Of Unmanned Helicopters Robust And Adaptive Fault-tolerant Control Technology

Considering the characteristics and safety requirements of unmanned helicopter, by the research of the fault-tolerant flight control system, this dissertation design fault-tolerant controller to make it achieve high reliability and safe capability. The main contributions are as followings:Firstly, considering the actuator faults of unmanned helicopter, a more general and practical model of actuator faults is presented. Based on the control gain margin, a method of robust tracking control-based fault tolerant flight control system is designed to deal with the problems of flight tracking control against actuator faults and model uncertainty, using the linear matrix inequality (LMI) method and H∞theory. The designed controller can guarantee the stability of the closed-loop system and acceptable lower level of tracking performance. The simulation results illustrate the efficiency of the proposed method.Secondly, considering the actuator failures and uncertainty of the system, a new model following adaptive flight control method is proposed for the plant in the presence of actuator fault and rapid changing nonlinear aerodynamic phenomena, which is a combination of direct adaptive control algorithm with model following control and RBF neural network. The RBF neural network is introduced to compensate the impact of actuator failures and the uncertainty of the system, using the tracking error to design neural network output weight learning algorithm and parameter update adaptation law. As a result, the PMF is guaranteed. It can prove that the closed-loop system is uniformly ultimately bounded stable based on Lyapunov function. Simulation results illustrate the efficiency of the proposed method.Thirdly, a method of the model-reference adaptive control-based sliding-mode control system is proposed in the presence of the parameter sharp jump caused by structural fault, in addition, the RBF neural network is introduced to eliminate large chattering and guarantee system robustness against large parameter variations and external disturbances.The on-line parameter adaptation law is derived based on Lyapunov function, as a result, the stability of the system can be guaranteed, and the outputs of aircraft can perfectly track the trajectory of the reference model, no failure information is required. The simulation show model-reference adaptive sliding-mode control can maintain the stability and handling qualities.