Research On Multi-model Fault Diagnosis And Fault Tolerant Control Of Hexacopters

Due to the simple structure and the low production cost,the multi-rotor UAV has been widely used in various fields in recent years.In these applications,the quadrotor is still the mainstay.However,with the depth of the research,it is found that the quadrotor is vulnerable in the external environment when flying.Then the flight stability will be affected.Especially when the actuator is completely stuck or completely failed,the quadrotor UAV will inevitably crash.Aiming at this problem,it is especially important to choose a multi-rotor UAV with good fault tolerance.The hexacopters has high hardware redundancy.After failures occur when flying,it can stabilize flight by self-regulation.Therefore,the hexacopters has been widely concerned by researchers.But its research on fault-tolerant control is still rare.As a result,this paper presents a multi-model fault diagnosis and fault-tolerant control method for single actuator of the six-rotor UAV which is completely stuck or completely failed.Firstly,this paper introduces the flight principle of the hexacopters and the establishment of the reference coordinate system,and builds the dynamic model of the hexacopters.This paper ignores some factors that have less impact on flight and then obtains an effective mathematical model.Secondly,for the completely stuck or completely failed of the single actuator of the hexacopters,the interactive multi-model algorithm is used for fault diagnosis.The algorithm establishes the fault model set when the actuator is completely stuck or completely failed,and uses the parallel filtering method to monitor the hexacopters system in real time to achieve the purpose of fault diagnosis.Then,the self-reconfigurable control system processes the UAV that has experienced a single actuator failure.The self-reconfiguration control system designed in this paper includes self-reconfiguration matrix and controller.The self-reconstruction matrix switches according to different fault models,then the lift of the drone is redistributed to return to a stable state.The role of the controller is to provide stable control in the event of fault occurrences.In this paper,the feedback linearized integral sliding mode controller is designed as the controller of the hexacopters.Finally,the effectiveness of the method is proved by simulation experiments.This method not only can accurately diagnose the actuator failure,but also can perform fault-tolerant control on the faulty system,to enable that the hexacopters can continue to fly or land smoothly after a failure.The comparison experiments show that the robustness and transient performance of the feedback linearized integral sliding mode control algorithm are better than the PID control algorithm.This paper provides a new idea for the fault diagnosis and fault-tolerant control of the hexacopters,and also lays a theoretical foundation for future flight experiments.