Research On Reconfigurable Flight Control System For SUAV Based On Intelligent Adaptive Control

Due to the recent advancement of small unmanned aerial vehicles,it urgently needs to improve the reliability and survivability of the flight control systems.When the aircraft is malfunction,it is required that the flight control system could quickly revise its control strategy or reconfigure its control system according to the faulty and damage characteristics so that the aircraft could continue its flight mission or return the base safely.This dissertation investigates how to reconfigure the flight control system through analyzing the situation of small unmanned aircraft based on the existing research,in order to solve the present reconfigurable problem.The main research contents can be summarized as follows:1.Based on Cascade ADRC based fault-tolerant control for a PVTOL aircraft with potential actuator failures,the PVTOL aircraft and the basic principle of the active disturbance rejection control are introduced,including the tracking differentiator,the extended state observer and the nonlinear state error feedback control law are also described in detail.For the convenience of analyzing and applying the the proposed method,the required model has been obtained by using the coordinate transformation for the PVTOL aircraft model decoupling due to the severe coupling between some variables.This approach ensures that the reference input value can be tracked rapidly and accurately.The stability and safety of the aircraft is much improved in the event of actuator failures.In addition,the Taylor differentiator is designed to improve the control precision based on the detailed research for tracking differentiator,and the system stability is also analyzed.2.According to exponential reaching law based variable structure model reference adaptive control of aircraft,the fault tolerant control is deployed to counteract through model reference adaptive control method and variable structure control technology when the actuator failure occurs.There is no need for accurate mathematical model of the aircraft and fault detection modules.Combined with exponential reaching law,the convergence rate is improved and the chattering is reduced.This approach ensures that the reference input value can be tracked rapidly and accurately.The safety and stability of the aircraft is much improved during the event of actuator failures,and the stability of the system is proved using Lyapunov stability theorem.3.Following the adaptive fault tolerant flight control based on LPV observer,the adverse effect caused by the actuator damage of the unmanned aerial vehicle can be eliminated using fault-tolerant and LPV technology based control strategy.Considering the complex adaptive control system,the fault detection and diagnosis module is joined in the system.The state feedback control is used as the baseline control when the aircraft is fault-free.When the fault occurs,the control strategy is switched automatically to the adaptive reconfigurable control.The aircraft can still complete predetermined tasks or return safely by using the fault information obtained through the FDD module.It ensures the flight safety during both the normal flight and the malfunction,avoiding the complexity of the system.Finally,the stability of the system is omproved using Lyapunov stability theorem.Considering the general aircraft fault,two situations,injury and stuck on the elevator and aileron,are selected to investigate in this dissertation.The developed method is verified through the simulation and experiment.Results show that the proposed method can eliminate the fault influence of aircraft and the proposed flight control system has good static and dynamic performance and robustness.