systems is then guaranteed by a common Lyapunov function.;All proposed approaches are effectively applied to the flexible HSV plant subject to failed actuators and sensors. The design of proposed FDI observers and fault tolerant controllers for the LPV model of faulty HSV with different fault scenarios are demonstrated and compared. The simulation studies based on the nonlinear model of faulty HSV with two types of tracking commands are conducted to check the effectiveness of LPV FDI observers and FTC controllers under different operating conditions. The simulation results indicates that the proposed FDI algorithm could achieve good fault decoupling and estimation of both actuator and sensor faults from the noisy measurements; the robust FTC algorithm could tolerant the all faulty scenarios and accomplish the altitude tracking tasks when the degradation level and fault estimation error are relatively small; the switching FTC could guarantee the stability of the arbitrary switching among different fault scenarios at each trim point, as well as maintain the optimal controlled performances over HSV flight envelop.