Research On Switched Fault Tolerant Control And Simulation Platform Of VTOL Aircraft

This paper studies nominal trajectory tracking control and fault tolerant tracking control of a thrust vectoring vertical take-off and landing aircraft. Switched system theory is applied to dynamic modeling of the multi-mode flight process. Based on feedback linearization and system decomposition techniques, two switching control algorithms are proposed to control both nominal case and faulty case of the VTOL aircraft. Simulation results in Matlab illustrate the effectiveness of the proposed nominal control and fault-tolerant control algorithms.To begin with, the background, purpose and significance of this research are introduced and the concepts of fault, fault tolerant control and switched system are systematically described. An overview of the research situation about VTOL aircraft is summarized, followed by the main tasks of this paper.Afterwards, the characteristics of multi-mode flight process of the VTOL aircraft are analyzed and the longitudinal dynamical model of each mode is presented. Also, the nonlinear switched system model and actuator fault model are described by simplifying the dynamical model of three flight modes, of which the purpose is to provide a mathematical model for the control design and simulation in the next.Furthermore, based on the switched system model of the VTOL aircraft, model transformation and system decomposition are firstly implemented to design nominal tracking controller for each mode, respectively, and then the closed-loop stability of the switched tracking error system is discussed by using common lyapunov function theory. Simulation results demonstrate that the nominal control algorithm can effectively achieve the goal of trajectory tracking control.At last, for the switched system model of which each mode exists actuator faults, three cascaded observer systems with two extended state fault diagnosis observers are designed for three modes respectively to estimate the unknown fault information, based on which, three fault tolerant tracking controllers that use optimal control and integral sliding mode control techniques are synthesized to guarantee the closed-loop stability of three faulty modes. The common lyapunov function and input to state stability theory are utilized to discuss the closed-loop stability of the whole switched tracking error system under arbitrary switching, and then a practical state dependent switching law is given for numerical simulation. Simulation results show the effectiveness of the proposed fault estimate algorithm and fault tolerant control algorithm.